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Drozdowski LA, Suh M, Park E, Clandinin MT, Thomson ABR. Dietary Gangliosides EnhanceIn VitroGlucose Uptake in Weanling Rats. JPEN J Parenter Enteral Nutr 2017; 31:423-9. [PMID: 17712152 DOI: 10.1177/0148607107031005423] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/15/2022]
Abstract
BACKGROUND The intestine adapts to environmental stimuli, such as modifications in dietary lipids. Dietary lipids modify brush border membrane (BBM) permeability and nutrient transporter activities. Gangliosides (GANG) are glycolipids present in human milk, but they are present only in low amounts in infant formula. Exogenous GANG are incorporated into cell membranes and increase their permeability. This study was undertaken to determine if feeding a 0.2% GANG-enriched diet for 2 weeks alters in vitro intestinal sugar absorption in weanling rats compared with an isocaloric control diet or diet enriched with polyunsaturated long-chain fatty acids. METHODS In vitro uptake of 34-96 mm glucose and fructose and morphological measurements were assessed on intestinal tissue of weanling rats. Western blotting, immunohistochemistry, Northern blotting, and reverse transcription-polymerase chain reaction were performed to determine the mRNA and protein abundance of the sugar transporters SGLT-1, GLUT2 and GLUT5. RESULTS Feeding GANG did not alter the rates of animal weight gain or intestinal morphology. GANG did not affect fructose uptake. Depending on the concentration of glucose, GANG increased jejunal uptake of higher concentrations of glucose by approximately 20%-60%. There were no changes in GLUT5 or GLUT2 protein or mRNA abundance. Similarly, there were no changes in SGLT-1 mRNA and protein abundance, as determined by Northern and Western blotting. However, using immunohistochemistry, SGLT-1 was lower in GANG than in controls. CONCLUSIONS The results of this study suggest that the enhanced uptake of glucose that results from feeding 0.2% GANG for 2 weeks to weanling rats may be regulated posttranslationally. Clearly any adjustment of the content of GANG in infant formula must be studied carefully.
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Affiliation(s)
- Laurie A Drozdowski
- Nutrition and Metabolism Group, Division of Gastroenterology, University of Alberta, Edmonton, Alberta, Canada
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Black tea may be a prospective adjunct for calcium supplementation to prevent early menopausal bone loss in a rat model of osteoporosis. J Osteoporos 2013; 2013:760586. [PMID: 23984184 PMCID: PMC3741960 DOI: 10.1155/2013/760586] [Citation(s) in RCA: 15] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 11/30/2012] [Revised: 06/10/2013] [Accepted: 06/20/2013] [Indexed: 12/03/2022] Open
Abstract
The present study was undertaken to find out the ability of black tea extract (BTE) as a suitable alternative of adjunct for calcium supplementation in treating an ovariectomized rat model of early osteoporosis. Female Wistar rats weighing 140-150 g were divided into four groups consisting of six animals in each group: (A) sham-operated control; (B) bilaterally ovariectomized; (C) bilaterally ovariectomized + BTE; (D) bilaterally ovariectomized + 17 β -estradiol. Results suggest that BTE could promote intestinal absorption of calcium significantly (P < 0.01 for duodenum and ileum; and P < 0.05 for jejunum). This was found associated with enhanced activities of two relevant intestinal mucosal enzymes alkaline phosphatase (P < 0.01 for duodenum, jejunum, and ileum) and Ca(2+) activated ATPase (P < 0.01 for duodenum, jejunum, and ileum). Such BTE-mediated promotion of calcium absorption was coupled with increase in serum estrogen titer (P < 0.01) and recovery of all urinary, bone, and serum osteoporotic marker parameters, including bone histological features. Serum parathyroid hormone level, however, was not altered in these animals (P > 0.05). A comparative study with 17 β -estradiol, a well-known adjunct for calcium supplementation, indicated that efficacy of BTE in maintaining skeletal health is close to that of 17 β -estradiol. This study suggests that simultaneous use of BTE is promising as a prospective candidate for adjunctive therapies for calcium supplementation in the early stage of menopausal bone changes.
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Karmakar S, Majumdar S, Maiti A, Choudhury M, Ghosh A, Das AS, Mitra C. Protective Role of Black Tea Extract against Nonalcoholic Steatohepatitis-Induced Skeletal Dysfunction. J Osteoporos 2011; 2011:426863. [PMID: 21772972 PMCID: PMC3135135 DOI: 10.4061/2011/426863] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 09/01/2010] [Revised: 03/20/2011] [Accepted: 03/20/2011] [Indexed: 01/30/2023] Open
Abstract
Aim. This paper aimed to examine the chemoprotective actions of aqueous black tea extract (BTE) against nonalcoholic steatohepatitis- (NASH-) induced skeletal changes in rats. Material. Wistar rats (body wt. 155-175 g) of both sexes, aged 4-5 months, were randomly assigned to 3 groups; Group A (control), Group B (60% high-fat diet; HFD), and Group C (HFD + 2.5% BTE). Methods. Several urinary (calcium, phosphate, creatinine, and calcium-to-creatinine ratio) serum (alkaline phosphatase and serum tartrate-resistant acid phosphatase), and molecular markers of bone turnover (receptor activator of NF-κB ligand (RANKL), osteoprotegerin (OPG), and estrogen) were tested. Also, several bone parameters (bone density, bone tensile strength, bone mineral content, and bone histology) and calcium homeostasis were checked. Results. Results indicated that HFD-induced alterations in urinary, serum, and bone parameters as well as calcium homeostasis, all could be significantly ameliorated by BTE supplementation. Conclusion. Results suggest a potential role of BTE as a protective agent against NASH-induced changes in bone metabolism in rats.
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Affiliation(s)
- Subhra Karmakar
- Pre-Clinical Physiology Laboratory, Tripura Institute of Paramedical Sciences, Hapania, Tripura 799014, India,Department of Physiology, Presidency College, Kolkata, Kolkata, India
| | - Sangita Majumdar
- Department of Physiology, Presidency College, Kolkata, Kolkata, India,Institute of Genetic Medicine and Genomic Science, Madhyamgram, Kolkata 700 128, India
| | - Anasuya Maiti
- Department of Physiology, Presidency College, Kolkata, Kolkata, India
| | - Monalisa Choudhury
- Pre-Clinical Physiology Laboratory, Tripura Institute of Paramedical Sciences, Hapania, Tripura 799014, India,Department of Physiology, Presidency College, Kolkata, Kolkata, India
| | - Aniruddha Ghosh
- Department of Physiology, Presidency College, Kolkata, Kolkata, India
| | - Asankur S. Das
- Pre-Clinical Physiology Laboratory, Tripura Institute of Paramedical Sciences, Hapania, Tripura 799014, India,Department of Physiology, Presidency College, Kolkata, Kolkata, India
| | - Chandan Mitra
- Pre-Clinical Physiology Laboratory, Tripura Institute of Paramedical Sciences, Hapania, Tripura 799014, India,Department of Physiology, Presidency College, Kolkata, Kolkata, India,*Chandan Mitra:
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Majumdar S, Karmakar S, Maiti A, Choudhury M, Ghosh A, Das AS, Mitra C. Arsenic-induced hepatic mitochondrial toxicity in rats and its amelioration by dietary phosphate. ENVIRONMENTAL TOXICOLOGY AND PHARMACOLOGY 2011; 31:107-118. [PMID: 21787675 DOI: 10.1016/j.etap.2010.09.011] [Citation(s) in RCA: 13] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 04/09/2010] [Revised: 09/16/2010] [Accepted: 09/17/2010] [Indexed: 05/31/2023]
Abstract
The present study was aimed to test the hypothesis that inorganic phosphate may reduce arsenic toxicity by decreasing its intestinal transference. Co-administration of inorganic phosphate (6.56 M) and arsenic (6.07 mM) in the intestinal loops of rats, in situ, caused significant reduction of arsenic transference. Short-term arsenic exposure (3mg/kg body weight/day for 30 days) caused liver damage evidenced by activities of liver enzymes and necroinflammatory changes. These effects of arsenic were coupled with enhanced mitochondrial swelling, inhibition of cytochrome c oxidase, Ca(2+)-ATPase, a decrease in mitochondrial calcium content, changes in indices of hepatic mitochondrial oxidative stress and iNOS expression. Arsenic also increased hepatic caspase 3 activity and DNA fragmentation. All these apoptosis-related molecular changes caused by arsenic could be alleviated by supplementation with inorganic phosphate, which likely suggests a protective role of phosphate against arsenic-induced hepatotoxic changes.
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Affiliation(s)
- Sangita Majumdar
- Department of Physiology, Presidency College, Kolkata 700 073, India.
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5
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Kuo P, Wishart JM, Bellon M, Smout AJ, Holloway RH, Fraser RJL, Horowitz M, Jones KL, Rayner CK. Effects of physiological hyperglycemia on duodenal motility and flow events, glucose absorption, and incretin secretion in healthy humans. J Clin Endocrinol Metab 2010; 95:3893-900. [PMID: 20501683 DOI: 10.1210/jc.2009-2514] [Citation(s) in RCA: 15] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 02/07/2023]
Abstract
CONTEXT Acute hyperglycemia slows gastric emptying, but its effects on small intestinal motor activity and glucose absorption are unknown. In type 2 diabetes, the postprandial secretion of glucose-dependent insulinotropic polypeptide (GIP) is preserved, but that of glucagon-like peptide-1 (GLP-1) is possibly reduced; whether the latter is secondary to hyperglycemia or diabetes per se is unknown. AIM The aim was to investigate the effects of acute hyperglycemia on duodenal motility and flow events, glucose absorption, and incretin hormone secretion. METHODS Nine healthy volunteers were studied on two occasions. A combined manometry/impedance catheter was positioned in the duodenum. Blood glucose was clamped at either 9 mmol/liter (hyperglycemia) or 5 mmol/liter (euglycemia) throughout the study. Manometry and impedance recordings continued between T=-10 min and T=180 min. Between T=0 and 60 min, an intraduodenal glucose infusion was given (approximately 3 kcal/min), together with 14C-labeled 3-O-methylglucose (3-OMG) to evaluate glucose absorption. RESULTS Hyperglycemia had no effect on duodenal pressure waves or flow events during the 60 min of intraduodenal glucose infusion, when compared to euglycemia. During hyperglycemia, there was an increase in plasma GIP (P<0.05) and 14C-3-OMG (P<0.05) but no effect on GLP-1 concentrations in response to the intraduodenal infusion, compared to euglycemia. CONCLUSION Acute hyperglycemia in the physiological range has no effect on duodenal pressure waves and flow events but is associated with increased GIP secretion and rate of glucose absorption in response to intraduodenal glucose.
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Affiliation(s)
- Paul Kuo
- Discipline of Medicine, University of Adelaide, Level 6, Eleanor Harrald Building, Royal Adelaide Hospital, Adelaide, Australia
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Wong TP, Debnam ES, Leung PS. Diabetes mellitus and expression of the enterocyte renin-angiotensin system: implications for control of glucose transport across the brush border membrane. Am J Physiol Cell Physiol 2009; 297:C601-10. [PMID: 19535516 DOI: 10.1152/ajpcell.00135.2009] [Citation(s) in RCA: 24] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022]
Abstract
Streptozotocin-induced (Type 1) diabetes mellitus (T1DM) in rats promotes jejunal glucose transport, but the trigger for this response remains unclear. Our recent work using euglycemic rats has implicated the enterocyte renin-angiotensin system (RAS) in control of sodium-dependent glucose transporter (SGLT1)-mediated glucose uptake across the jejunal brush border membrane (BBM). The aim of the present study was to examine whether expression of enterocyte RAS components is influenced by T1DM. The effects of mucosal addition of angiotensin II (AII) on [(14)C]-D-glucose uptake by everted diabetic jejunum was also determined. Two-week diabetes caused a fivefold increase in blood glucose level and reduced mRNA and protein expression of AII type 1 (AT(1)) and AT(2) receptors and angiotensin-converting enzyme in isolated jejunal enterocytes. Angiotensinogen expression was, however, stimulated by diabetes while renin was not detected in either control or diabetic enterocytes. Diabetes stimulated glucose uptake into everted jejunum by 58% and increased the BBM expression of SGLT1 and facilitated glucose transporter 2 (GLUT2) proteins, determined by Western blotting by 25% and 135%, respectively. Immunohistochemistry confirmed an enhanced BBM expression of GLUT2 in diabetes and also showed that this was due to translocation of the transporter from the basolateral membrane to BBM. AII (5 microM) or L-162313 (1 microM), a nonpeptide AII analog, decreased glucose uptake by 18% and 24%, respectively, in diabetic jejunum. This inhibitory action was fully accountable by an action on SGLT1-mediated transport and was abolished by the AT(1) receptor antagonist losartan (1 microM). The decreased inhibitory action of AII on in vitro jejunal glucose uptake in diabetes compared with that noted previously in jejunum from normal animals is likely to be due to reduced RAS expression in diabetic enterocytes, together with a disproportionate increase in GLUT2, compared with SGLT1 expression at the BBM.
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Affiliation(s)
- Tung Po Wong
- School of Biomedical Sciences, Faculty of Medicine, The Chinese Univ. of Hong Kong, Shatin, N.T., Hong Kong, China
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Drozdowski LA, Clandinin MT, Thomson ABR. Morphological, kinetic, membrane biochemical and genetic aspects of intestinal enteroplasticity. World J Gastroenterol 2009; 15:774-87. [PMID: 19230039 PMCID: PMC2653378 DOI: 10.3748/wjg.15.774] [Citation(s) in RCA: 17] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 02/06/2023] Open
Abstract
The process of intestinal adaptation (“enteroplasticity”) is complex and multifaceted. Although a number of trophic nutrients and non-nutritive factors have been identified in animal studies, successful, reproducible clinical trials in humans are awaited. Understanding mechanisms underlying this adaptive process may direct research toward strategies that maximize intestinal function and impart a true clinical benefit to patients with short bowel syndrome, or to persons in whom nutrient absorption needs to be maximized. In this review, we consider the morphological, kinetic and membrane biochemical aspects of enteroplasticity, focus on the importance of nutritional factors, provide an overview of the many hormones that may alter the adaptive process, and consider some of the possible molecular profiles. While most of the data is derived from rodent studies, wherever possible, the results of human studies of intestinal enteroplasticity are provided.
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Nicola JP, Basquin C, Portulano C, Reyna-Neyra A, Paroder M, Carrasco N. The Na+/I- symporter mediates active iodide uptake in the intestine. Am J Physiol Cell Physiol 2008; 296:C654-62. [PMID: 19052257 DOI: 10.1152/ajpcell.00509.2008] [Citation(s) in RCA: 112] [Impact Index Per Article: 6.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022]
Abstract
Absorption of dietary iodide, presumably in the small intestine, is the first step in iodide (I(-)) utilization. From the bloodstream, I(-) is actively taken up via the Na(+)/I(-) symporter (NIS) in the thyroid for thyroid hormone biosynthesis and in such other tissues as lactating breast, which supplies I(-) to the newborn in the milk. The molecular basis for intestinal I(-) absorption is unknown. We sought to determine whether I(-) is actively accumulated by enterocytes and, if so, whether this process is mediated by NIS and regulated by I(-) itself. NIS expression was localized exclusively at the apical surface of rat and mouse enterocytes. In vivo intestine-to-blood transport of pertechnetate, a NIS substrate, was sensitive to the NIS inhibitor perchlorate. Brush border membrane vesicles accumulated I(-) in a sodium-dependent, perchlorate-sensitive manner with kinetic parameters similar to those of thyroid cells. NIS was expressed in intestinal epithelial cell line 6, and I(-) uptake in these cells was also kinetically similar to that in thyrocytes. I(-) downregulated NIS protein expression and its own NIS-mediated transport both in vitro and in vivo. We conclude that NIS is functionally expressed on the apical surface of enterocytes, where it mediates active I(-) accumulation. Therefore, NIS is a significant and possibly central component of the I(-) absorption system in the small intestine, a system of key importance for thyroid hormone biosynthesis and thus systemic intermediary metabolism.
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Affiliation(s)
- Juan Pablo Nicola
- Dept. of Molecular Pharmacology, Albert Einstein College of Medicine, 1300 Morris Park Ave., Bronx, NY 10461, USA
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Drozdowski LA, Iordache C, Clandinin MT, Todd ZS, Gonnet M, Wild G, Uwiera RR, Thomson AB. Dexamethasone and GLP-2 administered to rat dams during pregnancy and lactation have late effects on intestinal sugar transport in their postweanling offspring. J Nutr Biochem 2008; 19:49-60. [DOI: 10.1016/j.jnutbio.2007.01.004] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/30/2006] [Revised: 01/11/2007] [Accepted: 01/11/2007] [Indexed: 01/31/2023]
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10
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Wong TP, Debnam ES, Leung PS. Involvement of an enterocyte renin-angiotensin system in the local control of SGLT1-dependent glucose uptake across the rat small intestinal brush border membrane. J Physiol 2007; 584:613-23. [PMID: 17702818 PMCID: PMC2277173 DOI: 10.1113/jphysiol.2007.138578] [Citation(s) in RCA: 47] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/13/2022] Open
Abstract
There is increasing evidence that locally produced angiotensin AII (AII) regulates the function of many tissues, but the involvement of enterocyte-derived AII in the control of intestinal transport is unknown. This study examined whether there is a local renin-angiotensin system (RAS) in rat villus enterocytes and assessed the effects of AII on SGLT1-dependent glucose transport across the brush border membrane (BBM). Gene and protein expression of angiotensinogen, ACE, and AT(1) and AT(2) receptors were studied in jejunal and ileal enterocytes using immunocytochemistry, Western blotting and RT-PCR. Mucosal uptake of d-[(14)C]glucose by everted intestinal sleeves before and after addition of AII (0-100 nm) to the mucosal buffer was measured in the presence or absence of the AT(1) receptor antagonist losartan (1 microm). Immunocytochemistry revealed the expression of angiotensinogen, ACE, and AT(1) and AT(2) receptors in enterocytes; immunoreactivity of AT(1) receptor and angiotensinogen proteins was especially pronounced at the BBM. Expression of angiotensinogen and AT(1) and AT(2) receptors, but not ACE, was greater in the ileum than the jejunum. Addition of AII to mucosal buffer inhibited phlorizin-sensitive (SGLT1-dependent) jejunal glucose uptake in a rapid and dose-dependent manner and reduced the expression of SGLT1 at the BBM. Losartan attenuated the inhibitory action of AII on glucose uptake. AII did not affect jejunal uptake of l-leucine. The detection of RAS components at the enterocyte BBM, and the rapid inhibition of SGLT1-dependent glucose uptake by luminal AII suggest that AII secretion exerts autocrine control of intestinal glucose transport.
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MESH Headings
- Angiotensin II/metabolism
- Angiotensin II Type 1 Receptor Blockers/pharmacology
- Angiotensinogen/genetics
- Angiotensinogen/metabolism
- Animals
- Autocrine Communication
- Blotting, Western
- Enterocytes/drug effects
- Enterocytes/metabolism
- Glucose/metabolism
- Ileum/cytology
- Ileum/drug effects
- Ileum/metabolism
- Immunohistochemistry
- In Vitro Techniques
- Jejunum/cytology
- Jejunum/drug effects
- Jejunum/metabolism
- Leucine/metabolism
- Losartan/pharmacology
- Male
- Microvilli/metabolism
- Peptidyl-Dipeptidase A/genetics
- Peptidyl-Dipeptidase A/metabolism
- Polymerase Chain Reaction
- RNA, Messenger/metabolism
- Rats
- Rats, Sprague-Dawley
- Receptor, Angiotensin, Type 1/genetics
- Receptor, Angiotensin, Type 1/metabolism
- Receptor, Angiotensin, Type 2/genetics
- Receptor, Angiotensin, Type 2/metabolism
- Renin-Angiotensin System/drug effects
- Renin-Angiotensin System/genetics
- Sodium-Glucose Transporter 1/metabolism
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Affiliation(s)
- Tung Po Wong
- Department of Physiology, Faculty of Medicine, The Chinese University of Hong Kong, Shatin, N.T., Hong Kong, China
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Abstract
Intestinal failure is a condition characterized by malnutrition and/or dehydration as a result of the inadequate digestion and absorption of nutrients. The most common cause of intestinal failure is short bowel syndrome, which occurs when the functional gut mass is reduced below the level necessary for adequate nutrient and water absorption. This condition may be congenital, or may be acquired as a result of a massive resection of the small bowel. Following resection, the intestine is capable of adaptation in response to enteral nutrients as well as other trophic stimuli. Identifying factors that may enhance the process of intestinal adaptation is an exciting area of research with important potential clinical applications.
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Abstract
Carbohydrates are an important component of the diet. The carbohydrates that we ingest range from simple monosaccharides (glucose, fructose and galactose) to disaccharides (lactose, sucrose) to complex polysaccharides. Most carbohydrates are digested by salivary and pancreatic amylases, and are further broken down into monosaccharides by enzymes in the brush border membrane (BBM) of enterocytes. For example, lactase-phloridzin hydrolase and sucrase-isomaltase are two disaccharidases involved in the hydrolysis of nutritionally important disaccharides. Once monosaccharides are presented to the BBM, mature enterocytes expressing nutrient transporters transport the sugars into the enterocytes. This paper reviews the early studies that contributed to the development of a working model of intestinal sugar transport, and details the recent advances made in understanding the process by which sugars are absorbed in the intestine.
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Affiliation(s)
- Laurie A Drozdowski
- Division of Gastroenterology, Department of Medicine, University of Alberta, 5150 Dentistry Pharmacy Building, Edmonton, Alberta T6G 2N8, Canada.
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Birecki CJ, Drozdowski LA, Suh M, Park EJ, Clandinin MT, Thomson ABR. Dietary gangliosides enhance in vitro lipid uptake in weanling rats. J Pediatr Gastroenterol Nutr 2006; 42:59-65. [PMID: 16385255 DOI: 10.1097/01.mpg.0000187567.79633.a7] [Citation(s) in RCA: 11] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 12/10/2022]
Abstract
BACKGROUND The intestine adapts morphologically or functionally in response to environmental stimuli. Dietary lipids modify brush border membrane (BBM) permeability and nutrient transporter activities. Gangliosides (GANG) are glycolipids in human milk that are present only in low amounts in infant formula. Exogenous GANG are incorporated into cell membranes and increase their permeability. The objective of this study was to determine whether feeding a GANG-enriched diet alters in vitro intestinal lipid absorption. METHODS Weanling rats were fed either (1) GANG-enriched diet; (2) diet enriched with polyunsaturated long-chain fatty acids; or (3) isocaloric control diet for 2 weeks, after which in vitro intestinal lipid uptake was measured. RESULTS Feeding GANG did not alter weight gain or intestinal morphology. Enhanced uptake of stearic acid (18:0) in the ileum and stearic and linoleic acid (18:2) in the jejunum was not associated with a change in the abundance of the ileal lipid binding protein (ILBP), the intestinal fatty acid binding protein (I-FABP), or the liver fatty acid binding protein (L-FABP). CONCLUSION We speculate that the enhanced uptake of long-chain fatty acids in weanling rats fed GANG may be caused by a modification in physical properties of the BBM.
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Affiliation(s)
- Celina J Birecki
- Nutrition and Metabolism Group, Division of Gastroenterology, Department of Medicine, University of Alberta, Edmonton, Alberta, Canada
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Drozdowski LA, Iordache C, Clandinin MT, Wild G, Todd Z, Thomson ABR. A combination of dexamethasone and glucagon-like peptide-2 increase intestinal morphology and glucose uptake in suckling rats. J Pediatr Gastroenterol Nutr 2006; 42:32-9. [PMID: 16385251 DOI: 10.1097/01.mpg.0000187246.60560.16] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 12/26/2022]
Abstract
OBJECTIVES Glucagon-like peptide (GLP)-2 enhances nutrient uptake in adult animals. Glucocorticosteroids accelerate intestinal ontogeny and increase nutrient uptake in adult animals. We hypothesized that administering GLP-2 and dexamethasone (DEX) to suckling rats will enhance sugar uptake and that this effect persists into the postweaning period. METHODS Suckling rats were treated for 10 days with GLP-2 (0.1 microg/g/d, twice daily), DEX (0.128 microg/g/d, once daily), GLP-2 + Dex (same doses as above), or placebo. The rate of intestinal uptake of glucose and fructose in sucklings (19-21 days old) and weanlings (49 days old) was assessed using an in vitro ring technique. RESULTS DEX reduced body weight in weanlings, whereas GLP-2 + DEX prevented this effect. In sucklings, GLP-2 + DEX increased ileal villous height and jejunal and ileal villous width and crypt depth. In sucklings, GLP-2 + DEX increased the maximal transport rate (Vmax) for jejunal glucose uptake, whereas DEX reduced the ileal Vmax. In weanlings, GLP-2 + DEX increased jejunal villous height, whereas ileal villous width and crypt depth were reduced. DEX increased the ileal Vmax and apparent affinity constant for glucose in weanlings. CONCLUSIONS The combination of these hormones may be useful in stimulating glucose uptake in the developing intestine, and giving DEX to sucklings may enhance glucose uptake in later life.
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Affiliation(s)
- Laurie A Drozdowski
- Nutrition and Metabolism Group, University of Alberta, Edmonton, Alberta, Canada
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Mukherjee M, Das AS, Das D, Mukherjee S, Mitra S, Mitra C. Role of oil extract of garlic (Allium sativum Linn.) on intestinal transference of calcium and its possible correlation with preservation of skeletal health in an ovariectomized rat model of osteoporosis. Phytother Res 2006; 20:408-15. [PMID: 16619371 DOI: 10.1002/ptr.1888] [Citation(s) in RCA: 24] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/07/2022]
Abstract
The present study was undertaken to examine the effects of an oil extract of garlic on the in vivo intestinal transference of calcium, and also to verify its role in maintaining the bone mineral content and bone tensile strength in an ovariectomized rat model of osteoporosis. The results suggest that, in this experimental model, oil extract of garlic promotes intestinal transference of calcium by modulating the activities of both intestinal alkaline phosphatase and Ca(2+) activated ATPase. Also the observed low bone mineral content and low bone tensile strength in these rats were significantly restored by garlic oil supplementation. Further, garlic oil supplementation was able to revive partially the bilateral ovariectomy-induced decrease in the serum estrogen titer. The serum parathyroid hormone level, however, was found unaltered in these rats. The garlic oil supplemented partial recovery in serum estrogen titer in bilaterally ovariectomized rat was found to be persistently associated with enhanced calcium transference and better preservation of bone mineral content. The results of this study propose that the phytoestrogenic efficacy of an oil extract of garlic prevents ovarian hormone deficiency induced bone mineral loss possibly by promoting intestinal transference of calcium through the partial revival of the serum estrogen titer.
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Drozdowski LA, Woudstra TD, Wild GE, Clandinin MT, Thomson ABR. Age-associated changes in intestinal fructose uptake are not explained by alterations in the abundance of GLUT5 or GLUT2. J Nutr Biochem 2005; 15:630-7. [PMID: 15542355 DOI: 10.1016/j.jnutbio.2004.06.003] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/07/2023]
Abstract
A reduction in nutrient absorption may contribute to malnourishment in the elderly. The objectives of this study were to determine the effects of aging on the absorption of fructose in rats, as well as the mechanisms of these adaptive changes. Male Fischer 344 rats aged 1, 9, and 24 months were fed standard Purina chow for 2 weeks (PMI #5001, PMI Nutritionals, Brentwood, MO). The uptake of (14)C-labeled D-fructose was determined in vitro using the intestinal sheet method. Intestinal samples were taken for RNA isolation and for brush border membrane (BBM) and basolateral membrane (BLM) preparation. Northern blotting, Western blotting, and immunohistochemistry were used to determine the effects of age and diet on GLUT5 and GLUT2. When expressed on the basis of intestinal or mucosal weights, aging was associated with a decline in jejunal and ileal fructose uptake, whereas jejunal fructose uptake was increased when expressed on the basis of serosal or mucosal surface area. The alterations in fructose uptake were not paralleled by changes in GLUT5 or GLUT2 abundance. These results indicate that 1) the effect of age on fructose uptake depends on the method used to express results, and 2) the age-associated changes in uptake are not explained by alterations in GLUT5 and GLUT2.
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Affiliation(s)
- Laurie A Drozdowski
- Nutrition and Metabolism Group, Division of Gastroenterology, Department of Medicine, 5146 Dentistry Pharmacy Building, University of Alberta, Edmonton, AB T6G 2N8, Canada
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17
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Drozdowski L, Woudstra T, Wild G, Clandinin MT, Thomson ABR. Dietary lipids modify the age-associated changes in intestinal uptake of fructose in rats. Am J Physiol Gastrointest Liver Physiol 2005; 288:G125-34. [PMID: 15513953 DOI: 10.1152/ajpgi.00311.2003] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 01/31/2023]
Abstract
Because reduced nutrient absorption may contribute to malnourishment in the elderly, age and diet modulate fructose uptake in mice, and alterations in fructose uptake may be paralleled by changes in the abundance of fructose transporters, the objectives of this study were to determine 1) the effects of aging on fructose absorption in rats, 2) the effect of feeding diets enriched with saturated fatty acids (SFA) vs. polyunsaturated fatty acids (PUFA), and 3) the mechanisms of these age-and diet-associated changes. Male Fischer 344 rats aged 1, 9, and 24 mo received isocaloric diets enriched with SFA or PUFA. The uptake of (14)C-labeled D-fructose was determined in vitro using the intestinal sheet method. Northern and Western blot analyses and immunohistochemistry were used to determine the abundance of sodium-independent glucose and fructose transporters (GLUT)2 and GLUT5. When expressed on the basis of mucosal surface area, jejunal fructose uptake was increased in 9 and 24 mo compared with 1-mo-old animals fed SFA. PUFA-fed animals demonstrated increased fructose uptake at 24 mo compared with younger animals. Ileal fructose uptake was increased with SFA vs. PUFA in 9-mo-old rats but was reduced with SFA in 1- and 24-mo-old rats. Variations in GLUT2 and GLUT5 abundance did not parallel changes in uptake. These results indicate that 1) age increases fructose uptake when expressed on the basis of mucosal surface area, 2) age influences the adaptive response to dietary lipid modifications, and 3) alterations in fructose uptake are not explained by variations in GLUT2 or GLUT5.
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Affiliation(s)
- L Drozdowski
- Nutrition and Metabolism Group, Division of Gastroenterology, University of Alberta, Edmonton, AB T6G 2C8, Canada
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18
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Drozdowski L, Woudstra T, Wild G, Clandindin MT, Thomson ABR. The age-associated decline in the intestinal uptake of glucose is not accompanied by changes in the mRNA or protein abundance of SGLT1. Mech Ageing Dev 2004; 124:1035-45. [PMID: 14659592 DOI: 10.1016/j.mad.2003.07.003] [Citation(s) in RCA: 21] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Abstract
Studies performed using human and animal models offer conflicting results regarding the effect of age on nutrient absorption. The objectives of this study were to determine (1) the effects of aging on the in vitro uptake of glucose in rats; and (2) the molecular mechanisms of these age-associated changes. Male Fischer 344 rats aged 1, 9 and 24 months were fed a standard laboratory diet (PMI # 5001). The uptake of 14C-labelled D-glucose was determined in vitro using the intestinal sheet method. Northern blotting, Western blotting and immunohistochemistry were used to determine the effects of age on the BBM sodium-dependent glucose transporter, SGLT1, and the BLM Na+K(+)-ATPase. When expressed on the basis of intestinal weight, mucosal weight or surface area, there was a reduction in glucose uptake in the 24-month-old animals. SGLT1, GLUT2 and Na+K(+)-ATPase mRNA and protein abundance did not parallel the changes seen in glucose uptake. These results indicate that (1) age reduces in vitro intestinal glucose uptake in the rat; and (2) this age-associated decline in glucose uptake was not explained by alterations in SGLT1, GLUT2 or Na+K(+)-ATPase.
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Affiliation(s)
- L Drozdowski
- Nutrition and Metabolism Group, Department of Medicine, Division of Gastroenterology, 5150 Dentistry Pharmacy Building, University of Alberta, Edmonton,Alta., Canada T6G 2N8
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19
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Li Q, Manolescu A, Ritzel M, Yao S, Slugoski M, Young JD, Chen XZ, Cheeseman CI. Cloning and functional characterization of the human GLUT7 isoform SLC2A7 from the small intestine. Am J Physiol Gastrointest Liver Physiol 2004; 287:G236-42. [PMID: 15033637 DOI: 10.1152/ajpgi.00396.2003] [Citation(s) in RCA: 79] [Impact Index Per Article: 3.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 01/31/2023]
Abstract
Facilitated glucose transporters (GLUTs) mediate transport of sugars across cell membranes by using the chemical gradient of sugars as the driving force. Improved cloning techniques and database analyses have expanded this family of proteins to a total of 14 putative members. In this work a novel hexose transporter isoform, GLUT7, has been cloned from a human intestinal cDNA library by using a PCR-based strategy (GenBank accession no. AY571960). The encoded protein is comprised of 524 amino acid residues and shares 68% similarity and 53% identity with GLUT5, its most closely related isoform. When GLUT7 was expressed in Xenopus oocytes, it showed high-affinity transport for glucose (K(m) = 0.3 mM) and fructose (IC(50) = 0.060 mM). Galactose, 2-deoxy-d-glucose, and xylose were not transported. Uptake of 100 microM d-glucose was not inhibited by 200 microM phloretin or 100 microM cytochalasin B. Northern blotting indicated that the mRNA for GLUT7 is present in the human small intestine, colon, testis, and prostate. Western blotting and immunohistochemistry of rat tissues with an antibody raised against the predicted COOH-terminal sequence confirmed expression of the protein in the small intestine and indicated that the transporter is predominantly expressed in the enterocytes' brush-border membrane. The unusual substrate specificity and close sequence identity with GLUT5 suggest that GLUT7 represents an intermediate between class II GLUTs and the class I member GLUT2. Comparison between these proteins may provide key information as to the structural determinants for the recognition of fructose as a substrate.
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Affiliation(s)
- Qiang Li
- Department of Physiology, University of Alberta, Rm. 7-22 Medical Sciences Bldg., Edmonton, Alberta T6G 2H7, Canada
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20
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Thiesen A, Drozdowski L, Iordache C, Neo CC, Woudstra TD, Xenodemetropoulos T, Keelan M, Clandinin MT, Thomson ABR, Wild G. Adaptation following intestinal resection: mechanisms and signals. Best Pract Res Clin Gastroenterol 2003; 17:981-95. [PMID: 14642861 DOI: 10.1016/s1521-6918(03)00097-0] [Citation(s) in RCA: 26] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 01/31/2023]
Abstract
The intestine has an inherent ability to adapt morphologically and functionally in response to internal and external environmental changes. The functional adaptations encompass modifications of the brush border membrane fluidity and permeability, as well as up- or down-regulation of carrier-mediated transport. Intestinal adaptation improves the nutritional status following the loss of a major portion of the small intestine, following chronic ingestion of ethanol, following sublethal doses of abdominal irradiation, in diabetes, in pregnancy and lactation, with ageing, and with fasting and malnutrition. Following intestinal resection, morphological and functional changes occur depending upon the extent of the intestine removed, the site studied, and the lipid content of the diet. Therefore, intestinal adaptation has important implications in the survival potential and welfare of the host. An understanding of the mechanisms of, and signals for, intestinal adaptation in the experimental setting forms the basis for the use of management strategies in humans with the short-bowel syndrome.
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Affiliation(s)
- A Thiesen
- Nutrition and Metabolism Research Group, Division of Gastroenterology, Department of Medicine, University of Alberta, 519 Newton Research Building, 205 College Plaza, 8215-112 Street, Edmonton, Alta, Canada T6G 2C2.
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21
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Thiesen A, Wild GE, Keelan M, Clandinin MT, Thomson ABR. Locally and systemically active glucocorticosteroids modify intestinal absorption of sugars in rats. J Appl Physiol (1985) 2003; 94:583-90. [PMID: 12391102 DOI: 10.1152/japplphysiol.00134.2002] [Citation(s) in RCA: 13] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/11/2022] Open
Abstract
Glucocorticosteroids enhance digestive and absorptive functions of the intestine of weaning and adult rats. This study was undertaken to assess the influence of treatment of weaning male rats with budesonide (Bud), prednisone (Pred), or control vehicle on the in vitro jejunal and ileal uptake of glucose and fructose. Bud and Pred had no effect on the uptake of d-glucose by sodium glucose transporter-1. In contrast, the uptake of d-fructose by GLUT-5 was similarly increased with Bud and with Pred. The increases in the uptake of fructose were not due to variations in the weight of the intestinal mucosa, food intake, or in GLUT-5 protein or mRNA expression. There were no steroid-associated changes in mRNA expression of c-myc, c-jun, c-fos, proglucagon, or selected cytokines. However, the abundance of ileal ornithine decarboxylase mRNA was increased with Pred. Giving postweaning rats 4 wk of Bud or Pred in doses equivalent to those used in clinical practice increases fructose but not glucose uptake. This enhanced uptake of fructose was likely regulated by posttranslational processes.
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Affiliation(s)
- A Thiesen
- Nutrition and Metabolism Research Group, Division of Gastroenterology, Department of Medicine, University of Alberta, Edmonton, Canada T6G 2C2
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22
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Au A, Gupta A, Schembri P, Cheeseman CI. Rapid insertion of GLUT2 into the rat jejunal brush-border membrane promoted by glucagon-like peptide 2. Biochem J 2002; 367:247-54. [PMID: 12095416 PMCID: PMC1222871 DOI: 10.1042/bj20020393] [Citation(s) in RCA: 122] [Impact Index Per Article: 5.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/08/2002] [Revised: 06/22/2002] [Accepted: 07/03/2002] [Indexed: 11/17/2022]
Abstract
A possible role for GLUT2 transiently expressed in the rat jejunal brush-border membrane (BBM) under the influence of glucagon-like peptide 2 (GLP-2) was investigated using in vivo perfusion of the intestinal lumen as well as isolation of membrane proteins and immunohistochemistry. A 1 h vascular infusion of GLP-2 in vivo doubled the rate of fructose absorption and this increase could be blocked by luminal phloretin. Immunohistochemistry of frozen sections of rat jejunum showed the expression of GLUT2 in both the basolateral and BBMs of mature enterocytes. Perfusion of the intestinal lumen with 50 mM D-glucose or vascular infusion of 800 pM GLP-2 for 1 h increased the expression of GLUT2 in the BBM. Quantification of these changes using Western blotting of biotinylated surface-exposed protein showed a doubling of the expression of GLUT2 in the BBM, but the effects of glucose and GLP-2 were not additive. These results indicate that vascular GLP-2 can promote the insertion of GLUT2 into the rat jejunal BBM providing a low-affinity/high-capacity route of entry for dietary hexoses.
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Affiliation(s)
- Anita Au
- Membrane Protein Research Group, Department of Physiology, Faculty of Medicine and Dentistry, University of Alberta, Edmonton, AB, T6G 2H7, Canada
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23
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Regulation of GLUT5, GLUT2 and intestinal brush-border fructose absorption by the extracellular signal-regulated kinase, p38 mitogen-activated kinase and phosphatidylinositol 3-kinase intracellular signalling pathways: implications for adaptation to diabetes. Biochem J 2001. [PMID: 10926840 DOI: 10.1042/0264-6021:3500163] [Citation(s) in RCA: 21] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/17/2022]
Abstract
We have investigated the role of the extracellular signal-regulated kinase (ERK), p38 and phosphatidylinositol 3-kinase (PI 3-kinase) pathways in the regulation of intestinal fructose transport. Different combinations of anisomycin, PD98059 and wortmannin had very different effects on fructose transport in perfused isolated loops of rat jejunum. Transport was stimulated maximally by anisomycin (2 microM) and blocked by SB203580 (20 microM), confirming involvement of the p38 pathway. PD98059 (50 microM) alone had little effect on fructose transport. However, it had a dramatic effect on stimulation by anisomycin, diminishing the K(a) 50-fold from 1 microM to 20 nM to show that the ERK pathway restrains the p38 pathway. The K(a) for diabetic jejunum was 30 nM and PD98059 had no effect. Transport in the presence of anisomycin was 3.4-fold that for anisomycin plus PD98059 plus wortmannin. Transport was mediated by both GLUT5 and GLUT2. In general, GLUT2 levels increased up to 4-fold within minutes and with only minimal changes in GLUT5 or SGLT1 levels, demonstrating that GLUT2 trafficks by a rapid trafficking pathway distinct from that of GLUT5 and SGLT1. GLUT2 intrinsic activity was regulated over a 9-fold range. It is concluded that there is extensive cross-talk between the ERK, p38 and PI 3-kinase pathways in their control of brush-border fructose transport by modulation of both the levels and intrinsic activities of GLUT5 and GLUT2. The potential of the intracellular signalling pathways to regulate short-term nutrient transport during the assimilation of a meal and longer-term adaptation to diabetes and hyperglycaemia is discussed.
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24
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King D, Fian MZ, Ejeta G, Asem EK, Adeola O. The effects of tannins on nutrient utilisation in the White Pekin duck. Br Poult Sci 2000; 41:630-9. [PMID: 11201445 DOI: 10.1080/713654982] [Citation(s) in RCA: 25] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/23/2022]
Abstract
1. Two experiments were conducted to determine the effects of tannins on nutrient utilisation in the White Pekin duck. 2. Experiment 1 was a rapid nutrient balance assay to determine the nitrogen (N) retention and metabolisable energy (ME) of maize, low-tannin sorghum (P-954063) (Sorghum bicolor (L). Moench) and high-tannin sorghum (IS-4225) cultivars for ducks. The assay lasted 120 h, with an initial 24 h food-deprivation period, a 48 h excreta collection period for endogenous losses and a 48 h excreta collection period for ingredient losses. The true metabolisable energy (TMEn) content was lower (P<0.05) in the high-tannin sorghum cultivar (13.85 MJ/kg) than the maize (14.94 MJ/kg) and the low-tannin sorghum cultivar (14.39 MJ/kg). True N retention was lower (P<0.05) for the high-tannin sorghum (0.24 g) than for maize (1.33 g) and low-tannin sorghum (1.1 g). 3. In experiment 2, the brush-border membrane vesicles technique was used to determine whether tannic acid caused inhibition of L-threonine transport across duck intestinal brush-border membrane. The brush-border membrane vesicles were mixed with tannic acid solutions (pH 7.4) to give gradient tannic acid concentrations of 0, 0.05, 0.10, 0.25, 0.50, 1.00 and 2.50%. As a fraction of the control (no tannic acid), the maximal inhibition of L-threonine transport (Imax) under the sodium-gradient condition was 77.10% (P<0.05). Under the sodium-free condition, the maximal inhibition of L-threonine transport (Imax) was 45.15% (P<0.05). 4. These results demonstrated that nutrient utilisation in the White Pekin duck was lower from the high-tannin sorghum cultivar than from the low-tannin sorghum cultivar. The results also suggested that the antinutritive effects of tannins in foodstuffs are due partly to their inhibitory action on intestinal brush-border bound amino acid transporter proteins.
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25
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Affiliation(s)
- C P Corpe
- Department of Medicine, University of Chicago, Illinois, USA
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26
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Fan MZ, Adeola O, McBurney MI, Cheeseman CI. Kinetic analysis of L-glutamine transport into porcine jejunal enterocyte brush-border membrane vesicles. Comp Biochem Physiol A Mol Integr Physiol 1998; 121:411-22. [PMID: 10048191 DOI: 10.1016/s1095-6433(98)10152-6] [Citation(s) in RCA: 24] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/01/2022]
Abstract
L-Glutamine transport into porcine jejunal enterocyte brush border membrane vesicles was studied. Uptake was mediated by a Na(+)-dependent and a Na(+)-independent pathway as well as by diffusion. The initial rates of glutamine uptake over a range of concentrations is both Na(+)-gradient and Na(+)-free conditions were analyzed and kinetic parameters were obtained. Na(+)-dependent glutamine transport had a K(m) of 0.77 +/- 0.16 mM and a Jmax of 70.7 +/- 5.8 pmol mg protein-1 s-1; Na(+)-independent glutamine transport had a K(m) of 3.55 +/- 0.78 mM and a Jmax of 55.1 +/- 6.6 pmol mg protein-1 s-1. The non-saturable component measured with HgCl2-poisoned brush border membrane vesicles in the Na(+)-free condition contained passive diffusion and non-specific membrane binding and was defined to be apparent glutamine diffusion and the glutamine permeability coefficient (Kdiff) was estimated to be Kdiff = 3.78 +/- 0.06 pmol 1 mg protein-1 mmol-1 s-1. Results of inhibition experiments showed that Na(+)-dependent glutamine uptake occurred primarily through the brush border system-B degree transporters, whereas Na(+)-independent glutamine uptake occurred via the system-L transporters. Furthermore, the kinetics of L-leucine and L-cysteine inhibition of L-glutamine uptake demonstrated that neutral amino acids sharing the same brush border transporters can effectively inhibit each other in their transport.
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Affiliation(s)
- M Z Fan
- Department of Animal Sciences, Purdue University, West Lafayette, IN 47907, USA
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27
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Islam N, Chanda S, Ghosh TK, Mitra C. Cold stress facilitates calcium mobilization from bone in an ovariectomized rat model of osteoporosis. THE JAPANESE JOURNAL OF PHYSIOLOGY 1998; 48:49-55. [PMID: 9538289 DOI: 10.2170/jjphysiol.48.49] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 02/07/2023]
Abstract
In an ovariectomized rat model of osteoporosis, the effects of cold stress on intestinal Ca2+ transference and rate of bone turnover were evaluated. In the ovariectomized rats, a significant reduction in intestinal transference of Ca2+ was associated with decreased activities of intestinal mucosal enzymes, alkaline phosphatase (AP), and calcium ATPase (Ca2+-ATPase) in all the different segments of small intestine in a descending gradient. The development of a high rate of bone turnover and osteoporosis in these animals was confirmed by significant alteration in plasma AP activity and calcium (Ca) level, urinary excretion of Ca and phosphate, and Ca : creatinine ratio. Cold stress in this model, apart from its unique influence in elevating plasma corticosterone and thyroid hormone level, enhanced all the above referred parameters studied in connection with intestinal transference of Ca2+, bone turnover rate, and osteoporosis. The results of this study emphasize that cold stress may have a positive influence on bone loss for an early development of hypogonadal osteoporosis in rats.
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Affiliation(s)
- N Islam
- Department of Physiology, Presidency College, Calcutta, India
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28
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Brubaker PL, Izzo A, Hill M, Drucker DJ. Intestinal function in mice with small bowel growth induced by glucagon-like peptide-2. THE AMERICAN JOURNAL OF PHYSIOLOGY 1997; 272:E1050-8. [PMID: 9227451 DOI: 10.1152/ajpendo.1997.272.6.e1050] [Citation(s) in RCA: 91] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 02/04/2023]
Abstract
Glucagon-like peptide-2 (GLP-2) stimulates small intestinal growth through induction of intestinal epithelial proliferation. To examine the physiology of GLP-2-induced bowel, mice were treated with GLP-2 (2.5 micrograms) or vehicle for 10 days. Small intestinal weight increased to 136 +/- 2% of controls in GLP-2-treated mice, in parallel with 1.4 +/- 0.1- and 1.9 +/- 0.5-fold increments in duodenal RNA and protein content, respectively (P < 0.05-0.001). Similarly, the activities of duodenal maltase, sucrase, lactase, glutamyl transpeptidase, and dipeptidyl-peptidase IV (215 +/- 28% of controls; P < 0.001) were increased by GLP-2. Oral or duodenal administration of glucose or maltose did not reveal any differences in the ability of GLP-2-treated mice to absorb these nutrients, possibly because of decreases in expression of the glucose transporters sodium-dependent glucose transporter-1 (SGLT-1) and GLUT-2. In contrast, absorption of leucine plus triolein was increased after duodenal administration in GLP-2-treated mice (P < 0.01-0.001). Finally, GLP-2 did not alter other markers of intestinal or pancreatic gene expression, including levels of mRNA transcripts for ornithine decarboxylase, multidrug resistance gene, amylase, proglucagon, proinsulin, and prosomatostatin. Thus induction of intestinal growth by GLP-2 in wild-type mice results in a normal-to-increased capacity for nutrient digestion and absorption in vivo.
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Affiliation(s)
- P L Brubaker
- Department of Physiology, University of Toronto, Ontario, Canada
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29
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Sharp PA, Debnam ES, Srai SK. Rapid enhancement of brush border glucose uptake after exposure of rat jejunal mucosa to glucose. Gut 1996; 39:545-50. [PMID: 8944563 PMCID: PMC1383267 DOI: 10.1136/gut.39.4.545] [Citation(s) in RCA: 30] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 02/03/2023]
Abstract
BACKGROUND Increased jejunal glucose transport after ingestion of carbohydrate rich diets may reflect higher concentrations of lumenal glucose. Normal processing of carbohydrate causes wide fluctuations in glucose concentration in the jejunal lumen and this raises the question of whether the high lumenal concentrations seen at peak digestion affect glucose uptake. AIMS To study the effects of 30 minute exposure of rat jejunal mucosa to glucose on sodium-glucose transporter (SGLT1) mediated glucose transport across the brush border membrane. METHODS Jejunal mucosa was exposed in vitro or in vivo to 25 mM glucose or 25 mM mannitol for 30 minutes. In addition, isolated villus enterocytes were incubated with mannitol or glucose for the same time. Brush border membrane vesicles were isolated from these preparations and phlorizin sensitive 3H-D-glucose accumulation was measured. RESULTS Lumenal glucose in vivo significantly enhanced SGLT1 mediated glucose uptake by 49.2-57.2%. For jejunal loops in vitro, the increase was 32.0-85.2%. Kinetic analysis disclosed a 50% greater Vmax for glucose uptake in each preparation. The facilitated and passive components of uptake were, however, unaffected by prior exposure to glucose. Incubation of villus enterocytes with 25 mM glucose did not influence glucose uptake by brush border membranes. Finally, exposure of intact mucosa to 20 mM galactose, a nonmetabolised sugar also transported by SGLT1, did not alter glucose transport. CONCLUSIONS Lumenal glucose promotes glucose transport by brush border membrane within 30 minutes. An intact mucosa is necessary for upregulation and evidence suggests that the response is mediated by locally acting mechanisms.
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Affiliation(s)
- P A Sharp
- Department of Physiology, Royal Free Hospital School of Medicine, London
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30
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Griffiths NM, François A, Dublineau I, Lebrun F, Joubert C, Aigueperse J, Gourmelon P. Exposure to either gamma or a mixed neutron/gamma field irradiation modifies vasoactive intestinal peptide receptor characteristics in membranes isolated from pig jejunum. Int J Radiat Biol 1996; 70:361-70. [PMID: 8800207 DOI: 10.1080/095530096145094] [Citation(s) in RCA: 10] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/02/2023]
Abstract
The effect of acute whole body exposure to ionizing radiation was investigated on intestinal vasoactive intestinal peptide (VIP) receptors and adenylate cyclase activity in membranes isolated from pig jejunum. Pigs under light anaesthesia were exposed to a single dose (6 Gy) of gamma (gamma) or to mixed neutron/gamma field (ratio 1:1; neutron/gamma) irradiation. Seven days after irradiation, plasma-membranes were prepared from post mortem jejunal mucosal scrapings. Marker enzyme activities (sucrase, leucine aminopeptidase (LAP), Na,K-ATPase) were measured in each preparation. The characteristics (KD, Bmax) of VIP receptors were determined using 125I-labelled VIP. In addition VIP-sensitive adenylate cyclase activity was measured. Results showed that enzyme activities were reduced following both gamma (sucrase 67%; LAP 53%; Na/K-ATPase 29%; N = 7) and neutron/gamma (sucrase 53%; LAP 59%; Na/K-ATPase 68%; N = 5) compared with control values (N = 5). VIP receptor affinity was decreased following either type of irradiation (gamma or neutron/gamma P < 0.01) and receptor numbers increased. Both VIP- and forskolin-stimulated adenylate cyclase activities were reduced but the sensitivity of the enzyme remained the same for VIP (EC50 values (nmol dm-3)-control-1.27 +/- 0.35; gamma-2.18 +/- 0.41; neutron/gamma-1.91 +/- 0.28). In conclusion, exposure to either gamma or neutron/gamma irradiation attenuates intestinal enzyme activities and VIP receptor affinity but increases VIP receptor numbers.
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Affiliation(s)
- N M Griffiths
- Institut de Protection et de Sûreté Nucléaire, Département de Protection de la santé de 1'Homme et de Dosimétrie, IPSN, FONTENAY-aux-ROSES, France
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31
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Corpe CP, Basaleh MM, Affleck J, Gould G, Jess TJ, Kellett GL. The regulation of GLUT5 and GLUT2 activity in the adaptation of intestinal brush-border fructose transport in diabetes. Pflugers Arch 1996; 432:192-201. [PMID: 8662294 DOI: 10.1007/s004240050124] [Citation(s) in RCA: 94] [Impact Index Per Article: 3.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/08/2023]
Abstract
The adaptation of d-fructose transport in rat jejunum to experimental diabetes has been studied. In vivo and in vitro perfusions of intact jejunum with d-fructose revealed the appearance of a phloretin-sensitive transporter in the brush-border membrane of streptozotocin-diabetic rats which was not detectable in normal rats. The nature of the transporters involved was investigated by Western blotting and by d-fructose transport studies using highly purified brush-border and basolateral membrane vesicles. GLUT5, the major transporter in the brush-border membrane of normal rats, was not inhibited by d-glucose or phloretin. In contrast, GLUT2, the major transporter in the basolateral membrane of normal rats, was strongly inhibited by both D-glucose and phloretin. In brush-border membrane vesicles from diabetic rats, GLUT5 levels were significantly enhanced; moreover the presence of GLUT2 was readily detectable and increased markedly as diabetes progressed. The differences in stereospecificity between GLUT2 and GLUT5 were used to show that both transporters contributed to the overall enhancement of d-fructose transport measured in brush-border membrane vesicles and in vitro isolated loops from diabetic rats. However, overall d-fructose uptake in vivo was diminished. The underlying mechanisms and functional consequences are discussed.
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Affiliation(s)
- C P Corpe
- Department of Biology, University of York, PO Box 373, York YO1 5YW, UK
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Schoeller C, Keelan M, Mulvey G, Stremmel W, Thomson AB. Oleic acid uptake into rat and rabbit jejunal brush border membrane. BIOCHIMICA ET BIOPHYSICA ACTA 1995; 1236:51-64. [PMID: 7794955 DOI: 10.1016/0005-2736(95)00035-2] [Citation(s) in RCA: 21] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 01/27/2023]
Abstract
Oleic acid uptake was studied using adult rabbit and rat jejunal brush border membrane vesicles. There was a reduction of oleic acid uptake following trypsin-treatment. Opposing Na+/H+ gradients (inward Na+ and outward H+ gradients) increased oleic acid uptake by about 40%, as compared with only an inward Na+ gradient, only an outward H+ gradient, or the absence of either Na+ or H+ gradients. The addition of mucin further increased the enhanced uptake of oleic acid observed in the presence of opposing Na+/H+ gradients. Amiloride, an inhibitor of the Na+/H+ exchanger, reduced by about 40% the uptake of oleic acid into sheets of rat jejunum, and this inhibitory effect was observed over a range of rates of stirring of the bulk phase. In rabbit jejunal brush border membrane vesicles, amiloride reduced oleic acid uptake in the presence but not in the absence of opposing Na+/H+ gradients, with a Ki of approx. 36 microM. Thus, oleic acid uptake occurs largely by partitioning of the lipid into the brush border membrane, influenced by a process which involves the activation of the brush border membrane Na+/H+ exchanger.
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Affiliation(s)
- C Schoeller
- Division of Gastroenterology, University of Alberta, Edmonton, Canada
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Madsen KL, Ariano D, Fedorak RN. Vanadate treatment rapidly improves glucose transport and activates 6-phosphofructo-1-kinase in diabetic rat intestine. Diabetologia 1995; 38:403-12. [PMID: 7796980 DOI: 10.1007/bf00410277] [Citation(s) in RCA: 18] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 01/27/2023]
Abstract
The effect of oral vanadate on intestinal sodium-dependent glucose transport and 6-phosphofructo-1-kinase (EC 2.7.1.11) activity was examined in male Sprague-Dawley rats following a 30-day period of non-treated streptozotocin-induced diabetes. Non-treated diabetic rats were hyperglycaemic and demonstrated increased intestinal sodium-dependent glucose transport and Na,K-ATPase activity compared with controls. These increases were associated with a significant decrease in the total activity and activity ratios (activity at 0.5 mmol/l fructose 6-phosphate at pH 7.0/activity at pH 8.0) of intestinal 6-phosphofructo-1-kinase and decreased levels of fructose 2,6-bisphosphate. Supplementation of drinking water with vanadate (0.5 mg/ml) resulted in a rapid decline in blood glucose levels to a slightly hyperglycaemic level. Jejunal glucose transport and Na,K-ATPase activity were normalized after 48 h of vanadate treatment. In contrast, ileal glucose transport was significantly reduced 12 h following beginning vanadate treatment even though Na,K-ATPase activity did not normalize until 36 h later. Km was significantly decreased in both jejunum and ileum by vanadate treatment indicating an increased affinity of the sodium-dependent intestinal glucose transporter for glucose. 6-phosphofructo-1-kinase total activity and susceptibility to ATP inhibition was completely restored after 12 h of vanadate treatment. This increase was associated with a rise in fructose 2,6-bisphosphate levels. Fasting rats for 12 h had no effect on glucose transport or 6-phosphofructo-1-kinase activity, indicating the anorectic effect of vanadate was not responsible for changes in either parameter. In contrast, cycloheximide prevented both the rise in 6-phosphofructo-1-kinase activity and the rise in fructose 2,6-bisphosphate levels, and the subsequent reduction in glucose transport, indicating a requirement for protein synthesis. The removal of vanadate resulted in an immediate return to pre-treatment blood glucose levels. In contrast, intestinal glucose transport and 6-phosphofructo-1-kinase activity remained at treatment levels up until 72 h, indicating that oral vanadate treatment can have prolonged beneficial effects on intestinal function. In conclusion, the treatment of streptozotocin-induced diabetic rats with oral vanadate results in an activation of 6-phosphofructo-1-kinase coupled with a normalization of intestinal sodium-dependent glucose transport. Vanadate may thus have a beneficial effect on intestinal function and may prove useful as oral adjunctive diabetic therapy.
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Affiliation(s)
- K L Madsen
- Department of Medicine, University of Alberta, Edmonton, Canada
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Hillgren KM, Kato A, Borchardt RT. In vitro systems for studying intestinal drug absorption. Med Res Rev 1995; 15:83-109. [PMID: 7537838 DOI: 10.1002/med.2610150202] [Citation(s) in RCA: 137] [Impact Index Per Article: 4.6] [Reference Citation Analysis] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/25/2023]
Affiliation(s)
- K M Hillgren
- Department of Pharmaceutical Chemistry, School of Pharmacy, University of Kansas, Lawrence 66045, USA
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Wolffram S, Unternährer R, Grenacher B, Scharrer E. Transport of citrate across the brush border and basolateral membrane of rat small intestine. COMPARATIVE BIOCHEMISTRY AND PHYSIOLOGY. PHYSIOLOGY 1994; 109:39-52. [PMID: 8076452 DOI: 10.1016/0300-9629(94)90310-7] [Citation(s) in RCA: 11] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 01/28/2023]
Abstract
It was the aim of the present study to investigate the transport of tricarboxylates (citrate, tricarballylate) across the basolateral membrane (BLM) of the small intestine. Experiments were performed using BLM vesicles isolated from the jejunum of rats. For comparison, some experiments with brush border membrane (BBM) vesicles were also performed. Finally, transfer of citrate and tricarballylate across the intestinal wall was investigated using sacs of everted small intestine. Uptake of citrate by BBM vesicles occurs by a Na+ gradient-driven transport mechanism specific for tri- and dicarboxylates. The partially protonated forms of citrate seem to be much better transported than the completely dissociated form, since lowering the extravesicular pH from 7.8 to 5.6 resulted in a marked stimulation of Na(+)-dependent citrate uptake. In contrast to citrate uptake across the BBM, uptake of citrate across the BLM was neither influenced by Na+ nor by pH changes. Neither structurally related tri- and dicarboxylates (tricarballylate, succinate) nor other organic and inorganic anions (e.g. lactate, p-aminohippurate, sulfate, chloride, bicarbonate) significantly influenced citrate uptake by BLM vesicles under cis-conditions. Uptake of citrate as a function of the extravesicular substrate concentration was linear over a concentration range from 0.1 to 10 mmol/l. Thus, citrate uptake under these conditions seems to be Na(+)-independent and not to be mediated by a carrier. However, preloading the BLMV with citrate clearly trans-stimulated the uptake of citrate and tricarballylate, respectively. Furthermore, citrate significantly inhibited tricarballylate uptake into BLMV preloaded with citrate. These results indicate uptake of tricarboxylates across the BLM by an exchange mechanism. Using sacs of everted small intestine, no transfer of intact citrate against a concentration gradient occurred, but some evidence for metabolization of citrate within the intestinal wall was obtained. In contrast, the non-metabolizable tricarboxylate tricarballylate was significantly accumulated in the serosal compartment of everted intestinal sacs.
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Affiliation(s)
- S Wolffram
- Institute of Veterinary Physiology, University of Zürich, Switzerland
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Thomson AB, Cheeseman CI, Keelan M, Fedorak R, Clandinin MT. Crypt cell production rate, enterocyte turnover time and appearance of transport along the jejunal villus of the rat. BIOCHIMICA ET BIOPHYSICA ACTA 1994; 1191:197-204. [PMID: 8155675 DOI: 10.1016/0005-2736(94)90249-6] [Citation(s) in RCA: 37] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 01/29/2023]
Abstract
Intestinal nutrient absorption is subject to adaptation with, for example, diabetes, diet lipid variations (isocaloric semisynthetic diets enriched with saturated (S) or polyunsaturated (P) fatty acids), ileal resection and abdominal irradiation. These models were used in rats to assess dynamic morphology and distribution of amino acid transporter along the villus. The enterocyte migration rate (EMR) was measured using [3H]thymidine; the vincristine metaphase arrest technique was used to determine the crypt cell production rate (CCPR); quantitative autoradiography was used to assess the time and age of enterocytes when the uptake of 1 and 20 mM [3H]leucine and [3H]lysine was initiated along the villus. The enhanced jejunal uptake of nutrients which occurs after a 50% distal enterectomy was associated with a fall in EMR and CCPR, yet the enhanced nutrient uptake which occurs in diabetes is not associated with any alteration in EMR, CCPR, enterocyte transport pool (ETP), i.e., the length of the enterocyte column along with the villus containing amino acid transporter) or expression of transporter along the villus. The reduced uptake of nutrients in rats fed P as compared with S was associated with increased rather than decreased ETP and age of the enterocytes at the tip of the villus. The reduced nutrient uptake which occurs 3 days after abdominal irradiation was associated with increased EMR and CCPR, and reduced ETP and age of enterocytes of the tip of the villus. However, 14 days after irradiation when nutrient transport remains reduced, these parameters have returned to normal. Thus, alterations in nutrient transport may be associated with changes in the dynamic morphology of the intestine, but the two processes are not necessarily interdependent. We speculate that the changes in the dynamic morphology of the intestine, and the changes of amino acid transport which occurs in these models of intestinal adaptation, are independently controlled.
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Affiliation(s)
- A B Thomson
- Department of Medicine, University of Alberta, Edmonton, Canada
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Miyamoto K, Hase K, Takagi T, Fujii T, Taketani Y, Minami H, Oka T, Nakabou Y. Differential responses of intestinal glucose transporter mRNA transcripts to levels of dietary sugars. Biochem J 1993; 295 ( Pt 1):211-5. [PMID: 8216218 PMCID: PMC1134840 DOI: 10.1042/bj2950211] [Citation(s) in RCA: 112] [Impact Index Per Article: 3.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/29/2023]
Abstract
Dietary sugars are known to stimulate intestinal glucose transport activity, but the specific signals involved are unknown. The Na(+)-dependent glucose co-transporter (SGLT1), the liver-type facilitative glucose transporter (GLUT2) and the intestinal-type facilitative glucose transporter (GLUT5) are all expressed in rat jejunum [Miyamoto, Hase, Taketani, Minami, Oka, Nakabou and Hagihira (1991) Biochem. Biophys. Res. Commun. 181, 1110-1117]. In the present study we have investigated the effects of dietary sugars on these glucose transporter genes. A high-glucose diet stimulated glucose transport activity and increased the levels of SGLT1 and GLUT2 mRNAs in rat jejunum. 3-O-Methylglucose, D-galactose, D-fructose, D-mannose and D-xylose can mimic the regulatory effect of glucose on the SGLT1 mRNA level in rat jejunum. However, only D-galactose and D-fructose increased the levels of GLUT2 mRNA. The GLUT5 mRNA level was increased significantly only by D-fructose. Our results suggest that the increase in intestinal transport activity in rats caused by dietary glucose is due to an increase in the levels of SGLT1 and GLUT2 mRNAs, and that these increases in mRNA may be caused by an enhancement of the transcriptional rate. Furthermore, for expression of the SGLT1 gene, the signal need not be a metabolizable or transportable substrate whereas, for expression of the GLUT2 gene, metabolism of the substrate in the liver may be necessary for signalling. Only D-fructose is an effective signal for expression of the GLUT5 gene.
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Affiliation(s)
- K Miyamoto
- Department of Nutrition, School of Medicine, University of Tokushima, Japan
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38
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Abstract
BACKGROUND The exact roles of disaccharidases and GLUT5 in the brush border membrane and GLUT2 in the basolateral membrane in the absorption of fructose across the intestine have not been fully determined. This paper describes characterization of fructose transport across the jejunal basolateral membrane using isolated membrane vesicles. METHODS Transport of fructose was measured using rapid filtration of vesicles. Luminal perfusion in vivo with glucose and fructose before vesicle preparation was used to assess modulation of GLUT2 activity. Western blotting measured the abundance of GLUT2 in the membrane. RESULTS The maximal rate of transport for fructose was 1100 pmol/mg protein/s and the Michaelis constant was 16 mmol/L. Fructose and glucose could completely inhibit the transport of each other. Perfusion of the intestinal lumen with fructose or glucose saline for 4 hours produced a fourfold increase in maximal fructose transport. CONCLUSIONS These data indicate that the one transport protein, GLUT2, is responsible for moving both fructose and glucose out of the enterocyte across the basolateral membrane under basal conditions. The activity of this, or a closely related carrier, is rapidly upregulated by the presence of hexoses in the intestinal lumen, explaining the potentiation of fructose absorption by luminal glucose and obviating any need to involve apical disaccharidases.
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Affiliation(s)
- C I Cheeseman
- Department of Physiology, University of Alberta, Edmonton, Canada
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39
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Debnam ES, Chowrimootoo G. Insulin induced hypoglycaemia and sugar transport across the brush border and basolateral membranes of rat jejunal enterocytes. Eur J Clin Invest 1993; 23:480-5. [PMID: 8405000 DOI: 10.1111/j.1365-2362.1993.tb00794.x] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 01/30/2023]
Abstract
Acute hypoglycaemia enhances intestinal sugar uptake but the mechanisms involved are unknown. Results from the present study show increased galactose movement across the brush border and basolateral membranes of isolated upper, but not mid-villus, jejunal enterocytes 45 min after intravenous administration of insulin to rats at a level which reduced by half plasma glucose concentration. Incubation of upper villus cells from uninjected animals with insulin (100 mU ml-1) for 40 min was without effect on brush border or basolateral sugar transport. Insulin treatment of rats did not affect glucose uptake by brush border vesicles prepared from upper villus cells when the process was driven by an inwardly directed 100 mM sodium thiocyanate gradient. In contrast, glucose uptake using a 100 mM inwardly directed sodium chloride gradient was reduced by 49% following hypoglycaemia. It is concluded that the enhanced sugar uptake following insulin hypoglycaemia involves both brush border and basolateral membranes of only the most mature villus cells at the villus tip. Upregulation of Na(+)-sugar cotransport at the brush border is best explained by an increased electrochemical driving force for Na(+)-sugar cotransport rather than increased numbers of transporters. The transport response is not due to a direct effect of insulin on the enterocyte and the possible systemic factors involved are discussed.
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Affiliation(s)
- E S Debnam
- Department of Physiology, Royal Free Hospital School of Medicine, London, UK
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40
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Ozols A. Some non-traditional aspects on the regulation of glucose assimilation in the small intestine. COMPARATIVE BIOCHEMISTRY AND PHYSIOLOGY. COMPARATIVE PHYSIOLOGY 1993; 105:785-91. [PMID: 8102964 DOI: 10.1016/0300-9629(93)90284-b] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 01/28/2023]
Abstract
1. The aim of this work was to give a new interpretation on the participation of several food factors in carbohydrate assimilation and metabolism regulation in the organism. 2. The main attention is paid to the probable role of vitamins A and D in these processes in enterocytes. 3. The importance of vitamins A and D and the minerals Zn and Ca has been considered in the regulation of insulin activity and glucose transport in these cells. 4. The views expressed in this paper are based on our own research results and analysis of data in the present literature.
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Affiliation(s)
- A Ozols
- Institute of Biology of Latvian Academy of Sciences, Laboratory of Biochemistry and Physiology of Animals, Salaspils
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41
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Miyamoto K, Takagi T, Fujii T, Matsubara T, Hase K, Taketani Y, Oka T, Minami H, Nakabou Y. Role of liver-type glucose transporter (GLUT2) in transport across the basolateral membrane in rat jejunum. FEBS Lett 1992; 314:466-70. [PMID: 1468587 DOI: 10.1016/0014-5793(92)81528-t] [Citation(s) in RCA: 14] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/27/2022]
Abstract
To obtain information on the regulation of glucose transport across the basolateral membrane (BLM) of intestinal epithelial cells, we measured the number of [3H]cytochalasin B binding sites and the level of liver-type glucose transporter (GLUT2) protein in the BLM in the jejunum of rats (i) with diabetes (ii) given a high-carbohydrate diet or (iii) with experimental hyperglycemia (12 h infusion of a high-glucose solution). A glucose uptake and the number of D-glucose inhibitable [3H]cytochalasin B binding sites in BLM vesicles were significantly increased in all three conditions. Western blot analysis showed that the amount of GLUT2 protein in BLM vesicles was increased in rats with diabetes and those given a high-carbohydrate diet, but not in those with experimental hyperglycemia. These results suggest that there is a mechanism for rapid regulation of glucose transport in the BLM that does not depend on change in the amount of GLUT2.
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Affiliation(s)
- K Miyamoto
- Department of Nutrition, School of Medicine, University of Tokushima, Japan
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42
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Debnam ES, Chowrimootoo G. Streptozotocin diabetes and sugar transport by rat ileal enterocytes: evidence for adaptation caused by an increased luminal nutrient load. BIOCHIMICA ET BIOPHYSICA ACTA 1992; 1107:86-92. [PMID: 1535513 DOI: 10.1016/0005-2736(92)90332-g] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 12/27/2022]
Abstract
Preparations of villus enterocytes and brush border membrane vesicles have been used to study the effects of streptozotocin-induced diabetes mellitus in rats on sugar transport across the brush border and basolateral membranes of ileal epithelial cells. In isolated cells, diabetes increased Na(+)-dependent galactose transport across the brush border of mid-villus but not upper villus cells. Galactose transport across the basolateral membrane was, however, enhanced by diabetes in both cell populations. Kinetic analysis of vesicle data suggested the presence of two transporters for Na(+)-dependent glucose transport. Diabetes induced a 5-fold increase in both KT and Vmax of the high-affinity/low-capacity system together with a 2-fold increase in the Vmax of the low-affinity/high-capacity transporter. Glucose was almost undetectable in the lumen of the upper and lower ileum in control animals but was present at high levels (26.1 +/- 4.3 mM and 6.5 +/- 1.3 mM) in diabetic rats. The possible significance of these changes in luminal sugar concentration in relation to the adaptation of transport across ileal enterocytes is discussed.
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Affiliation(s)
- E S Debnam
- Department of Physiology, Royal Free Hospital School of Medicine, London, UK
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43
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Cheeseman CI, Harley B. Adaptation of glucose transport across rat enterocyte basolateral membrane in response to altered dietary carbohydrate intake. J Physiol 1991; 437:563-75. [PMID: 1890649 PMCID: PMC1180063 DOI: 10.1113/jphysiol.1991.sp018611] [Citation(s) in RCA: 43] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/29/2022] Open
Abstract
1. The effect of changes in the carbohydrate content of the diet on D-glucose transport across the basolateral membrane of rat enterocytes has been compared with alterations in transport across the brush-border membrane. 2. Measurement of carrier-mediated D-glucose uptake across the jejunal brush border from animals fed a low- or high-carbohydrate diet showed a change in the maximal rate of transport by 7 days which was maintained for 14 days. The low-carbohydrate diet produced a progressive decline in uptake whereas the high-carbohydrate diet increased the transport. There was no alteration in the apparent affinity constant as a result of the dietary manipulations and no discernible trend for changes in the passive permeability to glucose. 3. Transport of D-glucose across the basolateral membrane was also affected by the dietary composition. After 7 days the maximal transport rate was greater in the animals fed the high-carbohydrate diet. However, while this increase was maintained for 14 days, uptake into vesicles prepared after 2 weeks on the low-carbohydrate diet showed a return to control levels. 4. A detailed analysis of the time course of these responses showed the effect on basolateral membrane transport to be inducible within 3 days of switching from the low- to the high-carbohydrate diet and could be reversed within a similar period. 5. Kinetic studies using purified basolateral membrane vesicles confirmed that the change in transport was the result of an increase in the maximal transport rate. Analysis of cytochalasin B binding to these membranes showed a parallel change in the number of glucose-inhibitable binding sites. 6. The component of the diet responsible for these changes was further investigated by replacing the glucose in the high-carbohydrate food with galactose, fructose, mannose or 3-O-methylglucose. Only glucose and fructose produced any significant change in the transport across the basolateral membrane. 7. It is concluded that in response to changes in the carbohydrate content of the diet there are alterations in the capacity for glucose transport across the basolateral membrane of the enterocyte as well as in the brush-border membrane. The change in transport across the basolateral membrane is best explained by an increase in the number of glucose carriers in this membrane.
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Affiliation(s)
- C I Cheeseman
- Department of Physiology, University of Alberta, Edmonton, Canada
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Satoh O, Koyama S, Yamada K, Kawasaki T. Changes in amino acid and glucose transport in brush-border membrane vesicles of hyperglycemic guinea-pig small intestine. BIOCHIMICA ET BIOPHYSICA ACTA 1991; 1063:155-61. [PMID: 1826612 DOI: 10.1016/0005-2736(91)90365-f] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 12/28/2022]
Abstract
Changes in intestinal transport of L-amino acid and D-glucose in streptozotocin (STZ)-induced hyperglycemic guinea-pig were examined using brush-border membrane vesicles. The vesicles were prepared from guinea-pigs on days 3, 10, and 21 after intravenous injection of STZ (150 mg/kg body weight), and from control animals injected with sodium citrate buffer (pH 4.5) in the same manner. Blood glucose concentration rose to greater than 300 mg/dl in the hyperglycemic guinea-pigs 24 h after STZ injection, and then remained constant. All vesicles obtained under different conditions showed a similar specific activity of alkaline phosphatase, a marker enzyme of the intestinal brush-border membrane, indicating a similar purity of the membrane vesicles. On day 3, Na(+)-dependent amino acid transport was found to be approx. 30% higher in the hyperglycemic than in the control group, and Na(+)-dependent glucose transport was 35% lower in the hyperglycemic than in the control group. On days 10 and 21, Na(+)-dependent amino acid transport had recovered to the control levels, whereas Na(+)-dependent glucose transport was twice as high as in the hyperglycemic than in the control group. Na(+)-independent amino acid and Na(+)-independent glucose transport showed no difference between the hyperglycemic and control groups after STZ injection. The changes in both Na(+)-dependent amino acid and glucose transport were attributed to significant changes in the Vmax values with no change in the apparent Km values. This study clearly demonstrates that hyperglycemia is associated with reciprocal changes in intestinal transport of amino acid and glucose in its acute phase, suggesting an important pathophysiological regulatory mechanism for absorption of nutrients by control of the numbers of specific carriers.
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Affiliation(s)
- O Satoh
- Department of Biochemistry, Hiroshima University School of Medicine, Japan
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Debnam ES, Ebrahim HY, Swaine DJ. Diabetes mellitus and sugar transport across the brush-border and basolateral membranes of rat jejunal enterocytes. J Physiol 1990; 424:13-25. [PMID: 2144023 PMCID: PMC1189798 DOI: 10.1113/jphysiol.1990.sp018052] [Citation(s) in RCA: 32] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/30/2022] Open
Abstract
1. The effects of streptozotocin-induced diabetes mellitus on active jejunal glucose uptake in vivo, and on galactose movement across the brush-border (phlorhizin-sensitive) and basolateral (phlorhizin-insensitive) membranes of isolated upper and mid-villus enterocytes has been studied. 2. Chronic diabetes increased unidirectional phlorhizin-sensitive galactose uptake by mid-villus but not upper villus cells. In contrast, phlorhizin-insensitive uptake by both cell populations was enhanced by diabetes. 3. Diabetes increased glucose absorption in vivo by mechanisms which were unrelated to hyperphagia. Mucosal hyperplasia acting together with an epithelium containing a higher proportion of mature enterocytes is the most likely explanation for the response. 4. We conclude that, during diabetes, the mid-villus region is an important site of adaptation with functional changes occurring at both the brush-border and basolateral membranes. The increased hexose transport ability of the basolateral membrane is retained during cell transit along the villus.
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Affiliation(s)
- E S Debnam
- Department of Physiology, Royal Free Hospital School of Medicine, London
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46
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Drai P, Albertini-Berhaut J, Lafaurie M, Sudaka P, Giudicelli J. Simultaneous preparation of basolateral and brush-border membrane vesicles from sea bass intestinal epithelium. BIOCHIMICA ET BIOPHYSICA ACTA 1990; 1022:251-9. [PMID: 2156552 DOI: 10.1016/0005-2736(90)90271-o] [Citation(s) in RCA: 11] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 12/30/2022]
Abstract
A method is described for simultaneous preparation of brush-border and basolateral sea bass enterocyte membranes using simple differential centrifugation and discontinuous sucrose gradient density centrifugation techniques. Basolateral membranes were purified with a Na+/K(+)-ATPase yield of about 11% of the original activity, with an enrichment factor of 12. The yield of maltase-glucoamylase, a specific marker of brush-border membranes, was also about 11% of the original activity, with 15-fold enrichment. The characteristics of these membrane preparations were determined. Electron microscopy analysis showed that these two membrane preparations were uniform in size and vesicular in nature. Orientation studies revealed that the luminal membrane vesicles were right-side out and 43% of the antiluminal membrane vesicles were sealed inside out. Investigation of D-glucose and L-leucine uptake showed that these two plasma membrane preparations retained their transport properties.
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Affiliation(s)
- P Drai
- Laboratoire de Biochimie, Faculté de Médecine, Nice, France
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47
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Banerjee AK, Raja K, Peters TJ. Effect of insulin induced hypoglycaemia on in vitro uptake of 3-O-methylglucose by rat jejunum. Gut 1989; 30:1348-53. [PMID: 2684803 PMCID: PMC1434410 DOI: 10.1136/gut.30.10.1348] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 01/02/2023]
Abstract
Acute hypoglycaemia (less than 2.0 mmol/l) selectively increased in vitro 3-O-methylglucose uptake by rat jejunum. In contrast, uptake of 3H-phenylalanine or 59Fe (III) was unchanged in the hypoglycaemic animals. The hypoglycaemia was accompanied by decreased tissue adenosine nucleotide energy charge. The increased uptake was phlorrhidzin-inhibitable and therefore reflected increased Na+ dependent glucose carrier activity. Cycloheximide did not block the increased 3-O-methylglucose uptake, implying that the mechanism is not the result of increased de novo carrier protein synthesis.
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Affiliation(s)
- A K Banerjee
- Division of Clinical Cell Biology, MRC Clinical Research Centre, Harrow, Middlesex
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48
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Dietary Carbohydrate and the Kinetics of Intestinal Functions in Relation to Hexose Absorption. DIETARY STARCHES AND SUGARS IN MAN: A COMPARISON 1989. [DOI: 10.1007/978-1-4471-1701-8_5] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 02/05/2023]
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49
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50
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Nutrient Transport Across Vertebrate Intestine. ADVANCES IN COMPARATIVE AND ENVIRONMENTAL PHYSIOLOGY 1988. [DOI: 10.1007/978-3-642-73375-8_4] [Citation(s) in RCA: 18] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 01/24/2023]
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