Orosomucoid in liver diseases

Table 1 A brief overview of the general properties of orosomucoid protein

General properties of orosomucoid protein
Chromosome location	9
Genes	AGP-A	AGP-B and AGP-B’
Product	ORM1	ORM2
Alleles	ORM1*S, ORM*F, ORM*F2	Monomorphic, except in Japan
Structure
Polypeptide chain	Single, 183 amino acids with disulfide bonds; There are 22 amino acid differences between ORM 1 and ORM2
Carbohydrate parts	Five N-linked potential glycosylation sites: Sialic acid, neutral hexoses, mannose, fructose, galactose and hexosamine. Alterations in fucosylation, sialylation, and branching affect its biological properties
Synthesis	Predominantly by hepatocytes and parenchymal cells. Extrahepatic secretion is rare (breast, endothelial cells, and tumor cells)
Secretion
Inflammatory mediators	Glucocorticoids, TNF-α, Interleukins: 1, 6, 8, 11
Exogenous factors	Phenobarbital, Rifampicin, Retinoic acid, Macrolides
Biological activities
Acute-phase reactant	Concentration is elevated 1-10 times during several pathological conditions. Infection, inflammation, tumor, surgery, tissue injury, sepsis, and necrosis
Immunomodulation	Inhibit leukocyte rolling/adhesion and migration and lymphocyte proliferation. Vitamin D-mediated macrophage deactivation. Agalacto/asialo derivative suppresses the immune response. ORM1 contributes to both anti- and proinflammatory signals to mediate mechanisms activated by the acute-phase response
Transporting protein	Drug-binding and transporting in the serum. The existence of two forms in the blood also has an influence the binding affinity. ORM1 binds warfarin, prazosin, imatinib, quinidine, and dipyridamole. ORM2 binds methadone, disopyramide, propafenone, and amitriptyline
Endothelial functions	Maintain the barrier function of capillaries. Regulate injury-induced angiogenesis. Enhance blood-brain barrier functional integrity. Beneficial effect on the glomerular barrier
Metabolism	ORM1 increases glucose uptake activity in adipocytes. A potential biomarker in distinguishing obese women with metabolic syndrome from those without metabolic disturbances

ORM: Orosomucoid; TNF-α: Tumor necrosis factor alpha.