Published online Oct 14, 2013. doi: 10.3748/wjg.v19.i38.6416
Revised: May 20, 2013
Accepted: June 19, 2013
Published online: October 14, 2013
Processing time: 231 Days and 21.8 Hours
AIM: To investigate the effect of quercetin supplementation on the myenteric neurons and glia in the cecum of diabetic rats.
METHODS: Total preparations of the muscular tunic were prepared from the ceca of twenty-four rats divided into the following groups: control (C), control supplemented with quercetin (200 mg/kg quercetin body weight) (CQ), diabetic (D) and diabetic supplemented with quercetin (DQ). Immunohistochemical double staining technique was performed with HuC/D (general population)/nitric oxide synthase (nNOS), HuC-D/S-100 and VIP. Density analysis of the general neuronal population HuC/D-IR, the nNOS-IR (nitrergic subpopulation) and the enteric glial cells (S-100) was performed, and the morphometry and the reduction in varicosity population (VIP-IR) in these populations were analyzed.
RESULTS: Diabetes promoted a significant reduction (25%) in the neuronal density of the HuC/D-IR (general population) and the nNOS-IR (nitrergic subpopulation) compared with the C group. Diabetes also significantly increased the areas of neurons, glial cells and VIP-IR varicosities. Supplementation with quercetin in the DQ group prevented neuronal loss in the general population and increased its area (P < 0.001) and the area of nitrergic subpopulation (P < 0.001), when compared to C group. Quercetin induced a VIP-IR and glial cells areas (P < 0.001) in DQ group when compared to C, CQ and D groups.
CONCLUSION: In diabetes, quercetin exhibited a neuroprotective effect by maintaining the density of the general neuronal population but did not affect the density of the nNOS subpopulation.
Core tip: The present study is the first to report a neuroprotective effect of the flavonoid quercetin in the general population of enteric neurons in the cecum of rats with experimental diabetes mellitus. Quercetin did not reduce the loss of nitrergic neurons in the diabetic rats. This observation suggests that selective changes in the neurochemical code of enteric neurons occur in the presence of quercetin. We propose a causal link between the area and number of glial cells and the size of VIP-IR (reduction in varicosity population) varicosities. Although this link is not fully understood, these observations provide a basis for further studies to clarify the link between glia and VIP-IR varicosities.