Region-dependent effects of diabetes and insulin-replacement on neuronal nitric oxide synthase- and heme oxygenase-immunoreactive submucous neurons

Abstract

AIMTo investigate the intestinal segment-specific effects of diabetes and insulin replacement on the density of different subpopulations of submucous neurons.METHODSTen weeks after the onset of type 1 diabetes samples were taken from the duodenum, ileum and colon of streptozotocin-induce diabetic, insulin-treated diabetic and sex- and age-matched control rats. Whole-mount preparations of submucous plexus were prepared from the different gut segments for quantitative fluorescent immunohistochemistry. The following double-immunostainings were performed: neuronal nitric oxide synthase (nNOS) and HuC/D, heme oxygenase (HO) 1 and peripherin, as well as HO2 and peripherin. The density of nNOS-, HO1- and HO2-immunoreactive (IR) neurons was determined as a percentage of the total number of submucous neurons.RESULTSThe total number of submucous neurons and the proportion of nNOS-, HO1- and HO2-IR subpopulations were not affected in the duodenal ganglia of control, diabetic and insulin-treated rats. While the total neuronal number did not change in either the ileum or the colon, the density of nitrergic neurons exhibited a 2- and 3-fold increase in the diabetic ileum and colon, respectively, which was further enhanced after insulin replacement. The presence of HO1- and HO2-IR submucous neurons was robust in the colon of controls (38.4%-50.8%), whereas it was significantly lower in the small intestinal segments (0.0%-4.2%, P < 0.0001). Under pathophysiological conditions the only alteration detected was an increase in the ileum and a decrease in the colon of the proportion of HO-IR neurons in insulin-treated diabetic animals.CONCLUSIONDiabetes and immediate insulin replacement induce the most pronounced region-specific alterations of nNOS-, HO1- and HO2-IR submucous neuronal density in the distal parts of the gut.

Small intestine remodeling in male Goto–Kakizaki rats

“…A previous study with obese mice (ob/ob) showed that neither the density nor area of the total population in the duodenum myenteric neurons are perturbed, but differences could be observed in the myenteric neuronal‐specific subpopulations (Spangeus & El‐Salhy, 2001). Notably, in streptozotocin‐induced diabetic animals, an increase in the nitrergic neuronal population of the submucosal plexus in the jejunum and colon was reported (Bódi et al, 2017).…”

Nitrergic Enteric Neurons in Health and Disease—Focus on Animal Models

“…In the submucous plexus, the proportion of nNOS-immunoreactive neurons was doubled in the ileum and tripled in the colon, but not in the duodenum of diabetic rats, while the total neuronal number remained unchanged, suggesting neurochemical adaptation of submucous neurons [35]. These results emphasize that the diabetic state affects the two enteric plexuses differentially.…”

Diabetic enteric neuropathy: imbalance between oxidative and antioxidative mechanisms

“…Moreover, it is proved that HO1ÀIR and HO2ÀIR neurons are present in very small amounts in the submucous plexus of the small intestine. 31 The slight expression of these antioxidants may contribute to significantly lower protection against different pathological stimuli in the ileum.…”