Immediate Insulin Treatment Prevents Diabetes-Induced Gut Region-Specific Increase in the Number of Myenteric Serotonergic Neurons

Abstract

To evaluate the effects of hyperglycemia and insulin treatment on the proportion of serotonin-immunoreactive (5-HT-IR) myenteric neurons, samples were taken from the duodenum, ileum, and colon of diabetic, insulin-treated diabetic, and control rats 10 weeks after the onset of streptozotocin-induced hyperglycemia. Myenteric whole-mount preparations were immunostained with anti-5-HT and pan-neuronal anti-HuCD markers. In controls, the 5-HT-IR myenteric neurons represent a small proportion (~2.5%) of the total neuronal number in the investigated gut segments. The proportion of 5-HT-IR myenteric neurons was significantly higher in the duodenum (p p p p p < 0.0001) compared to the untreated diabetics. Our study demonstrates that the proportion of 5-HT-IR myenteric neurons was enhanced in type 1 diabetes in a region-specific manner. Immediate insulin treatment prevents a higher hyperglycemia-induced amount of 5-HT-IR neurons and restores it to the control level in each investigated gut segment. Despite the low proportion of 5-HT-IR myenteric neurons, hyperglycemia-related changes of these neurons may play a crucial role in gastrointestinal symptoms in type 1 diabetes.

Keywords

• diabetic enteropathy
• gut segment specificity
• myenteric neurons
• serotonin
• type 1 diabetes
• enteric nervous system