Gastric Emptying in Animal Models of Human Diabetes: Correlation to Blood Glucose Level and Gut Neuroendocrine Peptide Content
Gastric emptying was measured in non-obese diabetic (NOD) and in obese diabetic mice. The feces were collected and the water content was determined. The neuroendocrine peptides known to regulate gastrointestinal motility, namely secretin, gastric inhibitory peptide (GIP), motilin, somatostatin, peptide YY (PYY), substance P, vasoactive intestinal polypeptide (VIP) and galanin, were measured in tissue extracts of different segments of the gut by radioimmunoassay. Whereas the gastric emptying of NOD mice was significantly slower than that of controls, that of the obese diabetic mice was unaltered. The gastric emptying of NOD mice, but not that of obese diabetic mice, correlated with the blood glucose level. The feces weight and water content in NOD mice was significantly higher than controls. The feces water content in obese diabetic mice was significantly lower than that of controls. The concentrations of antral somatostatin, VIP and galanin, and duodenal secretin as well as jejunal motilin in NOD mice were higher than those of controls. Duodenal GIP and colonic PYY concentration in NOD mice was lower than controls. Duodenal GIP and VIP, and colonic somatostatin and VIP levels were lower in obese diabetic mice than controls. Secretin and motilin levels correlated with gastric emptying in NOD mice. The high duodenal concentration of secretin might reflect high synthesis and release of this hormone, and may therefore be among the factors that caused slow gastric emptying in the NOD mice. The increase in concentration of motilin observed in NOD mice may be caused by impaired release of this hormone as a result of hyperglycemia. Whereas the high concentrations of antral VIP and galanin and the low level of colonic PYY in diabetic NOD mice may contribute to the development of diarrhea in NOD mice, the decreased levels of duodenal and colonic VIP and colonic somatostatin in obese diabetic mice may account for the constipation encountered in these animals.
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