The Effect Of Hyperglycemia On Gastric Emptying And Ghrelin Expression In Diabetic Rats

Objective To investigate the effect of hyperglycemia on gastric emptying and ghrelin expression in diabetic rats, then explore the relation between the gastric emptying disorder and ghrelin expression in different diabetic stage.Methods Sixty Wistar rats were randomly divided into three groups: normal control group, diabetes mellitus group and insulin-treated group. Diabetes was induced by intraperitoneal injection of streptozotocin (STZ). Insulin-treated diabetic rats were given Insulin Zinc Protamine (2U/animal) by subcutaneous injection every other day, beginning the 4th day after the STZ injection. One week and four weeks after the STZ injection, half of the rats were chosen from each group randomly. The body weight and the fasting blood glucose concentrations were measured. Gastric emptying was measured by intragastric administration of phenol red and the expression of gastric ghrelin and its mRNA were detected by immunohistochemistry and semi-quantitative RT- PCR separately.Results One week after the STZ injection, there were no significant differences in each group concerning the body weight. The fasting blood glucose levels of the insulin-treated group increased compared with the normal control group and decreased compared with the diabetes mellitus group. Gastric emptying rates, ghrelin integral optical density and ghrelin mRNA expression levels in the stomach of the insulin-treated group decreased compared with the normal control group and increased compared with the diabetes mellitus group. Four weeks after the STZ injection, the fasting blood glucose levels of the insulin-treated group still increased compared with the normal control group and decreased compared with the diabetes mellitus group. The body weight, gastric emptying rates and ghrelin integral optical density in the stomach of the diabetes mellitus group and insulin-treated group all decreased significantly compared with the normal control group, but ghrelin mRNA expression levels increased significantly. The difference between the diabetes mellitus group and insulin-treated group was not statistically significant.Conclusion The decreased expression and release of gastric ghrelin induced by the short-term hyperglycemia may participate in the delayed gastric emptying. The long-term hyperglycemia may enhance the expression and release of gastric ghrelin to stimulate food intake and maintain energy balance.