Dietary sucrose enhances insulin secretion of aging Fischer 344 rats

Male Fischer 344 rats, ages 6, 12 and 26 mo, were fed a diet containing either sucrose or cornstarch (66% by weight) for 4 mo. The effects of age and dietary sucrose on glucose-stimulated insulin secretion were evaluated in whole perfused pancreases and isolated islets of Langerhans, and by intra-arterial glucose administration. In addition, glucose responsiveness of beta-cells was measured by following the rate of glucose oxidation in isolated islets. There was no significant effect of age on glucose-stimulated insulin secretion of whole perfused pancreases and islets of Langerhans. There was, however, a significant main effect of sucrose feeding on insulin secretion. That is, whole perfused pancreases and islets of Langerhans isolated from rats fed sucrose vs. starch diets secreted more insulin in response to glucose. This effect was most pronounced in the 26-mo-old rats. In general, islet glucose oxidation rates, and responses to the in vivo glucose, did not differ among the groups. We conclude that alterations in glucose-stimulated insulin secretion with age more closely reflect changes in diet rather than aging per se.