Impaired incretin secretion and pancreatic dysfunction with older age and diabetes

Objective. To estimate the impact of aging and diabetes on insulin sensitivity, beta-cell function, adipocytokines, and incretin production. Methods. Hyperglycemic clamps, arginine tests and meal tolerance tests were performed in 50 non-obese subjects to measure insulin sensitivity (IS) and insulin secretion as well as plasma Keywords: levels of glucagon, GLP-1 and GIP. Patients with diabetes and healthy control subjects were Incretin divided into the following groups: middle-aged type 2 diabetes (MA-DM), aged Type 2 diabetes Beta-cell function (A-DM) and middle-aged or aged subjects with normal glucose tolerance (MA-NGT or A-NGT). Results. IS, as determined by the homeostasis model assessment, glucose infusion rate, and GLP-1 oral glucose insulin sensitivity, was reduced in the aged and DM groups compared with MA-Glucagon NGT, but it was similar in the MA-DM and A-DM groups. Insulinogenic index, first and second phase insulin secretion and the disposition indices, but not insulin response to arginine, were reduced in the aged and DM groups. Postprandial glucagon production was higher in MA-DM compared to MA-NGT. Whereas the GLP-1 production was reduced in A-DM, no differences between groups were observed in GIP production. Conclusions. In non-obese subjects, diabetes and aging impair insulin sensitivity. Insulin production is reduced by aging, and diabetes exacerbates this condition. Aging associated defects superimposed diabetic physiopathology, particularly regarding GLP-1 production. On the other hand, the glucose-independent secretion of insulin was preserved. Knowledge of the complex relationship between aging and diabetes could support the development of physiopathological and pharmacological based therapies. (c) 2014 Published by Elsevier Inc.