Effect of aging and diabetes on the enteroinsular axis

Background. The current studies were designed to examine the effect of agin g and diabetes on the enteroinsular axis. Methods. Healthy young control subjects (n = 10 young, age 23 +/- 1 years; body mass index [BMI] 24 +/- 1 kg/m(2)), healthy elderly subjects (n = 10; age 80 +/- 2 years; BMI 26 +/- 1 kg/m(2)), and elderly patients with type 2 diabetes (n = 10, age 76 +/- 2 years; BMI 26 +/- 2 kg/m(2)) underwent a 3- hour oral glucose tolerance test (glucose dose 40 gm/m(2)). Results. Insulin responses were not different between young controls and el derly patients with diabetes but were significantly lower in elderly patien ts with diabetes and young controls than in elderly controls (young control : 178 +/- 27 pM: elderly control: 355 +/- 57 pM elderly diabetes: 177 +/- 3 0 pM; p < .05 elderly control vs young control and elderly diabetes). Total glucagon-like peptide 1 (GLP-1) responses were not significantly different between young and elderly control, and patients with diabetes (young contr ol: 15 +/- 2 pM; old control: 8 +/- 2 pM; elderly diabetes: 12 +/- 3 pM; p = ns). Active GLP-1 responses were also not different between young and eld erly controls and patients with diabetes (young control: 5 +/- 1 pM; old co ntrol: 6 +/- 1 pM; elderly diabetes: 7 +/- 1 pM; p = ns). However, the diff erence between total and active GLP levels was significantly greater in the young controls (young control: 10 +/- 2 pM: old control: 2 +/- 2 pM elderl y diabetes: 4 +/- 2 pM; p < .05, young vs elderly). Glucose-dependent insul inotropic polypeptide responses were not different between young and elderl y controls and between elderly controls and patients witl diabetes but were significantly higher in elderly patients with diabetes than in young contr ols (young control: 97 +/- 12 pM; elderly control: 121 +/- 16 pM; elderly d iabetes: 173 +/- 27 pM; p < .05, young vs elderly diabetes). Glucagon respo nses were reduced in elderly controls but were similar in young controls an d elderly patients with diabetes (young control: 15 +/- 1 pM; elderly contr ol: 9 +/- 1 pK elderly diabetes: 16 +/- 1 pM: p < .01 elderly control vs yo ung control and elderly diabetes). Dipeptidyl peptidase IV levels were lowe r in both elderly controls and patients with diabetes when compared with yo ung controls (young control: 0.17 +/- 0.01 elderly control: 0.15 +/- 0.01; elderly diabetes 0.15 +/- 0.01 Delta OD/20 minutes; p < .05, elderly vs you ng). Conclusions. We conclude that normal aging and diabetes are associated with multiple changes in the enteroinsular axis.