Objective: To evaluate the effect of glutathione infusion on beta-cell response to glucose in elderly people with impaired glucose tolerance (IGT).
Research design and methods: Ten patients with normal glucose tolerance and 10 patients with IGT were matched for age (mean +/- SE, 72.1 +/- 2.8 vs. 71.0 +/- 3.4 yr), body mass index (23.1 +/- 1.1 vs. 22 +/- 2.1 kg/m2), and sex (6/4 vs. 5/5, men/women) underwent glutathione infusion (10 mg/min) under basal conditions and during 75-g oral glucose tolerance tests and intravenous glucose tolerance tests (0.33 g.kg body wt-1.3 min-1). Patients with IGT were also submitted to euglycemic-hyperinsulemic and hyperglycemic glucose clamps.
Results: In subjects with normal glucose tolerance, glutathione infusion failed to affect beta-cell response to glucose. In contrast, glutathione significantly potentiated glucose-induced insulin secretion in patients with IGT. Furthermore, in the latter group studied by hyperglycemic clamps, glutathione infusion significantly potentiated the beta-cell response to glucose when plasma glucose levels varied between 10 and 15 mM. This effect disappeared at plasma glucose levels greater than 15 mM. No effect of glutathione on insulin clearance and action was observed.
Conclusions: Glutathione infusion enhances insulin secretion in elderly people with IGT.