The stimulation of insulin secretion in non-insulin-dependent diabetic patients by amino acids and gliclazide in the basal and hyperglycemic state.

Sulfonylureas stimulate insulin secretion as their predominant contribution toward decreasing blood glucose in diabetic patients. We studied eight gliclazide-treated, non-insulin-dependent diabetic patients on two occasions with a protocol of basal observation for 30 minutes, a 60-minute infusion of randomized leucine or arginine, and a further 90-minute hyperglycemic clamp. Basal glucose was the same on both occasions (mean, 7.82 mmol/L for leucine v 7.79 for arginine, P = NS), and glucose levels declined to 7.50 and 7.25 mmol/L, respectively, by 30 minutes. After leucine infusion, the decline of glucose continued, but stabilized or reversed with arginine such that by the end of the infusions, glucose levels were 6.63 +/- 0.69 mmol/L for leucine and 7.62 +/- 0.67 for arginine (P < .02). Arginine caused a sharp increase in insulin secretion (from 17.8 mU/L to 43.8 mU/L in 6 minutes) at the onset of the infusion, and thereafter insulin secretion was not significantly different throughout either the amino acid or hyperglycemic clamp periods (mean, 42.1 v 44.7 mU/L, respectively, P = NS). By contrast, the leucine infusion caused little acute change in secretion, but augmented it with time from the basal period (17.2 mU/L) to the end of the infusion (29.4 mU/L). During the hyperglycemic clamp period, there was significant further augmentation of insulin secretion, increasing to 81.6 +/- 16 mU/L at the end of the study. Leucine significantly augmented insulin secretion compared with arginine (81.6 +/- 16 v 54.0 +/- 8.4 mU/L, respectively, P < .002). These data suggest that leucine is a better priming agent for sulfonylurea than arginine. Additive effects on insulin secretion may allow the use of combinations of branched chain amino acids (BCAAs) and sulfonylureas to augment insulin secretion in the presence of hyperglycemia.