Effect of dietary therapy on pancreatic beta cell function in noninsulin-dependent diabetes mellitus.

Twenty-four noninsulin-dependent diabetics, who were newly diagnosed or had discontinued therapy for at least 10 months, were studied for the effect of dietary therapy on pancreatic beta cell function. The mean fasting plasma glucose (176 +/- 14 vs 212 +/- 16 mg/dl, p less than 0.01) and glycosylated hemoglobin (HbA1c, 8.6 +/- 0.5 vs 9.4 +/- 0.6%, p less than 0.001) decreased significantly after 1 month of dietary control, although there was no significant change in mean body weight (57.4 +/- 2.0 vs 57.7 +/- 2.0 kg, p greater than 0.5). The mean incremental serum C-peptide (delta CP) response to oral glucose stimulation (OGTT) increased (4.6 +/- 0.6 vs 3.5 +/- 0.7 ng/ml, p less than 0.01), but that to intravenous glucagon (GT) did not (2.5 +/- 0.2 vs 2.7 +/- 0.2 ng/ml, p greater than 0.1). In 12 patients whose glycemic control improved after dietary treatment, there was a good correlation between the decrement in fasting plasma glucose and the increment in delta CP response to OGTT (r = 0.66, p less than 0.05). In conclusion: after 1 month of dietary therapy in noninsulin-dependent diabetics, (1) the serum C-peptide response to OGTT, but not to GT, improved; (2) the beta cell secretion increased only in those patients with improved glycemic control; (3) there was a good correlation between glycemic control and beta cell function.