[Relationship between plasma glucose level and insulin secretion in type 2 diabetic patients]

To investigate the association between insulin secretion and plasma glucose levels, and the potential effect of plasma glucose concentration on insulin secretion stimulated by glucose in patients with type 2 diabetes.

A total of 124 patients with type 2 diabetes were enrolled to undergo 75 g oral glucose tolerance test (OGTT) and insulin releasing test (IRT), 24 h after discontinuation of oral hypoglycemic agent or insulin injection. The plasma levels of glucose and insulin, effects of fasting and postprandial plasma levels of glucose and insulin, the time of maximal glucose value in OGTT, the ratio of maximal to basal glucose levels (M/Bg) were determined to assess their effects on the basal and stimulated insulin secretion.

Correlation test demonstrated that there was a significant inverse correlation between fasting blood glucose and the insulin levels measured at all the time points of IRT. The plasma glucose levels during OGTT were inversely correlated with plasma insulin levels during IRT (instead of basal insulin level), and the relations were especially significant of all the glucose levels at 5 time points during OGTT with the insulin levels at 1, 2 h, the maximal insulin level (Imax) and the maximal-to-basal insulin level ratio (M/Bi). The ratio of maximal glucose to fasting glucose was positively correlated with the insulin levels at the 5 time points and Imax. The Imax and M/Bi of the patients whose fasting glucose exceeded 11.1 mmol/L were roughly one third of those whose base blood glucose was less than 11.1 mmol/L (P<0.01); when the 2-hour glucose exceeded 16.7 mmo/L, a reduction of more than half occurred in Imax and M/Bi (P<0.01-0.05), which doubled when M/Bg was larger than 2.

Hyperglycemia (fasting or postprandial glucose) of type-2 diabetic patients has considerably destructive effect on dynamic insulin secretion.