Endogenous glucose production in type 2 diabetes: basal and postprandial. Role of diurnal rhythms.

Glycemia in type 2 diabetes is characterized by a nonsteady but stable diurnal cycle. This leads to morning fasting hyperglycemia. It arises from an underlying circadian pattern in endogenous glucose production because the metabolic clearance rate of glucose is decreased but constant. Therefore, it is important to use appropriate nonsteady tracer methods to measure this rate even under basal conditions. Postprandially, in diabetes, the endogenous glucose production continues to decrease, with only minor deviations from the slope of the basal curve. This suggests a decoupling of endogenous glucose production from the regulatory factors (insulin, glucose) that prevail under normal circumstances. As the duration of diabetes increases, metabolic clearance of glucose continues to deteriorate. This may be partially compensated by a decrease in glucose production. This rate remains, however, inappropriate because its impact on glycemia does not decline.