Loss of early insulin secretion leads to postprandial hyperglycaemia

Aims/Hypothesis. A loss of early-phase insulin response is common in Type 2 diabetic patients and in people with impaired glucose metabolism. It is hypothesized that this alteration is not simply a marker for the risk of developing diabetes, rather it is a an important pathogenetic mechanism causing excessive postprandial hyperglycaemia. Methods. Relevant literature on the epidemiology, physiopathology, and therapeutic intervention related to loss of early insulin secretion and postprandial hyperglycaemia has been analysed. Results. In response to intravenous glucose, insulin secretion is biphasic. This behaviour translates as a rapid release of insulin into the blood stream in response to the ingestion of carbohydrates or a mixed meal. The rapid increase in portal insulin concentration and the avid binding of the hormone to its receptor on liver cell membranes, account for a prompt suppression of endogenous glucose production and reduction of the rate of increase in plasma glucose concentrations. This has been supported by experimental studies carried out in both animals and humans: the selective abolition of early insulin secretion in healthy subjects results in impaired glucose tolerance, excessive glucose excursions, and possible hampering of the thermic effects of ingested carbohydrates. In nondiabetic subjects, the loss of early insulin secretion is a determinant for developing diabetes. The critical role of the early-phase insulin response in determining postprandial hyperglycaemia, is supported by an amelioration of glucose tolerance by restoring the acute rise in plasma insulin concentrations after the ingestion of both glucose and a mixed meal. This amelioration in plasma glucose profile can prevent late hyperglycaemia and hyperinsulinaemia. Conclusion/interpretation. Therapeutic approaches aimed at restoring a physiological pattern of insulin secretion could prove effective in reducing postprandial glucose excursions particularly in the early stage of Type 2 diabetes.