Insulin secretion in type 2 diabetes: clinical aspects.

Type 2 diabetes is a complex disease that involves insulin secretion abnormalities and defects in the action of insulin on its target tissues. Insulin resistance alone is not sufficient to lead to type 2 diabetes in the absence of a beta-cell defect. Patients with impaired glucose tolerance or in the early stages of type 2 diabetes always present with beta-cell secretion defects. In the early stages of type 2 diabetes, abnormalities in the physiological biphasic insulin secretion are already encountered, with very often a loss of the first phase insulin secretion. In this review, we discuss the methods to evaluate beta-cell function and their limitations, then their relationship with genetic knowledge. Currently, it is still impossible, in the absence of biological parameters characterizing the etiology of type 2 diabetes, to precisely correlate the insulin-secretion tests with the diagnosis of the disease. Autoimmune type 1 diabetes appears a useful model to study type 2 diabetes. The availability of individual genetic mapping will permit a reliable clinical evaluation and interpretation of tests of insulin secretion in the future.