[Metabolic markers of type I prediabetes]

Studies of the early metabolic alterations of type 1 diabetes aim at the quantification of the residual beta cell mass and its rate of destruction, as well as identifying predictive markers of insulin dependency. The first phase of insulin secretion during the intravenous glucose tolerance test has been mostly investigated. The test is satisfactorily reproducible provided it is standardized. The age and the insulin sensitivity of the subject should be taken into account when interpreting the results. Moreover, functional phenomenon that may be reversible may take part in the observed alterations of insulin secretion. The abolition of the first phase of insulin secretion always precedes insulin dependency, and has a good positive predictive value in subjects with anti-islet cell antibodies. However, some pre-diabetic subjects already have a low first phase insulin response from the first examination, which does not favour the hypothesis of a linear beta cell destruction and points to the heterogeneity of this stage of the disease. Conversely, profound metabolic alterations have been described with no progression towards insulin dependency, suggesting remission of the autoimmune process. The predictive value of the alterations of insulin secretion using other stimulus will be assessed by ongoing studies.