La glycémie postprandiale : du normal au pathologique*

Postprandial glucose excursions contribute to both chronic sustained hyperglycaemia and acute glucose fluctuations from peaks to nadirs. Lessons from physiology indicate that non diabetic persons spend half of their life in postprandial states. However, in normal subjects, postmeal glucose increments remain limited in duration and magnitude. Progression from normal stages to frank diabetes is a stepwise process. The first step from normal to impaired glucose tolerance (IGT) is characterised by a glycaemic deterioration limited to the postprandial period. The second step from IGT to diabetes corresponds to a loss of glycaemic control at the end of the night (dawn phenomenon) followed by a progressive increase in fasting glucose and by an additional deterioration of postmeal glucose excursions. This progression is explained by three main disorders (the biological triumvirat): a relentless defect in β-cell function, an insulin resistance that progresses over the time course of the disease, and an hepatic glucose overproduction that reaches a peak at the end of the overnight fast. These observations indicate that the monitoring of glycaemic disorders in type 2 diabetes should include the three parameters of the "glucose triad": the HbA1c, the fasting glucose and the postmeal values. More generally, the assessment of glycaemic profiles over daytime is helpful for choosing and tailoring the treatments according to whether the prandial or the basal hyperglycaemia is predominant.