Diabète de type 1 et environnement.

Abstract

Le diabète de type 1 est une maladie auto-immune dirigée contre les cellules β pancréatiques survenant sur un terrain génétique de susceptibilité. Les mécanismes du déclenchement de la maladie auto-immune ne sont pas connus mais semblent pouvoir intervenir très tôt dans la vie. La survenue de l’hyperglycémie est précédée d’une longue phase préclinique. L’absence de concordance complète pour la maladie chez les jumeaux monozygotes et l’augmentation rapide de l’incidence du diabète de type 1 suggèrent que des facteurs d’environnement peuvent moduler les stades initiaux et l’évolution de la maladie auto-immune.

Type 1 diabetes is a chronic autoimmune disease directed towards the pancreatic β-cells and resulting in absolute insulin deficiency. Its long preclinical stage is characterized by specific markers of ongoing autoimmune disease. Type 1 diabetes occurs in genetically predisposed individuals. However, in monozygotic twins, the concordance rate for the disease is only partial. This, and the rapid increase in the incidence of type 1 diabetes over the recent years suggest that environmental factors modulate the onset or the progression of the autoimmune process. Many putative agents, particularly viruses and diet factors, have been suspected, mainly on the basis of epidemiological studies. Among viruses, enteroviruses, particularly coxsackie, may either initiate the disease by materno-foetal infection or enhance autoimmune disease through bystander activation. A short duration of breast-feeding and the early introduction of cow's milk have been also epidemiologically involved in the onset of type 1 diabetes, but the mechanisms of this association remain elusive. The identification of environmental promoters of type 1 diabetes is a difficult task because various agents may be implicated, and some may be also protective as shown in experimental models. Prospective studies in at-risk individuals are needed to identify common environmental triggers of type 1 diabetes before primary prevention may be envisaged.