Diets rich in polyphenols and vitamin A inhibit the development of type I autoimmune diabetes in nonobese diabetic mice.

Type I juvenile diabetes mellitus is characterized by the infiltration of activated T lymphocytes and monocytes into the islets of Langerhans of the pancreas, resulting in inflammation and progressive destruction of the insulin-producing beta cells. We hypothesized that feeding nonobese diabetic (NOD) mice diets rich in polyphenols or vitamin A, both known modulators of immune function, would decrease the autoimmune inflammatory process associated with type I diabetes. NOD mice were fed a control diet (C) and diets containing either 1% freeze-dried grape powder (GP) or 250 IU vitamin A/g (VA; 0.262 micromol retinyl acetate/g) of food. Mice were considered diabetic and killed when blood glucose reached 13.9 mmol/L or greater. By approximately 7 mo of age, 71% of C mice progressed to diabetes. Incidence of diabetes was reduced to 33% (P < 0.05) and 25% (P < 0.05) in mice receiving 1% dietary grape powder and VA, respectively. Splenocytes from mice receiving both GP and VA had lower TNF-alpha production after LPS stimulation than C mice (P < 0.05). Histological analysis of pancreatic tissue showed a significant reduction in the severity of insulitis in the mice receiving GP and VA compared with C mice. These data suggest that diets rich in polyphenols or vitamin A have protective effects against autoimmune inflammatory attack of the islet beta cells and have the potential to reduce the onset and pathogenesis of autoimmune diabetes.