Diets rich in polyphenols and vitamin A inhibit type I autoimmune diabetes in non‐obese diabetic mice

Abstract

Type I juvenile diabetes is characterized by infiltration of activated T lymphocytes and monocytes into the islets of Langerhans of the pancreas (insulitis), resulting in the inflammation and progressive destruction of the insulin-producing beta cells. We hypothesized that feeding non-obese diabetic (NOD) mice diets rich in polyphenols or vitamin A, both known modulators of immune function, would decrease the inflammatory process associated with type I diabetes. NOD mice were fed control diet, diet containing 1% freeze-dried grape powder rich in polyphenols, or diet with 250 IU vitamin A/gram of food. Mice were euthanized when the blood glucose levels reached 250 mg/dl or greater. By approximately seven months of age, 71% of control mice progressed to diabetes. However, the incidence of diabetes was 33% in mice receiving 1% dietary grape powder and 25% in mice receiving vitamin A enriched diet. Splenocytes from mice were stimulated with mitogens and assayed for cytokine production. A statistically significant decrease in TNF-alpha production by the monocytic population in mice that received grape powder was observed. Mice receiving vitamin A showed a significant reduction of TNF-alpha production by both the T lymphocytic and monocytic populations. Histological analyses of pancreatic tissue showed a reduction in the severity of insulitis in the mice receiving the grape powder and vitamin A enriched diets compared to control mice. These data suggest that diets rich in polyphenols or vitamin A may have potential for reducing the onset and pathogenesis of autoimmune diabetes. Supported by NIH RO1AI50863 and USDA CRIS 5306-51530-013-00D.