0924 Vitamin D deficiency and development of diabetes

Epidemiological studies linking development of type 1 diabetes to vitamin D deficiency in humans have been around for the past decade. Evidence from case-control studies appears to be strong, showing for example that rickets during the first year of life is associated with an increased risk of type 1 diabetes during childhood (Odds Ratio 2.6) or that various forms of vitamin D supplementation reduce the risk of childhood onset type 1 diabetes (Odds Ratios ranging from one at 0.12 to several around 0.8). Vitamin D receptors have been found in beta cells as well as in cells of the immune system, leading to experiments in which high doses of 1,25dihydroxyD have been shown to prevent type 1 diabetes in animal models of the disease. The main mechanism of action is thought to be one of immune regulation since it has been demonstrated that 1,25dihydroxyD is one of the most powerful blockers of dendritic cell differentiation , blocks IL-2 secretion, inhibits lymphocyte proliferation and enhances regulator cell development. Other evidence exists in the demonstration of polymorphism in the CYP27B1 vitamin D metabolism gene in 7854 type 1 diabetics vs 8758 controls and 2774 affected families. The latter data speak more to an inherited defect of vitamin D metabolism leading to deficiency and predisposing to diabetes. There is also evidence for vitamin D deficiency in the case of type 2 diabetes with vitamin D deficient diabetics showing diminished beta cell function, or type 2 diabetics showing improved insulin responses to vitamin D supplementation. It therefore appears that vitamin D deficiency may play an important role in the pathogenesis of both forms of diabetes and greater understanding may assist with the development of strategies to prevent these major, chronic conditions

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Diabetologia 2005; 48: 1247-57
Diabetes 2007; 56: 2616-2621