Vitamin D status and the predictors of circulating T helper 1-type immunoglobulin levels in Iranian subjects with type 1 diabetes and their siblings: A case-control study
T. R. Neyestani
A. A. Saboor Yaraghi
M. R. Eshraghian
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Background: Vitamin D status has been linked to both T helper (Th)1/Th2 balance and susceptibility to type 1 diabetes (T1D). The present study aimed to evaluate vitamin D status and its relation to Th1/Th2 balance in subjects with T1D, their siblings and unrelated healthy controls during autumn and winter 2008-2009. Methods: A case-control study was conducted on subjects with T1D (n 1 =60) and two control groups comprising nondiabetic siblings (n 2 =60) and unrelated healthy controls (n 3 =60). Assessments of dietary intake, anthropometry, intact parathyroid hormone (iPTH) and 25(OH)D were performed. Serum levels of immunoglobulin (Ig)G 2 and IgE, as well as the IgG2/IgE ratio, were used to evaluate Th1/Th2 balance. Vitamin D status was defined based on circulating 25(OH)D as deficiency: < 27.5nm; insufficiency 27.5≤25(OH)D < 50nm; and sufficiency ≥50nm. Results: Vitamin D status did not differ significantly among the groups. Similarly, no significant difference in 25(OH)D, iPTH, IgG 2 , IgE and IgG 2 /IgE was found. In multiple regression analysis of pooled data, PTH and body mass index were the predictors of IgG 2 /IgE. In the diabetic group, both PTH and age and, in siblings, PTH only, were the predictors of IgG 2 /IgE ratio. Conclusions: These data suggest PTH as the major predictor of immune deviance towards the Th1 response in both type 1 diabetic subjects and their siblings. Considering that the active form of vitamin D suppresses PTH prod uction, it is hypothesised that vitamin D replenishment of just those who are genetically prone to the disease (i.e. siblings) may be regarded as a preventive measure against T1D. © 2012 National Nutrition and Food Technology Research Institute. Journal of Human Nutrition and Dietetics © 2012 The British Dietetic Association Ltd.