Prevalence of vitamin D receptor gene polymorphisms FokI and BsmI in Brazilian individuals with type 1 diabetes and their relation to β-cell autoimmunity and to remaining β-cell function

The effect of the vitamin D receptor (VDR) gene polymorphisms on susceptibility to type 1 diabetes (T1DM) is heterogeneous. Generic factors may also influence the residual beta-cell function. We studied the frequency of VDR FokI (rs10735810) and BsmI (rs154410) polymorphisms in T1DM and their relationship to beta-cell autoimmunity and residual beta-cell function. We genotyped 189T1DM (diabetes duration. 7.1 +/- 5.4 years) and 194 controls (C) by restriction length polymorphism-polymerase chain reaction. GAD65Ab, IA2Ab, ionized calcium (iCa), HbA(1c) and fasting C-peptide (FCP) were evaluated. FCP values greater than 0.6 ng/ml were considered as residual beta-cell function. The BsmI was more frequent in the C (bb Plus Bb 79.1 C vs. 66.1% T1DM, p = 0.006), and the FokI polymorphism frequencies were similar between T1DM and C. We did not observe differences in pancreatic autoantibody profiles according to VDR genotypes. We observed that T1DM with f allele tended to have lower residual pancreatic beta-cell function (5.8% ff and Ff vs. 14.3% FF. p = 0.074) with similar age, diabetes duration, AAb positivity, HbA(1c), and iCa. Age at diagnosis of T1DM with BsmI polymorphism tended to be greater (10.7 +/- 4.9 bb and Bb vs. 9.3 +/- 4.5 years BB, p = 0.06). 111 conclusion, the results Of this Study showed no relationship between VDR polymorphisms and beta-cell autoimmunity; however we observed a relationship with age and remaining beta-cell function in Brazilian individuals with T1DM. These data may contribute to understanding the heterogeneous relationship between genetic markers and clinical features observed in this disease. (C) 2009 Society. Published by Elsevier Inc. All rights reserved.