Vitamin D-associated polymorphisms are related to insulin resistance and vitamin D deficiency in polycystic ovary syndrome

Introduction Women with polycystic ovary syndrome (PCOS) frequently suffer from metabolic disturbances including insulin resistance (IR), which might be related to vitamin D metabolism. We aimed to investigate the association of polymorphisms in the vitamin D receptor ( VDR ) gene as well as vitamin D level-associated genes with metabolic and endocrine parameters in PCOS women. Moreover, we examined whether there are associations with PCOS susceptibility. Methods Metabolic, endocrine, and anthropometric measurements and oral glucose tolerance tests were performed in 545 PCOS and 145 control women. Genotyping of VDR ( Cdx2 , Bsm-I , Fok-I , Apa-I , and Taq-I ), GC , DHCR7 , and CYP2R1 polymorphisms was performed. Results 25-Hydroxyvitamin D (25(OH)D) levels showed significant negative correlation with IR and positive correlation with insulin sensitivity ( P <0.05 for all) in PCOS women. In PCOS women, the VDR Cdx2 ‘AA’ genotype was associated with lower fasting insulin ( P =0.039) and homeostatic model assessment-IR ( P =0.041) and higher quantitative insulin-sensitivity check index ( P =0.012) and MATSUDA index ( P =0.003). The VDR Apa-I ‘AA’ genotype was associated with lower testosterone ( P =0.028) levels. In PCOS women, 170 women (31.2%) presented with 25(OH)D levels <20 ng/ml. PCOS women carrying the GC ‘GG’ genotype and the DHCR7 ‘GG’ genotype had a significantly higher risk for 25(OH)D levels <20 ng/ml (OR 2.53 (1.27–5.06), P =0.009, and OR 2.66 (1.08–6.55), P =0.033 respectively) compared with PCOS women carrying the GC ‘TT’ genotype and DHCR ‘TT’ genotype in multivariate analyses. We observed no association of genetic variations and PCOS susceptibility. Conclusion VDR and vitamin D level-related variants are associated with metabolic and endocrine parameters including 25(OH)D levels in PCOS women.