The role of vitamin d receptor gene polymorphisms in obesity: a systematic review and meta-analysis

Introduction: Obesity has become a major global issue since it can increase the risk of fatal disease.  Genetic variation in the vitamin D receptor (VDR) gene is a potential candidate for obesity, though findings are inconclusive. Objectives: This meta-analysis aims to determine the association between VDR polymorphisms and obesity risk.Methods: All relevant studies from 1990 to January 2024 were screened using PubMed, Web of Science, Science Direct, and Scopus. This meta-analysis included studies meeting PROSPERO-registered eligibility criteria. Pooled odds ratios (OR) with 95% confidence intervals (CI) for six VDR gene polymorphisms (BsmI, FokI, TaqI, ApaI, and Cdx2) were generated using RevMan 5.4.Results: This meta-analysis included 23 studies with 5715 obese/overweight and 4887 non-obese individuals from China, Malaysia, Egypt, Turkey, India, Iran, UAE, Saudi Arabia, Czech Republic, Greece, USA, Denmark, Hungary, and Belgium. The findings show an association between VDR ApaI polymorphism and reduced obesity risk in homozygous models [aa vs. AA: OR=0.76, CI=0.60-0.97; P=0.03]. The TaqI variant is linked to increased obesity risk in Europeans under allelic [t vs. T: OR=1.33, CI=1.11-1.60; P=0.002], homozygous [tt vs. TT: OR=1.68, CI=1.13-2.50; P=0.010], dominant [tt vs. TT+Tt: OR=1.47, CI=1.07-2.03; P=0.02], and recessive [Tt+tt vs. TT: OR=1.43, CI=1.08-1.89; P=0.01] models.Conclusions: This meta-analysis suggests the aa genotype of VDR ApaI polymorphism may protect against obesity across populations. In Europeans, the t allele of VDR TaqI polymorphism is identified as an obesity risk factor