Tumor necrosis factor-alpha 308 G/A polymorphism and type 2 diabetes mellitus; a systematic review and meta-analysis

Context: Type 2 diabetes mellitus (T2DM) is a multi-factorial disease with several genetic and environmental factors known to be associated with the disease. Tumor necrosis factoralpha (TNF-α) acts on fat cells associated with increased insulin resistance and obesity and its increase can be associated with the prevalence of T2DM. Previous studies on the relationship between 308 G/A polymorphism in TNF-α and T2DM were not conclusive. The aim of this study was to investigate the association between 308 G/A polymorphism in TNF-α gene and T2DM using a systematic review and meta-analysis. Evidence Acquisitions: In this systematic review we searched all published studies about the association between TNF 308 G/A polymorphism and T2DM through databases such as Scopus, Science direct, PubMed and Google scholar. A fixed or random effect model was used on the basis of heterogeneity. The heterogeneity was assessed using the I2 index. We used STATA software (version 11.2) for data analysis.
In 22 selected papers, the total number of T2DM and control subject was 8485 and 8615, respectively. Odds ratios (ORs) with 95% confidence intervals(CI) for the GG genotype polymorphism 308 G/A in total, Asian populations and whites (Caucasian) were estimated as OR=0.98 (95% CI: 0.96-1.00), OR=0.96 (95% CI: 0.93 to 0.99) and OR=1.00 (95% CI: 0.97 to 1.40). The Publication Bias/or heterogeneity was observed in this study.
The present investigation have shown that 308 G/A polymorphism GG and GA genotypes in TNF-α gene cannot be considered as predictors of T2DM (P