Association of tumor necrosis factor alpha promoter polymorphism (TNF-α 238 G/A and TNF-α 308 G/A) with diabetic mellitus, diabetic retinopathy and diabetic nephropathy: a meta-analysis.

AIM: To examine the association between tumor necrosis factor alpha (TNF-α) polymorphism and risk for diabetic mellitus (DM), diabetic retinopathy (DR) and diabetic nephropathy (DN).
METHODS: Systematic searches of electronic databases such as PubMed, Medline, Web of knowledge and CNKI, as well as hand searching of the references of identified articles were performed. A total of 8979 subjects in 14 studies from 12 eligible publications were included in this meta-analysis (6 of 12 eligible studies were analyzed for TNF 238 G/A polymorphism and Type 1 DM (T1DM), 5 of 12 were analyzed for TNF 308 G/A polymorphism and DR in Type 2 DM (T2DM), and 3 of 12 were analyzed for TNF 308 G/A polymorphism and DN in T2DM). Pooled odds ratio (OR) with 95% confidence interval (CI) was calculated using fixed or random effects model. The I(2) statistics were used to evaluate between-study heterogeneity. Sensitivity analysis was also performed.
RESULTS: The results showed no evidence for significant association between TNF 238 G/A polymorphism and T1DM (for AA + GA versus GG: OR = 0.95, 95% CI = 0.48-1.88, p = 0.89), and also no association between TNF 308 G/A polymorphism and DR and DN risk in T2DM (for AA + GA versus GG: OR = 1.04, 95% CI = 0.87-1.25, p = 0.68; OR = 0.88, 95% CI = 0.71-1.08, p = 0.21; respectively). In addition, the similar results were obtained in the subgroup analysis based on the ethnicity.
CONCLUSIONS: In summary, results from this meta-analysis suggest that the TNF 238 G/A polymorphism was not associated with T1DM. No association between TNF 308 G/A polymorphism and DR and DN in T2DM was detected.