ABSTRACT. There are conflicting reports associating the TGF-β1 gene -C509T polymorphism with susceptibility to IgA nephropathy. We investigated this association through a meta-analysis. Case-control studies were searched up to January 2012; the genotype frequencies in the control group were found to be consistent with Hardy-Weinberg equilibrium. Publication bias was tested by funnel plot and the Egger regression test. Eight studies, comprising 1364 cases and 1483 controls, were included. Significant heterogeneity was observed (χ 2 = 18.29, P = 0.01). Under the random-effects model, the overall odds ratio (OR) was 1.01 [95% confidence interval (95%CI) = 0.74-1.38; P = 0.94]. In the subgroup analysis based on ethnicities, no significant effect was observed in the Asian descent groups (five comparisons, OR = 0.78; 95%CI = 0.53-1.15; moderate heterogeneity between studies). However, an association was observed in the European descent groups (OR = 1.5; 95%CI = 1.15-1.96; P = 0.003; no significant heterogeneity between studies). There was no evidence of publication bias according to funnel plot and the Egger regression test (a = -2.16, P = 0.23). There was heterogeneity between studies and no clear evidence of an association between the TGF-β1 gene -C509T polymorphism and susceptibility to IgA nephropathy in the worldwide population. Subgroup analysis suggests that the TGF-β1 gene -C509T polymorphism would not be a risk factor for IgA nephropathy in Asians but might play a role in Europeans. More studies are required for definitive conclusions.

The relationship between the Pro12Ala polymorphism of PPARγ and the risk of gestational diabetes mellitus remains unresolved. Here, we attempted to resolve this inconsistency. Case-control studies pertaining to the effect of the Pro12Ala polymorphism in the PPARγ protein and risk of gestational diabetes mellitus were extracted from the HuGE, PubMed, Web of Science, CNKI, and SinoMed databases after an extensive literature search. The studies were statistically analyzed using STATA (v.12.0) software. Twelve case-control studies composed of 2968 GDM cases and 5576 controls that fulfilled the inclusion criteria were included in this meta-analysis. We identified no significant relation between the Pro12Ala polymorphism of PPAR-γ and risk of GDM, when analyzed by the allele [G vs C: odds ratio (OR) = 0.85; 95% confidence interval (CI): 0.71-1.01] and dominant (CG+GG vs CC: OR = 0.86; 95% CI: 0.72-1.03) models. Subgroup analysis by ethnicity revealed that East Asian and Middle Eastern females expressing the A allele showed reduced susceptibility to GDM. Additionally, we observed significant differences between the East Asian, Middle Eastern, and Caucasian females (P = 0.008) with respect to GDM susceptibility. The results of this meta-analysis indicated the influence of ethnicity in determining GDM susceptibility, in the presence of a Pro12Ala polymorphism in PPARγ.