Association between the T869C polymorphism of transforming growth factor-beta 1 and diabetic nephropathy: a meta-analysis

Accumulating evidence has suggested that transforming growth factor-beta 1 (TGF-β1) is a functional candidate for diabetic nephropathy (DN). However, association studies investigating the relationship of TGF-β1 gene T869C polymorphism and DN generate inconsistent results. To comprehensively clarify this issue, we performed a meta-analysis to evaluate the impact of the polymorphism on DN. We searched studies from PubMed and China National Knowledge Infrastructure (CNKI) through March 2011. Pooled ORs were calculated under allelic/additive/dominant/recessive/over-dominant genetic models. Nine studies with 1776 cases and 1740 controls were included. Our results indicated that C allele of T869C conferred a significantly increased risk of DN compared with T allele (OR = 1.25, 95% CI: 1.05–1.48) for allelic contrast. Similar results were also found under additive (OR = 1.57, 95% CI: 1.10–2.23) and dominant (OR = 1.40, 95% CI: 1.06–1.85) genetic models. However, subgroup analyses stratified by types of diabetes showed that significantly increased risks were only observed in type 2 diabetic patients, and the association persistently existed in further analysis for Asian populations. As for type 1 diabetic subjects, no significant association was detected under all the genetic models (P > 0.05). Our meta-analysis suggested that the TGF-β1 T869C polymorphism conferred an elevated risk of DN. However, significant associations were only observed in type 2 diabetic patients.