The lack of association between interleukin-6 gene -174 G/C polymorphism and the risk of type 1 diabetes mellitus: a meta-analysis of 18,152 subjects.

Epidemiological studies have evaluated the association between interleukin-6 (IL-6) gene -174 G/C polymorphism and type 1 diabetes mellitus (T1DM) risk, but results of different studies have been inconsistent. The present meta-analysis was therefore designed to clarify these controversies. PubMed, Embase and Web of Science were searched from the first available year to March 25, 2012, as well as hand searching of the references of identified articles were performed. All studies investigating the association between IL-6 gene -174 G/C polymorphism and T1DM risk were included. Data analyses were carried out by Review Manager 5.1.2 and Stata 11.0. Seven studies were included in the final meta-analysis, covering a total of 9697 T1DM cases and 8455 controls. The results showed no evidence for significant association between IL-6 gene -174 G/C polymorphism and T1DM risk (for C/C+C/G vs. G/G: OR=1.30, 95% CI=0.84-2.00, p=0.24; for C/C vs. C/G+G/G: OR=1.10, 95% CI=0.75-1.60, p=0.63; for C/C vs. G/G: OR=1.34, 95% CI=0.75-2.42, p=0.33; for C allele vs. G allele: OR=1.16, 95% CI=0.88-1.53, p=0.30). In addition, the similar results were obtained in the subgroup analysis based on ethnicity. In summary, the present meta-analysis suggests that IL-6 gene -174 G/C polymorphism is not associated with T1DM risk. However, due to the small sample size in most of the included studies and the selection bias existed in some studies, the results should be interpreted with caution.