Elevated CpG island methylation of GCK gene predicts the risk of type 2 diabetes in Chinese males.

The GCK gene encodes hexokinase 4, which catalyzes the first step in most glucose metabolism pathways. The purpose of our study is to assess the contribution of GCK methylation to type 2 diabetes (T2D). GCK methylation was evaluated in 48 T2D cases and 48 age- and gender-matched controls using the bisulphite pyrosequencing technology. Among the four CpG sites in the methylation assay, CpG4 and the other three CpGs (CpG1-3) were not in high correlation (r<0.5). Significantly elevated methylation levels of GCK CpG4 methylation were observed in T2D patients than in the healthy controls (P=0.004). A breakdown analysis by gender indicated that the association between CpG4 methylation and T2D was specific to males (P=0.002). It is intriguing that another significant male-specific association was also found between GCK CpG4 methylation and total cholesterol (TC) concentration (r=0.304, P=0.036). Our results showed that elevated GCK CpG4 methylation might suggest a risk of T2D in Chinese males. Gender disparity in GCK CpG4 methylation might provide a clue to elaborate the pathogenesis of T2D.