Single Nucleotide Polymorphisms in Genes Encoding LKB1 (STK11), TORC2 (CRTC2) and AMPK Alpha2-subunit (PRKAA2) and Risk of Type 2 Diabetes

The LKB1-AMPK-TORC2 signaling pathway controls glucose homeostasis in the liver, and mediates therapeutic effects of insulin-sensitizing antidiabetic agents. To examine whether genetic variations in genes encoding components of this signaling pathway contribute to increased susceptibility to type 2 diabetes, we screened STK11 (LKB1) and CRTC2 (TORC2) genes for genetic variants and conducted a case-control study in 1787 unrelated Japanese individuals. Additionally, the previously described association between the PRKAA2 (AMPK alpha2-subunit) haplotype and type 2 diabetes was tested for replication. We observed associations of nominal significance with two SNPs, an intronic SNP in the STK11 (rs741765; OR 1.33, 95% CI 1.05-1.67, p=0.017, under a recessive genetic model), and a non-synonymous SNP in the CRTC2 (6909C>T: Arg379Cys; OR 3.01, 95% CI 1.18-7.66, p=0.016, under a dominant model), although neither withstood correction for multiple testing. We were unable to replicate the association between the PRKAA2 haplotype and type 2 diabetes: however, in the single SNP evaluation, an intronic PRKAA2 SNP (rs1418442) that had previously been reported to be associated with serum cholesterol levels in Caucasian females showed a weak association (OR 0.62, 95% CI 0.40-0.96, p=0.030, under a recessive model). Among the three genes investigated herein, gene-gene (SNP-SNP) interaction studies provided evidence for an interaction between STK11 and CRTC2 influencing susceptibility to type 2 diabetes. Our findings suggest that genetic variants of LKB1-AMPK-TORC2 pathway components may exert a weak influence on the occurrence of type 2 diabetes in Japanese.