Variations in the HHEX gene are associated with increased risk of type 2 diabetes in the Japanese population

Recently, several groups have carried out whole-genome association studies in European and European-origin populations and found novel type 2 diabetes-susceptibility genes, fat mass and obesity associated (FTO), solute carrier family 30 (zinc transporter), member 8 (SLC30A8), haematopoietically expressed homeobox (HHEX), exostoses (multiple) 2 (EXT2), CDK5 regulatory subunit associated protein 1-like 1 (CDKAL1), cyclin-dependent kinase inhibitor 2B (p15, inhibits CDK4) (CDKN2B) and insulin-like growth factor 2 mRNA binding protein 2 (IGF2BP2), which had not been in the list of functional candidates. The aim of this study was to determine the association between single nucleotide polymorphisms (SNPs) in these genes and type 2 diabetes in participants from the Japanese population.

Sixteen previously reported SNPs were genotyped in 864 Japanese type 2 diabetes individuals (535 men and 329 women; age 63.1 ± 9.5 years (mean±SD), BMI 24.3 ± 3.9 kg/m²) and 864 Japanese control individuals (386 men and 478 women; age 69.5 ± 6.8 years, BMI 23.8 ± 3.7 kg/m²).

The SNPs rs5015480 [odds ratio (OR) = 1.46 (95% CI 1.20–1.77), p = 2.0 × 10⁻⁴], rs7923837 [OR = 1.40 (95% CI 1.17–1.68), p = 2.0 × 10⁻⁴] and rs1111875 [OR = 1.30 (95% CI 1.11–1.52), p = 0.0013] in HHEX were significantly associated with type 2 diabetes with the same direction as previously reported. SNP rs8050136 in FTO was nominally associated with type 2 diabetes [OR = 1.22 (95% CI 1.03–1.46), p = 0.025]. SNPs in other genes such as rs7756992 in CDKAL1, rs10811661 in CDKN2B and rs13266634 in SLC30A8 showed nominal association with type 2 diabetes. rs7756992 in CDKAL1 and rs10811661 in CDKN2B were correlated with impaired pancreatic beta cell function as estimated by the homeostasis model assessment beta index (p = 0.023, p = 0.0083, respectively).