Contribution of type 2 diabetes associated loci in the Arabic population from Tunisia: a case-control study

Background: Candidate gene and genome-wide association studies have both reproducibly identified several common Single Nucleotide Polymorphisms (SNPs) that confer type 2 diabetes (T2D) risk in European populations. Our aim was to evaluate the contribution to T2D of five of these established T2D-associated loci in the Arabic population from Tunisia. Methods: A case-control design comprising 884 type 2 diabetic patients and 513 control subjects living in the East-Center of Tunisia was used to analyze the contribution to T2D of the following SNPs: E23K in KCNJ11/Kir6.2, K121Q in ENPP1, the -30G/A variant in the pancreatic beta-cell specific promoter of Glucokinase, rs7903146 in TCF7L2 encoding transcription factor 7-like2, and rs7923837 in HHEX encoding the homeobox, hematopoietically expressed transcription factor. Results: TCF7L2-rs7903146 T allele increased susceptibility to T2D (OR = 1.25 [1.06-1.47], P = 0.006) in our study population. This risk was 56% higher among subjects carrying the TT genotype in comparison to those carrying the CC genotype (OR = 1.56 [1.13-2.16], P = 0.002). No allelic or genotypic association with T2D was detected for the other studied polymorphisms. Conclusion: In the Tunisian population, TCF7L2-rs7903146 T allele confers an increased risk of developing T2D as previously reported in the European population and many other ethnic groups. In contrast, none of the other tested SNPs that influence T2D risk in the European population was associated with T2D in the Tunisian Arabic population. An insufficient power to detect minor allelic contributions or genetic heterogeneity of T2D between different ethnic groups can explain these findings.