FTO gene polymorphisms (rs9939609 and rs17817449) as predictors of Type 2 Diabetes Mellitus in obese Iraqi population

Abstract

Background: The variation of the SNPs in FTO (fat mass and obesity associated) gene are improved to be associated with obesity and type 2 diabetes (T2DM) in some ethnic groups for example in European while, this consistency is controversial in Asians and there were few studies in Iraqi population about the effect of this gene on the development of T2DM in obese patients. Therefore, the objective of this study is to investigate the impact of the two common FTO gene variants in the development of T2DM in obese Iraqi patients.

Methods: A case-control study in which the FTO gene variants rs9939609 and rs17817449 were genotyping in a total of 800 individuals, 400 T2DM obese patients (patients group) and 400 healthy control obese volunteers (control group) to explore the relation of these SNPs with T2DM in obese Iraqi population. The patients group was enrolled from diabetic clinic in Al Najaf al Ashraf based on WHO guidelines of T2DM. From whole blood the DNA was extraction and genotyped by using ScaI and AlwNI enzymes respectively in the PCR-RFLP technique. Multinomial logistic regression was applied to compare the proportions of genotypes and alleles. The odd's ratio, t-test P value at 95% confidence interval were measured before and after adjustment of BMI, age and sex adjustment. The genetic power, Hardy Weinberg equilibrium and haplotype analysis were tested in the present study.

Results: It was observed that the presence of T allele in the two SNPs rs9939609 and rs17817449 in the FTO gene polymorphisms was associated with increased risk for the development of T2DM in Iraqi obese individuals. The minor allele (T) in rs9939609 was significantly higher (P=0.0001) in T2DM (31.25%) when compared with that of the control obese group (20%). The Homozygous genotype (TT) significantly (OR=3.25, CI 95% 1.87-5.64, P=0.000) increased the risk of T2DM by three folds with respect to those of wild type (AA) after adjustment for age, sex and BMI, furthermore, it was significantly increased the risk in the dominant, recessive and additive models (P=0.000,0.000 and 0.0001 respectively). The T allele in rs17817449 was also significantly higher (P=0.0001) in patients group (36.25%) when compared with that of the control group (27.25%). The Heterozygous genotype (TG) significantly (OR=2.24, CI 95% 1.65-3.04, P=0.000) increased the risk of T2DM more than two folds with respect to those of wild type (GG) after adjustment for age, sex and BMI, and it was significantly increased the risk in the dominant models (P=0.000). In the relation to the phenotypic parameters the two SNPs were significantly associated with increased BMI, LDL, insulin and HOMA-IR and a decrease the HDL levels.

Conclusion: The FTO gene polymorphisms rs9939609 and rs17817449 play a role in the in the development of insulin resistance and hence occurrence of type 2 DM in obese patients.

Keywords: BMI; FTO gene; Iraq; Polymorphism; T2DM.