BackgroundLifestyle factors such as diet and physical activity have been shown to modify the association between fat mass and obesity–associated (FTO) gene variants and metabolic traits in several populations; however, there are no gene-lifestyle interaction studies, to date, among Asian Indians living in India. In this study, we examined whether dietary factors and physical activity modified the association between two FTO single nucleotide polymorphisms (rs8050136 and rs11076023) (SNPs) and obesity traits and type 2 diabetes (T2D).MethodsThe study included 734 unrelated T2D and 884 normal glucose-tolerant (NGT) participants randomly selected from the urban component of the Chennai Urban Rural Epidemiology Study (CURES). Dietary intakes were assessed using a validated interviewer administered semi-quantitative food frequency questionnaire (FFQ). Physical activity was based upon the self-report. Interaction analyses were performed by including the interaction terms in the linear/logistic regression model.ResultsThere was a significant interaction between SNP rs8050136 and carbohydrate intake (% energy) (Pinteraction = 0.04), where the ‘A’ allele carriers had 2.46 times increased risk of obesity than those with ‘CC’ genotype (P = 3.0 × 10−5) among individuals in the highest tertile of carbohydrate intake (% energy, 71 %). A significant interaction was also observed between SNP rs11076023 and dietary fibre intake (Pinteraction = 0.0008), where individuals with AA genotype who are in the 3rd tertile of dietary fibre intake had 1.62 cm lower waist circumference than those with ‘T’ allele carriers (P = 0.02). Furthermore, among those who were physically inactive, the ‘A’ allele carriers of the SNP rs8050136 had 1.89 times increased risk of obesity than those with ‘CC’ genotype (P = 4.0 × 10−5).ConclusionsThis is the first study to provide evidence for a gene-diet and gene-physical activity interaction on obesity and T2D in an Asian Indian population. Our findings suggest that the association between FTO SNPs and obesity might be influenced by carbohydrate and dietary fibre intake and physical inactivity. Further understanding of how FTO gene influences obesity and T2D through dietary and exercise interventions is warranted to advance the development of behavioral intervention and personalised lifestyle strategies, which could reduce the risk of metabolic diseases in this Asian Indian population.Electronic supplementary materialThe online version of this article (doi:10.1186/s12986-016-0098-6) contains supplementary material, which is available to authorized users.
Objective: To investigate the association of insulin receptor substrate-2 (IRS-2) G1057D polymorphism with type 2 diabetes and obesity in Asian Indians. Methods: The study comprised of 1193 normal glucose tolerant (NGT) subjects and 1018 subjects with type 2 diabetes, aged X20 years with an average body mass index of 23.774.6 and 25.374.2 kg/m 2 , respectively. The subjects were unrelated and randomly selected from the Chennai Urban Rural Epidemiology Study (CURES), a population-based study in Chennai in southern India. The G1057D polymorphism of the IRS-2 gene was genotyped using PCR-RFLP assay. Results: The genotype frequency of the IRS-2 G1057D polymorphism was significantly different between the NGT and type 2 diabetic groups (P ¼ 0.0007) in the total study subjects and among the obese subjects (P ¼ 0.00007). Logistic regression analysis showed that the DD genotype showed an increased susceptibility to diabetes with an odds ratio (adjusted for age and sex) of 2.19 (95% CI: 1.34-3.57, P ¼ 0.002) when compared to the GG þ GD genotype, among the obese subjects, but not in non obese subjects. In order to explore possible interaction with obesity, logistic regression analysis was performed and the coefficient corresponding to the interaction parameter (genotype  obesity) was significant (P ¼ 0.0001). Conclusion: In Asian Indians, the DD genotype increases susceptibility to type 2 diabetes by interacting with obesity.
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