The role of the genetic variants IRX3 rs3751723 and FTO rs9939609 in the obesity phenotypes of children and adolescents.

OBJECTIVE: We investigated the association of IRX3 SNP rs3751723 with anthropometric characteristics related to adiposity and potential relationships with FTO SNP rs9939609 in a population of Brazilian children and adolescents.

METHODS: A total of 871 children and adolescents between 7 and 17 years of age were recruited. Adiposity measurements and biochemical parameters were assessed. The variants were genotyped by real-time PCR. Analysis of multiple linear regression, multiple logistic regression, and generalised multifactor dimensionality reduction (GMDR) adjusted for sex, age and ethnicity were applied to test the polymorphisms association with obesity-related phenotypes and the interaction between them.

RESULTS: The analyses showed that IRX3 was associated with obesity and fat percentage (BF%). An association of FTO rs9939609 with body mass index (BMI) Z-Score and with waist circumference (WC) was detected. The odds ratios (OR) showed that IRX3 rs3751723 was associated with risk of obesity in additive model (p=0.017), recessive model (p=0.016) and with high BF% in all models. FTO rs9939609 was associated with risk of obesity in additive model (p=0.031), recessive (p=0.033) and with altered WC in all models. GMDR-based predictive models for the risk of obesity, altered WC and high BF% adjusted by age, ethnicity and sex suggested no interaction of the two loci.

CONCLUSIONS: The genetic variants rs3751723 and rs9939609 have an influence on the characteristics of adiposity; however, the effects of IRX3 and FTO investigated polymorphisms are independent in relation to adiposity parameters.