Abstract
BackgroundThe underlying mechanism of the effect of FTO genotype on body mass index (BMI) and body composition is unknown. The objective of the study was to investigate the association of FTO gene polymorphisms with anthropometric indices in adolescent boys after adjustments for dietary intake and physical activity.MethodsIn this school-based study, we enrolled 123 male adolescents without extra weight and 110 male adolescents with body mass index (BMI) higher than + 1 Z-score. The DNA samples were genotyped for the FTO gene polymorphisms by DNA Sequencing. BMI and body composition were assessed using bioelectrical impedance analyzer scale. Association of the FTO polymorphisms with Weight, height, BMI, body fat percent and skeletal muscle percent were investigated. Data on potential confounders (calorie intake and physical activity) were collected through the use of pre-tested questionnaires.ResultsAdolescents with higher BMI and body fat percent and lower skeletal muscle percent were more likely to have a newly found haplotype of rs9930506, rs9930501 & rs9932754 (GGT) in the first intron of the FTO with complete linkage disequilibrium (LD) compared with those with the lower BMI (6.15;2.28–16.63), body fat percent (9.54;0.92–47.44) and higher skeletal muscle percent (9.26;1.85–46.38). This association was not changed after controlling for age. Additional adjustments for calorie intake and physical activity did not alter the association.ConclusionsA haplotype in the first intron of the FTO gene had a strong association with obesity indices in adolescent boys after adjustments for calorie intake and physical activity. It’s suggested that the FTO genotype exert its effects on adolescents’ anthropometric indices as haplotype and through mechanisms other than changes in calorie intake and expenditure.Trial registrationThis paper reports the first phase of a comprehensive interventional study (Interactions of Genetics, lifestyle and anthropometrics study or IGLA study) and is retrospectively registered in the Iranian Registry of Clinical Trials as IRCT2016020925699N2. Date registered: April 24, 2016. (http://www.irct.ir/searchresult.php?id=25699&number=2).
Highlights
The underlying mechanism of the effect of Fat mass and obesity associated (FTO) genotype on body mass index (BMI) and body composition is unknown
The FTO genotype The A and G allele frequencies for these polymorphisms were 0.6 and 0.4, respectively, and the genotypes were in Hardy–Weinberg equilibrium
A complete linkage disequilibrium (LD) in a haplotype block composed of 3 Single-nucleotide polymorphisms (SNPs) (rs993275, rs9930506, rs9930501) encompassing 40 bp in all students was identified
Summary
The underlying mechanism of the effect of FTO genotype on body mass index (BMI) and body composition is unknown. Still there is no general agreement on the underlying mechanisms of effects of FTO on body weight. Recent studies showed that polymorphisms of FTO play key role on control of food intake. Many polymorphisms of the FTO gene are studied for the possible association with obesity. Some of these SNPs are rs178117449, rs9939609, rs3751812, rs1421085, rs9930506, and rs7202116 [14] and the recent studies have shown that the genotype of the rs9930506 polymorphism has the strongest influence on body weight and body composition [14, 15]
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