Abstract
BackgroundFTO gene variants have been associated with obesity phenotypes in sedentary and obese populations, but rarely with skeletal muscle and elite athlete phenotypes.MethodsIn 1089 participants, comprising 530 elite rugby athletes and 559 non-athletes, DNA was collected and genotyped for the FTO rs9939609 variant using real-time PCR. In a subgroup of non-resistance trained individuals (NT; n = 120), we also assessed structural and functional skeletal muscle phenotypes using dual energy x-ray absorptiometry, ultrasound and isokinetic dynamometry. In a subgroup of rugby athletes (n = 77), we assessed muscle power during a countermovement jump.ResultsIn NT, TT genotype and T allele carriers had greater total body (4.8% and 4.1%) and total appendicular lean mass (LM; 3.0% and 2.1%) compared to AA genotype, with greater arm LM (0.8%) in T allele carriers and leg LM (2.1%) for TT, compared to AA genotype. Furthermore, the T allele was more common (94%) in selected elite rugby union athletes (back three and centre players) who are most reliant on LM rather than total body mass for success, compared to other rugby athletes (82%; P = 0.01, OR = 3.34) and controls (84%; P = 0.03, OR = 2.88). Accordingly, these athletes had greater peak power relative to body mass than other rugby athletes (14%; P = 2 x 10-6).ConclusionCollectively, these results suggest that the T allele is associated with increased LM and elite athletic success. This has implications for athletic populations, as well as conditions characterised by low LM such as sarcopenia and cachexia.
Highlights
Fat mass and obesity associated (FTO) gene variants have been associated with obesity phenotypes in sedentary and obese populations, but rarely with skeletal muscle and elite athlete phenotypes
We show that the FTO rs9939609 protective T allele may be responsible for part of the inherited component of the interindividual variability in lean mass (LM)
Elite athletes who rely greatly on LM relative to total body mass for athletic success (RU back three and centre players, in this study) seem more likely to carry a protective T allele, have higher peak muscle power output relative to body mass and are likely to selected for appropriate playing positions as a result of these and other phenotypes
Summary
FTO gene variants have been associated with obesity phenotypes in sedentary and obese populations, but rarely with skeletal muscle and elite athlete phenotypes. BMI and body mass (3-10 kg) in comparison to protective allele carriers [5, 6] This greater body mass is likely to be adipose tissue [7,8,9,10,11], there exist some suggestions of greater lean mass (LM) in addition to fat mass [9, 12] and independent of fat intake and physical activity [9]. This suggests that FTO genotype may be related to muscle properties and is supported by evidence from a large UK twin study that related FTO SNPs with body composition while controlling for lean mass and fat mass (separately and combined). Considering the attenuation of FTO-associated obesity with environmental factors and the greater FTO-associated LM reported in obese populations [9, 12], investigating LM and associated phenotypes in healthy, non-obese, nonresistance trained individuals and habitually trained elite athletes would be worthwhile
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