Genetic determinants of habitual physical activity

Limited evidence indicates genes related to muscle performance may also influence habitual physical activity (PA). Genetic variants angiotensin-converting enzyme insertion/deletion (ACE I/D), ciliary neurotrophic factor (CNTF) 1357 A\u3eG, and brain-derived neurotrophic factor (BDNF) 196 G\u3eA, have associated with both PA and exercise performance. Additional research suggests genes involved with exercise performance, (i.e. energy metabolism, muscle function, neural function, and/or vascular function) or with diseases and conditions related to physical inactivity may also influence PA. These genes include vitamin D receptor (VDR), fat-mass and obesity related gene (FTO), and melanocortin 4 receptor (MC4R). These limited findings suggest genes related to exercise performance may influence PA. Thus, our purpose was to explore possible PA associations with genetic variants putatively involved in exercise performance. We hypothesize genetic variants thought to be involved in exercise performance will also influence habitual PA in healthy adults. Subjects (n=923) were adult men (Mean±SEM) (n=376, 23.6+0.3 yr, 25.0+0.2 kg·m−2 ) and women (n=547, 23 2+0.2 yr, 24.0+0.2 kg·m−2 ) from the FAMuSS study who have been genotyped for multiple genetic variants involved in energy metabolism, muscle, neural, and/or vascular function. Subjects underwent 12 wks (2 d/wk) of supervised unilateral resistance training (RT). Determinations of biceps muscle size (cross-sectional area, CSA) and isometric (MVC) and dynamic (1RM) strength preceded and followed RT. A subset of subjects (n=571) completed the Paffenbarger PA Questionnaire which derived these PA phenotypes: Distance walked (mi/wk); PA index (kcal/wk); energy expended performing vigorous and moderate intensity PA (kcal/wk), sports and recreation (kcal/wk); and time spent in vigorous, moderate, and light intensity PA (hr/wk), as well as sitting (hr/wk). MANCOVA tested for differences among genetic variants and PA phenotypes. Age and body mass index were covariates. In the overall sample, 56 genes associated with PA. Specifically 28 were energy metabolism genes, 18 muscle function, 8 neural function, and 13 vascular function. Previously implicated PA genes ACE, BDNF, FTO, MC4R, and VDR were among these associated genes. The multiple PA associations we report provide farther evidence that genes influencing exercise performance may also influence PA. These findings are preliminary and should be confirmed in prospective studies.