Body muscle gain and markers of cardiovascular disease susceptibility in young adulthood: Prospective cohort study

Background: The potential benefits of gaining body muscle mass and strength for atherogenic trait levels in young adulthood, and how these compare with the potential harms of gaining body fat, are unknown. Methods: Data were from first-generation offspring of the Avon Longitudinal Study of Parents and Children. Limb lean and total fat mass indices (kg/m) were derived from dual-energy X-ray absorptiometry scans at mean ages 10y, 13y, 18y, and 25y. Maximum handgrip strength was measured using a dynamometer at 12y and 25y, expressed as absolute grip (kg) and relative grip (grip / fat mass index). Linear regression models were used to examine associations of change in standardised measures of these from 10y or 12y to 25y with 228 cardiometabolic traits measured at 25y including metabolomics-derived apolipoprotein-B lipids, glycemic traits, and blood pressure. Changes in lean and fat mass indices across sub-periods of childhood (10y to 13y), adolescence (13y to 18y), and young adulthood (18y to 25y) were also examined with traits at 25y. Results: 3,262 participants (39% male) contributed to analyses. Correlations were positive between changes in lean and fat mass indices, but negative between changes in relative grip and fat mass index. SD-unit gain in limb lean mass index from 10y to 25y was positively associated with atherogenic traits including triglycerides in very-low-density lipoproteins (VLDL). This pattern was limited to lean gain in legs, whereas lean gain in arms was inversely associated with VLDL triglycerides, insulin, glycoprotein acetyls, and others; and was also positively associated with creatinine (a muscle product and positive control). This pattern for arm lean mass index was further specific to gains occurring between 13y and 18y, e.g. -0.13 SD (95% CI = -0.22, -0.04) for VLDL triglycerides. Changes in absolute and relative grip from 12y to 25y were both positively associated with creatinine, but only change in relative grip was also inversely associated with atherogenic traits, e.g. -0.31 SD (95% CI = -0.36, -0.25) for VLDL triglycerides. Change in fat mass index from 10y to 25y was more strongly associated with atherogenic traits including VLDL triglycerides at 0.45 SD (95% CI = 0.39, 0.52); these estimates were directionally consistent across sub-periods with a tendency for larger effect sizes with more recent gains. Associations of lean, grip, and fat indices with traits were more pronounced among males than females. Conclusions: Muscle strengthening is associated with lower atherogenic trait levels in young adulthood, but at a smaller magnitude than unfavourable associations of fat gain. Associations of muscle gain with such traits appear to be smaller and limited to gains occurring in adolescence. These results suggest that body muscle is less robustly associated with markers of cardiovascular disease susceptibility than body fat and may therefore be a lower priority intervention target.