Intron polymorphism in MYL1 gene is associated with individual cardiac trainability to endurance training in human myocardium

The aim of this study was to examine the association between polymorphism of the intron MYL1 and the genetic predisposition or trainability to endurance exercise in human myocardium.

The research consisted of two studies. The first study examined distributional differences in genotypes and alleles of MYL1 in endurance athletes (n=31) and untrained adults (N.=206). The second study examined association between the distributional differences in the genotypes and cardiac ability or trainability. Ninety-nine previously untrained men participated in an 18-week endurance training program with intensity between 95% and 105% of the ventilatory threshold. Cardiac output and cardiac index were assessed by echocardiography before and after training.

The first study demonstrated that the frequency of the genotype AA at RS1472955 was higher (0.48 vs. 0.30), and that of GG was lower (0.00 vs. 0.16) in the athlete group than that in the Control (all P<0.05, χ2 Test). The second study showed that:1) GG carriers had a lower training responsiveness than AA and GA carriers (P<0.05, z test);2) a decrease of cardiac output (10580±1461 to 10060±1421 mL/min, P<0.05, one-way ANOVA) and cardiac index (6511.8±962.3 to 6110.3±817.1 mL/m2, P<0.05) only occurred in AA carriers during low-intensity exercise (50W);3) the genotypes were significantly correlated to the magnitude of change caused by the endurance training in cardiac output (r=0.215, P<0.05, Pearson correlation) and cardiac index (r=0.221, P<0.05) in low-intensity exercise.

The findings suggested that the polymorphism of intron MYL1 was associated with endurance performance, specifically in endurance trainability, but not genetic predisposition, in human adults.