Association of myostatin gene polymorphism with echocardiographic and muscular ultrasonographic measurements in Hungarian thoroughbreds horses.

The g.66493737C/T polymorphism of the myostatin gene (MSTN) majorly influences muscle fiber composition and best race distance of Thoroughbreds. Thus, a better understanding of this process may lead to superior genetic exploitation for maximizing Thoroughbred athletic potential. Our objective is to investigate whether myostatin genotypes are associated with muscular development and cardiac variables of Thoroughbreds. Echocardiography and muscular ultrasonography were performed on three groups having C/C, C/T, and T/T genotypes, respectively. Each group consisted of 22 animals. Homogeneity of variance between the groups was checked by Levene's test. Multivariate analysis of variance was applied to determine differences in measured variables vs. MSTN genotypes. Fascicle length of anconeus and thickness of triceps brachii muscles showed significant differences between C/C and T/T genotypes (pFascicle-length-of-anconeus  = 0.004, pthickness-of-triceps-brachii  < 0.001). According to the primary outcome, there are associations between myostatin genotypes and cardiac variables. Aortic diameter at the sinus of Valsalva (end-diastole and end-systole) and aortic diameter at the valve (end-systole) indicated significant differences between C/C and T/T genotypes (paortic-diameter-at-the-sinus-of-Valsalva-end-diastole  = 0.015, paortic-diameter-at-the-sinus-of-Valsalva-end-systole  = 0.011, paortic-diameter-at-the-valve-end-systole  = 0.014). Pearson correlation effect sizes were rFascicle-length-of-anconeus  = 0.460, rthickness-of-triceps-brachii  = 0.590, raortic-diameter-at-the-sinus-of-Valsalva-end-diastole  = 0.423, raortic-diameter-at-the-sinus-of-Valsalva-end-systole  = 0.450, and raortic-diameter-at-the-valve-end-systole  = 0.462. C/C genotypes gave 22.1, 12.2, 6.3, 6.0, and 6.7% higher values compared to T/T genotypes, respectively. Differences regarding aortic diameter between genotype groups support the hypothesis that C/C animals have consequently increased cardiac output and aerobic capacity.