The Myostatin A2379G Polymorphism and Muscle Strength Among African Americans

Abstract

The Myostatin A2379G (MSTN A/G) polymorphism [non-synonymous (K153R)] may influence muscle strength, particularly among African Americans. PURPOSE: We investigated the effect of the MSTN A/G polymorphism and ethnicity on the muscle strength response to a 12 wk (2 d/wk) unilateral, upper-arm resistance training (RT) program. METHODS: Subjects (n=688) (mean ± SEM, 24.0 ± 0.2 yr) were men (n=280) and women (n=408) who had not RT in the previous yr. Ethnicity was self-disclosed and categorized into African American (n=24) compared to all others (n=644) including Caucasian (n=546), Asian (n=56), Hispanic (n=34), and other (n=28). MSTN genotype groups were catagorized as AA (n=650) and AG/GG (n=39). Isometric (MVC) and dynamic (1RM) muscle strength were measured pre- and post- RT on the non-dominant arm. Repeated measure ANCOVA tested muscle strength pre- and post-RT, and ANCOVA tested muscle strength change pre- to post-RT in absolute, relative (%), and allometric (kg·kg-0.67) terms with age and body mass index as covariates. resULt s: The MSTN A/G polymorphism did not influence muscle strength pre-, post- and pre-to-post RT among the total sample (p>0.05); however, significant MSTN genotype and ethnic group interactions were found for MVC but not 1RM (p<0.05). Among MSTN AA, absolute and allometric MVC did not differ pre- and post-RT between ethnic groups (P<0.05). However, among MSTN AG/GG, MVC was greater pre- (64.4 ± 5.3 vs 44.0 ± 4.0kg) and post-RT (71.5 ± 5.1 vs 50.9 ± 3.9 kg) among African American participants compared to others (p<0.05). Similarly, allometrically scaled MVC was greater pre- (3.7 ± 0.3 vs 2.6 ± 0.2 kg·kg-0.67) and post-RT (4.1 ± 0.3 vs 3.0 ± 0.2 kg·kg-0.67) among African American volunteers compared to others (p<0.05). The MVC increase pre- to post-RT did not differ between MSTN genotype and ethnic groups (P<0.05). CONCLUSIONS: Carriers of the MSTN G allele who were African American had greater MVC but not 1RM pre- and post-RT compared to those of other ethnic affiliations. No ethnic differences were found among MSTN AA homozygotes; nor did MSTN A/G polymorphism and ethnicity influence the muscle strength response to RT. Our findings suggest that MSTN A/G polymorphism modulates inherent muscle strength among African Americans that is subsequently overridden by RT. Supported by NIH-NINDS R01 NS40606–02