Polymorphic variation in the human myostatin (GDF-8) gene and association with strength measures in the Women's Health and Aging Study II cohort

OBJECTIVES: To determine whether polymorphic variation in the myostatin gen e differentially influences the maintenance of muscle strength in older adu lts, and to find supportive evidence in a cohort of older women. DESIGN: Correlation study of polymorphic variation in a cohort of older wom en. SETTING: Representatively sampled older female population living in the eas tern half of Baltimore, Maryland. PARTICIPANTS: Participants were 286 women, age 70 to 79. Of these, 81.1% we re Caucasian, 18.8% were African American, and 0.2% were Asian or Hispanic. MEASUREMENTS: Overall strength was measured with a dynamometer and defined as the sum of the strongest measures of hip, knee, and grip strength on the dominant side. RESULTS: We identified or confirmed six myostatin polymorphic variants in t he Women's Health and Aging Study II population. Of the polymorphisms, K153 R is the most common, with an allele frequency of 0.19 in African Americans . Unadjusted mean strength by genotype suggested lower muscle strength in t hose African-American women with the R genotype compared with those with th e K genotype (K/K: 72.50 +/- 13.9 kg (n = 39) vs K/R: 67.14 +/- 11.4 kg (n = 13) vs R/R: 63.1 +/- 11.3 kg (n = 3)). After adjustment for race in a lin ear regression model, the R genotype remained associated with lower strengt h levels (P = .04). Statistical significance decreased when body mass index and race were both added to the model (P = .09). CONCLUSIONS: Recognizing that small sample size in the study of genes of mo dest effect are unlikely to yield significant differences, these data sugge st an association of the R153 allele with lower strength in high-functionin g older women, which should be studied further in a larger cohort.