Associations of alpha-actinin-3 genotype with thigh muscle volume and physical performance in older adults with sarcopenia or pre-sarcopenia

Background: This cross-sectional study aimed to investigate the relationship of the ACTN3 genotype with thigh muscle volume and physical performance in older adults with sarcopenia or pre-sarcopenia. Methods: Data from 64 older Japanese adults (mean age 74.4 +/- 6.9 years, women 71.9%) with sarcopenia or presarcopenia were analyzed. Sarcopenia and pre-sarcopenia were defined using the Asian Working Group for Sarcopenia. We collected oral mucosa samples to determine the ACTN3 genotype. Thigh muscle volumes were measured using magnetic resonance imaging. Physical performance was assessed using the usual and maximum gait speed, timed up and go test, and five-repetition sit-to-stand test. Muscle strength was assessed using grip strength. Result: The ACTN3 genotype proportions were 20.3% for RR, 51.6% for RX, and 28.1% for XX. Participants with the RR genotype showed greater thigh muscle volume/ht(2) compared to those with the RX and XX ACTN3 genotypes (p < 0.05). The multiple linear regression analysis revealed that RX (p < 0.01) and XX (p < 0.01) ACTN3 genotypes, compared to RR, were associated with lower thigh muscle volume/ht(2) and with age, sex (reference; men), weight and maximum walking speed. There was no significant difference between physical performance and muscle strength between the ACTN3 genotypes. Conclusion: The ACTN3 genotype of the X allele was associated with decreased thigh muscle volume compared to the ACTN3 genotype of RR in older adults with sarcopenia or pre-sarcopenia.