ACTN3 genotype is associated with testosterone levels of athletes

α-Actinin-3 (ACTN3) has been proposed to regulate skeletal muscle differentiation and hypertrophy through its interaction with the signalling protein calcineurin. Since the inhibition of calcineurin potentiates the production of testosterone, we hypothesized that a-actinin-3 deficiency (predicted from the ACTN3 XX genotype) may influence serum levels of testosterone of athletes. Objective: To investigate the association of ACTN3 gene R577X polymorphism with resting testosterone levels in athletes. Methods: A total of 209 elite Russian athletes from different sports (119 males, 90 females) were genotyped for ACTN3 gene R577X polymorphism by real-time PCR. Resting testosterone was examined in serum of athletes using enzyme immunoassay. Results: The mean testosterone levels were significantly higher in both males and females with the ACTN3 R allele than in XX homozygotes (males: RR: 24.9 (5.7), RX: 21.8 (5.5), XX: 18.6 (4.9) ng · mL-1, P = 0.0071; females: RR: 1.43 (0.6), RX: 1.21 (0.71), XX: 0.79 (0.66) ng · mL -1, P = 0.0167). Conclusions: We found that the ACTN3 R allele was associated with high levels of testosterone in athletes, and this may explain, in part, the association between the ACTN3 RR genotype, skeletal muscle hypertrophy and power athlete status

SOD2 gene polymorphism and muscle damage markers in elite athletes

Exercise-induced oxidative stress is a state that primarily occurs in athletes involved in high-intensity sports when pro-oxidants overwhelm the antioxidant defense system to oxidize proteins, lipids, and nucleic acids. During exercise, oxidative stress is linked to muscle metabolism and muscle damage, because exercise increases free radical production. The T allele of the Ala16Val (rs4880 C/T) polymorphism in the mitochondrial superoxide dismutase 2 (SOD2) gene has been reported to reduce SOD2 efficiency against oxidative stress. In the present study we tested the hypothesis that the SOD2 TT genotype would be underrepresented in elite athletes involved in high-intensity sports and associated with increased values of muscle and liver damage biomarkers. The study involved 2664 Caucasian (2262 Russian and 402 Polish) athletes. SOD2 genotype and allele frequencies were compared to 917 controls. Muscle and liver damage markers [creatine kinase (CK), creatinine, alanine transaminase (ALT), aspartate transaminase (AST), alkaline phosphatase (ALP)] were examined in serum from 1444 Russian athletes. The frequency of the SOD2 TT genotype (18.6%) was significantly lower in power/strength athletes (n = 524) compared to controls (25.0%, p = 0.0076) or athletes involved in low-intensity sports (n = 180; 33.9%, p < 0.0001). Furthermore, the SOD2 T allele was significantly associated with increased activity of CK (females: p = 0.0144) and creatinine level (females: p = 0.0276; males: p = 0.0135) in athletes. Our data show that the SOD2 TT genotype might be unfavorable for high-intensity athletic events