title: Actn3 genotype is associated with testosterone levels of athletes.
abstract: 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 α-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.
authors.affiliation: Volga Region State Academy of Physical Culture, Sport and Tourism, Sport Technology Education Research Laboratory, Kazan, Russia ; Kazan State Medical University, Laboratory of Molecular Genetics, Kazan, Russia.
authors.forename: I I
authors.initials: II
authors.lastname: Ahmetov
authors.affiliation: DNA-Technology JSC, Moscow, Russian Federation.
authors.forename: A E
authors.initials: AE
authors.lastname: Donnikov
authors.affiliation: DNA-Technology JSC, Moscow, Russian Federation.
authors.forename: D Y
authors.initials: DY
authors.lastname: Trofimov
keywords: ACTN3; calcineurin; gene polymorphism; muscle hypertrophy; testosterone