title: Endurance exercise training enhances local sex steroidogenesis in skeletal muscle.
abstract: OBJECTIVE
  Endurance training improves skeletal muscular function including energy metabolism and structure. Sex steroid hormones partly contribute to the exercise-induced muscular adaptations. Recently, we demonstrated that skeletal muscle contains steroidogenic converting enzymes to synthesize sex steroid hormones and an acute endurance exercise activates local steroidogenesis in skeletal muscle. However, whether chronic endurance training leads to enhanced steroidogenesis in skeletal muscle is unknown. Here, we examined changes in steroidogenic enzymes and sex steroid hormones in the skeletal muscle after chronic endurance exercise training.
  
  
  METHODS
  Eleven male rats were divided into two groups: sedentary (n = 6) and trained (n = 5). Endurance training was performed on a treadmill (30 m·min(-1), 30 min) for 5 d·wk(-1) for 12 wk. The posttraining harvesting was performed 48 h after the last exercise training.
  
  
  RESULTS
  The mRNA expressions of 3β-HSD, aromatase cytochrome P450, and 5α-reductase in the skeletal muscle of trained rats were significantly higher than those of sedentary rats (P < 0.05). The protein expressions of aromatase cytochrome P450 and 5α-reductase in the skeletal muscle of trained rats were also significantly higher than those of sedentary rats (P < 0.05). The muscular dihydrotestosterone (DHT) concentrations in the skeletal muscle of trained rats were significantly higher than those of sedentary rats (P < 0.01), but there was no change in dehydroepiandrosterone, total testosterone, free testosterone, and estradiol. Furthermore, muscle weight corrected for body weight of trained rats was moderately correlated with the level of muscular DHT concentration in trained rats (r = 0.41, P < 0.05).
  
  
  CONCLUSIONS
  Endurance exercise training enhances the muscular DHT concentration through 5α-reductase in the skeletal muscle of rats, suggesting that local bioactive androgen metabolism may participate in exercise training-induced skeletal muscular adaptation.
authors.affiliation: Senshu University, Kanagawa, Japan.
authors.forename: Katsuji
authors.initials: K
authors.lastname: Aizawa
authors.forename: Motoyuki
authors.initials: M
authors.lastname: Iemitsu
authors.forename: Seiji
authors.initials: S
authors.lastname: Maeda
authors.forename: Noboru
authors.initials: N
authors.lastname: Mesaki
authors.forename: Takashi
authors.initials: T
authors.lastname: Ushida
authors.forename: Takayuki
authors.initials: T
authors.lastname: Akimoto
mesh_terms: D000818:Animals; D013196:Dihydrotestosterone / Q000378:metabolism*; D015971:Gene Expression Regulation, Enzymologic; D007564:Japan; D008297:Male; D018482:Muscle, Skeletal / Q000378:metabolism*; D010805:Physical Conditioning, Animal / Q000502:physiology*; D010807:Physical Endurance / Q000502:physiology*; D012333:RNA, Messenger / Q000378:metabolism; D051381:Rats; D017207:Rats, Sprague-Dawley; D060888:Real-Time Polymerase Chain Reaction
chemical_list: D012333:RNA, Messenger; D013196:Dihydrotestosterone