title: Bone plasticity in response to exercise is sex-dependent in rats.
abstract: OBJECTIVE
  To characterize the potential sexual dimorphism of bone in response to exercise.
  
  
  METHODS
  Young male and female Wistar rats were either submitted to 12 weeks of exercise or remained sedentary. The training load was adjusted at the mid-trial (week 6) by the maximal speed test. A mechanical test was performed to measure the maximal force, resilience, stiffness, and fracture load. The bone structure, formation, and resorption were obtained by histomorphometric analyses. Type I collagen (COL I) mRNA expression and tartrate-resistant acid phosphatase (TRAP) mRNA expression were evaluated by quantitative real-time PCR (qPCR).
  
  
  RESULTS
  The male and female trained rats significantly improved their maximum speed during the maximal exercise test (main effect of training; p<0.0001). The male rats were significantly heavier than the females, irrespective of training (main effect of sex; p<0.0001). Similarly, both the weight and length of the femur were greater for the male rats when compared with the females (main effect of sex; p<0.0001 and p<0.0001, respectively). The trabecular volume was positively affected by exercise in male and female rats (main effect of training; p = 0.001), whereas the trabecular thickness, resilience, mineral apposition rate, and bone formation rate increased only in the trained males (within-sex comparison; p<0.05 for all parameters), demonstrating the sexual dimorphism in response to exercise. Accordingly, the number of osteocytes increased significantly only in the trained males (within-sex comparison; p<0.05). Pearson's correlation analyses revealed that the COL I mRNA expression and TRAP mRNA expression were positively and negatively, respectively, related to the parameters of bone remodeling obtained from the histomorphometric analysis (r = 0.59 to 0.85; p<0.05).
  
  
  CONCLUSIONS
  Exercise yielded differential adaptations with respect to bone structure, biomechanical proprieties, and molecular signaling in male and female rats.
authors.affiliation: Nephrology Division, Medical School, University of São Paulo, São Paulo, Brazil.
authors.forename: Wagner S
authors.initials: WS
authors.lastname: Vicente
authors.forename: Luciene M
authors.initials: LM
authors.lastname: dos Reis
authors.forename: Rafael G
authors.initials: RG
authors.lastname: Graciolli
authors.forename: Fabiana G
authors.initials: FG
authors.lastname: Graciolli
authors.forename: Wagner V
authors.initials: WV
authors.lastname: Dominguez
authors.forename: Charles C
authors.initials: CC
authors.lastname: Wang
authors.forename: Tatiana L
authors.initials: TL
authors.lastname: Fonseca
authors.forename: Ana P
authors.initials: AP
authors.lastname: Velosa
authors.forename: Hamilton
authors.initials: H
authors.lastname: Roschel
authors.forename: Walcy R
authors.initials: WR
authors.lastname: Teodoro
authors.forename: Bruno
authors.initials: B
authors.lastname: Gualano
authors.forename: Vanda
authors.initials: V
authors.lastname: Jorgetti
mesh_terms: D000135:Acid Phosphatase / Q000235:genetics / Q000378:metabolism; D000818:Animals; D015415:Biomarkers / Q000378:metabolism; D024042:Collagen Type I / Q000235:genetics / Q000378:metabolism; D004548:Elasticity; D005260:Female; D005269:Femur / Q000033:anatomy & histology / Q000166:cytology / Q000502:physiology*; D050723:Fractures, Bone / Q000517:prevention & control; D015870:Gene Expression; D006244:Hardness; D007527:Isoenzymes / Q000235:genetics / Q000378:metabolism; D008297:Male; D010011:Osteocytes / Q000166:cytology / Q000502:physiology*; D010805:Physical Conditioning, Animal / Q000502:physiology*; D012333:RNA, Messenger / Q000235:genetics* / Q000378:metabolism; D051381:Rats; D017208:Rats, Wistar; D012737:Sex Factors; D000071681:Tartrate-Resistant Acid Phosphatase
chemical_list: D015415:Biomarkers; D024042:Collagen Type I; D007527:Isoenzymes; D012333:RNA, Messenger; D000135:Acid Phosphatase; D000071681:Tartrate-Resistant Acid Phosphatase