title: Obesity-related changes in bone structural and material properties in hyperphagic OLETF rats and protection by voluntary wheel running.
abstract: OBJECTIVE
  To examine how the development of obesity and the associated insulin resistance affect bone structural and material properties, and bone formation and resorption markers in the Otsuka Long-Evans Tokushima Fatty (OLETF) rat model.
  
  
  METHODS
  This was a 36-week study of sedentary, hyperphagic, male OLETF rats (OLETF-SED), exercise-treated OLETF rats (OLETF-EX) and sedentary non-hyperphagic controls (LETO-SED) with data collection at 13, 20, and 40 weeks of age (n = 5-8 animals per group per timepoint).
  
  
  RESULTS
  Body mass and fat (%) were significantly greater in OLETF-SED versus controls. OLETF-SED were insulin resistant at 13 and 20 weeks, with overt diabetes by 40 weeks. At 13weeks, OLETF-SED had lower total body BMC and BMD and serum P1NP compared with LETO-SED. Differences in total body BMC and BMD between OLETF-SED and LETO-SED persisted at 20 weeks, with reductions in total and cortical BMD of the tibia. OLETF-SED also had lesser femur diameter, cross-sectional area, polar moment of area, and torque at fracture than LETO-SED. By 40 weeks, OLETF-SED had elevated bone resorption and reduced intrinsic bone strength. OLETF-EX did not show the excessive weight gain, obesity, insulin resistance or diabetes observed in OLETF-SED. OLETF-EX had greater BMD than OLETF-SED, and structural and material properties of the femur were significantly increased in OLETF-EX relative to OLETF-SED and LETO-SED.
  
  
  CONCLUSIONS
  The negative skeletal effects of excessive adiposity and insulin resistance were evident early in the progressive obesity with lasting negative impacts on intrinsic and extrinsic bone strength. Exercise protected against obesity-associated skeletal changes with marked benefits on the biomechanical properties of bone.
authors.affiliation: Department of Nutrition and Exercise Physiology, University of Missouri-Columbia, Columbia, MO, USA. Electronic address: hintonp@missouri.edu.
authors.forename: Pamela S
authors.initials: PS
authors.lastname: Hinton
authors.affiliation: Department of Pediatrics, University of Arkansas for Medical Sciences, Little Rock, Arkansas, USA, Arkansas Children's Nutrition Center, Little Rock, AR, USA.
authors.forename: Kartik
authors.initials: K
authors.lastname: Shankar
authors.affiliation: Department of Nutrition and Exercise Physiology, University of Missouri-Columbia, Columbia, MO, USA.
authors.forename: Lynn M
authors.initials: LM
authors.lastname: Eaton
authors.affiliation: Research Service-Harry S Truman Memorial Veterans Medical Center, and Departments of Medicine-Division of Gastroenterology and Hepatology and Nutrition and Exercise Physiology, University of Missouri-Columbia, Columbia, MO, USA.
authors.forename: R Scott
authors.initials: RS
authors.lastname: Rector
mesh_terms: D000818:Animals; D001696:Biomechanical Phenomena; D015519:Bone Density; D001842:Bone and Bones / Q000473:pathology*; D024042:Collagen Type I / Q000097:blood; D006963:Hyperphagia / Q000378:metabolism*; D007333:Insulin Resistance; D008297:Male; D009765:Obesity / Q000378:metabolism* / Q000473:pathology; D015675:Osteocalcin / Q000097:blood; D010446:Peptide Fragments / Q000097:blood; D010805:Physical Conditioning, Animal; D011347:Procollagen / Q000097:blood; D051381:Rats; D020334:Rats, Inbred OLETF
chemical_list: D024042:Collagen Type I; D010446:Peptide Fragments; D011347:Procollagen; C047202:procollagen Type I N-terminal peptide; D015675:Osteocalcin
keywords: Bone strength; Bone turnover; Exercise; Insulin resistance; Obesity