title: Diet-induced obesity differentially regulates behavioral, biomechanical, and molecular risk factors for osteoarthritis in mice.
abstract: BACKGROUND
  Obesity is a major risk factor for the development of osteoarthritis in both weight-bearing and nonweight-bearing joints. The mechanisms by which obesity influences the structural or symptomatic features of osteoarthritis are not well understood, but may include systemic inflammation associated with increased adiposity. In this study, we examined biomechanical, neurobehavioral, inflammatory, and osteoarthritic changes in C57BL/6J mice fed a high-fat diet.
  
  
  METHODS
  Female C57BL/6J mice were fed either a 10% kcal fat or a 45% kcal fat diet from 9 to 54 weeks of age. Longitudinal changes in musculoskeletal function and inflammation were compared with endpoint neurobehavioral and osteoarthritic disease states. Bivariate and multivariate analyses were conducted to determine independent associations with diet, percentage body fat, and knee osteoarthritis severity. We also examined healthy porcine cartilage explants treated with physiologic doses of leptin, alone or in combination with IL-1α and palmitic and oleic fatty acids, to determine the effects of leptin on cartilage extracellular matrix homeostasis.
  
  
  RESULTS
  High susceptibility to dietary obesity was associated with increased osteoarthritic changes in the knee and impaired musculoskeletal force generation and motor function compared with controls. A high-fat diet also induced symptomatic characteristics of osteoarthritis, including hyperalgesia and anxiety-like behaviors. Controlling for the effects of diet and percentage body fat with a multivariate model revealed a significant association between knee osteoarthritis severity and serum levels of leptin, adiponectin, and IL-1α. Physiologic doses of leptin, in the presence or absence of IL-1α and fatty acids, did not substantially alter extracellular matrix homeostasis in healthy cartilage explants.
  
  
  CONCLUSIONS
  These results indicate that diet-induced obesity increases the risk of symptomatic features of osteoarthritis through changes in musculoskeletal function and pain-related behaviors. Furthermore, the independent association of systemic adipokine levels with knee osteoarthritis severity supports a role for adipose-associated inflammation in the molecular pathogenesis of obesity-induced osteoarthritis. Physiologic levels of leptin do not alter extracellular matrix homeostasis in healthy cartilage, suggesting that leptin may be a secondary mediator of osteoarthritis pathogenesis.
authors.affiliation: Department of Surgery, Duke University Medical Center, Durham, NC 27710, USA. Tim-Griffin@omrf.org
authors.forename: Timothy M
authors.initials: TM
authors.lastname: Griffin
authors.forename: Beverley
authors.initials: B
authors.lastname: Fermor
authors.forename: Janet L
authors.initials: JL
authors.lastname: Huebner
authors.forename: Virginia B
authors.initials: VB
authors.lastname: Kraus
authors.forename: Ramona M
authors.initials: RM
authors.lastname: Rodriguiz
authors.forename: William C
authors.initials: WC
authors.lastname: Wetsel
authors.forename: Li
authors.initials: L
authors.lastname: Cao
authors.forename: Lori A
authors.initials: LA
authors.lastname: Setton
authors.forename: Farshid
authors.initials: F
authors.lastname: Guilak
mesh_terms: D054392:Adipokines / Q000097:blood; D000818:Animals; D001522:Behavior, Animal / Q000502:physiology; D002356:Cartilage / Q000378:metabolism; D004041:Dietary Fats / Q000494:pharmacology*; D018450:Disease Progression; D005109:Extracellular Matrix / Q000378:metabolism; D005260:Female; D007375:Interleukin-1 / Q000097:blood; D051379:Mice; D008810:Mice, Inbred C57BL; D009043:Motor Activity / Q000502:physiology; D009765:Obesity / Q000453:epidemiology* / Q000378:metabolism*; D020370:Osteoarthritis, Knee / Q000453:epidemiology* / Q000378:metabolism* / Q000503:physiopathology; D010146:Pain / Q000453:epidemiology / Q000378:metabolism / Q000503:physiopathology; D012307:Risk Factors; D012720:Severity of Illness Index; D013552:Swine; D013705:Temporomandibular Joint Disorders / Q000453:epidemiology / Q000378:metabolism / Q000503:physiopathology; D046509:Tissue Culture Techniques
chemical_list: D054392:Adipokines; D004041:Dietary Fats; D007375:Interleukin-1