title: Glucosamine activates autophagy in vitro and in vivo.
abstract: OBJECTIVE
  Aging-associated changes in articular cartilage represent a main risk factor for osteoarthritis (OA). Autophagy is an essential cellular homeostasis mechanism. Aging-associated or experimentally induced defects in autophagy contribute to organismal- and tissue-specific aging, while enhancement of autophagy may protect against certain aging-related pathologies such as OA. The objective of this study was to determine whether glucosamine can activate autophagy.
  
  
  METHODS
  Chondrocytes from normal human articular cartilage were treated with glucosamine (0.1- 10 mM). Autophagy activation and phosphorylation levels of Akt, FoxO3, and ribosomal protein S6 were determined by Western blotting. Autophagosome formation was analyzed by confocal microscopy. Reporter mice systemically expressing green fluorescent protein (GFP) fused to light chain 3 (LC3) (GFP-LC3-transgenic mice) were used to assess changes in autophagy in response to starvation and glucosamine treatment.
  
  
  RESULTS
  Glucosamine treatment of chondrocytes activated autophagy, as indicated by increased LC3-II levels, formation of LC3 puncta, and increased LC3 turnover. This was associated with glucosamine-mediated inhibition of the Akt/FoxO3/mammalian target of rapamycin pathway. Administration of glucosamine to GFP-LC3-transgenic mice markedly activated autophagy in articular cartilage.
  
  
  CONCLUSIONS
  Glucosamine modulates molecular targets of the autophagy pathway in vitro and in vivo, and the enhancement of autophagy is mainly dependent on the Akt/FoxO/mTOR pathway. These findings suggest that glucosamine is an effective autophagy activator and should motivate future studies on the efficacy of glucosamine in modifying aging-related cellular changes and supporting joint health.
authors.affiliation: The Scripps Research Institute, La Jolla, CA, USA.
authors.forename: Beatriz
authors.initials: B
authors.lastname: Caramés
authors.forename: William B
authors.initials: WB
authors.lastname: Kiosses
authors.forename: Yukio
authors.initials: Y
authors.lastname: Akasaki
authors.forename: Diana C
authors.initials: DC
authors.lastname: Brinson
authors.forename: William
authors.initials: W
authors.lastname: Eap
authors.forename: James
authors.initials: J
authors.lastname: Koziol
authors.forename: Martin K
authors.initials: MK
authors.lastname: Lotz
mesh_terms: D000818:Animals; D001343:Autophagy / Q000187:drug effects*; D002358:Cartilage, Articular / Q000166:cytology*; D019902:Chondrocytes / Q000187:drug effects* / Q000502:physiology; D000071316:Forkhead Box Protein O3; D051858:Forkhead Transcription Factors / Q000187:drug effects / Q000378:metabolism; D005944:Glucosamine / Q000494:pharmacology*; D006801:Humans; D008099:Liver / Q000187:drug effects / Q000378:metabolism; D051379:Mice; D008822:Mice, Transgenic; D018613:Microscopy, Confocal; D008869:Microtubule-Associated Proteins / Q000187:drug effects / Q000378:metabolism; D010766:Phosphorylation / Q000187:drug effects; D051057:Proto-Oncogene Proteins c-akt / Q000187:drug effects / Q000378:metabolism; D038601:Ribosomal Protein S6 / Q000187:drug effects / Q000378:metabolism; D015398:Signal Transduction / Q000187:drug effects*; D058570:TOR Serine-Threonine Kinases / Q000187:drug effects / Q000378:metabolism
chemical_list: C499517:FOXO3 protein, human; D000071316:Forkhead Box Protein O3; D051858:Forkhead Transcription Factors; C477012:MAP1LC3A protein, human; D008869:Microtubule-Associated Proteins; D038601:Ribosomal Protein S6; C546842:MTOR protein, human; D051057:Proto-Oncogene Proteins c-akt; D058570:TOR Serine-Threonine Kinases; D005944:Glucosamine