title: Inhibition of fatty acid biosynthesis prevents adipocyte lipotoxicity on human osteoblasts in vitro.
abstract: Although increased bone marrow fat in age-related bone loss has been associated with lower trabecular mass, the underlying mechanism responsible remains unknown. We hypothesized that marrow adipocytes exert a lipotoxic effect on osteoblast function and survival through the reversible biosynthesis of fatty acids (FA) into the bone marrow microenvironment. We have used a two-chamber system to co-culture normal human osteoblasts (NHOst) with differentiating pre-adipocytes in the absence or presence of an inhibitor of FA synthase (cerulenin) and separated by an insert that allowed unidirectional trafficking of soluble factors only and prevented direct cell-cell contact. Supernatants were assayed for the presence of FA using mass spectophotometry. After 3 weeks in co-culture, NHOst showed significantly lower levels of differentiation and function based on lower mineralization and expression of alkaline phosphatase, osterix, osteocalcin and Runx2. In addition, NHOst survival was affected by the presence of adipocytes as determined by MTS-formazan and TUNEL assays as well as higher activation of caspases 3/7. These toxic effects were inhibited by addition of cerulenin. Furthermore, culture of NHOst with either adipocyte-conditioned media alone in the absence of adipocytes themselves or with the addition of the most predominant FA (stearate or palmitate) produced similar toxic results. Finally, Runx2 nuclear binding was affected by addition of either adipocyte conditioned media or FA into the osteogenic media. We conclude that the presence of FA within the marrow milieu can contribute to the age-related changes in bone mass and can be prevented by the inhibition of FA synthase.
authors.affiliation: Lady Davis Institute for Medical Research, McGill University, Montreal, Quebec, Canada.
authors.forename: Alexandre
authors.initials: A
authors.lastname: Elbaz
authors.forename: Xiying
authors.initials: X
authors.lastname: Wu
authors.forename: Daniel
authors.initials: D
authors.lastname: Rivas
authors.forename: Jeffrey M
authors.initials: JM
authors.lastname: Gimble
authors.forename: Gustavo
authors.initials: G
authors.lastname: Duque
mesh_terms: D017667:Adipocytes / Q000166:cytology / Q000187:drug effects* / Q000378:metabolism; D000328:Adult; D017209:Apoptosis / Q000187:drug effects; D002113:Calcification, Physiologic / Q000187:drug effects; D002454:Cell Differentiation / Q000187:drug effects; D002467:Cell Nucleus / Q000187:drug effects / Q000378:metabolism; D049109:Cell Proliferation / Q000187:drug effects; D002470:Cell Survival / Q000187:drug effects; D002569:Cerulenin / Q000494:pharmacology; D018920:Coculture Techniques; D050659:Core Binding Factor Alpha 1 Subunit / Q000235:genetics; D064429:Fatty Acid Synthases / Q000037:antagonists & inhibitors; D005227:Fatty Acids / Q000096:biosynthesis*; D005260:Female; D006801:Humans; D008055:Lipids / Q000633:toxicity*; D008297:Male; D010006:Osteoblasts / Q000166:cytology / Q000187:drug effects* / Q000378:metabolism*; D019308:Palmitic Acid / Q000494:pharmacology; D011485:Protein Binding / Q000187:drug effects; D013229:Stearic Acids / Q000494:pharmacology; D014158:Transcription, Genetic / Q000187:drug effects; D055815:Young Adult
chemical_list: D050659:Core Binding Factor Alpha 1 Subunit; D005227:Fatty Acids; D008055:Lipids; C493709:RUNX2 protein, human; D013229:Stearic Acids; D002569:Cerulenin; D019308:Palmitic Acid; C031183:stearic acid; D064429:Fatty Acid Synthases