title: The Sirtuin1 activator SRT3025 down-regulates sclerostin and rescues ovariectomy-induced bone loss and biomechanical deterioration in female mice.
abstract: Estrogen deficiency leads to rapid bone loss and skeletal fragility. Sclerostin, encoded by the sost gene, and a product of the osteocyte, is a negative regulator of bone formation. Blocking sclerostin increases bone mass and strength in animals and humans. Sirtuin1 (Sirt1), a player in aging and metabolism, regulates bone mass and inhibits sost expression by deacetylating histone 3 at its promoter. We asked whether a Sirt1-activating compound could rescue ovariectomy (OVX)-induced bone loss and biomechanical deterioration in 9-week-old C57BL/6 mice. OVX resulted in a substantial decrease in skeletal Sirt1 expression accompanied by an increase in sclerostin. Oral administration of SRT3025, a Sirt1 activator, at 50 and 100 mg/kg·d for 6 weeks starting 6 weeks after OVX fully reversed the deleterious effects of OVX on vertebral bone mass, microarchitecture, and femoral biomechanical properties. Treatment with SRT3025 decreased bone sclerostin expression and increased cortical periosteal mineralizing surface and serum propeptide of type I procollagen, a bone formation marker. In vitro, in the murine long bone osteocyte-Y4 osteocyte-like cell line SRT3025 down-regulated sclerostin and inactive β-catenin, whereas a reciprocal effect was observed with EX-527, a Sirt1 inhibitor. Sirt1 activation by Sirt1-activating compounds is a potential novel pathway to down-regulate sclerostin and design anabolic therapies for osteoporosis concurrently ameliorating other metabolic and age-associated conditions.
authors.affiliation: Endocrinology and Metabolism Service (H.A., E.C.-K., I.G., R.D.-P.), Department of Medicine, Hadassah-Hebrew University Medical Center, Jerusalem 91120, Israel; Laboratory of Bone Biomechanics (R.S., N.K.), Koret School of Veterinary Medicine, The Hebrew University of Jerusalem, Rehovot, 76100 Israel; Bone Laboratory (A.B.), The Hebrew University of Jerusalem, Jerusalem, 91120 Israel; Department of Anatomy and Cell Biology (T.M.B.), Division of Endocrinology, Indiana University School of Medicine, Indianapolis, Indiana 46202; and Department of Anatomy and Anthropology (Y.G.), Sackler School of Medicine, Tel Aviv University, Tel Aviv, 69978 Israel.
authors.forename: Hanna
authors.initials: H
authors.lastname: Artsi
authors.forename: Einav
authors.initials: E
authors.lastname: Cohen-Kfir
authors.forename: Irina
authors.initials: I
authors.lastname: Gurt
authors.forename: Ron
authors.initials: R
authors.lastname: Shahar
authors.forename: Alon
authors.initials: A
authors.lastname: Bajayo
authors.forename: Noga
authors.initials: N
authors.lastname: Kalish
authors.forename: Teresita M
authors.initials: TM
authors.lastname: Bellido
authors.forename: Yankel
authors.initials: Y
authors.lastname: Gabet
authors.forename: Rivka
authors.initials: R
authors.lastname: Dresner-Pollak
mesh_terms: D048868:Adaptor Proteins, Signal Transducing; D000818:Animals; D001696:Biomechanical Phenomena; D015519:Bone Density / Q000187:drug effects; D015536:Down-Regulation; D020536:Enzyme Activators / Q000008:administration & dosage*; D005260:Female; D006023:Glycoproteins / Q000235:genetics* / Q000378:metabolism; D006801:Humans; D036341:Intercellular Signaling Peptides and Proteins; D051379:Mice; D008810:Mice, Inbred C57BL; D015663:Osteoporosis, Postmenopausal / Q000188:drug therapy* / Q000201:enzymology / Q000378:metabolism* / Q000503:physiopathology; D010052:Ovariectomy / Q000009:adverse effects*; D056564:Sirtuin 1 / Q000235:genetics / Q000378:metabolism*
chemical_list: D048868:Adaptor Proteins, Signal Transducing; D020536:Enzyme Activators; D006023:Glycoproteins; D036341:Intercellular Signaling Peptides and Proteins; C486030:Sost protein, mouse; D056564:Sirtuin 1