title: Sirtuin1 promotes osteogenic differentiation through downregulation of peroxisome proliferator-activated receptor γ in MC3T3-E1 cells.
abstract: Osteoporosis is a skeletal disorder characterized by bone loss, resulting in architectural deterioration of the skeleton, decreased bone strength and an increased risk of fragility fractures. Strengthening osteogenesis is an effective way to relieve osteoporosis. Sirtuin1 (Sirt1) is a nicotinamide adenine dinucleotide (NAD(+))-dependent deacetylase, which is reported to be involved in improving osteogenesis. Sirt1 targets peroxisome proliferator-activated receptor γ (PPARγ) in the regulation of adipose tissues; however, the molecular mechanism of Sirt1 in osteogenic differentiation is still unknown. PPARγ tends to induce more adipogenic differentiation rather than osteogenic differentiation. Hence, we hypothesized that Sirt1 facilitates osteogenic differentiation through downregulation of PPARγ signaling. Mouse pre-osteoblastic MC3T3-E1 cells were cultured under osteogenic medium. Sirt1 was overexpressed through plasmid transfection. The results showed that high expression of Sirt1 was associated with increased osteogenic differentiation, as indicated by quantitative PCR and Western blot analysis of osteogenic markers, and Von Kossa staining. Sirt1 overexpression also directly and negatively regulated the expression of PPARγ and its downstream molecules. Use of the PPARγ agonist Rosiglitazone, reversed the effects of Sirt1 on osteogenic differentiation. Using constructed luciferase plasmids, we demonstrated a role of Sirt1 in inhibiting PPARγ-induced activity and expression of adipocyte-specific genes, including acetyl-coenzyme A carboxylase (Acc) and fatty acid binding protein 4 (Fabp4). The interaction between Sirt1 and PPARγ was further confirmed using co-immunoprecipitation analysis. Together, these results reveal a novel mechanism for Sirt1 in osteogenic differentiation through downregulation of PPARγ activity. These findings suggest that the Sirt1-PPARγ pathway may represent a potential target for enhancement of osteogenesis and treatment of osteoporosis.
authors.affiliation: Department of Orthopaedics, Chengdu Military General Hospital, Chengdu 610083, China.
authors.forename: Bo
authors.initials: B
authors.lastname: Qu
authors.affiliation: Department of Neurosurgery, Chengdu Military General Hospital, Chengdu 610083, China.
authors.forename: Yuan
authors.initials: Y
authors.lastname: Ma
authors.affiliation: Department of Orthopaedics, Xijing Hospital of The Fourth Military Medical University, Xi'an 710032, China.
authors.forename: Ming
authors.initials: M
authors.lastname: Yan
authors.affiliation: Department of Orthopaedics, Chengdu Military General Hospital, Chengdu 610083, China.
authors.forename: Kai
authors.initials: K
authors.lastname: Gong
authors.affiliation: Department of Orthopaedics, Chengdu Military General Hospital, Chengdu 610083, China.
authors.forename: Feng
authors.initials: F
authors.lastname: Liang
authors.affiliation: Department of Orthopaedics, Chengdu Military General Hospital, Chengdu 610083, China.
authors.forename: Shaolin
authors.initials: S
authors.lastname: Deng
authors.affiliation: Department of Orthopaedics, Chengdu Military General Hospital, Chengdu 610083, China.
authors.forename: Kai
authors.initials: K
authors.lastname: Jiang
authors.affiliation: Department of Orthopaedics, Chengdu Military General Hospital, Chengdu 610083, China.
authors.forename: Zehui
authors.initials: Z
authors.lastname: Ma
authors.affiliation: Department of Orthopaedics, Chengdu Military General Hospital, Chengdu 610083, China. Electronic address: xianmingpanxj@163.com.
authors.forename: Xianming
authors.initials: X
authors.lastname: Pan
mesh_terms: D000818:Animals; D041702:BALB 3T3 Cells; D002454:Cell Differentiation / Q000502:physiology*; D015536:Down-Regulation / Q000502:physiology; D051379:Mice; D010006:Osteoblasts / Q000166:cytology* / Q000502:physiology*; D010012:Osteogenesis / Q000502:physiology*; D047495:PPAR gamma / Q000378:metabolism*; D056564:Sirtuin 1 / Q000378:metabolism*
chemical_list: D047495:PPAR gamma; C470545:Sirt1 protein, mouse; D056564:Sirtuin 1
keywords: Osteogenic differentiation; Osteoporosis; PPARγ; Sirt1