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Kim K, Kim JH, Kim I, Seong S, Koh JT, Kim N. Sestrin2 inhibits RANKL-induced osteoclastogenesis through AMPK activation and ROS inhibition. Free Radic Biol Med 2024; 211:77-88. [PMID: 38101586 DOI: 10.1016/j.freeradbiomed.2023.12.009] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 09/12/2023] [Revised: 12/01/2023] [Accepted: 12/11/2023] [Indexed: 12/17/2023]
Abstract
Sestrins are stress-responsive proteins with antioxidant properties. They participate in cellular redox balance and protect against oxidative damage. This study investigated the effects of Sestrin2 (Sesn2) on osteoclast differentiation and function. Overexpressing Sesn2 in osteoclast precursor cells significantly inhibited receptor activator of nuclear factor κB ligand (RANKL)-induced osteoclastogenesis. This was assessed as reduced expression of various osteoclast markers, including c-Fos, nuclear factor of activated T cells 1 (NFATc1), osteoclast-associated receptor, tartrate-resistant acid phosphatase, and cathepsin K. Conversely, downregulation of Sesn2 produced the opposite effect. Mechanistically, Sesn2 overexpression enhanced AMPK activation and the nuclear translocation of nuclear factor erythroid-derived factor 2-related factor 2 (Nrf2), promoting antioxidant enzymes. Moreover, azithromycin (Azm) induced Sesn2 expression, which suppressed RANKL-induced osteoclast differentiation. Specifically, Azm treatment reduced RANKL-induced production of reactive oxygen species in osteoclasts. Furthermore, intraperitoneal administration of Azm ameliorated RANKL-induced bone loss by reducing osteoclast activity in mice. Taken together, our results suggested that Azm-induced Sesn2 act as a negative regulator of RANKL-induced osteoclast differentiation through the AMPK/NFATc1 signaling pathway. Concisely, targeting Sesn2 can be a potential pharmacological intervention in osteoporosis.
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Affiliation(s)
- Kabsun Kim
- Department of Pharmacology, Chonnam National University Medical School, Gwangju, 61469, Republic of Korea
| | - Jung Ha Kim
- Department of Pharmacology, Chonnam National University Medical School, Gwangju, 61469, Republic of Korea; Hard-Tissue Biointerface Research Center, School of Dentistry, Chonnam National University, Gwangju, 61186, Republic of Korea
| | - Inyoung Kim
- Department of Pharmacology, Chonnam National University Medical School, Gwangju, 61469, Republic of Korea
| | - Semun Seong
- Department of Pharmacology, Chonnam National University Medical School, Gwangju, 61469, Republic of Korea; Hard-Tissue Biointerface Research Center, School of Dentistry, Chonnam National University, Gwangju, 61186, Republic of Korea
| | - Jeong-Tae Koh
- Hard-Tissue Biointerface Research Center, School of Dentistry, Chonnam National University, Gwangju, 61186, Republic of Korea; Department of Pharmacology and Dental Therapeutics, School of Dentistry, Chonnam National University, Gwangju, 61186, Republic of Korea
| | - Nacksung Kim
- Department of Pharmacology, Chonnam National University Medical School, Gwangju, 61469, Republic of Korea; Hard-Tissue Biointerface Research Center, School of Dentistry, Chonnam National University, Gwangju, 61186, Republic of Korea.
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Luo W, Yao C, Sun J, Zhang B, Chen H, Miao J, Zhang Y. Alamandine attenuates ovariectomy-induced osteoporosis by promoting osteogenic differentiation via AMPK/eNOS axis. BMC Musculoskelet Disord 2024; 25:45. [PMID: 38200474 PMCID: PMC10777585 DOI: 10.1186/s12891-023-07159-2] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 05/22/2023] [Accepted: 12/29/2023] [Indexed: 01/12/2024] Open
Abstract
BACKGROUND Alamandine is a newly characterized peptide of renin angiotensin system. Our study aims to investigate the osteo-preservative effects of alamandine, explore underlying mechanism and bring a potential preventive strategy for postmenopausal osteoporosis in the future. METHODS An ovariectomy (OVX)-induced rat osteoporosis model was established for in vivo experiments. Micro-computed tomography and three-point bending test were used to evaluate bone strength. Histological femur slices were processed for immunohistochemistry (IHC). Bone turnover markers and nitric oxide (NO) concentrations in serum were determined with enzyme-linked immunosorbent assay (ELISA). The mouse embryo osteoblast precursor (MC3T3-E1) cells were used for in vitro experiments. The cell viability was analysed with a Cell Counting Kit‑8. We performed Alizarin Red S staining and alkaline phosphatase (ALP) activity assay to observe the differentiation status of osteoblasts. Western blotting was adopted to detect the expression of osteogenesis related proteins and AMP-activated protein kinase/endothelial nitric oxide synthase (AMPK/eNOS) in osteoblasts. DAF-FM diacetate was used for semi-quantitation of intracellular NO. RESULTS In OVX rats, alamandine alleviated osteoporosis and maintained bone strength. The IHC showed alamandine increased osteocalcin and collagen type I α1 (COL1A1) expression. The ELISA revealed alamandine decreased bone turnover markers and restored NO level in serum. In MC3T3-E1 cells, alamandine promoted osteogenic differentiation. Western blotting demonstrated that alamandine upregulated the expression of osteopontin, Runt-related transcription factor 2 and COL1A1. The intracellular NO was also raised by alamandine. Additionally, the activation of AMPK/eNOS axis mediated the effects of alamandine on MC3T3-E1 cells and bone tissue. PD123319 and dorsomorphin could repress the regulating effect of alamandine on bone metabolism. CONCLUSION Alamandine attenuates ovariectomy-induced osteoporosis by promoting osteogenic differentiation via AMPK/eNOS axis.
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Affiliation(s)
- Wanxin Luo
- Department of Orthopaedics, Affiliated Hospital of Nantong University, 20 Xisi Road, Nantong City, 226001, Jiangsu Province, PR China
| | - Chen Yao
- Department of Orthopaedics, Affiliated Hospital of Nantong University, 20 Xisi Road, Nantong City, 226001, Jiangsu Province, PR China
| | - Jie Sun
- Department of Orthopaedics, Affiliated Hospital of Nantong University, 20 Xisi Road, Nantong City, 226001, Jiangsu Province, PR China
| | - Bo Zhang
- Department of Orthopaedics, Affiliated Hospital of Nantong University, 20 Xisi Road, Nantong City, 226001, Jiangsu Province, PR China
| | - Hao Chen
- Department of Orthopaedics, Affiliated Hospital of Nantong University, 20 Xisi Road, Nantong City, 226001, Jiangsu Province, PR China
| | - Jin Miao
- Laboratory Animal Center of Nantong University, Medical School of Nantong University, Nantong City, 226001, Jiangsu Province, PR China
| | - Yafeng Zhang
- Department of Orthopaedics, Affiliated Hospital of Nantong University, 20 Xisi Road, Nantong City, 226001, Jiangsu Province, PR China.
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3
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Ribeiro MSP, Venturini LGR, Speck-Hernandez CA, Alabarse PVG, Xavier T, Taira TM, Duffles LF, Cunha FQ, Fukada SY. AMPKα1 negatively regulates osteoclastogenesis and mitigates pathological bone loss. J Biol Chem 2023; 299:105379. [PMID: 37871745 PMCID: PMC10692901 DOI: 10.1016/j.jbc.2023.105379] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/06/2023] [Revised: 09/25/2023] [Accepted: 10/04/2023] [Indexed: 10/25/2023] Open
Abstract
Osteoclasts are specialized cells responsible for bone resorption, a highly energy-demanding process. Focus on osteoclast metabolism could be a key for the treatment of osteolytic diseases including osteoporosis. In this context, AMP-activated protein kinase α1 (AMPKα1), an energy sensor highly expressed in osteoclasts, participates in the metabolic reconfiguration during osteoclast differentiation and activation. This study aimed to elucidate the role of AMPKα1 during osteoclastogenesis in vitro and its impact in bone loss in vivo. Using LysMcre/0AMPK⍺1f/f animals and LysMcre/0 as control, we evaluated how AMPKα1 interferes with osteoclastogenesis and bone resorption activity in vitro. We found that AMPKα1 is highly expressed in the early stages of osteoclastogenesis. Genetic deletion of AMPKα1 leads to increased gene expression of osteoclast differentiation and fusion markers. In addition, LysMcre/0AMPK⍺1f/f mice had an increased number and size of differentiated osteoclast. Accordingly, AMPKα1 negatively regulates bone resorption in vitro, as evidenced by the area of bone resorption in LysMcre/0AMPK⍺1f/f osteoclasts. Our data further demonstrated that AMPKα1 regulates mitochondrial fusion and fission markers upregulating Mfn2 and downregulating DRP1 (dynamics-related protein 1) and that Ctskcre/0AMPK⍺1f/f osteoclasts lead to an increase in the number of mitochondria in AMPK⍺1-deficient osteoclast. In our in vivo study, femurs from Ctskcre/0AMPK⍺1f/f animals exhibited bone loss associated with the increased number of osteoclasts, and there was no difference between Sham and ovariectomized group. Our data suggest that AMPKα1 acts as a negative regulator of osteoclastogenesis, and the depletion of AMPKα1 in osteoclast leads to a bone loss state similar to that observed after ovariectomy.
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Affiliation(s)
- Mariana S P Ribeiro
- Laboratory of Bone Biology, Department of BioMolecular Sciences, School of Pharmaceutical Sciences Ribeirão Preto, University of São Paulo, Ribeirão Preto, Brazil
| | - Lucas G R Venturini
- Laboratory of Bone Biology, Department of BioMolecular Sciences, School of Pharmaceutical Sciences Ribeirão Preto, University of São Paulo, Ribeirão Preto, Brazil
| | - Cesar A Speck-Hernandez
- Laboratory of Bone Biology, Department of BioMolecular Sciences, School of Pharmaceutical Sciences Ribeirão Preto, University of São Paulo, Ribeirão Preto, Brazil
| | - Paulo V G Alabarse
- Laboratory of Bone Biology, Department of BioMolecular Sciences, School of Pharmaceutical Sciences Ribeirão Preto, University of São Paulo, Ribeirão Preto, Brazil
| | - Thais Xavier
- Laboratory of Bone Biology, Department of BioMolecular Sciences, School of Pharmaceutical Sciences Ribeirão Preto, University of São Paulo, Ribeirão Preto, Brazil
| | - Thaise M Taira
- Laboratory of Bone Biology, Department of BioMolecular Sciences, School of Pharmaceutical Sciences Ribeirão Preto, University of São Paulo, Ribeirão Preto, Brazil
| | - Letícia F Duffles
- Laboratory of Bone Biology, Department of BioMolecular Sciences, School of Pharmaceutical Sciences Ribeirão Preto, University of São Paulo, Ribeirão Preto, Brazil
| | - Fernando Q Cunha
- Department of Pharmacology, Ribeirão Preto Medical School, University of São Paulo, Ribeirão Preto, Brazil; Center for Research in Inflammatory Diseases, CRID, Ribeirão Preto Medical School, University of São Paulo, Ribeirão Preto, Brazil
| | - Sandra Y Fukada
- Laboratory of Bone Biology, Department of BioMolecular Sciences, School of Pharmaceutical Sciences Ribeirão Preto, University of São Paulo, Ribeirão Preto, Brazil; Center for Research in Inflammatory Diseases, CRID, Ribeirão Preto Medical School, University of São Paulo, Ribeirão Preto, Brazil.
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4
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Shen Y, Jiang B, Lu W, Luo B, Zhou Y, Qian G. Dexamethasone-induced mitochondrial ROS-mediated inhibition of AMPK activity facilitates osteoblast necroptosis. Toxicol Res (Camb) 2023; 12:922-929. [PMID: 37915480 PMCID: PMC10615823 DOI: 10.1093/toxres/tfad080] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/16/2023] [Revised: 08/15/2023] [Accepted: 08/28/2023] [Indexed: 11/03/2023] Open
Abstract
Long-term or high-dose glucocorticoid use can lead to serious orthopedic complications, including femoral head necrosis. Both basic and clinical studies have shown that high doses dexamethasone (Dex) can directly induce osteoblasts death. This study investigated the mechanism underlying Dex induced osteoblast death. In this study, we showed that Dex induces osteoblast necroptosis, rather than apoptosis, through the inhibition of AMP-activated protein kinase (AMPK) activity. We also demonstrated that inactivation of AMPK-mediated necroptosis is through receptor-interacting protein kinase 3 (RIP3), but not RIP1. Furthermore, we found that Dex-induced necroptosis is dependent on mitochondrial reactive oxygen species (ROS) following with directly activation of RIP1 and inactivation of AMPK. These findings provide new insights into the mechanism of Dex-induced osteoblast death and may have implications for the development of new therapies for osteoporosis and other bone-related diseases.
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Affiliation(s)
- Yingchao Shen
- Department of Orthopaedics, Changshu Hospital Affiliated to Nanjing University of Chinese Medicine, No. 6, Huanghe Road, Changshu, Jiangsu 215500, China
| | - Bo Jiang
- Department of Hand and Foot Surgery, The Second Affiliated Hospital of Soochow University, No. 1055, Sanxiang Road, Suzhou, Jiangsu 215004, China
| | - Wei Lu
- Department of Orthopaedics, Changshu Hospital Affiliated to Nanjing University of Chinese Medicine, No. 6, Huanghe Road, Changshu, Jiangsu 215500, China
| | - Bin Luo
- Department of Orthopaedics, Changshu Hospital Affiliated to Nanjing University of Chinese Medicine, No. 6, Huanghe Road, Changshu, Jiangsu 215500, China
| | - Yuan Zhou
- Department of Orthopaedics, Changshu Hospital Affiliated to Nanjing University of Chinese Medicine, No. 6, Huanghe Road, Changshu, Jiangsu 215500, China
| | - Guiying Qian
- Department of Orthopaedics, Changshu Hospital Affiliated to Nanjing University of Chinese Medicine, No. 6, Huanghe Road, Changshu, Jiangsu 215500, China
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Choi EB, Agidigbi TS, Kang IS, Kim C. ERK Inhibition Increases RANKL-Induced Osteoclast Differentiation in RAW 264.7 Cells by Stimulating AMPK Activation and RANK Expression and Inhibiting Anti-Osteoclastogenic Factor Expression. Int J Mol Sci 2022; 23:13512. [PMID: 36362318 PMCID: PMC9656104 DOI: 10.3390/ijms232113512] [Citation(s) in RCA: 7] [Impact Index Per Article: 3.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/08/2022] [Revised: 10/20/2022] [Accepted: 10/30/2022] [Indexed: 08/13/2023] Open
Abstract
Bone absorption is necessary for the maintenance of bone homeostasis. An osteoclast (OC) is a monocyte-macrophage lineage cell that absorbs bone tissue. Extracellular signal-regulated kinases (ERKs) are known to play important roles in regulating OC growth and differentiation. In this study, we examined specific downstream signal pathways affected by ERK inhibition during OC differentiation. Our results showed that the ERK inhibitors PD98059 and U0126 increased receptor activator of NF-κB ligand (RANKL)-induced OC differentiation in RAW 264.7 cells, implying a negative role in OC differentiation. This is supported by the effect of ERK2-specific small interfering RNA on increasing OC differentiation. In contrast to our findings regarding the RAW 264.7 cells, the ERK inhibitors attenuated the differentiation of bone marrow-derived cells into OCs. The ERK inhibitors significantly increased the phosphorylation of adenosine 5'-monophosphate-activated protein kinase (AMPK) but not the activation of p38 MAPK, Lyn, and mTOR. In addition, while the ERK inhibition increased the expression of the RANKL receptor RANK, it decreased the expression of negative mediators of OC differentiation, such as interferon regulatory factor-8, B-cell lymphoma 6, and interferon-γ. These dichotomous effects of ERK inhibition suggest that while ERKs may play positive roles in bone marrow-derived cells, ERKs may also play negative regulatory roles in RAW 264.7 cells. These data provide important information for drug development utilizing ERK inhibitors in OC-related disease treatment.
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Affiliation(s)
- Eun-Bi Choi
- Laboratory for Leukocyte Signaling Research, Department of Pharmacology and Toxicology, College of Medicine, Inha University, Incheon 22212, Korea
- BK21 Program in Biomedical Science & Engineering, Inha University, Incheon 22212, Korea
| | - Taiwo Samuel Agidigbi
- Laboratory for Leukocyte Signaling Research, Department of Pharmacology and Toxicology, College of Medicine, Inha University, Incheon 22212, Korea
| | - In-Soon Kang
- Laboratory for Leukocyte Signaling Research, Department of Pharmacology and Toxicology, College of Medicine, Inha University, Incheon 22212, Korea
- BK21 Program in Biomedical Science & Engineering, Inha University, Incheon 22212, Korea
| | - Chaekyun Kim
- Laboratory for Leukocyte Signaling Research, Department of Pharmacology and Toxicology, College of Medicine, Inha University, Incheon 22212, Korea
- BK21 Program in Biomedical Science & Engineering, Inha University, Incheon 22212, Korea
- Convergent Research Center for Metabolism and Immunoregulation, Inha University, Incheon 22212, Korea
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6
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A Review of Signaling Transduction Mechanisms in Osteoclastogenesis Regulation by Autophagy, Inflammation, and Immunity. Int J Mol Sci 2022; 23:ijms23179846. [PMID: 36077242 PMCID: PMC9456406 DOI: 10.3390/ijms23179846] [Citation(s) in RCA: 7] [Impact Index Per Article: 3.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/09/2022] [Revised: 08/22/2022] [Accepted: 08/26/2022] [Indexed: 11/16/2022] Open
Abstract
Osteoclastogenesis is an ongoing rigorous course that includes osteoclast precursors fusion and bone resorption executed by degradative enzymes. Osteoclastogenesis is controlled by endogenous signaling and/or regulators or affected by exogenous conditions and can also be controlled both internally and externally. More evidence indicates that autophagy, inflammation, and immunity are closely related to osteoclastogenesis and involve multiple intracellular organelles (e.g., lysosomes and autophagosomes) and certain inflammatory or immunological factors. Based on the literature on osteoclastogenesis induced by different regulatory aspects, emerging basic cross-studies have reported the emerging disquisitive orientation for osteoclast differentiation and function. In this review, we summarize the partial potential therapeutic targets for osteoclast differentiation and function, including the signaling pathways and various cellular processes.
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7
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Drewe J, Boonen G, Culmsee C. Treat more than heat-New therapeutic implications of Cimicifuga racemosa through AMPK-dependent metabolic effects. PHYTOMEDICINE : INTERNATIONAL JOURNAL OF PHYTOTHERAPY AND PHYTOPHARMACOLOGY 2022; 100:154060. [PMID: 35338990 DOI: 10.1016/j.phymed.2022.154060] [Citation(s) in RCA: 2] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 06/21/2021] [Revised: 02/18/2022] [Accepted: 03/14/2022] [Indexed: 06/14/2023]
Abstract
BACKGROUND Cimicifuga racemosa extracts (CRE) have obtained a "well-established use status" in the treatment of postmenopausal (i.e., climacteric) complaints, which predominantly include vasomotor symptoms such as hot flushes and sweating, as well as nervousness, irritability, and metabolic changes. Although characteristic postmenopausal complaints are known for a very long time and the beneficial effects of CRE on climacteric symptoms are well accepted, both the pathophysiology of postmenopausal symptoms and the mechanism of action of CREs are not yet fully understood. In particular, current hypotheses suggest that changes in the α-adrenergic and serotonergic signaling pathways secondary to estrogen depletion are responsible for the development of hot flushes. PURPOSE Some of the symptoms associated with menopause cannot be explained by these hypotheses. Therefore, we attempted to extend our classic understanding of menopause by integrating of partly age-related metabolic impairments. METHODS A comprehensive literature survey was performed using the PubMed database for articles published through September 2021. The following search terms were used: (cimicifuga OR AMPK) AND (hot flush* OR hot flash* OR menopaus* OR osteoporos* OR cancer OR antioxida* OR cardiovasc*). No limits were set with respect to language, and the references cited in the articles retrieved were used to identify additional publications. RESULTS We found that menopause is a manifestation of the general aging process, with specific metabolic changes that aggravate menopausal symptoms, which are accelerated by estrogen depletion and associated neurotransmitter dysregulation. Cimicifuga extracts with their metabolic effects mitigate climacteric symptoms but may also modulate the aging process itself. Central to these effects are effects of CRE on the metabolic key regulator, the AMP-activated protein kinase (AMPK). CONCLUSIONS As an extension of this effect dimension, other off-label indications may appear attractive in the sense of repurposing of this herbal treatment.
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Affiliation(s)
- Jürgen Drewe
- Medical Department, Max Zeller Soehne AG, CH-8590 Romanshorn, Switzerland.
| | - Georg Boonen
- Medical Department, Max Zeller Soehne AG, CH-8590 Romanshorn, Switzerland
| | - Carsten Culmsee
- Institute of Pharmacology and Clinical Pharmacy, University of Marburg, D-35043 Marburg, Germany; Center for Mind, Brain and Behavior, D-35032 Marburg, Germany
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8
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Guo X, Liang M. Metformin alleviates dexamethasone-induced apoptosis by regulating autophagy via AMPK/mTOR/p70S6K in osteoblasts. Exp Cell Res 2022; 415:113120. [PMID: 35341775 DOI: 10.1016/j.yexcr.2022.113120] [Citation(s) in RCA: 7] [Impact Index Per Article: 3.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/20/2021] [Revised: 03/21/2022] [Accepted: 03/23/2022] [Indexed: 01/07/2023]
Abstract
Glucocorticoid (GC)-induced osteoporosis (GIOP) is the most common type of secondary osteoporosis. Osteoblast apoptosis induced by GCs is now considered as a crucial factor for GIOP. Many clinical, in vivo, and in vitro studies have shown that metformin has a beneficial effect on bone metabolism and bone formation. To investigate whether metformin could be used to treat GIOP, we explored the influence of metformin on dexamethasone (Dex)-induced apoptosis of osteoblasts and its underlying mechanisms. In this study, the CCK8 assay was used to determine the optimal metformin concentration and processing time. The expression levels of target proteins were examined by Western blot and immunofluorescence; the expression levels of target genes were tested by quantitative PCR. Apoptotic cells were detected using flow cytometry. Characteristics of autophagy were observed by transmission electron microscopy. An autophagy inhibitor was administered to investigate whether autophagy decreases apoptosis. Sh-AMPK transfection and an mTOR activator were used to investigate the role of AMPK/mTOR signaling in metformin-induced autophagy. The results showed that metformin alleviated Dex-induced apoptosis of osteoblasts accompanied by increased autophagy. Treatment with the autophagy inhibitor 3-methyladenine (3-MA) attenuated the effect of metformin on apoptosis, autophagy, and the AMPK/mTOR/p70S6K signaling pathway. The anti-apoptotic effect of metformin on osteoblasts is associated with the promotion of autophagy. Furthermore, sh-AMPK transfection and the mTOR activator MHY1485 impaired metformin-mediated inhibition of osteoblast apoptosis and promotion of autophagy. The AMPK/mTOR/p70S6K signaling pathway plays a role in metformin-mediated apoptosis suppression and autophagy promotion. In conclusion, metformin can alleviate Dex-induced osteoblast apoptosis by inducing autophagy via the AMPK/mTOR/p70S6K pathway. This study highlights the potential value of metformin in the treatment of GIOP.
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Affiliation(s)
- Xintong Guo
- Department of Geriatric Endocrinology, The First Affiliated Hospital of Guangxi Medical University, Nanning, Guangxi Province, China
| | - Min Liang
- Department of Geriatric Endocrinology, The First Affiliated Hospital of Guangxi Medical University, Nanning, Guangxi Province, China.
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9
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Banskota S, Wang H, Kwon YH, Gautam J, Gurung P, Haq S, Hassan FMN, Bowdish DM, Kim JA, Carling D, Fullerton MD, Steinberg GR, Khan WI. Salicylates Ameliorate Intestinal Inflammation by Activating Macrophage AMPK. Inflamm Bowel Dis 2020; 27:914-926. [PMID: 33252129 PMCID: PMC8128406 DOI: 10.1093/ibd/izaa305] [Citation(s) in RCA: 30] [Impact Index Per Article: 7.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 02/06/2020] [Indexed: 02/06/2023]
Abstract
BACKGROUND Inflammatory bowel diseases are the most common chronic intestinal inflammatory conditions, and their incidence has shown a dramatic increase in recent decades. Limited efficacy and questionable safety profiles with existing therapies suggest the need for better targeting of therapeutic strategies. Adenosine monophosphate-activated protein kinase (AMPK) is a key regulator of cellular metabolism and has been implicated in intestinal inflammation. Macrophages execute an important role in the generation of intestinal inflammation. Impaired AMPK in macrophages has been shown to be associated with higher production of proinflammatory cytokines; however, the role of macrophage AMPK in intestinal inflammation and the mechanism by which it regulates inflammation remain to be determined. In this study, we investigated the role of AMPK with a specific focus on macrophages in the pathogenesis of intestinal inflammation. METHODS A dextran sodium sulfate-induced colitis model was used to assess the disease activity index, histological scores, macroscopic scores, and myeloperoxidase level. Proinflammatory cytokines such as tumor necrosis factor-α, interleukin-6, and interleukin-1β were measured by enzyme-linked immunosorbent assay. Transient transfection of AMPKβ1 and LC3-II siRNA in RAW 264.7 cells was performed to elucidate the regulation of autophagy by AMPK. The expression of p-AMPK, AMPK, and autophagy markers (eg, LC3-II, p62, Beclin-1, and Atg-12) was analyzed by Western blot. RESULTS Genetic deletion of AMPKβ1 in macrophages upregulated the production of proinflammatory cytokines, aggravated the severity of dextran sodium sulfate-induced colitis in mice, which was associated with an increased nuclear translocation of nuclear factor-κB, and impaired autophagy both in vitro and in vivo. Notably, the commonly used anti-inflammatory 5-aminosalicylic acid (ie, mesalazine) and sodium salicylate ameliorated dextran sodium sulfate-induced colitis through the activation of macrophage AMPK targeting the β1 subunit. CONCLUSIONS Together, these data suggest that the development of therapeutic agents targeting AMPKβ1 may be effective in the treatment of intestinal inflammatory conditions including inflammatory bowel disease.
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Affiliation(s)
- Suhrid Banskota
- Farncombe Family Digestive Health Research Institute,Department of Pathology and Molecular Medicine
| | - Huaqing Wang
- Farncombe Family Digestive Health Research Institute,Department of Pathology and Molecular Medicine
| | - Yun Han Kwon
- Farncombe Family Digestive Health Research Institute,Department of Pathology and Molecular Medicine
| | - Jaya Gautam
- Centre for Metabolism, Obesity and Diabetes Research,Department of Medicine,Department of Biochemistry and Biomedical Sciences, McMaster University, Hamilton, Ontario, Canada
| | - Pallavi Gurung
- College of Pharmacy, Yeungnam University, Republic of Korea
| | - Sabah Haq
- Farncombe Family Digestive Health Research Institute,Department of Pathology and Molecular Medicine
| | - F M Nazmul Hassan
- Farncombe Family Digestive Health Research Institute,Department of Pathology and Molecular Medicine
| | | | - Jung-Ae Kim
- College of Pharmacy, Yeungnam University, Republic of Korea
| | - David Carling
- Division of Clinical Sciences, MRC London Institute of Medical Sciences, Imperial College, London, UK
| | - Morgan D Fullerton
- Department of Biochemistry, Microbiology and Immunology, Centre for Inflammation, Infection and Immunity, Centre for Catalysis Research and Innovation, University of Ottawa, Ottawa, Ontario, Canada
| | - Gregory R Steinberg
- Centre for Metabolism, Obesity and Diabetes Research,Department of Medicine,Department of Biochemistry and Biomedical Sciences, McMaster University, Hamilton, Ontario, Canada
| | - Waliul I Khan
- Farncombe Family Digestive Health Research Institute,Department of Pathology and Molecular Medicine,Address correspondence to: Waliul I. Khan, MBBS, PhD, FRCPath, Farncombe Family Digestive Health Research Institute, McMaster University Health Sciences Centre Room 3N7, 1280 Main Street West, Hamilton, Ontario, Canada ()
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10
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Tong X, Ganta RR, Liu Z. AMP-activated protein kinase (AMPK) regulates autophagy, inflammation and immunity and contributes to osteoclast differentiation and functionabs. Biol Cell 2020; 112:251-264. [PMID: 32445585 DOI: 10.1111/boc.202000008] [Citation(s) in RCA: 21] [Impact Index Per Article: 5.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/14/2020] [Revised: 05/19/2020] [Accepted: 05/19/2020] [Indexed: 02/06/2023]
Abstract
Osteoclasts are multinucleated giant cells, responsible for bone resorption. Osteoclast differentiation and function requires a series of cytokines to remove the old bone, which coordinates with the induction of bone remodelling by osteoblast-mediated bone formation. Studies have demonstrated that AMP-activated protein kinase (AMPK) play a negative regulatory role in osteoclast differentiation and function. Research involving AMPK, a nutrient and energy sensor, has primarily focused on osteoclast differentiation and function; thus, its role in autophagy, inflammation and immunity remains poorly understood. Autophagy is a conservative homoeostatic mechanism of eukaryotic cells, and response to osteoclast differentiation and function; however, how it interacts with inflammation remains unclear. Additionally, based on the regulatory function of different AMPK subunits for osteoclast differentiation and function, its activation is regulated by upstream factors to perform bone metabolism. This review summarises the critical role of AMPK-mediated autophagy, inflammation and immunity by upstream and downstream signalling during receptor activator of nuclear factor kappa-B ligand-induced osteoclast differentiation and function. This pathway may provide therapeutic targets for bone-related diseases, as well as function as a biomarker for bone homoeostasis.
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Affiliation(s)
- Xishuai Tong
- College of Veterinary Medicine, Yangzhou University, Yangzhou, Jiangsu, 225009, People's Republic of China.,Center of Excellence for Vector-Borne Diseases, Department of Diagnostic Medicine/Pathobiology, College of Veterinary Medicine, Kansas State University, Manhattan, Kansas, 66502, USA.,Jiangsu Co-innovation Center for Prevention and Control of Important Animal Infectious Diseases and Zoonoses, Yangzhou, Jiangsu, 225009, People's Republic of China.,Jiangsu Key Laboratory of Zoonosis, Yangzhou, Jiangsu, 225009, People's Republic of China.,Joint International Research Laboratory of Agriculture and Agri-Product Safety, the Ministry of Education of China, Yangzhou University, Yangzhou, Jiangsu, 225009, People's Republic of China
| | - Roman R Ganta
- Center of Excellence for Vector-Borne Diseases, Department of Diagnostic Medicine/Pathobiology, College of Veterinary Medicine, Kansas State University, Manhattan, Kansas, 66502, USA
| | - Zongping Liu
- College of Veterinary Medicine, Yangzhou University, Yangzhou, Jiangsu, 225009, People's Republic of China.,Jiangsu Co-innovation Center for Prevention and Control of Important Animal Infectious Diseases and Zoonoses, Yangzhou, Jiangsu, 225009, People's Republic of China.,Jiangsu Key Laboratory of Zoonosis, Yangzhou, Jiangsu, 225009, People's Republic of China.,Joint International Research Laboratory of Agriculture and Agri-Product Safety, the Ministry of Education of China, Yangzhou University, Yangzhou, Jiangsu, 225009, People's Republic of China
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11
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Ishikawa M, Williams G, Forcinito P, Ishikawa M, Petrie RJ, Saito K, Fukumoto S, Yamada Y. Pannexin 3 ER Ca 2+ channel gating is regulated by phosphorylation at the Serine 68 residue in osteoblast differentiation. Sci Rep 2019; 9:18759. [PMID: 31822768 PMCID: PMC6904572 DOI: 10.1038/s41598-019-55371-9] [Citation(s) in RCA: 8] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/11/2019] [Accepted: 11/19/2019] [Indexed: 12/31/2022] Open
Abstract
Pannexin 3 (Panx3) is a regulator of bone formation. Panx3 forms three distinct functional channels: hemichannels, gap junctions, and endoplasmic reticulum (ER) Ca2+ channels. However, the gating mechanisms of the Panx3 channels remain unclear. Here, we show that the Panx3 ER Ca2+ channel is modulated by phosphorylation of the serine 68 residue (Ser68) to promote osteoblast differentiation. Among the 17 candidate phosphorylation sites identified, the mutation of Ser68 to Ala (Ser68Ala) was sufficient to inhibit Panx3-mediated osteoblast differentiation via reduction of Osterix and ALP expression. Using a Ser68 phospho-specific antibody (P-Panx3) revealed Panx3 was phosphorylated in prehypertrophic, hypertrophic chondrocytes, and bone areas of the newborn growth plate. In osteogenic C2C12 cells, P-Panx3 was located on the ER membranes. Importantly, the Ser68Ala mutation only affected Panx3 ER Ca2+ channel function. Ser68 on Panx3 was phosphorylated by ATP stimulation and PI3K/Akt signaling. Finally, real-time FRET imaging and ratio analysis revealed that the Panx3 channel conformation was sensitive to ATP. Together, the phosphorylation of Panx3 at Ser68 is an essential step controlling the gating of the Panx3 ER Ca2+ channel to promote osteogenesis.
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Affiliation(s)
- Masaki Ishikawa
- Operative Dentistry, Tohoku University Graduate School of Dentistry, Sendai, 980-8575, Japan.
| | - Geneva Williams
- Molecular Biology Section, National Institute of Dental and Craniofacial Research, National Institutes of Health, Philadelphia, USA
| | - Patricia Forcinito
- Molecular Biology Section, National Institute of Dental and Craniofacial Research, National Institutes of Health, Philadelphia, USA
| | - Momoko Ishikawa
- Department of Pediatric Dentistry, Tohoku University Graduate School of Dentistry, Sendai, 980-8576, Japan
| | - Ryan J Petrie
- Department of Biology, Drexel University, Philadelphia, PA, 19104, USA
| | - Kan Saito
- Department of Pediatric Dentistry, Tohoku University Graduate School of Dentistry, Sendai, 980-8576, Japan
| | - Satoshi Fukumoto
- Department of Pediatric Dentistry, Tohoku University Graduate School of Dentistry, Sendai, 980-8576, Japan
| | - Yoshihiko Yamada
- Molecular Biology Section, National Institute of Dental and Craniofacial Research, National Institutes of Health, Philadelphia, USA
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12
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Xi G, D'Costa S, Wai C, Xia SK, Cox ZC, Clemmons DR. IGFBP-2 stimulates calcium/calmodulin-dependent protein kinase kinase 2 activation leading to AMP-activated protein kinase induction which is required for osteoblast differentiation. J Cell Physiol 2019; 234:23232-23242. [PMID: 31155724 DOI: 10.1002/jcp.28890] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/27/2019] [Accepted: 05/13/2019] [Indexed: 12/28/2022]
Abstract
Insulin-like growth factor-I (IGF-I) and insulin-like growth factor binding proteins-2 (IGFBP-2) function coordinately to stimulate osteoblast differentiation. Induction of AMP-activated protein kinase (AMPK) is required for differentiation and is stimulated by these two factors. These studies were undertaken to determine how these two peptides lead to activation of AMPK. Enzymatic inhibitors and small interfering RNA were utilized to attenuate calcium/calmodulin-dependent protein kinase kinase 2 (CaMKK2) activity in osteoblasts, and both manipulations resulted in failure to activate AMPK, thereby resulting in inhibition of osteoblast differentiation. IGFBP-2 and IGF-I stimulated an increase in CaMKK2, and inhibition of IGFBP-2 binding its receptor resulted in failure to induce CaMKK2 and AMPK activation. Injection of a peptide that contained the IGFBP-2 receptor-binding domain into IGFBP-2-/- mice activated CaMKK2 and injection of a CaMKK2 inhibitor into normal mice inhibited both CamKK2 and AMPK activation in osteoblasts. We conclude that induction of CaMKK2 by IGFBP-2 and IGF-I in osteoblasts is an important signaling event that occurs early in differentiation and is responsible for activation of AMPK, which is required for optimal osteoblast differentiation.
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Affiliation(s)
- Gang Xi
- Department of Medicine, University of North Carolina at Chapel Hill, Chapel Hill, North Carolina
| | - Susan D'Costa
- Department of Medicine, University of North Carolina at Chapel Hill, Chapel Hill, North Carolina
| | - Christine Wai
- Department of Medicine, University of North Carolina at Chapel Hill, Chapel Hill, North Carolina
| | - Shalier K Xia
- Department of Medicine, University of North Carolina at Chapel Hill, Chapel Hill, North Carolina
| | - Zach C Cox
- Department of Medicine, University of North Carolina at Chapel Hill, Chapel Hill, North Carolina
| | - David R Clemmons
- Department of Medicine, University of North Carolina at Chapel Hill, Chapel Hill, North Carolina
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13
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Glucose Restriction Promotes Osteocyte Specification by Activating a PGC-1α-Dependent Transcriptional Program. iScience 2019; 15:79-94. [PMID: 31039455 PMCID: PMC6488568 DOI: 10.1016/j.isci.2019.04.015] [Citation(s) in RCA: 14] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/22/2018] [Revised: 01/16/2019] [Accepted: 04/08/2019] [Indexed: 12/16/2022] Open
Abstract
Osteocytes, the most abundant of bone cells, differentiate while they remain buried within the bone matrix. This encasement limits their access to nutrients and likely affects their differentiation, a process that remains poorly defined. Here, we show that restriction in glucose supply promotes the osteocyte transcriptional program while also being associated with increased mitochondrial DNA levels. Glucose deprivation triggered the activation of the AMPK/PGC-1 pathway. AMPK and SIRT1 activators or PGC-1α overexpression are sufficient to enhance osteocyte gene expression in IDG-SW3 cells, murine primary osteoblasts, osteocytes, and organotypic/ex vivo bone cultures. Conversely, osteoblasts and osteocytes deficient in Ppargc1a and b were refractory to the effects of glucose restriction. Finally, conditional ablation of both genes in osteoblasts and osteocytes generate osteopenia and reduce osteocytic gene expression in mice. Altogether, we uncovered a role for PGC-1 in the regulation of osteocyte gene expression.
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14
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Wang Q, Wang G, Wang B, Yang H. Activation of TGR5 promotes osteoblastic cell differentiation and mineralization. Biomed Pharmacother 2018; 108:1797-1803. [PMID: 30372884 DOI: 10.1016/j.biopha.2018.08.093] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/16/2018] [Revised: 08/10/2018] [Accepted: 08/17/2018] [Indexed: 12/26/2022] Open
Abstract
Impairment of normal osteoblast differentiation has been associated with bone loss-related disorders, such as osteoporosis. Takeda G-protein coupled receptor 5 (TGR5) has been identified as an important modulator of bile acid and energy homeostasis. Little information regarding the effects of TGR5 on osteoblastic bone formation and matrix mineralization has been reported before. In the current study, we found that TGR5 was expressed in osteoblast-like cell line MC3T3-E1 cells. Osteogenic medium (OM) stimulation promoted the expression of TGR5 in a dose-dependent manner. Notably, treatment with the specific TGR5 agonist GPBARA increased ALP activity, matrix mineralization, and expressions of osteoblastic differentiation marker genes, such as ALP, OCN, and Osx, by promoting the expression of Runx-2. Silencing of TGR5 by transfection with TGR5 siRNA abolished these effects. Also, we found that the AMPK/eNOS pathway was involved in this process. Blockage of AMPK activation using its specific inhibitor compound C abolished the effect of GPBARA-induced increase in ALP activity, matrix mineralization, and expressions of osteoblastic differentiation marker genes. The obtained results provide a new insight into the physiological function of TGR5 in bone formation and suggest that TGR5 might be a novel therapeutic target for bone diseases.
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Affiliation(s)
- Qingfeng Wang
- Department of Orthopaedic Surgery, The First Affiliated Hospital of Soochow University, 188 Shizi Street, Suzhou 215006, Jiangsu, PR China
| | - Guoqiang Wang
- Department of Orthopaedic Surgery, The Forth Hospital, Baotou 014030, Inner Mongolia, PR China
| | - Bin Wang
- Department of Orthopaedic Surgery, The Second Affiliated Hospital of Xuzhou Medical University, Xuzhou 221006, Jiangsu, PR China
| | - Huilin Yang
- Department of Orthopaedic Surgery, The First Affiliated Hospital of Soochow University, 188 Shizi Street, Suzhou 215006, Jiangsu, PR China.
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15
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Abstract
Osteoclasts are defined as cells capable of excavating 3-dimensional resorption pits in bone and other mineralised tissues. They are derived from the differentiation/fusion of promonocytic precursors, and are usually large, multinucleated cells. In common with other cells from this myeloid lineage such as macrophages and dendritic cells, they are adapted to function in hypoxic, acidic environments. The process of bone resorption is rapid and is presumably highly energy-intensive, since osteoclasts must actively extrude protons to dissolve hydroxyapatite mineral, whilst secreting cathepsin K to degrade collagen, as well as maintaining a high degree of motility. Osteoclasts are well known to contain abundant mitochondria but they are also able to rely on glycolytic (anaerobic) metabolism to generate the ATP needed to power their activity. Their primary extracellular energy source appears to be glucose. Excessive accumulation of mitochondrial reactive oxygen species in osteoclasts during extended periods of high activity in oxygen-poor environments may promote apoptosis and help to limit bone resorption - a trajectory that could be termed "live fast, die young". In general, however, the metabolism of osteoclasts remains a poorly-investigated area, not least because of the technical challenges of studying actively resorbing cells in appropriate conditions.
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Affiliation(s)
- Timothy R Arnett
- Department of Cell & Developmental Biology, University College London, Gower Street, London WC1E 6BT, UK.
| | - Isabel R Orriss
- Department of Comparative Biomedical Sciences, Royal Veterinary College, Royal College Street, London NW1 0TU, UK.
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16
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Kanazawa I, Takeno A, Tanaka KI, Notsu M, Sugimoto T. Osteoblast AMP-activated protein kinase regulates glucose metabolism and bone mass in adult mice. Biochem Biophys Res Commun 2018; 503:1955-1961. [DOI: 10.1016/j.bbrc.2018.07.141] [Citation(s) in RCA: 7] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/24/2018] [Accepted: 07/27/2018] [Indexed: 01/07/2023]
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17
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Yan Z, Tian X, Zhu J, Lu Z, Yu L, Zhang D, Liu Y, Yang C, Zhu Q, Cao X. Metformin suppresses UHMWPE particle-induced osteolysis in the mouse calvaria by promoting polarization of macrophages to an anti-inflammatory phenotype. Mol Med 2018; 24:20. [PMID: 30134793 PMCID: PMC6016863 DOI: 10.1186/s10020-018-0013-x] [Citation(s) in RCA: 25] [Impact Index Per Article: 4.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/10/2018] [Accepted: 03/06/2018] [Indexed: 03/02/2023] Open
Abstract
Background Implant failure remains a major obstacle to successful treatment via TJA. Periprosthetic osteolysis and aseptic loosening are considered as proof of wear debris-induced disruption of local regulatory mechanisms related to excessive bone resorption associated with osteolysis and the damage at the bone-prosthesis interface. Therefore, there is an immediate need to explore strategies for limiting and curing periprosthetic osteolysis and aseptic loosening. Methods We analyzed the in vitro cytokine production by primary mouse bone marrow macrophages (BMMs) that were exposed to ultra-high molecular weight polyethylene (UHMWPE) particles and treated with metformin at different concentrations with or without 5-aminoimidazole-4-carboxamide ribonucleoside to activate or inhibit AMPK. A mouse calvarial model was used to examine the in vivo effects of metformin on UHMWPE particle-induced osteolysis. Results With particles, primary mouse BMMs secreted more pro-inflammatory cytokines tumor necrosis factor-α and interleukin (IL)-6. Treatment with metformin inhibited these variations and promoted the release of cytokine IL-10 with anti-inflammatory capability. In vivo, metformin reduced the production of pro-inflammatory cytokines, osteoclastogenesis, and osteolysis, increasing IL-10 production. Metformin also promoted the polarization of macrophages to an anti-inflammatory phenotype in vivo via AMPK activation. Discussion A crucial point in limiting and correcting the periprosthetic osteolysis and aseptic loosening is the inhibition of inflammatory factor production and osteoclast activation induced by activated macrophages. The ability of metformin to attenuate osteolysis induced in mouse calvaria by the particles was related to a reduction in osteoclast number and polarization of macrophages to an anti-inflammatory functional phenotype. Conclusions Metformin could limit the osteolysis induced by implant debris. Therefore, we hypothesized that metformin could be a potential drug for osteolysis induced by implant debris. Electronic supplementary material The online version of this article (10.1186/s10020-018-0013-x) contains supplementary material, which is available to authorized users.
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Affiliation(s)
- Zhao Yan
- PLA Institute of Orthopaedics, Xijing Hospital, Fourth Military Medical University, Xi'an, 710032, China
| | - Xiaoxi Tian
- Emergency department of Tangdu Hospital, Fourth Military Medical University, Xi'an, 710038, China
| | - Jinyu Zhu
- PLA Institute of Orthopaedics, Xijing Hospital, Fourth Military Medical University, Xi'an, 710032, China
| | - Zifan Lu
- State Key Laboratory of Cancer Biology, Department of Pharmacogenomics, Fourth Military Medical University, Xi'an, 710032, China
| | - Lifeng Yu
- PLA Institute of Orthopaedics, Xijing Hospital, Fourth Military Medical University, Xi'an, 710032, China
| | - Dawei Zhang
- PLA Institute of Orthopaedics, Xijing Hospital, Fourth Military Medical University, Xi'an, 710032, China
| | - Yanwu Liu
- PLA Institute of Orthopaedics, Xijing Hospital, Fourth Military Medical University, Xi'an, 710032, China
| | - Chongfei Yang
- PLA Institute of Orthopaedics, Xijing Hospital, Fourth Military Medical University, Xi'an, 710032, China
| | - Qingsheng Zhu
- PLA Institute of Orthopaedics, Xijing Hospital, Fourth Military Medical University, Xi'an, 710032, China.
| | - Xiaorui Cao
- PLA Institute of Orthopaedics, Xijing Hospital, Fourth Military Medical University, Xi'an, 710032, China.
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18
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Kanazawa I, Takeno A, Tanaka KI, Notsu M, Sugimoto T. Osteoblast AMP-Activated Protein Kinase Regulates Postnatal Skeletal Development in Male Mice. Endocrinology 2018; 159:597-608. [PMID: 29126229 DOI: 10.1210/en.2017-00357] [Citation(s) in RCA: 14] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 04/13/2017] [Accepted: 10/30/2017] [Indexed: 11/19/2022]
Abstract
Studies have shown that AMP-activated protein kinase (AMPK), a crucial regulator of energy homeostasis, plays important roles in osteoblast differentiation and mineralization. However, little is known about in vivo roles of osteoblastic AMPK in bone development. Thus, to investigate in vivo roles of osteoblast AMPK, we conditionally inactivated Ampk in osterix (Osx)-expressing cells by crossing Osx-Cre mice with floxed AMPKα1 to generate mice lacking AMPKα1 in osteoblasts (Ampk-/- mice). Compared with wild-type and Ampk+/- mice, Ampk-/- mice displayed retardation of postnatal bone development, although bone deformity was not observed at birth. Microcomputed tomography showed significant reductions in trabecular bone volume, cortical bone length, and density, as well as increased cortical porosity in femur as well as development defects of skull in 8-week-old Ampk-/- mice. Surprisingly, histomorphometric analysis demonstrated that the number of osteoclasts was significantly increased, although bone formation rate was not altered. Loss of trabecular network connections and mass, as well as shortened growth plates and reduced thickness of cartilage adjacent to the growth plate, was observed in Ampk-/- mice. In primary cultured osteoblasts from calvaria, the expressions of alkaline phosphatase, type 1 collagen, osteocalcin, bone morphogenetic protein 2, Runx2, and osterix were significantly inhibited in Ampk-/- osteoblasts, whereas the expression of receptor activator of nuclear κB ligand (RANKL) and the RANKL/osteoprotegerin ratio were significantly increased. These findings indicate that osteoblastic AMPK plays important roles in bone development in vivo and that deletion of AMPK in osteoblasts decreases osteoblastic differentiation and enhances bone turnover by increasing RANKL expression.
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Affiliation(s)
- Ippei Kanazawa
- Internal Medicine 1, Shimane University Faculty of Medicine, Shimane, Japan
| | - Ayumu Takeno
- Internal Medicine 1, Shimane University Faculty of Medicine, Shimane, Japan
| | - Ken-Ichiro Tanaka
- Internal Medicine 1, Shimane University Faculty of Medicine, Shimane, Japan
| | - Masakazu Notsu
- Internal Medicine 1, Shimane University Faculty of Medicine, Shimane, Japan
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19
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Zhang P, Liu X, Huang G, Bai C, Zhang Z, Li H. WITHDRAWN: Schisandrin B suppresses NLRP3 inflammasome activation to alleviate myocardial ischemia reperfusion injury via maintaining mitochondrial autophagy. Biochem Biophys Res Commun 2017; 494:425. [DOI: 10.1016/j.bbrc.2017.08.079] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/10/2017] [Accepted: 08/21/2017] [Indexed: 01/10/2023]
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20
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Abstract
Accumulating evidence has shown that bone and glucose metabolism are closely associated with each other. Since the risk of osteoporotic fractures is increased in patients with diabetes mellitus (DM), osteoporosis is recently recognized as one of diabetic complications, called DM-induced bone fragility. Previous studies showed that collagen cross-links of advanced glycation end products (AGEs) and dysfunctions of osteoblast and osteocyte are involved in DM-induced bone fragility. Circulating levels of AGEs and homocysteine are increased in patients with DM, and they directly impair the functions of osteoblast and osteocyte, resulting in decreased bone formation and bone remodeling. On the other hand, bone is recently recognized as an endocrine organ. Previous studies based on in vitro and animal studies showed that osteocalcin, which is specifically expressed in osteoblasts and secreted into the circulation, may regulate glucose homeostasis. Although several clinical studies reported the relationship between osteocalcin and glucose metabolism, further large-scale and intervention studies are necessary to confirm the beneficial effects of osteocalcin on glucose metabolism in human. It has been shown that adenosine monophosphate-activated protein kinase (AMPK), an intracellular energy sensor, is involved in bone metabolism. Adiponectin and metformin stimulate osteocalcin expression and the differentiation of osteoblasts via AMPK activation. Also, AMPK activation protects against oxidative stress-induced apoptosis of osteocytes. These findings suggest that AMPK in osteoblasts and osteocytes may be a therapeutic target for DM-induced bone fragility.
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Affiliation(s)
- Ippei Kanazawa
- Internal Medicine 1, Shimane University Faculty of Medicine, Izumo 693-8501, Japan
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21
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Mu W, Wang Z, Ma C, Jiang Y, Zhang N, Hu K, Li L, Wang Z. Metformin promotes the proliferation and differentiation of murine preosteoblast by regulating the expression of sirt6 and oct4. Pharmacol Res 2017; 129:462-474. [PMID: 29162538 DOI: 10.1016/j.phrs.2017.11.020] [Citation(s) in RCA: 34] [Impact Index Per Article: 4.9] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 05/04/2017] [Revised: 11/15/2017] [Accepted: 11/16/2017] [Indexed: 12/15/2022]
Abstract
Osteopenia, osteoporosis and bone salt metabolism disorder are common diseases in the aged and diabetics. From case reports of patients with T2DM, we have observed that metformin can decrease risk of bone fracture and promote bone formation. However, the underlying mechanism of metformin's effect on bone metabolism remains unknown. In our research, we show that metformin can promote proliferation of murine preosteoblast by regulating AMPK-mTORC2 and AKT-mTORC1 signaling axis. Furthermore, we have observed that metformin can promote SIRT6 expression before and during differentiation of murine preosteoblast. The interaction between SIRT6 and NF-κB is highly important in osteoblast differentiation just as the relationship between OPG and RANKL in the process of bone formation. During differentiation, we show that SIRT6 inhibits phosphorylation of NF-κB and that OPG increases while RANKL decrease in HG groups. In addition, ablation of sirt6 in mice causes phosphorylation of NF-κB at high-levels and RANKL increases slightly in femur bone cells. However, other bone formation marker proteins such as RUNX2, OSTERIX and OPG appear at low-levels in sirt6 KO mice. It has been confirmed that downregulation of OCT4 is critical incident in the differentiation of embryonic stem cells. Fortunately, we observe that SIRT6 can suppress OCT4 expression in murine preosteoblast and the expression of OCT4 is at high-level in sirt6 KO mice. Taken together, this study's results illuminate metformin's effect on bone metabolism under HG condition and help to elucidate why metformin can promote bone fracture healing of patients with T2DM.
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Affiliation(s)
- Wei Mu
- Protein Science Key Laboratory of the Ministry of Education, School of Pharmaceutical Sciences, Tsinghua University, Beijing, PR China
| | - Zhuoran Wang
- Protein Science Key Laboratory of the Ministry of Education, School of Pharmaceutical Sciences, Tsinghua University, Beijing, PR China
| | - Chuanyu Ma
- Department of Orthopedics, Clinical Bone Research Center, PLA 101 Hospital, Wuxi, PR China
| | - Yunyun Jiang
- Department of Orthopedics, Clinical Bone Research Center, PLA 101 Hospital, Wuxi, PR China
| | - Nannan Zhang
- Protein Science Key Laboratory of the Ministry of Education, School of Pharmaceutical Sciences, Tsinghua University, Beijing, PR China
| | - Kaiqiang Hu
- Protein Science Key Laboratory of the Ministry of Education, School of Pharmaceutical Sciences, Tsinghua University, Beijing, PR China
| | - Liyuan Li
- Protein Science Key Laboratory of the Ministry of Education, School of Pharmaceutical Sciences, Tsinghua University, Beijing, PR China
| | - Zhao Wang
- Protein Science Key Laboratory of the Ministry of Education, School of Pharmaceutical Sciences, Tsinghua University, Beijing, PR China.
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22
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Torre E. Molecular signaling mechanisms behind polyphenol-induced bone anabolism. PHYTOCHEMISTRY REVIEWS : PROCEEDINGS OF THE PHYTOCHEMICAL SOCIETY OF EUROPE 2017; 16:1183-1226. [PMID: 29200988 PMCID: PMC5696504 DOI: 10.1007/s11101-017-9529-x] [Citation(s) in RCA: 58] [Impact Index Per Article: 8.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 01/27/2017] [Accepted: 08/20/2017] [Indexed: 05/08/2023]
Abstract
For millennia, in the different cultures all over the world, plants have been extensively used as a source of therapeutic agents with wide-ranging medicinal applications, thus becoming part of a rational clinical and pharmacological investigation over the years. As bioactive molecules, plant-derived polyphenols have been demonstrated to exert many effects on human health by acting on different biological systems, thus their therapeutic potential would represent a novel approach on which natural product-based drug discovery and development could be based in the future. Many reports have provided evidence for the benefits derived from the dietary supplementation of polyphenols in the prevention and treatment of osteoporosis. Polyphenols are able to protect the bone, thanks to their antioxidant properties, as well as their anti-inflammatory actions by involving diverse signaling pathways, thus leading to bone anabolic effects and decreased bone resorption. This review is meant to summarize the research works performed so far, by elucidating the molecular mechanisms of action of polyphenols in a bone regeneration context, aiming at a better understanding of a possible application in the development of medical devices for bone tissue regeneration.
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Affiliation(s)
- Elisa Torre
- Nobil Bio Ricerche srl, Via Valcastellana, 26, 14037 Portacomaro, AT Italy
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23
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Fan Q, Li H, Liu Z, Zhang Z, Li H, Ding J, Zhang Z. Leptin inhibits AMPKα2 down-regulation induced decrease in the osteocytic MLO-Y4 cell proliferation and the expression of osteogenic markers. INTERNATIONAL JOURNAL OF CLINICAL AND EXPERIMENTAL PATHOLOGY 2017; 10:8544-8552. [PMID: 31966708 PMCID: PMC6965451] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Subscribe] [Scholar Register] [Received: 05/03/2017] [Accepted: 05/25/2017] [Indexed: 06/10/2023]
Abstract
AMP-activated protein kinase (AMPK) is of biological and clinical importance for regulating cellular and systemic energy homeostasis. Although AMPKα1, one of the two AMPK's catalytic subunit α, expresses in the bone and stimulates bone nodule formation, the role of AMPKα2 in osteogenesis remains incompletely understood. The aim of this study was to determine the role of AMPKα2 in osteocytic MLO-Y4 cellproliferation and the expression of osteogenic markers. The current study silenced AMPKα2 in MLO-Y4 cells by transfection with pLKO.1-AMPKα2-shRNA vector and analyzed cell proliferation and the expression of osteogenic markers in MLO-Y4 cells with or without 100 μg/ml leptin treatment through CCK-8, Real-time PCR, Western blot and RNA-seq assay. We found that knockdown of AMPKα2 significantly decreased the mRNA level of AMPKα2 and the cell proliferation of MLO-Y4 cellsas well as the mRNA and protein levels of OPG, OCN, OPN, ALP and BMP6 and the protein expression of p-Smad5/Smad5. However, leptin treatment increased the MLO-Y4 cell proliferation and the expression of these osteogenic markers in MLO-Y4 cells with or without AMPKα2 silencing. Furthermore, RNA-seq assay showed 1019 transcriptors decreased in AMPKα2-silencing group and 995 transcriptors increased in leptin group compared with control group, respectively. 737 transcriptors decreased in AMPKα2-silencing group and 1282 transcriptors increased inleptin group compared with AMPKα2-silencing+leptin group, respectively. These findings suggest that AMPKα2 knockdown inhibited MLO-Y4 cell proliferation and osteogenic marker expressions, which implicates an important role of AMPKα2 in osteogenesis in vitro.
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Affiliation(s)
- Qing Fan
- Department of Pediatric Orthopedics, Xin Hua Hospital Affiliated to Shanghai Jiao Tong University School of Medicine Shanghai, P. R. China
| | - Hao Li
- Department of Pediatric Orthopedics, Xin Hua Hospital Affiliated to Shanghai Jiao Tong University School of Medicine Shanghai, P. R. China
| | - Zhu Liu
- Department of Pediatric Orthopedics, Xin Hua Hospital Affiliated to Shanghai Jiao Tong University School of Medicine Shanghai, P. R. China
| | - Zhiqiang Zhang
- Department of Pediatric Orthopedics, Xin Hua Hospital Affiliated to Shanghai Jiao Tong University School of Medicine Shanghai, P. R. China
| | - Hai Li
- Department of Pediatric Orthopedics, Xin Hua Hospital Affiliated to Shanghai Jiao Tong University School of Medicine Shanghai, P. R. China
| | - Jing Ding
- Department of Pediatric Orthopedics, Xin Hua Hospital Affiliated to Shanghai Jiao Tong University School of Medicine Shanghai, P. R. China
| | - Ziming Zhang
- Department of Pediatric Orthopedics, Xin Hua Hospital Affiliated to Shanghai Jiao Tong University School of Medicine Shanghai, P. R. China
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Abstract
The rising incidence of metabolic diseases worldwide has prompted renewed interest in the study of intermediary metabolism and cellular bioenergetics. The application of modern biochemical methods for quantitating fuel substrate metabolism with advanced mouse genetic approaches has greatly increased understanding of the mechanisms that integrate energy metabolism in the whole organism. Examination of the intermediary metabolism of skeletal cells has been sparked by a series of unanticipated observations in genetically modified mice that suggest the existence of novel endocrine pathways through which bone cells communicate their energy status to other centers of metabolic control. The recognition of this expanded role of the skeleton has in turn led to new lines of inquiry directed at defining the fuel requirements and bioenergetic properties of bone cells. This article provides a comprehensive review of historical and contemporary studies on the metabolic properties of bone cells and the mechanisms that control energy substrate utilization and bioenergetics. Special attention is devoted to identifying gaps in our current understanding of this new area of skeletal biology that will require additional research to better define the physiological significance of skeletal cell bioenergetics in human health and disease.
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Affiliation(s)
- Ryan C Riddle
- Department of Orthopaedic Surgery, The Johns Hopkins University, Baltimore, Maryland; and The Baltimore Veterans Administration Medical Center, Baltimore, Maryland
| | - Thomas L Clemens
- Department of Orthopaedic Surgery, The Johns Hopkins University, Baltimore, Maryland; and The Baltimore Veterans Administration Medical Center, Baltimore, Maryland
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25
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Cheng J, Zhang T, Ji H, Tao K, Guo J, Wei W. Functional characterization of AMP-activated protein kinase signaling in tumorigenesis. Biochim Biophys Acta Rev Cancer 2016; 1866:232-251. [PMID: 27681874 DOI: 10.1016/j.bbcan.2016.09.006] [Citation(s) in RCA: 31] [Impact Index Per Article: 3.9] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/07/2016] [Revised: 09/22/2016] [Accepted: 09/23/2016] [Indexed: 12/13/2022]
Abstract
AMP-activated protein kinase (AMPK) is a ubiquitously expressed metabolic sensor among various species. Specifically, cellular AMPK is phosphorylated and activated under certain stressful conditions, such as energy deprivation, in turn to activate diversified downstream substrates to modulate the adaptive changes and maintain metabolic homeostasis. Recently, emerging evidences have implicated the potential roles of AMPK signaling in tumor initiation and progression. Nevertheless, a comprehensive description on such topic is still in scarcity, especially in combination of its biochemical features with mouse modeling results to elucidate the physiological role of AMPK signaling in tumorigenesis. Hence, we performed this thorough review by summarizing the tumorigenic role of each component along the AMPK signaling, comprising of both its upstream and downstream effectors. Moreover, their functional interplay with the AMPK heterotrimer and exclusive efficacies in carcinogenesis were chiefly explained among genetically altered mice models. Importantly, the pharmaceutical investigations of AMPK relevant medications have also been highlighted. In summary, in this review, we not only elucidate the potential functions of AMPK signaling pathway in governing tumorigenesis, but also potentiate the future targeted strategy aiming for better treatment of aberrant metabolism-associated diseases, including cancer.
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Affiliation(s)
- Ji Cheng
- Department of Gastrointestinal Surgery, Union Hospital, Tongji Medical College, Huazhong University of Science and Technology, Wuhan 430022, People's Republic of China; Department of Pathology, Beth Israel Deaconess Medical Center, Harvard Medical School, Boston, MA 02215, USA
| | - Tao Zhang
- Department of Pathology, Beth Israel Deaconess Medical Center, Harvard Medical School, Boston, MA 02215, USA
| | - Hongbin Ji
- Key Laboratory of Systems Biology, Institute of Biochemistry and Cell Biology, Shanghai Institutes for Biological Sciences, Chinese Academy of Science, Shanghai 200031, People's Republic of China
| | - Kaixiong Tao
- Department of Gastrointestinal Surgery, Union Hospital, Tongji Medical College, Huazhong University of Science and Technology, Wuhan 430022, People's Republic of China.
| | - Jianping Guo
- Department of Pathology, Beth Israel Deaconess Medical Center, Harvard Medical School, Boston, MA 02215, USA.
| | - Wenyi Wei
- Department of Pathology, Beth Israel Deaconess Medical Center, Harvard Medical School, Boston, MA 02215, USA.
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Wang YG, Han XG, Yang Y, Qiao H, Dai KR, Fan QM, Tang TT. Functional differences between AMPK α1 and α2 subunits in osteogenesis, osteoblast-associated induction of osteoclastogenesis, and adipogenesis. Sci Rep 2016; 6:32771. [PMID: 27600021 PMCID: PMC5013406 DOI: 10.1038/srep32771] [Citation(s) in RCA: 28] [Impact Index Per Article: 3.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/04/2016] [Accepted: 08/15/2016] [Indexed: 12/21/2022] Open
Abstract
The endocrine role of the skeleton-which is impaired in human diseases including osteoporosis, obesity and diabetes-has been highlighted previously. In these diseases, the role of AMPK, a sensor and regulator of energy metabolism, is of biological and clinical importance. Since AMPK’s main catalytic subunit α has two isoforms, it is unclear whether functional differences between them exist in the skeletal system. The current study overexpressed AMPKα1 and α2 in MC3T3-E1 cells, primary osteoblasts and mouse BMSCs by lentiviral transduction. Cells overexpressing AMPKα2 showed higher osteogenesis potential than AMPKα1, wherein androgen receptor (AR) and osteoactivin played important roles. RANKL and M-CSF were secreted at lower levels from cells overexpressing α2 than α1, resulting in decreased osteoblast-associated osteoclastogenesis. Adipogenesis was inhibited to a greater degree in 3T3-L1 cells overexpressing α2 than α1, which was modulated by AR. An abnormal downregulation of AMPKα2 was observed in human BMSCs exhibiting the fibrous dysplasia (FD) phenotype. Overexpression of AMPKα2 in these cells rescued the defect in osteogenesis, suggesting that AMPKα2 plays a role in FD pathogenesis. These findings highlight functional differences between AMPKα1 and α2, and provide a basis for investigating the molecular mechanisms of diseases associated with impaired functioning of the skeletal system.
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Affiliation(s)
- Yu-Gang Wang
- Shanghai Key Laboratory of Orthopedic Implants, Department of Orthopedic Surgery, Shanghai Ninth People's Hospital, Shanghai JiaoTong University School of Medicine, 639 Zhizaoju Road, Shanghai 200011, People's Republic of China
| | - Xiu-Guo Han
- Shanghai Key Laboratory of Orthopedic Implants, Department of Orthopedic Surgery, Shanghai Ninth People's Hospital, Shanghai JiaoTong University School of Medicine, 639 Zhizaoju Road, Shanghai 200011, People's Republic of China
| | - Ying Yang
- Shanghai Key Laboratory of Orthopedic Implants, Department of Orthopedic Surgery, Shanghai Ninth People's Hospital, Shanghai JiaoTong University School of Medicine, 639 Zhizaoju Road, Shanghai 200011, People's Republic of China
| | - Han Qiao
- Shanghai Key Laboratory of Orthopedic Implants, Department of Orthopedic Surgery, Shanghai Ninth People's Hospital, Shanghai JiaoTong University School of Medicine, 639 Zhizaoju Road, Shanghai 200011, People's Republic of China
| | - Ke-Rong Dai
- Shanghai Key Laboratory of Orthopedic Implants, Department of Orthopedic Surgery, Shanghai Ninth People's Hospital, Shanghai JiaoTong University School of Medicine, 639 Zhizaoju Road, Shanghai 200011, People's Republic of China
| | - Qi-Ming Fan
- Shanghai Key Laboratory of Orthopedic Implants, Department of Orthopedic Surgery, Shanghai Ninth People's Hospital, Shanghai JiaoTong University School of Medicine, 639 Zhizaoju Road, Shanghai 200011, People's Republic of China
| | - Ting-Ting Tang
- Shanghai Key Laboratory of Orthopedic Implants, Department of Orthopedic Surgery, Shanghai Ninth People's Hospital, Shanghai JiaoTong University School of Medicine, 639 Zhizaoju Road, Shanghai 200011, People's Republic of China
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Oh SJ, Gu DR, Jin SH, Park KH, Lee SH. Cytosolic malate dehydrogenase regulates RANKL-mediated osteoclastogenesis via AMPK/c-Fos/NFATc1 signaling. Biochem Biophys Res Commun 2016; 475:125-32. [PMID: 27179783 DOI: 10.1016/j.bbrc.2016.05.055] [Citation(s) in RCA: 20] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/06/2016] [Accepted: 05/10/2016] [Indexed: 01/15/2023]
Abstract
Cytosolic malate dehydrogenase (malate dehydrogenase 1, MDH1) plays pivotal roles in the malate/aspartate shuttle that might modulate metabolism between the cytosol and mitochondria. In this study, we investigated the role of MDH1 in osteoclast differentiation and formation. MDH1 expression was induced by receptor activator of nuclear factor kappa-B ligand (RANKL) treatment. Knockdown of MDH1 by infection with retrovirus containing MDH1-specific shRNA (shMDH1) reduced mature osteoclast formation and bone resorption activity. Moreover, the expression of marker genes associated with osteoclast differentiation was downregulated by shMDH1 treatment, suggesting a role of MDH1 in osteoclast differentiation. In addition, intracellular ATP production was reduced following the activation of adenosine 5' monophosphate-activated protein kinase (AMPK), a cellular energy sensor and negative regulator of RANKL-induced osteoclast differentiation, in shMDH1-infected osteoclasts compared to control cells. In addition, the expression of c-Fos and nuclear factor of activated T-cells, cytoplasmic 1 (NFATc1), a critical transcription factor of osteoclastogenesis, was decreased with MDH1 knockdown during RANKL-mediated osteoclast differentiation. These findings provide strong evidence that MDH1 plays a critical role in osteoclast differentiation and function via modulation of the intracellular energy status, which might affect AMPK activity and NFATc1 expression.
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Affiliation(s)
- Se Jeong Oh
- Department of Oral Microbiology and Immunology, College of Dentistry, Wonkwang University, Iksan, Jeonbuk 54538, Republic of Korea
| | - Dong Ryun Gu
- Department of Oral Microbiology and Immunology, College of Dentistry, Wonkwang University, Iksan, Jeonbuk 54538, Republic of Korea; Center for Metabolic Function Regulation (CMFR), School of Medicine, Wonkwang University, Iksan, Jeonbuk 54538, Republic of Korea
| | - Su Hyun Jin
- Center for Metabolic Function Regulation (CMFR), School of Medicine, Wonkwang University, Iksan, Jeonbuk 54538, Republic of Korea
| | - Keun Ha Park
- Department of Oral Microbiology and Immunology, College of Dentistry, Wonkwang University, Iksan, Jeonbuk 54538, Republic of Korea; Center for Metabolic Function Regulation (CMFR), School of Medicine, Wonkwang University, Iksan, Jeonbuk 54538, Republic of Korea
| | - Seoung Hoon Lee
- Department of Oral Microbiology and Immunology, College of Dentistry, Wonkwang University, Iksan, Jeonbuk 54538, Republic of Korea; Center for Metabolic Function Regulation (CMFR), School of Medicine, Wonkwang University, Iksan, Jeonbuk 54538, Republic of Korea; Wonkwang Institute of Biomaterials and Implant, Wonkwang University, Iksan, Jeonbuk 54538, Republic of Korea.
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Yang C, Li Z, Lai P, Bai X, Jin D. Chondrocyte-Specific Ablation of AMPKα1 Does Not Affect Bone Development or Pathogenesis of Osteoarthritis in Mice. DNA Cell Biol 2016; 35:156-62. [PMID: 26741062 DOI: 10.1089/dna.2015.3074] [Citation(s) in RCA: 10] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/07/2023] Open
Abstract
AMP-activated protein kinase (AMPK) acts as an intracellular sensor that modulates the energy balance within the cell. AMPKα1 is the dominant catalytic isoform expressed in the bone, but the significance of AMPKα1 in articular cartilage has not been well studied. In this study, we aimed to assess the in vivo function of AMPKα1 in chondrocytes. We created chondrocyte-specific AMPKα1 conditional knockout (KO) mice using Col2α1-Cre and analyzed and compared growth characteristics, HE staining, and AMPKα gene expression between wild-type (WT) mice and AMPKα1 conditional KO mice under normal physiological conditions or following activation of AMPK by metformin intake or treadmill exercise. Microcomputed tomography and safranin O-fast green staining were compared between WT and KO mice after induction of experimental osteoarthritis (OA). Our data showed that there was no somatic difference between WT mice and KO mice of the same age. Metformin intake and treadmill exercise did not alter the phenotype of KO mice, and no difference in cartilage degradation was observed in WT mice or in KO mice after induction of traumatic arthritis. We thought that chondrocyte-specific ablation of AMPKα1 had no effect on bone growth or on pathogenesis of OA in mice, probably because the feedback overexpression of AMPKα2 compensated for loss of AMPKα1 and maintained the combination of AMPKα subunits.
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Affiliation(s)
- Cheng Yang
- 1 Academy of Orthopedics, Guangdong Province, Department of Orthopedic Surgery, The Third Affiliated Hospital of Southern Medical University , Guangzhou, China
| | - Zhen Li
- 1 Academy of Orthopedics, Guangdong Province, Department of Orthopedic Surgery, The Third Affiliated Hospital of Southern Medical University , Guangzhou, China
| | - Pinglin Lai
- 1 Academy of Orthopedics, Guangdong Province, Department of Orthopedic Surgery, The Third Affiliated Hospital of Southern Medical University , Guangzhou, China .,2 Department of Cell Biology, School of Basic Medical Science, Southern Medical University , Guangzhou, China
| | - Xiaochun Bai
- 1 Academy of Orthopedics, Guangdong Province, Department of Orthopedic Surgery, The Third Affiliated Hospital of Southern Medical University , Guangzhou, China .,2 Department of Cell Biology, School of Basic Medical Science, Southern Medical University , Guangzhou, China
| | - Dadi Jin
- 1 Academy of Orthopedics, Guangdong Province, Department of Orthopedic Surgery, The Third Affiliated Hospital of Southern Medical University , Guangzhou, China
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Xi G, Rosen CJ, Clemmons DR. IGF-I and IGFBP-2 Stimulate AMPK Activation and Autophagy, Which Are Required for Osteoblast Differentiation. Endocrinology 2016; 157:268-81. [PMID: 26556533 PMCID: PMC4701891 DOI: 10.1210/en.2015-1690] [Citation(s) in RCA: 71] [Impact Index Per Article: 8.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 08/05/2015] [Accepted: 11/06/2015] [Indexed: 12/13/2022]
Abstract
IGF-I/insulin-like growth factor binding protein 2 (IGFBP-2) coordinately stimulate osteoblast differentiation but the mechanisms by which they function have not been determined. AMP-activated protein kinase (AMPK) is induced during differentiation and AMPK knockout mice have reduced bone mass. IGF-I modulates AMPK in other cell types; therefore, these studies determined whether IGF-I/IGFBP-2 stimulate AMPK activation and the mechanism by which AMPK modulates differentiation. Calvarial osteoblasts and MC-3T3 cells expressed activated AMPK early in differentiation and AMPK inhibitors attenuated differentiation. However, expression of constitutively activated AMPK inhibited differentiation. To resolve this discrepancy we analyzed the time course of AMPK induction. AMPK activation was required early in differentiation (day 3-6) but down-regulation of AMPK after day 9 was also necessary. IGF-I/IGFBP-2 induced AMPK through their respective receptors and blocking-receptor activation blocked AMPK induction. To determine the mechanism by which AMPK functioned we analyzed components of the autophagosome. Activated AMPK stimulated ULK-1 S555 phosphorylation as well as beclin-1 and microtubule-associated protein 1A/1B light-chain phosphatidylethanolamine conjugate (LC3II) induction. Inhibition of AMPK attenuated these changes and direct inhibition of autophagy inhibited differentiation. Conversely, expression of activated AMPK was associated with persistence of these changes beyond day 9 and inhibited differentiation. Blocking AMPK activation after day 9 down-regulated these autophagosome components and rescued differentiation. This allowed induction of mechanistic target of rapamycin and AKT, which suppressed autophagy. The results show that early induction of AMPK in response to IGF-I/IGFBP-2 followed by suppression is required for osteoblast differentiation. AMPK functions through stimulation of autophagy. The findings suggest that these early catabolic changes are important for determining the energy source for osteoblast respiration and down-regulation of these components may be required for induction of glycolysis, which is required during the final anabolic stages of differentiation.
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Affiliation(s)
- Gang Xi
- Department of Medicine (G.X., D.R.C.), University of North Carolina at Chapel Hill, Chapel Hill, North Carolina 27599; and Maine Medical Center Research Institute (C.J.R.), Scarborough, Maine 04074
| | - Clifford J Rosen
- Department of Medicine (G.X., D.R.C.), University of North Carolina at Chapel Hill, Chapel Hill, North Carolina 27599; and Maine Medical Center Research Institute (C.J.R.), Scarborough, Maine 04074
| | - David R Clemmons
- Department of Medicine (G.X., D.R.C.), University of North Carolina at Chapel Hill, Chapel Hill, North Carolina 27599; and Maine Medical Center Research Institute (C.J.R.), Scarborough, Maine 04074
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30
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Yokomoto-Umakoshi M, Kanazawa I, Takeno A, Tanaka KI, Notsu M, Sugimoto T. Activation of AMP-activated protein kinase decreases receptor activator of NF-κB ligand expression and increases sclerostin expression by inhibiting the mevalonate pathway in osteocytic MLO-Y4 cells. Biochem Biophys Res Commun 2016; 469:791-6. [DOI: 10.1016/j.bbrc.2015.12.072] [Citation(s) in RCA: 14] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/16/2015] [Accepted: 12/17/2015] [Indexed: 01/01/2023]
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31
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Inflammation and intracellular metabolism: new targets in OA. Osteoarthritis Cartilage 2015; 23:1835-42. [PMID: 26521729 PMCID: PMC4668929 DOI: 10.1016/j.joca.2014.12.016] [Citation(s) in RCA: 73] [Impact Index Per Article: 8.1] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 12/12/2014] [Accepted: 12/17/2014] [Indexed: 02/02/2023]
Abstract
Articular cartilage degeneration is hallmark of osteoarthritis (OA). Low-grade chronic inflammation in the joint can promote OA progression. Emerging evidence indicates that bioenergy sensors couple metabolism with inflammation to switch physiological and clinical phenotypes. Changes in cellular bioenergy metabolism can reprogram inflammatory responses, and inflammation can disturb cellular energy balance and increase cell stress. AMP-activated protein kinase (AMPK) and sirtuin 1 (SIRT1) are two critical bioenergy sensors that regulate energy balance at both cellular and whole-body levels. Dysregulation of AMPK and SIRT1 has been implicated in diverse human diseases and aging. This review reveals recent findings on the role of AMPK and SIRT1 in joint tissue homeostasis and OA, with a focus on how AMPK and SIRT1 in articular chondrocytes modulate intracellular energy metabolism during stress responses (e.g., inflammatory responses) and how these changes dictate specific effector functions, and discusses translational significance of AMPK and SIRT1 as new therapeutic targets for OA.
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32
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Abstract
Patients with type 2 diabetes mellitus (T2DM) have an increased risk of fragility fractures despite increased body weight and normal or higher bone mineral density. The mechanisms by which T2DM increases skeletal fragility are unclear. It is likely that a combination of factors, including a greater risk of falling, regional osteopenia, and impaired bone quality, contributes to the increased fracture risk. Drugs for the treatment of T2DM may also impact on the risk for fractures. For example, thiazolidinediones accelerate bone loss and increase the risk of fractures, particularly in older women. In contrast, metformin and sulfonylureas do not appear to have a negative effect on bone health and may, in fact, protect against fragility fracture. Animal models indicate a potential role for incretin hormones in bone metabolism, but there are only limited data on the impact of dipeptidyl peptidase-4 inhibitors and glucagon-like peptide-1 agonists on bone health in humans. Animal models also have demonstrated a role for amylin in bone metabolism, but clinical trials in patients with type 1 diabetes with an amylin analog (pramlintide) have not shown a significant impact on bone metabolism. The effects of insulin treatment on fracture risk are inconsistent with some studies showing an increased risk and others showing no effect. Finally, although there is limited information on the latest class of medications for the treatment of T2DM, the sodium-glucose co-transporter-2 inhibitors, these drugs do not seem to increase fracture risk. Because diabetes is an increasingly common chronic condition that can affect patients for many decades, further research into the effects of agents for the treatment of T2DM on bone metabolism is warranted. In this review, the physiological mechanisms and clinical impact of diabetes treatments on bone health and fracture risk in patients with T2DM are described.
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Affiliation(s)
- Matthew P Gilbert
- Division of Endocrinology and Diabetes (M.P.G.), The University of Vermont College of Medicine, Burlington, Vermont 05405; and Florida Hospital Diabetes and Translational Research Institutes and Sanford-Burnham Medical Research Institute, Orlando, Florida 32827
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Fullerton MD, Ford RJ, McGregor CP, LeBlond ND, Snider SA, Stypa SA, Day EA, Lhoták Š, Schertzer JD, Austin RC, Kemp BE, Steinberg GR. Salicylate improves macrophage cholesterol homeostasis via activation of Ampk. J Lipid Res 2015; 56:1025-33. [PMID: 25773887 PMCID: PMC4409279 DOI: 10.1194/jlr.m058875] [Citation(s) in RCA: 48] [Impact Index Per Article: 5.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/26/2015] [Indexed: 02/02/2023] Open
Abstract
Atherosclerosis stems from imbalances in lipid metabolism and leads to maladaptive inflammatory responses. The AMP-activated protein kinase (Ampk) is a highly conserved serine/threonine kinase that regulates many aspects of lipid and energy metabolism, although its specific role in controlling macrophage cholesterol homeostasis remains unclear. We sought to address this question by testing the effects of direct Ampk activators in primary bone marrow-derived macrophages from Ampk β1-deficient (β1−/−) mice. Macrophages from Ampk β1−/− mice had enhanced lipogenic capacity and diminished cholesterol efflux, although cholesterol uptake was unaffected. Direct activation of Ampk β1 via salicylate (the unacetylated form of aspirin) or A-769662 (a small molecule activator), decreased the synthesis of FAs and sterols in WT but not Ampk β1−/− macrophages. In lipid-laden macrophages, Ampk activation decreased cholesterol content (foam cell formation) and increased cholesterol efflux to HDL and apoA-I, effects that occurred in an Ampk β1-dependent manner. Increased cholesterol efflux was also associated with increased gene expression of the ATP binding cassette transporters, Abcg1 and Abca1. Moreover, in vivo reverse cholesterol transport was suppressed in mice that received Ampk β1−/− macrophages compared with the WT control. Our data highlight the therapeutic potential of targeting macrophage Ampk with new or existing drugs for the possible reduction in foam cell formation during the early stages of atherosclerosis.
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Affiliation(s)
- Morgan D Fullerton
- Divisions of Endocrinology and Metabolism McMaster University, Hamilton, Canada Department of Medicine, and Departments of Biochemistry and Biomedical Sciences McMaster University, Hamilton, Canada Department of Biochemistry, Microbiology, and Immunology, University of Ottawa, Ottawa, Canada
| | - Rebecca J Ford
- Divisions of Endocrinology and Metabolism McMaster University, Hamilton, Canada
| | - Chelsea P McGregor
- Department of Biochemistry, Microbiology, and Immunology, University of Ottawa, Ottawa, Canada
| | - Nicholas D LeBlond
- Department of Biochemistry, Microbiology, and Immunology, University of Ottawa, Ottawa, Canada
| | - Shayne A Snider
- Department of Biochemistry, Microbiology, and Immunology, University of Ottawa, Ottawa, Canada
| | - Stephanie A Stypa
- Divisions of Endocrinology and Metabolism McMaster University, Hamilton, Canada
| | - Emily A Day
- Divisions of Endocrinology and Metabolism McMaster University, Hamilton, Canada
| | - Šárka Lhoták
- Hamilton Centre for Kidney Research, St. Joseph's Healthcare Hamilton, Hamilton, Canada Nephrology, McMaster University, Hamilton, Canada
| | - Jonathan D Schertzer
- Department of Medicine, and Departments of Biochemistry and Biomedical Sciences McMaster University, Hamilton, Canada Pediatrics, McMaster University, Hamilton, Canada
| | - Richard C Austin
- Hamilton Centre for Kidney Research, St. Joseph's Healthcare Hamilton, Hamilton, Canada Nephrology, McMaster University, Hamilton, Canada
| | - Bruce E Kemp
- St. Vincent's Institute of Medical Research and Department of Medicine, University of Melbourne, Fitzroy, Australia
| | - Gregory R Steinberg
- Divisions of Endocrinology and Metabolism McMaster University, Hamilton, Canada Department of Medicine, and Departments of Biochemistry and Biomedical Sciences McMaster University, Hamilton, Canada
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Radaei F, Darvishi A, Gharibzadeh S. The Correlation between Osteoporosis Occurrences in Both Schizophrenia and Parkinson's Disease. Front Neurol 2014; 5:83. [PMID: 24917847 PMCID: PMC4040489 DOI: 10.3389/fneur.2014.00083] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Key Words] [Track Full Text] [Download PDF] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/13/2014] [Accepted: 05/16/2014] [Indexed: 12/01/2022] Open
Affiliation(s)
- Fatemeh Radaei
- Neural and Cognitive Sciences Laboratory, Biomedical Engineering Faculty, Amirkabir University of Technology , Tehran , Iran
| | - Asma Darvishi
- Tehran University of Medical Sciences , Tehran , Iran
| | - Shahriar Gharibzadeh
- Neural and Cognitive Sciences Laboratory, Biomedical Engineering Faculty, Amirkabir University of Technology , Tehran , Iran
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Chen H, Liu X, Chen H, Cao J, Zhang L, Hu X, Wang J. Role of SIRT1 and AMPK in mesenchymal stem cells differentiation. Ageing Res Rev 2014; 13:55-64. [PMID: 24333965 DOI: 10.1016/j.arr.2013.12.002] [Citation(s) in RCA: 71] [Impact Index Per Article: 7.1] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/30/2013] [Revised: 11/18/2013] [Accepted: 12/02/2013] [Indexed: 12/21/2022]
Abstract
The differentiation capabilities of mesenchymal stem cells (MSCs) compromise with age and with in vitro passages which could impair the efficacy of cell therapy and tissue engineering. However, how to maintain these capabilities is not fully understood. Calorie restriction (CR, decreasing caloric intake by 30-40%) could extend longevity and reduce aging-related diseases. Recent studies revealed that CR could influence the lineage determination of stem cells including MSCs. Two important mediators of CR might be silent mating type information regulation 2 homolog 1 (SIRT1), a NAD(+)-dependent deacetylase, and AMP-activated protein kinase (AMPK), an energy-sensing kinase. Evidences are mounting that both SIRT1 and AMPK play important roles in cell fate determination of MSCs. Herein, we intend to sum up our understanding about the role of SIRT1 and AMPK in osteogenic and adipogenic potential of MSCs. Metabolic process of MSCs differentiation and the putative interplay of SIRT1 and AMPK in this process was also discussed.
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Fong JE, Le Nihouannen D, Tiedemann K, Sadvakassova G, Barralet JE, Komarova SV. Moderate excess of pyruvate augments osteoclastogenesis. Biol Open 2013; 2:387-95. [PMID: 23616923 PMCID: PMC3625867 DOI: 10.1242/bio.20133269] [Citation(s) in RCA: 15] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/02/2012] [Accepted: 01/18/2013] [Indexed: 01/15/2023] Open
Abstract
Cell differentiation leads to adaptive changes in energy metabolism. Conversely, hyperglycemia induces malfunction of many body systems, including bone, suggesting that energy metabolism reciprocally affects cell differentiation. We investigated how the differentiation of bone-resorbing osteoclasts, large polykaryons formed through fusion and growth of cells of monocytic origin, is affected by excess of energy substrate pyruvate and how energy metabolism changes during osteoclast differentiation. Surprisingly, small increases in pyruvate (1–2 mM above basal levels) augmented osteoclastogenesis in vitro and in vivo, while larger increases were not effective in vitro. Osteoclast differentiation increased cell mitochondrial activity and ATP levels, which were further augmented in energy-rich conditions. Conversely, the inhibition of respiration significantly reduced osteoclast number and size. AMP-activated protein kinase (AMPK) acts as a metabolic sensor, which is inhibited in energy-rich conditions. We found that osteoclast differentiation was associated with an increase in AMPK levels and a change in AMPK isoform composition. Increased osteoclast size induced by pyruvate (1 mM above basal levels) was prevented in the presence of AMPK activator 5-amino-4-imidazole carboxamide ribonucleotide (AICAR). In keeping, inhibition of AMPK using dorsomorphin or siRNA to AMPKγ increased osteoclast size in control cultures to the level observed in the presence of pyruvate. Thus, we have found that a moderate excess of pyruvate enhances osteoclastogenesis, and that AMPK acts to tailor osteoclastogenesis to a cell's bioenergetics capacity.
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Affiliation(s)
- Jenna E Fong
- Faculty of Dentistry, McGill University , Montreal, QC H3A 1A4 , Canada
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37
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Kang H, Viollet B, Wu D. Genetic deletion of catalytic subunits of AMP-activated protein kinase increases osteoclasts and reduces bone mass in young adult mice. J Biol Chem 2013; 288:12187-96. [PMID: 23486478 DOI: 10.1074/jbc.m112.430389] [Citation(s) in RCA: 46] [Impact Index Per Article: 4.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/11/2022] Open
Abstract
AMP-activated protein kinase (AMPK) is a key regulator of cellular and systemic energy homeostasis and a potential therapeutic target for the intervention of cancer and metabolic disorders. However, the role of AMPK in bone homeostasis remains incompletely understood. Here we assessed the skeletal phenotype of mice lacking catalytic subunits of AMPK and found that mice lacking AMPKα1 (Prkaa1(-/-)) or AMPKα2 (Prkaa2(-/-)) had reduced bone mass compared with the WT mice, although the reduction was less in Prkaa2(-/-) mice than in Prkaa1(-/-) mice. Static and dynamic bone histomorphometric analyses revealed that Prkaa1(-/-) mice had an elevated rate of bone remodeling because of increases in bone formation and resorption, whereas AMPKα2 KO-induced bone mass reduction was largely attributable to elevated bone resorption. In agreement with our in vivo results, AMPKα deficiency was associated with increased osteoclastogenesis in vitro. Moreover, we found that AMPKα1 inhibited the receptor activator of nuclear factor κB (RANK) signaling, providing an explanation for AMPK-mediated inhibition of osteoclastogenesis. Therefore, our findings further underscore the importance of AMPK in bone homeostasis, in particular osteoclastogenesis, in young adult mammals.
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Affiliation(s)
- Heeseog Kang
- Department of Pharmacology and Vascular Biology and Therapeutic Program, Yale School of Medicine, New Haven, Connecticut 06520, USA.
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38
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Abstract
AMPK is an evolutionary conserved sensor of cellular energy status that is activated during exercise. Pharmacological activation of AMPK promotes glucose uptake, fatty acid oxidation, mitochondrial biogenesis, and insulin sensitivity; processes that are reduced in obesity and contribute to the development of insulin resistance. AMPK deficient mouse models have been used to provide direct genetic evidence either supporting or refuting a role for AMPK in regulating these processes. Exercise promotes glucose uptake by an insulin dependent mechanism involving AMPK. Exercise is important for improving insulin sensitivity; however, it is not known if AMPK is required for these improvements. Understanding how these metabolic processes are regulated is important for the development of new strategies that target obesity-induced insulin resistance. This review will discuss the involvement of AMPK in regulating skeletal muscle metabolism (glucose uptake, glycogen synthesis, and insulin sensitivity).
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Affiliation(s)
- Hayley M. O'Neill
- Protein Chemistry and Metabolism Unit, St. Vincent's Institute of Medical Research, Fitzroy, Australia
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Pantovic A, Krstic A, Janjetovic K, Kocic J, Harhaji-Trajkovic L, Bugarski D, Trajkovic V. Coordinated time-dependent modulation of AMPK/Akt/mTOR signaling and autophagy controls osteogenic differentiation of human mesenchymal stem cells. Bone 2013; 52:524-31. [PMID: 23111315 DOI: 10.1016/j.bone.2012.10.024] [Citation(s) in RCA: 187] [Impact Index Per Article: 17.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 05/09/2012] [Revised: 10/17/2012] [Accepted: 10/20/2012] [Indexed: 12/20/2022]
Abstract
We investigated the role of AMP-activated protein kinase (AMPK), Akt, mammalian target of rapamycin (mTOR), autophagy and their interplay in osteogenic differentiation of human dental pulp mesenchymal stem cells. The activation of various members of AMPK, Akt and mTOR signaling pathways and autophagy was analyzed by immunoblotting, while osteogenic differentiation was assessed by alkaline phosphatase staining and real-time RT-PCR/immunoblot quantification of osteocalcin, Runt-related transcription factor 2 and bone morphogenetic protein 2 mRNA and/or protein levels. Osteogenic differentiation of mesenchymal stem cells was associated with early (day 1) activation of AMPK and its target Raptor, coinciding with the inhibition of mTOR and its substrate p70S6 kinase. The early induction of autophagy was demonstrated by accumulation of autophagosome-bound LC3-II, upregulation of proautophagic beclin-1 and a decrease in the selective autophagic target p62. This was followed by the late activation of Akt/mTOR at days 3-7 of differentiation. The RNA interference-mediated silencing of AMPK, mTOR or autophagy-essential LC3β, as well as the pharmacological inhibitors of AMPK (compound C), Akt (10-DEBC hydrochloride), mTOR (rapamycin) and autophagy (bafilomycin A1, chloroquine and ammonium chloride), each suppressed mesenchymal stem cell differentiation to osteoblasts. AMPK knockdown prevented early mTOR inhibition and autophagy induction, as well as late activation of Akt/mTOR signaling, while Akt inhibition suppressed mTOR activation without affecting AMPK phosphorylation. Our data indicate that AMPK controls osteogenic differentiation of human mesenchymal stem cells through both early mTOR inhibition-mediated autophagy and late activation of Akt/mTOR signaling axis.
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Affiliation(s)
- Aleksandar Pantovic
- Institute of Microbiology and Immunology, School of Medicine, University of Belgrade, Dr Subotica 1, 11000 Belgrade, Serbia
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Ham J, Evans BAJ. An emerging role for adenosine and its receptors in bone homeostasis. Front Endocrinol (Lausanne) 2012; 3:113. [PMID: 23024635 PMCID: PMC3444801 DOI: 10.3389/fendo.2012.00113] [Citation(s) in RCA: 43] [Impact Index Per Article: 3.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 05/23/2012] [Accepted: 08/22/2012] [Indexed: 01/31/2023] Open
Abstract
Bone is continually being remodeled and defects in the processes involved lead to bone diseases. Many regulatory factors are known to influence remodeling but other mechanisms, hitherto unknown, may also be involved. Importantly, our understanding of these currently unknown mechanisms may lead to important new therapies for bone disease. It is accepted that purinergic signaling is involved in bone, and our knowledge of this area has increased significantly over the last 15 years, although most of the published work has studied the role of ATP and other signaling molecules via the P2 family of purinergic receptors. During the last few years, however, there has been increased interest within the bone field in the role of P1 receptors where adenosine is the primary signaling molecule. This review will bring together the current information available in relation to this expanding area of research.
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Affiliation(s)
- Jack Ham
- Institute of Molecular and Experimental Medicine, School of Medicine, Cardiff UniversityCardiff, Wales, UK
- Cardiff Institute of Tissue Engineering and Repair, School of Medicine, Cardiff UniversityCardiff, Wales, UK
| | - Bronwen A. J. Evans
- Institute of Molecular and Experimental Medicine, School of Medicine, Cardiff UniversityCardiff, Wales, UK
- Cardiff Institute of Tissue Engineering and Repair, School of Medicine, Cardiff UniversityCardiff, Wales, UK
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Jeyabalan J, Shah M, Viollet B, Roux JP, Chavassieux P, Korbonits M, Chenu C. Mice lacking AMP-activated protein kinase α1 catalytic subunit have increased bone remodelling and modified skeletal responses to hormonal challenges induced by ovariectomy and intermittent PTH treatment. J Endocrinol 2012; 214:349-58. [PMID: 22700192 PMCID: PMC3427644 DOI: 10.1530/joe-12-0184] [Citation(s) in RCA: 19] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Revised: 06/08/2012] [Accepted: 06/14/2012] [Indexed: 12/21/2022]
Abstract
AMP-activated protein kinase (AMPK) is a key regulator of cellular and body energy homeostasis. We previously demonstrated that AMPK activation in osteoblasts increases in vitro bone formation while deletion of the Ampkα1 (Prkaa1) subunit, the dominant catalytic subunit expressed in bone, leads to decreased bone mass in vivo. To investigate the cause of low bone mass in the Ampkα1(-/-) mice, we analysed bone formation and resorption in the tibia of these mice by dynamic histomorphometry and determined whether bone turnover can be stimulated in the absence of the Ampkα1 subunit. We subjected 12-week-old Ampkα1(+)(/)(+) and Ampkα1(-/-) mice to ovariectomy (OVX), intermittent PTH (iPTH) administration (80 μg/kg per day, 5 days/week) or both OVX and iPTH hormonal challenges. Tibiae were harvested from these mice and bone micro-architecture was determined by micro-computed tomography. We show for the first time that Ampkα1(-/-) mice have a high bone turnover at the basal level in favour of bone resorption. While both Ampkα1(+)(/)(+) and Ampkα1(-/-) mice lost bone mass after OVX, the bone loss in Ampkα1(-/-) mice was lower compared with controls. iPTH increased trabecular and cortical bone indexes in both ovariectomised Ampkα1(+)(/)(+) and Ampkα1(-/-) mice. However, ovariectomised Ampkα1(-/-) mice showed a smaller increase in bone parameters in response to iPTH compared with Ampkα1(+)(/)(+) mice. By contrast, non-ovariectomised Ampkα1(-/-) mice responded better to iPTH treatment than non-ovariectomised Ampkα1(+)(/)(+) mice. Overall, these data demonstrate that Ampkα1(-/-) mice are less affected by changes in bone turnover induced by OVX but respond better to the anabolic challenge induced by iPTH. These results suggest that AMPKα1 activation may play a role in the hormonal regulation of bone remodelling.
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Affiliation(s)
- J Jeyabalan
- Department of Veterinary Basic Sciences, Royal Veterinary College, London NW1 0TU, UK.
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Lee SH, Kim BJ, Choi HJ, Cho SW, Shin CS, Park SY, Lee YS, Lee SY, Kim HH, Kim GS, Koh JM. (-)-Epigallocathechin-3-gallate, an AMPK activator, decreases ovariectomy-induced bone loss by suppression of bone resorption. Calcif Tissue Int 2012; 90:404-10. [PMID: 22434366 DOI: 10.1007/s00223-012-9584-7] [Citation(s) in RCA: 18] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 11/13/2011] [Accepted: 02/18/2012] [Indexed: 12/25/2022]
Abstract
Previously, we showed that AMP-activated protein kinase (AMPK) negatively regulates receptor activator of nuclear factor-κB ligand-induced osteoclast formation in vitro. The present study investigated the effect of (-)-epigallocathechin-3-gallate (EGCG), an AMPK activator, on ovariectomy (OVX)-induced bone loss in mice. Female mice subjected to OVX were administered EGCG for 8 weeks. We measured total-body bone mineral density (BMD) before and after the operation at an interval of 4 weeks. We performed micro-computed tomography (micro-CT) of the tibia and bone histomorphometric examination of the femur. Western blot analysis was additionally performed, to detect levels of the phosphorylated and total forms of AMPK-α in calvarial extracts. EGCG prevented OVX-induced body weight gain. The OVX control did not show a significant increase in BMD values at baseline and after treatment, unlike the sham control. EGCG attenuated OVX-induced bone loss. Micro-CT experiments revealed that EGCG induced a significant increase in trabecular bone volume and trabecular number and a decrease in trabecular spacing compared to the OVX control. Histomorphometric analyses further showed that EGCG suppressed osteoclast surface and number. Phosphorylated AMPK expression was significantly elevated in bone following EGCG treatment. Our findings collectively indicate that EGCG decreases OVX-induced bone loss via inhibition of osteoclasts.
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Affiliation(s)
- Seung Hun Lee
- Division of Endocrinology and Metabolism, Asan Medical Center, College of Medicine, University of Ulsan, Songpa-Gu, Seoul, Republic of Korea
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Kim EK, Lim S, Park JM, Seo JK, Kim JH, Kim KT, Ryu SH, Suh PG. Human mesenchymal stem cell differentiation to the osteogenic or adipogenic lineage is regulated by AMP-activated protein kinase. J Cell Physiol 2012; 227:1680-7. [PMID: 21678424 DOI: 10.1002/jcp.22892] [Citation(s) in RCA: 80] [Impact Index Per Article: 6.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/13/2022]
Abstract
AMP-activated protein kinase (AMPK) is an energy-sensing kinase that has recently been shown to regulate the differentiation of preadipocytes and osteoblasts. However, the role of AMPK in stem cell differentiation is largely unknown. Using in vitro culture models, the present study demonstrates that AMPK is a critical regulatory factor for osteogenic differentiation. We observed that expression and phosphorylation of AMPK were increased during osteogenesis in human adipose tissue-derived mesenchymal stem cells (hAMSC). To elucidate the role of AMPK in osteogenic differentiation, we investigated the effect of AMPK inhibition or knockdown on mineralization of hAMSC. Compound C, an AMPK inhibitor, reduced mineralized matrix deposition and suppressed the expression of osteoblast-specific genes, including alkaline phosphatase (ALP), runt-related transcription factor 2 (RUNX2), and osteocalcin (OCN). Knockdown of AMPK by shRNA-lentivirus infection also reduced osteogenesis. In addition, inhibition or knockdown of AMPK during osteogenesis inhibited ERK phosphorylation, which is required for osteogenesis. Interestingly, inhibition of AMPK induced adipogenic differentiation of hAMSC, even in osteogenic induction medium (OIM). These results provide a potential mechanism involving AMPK activation in osteogenic differentiation of hAMSC and suggest that commitment of hAMSC to osteogenic or adipogenic lineage is governed by activation or inhibition of AMPK, respectively.
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Affiliation(s)
- Eung-Kyun Kim
- Division of Molecular and Life Sciences, Pohang University of Science and Technology, Pohang, Kyungbuk, Republic of Korea
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Abstract
There is increasing evidence that osteoporosis, similarly to obesity and diabetes, could be another disorder of energy metabolism. AMP-activated protein kinase (AMPK) has emerged over the last decade as a key sensing mechanism in the regulation of cellular energy homeostasis and is an essential mediator of the central and peripheral effects of many hormones on the metabolism of appetite, fat and glucose. Novel work demonstrates that the AMPK signaling pathway also plays a role in bone physiology. Activation of AMPK promotes bone formation in vitro and the deletion of α or β subunit of AMPK decreases bone mass in mice. Furthermore, AMPK activity in bone cells is regulated by the same hormones that regulate food intake and energy expenditure through AMPK activation in the brain and peripheral tissues. AMPK is also activated by antidiabetic drugs such as metformin and thiazolidinediones (TZDs), which also impact on skeletal metabolism. Interestingly, TZDs have detrimental skeletal side effects, causing bone loss and increasing the risk of fractures, although the role of AMPK mediation is still unclear. These data are presented in this review that also discusses the potential roles of AMPK in bone as well as the possibility for AMPK to be a future therapeutic target for intervention in osteoporosis.
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Affiliation(s)
- J Jeyabalan
- Royal Veterinary College, Royal College Street, London NW1 0TU, UK
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Mizutani J, Tokuda H, Matsushima-Nishiwaki R, Kato K, Kondo A, Natsume H, Kozawa O, Otsuka T. Involvement of AMP-activated protein kinase in TGF-β-stimulated VEGF synthesis in osteoblasts. Int J Mol Med 2012; 29:550-6. [PMID: 22294055 PMCID: PMC3577364 DOI: 10.3892/ijmm.2012.893] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/01/2011] [Accepted: 12/12/2011] [Indexed: 12/14/2022] Open
Abstract
It is generally recognized that AMP-activated protein kinase (AMPK) acts as a key regulator of energy homeostasis. We have previously shown that transforming growth factor-β (TGF-β) stimulates synthesis of vascular endothelial growth factor (VEGF) via p44/p42 mitogen-activated protein (MAP) kinase, stress-activated protein kinase/c-Jun N-terminal kinase (SAPK/JNK) and p38 MAP kinase in osteoblast-like MC3T3-E1 cells. In the present study, we investigated whether AMPK is involved in the TGF-β-stimulated VEGF synthesis in osteoblast-like MC3T3-E1 cells. TGF-β time-dependently induced the phosphorylation of the AMPK α-subunit (Thr172) and the AMPK β-subunit (Ser108). Compound C, an AMPK inhibitor, significantly reduced the TGF-β-stimulated VEGF release. The inhibitory effect of compound C was also observed in normal human osteoblasts (NHOst). Although compound C failed to affect the TGF-β-induced phosphorylation of SAPK/JNK, p38 MAP kinase or Smad2, it markedly suppressed the TGF-β-induced phosphorylation of both MEK1/2 and p44/p42 MAP kinase. In addition, compound C significantly suppressed the VEGF mRNA expression induced by TGF-β. Taken together, our results strongly suggest that AMPK is involved in TGF-β-stimulated VEGF synthesis, and that it functions at a point upstream of MEK1/2.
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Affiliation(s)
- Jun Mizutani
- Department of Orthopedic Surgery, Nagoya City University Graduate School of Medical Sciences, Mizuho-Cho, Mizuho-Ku, Nagoya 467-8601, Japan
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Stephenne X, Foretz M, Taleux N, van der Zon GC, Sokal E, Hue L, Viollet B, Guigas B. Metformin activates AMP-activated protein kinase in primary human hepatocytes by decreasing cellular energy status. Diabetologia 2011; 54:3101-10. [PMID: 21947382 PMCID: PMC3210354 DOI: 10.1007/s00125-011-2311-5] [Citation(s) in RCA: 199] [Impact Index Per Article: 15.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 07/30/2011] [Accepted: 08/18/2011] [Indexed: 01/27/2023]
Abstract
AIM/HYPOTHESIS The glucose-lowering drug metformin has been shown to activate hepatic AMP-activated protein kinase (AMPK), a master kinase regulating cellular energy homeostasis. However, the underlying mechanisms remain controversial and have never been investigated in primary human hepatocytes. METHODS Hepatocytes isolated from rat, mouse and human livers were treated with various concentrations of metformin. Isoform-specific AMPKα abundance and activity, as well as intracellular adenine nucleotide levels and mitochondrial oxygen consumption rates were determined at different time points. RESULTS Metformin dose- and time-dependently increased AMPK activity in rat and human hepatocytes, an effect associated with a significant rise in cellular AMP:ATP ratio. Surprisingly, we found that AMPKα2 activity was undetectable in human compared with rat hepatocytes, while AMPKα1 activities were comparable. Accordingly, metformin only increased AMPKα1 activity in human hepatocytes, although both AMPKα isoforms were activated in rat hepatocytes. Analysis of mRNA expression and protein levels confirmed that only AMPKα1 is present in human hepatocytes; it also showed that the distribution of β and γ regulatory subunits differed between species. Finally, we demonstrated that the increase in AMP:ATP ratio in hepatocytes from liver-specific Ampkα1/2 (also known as Prkaa1/2) knockout mice and humans is due to a similar and specific inhibition of the mitochondrial respiratory-chain complex 1 by metformin. CONCLUSIONS/INTERPRETATION Activation of hepatic AMPK by metformin results from a decrease in cellular energy status owing to metformin's AMPK-independent inhibition of the mitochondrial respiratory-chain complex 1. The unique profile of AMPK subunits found in human hepatocytes should be considered when developing new pharmacological agents to target the kinase.
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Affiliation(s)
- X. Stephenne
- Laboratory of Paediatric Hepatology and Cell Therapy, Université catholique de Louvain and Cliniques St Luc, Brussels, Belgium
| | - M. Foretz
- Inserm, U1016, Institut Cochin, Paris, France
- CNRS, UMR8104, Paris, France
- Université Paris Descartes, Paris, France
| | - N. Taleux
- Hormone and Metabolic Research Unit, Université catholique de Louvain and de Duve Institute, Brussels, Belgium
- Bioénergétique Fondamentale et Appliquée Inserm-U884, Université J. Fourier, Grenoble, France
| | - G. C. van der Zon
- Department of Molecular Cell Biology, Leiden University Medical Center, Postzone S1-P, Postbus 9600, 2300 RC Leiden, the Netherlands
| | - E. Sokal
- Laboratory of Paediatric Hepatology and Cell Therapy, Université catholique de Louvain and Cliniques St Luc, Brussels, Belgium
| | - L. Hue
- Hormone and Metabolic Research Unit, Université catholique de Louvain and de Duve Institute, Brussels, Belgium
| | - B. Viollet
- Inserm, U1016, Institut Cochin, Paris, France
- CNRS, UMR8104, Paris, France
- Université Paris Descartes, Paris, France
| | - B. Guigas
- Hormone and Metabolic Research Unit, Université catholique de Louvain and de Duve Institute, Brussels, Belgium
- Department of Molecular Cell Biology, Leiden University Medical Center, Postzone S1-P, Postbus 9600, 2300 RC Leiden, the Netherlands
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Galic S, Fullerton MD, Schertzer JD, Sikkema S, Marcinko K, Walkley CR, Izon D, Honeyman J, Chen ZP, van Denderen BJ, Kemp BE, Steinberg GR. Hematopoietic AMPK β1 reduces mouse adipose tissue macrophage inflammation and insulin resistance in obesity. J Clin Invest 2011; 121:4903-15. [PMID: 22080866 DOI: 10.1172/jci58577] [Citation(s) in RCA: 274] [Impact Index Per Article: 21.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/18/2011] [Accepted: 10/05/2011] [Indexed: 12/17/2022] Open
Abstract
Individuals who are obese are frequently insulin resistant, putting them at increased risk of developing type 2 diabetes and its associated adverse health conditions. The accumulation in adipose tissue of macrophages in an inflammatory state is a hallmark of obesity-induced insulin resistance. Here, we reveal a role for AMPK β1 in protecting macrophages from inflammation under high lipid exposure. Genetic deletion of the AMPK β1 subunit in mice (referred to herein as β1(-/-) mice) reduced macrophage AMPK activity, acetyl-CoA carboxylase phosphorylation, and mitochondrial content, resulting in reduced rates of fatty acid oxidation. β1(-/-) macrophages displayed increased levels of diacylglycerol and markers of inflammation, effects that were reproduced in WT macrophages by inhibiting fatty acid oxidation and, conversely, prevented by pharmacological activation of AMPK β1-containing complexes. The effect of AMPK β1 loss in macrophages was tested in vivo by transplantation of bone marrow from WT or β1(-/-) mice into WT recipients. When challenged with a high-fat diet, mice that received β1(-/-) bone marrow displayed enhanced adipose tissue macrophage inflammation and liver insulin resistance compared with animals that received WT bone marrow. Thus, activation of AMPK β1 and increasing fatty acid oxidation in macrophages may represent a new therapeutic approach for the treatment of insulin resistance.
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Affiliation(s)
- Sandra Galic
- St. Vincent's Institute of Medical Research, University of Melbourne, Fitzroy, Victoria, Australia
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Kim M, Tian R. Targeting AMPK for cardiac protection: opportunities and challenges. J Mol Cell Cardiol 2010; 51:548-53. [PMID: 21147121 DOI: 10.1016/j.yjmcc.2010.12.004] [Citation(s) in RCA: 57] [Impact Index Per Article: 4.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 09/01/2010] [Revised: 11/30/2010] [Accepted: 12/06/2010] [Indexed: 01/01/2023]
Abstract
AMP-activated protein kinase (AMPK) regulates cellular energy homeostasis and multiple biological processes in cell growth and survival, hence an attractive drug target. AMPK is a heterotrimeric protein consisting of α catalytic, β and γ regulatory subunits; two isoforms of each subunit are present in the heart. Studies using both genetic and pharmacological approaches have demonstrated important roles of AMPK in protecting the heart during ischemia/reperfusion injury as well as in pathological hypertrophy and failure. There is also emerging evidence suggesting isoform-specific function of AMPK, e.g. mutations of the γ2 subunit cause human cardiomyopathy. Thus, strategies avoiding the undesirable effects of altering γ2-AMPK activity, such as isoform selective activation of AMPK may lead to cardioprotective therapies with greater efficacy and safety. This article is part of a special issue entitled "Key Signaling Molecules in Hypertrophy and Heart Failure."
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Affiliation(s)
- Maengjo Kim
- Mitochondria and Metabolism Center, Department of Anesthesiology and Pain Medicine, University of Washington, Seattle, WA, USA
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Lee YS, Kim YS, Lee SY, Kim GH, Kim BJ, Lee SH, Lee KU, Kim GS, Kim SW, Koh JM. AMP kinase acts as a negative regulator of RANKL in the differentiation of osteoclasts. Bone 2010; 47:926-37. [PMID: 20696287 DOI: 10.1016/j.bone.2010.08.001] [Citation(s) in RCA: 110] [Impact Index Per Article: 7.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 05/12/2010] [Revised: 07/30/2010] [Accepted: 08/01/2010] [Indexed: 02/06/2023]
Abstract
INTRODUCTION AMP-activated protein kinase (AMPK) has been reported to stimulate differentiation and proliferation of osteoblasts, but the role of AMPK in the physiology of osteoclasts has not been investigated. METHOD Osteoclasts were differentiated from mouse BMMϕs. TRAP-positive multinucleated cells were considered to be osteoclasts using TRAP staining, and resorption area was determined by incubation of cells on dentine discs. Signaling pathways were investigated using Western blotting and RT-PCR. RESULTS RANKL induced phosphorylation/activation of AMPK-α in BMMϕs and stimulated formation of TRAP-positive multinucleated cells. Pharmacological inhibition of AMPK with compound C and siRNA-mediated knockdown of AMPK-α1, the predominant α-subunit isoform in BMMϕs, increased RANKL-induced formation of TRAP-positive multinucleated cells and bone resorption via activation of the downstream signaling elements p38, JNK, NF-κB, Akt, CREB, c-Fos, and NFATc1. STO-609, an inhibitor of CaMKK, completely blocked the RANKL-induced activation of AMPK-α, but KN-93, an inhibitor of CaMK, did not. siRNA-mediated TAK1 knockdown also blocked RANKL-induced activation of AMPK-α. The AMPK activators metformin, (-)-epigallocatechin-3-gallate, berberine, resveratrol, and α-lipoic acid dose-dependently suppressed formation of TRAP-positive multinucleated cells and bone resorption. CONCLUSION AMPK negatively regulates RANKL, possibly by acting through CaMKK and TAK1. Thus, the development of AMPK activators may be a useful strategy for inhibiting the resorption of bone that is stimulated under RANKL-activated conditions.
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Affiliation(s)
- Young-Sun Lee
- Asan Institute for Life Sciences, Seoul 138-736, Republic of Korea
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Shah M, Kola B, Bataveljic A, Arnett T, Viollet B, Saxon L, Korbonits M, Chenu C. AMP-activated protein kinase (AMPK) activation regulates in vitro bone formation and bone mass. Bone 2010; 47:309-19. [PMID: 20399918 PMCID: PMC3629687 DOI: 10.1016/j.bone.2010.04.596] [Citation(s) in RCA: 141] [Impact Index Per Article: 10.1] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 01/07/2010] [Revised: 04/09/2010] [Accepted: 04/10/2010] [Indexed: 02/06/2023]
Abstract
Adenosine 5'-monophosphate-activated protein kinase (AMPK), a regulator of energy homeostasis, has a central role in mediating the appetite-modulating and metabolic effects of many hormones and antidiabetic drugs metformin and glitazones. The objective of this study was to determine if AMPK can be activated in osteoblasts by known AMPK modulators and if AMPK activity is involved in osteoblast function in vitro and regulation of bone mass in vivo. ROS 17/2.8 rat osteoblast-like cells were cultured in the presence of AMPK activators (AICAR and metformin), AMPK inhibitor (compound C), the gastric peptide hormone ghrelin and the beta-adrenergic blocker propranolol. AMPK activity was measured in cell lysates by a functional kinase assay and AMPK protein phosphorylation was studied by Western Blotting using an antibody recognizing AMPK Thr-172 residue. We demonstrated that treatment of ROS 17/2.8 cells with AICAR and metformin stimulates Thr-172 phosphorylation of AMPK and dose-dependently increases its activity. In contrast, treatment of ROS 17/2.8 cells with compound C inhibited AMPK phosphorylation. Ghrelin and propranolol dose-dependently increased AMPK phosphorylation and activity. Cell proliferation and alkaline phosphatase activity were not affected by metformin treatment while AICAR significantly inhibited ROS 17/2.8 cell proliferation and alkaline phosphatase activity at high concentrations. To study the effect of AMPK activation on bone formation in vitro, primary osteoblasts obtained from rat calvaria were cultured for 14-17days in the presence of AICAR, metformin and compound C. Formation of 'trabecular-shaped' bone nodules was evaluated following alizarin red staining. We demonstrated that both AICAR and metformin dose-dependently increase trabecular bone nodule formation, while compound C inhibits bone formation. When primary osteoblasts were co-treated with AICAR and compound C, compound C suppressed the stimulatory effect of AICAR on bone nodule formation. AMPK is a alphabetagamma heterotrimer, where alpha is the catalytic subunit. RT-PCR analysis of AMPK subunits in ROS17/2.8 osteoblastic cells and in mouse tibia showed that the AMPKalpha1 subunit is the dominant isoform expressed in bone. We analysed the bone phenotype of 4month-old male wild type (WT) and AMPKalpha1-/- KO mice using micro-CT. Both cortical and trabecular bone compartments were smaller in the AMPK alpha1-deficient mice compared to the WT mice. Altogether, our data support a role for AMPK signalling in skeletal physiology.
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Affiliation(s)
- M. Shah
- Department of Veterinary Basic Sciences Royal Veterinary College, Royal College Street, London, NW1 OTU, UK
| | - B. Kola
- Department of Endocrinology Barts and the London Medical School, London, UK
| | - A. Bataveljic
- Department of Veterinary Basic Sciences Royal Veterinary College, Royal College Street, London, NW1 OTU, UK
| | - T.R. Arnett
- Department of Cell & Developmental Biology, University College London, London, UK
| | - B. Viollet
- Department of Endocrinology, Metabolism and Cancer, INSERM U567, CNRS UMR 8104, Université Paris Descartes, Paris, France
| | - L. Saxon
- Department of Veterinary Basic Sciences Royal Veterinary College, Royal College Street, London, NW1 OTU, UK
| | - M. Korbonits
- Department of Endocrinology Barts and the London Medical School, London, UK
| | - C. Chenu
- Department of Veterinary Basic Sciences Royal Veterinary College, Royal College Street, London, NW1 OTU, UK
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