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He Y, Liu Y, Li R, Xiang A, Chen X, Yu Q, Su P. The role of autophagy/lipophagy in the response of osteoblastic cells to hyperlipidemia (Review). Exp Ther Med 2024; 28:328. [PMID: 38979020 PMCID: PMC11229398 DOI: 10.3892/etm.2024.12617] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/12/2024] [Accepted: 04/10/2024] [Indexed: 07/10/2024] Open
Abstract
There has been interest in the connection between cardiovascular diseases and osteoporosis, both of which share hyperlipidemia as a common pathological basis. Osteoporosis is a progressive metabolic bone disease characterized by reduced bone mass, deteriorated bone microstructure, increased bone fragility and heightened risk of bone fractures. Dysfunction of osteoblastic cells, vital for bone formation, is induced by excessive internalization of lipids under hyperlipidemic conditions, forming the crux of hyperlipidemia-associated osteoporosis. Autophagy, a process fundamental to cell self-regulation, serves a critical role in osteoblastic cell function and bone formation. When activated by lipids, lipophagy inhibits osteoblastic cell differentiation in response to elevated lipid concentrations, resulting in reduced bone mass and osteoporosis. However, an in-depth understanding of the precise roles and mechanisms of lipophagy in the regulation of osteoblastic cell function is required. Study of the molecular mechanisms governing osteoblastic cell response to excessive lipids can result in a clearer understanding of osteoporosis; therefore, potential strategies for preventing hyperlipidemia-induced osteoporosis can be developed. The present review discusses recent progress in elucidating the molecular mechanisms of lipophagy in the regulation of osteoblastic cell function, offering insights into hyperlipidemia-induced osteoporosis.
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Affiliation(s)
- Yizhang He
- Shaanxi Provincial Key Laboratory of Ischemic Cardiovascular Disease, Institute of Basic and Translational Medicine, Xi'an Medical University, Xi'an, Shaanxi 710021, P.R. China
| | - Yantong Liu
- School of Basic Medical Sciences, Xi'an Medical University, Xi'an, Shaanxi 710021, P.R. China
| | - Ran Li
- Shaanxi Provincial Key Laboratory of Ischemic Cardiovascular Disease, Institute of Basic and Translational Medicine, Xi'an Medical University, Xi'an, Shaanxi 710021, P.R. China
| | - Aoqi Xiang
- Shaanxi Provincial Key Laboratory of Ischemic Cardiovascular Disease, Institute of Basic and Translational Medicine, Xi'an Medical University, Xi'an, Shaanxi 710021, P.R. China
| | - Xiaochang Chen
- Shaanxi Provincial Key Laboratory of Ischemic Cardiovascular Disease, Institute of Basic and Translational Medicine, Xi'an Medical University, Xi'an, Shaanxi 710021, P.R. China
| | - Qi Yu
- Shaanxi Provincial Key Laboratory of Ischemic Cardiovascular Disease, Institute of Basic and Translational Medicine, Xi'an Medical University, Xi'an, Shaanxi 710021, P.R. China
| | - Peihong Su
- Shaanxi Provincial Key Laboratory of Ischemic Cardiovascular Disease, Institute of Basic and Translational Medicine, Xi'an Medical University, Xi'an, Shaanxi 710021, P.R. China
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2
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Xu H, Yan S, Gerhard E, Xie D, Liu X, Zhang B, Shi D, Ameer GA, Yang J. Citric Acid: A Nexus Between Cellular Mechanisms and Biomaterial Innovations. ADVANCED MATERIALS (DEERFIELD BEACH, FLA.) 2024; 36:e2402871. [PMID: 38801111 PMCID: PMC11309907 DOI: 10.1002/adma.202402871] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 02/25/2024] [Revised: 05/07/2024] [Indexed: 05/29/2024]
Abstract
Citrate-based biodegradable polymers have emerged as a distinctive biomaterial platform with tremendous potential for diverse medical applications. By harnessing their versatile chemistry, these polymers exhibit a wide range of material and bioactive properties, enabling them to regulate cell metabolism and stem cell differentiation through energy metabolism, metabonegenesis, angiogenesis, and immunomodulation. Moreover, the recent US Food and Drug Administration (FDA) clearance of the biodegradable poly(octamethylene citrate) (POC)/hydroxyapatite-based orthopedic fixation devices represents a translational research milestone for biomaterial science. POC joins a short list of biodegradable synthetic polymers that have ever been authorized by the FDA for use in humans. The clinical success of POC has sparked enthusiasm and accelerated the development of next-generation citrate-based biomaterials. This review presents a comprehensive, forward-thinking discussion on the pivotal role of citrate chemistry and metabolism in various tissue regeneration and on the development of functional citrate-based metabotissugenic biomaterials for regenerative engineering applications.
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Affiliation(s)
- Hui Xu
- Department of Biomedical Engineering, The Pennsylvania State University, University Park, PA, 16802, USA
| | - Su Yan
- Department of Biomedical Engineering, The Pennsylvania State University, University Park, PA, 16802, USA
| | - Ethan Gerhard
- Department of Biomedical Engineering, The Pennsylvania State University, University Park, PA, 16802, USA
| | - Denghui Xie
- Department of Histology and Embryology, School of Basic Medical Sciences, Department of Orthopedic Surgery, The Third Affiliated Hospital of Southern Medical University, Southern Medical University, Guangzhou, 510515, P. R. China
- Academy of Orthopedics of Guangdong Province, Guangdong Provincial Key Laboratory of Bone and Joint Degeneration Diseases, Guangzhou, 510630, P. R. China
| | - Xiaodong Liu
- Research Center for Industries of the Future, Westlake University, Hangzhou, Zhejiang, 310030, P. R. China
- School of Life Sciences, Westlake University, Hangzhou, Zhejiang, 310030, P. R. China
- Westlake Laboratory of Life Sciences and Biomedicine, Hangzhou, Zhejiang, 310030, P. R. China
- Westlake Institute for Advanced Study, Hangzhou, Zhejiang, 310030, P. R. China
| | - Bing Zhang
- Research Center for Industries of the Future, Westlake University, Hangzhou, Zhejiang, 310030, P. R. China
- School of Life Sciences, Westlake University, Hangzhou, Zhejiang, 310030, P. R. China
- Westlake Laboratory of Life Sciences and Biomedicine, Hangzhou, Zhejiang, 310030, P. R. China
- Westlake Institute for Advanced Study, Hangzhou, Zhejiang, 310030, P. R. China
| | - Dongquan Shi
- Division of Sports Medicine and Adult Reconstructive Surgery, Department of Orthopedic Surgery, Nanjing Drum Tower Hospital, The Affiliated Hospital of Nanjing University Medical School, 321 Zhongshan Road, Nanjing, Jiangsu, 210008, P. R. China
| | - Guillermo A Ameer
- Department of Biomedical Engineering, Northwestern University, Evanston, IL, 60208, USA
- Center for Advanced Regenerative Engineering, Northwestern University, Evanston, IL, 60208, USA
- Department of Surgery, Feinberg School of Medicine, Northwestern University, Chicago, IL, 60611, USA
| | - Jian Yang
- Research Center for Industries of the Future, Westlake University, Hangzhou, Zhejiang, 310030, P. R. China
- Biomedical Engineering Program, School of Engineering, Westlake University, Hangzhou, Zhejiang, 310030, P. R. China
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3
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Vrščaj LA, Marc J, Ostanek B. Towards an enhanced understanding of osteoanabolic effects of PTH-induced microRNAs on osteoblasts using a bioinformatic approach. Front Endocrinol (Lausanne) 2024; 15:1380013. [PMID: 39086902 PMCID: PMC11289717 DOI: 10.3389/fendo.2024.1380013] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Figures] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 01/31/2024] [Accepted: 06/03/2024] [Indexed: 08/02/2024] Open
Abstract
In this study, we used a bioinformatic approach to construct a miRNA-target gene interaction network potentially involved in the anabolic effect of parathyroid hormone analogue teriparatide [PTH (1-34)] on osteoblasts. We extracted a dataset of 26 microRNAs (miRNAs) from previously published studies and predicted miRNA target interactions (MTIs) using four software tools: DIANA, miRWalk, miRDB, and TargetScan. By constructing an interactome of PTH-regulated miRNAs and their predicted target genes, we elucidated signaling pathways regulating pluripotency of stem cells, the Hippo signaling pathway, and the TGF-beta signaling pathway as the most significant pathways in the effects of PTH on osteoblasts. Furthermore, we constructed intersection of MTI networks for these three pathways and added validated interactions. There are 8 genes present in all three selected pathways and a set of 18 miRNAs are predicted to target these genes, according to literature data. The most important genes in all three pathways were BMPR1A, BMPR2 and SMAD2 having the most interactions with miRNAs. Among these miRNAs, only miR-146a-5p and miR-346 have validated interactions in these pathways and were shown to be important regulators of these pathways. In addition, we also propose miR-551b-5p and miR-338-5p for further experimental validation, as they have been predicted to target important genes in these pathways but none of their target interactions have yet been verified. Our wet-lab experiment on miRNAs differentially expressed between PTH (1-34) treated and untreated mesenchymal stem cells supports miR-186-5p from the literature obtained data as another prominent miRNA. The meticulous selection of miRNAs outlined will significantly support and guide future research aimed at discovering and understanding the crucial pathways of osteoanabolic PTH-epigenetic effects on osteoblasts. Additionally, they hold potential for the discovery of new PTH target genes, innovative biomarkers for the effectiveness and safety of osteoporosis-affected treatment, as well as novel therapeutic targets.
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Affiliation(s)
- Lucija Ana Vrščaj
- Department of Clinical Biochemistry, Faculty of Pharmacy, University of Ljubljana, Ljubljana, Slovenia
| | - Janja Marc
- Department of Clinical Biochemistry, Faculty of Pharmacy, University of Ljubljana, Ljubljana, Slovenia
- Clinical Institute of Clinical Chemistry and Biochemistry, University Clinical Centre Ljubljana, Ljubljana, Slovenia
| | - Barbara Ostanek
- Department of Clinical Biochemistry, Faculty of Pharmacy, University of Ljubljana, Ljubljana, Slovenia
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4
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Stegen S, Carmeliet G. Metabolic regulation of skeletal cell fate and function. Nat Rev Endocrinol 2024; 20:399-413. [PMID: 38499689 DOI: 10.1038/s41574-024-00969-x] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Accepted: 02/23/2024] [Indexed: 03/20/2024]
Abstract
Bone development and bone remodelling during adult life are highly anabolic processes requiring an adequate supply of oxygen and nutrients. Bone-forming osteoblasts and bone-resorbing osteoclasts interact closely to preserve bone mass and architecture and are often located close to blood vessels. Chondrocytes within the developing growth plate ensure that bone lengthening occurs before puberty, but these cells function in an avascular environment. With ageing, numerous bone marrow adipocytes appear, often with negative effects on bone properties. Many studies have now indicated that skeletal cells have specific metabolic profiles that correspond to the nutritional microenvironment and their stage-specific functions. These metabolic networks provide not only skeletal cells with sufficient energy, but also biosynthetic intermediates that are necessary for proliferation and extracellular matrix synthesis. Moreover, these metabolic pathways control redox homeostasis to avoid oxidative stress and safeguard cell survival. Finally, several intracellular metabolites regulate the activity of epigenetic enzymes and thus control the fate and function of skeletal cells. The metabolic profile of skeletal cells therefore not only reflects their cellular state, but can also drive cellular activity. Insight into skeletal cell metabolism will thus not only advance our understanding of skeletal development and homeostasis, but also of skeletal disorders, such as osteoarthritis, diabetic bone disease and bone malignancies.
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Affiliation(s)
- Steve Stegen
- Laboratory of Clinical and Experimental Endocrinology, Department of Chronic Diseases and Metabolism, KU Leuven, Leuven, Belgium
| | - Geert Carmeliet
- Laboratory of Clinical and Experimental Endocrinology, Department of Chronic Diseases and Metabolism, KU Leuven, Leuven, Belgium.
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5
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Qiu M, Chang L, Tang G, Ye W, Xu Y, Tulufu N, Dan Z, Qi J, Deng L, Li C. Activation of the osteoblastic HIF-1α pathway partially alleviates the symptoms of STZ-induced type 1 diabetes mellitus via RegIIIγ. Exp Mol Med 2024; 56:1574-1590. [PMID: 38945950 PMCID: PMC11297314 DOI: 10.1038/s12276-024-01257-4] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/07/2023] [Revised: 02/04/2024] [Accepted: 03/19/2024] [Indexed: 07/02/2024] Open
Abstract
The hypoxia-inducible factor-1α (HIF-1α) pathway coordinates skeletal bone homeostasis and endocrine functions. Activation of the HIF-1α pathway increases glucose uptake by osteoblasts, which reduces blood glucose levels. However, it is unclear whether activating the HIF-1α pathway in osteoblasts can help normalize glucose metabolism under diabetic conditions through its endocrine function. In addition to increasing bone mass and reducing blood glucose levels, activating the HIF-1α pathway by specifically knocking out Von Hippel‒Lindau (Vhl) in osteoblasts partially alleviated the symptoms of streptozotocin (STZ)-induced type 1 diabetes mellitus (T1DM), including increased glucose clearance in the diabetic state, protection of pancreatic β cell from STZ-induced apoptosis, promotion of pancreatic β cell proliferation, and stimulation of insulin secretion. Further screening of bone-derived factors revealed that islet regeneration-derived protein III gamma (RegIIIγ) is an osteoblast-derived hypoxia-sensing factor critical for protection against STZ-induced T1DM. In addition, we found that iminodiacetic acid deferoxamine (SF-DFO), a compound that mimics hypoxia and targets bone tissue, can alleviate symptoms of STZ-induced T1DM by activating the HIF-1α-RegIIIγ pathway in the skeleton. These data suggest that the osteoblastic HIF-1α-RegIIIγ pathway is a potential target for treating T1DM.
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Affiliation(s)
- Minglong Qiu
- Department of Orthopedics, Shanghai Key Laboratory for Prevention and Treatment of Bone and Joint Diseases, Shanghai Institute of Traumatology and Orthopedics, Ruijin Hospital, Shanghai Jiao Tong University School of Medicine, 197 Ruijin 2nd Road, Shanghai, 200025, China
| | - Leilei Chang
- Department of Orthopedics, Shanghai Key Laboratory for Prevention and Treatment of Bone and Joint Diseases, Shanghai Institute of Traumatology and Orthopedics, Ruijin Hospital, Shanghai Jiao Tong University School of Medicine, 197 Ruijin 2nd Road, Shanghai, 200025, China
| | - Guoqing Tang
- Kunshan Hospital of Traditional Chinese Medicine, Affiliated Hospital of Yangzhou University, 388 Zuchongzhi Road, Kunshan, 215300, Jiangsu, China
| | - Wenkai Ye
- Department of Orthopedics, Shanghai Key Laboratory for Prevention and Treatment of Bone and Joint Diseases, Shanghai Institute of Traumatology and Orthopedics, Ruijin Hospital, Shanghai Jiao Tong University School of Medicine, 197 Ruijin 2nd Road, Shanghai, 200025, China
| | - Yiming Xu
- Department of Orthopedics, Shanghai Key Laboratory for Prevention and Treatment of Bone and Joint Diseases, Shanghai Institute of Traumatology and Orthopedics, Ruijin Hospital, Shanghai Jiao Tong University School of Medicine, 197 Ruijin 2nd Road, Shanghai, 200025, China
| | - Nijiati Tulufu
- Department of Orthopedics, Shanghai Key Laboratory for Prevention and Treatment of Bone and Joint Diseases, Shanghai Institute of Traumatology and Orthopedics, Ruijin Hospital, Shanghai Jiao Tong University School of Medicine, 197 Ruijin 2nd Road, Shanghai, 200025, China
| | - Zhou Dan
- Department of Orthopedics, Shanghai Key Laboratory for Prevention and Treatment of Bone and Joint Diseases, Shanghai Institute of Traumatology and Orthopedics, Ruijin Hospital, Shanghai Jiao Tong University School of Medicine, 197 Ruijin 2nd Road, Shanghai, 200025, China
| | - Jin Qi
- Department of Orthopedics, Shanghai Key Laboratory for Prevention and Treatment of Bone and Joint Diseases, Shanghai Institute of Traumatology and Orthopedics, Ruijin Hospital, Shanghai Jiao Tong University School of Medicine, 197 Ruijin 2nd Road, Shanghai, 200025, China.
| | - Lianfu Deng
- Department of Orthopedics, Shanghai Key Laboratory for Prevention and Treatment of Bone and Joint Diseases, Shanghai Institute of Traumatology and Orthopedics, Ruijin Hospital, Shanghai Jiao Tong University School of Medicine, 197 Ruijin 2nd Road, Shanghai, 200025, China.
| | - Changwei Li
- Department of Orthopedics, Shanghai Key Laboratory for Prevention and Treatment of Bone and Joint Diseases, Shanghai Institute of Traumatology and Orthopedics, Ruijin Hospital, Shanghai Jiao Tong University School of Medicine, 197 Ruijin 2nd Road, Shanghai, 200025, China.
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6
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van Brakel F, Zhao Y, van der Eerden BC. Fueling recovery: The importance of energy coupling between angiogenesis and osteogenesis during fracture healing. Bone Rep 2024; 21:101757. [PMID: 38577251 PMCID: PMC10990718 DOI: 10.1016/j.bonr.2024.101757] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Figures] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 12/04/2023] [Revised: 03/20/2024] [Accepted: 03/23/2024] [Indexed: 04/06/2024] Open
Abstract
Approximately half of bone fractures that do not heal properly (non-union) can be accounted to insufficient angiogenesis. The processes of angiogenesis and osteogenesis are spatiotemporally regulated in the complex process of fracture healing that requires a substantial amount of energy. It is thought that a metabolic coupling between angiogenesis and osteogenesis is essential for successful healing. However, how this coupling is achieved remains to be largely elucidated. Here, we will discuss the most recent evidence from literature pointing towards a metabolic coupling between angiogenesis and osteogenesis. We will describe the metabolic profiles of the cell types involved during fracture healing as well as secreted products in the bone microenvironment (such as lactate and nitric oxide) as possible key players in this metabolic crosstalk.
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Affiliation(s)
- Fleur van Brakel
- Calcium and Bone Metabolism Laboratory, Department of Internal Medicine, Erasmus MC, Erasmus University Medical Center, Rotterdam, the Netherlands
| | - Yudong Zhao
- Calcium and Bone Metabolism Laboratory, Department of Internal Medicine, Erasmus MC, Erasmus University Medical Center, Rotterdam, the Netherlands
| | - Bram C.J. van der Eerden
- Calcium and Bone Metabolism Laboratory, Department of Internal Medicine, Erasmus MC, Erasmus University Medical Center, Rotterdam, the Netherlands
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7
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Zhou M, An YZ, Guo Q, Zhou HY, Luo XH. Energy homeostasis in the bone. Trends Endocrinol Metab 2024; 35:439-451. [PMID: 38242815 DOI: 10.1016/j.tem.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: 11/01/2023] [Revised: 12/19/2023] [Accepted: 12/21/2023] [Indexed: 01/21/2024]
Abstract
The bone serves as an energy reservoir and actively engages in whole-body energy metabolism. Numerous studies have determined fuel requirements and bioenergetic properties of bone under physiological conditions as well as the dysregulation of energy metabolism associated with bone metabolic diseases. Here, we review the main sources of energy in bone cells and their regulation, as well as the endocrine role of the bone in systemic energy homeostasis. Moreover, we discuss metabolic changes that occur as a result of osteoporosis. Exploration in this area will contribute to an enhanced comprehension of bone energy metabolism, presenting novel possibilities to address metabolic diseases.
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Affiliation(s)
- Min Zhou
- Department of Endocrinology, Endocrinology Research Center, Xiangya Hospital of Central South University, Changsha, Hunan 410008, PR China; National Clinical Research Center for Geriatric Disorders, Xiangya Hospital, Changsha, Hunan 410008, PR China; Key Laboratory of Aging-Related Bone and Joint Diseases Prevention and Treatment, Ministry of Education, Xiangya Hospital, Central South University, Changsha, PR China; Key Laboratory of Organ Injury, Aging and Regenerative Medicine of Hunan Province, Hunan 410008, PR China
| | - Yu-Ze An
- Department of Endocrinology, Endocrinology Research Center, Xiangya Hospital of Central South University, Changsha, Hunan 410008, PR China; National Clinical Research Center for Geriatric Disorders, Xiangya Hospital, Changsha, Hunan 410008, PR China; Key Laboratory of Aging-Related Bone and Joint Diseases Prevention and Treatment, Ministry of Education, Xiangya Hospital, Central South University, Changsha, PR China; Key Laboratory of Organ Injury, Aging and Regenerative Medicine of Hunan Province, Hunan 410008, PR China
| | - Qi Guo
- Department of Endocrinology, Endocrinology Research Center, Xiangya Hospital of Central South University, Changsha, Hunan 410008, PR China; National Clinical Research Center for Geriatric Disorders, Xiangya Hospital, Changsha, Hunan 410008, PR China; Key Laboratory of Aging-Related Bone and Joint Diseases Prevention and Treatment, Ministry of Education, Xiangya Hospital, Central South University, Changsha, PR China; Key Laboratory of Organ Injury, Aging and Regenerative Medicine of Hunan Province, Hunan 410008, PR China
| | - Hai-Yan Zhou
- Department of Endocrinology, Endocrinology Research Center, Xiangya Hospital of Central South University, Changsha, Hunan 410008, PR China; National Clinical Research Center for Geriatric Disorders, Xiangya Hospital, Changsha, Hunan 410008, PR China; Key Laboratory of Aging-Related Bone and Joint Diseases Prevention and Treatment, Ministry of Education, Xiangya Hospital, Central South University, Changsha, PR China; Key Laboratory of Organ Injury, Aging and Regenerative Medicine of Hunan Province, Hunan 410008, PR China.
| | - Xiang-Hang Luo
- Department of Endocrinology, Endocrinology Research Center, Xiangya Hospital of Central South University, Changsha, Hunan 410008, PR China; National Clinical Research Center for Geriatric Disorders, Xiangya Hospital, Changsha, Hunan 410008, PR China; Key Laboratory of Aging-Related Bone and Joint Diseases Prevention and Treatment, Ministry of Education, Xiangya Hospital, Central South University, Changsha, PR China; Key Laboratory of Organ Injury, Aging and Regenerative Medicine of Hunan Province, Hunan 410008, PR China.
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8
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Rutkowsky JM, Wong A, Toupadakis CA, Rutledge JC, Yellowley CE. Lipolysis products from triglyceride-rich lipoproteins induce stress protein ATF3 in osteoblasts. J Orthop Res 2024; 42:1033-1044. [PMID: 38044472 PMCID: PMC11009083 DOI: 10.1002/jor.25756] [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: 07/20/2023] [Revised: 11/07/2023] [Accepted: 11/28/2023] [Indexed: 12/05/2023]
Abstract
High fat diets overwhelm the physiological mechanisms for absorption, storage, and utilization of triglycerides (TG); consequently TG, TG-rich lipoproteins (TGRL), and TGRL remnants accumulate, circulate systemically, producing dyslipidemia. This associates with, or is causative for increased atherosclerotic cardiovascular risk, ischemic stroke, fatty liver disease, and pancreatitis. TGRL hydrolysis by endothelial surface-bound lipoprotein lipase (LPL) generates metabolites like free fatty acids which have proinflammatory properties. While osteoblasts utilize fatty acids as an energy source, dyslipidemia is associated with negative effects on the skeleton. In this study we investigated the effects of TGRL lipolysis products (TGRL-LP) on expression of a stress responsive transcription factor, termed activating transcription factor 3 (ATF3), reactive oxygen species (ROS), ATF3 target genes, and angiopoietin-like 4 (Angptl4) in osteoblasts. As ATF3 negatively associates with osteoblast differentiation, we also investigated the skeletal effects of global ATF3 deletion in mice. TGRL-LP increased expression of Atf3, proinflammatory proteins Ptgs2 and IL-6, and induced ROS in MC3T3-E1 osteoblastic cells. Angptl4 is an endogenous inhibitor of LPL which was transcriptionally induced by TGRL-LP, while recombinant Angptl4 prevented TG-driven Atf3 induction. Atf3 global knockout male mice demonstrated increased trabecular and cortical microarchitectural parameters. In summary, we find that TGRL-LP induce osteoblastic cell stress as evidenced by expression of ATF3, which may contribute to the negative impact of dyslipidemia in the skeleton. Further, concomitant induction of Angptl4 in osteoblasts might play a protective role by reducing local lipolysis.
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Affiliation(s)
| | - Alice Wong
- Department of Anatomy, Physiology and Cell Biology, School of Veterinary Medicine
| | | | - John C. Rutledge
- Department of Internal Medicine (Cardiology), School of Medicine, University of California Davis, Davis, CA 95616
| | - Clare E. Yellowley
- Department of Anatomy, Physiology and Cell Biology, School of Veterinary Medicine
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9
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Li X, Liang T, Dai B, Chang L, Zhang Y, Hu S, Guo J, Xu S, Zheng L, Yao H, Lian H, Nie Y, Li Y, He X, Yao Z, Tong W, Wang X, Chow DHK, Xu J, Qin L. Excess glucocorticoids inhibit murine bone turnover via modulating the immunometabolism of the skeletal microenvironment. J Clin Invest 2024; 134:e166795. [PMID: 38512413 DOI: 10.1172/jci166795] [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: 10/31/2022] [Accepted: 03/15/2024] [Indexed: 03/23/2024] Open
Abstract
Elevated bone resorption and diminished bone formation have been recognized as the primary features of glucocorticoid-associated skeletal disorders. However, the direct effects of excess glucocorticoids on bone turnover remain unclear. Here, we explored the outcomes of exogenous glucocorticoid treatment on bone loss and delayed fracture healing in mice and found that reduced bone turnover was a dominant feature, resulting in a net loss of bone mass. The primary effect of glucocorticoids on osteogenic differentiation was not inhibitory; instead, they cooperated with macrophages to facilitate osteogenesis. Impaired local nutrient status - notably, obstructed fatty acid transportation - was a key factor contributing to glucocorticoid-induced impairment of bone turnover in vivo. Furthermore, fatty acid oxidation in macrophages fueled the ability of glucocorticoid-liganded receptors to enter the nucleus and then promoted the expression of BMP2, a key cytokine that facilitates osteogenesis. Metabolic reprogramming by localized fatty acid delivery partly rescued glucocorticoid-induced pathology by restoring a healthier immune-metabolic milieu. These data provide insights into the multifactorial metabolic mechanisms by which glucocorticoids generate skeletal disorders, thus suggesting possible therapeutic avenues.
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Affiliation(s)
- Xu Li
- Musculoskeletal Research Laboratory, Department of Orthopedics and Traumatology, Faculty of Medicine
- Innovative Orthopedic Biomaterial and Drug Translational Research Laboratory, Li Ka Shing Institute of Health Sciences, and
| | - Tongzhou Liang
- Musculoskeletal Research Laboratory, Department of Orthopedics and Traumatology, Faculty of Medicine
- Innovative Orthopedic Biomaterial and Drug Translational Research Laboratory, Li Ka Shing Institute of Health Sciences, and
| | - Bingyang Dai
- Musculoskeletal Research Laboratory, Department of Orthopedics and Traumatology, Faculty of Medicine
- Innovative Orthopedic Biomaterial and Drug Translational Research Laboratory, Li Ka Shing Institute of Health Sciences, and
| | - Liang Chang
- Musculoskeletal Research Laboratory, Department of Orthopedics and Traumatology, Faculty of Medicine
- Innovative Orthopedic Biomaterial and Drug Translational Research Laboratory, Li Ka Shing Institute of Health Sciences, and
| | - Yuan Zhang
- School of Biomedical Sciences, Faculty of Medicine, The Chinese University of Hong Kong, Hong Kong, China
| | - Shiwen Hu
- Musculoskeletal Research Laboratory, Department of Orthopedics and Traumatology, Faculty of Medicine
- Innovative Orthopedic Biomaterial and Drug Translational Research Laboratory, Li Ka Shing Institute of Health Sciences, and
| | - Jiaxin Guo
- Musculoskeletal Research Laboratory, Department of Orthopedics and Traumatology, Faculty of Medicine
- Innovative Orthopedic Biomaterial and Drug Translational Research Laboratory, Li Ka Shing Institute of Health Sciences, and
| | - Shunxiang Xu
- Musculoskeletal Research Laboratory, Department of Orthopedics and Traumatology, Faculty of Medicine
- Innovative Orthopedic Biomaterial and Drug Translational Research Laboratory, Li Ka Shing Institute of Health Sciences, and
| | - Lizhen Zheng
- Musculoskeletal Research Laboratory, Department of Orthopedics and Traumatology, Faculty of Medicine
- Innovative Orthopedic Biomaterial and Drug Translational Research Laboratory, Li Ka Shing Institute of Health Sciences, and
| | - Hao Yao
- Musculoskeletal Research Laboratory, Department of Orthopedics and Traumatology, Faculty of Medicine
- Innovative Orthopedic Biomaterial and Drug Translational Research Laboratory, Li Ka Shing Institute of Health Sciences, and
| | - Hong Lian
- Beijing Key Laboratory of Preclinical Research and Evaluation for Cardiovascular Implant Materials, Animal Experimental Centre, and
| | - Yu Nie
- State Key Laboratory of Cardiovascular Disease, Fuwai Hospital, National Center for Cardiovascular Diseases, Chinese Academy of Medical Sciences and Peking Union Medical College, Beijing, China
| | - Ye Li
- Musculoskeletal Research Laboratory, Department of Orthopedics and Traumatology, Faculty of Medicine
- Innovative Orthopedic Biomaterial and Drug Translational Research Laboratory, Li Ka Shing Institute of Health Sciences, and
| | - Xuan He
- Musculoskeletal Research Laboratory, Department of Orthopedics and Traumatology, Faculty of Medicine
- Innovative Orthopedic Biomaterial and Drug Translational Research Laboratory, Li Ka Shing Institute of Health Sciences, and
| | - Zhi Yao
- Musculoskeletal Research Laboratory, Department of Orthopedics and Traumatology, Faculty of Medicine
- Innovative Orthopedic Biomaterial and Drug Translational Research Laboratory, Li Ka Shing Institute of Health Sciences, and
| | - Wenxue Tong
- Musculoskeletal Research Laboratory, Department of Orthopedics and Traumatology, Faculty of Medicine
- Innovative Orthopedic Biomaterial and Drug Translational Research Laboratory, Li Ka Shing Institute of Health Sciences, and
| | - Xinluan Wang
- Centre for Translational Medicine Research and Development, Shenzhen Institute of Advanced Technology, Chinese Academy of Sciences, Shenzhen, China
| | - Dick Ho Kiu Chow
- Musculoskeletal Research Laboratory, Department of Orthopedics and Traumatology, Faculty of Medicine
- Innovative Orthopedic Biomaterial and Drug Translational Research Laboratory, Li Ka Shing Institute of Health Sciences, and
| | - Jiankun Xu
- Musculoskeletal Research Laboratory, Department of Orthopedics and Traumatology, Faculty of Medicine
- Innovative Orthopedic Biomaterial and Drug Translational Research Laboratory, Li Ka Shing Institute of Health Sciences, and
| | - Ling Qin
- Musculoskeletal Research Laboratory, Department of Orthopedics and Traumatology, Faculty of Medicine
- Innovative Orthopedic Biomaterial and Drug Translational Research Laboratory, Li Ka Shing Institute of Health Sciences, and
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10
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Gao F, Hu Q, Chen W, Li J, Qi C, Yan Y, Qian C, Wan M, Ficke J, Zheng J, Cao X. Brain regulates weight bearing bone through PGE2 skeletal interoception: implication of ankle osteoarthritis and pain. Bone Res 2024; 12:16. [PMID: 38443372 PMCID: PMC10914853 DOI: 10.1038/s41413-024-00316-w] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/04/2023] [Revised: 01/12/2024] [Accepted: 01/15/2024] [Indexed: 03/07/2024] Open
Abstract
Bone is a mechanosensitive tissue and undergoes constant remodeling to adapt to the mechanical loading environment. However, it is unclear whether the signals of bone cells in response to mechanical stress are processed and interpreted in the brain. In this study, we found that the hypothalamus of the brain regulates bone remodeling and structure by perceiving bone prostaglandin E2 (PGE2) concentration in response to mechanical loading. Bone PGE2 levels are in proportion to their weight bearing. When weight bearing changes in the tail-suspension mice, the PGE2 concentrations in bones change in line with their weight bearing changes. Deletion of cyclooxygenase-2 (COX2) in the osteoblast lineage cells or knockout of receptor 4 (EP4) in sensory nerve blunts bone formation in response to mechanical loading. Moreover, knockout of TrkA in sensory nerve also significantly reduces mechanical load-induced bone formation. Moreover, mechanical loading induces cAMP-response element binding protein (CREB) phosphorylation in the hypothalamic arcuate nucleus (ARC) to inhibit sympathetic tyrosine hydroxylase (TH) expression in the paraventricular nucleus (PVN) for osteogenesis. Finally, we show that elevated PGE2 is associated with ankle osteoarthritis (AOA) and pain. Together, our data demonstrate that in response to mechanical loading, skeletal interoception occurs in the form of hypothalamic processing of PGE2-driven peripheral signaling to maintain physiologic bone homeostasis, while chronically elevated PGE2 can be sensed as pain during AOA and implication of potential treatment.
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Affiliation(s)
- Feng Gao
- Department of Orthopedic Surgery, Johns Hopkins University School of Medicine, Baltimore, Maryland, 21205, USA
| | - Qimiao Hu
- Department of Orthopedic Surgery, Johns Hopkins University School of Medicine, Baltimore, Maryland, 21205, USA
| | - Wenwei Chen
- Department of Orthopedic Surgery, Johns Hopkins University School of Medicine, Baltimore, Maryland, 21205, USA
- Department of Biomedical Engineering, Johns Hopkins University School of Medicine, Baltimore, Maryland, 21205, USA
| | - Jilong Li
- Department of Orthopedic Surgery, Johns Hopkins University School of Medicine, Baltimore, Maryland, 21205, USA
| | - Cheng Qi
- Department of Orthopedic Surgery, Johns Hopkins University School of Medicine, Baltimore, Maryland, 21205, USA
| | - Yiwen Yan
- Department of Orthopedic Surgery, Johns Hopkins University School of Medicine, Baltimore, Maryland, 21205, USA
| | - Cheng Qian
- Department of Orthopedic Surgery, Johns Hopkins University School of Medicine, Baltimore, Maryland, 21205, USA
| | - Mei Wan
- Department of Orthopedic Surgery, Johns Hopkins University School of Medicine, Baltimore, Maryland, 21205, USA
- Department of Biomedical Engineering, Johns Hopkins University School of Medicine, Baltimore, Maryland, 21205, USA
| | - James Ficke
- Department of Orthopedic Surgery, Johns Hopkins University School of Medicine, Baltimore, Maryland, 21205, USA
| | - Junying Zheng
- Department of Orthopedic Surgery, Johns Hopkins University School of Medicine, Baltimore, Maryland, 21205, USA
| | - Xu Cao
- Department of Orthopedic Surgery, Johns Hopkins University School of Medicine, Baltimore, Maryland, 21205, USA.
- Department of Biomedical Engineering, Johns Hopkins University School of Medicine, Baltimore, Maryland, 21205, USA.
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11
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Guo Q, Chen N, Patel K, Wan M, Zheng J, Cao X. Unloading-Induced Skeletal Interoception Alters Hypothalamic Signaling to Promote Bone Loss and Fat Metabolism. ADVANCED SCIENCE (WEINHEIM, BADEN-WURTTEMBERG, GERMANY) 2023; 10:e2305042. [PMID: 37880864 PMCID: PMC10724445 DOI: 10.1002/advs.202305042] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 07/23/2023] [Revised: 10/02/2023] [Indexed: 10/27/2023]
Abstract
Microgravity is the primary factor that affects human physiology in spaceflight, particularly bone loss and disturbances of the central nervous system. However, little is known about the cellular and molecular mechanisms of these effects. Here, it is reported that in mice hindlimb unloading stimulates expression of neuropeptide Y (NPY) and tyrosine hydroxylase (TH) in the hypothalamus, resulting in bone loss and altered fat metabolism. Enhanced expression of TH and NPY in the hypothalamus occurs downstream of a reduced prostaglandin E2 (PGE2)-mediated ascending interoceptive signaling of the skeletal interoception. Sympathetic antagonist propranolol or deletion of Adrb2 in osteocytes rescue bone loss in the unloading model. Moreover, depletion of TH+ sympathetic nerves or inhibition of norepinephrine release ameliorated bone resorption. Stereotactic inhibition of NPY expression in the hypothalamic neurons reduces the food intake with altered energy expenditure with a limited effect on bone, indicating hypothalamic neuroendocrine factor NPY in the facilitation of bone formation by sympathetic TH activity. These findings suggest that reduced PGE2-mediated interoceptive signaling in response to microgravity or unloading has impacts on the skeletal and central nervous systems that are reciprocally regulated.
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Affiliation(s)
- Qiaoyue Guo
- Department of Orthopedic SurgeryJohns Hopkins University School of MedicineBaltimoreMD21205USA
- Department of EndocrinologyEndocrinology Research CenterXiangya Hospital of Central South UniversityChangshaHunan410008China
| | - Ningrong Chen
- Department of Orthopedic SurgeryJohns Hopkins University School of MedicineBaltimoreMD21205USA
| | - Kalp Patel
- Department of Orthopedic SurgeryJohns Hopkins University School of MedicineBaltimoreMD21205USA
| | - Mei Wan
- Department of Orthopedic SurgeryJohns Hopkins University School of MedicineBaltimoreMD21205USA
| | - Junying Zheng
- Department of Orthopedic SurgeryJohns Hopkins University School of MedicineBaltimoreMD21205USA
| | - Xu Cao
- Department of Orthopedic SurgeryJohns Hopkins University School of MedicineBaltimoreMD21205USA
- Department of Biomedical EngineeringJohns Hopkins University School of MedicineBaltimoreMD21205USA
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12
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DeMambro VE, Tian L, Karthik V, Rosen CJ, Guntur AR. Effects of PTH on osteoblast bioenergetics in response to glucose. Bone Rep 2023; 19:101705. [PMID: 37576927 PMCID: PMC10412867 DOI: 10.1016/j.bonr.2023.101705] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 02/01/2023] [Revised: 05/29/2023] [Accepted: 07/13/2023] [Indexed: 08/15/2023] Open
Abstract
Parathyroid hormone acts through its receptor, PTHR1, expressed on osteoblasts, to control bone remodeling. Metabolic flexibility for energy generation has been demonstrated in several cell types dependent on substrate availability. Recent studies have identified a critical role for PTH in regulating glucose, fatty acid and amino acid metabolism thus stimulating both glycolysis and oxidative phosphorylation. Therefore, we postulated that PTH stimulates increased energetic output by osteoblasts either by increasing glycolysis or oxidative phosphorylation depending on substrate availability. To test this hypothesis, undifferentiated and differentiated MC3T3E1C4 calvarial pre-osteoblasts were treated with PTH to study osteoblast bioenergetics in the presence of exogenous glucose. Significant increases in glycolysis with acute ∼1 h PTH treatment with minimal effects on oxidative phosphorylation in undifferentiated MC3T3E1C4 in the presence of exogenous glucose were observed. In differentiated cells, the increased glycolysis observed with acute PTH was completely blocked by pretreatment with a Glut1 inhibitor (BAY-876) resulting in a compensatory increase in oxidative phosphorylation. We then tested the effect of PTH on the function of complexes I and II of the mitochondrial electron transport chain in the absence of glycolysis. Utilizing a novel cell plasma membrane permeability mitochondrial (PMP) assay, in combination with complex I and II specific substrates, slight but significant increases in basal and maximal oxygen consumption rates with 24 h PTH treatment in undifferentiated MC3T3E1C4 cells were noted. Taken together, our data demonstrate for the first time that PTH stimulates both increases in glycolysis and the function of the electron transport chain, particularly complexes I and II, during high energy demands in osteoblasts.
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Affiliation(s)
- Victoria E. DeMambro
- Center for Molecular Medicine, MaineHealth Institute for Research, Scarborough, ME, USA
- Graduate School of Biomedical Sciences and Engineering, University of Maine, Orono, ME, USA
| | - Li Tian
- Center for Molecular Medicine, MaineHealth Institute for Research, Scarborough, ME, USA
| | - Vivin Karthik
- Graduate School of Biomedical Sciences and Engineering, University of Maine, Orono, ME, USA
| | - Clifford J. Rosen
- Center for Molecular Medicine, MaineHealth Institute for Research, Scarborough, ME, USA
- Tufts University School of Medicine, Tufts University, Boston, MA, USA
- Graduate School of Biomedical Sciences and Engineering, University of Maine, Orono, ME, USA
| | - Anyonya R. Guntur
- Center for Molecular Medicine, MaineHealth Institute for Research, Scarborough, ME, USA
- Tufts University School of Medicine, Tufts University, Boston, MA, USA
- Graduate School of Biomedical Sciences and Engineering, University of Maine, Orono, ME, USA
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13
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Nandy A, Helderman RCM, Thapa S, Jayapalan S, Richards A, Narayani N, Czech MP, Rosen CJ, Rendina-Ruedy E. Lipolysis supports bone formation by providing osteoblasts with endogenous fatty acid substrates to maintain bioenergetic status. Bone Res 2023; 11:62. [PMID: 38001111 PMCID: PMC10673934 DOI: 10.1038/s41413-023-00297-2] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/15/2023] [Revised: 09/18/2023] [Accepted: 09/22/2023] [Indexed: 11/26/2023] Open
Abstract
Bone formation is a highly energy-demanding process that can be impacted by metabolic disorders. Glucose has been considered the principal substrate for osteoblasts, although fatty acids are also important for osteoblast function. Here, we report that osteoblasts can derive energy from endogenous fatty acids stored in lipid droplets via lipolysis and that this process is critical for bone formation. As such, we demonstrate that osteoblasts accumulate lipid droplets that are highly dynamic and provide the molecular mechanism by which they serve as a fuel source for energy generation during osteoblast maturation. Inhibiting cytoplasmic lipolysis leads to both an increase in lipid droplet size in osteoblasts and an impairment in osteoblast function. The fatty acids released by lipolysis from these lipid droplets become critical for cellular energy production as cellular energetics shifts towards oxidative phosphorylation during nutrient-depleted conditions. In vivo, conditional deletion of the ATGL-encoding gene Pnpla2 in osteoblast progenitor cells reduces cortical and trabecular bone parameters and alters skeletal lipid metabolism. Collectively, our data demonstrate that osteoblasts store fatty acids in the form of lipid droplets, which are released via lipolysis to support cellular bioenergetic status when nutrients are limited. Perturbations in this process result in impairment of bone formation, specifically reducing ATP production and overall osteoblast function.
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Affiliation(s)
- Ananya Nandy
- Department of Medicine, Division of Clinical Pharmacology, Vanderbilt University Medical Center, Nashville, TN, 37232, USA
| | - Ron C M Helderman
- Department of Medicine, Division of Clinical Pharmacology, Vanderbilt University Medical Center, Nashville, TN, 37232, USA
| | - Santosh Thapa
- Department of Medicine, Division of Clinical Pharmacology, Vanderbilt University Medical Center, Nashville, TN, 37232, USA
| | - Shobana Jayapalan
- Department of Medicine, Division of Clinical Pharmacology, Vanderbilt University Medical Center, Nashville, TN, 37232, USA
| | - Alison Richards
- Department of Medicine, Division of Clinical Pharmacology, Vanderbilt University Medical Center, Nashville, TN, 37232, USA
| | - Nikita Narayani
- Department of Medicine, Division of Clinical Pharmacology, Vanderbilt University Medical Center, Nashville, TN, 37232, USA
| | - Michael P Czech
- Program in Molecular Medicine, University of Massachusetts Chan Medical School, Worcester, MA, 01605, USA
| | | | - Elizabeth Rendina-Ruedy
- Department of Medicine, Division of Clinical Pharmacology, Vanderbilt University Medical Center, Nashville, TN, 37232, USA.
- Molecular Physiology and Biophysics, Vanderbilt University, Nashville, TN, 37232, USA.
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14
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Li Z, Rosen CJ. The Multifaceted Roles of Bone Marrow Adipocytes in Bone and Hematopoietic Homeostasis. J Clin Endocrinol Metab 2023; 108:e1465-e1472. [PMID: 37315208 DOI: 10.1210/clinem/dgad355] [Citation(s) in RCA: 2] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 03/10/2023] [Revised: 06/07/2023] [Accepted: 06/09/2023] [Indexed: 06/16/2023]
Abstract
Bone marrow adipose tissue (BMAT) makes up a significant portion of the marrow space, ranging from 50% to 70%, in healthy adults. It expands with aging, obesity, anorexia nervosa, and irradiation, which are conditions associated with skeletal complications or hematopoietic disorders. Therefore, BMAT has been viewed as a negative component of the bone marrow niche for decades, although the mechanisms and causative relationships have not been well-addressed. Of note, recent studies have revealed that BMAT is a multifaceted tissue that can serve as an energy reservoir to fuel osteoblasts and hematopoietic cells under stressful situations, and also acts as an endocrine/paracrine organ to suppress bone formation and support hematopoiesis at steady-state conditions. In this review, we summarize the uniqueness of BMAT, the complex findings of previous studies, and update our understanding of the physiological roles of BMAT in bone and hematopoietic metabolism based on a newly established bone marrow adipocyte-specific mouse model.
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Affiliation(s)
- Ziru Li
- Center for Molecular Medicine, MaineHealth Institute for Research, Scarborough, ME 04074, USA
| | - Clifford J Rosen
- Center for Molecular Medicine, MaineHealth Institute for Research, Scarborough, ME 04074, USA
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15
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Xiao X, Juan C, Drennon T, Uytingco CR, Vishlaghi N, Sokolowskei D, Xu L, Levi B, Sammarco MC, Tower RJ. Spatial transcriptomic interrogation of the murine bone marrow signaling landscape. Bone Res 2023; 11:59. [PMID: 37926705 PMCID: PMC10625929 DOI: 10.1038/s41413-023-00298-1] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/22/2023] [Revised: 09/19/2023] [Accepted: 09/28/2023] [Indexed: 11/07/2023] Open
Abstract
Self-renewal and differentiation of skeletal stem and progenitor cells (SSPCs) are tightly regulated processes, with SSPC dysregulation leading to progressive bone disease. While the application of single-cell RNA sequencing (scRNAseq) to the bone field has led to major advancements in our understanding of SSPC heterogeneity, stem cells are tightly regulated by their neighboring cells which comprise the bone marrow niche. However, unbiased interrogation of these cells at the transcriptional level within their native niche environment has been challenging. Here, we combined spatial transcriptomics and scRNAseq using a predictive modeling pipeline derived from multiple deconvolution packages in adult mouse femurs to provide an endogenous, in vivo context of SSPCs within the niche. This combined approach localized SSPC subtypes to specific regions of the bone and identified cellular components and signaling networks utilized within the niche. Furthermore, the use of spatial transcriptomics allowed us to identify spatially restricted activation of metabolic and major morphogenetic signaling gradients derived from the vasculature and bone surfaces that establish microdomains within the marrow cavity. Overall, we demonstrate, for the first time, the feasibility of applying spatial transcriptomics to fully mineralized tissue and present a combined spatial and single-cell transcriptomic approach to define the cellular components of the stem cell niche, identify cell‒cell communication, and ultimately gain a comprehensive understanding of local and global SSPC regulatory networks within calcified tissue.
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Affiliation(s)
- Xue Xiao
- Quantitative Biomedical Research Center, Peter O'Donnell Jr. School of Public Health, University of Texas Southwestern Medical Center, Dallas, TX, USA
| | - Conan Juan
- Department of Surgery, University of Texas Southwestern Medical Center, Dallas, TX, USA
| | - Tingsheng Drennon
- Department of Cell Biology & Applications, 10x Genomics, Pleasanton, CA, USA
| | - Cedric R Uytingco
- Department of Cell Biology & Applications, 10x Genomics, Pleasanton, CA, USA
| | - Neda Vishlaghi
- Department of Surgery, University of Texas Southwestern Medical Center, Dallas, TX, USA
| | - Dimitri Sokolowskei
- Department of Surgery, University of Texas Southwestern Medical Center, Dallas, TX, USA
| | - Lin Xu
- Quantitative Biomedical Research Center, Peter O'Donnell Jr. School of Public Health, University of Texas Southwestern Medical Center, Dallas, TX, USA
| | - Benjamin Levi
- Department of Surgery, University of Texas Southwestern Medical Center, Dallas, TX, USA
| | - Mimi C Sammarco
- Department of Surgery, Tulane School of Medicine, New Orleans, LA, USA
| | - Robert J Tower
- Department of Surgery, University of Texas Southwestern Medical Center, Dallas, TX, USA.
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16
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Tu WB, Christofk HR, Plath K. Nutrient regulation of development and cell fate decisions. Development 2023; 150:dev199961. [PMID: 37260407 PMCID: PMC10281554 DOI: 10.1242/dev.199961] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 06/02/2023]
Abstract
Diet contributes to health at all stages of life, from embryonic development to old age. Nutrients, including vitamins, amino acids, lipids and sugars, have instructive roles in directing cell fate and function, maintaining stem cell populations, tissue homeostasis and alleviating the consequences of aging. This Review highlights recent findings that illuminate how common diets and specific nutrients impact cell fate decisions in healthy and disease contexts. We also draw attention to new models, technologies and resources that help to address outstanding questions in this emerging field and may lead to dietary approaches that promote healthy development and improve disease treatments.
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Affiliation(s)
- William B. Tu
- Department of Biological Chemistry, David Geffen School of Medicine, University of California Los Angeles, Los Angeles, CA 90095, USA
| | - Heather R. Christofk
- Department of Biological Chemistry, David Geffen School of Medicine, University of California Los Angeles, Los Angeles, CA 90095, USA
- Jonsson Comprehensive Cancer Center; Eli and Edythe Broad Center of Regenerative Medicine and Stem Cell Research, University of California Los Angeles, Los Angeles, CA 90095, USA
| | - Kathrin Plath
- Department of Biological Chemistry, David Geffen School of Medicine, University of California Los Angeles, Los Angeles, CA 90095, USA
- Jonsson Comprehensive Cancer Center; Eli and Edythe Broad Center of Regenerative Medicine and Stem Cell Research, University of California Los Angeles, Los Angeles, CA 90095, USA
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17
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Gao F, Hu Q, Qi C, Wan M, Ficke J, Zheng J, Cao X. Mechanical loading-induced change of bone homeostasis is mediated by PGE2-driven hypothalamic interoception. RESEARCH SQUARE 2023:rs.3.rs-3325498. [PMID: 37790467 PMCID: PMC10543368 DOI: 10.21203/rs.3.rs-3325498/v1] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 10/05/2023]
Abstract
Bone is a mechanosensitive tissue and undergoes constant remodeling to adapt to the mechanical loading environment. However, it is unclear whether the signals of bone cells in response to mechanical stress are processed and interpreted in the brain. In this study, we found that the hypothalamus of the brain regulates bone remodeling and structure by perceiving bone PGE2 concentration in response to mechanical loading. Bone PGE2 levels are in proportion to their weight bearing. When weight bearing changes in the tail-suspension mice, the PGE2 concentrations in bones change in line with their weight bearing changes. Deletion of Cox2 or Pge2 in the osteoblast lineage cells or knockout Ep4 in sensory nerve blunts bone formation in response to mechanical loading. And sensory denervation also significantly reduces mechanical load-induced bone formation. Moreover, mechanical loading induces CREB phosphorylation in the hypothalamic ARC region to inhibit sympathetic TH expression in the PVN for osteogenesis. Finally, we show that elevated PGE2 is associated with ankle osteoarthritis (AOA) and pain. Together, our data demonstrate that in response to mechanical loading, skeletal interoception occurs in the form of hypothalamic processing of PGE2-driven peripheral signaling to maintain physiologic bone homeostasis, while chronically elevated PGE2 can be sensed as pain during AOA and implication of potential treatment.
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Affiliation(s)
- Feng Gao
- Department of Orthopedic Surgery and Department of Biomedical Engineering, Johns Hopkins University School of Medicine, Baltimore, Maryland 21205, USA
| | - Qimiao Hu
- Department of Orthopedic Surgery and Department of Biomedical Engineering, Johns Hopkins University School of Medicine, Baltimore, Maryland 21205, USA
| | - Cheng Qi
- Department of Orthopedic Surgery and Department of Biomedical Engineering, Johns Hopkins University School of Medicine, Baltimore, Maryland 21205, USA
| | - Mei Wan
- Department of Orthopedic Surgery and Department of Biomedical Engineering, Johns Hopkins University School of Medicine, Baltimore, Maryland 21205, USA
| | - James Ficke
- Department of Orthopedic Surgery and Department of Biomedical Engineering, Johns Hopkins University School of Medicine, Baltimore, Maryland 21205, USA
| | - Junying Zheng
- Department of Orthopedic Surgery and Department of Biomedical Engineering, Johns Hopkins University School of Medicine, Baltimore, Maryland 21205, USA
| | - Xu Cao
- Department of Orthopedic Surgery and Department of Biomedical Engineering, Johns Hopkins University School of Medicine, Baltimore, Maryland 21205, USA
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18
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Sabini E, Arboit L, Khan MP, Lanzolla G, Schipani E. Oxidative phosphorylation in bone cells. Bone Rep 2023; 18:101688. [PMID: 37275785 PMCID: PMC10238578 DOI: 10.1016/j.bonr.2023.101688] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 03/13/2023] [Revised: 05/15/2023] [Accepted: 05/22/2023] [Indexed: 06/07/2023] Open
Abstract
The role of energy metabolism in bone cells is an active field of investigation. Bone cells are metabolically very active and require high levels of energy in the form of adenosine triphosphate (ATP) to support their function. ATP is generated in the cytosol via glycolysis coupled with lactic acid fermentation and in the mitochondria via oxidative phosphorylation (OXPHOS). OXPHOS is the final convergent metabolic pathway for all oxidative steps of dietary nutrients catabolism. The formation of ATP is driven by an electrochemical gradient that forms across the mitochondrial inner membrane through to the activity of the electron transport chain (ETC) complexes and requires the presence of oxygen as the final electron acceptor. The current literature supports a model in which glycolysis is the main source of energy in undifferentiated mesenchymal progenitors and terminally differentiated osteoblasts, whereas OXPHOS appears relevant in an intermediate stage of differentiation of those cells. Conversely, osteoclasts progressively increase OXPHOS during differentiation until they become multinucleated and mitochondrial-rich terminal differentiated cells. Despite the abundance of mitochondria, mature osteoclasts are considered ATP-depleted, and the availability of ATP is a critical factor that regulates the low survival capacity of these cells, which rapidly undergo death by apoptosis. In addition to ATP, bioenergetic metabolism generates reactive oxygen species (ROS) and intermediate metabolites that regulate a variety of cellular functions, including epigenetics changes of genomic DNA and histones. This review will briefly discuss the role of OXPHOS and the cross-talks OXPHOS-glycolysis in the differentiation process of bone cells.
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Affiliation(s)
| | | | | | | | - Ernestina Schipani
- Corresponding author at: Department of Orthopaedic Surgery, University of Pennsylvania, Perelman Medical School, 310A Stemmler Hall, 3450 Hamilton Walk, Philadelphia, PA 19104, USA.
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19
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Menale C, Trinchese G, Aiello I, Scalia G, Dentice M, Mollica MP, Yoon NA, Diano S. Nutrient-Dependent Mitochondrial Fission Enhances Osteoblast Function. Nutrients 2023; 15:2222. [PMID: 37432387 DOI: 10.3390/nu15092222] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/07/2023] [Revised: 05/05/2023] [Accepted: 05/05/2023] [Indexed: 07/12/2023] Open
Abstract
BACKGROUND The bone synthesizing function of osteoblasts (OBs) is a highly demanding energy process that requires nutrients. However, how nutrient availability affects OBs behavior and bone mineralization remain to be fully understood. METHODS MC3T3-E1 cell line and primary OBs (OBs) cultures were treated with physiological levels of glucose (G; 5.5 mM) alone or with the addition of palmitic acid (G+PA) at different concentrations. Mitochondria morphology and activity were evaluated by fluorescence microscopy, qPCR, and oxygen consumption rate (OCR) measurement, and OBs function was assessed by mineralization assay. RESULTS The addition of non-lipotoxic levels of 25 μM PA to G increased mineralization in OBs. G+25 μM PA exposure reduced mitochondria size in OBs, which was associated with increased activation of dynamin-related protein 1, a mitochondrial fission protein, enhanced mitochondria OCR and ATP production, and increased expression of oxidative phosphorylation genes. Treatment with Mdivi-1, a putative inhibitor of mitochondrial fission, reduced osteogenesis and mitochondrial respiration in OBs. CONCLUSIONS Our results revealed that OBs function was enhanced in the presence of glucose and PA at 25 μM. This was associated with increased OBs mitochondrial respiration and dynamics. These results suggest a role for nutrient availability in bone physiology and pathophysiology.
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Affiliation(s)
- Ciro Menale
- Department of Clinical Medicine and Surgery, University of Naples "Federico II", 80131 Naples, Italy
| | - Giovanna Trinchese
- Department of Biology, University of Naples "Federico II", 80126 Naples, Italy
| | - Immacolata Aiello
- Department of Clinical Medicine and Surgery, University of Naples "Federico II", 80131 Naples, Italy
| | - Giulia Scalia
- CEINGE-Biotecnologie Avanzate Franco Salvatore, 80145 Naples, Italy
| | - Monica Dentice
- Department of Clinical Medicine and Surgery, University of Naples "Federico II", 80131 Naples, Italy
| | - Maria Pina Mollica
- Department of Biology, University of Naples "Federico II", 80126 Naples, Italy
- Centro Servizi Metrologici e Tecnologici Avanzati (CeSMA), Complesso Universitario di Monte Sant'Angelo, 80126 Naples, Italy
- Task Force on Microbiome Studies, University of Naples "Federico II", 80138 Naples, Italy
| | - Nal Ae Yoon
- Institute of Human Nutrition, Columbia University Irving Medical Center, New York, NY 10032, USA
| | - Sabrina Diano
- Institute of Human Nutrition, Columbia University Irving Medical Center, New York, NY 10032, USA
- Department of Molecular Pharmacology and Therapeutics, Columbia University Irving Medical Center, New York, NY 10032, USA
- Department of Physiology and Cellular Biophysics, Columbia University Irving Medical Center, New York, NY 10032, USA
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20
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Song F, Lee WD, Marmo T, Ji X, Song C, Liao X, Seeley R, Yao L, Liu H, Long F. Osteoblast-intrinsic defect in glucose metabolism impairs bone formation in type II diabetic male mice. eLife 2023; 12:e85714. [PMID: 37144869 PMCID: PMC10198725 DOI: 10.7554/elife.85714] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/21/2022] [Accepted: 05/04/2023] [Indexed: 05/06/2023] Open
Abstract
Skeletal fragility is associated with type 2 diabetes mellitus (T2D), but the underlying mechanism is not well understood. Here, in a mouse model for youth-onset T2D, we show that both trabecular and cortical bone mass is reduced due to diminished osteoblast activity. Stable isotope tracing in vivo with 13C-glucose demonstrates that both glycolysis and glucose fueling of the TCA cycle are impaired in diabetic bones. Similarly, Seahorse assays show suppression of both glycolysis and oxidative phosphorylation by diabetes in bone marrow mesenchymal cells as a whole, whereas single-cell RNA sequencing reveals distinct modes of metabolic dysregulation among the subpopulations. Metformin not only promotes glycolysis and osteoblast differentiation in vitro, but also improves bone mass in diabetic mice. Finally, osteoblast-specific overexpression of either Hif1a, a general inducer of glycolysis, or Pfkfb3 which stimulates a specific step in glycolysis, averts bone loss in T2D mice. The study identifies osteoblast-intrinsic defects in glucose metabolism as an underlying cause of diabetic osteopenia, which may be targeted therapeutically.
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Affiliation(s)
- Fangfang Song
- Translational Research Program in Pediatric Orthopedics, Department of Surgery, The Children’s Hospital of PhiladelphiaPhiladelphiaUnited States
- The State Key Laboratory Breeding Base of Basic Science of Stomatology and Key Laboratory for Oral Biomedicine of Ministry of Education, School and Hospital of Stomatology, Wuhan UniversityWuhanChina
| | - Won Dong Lee
- Lewis Sigler Institute for Integrative Genomics, Princeton UniversityPrincetonUnited States
| | - Tyler Marmo
- Translational Research Program in Pediatric Orthopedics, Department of Surgery, The Children’s Hospital of PhiladelphiaPhiladelphiaUnited States
| | - Xing Ji
- Translational Research Program in Pediatric Orthopedics, Department of Surgery, The Children’s Hospital of PhiladelphiaPhiladelphiaUnited States
| | - Chao Song
- Translational Research Program in Pediatric Orthopedics, Department of Surgery, The Children’s Hospital of PhiladelphiaPhiladelphiaUnited States
| | - Xueyang Liao
- Translational Research Program in Pediatric Orthopedics, Department of Surgery, The Children’s Hospital of PhiladelphiaPhiladelphiaUnited States
| | - Rebecca Seeley
- Translational Research Program in Pediatric Orthopedics, Department of Surgery, The Children’s Hospital of PhiladelphiaPhiladelphiaUnited States
| | - Lutian Yao
- Translational Research Program in Pediatric Orthopedics, Department of Surgery, The Children’s Hospital of PhiladelphiaPhiladelphiaUnited States
| | - Haoran Liu
- Department of Computer Science, New Jersey Institute of TechnologyNewarkUnited States
| | - Fanxin Long
- Translational Research Program in Pediatric Orthopedics, Department of Surgery, The Children’s Hospital of PhiladelphiaPhiladelphiaUnited States
- Deaprtment of Orthopedic Surgery, University of PennsylvaniaPhiladelphiaUnited States
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21
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Sautchuk R, Yu C, McArthur M, Massie C, Brookes PS, Porter GA, Awad H, Eliseev RA. Role of the Mitochondrial Permeability Transition in Bone Metabolism and Aging. J Bone Miner Res 2023; 38:522-540. [PMID: 36779737 PMCID: PMC10101909 DOI: 10.1002/jbmr.4787] [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: 07/26/2022] [Revised: 02/02/2023] [Accepted: 02/07/2023] [Indexed: 02/14/2023]
Abstract
The mitochondrial permeability transition pore (MPTP) and its positive regulator, cyclophilin D (CypD), play important pathophysiological roles in aging. In bone tissue, higher CypD expression and pore activity are found in aging; however, a causal relationship between CypD/MPTP and bone degeneration needs to be established. We previously reported that CypD expression and MPTP activity are downregulated during osteoblast (OB) differentiation and that manipulations in CypD expression affect OB differentiation and function. Using a newly developed OB-specific CypD/MPTP gain-of-function (GOF) mouse model, we here present evidence that overexpression of a constitutively active K166Q mutant of CypD (caCypD) impairs OB energy metabolism and function, and bone morphological and biomechanical parameters. Specifically, in a spatial-dependent and sex-dependent manner, OB-specific CypD GOF led to a decrease in oxidative phosphorylation (OxPhos) levels, higher oxidative stress, and general metabolic adaptations coincident with the decreased bone organic matrix content in long bones. Interestingly, accelerated bone degeneration was present in vertebral bones regardless of sex. Overall, our work confirms CypD/MPTP overactivation as an important pathophysiological mechanism leading to bone degeneration and fragility in aging. © 2023 American Society for Bone and Mineral Research (ASBMR).
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Affiliation(s)
- Rubens Sautchuk
- Center for Musculoskeletal ResearchUniversity of Rochester, Rochester, NY, USA
| | - Chen Yu
- Center for Musculoskeletal ResearchUniversity of Rochester, Rochester, NY, USA
| | - Matthew McArthur
- Center for Musculoskeletal ResearchUniversity of Rochester, Rochester, NY, USA
| | - Christine Massie
- Center for Musculoskeletal ResearchUniversity of Rochester, Rochester, NY, USA
- Department of Biomedical Engineering, University of Rochester, Rochester, NY, USA
| | - Paul S Brookes
- Department of Anesthesiology and Perioperative Medicine, University of Rochester, Rochester, NY, USA
- Department of Pharmacology & Physiology, University of Rochester, Rochester, NY, USA
| | - George A Porter
- Department of Pediatrics, Division of Cardiology, University of Rochester, Rochester, NY, USA
| | - Hani Awad
- Center for Musculoskeletal ResearchUniversity of Rochester, Rochester, NY, USA
- Department of Biomedical Engineering, University of Rochester, Rochester, NY, USA
| | - Roman A Eliseev
- Center for Musculoskeletal ResearchUniversity of Rochester, Rochester, NY, USA
- Department of Pharmacology & Physiology, University of Rochester, Rochester, NY, USA
- Department of Pathology, University of Rochester, Rochester, NY, USA
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22
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Alekos NS, Kushwaha P, Kim SP, Li Z, Abood A, Dirckx N, Aja S, Kodama J, Garcia-Diaz JG, Otsuru S, Rendina-Ruedy E, Wolfgang MJ, Riddle RC. Mitochondrial β-oxidation of adipose-derived fatty acids by osteoblasts fuels parathyroid hormone-induced bone formation. JCI Insight 2023; 8:e165604. [PMID: 36729662 PMCID: PMC10070112 DOI: 10.1172/jci.insight.165604] [Citation(s) in RCA: 5] [Impact Index Per Article: 5.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/20/2022] [Accepted: 02/01/2023] [Indexed: 02/03/2023] Open
Abstract
The energetic costs of bone formation require osteoblasts to coordinate their activities with tissues, like adipose, that can supply energy-dense macronutrients. In the case of intermittent parathyroid hormone (PTH) treatment, a strategy used to reduce fracture risk, bone formation is preceded by a change in systemic lipid homeostasis. To investigate the requirement for fatty acid oxidation by osteoblasts during PTH-induced bone formation, we subjected mice with osteoblast-specific deficiency of mitochondrial long-chain β-oxidation as well as mice with adipocyte-specific deficiency for the PTH receptor or adipose triglyceride lipase to an anabolic treatment regimen. PTH increased the release of fatty acids from adipocytes and β-oxidation by osteoblasts, while the genetic mouse models were resistant to the hormone's anabolic effect. Collectively, these data suggest that PTH's anabolic actions require coordinated signaling between bone and adipose, wherein a lipolytic response liberates fatty acids that are oxidized by osteoblasts to fuel bone formation.
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Affiliation(s)
- Nathalie S. Alekos
- Department of Orthopaedics, University of Maryland School of Medicine, Baltimore, Maryland, USA
- Graduate Program in Cellular and Molecular Medicine, Johns Hopkins University School of Medicine, Baltimore, Maryland, USA
| | - Priyanka Kushwaha
- Division of Rheumatology, Inflammation, and Immunity, Department of Medicine, Brigham and Women’s Hospital, Boston, Massachusetts, USA
| | - Soohyun P. Kim
- Department of Pathology, Johns Hopkins University School of Medicine, Baltimore, Maryland, USA
| | - Zhu Li
- Department of Orthopaedics, University of Maryland School of Medicine, Baltimore, Maryland, USA
| | - Abdullah Abood
- Center for Public Health Genomics, School of Medicine, University of Virginia, Charlottesville, Virginia, USA
| | - Naomi Dirckx
- Department of Orthopaedics, University of Maryland School of Medicine, Baltimore, Maryland, USA
| | - Susan Aja
- Center for Metabolism and Obesity Research, Johns Hopkins University School of Medicine, Baltimore, Maryland, USA
| | - Joe Kodama
- Department of Orthopaedics, University of Maryland School of Medicine, Baltimore, Maryland, USA
| | - Jean G. Garcia-Diaz
- Department of Orthopaedics, University of Maryland School of Medicine, Baltimore, Maryland, USA
- Graduate Program in Cellular and Molecular Medicine, Johns Hopkins University School of Medicine, Baltimore, Maryland, USA
| | - Satoru Otsuru
- Department of Orthopaedics, University of Maryland School of Medicine, Baltimore, Maryland, USA
| | - Elizabeth Rendina-Ruedy
- Department of Medicine and Division of Clinical Pharmacology, Vanderbilt University Medical Center, Nashville, Tennessee, USA
| | - Michael J. Wolfgang
- Department of Biological Chemistry, Johns Hopkins University School of Medicine, Baltimore, Maryland, USA
| | - Ryan C. Riddle
- Department of Orthopaedics, University of Maryland School of Medicine, Baltimore, Maryland, USA
- Research & Development Service, Baltimore Veterans Administration Medical Center, Baltimore, Maryland, USA
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23
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Lungu O, Toscani D, Burroughs-Garcia J, Giuliani N. The Metabolic Features of Osteoblasts: Implications for Multiple Myeloma (MM) Bone Disease. Int J Mol Sci 2023; 24:ijms24054893. [PMID: 36902326 PMCID: PMC10003241 DOI: 10.3390/ijms24054893] [Citation(s) in RCA: 1] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/27/2023] [Revised: 02/27/2023] [Accepted: 03/01/2023] [Indexed: 03/06/2023] Open
Abstract
The study of osteoblast (OB) metabolism has recently received increased attention due to the considerable amount of energy used during the bone remodeling process. In addition to glucose, the main nutrient for the osteoblast lineages, recent data highlight the importance of amino acid and fatty acid metabolism in providing the fuel necessary for the proper functioning of OBs. Among the amino acids, it has been reported that OBs are largely dependent on glutamine (Gln) for their differentiation and activity. In this review, we describe the main metabolic pathways governing OBs' fate and functions, both in physiological and pathological malignant conditions. In particular, we focus on multiple myeloma (MM) bone disease, which is characterized by a severe imbalance in OB differentiation due to the presence of malignant plasma cells into the bone microenvironment. Here, we describe the most important metabolic alterations involved in the inhibition of OB formation and activity in MM patients.
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Affiliation(s)
- Oxana Lungu
- Department of Medicine and Surgery, University of Parma, 43126 Parma, Italy
| | - Denise Toscani
- Department of Medicine and Surgery, University of Parma, 43126 Parma, Italy
| | | | - Nicola Giuliani
- Department of Medicine and Surgery, University of Parma, 43126 Parma, Italy
- Hematology, Azienda Ospedaliero-Universitaria di Parma, 43126 Parma, Italy
- Correspondence:
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24
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Common Regulators of Lipid Metabolism and Bone Marrow Adiposity in Postmenopausal Women. Pharmaceuticals (Basel) 2023. [DOI: 10.3390/ph16020322] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/22/2023] Open
Abstract
A variety of metabolic disorders are associated with a decrease in estradiol (E2) during natural or surgical menopause. Postmenopausal women are prone to excessive fat accumulation in skeletal muscle and adipose tissue due to the loss of E2 via abnormalities in lipid metabolism and serum lipid levels. In skeletal muscle and adipose tissue, genes related to energy metabolism and fatty acid oxidation, such as those encoding peroxisome proliferator-activated receptor-γ coactivator 1α (PGC-1α) and estrogen-related receptor alpha (ERRα), are downregulated, leading to increased fat synthesis and lipid metabolite accumulation. The same genes regulate lipid metabolism abnormalities in the bone marrow. In this review, abnormalities in lipid metabolism caused by E2 deficiency were investigated, with a focus on genes able to simultaneously regulate not only skeletal muscle and adipose tissue but also bone metabolism (e.g., genes encoding PGC-1α and ERRα). In addition, the mechanisms through which mesenchymal stem cells lead to adipocyte differentiation in the bone marrow as well as metabolic processes related to bone marrow adiposity, bone loss, and osteoporosis were evaluated, focusing on the loss of E2 and lipid metabolic alterations. The work reviewed here suggests that genes underlying lipid metabolism and bone marrow adiposity are candidate therapeutic targets for bone loss and osteoporosis in postmenopausal women.
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25
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Bensreti H, Alhamad DW, Gonzalez AM, Pizarro-Mondesir M, Bollag WB, Isales CM, McGee-Lawrence ME. Update on the Role of Glucocorticoid Signaling in Osteoblasts and Bone Marrow Adipocytes During Aging. Curr Osteoporos Rep 2023; 21:32-44. [PMID: 36564571 PMCID: PMC9936962 DOI: 10.1007/s11914-022-00772-5] [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] [Accepted: 11/15/2022] [Indexed: 12/25/2022]
Abstract
PURPOSE OF REVIEW Bone marrow adipose tissue (BMAT) in the skeleton likely plays a variety of physiological and pathophysiological roles that are not yet fully understood. In elucidating the complex relationship between bone and BMAT, glucocorticoids (GCs) are positioned to play a key role, as they have been implicated in the differentiation of bone marrow mesenchymal stem cells (BMSCs) between osteogenic and adipogenic lineages. The purpose of this review is to illuminate aspects of both endogenous and exogenous GC signaling, including the influence of GC receptors, in mechanisms of bone aging including relationships to BMAT. RECENT FINDINGS Harmful effects of GCs on bone mass involve several cellular pathways and events that can include BMSC differentiation bias toward adipogenesis and the influence of mature BMAT on bone remodeling through crosstalk. Interestingly, BMAT involvement remains poorly explored in GC-induced osteoporosis and warrants further investigation. This review provides an update on the current understanding of the role of glucocorticoids in the biology of osteoblasts and bone marrow adipocytes (BMAds).
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Affiliation(s)
- Husam Bensreti
- Department of Cellular Biology and Anatomy, Medical College of Georgia, Augusta University, Augusta, GA, USA
| | - Dima W Alhamad
- Department of Cellular Biology and Anatomy, Medical College of Georgia, Augusta University, Augusta, GA, USA
| | - Alejandro Marrero Gonzalez
- Department of Cellular Biology and Anatomy, Medical College of Georgia, Augusta University, Augusta, GA, USA
| | - Manuel Pizarro-Mondesir
- Department of Cellular Biology and Anatomy, Medical College of Georgia, Augusta University, Augusta, GA, USA
| | - Wendy B Bollag
- Department of Physiology, Medical College of Georgia, Augusta University, Augusta, GA, USA
- Charlie Norwood VA Medical Center, Augusta, GA, USA
| | - Carlos M Isales
- Department of Neuroscience and Regenerative Medicine, Medical College of Georgia, Augusta University, Augusta, GA, USA
- Department of Orthopaedic Surgery, Medical College of Georgia, Augusta University, Augusta, GA, USA
- Department of Medicine, Medical College of Georgia, Augusta University, Augusta, GA, USA
| | - Meghan E McGee-Lawrence
- Department of Cellular Biology and Anatomy, Medical College of Georgia, Augusta University, Augusta, GA, USA.
- Department of Orthopaedic Surgery, Medical College of Georgia, Augusta University, Augusta, GA, USA.
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26
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Chougule A, Baroi S, Czernik PJ, Crowe E, Chang MR, Griffin PR, Lecka-Czernik B. Osteocytes contribute via nuclear receptor PPAR-alpha to maintenance of bone and systemic energy metabolism. Front Endocrinol (Lausanne) 2023; 14:1145467. [PMID: 37181042 PMCID: PMC10173151 DOI: 10.3389/fendo.2023.1145467] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Figures] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 01/16/2023] [Accepted: 03/20/2023] [Indexed: 05/16/2023] Open
Abstract
Introduction The view that bone and energy metabolism are integrated by common regulatory mechanisms is broadly accepted and supported by multiple strands of evidence. This includes the well-characterized role of the PPARγ nuclear receptor, which is a common denominator in energy metabolism and bone metabolism. Little is known, however, about the role of PPARα nuclear receptor, a major regulator of lipid metabolism in other organs, in bone. Methods A side-by-side comparative study of 5-15 mo old mice with global PPARα deficiency (αKO) and mice with osteocyte-specific PPARα deficiency (αOTKO) in order to parse out the various activities of PPARα in the skeleton that are of local and systemic significance. This study included transcriptome analysis of PPARα-deficient osteocytes, and analyses of bone mass and bone microarchitecture, systemic energy metabolism with indirect calorimetry, and differentiation potential of hematopoietic and mesenchymal bone cell progenitors. These analyses were paired with in vitro studies of either intact or silenced for PPARα MLO-A5 cells to determine PPARα role in osteocyte bioenergetics. Results In osteocytes, PPARα controls large number of transcripts coding for signaling and secreted proteins which may regulate bone microenvironment and peripheral fat metabolism. In addition, PPARα in osteocytes controls their bioenergetics and mitochondrial response to stress, which constitutes up to 40% of total PPARα contribution to the global energy metabolism. Similarly to αKO mice, the metabolic phenotype of αOTKO mice (both males and females) is age-dependent. In younger mice, osteocyte metabolism contributes positively to global energetics, however, with aging the high-energy phenotype reverts to a low-energy phenotype and obesity develops, suggesting a longitudinal negative effect of impaired lipid metabolism and mitochondrial dysfunction in osteocytes deficient in PPARα. However, bone phenotype was not affected in αOTKO mice except in the form of an increased volume of marrow adipose tissue in males. In contrast, global PPARα deficiency in αKO mice led to enlarged bone diameter with a proportional increase in number of trabeculae and enlarged marrow cavities; it also altered differentiation of hematopoietic and mesenchymal marrow cells toward osteoclast, osteoblast and adipocyte lineages, respectively. Discussion PPARα role in bone is multileveled and complex. In osteocytes, PPARα controls the bioenergetics of these cells, which significantly contributes to systemic energy metabolism and their endocrine/paracrine function in controlling marrow adiposity and peripheral fat metabolism.
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Affiliation(s)
- Amit Chougule
- Department of Orthopaedic Surgery, College of Medicine and Life Sciences, University of Toledo, Toledo, OH, United States
- Center for Diabetes and Endocrine Research, College of Medicine and Life Sciences, University of Toledo, Toledo, OH, United States
| | - Sudipta Baroi
- Department of Orthopaedic Surgery, College of Medicine and Life Sciences, University of Toledo, Toledo, OH, United States
- Center for Diabetes and Endocrine Research, College of Medicine and Life Sciences, University of Toledo, Toledo, OH, United States
| | - Piotr J. Czernik
- Department of Orthopaedic Surgery, College of Medicine and Life Sciences, University of Toledo, Toledo, OH, United States
- Center for Diabetes and Endocrine Research, College of Medicine and Life Sciences, University of Toledo, Toledo, OH, United States
| | - Emily Crowe
- Department of Orthopaedic Surgery, College of Medicine and Life Sciences, University of Toledo, Toledo, OH, United States
| | - Mi Ra Chang
- Department of Molecular Medicine, UF Scripps Biomedical Research, University of Florida, Jupiter, FL, United States
| | - Patrick R. Griffin
- Department of Molecular Medicine, UF Scripps Biomedical Research, University of Florida, Jupiter, FL, United States
| | - Beata Lecka-Czernik
- Department of Orthopaedic Surgery, College of Medicine and Life Sciences, University of Toledo, Toledo, OH, United States
- Center for Diabetes and Endocrine Research, College of Medicine and Life Sciences, University of Toledo, Toledo, OH, United States
- Department of Physiology and Pharmacology, College of Medicine and Life Sciences, University of Toledo, Toledo, OH, United States
- *Correspondence: Beata Lecka-Czernik,
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27
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Lv X, Gao F, Cao X. Skeletal interoception in bone homeostasis and pain. Cell Metab 2022; 34:1914-1931. [PMID: 36257317 PMCID: PMC9742337 DOI: 10.1016/j.cmet.2022.09.025] [Citation(s) in RCA: 24] [Impact Index Per Article: 12.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 06/09/2022] [Revised: 09/07/2022] [Accepted: 09/26/2022] [Indexed: 01/24/2023]
Abstract
Accumulating evidence indicates that interoception maintains proper physiological status and orchestrates metabolic homeostasis by regulating feeding behaviors, glucose balance, and lipid metabolism. Continuous skeletal remodeling consumes a tremendous amount of energy to provide skeletal scaffolding, support muscle movement, store vital minerals, and maintain a niche for hematopoiesis, which are processes that also contribute to overall metabolic balance. Although skeletal innervation has been described for centuries, recent work has shown that skeletal metabolism is tightly regulated by the nervous system and that skeletal interoception regulates bone homeostasis. Here, we provide a general discussion of interoception and its effects on the skeleton and whole-body metabolism. We also discuss skeletal interoception-mediated regulation in the context of pathological conditions and skeletal pain as well as future challenges to our understanding of these process and how they can be leveraged for more effective therapy.
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Affiliation(s)
- Xiao Lv
- Center for Musculoskeletal Research, Department of Orthopaedic Surgery and Department of Biomedical Engineering, The Johns Hopkins University, Baltimore, MD 21205, USA
| | - Feng Gao
- Center for Musculoskeletal Research, Department of Orthopaedic Surgery and Department of Biomedical Engineering, The Johns Hopkins University, Baltimore, MD 21205, USA
| | - Xu Cao
- Center for Musculoskeletal Research, Department of Orthopaedic Surgery and Department of Biomedical Engineering, The Johns Hopkins University, Baltimore, MD 21205, USA.
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28
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Osteometabolism: Metabolic Alterations in Bone Pathologies. Cells 2022; 11:cells11233943. [PMID: 36497201 PMCID: PMC9735555 DOI: 10.3390/cells11233943] [Citation(s) in RCA: 13] [Impact Index Per Article: 6.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/25/2022] [Revised: 11/20/2022] [Accepted: 11/24/2022] [Indexed: 12/12/2022] Open
Abstract
Renewing interest in the study of intermediate metabolism and cellular bioenergetics is brought on by the global increase in the prevalence of metabolic illnesses. Understanding of the mechanisms that integrate energy metabolism in the entire organism has significantly improved with the application of contemporary biochemical tools for quantifying the fuel substrate metabolism with cutting-edge mouse genetic procedures. Several unexpected findings in genetically altered mice have prompted research into the direction of intermediate metabolism of skeletal cells. These findings point to the possibility of novel endocrine connections through which bone cells can convey their energy status to other metabolic control centers. Understanding the expanded function of skeleton system has in turn inspired new lines of research aimed at characterizing the energy needs and bioenergetic characteristics of these bone cells. Bone-forming osteoblast and bone-resorbing osteoclast cells require a constant and large supply of energy substrates such as glucose, fatty acids, glutamine, etc., for their differentiation and functional activity. According to latest research, important developmental signaling pathways in bone cells are connected to bioenergetic programs, which may accommodate variations in energy requirements during their life cycle. The present review article provides a unique perspective of the past and present research in the metabolic characteristics of bone cells along with mechanisms governing energy substrate utilization and bioenergetics. In addition, we discussed the therapeutic inventions which are currently being utilized for the treatment and management of bone-related diseases such as osteoporosis, rheumatoid arthritis (RA), osteogenesis imperfecta (OIM), etc., by modulating the energetics of bone cells. We further emphasized on the role of GUT-associated metabolites (GAMs) such as short-chain fatty acids (SCFAs), medium-chain fatty acids (MCFAs), indole derivates, bile acids, etc., in regulating the energetics of bone cells and their plausible role in maintaining bone health. Emphasis is importantly placed on highlighting knowledge gaps in this novel field of skeletal biology, i.e., "Osteometabolism" (proposed by our group) that need to be further explored to characterize the physiological importance of skeletal cell bioenergetics in the context of human health and bone related metabolic diseases.
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29
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Weber DR, Long F, Zemel BS, Kindler JM. Glycemic Control and Bone in Diabetes. Curr Osteoporos Rep 2022; 20:379-388. [PMID: 36214991 PMCID: PMC9549036 DOI: 10.1007/s11914-022-00747-6] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Accepted: 08/30/2022] [Indexed: 01/30/2023]
Abstract
PURPOSE OF REVIEW This review summarizes recent developments on the effects of glycemic control and diabetes on bone health. We discuss the foundational cellular mechanisms through which diabetes and impaired glucose control impact bone biology, and how these processes contribute to bone fragility in diabetes. RECENT FINDINGS Glucose is important for osteoblast differentiation and energy consumption of mature osteoblasts. The role of insulin is less clear, but insulin receptor deletion in mouse osteoblasts reduces bone formation. Epidemiologically, type 1 (T1D) and type 2 diabetes (T2D) associate with increased fracture risk, which is greater among people with T1D. Accumulation of cortical bone micro-pores, micro-vascular complications, and AGEs likely contribute to diabetes-related bone fragility. The effects of youth-onset T2D on peak bone mass attainment and subsequent skeletal fragility are of particular concern. Further research is needed to understand the effects of hyperglycemia on skeletal health through the lifecycle, including the related factors of inflammation and microvascular damage.
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Affiliation(s)
- David R Weber
- Division of Endocrinology and Diabetes, Department of Pediatrics, The Children's Hospital of Philadelphia, University of Pennsylvania Perelman School of Medicine, Philadelphia,, PA, USA
| | - Fanxin Long
- Department of Orthopedic Surgery, The Children's Hospital of Philadelphia, University of Pennsylvania Perelman School of Medicine, Philadelphia, PA, USA
| | - Babette S Zemel
- Division of Gastroenterology, Hepatology and Nutrition, Department of Pediatrics, The Children's Hospital of Philadelphia, University of Pennsylvania Perelman School of Medicine, Philadelphia, PA, USA.
- Division of GI, Hepatology & Nutrition, Roberts Center for Pediatric Research, 2716 South Street, 14th Floor/Room 14471, Philadelphia, PA, 19146, USA.
| | - Joseph M Kindler
- Department of Nutritional Sciences, University of Georgia, Athens, GA, USA
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30
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Thapa S, Nandy A, Rendina-Ruedy E. Endocrinal metabolic regulation on the skeletal system in post-menopausal women. Front Physiol 2022; 13:1052429. [PMID: 36439254 PMCID: PMC9691779 DOI: 10.3389/fphys.2022.1052429] [Citation(s) in RCA: 6] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/23/2022] [Accepted: 10/27/2022] [Indexed: 08/13/2023] Open
Abstract
Osteoporosis is a common endocrinologic disorder characterized as a chronic bone loss condition. Sexual dimorphism is ubiquitous in the incidence of osteoporosis with post-menopausal women being acutely affected. Gonadal sex hormones including estrogen act as crucial regulators of bone mass; therefore, loss of such hormones leads to an imbalance in skeletal turnover leading to osteoporosis. Estrogen can influence both bone formation as well as resorption by reducing osteoblast activity and enhancing osteoclastogenesis. Additionally, estrogen is a potent regulator of systemic metabolism. Recent studies have provided clues that estrogenic effect on bone might also involve alterations in bone cell metabolism and bioenergetic potential. While direct effects of gonadal hormones ability to alter intracellular metabolism of bone cells has not been studied, there is precedence within the literature that this is occurring and contributing to post-menopausal bone loss. This review aims to serve as a perspective piece detailing the prospective role of gonadal hormones regulating bone cell metabolic potential.
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Affiliation(s)
- Santosh Thapa
- Department of Medicine, Division of Clinical Pharmacology, Vanderbilt University Medical Center, Nashville, TN, United States
| | - Ananya Nandy
- Department of Medicine, Division of Clinical Pharmacology, Vanderbilt University Medical Center, Nashville, TN, United States
| | - Elizabeth Rendina-Ruedy
- Department of Medicine, Division of Clinical Pharmacology, Vanderbilt University Medical Center, Nashville, TN, United States
- Molecular Physiology and Biophysics, Vanderbilt University, Nashville, TN, United States
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31
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Carvalho AL, Brooks DJ, Barlow D, Langlais AL, Morrill B, Houseknecht KL, Bouxsein ML, Lian JB, King T, Farina NH, Motyl KJ. Sustained Morphine Delivery Suppresses Bone Formation and Alters Metabolic and Circulating miRNA Profiles in Male C57BL/6J Mice. J Bone Miner Res 2022; 37:2226-2243. [PMID: 36054037 PMCID: PMC9712245 DOI: 10.1002/jbmr.4690] [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: 03/17/2022] [Revised: 07/30/2022] [Accepted: 08/24/2022] [Indexed: 11/05/2022]
Abstract
Opioid use is detrimental to bone health, causing both indirect and direct effects on bone turnover. Although the mechanisms of these effects are not entirely clear, recent studies have linked chronic opioid use to alterations in circulating miRNAs. Here, we developed a model of opioid-induced bone loss to understand bone turnover and identify candidate miRNA-mediated regulatory mechanisms. We evaluated the effects of sustained morphine treatment on male and female C57BL/6J mice by treating with vehicle (0.9% saline) or morphine (17 mg/kg) using subcutaneous osmotic minipumps for 25 days. Morphine-treated mice had higher energy expenditure and respiratory quotient, indicating a shift toward carbohydrate metabolism. Micro-computed tomography (μCT) analysis indicated a sex difference in the bone outcome, where male mice treated with morphine had reduced trabecular bone volume fraction (Tb.BV/TV) (15%) and trabecular bone mineral density (BMD) (14%) in the distal femur compared with vehicle. Conversely, bone microarchitecture was not changed in females after morphine treatment. Histomorphometric analysis demonstrated that in males, morphine reduced bone formation rate compared with vehicle, but osteoclast parameters were not different. Furthermore, morphine reduced bone formation marker gene expression in the tibia of males (Bglap and Dmp1). Circulating miRNA profile changes were evident in males, with 14 differentially expressed miRNAs associated with morphine treatment compared with two differentially expressed miRNAs in females. In males, target analysis indicated hypoxia-inducible factor (HIF) signaling pathway was targeted by miR-223-3p and fatty acid metabolism by miR-484, -223-3p, and -328-3p. Consequently, expression of miR-223-3p targets, including Igf1r and Stat3, was lower in morphine-treated bone. In summary, we have established a model where morphine leads to a lower trabecular bone formation in males and identified potential mediating miRNAs. Understanding the sex-specific mechanisms of bone loss from opioids will be important for improving management of the adverse effects of opioids on the skeleton. © 2022 American Society for Bone and Mineral Research (ASBMR).
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Affiliation(s)
- Adriana Lelis Carvalho
- Center for Molecular Medicine, MaineHealth Institute for Research, MaineHealth, Scarborough, ME, USA
| | - Daniel J Brooks
- Center for Advanced Orthopaedic Studies, Beth Israel Deaconess Medical Center, Boston, MA, USA
| | - Deborah Barlow
- Department of Pharmacology, University of New England, Biddeford, ME, USA
| | - Audrie L. Langlais
- Center for Molecular Medicine, MaineHealth Institute for Research, MaineHealth, Scarborough, ME, USA
- Graduate School of Biomedical Sciences and Engineering, University of Maine, Orono, ME, USA
| | - Breanna Morrill
- Center for Molecular Medicine, MaineHealth Institute for Research, MaineHealth, Scarborough, ME, USA
| | - Karen L. Houseknecht
- Graduate School of Biomedical Sciences and Engineering, University of Maine, Orono, ME, USA
- Department of Biomedical Sciences, College of Osteopathic Medicine, University of New England, Biddeford, ME, USA
| | - Mary L. Bouxsein
- Center for Advanced Orthopaedic Studies, Beth Israel Deaconess Medical Center, Boston, MA, USA
| | - Jane B Lian
- Department of Biochemistry and University of Vermont Cancer Center, University of Vermont, Burlington, VT, USA
- Larner College of Medicine, University of Vermont Cancer Center, Burlington, VT, USA
- Northern New England Clinical and Translational Research Network, MaineHealth, Portland, ME
| | - Tamara King
- Center for Excellence in the Neurosciences, University of New England, Biddeford, ME, USA
- Graduate School of Biomedical Sciences and Engineering, University of Maine, Orono, ME, USA
- Department of Biomedical Sciences, College of Osteopathic Medicine, University of New England, Biddeford, ME, USA
| | - Nicholas H Farina
- Department of Biochemistry and University of Vermont Cancer Center, University of Vermont, Burlington, VT, USA
- Larner College of Medicine, University of Vermont Cancer Center, Burlington, VT, USA
- Northern New England Clinical and Translational Research Network, MaineHealth, Portland, ME
| | - Katherine J Motyl
- Center for Molecular Medicine, MaineHealth Institute for Research, MaineHealth, Scarborough, ME, USA
- Northern New England Clinical and Translational Research Network, MaineHealth, Portland, ME
- Graduate School of Biomedical Sciences and Engineering, University of Maine, Orono, ME, USA
- Tufts University School of Medicine, Tufts University, Boston, MA, USA
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32
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Role of Essential Amino Acids in Age-Induced Bone Loss. Int J Mol Sci 2022; 23:ijms231911281. [PMID: 36232583 PMCID: PMC9569615 DOI: 10.3390/ijms231911281] [Citation(s) in RCA: 11] [Impact Index Per Article: 5.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/25/2022] [Revised: 09/16/2022] [Accepted: 09/20/2022] [Indexed: 11/16/2022] Open
Abstract
Age-induced osteoporosis is a global problem. Essential amino acids (EAAs) work as an energy source and a molecular pathway modulator in bone, but their functions have not been systematically reviewed in aging bone. This study aimed to discuss the contribution of EAAs on aging bone from in vitro, in vivo, and human investigations. In aged people with osteoporosis, serum EAAs were detected changing up and down, without a well-established conclusion. The supply of EAAs in aged people either rescued or did not affect bone mineral density (BMD) and bone volume. In most signaling studies, EAAs were proven to increase bone mass. Lysine, threonine, methionine, tryptophan, and isoleucine can increase osteoblast proliferation, activation, and differentiation, and decrease osteoclast activity. Oxidized L-tryptophan promotes bone marrow stem cells (BMSCs) differentiating into osteoblasts. However, the oxidation product of tryptophan called kynurenine increases osteoclast activity, and enhances the differentiation of adipocytes from BMSCs. Taken together, in terms of bone minerals and volume, more views consider EAAs to have a positive effect on aging bone, but the function of EAAs in bone metabolism has not been fully demonstrated and more studies are needed in this area in the future.
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33
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Kushwaha P, Alekos NS, Kim SP, Li Z, Wolfgang MJ, Riddle RC. Mitochondrial fatty acid β-oxidation is important for normal osteoclast formation in growing female mice. Front Physiol 2022; 13:997358. [PMID: 36187756 PMCID: PMC9515402 DOI: 10.3389/fphys.2022.997358] [Citation(s) in RCA: 11] [Impact Index Per Article: 5.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/18/2022] [Accepted: 08/22/2022] [Indexed: 12/03/2022] Open
Abstract
Skeletal remodeling is an energy demanding process that is linked to nutrient availability and the levels of metabolic hormones. While recent studies have examined the metabolic requirements of bone formation by osteoblasts, much less is known about the energetic requirements of bone resorption by osteoclasts. The abundance of mitochondria in mature osteoclasts suggests that the production of an acidified micro-environment conducive to the ionization of hydroxyapatite, secretion of matrix-degrading enzymes, and motility during resorption requires significant energetic capacity. To investigate the contribution of mitochondrial long chain fatty acid β-oxidation to osteoclast development, we disrupted the expression of carnitine palmitoyltransferase-2 (Cpt2) in myeloid-lineage cells. Fatty acid oxidation increases dramatically in bone marrow cultures stimulated with RANKL and M-CSF and microCT analysis revealed that the genetic inhibition of long chain fatty acid oxidation in osteoclasts significantly increases trabecular bone volume in female mice secondary to reduced osteoclast numbers. In line with these data, osteoclast precursors isolated from Cpt2 mutants exhibit reduced capacity to form large-multinucleated osteoclasts, which was not rescued by exogenous glucose or pyruvate, and signs of an energetic stress response. Together, our data demonstrate that mitochondrial long chain fatty acid oxidation by the osteoclast is required for normal bone resorption as its inhibition produces an intrinsic defect in osteoclast formation.
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Affiliation(s)
- Priyanka Kushwaha
- Department of Orthopaedic Surgery, Johns Hopkins University School of Medicine, Baltimore, MD, United States
| | - Nathalie S. Alekos
- Department of Orthopaedic Surgery, Johns Hopkins University School of Medicine, Baltimore, MD, United States
| | - Soohyun P. Kim
- Department of Orthopaedic Surgery, Johns Hopkins University School of Medicine, Baltimore, MD, United States
| | - Zhu Li
- Department of Orthopaedics, University of Maryland School of Medicine, Baltimore, MD, United States
| | - Michael J. Wolfgang
- Department of Biological Chemistry, Johns Hopkins University School of Medicine, Baltimore, MD, United States
| | - Ryan C. Riddle
- Department of Orthopaedic Surgery, Johns Hopkins University School of Medicine, Baltimore, MD, United States,Department of Orthopaedics, University of Maryland School of Medicine, Baltimore, MD, United States,Baltimore Veterans Administration Medical Center, Baltimore, MD, United States,*Correspondence: Ryan C. Riddle,
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34
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Peng H, Hu B, Xie LQ, Su T, Li CJ, Liu Y, Yang M, Xiao Y, Feng X, Zhou R, Guo Q, Zhou HY, Huang Y, Jiang TJ, Luo XH. A mechanosensitive lipolytic factor in the bone marrow promotes osteogenesis and lymphopoiesis. Cell Metab 2022; 34:1168-1182.e6. [PMID: 35705079 DOI: 10.1016/j.cmet.2022.05.009] [Citation(s) in RCA: 37] [Impact Index Per Article: 18.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 02/23/2022] [Revised: 04/29/2022] [Accepted: 05/20/2022] [Indexed: 12/19/2022]
Abstract
Exercise can prevent osteoporosis and improve immune function, but the mechanism remains unclear. Here, we show that exercise promotes reticulocalbin-2 secretion from the bone marrow macrophages to initiate bone marrow fat lipolysis. Given the crucial role of lipolysis in exercise-stimulated osteogenesis and lymphopoiesis, these findings suggest that reticulocalbin-2 is a pivotal regulator of a local adipose-osteogenic/immune axis. Mechanistically, reticulocalbin-2 binds to a functional receptor complex, which is composed of neuronilin-2 and integrin beta-1, to activate a cAMP-PKA signaling pathway that mobilizes bone marrow fat via lipolysis to fuel the differentiation and function of mesenchymal and hematopoietic stem cells. Notably, the administration of recombinant reticulocalbin-2 in tail-suspended and old mice remarkably decreases bone marrow fat accumulation and promotes osteogenesis and lymphopoiesis. These findings identify reticulocalbin-2 as a novel mechanosensitive lipolytic factor in maintaining energy homeostasis in bone resident cells, and it provides a promising target for skeletal and immune health.
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Affiliation(s)
- Hui Peng
- Department of Endocrinology, Endocrinology Research Center, Xiangya Hospital of Central South University, Changsha, Hunan 410008, China
| | - Biao Hu
- Department of Endocrinology, Endocrinology Research Center, Xiangya Hospital of Central South University, Changsha, Hunan 410008, China
| | - Ling-Qi Xie
- Department of Endocrinology, Endocrinology Research Center, Xiangya Hospital of Central South University, Changsha, Hunan 410008, China
| | - Tian Su
- Department of Endocrinology, Endocrinology Research Center, Xiangya Hospital of Central South University, Changsha, Hunan 410008, China
| | - Chang-Jun Li
- Department of Endocrinology, Endocrinology Research Center, Xiangya Hospital of Central South University, Changsha, Hunan 410008, China
| | - Ya Liu
- Department of Endocrinology, Endocrinology Research Center, Xiangya Hospital of Central South University, Changsha, Hunan 410008, China
| | - Mi Yang
- Department of Endocrinology, Endocrinology Research Center, Xiangya Hospital of Central South University, Changsha, Hunan 410008, China
| | - Ye Xiao
- Department of Endocrinology, Endocrinology Research Center, Xiangya Hospital of Central South University, Changsha, Hunan 410008, China
| | - Xu Feng
- Department of Endocrinology, Endocrinology Research Center, Xiangya Hospital of Central South University, Changsha, Hunan 410008, China
| | - Rui Zhou
- Department of Endocrinology, Endocrinology Research Center, Xiangya Hospital of Central South University, Changsha, Hunan 410008, China
| | - Qi Guo
- Department of Endocrinology, Endocrinology Research Center, Xiangya Hospital of Central South University, Changsha, Hunan 410008, China
| | - Hai-Yan Zhou
- Department of Endocrinology, Endocrinology Research Center, Xiangya Hospital of Central South University, Changsha, Hunan 410008, China
| | - Yan Huang
- Department of Endocrinology, Endocrinology Research Center, Xiangya Hospital of Central South University, Changsha, Hunan 410008, China
| | - Tie-Jian Jiang
- Department of Endocrinology, Endocrinology Research Center, Xiangya Hospital of Central South University, Changsha, Hunan 410008, China
| | - Xiang-Hang Luo
- Department of Endocrinology, Endocrinology Research Center, Xiangya Hospital of Central South University, Changsha, Hunan 410008, China; National Clinical Research Center for Geriatric Disorders, Xiangya Hospital, Changsha, Hunan 410008, China; Key Laboratory of Organ Injury, Aging and Regenerative Medicine of Hunan Province, Hunan 410008, China.
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35
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Vlashi R, Zhang X, Wu M, Chen G. Wnt signaling: essential roles in osteoblast differentiation, bone metabolism and therapeutic implications for bone and skeletal disorders. Genes Dis 2022. [DOI: 10.1016/j.gendis.2022.07.011] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/16/2022] Open
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36
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Su W, Liu G, Mohajer B, Wang J, Shen A, Zhang W, Liu B, Guermazi A, Gao P, Cao X, Demehri S, Wan M. Senescent preosteoclast secretome promotes metabolic syndrome associated osteoarthritis through cyclooxygenase 2. eLife 2022; 11:e79773. [PMID: 35881544 PMCID: PMC9365389 DOI: 10.7554/elife.79773] [Citation(s) in RCA: 18] [Impact Index Per Article: 9.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/27/2022] [Accepted: 05/06/2022] [Indexed: 01/10/2023] Open
Abstract
Background Metabolic syndrome-associated osteoarthritis (MetS-OA) is a distinct osteoarthritis phenotype defined by the coexistence of MetS or its individual components. Despite the high prevalence of MetS-OA, its pathogenic mechanisms are unclear. The aim of this study was to determine the role of cellular senescence in the development of MetS-OA. Methods Analysis of the human osteoarthritis initiative (OAI) dataset was conducted to investigate the MRI subchondral bone features of MetS-human OA participants. Joint phenotype and senescent cells were evaluated in two MetS-OA mouse models: high-fat diet (HFD)-challenged mice and STR/Ort mice. In addition, the molecular mechanisms by which preosteoclasts become senescent as well as how the senescent preosteoclasts impair subchondral bone microenvironment were characterized using in vitro preosteoclast culture system. Results Humans and mice with MetS are more likely to develop osteoarthritis-related subchondral bone alterations than those without MetS. MetS-OA mice exhibited a rapid increase in joint subchondral bone plate and trabecular thickness before articular cartilage degeneration. Subchondral preosteoclasts undergo senescence at the pre- or early-osteoarthritis stage and acquire a unique secretome to stimulate osteoblast differentiation and inhibit osteoclast differentiation. Antagonizing preosteoclast senescence markedly mitigates pathological subchondral alterations and osteoarthritis progression in MetS-OA mice. At the molecular level, preosteoclast secretome activates COX2-PGE2, resulting in stimulated differentiation of osteoblast progenitors for subchondral bone formation. Administration of a selective COX2 inhibitor attenuated subchondral bone alteration and osteoarthritis progression in MetS-OA mice. Longitudinal analyses of the human Osteoarthritis Initiative (OAI) cohort dataset also revealed that COX2 inhibitor use, relative to non-selective nonsteroidal antiinflammatory drug use, is associated with less progression of osteoarthritis and subchondral bone marrow lesion worsening in participants with MetS-OA. Conclusions Our findings suggest a central role of a senescent preosteoclast secretome-COX2/PGE2 axis in the pathogenesis of MetS-OA, in which selective COX2 inhibitors may have disease-modifying potential. Funding This work was supported by the National Institutes of Health grant R01AG068226 and R01AG072090 to MW, R01AR079620 to SD, and P01AG066603 to XC.
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Affiliation(s)
- Weiping Su
- Department of Orthopaedic Surgery, Russell H. Morgan Department of Radiology and Radiological Science, The Johns Hopkins University School of MedicineBaltimoreUnited States
- Department of Orthopaedic Surgery, The Third Xiangya Hospital of Central South UniversityChangshaChina
| | - Guanqiao Liu
- Department of Orthopaedic Surgery, Russell H. Morgan Department of Radiology and Radiological Science, The Johns Hopkins University School of MedicineBaltimoreUnited States
- Division of Orthopaedics & Traumatology, Department of Orthopaedics, Southern Medical University Nanfang HospitalGuangzhouChina
| | - Bahram Mohajer
- Musculoskeletal Radiology, Russell H. Morgan Department of Radiology and Radiological Science, The Johns Hopkins University School of MedicineBaltimoreUnited States
| | - Jiekang Wang
- Department of Orthopaedic Surgery, Russell H. Morgan Department of Radiology and Radiological Science, The Johns Hopkins University School of MedicineBaltimoreUnited States
| | - Alena Shen
- University of Southern California, Dornsife College of Letters, Arts and SciencesLos AngelesUnited States
| | - Weixin Zhang
- Department of Orthopaedic Surgery, Russell H. Morgan Department of Radiology and Radiological Science, The Johns Hopkins University School of MedicineBaltimoreUnited States
| | - Bin Liu
- Department of Orthopaedic Surgery, Russell H. Morgan Department of Radiology and Radiological Science, The Johns Hopkins University School of MedicineBaltimoreUnited States
| | - Ali Guermazi
- Department of Radiology, Boston University School of MedicineBostonUnited States
| | - Peisong Gao
- Johns Hopkins Asthma & Allergy Center, Johns Hopkins University School of MedicineBaltimoreUnited States
| | - Xu Cao
- Department of Orthopaedic Surgery, Russell H. Morgan Department of Radiology and Radiological Science, The Johns Hopkins University School of MedicineBaltimoreUnited States
| | - Shadpour Demehri
- Musculoskeletal Radiology, Russell H. Morgan Department of Radiology and Radiological Science, The Johns Hopkins University School of MedicineBaltimoreUnited States
| | - Mei Wan
- Department of Orthopaedic Surgery, Russell H. Morgan Department of Radiology and Radiological Science, The Johns Hopkins University School of MedicineBaltimoreUnited States
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37
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Zhu M, Fan Z. The role of the Wnt signalling pathway in the energy metabolism of bone remodelling. Cell Prolif 2022; 55:e13309. [PMID: 35811348 DOI: 10.1111/cpr.13309] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/12/2022] [Revised: 06/07/2022] [Accepted: 06/24/2022] [Indexed: 11/28/2022] Open
Abstract
OBJECTIVES Bone remodelling is necessary to repair old and impaired bone caused by aging and its effects. Injury in the process of bone remodelling generally leads to the development of various bone diseases. Energy metabolism plays crucial roles in bone cell formation and function, the disorder of which will disrupt the balance between bone formation and bone resorption. MATERIALS AND METHODS Here, we review the intrinsic interactions between bone remodelling and energy metabolism and the role of the Wnt signalling pathway. RESULTS We found a close interplay between metabolic pathways and bone homeostasis, demonstrating that bone plays an important role in the regulation of energy balance. We also discovered that Wnt signalling is associated with multiple biological processes regulating energy metabolism in bone cells. CONCLUSIONS Thus, targeted regulation of Wnt signalling and the recovery of the energy metabolism function of bone cells are key means for the treatment of metabolic bone diseases.
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Affiliation(s)
- Mengyuan Zhu
- Laboratory of Molecular Signaling and Stem Cells Therapy, Beijing Key Laboratory of Tooth Regeneration and Function Reconstruction, Capital Medical University School of Stomatology, Beijing, China.,Research Unit of Tooth Development and Regeneration, Chinese Academy of Medical Sciences, Beijing, China
| | - Zhipeng Fan
- Laboratory of Molecular Signaling and Stem Cells Therapy, Beijing Key Laboratory of Tooth Regeneration and Function Reconstruction, Capital Medical University School of Stomatology, Beijing, China.,Research Unit of Tooth Development and Regeneration, Chinese Academy of Medical Sciences, Beijing, China
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38
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Li Z, Bowers E, Zhu J, Yu H, Hardij J, Bagchi DP, Mori H, Lewis KT, Granger K, Schill RL, Romanelli SM, Abrishami S, Hankenson KD, Singer K, Rosen CJ, MacDougald OA. Lipolysis of bone marrow adipocytes is required to fuel bone and the marrow niche during energy deficits. eLife 2022; 11:e78496. [PMID: 35731039 PMCID: PMC9273217 DOI: 10.7554/elife.78496] [Citation(s) in RCA: 33] [Impact Index Per Article: 16.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/09/2022] [Accepted: 06/21/2022] [Indexed: 11/13/2022] Open
Abstract
To investigate roles for bone marrow adipocyte (BMAd) lipolysis in bone homeostasis, we created a BMAd-specific Cre mouse model in which we knocked out adipose triglyceride lipase (ATGL, Pnpla2 gene). BMAd-Pnpla2-/- mice have impaired BMAd lipolysis, and increased size and number of BMAds at baseline. Although energy from BMAd lipid stores is largely dispensable when mice are fed ad libitum, BMAd lipolysis is necessary to maintain myelopoiesis and bone mass under caloric restriction. BMAd-specific Pnpla2 deficiency compounds the effects of caloric restriction on loss of trabecular bone in male mice, likely due to impaired osteoblast expression of collagen genes and reduced osteoid synthesis. RNA sequencing analysis of bone marrow adipose tissue reveals that caloric restriction induces dramatic elevations in extracellular matrix organization and skeletal development genes, and energy from BMAd is required for these adaptations. BMAd-derived energy supply is also required for bone regeneration upon injury, and maintenance of bone mass with cold exposure.
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Affiliation(s)
- Ziru Li
- University of Michigan Medical School, Department of Molecular & Integrative PhysiologyAnn ArborUnited States
| | - Emily Bowers
- University of Michigan Medical School, Department of PediatricsAnn ArborUnited States
| | - Junxiong Zhu
- Department of Orthopedic Surgery, University of Michigan Medical SchoolAnn ArborUnited States
- Department of Orthopedic Surgery, The Second Affiliated Hospital, Zhejiang University School of MedicineHangzhouChina
| | - Hui Yu
- University of Michigan Medical School, Department of Molecular & Integrative PhysiologyAnn ArborUnited States
| | - Julie Hardij
- University of Michigan Medical School, Department of Molecular & Integrative PhysiologyAnn ArborUnited States
| | - Devika P Bagchi
- University of Michigan Medical School, Department of Molecular & Integrative PhysiologyAnn ArborUnited States
| | - Hiroyuki Mori
- University of Michigan Medical School, Department of Molecular & Integrative PhysiologyAnn ArborUnited States
| | - Kenneth T Lewis
- University of Michigan Medical School, Department of Molecular & Integrative PhysiologyAnn ArborUnited States
| | - Katrina Granger
- University of Michigan Medical School, Department of Molecular & Integrative PhysiologyAnn ArborUnited States
| | - Rebecca L Schill
- University of Michigan Medical School, Department of Molecular & Integrative PhysiologyAnn ArborUnited States
| | - Steven M Romanelli
- University of Michigan Medical School, Department of Molecular & Integrative PhysiologyAnn ArborUnited States
| | - Simin Abrishami
- University of Michigan Medical School, Department of PediatricsAnn ArborUnited States
| | - Kurt D Hankenson
- Department of Orthopedic Surgery, University of Michigan Medical SchoolAnn ArborUnited States
| | - Kanakadurga Singer
- University of Michigan Medical School, Department of Molecular & Integrative PhysiologyAnn ArborUnited States
- University of Michigan Medical School, Department of PediatricsAnn ArborUnited States
| | | | - Ormond A MacDougald
- University of Michigan Medical School, Department of Molecular & Integrative PhysiologyAnn ArborUnited States
- University of Michigan Medical School, Department of Internal MedicineAnn ArborUnited States
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39
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Karsenty G, Khosla S. The crosstalk between bone remodeling and energy metabolism: A translational perspective. Cell Metab 2022; 34:805-817. [PMID: 35545088 PMCID: PMC9535690 DOI: 10.1016/j.cmet.2022.04.010] [Citation(s) in RCA: 38] [Impact Index Per Article: 19.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 02/09/2022] [Revised: 03/30/2022] [Accepted: 04/20/2022] [Indexed: 12/15/2022]
Abstract
Genetics in model organisms has progressively broken down walls that previously separated different disciplines of biology. One example of this holistic evolution is the recognition of the complex relationship that exists between the control of bone mass (bone remodeling) and energy metabolism in mammals. Numerous hormones orchestrate this crosstalk. In particular, the study of the leptin-mediated regulation of bone mass has not only revealed the existence of a central control of bone mass but has also led to the realization that sympathetic innervation is a major regulator of bone remodeling. This happened at a time when the use of drugs aiming at treating osteoporosis, the most frequent bone disease, has dwindled. This review will highlight the main aspects of the leptin-mediated regulation of bone mass and how this led to the realization that β-blockers, which block the effects of the sympathetic nervous system, may be a viable option to prevent osteoporosis.
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Affiliation(s)
- Gerard Karsenty
- Department of Genetics and Development, Vagelos College of Physicians and Surgeons, Columbia University, New York, NY, USA.
| | - Sundeep Khosla
- Kogod Center of Aging and Division of Endocrinology and Metabolism, Mayo Clinic College of Medicine and Science, Rochester, MN, USA.
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40
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Welhaven HD, Vahidi G, Walk ST, Bothner B, Martin SA, Heveran CM, June RK. The cortical bone metabolome of
C57BL
/
6J
mice is sexually dimorphic. JBMR Plus 2022; 6:e10654. [PMID: 35866150 PMCID: PMC9289981 DOI: 10.1002/jbm4.10654] [Citation(s) in RCA: 6] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 03/11/2022] [Revised: 05/05/2022] [Accepted: 05/23/2022] [Indexed: 11/13/2022] Open
Abstract
Cortical bone quality, which is sexually dimorphic, depends on bone turnover and therefore on the activities of remodeling bone cells. However, sex differences in cortical bone metabolism are not yet defined. Adding to the uncertainty about cortical bone metabolism, the metabolomes of whole bone, isolated cortical bone without marrow, and bone marrow have not been compared. We hypothesized that the metabolome of isolated cortical bone would be distinct from that of bone marrow and would reveal sex differences. Metabolite profiles from liquid chromatography–mass spectrometry (LC‐MS) of whole bone, isolated cortical bone, and bone marrow were generated from humeri from 20‐week‐old female C57Bl/6J mice. The cortical bone metabolomes were then compared for 20‐week‐old female and male C57Bl/6J mice. Femurs from male and female mice were evaluated for flexural material properties and were then categorized into bone strength groups. The metabolome of isolated cortical bone was distinct from both whole bone and bone marrow. We also found sex differences in the isolated cortical bone metabolome. Based on metabolite pathway analysis, females had higher lipid metabolism, and males had higher amino acid metabolism. High‐strength bones, regardless of sex, had greater tryptophan and purine metabolism. For males, high‐strength bones had upregulated nucleotide metabolism, whereas lower‐strength bones had greater pentose phosphate pathway metabolism. Because the higher‐strength groups (females compared with males, high‐strength males compared with lower‐strength males) had higher serum type I collagen cross‐linked C‐telopeptide (CTX1)/procollagen type 1 N propeptide (P1NP), we estimate that the metabolomic signature of bone strength in our study at least partially reflects differences in bone turnover. These data provide novel insight into bone bioenergetics and the sexual dimorphic nature of bone material properties in C57Bl/6 mice. © 2022 The Authors. JBMR Plus published by Wiley Periodicals LLC on behalf of American Society for Bone and Mineral Research.
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Affiliation(s)
- Hope D. Welhaven
- Department of Chemistry & Biochemistry Montana State University Bozeman MT
- Molecular Biosciences Program Montana State University Bozeman MT
| | - Ghazal Vahidi
- Department of Mechanical & Industrial Engineering Montana State University Bozeman MT
| | - Seth T. Walk
- Department of Microbiology and Cell Biology Montana State University Bozeman MT
| | - Brian Bothner
- Department of Chemistry & Biochemistry Montana State University Bozeman MT
| | - Stephen A. Martin
- Translational Biomarkers Core Laboratory Montana State University Bozeman MT
| | - Chelsea M. Heveran
- Department of Mechanical & Industrial Engineering Montana State University Bozeman MT
| | - Ronald K. June
- Department of Mechanical & Industrial Engineering Montana State University Bozeman MT
- Department of Microbiology and Cell Biology Montana State University Bozeman MT
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41
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Balakrishnan R, Thurmond DC. Mechanisms by Which Skeletal Muscle Myokines Ameliorate Insulin Resistance. Int J Mol Sci 2022; 23:4636. [PMID: 35563026 PMCID: PMC9102915 DOI: 10.3390/ijms23094636] [Citation(s) in RCA: 29] [Impact Index Per Article: 14.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/28/2022] [Revised: 04/17/2022] [Accepted: 04/18/2022] [Indexed: 12/17/2022] Open
Abstract
The skeletal muscle is the largest organ in the body and secretes circulating factors, including myokines, which are involved in various cellular signaling processes. Skeletal muscle is vital for metabolism and physiology and plays a crucial role in insulin-mediated glucose disposal. Myokines have autocrine, paracrine, and endocrine functions, serving as critical regulators of myogenic differentiation, fiber-type switching, and maintaining muscle mass. Myokines have profound effects on energy metabolism and inflammation, contributing to the pathophysiology of type 2 diabetes (T2D) and other metabolic diseases. Myokines have been shown to increase insulin sensitivity, thereby improving glucose disposal and regulating glucose and lipid metabolism. Many myokines have now been identified, and research on myokine signaling mechanisms and functions is rapidly emerging. This review summarizes the current state of the field regarding the role of myokines in tissue cross-talk, including their molecular mechanisms, and their potential as therapeutic targets for T2D.
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Affiliation(s)
| | - Debbie C. Thurmond
- Department of Molecular and Cellular Endocrinology, Arthur Riggs Diabetes and Metabolism Research Institute, City of Hope Beckman Research Institute, 1500 E. Duarte Road, Duarte, CA 91010, USA;
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42
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Endo- and Exometabolome Crosstalk in Mesenchymal Stem Cells Undergoing Osteogenic Differentiation. Cells 2022; 11:cells11081257. [PMID: 35455937 PMCID: PMC9024772 DOI: 10.3390/cells11081257] [Citation(s) in RCA: 5] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/03/2022] [Revised: 04/03/2022] [Accepted: 04/05/2022] [Indexed: 02/04/2023] Open
Abstract
This paper describes, for the first time to our knowledge, a lipidome and exometabolome characterization of osteogenic differentiation for human adipose tissue stem cells (hAMSCs) using nuclear magnetic resonance (NMR) spectroscopy. The holistic nature of NMR enabled the time-course evolution of cholesterol, mono- and polyunsaturated fatty acids (including ω-6 and ω-3 fatty acids), several phospholipids (phosphatidylcholine, phosphatidylethanolamine, sphingomyelins, and plasmalogens), and mono- and triglycerides to be followed. Lipid changes occurred almost exclusively between days 1 and 7, followed by a tendency for lipidome stabilization after day 7. On average, phospholipids and longer and more unsaturated fatty acids increased up to day 7, probably related to plasma membrane fluidity. Articulation of lipidome changes with previously reported polar endometabolome profiling and with exometabolome changes reported here in the same cells, enabled important correlations to be established during hAMSC osteogenic differentiation. Our results supported hypotheses related to the dynamics of membrane remodelling, anti-oxidative mechanisms, protein synthesis, and energy metabolism. Importantly, the observation of specific up-taken or excreted metabolites paves the way for the identification of potential osteoinductive metabolites useful for optimized osteogenic protocols.
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43
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Parathyroid hormone (PTH) regulation of metabolic homeostasis: An old dog teaches us new tricks. Mol Metab 2022; 60:101480. [PMID: 35338013 PMCID: PMC8980887 DOI: 10.1016/j.molmet.2022.101480] [Citation(s) in RCA: 24] [Impact Index Per Article: 12.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 11/29/2021] [Revised: 02/11/2022] [Accepted: 03/16/2022] [Indexed: 12/30/2022] Open
Abstract
BACKGROUND Late in the nineteenth century, it was theorized that a circulating product produced by the parathyroid glands could negatively impact skeletal homeostasis. A century later, intermittent administration of that protein, namely parathyroid hormone (PTH), was approved by the FDA and EMA as the first anabolic agent to treat osteoporosis. Yet, several unanswered but important questions remain about the skeletal actions of PTH. SCOPE OF REVIEW Current research efforts have focused on improving the efficacy of PTH treatment by designing structural analogs and identifying other targets (e.g., the PTH or the calcium sensing receptor). A unique but only recently described aspect of PTH action is its regulation of cellular bioenergetics and metabolism, namely in bone and adipose tissue but also in other tissues. The current review aims to provide a brief background on PTH's previously described actions on bone and highlights how PTH regulates osteoblast bioenergetics, contributing to greater bone formation. It will also shed light on how PTH could alter metabolic homeostasis through its actions in other cells and tissues, thereby impacting the skeleton in a cell non-autonomous manner. MAJOR CONCLUSIONS PTH administration enhances bone formation by targeting the osteoblast through transcriptional changes in several pathways; the most prominent is via adenyl cyclase and PKA. PTH and its related protein, PTHrP, also induce glycolysis and fatty acid oxidation in bone cells and drive lipolysis and thermogenic programming in adipocytes; the latter may indirectly but positively influence skeletal metabolism. While much work remains, alterations in cellular metabolism may also provide a novel mechanism related to PTH's temporal actions. Thus, the bioenergetic impact of PTH can be considered another of the myriad anabolic effects of PTH on the skeleton. Just as importantly from a translational perspective, the non-skeletal metabolic effects may lead to a better understanding of whole-body homeostasis along with new and improved therapies to treat musculoskeletal conditions.
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Little-Letsinger SE, Rubin J, Diekman B, Rubin CT, McGrath C, Pagnotti GM, Klett EL, Styner M. Exercise to Mend Aged-tissue Crosstalk in Bone Targeting Osteoporosis & Osteoarthritis. Semin Cell Dev Biol 2022; 123:22-35. [PMID: 34489173 PMCID: PMC8840966 DOI: 10.1016/j.semcdb.2021.08.011] [Citation(s) in RCA: 15] [Impact Index Per Article: 7.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/10/2021] [Revised: 08/16/2021] [Accepted: 08/19/2021] [Indexed: 12/16/2022]
Abstract
Aging induces alterations in bone structure and strength through a multitude of processes, exacerbating common aging- related diseases like osteoporosis and osteoarthritis. Cellular hallmarks of aging are examined, as related to bone and the marrow microenvironment, and ways in which these might contribute to a variety of age-related perturbations in osteoblasts, osteocytes, marrow adipocytes, chondrocytes, osteoclasts, and their respective progenitors. Cellular senescence, stem cell exhaustion, mitochondrial dysfunction, epigenetic and intracellular communication changes are central pathways and recognized as associated and potentially causal in aging. We focus on these in musculoskeletal system and highlight knowledge gaps in the literature regarding cellular and tissue crosstalk in bone, cartilage, and the bone marrow niche. While senolytics have been utilized to target aging pathways, here we propose non-pharmacologic, exercise-based interventions as prospective "senolytics" against aging effects on the skeleton. Increased bone mass and delayed onset or progression of osteoporosis and osteoarthritis are some of the recognized benefits of regular exercise across the lifespan. Further investigation is needed to delineate how cellular indicators of aging manifest in bone and the marrow niche and how altered cellular and tissue crosstalk impact disease progression, as well as consideration of exercise as a therapeutic modality, as a means to enhance discovery of bone-targeted therapies.
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Affiliation(s)
- SE Little-Letsinger
- Department of Medicine, Division of Endocrinology & Metabolism, University of North Carolina at Chapel Hill
| | - J Rubin
- Department of Medicine, Division of Endocrinology & Metabolism, University of North Carolina at Chapel Hill,North Carolina Diabetes Research Center (NCDRC), University of North Carolina at Chapel Hill,Department of Medicine, Thurston Arthritis Research Center (TARC), University of North Carolina at Chapel Hill
| | - B Diekman
- Department of Medicine, Thurston Arthritis Research Center (TARC), University of North Carolina at Chapel Hill,Joint Departments of Biomedical Engineering NC State & University of North Carolina at Chapel Hill
| | - CT Rubin
- Department of Biomedical Engineering, State University of New York at Stony Brook
| | - C McGrath
- Department of Medicine, Division of Endocrinology & Metabolism, University of North Carolina at Chapel Hill
| | - GM Pagnotti
- Dept of Endocrine, Neoplasia, and Hormonal Disorders, University Texas MD Anderson Cancer Center, Houston
| | - EL Klett
- Department of Medicine, Division of Endocrinology & Metabolism, University of North Carolina at Chapel Hill,Department of Nutrition, School of Public Health, University of North Carolina at Chapel Hill
| | - M Styner
- Department of Medicine, Division of Endocrinology & Metabolism, University of North Carolina at Chapel Hill,North Carolina Diabetes Research Center (NCDRC), University of North Carolina at Chapel Hill,Department of Medicine, Thurston Arthritis Research Center (TARC), University of North Carolina at Chapel Hill
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Abstract
PURPOSE OF REVIEW Osteoblasts are responsible for bone matrix production during bone development and homeostasis. Much is known about the transcriptional regulation and signaling pathways governing osteoblast differentiation. However, less is known about how osteoblasts obtain or utilize nutrients to fulfill the energetic demands associated with osteoblast differentiation and bone matrix synthesis. The goal of this review is to highlight and discuss what is known about the role and regulation of bioenergetic metabolism in osteoblasts with a focus on more recent studies. RECENT FINDINGS Bioenergetic metabolism has emerged as an important regulatory node in osteoblasts. Recent studies have begun to identify the major nutrients and bioenergetic pathways favored by osteoblasts as well as their regulation during differentiation. Here, we highlight how osteoblasts obtain and metabolize glucose, amino acids, and fatty acids to provide energy and other metabolic intermediates. In addition, we highlight the signals that regulate nutrient uptake and metabolism and focus on how energetic metabolism promotes osteoblast differentiation. Bioenergetic metabolism provides energy and other metabolites that are critical for osteoblast differentiation and activity. This knowledge contributes to a more comprehensive understanding of osteoblast biology and may inform novel strategies to modulate osteoblast differentiation and bone anabolism in patients with bone disorders.
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Affiliation(s)
- Leyao Shen
- Department of Internal Medicine, University of Texas Southwestern Medical Center, Dallas, TX, USA
| | - Guoli Hu
- Department of Internal Medicine, University of Texas Southwestern Medical Center, Dallas, TX, USA
| | - Courtney M Karner
- Department of Internal Medicine, University of Texas Southwestern Medical Center, Dallas, TX, USA.
- Charles and Jane Pak Center for Mineral Metabolism and Clinical Research, University of Texas Southwestern Medical Center, Dallas, TX, 75390, USA.
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Ye J, Xiao J, Wang J, Ma Y, Zhang Y, Zhang Q, Zhang Z, Yin H. The Interaction Between Intracellular Energy Metabolism and Signaling Pathways During Osteogenesis. Front Mol Biosci 2022; 8:807487. [PMID: 35155568 PMCID: PMC8832142 DOI: 10.3389/fmolb.2021.807487] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/02/2021] [Accepted: 12/20/2021] [Indexed: 11/28/2022] Open
Abstract
Osteoblasts primarily mediate bone formation, maintain bone structure, and regulate bone mineralization, which plays an important role in bone remodeling. In the past decades, the roles of cytokines, signaling proteins, and transcription factors in osteoblasts have been widely studied. However, whether the energy metabolism of cells can be regulated by these factors to affect the differentiation and functioning of osteoblasts has not been explored in depth. In addition, the signaling and energy metabolism pathways are not independent but closely connected. Although energy metabolism is mediated by signaling pathways, some intermediates of energy metabolism can participate in protein post-translational modification. The content of intermediates, such as acetyl coenzyme A (acetyl CoA) and uridine diphosphate N-acetylglucosamine (UDP-N-acetylglucosamine), determines the degree of acetylation and glycosylation in terms of the availability of energy-producing substrates. The utilization of intracellular metabolic resources and cell survival, proliferation, and differentiation are all related to the integration of metabolic and signaling pathways. In this paper, the interaction between the energy metabolism pathway and osteogenic signaling pathway in osteoblasts and bone marrow mesenchymal stem cells (BMSCs) will be discussed.
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Affiliation(s)
- Jiapeng Ye
- Wuxi TCM Hospital Affiliated to Nanjing University of Chinese Medicine, Nanjing University of Traditional Chinese Medicine, Nanjing, China
| | - Jirimutu Xiao
- Mongolian Medicine College, Inner Mongolia Medical University, Hohhot, China
| | - Jianwei Wang
- Department of Orthopedics and Traumatology, Wuxi TCM Hospital Affiliated to Nanjing University of Chinese Medicine, Wuxi, China
- *Correspondence: Jianwei Wang, ; Heng Yin,
| | - Yong Ma
- Wuxi TCM Hospital Affiliated to Nanjing University of Chinese Medicine, Nanjing University of Traditional Chinese Medicine, Nanjing, China
| | - Yafeng Zhang
- Department of Orthopedics and Traumatology, Wuxi TCM Hospital Affiliated to Nanjing University of Chinese Medicine, Wuxi, China
| | - Qiang Zhang
- Wuxi TCM Hospital Affiliated to Nanjing University of Chinese Medicine, Nanjing University of Traditional Chinese Medicine, Nanjing, China
| | - Zongrui Zhang
- Wuxi TCM Hospital Affiliated to Nanjing University of Chinese Medicine, Nanjing University of Traditional Chinese Medicine, Nanjing, China
| | - Heng Yin
- Department of Orthopedics and Traumatology, Wuxi TCM Hospital Affiliated to Nanjing University of Chinese Medicine, Wuxi, China
- *Correspondence: Jianwei Wang, ; Heng Yin,
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Naik AA, Sivaramakrishnan V. Systems analysis of steroid induced osteonecrosis shows role for heme and vitamin D in pathogenesis. GENE REPORTS 2021. [DOI: 10.1016/j.genrep.2021.101383] [Citation(s) in RCA: 3] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/12/2022]
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Cooper ID, Brookler KH, Crofts CAP. Rethinking Fragility Fractures in Type 2 Diabetes: The Link between Hyperinsulinaemia and Osteofragilitas. Biomedicines 2021; 9:1165. [PMID: 34572351 PMCID: PMC8472634 DOI: 10.3390/biomedicines9091165] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/22/2021] [Revised: 08/27/2021] [Accepted: 09/02/2021] [Indexed: 02/06/2023] Open
Abstract
Patients with type 2 diabetes mellitus (T2DM) and/or cardiovascular disease (CVD), conditions of hyperinsulinaemia, have lower levels of osteocalcin and bone remodelling, and increased rates of fragility fractures. Unlike osteoporosis with lower bone mineral density (BMD), T2DM bone fragility "hyperinsulinaemia-osteofragilitas" phenotype presents with normal to increased BMD. Hyperinsulinaemia and insulin resistance positively associate with increased BMD and fragility fractures. Hyperinsulinaemia enforces glucose fuelling, which decreases NAD+-dependent antioxidant activity. This increases reactive oxygen species and mitochondrial fission, and decreases oxidative phosphorylation high-energy production capacity, required for osteoblasto/cytogenesis. Osteocytes directly mineralise and resorb bone, and inhibit mineralisation of their lacunocanalicular space via pyrophosphate. Hyperinsulinaemia decreases vitamin D availability via adipocyte sequestration, reducing dendrite connectivity, and compromising osteocyte viability. Decreased bone remodelling and micropetrosis ensues. Trapped/entombed magnesium within micropetrosis fossilisation spaces propagates magnesium deficiency (MgD), potentiating hyperinsulinaemia and decreases vitamin D transport. Vitamin D deficiency reduces osteocalcin synthesis and favours osteocyte apoptosis. Carbohydrate restriction/fasting/ketosis increases beta-oxidation, ketolysis, NAD+-dependent antioxidant activity, osteocyte viability and osteocalcin, and decreases excess insulin exposure. Osteocalcin is required for hydroxyapatite alignment, conferring bone structural integrity, decreasing fracture risk and improving metabolic/endocrine homeodynamics. Patients presenting with fracture and normal BMD should be investigated for T2DM and hyperinsulinaemia.
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Affiliation(s)
- Isabella D. Cooper
- Translational Physiology Research Group, School of Life Sciences, University of Westminster, 115 New Cavendish Street, London W1W 6UW, UK
| | - Kenneth H. Brookler
- Research Collaborator, Aerospace Medicine and Vestibular Research Laboratory, Mayo Clinic, Scottsdale, AZ 85259, USA;
| | - Catherine A. P. Crofts
- School of Public Health and Interdisciplinary Studies, Faculty of Health and Environmental Sciences, Auckland University of Technology, Auckland 0627, New Zealand;
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Lv X, Gao F, Li TP, Xue P, Wang X, Wan M, Hu B, Chen H, Jain A, Shao Z, Cao X. Skeleton interoception regulates bone and fat metabolism through hypothalamic neuroendocrine NPY. eLife 2021; 10:e70324. [PMID: 34468315 PMCID: PMC8439655 DOI: 10.7554/elife.70324] [Citation(s) in RCA: 15] [Impact Index Per Article: 5.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/13/2021] [Accepted: 05/21/2021] [Indexed: 01/04/2023] Open
Abstract
The central nervous system regulates activity of peripheral organs through interoception. In our previous study, we have demonstrated that PGE2/EP4 skeleton interception regulate bone homeostasis. Here, we show that ascending skeleton interoceptive signaling downregulates expression of hypothalamic neuropeptide Y (NPY) and induce lipolysis of adipose tissue for osteoblastic bone formation. Specifically, the ascending skeleton interoceptive signaling induces expression of small heterodimer partner-interacting leucine zipper protein (SMILE) in the hypothalamus. SMILE binds to pCREB as a transcriptional heterodimer on Npy promoters to inhibit NPY expression. Knockout of EP4 in sensory nerve increases expression of NPY causing bone catabolism and fat anabolism. Importantly, inhibition of NPY Y1 receptor (Y1R) accelerated oxidation of free fatty acids in osteoblasts and rescued bone loss in AvilCre:Ptger4fl/fl mice. Thus, downregulation of hypothalamic NPY expression lipolyzes free fatty acids for anabolic bone formation through a neuroendocrine descending interoceptive regulation.
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Affiliation(s)
- Xiao Lv
- Department of Orthopaedic Surgery, Institute of Cell Engineering, and Department of Biomedical Engineering, The Johns Hopkins UniversityBaltimoreUnited States
- Department of Orthopaedics, Union Hospital, Tongji Medical College, Huazhong University of Science and TechnologyWuhanChina
| | - Feng Gao
- Department of Orthopaedic Surgery, Institute of Cell Engineering, and Department of Biomedical Engineering, The Johns Hopkins UniversityBaltimoreUnited States
- Department of Orthopaedics, Union Hospital, Tongji Medical College, Huazhong University of Science and TechnologyWuhanChina
| | - Tuo Peter Li
- Department of Orthopaedic Surgery, Institute of Cell Engineering, and Department of Biomedical Engineering, The Johns Hopkins UniversityBaltimoreUnited States
| | - Peng Xue
- Department of Orthopaedic Surgery, Institute of Cell Engineering, and Department of Biomedical Engineering, The Johns Hopkins UniversityBaltimoreUnited States
| | - Xiao Wang
- Department of Orthopaedic Surgery, Institute of Cell Engineering, and Department of Biomedical Engineering, The Johns Hopkins UniversityBaltimoreUnited States
| | - Mei Wan
- Department of Orthopaedic Surgery, Institute of Cell Engineering, and Department of Biomedical Engineering, The Johns Hopkins UniversityBaltimoreUnited States
| | - Bo Hu
- Department of Orthopaedic Surgery, Institute of Cell Engineering, and Department of Biomedical Engineering, The Johns Hopkins UniversityBaltimoreUnited States
| | - Hao Chen
- Department of Orthopaedic Surgery, Institute of Cell Engineering, and Department of Biomedical Engineering, The Johns Hopkins UniversityBaltimoreUnited States
| | - Amit Jain
- Department of Orthopaedic Surgery, Institute of Cell Engineering, and Department of Biomedical Engineering, The Johns Hopkins UniversityBaltimoreUnited States
| | - Zengwu Shao
- Department of Orthopaedics, Union Hospital, Tongji Medical College, Huazhong University of Science and TechnologyWuhanChina
| | - Xu Cao
- Department of Orthopaedic Surgery, Institute of Cell Engineering, and Department of Biomedical Engineering, The Johns Hopkins UniversityBaltimoreUnited States
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Abstract
PURPOSE OF REVIEW In this review, we provide a recent update on bioenergetic pathways in osteocytes and identify potential future areas of research interest. Studies have identified a role for regulation of bone formation and bone resorption through osteocyte mechanosensing and osteocyte secreted factors. Nevertheless, there is a paucity of studies on the bioenergetics and energy metabolism of osteocytes, which are required for the regulation of bone remodeling. RECENT FINDINGS Osteocytes are cells of the osteoblast lineage embedded in bone. The osteocyte lacunocanalicular network within the skeletal matrix is exposed to a unique hypoxic environment. Therefore, the bioenergetic requirements of these cells could differ from other bone cells due to its location in the ossified matrix and its role in bone regulation transduced by mechanical signals. Recent findings highlighted in this review provide some evidence that metabolism of these cells is dependent on their location due to the substrates present in the microenvironment and metabolic cues from stress pathways. Both glycolysis (glucose metabolism) and oxidative phosphorylation (mitochondrial dynamics, ROS generation) affect osteocyte function and viability. In this review, we provide evidence that is currently available about information regarding bioenergetics pathways in osteocytes. We discuss published studies showing a role for hypoxia-driven glucose metabolism in regulating osteocyte bioenergetics. We also provide information on various substrates that osteocytes could utilize to fuel energetic needs, namely pyruvate, amino acids, and fatty acids. This is based on some preliminary experimental evidence that is available in literature. The role of parathyroid hormone PTH and parathryoid hormone-related peptide PTHrP in bone anabolism and resorption, along with regulation of metabolic pathways in the cells of the skeletal niche, needs to be explored further. Mitochondrial metabolism has a role in osteocyte bioenergetics through substrate utilization, location of the osteocyte in the bone cortex, and mitochondrial biogenesis. While there are limitations in studying metabolic flux in traditional cell lines, there are now novel cell lines and sophisticated tools available to study osteocyte bioenergetics to help harness its potential in vivo in the future.
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Affiliation(s)
- Vivin Karthik
- Center for Molecular Medicine, Maine Medical Center Research Institute, 81 Research Drive, Scarborough, ME, 04074, USA
- Graduate School of Biomedical Sciences and Engineering, University of Maine, Orono, ME, USA
| | - Anyonya R Guntur
- Center for Molecular Medicine, Maine Medical Center Research Institute, 81 Research Drive, Scarborough, ME, 04074, USA.
- Graduate School of Biomedical Sciences and Engineering, University of Maine, Orono, ME, USA.
- Tufts University School of Medicine, Tufts University, Boston, MA, USA.
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