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Tomaszewska E, Burmańczuk N, Dobrowolski P, Świątkiewicz M, Donaldson J, Burmańczuk A, Mielnik-Błaszczak M, Kuc D, Milewski S, Muszyński S. The Protective Role of Alpha-Ketoglutaric Acid on the Growth and Bone Development of Experimentally Induced Perinatal Growth-Retarded Piglets. Animals (Basel) 2021; 11:E137. [PMID: 33435211 PMCID: PMC7826854 DOI: 10.3390/ani11010137] [Citation(s) in RCA: 3] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/23/2020] [Revised: 01/07/2021] [Accepted: 01/08/2021] [Indexed: 01/01/2023] Open
Abstract
The effect of alpha-ketoglutaric acid (AKG) supplementation to experimentally-induced, perinatal growth-retarded piglets was examined. Sows were treated with a synthetic glucocorticoid (Gc) during the last 25 days of pregnancy, and after the birth, piglets were randomly divided into three groups depending on the treatment. The Gc/Gc + AKG and Gc/AKG groups born by Gc-treated sows after the birth were treated with Gc or Gc + AKG for 35 days. Significantly lower serum growth hormone, IGF-I, osteocalcin, leptin, and cortisol concentrations were observed in the Gc/Gc + AKG group, while the bone alkaline phosphatase activity was significantly higher. Serum insulin concentration was higher in the control group. Serum alanine, lysine, histidine, and tryptophan concentrations were higher in the Gc/Gc + AKG and Gc/AKG groups. The perinatal action of Gc significantly affects histomorphometry of articular cartilage and trabecular bone and bone mechanics. The results clearly showed that dietary AKG had positive effects with regards to the profile of free amino acids. Taking into account the function of AKG as an energy donor and stimulator of collagen synthesis, it can be concluded that the anabolic role of AKG may be the main mechanism responsible for its protective effect against the GC-induced perinatal intensified catabolic state.
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Affiliation(s)
- Ewa Tomaszewska
- Department of Animal Physiology, Faculty of Veterinary Medicine, University of Life Sciences in Lublin, Akademicka St. 12, 20-950 Lublin, Poland;
| | - Natalia Burmańczuk
- Department of Animal Physiology, Faculty of Veterinary Medicine, University of Life Sciences in Lublin, Akademicka St. 12, 20-950 Lublin, Poland;
| | - Piotr Dobrowolski
- Department of Functional Anatomy and Cytobiology, Faculty of Biology and Biotechnology, Maria Curie-Sklodowska University, Akademicka St. 19, 20-033 Lublin, Poland;
| | - Małgorzata Świątkiewicz
- Department of Animal Nutrition and Feed Science, National Research Institute of Animal Production, Krakowska St. 1, 32-083 Balice, Poland;
| | - Janine Donaldson
- Faculty of Health Sciences, School of Physiology, University of the Witwatersrand, 7 York Road, Parktown, Johannesburg 2193, South Africa;
| | - Artur Burmańczuk
- Faculty of Veterinary Medicine, Institute of Preclinical Veterinary Sciences, University of Life Sciences in Lublin, Akademicka St. 12, 20-950 Lublin, Poland;
| | - Maria Mielnik-Błaszczak
- Department of Developmental Dentistry, Medical University of Lublin, 7 Karmelicka St., 20-081 Lublin, Poland; (M.M.-B.); (D.K.)
| | - Damian Kuc
- Department of Developmental Dentistry, Medical University of Lublin, 7 Karmelicka St., 20-081 Lublin, Poland; (M.M.-B.); (D.K.)
| | - Szymon Milewski
- Department of Biophysics, Faculty of Environmental Biology, University of Life Sciences in Lublin, Akademicka St. 13, 20-950 Lublin, Poland; (S.M.); (S.M.)
| | - Siemowit Muszyński
- Department of Biophysics, Faculty of Environmental Biology, University of Life Sciences in Lublin, Akademicka St. 13, 20-950 Lublin, Poland; (S.M.); (S.M.)
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Liu C, Zhao Q, Yu X. Bone Marrow Adipocytes, Adipocytokines, and Breast Cancer Cells: Novel Implications in Bone Metastasis of Breast Cancer. Front Oncol 2020; 10:561595. [PMID: 33123472 PMCID: PMC7566900 DOI: 10.3389/fonc.2020.561595] [Citation(s) in RCA: 9] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/13/2020] [Accepted: 08/27/2020] [Indexed: 02/05/2023] Open
Abstract
Accumulating discoveries highlight the importance of interaction between marrow stromal cells and cancer cells for bone metastasis. Bone is the most common metastatic site of breast cancer and bone marrow adipocytes (BMAs) are the most abundant component of the bone marrow microenvironment. BMAs are unique in their origin and location, and recently they are found to serve as an endocrine organ that secretes adipokines, cytokines, chemokines, and growth factors. It is reasonable to speculate that BMAs contribute to the modification of bone metastatic microenvironment and affecting metastatic breast cancer cells in the bone marrow. Indeed, BMAs may participate in bone metastasis of breast cancer through regulation of recruitment, invasion, survival, colonization, proliferation, angiogenesis, and immune modulation by their production of various adipocytokines. In this review, we provide an overview of research progress, focusing on adipocytokines secreted by BMAs and their potential roles for bone metastasis of breast cancer, and investigating the mechanisms mediating the interaction between BMAs and metastatic breast cancer cells. Based on current findings, BMAs may function as a pivotal modulator of bone metastasis of breast cancer, therefore targeting BMAs combined with conventional treatment programs might present a promising therapeutic option.
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Affiliation(s)
- Chang Liu
- Department of Endocrinology and Metabolism, Laboratory of Endocrinology and Metabolism, National Clinical Research Center for Geriatrics, West China Hospital, Sichuan University, Chengdu, China
| | - Qian Zhao
- Department of Endocrinology and Metabolism, Laboratory of Endocrinology and Metabolism, National Clinical Research Center for Geriatrics, West China Hospital, Sichuan University, Chengdu, China.,Department of General Practice, West China Hospital, Sichuan University, Chengdu, China
| | - Xijie Yu
- Department of Endocrinology and Metabolism, Laboratory of Endocrinology and Metabolism, National Clinical Research Center for Geriatrics, West China Hospital, Sichuan University, Chengdu, China
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Fadda SM, Abdelaleem EA, Mohamed RA, Mansour HM, Doudar NA. Is leptin receptor gene (Gln223Arg) polymorphism associated with disease susceptibility and severity in patients of primary knee osteoarthritis? THE EGYPTIAN RHEUMATOLOGIST 2020. [DOI: 10.1016/j.ejr.2019.04.006] [Citation(s) in RCA: 4] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
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Francisco V, Ruiz-Fernández C, Pino J, Mera A, González-Gay MA, Gómez R, Lago F, Mobasheri A, Gualillo O. Adipokines: Linking metabolic syndrome, the immune system, and arthritic diseases. Biochem Pharmacol 2019; 165:196-206. [DOI: 10.1016/j.bcp.2019.03.030] [Citation(s) in RCA: 90] [Impact Index Per Article: 18.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/16/2019] [Accepted: 03/19/2019] [Indexed: 12/12/2022]
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Tomaszewska E, Muszyński S, Dobrowolski P, Wiącek D, Tomczyk-Warunek A, Świetlicka I, Pierzynowski SG. Maternal HMB treatment affects bone and hyaline cartilage development in their weaned piglets via the leptin/osteoprotegerin system. J Anim Physiol Anim Nutr (Berl) 2019; 103:626-643. [PMID: 30659706 DOI: 10.1111/jpn.13060] [Citation(s) in RCA: 11] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/03/2018] [Revised: 12/13/2018] [Accepted: 12/16/2018] [Indexed: 01/14/2023]
Abstract
It has been demonstrated in animal studies that prenatal administration of β-hydroxy-β-methylbutyrate (HMB, metabolite of leucine) influences general growth and mechanical endurance of long bones in newborn offspring in sex-dependent manner. The present experiment was conducted to evaluate the effect of HMB treatment of pregnant sows on bone development in offspring at weaning. From 70th day until the 90th day of gestation, sows received either a basal diet (n = 12) or the same diet supplemented with HMB (n = 12) at the dose of 0.2 g/kg of body weight/day. Femora obtained from six males and females in each group weaned at the age of 35 days were examined. Maternal HMB treatment significantly enhanced body weight and changed bone morphology increasing femur mechanical strength in both sexes. Maternal HMB supplementation also elevated bone micro- and macroelement concentrations and enhanced content of proteoglycans in articular cartilage. Based on the obtained results, it can be concluded that maternal HMB supplementation in the mid-gestation period significantly accelerated bone development in both sexes by upregulation of a multifactorial system including leptin and osteoprotegerin. However, the sex (irrespective of the HMB treatment) was the factor which influenced the collagen structure in cartilages and trabecular bone, as demonstrated both by the Picrosirius red staining and performed analysis of thermal stability of collagenous tissues. The structural differences in collagen between males and females were presumably related to a different collagen maturity. No studies conducted so far provided a detailed morphological analysis of bone, articular cartilage, growth plate and the activities of the somatotropic and pituitary-gonadal axes, as well as leptin/osteoprotegerin system in weaned offspring prenatally treated with HMB. This study showed also the relationship between the maternal HMB treatment and bone osteometric and mechanical traits, hormones, and growth and bone turnover markers such as leptin, osteoprotegerin and insulin-like growth factor-1.
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Affiliation(s)
- Ewa Tomaszewska
- Department of Animal Physiology, Faculty of Veterinary Medicine, University of Life Sciences in Lublin, Lublin, Poland
| | - Siemowit Muszyński
- Department of Physics, Faculty of Production Engineering, University of Life Sciences in Lublin, Lublin, Poland
| | - Piotr Dobrowolski
- Department of Comparative Anatomy and Anthropology, Maria Curie-Skłodowska University, Lublin, Poland
| | - Dariusz Wiącek
- Bohdan Dobrzański Institute of Agrophysics of the Polish Academy of Sciences, Lublin, Poland
| | - Agnieszka Tomczyk-Warunek
- Department of Animal Physiology, Faculty of Veterinary Medicine, University of Life Sciences in Lublin, Lublin, Poland
| | - Izabela Świetlicka
- Department of Physics, Faculty of Production Engineering, University of Life Sciences in Lublin, Lublin, Poland
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Lee DW, Cho MS, Choe EY, Park SW, Song YM, Lee SC, Sung J. Epicardial Fat Thickness and Bone Mineral Content: The Healthy Twin Study in Korea. J Epidemiol 2018; 28:253-259. [PMID: 29332861 PMCID: PMC5911676 DOI: 10.2188/jea.je20170027] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/02/2022] Open
Abstract
Background The conventional concept of positive association between general obesity and bone health was challenged in recent studies reporting the different effects of specific fat deposition on bone health. In the present study, we investigated the association between epicardial fat and bone health. Methods We measured echocardiographic epicardial fat thickness (EFT) and bone mineral content (BMC) in a twin-family cohort of Koreans (n = 1,198; 525 men, 460 pre- and 213 post-menopausal women). A total 121 pairs of monozygotic twin (MZ) and 404 pairs of dizygotic twin and sibling pairs (DZ/Sib) were included. Results EFT was positively associated with BMC in total, as well as in three subgroups (β = 0.107, 0.076, and 0.058 for men, pre-, and post-menopausal women, respectively). The positive association between EFT and BMC remained for DZ/Sib difference analysis, but was absent for MZ comparisons. The positive association between BMI and BMC was consistent for DZ/Sib and MZ difference analysis. After adjusting for the effect of general obesity via BMI, the association between BMC and EFT was statistically non-significant (β = 0.020, 0.000, and −0.009 for men, pre-, and post-menopausal women, respectively). Conclusion Our findings do not support epicardial fat’s beneficial effects on bone health, whereas general adiposity has an osteotropic effect. The association between EFT and BMC is through common genetic component factors.
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Affiliation(s)
- Dong-Won Lee
- Department of Internal Medicine, Division of Gastroenterology, Korea University Ansan Hospital
| | - Min Soo Cho
- Heart Institute, Asan Medical Center, University of Ulsan College of Medicine
| | - Eun Yeong Choe
- Department of Internal Medicine, Division of Endocrinology, Yonsei University College of Medicine
| | - Seung Woo Park
- Department of Cardiology and Cardiovascular Imaging Center, Cardiac and Vascular Center, Samsung Medical Center, Sungkyunkwan University School of Medicine
| | - Yun-Mi Song
- Department of Family Medicine, Samsung Medical Center, Sungkyunkwan University School of Medicine
| | - Sang-Chol Lee
- Department of Cardiology and Cardiovascular Imaging Center, Cardiac and Vascular Center, Samsung Medical Center, Sungkyunkwan University School of Medicine
| | - Joohon Sung
- Department of Epidemiology, School of Public Health, Seoul National University.,Institute of Health and Environment, Seoul National University.,Bio-MAX Institute, Seoul National University
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Francisco V, Pino J, Gonzalez‐Gay MA, Mera A, Lago F, Gómez R, Mobasheri A, Gualillo O. Adipokines and inflammation: is it a question of weight? Br J Pharmacol 2018; 175:1569-1579. [PMID: 29486050 PMCID: PMC5913397 DOI: 10.1111/bph.14181] [Citation(s) in RCA: 103] [Impact Index Per Article: 17.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/30/2017] [Revised: 02/09/2018] [Accepted: 02/16/2018] [Indexed: 12/25/2022] Open
Abstract
Obesity has reached epidemic proportions in the Western society and is increasing in the developing world. It is considered as one of the major contributors to the global burden of disability and chronic diseases, including autoimmune, inflammatory and degenerative diseases. Research conducted on obesity and its complications over the last two decades has transformed the outdated concept of white adipose tissue (WAT) merely serving as an energy depot. WAT is now recognized as an active and inflammatory organ capable of producing a wide variety of factors known as adipokines. These molecules participate through endocrine, paracrine, autocrine or juxtacrine crosstalk mechanisms in a great variety of physiological or pathophysiological processes, regulating food intake, insulin sensitivity, immunity and inflammation. Although initially restricted to metabolic activities (regulation of glucose and lipid metabolism), adipokines currently represent a new family of proteins that can be considered key players in the complex network of soluble mediators involved in the pathophysiology of immune/inflammatory diseases. However, the complexity of the adipokine network in the pathogenesis and progression of inflammatory diseases has posed, since the beginning, the important question of whether it may be possible to target the mechanism(s) by which adipokines contribute to disease selectively without suppressing their physiological functions. Here, we explore in depth the most recent findings concerning the involvement of adipokines in inflammation and immune responses, in particular in rheumatic, inflammatory and degenerative diseases. We also highlight several possible strategies for therapeutic development and propose that adipokines and their signalling pathways may represent innovative therapeutic strategies for inflammatory disorders.
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Affiliation(s)
- Vera Francisco
- SERGAS (Servizo Galego de Saude) and IDIS (Instituto de Investigación Sanitaria de Santiago), The NEIRID Group (Neuroendocrine Interactions in Rheumatology and Inflammatory Diseases)Santiago University Clinical HospitalBuilding C, Travesía da Choupana S/NSantiago de Compostela15706Spain
| | - Jesus Pino
- SERGAS (Servizo Galego de Saude) and IDIS (Instituto de Investigación Sanitaria de Santiago), The NEIRID Group (Neuroendocrine Interactions in Rheumatology and Inflammatory Diseases)Santiago University Clinical HospitalBuilding C, Travesía da Choupana S/NSantiago de Compostela15706Spain
| | - Miguel Angel Gonzalez‐Gay
- Epidemiology, Genetics and Atherosclerosis Research Group on Systemic Inflammatory DiseasesUniversidad de Cantabria and IDIVAL, Hospital Universitario Marqués de ValdecillaAv. ValdecillaSantander39008Spain
| | - Antonio Mera
- SERGAS (Servizo Galego de Saude), Division of RheumatologySantiago University Clinical HospitalTravesía da Choupana S/NSantiago de Compostela15706Spain
| | - Francisca Lago
- SERGAS (Servizo Galego de Saude) and IDIS (Instituto de Investigación Sanitaria de Santiago), Department of Cellular and Molecular CardiologyCIBERCV (Centro de Investigación Biomédica en Red de Enfermedades Cardiovasculares), Building CTravesía da Choupana S/NSantiago de Compostela15706Spain
| | - Rodolfo Gómez
- Musculoskeletal Pathology Group. SERGAS (Servizo Galego de Saude) and IDIS (Instituto de Investigación Sanitaria de Santiago), Research Laboratory 9Santiago University Clinical HospitalSantiago de CompostelaSpain
| | - Ali Mobasheri
- Faculty of Health and Medical SciencesUniversity of SurreyGuildfordSurreyGU2 7XHUK
- School of Veterinary MedicineUniversity of SurreyGuildfordGU2 7ALUK
- Arthritis Research UK Centre for Sport, Exercise and Osteoarthritis, Arthritis Research UK Centre for Musculoskeletal Ageing ResearchQueen's Medical CentreNottinghamNG7 2UHUK
- State Research Institute Centre for Innovative MedicineSantariskiu 5Vilnius0866Republic of Lithuania
| | - Oreste Gualillo
- SERGAS (Servizo Galego de Saude) and IDIS (Instituto de Investigación Sanitaria de Santiago), The NEIRID Group (Neuroendocrine Interactions in Rheumatology and Inflammatory Diseases)Santiago University Clinical HospitalBuilding C, Travesía da Choupana S/NSantiago de Compostela15706Spain
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Abella V, Scotece M, Conde J, Pino J, Gonzalez-Gay MA, Gómez-Reino JJ, Mera A, Lago F, Gómez R, Gualillo O. Leptin in the interplay of inflammation, metabolism and immune system disorders. Nat Rev Rheumatol 2017; 13:100-109. [PMID: 28053336 DOI: 10.1038/nrrheum.2016.209] [Citation(s) in RCA: 323] [Impact Index Per Article: 46.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/13/2022]
Abstract
Leptin is one of the most relevant factors secreted by adipose tissue and the forerunner of a class of molecules collectively called adipokines. Initially discovered in 1994, its crucial role as a central regulator in energy homeostasis has been largely described during the past 20 years. Once secreted into the circulation, leptin reaches the central and peripheral nervous systems and acts by binding and activating the long form of leptin receptor (LEPR), regulating appetite and food intake, bone mass, basal metabolism, reproductive function and insulin secretion, among other processes. Research on the regulation of different adipose tissues has provided important insights into the intricate network that links nutrition, metabolism and immune homeostasis. The neuroendocrine and immune systems communicate bi-directionally through common ligands and receptors during stress responses and inflammation, and control cellular immune responses in several pathological situations including immune-inflammatory rheumatic diseases. This Review discusses the latest findings regarding the role of leptin in the immune system and metabolism, with particular emphasis on its effect on autoimmune and/or inflammatory rheumatic diseases, such as rheumatoid arthritis and osteoarthritis.
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Affiliation(s)
- Vanessa Abella
- SERGAS (Servizo Galego de Saude) and IDIS (Instituto de Investigación Sanitaria de Santiago), The NEIRID Group (Neuroendocrine Interactions in Rheumatology and Inflammatory Diseases), Santiago University Clinical Hospital, Building C, Travesía da Choupana S/N, Santiago de Compostela 15706, Spain
| | - Morena Scotece
- SERGAS (Servizo Galego de Saude) and IDIS (Instituto de Investigación Sanitaria de Santiago), The NEIRID Group (Neuroendocrine Interactions in Rheumatology and Inflammatory Diseases), Santiago University Clinical Hospital, Building C, Travesía da Choupana S/N, Santiago de Compostela 15706, Spain
| | - Javier Conde
- SERGAS (Servizo Galego de Saude) and IDIS (Instituto de Investigación Sanitaria de Santiago), The NEIRID Group (Neuroendocrine Interactions in Rheumatology and Inflammatory Diseases), Santiago University Clinical Hospital, Building C, Travesía da Choupana S/N, Santiago de Compostela 15706, Spain
| | - Jesús Pino
- SERGAS (Servizo Galego de Saude), Santiago University Clinical Hospital, Division of Orthopaedic Surgery and Traumatology, Travesía da Choupana S/N, Santiago de Compostela 15706, Spain
| | - Miguel Angel Gonzalez-Gay
- Epidemiology, Genetics and Atherosclerosis Research Group on Systemic Inflammatory Diseases, Universidad de Cantabria and IDIVAL, Hospital Universitario Marqués de Valdecilla, Av. Valdecilla, Santander 39008, Spain
| | - Juan J Gómez-Reino
- SERGAS (Servizo Galego de Saude), Santiago University Clinical Hospital, Division of Rheumatology, Travesía da Choupana S/N, Santiago de Compostela 15706, Spain
| | - Antonio Mera
- SERGAS (Servizo Galego de Saude), Santiago University Clinical Hospital, Division of Rheumatology, Travesía da Choupana S/N, Santiago de Compostela 15706, Spain
| | - Francisca Lago
- SERGAS (Servizo Galego de Saude) and IDIS (Instituto de Investigación Sanitaria de Santiago), Department of Cellular and Molecular Cardiology, CIBERCV (Centro de Investigación Biomédica en Red de Enfermedades Cardiovasculares), Building C, Travesía da Choupana S/N, Santiago de Compostela 15706, Spain
| | - Rodolfo Gómez
- SERGAS (Servizo Galego de Saude) and IDIS (Instituto de Investigación Sanitaria de Santiago), The NEIRID Group (Neuroendocrine Interactions in Rheumatology and Inflammatory Diseases), Santiago University Clinical Hospital, Building C, Travesía da Choupana S/N, Santiago de Compostela 15706, Spain
| | - Oreste Gualillo
- SERGAS (Servizo Galego de Saude) and IDIS (Instituto de Investigación Sanitaria de Santiago), The NEIRID Group (Neuroendocrine Interactions in Rheumatology and Inflammatory Diseases), Santiago University Clinical Hospital, Building C, Travesía da Choupana S/N, Santiago de Compostela 15706, Spain
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Spaceflight-induced vertebral bone loss in ovariectomized rats is associated with increased bone marrow adiposity and no change in bone formation. NPJ Microgravity 2016; 2:16016. [PMID: 28725730 PMCID: PMC5515514 DOI: 10.1038/npjmgrav.2016.16] [Citation(s) in RCA: 15] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/04/2015] [Revised: 02/10/2016] [Accepted: 03/13/2016] [Indexed: 11/22/2022] Open
Abstract
There is often a reciprocal relationship between bone marrow adipocytes and osteoblasts, suggesting that marrow adipose tissue (MAT) antagonizes osteoblast differentiation. MAT is increased in rodents during spaceflight but a causal relationship between MAT and bone loss remains unclear. In the present study, we evaluated the effects of a 14-day spaceflight on bone mass, bone resorption, bone formation, and MAT in lumbar vertebrae of ovariectomized (OVX) rats. Twelve-week-old OVX Fischer 344 rats were randomly assigned to a ground control or flight group. Following flight, histological sections of the second lumbar vertebrae (n=11/group) were stained using a technique that allowed simultaneous quantification of cells and preflight fluorochrome label. Compared with ground controls, rats flown in space had 32% lower cancellous bone area and 306% higher MAT. The increased adiposity was due to an increase in adipocyte number (224%) and size (26%). Mineral apposition rate and osteoblast turnover were unchanged during spaceflight. In contrast, resorption of a preflight fluorochrome and osteoclast-lined bone perimeter were increased (16% and 229%, respectively). The present findings indicate that cancellous bone loss in rat lumbar vertebrae during spaceflight is accompanied by increased bone resorption and MAT but no change in bone formation. These findings do not support the hypothesis that increased MAT during spaceflight reduces osteoblast activity or lifespan. However, in the context of ovarian hormone deficiency, bone formation during spaceflight was insufficient to balance increased resorption, indicating defective coupling. The results are therefore consistent with the hypothesis that during spaceflight mesenchymal stem cells are diverted to adipocytes at the expense of forming osteoblasts.
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