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Abstract
Concerning diet-induced thermogenesis, methodological issues relate mainly to the interpretation of measurements, rather than to the technical methodology as such. In the following, we point to a series of issues where the analysis often suggests the occurrence of UCP1-related diet-induced thermogenesis but where the observations are often the consequences of a process that has induced leanness rather than being the cause of them. We particularly emphasize the necessity of focusing on the total organism when interpreting biochemical and molecular data, where the concept of total tissue values rather than relative data better reflects physiologically important alterations. We stress the importance of performing experiments at thermoneutrality in order to obtain clinically relevant data and stress that true thermogenic agents may be overlooked if this is not done.
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Affiliation(s)
- Jan Nedergaard
- Department of Molecular Biosciences, The Wenner-Gren Institute, Stockholm University, Stockholm, Sweden.
| | - Barbara Cannon
- Department of Molecular Biosciences, The Wenner-Gren Institute, Stockholm University, Stockholm, Sweden.
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2
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Serdan TDA, Masi LN, Pereira JNB, Rodrigues LE, Alecrim AL, Scervino MVM, Diniz VLS, Dos Santos AAC, Filho CPBS, Alba-Loureiro TC, Marzuca-Nassr GN, Bazotte RB, Gorjão R, Pithon-Curi TC, Curi R, Hirabara SM. Impaired brown adipose tissue is differentially modulated in insulin-resistant obese wistar and type 2 diabetic Goto-Kakizaki rats. Biomed Pharmacother 2021; 142:112019. [PMID: 34403962 DOI: 10.1016/j.biopha.2021.112019] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/12/2021] [Revised: 07/29/2021] [Accepted: 08/07/2021] [Indexed: 12/13/2022] Open
Abstract
Brown adipose tissue (BAT) is a potential target to treat obesity and diabetes, dissipating energy as heat. Type 2 diabetes (T2D) has been associated with obesogenic diets; however, T2D was also reported in lean individuals to be associated with genetic factors. We aimed to investigate the differences between obese and lean models of insulin resistance (IR) and elucidate the mechanism associated with BAT metabolism and dysfunction in different IR animal models: a genetic model (lean GK rats) and obese models (diet-induced obese Wistar rats) at 8 weeks of age fed a high-carbohydrate (HC), high-fat (HF) diet, or high-fat and high-sugar (HFHS) diet for 8 weeks. At 15 weeks of age, BAT glucose uptake was evaluated by 18F-FDG PET under basal (saline administration) or stimulated condition (CL316,243, a selective β3-AR agonist). After CL316, 243 administrations, GK animals showed decreased glucose uptake compared to HC animals. At 16 weeks of age, the animals were euthanized, and the interscapular BAT was dissected for analysis. Histological analyses showed lower cell density in GK rats and higher adipocyte area compared to all groups, followed by HFHS and HF compared to HC. HFHS showed a decreased batokine FGF21 protein level compared to all groups. However, GK animals showed increased expression of genes involved in fatty acid oxidation (CPT1 and CPT2), BAT metabolism (Sirt1 and Pgc1-α), and obesogenic genes (leptin and PAI-1) but decreased gene expression of glucose transporter 1 (GLUT-1) compared to other groups. Our data suggest impaired BAT function in obese Wistar and GK rats, with evidence of a whitening process in these animals.
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Affiliation(s)
| | - Laureane Nunes Masi
- Interdisciplinary Postgraduate Program in Health Sciences, Cruzeiro do Sul University, São Paulo, Brazil
| | | | - Luiz Eduardo Rodrigues
- Interdisciplinary Postgraduate Program in Health Sciences, Cruzeiro do Sul University, São Paulo, Brazil
| | - Amanda Lins Alecrim
- Interdisciplinary Postgraduate Program in Health Sciences, Cruzeiro do Sul University, São Paulo, Brazil
| | | | | | | | | | | | | | | | - Renata Gorjão
- Interdisciplinary Postgraduate Program in Health Sciences, Cruzeiro do Sul University, São Paulo, Brazil
| | - Tania Cristina Pithon-Curi
- Interdisciplinary Postgraduate Program in Health Sciences, Cruzeiro do Sul University, São Paulo, Brazil
| | - Rui Curi
- Interdisciplinary Postgraduate Program in Health Sciences, Cruzeiro do Sul University, São Paulo, Brazil
| | - Sandro Massao Hirabara
- Interdisciplinary Postgraduate Program in Health Sciences, Cruzeiro do Sul University, São Paulo, Brazil
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Activation of Cx43 Hemichannels Induces the Generation of Ca 2+ Oscillations in White Adipocytes and Stimulates Lipolysis. Int J Mol Sci 2021; 22:ijms22158095. [PMID: 34360859 PMCID: PMC8347185 DOI: 10.3390/ijms22158095] [Citation(s) in RCA: 13] [Impact Index Per Article: 4.3] [Reference Citation Analysis] [Abstract] [Key Words] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/29/2021] [Revised: 07/22/2021] [Accepted: 07/26/2021] [Indexed: 12/11/2022] Open
Abstract
The aim of the study was to investigate the mechanisms of Ca2+ oscillation generation upon activation of connexin-43 and regulation of the lipolysis/lipogenesis balance in white adipocytes through vesicular ATP release. With fluorescence microscopy it was revealed that a decrease in the concentration of extracellular calcium ([Ca2+]ex) results in two types of Ca2+ responses in white adipocytes: Ca2+ oscillations and transient Ca2+ signals. It was found that activation of the connexin half-channels is involved in the generation of Ca2+ oscillations, since the blockers of the connexin hemichannels-carbenoxolone, octanol, proadifen and Gap26-as well as Cx43 gene knockdown led to complete suppression of these signals. The activation of Cx43 in response to the reduction of [Ca2+]ex was confirmed by TIRF microscopy. It was shown that in response to the activation of Cx43, ATP-containing vesicles were released from the adipocytes. This process was suppressed by knockdown of the Cx43 gene and by bafilomycin A1, an inhibitor of vacuolar ATPase. At the level of intracellular signaling, the generation of Ca2+ oscillations in white adipocytes in response to a decrease in [Ca2+]ex occurred due to the mobilization of the Ca2+ ions from the thapsigargin-sensitive Ca2+ pool of IP3R as a result of activation of the purinergic P2Y1 receptors and phosphoinositide signaling pathway. After activation of Cx43 and generation of the Ca2+ oscillations, changes in the expression levels of key genes and their encoding proteins involved in the regulation of lipolysis were observed in white adipocytes. This effect was accompanied by a decrease in the number of adipocytes containing lipid droplets, while inhibition or knockdown of Cx43 led to inhibition of lipolysis and accumulation of lipid droplets. In this study, we investigated the mechanism of Ca2+ oscillation generation in white adipocytes in response to a decrease in the concentration of Ca2+ ions in the external environment and established an interplay between periodic Ca2+ modes and the regulation of the lipolysis/lipogenesis balance.
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Bashir S, Elegunde B, Morgan WA. Inhibition of lipolysis: A novel explanation for the hypothermic actions of acetaminophen in non-febrile rodents. Biochem Pharmacol 2019; 172:113774. [PMID: 31870769 DOI: 10.1016/j.bcp.2019.113774] [Citation(s) in RCA: 9] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Key Words] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/24/2019] [Accepted: 12/18/2019] [Indexed: 12/13/2022]
Abstract
Acetaminophen is both widely used to treat children with fever and is also responsible for thousands being hospitalised annually. Historically the antipyretic actions of acetaminophen were attributed to the inhibition of cyclooxygenase (COX-1/2) enzymes and more recently a novel COX-1 variant (COX-3) located in the brain. However, the evidence for acetaminophen-mediated COX inhibition remains contentious. This study assesses the impact of acetaminophen and other putative COX-3 inhibitors on the release of fatty acids during lipolysis as an alternative mechanism by which antipyretics can reduce body temperature during fever. 3T3-L1 adipocytes, primary brown adipocytes and isolated mitochondria were exposed to COX-3 inhibitors and lipolysis and mitochondrial electron transport chain function assessed. Acetaminophen, aminopyrine and antipyrine at 1-10 mM caused a significant decrease (up to 70%; P < 0.01, from control) in lipolysis within 1, 3 and 24 h without affecting cell viability. The inhibition was observed regardless of where along its signalling pathway lipolysis was stimulated. All three compounds were found to significantly attenuate mitochondrial function by up to 30% for complex I and 40% for complex II (P < 0.01, from control). These novel observations combined with the known limited inhibition of the COX enzymes by acetaminophen suggest both the antipyretic and hypothermia induced by acetaminophen and related compounds could be attributed to the direct inhibition of lipolysis and mitochondrial function, rather than cyclooxygenase inhibition centrally. Further these observations could provide new drug targets for reducing fever with the added bonus of fewer individuals being hospitalized by accidental acetaminophen overdose.
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Affiliation(s)
- Shazma Bashir
- The Medicines Research Group, School of Health, Sport and Bioscience, University of East London, Romford Road, Stratford, London E15 4 LZ, UK
| | - Busayo Elegunde
- The Medicines Research Group, School of Health, Sport and Bioscience, University of East London, Romford Road, Stratford, London E15 4 LZ, UK
| | - Winston A Morgan
- The Medicines Research Group, School of Health, Sport and Bioscience, University of East London, Romford Road, Stratford, London E15 4 LZ, UK.
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5
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Steiner AA, Flatow EA, Brito CF, Fonseca MT, Komegae EN. Respiratory gas exchange as a new aid to monitor acidosis in endotoxemic rats: relationship to metabolic fuel substrates and thermometabolic responses. Physiol Rep 2017; 5:5/1/e13100. [PMID: 28082427 PMCID: PMC5256159 DOI: 10.14814/phy2.13100] [Citation(s) in RCA: 7] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/18/2016] [Revised: 12/01/2016] [Accepted: 12/03/2016] [Indexed: 11/26/2022] Open
Abstract
This study introduces the respiratory exchange ratio (RER; the ratio of whole‐body CO2 production to O2 consumption) as an aid to monitor metabolic acidosis during the early phase of endotoxic shock in unanesthetized, freely moving rats. Two serotypes of lipopolysaccharide (lipopolysaccharide [LPS] O55:B5 and O127:B8) were tested at shock‐inducing doses (0.5–2 mg/kg). Phasic rises in RER were observed consistently across LPS serotypes and doses. The RER rise often exceeded the ceiling of the quotient for oxidative metabolism, and was mirrored by depletion of arterial bicarbonate and decreases in pH. It occurred independently of ventilatory adjustments. These data indicate that the rise in RER results from a nonmetabolic CO2 load produced via an acid‐induced equilibrium shift in the bicarbonate buffer. Having validated this new experimental aid, we asked whether acidosis was interconnected with the metabolic and thermal responses that accompany endotoxic shock in unanesthetized rats. Contrary to this hypothesis, however, acidosis persisted regardless of whether the ambient temperature favored or prevented downregulation of mitochondrial oxidation and regulated hypothermia. We then asked whether the substrate that fuels aerobic metabolism could be a relevant factor in LPS‐induced acidosis. Food deprivation was employed to divert metabolism away from glucose oxidation and toward fatty acid oxidation. Interestingly, this intervention attenuated the RER response to LPS by 58%, without suppressing other key aspects of systemic inflammation. We conclude that acid production in unanesthetized rats with endotoxic shock results from a phasic activation of glycolysis, which occurs independently of physiological changes in mitochondrial oxidation and body temperature.
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Affiliation(s)
- Alexandre A Steiner
- Department of Immunology, Institute of Biomedical Sciences, University of São Paulo, São Paulo, Brazil
| | - Elizabeth A Flatow
- Department of Immunology, Institute of Biomedical Sciences, University of São Paulo, São Paulo, Brazil
| | - Camila F Brito
- Department of Immunology, Institute of Biomedical Sciences, University of São Paulo, São Paulo, Brazil
| | - Monique T Fonseca
- Department of Immunology, Institute of Biomedical Sciences, University of São Paulo, São Paulo, Brazil
| | - Evilin N Komegae
- Department of Immunology, Institute of Biomedical Sciences, University of São Paulo, São Paulo, Brazil
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6
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Hunt CM, Papay JI, Stanulovic V, Regev A. Drug rechallenge following drug-induced liver injury. Hepatology 2017; 66:646-654. [PMID: 28295448 DOI: 10.1002/hep.29152] [Citation(s) in RCA: 48] [Impact Index Per Article: 6.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 11/28/2016] [Revised: 01/29/2017] [Accepted: 03/02/2017] [Indexed: 12/14/2022]
Abstract
UNLABELLED Drug-induced hepatocellular injury is identified internationally by alanine aminotransferase (ALT) levels equal to or exceeding 5× the upper limit of normal (ULN) appearing within 3 months of drug initiation, after alternative causes are excluded. Upon withdrawing the suspect drug, ALT generally decrease by 50% or more. With drug readministration, a positive rechallenge has recently been defined by an ALT level of 3-5× ULN or greater. Nearly 50 drugs are associated with positive rechallenge after drug-induced liver injury (DILI): antimicrobials; and central nervous system, cardiovascular and oncology therapeutics. Drugs associated with high rates of positive rechallenge exhibit multiple risk factors: daily dose >50 mg, an increased incidence of ALT elevations in clinical trials, immunoallergic clinical injury, and mitochondrial impairment in vitro. These drug factors interact with personal genetic, immune, and metabolic factors to influence positive rechallenge rates and outcomes. Drug rechallenge following drug-induced liver injury is associated with up to 13% mortality in prospective series of all prescribed drugs. In recent oncology trials, standardized systems have enabled safer drug rechallenge with weekly liver chemistry monitoring during the high-risk period and exclusion of patients with hypersensitivity. However, high positive rechallenge rates with other innovative therapeutics suggest that caution should be taken with rechallenge of high-risk drugs. CONCLUSION For critical medicines, drug rechallenge may be appropriate when 1) no safer alternatives are available, 2) the objective benefit exceeds the risk, and 3) patients are fully informed and consent, can adhere to follow-up, and alert providers to hepatitis symptoms. To better understand rechallenge outcomes and identify key risk factors for positive rechallenge, additional data are needed from controlled clinical trials, prospective registries, and large health care databases. (Hepatology 2017;66:646-654).
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Affiliation(s)
- Christine M Hunt
- Department of Medicine, Duke University Medical Center, Durham, NC.,Durham Veterans Administration Medical Center, Durham, NC
| | - Julie I Papay
- Global Patient Safety, UCB BioSciences, Research Triangle Park, NC
| | - Vid Stanulovic
- Accelsiors Clinical Research Organization and Consultancy, Budapest, Hungary.,Semmelweis University School of Pharmacy, Budapest, Hungary
| | - Arie Regev
- Global Patient Safety, Eli Lilly and Company, Indianapolis, IN
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Olsen JM, Csikasz RI, Dehvari N, Lu L, Sandström A, Öberg AI, Nedergaard J, Stone-Elander S, Bengtsson T. β 3-Adrenergically induced glucose uptake in brown adipose tissue is independent of UCP1 presence or activity: Mediation through the mTOR pathway. Mol Metab 2017; 6:611-619. [PMID: 28580291 PMCID: PMC5444022 DOI: 10.1016/j.molmet.2017.02.006] [Citation(s) in RCA: 75] [Impact Index Per Article: 10.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 01/20/2017] [Revised: 02/10/2017] [Accepted: 02/15/2017] [Indexed: 01/22/2023] Open
Abstract
Objective Today, the presence and activity of brown adipose tissue (BAT) in adult humans is generally equated with the induced accumulation of [2-18F]2-fluoro-2-deoxy-d-glucose ([18F]FDG) in adipose tissues, as investigated by positron emission tomography (PET) scanning. In reality, PET-FDG is currently the only method available for in vivo quantification of BAT activity in adult humans. The underlying assumption is that the glucose uptake reflects the thermogenic activity of the tissue. Methods To examine this basic assumption, we here followed [18F]FDG uptake by PET and by tissue [3H]-2-deoxy-d-glucose uptake in wildtype and UCP1(−/−) mice, i.e. in mice that do or do not possess the unique thermogenic and calorie-consuming ability of BAT. Results Unexpectedly, we found that β3-adrenergically induced (by CL-316,243) glucose uptake was UCP1-independent. Thus, whereas PET-FDG scans adequately reflect glucose uptake, this acute glucose uptake is not secondary to thermogenesis but is governed by an independent cellular signalling, here demonstrated to be mediated via the previously described KU-0063794-sensitive mTOR pathway. Conclusions Thus, PET-FDG scans do not exclusively reveal active BAT deposits but rather any tissue possessing an adrenergically-mediated glucose uptake pathway. In contrast, we found that the marked glucose uptake-ameliorating effect of prolonged β3-adrenergic treatment was UCP1 dependent. Thus, therapeutically, UCP1 activity is required for any anti-diabetic effect of BAT activation. β3-adrenergically glucose uptake in BAT is UCP1-independent. Glucose uptake is not secondary to thermogenesis but is through the mTOR pathway. Both glucose uptake and thermogenesis are needed to fully effect glucose homeostasis.
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Affiliation(s)
- Jessica M Olsen
- Department of Molecular Biosciences, The Wenner-Gren Institute, Stockholm University, SE-106 91, Stockholm, Sweden
| | - Robert I Csikasz
- Department of Molecular Biosciences, The Wenner-Gren Institute, Stockholm University, SE-106 91, Stockholm, Sweden
| | - Nodi Dehvari
- Department of Molecular Biosciences, The Wenner-Gren Institute, Stockholm University, SE-106 91, Stockholm, Sweden
| | - Li Lu
- Karolinska Experimental Research and Imaging Center, Karolinska University Hospital, Solna, SE-171 76, Stockholm, Sweden.,Department of Clinical Neurosciences, Karolinska Institutet, SE-171 77, Stockholm, Sweden
| | - Anna Sandström
- Department of Molecular Biosciences, The Wenner-Gren Institute, Stockholm University, SE-106 91, Stockholm, Sweden
| | - Anette I Öberg
- Department of Molecular Biosciences, The Wenner-Gren Institute, Stockholm University, SE-106 91, Stockholm, Sweden
| | - Jan Nedergaard
- Department of Molecular Biosciences, The Wenner-Gren Institute, Stockholm University, SE-106 91, Stockholm, Sweden
| | - Sharon Stone-Elander
- Department of Clinical Neurosciences, Karolinska Institutet, SE-171 77, Stockholm, Sweden.,Department of Neuroradiology, Karolinska University Hospital Solna, SE-171 76, Stockholm, Sweden
| | - Tore Bengtsson
- Department of Molecular Biosciences, The Wenner-Gren Institute, Stockholm University, SE-106 91, Stockholm, Sweden
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8
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Mao L, Nie B, Nie T, Hui X, Gao X, Lin X, Liu X, Xu Y, Tang X, Yuan R, Li K, Li P, Ding K, Wang Y, Xu A, Fei J, Han W, Liu P, Madsen L, Kristiansen K, Zhou Z, Ding S, Wu D. Visualization and Quantification of Browning Using a Ucp1-2A-Luciferase Knock-in Mouse Model. Diabetes 2017; 66:407-417. [PMID: 28108609 DOI: 10.2337/db16-0343] [Citation(s) in RCA: 29] [Impact Index Per Article: 4.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 03/15/2016] [Accepted: 10/31/2016] [Indexed: 11/13/2022]
Abstract
Both mammals and adult humans possess classic brown adipocytes and beige adipocytes, and the amount and activity of these adipocytes are considered key factors in combating obesity and its associated metabolic diseases. Uncoupling protein 1 (Ucp1) is the functional marker of both brown and beige adipocytes. To facilitate a reliable, easy, and sensitive measurement of Ucp1 expression both in vivo and in vitro, we generated a Ucp1-2A-luciferase knock-in mouse by deleting the stop codon for the mouse Ucp1 gene and replacing it with a 2A peptide. This peptide was followed by the luciferase coding sequence to recapitulate the expression of the Ucp1 gene at the transcriptional and translational levels. With this mouse, we discovered a cold-sensitive brown/beige adipose depot underneath the skin of the ears, which we named uBAT. Because of the sensitivity and high dynamic range of luciferase activity, the Ucp1-2A-luciferase mouse is useful for both in vitro quantitative determination and in vivo visualization of nonshivering thermogenesis. With the use of this model, we identified and characterized axitinib, an oral small-molecule tyrosine kinase inhibitor, as an effective browning agent.
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Affiliation(s)
- Liufeng Mao
- CAS Key Laboratory of Regenerative Biology, Joint School of Life Sciences, Guangzhou Medical University, and Guangzhou Institute of Biomedicine and Health, Chinese Academy of Sciences, Guangzhou, China
| | - Baoming Nie
- Gladstone Institute of Cardiovascular Disease, Department of Pharmaceutical Chemistry, University of California, San Francisco, San Francisco, CA
| | - Tao Nie
- CAS Key Laboratory of Regenerative Biology, Joint School of Life Sciences, Guangzhou Medical University, and Guangzhou Institute of Biomedicine and Health, Chinese Academy of Sciences, Guangzhou, China
| | - Xiaoyan Hui
- Department of Medicine, The University of Hong Kong, Hong Kong
| | - Xuefei Gao
- Wellcome Sanger Institute, Cambridge, U.K
| | - Xiaoliang Lin
- Research & Development Center, Infinitus (China) Company Ltd., Guangzhou, China
| | - Xin Liu
- Shenzhen Institutes of Advanced Technology, Chinese Academy of Sciences, Shenzhen, China
| | - Yong Xu
- CAS Key Laboratory of Regenerative Biology, Joint School of Life Sciences, Guangzhou Medical University, and Guangzhou Institute of Biomedicine and Health, Chinese Academy of Sciences, Guangzhou, China
| | - Xiaofeng Tang
- CAS Key Laboratory of Regenerative Biology, Joint School of Life Sciences, Guangzhou Medical University, and Guangzhou Institute of Biomedicine and Health, Chinese Academy of Sciences, Guangzhou, China
| | - Ran Yuan
- CAS Key Laboratory of Regenerative Biology, Joint School of Life Sciences, Guangzhou Medical University, and Guangzhou Institute of Biomedicine and Health, Chinese Academy of Sciences, Guangzhou, China
| | - Kuai Li
- CAS Key Laboratory of Regenerative Biology, Joint School of Life Sciences, Guangzhou Medical University, and Guangzhou Institute of Biomedicine and Health, Chinese Academy of Sciences, Guangzhou, China
| | - Peng Li
- CAS Key Laboratory of Regenerative Biology, Joint School of Life Sciences, Guangzhou Medical University, and Guangzhou Institute of Biomedicine and Health, Chinese Academy of Sciences, Guangzhou, China
| | - Ke Ding
- CAS Key Laboratory of Regenerative Biology, Joint School of Life Sciences, Guangzhou Medical University, and Guangzhou Institute of Biomedicine and Health, Chinese Academy of Sciences, Guangzhou, China
| | - Yu Wang
- CAS Key Laboratory of Regenerative Biology, Joint School of Life Sciences, Guangzhou Medical University, and Guangzhou Institute of Biomedicine and Health, Chinese Academy of Sciences, Guangzhou, China
- Department of Medicine, The University of Hong Kong, Hong Kong
| | - Aimin Xu
- CAS Key Laboratory of Regenerative Biology, Joint School of Life Sciences, Guangzhou Medical University, and Guangzhou Institute of Biomedicine and Health, Chinese Academy of Sciences, Guangzhou, China
- Department of Medicine, The University of Hong Kong, Hong Kong
| | - Jian Fei
- Shanghai Nan Fang Model Organism Research Center, Shanghai, China
| | - Weiping Han
- Singapore Bioimaging Consortium and Institute of Molecular and Cell Biology, Agency for Science, Technology and Research, Singapore
| | - Pentao Liu
- Wellcome Sanger Institute, Cambridge, U.K
| | - Lise Madsen
- National Institute of Nutrition and Seafood Research, Bergen, Norway
- Laboratory of Genomics and Molecular Biomedicine, Department of Biology, University of Copenhagen, Copenhagen, Denmark
- Beijing Genomics Institute-Shenzhen, Shenzhen, China
| | - Karsten Kristiansen
- Laboratory of Genomics and Molecular Biomedicine, Department of Biology, University of Copenhagen, Copenhagen, Denmark
- Beijing Genomics Institute-Shenzhen, Shenzhen, China
| | - Zhiguang Zhou
- Diabetes Center, The Second Xiangya Hospital, Institute of Metabolism and Endocrinology, Central South University, Changsha, China
| | - Sheng Ding
- Gladstone Institute of Cardiovascular Disease, Department of Pharmaceutical Chemistry, University of California, San Francisco, San Francisco, CA
| | - Donghai Wu
- CAS Key Laboratory of Regenerative Biology, Joint School of Life Sciences, Guangzhou Medical University, and Guangzhou Institute of Biomedicine and Health, Chinese Academy of Sciences, Guangzhou, China
- Joint School of Biological Sciences, Guangzhou Institute of Biomedicine and Health, Guangzhou Medical University, Guangzhou, China
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9
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Fischer AW, Shabalina IG, Mattsson CL, Abreu-Vieira G, Cannon B, Nedergaard J, Petrovic N. UCP1 inhibition in Cidea-overexpressing mice is physiologically counteracted by brown adipose tissue hyperrecruitment. Am J Physiol Endocrinol Metab 2017; 312:E72-E87. [PMID: 27923808 DOI: 10.1152/ajpendo.00284.2016] [Citation(s) in RCA: 35] [Impact Index Per Article: 5.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 07/18/2016] [Revised: 12/02/2016] [Accepted: 12/05/2016] [Indexed: 12/21/2022]
Abstract
Cidea is a gene highly expressed in thermogenesis-competent (UCP1-containing) adipose cells, both brown and brite/beige. Here, we initially demonstrate a remarkable adipose-depot specific regulation of Cidea expression. In classical brown fat, Cidea mRNA is expressed continuously and invariably, irrespective of tissue recruitment. However, Cidea protein levels are regulated posttranscriptionally, being conspicuously induced in the thermogenically recruited state. In contrast, in brite fat, Cidea protein levels are regulated at the transcriptional level, and Cidea mRNA and protein levels are proportional to tissue "briteness." Although routinely followed as a thermogenic molecular marker, Cidea function is not clarified. Here, we employed a gain-of-function approach to examine a possible role of Cidea in the regulation of thermogenesis. We utilized transgenic aP2-hCidea mice that overexpress human Cidea in all adipose tissues. We demonstrate that UCP1 activity is markedly suppressed in brown-fat mitochondria isolated from aP2-hCidea mice. However, mitochondrial UCP1 protein levels were identical in wild-type and transgenic mice. This implies a regulatory effect of Cidea on UCP1 activity, but as we demonstrate that Cidea itself is not localized to mitochondria, we propose an indirect inhibitory effect. The Cidea-induced inhibition of UCP1 activity (observed in isolated mitochondria) is physiologically relevant since the mice, through an appropriate homeostatic compensatory mechanism, increased the total amount of UCP1 in the tissue to exactly match the diminished thermogenic capacity of the UCP1 protein and retain unaltered nonshivering thermogenic capacity. Thus, we verified Cidea as being a marker of thermogenesis-competent adipose tissues, but we conclude that Cidea, unexpectedly, functions molecularly as an indirect inhibitor of thermogenesis.
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Affiliation(s)
- Alexander W Fischer
- Department of Molecular Biosciences, The Wenner-Gren Institute, Stockholm University, Stockholm, Sweden
- Department of Biochemistry and Molecular Cell Biology, University Medical Center Hamburg-Eppendorf, Hamburg, Germany; and
| | - Irina G Shabalina
- Department of Molecular Biosciences, The Wenner-Gren Institute, Stockholm University, Stockholm, Sweden
| | - Charlotte L Mattsson
- Department of Cell and Molecular Biology, Karolinska Institutet, Stockholm, Sweden
| | - Gustavo Abreu-Vieira
- Department of Molecular Biosciences, The Wenner-Gren Institute, Stockholm University, Stockholm, Sweden
| | - Barbara Cannon
- Department of Molecular Biosciences, The Wenner-Gren Institute, Stockholm University, Stockholm, Sweden
| | - Jan Nedergaard
- Department of Molecular Biosciences, The Wenner-Gren Institute, Stockholm University, Stockholm, Sweden
| | - Natasa Petrovic
- Department of Molecular Biosciences, The Wenner-Gren Institute, Stockholm University, Stockholm, Sweden;
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10
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Cheng Y, Mitchell-Flack MJ, Wang A, Levy RJ. Carbon monoxide modulates cytochrome oxidase activity and oxidative stress in the developing murine brain during isoflurane exposure. Free Radic Biol Med 2015; 86:191-9. [PMID: 26032170 PMCID: PMC4568063 DOI: 10.1016/j.freeradbiomed.2015.05.029] [Citation(s) in RCA: 25] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 01/05/2015] [Revised: 05/01/2015] [Accepted: 05/21/2015] [Indexed: 12/22/2022]
Abstract
Commonly used anesthetics induce widespread neuronal degeneration in the developing mammalian brain via the oxidative-stress-associated mitochondrial apoptosis pathway. Dysregulation of cytochrome oxidase (CcOX), the terminal oxidase of the electron transport chain, can result in reactive oxygen species (ROS) formation. Isoflurane has previously been shown to activate this enzyme. Carbon monoxide (CO), as a modulator of CcOX, is of interest because infants and children are routinely exposed to CO during low-flow anesthesia. We have recently demonstrated that low concentrations of CO limit and prevent isoflurane-induced neurotoxicity in the forebrains of newborn mice in a dose-dependent manner. However, the effect of CO on CcOX in the context of anesthetic-induced oxidative stress is unknown. Seven-day-old male CD-1 mice underwent 1h exposure to 0 (air), 5, or 100ppm CO in air with or without isoflurane. Exposure to isoflurane or CO independently increased CcOX kinetic activity and increased ROS within forebrain mitochondria. However, exposure to CO combined with isoflurane paradoxically limited CcOX activation and oxidative stress. There were no changes seen in steady-state levels of CcOX I protein, indicating post-translational modification of CcOX as an etiology for changes in enzyme activity. CO exposure led to differential effects on CcOX subunit I tyrosine phosphorylation depending on concentration, while combined exposure to isoflurane with CO markedly increased the enzyme phosphorylation state. Phosphorylation of tyrosine 304 of CcOX subunit I has been shown to result in strong enzyme inhibition, and the relative reduction in CcOX kinetics following exposure to CO combined with isoflurane may have been due, in part, to such phosphorylation. Taken together, the data suggest that CO modulates CcOX in the developing brain during isoflurane exposure, thereby limiting oxidative stress. These CO-mediated effects could have implications for the development of low-flow anesthesia in infants and children to prevent anesthesia-induced oxidative stress.
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Affiliation(s)
- Ying Cheng
- Division of Anesthesiology and Pain Medicine, Children's National Medical Center, The George Washington University School of Medicine and Health Sciences
| | - Marisa J Mitchell-Flack
- Department of Anesthesiology, College of Physicians and Surgeons of Columbia University, 622W. 168th Street, New York, NY 10032, USA
| | - Aili Wang
- Department of Anesthesiology, College of Physicians and Surgeons of Columbia University, 622W. 168th Street, New York, NY 10032, USA
| | - Richard J Levy
- Department of Anesthesiology, College of Physicians and Surgeons of Columbia University, 622W. 168th Street, New York, NY 10032, USA.
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Impact of Hyperpolarization-activated, Cyclic Nucleotide-gated Cation Channel Type 2 for the Xenon-mediated Anesthetic Effect: Evidence from In Vitro and In Vivo Experiments. Anesthesiology 2015; 122:1047-59. [PMID: 25782754 DOI: 10.1097/aln.0000000000000635] [Citation(s) in RCA: 12] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/01/2023]
Abstract
BACKGROUND The thalamus is thought to be crucially involved in the anesthetic state. Here, we investigated the effect of the inhaled anesthetic xenon on stimulus-evoked thalamocortical network activity and on excitability of thalamocortical neurons. Because hyperpolarization-activated, cyclic nucleotide-gated cation (HCN) channels are key regulators of neuronal excitability in the thalamus, the effect of xenon on HCN channels was examined. METHODS The effects of xenon on thalamocortical network activity were investigated in acutely prepared brain slices from adult wild-type and HCN2 knockout mice by means of voltage-sensitive dye imaging. The influence of xenon on single-cell excitability in brain slices was investigated using the whole-cell patch-clamp technique. Effects of xenon on HCN channels were verified in human embryonic kidney cells expressing HCN2 channels. RESULTS Xenon concentration-dependently diminished thalamocortical signal propagation. In neurons, xenon reduced HCN channel-mediated Ih current amplitude by 33.4 ± 12.2% (at -133 mV; n = 7; P = 0.041) and caused a left-shift in the voltage of half-maximum activation (V1/2) from -98.8 ± 1.6 to -108.0 ± 4.2 mV (n = 8; P = 0.035). Similar effects were seen in human embryonic kidney cells. The impairment of HCN channel function was negligible when intracellular cyclic adenosine monophosphate level was increased. Using HCN2 mice, we could demonstrate that xenon did neither attenuate in vitro thalamocortical signal propagation nor did it show sedating effects in vivo. CONCLUSIONS Here, we clearly showed that xenon impairs HCN2 channel function, and this impairment is dependent on intracellular cyclic adenosine monophosphate levels. We provide evidence that this effect reduces thalamocortical signal propagation and probably contributes to the hypnotic properties of xenon.
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12
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Abstract
Brown adipose tissue (BAT) plays a key role in energy homeostasis and thermogenesis in animals, conferring protection against diet-induced obesity and hypothermia through the action of uncoupling protein 1 (UCP1). Recent metabolic imaging studies using positron emission tomography computerized tomography (PET-CT) scanning have serendipitously revealed significant depots of BAT in the cervical-supraclavicular regions, demonstrating persistence of BAT beyond infancy. Subsequent cold-stimulated PET-CT studies and direct histological examination of adipose tissues have demonstrated that BAT is highly prevalent in adult humans. BAT activity correlates positively with increment of energy expenditure during cold exposure and negatively with age, body mass index, and fasting glycemia, suggesting regulatory links between BAT, cold-induced thermogenesis, and energy metabolism. Human BAT tissue biopsies express UCP1 and harbor inducible precursors that differentiate into UCP1-expressing adipocytes in vitro. These recent discoveries represent a metabolic renaissance for human adipose biology, overturning previous belief that BAT had no relevance in adult humans. They also have implications for the understanding of the pathogenesis and treatment of obesity and its metabolic sequelae.
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Affiliation(s)
- Paul Lee
- School of Medicine, University of Queensland, Brisbane, Queensland 4107, Australia.
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Zhang X, Kuo C, Moore A, Ran C. In vivo optical imaging of interscapular brown adipose tissue with (18)F-FDG via Cerenkov luminescence imaging. PLoS One 2013; 8:e62007. [PMID: 23637947 PMCID: PMC3634850 DOI: 10.1371/journal.pone.0062007] [Citation(s) in RCA: 35] [Impact Index Per Article: 3.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/04/2012] [Accepted: 03/16/2013] [Indexed: 01/21/2023] Open
Abstract
Objective Brown adipose tissue (BAT), a specialized tissue for thermogenesis, plays important roles for metabolism and energy expenditure. Recent studies validated BAT’s presence in human adults, making it an important re-emerging target for various pathologies. During this validation, PET images with 18F-FDG showed significant uptake of 18F-FDG by BAT under certain conditions. Here, we demonstrated that Cerenkov luminescence imaging (CLI) using 18F-FDG could be utilized for in vivo optical imaging of BAT in mice. Methods Mice were injected with 18F-FDG and imaged 60 minutes later with open filter and 2 minute acquisition. In vivo activation of BAT was performed by norepinephrine and cold treatment under isoflurane or ketamine anesthesia. Spectral unmixing and 3D imaging reconstruction were conducted with multiple-filter CLI images. Results 1) It was feasible to use CLI with 18F-FDG to image interscapular BAT in mice, with the majority of the signal (>85%) at the interscapular site originating from BAT; 2) The method was reliable because excellent correlations between in vivo CLI, ex vivo CLI, and ex vivo radioactivity were observed; 3) CLI could be used for monitoring BAT activation under different conditions; 4) CLI signals from the group under short-term isoflurane anesthesia were significantly higher than that from the group under long-term anesthesia; 5) The CLI spectrum of 18F-FDG with a peak at 640 nm in BAT after spectral unmixing reflected the actual context of BAT; 6) Finally 3D reconstruction images showed excellent correlation between the source of the light signal and the location and physical shape of BAT. Conclusion CLI with 18F-FDG is a feasible and reliable method for imaging BAT in mice. Compared to PET imaging, CLI is significantly cheaper, faster for 2D planar imaging and easier to use. We believe that this method could be used as an important tool for researchers investigating BAT.
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Affiliation(s)
- Xueli Zhang
- Molecular Imaging Laboratory, MGH/MIT/HMS Athinoula A. Martinos Center for Biomedical Imaging, Department of Radiology, Massachusetts General Hospital/Harvard Medical School, Charlestown, Massachusetts, United States of America
- Center for Drug Discovery, School of Pharmacy, China Pharmaceutical University, Nanjing, China
| | - Chaincy Kuo
- Caliper, a Perkin Elmer Company, Alameda, California, United States of America
| | - Anna Moore
- Molecular Imaging Laboratory, MGH/MIT/HMS Athinoula A. Martinos Center for Biomedical Imaging, Department of Radiology, Massachusetts General Hospital/Harvard Medical School, Charlestown, Massachusetts, United States of America
- * E-mail: (CR); (AM)
| | - Chongzhao Ran
- Molecular Imaging Laboratory, MGH/MIT/HMS Athinoula A. Martinos Center for Biomedical Imaging, Department of Radiology, Massachusetts General Hospital/Harvard Medical School, Charlestown, Massachusetts, United States of America
- * E-mail: (CR); (AM)
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Nicoll A, Moore D, Njoku D, Hockey B. Repeated exposure to modern volatile anaesthetics may cause chronic hepatitis as well as acute liver injury. BMJ Case Rep 2012; 2012:bcr-2012-006543. [PMID: 23131606 DOI: 10.1136/bcr-2012-006543] [Citation(s) in RCA: 11] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/04/2022] Open
Abstract
Volatile anaesthetic agents are known to cause acute hepatitis and fulminant hepatic failure in susceptible individuals. Four patients were identified with prolonged liver injury due to volatile anaesthetic-induced hepatitis. Three had liver biopsy confirmation and all gave blood for specific diagnostic tests (TFA and CYP 2E1 IgG4 antibodies). The Roussel Uclaf Causality Assessment Method (RUCAM) drug causality scale was used to determine the likelihood of volatile anaesthetics causing the chronic liver injury. We describe four cases of volatile anaesthetic hepatitis in which three evolved into chronic hepatitis. The fourth followed a more typical pattern of acute hepatitis; however, resolution took a few months. These cases all occurred with modern volatile anaesthetics, predominantly sevoflurane, and all cases were proven with specific antibody tests, liver histology and a drug causality scale. This is the first report of chronic liver injury due to volatile anaesthetic exposure.
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Affiliation(s)
- Amanda Nicoll
- Department of Gastroenterology and Hepatology, Royal Melbourne Hospital, Melbourne, Victoria, Australia.
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15
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Analysis of uncoupling protein 2-deficient mice upon anaesthesia and sedation revealed a role for UCP2 in locomotion. PLoS One 2012; 7:e41846. [PMID: 22900002 PMCID: PMC3416814 DOI: 10.1371/journal.pone.0041846] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/05/2011] [Accepted: 06/29/2012] [Indexed: 11/19/2022] Open
Abstract
General anaesthesia is associated with hypothermia, oxidative stress, and immune depression. Uncoupling Protein (UCP2) is a member of the mitochondrial carrier family present in many organs including the spleen, the lung and the brain. A role of UCP2 in the activation of the inflammatory/immune cells, in the secretion of hormones, and in the excitability of neurons by regulating the production of reactive oxygen species has been discussed. Because of the side effects of anaesthesia listed above, we aimed to question the expression and the function of UCP2 during anaesthesia. Induction of anaesthesia with ketamine (20 mg/kg) or isoflurane (3.6%) and induction of sedation with the α2 adrenergic receptor agonist medetomidine (0.2 mg/kg) stimulated infiltration of immune cells in the lung and increased UCP2 protein content in the lung, in both immune and non-immune cells. UCP2 content in the lung inversely correlated with body temperature decrease induced by medetomidine treatment. Challenge of the Ucp2−/− mice with isoflurane and medetomidine revealed an earlier behavioral recovery phenotype. Transponder analysis of body temperature and activity showed no difference between Ucp2−/− and control mice in basal conditions. However, upon an acute decrease of body temperature induced by medetomidine, Ucp2−/− mice exhibited increased locomotion activity. Together, these results show that UCP2 is rapidly mobilized during anaesthesia and sedation in immune cells, and suggest a role of UCP2 in locomotion.
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Betz MJ, Bielohuby M, Mauracher B, Abplanalp W, Müller HH, Pieper K, Ramisch J, Tschöp MH, Beuschlein F, Bidlingmaier M, Slawik M. Isoenergetic feeding of low carbohydrate-high fat diets does not increase brown adipose tissue thermogenic capacity in rats. PLoS One 2012; 7:e38997. [PMID: 22720011 PMCID: PMC3374780 DOI: 10.1371/journal.pone.0038997] [Citation(s) in RCA: 18] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/11/2012] [Accepted: 05/14/2012] [Indexed: 01/24/2023] Open
Abstract
Low-carbohydrate, high-fat (LC-HF) diets are popular for inducing weight loss in overweighed adults. Adaptive thermogenesis increased by specific effects of macronutrients on energy expenditure has been postulated to induce this weight loss. We studied brown adipose tissue (BAT) morphology and function following exposure to different LC-HF diets.
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Affiliation(s)
- Matthias J. Betz
- Endocrine Research Unit, Medizinische Klinik und Poliklinik IV, Klinikum der LMU, Munich, Germany
| | - Maximilian Bielohuby
- Endocrine Research Unit, Medizinische Klinik und Poliklinik IV, Klinikum der LMU, Munich, Germany
| | - Brigitte Mauracher
- Endocrine Research Unit, Medizinische Klinik und Poliklinik IV, Klinikum der LMU, Munich, Germany
| | - William Abplanalp
- Department of Medicine, Metabolic Diseases Institute, University of Cincinnati, Cincinnati, Ohio, United States of America
| | - Hans-Helge Müller
- Institute for Medical Informatics, Biometry and Epidemiology, Ludwig-Maximilians University, Munich, Germany
| | - Korbinian Pieper
- Clinic of Small Animal Surgery and Reproduction, Centre of Clinical Veterinary Medicine, Ludwig-Maximilians University, Munich, Germany
| | - Juliane Ramisch
- Endocrine Research Unit, Medizinische Klinik und Poliklinik IV, Klinikum der LMU, Munich, Germany
| | - Matthias H. Tschöp
- Institute for Diabetes and Obesity, Helmholtz Centre for Health and Environment and Technical University, Munich, Germany
| | - Felix Beuschlein
- Endocrine Research Unit, Medizinische Klinik und Poliklinik IV, Klinikum der LMU, Munich, Germany
| | - Martin Bidlingmaier
- Endocrine Research Unit, Medizinische Klinik und Poliklinik IV, Klinikum der LMU, Munich, Germany
| | - Marc Slawik
- Endocrine Research Unit, Medizinische Klinik und Poliklinik IV, Klinikum der LMU, Munich, Germany
- * E-mail:
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Hunt CM. Mitochondrial and immunoallergic injury increase risk of positive drug rechallenge after drug-induced liver injury: a systematic review. Hepatology 2010; 52:2216-22. [PMID: 21105110 DOI: 10.1002/hep.24022] [Citation(s) in RCA: 31] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 01/15/2023]
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18
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Hunt CM, Papay JI, Rich DS, Abissi CJ, Russo MW. The evaluation of drug rechallenge: the casopitant Phase III program. Regul Toxicol Pharmacol 2010; 58:539-43. [PMID: 20932869 DOI: 10.1016/j.yrtph.2010.09.014] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/29/2010] [Revised: 09/26/2010] [Accepted: 09/27/2010] [Indexed: 10/19/2022]
Abstract
Drug rechallenge (or reinitiation), following an event of drug-induced liver injury, is associated with 13% mortality in prospective series. Rechallenge generally results in much more rapid injury than the initial liver event. The neurokinin-1 antagonist casopitant or its placebo was administered cyclically with ondansetron and dexamethasone in two randomized chemotherapy-induced nausea and vomiting clinical trials in nearly 3000 subjects. Grade 3 ALT elevations were observed in up to 2% of subjects receiving casopitant or placebo treatment. Similar rates of positive rechallenge were observed in the casopitant 8/29 (28%) and placebo groups 2/8 (25%), with no Grade 4 ALT elevations, hypersensitivity or liver-related serious adverse events. Publishing available rechallenge data (positive and negative) will advance our clinical understanding. Rechallenge should only be considered when the potential drug benefit exceeds the risk.
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Mendez-Figueroa H, Shchelochkov OA, Shaibani A, Aagaard-Tillery K, Shinawi MS. Clinical and biochemical improvement of very long-chain acyl-CoA dehydrogenase deficiency in pregnancy. J Perinatol 2010; 30:558-62. [PMID: 20668464 DOI: 10.1038/jp.2009.198] [Citation(s) in RCA: 13] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/09/2022]
Abstract
Very long-chain acyl-CoA dehydrogenase (VLCAD) deficiency is an enzymatic defect of the fatty acid (FA) beta oxidation pathway. In catabolic states, such as labor and early postpartum period, patients are potentially prone to metabolic decompensation and subsequent rhabdomyolysis with increased risk for myoglobinuria and renal insufficiency. We report a 21-year-old primigravida with a previously characterized VLCAD deficiency, who experienced frequent and unprovoked episodes of rhabdomyolysis before pregnancy. As there was no published experience to guide her management, a detailed multidisciplinary care plan was established to minimize the potential morbidity. Although there is little known about the antenatal course of gravidae affected by VLCAD, we predicted that placental and fetal beta-oxidation in an unaffected pregnancy may temporize or even improve maternal FA beta-oxidation. Consistent with our prediction, we observed a significant clinical and biochemical improvement throughout her pregnancy, and she delivered vaginally with an uncomplicated postpartum course. We conclude that although VLCAD deficiency can present a therapeutic challenge during pregnancy, the beneficial placento-maternal metabolic interactions and the implementation of a proper peripartum management reassure a successful antenatal and perinatal outcome.
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Affiliation(s)
- H Mendez-Figueroa
- Department of Obstetrics and Gynecology, Baylor College of Medicine, Houston, TX 63110, USA
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20
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Shabalina IG, Backlund EC, Bar-Tana J, Cannon B, Nedergaard J. Within brown-fat cells, UCP1-mediated fatty acid-induced uncoupling is independent of fatty acid metabolism. BIOCHIMICA ET BIOPHYSICA ACTA-BIOENERGETICS 2008; 1777:642-50. [PMID: 18489899 DOI: 10.1016/j.bbabio.2008.04.038] [Citation(s) in RCA: 33] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 02/01/2008] [Revised: 03/30/2008] [Accepted: 04/23/2008] [Indexed: 12/21/2022]
Abstract
In the present investigation, we have utilized the availability of UCP1(-/-) mice to examine a wide range of previously proposed lipid activators of Uncoupling Protein 1 (UCP1) in its native environment, i.e. in the brown-fat cells. A non-metabolizable fatty acid analogue, beta,beta cent-methyl-substituted hexadecane alpha,omega-dicarboxylic acid (Medica-16) is a potent UCP1 (re)activator in brown-fat cells, despite its bipolar structure. All-trans-retinoic acid activates UCP1 within cells, whereas beta-carotene only does so after metabolism. The UCP1-dependent effects of fatty acids are positively correlated with their chain length. Medium-chain fatty acids are potent UCP1 activators in cells, despite their lack of protonophoric properties in mitochondrial membranes. Thus, neither the ability to be metabolized nor an innate uncoupling/protonophoric ability is a necessary property of UCP1 activators within brown-fat cells.
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Affiliation(s)
- Irina G Shabalina
- The Wenner-Gren Institute, The Arrhenius Laboratories F3, Stockholm University, SE-106 91 Stockholm, Sweden
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21
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Nedergaard J, Bengtsson T, Cannon B. Unexpected evidence for active brown adipose tissue in adult humans. Am J Physiol Endocrinol Metab 2007; 293:E444-52. [PMID: 17473055 DOI: 10.1152/ajpendo.00691.2006] [Citation(s) in RCA: 1279] [Impact Index Per Article: 75.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 02/07/2023]
Abstract
The contention that brown adipose tissue is absent in adult man has meant that processes attributed to active brown adipose tissue in experimental animals (mainly rodents), i.e., classical nonshivering thermogenesis, adaptive adrenergic thermogenesis, diet-induced thermogenesis, and antiobesity, should be either absent or attributed to alternative (unknown) mechanisms in man. However, serendipidously, as a consequence of the use of fluorodeoxyglucose positron emission tomography (FDG PET) to trace tumor metastasis, observations that may change that notion have recently been made. These tomography scans have visualized symmetrical areas of increased tracer uptake in the upper parts of the human body; these areas of uptake correspond to brown adipose tissue. We examine here the published observations from a viewpoint of human physiology. The human depots are somewhat differently located from those in rodents, the main depots being found in the supraclavicular and the neck regions with some additional paravertebral, mediastinal, para-aortic, and suprarenal localizations (but no interscapular). Brown adipose tissue activity in man is acutely cold induced and is stimulated via the sympathetic nervous system. The prevalence of active brown adipose tissue in normal adult man can be only indirectly estimated, but it would seem that the prevalence of active brown adipose tissue in the population may be at least in the range of some tens of percent. We conclude that a substantial fraction of adult humans possess active brown adipose tissue that thus has the potential to be of metabolic significance for normal human physiology as well as to become pharmaceutically activated in efforts to combat obesity.
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Affiliation(s)
- Jan Nedergaard
- The Wenner-Gren Institute, The Arrhenius Laboratories F3, Stockholm University, SE-106 91 Stockholm, Sweden.
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Golozoubova V, Cannon B, Nedergaard J. UCP1 is essential for adaptive adrenergic nonshivering thermogenesis. Am J Physiol Endocrinol Metab 2006; 291:E350-7. [PMID: 16595854 DOI: 10.1152/ajpendo.00387.2005] [Citation(s) in RCA: 175] [Impact Index Per Article: 9.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 02/08/2023]
Abstract
Participation of brown adipose tissue [through the action of the uncoupling protein-1 (UCP1)] in adaptive adrenergic nonshivering thermogenesis is recognized, but the existence of a response to adrenergic stimulation in UCP1-ablated mice implies that a mechanism for an alternative adaptive adrenergic thermogenesis may exist. Here, we have used UCP1-ablated mice to examine the existence of an alternative adaptive adrenergic nonshivering thermogenesis, examined as the oxygen consumption response to systemically injected norepinephrine into anesthetized or conscious mice acclimated to different temperatures. We confirm that UCP1-dependent adrenergic nonshivering thermogenesis is adaptive, but we demonstrate that the adrenergic UCP1-independent thermogenesis is not recruitable by cold acclimation. Thus, at least in the mouse, no other proteins or enzymatic pathways exist that can participate in or with time take over the UCP1 mediation of adaptive adrenergic nonshivering thermogenesis, even in the total absence of UCP1. UCP1 is thus the only protein capable of mediating cold acclimation-recruited adaptive adrenergic nonshivering thermogenesis.
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Affiliation(s)
- Valeria Golozoubova
- The Wenner-Gren Institute, The Arrhenius Laboratories F3, Stockholm University, SE-106 91, Stockholm, Sweden
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