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Sekar J, Attaway AH. The intersection of HIF-1α, O-GlcNAc, and skeletal muscle loss in chronic obstructive pulmonary disease. Glycobiology 2023; 33:873-878. [PMID: 37812446 PMCID: PMC10859630 DOI: 10.1093/glycob/cwad081] [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: 06/15/2023] [Revised: 09/29/2023] [Accepted: 10/04/2023] [Indexed: 10/10/2023] Open
Abstract
Sarcopenia, defined as the loss of muscle mass and strength, is a major cause of morbidity and mortality in COPD (chronic obstructive pulmonary disease) patients. However, the molecular mechanisms that cause sarcopenia remain to be determined. In this review, we will highlight the unique molecular and metabolic perturbations that occur in the skeletal muscle of COPD patients in response to hypoxia, and emphasize important areas of future research. In particular, the mechanisms related to the glycolytic shift that occurs in skeletal muscle in response to hypoxia may occur via a hypoxia-inducible factor 1-alpha (HIF-1α)-mediated mechanism. Upregulated glycolysis in skeletal muscle promotes a unique post-translational glycosylation of proteins known as O-GlcNAcylation, which further shifts metabolism toward glycolysis. Molecular changes in the skeletal muscle of COPD patients are associated with fiber-type shifting from Type I (oxidative) muscle fibers to Type II (glycolytic) muscle fibers. The metabolic shift toward glycolysis caused by HIF-1α and O-GlcNAc modified proteins suggests a potential cause for sarcopenia in COPD, which is an emerging area of future research.
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Affiliation(s)
- Jinendiran Sekar
- Division of Infectious Diseases, Harbor-UCLA Medical Center, 1000 West Carson Street, MRL Building, Box 466; Torrance, CA 90502, United States
- The Lundquist Institute for Biomedical Innovation at Harbor-UCLA Medical Center, 1124 W Carson St, Torrance, CA 90502, United States
| | - Amy H Attaway
- Respiratory Institute, Cleveland Clinic, Cleveland Clinic Main Campus, Mail Code A90, 9500 Euclid Avenue, Cleveland, OH 44195, United States
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Decker ST, Matias AA, Bannon ST, Madden JP, Alexandrou-Majaj N, Layec G. Effects of cigarette smoke on in situ mitochondrial substrate oxidation of slow- and fast-twitch skeletal muscles. Life Sci 2023; 315:121376. [PMID: 36646379 DOI: 10.1016/j.lfs.2023.121376] [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: 10/05/2022] [Revised: 12/23/2022] [Accepted: 01/03/2023] [Indexed: 01/15/2023]
Abstract
Epidemiological and clinical evidence suggests that cigarette smoke exposure alters glucose and fatty acid metabolism, leading to greater susceptibility to metabolic disorders. However, the effects of cigarette smoke exposure on mitochondrial substrate oxidation in the skeletal muscle are still poorly understood. Accordingly, this study aimed to examine the acute effects of cigarette smoke on mitochondrial respiratory capacity, sensitivity, and concurrent utilization of palmitoylcarnitine (PC), a long-chain fatty acid, and pyruvate, a product of glycolysis, in permeabilized gastrocnemius and soleus muscle fibers exposed to an acute (1 h) dose (4 %) of cigarette smoke concentrate. Cigarette smoke decreased both mitochondrial respiratory capacity (CONTROL: 50.4 ± 11.8 pmolO2/s/mgwt and SMOKE: 22.3 ± 4.4 pmolO2/s/mgwt, p < 0.01) and sensitivity for pyruvate (CONTROL: 0.10 ± 0.04 mM and SMOKE: 0.11 ± 0.04 mM, p < 0.01) in the gastrocnemius muscle. In the soleus, only the sensitivity for pyruvate-stimulated mitochondrial respiration trended toward a decrease (CONTROL: 0.11 ± 0.04 mM and SMOKE: 0.23 ± 0.15 mM, p = 0.08). In contrast, cigarette smoke did not significantly alter palmitoylcarnitine-stimulated mitochondrial respiration in either muscle. In the control condition, pyruvate-supported respiration was inhibited by the concurrent addition of palmitoylcarnitine in the fast-twitch gastrocnemius muscle (-27.1 ± 19.7 %, p < 0.05), but not in the slow-twitch soleus (-9.2 ± 17.0 %). With cigarette smoke, the addition of palmitoylcarnitine augmented the maximal respiration rate stimulated by the concurrent addition of pyruvate in the gastrocnemius (+18.5 ± 39.3 %, p < 0.05). However, cigarette smoke still significantly impaired mitochondrial respiratory capacity with combined substrates compared to control (p < 0.05). Our findings underscore that cigarette smoke directly impairs mitochondrial respiration of carbohydrate-derived substrates and is a primary mechanism underlying cigarette smoke-induced muscle dysfunction, which leads to a vicious cycle involving excess glucose conversion into fatty acids and lipotoxicity.
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Affiliation(s)
- Stephen T Decker
- Department of Kinesiology, University of Massachusetts Amherst, USA
| | - Alexs A Matias
- Department of Kinesiology, University of Massachusetts Amherst, USA
| | - Sean T Bannon
- Department of Kinesiology, University of Massachusetts Amherst, USA
| | - Jack P Madden
- Department of Kinesiology, University of Massachusetts Amherst, USA
| | | | - Gwenael Layec
- Department of Kinesiology, University of Massachusetts Amherst, USA; Institute for Applied Life Science, University of Massachusetts Amherst, USA.
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3
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Kwon OS, Decker ST, Zhao J, Hoidal JR, Heuckstadt T, Sanders KA, Richardson RS, Layec G. The receptor for advanced glycation end products (RAGE) is involved in mitochondrial function and cigarette smoke-induced oxidative stress. Free Radic Biol Med 2023; 195:261-269. [PMID: 36586455 DOI: 10.1016/j.freeradbiomed.2022.12.089] [Citation(s) in RCA: 3] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 10/01/2022] [Revised: 12/14/2022] [Accepted: 12/24/2022] [Indexed: 12/30/2022]
Abstract
The mechanisms underlying muscle dysfunction with Chronic Obstructive Pulmonary Disease (COPD) are poorly understood. Indirect evidence has recently suggested a role of Advanced Glycation End Products (AGEs) and their receptor (RAGE) in the pathophysiology of COPD. Accordingly, this study aimed to examine the redox balance and mitochondrial alterations in the skeletal muscle of a mouse model deficient in the receptor for AGE (RAGE-KO) and wild-type C57BL/6 exposed to cigarette smoke for 8-months using immunoblotting, spectrophotometry, and high-resolution respirometry. Cigarette smoke exposure increased by two-fold 4-HNE levels (P < 0.001), a marker of oxidative stress, and markedly downregulated contractile proteins, mitochondrial respiratory complexes, and uncoupling proteins levels (P < 0.001). Functional alterations with cigarette smoke exposure included a greater reliance on complex-I supported respiration (P < 0.01) and lower relative respiratory capacity for fatty acid (P < 0.05). RAGE knockout resulted in 47% lower 4-HNE protein levels than the corresponding WT control mice exposed to cigarette smoke (P < 0.05), which was partly attributed to increased Complex III protein levels. Independent of cigarette smoke exposure, RAGE KO decreased mitochondrial specific maximal respiration (P < 0.05), resulting in a compensatory increase in mitochondrial content measured by citrate synthase activity (P < 0.001) such that muscle respiratory capacity remained unaltered. Together, these findings suggest that knockout of RAGE protected the skeletal muscle against oxidative damage induced by 8 months of cigarette smoke exposure. In addition, this study supports a role for RAGE in regulating mitochondrial content and function and can thus serve as a potential therapeutic target.
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Affiliation(s)
- Oh Sung Kwon
- Department of Kinesiology, University of Connecticut, Storrs, CT, USA; UConn Center on Aging and Department of Orthopaedic Surgery, University of Connecticut, School of Medicine, Farmington, CT, USA; Geriatric Research, Education, and Clinical Center, George E. Whalen VA Medical Center, Salt Lake City, UT, USA; Department of Internal Medicine, Division of Geriatrics, University of Utah, Salt Lake City, UT, USA
| | - Stephen T Decker
- Department of Kinesiology, University of Massachusetts Amherst, USA
| | - Jia Zhao
- Geriatric Research, Education, and Clinical Center, George E. Whalen VA Medical Center, Salt Lake City, UT, USA; Department of Internal Medicine, Division of Geriatrics, University of Utah, Salt Lake City, UT, USA
| | - John R Hoidal
- George E. Wahlen Department of Veterans Affairs Medical Center, Salt Lake City, UT, USA; Department of Internal Medicine, Pulmonary Division, University of Utah, Salt Lake City, UT, USA; Division of Respiratory, Critical Care, and Occupational Pulmonary Medicine, University of Utah, Salt Lake City, UT, USA
| | - Thomas Heuckstadt
- George E. Wahlen Department of Veterans Affairs Medical Center, Salt Lake City, UT, USA; Department of Internal Medicine, Pulmonary Division, University of Utah, Salt Lake City, UT, USA; Division of Respiratory, Critical Care, and Occupational Pulmonary Medicine, University of Utah, Salt Lake City, UT, USA
| | - Karl A Sanders
- George E. Wahlen Department of Veterans Affairs Medical Center, Salt Lake City, UT, USA; Department of Internal Medicine, Pulmonary Division, University of Utah, Salt Lake City, UT, USA; Division of Respiratory, Critical Care, and Occupational Pulmonary Medicine, University of Utah, Salt Lake City, UT, USA
| | - Russell S Richardson
- Geriatric Research, Education, and Clinical Center, George E. Whalen VA Medical Center, Salt Lake City, UT, USA; Department of Internal Medicine, Division of Geriatrics, University of Utah, Salt Lake City, UT, USA; Department of Nutrition and Integrative Physiology, University of Utah, Salt Lake City, UT, USA
| | - Gwenael Layec
- Department of Kinesiology, University of Massachusetts Amherst, USA; Institute of Applied Life Science, University of Massachusetts Amherst, USA.
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Sanders KJC, Wierts R, van Marken Lichtenbelt WD, de Vos-Geelen J, Plasqui G, Kelders MCJM, Schrauwen-Hinderling VB, Bucerius J, Dingemans AMC, Mottaghy FM, Schols AMWJ. Brown adipose tissue activation is not related to hypermetabolism in emphysematous chronic obstructive pulmonary disease patients. J Cachexia Sarcopenia Muscle 2022; 13:1329-1338. [PMID: 35166050 PMCID: PMC8978002 DOI: 10.1002/jcsm.12881] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 11/15/2020] [Revised: 09/27/2021] [Accepted: 11/01/2021] [Indexed: 12/30/2022] Open
Abstract
BACKGROUND Brown adipose tissue (BAT) has been primarily researched as a potential target for mitigating obesity. However, the physiological significance of BAT in relation to cachexia remains poorly understood. The objective of this study was to investigate the putative contribution of BAT on different components of energy metabolism in emphysematous chronic obstructive pulmonary disease (COPD) patients. METHODS Twenty COPD patients (mean ± SD age 62 ± 6, 50% female, median [range] BMI 22.4 [15.1-32.5] kg/m2 and 85% low FFMI) were studied. Basal metabolic rate (BMR) was assessed by ventilated hood, total daily energy expenditure (TDEE) by doubly labelled water and physical activity by triaxial accelerometry. BMR was adjusted for fat-free mass (FFM) as assessed by deuterium dilution. Analysis of BAT and WAT was conducted in a subset of ten patients and six age-matched, gender-matched and BMI-matched healthy controls. BAT glucose uptake was assessed by means of cold-stimulated integrated [18F]FDG positron-emission tomography and magnetic resonance imaging. WAT was collected from subcutaneous abdominal biopsies to analyse metabolic and inflammatory gene expression levels. Lung function was assessed by spirometry and body plethysmography and systemic inflammation by high sensitivity C-reactive protein. RESULTS Mean TDEE was 2209 ± 394 kcal/day, and mean BMR was 1449 ± 214 kcal/day corresponding to 120% of predicted. FFM-adjusted BMR did not correlate with lung function or C-reactive protein. Upon cooling, energy expenditure increased, resulting in a non-shivering thermogenesis of (median [range]) 20.1% [3.3-41.3] in patients and controls. Mean BAT glucose uptake was comparable between COPD and controls (1.5 [0.1-6.2] vs. 1.1 [0.7-3.9]). In addition, no correlation was found between BMR adjusted for FFM and BAT activity or between cold-induced non-shivering energy expenditure and BAT activity. Gene expression levels of the brown adipocyte or beige markers were also comparable between the groups. No (serious) adverse events were reported. CONCLUSIONS Although COPD patients were hypermetabolic at rest, no correlation was found between BMR or TDEE and BAT activity. Furthermore, both BAT activity and gene expression levels of the brown adipocyte or beige markers were comparable between COPD patients and controls.
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Affiliation(s)
- Karin J C Sanders
- Department of Respiratory Medicine, NUTRIM School of Nutrition and Translational Research in Metabolism, Maastricht University Medical Centre, Maastricht, The Netherlands
| | - Roel Wierts
- Department of Radiology and Nuclear Medicine, Maastricht University Medical Centre, Maastricht, The Netherlands
| | - Wouter D van Marken Lichtenbelt
- Department of Nutrition and Movement Sciences, NUTRIM School of Nutrition and Translational Research in Metabolism, Maastricht University Medical Centre, Maastricht, The Netherlands
| | - Judith de Vos-Geelen
- Department of Internal Medicine, Division of Medical Oncology, GROW School for Oncology and Developmental Biology, Maastricht University Medical Centre, Maastricht, The Netherlands
| | - Guy Plasqui
- Department of Nutrition and Movement Sciences, NUTRIM School of Nutrition and Translational Research in Metabolism, Maastricht University Medical Centre, Maastricht, The Netherlands
| | - Marco C J M Kelders
- Department of Respiratory Medicine, NUTRIM School of Nutrition and Translational Research in Metabolism, Maastricht University Medical Centre, Maastricht, The Netherlands
| | - Vera B Schrauwen-Hinderling
- Department of Nutrition and Movement Sciences, NUTRIM School of Nutrition and Translational Research in Metabolism, Maastricht University Medical Centre, Maastricht, The Netherlands.,Department of Radiology and Nuclear Medicine, NUTRIM School for Nutrition and Translational Research in Maastricht, Maastricht University Medical Centre, Maastricht, The Netherlands
| | - Jan Bucerius
- Department of Radiology and Nuclear Medicine and CARIM School for Cardiovascular Research Institute Maastricht, Maastricht University Medical Centre, Maastricht, The Netherlands.,Department of Nuclear Medicine, University Medicine Göttingen, Georg-August-University Göttingen, Göttingen, Germany
| | | | - Felix M Mottaghy
- Department of Radiology and Nuclear Medicine, Maastricht University Medical Centre, Maastricht, The Netherlands.,Department of Nuclear Medicine and CIO ABCD, University Hospital RWTH Aachen University, Aachen, Germany
| | - Annemie M W J Schols
- Department of Respiratory Medicine, NUTRIM School of Nutrition and Translational Research in Metabolism, Maastricht University Medical Centre, Maastricht, The Netherlands
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5
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Decker ST, Kwon OS, Zhao J, Hoidal JR, Heuckstadt T, Richardson RS, Sanders KA, Layec G. Skeletal muscle mitochondrial adaptations induced by long-term cigarette smoke exposure. Am J Physiol Endocrinol Metab 2021; 321:E80-E89. [PMID: 34121449 PMCID: PMC8321829 DOI: 10.1152/ajpendo.00544.2020] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 11/02/2020] [Revised: 03/17/2021] [Accepted: 03/18/2021] [Indexed: 12/18/2022]
Abstract
Because patients with chronic obstructive pulmonary disease (COPD) are often physically inactive, it is still unclear whether the lower respiratory capacity in the locomotor muscles of these patients is due to cigarette smoking per se or is secondary to physical deconditioning. Accordingly, the purpose of this study was to examine mitochondrial alterations in the quadriceps muscle of 10 mice exposed to 8 mo of cigarette smoke, a sedentary mouse model of emphysema, and 9 control mice, using immunoblotting, spectrophotometry, and high-resolution respirometry in permeabilized muscle fibers. Mice exposed to smoke displayed a twofold increase in the oxidative stress marker, 4-HNE, (P < 0.05) compared with control mice. This was accompanied by significant decrease in protein expression of UCP3 (65%), ANT (58%), and mitochondrial complexes II-V (∼60%-75%). In contrast, maximal ADP-stimulated respiration with complex I and II substrates (CON: 23.6 ± 6.6 and SMO: 19.2 ± 8.2 ρM·mg-1·s-1) or octanoylcarnitine (CON: 21.8 ± 9.0 and SMO: 16.5 ± 6.6 ρM·mg-1·s-1) measured in permeabilized muscle fibers, as well as citrate synthase activity, were not significantly different between groups. Collectively, our findings revealed that sedentary mice exposed to cigarette smoke for 8 mo, which is typically associated with pulmonary inflammation and emphysema, exhibited a preserved mitochondrial respiratory capacity for various substrates, including fatty acid, in the skeletal muscle. However, the mitochondrial adaptations induced by cigarette smoke favored the development of chronic oxidative stress, which can indirectly contribute to augment the susceptibility to muscle fatigue and exercise intolerance.NEW & NOTEWORTHY It is unclear whether the exercise intolerance and skeletal muscle mitochondrial dysfunction observed in patients with COPD is due to cigarette smoke exposure, per se, or if they are secondary consequences to inactivity. Herein, while long-term exposure to cigarette smoke induces oxidative stress and an altered skeletal muscle phenotype, cigarette smoke does not directly contribute to mitochondrial dysfunction. With this evidence, we demonstrate the critical role of physical inactivity in cigarette smoke-related skeletal muscle dysfunction.
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Affiliation(s)
- Stephen T Decker
- Department of Kinesiology, University of Massachusetts Amherst, Amherst, Massachusetts
| | - Oh-Sung Kwon
- Department of Kinesiology, University of Connecticut, Storrs, Connecticut
- UConn Center on Aging and Department of Orthopaedic Surgery, University of Connecticut, School of Medicine, Farmington, Connecticut
- Geriatric Research, Education, and Clinical Center, George E. Wahlen VA Medical Center, Salt Lake City, Utah
- Department of Internal Medicine, Division of Geriatrics, University of Utah, Salt Lake City, Utah
| | - Jia Zhao
- Geriatric Research, Education, and Clinical Center, George E. Wahlen VA Medical Center, Salt Lake City, Utah
- Department of Internal Medicine, Division of Geriatrics, University of Utah, Salt Lake City, Utah
| | - John R Hoidal
- Department of Internal Medicine, Pulmonary Division, University of Utah, Salt Lake City, Utah
- George E. Wahlen Department of Veterans Affairs Medical Center, Salt Lake City, Utah
- Division of Respiratory, Critical Care, and Occupational Pulmonary Medicine, University of Utah, Salt Lake City, Utah
| | - Thomas Heuckstadt
- Department of Internal Medicine, Pulmonary Division, University of Utah, Salt Lake City, Utah
- George E. Wahlen Department of Veterans Affairs Medical Center, Salt Lake City, Utah
- Division of Respiratory, Critical Care, and Occupational Pulmonary Medicine, University of Utah, Salt Lake City, Utah
| | - Russell S Richardson
- Geriatric Research, Education, and Clinical Center, George E. Wahlen VA Medical Center, Salt Lake City, Utah
- Department of Internal Medicine, Division of Geriatrics, University of Utah, Salt Lake City, Utah
- Department of Nutrition and Integrative Physiology, University of Utah, Salt Lake City, Utah
| | - Karl A Sanders
- Department of Internal Medicine, Pulmonary Division, University of Utah, Salt Lake City, Utah
- George E. Wahlen Department of Veterans Affairs Medical Center, Salt Lake City, Utah
- Division of Respiratory, Critical Care, and Occupational Pulmonary Medicine, University of Utah, Salt Lake City, Utah
| | - Gwenael Layec
- Department of Kinesiology, University of Massachusetts Amherst, Amherst, Massachusetts
- Institute of Applied Life Science, University of Massachusetts Amherst, Amherst, Massachusetts
- Geriatric Research, Education, and Clinical Center, George E. Wahlen VA Medical Center, Salt Lake City, Utah
- Department of Internal Medicine, Division of Geriatrics, University of Utah, Salt Lake City, Utah
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6
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Machado FVC, Pitta F, Hernandes NA, Bertolini GL. Physiopathological relationship between chronic obstructive pulmonary disease and insulin resistance. Endocrine 2018; 61:17-22. [PMID: 29512058 DOI: 10.1007/s12020-018-1554-z] [Citation(s) in RCA: 11] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 10/23/2017] [Accepted: 01/31/2018] [Indexed: 12/16/2022]
Abstract
PURPOSE Chronic obstructive pulmonary disease (COPD) is characterized by persistent and progressive airflow obstruction that is associated with an abnormal chronic inflammatory response in the airways and lungs to noxious particles. COPD often leads to physical inactivity and deconditioning that added to inappropriate/excessive inflammatory responses leads to systemic consequences. Studies have shown that metabolic syndrome and manifested diabetes are more frequent in COPD than in healthy subjects; a possible explanation is that different pathophysiological aspects of COPD can lead to insulin resistance. Thus, this mini-review aims to present the main studies suggesting a pathophysiological relationship between COPD and insulin resistance. METHODS A review of literature was conducted using PubMed and Web of Science databases with the aim of searching for studies supporting a relationship between COPD and insulin resistance. RESULTS A physiopathological relationship between COPD and insulin resistance was found, supported in part due to common risk factors presented by these two conditions, such as smoking and physical inactivity. Also, systemic effects (worsening of physical inactivity and sedentary behavior, inflammation and oxidative stress, body composition abnormalities) and the corticosteroid treatment of patients with COPD may play a role. CONCLUSION Patients with COPD should be screened for abnormalities in insulin sensitivity in order to reduce morbidity and improve health status in this population.
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Affiliation(s)
- Felipe Vilaça Cavallari Machado
- Department of Physiotherapy, Laboratory of Research in Respiratory Physiotherapy (LFIP), State University of Londrina (UEL), Londrina, Paraná, Brazil
| | - Fabio Pitta
- Department of Physiotherapy, Laboratory of Research in Respiratory Physiotherapy (LFIP), State University of Londrina (UEL), Londrina, Paraná, Brazil
| | - Nidia Aparecida Hernandes
- Department of Physiotherapy, Laboratory of Research in Respiratory Physiotherapy (LFIP), State University of Londrina (UEL), Londrina, Paraná, Brazil
| | - Gisele Lopes Bertolini
- Department of Physiological Sciences, State University of Londrina (UEL), Londrina, Paraná, Brazil.
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Iepsen UW, Munch GW, Rugbjerg M, Ryrsø CK, Secher NH, Hellsten Y, Lange P, Pedersen BK, Thaning P, Mortensen SP. Leg blood flow is impaired during small muscle mass exercise in patients with COPD. J Appl Physiol (1985) 2017; 123:624-631. [DOI: 10.1152/japplphysiol.00178.2017] [Citation(s) in RCA: 10] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/24/2017] [Revised: 07/05/2017] [Accepted: 07/12/2017] [Indexed: 11/22/2022] Open
Abstract
Skeletal muscle blood flow is regulated to match the oxygen demand and dysregulation could contribute to exercise intolerance in patients with chronic obstructive pulmonary disease (COPD). We measured leg hemodynamics and metabolites from vasoactive compounds in muscle interstitial fluid and plasma at rest, during one-legged knee-extensor exercise, and during arterial infusions of sodium nitroprusside (SNP) and acetylcholine (ACh), respectively. Ten patients with moderate to severe COPD and eight age- and sex-matched healthy controls were studied. During knee-extensor exercise (10 W), leg blood flow was lower in the patients compared with the controls (1.82 ± 0.11 vs. 2.36 ± 0.14 l/min, respectively; P < 0.05), which compromised leg oxygen delivery (372 ± 26 vs. 453 ± 32 ml O2/min, respectively; P < 0.05). At rest, plasma endothelin-1 (vasoconstrictor) was higher in the patients with COPD ( P < 0.05) and also tended to be higher during exercise ( P = 0.07), whereas the formation of interstitial prostacyclin (vasodilator) was only increased in the controls. There was no difference between groups in the nitrite/nitrate levels (vasodilator) in plasma or interstitial fluid during exercise. Moreover, patients and controls showed similar vasodilatory capacity in response to both endothelium-independent (SNP) and endothelium-dependent (ACh) stimulation. The results suggest that leg muscle blood flow is impaired during small muscle mass exercise in patients with COPD possibly due to impaired formation of prostacyclin and increased levels of endothelin-1. NEW & NOTEWORTHY This study demonstrates that chronic obstructive pulmonary disease (COPD) is associated with a reduced blood flow to skeletal muscle during small muscle mass exercise. In contrast to healthy individuals, interstitial prostacyclin levels did not increase during exercise and plasma endothelin-1 levels were higher in the patients with COPD.
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Affiliation(s)
- U. W. Iepsen
- Centre of Inflammation and Metabolism and the Centre for Physical Activity Research, Rigshospitalet, University of Copenhagen, Copenhagen, Denmark
| | - G. W. Munch
- Centre of Inflammation and Metabolism and the Centre for Physical Activity Research, Rigshospitalet, University of Copenhagen, Copenhagen, Denmark
| | - M. Rugbjerg
- Centre of Inflammation and Metabolism and the Centre for Physical Activity Research, Rigshospitalet, University of Copenhagen, Copenhagen, Denmark
| | - C. K. Ryrsø
- Centre of Inflammation and Metabolism and the Centre for Physical Activity Research, Rigshospitalet, University of Copenhagen, Copenhagen, Denmark
| | - N. H. Secher
- Department of Anesthesiology, the Copenhagen Muscle Research Center, Rigshospitalet, University of Copenhagen, Copenhagen, Denmark
| | - Y. Hellsten
- Department of Nutrition, Exercise and Sports, University of Copenhagen, Copenhagen, Denmark
| | - P. Lange
- Centre of Inflammation and Metabolism and the Centre for Physical Activity Research, Rigshospitalet, University of Copenhagen, Copenhagen, Denmark
- Department of Respiratory Medicine, University Hospital Hvidovre, Hvidovre, Denmark
- Department of Public Health, Section of Social Medicine, University of Copenhagen, Copenhagen, Denmark; and
| | - B. K. Pedersen
- Centre of Inflammation and Metabolism and the Centre for Physical Activity Research, Rigshospitalet, University of Copenhagen, Copenhagen, Denmark
| | - P. Thaning
- Centre of Inflammation and Metabolism and the Centre for Physical Activity Research, Rigshospitalet, University of Copenhagen, Copenhagen, Denmark
- Department of Respiratory Medicine, University Hospital Hvidovre, Hvidovre, Denmark
| | - S. P. Mortensen
- Centre of Inflammation and Metabolism and the Centre for Physical Activity Research, Rigshospitalet, University of Copenhagen, Copenhagen, Denmark
- Department of Cardiovascular and Renal Research, University of Southern Denmark, Odense, Denmark
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8
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Layec G, Hart CR, Trinity JD, Kwon OS, Rossman MJ, Broxterman RM, Le Fur Y, Jeong EK, Richardson RS. Oxygen delivery and the restoration of the muscle energetic balance following exercise: implications for delayed muscle recovery in patients with COPD. Am J Physiol Endocrinol Metab 2017; 313:E94-E104. [PMID: 28292763 PMCID: PMC6109703 DOI: 10.1152/ajpendo.00462.2016] [Citation(s) in RCA: 8] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 12/22/2016] [Revised: 03/03/2017] [Accepted: 03/13/2017] [Indexed: 11/22/2022]
Abstract
Patients with chronic obstructive pulmonary disease (COPD) experience a delayed recovery from skeletal muscle fatigue following exhaustive exercise that likely contributes to their progressive loss of mobility. As this phenomenon is not well understood, this study sought to examine postexercise peripheral oxygen (O2) transport and muscle metabolism dynamics in patients with COPD, two important determinants of muscle recovery. Twenty-four subjects, 12 nonhypoxemic patients with COPD and 12 healthy subjects with a sedentary lifestyle, performed dynamic plantar flexion exercise at 40% of the maximal work rate (WRmax) with phosphorus magnetic resonance spectroscopy (31P-MRS), near-infrared spectroscopy (NIRS), and vascular Doppler ultrasound assessments. The mean response time of limb blood flow at the offset of exercise was significantly prolonged in patients with COPD (controls: 56 ± 27 s; COPD: 120 ± 87 s; P < 0.05). In contrast, the postexercise time constant for capillary blood flow was not significantly different between groups (controls: 49 ± 23 s; COPD: 51 ± 21 s; P > 0.05). The initial postexercise convective O2 delivery (controls: 0.15 ± 0.06 l/min; COPD: 0.15 ± 0.06 l/min) and the corresponding oxidative adenosine triphosphate (ATP) demand (controls: 14 ± 6 mM/min; COPD: 14 ± 6 mM/min) in the calf were not significantly different between controls and patients with COPD (P > 0.05). The phosphocreatine resynthesis time constant (controls: 46 ± 20 s; COPD: 49 ± 21 s), peak mitochondrial phosphorylation rate, and initial proton efflux were also not significantly different between groups (P > 0.05). Therefore, despite perturbed peripheral hemodynamics, intracellular O2 availability, proton efflux, and aerobic metabolism recovery in the skeletal muscle of nonhypoxemic patients with COPD are preserved following plantar flexion exercise and thus are unlikely to contribute to the delayed recovery from exercise in this population.
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Affiliation(s)
- Gwenael Layec
- Department of Medicine, Division of Geriatrics, University of Utah, Salt Lake City, Utah;
- Geriatric Research, Education, and Clinical Center, George E. Whalen Veterans Affairs Medical Center, Salt Lake City, Utah
- Department of Nutrition and Integrative Physiology, University of Utah, Salt Lake City, Utah
| | - Corey R Hart
- Geriatric Research, Education, and Clinical Center, George E. Whalen Veterans Affairs Medical Center, Salt Lake City, Utah
- Department of Exercise and Sport Science, University of Utah, Salt Lake City, Utah
| | - Joel D Trinity
- Department of Medicine, Division of Geriatrics, University of Utah, Salt Lake City, Utah
- Geriatric Research, Education, and Clinical Center, George E. Whalen Veterans Affairs Medical Center, Salt Lake City, Utah
- Department of Nutrition and Integrative Physiology, University of Utah, Salt Lake City, Utah
| | - Oh-Sung Kwon
- Department of Medicine, Division of Geriatrics, University of Utah, Salt Lake City, Utah
- Geriatric Research, Education, and Clinical Center, George E. Whalen Veterans Affairs Medical Center, Salt Lake City, Utah
| | - Matthew J Rossman
- Geriatric Research, Education, and Clinical Center, George E. Whalen Veterans Affairs Medical Center, Salt Lake City, Utah
- Department of Exercise and Sport Science, University of Utah, Salt Lake City, Utah
| | - Ryan M Broxterman
- Department of Medicine, Division of Geriatrics, University of Utah, Salt Lake City, Utah
- Geriatric Research, Education, and Clinical Center, George E. Whalen Veterans Affairs Medical Center, Salt Lake City, Utah
| | - Yann Le Fur
- Centre de Résonance Magnétique Biologique et Médicale, Aix-Marseille Universite, Centre National de la Recherche Scientifique, Marseille, France; and
| | - Eun-Kee Jeong
- Department of Radiology and Utah Center for Advanced Imaging Research, University of Utah, Salt Lake City, Utah
| | - Russell S Richardson
- Department of Medicine, Division of Geriatrics, University of Utah, Salt Lake City, Utah
- Geriatric Research, Education, and Clinical Center, George E. Whalen Veterans Affairs Medical Center, Salt Lake City, Utah
- Department of Nutrition and Integrative Physiology, University of Utah, Salt Lake City, Utah
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9
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Alekseev AE, Guzun R, Reyes S, Pison C, Schlattner U, Selivanov VA, Cascante M. Restrictions in ATP diffusion within sarcomeres can provoke ATP-depleted zones impairing exercise capacity in chronic obstructive pulmonary disease. Biochim Biophys Acta Gen Subj 2016; 1860:2269-78. [PMID: 27130881 DOI: 10.1016/j.bbagen.2016.04.018] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Key Words] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/25/2016] [Revised: 04/21/2016] [Accepted: 04/23/2016] [Indexed: 11/29/2022]
Abstract
BACKGROUND Chronic obstructive pulmonary disease (COPD) is characterized by the inability of patients to sustain a high level of ventilation resulting in perceived exertional discomfort and limited exercise capacity of leg muscles at average intracellular ATP levels sufficient to support contractility. METHODS Myosin ATPase activity in biopsy samples from healthy and COPD individuals was implemented as a local nucleotide sensor to determine ATP diffusion coefficients within myofibrils. Ergometric parameters clinically measured during maximal exercise tests in both groups were used to define the rates of myosin ATPase reaction and aerobic ATP re-synthesis. The obtained parameters in combination with AK- and CK-catalyzed reactions were implemented to compute the kinetic and steady-state spatial ATP distributions within control and COPD sarcomeres. RESULTS The developed reaction-diffusion model of two-dimensional sarcomeric space identified similar, yet extremely low nucleotide diffusion in normal and COPD myofibrils. The corresponding spatio-temporal ATP distributions, constructed during imposed exercise, predicted in COPD sarcomeres a depletion of ATP in the zones of overlap between actin and myosin filaments along the center axis at average cytosolic ATP levels similar to healthy muscles. CONCLUSIONS ATP-depleted zones can induce rigor tension foci impairing muscle contraction and increase a risk for sarcomere damages. Thus, intra-sarcomeric diffusion restrictions at limited aerobic ATP re-synthesis can be an additional risk factor contributing to the muscle contractile deficiency experienced by COPD patients. GENERAL SIGNIFICANCE This study demonstrates how restricted substrate mobility within a cellular organelle can provoke an energy imbalance state paradoxically occurring at abounding average metabolic resources.
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Affiliation(s)
- Alexey E Alekseev
- Marriott Heart Disease Research Program, Division of Cardiovascular Diseases, Department of Internal Medicine, Department of Molecular Pharmacology & Experimental Therapeutics, Department of Medical Genetics, Mayo Clinic, 200 First St. SW, Rochester, MN, USA; Institute of Theoretical and Experimental Biophysics, Russian Academy of Science, Institutskaya 3, Pushchino, Moscow Region 142290, Russia.
| | - Rita Guzun
- Univ. Grenoble Alpes, Laboratory of Fundamental and Applied Bioenergetics (LBFA), and SFR Environmental and Systems Biology (BEeSy), Grenoble, France; Inserm, U1055, Grenoble, France
| | - Santiago Reyes
- Marriott Heart Disease Research Program, Division of Cardiovascular Diseases, Department of Internal Medicine, Department of Molecular Pharmacology & Experimental Therapeutics, Department of Medical Genetics, Mayo Clinic, 200 First St. SW, Rochester, MN, USA
| | - Christophe Pison
- Univ. Grenoble Alpes, Laboratory of Fundamental and Applied Bioenergetics (LBFA), and SFR Environmental and Systems Biology (BEeSy), Grenoble, France; Inserm, U1055, Grenoble, France; Clinique Universitaire de Pneumologie, Pôle Thorax et Vaisseaux, Centre Hospitalier et Universitaire des Alpes, CS10217, 38043 Grenoble Cedex 9, France
| | - Uwe Schlattner
- Univ. Grenoble Alpes, Laboratory of Fundamental and Applied Bioenergetics (LBFA), and SFR Environmental and Systems Biology (BEeSy), Grenoble, France; Inserm, U1055, Grenoble, France
| | - Vitaly A Selivanov
- Departament de Bioquimica i Biologia Molecular, Facultat de Biologia, Universitat de Barcelona, and IBUB Barcelona, Gran Via de les Corts Catalanes 585, 08007 Barcelona, Spain
| | - Marta Cascante
- Departament de Bioquimica i Biologia Molecular, Facultat de Biologia, Universitat de Barcelona, and IBUB Barcelona, Gran Via de les Corts Catalanes 585, 08007 Barcelona, Spain.
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10
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Wells CE, Polkey MI, Baker EH. Insulin resistance is associated with skeletal muscle weakness in COPD. Respirology 2015; 21:689-96. [DOI: 10.1111/resp.12716] [Citation(s) in RCA: 12] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/26/2015] [Revised: 10/21/2015] [Accepted: 10/21/2015] [Indexed: 12/25/2022]
Affiliation(s)
- Claire E Wells
- Institute of Infection and Immunity (mail point J1A); St George's, University of London; London UK
| | - Michael I Polkey
- NIHR Respiratory Biomedical Research Unit; Royal Brompton and Harefield NHS Foundation Trust and Imperial College; London UK
| | - Emma H Baker
- Institute of Infection and Immunity (mail point J1A); St George's, University of London; London UK
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11
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Remels AHV, Gosker HR, Verhees KJP, Langen RCJ, Schols AMWJ. TNF-α-induced NF-κB activation stimulates skeletal muscle glycolytic metabolism through activation of HIF-1α. Endocrinology 2015; 156:1770-81. [PMID: 25710281 DOI: 10.1210/en.2014-1591] [Citation(s) in RCA: 59] [Impact Index Per Article: 6.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 12/25/2022]
Abstract
A shift in quadriceps muscle metabolic profile toward decreased oxidative metabolism and increased glycolysis is a consistent finding in chronic obstructive pulmonary disease (COPD). Chronic inflammation has been proposed as a trigger of this pathological metabolic adaptation. Indeed, the proinflammatory cytokine TNF-α impairs muscle oxidative metabolism through activation of the nuclear factor-κB (NF-κB) pathway. Putative effects on muscle glycolysis, however, are unclear. We hypothesized that TNF-α-induced NF-κB signaling stimulates muscle glycolytic metabolism through activation of the glycolytic regulator hypoxia-inducible factor-1α (HIF-1α). Wild-type C2C12 and C2C12-IκBα-SR (blocked NF-κB signaling) myotubes were stimulated with TNF-α, and its effects on glycolytic metabolism and involvement of the HIF pathway herein were investigated. As proof of principle, expression of HIF signaling constituents was investigated in quadriceps muscle biopsies of a previously well-characterized cohort of clinically stable patients with severe COPD and healthy matched controls. TNF-α increased myotube glucose uptake and lactate production and enhanced the activity and expression levels of multiple effectors of muscle glycolytic metabolism in a NF-κB-dependent manner. In addition, TNF-α activated HIF signaling, which required classical NF-κB activation. Moreover, the knockdown of HIF-1α largely attenuated TNF-α-induced increases in glycolytic metabolism. Accordingly, the mRNA levels of HIF-1α and the HIF-1α target gene, vascular endothelial growth factor (VEGF), were increased in muscle biopsies of COPD patients compared with controls, which was most pronounced in the patients with high levels of muscle TNF-α. In conclusion, these data show that TNF-α-induced classical NF-κB activation enhances muscle glycolytic metabolism in a HIF-1α-dependent manner.
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Affiliation(s)
- A H V Remels
- NUTRIM School of Nutrition and Translational Research in Metabolism, Department of Respiratory Medicine, Maastricht University Medical Center +, 6202 AZ Maastricht, the Netherlands
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12
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Maltais F, Decramer M, Casaburi R, Barreiro E, Burelle Y, Debigaré R, Dekhuijzen PNR, Franssen F, Gayan-Ramirez G, Gea J, Gosker HR, Gosselink R, Hayot M, Hussain SNA, Janssens W, Polkey MI, Roca J, Saey D, Schols AMWJ, Spruit MA, Steiner M, Taivassalo T, Troosters T, Vogiatzis I, Wagner PD. An official American Thoracic Society/European Respiratory Society statement: update on limb muscle dysfunction in chronic obstructive pulmonary disease. Am J Respir Crit Care Med 2014; 189:e15-62. [PMID: 24787074 DOI: 10.1164/rccm.201402-0373st] [Citation(s) in RCA: 680] [Impact Index Per Article: 68.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/11/2022] Open
Abstract
BACKGROUND Limb muscle dysfunction is prevalent in chronic obstructive pulmonary disease (COPD) and it has important clinical implications, such as reduced exercise tolerance, quality of life, and even survival. Since the previous American Thoracic Society/European Respiratory Society (ATS/ERS) statement on limb muscle dysfunction, important progress has been made on the characterization of this problem and on our understanding of its pathophysiology and clinical implications. PURPOSE The purpose of this document is to update the 1999 ATS/ERS statement on limb muscle dysfunction in COPD. METHODS An interdisciplinary committee of experts from the ATS and ERS Pulmonary Rehabilitation and Clinical Problems assemblies determined that the scope of this document should be limited to limb muscles. Committee members conducted focused reviews of the literature on several topics. A librarian also performed a literature search. An ATS methodologist provided advice to the committee, ensuring that the methodological approach was consistent with ATS standards. RESULTS We identified important advances in our understanding of the extent and nature of the structural alterations in limb muscles in patients with COPD. Since the last update, landmark studies were published on the mechanisms of development of limb muscle dysfunction in COPD and on the treatment of this condition. We now have a better understanding of the clinical implications of limb muscle dysfunction. Although exercise training is the most potent intervention to address this condition, other therapies, such as neuromuscular electrical stimulation, are emerging. Assessment of limb muscle function can identify patients who are at increased risk of poor clinical outcomes, such as exercise intolerance and premature mortality. CONCLUSIONS Limb muscle dysfunction is a key systemic consequence of COPD. However, there are still important gaps in our knowledge about the mechanisms of development of this problem. Strategies for early detection and specific treatments for this condition are also needed.
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13
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Musculoskeletal disorders in chronic obstructive pulmonary disease. BIOMED RESEARCH INTERNATIONAL 2014; 2014:965764. [PMID: 24783225 PMCID: PMC3982416 DOI: 10.1155/2014/965764] [Citation(s) in RCA: 49] [Impact Index Per Article: 4.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 09/20/2013] [Accepted: 02/13/2014] [Indexed: 12/17/2022]
Abstract
Chronic obstructive pulmonary disease (COPD) is a lung disease characterized by airway obstruction and inflammation but also accompanied by several extrapulmonary consequences, such as skeletal muscle weakness and osteoporosis. Skeletal muscle weakness is of major concern, since it leads to poor functional capacity, impaired health status, increased healthcare utilization, and even mortality, independently of lung function. Osteoporosis leads to fractures and is associated with increased mortality, functional decline, loss of quality of life, and need for institutionalization. Therefore, the presence of the combination of these comorbidities will have a negative impact on daily life in patients with COPD. In this review, we will focus on these two comorbidities, their prevalence in COPD, combined risk factors, and pathogenesis. We will try to prove the clustering of these comorbidities and discuss possible preventive or therapeutic strategies.
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14
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Cissik JM. The Effects of Chronic Obstructive Pulmonary Disease. Strength Cond J 2013. [DOI: 10.1519/ssc.0b013e31829776b3] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/08/2022]
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15
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Remels AHV, Gosker HR, Langen RCJ, Schols AMWJ. The mechanisms of cachexia underlying muscle dysfunction in COPD. J Appl Physiol (1985) 2013; 114:1253-62. [DOI: 10.1152/japplphysiol.00790.2012] [Citation(s) in RCA: 107] [Impact Index Per Article: 9.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/18/2022] Open
Abstract
Pulmonary cachexia is a prevalent, debilitating, and well-recognized feature of COPD associated with increased mortality and loss of peripheral and respiratory muscle function. The exact cause and underlying mechanisms of cachexia in COPD are still poorly understood. Increasing evidence, however, shows that pathological changes in intracellular mechanisms of muscle mass maintenance (i.e., protein turnover and myonuclear turnover) are likely involved. Potential factors triggering alterations in these mechanisms in COPD include oxidative stress, myostatin, and inflammation. In addition to muscle wasting, peripheral muscle in COPD is characterized by a fiber-type shift toward a more type II, glycolytic phenotype and an impaired oxidative capacity (collectively referred to as an impaired oxidative phenotype). Atrophied diaphragm muscle in COPD, however, displays an enhanced oxidative phenotype. Interestingly, intrinsic abnormalities in (lower limb) peripheral muscle seem more pronounced in either cachectic patients or weight loss-susceptible emphysema patients, suggesting that muscle wasting and intrinsic changes in peripheral muscle's oxidative phenotype are somehow intertwined. In this manuscript, we will review alterations in mechanisms of muscle mass maintenance in COPD and discuss the involvement of oxidative stress, inflammation, and myostatin as potential triggers of cachexia. Moreover, we postulate that an impaired muscle oxidative phenotype in COPD can accelerate the process of cachexia, as it renders muscle in COPD less energy efficient, thereby contributing to an energy deficit and weight loss when not dietary compensated. Furthermore, loss of peripheral muscle oxidative phenotype may increase the muscle's susceptibility to inflammation- and oxidative stress-induced muscle damage and wasting.
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Affiliation(s)
- A. H. V. Remels
- NUTRIM School for Nutrition, Toxicology and Metabolism, Department of Respiratory Medicine, Maastricht University Medical Centre +, Maastricht, the Netherlands
| | - H. R. Gosker
- NUTRIM School for Nutrition, Toxicology and Metabolism, Department of Respiratory Medicine, Maastricht University Medical Centre +, Maastricht, the Netherlands
| | - R. C. J. Langen
- NUTRIM School for Nutrition, Toxicology and Metabolism, Department of Respiratory Medicine, Maastricht University Medical Centre +, Maastricht, the Netherlands
| | - A. M. W. J. Schols
- NUTRIM School for Nutrition, Toxicology and Metabolism, Department of Respiratory Medicine, Maastricht University Medical Centre +, Maastricht, the Netherlands
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16
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Puente-Maestu L, Lázaro A, Humanes B. Metabolic derangements in COPD muscle dysfunction. J Appl Physiol (1985) 2013; 114:1282-90. [PMID: 23288549 DOI: 10.1152/japplphysiol.00815.2012] [Citation(s) in RCA: 26] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/10/2023] Open
Abstract
Mitochondrial muscle alterations are common in patients with chronic obstructive pulmonary disease (COPD) and manifest mainly as decreased oxidative capacity and excessive production of reactive oxygen species (ROS). The significant loss of oxidative capacity observed in the quadriceps of COPD patients is mainly due to reduced mitochondrial content in the fibers, a finding consistent with the characteristic loss of type I fibers observed in that muscle. Decreased oxidative capacity does not directly limit maximum performance; however, it is associated with increased lactate production at lower exercise intensity and reduced endurance. Since type I fiber atrophy does not occur in respiratory muscles, the loss of such fibers in the quadriceps could be to the result of disuse. In contrast, excessive production of ROS and oxidative stress are observed in both the respiratory muscles and the quadriceps of COPD patients. The causes of increased ROS production are not clear, and a number of different mechanisms can play a role. Several mitochondrial alterations in the quadriceps of COPD patients are similar to those observed in diabetic patients, thus suggesting a role for muscle alterations in this comorbidity. Amino acid metabolism is also altered. Expression of peroxisome proliferator-activated receptor-γ coactivator-1α mRNA is low in the quadriceps of COPD patients, which could also be a consequence of type I fiber loss; nevertheless, its response to exercise is not altered. Patterns of muscle cytochrome oxidase gene activation after training differ between COPD patients and healthy subjects, and the profile is consistent with hypoxic stress, even in nonhypoxic patients.
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Affiliation(s)
- Luis Puente-Maestu
- Servicio de Neumología, Hospital General Gregorio Marañón, Universidad Complutense de Madrid, Instituto de Investigación Sanitaria Gregorio Marañón, Madrid, Spain.
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17
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Mirrakhimov AE. Chronic obstructive pulmonary disease and glucose metabolism: a bitter sweet symphony. Cardiovasc Diabetol 2012; 11:132. [PMID: 23101436 PMCID: PMC3499352 DOI: 10.1186/1475-2840-11-132] [Citation(s) in RCA: 86] [Impact Index Per Article: 7.2] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 08/31/2012] [Accepted: 10/04/2012] [Indexed: 01/05/2023] Open
Abstract
Chronic obstructive pulmonary disease, metabolic syndrome and diabetes mellitus are common and underdiagnosed medical conditions. It was predicted that chronic obstructive pulmonary disease will be the third leading cause of death worldwide by 2020. The healthcare burden of this disease is even greater if we consider the significant impact of chronic obstructive pulmonary disease on the cardiovascular morbidity and mortality. Chronic obstructive pulmonary disease may be considered as a novel risk factor for new onset type 2 diabetes mellitus via multiple pathophysiological alterations such as: inflammation and oxidative stress, insulin resistance, weight gain and alterations in metabolism of adipokines. On the other hand, diabetes may act as an independent factor, negatively affecting pulmonary structure and function. Diabetes is associated with an increased risk of pulmonary infections, disease exacerbations and worsened COPD outcomes. On the top of that, coexistent OSA may increase the risk for type 2 DM in some individuals. The current scientific data necessitate a greater outlook on chronic obstructive pulmonary disease and chronic obstructive pulmonary disease may be viewed as a risk factor for the new onset type 2 diabetes mellitus. Conversely, both types of diabetes mellitus should be viewed as strong contributing factors for the development of obstructive lung disease. Such approach can potentially improve the outcomes and medical control for both conditions, and, thus, decrease the healthcare burden of these major medical problems.
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MESH Headings
- Adipokines/blood
- Adult
- Aged
- Animals
- Blood Glucose/metabolism
- Comorbidity
- Diabetes Mellitus, Type 2/blood
- Diabetes Mellitus, Type 2/diagnosis
- Diabetes Mellitus, Type 2/epidemiology
- Diabetes Mellitus, Type 2/physiopathology
- Diabetes Mellitus, Type 2/therapy
- Endothelium, Vascular/metabolism
- Endothelium, Vascular/physiopathology
- Female
- Humans
- Inflammation Mediators/blood
- Lung/metabolism
- Lung/physiopathology
- Male
- Middle Aged
- Oxidative Stress
- Prognosis
- Pulmonary Disease, Chronic Obstructive/blood
- Pulmonary Disease, Chronic Obstructive/diagnosis
- Pulmonary Disease, Chronic Obstructive/epidemiology
- Pulmonary Disease, Chronic Obstructive/physiopathology
- Pulmonary Disease, Chronic Obstructive/therapy
- Risk Factors
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Affiliation(s)
- Aibek E Mirrakhimov
- Kyrgyz State Medical Academy named by I,K, Akhunbaev, Akhunbaev street 92, Bishkek 720020, Kyrgyzstan.
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Kao CC, Hsu JWC, Bandi V, Hanania NA, Kheradmand F, Jahoor F. Glucose and pyruvate metabolism in severe chronic obstructive pulmonary disease. J Appl Physiol (1985) 2011; 112:42-7. [PMID: 22016370 DOI: 10.1152/japplphysiol.00599.2011] [Citation(s) in RCA: 28] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022] Open
Abstract
The mechanisms leading to weight loss in patients with chronic obstructive pulmonary disease (COPD) are poorly understood but may involve alterations in macronutrient metabolism. Changes in muscle oxidative capacity and lactate production during exercise suggest glucose metabolism may be altered in COPD subjects. The objective of this study was to determine differences in the rates of glucose production and clearance, the rate of glycolysis (pyruvate production), and oxidative and nonoxidative pyruvate disposal in subjects with severe COPD compared with healthy controls. The in vivo rates of glucose production and clearance were measured in 14 stable outpatients with severe COPD (seven with low and seven with preserved body mass indexes) and 7 healthy controls using an intravenous infusion of [(2)H(2)]glucose. Additionally, pyruvate production and oxidative and non-oxidative pyruvate disposal were measured using intravenous infusions of [(13)C]bicarbonate and [(13)C]pyruvate. Endogenous glucose flux and glucose clearance were significantly faster in the combined COPD subjects (P = 0.002 and P < 0.001, respectively). This difference remained significant when COPD subjects were separated by body mass index. Pyruvate flux and oxidation were significantly higher in the combined COPD subjects than controls (P = 0.02 for both), but there was no difference in nonoxidative pyruvate disposal or plasma lactate concentrations between the two groups. In subjects with severe COPD, there are alterations in glucose metabolism leading to increased glucose production and faster glucose metabolism by glycolysis and oxidation compared with controls. However, no difference in glucose conversion to lactate via pyruvate reduction is observed.
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Affiliation(s)
- Christina C Kao
- Department of Medicine, Section of Pulmonary, Critical Care, and Sleep Medicine, Baylor College of Medicine, Houston, Texas, USA.
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19
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Franssen FME, Sauerwein HP, Ackermans MT, Rutten EPA, Wouters EFM, Schols AMWJ. Increased postabsorptive and exercise-induced whole-body glucose production in patients with chronic obstructive pulmonary disease. Metabolism 2011; 60:957-64. [PMID: 21056887 DOI: 10.1016/j.metabol.2010.09.004] [Citation(s) in RCA: 22] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 05/18/2010] [Revised: 09/09/2010] [Accepted: 09/11/2010] [Indexed: 01/04/2023]
Abstract
Skeletal muscle biopsy studies have consistently shown a decreased oxidative phenotype in patients with moderate to severe chronic obstructive pulmonary disease (COPD). Limited information is available regarding potential adaptations or abnormalities in anaerobic metabolism and glucose homeostasis. Whole-body glucose production was assessed at rest and during exercise in COPD patients with moderate disease severity (forced expiratory volume in 1 second, 52% ± 3%), prestratified into normal-weight (n = 7; body mass index [BMI], 27.5 ± 0.9 kg·m(-2)) and underweight subjects (n = 6; BMI, 20.6 ± 0.7 kg·m(-2)), and in 8 healthy controls matched for age and BMI with the normal-weight COPD group. Glucose tolerance was normal in all subjects. Rate of appearance (R(a)) of glucose at rest and during submaximal cycling exercise was measured in postabsorptive state by infusion of stable isotope tracer [6,6-(2)H(2)]glucose. Resting glucose R(a) was significantly enhanced in underweight COPD patients compared with controls (16.7 ± 0.3 vs 15.1 ± 0.4 μmol·kg fat-free mass(-1)·min(-1), P < .05) and was inversely related to fat-free mass (r = -0.75, P < .01). Furthermore, the exercise-induced increase in glucose R(a) was enhanced in COPD patients (81.9% ± 3.4% vs 72.1% ± 2.0%, P = .05), resulting in elevated end-of-exercise glucose output. Differences were most pronounced in underweight patients, who were also characterized by enhanced plasma catecholamine levels and decreased insulin concentrations (all, P < .05). In normal-weight patients, there was evidence for decreased insulin sensitivity assessed by homeostatic modeling technique. Whole-body glucose production is increased in underweight COPD patients with normal glucose tolerance. It is hypothesized that lowered body weight in COPD has unique effects on glucose uptake despite reduced skeletal muscle oxidative capacity, relative hypoxemia, and sympathetic activation.
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Affiliation(s)
- Frits M E Franssen
- Department of Respiratory Medicine, NUTRIM School for Nutrition, Toxicology and Metabolism, Maastricht University Medical Centre, PO Box 5800, 6202 AZ Maastricht, The Netherlands.
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Layec G, Haseler LJ, Hoff J, Richardson RS. Evidence that a higher ATP cost of muscular contraction contributes to the lower mechanical efficiency associated with COPD: preliminary findings. Am J Physiol Regul Integr Comp Physiol 2011; 300:R1142-7. [PMID: 21307358 DOI: 10.1152/ajpregu.00835.2010] [Citation(s) in RCA: 34] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022]
Abstract
Impaired metabolism in peripheral skeletal muscles potentially contributes to exercise intolerance in chronic obstructive pulmonary disease (COPD). We used (31)P-magnetic resonance spectroscopy ((31)P-MRS) to examine the energy cost and skeletal muscle energetics in six patients with COPD during dynamic plantar flexion exercise compared with six well-matched healthy control subjects. Patients with COPD displayed a higher energy cost of muscle contraction compared with the controls (control: 6.1 ± 3.1% of rest·min(-1)·W(-1), COPD: 13.6 ± 8.3% of rest·min(-1)·W(-1), P = 0.01). Although, the initial phosphocreatine resynthesis rate was also significantly attenuated in patients with COPD compared with controls (control: 74 ± 17% of rest/min, COPD: 52 ± 13% of rest/min, P = 0.04), when scaled to power output, oxidative ATP synthesis was similar between groups (6.5 ± 2.3% of rest·min(-1)·W(-1) in control and 7.8 ± 3.9% of rest·min(-1)·W(-1) in COPD, P = 0.52). Therefore, our results reveal, for the first time that in a small subset of patients with COPD a higher ATP cost of muscle contraction may substantially contribute to the lower mechanical efficiency previously reported in this population. In addition, it appears that some patients with COPD have preserved mitochondrial function and normal energy supply in lower limb skeletal muscle.
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Affiliation(s)
- Gwenael Layec
- Veterans Affairs Medical Center, 500 Foothill Dr., Salt Lake City, UT 84148, USA.
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21
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Saey D, Lemire BB, Gagnon P, Bombardier É, Tupling AR, Debigaré R, Côté CH, Maltais F. Quadriceps metabolism during constant workrate cycling exercise in chronic obstructive pulmonary disease. J Appl Physiol (1985) 2011; 110:116-24. [DOI: 10.1152/japplphysiol.00153.2010] [Citation(s) in RCA: 32] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022] Open
Abstract
Impaired resting metabolism in peripheral muscles potentially contributes to exercise intolerance in chronic obstructive pulmonary disease (COPD). This study investigated the cytosolic energy metabolism of the quadriceps, from glycogen degradation to lactate accumulation, in exercising patients with COPD, in comparison to healthy controls. We measured, in 12 patients with COPD and 10 control subjects, resting and post-cycling exercise quadriceps levels of 1) energy substrates and end products of glycolysis (glycogen, glucose, pyruvate, and lactate) and intermediate markers of glycolysis (glucose-6-phosphate, glucose-1-phosphate, fructose-6-phosphate) and 2) the activity of key enzymes involved in the regulation of glycolysis (phosphofructokinase, lactate dehydrogenase). Exercise intensity ( P < 0.01), duration ( P = 0.049), and total work ( P < 0.01) were reduced in patients with COPD. The variations in energy substrates and end products of glycolysis after cycling exercise were of similar magnitude in patients with COPD and controls. Glucose-6-phosphate ( P = 0.036) and fructose-6-phosphate ( P = 0.042) were significantly elevated in patients with COPD after exercise. Phosphofructokinase ( P < 0.01) and lactate dehydrogenase ( P = 0.02) activities were greater in COPD. Muscle glycogen utilization ( P = 0.022) and lactate accumulation ( P = 0.025) per unit of work were greater in COPD. We conclude that cycling exercise induced changes in quadriceps metabolism in patients with COPD that were of similar magnitude to those of healthy controls. These intramuscular events required a much lower exercise work load and time to occur in COPD. Our data suggest a greater reliance on glycolysis during exercise in COPD, which may contribute to exercise intolerance in COPD.
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Affiliation(s)
- Didier Saey
- Centre de recherche, Institut Universitaire de cardiologie et de pneumologie de Québec, Université Laval, Sainte-Foy, Quebec, Canada
| | - Bruno B. Lemire
- Centre de recherche, Institut Universitaire de cardiologie et de pneumologie de Québec, Université Laval, Sainte-Foy, Quebec, Canada
| | - Philippe Gagnon
- Centre de recherche, Institut Universitaire de cardiologie et de pneumologie de Québec, Université Laval, Sainte-Foy, Quebec, Canada
| | - Éric Bombardier
- Department of Kinesiology, University of Waterloo, Waterloo, Ontario, Canada; and
| | - A. Russell Tupling
- Department of Kinesiology, University of Waterloo, Waterloo, Ontario, Canada; and
| | - Richard Debigaré
- Centre de recherche, Institut Universitaire de cardiologie et de pneumologie de Québec, Université Laval, Sainte-Foy, Quebec, Canada
| | - Claude H. Côté
- Centre de recherche du Centre hospitalier universitaire de Québec, Pavillon CHUL, Université Laval, Sainte-Foy, Quebec, Canada
| | - François Maltais
- Centre de recherche, Institut Universitaire de cardiologie et de pneumologie de Québec, Université Laval, Sainte-Foy, Quebec, Canada
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Amann M, Regan MS, Kobitary M, Eldridge MW, Boutellier U, Pegelow DF, Dempsey JA. Impact of pulmonary system limitations on locomotor muscle fatigue in patients with COPD. Am J Physiol Regul Integr Comp Physiol 2010; 299:R314-24. [PMID: 20445160 DOI: 10.1152/ajpregu.00183.2010] [Citation(s) in RCA: 108] [Impact Index Per Article: 7.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022]
Abstract
We examined the effects of respiratory muscle work [inspiratory (W(r-insp)); expiratory (W(r-exp))] and arterial oxygenation (Sp(O(2))) on exercise-induced locomotor muscle fatigue in patients with chronic obstructive pulmonary disease (COPD). Eight patients (FEV, 48 +/- 4%) performed constant-load cycling to exhaustion (Ctrl; 9.8 +/- 1.2 min). In subsequent trials, the identical exercise was repeated with 1) proportional assist ventilation + heliox (PAV); 2) heliox (He:21% O(2)); 3) 60% O(2) inspirate (hyperoxia); or 4) hyperoxic heliox mixture (He:40% O(2)). Five age-matched healthy control subjects performed Ctrl exercise at the same relative workload but for 14.7 min ( approximately best COPD performance). Exercise-induced quadriceps fatigue was assessed via changes in quadriceps twitch force (Q(tw,pot)) from before to 10 min after exercise in response to supramaximal femoral nerve stimulation. During Ctrl, absolute workload (124 +/- 6 vs. 62 +/- 7 W), W(r-insp) (207 +/- 18 vs. 301 +/- 37 cmH(2)O x s x min(-1)), W(r-exp) (172 +/- 15 vs. 635 +/- 58 cmH(2)O x s x min(-1)), and Sp(O(2)) (96 +/- 1% vs. 87 +/- 3%) differed between control subjects and patients. Various interventions altered W(r-insp), W(r-exp), and Sp(O(2)) from Ctrl (PAV: -55 +/- 5%, -21 +/- 7%, +6 +/- 2%; He:21% O(2): -16 +/- 2%, -25 +/- 5%, +4 +/- 1%; hyperoxia: -11 +/- 2%, -17 +/- 4%, +16 +/- 4%; He:40% O(2): -22 +/- 2%, -27 +/- 6%, +15 +/- 4%). Ten minutes after Ctrl exercise, Q(tw,pot) was reduced by 25 +/- 2% (P < 0.01) in all COPD and 2 +/- 1% (P = 0.07) in healthy control subjects. In COPD, DeltaQ(tw,pot) was attenuated by one-third after each interventional trial; however, most of the exercise-induced reductions in Q(tw,pot) remained. Our findings suggest that the high susceptibility to locomotor muscle fatigue in patients with COPD is in part attributable to insufficient O(2) transport as a consequence of exaggerated arterial hypoxemia and/or excessive respiratory muscle work but also support a critical role for the well-known altered intrinsic muscle characteristics in these patients.
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Affiliation(s)
- Markus Amann
- John Rankin Laboratory of Pulmonary Medicine, University of Wisconsin-Madison Medical School, Madison, Wisconsin, USA.
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Green HJ, Bombardier E, Burnett ME, D'Arsigny CL, Iqbal S, Webb KA, Ouyang J, O'Donnell DE. Cellular assessment of muscle in COPD: case studies of two males. Int J Gen Med 2009; 2:227-42. [PMID: 20360908 PMCID: PMC2840564 DOI: 10.2147/ijgm.s5981] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/06/2009] [Indexed: 11/23/2022] Open
Abstract
The objective of this paper is to provide an overview of the recent developments in muscle physiology and biochemistry in general, and with respect to chronic obstructive pulmonary disease (COPD) specifically. As a way of illustration, we have presented data on the remodeling that occurs in vastus lateralis in two patients with COPD (COPD #1, forced expiratory volume in one second/forced vital capacity [FEV1/FVC] = 63%; COPD #2, FEV1/FVC = 41%) exhibiting differences in muscle wasting as compared to healthy controls (CON; FEV1/FVC = 111 ± 2.2%, n = 4). Type I fibers percentages were lower in both COPD #1 (16.7) and COPD #2 (24.9) compared to CON (57.3 ± 5.2). Cross sectional area of the type I fibers of the patients ranged between 65%–68% of CON and for the type II subtypes (IIA, IIAX, IIX) between 74% and 89% (COPD #1) and 17%–32% (COPD #2). A lower number of capillary contacts were observed for all fiber types in COPD #1 but not COPD #2. Lower concentrations of adenosine triphosphate (ATP) (24%–26%) and phosphocreatine (18%–20%), but not lactate occurred in COPD. In contrast to COPD #1, who displayed normal glucose transporter content, GLUT1 and GLUT4 were only 71% and 54%, respectively of CON in COPD #2. Lower monocarboxylate contents were found for MCT1 in both COPD #1 (63%) and COPD #2 (41%) and for MCT4 (78%) in COPD #1. Maximal oxidative enzyme activities (Vmax) for COPD #2 ranged between 37% (succinic dehydrogenase) and 70% (cytochrome C oxidase) of CON. For the cytosolic enzymes, Vmax ranged between 89% (hexokinase) to 31% (pyruvate kinase) of CON. Depressions were also observed in Vmax of the Na+-K+-ATPase for COPD #1 (66% of CON) but not COPD #2 (92% of CON) while Vmax of the Ca2+-ATPase was near normal in COPD #1 (84% CON). It is concluded that disturbances can occur in muscle to a wide range of excitation, contraction and metabolic processes in COPD.
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Affiliation(s)
- Howard J Green
- Department of Kinesiology, University of Waterloo, Waterloo, ON, Canada
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The pathophysiology of cachexia in chronic obstructive pulmonary disease. Curr Opin Support Palliat Care 2009; 3:282-7. [DOI: 10.1097/spc.0b013e328331e91c] [Citation(s) in RCA: 25] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/30/2022]
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Green HJ, Burnett ME, D'Arsigny CL, Webb KA, McBride I, Ouyang J, O'Donnell DE. Vastus lateralis NA+-K+-ATpase activity, protein, and isoform distribution in chronic obstructive pulmonary disease. Muscle Nerve 2009; 40:62-8. [DOI: 10.1002/mus.21296] [Citation(s) in RCA: 10] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/09/2022]
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Gualano B, Artioli GG, Poortmans JR, Lancha Junior AH. Exploring the therapeutic role of creatine supplementation. Amino Acids 2009; 38:31-44. [PMID: 19253023 DOI: 10.1007/s00726-009-0263-6] [Citation(s) in RCA: 99] [Impact Index Per Article: 6.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/05/2009] [Accepted: 02/11/2009] [Indexed: 12/12/2022]
Abstract
Creatine (Cr) plays a central role in energy provision through a reaction catalyzed by phosphorylcreatine kinase. Furthermore, this amine enhances both gene expression and satellite cell activation involved in hypertrophic response. Recent findings have indicated that Cr supplementation has a therapeutic role in several diseases characterized by atrophic conditions, weakness, and metabolic disturbances (i.e., in the muscle, bone, lung, and brain). Accordingly, there has been an evidence indicating that Cr supplementation is capable of attenuating the degenerative state in some muscle disorders (i.e., Duchenne and inflammatory myopathies), central nervous diseases (i.e., Parkinson's, Huntington's, and Alzheimer's), and bone and metabolic disturbances (i.e., osteoporosis and type II diabetes). In light of this, Cr supplementation could be used as a therapeutic tool for the elderly. The aim of this review is to summarize the main studies conducted in this field and to highlight the scientific and clinical perspectives of this promising therapeutic supplement.
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Affiliation(s)
- Bruno Gualano
- Laboratory of Applied Nutrition and Metabolism, School of Physical Education and Sport, University of São Paulo, São Paulo, Brazil.
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Green HJ, Burnett ME, D'Arsigny C, Iqbal S, Ouyang J, Webb KA, O'Donnell DE. Muscle fiber type characteristics in females with chronic obstructive pulmonary disease. A preliminary study. J Mol Histol 2009; 40:41-51. [PMID: 19205906 DOI: 10.1007/s10735-009-9211-8] [Citation(s) in RCA: 11] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/05/2008] [Accepted: 01/19/2009] [Indexed: 10/21/2022]
Abstract
Chronic obstructive pulmonary disease (COPD) is known to elicit intrinsic abnormalities in male skeletal muscle. However, it is unclear to what extent these changes occur in women and whether they are fiber-type specific. We investigated fiber-type specific differences in selected histochemical properties in muscle obtained from women with moderate to severe COPD compared to healthy control (CON) women. Tissue was obtained from the vastus lateralis in five COPD patients (age 66.9 +/- 2.6 years; FEV1 = 43 +/- 7%) and eight CON (age 68 +/- 4.9 years; FEV1 = 113 +/- 4.2%). Compared to CON, the distribution (30.6 +/- 5.2 vs. 57.9 +/- 4.6%) and cross sectional area of type I (CSA, 5660 +/- 329 vs. 3586 +/- 257 microm2) and type IIA (2770 +/- 302 vs. 2099 +/- 206 microm2) were lower (P < 0.05) and higher (P < 0.05), respectively, in COPD. Disease state did not alter either the distribution or CSA of the IIA, IIAX or type X subtypes. Although differences were found between fiber types in the number of capillary contacts (n) (I > IIAX, IIX; IIA > IIX) and the capillaries per CSA (microm210(-3)) (I < IIA, IIAX, IIX), no differences were found between CON and COPD. Succinic dehydrogenase activity and sarcoplasmic reticulum (SR) Ca2+-ATPase activity, measured photometrically (OD units), were higher (P < 0.05), and lower (P < 0.05), respectively, in type I compared to the type II fiber subtypes. These properties were not altered with COPD. COPD in females is accompanied by a higher percent of type II fibers, a larger CSA of type I and type IIA fibers, both of which occur in the absence of differences in oxidative potential and the potential for SR Ca2+-sequestration.
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Affiliation(s)
- Howard J Green
- Department of Kinesiology, University of Waterloo, Waterloo, ON N2L 3G1, Canada.
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