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Dalle S, Schouten M, Ramaekers M, Koppo K. The cannabinoid receptor 1 antagonist AM6545 stimulates the Akt-mTOR axis and in vivo muscle protein synthesis in a dexamethasone-induced muscle atrophy model. Mol Cell Endocrinol 2023; 563:111854. [PMID: 36682621 DOI: 10.1016/j.mce.2023.111854] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 08/29/2022] [Revised: 12/14/2022] [Accepted: 01/12/2023] [Indexed: 01/21/2023]
Abstract
Cannabinoid receptor 1 (CB1) antagonists were shown to stimulate in vitro muscle protein synthesis, but this has never been confirmed in vivo. Therefore, this study investigated whether treatment with the CB1 antagonist AM6545 upregulates in vivo muscle anabolism. Chronic AM6545 treatment stimulated the Akt-mTOR axis and protein synthesis (+22%; p = 0.002) in the Tibialis Anterior, which protected mice from dexamethasone-induced muscle loss (-1% vs. -6% compared to healthy controls; p = 0.02). Accordingly, acute AM6545 treatment stimulated protein synthesis (+44%; p = 0.04) in the Tibialis Anterior but not Soleus. The anabolic upregulation was accompanied by ERK1/2 activation, whereas protein kinase A signaling remained unaffected, suggesting a CB1-independent mechanism. The present study for the first time shows that the CB1 antagonist AM6545 can upregulate the Akt-mTOR axis and in vivo muscle protein synthesis. However, future work applying genetic approaches should further uncover the signaling pathways via which AM6545 enhances muscle anabolism.
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Affiliation(s)
- Sebastiaan Dalle
- Exercise Physiology Research Group, Department of Movement Sciences, KU Leuven, Tervuursevest 101, 3001, Leuven, Belgium.
| | - Moniek Schouten
- Exercise Physiology Research Group, Department of Movement Sciences, KU Leuven, Tervuursevest 101, 3001, Leuven, Belgium.
| | - Monique Ramaekers
- Exercise Physiology Research Group, Department of Movement Sciences, KU Leuven, Tervuursevest 101, 3001, Leuven, Belgium.
| | - Katrien Koppo
- Exercise Physiology Research Group, Department of Movement Sciences, KU Leuven, Tervuursevest 101, 3001, Leuven, Belgium.
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2
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Dalle S, Schouten M, Meeus G, Slagmolen L, Koppo K. Molecular networks underlying cannabinoid signaling in skeletal muscle plasticity. J Cell Physiol 2022; 237:3517-3540. [PMID: 35862111 DOI: 10.1002/jcp.30837] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/13/2022] [Revised: 07/01/2022] [Accepted: 07/08/2022] [Indexed: 11/07/2022]
Abstract
The cannabinoid system is ubiquitously present and is classically considered to engage in neural and immunity processes. Yet, the role of the cannabinoid system in the whole body and tissue metabolism via central and peripheral mechanisms is increasingly recognized. The present review provides insights in (i) how cannabinoid signaling is regulated via receptor-independent and -dependent mechanisms and (ii) how these signaling cascades (might) affect skeletal muscle plasticity and physiology. Receptor-independent mechanisms include endocannabinoid metabolism to eicosanoids and the regulation of ion channels. Alternatively, endocannabinoids can act as ligands for different classic (cannabinoid receptor 1 [CB1 ], CB2 ) and/or alternative (e.g., TRPV1, GPR55) cannabinoid receptors with a unique affinity, specificity, and intracellular signaling cascade (often tissue-specific). Antagonism of CB1 might hold clues to improve oxidative (mitochondrial) metabolism, insulin sensitivity, satellite cell growth, and muscle anabolism, whereas CB2 agonism might be a promising way to stimulate muscle metabolism and muscle cell growth. Besides, CB2 ameliorates muscle regeneration via macrophage polarization toward an anti-inflammatory phenotype, induction of MyoD and myogenin expression and antifibrotic mechanisms. Also TRPV1 and GPR55 contribute to the regulation of muscle growth and metabolism. Future studies should reveal how the cannabinoid system can be targeted to improve muscle quantity and/or quality in conditions such as ageing, disease, disuse, and metabolic dysregulation, taking into account challenges that are inherent to modulation of the cannabinoid system, such as central and peripheral side effects.
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Affiliation(s)
- Sebastiaan Dalle
- Department of Movement Sciences, Exercise Physiology Research Group, KU Leuven, Leuven, Belgium
| | - Moniek Schouten
- Department of Movement Sciences, Exercise Physiology Research Group, KU Leuven, Leuven, Belgium
| | - Gitte Meeus
- Department of Movement Sciences, Exercise Physiology Research Group, KU Leuven, Leuven, Belgium
| | - Lotte Slagmolen
- Department of Movement Sciences, Exercise Physiology Research Group, KU Leuven, Leuven, Belgium
| | - Katrien Koppo
- Department of Movement Sciences, Exercise Physiology Research Group, KU Leuven, Leuven, Belgium
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3
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Skagen C, Nyman TA, Peng XR, O'Mahony G, Kase ET, Rustan AC, Thoresen GH. Chronic treatment with terbutaline increases glucose and oleic acid oxidation and protein synthesis in cultured human myotubes. CURRENT RESEARCH IN PHARMACOLOGY AND DRUG DISCOVERY 2021; 2:100039. [PMID: 34909668 PMCID: PMC8663959 DOI: 10.1016/j.crphar.2021.100039] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/04/2021] [Revised: 05/28/2021] [Accepted: 06/02/2021] [Indexed: 12/04/2022] Open
Abstract
Objective In vivo studies have reported several beneficial metabolic effects of β-adrenergic receptor agonist administration in skeletal muscle, including increased glucose uptake, fatty acid metabolism, lipolysis and mitochondrial biogenesis. Although these effects have been widely studied in vivo, the in vitro data are limited to mouse and rat cell lines. Therefore, we sought to discover the effects of the β2-adrenergic receptor agonist terbutaline on metabolism and protein synthesis in human primary skeletal muscle cells. Methods Human cultured myotubes were exposed to terbutaline in various concentrations (0.01–30 μM) for 4 or 96 h. Thereafter uptake of [14C]deoxy-D-glucose, oxydation of [14C]glucose and [14C]oleic acid were measured. Incorporation of [14C]leucine, gene expression by qPCR and proteomics analyses by mass spectrometry by the STAGE-TIP method were performed after 96 h exposure to 1 and 10 μM of terbutaline. Results The results showed that 4 h treatment with terbutaline in concentrations up to 1 μM increased glucose uptake in human myotubes, but also decreased both glucose and oleic acid oxidation along with oleic acid uptake in concentrations of 10–30 μM. Moreover, administration of terbutaline for 96 h increased glucose uptake (in terbutaline concentrations up to 1 μM) and oxidation (1 μM), as well as oleic acid oxidation (0.1–30 μM), leucine incorporation into cellular protein (1–10 μM) and upregulated several pathways related to mitochondrial metabolism (1 μM). Data are available via ProteomeXchange with identifier PXD024063. Conclusion These results suggest that β2-adrenergic receptor have direct effects in human skeletal muscle affecting fuel metabolism and net protein synthesis, effects that might be favourable for both type 2 diabetes and muscle wasting disorders. The metabolic effects of terbutaline were studied in human primary myotubes. Acute treatment with terbutaline increased glucose uptake. Chronic treatment with terbutaline increased glucose and oleic acid oxidation. Chronic treatment with terbutaline increased protein synthesis. Proteomics analysis revealed an increase in mitochondrial proteins.
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Affiliation(s)
- Christine Skagen
- Section for Pharmacology and Pharmaceutical Biosciences, Department of Pharmacy, University of Oslo, Norway
| | - Tuula A Nyman
- Department of Immunology, Institute of Clinical Medicine, University of Oslo and Oslo University Hospital, Norway
| | - Xiao-Rong Peng
- Bioscience Metabolism, Research and Early Development Cardiovascular, Renal and Metabolism, BioPharmaceuticals R&D, AstraZeneca, Gothenburg, Sweden
| | - Gavin O'Mahony
- Medicinal Chemsitry, Research and Early Development Cardiovascular, Renal and Metabolism, BioPharmaceuticals R&D, AstraZeneca, Gothenburg, Sweden
| | - Eili Tranheim Kase
- Section for Pharmacology and Pharmaceutical Biosciences, Department of Pharmacy, University of Oslo, Norway
| | - Arild Chr Rustan
- Section for Pharmacology and Pharmaceutical Biosciences, Department of Pharmacy, University of Oslo, Norway
| | - G Hege Thoresen
- Section for Pharmacology and Pharmaceutical Biosciences, Department of Pharmacy, University of Oslo, Norway.,Department of Pharmacology, Institute of Clinical Medicine, University of Oslo, Norway
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4
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Saleh AA, Alhotan RA, Alharthi AS, Nassef E, Kassab MA, Farrag FA, Hendam BM, Abumnadour MMA, Shukry M. Insight View on the Role of in Ovo Feeding of Clenbuterol on Hatched Chicks: Hatchability, Growth Efficiency, Serum Metabolic Profile, Muscle, and Lipid-Related Markers. Animals (Basel) 2021; 11:ani11082429. [PMID: 34438887 PMCID: PMC8388663 DOI: 10.3390/ani11082429] [Citation(s) in RCA: 4] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/21/2021] [Revised: 08/08/2021] [Accepted: 08/13/2021] [Indexed: 11/16/2022] Open
Abstract
Simple Summary This study examined the effects of ovo injection of clenbuterol on fat deposition and growth performance in chickens, which is prejudicial to poultry consumers and muscle growth-related genes, egg hatchability, and fertility. The achieved result showed a definite effect of clenbuterol on body gain and hatchability. It decreased fat deposition and upregulation of muscle growth-related gene expressions accompanied by modulation of fatty and amino acid composition, reflecting a new insight into the intracellular pathways of clenbuterol supplementation on chicks. Abstract The present study aimed to assess the in ovo administration of clenbuterol on chick fertility, growth performance, muscle growth, myogenic gene expression, fatty acid, amino acid profile, intestinal morphology, and hepatic lipid-related gene expressions. In this study, 750 healthy fertile eggs from the local chicken breed Dokki-4 strain were analyzed. Fertile eggs were randomly divided into five experimental groups (150 eggs/3 replicates for each group). On day 14 of incubation, in addition to the control group, four other groups were established where 0.5 mL of worm saline (30 °C) was injected into the second group of eggs. In the third, fourth, and fifth groups, 0.5 mL of worm saline (30 °C), 0.9% of NaCl, and 10, 15, and 20 ppm of clenbuterol were injected into the eggs. Results suggested that clenbuterol increased growth efficiency up to 12 weeks of age, especially at 15 ppm, followed by 10 ppm, decreased abdominal body fat mass, and improved hatchability (p < 0.01). Clenbuterol also modulated saturated fatty acid levels in the breast muscles and improved essential amino acids when administered at 10 and 15 ppm. Additionally, clenbuterol at 15 ppm significantly decreased myostatin gene expression (p < 0.01) and considerably increased IGF1r and IGF-binding protein (IGFBP) expression. Clenbuterol administration led to a significant upregulation of hepatic PPARα, growth hormone receptor, and Lipoprotein lipase (LPL) mRNA expression with a marked decrease in fatty acid synthase (FAS) and sterol regulatory element-binding protein 1 (SREBP-1c) expression. In conclusion, the current study revealed that in ovo injection of clenbuterol showed positive effects on the growth of hatched chicks through reduced abdominal fat deposition, improved intestinal morphology, and modulation of hepatic gene expressions in myogenesis, lipogenesis, and lipolysis.
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Affiliation(s)
- Ahmed A. Saleh
- Department of Poultry Production, Faculty of Agriculture, Kafrelsheikh University, Kafrelsheikh 33516, Egypt
- Correspondence: (A.A.S.); (M.S.)
| | - Rashed A. Alhotan
- Department of Animal Production, College of Food and Agriculture Sciences, King Saud University, P.O. Box 2460, Riyadh 11451, Saudi Arabia; (R.A.A.); (A.S.A.)
| | - Abdulrahman S. Alharthi
- Department of Animal Production, College of Food and Agriculture Sciences, King Saud University, P.O. Box 2460, Riyadh 11451, Saudi Arabia; (R.A.A.); (A.S.A.)
| | - Eldsokey Nassef
- Department of Nutrition and Clinical Nutrition, Faculty of Veterinary Medicine, Kafrelsheikh University, Kafrelsheikh 33516, Egypt;
| | - Mohamed A. Kassab
- Department of Histology, Faculty of Veterinary Medicine, Kafrelsheikh University, Kafrelsheikh 33516, Egypt;
| | - Foad A. Farrag
- Department of Anatomy and Embryology, Faculty of Veterinary Medicine, Kafrelsheikh University, Kafrelsheikh 33516, Egypt;
| | - Basma M. Hendam
- Genetics and Genetic Engineering, Department of Husbandry and Development of Animal Wealth, Faculty of Veterinary Medicine, Mansoura University, Mansoura 35516, Egypt;
| | - Mohamed M. A. Abumnadour
- Department of Anatomy and Embryology, Faculty of Veterinary Medicine, Alexandria University, Edfina 22756, Egypt;
| | - Mustafa Shukry
- Department of Physiology, Faculty of Veterinary Medicine, Kafrelsheikh University, Kafrelsheikh 33516, Egypt
- Correspondence: (A.A.S.); (M.S.)
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Hostrup M, Reitelseder S, Jessen S, Kalsen A, Nyberg M, Egelund J, Kreiberg M, Kristensen CM, Thomassen M, Pilegaard H, Backer V, Jacobson GA, Holm L, Bangsbo J. Beta 2 -adrenoceptor agonist salbutamol increases protein turnover rates and alters signalling in skeletal muscle after resistance exercise in young men. J Physiol 2018; 596:4121-4139. [PMID: 29968301 DOI: 10.1113/jp275560] [Citation(s) in RCA: 39] [Impact Index Per Article: 6.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/12/2018] [Accepted: 06/29/2018] [Indexed: 01/08/2023] Open
Abstract
KEY POINTS Animal models have shown that beta2 -adrenoceptor stimulation increases protein synthesis and attenuates breakdown processes in skeletal muscle. Thus, the beta2 -adrenoceptor is a potential target in the treatment of disuse-, disease- and age-related muscle atrophy. In the present study, we show that a few days of oral treatment with the commonly prescribed beta2 -adrenoceptor agonist, salbutamol, increased skeletal muscle protein synthesis and breakdown during the first 5 h after resistance exercise in young men. Salbutamol also counteracted a negative net protein balance in skeletal muscle after resistance exercise. Changes in protein turnover rates induced by salbutamol were associated with protein kinase A-signalling, activation of Akt2 and modulation of mRNA levels of growth-regulating proteins in skeletal muscle. These findings indicate that protein turnover rates can be augmented by beta2 -adrenoceptor agonist treatment during recovery from resistance exercise in humans. ABSTRACT The effect of beta2 -adrenoceptor stimulation on skeletal muscle protein turnover and intracellular signalling is insufficiently explored in humans, particularly in association with exercise. In a randomized, placebo-controlled, cross-over study investigating 12 trained men, the effects of beta2 -agonist (6 × 4 mg oral salbutamol) on protein turnover rates, intracellular signalling and mRNA response in skeletal muscle were investigated 0.5-5 h after quadriceps resistance exercise. Each trial was preceded by a 4-day lead-in treatment period. Leg protein turnover rates were assessed by infusion of [13 C6 ]-phenylalanine and sampling of arterial and venous blood, as well as vastus lateralis muscle biopsies 0.5 and 5 h after exercise. Furthermore, myofibrillar fractional synthesis rate, intracellular signalling and mRNA response were measured in muscle biopsies. The mean (95% confidence interval) myofibrillar fractional synthesis rate was higher for salbutamol than placebo [0.079 (95% CI, 0.064 to 0.093) vs. 0.066 (95% CI, 0.056 to 0.075%) × h-1 ] (P < 0.05). Mean net leg phenylalanine balance 0.5-5 h after exercise was higher for salbutamol than placebo [3.6 (95% CI, 1.0 to 6.2 nmol) × min-1 × 100 gLeg Lean Mass-1 ] (P < 0.01). Phosphorylation of Akt2, cAMP response element binding protein and PKA substrate 0.5 and 5 h after exercise, as well as phosphorylation of eEF2 5 h after exercise, was higher (P < 0.05) for salbutamol than placebo. Calpain-1, Forkhead box protein O1, myostatin and Smad3 mRNA content was higher (P < 0.01) for salbutamol than placebo 0.5 h after exercise, as well as Forkhead box protein O1 and myostatin mRNA content 5 h after exercise, whereas ActivinRIIB mRNA content was lower (P < 0.01) for salbutamol 5 h after exercise. These observations suggest that beta2 -agonist increases protein turnover rates in skeletal muscle after resistance exercise in humans, with concomitant cAMP/PKA and Akt2 signalling, as well as modulation of mRNA response of growth-regulating proteins.
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Affiliation(s)
- Morten Hostrup
- Section of Integrative Physiology, Department of Nutrition, Exercise and Sports, University of Copenhagen, Copenhagen, Denmark.,Department of Respiratory Medicine, Bispebjerg University Hospital, Copenhagen, Denmark
| | - Søren Reitelseder
- Institute of Sports Medicine Copenhagen, Department of Orthopedic Surgery M, Bispebjerg University Hospital, Copenhagen, Denmark
| | - Søren Jessen
- Section of Integrative Physiology, Department of Nutrition, Exercise and Sports, University of Copenhagen, Copenhagen, Denmark.,Department of Respiratory Medicine, Bispebjerg University Hospital, Copenhagen, Denmark
| | - Anders Kalsen
- Section of Integrative Physiology, Department of Nutrition, Exercise and Sports, University of Copenhagen, Copenhagen, Denmark.,Department of Respiratory Medicine, Bispebjerg University Hospital, Copenhagen, Denmark
| | - Michael Nyberg
- Section of Integrative Physiology, Department of Nutrition, Exercise and Sports, University of Copenhagen, Copenhagen, Denmark
| | - Jon Egelund
- Section of Integrative Physiology, Department of Nutrition, Exercise and Sports, University of Copenhagen, Copenhagen, Denmark
| | - Michael Kreiberg
- Department of Respiratory Medicine, Bispebjerg University Hospital, Copenhagen, Denmark
| | | | - Martin Thomassen
- Section of Integrative Physiology, Department of Nutrition, Exercise and Sports, University of Copenhagen, Copenhagen, Denmark
| | - Henriette Pilegaard
- Department of Biology, University of Copenhagen, Copenhagen, Copenhagen, Denmark
| | - Vibeke Backer
- Department of Respiratory Medicine, Bispebjerg University Hospital, Copenhagen, Denmark
| | - Glenn A Jacobson
- Division of Pharmacy, School of Medicine, University of Tasmania, Hobart, Australia
| | - Lars Holm
- Institute of Sports Medicine Copenhagen, Department of Orthopedic Surgery M, Bispebjerg University Hospital, Copenhagen, Denmark.,Department of Biomedical Sciences, Faculty of Health and Medical Sciences, University of Copenhagen, Copenhagen, Denmark.,School of Sport Exercise and Rehabilitation Sciences, University of Birmingham, Birmingham, UK
| | - Jens Bangsbo
- Section of Integrative Physiology, Department of Nutrition, Exercise and Sports, University of Copenhagen, Copenhagen, Denmark
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6
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Ijiri D, Ishitani K, Shimamoto S, Ishimaru Y, Ohtsuka A. The effects of intraperitoneal clenbuterol injection on protein degradation and myostatin expression differ between the sartorius and pectoral muscles of neonatal chicks. Gen Comp Endocrinol 2014; 206:111-7. [PMID: 25117456 DOI: 10.1016/j.ygcen.2014.07.023] [Citation(s) in RCA: 13] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 03/28/2014] [Revised: 07/25/2014] [Accepted: 07/26/2014] [Indexed: 11/29/2022]
Abstract
The purpose of this study was to investigate the effects of injection of the β2-adrenergic receptor agonist clenbuterol on the skeletal muscles of neonatal chicks (Gallus gallus domesticus). One-day-old chicks were randomly divided into four groups and given a single intraperitoneal injection of clenbuterol (0.01, 0.1, or 1mg/kg) or phosphate-buffered saline. Twenty-four hours after the injection, the sartorius muscles (which consist of both slow- and fast-twitch fibers) of chicks that received 0.01 or 0.1mg/kg clenbuterol were significantly heavier than those of controls, while there were no between-group differences in the weight of the pectoral muscles, which consist of only fast-twitch fibers. Muscle free N(t)-methylhistidine, regarded as an index of myofibrillar proteolysis, was decreased in the sartorius muscle of the clenbuterol-injected chicks, while it was not affected in the pectoral muscles. In the sartorius muscle of the clenbuterol-injected chicks, myostatin and atrogin-1/MAFbx mRNA expressions were decreased, while insulin-like growth factor-I was unaffected. These observations suggested, in 1-day-old chicks, clenbuterol might increase mass of the sartorius muscle by decreasing myostatin gene expression and protein degradation.
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Affiliation(s)
- Daichi Ijiri
- Department of Biochemical Science and Technology, Kagoshima University, 1-21-24 Korimoto, Kagoshima 890-0065, Japan.
| | - Kanae Ishitani
- Department of Biochemical Science and Technology, Kagoshima University, 1-21-24 Korimoto, Kagoshima 890-0065, Japan
| | - Saki Shimamoto
- Department of Biochemical Science and Technology, Kagoshima University, 1-21-24 Korimoto, Kagoshima 890-0065, Japan
| | - Yoshitaka Ishimaru
- Department of Biochemical Science and Technology, Kagoshima University, 1-21-24 Korimoto, Kagoshima 890-0065, Japan
| | - Akira Ohtsuka
- Department of Biochemical Science and Technology, Kagoshima University, 1-21-24 Korimoto, Kagoshima 890-0065, Japan
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7
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McDonald FB, Skelly JR, O'Halloran KD. The β2 -adrenoceptor agonist terbutaline recovers rat pharyngeal dilator muscle force decline during severe hypoxia. Oral Dis 2014; 21:e121-7. [PMID: 24725067 DOI: 10.1111/odi.12247] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/03/2014] [Revised: 03/28/2014] [Accepted: 04/08/2014] [Indexed: 11/28/2022]
Abstract
RATIONALE Obstructive sleep apnoea syndrome (OSAS) is a debilitating condition characterized by recurrent occlusions of the pharyngeal airway during sleep accompanied by arterial hypoxaemia. Upper airway muscle dysfunction is implicated in the pathophysiology of OSAS. Pharmacological agents that improve muscle contractile and endurance properties may have therapeutic value. AIM We tested the hypothesis that the β(2) -adrenoceptor agonist terbutaline improves rat sternohyoid muscle performance especially during hypoxic stress. METHODS Isometric contractile and endurance properties were examined ex vivo in Krebs solution at 35°C. Muscles were incubated in tissue baths under hyperoxic (95% O(2) /5% CO(2)) conditions in the absence (control) or presence of the β(2) -adrenoceptor agonist terbutaline (1 μM). In additional experiments under hypoxic (95% N(2) /5% CO(2)) conditions, the effects of terbutaline were examined in the presence of the β-adrenoceptor antagonist propranolol (1 μM). RESULTS Hypoxia significantly impaired sternohyoid force production. Terbutaline completely recovered hypoxic depression of force, an effect that was blocked by co-application with propranolol. CONCLUSION The β(2) -adrenoceptor agonist terbutaline completely recovers hypoxic depression of upper airway muscle force. β(2) -adrenoceptor agonists warrant investigation in animal models of OSAS reporting upper airway and diaphragm muscle dysfunction.
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Affiliation(s)
- F B McDonald
- School of Medicine and Medical Science, University College Dublin, Dublin, Ireland
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8
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Sumi K, Higashi S, Natsume M, Kawahata K, Nakazato K. Temporal changes in ERK phosphorylation are harmonious with 4E-BP1, but not p70S6K, during clenbuterol-induced hypertrophy in the rat gastrocnemius. Appl Physiol Nutr Metab 2014; 39:902-10. [PMID: 24941107 DOI: 10.1139/apnm-2013-0431] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/04/2023]
Abstract
Extracellular signal-regulated kinase (ERK) is required for clenbuterol (CB)-dependent fast-type myofibril enlargement; however, its contribution to translation control is unclear. ERK mediates translational regulation through mammalian target of rapamycin complex 1 (mTORC1) activation and (or) mTORC1-independent pathways. In this study, we aimed to investigate the role of ERK in translational control during CB-induced muscular hypertrophy by measuring time-dependent changes in the phosphorylation statuses of ERK, p70 ribosomal S6 kinase (p70S6K; an indicator of mTORC1 activity), 4E-binding protein 1 (4E-BP1), eukaryotic elongation factor 2 (eEF2), and other related signaling molecules in rat gastrocnemius muscles. Five-day administration of CB induced phenotypes associated with muscular hypertrophy (significant increases in wet weight and isometric ankle flexion torque in the gastrocnemius muscle), but was not accompanied by elevated ERK or p70S6K phosphorylation. One-day administration of CB caused significant increases in the phosphorylation of ERK, p70S6K, and 4E-BP1. In contrast, 3-day administration of CB caused significant increases in the phosphorylation of ERK and 4E-BP1, but not p70S6K. In addition, positive correlations were observed between ERK and 4E-BP1 on days 1 and 3, whereas a correlation between ERK and p70S6K was only observed on day 1. eEF2 phosphorylation was unchanged on both days 1 and 3. These findings suggest that ERK accelerates the initiation of translation, but does not support the involvement of ERK in translational elongation. Furthermore, ERK may play a major role in promoting translational initiation by mediating the phosphorylation of 4E-BP1, and may contribute to the initial activation of mTORC1 during CB administration.
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Affiliation(s)
- Koichiro Sumi
- a Food Science Research Laboratories, R&D Division, Meiji Co., Ltd. 540 Naruda, Odawara, 540 Naruda, Odawara, Kanagawa 250-0862, Japan
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9
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Abstract
Airway smooth muscle has classically been of interest for its contractile response linked to bronchoconstriction. However, terminally differentiated smooth muscle cells are phenotypically plastic and have multifunctional capacity for proliferation, cellular hypertrophy, migration, and the synthesis of extracellular matrix and inflammatory mediators. These latter properties of airway smooth muscle are important in airway remodeling which is a structural alteration that compounds the impact of contractile responses on limiting airway conductance. In this overview, we describe the important signaling components and the functional evidence supporting a view of smooth muscle cells at the core of fibroproliferative remodeling of hollow organs. Signal transduction components and events are summarized that control the basic cellular processes of proliferation, cell survival, apoptosis, and cellular migration. We delineate known intracellular control mechanisms and suggest future areas of interest to pursue to more fully understand factors that regulate normal myocyte function and airway remodeling in obstructive lung diseases.
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Affiliation(s)
- William T Gerthoffer
- Department of Biochemistry and Molecular Biology, University of South Alabama, Mobile, Alabama, USA.
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10
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Sato S, Nomura S, Kawano F, Tanihata J, Tachiyashiki K, Imaizumi K. Adaptive effects of the beta2-agonist clenbuterol on expression of beta2-adrenoceptor mRNA in rat fast-twitch fiber-rich muscles. J Physiol Sci 2010; 60:119-27. [PMID: 20033361 PMCID: PMC10716947 DOI: 10.1007/s12576-009-0075-1] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/07/2009] [Accepted: 11/23/2009] [Indexed: 10/20/2022]
Abstract
Administration of the beta(2)-agonist clenbuterol has been shown to reduce the expression of beta(2)-adrenoceptor (AR) mRNA in fast-twitch fiber-rich (extensor digitorum longus, EDL) muscle without changing that in slow-twitch fiber-rich (soleus, SOL) muscle in rats. However, the regulatory mechanism for muscle fiber type-dependent down-regulation of the expression of beta(2)-AR mRNA induced by clenbuterol is still unclear. Therefore, mRNA expression of transcriptional and post-transcriptional regulatory factors for beta(2)-AR mRNA levels in fast-twitch fiber-rich (EDL and plantaris, PLA) and slow-twitch fiber-rich (SOL) muscles in clenbuterol-administered (1.0 mg/kg body weight/day for 10 days, subcutaneous) rats was studied by real-time reverse transcription-polymerase chain reaction. Administration of clenbuterol significantly reduced expression of beta(2)-AR mRNA in EDL and PLA muscles without changing that in SOL muscle. Administration of clenbuterol also significantly reduced the mRNA expression of transcriptional regulatory factor (glucocorticoid receptor) and mRNA stabilizing factor (Hu antigen R) in EDL and PLA muscles without changing those in SOL muscle. These results suggest that muscle fiber type-dependent effects of clenbuterol on expression of beta(2)-AR mRNA are closely related to the down-regulation of mRNA expression of transcriptional and post-transcriptional regulatory factors for beta(2)-AR mRNA levels.
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MESH Headings
- Adaptation, Physiological/drug effects
- Adaptation, Physiological/physiology
- Adrenergic beta-Agonists/pharmacology
- Animals
- Cells, Cultured
- Clenbuterol/pharmacology
- Gene Expression Regulation/drug effects
- Gene Expression Regulation/physiology
- Male
- Muscle Fibers, Fast-Twitch/drug effects
- Muscle Fibers, Fast-Twitch/physiology
- RNA, Messenger/metabolism
- Rats
- Rats, Sprague-Dawley
- Receptors, Adrenergic, beta-3/genetics
- Receptors, Adrenergic, beta-3/metabolism
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Affiliation(s)
- Shogo Sato
- Laboratory of Physiological Sciences, Faculty of Human Sciences, Waseda University, 2-579-15 Mikajima, Tokorozawa, Saitama 359-1192 Japan
| | - Sachiko Nomura
- Graduate School of Medicine, Osaka University, 1-17 Machikaneyama, Toyonaka, Osaka 560-0043 Japan
| | - Fuuun Kawano
- Graduate School of Arts and Sciences, The University of Tokyo, 3-8-1 Komaba, Meguro-ku, Tokyo, 153-8902 Japan
| | - Jun Tanihata
- Laboratory of Rehabilitation Biomedical Sciences, Faculty of Human Sciences, Waseda University, 2-579-15 Mikajima, Tokorozawa, Saitama 359-1192 Japan
| | - Kaoru Tachiyashiki
- Department of Living and Health Sciences, Graduate School of Joetsu University of Education, 1 Yamayashiki, Joetsu, Niigata 943-8512 Japan
| | - Kazuhiko Imaizumi
- Laboratory of Physiological Sciences, Faculty of Human Sciences, Waseda University, 2-579-15 Mikajima, Tokorozawa, Saitama 359-1192 Japan
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11
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Kong J, Jiang L, Su X, Qin J, Du Y, Lin B. Integrated microfluidic immunoassay for the rapid determination of clenbuterol. LAB ON A CHIP 2009; 9:1541-7. [PMID: 19458860 DOI: 10.1039/b818430e] [Citation(s) in RCA: 46] [Impact Index Per Article: 3.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/13/2023]
Abstract
An integrated microfluidic immunoassay system was established for high throughput analysis of clenbuterol. This system consisted of an integrated microchip and a linear confocal laser induced fluorescence (LIF) scanner. The microchip was composed of three layers: a fluidic channel layer, a PDMS membrane layer and a pneumatic control layer. The multi-layer chip was integrated with 36 pneumatic micro-valves and multiple micro-pumps to realize the flexible reagent delivery, facilitating the automatic assays with less consumption of samples and reduced analysis time. The homemade LIF scanner was able to simultaneously detect multi-channels and provide the potential capability of high throughput assays. The performance of the system was demonstrated by the determination of clenbuterol, one of the most widely used beta-agonists. Under the optimal conditions, the linear range and the limit of detection of clenbuterol were 0 approximately 5.0 ng mL(-1) and 0.088 ng mL(-1), respectively. The recovery rates determined with pig urine samples of 1.0 ng mL(-1) and 2.0 ng mL(-1) were 98.74% and 102.51% (n = 3), respectively. The total detection time was less than 30 min. The system had the potential application for rapid detection of multiple beta-agonists in clinical, pharmaceutical and chemical analyses.
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Affiliation(s)
- Jing Kong
- Dalian Institute of Chemical Physics, Chinese Academy of Sciences, Dalian, 116023, China
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12
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Ramos BP, Colgan LA, Nou E, Arnsten AF. Beta2 adrenergic agonist, clenbuterol, enhances working memory performance in aging animals. Neurobiol Aging 2008; 29:1060-9. [PMID: 17363115 PMCID: PMC3154024 DOI: 10.1016/j.neurobiolaging.2007.02.003] [Citation(s) in RCA: 57] [Impact Index Per Article: 3.6] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/17/2006] [Revised: 01/29/2007] [Accepted: 02/05/2007] [Indexed: 11/29/2022]
Abstract
Previous studies using a mixed beta1 and beta2 adrenergic antagonist, propanolol, have indicated that beta adrenoceptors have little effect on the cognitive functioning of the prefrontal cortex. However, recent studies have suggested that endogenous stimulation of beta1 adrenoceptors impairs working memory in both rats and monkeys. Since propanolol has no effect on cognition, we hypothesized that activation of beta2 adrenoceptors might improve performance in a working memory task. We tested this hypothesis by observing the effects of the beta2 agonist, clenbuterol, on spatial working memory performance. Clenbuterol was either infused directly into the prefrontal cortex (rats) or administered systemically (monkeys). Results demonstrated that clenbuterol improved performance in many young and aged rats and monkeys who performed poorly under control conditions. Actions at beta2 adrenoceptors were confirmed by challenging the clenbuterol response with the beta2 adrenergic antagonist, ICI 118,551. The effects of clenbuterol were not universal and depended on the cognitive status of the animal: the drug moderately improved only a subset of animals with working memory impairment.
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Affiliation(s)
- Brian P. Ramos
- Yale University School of Medicine, Department of Neurobiology, SHM C-300, 333 Cedar Street, New Haven, CT 06510, USA
| | - Leslie A. Colgan
- Yale University School of Medicine, Department of Neurobiology, SHM C-300, 333 Cedar Street, New Haven, CT 06510, USA
| | - Eric Nou
- Yale University School of Medicine, Department of Neurobiology, SHM C-300, 333 Cedar Street, New Haven, CT 06510, USA
| | - Amy F.T. Arnsten
- Yale University School of Medicine, Department of Neurobiology, SHM C-300, 333 Cedar Street, New Haven, CT 06510, USA
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13
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Hershenson MB, Brown M, Camoretti-Mercado B, Solway J. Airway smooth muscle in asthma. ANNUAL REVIEW OF PATHOLOGY-MECHANISMS OF DISEASE 2008; 3:523-55. [PMID: 18039134 DOI: 10.1146/annurev.pathmechdis.1.110304.100213] [Citation(s) in RCA: 59] [Impact Index Per Article: 3.7] [Reference Citation Analysis] [Abstract] [Subscribe] [Scholar Register] [Indexed: 11/09/2022]
Abstract
Airway smooth muscle plays a multifaceted role in the pathogenesis of asthma. We review the current understanding of the contribution of airway myocytes to airway inflammation, airway wall remodeling, and airflow obstruction in this prevalent disease syndrome. Together, these roles make airway smooth muscle an attractive target for asthma therapy.
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Affiliation(s)
- Marc B Hershenson
- Department of Pediatrics and Communicable Diseases, University of Michigan, Ann Arbor, MI 48109, USA.
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14
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Downie D, Delday MI, Maltin CA, Sneddon AA. Clenbuterol increases muscle fiber size and GATA-2 protein in rat skeletal muscle in utero. Mol Reprod Dev 2008; 75:785-94. [DOI: 10.1002/mrd.20795] [Citation(s) in RCA: 11] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022]
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15
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McCarthy JJ, Esser KA. Counterpoint: Satellite cell addition is not obligatory for skeletal muscle hypertrophy. J Appl Physiol (1985) 2007; 103:1100-2; discussion 1102-3. [PMID: 17724306 DOI: 10.1152/japplphysiol.00101.2007a] [Citation(s) in RCA: 67] [Impact Index Per Article: 3.9] [Reference Citation Analysis] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022] Open
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16
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Burniston JG, McLean L, Beynon RJ, Goldspink DF. Anabolic effects of a non-myotoxic dose of the beta2-adrenergic receptor agonist clenbuterol on rat plantaris muscle. Muscle Nerve 2007; 35:217-23. [PMID: 17058275 PMCID: PMC1852641 DOI: 10.1002/mus.20684] [Citation(s) in RCA: 31] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/07/2022]
Abstract
Previous investigations of the effects of clenbuterol have used suprapharmacological doses that induce myocyte death, alter muscle phenotype, and do not approximate the proposed therapeutic dose for humans. Recently, we reported that smaller doses of clenbuterol induce muscle growth without causing myocyte death. In the present study we used histochemical and proteomic techniques to investigate the molecular effects of this dose. Male Wistar rats (n = 6, per group) were infused with saline or 10 microg/kg/day clenbuterol via subcutaneously implanted osmotic pumps. After 14 days the animals' plantaris muscles were isolated for histochemical and proteomic analyses. Clenbuterol induced significant muscle growth with concomitant protein accretion and preferential hypertrophy of fast oxidative glycolytic fibers. Clenbuterol reduced the optical density of mitochondrial staining in fast fibers by 20% and the glycogen content of the muscle by 30%. Differential analysis of two-dimensional gels showed that heat shock protein 72 and beta-enolase increased, whereas aldolase A, phosphogylcerate mutase, and adenylate kinase decreased. Only heat shock protein 72 has previously been investigated in clenbuterol-treated muscles. The clenbuterol-induced increase in muscle growth was concomitant with qualitative changes in the muscle's proteome that need to be considered when proposing therapeutic uses for this agent.
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Affiliation(s)
- Jatin G Burniston
- Muscle Physiology and Proteomics Laboratory, Research Institute for Sport and Exercise Sciences, Liverpool John Moores University, Webster Street, Liverpool L3 2ET, UK.
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17
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Kline WO, Panaro FJ, Yang H, Bodine SC. Rapamycin inhibits the growth and muscle-sparing effects of clenbuterol. J Appl Physiol (1985) 2007; 102:740-7. [PMID: 17068216 DOI: 10.1152/japplphysiol.00873.2006] [Citation(s) in RCA: 129] [Impact Index Per Article: 7.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022] Open
Abstract
Clenbuterol and other β2-adrenergic agonists are effective at inducing muscle growth and attenuating muscle atrophy through unknown mechanisms. This study tested the hypothesis that clenbuterol-induced growth and muscle sparing is mediated through the activation of Akt and mammalian target of rapamycin (mTOR) signaling pathways. Clenbuterol was administered to normal weight-bearing adult rats to examine the growth-inducing effects and to adult rats undergoing muscle atrophy as the result of hindlimb suspension or denervation to examine the muscle-sparing effects. The pharmacological inhibitor rapamycin was administered in combination with clenbuterol in vivo to determine whether activation of mTOR was involved in mediating the effects of clenbuterol. Clenbuterol administration increased the phosphorylation status of PKB/Akt, S6 kinase 1/p70s6k, and eukaryotic initiation factor 4E binding protein 1/PHAS-1. Clenbuterol treatment induced growth by 27–41% in normal rats and attenuated muscle loss during hindlimb suspension by 10–20%. Rapamycin treatment resulted in a 37–97% suppression of clenbuterol-induced growth and a 100% reduction of the muscle-sparing effect. In contrast, rapamycin was unable to block the muscle-sparing effects of clenbuterol after denervation. Clenbuterol was also shown to suppress the expression of the MuRF1 and MAFbx transcripts in muscles from normal, denervated, and hindlimb-suspended rats. These results demonstrate that the effects of clenbuterol are mediated, in part, through the activation of Akt and mTOR signaling pathways.
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Affiliation(s)
- William O Kline
- Univ. of California, Davis, Section of Neurobiology, Physiology, and Behavior, One Shields Ave., Davis, California 95616, USA
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18
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Burniston JG, Clark WA, Tan LB, Goldspink DF. Dose-dependent separation of the hypertrophic and myotoxic effects of the beta(2)-adrenergic receptor agonist clenbuterol in rat striated muscles. Muscle Nerve 2006; 33:655-63. [PMID: 16411205 PMCID: PMC1828609 DOI: 10.1002/mus.20504] [Citation(s) in RCA: 29] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/08/2022]
Abstract
Muscle growth in response to large doses (milligrams per kilogram) of beta(2)-adrenergic receptor agonists has been reported consistently. However, such doses may also induce myocyte death in the heart and skeletal muscles and hence may not be safe doses for humans. We report the hypertrophic and myotoxic effects of different doses of clenbuterol. Rats were infused with clenbuterol (range, 1 microg to 1 mg.kg(-1)) for 14 days. Muscle protein content, myofiber cross-sectional area, and myocyte death were then investigated. Infusions of >or=10 microg.kg(-1).d(-1) of clenbuterol significantly (P<0.05) increased the protein content of the heart (12%-15%), soleus (12%), plantaris (18%-29%), and tibialis anterior (11%-22%) muscles, with concomitant myofiber hypertrophy. Larger doses (100 microg or 1 mg) induced significant (P<0.05) myocyte death in the soleus (peak 0.2+/-0.1% apoptosis), diaphragm (peak 0.15+/-0.1% apoptosis), and plantaris (peak 0.3+/-0.05% necrosis), and significantly increased the area fraction of collagen in the myocardium. These data show that the low dose of 10 microg.kg(-1).d(-1) can be used in rats to investigate the anabolic effects of clenbuterol in the absence of myocyte death.
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Affiliation(s)
- Jatin G Burniston
- Research Institute for Sport & Exercise Sciences, Liverpool John Moores University, Webster Street, Liverpool L3 2ET, UK.
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19
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Goldsmith AM, Bentley JK, Zhou L, Jia Y, Bitar KN, Fingar DC, Hershenson MB. Transforming growth factor-beta induces airway smooth muscle hypertrophy. Am J Respir Cell Mol Biol 2005; 34:247-54. [PMID: 16239645 PMCID: PMC2644185 DOI: 10.1165/rcmb.2005-0166oc] [Citation(s) in RCA: 74] [Impact Index Per Article: 3.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/24/2022] Open
Abstract
Although smooth muscle hypertrophy is present in asthmatic airways, little is known about the biochemical pathways regulating airway smooth muscle protein synthesis, cell size, or accumulation of contractile apparatus proteins. We sought to develop a model of airway smooth muscle hypertrophy in primary cells using a physiologically relevant stimulus. We hypothesized that transforming growth factor (TGF)-beta induces hypertrophy in primary bronchial smooth muscle cells. Primary human bronchial smooth muscle cells isolated from unacceptable lung donor tissue were studied. Cells were seeded on uncoated plastic dishes at 50% confluence and TGF-beta was added. Experiments were performed in the absence of serum. TGF-beta increased cell size and total protein synthesis, expression of alpha-smooth muscle actin and smooth muscle myosin heavy chain, formation of actomyosin filaments, and cell shortening to acetylcholine. Further, TGF-beta increased airway smooth muscle alpha-actin synthesis in the presence of the transcriptional inhibitor actinomycin D, evidence that translational control is a physiologically important element of the observed hypertrophy. TGF-beta induced the phosphorylation of eukaryotic translation initiation factor-4E-binding protein, a signaling event specifically involved in translational control. Finally, two inhibitors of 4E-binding protein phosphorylation, the phosphoinositol 3-kinase inhibitor LY294002 and a phosphorylation site mutant of 4E-binding protein-1 that dominantly inhibits eukaryotic initiation factor-4E, each blocked TGF-beta-induced alpha-actin expression and cell enlargement. We conclude that TGF-beta induces hypertrophy of primary bronchial smooth muscle cells. Further, phosphorylation of 4E-binding protein is required for the observed hypertrophy.
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Affiliation(s)
- Adam M Goldsmith
- Department of Pediatrics and Communicable Diseases, University of Michigan, Ann Arbor, MI, USA
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20
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Biolo G, Antonione R, Barazzoni R, Zanetti M, Guarnieri G. Mechanisms of altered protein turnover in chronic diseases: a review of human kinetic studies. Curr Opin Clin Nutr Metab Care 2003; 6:55-63. [PMID: 12496681 DOI: 10.1097/00075197-200301000-00009] [Citation(s) in RCA: 23] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/25/2022]
Abstract
PURPOSE OF REVIEW Changes in hormone secretion, tissue perfusion, oxygen availability, energy-protein intake, free amino acid pattern, hydration state, acid-base balance as well as activation of the systemic inflammatory response may affect protein synthesis and degradation. The overall purpose of this review is to describe how these factors may interact to change protein turnover in the different directions seen in kinetic studies in humans. RECENT FINDINGS Evidence indicates that, in vivo, changes of protein synthesis and degradation are strictly related. When protein synthesis is primarily suppressed, protein degradation is found to be unchanged or even slightly decreased. When protein degradation is primarily accelerated, the rate of synthesis is unchanged or even increased. Chronic disease states can, therefore, be characterized either by decreased or accelerated protein turnover. Apparent discrepancies among various studies in chronic uraemia, liver cirrhosis, chronic obstructive pulmonary disease and cancer may stem from the fact that the pathogenesis of protein metabolism abnormalities is multifactorial. When the effects of inflammatory mediators and stress hormones start overwhelming factors that tend to decrease protein synthesis and turnover (decreased protein-energy intake, physical activity, tissue oxygen delivery, leucine levels, etc.), the rate of protein degradation and turnover may increase. SUMMARY Low-protein turnover conditions are usually associated with the adequate sparing of body proteins, whereas in high-protein turnover conditions protein loss may proceed at a faster rate. Nonetheless, impaired recovery from acute complications and the reduced renewal of damaged and toxic proteins are potential undesired consequences of low-protein turnover.
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21
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Canu M, Stevens L, Ricart-Firinga C, Picquet F, Falempin M. Effect of the beta(2)-agonist clenbuterol on the locomotor activity of rat submitted to a 14-day period of hypodynamia-hypokinesia. Behav Brain Res 2001; 122:103-12. [PMID: 11287081 DOI: 10.1016/s0166-4328(01)00178-4] [Citation(s) in RCA: 13] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/18/2022]
Abstract
The beta(2)-adrenergic agonist clenbuterol is known for its anabolic action on normal and atrophied muscles. The aim of this work was to evaluate if chronic clenbuterol administration could prevent alterations in the locomotor activity induced by hindlimb suspension. The effects of clenbuterol were evaluated in three studies: muscle morphological characteristics, observation of locomotor movement and electromyographic activity of soleus and gastrocnemius muscles. Rats were divided into four groups: control (CON, morphological study only), hindlimb suspended (HS), clenbuterol administered (CB, 2 mg kg(-1) per day in drinking water), and hindlimb suspended+clenbuterol administered (HSCB). The soleus muscle weight was reduced in the two suspended groups (HS and HSCB) but did not change after clenbuterol treatment. By contrast, the gastrocnemius weight was not affected by suspension but was increased by clenbuterol (CB and HSCB). Some locomotor deficits were always observed in HS rats (unstable gait, ankle hyperextension, ellipsis). Clenbuterol administration did not prevent these perturbations. Cycle duration and soleus burst duration were increased in the three groups. Soleus mean EMG (burst area/duration) was decreased in HS rats, but not in the two other groups. For the gastrocnemius, burst duration was increased in CB rats, decreased in HSCB rats and unchanged in HS ones; mean EMG did not change. In conclusion, clenbuterol cannot be used as a countermeasure to reduce the alteration in locomotor performance. Moreover, our results suggest that this alteration is specifically related to changes in neuronal properties.
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Affiliation(s)
- M Canu
- Laboratoire de Plasticité Neuromusculaire, Université des Sciences et Technologies de Lille, Bât. SN4, F-59655, Cedex, Villeneuve d'Ascq, France.
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22
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von Deutsch DA, Abukhalaf IK, Wineski LE, Aboul-Enein HY, Pitts SA, Parks BA, Oster RA, Paulsen DF, Potter DE. Beta-agonist-induced alterations in organ weights and protein content: comparison of racemic clenbuterol and its enantiomers. Chirality 2000; 12:637-48. [PMID: 10897101 DOI: 10.1002/1520-636x(2000)12:8<637::aid-chir6>3.0.co;2-w] [Citation(s) in RCA: 31] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/10/2022]
Abstract
Clenbuterol is a relatively selective beta2-adrenergic partial agonist that has bronchodilator activity. This drug has been investigated as a potential countermeasure to microgravity- or disuse-induced skeletal muscle atrophy because of presumed anabolic effects. The purpose of this study was to: 1) analyze the anabolic effect of clenbuterol's (-)-R and (+)-S enantiomers (0.2 mg/kg) on muscles (cardiac and skeletal) and other organs; and 2) compare responses of enantiomers to the racemate (0.4 mg/kg and 1.0 mg/kg). Male Sprague Dawley rats were treated with: a) racemic clenbuterol (rac-clenbuterol, 0.4 or 1.0 mg/kg); b) enantiomers [clenbuterol (-)-R or (+)-S]; or c) vehicle (1.0 mL/kg buffered saline). Anabolic activity was determined by measuring tissue mass and protein content. HPLC teicoplanin chiral stationary phase was used to directly resolve racemic clenbuterol to its individual enantiomers. In skeletal muscle, both enantiomers had equal anabolic activity, and the effects were muscle- and anatomic region-specific in magnitude. Although the enantiomers did not affect the ventricular mass to body weight ratio, clenbuterol (+)-S induced a small but significant increase in ventricular mass. Both clenbuterol enantiomers produced significant increases in skeletal muscle mass, while being less active in producing cardiac ventricular muscle hypertrophy than the racemic mixture.
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Affiliation(s)
- D A von Deutsch
- Musculoskeletal Research Group, Space Medicine and Life Sciences Research Center, Morehouse School of Medicine, Atlanta, Georgia 30310-1495, USA.
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Criswell DS, Powers SK, Herb RA. Clenbuterol-induced fiber type transition in the soleus of adult rats. EUROPEAN JOURNAL OF APPLIED PHYSIOLOGY AND OCCUPATIONAL PHYSIOLOGY 1996; 74:391-6. [PMID: 8954285 DOI: 10.1007/bf02337718] [Citation(s) in RCA: 35] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 02/03/2023]
Abstract
This study examined the effects of 6 weeks of treatment with the beta(2)-adrenoceptor agonist, clenbuterol, on the soleus muscle of adult female Sprague-Dawley rats. Animals (4 months old) were divided into two groups: clenbuterol treated (CL, n = 7) (2 mg.kg-1 body mass injected subcutaneously every other day), and control (CON, n = 7) (injected with isotonic saline). Post-treatment body weights were approximately 5% greater in the CL group compared to CON (P < 0.05). Polyacrylamide gel electrophoresis (SDS-PAGE) of soleus myofibrillar protein indicated a clenbuterol-induced decrease (P < 0.05) in the relative percentage of type I myosin heavy chain (MHC) with a concomitant increase (P < 0.05) in type IIdx MHC, while the proportion of type IIa MHC was unaffected. ATPase fiber typing revealed increases (P < 0.05) in the proportion of type II fibers expressed both as a percentage of total fiber number and total cross-sectional area (CSA). Finally, mean type II fiber CSA was approximately 25% greater (P < 0.05) in the CL groups as compared to the CON group. These data indicate that clenbuterol treatment results in alterations in the MHC phenotype and an increased proportion of type II fiber CSA in the soleus of adult rats. These observations were due to an increase in the total number of type II fibers, as well as hypertrophy of these fibers. Thus, the relative increase in the number of histochemically determined type II fibers and the emergence of the normally unexpressed type IIdx MHC isoform in the soleus suggest a clenbuterol-induced transition of muscle fiber phenotype as well as selective hypertrophy of the type II fibers.
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Affiliation(s)
- D S Criswell
- Dept. of Exercise and Sport Sciences, University of Florida, Gainesville 32611, USA
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