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Espino-Gonzalez E, Dalbram E, Mounier R, Gondin J, Farup J, Jessen N, Treebak JT. Impaired skeletal muscle regeneration in diabetes: From cellular and molecular mechanisms to novel treatments. Cell Metab 2024; 36:1204-1236. [PMID: 38490209 DOI: 10.1016/j.cmet.2024.02.014] [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: 09/07/2023] [Revised: 01/10/2024] [Accepted: 02/22/2024] [Indexed: 03/17/2024]
Abstract
Diabetes represents a major public health concern with a considerable impact on human life and healthcare expenditures. It is now well established that diabetes is characterized by a severe skeletal muscle pathology that limits functional capacity and quality of life. Increasing evidence indicates that diabetes is also one of the most prevalent disorders characterized by impaired skeletal muscle regeneration, yet underlying mechanisms and therapeutic treatments remain poorly established. In this review, we describe the cellular and molecular alterations currently known to occur during skeletal muscle regeneration in people with diabetes and animal models of diabetes, including its associated comorbidities, e.g., obesity, hyperinsulinemia, and insulin resistance. We describe the role of myogenic and non-myogenic cell types on muscle regeneration in conditions with or without diabetes. Therapies for skeletal muscle regeneration and gaps in our knowledge are also discussed, while proposing future directions for the field.
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Affiliation(s)
- Ever Espino-Gonzalez
- Novo Nordisk Foundation Center for Basic Metabolic Research, Faculty of Health and Medical Sciences, University of Copenhagen, Copenhagen 2200, Denmark
| | - Emilie Dalbram
- Novo Nordisk Foundation Center for Basic Metabolic Research, Faculty of Health and Medical Sciences, University of Copenhagen, Copenhagen 2200, Denmark
| | - Rémi Mounier
- Institut NeuroMyoGène, Unité Physiopathologie et Génétique du Neurone et du Muscle, Université Claude Bernard Lyon 1, CNRS UMR 5261, Inserm U1315, Univ Lyon, Lyon, France
| | - Julien Gondin
- Institut NeuroMyoGène, Unité Physiopathologie et Génétique du Neurone et du Muscle, Université Claude Bernard Lyon 1, CNRS UMR 5261, Inserm U1315, Univ Lyon, Lyon, France
| | - Jean Farup
- Department of Biomedicine, Aarhus University, Aarhus 8000, Denmark; Steno Diabetes Center Aarhus, Aarhus University Hospital, Aarhus 8200, Denmark
| | - Niels Jessen
- Department of Biomedicine, Aarhus University, Aarhus 8000, Denmark; Steno Diabetes Center Aarhus, Aarhus University Hospital, Aarhus 8200, Denmark; Department of Clinical Pharmacology, Aarhus University Hospital, Aarhus 8200, Denmark
| | - Jonas T Treebak
- Novo Nordisk Foundation Center for Basic Metabolic Research, Faculty of Health and Medical Sciences, University of Copenhagen, Copenhagen 2200, Denmark.
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Tack W, De Cock AM, Dirinck EL, Bastijns S, Ariën F, Perkisas S. Pathophysiological interactions between sarcopenia and type 2 diabetes: A two-way street influencing diagnosis and therapeutic options. Diabetes Obes Metab 2024; 26:407-416. [PMID: 37854007 DOI: 10.1111/dom.15321] [Citation(s) in RCA: 2] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 08/20/2023] [Revised: 09/24/2023] [Accepted: 09/25/2023] [Indexed: 10/20/2023]
Abstract
This review will try to elucidate the interconnected pathophysiology of sarcopenia and type 2 diabetes (T2D) and will try to identify a common pathway to explain their development. To this end, the PubMed and Scopus databases were searched for articles published about the underlying pathophysiology, diagnosis and treatment of both sarcopenia and T2D. The medical subject heading (MeSH) terms 'sarcopenia' AND 'diabetes mellitus' AND ('physiopathology' OR 'diagnosis' OR 'therapeutics' OR 'aetiology' OR 'causality') were used. After screening, 32 papers were included. It was evident that sarcopenia and T2D share multiple pathophysiological mechanisms. Common changes in muscle architecture consist of a shift in myocyte composition, increased myosteatosis and a decreased capacity for muscle regeneration. Further, both diseases are linked to an imbalance in myokine and sex hormone production. Chronic low-grade inflammation and increased levels of oxidative stress are also known pathophysiological contributors. In the future, research efforts should be directed towards discovering common checkpoints in the development of T2D and sarcopenia as possible shared therapeutic targets for both diseases. Current treatment for T2D with biguanides, incretins and insulin may already convey a protective effect on the development of sarcopenia. Furthermore, attention should be given to early diagnosis of sarcopenia within the population of people with T2D, given the sizeable physical and medical burden it encompasses. A combination of simple diagnostic techniques could be used at regular diabetes check-ups to identify sarcopenia at an early stage and start lifestyle modifications and treatment as soon as possible.
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Affiliation(s)
- Wouter Tack
- ZNA (ZiekenhuisNetwerk Antwerpen), University Center for Geriatrics, Antwerp, Belgium
| | - Anne-Marie De Cock
- ZNA (ZiekenhuisNetwerk Antwerpen), University Center for Geriatrics, Antwerp, Belgium
- Department of Family Medicine and Population Health, University of Antwerp, Antwerp, Belgium
| | - Eveline Lia Dirinck
- Department of Endocrinology, Diabetology and Metabolism, Anwerp University Hospital, Edegem, Belgium
| | - Sophie Bastijns
- ZNA (ZiekenhuisNetwerk Antwerpen), University Center for Geriatrics, Antwerp, Belgium
| | - Femke Ariën
- ZNA (ZiekenhuisNetwerk Antwerpen), University Center for Geriatrics, Antwerp, Belgium
| | - Stany Perkisas
- ZNA (ZiekenhuisNetwerk Antwerpen), University Center for Geriatrics, Antwerp, Belgium
- Department of Family Medicine and Population Health, University of Antwerp, Antwerp, Belgium
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Petrelli M. Sarcopenia, malnutrition, and frailty: disease implications for geriatric DM patients. JOURNAL OF GERONTOLOGY AND GERIATRICS 2021. [DOI: 10.36150/2499-6564-n449] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022]
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Jang HC. Diabetes and Muscle Dysfunction in Older Adults. Ann Geriatr Med Res 2019; 23:160-164. [PMID: 32743306 PMCID: PMC7370755 DOI: 10.4235/agmr.19.0038] [Citation(s) in RCA: 18] [Impact Index Per Article: 3.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/03/2019] [Accepted: 11/19/2019] [Indexed: 12/25/2022] Open
Abstract
Aging and diabetes are both risk factors for functional decline or disability in older adults with diabetes. Recent studies demonstrated that the presence of diabetes significantly increases the risk of sarcopenia, frailty, and geriatric syndrome including falls, hospitalization, disability, and mortality in older adults. They have also suggested that sarcopenia, frailty, and geriatric syndrome should be categorized as a third category of complications in addition to the traditional micro- and macro-vascular complications leading to disability in older adults with diabetes. Prevention of functional decline is a crucial strategy in geriatric management. Recovery of functional independence from dependence or disability is uncommon and lengthy. Assessments of functional status and geriatric syndrome including sarcopenia or frailty should be mandatory in older adults with diabetes to promote early interventions based on physical exercise and nutrition education. This brief review discussed age-associated and diabetes-associated muscle changes and their association with functional decline.
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Affiliation(s)
- Hak Chul Jang
- Department of Internal Medicine, Seoul National University Bundang Hospital, Seoul National University College of Medicine, Seongnam, Korea
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Ma B, He X, Lu Z, Zhang L, Li J, Jiang Y, Zhou G, Gao F. Chronic heat stress affects muscle hypertrophy, muscle protein synthesis and uptake of amino acid in broilers via insulin like growth factor-mammalian target of rapamycin signal pathway. Poult Sci 2019; 97:4150-4158. [PMID: 29982693 DOI: 10.3382/ps/pey291] [Citation(s) in RCA: 46] [Impact Index Per Article: 9.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/29/2018] [Accepted: 06/13/2018] [Indexed: 12/13/2022] Open
Abstract
Heat stress markedly impairs the growth performance of broilers, such as the reduction of breast muscle mass and yield. The aim of this study was to examine the molecular mechanism of depressed muscle mass and yield caused by heat stress. A total of 144 (28-day-old) male broilers were allocated randomly into 3 treatment groups: (1) the normal control group (environment temperature was 22°C), (2) the heat stress group (environment temperature was 32°C), (3) the pair-fed group (environment temperature was 22°C and pair-fed to heat stress group). The experiment lasted for 14 d (from the age of 28 to 42 d). After 14 d of heat exposure, heat stress decreased (P < 0.05) broiler average daily gain, breast muscle mass, and muscle yield, and increased (P < 0.05) feed to gain ratio. After 14 d of heat exposure, heat stress increased (P < 0.05) the activities of aspartate aminotransferase and the concentrations of uric acid and most amino acids in serum, and reduced (P < 0.05) the concentration of insulin like growth factor 1 (IGF-1) in serum. Additionally, heat stress decreased (P < 0.05) the mRNA expressions of IGF-1, IGF-1 receptor, insulin receptor substrate 1, mammalian target of rapamycin (mTOR), the 70 kD ribosomal protein S6 kinase, myogenic differentiation, myogenin, solute carrier family 38 member 2, solute carrier family 7 member 5, and solute carrier family 3 member 2 of the breast muscle. In conclusion, chronic heat stress resulted in lower breast muscle mass and yield, and decreased muscle protein synthesis and amino acid transportation by downregulating IGFs-mTOR signal pathway. These findings have important practical significance in discovering effective means to alleviate muscle loss caused by chronic heat stress.
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Affiliation(s)
- Bingbing Ma
- College of Animal Science and Technology, Key Laboratory of Animal Origin Food Production and Safety Guarantee of Jiangsu Province, Jiangsu Collaborative Innovation Center of Meat Production and Processing, Quality and Safety Control, Nanjing Agricultural University, Nanjing 210095, P. R. China
| | - Xiaofang He
- College of Animal Science and Technology, Key Laboratory of Animal Origin Food Production and Safety Guarantee of Jiangsu Province, Jiangsu Collaborative Innovation Center of Meat Production and Processing, Quality and Safety Control, Nanjing Agricultural University, Nanjing 210095, P. R. China
| | - Zhuang Lu
- College of Animal Science and Technology, Key Laboratory of Animal Origin Food Production and Safety Guarantee of Jiangsu Province, Jiangsu Collaborative Innovation Center of Meat Production and Processing, Quality and Safety Control, Nanjing Agricultural University, Nanjing 210095, P. R. China
| | - Lin Zhang
- College of Animal Science and Technology, Key Laboratory of Animal Origin Food Production and Safety Guarantee of Jiangsu Province, Jiangsu Collaborative Innovation Center of Meat Production and Processing, Quality and Safety Control, Nanjing Agricultural University, Nanjing 210095, P. R. China
| | - Jiaolong Li
- College of Animal Science and Technology, Key Laboratory of Animal Origin Food Production and Safety Guarantee of Jiangsu Province, Jiangsu Collaborative Innovation Center of Meat Production and Processing, Quality and Safety Control, Nanjing Agricultural University, Nanjing 210095, P. R. China
| | - Yun Jiang
- Ginling College, Nanjing Normal University, Nanjing 210097, P.R. China
| | - Guanghong Zhou
- College of Animal Science and Technology, Key Laboratory of Animal Origin Food Production and Safety Guarantee of Jiangsu Province, Jiangsu Collaborative Innovation Center of Meat Production and Processing, Quality and Safety Control, Nanjing Agricultural University, Nanjing 210095, P. R. China
| | - Feng Gao
- College of Animal Science and Technology, Key Laboratory of Animal Origin Food Production and Safety Guarantee of Jiangsu Province, Jiangsu Collaborative Innovation Center of Meat Production and Processing, Quality and Safety Control, Nanjing Agricultural University, Nanjing 210095, P. R. China
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Abstract
The mechanistic target of rapamycin (mTOR) is an evolutionarily conserved serine/threonine kinase that senses and integrates environmental information into cellular regulation and homeostasis. Accumulating evidence has suggested a master role of mTOR signalling in many fundamental aspects of cell biology and organismal development. mTOR deregulation is implicated in a broad range of pathological conditions, including diabetes, cancer, neurodegenerative diseases, myopathies, inflammatory, infectious, and autoimmune conditions. Here, we review recent advances in our knowledge of mTOR signalling in mammalian physiology. We also discuss the impact of mTOR alteration in human diseases and how targeting mTOR function can treat human diseases.
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Affiliation(s)
- Yassine El Hiani
- a Department of Physiology and Biophysics, Dalhousie University, PO Box 15000, Halifax, NS B3H 4R2, Canada
| | - Emmanuel Eroume-A Egom
- b Jewish General Hospital and Lady Davis Institute for Medical Research, Montreal, QC H3T 1E2, Canada
| | - Xian-Ping Dong
- a Department of Physiology and Biophysics, Dalhousie University, PO Box 15000, Halifax, NS B3H 4R2, Canada
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Mu X, Tang Y, Takayama K, Chen W, Lu A, Wang B, Weiss K, Huard J. RhoA/ROCK inhibition improves the beneficial effects of glucocorticoid treatment in dystrophic muscle: implications for stem cell depletion. Hum Mol Genet 2018; 26:2813-2824. [PMID: 28549178 DOI: 10.1093/hmg/ddx117] [Citation(s) in RCA: 9] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/22/2016] [Accepted: 03/10/2017] [Indexed: 12/31/2022] Open
Abstract
Glucocorticoid treatment represents a standard palliative treatment for Duchenne muscular dystrophy (DMD) patients, but various adverse effects have limited this treatment. In an effort to understand the mechanism(s) by which glucocorticoids impart their effects on the dystrophic muscle, and potentially reduce the adverse effects, we have studied the effect of prednisolone treatment in dystrophin/utrophin double knockout (dKO) mice, which exhibit a severe dystrophic phenotype due to rapid muscle stem cell depletion. Our results indicate that muscle stem cell depletion in dKO muscle is related to upregulation of mTOR, and that prednisolone treatment reduces the expression of mTOR and other pro-inflammatory mediators, consequently slowing down muscle stem cell depletion. However, prednisolone treatment was unable to improve the myogenesis of stem cells and reduce fibrosis in dKO muscle. We then studied whether glucocorticoid treatment can be improved by co-administration of an inhibitor of RhoA/ROCK signaling, which can be activated by glucocorticoids and was found in our previous work to be over-activated in dystrophic muscle. Our results indicate that the combination of RhoA/ROCK inhibition and glucocorticoid treatment in dystrophic muscle have a synergistic effect in alleviating the dystrophic phenotype. Taken together, our study not only shed light on the mechanism by which glucocorticoid imparts its beneficial effect on dystrophic muscle, but also revealed the synergistic effect of RhoA/ROCK inhibition and glucocorticoid treatment, which could lead to the development of more efficient therapeutic approaches for treating DMD patients.
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Affiliation(s)
- Xiaodong Mu
- Department of Orthopaedic Surgery, University of Texas Health Science Center at Houston, Houston, TX 77054, USA.,Center for Regenerative Sports Medicine, Steadman Philippon Research Institute, Vail, CO 81657, USA
| | - Ying Tang
- Department of Orthopaedic Surgery, University of Pittsburgh, Pittsburgh, PA 15219, USA
| | - Koji Takayama
- Department of Orthopaedic Surgery, Kobe University Graduate School of Medicine, Kobe 650-0017, Japan
| | - Wanqun Chen
- Department of Orthopaedic Surgery, University of Texas Health Science Center at Houston, Houston, TX 77054, USA.,Department of Biochemistry and Molecular Biology, Jinan University, Guangdong, China
| | - Aiping Lu
- Department of Orthopaedic Surgery, University of Texas Health Science Center at Houston, Houston, TX 77054, USA.,Center for Regenerative Sports Medicine, Steadman Philippon Research Institute, Vail, CO 81657, USA
| | - Bing Wang
- Department of Orthopaedic Surgery, University of Pittsburgh, Pittsburgh, PA 15219, USA
| | - Kurt Weiss
- Department of Orthopaedic Surgery, University of Pittsburgh, Pittsburgh, PA 15219, USA
| | - Johnny Huard
- Department of Orthopaedic Surgery, University of Texas Health Science Center at Houston, Houston, TX 77054, USA.,Center for Regenerative Sports Medicine, Steadman Philippon Research Institute, Vail, CO 81657, USA
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Abstract
Populations are aging and the prevalence of diabetes mellitus is increasing tremendously. The number of older people with diabetes is increasing unexpectedly. Aging and diabetes are both risk factors for functional disability. Thus, increasing numbers of frail or disabled older patients with diabetes will increase both direct and indirect health-related costs. Diabetes has been reported as an important risk factor of developing physical disability in older adults. Older people with diabetes have lower muscle mass and weaker muscle strength. In addition, muscle quality is poorer in diabetic patients. Sarcopenia and frailty have a common soil and may share a similar pathway for multiple pathologic processes in older people. Sarcopenia is thought to be an intermediate step in the development of frailty in patients with diabetes. Thus, early detection of sarcopenia and frailty in older adults with diabetes should be routine clinical practice to prevent frailty or to intervene earlier in frail patients.
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Affiliation(s)
- Hak Chul Jang
- Department of Internal Medicine, Seoul National University Bundang Hospital, Seoul National University College of Medicine, Seongnam, Korea.
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Mechanical stretch activates mammalian target of rapamycin and AMP-activated protein kinase pathways in skeletal muscle cells. Mol Cell Biochem 2015; 406:285-92. [PMID: 25971373 DOI: 10.1007/s11010-015-2446-7] [Citation(s) in RCA: 15] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/06/2015] [Accepted: 05/07/2015] [Indexed: 10/23/2022]
Abstract
Cellular protein synthesis is believed to be antagonistically regulated by mammalian target of rapamycin (mTOR) and AMP-activated protein kinase (AMPK) signaling pathways. In the present study, we examined the relationship between mTOR/p70 S6 kinase (p70S6K) and AMPK in response to mechanical stretch. C2C12 myoblasts were grown on a silicone elastomer chamber to confluence and further cultured in differentiation medium for 4 days to form multinucleated myotubes. Cells were subjected to 15% cyclic uniaxial stretch for 4 h at a frequency of 1 Hz. Phosphorylation of p70S6K at threonine 389 and AMPK at threonine 172 of the catalytic α subunit were concomitantly increased by mechanical stretch. Stimulation of the mTOR pathway by adding leucine and insulin increased the phosphorylation of p70S6K without inactivation of AMPK. In contrast, addition of compound C, a pharmacological inhibitor of AMPK, increased the phosphorylation of p70S6K in stretched cells. Activation of AMPK by the addition of 5-amino-4-imidazolecarboxamide ribonucleoside reduced the phosphorylation of p70S6K in response to mechanical stretch. In conclusion, crosstalk between mTOR and AMPK signaling was not tightly regulated in response to physiological stimuli, such as mechanical stress and/or nutrients. However, pharmacological modulation of AMPK influenced the mTOR/p70S6K signaling pathway.
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11
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Effect of rapamycin on immunity induced by vector-mediated dystrophin expression in mdx skeletal muscle. Sci Rep 2012; 2:399. [PMID: 22570764 PMCID: PMC3347316 DOI: 10.1038/srep00399] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/22/2011] [Accepted: 04/23/2012] [Indexed: 02/06/2023] Open
Abstract
Duchenne muscular dystrophy (DMD) is caused by mutations in the dystrophin gene. Therapeutic gene replacement of a dystrophin cDNA into dystrophic muscle can provide functional dystrophin protein to the tissue. However, vector-mediated gene transfer is limited by anti-vector and anti-transgene host immunity that causes rejection of the therapeutic protein. We hypothesized that rapamycin (RAPA) would diminish immunity due to vector-delivered recombinant dystrophin in the adult mdx mouse model for DMD. To test this hypothesis, we injected limb muscle of mdx mice with RAPA-containing, poly-lactic-co-glycolic acid (PLGA) microparticles prior to dystrophin gene transfer and analyzed treated tissue after 6 weeks. RAPA decreased host immunity against vector-mediated dystrophin protein, as demonstrated by decreased cellular infiltrates and decreased anti-dystrophin antibody production. The interpretation of the effect of RAPA on recombinant dystrophin expression was complex because of an effect of PLGA microparticles.
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Imoto A, Yokoyama T, Suwa K, Yamasaki F, Yatabe T, Yokoyama R, Yamashita K, Selldén E. Bolus oral or continuous intestinal amino acids reduce hypothermia during anesthesia in rats. J Nutr Sci Vitaminol (Tokyo) 2010; 56:104-8. [PMID: 20495291 DOI: 10.3177/jnsv.56.104] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/27/2022]
Abstract
We hypothesized that, with oral or intestinal administration of amino acids (AA), we may reduce hypothermia during general anesthesia as effectively as with intravenous AA. We, therefore, examined the effect of bolus oral and continuous intestinal AA in preventing hypothermia in rats. Male Wistar rats were anesthetized with sevoflurane for induction and with propofol for maintenance. In the first experiment, 30 min before anesthesia, rats received one bolus 42 mL/kg of AA solution (100 g/L) or saline orally. Then for the next 3 h during anesthesia, they received 14 mL/kg/h of AA and/or saline intravenously. They were in 4 groups: I-A/A, both AA; I-A/S, oral AA and intravenous saline; I-S/A, oral saline and intravenous AA; I-S/S, both saline. In the second experiment, rats received 14 mL/kg/h duodenal AA and/or saline for 2 h. They were in 3 groups: II-A/S, duodenal AA and intravenous saline; II-S/A, duodenal saline and intravenous AA; II-S/S, both saline. Core body temperature was measured rectally. After the second experiment, serum electrolytes were examined. In both experiments, rectal temperature decreased in all groups during anesthesia. However, the decrease in rectal temperature was significantly less in groups receiving AA than in groups receiving only saline. In the second experiment, although there was no significant difference in the decrease in body temperature between II-A/S and II-S/A, Na(+) concentration was significantly lower in II-S/A. In conclusion, AA, administered orally or intestinally, tended to keep the body temperature stable during anesthesia without disturbing electrolyte balance. These results suggest that oral or enteral AA may be useful for prevention of hypothermia in patients.
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Affiliation(s)
- Akinobu Imoto
- Department of Anesthesiology and Critical Care Medicine, Kochi Medical School, Nankoku, Japan
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Richmond SR, Touchberry CD, Gallagher PM. Forskolin attenuates the action of insulin on the Akt–mTOR pathway in human skeletal muscle. Appl Physiol Nutr Metab 2009; 34:916-25. [DOI: 10.1139/h09-096] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022]
Abstract
Forskolin (FSK) is capable of both stimulating and inhibiting the intracellular signaling pathways of protein synthesis tissues other than skeletal muscle. The purpose of this investigation was to determine if FSK administration affects various elements of the protein kinase B (Akt)–mammalian target of rapamycin (mTOR) pathway in human skeletal muscle. Ten (n = 10) healthy, young (21.6 ± 1.3 years), nonobese (body mass index = 25.5 ± 3.5 kg·m–2), recreationally active males were selected for participation. Following an 8 h fast, 2 muscle biopsies of the vastus lateralis were performed. The samples were sectioned and exposed to 4 in vitro treatment conditions: basal, FSK, insulin (INS), and FSK+INS. The samples were then analyzed for total and phosphorylated levels of Akt, mTOR, S6 kinase (S6K1), and 4E binding protein (4EBP1). Akt phosphorylation was significantly greater in the INS-treated samples compared with the basal and FSK conditions (p = 0.007). Furthermore, the ratio of phosphorylated Akt to total Akt (P/T) was higher in the INS samples compared with the basal and FSK samples (p = 0.001). There were no differences in mTOR phosphorylation among the 4 groups; however, total mTOR was significantly greater in the FSK+INS group (p = 0.006). There were also no differences in phosphorylated or total levels of S6K1 among the 4 groups. However, 4EBP1 phosphorylation was significantly greater in the INS-treated samples compared with the basal (p = 0.003) and FSK (p = 0.004) treatments. There were no differences in the ratio of phosphorylated 4EBP1 to total 4EBP1 (P/T) among the 4 groups. These results indicate that FSK does not activate the Akt–mTOR pathway in human skeletal muscle; however, these results suggest that FSK may inhibit the actions of INS on this pathway.
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Affiliation(s)
- Scott R. Richmond
- Applied Physiology Laboratory, University of Kansas, Lawrence, KS 66045, USA
| | - Chad D. Touchberry
- Applied Physiology Laboratory, University of Kansas, Lawrence, KS 66045, USA
| | - Philip M. Gallagher
- Applied Physiology Laboratory, University of Kansas, Lawrence, KS 66045, USA
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Han B, Tong J, Zhu MJ, Ma C, Du M. Insulin-like growth factor-1 (IGF-1) and leucine activate pig myogenic satellite cells through mammalian target of rapamycin (mTOR) pathway. Mol Reprod Dev 2008; 75:810-7. [DOI: 10.1002/mrd.20832] [Citation(s) in RCA: 66] [Impact Index Per Article: 4.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/15/2022]
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15
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Yamaoka I, Doi M, Nakayama M, Ozeki A, Mochizuki S, Sugahara K, Yoshizawa F. Intravenous administration of amino acids during anesthesia stimulates muscle protein synthesis and heat accumulation in the body. Am J Physiol Endocrinol Metab 2006; 290:E882-8. [PMID: 16352675 DOI: 10.1152/ajpendo.00333.2005] [Citation(s) in RCA: 27] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/22/2022]
Abstract
The present study was conducted to determine the contribution of muscle protein synthesis to the prevention of anesthesia-induced hypothermia by intravenous administration of an amino acid (AA) mixture. We examined the changes of intraperitoneal temperature (Tcore) and the rates of protein synthesis (K(s)) and the phosphorylation states of translation initiation regulators and their upstream signaling components in skeletal muscle in conscious (Nor) or propofol-anesthetized (Ane) rats after a 3-h intravenous administration of a balanced AA mixture or saline (Sal). Compared with Sal administration, the AA mixture administration markedly attenuated the decrease in Tcore in rats during anesthesia, whereas Tcore in the Nor-AA group became slightly elevated during treatment. Stimulation of muscle protein synthesis resulting from AA administration was observed in each case, although K(s) remained lower in the Ane-AA group than in the Nor-Sal group. AA administration during anesthesia significantly increased insulin concentrations to levels approximately 6-fold greater than in the Nor-AA group and enhanced phosphorylation of eukaryotic initiation factor 4E-binding protein-1 (4E-BP1) and ribosomal protein S6 protein kinase relative to all other groups and treatments. The alterations in the Ane-AA group were accompanied by hyperphosphorylation of protein kinase B and the mammalian target of rapamycin (mTOR). These results suggest that administration of an AA mixture during anesthesia stimulates muscle protein synthesis via insulin-mTOR-dependent activation of translation initiation regulators caused by markedly elevated insulin and, thereby, facilitates thermal accumulation in the body.
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Affiliation(s)
- Ippei Yamaoka
- Division of Pharmacology, Drug Safety and Metabolism, Otsuka Pharmaceutical Factory, Naruto, Tokushima 772-8601, Japan.
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Abstract
PURPOSE OF REVIEW Congestive heart failure is increasing in prevalence and represents a major public health problem. The syndrome of advanced heart failure often includes muscle wasting, commonly termed cardiac cachexia, which is a predictor of poor outcome. Mechanisms of cardiac cachexia are poorly understood, but there is recent evidence that increased angiotensin II, interacting with the insulin-like growth factor-1 system, plays an important role. RECENT FINDINGS In animals, angiotensin II produces weight loss through a pressor-independent mechanism, accompanied by decreased levels of circulating and skeletal muscle insulin-like growth factor-1 and increased mRNA levels of the ubiquitin ligases atrogin-1 and Muscle RING finger-1 in skeletal muscle. Reduced insulin-like growth factor-1 action in muscle leads to increased proteolysis, through the ubiquitin-proteasome pathway, and increased apoptosis. These changes are blocked by muscle-specific expression of insulin-like growth factor-1, likely to be via the Akt/mTOR/p70S6K signaling pathway. SUMMARY The link between insulin-like growth factor-1, the ubiquitin-proteasome pathway, and angiotensin II effects has widespread clinical implications for the understanding of mechanisms of catabolic conditions. Therapeutic interventions targeting cross-talk mechanisms between angiotensin II and insulin-like growth factor-1 effects could provide new approaches for the treatment of muscle wasting.
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van der Velden JLJ, Langen RCJ, Kelders MCJM, Wouters EFM, Janssen-Heininger YMW, Schols AMWJ. Inhibition of glycogen synthase kinase-3β activity is sufficient to stimulate myogenic differentiation. Am J Physiol Cell Physiol 2006; 290:C453-62. [PMID: 16162663 DOI: 10.1152/ajpcell.00068.2005] [Citation(s) in RCA: 79] [Impact Index Per Article: 4.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/20/2022]
Abstract
Skeletal muscle atrophy is a prominent and disabling feature of chronic wasting diseases. Prevention or reversal of muscle atrophy by administration of skeletal muscle growth (hypertrophy)-stimulating agents such as insulin-like growth factor I (IGF-I) could be an important therapeutic strategy in these diseases. To elucidate the IGF-I signal transduction responsible for muscle formation (myogenesis) during muscle growth and regeneration, we applied IGF-I to differentiating C2C12myoblasts and evaluated the effects on phosphatidylinositol 3-kinase (PI3K)/Akt/glycogen synthase kinase-3β (GSK-3β) signaling and myogenesis. IGF-I caused phosphorylation and inactivation of GSK-3β activity via signaling through the PI3K/Akt pathway. We assessed whether pharmacological inhibition of GSK-3β with lithium chloride (LiCl) was sufficient to stimulate myogenesis. Addition of IGF-I or LiCl stimulated myogenesis, evidenced by increased myotube formation, muscle creatine kinase (MCK) activity, and troponin I (TnI) promoter transactivation during differentiation. Moreover, mRNAs encoding MyoD, Myf-5, myogenin, TnI-slow, TnI-fast, MCK, and myoglobin were upregulated in myoblasts differentiated in the presence of IGF-I or LiCl. Importantly, blockade of GSK-3β inhibition abrogated IGF-I- but not LiCl-dependent stimulation of myogenic mRNA accumulation, suggesting that the promyogenic effects of IGF-I require GSK-3β inactivation and revealing an important negative regulatory role for GSK-3β in myogenesis. Therefore, this study identifies GSK-3β as a potential target for pharmacological stimulation of muscle growth.
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Vary T, Lynch C. Nutrient Signaling to Muscle and Adipose Tissue by Leucine. OXIDATIVE STRESS AND DISEASE 2005. [DOI: 10.1201/9781420028362.pt2] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 01/14/2023]
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Baum JI, O'Connor JC, Seyler JE, Anthony TG, Freund GG, Layman DK. Leucine reduces the duration of insulin-induced PI 3-kinase activity in rat skeletal muscle. Am J Physiol Endocrinol Metab 2005; 288:E86-91. [PMID: 15339747 DOI: 10.1152/ajpendo.00272.2004] [Citation(s) in RCA: 40] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/22/2022]
Abstract
Leucine (Leu) is known to stimulate translation initiation of protein synthesis at mammalian target of rapamycin (mTOR) in the insulin signaling pathway. However, potential feedback from mTOR to upstream aspects of the insulin signaling pathway remains controversial. This study evaluates the impact of a physiological oral dose of Leu and/or carbohydrate (CHO) on upstream elements of the insulin signaling pathway using phosphatidylinositol 3-kinase (PI 3-kinase) activity and glucose uptake as markers for insulin sensitivity and glucose homeostasis. Rats (approximately 200 g) were fasted 12 h and administered oral doses of CHO (1.31 g glucose, 1.31 g sucrose), Leu (270 mg), or CHO plus Leu. Animals were killed at 15, 30, 60, and 90 min after treatment. Plasma and gastrocnemius muscles were collected for analyses. Treatments were designed to produce elevated blood glucose and insulin with basal levels of Leu (CHO); elevated Leu with basal levels of glucose and insulin (Leu); or a combined increase of glucose, insulin, and Leu (CHO + Leu). The CHO treatment stimulated PI 3-kinase activity and glucose uptake with no effect on the downstream translation initiation factor eIF4E. Leu alone stimulated the release of the translation initiation factor eIF4E from 4E-BP1 with no effects on PI 3-kinase activity or glucose uptake. The CHO + Leu treatment reduced the magnitude and duration of the PI 3-kinase response but maintained glucose uptake similar to the CHO treatment and eIF4E levels similar to the Leu treatment. These findings demonstrate that Leu reduces insulin-stimulated PI 3-kinase activity while increasing downstream translation initiation and with no effect on net glucose transport in skeletal muscle.
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Affiliation(s)
- Jamie I Baum
- Division of Nutritional Sciences, Department of Food Science and Human Nutrition, University of Illinois Urbana-Champaign, Urbana, Illinois, USA
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Lang CH, Frost RA. Differential effect of sepsis on ability of leucine and IGF-I to stimulate muscle translation initiation. Am J Physiol Endocrinol Metab 2004; 287:E721-30. [PMID: 15186995 DOI: 10.1152/ajpendo.00132.2004] [Citation(s) in RCA: 45] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 12/22/2022]
Abstract
Polymicrobial sepsis impairs skeletal muscle protein synthesis, which results from impairment in translation initiation under basal conditions. The purpose of the present study was to test the hypothesis that sepsis also impairs the anabolic response to amino acids, specifically leucine (Leu). Sepsis was induced by cecal ligation and puncture, and 24 h later, Leu or saline (Sal) was orally administered to septic and time-matched nonseptic rats. The gastrocnemius was removed 20 min later for assessment of protein synthesis and signaling components important in peptide-chain initiation. Oral Leu increased muscle protein synthesis in nonseptic rats. Leu was unable to increase protein synthesis in muscle from septic rats, and synthetic rates remained below those observed in nonseptic + Sal rats. In nonseptic + Leu rats, phosphorylation of eukaryotic initiation factor (eIF)4E-binding protein 1 (4E-BP1) in muscle was markedly increased compared with values from time-matched Sal-treated nonseptic rats. This change was associated with redistribution of eIF4E from the inactive eIF4E.4E-BP1 to the active eIF4E.eIF4G complex. In septic rats, Leu-induced phosphorylation of 4E-BP1 and changes in eIF4E distribution were completely abrogated. Sepsis also antagonized the Leu-induced increase in phosphorylation of S6 kinase 1 and ribosomal protein S6. Sepsis attenuated Leu-induced phosphorylation of mammalian target of rapamycin and eIF4G. The ability of sepsis to inhibit anabolic effects of Leu could not be attributed to differences in plasma concentrations of insulin, insulin-like growth factor I, or Leu between groups. In contrast, the ability of exogenous insulin-like growth factor I to stimulate the same signaling components pertaining to translation initiation was not impaired by sepsis. Hence, sepsis produces a relatively specific Leu resistance in skeletal muscle that impairs the ability of this amino acid to stimulate translation initiation and protein synthesis.
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Affiliation(s)
- Charles H Lang
- Department of Cellular and Molecular Physiology, H166, Pennsylvania State University College of Medicine, 500 University Dr., Hershey 17033, USA.
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Lynch CJ, Halle B, Fujii H, Vary TC, Wallin R, Damuni Z, Hutson SM. Potential role of leucine metabolism in the leucine-signaling pathway involving mTOR. Am J Physiol Endocrinol Metab 2003; 285:E854-63. [PMID: 12812918 DOI: 10.1152/ajpendo.00153.2003] [Citation(s) in RCA: 88] [Impact Index Per Article: 4.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 12/26/2022]
Abstract
Leucine has been shown to stimulate adipose tissue protein synthesis in vivo as well as leptin secretion, protein synthesis, hyper-plastic growth, and tissue morphogenesis in in vitro experiments using freshly isolated adipocytes. Recently, others have proposed that leucine oxidation in the mitochondria may be required to activate the mammalian target of rapamycin (mTOR), the cytosolic Ser/Thr protein kinase that appears to mediate some of these effects. The first irreversible and rate-limiting step in leucine oxidation is catalyzed by the branched-chain alpha-keto acid dehydrogenase (BCKD) complex. The activity of this complex is regulated acutely by phosphorylation of the E1alpha-subunit at Ser293 (S293), which inactivates the complex. Because the alpha-keto acid of leucine regulates the activity of BCKD kinase, it has been suggested as a potential target for leucine regulation of mTOR. To study the regulation of BCKD phosphorylation and its potential link to mTOR activation, a phosphopeptide-specific antibody recognizing this site was developed and characterized. Phospho-S293 (pS293) immunoreactivity in liver corresponded closely to diet-induced changes in BCKD activity state. Immunoreactivity was also increased in TREMK-4 cells after the induction of BCKD kinase by a drug-inducible promoter. BCKD S293 phosphorylations in adipose tissue and gastrocnemius (which is mostly inactive in vivo) were similar. This suggests that BCKD complex in epididymal adipose tissue from food-deprived rats is mostly inactive (unable to oxidize leucine), as is the case in muscle. To begin to test the leucine oxidation hypothesis of mTOR activation, the dose-dependent effects of orally administered leucine on acute activation of S6K1 (an mTOR substrate) and BCKD were compared using the pS293 antibodies. Increasing doses of leucine directly correlated with increases in plasma leucine concentration. Phosphorylation of S6K1 (Thr389, the phosphorylation site leading to activation) in adipose tissue was maximal at a dose of leucine that increased plasma leucine approximately threefold. Changes in BCKD phosphorylation state required higher plasma leucine concentrations. The results seem more consistent with a role for BCKD and BCKD kinase in the activation of leucine metabolism/oxidation than in the activation of the leucine signal to mTOR.
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Affiliation(s)
- Christopher J Lynch
- Department of Cellular & Molecular Physiology (MC H166, Rm C4757), Penn State College of Medicine, 500 University Drive, Hershey, PA 17033, USA.
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