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Ducharme JB, McKenna ZJ, Deyhle MR. Exercise mitigates the Toll of muscle atrophy: A narrative review of the effects of exercise on Toll-like receptor-4 in leukocytes and skeletal muscle. Am J Physiol Cell Physiol 2022; 322:C581-C589. [PMID: 35171696 DOI: 10.1152/ajpcell.00005.2022] [Citation(s) in RCA: 7] [Impact Index Per Article: 3.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022]
Abstract
Conditions characterized by muscle wasting such as cachexia and sarcopenia are devastating at the individual level, and they place a profound burden on public health. Evidence suggests that inflammation is likely a mechanistic contributor to the pathogenesis of these conditions. One specific molecule, lipopolysaccharide, has gained attention due to its role in initiating inflammation. Toll-like receptor-4 is the primary receptor for lipopolysaccharide and has been shown to be implicit in the downstream proinflammatory response associated with lipopolysaccharide. Importantly, Toll-like receptor-4 is expressed on various cell types throughout the human body such as leukocytes and skeletal muscle fibers and may have site-specific effects that contribute to muscle wasting conditions based on the location in which activation occurs. Accordingly, reducing proinflammatory signaling at these locations may be an effective strategy at mitigating muscle wasting. Regular exercise training is believed to elicit anti-inflammatory adaptations, but the mechanisms by which this occurs are yet to be fully understood. Understanding the mechanisms by which Toll-like receptor-4 activation contributes to muscle wasting and how exercise affects this, may allow for the development of a non-pharmacological therapeutic intervention. Therefore, in this review, we summarize the current understanding of the lipopolysaccharide/Toll-like receptor-4 axis in leukocytes and skeletal muscle fibers on the pathogenesis of muscle wasting conditions and we critically examine the current evidence regarding the effects of exercise on this axis.
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Affiliation(s)
- Jeremy B Ducharme
- Department of Health, Exercise, and Sport Sciences, University of New Mexico, Albuquerque, NM, United States
| | - Zachary J McKenna
- Department of Health, Exercise, and Sport Sciences, University of New Mexico, Albuquerque, NM, United States
| | - Michael R Deyhle
- Department of Health, Exercise, and Sport Sciences, University of New Mexico, Albuquerque, NM, United States
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2
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Mose M, Møller N, Jessen N, Mikkelsen UR, Christensen B, Rakvaag E, Hartmann B, Holst JJ, Jørgensen JOL, Rittig N. β-Lactoglobulin Is Insulinotropic Compared with Casein and Whey Protein Ingestion during Catabolic Conditions in Men in a Double-Blinded Randomized Crossover Trial. J Nutr 2021; 151:1462-1472. [PMID: 33693737 DOI: 10.1093/jn/nxab010] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/22/2020] [Revised: 11/23/2020] [Accepted: 01/12/2021] [Indexed: 11/15/2022] Open
Abstract
BACKGROUND Muscle loss during acute infectious disease is mainly triggered by inflammation, immobilization, and malnutrition. OBJECTIVE The objective was to compare muscle protein kinetics and metabolism following ingestion of the dairy protein supplements β-lactoglobulin (BLG), casein (CAS), and whey (WHE) during controlled catabolic conditions. METHODS We used a randomized crossover design (registered at clinicaltrials.gov as NCT03319550) to investigate 9 healthy male participants [age: 20-40 y; BMI (in kg/m2) 20-30] who were randomly assigned servings of BLG, CAS, or WHE (0.6 g protein/kg, one-third as bolus and two-thirds as sip every 20 min) on 3 separate occasions separated by ∼6-8 wk. The participants received an infusion of lipopolysaccharide (1 ng/kg) combined with 36 h of fasting and bed rest before each study day, mimicking a clinical catabolic condition. The forearm model and isotopic tracer techniques were used to quantify muscle protein kinetics. Muscle biopsy specimens were obtained and intramyocellular signaling investigated using Western blot. RESULTS BLG, CAS, and WHE improved the net balance of phenylalanine (NBphe) from baseline with ∼75% (P < 0.001) with no difference between interventions (primary outcome, P < 0.05). No difference in rates of appearance and disappearance of phenylalanine or in intramyocellular signaling activation was found between interventions (secondary outcomes). The incremental AUC for serum insulin was 62% higher following BLG compared with CAS (P < 0.001) and 30% higher compared with WHE (P = 0.002), as well as 25% higher in WHE compared with CAS (P = 0.006). Following BLG consumption, plasma concentrations of glucose-dependent insulinotropic peptide (GIP) increased 70% compared with CAS (P = 0.001) and increased 34% compared with WHE (P = 0.06). No significant difference was found between WHE and CAS (P = 0.12). CONCLUSION BLG, WHE, and CAS have similar effects on muscle in young male participants during catabolic conditions. BLG showed specific, possibly GIP-dependent, insulinotropic properties, which may have future clinical implications.
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Affiliation(s)
- Maike Mose
- Department of Endocrinology and Internal Medicine, Aarhus University Hospital, Aarhus, Denmark
| | - Niels Møller
- Department of Endocrinology and Internal Medicine, Aarhus University Hospital, Aarhus, Denmark.,Steno Diabetes Center Aarhus, Aarhus University Hospital, Aarhus, Denmark
| | - Niels Jessen
- Steno Diabetes Center Aarhus, Aarhus University Hospital, Aarhus, Denmark.,Department of Clinical Pharmacology, Aarhus University Hospital, Aarhus, Denmark.,Department of Biomedicine, Aarhus University, Aarhus, Denmark
| | | | | | - Elin Rakvaag
- Department of Endocrinology and Internal Medicine, Aarhus University Hospital, Aarhus, Denmark.,NNF Center for Basic Metabolic Research and Department of Biomedical Science, University of Copenhagen, Copenhagen, Denmark
| | | | | | | | - Nikolaj Rittig
- Department of Endocrinology and Internal Medicine, Aarhus University Hospital, Aarhus, Denmark.,Steno Diabetes Center Aarhus, Aarhus University Hospital, Aarhus, Denmark
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3
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Takegaki J, Ogasawara R, Kouzaki K, Fujita S, Nakazato K, Ishii N. The distribution of eukaryotic initiation factor 4E after bouts of resistance exercise is altered by shortening of recovery periods. J Physiol Sci 2020; 70:54. [PMID: 33148163 PMCID: PMC10717013 DOI: 10.1186/s12576-020-00781-y] [Citation(s) in RCA: 4] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/08/2020] [Accepted: 10/22/2020] [Indexed: 11/10/2022]
Abstract
Insufficient duration of recovery between resistance exercise bouts reduces the effects of exercise training, but the influence on muscle anabolic responses is not fully understood. Here, we investigated the changes in the distribution of eukaryotic initiation factor (eIF) 4E, a key regulator of translation initiation, and related factors in mouse skeletal muscle after three successive bouts of resistance exercise with three durations of recovery periods (72 h: conventional, 24 h: shorter, and 8 h: excessively shorter). Bouts of resistance exercise dissociated eIF4E from eIF4E binding protein 1, with the magnitude increasing with shorter recovery. Whereas bouts of resistance exercise with 72 h recovery increased the association of eIF4E and eIF4G, those with shorter recovery did not. Similar results were observed in muscle protein synthesis. These results suggest that insufficient recovery inhibited the association of eIF4E and eIF4G, which might cause attenuation of protein synthesis activation after bouts of resistance exercise.
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Affiliation(s)
- Junya Takegaki
- Department of Life Sciences, Graduate School of Arts and Sciences, The University of Tokyo, Tokyo, Japan.
- Ritsumeikan Global Innovation Research Organization, Ritsumeikan University, 1-1-1 Noji-higashi, Kusatsu, Shiga, 525-8577, Japan.
| | - Riki Ogasawara
- Department of Life Science and Applied Chemistry, Nagoya Institute of Technology, Nagoya, Japan
| | - Karina Kouzaki
- Graduate School of Health and Sport Science, Nippon Sport Science University, Tokyo, Japan
| | - Satoshi Fujita
- Faculty of Sport and Health Science, Ritsumeikan University, Kusatsu, Shiga, Japan
| | - Koichi Nakazato
- Graduate School of Health and Sport Science, Nippon Sport Science University, Tokyo, Japan
| | - Naokata Ishii
- Department of Life Sciences, Graduate School of Arts and Sciences, The University of Tokyo, Tokyo, Japan
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4
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Li N, Jiang P, Chen A, Luo X, Jing Y, Yang L, Kang D, Chen Q, Liu J, Chang J, Jellusova J, Miller H, Westerberg L, Wang CY, Gong Q, Liu C. CX3CR1 positively regulates BCR signaling coupled with cell metabolism via negatively controlling actin remodeling. Cell Mol Life Sci 2020; 77:4379-4395. [PMID: 32016488 PMCID: PMC11105092 DOI: 10.1007/s00018-019-03416-7] [Citation(s) in RCA: 4] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/01/2019] [Revised: 11/12/2019] [Accepted: 12/09/2019] [Indexed: 12/16/2022]
Abstract
As an important chemokine receptor, the role of CX3CR1 has been studied extensively on the migration of lymphocytes including T and B cells. Although CX3CR1+ B cells have immune suppressor properties, little is known about its role on the regulation of BCR signaling and B cell differentiation as well as the underlying molecular mechanism. We have used CX3CR1 KO mice to study the effect of CX3CR1 deficiency on BCR signaling and B cell differentiation. Interestingly, we found that proximal BCR signaling, such as the activation of CD19, BTK and SHIP was reduced in CX3CR1 KO B cells upon antigenic stimulation. However, the activation of mTORC signaling was enhanced. Mechanistically, we found that the reduced BCR signaling in CX3CR1 KO B cells was due to reduced BCR clustering, which is caused by the enhanced actin accumulation by the plasma membrane via increased activation of WASP. This caused an increased differentiation of MZ B cells in CX3CR1 KO mice and an enhanced generation of plasma cells (PC) and antibodies. Our study shows that CX3CR1 regulates BCR signaling via actin remodeling and affects B cell differentiation and the humoral immune response.
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Affiliation(s)
- Na Li
- Clinical Molecular Immunology Center, Department of Immunology, School of Medicine, Yangtze University, Jingzhou, 434023, China
| | - Panpan Jiang
- Department of Pathogen Biology, School of Basic Medicine, Tongji Medical College, Huazhong University of Science and Technology, Wuhan, 430030, China
| | - Anwei Chen
- Chongqing Key Laboratory of Child Infection and Immunity, Children's Hospital of Chongqing Medical University, Chongqing, 400016, China
| | - Xi Luo
- The Center for Biomedical Research, Key Laboratory of Organ Transplantation, Ministry of Education and Chinese Academy of Medical Sciences, NHC Key Laboratory of Organ Transplantation, Tongji Hospital, Tongji Medical College, Huazhong University of Science and Technology, Wuhan, 430030, China
| | - Yukai Jing
- Department of Pathogen Biology, School of Basic Medicine, Tongji Medical College, Huazhong University of Science and Technology, Wuhan, 430030, China
| | - Lu Yang
- Department of Pathogen Biology, School of Basic Medicine, Tongji Medical College, Huazhong University of Science and Technology, Wuhan, 430030, China
| | - Danqing Kang
- Department of Pathogen Biology, School of Basic Medicine, Tongji Medical College, Huazhong University of Science and Technology, Wuhan, 430030, China
| | - Qiuyue Chen
- Clinical Molecular Immunology Center, Department of Immunology, School of Medicine, Yangtze University, Jingzhou, 434023, China
| | - Ju Liu
- Department of Pathogen Biology, School of Basic Medicine, Tongji Medical College, Huazhong University of Science and Technology, Wuhan, 430030, China
| | - Jiang Chang
- Department of Pathogen Biology, School of Basic Medicine, Tongji Medical College, Huazhong University of Science and Technology, Wuhan, 430030, China
| | - Julia Jellusova
- BIOSS Centre for Biological Signalling Studies, Albert Ludwigs University of Freiburg, 79104, Freiburg Im Breisgau, Baden-Württemberg, Germany
| | - Heather Miller
- Department of Intracellular Pathogens, National Institute of Allergy and Infectious Diseases, Bethesda, MT, 59840, USA
| | - Lisa Westerberg
- Department of Microbiology Tumor and Cell Biology, KarolinskaInstitutet, Stockholm, 17177, Sweden
| | - Cong-Yi Wang
- The Center for Biomedical Research, Key Laboratory of Organ Transplantation, Ministry of Education and Chinese Academy of Medical Sciences, NHC Key Laboratory of Organ Transplantation, Tongji Hospital, Tongji Medical College, Huazhong University of Science and Technology, Wuhan, 430030, China
| | - Quan Gong
- Clinical Molecular Immunology Center, Department of Immunology, School of Medicine, Yangtze University, Jingzhou, 434023, China.
| | - Chaohong Liu
- Department of Pathogen Biology, School of Basic Medicine, Tongji Medical College, Huazhong University of Science and Technology, Wuhan, 430030, China.
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5
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Zhao Y, Li JY, Jiang Q, Zhou XQ, Feng L, Liu Y, Jiang WD, Wu P, Zhou J, Zhao J, Jiang J. Leucine Improved Growth Performance, Muscle Growth, and Muscle Protein Deposition Through AKT/TOR and AKT/FOXO3a Signaling Pathways in Hybrid Catfish Pelteobagrus v achelli × Leiocassis longirostris. Cells 2020; 9:cells9020327. [PMID: 32019276 PMCID: PMC7072317 DOI: 10.3390/cells9020327] [Citation(s) in RCA: 21] [Impact Index Per Article: 5.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/25/2019] [Revised: 01/21/2020] [Accepted: 01/29/2020] [Indexed: 02/06/2023] Open
Abstract
(1) Background: l-leucine (Leu) plays a positive role in regulating protein turnover in skeletal muscle in mammal. However, the molecular mechanism for the effects of Leu on muscle growth and protein deposition is not clearly demonstrated in fish. This study investigated the effects of dietary Leu on growth performance and muscle growth, protein synthesis, and degradation-related signaling pathways of hybrid catfish (Pelteobagrus vachelli♀ × Leiocassis longirostris♂). (2) Methods: A total of 630 hybrid catfish (23.19 ± 0.20 g) were fed 6 different experimental diets containing graded levels of Leu at 10.0 (control), 15.0, 20.0, 25.0, 30.0, 35.0, and 40.0 g Leu kg-1 for 8 weeks. (3) Results: Results showed that dietary Leu increased percent weight gain (PWG), specific growth rate (SGR), FI (feed intake), feed efficiency (FE), protein efficiency ratio (PER), muscle fibers diameter, and muscle fibers density; up-regulated insulin-like growth factor I (IGF-I), insulin-like growth factor I receptor (IGF-IR), proliferating cell nuclear antigen (PCNA), myogenic regulation factors (MyoD, Myf5, MyoG, and Mrf4), and MyHC mRNA levels; increased muscle protein synthesis via regulating the AKT/TOR signaling pathway; and attenuated protein degradation via regulating the AKT/FOXO3a signaling pathway. (4) Conclusions: These results suggest that Leu has potential role to improve muscle growth and protein deposition in fish, which might be due to the regulation of IGF mRNA expression, muscle growth related gene, and protein synthesis and degradation-related signaling pathways. Based on the broken-line model, the Leu requirement of hybrid catfish (23.19-54.55 g) for PWG was estimated to be 28.10 g kg-1 of the diet (73.04 g kg-1 of dietary protein). These results will improve our understanding of the mechanisms responsible for muscle growth and protein deposition effects of Leu in fish.
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Affiliation(s)
- Ye Zhao
- College of Animal Science and Technology, Sichuan Agricultural University, Chengdu 611130, China
| | - Jin-Yang Li
- College of Animal Science and Technology, Sichuan Agricultural University, Chengdu 611130, China
| | - Qin Jiang
- College of Animal Science and Technology, Sichuan Agricultural University, Chengdu 611130, China
| | - Xiao-Qiu Zhou
- Animal Nutrition Institute, Sichuan Agricultural University, Chengdu 611130, China
- Fish Nutrition and Safety Production University Key Laboratory of Sichuan Province, Sichuan Agricultural University, Chengdu 611130, China
| | - Lin Feng
- Animal Nutrition Institute, Sichuan Agricultural University, Chengdu 611130, China
- Fish Nutrition and Safety Production University Key Laboratory of Sichuan Province, Sichuan Agricultural University, Chengdu 611130, China
| | - Yang Liu
- Animal Nutrition Institute, Sichuan Agricultural University, Chengdu 611130, China
- Fish Nutrition and Safety Production University Key Laboratory of Sichuan Province, Sichuan Agricultural University, Chengdu 611130, China
| | - Wei-Dan Jiang
- Animal Nutrition Institute, Sichuan Agricultural University, Chengdu 611130, China
- Fish Nutrition and Safety Production University Key Laboratory of Sichuan Province, Sichuan Agricultural University, Chengdu 611130, China
| | - Pei Wu
- Animal Nutrition Institute, Sichuan Agricultural University, Chengdu 611130, China
- Fish Nutrition and Safety Production University Key Laboratory of Sichuan Province, Sichuan Agricultural University, Chengdu 611130, China
| | - Jian Zhou
- Fisheries Institute of Sichuan Academy of Agricultural Science, Chengdu 611731, China
| | - Juan Zhao
- Animal Nutrition Institute, Sichuan Agricultural University, Chengdu 611130, China
| | - Jun Jiang
- College of Animal Science and Technology, Sichuan Agricultural University, Chengdu 611130, China
- Fish Nutrition and Safety Production University Key Laboratory of Sichuan Province, Sichuan Agricultural University, Chengdu 611130, China
- Correspondence: ; Tel.: +86-28-8629-1133
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6
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Ono Y, Maejima Y, Saito M, Sakamoto K, Horita S, Shimomura K, Inoue S, Kotani J. TAK-242, a specific inhibitor of Toll-like receptor 4 signalling, prevents endotoxemia-induced skeletal muscle wasting in mice. Sci Rep 2020; 10:694. [PMID: 31959927 PMCID: PMC6970997 DOI: 10.1038/s41598-020-57714-3] [Citation(s) in RCA: 75] [Impact Index Per Article: 18.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/14/2019] [Accepted: 01/07/2020] [Indexed: 02/07/2023] Open
Abstract
Circulating lipopolysaccharide (LPS) concentrations are often elevated in patients with sepsis or various endogenous diseases related to bacterial translocation from the gut. Systemic inflammatory responses induced by endotoxemia induce severe involuntary loss of skeletal muscle, termed muscle wasting, which adversely affects the survival and functional outcomes of these patients. Currently, no drugs are available for the treatment of endotoxemia-induced skeletal muscle wasting. Here, we tested the effects of TAK-242, a Toll-like receptor 4 (TLR4)-specific signalling inhibitor, on myotube atrophy in vitro and muscle wasting in vivo induced by endotoxin. LPS treatment of murine C2C12 myotubes induced an inflammatory response (increased nuclear factor-κB activity and interleukin-6 and tumour necrosis factor-α expression) and activated the ubiquitin-proteasome and autophagy proteolytic pathways (increased atrogin-1/MAFbx, MuRF1, and LC-II expression), resulting in myotube atrophy. In mice, LPS injection increased the same inflammatory and proteolytic pathways in skeletal muscle and induced atrophy, resulting in reduced grip strength. Notably, pretreatment of cells or mice with TAK-242 reduced or reversed all the detrimental effects of LPS in vitro and in vivo. Collectively, our results indicate that pharmacological inhibition of TLR4 signalling may be a novel therapeutic intervention for endotoxemia-induced muscle wasting.
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Affiliation(s)
- Yuko Ono
- Department of Disaster and Emergency Medicine, Graduate School of Medicine, Kobe University, Kobe, 650-0017, Japan. .,Department of Bioregulation and Pharmacological Medicine, School of Medicine, Fukushima Medical University, Fukushima, 960-1295, Japan.
| | - Yuko Maejima
- Department of Bioregulation and Pharmacological Medicine, School of Medicine, Fukushima Medical University, Fukushima, 960-1295, Japan
| | - Masafumi Saito
- Department of Disaster and Emergency Medicine, Graduate School of Medicine, Kobe University, Kobe, 650-0017, Japan
| | - Kazuho Sakamoto
- Department of Bio-Informational Pharmacology, School of Pharmaceutical Sciences, University of Shizuoka, Shizuoka, 422-8526, Japan
| | - Shoichiro Horita
- Department of Bioregulation and Pharmacological Medicine, School of Medicine, Fukushima Medical University, Fukushima, 960-1295, Japan
| | - Kenju Shimomura
- Department of Bioregulation and Pharmacological Medicine, School of Medicine, Fukushima Medical University, Fukushima, 960-1295, Japan
| | - Shigeaki Inoue
- Department of Disaster and Emergency Medicine, Graduate School of Medicine, Kobe University, Kobe, 650-0017, Japan
| | - Joji Kotani
- Department of Disaster and Emergency Medicine, Graduate School of Medicine, Kobe University, Kobe, 650-0017, Japan
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7
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Ten Have GAM, Engelen MPKJ, Wolfe RR, Deutz NEP. Inhibition of jejunal protein synthesis and breakdown in Pseudomonas aeruginosa-induced sepsis pig model. Am J Physiol Gastrointest Liver Physiol 2019; 316:G755-G762. [PMID: 30978112 PMCID: PMC6620581 DOI: 10.1152/ajpgi.00407.2018] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 01/31/2023]
Abstract
Maintenance of gut integrity has long been recognized as crucial for survival in sepsis, but alterations in protein metabolism have not previously been documented. Therefore, in the present study, we measured in a Pseudomonas aeruginosa-induced porcine sepsis model fractional protein synthesis (FSR) and breakdown rates (FBR) in jejunal mucosa in a fasted, conscious state. FSR was measured by the incorporation rate of stable tracer amino acid (l-[ring-13C6]phenylalanine) into tissue protein. FBR was determined using the relation between blood arterial enrichment and intracellular enrichment of phenylalanine in consecutive mucosal biopsies after a pulse of l-[15N]phenylalanine. Additionally, we determined the FSR in jejunum, ileum, liver, muscle, and lung tissue. We found in this sham-controlled acute sepsis pig model (control: n = 9; sepsis: n = 13) that jejunal mucosal protein turnover is reduced with both decreased FSR (control: 3.29 ± 0.22; sepsis: 2.32 ± 0.12%/h, P = 0.0008) and FBR (control: 0.72 ± 0.12; sepsis: 0.34 ± 0.04%/h, P = 0.006). We also found that FSR was unchanged in ileum and muscle, whereas it was higher in the liver (control: 0.87 ± 0.05; sepsis: 1.05 ± 0.06%/h, P = 0.041). Our data, obtained with a translational acute sepsis model, suggest that jejunal mucosal protein metabolism is diminished in acute sepsis. Comparison with other tissues indicates that the most serious acute metabolic changes in sepsis occur in the jejunum rather than the muscle. NEW & NOTEWORTHY In a highly translational acute sepsis model, presented data suggest that jejunal mucosal protein metabolism is diminished in acute sepsis, even if the origin of the sepsis is not located in the gut. Comparison with other tissues indicates that the most serious acute changes in the protein synthesis rates in sepsis occur in the gut rather than the muscle. Therefore, we hypothesize that preventing a compromised gut is critical to maintain gut function during sepsis.
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Affiliation(s)
- Gabriëlla A. M. Ten Have
- 1Center for Translational Research in Aging and Longevity, Department of Health and Kinesiology, Texas A & M University, College Station, Texas,2Donald W. Reynolds Institute on Aging, University of Arkansas for Medical Sciences, Little Rock, Arkansas
| | - Mariëlle P. K. J. Engelen
- 1Center for Translational Research in Aging and Longevity, Department of Health and Kinesiology, Texas A & M University, College Station, Texas,2Donald W. Reynolds Institute on Aging, University of Arkansas for Medical Sciences, Little Rock, Arkansas
| | - Robert R. Wolfe
- 2Donald W. Reynolds Institute on Aging, University of Arkansas for Medical Sciences, Little Rock, Arkansas
| | - Nicolaas E. P. Deutz
- 1Center for Translational Research in Aging and Longevity, Department of Health and Kinesiology, Texas A & M University, College Station, Texas,2Donald W. Reynolds Institute on Aging, University of Arkansas for Medical Sciences, Little Rock, Arkansas
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8
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Rudar M, Huber LA, Zhu CL, de Lange CFM. Effects of dietary leucine supplementation and immune system stimulation on plasma AA concentrations and tissue protein synthesis in starter pigs. J Anim Sci 2019; 97:829-838. [PMID: 30476328 DOI: 10.1093/jas/sky449] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/15/2018] [Accepted: 11/20/2018] [Indexed: 01/08/2023] Open
Abstract
Immune system stimulation (ISS) adversely affects protein and AA metabolism and reduces productivity in pigs. Leucine (Leu) has a regulatory role in skeletal muscle protein turnover, which may be affected by ISS. The objective of this study was to evaluate the effects of ISS and dietary Leu supplementation on the protein fractional synthesis rate (FSR) of various tissues in pigs. Yorkshire barrows were surgically fitted with jugular vein catheters and assigned to one of three dietary treatments: (i) CON, 1.36% standardized ileal digestible (SID) Leu; (ii) LEU-M, 2.04% SID Leu; and (iii) LEU-H, 2.72% SID Leu. The diets were formulated to contain all essential AA 10% above estimated requirements for maximum whole-body protein deposition for this BW range. At the start of the 36-h challenge period (initial BW = 14.5 ± 0.8 kg), ISS was induced in pigs with lipopolysaccharide (ISS+; n = 7, 8, and 7 for CON, LEU-M, and LEU-H pigs, respectively); a subset of CON pigs was injected with sterile saline (ISS-; n = 6). During challenge period, pigs were fed every 4 h and feed intake of ISS- pigs was kept equal to ISS+ pigs. At the end of the challenge period, FSR of liver, plasma, gastrocnemius, and LD proteins were determined with a flooding dose of l-[ring-2H5]phenylalanine (40 mol%). All essential AA, most nonessential AA, and plasma urea-N peaked at 12 h and declined to baseline levels at 36 h after ISS was induced in ISS+ pigs (P < 0.05), whereas plasma AA and urea-N concentrations were constant in ISS- pigs. At 36 h, dietary Leu supplementation resulted in a linear decline in plasma isoleucine, valine, glutamine, and urea nitrogen concentrations (P < 0.05), whereas plasma Leu concentration was unaffected. Liver protein FSR was increased in ISS+ pigs (P < 0.05), whereas plasma and skeletal muscle protein FSR was not affected by ISS. Dietary Leu supplementation tended to diminish liver protein FSR (linear reduction; P = 0.052) and increase gastrocnemius protein FSR (linear increase; P = 0.085) in ISS+ pigs. Leucine supplementation above estimated requirements may support repartitioning of AA from visceral to peripheral protein deposition during ISS.
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Affiliation(s)
- Marko Rudar
- Department of Animal Biosciences, University of Guelph, Guelph, ON, Canada
| | - Lee-Anne Huber
- Department of Animal Biosciences, University of Guelph, Guelph, ON, Canada
| | - Cuilan L Zhu
- Department of Animal Biosciences, University of Guelph, Guelph, ON, Canada
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9
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Rudar M, Fiorotto ML, Davis TA. Regulation of Muscle Growth in Early Postnatal Life in a Swine Model. Annu Rev Anim Biosci 2018; 7:309-335. [PMID: 30388025 DOI: 10.1146/annurev-animal-020518-115130] [Citation(s) in RCA: 23] [Impact Index Per Article: 3.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/06/2023]
Abstract
Skeletal muscle growth during the early postnatal period is rapid in the pig and dependent on the capacity of muscle to respond to anabolic and catabolic stimuli. Muscle mass is driven by the balance between protein synthesis and degradation. Among these processes, muscle protein synthesis in the piglet is exceptionally sensitive to the feeding-induced postprandial changes in insulin and amino acids, whereas muscle protein degradation is affected only during specific catabolic states. The developmental decline in the response of muscle to feeding is associated with changes in the signaling pathways located upstream and downstream of the mechanistic target of rapamycin protein complex. Additionally, muscle growth is supported by an accretion of nuclei derived from satellite cells. Activated satellite cells undergo proliferation, differentiation, and fusion with adjacent growing muscle fibers. Enhancing early muscle growth through modifying protein synthesis, degradation, and satellite cell activity is key to maximizing performance, productivity, and lifelong pig health.
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Affiliation(s)
- Marko Rudar
- USDA/ARS Children's Nutrition Research Center, Baylor College of Medicine, Houston, Texas 77030, USA; , ,
| | - Marta L Fiorotto
- USDA/ARS Children's Nutrition Research Center, Baylor College of Medicine, Houston, Texas 77030, USA; , ,
| | - Teresa A Davis
- USDA/ARS Children's Nutrition Research Center, Baylor College of Medicine, Houston, Texas 77030, USA; , ,
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10
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11
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Bonvini A, Coqueiro AY, Tirapegui J, Calder PC, Rogero MM. Immunomodulatory role of branched-chain amino acids. Nutr Rev 2018; 76:840-856. [DOI: 10.1093/nutrit/nuy037] [Citation(s) in RCA: 30] [Impact Index Per Article: 5.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/07/2023] Open
Affiliation(s)
- Andrea Bonvini
- Department of Food and Experimental Nutrition, Faculty of Pharmaceutical Sciences, University of São Paulo, São Paulo, Brazil
| | - Audrey Y Coqueiro
- Department of Food and Experimental Nutrition, Faculty of Pharmaceutical Sciences, University of São Paulo, São Paulo, Brazil
| | - Julio Tirapegui
- Department of Food and Experimental Nutrition, Faculty of Pharmaceutical Sciences, University of São Paulo, São Paulo, Brazil
| | - Philip C Calder
- Human Development and Health Academic Unit, Faculty of Medicine, University of Southampton, Southampton, United Kingdom
- NIHR Southampton Biomedical Research Centre, University Hospital Southampton NHS Foundation Trust and University of Southampton, Southampton, United Kingdom
| | - Marcelo M Rogero
- Department of Nutrition, Faculty of Public Health, University of São Paulo, São Paulo, Brazil
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12
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Lynch GS, Koopman R. Dietary meat and protection against sarcopenia. Meat Sci 2018; 144:180-185. [DOI: 10.1016/j.meatsci.2018.06.023] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/17/2018] [Revised: 06/15/2018] [Accepted: 06/18/2018] [Indexed: 12/25/2022]
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13
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Bufadienolides from Venenum Bufonis Inhibit mTOR-Mediated Cyclin D1 and Retinoblastoma Protein Leading to Arrest of Cell Cycle in Cancer Cells. EVIDENCE-BASED COMPLEMENTARY AND ALTERNATIVE MEDICINE 2018; 2018:3247402. [PMID: 30108651 PMCID: PMC6077658 DOI: 10.1155/2018/3247402] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 03/13/2018] [Revised: 05/15/2018] [Accepted: 06/13/2018] [Indexed: 02/08/2023]
Abstract
Objective Bufadienolides, the main components in Venenum Bufonis secreted from toads, have been proved to be with significant anticancer activity aside from the positive inotropic action as cardenolides. Here an underlying anticancer mechanism was further elucidated for an injection made from Venenum Bufonis containing nine bufadienolides. Methods One solution reagent and cell cycle analyses were for determining effect of bufadienolides on cancer cells. Western blotting was used for protein expression. Results Bufadienolides inhibit cell proliferation and arrest cells in G1 phase. Bufadienolides also inhibit the mammalian target of rapamycin (mTOR) signaling pathway, which is evidenced by the data that bufadienolides inhibit type I insulin-like growth factor- (IGF-1-) activated phosphorylation of mTOR by a concentration- and time-dependent way, as well as phosphorylation of p70 S6 kinase 1 (S6K1) and eukaryotic initiation factor 4E (eIF4E) binding protein 1 (4E-BP1). Subsequent results indicated that cyclin D1 expression and phosphorylation of retinoblastoma protein (Rb)—two characterized regulators in cell cycle of G1—are also inhibited and the process is dependent on mTOR pathway. Conclusion Bufadienolides inhibit proliferation partially due to arresting cell cycle in G1 phase, which is mediated by inhibiting mTOR-cyclin D1/Rb signal pathway.
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Holeček M. Branched-chain amino acids in health and disease: metabolism, alterations in blood plasma, and as supplements. Nutr Metab (Lond) 2018; 15:33. [PMID: 29755574 PMCID: PMC5934885 DOI: 10.1186/s12986-018-0271-1] [Citation(s) in RCA: 376] [Impact Index Per Article: 62.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/07/2018] [Accepted: 04/18/2018] [Indexed: 02/07/2023] Open
Abstract
Branched-chain amino acids (BCAAs; valine, leucine, and isoleucine) are essential amino acids with protein anabolic properties, which have been studied in a number of muscle wasting disorders for more than 50 years. However, until today, there is no consensus regarding their therapeutic effectiveness. In the article is demonstrated that the crucial roles in BCAA metabolism play: (i) skeletal muscle as the initial site of BCAA catabolism accompanied with the release of alanine and glutamine to the blood; (ii) activity of branched-chain keto acid dehydrogenase (BCKD); and (iii) amination of branched-chain keto acids (BCKAs) to BCAAs. Enhanced consumption of BCAA for ammonia detoxification to glutamine in muscles is the cause of decreased BCAA levels in liver cirrhosis and urea cycle disorders. Increased BCKD activity is responsible for enhanced oxidation of BCAA in chronic renal failure, trauma, burn, sepsis, cancer, phenylbutyrate-treated subjects, and during exercise. Decreased BCKD activity is the main cause of increased BCAA levels and BCKAs in maple syrup urine disease, and plays a role in increased BCAA levels in diabetes type 2 and obesity. Increased BCAA concentrations during brief starvation and type 1 diabetes are explained by amination of BCKAs in visceral tissues and decreased uptake of BCAA by muscles. The studies indicate beneficial effects of BCAAs and BCKAs in therapy of chronic renal failure. New therapeutic strategies should be developed to enhance effectiveness and avoid adverse effects of BCAA on ammonia production in subjects with liver cirrhosis and urea cycle disorders. Further studies are needed to elucidate the effects of BCAA supplementation in burn, trauma, sepsis, cancer and exercise. Whether increased BCAA levels only markers are or also contribute to insulin resistance should be known before the decision is taken regarding their suitability in obese subjects and patients with type 2 diabetes. It is concluded that alterations in BCAA metabolism have been found common in a number of disease states and careful studies are needed to elucidate their therapeutic effectiveness in most indications.
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Affiliation(s)
- Milan Holeček
- Department of Physiology, Faculty of Medicine in Hradec Kralove, Charles University, Simkova 870, 500 03, Hradec Kralove, Czech Republic
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15
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Linking Cancer Cachexia-Induced Anabolic Resistance to Skeletal Muscle Oxidative Metabolism. OXIDATIVE MEDICINE AND CELLULAR LONGEVITY 2017; 2017:8018197. [PMID: 29375734 PMCID: PMC5742498 DOI: 10.1155/2017/8018197] [Citation(s) in RCA: 33] [Impact Index Per Article: 4.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 09/22/2017] [Accepted: 11/06/2017] [Indexed: 01/03/2023]
Abstract
Cancer cachexia, a wasting syndrome characterized by skeletal muscle depletion, contributes to increased patient morbidity and mortality. While the intricate balance between protein synthesis and breakdown regulates skeletal muscle mass, the suppression of basal protein synthesis may not account for the severe wasting induced by cancer. Therefore, recent research has shifted to the regulation of “anabolic resistance,” which is the impaired ability of nutrition and exercise to stimulate protein synthesis. Emerging evidence suggests that oxidative metabolism can regulate both basal and induced muscle protein synthesis. While disrupted protein turnover and oxidative metabolism in cachectic muscle have been examined independently, evidence suggests a linkage between these processes for the regulation of cancer-induced wasting. The primary objective of this review is to highlight the connection between dysfunctional oxidative metabolism and cancer-induced anabolic resistance in skeletal muscle. First, we review oxidative metabolism regulation of muscle protein synthesis. Second, we describe cancer-induced alterations in the response to an anabolic stimulus. Finally, we review a role for exercise to inhibit cancer-induced anabolic suppression and mitochondrial dysfunction.
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16
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Crowell KT, Kelleher SL, Soybel DI, Lang CH. Marginal dietary zinc deprivation augments sepsis-induced alterations in skeletal muscle TNF-α but not protein synthesis. Physiol Rep 2017; 4:4/21/e13017. [PMID: 27811170 PMCID: PMC5112495 DOI: 10.14814/phy2.13017] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/17/2016] [Accepted: 10/04/2016] [Indexed: 12/11/2022] Open
Abstract
Severe zinc deficiency is associated with an increased systemic inflammatory response and mortality after sepsis. However, the impact of mild zinc deficiency, which is more common in populations with chronic illnesses and sepsis, is unknown. In this study, we hypothesized that marginal dietary Zn deprivation (ZM) would amplify tissue inflammation and exacerbate the sepsis-induced decrease in muscle protein synthesis. Adult male C57BL/6 mice were fed a zinc-adequate (ZA) or ZM diet (30 or 10 mg Zn/kg, respectively) over 4 weeks, peritonitis was induced by cecal ligation and puncture (CLP), and mice were examined at either 24 h (acute) or 5 days (chronic) post-CLP Acute sepsis decreased the in vivo rate of skeletal muscle protein synthesis and the phosphorylation of the mTOR substrate 4E-BP1. Acutely, sepsis increased TNF-α and IL-6 mRNA in muscle, and the increase in TNF-α was significantly greater in ZM mice. However, muscle protein synthesis and 4E-BP1 phosphorylation returned to baseline 5 days post-CLP in both ZA and ZM mice. Protein degradation via markers of the ubiquitin proteasome pathway was increased in acute sepsis, yet only MuRF1 mRNA was increased in chronic sepsis and ZM amplified this elevation. Our data suggest that mild zinc deficiency increases TNF-α in muscle acutely after sepsis but does not significantly modulate the rate of muscle protein synthesis.
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Affiliation(s)
- Kristen T Crowell
- Department of Surgery, College of Medicine, Pennsylvania State University, Hershey, Pennsylvania
| | - Shannon L Kelleher
- Department of Surgery, College of Medicine, Pennsylvania State University, Hershey, Pennsylvania.,Department of Cellular and Molecular Physiology, College of Medicine, Pennsylvania State University, Hershey, Pennsylvania.,Department of Pharmacology, College of Medicine, Pennsylvania State University, Hershey, Pennsylvania.,Department of Nutritional Sciences, Pennsylvania State University, University Park, Pennsylvania
| | - David I Soybel
- Department of Surgery, College of Medicine, Pennsylvania State University, Hershey, Pennsylvania.,Department of Cellular and Molecular Physiology, College of Medicine, Pennsylvania State University, Hershey, Pennsylvania.,Department of Nutritional Sciences, Pennsylvania State University, University Park, Pennsylvania
| | - Charles H Lang
- Department of Surgery, College of Medicine, Pennsylvania State University, Hershey, Pennsylvania .,Department of Cellular and Molecular Physiology, College of Medicine, Pennsylvania State University, Hershey, Pennsylvania
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Rudar M, Zhu CL, de Lange CFM. Effect of supplemental dietary leucine and immune system stimulation on whole-body nitrogen utilization in starter pigs. J Anim Sci 2017; 94:2366-77. [PMID: 27285913 DOI: 10.2527/jas.2015-0120] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/01/2023] Open
Abstract
The increase in circulating pro-inflammatory cytokines following an immune challenge (e.g., with bacterial lipopolysaccharide [LPS]) causes a disruption in normal AA metabolism and increases visceral protein synthesis at the expense of muscle protein synthesis. The objective of this study was to determine the effect of supplemental dietary Leu on the dynamics of whole body nitrogen (N) retention in starter pigs before and after immune system stimulation (ISS) induced by LPS. A total of 28 starter pigs (14.46 ± 0.73 kg BW) were assigned to isoenergetic and isonitrogenous diets formulated to supply essential AA 10% above estimated requirements for maximum whole-body protein deposition (PD) and to contain increasing amounts of Leu: CON (1.36% SID Leu); LEU-M (2.04% SID Leu); and LEU-H (2.72% SID Leu). Pigs were housed in metabolic crates, scale-fed every 4 h based on BW, and adjusted to dietary treatments for 5 d. The 108-h N-balance experiment was divided into two periods: prechallenge (before LPS challenge; six 12-h collections) and challenge (after LPS challenge; three 12-h collections) periods. In both periods, blood was collected to determine plasma AA and urea N concentrations. At the start of the challenge period, one-half of the pigs fed CON and all pigs fed LEU-M and LEU-H were challenged with LPS (ISS+; 30 µg/kg injected intramuscularly); the remaining pigs fed CON were injected with saline (ISS-). Whole-body N retention was determined during subsequent 12-h collections. Plasma free Leu concentration increased linearly with increasing Leu content in the diet before LPS was administered (CON, 124 µmol/L; LEU-M, 185 µmol/L; LEU-H, 227 µmol/L; < 0.01). During the prechallenge period, N retention was lower in pigs fed LEU-M ( < 0.01) and there was no difference between pigs fed CON and LEU-H (7.91, 7.18, and 7.71 g/12 h for CON, LEU-M, and LEU-H, respectively). During the challenge period, N retention in pigs fed CON was higher in ISS- than ISS+ (5.37 vs. 3.83 g/12 h; < 0.01) but was not affected by diet in ISS+ pigs (3.83, 3.21, and 3.45 g/12 h for CON, LEU-M, and LEU-H, respectively; > 0.10). In healthy pigs, feeding a high excess of dietary Leu induced an anabolic response to compensate for reduced N retention that occurred in pigs fed an intermediate excess of dietary Leu. There was no effect of supplemental Leu on N retention in pigs after an LPS challenge.
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Rudar M, Zhu CL, de Lange CF. Dietary Leucine Supplementation Decreases Whole-Body Protein Turnover before, but Not during, Immune System Stimulation in Pigs. J Nutr 2017; 147:45-51. [PMID: 27798336 DOI: 10.3945/jn.116.236893] [Citation(s) in RCA: 9] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/07/2016] [Revised: 07/10/2016] [Accepted: 10/03/2016] [Indexed: 11/14/2022] Open
Abstract
BACKGROUND Immune system stimulation (ISS) adversely affects protein metabolism and reduces pig productivity. Leu has a regulatory role in skeletal muscle and whole-body protein turnover, which may be affected by ISS. OBJECTIVE We sought to determine the effect of supplemental Leu intake on whole-body protein turnover in pigs before and during ISS. METHODS Pigs [mean ± SD initial body weight (BW): 10.6 ± 1.1 kg] were surgically fitted with jugular vein catheters and assigned to 1 of 3 treatments: 1.36% standardized ileal-digestible (SID) Leu (CON; n = 13); 2.04% SID Leu (LEU-M; n = 8); and 2.72% SID Leu (LEU-H; n = 7). Pigs were infused continuously with 0.66 ± 0.05 mmol 15N ⋅ kg BW-1 ⋅ d-1 to determine whole-body protein kinetics. The study consisted of a 72-h prechallenge period followed by a 36-h challenge period. At the start of the challenge period, ISS was induced in all LEU-M and LEU-H pigs and half of the CON pigs with LPS (ISS+); the remaining CON pigs were administered saline (ISS-). RESULTS Whole-body protein synthesis (309, 273, and 260 ± 14 mmol N ⋅ kg BW-1 ⋅ d-1 for CON, LEU-M, and LEU-H pigs, respectively) and protein degradation (233, 203, and 185 ± 14 mmol N ⋅ kg BW-1 ⋅ d-1 for CON, LEU-M, and LEU-H pigs, respectively) were reduced with increasing Leu intake during the prechallenge period (P < 0.05). ISS reduced whole-body protein synthesis (203 compared with 169 ± 12 mmol N ⋅ kg BW-1 ⋅ d-1 for ISS- and ISS+ pigs fed CON, respectively; P < 0.05) and protein deposition (PD) (64.9 compared with 45.0 ± 2.9 mmol N ⋅ kg BW-1 ⋅ d-1 for ISS- and ISS+ pigs fed CON, respectively; P < 0.01), whereas ISS did not affect whole-body protein degradation. Leu intake did not affect whole-body protein synthesis or degradation in ISS+ pigs. CONCLUSIONS Our results indicate that supplemental Leu intake improves the efficiency of PD rather than PD directly in healthy pigs but did not affect whole-body protein turnover during ISS.
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Affiliation(s)
- Marko Rudar
- Department of Animal Biosciences, University of Guelph, Guelph, Ontario, Canada
| | - Cuilan L Zhu
- Department of Animal Biosciences, University of Guelph, Guelph, Ontario, Canada
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Hernandez-García AD, Columbus DA, Manjarín R, Nguyen HV, Suryawan A, Orellana RA, Davis TA. Leucine supplementation stimulates protein synthesis and reduces degradation signal activation in muscle of newborn pigs during acute endotoxemia. Am J Physiol Endocrinol Metab 2016; 311:E791-E801. [PMID: 27624100 PMCID: PMC5241557 DOI: 10.1152/ajpendo.00217.2016] [Citation(s) in RCA: 26] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 06/07/2016] [Accepted: 09/06/2016] [Indexed: 11/22/2022]
Abstract
Sepsis disrupts skeletal muscle proteostasis and mitigates the anabolic response to leucine (Leu) in muscle of mature animals. We have shown that Leu stimulates muscle protein synthesis (PS) in healthy neonatal piglets. To determine if supplemental Leu can stimulate PS and reduce protein degradation (PD) signaling in neonatal muscle during endotoxemia, overnight-fasted neonatal pigs were infused for 8 h with LPS or saline while plasma amino acids, glucose, and insulin were maintained at fasting levels during pancreatic-substrate clamps. Leu or saline was infused during the last hour. Markers of PS and PD were determined in skeletal muscle. Compared with controls, Leu increased PS in longissimus dorsi (LD), gastrocnemius, and soleus muscles. LPS decreased PS in these three muscles by 36%, 28%, and 38%, but Leu antagonized that reduction by increasing PS by 84%, 81%, and 83%, respectively, when supplemented to LPS. Leu increased eukaryotic translation initiation factor (eIF)3b-raptor interactions, eIF4E-binding protein-1, and S6 kinase 1 phosphorylation as well as eIF4E·eIF4G complex formation in LD, gastrocnemius, and soleus muscles of control and LPS-treated pigs. In LD muscle, LPS increased the light chain (LC)3-II-to-LC3 ratio and muscle-specific RING finger (MuRF-1) abundance but not atrogin-1 abundance or AMP-activated protein kinase-α phosphorylation. Leu supplementation to LPS-treated pigs reduced the LC3-II-to-LC3 ratio, MuRF-1 abundance, and AMP-activated protein kinase-α phosphorylation compared with LPS alone. In conclusion, parenteral Leu supplementation attenuates the LPS-induced reduction in PS by stimulating mammalian target of rapamycin complex 1-dependent translation and may reduce PD by attenuating autophagy-lysosome and MuRF-1 signaling in neonatal skeletal muscle.
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Affiliation(s)
- Adriana D Hernandez-García
- Children's Nutrition Research Center, United States Department of Agriculture/Agricultural Research Service, Houston, Texas; and Critical Care Section, Department of Pediatrics, Baylor College of Medicine, Houston, Texas
| | - Daniel A Columbus
- Children's Nutrition Research Center, United States Department of Agriculture/Agricultural Research Service, Houston, Texas; and
| | - Rodrigo Manjarín
- Children's Nutrition Research Center, United States Department of Agriculture/Agricultural Research Service, Houston, Texas; and
| | - Hanh V Nguyen
- Children's Nutrition Research Center, United States Department of Agriculture/Agricultural Research Service, Houston, Texas; and
| | - Agus Suryawan
- Children's Nutrition Research Center, United States Department of Agriculture/Agricultural Research Service, Houston, Texas; and
| | - Renán A Orellana
- Children's Nutrition Research Center, United States Department of Agriculture/Agricultural Research Service, Houston, Texas; and Critical Care Section, Department of Pediatrics, Baylor College of Medicine, Houston, Texas
| | - Teresa A Davis
- Children's Nutrition Research Center, United States Department of Agriculture/Agricultural Research Service, Houston, Texas; and
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Ham DJ, Caldow MK, Chhen V, Chee A, Wang X, Proud CG, Lynch GS, Koopman R. Glycine restores the anabolic response to leucine in a mouse model of acute inflammation. Am J Physiol Endocrinol Metab 2016; 310:E970-81. [PMID: 27094036 DOI: 10.1152/ajpendo.00468.2015] [Citation(s) in RCA: 20] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 10/30/2015] [Accepted: 04/18/2016] [Indexed: 12/23/2022]
Abstract
Amino acids, especially leucine, potently stimulate protein synthesis and reduce protein breakdown in healthy skeletal muscle and as a result have received considerable attention as potential treatments for muscle wasting. However, the normal anabolic response to amino acids is impaired during muscle-wasting conditions. Although the exact mechanisms of this anabolic resistance are unclear, inflammation and ROS are believed to play a central role. The nonessential amino acid glycine has anti-inflammatory and antioxidant properties and preserves muscle mass in calorie-restricted and tumor-bearing mice. We hypothesized that glycine would restore the normal muscle anabolic response to amino acids under inflammatory conditions. Relative rates of basal and leucine-stimulated protein synthesis were measured using SUnSET methodology 4 h after an injection of 1 mg/kg lipopolysaccharide (LPS). Whereas leucine failed to stimulate muscle protein synthesis in LPS-treated mice pretreated with l-alanine (isonitrogenous control), leucine robustly stimulated protein synthesis (+51%) in mice pretreated with 1 g/kg glycine. The improvement in leucine-stimulated protein synthesis was accompanied by a higher phosphorylation status of mTOR, S6, and 4E-BP1 compared with l-alanine-treated controls. Despite its known anti-inflammatory action in inflammatory cells, glycine did not alter the skeletal muscle inflammatory response to LPS in vivo or in vitro but markedly reduced DHE staining intensity, a marker of oxidative stress, in muscle cross-sections and attenuated LPS-induced wasting in C2C12 myotubes. Our observations in male C57BL/6 mice suggest that glycine may represent a promising nutritional intervention for the attenuation of skeletal muscle wasting.
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Affiliation(s)
- Daniel J Ham
- Basic and Clinical Myology Laboratory, Department of Physiology, University of Melbourne, Melbourne, Victoria, Australia
| | - Marissa K Caldow
- Basic and Clinical Myology Laboratory, Department of Physiology, University of Melbourne, Melbourne, Victoria, Australia
| | - Victoria Chhen
- Basic and Clinical Myology Laboratory, Department of Physiology, University of Melbourne, Melbourne, Victoria, Australia
| | - Annabel Chee
- Basic and Clinical Myology Laboratory, Department of Physiology, University of Melbourne, Melbourne, Victoria, Australia
| | - Xuemin Wang
- Nutrition and Metabolism, South Australian Health and Medical Research Institute, Adelaide, South Austrailia, Australia; and School of Biological Sciences, University of Adelaide, Adelaide, South Australia, Australia
| | - Christopher G Proud
- Nutrition and Metabolism, South Australian Health and Medical Research Institute, Adelaide, South Austrailia, Australia; and School of Biological Sciences, University of Adelaide, Adelaide, South Australia, Australia
| | - Gordon S Lynch
- Basic and Clinical Myology Laboratory, Department of Physiology, University of Melbourne, Melbourne, Victoria, Australia
| | - René Koopman
- Basic and Clinical Myology Laboratory, Department of Physiology, University of Melbourne, Melbourne, Victoria, Australia;
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Schwaederlé M, Daniels GA, Piccioni DE, Fanta PT, Schwab RB, Shimabukuro KA, Parker BA, Kurzrock R. Cyclin alterations in diverse cancers: Outcome and co-amplification network. Oncotarget 2015; 6:3033-42. [PMID: 25596748 PMCID: PMC4413635 DOI: 10.18632/oncotarget.2848] [Citation(s) in RCA: 27] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/03/2014] [Accepted: 12/05/2014] [Indexed: 11/25/2022] Open
Abstract
Cyclin genes are key regulatory components of the cell cycle. With the development of new agents, cyclin-related genes are becoming increasingly important as they can be targeted. Yet, the biological implications of these alterations have not been fully studied. Clinical characteristics and outcome parameters were compared for patients harboring cyclin alterations versus not. CCN alterations were found in 13% of our population (50/392; all amplifications) and were associated with breast cancer (P < 0.0001), a higher median number of concomitant molecular alterations (P < 0.0001), and liver metastases (P = 0.046). Harboring a cyclin amplification was not associated with overall survival, the time to metastasis/recurrence, nor with the best progression-free survival. In a Cox regression model, gastrointestinal histology (P < 0.0001), PTEN (P < 0.0001), and CDK alterations (P = 0.041) had a significant association with poorer overall survival. CCN amplifications significantly correlated with alterations in FGF/FGFR family genes as well as in MET and ARFRP1. An extended correlation study shed light on a network of co-amplifications influenced in part by genes that were localized on the same amplicons. CCN amplifications are common across cancers and had distinctive biological associations. Customized combinations targeting the cyclin pathway as well as the extended co-amplification network may be necessary in order to address resistance mechanisms.
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Affiliation(s)
- Maria Schwaederlé
- Center for Personalized Cancer Therapy, and Division of Hematology and Oncology, UCSD Moores Cancer Center, La Jolla, USA
| | - Gregory A Daniels
- Center for Personalized Cancer Therapy, and Division of Hematology and Oncology, UCSD Moores Cancer Center, La Jolla, USA
| | - David E Piccioni
- Center for Personalized Cancer Therapy, and Division of Hematology and Oncology, UCSD Moores Cancer Center, La Jolla, USA
| | - Paul T Fanta
- Center for Personalized Cancer Therapy, and Division of Hematology and Oncology, UCSD Moores Cancer Center, La Jolla, USA
| | - Richard B Schwab
- Center for Personalized Cancer Therapy, and Division of Hematology and Oncology, UCSD Moores Cancer Center, La Jolla, USA
| | - Kelly A Shimabukuro
- Center for Personalized Cancer Therapy, and Division of Hematology and Oncology, UCSD Moores Cancer Center, La Jolla, USA
| | - Barbara A Parker
- Center for Personalized Cancer Therapy, and Division of Hematology and Oncology, UCSD Moores Cancer Center, La Jolla, USA
| | - Razelle Kurzrock
- Center for Personalized Cancer Therapy, and Division of Hematology and Oncology, UCSD Moores Cancer Center, La Jolla, USA
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Asano S, Arvapalli R, Manne NDPK, Maheshwari M, Ma B, Rice KM, Selvaraj V, Blough ER. Cerium oxide nanoparticle treatment ameliorates peritonitis-induced diaphragm dysfunction. Int J Nanomedicine 2015; 10:6215-25. [PMID: 26491293 PMCID: PMC4599716 DOI: 10.2147/ijn.s89783] [Citation(s) in RCA: 12] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/23/2022] Open
Abstract
The severe inflammation observed during sepsis is thought to cause diaphragm dysfunction, which is associated with poor patient prognosis. Cerium oxide (CeO2) nanoparticles have been posited to exhibit anti-inflammatory and antioxidative activities suggesting that these particles may be of potential use for the treatment of inflammatory disorders. To investigate this possibility, Sprague Dawley rats were randomly assigned to the following groups: sham control, CeO2 nanoparticle treatment only (0.5 mg/kg iv), sepsis, and sepsis+CeO2 nanoparticles. Sepsis was induced by the introduction of cecal material (600 mg/kg) directly into the peritoneal cavity. Nanoparticle treatment decreased sepsis-associated impairments in diaphragmatic contractile (P(o)) function (sham: 25.6±1.6 N/cm(2) vs CeO2: 23.4±0.8 N/cm(2) vs Sep: 15.9±1.0 N/cm(2) vs Sep+CeO2: 20.0±1.0 N/cm(2), P<0.05). These improvements in diaphragm contractile function were accompanied by a normalization of protein translation signaling (Akt, FOXO-1, and 4EBP1), diminished proteolysis (caspase 8 and ubiquitin levels), and decreased inflammatory signaling (Stat3 and iNOS). Histological analysis suggested that nanoparticle treatment was associated with diminished sarcolemma damage and diminished inflammatory cell infiltration. These data indicate CeO2 nanoparticles may improve diaphragmatic function in the septic laboratory rat.
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Affiliation(s)
- Shinichi Asano
- Center for Diagnostic Nanosystems, Marshall University, Huntington, WV, USA ; Department of Pharmacology, Pharmaceutical Sciences and Research, School of Pharmacy, Marshall University, Huntington, WV, USA
| | | | - Nandini D P K Manne
- Center for Diagnostic Nanosystems, Marshall University, Huntington, WV, USA ; Department of Pharmacology, Pharmaceutical Sciences and Research, School of Pharmacy, Marshall University, Huntington, WV, USA
| | - Mani Maheshwari
- Center for Diagnostic Nanosystems, Marshall University, Huntington, WV, USA ; Department of Pharmacology, Physiology and Toxicology, Joan C Edwards School of Medicine, Marshall University, Huntington, WV, USA
| | - Bing Ma
- Center for Diagnostic Nanosystems, Marshall University, Huntington, WV, USA ; Department of Pharmacology, Pharmaceutical Sciences and Research, School of Pharmacy, Marshall University, Huntington, WV, USA
| | - Kevin M Rice
- Center for Diagnostic Nanosystems, Marshall University, Huntington, WV, USA
| | - Vellaisamy Selvaraj
- Center for Diagnostic Nanosystems, Marshall University, Huntington, WV, USA ; Department of Pharmacology, Pharmaceutical Sciences and Research, School of Pharmacy, Marshall University, Huntington, WV, USA
| | - Eric R Blough
- Center for Diagnostic Nanosystems, Marshall University, Huntington, WV, USA ; Department of Pharmacology, Pharmaceutical Sciences and Research, School of Pharmacy, Marshall University, Huntington, WV, USA ; Department of Pharmacology, Physiology and Toxicology, Joan C Edwards School of Medicine, Marshall University, Huntington, WV, USA
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Interactions between Autophagy and Bacterial Toxins: Targets for Therapy? Toxins (Basel) 2015; 7:2918-58. [PMID: 26248079 PMCID: PMC4549733 DOI: 10.3390/toxins7082918] [Citation(s) in RCA: 18] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/01/2015] [Revised: 07/27/2015] [Accepted: 07/28/2015] [Indexed: 01/07/2023] Open
Abstract
Autophagy is a physiological process involved in defense mechanisms for clearing intracellular bacteria. The autophagic pathway is finely regulated and bacterial toxins interact with this process in a complex manner. Bacterial toxins also interact significantly with many biochemical processes. Evaluations of the effects of bacterial toxins, such as endotoxins, pore-forming toxins and adenylate cyclases, on autophagy could support the development of new strategies for counteracting bacterial pathogenicity. Treatment strategies could focus on drugs that enhance autophagic processes to improve the clearance of intracellular bacteria. However, further in vivo studies are required to decipher the upregulation of autophagy and potential side effects limiting such approaches. The capacity of autophagy activation strategies to improve the outcome of antibiotic treatment should be investigated in the future.
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Marik PE. Feeding critically ill patients the right 'whey': thinking outside of the box. A personal view. Ann Intensive Care 2015; 5:51. [PMID: 26055186 PMCID: PMC4460184 DOI: 10.1186/s13613-015-0051-2] [Citation(s) in RCA: 47] [Impact Index Per Article: 5.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/03/2015] [Accepted: 05/15/2015] [Indexed: 01/02/2023] Open
Abstract
Atrophy of skeletal muscle mass is an almost universal problem in survivors of critical illness and is associated with significant short- and long-term morbidity. Contrary to common practice, the provision of protein/amino acids as a continuous infusion significantly limits protein synthesis whereas intermittent feeding maximally stimulates skeletal muscle synthesis. Furthermore, whey-based protein (high in leucine) increases muscle synthesis compared to soy or casein-based protein. In addition to its adverse effects on skeletal muscle synthesis, continuous feeding is unphysiological and has adverse effects on glucose and lipid metabolism and gastrointestinal function. I propose that critically ill patients' be fed intermittently with a whey-based formula and that such an approach is likely to be associated with better glycemic control, less hepatic steatosis and greater preservation of muscle mass. This paper provides the scientific basis for my approach to intermittent feeding of critically ill patients.
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Affiliation(s)
- Paul E Marik
- Division of Pulmonary and Critical Care Medicine, Eastern Virginia Medical School, 825 Fairfax Av, Suite 410, Norfolk, VA, 23507, USA,
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Salutary effect of aurintricarboxylic acid on endotoxin- and sepsis-induced changes in muscle protein synthesis and inflammation. Shock 2015; 41:420-8. [PMID: 24430547 DOI: 10.1097/shk.0000000000000128] [Citation(s) in RCA: 13] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/08/2023]
Abstract
Small molecule nonpeptidyl molecules are potentially attractive drug candidates as adjunct therapies in the treatment of sepsis-induced metabolic complications. As such, the current study investigates the use of aurintricarboxylic acid (ATA), which stimulates insulinlike growth factor 1 receptor and AKT signaling, for its ability to ameliorate the protein metabolic effects of endotoxin (lipopolysaccharide [LPS]) + interferon γ (IFN-γ) in C2C12 myotubes and sepsis in skeletal muscle. Aurintricarboxylic acid dose- and time-dependently increases mTOR (mammalian or mechanistic target of rapamycin)-dependent protein synthesis. Pretreatment with ATA prevents the LPS/IFN-γ-induced decrease in protein synthesis at least in part by maintaining mTOR kinase activity, whereas posttreatment with ATA is able to increase protein synthesis when added up to 6 h after LPS/IFN-γ. Aurintricarboxylic acid also reverses the amino acid resistance, which is detected in response to nutrient deprivation. Conversely, ATA decreases the basal rate of protein degradation and prevents the LPS/IFN-γ increase in proteolysis, and the latter change is associated reduced atrogin 1 and MuRF1 mRNA. The ability of ATA to antagonize LPS/IFN-γ-induced changes in protein metabolism was associated with its ability to prevent the increases in interleukin 6 and nitric oxide synthase 2 and decreases in insulinlike growth factor 1. In vivo studies indicate ATA acutely increases skeletal muscle, but not cardiac, protein synthesis and attenuates the loss of lean body mass over 5 days. These data suggest ATA and other small molecule agonists of endogenous anabolic hormones may prove beneficial in treating sepsis by decreasing the inflammatory response and improving muscle protein balance.
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A therapeutic approach to treat prostate cancer by targeting Nm23-H1/h-Prune interaction. Naunyn Schmiedebergs Arch Pharmacol 2014; 388:257-69. [PMID: 25138575 DOI: 10.1007/s00210-014-1035-8] [Citation(s) in RCA: 16] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/30/2014] [Accepted: 08/11/2014] [Indexed: 01/05/2023]
Abstract
Nm23-H1 is a metastasis suppressor gene whose overexpression is associated with both reduced cell motility in various cancers and increased metastatic potential in neuroblastomas, osteosarcomas, and hematological malignances. We previously reported that Nm23-H1 exerts tumor suppressor action in prostate cancer cells and that h-Prune, which is overexpressed in various tumor types, binds Nm23-H1. Moreover, blockage of the Nm23-H1/h-Prune interaction with a competitive permeable peptide (CPP) attenuates migration of breast and neuroblastoma cells. This series of events suggests that the Nm23-H1/h-Prune protein complex regulates cancer progression and that its specific impairment could be a new therapeutic strategy in oncology. We found that CPP leads to inhibition of the AKT/mTORv and NF-kBv signaling pathways and also activates apoptosis. To obtain a proof-of-concept of our hypothesis, we used a xenograft model of prostate cancer to evaluate whether impairment of this complex using CPP results in an anti-tumoral effect. Using a mouse orthotopic model with bioluminescent imaging, we show evidences that CPP reduces prostate cancer metastases formation. In conclusion, CPP being able to impair formation of the h-Prune/Nm23-H1 complex holds promise for the treatment of prostate cancer.
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Zhang S, Ren M, Zeng X, He P, Ma X, Qiao S. Leucine stimulates ASCT2 amino acid transporter expression in porcine jejunal epithelial cell line (IPEC-J2) through PI3K/Akt/mTOR and ERK signaling pathways. Amino Acids 2014; 46:2633-42. [PMID: 25063204 DOI: 10.1007/s00726-014-1809-9] [Citation(s) in RCA: 38] [Impact Index Per Article: 3.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/24/2014] [Accepted: 06/06/2014] [Indexed: 10/25/2022]
Abstract
Leucine has been shown to influence intestinal protein metabolism, cell proliferation and migration. Furthermore, our previous study demonstrated that branched-chain amino acids could modulate the intestinal amino acid and peptide transporters in vivo. As the possible mechanisms are still largely unknown, in the present work, we studied the transcriptional and translational regulation of leucine on amino acid transporter production in IPEC-J2 cells and the signaling pathways involved. Treatment of IPEC-J2 cells with 7.5 mM leucine enhanced the mRNA expression of the Na(+)-neutral AA exchanger 2 (ASCT2) and 4F2 heavy chain (4F2hc) and caused an increase in ASCT2 protein expression. Leucine also activated phosphorylation of 4E-BP1 and eIF4E through the phosphorylation of mTOR, Akt and ERK signaling pathways in IPEC-J2 cells. Pre-treatment of IPEC-J2 cells with inhibitors of mTOR and Akt (rapamycin and wortmannin) or an inhibitor of ERK (PD098059) for 30 min before leucine treatment attenuated the positive effect of leucine in enhancing the protein abundance of ASCT2. These results demonstrate that leucine could up-regulate the expression of the amino acid transporters (ASCT2) through transcriptional and translational regulation by ERK and PI3K/Akt/mTOR activation.
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Affiliation(s)
- Shihai Zhang
- State Key Laboratory of Animal Nutrition, Ministry of Agriculture Feed Industry Centre, College of Animal Science and Technology, China Agricultural University, Beijing, 100193, China
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28
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The emerging role of mTOR signalling in antibacterial immunity. Immunol Cell Biol 2014; 92:346-53. [PMID: 24518980 DOI: 10.1038/icb.2014.3] [Citation(s) in RCA: 25] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/03/2013] [Revised: 12/17/2013] [Accepted: 12/18/2013] [Indexed: 12/14/2022]
Abstract
Mammalian target of rapamycin (mTOR) is a central regulator of cellular metabolic homeostasis that is highly conserved in evolution. Recent evidence has revealed the existence of a complex interplay between mTOR signalling and immunity. We review here the emerging role of mTOR signalling in the regulation of Toll-like receptor-dependent innate responses and in the activation of T cells and antigen-presenting cells. We also highlight the importance of amino-acid starvation-driven mTOR inhibition in the control of autophagy and intracellular bacterial clearance.
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Verhees KJP, Pansters NAM, Baarsma HA, Remels AHV, Haegens A, de Theije CC, Schols AMWJ, Gosens R, Langen RCJ. Pharmacological inhibition of GSK-3 in a guinea pig model of LPS-induced pulmonary inflammation: II. Effects on skeletal muscle atrophy. Respir Res 2013; 14:117. [PMID: 24180420 PMCID: PMC4176095 DOI: 10.1186/1465-9921-14-117] [Citation(s) in RCA: 15] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/15/2013] [Accepted: 10/14/2013] [Indexed: 11/10/2022] Open
Abstract
BACKGROUND Chronic obstructive pulmonary disease (COPD) is accompanied by pulmonary inflammation and associated with extra-pulmonary manifestations, including skeletal muscle atrophy. Glycogen synthase kinase-3 (GSK-3) has been implicated in the regulation of muscle protein- and myonuclear turnover; two crucial processes that determine muscle mass. In the present study we investigated the effect of the selective GSK-3 inhibitor SB216763 on muscle mass in a guinea pig model of lipopolysaccharide (LPS)-induced pulmonary inflammation-associated muscle atrophy. METHODS Guinea pigs were pretreated with either intranasally instilled SB216763 or corresponding vehicle prior to each LPS/saline challenge twice weekly. Pulmonary inflammation was confirmed and indices of muscle mass were determined after 12 weeks. Additionally, cultured skeletal muscle cells were incubated with tumor necrosis factor α (TNF-α) or glucocorticoids (GCs) to model the systemic effects of pulmonary inflammation on myogenesis, in the presence or absence of GSK-3 inhibitors. RESULTS Repeated LPS instillation induced muscle atrophy based on muscle weight and muscle fiber cross sectional area. Intriguingly, GSK-3 inhibition using SB216763 prevented the LPS-induced muscle mass decreases and myofiber atrophy. Indices of protein turnover signaling were unaltered in guinea pig muscle. Interestingly, inhibition of myogenesis of cultured muscle cells by TNF-α or synthetic GCs was prevented by GSK-3 inhibitors. CONCLUSIONS In a guinea pig model of LPS-induced pulmonary inflammation, GSK-3 inhibition prevents skeletal muscle atrophy without affecting pulmonary inflammation. Resistance to inflammation- or GC-induced impairment of myogenic differentiation, imposed by GSK-3 inhibition, suggests that sustained myogenesis may contribute to muscle mass maintenance despite persistent pulmonary inflammation. Collectively, these results warrant further exploration of GSK-3 as a potential novel drug target to prevent or reverse muscle wasting in COPD.
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Affiliation(s)
- Koen J P Verhees
- Department of Respiratory Medicine, School for Nutrition, Toxicology and Metabolism (NUTRIM), Maastricht University Medical Centre + (MUMC+), PO box 5800, 6202, AZ Maastricht, The Netherlands.
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30
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Holecek M. Branched-chain amino acids and ammonia metabolism in liver disease: Therapeutic implications. Nutrition 2013; 29:1186-91. [DOI: 10.1016/j.nut.2013.01.022] [Citation(s) in RCA: 69] [Impact Index Per Article: 6.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/21/2012] [Revised: 01/24/2013] [Accepted: 01/30/2013] [Indexed: 01/02/2023]
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31
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Gueret G, Guillouet M, Vermeersch V, Guillard E, Talarmin H, Nguyen BV, Rannou F, Giroux-Metges MA, Pennec JP, Ozier Y. [ICU acquired neuromyopathy]. ACTA ACUST UNITED AC 2013; 32:580-91. [PMID: 23958176 DOI: 10.1016/j.annfar.2013.05.011] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/15/2012] [Accepted: 05/08/2013] [Indexed: 12/19/2022]
Abstract
ICU acquired neuromyopathy (IANM) is the most frequent neurological pathology observed in ICU. Nerve and muscle defects are merged with neuromuscular junction abnormalities. Its physiopathology is complex. The aim is probably the redistribution of nutriments and metabolism towards defense against sepsis. The main risk factors are sepsis, its severity and its duration of evolution. IANM is usually diagnosed in view of difficulties in weaning from mechanical ventilation, but electrophysiology may allow an earlier diagnosis. There is no curative therapy, but early treatment of sepsis, glycemic control as well as early physiotherapy may decrease its incidence. The outcomes of IANM are an increase in morbi-mortality and possibly long-lasting neuromuscular abnormalities as far as tetraplegia.
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Affiliation(s)
- G Gueret
- Pôle anesthésie réanimations soins intensifs blocs opératoires urgences (ARSIBOU), CHRU de Brest, boulevard Tanguy-Prigent, 29200 Brest, France; Laboratoire de physiologie, faculté de médecine et des sciences de la santé, EA 1274 (mouvement, sport santé), université de Bretagne-Occidentale, 22, avenue Camille-Desmoulins, 29200 Brest, France; Université européenne de Bretagne, 5, boulevard Laennec, 35000 Rennes, France.
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Klein BY, Tamir H, Hirschberg DL, Glickstein SB, Welch MG. Oxytocin modulates mTORC1 pathway in the gut. Biochem Biophys Res Commun 2013; 432:466-71. [PMID: 23410756 DOI: 10.1016/j.bbrc.2013.01.121] [Citation(s) in RCA: 23] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/13/2013] [Accepted: 01/29/2013] [Indexed: 12/12/2022]
Abstract
Our recent findings of a weaning-related pattern of oxytocin (OT) and OT receptor (OTR) expression in the rat enteric nervous system and in villus-crypt enterocytes, together with the known high level and stability of OT in breast milk support that OT may play a role in gut function and development. We previously described a biphasic dose-response of the PI3K/Akt pathway in gut cells treated with OT. Activation peaked at 62.5 nM OT (30 min) and coincided with OTR internalization. Here we use automated Western blotting to further explore OT-elicited changes in Akt and pAkt(T308), as well as in downstream substrates p70 S6 kinase-1 (S6K1) and eIF-4E binding protein 1 (4E-BP1). Relative to fresh growth medium (FGM) alone, our results showed OT in FGM reduced the abundance and phosphorylation of S6K1 and the phosphorylation of 4E-BP1, both substrates of mammalian target of rapamycin complex 1 (mTORC1). Phosphorylation of mTORC1 regulator, Raptor(S792), was increased by high and low OT concentrations, with predicted inhibitory effects on mTORC1. OT thus downregulates anabolic effects induced by FGM activity catalyzed by mTORC1. OT is a regulator of the PI3K/Akt/mTORC1 pathway in Caco2BB cells and may modulate translation in gut cells.
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Affiliation(s)
- Benjamin Y Klein
- Department of Pathology & Cell Biology, Columbia University College of Physicians and Surgeons, New York, NY 10032, USA.
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Abstract
Recent advances in elucidating the mechanisms that control body protein synthesis and degradation both expand and complicate our understanding of how these processes are regulated. This review presents an introduction to the multiple regulatory systems involved, emphasizing the number of potential controls. These include gene transcription, gene activation or suppression, activation or suppression of mRNA translation and activation or suppression of signaling pathways. The complexity of these interacting controls presents a challenge to our understanding of the overall coordinated regulation of protein synthesis and degradation and its response to any particular stimulus. Specific examples are used to illustrate regulatory mechanisms, including the ways in which protein metabolism is regulated by the amino acid leucine. In addition to regulation associated with gene expression and post-translational control, the expanding field of epigenetics adds another layer of complexity, including trans-generational responses to nutrient intake, highlighting the potential for long-term impact of nutritional experience on the metabolism of subsequent generations.
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Kirschey S, Wagner S, Hess G. Relapsed and/or Refractory Mantle Cell Lymphoma: What Role for Temsirolimus? CLINICAL MEDICINE INSIGHTS-ONCOLOGY 2012; 6:153-64. [PMID: 22550404 PMCID: PMC3306245 DOI: 10.4137/cmo.s7327] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Indexed: 11/05/2022]
Abstract
Mantle Cell Lymphoma (MCL) is associated with a dismal prognosis. Recently, along with the improved understanding of the pathophysiology of this disease, new first line regimens have been established and in addition novel treatment options have entered the clinical arena. In consequence, prognosis of the disease has fortunately improved. We here focus on the rationale, current clinical knowledge and future concepts of Temsirolimus, an inhibitor of mTOR, in the treatment of MCL. At this time this drug has been shown to be effective as single agent for relapsed disease and early combination data show promising results. In addition, with a brief outline of other treatment options, we aim to guide at which place in the current treatment algorithms Temsirolimus can be integrated into the treatment of MCL patients.
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Affiliation(s)
- Sebastian Kirschey
- Department of Hematology, Oncology, and Pneumology, University Medical School, Johannes Gutenberg-University, Langenbeckstr. 1, 55131 Mainz
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Frost RA, Lang CH. mTor signaling in skeletal muscle during sepsis and inflammation: where does it all go wrong? Physiology (Bethesda) 2011; 26:83-96. [PMID: 21487027 DOI: 10.1152/physiol.00044.2010] [Citation(s) in RCA: 81] [Impact Index Per Article: 6.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/19/2022] Open
Abstract
The mammalian target of rapamycin (mTOR) is an evolutionarily conserved protein kinase that exquisitely regulates protein metabolism in skeletal muscle. mTOR integrates input from amino acids, growth factors, and intracellular cues to make or break muscle protein. mTOR accomplishes this task by stimulating the phosphorylation of substrates that control protein translation while simultaneously inhibiting proteasomal and autophagic protein degradation. In a metabolic twist of fate, sepsis induces muscle atrophy in part by the aberrant regulation of mTOR. In this review, we track the steps of normal mTOR signaling in muscle and examine where they go astray in sepsis and inflammation.
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Affiliation(s)
- Robert A Frost
- Department of Cellular and Molecular Physiology, Pennsylvania State University College of Medicine, Hershey, Pennsylvania, USA
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Tarabees R, Hill D, Rauch C, Barrow PA, Loughna PT. Endotoxin transiently inhibits protein synthesis through Akt and MAPK mediating pathways in C2C12 myotubes. Am J Physiol Cell Physiol 2011; 301:C895-902. [PMID: 21775707 DOI: 10.1152/ajpcell.00387.2010] [Citation(s) in RCA: 21] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022]
Abstract
In this study, the effect of lipopolysaccharide (LPS) on protein synthesis (PS) and intracellular signaling factors that regulate it have been investigated in C2C12 murine-derived myotubes. In particular, the role of Akt/mammalian target of rapamycin (mTOR) and the mitogen-activated protein kinases (MAPKs) [p38 and extracelluar regulated protein kinase (ERK1/2)] have been examined. The direct effect of LPS on PS was measured at 3 and 18 h. LPS significantly decreased PS at 3 h but not at the 18-h time point. This effect was preceded by decreased Akt phosphorylation at 5 and 30 min after LPS administration. The mTOR phosphorylation exhibited a long time dose-dependent increase at all the time points. Similarly, the activity-related phosphorylation of p38 and ERK1/2 significantly increased in a time- and dose-dependent manner at all the time points. Polymyxin B abolished the LPS-induced decrease in PS rate. The phosphatidylinositol 3-kinase inhibitor LY-0294002 in combination with LPS significantly decreased the rate of PS by 81% and alone by 66%, respectively, for the 3- and 18-h time points, whereas p38 and ERK inhibitors in combination with LPS significantly decreased the rate PS rate at the 18-h time point by 41% and 59%, respectively, compared with control cells. In conclusion, LPS alone transiently decreased the rate of PS by 50% at 3 h; this effect is most likely mediated via the Toll-like receptor 4 (TLR4)-Akt/mTOR pathway, and both p38 and ERK when inhibited in the presence of LPS at 3 h have a similar effect in preventing the LPS-induced reduction in PS.
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Affiliation(s)
- R Tarabees
- School of Veterinary Medicine and Science, Sutton Bonington Campus, Univ. of Nottingham, Loughborough, UK
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Sepsis-induced alterations in protein-protein interactions within mTOR complex 1 and the modulating effect of leucine on muscle protein synthesis. Shock 2011; 35:117-25. [PMID: 20577146 DOI: 10.1097/shk.0b013e3181ecb57c] [Citation(s) in RCA: 37] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/21/2023]
Abstract
Sepsis-induced muscle atrophy is produced in part by decreased protein synthesis mediated by inhibition of mTOR (mammalian target of rapamycin). The present study tests the hypothesis that alteration of specific protein-protein interactions within the mTORC1 (mTOR complex 1) contributes to the decreased mTOR activity observed after cecal ligation and puncture in rats. Sepsis decreased in vivo translational efficiency in gastrocnemius and reduced the phosphorylation of eukaryotic initiation factor (eIF) 4E-binding protein (BP) 1, S6 kinase (S6K) 1, and mTOR, compared with time-matched pair-fed controls. Sepsis decreased T246-phosphorylated PRAS40 (proline-rich Akt substrate 40) and reciprocally increased S792-phosphorylated raptor (regulatory associated protein of mTOR). Despite these phosphorylation changes, sepsis did not alter PRAS40 binding to raptor. The amount of the mTOR-raptor complex did not differ between groups. In contrast, the binding and retention of both 4E-BP1 and S6K1 to raptor were increased, and, conversely, the binding of raptor with eIF3 was decreased in sepsis. These changes in mTORC1 in the basal state were associated with enhanced 5'-AMP activated kinase activity. Acute in vivo leucine stimulation increased muscle protein synthesis in control, but not septic rats. This muscle leucine resistance was associated with coordinated changes in raptor-eIF3 binding and 4E-BP1 phosphorylation. Overall, our data suggest the sepsis-induced decrease in muscle protein synthesis may be mediated by the inability of 4E-BP1 and S6K1 to be phosphorylated and released from mTORC1 as well as the decreased recruitment of eIF3 necessary for a functional 48S complex. These data provide additional mechanistic insight into the molecular mechanisms by which sepsis impairs both basal protein synthesis and the anabolic response to the nutrient signal leucine in skeletal muscle.
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Jespersen JG, Nedergaard A, Reitelseder S, Mikkelsen UR, Dideriksen KJ, Agergaard J, Kreiner F, Pott FC, Schjerling P, Kjaer M. Activated protein synthesis and suppressed protein breakdown signaling in skeletal muscle of critically ill patients. PLoS One 2011; 6:e18090. [PMID: 21483870 PMCID: PMC3069050 DOI: 10.1371/journal.pone.0018090] [Citation(s) in RCA: 35] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/17/2010] [Accepted: 02/20/2011] [Indexed: 12/25/2022] Open
Abstract
Background Skeletal muscle mass is controlled by myostatin and Akt-dependent signaling on mammalian target of rapamycin (mTOR), glycogen synthase kinase 3β (GSK3β) and forkhead box O (FoxO) pathways, but it is unknown how these pathways are regulated in critically ill human muscle. To describe factors involved in muscle mass regulation, we investigated the phosphorylation and expression of key factors in these protein synthesis and breakdown signaling pathways in thigh skeletal muscle of critically ill intensive care unit (ICU) patients compared with healthy controls. Methodology/Principal Findings ICU patients were systemically inflamed, moderately hyperglycemic, received insulin therapy, and showed a tendency to lower plasma branched chain amino acids compared with controls. Using Western blotting we measured Akt, GSK3β, mTOR, ribosomal protein S6 kinase (S6k), eukaryotic translation initiation factor 4E binding protein 1 (4E-BP1), and muscle ring finger protein 1 (MuRF1); and by RT-PCR we determined mRNA expression of, among others, insulin-like growth factor 1 (IGF-1), FoxO 1, 3 and 4, atrogin1, MuRF1, interleukin-6 (IL-6), tumor necrosis factor α (TNF-α) and myostatin. Unexpectedly, in critically ill ICU patients Akt-mTOR-S6k signaling was substantially higher compared with controls. FoxO1 mRNA was higher in patients, whereas FoxO3, atrogin1 and myostatin mRNAs and MuRF1 protein were lower compared with controls. A moderate correlation (r2 = 0.36, p<0.05) between insulin infusion dose and phosphorylated Akt was demonstrated. Conclusions/Significance We present for the first time muscle protein turnover signaling in critically ill ICU patients, and we show signaling pathway activity towards a stimulation of muscle protein synthesis and a somewhat inhibited proteolysis.
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Affiliation(s)
- Jakob G Jespersen
- Department of Orthopedic Surgery M, Institute of Sports Medicine Copenhagen, Bispebjerg Hospital and Center for Healthy Aging, Faculty of Health Sciences, University of Copenhagen, Copenhagen, Denmark.
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Frost RA, Pereyra E, Lang CH. Ethyl pyruvate preserves IGF-I sensitivity toward mTOR substrates and protein synthesis in C2C12 myotubes. Endocrinology 2011; 152:151-63. [PMID: 21106878 PMCID: PMC3219047 DOI: 10.1210/en.2010-0248] [Citation(s) in RCA: 11] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 12/14/2022]
Abstract
Bacterial infection decreases skeletal muscle protein synthesis via inhibition of the mammalian target of rapamycin (mTOR), a key regulator of translation initiation. To better define the mechanism by which muscle mTOR activity is decreased, we used an in vitro model of C2C12 myotubes treated with endotoxin [lipopolysaccharide (LPS)]and interferon (IFN)-γ to determine whether stable lipophilic pyruvate derivatives restore mTOR signaling. Myotubes treated with a combination of LPS and IFNγ down-regulated the phosphorylation of the mTOR substrates S6 kinase-1 and 4E binding protein-1. The phosphorylation of ribosomal protein S6 was decreased, whereas phosphorylation of elongation factor-2 was enhanced; all results consistent with defects in both translation initiation and elongation. LPS/IFNγ decreased protein synthesis 60% in myotubes. Treatment with methyl or ethyl pyruvate partially protected against the LPS/IFNγ-induced fall in mTOR signaling. The protective effect of ethyl and methyl pyruvate could not be replicated by an equimolar amount of sodium pyruvate. Although LPS/IFNγ treated myotubes were initially IGF-I responsive, prolonged exposure (≥ 17 h) resulted in IGF-I resistance at the level of mTOR despite normal IGF-I receptor phosphorylation. Ethyl pyruvate treatment restored IGF-I sensitivity as evidenced by the left shift in the IGF-I dose-response curve and maintained IGF-I responsiveness for a prolonged period of time. Ethyl pyruvate also restored IGF-I-stimulated protein synthesis in LPS/IFNγ-treated myotubes. Cotreatment with N-acetyl cysteine or ascorbic acid also preserved IGF-I sensitivity and mTOR activity. The data suggest that the combination of LPS and IFNγ inhibits mTOR activity and that prolonged exposure induces IGF-I resistance in myotubes. Lipophilic pyruvate derivatives and antioxidants show promise at rescuing mTOR activity and muscle protein synthesis by maintaining IGF-I sensitivity in this model.
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Affiliation(s)
- Robert A Frost
- Department of Cellular and Molecular Physiology (H166), Pennsylvania State University College of Medicine, 500 University Drive, Hershey, Pennsylvania 17033, USA.
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Puleo F, Meirelles K, Navaratnarajah M, Fitzpatrick L, Shumate ML, Cooney RN, Lang CH. Skeletal muscle catabolism in trinitrobenzene sulfonic acid-induced murine colitis. Metabolism 2010; 59:1680-90. [PMID: 20546811 PMCID: PMC2941564 DOI: 10.1016/j.metabol.2010.03.021] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 11/19/2009] [Revised: 03/25/2010] [Accepted: 03/30/2010] [Indexed: 02/07/2023]
Abstract
The present study determined whether the muscle atrophy produced by colitis is associated with altered rates of muscle protein synthesis or degradation, as well as the potential role of the local (eg, muscle) insulin-like growth factor (IGF) system and muscle-specific ubiquitin E3 ligases atrogin-1 and MuRF1 in mediating altered muscle protein balance. Colitis was induced in C57BL/6 mice by intrarectal administration of trinitrobenzene sulfonic acid (TNBS), and blood and tissues were collected on day 10. Mice with inflammatory bowel disease demonstrated reduced skeletal muscle mass and protein content, whereas colonic segment weight and gross damage score were both increased in mice with colitis, compared with time-matched control values. There was no change in muscle protein synthesis in mice with inflammatory bowel disease; but there was an increased protein breakdown (45%), proteasome activity (85%), and messenger RNA (mRNA) expression for atrogin-1 and MuRF1 (200%-300%) in muscle. These changes were associated with a reduction in liver (but not muscle) IGF-I mRNA as well as a reduction in both total and free IGF-I in the blood. Colitis decreased the hepatic content of IGF binding protein (IGFBP)-3 mRNA by 40% and increased IGFBP-1 mRNA by 100%. In contrast, colitis did alter IGFBP mRNAs in muscle. The tumor necrosis factor-α, interleukin-6, and nitric oxide synthase 2 mRNA content of both liver and skeletal muscle was increased in TNBS-treated mice; and plasma tumor necrosis factor-α and interleukin-6 concentrations were also elevated. These data suggest that TNBS-induced colitis is independent of a change in muscle protein synthesis but dependent on stimulation of protein degradation via increased expression of muscle-specific atrogenes, which may be mediated in part by the reduction in circulating concentration of IGF-I and the concomitant increase in inflammatory mediators observed in the blood and muscle per se.
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Affiliation(s)
- Frances Puleo
- Department of Surgery, Penn State College of Medicine, Hershey, PA 17033
| | - Katia Meirelles
- Department of Surgery, Penn State College of Medicine, Hershey, PA 17033
| | | | - Leo Fitzpatrick
- Department of Pharmacology, Penn State College of Medicine, Hershey, PA 17033
| | | | - Robert N. Cooney
- Department of Surgery, Penn State College of Medicine, Hershey, PA 17033
- Department of Cellular and Molecular Physiology, Penn State College of Medicine, Hershey, PA 17033
| | - Charles H. Lang
- Department of Surgery, Penn State College of Medicine, Hershey, PA 17033
- Department of Cellular and Molecular Physiology, Penn State College of Medicine, Hershey, PA 17033
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Lang CH, Lynch CJ, Vary TC. BCATm deficiency ameliorates endotoxin-induced decrease in muscle protein synthesis and improves survival in septic mice. Am J Physiol Regul Integr Comp Physiol 2010; 299:R935-44. [PMID: 20554928 DOI: 10.1152/ajpregu.00297.2010] [Citation(s) in RCA: 28] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022]
Abstract
Endotoxin (LPS) and sepsis decrease mammalian target of rapamycin (mTOR) activity in skeletal muscle, thereby reducing protein synthesis. Our study tests the hypothesis that inhibition of branched-chain amino acid (BCAA) catabolism, which elevates circulating BCAA and stimulates mTOR, will blunt the LPS-induced decrease in muscle protein synthesis. Wild-type (WT) and mitochondrial branched-chain aminotransferase (BCATm) knockout mice were studied 4 h after Escherichia coli LPS or saline. Basal skeletal muscle protein synthesis was increased in knockout mice compared with WT, and this change was associated with increased eukaryotic initiation factor (eIF)-4E binding protein-1 (4E-BP1) phosphorylation, eIF4E.eIF4G binding, 4E-BP1.raptor binding, and eIF3.raptor binding without a change in the mTOR.raptor complex in muscle. LPS decreased muscle protein synthesis in WT mice, a change associated with decreased 4E-BP1 phosphorylation as well as decreased formation of eIF4E.eIF4G, 4E-BP1.raptor, and eIF3.raptor complexes. In BCATm knockout mice given LPS, muscle protein synthesis only decreased to values found in vehicle-treated WT control mice, and this ameliorated LPS effect was associated with a coordinate increase in 4E-BP1.raptor, eIF3.raptor, and 4E-BP1 phosphorylation. Additionally, the LPS-induced increase in muscle cytokines was blunted in BCATm knockout mice, compared with WT animals. In a separate study, 7-day survival and muscle mass were increased in BCATm knockout vs. WT mice after polymicrobial peritonitis. These data suggest that elevating blood BCAA is sufficient to ameliorate the catabolic effect of LPS on skeletal muscle protein synthesis via alterations in protein-protein interactions within mTOR complex-1, and this may provide a survival advantage in response to bacterial infection.
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Affiliation(s)
- Charles H Lang
- Department of Cellular and Molecular Physiology, and Surgery, Pennsylvania State University College of Medicine, Hershey, Pennsylvania, USA.
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Lang CH, Frost RA, Bronson SK, Lynch CJ, Vary TC. Skeletal muscle protein balance in mTOR heterozygous mice in response to inflammation and leucine. Am J Physiol Endocrinol Metab 2010; 298:E1283-94. [PMID: 20388826 PMCID: PMC2886531 DOI: 10.1152/ajpendo.00676.2009] [Citation(s) in RCA: 48] [Impact Index Per Article: 3.4] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 12/22/2022]
Abstract
Sepsis and lipopolysaccharide (LPS) may decrease skeletal muscle protein synthesis by impairing mTOR (mammalian target of rapamycin) activity. The role of mTOR in regulating muscle protein synthesis was assessed in wild-type (WT) and mTOR heterozygous (+/-) mice under basal conditions and in response to LPS and/or leucine stimulation. No difference in body weight of mTOR(+/-) mice was observed compared with WT mice; whereas whole body lean body mass was reduced. Gastrocnemius weight was decreased in mTOR(+/-) mice, which was attributable in part to a reduced rate of basal protein synthesis. LPS decreased muscle protein synthesis in WT and mTOR(+/-) mice to the same extent. Reduced muscle protein synthesis in mTOR(+/-) mice under basal and LPS-stimulated conditions was associated with lower 4E-BP1 and S6K1 phosphorylation. LPS also decreased PRAS40 phosphorylation and increased phosphorylation of raptor and IRS-1 (Ser(307)) to the same extent in WT and mTOR(+/-) mice. Muscle atrogin-1 and MuRF1 mRNA content was elevated in mTOR(+/-) mice under basal conditions, implying increased ubiquitin-proteasome-mediated proteolysis, but the LPS-induced increase in these atrogenes was comparable between groups. Plasma insulin and IGF-I as well as tissue expression of TNFalpha, IL-6, or NOS2 did not differ between WT and mTOR(+/-) mice. Finally, whereas LPS impaired the ability of leucine to stimulate muscle protein synthesis and 4E-BP1 phosphorylation in WT mice, this inflammatory state rendered mTOR(+/-) mice leucine unresponsive. These data support the idea that the LPS-induced reduction in mTOR activity is relatively more important in regulating skeletal muscle mass in response to nutrient stimulation than under basal conditions.
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Affiliation(s)
- Charles H Lang
- Department of Cellular and Molecular Physiology, The Pennsylvania State University College of Medicine, Hershey, PA 17033, USA.
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Endotoxin and interferon-gamma inhibit translation in skeletal muscle cells by stimulating nitric oxide synthase activity. Shock 2010; 32:416-26. [PMID: 19295495 DOI: 10.1097/shk.0b013e3181a034d2] [Citation(s) in RCA: 34] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/19/2022]
Abstract
The purpose of the present study was to test the hypothesis that endogenous NO negatively affects translation in skeletal muscle cells after exposure to a combination of endotoxin (LPS) and interferon-gamma (IFN-gamma). Individually, LPS and IFN-gamma did not alter protein synthesis, but in combination, they inhibited protein synthesis by 80% in C2C12 myotubes. The combination of LPS and IFN-gamma dramatically downregulated the autophosphorylation of the mammalian target of rapamycin and its substrates S6K1 and 4EBP-1. The phosphorylation of ribosomal protein S6 was decreased, whereas phosphorylation of elongation factor 2 and raptor was enhanced, consistent with defects in both translation initiation and elongation. Reduced S6 phosphorylation occurred 8 to 18 h after LPS/IFN-gamma and coincided with a prolonged upregulation of NOS2 messenger RNA and protein. NOS2 protein expression and the LPS/IFN-gamma-induced fall in phosphorylated S6 were prevented by the proteasome inhibitor MG-132. The general NOS inhibitor, L-NAME, and the specific NOS2 inhibitor, 1400W, also prevented the LPS/IFN-gamma-induced decrease in protein synthesis and restored translational signaling. LPS/IFN-gamma downregulated the phosphorylation of multiple Akt substrates, including the proline-rich Akt substrate 40, while enhancing the phosphorylation of raptor on a 5'-AMP-activated kinase (AMPK)-regulated site. The negative effects of LPS/IFN-gamma were blunted by the AMPK inhibitor compound C. The data suggest that, in combination, LPS and IFN-gamma induce a prolonged expression of NOS2 and excessive production of NO that reciprocally alter Akt and AMPK activity and consequently downregulate translation via reduced mammalian target of rapamycin signaling.
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Holecek M. Three targets of branched-chain amino acid supplementation in the treatment of liver disease. Nutrition 2010; 26:482-90. [PMID: 20071143 DOI: 10.1016/j.nut.2009.06.027] [Citation(s) in RCA: 104] [Impact Index Per Article: 7.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/10/2009] [Revised: 06/08/2009] [Accepted: 06/24/2009] [Indexed: 12/18/2022]
Abstract
The article explains the pathogenesis of disturbances in branched-chain amino acid (BCAA; valine, leucine, and isoleucine) and protein metabolism in various forms of hepatic injury and it is suggested that the main cause of decrease in plasma BCAA concentration in liver cirrhosis is hyperammonemia. Three possible targets of BCAA supplementation in hepatic disease are suggested: (1) hepatic encephalopathy, (2) liver regeneration, and (3) hepatic cachexia. The BCAA may ameliorate hepatic encephalopathy by promoting ammonia detoxification, correction of the plasma amino acid imbalance, and by reduced brain influx of aromatic amino acids. The influence of BCAA supplementation on hepatic encephalopathy could be more effective in chronic hepatic injury with hyperammonemia and low concentrations of BCAA in blood than in acute hepatic illness, where hyperaminoacidemia frequently develops. The favorable effect of BCAA on liver regeneration and nutritional state of the body is related to their stimulatory effect on protein synthesis, secretion of hepatocyte growth factor, glutamine production and inhibitory effect on proteolysis. Presumably the beneficial effect of BCAA on hepatic cachexia is significant in compensated liver disease with decreased plasma BCAA concentrations, whereas it is less pronounced in hepatic diseases with inflammatory complications and enhanced protein turnover. It is concluded that specific benefits associated with BCAA supplementation depend significantly on the type of liver disease and on the presence of inflammatory reaction. An important task for clinical research is to identify groups of patients for whom BCAA treatment can significantly improve the health-related quality of life and the prognosis of hepatic disease.
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Affiliation(s)
- Milan Holecek
- Department of Physiology, Charles University in Prague, Faculty of Medicine in Hradec Kralove, Czech Republic.
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Jiao Q, Pruznak AM, Huber D, Vary TC, Lang CH. Castration differentially alters basal and leucine-stimulated tissue protein synthesis in skeletal muscle and adipose tissue. Am J Physiol Endocrinol Metab 2009; 297:E1222-32. [PMID: 19755668 PMCID: PMC2781348 DOI: 10.1152/ajpendo.00473.2009] [Citation(s) in RCA: 27] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 01/19/2023]
Abstract
Reduced testosterone as a result of catabolic illness or aging is associated with loss of muscle and increased adiposity. We hypothesized that these changes in body composition occur because of altered rates of protein synthesis under basal and nutrient-stimulated conditions that are tissue specific. The present study investigated such mechanisms in castrated male rats (75% reduction in testosterone) with demonstrated glucose intolerance. Over 9 wk, castration impaired body weight gain, which resulted from a reduced lean body mass and preferential sparing of adipose tissue. Castration decreased gastrocnemius weight, but this atrophy was not associated with reduced basal muscle protein synthesis or differences in plasma IGF-I, insulin, or individual amino acids. However, oral leucine failed to normally stimulate muscle protein synthesis in castrated rats. In addition, castration-induced atrophy was associated with increased 3-methylhistidine excretion and in vitro-determined ubiquitin proteasome activity in skeletal muscle, changes that were associated with decreased atrogin-1 or MuRF1 mRNA expression. Castration decreased heart and kidney weight without reducing protein synthesis and did not alter either cardiac output or glomerular filtration. In contradistinction, the weight of the retroperitoneal fat depot was increased in castrated rats. This increase was associated with an elevated rate of basal protein synthesis, which was unresponsive to leucine stimulation. Castration also decreased whole body fat oxidation. Castration increased TNFα, IL-1α, IL-6, and NOS2 mRNA in fat but not muscle. In summary, the castration-induced muscle wasting results from an increased muscle protein breakdown and the inability of leucine to stimulate protein synthesis, whereas the expansion of the retroperitoneal fat depot appears mediated in part by an increased basal rate of protein synthesis-associated increased inflammatory cytokine expression.
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Affiliation(s)
- Qianning Jiao
- Cell & Molecular Physiology (H166 Penn State College of Medicine, Hershey, PA 17033-0850, USA.
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de Montmollin E, Aboab J, Mansart A, Annane D. Bench-to-bedside review: Beta-adrenergic modulation in sepsis. CRITICAL CARE : THE OFFICIAL JOURNAL OF THE CRITICAL CARE FORUM 2009; 13:230. [PMID: 19863760 PMCID: PMC2784350 DOI: 10.1186/cc8026] [Citation(s) in RCA: 104] [Impact Index Per Article: 6.9] [Reference Citation Analysis] [Abstract] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Indexed: 12/14/2022]
Abstract
Sepsis, despite recent therapeutic progress, still carries unacceptably high mortality rates. The adrenergic system, a key modulator of organ function and cardiovascular homeostasis, could be an interesting new therapeutic target for septic shock. β-Adrenergic regulation of the immune function in sepsis is complex and is time dependent. However, β2 activation as well as β1 blockade seems to downregulate proinflammatory response by modulating the cytokine production profile. β1 blockade improves cardiovascular homeostasis in septic animals, by lowering myocardial oxygen consumption without altering organ perfusion, and perhaps by restoring normal cardiovascular variability. β-Blockers could also be of interest in the systemic catabolic response to sepsis, as they oppose epinephrine which is known to promote hyperglycemia, lipid and protein catabolism. The role of β-blockers in coagulation is less clear cut. They could have a favorable role in the septic pro-coagulant state, as β1 blockade may reduce platelet aggregation and normalize the depressed fibrinolytic status induced by adre-nergic stimulation. Therefore, β1 blockade as well as β2 activation improves sepsis-induced immune, cardiovascular and coagulation dysfunctions. β2 blocking, however, seems beneficial in the metabolic field. Enough evidence has been accumulated in the literature to propose β- adrenergic modulation, β1 blockade and β2 activation in particular, as new promising therapeutic targets for septic dyshomeostasis, modulating favorably immune, cardiovascular, metabolic and coagulation systems.
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Affiliation(s)
- Etienne de Montmollin
- Service de Réanimation Polyvalente de l'Hôpital Raymond Poincaré, 92380 Garches, France.
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Nystrom G, Pruznak A, Huber D, Frost RA, Lang CH. Local insulin-like growth factor I prevents sepsis-induced muscle atrophy. Metabolism 2009; 58:787-97. [PMID: 19375133 PMCID: PMC2759714 DOI: 10.1016/j.metabol.2009.01.015] [Citation(s) in RCA: 44] [Impact Index Per Article: 2.9] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 10/09/2008] [Accepted: 01/03/2009] [Indexed: 01/20/2023]
Abstract
The present study tests the hypotheses that local bioavailability of insulin-like growth factor I (IGF-I) is capable of regulating muscle protein balance and that muscle-directed IGF-I can selectively maintain muscle mass during bacterial infection. Initial studies in C57BL/6 mice demonstrated that increasing or decreasing bioavailable IGF-I within muscle by local administration of either Leu(24) Ala(31) IGF-I or IGF binding protein 1, respectively, produced proportional changes in surrogate markers (eg, phosphorylation of 4E-BP1 and S6K1) of protein synthesis. We next examined the ability of a sustained local administration of IGF-I to prevent sepsis-induced muscle atrophy over a 5-day period. At the time of cecal ligation and puncture or sham surgery, mice had a time-release pellet containing IGF-I implanted next to the gastrocnemius and a placebo pellet placed in the contralateral limb. Data indicated that IGF-I released locally only affected the adjacent muscle and was not released into the circulation. Gastrocnemius from septic mice containing the placebo pellet was atrophied and had a reduced IGF-I protein content. In contrast, locally directed IGF-I increased IGF-I protein within adjacent muscle to basal control levels. This change was associated with a proportional increase in muscle weight and protein, as well as increased phosphorylation of 4E-BP1 and the redistribution of eIF4E from the inactive eIF4E4EBP1 complex to the active eIF4EeIF4G complex. Local IGF-I also prevented the sepsis-induced increase in atrogin-1 messenger RNA in the exposed muscle. Finally, local IGF-I prevented the sepsis-induced increase in muscle interleukin-6 messenger RNA. Thus, muscle-directed IGF-I attenuates the sepsis-induced atrophic response apparently by increasing muscle protein synthesis and potentially decreasing proteolysis. Collectively, our data suggest that agents that increase the bioavailability of IGF-I within muscle per se might be effective in ameliorating the sepsis-induced loss of muscle mass without having undesirable effects on metabolic processes in distant organs.
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Affiliation(s)
- Gerald Nystrom
- Department of Cellular and Molecular Physiology, College of Medicine, Pennsylvania State University, Hershey, PA 17033, USA
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Hundal HS, Taylor PM. Amino acid transceptors: gate keepers of nutrient exchange and regulators of nutrient signaling. Am J Physiol Endocrinol Metab 2009; 296:E603-13. [PMID: 19158318 PMCID: PMC2670634 DOI: 10.1152/ajpendo.91002.2008] [Citation(s) in RCA: 226] [Impact Index Per Article: 15.1] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/22/2022]
Abstract
Amino acid transporters at the surface of cells are in an ideal location to relay nutritional information, as well as nutrients themselves, to the cell interior. These transporters are able to modulate signaling downstream of intracellular amino acid receptors by regulating intracellular amino acid concentrations through processes of coupled transport. The concept of dual-function amino acid transporter/receptor (or "transceptor") proteins is well established in primitive eukaryotes such as yeast, where detection of extracellular amino acid deficiency leads to upregulation of proteins involved in biosynthesis and transport of the deficient amino acid(s). The evolution of the "extracellular milieu" and nutrient-regulated endocrine controls in higher eukaryotes, alongside their frequent inability to synthesize all proteinaceous amino acids (and, hence, the requirement for indispensable amino acids in their diet), appears to have lessened the priority of extracellular amino acid sensing as a stimulus for metabolic signals. Nevertheless, recent studies of amino acid transporters in flies and mammalian cell lines have revealed perhaps unanticipated "echoes" of these transceptor functions, which are revealed by cellular stresses (notably starvation) or gene modification/silencing. APC-transporter superfamily members, including slimfast, path, and SNAT2 all appear capable of sensing and signaling amino acid availability to the target of rapamycin (TOR) pathway, possibly through PI 3-kinase-dependent mechanisms. We hypothesize (by extrapolation from knowledge of the yeast Ssy1 transceptor) that, at least for SNAT2, the transceptor discriminates between extracellular and intracellular amino acid stimuli when evoking a signal.
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Affiliation(s)
- Harinder S Hundal
- Division of Molecular Physiology, Sir James Black Centre, College of Life Sciences, University of Dundee, Dundee, DD1 5EH, UK.
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Pruznak AM, Kazi AA, Frost RA, Vary TC, Lang CH. Activation of AMP-activated protein kinase by 5-aminoimidazole-4-carboxamide-1-beta-D-ribonucleoside prevents leucine-stimulated protein synthesis in rat skeletal muscle. J Nutr 2008; 138:1887-94. [PMID: 18806097 PMCID: PMC2596722 DOI: 10.1093/jn/138.10.1887] [Citation(s) in RCA: 48] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/27/2022] Open
Abstract
Several stress conditions are characterized by activation of 5'-AMP-activated protein kinase (AMPK) and the development of leucine resistance in skeletal muscle. In the present study, we determined whether direct activation of the AMPK by 5-aminoimidazole-4-carboxamide-1-beta-D-ribonucleoside (AICAR) prevents the characteristic leucine-induced increase in protein synthesis by altering mammalian target of rapamycin (mTOR) signal transduction. Rats were injected with AICAR or saline (Sal) and 1 h thereafter received an oral gavage of leucine (or Sal). Efficacy of AICAR was verified by increased AMPK phosphorylation. AICAR decreased basal in vivo muscle (gastrocnemius) protein synthesis and completely prevented the leucine-induced increase, independent of a change in muscle adenine nucleotide concentration. AICAR also prevented the hyperphosphorylation of eukaryotic initiation factor (eIF) 4E binding protein (4E-BP1), ribosomal protein S6 kinase (S6K1), S6, and eIF4G in response to leucine, suggesting a decrease in mTOR activity. Moreover, AICAR prevented the leucine-induced redistribution of eIF4E from the inactive eIF4E.4E-BP1 to the active eIF4E.eIF4G complex. This ability of AICAR to produce muscle leucine resistance could not be attributed to a change in phosphorylation of tuberous sclerosis complex (TSC)2, the formation of a TSC1.TSC2 complex, the binding of raptor with mTOR, or the phosphorylation of eukaryotic elongation factor-2. However, the inhibitory actions of AICAR were associated with reduced phosphorylation of proline-rich Akt substrate-40 and increased phosphorylation of raptor, which represent potential mechanisms by which AICAR might be expected to inhibit leucine-induced increases in mTOR activity and protein synthesis under in vivo conditions.
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Affiliation(s)
- Anne M Pruznak
- Department of Cellular and Molecular Physiology, Pennsylvania State College of Medicine, Hershey, PA 17033, USA
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Abstract
Muscle wasting in sepsis reflects activation of multiple proteolytic mechanisms, including lyosomal and ubiquitin-proteasome-dependent protein breakdown. Recent studies suggest that activation of the calpain system also plays an important role in sepsis-induced muscle wasting. Perhaps the most important consequence of calpain activation in skeletal muscle during sepsis is disruption of the sarcomere, allowing for the release of myofilaments (including actin and myosin) that are subsequently ubiquitinated and degraded by the 26S proteasome. Other important consequences of calpain activation that may contribute to muscle wasting during sepsis include degradation of certain transcription factors and nuclear cofactors, activation of the 26S proteasome, and inhibition of Akt activity, allowing for downstream activation of Foxo transcription factors and GSK-3beta. The role of calpain activation in sepsis-induced muscle wasting suggests that the calpain system may be a therapeutic target in the prevention and treatment of muscle wasting during sepsis. Furthermore, because calpain activation may also be involved in muscle wasting caused by other conditions, including different muscular dystrophies and cancer, calpain inhibitors may be beneficial not only in the treatment of sepsis-induced muscle wasting but in other conditions causing muscle atrophy as well.
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Affiliation(s)
- Ira J Smith
- Department of Surgery, Beth Israel Deaconess Medical Center, Harvard Medical School, Boston, Massachusetts, USA
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