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Mora S, Adegoke OAJ. Maintenance of the branched-chain amino acid transporter LAT1 counteracts myotube atrophy following chemotherapy. Am J Physiol Cell Physiol 2024; 326:C866-C879. [PMID: 38284122 DOI: 10.1152/ajpcell.00537.2023] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/13/2023] [Revised: 01/14/2024] [Accepted: 01/18/2024] [Indexed: 01/30/2024]
Abstract
Prevention/management of cachexia remains a critical issue in muscle wasting conditions. The branched-chain amino acids (BCAA) have anabolic properties in skeletal muscle, but their use in treating cachexia has minimal benefits. This may be related to altered BCAA metabolism consequent to the use of chemotherapy, a main cancer treatment. Since this topic is minimally studied, we investigated the effect of chemotherapy on BCAA concentrations, transporter expression, and their metabolism. L6 myotubes were treated with vehicle (1.4 μL/mL DMSO) or a chemotherapy drug cocktail, FOLFIRI [CPT-11 (20 μg/mL), leucovorin (10 μg/mL), and 5-fluorouracil (50 μg/mL)] for 24-48 h. Chemotherapy reduced myotube diameter (-43%), myofibrillar protein content (-50%), and phosphorylation of the mechanistic target of rapamycin complex 1 (mTORC1) substrate S6K1thr389 (-80%). Drug-treated myotubes exhibited decreased BCAA concentrations (-52%) and expression of their transporter, L-type amino acid transporter 1 (LAT1; -67%). BCAA transaminase BCAT2 level was increased, but there was a reduction in PP2CM (-54%), along with increased inhibitory phosphorylation of BCKD-E1αser293 (+98%), corresponding with decreased BCKD enzyme activity (-23%) in chemotherapy-treated myotubes. Decreases in BCAA concentrations were a later response, preceded by decreases in LAT1 and BCKD activity. Although supplementation with the BCAA restored myotube BCAA levels, it had minimal effects on preventing the loss of myofibrillar proteins. However, RNAi-mediated depletion of neural precursor cell-expressed developmentally downregulated gene 4 (NEdd4), the protein ligase responsible for ubiquitin-dependent degradation of LAT1, attenuated the effects of chemotherapy on BCAA concentrations, anabolic signaling, protein synthesis, and myofibrillar protein abundance. Thus, if our findings are validated in preclinical models, interventions regulating muscle amino acid transporters might represent a promising strategy to treat cachexia.NEW & NOTEWORTHY This is the first study to attenuate chemotherapy-induced myotube atrophy by manipulating a BCAA transporter. Our findings suggest that positive regulation of amino acid transporters may be a promising strategy to treat cachexia.
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Affiliation(s)
- Stephen Mora
- School of Kinesiology and Health Science and Muscle Health Research Centre, York University, Toronto, Ontario, Canada
| | - Olasunkanmi A J Adegoke
- School of Kinesiology and Health Science and Muscle Health Research Centre, York University, Toronto, Ontario, Canada
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2
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Rivera CN, Smith CE, Draper LV, Kee ME, Cook NE, McGovern MR, Watne RM, Wommack AJ, Vaughan RA. The BCKDH kinase inhibitor BT2 promotes BCAA disposal and mitochondrial proton leak in both insulin-sensitive and insulin-resistant C2C12 myotubes. J Cell Biochem 2024; 125:e30520. [PMID: 38226684 DOI: 10.1002/jcb.30520] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/27/2023] [Revised: 11/29/2023] [Accepted: 12/21/2023] [Indexed: 01/17/2024]
Abstract
Elevated circulating branched-chain amino acids (BCAAs) have been correlated with the severity of insulin resistance, leading to recent investigations that stimulate BCAA metabolism for the potential benefit of metabolic diseases. BT2 (3,6-dichlorobenzo[b]thiophene-2-carboxylic acid), an inhibitor of branched-chain ketoacid dehydrogenase kinase, promotes BCAA metabolism by enhancing BCKDH complex activity. The purpose of this report was to investigate the effects of BT2 on mitochondrial and glycolytic metabolism, insulin sensitivity, and de novo lipogenesis both with and without insulin resistance. C2C12 myotubes were treated with or without low or moderate levels of BT2 with or without insulin resistance. Western blot and quantitative real-time polymerase chain reaction were used to assess protein and gene expression, respectively. Mitochondrial, nuclei, and lipid content were measured using fluorescent staining and microscopy. Cell metabolism was assessed via oxygen consumption and extracellular acidification rate. Liquid chromatography-mass spectrometry was used to quantify BCAA media content. BT2 treatment consistently promoted mitochondrial uncoupling following 24-h treatment, which occurred largely independent of changes in expressional profiles associated with mitochondrial biogenesis, mitochondrial dynamics, BCAA catabolism, insulin sensitivity, or lipogenesis. Acute metabolic studies revealed a significant and dose-dependent effect of BT2 on mitochondrial proton leak, suggesting BT2 functions as a small-molecule uncoupler. Additionally, BT2 treatment consistently and dose-dependently reduced extracellular BCAA levels without altering expression of BCAA catabolic enzymes or pBCKDHa activation. BT2 appears to act as a small-molecule mitochondrial uncoupler that promotes BCAA utilization, though the interplay between these two observations requires further investigation.
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Affiliation(s)
- Caroline N Rivera
- Department of Health and Human Performance, High Point University, High Point, North Carolina, USA
| | - Carly E Smith
- Department of Health and Human Performance, High Point University, High Point, North Carolina, USA
| | - Lillian V Draper
- Department of Health and Human Performance, High Point University, High Point, North Carolina, USA
| | - Madison E Kee
- Department of Health and Human Performance, High Point University, High Point, North Carolina, USA
| | - Norah E Cook
- Department of Health and Human Performance, High Point University, High Point, North Carolina, USA
| | - Macey R McGovern
- Department of Health and Human Performance, High Point University, High Point, North Carolina, USA
| | - Rachel M Watne
- Department of Chemistry, High Point University, High Point, North Carolina, USA
| | - Andrew J Wommack
- Department of Chemistry, High Point University, High Point, North Carolina, USA
| | - Roger A Vaughan
- Department of Health and Human Performance, High Point University, High Point, North Carolina, USA
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3
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Roberts MD, McCarthy JJ, Hornberger TA, Phillips SM, Mackey AL, Nader GA, Boppart MD, Kavazis AN, Reidy PT, Ogasawara R, Libardi CA, Ugrinowitsch C, Booth FW, Esser KA. Mechanisms of mechanical overload-induced skeletal muscle hypertrophy: current understanding and future directions. Physiol Rev 2023; 103:2679-2757. [PMID: 37382939 PMCID: PMC10625844 DOI: 10.1152/physrev.00039.2022] [Citation(s) in RCA: 7] [Impact Index Per Article: 7.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/11/2023] [Revised: 06/12/2023] [Accepted: 06/21/2023] [Indexed: 06/30/2023] Open
Abstract
Mechanisms underlying mechanical overload-induced skeletal muscle hypertrophy have been extensively researched since the landmark report by Morpurgo (1897) of "work-induced hypertrophy" in dogs that were treadmill trained. Much of the preclinical rodent and human resistance training research to date supports that involved mechanisms include enhanced mammalian/mechanistic target of rapamycin complex 1 (mTORC1) signaling, an expansion in translational capacity through ribosome biogenesis, increased satellite cell abundance and myonuclear accretion, and postexercise elevations in muscle protein synthesis rates. However, several lines of past and emerging evidence suggest that additional mechanisms that feed into or are independent of these processes are also involved. This review first provides a historical account of how mechanistic research into skeletal muscle hypertrophy has progressed. A comprehensive list of mechanisms associated with skeletal muscle hypertrophy is then outlined, and areas of disagreement involving these mechanisms are presented. Finally, future research directions involving many of the discussed mechanisms are proposed.
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Affiliation(s)
- Michael D Roberts
- School of Kinesiology, Auburn University, Auburn, Alabama, United States
| | - John J McCarthy
- Department of Physiology, College of Medicine, University of Kentucky, Lexington, Kentucky, United States
| | - Troy A Hornberger
- Department of Comparative Biosciences, University of Wisconsin-Madison, Madison, Wisconsin, United States
| | - Stuart M Phillips
- Department of Kinesiology, McMaster University, Hamilton, Ontario, Canada
| | - Abigail L Mackey
- Institute of Sports Medicine Copenhagen, Department of Orthopedic Surgery, Copenhagen University Hospital-Bispebjerg and Frederiksberg, and Department of Clinical Medicine, University of Copenhagen, Copenhagen, Denmark
| | - Gustavo A Nader
- Department of Kinesiology and Huck Institutes of the Life Sciences, The Pennsylvania State University, University Park, Pennsylvania, United States
| | - Marni D Boppart
- Department of Kinesiology and Community Health, University of Illinois at Urbana-Champaign, Urbana, Illinois, United States
| | - Andreas N Kavazis
- School of Kinesiology, Auburn University, Auburn, Alabama, United States
| | - Paul T Reidy
- Department of Kinesiology, Nutrition and Health, Miami University, Oxford, Ohio, United States
| | - Riki Ogasawara
- Healthy Food Science Research Group, Cellular and Molecular Biotechnology Research Institute, National Institute of Advanced Industrial Science and Technology (AIST), Tsukuba, Japan
| | - Cleiton A Libardi
- MUSCULAB-Laboratory of Neuromuscular Adaptations to Resistance Training, Department of Physical Education, Federal University of São Carlos, São Carlos, Brazil
| | - Carlos Ugrinowitsch
- School of Physical Education and Sport, University of São Paulo, São Paulo, Brazil
| | - Frank W Booth
- Department of Biomedical Sciences, University of Missouri, Columbia, Missouri, United States
| | - Karyn A Esser
- Department of Physiology and Aging, College of Medicine, University of Florida, Gainesville, Florida, United States
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4
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Bersiner K, Park SY, Schaaf K, Yang WH, Theis C, Jacko D, Gehlert S. Resistance exercise: a mighty tool that adapts, destroys, rebuilds and modulates the molecular and structural environment of skeletal muscle. Phys Act Nutr 2023; 27:78-95. [PMID: 37583075 PMCID: PMC10440184 DOI: 10.20463/pan.2023.0021] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/26/2023] [Revised: 06/29/2023] [Accepted: 06/30/2023] [Indexed: 08/17/2023] Open
Abstract
PURPOSE Skeletal muscle regulates health and performance by maintaining or increasing strength and muscle mass. Although the molecular mechanisms in response to resistance exercise (RE) significantly target the activation of protein synthesis, a plethora of other mechanisms and structures must be involved in orchestrating the communication, repair, and restoration of homeostasis after RE stimulation. In practice, RE can be modulated by variations in intensity, continuity and volume, which affect molecular responses and skeletal muscle adaptation. Knowledge of these aspects is important with respect to planning of training programs and assessing the impact of RE training on skeletal muscle. METHODS In this narrative review, we introduce general aspects of skeletal muscle substructures that adapt in response to RE. We further highlighted the molecular mechanisms that control human skeletal muscle anabolism, degradation, repair and memory in response to acute and repeated RE and linked these aspects to major training variables. RESULTS Although RE is a key stimulus for the activation of skeletal muscle anabolism, it also induces myofibrillar damage. Nevertheless, to increase muscle mass accompanied by a corresponding adaptation of the essential substructures of the sarcomeric environment, RE must be continuously repeated. This requires the permanent engagement of molecular mechanisms that re-establish skeletal muscle integrity after each RE-induced muscle damage. CONCLUSION Various molecular regulators coordinately control the adaptation of skeletal muscle after acute and repeated RE and expand their actions far beyond muscle growth. Variations of key resistance training variables likely affect these mechanisms without affecting muscle growth.
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Affiliation(s)
- Käthe Bersiner
- Department for Biosciences of Sports, Institute of Sports Science, University of Hildesheim, Hildesheim, Germany
| | - So-Young Park
- Graduate School of Sports Medicine, CHA University, Pocheon, Republic of Korea
| | - Kirill Schaaf
- Department of Molecular and Cellular Sports Medicine, Institute of Cardiovascular Research and Sports Medicine, German Sport University Cologne, Cologne, Germany
| | - Woo-Hwi Yang
- Graduate School of Sports Medicine, CHA University, Pocheon, Republic of Korea
- Department of Medicine, General Graduate School, CHA University, Pocheon, Republic of Korea
| | - Christian Theis
- Center for Anaesthesiology, Helios University Hospital Wuppertal, Wuppertal, Germany
| | - Daniel Jacko
- Department of Molecular and Cellular Sports Medicine, Institute of Cardiovascular Research and Sports Medicine, German Sport University Cologne, Cologne, Germany
| | - Sebastian Gehlert
- Department for Biosciences of Sports, Institute of Sports Science, University of Hildesheim, Hildesheim, Germany
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Rivera CN, Watne RM, Brown ZA, Mitchell SA, Wommack AJ, Vaughan RA. Effect of AMPK activation and glucose availability on myotube LAT1 expression and BCAA utilization. Amino Acids 2023; 55:275-286. [PMID: 36547760 DOI: 10.1007/s00726-022-03224-7] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/14/2022] [Accepted: 12/01/2022] [Indexed: 12/24/2022]
Abstract
Those with insulin resistance often display increased circulating branched-chain amino acids (BCAA), which has been largely attributable to reduced BCAA catabolic capacity. Metabolic stimuli such as exercise activates AMP-activated kinase (AMPK), which promotes the metabolism of BCAA and induction/activation of BCAA catabolic enzymes. Though much attention has been paid to BCAA catabolic machinery, few studies have assessed the effect of AMPK activation on the predominant BCAA transporter, L-type amino acid transporter 1 (LAT1). This study assessed the effect of AMPK activation on LAT1 expression via common chemical AMPK activators in a cell model of skeletal muscle. C2C12 myotubes were treated with either 1 mM AICAR, 1 mM Metformin, or filter-sterilized water (control) for 24 h with either low- (5 mM) or high-glucose (25 mM) media. LAT1 and pAMPK protein content were measured via western blot. BCAA media content was measured using liquid chromatography-mass spectrometry. AICAR treatment significantly increased pAMPK and reduced LAT1 expression. Collectively, pAMPK and LAT1 displayed a significant inverse relationship independent of glucose levels. During low-glucose experiments, AICAR-treated cells had higher BCAA media content compared to other groups, and an inverse relationship between LAT1 and BCAA media content was observed, however, these effects were not consistently observed during high-glucose conditions. Further investigation with AICAR with and without concurrent LAT1 inhibition (via JPH203) also revealed reduced BCAA utilization in AICAR-treated cells regardless of LAT1 inhibition (which also independently reduced BCAA utilization). pAMPK activation via AICAR (but not Metformin) may reduce LAT1 expression and BCAA uptake in a glucose-dependent manner.
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Affiliation(s)
- Caroline N Rivera
- Department of Exercise Science, High Point University, One University Parkway, High Point, NC, 27268, USA
| | - Rachel M Watne
- Department of Chemistry, High Point University, One University Parkway, High Point, NC, 27268, USA
| | - Zoe A Brown
- Department of Chemistry, High Point University, One University Parkway, High Point, NC, 27268, USA
| | - Samantha A Mitchell
- Department of Chemistry, High Point University, One University Parkway, High Point, NC, 27268, USA
| | - Andrew J Wommack
- Department of Chemistry, High Point University, One University Parkway, High Point, NC, 27268, USA
| | - Roger A Vaughan
- Department of Exercise Science, High Point University, One University Parkway, High Point, NC, 27268, USA.
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6
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Tinline-Goodfellow CT, Lees MJ, Hodson N. The skeletal muscle fiber periphery: A nexus of mTOR-related anabolism. SPORTS MEDICINE AND HEALTH SCIENCE 2022; 5:10-19. [PMID: 36994172 PMCID: PMC10040390 DOI: 10.1016/j.smhs.2022.11.004] [Citation(s) in RCA: 2] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/15/2022] [Revised: 11/16/2022] [Accepted: 11/23/2022] [Indexed: 12/02/2022] Open
Abstract
Skeletal muscle anabolism is driven by numerous stimuli such as growth factors, nutrients (i.e., amino acids, glucose), and mechanical stress. These stimuli are integrated by the mechanistic target of rapamycin (mTOR) complex 1 (mTORC1) signal transduction cascade. In recent years, work from our laboratory and elsewhere has sought to unravel the molecular mechanisms underpinning the mTOR-related activation of muscle protein synthesis (MPS), as well as the spatial regulation of these mechanisms within the skeletal muscle cell. These studies have suggested that the skeletal muscle fiber periphery is a region of central importance in anabolism (i.e., growth/MPS). Indeed, the fiber periphery is replete with the substrates, molecular machinery, and translational apparatus necessary to facilitate MPS. This review provides a summary of the mechanisms underpinning the mTOR-associated activation of MPS from cell, rodent, and human studies. It also presents an overview of the spatial regulation of mTORC1 in response to anabolic stimuli and outlines the factors that distinguish the periphery of the cell as a highly notable region of skeletal muscle for the induction of MPS. Future research should seek to further explore the nutrient-induced activation of mTORC1 at the periphery of skeletal muscle fibers.
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Affiliation(s)
| | - Matthew J. Lees
- Faculty of Kinesiology and Physical Education, University of Toronto, Canada
| | - Nathan Hodson
- Faculty of Kinesiology and Physical Education, University of Toronto, Canada
- Institute of Sport, Manchester Metropolitan University, Manchester, United Kingdom
- Department of Sport and Exercise Sciences, Manchester Metropolitan University, Manchester, United Kingdom
- Corresponding author. Faculty of Kinesiology and Physical Education, University of Toronto, Canada.
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7
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Roberson PA, Jefferson LS, Kimball SR. Convergence of signaling pathways in mediating actions of leucine and IGF-1 on mTORC1 in L6 myoblasts. Am J Physiol Cell Physiol 2022; 323:C804-C812. [PMID: 35912992 PMCID: PMC9448342 DOI: 10.1152/ajpcell.00183.2022] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/02/2022] [Revised: 07/27/2022] [Accepted: 07/28/2022] [Indexed: 11/22/2022]
Abstract
Leucine and insulin-like growth factor-1 (IGF-1) are important regulators of protein synthesis in skeletal muscle. The mechanistic target of rapamycin complex 1 (mTORC1) is of particular importance in their mechanism of action. In the present study, pathways through which leucine and IGF-1 converge to mediate activation of mTORC1 were examined in L6 myoblasts that were deprived of leucine and serum followed by readdition of either leucine or IGF-1. Compared with leucine- and serum-deprived myoblasts, IGF-1, but not leucine, promoted phosphorylation of protein kinase B (AKT), tuberous sclerosis complex 2 (TSC2), and the autophosphorylation site on mTOR (S2481) and also stimulated mTOR kinase activity in mTOR immunoprecipitated samples. Both leucine and IGF-1 promoted phosphorylation of mTOR on S2448. The association of mTOR with the regulatory-associated protein of mTOR (Raptor) was altered by IGF-1 treatment and trended (P = 0.065) to be altered by leucine treatment. Alterations in the association of mTOR with Raptor were proportional to changes in phosphorylation of the mTOR substrates, eIF4E-binding protein 1 (4E-BP1), and ribosomal protein S6 Kinase-β1 (p70S6K1). Surprisingly, leucine, but not IGF-1, stimulated protein synthesis suggesting a unique role for nutrients in regulating protein synthesis. Overall, the results are consistent with a model whereby IGF-1 stimulates phosphorylation of 4E-BP1 and p70S6K1 in L6 myoblasts through an AKT-TSC2-mTORC1 signaling pathway that also involves changes in the interaction between mTOR and Raptor. In contrast, leucine signaling to mTOR results in alterations in certain mTOR phosphorylation sites and the interaction between mTOR and Raptor and stimulates protein synthesis.
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Affiliation(s)
- Paul A Roberson
- Department of Cellular and Molecular Physiology, Penn State College of Medicine, Hershey, Pennsylvania
| | - Leonard S Jefferson
- Department of Cellular and Molecular Physiology, Penn State College of Medicine, Hershey, Pennsylvania
| | - Scot R Kimball
- Department of Cellular and Molecular Physiology, Penn State College of Medicine, Hershey, Pennsylvania
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8
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Collao N, Akohene-Mensah P, Nallabelli J, Binet ER, Askarian A, Lloyd J, Niemiro GM, Beals JW, van Vliet S, Rajgara R, Saleh A, Wiper-Bergeron N, Paluska SA, Burd NA, De Lisio M. The Role of L-type Amino Acid Transporter 1 (Slc7a5) During In Vitro Myogenesis. Am J Physiol Cell Physiol 2022; 323:C595-C605. [PMID: 35848618 DOI: 10.1152/ajpcell.00162.2021] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022]
Abstract
Satellite cells are required for muscle regeneration, remodeling, and repair through their activation, proliferation, and differentiation; however, how dietary factors regulate this process remains poorly understood. The L-Type amino acid transporter 1 (LAT1) transports amino acids, such as leucine, into mature myofibers, which then stimulates protein synthesis and anabolic signaling. However, whether LAT1 is expressed on myoblasts and is involved in regulating myogenesis is unknown. The aim of this study was to characterize the expression and functional relevance of LAT1 during different stages of myogenesis and in response to growth and atrophic conditions in vitro. We determined that LAT1 is expressed by C2C12 and human primary myoblasts, and its gene expression is lower during differentiation (p<0.05). Pharmacological inhibition and genetic knockdown of LAT1 impaired myoblast viability, differentiation, and fusion (all p<0.05). LAT1 protein content in C2C12 myoblasts was not significantly altered in response to different leucine concentrations in cell culture media or in two in vitro atrophy models. However, LAT1 content was decreased in myotubes under atrophic conditions in vitro (p<0.05). These findings indicate that LAT1 is stable throughout myogenesis and in response to several in vitro conditions that induce muscle remodeling. Further, amino acid transport through LAT1 is required for normal myogenesis in vitro.
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Affiliation(s)
- Nicolas Collao
- School of Human Kinetics, University of Ottawa, Ottawa, ON, Canada
| | | | - Julian Nallabelli
- Departments of Kinesiology and Community Health, University of Illinois at Urbana-Champaign, Urbana, IL, United States
| | - Emileigh R Binet
- School of Human Kinetics, University of Ottawa, Ottawa, ON, Canada
| | - Ali Askarian
- School of Human Kinetics, University of Ottawa, Ottawa, ON, Canada
| | - Jessica Lloyd
- School of Human Kinetics, University of Ottawa, Ottawa, ON, Canada
| | - Grace M Niemiro
- Departments of Kinesiology and Community Health, University of Illinois at Urbana-Champaign, Urbana, IL, United States
| | - Joseph W Beals
- Departments of Kinesiology and Community Health, University of Illinois at Urbana-Champaign, Urbana, IL, United States
| | - Stephan van Vliet
- Departments of Kinesiology and Community Health, University of Illinois at Urbana-Champaign, Urbana, IL, United States
| | - Rashida Rajgara
- Department of Cellular and Molecular Medicine and Centre on Neuromuscular Disease, University of Ottawa, Ottawa, ON, Canada
| | - Aisha Saleh
- Department of Cellular and Molecular Medicine and Centre on Neuromuscular Disease, University of Ottawa, Ottawa, ON, Canada
| | - Nadine Wiper-Bergeron
- Department of Cellular and Molecular Medicine and Centre on Neuromuscular Disease, University of Ottawa, Ottawa, ON, Canada
| | - Scott A Paluska
- Departments of Kinesiology and Community Health, University of Illinois at Urbana-Champaign, Urbana, IL, United States
| | - Nicholas A Burd
- Departments of Kinesiology and Community Health, University of Illinois at Urbana-Champaign, Urbana, IL, United States
| | - Michael De Lisio
- School of Human Kinetics, University of Ottawa, Ottawa, ON, Canada.,Departments of Kinesiology and Community Health, University of Illinois at Urbana-Champaign, Urbana, IL, United States.,Department of Cellular and Molecular Medicine and Centre on Neuromuscular Disease, University of Ottawa, Ottawa, ON, Canada
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9
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Fox CD, Mesquita PHC, Godwin JS, Angleri V, Damas F, Ruple BA, Sexton CL, Brown MD, Kavazis AN, Young KC, Ugrinowitsch C, Libardi CA, Roberts MD. Frequent Manipulation of Resistance Training Variables Promotes Myofibrillar Spacing Changes in Resistance-Trained Individuals. Front Physiol 2021; 12:773995. [PMID: 34975527 PMCID: PMC8715010 DOI: 10.3389/fphys.2021.773995] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/10/2021] [Accepted: 11/17/2021] [Indexed: 11/21/2022] Open
Abstract
We sought to determine if manipulating resistance training (RT) variables differentially altered the expression of select sarcoplasmic and myofibril proteins as well as myofibrillar spacing in myofibers. Resistance-trained men (n = 20; 26 ± 3 years old) trained for 8 weeks where a randomized leg performed either a standard (CON) or variable RT protocol (VAR: manipulation of load, volume, muscle action, and rest intervals at each RT session). A pre-training (PRE) vastus lateralis biopsy was obtained from a randomized single leg, and biopsies were obtained from both legs 96 h following the last training bout. The sarcoplasmic protein pool was assayed for proteins involved in energy metabolism, and the myofibril protein pool was assayed for relative myosin heavy chain (MHC) and actin protein abundances. Sections were also histologically analyzed to obtain myofibril spacing characteristics. VAR resulted in ~12% greater volume load (VL) compared to CON (p < 0.001). The mean fiber cross-sectional area increased following both RT protocols [CON: 14.6% (775.5 μm2), p = 0.006; VAR: 13.9% (743.2 μm2), p = 0.01 vs. PRE for both], but without significant differences between protocols (p = 0.79). Neither RT protocol affected a majority of assayed proteins related to energy metabolism, but both training protocols increased hexokinase 2 protein levels and decreased a mitochondrial beta-oxidation marker (VLCAD protein; p < 0.05). Citrate synthase activity levels increased with CON RT (p < 0.05), but not VAR RT. The relative abundance of MHC (summed isoforms) decreased with both training protocols (p < 0.05). However, the relative abundance of actin protein (summed isoforms) decreased with VAR only (13.5 and 9.0%, respectively; p < 0.05). A decrease in percent area occupied by myofibrils was observed from PRE to VAR (−4.87%; p = 0.048), but not for the CON (4.53%; p = 0.979). In contrast, there was an increase in percent area occupied by non-contractile space from PRE to VAR (10.14%; p = 0.048), but not PRE to CON (0.72%; p = 0.979). In conclusion, while both RT protocols increased muscle fiber hypertrophy, a higher volume-load where RT variables were frequently manipulated increased non-contractile spacing in resistance-trained individuals.
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Affiliation(s)
- Carlton D. Fox
- School of Kinesiology, Auburn University, Auburn, AL, United States
| | | | - Joshua S. Godwin
- School of Kinesiology, Auburn University, Auburn, AL, United States
| | - Vitor Angleri
- MUSCULAB, Laboratory of Neuromuscular Adaptations to Resistance Training, Department of Physical Education, Federal University of São Carlos, São Carlos, Brazil
| | - Felipe Damas
- MUSCULAB, Laboratory of Neuromuscular Adaptations to Resistance Training, Department of Physical Education, Federal University of São Carlos, São Carlos, Brazil
| | - Bradley A. Ruple
- School of Kinesiology, Auburn University, Auburn, AL, United States
| | - Casey L. Sexton
- School of Kinesiology, Auburn University, Auburn, AL, United States
| | - Michael D. Brown
- School of Kinesiology, Auburn University, Auburn, AL, United States
| | | | - Kaelin C. Young
- School of Kinesiology, Auburn University, Auburn, AL, United States
- Department of Cell Biology and Physiology, Edward Via College of Osteopathic Medicine – Auburn Campus, Auburn, AL, United States
| | - Carlos Ugrinowitsch
- School of Physical Education and Sport, University of São Paulo, São Paulo, Brazil
| | - Cleiton A. Libardi
- MUSCULAB, Laboratory of Neuromuscular Adaptations to Resistance Training, Department of Physical Education, Federal University of São Carlos, São Carlos, Brazil
- *Correspondence: Cleiton A. Libardi, ; Michael D. Roberts,
| | - Michael D. Roberts
- School of Kinesiology, Auburn University, Auburn, AL, United States
- Department of Cell Biology and Physiology, Edward Via College of Osteopathic Medicine – Auburn Campus, Auburn, AL, United States
- *Correspondence: Cleiton A. Libardi, ; Michael D. Roberts,
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10
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Abou Sawan S, Hodson N, Tinline-Goodfellow C, West DWD, Malowany JM, Kumbhare D, Moore DR. Incorporation of Dietary Amino Acids Into Myofibrillar and Sarcoplasmic Proteins in Free-Living Adults Is Influenced by Sex, Resistance Exercise, and Training Status. J Nutr 2021; 151:3350-3360. [PMID: 34486662 DOI: 10.1093/jn/nxab261] [Citation(s) in RCA: 3] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/13/2021] [Revised: 06/25/2021] [Accepted: 07/15/2021] [Indexed: 12/24/2022] Open
Abstract
BACKGROUND Acute exercise increases the incorporation of dietary amino acids into de novo myofibrillar proteins after a single meal in controlled laboratory studies in males. It is unclear whether this extends to free-living settings or is influenced by training or sex. OBJECTIVES We determined the effects of exercise, training status, and sex on 24-hour free-living dietary phenylalanine incorporation into skeletal muscle proteins. METHODS In a parallel group design, recreationally active males (mean ± SD age, 23 ± 3 years; BMI. 23.4 ± 2.9 kg/m2; n = 10) and females (age 24 ± 5 years; BMI, 23.1 ± 3.9 kg/m2; n = 9) underwent 8 weeks of whole-body resistance exercise 3 times a week. Controlled diets containing 1.6 g/kg-1/d-1 (amino acids modelled after egg), enriched to 10% with [13C6] or [2H5]phenylalanine, were consumed before and after an acute bout of resistance exercise. Fasted muscle biopsies were obtained before [untrained, pre-exercise condition (REST ] and 24 hours after an acute bout of resistance exercise in untrained (UT) and trained (T) states to determine dietary phenylalanine incorporation into myofibrillar (ΔMyo) and sarcoplasmic (ΔSarc) proteins, intracellular mechanistic target of rapamycin (mTOR) colocalization with ulex europaeus agglutinin-1 (UEA-1; capillary marker; immunofluorescence), and amino acid transporter expression (Western blotting). RESULTS The ΔMyo values were ∼62% greater (P < 0.01) in females than males at REST. The ΔMyo values increased above REST by ∼51% during UT and ∼30% in T (both P < 0.01) in males, remained unchanged in females during UT, and were ∼33% lower at T when compared to UT (P = 0.013). Irrespective of sex, ΔMyo and ΔSarc were decreased at T compared to UT (P ≤ 0.026). Resistance training increased mTOR colocalization with UEA-1 (P = 0.004), while L amino acid transporter 1, which was greater in males (P < 0.01), and sodium-coupled neutral amino acid transporter 2 protein expression were not affected by acute exercise (P ≥ 0.33) or training (P ≥ 0.45). CONCLUSIONS The exercise-induced incorporation of dietary phenylalanine into myofibrillar and sarcoplasmic proteins is attenuated after training regardless of sex, suggesting a reduced reliance on dietary amino acids for postexercise skeletal muscle remodeling in the T state.
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Affiliation(s)
- Sidney Abou Sawan
- Faculty of Kinesiology and Physical Education, University of Toronto, Toronto, Ontario, Canada
| | - Nathan Hodson
- Faculty of Kinesiology and Physical Education, University of Toronto, Toronto, Ontario, Canada
| | | | - Daniel W D West
- Faculty of Kinesiology and Physical Education, University of Toronto, Toronto, Ontario, Canada.,Toronto Rehabilitation Institute, Toronto, Canada
| | - Julia M Malowany
- Faculty of Kinesiology and Physical Education, University of Toronto, Toronto, Ontario, Canada
| | | | - Daniel R Moore
- Faculty of Kinesiology and Physical Education, University of Toronto, Toronto, Ontario, Canada
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Mazzulla M, Hodson N, Lees M, Scaife PJ, Smith K, Atherton PJ, Kumbhare D, Moore DR. LAT1 and SNAT2 Protein Expression and Membrane Localization of LAT1 Are Not Acutely Altered by Dietary Amino Acids or Resistance Exercise Nor Positively Associated with Leucine or Phenylalanine Incorporation in Human Skeletal Muscle. Nutrients 2021; 13:nu13113906. [PMID: 34836160 PMCID: PMC8624011 DOI: 10.3390/nu13113906] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/04/2021] [Revised: 10/13/2021] [Accepted: 10/22/2021] [Indexed: 12/26/2022] Open
Abstract
The influx of essential amino acids into skeletal muscle is primarily mediated by the large neutral amino acid transporter 1 (LAT1), which is dependent on the glutamine gradient generated by the sodium-dependent neutral amino acid transporter 2 (SNAT2). The protein expression and membrane localization of LAT1 may be influenced by amino acid ingestion and/or resistance exercise, although its acute influence on dietary amino acid incorporation into skeletal muscle protein has not been investigated. In a group design, healthy males consumed a mixed carbohydrate (0.75 g·kg-1) crystalline amino acid (0.25 g·kg-1) beverage enriched to 25% and 30% with LAT1 substrates L-[1-13C]leucine (LEU) and L-[ring-2H5]phenylalanine (PHE), respectively, at rest (FED: n = 7, 23 ± 5 y, 77 ± 4 kg) or after a bout of resistance exercise (EXFED: n = 7, 22 ± 2 y, 78 ± 11 kg). Postprandial muscle biopsies were collected at 0, 120, and 300 min to measure transporter protein expression (immunoblot), LAT1 membrane localization (immunofluorescence), and dietary amino acid incorporation into myofibrillar protein (ΔLEU and ΔPHE). Basal LAT1 and SNAT2 protein contents were correlated with each other (r = 0.55, p = 0.04) but their expression did not change across time in FED or EXFED (all, p > 0.05). Membrane localization of LAT1 did not change across time in FED or EXFED whether measured as outer 1.5 µm intensity or membrane-to-fiber ratio (all, p > 0.05). Basal SNAT2 protein expression was not correlated with ΔLEU or ΔPHE (all, p ≥ 0.05) whereas basal LAT1 expression was negatively correlated with ΔPHE in FED (r = -0.76, p = 0.04) and EXFED (r = -0.81, p = 0.03) but not ΔLEU (p > 0.05). Basal LAT1 membrane localization was not correlated with ΔLEU or ΔPHE (all, p > 0.05). Our results suggest that LAT1/SNAT2 protein expression and LAT1 membrane localization are not influenced by acute anabolic stimuli and do not positively influence the incorporation of dietary amino acids for de novo myofibrillar protein synthesis in healthy young males.
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Affiliation(s)
- Michael Mazzulla
- Department of Exercise Sciences, Faculty of Kinesiology and Physical Education, University of Toronto, Toronto, ON M5S 2C9, Canada; (M.M.); (N.H.); (M.L.)
| | - Nathan Hodson
- Department of Exercise Sciences, Faculty of Kinesiology and Physical Education, University of Toronto, Toronto, ON M5S 2C9, Canada; (M.M.); (N.H.); (M.L.)
| | - Matthew Lees
- Department of Exercise Sciences, Faculty of Kinesiology and Physical Education, University of Toronto, Toronto, ON M5S 2C9, Canada; (M.M.); (N.H.); (M.L.)
| | - Paula J. Scaife
- MRC-Versus Arthritis Centre for Musculoskeletal Ageing Research and NIHR Nottingham BRC, Centre of Metabolism, Ageing and Physiology, School of Medicine, University of Nottingham, Derby DE22 3DT, UK; (P.J.S.); (K.S.); (P.J.A.)
| | - Kenneth Smith
- MRC-Versus Arthritis Centre for Musculoskeletal Ageing Research and NIHR Nottingham BRC, Centre of Metabolism, Ageing and Physiology, School of Medicine, University of Nottingham, Derby DE22 3DT, UK; (P.J.S.); (K.S.); (P.J.A.)
| | - Philip J. Atherton
- MRC-Versus Arthritis Centre for Musculoskeletal Ageing Research and NIHR Nottingham BRC, Centre of Metabolism, Ageing and Physiology, School of Medicine, University of Nottingham, Derby DE22 3DT, UK; (P.J.S.); (K.S.); (P.J.A.)
| | - Dinesh Kumbhare
- Department of Medicine, University of Toronto, Toronto, ON M5S 2C9, Canada;
| | - Daniel R. Moore
- Department of Exercise Sciences, Faculty of Kinesiology and Physical Education, University of Toronto, Toronto, ON M5S 2C9, Canada; (M.M.); (N.H.); (M.L.)
- Correspondence: ; Tel.: +1-(416)-946-4088
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Pohl A, Schünemann F, Bersiner K, Gehlert S. The Impact of Vegan and Vegetarian Diets on Physical Performance and Molecular Signaling in Skeletal Muscle. Nutrients 2021; 13:3884. [PMID: 34836139 PMCID: PMC8623732 DOI: 10.3390/nu13113884] [Citation(s) in RCA: 6] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/13/2021] [Revised: 10/27/2021] [Accepted: 10/28/2021] [Indexed: 12/12/2022] Open
Abstract
Muscular adaptations can be triggered by exercise and diet. As vegan and vegetarian diets differ in nutrient composition compared to an omnivorous diet, a change in dietary regimen might alter physiological responses to physical exercise and influence physical performance. Mitochondria abundance, muscle capillary density, hemoglobin concentration, endothelial function, functional heart morphology and availability of carbohydrates affect endurance performance and can be influenced by diet. Based on these factors, a vegan and vegetarian diet possesses potentially advantageous properties for endurance performance. Properties of the contractile elements, muscle protein synthesis, the neuromuscular system and phosphagen availability affect strength performance and can also be influenced by diet. However, a vegan and vegetarian diet possesses potentially disadvantageous properties for strength performance. Current research has failed to demonstrate consistent differences of performance between diets but a trend towards improved performance after vegetarian and vegan diets for both endurance and strength exercise has been shown. Importantly, diet alters molecular signaling via leucine, creatine, DHA and EPA that directly modulates skeletal muscle adaptation. By changing the gut microbiome, diet can modulate signaling through the production of SFCA.
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Affiliation(s)
- Alexander Pohl
- Department of Biosciences of Sport Science, Institute of Sport Science, University of Hildesheim, 31141 Hildesheim, Germany; (F.S.); (K.B.); (S.G.)
| | - Frederik Schünemann
- Department of Biosciences of Sport Science, Institute of Sport Science, University of Hildesheim, 31141 Hildesheim, Germany; (F.S.); (K.B.); (S.G.)
| | - Käthe Bersiner
- Department of Biosciences of Sport Science, Institute of Sport Science, University of Hildesheim, 31141 Hildesheim, Germany; (F.S.); (K.B.); (S.G.)
| | - Sebastian Gehlert
- Department of Biosciences of Sport Science, Institute of Sport Science, University of Hildesheim, 31141 Hildesheim, Germany; (F.S.); (K.B.); (S.G.)
- Department for Molecular and Cellular Sports Medicine, German Sports University Cologne, 50933 Cologne, Germany
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Moore DR. Protein Requirements for Master Athletes: Just Older Versions of Their Younger Selves. Sports Med 2021; 51:13-30. [PMID: 34515969 PMCID: PMC8566396 DOI: 10.1007/s40279-021-01510-0] [Citation(s) in RCA: 7] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Accepted: 06/18/2021] [Indexed: 12/24/2022]
Abstract
It is established that protein requirements are elevated in athletes to support their training and post-exercise recovery and adaptation, especially within skeletal muscle. However, research on the requirements for this macronutrient has been performed almost exclusively in younger athletes, which may complicate their translation to the growing population of Master athletes (i.e. > 35 years old). In contrast to older (> 65 years) untrained adults who typically demonstrate anabolic resistance to dietary protein as a primary mediator of the ‘normal’ age-related loss of muscle mass and strength, Master athletes are generally considered successful models of aging as evidenced by possessing similar body composition, muscle mass, and aerobic fitness as untrained adults more than half their age. The primary physiology changes considered to underpin the anabolic resistance of aging are precipitated or exacerbated by physical inactivity, which has led to higher protein recommendations to stimulate muscle protein synthesis in older untrained compared to younger untrained adults. This review puts forth the argument that Master athletes have similar muscle characteristics, physiological responses to exercise, and protein metabolism as young athletes and, therefore, are unlikely to have protein requirements that are different from their young contemporaries. Recommendations for protein amount, type, and pattern will be discussed for Master athletes to enhance their recovery from and adaptation to resistance and endurance training.
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Affiliation(s)
- Daniel R Moore
- Faculty of Kinesiology and Physical Education, University of Toronto, 100 Devonshire Place, Toronto, ON, M5S 2C9, Canada.
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