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Pajski ML, Byrd C, Nandigama N, Seguin E, Seguin A, Fennell A, Graber TG. Endurance exercise preserves physical function in adult and older male C57BL/6 mice: high intensity interval training (HIIT) versus voluntary wheel running (VWR). Front Aging 2024; 5:1356954. [PMID: 38523671 PMCID: PMC10958787 DOI: 10.3389/fragi.2024.1356954] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Grants] [Track Full Text] [Figures] [Subscribe] [Scholar Register] [Received: 12/16/2023] [Accepted: 02/23/2024] [Indexed: 03/26/2024]
Abstract
Exercise has been shown to improve physical function, mitigate aspects of chronic disease and to potentially alter the trajectory of age-related onset of frailty and sarcopenia. Reliable and valid preclinical models are necessary to elucidate the underlying mechanisms at the intersection of age, exercise, and functional decline. The purpose of this study was to compare, head to head, the effects of two common pre-clinical models of endurance exercise: high intensity interval training (HIIT) and voluntary wheel running (VWR). The hypothesis was that a prescribed and regimented exercise program, HIIT, would prove to be a superior training method to unregulated voluntary exercise, VWR. To investigate this hypothesis, we evaluated adult (n = 24, designated 10 m, aged 6 months at the beginning of the study, 10 months at its completion) and older adult (n = 18, designated 26 m, aging from 22 months to 26 months over the course of the study) C57BL/6 male mice. These mice were randomly assigned (with selection criteria) to a 13-week program of voluntary wheel running (VWR), high intensity interval training (HIIT), or sedentary control (SED). The functional aptitude of each mouse was determined pre- and post-training using our composite CFAB (comprehensive functional assessment battery) scoring system consisting of voluntary wheel running (volitional exercise and activity rate), treadmill (endurance), rotarod (overall motor function), grip meter (forelimb strength), and inverted cling (whole body strength/endurance). To measure sarcopenia, we tracked body mass, body composition (with EchoMRI), plantar flexor torque (in 10 m), and measured muscle wet mass post-training. Overall, adult CFAB scores decreased while body mass and percent body fat increased as they matured; however, exercise significantly mitigated the changes (p < 0.05) compared to SED. Older adults demonstrated preservation of function (CFAB) and reduced body fat (p < 0.05) compared to SED. To conclude, both types of exercise maintained physical function equally in older mice.
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Affiliation(s)
- Megan L. Pajski
- Department of Physical Therapy, East Carolina University, Greenville, NC, United States
| | - Chris Byrd
- Department of Physical Therapy, East Carolina University, Greenville, NC, United States
| | - Nainika Nandigama
- Department of Public Health, East Carolina University, Greenville, NC, United States
| | - Emily Seguin
- Department of Kinesiology, East Carolina University, Greenville, NC, United States
| | - Anna Seguin
- Department of Kinesiology, East Carolina University, Greenville, NC, United States
| | - Alyssa Fennell
- Department of Kinesiology, East Carolina University, Greenville, NC, United States
| | - Ted G. Graber
- Department of Physical Therapy, East Carolina University, Greenville, NC, United States
- Department of Kinesiology, East Carolina University, Greenville, NC, United States
- Department of Physiology, East Carolina University, Greenville, NC, United States
- East Carolina Obesity and Diabetes Institute, East Carolina University, Greenville, NC, United States
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2
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Maroto R, Graber TG, Romsdahl TB, Kudlicki A, Russell WK, Rasmussen BB. Metabolomic and Lipidomic Signature of Skeletal Muscle with Constitutively Active Mechanistic Target of Rapamycin Complex 1. J Nutr 2023; 153:3397-3405. [PMID: 37898335 PMCID: PMC10739780 DOI: 10.1016/j.tjnut.2023.10.016] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/13/2023] [Revised: 09/07/2023] [Accepted: 10/03/2023] [Indexed: 10/30/2023] Open
Abstract
BACKGROUND Regulation of mechanistic target of rapamycin complex 1 (mTORC1) plays an important role in aging and nutrition. For example, caloric restriction reduces mTORC1 signaling and extends lifespan, whereas nutrient abundance and obesity increase mTORC1 signaling and reduce lifespan. Skeletal muscle-specific knockout (KO) of DEP domain-containing 5 protein (DEPDC5) results in constitutively active mTORC1 signaling, muscle hypertrophy and an increase in mitochondrial respiratory capacity. The metabolic profile of skeletal muscle, in the setting of hyperactive mTORC1 signaling, is not well known. OBJECTIVES To determine the metabolomic and lipidomic signature in skeletal muscle from female and male wild-type (WT) and DEPDC5 KO mice. METHODS Tibialis anterior (TA) muscles from WT and transgenic (conditional skeletal muscle-specific DEPDC5 KO) were obtained from female and male adult mice. Polar metabolites and lipids were extracted using a Bligh-Dyer extraction from 5 samples per group and identified and quantified by LC-MS/MS. Resulting analyte peak areas were analyzed with t-test, analysis of variance, and Volcano plots for group comparisons (e.g., WT compared with KO) and multivariate statistical analysis for genotype and sex comparisons. RESULTS A total of 162 polar metabolites (organic acids, amino acids, and amines and acyl carnitines) and 1141 lipid metabolites were detected in TA samples by LC-MS/MS. Few polar metabolites showed significant differences in KO muscles compared with WT within the same sex group. P-aminobenzoic acid, β-alanine, and dopamine were significantly higher in KO male muscle whereas erythrose-4-phosphate and oxoglutaric acid were significantly reduced in KO females. The lipidomic profile of the KO groups revealed an increase of muscle phospholipids and reduced triacylglycerol and diacylglycerol compared with the WT groups. CONCLUSIONS Sex differences were detected in polar metabolome and lipids were dependent on genotype. The metabolomic profile of mice with hyperactive skeletal muscle mTORC1 is consistent with an upregulation of mitochondrial function and amino acid utilization for protein synthesis.
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Affiliation(s)
- Rosario Maroto
- Department of Biochemistry & Molecular Biology, University of Texas Medical Branch, Galveston, TX, United States.
| | - Ted G Graber
- Department of Physical Therapy, East Carolina University, Greenville, NC, United States
| | - Trevor B Romsdahl
- Department of Biochemistry & Molecular Biology, University of Texas Medical Branch, Galveston, TX, United States
| | - Andrzej Kudlicki
- Department of Biochemistry & Molecular Biology, University of Texas Medical Branch, Galveston, TX, United States
| | - William K Russell
- Department of Biochemistry & Molecular Biology, University of Texas Medical Branch, Galveston, TX, United States
| | - Blake B Rasmussen
- Department of Biochemistry & Molecular Biology, University of Texas Medical Branch, Galveston, TX, United States; Department of Biochemistry & Structural Biology, University of Texas Health Science Center at San Antonio, San Antonio, TX, United States.
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3
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Pi A, Villivalam SD, Kang S. The Molecular Mechanisms of Fuel Utilization during Exercise. Biology (Basel) 2023; 12:1450. [PMID: 37998049 PMCID: PMC10669127 DOI: 10.3390/biology12111450] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 09/29/2023] [Revised: 11/16/2023] [Accepted: 11/17/2023] [Indexed: 11/25/2023]
Abstract
Exercise is widely recognized for its positive impact on human health and well-being. The process of utilizing substrates in skeletal muscle during exercise is intricate and governed by complex mechanisms. Carbohydrates and lipids serve as the primary fuel sources for skeletal muscle during exercise. It is now understood that fuel selection during exercise is not solely determined by physical activity itself but is also influenced by the overall metabolic state of the body. The balance between lipid and carbohydrate utilization significantly affects exercise capacity, including endurance, fatigue, and overall performance. Therefore, comprehensively understanding the regulation of substrate utilization during exercise is of utmost importance. The aim of this review is to provide an extensive overview of the current knowledge regarding the pathways involved in the regulation of substrate utilization during exercise. By synthesizing existing research, we can gain a holistic perspective on the intricate relationship between exercise, metabolism, and fuel selection. This advanced understanding has the potential to drive advancements in the field of exercise science and contribute to the development of personalized exercise strategies for individuals looking to optimize their performance and overall health.
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Affiliation(s)
| | | | - Sona Kang
- Nutritional Sciences and Toxicology Department, University of California Berkeley, Berkeley, CA 94720, USA
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4
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Graber TG, Maroto R, Thompson JK, Widen SG, Man Z, Pajski ML, Rasmussen BB. Skeletal Muscle Transcriptome Alterations Related to Declining Physical Function in Older Mice. J Ageing Longev 2023; 3:159-178. [PMID: 37876943 PMCID: PMC10597580 DOI: 10.3390/jal3020013] [Citation(s) in RCA: 1] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 10/26/2023]
Abstract
One inevitable consequence of aging is the gradual deterioration of physical function and exercise capacity, driven in part by the adverse effect of age on muscle tissue. We hypothesized that relationships exist between age-related differentially expressed genes (DEGs) in skeletal muscle and age-associated declines in physical function and exercise capacity. Previously, male C57BL/6mice (6m, months old, 24m, and 28m) were tested for physical function using a composite scoring system (comprehensive functional assessment battery, CFAB) comprised of five well-validated tests of physical function. In this study, total RNA was isolated from tibialis anterior samples (n = 8) randomly selected from each age group in the parent study. Using Next Generation Sequencing RNAseq to determine DEGs during aging (6m vs. 28m, and 6m vs. 24m), we found a greater than five-fold increase in DEGs in 28m compared to the 24m. Furthermore, regression of the normalized expression of each DEG with the CFAB score of the corresponding mouse revealed many more DEGs strongly associated (R ≥ |0.70|) with functional status in the older mice. Gene ontology results indicate highly enriched axon guidance and acetyl choline receptor gene sets, suggesting that denervation/reinnervation flux might potentially play a critical role in functional decline. We conclude that specific age-related DEG patterns are associated with declines in physical function, and the data suggest accelerated aging occurring between 24 and 28 months.
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Affiliation(s)
- Ted G. Graber
- Department of Physical Therapy, East Carolina University, Greenville, NC 27834, USA
| | - Rosario Maroto
- Department of Biochemistry & Molecular Biology, University of Texas Medical Branch, Galveston, TX 77555, USA
| | - Jill K. Thompson
- Department of Biochemistry & Molecular Biology, University of Texas Medical Branch, Galveston, TX 77555, USA
| | - Steven G. Widen
- Department of Biochemistry & Molecular Biology, University of Texas Medical Branch, Galveston, TX 77555, USA
| | - Zhaohui Man
- Bioinformatics and Analytics Research Collaborative, University of North Carolina-Chapel Hill, Chapel Hill, NC 27514, USA
| | - Megan L. Pajski
- Department of Physical Therapy, East Carolina University, Greenville, NC 27834, USA
| | - Blake B. Rasmussen
- Department of Biochemistry & Molecular Biology, University of Texas Medical Branch, Galveston, TX 77555, USA
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5
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Kaiser MS, Milan G, Ham DJ, Lin S, Oliveri F, Chojnowska K, Tintignac LA, Mittal N, Zimmerli CE, Glass DJ, Zavolan M, Rüegg MA. Dual roles of mTORC1-dependent activation of the ubiquitin-proteasome system in muscle proteostasis. Commun Biol 2022; 5:1141. [PMID: 36302954 PMCID: PMC9613904 DOI: 10.1038/s42003-022-04097-y] [Citation(s) in RCA: 7] [Impact Index Per Article: 3.5] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/15/2022] [Accepted: 10/11/2022] [Indexed: 12/02/2022] Open
Abstract
Muscle size is controlled by the PI3K-PKB/Akt-mTORC1-FoxO pathway, which integrates signals from growth factors, energy and amino acids to activate protein synthesis and inhibit protein breakdown. While mTORC1 activity is necessary for PKB/Akt-induced muscle hypertrophy, its constant activation alone induces muscle atrophy. Here we show that this paradox is based on mTORC1 activity promoting protein breakdown through the ubiquitin-proteasome system (UPS) by simultaneously inducing ubiquitin E3 ligase expression via feedback inhibition of PKB/Akt and proteasome biogenesis via Nuclear Factor Erythroid 2-Like 1 (Nrf1). Muscle growth was restored by reactivation of PKB/Akt, but not by Nrf1 knockdown, implicating ubiquitination as the limiting step. However, both PKB/Akt activation and proteasome depletion by Nrf1 knockdown led to an immediate disruption of proteome integrity with rapid accumulation of damaged material. These data highlight the physiological importance of mTORC1-mediated PKB/Akt inhibition and point to juxtaposed roles of the UPS in atrophy and proteome integrity. Exploring the relationship between mTORC1 and the ubiquitin-proteasome system, light is shed on the paradox between mTORC1-mediated muscle hypertrophy induced by PKB/Akt and the muscle atrophy induced by mTORC1 alone.
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Affiliation(s)
- Marco S Kaiser
- Biozentrum, University of Basel, Basel, Switzerland.,BIOREBA AG, Christoph Merian-Ring 7, 4153, Reinach, Switzerland
| | - Giulia Milan
- Biozentrum, University of Basel, Basel, Switzerland. .,Department of Biomedicine, University of Basel, Hebelstrasse 20, 4031, Basel, Switzerland.
| | - Daniel J Ham
- Biozentrum, University of Basel, Basel, Switzerland.
| | - Shuo Lin
- Biozentrum, University of Basel, Basel, Switzerland
| | | | - Kathrin Chojnowska
- Biozentrum, University of Basel, Basel, Switzerland.,AstraZeneca AG, Neuhofstrasse 34, 6340, Baar, Switzerland
| | - Lionel A Tintignac
- Biozentrum, University of Basel, Basel, Switzerland.,Neuromuscular Research Group, Departments of Neurology and Biomedicine, University of Basel, University Hospital Basel, Basel, Switzerland
| | | | - Christian E Zimmerli
- Biozentrum, University of Basel, Basel, Switzerland.,Department of Molecular Sociology, Max Planck Institute of Biophysics, Max-von-Laue-Straße 3, 60438, Frankfurt am Main, Germany
| | - David J Glass
- Novartis Institutes for Biomedical Research, Cambridge, MA, USA.,Regeneron Pharmaceuticals, Tarrytown, NY, USA
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6
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Cho CS, Kim Y, Park SR, Kim B, Davis C, Hwang I, Brooks SV, Lee JH, Kim M. Simultaneous loss of TSC1 and DEPDC5 in skeletal and cardiac muscles produces early-onset myopathy and cardiac dysfunction associated with oxidative damage and SQSTM1/p62 accumulation. Autophagy 2022; 18:2303-2322. [PMID: 34964695 PMCID: PMC9542799 DOI: 10.1080/15548627.2021.2016255] [Citation(s) in RCA: 5] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/31/2022] Open
Abstract
By promoting anabolism, MTORC1 is critical for muscle growth and maintenance. However, genetic MTORC1 upregulation promotes muscle aging and produces age-associated myopathy. Whether MTORC1 activation is sufficient to produce myopathy or indirectly promotes it by accelerating tissue aging is elusive. Here we examined the effects of muscular MTORC1 hyperactivation, produced by simultaneous depletion of TSC1 and DEPDC5 (CKM-TD). CKM-TD mice produced myopathy, associated with loss of skeletal muscle mass and force, as well as cardiac failure and bradypnea. These pathologies were manifested at eight weeks of age, leading to a highly penetrant fatality at around twelve weeks of age. Transcriptome analysis indicated that genes mediating proteasomal and macroautophagic/autophagic pathways were highly upregulated in CKM-TD skeletal muscle, in addition to inflammation, oxidative stress, and DNA damage signaling pathways. In CKM-TD muscle, autophagosome levels were increased, and the AMPK and ULK1 pathways were activated; in addition, autophagy induction was not completely blocked in CKM-TD myotubes. Despite the upregulation of autolysosomal markers, CKM-TD myofibers exhibited accumulation of autophagy substrates, such as SQSTM1/p62 and ubiquitinated proteins, suggesting that the autophagic activities were insufficient. Administration of a superoxide scavenger, tempol, normalized most of these molecular pathologies and subsequently restored muscle histology and force generation. However, CKM-TD autophagy alterations were not normalized by rapamycin or tempol, suggesting that they may involve non-canonical targets other than MTORC1. These results collectively indicate that the concomitant muscle deficiency of TSC1 and DEPDC5 can produce early-onset myopathy through accumulation of oxidative stress, which dysregulates myocellular homeostasis.Abbreviations: AMPK: AMP-activated protein kinase; CKM: creatine kinase, M-type; COX: cytochrome oxidase; DEPDC5: DEP domain containing 5, GATOR1 subcomplex subunit; DHE: dihydroethidium; EDL: extensor digitorum longus; EIF4EBP1: eukaryotic translation initiation factor 4E binding protein 1; GAP: GTPase-activating protein; GTN: gastrocnemius; MTORC1: mechanistic target of rapamycin kinase complex 1; PLA: plantaris; QUAD: quadriceps; RPS6KB/S6K: ribosomal protein S6 kinase beta; SDH: succinate dehydrogenase; SOL: soleus; SQSTM1: sequestosome 1; TA: tibialis anterior; TSC1: TSC complex subunit 1; ULK1: unc-51 like autophagy activating kinase 1.
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Affiliation(s)
- Chun-Seok Cho
- Department of Molecular & Integrative Physiology, University of Michigan, Ann Arbor, MI, 48109, USA
| | - Yongsung Kim
- Department of Molecular & Integrative Physiology, University of Michigan, Ann Arbor, MI, 48109, USA
| | - Sung-Rye Park
- Department of Molecular & Integrative Physiology, University of Michigan, Ann Arbor, MI, 48109, USA
| | - Boyoung Kim
- Department of Molecular & Integrative Physiology, University of Michigan, Ann Arbor, MI, 48109, USA
| | - Carol Davis
- Department of Molecular & Integrative Physiology, University of Michigan, Ann Arbor, MI, 48109, USA
| | - Irene Hwang
- Department of Molecular & Integrative Physiology, University of Michigan, Ann Arbor, MI, 48109, USA
| | - Susan V. Brooks
- Department of Molecular & Integrative Physiology, University of Michigan, Ann Arbor, MI, 48109, USA
| | - Jun Hee Lee
- Department of Molecular & Integrative Physiology, University of Michigan, Ann Arbor, MI, 48109, USA,CONTACT Jun Hee Lee Department of Molecular & Integrative Physiology, University of Michigan, Ann Arbor, MI, 48109, USA
| | - Myungjin Kim
- Department of Molecular & Integrative Physiology, University of Michigan, Ann Arbor, MI, 48109, USA,Myungjin Kim
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7
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Abstract
DEPDC5-related epilepsy, caused by pathogenic germline variants(with or without additional somatic variants in the brain) of DEPDC5 (Dishevelled, Egl-10 and Pleckstrin domain-containing protein 5) gene, is a newly discovered predominantly focal epilepsy linked to enhanced mTORC1 pathway. DEPDC5-related epilepsy includes several familial epilepsy syndromes, including familial focal epilepsy with variable foci (FFEVF) and rare sporadic nonlesional focal epilepsy. DEPDC5 has been identified as one of the more common epilepsy genes linked to infantile spasms and sudden unexpected death (SUDEP). Although intelligence usually is unaffected in DEPDC5-related epilepsy, some people have been diagnosed with intellectual disabilities, autism spectrum disorder, and other psychiatric problems. DEPDC5 variants have also been found in 20% of individuals with various brain abnormalities, challenging the traditional distinction between lesional and nonlesional epilepsies. The most exciting development of DEPDC5 variants is the possibility of precision therapeutics using mTOR inhibitors, as evidenced with phenotypic rescue in many animal models. However, more research is needed to better understand the functional impact of diverse (particularly missense or splice-region) variants, the specific involvement of DEPDC5 in epileptogenesis, and the creation and utilization of precision therapies in humans. Precision treatments for DEPDC5-related epilepsy will benefit not only a small number of people with the condition, but they will also pave the way for new therapeutic approaches in epilepsy (including acquired epilepsies in which mTORC1 activation occurs, for example, post-traumatic epilepsy) and other neurological disorders involving a dysfunctional mTOR pathway.
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Affiliation(s)
- Debopam Samanta
- Child Neurology Section, Department of Pediatrics, University of Arkansas for Medical Sciences, Little Rock, AR, United States.
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8
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Ebert SM, Rasmussen BB, Judge AR, Judge SM, Larsson L, Wek RC, Anthony TG, Marcotte GR, Miller MJ, Yorek MA, Vella A, Volpi E, Stern JI, Strub MD, Ryan Z, Talley JJ, Adams CM. Biology of Activating Transcription Factor 4 (ATF4) and Its Role in Skeletal Muscle Atrophy. J Nutr 2022; 152:926-938. [PMID: 34958390 PMCID: PMC8970988 DOI: 10.1093/jn/nxab440] [Citation(s) in RCA: 19] [Impact Index Per Article: 9.5] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/08/2021] [Revised: 12/17/2021] [Accepted: 12/23/2021] [Indexed: 12/30/2022] Open
Abstract
Activating transcription factor 4 (ATF4) is a multifunctional transcription regulatory protein in the basic leucine zipper superfamily. ATF4 can be expressed in most if not all mammalian cell types, and it can participate in a variety of cellular responses to specific environmental stresses, intracellular derangements, or growth factors. Because ATF4 is involved in a wide range of biological processes, its roles in human health and disease are not yet fully understood. Much of our current knowledge about ATF4 comes from investigations in cultured cell models, where ATF4 was originally characterized and where further investigations continue to provide new insights. ATF4 is also an increasingly prominent topic of in vivo investigations in fully differentiated mammalian cell types, where our current understanding of ATF4 is less complete. Here, we review some important high-level concepts and questions concerning the basic biology of ATF4. We then discuss current knowledge and emerging questions about the in vivo role of ATF4 in one fully differentiated cell type, mammalian skeletal muscle fibers.
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Affiliation(s)
- Scott M Ebert
- Department of Internal Medicine, Division of Endocrinology, Diabetes, Metabolism and Nutrition, Mayo Clinic, Rochester, MN, USA
- Emmyon, Inc., Rochester, MN, USA
| | - Blake B Rasmussen
- Emmyon, Inc., Rochester, MN, USA
- Department of Nutrition, Metabolism and Rehabilitation Sciences, University of Texas Medical Branch, Galveston, TX, USA
| | - Andrew R Judge
- Emmyon, Inc., Rochester, MN, USA
- Department of Physical Therapy, University of Florida, Gainesville, FL, USA
| | - Sarah M Judge
- Department of Physical Therapy, University of Florida, Gainesville, FL, USA
| | - Lars Larsson
- Department of Physiology and Pharmacology, Karolinska, Stockholm, Sweden
| | - Ronald C Wek
- Department of Biochemistry and Molecular Biology, Indiana University, Indianapolis, IN, USA
| | - Tracy G Anthony
- Department of Nutritional Sciences, Rutgers University, New Brunswick, NJ, USA
| | - George R Marcotte
- Department of Internal Medicine, Division of Endocrinology, Diabetes, Metabolism and Nutrition, Mayo Clinic, Rochester, MN, USA
- Department of Internal Medicine, University of Iowa, Iowa City, IA, USA
| | - Matthew J Miller
- Department of Internal Medicine, Division of Endocrinology, Diabetes, Metabolism and Nutrition, Mayo Clinic, Rochester, MN, USA
- Department of Internal Medicine, University of Iowa, Iowa City, IA, USA
| | - Mark A Yorek
- Department of Internal Medicine, University of Iowa, Iowa City, IA, USA
- Department of Internal Medicine, Iowa City VA Medical Center, Iowa City, IA, USA
| | - Adrian Vella
- Department of Internal Medicine, Division of Endocrinology, Diabetes, Metabolism and Nutrition, Mayo Clinic, Rochester, MN, USA
- Emmyon, Inc., Rochester, MN, USA
| | - Elena Volpi
- Department of Nutrition, Metabolism and Rehabilitation Sciences, University of Texas Medical Branch, Galveston, TX, USA
| | - Jennifer I Stern
- Department of Internal Medicine, Division of Endocrinology, Diabetes, Metabolism and Nutrition, Mayo Clinic, Rochester, MN, USA
| | - Matthew D Strub
- Department of Internal Medicine, Division of Endocrinology, Diabetes, Metabolism and Nutrition, Mayo Clinic, Rochester, MN, USA
| | - Zachary Ryan
- Department of Internal Medicine, Division of Endocrinology, Diabetes, Metabolism and Nutrition, Mayo Clinic, Rochester, MN, USA
| | | | - Christopher M Adams
- Department of Internal Medicine, Division of Endocrinology, Diabetes, Metabolism and Nutrition, Mayo Clinic, Rochester, MN, USA
- Emmyon, Inc., Rochester, MN, USA
- Department of Internal Medicine, Iowa City VA Medical Center, Iowa City, IA, USA
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9
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Bacq A, Roussel D, Bonduelle T, Zagaglia S, Maletic M, Ribierre T, Adle‐Biassette H, Marchal C, Jennesson M, An I, Picard F, Navarro V, Sisodiya SM, Baulac S. Cardiac Investigations in Sudden Unexpected Death in DEPDC5-Related Epilepsy. Ann Neurol 2022; 91:101-116. [PMID: 34693554 PMCID: PMC9299146 DOI: 10.1002/ana.26256] [Citation(s) in RCA: 3] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/13/2021] [Revised: 10/20/2021] [Accepted: 10/21/2021] [Indexed: 12/17/2022]
Abstract
OBJECTIVE Germline loss-of-function mutations in DEPDC5, and in its binding partners (NPRL2/3) of the mammalian target of rapamycin (mTOR) repressor GATOR1 complex, cause focal epilepsies and increase the risk of sudden unexpected death in epilepsy (SUDEP). Here, we asked whether DEPDC5 haploinsufficiency predisposes to primary cardiac defects that could contribute to SUDEP and therefore impact the clinical management of patients at high risk of SUDEP. METHODS Clinical cardiac investigations were performed in 16 patients with pathogenic variants in DEPDC5, NPRL2, or NPRL3. Two novel Depdc5 mouse strains, a human HA-tagged Depdc5 strain and a Depdc5 heterozygous knockout with a neuron-specific deletion of the second allele (Depdc5c/- ), were generated to investigate the role of Depdc5 in SUDEP and cardiac activity during seizures. RESULTS Holter, echocardiographic, and electrocardiographic (ECG) examinations provided no evidence for altered clinical cardiac function in the patient cohort, of whom 3 DEPDC5 patients succumbed to SUDEP and 6 had a family history of SUDEP. There was no cardiac injury at autopsy in a postmortem DEPDC5 SUDEP case. The HA-tagged Depdc5 mouse revealed expression of Depdc5 in the brain, heart, and lungs. Simultaneous electroencephalographic-ECG records on Depdc5c/- mice showed that spontaneous epileptic seizures resulting in a SUDEP-like event are not preceded by cardiac arrhythmia. INTERPRETATION Mouse and human data show neither structural nor functional cardiac damage that might underlie a primary contribution to SUDEP in the spectrum of DEPDC5-related epilepsies. ANN NEUROL 2022;91:101-116.
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Affiliation(s)
- Alexandre Bacq
- Sorbonne University, Paris Brain Institute (ICM), Inserm, CNRS, AP‐HP, Pitié‐Salpêtrière HospitalParisFrance
| | - Delphine Roussel
- Sorbonne University, Paris Brain Institute (ICM), Inserm, CNRS, AP‐HP, Pitié‐Salpêtrière HospitalParisFrance
| | - Thomas Bonduelle
- Sorbonne University, Paris Brain Institute (ICM), Inserm, CNRS, AP‐HP, Pitié‐Salpêtrière HospitalParisFrance
- Epilepsy and Neurology Department, Bordeaux University Hospital CenterBordeauxFrance
| | - Sara Zagaglia
- Department of Clinical and Experimental EpilepsyUniversity College London Queen Square Institute of NeurologyLondonUK
- Chalfont Centre for EpilepsyBucksUK
| | - Marina Maletic
- Sorbonne University, Paris Brain Institute (ICM), Inserm, CNRS, AP‐HP, Pitié‐Salpêtrière HospitalParisFrance
| | - Théo Ribierre
- Sorbonne University, Paris Brain Institute (ICM), Inserm, CNRS, AP‐HP, Pitié‐Salpêtrière HospitalParisFrance
| | - Homa Adle‐Biassette
- Pathological Anatomy Department, University of Paris, AP‐HP, Lariboisière Hospital, DMU, DREAM, UMR 1141, INSERMParisFrance
| | - Cécile Marchal
- Epilepsy and Neurology Department, Bordeaux University Hospital CenterBordeauxFrance
| | - Mélanie Jennesson
- Department of PediatricsAmerican Memorial Hospital, Reims University Hospital CenterReimsFrance
| | - Isabelle An
- Epileptology Unit and Reference Center of Rare Epilepsies, Pitié‐Salpêtrière Hospital, AP‐HPParisFrance
| | - Fabienne Picard
- EEG and Epilepsy Unit, Department of Clinical NeurosciencesUniversity Hospitals and Faculty of Medicine of GenevaGenevaSwitzerland
| | - Vincent Navarro
- Sorbonne University, Paris Brain Institute (ICM), Inserm, CNRS, AP‐HP, Pitié‐Salpêtrière HospitalParisFrance
- Epileptology Unit and Reference Center of Rare Epilepsies, Pitié‐Salpêtrière Hospital, AP‐HPParisFrance
| | - Sanjay M. Sisodiya
- Department of Clinical and Experimental EpilepsyUniversity College London Queen Square Institute of NeurologyLondonUK
- Chalfont Centre for EpilepsyBucksUK
| | - Stéphanie Baulac
- Sorbonne University, Paris Brain Institute (ICM), Inserm, CNRS, AP‐HP, Pitié‐Salpêtrière HospitalParisFrance
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10
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Abstract
The SEA complex was described for the first time in yeast Saccharomyces cerevisiae ten years ago, and its human homologue GATOR complex two years later. During the past decade, many advances on the SEA/GATOR biology in different organisms have been made that allowed its role as an essential upstream regulator of the mTORC1 pathway to be defined. In this review, we describe these advances in relation to the identification of multiple functions of the SEA/GATOR complex in nutrient response and beyond and highlight the consequence of GATOR mutations in cancer and neurodegenerative diseases.
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11
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El Ayadi A, Tapking C, Prasai A, Rontoyanni VG, Abdelrahman DR, Cui W, Fang G, Bhattarai N, Murton AJ. Cafeteria Diet Impacts the Body Weight and Energy Expenditure of Brown Norway Rats in an Apparent Age Dependent Manner, but Has no Effect on Muscle Anabolic Sensitivity to Nutrition. Front Nutr 2021; 8:719612. [PMID: 34568406 PMCID: PMC8459992 DOI: 10.3389/fnut.2021.719612] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/02/2021] [Accepted: 08/16/2021] [Indexed: 12/02/2022] Open
Abstract
While obesity blunts the ability of muscle to mount a protein synthetic response to an amino acid infusion in older adults, it is unclear if this insensitivity to nutrition persists long term and in response to complete foods is unknown. To address this, young (2 months old) and old (17–20 months old) Brown Norway rats were randomized to receive either chow or a 12 wk diet of calorie-dense human foods. At wk 10 drinking water was supplemented with 2% heavy water, followed 2 weeks later by a flooding dose of [2H5]-phenylalanine and an oral leucine bolus, allowing the short and long-term effects of age and diet on muscle protein synthesis rates to be determined. The experimental diet increased energy intake in both young (7.4 ± 0.9%) and old (18.2 ± 1.8%) animals (P < 0.01), but only led to significant increases in body weight in the former (young: 10.2 ± 3.0% (P < 0.05) and old: 3.1 ± 5.1% (NS) vs. age-matched controls). Notably, energy expenditure in response to the cafeteria diet was increased in old animals only (chow: 5.1 ± 0.4; cafe: 8.2 ± 1.6 kcal.kg b.w−1.h−1; P < 0.05). Gastrocnemius protein fractional synthetic rates in response to either an acute leucine bolus or two weeks of feeding were equivalent across groups irrespective of age or diet. Rodents in old age appear capable of preventing weight gain in response to a calorie-dense diet by increasing energy expenditure while maintaining the anabolic sensitivity of muscle to nutrition; the mechanisms of which could have important implications for the aging obese human.
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Affiliation(s)
- Amina El Ayadi
- Department of Surgery, School of Medicine, University of Texas Medical Branch, Galveston, TX, United States
| | - Christian Tapking
- Department of Surgery, School of Medicine, University of Texas Medical Branch, Galveston, TX, United States
| | - Anesh Prasai
- Department of Surgery, School of Medicine, University of Texas Medical Branch, Galveston, TX, United States
| | - Victoria G Rontoyanni
- Department of Surgery, School of Medicine, University of Texas Medical Branch, Galveston, TX, United States
| | - Doaa R Abdelrahman
- Department of Surgery, School of Medicine, University of Texas Medical Branch, Galveston, TX, United States.,Sealy Center on Aging, University of Texas Medical Branch, Galveston, TX, United States
| | - Weihua Cui
- Department of Anesthesiology, School of Medicine, University of Texas Medical Branch, Galveston, TX, United States
| | - Geping Fang
- Department of Surgery, School of Medicine, University of Texas Medical Branch, Galveston, TX, United States
| | - Nisha Bhattarai
- Department of Surgery, School of Medicine, University of Texas Medical Branch, Galveston, TX, United States
| | - Andrew J Murton
- Department of Surgery, School of Medicine, University of Texas Medical Branch, Galveston, TX, United States.,Sealy Center on Aging, University of Texas Medical Branch, Galveston, TX, United States.,Institute of Translation Sciences, University of Texas Medical Branch, Galveston, TX, United States
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12
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Abstract
Skeletal muscle demonstrates a high degree of adaptability in response to changes in mechanical input. The phenotypic transformation in response to mechanical cues includes changes in muscle mass and force generating capabilities, yet the molecular pathways that govern skeletal muscle adaptation are still incompletely understood. While there is strong evidence that mechanotransduction pathways that stimulate protein synthesis play a key role in regulation of muscle mass, there are likely additional mechano-sensitive mechanisms important for controlling functional muscle adaptation. There is emerging evidence that the cell nucleus can directly respond to mechanical signals (i.e., nuclear mechanotransduction), providing a potential additional level of cellular regulation for controlling skeletal muscle mass. The importance of nuclear mechanotransduction in cellular function is evident by the various genetic diseases that arise from mutations in proteins crucial to the transmission of force between the cytoskeleton and the nucleus. Intriguingly, these diseases preferentially affect cardiac and skeletal muscle, suggesting that nuclear mechanotransduction is critically important for striated muscle homeostasis. Here we discuss our current understanding for how the nucleus acts as a mechanosensor, describe the main cytoskeletal and nuclear proteins involved in the process, and propose how similar mechanoresponsive mechanisms could occur in the unique cellular environment of a myofiber. In addition, we examine how nuclear mechanotransduction fits into our current framework for how mechanical stimuli regulates skeletal muscle mass.
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Affiliation(s)
- Maria J A van Ingen
- Biomolecular Sciences, Faculty of Science, Vrije Universiteit Amsterdam, Amsterdam, Netherlands
| | - Tyler J Kirby
- Department of Physiology, Amsterdam Cardiovascular Sciences, Amsterdam Movement Sciences, Amsterdam UMC, Amsterdam, Netherlands
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13
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Graber TG, Maroto R, Fry CS, Brightwell CR, Rasmussen BB. Measuring Exercise Capacity and Physical Function in Adult and Older Mice. J Gerontol A Biol Sci Med Sci 2021; 76:819-824. [PMID: 32822475 PMCID: PMC8087272 DOI: 10.1093/gerona/glaa205] [Citation(s) in RCA: 15] [Impact Index Per Article: 5.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/17/2019] [Indexed: 11/12/2022] Open
Abstract
The inability of older adults to maintain independence is a consequence of sarcopenia and frailty. In order to identify the molecular mechanisms responsible for decreased physical function, it will be critical to utilize a small animal model. The main purpose of this study was to develop a composite Comprehensive Functional Assessment Battery (CFAB) of well-validated tests to determine physical function and exercise capacity in 3 age groups of male C57BL/6 mice (6 months old, n = 29; 24 months old, n = 24; 28+ months old, n = 28). To measure physical function in mice, we used rotarod (overall motor function), grip meter (forelimb strength), treadmill (endurance), inverted cling (strength/endurance), voluntary wheel running (volitional exercise and activity rate), and muscle performance with in vivo contractile physiology (dorsiflexor torque). We hypothesized that CFAB would be a valid means to assess the physical function of a given mouse across the life span. In addition, we proposed that CFAB could be used to determine relationships between different parameters associated with sarcopenia. We found that there was an overall age-related significant decline (p < .05) in all measurements, and the CFAB score demonstrated that some individual mice (the upper quartile) retained the functional capacity of average mice 1 cohort younger. We conclude that the CFAB is a powerful, repeatable, and noninvasive tool to assess and compare physical function and assess complex motor task ability in mice, which will enable researchers to easily track performance at the individual mouse level.
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Affiliation(s)
- Ted G Graber
- Department of Physical Therapy, East Carolina University, Greenville, North Carolina
| | - Rosario Maroto
- Department of Nutrition and Metabolism, University of Texas Medical Branch, Galveston
| | - Christopher S Fry
- Department of Nutrition and Metabolism, University of Texas Medical Branch, Galveston
- Department of Athletic Training and Clinical Nutrition, University of Kentucky, Lexington
| | - Camille R Brightwell
- Department of Athletic Training and Clinical Nutrition, University of Kentucky, Lexington
- Cell Biology PhD Program, University of Texas Medical Branch, Galveston
| | - Blake B Rasmussen
- Department of Nutrition and Metabolism, University of Texas Medical Branch, Galveston
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14
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Zhao Y, Cholewa J, Shang H, Yang Y, Ding X, Wang Q, Su Q, Zanchi NE, Xia Z. Advances in the Role of Leucine-Sensing in the Regulation of Protein Synthesis in Aging Skeletal Muscle. Front Cell Dev Biol 2021; 9:646482. [PMID: 33869199 PMCID: PMC8047301 DOI: 10.3389/fcell.2021.646482] [Citation(s) in RCA: 8] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/27/2020] [Accepted: 03/04/2021] [Indexed: 12/21/2022] Open
Abstract
Skeletal muscle anabolic resistance (i.e., the decrease in muscle protein synthesis (MPS) in response to anabolic stimuli such as amino acids and exercise) has been identified as a major cause of age-related sarcopenia, to which blunted nutrition-sensing contributes. In recent years, it has been suggested that a leucine sensor may function as a rate-limiting factor in skeletal MPS via small-molecule GTPase. Leucine-sensing and response may therefore have important therapeutic potential in the steady regulation of protein metabolism in aging skeletal muscle. This paper systematically summarizes the three critical processes involved in the leucine-sensing and response process: (1) How the coincidence detector mammalian target of rapamycin complex 1 localizes on the surface of lysosome and how its crucial upstream regulators Rheb and RagB/RagD interact to modulate the leucine response; (2) how complexes such as Ragulator, GATOR, FLCN, and TSC control the nucleotide loading state of Rheb and RagB/RagD to modulate their functional activity; and (3) how the identified leucine sensor leucyl-tRNA synthetase (LARS) and stress response protein 2 (Sestrin2) participate in the leucine-sensing process and the activation of RagB/RagD. Finally, we discuss the potential mechanistic role of exercise and its interactions with leucine-sensing and anabolic responses.
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Affiliation(s)
- Yan Zhao
- Exercise Physiology and Biochemistry Laboratory, College of Physical Education, Jinggangshan University, Ji'an, China
| | - Jason Cholewa
- Department of Exercise Physiology, University of Lynchburg, Lynchburg, VA, United States
| | - Huayu Shang
- School of Sport Medicine and Health, Chengdu Sport University, Chengdu, China
| | - Yueqin Yang
- Hubei Provincial Collaborative Innovation Center for Exercise and Health Promotion, College of Health Science, Wuhan Sports University, Wuhan, China
| | - Xiaomin Ding
- Exercise Physiology and Biochemistry Laboratory, College of Physical Education, Jinggangshan University, Ji'an, China
| | - Qianjin Wang
- Exercise Physiology and Biochemistry Laboratory, College of Physical Education, Jinggangshan University, Ji'an, China
| | - Quansheng Su
- School of Sport Medicine and Health, Chengdu Sport University, Chengdu, China
| | - Nelo Eidy Zanchi
- Department of Physical Education, Federal University of Maranhão (UFMA), São Luís-MA, Brazil.,Laboratory of Cellular and Molecular Biology of Skeletal Muscle (LABCEMME), São Luís-MA, Brazil
| | - Zhi Xia
- Exercise Physiology and Biochemistry Laboratory, College of Physical Education, Jinggangshan University, Ji'an, China.,School of Sport Medicine and Health, Chengdu Sport University, Chengdu, China
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15
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Suginohara T, Wakabayashi K, Ato S, Ogasawara R. Effect of 2-deoxyglucose-mediated inhibition of glycolysis on the regulation of mTOR signaling and protein synthesis before and after high-intensity muscle contraction. Metabolism 2021; 114:154419. [PMID: 33161019 DOI: 10.1016/j.metabol.2020.154419] [Citation(s) in RCA: 6] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 08/27/2020] [Revised: 10/29/2020] [Accepted: 11/02/2020] [Indexed: 02/07/2023]
Abstract
BACKGROUND Glycolysis controls mTORC1 signaling and protein synthesis. In skeletal muscle, glucose metabolism increases with both exercise/contraction intensity and volume, and therefore, high-intensity muscle contraction (HiMC) such as resistance exercise facilitates glycolysis including glucose uptake and glycogen breakdown. However, it is unknown whether glycolysis regulates HiMC-induced mTORC1 activation and increase in protein synthesis. METHODS To determine whether glycolysis regulates basal and HiMC-induced mTORC1 signaling and protein synthesis, we employed 2-deoxyglucose (2-DG) to inhibit glycolysis and isometrically contracted the gastrocnemius muscle of Sprague Dawley rats using percutaneous electrical stimulation. RESULTS Inhibition of glycolysis by 2-DG inhibited basal phosphorylation of p70S6K and 4E-BP1 (downstream targets of mTORC1) and protein synthesis (all P < 0.05) independent of AMPK phosphorylation. AMPK phosphorylation was comparably increased after HiMC at 0 h post HiMC and returned to basal levels 6 h post HiMC in both vehicle- and 2-DG-treated groups. Glycolysis inhibition attenuated muscle contraction-induced phosphorylation of 4E-BP1 at 6 h post HiMC (P < 0.05) but not p70S6K phosphorylation and protein synthesis. CONCLUSION Although glycolysis is involved in basal but not HiMC-induced muscle protein synthesis, it regulates both basal and HiMC-induced mTORC1 signaling, and may play key roles in skeletal muscle adaptation to HiMC.
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Affiliation(s)
- Takeshi Suginohara
- Department of Life Science and Applied Chemistry, Nagoya Institute of Technology, Nagoya, Japan
| | - Koki Wakabayashi
- Department of Life Science and Applied Chemistry, Nagoya Institute of Technology, Nagoya, Japan
| | - Satoru Ato
- Department of Life Science and Applied Chemistry, Nagoya Institute of Technology, Nagoya, Japan
| | - Riki Ogasawara
- Department of Life Science and Applied Chemistry, Nagoya Institute of Technology, Nagoya, Japan.
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16
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Rasmussen BB, Adams CM. ATF4 Is a Fundamental Regulator of Nutrient Sensing and Protein Turnover. J Nutr 2020; 150:979-980. [PMID: 32190894 PMCID: PMC7198309 DOI: 10.1093/jn/nxaa067] [Citation(s) in RCA: 6] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/13/2020] [Revised: 02/12/2020] [Accepted: 02/25/2020] [Indexed: 01/11/2023] Open
Affiliation(s)
- Blake B Rasmussen
- Department of Nutrition & Metabolism, University of Texas Medical Branch at Galveston, Galveston, TX, USA,Address correspondence to BBR (e-mail: )
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17
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Zhu M, Wang XQ. Regulation of mTORC1 by Small GTPases in Response to Nutrients. J Nutr 2020; 150:1004-1011. [PMID: 31965176 DOI: 10.1093/jn/nxz301] [Citation(s) in RCA: 17] [Impact Index Per Article: 4.3] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/15/2019] [Revised: 10/07/2019] [Accepted: 11/18/2019] [Indexed: 12/15/2022] Open
Abstract
Mechanistic target of rapamycin complex 1 (mTORC1) is a highly evolutionarily conserved serine/threonine kinase that regulates cell growth and metabolism in response to multiple environmental cues, such as nutrients, hormones, energy, and stress. Deregulation of mTORC1 can lead to diseases such as diabetes, obesity, and cancer. A series of small GTPases, including Rag, Ras homolog enriched in brain (Rheb), adenosine diphosphate ribosylation factor 1 (Arf1), Ras-related protein Ral-A, Ras homolog (Rho), and Rab, are involved in regulating mTORC1 in response to nutrients, and mTORC1 is differentially regulated via these small GTPases according to specific conditions. Leucine and arginine sensing are considered to be well-confirmed amino acid-sensing signals, activating mTORC1 via a Rag GTPase-dependent mechanism as well as the Ragulator complex and vacuolar H+-adenosine triphosphatase (v-ATPase). Glutamine promotes mTORC1 activation via Arf1 independently of the Rag GTPase. In this review, we summarize current knowledge regarding the regulation of mTORC1 activity by small GTPases in response to nutrients, focusing on the function of small GTPases in mTORC1 activation and how small GTPases are regulated by nutrients.
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Affiliation(s)
- Min Zhu
- College of Animal Science, South China Agricultural University/Guangdong Provincial Key Laboratory of Animal Nutrition Control/National Engineering Research Center for Breeding Swine Industry, Guangzhou, Guangdong, China
| | - Xiu-Qi Wang
- College of Animal Science, South China Agricultural University/Guangdong Provincial Key Laboratory of Animal Nutrition Control/National Engineering Research Center for Breeding Swine Industry, Guangzhou, Guangdong, China
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18
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Adegoke OAJ, Beatty BE, Kimball SR, Wing SS. Interactions of the super complexes: When mTORC1 meets the proteasome. Int J Biochem Cell Biol 2019; 117:105638. [PMID: 31678320 DOI: 10.1016/j.biocel.2019.105638] [Citation(s) in RCA: 9] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/28/2019] [Revised: 10/18/2019] [Accepted: 10/20/2019] [Indexed: 12/30/2022]
Abstract
Homeostatic regulation of energy and metabolic status requires that anabolic and catabolic signaling pathways be precisely regulated and coordinated. Mammalian/mechanistic target of rapamycin complex 1 (mTORC1) is a mega protein complex that promotes energy-consuming anabolic processes of protein and nucleic acid synthesis as well lipogenesis in times of energy and nutrient abundance. However, it is best characterized as the regulator of steps leading to protein synthesis. The ubiquitin-proteasome proteolytic system (UPS) is a major intracellular proteolytic system whose activity is increased during periods of nutrient scarcity and in muscle wasting conditions such as cachexia. Recent studies have examined the impact of mTORC1 on levels and functions of the 26S proteasome, the mega protease complex of the UPS. Here we first briefly review current understanding of the regulation of mTORC1, the UPS, and the 26S proteasome complex. We then review evidence of the effect of each complex on the abundance and functions of the other. Given the fact that drugs that inhibit either complex are either in clinical trials or are approved for treatment of cancer, a muscle wasting condition, we identify studying the effect of combinatory mTORC1-proteasome inhibition on skeletal muscle mass and health as a critical area requiring investigation.
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Affiliation(s)
- Olasunkanmi A J Adegoke
- School of Kinesiology and Health Science, and Muscle Health Research Centre, York University, 4700 Keele Street, Toronto, Ontario, M3J 1P3 Canada.
| | - Brendan E Beatty
- School of Kinesiology and Health Science, and Muscle Health Research Centre, York University, 4700 Keele Street, Toronto, Ontario, M3J 1P3 Canada
| | - Scot R Kimball
- Department of Cellular and Molecular Physiology, The Pennsylvania State University College of Medicine, Hershey, PA 17033, USA
| | - Simon S Wing
- Department of Medicine, McGill University and the Research Institute of the McGill University Health Centre, the Montreal Diabetes Research Centre, Montréal, Quebec, H4A 3J1. Canada
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19
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Abstract
The ability of myofibers to sense and respond appropriately to mechanical signals is one of the primary determinants of the skeletal muscle phenotype. In response to a change in mechanical load, muscle cells alter their protein metabolism, primarily through the regulation of protein synthesis rate. Protein synthesis rates are determined by both translation efficiency and translational capacity within the muscle. Translational capacity is strongly determined by the ribosome content of the muscle; thus the regulation of ribosomal biogenesis by mechanical inputs has been an area of recent interest. Despite the clear association between mechanical signals and changes in protein metabolism, the molecular pathways that link these events are still not fully elucidated. This review focuses on recent studies looking at how mechanosignaling impacts translational events. The role of impaired mechanotransduction in aging is discussed, as is the connection between age-dependent signaling defects and compromised ribosomal biogenesis during mechanical overload. Finally, emerging evidence suggests that the nucleus can act as a mechanosensitive element and that this mode of mechanotransduction may have an important role in skeletal muscle physiology and adaptation.
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Affiliation(s)
- Tyler J Kirby
- Nancy E. and Peter C. Meinig School of Biomedical Engineering, Cornell University, Ithaca, New York.,Weill Institute for Cell and Molecular Biology, Cornell University, Ithaca, New York
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