scholarly journals The Physiology of Heat Stress: A Shift in Metabolic Priorities at the Systemic and Cellular Levels

Ceiba ◽  
2016 ◽  
Vol 54 (1) ◽  
pp. 50-58
Author(s):  
Robert P. Rhoads ◽  
Lance H. Baumgard ◽  
Lidan Zhao
Keyword(s):  
Skeletal Muscle ◽  
Heat Stress ◽  
Feed Intake ◽  
Energy Homeostasis ◽  
Molecular Mechanisms ◽  
Well Being ◽  
Production Performance ◽  
Whole Body ◽  
Energy Status ◽  
Whole Body Metabolism

At the onset of heat stress, cattle initiate a series of whole body adaptations in an effort to cope with and dissipate additional heat load. These include well-known physiological changes such as increased respiration rate and sweating rate and decreased feed intake. Environmentally induced hyperthermia in ruminants depresses production as a consequence of reduced feed intake but it is unclear how shifts in metabolism may further affect production performance and physiological acclimation. Our evidence indicates that cattle experiencing heat stress do not appear to engage metabolic and glucose-sparing adaptations consistent with their plane of nutrition. In this context, the liver is uniquely positioned to direct exogenously and endogenously derived nutrients for use by other metabolically active tissues such as the mammary gland and skeletal muscle. Despite the prominent role of the liver in whole-body metabolism, alterations in the molecular mechanisms leading to hepatic adaptation during heat challenge are unclear. We are using management tools and metabolic modifiers, such as bovine somatotropin, in an attempt to better understand and improve hepatic function during heat stress. Because a large proportion of an animal’s mass is comprised of skeletal muscle, alterations in skeletal muscle metabolism and function can have a profound impact on whole-animal energy metabolism and nutrient homeostasis especially during periods of stress.  We have initiated studies to understand how hyperthermia influences the set points of several metabolic pathways within skeletal muscle. It appears that during heat stress bovine skeletal muscle experiences mitochondrial dysfunction leading to impaired cellular energy status. Finally, investigations into adipose tissue metabolism demonstrate impaired lipolytic functions likely due to a refractory nature to adrenergic stimuli. Taken together, this may have broad implications for the reduced production and heat intolerance seen during heat stress especially if tissue(s) are not able to make necessary contributions to whole-body energy homeostasis. Accurately understanding the biological mechanism(s) by which thermal stress reduces animal performance is critical for developing novel approaches (i.e. genetic, managerial and nutritional) to preserve growth and lactation especially given the critical importance of nutrients, such as glucose, to animal production and well being in these situations.

scholarly journals Targeting Mitochondria by SS-31 Ameliorates the Whole Body Energy Status in Cancer- and Chemotherapy-Induced Cachexia

Cancers ◽  
2021 ◽  
Vol 13 (4) ◽  
pp. 850
Author(s):  
Riccardo Ballarò ◽  
Patrizia Lopalco ◽  
Valentina Audrito ◽  
Marc Beltrà ◽  
Fabrizio Pin ◽  
...  
Keyword(s):  
Skeletal Muscle ◽  
Mitochondrial Function ◽  
Energy Homeostasis ◽  
Mitochondrial Protein ◽  
Oxidative Capacity ◽  
Whole Body ◽  
Energy Status ◽  
Protein Loss ◽  
Muscle Weight ◽  
Intracellular Atp

Objective: Cachexia is a complex metabolic syndrome frequently occurring in cancer patients and exacerbated by chemotherapy. In skeletal muscle of cancer hosts, reduced oxidative capacity and low intracellular ATP resulting from abnormal mitochondrial function were described. Methods: The present study aimed at evaluating the ability of the mitochondria-targeted compound SS-31 to counteract muscle wasting and altered metabolism in C26-bearing (C26) mice either receiving chemotherapy (OXFU: oxaliplatin plus 5-fluorouracil) or not. Results: Mitochondrial dysfunction in C26-bearing (C26) mice associated with alterations of cardiolipin fatty acid chains. Selectively targeting cardiolipin with SS-31 partially counteracted body wasting and prevented the reduction of glycolytic myofiber area. SS-31 prompted muscle mitochondrial succinate dehydrogenase (SDH) activity and rescued intracellular ATP levels, although it was unable to counteract mitochondrial protein loss. Progressively increased dosing of SS-31 to C26 OXFU mice showed transient (21 days) beneficial effects on body and muscle weight loss before the onset of a refractory end-stage condition (28 days). At day 21, SS-31 prevented mitochondrial loss and abnormal autophagy/mitophagy. Skeletal muscle, liver and plasma metabolomes were analyzed, showing marked energy and protein metabolism alterations in tumor hosts. SS-31 partially modulated skeletal muscle and liver metabolome, likely reflecting an improved systemic energy homeostasis. Conclusions: The results suggest that targeting mitochondrial function may be as important as targeting protein anabolism/catabolism for the prevention of cancer cachexia. With this in mind, prospective multi-modal therapies including SS-31 are warranted.

scholarly journals Na,K-ATPase regulation in skeletal muscle

2016 ◽  
Vol 311 (1) ◽  
pp. E1-E31 ◽  
Author(s):  
Sergej Pirkmajer ◽  
Alexander V. Chibalin
Keyword(s):  
Skeletal Muscle ◽  
Molecular Mechanisms ◽  
Dynamic Range ◽  
The Body ◽  
Whole Body ◽  
Energy Status ◽  
Muscle Energy ◽  
Energy Sensing ◽  
Intracellular Storage ◽  
Amp Activated Protein Kinase

Skeletal muscle contains one of the largest and the most dynamic pools of Na,K-ATPase (NKA) in the body. Under resting conditions, NKA in skeletal muscle operates at only a fraction of maximal pumping capacity, but it can be markedly activated when demands for ion transport increase, such as during exercise or following food intake. Given the size, capacity, and dynamic range of the NKA pool in skeletal muscle, its tight regulation is essential to maintain whole body homeostasis as well as muscle function. To reconcile functional needs of systemic homeostasis with those of skeletal muscle, NKA is regulated in a coordinated manner by extrinsic stimuli, such as hormones and nerve-derived factors, as well as by local stimuli arising in skeletal muscle fibers, such as contractions and muscle energy status. These stimuli regulate NKA acutely by controlling its enzymatic activity and/or its distribution between the plasma membrane and the intracellular storage compartment. They also regulate NKA chronically by controlling NKA gene expression, thus determining total NKA content in skeletal muscle and its maximal pumping capacity. This review focuses on molecular mechanisms that underlie regulation of NKA in skeletal muscle by major extrinsic and local stimuli. Special emphasis is given to stimuli and mechanisms linking regulation of NKA and energy metabolism in skeletal muscle, such as insulin and the energy-sensing AMP-activated protein kinase. Finally, the recently uncovered roles for glutathionylation, nitric oxide, and extracellular K+ in the regulation of NKA in skeletal muscle are highlighted.

scholarly journals Signaling Pathways That Control Muscle Mass

2020 ◽  
Vol 21 (13) ◽  
pp. 4759 ◽  
Author(s):  
Anna Vainshtein ◽  
Marco Sandri
Keyword(s):  
Skeletal Muscle ◽  
Signaling Pathways ◽  
Muscle Mass ◽  
Molecular Mechanisms ◽  
Whole Body ◽  
Control Muscle ◽  
Health And Wellbeing ◽  
Multiple Protein ◽  
Wide Range ◽  
Whole Body Metabolism

The loss of skeletal muscle mass under a wide range of acute and chronic maladies is associated with poor prognosis, reduced quality of life, and increased mortality. Decades of research indicate the importance of skeletal muscle for whole body metabolism, glucose homeostasis, as well as overall health and wellbeing. This tissue’s remarkable ability to rapidly and effectively adapt to changing environmental cues is a double-edged sword. Physiological adaptations that are beneficial throughout life become maladaptive during atrophic conditions. The atrophic program can be activated by mechanical, oxidative, and energetic distress, and is influenced by the availability of nutrients, growth factors, and cytokines. Largely governed by a transcription-dependent mechanism, this program impinges on multiple protein networks including various organelles as well as biosynthetic and quality control systems. Although modulating muscle function to prevent and treat disease is an enticing concept that has intrigued research teams for decades, a lack of thorough understanding of the molecular mechanisms and signaling pathways that control muscle mass, in addition to poor transferability of findings from rodents to humans, has obstructed efforts to develop effective treatments. Here, we review the progress made in unraveling the molecular mechanisms responsible for the regulation of muscle mass, as this continues to be an intensive area of research.

Regulation of skeletal muscle energy/nutrient-sensing pathways during metabolic adaptation to fasting in healthy humans

2014 ◽  
Vol 307 (10) ◽  
pp. E885-E895 ◽  
Author(s):  
Marjolein A. Wijngaarden ◽  
Leontine E. H. Bakker ◽  
Gerard C. van der Zon ◽  
Peter A. C. 't Hoen ◽  
Ko Willems van Dijk ◽  
...  
Keyword(s):  
Skeletal Muscle ◽  
Protein Kinase ◽  
Lipid Oxidation ◽  
Energy Homeostasis ◽  
Nutrient Sensing ◽  
Whole Body ◽  
Metabolic Adaptation ◽  
Protein Kinase Activity ◽  
Short Term ◽  
Muscle Energy

During fasting, rapid metabolic adaptations are required to maintain energy homeostasis. This occurs by a coordinated regulation of energy/nutrient-sensing pathways leading to transcriptional activation and repression of specific sets of genes. The aim of the study was to investigate how short-term fasting affects whole body energy homeostasis and skeletal muscle energy/nutrient-sensing pathways and transcriptome in humans. For this purpose, 12 young healthy men were studied during a 24-h fast. Whole body glucose/lipid oxidation rates were determined by indirect calorimetry, and blood and skeletal muscle biopsies were collected and analyzed at baseline and after 10 and 24 h of fasting. As expected, fasting induced a time-dependent decrease in plasma insulin and leptin levels, whereas levels of ketone bodies and free fatty acids increased. This was associated with a metabolic shift from glucose toward lipid oxidation. At the molecular level, activation of the protein kinase B (PKB/Akt) and mammalian target of rapamycin pathways was time-dependently reduced in skeletal muscle during fasting, whereas the AMP-activated protein kinase activity remained unaffected. Furthermore, we report some changes in the phosphorylation and/or content of forkhead protein 1, sirtuin 1, and class IIa histone deacetylase 4, suggesting that these pathways might be involved in the transcriptional adaptation to fasting. Finally, transcriptome profiling identified genes that were significantly regulated by fasting in skeletal muscle at both early and late time points. Collectively, our study provides a comprehensive map of the main energy/nutrient-sensing pathways and transcriptomic changes during short-term adaptation to fasting in human skeletal muscle.

Exercise and MEF2–HDAC interactions

2007 ◽  
Vol 32 (5) ◽  
pp. 852-856 ◽  
Author(s):  
Sean L. McGee
Keyword(s):  
Skeletal Muscle ◽  
Protein Kinase ◽  
Nuclear Export ◽  
Energy Homeostasis ◽  
Whole Body ◽  
Positive Health ◽  
Exercise Induced ◽  
Amp Activated Protein Kinase ◽  
Body Energy ◽  
Skeletal Muscle Adaptations

Exercise increases the metabolic capacity of skeletal muscle, which improves whole-body energy homeostasis and contributes to the positive health benefits of exercise. This is, in part, mediated by increases in the expression of a number of metabolic enzymes, regulated largely at the level of transcription. At a molecular level, many of these genes are regulated by the class II histone deacetylase (HDAC) family of transcriptional repressors, in particular HDAC5, through their interaction with myocyte enhancer factor 2 transcription factors. HDAC5 kinases, including 5′-AMP-activated protein kinase and protein kinase D, appear to regulate skeletal muscle metabolic gene transcription by inactivating HDAC5 and inducing HDAC5 nuclear export. These mechanisms appear to participate in exercise-induced gene expression and could be important for skeletal muscle adaptations to exercise.

Skeletal muscle thermogenesis enables aquatic life in the smallest marine mammal

Science ◽  
2021 ◽  
Vol 373 (6551) ◽  
pp. 223-225
Author(s):  
Traver Wright ◽  
Randall W. Davis ◽  
Heidi C. Pearson ◽  
Michael Murray ◽  
Melinda Sheffield-Moore
Keyword(s):  
Skeletal Muscle ◽  
Metabolic Rate ◽  
Basal Metabolic Rate ◽  
Tissue Level ◽  
Whole Body ◽  
Sea Otter ◽  
Aquatic Life ◽  
Respiratory Capacity ◽  
Metabolic Remodeling ◽  
Whole Body Metabolism

Basal metabolic rate generally scales with body mass in mammals, and variation from predicted levels indicates adaptive metabolic remodeling. As a thermogenic adaptation for living in cool water, sea otters have a basal metabolic rate approximately three times that of the predicted rate; however, the tissue-level source of this hypermetabolism is unknown. Because skeletal muscle is a major determinant of whole-body metabolism, we characterized respiratory capacity and thermogenic leak in sea otter muscle. Compared with that of previously sampled mammals, thermogenic muscle leak capacity was elevated and could account for sea otter hypermetabolism. Muscle respiratory capacity was modestly elevated and reached adult levels in neonates. Premature metabolic development and high leak rate indicate that sea otter muscle metabolism is regulated by thermogenic demand and is the source of basal hypermetabolism.

scholarly journals Skeletal muscle enhancer interactions identify genes controlling whole-body metabolism

2020 ◽  
Vol 11 (1) ◽  
Author(s):  
Kristine Williams ◽  
Lars R. Ingerslev ◽  
Jette Bork-Jensen ◽  
Martin Wohlwend ◽  
Ann Normann Hansen ◽  
...  
Keyword(s):  
Skeletal Muscle ◽  
Whole Body ◽  
Whole Body Metabolism

scholarly journals MON-647 Mechanisms of Insulin Resistance in Skeletal Muscle in Women with PCOS

2020 ◽  
Vol 4 (Supplement_1) ◽  
Author(s):  
Alba Moreno-Asso ◽  
Luke C McIlvenna ◽  
Rhiannon K Patten ◽  
Andrew J McAinch ◽  
Raymond J Rodgers ◽  
...  
Keyword(s):  
Insulin Resistance ◽  
Skeletal Muscle ◽  
Glucose Uptake ◽  
Molecular Mechanisms ◽  
Transforming Growth Factor ◽  
Reproductive Age ◽  
Whole Body ◽  
Dependent Manner ◽  
Cultured Myotubes ◽  
Tgfβ Superfamily

Abstract Polycystic ovary syndrome (PCOS) is the most common female endocrine disorder affecting metabolic, reproductive and mental health of 8-13% of reproductive-age women. Insulin resistance (IR) appears to underpin the pathophysiology of PCOS and is present in approximately 85% of women with PCOS. This underlying IR has been identified as unique from, but synergistic with, obesity-induced IR (1). Skeletal muscle accounts for up to 85% of whole body insulin-stimulated glucose uptake, however, in PCOS this is reduced about 27% when assessed by hyperinsulinemic euglycemic clamp (2). Interestingly, this reduced insulin-stimulated glucose uptake observed in skeletal muscle tissue is not retained in cultured myotubes (3), suggesting that environmental factors may play a role in this PCOS-specific IR. Yet, the molecular mechanisms regulating IR remain unclear (4). Previous work suggested that Transforming Growth Factor Beta (TGFβ) superfamily ligands may be involved in the metabolic morbidity associated with PCOS (5). In this study, we investigated the effects of TGFβ1 (1, 5ng/ml), and the Anti-Müllerian hormone (AMH; 5, 10, 30ng/ml), a novel TGFβ superfamily ligand elevated in women with PCOS, as causal factors of IR in cultured myotubes from women with PCOS (n=10) and healthy controls (n=10). AMH negatively affected glucose uptake and insulin signalling increasing p-IRS1 (ser312) in a dose-dependent manner in myotubes from both women with and without PCOS. AMH did not appear to activate the canonical TGFβ/BMP signalling pathway. Conversely, TGFβ1 had an opposite effect in both PCOS and control myotubes cultures, decreasing phosphorylation of IRS1 (ser312) and enhancing glucose uptake via Smad2/3 signalling. In conclusion, these results suggest that AMH may play a role in skeletal muscle IR observed in PCOS, however, further research is required to elucidate its mechanisms of action and broader impact in this syndrome. References: (1) Stepto et al. Hum Reprod 2013 Mar;28(3):777-784. (2) Cassar et al. Hum Reprod 2016 Nov;31(11):2619-2631. (3) Corbould et al., Am J Physiol-Endoc 2005 May;88(5):E1047-54. (4) Stepto et al. J Clin Endocrinol Metab, 2019 Nov 1;104(11):5372-5381. (5) Raja-Khan et al. Reprod Sci 2014 Jan;21(1):20-31.

Molecular Regulation of Energy Balance

2019 ◽  
Author(s):  
D. Grahame Hardie ◽  
A. Mark Evans
Keyword(s):  
Energy Balance ◽  
Energy Homeostasis ◽  
Adenine Nucleotides ◽  
Kinase Domain ◽  
Cellular Level ◽  
Whole Body ◽  
Energy Status ◽  
Α Subunit ◽  
Cellular Energy ◽  
Synthetic Drugs

AMP-activated protein kinase (AMPK) is a sensor of cellular energy status that monitors the levels of AMP and ADP relative to ATP. If increases in AMP:ATP and/or ADP:ATP ratios are detected (indicating a reduction in cellular energy status), AMPK is activated by the canonical mechanism involving both allosteric activation and enhanced net phosphorylation at Thr172 on the catalytic subunit. Once activated, AMPK phosphorylates dozens of downstream targets, thus switching on catabolic pathways that generate ATP and switching off anabolic pathways and other energy-consuming processes. AMPK can also be activated by non-canonical mechanisms, triggered either by glucose starvation by a mechanism independent of changes in adenine nucleotides, or by increases in intracellular Ca2+ in response to hormones, mediated by the alternate upstream kinase CaMKK2. AMPK is expressed in almost all eukaryotic cells, including neurons, as heterotrimeric complexes comprising a catalytic α subunit and regulatory β and γ subunits. The α subunits contain the kinase domain and regulatory regions that interact with the other two subunits. The β subunits contain a domain that, with the small lobe of the kinase domain on the α subunit, forms the “ADaM” site that binds synthetic drugs that are potent allosteric activators of AMPK, while the γ subunits contain the binding sites for the classical regulatory nucleotides, AMP, ADP, and ATP. Although much undoubtedly remains to be discovered about the roles of AMPK in the nervous system, emerging evidence has confirmed the proposal that, in addition to its universal functions in regulating energy balance at the cellular level, AMPK also has cell- and circuit-specific roles at the whole-body level, particularly in energy homeostasis. These roles are mediated by phosphorylation of neural-specific targets such as ion channels, distinct from the targets by which AMPK regulates general, cell-autonomous energy balance. Examples of these cell- and circuit-specific functions discussed in this review include roles in the hypothalamus in balancing energy intake (feeding) and energy expenditure (thermogenesis), and its role in the brainstem, where it supports the hypoxic ventilatory response (breathing), increasing the supply of oxygen to the tissues during systemic hypoxia.

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