Journal articles: 'Anabolic resistance'

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Morton, Robert W., Daniel A. Traylor, Peter J. M. Weijs, and Stuart M. Phillips. "Defining anabolic resistance." Current Opinion in Critical Care 24, no. 2 (April 2018): 124–30. http://dx.doi.org/10.1097/mcc.0000000000000488.

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Engelen, Mariëlle P. K. J., Barbara S. van der Meij, and Nicolaas E. P. Deutz. "Protein anabolic resistance in cancer." Current Opinion in Clinical Nutrition and Metabolic Care 19, no. 1 (January 2016): 39–47. http://dx.doi.org/10.1097/mco.0000000000000236.

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Mitchell, Cameron J., Randall F. D'Souza, Vandre C. Figueiredo, Alex Chan, Kirsten Aasen, Brenan Durainayagam, Sarah Mitchell, et al. "Effect of dietary arachidonic acid supplementation on acute muscle adaptive responses to resistance exercise in trained men: a randomized controlled trial." Journal of Applied Physiology 124, no. 4 (April 1, 2018): 1080–91. http://dx.doi.org/10.1152/japplphysiol.01100.2017.

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Arachidonic acid (ARA), a polyunsaturated ω-6 fatty acid, acts as precursor to a number of prostaglandins with potential roles in muscle anabolism. It was hypothesized that ARA supplementation might enhance the early anabolic response to resistance exercise (RE) by increasing muscle protein synthesis (MPS) via mammalian target of rapamycin (mTOR) pathway activation and/or the late anabolic response by modulating ribosome biogenesis and satellite cell expansion. Nineteen men with ≥1 yr of resistance-training experience were randomized to consume either 1.5 g daily ARA or a corn-soy-oil placebo in a double-blind manner for 4 wk. Participants then undertook fasted RE (8 sets each of leg press and extension at 80% 1-repetition maximum), with vastus lateralis biopsies obtained before exercise, immediately postexercise, and at 2, 4, and 48 h of recovery. MPS (measured via stable isotope infusion) was not different between groups ( P = 0.212) over the 4-h recovery period. mTOR pathway members p70 S6 kinase and S6 ribosomal protein were phosphorylated postexercise ( P < 0.05), with no difference between groups. 45S preribosomal RNA increased 48 h after exercise only in ARA ( P = 0.012). Neural cell adhesion molecule-positive satellite cells per fiber increased 48 h after exercise ( P = 0.013), with no difference between groups ( P = 0.331). Prior ARA supplementation did not alter the acute anabolic response to RE in previously resistance-trained men; however, at 48 h of recovery, ribosome biogenesis was stimulated only in the ARA group. The findings do not support a mechanistic link between ARA and short-term anabolism, but ARA supplementation in conjunction with resistance training may stimulate increases in translational capacity. NEW & NOTEWORTHY Four weeks of daily arachidonic acid supplementation in trained men did not alter their acute muscle protein synthetic or anabolic signaling response to resistance exercise. However, 48 h after exercise, men supplemented with arachidonic acid showed greater ribosome biogenesis and a trend toward greater change in satellite cell content. Chronic arachidonic acid supplementation does not appear to regulate the acute anabolic response to resistance exercise but may augment muscle adaptation in the following days of recovery.

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Dardevet, Dominique, Didier Rémond, Marie-Agnès Peyron, Isabelle Papet, Isabelle Savary-Auzeloux, and Laurent Mosoni. "Muscle Wasting and Resistance of Muscle Anabolism: The “Anabolic Threshold Concept” for Adapted Nutritional Strategies during Sarcopenia." Scientific World Journal 2012 (2012): 1–6. http://dx.doi.org/10.1100/2012/269531.

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Skeletal muscle loss is observed in several physiopathological situations. Strategies to prevent, slow down, or increase recovery of muscle have already been tested. Besides exercise, nutrition, and more particularly protein nutrition based on increased amino acid, leucine or the quality of protein intake has generated positive acute postprandial effect on muscle protein anabolism. However, on the long term, these nutritional strategies have often failed in improving muscle mass even if given for long periods of time in both humans and rodent models. Muscle mass loss situations have been often correlated to a resistance of muscle protein anabolism to food intake which may be explained by an increase of the anabolic threshold toward the stimulatory effect of amino acids. In this paper, we will emphasize how this anabolic resistance may affect the intensity and the duration of the muscle anabolic response at the postprandial state and how it may explain the negative results obtained on the long term in the prevention of muscle mass. Sarcopenia, the muscle mass loss observed during aging, has been chosen to illustrate this concept but it may be kept in mind that it could be extended to any other catabolic states or recovery situations.

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Nilsson, Mats I., Nicholas P. Greene, Justin P. Dobson, Michael P. Wiggs, Heath G. Gasier, Brandon R. Macias, Kevin L. Shimkus, and James D. Fluckey. "Insulin resistance syndrome blunts the mitochondrial anabolic response following resistance exercise." American Journal of Physiology-Endocrinology and Metabolism 299, no. 3 (September 2010): E466—E474. http://dx.doi.org/10.1152/ajpendo.00118.2010.

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Metabolic risk factors associated with insulin resistance syndrome may attenuate augmentations in skeletal muscle protein anabolism following contractile activity. The purpose of this study was to investigate whether or not the anabolic response, as defined by an increase in cumulative fractional protein synthesis rates (24-h FSR) following resistance exercise (RE), is blunted in skeletal muscle of a well-established rodent model of insulin resistance syndrome. Four-month-old lean ( Fa/?) and obese ( fa/fa) Zucker rats engaged in four lower body RE sessions over 8 days, with the last bout occurring 16 h prior to muscle harvest. A priming dose of deuterium oxide (2H2O) and 2H2O-enriched drinking water were administered 24 h prior to euthanization for assessment of cumulative FSR. Fractional synthesis rates of mixed (−5%), mitochondrial (−1%), and cytosolic (+15%), but not myofibrillar, proteins (−16%, P = 0.012) were normal or elevated in gastrocnemius muscle of unexercised obese rats. No statistical differences were found in the anabolic response of cytosolic and myofibrillar subfractions between phenotypes, but obese rats were not able to augment 24-h FSR of mitochondria to the same extent as lean rats following RE (+14% vs. +28%, respectively). We conclude that the mature obese Zucker rat exhibits a mild, myofibrillar-specific suppression in basal FSR and a blunted mitochondrial response to contractile activity in mixed gastrocnemius muscle. These findings underscore the importance of assessing synthesis rates of specific myocellular subfractions to fully elucidate perturbations in basal protein turnover rates and differential adaptations to exercise stimuli in metabolic disease.

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Murphy, Chaise, and Karsten Koehler. "Caloric restriction induces anabolic resistance to resistance exercise." European Journal of Applied Physiology 120, no. 5 (March 31, 2020): 1155–64. http://dx.doi.org/10.1007/s00421-020-04354-0.

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Murton, Andrew J. "Muscle protein turnover in the elderly and its potential contribution to the development of sarcopenia." Proceedings of the Nutrition Society 74, no. 4 (March 31, 2015): 387–96. http://dx.doi.org/10.1017/s0029665115000130.

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The underlying aetiology of sarcopenia appears multifaceted and not yet fully defined, but ultimately involves the gradual loss of muscle protein content over time. The present evidence suggests that the loss of lean tissue in the elderly is exacerbated by low dietary protein intake. Moreover, acute stable-isotope-based methodologies have demonstrated that the muscle anabolic response to a given amount of protein may decline with age, a phenomenon that has been termed anabolic resistance. Although the mechanism responsible for the inability of muscle to mount a satisfactory anabolic response to protein provision with increasing age is presently unknown, it does not appear due to impaired digestion or absorption of dietary protein. Rather, the issue could reside with any combination of: a diminished delivery of amino acids to peripheral tissues, impaired uptake of amino acids into muscle cells, or an inability of amino acids to elicit intracellular events pivotal for anabolism to occur. Despite the presence of anabolic resistance to dietary protein, present evidence suggests that protein supplementation may be able to overcome these issues, particularly when combined with resistance exercise programmes. As such, protein supplementation may prove to be an effective approach to delay the loss of muscle mass with age and has led to calls for the recommended daily intake of protein to be increased for the elderly population.

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Pereira, Ericson, Samuel Jorge Moyses, Sérgio Aparecido Ignácio, Daniel Komarchewski Mendes, Diego Sgarbi da Silva, Everdan Carneiro, Ana Maria Trindade Grégio Hardy, Edvaldo Antônio Ribeiro Rosa, Patrícia Vida Cassi Bettega, and Aline Cristina Batista Rodrigues Johann. "Anabolic steroids among resistance training practitioners." PLOS ONE 14, no. 10 (October 16, 2019): e0223384. http://dx.doi.org/10.1371/journal.pone.0223384.

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Rennie, Michael J. "Anabolic resistance in critically ill patients." Critical Care Medicine 37 (October 2009): S398—S399. http://dx.doi.org/10.1097/ccm.0b013e3181b6ec1f.

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Drummond, Micah J., Robin L. Marcus, and Paul C. LaStayo. "Targeting Anabolic Impairment in Response to Resistance Exercise in Older Adults with Mobility Impairments: Potential Mechanisms and Rehabilitation Approaches." Journal of Aging Research 2012 (2012): 1–8. http://dx.doi.org/10.1155/2012/486930.

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Muscle atrophy is associated with healthy aging (i.e., sarcopenia) and may be compounded by comorbidities, injury, surgery, illness, and physical inactivity. While a bout of resistance exercise increases protein synthesis rates in healthy young skeletal muscle, the effectiveness of resistance exercise to mount a protein synthetic response is less pronounced in older adults. Improving anabolic sensitivity to resistance exercise, thereby enhancing physical function, is most critical in needy older adults with clinical conditions that render them “low responders”. In this paper, we discuss potential mechanisms contributing to anabolic impairment to resistance exercise and highlight the need to improve anabolic responsiveness in low responders. This is followed with evidence suggesting that the recovery period of resistance exercise provides an opportunity to amplify the exercise-induced anabolic response using protein/essential amino acid ingestion. This anabolic strategy, if repeated chronically, may improve lean muscle gains, decrease time to recovery of function during periods of rehabilitation, and overall, maintain/improve physical independence and reduce mortality rates in older adults.

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Ato, Satoru, Takahiro Mori, Yuki Fujita, Taiga Mishima, and Riki Ogasawara. "Short-term high-fat diet induces muscle fiber type-selective anabolic resistance to resistance exercise." Journal of Applied Physiology 131, no. 2 (August 1, 2021): 442–53. http://dx.doi.org/10.1152/japplphysiol.00889.2020.

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A high-fat diet is known to rapidly induce obesity, insulin resistance, and anabolic resistance to nutrition within a month. However, the influence of a short-term high-fat diet on the response of muscle protein synthesis to acute resistance exercise is unclear. We observed that a short-term high-fat diet causes obesity, insulin resistance, intramuscular lipid droplet accumulation, and anabolic resistance to resistance exercise specifically in type I and IIa fibers.

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Montalvo, Ryan N., Justin P. Hardee, Brandon N. VanderVeen, and James A. Carson. "Resistance Exercise’s Ability to Reverse Cancer-Induced Anabolic Resistance." Exercise and Sport Sciences Reviews 46, no. 4 (October 2018): 247–53. http://dx.doi.org/10.1249/jes.0000000000000159.

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Watson, Matthew D., Brett L. Cross, and Gregory J. Grosicki. "Evidence for the Contribution of Gut Microbiota to Age-Related Anabolic Resistance." Nutrients 13, no. 2 (February 23, 2021): 706. http://dx.doi.org/10.3390/nu13020706.

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Globally, people 65 years of age and older are the fastest growing segment of the population. Physiological manifestations of the aging process include undesirable changes in body composition, declines in cardiorespiratory fitness, and reductions in skeletal muscle size and function (i.e., sarcopenia) that are independently associated with mortality. Decrements in muscle protein synthetic responses to anabolic stimuli (i.e., anabolic resistance), such as protein feeding or physical activity, are highly characteristic of the aging skeletal muscle phenotype and play a fundamental role in the development of sarcopenia. A more definitive understanding of the mechanisms underlying this age-associated reduction in anabolic responsiveness will help to guide promyogenic and function promoting therapies. Recent studies have provided evidence in support of a bidirectional gut-muscle axis with implications for aging muscle health. This review will examine how age-related changes in gut microbiota composition may impact anabolic response to protein feeding through adverse changes in protein digestion and amino acid absorption, circulating amino acid availability, anabolic hormone production and responsiveness, and intramuscular anabolic signaling. We conclude by reviewing literature describing lifestyle habits suspected to contribute to age-related changes in the microbiome with the goal of identifying evidence-informed strategies to preserve microbial homeostasis, anabolic sensitivity, and skeletal muscle with advancing age.

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Shad, Brandon J., Janice L. Thompson, and Leigh Breen. "Does the muscle protein synthetic response to exercise and amino acid-based nutrition diminish with advancing age? A systematic review." American Journal of Physiology-Endocrinology and Metabolism 311, no. 5 (November 1, 2016): E803—E817. http://dx.doi.org/10.1152/ajpendo.00213.2016.

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The precise role of age-related muscle anabolic resistance in the progression of sarcopenia and functional decline in older individuals is unclear. The present aim was to assess whether the muscle protein synthesis (MPS) response to acute exercise (endurance or resistance) and/or amino acid-based nutrition is attenuated in older compared with young individuals. A systematic review was conducted on studies that directly examined the influence of age on the MPS response to exercise and/or amino acid-based nutrition. Each study arm was synthesized and reported as providing sufficient or insufficient “evidence of age-related muscle anabolic resistance”. Subsequently, three models were established to compare age-related differences in the MPS response to 1) exercise alone, 2) amino acid-based nutrition alone, or 3) the combination of exercise and amino acid-based nutrition. Following exercise alone, 8 of the 17 study arms provided sufficient evidence of age-related muscle anabolic resistance, while in response to amino acid-based nutrition alone, 8 of the 21 study arms provided sufficient evidence of age-related muscle anabolic resistance. When exercise and amino acid-based nutrition were combined, only 2 of the 10 study arms provided sufficient evidence of age-related muscle anabolic resistance. Our results highlight that optimization of exercise and amino acid-based nutrition is sufficient to induce a comparable MPS response between young and older individuals. However, the exercise volume completed and/or the amino acid/protein dose and leucine content must exceed a certain threshold to stimulate equivalent MPS rates in young and older adults, below which age-related muscle anabolic resistance may become apparent.

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Galvão, Daniel A., Robert U. Newton, and Dennis R. Taaffe. "Anabolic Responses to Resistance Training in Older Men and Women: A Brief Review." Journal of Aging and Physical Activity 13, no. 3 (July 2005): 343–58. http://dx.doi.org/10.1123/japa.13.3.343.

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Resistance training has been shown to be the most effective exercise mode to induce anabolic adaptations in older men and women. Advances in imaging techniques and histochemistry have increased the ability to detect such changes, confirming the high level of adaptability that remains in aging skeletal muscle. This brief review presents a summary of the resistance-training studies that directly compare chronic anabolic responses to training in older (>60 years) men and women. Sixteen studies are summarized, most of which indicate similar relative anabolic responses between older men and women after resistance training. Relatively small sample sizes in most of the interventions limited their ability to detect significant sex differences and should be considered when interpreting these studies. Future research should incorporate larger sample sizes with multiple measurement time points for anabolic responses.

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Pereira, Ericson, Samuel Jorge Moyses, Sérgio Aparecido Ignácio, Daniel Komarchewski Mendes, Diego Sgarbi da Silva, Everdan Carneiro, Ana Maria Trindade Grégio Hardy, Edvaldo Antônio Ribeiro Rosa, Patrícia Vida Cassi Bettega, and Aline Cristina Batista Rodrigues Johann. "Correction: Anabolic steroids among resistance training practitioners." PLOS ONE 14, no. 12 (December 9, 2019): e0226208. http://dx.doi.org/10.1371/journal.pone.0226208.

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Murphy, Chaise, and Karsten Koehler. "Correction to: Caloric restriction induces anabolic resistance to resistance exercise." European Journal of Applied Physiology 121, no. 10 (June 28, 2021): 2941. http://dx.doi.org/10.1007/s00421-021-04750-0.

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Rivas, Donato A., Nicholas P. Rice, Yassine Ezzyat, Devin J. McDonald, Brittany E. Cooper, and Roger A. Fielding. "Sphingosine-1-phosphate analog FTY720 reverses obesity but not age-induced anabolic resistance to muscle contraction." American Journal of Physiology-Cell Physiology 317, no. 3 (September 1, 2019): C502—C512. http://dx.doi.org/10.1152/ajpcell.00455.2018.

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Sarcopenia, the age-associated loss of skeletal muscle mass and function, is coupled with declines in physical functioning leading to subsequent higher rates of disability, frailty, morbidity, and mortality. Aging and obesity independently contribute to muscle atrophy that is assumed to be a result of the activation of mutual physiological pathways. Understanding mechanisms contributing to the induction of skeletal muscle atrophy with aging and obesity is important for determining targets that may have pivotal roles in muscle loss in these conditions. We find that aging and obesity equally induce an anabolic resistance to acute skeletal muscle contraction as observed with decreases in anabolic signaling activation after contraction. Furthermore, treatment with the sphingosine-1-phosphate analog FTY720 for 4 wk increased lean mass and strength, and the anabolic signaling response to contraction was improved in obese but not older animals. To determine the role of chronic inflammation and different fatty acids on anabolic resistance in skeletal muscle cells, we overexpressed IKKβ with and without exposure to saturated fatty acid (SFA; palmitic acid), polyunsaturated fatty acid (eicosapentaenoic acid), and monounsaturated fatty acid (oleic acid). We found that IKKβ overexpression increased inflammation markers in muscle cells, and this chronic inflammation exacerbated anabolic resistance in response to SFA. Pretreatment with FTY720 reversed the inflammatory effects of palmitic acid in the muscle cells. Taken together, these data demonstrate chronic inflammation can induce anabolic resistance, SFA aggravates these effects, and FTY720 can reverse this by decreasing ceramide accumulation in skeletal muscle.

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Tipton, Kevin D., Tabatha A. Elliott, Arny A. Ferrando, Asle A. Aarsland, and Robert R. Wolfe. "Stimulation of muscle anabolism by resistance exercise and ingestion of leucine plus protein." Applied Physiology, Nutrition, and Metabolism 34, no. 2 (April 2009): 151–61. http://dx.doi.org/10.1139/h09-006.

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Leucine is known to stimulate muscle protein synthesis and anabolism. However, evidence for the efficacy of additional leucine to enhance the response of muscle anabolism to resistance exercise and protein ingestion is unclear. Thus, we investigated the response of net muscle protein balance to ingestion of additional leucine with protein in association with resistance exercise. Two groups of untrained subjects performed an intense bout of leg resistance exercise following ingestion of 1 of 2 drinks: flavored water (PL); or 16.6 g of whey protein + 3.4 g of leucine (W+L). Arteriovenous amino acid balance across the leg was measured to assess the anabolic response of muscle in each group. Arterial amino acid concentrations increased in response to ingestion of W+L. Amino acid concentrations peaked between 60 and 120 min after ingestion, and then declined to baseline values. Valine concentration decreased to levels significantly lower than baseline. Net balance of leucine, threonine, and phenylalanine did not change following PL ingestion, but increased and remained elevated above baseline for 90–120 min following W+L ingestion. Leucine (138 ± 37 and –23 ± 23 mg), phenylalanine (58 ± 28 and –38 ± 14 mg), and threonine (138 ± 37 and –23 ± 23 mg) uptake was greater for W+L than for PL over the 5.5 h following drink ingestion. Our results indicate that the whey protein plus leucine in healthy young volunteers results in an anabolic response in muscle that is not greater than the previously reported response to whey protein alone.

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Arazi, Hamid, Hadi Rohani, Ahmad Ghiasi, and Nasrin Abdi Keikanloo. "Resistance training & beta-hydroxy-beta-methylbutyrate supplementation on hormones." Revista Brasileira de Medicina do Esporte 21, no. 5 (October 2015): 386–89. http://dx.doi.org/10.1590/1517-869220152105113281.

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RESUMO Introduction: In recent years, there was an increased interest on the effects of beta-hydroxy-beta-methylbutyrate (HMB) supplementation on skeletal muscle due to its anti-catabolic effects. Objectives: To investigate the effect of HMB supplementation on body composition, muscular strength and anabolic-catabolic hormones after resistance training. Methods: Twenty amateur male athletes were randomly assigned to supplement and control groups in a double-blind crossover design and participated in four weeks resistance training. Before and after the test period fasting blood samples were obtained to determine anabolic (the growth hormone and testosterone) and catabolic (cortisol) hormones, and fat mass, lean body mass (LBM) and muscular strength were measured. Dependent and independent t-tests were used to analyze data. Results: After the training period, there were no significant differen-ces between the groups with respect to fat mass, LBM and anabolic-catabolic hormones. HMB supplementation resulted in a significantly greater strength gain (p≤0.05). Conclusion: Greater increase in strength for HMB group was not accompanied by body composition and basal circulating anabolic-catabolic hormonal changes. It seems that HMB supplementation may have beneficial effects on neurological adaptations of strength gain.

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Hardee, Justin P., Ryan N. Montalvo, and James A. Carson. "Linking Cancer Cachexia-Induced Anabolic Resistance to Skeletal Muscle Oxidative Metabolism." Oxidative Medicine and Cellular Longevity 2017 (2017): 1–14. http://dx.doi.org/10.1155/2017/8018197.

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Cancer cachexia, a wasting syndrome characterized by skeletal muscle depletion, contributes to increased patient morbidity and mortality. While the intricate balance between protein synthesis and breakdown regulates skeletal muscle mass, the suppression of basal protein synthesis may not account for the severe wasting induced by cancer. Therefore, recent research has shifted to the regulation of “anabolic resistance,” which is the impaired ability of nutrition and exercise to stimulate protein synthesis. Emerging evidence suggests that oxidative metabolism can regulate both basal and induced muscle protein synthesis. While disrupted protein turnover and oxidative metabolism in cachectic muscle have been examined independently, evidence suggests a linkage between these processes for the regulation of cancer-induced wasting. The primary objective of this review is to highlight the connection between dysfunctional oxidative metabolism and cancer-induced anabolic resistance in skeletal muscle. First, we review oxidative metabolism regulation of muscle protein synthesis. Second, we describe cancer-induced alterations in the response to an anabolic stimulus. Finally, we review a role for exercise to inhibit cancer-induced anabolic suppression and mitochondrial dysfunction.

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Ni Lochlainn, Mary, Ruth Bowyer, and Claire Steves. "Dietary Protein and Muscle in Aging People: The Potential Role of the Gut Microbiome." Nutrients 10, no. 7 (July 20, 2018): 929. http://dx.doi.org/10.3390/nu10070929.

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Muscle mass, strength, and physical function are known to decline with age. This is associated with the development of geriatric syndromes including sarcopenia and frailty. Dietary protein is essential for skeletal muscle function. Resistance exercise appears to be the most beneficial form of physical activity for preserving skeletal muscle and a synergistic effect has been noted when this is combined with dietary protein. However, older adults have shown evidence of anabolic resistance, where greater amounts of protein are required to stimulate muscle protein synthesis, and response is variable. Thus, the recommended daily amount of protein is greater for older people. The aetiologies and mechanisms responsible for anabolic resistance are not fully understood. The gut microbiota is implicated in many of the postulated mechanisms for anabolic resistance, either directly or indirectly. The gut microbiota change with age, and are influenced by dietary protein. Research also implies a role for the gut microbiome in skeletal muscle function. This leads to the hypothesis that the gut microbiome might modulate individual response to protein in the diet. We summarise the existing evidence for the role of the gut microbiota in anabolic resistance and skeletal muscle in aging people, and introduce the metabolome as a tool to probe this relationship in the future.

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Houston, Michael E. "Gaining Weight: The Scientific Basis of Increasing Skeletal Muscle Mass." Canadian Journal of Applied Physiology 24, no. 4 (August 1, 1999): 305–16. http://dx.doi.org/10.1139/h99-024.

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Most athletes today tend to have a larger muscle mass than their predecessors. Better training and nutrition practices are responsible for much of this difference, but whatever the mechanism, the balance between muscle protein synthesis and breakdown must be in favor of increased muscle protein. Applying new techniques for measuring whole body and muscle protein synthesis to resistance exercise has led to some interesting results. In the recovery period following resistance exercise, both muscle protein synthesis and breakdown are accelerated in the fasted state. Ingestion of carbohydrate or carbohydrate and protein during recovery further increases muscle protein synthesis, due in part to an improved anabolic hormone environment. In addition, the anabolic effect of a resistance training bout may last well beyond 48 hours. Using information obtained from research studies, better training and dietary practices can optimize the benefits from resistance training, Key words: protein synthesis, protein breakdown, anabolic hormones, nutrition, resistance training

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Hodson, Nathan, Daniel W. D. West, Andrew Philp, Nicholas A. Burd, and Daniel R. Moore. "Molecular regulation of human skeletal muscle protein synthesis in response to exercise and nutrients: a compass for overcoming age-related anabolic resistance." American Journal of Physiology-Cell Physiology 317, no. 6 (December 1, 2019): C1061—C1078. http://dx.doi.org/10.1152/ajpcell.00209.2019.

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Skeletal muscle mass, a strong predictor of longevity and health in humans, is determined by the balance of two cellular processes, muscle protein synthesis (MPS) and muscle protein breakdown. MPS seems to be particularly sensitive to changes in mechanical load and/or nutritional status; therefore, much research has focused on understanding the molecular mechanisms that underpin this cellular process. Furthermore, older individuals display an attenuated MPS response to anabolic stimuli, termed anabolic resistance, which has a negative impact on muscle mass and function, as well as quality of life. Therefore, an understanding of which, if any, molecular mechanisms contribute to anabolic resistance of MPS is of vital importance in formulation of therapeutic interventions for such populations. This review summarizes the current knowledge of the mechanisms that underpin MPS, which are broadly divided into mechanistic target of rapamycin complex 1 (mTORC1)-dependent, mTORC1-independent, and ribosomal biogenesis-related, and describes the evidence that shows how they are regulated by anabolic stimuli (exercise and/or nutrition) in healthy human skeletal muscle. This review also summarizes evidence regarding which of these mechanisms may be implicated in age-related skeletal muscle anabolic resistance and provides recommendations for future avenues of research that can expand our knowledge of this area.

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Kraemer, William J., Nicholas A. Ratamess, and Bradley C. Nindl. "Recovery responses of testosterone, growth hormone, and IGF-1 after resistance exercise." Journal of Applied Physiology 122, no. 3 (March 1, 2017): 549–58. http://dx.doi.org/10.1152/japplphysiol.00599.2016.

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The complexity and redundancy of the endocrine pathways during recovery related to anabolic function in the body belie an oversimplistic approach to its study. The purpose of this review is to examine the role of resistance exercise (RE) on the recovery responses of three major anabolic hormones, testosterone, growth hormone(s), and insulin-like growth factor 1. Each hormone has a complexity related to differential pathways of action as well as interactions with binding proteins and receptor interactions. Testosterone is the primary anabolic hormone, and its concentration changes during the recovery period depending on the upregulation or downregulation of the androgen receptor. Multiple tissues beyond skeletal muscle are targeted under hormonal control and play critical roles in metabolism and physiological function. Growth hormone (GH) demonstrates differential increases in recovery with RE based on the type of GH being assayed and workout being used. IGF-1 shows variable increases in recovery with RE and is intimately linked to a host of binding proteins that are essential to its integrative actions and mediating targeting effects. The RE stress is related to recruitment of muscle tissue with the glandular release of hormones as signals to target tissues to support homeostatic mechanisms for metabolism and tissue repair during the recovery process. Anabolic hormones play a crucial role in the body’s response to metabolism, repair, and adaptive capabilities especially in response to anabolic-type RE. Changes of these hormones following RE during recovery in the circulatory biocompartment of blood are reflective of the many mechanisms of action that are in play in the repair and recovery process.

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Burd, Nicholas A., Stefan H. Gorissen, and Luc J. C. van Loon. "Anabolic Resistance of Muscle Protein Synthesis with Aging." Exercise and Sport Sciences Reviews 41, no. 3 (July 2013): 169–73. http://dx.doi.org/10.1097/jes.0b013e318292f3d5.

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Bamman, M. M., A. Goodman, G. R. Hunter, J. R. Shipp, and B. A. Gower. "ACUTE ANABOLIC HORMONE RESPONSE FOLLOWING ECCENTRIC RESISTANCE EXERCISE." Medicine & Science in Sports & Exercise 31, Supplement (May 1999): S325. http://dx.doi.org/10.1097/00005768-199905001-01626.

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Roberts, Michael D., Matthew A. Romero, Christopher B. Mobley, Petey W. Mumford, Paul A. Roberson, Cody T. Haun, Christopher G. Vann, et al. "Skeletal muscle mitochondrial volume and myozenin-1 protein differences exist between high versus low anabolic responders to resistance training." PeerJ 6 (July 27, 2018): e5338. http://dx.doi.org/10.7717/peerj.5338.

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Background We sought to examine how 12 weeks of resistance exercise training (RET) affected skeletal muscle myofibrillar and sarcoplasmic protein levels along with markers of mitochondrial physiology in high versus low anabolic responders. Methods Untrained college-aged males were classified as anabolic responders in the top 25th percentile (high-response cluster (HI); n = 13, dual x-ray absorptiometry total body muscle mass change (Δ) = +3.1 ± 0.3 kg, Δ vastus lateralis (VL) thickness = +0.59 ± 0.05 cm, Δ muscle fiber cross sectional area = +1,426 ± 253 μm2) and bottom 25th percentile (low-response cluster (LO); n = 12, +1.1 ± 0.2 kg, +0.24 ± 0.07 cm, +5 ± 209 μm2; p < 0.001 for all Δ scores compared to HI). VL muscle prior to (PRE) and following RET (POST) was assayed for myofibrillar and sarcoplasmic protein concentrations, myosin and actin protein content, and markers of mitochondrial volume. Proteins related to myofibril formation, as well as whole lysate PGC1-α protein levels were assessed. Results Main effects of cluster (HI > LO, p = 0.018, Cohen’s d = 0.737) and time (PRE > POST, p = 0.037, Cohen’s d = −0.589) were observed for citrate synthase activity, although no significant interaction existed (LO PRE = 1.35 ± 0.07 mM/min/mg protein, LO POST = 1.12 ± 0.06, HI PRE = 1.53 ± 0.11, HI POST = 1.39 ± 0.10). POST myofibrillar myozenin-1 protein levels were up-regulated in the LO cluster (LO PRE = 0.96 ± 0.13 relative expression units, LO POST = 1.25 ± 0.16, HI PRE = 1.00 ± 0.11, HI POST = 0.85 ± 0.12; within-group LO increase p = 0.025, Cohen’s d = 0.691). No interactions or main effects existed for other assayed markers. Discussion Our data suggest myofibrillar or sarcoplasmic protein concentrations do not differ between HI versus LO anabolic responders prior to or following a 12-week RET program. Greater mitochondrial volume in HI responders may have facilitated greater anabolism, and myofibril myozenin-1 protein levels may represent a biomarker that differentiates anabolic responses to RET. However, mechanistic research validating these hypotheses is needed.

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Adams, G. R., F. Haddad, P. W. Bodell, P. D. Tran, and K. M. Baldwin. "Combined isometric, concentric, and eccentric resistance exercise prevents unloading-induced muscle atrophy in rats." Journal of Applied Physiology 103, no. 5 (November 2007): 1644–54. http://dx.doi.org/10.1152/japplphysiol.00669.2007.

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Previously, we reported that an isometric resistance training program that was effective in stimulating muscle hypertrophy in ambulatory rats could not completely prevent muscle atrophy during unloading (Haddad F, Adams GR, Bodell PW, Baldwin KM. J Appl Physiol 100: 433–441, 2006). These results indicated that preventing muscle atrophy does not appear to be simply a function of providing an anabolic stimulus. The present study was undertaken to determine if resistance training, with increased volume (3-s contractions) and incorporating both static and dynamic components, would be effective in preventing unloading-induced muscle atrophy. Rats were exposed to 5 days of muscle unloading via tail suspension. During that time one leg received electrically stimulated resistance exercise (RE) that included an isometric, concentric, and eccentric phase. The results of this study indicate that this combined-mode RE provided an anabolic stimulus sufficient to maintain the mass and myofibril content of the trained but not the contralateral medial gastrocnemius (MG) muscle. Relative to the contralateral MG, the RE stimulus increased the amount of total RNA (indicative of translational capacity) as well as the mRNA for several anabolic/myogenic markers such as insulin-like growth factor-I, myogenin, myoferlin, and procollagen III-α-1 and decreased that of myostatin, a negative regulator of muscle size. The combined-mode RE protocol also increased the activity of anabolic signaling intermediates such as p70S6 kinase. These results indicate that a combination of static- and dynamic-mode RE of sufficient volume provides an effective stimulus to stimulate anabolic/myogenic mechanisms to counter the initial stages of unloading-induced muscle atrophy.

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Abou Sawan, Sidney, Michael Mazzulla, Daniel R. Moore, and Nathan Hodson. "More than just a garbage can: emerging roles of the lysosome as an anabolic organelle in skeletal muscle." American Journal of Physiology-Cell Physiology 319, no. 3 (September 1, 2020): C561—C568. http://dx.doi.org/10.1152/ajpcell.00241.2020.

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Skeletal muscle is a highly plastic tissue capable of remodeling in response to a range of physiological stimuli, including nutrients and exercise. Historically, the lysosome has been considered an essentially catabolic organelle contributing to autophagy, phagocytosis, and exo-/endocytosis in skeletal muscle. However, recent evidence has emerged of several anabolic roles for the lysosome, including the requirement for autophagy in skeletal muscle mass maintenance, the discovery of the lysosome as an intracellular signaling hub for mechanistic target of rapamycin complex 1 (mTORC1) activation, and the importance of transcription factor EB/lysosomal biogenesis-related signaling in the regulation of mTORC1-mediated protein synthesis. We, therefore, propose that the lysosome is an understudied organelle with the potential to underpin the skeletal muscle adaptive response to anabolic stimuli. Within this review, we describe the molecular regulation of lysosome biogenesis and detail the emerging anabolic roles of the lysosome in skeletal muscle with particular emphasis on how these roles may mediate adaptations to chronic resistance exercise. Furthermore, given the well-established role of amino acids to support muscle protein remodeling, we describe how dietary proteins “labeled” with stable isotopes could provide a complementary research tool to better understand how lysosomal biogenesis, autophagy regulation, and/or mTORC1-lysosomal repositioning can mediate the intracellular usage of dietary amino acids in response to anabolic stimuli. Finally, we provide avenues for future research with the aim of elucidating how the regulation of this important organelle could mediate skeletal muscle anabolism.

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Tamaki, Tetsuro, Shuichi Uchiyama, Yoshiyasu Uchiyama, Akira Akatsuka, Roland R. Roy, and V. Reggie Edgerton. "Anabolic steroids increase exercise tolerance." American Journal of Physiology-Endocrinology and Metabolism 280, no. 6 (June 1, 2001): E973—E981. http://dx.doi.org/10.1152/ajpendo.2001.280.6.e973.

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The influence of an anabolic androgenic steroid (AAS) on thymidine and amino acid uptake in rat hindlimb skeletal muscles during 14 days after a single exhaustive bout of weight lifting was determined. Adult male rats were divided randomly into Control or Steroid groups. Nandrolone decanoate was administered to the Steroid group 1 wk before the exercise bout. [3H]thymidine and [14C]leucine labeling were used to determine the serial changes in cellular mitotic activity, amino acid uptake, and myosin synthesis. Serum creatine kinase (CK) activity, used as a measure of muscle damage, increased 30 and 60 min after exercise in both groups. The total amount of weight lifted was higher, whereas CK levels were lower in Steroid than in Control rats. [3H]thymidine uptake peaked 2 days after exercise in both groups and was 90% higher in Control than in Steroid rats, reflecting a higher level of muscle damage. [14C]leucine uptake was ∼80% higher at rest and recovered 33% faster postexercise in Steroid than in Control rats. In a separate group of rats, the in situ isometric mechanical properties of the plantaris muscle were determined. The only significant difference was a higher fatigue resistance in the Steroid compared with the Control group. Combined, these results indicate that AAS treatment 1) ameliorates CK efflux and the uptake of [3H]thymidine and enhances the rate of protein synthesis during recovery after a bout of weight lifting, all being consistent with there being less muscle damage, and 2) enhances in vivo work capacity and the in situ fatigue resistance of a primary plantarflexor muscle.

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Haran, Prashanth H., Donato A. Rivas, and Roger A. Fielding. "Role and potential mechanisms of anabolic resistance in sarcopenia." Journal of Cachexia, Sarcopenia and Muscle 3, no. 3 (May 16, 2012): 157–62. http://dx.doi.org/10.1007/s13539-012-0068-4.

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Lees, Matthew J., Oliver J. Wilson, Erin K. Webb, Daniel A. Traylor, Todd Prior, Antonis Elia, Paul S. Harlow, et al. "Novel Essential Amino Acid Supplements Following Resistance Exercise Induce Aminoacidemia and Enhance Anabolic Signaling Irrespective of Age: A Proof-of-Concept Trial." Nutrients 12, no. 7 (July 12, 2020): 2067. http://dx.doi.org/10.3390/nu12072067.

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We investigated the effects of ingesting a leucine-enriched essential amino acid (EAA) gel alone or combined with resistance exercise (RE) versus RE alone (control) on plasma aminoacidemia and intramyocellular anabolic signaling in healthy younger (28 ± 4 years) and older (71 ± 3 years) adults. Blood samples were obtained throughout the three trials, while muscle biopsies were collected in the postabsorptive state and 2 h following RE, following the consumption of two 50 mL EAA gels (40% leucine, 15 g total EAA), and following RE with EAA (combination (COM)). Protein content and the phosphorylation status of key anabolic signaling proteins were determined via immunoblotting. Irrespective of age, during EAA and COM peak leucinemia (younger: 454 ± 32 µM and 537 ± 111 µM; older: 417 ± 99 µM and 553 ± 136 µM) occurred ~60–120 min post-ingestion (younger: 66 ± 6 min and 120 ± 60 min; older: 90 ± 13 min and 78 ± 12 min). In the pooled sample, the area under the curve for plasma leucine and the sum of branched-chain amino acids was significantly greater in EAA and COM compared with RE. For intramyocellular signaling, significant main effects were found for condition (mTOR (Ser2481), rpS6 (Ser235/236)) and age (S6K1 (Thr421/Ser424), 4E-BP1 (Thr37/46)) in age group analyses. The phosphorylation of rpS6 was of similar magnitude (~8-fold) in pooled and age group data 2 h following COM. Our findings suggest that a gel-based, leucine-enriched EAA supplement is associated with aminoacidemia and a muscle anabolic signaling response, thus representing an effective means of stimulating muscle protein anabolism in younger and older adults following EAA and COM.

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Jonker, Renate, Mariëlle P. K. J. Engelen, and Nicolaas E. P. Deutz. "Role of specific dietary amino acids in clinical conditions." British Journal of Nutrition 108, S2 (August 2012): S139—S148. http://dx.doi.org/10.1017/s0007114512002358.

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In a variety of chronic and acute disease states, alterations in protein synthesis, breakdown and protein turnover rates occur that are related to the loss of body protein and skeletal muscle wasting. A key observation is the stimulation of protein breakdown in muscle and the stimulation of protein synthesis in the splanchnic area; mainly liver. An altered splanchnic extraction of amino acids as well as an anabolic resistance to dietary protein, related to stress, disuse and aging play a key role in the pathogenesis of muscle wasting in these conditions. To overcome these factors, specific dietary protein and amino acid diets have been introduced. The main focus of these diets is the quantity and quality of dietary proteins and whether a balanced mixture or solely dietary essential amino acids are required with or without higher intake levels of specific amino acids. Specifically in cancer patients, stimulated muscle protein synthesis has been obtained by increasing the amount of protein in a meal and by providing additional leucine. Also in other chronic diseases such as chronic obstructive pulmonary disease and cystic fibrosis, meals with specific dietary proteins and specific combinations of dietary essential amino acids are able to stimulate anabolism. In acute diseases, a special role for the amino acid arginine and its precursor citrulline as anabolic drivers has been observed. Thus, there is growing evidence that modifying the dietary amino acid composition of a meal will positively influence the net balance between muscle protein synthesis and breakdown, leading to muscle protein anabolism in a variety of chronic and acute disease states. Specific amino acids with anabolic potential are leucine, arginine and citrulline.

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Takegaki, Junya, Kohei Sase, Jun Yasuda, Daichi Shindo, Hiroyuki Kato, Sakiko Toyoda, Toshiyuki Yamada, Yasushi Shinohara, and Satoshi Fujita. "The Effect of Leucine-Enriched Essential Amino Acid Supplementation on Anabolic and Catabolic Signaling in Human Skeletal Muscle after Acute Resistance Exercise: A Randomized, Double-Blind, Placebo-Controlled, Parallel-Group Comparison Trial." Nutrients 12, no. 8 (August 12, 2020): 2421. http://dx.doi.org/10.3390/nu12082421.

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Resistance exercise transiently activates anabolic and catabolic systems in skeletal muscle. Leucine-enriched essential amino acids (LEAAs) are reported to stimulate the muscle anabolic response at a lower dose than whey protein. However, little is known regarding the effect of LEAA supplementation on the resistance exercise-induced responses of the anabolic and catabolic systems. Here, we conducted a randomized, double-blind, placebo-controlled, parallel-group comparison trial to investigate the effect of LEAA supplementation on mechanistic target of rapamycin complex 1 (mTORC1), the ubiquitin–proteasome system and inflammatory cytokines after a single bout of resistance exercise in young men. A total of 20 healthy young male subjects were supplemented with either 5 g of LEAA or placebo, and then they performed 10 reps in three sets of leg extensions and leg curls (70% one-repetition maximum). LEAA supplementation augmented the phosphorylation of mTORSer2448 (+77.1%, p < 0.05), p70S6KThr389 (+1067.4%, p < 0.05), rpS6Ser240/244 (+171.3%, p < 0.05) and 4EBP1Thr37/46 (+33.4%, p < 0.05) after resistance exercise. However, LEAA supplementation did not change the response of the ubiquitinated proteins, MuRF-1 and Atrogin-1 expression. Additionally, the mRNA expression of IL-1β and IL-6 did not change. These data indicated that LEAA supplementation augments the effect of resistance exercise by enhancing mTORC1 signal activation after exercise.

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Kim, Il-Young, Sanghee Park, Ellen T. H. C. Smeets, Scott Schutzler, Gohar Azhar, Jeanne Y. Wei, Arny A. Ferrando, and Robert R. Wolfe. "Consumption of a Specially-Formulated Mixture of Essential Amino Acids Promotes Gain in Whole-Body Protein to a Greater Extent than a Complete Meal Replacement in Older Women with Heart Failure." Nutrients 11, no. 6 (June 17, 2019): 1360. http://dx.doi.org/10.3390/nu11061360.

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Heart failure in older individuals is normally associated with a high body mass index and relatively low lean body mass due to, in part, a resistance to the normal anabolic effect of dietary protein. In this study we have investigated the hypothesis that consumption of a specially-formulated composition of essential amino acids (HiEAAs) can overcome anabolic resistance in individuals with heart failure and stimulate the net gain of body protein to a greater extent than a commercially popular protein-based meal replacement beverage with greater caloric but lower essential amino acid (EAA) content (LoEAA). A randomized cross-over design was used. Protein kinetics were determined using primed continuous infusions of L-(2H5)phenylalanine and L-(2H2)tyrosine in the basal state and for four hours following consumption of either beverage. Both beverages induced positive net protein balance (i.e., anabolic response). However, the anabolic response was more than two times greater with the HiEAA than the LoEAA (p < 0.001), largely through a greater suppression of protein breakdown (p < 0.001). Net protein accretion (g) was also greater in the HiEAA when data were normalized for either amino acid or caloric content (p < 0.001). We conclude that a properly formulated EAA mixture can elicit a greater anabolic response in individuals with heart failure than a protein-based meal replacement. Since heart failure is often associated with obesity, the minimal caloric value of the HiEAA formulation is advantageous.

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Garma, T., C. Kobayashi, F. Haddad, G. R. Adams, P. W. Bodell, and K. M. Baldwin. "Similar acute molecular responses to equivalent volumes of isometric, lengthening, or shortening mode resistance exercise." Journal of Applied Physiology 102, no. 1 (January 2007): 135–43. http://dx.doi.org/10.1152/japplphysiol.00776.2006.

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The present study was undertaken to test the hypothesis that the contraction mode of action [static-isometric (Iso), shortening-concentric (Con), or lengthening-eccentric (Ecc)] used to stress the muscle provides a differential mechanical stimulus eliciting greater or lesser degrees of anabolic response at the initiation of a resistance training program. We performed an acute resistance training study in which different groups of rodents completed four training sessions in either the Iso, Con, or Ecc mode of contraction under conditions of activation and movement specifically designed to elicit equivalent volumes of force accumulation. The results of this experiment indicate that the three modes of contraction produced nearly identical cell signaling, indicative of an anabolic response involving factors such as increased levels of mRNA for IGF-I, procollagen III α1, decreased myostatin mRNA, and increased total RNA concentration. The resulting profiles collectively provide evidence that pure mode of muscle action, in and of itself, does not appear to be a primary variable in determining the efficacy of increased loading paradigms with regard to the initiation of selected muscle anabolic responses.

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Rudar, Marko, Jane K. Naberhuis, Agus Suryawan, Hanh V. Nguyen, Barbara Stoll, Candace C. Style, Mariatu A. Verla, et al. "Prematurity blunts the insulin- and amino acid-induced stimulation of translation initiation and protein synthesis in skeletal muscle of neonatal pigs." American Journal of Physiology-Endocrinology and Metabolism 320, no. 3 (March 1, 2021): E551—E565. http://dx.doi.org/10.1152/ajpendo.00203.2020.

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Extrauterine growth faltering is a major complication of premature birth, but the underlying cause is poorly understood. Our results demonstrate that preterm birth blunts both the insulin-and amino acid-induced activation of mTORC1-dependent translation initiation and protein synthesis in skeletal muscle, thereby limiting the anabolic response to feeding. This anabolic resistance likely contributes to the reduced accretion of lean mass and extrauterine growth restriction of premature infants.

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Roberson, Paul A., Kevin L. Shimkus, Jaclyn E. Welles, Dandan Xu, Abigale L. Whitsell, Eric M. Kimball, Leonard S. Jefferson, and Scot R. Kimball. "A time course for markers of protein synthesis and degradation with hindlimb unloading and the accompanying anabolic resistance to refeeding." Journal of Applied Physiology 129, no. 1 (July 1, 2020): 36–46. http://dx.doi.org/10.1152/japplphysiol.00155.2020.

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Hindlimb unloading causes significant skeletal muscle atrophy by adversely affecting the balance between protein synthesis and breakdown. This study demonstrates a more complete time course for changes in biomarkers associated with protein synthesis and breakdown and investigates the associated anabolic resistance to an anabolic stimulus following hindlimb unloading. These data in concert with information from other studies provide a basis for designing future experiments to optimally interrogate a desired cellular biomarker or pathway.

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Kawamura, Aki, Wataru Aoi, Ryo Abe, Yukiko Kobayashi, Masashi Kuwahata, and Akane Higashi. "Astaxanthin-, β-Carotene-, and Resveratrol-Rich Foods Support Resistance Training-Induced Adaptation." Antioxidants 10, no. 1 (January 14, 2021): 113. http://dx.doi.org/10.3390/antiox10010113.

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Resistance training adaptively increases the muscle strength associated with protein anabolism. Previously, we showed that the combined intake of astaxanthin, β-carotene, and resveratrol can accelerate protein anabolism in the skeletal muscle of mice. The purpose of this study was to investigate the effect of anabolic nutrient-rich foods on muscle adaptation induced by resistance training. Twenty-six healthy men were divided into control and intervention groups. All participants underwent a resistance training program twice a week for 10 weeks. Astaxanthin-, β-carotene-, and resveratrol-rich foods were provided to the intervention group. Body composition, nutrient intake, maximal voluntary contraction of leg extension, oxygen consumption, and serum carbonylated protein level were measured before and after training. The skeletal muscle mass was higher after training than before training in both groups (p < 0.05). Maximal voluntary contraction was increased after training in the intervention group (p < 0.05), but not significantly increased in the control group. Resting oxygen consumption was higher after training in the intervention group only (p < 0.05). As an oxidative stress marker, serum carbonylated protein level tended to be lower immediately after exercise than before exercise in the intervention group only (p = 0.056). Intake of astaxanthin-, β-carotene-, and resveratrol-rich foods supported resistance training-induced strength and metabolic adaptations.

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Weekers, Frank, and Greet Van den Berghe. "Endocrine modifications and interventions during critical illness." Proceedings of the Nutrition Society 63, no. 3 (August 2004): 443–50. http://dx.doi.org/10.1079/pns2004373.

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The ongoing hypermetabolic response in patients with prolonged critical illness leads to the loss of lean tissue mass. Since the cachexia of prolonged illness is usually associated with low concentrations of anabolic hormones, hormonal intervention has been thought to be beneficial. However, most interventions have been shown to be ineffective and their indiscriminate use even causes harm. Before considering endocrine intervention in these frail patients, a detailed understanding of the neuroendocrinology of the stress response is warranted. It is now clear that the acute phase and the later phase of critical illness behave differently from an endocrinological point of view. The acute stress reponse consists primarily of an actively-secreting pituitary in the presence of low circulating peripheral anabolic hormones, suggesting resistance of the peripheral tissues to the effects of anterior pituitary hormones. However, when the disease process becomes prolonged, there is a uniformly-reduced pulsatile secretion of anterior pituitary hormones with proportionally reduced concentrations of peripheral anabolic hormones. The origin of this suppressed pituitary secretion is located in the hypothalamus, as hypothalamic secretagogues can reactivate the anterior pituitary and restore pulsatile secretion. The reactivated pituitary secretion is accompanied by an increase in peripheral target hormones, indicating at least partial sensitivity of these tissues to anterior pituitary hormones in this chronic phase of illness. Thus, endocrine intervention with a combination of hypothalamic secretagogues that more completely reactivate the anterior pituitary could be a more physiological and effective strategy for inducing anabolism in patients with prolonged critical illness.

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Rivas, Donato A., Fei Peng, Townsend Benard, Adelino Sanchez Ramos da Silva, Roger A. Fielding, and Lee M. Margolis. "miR-19b-3p is associated with a diametric response to resistance exercise in older adults and regulates skeletal muscle anabolism via PTEN inhibition." American Journal of Physiology-Cell Physiology 321, no. 6 (December 1, 2021): C977—C991. http://dx.doi.org/10.1152/ajpcell.00190.2021.

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Understanding paradoxical responses to anabolic stimulation and identifying the mechanisms for this inconsistency in mobility-limited older adults may provide new targets for the treatment of sarcopenia. Our laboratory has discovered that dysregulation in microRNA (miRNA) that target anabolic pathways is a potential mechanism resulting in age-associated decreases in skeletal muscle mass and function (sarcopenia). The objective of the current study was to assess circulating miRNA expression profiles in diametric response of leg lean mass in mobility-limited older individuals after a 6-mo progressive resistance exercise training intervention (PRET) and determine the influence of differentially expressing miRNA on regulation of skeletal muscle mass. Participants were dichotomized by gain (Gainers; mean +561.4 g, n = 33) or loss (Losers; mean −589.8 g, n = 40) of leg lean mass after PRET. Gainers significantly increased fat-free mass 2.4% vs. −0.4% for Losers. Six miRNA (miR-1-3p, miR-19b-3p, miR-92a, miR-126, miR-133a-3p, and miR-133b) were significantly identified to be differentially expressed between Gainers and Losers, with miR-19b-3p being the miRNA most highly associated with increases in fat-free mass. Using an aging mouse model, we then assessed if miR-19b-3p expression was different in young mice with larger muscle mass compared with older mice. Circulating and skeletal muscle miR-19b-3p expression was higher in young compared with old mice and was positively associated with muscle mass and grip strength. We then used a novel integrative approach to determine if differences in circulating miR-19b-3p potentially translate to augmented anabolic response in human skeletal muscle cells in vitro. Results from this analysis identified that overexpression of miR-19b-3p targeted and downregulated PTEN by 64% to facilitate significant ∼50% increase in muscle protein synthetic rate as measured with SUnSET. The combine results of these three models identify miR-19b-3p as a potent regulator of muscle anabolism that may contribute to an inter-individual response to PRET in mobility-limited older adults.

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Drummond, Micah J., John J. McCarthy, Christopher S. Fry, Karyn A. Esser, and Blake B. Rasmussen. "Aging differentially affects human skeletal muscle microRNA expression at rest and after an anabolic stimulus of resistance exercise and essential amino acids." American Journal of Physiology-Endocrinology and Metabolism 295, no. 6 (December 2008): E1333—E1340. http://dx.doi.org/10.1152/ajpendo.90562.2008.

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Sarcopenia, skeletal muscle loss during aging, is associated with increased falls, fractures, morbidity, and loss of independence. MicroRNAs (miRNAs) are novel posttranscriptional regulators. The role of miRNAs in cell size regulation after an anabolic stimulus in human skeletal muscle is unknown. We hypothesized that aging would be associated with a differential expression of skeletal muscle primary miRNA (pri-miRNA) and mature miRNA (miR). To test this hypothesis, we used real-time PCR and immunoblotting before and after an anabolic stimulus (resistance exercise + ingestion of a 20-g leucine-enriched essential amino acid solution) to measure the expression of muscle-specific miRNAs (miR-1, miR-133a, and miR-206), upstream regulators (MyoD and myogenin), and downstream targets [insulin-like growth factor-I, histone deacetylase-4, myocyte enhancing factor-2, and Ras homolog enriched in brain (Rheb)] in skeletal muscle of young and older men. Muscle biopsies were obtained at baseline and 3 and 6 h after exercise. At baseline, we found pri-miRNA-1-1, -1-2, -133a-1, and -133a-2 expression elevated in older compared with young men ( P < 0.05). Pri-miRNA-1-2, -133a-1, and -133a-2 were reduced at 6 h after exercise only in the young men compared with baseline, whereas pri-miRNA-206 was elevated at different postexercise time points in older and young men ( P < 0.05). Compared with baseline, miR-1 was reduced only in the young men, whereas Rheb protein was increased in both age groups after the anabolic stimulus ( P < 0.05). We conclude that skeletal muscle primary and mature miRNA expression in young men is readily altered by an anabolic stimulus of resistance exercise + essential amino acid ingestion. However, aging is associated with higher basal skeletal muscle primary miRNA expression and a dysregulated miRNA response after the anabolic stimulus.

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Deger, Serpil M., Jennifer R. Hewlett, Jorge Gamboa, Charles D. Ellis, Adriana M. Hung, Edward D. Siew, Cindy Mamnungu, et al. "Insulin resistance is a significant determinant of sarcopenia in advanced kidney disease." American Journal of Physiology-Endocrinology and Metabolism 315, no. 6 (December 1, 2018): E1108—E1120. http://dx.doi.org/10.1152/ajpendo.00070.2018.

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Maintenance hemodialysis (MHD) patients display significant nutritional abnormalities. Insulin is an anabolic hormone with direct effects on skeletal muscle (SM). We examined the anabolic actions of insulin, whole-body (WB), and SM protein turnover in 33 MHD patients and 17 participants without kidney disease using hyperinsulinemic-euglycemic-euaminoacidemic (dual) clamp. Gluteal muscle biopsies were obtained before and after the dual clamp. At baseline, WB protein synthesis and breakdown rates were similar in MHD patients. During dual clamp, controls had a higher increase in WB protein synthesis and a higher suppression of WB protein breakdown compared with MHD patients, resulting in statistically significantly more positive WB protein net balance [2.02 (interquartile range [IQR]: 1.79 and 2.36) vs. 1.68 (IQR: 1.46 and 1.91) mg·kg fat-free mass−1·min−1 for controls vs. for MHD patients, respectively, P < 0.001]. At baseline, SM protein synthesis and breakdown rates were higher in MHD patients versus controls, but SM net protein balance was similar between groups. During dual clamp, SM protein synthesis increased statistically significantly more in controls compared with MHD patients ( P = 0.03), whereas SM protein breakdown decreased comparably between groups. SM net protein balance was statistically significantly more positive in controls compared with MHD patients [67.3 (IQR: 46.4 and 97.1) vs. 15.4 (IQR: −83.7 and 64.7) μg·100 ml−1·min−1 for controls and MHD patients, respectively, P = 0.03]. Human SM biopsy showed a positive correlation between glucose and leucine disposal rates, phosphorylated AKT to AKT ratio, and muscle mitochondrial markers in controls but not in MHD patients. Diminished response to anabolic actions of insulin in the stimulated setting could lead to muscle wasting in MHD patients.

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Rennie, Michael J. "Anabolic resistance: the effects of aging, sexual dimorphism, and immobilization on human muscle protein turnoverThis paper is one of a selection of papers published in this Special Issue, entitled 14th International Biochemistry of Exercise Conference – Muscles as Molecular and Metabolic Machines, and has undergone the Journal’s usual peer review process." Applied Physiology, Nutrition, and Metabolism 34, no. 3 (June 2009): 377–81. http://dx.doi.org/10.1139/h09-012.

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In healthy active older persons, there is no derangement of muscle protein metabolism. However, there is a major deficit in the ability of older muscles to regulate their maintenance during feeding and exercise. The dose–response relationship between myofibrillar protein synthesis and the availability of essential amino acids (EAA) is shifted down and to the right, and giving extra amino acids is unable to overcome this. There is no sex difference in basal or fed muscle protein metabolism in the young, but postmenopausal women have a greater anabolic resistance than older men. Anabolic resistance is also shown by the decreased phosphorylation in the PKB–mTOR–eIF4BP1 pathway in response to increased EAA. The muscle synthetic system is refractory to EAA provision, irrespective of the availability of insulin, insulin-like growth factor 1, and growth hormone. However, insulin is a major regulator of muscle protein breakdown, and there is a blunting of the ability of older muscle to decrease proteolysis in response to low concentrations of insulin, such as those observed after a light breakfast. Providing more EAA seems not to be useful, and modern N-balance data confirm that the dietary protein requirements of older persons are not increased. The sigmoidal dose–response relationship between muscle protein synthesis and resistance exercise intensity is shifted downward and to the right in older men. Decreased physical activity itself, even in young subjects, can produce anabolic resistance of muscle protein synthesis, which cannot be overcome by increasing amino acid availability. Exercise may retune the amino acid and (or) insulin sensitivity of muscle in older people.

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Bellar, Annette, Nicole Welch, and Srinivasan Dasarathy. "Exercise and physical activity in cirrhosis: opportunities or perils." Journal of Applied Physiology 128, no. 6 (June 1, 2020): 1547–67. http://dx.doi.org/10.1152/japplphysiol.00798.2019.

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Reduced exercise capacity and impaired physical performance are observed in nearly all patients with liver cirrhosis. Physical activity and exercise are physiological anabolic stimuli that can reverse dysregulated protein homeostasis or proteostasis and potentially increase muscle mass and contractile function in healthy subjects. Cirrhosis is a state of anabolic resistance, and unlike the beneficial responses to exercise reported in physiological states, there are few systematic studies evaluating the response to exercise in cirrhosis. Hyperammonemia is a mediator of the liver-muscle axis with net skeletal muscle ammonia uptake in cirrhosis causing signaling perturbations, mitochondrial dysfunction with decreased ATP content, modifications of contractile proteins, and impaired ribosomal function, all of which contribute to anabolic resistance in cirrhosis and have the potential to impair the beneficial responses to exercise. English language-publications in peer-reviewed journals that specifically evaluated the impact of exercise in cirrhosis were reviewed. Most studies evaluated responses to endurance exercise, and readouts included peak or maximum oxygen utilization, grip strength, and functional capacity. Endurance exercise for up to 12 wk is clinically tolerated in well-compensated cirrhosis. Data on the safety of resistance exercise are conflicting. Nutritional supplements enhance the benefits of exercise in healthy subjects but have not been evaluated in cirrhosis. Whether the beneficial physiological responses with endurance exercise and increase in muscle mass with resistance exercise that occur in healthy subjects also occur in cirrhotics is not known. Specific organ-system responses, changes in body composition, or improved long-term clinical outcomes with exercise in cirrhosis need evaluation.

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Ogasawara, Riki, Koji Kobayashi, Arata Tsutaki, Kihyuk Lee, Takashi Abe, Satoshi Fujita, Koichi Nakazato, and Naokata Ishii. "mTOR signaling response to resistance exercise is altered by chronic resistance training and detraining in skeletal muscle." Journal of Applied Physiology 114, no. 7 (April 1, 2013): 934–40. http://dx.doi.org/10.1152/japplphysiol.01161.2012.

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Resistance training-induced muscle anabolism and subsequent hypertrophy occur most rapidly during the early phase of training and become progressively slower over time. Currently, little is known about the intracellular signaling mechanisms underlying changes in the sensitivity of muscles to training stimuli. We investigated the changes in the exercise-induced phosphorylation of hypertrophic signaling proteins during chronic resistance training and subsequent detraining. Male rats were divided into four groups: 1 bout (1B), 12 bouts (12B), 18 bouts (18B), and detraining (DT). In the DT group, rats were subjected to 12 exercise sessions, detrained for 12 days, and then were subjected to 1 exercise session before being killed. Isometric training consisted of maximum isometric contraction, which was produced by percutaneous electrical stimulation of the gastrocnemius muscle every other day. Muscles were removed 24 h after the final exercise session. Levels of total and phosphorylated p70S6K, 4E-BP1, rpS6, and p90RSK levels were measured, and phosphorylation of p70S6K, rpS6, and p90RSK was elevated in the 1B group compared with control muscle (CON) after acute resistance exercise, whereas repeated bouts of exercise suppressed those phosphorylation in both 12B and 18B groups. Interestingly, these phosphorylation levels were restored after 12 days of detraining in the DT group. On the contrary, phosphorylation of 4E-BP1 was not altered with chronic training and detraining, indicating that, with chronic resistance training, anabolic signaling becomes less sensitive to resistance exercise stimuli but is restored after a short detraining period.

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Moro, Tatiana, Camille R. Brightwell, Rachel R. Deer, Ted G. Graber, Elfego Galvan, Christopher S. Fry, Elena Volpi, and Blake B. Rasmussen. "Effect Of Resistance Exercise Training On Anabolic Resistance To Amino Acids In Healthy Older Adults." Medicine & Science in Sports & Exercise 50, no. 5S (May 2018): 370. http://dx.doi.org/10.1249/01.mss.0000536300.72296.fb.

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HOFFMAN, JAY R., JOOHEE IM, KENNETH W. RUNDELL, JIE KANG, SHOKO NIOKA, BARRY A. SPEIRING, RYOTO KIME, and BRITTON CHANCE. "Effect of Muscle Oxygenation during Resistance Exercise on Anabolic Hormone Response." Medicine & Science in Sports & Exercise 35, no. 11 (November 2003): 1929–34. http://dx.doi.org/10.1249/01.mss.0000093613.30362.df.

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COHEN, JONATHAN C., and ROSEMARY HICKMAN. "Insulin Resistance and Diminished Glucose Tolerance in Powerlifters Ingesting Anabolic Steroids*." Journal of Clinical Endocrinology & Metabolism 64, no. 5 (May 1987): 960–63. http://dx.doi.org/10.1210/jcem-64-5-960.

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Journal articles on the topic 'Anabolic resistance'

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