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Dietary Influence on Muscle Protein Synthesis and Hypertrophy
Published in Peter M. Tiidus, Rebecca E. K. MacPherson, Paul J. LeBlanc, Andrea R. Josse, The Routledge Handbook on Biochemistry of Exercise, 2020
James McKendry, Stuart M. Phillips
Skeletal muscle constitutes ∼40% of total body mass and plays a critical role in a multitude of mechanical and metabolic functions. Specifically, muscle serves as the principal site for amino acid (AA) storage, contributes (due to its mass) to basal metabolism, and enables locomotion and athletic performance by way of contractile activity (41). Moreover, skeletal muscle mass is, in certain situations, related to all-cause mortality (99). The size and quality of skeletal muscle decline with advancing age, which increases the risk of disease development and mobility impairment (22). Accordingly, the development, and conservation, of skeletal muscle throughout the lifespan with appropriate lifestyle habits should be a principal focus for individuals looking to maximize athletic performance and enhance quality of life with age. Skeletal muscle is a highly plastic tissue, the malleability of which involves the sensing of internal and external signals and orchestrating an appropriate adaptive response. Significant progress has been made in the field of skeletal muscle protein metabolism. As such, skeletal muscle turnover is regulated by two intricately controlled processes, muscle protein synthesis (MPS) and muscle protein breakdown (MPB) (88). The balance between these two processes determines whether skeletal muscle is built (hypertrophy) or lost (atrophy). Importantly, MPS, and to some extent MPB, can be modified by a number of physiological and environmental stimuli.
Metabolism
Published in Peter Kam, Ian Power, Michael J. Cousins, Philip J. Siddal, Principles of Physiology for the Anaesthetist, 2020
Peter Kam, Ian Power, Michael J. Cousins, Philip J. Siddal
Proteins are synthesized from amino acids. However, as essential amino acids cannot be synthesized within the body, protein synthesis may be limited by the availability of one or more of these. Proteins synthesized form muscle protein, serum proteins, connective tissue and enzymes. In fasting states, gluconeogenesis utilizes amino acids from the breakdown of muscle and liver proteins.
Protein Needs of Athletes
Published in David Lightsey, The Myths about Nutrition Science, 2019
There is a total of 20 amino acids which are required for the structure of any muscle protein. Eleven of these are considered non-essential because your body synthesizes them. The remaining nine must be present during the process of muscle synthesis or development. The absence of any one of these nine will prevent this synthesis from taking place. The branched-chain amino acids (BCAAs) are only three of the nine essential ones needed for synthesis of new muscle tissue. So, it is completely illogical to assume that you can manufacture new muscle fiber without all the materials (all nine essential amino acids, not just three) to do so. An analogy would be to approach an architect to build a new home using only 33% of the needed material. See what kind of a response you receive. It will not be flattering.
Identifying areas of improvement in nursing knowledge regarding hepatic encephalopathy management
Published in Journal of Community Hospital Internal Medicine Perspectives, 2021
Aalam Sohal, Victoria Green, Sunny Sandhu, Marina Roytman
- Protein/calorie malnutrition is a common and underrecognized complication of cirrhosis [20]. Besides the liver, muscle tissue also plays an important role in removal of circulating ammonia [21]. Loss of skeletal mass may lead to decreased toxin clearance and as a result neuropsychiatric symptoms due to hepatic encephalopathy. The International Society for Hepatic Encephalopathy and Nitrogen Metabolism (SHEN) developed a consensus document in 2013. As per the document, dietary protein restriction should be avoided. There are studies which document that patients with hepatic encephalopathy can tolerate normoproteinemic diets and are able to benefit from them. Small frequent meals avoid undue gluconeogenesis in the liver and muscle. Amino acids are a substrate for gluconeogenesis and can lead to proteolysis of the skeletal muscle protein. This coupled with decreased protein synthesis is a frequent cause of sarcopenia in cirrhotics. As a result, small frequent meals with high protein were recommended by the society [22].
Amino acids in post-stroke rehabilitation
Published in Nutritional Neuroscience, 2021
Dhanasekar Karukkupalayam Ramasamy, Trayambak Dutta, Vellaichamy Kannan, Venkatraman Chandramouleeswaran
Nutritional intervention in the form of amino acid supplementation can lead to improvement of muscle bulk and functional capacity during the early post-stroke rehabilitation period [14]. The availability of amino acids is regarded as a rate-limiting step in muscle protein synthesis [15]. Therefore, supplementation of amino acids can stimulate muscle protein synthesis and increase the anabolic activity [14]. Amino Acids restore skeletal muscle function and physical performance. Amino acids also contribute to physical independence and enhance the effectiveness of post-stroke rehabilitation. The availability of amino acids reduces muscle wasting after stroke. In this review, we have compiled the available data on the benefits of oral amino acids supplementation in post-stroke rehabilitation.
Differences In Nutritional And Physical Health Indicators Among Older African Americans, European Americans, And Hispanic Americans
Published in Journal of Nutrition in Gerontology and Geriatrics, 2019
Sareen S. Gropper, Ruth M. Tappen, Edgar Ramos Vieira
A contributing factor to the age-related changes in muscle, frailty, and malnutrition is insufficient protein intake. Low protein intake negatively impacts nutritional status, diminishes muscle mass, strength, and function, and increases risk of morbidity and mortality.10 Muscle loss represents a marker for functional protein depletion.11 Sufficient quantities of protein must be consumed to reduce muscle atrophy and stimulate muscle protein synthesis.4,12–16 Higher dietary protein intakes have been associated with significantly greater muscle mass maintenance and function in community-dwelling older adults.17–20 In the Health, Aging, and Body Composition Study, participants with a protein intake of 1.2 (±0.4) g protein/kg body weight lost significantly less lean mass over a 3-year period than participants consuming 0.8 (±0.3) g protein/kg body weight.17 However, many older adults fail to consume adequate protein levels.21–24 Data from the National Health and Nutrition Examination Surveys (NHANES) II and III demonstrated that energy intake declined with aging, and while the percentage of energy derived from protein remained constant, absolute protein intake in grams declined.21,22 Data from NHANES 2005–2006 showed that about 20% of women and 5% of men aged 51–70 years, and about 24% of women and 12% of men older than 70 years ingested less than the 0.66 g/kg body weight protein requirement.22,23