Whole-Body Regulation of Energy Expenditure, Exercise Fuel Selection, and Dietary Recommendations
Peter M. Tiidus, Rebecca E. K. MacPherson, Paul J. LeBlanc, Andrea R. Josse in The Routledge Handbook on Biochemistry of Exercise, 2020
The next greatest energy store for humans is protein, perhaps 25,000–30,000 kcal in a 70-kg male. However, protein is a minimal contributor as a fuel for muscle contraction, typically because the vast majority of this protein energy is found in either structural (skeletal muscle) or functional (enzymes, hormones, etc.) protein. Protein is made up of amino acids (AAs), which can be oxidized (providing ∼4 kcal•g−1) for exercise fuel when other energy sources have become low, but this is a last resort, as it is like burning the walls of a house or the functional components of a furnace in order to keep the place warm. Experimental data indicate that AA oxidation contributes <5% of exercise energy in most exercise situations, increasing to perhaps a maximum of 10% with very prolonged exercise when CHO availability is reduced significantly (36, 37). Consequently, although substantial, protein energy typically does not contribute significantly to exercise fuel. However, meeting dietary protein requirements remains critical for athletes because AAs are needed to repair muscle contraction–induced structural damage, as well as to maximize the exercise training adaptative responses of both hormones and enzymes.
Protein
Linda M. Castell, Samantha J. Stear (Nottingham), Louise M. Burke in Nutritional Supplements in Sport, Exercise and Health, 2015
Arguably one of the most debated topics in sports nutrition revolves around optimal protein consumption for athletic performance. Various studies have shown that the type, amount and timing of protein ingestion may be of relevance to maximize skeletal muscle recovery and the long-term adaptation, e.g. hypertrophy, increased strength or fatigue-resistant muscles (Cermak et al., 2012b). Skeletal muscle mass is regulated by changes in muscle protein synthesis (MPS) and muscle protein breakdown (MPB), which ultimately define the overall net muscle protein balance. A positive net muscle protein balance is required to maximise skeletal muscle recovery and the longer term adaptation. From the standpoint of athletic performance, skeletal muscle protein turnover is important to repair any damaged/dysfunctional proteins and to facilitate adaptations in the contractile (e.g. myofibrillar) and/or energy-producing (e.g. mitochondrial) proteins of skeletal muscle. Performing an acute bout of either resistance (Biolo et al., 1995; Phillips et al., 1997) or endurance exercise (Sheffield-Moore et al., 2004) stimulates skeletal muscle protein turnover, with MPS being the major variable that improves net muscle protein balance during post-exercise recovery.
Metabolic Interventions for Sarcopenic Obesity
Kohlstadt Ingrid, Cintron Kenneth in Metabolic Therapies in Orthopedics, Second Edition, 2018
It is well established that eating more than 30 g of protein at a meal does result in a further stimulation of muscle protein synthesis. This suggests that there is a protein threshold of ~25–30 g of protein per meal [59, 60]. However, with increasing age it may become more difficult to consume 30 g of protein per meal. There are several risk factors for reduced protein intake in adults including reduced energy needs, difficulty acquiring and preparing food, overall reduction in energy and protein intake due to changes in appetite, changes in food preference, and/or food insecurity [44]. Therefore, when incorporating protein into the diet of older adults it is important to consider protein density, the grams of protein provided per calorie of protein food source [46]. It is especially important to consider protein density when designing diets for older adults with sarcopenic obesity, to ensure that the calories consumed count towards maintaining muscle mass. Estimated protein density per protein source can be found in Figure 12.2. In addition, a list of specific food sources and the quantity needed to maximize muscle protein synthesis can be found in Table 12.6. Since consuming 30 g of protein from whole-food sources may be difficult for some older adults, supplementation with EAAs could be an alternative strategy.
Risk of overhydration and low lean tissue index as measured using a body composition monitor in patients on hemodialysis: a systemic review and meta-analysis
Published in Renal Failure, 2018
Seun Deuk Hwang, Jin Ho Lee, Seoung Woo Lee, Joong Kyung Kim, Moon-Jae Kim, Joon Ho Song
The LTI is an important measurement related to the amount of skeletal muscle and reflects patients nutritional status. Malnutrition is defined as an imbalance between intake and utilization and results in altered metabolism, impaired function and a loss of body mass and skeletal muscle [32]. Nutritional status is an established risk factor for morbidity and mortality in the general population and patients on HD [33]. Skeletal muscle is considered the main source of protein in the body and protein is essential for antibody production, wound healing and white blood cell production during acute or chronic illnesses. If muscle is depleted, there is less protein to fuel these bodily functions, thereby enhancing the risk for disability and functional impairment while reducing muscle power and/or physical function [34]. Protein energy wasting is associated with an increased morbidity, mortality and an impaired quality-of-life. Several markers, including low body mass index (weight/height2), serum albumin, serum cholesterol and an elevated C-reactive protein, either as an isolated metric or incorporated as part of a score, have been previously associated with undernutrition in patients on HD [35]. However, these parameters have not been clearly related to prognosis in this patient population. LTI has recently been reported to be an easily measured parameter for lean mass that can be followed and monitored to assess risk and protein-energy wasting in patients on HD [36].
Highly effective biosynthesis of N-acetylated human thymosin β4 (Tβ4) in Escherichia coli
Published in Artificial Cells, Nanomedicine, and Biotechnology, 2018
Rui Yu, Sai Cao, Yanhong Liu, Xinxi Si, Ting Fang, Xu Sun, Hongmei Dai, Junjie Xu, Hongqing Fang, Wei Chen
E. coli DH5α was used for all plasmid propagation. E. coli BL21 (DE3) was used for expressing proteins. Plasmids pET22b (+) was used as expression vectors. Plasmids pBR322, all the restriction enzymes, T4 DNA ligase, Pyrobest™ DNA polymerase, DNA molecular weight marker were from TaKaRa Biotechnology (Dalian, China). Protein low molecular weight marker was purchased from GE Healthcare. Synthetic Tβ4 (sTβ4) was the product of ProSpec (Ness Ziona, Israel). Actin proteins from human platelet, rabbit skeletal muscle and bovine cardiac muscle were products of Cytoskeleton (Denver, CO). N-(3-Dimethyla minopropyl)-N′-ethylcarbodiimide (EDC), N-hydroxysulfosuccinimide (Sulfo-NHS) and scopolamine hydrobromate were products of Merck (Darmstadt, Germany). Other chemicals used in this study were of analytical or higher grade. The genes synthesis and DNA sequencing were all performed by Shanghai Sangon Biological Engineering Technology and Services (Sangon; Shanghai, China).
Serum and plasma amino acids as markers of prediabetes, insulin resistance, and incident diabetes
Published in Critical Reviews in Clinical Laboratory Sciences, 2018
C. Gar, M. Rottenkolber, C. Prehn, J. Adamski, J. Seissler, A. Lechner
Protein provides the most important structural and functional components of the human body. Muscle protein in particular also serves as an energy store. Protein-derived amino acids are constantly turned over and transported between organs and the blood stream. In anabolic phases, dietary amino acids are added to the body’s protein pool. These phases alternate with catabolic states, which occur with energy deprivation or when dietary protein is available in excess of structural requirements. Then energy is provided by the breakdown of endogenous protein and amino acids can be used for gluconeogenesis [16]. Over-activation of gluconeogenesis occurs in most cases of prediabetes and T2D [17,18]. Glucagon stimulates this process in the liver and, to a lower extent, in the kidneys [16]. After deamination, amino acids form keto acids like acetyl-CoA (derived from leucine, isoleucine, lysine, and tryptophan), alpha-ketoglutarate (derived from glutamate, glutamine, arginine, proline, and histidine), succinyl-CoA (derived from valine), and fumarate (derived from aspartate, asparagine, tyrosine, and phenylalanine), which are further metabolized to oxaloacetate in the Krebs-cycle (Figure 1) [16,19]. Deamination of asparagine and aspartate directly forms oxaloacetate and alanine; the deamination of cysteine, glycine, serine, and tryptophan form pyruvate. Oxaloacetate and pyruvate feed gluconeogenesis [16,19]. Among the amino acids, alanine and glutamine are the most important gluconeogenic precursors in liver (major site of gluconeogenesis) [20–22].
Related Knowledge Centers
- Bone
- Muscle
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- Skeleton
- Somatic Nervous System
- Striated Muscle Tissue
- Tendon
- Cardiac Muscle
- Muscular System
- Muscle Cell