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International Journal of Sport... Mar 2001Exercise has a profound effect on muscle growth, which can occur only if muscle protein synthesis exceeds muscle protein breakdown; there must be a positive muscle... (Review)
Review
Exercise has a profound effect on muscle growth, which can occur only if muscle protein synthesis exceeds muscle protein breakdown; there must be a positive muscle protein balance. Resistance exercise improves muscle protein balance, but, in the absence of food intake, the balance remains negative (i.e., catabolic). The response of muscle protein metabolism to a resistance exercise bout lasts for 24-48 hours; thus, the interaction between protein metabolism and any meals consumed in this period will determine the impact of the diet on muscle hypertrophy. Amino acid availability is an important regulator of muscle protein metabolism. The interaction of postexercise metabolic processes and increased amino acid availability maximizes the stimulation of muscle protein synthesis and results in even greater muscle anabolism than when dietary amino acids are not present. Hormones, especially insulin and testosterone, have important roles as regulators of muscle protein synthesis and muscle hypertrophy. Following exercise, insulin has only a permissive role on muscle protein synthesis, but it appears to inhibit the increase in muscle protein breakdown. Ingestion of only small amounts of amino acids, combined with carbohydrates, can transiently increase muscle protein anabolism, but it has yet to be determined if these transient responses translate into an appreciable increase in muscle mass over a prolonged training period.
Topics: Amino Acids; Dietary Carbohydrates; Energy Intake; Energy Metabolism; Exercise; Humans; Insulin; Muscle Development; Muscle Proteins; Muscle, Skeletal; Testosterone
PubMed: 11255140
DOI: 10.1123/ijsnem.11.1.109 -
International Journal of Sport... May 2021Branched-chain amino acids (BCAA) are one of the most popular sports supplements, marketed under the premise that they enhance muscular adaptations. Despite their... (Review)
Review
Branched-chain amino acids (BCAA) are one of the most popular sports supplements, marketed under the premise that they enhance muscular adaptations. Despite their prevalent consumption among athletes and the general public, the efficacy of BCAA has been an ongoing source of controversy in the sports nutrition field. Early support for BCAA supplementation was derived from extrapolation of mechanistic data on their role in muscle protein metabolism. Of the three BCAA, leucine has received the most attention because of its ability to stimulate the initial acute anabolic response. However, a substantial body of both acute and longitudinal research has now accumulated on the topic, affording the ability to scrutinize the effects of BCAA and leucine from a practical standpoint. This article aims to critically review the current literature and draw evidence-based conclusions about the putative benefits of BCAA or leucine supplementation on muscle strength and hypertrophy as well as illuminate gaps in the literature that warrant future study.
Topics: Age Factors; Amino Acids, Branched-Chain; Dietary Proteins; Dietary Supplements; Humans; Leucine; Muscle Proteins; Muscle Strength; Muscle, Skeletal; Resistance Training
PubMed: 33741748
DOI: 10.1123/ijsnem.2020-0356 -
Journal of Applied Physiology... Jun 2009Skeletal muscle demonstrates extraordinary mutability in its responses to exercise of different modes, intensity, and duration, which must involve alterations of muscle... (Review)
Review
Skeletal muscle demonstrates extraordinary mutability in its responses to exercise of different modes, intensity, and duration, which must involve alterations of muscle protein turnover, both acutely and chronically. Here, we bring together information on the alterations in the rates of synthesis and degradation of human muscle protein by different types of exercise and the influences of nutrition, age, and sexual dimorphism. Where possible, we summarize the likely changes in activity of signaling proteins associated with control of protein turnover. Exercise of both the resistance and nonresistance types appears to depress muscle protein synthesis (MPS), whereas muscle protein breakdown (MPB) probably remains unchanged during exercise. However, both MPS and MPB are elevated after exercise in the fasted state, when net muscle protein balance remains negative. Positive net balance is achieved only when amino acid availability is increased, thereby raising MPS markedly. However, postexercise-increased amino acid availability is less important for inhibiting MPB than insulin, the secretion of which is stimulated most by glucose availability, without itself stimulating MPS. Exercise training appears to increase basal muscle protein turnover, with differential responses of the myofibrillar and mitochondrial protein fractions to acute exercise in the trained state. Aging reduces the responses of myofibrillar protein and anabolic signaling to resistance exercise. There appear to be few, if any, differences in the response of young women and young men to acute exercise, although there are indications that, in older women, the responses may be blunted more than in older men.
Topics: Energy Metabolism; Exercise; Female; Humans; Male; Muscle Proteins; Muscle, Skeletal; Physical Fitness
PubMed: 19164770
DOI: 10.1152/japplphysiol.91481.2008 -
American Journal of Physiology. Cell... Jun 2022Decreased skeletal muscle contractile activity (disuse) or unloading leads to muscle mass loss, also known as muscle atrophy. The balance between muscle protein... (Review)
Review
Decreased skeletal muscle contractile activity (disuse) or unloading leads to muscle mass loss, also known as muscle atrophy. The balance between muscle protein synthesis (MPS) and muscle protein breakdown (MPB) is the primary determinant of skeletal muscle mass. A reduced mechanical load on skeletal muscle is one of the main external factors leading to muscle atrophy. However, endocrine and inflammatory factors can act synergistically in catabolic states, amplifying the atrophy process and accelerating its progression. In addition, older individuals display aging-induced anabolic resistance, which can predispose this population to more pronounced effects when exposed to periods of reduced physical activity or mechanical unloading. Different cellular mechanisms contribute to the regulation of muscle protein balance during skeletal muscle atrophy. This review summarizes the effects of muscle disuse on muscle protein balance and the molecular mechanisms involved in muscle atrophy in the absence or presence of disease. Finally, a discussion of the current literature describing efficient strategies to prevent or improve the recovery from muscle atrophy is also presented.
Topics: Aging; Humans; Muscle Proteins; Muscle, Skeletal; Muscular Atrophy; Muscular Disorders, Atrophic
PubMed: 35476500
DOI: 10.1152/ajpcell.00425.2021 -
Journal of the International Society of... 2017The branched chain amino acids (BCAAs) are leucine, valine and isoleucine. A multi-million dollar industry of nutritional supplements has grown around the concept that... (Review)
Review
The branched chain amino acids (BCAAs) are leucine, valine and isoleucine. A multi-million dollar industry of nutritional supplements has grown around the concept that dietary supplements of BCAAs alone produce an anabolic response in humans driven by a stimulation of muscle protein synthesis. In this brief review the theoretical and empirical bases for that claim are discussed. Theoretically, the maximal stimulation of muscle protein synthesis in the post-absorptive state in response to BCAAs alone is the difference between muscle protein breakdown and muscle protein synthesis (about 30% greater than synthesis), because the other EAAs required for synthesis of new protein can only be derived from muscle protein breakdown. Realistically, a maximal increase in muscle protein synthesis of 30% is an over-estimate because the obligatory oxidation of EAAs can never be completely suppressed. An extensive search of the literature has revealed no studies in human subjects in which the response of muscle protein synthesis to orally-ingested BCAAs alone was quantified, and only two studies in which the effect of intravenously infused BCAAs alone was assessed. Both of these intravenous infusion studies found that BCAAs decreased muscle protein synthesis as well as protein breakdown, meaning a decrease in muscle protein turnover. The catabolic state in which the rate of muscle protein breakdown exceeded the rate of muscle protein synthesis persisted during BCAA infusion. We conclude that the claim that consumption of dietary BCAAs stimulates muscle protein synthesis or produces an anabolic response in human subjects is unwarranted.
Topics: Amino Acids, Branched-Chain; Anabolic Agents; Diet; Dietary Supplements; Humans; Muscle Proteins; Protein Biosynthesis
PubMed: 28852372
DOI: 10.1186/s12970-017-0184-9 -
Nutrients Dec 2020Ingesting protein-containing supplements and foods provides essential amino acids (EAA) necessary to increase muscle and whole-body protein synthesis (WBPS). Large...
Ingesting protein-containing supplements and foods provides essential amino acids (EAA) necessary to increase muscle and whole-body protein synthesis (WBPS). Large variations exist in the EAA composition of supplements and foods, ranging from free-form amino acids to whole protein foods. We sought to investigate how changes in peripheral EAA after ingesting various protein and free amino acid formats altered muscle and whole-body protein synthesis. Data were compiled from four previous studies that used primed, constant infusions of L-(ring-H)-phenylalanine and L-(3,3-H)-tyrosine to determine fractional synthetic rate of muscle protein (FSR), WBPS, and circulating EAA concentrations. Stepwise regression indicated that max EAA concentration (EAAC; R = 0.524, < 0.001), EAAC (R = 0.341, < 0.001), and change in EAA concentration (ΔEAA; R = 0.345, < 0.001) were the strongest predictors for postprandial FSR, Δ (change from post absorptive to postprandial) FSR, and ΔWBPS, respectively. Within our dataset, the stepwise regression equation indicated that a 100% increase in peripheral EAA concentrations increases FSR by ~34%. Further, we observed significant ( < 0.05) positive (R = 0.420-0.724) correlations between the plasma EAA area under the curve above baseline, EAAC, ΔEAA, and rate to EAAC to postprandial FSR, ΔFSR, and ΔWBPS. Taken together our results indicate that across a large variety of EAA/protein-containing formats and food, large increases in peripheral EAA concentrations are required to drive a robust increase in muscle and whole-body protein synthesis.
Topics: Aging; Amino Acids; Amino Acids, Essential; Dietary Supplements; Eating; Food; Humans; Kinetics; Male; Metabolism; Muscle Proteins; Muscle, Skeletal; Phenylalanine; Postprandial Period; Protein Biosynthesis; Whey Proteins
PubMed: 33276485
DOI: 10.3390/nu12123717 -
Amino Acids Dec 2018The postprandial rise in essential amino acid (EAA) concentrations modulates the increase in muscle protein synthesis rates after protein ingestion. The EAA content and...
The postprandial rise in essential amino acid (EAA) concentrations modulates the increase in muscle protein synthesis rates after protein ingestion. The EAA content and AA composition of the dietary protein source contribute to the differential muscle protein synthetic response to the ingestion of different proteins. Lower EAA contents and specific lack of sufficient leucine, lysine, and/or methionine may be responsible for the lower anabolic capacity of plant-based compared with animal-based proteins. We compared EAA contents and AA composition of a large selection of plant-based protein sources with animal-based proteins and human skeletal muscle protein. AA composition of oat, lupin, wheat, hemp, microalgae, soy, brown rice, pea, corn, potato, milk, whey, caseinate, casein, egg, and human skeletal muscle protein were assessed using UPLC-MS/MS. EAA contents of plant-based protein isolates such as oat (21%), lupin (21%), and wheat (22%) were lower than animal-based proteins (whey 43%, milk 39%, casein 34%, and egg 32%) and muscle protein (38%). AA profiles largely differed among plant-based proteins with leucine contents ranging from 5.1% for hemp to 13.5% for corn protein, compared to 9.0% for milk, 7.0% for egg, and 7.6% for muscle protein. Methionine and lysine were typically lower in plant-based proteins (1.0 ± 0.3 and 3.6 ± 0.6%) compared with animal-based proteins (2.5 ± 0.1 and 7.0 ± 0.6%) and muscle protein (2.0 and 7.8%, respectively). In conclusion, there are large differences in EAA contents and AA composition between various plant-based protein isolates. Combinations of various plant-based protein isolates or blends of animal and plant-based proteins can provide protein characteristics that closely reflect the typical characteristics of animal-based proteins.
Topics: Amino Acids; Amino Acids, Essential; Chromatography, Liquid; Functional Food; Humans; Muscle Proteins; Muscle, Skeletal; Plant Proteins, Dietary; Protein Biosynthesis; Tandem Mass Spectrometry
PubMed: 30167963
DOI: 10.1007/s00726-018-2640-5 -
Journal of Applied Physiology... Mar 2017Exercise results in the rapid remodeling of skeletal muscle. This process is underpinned by acute and chronic changes in both gene and protein synthesis. In this short... (Review)
Review
Exercise results in the rapid remodeling of skeletal muscle. This process is underpinned by acute and chronic changes in both gene and protein synthesis. In this short review we provide a brief summary of our current understanding regarding how exercise influences these processes as well as the subsequent impact on muscle protein turnover and resultant shift in muscle phenotype. We explore concepts of ribosomal biogenesis and the potential role of increased translational capacity vs. translational efficiency in contributing to muscular hypertrophy. We also examine whether high-intensity sprinting-type exercise promotes changes in protein turnover that lead to hypertrophy or merely a change in mitochondrial content. Finally, we propose novel areas for future study that will fill existing knowledge gaps in the fields of translational research and exercise science.
Topics: Adaptation, Physiological; Animals; Gene Expression Regulation; Humans; Muscle Contraction; Muscle Proteins; Muscle, Skeletal; Protein Biosynthesis; Recovery of Function; Resistance Training
PubMed: 27742803
DOI: 10.1152/japplphysiol.00613.2016 -
Sports Medicine (Auckland, N.Z.) Sep 2021There is a global trend of an increased interest in plant-based diets. This includes an increase in the consumption of plant-based proteins at the expense of... (Review)
Review
There is a global trend of an increased interest in plant-based diets. This includes an increase in the consumption of plant-based proteins at the expense of animal-based proteins. Plant-derived proteins are now also frequently applied in sports nutrition. So far, we have learned that the ingestion of plant-derived proteins, such as soy and wheat protein, result in lower post-prandial muscle protein synthesis responses when compared with the ingestion of an equivalent amount of animal-based protein. The lesser anabolic properties of plant-based versus animal-derived proteins may be attributed to differences in their protein digestion and amino acid absorption kinetics, as well as to differences in amino acid composition between these protein sources. Most plant-based proteins have a low essential amino acid content and are often deficient in one or more specific amino acids, such as lysine and methionine. However, there are large differences in amino acid composition between various plant-derived proteins or plant-based protein sources. So far, only a few studies have directly compared the muscle protein synthetic response following the ingestion of a plant-derived protein versus a high(er) quality animal-derived protein. The proposed lower anabolic properties of plant- versus animal-derived proteins may be compensated for by (i) consuming a greater amount of the plant-derived protein or plant-based protein source to compensate for the lesser quality; (ii) using specific blends of plant-based proteins to create a more balanced amino acid profile; (iii) fortifying the plant-based protein (source) with the specific free amino acid(s) that is (are) deficient. Clinical studies are warranted to assess the anabolic properties of the various plant-derived proteins and their protein sources in vivo in humans and to identify the factors that may or may not compromise the capacity to stimulate post-prandial muscle protein synthesis rates. Such work is needed to determine whether the transition towards a more plant-based diet is accompanied by a transition towards greater dietary protein intake requirements.
Topics: Amino Acids, Essential; Animals; Dietary Proteins; Eating; Humans; Muscle Proteins; Muscle, Skeletal
PubMed: 34515966
DOI: 10.1007/s40279-021-01540-8 -
Applied Physiology, Nutrition, and... Jul 2022The interest in a diet with a higher proportion of plant-based foods to animal-based foods is a global food pattern trend. However, there are concerns regarding adopting... (Review)
Review
The interest in a diet with a higher proportion of plant-based foods to animal-based foods is a global food pattern trend. However, there are concerns regarding adopting plants as the main dietary protein source to support muscle protein synthesis (MPS) and muscle mass. These concerns are centered on three issues: lower protein bioavailability due to antinutritional compounds in plants, lower per-serve scores of protein at similar energy intake, and amino acid scores of plants being lower than optimal. We aimed here to synthesize and discuss evidence around plant protein in human nutrition focusing on the capacity of these proteins to stimulate MPS as a key part of gaining or maintaining muscle mass. In this review, we addressed the issues of plant protein quality and provided evidence for how plant proteins can be made more effective to stimulate MPS and support muscle mass in partial or total replacement of consumption of products of animal origin. Plant proteins are known, in general, to have lower protein quality scores than animal proteins, and this may have important implications, especially for those aiming to increase their skeletal muscle mass through exercise. A plant-based diet has been postulated to have lower protein quality limiting MPS responses and potentially compromising exercise-induced gains in muscle mass. Current evidence shows that plant proteins can stimulate MPS, as can whole foods, especially when combining food groups, increasing portion sizes, and optimizing amino acid bioavailability through processing or common preparation methods.
Topics: Amino Acids; Animals; Dietary Proteins; Humans; Muscle Proteins; Muscle, Skeletal; Plant Proteins
PubMed: 35508011
DOI: 10.1139/apnm-2021-0806