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muscle protein anabolic response

Protein blend ingestion following resistance exercise promotes human muscle protein synthesis. This increase in transport results in greater incorporation of these amino acids including those derived from ingested protein into muscle protein Pennings et al. The loss of muscle with age i. This comparison needs to be performed before it can be concluded with certainty that the difference between these studies is due to the amount of muscle mass involved in the exercise. Consumption of fluid skim milk promotes greater muscle protein accretion after resistance exercise than does consumption of an isonitrogenous and isoenergetic soy-protein beverage. Leucine supplementation chronically improves muscle protein synthesis in older adults consuming the RDA for protein. Worth mentioning is the recent appearance of many new unconventional plant-based protein sources, including aquatic algae e.

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Because the protein digestion rates of both sources are equal 19 , these findings are likely attributed to the differences in EAA content Table 3 , Figure 1. However, following resistance exercise, MPS was greater with ingestion of 40 g, but not 20 g, of soy protein Yang et al. Protein ingestion to stimulate myofibrillar protein synthesis requires greater relative protein intakes in healthy older versus younger men. What is the relationship between the acute muscle protein synthetic response and changes in muscle mass? Learn how this amazing natural hormone can promote muscle gain!

Of particular interest is the plant-based protein source quinoa, which can be considered a high-quality protein source on the basis of its relative high lysine 6. Lysine A and methionine B concentrations of various protein sources. Recent studies have described leucine as the most potent AA responsible for the postprandial stimulation of MPS It is now generally believed that the leucine content of a protein source is an important and independent predictor of its capacity to stimulate postprandial MPS 50 , 76 , It was shown that the ingestion of whey and soy protein, both acid soluble 53 , resulted in a more rapid appearance of leucine in the blood than with the ingestion of casein protein.

Furthermore, the highest level of leucinemia and subsequent stimulation of MPS was observed after the ingestion of whey protein An interesting observation is that the consumption of soy protein led to greater MPS rates than did the consumption of the animal-derived casein protein It was speculated that the slower digestion rate of casein protein and subsequent slower aminoacidemia provided a lesser stimulus for muscle anabolism than did the ingestion of soy protein.

These findings further point toward the rapid, large, and transient increase in systemic leucine concentrations as an important driver of the postprandial increase in MPS. Comparison of the different protein sources reveals that the leucine content of whey is highest, with Unsurprisingly, whey protein is generally considered the superior protein source for the stimulation of postprandial MPS when compared with other rapidly digested protein sources such as soy protein isolate 19 and hydrolyzed casein 17 , which have leucine contents of 8.

Animal-based protein sources generally contain more leucine than do plant-based proteins. The higher leucine content may be a key factor responsible for the proposed greater capacity of animal-based proteins to stimulate postprandial MPS rates when compared with the ingestion of various plant-based proteins From this perspective, maize-derived protein represents an interesting exception because it has a relative high leucine content of However, comparisons of maize protein isolate to other animal- and plant-derived proteins for the stimulation of postprandial MPS remain to be conducted.

On the basis of differences in leucine content between the various plant-based proteins, it could be expected that substantial differences exist in the capacity of individual plant-based protein sources to stimulate postprandial MPS rates. Leucine concentrations of various protein sources. The dashed line provides a comparison of the protein source most abundant in leucine i.

Acute measurements of MPS are often assumed to predict longer-term phenotypic outcomes i. It has been well established that the ingestion of soy protein results in lower postprandial MPS rates than does the ingestion of beef 31 , whey 19 , 21 , or milk 32 , both at rest and during recovery from exercise.

This begets the question as to whether chronic intake of plant- vs. In agreement, Volek et al. Similarly, Campbell et al. Later it was demonstrated that increasing daily dietary protein intake from 0. Overall, these findings imply that the ingestion of higher amounts of protein may reduce the proposed differences in the capacity of different protein sources plant vs.

Indeed, it could be hypothesized that the ingestion of greater quantities of plant-based proteins may compensate for the lower EAA content, thereby improving the potential of plant-based proteins to support skeletal muscle mass gains. Collectively, the studies that provided greater amounts of plant-based proteins showed minimized differences in lean mass gain with resistance exercise when compared with the ingestion of animal-based proteins.

Although the data above are only applicable to the specific population engaged in resistance exercise, divergent phenotypic outcomes with regard to plant- vs. A greater proportion of daily protein intake derived from animal- vs. For instance, long-term vegetarianism in older women has been reported to compromise muscle mass maintenance when compared with consumers of an omnivorous diet Although more long-term studies are required, it appears that prolonged lifelong vegetarianism can result in lower muscle mass maintenance across the life span.

Aging has been associated with a progressive decline in skeletal muscle mass and appears to be driven in part by a greater anabolic resistance of skeletal muscle tissue to dietary protein ingestion Given the importance of skeletal muscle mass for metabolic health and physical functioning 88 , strategies to improve the sensitivity of skeletal muscle tissue to the anabolic properties of plant-based proteins could be of particular interest for aging populations. In addition, strategies to enhance the anabolic response to the ingestion of plant-based proteins may increase consumer demand, thereby supporting global sustainability, and reduce the costs associated with the production of high-quality-protein—dense foods.

As mentioned, plant-based proteins contain fewer EAAs than do animal-based proteins. In the section above, we argued that the ingestion of greater amounts of plant-based protein per meal, consequently ingesting greater amounts of EAAs and notably leucine , may compensate for the lower muscle anabolic properties of plant- vs.

Further evidence for such a notion is found in acute work studying the postprandial MPS response to plant- vs. Specifically, Norton et al. However, recent data in elderly men suggest that the consumption of greater amounts of plant-based proteins, as a strategy to maximize postprandial MPS rates, may not per se provide a feasible solution More specifically, Yang et al.

These findings suggest that part of the soy protein—derived AAs are directed more toward oxidation than used for de novo MPS when compared with whey protein ingestion. Moreover, because 20 g whey and soy protein did not maximize the postprandial MPS response in these older individuals, the study provided further evidence to support the idea that aging muscle requires more leucine to maximally stimulate MPS rates It is evident that consuming such a large amount of protein in a single meal is far from practical.

Therefore, simply increasing the amount of dietary protein consumed per meal may not be the most feasible solution to the problem, especially in a more clinical setting in which food intake is compromised. However, we must note that research into the dose dependency of different plant-based protein sources to maximize MPS is warranted. Amount of dietary protein to, theoretically, maximize postprandial MPS 1. Amount of protein source to be ingested to maximize postexercise MPS rates in response to feeding in young subjects.

Data are ranked from high to low by leucine content. A higher leucine content suggests that a lower amount of dietary protein from a given source is needed to maximize postprandial MPS rates.

The third column amount of protein to be ingested per meal represents a theoretical value using whey protein as a standard of reference. The representative amounts for whey and casein assume isolated protein sources, whereas all other protein sources are expressed as representative amounts of the intact food source.

MPS, muscle protein synthesis. The leucine content of a meal appears to be of fundamental importance to postprandial stimulation of MPS, especially in older populations 50 and in more clinically compromised patient groups Previously, Rieu et al. Similar observations were reported by Katsanos et al. We recently investigated the impact of ingesting intrinsically L-[1- 13 C]phenylalanine—labeled micellar casein with or without the addition of free leucine on postprandial MPS in elderly individuals.

The coingestion of free leucine 2. Moreover, these stimulating effects of leucine are likely maintained with chronic administration of a higher leucine diet. However, the clinical relevance of leucine supplementation as a dietary strategy to gain muscle mass remains questionable. We failed to demonstrate measurable increases in skeletal muscle mass or strength after 3 and 6 mo of leucine supplementation of 7.

A possible issue with crystalline leucine supplementation to the diet may be the plasma- and tissue-depleting effects on the other BCAAs valine and isoleucine. Thereafter, plasma valine and isoleucine concentrations remained stable.

Whether this decline in fasting plasma valine and isoleucine concentration is of physiologic relevance remains debatable, because the basal concentrations did not decline further and always remained within a normal physiologic range.

Moreover, many studies showed an improvement in postprandial MPS with several grams of free leucine supplementation 72 , 75 , 92 , These data suggest that the addition of a few grams of crystalline AAs to a dietary protein source is unlikely to negatively affect protein metabolism and may in fact improve the skeletal muscle anabolic response in settings in which dietary protein intake is substantially lowered. Work assessing the acute or long-term muscle anabolic response in humans to the ingestion of plant-based protein sources fortified with free leucine is currently limited.

However, there is evidence to suggest that the addition of free leucine to plant-based proteins may be a viable option to improve its anabolic properties. In addition, animal work by Norton et al. Overall, the addition of a several grams of free leucine to plant-based protein formulas and foods may provide an effective strategy to enhance the anabolic properties of plant-based protein sources. This may impair the postprandial MPS response after the ingestion of plant-based protein sources when compared with animal-based proteins 56 — Nonetheless, some evidence exists that lysine fortification may be a worthwhile strategy to investigate.

The first large lysine fortification trials were performed in the late s and early s — However, these studies failed to reveal a beneficial effect of lysine fortification of rice, maize, or wheat on the growth rates of children.

A decade later, thorough review of these studies revealed flaws in terms of design and conduct These factors may have confounded the findings, thereby making it difficult to draw firm conclusions with regard to the impact of lysine fortification as a nutritional strategy to augment growth rates In later, well-controlled experiments, beneficial effects of lysine fortification have been observed. For instance, Zhao et al.

Moreover, the authors observed a trend for decreased triceps skinfold thickness, suggesting that the weight gain was attributed to increases in LBM rather than fat mass Similar findings were made in other work that examined the growth rates of infants with the consumption of lysine-fortified wheat 98 and lysine-fortified maize Taken together, these findings provide additional support for the notion that the fortification of plant-based foods with crystalline AAs may improve their anabolic properties.

However, future work comparing the fortification of plant-based protein sources with free AAs vs. Selective breeding or genetic manipulation may also serve as a useful strategy to improve the EAA composition and digestibility of plant-based proteins and, as such, improve their anabolic properties.

QMP has been produced by selective breeding of maize with a single gene mutation that results in increased lysine and tryptophan content Nonetheless, QMP consumption has been shown to augment growth rates of infants in underdeveloped countries, where maize comprises a large majority of daily protein intake Thus, the application of selective breeding or a genetic enhancement strategy to increase the EAA content may represent an effective strategy to improve the skeletal muscle anabolic response to plant protein ingestion and could be of particular relevance in populations who consume diets rich in plant-based foods i.

Several recent articles have investigated the anabolic properties of ingesting a combination of plant and dairy proteins in a single meal i. For example, Reidy et al. The authors reported no measurable differences in the MPS response during the 4-h postexercise recovery period with the ingestion of either These results are not surprising given that nearly equal amounts of EAAs 8.

It is evident that plant-based proteins will contribute to the postprandial increase in MPS and that they can be applied effectively in protein blends designed to support muscle mass gains. This is of particular relevance in postexercise conditions in which the muscle is even more sensitive to the anabolic properties of AAs 13 , However, animal-based proteins, and dairy proteins in particular, contain higher amounts of leucine than do similar amounts of plant-based proteins Table 3 , Figure 3.

A reduction in the amount of leucine consumed may have relatively little impact on the postprandial increase in MPS rates during postexercise recovery in healthy young individuals However, consuming a protein source or protein blend with a low leucine content will likely be of greater impact on stimulating postprandial muscle protein accretion in older and more clinically compromised populations.

Although the consumption of a mixture of plant- and animal-based protein sources is generic to most individuals, vegans consume a strictly plant-based diet. This more recent study assessed MPS in 30 participants compared to 12 per group Witard et al.

So, it is conceivable that the difference between 40 g and 20 g reported in the previous studies was real, but the statistical power was low and thus the real, physiological difference between doses could not be detected. Therefore, a second and possibly more likely explanation for the different results between studies was the exercise bout employed i. Of course, since the responses to whole-body resistance exercise and leg-only exercise have never been directly compared, we cannot rule out other possibilities to explain the discrepancies between the studies.

However, if the most likely explanation for the difference in results was the resistance exercise routines used, a physiological mechanism to explain these results is proposed in Figures 1 and 2.

Essentially, it is based on the fact that the overall demand for amino acids will be greater with the involvement of more muscle during exercise, thus reducing the availability of amino acids to any given quantity of muscle. Nutritive blood flow to contracted muscle is increased following resistance exercise Biolo et al.

With this reasoning, whole-body resistance exercise led to a broader dispersal of blood flow to muscle such that the supply of amino acids to each individual muscle was limited when 20 g was ingested. However, the ingestion of the 40 g protein dose provided enough amino acids to ensure sufficient delivery and availability of amino acids to further increase MPS following whole-body resistance exercise.

The fact that the myofibrillar MPS rate we observed was reduced in our recent study Macnaughton et al. The reduced response of MPS to the whole-body exercise may have obscured any differences present between weightlifters with different amounts of muscle mass.

However, once again, until a comparison between whole-body to leg-only exercise has been made, we cannot conclude with absolute certainty that the response of MPS is different to these two types of resistance exercise. The loss of muscle with age i. Clearly, all exercise and nutrition interventions that can help maintain, or even increase, muscle mass will be important for healthy ageing. Resistance exercise is a well-established means of increasing muscle mass in older adults as reviewed in the American College of Sports Medicine position stand Chodzko-Zajko et al.

Protein intake in association with resistance exercise increases the MPS response. However, the optimal dose of protein to maximize the response of MPS to resistance exercise leading to gains in muscle mass is not certain in older adults.

The metabolic changes that lead to muscle loss with age are not understood entirely. It now seems clear that the basal state fasted and rested rate of MPS is essentially the same in young and older adults Volpi et al. Resistance exercise and protein nutrition are well-accepted interventions to counter age-related muscle loss.

It is important to understand the dose response relationship between MPS and protein intake in older adults to help formulate appropriate recommendations for exercise and nutrition to counter sarcopenia and dynapenia decrease in strength.

Work from the laboratory of the late Professor Mike Rennie showed that stimulation of myofibrillar MPS was less for older adults than young with the ingestion of essential amino acids up to a dose of 20 g - equivalent to roughly 40 g of intact protein Cuthbertson et al. We subsequently compiled data from several studies to garner information on the response to a single dose ingestion relative to total and lean body mass in young and older adults under resting conditions Moore et al.

The findings were consistent with the concept of anabolic resistance and the differences between young and older adults were marked when examined relative to lean body mass.

The point where no further increase in MPS occurred with increasing protein ingestion was 0. It is interesting to note that consuming 0. This is the same amount that was associated with greater retention of lean body mass by older men Houston et al. However, these results were measured under resting conditions. Since exercise, particularly resistance exercise, has a profound influence on the response of MPS to protein ingestion for up to 24 h following exercise Burd et al.

The resistance of muscle to anabolic stimulation appears to impact the relationship between protein dose and the MPS response in older adults. They reported that the ingestion of 20 g was maximally effective for MPS stimulation at rest in these older participants, as there was no further increase with ingestion of 40 g of whey protein. However, Pennings et al. There is no obvious explanation for the discrepancy between these two studies. Nevertheless, resistance exercise enhanced the ability of the muscle to utilize ingested protein-derived amino acids for MPS in older men Pennings et al.

MPS was also greater at each dose of protein ingested in older adults in the Yang et al. On the other hand, unlike the earlier studies in young adults performing leg-only resistance exercise, the response of myofibrillar MPS to 40 g of protein was greater than the response to 20 g and there was no clear plateau in the MPS response Yang et al.

So, it is unknown if ingestion of even higher doses of protein following exercise will further stimulate MPS in older men. Nevertheless, it seems clear that the dose response relationship between protein ingestion and MPS following resistance exercise is altered in older adults, at least with leg-only exercise. Another important factor that influences the response of MPS to protein ingestion following exercise is the source of ingested protein.

The amino acid composition and digestive properties of a protein are considered to be important factors that impact MPS Witard et al. The leucine content of the protein is considered to be the most important factor to maximize MPS.

In this theory, the proteins with a greater proportion of leucine would be predicted to stimulate greater postprandial MPS. Another consideration for determining postprandial MPS is the digestive properties of the protein. There is evidence that, all else being equal, the protein that produces the fastest rise in the blood leucine concentration stimulates MPS to the greater extent West et al.

The faster rise in blood leucine explains why whey protein results in greater MPS following resistance exercise than micellar casein Tang et al. These differential characteristics among different proteins will impact the relationship of the single meal dose that is ingested to the response of MPS following exercise. There is relatively little information available on the response of MPS to various doses of protein other than whey protein.

Given the importance of the leucine composition to the response of MPS, it is believed that proteins that contain less leucine, such as plant proteins, van Vliet et al. At rest, the MPS response following ingestion of 20 or 40 g of soy protein was not greater than ingestion of no protein at all.

However, following resistance exercise, MPS was greater with ingestion of 40 g, but not 20 g, of soy protein Yang et al. Moreover, the MPS response to soy protein ingestion was less than with ingestion of whey protein at all doses of protein at rest and following exercise. Thus, these data are consistent with the leucine threshold concept suggesting that ingestion of greater amounts of so-called inferior protein sources those with lower leucine composition , is necessary to maximally stimulate MPS.

Unfortunately, this is the only study to date to systematically investigate the response of MPS to increasing doses of plant proteins in humans and there are no available data on younger individuals.

Nevertheless, since plant proteins typically contain less leucine than animal proteins van Vliet et al. Thus, it would be interesting to determine dose response curves for various plant proteins, particularly sources with higher leucine compositions, like legumes or quinoa van Vliet et al.

There have been a limited number of attempts to investigate the response of MPS to various blends of proteins and free amino acids designed to manipulate the proportion of leucine Atherton et al.

However, no systematic investigation of the dose response relationship of ingested protein blends with post-exercise MPS has been performed. More specifically, it's a hormone released by the pancreas in response to nutrient availability. Learn how this amazing natural hormone can promote muscle gain!

I nsulin is one of the body's most anabolic muscle-building hormones. A meal high in carbohydrates , protein , or both causes a rise in circulating insulin. Insulin acts on its target cells to increase uptake and storage of key muscle-building nutrients. Insulin increases nutrient transporters to shuttle glucose and Amino Acids into the muscle cell, while preventing the catabolism of those nutrients stored as carbohydrates, protein, or fat.

As such, an increase in insulin levels creates an optimal anabolic environment favorable to muscle growth. Manipulating this natural metabolic response is all the more critical immediately after your workout. Providing your muscles with protein and carbohydrates just before a workout prevents muscle protein from being used for energy.

But the post-workout period is even more important when it comes to maximizing muscle growth. Intensely trained muscles are starving for nutrients to fuel muscle protein synthesis, otherwise known as muscle hypertrophy or growth, particularly in the form of amino acids from protein and glucose from simple carbohydrates. Research has shown that after an intense workout, your body is more likely to synthesize muscle instead of building up fat stores, even if you take in a large amount of simple carbohydrates.

This is a very important point. The popular misconception is that a large serving of fast-absorbing carbohydrates causes fat stores to increase.

Iamges: muscle protein anabolic response

muscle protein anabolic response

Furthermore, most plant proteins have a relatively low leucine content, which may further reduce their anabolic properties when compared with animal proteins.

muscle protein anabolic response

Supplementation of a suboptimal protein dose with leucine or essential amino acids: Another important factor that influences the response of MPS to protein ingestion following exercise is the source of ingested protein.

muscle protein anabolic response

Although more long-term studies are required, it appears that prolonged lifelong vegetarianism can result in lower muscle mass maintenance across the life span. This means that the body's extra insulin release, when timed correctly, promotes muscle mass. Skeletal muscle protein metabolism in the elderly: This is a very important point. However, we must note that research into the dose dependency of different plant-based protein sources anbolic maximize MPS is warranted. Whey protein stimulates postprandial muscle protein accretion more effectively than do casein and casein hydrolysate in muscle protein anabolic response men.