Nutritional interventions to promote post-exercise muscle protein synthesis

Liposome-Enabled Nanomaterials for Muscle Regeneration

Muscle regeneration is a vital biological process that is crucial for maintaining muscle function and integrity, particularly for the treatment of muscle diseases such as sarcopenia and muscular dystrophy. Generally, muscular tissues can self-repair and regenerate under various conditions, including acute or chronic injuries, aging, and genetic mutation. However, regeneration becomes challenging beyond a certain threshold, particularly in severe muscle injuries or progressive diseases. In recent years, liposome-based nanotechnologies have shown potential as promising therapeutic strategies for muscle regeneration. Liposomes offer an adaptable platform for targeted drug delivery due to their cell membrane-like structure and excellent biocompatibility. They can enhance drug solubility, stability, and targeted delivery while minimizing systemic side effects by different mechanisms. This review summarizes recent advancements, discusses current applications and mechanisms, and highlights challenges and future directions for possible clinical translation of liposome-based nanomaterials in the treatment of muscle diseases. It is hoped this review offers new insights into the development of liposome-enabled nanomedicine to address current limitations.

Postprandial Aminoacidemia Following the Ingestion of Alternative and Sustainable Proteins in Humans: A Narrative Review

There is a pressing need to expand the production and consumption of alternative protein sources from plants, fungi, insects, and algae from both nutritional and sustainability perspectives. It is well known that the postprandial rise in plasma amino acid concentrations and subsequent muscle anabolic response is greater after the ingestion of animal-derived protein sources, such as dairy, meat, and eggs, than plant-based proteins. However, emerging evidence shows that a similar muscle anabolic response is observed-despite a lower and slower postprandial aminoacidemia-after the ingestion of alternative protein sources compared with animal-derived protein sources. Therefore, a comprehensive analysis of plasma amino acid kinetics after the ingestion of alternative protein sources would play a significant role in recognizing and identifying the anabolic properties of these protein sources, allowing for the implementation of the best nutritional intervention strategies, contributing to more sustainable food production, and developing new medical nutritional products with optimal impacts on muscle mass, strength, and function, both in terms of health and disease. Therefore, this narrative review is focused on postprandial amino acid kinetics (the area under the curve, peak, and time to reach the peak concentration of amino acids) based on experimental randomized controlled trials performed in young and older adults following the ingestion of different novel, sustainable, and alternative protein sources.

Efficacy of Pea Protein Supplementation in Combination with a Resistance Training Program on Muscle Performance in a Sedentary Adult Population: A Randomized, Comparator-Controlled, Parallel Clinical Trial

Animal-sourced whey protein (WPr) is the most popular protein supplement among consumers and has been shown to improve muscle mass and strength. However, due to allergies, dietary restrictions/personal choices, and growing demand, alternative protein sources are warranted. Sedentary adults were randomized to pea protein (PPr) or WPr in combination with a weekly resistance training program for 84 days. Changes in whole-body muscle strength (WBMS) including handgrip, lower body, and upper body strength, body composition, and product perception were assessed. The safety outcomes included adverse events, vital signs, clinical chemistry, and hematology. There were no significant differences in the change in WBMS, muscle mass, or product perception and likability scores between the PPr and WPr groups. The participants supplemented with PPr had a 16.1% improvement in WBMS following 84 days of supplementation (p = 0.01), while those taking WPr had an improvement of 11.1% (p = 0.06). Both study products were safe and well-tolerated in the enrolled population. Eighty-four days of PPr supplementation resulted in improvements in strength and muscle mass comparable to WPr when combined with a resistance training program in a population of healthy sedentary adults. PPr may be considered as a viable alternative to animal-sourced WPr without sacrificing muscular gains and product enjoyment.

Post-prandial muscle protein synthesis rates following the ingestion of pea-derived protein do not differ from ingesting an equivalent amount of milk-derived protein in healthy, young males

PURPOSE

Plant-derived proteins have received considerable attention as an alternative to animal-derived proteins. However, plant-derived proteins are considered to have less anabolic properties when compared with animal-derived proteins. The lower muscle protein synthesis rates following ingestion of plant- compared with animal-derived protein have been attributed to the lower essential amino acid content of plant-derived proteins and/or their specific amino acid deficiencies. This study aimed to compare post-prandial muscle protein synthesis rates following the ingestion of 30 g pea-derived protein with 30 g milk-derived protein in healthy, young males.

METHODS

In a randomized, double-blind, parallel-group design, 24 young males (24 ± 3 y) received a primed continuous L-[ring-13C6]-phenylalanine infusion after which they ingested 30 g pea (PEA) or 30 g milk-derived protein (MILK). Blood and muscle biopsies were collected frequently for 5 h to assess post-prandial plasma amino acid profiles and subsequent post-prandial muscle protein synthesis rates.

RESULTS

MILK increased plasma essential amino acid concentrations more than PEA over the 5 h post-prandial period (incremental area under curve 151 ± 31 vs 102 ± 15 mmol∙300 min∙L-1, respectively; P < 0.001). Ingestion of both MILK and PEA showed a robust muscle protein synthetic response with no significant differences between treatments (0.053 ± 0.013 and 0.053 ± 0.017%∙h-1, respectively; P = 0.96).

CONCLUSION

Post-prandial muscle protein synthesis rates following the ingestion of 30 g pea-derived protein do not differ from the response following ingestion of an equivalent amount of milk-derived protein. International Clinical Trials Registry Platform (NTR6548; 27-06-2017).

Partly Substituting Whey for Collagen Peptide Supplementation Improves Neither Indices of Muscle Damage Nor Recovery of Functional Capacity During Eccentric Exercise Training in Fit Males

Previous studies showed that collagen peptide supplementation along with resistance exercise enhance muscular recovery and function. Yet, the efficacy of collagen peptide supplementation in addition to standard nutritional practices in athletes remains unclear. Therefore, the objective of the study was to compare the effects of combined collagen peptide (20 g) and whey protein (25 g) supplementation with a similar daily protein dose (45 g) of whey protein alone on indices of muscle damage and recovery of muscular performance during eccentric exercise training. Young fit males participated in a 3-week training period involving unilateral eccentric exercises for the knee extensors. According to a double-blind, randomized, parallel-group design, before and after training, they received either whey protein (n = 11) or whey protein + collagen peptides (n = 11). Forty-eight hours after the first training session, maximal voluntary isometric and dynamic contraction of the knee extensors were transiently impaired by ∼10% (Ptime < .001) in whey protein and whey protein + collagen peptides, while creatine kinase levels were doubled in both groups (Ptime < .01). Furthermore, the training intervention improved countermovement jump performance and maximal voluntary dynamic contraction by respectively 8% and 10% (Ptime < .01) and increased serum procollagen type 1N-terminal peptide concentration by 10% (Ptime < .01). However, no differences were found for any of the outcomes between whey and whey protein + collagen peptides. In conclusion, substituting a portion of whey protein for collagen peptide, within a similar total protein dose, improved neither indices of eccentric muscle damage nor functional outcomes during eccentric training.

The muscle protein synthetic response following corn protein ingestion does not differ from milk protein in healthy, young adults

Plant-derived proteins are generally believed to possess lesser anabolic properties when compared with animal-derived proteins. This is, at least partly, attributed to the lower leucine content of most plant-derived proteins. Corn protein has a leucine content that is highest among most plant-derived proteins and it even exceeds the levels observed in animal-derived proteins such as whey protein. Therefore, this study aimed to compare muscle protein synthesis rates following the ingestion of 30 g corn protein and a 30 g blend of corn plus milk protein with 30 g milk protein. In a randomized, double blind, parallel-group design, 36 healthy young males (26 ± 4 y) received primed continuous L-[ring-13C6]-phenylalanine infusions and ingested 30 g corn protein (CORN), 30 g milk protein (MILK), or a 30 g proteinblend with 15 g corn plus 15 g milk protein (CORN + MILK). Blood and muscle biopsies were collected for 5 h following protein ingestion to assess post-prandial plasma amino acid profiles and myofibrillar protein synthesis rates. The results show that Ingestion of protein increased myofibrillar protein synthesis rates from basal post-absorptive values in all treatments(P < 0.001). Post-prandial myofibrillar protein synthesis rates did not differ between CORN vs MILK (0.053 ± 0.013 vs 0.053 ± 0.013%∙h-1, respectively; t-test P = 0.90), or between CORN + MILK vs MILK (0.052 ± 0.024 vs 0.053 ± 0.013%∙h-1, respectively; t-test P = 0.92). Ingestion of 30 g corn protein, 30 g milk protein, or a blend of 15 g corn plus 15 g milk protein robustly increases muscle protein synthesis rates in young males. The muscle protein synthetic response to the ingestion of 30 g corn-derived protein does not differ from the ingestion of an equivalent amount of milk protein in healthy, young males. Clinical Trial Registry number. NTR6548 (registration date: 27-06-2017) https://www.trialregister.nl/ .

The Muscle Protein Synthetic Response to the Ingestion of a Plant-Derived Protein Blend Does Not Differ from an Equivalent Amount of Milk Protein in Healthy Young Males

BACKGROUND

Plant-derived proteins are considered to have lesser anabolic properties when compared with animal-derived proteins. The attenuated rise in muscle protein synthesis rates following ingestion of plant-derived compared with animal-derived protein has been, at least partly, attributed to deficiencies in specific amino acids such as leucine, lysine, and/or methionine. Combining different plant-derived proteins could provide plant-derived protein blends with a more balanced amino acid profile.

OBJECTIVES

This study aimed to compare postprandial muscle protein synthesis rates following the ingestion of 30 g milk protein with a 30 g blend combining wheat, corn, and pea protein in healthy young men.

METHODS

In a randomized, double-blind, parallel-group design, 24 young males (aged 24 ± 4 y) received a primed continuous l-[ring-13C6]-phenylalanine infusion after which they ingested 30 g milk protein (MILK) or a 30 g plant-derived protein blend combining 15 g wheat, 7.5 g corn, and 7.5 g pea protein (PLANT-BLEND). Blood and muscle biopsies were collected frequently for 5 h to assess postprandial plasma amino acid profiles (secondary outcome) and subsequent muscle protein synthesis rates (primary outcome). Data were analyzed by 2-factor repeated measures ANOVA and 2-samples t tests.

RESULTS

MILK increased plasma essential amino acid concentrations more than PLANT-BLEND over the 5 h postprandial period (incremental AUC = 151 ± 31 compared with 79 ± 12 mmol·300 min·L-1, respectively; P < 0.001). Ingestion of both MILK and PLANT-BLEND increased myofibrillar protein synthesis rates (P < 0.001), with no significant differences between treatments (0.053 ± 0.013%/h and 0.064 ± 0.016%/h, respectively; P = 0.08).

CONCLUSIONS

Ingestion of 30 g plant-derived protein blend combining wheat-, corn-, and pea-derived protein increases muscle protein synthesis rates in healthy young males. The muscle protein synthetic response to the ingestion of 30 g of this plant-derived protein blend does not differ from the ingestion of an equivalent amount of a high-quality animal-derived protein.Clinical trial registry number for Nederlands Trial Register: NTR6548 (https://trialsearch.who.int/Trial2.aspx?TrialID=NTR6548).

Short communication: Leucine, but not muscle contractions, stimulates protein synthesis in isolated EDL muscles from golden geckos

Resistance exercise and protein ingestion stimulate muscle protein synthesis in mammals and the combination of both stimuli exert an additive effect. However, mechanisms regulating muscle mass may be different in ectothermic vertebrates because these animals are adapted to low energy consumption, short bouts of physical activity, and prolonged periods of inactivity. Here, we investigated the effects of administration of leucine and simulated resistance exercise induced by electrical stimulation (ES) on protein synthesis rate in isolated extensor digitorum longus muscle from golden geckos (Gekko badenii). Muscles were placed in Krebs-Ringer buffer equilibrated with O₂ (97%) and CO₂ (3%) at 30 °C. One muscle from each animal was subjected to one of three interventions: 1) administration of leucine (0.5 mM) at rest, 2) isometric contractions evoked by ES, or 3) a combination of contractions and leucine, while the contralateral muscle served as untreated control. The rate of protein synthesis was measured through pyromycin-labeling. Administration of leucine led to a 2.75 (±1.88)-fold rise in protein synthesis rate in inactive muscles, whereas isometric contractions had no effect (0.67 ± 0.37-fold). The combination of isometric contractions and leucine did not affect protein synthesis rate (1.02 ± 0.34-fold), suggesting that muscle contractions attenuated the positive influence of leucine. Our study identifies leucine as a potent positive regulator of muscle protein synthesis in golden geckos, but also demonstrates that muscle contraction is not. More studies should be conducted in other taxonomic groups of ectothermic vertebrates to identify whether this is a general pattern.

“Food First but Not Always Food Only”: Recommendations for Using Dietary Supplements in Sport

The term “food first” has been widely accepted as the preferred strategy within sport nutrition, although there is no agreed definition of this and often limited consideration of the implications. We propose that food first should mean “where practically possible, nutrient provision should come from whole foods and drinks rather than from isolated food components or dietary supplements.” There are many reasons to commend a food first strategy, including the risk of supplement contamination resulting in anti-doping violations. However, a few supplements can enhance health and/or performance, and therefore a food only approach could be inappropriate. We propose six reasons why a food only approach may not always be optimal for athletes: (a) some nutrients are difficult to obtain in sufficient quantities in the diet, or may require excessive energy intake and/or consumption of other nutrients; (b) some nutrients are abundant only in foods athletes do not eat/like; (c) the nutrient content of some foods with established ergogenic benefits is highly variable; (d) concentrated doses of some nutrients are required to correct deficiencies and/or promote immune tolerance; (e) some foods may be difficult to consume immediately before, during or immediately after exercise; and (f) tested supplements could help where there are concerns about food hygiene or contamination. In these situations, it is acceptable for the athlete to consider sports supplements providing that a comprehensive risk minimization strategy is implemented. As a consequence, it is important to stress that the correct terminology should be “food first but not always food only.”

No differences in muscle protein synthesis rates following ingestion of wheat protein, milk protein, and their protein blend in healthy, young males

Plant-derived proteins have been suggested to have less anabolic properties when compared with animal-derived proteins. Whether blends of plant- and animal-derived proteins can compensate for their lesser anabolic potential has not been assessed. The present study compares post-prandial muscle protein synthesis rates following the ingestion of milk protein with wheat protein or a blend of wheat plus milk protein in healthy, young males. In a randomised, double-blind, parallel-group design, 36 males (23 (sd 3) years) received a primed continuous L-[ring-13C6]-phenylalanine infusion after which they ingested 30 g milk protein (MILK), 30 g wheat protein (WHEAT) or a 30 g blend combining 15 g wheat plus 15 g milk protein (WHEAT+MILK). Blood and muscle biopsies were collected frequently for 5 h to assess post-prandial plasma amino acid profiles and subsequent myofibrillar protein synthesis rates. Ingestion of protein increased myofibrillar protein synthesis rates in all treatments (P < 0·001). Post-prandial myofibrillar protein synthesis rates did not differ between MILK v. WHEAT (0·053 (sd 0·013) v. 0·056 (sd 0·012) %·h-1, respectively; t test P = 0·56) or between MILK v. WHEAT+MILK (0·053 (sd 0·013) v. 0·059 (sd 0·025) %·h-1, respectively; t test P = 0·46). In conclusion, ingestion of 30 g milk protein, 30 g wheat protein or a blend of 15 g wheat plus 15 g milk protein increases muscle protein synthesis rates in young males. Furthermore, muscle protein synthesis rates following the ingestion of 30 g milk protein do not differ from rates observed after ingesting 30 g wheat protein or a blend with 15 g milk plus 15 g wheat protein in healthy, young males.

Potential health benefits of edible insects

Animal-based foods have traditionally been viewed as dietary staples because they provide many essential nutrients; however, edible insects have the potential to serve as healthy, sustainable alternatives to these because of their nutrient contents. Edible insects may have superior health benefits due to their high levels of vitamin B₁₂, iron, zinc, fiber, essential amino acids, omega-3 and omega-6 fatty acids, and antioxidants. The addition of edible insects such as crickets to the human diet could offer a myriad of environmental and nutritional benefits including an overall reduction in greenhouse gas emissions, decreased agricultural use of land and water, improved prevention and management of chronic diseases like diabetes, cancer, and cardiovascular disease, and enhanced immune function. Future research should aim to understand the beneficial effects of whole insects or insect isolates in comparison to traditional animal- and plant-based foodstuffs. Ultimately, insects have the potential to be used as meat substitutes or dietary supplements, resulting in human health and environmental benefits. The purpose of this review is to provide additional insight on the nutrient composition of edible insects, their potential use as meat substitutes or dietary supplements, the associated health and wellness benefits, and their potential role in exercise performance.

UEFA expert group statement on nutrition in elite football. Current evidence to inform practical recommendations and guide future research

Football is a global game which is constantly evolving, showing substantial increases in physical and technical demands. Nutrition plays a valuable integrated role in optimising performance of elite players during training and match-play, and maintaining their overall health throughout the season. An evidence-based approach to nutrition emphasising, a 'food first' philosophy (ie, food over supplements), is fundamental to ensure effective player support. This requires relevant scientific evidence to be applied according to the constraints of what is practical and feasible in the football setting. The science underpinning sports nutrition is evolving fast, and practitioners must be alert to new developments. In response to these developments, the Union of European Football Associations (UEFA) has gathered experts in applied sports nutrition research as well as practitioners working with elite football clubs and national associations/federations to issue an expert statement on a range of topics relevant to elite football nutrition: (1) match day nutrition, (2) training day nutrition, (3) body composition, (4) stressful environments and travel, (5) cultural diversity and dietary considerations, (6) dietary supplements, (7) rehabilitation, (8) referees and (9) junior high-level players. The expert group provide a narrative synthesis of the scientific background relating to these topics based on their knowledge and experience of the scientific research literature, as well as practical experience of applying knowledge within an elite sports setting. Our intention is to provide readers with content to help drive their own practical recommendations. In addition, to provide guidance to applied researchers where to focus future efforts.

Challenging energy balance - during sensitivity to food reward and modulatory factors implying a risk for overweight - during body weight management including dietary restraint and medium-high protein diets

Energy balance is a key concept in the etiology and prevalence of obesity and its co-morbidities, as well as in the development of possible treatments. If energy intake exceeds energy expenditure, a positive energy balance develops and the risk for overweight, obesity, and its co-morbidities increases. Energy balance is determined by energy homeostasis, and challenged by sensitivity to food reward, and to modulatory factors such as circadian misalignment, high altitude, environmental temperature, and physical activity. Food reward and circadian misalignment increase the risk for overweight and obesity, while high altitude, changes in environmental temperature, or physical activity modulate energy balance in different directions. Modulations by hypobaric hypoxia, lowering environmental temperature, or increasing physical activity have been hypothesized to contribute to body weight loss and management, yet no clear evidence has been shown. Dietary approach as part of a lifestyle approach for body weight management should imply reduction of energy intake including control of food reward, thereby sustaining satiety and fat free body mass, sustaining energy expenditure. Green tea catechins and capsaicin in red pepper in part meet these requirements by sustaining energy expenditure and increasing fat oxidation, while capsaicin also suppresses hunger and food intake. Protein intake of at least 0,8 g/kg body weight meets these requirements in that it, during decreased energy intake, increases food intake control including control of food reward, and counteracts adaptive thermogenesis. Prevention of overweight and obesity is underscored by dietary restraint, implying control of sensitivity to challenges to energy balance such as food reward and circadian misalignment. Treatment of overweight and obesity may be possible using a medium-high protein diet (0,8-1,2 g/kg), together with increased dietary restraint, while controlling challenges to energy balance.

The Effect of Carbohydrate Ingestion Following Eccentric Resistance Exercise on AKT/mTOR and ERK Pathways: A Randomized, Double-Blinded, Crossover Study

Purpose: To determine the acute effects of carbohydrate (CHO) ingestion following a bout of maximal eccentric resistance exercise on key anabolic kinases of mammalian target of rapamycin and extracellular signal-regulated kinase (ERK) pathways. The authors’ hypothesis was that the activation of anabolic signaling pathways known to be upregulated by resistance exercise would be further stimulated by the physiological hyperinsulinemia resulting from CHO supplementation. Methods: Ten resistance-trained men were randomized in a crossover, double-blind, placebo (PLA)-controlled manner to ingest either a noncaloric PLA or 3 g/kg of CHO beverage throughout recovery from resistance exercise. Muscle biopsies were collected at rest, immediately after a single bout of intense lower body resistance exercise, and after 3 hr of recovery. Results: CHO ingestion elevated plasma glucose and insulin concentrations throughout recovery compared with PLA ingestion. The ERK pathway (phosphorylation of ERK1/2 [Thr202/Tyr204], RSK [Ser380], and p70S6K [Thr421/Ser424]) was markedly activated immediately after resistance exercise, without any effect of CHO supplementation. The phosphorylation state of AKT (Thr308) was unchanged postexercise in the PLA trial and increased at 3 hr of recovery above resting with ingestion of CHO compared with PLA. Despite stimulating-marked phosphorylation of AKT, CHO ingestion did not enhance resistance exercise–induced phosphorylation of p70S6K (Thr389) and rpS6 (Ser235/236 and Ser240/244). Conclusion: CHO supplementation after resistance exercise and hyperinsulinemia does not influence the ERK pathway nor the mTORC1 target p70S6K and its downstream proteins, despite the increased AKT phosphorylation.

The Muscle Protein Synthetic Response to Whey Protein Ingestion Is Greater in Middle-Aged Women Compared With Men

RATIONALE

Muscle mass maintenance is largely regulated by the postprandial rise in muscle protein synthesis rates. It remains unclear whether postprandial protein handling differs between women and men.

METHODS

Healthy men (43 ± 3 years; body mass index, 23.4 ± 0.4 kg/m2; n = 12) and women (46 ± 2 years; body mass index, 21.3 ± 0.5 kg/m2; n = 12) received primed continuous infusions of l-[ring-2H5]-phenylalanine and l-[ring-3,5-2H2]-tyrosine and ingested 25 g intrinsically l-[1-13C]-phenylalanine-labeled whey protein. Blood samples and muscle biopsies were collected to assess dietary protein digestion and amino acid absorption kinetics as well as basal and postprandial myofibrillar protein synthesis rates.

RESULTS

Plasma phenylalanine and leucine concentrations rapidly increased after protein ingestion (both P < 0.001), with no differences between middle-aged women and men (Time × Sex, P = 0.307 and 0.529, respectively). The fraction of dietary protein-derived phenylalanine that appeared in the circulation over the 5-hour postprandial period averaged 56 ± 1% and 53 ± 1% in women and men, respectively (P = 0.145). Myofibrillar protein synthesis rates increased (Time, P = 0.010) from 0.035 ± 0.004%/h and 0.030 ± 0.002%/h in the postabsorptive state (t test, P = 0.319) to 0.045 ± 0.002%/h and 0.034 ± 0.002%/h in the 5-hour postprandial phase in middle-aged women and men, respectively, with higher postprandial myofibrillar protein synthesis rates in women compared with men (t test, P = 0.005). Middle-aged women showed a greater increase in myofibrillar protein synthesis rates during the early (0 to 2 hours) postprandial period compared with men (Time × Sex, P = 0.001).

CONCLUSIONS

There are no differences in postabsorptive myofibrillar protein synthesis rates between middle-aged women and men. The myofibrillar protein synthetic response to the ingestion of 25 g whey protein is greater in women than in men.

Skeletal muscle performance and ageing

The world population is ageing rapidly. As society ages, the incidence of physical limitations is dramatically increasing, which reduces the quality of life and increases healthcare expenditures. In western society, ~30% of the population over 55 years is confronted with moderate or severe physical limitations. These physical limitations increase the risk of falls, institutionalization, co-morbidity, and premature death. An important cause of physical limitations is the age-related loss of skeletal muscle mass, also referred to as sarcopenia. Emerging evidence, however, clearly shows that the decline in skeletal muscle mass is not the sole contributor to the decline in physical performance. For instance, the loss of muscle strength is also a strong contributor to reduced physical performance in the elderly. In addition, there is ample data to suggest that motor coordination, excitation-contraction coupling, skeletal integrity, and other factors related to the nervous, muscular, and skeletal systems are critically important for physical performance in the elderly. To better understand the loss of skeletal muscle performance with ageing, we aim to provide a broad overview on the underlying mechanisms associated with elderly skeletal muscle performance. We start with a system level discussion and continue with a discussion on the influence of lifestyle, biological, and psychosocial factors on elderly skeletal muscle performance. Developing a broad understanding of the many factors affecting elderly skeletal muscle performance has major implications for scientists, clinicians, and health professionals who are developing therapeutic interventions aiming to enhance muscle function and/or prevent mobility and physical limitations and, as such, support healthy ageing.

Dietary Protein and Energy Balance in Relation to Obesity and Co-morbidities

Dietary protein is effective for body-weight management, in that it promotes satiety, energy expenditure, and changes body-composition in favor of fat-free body mass. With respect to body-weight management, the effects of diets varying in protein differ according to energy balance. During energy restriction, sustaining protein intake at the level of requirement appears to be sufficient to aid body weight loss and fat loss. An additional increase of protein intake does not induce a larger loss of body weight, but can be effective to maintain a larger amount of fat-free mass. Protein induced satiety is likely a combined expression with direct and indirect effects of elevated plasma amino acid and anorexigenic hormone concentrations, increased diet-induced thermogenesis, and ketogenic state, all feed-back on the central nervous system. The decline in energy expenditure and sleeping metabolic rate as a result of body weight loss is less on a high-protein than on a medium-protein diet. In addition, higher rates of energy expenditure have been observed as acute responses to energy-balanced high-protein diets. In energy balance, high protein diets may be beneficial to prevent the development of a positive energy balance, whereas low-protein diets may facilitate this. High protein-low carbohydrate diets may be favorable for the control of intrahepatic triglyceride IHTG in healthy humans, likely as a result of combined effects involving changes in protein and carbohydrate intake. Body weight loss and subsequent weight maintenance usually shows favorable effects in relation to insulin sensitivity, although some risks may be present. Promotion of insulin sensitivity beyond its effect on body-weight loss and subsequent body-weight maintenance seems unlikely. In conclusion, higher-protein diets may reduce overweight and obesity, yet whether high-protein diets, beyond their effect on body-weight management, contribute to prevention of increases in non-alcoholic fatty liver disease NAFLD, type 2 diabetes and cardiovascular diseases is inconclusive.

Comparing the effects of two distinct eccentric modalities to traditional resistance training in resistance trained, higher functioning older adults

BACKGROUND

The effects of eccentric resistance exercise are of interest in the older adult cohort, but to our knowledge, there is no research on the relative effects of different eccentric modalities on a range of outcomes in higher functioning, resistance trained older adults.

METHODS

33 resistance-trained older adults (aged 67±4.5years) were randomized into one of three supervised training groups: traditional (TRE), eccentric only (ERE) or eccentrically biased resistance exercise (EBRE) on a 45°, plate-loaded leg press machine. Participants trained twice per week with maximal strength, functional capacity, body composition and blood biomarkers measured before and after the eight-week intervention.

RESULTS

Both eccentric and concentric strength, and important functional tasks for independent living significantly improved independent of group. Body composition and blood biomarkers were found to significantly improve in the EBRE group only however, no statistical differences were found between groups.

CONCLUSION

Compared to traditional resistance training, the two eccentric modalities investigated here were equally effective for improvements in maximum muscular strength, functional capacity, body composition and metabolic biomarkers. When training the resistance trained older adult, very heavy isoinertial external loads (at least 70% of one repetition maximum) are effective irrespective of contraction mode. With heavy strength training, resistance trained older adults can continue to expect improvements in health and function.

Variation in Protein Origin and Utilization: Research and Clinical Application

Muscle health can be rapidly compromised in clinical environments. Modifiable strategies to preserve metabolic homeostasis in adult patient populations include physical activity and pharmacologic support; however, optimizing dietary practices, or more specifically protein intake, is a necessary prerequisite for any other treatment strategy to be fully effective. Simply increasing protein intake is a well-intentioned but often unfocused strategy to protect muscle health in an intensive care setting. Protein quality is a frequently overlooked factor with the potential to differentially influence health outcomes. Quality can be assessed by a variety of techniques, with digestible indispensable amino acid score being the current and most comprehensive technique endorsed by the Food and Agriculture Organization. In practical terms, animal-based proteins are consistently scored higher in quality compared with incomplete proteins, regardless of the assessment method. Consequently, choosing parenteral and/or enteral feeding options that contain high-quality proteins, rich in the branched-chain amino acid leucine, may help establish a dietary framework with the potential to support clinical practice and improve health outcomes in critically ill patients.

Protein intake and lean body mass preservation during energy intake restriction in overweight older adults

BACKGROUND

Dietary-induced weight loss is generally accompanied by a decline in skeletal muscle mass. The loss of muscle mass leads to a decline in muscle strength and impairs physical performance. A high dietary protein intake has been suggested to allow muscle mass preservation during energy intake restriction.

OBJECTIVE

To investigate the impact of increasing dietary protein intake on lean body mass, strength and physical performance during 12 weeks of energy intake restriction in overweight older adults.

DESIGN

Sixty-one overweight and obese men and women (63±5 years) were randomly assigned to either a high protein diet (HP; 1.7 g kg(-1) per day; n=31) or normal protein diet (NP; 0.9 g kg(-1) per day; n=30) during a 12-week 25% energy intake restriction. During this controlled dietary intervention, 90% of the diet was provided by the university. At baseline and after the intervention, body weight, lean body mass (dual-energy X-ray absorptiometry), leg strength (1-repetition maximum), physical performance (Short Physical Performance Battery, 400 m) and habitual physical activity (actigraph) were assessed.

RESULTS

Body weight declined in both groups with no differences between the HP and NP groups (-8.9±2.9 versus -9.1±3.4 kg, respectively; P=0.584). Lean body mass declined by 1.8±2.2 and 2.1±1.4 kg, respectively, with no significant differences between groups (P=0.213). Leg strength had decreased during the intervention by 8.8±14.0 and 8.9±12.8 kg, with no differences between groups (P=0.689). Physical performance as measured by 400 m walking speed improved in both groups, with no differences between groups (P=0.219).

CONCLUSIONS

Increasing protein intake above habitual intake levels (0.9 g kg(-1) per day) does not preserve lean body mass, strength or physical performance during prolonged energy intake restriction in overweight older adults.

Collagen peptide supplementation in combination with resistance training improves body composition and increases muscle strength in elderly sarcopenic men: a randomised controlled trial

Protein supplementation in combination with resistance training may increase muscle mass and muscle strength in elderly subjects. The objective of this study was to assess the influence of post-exercise protein supplementation with collagen peptides v. placebo on muscle mass and muscle function following resistance training in elderly subjects with sarcopenia. A total of fifty-three male subjects (72·2 (sd 4·68) years) with sarcopenia (class I or II) completed this randomised double-blind placebo-controlled study. All the participants underwent a 12-week guided resistance training programme (three sessions per week) and were supplemented with either collagen peptides (treatment group (TG)) (15 g/d) or silica as placebo (placebo group (PG)). Fat-free mass (FFM), fat mass (FM) and bone mass (BM) were measured before and after the intervention using dual-energy X-ray absorptiometry. Isokinetic quadriceps strength (IQS) of the right leg was determined and sensory motor control (SMC) was investigated by a standardised one-leg stabilisation test. Following the training programme, all the subjects showed significantly higher (P<0·01) levels for FFM, BM, IQS and SMC with significantly lower (P<0·01) levels for FM. The effect was significantly more pronounced in subjects receiving collagen peptides: FFM (TG +4·2 (sd 2·31) kg/PG +2·9 (sd 1·84) kg; P<0·05); IQS (TG +16·5 (sd 12·9) Nm/PG +7·3 (sd 13·2) Nm; P<0·05); and FM (TG -5·4 (sd 3·17) kg/PG -3·5 (sd 2·16) kg; P<0·05). Our data demonstrate that compared with placebo, collagen peptide supplementation in combination with resistance training further improved body composition by increasing FFM, muscle strength and the loss in FM.

The effects of protein supplements on muscle mass, strength, and aerobic and anaerobic power in healthy adults: a systematic review

BACKGROUND

Protein supplements are frequently consumed by athletes and recreationally active adults to achieve greater gains in muscle mass and strength and improve physical performance.

OBJECTIVE

This review provides a systematic and comprehensive analysis of the literature that tested the hypothesis that protein supplements accelerate gains in muscle mass and strength resulting in improvements in aerobic and anaerobic power. Evidence statements were created based on an accepted strength of recommendation taxonomy.

DATA SOURCES

English language articles were searched through PubMed and Google Scholar using protein and supplements together with performance, exercise, strength, and muscle, alone or in combination as keywords. Additional articles were retrieved from reference lists found in these papers.

STUDY SELECTION

Studies recruiting healthy adults between 18 and 50 years of age that evaluated the effects of protein supplements alone or in combination with carbohydrate on a performance metric (e.g., one repetition maximum or isometric or isokinetic muscle strength), metrics of body composition, or measures of aerobic or anaerobic power were included in this review. The literature search identified 32 articles which incorporated test metrics that dealt exclusively with changes in muscle mass and strength, 5 articles that implemented combined resistance and aerobic training or followed participants during their normal sport training programs, and 1 article that evaluated changes in muscle oxidative enzymes and maximal aerobic power.

STUDY APPRAISAL AND SYNTHESIS METHODS

All papers were read in detail, and examined for experimental design confounders such as dietary monitoring, history of physical training (i.e., trained and untrained), and the number of participants studied. Studies were also evaluated based on the intensity, frequency, and duration of training, the type and timing of protein supplementation, and the sensitivity of the test metrics.

RESULTS

For untrained individuals, consuming supplemental protein likely has no impact on lean mass and muscle strength during the initial weeks of resistance training. However, as the duration, frequency, and volume of resistance training increase, protein supplementation may promote muscle hypertrophy and enhance gains in muscle strength in both untrained and trained individuals. Evidence also suggests that protein supplementation may accelerate gains in both aerobic and anaerobic power.

LIMITATIONS

To demonstrate measureable gains in strength and performance with exercise training and protein supplementation, many of the studies reviewed recruited untrained participants. Since skeletal muscle responses to exercise and protein supplementation differ between trained and untrained individuals, findings are not easily generalized for all consumers who may be considering the use of protein supplements.

CONCLUSIONS

This review suggests that protein supplementation may enhance muscle mass and performance when the training stimulus is adequate (e.g., frequency, volume, duration), and dietary intake is consistent with recommendations for physically active individuals.

Combined effects of androgen anabolic steroids and physical activity on the hypothalamic-pituitary-gonadal axis

Analysing effects of pharmaceutical substances and training on feedback mechanisms of the hypothalamic-pituitary-gonadal axis may be helpful to quantify the benefit of strategies preventing loss of muscle mass, and in the fight against doping. In this study we analysed combined effects of anabolic steroids and training on the hypothalamic-pituitary-gonadal axis. Therefore intact male Wistar rats were dose-dependently treated with metandienone, estradienedione and the selective androgen receptor modulator (SARM) S-1. In serum cortisol, testosterone, 17β-estradiol (E2), prolactin, inhibin B, follicle-stimulating hormone (FSH), luteinizing hormone (LH), Insulin-like growth factor 1 (IGF-1), and thyroxine (T4) concentrations were determined. Six human volunteers were single treated with 1-androstenedione. In addition abusing and clean body builders were analysed. Serum concentrations of inhibin B, IGF-1, cortisol, prolactin, T4, thyroid-stimulating hormone (TSH), testosterone and LH were determined. In rats, administration of metandienone, estradienedione and S-1 resulted in an increase of muscle fiber diameter. Metandienone and estradienedione but not S-1 administration significantly decreases LH and inhibin B serum concentration. Administration of estradienedione resulted in an increase of E2 and S-1 in an increase of cortisol. Single administration of 1-androstenedione in humans decreased cortisol and inhibin B serum concentrations. LH was not affected. In abusing body builders a significantly decrease of LH, TSH and inhibin B and an increase of prolactin, IGF-1 and T4 was detected. In clean body builders only T4 and TSH were affected.

Pea proteins oral supplementation promotes muscle thickness gains during resistance training: a double-blind, randomized, Placebo-controlled clinical trial vs. Whey protein

Background

The effects of protein supplementation on muscle thickness and strength seem largely dependent on its composition. The current study aimed at comparing the impact of an oral supplementation with vegetable Pea protein (NUTRALYS®) vs. Whey protein and Placebo on biceps brachii muscle thickness and strength after a 12-week resistance training program.

Methods

One hundred and sixty one males, aged 18 to 35 years were enrolled in the study and underwent 12 weeks of resistance training on upper limb muscles. According to randomization, they were included in the Pea protein (n = 53), Whey protein (n = 54) or Placebo (n = 54) group. All had to take 25 g of the proteins or placebo twice a day during the 12-week training period. Tests were performed on biceps muscles at inclusion (D0), mid (D42) and post training (D84). Muscle thickness was evaluated using ultrasonography, and strength was measured on an isokinetic dynamometer.

Results

Results showed a significant time effect for biceps brachii muscle thickness (P < 0.0001). Thickness increased from 24.9 ± 3.8 mm to 26.9 ± 4.1 mm and 27.3 ± 4.4 mm at D0, D42 and D84, respectively, with only a trend toward significant differences between groups (P = 0.09). Performing a sensitivity study on the weakest participants (with regards to strength at inclusion), thickness increases were significantly different between groups (+20.2 ± 12.3%, +15.6 ± 13.5% and +8.6 ± 7.3% for Pea, Whey and Placebo, respectively; P < 0.05). Increases in thickness were significantly greater in the Pea group as compared to Placebo whereas there was no difference between Whey and the two other conditions. Muscle strength also increased with time with no statistical difference between groups.

Conclusions

In addition to an appropriate training, the supplementation with pea protein promoted a greater increase of muscle thickness as compared to Placebo and especially for people starting or returning to a muscular strengthening. Since no difference was obtained between the two protein groups, vegetable pea proteins could be used as an alternative to Whey-based dietary products.

Trial registration

The present trial has been registered at ClinicalTrials.gov (NCT02128516).

Effects of protein in combination with carbohydrate supplements on acute or repeat endurance exercise performance: a systematic review

BACKGROUND

Protein supplements are consumed frequently by athletes and recreationally active adults for various reasons, including improved exercise performance and recovery after exercise. Yet, far too often, the decision to purchase and consume protein supplements is based on marketing claims rather than available evidence-based research.

OBJECTIVE

The purpose of this review was to provide a systematic and comprehensive analysis of the literature that tested the hypothesis that protein supplements, when combined with carbohydrate, directly enhance endurance performance by sparing muscle glycogen during exercise and increasing the rate of glycogen restoration during recovery. The analysis was used to create evidence statements based on an accepted strength of recommendation taxonomy.

DATA SOURCES

English language articles were searched with PubMed and Google Scholar using protein and supplements together with performance, exercise, competition, and muscle, alone or in combination as keywords. Additional articles were retrieved from reference lists found in these papers.

STUDY SELECTION

Inclusion criteria specified recruiting healthy active adults less than 50 years of age and evaluating the effects of protein supplements in combination with carbohydrate on endurance performance metrics such as time-to-exhaustion, time-trial, or total power output during sprint intervals. The literature search identified 28 articles, of which 26 incorporated test metrics that permitted exclusive categorization into one of the following sections: ingestion during an acute bout of exercise (n = 11) and ingestion during and after exercise to affect subsequent endurance performance (n = 15). The remaining two articles contained performance metrics that spanned both categories.

STUDY APPRAISAL AND SYNTHESIS METHODS

All papers were read in detail and searched for experimental design confounders such as energy content of the supplements, dietary control, use of trained or untrained participants, number of subjects recruited, direct measures of muscle glycogen utilization and restoration, and the sensitivity of the test metrics to explain the discrepant findings.

RESULTS

Our evidence statements assert that when carbohydrate supplementation was delivered at optimal rates during or after exercise, protein supplements provided no further ergogenic effect, regardless of the performance metric used. In addition, the limited data available suggested recovery of muscle glycogen stores together with subsequent rate of utilization during exercise is not related to the potential ergogenic effect of protein supplements.

LIMITATIONS

Many studies lacked ability to measure direct effects of protein supplementation on muscle metabolism through determination of muscle glycogen, kinetic assessments of protein turnover, or changes in key signaling proteins, and therefore could not substantiate changes in rates of synthesis or degradation of protein. As a result, the interpretation of their data was often biased and inconclusive since they lacked ability to test the proposed underlying mechanism of action.

CONCLUSIONS

When carbohydrate is delivered at optimal rates during or after endurance exercise, protein supplements appear to have no direct endurance performance enhancing effect.

Tracking of environmental determinants of bone structure and strength development in healthy boys: an eight-year follow up study on the positive interaction between physical activity and protein intake from prepuberty to mid-late adolescence

High protein (> median:Hprot) vs. moderate (< median:MProt) intake was shown to enhance the positive impact of high physical activity (HPA) on proximal femur BMC/aBMD/Area in healthy prepubertal boys. We tested the hypothesis that this synergistic effect would track and influence bone structure and strength until mid-adolescence. BMC/aBMD/Area was measured at femoral neck (FN) and total hip (TotHip) by DXA in 176 boys at 7.4 ± 0.4 and 15.2 ± 0.5 years (± SD). Distal tibia (DistTib) microstructure and strength were also assessed at 15.2 years by high-resolution peripheral computerized tomography (HR-pQCT) and micro-finite element analysis (µFEA). The positive impact of HProt vs. MProt on FN and TotHip BMC/aBMD/Area, recorded at 7.4 years remained unabated at 15.2 years. At this age, at DistTib, HProt-HPA vs. MProt-HPA was associated (p < 0.001) with larger cross-sectional area (CSA, mm(2) ), trabecular number (Tb.N, mm(-1) ) and lower trabecular separation (Tb.Sp, µm). The interaction between physical activity and protein intake was significant for CSA (p = 0.012) and Tb.N (p = 0.043). Under MProt (38.0 ± 6.9 g.d(-1)), a difference in PA from 168 ± 40 to 303 ± 54 kcal.d(-1) was associated with greater stiffness (kN/mm) and failure load (N) of +0.16 and +0.14 Z-score, respectively. In contrast, under HProt (56.2 ± 9.5 g.d(-1) ), a difference in PA of similar magnitude, from 167 ± 33 to 324 ± 80 kcal.d(-1) , was associated with a larger difference in stiffness and failure load of +0.50 and +0.57 Z-score, respectively. In conclusion, the positive influence of relatively HProt on the impact of HPA on proximal femur macrostructure tracks from prepuberty to mid-late puberty. At this stage, the impact of HProt on HPA is also associated with microstructural changes that should confer greater mechanical resistance to weight-bearing bones. These results underscore the importance of protein intake and exercise synergistic interaction in the early prevention of adult osteoporosis.

Evidence for an interaction between exercise and nutrition for improving bone and muscle health

Regular exercise and adequate nutrition, particularly dietary calcium, vitamin D, and protein, are prescribed as strategies to optimize peak bone mass and maintain bone and muscle health throughout life. Although the mechanism of action of exercise and nutrition on bone and muscle health are different-exercise has a site-specific modifying effect, whereas nutrition has a permissive generalized effect-there is evidence that combining calcium (or calcium rich dairy foods) or dietary protein with exercise can have a synergetic effect on bone mass and muscle health, respectively. However, many questions still remain as to whether there is a threshold level for these nutrients to optimize the exercise-induced gains. Further studies are also needed to investigate whether other dietary factors, such as vitamin D, soy isoflavones or omega-3 fatty acids, or a multinutrient supplement, can enhance the effects of exercise on bone and muscle health.

The association of early life supplemental nutrition with lean body mass and grip strength in adulthood: evidence from APCAPS

In the present study, we examined the associations of early nutrition with adult lean body mass (LBM) and muscle strength in a birth cohort that was established to assess the long-term impact of a nutrition program. Participants (n = 1,446, 32% female) were born near Hyderabad, India, in 29 villages from 1987 to 1990, during which time only intervention villages (n = 15) had a government program that offered balanced protein-calorie supplementation to pregnant women and children. Participants’ LBM and appendicular skeletal muscle mass were measured using dual energy x-ray absorptiometry; grip strength and information on lifestyle indicators, including diet and physical activity level, were also obtained. Ages (mean = 20.3 years) and body mass indexes (weight (kg)/height (m)²; mean = 19.5) of participants in 2 groups were similar. Current dietary energy intake was higher in the intervention group. Unadjusted LBM and grip strength were similar in 2 groups. After adjustment for potential confounders, the intervention group had lower LBM (β = −0.75; P = 0.03), appendicular skeletal muscle mass, and grip strength than did controls, but these differences were small in magnitude (<0.1 standard deviation). Multivariable regression analyses showed that current socioeconomic position, energy intake, and physical activity level had a positive association with adult LBM and muscle strength. This study could not detect a “programming” effect of early nutrition supplementation on adult LBM and muscle strength.

Alcohol ingestion impairs maximal post-exercise rates of myofibrillar protein synthesis following a single bout of concurrent training

Introduction

The culture in many team sports involves consumption of large amounts of alcohol after training/competition. The effect of such a practice on recovery processes underlying protein turnover in human skeletal muscle are unknown. We determined the effect of alcohol intake on rates of myofibrillar protein synthesis (MPS) following strenuous exercise with carbohydrate (CHO) or protein ingestion.

Methods

In a randomized cross-over design, 8 physically active males completed three experimental trials comprising resistance exercise (8×5 reps leg extension, 80% 1 repetition maximum) followed by continuous (30 min, 63% peak power output (PPO)) and high intensity interval (10×30 s, 110% PPO) cycling. Immediately, and 4 h post-exercise, subjects consumed either 500 mL of whey protein (25 g; PRO), alcohol (1.5 g·kg body mass⁻¹, 12±2 standard drinks) co-ingested with protein (ALC-PRO), or an energy-matched quantity of carbohydrate also with alcohol (25 g maltodextrin; ALC-CHO). Subjects also consumed a CHO meal (1.5 g CHO·kg body mass⁻¹) 2 h post-exercise. Muscle biopsies were taken at rest, 2 and 8 h post-exercise.

Results

Blood alcohol concentration was elevated above baseline with ALC-CHO and ALC-PRO throughout recovery (P<0.05). Phosphorylation of mTOR^Ser2448 2 h after exercise was higher with PRO compared to ALC-PRO and ALC-CHO (P<0.05), while p70S6K phosphorylation was higher 2 h post-exercise with ALC-PRO and PRO compared to ALC-CHO (P<0.05). Rates of MPS increased above rest for all conditions (∼29–109%, P<0.05). However, compared to PRO, there was a hierarchical reduction in MPS with ALC-PRO (24%, P<0.05) and with ALC-CHO (37%, P<0.05).

Conclusion

We provide novel data demonstrating that alcohol consumption reduces rates of MPS following a bout of concurrent exercise, even when co-ingested with protein. We conclude that alcohol ingestion suppresses the anabolic response in skeletal muscle and may therefore impair recovery and adaptation to training and/or subsequent performance.

Periodized resistance training with and without supplementation improve body composition and performance in older men

PURPOSE

To examine the effects of 12 weeks of periodized resistance training (RT) with and without combined creatine and whey protein supplementation on changes in body composition, muscular strength, and functional performance.

METHODS

Twenty-two male volunteers (68.1 ± 6.1 years) were randomly assigned to one of three groups: RT plus supplementation (RTS, n = 7); RT only (RT, n = 7); or control (C, n = 8). RTS consumed 0.3 g/kg/day of creatine for 5 days followed by 0.07 g/kg/day. RTS also consumed one 35 g liquid protein ready-to-drink daily. RT and RTS trained 3 days/week.

RESULTS

Following 12 weeks of training, there were no significant differences in the main measured outcome variables between RT and RTS. RTS increased relative (% change) lean body mass (LBM, 3.3 ± 3.1 %) compared with C (p = 0.01). Compared to baseline, RT increased LBM at week 6 (60.2 ± 8.3 to 61.6 ± 9.4 kg; p < 0.05), and decreased fat mass (20.8 ± 4.2 to 19.0 ± 3.9 kg; p = 0.05) and percentage body fat at week 12 (25.7 ± 3.8 to 23.8 ± 4.0 %; p = 0.05); RTS increased LBM at week 6 (p < 0.01) and week 12 (56.4 ± 4.3 to 58.2 ± 3.4 kg; p < 0.01), and decreased percentage body fat at week 12 (23.9 ± 4.4 to 22.0 ± 4.4 %; p < 0.01). In addition, compared to C, relative bench press 1-RM increased for RTS (72.4 ± 62.2 %; p < 0.01) and RT (50.1 ± 21.5 %; p = 0.05); relative leg press 1-RM increased for RTS (129.6 ± 39.4 %; p < 0.0001) and RT (112.9 ± 22.7 %; p < 0.0001); RTS increased relative Margaria stair-climbing power (38.3 ± 30.4 %; p < 0.05); and, relative 400-m walk time decreased for RT (-11 ± 9.2 %; p < 0.05) and RTS (-9.6 ± 9.4 %; p = 0.05). RT increased estimated VO2Max at week 6 (p < 0.01) and 12 (34.6 ± 1.9 to 36.4 ± 2.7 ml/kg/min; p = 0.01) compared to baseline. Lastly, RTS increased estimated VO2Max at week 12 (36.3 ± 2.7 to 37.5 ± 3.3 ml/kg/min; p = 0.05) compared to baseline.

CONCLUSION

Creatine and whey protein supplementation may not provide additional benefits in older adults performing periodized RT to augment muscular and functional performance.

The muscle protein synthetic response to the combined ingestion of protein and carbohydrate is not impaired in healthy older men

Aging is associated with a progressive decline in skeletal muscle mass. It has been hypothesized that an attenuated muscle protein synthetic response to the main anabolic stimuli may contribute to the age-related loss of muscle tissue. The aim of the present study was to compare the muscle protein synthetic response following ingestion of a meal-like amount of dietary protein plus carbohydrate between healthy young and older men. Twelve young (21 ± 1 years) and 12 older (75 ± 1 years) men consumed 20 g of intrinsically L-[1-(13)C]phenylalanine-labeled protein with 40 g of carbohydrate. Ingestion of specifically produced intrinsically L-[1-(13)C]phenylalanine-labeled protein allowed us to assess the subsequent incorporation of casein-derived amino acids into muscle protein. Blood samples were collected at regular intervals, with muscle biopsies obtained prior to and 2 and 6 h after protein plus carbohydrate ingestion. The acute post-prandial rise in plasma glucose and insulin concentrations was significantly greater in the older compared with the younger males. Plasma amino acid concentrations increased rapidly following drink ingestion in both groups. However, plasma leucine concentrations were significantly lower at t = 90 min in the older when compared with the young group (P < 0.05). Muscle protein-bound L-[1-(13)C]phenylalanine enrichments increased to 0.0071 ± 0.0016 and 0.0072 ± 0.0013 mole percent excess (MPE) at 2 h and 0.0229 ± 0.0016 and 0.0213 ± 0.0024 MPE at 6 h following ingestion of the intrinsically labeled protein in the young and older males, respectively, with no differences between groups (P > 0.05). We conclude that the use of dietary protein-derived amino acids for muscle protein synthesis is not impaired in healthy older men following intake of protein plus carbohydrate.

Patient Activation through Counseling and Exercise--Acute Leukemia (PACE-AL)--a randomized controlled trial

Background

Patients with acute leukemia experience a substantial symptom burden and are at risk of developing infections throughout the course of repeated cycles of intensive chemotherapy. Physical activity in recent years has been a strategy for rehabilitation in cancer patients to remedy disease and treatment related symptoms and side effects. To date, there are no clinical practice exercise guidelines for patients with acute leukemia undergoing induction and consolidation chemotherapy. A randomized controlled trial is needed to determine if patients with acute leukemia can benefit by a structured and supervised counseling and exercise program.

Methods/design

This paper presents the study protocol: Patient Activation through Counseling and Exercise – Acute Leukemia (PACE-AL) trial, a two center, randomized controlled trial of 70 patients with acute leukemia (35 patients/study arm) following induction chemotherapy in the outpatient setting. Eligible patients will be randomized to usual care or to the 12 week exercise and counseling program. The intervention includes 3 hours + 30 minutes per week of supervised and structured aerobic training (moderate to high intensity 70 - 80%) on an ergometer cycle, strength exercises using hand weights and relaxation exercise. Individual health counseling sessions include a self directed home walk program with a step counter. The primary endpoint is functional performance/exercise capacity (6 minute walk distance). The secondary endpoints are submaximal VO₂ max test, sit to stand and bicep curl test, physical activity levels, patient reported outcomes (quality of life, anxiety and depression, symptom prevalence, intensity and interference). Evaluation of clinical outcomes will be explored including incidence of infection, hospitalization days, body mass index, time to recurrence and survival. Qualitative exploration of patients’ health behavior and experiences.

Discussion

PACE-AL will provide evidence of the effect of exercise and health promotion counseling on functional and physical capacity, the symptom burden and quality of life in patients with acute leukemia during out patient management. The results will inform clinical practice exercise guidelines and rehabilitation programs for patients undergoing treatment for acute leukemia. Optimizing the treatment and care pathway may ease the transition for patients from illness to the resumption of everyday activities.

Trial registration

ClinicalTrials.gov Identifier: NCT01404520.

Preventing malnutrition in home-dwelling elderly individuals

The aim of this article is to provide an overview of the role of the nurse in the identification and prevention of malnutrition in home dwelling elderly individuals. It will examine the causes and prevalence of malnutrition outlining the factors that may place older home-dwelling people at risk of developing this serious nutritional disorder. The remainder of the article will provide an in-depth focussed discussion on the role of the community nurse in the assessment and prevention of malnutrition, with recommendations for the improvement of clinical practice.

Dietary protein digestion and absorption are impaired during acute postexercise recovery in young men

Previously, we demonstrated that exercise can cause small intestinal injury, leading to loss of gut barrier function. The functional consequences of such exercise-induced intestinal injury on subsequent food digestion and absorption are unclear. The present study determined the impact of resistance-type exercise on small intestinal integrity and in vivo dietary protein digestion and absorption kinetics. Twenty-four young males ingested 20 g specifically produced intrinsically l-[1-13C]phenylalanine-labeled protein at rest or after performing a single bout of resistance-type exercise. Continuous intravenous infusions with l-[ring-2H5]phenylalanine were employed, and blood samples were collected regularly to assess in vivo protein digestion and absorption kinetics and to quantify plasma levels of intestinal fatty-acid binding protein (I-FABP) as a measure of small intestinal injury. Plasma I-FABP levels were increased after exercise by 35%, reaching peak values of 344 ± 53 pg/ml compared with baseline 254 ± 31 pg/ml ( P < 0.05). In resting conditions, I-FABP levels remained unchanged. Dietary protein digestion and absorption rates were reduced during postexercise recovery when compared with resting conditions ( P < 0.001), with average peak exogenous phenylalanine appearance rates of 0.18 ± 0.04 vs. 0.23 ± 0.03 mmol phenylalanine·kg lean body mass−1·min−1, respectively. Plasma I-FABP levels correlated with in vivo rates of dietary protein digestion and absorption ( r S = −0.57, P < 0.01). Resistance-type exercise induces small intestinal injury in healthy, young men, causing impairments in dietary protein digestion and absorption kinetics during the acute postexercise recovery phase. To the best of our knowledge, this is first evidence that shows that exercise attenuates dietary protein digestion and absorption kinetics during acute postexercise recovery.

Nutritional strategies to attenuate muscle disuse atrophy

Situations such as recovery from injury or illness require otherwise healthy humans to undergo periods of disuse, which lead to considerable losses of skeletal muscle mass and, subsequently, numerous negative health consequences. It has been established that prolonged disuse (>10 days) leads to a decline in basal and postprandial rates of muscle protein synthesis, without an apparent change in muscle protein breakdown. It also seems, however, that an early and transient (1-5 days) increase in basal muscle protein breakdown may also contribute to disuse atrophy. A period of disuse reduces energy requirements and appetite. Consequently, food intake generally declines, resulting in an inadequate dietary protein consumption to allow proper muscle mass maintenance. Evidence suggests that maintaining protein intake during a period of disuse attenuates disuse atrophy. Furthermore, supplementation with dietary protein and/or essential amino acids can be applied to further aid in muscle mass preservation during disuse. Such strategies are of particular relevance to the older patient at risk of developing sarcopenia. More work is required to elucidate the impact of disuse on basal and postprandial rates of muscle protein synthesis and breakdown. Such information will provide novel targets for nutritional interventions to further attenuate muscle disuse atrophy and, as such, support healthy aging.

The role of mTORC1 in regulating protein synthesis and skeletal muscle mass in response to various mechanical stimuli

Skeletal muscle plays a fundamental role in mobility, disease prevention, and quality of life. Skeletal muscle mass is, in part, determined by the rates of protein synthesis, and mechanical loading is a major regulator of protein synthesis and skeletal muscle mass. The mammalian/mechanistic target of rapamycin (mTOR), found in the multi-protein complex, mTORC1, is proposed to play an essential role in the regulation of protein synthesis and skeletal muscle mass. The purpose of this review is to examine the function of mTORC1 in relation to protein synthesis and cell growth, the current evidence from rodent and human studies for the activation of mTORC1 signaling by different types of mechanical stimuli, whether mTORC1 signaling is necessary for changes in protein synthesis and skeletal muscle mass that occur in response to different types of mechanical stimuli, and the proposed molecular signaling mechanisms that may be responsible for the mechanical activation of mTORC1 signaling.

Consilience in sarcopenia of cirrhosis

Cirrhosis is the consequence of progression of many forms of necro-inflammatory disorders of the liver with hepatic fibrosis, hepatocellular dysfunction, and vascular remodeling. Reversing the primary hepatic disorder, liver transplantation, and controlling the complications are the major management goals. Since the former options are not available to the majority of cirrhotics, treating complications remains the mainstay of therapy. Sarcopenia and/or cachexia is the most common complication and adversely affects survival, quality of life, development of other complications of cirrhosis, and outcome after liver transplantation. With the increase in number of cirrhotic patients with hepatitis C and nonalcoholic fatty liver disease, the number of patients waiting for a liver transplantation is likely to continue to increase above the currently estimated 72.3/100,000 population. One of the critical clinical questions is to determine if we can treat sarcopenia of cirrhosis without transplantation. No effective therapies exist to treat sarcopenia because the mechanism(s) of sarcopenia in cirrhosis is as yet unknown. The reasons for this include the predominantly descriptive studies to date and the advances in our understanding of skeletal muscle biology and molecular regulation of atrophy and hypertrophy not being translated into the clinical practice of hepatology. Satellite cell biology, muscle autophagy and apoptosis, and molecular signaling abnormalities in the skeletal muscle of cirrhotics are also not known. Aging of the cirrhotic and transplanted population, use of mTOR inhibitors, and the lack of definitive outcome measures to define sarcopenia and cachexia in this population add to the difficulty in increasing our understanding of hepatic sarcopenia/cachexia and developing treatment options. Recent data on the role of myostatin, AMP kinase, impaired mTOR signaling resulting in anabolic resistance in animal models, and the rapidly developing field of nutriceuticals as signaling molecules need to be evaluated in human cirrhotics. Finally, the benefits of exercise reported in other disease states with sarcopenia may not be safe in cirrhotics due to the risk of gastrointestinal variceal bleeding due to an increase in portal pressure. This article focuses on the problems facing both muscle biologists and hepatologists in developing a comprehensive approach to sarcopenia in cirrhosis.

Dietary protein for athletes: from requirements to optimum adaptation

Opinion on the role of protein in promoting athletic performance is divided along the lines of how much aerobic-based versus resistance-based activity the athlete undertakes. Athletes seeking to gain muscle mass and strength are likely to consume higher amounts of dietary protein than their endurance-trained counterparts. The main belief behind the large quantities of dietary protein consumption in resistance-trained athletes is that it is needed to generate more muscle protein. Athletes may require protein for more than just alleviation of the risk for deficiency, inherent in the dietary guidelines, but also to aid in an elevated level of functioning and possibly adaptation to the exercise stimulus. It does appear, however, that there is a good rationale for recommending to athletes protein intakes that are higher than the RDA. Our consensus opinion is that leucine, and possibly the other branched-chain amino acids, occupy a position of prominence in stimulating muscle protein synthesis; that protein intakes in the range of 1.3-1.8 g · kg(-1) · day(-1) consumed as 3-4 isonitrogenous meals will maximize muscle protein synthesis. These recommendations may also be dependent on training status: experienced athletes would require less, while more protein should be consumed during periods of high frequency/intensity training. Elevated protein consumption, as high as 1.8-2.0 g · kg(-1) · day(-1) depending on the caloric deficit, may be advantageous in preventing lean mass losses during periods of energy restriction to promote fat loss.

Leucine as a pharmaconutrient to prevent and treat sarcopenia and type 2 diabetes

Amino acids function as precursors for de novo protein synthesis. In addition, however, they play a key role as nutritional signals that regulate multiple cellular processes. There is ample in vitro and in vivo evidence showing that muscle tissue responds to increases in amino acid availability via signal transduction pathways that are also regulated by insulin, glucagon, growth hormone, and insulin growth factor 1. The increased amino acid availibility results in the upregulation of mRNA translation, thereby increasing muscle protein synthesis, which, in turn, leads to greater net muscle protein accretion. These findings have been particularly pronounced for the amino acid leucine. Furthermore, leucine has the ability to act as a strong insulin secretagogue. Consequently, it has been suggested that leucine represents an effective pharmaconutrient for the prevention and treatment of sarcopenia and type 2 diabetes. In accordance, recent in vivo studies in humans show that free leucine ingestion can reverse the blunted response of muscle protein synthesis to amino acid/protein intake in the elderly. Although short-term studies suggest that leucine supplementation can stimulate muscle mass accretion in the elderly, there are no long-term nutritional intervention studies to confirm this or the other proposed benefits of leucine as a pharmaconutrient.

Malnutrition in cirrhosis: contribution and consequences of sarcopenia on metabolic and clinical responses

Malnutrition is the most common, reversible complication of cirrhosis that adversely affects survival, response to other complications, and quality of life. Sarcopenia, or loss of skeletal muscle mass, and loss of adipose tissue and altered substrate use as a source of energy are the 2 major components of malnutrition in cirrhosis. Current therapies include high protein supplementation especially as a late evening snack. Exercise protocols have the potential of aggravating hyperammonemia and portal hypertension. Recent advances in understanding the molecular regulation of muscle mass has helped identify potential novel therapeutic targets including myostatin antagonists, and mTOR resistance.

Carbohydrates for Physical Activity

Intake of carbohydrates above the dietary guidelines to support performance of physical activity is common but may be unnecessary and counterproductive. Sports nutrition guidelines have not been designed to incorporate characteristics that may make high carbohydrate consumption a source of metabolic stress that may increase oxidative stress, inflammation, and lipogenesis. This metabolic stress is linked to the physiology underlying the development of insulin resistance, type 2 diabetes mellitus, and cardiovascular diseases. This review describes research-based evidence to aid in bridging the gap between dietary guidelines for overall health and those to support physical activity. Characteristics that increase the likelihood of metabolic stress resulting from carbohydrate intake include overweight and obesity, central/visceral adiposity, older age, sedentary lifestyle, and caloric state. Carbohydrate-based foods that provide the most health benefits are whole grains, beans and legumes, fruits, and vegetables. Carbohydrate-based foods that most readily elicit metabolic stress are those with added sugars and refined grains or that have a high glycemic index. A checklist that incorporates both the number of these characteristics and prevailing guidelines for nutrition and physical activity is presented. This may be useful in determining whether additional carbohydrates are needed to support the physical activity level of the individual.

Leucine as a pharmaconutrient in health and disease

PURPOSE OF REVIEW

Amino acids do not merely represent precursors for de-novo protein synthesis, but also function as nutritional signals regulating various metabolic processes. In fact, ample evidence has been generated to show that various tissues respond to changes in amino acid availability via signal transduction pathways that are also regulated by hormones such as insulin, glucagon, and insulin-like growth factor 1.

RECENT FINDINGS

Amino acids, and leucine in particular, can act as strong insulin secretagogues when administered in combination with carbohydrate. Leucine administration can be applied effectively to improve postprandial glycemic control. Furthermore, amino acids have been shown to stimulate mRNA translation, thereby increasing muscle protein synthesis and stimulating net protein accretion in an insulin-independent manner. These anabolic properties of amino acids have been mainly attributed to the essential amino acids, and leucine in particular. In accordance, the recent in-vivo human studies show that leucine ingestion can augment the blunted muscle protein synthetic response to protein or amino acid ingestion in elderly men.

SUMMARY

Leucine has been proposed as a promising pharmaconutrient in the prevention and treatment of sarcopenia and/or type 2 diabetes. Though there are numerous applications for the proposed benefits of leucine in health and disease, the recent long-term nutritional intervention studies do not confirm the clinical efficacy of leucine as a pharmaconutrient.