Effectiveness of essential amino acid supplementation in stimulating whole body net protein anabolism is comparable between COPD patients and healthy older adults

Prolonged increase in glutamate whole body and intracellular production in older adults with COPD and healthy controls post-resistance exercise

BACKGROUND

Exercise training is essential for pulmonary rehabilitation in chronic obstructive pulmonary disease (COPD), yet patient responsiveness varies widely. We previously observed metabolic disturbances in amino acids critical for muscle health-such as glutamate, glutamine, branched-chain amino acids (BCAAs), and taurine-in COPD patients after an endurance exercise session, possibly related to increased energy demands and oxidative stress. However, the impact of resistance exercise on these metabolic pathways remains unclear.

METHODS

We measured plasma concentration, whole-body production (WBP), and intracellular production of glutamate, glutamine, BCAAs, and taurine using stable isotope pulse techniques in 24 COPD and 25 healthy older participants. Measurements were obtained before, and at 1 and 24 h after, a resistance exercise session.

RESULTS

At baseline, COPD participants exhibited lower WBP of glutamine, taurine, and BCAAs compared to healthy participants (p < 0.05). Resistance exercise increased WBP of glutamate by 37-42 %, glutamine by 9-10 %, and intracellular glutamate production by 37-40 %, while decreasing WBP of taurine by 7 % (all p < 0.0001). These effects persisted at 24 h post-exercise (p < 0.05). Although WBP of BCAAs remained unchanged, plasma leucine and isoleucine levels decreased by 16 % and 13 %, respectively, in COPD participants post-exercise (p < 0.05).

CONCLUSIONS

A single resistance exercise session alters glutamate-related metabolism for at least 24 h in healthy and COPD participants. A high BCAA clearance is likely required to rapidly upregulate glutamate production in COPD to meet increased energy demands, but this occurs at the cost of lowering plasma levels of BCAA necessary for muscle anabolism.

CLINICAL TRIAL REGISTRY

Trial registration ClinicalTrials.gov: NCT02780219.

Effect of protein and amino acids supplements on muscle strength and physical performance: A scoping review of randomized controlled trials

Protein and amino acid supplementation is an effective intervention that significantly enhances physical function and reduces frailty and sarcopenia in older adults. This scoping review aims to map and synthesize the available evidence on the effects of various types of protein and amino acid supplementation in this population. Following the PRISMA-ScR guidelines, we conducted a literature search to identify clinical trials examining the effects of protein and amino acid supplementation, with or without physical exercise, on muscle strength, physical performance, and body composition in healthy, frail, or sarcopenic older adults. Our analysis of 80 trials with a total of 5290 participants examines the evidence for the effectiveness of protein supplementation in enhancing muscle strength and body composition. Whey protein, creatine, milk protein, leucine, essential amino acids, and soy protein were the most used types of protein, and our findings indicate that whey protein, creatine, and milk protein yield the best results when used in conjunction with resistance training. Additionally, leucine and milk protein have shown the potential to enhance body composition even without concurrent resistance training. In conclusion, studies on the effectiveness of whey protein in improving muscle strength and body composition in older adults with resistance training are inconsistent. More research is required to explore the potential benefits of soy and leucine-enriched supplements. Protein supplementation's impact on physical performance remains inconclusive. Further studies are needed to determine the effects of protein types and supplementation on muscle-related parameters in older adults.

Consideration of the role of protein quality in determining dietary protein recommendations

The quality of a dietary protein refers to its ability to provide the EAAs necessary to meet dietary requirements. There are 9 dietary amino acids that cannot be metabolically produced in the body and therefore must be consumed as part of the diet to avoid adverse metabolic consequences. These essential amino acids (EAAs) serve a variety of roles in the body. The amount and profile of the dietary EAAs relative to the individual EAA requirements and the digestibility of the dietary protein are the key factors that determine its quality. Currently the Digestible Indispensable Amino Acid Score (DIAAS) is the best available approach to quantifying protein quality. The most prominent metabolic role of dietary EAAs is to stimulate protein synthesis by serving as signals to activate molecular mechanisms responsible for the initiation of protein synthesis and, most importantly, to provide the necessary precursors for the synthesis of complete proteins. Current dietary recommendations generally do not consider protein quality. Accounting for protein quality in dietary patterns can be accomplished while staying within established ranges for dietary protein consumption. Poor protein quality can be compensated for to some extent by eating more low-quality protein, but to be effective ("complementary") the limiting EAA must differ between the low-quality protein and the base diet to which it is being supplemented. Adding a high-quality protein to a dietary pattern based on low-quality protein is more effective in meeting EAA goals than increasing the amount of low-quality protein, even if the low-quality proteins are complementary. Further, reliance entirely on low-quality protein food sources, particularly in circumstances that may benefit from a level of dietary EAAs greater than minimal requirements, is likely to include excessive caloric consumption. While protein consumption in high-income nations is generally perceived to be adequate or even excessive, assessment of dietary patterns indicates that a significant percentage of individuals may fall short of meeting optimal levels of EAA consumption, especially in circumstances such as aging in which the optimal EAA consumption is greater than basal values for healthy young individuals. The case is made that protein quality is an important consideration in meeting EAA requirements.

Practical Guidelines by the Andalusian Group for Nutrition Reflection and Investigation (GARIN) on Nutritional Management of Patients with Chronic Obstructive Pulmonary Disease: A Review

Malnutrition is common in chronic obstructive pulmonary disease (COPD) patients and is associated with worse lung function and greater severity. This review by the Andalusian Group for Nutrition Reflection and Investigation (GARIN) addresses the nutritional management of adult COPD patients, focusing on Morphofunctional Nutritional Assessment and intervention in clinical practice. A systematic literature search was performed using the Preferred Reporting Items for Systematic Reviews and Meta-Analyses (PRISMA) methodology, followed by critical appraisal based on Scottish Intercollegiate Guidelines Network (SIGN) guidelines. Recommendations were graded according to the European Society for Clinical Nutrition and Metabolism (ESPEN) system. The results were discussed among GARIN members, with consensus determined using a Likert scale. A total of 24 recommendations were made: 2(A), 6(B), 2(O), and 14(GPP). Consensus exceeded 90% for 17 recommendations and was 75-90% for 7. The care of COPD patients is approached from a nutritional perspective, emphasizing nutritional screening, morphofunctional assessment, and food intake in early disease stages. Nutritional interventions include dietary advice, recommendations on food group intake, and the impact of specialized nutritional treatment, particularly oral nutritional supplements. Other critical aspects, such as physical activity and quality of life, are also analyzed. These recommendations provide practical guidance for managing COPD patients nutritionally in clinical practice.

Effect of Macronutrients or Micronutrients Supplementation on Nutritional Status, Physical Functional Capacity and Quality of Life in Patients with COPD: A Systematic Review and Meta-Analysis

Given the importance that a correct and balanced nutrition has on patients with chronic obstructive pulmonary disease (COPD), supplementation of macro and micronutrients has been proposed, but the results of previous meta-analyses are contrasting. We performed an update of the latest evidence through a systematic review and meta-analysis of studies to assess the role of nutritional supplements in improving nutritional status, pulmonary function, physical performance, and quality of life of these patients.We included randomized controlled trials (RCTs) published between 01-01-2010 and 11-01-2023 evaluating the effectiveness of nutritional support in patients affected by stable COPD with an intervention of at least 2 weeks. Primary outcomes were changes in body mass index (BMI) and fat free mass index (FFMI). Secondary outcomes were exercise tolerance (6-min walking test, 6MWT), quality of life (St George's Respiratory Questionnaire, SGRQ) and respiratory function (FEV1). According with supplements type (macronutrients or micronutrients), we calculated the pooled adjusted mean difference (MD) and 95% confidence intervals (95%CIs) of the selected outcomes, using random-effects models in presence of high heterogeneity (I2>50%) or fixed-effects models otherwise. The risk of publication bias was evaluated with the trim and fill method.From 967 articles, 20 RCTs were included. Macronutrients supplementation improved BMI (MD 1.0 kg/m2, 95%CI 0.21-1.79), FFMI (MD 0.77 Kg/m2, 95%CI 0.48-1.06), 6MQT (MD 68.39 m, 95%CI 40.07-96.71), and SGRQ (MD -5.14, 95% CI -7.31-2.97), while it does not ameliorate respiratory function (MD 0.26% 95%CI -1.87-2.40). Micronutrients supplementation alone did not improve any of the considered outcomes.

International Society of Sports Nutrition Position Stand: Effects of essential amino acid supplementation on exercise and performance

Position Statement: The International Society of Sports Nutrition (ISSN) presents this position based on a critical examination of literature surrounding the effects of essential amino acid (EAA) supplementation on skeletal muscle maintenance and performance. This position stand is intended to provide a scientific foundation to athletes, dietitians, trainers, and other practitioners as to the benefits of supplemental EAA in both healthy and resistant (aging/clinical) populations. EAAs are crucial components of protein intake in humans, as the body cannot synthesize them. The daily recommended intake (DRI) for protein was established to prevent deficiencies due to inadequate EAA consumption. The following conclusions represent the official position of the Society: 1. Initial studies on EAAs' effects on skeletal muscle highlight their primary role in stimulating muscle protein synthesis (MPS) and turnover. Protein turnover is critical for replacing degraded or damaged muscle proteins, laying the metabolic foundation for enhanced functional performance. Consequently, research has shifted to examine the effects of EAA supplementation - with and without the benefits of exercise - on skeletal muscle maintenance and performance. 2. Supplementation with free-form EAAs leads to a quick rise in peripheral EAA concentrations, which in turn stimulates MPS. 3. The safe upper limit of EAA intake (amount), without inborn metabolic disease, can easily accommodate additional supplementation. 4. At rest, stimulation of MPS occurs at relatively small dosages (1.5-3.0 g) and seems to plateau at around 15-18 g. 5. The MPS stimulation by EAAs does not require non-essential amino acids. 6. Free-form EAA ingestion stimulates MPS more than an equivalent amount of intact protein. 7. Repeated EAA-induced MPS stimulation throughout the day does not diminish the anabolic effect of meal intake. 8. Although direct comparisons of various formulas have yet to be investigated, aging requires a greater proportion of leucine to overcome the reduced muscle sensitivity known as "anabolic resistance." 9. Without exercise, EAA supplementation can enhance functional outcomes in anabolic-resistant populations. 10. EAA requirements rise in the face of caloric deficits. During caloric deficit, it's essential to meet whole-body EAA requirements to preserve anabolic sensitivity in skeletal muscle.

Advances in metabolomics of chronic obstructive pulmonary disease

Chronic obstructive pulmonary disease (COPD) is a chronic lung disease with limited airflow. COPD is characterized by chronic bronchitis and emphysema, and is often accompanied by malnutrition with fatigue, muscle weakness, and an increased risk of infection. Although the pulmonary function test is used as the gold criterion for diagnosing COPD, it is unable to identify early COPD or classify the subtypes, thereby impeding early intervention and the precise diagnosis of COPD. Recent evidence suggests that metabolic dysfunction, such as changes in lipids, amino acids, glucose, nucleotides, and microbial metabolites in the lungs and intestine, have a great potential for diagnosing COPD in the early stage. However, a comprehensive summary of these metabolites and their effects on COPD is still lacking. This review summarizes the metabolites that are changed in COPD and highlights some promising early diagnostic markers and therapeutic targets. We emphasize that intensified dietary management may be among the most feasible methods to improve metabolism in the body.

Sex related differences in muscle health and metabolism in chronic obstructive pulmonary disease

BACKGROUND & AIMS

Sex differences in muscle function and mass, dyspnea, and clinical outcomes have been observed in patients with Chronic Obstructive Pulmonary Disease (COPD) despite a similar level of airflow obstruction. Protein and amino acid metabolism is altered in COPD, however, it remains unclear whether a difference in metabolic signature exists between males and females with COPD that may explain the observed differences in muscle health and clinical outcomes.

METHODS

In 234 moderate to severe COPD patients (males/females: 113/121) and 182 healthy controls (males/females: 77/105), we assessed, besides presence of comorbidities and clinical features, muscle function by handgrip and leg dynamometry, and body composition by dual-energy x-ray absorptiometry. In the postabsorptive state, a mixture of 18 stable isotopes of amino acids was administered by pulse and arterialized blood was sampled for 2 h. Amino acid concentrations and enrichments were analyzed by LC-MS/MS to calculate whole body (net) protein breakdown (WBnetPB) and whole body production (WBP) rates (μmol/hour) of the amino acids playing a known role in muscle health. Statistics was done by ANCOVA to examine the effects of sex, COPD, and sex-by-COPD interaction with as covariates age and lean mass. Significance was set as p < 0.05.

RESULTS

Lung function was comparable between males and females with COPD. Being a female and presence of COPD were independently associated with lower appendicular lean mass, muscle strength, and WBnetPB (p < 0.05). Being a male was associated with higher visceral adipose tissue, C-reactive protein (CRP) (p < 0.05), and higher prevalence of heart failure and obstructive sleep apnea. Sex-by-COPD interactions were found indicating lower fat mass (p = 0.0005) and WBPs of phenylalanine (measure of whole body protein turnover) and essential amino acids (p < 0.05), particularly in COPD females. Higher visceral adipose tissue (p = 0.025), CRP (p < 0.0001), and WBP of tau-methylhistidine (p = 0.010) (reflecting enhanced myofibrillar protein breakdown) were observed in COPD males.

CONCLUSIONS

Presence of sex specific changes in protein and amino acid metabolism and cardiometabolic health in COPD need to be considered when designing treatment regimens to restore muscle health in males and females with COPD.

CLINICAL TRIAL REGISTRY

www.

CLINICALTRIALS

gov, NCT01787682, NCT01624792, NCT02157844, NCT02065141, NCT02770092, NCT02780219, NCT03327181, NCT03796455, NCT01173354, NCT01154400.

Abdominal obesity in COPD is associated with specific metabolic and functional phenotypes

BACKGROUND

Abdominal obesity (AO) is linked to reduced health status and mortality. While it is known that AO is prevalent in chronic obstructive pulmonary disease (AO-COPD), the specific metabolic and functional consequences associated with AO-COPD remain understudied.

METHODS

We studied 199 older adults with COPD and 168 control subjects with and without AO and assessed visceral adipose tissue (VAT) by dual-energy X-ray absorptiometry. VAT > 70th percentile of the control group qualified a subject as AO in a sex specific manner. We measured plasma concentrations and whole body production (WBP) rates of multiple amino acids to assess the metabolic profile. We assessed medical history, body composition by Dual-Energy X-ray Absorptiometry, muscle strength, and cognitive function. We performed statistics by analysis of covariance (p) and FDR (q) for multiple comparisons.

RESULTS

AO-COPD subjects had 27% more VAT (q < 0.01) than AO-Control subjects despite correction for BMI. Branched-chain amino acid concentrations and WBP rates were generally elevated in AO-COPD but whole body clearance rate was only elevated in COPD. Metabolic syndrome comorbidities (p < 0.01) and systemic inflammation (P < 0.05) were most prevalent in the AO-COPD group. Muscle strength was reduced in COPD subjects (p < 0.001), but partially preserved when combined with AO. Cognitive dysfunction and mood disturbances were present in COPD subjects (p < 0.001) with worst performers in AO-COPD (q < 0.05).

CONCLUSION

The presence of AO is associated with specific metabolic and functional phenotypes in COPD. Clinical trial registry Trial registration ClinicalTrials.gov. In the present paper, we report an analysis of the baseline measurements of COPD subjects and healthy controls from the study numbers: NCT01787682, NCT01787682, NCT02157844, NCT02082418, NCT02065141, NCT02770092, NCT02908425, NCT03159390, NCT02780219, NCT03327181, NCT03796455, NCT04928872, NCT04461236, NCT01173354, NCT01154400.

Nutritional Status and Body Composition in Patients Suffering From Chronic Respiratory Diseases and Its Correlation With Pulmonary Rehabilitation

As part of an individualized intervention to improve the physical, emotional, and social functioning of patients with chronic respiratory diseases in general and chronic obstructive pulmonary disease in particular, awareness of the presence and consequences of changes in body composition increased enormously during the last decades, and nutritional intervention is considered as an essential component in the comprehensive approach of these patients. This review describes the prevalence and the clinical impact of body composition changes and also provides an update of current intervention strategies. It is argued that body composition, preferentially a three-component evaluation of fat, lean, and bone mass, must become part of a thorough assessment of every patient, admitted for pulmonary rehabilitation.

How to Increase Muscle Mass in Critically Ill Patients: Lessons Learned from Athletes and Bodybuilders

PURPOSE OF REVIEW

Decades of research on nutrition and exercise on athletes and bodybuilders has yielded various strategies to promote anabolism and improve muscle health and growth. We reviewed these interventions in the context of muscle loss in critically ill patients.

RECENT FINDINGS

For critically ill patients, ensuring optimum protein intake is important, potentially using a whey-containing source and supplemented with vitamin D and leucine. Agents like hydroxyl β-methylbutyrate and creatine can be used to promote muscle synthesis. Polyunsaturated fatty acids stimulate muscle production as well as have anti-inflammatory properties that may be useful in critical illness. Adjuncts like oxandralone promote anabolism. Resistance training has shown mixed results in the ICU setting but needs to be explored further with specific outcomes. Critically ill patients suffer from severe proteolysis during hospitalization as well as persistent inflammation, immunosuppression, and catabolism syndrome after discharge. High protein supplementation, ergogenic aids, anti-inflammatories, and anabolic adjuncts have shown potential in alleviating muscle loss and should be used in intensive care units to optimize patient recovery.

Preoperative Management of Surgical Patients Using Dietary Supplements: Society for Perioperative Assessment and Quality Improvement (SPAQI) Consensus Statement

The widespread use of complementary products poses a challenge to clinicians in the perioperative period and may increase perioperative risk. Because dietary supplements are regulated differently from traditional pharmaceuticals and guidance is often lacking, the Society for Perioperative Assessment and Quality Improvement convened a group of experts to review available literature and create a set of consensus recommendations for the perioperative management of these supplements. Using a modified Delphi method, the authors developed recommendations for perioperative management of 83 dietary supplements. We have made our recommendations to discontinue or continue a dietary supplement based on the principle that without a demonstrated benefit, or with a demonstrated lack of harm, there is little downside in temporarily discontinuing an herbal supplement before surgery. Discussion with patients in the preoperative visit is a crucial time to educate patients as well as gather vital information. Patients should be specifically asked about use of dietary supplements and cannabinoids, as many will not volunteer this information. The preoperative clinic visit provides the best opportunity to educate patients about the perioperative management of various supplements as this visit is typically scheduled at least 2 weeks before the planned procedure.

The impact of L-branched-chain amino acids and L-leucine on malnutrition, sarcopenia, and other outcomes in patients with chronic liver disease

INTRODUCTION

Metabolic and hormonal disorders resulting from chronic liver diseases culminate in increased proteolysis and decreased protein synthesis, which contributes to the development and progression of malnutrition and, consequently, sarcopenia. Nutritional management of sarcopenia in liver cirrhosis is a continuously evolving field and data on essential amino acid supplementation in chronic liver diseases is scarce.

AREAS COVERED

This review encompasses the current literature on oral amino acids supplementation in patients with chronic liver disease or patients with liver cirrhosis to try to elucidate the possible effects of L-branched-chain amino acids and isolated L-leucine as a therapeutic approach to malnutrition and sarcopenia.

EXPERT COMMENTARY

To ensure an optimal nutritional status and to reduce sarcopenia, it is necessary to assess nutritional status in all patients with liver cirrhosis and to apply nutritional interventions accordingly. The supply of calories, proteins, and essential amino acids is necessary for the maintenance of muscle mass and function. Although supplementation of L-branched-chain amino acids plays an important role in liver disease, L-leucine has been described as the main amino acid involved in protein turnover, reducing proteolysis, and stimulating protein synthesis.

Daily Consumption of a Specially Formulated Essential Amino Acid-Based Dietary Supplement Improves Physical Performance in Older Adults With Low Physical Functioning

We have investigated the hypothesis that nutritional supplementation of the diet in low-physical-functioning older individuals with a specially formulated composition based on essential amino acids (EAAs) would improve physical function as compared to supplementation with the same amount of whey protein. A third group of comparable volunteers were given nutrition education but no supplementation of the diet. After 6 weeks of whey protein supplementation (n = 32), there was no effect on the distance walked in 6 minutes, but the distance walked improved significantly from the pre-value after 12 weeks of whey supplementation. EAA consumption (n = 28) significantly improved walking distance at both 6 and 12 weeks. The distance walked at 12 weeks (419.0 ± 25.0 m) was 35.4 m greater than the pre-value of 384.0 ± 23.0 m (p < .001). The increase in distance walked by the EAA group was also significantly greater than that in the whey group at both 6 and 12 weeks (p < .01). In contrast, a decrease in distance walked was observed in the control group (n = 32) (not statistically significant, NS). EAA supplementation also improved grip strength and leg strength, and decreased body weight and fat mass. Plasma low-density lipoprotein concentration was significantly reduced in the EAA group, as well as the concentration of macrophage migration inhibitory factor. There were no adverse responses in any groups, and compliance was greater than 95% in all individuals consuming supplements. We conclude that dietary supplementation with an EAA-based composition may be a beneficial therapy in older individuals with low physical functional capacity. Clinical Trials Registration Number: This study was registered with ClinicalTrials.gov: NCT03424265-"Nutritional interventions in heart failure."

The Effects of Cow-Milk Protein Supplementation in Elderly Population: Systematic Review and Narrative Synthesis

BACKGROUND

To review currently available evidence on the effect of cow-milk proteins supplementation (CPS) on health in the elderly.

METHODS

Five electronic databases (Pubmed, Web of Science, Embase, Cochrane Library, ClinicalTrials.gov) were searched for studies about CPS among older people. All types of publications were included, with the exception of systematic reviews, meta-analyses, opinion letters, editorials, case reports, conference abstracts and comments. An additional search in Google Scholar and a manual review of the reference lists were performed.

RESULTS

Overall, 103 studies were included. Several studies explored the role of CPS in the preservation or improvement of muscle mass among healthy subjects (40 studies) and pre-frail, frail or sarcopenic patients (14), with evidence of beneficial effects. Other studies assessed the effect of CPS on bones (12), cardiovascular disease (8), inflamm-aging (7), chronic pulmonary disease (4), neurocognitive function (4), and vaccines (2), with weak evidence of positive effects. Seven studies in the field of protein metabolism investigated the role of CPS as an important contributor to nutritional needs. Other investigational areas are considered in the last five studies.

CONCLUSIONS

The beneficial effects of CPS in achieving aged-related nutritional goals, in preserving muscle mass and in recovering after hospitalization may be particularly relevant in the elderly.

Whey protein ingestion in elderly diet and the association with physical, performance and clinical outcomes

Nutrition is critical to the health of the elderly, since most of them have a deficiency in key nutrient. The use of whey protein may be a food strategy to increase protein intake. The objective of this work was to evaluate the ingestion of whey protein for the elderly and the association with physical performance and clinical outcomes. A systematic review was conducted in order to find papers that shed some light in the correlation between whey protein and the elderly.

INCLUSION CRITERIA

population: elderly; intervention: use of whey protein when compared to control group; outcome: related to health, nutrition, or quality of life.

DATABASE

PubMed, with papers published in the last 5 years.

SEARCH STRATEGY

(elder OR senior OR elderly OR aging OR aged OR old OR older) AND (whey OR "whey protein"). 35 papers were selected of which 22 had a physical performance outcome and 13 had clinical outcomes. Studies indicate that whey protein supplements promote protein synthesis in the elderly, improving muscle performance and aerobic capacity, protecting against sarcopenia and reducing the risk for falls. In the papers studied, the age group considered to be elderly was ≥65 years in 27 papers and ≥60 years in the other 8 papers. Whey protein also appears to contribute to improved health, recovery from disease, prevention of cardiovascular and metabolic risks, and hepatic steatosis complications. Data suggest that whey protein supplements may be promising for the health improvement of the elderly.

Muscle Mass Loss in the Older Critically Ill Population: Potential Therapeutic Strategies

Skeletal muscle plays a critical role in everyday life, and its age-associated reduction has severe health consequences. The pre-existing presence of sarcopenia, combined with anabolic resistance, protein undernutrition, and the pro-catabolic/anti-anabolic milieu induced by aging and exacerbated in critical care, may accelerate the rate at which skeletal muscle is lost in patients with critical illness. Advancements in intensive care unit (ICU)-care provision have drastically improved survival rates; therefore, attention can be redirected toward other significant issues affecting ICU patients (e.g., length of stay, days on ventilation, nosocomial disease development, etc.). Thus, strategies targeting muscle mass and function losses within an ICU setting are essential to improve patient-related outcomes. Notably, loading exercise and protein provision are the most compelling. Many older ICU patients seldom meet the recommended protein intake, and loading exercise is difficult to conduct in the ICU. Nevertheless, the incorporation of physical therapy (PT), neuromuscular electrical stimulation, and early mobilization strategies may be beneficial. Furthermore, a number of nutrition practices within the ICU have been shown to improve patient-related outcomes ((e.g., feeding strategy [i.e., oral, early enteral, or parenteral]), be hypocaloric (∼70%-80% energy requirements), and increase protein provision (∼1.2-2.5 g/kg/d)). The aim of this brief review is to discuss the dysregulation of muscle mass maintenance in an older ICU population and highlight the potential benefits of strategic nutrition practice, specifically protein, and PT within the ICU. Finally, we provide some general guidelines that may serve to counteract muscle mass loss in patients with critical illness.

Identifying Protein-metabolite Networks Associated with COPD Phenotypes

Chronic obstructive pulmonary disease (COPD) is a disease in which airflow obstruction in the lung makes it difficult for patients to breathe. Although COPD occurs predominantly in smokers, there are still deficits in our understanding of the additional risk factors in smokers. To gain a deeper understanding of the COPD molecular signatures, we used Sparse Multiple Canonical Correlation Network (SmCCNet), a recently developed tool that uses sparse multiple canonical correlation analysis, to integrate proteomic and metabolomic data from the blood of 1008 participants of the COPDGene study to identify novel protein-metabolite networks associated with lung function and emphysema. Our aim was to integrate -omic data through SmCCNet to build interpretable networks that could assist in the discovery of novel biomarkers that may have been overlooked in alternative biomarker discovery methods. We found a protein-metabolite network consisting of 13 proteins and 7 metabolites which had a -0.34 correlation (p-value = 2.5 × 10^-28) to lung function. We also found a network of 13 proteins and 10 metabolites that had a -0.27 correlation (p-value = 2.6 × 10^-17) to percent emphysema. Protein-metabolite networks can provide additional information on the progression of COPD that complements single biomarker or single -omic analyses.

Respiratory

Lung disease rivals the position for the top cause of death worldwide. Causes and pathology of the myriad lung diseases are varied, yet nutrition can either affect the outcome or support treatment in the majority of cases. This chapter explores the modifiable risk factors, from lifestyle changes to dietary intake to specific nutrients, anti-nutrients, and toxins helpful for the nutritionist or dietitian working with lung disease patients. General lung health is discussed, and three major disease states are explored in detail, including alpha-1 antitrypsin deficiency, asthma, and idiopathic pulmonary fibrosis. Although all lung diseases have diverse causes, many integrative and functional medical nutrition therapies are available and are not being utilized in practice today. This chapter begins the path toward better nutrition education for the integrative and functional medicine professional.

Disruption of histidine and energy homeostasis in chronic obstructive pulmonary disease

Background

Chronic obstructive pulmonary disease (COPD) is a systemic condition that is too complex to be assessed by lung function alone. Metabolomics has the potential to help understand the mechanistic underpinnings that contribute to COPD pathogenesis. Since blood metabolomics may be affected by sex and body mass index (BMI), the aim of this study was to determine the metabolomic variability in male smokers with and without COPD who have a narrow BMI range.

Methods

We compared the quantitative proton nuclear magnetic resonance acquired serum metabolomics of a male Chinese Han population of non-smokers without COPD, and smokers with and without COPD. We also assessed the impact of smoking status on metabolite concentrations and the associations between metabolite concentrations and inflammatory markers such as serum interleukin-6 and histamine, and blood cell differential (%). Metabolomics data were log-transformed and auto-scaled for parametric statistical analysis. Mean normalized metabolite concentration values and continuous demographic variables were compared by Student’s t-test with Welch correction or ANOVA with post-hoc Tukey’s test, as applicable; t-test p-values for metabolomics data were corrected for false discovery rate (FDR). A Pearson association matrix was built to evaluate the relationship between metabolite concentrations, clinical parameters and markers of inflammation.

Results

Twenty-eight metabolites were identified and quantified. Creatine, glycine, histidine, and threonine concentrations were reduced in COPD patients compared to non-COPD smokers (FDR ≤15%). Concentrations of these metabolites were inversely correlated with interleukin-6 levels. COPD patients had overall dampening of metabolite concentrations including energy-related metabolic pathways such as creatine metabolism. They also had higher histamine levels and percent basophils compared to smokers without COPD.

Conclusion

COPD is associated with alterations in the serum metabolome, including a disruption in the histidine-histamine and creatine metabolic pathways. These findings support the use of metabolomics to understand the pathogenic mechanisms involved in COPD.

Trial registrationwww.clinicaltrials.gov, NCT03310177.

New advances in stable tracer methods to assess whole-body protein and amino acid metabolism

PURPOSE OF REVIEW

Stable isotope methods have been used for many years to assess whole-body protein and amino acid kinetics in healthy conditions and in response to aging, exercise and (clinically stable) disease states.

RECENT FINDINGS

In recent years, tracer research expanded to the anabolic response to feeding in critical illness and its use during acute metabolic stressors. Furthermore, new isotope approaches and tracer insights have been obtained. In the postabsorptive state, the novel tracer pulse approach has several advantages above the established continuous tracer approach because of the metabolic information that can be obtained, easy applicability, and low tracer costs. The use of bolus versus sip-feeding approaches to assess the anabolic response to a meal is dependent on the research question and its feasibility. Promising new tracer approaches have been developed to measure the anabolic capacity, and protein digestibility and absorption. Advances have been made in the field of mass spectrometry in low enrichment analysis.

SUMMARY

Novel tracer approaches are available that can more readily be used in critical illness and during acute metabolic stressors. Besides the use of tracer application in various clinical conditions, more research is needed on how to incorporate isotopes on an individual level.

Dietary protein and exercise for preservation of lean mass and perspectives on type 2 diabetes prevention

Sedentary lifestyle and aging favor the increasing prevalence of obesity and type 2 diabetes and their comorbidities. The loss of lean body mass reduces muscle strength, resulting in impaired functional capacity and leading to increased risks of chronic diseases with advancing age. Besides aging, conditions such as inappetence, social isolation, and inadequate dietary intake cause the loss of lean body mass and increased abdominal fatty mass, resulting in sarcopenic obesity and predisposition to type 2 diabetes. Compared to younger people, this condition is more common in the elderly owing to natural changes in body composition associated with aging. Lifestyle changes such as increased physical activity and improved dietary behaviors are effective for preventing the occurrence of comorbidities. Regarding muscle nutrition, besides caloric adequacy, meeting the requirements for the consumption of dietary amino acids and proteins is important for treating sarcopenia and sarcopenic obesity because muscle tissue mainly consists of proteins and is, therefore, the largest reservoir of amino acids in the body. Thus, this review discusses the effects of dietary protein on the preservation of lean body mass, improvements in the functional capacity of muscle tissue, and prevention of chronic diseases such as type 2 diabetes. In addition, we address the effects of regular physical training associated with dietary protein strategies on lean body mass, body fat loss, and muscle strength in the elderly at a risk for type 2 diabetes development.

Whole body protein anabolism in COPD patients and healthy older adults is not enhanced by adding either carbohydrates or leucine to a serving of protein

BACKGROUND & AIMS

Carbohydrates (CHO) and leucine (LEU) both have insulinotropic properties, and could therefore enhance the protein anabolic capacity of dietary proteins, which are important nutrients in preventing muscle loss in patients with Chronic Obstructive Pulmonary Disease (COPD). LEU is also known to activate protein anabolic signaling pathways independent of insulin. Based on our previous findings in COPD, we hypothesized that whole body protein anabolism is enhanced to a comparable extent by the separate and combined co-ingestion of CHO and LEU with protein.

METHODS

To disentangle the protein anabolic effects of CHO and/or free LEU when co-ingested with a high-quality protein, we studied 10 patients with moderate to very severe COPD and dyspnea (GOLD: II-IV, mMRC dyspnea scale ≥ 2), at risk for muscle loss, and 10 healthy age- and gender-matched controls. On four occasions, in a single-blind randomized crossover design, each subject ingested a drink containing 0.6 g/kg fat-free mass (ffm) hydrolyzed casein protein with, a) no add-ons (protein), b) 0.3 g/kg ffm CHO (protein + CHO), c) 0.095 g/kg ffm leucine (protein + LEU), d) both add-ons (protein + CHO + LEU). Whole body protein breakdown (PB), protein synthesis (PS), and net protein balance (= PS - PB) were measured by IV primed and continuous infusion of L-[ring-2H5]-phenylalanine and L-[13C9,15N]-tyrosine. L-[15N]-phenylalanine was added to the protein drinks to measure splanchnic extraction.

RESULTS

In both groups, whole body PS, PB and net protein balance responses were comparable between the four protein drinks, despite higher postprandial plasma LEU concentrations for the LEU supplemented drinks (P < 0.05), and higher insulin concentrations for the CHO supplemented drinks as compared to the protein only drink (P < 0.05).

CONCLUSIONS

Adding CHO and/or LEU to a serving of high-quality protein does not further augment whole body protein anabolism in dyspneic COPD patients at risk for muscle loss or healthy older adults.

TRIAL REGISTRY

ClinicalTrials.gov; No. NCT01734473; URL: www.clinicaltrials.gov.

Preserved anabolic threshold and capacity as estimated by a novel stable tracer approach suggests no anabolic resistance or increased requirements in weight stable COPD patients

BACKGROUND & AIMS

Assessing the ability to respond anabolic to dietary protein intake during illness provides important insight in the capacity of lean body mass maintenance. We applied a newly developed stable tracer approach to assess in one session in patients with chronic obstructive pulmonary disease (COPD) and healthy older adults both the minimal amount of protein intake to obtain protein anabolism (anabolic threshold) and the efficiency of dietary protein to promote protein anabolism (anabolic capacity).

METHODS

We studied 12 clinically and weight stable patients with moderate to very severe COPD (mean ± SE forced expiratory volume in 1 s: 36 ± 3% of predicted) and 10 healthy age-matched older adults. At 2-h intervals and in consecutive order, all participants consumed a mixture of 0.0, 0.04, 0.10 and 0.30 g hydrolyzed casein protein×kg ffm-1×2 h-1 and carbohydrates (2:1). We assessed whole body protein synthesis (PS), breakdown (PB), net PS (PS-PB) and net protein balance (phenylalanine (PHE) intake - PHE to tyrosine (TYR) hydroxylation) by IV primed and continuous infusion of L-[ring-2H5]PHE and L-[13C9,15N]-TYR. Anabolic threshold (net protein balance = 0) and capacity (slope) were determined on an individual basis from the assumed linear relationship between protein intake and net protein balance.

RESULTS

We confirmed a linear relationship between protein intake and net protein balance for all participants (R2 range: 0.9988-1.0, p ≤ 0.0006). On average, the anabolic threshold and anabolic capacity were comparable between the groups (anabolic threshold COPD vs. healthy: 3.82 ± 0.31 vs. 4.20 ± 0.36 μmol PHE × kg ffm-1 × hr-1; anabolic capacity COPD vs. healthy: 0.952 ± 0.007 and 0.954 ± 0.004). At protein intake around the anabolic threshold (0.04 and 0.10 g protein×kg ffm-1×2 h-1), the increase in net PS resulted mainly from PB reduction (p < 0.0001) whereas at a higher protein intake (0.30 g protein×kg ffm-1×2 h-1) PS was also stimulated (p < 0.0001).

CONCLUSIONS

The preserved anabolic threshold and capacity in clinically and weight stable COPD patients suggests no disease related anabolic resistance and/or increased protein requirements.

TRIAL REGISTRY

ClinicalTrials.gov; No. NCT01734473; URL: www.clinicaltrials.gov.

Defining anabolic resistance: implications for delivery of clinical care nutrition

PURPOSE OF REVIEW

Skeletal muscle mass with aging, during critical care, and following critical care is a determinant of quality of life and survival. In this review, we discuss the mechanisms that underpin skeletal muscle atrophy and recommendations to offset skeletal muscle atrophy with aging and during, as well as following, critical care.

RECENT FINDINGS

Anabolic resistance is responsible, in part, for skeletal muscle atrophy with aging, muscle disuse, and during disease states. Anabolic resistance describes the reduced stimulation of muscle protein synthesis to a given dose of protein/amino acids and contributes to declines in skeletal muscle mass. Physical inactivity induces: anabolic resistance (that is likely exacerbated with aging), insulin resistance, systemic inflammation, decreased satellite cell content, and decreased capillary density. Critical illness results in rapid skeletal muscle atrophy that is a result of both anabolic resistance and enhanced skeletal muscle breakdown.

SUMMARY

Insofar as atrophic loss of skeletal muscle mass is concerned, anabolic resistance is a principal determinant of age-induced losses and appears to be a contributor to critical illness-induced skeletal muscle atrophy. Older individuals should perform exercise using both heavy and light loads three times per week, ingest at least 1.2 g of protein/kg/day, evenly distribute their meals into protein boluses of 0.40 g/kg, and consume protein within 2 h of retiring for sleep. During critical care, early, frequent, and multimodal physical therapies in combination with early, enteral, hypocaloric energy (∼10-15 kcal/kg/day), and high-protein (>1.2 g/kg/day) provision is recommended.

Nutrition-related factors associated with waiting list mortality in patients with interstitial lung disease: A retrospective cohort study

Japanese patients with interstitial lung disease (ILD) sometimes die waiting for lung transplantation (LTx) because it takes about 2 years to receive it in Japan. We evaluated nutrition-related factors associated with waiting list mortality. Seventy-six ILD patients were hospitalized in Kyoto University Hospital at registration for LTx from 2013 to 2015. Among them, 40 patients were included and analyzed. Patient background was as follows: female, 30%; age, 50.3 ± 6.9 years; body mass index, 21.1 ± 4.0 kg/m² ; 6-minute walk distance (6MWD), 356 ± 172 m; serum albumin, 3.8 ± 0.4 g/dL; serum transthyretin (TTR), 25.3 ± 7.5 mg/dL; and C-reactive protein, 0.5 ± 0.5 mg/dL. Median observational period was 497 (range 97-1015) days, and median survival time was 550 (95% CI 414-686) days. Survival rate was 47.5%, and mortality rate was 38.7/100 person-years. Cox analyses showed that TTR (HR 0.791, 95% CI 0.633-0.988) and 6MWD (HR 0.795, 95% CI 0.674-0.938) were independently correlated with mortality and were influenced by body fat mass and leg skeletal muscle mass, respectively. It is suggested that nutritional markers and exercise capacity are important prognostic markers in waitlisted patients, but further study is needed to determine whether nutritional intervention or exercise can change outcomes.

Systematic review and meta-analysis of the effect of protein and amino acid supplements in older adults with acute or chronic conditions

The loss of lean body mass, muscle strength and physical function causes significant problems in older adults. Protein and amino acid supplements can preserve muscle strength but the effect on function is variable. We conducted a systematic literature review and meta-analysis to investigate the effect of protein and amino acid supplementation on fat-free mass, muscle strength and physical function in malnourished, frail, sarcopenic, dependent or elderly with acute or chronic conditions, with or without rehabilitation exercise. Databases searched included Medline, BIOSIS, CINAHL, Cochrane Library, EBM Reviews, Embase, Pre-Medline, ProQuest, PubMed and Scopus. Retrieved articles were assessed by two reviewers using the Cochrane Risk of Bias (ROB) Tool. In all, thirty nine randomised controlled trails (n 4274) were included. The studies used a range of protein or essential amino acid (EAA) supplements in a variety of settings, including hospital, community and long-term care. Only seven studies had low ROB and no effect of supplementation was found on any outcomes. Analysis of all thirty-nine studies suggest protein and EAA supplements may improve fat-free mass, muscle strength and physical function (standardised mean difference 0·21-0·27, all P<0·005), but significant heterogeneity and ROB was evident. Predetermined subgroup analysis found undernourished elderly benefitted most; EAA were the most effective supplements and small beneficial effects were seen without rehabilitation exercise. The high heterogeneity and few studies with low ROB limits the conclusions and more high quality studies are needed to determine the best nutritional strategies for the maintenance of strength and function with increasing age.

Contraction and nutrition interaction promotes anabolism in cachectic muscle

PURPOSE OF REVIEW

Cachexia is a disease-related multifactorial syndrome characterized by inflammation, massive muscle protein catabolism and carbohydrate and lipid metabolism disorder.Several studies tried to define the impact of either nutrition or physical exercise (single approach strategy) or their combination (multimodal approach strategy) on prevention and/or treatment of muscle wasting in cachectic patients.

RECENT FINDINGS

Single approach strategies (i.e. nutrition or physical exercise) have the potential of preventing and improving features of the cachexia syndrome possibly with a differential impact according to the underlying disease. Limited information is available on the beneficial effect of multimodal approach strategies.

SUMMARY

Multimodal approaches appear to be more effective than those based on single interventions in physiological condition and in cachectic patients with COPD or chronic kidney disease. Further studies, however, are required in cachexia induced by heart failure, cancer and critical illness.

Implications of low muscle mass across the continuum of care: a narrative review

Abnormalities in body composition can occur at any body weight. Low muscle mass is a predictor of poor morbidity and mortality and occurs in several populations. This narrative review provides an overview of the importance of low muscle mass on health outcomes for patients in inpatient, outpatient and long-term care clinical settings. A one-year glimpse at publications that showcases the rapidly growing research of body composition in clinical settings is included. Low muscle mass is associated with outcomes such as higher surgical and post-operative complications, longer length of hospital stay, lower physical function, poorer quality of life and shorter survival. As such, the potential clinical benefits of preventing and reversing this condition are likely to impact patient outcomes and resource utilization/health care costs. Clinically viable tools to measure body composition are needed for routine screening and intervention. Future research studies should elucidate the effectiveness of multimodal interventions to counteract low muscle mass for optimal patient outcomes across the healthcare continuum. Key messages Low muscle mass is associated with several negative outcomes across the healthcare continuum. Techniques to identify and counteract low muscle mass in clinical settings are needed.

Polyunsaturated fatty acids, polyphenols, amino acids, prebiotics: can they help to tackle cancer cachexia and related inflammation?

PURPOSE OF REVIEW

Recent studies have highlighted the importance of developing a multimodal therapeutic strategy for cancer cachectic patients. Considering the central role of metabolism and anorexia in this disease, optimized nutritional advice should be an integral part of this strategy. Current recommendations mainly focus on meeting caloric requirements. However, a few studies suggest the great potential of foods naturally enriched in nutrients presenting interesting physiological properties and the interest of using them in the management of cachectic patients. Among them, prebiotics show the capacity to control inflammation in several debilitating diseases. In this context, this review aims to summarize the most recent findings related to functional foods and nutrients and cancer cachexia, and to discuss the potential use of prebiotics in this context.

RECENT FINDINGS

Even though there is a clear need for more research in the field, data from both humans and animal models support the promising benefits of functional foods and nutrients in cancer cachexia.

SUMMARY

Altogether, these studies offer new insights into the potential contribution of nutrition to cancer patient management. Functional foods, by downregulating inflammatory pathways, could decrease cachexia severity and contribute to the improvement of cancer patients' quality of life.

Is β-hydroxy β-methylbutyrate an effective anabolic agent to improve outcome in older diseased populations?

PURPOSE OF REVIEW

β-Hydroxy β-methylbutyrate (HMB) has been used for many years in athletes for muscle buildup and strength, and endurance enhancement. In recent years, its interest quickly expanded in older (diseased) populations and during (exercise) rehabilitation and recovery from hospitalization and surgery. We will discuss recent literature about HMB metabolism, its pharmacokinetics compared with the frequently used metabolite leucine, effectiveness of HMB to improve outcome in older diseased adults, and novel approaches for HMB use.

RECENT FINDINGS

HMB supplementation resulted in positive outcomes on muscle mass and functionality, related to its anabolic and anticatabolic properties and prolonged half-life time in blood. Furthermore, it was able to increase the benefits of (exercise) rehabilitation programs to enhance recovery from illness or medical procedures. There is promising evidence that HMB might support bone density, improve cognitive function, and reduce abdominal obesity, which is of importance particularly in the older (diseased) population.

SUMMARY

The older diseased population might benefit from dietary HMB because of its established positive properties as well as its long lasting (pharmacological) effect. In addition to evaluating its efficacy and application in various clinical conditions, more research is needed into the mechanisms of action, the optimal dosage, and its potential additional beneficial effects on outcome.

Metabolic Profiling of Amino Acids Associated with Mortality in Patients with Acute Paraquat Poisoning

Background

Paraquat is a major cause of fatal poisoning after ingestion in many parts of Asia and the Pacific nations. However, optimal prognostic indicators to evaluate patient mortality have not been unequivocally established. Following acute paraquat poisoning, a number of amino acids (AA), are abnormally expressed in metabolic pathways. However, the alterations in AA metabolite levels after paraquat poisoning remain unknown in humans.

Material/Methods

In the present study, 40 patients were enrolled, of whom 16 survived and 24 died. A metabolomics approach was used to assess changes in AA metabolites in plasma and its potential prognostic value following paraquat poisoning. Mass spectrometry (MS) based on metabolite identification was conducted.

Results

Twenty-five AA levels in plasma were abnormally expressed in non-survivor patients. Among them, creatinine, indolelactate, and 3-(4-hydroxyphenyl)lactate were found to be highly correlated with paraquat death prediction. It was noted that the intensity levels of these 3 AA metabolites in the non-survivor group were substantially higher than in the survivor group. Furthermore, we examined receiver operating characteristic (ROC) curves for clinical validation. ROC results showed that 3-(4-hydroxyphenyl)lactate had the highest AUC of 0.84, while indolelactate and creatinine had AUCs of 0.75 and 0.83, respectively, suggesting that they can be used to predict the clinical outcome (although this methodology is expensive to implement).

Conclusions

Metabolic profiling of AA levels could be a reliable tool to identify effective indicators for the early high precision prognosis of paraquat poisoning.

Protein in the Hospital: Gaining Perspective and Moving Forward

Provision of adequate protein is crucial for optimizing outcomes in hospitalized patients. However, the methodologies upon which current recommendations are based have limitations, and little is known about true requirements in any clinical population. In this tutorial, we aim to give clinicians an understanding of how current protein recommendations were developed, an appreciation for the limitations of these recommendations, and an overview of more sophisticated approaches that can be applied to better define protein requirements. A broader perspective of the challenges and opportunities in determining clinical protein requirements can help clinicians think critically about the individualized nutrition care they provide to their patients with the goal of administering adequate protein to optimize outcomes.

A critical evaluation of the anabolic response after bolus or continuous feeding in COPD and healthy older adults

After bolus and continuous enteral feeding of the same protein, different digestion and absorption kinetics and anabolic responses are observed. Establishing which mode of feeding has the highest anabolic potential in patients with chronic obstructive pulmonary disease (COPD) may aid in the prevention of muscle wasting, but an important confounding factor is the duration of assessments after bolus feeding. We hypothesized that the anabolic response to bolus and continuous feeding in COPD patients is comparable when methodological issues are addressed. Twenty-one older adults (12 patients with stage II-IV COPD and 9 healthy controls) were studied after intake of a fast-absorbing hydrolyzed casein protein-carbohydrate mixture either as a single bolus or as small sips (crossover design). Whole body protein synthesis (PS), breakdown (PB), net PS (PS - PB) protein efficiency (netPSPE), net protein balance (phenylalanine (PHE) intake - PHE hydroxylation) protein efficiency (netBalPE), and splanchnic PHE extraction (SPE_PHE) were assessed using stable isotope tracer methodology. Bolus feeding assessments were done at 90, 95, and 99% of the calculated duration of the anabolic response. At 99%, netBalPE was higher for sip feeding than bolus feeding in both groups (P<0.0001). Nevertheless, bolus feeding was associated with a lower SPE_PHE (P<0.0001) and higher netPSPE (P<0.0001). At 90% compared with 99%, PS and netBalPE after bolus feeding was significantly overestimated. In conclusion, several factors complicate a comparison of the anabolic capacity of bolus and continuous feeding in acute studies, including the critical role of SPE calculation and assumptions, and the duration of postprandial assessments after bolus feeding.

Metabolic phenotyping using kinetic measurements in young and older healthy adults

BACKGROUND

The aging process is often associated with the presence of sarcopenia. Although changes in the plasma concentration of several amino acids have been observed in older adults, it remains unclear whether these changes are related to disturbances in whole body production and/or interconversions.

METHODS

We studied 10 healthy young (~22.7y) and 17 older adults (~64.8y) by administering a mixture of stable amino acid tracers in a pulse and in a primed constant infusion. We calculated whole body production (WBP) and metabolite to metabolite interconversions. In addition, we measured body composition, muscle function, and provided questionnaires to assess daily dietary intake, physical activity, mood (anxiety, depression) and markers of cognitive function. Plasma enrichments and metabolite concentrations were measured by GC- and LC-MS/MS and statistics were performed by student t-test.

RESULTS

Older adults had a 11% higher body mass index (p=0.04) and 27% reduced peak leg extension force (p=0.02) than the younger group, but comparable values for muscle mass, mood and cognitive function. Although small differences in several plasma amino acid concentrations were observed, we found older adults had about 40% higher values of WBP for glutamine (221±27 vs. 305±21μmol/kgffm/h, p=0.03) and tau-methylhistidine (0.15±0.01 vs. 0.21±0.02μmol/kgffm/h, p=0.04), 26% lower WBP value for arginine (59±4 vs. 44±4μmol/kgffm/h, p=0.02) and a reduction in WBP (50%; 1.23±0.15 vs. 0.69±0.06μmol/kgffm/h, p=0.001) and concentration (25%; 3.5±0.3μmol/l vs. 2.6±0.2μmol/l, p=0.01) for β-Hydroxy β-Methylbutyrate. No differences were observed in protein catabolism. Clearance of arginine was decreased (27%, p=0.03) and clearance of glutamine (58%, p=0.01), leucine (67%, p=0.001) and KIC (76%, p=0.004) were increased in older adults.

CONCLUSIONS

Specific differences exist between young and older adults in amino acid metabolism.

Nutrient modulation in the management of disease-induced muscle wasting: evidence from human studies

PURPOSE OF REVIEW

In addition to being essential for movement, skeletal muscles act as both a store and source of key macronutrients. As such, muscle is an important tissue for whole body homeostasis, undergoing muscle wasting in times of starvation, disease, and stress, for example, to provide energy substrates for other tissues. Yet, muscle wasting is also associated with disability, comorbidities, and mortality. As nutrition is so crucial to maintaining muscle homeostasis 'in health', it has been postulated that muscle wasting in cachexia syndromes may be alleviated by nutritional interventions. This review will highlight recent work in this area in relation to muscle kinetics, the acute metabolic (e.g. dietary protein), and longer-term effects of dietary interventions.

RECENT FINDINGS

Whole body and skeletal muscle protein synthesis invariably exhibit deranged kinetics (favouring catabolism) in wasting states; further, many of these conditions harbour blunted anabolic responses to protein nutrition compared with healthy controls. These derangements underlie muscle wasting. Recent trials of essential amino acid and protein-based nutrition have shown some potential for therapeutic benefit.

SUMMARY

Nutritional modulation, particularly of dietary amino acids, may have benefits to prevent or attenuate disease-induced muscle wasting. Nonetheless, there remains a lack of recent studies exploring these key concepts to make conclusive recommendations.