Role of dietary protein in the sarcopenia of aging

Muscle wasting in young patients with dilated cardiomyopathy

BACKGROUND

Muscle wasting can be accelerated by chronic diseases such as heart failure and is one of the major causes of disability, morbidity, and mortality in this population. We aimed to investigate the incidence of muscle wasting and its associated factors in dilated cardiomyopathy patients younger than 55 years of age.

METHODS

Between April 2014 and December 2015, all symptomatic patients with a diagnosis of non-ischaemic dilated cardiomyopathy who were referred to heart failure clinic were included in our study. Dual energy X-ray absorptiometry was used to evaluate body composition and identify muscle wasting. Muscle mass was calculated as the ratio of an individual's total lean mass of legs and arms (also called appendicular skeletal muscle) to their squared height (kg/m² ). The muscle mass values of less than 5.45 kg/m² for women and 7.26 kg/m² for men were considered low.

RESULTS

A total of 55 patients (32 male) were included. The mean (standard deviation) of age was 37.3 (10.1) years, and the mean of left ventricular ejection fraction was 21.4%. Most of the patients were in the New York Heart Association classes of II and II-III. Twenty-six patients (47.3%) met criteria for muscle wasting. Patients with muscle wasting had lower left ventricular ejection fraction, lower 6-min walk distance, and higher New York Heart Association function class and hospitalization rate.

CONCLUSIONS

We concluded that muscle wasting might be present in younger patients with heart failure, particularly in those who are in worse clinical condition.

A Pilot Randomized Cross-Over Trial to Examine the Effect of Kiwifruit on Satiety and Measures of Gastric Comfort in Healthy Adult Males

‘Hayward’ kiwifruit anecdotally are associated with improved gastrointestinal comfort following the consumption of high protein meals, possibly because of the presence of a protease enzyme, actinidin. The study aimed to use SmartPill™ technology to investigate the acute effect of kiwifruit with actinidin (Actinidia chinensis var. deliciosa ‘Hayward’) and kiwifruit without actinidin (A. chinensis var. chinensis ‘Hort16A’) on digestion of a large protein meal. Ten healthy male subjects were recruited. The participants attended the clinic three times, having fasted overnight. They consumed a test meal consisting of 400 g lean steak and two ‘Hort16A’ or two ‘Hayward kiwifruit’. Subjects completed visual analogue scales (VAS) by rating feelings of hunger, satisfaction, fullness, and comfort and swallowed a SmartPill™ before completing further VAS scales. After 5 h, participants consumed an ad libitum lunch to assess satiety. SmartPill™ transponders were worn for five days. There were no significant differences in gastric emptying time, small bowel, or colonic transit time between the two kiwifruit arms of the study measured by SmartPill™. Similarly, no significant differences were observed in VAS satiety measures or energy consumption at the ad libitum meal. However, the measurement of overall gastric comfort tended to be lower, and bloating was significantly reduced following the consumption of the steak meal with ‘Hayward’ kiwifruit (p < 0.028). Conclusions: The SmartPill™ is marketed as a diagnostic tool for patients presenting with gastrointestinal disorders and is usually used with a standard ‘SmartBar’. This small pilot study suggests that it is less likely to measure gastric emptying effectively following a high protein meal, as it may be delayed because of the meal’s physical consistency. However, green kiwifruit, containing actinidin, may reduce bloating and other measures of gastric discomfort in healthy males. Possible future studies could use repeated measures with more readily digested protein and larger numbers of participants.

Despite Inflammation, Supplemented Essential Amino Acids May Improve Circulating Levels of Albumin and Haemoglobin in Patients after Hip Fractures

Essential amino acids (EAAs) are nutritional substrates that promote body protein synthesis; thus we hypothesised that their supplementation may improve circulating albumin (Alb) and haemoglobin (Hb) in rehabilitative elderly patients following hip fractures (HF). Out of the 145 HF patients originally enrolled in our study, 112 completed the protocol. These subjects were divided into two randomised groups, each containing 56 patients. For a period of two months, one group (age 81.4 ± 8.1 years; male/female 27/29) received a placebo, and the other (age 83.1 ± 7.5 years; male/female 25/31) received 4 + 4 g/day oral EAAs. At admission, the prevalence of both hypoAlb (<3.5 g/dL) and hypoHb (<13 g/dL male, <12 g/dL female) was similar in the placebo group (64.3% hypoAlb, 66% hypoHb) and the treated group of patients (73.2% hypoAlb, 67.8% hypoHb). At discharge, however, the prevalence of hypoAlb had reduced more in EAAs than in placebo subjects (31.7% in EAAs vs. 77.8% in placebo; p < 0.001). There was a 34.2% reduction of anaemia in hypoHb in EAA subjects and 18.9% in placebo subjects, but the difference was not statistically significant. Oral supplementation of EAAs improves hypoAlb and, to a lesser extent, Hb in elderly rehabilitative subjects with hip fractures. Anaemia was reduced in more than one third of patients, which, despite not being statistically significant, may be clinically relevant.

Impact of poor muscle strength on clinical and service outcomes of older people during both acute illness and after recovery

Background

Although Low muscle strength is an important predictor of functional decline in older people, however information on its impact on clinical and service outcomes in acute care settings is still lacking. The aim of this study is to measure the impact of low muscle strength on clinical and service outcomes in older adults during both acute illness and recovery.

Methods

Randomly selected 432 hospitalised older patients had their clinical characteristics and nutritional status assessed within 72 h of admission, at 6 weeks and at 6 months. Low muscle strength-hand grip was defined using the European Working Group criteria. Health outcome measures including nutritional status, length of hospital stay, disability, discharge destination, readmission and mortality were also measured.

Results

Among the 432 patients recruited, 308 (79%) had low muscle strength at baseline. Corresponding figures at 6 weeks and at 6 months were 140 (73%) and 158 (75%). Patients with poor muscle strength were significantly older, increasingly disabled, malnourished and stayed longer in hospital compared with those with normal muscle strength. A significantly higher number of patients with normal muscle strength discharged home independently compared with those with poor muscle strength (p < 0.05). One-year death rate was lower in patients with normal muscle strength 5(6%), compared with those with poor muscle strength 52(15%), however, results were not statistically significant after adjusting for other poor prognostic indicators [adjusted hazard ratio 0.74 (95% CI: 0.14–3.87), p = 0.722].

Conclusion

Poor muscle strength in older people is associated with poor clinical service outcomes during both acute illness and recovery.

Design of a randomized trial to determine the optimum protein intake to preserve lean body mass and to optimize response to a promyogenic anabolic agent in older men with physical functional limitation

The dietary protein allowance for older men to maintain lean body mass and muscle strength and to accrue optimal anabolic responses to promyogenic stimuli is poorly characterized. The OPTIMEN trial was designed to assess in older men with moderate physical dysfunction and insufficient habitual protein intake (<recommended dietary allowance, RDA, 0.8g·kg^-1·d^-1) the efficacy of consuming diets containing 163% RDA (1.3g·kg^-1·d^-1) for protein, compared to RDA, to increase lean mass, muscle performance, and physical function. A second aim was to determine whether increasing protein intake to 1.3 versus 0.8g·kg^-1·d^-1 would augment anabolic responses to a promyogenic agent, testosterone. For this randomized, double-blind, placebo-controlled six-month intervention trial, 92 men, 65years or older, with Short Physical Performance Battery scores 3-10, and habitual protein intakes <RDA, were assigned to one of four groups: 100% RDA plus placebo intramuscular injections weekly; 100% RDA plus weekly intramuscular injections of 100mg testosterone enanthate; 163% RDA plus placebo injections; or 163% RDA plus testosterone injections. All participants received portion-controlled packaged meals and group-specific dietary supplements containing either mixtures of casein and whey or carbohydrate, with identical appearance. The primary outcome was change in lean body mass assessed using dual energy X-ray absorptiometry. Secondary outcomes included maximal voluntary strength and power in leg press and chest press exercises, 6-minute walking distance, stair climbing power, and self-reported physical function. Results of the OPTIMEN trial have important implications for dietary protein guidance and policy, and efficacy of promyogenic drugs.

Exercise and Protein Intake: A Synergistic Approach against Sarcopenia

Sarcopenia, the age-dependent loss of muscle mass and function/strength, is increasingly recognized as a major risk factor for adverse outcomes in frail older people. As such, the skeletal muscle is a relevant target for interventions aimed at preventing or postponing the occurrence of negative health-related events in late life. The association among physical inactivity, insufficient intake of energy and protein, and poor muscle health in older adults suggests that physical exercise and targeted nutritional supplementation may offer substantial therapeutic gain against sarcopenia and its negative correlates. This view is supported by observational studies as well as by small-scale clinical trials. In this review, we summarize the available evidence on the beneficial effects of behavioral interventions on sarcopenia. We also briefly describe how the knowledge gathered so far has been used to design the “Sarcopenia and Physical fRailty IN older people: multicomponenT Treatment strategies” (SPRINTT) project. The randomized clinical trial conducted within SPRINTT will provide robust evidence on the effectiveness of exercise and nutrition at preventing negative outcomes associated with sarcopenia and physical frailty.

Protein Intake and Mobility Limitation in Community-Dwelling Older Adults: the Health ABC Study

OBJECTIVES

The current Recommended Dietary Allowance (RDA) for protein is based on short-term nitrogen balance studies in young adults and may underestimate the amount needed to optimally preserve physical function in older adults. We examined the association between protein intake and the onset of mobility limitation over 6 years of follow-up in older adults in the Health ABC study.

DESIGN

Prospective cohort study.

SETTING

Memphis, Tennessee and Pittsburgh, Pennsylvania.

PARTICIPANTS

Community-dwelling, initially well-functioning adults aged 70-79 years (n = 1998).

MEASUREMENTS

Protein intake (g/kg body weight/d) was calculated using an interviewer-administered 108-item food frequency questionnaire at baseline. Mobility limitation was assessed semi-annually and defined as reporting any difficulty walking one-quarter of a mile or climbing 10 steps on 2 consecutive 6-month contacts. The association between protein intake and incident mobility limitation was examined using Cox proportional hazard regression models adjusting for demographics, behavioral characteristics, chronic conditions, total energy intake, and height.

RESULTS

Mean (SD) protein intake was 0.91 (0.38) g/kg body weight/d, with 43% reporting intakes less than the RDA (0.8 g/kg body weight/d). During 6 years of follow-up, 705 participants (35.3%) developed mobility limitations. Compared to participants in the upper tertile of protein intake (≥1.0 g/kg body weight/d), participants in the lower two tertiles of protein intake (<0.7 and 0.7 -<1.0 g/kg body weight/d) were at greater risk of developing mobility limitation over 6 years of follow-up (RR (95% CI): 1.86 (1.41-2.44) and 1.49 (1.20-1.84), respectively).

CONCLUSION

Lower protein intake was associated with increased risk of mobility limitation in community-dwelling, initially well-functioning older adults. These results suggest that protein intakes of ≥1.0 g/kg body weight/d may be optimal for maintaining physical function in older adults.

Reduced muscular fatigue after a 12-week leucine-rich amino acid supplementation combined with moderate training in elderly: a randomised, placebo-controlled, double-blind trial

Background

Age-related muscle loss is characterised by a progressing decrease in muscle mass, strength and function. Besides resistance training and physical activity, appropriate nutrition that is rich in protein, especially branched-chain amino acids, is very important to support training effects and positively influence the protein synthesis to degradation ratio.

Aim

The purpose of this study was to evaluate the effect of a 12-week leucine-rich amino acid supplementation in combination with moderate training.

Methods

Forty-eight healthy subjects exercised for 30 min three times per week and received either a leucine-rich amino acid supplementation or a placebo. Before and after supplementation, volunteers performed an exhaustive eccentric exercise protocol. Maximal concentric strength, muscle soreness, creatine kinase (CK), type II collagen collagenase cleavage neoepitope (C2C), C propeptide of type II procollagen (CP2) and safety assessments were performed before exercise and after 3, 24, 48 and 72 hours.

Results

The supplementation with leucine resulted in reduced loss of strength at 0 and 3 hours after downhill walking compared with the placebo (p=0.0439). The reduction of C2C/CP2 ratio deflection was significantly increased (p=0.038) due to leucine compared with the placebo. The same tendency could be observed for the recovery phase. No significant supplement effects for muscle soreness and CK could be observed.

Conclusion

The principle findings show that leucine-rich amino acid supplementation can counteract the negative effects of eccentric exercise. The treatment resulted in a reduction of exercise-induced strength loss.

Balanço de macronutrientes na dieta de idosos brasileiros: análises da Pesquisa Nacional de Alimentação 2008-2009

RESUMO: Objetivo: Analisar a contribuição de proteína, lipídio e carboidrato no total de energia da dieta de idosos das diferentes regiões brasileiras. Métodos: Foram analisados dados de 4.286 idosos (60 a 104 anos) provenientes da Pesquisa de Orçamentos Familiares 2008/2009. Baseado no consumo obtido por dois registros alimentares, o programa Multiple Source Method estimou o consumo habitual de macronutrientes e gordura saturada. As recomendações do Institute of Medicine (IOM), segundo os Acceptable Macronutrient Distribution Ranges (AMDR), foram utilizadas para avaliar a participação relativa dos macronutrientes de acordo com percentual energético (PE). Modelos de regressão linear identificaram diferenças entre PE dos macronutrientes, situação do domicílio, macrorregiões e gênero. Resultados: A proteína foi o macronutriente que apresentou maior concordância com o AMDR (99,8%). Com relação ao PE lipídico, observou-se que 9,2% da população ficaram acima da recomendação, sendo o dobro do encontrado para carboidrato (4,9%) e nove vezes o percentual de idosos, cujo PE-proteico (1,0%) foi acima do recomendado. Em 14,5% dos idosos a ingestão de carboidratos foi abaixo da AMDR, sendo que essas dietas apresentaram maior PE lipídico (β = 8,19; p < 0,001), revelando que 50% dos idosos que consumiam carboidratos abaixo do PE recomendado apresentou um consumo excessivo de lipídio. Segundo macrorregiões, o Centro-Oeste foi o único a apresentar diferença para carboidrato, sendo esta de menor percentual (51,6%; p < 0,05). A região Sul (17,9%; p < 0,01) apresentou o menor PE proteico e o maior de lipídios (28,7%; p < 0,01). Conclusões: A elevada frequência de inadequação da ingestão de lipídio pode significar uma pior qualidade da dieta, contribuindo com o aumento no risco de desenvolvimento de doenças crônicas.

Effect of a High-Protein Energy-Restricted Diet Combined with Resistance Training on Metabolic Profile in Older Individuals with Metabolic Impairments

Adequate protein intake and resistance training are effective strategies to maintain muscle mass, but the effect of their combination on metabolic profile during weight loss remains to be determined in older adults. The main objective of this study was to determine the effect of a 16-week high-protein caloric restriction combined with resistance training on chronic disease risk factors in obese older individuals with metabolic impairments. A total of 26 overweight adults aged between 60 and 75 years (BMI 32.4 ± 3.9 kg/m2) with at least 2 factors of the metabolic syndrome participated in this study and were randomized into two groups: 1) high-protein caloric restriction (HP; n= 12) and 2) high-protein caloric restriction combined with dynamic-resistance training (HP+RT; n=14). Caloric intake was reduced by 500 kcal/d in all participants and protein intake equated 25-30% of total calories (~1.4 g/kg/d). Exercise training consisted of 3 session/week of resistance training on pulley machines. Outcome measures included total and trunk fat mass (FM), total and appendicular lean body mass (LBM), fasting glucose level, lipid profile and blood pressure. Our results showed that total and trunk FM (all p<0.0001) as well as fasting glucose (p<0.0001), triglycerides (p=0.002) and total cholesterol (p=0.03) levels decreased similarly in both groups. However, total (p=0.04) and appendicular (p=0.02) LBM decreased in the HP group only. Our data show that high-protein energy restriction improves health profile of obese elderly at high risk of chronic disease but needs to be combined with resistance training to maintain LBM.

Inadequacy of Body Weight-Based Recommendations for Individual Protein Intake-Lessons from Body Composition Analysis

Current body weight-based protein recommendations are ignoring the large variability in body composition, particularly lean mass (LM), which drives protein requirements. We explored and highlighted the inter-individual variability of weight versus body composition-adjusted protein intakes by secondary analysis in three cohorts of (1) 574 healthy adults (mean ± SD age: 41.4 ± 15.2 years); (2) 403 cirrhotic patients (age: 44.7 ± 12.3 years) and (3) 547 patients with lung cancer (age: 61.3 ± 8.2 years). LM was assessed using different devices (magnetic resonance imaging, dual-energy X-ray absorptiometry, computer tomography, total body potassium and bioelectrical impedance), body weight-based protein intake, its ratio (per kg LM) and mean protein requirement were calculated. Variability in protein intake in all cohorts ranged from 0.83 to 1.77 g protein per kg LM per day using (theoretical protein intake of 60 g protein per day). Calculated mean protein requirement was 1.63 g protein per kg LM per day; consequently, 95.3% of healthy subjects, 100% of cirrhotic and 97.4% of cancer patients would present with a low protein intake per kg LM. Weight-adjusted recommendations are inadequate to address the LM specific differences in protein needs of healthy subjects or clinical populations. Absolute protein intake seems to be more relevant compared to the relative proportion of protein, which in turn changes with different energy needs.

Protein Intake and Breast Cancer Survival in the Nurses' Health Study

Purpose Greater protein intake has been associated with better breast cancer survival in several prospective studies, including among 1,982 women in the Nurses' Health Study. We proposed to extend this previous finding. We hypothesized that protein, essential amino acid, branched-chain amino acid, and leucine intakes are associated with improved survival and that these associations are stronger in tumors expressing insulin receptor (IR). Patients and Methods We included 6,348 women diagnosed with stage I to III breast cancer between 1976 and 2004. There were 1,046 distant recurrences. Relative risks (RRs) and 95% CIs were calculated according to quintiles of updated postdiagnostic diet using adjusted Cox proportional hazards models based on follow-up until 2010. Results There was an inverse association between energy-adjusted protein intake and recurrence. Multivariable RRs for increasing quintiles of intake compared with the lowest were 0.95 (95% CI, 0.79 to 1.15), 0.92 (95% CI, 0.76 to 1.11), 0.75 (95% CI, 0.61 to 0.91), and 0.84 (95% CI, 0.69 to 1.03; trend P = .02). For animal protein intake, the RRs were 0.88 (95% CI, 0.73 to 1.06), 0.85 (95% CI, 0.70 to 1.02), 0.75 (95% CI, 0.62 to 0.92), and 0.78 (95% CI, 0.63 to 0.95; trend P = .003). Neither essential amino acids, branched-chain amino acids, nor any individual amino acid stood out as being the source of the association. The association also did not differ by IR status. There was no clear association with any protein-containing foods. Conclusion We found a modest survival advantage with higher intake of protein, regardless of IR status. There was no clear mechanism for this association, although it is consistent with prior studies. Our data suggest that there is likely no advantage for women with a history of breast cancer in restricting protein intake or protein-containing foods.

Effects of a nutrition plus exercise programme on physical function in sarcopenic obese elderly people: study protocol for a randomised controlled trial

INTRODUCTION

With a rapidly ageing population, sarcopenic obesity, defined as decreased muscle mass and function combined with increased body fat, is a complex health problem. Although sarcopenic obesity contributes to a decline in physical function and exacerbates frailty in older adults, evidence from clinical trials about the effect of exercise and nutrition on this complex syndrome in Chinese older adults is lacking.

METHODS AND ANALYSIS

We devised a study protocol for a single-blind randomised controlled trial. Sarcopenia is described as age-related decline in muscle mass plus low muscle strength and/or low physical performance. Obesity is defined as a percentage of body fat above the 60th centile. Ninety-two eligible participants will be randomly assigned to a control group, nutrition group, exercise group and nutrition plus exercise group to receive an 8-week intervention and 12-week follow-up. The primary outcomes will be the change in short physical performance battery scores, grip strength and 6 m usual gait speed. The secondary outcomes will include basic activities of daily living scores, instrumental activity daily living scores, body composition and body anthropometric indexes. For all main analyses, the principle of intention-to-treat will be used.

ETHICS AND DISSEMINATION

This study was approved by the medical ethics committee of Zhejiang Hospital on 25 November 2015. The study will present data targeting the clinical effects of nutrition and exercise on physical function and body composition in a Chinese older population with sarcopenic obesity. The results will help to provide important clinical evidence of the role of complex non-pharmaceutical interventions for sarcopenic obese older people. The findings of this study will be submitted to peer-reviewed medical journals for publication and presented at relevant academic conferences.

TRIAL REGISTRATION NUMBER

ChiCTR-IOR-15007501; Pre-results.

Relation between mealtime distribution of protein intake and lean mass loss in free-living older adults of the NuAge study

BACKGROUND

Studies have shown that an even protein intake distribution across meals increased 24-h muscle protein synthesis in young adults compared with a skewed intake. Whether this short-term result translates into long-term preservation of lean mass (LM) in older adults remains unknown.

OBJECTIVE

The aim was to examine the extent to which protein quantity and distribution are associated with LM and appendicular LM (aLM), and their 2-y decline, in community-dwelling older adults.

DESIGN

Baseline and 2-y follow-up data from 351 men and 361 women (aged 67-84 y) in the NuAge study (Quebec Longitudinal Study on Nutrition as a Determinant of Successful Aging) with available body-composition data (by dual-energy X-ray absorptiometry) were used. Food intake was assessed with the use of three 24-h food recalls collected at baseline and 3 collected at the 2-y follow-up. Protein distribution across meals was calculated as the CV of protein ingested per meal, with lower values reflecting evenness of protein intake. Linear mixed-model analysis was performed to examine changes in LM and aLM across time, by sex, as conditioned by the quantity and distribution of protein intake, adjusted for potential covariates.

RESULTS

Over 2 y, LM declined in both men (-2.5% ± 4.0%) and women (-2.0% ± 3.4%) (P < 0.05), whereas aLM loss was not significant (men: -1.5% ± 4.8%; women: -1.2% ± 5.3%; P > 0.05). The decline in LM was not independently affected by the quantity and distribution of protein intake. Yet men and women with evenly distributed protein intakes and men with high protein intakes showed higher LM or aLM throughout the entire follow-up period, even after potential confounders were controlled for (P < 0.05).

CONCLUSIONS

Our results suggest that greater protein intakes and a more even distribution across meals are modifiable factors associated with higher muscle mass in older adults but not with losses over 2 y. Interventional studies should determine longer-term effects on preserving LM with aging.

Protein Requirements during Aging

Protein recommendations for elderly, both men and women, are based on nitrogen balance studies. They are set at 0.66 and 0.8 g/kg/day as the estimated average requirement (EAR) and recommended dietary allowance (RDA), respectively, similar to young adults. This recommendation is based on single linear regression of available nitrogen balance data obtained at test protein intakes close to or below zero balance. Using the indicator amino acid oxidation (IAAO) method, we estimated the protein requirement in young adults and in both elderly men and women to be 0.9 and 1.2 g/kg/day as the EAR and RDA, respectively. This suggests that there is no difference in requirement on a gender basis or on a per kg body weight basis between younger and older adults. The requirement estimates however are ~40% higher than the current protein recommendations on a body weight basis. They are also 40% higher than our estimates in young men when calculated on the basis of fat free mass. Thus, current recommendations may need to be re-assessed. Potential rationale for this difference includes a decreased sensitivity to dietary amino acids and increased insulin resistance in the elderly compared with younger individuals.

Counteracting Age-related Loss of Skeletal Muscle Mass: a clinical and ethnological trial on the role of protein supplementation and training load (CALM Intervention Study): study protocol for a randomized controlled trial

Background

Aging is associated with decreased muscle mass and functional capacity, which in turn decrease quality of life. The number of citizens over the age of 65 years in the Western world will increase by 50 % over the next four decades, and this demographic shift brings forth new challenges at both societal and individual levels. Only a few longitudinal studies have been reported, but whey protein supplementation seems to improve muscle mass and function, and its combination with heavy strength training appears even more effective. However, heavy resistance training may reduce adherence to training, thereby attenuating the overall benefits of training. We hypothesize that light load resistance training is more efficient when both adherence and physical improvement are considered longitudinally. We launched the interdisciplinary project on Counteracting Age-related Loss of Skeletal Muscle Mass (CALM) to investigate the impact of lifestyle changes on physical and functional outcomes as well as everyday practices and habits in a qualitative context.

Methods

We will randomize 205 participants older than 65 years to be given 1 year of two daily nutrient supplements with 10 g of sucrose and 20 g of either collagen protein, carbohydrates, or whey. Further, two groups will perform either heavy progressive resistance training or light load training on top of the whey supplement.

Discussion

The primary outcome of the CALM Intervention Study is the change in thigh cross-sectional area. Moreover, we will evaluate changes in physical performance, muscle fiber type and acute anabolic response to whey protein ingestion, sensory adaptation, gut microbiome, and a range of other measures, combined with questionnaires on life quality and qualitative interviews with selected subjects. The CALM Intervention Study will generate scientific evidence and recommendations to counteract age-related loss of skeletal muscle mass in elderly individuals.

Trial registration

ClinicalTrials.gov NCT02034760. Registered on 10 January 2014.

ClinicalTrials.gov NCT02115698. Registered on 14 April 2014.

Danish regional committee of the Capital Region H-4-2013-070. Registered on 4 July 2013.

Danish Data Protection Agency 2012-58-0004 – BBH-2015-001 I-Suite 03432. Registered on 9 January 2015.

Sodium nitrate co-ingestion with protein does not augment postprandial muscle protein synthesis rates in older, type 2 diabetes patients

The age-related anabolic resistance to protein ingestion is suggested to be associated with impairments in insulin-mediated capillary recruitment and postprandial muscle tissue perfusion. The present study investigated whether dietary nitrate co-ingestion with protein improves muscle protein synthesis in older, type 2 diabetes patients. Twenty-four men with type 2 diabetes (72 ± 1 yr, 26.7 ± 1.4 m/kg(2) body mass index, 7.3 ± 0.4% HbA1C) received a primed continuous infusion of l-[ring-(2)H5]phenylalanine and l-[1-(13)C]leucine and ingested 20 g of intrinsically l-[1-(13)C]phenylalanine- and l-[1-(13)C]leucine-labeled protein with (PRONO3) or without (PRO) sodium nitrate (0.15 mmol/kg). Blood and muscle samples were collected to assess protein digestion and absorption kinetics and postprandial muscle protein synthesis rates. Upon protein ingestion, exogenous phenylalanine appearance rates increased in both groups (P < 0.001), resulting in 55 ± 2% and 53 ± 2% of dietary protein-derived amino acids becoming available in the circulation over the 5h postprandial period in the PRO and PRONO3 groups, respectively. Postprandial myofibrillar protein synthesis rates based on l-[ring-(2)H5]phenylalanine did not differ between groups (0.025 ± 0.004 and 0.021 ± 0.007%/h over 0-2 h and 0.032 ± 0.004 and 0.030 ± 0.003%/h over 2-5 h in PRO and PRONO3, respectively, P = 0.7). No differences in incorporation of dietary protein-derived l-[1-(13)C]phenylalanine into de novo myofibrillar protein were observed at 5 h (0.016 ± 0.002 and 0.014 ± 0.002 mole percent excess in PRO and PRONO3, respectively, P = 0.8). Dietary nitrate co-ingestion with protein does not modulate protein digestion and absorption kinetics, nor does it further increase postprandial muscle protein synthesis rates or the incorporation of dietary protein-derived amino acids into de novo myofibrillar protein in older, type 2 diabetes patients.

The Current Understanding of Sarcopenia: Emerging Tools and Interventional Possibilities

The purpose of this review is to provide health practitioners and physicians the most current state of the research on sarcopenia, its consequences, and to offer a summary of consensus guidelines for identification based on the most recent and compelling investigations and analyses. To accomplish this, the causes and consequences of sarcopenia will be described, and definitions and screening methods are updated. Importantly, interventional recommendations for sarcopenia will be discussed with a special emphasis on the effects of resistance training on sarcopenia-related outcomes. Furthermore, due to the increasing usage of hormone treatment as a strategy to combat sarcopenia, special consideration on the effects of hormone changes with aging and as interventions will be briefly reviewed.

Protein Intake and Muscle Health in Old Age: From Biological Plausibility to Clinical Evidence

The provision of sufficient amounts of dietary proteins is central to muscle health as it ensures the supply of essential amino acids and stimulates protein synthesis. Older persons, in particular, are at high risk of insufficient protein ingestion. Furthermore, the current recommended dietary allowance for protein (0.8 g/kg/day) might be inadequate for maintaining muscle health in older adults, probably as a consequence of "anabolic resistance" in aged muscle. Older individuals therefore need to ingest a greater quantity of protein to maintain muscle function. The quality of protein ingested is also essential to promoting muscle health. Given the role of leucine as the master dietary regulator of muscle protein turnover, the ingestion of protein sources enriched with this essential amino acid, or its metabolite β-hydroxy β-methylbutyrate, is thought to offer the greatest benefit in terms of preservation of muscle mass and function in old age.

Sarcopenia and Dynapenia in Patients With Parkinsonism

OBJECTIVES

To estimate prevalence of sarcopenia and dynapenia in outpatients with Parkinson disease (PD) and to investigate their association with the features of the disease.

DESIGN

Cross-sectional study.

SETTING

A specialized tertiary care center.

PARTICIPANTS

Consecutive patients (n = 364) aged 65 years or older, affected by parkinsonian syndromes.

MEASUREMENTS

Skeletal muscle mass (SMM), as well as strength and gait speed (GS) were assessed by bioimpedence analysis, handgrip dynamometry, and the 4-meter walking test, respectively. Based on these assessments, sarcopenia was diagnosed using the European Working Group on Sarcopenia in Older People criteria. Dynapenia was defined as handgrip strength less than 30 kg in men and less than 20 kg in women.

RESULTS

In total, 235 patients (64.6%) had a diagnosis of idiopathic PD. Low SMM index was recorded in 27 patients. Due to gait disturbances and postural instability, GS could not be measured in 98 patients and was found to be reduced in 61.3% of those assessed. Prevalence of sarcopenia and dynapenia was 6.6% (95% confidence interval [CI] 4.3-9.7) and 75.5% (95% CI 70.8-79.9), respectively. Sarcopenia tended to be higher in patients unable to perform GS assessment and was unrelated to the type of parkinsonian syndrome. It was associated with older age, longer disease duration, more severe disease, and higher disability in activities of daily living, as assessed by disease-specific clinical rating scale. Dynapenia was directly associated with parkinsonism other than PD, older age, and disability, whereas regular physical therapy appeared to be a preventive factor. However, it was unrelated to disease duration and severity. Finally, the disability score of activities of daily living was inversely correlated with handgrip strength and GS, whereas no association was found with SMM index.

CONCLUSION

Being primarily motor disorders, parkinsonian syndromes are characterized by progressive disability in performing activities of daily living. Impaired functional status is a prominent feature of this patient population, independently of disease duration and severity. Sarcopenia is mainly related to advancing disease and, due to a significant sparing of SMM, is an infrequent condition, likely to play a minor role in disability. Several factors could be responsible for this favorable body composition (eg, motor symptoms, levodopa therapy) and deserve further investigation. The prognostic impact of sarcopenia also needs to be addressed.

A Contribution of Beef to Human Health: A Review of the Role of the Animal Production Systems

Meat and meat products constitute important source of protein, fat, and several functional compounds. Although beef consumption may implicate possible negative impacts on human health, its consumption can also contribute to human health. Quality traits of beef, as well as its nutritional properties, depend on animal genetics, feeding, livestock practices, and post mortem procedures. Available data show that emerging beef production systems are able to improve both, quality and nutritional traits of beef in a sustainable way. In this context, Argentina's actions are aimed at maximising beef beneficial effects and minimising its negative impact on human health, in a way of contributing to global food security.

Long-Term Body Composition Changes in Women Following Roux-en-Y Gastric Bypass Surgery

BACKGROUND

Although most individuals experience successful weight loss following Roux-en-Y gastric bypass (RYGB), weight regain is a concern, the composition of which is not well documented. Our aim was to evaluate changes in body composition and handgrip strength as a measure of functional status in participants from a previous 1-year post-RYGB longitudinal study who had undergone RYGB approximately 9 years prior.

METHODS

Five women from an original larger cohort were monitored pre-RYGB and 1.5 months, 6 months, 1 year, and 9 years post-RYGB. Body composition was assessed at all time points using dual energy x-ray absorptiometry and multiple dilution. Handgrip strength was measured using a digital isokinetic hand dynamometer (Takei Scientific Instruments, Ltd, Tokyo, Japan).

RESULTS

Mean time to final follow-up was 8.7 years. Lean soft tissue (LST) loss over the ~9-year period was on average 11.9 ± 5.6 kg. Compared with 1-year post-RYGB, 9-year LST was 4.4 ± 3.0 kg lower ( P = .03). Fat-free mass decreased over the 9-year period by 12.6 ± 5.8 kg. Mean fat mass (FM) decreased from 75.4 ± 22.6 kg pre-RYGB to 35.5 ± 21.5 kg 1 year post-RYGB but then trended toward an increase of 8.6 ± 7.0 kg between 1 year and 9 years post-RYGB ( P = .053). Loss of LST was correlated with loss of handgrip strength ( r = 0.64, P = .0005).

CONCLUSION

The continued loss of lean mass associated with decreased handgrip strength occurring with long-term trend toward FM regain post-RYGB is concerning. The loss of LST and functional strength carries particular implications for the aging bariatric population and should be investigated further.

Muscle Mass Index and Animal Source of Dietary Protein Are Positively Associated with Insulin Resistance in Participants of the NuAge Study

OBJECTIVES

Contribute evidence towards the complex interrelationships of body composition, insulin sensitivity and protein intake independently from adiposity in an older population.

DESIGN

This is a cross-sectional analysis of an existing dataset in which a literature-supported model linking together the variables of interest is tested using path analysis.

SETTING

The loss of muscle mass has been implicated in the development of insulin resistance. We propose to test associations of muscle mass with insulin sensitivity and their respective associations with animal and vegetable sources of protein intake, independently from adiposity.

PARTICIPANTS

Non-diabetic participants aged 68-82 years from the NuAge study with all available measures (n=441) were included.

MEASUREMENTS

A model considering age, sex, chronic diseases, physical activity; smoking and sources of protein intake influencing body composition components and insulin sensitivity was created and tested with Path Analysis for their independent associations. Muscle mass index (MMI; kg/height in m2) and % body fat were derived from DXA and BIA. Insulin resistance was estimated by the Homeostatic Model Assessment for Insulin Resistance (HOMA-IR) score and physical activity by the Physical Activity Scale for the Elderly (PASE) questionnaire. Protein intakes were obtained from three non-consecutive 24h-diet recalls.

RESULTS

In the final model, direct positive associations were observed between HOMA-IR score and MMI (ß=0.42; 95%CI: 0.24; 0.6) and % body fat (ß=0.094; 95%CI: 0.07; 0.11). There were no direct associations between animal protein intake and MMI or with HOMA-IR. There was a significant direct negative association between plant protein intake and MMI (ß= -0.068; 95%CI: -0.13; -0.003) and significant indirect associations mediated through MMI and % body fat between HOMA-IR and animal protein intake (ß=0.0321; 95%CI: 0.01; 0.05), as well as plant protein intake (ß= -0.07; 95%CI: -0.1; 0.0).

CONCLUSIONS

Our final model indicated that MMI and HOMA score were significantly positively associated. Protein intake sources were related to HOMA-IR score differently through MMI and % body fat, respectively.

A Prospective Cohort Study to Examine the Association Between Dietary Patterns and Sarcopenia in Chinese Community-Dwelling Older People in Hong Kong

OBJECTIVES

Dietary pattern analysis has recently emerged as an alternative approach to investigate the association between diet and sarcopenia. This study examined the association of dietary patterns with sarcopenia in Chinese community-dwelling older people.

METHODS

Chinese men and women aged 65 years or older participating in a cohort study examining the risk factors for osteoporosis completed a validated food frequency questionnaire at baseline between 2001 and 2003. Adherence to a priori dietary patterns, namely the Diet Quality Index-International (DQI-I) and the Mediterranean Diet Score (MDS) was assessed. Factor analysis identified 3 a posterior dietary patterns: "vegetables-fruits," "snacks-drinks-milk products," and "meat-fish." Sarcopenia was defined using the Asian Working Group for Sarcopenia algorithm. Multiple logistic regression was used for cross-sectional analysis (n = 3957) to assess the associations between dietary patterns and prevalent sarcopenia, and for longitudinal analysis (n = 2948) on their associations with 4-year incident sarcopenia with adjustment for sociodemographic and lifestyle factors.

RESULTS

There were 290 (7.3%) (185 men, 105 women) sarcopenic cases at baseline and 264 (9.0%) (160 men, 104 women) incident sarcopenic cases at the 4-year follow-up. At baseline, men in the highest quartile of DQI-I had reduced odds of sarcopenia (Adjusted OR 0.50, 95% CI 0.31-0.81, Ptrend = .004) compared with men in the lowest quartile. Men in the highest quartile of "vegetables-fruits" pattern score (Adjusted OR 0.60, 95% CI 0.36-0.99, Ptrend = .034) showed lower likelihood of sarcopenia compared with men in the lowest quartile. Higher quartile of "snacks-drinks-milk products" pattern score was associated with lower odds of sarcopenia in men (Adjusted OR 0.41, 95% CI 0.24-0.70, Ptrend < .001). There was no association between dietary patterns and prevalent sarcopenia in women. None of the dietary patterns was associated with incident sarcopenia at 4-year in both sexes.

CONCLUSIONS

Higher DQI-I, higher "vegetables-fruits" dietary pattern score, and higher "snacks-drinks-milk products" dietary pattern score were associated with lower odds of prevalent sarcopenia in Chinese older men.

Skeletal muscle homeostasis and plasticity in youth and ageing: impact of nutrition and exercise

Skeletal muscles comprise a substantial portion of whole body mass and are integral for locomotion and metabolic health. Increasing age is associated with declines in both muscle mass and function (e.g. strength‐related performance, power) with declines in muscle function quantitatively outweighing those in muscle volume. The mechanisms behind these declines are multi‐faceted involving both intrinsic age‐related metabolic dysregulation and environmental influences such as nutritional and physical activity. Ageing is associated with a degree of ‘anabolic resistance’ to these key environmental inputs, which likely accelerates the intrinsic processes driving ageing. On this basis, strategies to sensitize and/or promote anabolic responses to nutrition and physical activity are likely to be imperative in alleviating the progression and trajectory of sarcopenia. Both resistance‐ and aerobic‐type exercises are likely to confer functional and health benefits in older age, and a clutch of research suggests that enhancement of anabolic responsiveness to exercise and/or nutrition may be achieved by optimizing modifications of muscle‐loading paradigms (workload, volume, blood flow restriction) or nutritional support (e.g. essential amino acid/leucine) patterns. Nonetheless, more work is needed in which a more holistic view in ageing studies is taken into account. This should include improved characterization of older study recruits, that is physical activity/nutritional behaviours, to limit confounding variables influencing whether findings are attributable to age, or other environmental influences. Nonetheless, on balance, ageing is associated with declines in muscle mass and function and a partially related decline in aerobic capacity. There is also good evidence that metabolic flexibility is impaired in older age.

Sarcopenic Obesity: An Appraisal of the Current Status of Knowledge and Management in Elderly People

Today's increased life expectancy highlights both age-related changes in body composition and a higher prevalence of obesity. Sarcopenic obesity (SO) is assuming a prominent role in cardio-metabolic risk because of the double metabolic burden derived from low muscle mass (sarcopenia) and excess adiposity (obesity). This review evaluates the related studies that have been published over the past 10 years in order to give an updated overview of this new syndrome. There is no consensus on the definition of SO due to the wide heterogeneity of diagnostic criteria and choice of body composition components needed to assess this phenotype. There is a growing body of evidence that the ethio-pathogenesis of SO is complex and multi-factorial, as the consequences are a combination of the outcomes of both sarcopenia and obesity, where the effects are maximised. In order to manage SO, it is important to make lifestyle changes that incorporate weight loss, physical exercise and protein supplementation.

Protein Supplementation at Breakfast and Lunch for 24 Weeks beyond Habitual Intakes Increases Whole-Body Lean Tissue Mass in Healthy Older Adults

BACKGROUND

Key areas of research on the preservation of lean tissue mass (LTM) during aging are determinations of the protein requirement and optimal protein intake at meals.

OBJECTIVE

The aim of this study was to determine the effect of protein supplementation at breakfast and lunch for 24 wk beyond habitual intakes on whole-body LTM in healthy adults aged 50-70 y.

METHODS

In a single-blinded, randomized, controlled design, 60 healthy older men and women (aged 61 ± 5 y) with a body mass index (in kg/m(2)) of 25.8 ± 3.6 consumed either 0.165 g/kg body mass of a milk-based protein matrix (PRO) or an isoenergetic, nonnitrogenous maltodextrin control (CON) at breakfast and midday meals, the lower protein-containing meals of the day, for 24 wk. Dual-energy X-ray absorptiometry was used to measure the change in LTM.

RESULTS

After the intervention, protein intake in the PRO group increased from 0.23 ± 0.1 to 0.40 ± 0.1 g/kg for breakfast and from 0.31 ± 0.2 to 0.47 ± 2 g/kg for the midday meal. In response, LTM increased by 0.45 (95% CI: 0.06, 0.83) kg in the PRO group compared with a decrease of 0.16 (95% CI: -0.49, 0.17) kg in the CON group (P = 0.006). Appendicular LTM accounted for the majority of the difference in LTM, increasing by 0.27 (95% CI: 0.05, 0.48) kg in the PRO group compared with no change in the CON group (P = 0.002).

CONCLUSIONS

Protein supplementation at breakfast and lunch for 24 wk in healthy older adults resulted in a positive (+0.6 kg) difference in LTM compared with an isoenergetic, nonnitrogenous maltodextrin control. These observations suggest that an optimized and balanced distribution of meal protein intakes could be beneficial in the preservation of lean tissue mass in the elderly. This trial was registered at clinicaltrials.gov as NCT02529124.

Satellite cells in human skeletal muscle plasticity

Skeletal muscle satellite cells are considered to play a crucial role in muscle fiber maintenance, repair and remodeling. Our knowledge of the role of satellite cells in muscle fiber adaptation has traditionally relied on in vitro cell and in vivo animal models. Over the past decade, a genuine effort has been made to translate these results to humans under physiological conditions. Findings from in vivo human studies suggest that satellite cells play a key role in skeletal muscle fiber repair/remodeling in response to exercise. Mounting evidence indicates that aging has a profound impact on the regulation of satellite cells in human skeletal muscle. Yet, the precise role of satellite cells in the development of muscle fiber atrophy with age remains unresolved. This review seeks to integrate recent results from in vivo human studies on satellite cell function in muscle fiber repair/remodeling in the wider context of satellite cell biology whose literature is largely based on animal and cell models.

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 Skeletal Muscle Anabolic Response to Plant- versus Animal-Based Protein Consumption

Clinical and consumer market interest is increasingly directed toward the use of plant-based proteins as dietary components aimed at preserving or increasing skeletal muscle mass. However, recent evidence suggests that the ingestion of the plant-based proteins in soy and wheat results in a lower muscle protein synthetic response when compared with several animal-based proteins. The possible lower anabolic properties of plant-based protein sources may be attributed to the lower digestibility of plant-based sources, in addition to greater splanchnic extraction and subsequent urea synthesis of plant protein-derived amino acids compared with animal-based proteins. The latter may be related to the relative lack of specific essential amino acids in plant- as opposed to animal-based proteins. Furthermore, most plant proteins have a relatively low leucine content, which may further reduce their anabolic properties when compared with animal proteins. However, few studies have actually assessed the postprandial muscle protein synthetic response to the ingestion of plant proteins, with soy and wheat protein being the primary sources studied. Despite the proposed lower anabolic properties of plant vs. animal proteins, various strategies may be applied to augment the anabolic properties of plant proteins. These may include the following: 1) fortification of plant-based protein sources with the amino acids methionine, lysine, and/or leucine; 2) selective breeding of plant sources to improve amino acid profiles; 3) consumption of greater amounts of plant-based protein sources; or 4) ingesting multiple protein sources to provide a more balanced amino acid profile. However, the efficacy of such dietary strategies on postprandial muscle protein synthesis remains to be studied. Future research comparing the anabolic properties of a variety of plant-based proteins should define the preferred protein sources to be used in nutritional interventions to support skeletal muscle mass gain or maintenance in both healthy and clinical populations.

Intramuscular phosphagen status and the relationship to muscle performance across the age spectrum

PURPOSE

To examine age-related differences in intramuscular concentrations of adenosine triphosphate (ATP), free creatine (FCr), phosphocreatine (PCr) and total creatine (TCr) and if these differences were related to muscle performance.

METHODS

Forty-two healthy, non-sedentary, males between 20 and 76 years provided muscle samples to determine [ATP], [FCr], [PCr], and [TCr]. Maximal strength and endurance were assessed and correlated with intramuscular variables.

RESULTS

Intramuscular [ATP] decreased by 13.5% (p = 0.013) in the older cohort (18.0 ± 0.6 mmol/kg dry wt) vs. the young cohort (20.8 ± 0.9 mmol/kg dry wt) and was significantly correlated to age (r = -0.38, p = 0.008). No other differences were observed between age groups for intramuscular [PCr], [FCr], [TCr], or [PCr]:[TCr] (p > 0.05). The older cohort consumed significantly less (p < 0.05) dietary protein when compared to the young cohort. Bivariate correlations were found for intramuscular [ATP] and lower body 1RM (r = 0.24, p = 0.066), leg press volume and free creatine (r = 0.325, p = 0.036) and leg press repetitions and free creatine (r = 0.373, p = 0.015). Partial correlations controlling for age eliminated the relationship between [ATP] and 1RM while intramuscular free creatine and leg press repetitions remained significant (p < 0.05) and leg press volume approached significance (p = 0.095).

CONCLUSION

These results expand upon previous observations indicative of age-related reductions in intramuscular [ATP] and dietary protein intake. The lack of change in other intramuscular PCr system markers are suggestive of dysfunctions at the mitochondrial level while the impact of neuromuscular changes, lean mass cross-sectional area and differences in physical activity are also important.

Protein Requirements and Recommendations for Older People: A Review

Declines in skeletal muscle mass and strength are major contributors to increased mortality, morbidity and reduced quality of life in older people. Recommended Dietary Allowances/Intakes have failed to adequately consider the protein requirements of the elderly with respect to function. The aim of this paper was to review definitions of optimal protein status and the evidence base for optimal dietary protein. Current recommended protein intakes for older people do not account for the compensatory loss of muscle mass that occurs on lower protein intakes. Older people have lower rates of protein synthesis and whole-body proteolysis in response to an anabolic stimulus (food or resistance exercise). Recommendations for the level of adequate dietary intake of protein for older people should be informed by evidence derived from functional outcomes. Randomized controlled trials report a clear benefit of increased dietary protein on lean mass gain and leg strength, particularly when combined with resistance exercise. There is good consistent evidence (level III-2 to IV) that consumption of 1.0 to 1.3 g/kg/day dietary protein combined with twice-weekly progressive resistance exercise reduces age-related muscle mass loss. Older people appear to require 1.0 to 1.3 g/kg/day dietary protein to optimize physical function, particularly whilst undertaking resistance exercise recommendations.

The effects of a protein enriched diet with lean red meat combined with a multi-modal exercise program on muscle and cognitive health and function in older adults: study protocol for a randomised controlled trial

Background

Age-related muscle wasting has been strongly implicated with falls and fractures in the elderly, but it has also been associated with cognitive decline and dementia. Progressive resistance training (PRT) and adequate dietary protein are recognised as important contributors to the maintenance of muscle health and function in older adults. However, both factors also have the potential to improve brain function and prevent cognitive decline via several pathways, including the regulation of various growth and neurotrophic factors [insulin-like growth factor-1 (IGF-1)]; brain-derived growth factor (BDNF)] and/or the modulation of systemic inflammation. The primary aim of this study is to investigate whether a modest increase in dietary protein achieved through the consumption of lean red meat three days per week, when combined with PRT, can enhance muscle mass, size and strength and cognitive function in community-dwelling older people.

Methods/Design

The study design is a 48-week randomised controlled trial consisting of a 24-week intervention with a 24-week follow-up. Men and women (n=152) aged 65 years and over residing in the community will be randomly allocated to: 1) PRT and provided with 220 g (raw weight) of lean red meat to be cooked and divided into two 80 g servings on each of the three days that they complete their exercise session, or 2) control PRT in which participants will be provided with and advised to consume ≥1 serving (~1/2 cup) of rice and/or pasta or 1 medium potato on each of the three training days. The primary outcome measures will be muscle mass, size and strength and cognitive function. Secondary outcomes will include changes in: muscle function, neural health (corticospinal excitability and inhibition and voluntary activation), serum IGF-1 and BDNF, adipokines and inflammatory markers, fat mass and inter-/intra-muscular fat, blood pressure, lipids and health-related quality of life. All outcome measures will be assessed at baseline and 24 weeks, with the exception of cognitive function and the various neurobiological and inflammatory markers which will also be assessed at week 12.

Discussion

The findings from this study will provide important new information on whether a modest increase in dietary protein achieved through the ingestion of lean red meat can enhance the effects of PRT on muscle mass, size and strength as well as cognitive function in community-dwelling older adults. If successful, the findings will form the basis for more precise exercise and nutrition guidelines for the management and prevention of age-related changes in muscle and neural health and cognitive function in the elderly.

Trial registration

Australian New Zealand Clinical Trials Registry: ACTRN12613001153707. Date registered 16^th October, 2013.

Hypovitaminosis D and frailty: Epiphenomenon or causal?

Vitamin D is not only a key component in the maintenance of calcium homeostasis and bone health, but has also been implicated in a myriad of other non-skeletal biologic systems. The frailty syndrome is an emerging and increasingly important concept in the field of aging, with the "physical" clinical phenotype being initially presented as the operational definition. The relationship between vitamin D and frailty is postulated to be largely mediated via the development of sarcopenia, a condition characterised by a combination of the reduction of muscle mass, plus either muscle strength or performance. Several molecular pathways may account for the development of muscle wasting in sarcopenia, and there is mounting epidemiological and laboratory evidence that supports a role of vitamin D on muscle cell proliferation and function. Although observational studies on vitamin D and frailty have not definitively established an independent relationship, interventional studies of the effect of supplemental vitamin D have yielded a positive influence on the frailty status, mainly via improvements in the physical performance. Further studies that are adequately powered and well-designed are warranted in an attempt to establish a causal relationship between vitamin D and frailty. In the absence of a consensus on the definition of the frailty syndrome, an appropriate and well-validated measure instrument for this health outcome would be recommended in the realm of frailty research.

Update on protein intake: importance of milk proteins for health status of the elderly

Loss of lean body mass that occurs with aging is the primary endpoint with which sarcopenia is defined. Furthermore, loss of muscle mass is central to the development of many adverse health issues in the elderly. Consequently, the response of lean body mass to nutritional interventions, particularly to dietary protein, has been a commonly measured endpoint. However, increased protein intake has been associated with improved markers for cardiovascular health, improved bone health, management of weight and metabolic diseases, and reduced all-cause mortality. Strength, rather than lean body mass, may be a more accurate indicator of health, especially in the elderly. The recommended dietary allowance for protein has been set at 0.8 g/kg/day. Because the average protein intake in the United States is approximately 1.2 g/kg/day, it appears that the average protein intake is above the recommended dietary allowance but below the low end of the acceptable macronutrient distribution range recommended by expert committees of the National Academy of Sciences and below the dietary intake levels suggested by the US Department of Agriculture in the Dietary Guidelines.

Fast-digestive protein supplement for ten days overcomes muscle anabolic resistance in healthy elderly men

BACKGROUND/OBJECTIVE

Adequate protein intake is crucial to maintain muscle protein content in elderly subjects, but quality of dietary proteins should be considered. The aim was to determine whether soluble milk protein offers an original strategy to increase muscle anabolism in elderly subjects via a synergistic effect of fast-digesting proteins together with a unique essential AA content.

DESIGN

We investigated the effect of a 10-day adequate-protein (AP) or high-protein (HP) diet together with the protein source as caseins (CAS) or soluble milk proteins (PRO) on specific muscle protein fractional synthesis rates (FSRs) in healthy elderly men (71.8 ± 2.4 yr, n = 31). The isotopic study consisted of two periods of 4 h each: a post-absorptive and a postprandial period. The fed state was defined by consumption of either 15 g or 30 g of PRO or CAS, given fractionally every 20 min for 4 h. Soluble milk proteins are produced using a membrane process directly from pasteurized milk.

MEASUREMENTS

Specific muscle protein FSRs were measured during both postabsorptive and postprandial period using a continuous infusion of l-[1-(13)C]leucine.

RESULTS

FSR of sarcoplasmic muscle proteins and actin did not increase significantly in the postprandial state compared to postabsorptive state, whereas myosin FSR rate was increased by feeding whatever the protein source in HP groups (0.024 ± 0.005 vs 0.053 ± 0.011% h(-1), P < 0.05 and 0.026 ± 0.004 vs 0.050 ± 0.005% h(-1), P < 0.004 for PRO HP and CAS HP) but only with the PRO meal in the AP groups (0.031 ± 0.003 vs 0.062 ± 0.009% h(-1), P < 0.03 for PRO AP). Mitochondrial muscle protein FSR was also increased by feeding, irrespective of the protein quantity, but only in PRO meal groups (P < 0.02).

CONCLUSION

Fast-digesting soluble milk proteins improved postprandial muscle protein synthesis, especially mitochondrial muscle proteins and myosin fractional synthesis rates, in elderly subjects.

Persistent inflammatory, immunosuppressed, catabolic syndrome (PICS): A new phenotype of multiple organ failure

A new phenotype of multiple organ failure has appeared: Persistent Inflammatory, Immunosuppressed, Catabolic Syndrome (PICS). Comorbidities and age >65 years have been established as the leading risk factors for PICS. As the percentage of elderly people continues to increase the prevalence of PICS in our ICUs will surely grow. Malnutrition (despite appropriate supplementation), recurrent nosocomial infections, frailty, ventilator dependence, and an indolent death depicts the central theme that plagues PICS patients. Aligned with the recently awarded P50 grant by NIGMS entitled, "PICS: A New Horizon for Surgical Critical Care", and the University Of Florida's Sepsis and Critical Illness Research Center will investigate the genetic make-up of PICS patients, better understand frailty and the implication in trauma patients, and hopefully elucidate new therapies. Currently, there are no therapies to combat PICS aside from nutritional inference elaborated after reviewing the literature on Burns, Cachexia, and Sarcopenia.

Dietary Protein Requirement of Men >65 Years Old Determined by the Indicator Amino Acid Oxidation Technique Is Higher than the Current Estimated Average Requirement

BACKGROUND

The current estimated average requirement (EAR) and RDA for protein of 0.66 and 0.8 g ⋅ kg-1 ⋅ d-1, respectively, for adults, including older men, are based on nitrogen balance data analyzed by monolinear regression. Recent studies in young men and older women that used the indicator amino acid oxidation (IAAO) technique suggest that those values may be too low. This observation is supported by 2-phase linear crossover analysis of the nitrogen balance data.

OBJECTIVE

The main objective of this study was to determine the protein requirement for older men by using the IAAO technique.

METHODS

Six men aged >65 y were studied; each individual was tested 7 times with protein intakes ranging from 0.2 to 2.0 g ⋅ kg-1 ⋅ d-1 in random order for a total of 42 studies. The diets provided energy at 1.5 times the resting energy expenditure and were isocaloric. Protein was consumed hourly for 8 h as an amino acid mixture with the composition of egg protein with L-[1-13C]phenylalanine as the indicator amino acid. The group mean protein requirement was determined by applying a mixed-effects change-point regression analysis to F13CO2 (label tracer oxidation in breath 13CO2), which identified a breakpoint in F13CO2 in response to graded intakes of protein.

RESULTS

The estimated protein requirement and RDA for older men were 0.94 and 1.24 g ⋅ kg-1 ⋅ d-1, respectively, which are not different from values we published using the same method in young men and older women.

CONCLUSIONS

The current intake recommendations for older adults for dietary protein of 0.66 g ⋅ kg-1 ⋅ d-1 for the EAR and 0.8 g ⋅ kg-1 ⋅ d-1 for the RDA appear to be underestimated by ∼30%. Future longer-term studies should be conducted to validate these results. This trial was registered at clinicaltrials.gov as NCT01948492.

A dose- rather than delivery profile-dependent mechanism regulates the "muscle-full" effect in response to oral essential amino acid intake in young men

BACKGROUND

The anabolic response of skeletal muscle to essential amino acids (EAAs) is dose dependent, maximal at modest doses, and short lived, even with continued EAA availability, a phenomenon termed "muscle-full." However, the effect of EAA ingestion profile on muscle metabolism remains undefined.

OBJECTIVE

We determined the effect of Bolus vs. Spread EAA feeding in young men and hypothesized that muscle-full is regulated by a dose-, not delivery profile-, dependent mechanism.

METHODS

We provided 16 young healthy men with 15 g mixed-EAA, either as a single dose ("Bolus"; n = 8) or in 4 fractions at 45-min intervals ("Spread"; n = 8). Plasma insulin and EAA concentrations were assayed by ELISA and ion-exchange chromatography, respectively. Limb blood flow by was determined by Doppler ultrasound, muscle microvascular flow by Sonovue (Bracco) contrast-enhanced ultrasound, and phosphorylation of mammalian target of rapamycin complex 1 substrates by immunoblotting. Intermittent muscle biopsies were taken to quantify myofibrillar-bound (13)C6-phenylalanine to determine muscle protein synthesis (MPS).

RESULTS

Bolus feeding achieved rapid insulinemia (13.6 μIU · mL(-1), 25 min after commencement of feeding), aminoacidemia (∼2500 μM at 45 min), and capillary recruitment (+45% at 45 min), whereas Spread feeding achieved attenuated insulin responses, gradual low-amplitude aminoacidemia (peak: ∼1500 μM at 135 min), and no detectable capillary recruitment (all P < 0.01 vs. Bolus). Despite these differences, identical anabolic responses were observed; fasting fractional synthetic rates of 0.054% · h(-1) (Bolus) and 0.066% · h(-1) (Spread) increased to 0.095% and 0.104% · h(-1) (no difference in increment or final values between regimens). With both Spread and Bolus feeding strategies, a latency of at least 90 min was observed before an upswing in MPS was evident. Similarly with both feeding strategies, MPS returned to fasting rates by 180 min despite elevated circulating EAAs.

CONCLUSION

These data do not support EAA delivery profile as an important determinant of anabolism in young men at rest, nor rapid aminoacidemia/leucinemia as being a key factor in maximizing MPS. This trial was registered at clinicaltrials.gov as NCT01735539.