Similar effects of leucine rich and regular dairy products on muscle mass and functions of older polymyalgia rheumatica patients: a randomized crossover trial

Effects of cheese ingestion on muscle mass and strength in possible sarcopenia women: an open-label, parallel-group study

BACKGROUND

Nutrient-rich cheese supplements were demonstrated to have improvements in markers of sarcopenia in healthy elders. However, the potential effects of cheese in individuals with possible sarcopenia remain unknown.

METHOD

This 90-day randomized controlled trial (RCT) included 68 women aged 60-80 years with possible sarcopenia in China, who were randomly assigned to three groups: Control group (CG), Original cheese group (OG: 9.0 g protein; 322.8 mg calcium), and Golden cheese group (GG: 12.7 g protein; 802.1 mg calcium). OG and GG were instructed to consume their habitual diet along with 4 slices of supplied cheese, while CG was directed to maintain their usual dietary habits. Face-to-face interviews, anthropometric measurements, and blood sample collection were conducted at baseline, midway (60 days), and the end of the trial.

RESULT

At the end of the trial, the primary outcome, changes of Skeletal Muscle Mass Index (SMI) were found to be higher in OG (0.18 ± 0.02 kg/m2) and GG (0.14 ± 0.02 kg/m2) compared to CG (0.09 ± 0.02 kg/m2). The secondary outcome, changes of handgrip strength were higher in GG (1.82 ± 4.16 kg) than CG (-0.61 ± 3.78 kg). There were no significant differences in makers for muscle function between three groups (P > 0.05). In the self-comparison, Creatinine/Cystatin C significantly increased in both OG and GG. In addition, OG had a significant increase in changes of free and total carnitine compared to CG.

CONCLUSION

Both golden and original cheese supplementation enhanced muscle strength and mass in older women with possible sarcopenia. The mechanism behind this effect may be linked to muscle cell energy metabolism.

TRIAL REGISTRATION

The present study was registered in the Chinese Clinical Trial Registry with the registration number ChiCTR2300078720 (retrospectively registered, 20231215).

The impact of leucine supplementation on body composition and glucose tolerance following energy restriction: an 8-week RCT in adults at risk of the metabolic syndrome

BACKGROUND

L-Leucine (Leu) supplementation may benefit fat-free mass (FFM) per se and glucose metabolism.

OBJECTIVES

To determine whether Leu supplementation during energy restriction blunted the loss of FFM, enhanced the loss of fat mass (FM) and improved glucose tolerance.

DESIGN

Thirty-seven adults, aged 20-65 years, with increased waist circumference and at least one other metabolic syndrome (MetS) component, were selected. We employed a two-arm parallel, double blind, randomized control trial (RCT) design. Participants were randomly assigned to an intervention group (leucine - 3 g/d) or placebo (lactose - 2.67 g/d), while following an individualised energy restricted diet for an 8-week period. Detailed body composition (DEXA), oral glucose tolerance test (OGTT), insulin and components of MetS were measured before and after the trial. Analysis of covariance (ANCOVA) assessed the effect of Leu on an intention-to-treat (ITT) principle. Bootstrapping method with 1000 bootstrap samples was used to derive parameter estimates, standard errors, p-values, and 95% confidence intervals for all outcomes.

RESULTS

Adjusted for baseline values and other covariates, FFM (p = 0.045) and lean tissue mass (LTM) (p = 0.050) were significantly higher following Leu. These outcomes were modified by a significant treatment x sex interaction that indicated Leu had the greater effect in men. However, on adjustment for body composition changes, there was no difference in insulin sensitivity, oral glucose tolerance, or change in MetS components following Leu.

CONCLUSION

Short-term leucine supplementation during energy restriction resulted in a greater preservation of FFM and LTM particularly in men, but did not impact glucose metabolism.

Structural characterization and functional properties of CNPP, a byproduct formed during CPP preparation

Casein nonphosphopeptide (CNPP), a byproduct formed during the preparation of casein phosphopeptide (CPP), is often discarded on a large scale. Although our previous studies have demonstrated the ameliorative effect of CNPP on muscle wasting disorders, its structure-function mechanism is still unclear. Therefore, considering the great influence of structural characteristics on function, this study aims to explain the potential mechanism by characterizing the physicochemical and functional properties of CNPP. The results of structural characterization indicated that CNPP was of low molecular weight and composed of the complete range of amino acids; it was particularly rich in leucine. Compared with casein, CNPP had a lower molecular size and total/free sulfhydryl content (reduced 2.44 and 2.02 µmol/g in CNPP, respectively). Additionally, Fourier transform infrared spectroscopic analysis revealed that enzymatic hydrolysis caused protein unfolding, and the content of β-turns and random coils reached 50.20% and 10.67%, respectively. Fluorescence-dependent detection of CNPP indicated a reduction of spectral intensity and the occurrence of a red shift. The changes in the structure of CNPP significantly affected its functional characteristics. CNPP has better solubility, foaming, and digestion properties than those of casein and whey protein. Specifically, the foam stability and emulsification properties decreased in the order of casein > CNPP > whey protein. The present study can provide a substantial basis for future application of CNPP as a functional ingredient against sarcopenia.

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.

The effects of resistance training with or without peanut protein supplementation on skeletal muscle and strength adaptations in older individuals

Several studies suggest resistance training (RT) while supplementing with various protein supplements can enhance strength and muscle mass in older individuals. However, to date, no study has examined the effects of RT with a peanut protein powder (PP) supplement on these outcomes. Herein, 39 older, untrained individuals (n = 17 female, n = 22 male; age = 58.6 ± 8.0 years; body mass index =28.7 ± 5.8) completed a 6-week (n = 22) or 10-week (n = 17) RT program, where full-body training was implemented twice weekly (ClinicalTrials.gov trial registration NCT04015479; registered July 11, 2019). Participants in each program were randomly assigned to consume either a PP supplement once per day (75 total g powder providing 30 g protein, > 9.2 g essential amino acids, ~ 315 kcal; n = 20) or no supplement (CTL; n = 19). Right leg vastus lateralis (VL) muscle biopsies were obtained prior to and 24 h following the first training bout in all participants to assess the change in myofibrillar protein synthetic rates (MyoPS) as measured via the deuterium-oxide (D₂O) tracer method. Pre- and Post-intervention testing in all participants was conducted using dual energy x-ray absorptiometry (DXA), VL ultrasound imaging, a peripheral quantitative computed tomography (pQCT) scan at the mid-thigh, and right leg isokinetic dynamometer assessments. Integrated MyoPS rates over a 24-h period were not significantly different (p < 0.05) between supplement groups following the first training bout. Regarding chronic changes, there were no significant supplement-by-time interactions in DXA-derived fat mass, lean soft tissue mass or percent body fat between supplementation groups. There was, however, a significant increase in VL thickness in PP versus CTL participants when the 6- and 10-week cohorts were pooled (interaction p = 0.041). There was also a significant increase in knee flexion torque in the 10-week PP group versus the CTL group (interaction p = 0.032). In conclusion, a higher-protein, defatted peanut powder supplement in combination with RT positively affects select markers of muscle hypertrophy and strength in an untrained, older adult population. Moreover, subanalyses indicated that gender did not play a role in these adaptations.

Effect of Dairy Protein Intake on Muscle Mass among Korean Adults: A Prospective Cohort Study

This cohort study aimed to identify the associations of dairy protein intake with the risk of developing a low muscle mass during a 12-year follow-up period, using data from 4412 middle-aged Korean Genome and Epidemiology Study participants with a normal baseline muscle mass. Dairy protein intake at baseline was assessed using a semi-quantitative Food Frequency Questionnaire. Skeletal muscle mass index (SMI), defined as the weight-adjusted skeletal muscle mass, was measured biennially using multi-frequency bioelectrical impedance analyses. Cox proportional hazards regression analysis was used to calculate multivariable-adjusted hazard ratios (HRs) and 95% confidence intervals (CIs). Overall, 395 subjects developed a low SMI (%) during an average follow-up of 141 (19-152) months. The average consumption of milk and other dairy products was 73.6 and 104.1 g/day, respectively. In men, a higher dairy protein intake was associated with a decreased risk of developing a low SMI (tertile 3 [T3] vs. T1, HR: 0.63; 95% CI: 0.42, 0.94; p for trend = 0.029). In a stratified analysis according to a total protein intake, this association was stronger in the lower-protein intake group (HR: 0.59; 95% CI: 0.35, 0.99; p for trend = 0.036) but not detected in the higher-protein intake group. Men who consumed milk ≥1 time/day had a significantly lower risk of developing a low SMI (HR: 0.62; 95% CI: 0.39, 0.98; p for trend = 0.023). No significant associations were observed in women. In summary, dairy consumption appears to be beneficial for decreasing the risk of developing a low muscle mass in middle-aged Korean men.

Beneficial Effects of Leucine Supplementation on Criteria for Sarcopenia: A Systematic Review

Objective: Treating sarcopenia remains a challenge, and nutritional interventions present promising approaches. We summarize the effects of leucine supplementation in treating older individuals with sarcopenia associated with aging or to specific disorders, and we focus on the effect of leucine supplementation on various sarcopenia criteria, e.g., muscular strength, lean mass, and physical performance. Methods: A literature search for articles related to this topic was performed on the relevant databases, e.g., the PubMed/Medline, Embase, EBSCO, Cochrane, Lilacs, and Dialnet. The identified articles were reviewed according to Preferred Reporting Items for Systematic reviews and meta-analyses (PRISMA) guidelines. Results: Of the 163 articles we consulted, 23 met our inclusion criteria, analysing the effect of leucine or leucine-enriched protein in the treatment of sarcopenia, and 13 of these studies were based on randomized and placebo-controlled trials (RCTs). In overall terms, the published results show that administration of leucine or leucine-enriched proteins (range 1.2–6 g leucine/day) is well-tolerated and significantly improves sarcopenia in elderly individuals, mainly by improving lean muscle-mass content and in this case most protocols also include vitamin D co-administration. The effect of muscular strength showed mix results, and the effect on physical performance has seldom been studied. For sarcopenia-associated with specific disorders, the most promising effects of leucine supplementation are reported for the rehabilitation of post-stroke patients and in those with liver cirrhosis. Further placebo-controlled trials will be necessary to determine the effects of leucine and to evaluate sarcopenia with the criteria recommended by official Working Groups, thereby limiting the variability of methodological issues for sarcopenia measurement across studies.

Advantage of Dairy for Improving Aging Muscle

The risk of sarcopenia increases with aging. Malnutrition in the elderly population is an important risk factor for sarcopenia. Calcium (Ca), phosphate (P), vitamin D and protein are key nutrients for the human body and affect muscle mass and quality. Dairy products are rich in these nutrients, which implicates that dairy products might be ideal for elderly population. This systematic review highlights the effects of dairy products on muscle mass, muscle strength and body performance in the elderly population in the perspective of Ca, P, vitamin D and protein.

The Role of Muscle Mass Gain Following Protein Supplementation Plus Exercise Therapy in Older Adults with Sarcopenia and Frailty Risks: A Systematic Review and Meta-Regression Analysis of Randomized Trials

Aging and frailty are associated with a high risk of lean mass (LM) loss, which leads to physical disability and can be effectively alleviated by protein supplementation (PS) and muscle strengthening exercise (MSE). In this study, the associations between LM gain and PS + MSE efficacy (measured using physical outcomes) in elderly patients with a high risk of sarcopenia or frailty were identified. A comprehensive search of online databases was performed to identify randomized controlled trials (RCTs) reporting the efficacy of PS + MSE in elderly patients with sarcopenia or frailty. The included RCTs were analyzed using meta-analysis and risk of bias assessment. We finally included 19 RCTs in this meta-analysis with a median (range/total) Physiotherapy Evidence Database score of 7/10 (5-9/10). The PS + MSE group exhibited significant improvements in the whole-body LM (standard mean difference (SMD) = 0.66; p < 0.00001), appendicular LM (SMD = 0.35; p < 0.00001), leg strength (SMD = 0.65; p < 0.00001), and walking capability (SMD = 0.33; p = 0.0006). Meta-regression analyses showed that changes in appendicular LM were significantly associated with the effect sizes of leg strength (β = 0.08; p = 0.003) and walking capability (β = 0.17; p = 0.04), respectively. Our findings suggest that LM gain after PS + MSE significantly contributes to the efficacy of the intervention in terms of muscle strength and physical mobility in elderly patients with a high risk of sarcopenia or frailty.

Role of Functional Fortified Dairy Products in Cardiometabolic Health: A Systematic Review and Meta-analyses of Randomized Clinical Trials

There is insufficient evidence on the role of functional fortified dairy products in improving health and in preventing risk factors associated with noncommunicable chronic diseases. This systematic review was conducted to summarize effects of the consumption of fortified dairy products on biomarkers of cardiometabolic risk. MEDLINE and SCOPUS databases were used to perform searches to include studies published up to 30 April 2018. Randomized clinical trials with human subjects consuming dairy products fortified with phytosterols, FAs, vitamins or minerals and relating this consumption with cardiometabolic health were included in this review. Risk of bias assessment according to Cochrane guidelines was performed to determine the quality of the trials. Forty-one studies were finally selected for this synthesis; the selected studies tested dairy products fortified with the following nutrients and bioactive components: phytosterols (n = 31), FAs (n = 8), and vitamin D (n = 2). We found that the consumption of phytosterol-fortified dairy, led to an overall LDL cholesterol reduction of -0.36 (-0.41, -0.31) mmol/L, P < 0.001; this decrease was mainly related to the dosage. Likewise, consumption of ω-3 FA-fortified dairy products resulted in a plasma LDL cholesterol reduction of -0.18 (-0.27, -0.09) mmol/L as well as a decrease of -0.18 (-0.32, -0.05) mmol/L in triacylglycerols (TG). Performing meta-analyses of the consumption of dairy products fortified with vitamin D or FAs other than ω-3 FAs and biomarkers of cardiometabolic risk was not possible because of the few available publications. Our results indicate that consumption of dairy products fortified with phytosterols and ω-3 FAs can lead to a reduction of LDL cholesterol and consumption of fortified dairy products fortified with ω-3 FAs can reduce TG concentration. However, more studies with homogeneous designs are needed to determine the advantages of using dairy products as fortification vehicles to prevent cardiometabolic risk.

Prospective Views for Whey Protein and/or Resistance Training Against Age-related Sarcopenia

Skeletal muscle aging is characterized by decline in skeletal muscle mass and function along with growing age, which consequently leads to age-related sarcopenia, if without any preventive timely treatment. Moreover, age-related sarcopenia in elder people would contribute to falls and fractures, disability, poor quality of life, increased use of hospital services and even mortality. Whey protein (WP) and/or resistance training (RT) has shown promise in preventing and treating age-related sarcopenia. It seems that sex hormones could be potential contributors for gender differences in skeletal muscle and age-related sarcopenia. In addition, skeletal muscle and the development of sarcopenia are influenced by gut microbiota, which in turn is affected by WP or RT. Gut microbiota may be a key factor for WP and/or RT against age-related sarcopenia. Therefore, focusing on sex hormones and gut microbiota may do great help for preventing, treating and better understanding age-related sarcopenia.

The Impact of Dairy Protein Intake on Muscle Mass, Muscle Strength, and Physical Performance in Middle-Aged to Older Adults with or without Existing Sarcopenia: A Systematic Review and Meta-Analysis

Sarcopenia is an age-related condition associated with a progressive loss of muscle mass and strength. Insufficient protein intake is a risk factor for sarcopenia. Protein supplementation is suggested to improve muscle anabolism and function in younger and older adults. Dairy products are a good source of high-quality proteins. This review evaluates the effectiveness of dairy proteins on functions associated with sarcopenia in middle-aged and older adults. Randomized controlled trials were identified using PubMed, CINAHL/EBSCO, and Web of Science databases (last search: 10 May 2017) and were quality assessed. The results of appendicular muscle mass and muscle strength of handgrip and leg press were pooled using a random-effects model. The analysis of the Short Physical Performance Battery is presented in narrative form. Adverse events and tolerability of dairy protein supplementation were considered as secondary outcomes. Fourteen studies involving 1424 participants aged between 61 and 81 y met the inclusion criteria. Dairy protein significantly increased appendicular muscle mass (0.13 kg; 95% CI: 0.01, 0.26 kg; P = 0.04); however, it had no effect on improvement in handgrip (0.84 kg; 95% CI: -0.24, 1.93 kg; P = 0.13) or leg press (0.37 kg; 95% CI: -4.79, 5.53 kg; P = 0.89). The effect of dairy protein on the Short Physical Performance Battery was inconclusive. Nine studies reported the dairy protein to be well tolerated with no serious adverse events. Although future high-quality research is required to establish the optimal type of dairy protein, the present systematic review provides evidence of the beneficial effect of dairy protein as a potential nutrition strategy to improve appendicular muscle mass in middle-aged and older adults.

Effects of casein non-phosphopeptide on the development of rat muscle analyzed using computed tomography scanning technology

The effects of casein non-phosphopeptide (CNPP) on the muscle development of healthy rats and selected blood hormones levels were investigated. CT technology and the ELISA kit were employed to detect the cross-sectional area of each muscle group and blood hormone levels, respectively. The cross-sectional area of the trunk and lower limb muscles of resistance exercise group (REG) rats that were administered a high daily dose of CNPP for 50 days increased more significantly than that of the blank group rats, no exercise group (NEG) rats administered with the same daily dose of CNPP, and REG rats administered with the same daily dose of lactalbumin (P < 0.05).The more enhanced development of trunk and lower limb muscles in CNPP-administered REG rats was associated with a higher blood level of insulin, while no clear trends in blood levels of growth hormone and testosterone were observed. The present results have demonstrated that a combination of physical exercise and diet supplementation with CNPP can synergistically improve muscle mass.

Effects of protein supplementation combined with resistance exercise on body composition and physical function in older adults: a systematic review and meta-analysis

Background: Overweight and obese older people face a high risk of muscle loss and impaired physical function, which may contribute to sarcopenic obesity. Resistance exercise training (RET) has a beneficial effect on muscle protein synthesis and can be augmented by protein supplementation (PS). However, whether body weight affects the augmentation of muscular and functional performance in response to PS in older people undergoing RET remains unclear.Objective: This study was conducted to identify the effects of PS on the body composition and physical function of older people undergoing RET.Design: We performed a comprehensive search of online databases to identify randomized controlled trials (RCTs) reporting the efficacy of PS for lean mass gain, strength gain, and physical mobility improvements in older people undergoing RET.Results: We included 17 RCTs; the overall mean ± SD age and body mass index (BMI; in kg/m²) in these RCTs were 73.4 ± 8.1 y and 29.7 ± 5.5, respectively. The participants had substantially greater lean mass and leg strength gains when PS and RET were used than with RET alone, with the standard mean differences (SMDs) being 0.58 (95% CI: 0.32, 0.84) and 0.69 (95% CI: 0.39, 0.98), respectively. The subgroup of studies with a mean BMI ≥30 exhibited substantially greater lean mass (SMD: 0.53; 95% CI: 0.19, 0.87) and leg strength (SMD: 0.88; 95% CI: 0.42, 1.34) gains in response to PS. The subgroup of studies with a mean BMI <30 also exhibited relevant gains in response to PS.Conclusions: Compared with RET alone, PS combined with RET may have a stronger effect in preventing aging-related muscle mass attenuation and leg strength loss in older people, which was found in studies with a mean BMI ≥30 and in studies with a mean BMI <30. Clinicians could use nutrition supplement and exercise strategies, especially PS plus RET, to effectively improve the physical activity and health status of all older patients.

Muscle atrophy as pre-sarcopenia in Japanese patients with chronic liver disease: computed tomography is useful for evaluation

BACKGROUND/AIM

The definition of muscle atrophy (pre-sarcopenia) and its diagnostic criteria have not been well reported. To elucidate the frequency of pre-sarcopenia in chronic liver disease (CLD), we examined clinical features of Japanese CLD patients using abdominal computed tomography (CT) findings.

METHODS

We enrolled 988 CLD (736 with naïve hepatocellular carcinoma) and 372 normal control subjects (NCs). The psoas muscle area index [PI, psoas muscle area at the mid-L3 level in CT (cm(2))/height (m)(2)] was calculated using personal computer software. The cut-off level for pre-sarcopenia was defined as less than two standard deviations (SDs) below the mean PI value in the NCs under 55 years old [males, 45.6 ± 5.7 years (n = 61), 4.24 cm(2)/m(2); females, 47.0 ± 6.1 years (n = 49), 2.50 cm(2)/m(2)]. Elderly was defined as 65 years or older. Clinical features were retrospectively evaluated.

RESULTS

In the CLD group (HCV:HBV:HBV and HCV:alcohol:non-HBV and HCV = 652:88:7:82:159), pre-sarcopenia was observed in 15.3% of patients with chronic hepatitis (CH), 24.4% of those with liver cirrhosis (LC) Child-Pugh A, 37.7% of those with LC Child-Pugh B, and 37.1% of those with LC Child-Pugh C. A comparison between NC and CH by age (<55, 55-64, 65-74, ≥75 years) showed that the frequency of pre-sarcopenia was higher in CH regardless of age (1.8 vs. 3.6%, 3.2 vs. 15.9%, 4.9 vs. 13.4%, 14.3 vs. 20.2%, respectively). PI values showed correlations with BMI (r = 0.361), age (r = -0.167), albumin (r = 0.115), and branched-chain amino acids (r = 0.199) (P < 0.01).

CONCLUSION

Retrospective evaluate for pre-sarcopenia was easy to perform with CT findings. Nutrition and exercise instruction should be considered for early stage and even non-elderly CLD as well as LC.

Outcome Measures in Polymyalgia Rheumatica. A Systematic Review

Objective.

To identify the instruments used to assess polymyalgia rheumatica (PMR) in published studies.

Methods.

A systematic literature review of clinical trials and longitudinal observational studies related to PMR, published from 1970 to 2014, was carried out. All outcome and assessment instruments were extracted and categorized according to core areas and domains, as defined by the OMERACT (Outcome Measures in Rheumatology) Filter 2.0.

Results.

Thirty-five articles (3221 patients) were included: 12 randomized controlled trials (RCT); 3 nonrandomized trials; and 20 observational studies. More than 20 domains were identified, measured by 29 different instruments. The most frequently used measures were pain, morning stiffness, patient global assessment and physician global assessment, erythrocyte sedimentation rate, and C-reactive protein. The definition of outcomes varied considerably between studies.

Conclusion.

The outcome measures and instruments used in PMR are numerous and diversely defined. The establishment of a core set of validated and standardized outcome measurements is needed.

Understanding the gastrointestinal tract of the elderly to develop dietary solutions that prevent malnutrition

Although the prevalence of malnutrition in the old age is increasing worldwide a synthetic understanding of the impact of aging on the intake, digestion, and absorption of nutrients is still lacking. This review article aims at filling the gap in knowledge between the functional decline of the aging gastrointestinal tract (GIT) and the consequences of malnutrition on the health status of elderly. Changes in the aging GIT include the mechanical disintegration of food, gastrointestinal motor function, food transit, chemical food digestion, and functionality of the intestinal wall. These alterations progressively decrease the ability of the GIT to provide the aging organism with adequate levels of nutrients, what contributes to the development of malnutrition. Malnutrition, in turn, increases the risks for the development of a range of pathologies associated with most organ systems, in particular the nervous-, muscoskeletal-, cardiovascular-, immune-, and skin systems. In addition to psychological, economics, and societal factors, dietary solutions preventing malnutrition should thus propose dietary guidelines and food products that integrate knowledge on the functionality of the aging GIT and the nutritional status of the elderly. Achieving this goal will request the identification, validation, and correlative analysis of biomarkers of food intake, nutrient bioavailability, and malnutrition.

The effectiveness of leucine on muscle protein synthesis, lean body mass and leg lean mass accretion in older people: a systematic review and meta-analysis

In the present study, we performed a meta-analysis to assess the ability of leucine supplementation to increase the muscle protein fraction synthetic rate and to augment lean body mass or leg lean mass in elderly patients. A literature search was conducted on Medline, Cochrane, EMBASE and Google Scholar databases up to 31 December 2013 for clinical trials that investigated the administration of leucine as a nutrient that affects muscle protein metabolism and muscle mass in elderly subjects. The included studies were randomised controlled trials. The primary outcome for the meta-analysis was the protein fractional synthetic rate. Secondary outcomes included lean body mass and leg lean mass. A total of nine studies were included in the meta-analysis. The results showed that the muscle protein fractional synthetic rate after intervention significantly increased in the leucine group compared with the control group (pooled standardised difference in mean changes 1·08, 95% CI 0·50, 1·67; P< 0·001). No difference was found between the groups in relation to lean body mass (pooled standardised difference in mean changes 0·18, 95% CI - 0·18, 0·54; P= 0·318) or leg lean mass (pooled standardised difference in mean changes 0·006, 95% CI - 0·32, 0·44; P= 0·756). These findings suggest that leucine supplementation is useful to address the age-related decline in muscle mass in elderly individuals, as it increases the muscle protein fractional synthetic rate.

Nutrient-rich dairy proteins improve appendicular skeletal muscle mass and physical performance, and attenuate the loss of muscle strength in older men and women subjects: a single-blind randomized clinical trial

Background

At present, it is unknown whether the use of nutrient-rich dairy proteins improves the markers of sarcopenia syndrome. Therefore, our proposal was to investigate whether adding 210 g of ricotta cheese daily would improve skeletal muscle mass, handgrip strength, and physical performance in non-sarcopenic older subjects.

Subjects and methods

This was a single-blind randomized clinical trial that included two homogeneous, randomized groups of men and women over 60 years of age. Participants in the intervention group were asked to consume their habitual diet but add 210 g of ricotta cheese (IG/HD + RCH), while the control group was instructed to consume only their habitual diet (CG/HD). Basal and 12-week follow-up measurements included appendicular skeletal muscle mass (ASMM) by dual-energy X-ray absorptiometry, handgrip strength by a handheld dynamometer, and physical performance using the short physical performance battery (SPPB) and the stair-climb power test (SCPT). The main outcomes were relative changes in ASMM, strength, SPPB, and SCPT.

Results

ASMM increased in the IG/HD + RCH (0.6±3.5 kg), but decreased in the CG/HD (−1.0±2.6). The relative change between groups was statistically significant (P=0.009). The relative change in strength in both groups was negative, but the loss of muscle strength was more pronounced in CG/HD, though in this regard statistical analysis found only a tendency (P=0.07). The relative change in the balance-test scores was positive for the IG/HD + RCH, while in the CG/HD it was negative, as those individuals had poorer balance. In this case, the relative change between groups did reach statistical significance.

Conclusion

The addition of 210 g of ricotta cheese improves ASMM and balance-test scores, while attenuating the loss of muscle strength. These results suggest that adding ricotta cheese to the habitual diet is a promising dietetic strategy that may improve the markers of sarcopenia in subjects without a pronounced loss of ASMM or sarcopenia.

Sarcopenia: a clinical review

Although sarcopenia has been used to define muscle mass loss in older subjects, muscle mass is not directly linked to muscle function. Recent definitions consider sarcopenia as a syndrome characterized by progressive and generalized loss of skeletal muscle mass and strength with a risk of adverse outcomes, such as physical disability, poor quality of life, and death. It is closely linked with physical frailty, and also with other muscle wasting disorders, including cachexia and malnutrition. This review focuses on the incorporation of sarcopenia into clinical practice, reviews case finding and diagnosis of sarcopenia, proposes a syndromic approach for the diagnostic work-up of sarcopenic patients, and looks at intervention trials with physical exercise and nutrition, as drugs to treat this condition are not expected to be available in the near future.

Physiological effects beyond the significant gain in muscle mass in sarcopenic elderly men: evidence from a randomized clinical trial using a protein-rich food

BACKGROUND

Sarcopenia is strongly associated with an inadequate intake of dietary protein. Dietary protein supplementation boosts muscle-protein synthesis and increases muscle mass in the elderly. This study tested whether adding a protein-rich food, ricotta cheese, to the habitual diet increased total appendicular skeletal muscle mass and strength in elderly people.

METHODS

Participants (n = 40), were sarcopenic elderly men and women over 60 years of age. Two comparison groups were formed at random and followed for 3 months: the intervention group received 210 g/day of ricotta cheese plus the habitual diet, while the control group followed the habitual diet with no additional intervention. Total appendicular skeletal muscle (TASM) was assessed by dual-energy X-ray absorptiometry, while strength was measured using a handheld dynamometer at baseline and after the intervention period. The primary outcomes were the percentage of relative change in TASM and strength.

RESULTS

The percentage of relative change in TASM was not significant between the groups after the intervention period. Muscle strength improved in the intervention group, but showed only a tendency towards significance (P = 0.06). Secondary analysis showed that the men in the intervention group gained 270 g in TASM compared to those in the control group, and improved their fasting insulin levels (P = 0.05), muscle strength, lean body mass in the arms, and body weight variables.

CONCLUSION

The results of this study indicate that a nutritional intervention using a high-quality protein food, specifically ricotta cheese, in order to increase the amount of protein intake might not be regarded as fully promising in elderly men and women with sarcopenia. However, the gender effects on muscle strength, lean tissue in the arms, homeostatic assessment of insulin resistance, and body weight detected in this study suggest that additional research is needed on elderly male subjects with sarcopenia.

Impact of leucine on energy balance

Body weight is determined by the balance between energy intake and energy expenditure. When energy intake exceeds energy expenditure, the surplus energy is stored as fat in the adipose tissue, which causes its expansion and may even lead to the development of obesity. Thus, there is a growing interest to develop dietary interventions that could reduce the current obesity epidemic. In this regard, data from a number of in vivo and in vitro studies suggest that the branched-chain amino acid leucine influences energy balance. However, this has not been consistently reported. Here, we review the literature related to the effects of leucine on energy intake, energy expenditure and lipid metabolism as well as its effects on the cellular activity in the brain (hypothalamus) and in peripheral tissues (gastro-intestinal tract, adipose tissue, liver and muscle) regulating the above physiological processes. Moreover, we discuss how obesity may influence the actions of this amino acid.