Efficacy of beta-hydroxy-beta-methylbutyrate supplementation in maintenance hemodialysis patients

Clinical features and molecular mechanism of muscle wasting in end stage renal disease

Muscle wasting in end-stage renal disease (ESRD) is an escalating issue due to the increasing global prevalence of ESRD and its significant clinical impact, including a close association with elevated mortality risk. The phenomenon of muscle wasting in ESRD, which exceeds the rate of muscle loss observed in the normal aging process, arises from multifactorial processes. This review paper aims to provide a comprehensive understanding of muscle wasting in ESRD, covering its epidemiology, underlying molecular mechanisms, and current and emerging therapeutic interventions. It delves into the assessment techniques for muscle mass and function, before exploring the intricate metabolic and molecular pathways that lead to muscle atrophy in ESRD patients. We further discuss various strategies to mitigate muscle wasting, including nutritional, pharmacological, exercise, and physical modalities intervention. This review seeks to provide a solid foundation for future research in this area, fostering a deeper understanding of muscle wasting in ESRD, and paving the way for the development of novel strategies to improve patient outcomes. [BMB Reports 2023; 56(8): 426-438].

Redox Signaling in Chronic Kidney Disease-Associated Cachexia

Redox signaling alterations contribute to chronic kidney disease (CKD)-associated cachexia. This review aims to summarize studies about redox pathophysiology in CKD-associated cachexia and muscle wasting and to discuss potential therapeutic approaches based on antioxidant and anti-inflammatory molecules to restore redox homeostasis. Enzymatic and non-enzymatic systems of antioxidant molecules have been studied in experimental models of kidney diseases and patients with CKD. Oxidative stress is increased by several factors present in CKD, including uremic toxins, inflammation, and metabolic and hormone alterations, leading to muscle wasting. Rehabilitative nutritional and physical exercises have shown beneficial effects for CKD-associated cachexia. Anti-inflammatory molecules have also been tested in experimental models of CKD. The importance of oxidative stress has been shown by experimental studies in which antioxidant therapies ameliorated CKD and its associated complications in the 5/6 nephrectomy model. Treatment of CKD-associated cachexia is a challenge and further studies are necessary to investigate potential therapies involving antioxidant therapy.

Effects of beta-hydroxy beta-methyl butyrate calcium combined with exercise therapy in patients with cardiac disease: a study protocol for clinical trial

INTRODUCTION

The current treatment for heart disease consists of exercise therapy in addition to pharmacotherapy, nutritional support and lifestyle guidance. In general, nutritional support focuses on protein, salt and energy restrictions, with no active protein or amino acid intake in cases involving moderate or higher renal failure. From this perspective, patients with cardiac disease are at high risk of frailty.Beta-hydroxy beta-methyl butyrate (HMB) is a metabolite of leucine. HMB is widely used for muscle strengthening and can be safely ingested even by patients with renal failure. The proposed study protocol will investigate the effects of HMB-calcium (HMB-Ca) administered in combination with comprehensive cardiac rehabilitation for muscle strength, muscle mass and cardiac function in patients with cardiac disease during the convalescent period. The primary outcome will be knee extensor strength. Secondary outcomes will be gross isometric limb strength and skeletal muscle mass.

METHODS AND ANALYSIS

This study will be a single-blinded, randomised, controlled trial with parallel comparisons between two groups. The study period will be 60 days from the start of outpatient cardiac rehabilitation. Participants will be randomly divided into two groups: an HMB group consuming HMB-Ca one time per day for 60 days; and a Placebo group consuming reduced maltose once one time per day for 60 days. Exercise therapy will be performed by both groups.

ETHICS AND DISSEMINATION

The study protocol will be published in a peer-reviewed journal. Ethics approval was provided by the Showa University Clinical Research Review Board.

TRIAL REGISTRATION NUMBER

jRCTs031220139; Japan Registry of Clinical Trails.

Measuring quality of life in trials including patients on haemodialysis: methodological issues surrounding the use of the Kidney Disease Quality of Life Questionnaire

BACKGROUND

Haemodialysis (HD) treatment causes a significant decrease in quality of life (QoL). When enrolled in a clinical trial, some patients are lost prior to follow-up because they die or they receive a kidney transplant. It is unclear how these patients are dealt with in the analysis of QoL data. There are questions surrounding the consistency of how QoL measures are used, reported and analysed.

METHODS

A systematic search of electronic databases for trials measuring QoL in HD patients using any variation of the Kidney Disease Quality of Life (KDQoL) Questionnaire was conducted. The review was conducted in Covidence version 2. Quantitative analysis was conducted in Stata version 16.

RESULTS

We included 61 trials in the review, of which 82% reported dropouts. The methods to account for missing data due to dropouts include imputation (7%) and complete case analysis (72%). Few trials (7%) conducted a sensitivity analysis to assess the impact of missing data on the study results. Single imputation techniques were used, but are only valid under strong assumptions regarding the type and pattern of missingness. There was inconsistency in the reporting of the KDQoL, with many articles (70%) amending the validated questionnaires or reporting only statistically significant results.

CONCLUSIONS

Missing data are not dealt with according to the missing data mechanism, which may lead to biased results. Inconsistency in the use of patient-reported outcome measures raises questions about the validity of these trials. Methodological issues in nephrology trials could be a contributing factor to why there are limited effective interventions to improve QoL in this patient group.

PROSPERO REGISTRATION

CRD42020223869.

Rehabilitation Nutrition in Patients with Chronic Kidney Disease and Cachexia

Rehabilitation nutrition is a proposed intervention strategy to improve nutritional status and physical function. However, rehabilitation nutrition in patients with cachexia and protein-energy wasting (PEW), which are the main nutrition-related problems in patients with chronic kidney disease (CKD), has not been fully clarified. Therefore, this review aimed to summarize the current evidence and interventions related to rehabilitation nutrition for cachexia and PEW in patients with CKD. CKD is a serious condition worldwide, with a significant impact on patient prognosis. In addition, CKD is easily complicated by nutrition-related problems such as cachexia and PEW owing to disease background- and treatment-related factors, which can further worsen the prognosis. Although nutritional management and exercise therapy are reportedly effective for cachexia and PEW, the effectiveness of combined nutrition and exercise interventions is less clear. In the future, rehabilitation nutrition addressing the nutritional problems associated with CKD will become more widespread as more scientific evidence accumulates. In clinical practice, early intervention in patients with CKD involving both nutrition and exercise after appropriate assessment may be necessary to improve patient outcomes.

The Effect of Non-Pharmacological and Pharmacological Interventions on Measures Associated with Sarcopenia in End-Stage Kidney Disease: A Systematic Review and Meta-Analysis

This systematic review and meta-analysis provides a synthesis of the available evidence for the effects of interventions on outcome measures associated with sarcopenia in end-stage kidney disease (ESKD). Thirteen databases were searched, supplemented with internet and hand searching. Randomised controlled trials of non-pharmacological or pharmacological interventions in adults with ESKD were eligible. Trials were restricted to those which had reported measures of sarcopenia. Primary outcome measures were hand grip strength and sit-to-stand tests. Sixty-four trials were eligible (with nineteen being included in meta-analyses). Synthesised data indicated that intradialytic exercise increased hand grip strength (standardised mean difference, 0.58; 0.24 to 0.91; p = 0.0007; I2 = 40%), and sit-to-stand (STS) 60 score (mean difference, 3.74 repetitions; 2.35 to 5.14; p < 0.001; I2 = 0%). Intradialytic exercise alone, and protein supplementation alone, resulted in no statistically significant change in STS5 (−0.78 s; −1.86 to 0.30; p = 0.16; I2 = 0%), and STS30 (MD, 0.97 repetitions; −0.16 to 2.10; p = 0.09; I2 = 0%) performance, respectively. For secondary outcomes, L-carnitine and nandrolone-decanoate resulted in significant increases in muscle quantity in the dialysis population. Intradialytic exercise modifies measures of sarcopenia in the haemodialysis population; however, the majority of trials were low in quality. There is limited evidence for efficacious interventions in the peritoneal dialysis and transplant recipient populations.

Muscle Status Response to Oral Nutritional Supplementation in Hemodialysis Patients With Protein Energy Wasting: A Multi-Center Randomized, Open Label-Controlled Trial

Background: Muscle wasting, observed in patients with end-stage kidney disease and protein energy wasting (PEW), is associated with increased mortality for those on hemodialysis (HD). Oral nutritional supplementation (ONS) and nutrition counseling (NC) are treatment options for PEW but research targeting muscle status, as an outcome metric, is limited.

Aim: We compared the effects of combined treatment (ONS + NC) vs. NC alone on muscle status and nutritional parameters in HD patients with PEW.

Methods: This multi-center randomized, open label-controlled trial, registered under ClinicalTrials.gov (Identifier no. NCT04789031), recruited 56 HD patients identified with PEW using the International Society of Renal Nutrition and Metabolism criteria. Patients were randomly allocated to intervention (ONS + NC, n = 29) and control (NC, n = 27) groups. The ONS + NC received commercial renal-specific ONS providing 475 kcal and 21.7 g of protein daily for 6 months. Both groups also received standard NC during the study period. Differences in quadriceps muscle status assessed using ultrasound (US) imaging, arm muscle area and circumference, bio-impedance spectroscopy (BIS), and handgrip strength (HGS) methods were analyzed using the generalized linear model for repeated measures.

Results: Muscle indices as per US metrics indicated significance (p < 0.001) for group × time interaction only in the ONS + NC group, with increases by 8.3 and 7.7% for quadriceps muscle thickness and 4.5% for cross-sectional area (all p < 0.05). This effect was not observed for arm muscle area and circumference, BIS metrics and HGS in both the groups. ONS + NC compared to NC demonstrated increased dry weight (p = 0.039), mid-thigh girth (p = 0.004), serum prealbumin (p = 0.005), normalized protein catabolic rate (p = 0.025), and dietary intakes (p < 0.001), along with lower malnutrition–inflammation score (MIS) (p = 0.041). At the end of the study, lesser patients in the ONS + NC group were diagnosed with PEW (24.1%, p = 0.008) as they had achieved dietary adequacy with ONS provision.

Conclusion: Combination of ONS with NC was effective in treating PEW and contributed to a gain in the muscle status as assessed by the US, suggesting that the treatment for PEW requires nutritional optimization via ONS.

The effects of amino acid/protein supplementation in patients undergoing hemodialysis: A systematic review and meta-analysis of randomized controlled trials

BACKGROUND & AIMS

We evaluated the efficacy of the intervention consisting of amino acid/protein supplementation on muscle mass, muscle strength and physical function in patients on hemodialysis.

METHODS

This systematic review and meta-analysis identified potential studies through a systematic search of 4 electronic databases and references from eligible studies from database inception to August 2020. We included only randomized controlled trials reporting the efficacy of amino acid/protein supplementation on muscle mass, muscle strength and physical function in patients on hemodialysis.

RESULTS

Of 6529 unique citation records, 4 studies including 243 participants were selected for inclusion in the meta-analysis. Although there were no significant differences in muscle mass and muscle strength between the intervention and control groups, amino acid/protein supplementation was shown to significantly improve physical function (shuttle walk, MD 32.7, 95% CI 21.7 to 43.7, P < 0.001; gait speed, MD 0.07, 95% CI 0.01 to 0.13, P = 0.02; timed up and go, MD -0.42, 95% CI -0.68 to -0.15, P = 0.002) in patients on hemodialysis.

CONCLUSIONS

We confirmed the positive effect of amino acid/protein supplementation on physical function in people undergoing hemodialysis. However, there is still insufficient evidence, and more rigorously designed randomized controlled trials with high quality are needed.

Maintenance of Skeletal Muscle to Counteract Sarcopenia in Patients with Advanced Chronic Kidney Disease and Especially Those Undergoing Hemodialysis

Life extension in modern society has introduced new concepts regarding such disorders as frailty and sarcopenia, which has been recognized in various studies. At the same time, cutting-edge technology methods, e.g., renal replacement therapy for conditions such as hemodialysis (HD), have made it possible to protect patients from advanced lethal chronic kidney disease (CKD). Loss of muscle and fat mass, termed protein energy wasting (PEW), has been recognized as prognostic factor and, along with the increasing rate of HD introduction in elderly individuals in Japan, appropriate countermeasures are necessary. Although their origins differ, frailty, sarcopenia, and PEW share common components, among which skeletal muscle plays a central role in their etiologies. The nearest concept may be sarcopenia, for which diagnosis techniques have recently been reported. The focus of this review is on maintenance of skeletal muscle against aging and CKD/HD, based on muscle physiology and pathology. Clinically relevant and topical factors related to muscle wasting including sarcopenia, such as vitamin D, myostatin, insulin (related to diabetes), insulin-like growth factor I, mitochondria, and physical inactivity, are discussed. Findings presented thus far indicate that in addition to modulation of the aforementioned factors, exercise combined with nutritional supplementation may be a useful approach to overcome muscle wasting and sarcopenia in elderly patients undergoing HD treatments.

How to Overcome Anabolic Resistance in Dialysis-Treated Patients?

A current hypothesis is that dialysis-treated patients are "anabolic resistant" i. e., their muscle protein synthesis (MPS) response to anabolic stimuli is blunted, an effect which leads to muscle wasting and poor physical performance in aging and in several chronic diseases. The importance of maintaining muscle mass and MPS is often neglected in dialysis-treated patients; better than to describe mechanisms leading to energy-protein wasting, the aim of this narrative review is to suggest possible strategies to overcome anabolic resistance in this patient's category. Food intake, in particular dietary protein, and physical activity, are the two major anabolic stimuli. Unfortunately, dialysis patients are often aged and have a sedentary behavior, all conditions which per se may induce a state of "anabolic resistance." In addition, patients on dialysis are exposed to amino acid or protein deprivation during the dialysis sessions. Unfortunately, the optimal amount and formula of protein/amino acid composition in supplements to maximixe MPS is still unknown in dialysis patients. In young healthy subjects, 20 g whey protein maximally stimulate MPS. However, recent observations suggest that dialysis patients need greater amounts of proteins than healthy subjects to maximally stimulate MPS. Since unneccesary amounts of amino acids could stimulate ureagenesis, toxins and acid production, it is urgent to obtain information on the optimal dose of proteins or amino acids/ketoacids to maximize MPS in this patients' population. In the meantime, the issue of maintaining muscle mass and function in dialysis-treated CKD patients needs not to be overlooked by the kidney community.

The effect of oral nutritional supplement on muscle fitness of patients undergoing dialysis: A systematic review and meta-analysis

AIM

To summarize evidence regarding the effects of oral nutritional supplement on muscle fitness of patients undergoing dialysis.

DESIGN

A systematic review and meta-analysis.

REVIEW SOURCES

Five English databases (CENTRAL, PubMed, EMBASE, CINHAL, and Web of Science) and four Chinese databases (CNKI, WanFang, SinoMed, and VIP) were searched from inception to 31 July 2019 and only randomized controlled trials were included.

REVIEW METHODS

Two reviewers independently searched these databases, selected trials, conducted bias assessment, extracted the data. Random-effects meta-analysis was conducted to assess the effect size. The predetermined subgroup included type of oral nutritional supplement (a mixture of macronutrients, whey protein, essential amino-acids, and other nutrients) and intervention duration (over and less than 48 weeks). The subgroup analyses and sensitivity analyses were conducted to explore source of heterogeneity and robustness of results.

RESULTS

Sixteen studies (910 participants) meeting the inclusion criteria were identified and included in this systematic review. Subgroup analysis showed that supplying a mixture of macronutrients (MD [MD] = 2.36 kg, 95% CI [0.45, 4.26], I²  = 0.00%), an intervention duration of 48 weeks (MD = 4.05 kg, 95% CI [1.43, 6.67], I²  = 0.00%) had some effects on increasing lean body mass. No effects of oral nutritional supplement were found on improving muscle strength or physical performance.

CONCLUSION

A mixture of macronutrients and an intervention duration as long as 48 weeks had some significant effects on improving lean body mass of patients undergoing dialysis. No effect of oral nutritional supplement on muscle strength or physical performance were found but with limited evidence.

IMPACT

No existing reviews have ever focused on improving muscle fitness of patients undergoing dialysis. This systematic review and meta-analysis provided evidence of oral nutritional supplement on keeping muscle fitness of these patients and suggested possible type of oral nutritional supplement and intervention duration for clinical practice.

Sarcopenia in chronic kidney disease: what have we learned so far?

The term sarcopenia was first introduced in 1988 by Irwin Rosenberg to define a condition of muscle loss that occurs in the elderly. Since then, a broader definition comprising not only loss of muscle mass, but also loss of muscle strength and low physical performance due to ageing or other conditions, was developed and published in consensus papers from geriatric societies. Sarcopenia was proposed to be diagnosed based on operational criteria using two components of muscle abnormalities, low muscle mass and low muscle function. This brought awareness of an important nutritional derangement with adverse outcomes for the overall health. In parallel, many studies in patients with chronic kidney disease (CKD) have shown that sarcopenia is a prevalent condition, mainly among patients with end stage kidney disease (ESKD) on hemodialysis (HD). In CKD, sarcopenia is not necessarily age-related as it occurs as a result of the accelerated protein catabolism from the disease and from the dialysis procedure per se combined with low energy and protein intakes. Observational studies showed that sarcopenia and especially low muscle strength is associated with worse clinical outcomes, including worse quality of life (QoL) and higher hospitalization and mortality rates. This review aims to discuss the differences in conceptual definition of sarcopenia in the elderly and in CKD, as well as to describe etiology of sarcopenia, prevalence, outcome, and interventions that attempted to reverse the loss of muscle mass, strength and mobility in CKD and ESKD patients.

Effect of administration of β-hydroxy-β-methyl butyrate-enriched formula after liver transplantation: A pilot randomized controlled trial

OBJECTIVE

Most patients undergoing liver transplantation (LT) have decreased skeletal muscle mass, malnutrition, and decreased physical activity levels. These comorbidities may prevent early recovery after surgery. The aim of this study was to examine the effects of oral nutritional formula-enriched β-hydroxy-β-methyl-butyrate (HMB), a leucine metabolite that promotes muscle synthesis and suppresses proteolysis, on postoperative sarcopenia and other outcomes after adult-to-adult living donor LT (LDLT).

METHODS

Thirty-three consecutive patients who underwent adult LDLT between March 2017 and October 2018 and who met inclusion criteria were randomly assigned in a 1:1 ratio to the HMB or control group. Patients in the HMB group received two packs of HMB-rich nutrients per day, which contained calcium-HMB (1500 mg), l-arginine (7000 mg), and l -glutamine (7000 mg) per pack orally or enterally from postoperative day 1 to 30 with postoperative rehabilitation. The primary endpoint was grip strength (GS) at 2 mo after LDLT. Secondary endpoints included GS at 1 mo after LDLT, skeletal muscle mass index (SMI) at 1 and 2 mo after LDLT, laboratory findings, incidence of postoperative bacteremia, and postoperative hospital length of stay (LOS).

RESULTS

Twelve patients in the HMB group and 11 in the control group were included in the final analysis. GS at 1 and 2 mo and SMI values at 2 mo were significantly higher in the HMB group than in the control group (GS: both P < 0.001, SMI: P = 0.04). In the HMB group, white blood cell count 3 wk after LDLT was significantly lower (P = 0.005), and postoperative hospital LOS was significantly shorter (P = 0.028) compared with the control group. The incidence of postoperative bacteremia was lower in the HMB group.

CONCLUSIONS

Postoperative administration of HMB-enriched formula with rehabilitation significantly increased GS at 1 and 2 mo and SMI at 2 mo and shortened postoperative hospital LOS after LDLT.

Oral protein-based supplements versus placebo or no treatment for people with chronic kidney disease requiring dialysis

BACKGROUND

Malnutrition is common in patients with chronic kidney disease (CKD) on dialysis. Oral protein-based nutritional supplements are often provided to patients whose oral intake is otherwise insufficient to meet their energy and protein needs. Evidence for the effectiveness of oral protein-based nutritional supplements in this population is limited.

OBJECTIVES

The aims of this review were to determine the benefits and harms of using oral protein-based nutritional supplements to improve the nutritional state of patients with CKD requiring dialysis.

SEARCH METHODS

We searched the Cochrane Kidney and Transplant Register of Studies up to 12 December 2019 through contact with the Information Specialist using search terms relevant to this review. Studies in the Register are identified through searches of CENTRAL, MEDLINE, and EMBASE, conference proceedings, the International Clinical Trials Register (ICTRP) Search Portal and ClinicalTrials.gov.

SELECTION CRITERIA

Randomised controlled trials (RCTs) of patients with CKD requiring dialysis that compared oral protein-based nutritional supplements to no oral protein-based nutritional supplements or placebo.

DATA COLLECTION AND ANALYSIS

Two authors independently assessed studies for eligibility, risk of bias, and extracted data from individual studies. Summary estimates of effect were obtained using a random-effects model, and results were expressed as risk ratios and their 95% confidence intervals (CI) for dichotomous outcomes, and mean difference and 95% CI for continuous outcomes.

MAIN RESULTS

Twenty-two studies (1278 participants) were included in this review. All participants were adults on maintenance dialysis of whom 79% were on haemodialysis (HD) and 21% peritoneal dialysis. The follow-up period ranged from one to 12 months. The majority of studies were at unclear risk of selection, performance, and reporting bias. The detection bias was high for self-reported outcomes. Oral protein-based nutritional supplements probably lead to a higher mean change in serum albumin compared to the control group (16 studies, 790 participants: MD 0.19 g/dL, 95% CI 0.05 to 0.33; moderate certainty evidence), although there was considerable heterogeneity in the combined analysis (I² = 84%). The increase was more evident in HD participants (10 studies, 526 participants: MD 0.28 g/dL, 95% CI 0.11 to 0.46; P = 0.001 for overall effect) and malnourished participants (8 studies, 405 participants: MD 0.31 g/dL, 95% CI 0.10 to 0.52, P = 0.003 for overall effect). Oral protein-based nutritional supplements also probably leads to a higher mean serum albumin at the end of the intervention (14 studies, 715 participants: MD 0.14 g/dL, 95% CI 0 to 0.27; moderate certainty evidence), however heterogeneity was again high (I² = 80%). Again the increase was more evident in HD participants (9 studies, 498 participants: MD 0.21 g/dL, 95% CI 0.03 to 0.38; P = 0.02 for overall effect) and malnourished participants (7 studies, 377 participants: MD 0.25 g/dL, 95% CI 0.02 to 0.47; P = 0.03 for overall effect). Compared to placebo or no supplement, low certainty evidence showed oral protein-based nutritional supplements may result in a higher serum prealbumin (4 studies, 225 participants: MD 2.81 mg/dL, 95% CI 2.19 to 3.43), and mid-arm muscle circumference (4 studies, 216 participants: MD 1.33 cm, 95% CI 0.24 to 2.43) at the end of the intervention. Compared to placebo or no supplement, oral protein-based nutritional supplements may make little or no difference to weight (8 studies, 365 participants: MD 2.83 kg, 95% CI -0.43 to 6.09; low certainty evidence), body mass index (9 studies, 368 participants: MD -0.04 kg/m², 95% CI -0.74 to 0.66; moderate certainty evidence) and lean mass (5 studies, 189 participants: MD 1.27 kg, 95% CI -1.61 to 4.51; low certainty evidence). Due to very low quality of evidence, it is uncertain whether oral protein-based nutritional supplements affect triceps skinfold thickness, mid-arm circumference, C-reactive protein, Interleukin 6, serum potassium, or serum phosphate. There may be little or no difference in the risk of developing gastrointestinal intolerance between participants who received oral protein-based nutritional supplements compared with placebo or no supplement (6 studies, 426 participants: RR 2.81, 95% CI 0.58 to 13.65, low certainty evidence). It was not possible to draw conclusions about cost or quality of life, and deaths were not reported as a study outcome in any of the included studies.

AUTHORS' CONCLUSIONS

Overall, it is likely that oral protein-based nutritional supplements increase both mean change in serum albumin and serum albumin at end of intervention and may improve serum prealbumin and mid-arm muscle circumference. The improvement in serum albumin was more evident in haemodialysis and malnourished participants. However, it remains uncertain whether these results translate to improvement in nutritional status and clinically relevant outcomes such as death. Large well-designed RCTs in this population are required.

Intradialytic Nutrition and Hemodialysis Prescriptions: A Personalized Stepwise Approach

Dialysis and nutrition are two sides of the same coin—dialysis depurates metabolic waste that is typically produced by food intake. Hence, dietetic restrictions are commonly imposed in order to limit potassium and phosphate and avoid fluid overload. Conversely, malnutrition is a major challenge and, albeit to differing degrees, all nutritional markers are associated with survival. Dialysis-related malnutrition has a multifactorial origin related to uremic syndrome and comorbidities but also to dialysis treatment. Both an insufficient dialysis dose and excessive removal are contributing factors. It is thus not surprising that dialysis alone, without proper nutritional management, often fails to be effective in combatting malnutrition. While composite indexes can be used to identify patients with poor prognosis, none is fully satisfactory, and the definitions of malnutrition and protein energy wasting are still controversial. Furthermore, most nutritional markers and interventions were assessed in hemodialysis patients, while hemodiafiltration and peritoneal dialysis have been less extensively studied. The significant loss of albumin in these two dialysis modalities makes it extremely difficult to interpret common markers and scores. Despite these problems, hemodialysis sessions represent a valuable opportunity to monitor nutritional status and prescribe nutritional interventions, and several approaches have been tried. In this concept paper, we review the current evidence on intradialytic nutrition and propose an algorithm for adapting nutritional interventions to individual patients.

β-Hydroxy-β-methylbutyrate and its impact on skeletal muscle mass and physical function in clinical practice: a systematic review and meta-analysis

BACKGROUND

Loss of skeletal muscle mass and muscle weakness are common in a variety of clinical conditions with both wasting and weakness associated with an impairment of physical function. β-Hydroxy-β-methylbutyrate (HMB) is a nutrition supplement that has been shown to favorably influence muscle protein turnover and thus potentially plays a role in ameliorating skeletal muscle wasting and weakness.

OBJECTIVES

The aim of this study was to investigate the efficacy of HMB alone, or supplements containing HMB, on skeletal muscle mass and physical function in a variety of clinical conditions characterized by loss of skeletal muscle mass and weakness.

METHODS

A systematic review and meta-analysis of randomized controlled trials reporting outcomes of muscle mass, strength, and physical function was performed. Two reviewers independently performed screening, data extraction, and risk-of-bias assessment. Outcome data were synthesized through meta-analysis with the use of a random-effects model and data presented as standardized mean differences (SMDs).

RESULTS

Fifteen randomized controlled trials were included, involving 2137 patients. Meta-analysis revealed some evidence to support the effect of HMB alone, or supplements containing HMB, on increasing skeletal muscle mass (SMD = 0.25; 95% CI: -0.00, 0.50; z = 1.93; P = 0.05; I2 = 58%) and strong evidence to support improving muscle strength (SMD = 0.31; 95% CI: 0.12, 0.50; z = 3.25; P = 0.001; I2 = 0%). Effect sizes were small. No effect on bodyweight (SMD = 0.16; 95% CI: -0.08, 0.41; z = 1.34; P = 0.18; I2 = 67%) or any other outcome was found. No study was considered to have low risk of bias in all categories.

CONCLUSION

HMB, and supplements containing HMB, increased muscle mass and strength in a variety of clinical conditions, although the effect size was small. Given the bias associated with many of the included studies, further high-quality studies should be undertaken to enable interpretation and translation into clinical practice. The trial was registered on PROSPERO as CRD42017058517.

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

PURPOSE OF REVIEW

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

RECENT FINDINGS

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

SUMMARY

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

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

PURPOSE OF REVIEW

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

RECENT FINDINGS

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

SUMMARY

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

Beta-hydroxy-beta-methylbutyrate supplementation and skeletal muscle in healthy and muscle-wasting conditions

Beta-hydroxy-beta-methylbutyrate (HMB) is a metabolite of the essential amino acid leucine that has been reported to have anabolic effects on protein metabolism. The aims of this article were to summarize the results of studies of the effects of HMB on skeletal muscle and to examine the evidence for the rationale to use HMB as a nutritional supplement to exert beneficial effects on muscle mass and function in various conditions of health and disease. The data presented here indicate that the beneficial effects of HMB have been well characterized in strength-power and endurance exercise. HMB attenuates exercise-induced muscle damage and enhances muscle hypertrophy and strength, aerobic performance, resistance to fatigue, and regenerative capacity. HMB is particularly effective in untrained individuals who are exposed to strenuous exercise and in trained individuals who are exposed to periods of high physical stress. The low effectiveness of HMB in strength-trained athletes could be due to the suppression of the proteolysis that is induced by the adaptation to training, which may blunt the effects of HMB. Studies performed with older people have demonstrated that HMB can attenuate the development of sarcopenia in elderly subjects and that the optimal effects of HMB on muscle growth and strength occur when it is combined with exercise. Studies performed under in vitro conditions and in various animal models suggest that HMB may be effective in treatment of muscle wasting in various forms of cachexia. However, there are few clinical reports of the effects of HMB on muscle wasting in cachexia; in addition, most of these studies evaluated the therapeutic potential of combinations of various agents. Therefore, it has not been possible to determine whether HMB was effective or if there was a synergistic effect. Although most of the endogenous HMB is produced in the liver, there are no reports regarding the levels and the effects of HMB supplementation in subjects with liver disease. Several studies have suggested that anabolic effects of HMB supplementation on skeletal muscle do not occur in healthy, non-exercising subjects. It is concluded that (i) HMB may be applied to enhance increases in the mass and strength of skeletal muscles in subjects who exercise and in the elderly and (ii) studies examining the effects of HMB administered alone are needed to obtain conclusions regarding the specific effectiveness in attenuating muscle wasting in various muscle-wasting disorders.