Impact of the calcium form of β-hydroxy-β-methylbutyrate upon human skeletal muscle protein metabolism

Superior bioavailability of the calcium salt form of β-hydroxy-β-methylbutyrate compared with the free acid form

We investigated the bioavailability of the calcium salt (HMB-Ca) and the free acid (HMB-FA) forms of β-hydroxy-β-methylbutyrate (HMB). Sixteen young individuals received the following treatments on three different occasions in a counterbalanced crossover fashion: (1) HMB-FA in clear capsules; (2) HMB-Ca in gelatine capsules; (3) HMB-Ca dissolved in water. All treatments provided 1 g of HMB. Blood samples were taken before and on multiple time points following ingestion. The following parameters were calculated: peak plasma (Cmax), time to peak (Tmax), slope of HMB appearance in blood, area under the curve (AUC), half-life time (t1/2) and relative bioavailability (HMB-Ca in water set as reference). All treatments led to rapid and large increases in plasma HMB. HMB-Ca in capsules and in water showed similar plasma HMB values across time (p = 0.438). HMB-FA resulted in lower concentrations vs. the other treatments (both p < 0.001). AUC (HMB-Ca in capsules: 50,078 ± 10,507; HMB-Ca in water: 47,871 ± 10,783; HMB-FA: 29,130 ± 12,946 µmol L-1 × 720 min), Cmax (HMB-Ca in capsules: 229.2 ± 65.9; HMB-Ca in water: 249.7 ± 49.7; HMB-FA: 139.1 ± 67.2 µmol L-1) and relative bioavailability (HMB-Ca in capsules: 104.8 ± 14.9%; HMB-FA: 61.5 ± 17.0%) were lower in HMB-FA vs. HMB-Ca (all p < 0.001). HMB-Ca in water resulted in the fastest Tmax (43 ± 22 min) compared to HMB-Ca in capsules (79 ± 40 min) and HMB-FA (78 ± 21 min) (all p < 0.05), while t1/2 was similar between treatments. To conclude, HMB-Ca exhibited superior bioavailability compared to HMB-FA, with HMB-Ca in water showing faster absorption. Elimination kinetics were similar across all forms, suggesting that the pharmaceutical form of HMB affects the absorption rates, but not its distribution or elimination.

Supplementation with β-hydroxy-β-methylbutyrate after resistance training in post-acute care patients with sarcopenia: A randomized, double-blind placebo-controlled trial

OBJECTIVES

This study aimed to evaluate the efficacy of adding β-hydroxy-β- methylbutyrate (HMB) supplementation to a 12-week exercise-based rehabilitation program in older adults with sarcopenia after discharge from a post-acute geriatric rehabilitation unit.

STUDY DESIGN

A randomized, double-blind, placebo-controlled trial with two parallel groups. The intervention group received 3 g/day of Ca-HMB and participated in a 12- week resistance training program (3 sessions/week). The control group received a placebo and followed the same training program.

MAIN OUTCOME MEASURES

The primary outcomes were the improvements of handgrip strength and physical performance assessed through the Short Physical Performance Battery (SPPB) and 4-meter gait speed; and handgrip strength. All variables were assessed at baseline, post-intervention, and 1-year follow-up.

RESULTS

After completing the 12-week exercise program, the intervention group showed significant improvements in SPPB-Balance (1.3, 95 %CI 0.3 to 2.4) and total SPPB score (2.2, 95 %CI 0.4 to 4.0). Intra-group analysis demonstrated gains in the SPPB-Chair Stand (0.7 points, 95 %CI 0.0 to 1.4) and total SPPB score (2.1 points, 95 %CI 0.3 to 3.9) in the intervention group. Improvements in handgrip strength were observed in women (3.7 kg, 95 %CI: 0.2 to 7.3) at the end of the intervention, and persisted at the 1-year follow-up.

CONCLUSIONS

Our findings suggest that the supplementation of 3 g/day of Ca-HMB with resistance exercise may significantly enhance muscle strength and physical performance among older women with sarcopenia after recent hospitalization. Given this study's limitations, the intervention's effectiveness cannot be drawn, and further studies are needed.

Combined Exercise Training and Nutritional Interventions or Pharmacological Treatments to Improve Exercise Capacity and Body Composition in Chronic Obstructive Pulmonary Disease: A Narrative Review

Chronic obstructive pulmonary disease (COPD) is a chronic respiratory disease that is associated with significant morbidity, mortality, and healthcare costs. The burden of respiratory symptoms and airflow limitation can translate to reduced physical activity, in turn contributing to poor exercise capacity, muscle dysfunction, and body composition abnormalities. These extrapulmonary features of the disease are targeted during pulmonary rehabilitation, which provides patients with tailored therapies to improve the physical and emotional status. Patients with COPD can be divided into metabolic phenotypes, including cachectic, sarcopenic, normal weight, obese, and sarcopenic with hidden obesity. To date, there have been many studies performed investigating the individual effects of exercise training programs as well as nutritional and pharmacological treatments to improve exercise capacity and body composition in patients with COPD. However, little research is available investigating the combined effect of exercise training with nutritional or pharmacological treatments on these outcomes. Therefore, this review focuses on exploring the potential additional beneficial effects of combinations of exercise training and nutritional or pharmacological treatments to target exercise capacity and body composition in patients with COPD with different metabolic phenotypes.

Cancer Cachexia: Underlying Mechanisms and Potential Therapeutic Interventions

Cancer cachexia, a multifactorial metabolic syndrome developed during malignant tumor growth, is characterized by an accelerated loss of body weight accompanied by the depletion of skeletal muscle mass. This debilitating condition is associated with muscle degradation, impaired immune function, reduced functional capacity, compromised quality of life, and diminished survival in cancer patients. Despite the lack of the known capability of fully reversing or ameliorating this condition, ongoing research is shedding light on promising preclinical approaches that target the disrupted mechanisms in the pathophysiology of cancer cachexia. This comprehensive review delves into critical aspects of cancer cachexia, including its underlying pathophysiological mechanisms, preclinical models for studying the progression of cancer cachexia, methods for clinical assessment, relevant biomarkers, and potential therapeutic strategies. These discussions collectively aim to contribute to the evolving foundation for effective, multifaceted counteractive strategies against this challenging condition.

Does β-Hydroxy-β-Methylbutyrate Have Any Potential to Support the Treatment of Duchenne Muscular Dystrophy in Humans and Animals?

Skeletal muscle is the protein reservoir of our body and an important regulator of glucose and lipid homeostasis. The dystrophin gene is the largest gene and has a key role in skeletal muscle construction and function. Mutations in the dystrophin gene cause Duchenne and Becker muscular dystrophy in humans, mice, dogs, and cats. Duchenne muscular dystrophy (DMD) is an X-linked neuromuscular condition causing progressive muscle weakness and premature death. β-hydroxy β-methylbutyrate (HMB) prevents deleterious muscle responses under pathological conditions, including tumor and chronic steroid therapy-related muscle losses. The use of HMB as a dietary supplement allows for increasing lean weight gain; has a positive immunostimulatory effect; is associated with decreased mortality; and attenuates sarcopenia in elderly animals and individuals. This study aimed to identify some genes, metabolic pathways, and biological processes which are common for DMD and HMB based on existing literature and then discuss the consequences of that interaction.

Personalized nutrition therapy in critical care: 10 expert recommendations

Personalization of ICU nutrition is essential to future of critical care. Recommendations from American/European guidelines and practice suggestions incorporating recent literature are presented. Low-dose enteral nutrition (EN) or parenteral nutrition (PN) can be started within 48 h of admission. While EN is preferred route of delivery, new data highlight PN can be given safely without increased risk; thus, when early EN is not feasible, provision of isocaloric PN is effective and results in similar outcomes. Indirect calorimetry (IC) measurement of energy expenditure (EE) is recommended by both European/American guidelines after stabilization post-ICU admission. Below-measured EE (~ 70%) targets should be used during early phase and increased to match EE later in stay. Low-dose protein delivery can be used early (~ D1-2) (< 0.8 g/kg/d) and progressed to ≥ 1.2 g/kg/d as patients stabilize, with consideration of avoiding higher protein in unstable patients and in acute kidney injury not on CRRT. Intermittent-feeding schedules hold promise for further research. Clinicians must be aware of delivered energy/protein and what percentage of targets delivered nutrition represents. Computerized nutrition monitoring systems/platforms have become widely available. In patients at risk of micronutrient/vitamin losses (i.e., CRRT), evaluation of micronutrient levels should be considered post-ICU days 5-7 with repletion of deficiencies where indicated. In future, we hope use of muscle monitors such as ultrasound, CT scan, and/or BIA will be utilized to assess nutrition risk and monitor response to nutrition. Use of specialized anabolic nutrients such as HMB, creatine, and leucine to improve strength/muscle mass is promising in other populations and deserves future study. In post-ICU setting, continued use of IC measurement and other muscle measures should be considered to guide nutrition. Research on using rehabilitation interventions such as cardiopulmonary exercise testing (CPET) to guide post-ICU exercise/rehabilitation prescription and using anabolic agents such as testosterone/oxandrolone to promote post-ICU recovery is needed.

Effects of casein phosphopeptides on thermal stability and sensory quality of whey protein emulsions containing calcium beta-hydroxy-beta-methylbutyrate

This study aimed to elucidate the effect of casein phosphopeptides (CPP) on the thermal stability and sensory quality of whey protein emulsions containing calcium beta-hydroxy-beta-methylbutyrate (WPEs-HMB-Ca). The interaction mechanism among CPP, HMBCa, and WP in the emulsions before and after autoclaving (121 °C, 15 min) was systematically investigated from macroscopic external and microscopic molecular perspectives. It was found that WPEs-HMB-Ca treated by autoclaving resulted in an increase in droplet size (d_4,3 = 24.09 μm) due to aggregation/flocculation of proteins, along with a stronger odor with higher viscosity, compared to those without autoclaving. When CPP:HMB-Ca = 1:25 (w/w) in the emulsion, the droplets exhibited a more uniform and consistent state in the emulsion. In addition, CPP was able to inhibit the formation of complex spatial network structures of proteins during autoclaving by binding with Ca²⁺, thus improving the thermal stability and storage stability of WPEs-HMB-Ca. This work might provide theoretical guidance for developing functional milk drinks with good thermal stability and flavor.

Impact of ß-hydroxy-ß-methylbutyrate (HMB) in critically ill patients on the endocrine axis - A post-hoc cohort study of the HMB-ICU trial

BACKGROUND

β-hydroxy-β-methylbutyrate (HMB) might improve muscle function and maintain its mass in critically ill patients. We aimed to investigate whether the administration of HMB influenced the plasma levels of growth hormone (GH)/insulin-like growth factor-1 (IGF-1), C-peptide, and 25-OH vitamin-D.

METHODS

Post-hoc analysis of the study HMB-ICU, a randomized, placebo-controlled double-blind trial.

INCLUSION CRITERIA

Intensive care unit (ICU) patients depending on mechanical ventilation on day 3 with functional gastrointestinal tract. Patients were randomized to HMB (3 g/day) or placebo (maltodextrin) from day 4 on, for 30 days. Blood samples were collected on days 4 and 15. We determined the GH, C-peptide, 25-OH vitamin-D, and IGF-1. Statistics by ANCOVA.

RESULTS

Blood samples of 26 patients were available on day 4, and 23 on day 15. While age and severity of disease did not differ, diabetes was more frequent in the HMB group (p = 0.041), and obesity was more frequent in the placebo group (p = 0.021). Glucose intake, blood glucose (BG) and amount of insulin to maintain blood glucose between 6 and 8 mM did not differ between groups. There was no difference between groups for C-peptide, GH, IGF-1, and 25-OH vitamin-D. IGF-1 increased significantly from day 4-15 (p = 0.026) in both groups.

CONCLUSION

Subject to possible insufficient power of the study, we did not reach conclusive results. HMB intervention does not affect significantly the plasma concentrations of insulin, GH/IGF axis activity, C-peptide, and 25-OH vitamin-D.

CLINICALTRIALS

GOV IDENTIFIER

NCT03628365.

Small-Scale Randomized Controlled Trial to Explore the Impact of β-Hydroxy-β-Methylbutyrate Plus Vitamin D3 on Skeletal Muscle Health in Middle Aged Women

β-Hydroxy-β-methylbutyrate (HMB), a leucine metabolite, can increase skeletal muscle size and function. However, HMB may be less effective at improving muscle function in people with insufficient Vitamin D3 (25-OH-D < 30 ng/mL) which is common in middle-aged and older adults. Therefore, we tested the hypothesis that combining HMB plus Vitamin D3 (HMB + D) supplementation would improve skeletal muscle size, composition, and function in middle-aged women. In a double-blinded fashion, women (53 ± 1 yrs, 26 ± 1 kg/m2, n = 43) were randomized to take placebo or HMB + D (3 g Calcium HMB + 2000 IU D per day) during 12 weeks of sedentary behavior (SED) or resistance exercise training (RET). On average, participants entered the study Vitamin D3 insufficient while HMB + D increased 25-OH-D to sufficient levels after 8 and 12 weeks. In SED, HMB + D prevented the loss of arm lean mass observed with placebo. HMB + D increased muscle volume and decreased intermuscular adipose tissue (IMAT) volume in the thigh compared to placebo but did not change muscle function. In RET, 12-weeks of HMB + D decreased IMAT compared to placebo but did not influence the increase in skeletal muscle volume or function. In summary, HMB + D decreased IMAT independent of exercise status and may prevent the loss or increase muscle size in a small cohort of sedentary middle-aged women. These results lend support to conduct a longer duration study with greater sample size to determine the validity of the observed positive effects of HMB + D on IMAT and skeletal muscle in a small cohort of middle-aged women.

An umbrella review of systematic reviews of β-hydroxy-β-methyl butyrate supplementation in ageing and clinical practice

The compound β-hydroxy-β-methyl butyrate (HMB) is proposed to increase or mitigate the loss of skeletal muscle and improve muscle function. We undertook a review of systematic reviews of HMB supplementation to promote gains or mitigate muscle loss in ageing and clinical populations. Following PRISMA guidelines, we searched for systematic reviews reporting the effect of HMB in our target populations. Dual-energy X-ray absorptiometry (DXA) measured lean soft-tissue mass (LSTM) was accepted as a proxy for muscle. We identified 15 systematic reviews that met our inclusion criteria, which were independently evaluated. The methodological quality of the reviews was assessed using A Measurement Tool to Assess Systematic Reviews (AMSTAR), and standardized effectiveness statements were generated. Five of 15 studies found some evidence that HMB augmented LSTM; the remaining 10 studies reported some evidence favouring no difference (6/10 studies) or insufficient evidence to determine an effect (4/10 studies). Of the 12 studies that evaluated strength, 4/12 found some evidence, 5/12 found some evidence of no effect with one article finding some evidence in favour of patients in peri-hospitalized and no evidence for those that are community-dwelling, 4/12 had insufficient evidence to determine an effect, and 1/12 had insufficient evidence. No]study reported a positive effect of HMB on physical function; however, 2/10 studies found some evidence favouring no effect, and 7/10 studies reported insufficient evidence to determine an effect. The effectiveness of HMB supplementation in augmenting LSTM was heterogeneous, with most reviews finding no effect or inconclusive evidence to determine an effect. Most reviews concluded that HMB supplementation did not affect strength outcome measures or studies were inconclusive. The current evidence is insufficient to assess the impact of HMB supplementation on functional outcome measures. Our analysis shows minor, inconsistent support for HMB as part of an oral nutritional supplement or as a stand-alone supplement (or combined with other amino acids) to increase or promote retention of LSTM, improve strength, and no evidence that it improves physical function in older persons or clinical populations.

Nutritional co-therapy with 1,3-butanediol and multi-ingredient antioxidants enhances autophagic clearance in Pompe disease

Alglucosidase alpha is an orphan drug approved for enzyme replacement therapy (ERT) in Pompe disease (PD); however, its efficacy is limited in skeletal muscle because of a partial blockage of autophagic flux that hinders intracellular trafficking and enzyme delivery. Adjunctive therapies that enhance autophagic flux and protect mitochondrial integrity may alleviate autophagic blockage and oxidative stress and thereby improve ERT efficacy in PD. In this study, we compared the benefits of ERT combined with a ketogenic diet (ERT-KETO), daily administration of an oral ketone precursor (1,3-butanediol; ERT-BD), a multi-ingredient antioxidant diet (ERT-MITO; CoQ10, α-lipoic acid, vitamin E, beetroot extract, HMB, creatine, and citrulline), or co-therapy with the ketone precursor and multi-ingredient antioxidants (ERT-BD-MITO) on skeletal muscle pathology in GAA-KO mice. We found that two months of 1,3-BD administration raised circulatory ketone levels to ≥1.2 mM, attenuated autophagic buildup in type 2 muscle fibers, and preserved muscle strength and function in ERT-treated GAA-KO mice. Collectively, ERT-BD was more effective vs. standard ERT and ERT-KETO in terms of autophagic clearance, dampening of oxidative stress, and muscle maintenance. However, the addition of multi-ingredient antioxidants (ERT-BD-MITO) provided the most consistent benefits across all outcome measures and normalized mitochondrial protein expression in GAA-KO mice. We therefore conclude that nutritional co-therapy with 1,3-butanediol and multi-ingredient antioxidants may provide an alternative to ketogenic diets for inducing ketosis and enhancing autophagic flux in PD patients.

β-Hydroxy-β-methylbutyrate (HMB) supplementation and functional outcomes in multi-trauma patients: a study protocol for a pilot randomised clinical trial (BOOST trial)

Background

There are no therapies proven to diminish the muscle wasting that occurs in patients after major trauma who are admitted to the intensive care unit (ICU). β-Hydroxy-β-methylbutyrate (HMB) is a nutrition intervention that may attenuate muscle loss and, thereby, improve recovery. The primary aim of this study is to determine the feasibility of a blinded randomised clinical trial of HMB supplementation to patients after major trauma who are admitted to the ICU. Secondary aims are to establish estimates for the impact of HMB when compared to placebo on muscle mass and nutrition-related patient outcomes.

Methods

This prospective, single-centre, blinded, randomised, placebo-controlled, parallel-group, feasibility trial with allocation concealment will recruit 50 participants over 18 months. After informed consent, participants will be randomised [1:1] to receive either the intervention (three grams of HMB dissolved in either 150 ml of orange juice for those allowed oral intake or 150 ml of water for those being enterally fed) or placebo (150 ml of orange juice for those allowed oral intake or 150 ml of water for those being enterally fed). The intervention will be commenced in ICU, continued after ICU discharge and ceased at hospital discharge or day 28 post randomisation, whichever occurs first. The primary outcome is the feasibility of administering the intervention. Secondary outcomes include change in muscle thickness using ultrasound and other nutritional and patient-centred outcomes.

Discussion

This study aims to determine the feasibility of administering HMB to critically ill multi-trauma patients throughout ICU admission until hospital discharge. Results will inform design of a larger randomised clinical trial.

Trial registration

The protocol is registered with Australian New Zealand Clinical Trials Registry (ANZCTR) ANZCTR: 12620001305910. UTN: U1111-1259-5534.

Nutritional Approach to Cancer Cachexia: A Proposal for Dietitians

Cachexia is one of the most common, related factors of malnutrition in cancer patients. Cancer cachexia is a multifactorial syndrome characterized by persistent loss of skeletal muscle mass and fat mass, resulting in irreversible and progressive functional impairment. The skeletal muscle loss cannot be reversed by conventional nutritional support, and a combination of anti-inflammatory agents and other nutrients is recommended. In this review, we reviewed the effects of nutrients that are expected to combat muscle loss caused by cancer cachexia (eicosapentaenoic acid, β-hydroxy-β-methylbutyrate, creatine, and carnitine) to propose nutritional approaches that can be taken at present. Current evidence is based on the intake of nutrients as supplements; however, the long-term and continuous intake of nutrients as food has the potential to be useful for the body. Therefore, in addition to conventional nutritional support, we believe that it is important for the dietitian to work with the clinical team to first fully assess the patient’s condition and then to safely incorporate nutrients that are expected to have specific functions for cancer cachexia from foods and supplements.

β-Hydroxy β-methylbutyrate supplementation to adult Thoroughbred geldings increases type IIA fiber content in the gluteus medius

Consumption of β-hydroxy β-methylbutyrate (HMB) alters muscle composition and metabolism leading to strength and agility improvements in human athletes. To determine if HMB affects athletic performance and muscle function in horses, Thoroughbred geldings were fed a control (CON; n = 5) or HMB (n = 6) supplement for 6 wk prior to completing a standardized exercise test (SET). Gluteus medius (GM) muscle biopsies were obtained before the SET for fiber typing. Heart rate, biceps femoris (BF) and semitendinosus (ST) surface electromyograms (EMG), and fore and hind limbs metacarpophalangeal joint angles were captured at the gallop of the SET. Results demonstrate that HMB supplementation increased (P < 0.05) the percentage of type IIA and IIA/X muscle fibers in the GM with a corresponding decrease (P < 0.05) in type IIX fibers. The percentage of type I fibers was unaffected by diet. Supplementation with HMB did not result in any measurable effects on performance or biomechanical properties by comparison to CON. Supplementation with HMB resulted in an increase (P < 0.05) in ST median frequency at speeds of 10 m/s and greater. Increasing treadmill speed resulted in an increase (P < 0.05) in stride length and the maximal proximal forelimb fetlock angle, and a decrease (P < 0.05) in stance phase time of the gait cycle. Integrated EMG (iEMG) increased (P < 0.05) with increasing treadmill speeds for both the BF and ST with the BF exhibiting greater (P < 0.05) iEMG values than the ST. In summary, HMB increased the percentage of type IIA GM fibers, which did not translate into improved performance.

The Anabolic Response to Plant-Based Protein Ingestion

There is a global trend of an increased interest in plant-based diets. This includes an increase in the consumption of plant-based proteins at the expense of animal-based proteins. Plant-derived proteins are now also frequently applied in sports nutrition. So far, we have learned that the ingestion of plant-derived proteins, such as soy and wheat protein, result in lower post-prandial muscle protein synthesis responses when compared with the ingestion of an equivalent amount of animal-based protein. The lesser anabolic properties of plant-based versus animal-derived proteins may be attributed to differences in their protein digestion and amino acid absorption kinetics, as well as to differences in amino acid composition between these protein sources. Most plant-based proteins have a low essential amino acid content and are often deficient in one or more specific amino acids, such as lysine and methionine. However, there are large differences in amino acid composition between various plant-derived proteins or plant-based protein sources. So far, only a few studies have directly compared the muscle protein synthetic response following the ingestion of a plant-derived protein versus a high(er) quality animal-derived protein. The proposed lower anabolic properties of plant- versus animal-derived proteins may be compensated for by (i) consuming a greater amount of the plant-derived protein or plant-based protein source to compensate for the lesser quality; (ii) using specific blends of plant-based proteins to create a more balanced amino acid profile; (iii) fortifying the plant-based protein (source) with the specific free amino acid(s) that is (are) deficient. Clinical studies are warranted to assess the anabolic properties of the various plant-derived proteins and their protein sources in vivo in humans and to identify the factors that may or may not compromise the capacity to stimulate post-prandial muscle protein synthesis rates. Such work is needed to determine whether the transition towards a more plant-based diet is accompanied by a transition towards greater dietary protein intake requirements.

Metabolic flux analysis of branched-chain amino and keto acids (BCAA, BCKA) and β-hydroxy β-methylbutyric acid across multiple organs in the pig

Branched-chain amino acids (BCAA) and their metabolites the branched-chain keto acids (BCKA) and β-hydroxy β-methylbutyric acid (HMB) are involved in the regulation of key signaling pathways in the anabolic response to a meal. However, their (inter)organ kinetics remain unclear. Therefore, branched-chain amino acids (BCAA) [leucine (Leu), valine (Val), isoleucine (Ile)], BCKA [α-ketoisocaproic acid (KIC), 3-methyl-2-oxovaleric acid (KMV), 2-oxoisovalerate (KIV)], and HMB across organ net fluxes were measured. In multi-catheterized pigs (n = 12, ±25 kg), net fluxes across liver, portal drained viscera (PDV), kidney, and hindquarter (HQ, muscle compartment) were measured before and 4 h after bolus feeding of a complete meal (30% daily intake) in conscious state. Arterial and venous plasma were collected and concentrations were measured by LC- or GC-MS/MS. Data are expressed as mean [95% CI] and significance (P < 0.05) from zero by the Wilcoxon Signed Rank Test. In the postabsorptive state (in nmol/kg body wt/min), the kidney takes up HMB (3.2[1.3,5.0]) . BCKA is taken up by PDV (144[13,216]) but no release by other organs. In the postprandial state, the total net fluxes over 4 h (in µmol/kg body wt/4 h) showed a release of all BCKA by HQ (46.2[34.2,58.2]), KIC by the PDV (12.3[7.0,17.6]), and KIV by the kidney (10.0[2.3,178]). HMB was released by the liver (0.76[0.49,1.0]). All BCKA were taken up by the liver (200[133,268]). Substantial differences are present in (inter)organ metabolism and transport among the BCAA and its metabolites BCKA and HMB. The presented data in a translation animal model are relevant for the future development of optimized clinical nutrition.NEW & NOTEWORTHY Branched-chain amino acids (BCAA) and their metabolites the branched-chain keto acids (BCKA) and β-hydroxy β-methylbutyric acid (HMB) are involved in the regulation of key signaling pathways in the anabolic response to a meal. Substantial differences are present in (inter)organ metabolism and transport among the BCAA and its metabolites BCKA and HMB. The presented data in a translation animal model are relevant for the future development of optimized clinical nutrition.

Nutrients to mitigate osteosarcopenia: the role of protein, vitamin D and calcium

PURPOSE OF REVIEW

Osteosarcopenia (the joint loss of bone density and muscle mass and function) is an emerging geriatric syndrome, which associates with poor health outcomes. Several nutrients including protein, vitamin D and calcium interact (directly or through absorption properties) to regulate muscle and bone metabolism. We provided an update on the efficacy of these nutrients on musculoskeletal outcomes in older adults with, or at risk of, osteosarcopenia.

RECENT FINDINGS

Randomized trials show that correcting vitamin D and calcium deficiencies to meet the recommended dietary allowance (RDA) increases bone density and reduces fracture (but not falls) risk. Supplementing above the RDA with protein supports gains in lean mass and lumbar-spine bone density; however, there is inconclusive evidence for muscle strength, physical function or other bone density sites. A likely explanation for this relates to the significant heterogeneity between trials regarding protein dose, type and timing, as well as baseline protein intake. Further high-quality trials are needed in older osteosarcopenic adults to investigate the effects of protein (while correcting vitamin D and calcium deficiencies) on clinically meaningful outcomes such as activities of daily living, falls and fractures.

SUMMARY

An adequate intake of protein (1.2-1.5 g/kg/day), vitamin D (800 IU/day) and calcium (1000-1200 mg/day), is well tolerated and effective at mitigating some aspects of osteosarcopenia such as lean mass, bone density and fracture risk.

Oral Nutritional Supplement with β-hydroxy-β-methylbutyrate (HMB) Improves Nutrition, Physical Performance and Ameliorates Intramuscular Adiposity in Pre-Frail Older Adults: A Randomized Controlled Trial

OBJECTIVES

Supplementation of high protein oral nutrition shakes supplemented with β-hydroxy-β-methylbutyrate (HP-HMB) has been shown to improve muscle mass, muscle strength, and physical performance in older adults, but the roles of HP-HMB supplementation on the intramuscular adiposity remained unknown. This 12-week randomized controlled trial evaluated the changes of muscle mass, muscle strength, physical performance and intramuscular adiposity among community-dwelling pre-frail older persons.

METHODS

This was an open-label, parallel group, randomized controlled trail that enrolled 70 community-dwelling pre-frail older persons without active or uncontrolled conditions, disability or dementia. The intervention group was provided with two services of HP HMB (Ensure® Plus Advance containing 3g HMB) per day for 12 weeks, and the control group was provided with professional nutritional counselling for sufficient protein intake. All participants received functional assessments, laboratory tests and magnetic resonance imaging (MRI) of the dominant leg before and after study. Intramuscular adipose tissue (IMAT) and the mid-thigh cross-sectional area (CSA) of muscle were obtained by MRI, and the IMAT-to-CSA ratio was calculated to evaluate intramuscular adiposity.

RESULTS

Overall, 62 participants (mean age: 71.1±3.8 years, 69.4% female) completed the study (HP-HMB group: 29, control group: 33) and comparisons of baseline characteristics between groups were not statistically different. For the primary outcome, HP-HMB group showed significant improvements in the CSA of mid-thigh muscle (mean increase of CSA: 149.1±272.3 for HMB group vs -22.9±309.1 mm2 for control group, P=0.045). The improvement of MNA-SF was borderline (0.28±0.75 vs. -0.15±0.94, P=0.064), but serum levels of Vit D were significantly increased in the HMB group (3.83±8.18 vs. -1.30±4.81 ng/mL, P=0.002). Moreover, the body weight and BMI were significantly increased in the HMB group (1.10±1.18 vs. 0.24±1.13 kg, P=0.005; 0.56±0.68 vs. 0.22±0.47 kg/m2, P=0.019). In particular, the IMAT-to-CSA ratio was reduced in the HMB group (-0.38±1.21 vs. -0.02±2.56 %, P=0.06). Using the generalized estimating equation, we found that SPPB score in chair rise test was significantly improved (β=0.71, 95% C.I.0.09-1.33, P=0.026).

CONCLUSIONS

The 12-week supplementation with high protein oral nutrition shake supplemented with 3g HMB per day significantly increased muscle mass, as well as nutritional status and physical performance, and ameliorated the intramuscular adiposity of pre-frail older persons. Further study is needed to explore the long-term benefits of HP-HMB supplementation on muscle and metabolic health for older adults.

β-hydroxy-β-methylbutyrate supplementation in older persons - an update

PURPOSE OF REVIEW

The interest in the use of beta-hydroxy-beta-methylbutyrate (HMB) as an intervention to prevent and treat sarcopenia has increased over recent years. The purpose of this review is to explore recent evidence pertaining to the mechanism of action of HMB and how this may influence changes in lean mass and strength in older persons who are both hospitalized and living in the community.

RECENT FINDINGS

No new studies have been published over the last 2 years investigating the effect of HMB in older persons who are hospitalized, aside from one posthoc analysis of a randomized controlled trial exploring the effect of a high protein oral nutrition supplement containing HMB on handgrip strength and nutritional status. Three studies recruiting community-dwelling older adults have been published, but results are influenced by suboptimal methodological quality.

SUMMARY

Recent data suggest the need for high-quality studies investigating the effectiveness of HMB to improve outcomes related to sarcopenia in both hospitalized and community-dwelling older persons.

PGC-1α-Targeted Therapeutic Approaches to Enhance Muscle Recovery in Aging

Impaired muscle recovery (size and strength) following a disuse period commonly occurs in older adults. Many of these individuals are not able to adequately exercise due to pain and logistic barriers. Thus, nutritional and pharmacological therapeutics, that are translatable, are needed to promote muscle recovery following disuse in older individuals. Peroxisome proliferator-activated receptor gamma coactivator 1-alpha (PGC-1α) may be a suitable therapeutic target due to pleiotropic regulation of skeletal muscle. This review focuses on nutritional and pharmacological interventions that target PGC-1α and related Sirtuin 1 (SIRT1) and 5' AMP-activated protein kinase (AMPKα) signaling in muscle and thus may be rapidly translated to prevent muscle disuse atrophy and promote recovery. In this review, we present several therapeutics that target PGC-1α in skeletal muscle such as leucine, β-hydroxy-β-methylbuyrate (HMB), arginine, resveratrol, metformin and combination therapies that may have future application to conditions of disuse and recovery in humans.

The impact of acute beta-hydroxy-beta-methylbutyrate (HMB) ingestion on glucose and insulin kinetics in young and older men

Insulin resistance (IR) is a key feature in the development of numerous metabolic diseases. The cornerstone for treatment for IR remains diet and exercise, however these have poor rates of adherence. Beta-hydroxy-beta-methylbutyrate (HMB) is a nutraceutical with contentious effects on IR in animal models. The aim of this study was to evaluate the impact of acute HMB on IR in humans during an oral glucose tolerance test (OGTT). Young and older male volunteers underwent two 75 g OGTT with or without 3 g HMB. In young men, HMB significantly reduced the insulin area-under-the-curve (AUC), with no difference in glucose AUC, resulting in a numerical increase in the Cederholm index of insulin sensitivity. In older men, HMB had no effect on insulin or glucose responses. In conclusion, acute HMB may improve IR following a glucose load in young men; however, this does not appear to be sustained into older age.

Skeletal Muscle Recovery from Disuse Atrophy: Protein Turnover Signaling and Strategies for Accelerating Muscle Regrowth

Skeletal muscle fibers have a unique capacity to adjust their metabolism and phenotype in response to alternations in mechanical loading. Indeed, chronic mechanical loading leads to an increase in skeletal muscle mass, while prolonged mechanical unloading results in a significant decrease in muscle mass (muscle atrophy). The maintenance of skeletal muscle mass is dependent on the balance between rates of muscle protein synthesis and breakdown. While molecular mechanisms regulating protein synthesis during mechanical unloading have been relatively well studied, signaling events implicated in protein turnover during skeletal muscle recovery from unloading are poorly defined. A better understanding of the molecular events that underpin muscle mass recovery following disuse-induced atrophy is of significant importance for both clinical and space medicine. This review focuses on the molecular mechanisms that may be involved in the activation of protein synthesis and subsequent restoration of muscle mass after a period of mechanical unloading. In addition, the efficiency of strategies proposed to improve muscle protein gain during recovery is also discussed.

Long-term Effects of Calcium β-Hydroxy-β-Methylbutyrate and Vitamin D3 Supplementation on Muscular Function in Older Adults With and Without Resistance Training: A Randomized, Double-blind, Controlled Study

The primary aim of this study was to determine whether supplementation with calcium β-hydroxy-β-methylbutyrate (HMB) and vitamin D₃ (D) would enhance muscle function and strength in older adults. Older adults over 60 years of age with insufficient circulating 25-hydroxy-vitamin D (25OH-D) levels were enrolled in a double-blinded controlled 12-month study. Study participants were randomly assigned to treatments consisting of: (a) Control + no exercise, (b) HMB+D + no exercise, (c) Control + exercise, and (d) HMB+D + exercise. The study evaluated 117 participants via multiple measurements over the 12 months that included body composition, strength, functionality, and questionnaires. HMB+D had a significant benefit on lean body mass within the nonexercise group at 6 months (0.44 ± 0.27 kg, HMB+D vs −0.33 ± 0.28 kg, control, p < .05). In nonexercisers, improvement in knee extension peak torque (60°/s) was significantly greater in HMB+D-supplemented participants than in the nonsupplemented group (p = .04) at 3 months, 10.9 ± 5.7 Nm and −5.2 ± 5.9 Nm, respectively. A composite functional index, integrating changes in handgrip, Get Up, and Get Up and Go measurements, was developed. HMB+D + no exercise resulted in significant increases in the functional index compared with those observed in the control + no exercise group at 3 (p = .03), 6 (p = .04), and 12 months (p = .04). Supplementation with HMB+D did not further improve the functional index within the exercising group. This study demonstrated the potential of HMB and vitamin D₃ supplementation to enhance muscle strength and physical functionality in older adults, even in individuals not engaged in an exercise training program.

Dietary protein, exercise, ageing and physical inactivity: interactive influences on skeletal muscle proteostasis

Dietary protein is a pre-requisite for the maintenance of skeletal muscle mass; stimulating increases in muscle protein synthesis (MPS), via essential amino acids (EAA), and attenuating muscle protein breakdown, via insulin. Muscles are receptive to the anabolic effects of dietary protein, and in particular the EAA leucine, for only a short period (i.e. about 2-3 h) in the rested state. Thereafter, MPS exhibits tachyphylaxis despite continued EAA availability and sustained mechanistic target of rapamycin complex 1 signalling. Other notable characteristics of this 'muscle full' phenomenon include: (i) it cannot be overcome by proximal intake of additional nutrient signals/substrates regulating MPS; meaning a refractory period exists before a next stimulation is possible, (ii) it is refractory to pharmacological/nutraceutical enhancement of muscle blood flow and thus is not induced by muscle hypo-perfusion, (iii) it manifests independently of whether protein intake occurs in a bolus or intermittent feeding pattern, and (iv) it does not appear to be dependent on protein dose per se. Instead, the main factor associated with altering muscle full is physical activity. For instance, when coupled to protein intake, resistance exercise delays the muscle full set-point to permit additional use of available EAA for MPS to promote muscle remodelling/growth. In contrast, ageing is associated with blunted MPS responses to protein/exercise (anabolic resistance), while physical inactivity (e.g. immobilisation) induces a premature muscle full, promoting muscle atrophy. It is crucial that in catabolic scenarios, anabolic strategies are sought to mitigate muscle decline. This review highlights regulatory protein turnover interactions by dietary protein, exercise, ageing and physical inactivity.

The Effects of Calcium-β-Hydroxy-β-Methylbutyrate on Aging-Associated Apoptotic Signaling and Muscle Mass and Function in Unloaded but Nonatrophied Extensor Digitorum Longus Muscles of Aged Rats

Beta-hydroxy-beta-methylbutyrate (HMB), a naturally occurring leucine metabolite, has been shown to attenuate plantar flexor muscle loss and increase myogenic stem cell activation during reloading after a period of significant muscle wasting by disuse in old rodents. However, it was less clear if HMB would alter dorsiflexor muscle response to unloading or reloading when there was no significant atrophy that was induced by unloading. In this study, we tested if calcium HMB (Ca-HMB) would improve muscle function and alter apoptotic signaling in the extensor digitorum longus (EDL) of aged animals that were unloaded but did not undergo atrophy. The EDL muscle was unloaded for 14 days by hindlimb suspension (HS) in aged (34-36 mo.) male Fisher 344 × Brown Norway rats. The rats were removed from HS and allowed normal cage ambulation for 14 days of reloading (R). Throughout the study, the rats were gavaged daily with 170 mg of Ca-HMB or water 7 days prior to HS, then throughout 14 days of HS and 14 days of recovery after removing HS. The animals' body weights were significantly reduced by ~18% after 14 days of HS and continued to decline by ~22% during R as compared to control conditions; however, despite unloading, EDL did not atrophy by HS, nor did it increase in mass after R. No changes were observed in EDL twitch contraction time, force production, fatigue resistance, fiber cross-sectional area, or markers of nuclear apoptosis (myonuclei + satellite cells) after HS or R. While HS and R increased the proapoptotic Bax protein abundance, BCL-2 abundance was also increased as was the frequency of TUNEL-positive myonuclei and satellite cells, yet muscle mass and fiber cross-sectional area did not change and Ca-HMB treatment had no effect reducing apoptotic signaling. These data indicate that (i) increased apoptotic signaling preceded muscle atrophy or occurred without significant EDL atrophy and (ii) that Ca-HMB treatment did not improve EDL signaling, muscle mass, or muscle function in aged rats, when HS and R did not impact mass or function.

The addition of β-Hydroxy β-Methylbutyrate (HMB) to creatine monohydrate supplementation does not improve anthropometric and performance maintenance across a collegiate rugby season

BACKGROUND

Muscular damage sustained while playing rugby may hinder performance across a season. β-Hydroxy β-Methylbutyrate (HMB) may help attenuate muscle damage and maintain lean mass and performance. This study sought to determine the effect of combining HMB with creatine monohydrate supplementation on measures of stress and muscle damage, body composition, strength and sprinting kinetics throughout a rugby season.

METHODS

This double-blind, cross-over investigation recruited 16 male collegiate rugby players to provide resting blood samples and complete assessments of body composition, strength and sprinting performance prior to their fall season (PREFALL). After testing, the athletes were matched for fat-free mass and assigned to consume one of two supplementation regimens for 6 weeks: 5 g HMB + 5 g creatine per day (HMB-Cr: 20.9 ± 1.1 years; 177 ± 2 cm; 88.4 ± 4.9 kg) or 5 g creatine + 5 g placebo per day (Cr: 21.4 ± 2.1 years; 179 ± 2 cm; 88.3 ± 4.9 kg). After 6 weeks (POSTFALL), PREFALL testing was repeated in 13 of the original 16 athletes before a 10-wk wash-out period. Athletes who returned for the spring season (n = 8) repeated all fall-season procedures and testing prior to (PRESPRING) and following (POSTSPRING) their 6-wk spring season, except they were assigned to the opposite supplementation regimen.

RESULTS

Linear mixed models with repeated measures revealed group x time interactions (p <  0.05) for observed for several measures but did not consistently and positively favor one group. During the fall season, knee extensor peak torque was reduced by 40.7 ± 28.1 Nm (p = 0.035) for HMB-Cr but remained consistent for Cr, and no group differences or changes were noted in the spring. In the spring, greater knee flexor rate of torque development (~ 149 Nm·sec- 1, p = 0.003) and impulse (~ 4.5 Nm·sec, p = 0.022) were observed in Cr at PRESPRING but not at POSTSPRING. Although significant interactions were found for cortisol concentrations, vastus lateralis pennation angle, and sprinting force, post-hoc analysis only revealed differences between fall and spring seasons. No other differences were observed.

CONCLUSIONS

The combination of HMB and creatine monohydrate supplementation does not provide a greater ergogenic benefit compared to creatine monohydrate supplementation alone. Body composition, strength, and sprinting ability did not change across the season with creatine monohydrate supplementation.

Nutritional Strategies to Offset Disuse-Induced Skeletal Muscle Atrophy and Anabolic Resistance in Older Adults: From Whole-Foods to Isolated Ingredients

Preserving skeletal muscle mass and functional capacity is essential for healthy ageing. Transient periods of disuse and/or inactivity in combination with sub-optimal dietary intake have been shown to accelerate the age-related loss of muscle mass and strength, predisposing to disability and metabolic disease. Mechanisms underlying disuse and/or inactivity-related muscle deterioration in the older adults, whilst multifaceted, ultimately manifest in an imbalance between rates of muscle protein synthesis and breakdown, resulting in net muscle loss. To date, the most potent intervention to mitigate disuse-induced muscle deterioration is mechanical loading in the form of resistance exercise. However, the feasibility of older individuals performing resistance exercise during disuse and inactivity has been questioned, particularly as illness and injury may affect adherence and safety, as well as accessibility to appropriate equipment and physical therapists. Therefore, optimising nutritional intake during disuse events, through the introduction of protein-rich whole-foods, isolated proteins and nutrient compounds with purported pro-anabolic and anti-catabolic properties could offset impairments in muscle protein turnover and, ultimately, the degree of muscle atrophy and recovery upon re-ambulation. The current review therefore aims to provide an overview of nutritional countermeasures to disuse atrophy and anabolic resistance in older individuals.

Supplementation with the Leucine Metabolite β-hydroxy-β-methylbutyrate (HMB) does not Improve Resistance Exercise-Induced Changes in Body Composition or Strength in Young Subjects: A Systematic Review and Meta-Analysis

β-hydroxy-β-methylbutyrate (HMB) is a leucine metabolite that is purported to increase fat-free mass (FFM) gain and performance in response to resistance exercise training (RET). The aim of this systematic review and meta-analysis was to determine the efficacy of HMB supplementation in augmenting FFM and strength gains during RET in young adults. Outcomes investigated were: total body mass (TBM), FFM, fat mass (FM), total single repetition maximum (1RM), bench press (BP) 1RM, and lower body (LwB) 1RM. Databases consulted were: Medical Literature Analysis and Retrieval System Online (Medline), Excerpta Medica database (Embase), The Cumulative Index to Nursing and Allied Health Literature (CINAHL), and SportDiscus. Fourteen studies fit the inclusion criteria; however, 11 were analyzed after data extraction and funnel plot analysis exclusion. A total of 302 participants (18-45 y) were included in body mass and composition analysis, and 248 were included in the strength analysis. A significant effect was found on TBM. However, there were no significant effects for FFM, FM, or strength outcomes. We conclude that HMB produces a small effect on TBM gain, but this effect does not translate into significantly greater increases in FFM, strength or decreases in FM during periods of RET. Our findings do not support the use of HMB aiming at improvement of body composition or strength with RET.

Metabolic aspects of muscle wasting during critical illness

PURPOSE OF REVIEW

Skeletal muscle wasting during critical illness is the result of disturbed metabolism. No proven effective interventions targeting skeletal muscle mass and function during critical illness currently exist. This review summarizes recent advances regarding the complexity of metabolic factors involved and the challenge of establishing the clinical effects of metabolic interventions targeting the muscle.

RECENT FINDINGS

Although the catabolic state is limited to the acute phase of critical illness, its subsequent impact on muscle mass and function persists long after ICU discharge. Immobilization, inflammation and disturbed muscle energy and nutrient metabolism are key drivers of muscle protein loss. Current research focuses on the effects of enhanced protein provision, specific substrate delivery and physical exercise. Whilst some interventions have been successful at improving muscle mass, these effects do not always carry over into muscle function or strength.

SUMMARY

Increased understanding of metabolic derangements during critical illness provides new potential targets for treatment. The potential of dietary protein to attenuate the muscle protein catabolic state has yet to be established in clinical trials. Basic research should focus on ways to further improve the anabolic potential of nutrition by unravelling mechanisms that regulate anabolic and catabolic pathways and energy metabolism.

Comprehensive metabolic flux analysis to explain skeletal muscle weakness in COPD

BACKGROUND & AIMS

Metabolic characterization of a well-defined group of patients could be a powerful tool in revealing metabolic signatures to explain limb muscle weakness in chronic diseases. Studies are currently limited in Chronic Obstructive Pulmonary Disease (COPD) to the identification of differential amino acid concentrations but lack comprehensive analysis of the flux through relevant muscle function related metabolic pathways.

METHODS

In 23 stable patients with moderate to very severe COPD and 19 healthy controls, a comprehensive metabolic flux analysis was conducted by administering an intravenous pulse and primed constant infusion of multiple stable tracers of amino acids known to play a role in muscle health. Blood samples were obtained to calculate production (WBP) and interconversion rates, and plasma concentrations of these amino acids. Lower and upper limb muscle strength, muscle mass, lung function, physical activity level, and disease history and characteristics were assessed.

RESULTS

The COPD group was characterized by lower and upper limb muscle weakness (P < 0.01) despite preserved muscle mass. Higher values were found in COPD for plasma glutamine, WBP of leucine (P < 0.001), 3-methylhistidine (P < 0.01) (marker of enhanced myofibrillar protein breakdown), citrulline (P < 0.05), and arginine to citrulline conversion (P < 0.05) (reflecting enhanced nitric oxide synthesis). Plasma concentration of β-hydroxy β-methylbutyrate (HMB with anticatabolic, anabolic and contractile properties), WBP of glycine (precursor of creatine and glutathione), and transcutaneous O₂ saturation explained up to 79% and 65% of the variation in strength of the lower and upper limb muscles, respectively, in COPD.

CONCLUSIONS

Comprehensive metabolic flux analysis revealed a homogenous metabolic signature in stable patients with COPD and a specific metabolic profile in those with skeletal muscle weakness.

CLINICAL TRIAL REGISTRY

ClinicalTrials.gov; No. NCT01787682; URL: www.clinicaltrials.gov.

Branched-chain amino acid and branched-chain ketoacid ingestion increases muscle protein synthesis rates in vivo in older adults: a double-blind, randomized trial

BACKGROUND

Protein ingestion increases muscle protein synthesis rates. However, limited data are currently available on the effects of branched-chain amino acid (BCAA) and branched-chain ketoacid (BCKA) ingestion on postprandial muscle protein synthesis rates.

OBJECTIVE

The aim of this study was to compare the impact of ingesting 6 g BCAA, 6 g BCKA, and 30 g milk protein (MILK) on the postprandial rise in circulating amino acid concentrations and subsequent myofibrillar protein synthesis rates in older males.

METHODS

In a parallel design, 45 older males (age: 71 ± 1 y; BMI: 25.4 ± 0.8 kg/m2) were randomly assigned to ingest a drink containing 6 g BCAA, 6 g BCKA, or 30 g MILK. Basal and postprandial myofibrillar protein synthesis rates were assessed by primed continuous l-[ring-13C6]phenylalanine infusions with the collection of blood samples and muscle biopsies.

RESULTS

Plasma BCAA concentrations increased following test drink ingestion in all groups, with greater increases in the BCAA and MILK groups compared with the BCKA group (P < 0.05). Plasma BCKA concentrations increased following test drink ingestion in all groups, with greater increases in the BCKA group compared with the BCAA and MILK groups (P < 0.05). Ingestion of MILK, BCAA, and BCKA significantly increased early myofibrillar protein synthesis rates (0-2 h) above basal rates (from 0.020 ± 0.002%/h to 0.042 ± 0.004%/h, 0.022 ± 0.002%/h to 0.044 ± 0.004%/h, and 0.023 ± 0.003%/h to 0.044 ± 0.004%/h, respectively; P < 0.001), with no differences between groups (P > 0.05). Myofibrillar protein synthesis rates during the late postprandial phase (2-5 h) remained elevated in the MILK group (0.039 ± 0.004%/h; P < 0.001), but returned to baseline values following BCAA and BCKA ingestion (0.024 ± 0.005%/h and 0.024 ± 0.005%/h, respectively; P > 0.05).

CONCLUSIONS

Ingestion of 6 g BCAA, 6 g BCKA, and 30 g MILK increases myofibrillar protein synthesis rates during the early postprandial phase (0-2 h) in vivo in healthy older males. The postprandial increase following the ingestion of 6 g BCAA and BCKA is short-lived, with higher myofibrillar protein synthesis rates only being maintained following the ingestion of an equivalent amount of intact milk protein. This trial was registered at Nederlands Trial Register (www.trialregister.nl) as NTR6047.

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.

Equivalent Hypertrophy and Strength Gains in β-Hydroxy-β-Methylbutyrate- or Leucine-supplemented Men

Ingestion of proteins with high leucine content during resistance training (RT) can augment hypertrophy. Some data suggest that a leucine metabolite, β-hydroxy, β-methylbutyrate (HMB), is substantially more anabolically efficacious than leucine.

PURPOSE

We aimed to test whether supplementation with HMB versus leucine, added to whey protein, would result in differential muscle hypertrophy and strength gains in young men performing RT.

METHODS

Twenty-six resistance-trained men (23 ± 2 yr) performed 12 wk of RT with three phases. Phase 1: 8 wk of periodized RT (three training sessions per week). Phase 2: 2 wk overreaching period (five sessions per week). Phase 3: 2 wk taper (three sessions per week). Participants were randomly assigned to twice daily ingestion of: whey protein (25 g) plus HMB (1.5 g) (whey+HMB; n = 13) or whey protein (25 g) plus leucine (1.5 g) (whey+leu; n = 13). Skeletal muscle biopsies were performed before and after RT. Measures of fat- and bone-free mass, vastus lateralis (VL) muscle thickness and muscle cross-sectional area (CSA) (both by ultrasound), muscle fiber CSA, and 1-repetition maximum (1-RM) strength tests were determined.

RESULTS

We observed increases in fat- and bone-free mass, VL muscle thickness, muscle CSA and fiber type CSA and 1-RM strength with no differences between groups at any phase. We observed no differences between groups or time-group interactions in hormone concentrations at any phase of the RT program.

CONCLUSIONS

β-Hydroxy-β-methylbutyrate added to whey did not result in greater increases in any measure of muscle mass, strength, or hormonal concentration compared to leucine added to whey. Our results show that HMB is no more effective in stimulating RT-induced hypertrophy and strength gains than leucine.

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.

Branched Chain Amino Acids: Beyond Nutrition Metabolism

Branched chain amino acids (BCAAs), including leucine (Leu), isoleucine (Ile), and valine (Val), play critical roles in the regulation of energy homeostasis, nutrition metabolism, gut health, immunity and disease in humans and animals. As the most abundant of essential amino acids (EAAs), BCAAs are not only the substrates for synthesis of nitrogenous compounds, they also serve as signaling molecules regulating metabolism of glucose, lipid, and protein synthesis, intestinal health, and immunity via special signaling network, especially phosphoinositide 3-kinase/protein kinase B/mammalian target of rapamycin (PI3K/AKT/mTOR) signal pathway. Current evidence supports BCAAs and their derivatives as the potential biomarkers of diseases such as insulin resistance (IR), type 2 diabetes mellitus (T2DM), cancer, and cardiovascular diseases (CVDs). These diseases are closely associated with catabolism and balance of BCAAs. Hence, optimizing dietary BCAA levels should have a positive effect on the parameters associated with health and diseases. This review focuses on recent findings of BCAAs in metabolic pathways and regulation, and underlying the relationship of BCAAs to related disease processes.

Branched-chain amino acids in liver diseases

Branched chain amino acids (BCAAs) are involved in various bioprocess such as protein metabolism, gene expression, insulin resistance and proliferation of hepatocytes. BCAAs have also been reported to suppress the growth of hepatocellular carcinoma (HCC) cells in vitro and to be required for immune cells to perform the function. In advanced cirrhotic patients, it has been clarified that serum concentrations of BCAA are decreased, whereas those of aromatic amino acids (AAAs) are increased. These alterations are thought to be the causes of hepatic encephalopathy (HE), sarcopenia and hepatocarcinogenesis and may be associated with the poor prognosis of patients with these conditions. Administration of BCAA-rich medicines has shown positive results in patients with cirrhosis.