Nutritional role of the leucine metabolite β-hydroxy β-methylbutyrate (HMB)

International Society of Sports Nutrition Position Stand: beta-hydroxy-beta-methylbutyrate (HMB)

Position Statement: The International Society of Sports Nutrition (ISSN) bases the following position stand on a critical analysis of the literature on the use of beta-hydroxy-beta-methylbutyrate (HMB) as a nutritional supplement. The ISSN has concluded the following. 1. HMB can be used to enhance recovery by attenuating exercise induced skeletal muscle damage in trained and untrained populations. 2. If consuming HMB, an athlete will benefit from consuming the supplement in close proximity to their workout. 3. HMB appears to be most effective when consumed for 2 weeks prior to an exercise bout. 4. Thirty-eight mg·kg·BM-1 daily of HMB has been demonstrated to enhance skeletal muscle hypertrophy, strength, and power in untrained and trained populations when the appropriate exercise prescription is utilized. 5. Currently, two forms of HMB have been used: Calcium HMB (HMB-Ca) and a free acid form of HMB (HMB-FA). HMB-FA may increase plasma absorption and retention of HMB to a greater extent than HMB-CA. However, research with HMB-FA is in its infancy, and there is not enough research to support whether one form is superior. 6. HMB has been demonstrated to increase LBM and functionality in elderly, sedentary populations. 7. HMB ingestion in conjunction with a structured exercise program may result in greater declines in fat mass (FM). 8. HMB's mechanisms of action include an inhibition and increase of proteolysis and protein synthesis, respectively. 9. Chronic consumption of HMB is safe in both young and old populations.

Effects of combined maternal administration with alpha-ketoglutarate (AKG) and β-hydroxy-β-methylbutyrate (HMB) on prenatal programming of skeletal properties in the offspring

BACKGROUND

Nutritional manipulations during fetal growth may induce long-term metabolic effects in postnatal life. The aim of the study was to test whether combined treatment of pregnant sows with alpha-ketoglutarate and β-hydroxy-β-methylbutyrate induces additive long-term effects on skeletal system properties in the offspring.

METHODS

The study was performed on 290 pigs obtained from 24 sows divided into 4 equal groups and subjected to experimental treatment during two weeks before delivery. The first group consisted of control sows, while the second group received alpha-ketoglutarate. The third group was treated with β-hydroxy-β-methylbutyrate and the fourth group underwent combined administration of alpha-ketoglutarate and β-hydroxy-β-methylbutyrate. Piglets obtained from sows were reared until slaughter age to perform morphometric, densitometric and mechanical analyses of femur. Serum evaluations of growth hormone, insulin-like growth factor-1, bone-specific alkaline phosphatase and osteocalcin were performed in newborns and 90-day old piglets; additionally, plasma amino acid concentration was measured in newborns.

RESULTS

Maternal treatment with alpha-ketoglutarate and β-hydroxy-β-methylbutyrate significantly reduced fattening time and increased birth body weight, daily body weight gain, bone weight, volumetric bone mineral density, geometrical parameters and mechanical endurance of femur. These effects were associated with increased serum concentrations of growth hormone, insulin-like growth factor-1, bone-specific alkaline phosphatase and osteocalcin. Furthermore, alpha-ketoglutarate and β-hydroxy-β-methylbutyrate administered solely or in combination significantly increased plasma level of 19 amino acids.

CONCLUSIONS

Hormonal and amino acid evaluations in pigs indicate additive effects of AKG and HMB on systemic growth and development; however, determination of bone properties has not shown such phenomenon.

Effects of dairy consumption on SIRT1 and mitochondrial biogenesis in adipocytes and muscle cells

BACKGROUND

Recent data from this laboratory suggest that components of dairy foods may serve as activators of SIRT1 (Silent Information Regulator Transcript 1), and thereby participate in regulation of glucose and lipid metabolism. In this study, an ex-vivo/in-vitro approach was used to examine the integrated effects of dairy diets on SIRT1 activation in two key target tissues (adipose and muscle tissue).

METHODS

Serum from overweight and obese subjects fed low or high dairy diets for 28 days was added to culture medium (similar to conditioned media) to treat cultured adipocytes and muscle cells for 48 hours.

RESULTS

Treatment with high dairy group conditioned media resulted in 40% increased SIRT1 gene expression in both tissues (p < 0.01) and 13% increased enzyme activity in adipose tissue compared to baseline. This was associated with increased gene expression of peroxisome proliferator-activated receptor-gamma coactivator 1 alpha (PGC-1α), nuclear respiratory factor 1 (NRF1), cytochrome oxidase c subunit 7 (Cox 7), NADH dehydrogenase and uncoupling protein 2 (UCP2) in adipocytes as well as uncoupling protein 3 (UCP3), NRF1 and Cox 7 in muscle cells (p < 0.05). Further, direct incubation of physiological concentrations of leucine and its metabolites α-Ketoisocaproic acid (KIC) and β-hydroxy-methylbuteric acid (HMB) with recombinant human SIRT1 enzyme resulted in 30 to 50% increase of SIRT1 activity (p < 0.05).

CONCLUSIONS

These data indicate that dairy consumption leads to systemic effects, which may promote mitochondrial biogenesis in key target tissues such as muscle and adipose tissue both by direct activation of SIRT1 as well as by SIRT1-independent pathways.

Metabolic and functional effects of beta-hydroxy-beta-methylbutyrate (HMB) supplementation in skeletal muscle

Beta-hydroxy-beta-methylbutyrate (HMB) is a metabolite derived from leucine. The anti-catabolic effect of HMB is well documented but its effect upon skeletal muscle strength and fatigue is still uncertain. In the present study, male Wistar rats were supplemented with HMB (320 mg/kg per day) for 4 weeks. Placebo group received saline solution only. Muscle strength (twitch and tetanic force) and resistance to acute muscle fatigue of the gastrocnemius muscle were evaluated by direct electrical stimulation of the sciatic nerve. The content of ATP and glycogen in red and white portions of gastrocnemius muscle were also evaluated. The effect of HMB on citrate synthase (CS) activity was also investigated. Muscle tetanic force was increased by HMB supplementation. No change was observed in time to peak of contraction and relaxation time. Resistance to acute muscle fatigue during intense contractile activity was also improved after HMB supplementation. Glycogen content was increased in both white (by fivefold) and red (by fourfold) portions of gastrocnemius muscle. HMB supplementation also increased the ATP content in red (by twofold) and white (1.2-fold) portions of gastrocnemius muscle. CS activity was increased by twofold in red portion of gastrocnemius muscle. These results support the proposition that HMB supplementation have marked change in oxidative metabolism improving muscle strength generation and performance during intense contractions.

Effect of β-hydroxy-β-methylbutyrate (HMB) administration on volumetric bone mineral density, and morphometric and mechanical properties of tibia in male turkeys

This study was performed to investigate the effects of β-hydroxy-β-methylbutyrate (HMB) administration on skeletal system properties in turkeys. Thirty-two males were randomly divided into two groups at the age of 35 days of life. The first group included control turkeys (n = 16) treated with placebo, while the second group of birds (HMB group; n = 16) was administered orally with calcium salt of HMB during the last 15 weeks of life. The turkeys were sacrificed at the age of 20 weeks and tibia was isolated for analysis of bone geometrical parameters, volumetric bone mineral density (vBMD) and mechanical properties. Furthermore, assessment of free amino acid concentrations in plasma was performed. The results showed a 6.3% increase of vBMD of tibia in response to HMB treatment (p < 0.01). Cross-sectional area, second moment of inertia, maximum elastic strength and ultimate strength of tibia were significantly increased in HMB-treated turkeys by 21.3%, 49.0%, 27.2% and 28.3%, respectively (p ≤ 0.01). β-hydroxy-β-methylbutyrate administration increased plasma concentrations of proline,glutamate, leucine, isoleucine, valine, alanine, aspartate, phenylalanine and cysteic acid (p < 0.05). These results indicate that long-term administration of HMB improves vBMD, and geometrical and mechanical properties of skeletal system in turkeys, and that these effects are associated with improved plasma amino acid concentrations.

Chronic supplementation of beta-hydroxy-beta methylbutyrate (HMβ) increases the activity of the GH/IGF-I axis and induces hyperinsulinemia in rats

OBJECTIVE

Beta-hydroxy-beta-methylbutyrate (HMβ) is a metabolite of leucine widely used for improving sports performance. Although HMβ is recognized to promote anabolic or anti-catabolic effects on protein metabolism, the impact of its long-term use on skeletal muscle and/or genes that control the skeletal protein balance is not fully known. This study aimed to investigate whether chronic HMβ treatment affects the activity of GH/IGF-I axis and skeletal muscle IGF-I and myostatin mRNA expression.

DESIGN

Rats were treated with HMβ (320mg/kg BW) or vehicle, by gavage, for 4 weeks, and killed by decapitation. Blood was collected for evaluation of serum insulin, glucose and IGF-I concentrations. Samples of pituitary, liver, extensor digitorum longus (EDL) and soleus muscles were collected for total RNA or protein extraction to evaluate the expression of pituitary growth hormone (GH) gene (mRNA and protein), hepatic insulin-like growth factor I (IGF-I) mRNA, skeletal muscle IGF-I and myostatin mRNA by Northern blotting/real time-PCR, or Western blotting.

RESULTS

Chronic HMβ treatment increased the content of pituitary GH mRNA and GH, hepatic IGF-I mRNA and serum IGF-I concentration. No changes were detected on skeletal muscle IGF-I and myostatin mRNA expression. However, the HMβ-treated rats although normoglycemic, exhibited hyperinsulinemia.

CONCLUSIONS

The data presented herein extend the body of evidence on the potential role of HMβ-treatment in stimulating GH/IGF-I axis activity. In spite of this effect, HMβ supplementation also induces an apparent insulin resistance state which might limit the beneficial aspects of the former results, at least in rats under normal nutritional status and health conditions.

β-Hydroxy-β-methylbutyrate (HMβ) supplementation stimulates skeletal muscle hypertrophy in rats via the mTOR pathway

β-Hydroxy-β-methylbutyrate (HMβ) supplementation is used to treat cancer, sepsis and exercise-induced muscle damage. However, its effects on animal and human health and the consequences of this treatment in other tissues (e.g., fat and liver) have not been examined. The purpose of this study was to evaluate the effects of HMβ supplementation on skeletal muscle hypertrophy and the expression of proteins involved in insulin signalling. Rats were treated with HMβ (320 mg/kg body weight) or saline for one month. The skeletal muscle hypertrophy and insulin signalling were evaluated by western blotting, and hormonal concentrations were evaluated using ELISAs. HMβ supplementation induced muscle hypertrophy in the extensor digitorum longus (EDL) and soleus muscles and increased serum insulin levels, the expression of the mammalian target of rapamycin (mTOR) and phosphorylation of p70S6K in the EDL muscle. Expression of the insulin receptor was increased only in liver. Thus, our results suggest that HMβ supplementation can be used to increase muscle mass without adverse health effects.

Free acid gel form of β-hydroxy-β-methylbutyrate (HMB) improves HMB clearance from plasma in human subjects compared with the calcium HMB salt

The leucine metabolite, β-hydroxy-β-methylbutyrate (HMB), is a nutritional supplement that increases lean muscle and strength with exercise and in disease states. HMB is presently available as the Ca salt (CaHMB). The present study was designed to examine whether HMB in free acid gel form will improve HMB availability to tissues. Two studies were conducted and in each study four males and four females were given three treatments in a randomised, cross-over design. Treatments were CaHMB (gelatin capsule, 1 g), equivalent HMB free acid gel swallowed (FASW) and free acid gel held sublingual for 15 s then swallowed (FASL). Plasma HMB was measured for 3 h following treatment in study 1 and 24 h with urine collection in study 2. In both the studies, the times to peak plasma HMB were 128 (sem 11), 38 (sem 4) and 38 (sem 1) min (P < 0·0001) for CaHMB, FASW and FASL, respectively. The peak concentrations were 131 (sem 6), 249 (sem 14) and 239 (sem 14) μmol/l (P < 0·0001) for CaHMB, FASW and FASL, respectively. The areas under the curve were almost double for FASW and FASL (P < 0·0001). Daily urinary HMB excretion was not significantly increased resulting in more HMB retained (P < 0·003) with FASW and FASL. Half-lives were 3·17 (sem 0·22), 2·50 (sem 0·13) and 2·51 (sem 0·14) h for CaHMB, FASW and FASL, respectively (P < 0·004). Free acid gel resulted in quicker and greater plasma concentrations (+185 %) and improved clearance (+25 %) of HMB from plasma. In conclusion, HMB free acid gel could improve HMB availability and efficacy to tissues in health and disease.

Influence of in ovo injection of disaccharides, glutamine and β-hydroxy-β-methylbutyrate on the development of small intestine in duck embryos and neonates

1. The objective of the present study was to examine the effect of in ovo injection of disaccharides (DS), disaccharides and glutamine (DS + Gln) or disaccharides and β-hydroxy-β-methylbutyrate (DS + HMB) at d 23 of incubation on the development of the small intestine. 2. In DS + Gln-injected ducks, the greatest relative small intestine mass and muscularis layer thickness among 4 treatments was observed from d 25 of incubation to 7 d of age. 3. Jejunal sucrase activity in DS-injected ducks was significantly greater than in controls at hatch and on d 7. 4. In DS + HMB-treated ducks, a tendency toward slightly higher jejunal DNA concentration was observed throughout the experiment. 5. Greater body weight was found in DS + Gln and DS + HMB treated ducks in the first two weeks. However, there was no significant difference in the market weight (35 d) of ducks among the 4 treatments. 6. The results of present study suggest that administering disaccharides and Gln, or disaccharides and HMB, to the duck embryos exerted a beneficial effect on the early development of small intestine and on growth performance.

Exercise-induced muscle damage is not attenuated by beta-hydroxy-beta-methylbutyrate and alpha-ketoisocaproic acid supplementation

The purpose of this study was to examine the effects of combined oral beta-hydroxy-beta-methylbutyrate (HMB) and alpha-ketoisocaproic acid (KIC) supplementation on indices of exercise-induced muscle damage (EIMD) after an acute bout of eccentric-biased exercise. Fourteen male subjects were allocated to 2 groups: a placebo group (3 g.d corn flour, N = 7) or an HMB + KIC group (3 g.d HMB and 0.3 g.d KIC, N = 7). Supplementation commenced 11 days before a 40-minute bout of downhill running and continued for 3 days post-exercise. Delayed-onset muscle soreness, mid-thigh girth, knee extensor range of motion, serum creatine kinase (CK) activity, and isometric and concentric torque were assessed pre-exercise and at 24, 48, and 72 hours post-exercise. Delayed-onset muscle soreness, CK activity, and isometric and concentric torque all changed over the 72-hour period (p < 0.05); however, HMB + KIC had no significant effect on any of the indices of muscle damage. Although 14 days HMB and KIC supplementation did not attenuate indices of EIMD after an acute bout of unaccustomed eccentric-biased exercise, there was a trend for a more rapid rate of recovery in isometric and isokinetic muscle function. beta-hydroxy-beta-methylbutyrate and KIC may therefore provide limited benefit in the recovery of muscle function after EIMD in untrained subjects or after unaccustomed exercise.

Effects of beta-hydroxy-beta-methylbutyrate supplementation during resistance training on strength, body composition, and muscle damage in trained and untrained young men: a meta-analysis

Beta-hydroxy-beta-methylbutyrate (HMB) is a popular supplement in the resistance training community, with its use supported by claims of increased strength, muscle growth, and improved recovery; however, research outcomes are variable. Therefore, we meta-analyzed the effectiveness of HMB on strength, body composition, and muscle damage. Nine qualifying studies yielded 14 comparisons subcategorized by training experience (trained, untrained) to provide 12-13 estimates of strength (upper body, lower body, overall average), 13 estimates of fat and fat-free mass, and 7 estimates of the muscle-damage marker creatine kinase. The meta-analysis comprised 394 subjects (age 23 +/- 2 years, mean +/- between-study SD) with 5 +/- 2 weeks' intervention and 5 +/- 6 h.wk of training. The estimates were analyzed using a meta-analytic mixed model with study sample size as the weighting factor that included the main-effect covariates to control for between-study differences in HMB dose, intervention duration, training load, and dietary cointervention. To interpret magnitudes, meta-analyzed effects were standardized using the composite baseline between-subject SD and were qualified using modified Cohen effect size thresholds. There were small benefits to lower-body (mean +/- 90% confidence limit: 9.9% +/- 5.9%) and average strength (6.6 +/- 5.7%), but only negligible gains for upper-body strength (2.1 +/- 5.5%) were observed in untrained lifters. In trained lifters, all strength outcomes were trivial. Combined (all studies), the overall average strength increase was trivial (3.7 +/- 2.4%), although uncertainty allows for a small benefit. Effects on fat and fat-free mass were trivial, and results regarding creatine kinase were unclear. Supplementation with HMB during resistance training incurs small but clear overall and leg strength gains in previously untrained men, but effects in trained lifters are trivial. The HMB effect on body composition is inconsequential. An explanation for strength gains in previously untrained lifters requires further research.

Animal models of maple syrup urine disease

Maple syrup urine disease (MSUD) is an inherited aminoacidopathy resulting from dysfunction of the branched-chain keto acid dehydrogenase (BCKDH) complex. This disease is currently treated primarily by dietary restriction of branched-chain amino acids (BCAAs). However, dietary compliance is often challenging. Conversely, liver transplantation significantly improves outcomes, but donor organs are scarce and there are high costs and potential risks associated with this invasive procedure. Therefore, improved treatment options for MSUD are needed. Development of novel treatments could be facilitated by animal models that accurately mimic the human disease. Animal models provide a useful system in which to explore disease mechanisms and new preclinical therapies. Here we review MSUD and currently available animal models and their corresponding relevance to the human disorder. Using animal models to gain a more complete understanding of the pathophysiology behind the human disease may lead to new or improved therapies to treat or potentially cure the disorder.

The prevention and treatment of exercise-induced muscle damage

Exercise-induced muscle damage (EIMD) can be caused by novel or unaccustomed exercise and results in a temporary decrease in muscle force production, a rise in passive tension, increased muscle soreness and swelling, and an increase in intramuscular proteins in blood. Consequently, EIMD can have a profound effect on the ability to perform subsequent bouts of exercise and therefore adhere to an exercise training programme. A variety of interventions have been used prophylactically and/or therapeutically in an attempt to reduce the negative effects associated with EIMD. This article focuses on some of the most commonly used strategies, including nutritional and pharmacological strategies, electrical and manual therapies and exercise. Long-term supplementation with antioxidants or beta-hydroxy-beta-methylbutyrate appears to provide a prophylactic effect in reducing EIMD, as does the ingestion of protein before and following exercise. Although the administration of high-dose NSAIDs may reduce EIMD and muscle soreness, it also attenuates the adaptive processes and should therefore not be prescribed for long-term treatment of EIMD. Whilst there is some evidence that stretching and massage may reduce muscle soreness, there is little evidence indicating any performance benefits. Electrical therapies and cryotherapy offer limited effect in the treatment of EIMD; however, inconsistencies in the dose and frequency of these and other interventions may account for the lack of consensus regarding their efficacy. Both as a cause and a consequence of this, there are very few evidence-based guidelines for the application of many of these interventions. Conversely, there is unequivocal evidence that prior bouts of eccentric exercise provide a protective effect against subsequent bouts of potentially damaging exercise. Further research is warranted to elucidate the most appropriate dose and frequency of interventions to attenuate EIMD and if these interventions attenuate the adaptation process. This will both clarify the efficacy of such strategies and provide guidelines for evidence-based practice.

3-Hydroxy-3-methylbutyrate administration diminishes fundectomy-induced osteopenia of the lumbar spine in pigs

OBJECTIVE

The aim of the study was to test the hypothesis that oral administration with 3-hydroxy-3-methylbutyrate (HMB) positively influences bone metabolism and diminishes fundectomy-induced osteopenia of the axial skeleton in pigs. The pig model was chosen because of its recognized physiologic and anatomic similarities of the gastrointestinal tract and skeletal system to those of humans.

METHODS

Eighteen male pigs were divided into three weight-matched groups at 40 d of life. Animals from the first and second groups were subjected to experimental fundectomy and the third group was sham operated. Starting the day after the fundectomy, the first and second groups received placebo and HMB, respectively. Animals were sacrificed at the age of 8 mo to obtain L(5) and L(6) vertebrae for analysis. The effects of HMB administration on plasma amino acids concentrations, bone mineral density, morphology, and mechanical properties of the lumbar vertebrae were determined.

RESULTS

The HMB treatment increased the weight of the vertebrae, bone mineral density, bone mineral content, total bone volume, trabecular bone mineral density, mean volumetric bone mineral density, calcium hydroxyapatite density in the trabecular and cortical bones, and plasma amino acid concentrations in the fundectomized pigs (P < 0.05). Mechanical strength of the spine, expressed by the values of ultimate force, Young's modulus, ultimate stress, stiffness, and work to the ultimate force point was increased in HMB-treated pigs (P < 0.05).

CONCLUSION

HMB administration to fundectomized pigs improved plasma amino acids concentrations and diminished development of fundectomy-induced osteopenia of the axial skeleton.

Atualizações sobre beta-hidroxi-beta-metilbutirato: suplementação e efeitos sobre o catabolismo de proteínas

O beta-hidroxi-beta-metilbutirato, metabólito do aminoácido leucina, vem sendo utilizado como suplemento alimentar, em situações específicas, com o intuito de aumentar ou manter a massa isenta de gordura. Os relatos dos efeitos do beta-hidroxi-beta-metilbutirato em estudos recentes fizeram crescer as expectativas sobre sua utilização em casos patológicos. Também foram demonstrados melhores resultados, quando da sua ingestão, no treinamento de força em indivíduos iniciantes e em idosos. Em humanos o beta-hidroxi-beta-metilbutirato tem sido usado como agente anti-catabólico, e em modelos animais foi demonstrado ser eficaz em inibir a atividade de vias proteolíticas em células musculares de indivíduos caquéticos in vitro e in vivo. Os mecanismos participantes desses processos envolvem: a inibição da atividade do sistema ubiquitina proteossoma ATP-dependente, a inibição de vias de sinalização com participação da proteína quinase C-alfa e a diminuição da concentração citoplasmática do fator nuclear - kappa B livre, eventos relacionados ao decréscimo da proteólise em células musculares.

Effects of beta-hydroxy-beta-methylbutyrate (HMB) on exercise performance and body composition across varying levels of age, sex, and training experience: A review

The leucine metabolite beta-hydroxy-beta-methylbutyrate (HMB) has been extensively used as an ergogenic aid; particularly among bodybuilders and strength/power athletes, who use it to promote exercise performance and skeletal muscle hypertrophy. While numerous studies have supported the efficacy of HMB in exercise and clinical conditions, there have been a number of conflicting results. Therefore, the first purpose of this paper will be to provide an in depth and objective analysis of HMB research. Special care is taken to present critical details of each study in an attempt to both examine the effectiveness of HMB as well as explain possible reasons for conflicting results seen in the literature. Within this analysis, moderator variables such as age, training experience, various states of muscle catabolism, and optimal dosages of HMB are discussed. The validity of dependent measurements, clustering of data, and a conflict of interest bias will also be analyzed. A second purpose of this paper is to provide a comprehensive discussion on possible mechanisms, which HMB may operate through. Currently, the most readily discussed mechanism has been attributed to HMB as a precursor to the rate limiting enzyme to cholesterol synthesis HMG-coenzyme A reductase. However, an increase in research has been directed towards possible proteolytic pathways HMB may operate through. Evidence from cachectic cancer studies suggests that HMB may inhibit the ubiquitin-proteasome proteolytic pathway responsible for the specific degradation of intracellular proteins. HMB may also directly stimulate protein synthesis, through an mTOR dependent mechanism. Finally, special care has been taken to provide future research implications.

Amino acids and immune function

A deficiency of dietary protein or amino acids has long been known to impair immune function and increase the susceptibility of animals and humans to infectious disease. However, only in the past 15 years have the underlying cellular and molecular mechanisms begun to unfold. Protein malnutrition reduces concentrations of most amino acids in plasma. Findings from recent studies indicate an important role for amino acids in immune responses by regulating: (1) the activation of T lymphocytes, B lymphocytes, natural killer cells and macrophages; (2) cellular redox state, gene expression and lymphocyte proliferation; and (3) the production of antibodies, cytokines and other cytotoxic substances. Increasing evidence shows that dietary supplementation of specific amino acids to animals and humans with malnutrition and infectious disease enhances the immune status, thereby reducing morbidity and mortality. Arginine, glutamine and cysteine precursors are the best prototypes. Because of a negative impact of imbalance and antagonism among amino acids on nutrient intake and utilisation, care should be exercised in developing effective strategies of enteral or parenteral provision for maximum health benefits. Such measures should be based on knowledge about the biochemistry and physiology of amino acids, their roles in immune responses, nutritional and pathological states of individuals and expected treatment outcomes. New knowledge about the metabolism of amino acids in leucocytes is critical for the development of effective means to prevent and treat immunodeficient diseases. These nutrients hold great promise in improving health and preventing infectious diseases in animals and humans.

Prenatal programming of skeletal development in the offspring: effects of maternal treatment with beta-hydroxy-beta-methylbutyrate (HMB) on femur properties in pigs at slaughter age

Alteration in fetal growth and development in response to prenatal environmental conditions such as nutrition has long-term or permanent effects during postnatal life. The aim of this study was to investigate effects of beta-hydroxy-beta-methylbutyrate (HMB) treatment of sows during the last 2 weeks of pregnancy on programming of skeletal development in the offspring. The study was performed on 141 pigs born by 12 sows of Polish Landrace breed. Two weeks before delivery, pregnant sows were divided into two groups. The first group consisted of control sows (N=6) that were treated with placebo. Sows that were orally treated with beta-hydroxy-beta-methylbutyrate (N=6) at the dosage of 0.05 g/kg of body weight per day belonged to the second group. Newborn piglets were weighed and subjected to blood collection for determination of serum levels of growth hormone (GH), insulin-like growth factor-1 (IGF-1), insulin, leptin, glucose and bone alkaline phosphatase (BAP) activity and lipid profile. At the age of 6 months, the piglets were slaughtered, their femur was isolated for analysis and assessment of lean meat content of carcasses was performed. The effects of maternal administration with HMB on skeletal properties in the offspring were evaluated in relation to bone mineral density and geometrical and mechanical properties. Maternal treatment with HMB increased serum levels of GH, IGF-1 and BAP activity in the newborns by 38.0%, 20.0% and 26.0%, respectively (P<0.01). HMB administration significantly increased volumetric bone mineral density of the trabecular and cortical bone of femur in the offspring at the age of 6 months (P<0.001). The weight of femur and geometrical parameters such as cross-sectional area, second moment of inertia, mean relative wall thickness and cortical index were significantly increased after HMB treatment (P<0.05). HMB induced higher values of maximum elastic strength and ultimate strength of femur (P<0.01). Furthermore, lean meat content of carcass was significantly increased in the females born by HMB-treated sows (P<0.05). The obtained results showed that maternal administration with HMB has positive long-term effects on bone tissue and improves volumetric bone mineral density, geometrical and mechanical properties of femur in the offspring. These effects were connected with increased level of GH and IGF-1 in the newborns indicating involvement of improved somatotrophic axis function in prenatal programming of skeletal development in pigs.

β-Hydoxy-β-methylbutyrate supplementation affects Walker 256 tumor-bearing rats in a time-dependent manner

BACKGROUND & AIMS

Cancer cachexia affects intermediary metabolism with intense and general catabolism. Walker 256 tumor is a model injected either subcutaneously (Sc) or intraperitoneally (Ip), with different metabolic features. Beta-hydroxy beta-methylbutyrate (HMbeta) is a leucine metabolite with anti-catabolic properties, the aim of this study being to investigate its effects on metabolic parameters in both tumor models.

METHODS

Controls (subcutaneous control group (ScC) and intraperitoneal control group (IpC)) and supplemented animals (subcutaneous supplemented group (ScS) and intraperitoneal supplemented group (IpS)) showed these results.

RESULTS

Protein Sc values were (47.8%) lower than Ip groups. Sc group fat content was (65.16%) higher than Ip groups. Liver glycogen value for Sc groups was (38.4%) higher than Ip groups. Muscle glycogen value for Sc groups were (2.75 times) higher than Ip groups. Corticosterone and insulin values were lower (44.53%) and higher (45.94%), respectively, in Sc when compared with Ip groups. Glucose and lactate values for ScS were the lowest (61.7% and 41.53%) compared to other groups. ScC glutamine value was the highest (40.8%) of all groups. Glutamate Sc values were (42.65%) lower than Ip groups. Sc groups showed greater survival time compared with Ip groups. ScS group showed 100% increase in survival time when compared with ScC.

CONCLUSIONS

HMbeta supplementation can increase survival time and promotes metabolic changes in cancer-bearing animals, but it seems to work in a time-dependent manner.

??-Hydroxy-??-Methylbutyrate Supplementation in Critically Ill Trauma Patients

BACKGROUND

Negative nitrogen balance and skeletal muscle loss are common in critically injured patients and may contribute to morbidity, mortality and resource utilization. Juven, an enteral supplement which is a combination of beta-hydroxy-beta-methylbutyrate (HMB), arginine (ARG), and glutamine (GLN) has been shown to restore muscle in cachetic acquired immunodeficiency syndrome (AIDS) and cancer patients. More recently HMB has been shown to attenuate cancer-induced muscle loss by decreasing muscle proteolysis. The purpose of this study was to analyze whether HMB alone or in combination with ARG and GLN would have a similar effect on critically injured trauma patients. We hypothesized that nitrogen balance would be improved and muscle proteolysis decreased with HMB and HMB/ARG/GLN supplementation.

METHODS

There were 100 adult trauma patients with Injury Severity Score (ISS) >18 were enrolled in this prospective, randomized, blinded study. All patients received standard tube feeds and one of three iso-nitrogenous supplements; HMB, HMB/ARG/ GLN, or placebo (PLAC) for 28 days. Urine, serum, and clinical data were collected for 72 patients receiving at least 7 days of supplementation during the first 14 days of treatment. Urinary 3-methylhistidine (3-MH) was used as a proxy for muscle proteolysis.

RESULTS

The three groups were similar in age, gender, mechanism, and severity of injury, with the average ISS being 31.9. Utilizing covariant (ISS) repeated measure (days 1-14) mixed model (SAS) analysis, there was a significant treatment effect (p = 0.05) on nitrogen balance (g/d). Change in nitrogen balance from the first 7 days to the last 7 days was -4.3 for the HMB and -5.6 g/d HMB/ARG/GLN groups compared with -8.9 g/d for the PLAC group. 3-MH to creatinine ratios were not different in the PLAC group as compared with the HMB/ARG/GLN and HMB groups (Treatment Effect, p = 0.80).

CONCLUSIONS

These data suggest that supplementation with HMB alone may improve nitrogen balance in critically injured adult patients and that this effect is not a result of lowered muscle protein turnover as originally hypothesized.

Dietary toxicity of calcium β-hydroxy-β-methyl butyrate (CaHMB)

HMB, 3-hydroxy-3-methyl butyrate, is of interest as a dietary supplement and a possible component of functional and medical foods. The purpose of this study was to evaluate the toxicity of the calcium salt of HMB, calcium 3-hydroxy-3-methyl butyrate (CaHMB, monohydrate, food grade), when administered daily in the diet of rats for at least 90 days. Male and female Crl:CD (SD)IGS BR animals were assigned to four groups. Each group received diets containing the carrier or 1%, 2%, or 5% of CaHMB mixed with diet. Assessment of toxicity was based on mortality, clinical observations, body weights, food consumption, and clinical and anatomic pathology evaluations. Administration of CaHMB in basal diet for 91 days was tolerated well. There were no unscheduled sacrifices or deaths. There were no CaHMB-related adverse effects on clinical observations, body weights, food consumption, clinical chemistry, hematology, absolute or relative organ weights, or macroscopic or microscopic observations. A statistically significant increase in inorganic phosphorous was observed in male animals in the 5% feeding group; however, this effect was not considered adverse. Based on the results of this study, the no-observed-adverse-effect level (NOAEL) was considered to be 5% of CaHMB mixed with diet (3.49 g/kg BW for males and 4.16 g/kg BW for females).

The effect of early nutrition on satellite cell dynamics in the young turkey

Early posthatch satellite cell mitotic activity is an important aspect of muscle development. An understanding of the interplay between nutrition and satellite cell mitotic activity will lead to more efficient meat production. The objective of this study was to test the influence of the leucine metabolite, beta-hydroxy beta-methylbutyrate (HMB), and feed deprivation on muscle development in the early posthatch poult. Male Nicholas poults were placed on 1 of 4 treatments: immediately fed a starter diet with 0.1% HMB (IF-HMB), immediately fed a starter diet containing 0.1% Solka-Floc for a control (IF-No HMB), feed and water withheld for 48 h immediately posthatch and then fed the HMB diet (WF-HMB), and feed and water withheld for 48 h immediately posthatch and then fed the control starter diet (WF-No HMB). 5-bromo-2'-deoxyuridine (BrdU) was injected intra-abdominally into all poults to label mitotically active satellite cells. The pectoralis thoracicus was harvested 2 h after the BrdU injection. Immunohistochemistry for BrdU, Pax7, and laminin along with computer-based image analysis was used to study muscle development. IF-HMB poults had higher body weights (P < 0.01) at 48 h and 1 wk of age and had higher satellite cell mitotic activity at 48 h of age (P < 0.01) compared with the IF-No HMB and WF poults. Therefore, dietary supplementation of HMB may have an anabolic effect on early posthatch muscle.

In ovo feeding improves energy status of late-term chicken embryos

Maintenance of glucose homeostasis during late-term embryonic development is dependent upon the amount of glucose held in reserve primarily in the form of glycogen in the liver and upon the degree of glucose generated by gluconeogenesis from protein first mobilized from amnion albumen and then from muscle. Insufficient glycogen and albumen will force the embryo to mobilize more muscle protein toward gluconeogenesis, thus restricting growth of the late-term embryo and hatchling. We hypothesize that administration of available carbohydrates to the amnion will improve glycogen reserves and spare muscle protein mobilization for gluconeogenesis during late-term embryonic and posthatch neonatal development. Our hypothesis was tested by comparing BW gain, liver glycogen reserves, and muscle weight of in ovo fed and control embryos during last days of embryonic incubation until 25 d after hatching. We examined, using 600 birds from 2 different strains of commercial boilers, body and muscle weights and glycogen reserves following feeding embryos at d 17.5 of incubation with a solution containing maltose, sucrose, dextrin, and beta-hydroxy-beta-methylbutyrate (HMB). Providing carbohydrates and HMB to late-term embryos increased hatching weights by 5 to 6% over controls, improved liver glycogen by 2- to 5-fold, and elevated relative breast muscle size by 6 to 8%. These weight advantages were sustained through the end of the experiments at 25 d of age. It is reasonable to assume that the elevated glycogen levels in the in ovo treatment reduce the need to produce glucose via gluconeogenesis and, therefore, contribute to less use of muscle protein and hence a greater percentage of pectoral muscle weight in the in ovo birds.

Nutritional therapy improves function and complements corticosteroid intervention inmdx mice

Corticosteroid therapy for Duchenne muscular dystrophy is effective but associated with long-term side effects. To determine the potential therapeutic benefit from four nutritional compounds (creatine monohydrate, conjugated linoleic acid, alpha-lipoic acid, and beta-hydroxy-beta-methylbutyrate) alone, in combination, and with corticosteroids (prednisolone), we evaluated the effects on several variables in exercising mdx mice. Outcome measures included grip strength, rotarod performance, serum creatine kinase levels, muscle metabolites, internalized myonuclei, and retroperitoneal fat pad weight. In isolation, each nutritional treatment showed some benefit, with the combination therapy showing the most consistent benefits. Prednisolone and the combination therapy together provided the most consistent evidence of efficacy; increased peak grip strength (P < 0.05), decreased grip strength fatigue (P < 0.05), decreased number of internalized myonuclei (P < 0.01), and smaller retroperitoneal fat pad stores (P < 0.001). This study provided evidence for therapeutic benefit from a four-compound combination therapy alone, and in conjunction with corticosteroids in the mdx model of DMD.

Attenuation of Proteasome-Induced Proteolysis in Skeletal Muscle by β-Hydroxy-β-Methylbutyrate in Cancer-Induced Muscle Loss

Loss of skeletal muscle is an important determinant of survival in patients with cancer-induced weight loss. The effect of the leucine metabolite β-hydroxy-β-methylbutyrate (HMB) on the reduction of body weight loss and protein degradation in the MAC16 model of cancer-induced weight loss has been compared with that of eicosapentaenoic acid (EPA), a recognized inhibitor of protein degradation. HMB was found to attenuate the development of weight loss at a dose greater than 0.125 g/kg accompanied by a small reduction in tumor growth rate. When EPA was used at a suboptimal dose level (0.6 g/kg) the combination with HMB seemed to enhance the anticachectic effect. Both treatments caused an increase in the wet weight of soleus muscle and a reduction in protein degradation, although there did not seem to be a synergistic effect of the combination. Proteasome activity, determined by the “chymotrypsin-like” enzyme activity, was attenuated by both HMB and EPA. Protein expression of the 20S α or β subunits was reduced by at least 50%, as were the ATPase subunits MSS1 and p42 of the 19S proteasome regulatory subunit. This was accompanied by a reduction in the expression of E214k ubiquitin-conjugating enzyme. The combination of EPA and HMB was at least as effective or more effective than either treatment alone. Attenuation of proteasome expression was reflected as a reduction in protein degradation in gastrocnemius muscle of cachectic mice treated with HMB. In addition, HMB produced a significant stimulation of protein synthesis in skeletal muscle. These results suggest that HMB preserves lean body mass and attenuates protein degradation through down-regulation of the increased expression of key regulatory components of the ubiquitin-proteasome proteolytic pathway, together with stimulation of protein synthesis.

Effects of in ovo feeding of carbohydrates and beta-hydroxy-beta-methylbutyrate on the development of chicken intestine

Early development of the digestive tract is crucial for achieving maximal growth and development of chickens. Because the late-term embryo naturally consumes the amniotic fluids, insertion of a nutrient solution into the embryonic amniotic fluid [in ovo (IO) feeding] may enhance development. This study examined the effect of IO feeding on d 17.5 of incubation of carbohydrates (CHO) and beta-hydroxy-beta-methylbutyrate (HMB) on small intestinal development of chickens during the pre and posthatch periods. Results shows that 48 h post-IO feeding procedure all IO feeding treatments exhibited increased villus width and surface area compared with the control group. At d 3 posthatch the surface area of an average villi was increased by 45% for the HMB IO group and by 33% for the CHO and CHO+HMB IO groups compared with controls (noninjected fertile eggs). The activity of jejunal sucrase-isomaltase (SI) was higher (P < 0.05) 48 h after IO feeding in all the IO fed embryos, whereas at day of hatch and at d 3 the CHO+HMB IO group had the highest maltase activity (P < 0.05), which was approximately 50% greater than control embryos. These observations indicated that small intestines of IO fed hatchlings were functionally at a similar stage of development as a conventionally fed 2-d-old chick. Body weight of all IO fed hatchlings was greater than controls, and these differences (P < 0.05) were sustained until the end of the experiment (10 d). At d 10 chicks that were IO fed with CHO had BW that were 2.2% higher, whereas HMB and CHO+HMB IO fed chicks showed 5 to 6.2% BW increase, respectively, compared with controls. The current study shows that the administration of exogenous nutrients into the amnion enhanced intestinal development by increasing the size of the villi and by increasing the intestinal capacity to digest disaccharides. This advantage probably leads to higher BW in IO fed chicks.

Mechanism of the Attenuation of Proteolysis-Inducing Factor Stimulated Protein Degradation in Muscle by β-Hydroxy-β-Methylbutyrate

The leucine metabolite beta-hydroxy-beta-methylbutyrate (HMB) prevents muscle protein degradation in cancer-induced weight loss through attenuation of the ubiquitin-proteasome proteolytic pathway. To investigate the mechanism of this effect, the action of HMB on protein breakdown and intracellular signaling leading to increased proteasome expression by the tumor factor proteolysis-inducing factor (PIF) has been studied in vitro using murine myotubes as a surrogate model of skeletal muscle. A comparison has been made of the effects of HMB and those of eicosapentaenoic acid (EPA), a known inhibitor of PIF signaling. At a concentration of 50 mumol/L, EPA and HMB completely attenuated PIF-induced protein degradation and induction of the ubiquitin-proteasome proteolytic pathway, as determined by the "chymotrypsin-like" enzyme activity, as well as protein expression of 20S proteasome alpha- and beta-subunits and subunit p42 of the 19S regulator. The primary event in PIF-induced protein degradation is thought to be release of arachidonic acid from membrane phospholipids, and this process was attenuated by EPA, but not HMB, suggesting that HMB might act at another step in the PIF signaling pathway. EPA and HMB at a concentration of 50 mumol/L attenuated PIF-induced activation of protein kinase C and the subsequent degradation of inhibitor kappaBalpha and nuclear accumulation of nuclear factor kappaB. EPA and HMB also attenuated phosphorylation of p42/44 mitogen-activated protein kinase by PIF, thought to be important in PIF-induced proteasome expression. These results suggest that HMB attenuates PIF-induced activation and increased gene expression of the ubiquitin-proteasome proteolytic pathway, reducing protein degradation.

Effect of β-hydroxy-β-methylbutyrate, arginine, and lysine supplementation on strength, functionality, body composition, and protein metabolism in elderly women

OBJECTIVE

With advancing age, there is a gradual loss of muscle mass, strength, and functionality. The current studies were conducted to determine whether a mixture of specific nutrients, arginine and lysine, which support protein synthesis, and beta-hydroxy-beta-methylbutyrate (HMB), which can slow protein breakdown, could blunt the gradual loss of muscle that occurs in the elderly, thus improving strength and functionality.

METHODS

In double-blind studies conducted at two separate sites, women (mean 76.7 y) were randomized to a placebo group (n = 23) or an experimental treatment group (2 g beta-hydroxy-beta-methylbutyrate, 5 g arginine, and 1.5 g lysine daily; n = 27).

RESULTS

After 12 wk, there was a 17% improvement in the "get-up-and-go" functionality test in the experimental group (-2.3 +/- 0.5 s) but no change in the placebo group (0.0 +/- 0.5 s; P = 0.002). The improvement in functionality also was reflected by increased limb circumference, leg strength, and handgrip strength (all P < 0.05) and positive trends in fat-free mass (P = 0.08). Whole-body protein synthesis, estimated with the (15)N-glycine tracer technique over a 24-h free-living period, increased approximately 20% in the experimental treatment group as opposed to the placebo group (P = 0.03).

CONCLUSION

These studies indicated that daily supplementation of beta-hydroxy-beta-methylbutyrate, arginine, and lysine for 12 wk positively alters measurements of functionality, strength, fat-free mass, and protein synthesis, suggesting that the strategy of targeted nutrition has the ability to affect muscle health in elderly women.

Popular sports supplements and ergogenic aids

This article reviews the evidence-based ergogenic potential and adverse effects of 14 of the most common products in use by recreational and elite athletes today. Both legal and prohibited products are discussed. This is an aggressively marketed and controversial area of sports medicine worldwide. It is therefore prudent for the clinician to be well versed in the more popular supplements and drugs reputed to be ergogenic in order to distinguish fact from fiction.Antioxidants, proteins and amino acids are essential components of diet, but additional oral supplementation does not increase endurance or strength. Caffeine is ergogenic in certain aerobic activities. Creatine is ergogenic in repetitive anaerobic cycling sprints but not running or swimming. Ephedrine and pseudoephedrine may be ergogenic but have detrimental cardiovascular effects. Erythropoietin is ergogenic but increases the risk of thromboembolic events. beta-Hydroxy-beta-methylbutyrate has ergogenic potential in untrained individuals, but studies are needed on trained individuals. Human growth hormone and insulin growth factor-I decrease body fat and may increase lean muscle mass when given subcutaneously. Pyruvate is not ergogenic. The androgenic precursors androstenedione and dehydroepiandrosterone have not been shown to increase any parameters of strength and have potentially significant adverse effects. Anabolic steroids increase protein synthesis and muscle mass but with many adverse effects, some irreversible. Supplement claims on labels of product content and efficacy can be inaccurate and misleading.

Effects of a leucine-rich diet on body composition during nutritional recovery in rats

OBJECTIVE

Protein malnutrition is characterized by a number of morphologic and physiologic alterations, including intestinal mucosal atrophy and impaired nutrient absorption. Impaired absorption accentuates nutritional deficiency and accelerates body weight loss and changes in body chemistry. Because leucine is a ketogenic and oxidative amino acid and stimulates the protein synthesis, we examined the ability of young rats to recover from protein malnutrition by feeding them a control balanced or a leucine-rich diet for 60 d.

METHODS

At the end of the 60-d period, body, liver, and muscle weights; glucose, methionine, and leucine intestinal absorption; and carcass chemical composition were evaluated.

RESULTS

Body weight gain was higher in the control balanced and leucine-rich groups than in control rats, indicating that adequate refeeding allows body weight to recover in these groups. Methionine and glucose absorptions were impaired in malnourished rats but were restored after nutritional recovery. The leucine-rich diet resulted in an increase in carcass collagen nitrogen but maintained the carcass structural nitrogen.

CONCLUSIONS

These results indicated that leucine supplementation during nutritional recovery from protein malnutrition improves protein carcass restoration. However, the precise mechanism of the leucine effects involved in this response remains to be elucidated.