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PubMed2026

Biological Mechanisms Underlying the Cardiovascular Effects of Branched-Chain Amino Acids: A Proteome-Wide Mendelian Randomization Study.

BACKGROUND: Ischemic heart disease (IHD) is the leading cause of morbidity and mortality. Branched-chain amino acids (BCAAs) are associated with higher IHD risk, but the underlying biological pathways remain unclear. OBJECTIVES: This study aims to explore these pathways using 2-step proteome-wide Mendelian randomization. METHODS: We examined the associations between genetic proxies for BCAAs and 2922 proteins in the United Kingdom Biobank Pharma Proteomics Project, supplemented by a meta-analysis with data from deCODE to identify proteins associated with BCAAs. Next, we tested their effects on IHD risk using Coronary Artery Disease Genome-wide Replication and Meta-analysis plus Coronary Artery Disease Genetics Consortium (122,733 cases and 424,528 controls) and replicated in FinnGen (31,640 cases and 187,152 controls). We conducted sensitivity analyses using genetic instruments from deCODE. Proteins associated with IHD risk and, in a consistent direction, with genetically predicted BCAAs were considered potential mediators. RESULTS: Genetic proxies for BCAAs were associated with 40 proteins. Among these, 6 proteins showed consistent evidence of mediation, including complement C1s subcomponent, coagulation factor II, granulin, proprotein convertase subtilisin/kexin type 9, sex hormone-binding globulin, and V-set and transmembrane domain-containing protein 2-like. These proteins are involved in inflammation, coagulation, lipid metabolism, and cellular stress response. All associations were robust across different analytical methods and replicated in independent datasets. Mediation analysis showed that these proteins accounted for 6.5% to 32.1% of the association between BCAAs and IHD risk. CONCLUSIONS: This study identified 6 proteins that potentially link BCAAs to IHD, implicating pathways related to inflammation, coagulation, lipid metabolism, and cellular stress responses. To our knowledge, these findings provide novel mechanistic insights into the BCAA-IHD relationship and highlight potential protein targets for future prevention and intervention strategies.

Amino Acids, Branched-Chain↗
PubMed1997

Effect of dietary supplementation with branched-chain amino acids on spontaneous motor activity and muscle function in beta,beta'-iminodipropionitrile-treated rats: a model for motorneuropathy.

Beta,beta'-iminodipropionitrile (IDPN)-induced muscle weakness in rats is a model for motorneuropathy diseases. The effects of oral administration of branched-chain amino acids on the progression of muscle weakness and muscle atrophy induced by the administration of IDPN in the drinking water, were investigated in this study. The spontaneous motor activity of the animals, as measured with a running wheel, slowly declined after IDPN administration, reaching a steady and low level at approximately week 15. Progressive muscle weakness and muscle atrophy were observed beginning at approximately 15 weeks after the initiation of administration of IDPN. Administration of branched-chain amino acids (BCAA) as a dietary supplement did not improve the lowered spontaneous motor activity seen in IDPN animals, but it did significantly improve measures of postural weakness and muscle strength [range of F values (2, 24) = 4.1-9.5, p < 0.05]. Plasma creatinine of the IDPN-treated rats was markedly elevated, and BCAA administration also significantly suppressed this elevation [F(2, 24) = 41.2, p < 0.05]. Moreover, although BCAA in plasma were elevated in the rats administered BCAA [range of F values (2, 21) = 25.7-29.7, p < 0.05], skeletal muscle showed no differences (at the p < 0.05 level) in the amounts of BCAA, whether or not BCAA were administered. These data suggest that the BCAA taken up in the skeletal muscle were utilized in the muscle of motorneuropathic rats and improved muscle function, such as energy metabolism, and that the BCAA treatment is one important therapeutic approach for retarding the progression of muscle weakness seen in certain neuromuscular disorders.

Amino Acids, Branched-Chain↗
PubMed1998

The effects of branched chain amino acid infusion on pain perception and plasma concentrations of monoamines.

Infusions of branched chain amino acids (BCAA) have been shown to have several CNS-mediated effects including antinociceptive action. We investigated the effects of BCAA infusion on pain perception, respiratory control, and plasma monoamine concentrations. Six healthy female volunteers were given in a double-blind, random, crossover design an 8-h infusion (1.75 ml/kg/h) of either (a) Ringers lactate, (b) conventional 4% amino acid solution, or (c) 4% BCAA solution with intervals of at least 48 h. Respiratory control was evaluated with continuous capnography. Pain perception was measured using dental dolorimetry for sharp pain, and pain transmitted by afferent C-fibers was evaluated with tourniquet test. Changes in vigilance were measured using critical flicker fusion technique. Evaluations were made for baseline, and after 2.5, 5, and 8 h. Plasma samples were collected at the same time points for amino acid and monoamine analysis. BCAA infusion resulted in significant increases of plasma concentrations of all BCAAs, with a simultaneous decrease in concentrations of aromatic amino acids. Of the measured monoamines and their metabolites dihydroxyphenylacetic acid (DOPAC) decreased, showing significant treatment effect for BCAA. Despite these changes no significant effect of BCAAs on respiratory control, vigilance, or pain perception was observed. In conclusion, despite significant changes in plasma concentrations of both amino acids and DOPAC, BCAA infusion did not show any clinically relevant antinociceptive effect.

3,4-Dihydroxyphenylacetic Acid↗
PubMed1999

Renal clearance of branched-chain L-amino and 2-oxo acids in maple syrup urine disease.

In maple syrup urine disease (MSUD), branched-chain L-amino (BCAA) and 2-oxo acids (BCOA) accumulate in body fluids owing to an inherited deficiency of branched-chain 2-oxo acid dehydrogenase complex activity. In MSUD, little information is available on the significance of urinary disposal of branched-chain compounds. We examined the renal clearance of leucine, valine, isoleucine and alloisoleucine, and their corresponding 2-oxo acids 4-methyl-2-oxopentanoate (KIC), 3-methyl-2-oxobutanoate (KIV), (S)-(S-KMV), and (R)-3-methyl-2-oxopentanoate (R-KMV), using pairs of plasma and urine samples (n = 63) from 10 patients with classical MSUD. The fractional renal excretion of free BCAA was in the normal range (< 0.5%) and independent of the plasma concentrations. The excretion of bound (N-acylated) BCAA was normal and not significantly dependent on the BCAA plasma concentrations. The fractional renal excretion of BCOA was in the order KIC << KIV < R-KMV < or = S-KMV (range (%): KIC 0.1-25; KIV 0.14-21.3; S-KMV 0.26-24.6; R-KMV 0.1-35.9), significantly correlated with the KIC plasma concentrations, and generally higher than that of the related BCAA. The results show that the renal excretion of free BCAA as well as of the acylated derivatives is negligible. The renal excretion of BCOA, however, to some extent counteracts increases in BCAA concentrations and thus contributes to the lowering of total BCAA pools in MSUD.

Adolescent↗
PubMed2006

The case for regulating indispensable amino acid metabolism: the branched-chain alpha-keto acid dehydrogenase kinase-knockout mouse.

BCAAs (branched-chain amino acids) are indispensable (essential) amino acids that are required for body protein synthesis. Indispensable amino acids cannot be synthesized by the body and must be acquired from the diet. The BCAA leucine provides hormone-like signals to tissues such as skeletal muscle, indicating overall nutrient sufficiency. BCAA metabolism provides an important transport system to move nitrogen throughout the body for the synthesis of dispensable (non-essential) amino acids, including the neurotransmitter glutamate in the central nervous system. BCAA metabolism is tightly regulated to maintain levels high enough to support these important functions, but at the same time excesses are prevented via stimulation of irreversible disposal pathways. It is well known from inborn errors of BCAA metabolism that dysregulation of the BCAA catabolic pathways that leads to excess BCAAs and their alpha-keto acid metabolites results in neural dysfunction. In this issue of Biochemical Journal, Joshi and colleagues have disrupted the murine BDK (branched-chain alpha-keto acid dehydrogenase kinase) gene. This enzyme serves as the brake on BCAA catabolism. The impaired growth and neurological abnormalities observed in this animal show conclusively the importance of tight regulation of indispensable amino acid metabolism.

3-Methyl-2-Oxobutanoate Dehydrogenase (Lipoamide)↗
PubMed2000

Effect of hyperinsulinemia on myocardial amino acid uptake in patients with coronary artery disease.

Branched-chain amino acids (BCAAs) are oxidative energy substrates for the heart and may exert anabolic effects on myocardial protein. The factors regulating their myocardial uptake in patients with ischemic heart disease are therefore of interest. To examine whether myocardial BCAA utilization is influenced by the circulating insulin concentration, in 10 patients with chronic ischemic heart disease, we measured transmyocardial amino acid balance during fasting and again during a 90-minute euglycemic insulin infusion (plasma insulin, 218+/-25 microU x mL(-1)) with plasma BCAA concentrations held constant by coinfusion. In the fasting state, the myocardial fractional extraction of leucine (8%), isoleucine (9%), and valine (5%) from arterial plasma was slightly greater than that of glucose (3%), while net myocardial BCAA uptake (leucine, 409+/-207 nmol x min(-1); isoleucine, 220+/-144 nmol x min(-1); valine, 407+/-326 nmol x min(-1); and total BCAA uptake, 1.0+/-0.3 micromol x min(-1)) was about 13% that of glucose (8+/-2 micromol x min(-1)). During euglycemic hyperinsulinemia, myocardial glucose uptake increased 3-fold, but there was no change in the arterial-coronary sinus balance or net myocardial uptake of any BCAA under conditions where their plasma concentrations were held constant. Instead, the myocardial uptake of each BCAA correlated positively with its concentration in arterial plasma. These results demonstrate that in patients with cardiovascular disease, myocardial utilization of BCAAs is insensitive to the circulating insulin level and is regulated instead by their availability in arterial plasma. Hyperinsulinemia reduced the magnitude of both net glutamate uptake and alanine release, suggesting a possible salutary effect on myocardial oxidative efficiency.

Aged↗
PubMed2002

The branched-chain amino acid requirement of parenterally fed neonatal piglets is less than the enteral requirement.

The requirements for branched-chain amino acids (BCAA), isoleucine, leucine and valine, in neonates have not been determined previously. Furthermore, the BCAA are considered to be catabolized primarily in the muscle and their metabolism in the small intestine has received little attention. In this study, the parenteral and enteral BCAA requirements were determined by the indicator amino acid oxidation (IAAO) technique. Male Yorkshire piglets (n = 32) received amino acid-based diets containing adequate nutrients for 5 d. On d 6 and 8, the piglets were randomly assigned to one of the test diets containing a fixed ratio of BCAA (1:1.8:1.2; isoleucine/leucine/valine). Diets were infused continuously via intravenous catheters for parenterally fed piglets or via gastric catheters for enterally fed piglets. Phenylalanine kinetics and oxidation were determined from a 4-h primed, constant infusion of L-[1-(14)C]phenylalanine. Phenylalanine oxidation (% of dose) decreased linearly (P < 0.05) as the BCAA intake increased from 0.2 to 1.53 g/(kg. d) and from 0.2 to 2.64 g/(kg. d) for parenterally and enterally fed piglets, respectively, after which the phenylalanine oxidation was low and the slope was not different from zero. Using breakpoint analysis, the mean total BCAA requirements were determined to be 1.53 and 2.64 g/(kg. d) for parenterally and enterally fed piglets, respectively. Thus, the parenteral requirement for total BCAA is 56% of the enteral requirement, suggesting that 44% of total BCAA is extracted by first-pass splanchnic metabolism.

Amino Acids, Branched-Chain↗
PubMed2003

Valine may be the first limiting branched-chain amino acid in egg protein in men.

Recently, we defined an estimate for total branched-chain amino acids (BCAA) using the indicator amino acid oxidation technique in men fed the three BCAA (leucine, isoleucine and valine) in the proportion present in egg protein. Although egg protein is regarded as a high quality dietary protein source, it is not known whether the proportions of the three BCAA are optimal. Five men with known total BCAA requirements were restudied. Each men was studied with isoleucine, leucine or valine held constant at that individual's requirement level while the intake of the other two BCAA was reduced; one BCAA was held constant and the intake of the other two was reduced by 10 and 20% in random order. The label appearance from the oxidation of L-[13C]-phenylalanine to 13CO2 (F13CO2) in breath was monitored in response to the change in amino acid intake. When either isoleucine or leucine was held constant, and the other two BCAA reduced by 20% (valine and leucine, or valine and isoleucine, respectively) F13CO2 increased (P = 0.007, P = 0.038, respectively). We conclude that valine may be the first limiting BCAA in egg protein.

Adult↗
PubMed2003

The total branched-chain amino acid requirement in young healthy adult men determined by indicator amino acid oxidation by use of L-[1-13C]phenylalanine.

Previous recommendations for branched-chain amino acids (BCAA), based on nitrogen balance studies, were found to be low in a series of stable isotope-labeled amino acid studies. The BCAA requirement was increased in the new dietary reference intake (DRI) report on the basis of a series of stable isotope studies examining the requirement of leucine and valine individually, but not isoleucine. To reduce the possibility of interactions among these amino acids and imbalances in the mixture affecting the estimate of requirements, we decided to determine the requirement for the total BCAA of young healthy adult men, receiving a mixture of BCAA based on the proportion of these amino acids in egg protein, by use of indicator amino acid oxidation. Seven men were assigned to receive nine graded intakes of a BCAA mixture in random order: 34, 50, 66, 80, 100, 120, 140, 160 and 180 mg/(kg. d). The rate of release of (13)CO(2) from the oxidation of L-[1-(13)C]phenylalanine (F (13)CO(2)) was measured and a two-phase linear regression crossover model was applied to determine total BCAA requirement. The mean requirement and population-safe level (upper limit of 95% confidence interval) of the total BCAA were 144 and 210 mg/(kg. d), respectively. Based on the balance of BCAA in egg protein, our estimate for the mean leucine requirement is 55 mg/(kg. d), which is substantially higher than the 34 mg/(kg. d) recommended by the DRI.

Amino Acids, Branched-Chain↗
PubMed2006

Exercise-dependent preference for a mixture of branched-chain amino acids and homeostatic control of brain serotonin in exercising rats.

In this article we discuss studies showing that rats are able to regulate their intake of BCAA depending on the level of exercise, and that they will choose a solution of BCAA over water during times of intense exercise. We found that the voluntary intake of a solution made of BCAA, L-arginine and L-glutamine positively correlated with the timing and volume of exercise during the dark (active) period of the circadian rhythm. In the second behavioral protocol in which rats were fed BCAA fortified diet (2.0%, wt:wt), we observed voluntarily increased volume of physical activity beginning from d 4 of feeding on. In the second, neuro-behavioral, part of the study we measured the brain content of 5-hydroxytryptamine (5-HT) as well as plasma amino acid profiles in well-trained exercising rats to test a hypothesis that BCAA may alleviate central aspects of fatigue. A solution made of BCAA, L-arginine, and L-glutamine applied before running elevated the BCAA/tryptophan plasma ratio at the end of and after running, and decreased 5-HT release in the lateral hypothalamus and amygdala after running, when compared with the controls. The exercise-related shift in the fluid preference toward a BCAA-based solution suggests an ergogenic benefit. The forced-running study shows the lateral hypothalamus and possibly amygdala might be the critical brain regions implied in the central effects of a BCAA-based solution.

Amino Acids, Branched-Chain↗
PubMed1986

Branched chain amino acid uptake and muscle free amino acid concentrations predict postoperative muscle nitrogen balance.

Amino acid solutions rich in branched chain amino acids (BCAA) are commonly utilized both clinically and in experimental protocols in an attempt to reduce skeletal muscle and whole body protein catabolism. To investigate the effectiveness of BCAA infusion, amino acid formulas containing varying concentrations of BCAA were given during operation in this study to three groups of dogs undergoing a standard laparotomy and retroperitoneal dissection. A fourth group was given saline alone. With the use of previously described hindquarter flux techniques, individual and total amino acid nitrogen exchange rates were measured and utilized in estimating skeletal muscle protein catabolism. Intracellular free amino acid concentrations were measured in percutaneous muscle biopsy samples. Although there was no relationship with the rate of BCAA infusion, there was a significant correlation between the rate of BCAA uptake by muscle and diminished total nitrogen release from hindquarter skeletal muscle after operation. There was also a significant relationship between muscle nitrogen balance and the postoperative change in the muscle concentration of either total amino acids or the single amino acid glutamine. When combined in a single equation, BCAA uptake and the change in muscle free amino acid concentration predict skeletal muscle nitrogen release with an r = 0.86. Thus, the rate of BCAA uptake and the free glutamine or total amino acid concentration in muscle appear to be independent predictors of muscle nitrogen balance. The nitrogen-sparing effect of BCAA in skeletal muscle is unrelated to infusion concentration or rate of infusion.

Amino Acids↗
PubMed1988

Inhibition of post-traumatic septic proteolysis and ureagenesis and stimulation of hepatic acute-phase protein production by branched-chain amino acid TPN.

Previous studies have shown that severe sepsis after major trauma results in the reprioritization of release of hepatic acute-phase proteins (APP). They suggest competition for leucine for nutritional utilization may be responsible. To test this hypothesis, a branched-chain enriched (46.6%) amino acid mixture (BCAA) was administered on a prospective randomized basis with standard TPN therapy to 16 septic post-trauma patients. After sepsis was diagnosed, a randomized therapy (control-TPN or BCAA-TPN) was given for 12 days, or until death occurred. Total calories and amino acid nitrogen (N) administered were not different in the two groups (t-test) and q 8 h (347 study periods) amino acid clearances, urinary urea nitrogen excretion, muscle proteolysis from 3-methyl-histidine (3-MH) excretion, and standard indices of sepsis severity and hepatic function were measured, as well as platelets (PLAT), leucocytes (WBC), albumin (ALB), and six acute-phase proteins: C-reactive protein (CRP), alpha-1-antitrypsin (A1TRIP), fibrinogen (FIBRIN), alpha-2-macroglobulin (AMACRO), ceruloplasmin (CERUL), and transferrin (TRANS). Using Scheffé analysis of all contrasts the data showed: BCAA resulted in a fall in 24-hour urea N excretion (24.0 to 20.0 gm/24 hr) and in proteolysis (138 to 126 gm/24 hr) (p less than 0.0001). Prestudy CRP levels were all elevated, but compared to control where APP reprioritization occurred, over the initial 10 days of therapy BCAA patients had a more rapid fall in CRP with a more rapid rise in FIBRIN, TRANS, CERUL, ALBUMIN, AMACRO, and A1TRIP (all p less than 0.0001) relative to CRP. Also, the sepsis-reduced clearances of glutamine and glutamate, alanine, and proline were increased (p less than 0.0001) during BCAA even though urea nitrogen production was reduced (p less than 0.0001). The increase in leucine clearance with BCAA-enriched TPN was positively correlated (r2 = 0.601; p less than 0.0001) with the increase in the sum of all APP and ALB and was also associated with an increase both in FIBRIN and in platelets (p less than 0.0001). The BCAA-related increase in FIBRIN (9.1 to 11.9 mg/ml) occurred at the same time as a fall in prothrombin time (p less than 0.0001). BCAA-enriched TPN reduced proteolysis and amino acid catabolism and appeared to increase the levels of the more rapidly appearing anti-inflammatory and nutritional hepatic APP and formed coagulation elements in post-traumatic sepsis.

Acute-Phase Proteins↗
PubMed1998

Branched-chain amino acids prolong exercise during heat stress in men and women.

To assess the effect of branched-chain amino acids (BCAA) supplementation on endurance performance in the heat, six women and seven men participated in two trials of rest in the heat (Ta = 34.4 +/- 1.8 degrees C; rh = 39 +/- 14%), followed by 40% VO2peak exercise to exhaustion. Subjects ingested 5 mL x kg(-1) of a placebo (PLAC) or BCAA drink every 30 min. Cycle time to exhaustion increased during BCAA (153.1 +/- 13.3 vs 137.0 +/- 12.2 min, P < 0.05) for men and women. Plasma glucose was maintained at baseline values for both drinks; however, women had significantly higher concentrations (5.9 +/- 0.6 vs 4.0 +/- 0.2 mM, P < 0.05). Plasma free fatty acids and ammonia were not influenced by drink or gender but increased over time. BCAA resulted in a significant (P < 0.05) increase in plasma BCAA (1209 +/- 119 vs 496 +/- 44 microM), while F-TRP (9.6 +/- 0.9 vs 12.0 +/- 1.3 microM) and F-TRP:BCAA were decreased (0.009 +/- 0.001 vs 0.024 +/- 0.003 ND) in both men and women. Cardiovascular and thermoregulatory data were similar between treatments for all subjects. Psychological data were not influenced by BCAA. These results indicate BCAA supplementation prolongs moderate exercise performance in the heat.

Adolescent↗
PubMed1990

Respiratory and sleep patterns during nocturnal infusions of branched chain amino acids.

In the awake, normal subject, infusions of branched chain amino acids (BCAA) alter the ventilatory response to CO2. If this effect extends to the sleep state, it could contribute to our understanding of the neurophysiology of the sleep state as well as having clinical utility in ameliorating or preventing apnea syndromes. This study examined the effect of nocturnal BCAA infusion on sleep patterns (as measured by EEG, chest wall motion, Sao2 and end-tidal CO2) in five normal male subjects. Subjects were monitored with a polysomnograph from 21.00 to 7.00. Each subject was studied double-blind in random order on three occasions: a) baseline, no infusion (B); b) control, with normal saline infusion (S); and c) treatment, infusion of BCAA (BCAA). Sleep pattern analysis did not demonstrate any measurable effect of the BCAA infusion. End-tidal CO2 levels during BCAA infusion were lower than during baseline or control nights (mean +/- s.d.; BCAA: 5.8 +/- 0.7 kPa vs. B: 6.9 +/- 0.1 kPa, P less than 0.01 and S: 6.7 +/- 0.4 kPa, P less than 0.05). This study demonstrates that nocturnal BCAA infusions have effects on respiratory control during sleep; further clinical studies are required to determine whether these data have implications for disease states.

Adult↗
PubMedDate not supplied

Influence of glutamine and branched chain amino acids on the jejunal atrophy associated with parenteral nutrition.

Infusions of conventional parenteral nutrients (CPN) are associated with gut atrophy. This may be due to the absence of glutamine in such solutions. Although glutamine is a preferred gut nutrient, it is excluded from CPN because it is unstable at room temperature. This problem may be circumvented either directly by the infusion of fresh solutions of glutamine, or indirectly by the infusion of branched chain amino acids (BCAA). We evaluated the effect of infusing either glutamine, BCAA, or glutamine plus BCAA-enriched CPN on the rat jejunum. Sixty male Wistar rats were randomized to receive 6 days of either conventional parenteral nutrition (CPN), CPN plus 1.5% glutamine (GLN), CPN plus 2% BCAA (BCAA), CPN plus 0.8% BCAA and 1.0% glutamine (GLN/BCAA), or a normal oral diet (Chow). Standardized segments of jejunum were then removed for assessment. Compared with the CPN group, both the GLN/BCAA and the BCAA groups had greater mucosal weights (P less than 0.05) and mucosal protein concentrations (P less than 0.05), the GLN/BCAA group had greater jejunal weights (P less than 0.05), and the GLN group had an increased jejunal weight (P less than 0.05) and a higher crypt cell production rate (P less than 0.05). We conclude that the infusion of glutamine or BCAA-enriched parenteral nutrition improves jejunal morphology compared with conventional parenteral nutrition.

Amino Acids, Branched-Chain↗
PubMed2002

Cloning and inactivation of a branched-chain-amino-acid aminotransferase gene from Staphylococcus carnosus and characterization of the enzyme.

Staphylococcus carnosus and Staphylococcus xylosus are widely used as aroma producers in the manufacture of dried fermented sausages. Catabolism of branched-chain amino acids (BCAAs) by these strains contributes to aroma formation by production of methyl-branched aldehydes and carboxy acids. The first step in the catabolism is most likely a transamination reaction catalyzed by BCAA aminotransferases (IlvE proteins). In this study, we cloned the ilvE gene from S. carnosus by using degenerate oligonucleotides and PCR. We found that the deduced amino acid sequence was 80% identical to that of the corresponding enzyme in Staphylococcus aureus and that the ilvE gene was constitutively expressed as a monocistronic transcript. To study the influence of ilvE on BCAA catabolism, we constructed an ilvE deletion mutant by gene replacement. The IlvE protein from S. carnosus was shown mainly to catalyze the transamination of isoleucine, valine, leucine, and, to some extent, methionine using pyridoxal 5'-phosphate as a coenzyme. The ilvE mutant degraded less than 5% of the BCAAs, while the wild-type strain degraded 75 to 95%. Furthermore, the mutant strain produced approximately 100-fold less of the methyl-branched carboxy acids, 2-methylpropanoic acid, 2-methylbutanoic acid, and 3-methylbutanoic acid, which derived from the BCAA catabolism, clearly emphasizing the role of IlvE in aroma formation. In contrast to previous reports, we found that IlvE was the only enzyme that catalyzed the deamination of BCAAs in S. carnosus. The ilvE mutant strain showed remarkably lower growth rate and biomass yield compared to those of the wild-type strain when grown in rich medium. Normal growth rate and biomass yield were restored by addition of the three BCAA-derived alpha-keto acids, showing that degradation products of BCAAs were essential for optimal cell growth.

Amino Acids, Branched-Chain↗
PubMed2004

Branched-chain amino acids increase p70S6k phosphorylation in human skeletal muscle after resistance exercise.

The aim of the study was to investigate the effect of resistance exercise alone or in combination with oral intake of branched-chain amino acids (BCAA) on phosphorylation of the 70-kDa S6 protein kinase (p70(S6k)) and mitogen-activated protein kinase (MAPK), extracellular signal-regulated kinase (ERK1/2), and p38 MAPK in skeletal muscle. Seven male subjects performed one session of quadriceps muscle resistance training (4 x 10 repetitions at 80% of one repetition maximum) on two occasions. In a randomized order, double-blind, crossover test, subjects ingested a solution of BCAA or placebo during and after exercise. Ingestion of BCAA increased plasma concentrations of isoleucine, leucine, and valine during exercise and throughout recovery after exercise (2 h postexercise), whereas no change was noted after the placebo trial. Resistance exercise led to a robust increase in p70(S6k) phosphorylation at Ser(424) and/or Thr(421), which persisted 1 and 2 h after exercise. BCAA ingestion further enhanced p70(S6k) phosphorylation 3.5-fold during recovery. p70(S6k) phosphorylation at Thr(389) was unaltered directly after resistance exercise. However, during recovery, Thr(389) phosphorylation was profoundly increased, but only during the BCAA trial. Furthermore, phosphorylation of the ribosomal protein S6 was also increased in the recovery period only during the BCAA trial. Exercise led to a marked increase in ERK1/2 and p38 MAPK phosphorylation, which was completely suppressed upon recovery and unaltered by BCAA. In conclusion, BCAA, ingested during and after resistance exercise, mediate signal transduction through p70(S6k) in skeletal muscle.

Administration, Oral↗
PubMed1993

Branched-chain amino acid supplementation augments plasma ammonia responses during exercise in humans.

This study examined the effects of branched-chain amino acid (BCAA) supplementation on amino acid and ammonia (NH3) responses during prolonged exercise in humans. Seven men cycled for 60 min at 75% of maximal O2 uptake after 45 min of either placebo (dextrose, 77 mg/kg) or BCAA (leucine + isoleucine + valine, 77 mg/kg) supplementation. Plasma samples (antecubital vein) were collected at rest and during exercise and analyzed for plasma NH3 and amino acids, whole blood glucose and lactate, and serum free fatty acids and glycerol. After BCAA administration, plasma BCAA levels increased from 375 +/- 22 to 760 +/- 80 microM (P < 0.05) by the onset of exercise and remained elevated throughout the experiment. Plasma NH3 concentrations increased continually during exercise for both trials and were higher (P < 0.05) after BCAA supplementation than after placebo administration. The mean plasma NH3 increase from rest to 60 min was 79 +/- 10 and 53 +/- 4 microM for BCAA and placebo trials, respectively. Plasma alanine and glutamine concentrations were elevated (P < 0.05) during exercise for both treatments. However, only glutamine concentrations were greater (P < 0.05) for BCAA trial than for placebo trial during exercise. There were no significant differences between treatments for glucose, lactate, free fatty acids, and glycerol or any other plasma amino acid. These data suggest that increased BCAA availability before exercise, when initial muscle glycogen is normal, results in significantly greater plasma NH3 responses during exercise than does placebo administration.

Adenosine Monophosphate↗