Plasma BCAA Research Articles

Intake of Branched-Chain Amino Acids Is Associated With Higher Plasma BCAA Concentrations: An Analysis of Data From the PREMIER Study

Intake of Branched-Chain Amino Acids Is Associated With Higher Plasma BCAA Concentrations: An Analysis of Data From the PREMIER Study

Sex differences in cachexia and branched-chain amino acid metabolism following chemotherapy in mice.

Chemotherapy is a major contributor to cachexia, but studies often investigate male animals. Here, we investigated whether sex modifies the effects of chemotherapy on cachexia and BCAA metabolism. Ten-week-old CD2F1 male and female mice were treated with the chemotherapy drug cocktail folfiri (50 mg/kg 5-fluorouracil, 90 mg/kg leucovorin, and 24 mg/kg CPT11) (drug) or vehicle twice a week for 6 weeks. Insulin tolerance tests were conducted and BCAA levels and metabolism were measured in plasma and tissues. Drug treatment reduced body and skeletal muscle weights and anabolic signaling in both sexes, with females showing worsened outcomes (p < 0.05 for all). Drug treatment increased plasma BCAA only in males, but BCAA concentrations in the skeletal muscle of both sexes were decreased; this decrease was more profound in males (p = 0.0097). In addition, muscle expression of the BCAA transporter LAT1 was reduced; this reduction was more severe in females (p = 0.0264). In both sexes, the (inhibitory) phosphorylation of BCKD-E1αser293 was increased along with decreased BCKD activity. In the liver, drug treatment increased BCAA concentrations and LAT1 expression, but BCKD activity was suppressed in both sexes (p < 0.05 for all). Our results demonstrate that altered BCAA metabolism may contribute to chemotherapy-induced cachexia in a sex-dependent manner.

The Effect of 8-Week Protein Supplementation with a Simple Exercise Program on Body Composition, Muscle Strength, and Amino Acid OMICS among Healthy Sedentary Indians: A Randomized, Double-Blind, Placebo-Controlled Trial.

Dietary protein plays a crucial role in the modulation of several physiological processes to sustain health and well-being. There is robust evidence of enhanced muscle protein synthesis, improved physical fitness, body composition, and performance contributed by protein supplementation combined with exercise among trained individuals or athletes. Evidence of the efficacy of such intervention on healthy adults having a sedentary lifestyle is limited. The objective of this study was to evaluate the impact of 12 g of additional protein in the form of a protein supplement compared to a placebo combined with a simple exercise program on plasma amino acid level, body composition, and muscle strength among healthy Indian adults having a relatively sedentary lifestyle. This double-blinded, randomized controlled trial was conducted on sedentary healthy adults 20-45 years of age, with a body mass index (BMI) between 18.5 and 27.9 kg/m2. Eighty-two participants were randomized into either the protein (intervention) or placebo (control) group. The exercise regime was the same for both groups. Out of 82 randomized participants, 58 completed the intervention. Blood tests were conducted for the amino acid OMICS measurement followed by dual-energy X-ray absorptiometry (DXA) for body composition and isokinetic dynamometry for muscle strength. A significant improvement was observed in the lean mass (kg) and appendicular muscle mass (AMM) adjusted for weight in the intervention group compared to the control group (p < 0.05). The muscle strength and contractile quality were comparable in the 2 groups. Plasma BCAA showed a significant negative association with body fat % (r = -0.43, p < 0.05 for the intervention group and r = -0.33, p = 0.07 for the control group) and a positive association with lean body mass % (r = 0.56, p < 0.01 in the intervention group vs r = 0.29, p = 0.10 in the control group) in the intervention group compared to control. In conclusion, this study highlighted the value of incorporating a lifestyle intervention including protein supplementation with simple exercises to optimize body composition in sedentary healthy individuals. This trial is registered with CTRI/2018/12/016777.

Eicosapentaenoic acid and branched-chain amino acids fortified complete nutrition drink improved muscle strength in older individuals with inadequate protein intake.

Elevated inflammation and negative nutritional balance contribute to sarcopenia, a progressive loss of muscle mass, strength, and function. This study investigated the effect of energy supplementation and the combination of anti-inflammatory factor (eicosapentaenoic acid; EPA) and muscle-synthesis promotor (branched-chain amino acids; BCAA) on body composition, muscle, and inflammatory biomarkers in elderly with inadequate protein intake. A randomized blinded placebo-controlled trial was conducted on 84 elderly with inadequate protein intake. The participants were randomly assigned into four groups receiving a complete nutrition drink; (1) control formula, (2) fortified with 2.2 g EPA, (3) with 2.2 g EPA and 5 g BCAA (2:1:1 of Leu: Ile: Val), and (4) with 2.2 g EPA plus 5g BCAA (4:1:1 of Leu: Ile: Val). Each subject consumed two sachets of the drink to gain 500 kcal/day and performed arm muscle exercises for 3 weeks. Body compositions and handgrip strength were measured using BIA and a dynamometer, respectively. Plasma EPA and BCAA levels were determined using LC-MS/MS to ensure compliance. Muscle protein biomarkers including histidine, β-alanine, and carnosine were measured using LC-MS/MS. Serum inflammatory (IL-6) and anti-inflammatory cytokines (IL-10) were measured by using ELISA. No symptoms and signs of adverse events were observed. The right arm muscle mass and handgrip strength were significantly increased after consuming a complete nutrition drink fortified with EPA + BCAA 2:1:1 and 4:1:1 of Leu: Ile: Val (p < 0.05 and p < 0.01, respectively. Consistently, consuming such combinatory formula non-significantly elevated carnosine with reduced histidine, and increased IL-10 with decreased IL-6. All relevant intervention groups showed a significant increase in plasma levels of BCAA and EPA. Consuming a complete nutrition drink fortified with 2.2g EPA and 5g BCAA 2:1:1 or 4:1:1 of Leu: Ile: Val for 3 weeks may increase right arm muscle mass and strength in elderly with inadequate protein intake. The tendency of increased dipeptide (carnosine)/decreased free amino acid (histidine) suggests a shift toward muscle protein synthesis. The trend of decreased inflammatory/increased anti-inflammatory cytokines suggests an anti-inflammatory effect. Future long-term studies are warranted to confirm the combinatory effect of BCAA and EPA in the prevention of sarcopenia. Thailand Clinical Trial Registry No. TCTR20230116005.

Systematic analysis of relationships between plasma branched-chain amino acid concentrations and cardiometabolic parameters: an association and Mendelian randomization study

BackgroundBranched-chain amino acids (BCAAs; valine, leucine, and isoleucine) are essential amino acids that are associated with an increased risk of cardiometabolic diseases (CMD). However, there are still only limited insights into potential direct associations between BCAAs and a wide range of CMD parameters, especially those remaining after correcting for covariates and underlying causal relationships.MethodsTo shed light on these relationships, we systematically characterized the associations between plasma BCAA concentrations and a large panel of 537 CMD parameters (including atherosclerosis-related parameters, fat distribution, plasma cytokine concentrations and cell counts, circulating concentrations of cardiovascular-related proteins and plasma metabolites) in 1400 individuals from the Dutch population cohort LifeLines DEEP and 294 overweight individuals from the 300OB cohort. After correcting for age, sex, and BMI, we assessed associations between individual BCAAs and CMD parameters. We further assessed the underlying causality using Mendelian randomization.ResultsA total of 838 significant associations were detected for 409 CMD parameters. BCAAs showed both common and specific associations, with the most specific associations being detected for isoleucine. Further, we found that obesity status substantially affected the strength and direction of associations for valine, which cannot be corrected for using BMI as a covariate. Subsequent univariable Mendelian randomization (UVMR), after removing BMI-associated SNPs, identified seven significant causal relationships from four CMD traits to BCAA levels, mostly for diabetes-related parameters. However, no causal effects of BCAAs on CMD parameters were supported.ConclusionsOur cross-sectional association study reports a large number of associations between BCAAs and CMD parameters. Our results highlight some specific associations for isoleucine, as well as obesity-specific effects for valine. MR-based causality analysis suggests that altered BCAA levels can be a consequence of diabetes and alteration in lipid metabolism. We found no MR evidence to support a causal role for BCAAs in CMD. These findings provide evidence to (re)evaluate the clinical importance of individual BCAAs in CMD diagnosis, prevention, and treatment.

Caloric restriction improves glycaemic control without reducing plasma branched-chain amino acids or keto-acids in obese men

Higher plasma leucine, isoleucine and valine (BCAA) concentrations are associated with diabetes, obesity and insulin resistance (IR). Here, we evaluated the effects of 6-weeks very-low calorie diet (VLCD) upon fasting BCAA in overweight (OW) non-diabetic men, to explore associations between circulating BCAA and IR, before and after a weight loss intervention. Fasting plasma BCAAs were quantified in an OW (n = 26; BMI 32.4 ± 3 kg/m2; mean age 44 ± 9 y) and a normal-weight (NW) group (n = 26; BMI 24 ± 3.1 kg/m2; mean age 32 ± 12.3 y). Ten of the OW group (BMI 32.2 ± 4 kg/m2; 46 ± 8 y) then underwent 6-weeks of VLCD (600–800 kcal/day). Fasting plasma BCAA (gas chromatography-mass spectrometry), insulin sensitivity (HOMA-IR) and body-composition (DXA) were assessed before and after VLCD. Total BCAA were higher in OW individuals (sum leucine/isoleucine/valine: 457 ± 85 µM) compared to NW control individuals (365 ± 78 µM, p < 0.001). Despite significant weight loss (baseline 103.9 ± 12.3 to 93 ± 9.6 kg and BMI 32.2 ± 4 to 28.9 ± 3.6 kg/m2), no changes were observed in BCAAs after 6-weeks of VLCD. Moreover, although VLCD resulted in a significant reduction in HOMA-IR (baseline 1.19 ± 0.62 to 0.51 ± 0.21 post-VLCD; p < 0.001), Pearson’s r revealed no relationships between BCAA and HOMA-IR, either before (leucine R2: 2.49e−005, p = 0.98; isoleucine R2: 1.211−e006, p = 0.9; valine R2: 0.004, p = 0.85) or after VLCD (leucine R2: 0.003, p = 0.86; isoleucine R2: 0.006, p = 0.82; valine R2: 0.002, p = 0.65). Plasma BCAA are higher in OW compared to NW individuals. However, while 6-weeks VLCD reduced body weight and IR in OW individuals, this was not associated with reductions in BCAA. This suggests that studies demonstrating links between BCAA and insulin resistance in OW individuals, are complex and are not normalised by simply losing weight.

Review: Influence of postabsorptive metabolism on essential amino acid partitioning in lactating dairy cows

In the lactating cow, essential amino acids (EAAs) absorbed from the gut are partitioned to mammary and extra-mammary tissues via blood plasma circulation. There is also entry of EAA into plasma from the breakdown of proteins in the cow’s body. A balance model across plasma was solved to integrate entry rates of branched-chain (BCAA) and non-branched-chain EAA (NBAA) with their corresponding rate constants for clearance by mammary glands and the remainder of the body, for selected glucose and fat infusion experiments. Endogenous EAA entry from whole-body proteolysis was reduced by glucose and unchanged or increased by fat, the efficiency of net plasma BCAA clearance by mammary and extra-mammary tissues was elevated by glucose but slightly reduced by fat, and the efficiency of extra-mammary NBAA clearance may have decreased during glucose infusion but it was not affected or slightly increased by fat. These differences between glucose and fat responses can be accounted for by insulin and glucagon. Insulin suppresses endogenous EAA entry through mechanistic target of rapamycin complex 1, integrated stress response, and glycogen synthase kinase 3 signaling networks in skeletal muscle. While these networks can also regulate protein synthesis rates in muscle and the extra-mammary body, they exhibit low sensitivities to insulin in lactating ruminants. However, in the mammary glands, via these same networks, insulin stimulates clearance of EAA from plasma, although the drive to maintain a set point for milk protein yield takes precedence over nutritional signals. The glucose-induced increase in mammary BCAA clearance without an effect on NBAA clearance is due to a pronounced decrease in plasma BCAA concentrations. Because NBAAs do not experience a similar decline in concentration, the BCAA effect must be due to their metabolic transformation as opposed to sequestration in proteins. In adipose, the products of BCAA catabolism are lipogenic precursors. We propose that faster lipogenesis in adipose tissue, stimulated by glucose infusion, also promotes the uptake of precursor BCAA from plasma, causing a drop in their circulating concentrations. In addition, insulin stimulates BCAA oxidation in muscle as an alternative fuel to fatty acids. A lower efficiency of extra-mammary NBAA clearance during glucose infusion may be the consequence of decreased hepatic expression of AA-catabolizing enzymes in response to low glucagon concentration. The proportion of EAA entry partitioned to the mammary glands is a culmination of regulatory shifts at all of the points discussed above according to a regulated or unfair competition between mammary and extra-mammary processes.

Association of Modifiable Lifestyle Factors with Plasma Branched-Chain Amino Acid Metabolites in Women

BackgroundCirculating branched-chain amino acids (BCAAs—isoleucine, leucine, and valine) are strongly associated with higher risk of incident type 2 diabetes (T2D); however, determinants of elevated fasting BCAA concentrations are largely unknown. ObjectivesWe aimed to characterize the modifiable lifestyle factors related to plasma BCAAs. MethodsWe performed a cross-sectional analysis among n = 18,897 women (mean ± SD age: 54.9 ± 7.2 y) in the Women’s Health Study, free of T2D and cardiovascular disease at baseline blood draw. Lifestyle factors, weight, and height were self-reported via questionnaire, including smoking status, alcohol, leisure-time physical activity (LTPA), diet quality scores [2010 Alternative Healthy Eating Index (without alcohol) (aHEI); alternate Mediterranean Diet (aMED)], and dietary sources of BCAAs. Plasma BCAAs were quantified via NMR spectroscopy. We calculated multivariable-adjusted percentage mean differences (95% CIs) and P values for linear trend of BCAAs stratified by categoric lifestyle factors. We estimated R2 from univariate cubic spline regression models to estimate the variability in BCAAs explained. ResultsCompared with women with BMI (in kg/m2) <25.0, BCAAs were 8.6% (95% CI: 8.0%, 9.3%), 15.3% (95% CI: 14.4%, 16.3%), and 21.0% (95% CI: 18.2%, 23.9%) higher for the BMI strata 25.0–29.9, 30.0–39.9, and ≥40.0, respectively (P-trend < 0.0001). Women with higher LTPA and higher alcohol intake compared with lower had modestly (∼1%) lower plasma BCAAs (P-trend = 0.014 and 0.0003, respectively). Differences in smoking status, aHEI, and aMED score were not related to plasma BCAAs. Women with higher dietary BCAAs had dose-response higher plasma BCAA concentrations, 3.4% (95% CI: 2.5%, 4.4%) higher when comparing the highest with the lowest quintile (P-trend < 0.0001). BMI explained 11.6% of the variability of BCAAs, whereas other factors explained between 0.1% and 1%. ConclusionsOur findings among a large cohort of US women indicate that BMI, but less so diet, physical activity, and other lifestyle factors, is related to plasma BCAAs.This trial was registered at clinicaltrials.gov as NCT00000479.

AACE2021-A-1048: Effect of Dietary Intake of Branched Chain Amino Acids on Type 2 Diabetic Patients Control

BCAAs up regulate glucose transporters and activate insulin secretion has been widely demonstrated. However, several researchers have suggested that excessive intake of amino acids could lead to inhibition of insulin signalling. BCAAs may induce insulin resistance through m TOR activation. insulin resistance may be linked with high intake of BCAAs, Controversies remain on whether an increase in plasma BCAA levels is a cause or consequence of insulin resistance. The aim of the study is to measure the effect of consumption of BCCAs on lipid profile and glucose level in type 2 obese diabetic patients. Participants enrolled in the study 280 patients (139 male,141 female) with type 2 diabetes for more than 5 years Attending Endocrinology out patient clinic. Written consent was obtained from all participants Anthropometric measurement (height, weight, waist circumference, body mass index Dietary assessment participants had to complete food frequency questionnaire (24 hour recall)for 5 days and analysis for branched chain amino acid intake was performed using food composition table, life style ,socio-demographic level, laboratory investigations including, fasting glucose, HbA1c, cholesterol, triglyceride, LDL, HDL. Mean Age 38.24±4.28 ,male 49.6%, female 50.4%, diabetes duration 8.86±2.26 years, BMI; 29.89 ±3.02, protein intake 77.75±14.76 g, Leucine 4.75±1.01g, valine 4.04±0.89 g, Isoleucine 4.09±0.92 g, fasting glucose 206.60 ±51.01mg A1C 9.33±1.18, cholesterol 238.79±40.37 mg/dl, triglycerides 103.47±14.01mg/dl LDL178.20 ±43.32 mg/dl/ HDL 44.03±9.55mg/dl. All of our patients took higher load for age and ideal weight of (leucine,valine, and isoleucine is likely to be 0.04,0.017-0.02 ,and 0.019 g /kg respective) mainly from plant source protein Regarding correlation with A1C (Valine p 0.01,r 0.02/isoliosine p 0.08 r 0.156) Regarding correlation with LDL (liosine p 0.07 r 0.156). High BCCAs intake mainly from plant source is associated with dyslipidaemia and poor glycaemic control .proper dietary counselling is important in diabetic.

Effect of the BCAT2 polymorphism (rs11548193) on plasma branched-chain amino acid concentrations after dietary intervention in subjects with obesity and insulin resistance.

Branched-chain amino acids (BCAA) are considered markers of insulin resistance (IR) in subjects with obesity. In this study, we evaluated whether the presence of the SNP of the branched-chain aminotransferase 2 (BCAT2) gene can modify the effect of a dietary intervention (DI) on the plasma concentration of BCAA in subjects with obesity and IR. A prospective cohort study of adult subjects with obesity, BMI ≥ 30 kg/m2, homeostatic model assessment-insulin resistance (HOMA-IR ≥ 2·5) no diagnosed chronic disease, underwent a DI with an energy restriction of 3140 kJ/d and nutritional education for 1 month. Anthropometric measurements, body composition, blood pressure, resting energy expenditure, oral glucose tolerance test results, serum biochemical parameters and the plasma amino acid profile were evaluated before and after the DI. SNP were assessed by the TaqMan SNP genotyping assay. A total of eighty-two subjects were included, and fifteen subjects with a BCAT2 SNP had a greater reduction in leucine, isoleucine, valine and the sum of BCAA. Those subjects also had a greater reduction in skeletal muscle mass, fat-free mass, total body water, blood pressure, muscle strength and biochemical parameters after 1 month of the DI and adjusting for age and sex. This study demonstrated that the presence of the BCAT2 SNP promotes a greater reduction in plasma BCAA concentration after adjusting for age and sex, in subjects with obesity and IR after a 1-month energy-restricted DI.

Chronically elevated branched chain amino acid levels are pro-arrhythmic.

AimsCardiac arrhythmias comprise a major health and economic burden and are associated with significant morbidity and mortality, including cardiac failure, stroke, and sudden cardiac death (SCD). Development of efficient preventive and therapeutic strategies is hampered by incomplete knowledge of disease mechanisms and pathways. Our aim is to identify novel mechanisms underlying cardiac arrhythmia and SCD using an unbiased approach.Methods and resultsWe employed a phenotype-driven N-ethyl-N-nitrosourea mutagenesis screen and identified a mouse line with a high incidence of sudden death at young age (6–9 weeks) in the absence of prior symptoms. Affected mice were found to be homozygous for the nonsense mutation Bcat2p.Q300*/p.Q300* in the Bcat2 gene encoding branched chain amino acid transaminase 2. At the age of 4–5 weeks, Bcat2p.Q300*/p.Q300* mice displayed drastic increase of plasma levels of branch chain amino acids (BCAAs—leucine, isoleucine, valine) due to the incomplete catabolism of BCAAs, in addition to inducible arrhythmias ex vivo as well as cardiac conduction and repolarization disturbances. In line with these findings, plasma BCAA levels were positively correlated to electrocardiogram indices of conduction and repolarization in the German community-based KORA F4 Study. Isolated cardiomyocytes from Bcat2p.Q300*/p.Q300* mice revealed action potential (AP) prolongation, pro-arrhythmic events (early and late afterdepolarizations, triggered APs), and dysregulated calcium homeostasis. Incubation of human pluripotent stem cell-derived cardiomyocytes with elevated concentration of BCAAs induced similar calcium dysregulation and pro-arrhythmic events which were prevented by rapamycin, demonstrating the crucial involvement of mTOR pathway activation.ConclusionsOur findings identify for the first time a causative link between elevated BCAAs and arrhythmia, which has implications for arrhythmogenesis in conditions associated with BCAA metabolism dysregulation such as diabetes, metabolic syndrome, and heart failure.

61 Effect of branched-chain amino acid and N-acetylcysteine supplementation post-exercise on muscle mTOR signaling in exercising horses

Recovery from intense exercise is crucial in the equine athlete and numerous nutritional interventions have been proposed to benefit exercise recovery. Branched-chain amino acids (leucine, isoleucine, valine; BCAA) have been associated with improved muscle protein synthesis post-exercise. N-acetylcysteine (NAC) is a precursor to glutathione, a powerful antioxidant involved in many biological pathways, and supplementation has been reported to improve exercise performance and oxidative stress. However, there is some evidence that NAC may disrupt the mTOR signaling pathways associated with protein synthesis. The objective of this study was to determine if there is an undesirable effect on the mTOR pathway with NAC supplementation or if concurrent supplementation with BCAAs might counteract this effect. Eight conditioned Thoroughbred geldings (9.5 ± 2.7 years, 581 ± 65kg, BW) were fed a grain meal 30 m post-exercise supplemented with nothing (control), BCAA (20 g/d; 2:1:1 Leu:Ile:Val), NAC (10 g/d), or both for 21 d in a replicated Latin square design. On d 20 of supplementation, horses performed a standardized exercise test on a high-speed treadmill including a 1.5 mi gallop at a target heart rate of 180–190 bpm. Relative to exercise, blood samples were collected at −24 h, every 30 m for 1 h before and 4 h after exercise, and at 24 h. Plasma was subsequently analyzed for amino acid concentrations using HPLC. Muscle samples were collected from the gluteus medius by percutaneous muscle biopsy at −24, 1, 4, and 24 h relative to exercise for evaluation of major proteins in the mTOR pathway using Western immunoblot analysis. Data were analyzed using PROC MIXED with repeated measures (SAS v9.4) using treatment, time, and their interaction as fixed effects. Exercise increased plasma levels of alanine, leucine, and isoleucine (P < 0.001), but not valine (P > 0.05). BCAA alone and in combination with NAC elevated plasma BCAA concentrations post-feeding for at least 4 h post-exercise (P < 0.001). Regardless of treatment, exercise resulted in the activation of Akt and rpS6 (P < 0.001) at 1 h and 4 h post-exercise, respectively. Importantly, NAC did not adversely affect the activation of any mTOR signaling proteins relative to control (P > 0.05). The greatest effect on mTOR signaling was due to exercise. At the dosage supplemented, NAC did not have detrimental effects on the activation of the mTOR pathway. These results provide novel preliminary data on the safety of NAC supplementation in exercising horses in regards to the mTOR pathway and protein synthesis.

Low Dose Brain Radiation Reduces Elevated Plasma Branch Chain Amino Acid Levels in APP/PS1 Mice

Branch Chain Amino Acids (BCAA) have recently been implicated in Alzheimer’s Disease (AD). We previously showed that low dose brain radiation (RT) [5 fractions of 2 Gy] reduces amyloid-beta plaque burden and results in improved cognition in the APP/PS1 model of AD. In this study we investigated whether this schedule of radiation altered the metabolomic profile of serum. 10 month old male (M) and female (F) APP/PS1 mice were either treated with whole brain radiotherapy (5 x 2 Gy) or received sham irradiation. Eight weeks later the animals were euthanized and blood, urine and brain tissue collected. 1H NMR spectra were acquired. 256 transients were acquired for each sample and chemical shifts (δ) are reported in parts per million (ppm). Analysis included: 3 F and 5 M with no transgene (as a background controls), 5 F who received no RT, 7 F who received RT, 12 M who received RT and 12 M who received no RT. A total of 46 metabolites were analyzed. The most significantly changed metabolites were the BCAAs leucine, isoleucine and valine.. The effect was most pronounced in female mice where levels were reduced to those found in non-transgenic mice. APP/PS1 mice spontaneously display increased plasma BCAA, suggesting that AD pathology potentiates defects in BCAA metabolism, putting patients with AD at a higher risk of BCAA-induced brain damage. Reduction of these levels by low dose radiation may be beneficial.

146 Prematurity Blunts the Protein Synthetic Response of Skeletal Muscle to Insulin and Amino Acids

Abstract Livestock animals are important dual-purpose models that benefit both agricultural and biomedical research. The neonatal pig is an appropriate model for the human infant to assess long-term effects of early life nutrition on growth and metabolic outcomes. Previously we have demonstrated that prematurity blunts the feeding-induced stimulation of translation initiation and protein synthesis in skeletal muscle of neonatal pigs. The objective of this study was to determine whether reduced sensitivity to insulin and/or amino acids drives this blunted response. Pigs were delivered by caesarean section at preterm (PT, 103 d gestation) or at term (T, 112 d gestation) and fed parenterally for 4 d. On day 4, pigs were subject to euinsulinemic-euaminoacidemic-euglycemic (FAST), hyperinsulinemic-euaminoacidemic-euglycemic (INS), or euinsulinemic-hyperaminoacidemic-euglycemic (AA) clamps for 120 min, yielding six treatments: PT-FAST (n = 7), PT-INS (n = 9), PT-AA (n = 9), T-FAST (n = 8), T-INS (n = 9), and T-AA (n = 9). A flooding dose of L-[4-3H]Phe was injected into pigs 30 min before euthanasia. Birth weight and relative body weight gain were lower in PT than T pigs (P &amp;lt; 0.001). Plasma insulin concentration was increased from ~3 to ~100 µU/mL in INS compared to FAST and AA pigs (P &amp;lt; 0.001); plasma BCAA concentration was increased from ~250 to ~1,000 µmol/L in AA compared to FAST and INS pigs (P &amp;lt; 0.001). Despite achieving similar insulin and amino acid levels, longissimus dorsi AKT phosphorylation, mechanistic target of rapamycin (mTOR)·Rheb abundance, mTOR activation, and protein synthesis were lower in PT-INS than T-INS pigs (Table 1). Although amino-acid induced dissociation of Sestrin2 from GATOR2 was not affected by prematurity, mTOR·RagA abundance, mTOR·RagC abundance, mTOR activation, and protein synthesis were lower in PT-AA than T-AA pigs. The impaired capacity of premature skeletal muscle to respond to insulin or amino acids and promote protein synthesis likely contributes to reduced lean mass accretion. Research was supported by NIH and USDA.

The Effects Of A Protease Enzyme Blend On The Amino Acid Response To Resistance Exercise

PURPOSE: The aim of the current study was to examine the efficacy of whey protein ingestion with or without a protease enzyme complex on amino acid (AA) availability following acute lower-body resistance exercise. METHODS: Ten resistance trained men (24.4±4.1yr, 179.1±8.6cm, 92.6±10.4kg) with at least one year of resistance training experience volunteered to participate in this placebo-controlled, randomized, cross-over designed study. Following an overnight fast, participants performed lower-body acute resistance exercises consisting of four sets each of the leg press and leg extension exercises (8-10 repetitions at 75% of 1RM) followed by consumption of one of three drinks of equivalent volume, taste, and appearance which consisted of either: (a) 26g whey protein + 250 mg protease supplement + whey (PW) (b) 26g whey protein (W), or (c) a non-caloric flavored water drink (PL). Blood samples were collected before exercise, immediately-post (0min), 30-, 60-, 90-, 120-, and 180-minutes post-exercise (30min, 60min, 90min, 120min, 180min respectively). Plasma amino acid samples were analyzed for essential (EAA), branched-chained (BCAA), and leucine concentrations via liquid chromatography-mass spectrometry (LC-MS). A 2-way repeated measures analysis of variance (ANOVA) was used to identify differences between treatments over time. Area under the curve was calculated via the trapezoidal technique and analyzed via a one-way ANOVA. RESULTS: Significant main effects for time (p<0.001) and time x group interactions (p<0.001) were found for leucine, BCAA, and EAA. PW drink resulted in significantly greater plasma leucine, BCAA and EAA concentrations at 30 min compared to PL (p<0.001) while not different than W. Leucine was significantly elevated at 30min (p=0.007) and EAAs at 180min (p=0.004) compared to 0min for PW. The AUC for PW and W were both significantly elevated for leucine, BCAAs and EAAs compared to PL (p<0.001). CONCLUSION: While no significant differences were found between the W and PW supplementation groups during the 3-hr period after resistance training; the PW group produced significantly greater leucine concentrations at 30min and for EAAs at 180min than PL compared to 0min. Results indicate that PW may provide a modest improvement of AA appearance in blood following acute resistance exercise.

Evaluation of dietary treatment and amino acid supplementation in organic acidurias and urea-cycle disorders: On the basis of information from a European multicenter registry.

Organic acidurias (OAD) and urea-cycle disorders (UCD) are rare inherited disorders affecting amino acid and protein metabolism. As dietary practice varies widely, we assessed their long-term prescribed dietary treatment against published guideline and studied plasma amino acids levels. We analyzed data from the first visit recorded in the European registry and network for intoxication type metabolic diseases (E-IMD, Chafea no. 2010 12 01). In total, 271 methylmalonic aciduria (MMA) and propionic aciduria (PA) and 361 UCD patients were included. Median natural protein prescription was consistent with the recommended daily allowance (RDA), plasma L-valine (57%), and L-isoleucine (55%) levels in MMA and PA lay below reference ranges. Plasma levels were particularly low in patients who received amino acid mixtures (AAMs-OAD) and L-isoleucine:L-leucine:L-valine (BCAA) ratio was 1.0:3.0:3.2. In UCD patients, plasma L-valine, L-isoleucine, and L-leucine levels lay below reference ranges in 18%, 30%, and 31%, respectively. In symptomatic UCD patients who received AAM-UCD, the median natural protein prescription lay below RDA, while their L-valine and L-isoleucine levels and plasma BCAA ratios were comparable to those in patients who did not receive AAM-UCD. Notably, in patients with ornithine transcarbamylase syndrome (OTC-D), carbamylphosphate synthetase 1 syndrome (CPS1-D) and hyperammonemia-hyperornithinemia-homocitrullinemia (HHH) syndrome selective L-citrulline supplementation resulted in higher plasma L-arginine levels than selective L-arginine supplementation. In conclusion, while MMA and PA patients who received AAMs-OAD had very low BCAA levels and disturbed plasma BCAA ratios, AAMs-UCD seemed to help UCD patients obtain normal BCAA levels. In patients with OTC-D, CPS1-D, and HHH syndrome, selective L-citrulline seemed preferable to selective L-arginine supplementation.

Protein synthesis signaling in skeletal muscle is refractory to whey protein ingestion during a severe energy deficit evoked by prolonged exercise and caloric restriction.

Exercise and protein ingestion preserve muscle mass during moderate energy deficits. To determine the molecular mechanisms by which exercise and protein ingestion may spare muscle mass during severe energy deficit (5500 kcal/day). Fifteen overweight, but otherwise healthy men, underwent a pre-test (PRE), caloric restriction (3.2 kcals/kg body weight/day) + exercise (45 min one-arm cranking + 8 h walking) for 4 days (CRE), followed by a control diet (CD) for 3 days, with a caloric content similar to pre-intervention while exercise was reduced to less than 10,000 steps per day. During CRE, participants ingested either whey protein (PRO, n = 8) or sucrose (SU, n = 7) (0.8 g/kg body weight/day). Muscle biopsies were obtained from the trained and untrained deltoid, and vastus lateralis. Following CRE and CD, serum concentrations of leptin, insulin, and testosterone were reduced, whereas cortisol and the catabolic index (cortisol/total testosterone) increased. The Akt/mTor/p70S6K pathway and total eIF2α were unchanged, while total 4E-BP1 and Thr37/464E-BP1 were higher. After CRE, plasma BCAA and EAA were elevated, with a greater response in PRO group, and total GSK3β, pSer9GSK3β, pSer51eIF2α, and pSer51eIF2α/total eIF2α were reduced, with a greater response of pSer9GSK3β in the PRO group. The changes in signaling were associated with the changes in leptin, insulin, amino acids, cortisol, cortisol/total testosterone, and lean mass. During severe energy deficit, pSer9GSK3β levels are reduced and human skeletal muscle becomes refractory to the anabolic effects of whey protein ingestion, regardless of contractile activity. These effects are associated with the changes in lean mass and serum insulin, testosterone, and cortisol concentrations.

Dietary Intakes and Circulating Concentrations of Branched-Chain Amino Acids in Relation to Incident Type 2 Diabetes Risk Among High-Risk Women with a History of Gestational Diabetes Mellitus.

Circulating branched-chain amino acids (BCAAs; isoleucine, leucine, valine) are consistently associated with increased type 2 diabetes (T2D) risk, but the relationship with dietary intake of BCAAs is less clear. The longitudinal Nurses' Health Study II cohort conducted a blood collection from 1996 to 1999. We profiled plasma metabolites among 172 incident T2D cases and 175 age-matched controls from women reporting a history of gestational diabetes before blood draw. We estimated dietary energy-adjusted BCAAs from food frequency questionnaires. We used conditional logistic regression models to estimate odds ratios (OR) and 95% CI of T2D risk across quartiles (Q1-Q4) of BCAAs, adjusting for age, body mass index (BMI), physical activity, family history, and other established risk factors. We also assessed joint exposure to below/above medians of diet and plasma concentrations, with lower diet/lower plasma as reference. Dietary and plasma BCAA concentrations were positively associated with incident T2D (diet Q4 vs Q1 OR = 4.6, CI = 1.6, 13.4; plasma Q4 vs Q1 OR = 4.4, CI = 1.4, 13.4). Modeling the joint association indicated that higher diet BCAAs were associated with T2D when plasma concentrations were also higher (OR = 6.0, CI = 2.1, 17.2) but not when concentrations were lower (OR = 1.6, CI = 0.61, 4.1). Conversely, higher plasma BCAAs were associated with increased T2D for either lower or higher diet. Independent of BMI and other risk factors, higher diet and plasma BCAA concentrations were associated with an increased incident T2D risk among high-risk women with a history of gestational diabetes, supporting impaired BCAA metabolism as conferring T2D risk.

Abstract 048: Circulating Branched-Chain Amino Acids and Incident Cardiovascular Disease in a Prospective Cohort of US Women

Introduction: Recent metabolomics studies have identified circulating levels of branched-chain amino acids (BCAAs; isoleucine, leucine, valine) as strong predictors of type 2 diabetes (T2D). Whether BCAAs are implicated in cardiovascular disease (CVD) risk has not been established. Hypothesis: We hypothesized that higher baseline levels of plasma BCAAs are associated with an elevated risk of incident CVD events, and evaluated whether this relationship was dependent on an intermediate diagnosis of T2D. Methods: Participants enrolled in the Women’s Health Study prospective cohort were eligible if they did not report CVD or cancer prior to baseline blood collection (N=27,172, mean baseline age=54.7 years). Plasma BCAA metabolites were measured via proton NMR spectroscopy, ln-transformed, and standardized for analysis. We used multivariable Cox proportional regression models to estimate hazard ratios (HR) and 95% confidence intervals (CI) per standard deviation (SD) of total and individual BCAAs with incident CVD (myocardial infarction [MI], stroke, coronary revascularization). Results: 1,917 confirmed CVD events occurred over follow-up (mean 18.6 years). In models adjusted for age, body mass index, smoking status, diet quality, physical activity, and other established CVD risk factors, total BCAAs were positively associated with CVD (per SD, HR=1.13, CI=1.08 to 1.19), comparable in magnitude to the association of LDL cholesterol with CVD (per SD, HR=1.15, CI=1.09 to 1.21). In particular, BCAAs were associated with coronary events (MI: HR=1.21, CI=1.10 to 1.33; revascularization: HR=1.15, CI=1.07 to 1.23), but not with stroke (HR=1.07, CI=0.98 to 1.15). The BCAA-CVD relationship was notably greater (p-interaction=0.008) among participants who developed T2D prior to a CVD event (HR=1.25, CI=1.13 to 1.39), vs. women without T2D (HR=1.07, CI=1.01 to 1.13). Isoleucine, leucine, and valine were each associated with CVD (p&lt;0.05). Further adjusting for biomarkers of potential intermediates, HbA1c, lipids, and a lipoprotein-based insulin resistance score entirely eliminated the associations of BCAAs with CVD. Conclusions: Circulating plasma BCAAs were positively associated with long-term incident CVD in a cohort of US women, in particular among women who developed T2D prior to a CVD event. Impaired BCAA metabolism may represent a shared pathway of insulin resistance that links the risks of T2D and CVD.

Effect of light-load resistance exercise on postprandial amino acid transporter expression in elderly men.

An impaired amino acid sensing is associated with age‐related loss of skeletal muscle mass. We tested whether light‐load resistance exercise (LL‐RE) affects postprandial amino acid transporter (AAT) expression in aging skeletal muscle. Untrained, healthy men (age: +65 years) were subjected to 13 h of supine rest. After 2 1/2 h of rest, unilateral LL‐RE was conducted (leg extensions, 10 sets of 36 repetitions) at 16% 1RM. Thereafter, the subjects were randomized into groups that orally ingested 40 g of whey protein either as hourly drinks (4 g per drink) (PULSE, N = 10) or two boluses (28 g at 0 h and 12 g at 7 h) (BOLUS, N = 10), or hourly isocaloric maltodextrin drinks (placebo, N = 10). Quadriceps muscle biopsies were taken at 0, 3, 7, and 10 h postexercise from both the resting and exercised leg, from which the membrane protein and mRNA expression of select AATs were analyzed by Western Blot and RT‐PCR, respectively. LAT1 and PAT1 protein expression increased in response to LL‐RE in the PULSE group, and SNAT2 and PAT1 protein expression increased in the BOLUS group when plasma BCAA concentration was low. In all three groups, LL‐RE increased LAT1 mRNA expression, whereas a time course decrease in SNAT2 mRNA expression was observed. LL‐RE increased membrane‐associated AAT protein expression and mRNA expression. Altered AAT protein expression was only seen in groups that ingested whey protein, with the greatest effect observed after hourly feeding. This points toward an importance of AATs in the anabolic response following LL‐RE and protein intake.