Amino Acid Beverage Research Articles

Exertional heat stress promotes the presence of bacterial DNA in plasma: A counterbalanced randomised controlled trial

ObjectivesThe primary aim was to explore the impact of exertional-heat stress (EHS) promoted exercise-associated bacteraemia. A secondary aim was to examine if an amino acid beverage (AAB) intervention may mitigate exercise-associated bacteraemia. DesignCounterbalanced randomised control trial. MethodsTwenty endurance trained male participants completed two randomised EHS trials. On one occasion, participants consumed a 237 mL AAB twice daily for 7 days prior, immediately before and every 20 min during EHS (2 h running at 60 % V̇O2max in 35 °C). On the other occasion, a water volume control (CON) equivalent was consumed. Whole blood samples were collected pre- and immediately post-EHS, and were analysed for plasma DNA concentration by fluorometer quantification after microbial extraction, and bacterial relative abundance by next generation 16s rRNA gene sequencing. ResultsIncreased concentration of microbial DNA in plasma pre- to post-EHS was observed on CON (pre-EHS 0.014 ng/μL, post-EHS 0.039 ng/μL) (p < 0.001) and AAB (pre-EHS 0.015 ng/μL, post-EHS 0.031 ng/μL) (p < 0.001). The magnitude of change from pre- to post-exercise on AAB was 40 % lower, but no significant difference was observed versus CON (p = 0.455). Predominant bacterial groups identified included: phyla-Proteobacteria (88.0 %), family-Burkholderiaceae (59.1 %), and genus-Curvibacter (58.6 %). No significant variation in absolute and relative change in α-diversity and relative abundance for phyla, family, and genus bacterial groups was observed in AAB versus CON. ConclusionsThe increased presence of microbial-bacterial DNA in systemic circulation in response to EHS appears positive in all participants. An amino acid beverage supplementation period prior to and consumption during EHS did not provide significant attenuation of EHS-associated bacteraemia.

Effectiveness of an amino acid beverage formulation in diarrhea-predominant irritable bowel syndrome: A pragmatic real-world study.

Amino-acid based medical foods have shown promise in alleviating symptoms of drug induced gastrointestinal side effects; particularly, diarrhea-predominant symptoms. Irritable bowel syndrome (IBS) is a gastrointestinal disorder that affects up to 9% of people globally, with diarrhea predominant IBS (IBS-D) being the most prevalent subtype. Further trials are needed to explore potential added benefits when integrated into standard care for IBS-D. To assess the effectiveness of an amino acid-based medical food as an adjunct to standard of care for adults with IBS-D. This is a pragmatic, real world, open label, single arm study comparing a 2-week baseline assessment to a 2-week intervention period. One hundred adults, aged 18 to 65 years, with IBS-D, according to Rome IV criteria, were enrolled after completing a 2-week baseline assessment period and received a 2-week supply of an amino acid based medical food which was consumed at home twice daily on top of their standard of care. The primary outcome was an assessment of tolerability after 2-weeks of consumption, while secondary outcomes included changes in stool consistency (Bristol Stool Form Scale), severity of abdominal pain & discomfort, symptoms of urgency, Global Improvement Survey (GIS), and the IBS severity scoring system (IBS-SSS). The test product was well-tolerated as each participant successfully completed the full 14-day trial, and there were no instances of dropouts or discontinuation of the study product reported. Forty percent of participants achieved a 50% or more reduction in the number of days with type 6-7 bowel movements (IBS-D stool consistency responders). Fifty-three percent of participants achieved a clinically meaningful reduction of 30% in mean weekly pain scores, and 55% experienced the same for mean weekly discomfort scores (IBS-D pain and discomfort responders). Participants experienced a mean -109.4 (95% confidence interval: -130.1, -88.8) point reduction on the IBS-SSS and 52% experienced a minimally clinically important difference of > 95 points. An IBS-SSS category shift from severe to moderate or mild occurred in 69% of participants. For functional symptoms, 76% of participants reported symptom relief on the GIS. The amino acid-based medical food was well-tolerated, when added to the standard of care, and demonstrated improvements in both overall IBS symptom severity and IBS-D symptoms within just 2 wk.

Amino Acid-Based Beverage Interventions Ameliorate Exercise-Induced Gastrointestinal Syndrome in Response to Exertional-Heat Stress: The Heat Exertion Amino Acid Technology (HEAAT) Study.

The study aimed to determine the effects of two differing amino acid beverage interventions on biomarkers of intestinal epithelial integrity and systemic inflammation in response to an exertional-heat stress challenge. One week after the initial assessment, participants (n = 20) were randomly allocated to complete two exertional-heat stress trials, with at least 1 week washout. Trials included a water control trial (CON), and one of two possible amino acid beverage intervention trials (VS001 or VS006). On VS001 (4.5g/L) and VS006 (6.4g/L), participants were asked to consume two 237-ml prefabricated doses daily for 7days before the exertional-heat stress, and one 237-ml dose immediately before, and every 20min during 2-hr running at 60% maximal oxygen uptake in 35 °C ambient conditions. A water volume equivalent was provided on CON. Whole blood samples were collected pre-, immediately post-, 1 and 2hr postexercise, and analyzed for plasma concentrations of cortisol, intestinal fatty acid protein, soluble CD14, and immunoglobulin M (IgM) by ELISA, and systemic inflammatory cytokines by multiplex. Preexercise resting biomarker concentrations for all variables did not significantly differ between trials (p > .05). A lower response magnitude for intestinal fatty acid protein (mean [95% CI]: 249 [60, 437]pg/ml, 900 [464, 1,336]pg/ml), soluble CD14 (-93 [-458, 272]ng/ml, 12 [-174, 197]ng/ml), and IgM (-6.5 [-23.0, 9.9]MMU/ml, -10.4 [-16.2, 4.7]MMU/ml) were observed on VS001 and V006 compared with CON (p < .05), respectively. Systemic inflammatory response profile was lower on VS001, but not VS006, versus CON (p < .05). Total gastrointestinal symptoms did not significantly differ between trials. Amino acid beverages' consumption (i.e.,4.5-6.4g/L), twice daily for 7days, immediately before, and during exertional-heat stress ameliorated intestinal epithelial integrity and systemic inflammatory perturbations associated with exercising in the heat, but without exacerbating gastrointestinal symptoms.

Carbon Quantum Dots from Pomelo Peel as Fluorescence Probes for "Turn-Off-On" High-Sensitivity Detection of Fe3+ and L-Cysteine.

This study designed a “turn-off–on” fluorescence analysis method based on carbon quantum dots (CQDs) to detect metal ions and amino acids in real sample systems. CQDs were derived from green pomelo peel via a one-step hydrothermal process. The co-doped CQDs with N and S atoms imparted excellent optical properties (quantum yield = 17.31%). The prepared CQDs could be used as fluorescent “turn-off” probes to detect Fe3+ with a limit of detection of 0.086 µM, a linear detection range of 0.1–160 µM, and recovery of 83.47–106.53% in water samples. The quenched CQD fluorescence could be turned on after adding L-cysteine (L-Cys), which allowed detection of L-Cys with a detection limit of 0.34 µM and linear range of 0.4–85 µM. Recovery of L-Cys in amino acid beverage was 87.08–122.74%. Visual paper-based testing strips and cellulose/CQDs composite hydrogels could be also used to detect Fe3+ and L-Cys.

LAT1 and SNAT2 Protein Expression and Membrane Localization of LAT1 Are Not Acutely Altered by Dietary Amino Acids or Resistance Exercise Nor Positively Associated with Leucine or Phenylalanine Incorporation in Human Skeletal Muscle.

The influx of essential amino acids into skeletal muscle is primarily mediated by the large neutral amino acid transporter 1 (LAT1), which is dependent on the glutamine gradient generated by the sodium-dependent neutral amino acid transporter 2 (SNAT2). The protein expression and membrane localization of LAT1 may be influenced by amino acid ingestion and/or resistance exercise, although its acute influence on dietary amino acid incorporation into skeletal muscle protein has not been investigated. In a group design, healthy males consumed a mixed carbohydrate (0.75 g·kg−1) crystalline amino acid (0.25 g·kg−1) beverage enriched to 25% and 30% with LAT1 substrates L-[1-13C]leucine (LEU) and L-[ring-2H5]phenylalanine (PHE), respectively, at rest (FED: n = 7, 23 ± 5 y, 77 ± 4 kg) or after a bout of resistance exercise (EXFED: n = 7, 22 ± 2 y, 78 ± 11 kg). Postprandial muscle biopsies were collected at 0, 120, and 300 min to measure transporter protein expression (immunoblot), LAT1 membrane localization (immunofluorescence), and dietary amino acid incorporation into myofibrillar protein (ΔLEU and ΔPHE). Basal LAT1 and SNAT2 protein contents were correlated with each other (r = 0.55, p = 0.04) but their expression did not change across time in FED or EXFED (all, p > 0.05). Membrane localization of LAT1 did not change across time in FED or EXFED whether measured as outer 1.5 µm intensity or membrane-to-fiber ratio (all, p > 0.05). Basal SNAT2 protein expression was not correlated with ΔLEU or ΔPHE (all, p ≥ 0.05) whereas basal LAT1 expression was negatively correlated with ΔPHE in FED (r = −0.76, p = 0.04) and EXFED (r = −0.81, p = 0.03) but not ΔLEU (p > 0.05). Basal LAT1 membrane localization was not correlated with ΔLEU or ΔPHE (all, p > 0.05). Our results suggest that LAT1/SNAT2 protein expression and LAT1 membrane localization are not influenced by acute anabolic stimuli and do not positively influence the incorporation of dietary amino acids for de novo myofibrillar protein synthesis in healthy young males.

Acute depletion of dopamine precursors in the human brain: effects on functional connectivity and alcohol attentional bias.

Individuals who abuse alcohol often show exaggerated attentional bias (AB) towards alcohol-related cues, which is thought to reflect reward conditioning processes. Rodent studies indicate that dopaminergic pathways play a key role in conditioned responses to reward- and alcohol-associated cues. However, investigation of the dopaminergic circuitry mediating this process in humans remains limited. We hypothesized that depletion of central dopamine levels in adult alcohol drinkers would attenuate AB and that these effects would be mediated by altered function in frontolimbic circuitry. Thirty-four male participants (22-38 years, including both social and heavy drinkers) underwent a two-session, placebo-controlled, double-blind dopamine precursor depletion procedure. At each visit, participants consumed either a balanced amino acid (control) beverage or an amino acid beverage lacking dopamine precursors (order counterbalanced), underwent resting-state fMRI, and completed behavioral testing on three AB tasks: an alcohol dot-probe task, an alcohol attentional blink task, and a task measuring AB to a reward-conditioned cue. Dopamine depletion significantly diminished AB in each behavioral task, with larger effects among subjects reporting higher levels of binge drinking. The depletion procedure significantly decreased resting-state functional connectivity among ventral tegmental area, striatum, amygdala, and prefrontal regions. Beverage-related AB decreases were mediated by decreases in functional connectivity between the fronto-insular cortex and striatum and, for alcohol AB only, between anterior cingulate cortex and amygdala. The results support a substantial role for dopamine in AB, and suggest specific dopamine-modulated functional connections between frontal, limbic, striatal, and brainstem regions mediate general reward AB versus alcohol AB.

Effects of carbohydrate and branched-chain amino acid beverage ingestion during acute upper body resistance exercise on performance and postexercise hormone response.

The purpose of this investigation was to examine the individual and combined effects of ingesting carbohydrates (CHO) and branched-chain amino acids (BCAA) during high-volume upper body resistance exercise (RE) on markers of catabolism and performance. Thirteen resistance-trained males completed 4 experimental trials with supplementation, ingesting beverages containing CHO, BCAA, CHO+BCAA, or placebo (PLA) in a randomized, double-blind design. The beverages were ingested in 118-mL servings 6 times during an ∼60-min RE session consisting of bench press, bent-over row, incline press, and close-grip row. Each RE was performed with 5 sets of repetitions at 65% 1-repetition maximum until volitional fatigue. Blood samples were collected at baseline, immediately postexercise, and 60 min postexercise to assess glucose and insulin. Cortisol was assessed immediately and at 60 min postexercise. No significant performance benefits were observed for any RE. CHO+BCAA (152.4 ± 71.4 ng/mL) resulted in the lowest cortisol levels, which was lower than BCAA and PLA (193.7 ± 88.5, 182.8 ± 67.5 ng/mL, p < 0.05), but not different from CHO (165 ± 76.5 ng/mL, p = 0.342). Postexercise insulin concentrations were significantly higher with CHO (4.79 ± 3.4 mU/L) compared with BCAA and PLA (3.7 ± 2.0, 3.5 ± 1.8 mU/L, p < 0.05), but not different from CHO+BCAA (4.3 ± 2.5 mU/L, p = 0.339). There was no treatment effect for glucose, but glucose significantly increased from baseline to immediately postexercise and significantly decreased at 60 min postexercise. Ingesting beverages containing CHO with or without BCAA during upper body resistance exercise may promote a more favorable postexercise less catabolic environment.

Do anabolic nutritional supplements stimulate human growth hormone secretion in elderly women with heart failure?

Growth hormone treatment has gained attention over the past decade as a treatment for heart failure. Human growth hormone (HGH) must be administered by injections (usually daily), so there is considerable advantage to stimulation of endogenous secretion by amino acid‐based nutritional supplementation. However, studies investigating the effect of amino acid (AA) supplementation show conflicting results. Therefore, in this study we aimed to investigate the effect of nutritional supplementation on HGH production in elderly women with heart failure. Eight elderly women with heart failure participated in this randomized cross‐over study. Plasma HGH concentration was measured before and for 4 h following ingestion of a mixture of protein, carbohydrate, and fat or an AA beverage. HGH concentration was determined with ELISA kits and AA concentrations were analyzed by Liquid Chromatography–Mass Spectrometry (LCMS). Linear mixed models was performed to analyze the effect of time, treatment, and interaction. Plasma arginine and lysine concentrations were significantly higher after consumption of the AA drink compared to the mixture of protein, carbohydrate, and fat. Nonetheless, only ingestion of the protein, carbohydrate, and fat mixture (meal replacement) increased HGH concentration. HGH concentration was increased in elderly women with heart failure following consumption of a meal replacement containing protein, carbohydrate, and fat. Consumption of a mixture of amino acids failed to increase HGH concentration despite significantly greater elevations in plasma amino acid concentrations, including arginine and lysine. The stimulatory effect of the protein/carbohydrate/fat mixture was presumably mediated by factors other than increases in free amino acid concentrations.

Age moderates the effect of acute dopamine depletion on passive avoidance learning

Despite extensive links between reinforcement-based learning and dopamine (DA), studies to date have not found consistent effects of acute DA reduction on reinforcement learning in both men and women. Here, we tested the effects of reducing DA on reward- and punishment-based learning using the deterministic passive avoidance learning (PAL) task. We tested 16 (5 female) adults (ages 22–40) in a randomized, cross-over design to determine whether reducing global DA by administering an amino acid beverage deficient in the DA precursors, phenylalanine and tyrosine (P/T[-]), would affect PAL task performance. We found that P/T[-] beverage effects on PAL performance were modulated by age. Specifically, we found that P/T depletion significantly improved learning from punishment with increasing participant age. Participants committed 1.49 fewer passive avoidance errors per additional year of age (95% CI, −0.71 – −2.27, r=−0.74, p=0.001). Moreover, P/T depletion improved learning from punishment in adults (ages 26–40) while it impaired learning from punishment in emerging adults (ages 22–25). We observed similar, but non-significant trends in learning from reward. While there was no overall effect of P/T-depletion on reaction time (RT), there was a relationship between the effect of P/T depletion on PAL performance and RT; those who responded more slowly on the P/T[-] beverage also made more errors on the P/T[-] beverage. When P/T-depletion slowed RT after a correct response, there was a worsening of PAL task performance; there was no similar relationship for the RT after an incorrect response and PAL task performance. Moreover, among emerging adults, changes in mood on the P/T[-] beverage negatively correlated with learning from reward on the P/T[-] beverage. Together, we found that both reward- and punishment-based learning are sensitive to central catecholamine levels, and that these effects of acute DA reduction vary with age.

The effect of an amino acid beverage on glucose response and glycogen replenishment after strenuous exercise.

We previously reported that an amino acid mixture (AA) was able to lower the glucose response to an oral glucose challenge in both rats and humans. Increased glucose uptake and glycogen storage in muscle might be associated with the faster blood glucose clearance. We therefore tested the effect of two different doses of AA provided with a carbohydrate supplement on blood glucose homeostasis and muscle glycogen replenishment in human subjects after strenuous aerobic exercise. Ten subjects received a carbohydrate (1.2g/kg body weight, CHO), CHO/HAA (CHO+13g AA), or CHO/LAA (CHO+6.5g AA) supplement immediately and 2h after an intense cycling bout. Muscle biopsies were performed immediately and 4h after exercise. The glucose responses for CHO/HAA and CHO/LAA during recovery were significantly lower than CHO, as was the glucose area under the curve (CHO/HAA 1259.9±27.7, CHO/LAA 1251.5±47.7, CHO 1376.8±52.9mmol/L 4h, p<0.05). Glycogen storage rate was significantly lower in CHO/HAA compared with CHO, while it did not differ significantly between CHO/LAA or CHO (CHO/HAA 15.4±2.0, CHO/LAA 18.1±2.0, CHO 21.5±1.4µmol/g wet muscle 4h). CHO/HAA caused a significantly higher insulin response and a greater effect on mTOR and Akt/PKB phosphorylation compared with CHO. Phosphorylation of AS160 and glycogen synthase did not differ across treatments. Likewise, there were no differences in blood lactate across treatments. The AA lowered the glucose response to a carbohydrate supplement after strenuous exercise. However, it was not effective in facilitating subsequent muscle glycogen storage.

Effects of Acute Dopamine Precusor Depletion on Immediate Reward Selection Bias and Working Memory Depend on Catechol-O-methyltransferase Genotype

Little agreement exists as to acute dopamine (DA) manipulation effects on intertemporal choice in humans. We previously found that catechol-O-methyltransferase (COMT) Val158Met genotype predicts individual differences in immediate reward selection bias among adults. Moreover, we and others have shown that the relationship between COMT genotype and immediate reward bias is inverted in adolescents. No previous pharmacology studies testing DA manipulation effects on intertemporal choice have accounted for COMT genotype, and many have included participants in the adolescent age range (18-21 years) as adults. Moreover, many studies have included female participants without strict cycle phase control, although recent evidence demonstrates that cyclic estradiol elevations interact with COMT genotype to affect DA-dependent cognition. These factors may have interacted with DA manipulations in past studies, potentially occluding detection of effects. Therefore, we predicted that, among healthy male adults (ages 22-40 years), frontal DA tone, as indexed by COMT genotype, would interact with acute changes in DA signaling to affect intertemporal choice. In a double-blind, placebo-controlled design, we decreased central DA via administration of an amino acid beverage deficient in the DA precursors, phenylalanine and tyrosine, and tested effects on immediate reward bias in a delay-discounting (DD) task and working memory (WM) in an n-back task. We found no main effect of beverage on DD or WM performance but did find significant beverage*genotype effects. These results suggest that the effect of DA manipulations on DD depends on individual differences in frontal DA tone, which may have impeded some past efforts to characterize DA's role in immediate reward bias in humans.

Dietary Tyrosine/Phenylalanine Depletion Effects on Behavioral and Brain Signatures of Human Motivational Processing

Dopamine (DA) neurotransmission is critical for motivational processing. We assessed whether disruption of DA synthesis in healthy controls using an amino-acid beverage devoid of catecholamine precursors (tyrosine-phenylalanine depletion (TPD)) would blunt recruitment of the nucleus accumbens (NAcc) by rewards. Sixteen controls ingested each of a tyr/phe-depleting beverage (DEP) or a tyr/phe-balanced (BAL) control beverage in two laboratory visits. Five hours after consumption of each drink, subjects underwent functional magnetic resonance imaging while they viewed anticipatory cues to respond to a target to either win money or avoid losing money. TPD did not exert main effects on mood or on task behavior, but affected brain activation. In right NAcc, TPD blunted activation by anticipation of high rewards. In left NAcc, recruitment anticipating high rewards was modulated by individual differences in mood change across the DEP drink day, where subjects whose mood worsened following TPD (relative to within-day mood change under BAL conditions) also showed lower activation under DEP conditions relative to BAL conditions. Exploratory analysis indicated that TPD qualitatively blunted the voxel-wise spatial extent of suprathreshold activation by reward anticipation. Finally, loss outcomes activated anterior insula under DEP conditions but not under BAL conditions. These data indicate that: (1) dietary depletion of catacholamine precursors will blunt dopaminergic mesolimbic activity, and (2) in controls, synthetic pathways of this neurocircuitry maintain sufficient buffering capacity to resist an effect on motivated behavior. Additional studies are needed to determine if clinical populations would show similar resistance to behavioral effects of TPD.

The effect of acute tyrosine phenylalanine depletion on emotion-based decision-making in healthy adults

Despite interest in dopamine's role in emotion-based decision-making, few reports of the effects of dopamine manipulations are available in this area in humans. This study investigates dopamine's role in emotion-based decision-making through a common measure of this construct, the Iowa Gambling Task (IGT), using Acute Tyrosine Phenylalanine Depletion (ATPD). In a between-subjects design, 40 healthy adults were randomized to receive either an ATPD beverage or a balanced amino acid beverage (a control) prior to completing the IGT, as well as pre- and post-manipulation blood draws for the neurohormone prolactin. Together with conventional IGT performance metrics, choice selections and response latencies were examined separately for good and bad choices before and after several key punishment events. Changes in response latencies were also used to predict total task performance. Prolactin levels increased significantly in the ATPD group but not in the control group. However, no significant group differences in performance metrics were detected, nor were there sex differences in outcome measures. However, the balanced group's bad deck latencies speeded up across the task, while the ATPD group's latencies remained adaptively hesitant. Additionally, modulation of latencies to the bad decks predicted total score for the ATPD group only. One interpretation is that ATPD subtly attenuated reward salience and altered the approach by which individuals achieved successful performance, without resulting in frank group differences in task performance.

Acute tryptophan depletion in accordance with body weight: influx of amino acids across the blood–brain barrier

Acute tryptophan depletion (ATD) is a method of reducing central nervous serotonin (5-HT) synthesis in humans by administering an amino acid (AA) beverage lacking in tryptophan (TRP), the physiological precursor of 5-HT. However, to date, the use of conventional ATD protocols in children and adolescents was limited due to frequently observed side effects (e.g., vomiting and nausea). This study investigated the effects of diminished central nervous system 5-HT synthesis on plasma concentrations of relevant AAs and TRP influx into the brain in 24 healthy young adults using the ATD procedure Moja-De, a test protocol that has been used in preliminary research in youths. Twenty-four healthy participants received ATD and a TRP-balanced amino acid load (BAL) using a randomized double-blind within-subject crossover design. Plasma concentrations of the relevant AAs that compete with TRP on the same transport system were assessed at baseline and 90, 180, and 240 min after ATD/BAL intake. TRP influx across the blood–brain barrier was calculated using Michaelis–Menten kinetics with a correction for multiple substrate competition, indicating a significant decrease in TRP influx into the central nervous system under Moja-De. ATD Moja-De decreased TRP influx into the brain and central nervous system 5-HT synthesis safely and effectively and was well tolerated, allowing it to be used in children and adolescents. Future research into other secondary, compensatory effects induced by ATD in patients with neuropsychiatric disorders and healthy populations is needed. ATD Moja-De allows this type of research with a focus on a developmental viewpoint.Electronic supplementary materialThe online version of this article (doi:10.1007/s00702-012-0793-z) contains supplementary material, which is available to authorized users.

The Effects of Acute Tryptophan Depletion on Reactive Aggression in Adults with Attention-Deficit/Hyperactivity Disorder (ADHD) and Healthy Controls

BackgroundThe neurotransmitter serotonin (5-HT) has been linked to the underlying neurobiology of aggressive behavior, particularly with evidence from studies in animals and humans. However, the underlying neurobiology of aggression remains unclear in the context of attention-deficit/hyperactivity disorder (ADHD), a disorder known to be associated with aggression and impulsivity. We investigated the effects of acute tryptophan depletion (ATD), and the resulting diminished central nervous serotonergic neurotransmission, on reactive aggression in healthy controls and adults with ADHD.Methodology/Principal FindingsTwenty male patients with ADHD and twenty healthy male controls were subjected to ATD with an amino acid (AA) beverage that lacked tryptophan (TRP, the physiological precursor of 5-HT) and a TRP-balanced AA beverage (BAL) in a double-blind, within-subject crossover-study over two study days. We assessed reactive aggression 3.25 hours after ATD/BAL intake using a point-subtraction aggression game (PSAG) in which participants played for points against a fictitious opponent. Point subtraction was taken as a measure for reactive aggression. Lowered rates of reactive aggression were found in the ADHD group under ATD after low provocation (LP), with controls showing the opposite effect. In patients with ADHD, trait-impulsivity was negatively correlated with the ATD effect on reactive aggression after LP. Statistical power was limited due to large standard deviations observed in the data on point subtraction, which may limit the use of this particular paradigm in adults with ADHD.Conclusions/SignificanceTogether with previous findings, the data provide preliminary evidence of an inverse association between trait-impulsivity and the ATD effect on reactive aggression after LP (as assessed by the PSAG) in patients with ADHD and that this relationship can be found in both adolescents and adults. Because of limited statistical power larger sample sizes are needed to find main effects of ATD/BAL administration on reactive aggression in adults with ADHD.

Effects of acute combined serotonin and dopamine depletion on cue-induced drinking intention/desire and cognitive function in patients with alcohol dependence

BackgroundAlcohol cues can precipitate the desire to drink and cause relapse in recovering alcohol-dependent patients. Serotonin and dopamine may play a role in alcohol cue-induced craving. Acute combined tryptophan (Trp), tyrosine (Tyr), and phenylalanine (Phe) depletion (CMD) in the diet attenuates the synthesis of serotonin and dopamine in the human brain. However, no study of the effects of acute CMD has been previously conducted. Therefore, we investigated whether the attenuation of serotonin and dopamine synthesis changes cue-induced alcohol craving in recently abstinent alcoholics. MethodsIn this double-blind, randomized, placebo-controlled, crossover design, 12 male patients who met the Diagnostic and Statistical Manual of Mental Disorders, 4th edition, criteria for alcohol dependence were divided into two conditions: (1) monoamine depletion (i.e., consumption of a concentrated amino acid beverage that resulted in a rapid and significant decrease in plasma-free Tyr/Phe/Trp) and (2) balanced condition (i.e., consumption of a similar beverage that contained Tyr/Phe/Trp). The participants were scheduled for two experimental sessions, with an interval of ≥7 days. The cue-induced craving test session was conducted 6h after each amino acid beverage administration. Drinking urge, blood pressure, heart rate, working memory, and attention/psychomotor performance were assessed before and after administration. ResultsCompared with the balanced condition, the monoamine depletion condition significantly increased drinking intention/desire and diastolic blood pressure. Cognitive performance was not different between the two conditions. ConclusionsAcute combined serotonin and dopamine depletion may increase drinking intention/desire and diastolic blood pressure without influencing cognitive function.

Effect Of an Amino Acid Supplement on Glucose Tolerance in Healthy Overweight Adults

It is estimated that two-thirds of the adult population and a growing number of children in US are overweight or obese. Overweight is considered the single strongest predictor of type 2 diabetes, which is primarily characterized by insulin resistance and hyperglycemia. Amino acids, such as leucine and isoleucine, have been shown to improve blood glucose tolerance in rats. PURPOSE: To determine whether an amino acid mixture could improve the blood glucose clearance of healthy overweight men and women following an oral glucose tolerance test (OGTT). METHODS: Twenty-two overweight healthy subjects (31±2 yrs, BMI 34.6±1.1 kg/m2) completed two OGTT after consuming two different test beverages. The amino acid beverage (CHO/AA) contained 12.395g amino acid mixture consisting of isoleucine, leucine, cystine 2HCl, methionine and valine in a 12 oz solution. The control beverage (CHO) consisted of a 12 oz placebo drink. Both beverages were mixed with a 10 oz orange-flavored drink containing 100g dextrose to make a drink totaling 22 oz. Venous blood samples were drawn 10min before the drinks, and 15, 30, 60, 120 and 180min after the drinks. RESULTS: During the OGTT, the plasma glucose response for the CHO/AA treatment was significantly lower than that of the CHO treatment, which was supported by the finding that the glucose AUC for the CHO/AA treatment was significantly lower than that for the CHO treatment (806.9±31.4 vs. 942.6±40.6 mmol/L/3h, p<0.05). The plasma glucose levels were significantly lower during the CHO/AA treatment than the CHO treatment at 30, 60, 120, and 180 min post supplementation (5.4±0.2 vs. 6.3±0.2, 4.7±0.3 vs. 5.6±0.4, 4.2±0.2 vs. 4.9±0.3, 3.9±0.2 vs. 4.4±0.2 mmol/L, respectively, p<0.05). However, there were no significant differences in plasma insulin (p=0.343) and c-peptide (p=0.079) responses between treatments. A significant treatment effect was found in plasma glucagon (p<0.05). The amino acid mixture had no significant effects on plasma FFA, triglyceride, and lactate. CONCLUSION: An amino acid mixture, composed of 5 amino acids, lowers the glucose response to an OGTT in healthy overweight subjects in an insulin-independent manner. Supported by Abbott Laboratories.

Effects Of Branch-chain Amino Acids And Arginine Drink On Post-exercise Metabolic Response

Chia-Jung Chung, Yi-An Lin, Mei-Chich Hsu National Taiwan Sport University, Taoyuan, Taiwan Branched-chain amino acid (BCAA) has been reported to increase the endurance exercise capacity, increase protein synthesis, decrease rating of perceived exertion and mental fatigue, attenuate muscle protein breakdown induced by exercise, and promote recovery from the damage. However, the effects of the combined BCAA and arginine beverage on post-exercise metabolic response have yet to be elucidated. PURPOSE: This study was to investigate the effects of branched-chain amino acid and arginine combined beverage (BA) on acute metabolic responses during recovery after a single bout of exhaustive exercise. METHODS: Fourteen healthy males were assigned to drink either BA or placebo (PL) on two sessions separated by 2 weeks. Blood samples of each subject were collected before exercise, and 0, 10, 20, 40, 60, 120 min and 24 hr after exercise, respectively. RESULTS: There were no significant differences in the levels of lactate, ammonia, creatine kinase, and glycerol between the two groups were observed at any of the time points. However, the blood glucose was significantly higher in the BA trial as compared to that in the PL trial at the 40 and 60-min recovery period (94.7 ± 4.5 mg/dL vs. 83.1 ± 2.8 mg/dL, p<0.05). The insulin concentration was higher in the BA trial as compared to that in the PL trial at the 40 and 60-min recovery period (31.6 ± 5.6 μU/mL vs. 15.5 ± 2.6 μU/mL, 30.1 ± 7.1 μU/mL vs. 10.6 ± 1.1 μU/ mL, p<0.05). Furthermore, the free fatty acid levels at the 60 and 120-min recovery period were significantly lower in the BA trial compared to that in the PL trial (0.18 ± 0.22 mmol/L vs. 0.3 ± 0.1 mmol/L, 0.4 ± 0.1 mmol/L vs. 0.6 ± 0.1 mmol/L, p<0.05). CONCLUSION: Consuming amino acid compound beverage during recovery period could increase blood glucose and insulin concentrations, and increase free fatty acid availability in muscle. Thus, branched-chain amino acid and arginine combined beverage supplementation may benefit recovery after exercise.

The effects of alcohol on laboratory-measured impulsivity after l-Tryptophan depletion or loading

Indirect evidence supports a link between serotonergic activity and individual differences in the behavioral response to alcohol, but few studies have experimentally demonstrated that an individual's biological state can influence the sensitivity to alcohol-induced behaviors. Our purpose was to temporarily modify serotonin synthesis in healthy individuals to determine how altered biological states may interact with alcohol administration to affect impulsive behavior. In a repeated-measures design, 18 normal controls consumed a 50-g L: -tryptophan (Trp) depleting (ATD) or loading (ATL) amino-acid beverage that temporarily decreased or increased (respectively) serotonin synthesis before receiving either a moderate dose of alcohol (0.65 g/kg) or placebo. All participants completed three impulsivity testing sessions on each of the five experimental days. Session one was a baseline session. Session two included testing after ATD-only or ATL-only. Session three included: (1) placebo after ATL (ATL+PBO); (2) placebo after ATD (ATD+PBO); (3) alcohol after ATL (ATL+ALC); (4) alcohol after ATD (ATD+ALC); and (5) Alcohol-only conditions. Impulsivity was assessed using the Immediate Memory Task (Dougherty et al., Behav Res Methods Instrum Comput 34:391-398, 2002), a continuous performance test yielding commission errors that have been previously validated as a component of impulsive behavior. Primary findings were that ATD-only increased impulsive responding compared to ATL-only, and ATD+ALC increased commission errors to levels higher than either the ATL+ALC or Alcohol-only conditions. These findings demonstrate that reduced serotonin synthesis can produce increased impulsivity even among non-impulsive normal controls, and that the behavioral effects of alcohol are, in part, dependent on this biological state.

Branched Chain Amino Acid Supplementation and Exercise Performance

PURPOSE: To determine whether consumption of an iso-caloric carbohydrate and branched-chain amino acid (BCAA) beverage versus a carbohydrate-only (CHO) beverage affects endurance cycling performance, fuel use, and blood glucose and lactate concentrations. METHODS: Eight competitive male cyclists and triathletes (29.9 ± 2.7 yrs) cycled at 75% VO2max for 90 minutes followed by a ride to exhaustion at 85% VO2max. Exercise started 2–3 hours after standardized breakfast, diet was controlled for the 12 hours prior to exercise and subjects were well rested to ensure adequate glycogen stores. Subjects consumed 7ml/kg body weight of double-blinded and randomly assigned, CHO (3.6%) plus BCAA (0.8%) or CHO only (4.6%) beverage before and after exercise and 1.8ml/kg body weight every 15 minutes during exercise. Oxygen consumption(VOA respiratory exchange ratio (RER), rate of perceived exertion (RPE), heart rate (HR), blood glucose, lactate and hematocrit concentrations were collected 15 minutes before, every 15 minutes during, and immediately following exercise. Time to exhaustion was measured as the time cycled before dropping below 60 rpm. RESULTS: Body weight (CHO + BCAA = 74.7 ± 5.7 kg vs. CHO only = 74.7 ± 5.6 kg), % body fat (CHO + BCAA =9.8 ±1.7% vs. CHO only = 9.5 ± 1.5%) and VO2max (CHO + BCAA = 59.0 ± 2.8 ml/kg/min vs. CHO only = 59.5 ± 3.0 ml/kg/ min) did not change significantly (p >0.05) between the two beverage protocols. Time to exhaustion was not significantly (p >0.05) different between the two treatments (CHO + BCAA = 15.8 ±2.9 min vs. CHO only = 14.9 ± 3.2 min). There was also no significant difference between the groups in VO2, RER, RPE, HR, glucose, lactate or hematocrit concentrations at rest or during exercise. CONCLUSIONS: Although ingestion of an isocaloric branched chain amino acid plus carbohydrate solution before and during prolonged exercise was able to adequately maintain blood glucose homeostasis, exercise performance, measured by time to exhaustion, was not significantly different compared to ingestion of a carbohydrate only solution.