Forgot your password?
New user?
New Window Opens on the Secret Life of Microbes: Scientists Develop First Microbial Profiles of Ecosystems
CAS announces the release of SciFinder Scholar for Mac OS X
Press Releases
Press Releases
| Check out our New Publishers' Select for Free Articles |
Amino Acids: The Forum for Amino Acid, Peptide and Protein Research (v.20, #1)
Plasma lactate, GH and GH-binding protein levels in exercise following BCAA supplementation in athletes by E. F. De Palo; R. Gatti; E. Cappellin; C. Schiraldi; C. B. De Palo; P. Spinella (pp. 1-11).
Branched chain amino acids (BCAA) stimulate protein synthesis, and growth hormone (GH) is a mediator in this process. A pre-exercise BCAA ingestion increases muscle BCAA uptake and use. Therefore after one month of chronic BCAA treatment (0.2 g kg−1 of body weight), the effects of a pre-exercise oral supplementation of BCAA (9.64 g) on the plasma lactate (La) were examined in triathletes, before and after 60 min of physical exercise (75% of VO2max). The plasma levels of GH (pGH) and of growth hormone binding protein (pGHBP) were also studied. The end-exercise La of each athlete was higher than basal. Furthermore, after the chronic BCAA treatment, these end-exercise levels were lower than before this treatment (8.6 ± 0.8 mmol L−1 after vs 12.8 ± 1.0 mmol L−1 before treatment; p < 0.05 [mean ± std. err.]). The end-exercise pGH of each athlete was higher than basal (p < 0.05). Furthermore, after the chronic treatment, this end-exercise pGH was higher (but not significantly, p = 0.08) than before this treatment (12.2 ± 2.0 ng mL−1 before vs 33.8 ± 13.6 ng mL−1 after treatment). The end-exercise pGHBP was higher than basal (p < 0.05); and after the BCAA chronic treatment, this end-exercise pGHBP was 738 ± 85 pmol L−1 before vs 1691 ± 555 pmol L−1 after. pGH/pGHBP ratio was unchanged in each athlete and between the groups, but a tendency to increase was observed at end-exercise.The lower La at the end of an intense muscular exercise may reflect an improvement of BCAA use, due to the BCAA chronic treatment. The chronic BCAA effects on pGH and pGHBP might suggest an improvement of muscle activity through protein synthesis.
Keywords: Keywords: Amino acids; Growth hormone binding protein (GHBP); Branched-chain amino acids (BCAA); Physical exercise; Lactic acid
Changes in plasma and urinary taurine and amino acids in runners immediately and 24 h after a marathon by C. Cuisinier; R. J. Ward; M. Francaux; X. Sturbois; P. de Witte (pp. 13-23).
Changes in urinary and plasma taurine and amino acids have been evaluated in trained runners competing in the Rotterdam Marathon, 1998, both immediately after completing the event and 24 h after recovery. There were significant changes in the urinary amino acids excretion, the majority showing a significant decrease both immediately at the completion of the Marathon and after 24 h recovery. In contrast urinary taurine excretion increased immediately post Marathon, although not significantly as the range of results was wide. Such changes in urinary taurine correlated with percentage changes in plasma creatine kinase both immediately post race, (r = 0.972, P < 0.001), and 24 h later (r = 0.872, P < 0.001), possibly indicating that the source of the taurine was muscle. Significant correlations between the individual values for urinary and plasma amino acids in all of the athletes were calculated for taurine (r = 0.528), glycine (r = 0.853), threonine (r = 0.749), alanine (r = 0.747), serine (r = 0.620), glutamine (0.614), arginine (r = 0.507), histidine (r = 0.470) and valine (r = 0.486).Changes in the mean plasma concentrations of amino acids were comparable to our previously published data (Ward et al., 1999) the majority showing significant decreases immediately and 24 h post Marathon, such an adaptation being due primarily to their utilisation for gluconeogenesis. However, in contrast, the mean taurine concentrations were significantly elevated both post race, P < 0.01 and after 24 h, P < 0.05.The physiological response by the muscle to exhaustive exercise, particularly with regard to changes in plasma and urinary taurine concentrations remain to be elucidated, but is probably related to muscle function impairment. The increase in taurine urinary excretion could be used as an indicator of muscle damage occurring during exhaustive exercise. Whether taurine supplementation would minimise such changes is an interesting scientific question and merits investigation.
Keywords: Keywords: Amino acids; Taurine; Exercise; Urine; Plasma
Amino acids and central fatigue by E. Blomstrand (pp. 25-34).
There is an increasing interest in the mechanisms behind central fatigue, particularly in relation to changes in brain monoamine metabolism and the influence of specific amino acids on fatigue. Several studies in experimental animals have shown that physical exercise increases the synthesis and metabolism of brain 5-hydroxytryptamine (5-HT). Support for the involvement of 5-HT in fatigue can be found in studies where the brain concentration of 5-HT has been altered by means of pharmacological agents. When the 5-HT level was elevated in this way the performance was impaired in both rats and human subjects, and in accordance with this a decrease in the 5-HT level caused an improvement in running performance in rats. The precursor of 5-HT is the amino acid tryptophan and the synthesis of 5-HT in the brain is thought to be regulated by the blood supply of free tryptophan in relation to other large neutral amino acids (including the branched-chain amino acids, BCAA) since these compete with tryptophan for transport into the brain. Studies in human subjects have shown that the plasma ratio of free tryptophan/BCAA increases during and, particularly, after sustained exercise. This would favour the transport of tryptophan into the brain and also the synthesis and release of 5-HT which may lead to central fatigue. Attempts have been made to influence the 5-HT level by giving BCAA to human subjects during different types of sustained heavy exercise. The results indicate that ingestion of BCAA reduces the perceived exertion and mental fatigue during exercise and improves cognitive performance after the exercise. In addition, in some situations ingestion of BCAA might also improve physical performance; during exercise in the heat or in a competitive race when the central component of fatigue is assumed to be more pronounced than in a laboratory experiment. However, more experiments are needed to further clarify the effect of BCAA and also of tryptophan ingestion on physical performance and mental fatigue.
Keywords: Keywords: Amino acids; Branched-chain amino acids; Central fatigue; Performance
Influence of exercise on serotonergic neuromodulation in the brain by H. Weicker; H. K. Strüder (pp. 35-47).
Implications of exercise on serotonergic neuromodulation in the brain have been investigated in two studies. Acute paroxetine (selective serotonin (5-HT) reuptake inhibitor) administration to endurance athletes, who performed a cycle ergometer test to exhaustion at moderate intensity, reduced time to exhaustion and post exercise cognitive performance in comparison to trials with placebo or BCAA administration. Furthermore, during a 3-week moderate endurance training of sedentary males basaline values of Bmax of 5-HT transporters (5-HTT) and 5-HT2A receptors (5-HT2AR) on isolated platelet membranes increased while plasma prolactin (PRL) concentrations decreased as well as mood and physical efficiency improved. In contrast, after an excessive training program over four weeks, well-trained endurance athletes showed no change of Bmax of 5-HTT, but a decline of 5-HT2AR density and an increase in basal plasma PRL concentration. Mood was impaired and central fatigue increased. Thus, the impact of exercise on 5-HT neurotransmission may depend on training state of athletes and extent of exertion. The theoretical background of the implication of exercise and the effect of long lasting exhaustive exercise in athletes on mental and physical efficiency or central fatigue are evaluated. The significance of the primary disturbance of central neuromodulation and dysfunction of 5-HTT, 5-HT receptor subtypes and the phosphoinositol signal transduction as well as the limited modulation capacity of the 5-HT system in overstrain are also addressed.
Keywords: Keywords: Amino acids; 5-HT transporter; 5-HT2A receptor; 5-HT reuptake inhibition; Overstrain
The relation between glutamine and the immunodepression observed in exercise by L. M. Castell; E. A. Newsholme (pp. 49-61).
Glutamine is the most abundant amino acid in the body. It is an important fuel for some key cells of the immune system. Both the plasma concentration of glutamine and the functional ability of immune cells in the blood are decreased after prolonged, exhaustive exercise. Glutamine feeding has had beneficial effects in clinical situations, and the provision of glutamine after intensive exercise has decreased the incidence of infections, particularly of upper respiratory tract infections. However, the precise effect of glutamine on immunodepression in this situation is not yet established.
Keywords: Keywords: Amino acids; Glutamine; Exhaustive exercise; Immunodepression
Readiness potential in different states of physical activation and after ingestion of taurine and/or caffeine containing drinks by T. Barthel; D. Mechau; T. Wehr; R. Schnittker; H. Liesen; M. Weiß (pp. 63-73).
To investigate the influence of taurine and caffeine containing drinks and physical stress on the cortical movement-preparation, the readiness potentials or "Bereitschaftspotentiale" (BPs), preceding voluntary self-placed pedalling movements, were examined after different states of exhaustion on an ergometer. 15 (13 right-handed) healthy men, aged between 22–30, participated in a randomised, cross over, double-blind, placebo controlled study.BPs were averaged out of artefact free EEG-segments from more than 90 triggered events, measured at 17 electrodes of the 10 : 20 system. With increasing effort the BPs were enlarged differently depending on the drink consumed. In placebo trials after exhaustive exercise premovement negative potential curves could be seen even in frontal areas. With caffeine the BPs increased after lower workload, achieving a level, which was reached in the placebo trials only after submaximal physical activation. Furthermore a significant shortening of premovement-brain-potentials in frontal and parietal regions could be seen in the caffeine trials at rest. Taurine admixture seems to inhibit this effects.
Keywords: Keywords: Amino acids; Bereitschaftspotential; Readiness potential; Movement-preparation; Taurine; Caffeine; Exercise
The influence of a taurine containing drink on cardiac parameters before and after exercise measured by echocardiography by M. Baum; M. Weiß (pp. 75-82).
To determine the effect of the taurine containing drink "Red Bull" on cardiac parameters thirteen endurance trained subjects performed an exhaustive bout of endurance exercise at three different times. Prior to the exercise the original "Red Bull" drink, a similar drink without taurine, containing caffeine, and a "placebo" drink without caffeine and without taurine were ingested by the subjects in a double-blind cross-over design. Echocardiographic examinations were performed before the drinks, 40 minutes after the drinks prior to the exercise and in the regeneration period after exercise. Stroke volume was significantly influenced only in the "Red Bull group" (80,4 ± 21,4 ml before drink vs. 97,5 ± 26,2 ml in the regeneration period), mainly due to a reduced endsystolic diameter and volume. Furthermore in this group the peak late diastolic inflow (VA) in the regeneration period was significantly higher compared with the pre-exercise levels. This observation was also made in the caffeine group but without any consequences on ventricular function. The results of the present study show an influence of the original caffeine and taurine containing drink (Red Bull) on parameters of the cardiac contractility.
Keywords: Keywords: Amino acids; Taurine; Caffeine; Exercise; Echocardiographic measurements
Beneficial effects of an "energy drink" given to sleepy drivers by J. A. Horne; L. A. Reyner (pp. 83-89).
500 ml of a glucose based "energy" drink versus a control without the active ingredients (caffeine, taurine, glucuronolactone) were given double blind to 11 sleepy participants driving an interactive real-car driving simulator. Lane drifting and a secondary task (reaction time) were measured for two hours post-treatment. The energy drink significantly improved both indices, particularly for the first hour.
Keywords: Keywords: Amino acids; Energy drink; Caffeine; Taurine; Sleepiness; Driving