Gene/Protein Disease Symptom Drug Enzyme Compound
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Query: UMLS:C0015672 (fatigue)
 51,768 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

The neurotransmitter serotonin (5-hydroxytryptamine, 5-HT) has been shown to modulate various physiological and psychological functions such as fatigue. Altered regulation of the serotonergic system has been suggested to play a role in response to exercise stress. In the present study, the influence was investigated of acute endurance exercise and short-term increase in the amount of training on the concentrations of the 5-HT precursor tryptophan (TRP), of prolactin (PRL) and of branched-chain amino acids (BCAA) in the blood, as well as on the binding of [3H]ketanserin to the serotonin-2A (5-HT2A) receptors on platelets. Nine healthy endurance-trained men were tested the day before (I) and after (II) a 9-day training programme. Samples of venous blood were drawn after an overnight fast and following 5 h of cycling. Fasted and post-exercise plasma concentrations of free TRP, BCAA and free TRP:BCAA ratio did not differ between I and II. A significant decrease of plasma BCAA (P < 0.01) and significant augmentations of plasma free TRP, free TRP:BCAA ratio and PRL (P < 0.01) were found post-exercise. The increase in plasma PRL was smaller in II compared with I. Acute endurance exercise reduced the density of platelet 5-HT2A receptor [3H]ketanserin binding sites at I and II (P < 0.05). The basal density of the binding sites and the affinity of [3H]ketanserin for these binding sites were unaffected by an increase in the amount of training. The present results support the hypothesis that acute endurance exercise may increase 5-HT availability. This was reflected in the periphery by increased concentration of the 5-HT precursor free TRP, by increased plasma PRL concentration, and by a reduction of 5-HT2A receptors on platelets. It remains to be resolved whether these alterations in the periphery occur in parallel with an increase in the availability of 5-HT in the brain.
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PMID:Effect of acute and chronic exercise on plasma amino acids and prolactin concentrations and on [3H]ketanserin binding to serotonin2A receptors on human platelets. 1009 Jun 30

The seasonal pattern of L-tryptophan was studied in a Fairbanks, Alaska, population that was unadapted to the extreme light variations of the North. Previously, this population was shown to exhibit seasonal behavior effects such as increases in fatigue and sleep duration, as well as endocrine effects such as increases in melatonin levels and phase shifting. Caloric and macronutrient intake have been reported to vary seasonally in humans, thereby potentially influencing the plasma levels of L-tryptophan, which is a precursor of serotonin and melatonin. Plasma levels of L-tryptophan from volunteers, whose average duration of stay in Alaska was eight months, were determined by automated amino acid analysis. Prominent results included finding increased levels in the winter at several different diurnal time points. These findings support hypotheses which relate underlying physiological adaptations to the North to the increased incidence of behavioral disorders such as depression and alcoholism.
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PMID:Seasonal variation of the amino acid, L-tryptophan, in interior Alaska. 1009 12

There is some evidence that the neurotransmitter serotonin (5-hydroxytryptamine; 5-HT) may be involved in the pathogenesis of seasonal affective disorder (SAD). Short-term tryptophan (TRP) depletion was carried out in 18 drug-free remitted patients who met DSM-IV criteria for SAD. Behavioral effects were measured with the Hamilton Depression Rating Scale (HDRS) both 24 h before and 24 h after TRP depletion. Some of the patients showed behavioral responses such as lowered mood, feelings of guilt, loss of interest, agitation, loss of energy, fatigue, social withdrawal, increased appetite, and carbohydrate craving. It was the aim of our study to investigate whether the genotypes of the serotonin transporter gene were associated with symptoms of transient depressive relapse after TRP depletion. In addition, we matched the SAD patients with healthy control subjects to see if alleles and genotypes of the serotonin transporter gene were associated with SAD. High molecular weight DNA was isolated from peripheral blood leukocytes using standard methods. For the 5-HTT receptor gene, a 17-bp repetitive element of intron 2 was genotyped (variable number tandem repeat, VNTR). Alterations in HDRS scores after TRP depletion showed no significant association with alleles or genotypes of the 5-HTT gene, although heterozygotes showed a trend toward increased HDRS scores. The serotonin transporter is known to play a critical role in the termination of serotonergic neurotransmission by sodium-dependent uptake of 5-HT into the presynaptic neuron. The present study in a small group of SAD patients was unable to demonstrate that the 5-HTT gene plays a role in the pathogenesis of SAD or in short-term depressive relapse after TRP depletion.
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PMID:Behavioral effects of tryptophan depletion in seasonal affective disorder associated with the serotonin transporter gene? 1033 77

Although current research suggests that individuals involved in either high-intensity resistance or endurance exercise may have an increased need for dietary protein, the available research is either equivocal or negative relative to the ergogenic effects of supplementation with individual amino acids. Although some research suggests that the induction of hyperaminoacidemia via intravenous infusion of a balanced amino acid mixture may induce an increased muscle protein synthesis after exercise, no data support the finding that oral supplementation with amino acids, in contrast to dietary protein, as the source of amino acids is more effective. Some well-controlled studies suggest that aspartate salt supplementation may enhance endurance performance, but other studies do not, meriting additional research. Current data, including results for several well-controlled studies, indicated that supplementation with arginine, ornithine, or lysine, either separately or in combination, does not enhance the effect of exercise stimulation on either hGH or various measures of muscular strength or power in experienced weightlifters. Plasma levels of BCAA and tryptophan may play important roles in the cause of central fatigue during exercise, but the effects of BCAA or tryptophan supplementation do not seem to be effective ergogenics for endurance exercise performance, particularly when compared with carbohydrate supplementation, a more natural choice. Although glutamine supplementation may increase plasma glutamine levels, its effect on enhancement of the immune system and prevention of adverse effects of the overtraining syndrome are equivocal. Glycine, a precursor for creatine, does not seem to possess the ergogenic potential of creatine supplementation. Research with metabolic by-products of amino acid metabolism is in its infancy, and current research findings are equivocal relative to ergogenic applications. In general, physically active individuals are advised to obtain necessary amino acids through consumption of natural, high-quality protein foods.
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PMID:Facts and fallacies of purported ergogenic amino acid supplements. 1041 Aug 46

A recent major theory was that a meal high in carbohydrate increased the rate that tryptophan enters the brain, leading to an increase in the level of the neurotransmitter serotonin that modulates mood. Although such a mechanism may be important under laboratory conditions it is unlikely to be of significance following the eating of any typical meal. As little as 2-4% of the calories of a meal as protein will prevent an increased availability of tryptophan. Arguably the food with the greatest impact on mood is chocolate. Those who crave chocolate tend to do so when they feel emotionally low. There have been a series of suggestions that chocolate's mood elevating properties reflect 'drug-like' constituents including anandamines, caffeine, phenylethylamine and magnesium. However, the levels of these substances are so low as to preclude such influences. As all palatable foods stimulate endorphin release in the brain this is the most likely mechanism to account for the elevation of mood. A deficiency of many vitamins is associated with psychological symptoms. In some elderly patients folate deficiency is associated with depression. In four double-blind studies an improvement in thiamine status was associated with improved mood. Iron deficiency anaemia is common, particularly in women, and is associated with apathy, depression and rapid fatigue when exercising.
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PMID:The effects of nutrients on mood. 1061 80

We determined the participation of the cellular compartment in the changes of plasma amino acid concentrations during maximal exercise test on a cycle ergometer. Following an overnight fast, male athletes were submitted to a maximal exercise test until fatigue (for 25 min approximately) to determine maximal oxygen uptake. The amino acid concentrations in total blood, plasma, and blood cells were determined before and after the maximal exercise test. Most essential amino acids were decreased significantly in the total blood concentration as a result of the maximal exercise test. However, the concentrations of most nonessential amino acids tended to be significantly increased. Amino acid concentration was increased most in plasma. Concentrations of blood cell alanine and proline were significantly increased by 26% and 15%, respectively, after the maximal exercise test. No significant differences in blood cell concentrations of other amino acids induced by the exercise test were found, although the amount of tryptophan in blood cells was increased after exhaustive exercise.
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PMID:Participation of blood cells in the changes of blood amino acid concentrations during maximal exercise. 1071 92

Tryptophan is the precursor for the neurotransmitter 5-hydroxytryptamine (5-HT), which is involved in fatigue and sleep. It is present in bound and free from in the blood, where the concentration is controlled by albumin binding to tryptophan. An increase in plasma free tryptophan leads to an increased rate of entry of tryptophan into the brain. This should lead to a higher level of 5-HT which may cause central fatigue. Central fatigue is implicated in clinical conditions such as chronic fatigue syndrome and post-operative fatigue. Increased plasma free tryptophan leads to an increase in the plasma concentration ratio of free tryptophan to the branched chain amino acids (BCAA) which compete with tryptophan for entry into the brain across the blood-brain barrier. The plasma concentrations of these amino acids were measured in chronic fatigue syndrome patients (CFS) before and after exercise (Castell et al., 1998), and in patients undergoing major surgery (Yamamoto et al., 1997). In the CFS patients, the pre-exercise concentration of plasma free tryptophan was higher than in controls (p < 0.05) but did not change during or after exercise. This might indicate an abnormally high level of brain 5-HT in CFS patients leading to persistent fatigue. In the control group, plasma free tryptophan was increased after maximal exercise (p < 0.001), returning towards baseline levels 60 min later. The apparent failure of the CFS patients to change the plasma free tryptophan concentration or the free tryptophan/BCAA ratio during exercise may indicate increased sensitivity of brain 5-HT receptors, as has been demonstrated in other studies (Cleare et al., 1995). In post-operative recovery after major surgery plasma free tryptophan concentrations were markedly increased compared with baseline levels; the plasma free tryptophan/BCAA concentration ratio was also increased after surgery. Plasma albumin concentrations were decreased after surgery: this may account for the increase in plasma free tryptophan levels. Provision of BCAA has improved mental performance in athletes after endurance exercise (Blomstrand et al., 1995, 1997). It is suggested that BCAA supplementation may help to counteract the effects of an increase in plasma free tryptophan, and may thus improve the status of patients during or after some clinically stressful conditions.
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PMID:The role of tryptophan in fatigue in different conditions of stress. 1072 Nov 21

Nagase genetically analbuminemic rats (NAR) were run to fatigue. Administration of branched chain amino acids (BCAA) before exhaustive exercise, resulted in a post-fatigue decreased tryptophan uptake (-22%, p < 0.05) and 5-hydroxytryptophan (5-HTP) uptake (-29%, p < 0.01) into the synaptosomes isolated from the striatum when compared with saline administration. At the same time, NAR who received either BCAA or 2-aminobicyclo[2,2,1]heptane-2-carboxylic acid (BCH, a specific inhibitor for the L-system transporter) had a considerably prolonged run time to exhaustion (by twofold), compared to those who received either saline or albumin treatments. When classified by run time, it was of interest that, when the data for BCAA and BCH treatments for the longer run time NAR (Group B) was combined, it gave rise to a significant decrease in synaptosomal tryptophan and 5-HTP of a similar magnitude to that observed with BCAA alone. These levels were lower than those observed in NAR in the shorter run time group (Group A) for all treatments. These results support the view that an activated serotonergic function may be involved in central fatigue, which can be diminished by inhibition of the L-system transporter.
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PMID:Diminished central fatigue by inhibition of the L-system transporter for the uptake of tryptophan. 1077

The aim of this study was to investigate whether in stress-prone subjects, carbohydrate-rich, protein-poor food (CR/PP) diminished depressive mood and a cortisol response under controllable as well as uncontrollable laboratory stress. Twenty-two subjects with high stress proneness (HS) and 23 subjects with low stress proneness (LS) participated in a controllable- and uncontrollable-stress experiment during either a CR/PP or protein-rich, carbohydrate-poor (PR/CP) diet. Both controllable and uncontrollable laboratory stress significantly increased pulse rate and skin conductance in HS and LS subjects, whereas uncontrollable stress increased feelings of depression, anger, tension, and fatigue and decreased feelings of vigor. Only in HS subjects, a cortisol response and feelings of depression became lower under the CR/PP diet condition, irrespective of the controllability of the laboratory stressor, suggesting an increased ability to cope with stress. Because the CR/PP diet compared with the PR/CP diet previously has been found to cause a 42% increase in plasma tryptophan/SigmaLNAA, seen as an indirect measure of increases in brain serotonin levels, the present results suggest that an enhanced serotonin function in HS subjects may be involved.
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PMID:Effects of food on cortisol and mood in vulnerable subjects under controllable and uncontrollable stress. 1100 32

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.
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PMID:Amino acids and central fatigue. 1131 Sep 28


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