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Query: UMLS:C0015672 (fatigue)
 51,768 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

The amino acid imbalance hypothesis should explain the fatigue originating in the brain during sustained exercise or over-training as a branched-chain (BCAA)/aromatic amino acids (AAA) imbalance with increased brain tryptophan uptake and 5-hydroxytryptamine synthesis. The serum amino acid profile was determined in 9 ultra-triathletes before and after completing the 1993 Colmar ultra-triathlon to additionally analyse the extent of this amino acid imbalance during such an extreme prolonged contest lasting more than 23 hours. The summed serum concentration of 25 amino acids decreased by 18% from 3962 +/- 846 to 3255 +/- 694 umol.l-1 likely reflecting a catabolic state of the organism with a decrease in 18 individual amino acids by 9-56%, an increase in cystine (+38%), methionine (+24%), tyrosine (+10%), phenylalanine (+12%), free tryptophan (+74%), and constant glutamine, leucine and total tryptophan levels. Since plasma volume increased by approximately 7.6% with a 3.3 kg body mass decrease in the athletes during the ultra triathlon, a decrease in intra-cellular water with an extra-cellular fluid increase is hypothesized. This decrease in cellular hydration state is seen as a protein-catabolic signal.
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PMID:Serum amino acid concentrations in nine athletes before and after the 1993 Colmar ultra triathlon. 764 5

Since the first comprehensive description of the symptoms of FMS by Yunus et al (1981), numerous investigations have confirmed that FMS is a clinical entity. However, the aetiology of the syndrome is still not fully elucidated. It seems, however, logical to place the origin of the disorder in the muscle. Muscle pain, especially at the muscle-tendon junctions, fatigue and stiffness are the first symptoms. A malfunction of energy metabolism has been detected in part of the muscle fibres. However, it has to be considered that the muscle is not an isolated entity. Its activity is controlled by segmentally arranged motor units of the ventral horn of the spinal cord in response to proprioceptive afferent signals arising in the muscle spindles or in other sensory elements including nociceptors. Together with supraspinal descending inputs, the spinal motor neurone pool is the common final pathway for segmental and suprasegmental inputs, making the motor system extremely powerful for adaptive adjustments but also vulnerable if deficits occur in either of these input levels. A second, recently discovered abnormality seen in FMS is a lowered serotonin level in peripheral and most likely also central structures. The underlying mechanism seems to be defective absorption of the precursor amino acid tryptophan from the gut. Serotonin is involved centrally in the regulation of the sleep pattern, and at the spinal level it acts as a 'gain setter' of motoneurone excitability and suppresses signal transmission of noxious stimuli in dorsal horn neurones. Either of these two disturbances, muscle energy depletion or serotonin deficiency, could by itself evoke many of the symptoms of FMS, and their combined appearance will perpetuate the disease. Depressed levels of somatomedin C, caused by a deficit of stage 4 sleep-dependent release of GH, might represent an additional factor in preventing proper development or repair of myoskeletal structures. Malabsorption of certain amino acids, possibly due to a genetic disorder of gut transport mechanisms, may constitute an additional deleterious factor. The abnormalities found in the HPA and HPT axis may be seen as an attempt of the organism to restore homeostasis. The stimulus eliciting this counter-regulatory reaction may be pain or other afferent signals which normally do not reach the central nervous system. It is doubtful whether the unspecific activation of the HPA axis in a non-inflammatory disease is beneficial.(ABSTRACT TRUNCATED AT 400 WORDS)
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PMID:Neuromediator and hormonal perturbations in fibromyalgia syndrome: results of chronic stress? 785 Aug 79

Acute tryptophan depletion, which may reduce brain serotonin synthesis in humans, was evaluated in bulimic and normal subjects assessing its effects on the plasma ratio of tryptophan to the sum of the other large, neutral amino acids (TRP/sigma LNAA). Thirteen bulimic and 9 control women ingested an amino acid mixture containing either 2.3 g (control mixture) or 0 g of tryptophan (active mixture), in combination with 100 g of the other amino acids. Six healthy male volunteers were also studied, using a similar mixture containing 4.6 g of tryptophan. Bulimic and control women both experienced sizable reductions in the plasma TRP/sigma LNAA ratio, compared to baseline values, for both the active mixture (10% of baseline) or the control mixture (45% of baseline). For bulimic women, the active mixture produced a significant increase in fatigue and a trend toward increased anxiety and indecisiveness. The control mixture did not maintain baseline TRP/sigma LNAA ratios so we identified a control amino acid mixture that does not cause a drop in the plasma TRP/sigma LNAA ratio when ingested (4.6 g tryptophan in combination with 100 g of other amino acids). An oral, tryptophan-deficient amino acid mixture produced acute, substantial reductions in the plasma TRP/sigma LNAA ratio in all subjects, suggesting that the treatment should reduce brain tryptophan uptake and serotonin synthesis. A control mixture containing tryptophan was also identified that maintains the plasma TRP/sigma LNAA ratio at pretreatment values.
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PMID:Acute tryptophan depletion in bulimia: effects on large neutral amino acids. 801 85

Healthy sleeping habits is a complex balance between behaviour, environment and circadian rhythm. The quality of sleep can be improved by behaviour, e.g. eating tryptophan and carbohydrate rich foods, physical exercise in the afternoon or a cold shower just before going to bed. Total sleep time is maximal in thermoneutrality and decreases above and below the thermoneutrality zone. Thermoneutrality is reached for an environmental temperature of 30-32 degrees C without night clothing or of 16-19 degrees with a pyjama and at least one sheet. Noise also modifies sleep structure and above 50dB shortens total sleeping time. Although subjects do become subjectively accustomed to noise, vegetative cardiovascular reactivity to environmental noise remains unchanged. The spontaneous circadian awake/sleep cycle is 25 hours, slightly longer than the body temperature cycle, but when subjects are exposed to environmental synchronization, the two cycles coincide. In individuals undergoing temporal isolation, the two rhythms become independent often leading to subjective discomfort and fatigue. Certain factors including age can favour internal desynchronization. Other factors may include social contact, stress due to mental work load, and constant lighting which could lengthen the awake/sleep cycle. Caffeine blocks the receptors of adenosine, and thus its effects of inhibiting neurotransmission. Intake 30 to 60 minutes before sleeping shortens total sleep time and increases the duration of stage 2 and shortens stage 3 and 4. Alcohol may act as a relaxing, sedative agent when consumed just before sleeping but can also lead to night-time awakening due to sympathetic activation which does not return to baseline levels until the blood alcohol levels have returned to 0. Nicotine has a biphasic effect on sleep: at low concentrations, it leads to relaxation and sedation and at high concentrations inhibits sleep. A careful study of sleeping habits is the first step in evaluating complains of insomnia or hypersomnia. Before relying on drugs, treatment should start with attention to the sleep environment and personal habits.
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PMID:[Prevention and treatment of sleep disorders through regulation] of sleeping habits]. 802 26

We describe four Italian adolescents in whom a persistent, debilitating fatigue appeared after therapeutic ingestion of products containing L-tryptophan and subsequent to the development of a transient rise in eosinophil count and severe myalgia (Eosinophilia Myalgia Syndrome-EMS). Their clinical picture was indistinguishable from that of the so-called Chronic Fatigue Syndrome. A chronic fatigue may occur after diverse triggering agents and its represents the peculiar clinical evolution of these four paediatric cases of EMS.
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PMID:Chronic fatigue: a peculiar evolution of eosinophilia myalgia syndrome following treatment with L-tryptophan in four Italian adolescents. 803 24

Eosinophilia-myalgia syndrome (EMS) is a multisystem illness of uncertain pathogenesis that occurred in an epidemic related to the ingestion of contaminated L-tryptophan. To investigate the role of immune dysfunction in EMS we prospectively measured a serologic index of T-cell activation, the soluble interleukin-2 receptor (sIL-2R), in 7 patients followed into the late stages of the illness. As a group, EMS patients had significantly elevated sIL-2R levels throughout the study. Five patients suffered chronic symptoms of myalgia, arthralgia, muscle cramps, fatigue, or subjective memory impairment and all had persistently elevated sIL-2R levels. Two patients had near-resolution of EMS and normal sIL-2R levels. We conclude that chronic symptoms are common in EMS and are associated with persistent T-cell activation as measured by serum sIL-2R levels. These findings suggest that immunosuppressive treatment may be beneficial in EMS.
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PMID:Chronic immune activation in the eosinophilia-myalgia syndrome. 793 35

Nineteen bulimic women and 22 age-matched controls were randomly assigned to receive 25 g of glucose or a placebo injection under double-blind conditions. Blood samples of glucose, insulin, and glucagon, and psychometric assessments of mood and food cravings were obtained 10 min before, and 0, 5, 10, 20, 30, 45, and 60 min after injection. Blood levels of the large neutral amino acids (LNAAs) tryptophan, tyrosine, leucine, valine, phenylalanine, and leucine were determined at 10 min before and 60 min after the injection. Bulimic subjects were found to report more symptoms of distressed mood throughout the entire monitoring period than controls. Five minutes following glucose ingestion the self-reports of depression, fatigue, anxiety, and bewilderment rose to a level among the bulimic subjects that was above that at baseline, and was higher than that of bulimia nervosa (BN) subjects receiving placebo. No comparable change in mood was observed among controls. Blood glucose levels were correlated with mood in the bulimic group, but not in controls. In addition, the glucose injection induced a heightened urge to binge in the bulimic group (compared to placebo at 10 and 60 min), whereas reducing food cravings (for sweets) in the controls (at 5 min). When collapsed across time and injection condition, the blood glucose level of bulimics was lower than that of controls. There were no differences in insulin response between the groups. The bulimic group was found to have lower baseline levels of blood tryptophan, whereas no differences in the tryptophan/LNAA ratio were observed either at baseline or following glucose.(ABSTRACT TRUNCATED AT 250 WORDS)
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PMID:A double-blind placebo-controlled glucose challenge in bulimia nervosa: psychological effects. 844 64

Fat oxidation provides a fuel for many tissues and it provides an important signal to decrease glucose utilization and oxidation in muscle and so conserve glucose for essential organs such as the brain. The control of fatty acid oxidation is achieved in part through its plasma concentrations, which may be precisely controlled by the triacylglycerol-fatty acid substrate cycle, which can also, if oxidation is taken into account, be viewed as a branch point in this important pathway. Branch points may provide precision in regulation if one of the fluxes at the branch is low compared with the other flux. Both branch points and substrate cycles are energetically expensive and may account for some of the increases in energy expenditure in conditions of injury, burns, and sepsis and in the postexercise condition. Fatty acids, through effects on plasma free tryptophan concentrations and hence 5-hydroxytryptamine concentrations in the brain, may play a role in central fatigue. Polyunsaturated fatty acids are claimed to have immunosuppressive properties. Work has been done to provide a biochemical analysis of how they might influence some functions of cells of the immune system.
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PMID:The regulatory, informational, and immunomodulatory roles of fat fuels. 847 91

The influence of simple carbohydrate, complex carbohydrate, protein, and delayed meal conditions on plasma tryptophan ratios and mood of normal subjects was investigated. In Experiment 1, 27 women consumed 1 of 4 meal conditions, had blood samples drawn, and completed mood assessment measures before and at 5 times during the next 3 hr. Experiment 2 replicated Experiment 1 except that blood samples were not drawn and an additional simple carbohydrate condition was included. The carbohydrate meal conditions elevated blood glucose levels and plasma ratio of tryptophan to other large neutral amino acids over that of the protein condition. A decline in feelings of fatigue and distress occurred 30 min postprandial regardless of condition and persisted for the rest of the study.
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PMID:Effect of meal composition on mood. 848 99

It has been hypothesized that fatigue and prolactin (PRL) changes during endurance exercise are influenced by serotonin synthesis, and in turn, release. Such a change is thought to occur through an increase in blood free tryptophan (TRP) and a concomitant decrease in those large neutral amino acids (LNAA) which compete with free TRP for entry into the brain. For further investigation, 10 healthy athletes were randomly subjected to three test units (TU), each consisting of a treadmill run for 90 min. The speed was adjusted to a blood lactate level of 2 mmol/l. During the first 30 min of exercise infusions of 500 ml saline (TU I), 500 ml saline with amino acids (TU II) or 500 ml saline with 30 U heparin/kg following an oral soy oil solution given 1 h before (TU III) were administered. Rate of perceived exertion (RPE), heart rate and running speed were recorded during exercise. Venous blood samples were taken after a 10 h fast, at rest, after 10, 50 and 90 min of exercise as well as 10 and 30 min post-exercise. PRL, insulin, glucose, ammonia, lactate, triglycerides (TG), free fatty acids (FFA) and amino acids were determined in each sample. No significant differences were found in RPE. PRL increased (p < 0.01) in all TU. TG and heparin administration resulted in an increase (p <0.01) in FFA, which correlated (p < 0.01) with free TRP and the ratio of free TRP/TRP. Artificial increase in free TRP in TU III did not affect plasma PRL level. The amino acid infusion in TU II induced an increase in LNAA but had no significant effect on PRL. PRL and ammonia peaked at the end of exercise. We conclude that neither exercise-induced PRL secretion nor RPE are affected by changes in circulating free TRP and LNAA under the present conditions.
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PMID:Alterations in plasma free tryptophan and large neutral amino acids do not affect perceived exertion and prolactin during 90 min of treadmill exercise. 883 6


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