Document Detail

Ammonia metabolism, the brain and fatigue; revisiting the link.
MedLine Citation:
PMID:  20138956     Owner:  NLM     Status:  MEDLINE    
This review addresses the ammonia fatigue theory in light of new evidence from exercise and disease studies and aims to provide a view of the role of ammonia during exercise. Hyperammonemia is a condition common to pathological liver disorders and intense or exhausting exercise. In pathology, hyperammonemia is linked to impairment of normal brain function and the onset of the neurological condition, hepatic encephalopathy. Elevated blood ammonia concentrations arise due to a diminished capacity for removal via the liver and lead to increased exposure of organs, such as the brain, to the toxic effects of ammonia. High levels of brain ammonia can lead to deleterious alterations in astrocyte morphology, cerebral energy metabolism and neurotransmission, which may in turn impact on the functioning of important signalling pathways within the neuron. Such changes are believed to contribute to the disturbances in neuropsychological function, in particular the learning, memory, and motor control deficits observed in animal models of liver disease and also patients with cirrhosis. Hyperammonemia in exercise occurs as a result of an increased production by contracting muscle, through adenosine monophosphate (AMP) deamination (the purine nucleotide cycle) and branched chain amino acid (BCAA) deamination prior to oxidation. Plasma concentrations of ammonia during exercise often achieve or exceed those measured in liver disease patients, resulting in increased cerebral uptake. In this article we propose that exercise-induced hyperammonemia may lead to concomitant disturbances in brain function, potentially through similar mechanisms underpinning pathology, which may impact on performance as fatigue or reduced function, especially during extreme exercise.
Daniel J Wilkinson; Nicholas J Smeeton; Peter W Watt
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Publication Detail:
Type:  Journal Article; Research Support, Non-U.S. Gov't; Review     Date:  2010-02-04
Journal Detail:
Title:  Progress in neurobiology     Volume:  91     ISSN:  1873-5118     ISO Abbreviation:  Prog. Neurobiol.     Publication Date:  2010 Jul 
Date Detail:
Created Date:  2010-05-24     Completed Date:  2010-09-24     Revised Date:  -    
Medline Journal Info:
Nlm Unique ID:  0370121     Medline TA:  Prog Neurobiol     Country:  England    
Other Details:
Languages:  eng     Pagination:  200-19     Citation Subset:  IM    
Department of Sport and Exercise Science, Chelsea School, University of Brighton, 30 Carlisle Road, Eastbourne, UK.
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MeSH Terms
Ammonia / metabolism*
Brain / metabolism*
Fatigue / metabolism*
Models, Biological*
Signal Transduction*
Reg. No./Substance:

From MEDLINE®/PubMed®, a database of the U.S. National Library of Medicine

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