title: Effects of hyperammonemia on brain energy metabolism: controversial findings in vivo and in vitro.
abstract: The literature related to the effects of elevated plasma ammonia levels on brain energy metabolism is abundant, but heterogeneous in terms of the conclusions. Thus, some studies claim that ammonia has a direct, inhibitory effect on energy metabolism whereas others find no such correlation. In this review, we discuss both recent and older literature related to this controversial topic. We find that it has been consistently reported that hepatic encephalopathy and concomitant hyperammonemia lead to reduced cerebral oxygen consumption. However, this may not be directly linked to an effect of ammonia but related to the fact that hepatic encephalopathy is always associated with reduced brain activity, a condition clearly characterized by a decreased CMRO2. Whether this may be related to changes in GABAergic function remains to be elucidated.
authors.affiliation: Department of Drug Design and Pharmacology, Faculty of Health and Medical Sciences, University of Copenhagen, Universitetsparken 2, 2100, Copenhagen Ø, Denmark.
authors.forename: Arne
authors.initials: A
authors.lastname: Schousboe
authors.forename: Helle S
authors.initials: HS
authors.lastname: Waagepetersen
authors.forename: Renata
authors.initials: R
authors.lastname: Leke
authors.forename: Lasse K
authors.initials: LK
authors.lastname: Bak
mesh_terms: D000818:Animals; D001253:Astrocytes / Q000378:metabolism; D001921:Brain / Q000378:metabolism*; D002478:Cells, Cultured; D004734:Energy Metabolism; D059330:GABAergic Neurons / Q000378:metabolism; D005947:Glucose / Q000378:metabolism; D018698:Glutamic Acid / Q000502:physiology; D006801:Humans; D022124:Hyperammonemia / Q000378:metabolism*; D007773:Lactates / Q000378:metabolism; D017093:Liver Failure / Q000378:metabolism; D009474:Neurons / Q000378:metabolism; D010101:Oxygen Consumption; D009435:Synaptic Transmission; D005680:gamma-Aminobutyric Acid / Q000096:biosynthesis
chemical_list: D007773:Lactates; D018698:Glutamic Acid; D005680:gamma-Aminobutyric Acid; D005947:Glucose