| Nutrition during brain activation: does cell-to-cell lactate shuttling contribute significantly to sweet and sour food for thought? | |
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MedLine Citation:
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PMID: 15145548 Owner: NLM Status: MEDLINE |
Abstract/OtherAbstract:
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Functional activation of astrocytic metabolism is believed, according to one hypothesis, to be closely linked to excitatory neurotransmission and to provide lactate as fuel for oxidative metabolism in neighboring neurons. However, review of emerging evidence suggests that the energetic demands of activated astrocytes are higher and more complex than recognized and much of the lactate presumably produced by astrocytes is not locally oxidized during activation. In vivo activation studies in normal subjects reveal that the rise in consumption of blood-borne glucose usually exceeds that of oxygen, especially in retina compared to brain. When the contribution of glycogen, the brain's major energy reserve located in astrocytes, is taken into account the magnitude of the carbohydrate-oxygen utilization mismatch increases further because the magnitude of glycogenolysis greatly exceeds the incremental increase in utilization of blood-borne glucose. Failure of local oxygen consumption to equal that of glucose plus glycogen in vivo is strong evidence against stoichiometric transfer of lactate from astrocytes to neighboring neurons for oxidation. Thus, astrocytes, not nearby neurons, use the glycogen for energy during physiological activation in normal brain. These findings plus apparent compartmentation of metabolism of glycogen and blood-borne glucose during activation lead to our working hypothesis that activated astrocytes have high energy demands in their fine perisynaptic processes (filopodia) that might be met by glycogenolysis and glycolysis coupled to rapid lactate clearance. Tissue culture studies do not consistently support the lactate shuttle hypothesis because key elements of the model, glutamate-induced increases in glucose utilization and lactate release, are not observed in many astrocyte preparations, suggesting differences in their oxidative capacities that have not been included in the model. In vivo nutritional interactions between working neurons and astrocytes are not as simple as implied by "sweet (glucose-glycogen) and sour (lactate) food for thought." |
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Authors:
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Gerald A Dienel; Nancy F Cruz |
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Publication Detail:
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Type: Journal Article; Research Support, U.S. Gov't, P.H.S.; Review |
Journal Detail:
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Title: Neurochemistry international Volume: 45 ISSN: 0197-0186 ISO Abbreviation: Neurochem. Int. Publication Date: 2004 Jul-Aug |
Date Detail:
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Created Date: 2004-05-17 Completed Date: 2004-07-26 Revised Date: 2008-11-21 |
Medline Journal Info:
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Nlm Unique ID: 8006959 Medline TA: Neurochem Int Country: England |
Other Details:
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Languages: eng Pagination: 321-51 Citation Subset: IM |
Affiliation:
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Department of Neurology, Slot 830, University of Arkansas for Medical Sciences, Room 715, Shorey Building, 4301 W. Markham Street, Little Rock, AR 72205, USA. gadienel@uams.edu |
Export Citation:
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| MeSH Terms | |
Descriptor/Qualifier:
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Anesthesia Animals Astrocytes / cytology, physiology Brain / physiology* Cell Communication / physiology* Cerebrovascular Circulation / physiology Humans Models, Neurological Nutritional Physiological Phenomena Synaptic Transmission / physiology Taste* |
| Grant Support | |
ID/Acronym/Agency:
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NS36728/NS/NINDS NIH HHS; NS38230/NS/NINDS NIH HHS |
From MEDLINE®/PubMed®, a database of the U.S. National Library of Medicine
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