Document Detail

Glycogenin activity and mRNA expression in response to volitional exhaustion in human skeletal muscle.
MedLine Citation:
PMID:  15860684     Owner:  NLM     Status:  MEDLINE    
Glycogenolysis results in the selective catabolism of individual glycogen granules by glycogen phosphorylase. However, once the carbohydrate portion of the granule is metabolized, the fate of glycogenin, the protein primer of granule formation, is not known. To examine this, male subjects (n = 6) exercised to volitional exhaustion (Exh) on a cycle ergometer at 75% maximal O2 uptake. Muscle biopsies were obtained at rest, 30 min, and Exh (99 +/- 10 min). At rest, total glycogen concentration was 497 +/- 41 and declined to 378 +/- 51 mmol glucosyl units/kg dry wt following 30 min of exercise (P < 0.05). There were no significant changes in proglycogen, macroglycogen, glycogenin activity, or mRNA in this period (P > or = 0.05). Exh resulted in decreases in total glycogen, proglycogen, and macroglycogen as well as glycogenin activity (P < 0.05). These decrements were associated with a 1.9 +/- 0.4-fold increase in glycogenin mRNA over resting values (P < 0.05). Glycogenolysis in the initial exercise period (0-30 min) was not adequate to induce changes in glycogenin; however, later in exercise when concentration and granule number decreased further, decrements in glycogenin activity and increases in glycogenin mRNA were demonstrated. Results show that glycogenin becomes inactivated with glycogen catabolism and that this event coincides with an increase in glycogenin gene expression as exercise and glycogenolysis progress.
Jane Shearer; Terry E Graham; Danielle S Battram; Deborah L Robinson; Erik A Richter; Rhonda J Wilson; Marica Bakovic
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Publication Detail:
Type:  Clinical Trial; Journal Article; Research Support, Non-U.S. Gov't     Date:  2005-04-28
Journal Detail:
Title:  Journal of applied physiology (Bethesda, Md. : 1985)     Volume:  99     ISSN:  8750-7587     ISO Abbreviation:  J. Appl. Physiol.     Publication Date:  2005 Sep 
Date Detail:
Created Date:  2005-08-16     Completed Date:  2005-10-27     Revised Date:  2013-09-26    
Medline Journal Info:
Nlm Unique ID:  8502536     Medline TA:  J Appl Physiol (1985)     Country:  United States    
Other Details:
Languages:  eng     Pagination:  957-62     Citation Subset:  IM    
Department of Human Biology and Nutritional Sciences, University of Guelph, Ontario, Canada.
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MeSH Terms
Enzyme Activation
Gene Expression Regulation, Enzymologic / physiology
Glucosyltransferases / genetics,  metabolism*
Glycogen / genetics,  metabolism*
Glycoproteins / genetics,  metabolism*
Muscle Contraction / physiology*
Muscle, Skeletal / physiology*
Physical Endurance / physiology*
Physical Exertion / physiology*
RNA, Messenger / metabolism*
Volition / physiology
Reg. No./Substance:
0/Glycoproteins; 0/RNA, Messenger; 0/glycogenin; 9005-79-2/Glycogen; EC 2.4.1.-/Glucosyltransferases

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

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