Document Detail


Effect of nutritional status on insulin sensitivity in vivo and tissue enzyme activities in the rat.
MedLine Citation:
PMID:  2499304     Owner:  NLM     Status:  MEDLINE    
Abstract/OtherAbstract:
The hyperinsulinaemic-glucose-clamp technique, in combination with measurement of glucose turnover in conscious unrestrained rats, was used to assess the effects of nutritional status on insulin sensitivity in vivo and glucose metabolism. Liver, heart and quadriceps skeletal-muscle glycogen content and activities of pyruvate dehydrogenase (PDH) and glycogen synthase were measured both basally and at the end of a 2.5 h glucose clamp (insulin 85 munits/h) in rats 6, 24 and 48 h after food withdrawal. Clamp glucose requirement and glucose turnover were unchanged by fasting. Activation of glycogen synthase and glycogen deposition in liver and skeletal muscle during the clamps were also not impaired in rats after a prolonged fast. By contrast with skeletal muscle, activation of cardiac-muscle glycogen synthase and glycogen deposition during the clamps were markedly impaired by 24 h of fasting and were undetectable at 48 h. Skeletal-muscle PDH activity fell with more prolonged fasting (6 h, 15.3 +/- 3.4%; 24 h, 4.7 +/- 0.7%; 48 h, 4.3 +/- 0.6% active; P less than 0.005), but at 24 and 48 h was stimulated by the clamp to values unchanged by the duration of fasting. Stimulation of cardiac PDH activity by the clamp was, however, impaired in rats fasted for 24 or 48 h. Basal hepatic PDH did not change significantly with fasting (6 h, 5.3 +/- 1.1%; 24 h, 4.6 +/- 0.7%; 48 h, 3.9 +/- 0.5%), and, although it could be partly restored at 24 h, very little stimulation occurred at 48 h. Hepatic pyruvate kinase and acetyl-CoA carboxylase activity were both stimulated by the clamps, and this was not impaired with more prolonged fasting. During the glucose clamps, blood concentrations of lactate, pyruvate and alanine were increased to a greater extent in rats fasted for 24 and 48 h than in rats studied 6 h after food withdrawal. The findings suggest that, although sensitivity to insulin of whole-body glucose disposal is unchanged with fasting, there may be qualitative differences in the metabolism of glucose.
Authors:
Y T Kruszynska; J G McCormack
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Publication Detail:
Type:  Journal Article; Research Support, Non-U.S. Gov't    
Journal Detail:
Title:  The Biochemical journal     Volume:  258     ISSN:  0264-6021     ISO Abbreviation:  Biochem. J.     Publication Date:  1989 Mar 
Date Detail:
Created Date:  1989-06-27     Completed Date:  1989-06-27     Revised Date:  2009-11-18    
Medline Journal Info:
Nlm Unique ID:  2984726R     Medline TA:  Biochem J     Country:  ENGLAND    
Other Details:
Languages:  eng     Pagination:  699-707     Citation Subset:  IM    
Affiliation:
Department of Medicine, Royal Free Hospital, London, U.K.
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MeSH Terms
Descriptor/Qualifier:
Animals
Fasting*
Glucose / metabolism
Glycogen / analysis
Glycogen Synthase / metabolism*
Heart / drug effects
Insulin / pharmacology*
Liver / drug effects,  enzymology
Male
Muscles / drug effects,  enzymology
Myocardium / enzymology
Nutritional Status*
Pyruvate Dehydrogenase Complex / metabolism*
Rats
Rats, Inbred Strains
Chemical
Reg. No./Substance:
0/Pyruvate Dehydrogenase Complex; 11061-68-0/Insulin; 50-99-7/Glucose; 9005-79-2/Glycogen; EC 2.4.1.11/Glycogen Synthase
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