Document Detail


Quantifying reductive carboxylation flux of glutamine to lipid in a brown adipocyte cell line.
MedLine Citation:
PMID:  18364355     Owner:  NLM     Status:  MEDLINE    
Abstract/OtherAbstract:
We previously reported that glutamine was a major source of carbon for de novo fatty acid synthesis in a brown adipocyte cell line. The pathway for fatty acid synthesis from glutamine may follow either of two distinct pathways after it enters the citric acid cycle. The glutaminolysis pathway follows the citric acid cycle, whereas the reductive carboxylation pathway travels in reverse of the citric acid cycle from alpha-ketoglutarate to citrate. To quantify fluxes in these pathways we incubated brown adipocyte cells in [U-(13)C]glutamine or [5-(13)C]glutamine and analyzed the mass isotopomer distribution of key metabolites using models that fit the isotopomer distribution to fluxes. We also investigated inhibitors of NADP-dependent isocitrate dehydrogenase and mitochondrial citrate export. The results indicated that one third of glutamine entering the citric acid cycle travels to citrate via reductive carboxylation while the remainder is oxidized through succinate. The reductive carboxylation flux accounted for 90% of all flux of glutamine to lipid. The inhibitor studies were compatible with reductive carboxylation flux through mitochondrial isocitrate dehydrogenase. Total cell citrate and alpha-ketoglutarate were near isotopic equilibrium as expected if rapid cycling exists between these compounds involving the mitochondrial membrane NAD/NADP transhydrogenase. Taken together, these studies demonstrate a new role for glutamine as a lipogenic precursor and propose an alternative to the glutaminolysis pathway where flux of glutamine to lipogenic acetyl-CoA occurs via reductive carboxylation. These findings were enabled by a new modeling tool and software implementation (Metran) for global flux estimation.
Authors:
Hyuntae Yoo; Maciek R Antoniewicz; Gregory Stephanopoulos; Joanne K Kelleher
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Publication Detail:
Type:  Journal Article; Research Support, N.I.H., Extramural     Date:  2008-03-25
Journal Detail:
Title:  The Journal of biological chemistry     Volume:  283     ISSN:  0021-9258     ISO Abbreviation:  J. Biol. Chem.     Publication Date:  2008 Jul 
Date Detail:
Created Date:  2008-07-21     Completed Date:  2008-09-08     Revised Date:  2013-06-05    
Medline Journal Info:
Nlm Unique ID:  2985121R     Medline TA:  J Biol Chem     Country:  United States    
Other Details:
Languages:  eng     Pagination:  20621-7     Citation Subset:  IM    
Affiliation:
Department of Chemistry and Department of Chemical Engineering, Bioinformatics and Metabolic Engineering Laboratory, Massachusetts Institute of Technology, Cambridge, MA 02139, USA.
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MeSH Terms
Descriptor/Qualifier:
Acetyl Coenzyme A / chemistry
Adipocytes, Brown / cytology*
Animals
Carboxylic Acids / chemistry*
Cell Differentiation
Cell Line
Citric Acid Cycle
Fatty Acids / chemistry
Glutamine / chemistry*
Isocitrate Dehydrogenase / chemistry
Ketoglutaric Acids / chemistry
Lipids / chemistry*
Mice
Mitochondria / enzymology
Oxalates / chemistry
Grant Support
ID/Acronym/Agency:
DK 075850/DK/NIDDK NIH HHS
Chemical
Reg. No./Substance:
0/Carboxylic Acids; 0/Fatty Acids; 0/Ketoglutaric Acids; 0/Lipids; 0/Oxalates; 328-50-7/alpha-ketoglutaric acid; 3687-15-8/oxalomalic acid; 56-85-9/Glutamine; 72-89-9/Acetyl Coenzyme A; EC 1.1.1.41/Isocitrate Dehydrogenase
Comments/Corrections

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


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