Document Detail

Metabolic flux analysis of hepatocyte function in hormone- and amino acid-supplemented plasma.
MedLine Citation:
PMID:  12749840     Owner:  NLM     Status:  MEDLINE    
Understanding the metabolic and regulatory pathways of hepatocytes is important for biotechnological applications involving liver cells. Previous attempts to culture hepatocytes in plasma yielded poor functional results. Recently we reported that hormone (insulin and hydrocortisone) and amino acid supplementation reduces intracellular lipid accumulation and restores liver-specific function in hepatocytes exposed to heparinized human plasma. In the current study, we performed metabolic flux analysis (MFA) using a simplified metabolic network model of cultured hepatocytes to quantitively estimate the changes in lipid metabolism and relevant intracellular pathways in response to hormone and amino acid supplementation. The model accounts for the majority of central carbon and nitrogen metabolism, and assumes pseudo-steady-state with no metabolic futile cycles. We found that beta-oxidation and tricarboxylic acid (TCA) cycle fluxes were upregulated by both hormone and amino acid supplementation, thus enhancing the rate of lipid oxidation. Concomitantly, hormone and amino acid supplementation increased gluconeogenic fluxes. This, together with an increased rate of glucose clearance, caused an increase in predicted glycogen synthesis. Urea synthesis was primarily derived from ammonia and aspartate generated through transamination reactions, while exogenous ammonia removal accounted for only 3-6% of the urea nitrogen. Amino acid supplementation increased the endogenous synthesis of oxaloacetate, and in turn that of aspartate, a necessary substrate for the urea cycle. These findings from MFA provide cues as to which genes/pathways relevant to fatty acid oxidation, urea production, and gluconeogenesis may be upregulated by plasma supplementation, and are consistent with current knowledge of hepatic amino acid metabolism, which provides further credence to this approach for evaluating the metabolic state of hepatocytes under various environmental conditions.
Christina Chan; François Berthiaume; Kyongbum Lee; Martin L Yarmush
Publication Detail:
Type:  Comparative Study; Evaluation Studies; Journal Article; Research Support, Non-U.S. Gov't; Research Support, U.S. Gov't, P.H.S.; Validation Studies    
Journal Detail:
Title:  Metabolic engineering     Volume:  5     ISSN:  1096-7176     ISO Abbreviation:  Metab. Eng.     Publication Date:  2003 Jan 
Date Detail:
Created Date:  2003-05-16     Completed Date:  2004-01-22     Revised Date:  2007-11-14    
Medline Journal Info:
Nlm Unique ID:  9815657     Medline TA:  Metab Eng     Country:  United States    
Other Details:
Languages:  eng     Pagination:  1-15     Citation Subset:  IM    
Center For Engineering in Medicine/Surgical Services, Massachusetts General Hospital, Harvard Medical School, and The Shriners Hospitals for Children, 55 Fruit Street, Bigelow 1401, Boston, MA 02114, USA.
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MeSH Terms
Albumins / biosynthesis
Amino Acids / pharmacology*
Ammonia / metabolism
Cell Culture Techniques / methods*
Cells, Cultured
Computer Simulation
Energy Metabolism / physiology
Hepatocytes / cytology,  drug effects,  metabolism*
Hormones / metabolism,  pharmacology*
Hydrocortisone / metabolism,  pharmacology
Insulin / metabolism,  pharmacology
Lipid Metabolism*
Models, Biological*
Plasma / metabolism*
Rats, Inbred Lew
Triglycerides / metabolism
Urea / metabolism
Grant Support
Reg. No./Substance:
0/Albumins; 0/Amino Acids; 0/Hormones; 0/Triglycerides; 11061-68-0/Insulin; 50-23-7/Hydrocortisone; 57-13-6/Urea; 7664-41-7/Ammonia

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

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