Metabolic flux analysis of hepatocyte function in hormone- and amino acid-supplemented plasma

Christina Chan, François Berthiaume, Kyongbum Lee, Martin L. Yarmush

Research output: Contribution to journalArticle

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Abstract

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 β-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.

LanguageEnglish (US)
Pages1-15
Number of pages15
JournalMetabolic Engineering
Volume5
Issue number1
DOIs
StatePublished - Jan 2003

Profile

Metabolic Flux Analysis
Hormones
Amino acids
Hepatocytes
Fluxes
Plasmas
Amino Acids
Urea
Metabolic Networks and Pathways
Ammonia
Metabolism
Aspartic Acid
Liver
Oxidation
Lipids
Nitrogen
Substrate Cycling
Cortisol
Plasma (human)
Oxaloacetic Acid

ASJC Scopus subject areas

  • Biophysics
  • Bioengineering
  • Endocrinology, Diabetes and Metabolism

Cite this

Metabolic flux analysis of hepatocyte function in hormone- and amino acid-supplemented plasma. / Chan, Christina; Berthiaume, François; Lee, Kyongbum; Yarmush, Martin L.

In: Metabolic Engineering, Vol. 5, No. 1, 01.2003, p. 1-15.

Research output: Contribution to journalArticle

Chan, Christina ; Berthiaume, François ; Lee, Kyongbum ; Yarmush, Martin L./ Metabolic flux analysis of hepatocyte function in hormone- and amino acid-supplemented plasma. In: Metabolic Engineering. 2003 ; Vol. 5, No. 1. pp. 1-15
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