Quantitative analysis of acetoacetate metabolism in as-30d hepatoma
cells using 13c and 14c isotopic techniques.
Holleran, Anne L., Gary Fiskum, and Joanne K. Kelleher.
Department of Physiology, and Biochemistry and Molecular Biology,
The George Washington University School, of Medicine and Health
Sciences, Washington, D.C., USA 20037
APStracts 4:0031E, 1997.
Experimental hepatoma cells utilize acetoacetate as an oxidative
energy source and as a precursor for lipid synthesis. The
significance of ketone body metabolism in tumors lies in the study of
tumor-host metabolism and the ketonemic condition that is often
present in cancer patients. The quantitative importance of
acetoacetate and glucose was investigated in AS-30D cells using 13C
and 14C isotopic methods. In addition, the effects of acetoacetate
were compared to those of dichloroacetic acid (DCA), an activator of
pyruvate dehydrogenase (PDH). The 14CO2 ratios method evaluated the
entry of pyruvate into the tricarboxylic acid (TCA) cycle and
revealed that acetoacetate diverted pyruvate from pyruvate
dehydrogenase to pyruvate carboxylation. In contrast, DCA increased
the oxidation of glucose largely through PDH indicating that PDH is
not maximally active in the absence of DCA. Isotopomer Spectral
Analysis of lipid synthesis demonstrated that, in the absence of
acetoacetate, glucose supplied 65% of the acetyl CoA used for de novo
lipogenesis. When 5 mM acetoacetate was included in the incubation,
glucose was displaced as a lipogenic precursor and acetoacetate
supplied 85% of the acetyl CoA for lipogenesis versus only 2% for
glucose. Thus, AS-30D cells have a large capacity for acetoacetate
utilization for de novo lipogenesis.
Received 26 June 1996; accepted in final form 18 December 1996.
APS Manuscript Number E279-6.
Article publication pending Am. J. Physiol. (Endocrinol. Metab.).
ISSN 1080-4757 Copyright 1997 The American Physiological Society.
Published in APStracts on 19 February 1997