AJP - Gastrointestinal and Liver Physiology, Vol 270, Issue 5 852-G859, Copyright © 1996 by American Physiological Society
Nutritional efficiency of succinic acid and glutamic acid dimethyl esters in colon carcinoma cells
T. M. Zhang, H. Jijakli and W. J. Malaisse
Laboratory of Experimental Medicine, Brussels Free University, Belgium.
The dimethyl esters of succinic acid (SAD) and glutamic acid (GME) were
found to be efficiently metabolized in colon carcinoma cells of the Caco-2
line. The rate of [1,4-14C]SAD and [2,3-14C]SAD conversion to radioactive
acidic metabolites, CO2, amino acids, pyruvic acid, and lactic acid
suggested that the catabolism of the ester-derived succinic acid occurred
mainly through the sequence of reactions catalyzed by succinate
dehydrogenase, fumarase, and the malic enzyme. This coincided with a marked
sparing action of SAD on the utilization of D-[2-(3)H]glucose and
D-[5-(3)H]glucose and generation of 14C-labeled acid metabolites, CO2, and
lactic acid from D-[U-14C]glucose by the enterocytes. Likewise, the
conversion of [U-14C]GME to 14C-labeled amino acids, its oxidation compared
with that of [1-(14)C]GME, and the production of NH4+ in the absence or
presence of GME indicated efficient catabolism of the latter ester. Like
SAD, GME decreased the utilization of D-[5-(3)H]glucose and generation of
14C-labeled acidic metabolites, pyruvate, and CO2 from D-[6-(14)C]glucose,
while increasing the generation of 14C-labeled amino acids from the labeled
hexose. The oxidation of D-[6-(14)C]glucose was even more severely
inhibited by GME. In normal rat intestinal cells, SAM, SAD, and GME also
exerted a marked sparing action on D-[U-14C]glucose oxidation. The present
findings suggest, therefore, that these esters could possibly be used to
sustain ATP generation in intestinal cells.
