The oxidation of glucose carbon entering the tca cycle is reduced by
glutamine in rat small intestine epithelial cells.
Kight, Cassandra E., and Sharon E. Fleming.
Department of Nutritional Sciences, University of California, Berkeley CA
94720
APStracts 2:0004G, 1995.
The influence of glutamine on glucose oxidation was assessed in epithelial
cells isolated from the mucosa of the proximal, mid and distal small
intestine of young, fed, male rats. Glucose oxidation declined along the
length of the small intestine, with values from the mid and distal segments
representing ca. 55 and 40%, respectively, of the value from the proximal
segment. A gradient along the small intestine was noted also in the influence
of glutamine on glucose oxidation: glutamine suppressed glucose oxidation ca.
60% in the proximal small intestine, 39% in the mid intestine and 31% in the
distal small intestine. Glutamine suppressed the oxidation of glucose carbon
that entered the TCA cycle, and this was determined using CO2 ratios derived
from acetate and glucose isotopes. In cells from the proximal segment, the
probability that carbon entering the cycle would complete one full turn was
reduced by glutamine from 0.77 to 0.28. The entry of glucose-derived pyruvate
into the TCA cycle did not appear to be influenced by the presence of
glutamine, however. Glutamine had no influence on the proportion of glucose
metabolism that occurred via the pentose phosphate pathway (which averaged 5%
or less), but reduced flux of carbon through pyruvate carboxylase relative to
flux through pyruvate dehydrogenase from 40% to 9% in cells from the proximal
segment. These data suggest that, in the presence of glutamine, the fate of
pyruvate carbon (derived from glucose or elsewhere) entering the TCA cycle is
altered from that of oxidation to anaplerosis and subsequent efflux of TCA
cycle intermediates into newly synthesized compounds.
Received 1 August 1994; accepted in final form 10 January 1995.
APS Manuscript Number G287-4.
Article publication pending Am. J. Physiol. (Gastrointest. Liver Physiology).
ISSN 1080-4757 Copyright 1995 The American Physiological Society.
Published in APStracts on 23 February 1995.