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J. Biol. Chem., Vol. 277, Issue 33, 29444-29454, August 16, 2002
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From the Centre d'Etudes Métaboliques par Spectroscopie de
Résonance Magnétique (INSERM U 499), Pavillon P,
Hôpital Edouard Herriot, place d'Arsonval,
69374 Lyon Cedex 08, France
Although acetate, the main circulating volatile
fatty acid in humans and animals, is metabolized at high rates by the
renal tissue, little is known about the precise fate of its carbons and
about the regulation of its renal metabolism. Therefore, we studied the
metabolism of variously labeled [13C]acetate and
[14C]acetate molecules and its regulation by alanine,
which is also readily metabolized by the kidney, in isolated rabbit
renal proximal tubules. With acetate as the sole substrate, 72% of the
C-1 and 49% of the C-2 of acetate were released as CO2;
with acetate plus alanine, the corresponding values were decreased to
49 and 25%. The only other important products formed from the acetate
carbons were glutamine, and to a smaller extent, glutamate. By
combining 13C NMR and radioactive and enzymatic
measurements with a novel model of acetate metabolism, fluxes through
the enzymes involved were calculated. Thanks to its anaplerotic effect,
alanine caused a stimulation of acetate removal and a large increase in
fluxes through pyruvate carboxylase, citrate synthase, and the enzymes involved in glutamate and glutamine synthesis but not in flux through
The Anaplerotic Substrate Alanine Stimulates Acetate
Incorporation into Glutamate and Glutamine in Rabbit Kidney
Tubules
A 13C NMR STUDY*
-ketoglutarate dehydrogenase. We conclude that the
anaplerotic substrate alanine not only accelerates the disposal of
acetate but also prevents the wasting of the latter compound as
CO2.
*
The costs of publication of this
article were defrayed in part by the
payment of page charges. The article
must therefore be hereby marked
"advertisement" in
accordance with 18 U.S.C. Section
1734 solely to indicate this fact.
To whom correspondence should be addressed. Tel.:
33-4-78-77-86-65; Fax: 33-4-78-77-87-39; E-mail:
morel@laennec.univ-lyon1.fr.
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