Measuring gluconeogenesis with [2-13c]glycerol and mass isotopomer
distribution analysis of glucose.
Odile, Peroni, Large Val[acute]erie, and Beylot Michel.
INSERM U. 197, Facult[acute]e de M[acute]edecine Alexis Carrel, rue
G. Paradin, 69372 Lyon C[acute]edex 08. France
APStracts 2:0087E, 1995.
We tested the validity of the use of [2-13C]glycerol and of the mass
isotopomer distribution analysis of glucose for measuring
gluconeogenesis in vitro and in vivo. When isolated rat livers (48 h
starved) were infused with labeled glycerol without or with lactate +
pyruvate we found that gluconeogenesis accounted for more than 90 %
of glucose production. When glucose was added to the infusate so that
glucose produced by the liver represented only 80 or 45 % of total
glucose output, this dilution could be calculated from the mass
isotopomer distribution of glucose. When post-absorptive and starved
rats were infused with [2-13C]glycerol we found that gluconeogenesis
accounted for 54+/-2 and 89+/-1 % respectively of glucose production.
However accurate measures could be obtained, particularly in post
-absorptive rats, only with high tracer infusion rates (representing
at least 50 % of endogenous glycerol production rate). These infusion
rates resulted in both groups of rats in an increase of both total
glycerol turnover rate and gluconeogenesis from glycerol. In addition
hepatic concentration of glycerol-3 phosphate were increased. In
conclusion, [2-13C]glycerol infusion and mass isotopomer distribution
analysis of glucose appears as a useful method for studies of
gluconeogenesis in vitro and in vivo ; however, accutate measurements
in vivo can be obtained only at the expense of some perturbation of
the metabolic pathway studied.
Received 6 February 1995; accepted in final form 18 April 1995.
APS Manuscript Number E49-5.
Article publication pending Am. J. Physiol. (Endocrinol. Metab.).
ISSN 1080-4757 Copyright 1995 The American Physiological Society.
Published in APStracts on 2 May 1995.