AJP - Regulatory, Integrative and Comparative Physiology, Vol 246, Issue 6 1011-R1014, Copyright © 1984 by American Physiological Society
Hepatic palmitate metabolism in fasting Zucker rats: effect of lactate on partitioning
M. J. Azain and R. J. Martin
Hepatocytes were isolated from 48-h fasted lean and obese Zucker rats and
incubated with [1-14C] palmitate. The partitioning of fatty acids to
oxidation and esterification products and the effect of lactate or glucose
on this partitioning were studied. With palmitate as the only substrate,
the cells from the lean rats oxidized 80% of the palmitate that was
metabolized compared with only 35% oxidation in the cells from the obese
rats. Thus fatty acid esterification remained the predominate pathway of
palmitate metabolism in the hepatocytes from fasting obese rats. The
addition of lactate to the cells from the lean rats decreased oxidation and
increased esterification to levels similar to those in the obese rat
hepatocytes. Glucose had similar effects on esterification in lean rat
hepatocytes but was less potent than lactate. The cells from the obese rats
were insensitive to the addition of lactate or glucose. These studies
indicate that the inability of hepatocytes from obese rats to induce
ketogenesis from exogenous fatty acids after a 48-h fast and their
insensitivity to added lactate or glucose may be related to the
availability of endogenous energy sources in the obese liver that can be
oxidized and thus inhibit ketogenesis and support fatty acid
esterification.
