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Exercise Science Research Institute, Arizona State University, Tempe, Arizona
A high-sucrose (SU)
diet increases gluconeogenesis (GNG) in the liver. The present study
was conducted to determine the contribution of periportal (PP) and
perivenous (PV) cell populations to this SU-induced increase in GNG.
Male Sprague-Dawley rats were fed an SU (68% sucrose) or starch (ST,
68% starch) diet for 1 wk, and hepatocytes were isolated from the PP
or PV region of the liver acinus. Hepatocytes were incubated for 1 h in the presence of various gluconeogenic substrates, and glucose
release into the medium was used to estimate GNG. When incubated in the
presence of 5 mM lactate, which enters GNG at the level of pyruvate,
glucose release
(nmol · h
1 · mg1) was
significantly increased by the SU diet in both PP (84.8 ± 3.4 vs.
70.4 ± 2.6) and PV (64.3 ± 2.5 vs. 38.2 ± 2.1) cells. Addition of palmitate (0.5 mM) increased glucose release from lactate
in PP cells by 11.6 ± 0.5 and 20.6 ± 1.5% and in
PV cells by 11.0 ± 4.4 and 51.1 ± 9.1% in SU and
ST, respectively. When cells were incubated with 5 mM dihydroxyacetone
(DHA), which enters GNG at the triosephosphate level, glucose release
was significantly increased by the SU diet in both cell types. In
contrast, glucose release from fructose (0.5 mM) was significantly
increased by the SU diet in PV cells only. These changes in glucose
release were accompanied by significant increases in the maximal
specific activities of glucose-6-phosphatase (G-6-Pase) and
phosphoenolpyruvate carboxykinase (PEPCK) in both PP and PV
cells. These data suggest that the SU diet influences GNG in both PP
and PV cell populations. It appears that SU feeding produces changes in
GNG via alterations in at least two critical enzymes, G-6-Pase and PEPCK.
liver; diet composition; glucose production
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