A high-sucrose diet increases gluconeogenic capacity in isolated periportal and perivenous rat hepatocytes

Abstract

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 · mg−1) 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 phospho enolpyruvate 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.