Published 2001 | Version v1
Journal article

Implications of the simultaneous occurrence of glycolysis and gluconeogenesis in hepatocytes from normal and hyperthyroid rats

  • 1. Flinders University, Adelaide, SA (Australia). School of Medicine, Departments of Medical Biochemistry
  • 2. Flinders University, Adelaide, SA (Australia). School of Medicine, Human Physiology

Description

The mammalian liver has the capability for both glycolysis and gluconeogenesis. In the fasting state, metabolites such as lactate and glycerol, generated in the peripheral tissues, are taken up by the liver and converted to glucose. However, hepatocytes from fasted animals are also capable of substantial rates of glycolysis. It is generally assumed that glycolysis and gluconeogenesis do not occur simultaneously in the same cell, but rather the metabolic conditions that facilitate flux through one pathway impair flow in the opposite direction. The actual direction of flow at any given moment is thought to be determined by regulatory mechanisms that control flux through the enzymatic steps specific to glycolysis and gluconeogenesis. The rates of glycolysis from [6-3H]glucose and gluconeogenesis from [U-14C]glycerol were determined in isolated hepatocytes from fasted normal and hyperthyroid rats. We observed that glycolysis from glucose and glucose synthesis from glycerol occurred simultaneously at substantial rates in hepatocytes from normal rats and that gluconeogenesis, but not glycolysis, was increased twofold in hepatocytes from thyroid treated rats. In the hyperthyroid state, the rate of glycolysis from glucose was approximately equal to the rate of glucose formation from glycerol. Hence, metabolism and ATP turnover were stimulated without substantially altering steady-state concentrations of glucose. The concomitant operation of hepatic glycolysis and gluconeogenesis may be a mechanism that accounts in part for the calorigenic effect of thyroid hormone. Since hepatocyles are generally impermeable to phosphorylated metabolites, our observations suggest that glycolysis, and phosphorylation of glycerol take place in the same cells, and that the occurrence of simultaneous glycolysis and gluconeogenesis is an indication of channelling within the hepatocyte cytoplasm of individual hepatocytes

Additional details

Publishing Information

Journal Title
Proceedings of the Australian Society for Biochemistry and Molecular Biology
Journal Volume
33
Journal Page Range
p. POS1-029
ISSN
1038-2232
CODEN
PSBBEX

Conference

Title
ComBio 2001. 45th Australian Society for Biochemistry and Molecular Biology (ASBMB), 41st Annual Australian Society of Plant Physiologists Inc., Annual New Zealand Society for Cell and Developmental Biology Inc., International Proteomics Conference (IPC 2001)
Dates
1-4 Oct 2001
Place
Canberra (Australia)