Stimulation of hepatic glycogen synthesis by amino acids

Abstract

Hepatocytes isolated from livers of fasted rats form little glycogen from glucose or lactate at concentrations below 20 mM. Glycogen is formed in substantial quantities at a glucose concentration of 60 mM. In the presence of 10 mM glucose, 20-30% as much glycogen as glucose is formed from fructose, sorbitol, or dihydroxyacetone. The addition of either glutamine, alanine, or asparagine stimulates the formation of glycogen from lactate 10- to 40-fold. The formation of glucose and glycogen is then about equal, and glycogen deposition in hepatocytes is similar to rates attained in vivo after fasted rats are refed. The amino acids stimulate 1.5- to 2-fold glycogen synthesis from fructose, and 2- to 4-fold synthesis from dihyDROXYACETONE. Ammonium chloride is about one-half as effective as amino acids in stimulating glycogen synthesis when glucose with lactate are substrates. It increased glycogen synthesis 25-50% from fructose but inhibited synthesis from dihydroxyacetone plus glucose.