Fructose effect to enhance liver glycogen deposition is due to inhibition of glycogenolysis
The effect of fructose on glycogen degradation was examined by measuring flux of (/sup 14/C) from prelabeled glycogen in perfused rat livers. During 2 h refeeding of fasted rats hepatic glycogen was labeled by injection of (U /sup 14/C) galactose (0.1 mg and 0.02 ..mu..Ci/g of body weight). Refed livers were perfused for 30 min with glucose only (10 mM) and for 60 min with glucose (10 mM) without (n=5) or with fructose (1, 2, 10 mM; n=5 for each). With fructose, label production immediately declined and remained suppressed through the end of perfusion (P < 0.05). Suppression was dose-dependent: steady state label production was suppressed 45, 64, and 72% by 1, 2, and 10 mM fructose (P < 0.0001), without significant changes in glycogen synthase or phosphorylase. These results suggest the existence of allosteric inhibition of phosphorylase in the presence of fructose. Fructose 1-phosphate (F1P) accumulated in proportion to fructose (0.11 +/- 0.01 without fructose, 0.86 +/- 0.03, 1.81 +/- 0.18, and 8.23 +/- 0.6 ..mu..moles/g of liver with 1, 2, and 10 mM fructose. Maximum inhibition of phosphorylase was 82%; FIP concentration for half inhibition was 0.57 ..mu..moles/g of liver, well within the concentration of F1P attained in refeeding. Fructose enhances net glycogen synthesis in liver by suppressing glycogenolysis and the suppression is presumably caused by allosteric inhibition of phosphorylase by F1P.
- Research Organization:
- Univ. of Southern California School of Medicine, Los Angeles
- OSTI ID:
- 5941665
- Report Number(s):
- CONF-870644-; TRN: 87-039126
- Journal Information:
- Fed. Proc., Fed. Am. Soc. Exp. Biol.; (United States), Vol. 46:6; Conference: 78. annual meeting of the American Society of Biological Chemists conference, Philadelphia, PA, USA, 7 Jun 1987
- Country of Publication:
- United States
- Language:
- English
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FRUCTOSE
BIOCHEMICAL REACTION KINETICS
GLYCOGEN
METABOLISM
PHOSPHOTRANSFERASES
INHIBITION
BIOSYNTHESIS
CARBON 14 COMPOUNDS
DOSE-RESPONSE RELATIONSHIPS
GALACTOSE
GLYCOLYSIS
LIVER
RATS
TRACER TECHNIQUES
ALDEHYDES
ANIMALS
BODY
CARBOHYDRATES
DIGESTIVE SYSTEM
ENZYMES
GLANDS
HEXOSES
ISOTOPE APPLICATIONS
KETONES
KINETICS
LABELLED COMPOUNDS
MAMMALS
MONOSACCHARIDES
ORGANIC COMPOUNDS
ORGANS
PHOSPHORUS-GROUP TRANSFERASES
POLYSACCHARIDES
REACTION KINETICS
RODENTS
SACCHARIDES
SYNTHESIS
TRANSFERASES
VERTEBRATES
550501* - Metabolism- Tracer Techniques