title: Liver glucose metabolism in humans.
abstract: Information about normal hepatic glucose metabolism may help to understand pathogenic mechanisms underlying obesity and diabetes mellitus. In addition, liver glucose metabolism is involved in glycosylation reactions and connected with fatty acid metabolism. The liver receives dietary carbohydrates directly from the intestine via the portal vein. Glucokinase phosphorylates glucose to glucose 6-phosphate inside the hepatocyte, ensuring that an adequate flow of glucose enters the cell to be metabolized. Glucose 6-phosphate may proceed to several metabolic pathways. During the post-prandial period, most glucose 6-phosphate is used to synthesize glycogen via the formation of glucose 1-phosphate and UDP-glucose. Minor amounts of UDP-glucose are used to form UDP-glucuronate and UDP-galactose, which are donors of monosaccharide units used in glycosylation. A second pathway of glucose 6-phosphate metabolism is the formation of fructose 6-phosphate, which may either start the hexosamine pathway to produce UDP-N-acetylglucosamine or follow the glycolytic pathway to generate pyruvate and then acetyl-CoA. Acetyl-CoA may enter the tricarboxylic acid (TCA) cycle to be oxidized or may be exported to the cytosol to synthesize fatty acids, when excess glucose is present within the hepatocyte. Finally, glucose 6-phosphate may produce NADPH and ribose 5-phosphate through the pentose phosphate pathway. Glucose metabolism supplies intermediates for glycosylation, a post-translational modification of proteins and lipids that modulates their activity. Congenital deficiency of phosphoglucomutase (PGM)-1 and PGM-3 is associated with impaired glycosylation. In addition to metabolize carbohydrates, the liver produces glucose to be used by other tissues, from glycogen breakdown or from de novo synthesis using primarily lactate and alanine (gluconeogenesis).
authors.affiliation: Nephrology Division, Hospital General Juan Cardona, c/ Pardo Bazán s/n, 15406 Ferrol, Spain madevaa@yahoo.com.
authors.forename: María M
authors.initials: MM
authors.lastname: Adeva-Andany
authors.affiliation: Nephrology Division, Hospital General Juan Cardona, c/ Pardo Bazán s/n, 15406 Ferrol, Spain.
authors.forename: Noemi
authors.initials: N
authors.lastname: Pérez-Felpete
authors.affiliation: Nephrology Division, Hospital General Juan Cardona, c/ Pardo Bazán s/n, 15406 Ferrol, Spain.
authors.forename: Carlos
authors.initials: C
authors.lastname: Fernández-Fernández
authors.affiliation: Nephrology Division, Hospital General Juan Cardona, c/ Pardo Bazán s/n, 15406 Ferrol, Spain.
authors.forename: Cristóbal
authors.initials: C
authors.lastname: Donapetry-García
authors.affiliation: Nephrology Division, Hospital General Juan Cardona, c/ Pardo Bazán s/n, 15406 Ferrol, Spain.
authors.forename: Cristina
authors.initials: C
authors.lastname: Pazos-García
mesh_terms: D005947:Glucose / Q000378:metabolism*; D006031:Glycosylation; D006801:Humans; D050356:Lipid Metabolism / Q000502:physiology; D008099:Liver / Q000378:metabolism*; D011499:Protein Processing, Post-Translational / Q000502:physiology; D015398:Signal Transduction / Q000502:physiology
chemical_list: D005947:Glucose
keywords: diabetes; glucokinase; glucose; hexosamine pathway; pentose phosphate pathway