title: A potential new role for muscle in blood glucose homeostasis.
abstract: The breakdown of tissue glycogen into glucose is critical for blood glucose homeostasis between meals. In the final steps of glycogenolysis, intracellular glucose 6-phosphate (Glc-6-P) is transported into the endoplasmic reticulum where it is hydrolyzed to glucose by glucose-6-phosphatase (Glc-6-Pase). Although the majority of body glycogen is stored in the muscle, the current dogma holds that Glc-6-Pase (now named Glc-6-Pase-alpha) is expressed only in the liver, kidney, and intestine, implying that muscle glycogen cannot contribute to interprandial blood glucose homeostasis. Recently we reported a second Glc-6-P hydrolase, Glc-6-Pase-beta. Glc-6-Pase-beta shares kinetic and structural similarities to Glc-6-Pase-alpha and couples with the Glc-6-P transporter to form an active Glc-6-Pase complex (Shieh, J.-J., Pan, C.-J., Mansfield, B. C., and Chou, J. Y. (2003) J. Biol. Chem. 278, 47098-47103). Here we demonstrate that muscle expresses both Glc-6-Pase-beta and Glc-6-P transporter and that they can couple to form an active Glc-6-Pase complex. Our data suggest that muscle may have a previously unrecognized role in interprandial glucose homeostasis.
authors.affiliation: Section on Cellular Differentiation, Heritable Disorders Branch, NICHD, National Institutes of Health, Bethesda, Maryland 20892, USA.
authors.forename: Jeng-Jer
authors.initials: JJ
authors.lastname: Shieh
authors.forename: Chi-Jiunn
authors.initials: CJ
authors.lastname: Pan
authors.forename: Brian C
authors.initials: BC
authors.lastname: Mansfield
authors.forename: Janice Yang
authors.initials: JY
authors.lastname: Chou
mesh_terms: D000256:Adenoviridae / Q000235:genetics; D000818:Animals; D001786:Blood Glucose / Q000502:physiology*; D015152:Blotting, Northern; D015153:Blotting, Western; D019556:COS Cells; D018076:DNA, Complementary / Q000378:metabolism; D005947:Glucose / Q000378:metabolism; D005952:Glucose-6-Phosphatase / Q000096:biosynthesis* / Q000737:chemistry; D019298:Glucose-6-Phosphate / Q000378:metabolism; D006003:Glycogen / Q000378:metabolism; D006863:Hydrogen-Ion Concentration; D006868:Hydrolysis; D007700:Kinetics; D008099:Liver / Q000378:metabolism; D051379:Mice; D018482:Muscle, Skeletal / Q000378:metabolism; D009132:Muscles / Q000201:enzymology* / Q000378:metabolism / Q000502:physiology*; D011485:Protein Binding; D013997:Time Factors
chemical_list: D001786:Blood Glucose; D018076:DNA, Complementary; D019298:Glucose-6-Phosphate; D006003:Glycogen; D005952:Glucose-6-Phosphatase; D005947:Glucose