title: Fiber type effects on contraction-stimulated glucose uptake and GLUT4 abundance in single fibers from rat skeletal muscle.
abstract: To fully understand skeletal muscle at the cellular level, it is essential to evaluate single muscle fibers. Accordingly, the major goals of this study were to determine if there are fiber type-related differences in single fibers from rat skeletal muscle for: 1) contraction-stimulated glucose uptake and/or 2) the abundance of GLUT4 and other metabolically relevant proteins. Paired epitrochlearis muscles isolated from Wistar rats were either electrically stimulated to contract (E-Stim) or remained resting (No E-Stim). Single fibers isolated from muscles incubated with 2-deoxy-d-[(3)H]glucose (2-DG) were used to determine fiber type [myosin heavy chain (MHC) isoform protein expression], 2-DG uptake, and abundance of metabolically relevant proteins, including the GLUT4 glucose transporter. E-Stim, relative to No E-Stim, fibers had greater (P < 0.05) 2-DG uptake for each of the isolated fiber types (MHC-IIa, MHC-IIax, MHC-IIx, MHC-IIxb, and MHC-IIb). However, 2-DG uptake for E-Stim fibers was not significantly different among these five fiber types. GLUT4, tethering protein containing a UBX domain for GLUT4 (TUG), cytochrome c oxidase IV (COX IV), and filamin C protein levels were significantly greater (P < 0.05) in MHC-IIa vs. MHC-IIx, MHC-IIxb, or MHC-IIb fibers. TUG and COX IV in either MHC-IIax or MHC-IIx fibers exceeded values for MHC-IIxb or MHC-IIb fibers. GLUT4 levels for MHC-IIax fibers exceeded MHC-IIxb fibers. GLUT4, COX IV, filamin C, and TUG abundance in single fibers was significantly (P < 0.05) correlated with each other. Differences in GLUT4 abundance among the fiber types were not accompanied by significant differences in contraction-stimulated glucose uptake.
authors.affiliation: Muscle Biology Laboratory, School of Kinesiology, University of Michigan, Ann Arbor, Michigan;
authors.forename: Carlos M
authors.initials: CM
authors.lastname: Castorena
authors.affiliation: Muscle Biology Laboratory, School of Kinesiology, University of Michigan, Ann Arbor, Michigan;
authors.forename: Edward B
authors.initials: EB
authors.lastname: Arias
authors.affiliation: Muscle Biology Laboratory, School of Kinesiology, University of Michigan, Ann Arbor, Michigan;
authors.forename: Naveen
authors.initials: N
authors.lastname: Sharma
authors.affiliation: Section of Endocrinology and Metabolism, Department of Internal Medicine, Yale University School of Medicine, New Haven, Connecticut; Department of Cell Biology, Yale University School of Medicine, New Haven, Connecticut;
authors.forename: Jonathan S
authors.initials: JS
authors.lastname: Bogan
authors.affiliation: Muscle Biology Laboratory, School of Kinesiology, University of Michigan, Ann Arbor, Michigan; Department of Molecular and Integrative Physiology, University of Michigan, Ann Arbor, Michigan; and Institute of Gerontology, University of Michigan, Ann Arbor, Michigan gcartee@umich.edu.
authors.forename: Gregory D
authors.initials: GD
authors.lastname: Cartee
mesh_terms: D000818:Animals; D001692:Biological Transport; D003847:Deoxyglucose / Q000493:pharmacokinetics; D005947:Glucose / Q000378:metabolism*; D051275:Glucose Transporter Type 4 / Q000378:metabolism*; D008297:Male; D009119:Muscle Contraction / Q000502:physiology*; D018485:Muscle Fibers, Skeletal / Q000145:classification / Q000502:physiology*; D018482:Muscle, Skeletal / Q000378:metabolism*; D018995:Myosin Heavy Chains / Q000378:metabolism; D020033:Protein Isoforms / Q000378:metabolism; D051381:Rats; D017208:Rats, Wistar
chemical_list: D051275:Glucose Transporter Type 4; D020033:Protein Isoforms; C495694:Slc2a4 protein, rat; D003847:Deoxyglucose; D018995:Myosin Heavy Chains; D005947:Glucose
keywords: exercise; glucose transport; glucose transporter; myofiber; myosin heavy chain