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Fiber Type Heterogeneity for Glucose Uptake by Single IIA, IIB, IIX and IIB/X Fibers from Rat Epitrochlearis Muscle
Author(s) -
MacKrell James,
Cartee Gregory D.
Publication year - 2011
Publication title -
the faseb journal
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.709
H-Index - 277
eISSN - 1530-6860
pISSN - 0892-6638
DOI - 10.1096/fasebj.25.1_supplement.lb585
Subject(s) - medicine , endocrinology , skeletal muscle , myosin , chemistry , fiber , glucose transporter , insulin , fiber type , glucose uptake , biology , biochemistry , organic chemistry
Models for studying glucose uptake (GU) by cultured muscle cells are valuable, but lack important characteristics of authentic skeletal muscle. Studies that evaluate skeletal muscle must be mindful of its fiber type heterogeneity. Our aim was to determine the effect of fiber type on GU by single fibers from skeletal muscle employing a novel single fiber GU method with a standard method for classifying fiber type (myosin heavy chain, MHC). Rat epitrochlearis muscles underwent an ex vivo incubation protocol with [3H]‐2‐deoxyglucose (2DG) ± 12nM insulin. Following collagenase treatment of the muscle, non‐permeabilized single fibers were dissected and analyzed for fiber volume, MHC, and GU (2DG accumulation relative to fiber volume, nmol/mm3). Basal GU did not differ among fiber types. ANOVA revealed a significant difference for insulin‐stimulated GU between IIA fibers vs. all other measured fiber types (IIA > IIB, IIX, IIB/X), and a significant difference between IIB/X vs. IIB fibers (IIB/X > IIB). Insulin‐stimulated GU was independently inhibited by cytochalasin B (25μM) or wortmannin (0.5μM), verifying fiber 2DG accumulation occurred via glucose transporter‐mediated uptake and in a PI3K‐dependent manner. The current data extend insights from whole muscle experiments which are limited because they cannot unambiguously identify differences attributable to fiber types. Support : NIH (NIDDK 71771 & AG10026)