A Novel Method to Measure Glucose Uptake and Myosin Heavy Chain Isoform Expression of Single Fibers From Rat Skeletal Muscle

Skeletal muscle includes many individual fibers with diverse phenotypes. A barrier to understanding muscle glucose uptake at the cellular level has been the absence of a method to measure glucose uptake by single fibers from mammalian skeletal muscle. This study's primary objective was to develop a procedure to measure glucose uptake by single fibers from rat skeletal muscle. Rat epitrochlearis muscles were incubated ex vivo with [H-3]-2-deoxy-D-glucose, with or without insulin or AICAR, before isolation of similar to 10-30 single fibers from each muscle. Fiber type (myosin heavy chain [MHC] isoforrn) and glucose uptake were determined for each single fiber. Insulin-stimulated glucose uptake (which was cytochalasin B inhibitable) varied according to MHC isoform expression, with similar to 2-fold greater values for IIA versus IIB or IIX fibers and similar to 1.3-fold greater for hybrid (IIB/X) versus IIB fibers. In contrast, AICAR-stimulated glucose uptake was similar to 1.5-fold greater for IIB versus IIA, fibers. A secondary objective was to assess insulin resistance of single fibers from obese versus lean Zucker rats. Genotype differences were observed for insulin-stimulated glucose uptake and inhibitor kappa B (I kappa B)-beta abundance in single fibers (obese less than lean), with decrements for glucose uptake (44-58%) and I kappa B-beta (25-32%) in each fiber type. This novel method creates a unique opportunity for future research focused on understanding muscle glucose uptake at the cellular level. Diabetes 61:995-1003, 2012