Novel single skeletal muscle fiber analysis reveals a fiber type-selective effect of acute exercise on glucose uptake

One exercise session can induce subsequently elevated insulin sensitivity that is largely attributable to greater insulin-stimulated glucose uptake by skeletal muscle. Because skeletal muscle is a heterogeneous tissue comprised of diverse fiber types, our primary aim was to determine exercise effects on insulin-independent and insulin-dependent glucose uptake by single fibers of different fiber types. We hypothesized that each fiber type featuring elevated insulin-independent glucose uptake immediately postexercise (IPEX) would be characterized by increased insulin-dependent glucose uptake at 3.5 h postexercise (3.5hPEX). Rat epitrochlearis muscles were isolated and incubated with 2-[3H]deoxyglucose. Muscles from IPEX and sedentary (SED) controls were incubated without insulin. Muscles from 3.5hPEX and SED controls were incubated ± insulin. Glucose uptake (2-[3H]deoxyglucose accumulation) and fiber type (myosin heavy chain isoform expression) were determined for single fibers dissected from the muscles. Major new findings included the following: 1) insulin-independent glucose uptake was increased IPEX in single fibers of each fiber type (types I, IIA, IIB, IIBX, and IIX), 2) glucose uptake values from insulin-stimulated type I and IIA fibers exceeded the values for the other fiber types, 3) insulin-stimulated glucose uptake for type IIX exceeded IIB fibers, and 4) the 3.5hPEX group vs. SED had greater insulin-stimulated glucose uptake in type I, IIA, IIB, and IIBX but ...
Source: AJP: Endocrinology and Metabolism - Category: Endocrinology Authors: Tags: Articles Source Type: research