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Am J Physiol Endocrinol Metab. 2016 Nov 1;311(5):E818-E824. doi: 10.1152/ajpendo.00289.2016. Epub 2016 Sep 6.

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

Author information

1
Muscle Biology Laboratory, School of Kinesiology, University of Michigan, Ann Arbor, Michigan; gcartee@umich.edu.
2
Department of Molecular and Integrative Physiology, University of Michigan, Ann Arbor, Michigan; and.
3
Institute of Gerontology, University of Michigan, Ann Arbor, Michigan.
4
Muscle Biology Laboratory, School of Kinesiology, University of Michigan, Ann Arbor, Michigan.

Abstract

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 not type IIX fibers. Insulin-dependent glucose uptake was increased at 3.5hPEX in each fiber type except for IIX fibers, although insulin-independent glucose uptake was increased IPEX in all fiber types (including type IIX). Single fiber analysis enabled the discovery of this fiber type-related difference for postexercise, insulin-stimulated glucose uptake.

KEYWORDS:

exercise; glucose transport; insulin sensitivity and insulin resistance

PMID:
27600826
PMCID:
PMC5130359
DOI:
10.1152/ajpendo.00289.2016
[Indexed for MEDLINE]
Free PMC Article

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