Control of glycogen synthesis is shared between glucose transport and glycogen synthase in skeletal muscle fibers

Iñaki Azpiazu, Jill Manchester, Alexander Skurat, Peter Roach, John C. Lawrence

Research output: Contribution to journalArticle

46 Citations (Scopus)

Abstract

The effects of transgenic overexpression of glycogen synthase in different types of fast-twitch muscle fibers were investigated in individual fibers from the anterior tibialis muscle. Glycogen synthase was severalfold higher in all transgenic fibers, although the extent of overexpression was twofold greater in type IIB fibers. Effects of the transgene on increasing glycogen and phosphorylase and on decreasing UDP-glucose were also more pronounced in type IIB fibers. However, in any grouping of fibers having equivalent malate dehydrogenase activity (an index of oxidative potential), glycogen was higher in the transgenic fibers. Thus increasing synthase is sufficient to enhance glycogen accumulation in all types of fast-twitch fibers. Effects on glucose transport and glycogen synthesis were investigated in experiments in which diaphragm, extensor digitorum longus (EDL), and soleus muscles were incubated in vitro. Transport was not increased by the transgene in any of the muscles. The transgene increased basal [14C]glucose into glycogen by 2.5-fold in the EDL, which is composed primarily of IIB fibers. The transgene also enhanced insulin-stimulated glycogen synthesis in the diaphragm and soleus muscles, which are composed of oxidative fiber types. We conclude that increasing glycogen synthase activity increases the rate of glycogen synthesis in both oxidative and glycolytic fibers, implying that the control of glycogen accumulation by insulin in skeletal muscle is distributed between the glucose transport and glycogen synthase steps.

Original languageEnglish
JournalAmerican Journal of Physiology - Endocrinology and Metabolism
Volume278
Issue number2 41-2
StatePublished - Feb 2000

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Glycogen Synthase
Skeletal Muscle Fibers
Glycogen
Muscle
Glucose
Fibers
Transgenes
Skeletal Muscle
Diaphragm
Fast-Twitch Muscle Fibers
Insulin
Uridine Diphosphate Glucose
Glycogen Phosphorylase
Diaphragms
Muscles
Malate Dehydrogenase

Keywords

  • Insulin
  • Muscle fiber type
  • Phosphorylase
  • Uridine diphosphate-glucose

ASJC Scopus subject areas

  • Physiology
  • Endocrinology
  • Biochemistry
  • Physiology (medical)

Cite this

Control of glycogen synthesis is shared between glucose transport and glycogen synthase in skeletal muscle fibers. / Azpiazu, Iñaki; Manchester, Jill; Skurat, Alexander; Roach, Peter; Lawrence, John C.

In: American Journal of Physiology - Endocrinology and Metabolism, Vol. 278, No. 2 41-2, 02.2000.

Research output: Contribution to journalArticle

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