Regulation of initiation of protein synthesis by insulin in skeletal muscle

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Abstract

Protein synthesis is impaired in skeletal muscle and heart from diabetic rats. In muscles composed primarily of slow-twitch fibres (e.g. heart or soleus), the inhibition of protein synthesis can be accounted for entirely by a decrease in the amount of RNA. In contrast, in muscles of mixed fibre composition (e.g. gastrocnemius or psoas), the inhibition of protein synthesis is associated with an impairment in peptide-chain initiation. We have found that the inhibition of peptide-chain initiation that occurs in muscles composed of mixed fast-twitch fibres involves eukaryotic initiation factor 2B (eIF-2B). Thus, eIF-2B activity is inhibited in gastrocnemius and psoas but not heart or soleus from diabetic rats. In other systems eIF-2B activity is regulated by phosphorylation of the α-subunit of a second initiation factor, eIF-2. However, we have found no change in the phosphorylation state of eIF-2α in either fast-or slow-twitch muscles from diabetic compared to control animals. Instead, the available evidence suggests that eIF-2B activity may be modulated by an alternate mechanism such as a change in the extent of phosphorylation of the 82,000 Mr subunit of the factor or a change in the NADPH/NADP+ ratio.

Original languageEnglish (US)
Pages (from-to)134-139
Number of pages6
JournalActa Diabetologica
Volume28
Issue number2
DOIs
StatePublished - Jun 1 1991

All Science Journal Classification (ASJC) codes

  • Internal Medicine
  • Endocrinology, Diabetes and Metabolism
  • Endocrinology

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