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Updated: Aug 30, 2026

Glucose Uptake Measurement and Response to Insulin Stimulation in In Vitro Cultured Human Primary Myotubes
Published on: June 25, 2017
Effect of insulin upon protein degradation in cultured human myocytes
R G Roberts1, C P F Redfern, T H J Goodship
1Department of Nephrology, School of Clinical Medical Sciences, University of Newcastle upon Tyne, Newcastle upon Tyne, UK.
Background:
The anabolic effects of insulin are well recognized but the mechanism by which insulin decreases muscle protein degradation in human is unclear. However, in a variety of catabolic conditions it is believed to be changes in the activity of the ATP-dependent ubiquitin proteolytic pathway that are responsible for changes in protein degradation in skeletal muscle. The aim of this study was to test the hypothesis that insulin regulates the ATP-dependent ubiquitin proteolytic pathway in human muscle.
Material And Methods:
The effects of insulin and acidosis on protein degradation were measured in human myocytes using L-[14C]phenylalanine. The effect of insulin on the activity of the ATP-dependent ubiquitin pathway was assessed from the mRNA expression of ubiquitin and the ubiquitin-conjugating enzyme E214k in human myocytes.
Results And Conclusions:
Coincubation of human myocytes with 100 nM of insulin was associated with a significant reduction in protein degradation. Metabolic acidosis is known to increase skeletal muscle protein degradation rates, and in our experiments protein degradation at a pH of 7.0 was significantly higher than pH 7.35. Eight-hour exposure to 100 nM of insulin resulted in a significant reduction in the expression of E214k but no change in the expression of ubiquitin.
Conclusions:
In human muscle we have demonstrated regulation by insulin of the ATP-dependent ubiquitin pathway at the level of ubiquitin conjugation.
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