Lookup NU author(s): Dr Chris Redfern,
Professor Tim Goodship
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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.
Author(s): Roberts, R.G., Redfern, C.P.F., Goodship, T.H.J.
Publication type: Article
Publication status: Published
Journal: European Journal of Clinical Investigation
Print publication date: 01/10/2003
ISSN (print): 0014-2972
ISSN (electronic): 1365-2362
PubMed id: 14511357
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