Alterations of proteasome activities in skeletal muscle tissue of diabeticrats

During the last years many investigations have shown that a major catalyst within the mechanism of skeletal muscle wasting occuring under conditions l ike sepsis, injuries, trauma, cancer cachexia, chronic acidosis, fasting, g lucocorticoid treatment, and insulinopenia is the ubiquitin-proteasome syst em. Evidence for this was obtained by findings that the rate of ATP-depende nt protein degradation is increased, that m-RNA concentrations of several p roteasome subunits and ubiquitin are increased and the amount of ubiquitin- protein conjugates is elevated under these conditions. Additionally, the en hanced protein breakdown was shown to be suppressed by proteasome inhibitor s. In the present report we show that most but not all of the proteolytic a ctivities of partially purified 20S/26S proteasomes from skeletal muscle of rats increase after induction of Diabetes mellitus. This finding suggests that part of the mechanism of acceleration of muscle protein breakdown is d ue to changes in proteasome activities.