Muscle ubiquitin m-RNA levels in patients with end-stage renal disease on maintenance hemodialysis

Background: Loss of lean body mass is frequently reported in patients with end-stage renal disease (ESRD). Inadequate nutrient intake, superimposed illnesses, endocrine disorders, uremia and acidosis are some of the potential causes of muscle depletion. Previous reports on experimental models show that lean body mass depletion results from enhancement of muscle tissue protein catabolism, mainly associated with activation of ATP-ubiquitin-dependent proteolysis. Little is known, however, about the affects on this proteolytic system in ESRD patients on maintenance hemodialysis (HD)). The present study was designed to investigate the expression of ubiquitin mRNAs in skeletal muscle of patients with ESRD on maintenance HD. Methods: Biopsies from the rectus abdominis muscle were obtained from eight ESRD patients and from six control subjects undergoing surgery for benign disease. Ubiquitin mRNA levels were measured by Northern blotting analysis. Results: Patients with ESRD had mild metabolic acidosis, as a result of chronic intermittent HD. There were no significant differences between HD patients and controls with regard to the 1.2kb polyubiquitin mRNA species (332.9 +/- 139 vs 324.2 +/- 60; ns), but the levels of the 2.4 kb mRNA species were significantly lower in HD patients than in controls (1687 +/- 542 vs 2529.9 +/- 325, p = 0.01). No correlation was observed between ubiquitin mRNA levels and nutritional parameters and degree of acidosis. Conclusions: The present study found that the ubiquitin mRNA levels were not increased in the muscle of stable, mildly acidotic hemodialysis patients.