Muscle biopsy studies in chronically uremic patients: evidence for malnutrition

Evidence for muscle protein wasting and abnormal muscle metabolism is common in uremia. Muscle DNA content is considered a reliable reference standard in normal and undernourished adults. Muscle RNA content rapidly changes during starvation and refeeding. The ratio of noncollagen alkali-soluble proteins (ASP) to DNA is considered to be an estimate of the cytoplasmic volume of a single cell, and the RNA: DNA ratio is an index of the ribosomal capacity for protein synthesis. Muscle DNA, RNA, ASP, water, and fat content were determined in muscle biopsy specimens from chronically uremic patients receiving conservative treatment (CT), maintenance hemodialysis (two centers), or CAPD. Nutrient intake was low and the anthropometric indices were decreased in all groups of patients, except in the hemodialysis patients from one center. Serum proteins and muscle ASP: DNA and RNA: DNA ratios were decreased. The nutritional status was reassessed in some malnourished CAPD patients after about one year of careful nutritional advice and was unchanged. These results suggest that chronically uremic patients on CT are often malnourished, primarily because of an inadequate protein and/or energy intake. Muscle nucleic acid and protein content are useful tools for nutritional assessment at a cellular level in humans with chronic renal failure and can be used to monitor the response to nutritional therapy.