Muscle Protein Degradation in Severely Malnourished Patients With Chronic Obstructive Pulmonary Disease Subject to Short-Term Total Parenteral Nutrition

Patients with chronic obstructive pulmonary disease (COPD) often lose weight and muscle mass with progression of the disease. Muscle protein degradation in patients with COPD has never been examined before and during hypercaloric feeding. Eight severely malnourished patients with COPD were examined at home consuming their usual intake, in the hospital after 3 days of a meat-free regular oral diet (period B), and during a hypercaloric (55 kcal/kg) high-lipid (55%) parenteral formula (total parenteral nutrition [TPN]). During period B, 8 well-nourished patients and 10 malnourished cancer patients were used as control groups. Measurements included plasma assays, leg blood flow, leg exchange (of 3-methylhistidine [3MeH], glucose, lactate, and oxygen) and urinary measures of 3MeH, creatinine, and nitrogen. During period B, net release of 3MeH across the leg in patients with COPD was similar to that in well-nourished control subjects and cachectic cancer patients. In COPD patients, there was only a transient decrease in leg exchange values of 3MeH with administration of TPN. COPD patients demonstrated a reduction (p < .01) in urinary 3MeH excretion and an increase in nitrogen balance (p < .01) with TPN compared with period B. The decrease in muscle protein degradation with administration of TPN accounts for about 50% of the increase in nitrogen retention in patients with COPD. These data suggest that in severely malnourished patients with COPD the weight loss is not dependent on increased rates of skeletal muscle protein degradation; nevertheless, degradation rates attenuate with a positive nitrogen balance during nutrition repletion. (Journal of Parenteral and Enteral Nutrition 16: 248-254, 1992)