OBJECTIVETo investigate the effect of tumor necrosis factor-α (TNF-α) on nutritional status and proteolysis of respiratory muscle in a rat model of chronic obstructive pulmonary disease (COPD).

METHODSNinety healthy male adult Wistar rats were randomly divided into model group (A) and normal control group (B). COPD malnutrition rat models were established by cigarettes smoke and nutrient limitation and divided into normal nutrition COPD group (A(1)), malnutrition COPD group (A(2)), and malnutrition COPD intervention group (A(3)). In group A(3), the rats received intravenous injection of TNF-α mAb (0.1 mg/kg). TNF-α levels in the serum and respiratory muscle homogenates were measured using enzyme-linked immunosorbent assay (ELISA), and plasma levels of glucose, albumin, and triglyceride were measured with an automatic biochemistry analyzer. High-performance liquid chromatography was used to measure the contents of 3-methylhistidine and tyrosine in the respiratory muscle homogenates.

RESULTSThe serum TNF-α level and plasma levels of glucose and triglyceride were significantly higher but the plasma albumin level was significantly lower in group A(2) than in groups B, A(1), and A(3) (P<0.01). The contents of 3-MH and Tyr in the respiratory muscle homogenates were significantly higher in group A(2) than in the other 3 groups (P<0.01, P<0.01). TNF-α in the respiratory muscle showed a strong positive correlation to 3-MH and Tyr.

CONCLUSIONTNF-α is one of the causes of increased proteolysis of the respiratory muscle.