Increased serum inflammatory markers in the absence of clinical and skeletal muscle inflammation in patients with chronic obstructive pulmonary disease.

BACKGROUND: Muscle wasting and cachexia are common occurrences in patients with chronic obstructive pulmonary disease (COPD).
OBJECTIVES: The current study aimed to investigate markers of inflammation in the circulation and skeletal muscle that might be associated with development of muscle wasting.
METHODS: Three groups of patients with mild, moderate and severe COPD and matched healthy controls were recruited. Serum levels of C-reactive protein (CRP), high-sensitivity CRP (hs-CRP), IL-6, IL-8, TNF-alpha, cortisol, insulin-like growth factor 1 (IGF-1), leptin and ghrelin were analysed. Skeletal muscle inflammation was investigated microscopically using a panel of antibodies and standard staining for inflammatory cell infiltration.
RESULTS: All COPD patients were clinically stable, with no sign of inflammation and normal CRP values. Compared to controls, significantly increased hs-CRP levels were observed in all COPD patient groups. Significant rises in IL-6 levels were first observed in moderate COPD, while IL-8 levels were significantly elevated at the late severe stage. Circulating levels of TNF-alpha, cortisol, IGF-1, leptin and ghrelin were similar to control levels. No microscopic signs of skeletal muscle inflammation were observed.
CONCLUSION: Our results identify hs-CRP as an early marker of inflammation that is significantly increased in the circulation even in mild COPD. Serum interleukin levels appear to be increased with disease progress. These changes were manifested in the absence of any clinical signs of disease exacerbation, evidence of skeletal muscle inflammation or hormonal changes.