Increased resting energy expenditure is related to plasmaTNF-α concentration in stable COPD patients

The objective of this study was to test whether increased resting energy expenditure (REE) in chronic obstructive pulmonary disease (COPD) patients is related to increased cost of breathing and/or to increased cytokine production. In 36 non-inflammatory (CRP: 17.6 ± 13.1 mg.l−1, mean ± SD; orosomucoid: 0.71 ± 0.18 g.l−1), non-malnourished(BMI: 23.6 ± 4.3 kg. m−2), clinically stable, non severely hypoxic COPD patient (60.5 ± 8.9 years) we measured REE, pulmonary function and plasma cytokine concentrations (TNF-α, IL1 and IL6). REE was increased by 10 ± 11% (P< 0.001) above predicted values. Plasma TNF-α concentration was increased in all patients (mean value 26.3 ± 14.3 pg.ml−1). Excess REE (with respect to values predicted by Harris-Benedict equations) was correlated with plasma TNF-α concentration (P< 0.005), but not with the degree of airway obstruction, lung overinflation, or with oxygen cost of breathing. Theophylline treatment resulted in a significant increase in REE by 15%. In conclusion: non-malnourished, clinically stable, non-severely hypoxic COPD patients display anincreased REE that is related with plasma TNF-α concentration (without apparent systemic inflammation) and to theophylline treatment, but that is independent of parameters of respiratory function