Background: Weight loss is common in patients with chronic obstructive pulmonary disease (COPD). However, the mechanisms of this weight loss are still unclear.
Methods: Sixty male patients with stable COPD and 45 healthy male controls participated in this study. The COPD patients were divided into two groups, that is, the emphysema and chronic bronchitis groups, by the transfer coefficient of carbon monoxide. The body composition, resting energy expenditure (REE), plasma leptin levels and serum tumor necrosis factor-alpha (TNF-alpha) were measured in all the study participants. The difference and correlation of these parameters were investigated between the two groups.
Results: Emphysematous patients were characterized by a lower body mass index (BMI) and fat-mass (FM) compared with the chronic bronchitis patients (p < 0.001). The plasma leptin levels, as corrected for the FM, were not different between the COPD patients and healthy controls (78.3 +/- 30.9 pg/mL/kg vs. 70.9 +/- 17.3 pg/mL/kg, respectively), and the plasma leptin levels, as adjusted for the FM, were also not different between the two groups of COPD patients. In the chronic bronchitis patients, the plasma leptin concentration was correlated with the BMI (r = 0.866, p < 0.001) but it was not correlated with the BMI in the emphysema patients. The serum TNF-alpha levels were higher in the stable COPD patients than those in the controls, but there was no statistical difference (10.7 +/- 18.6 pg/mL vs. 7.2 x 3.5 pg/mL, respectively, p0.05). The leptin concentration was well correlated with the BMI and %FM in the patients with chronic bronchitis and the leptin concentration was only correlated with the %FM (r = 0.450, p = 0.027) in emphysema patients. There was no correlation between the plasma leptin concentration, as adjusted for the fat mass, and the activity of the TNF-alpha system.
Conclusion: The interaction of leptin and the activity of the TNF-alpha system in the pathogenesis of tissue depletion may not play an important role in chronic stable COPD patients.