Background: Recent studies have provided evidence for a link between leptin and tumor necrosis factor-alpha (TNF-alpha). Insulin-like growth factor I (IGF-I) mediates the metabolic effects of growth hormone (GH). The GH axis is believed to be suppressed in chronic obstructive pulmonary disease (COPD). The aim of this study is to find out whether acute exacerbations of COPD are followed by changes in plasma leptin and insulin-like growth factor I (IGF-I) levels and furthermore, whether these changes are related to systemic inflammation.
Methods: We measured serum leptin, IGF-I, TNF-alpha, interleukin 1 beta (IL-1 beta), interleukin 6 (IL-6) and interleukin 8 (IL-8) levels in 52 COPD patients with acute exacerbation on admission to hospital (Day 1) and two weeks later (Day 15). 25 healthy age-matched subjects served as controls. COPD patients were also divided into two subgroups (29 with chronic bronchitis and 23 with emphysema). Serum leptin and IGF-I were measured by radioimmunoassay and TNF-alpha, IL-1 beta, IL-6 and IL-8 were measured by ELISA.
Results: Serum leptin levels were significantly higher and serum IGF-I levels significantly lower in COPD patients on Day 1 than in healthy controls (p < 0.001). A positive correlation was observed between leptin and TNF-alpha on Day 1 (r = 0.620, p < 0.001). Emphysematous patients had significantly lower IGF-I levels compared to those with chronic bronchitis both on Day 1 and Day 15 (p = 0.003 and p < 0.001 respectively).
Conclusion: Inappropriately increased circulating leptin levels along with decreased IGF-I levels occurred during acute exacerbations of COPD. Compared to chronic bronchitis, patients with emphysema had lower circulating IGF-I levels both at the onset of the exacerbation and two weeks later.