Adiposity and pulmonary function: Relationship with body fat distribution and systemic inflammation

Purpose: Obesity is associated with changes in pulmonary function and increased systemic inflammation. We explored the relationships among adiposity, body fat distribution indices, serum inflammatory markers and pulmonary function. Methods: This was a post-hoc cross-sectional analysis that included subjects who had previously participated in randomized studies on obesity at our centre. Non-smoking sedentary men (282 subjects, mean age 42) without respiratory diseases were studied. BMI, waist circumference (WC), visceral and subcutaneous adipose tissue (AT), lung residual volume (RV), vital capacity (VC) and expiratory reserve volume (ERV) were measured. Serum leptin, adiponectin, tumor necrosis factor alpha (TNF-α) and high-sensitive C-reactive protein (hs-CRP) levels were measured. Results: In subjects with metabolic syndrome (n=124), percent predicted ERV and RV were significantly associated with BMI (ERV: r=-0.19, p=0.02, RV: r=-0.28, p=0.0007), WC (r=-0.20, p=0.02, r=-0.26, p=0.002), visceral (r=-0.22, p=0.007, r=-0.25, p=0.002) and subcutaneous AT (r=-0.19, p=0.02, r=-0.28, p=0.0007). Percent predicted VC correlated with visceral (r=-0.20, p=0.02) and subcutaneous AT (r=-0.18, p=0.03). Leptin was strongly correlated with BMI (MS/no-MS: r=0.52, p=0.0005/r=0.62, p < 0.0001), WC (r=0.41, p=0.008/r=0.49, p < 0.0001), visceral (r=0.27,p=0.09/0.43, p < 0.0001) and subcutaneous AT (r=0.46, p=0.003/r=0.66, p < 0.0001), while adiponectin levels were associated in subjects with no-MS with WC (r=-0.20, p=0.01), visceral (r=-0.22, p=0.008), and subcutaneous AT (r=-0.17, p=0.05). When adjusted for anthropometric measures, neither ERV, RV nor VC was significantly correlated with serum leptin, adiponectin, TNF-α, or hs-CRP levels. Conclusion: These results suggest that the influence of obesity on lung function in healthy subjects is mostly mediated by mechanical factors. Furthermore, not only BMI but also the pattern of fat distribution should be considered when studying associations between adiposity indices and mechanical or inflammatory variables potentially associated with pulmonary function