Abstract: BACKGROUND: Tumor necrosis factor-α (TNF-α), interleukin-6 (IL-6) and transforming growth factor-β (TGF-β) are important systemic inflammation-related factors that have been clinically clearly related to the pathogenesis and development of chronic obstructive pulmonary disease (COPD). However, their relationship with COPD combined with osteoporosis is rarely reported.
OBJECTIVE: To explore the clinical significance of serum TNF-α, TGF-β and IL-6 levels in patients with COPD combined with osteoporosis.
METHODS: A total of 120 COPD patients were selected as the research subjects in accordance with the principle of prospective case control. According to their bone mass, the patients were assigned into a COPD with normal bone mass group, a COPD with osteopenia group and a COPD with osteoporosis group (n=40 per group). The clinical data, serum TNF-α, TGF-β1, and IL-6 levels were compared among three groups. A correlation analysis was conducted between serum TNF-α, TGF-β1, IL-6 and lung function, bone mineral density, and bone metabolism in the COPD with osteoporosis group. Partial correlation analysis was used to analyze the relationship between serum TNF-α, TGF-β1, IL-6 and COPD combined with osteoporosis. The receiver operating characteristic curve was used to evaluate the diagnostic value of serum TNF-α, TGF-β1, and IL-6. The study protocol was implemented in line with the relevant ethics requirements of the Affiliated Hospital of Qinghai University.
RESULTS AND CONCLUSION: Pearson correlation analysis showed that serum TNF-α and IL-6 in COPD with osteoporosis group were negatively correlated with the forced expiratory volume in one second as a percentage of the predicted value (FEVl%Pre), the ratio of the forced expiratory volume in one second to forced vital capacity (FEV1/FVC), and bone mineral density of the lumbar spine and femoral neck, as well as positively correlated with osteoprotegerin and degradation product of β-cross linked C-telope-ptide of type I collagen. The level of TGF-β1 was positively correlated with FEV1%Pre, FEV1/FVC, and bone mineral density of the lumbar spine and femoral neck, and negatively correlated with steoprotegerin and degradation product of β-cross linked C-telope-ptide of type I collagen (P < 0.05). After controlling lung function, bone metabolism, bone mineral density and other factors, serum TNF-α, TGF-β1, and IL-6 were still significantly correlated with COPD combined with osteoporosis (P < 0.05); the area under the receiver operating characteristic curve of serum TNF-α, TGF-β1, and IL-6 in the diagnosis of COPD with osteopenia and COPD with osteoporosis were 0.870 and 0.850, respectively. To conclude, serum levels of TNF-α, TGF-β1, and IL-6 are related to lung function and bone metabolism. The combined detection of the three can provide a reference for clinical evaluation of COPD combined with osteoporosis. 

Key words: chronic obstructive pulmonary disease, osteoporosis, tumor necrosis factor-α, transforming growth factor-β, interleukin-6, bone mass