[Correlation analysis of serum secreted frizzled-related protein 5 levels with airway inflammation and insulin resistance in chronic obstructive pulmonary disease patients].

Objective: To investigate the relationship between serum secreted frizzled-related protein 5(sfrp5) levels, insulin resistance, and airway inflammation in patients with chronic obstructive pulmonary disease(COPD). Method: A total of 178 COPD patients visiting our respiratory outpatient clinic from February 2015 to January 2017 were enrolled, and 99 healthy control subjects from the same time period were selected. Serum sfrp5 levels were compared between the 2 groups. Serum sfrp5 and inflammatory cytokines in induced sputum were observed in the 4 subgroups: insulin resistant COPD group [homeostasis model assessment of insulin resistance (HOMA-IR)≥2.29], non-insulin resistant COPD group, non-COPD insulin resistant group, and healthy control group. Results: Serum sfrp5 levels were found to be significantly higher in the COPD group as compared to the healthy control group ( t =-14.29, P <0.001). Serum sfrp5 levels in the insulin resistant COPD group [(8±3)ng/ml] were significantly lower than that of the non-insulin resistant COPD group [(10±5)ng/ml], non-COPD insulin resistant group [(13±3)ng/ml], and normal control group [(14±4)ng/ml, F =35.85, P <0.01]. The insulin resistant COPD group had higher levels of In(Homa-IR), as well as tumor necrosis factor-α (TNF-α) and interleukin-6 (IL-6) in induced sputum as compared to the non-insulin resistant COPD group, non-COPD insulin resistant group, and healthy control group ( F values were 64.968, 41.40, 64.15, respectively, P value <0.01 for all items). The non-insulin resistant COPD group had higher levels of In(HOMA-IR) as well as TNF-α and IL-6 in induced sputum as compared to the non-COPD insulin resistant group and healthy control group. FEV(1)/FVC and FEV(1)% predicted were significantly lower in the insulin resistant COPD group as compared to those of non-insulin resistant COPD group and non-COPD insulin resistant group, and healthy control group ( F values were 2.481 and 8.37, respectively, P value<0.05 for all items). FEV(1)/FVC and FEV(1)% predicted were significantly lower in the non-insulin resistant COPD group as compared to those of the healthy control group and non-COPD insulin-resistant group. Serum sfrp5 levels were positively correlated to FEV(1)/FVC and FEV(1) predicted ( r values were 0.466 and 0.412, respectively; P values were <0.001 and 0.007, respectively) and inversely correlated to In(HOMA-IR) and TNF-α and IL-6 in induced sputum ( r values were -0.304, -0.459, -0.517, respectively; P values were <0.001, 0.002, <0.001, respectively). BMI, ln(HOMA-IR), and IL-6 in induced sputum were independent related factors ( r (2) values were 0.286, 0.176, 14.69, respectively; P values were <0.01 for all items) Conclusion: Sfrp5 may be concurrently associated with COPD and insulin resistance; insulin resistance may be associated with airway inflammation and airflow limitation. Sfrp5 may be involved in the development of COPD and may be the key link by which insulin resistance exerts its effects on airway inflammation.