Correlation Analysis Of Serum SFRP5 Levels With Airway Inflammation And Insulin Resistance In COPD Patients

Objective:To study the correlation between serum secreted Frizzled-related protein 5 (SFRP5)levels and insulin resistance,airflow limitation,and airway inflammation in chronic obstructive pulmonary disease(COPD)patients.Methods:One hundred and seventy-eight COPD patients attending our hospital's respiratory outpatient clinic from February 2015 to January 2017 and ninety-nine healthy subjects attending our physical checkup center during the same time period were enrolled into the study.Serum SFRP5 levels,parameters for glucose metabolism,and pulmonary function were measured,as well as inflammatory cytokines in induced sputum.Homeostatic model assessment of insulin resistance (HOMA-IR)was calculated.COPD patients and healthy control subjects were divided into four groups based on HOMA-IR:insulin resistant COPD(IR-COPD)group,non-insulin resistant COPD(NIR-COPD)group,insulin resistant(IR)group,and non-insulin resistant(NIR)healthy control group.Differences in the parameters were compared between the groups,and correlation analysis was performed.Results:(1)Serum SFRP5 levels were decreased in the COPD group compared to that of the healthy control group(t=-14.29,p<0.001);(2)Serum SFRP5 levels were lower in the IR-COPD group compared to that of the NIR-COPD group,IR group,and NIR healthy control group(F=35.85,p<0.01);(3)Tumor necrosis factor-?(TNF-?)and interleukin-6(IL-6)levels in induced sputum and ln(HOMA-IR)in the IR-COPD group were elevated compared to that of the NIR-COPD group,IR group,and NIR healthy control group(F values were 41.40,64.15,64.968,respectively;p values were<0.01,<0.01,and<0.001,respectively);(4)FEV1%predicted(FEV1%pred)and FEV1/FVC values were decreased in the IR-COPD group compared to that of the NIR-COPD group,IR group,and NIR healthy control group(F values were 8.37 and2.481,respectively;p values were<0.05 for all items);(5)Serum SFRP5 levels shared a positive correlation with FEV1%pred and FEV1/FVC(r values were 0.412and 0.466,respectively;p values were 0.007 and<0.001,respectively)and a negative correlation with TNF-?and IL-6 levels in induced sputum and ln(HOMA-IR)(rvalues were-0.459,-0.517,and-0.304,respectively;p values were 0.002,<0.001,and<0.001,respectively);(6)ln(HOMA-IR),body mass index(BMI),and IL-6 in induced sputum were independently related to serum SFRP5(r~2 values were 0.176,0.286,14.69,respectively;p values were<0.010,<0.010,and<0.001,respectively).Conclusion:Serum SFRP5 is associated with COPD and insulin resistance;insulin resistance may be associated with airway inflammation and airflow limitation.SFRP5 may play a role in the pathogenesis of COPD.Insulin resistance may exert its effects on airway inflammation through modulation of SFRP5.