Serum osteoprotegerin (OPG) and osteopontin (OPN) in patients with COPD during two-year follow-up study

The aim of our study was to explore the possible role of OPG and OPN levels as biomarkers in COPD. We measured OPG and OPN in the serum of 22 controls and all together 58 COPD patients. The levels of OPG were higher in controls (2.25±0.50 vs. 1.10±0.18 ng/ml, p=0.008). Patients with more advanced GOLD stages (III+IV), as well as the common exacerbators had lower OPG than patients with a disease in initial stages (0.68±0.06 vs. 1.34±0.28 ng/ml, p=0.08) and than non-common exacerbators (0.73±0.06 vs. 1.39±0.31 ng/ml, p=0.067). Patients with stable or improved FEV1% pr. during the follow-up period had higher OPG than those with decline FEV1% pr. (p=0.034). A significant positive correlation was seen at the end of the followed-up period between OPG and FEV1% pr. (Rho=0.373, p=0.006). The non-symptomatic patients (CAT points <10) had higher OPG levels than symptomatic (2.07±0.77 vs. 0.91±0.15 ng/ml, p=0.017). OPN concentration was higher in controls (13.18±0.64 vs.10.39±0.24 ng/ml, p<0.0001). COPD patients with normal BMI had lowed OPN than obese ones (9.63±0.46 ng/ml vs. 10.97±0.48 ng/ml, p= 0.038). Non-symptomatic males at the end of the follow-up had lower OPN compared to symptomatic (8.99±0.36 vs. 10.43±0.29 ng/ml, p=0.084). A strong trend toward significantly positive correlation between OPN and the percentage of neutrophils was found (Rho=0.265, p=0.060), especially in patients with early GOLD stages (Rho=0.455, p=0.009). According to our studies, the low OPG might be used as biomarker for unfavorable progression of COPD. OPN might also be related to COPD, but more studies should be done in order to reveal its role as reliable biomarker for the disease.