Osteopontin in patients with chronic obstructive pulmonary disease and coronary heart disease

Abstract

Background: Osteopontin is a protein expressed by various cell types, such as endothelial and epithelial cells, osteoclasts, hepatocytes, smooth muscle cells, activated macrophages, and T-cells. Cardiomyocytes, heart fibroblasts, endothelial cells of coronary arteries express osteopontin in response to hypoxia, inflammation, toxic factors, mechanical strain, and other stimuli.
 Aim: To study osteopontin levels in patients with chronic obstructive pulmonary disease (COPD) depending on concomitant ischemic heart disease (IHD), to identify an association between osteopontin levels with severity of COPD and functional lung test parameters.
 Materials and methods: This open-label, prospective, non-randomized comparative study with parallel groups included 99 patients with COPD grades AD by GOLD, with 49 of them having confirmed comorbid stable IHD. Serum osteopontin levels were measured by immunoenzyme assay (Human Osteopontin Platinum ELISA; Bender MedSystems, Austria). The data is given as medians and quartiles (Me [Q1; Q3]). In all patients we performed functional lung tests with bronchodilation, a 6-minute walking test, BODE index assessment, as well as CAT and mMRC questionnaires were used.
 Results: In the patients with COPD and IHD, the osteopontin levels were higher than in the patients with COPD without IHD (85.55 [46.86; 110.91] vs 55.43 [20.76; 89.64] ng/mL, respectively; p = 0.027). Osteopontin levels in the patients with all COPD grades and IHD were higher than in those without IHD, but the difference was significant only in GOLD grade B patients (91.28 [73.04; 110.91] vs 37.81 [22.54; 82.95] ng/mL, respectively, р = 0.028) and GOLD grade D patients (80.79 [34.65; 111.11] vs 37.46 [13.32; 109.5] ng/mL, respectively, р = 0.027).
 Conclusion: A significant increase of osteopontin levels in comorbid patients with COPD and stable IHD found in this study has not been previously known. It is necessary to perform further studies to identify a threshold level of osteopontin predictive of the risk of COPD exacerbations or cardiovascular events. This would help to improve medical treatment of COPD patients, as well as to identify the risk groups.