Identification and Evaluation of Angiogenesis-Related Proteins That Predict Major Adverse Cardiovascular Events in Patients with Peripheral Artery Disease

Background: The most common cause of death in patients with peripheral artery disease (PAD) are major adverse cardiovascular events (MACEs), including myocardial infarction (MI) and stroke. However, data on biomarkers that could be used to help predict MACEs in patients with PAD to guide clinical decision making is limited. Angiogenesis-related proteins have been demonstrated to play an important role in systemic atherosclerosis and may act as prognostic biomarkers for MACEs in patients with PAD. In this study, we evaluated a large panel of angiogenesis-related proteins and identified specific biomarkers associated with MACEs in patients with PAD. Methods: We conducted a prognostic study using a prospectively recruited cohort of 406 patients (254 with PAD and 152 without PAD). Plasma concentrations of 22 circulating angiogenesis-related proteins were measured at baseline, and the cohort was followed for 2 years. The primary outcome was 2-year MACEs (composite of MI, stroke, or death). Plasma protein concentrations were compared between PAD patients with and without 2-year MACEs using Mann–Whitney U tests. Differentially expressed proteins were further investigated in terms of their prognostic potential. Specifically, Cox proportional hazards analysis was performed to determine the independent association between differentially expressed proteins and 2-year MACEs, controlling for all baseline demographic and clinical characteristics, including existing coronary artery disease and cerebrovascular disease. Kaplan–Meier analysis was conducted to assess 2-year freedom from MACEs in patients with low vs. high levels of the differentially expressed proteins based on median plasma concentrations. Results: The mean age of the cohort was 68.8 (SD 11.1), and 134 (33%) patients were female. Two-year MACEs occurred in 63 (16%) individuals. The following proteins were significantly elevated in PAD patients with 2-year MACEs compared to those without 2-year MACEs: endostatin (69.15 [SD 58.15] vs. 51.34 [SD 29.07] pg/mL, p < 0.001), angiopoietin-like protein 4 (ANGPTL4) (0.20 [SD 0.09] vs. 0.12 [SD 0.04] pg/mL, p < 0.001), and ANGPTL3 (51.57 [SD 21.92] vs. 45.16 [SD 21.90] pg/mL, p = 0.001). Cox proportional hazards analysis demonstrated that these three proteins were independently associated with 2-year MACEs after adjusting for all baseline demographic and clinical characteristics: endostatin (HR 1.39 [95% CI 1.12–1.71] p < 0.001), ANGPTL4 (HR 1.35 [95% CI 1.08–1.68], p < 0.001), and ANGPTL3 (HR 1.35 [95% CI 1.12–1.63], p < 0.001). Over a 2-year follow-up period, patients with higher levels of endostatin, ANGPTL4, and ANGPTL3 had a lower freedom from MACEs. Supplementary analysis demonstrated that these three proteins were not significantly associated with 2-year MACEs in patients without PAD. Conclusions: Among a panel of 22 angiogenesis-related proteins, endostatin, ANGPTL4, and ANGPTL3 were identified to be independently and specifically associated with 2-year MACEs in patients with PAD. Measurement of plasma concentrations of these proteins can support MACE risk stratification in patients with PAD, thereby informing clinical decisions on multidisciplinary referrals to cardiologists, neurologists, and vascular medicine specialists and guiding aggressiveness of medical treatment, thereby improving cardiovascular outcomes in patients with PAD.