Molecule, Ang-1, Fails as Blood Biomarker of PH or Its Likely Severity in Study

A molecule linked to pulmonary hypertension (PH) in earlier studies failed to serve as a biomarker of disease severity or prognosis in a new study, which analyzed blood levels of the factor in people with various types of lung hypertension.

Although the molecule, known as Ang-1, does not appear to be a suitable blood test marker for discriminating between patients with lung hypertension and those with similar symptoms, the finding does not disprove earlier studies showing that it drives disease processes.

The study, “Circulating Angiopoietin-1 Is Not a Biomarker of Disease Severity or Prognosis in Pulmonary Hypertension,” was published in the journal PLOS ONE.

A research team at Justus-Liebig-University in Germany enrolled 151 patients with idiopathic pulmonary arterial hypertension (PAH), connective tissue disease (CTD)-PAH, PH caused by left heart disease, and chronic thromboembolic PH (CTEPH). Each group was composed of 32 to 41 patients.

Patients were recruited from the clinical center, where they had a right heart catheterization examination done because of suspected lung hypertension. The team also recruited 41 individuals who were not diagnosed with PH after the examination.

Blood Ang-1 levels were similar in all groups, with no statistical differences from controls. Patients with idiopathic PAH had a nearly significant difference when compared to controls.

Researchers could also not find any links between the levels of Ang-1 and exercise capacity, measured by the 6-minute walk distance test.

During the study, in which patients were followed for an average of 31.5 months, 29.7 percent of the patients died. Ang-1 levels could not be tied to transplant-free survival rates in the entire patient group, or in any subgroup. Likewise, Ang-1 levels did not correlate with the time it took for patients’ conditions to worsen.

The growth factor Ang-1 has been the focus of numerous previous studies, in both animal models and human cells, where scientists observed that abnormal levels cause changes in lung blood vessels.

In patients, studies have also found abnormal levels in lung tissue. But the new research strongly suggests that these changes are not mirrored by Ang-1’s presence in the blood, particularly when considering it as a tool to aid disease prognosis or to distinguish patients with lung hypertension from others with similar symptoms.

“Despite a strong pathophysiological association in experimental studies, this first comprehensive analysis of Ang-1 in PH subgroups suggests that Ang-1 is not a predictive and clinically relevant biomarker in PH,” the researchers concluded.