Reduced levels of decorin proteins in the blood may be linked to a lower risk of death among patients with idiopathic pulmonary fibrosis (IPF) who have experienced acute exacerbations, researchers suggest.
Their findings were reported in the study, “Serum decorin is a potential prognostic biomarker in patients with acute exacerbation of idiopathic pulmonary fibrosis,” published in the Journal of Thoracic Disease.
Acute worsening of respiratory function, also known as acute exacerbations, can have a significant negative impact on the clinical outcome of patients with IPF. These acute events have been reported to occur in about 8.6% of IPF cases one year after diagnosis, increasing to 23.9% three years after diagnosis.
After the onset of acute exacerbations, the death rate of IPF patients is about 50%. This high mortality rate highlights the importance of recognizing risk factors that could contribute to the development of these acute events to ensure adequate prevention.
Researchers in Japan have now evaluated the role of the decorin protein in the development and progression of acute exacerbations in patients with IPF and idiopathic interstitial pneumonia (IIP), which is also a fibrotic lung disease. Decorin is known to regulate inflammation and wound healing.
In IPF, decorin can be found at fibrotic lesions and was shown to prevent lung fibrosis in mice. This protein was also shown to inhibit collagen production by fibroblasts, which is a key mechanism in fibrosis progression.
The team evaluated the levels of decorin in blood samples collected from 21 IPF patients, 35 patients with IIP (other than IPF) who were hospitalized due to acute exacerbations, and 36 healthy volunteers. They also evaluated the protein levels in 97 patients who had stable IIP (no disease exacerbations).
Researchers found that IIP patients who had acute exacerbations had reduced levels of decorin by about 23.8% (7,183.8 vs. 9,430.2 ng/mL), compared with stable IIP patients, and 35.7% (7,183.8 vs. 11,171.9 ng/mL), compared with healthy controls.
The team also compared the levels of decorin in 34 IIP patients between when they were clinically stable and during an acute exacerbation period. The analysis showed that blood decorin levels were significantly lower during an acute exacerbation than in the clinically stable phase in IPF patients, with a mean reduction of about 21.4% (6,894.5 vs. 8,778.5 ng/mL). However, this difference was not found in the non-IPF patient subgroup.
Further analysis failed to find any correlation between blood decorin levels and any clinical parameter after hospital admission due to acute exacerbation, including blood laboratory results, SIRS score, and APACHE II score — two commonly used prognostic measures.
Overall, the survival rate 60 days after hospital admission was 53.6% in IIP patients. Comparison of mean decorin levels between survivors and non-survivors did not reveal a significant difference.
However, when the team divided IPF patients into high and low blood decorin groups — using median decorin level as a reference — the survival rate was significantly higher in patients with low decorin levels than in those with high levels. Still, the team could not find any significant differences in clinical parameters except PF ratio, which is the arterial partial pressure of carbon dioxide/fraction of inspiratory oxygen ratio, a measure of respiratory function.
Overall, the team found that “decorin levels were lower in IIP patients than in HVs [healthy volunteers], and decreased during AE [acute exacerbation];” that “decorin levels during AE were not correlated with any clinical characteristics except for PF ratio in IPF patients; and [that] “IPF patients with lower serum decorin levels had better prognosis than those with higher levels after the onset of AE.”
Based on these results, the team believes that “[blood] decorin level is a potential prognostic biomarker after the onset of acute exacerbations in patients with IPF.”
Still, additional studies are necessary to clarify the role of decorin in the underlying mechanisms of both IPF and IIP.