June 10th, 2011
A New Biomarker From the Lungs
A new study raises the possibility that a protein produced in the lungs may improve the prediction of cardiovascular disease. In a paper in the European Journal of Cardiology, John Hill and colleagues report on their research with surfactant protein-D (SP-D). Produced in the lungs, SP-D levels increase in the general circulation following lung injury and lung inflammation.
The researchers measured SP-D levels in 806 patients undergoing coronary angiography to determine its value in predicting cardiovascular risk. They then measured SP-D levels in a replication cohort of 4,468 current and former smokers with no known history of coronary disease.
SP-D levels were significantly higher in the patients who died during followup than in survivors (median 85.4 vs. 64.8 ng/mL; p<0.0001). The risk of dying was 4.4-fold higher among those in the highest SP-D quintile compared to those in the lowest quintile. This effect was independent of age, sex, and lipids.
The authors point out that there are currently no generally accepted biomarkers for chronic lung inflammation, although chronic lung inflammation is known to be closely tied to CV risk and mortality. The study was unable to assess whether SP-D is a biomarker for, or plays an active role, in CVD. They speculate that SP-D plays an important anti-inflammatory and anti-oxidant role in the lungs, but may have an adverse atherogenic effect in the systemic circulation. They conclude:
“…we found that circulating SP-D levels are strongly predictive of future risk of cardiovascular mortality, independent of well-established risk factors. These data implicate lung inflammation in the pathogenesis of heart and blood vessel disease and raise the possibility of using this protein as a biomarker to risk stratify CVD patients above and beyond traditional risk factors such as serum cholesterol and C-reactive protein.”