Plasma levels of cathepsins L, K, and V and risks of abdominal aortic aneurysms: a randomized population-based study

Background: Cathepsin L (CatL), cathepsin K (CatK), and cathepsin V (CatV) are potent elastases implicated in human arterial wall remodeling. Whether plasma levels of these cathepsins are altered in patients with abdominal aortic aneurysms (AAAs) remains unknown. Methods and results: Plasma samples were collected from 476 male AAA patients and 200 age-matched male controls to determine CatL, CatK, and CatV levels by ELISA. Student's t-test demonstrated significantly higher plasma CatL levels in AAA patients than in controls (P<0.0001), whereas CatK and CatV levels were lower in AAA patients than in controls (P=0.052, P=0.025). ROC curve analysis confirmed higher plasma CatL levels in AAA patients than in controls (P<0.001). As potential confounders, current smoking and use of angiotensin-converting enzyme (ACE) inhibitors, aspirin, clopidogrel, and statins associated with significantly increased plasma CatL. Pearson's correlation test demonstrated that plasma CatL associated positively with CatS (r=0.43, P<0.0001), body-mass index (BMI) (r=0.07, P=0.047) and maximal aortic diameter (r=0.29, P<0.001), and negatively with lowest measured ankle-brachial index (ABI) (r=-0.22, P<0.001). Plasma CatL remained associated positively with CatS (r=0.43, P<0.0001) and aortic diameter (r=0.212, P<0.001) and negatively with ABI (r=-0.10, P=0.011) after adjusting for the aforementioned potential confounders in a partial correlation analysis. Multivariate logistic regression analysis indicated that plasma CatL was a risk factor of AAA before (odds ratio [OR]=3.04, P<0.001) and after (OR=2.42, P<0.001) the same confounder adjustment. Conclusions: Correlation of plasma CatL levels with aortic diameter and the lowest ABI suggest that this cysteinyl protease plays a detrimental role in the pathogenesis of human peripheral arterial diseases and AAAs.