Association between antibodies against calcifying nanoparticles and mitral annular calcification

Mechanisms leading to vascular and tissue calcification are not yet fully understood. Previously, an association has been demonstrated between a controversial calcifying nanoparticle (CNP; also known as 'nanobacteria') and vascular calcification and kidney stone formation. The study aim was to evaluate a possible association between mitral annular calcification (MAC) and CNP infection.

A total of 93 patients with MAC, detected using echocardiography, and 94 asymptomatic subjects without valvular and coronary artery calcification, were enrolled in the study. The serum levels of anti-CNP-antibodies were monitored in all subjects.

Patients with MAC were generally older and had a higher prevalence of systemic hypertension, diabetes mellitus, and dyslipidemia. The anti-CNP-antibody titers, which were significantly associated with MAC (p < 0.0001), were increased with older age and MAC thickness, but decreased in line with serum levels of HDL-cholesterol (p < 0.0001). In order to provide a cut-off point for anti-CNP-antibodies when detecting MAC, a receiver operating characteristic curve was created. Serum CNP-antibody levels above 0.19 units/ml showed a sensitivity of 73%, a specificity of 72%, and positive and negative predictive values of 72% and 73%, respectively. Multivariate logistic regression analysis revealed that increasing age, systemic hypertension, diabetes, HDL-cholesterol levels and high anti-CNP titers were risk factors that were independently associated with calcification in the mitral annuli.

The study results suggested that CNP might play an important role in the pathogenesis of MAC.