Neutrophil Gelatinase-associated Lipocalin: A Potential Predictor of Embolic Events in Endocarditis

Background: As the complication of infective endocarditis (IE), embolic events are associated with increased mortality and morbidity. However, there are no reliable indicators to predict embolism. The aim of this study was to evaluate neutrophil gelatinase-associated lipocalin (NGAL) as a biomarker to identify IE patients at high risk of embolism.

Methods: We conducted a prospective observational study of IE patients from January 2018 to December 2020. Plasma NGAL levels were measured in 88 IE patients (37 patients with embolic events and 51 patients without embolic events), 91 noninfectious heart valve disease patients, and 20 healthy blood donors by enzyme-linked immunosorbent assay. Native valve tissue was obtained from 16 IE patients and 16 noninfectious heart valve disease patients. Western blot and immunohistochemical staining were performed to detect NGAL and matrix metalloproteinase-9.

Results: Higher levels of NGAL were observed in IE patients than in noninfectious heart valve disease patients (P < .001) or healthy blood donors (P < .01). In addition, NGAL levels were higher in IE patients with embolic events compared with patients not having embolic events (P < .001). Receiver-operating characteristics analysis demonstrated that NGAL acted as a potential embolic events predictor with the cutoff value of 166.78 ng/mL. The IE patients with higher NGAL levels had significantly more severe native valve morphologic changes. The NGAL was colocalized with matrix metalloproteinase-9, and their expression in the valves of IE patients was higher than in those of noninfectious heart valve disease patients.

Conclusions: Neutrophil gelatinase-associated lipocalin is a potential predictor of embolic events in IE. That may be attributed to its potency of increasing the proteolytic activity of matrix metalloproteinase-9, which leads to valve morphologic impairment.