MD-2 is a new predictive biomarker in dilated cardiomyopathy and exerts direct effects in isolated cardiomyocytes

BACKGROUND: Myeloid differentiation factor-2 (MD-2) has been shown to be an important modulator of the innate immune system, but its role in cardiac diseases is unknown. We investigated whether MD-2 plays a role as risk predictor and contributor in dilated cardiomyopathy (DCM).

METHODS AND RESULTS: We included 174 patients with reduced left ventricular (LV) ejection fraction (LVEF <45%) due to DCM. Coronary artery disease and severe valvular diseases were excluded in all patients by angiography or echocardiography. Cardiac inflammation, viral infection and MD-2 expression were analyzed from right ventricular endomyocardial biopsies. MD-2 was quantified by ELISA in serum upon first hospital admission. Myocyte contractility and inflammatory response after stimulation with recombinant MD-2 protein were analyzed in isolated rat cardiomyocytes. Median follow-up of the patients was 3.51 years (2.73; 4.48) with 34 deaths. Absolute mortality risk increases in patients displaying a MD-2 serum concentration greater than the median (302 ng/ml) was 23% (P < 0.0001). Age- and sex-adjusted Cox regression analyses demonstrated that mortality risk was highly related to MD-2 concentrations (P < 0.001), but not to age or sex. An increase of 100 ng/ml in the MD-2 level was associated with an absolute mortality risk increase of 50.4%. Receiver operating characteristic (ROC) analyses showed no difference between MD-2 and nterminal-pro brain natriuretic peptide (NT-pro-BNP), while the combination of both MD-2 and NT-pro-BNP resulted in a significantly increased capability of risk prediction when compared to NT-pro-BNP alone (P = 0.014). In-vitro, recombinant MD-2 decreases cell shortening and modulates cytokine activation in isolated cardiomyocytes.

CONCLUSION: MD-2 predicts long-term outcome in DCM patients and improves mortality risk prediction capability compared to NT-pro-BNP alone. In addition, MD-2 exerts direct negative inotropic effects on isolated cardiomyocytes in-vitro. Further randomized trials should confirm MD-2 as a diagnostic and therapeutic target.