Abstract Body (Do not enter title and authors here): Background: Mitochondrial dysfunction contributes to heart failure (HF) progression via diminished energy supply, release of reactive oxygen species, and increased cell death. However, there has yet to be clinically relevant biomarkers that address mitochondrial-mediated cardiac injury in patients. Humanin (HN) is a mitochondria-derived peptide that protects cells through the interference of apoptosis and reduction of oxidative stress. The objectives of our study were to measure circulating plasma HN levels in patients with HF with reduced ejection fraction and describe the relationship of HN to validated, clinically relevant measures of HF.
Methods: We conducted a prospective cohort study. To be included in the study, patients must have: 1) left ventricular ejection fraction <40%, 2) high risk of future clinical instability, 3) medication and device treatment according to guidelines, and 4) stable medical therapy for at least 30 days prior to screening. Plasma HN levels were measured at time of study enrollment by an enzyme-linked immunoassay. Statistical analyses were performed to evaluate the relationships between HN levels and demographic variables, quantitative measures of HF, and clinical outcomes.
Results: 54 HF patients were included in the study. Age and sex were not significantly associated with HN level. There was a significant difference in mean HN level by race with highest HN level seen in Caucasians and the lowest HN level seen in Hispanics (1310 pg/ml vs. 630 pg/ml, p=0.012). There was a significant inverse correlation between NT-proBNP level and HN level (r=-0.46, p <0.001). After adjusting for race, higher NT-proBNP level, as both a continuous and categorical variable, was significantly associated with lower HN level. Furthermore, HN level was significantly lower in patients who died within 6 months compared to those who did not (520.7 pg/ml vs. 1146.9 pg/ml, p=0.013). After adjusting for race, lower HN level was significantly associated with increased odds of 6-month mortality (OR=0.784, 95% CI 0.620-0.943, p=0.018).
Conclusions: To the best of our knowledge, this is the first study to describe plasma HN levels in HF patients. Its significant correlation with mortality and NT-proBNP level supports a potential role for HN as a novel prognostic biomarker in HF with reduced ejection fraction.