Beneficial effects of sacubitril/valsartan in heart failure with reduced ejection fraction: pas à cause du BNP?

B-Type Natriuretic Peptide (BNP) Revisited—Is BNP Still a Biomarker for Heart Failure in the Angiotensin Receptor/Neprilysin Inhibitor Era?

Simple Summary

Active BNP-32, less active proBNP-108, and inactive N-terminal proBNP-76 all circulate in the blood. The circulating protease neprilysin has lower substrate specificity for BNP than ANP, while proBNP and N-terminal proBNP are not degraded by neprilysin. Currently available BNP immunoassays react with both mature BNP and proBNP; therefore, measured plasma BNP is mature BNP + proBNP. Because ARNI administration increases mature BNP, measured plasma BNP initially increases with ARNI administration by the amount of the increase in mature BNP. Later, ARNI administration reduces myocardial wall stress, and the resultant reduction in BNP production more than offsets the increase of mature BNP due to inhibition of degradation by neprilysin, resulting in lower plasma BNP levels. In the ARNI era, BNP remains a useful biomarker for heart failure, though mild increases early during ARNI administration should be taken into consideration.

Abstract

Myocardial wall stress, cytokines, hormones, and ischemia all stimulate B-type (or brain) natriuretic peptide (BNP) gene expression. Within the myocardium, ProBNP-108, a BNP precursor, undergoes glycosylation, after which a portion is cleaved by furin into mature BNP-32 and N-terminal proBNP-76, depending on the glycosylation status. As a result, active BNP, less active proBNP, and inactive N-terminal proBNP all circulate in the blood. There are three major pathways for BNP clearance: (1) cellular internalization via natriuretic peptide receptor (NPR)-A and NPR-C; (2) degradation by proteases in the blood, including neprilysin, dipeptidyl-peptidase-IV, insulin degrading enzyme, etc.; and (3) excretion in the urine. Because neprilysin has lower substrate specificity for BNP than atrial natriuretic peptide (ANP), the increase in plasma BNP after angiotensin receptor neprilysin inhibitor (ARNI) administration is much smaller than the increase in plasma ANP. Currently available BNP immunoassays react with both mature BNP and proBNP. Therefore, BNP measured with an immunoassay is mature BNP + proBNP. ARNI administration increases mature BNP but not proBNP, as the latter is not degraded by neprilysin. Consequently, measured plasma BNP initially increases with ARNI administration by the amount of the increase in mature BNP. Later, ARNI reduces myocardial wall stress, and the resultant reduction in BNP production more than offsets the increase in mature BNP mediated by inhibiting degradation by neprilysin, which lowers plasma BNP levels. These results suggest that even in the ARNI era, BNP can be used for diagnosis and assessment of the pathophysiology and prognosis of heart failure, though the mild increases early during ARNI administration should be taken into consideration.

Effect of Sacubitril/Valsartan on circulating catecholamine levels during a 6-month follow-up in heart failure patients. Timeo Danaos et dona ferentes?

We assessed the effect of Sacubitril/Valsartan on circulating catecholamine levels in patients with HF in an observational cohort study. We included 108 consecutive HF patients attending our HF Outpatients Clinic who were eligible to Sacubitril/Valsartan according to the PARADIGM-HF inclusion and exclusion criteria. We furthermore included 58 stable HF patients under optimal medical therapy as a control group. Norepinephrine and epinephrine were measured with immunoradiometric assays at baseline, at 3- and at 6-month time follow-up. Compared to baseline levels there was no change at three months in epinephrine (p = 0.177) or norepinephrine (p = 0.815) concentrations. At 6 months norepinephrine remained unchanged (p = 0.359). However, at 6 months we observed a significant increase in epinephrine levels compared to baseline [66 pg/mL (37-93) vs 38 pg/mL (18-74), p < 0.001]. In the control group no change was observed in epinephrine levels compared to baseline (p = 0.838). This study is the first to report on the effect of the new drug Sacubitril/Valsartan on circulating catecholamine levels in HF patients. Our data show a significant increase in epinephrine levels during a 6 month follow up in stable HF patients.