Mechanism(s) Underlying Cardiovascular Effects of ARB/NEP Inhibition - Aim 2

Inclusion Criteria: 1. Stable patients with a reduced EF 1. EF less than or equal to 40% (confirmed by echocardiogram within the last six months), and 2. history of symptoms of New York Heart Association class I, II or III HF 3. stable clinical symptoms including no hospitalizations for the last six months 4. treatment with a stable dose of an ACEi or ARB and with a beta blocker (unless contraindicated or not tolerated) for at least four weeks 5. treatment with a stable dose of an MR antagonist for at least four weeks unless not possible due to renal function or serum potassium. 2. For female subjects, the following conditions must be met: 1. postmenopausal status for at least one year, or 2. status post-surgical sterilization Exclusion Criteria: 1. History of hypersensitivity or allergy to any of the study drugs, drugs of similar chemical classes, ACEi, ARBs, or NEPi, as well as known or suspected contraindications to the study drugs 2. History of angioedema 3. History of pancreatitis or known pancreatic lesions 4. History of decompensated HF within the last six months (exacerbation of chronic HF manifested by signs and symptoms that required intravenous therapy or hospitalization) 5. History of heart transplant or on a transplant list or with left ventricular assistance device 6. Symptomatic hypotension and/or a SBP\<100 mmHg at screening or \<90 mmHg during the study 7. Serum potassium \>5.2 mmol/L at screening or \>5.4 mmol/L during the study 8. Acute coronary syndrome, cardiac, carotid, or other major cardiovascular surgery, percutaneous coronary intervention, or carotid angioplasty within six months prior to screening 9. Coronary or carotid artery disease likely to require surgical or percutaneous intervention within six months of screening 10. History of serious neurologic disease such as cerebral hemorrhage, stroke, seizure, or transient ischemic attack within six months 11. History of ventricular arrhythmia with syncopal episodes 12. Symptomatic bradycardia or second- or third-degree atrioventricular block without a pacemaker 13. Presence of hemodynamically significant mitral and/or aortic valve disease, except mitral regurgitation secondary to LV dilatation 14. Presence of other hemodynamically significant obstructive lesions of the left ventricular outflow tract, including aortic and subaortic stenosis 15. Type 1 diabetes 16. Poorly controlled type 2 diabetes mellitus (T2DM), defined as a HgbA1c \>9% 17. Hematocrit \<35% 18. Impaired renal function (eGFR of \<30mL/min/1.73 m2) as determined by the four-variable Modification of Diet in Renal Disease (MDRD) equation, where serum creatinine (Scr) is expressed in mg/dL and age in years: eGFR (mL/min/1.73m2)=175 • Scr-1.154 • age-0.203 • (1.212 if Black) • (0.742 if female) 19. Use of hormone-replacement therapy 20. Breast feeding and pregnancy 21. History or presence of immunological or hematological disorders 22. History of malignancy other than non-melanoma skin cancer 23. Diagnosis of asthma requiring use of inhaled beta agonist more than once a week 24. Clinically significant gastrointestinal impairment that could interfere with drug absorption 25. Impaired hepatic function \[aspartate amino transaminase (AST) and/or alanine amino transaminase (ALT) \>3.0 x upper limit of normal range\] 26. Any underlying or acute disease requiring regular medication which could possibly pose a threat to the subject or make implementation of the protocol or interpretation of the study results difficult, such as arthritis treated with non-steroidal anti-inflammatory drugs 27. Treatment with chronic systemic glucocorticoid therapy within the last year 28. Treatment with lithium salts 29. History of alcohol or drug abuse 30. Treatment with any investigational drug in the one month preceding the study 31. Mental conditions rendering the subject unable to understand the nature, scope, and possible consequences of the study 32. Inability to comply with the protocol, e.g., uncooperative attitude, inability to return for follow-up visits, and unlikelihood of completing the study