Ketones, SGLT2, HFrEF

The study team will examine the effects of elevated plasma ketone levels following initiation of SGLT2 inhibitor therapy in high-risk type 2 diabetes mellitus (T2DM) individuals with heart failure (HF) with reduced ejection fraction (HFrEF) providing an energy-rich fuel that is taken up with great avidity by the myocardium, to measure change in Left Ventricle diastolic and systolic function

The study team will examine the effects of elevated plasma ketones caused by 12-week treatment with an SGLT2i (empagliflozin) treatment in participants with T2DM and HF. The study team will focus on three possible mechanisms of action for these effects and test the following:

(i) Skeletal muscle bioenergetics. Using 31P-MRS, the team will quantify phosphocreatine \[PCr\], ATP, inorganic phosphate, phosphodiester, and intracellular pH. With 1H-MRS, and will measure intramyocellular lipid content at rest and ATPmax production after exercise. The team will examine the relationships between phosphorous metabolite concentrations, intramyocellular lipid content, and ATP generation before and after 12 weeks of SGLT2 inhibition.

(ii) LV systolic and diastolic function using cardiac MRI in type 2 diabetic patients with Class II-III NYHA heart failure and reduced EF.

(iii) To examine the contribution of the SGLT2i-induced increase in plasma ketone concentration on myocardial function and myocardial blood flow by inhibiting the rise in plasma ketone concentration with acipimox while continuing empagliflozin.

(iv) Improvements in Patient-Reported Outcomes (PRO). Kansas City Cardiomyopathy Questionnaire ( KCCQ) scoring will be used to evaluate self-reported physical function and well-being. This tool is a well-developed and validated method to obtain patient self-reported parameters of health in adults.

Eligibility Criteria:
Inclusion Criteria:

* Type 2 Diabetes Mellitus
* Class II-III New York Heart Association (NYHA) heart failure and reduced ejection fraction (EF) \<50%
* Age 18-80 years
* BMI 23-38 kg/m2
* Glycated hemoglobin (HbA1c) 5.5-10%
* Blood Pressure (BP) ≤ 145/85 mmHg
* Estimated glomerular filtration rate (eGFR) ≥30 ml/min•1.73 m2
* Stable dose of guideline-directed medications for heart failure
* Stable body weight (±4 pounds) over the last 3 months

Exclusion Criteria:

* Heart failure due to restrictive cardiomyopathy, active myocarditis, constrictive pericarditis, severe valvular heart disease, hypertrophic obstructive cardiomyopathy.
* Significant change in diuretic management during the month prior to screening (defined by doubling of diuretic dose or addition of another heart failure medication)
* Type 2 Diabetics treated with Dipeptidyl Peptidase-4 Inhibitor (DPP4i) or pioglitazone
* Pregnancy, lactation, or plans to become pregnant. A negative pregnancy test will be performed before each MRI study to assess current status. For women of child-bearing age (WOCBA) willingness to use contraception, if applicable.
* Allergy/sensitivity to study drugs or their ingredients.
* Cancer.
* Current drug or alcohol use or dependence that, in the opinion of the site investigator, would interfere with adherence to study requirements.
* Inability or unwillingness of individual or legal guardian/representative to give written informed consent.