Studies of Empagliflozin and Its Cardiovascular, Renal and Metabolic Effects

Inclusion Criteria: * Written informed consent * Male or female, aged ≥18 years age * Type 2 DM (diet-controlled or on stable treatment) or prediabetes * Stable treatment defined as no change in oral therapy agents or doses for diabetes mellitus and (where applicable) \<10% change in average total daily insulin dose over last 6 weeks * HbA1c ≤97 mmol/mol (11%) (routine available data from medical records, recorded in the last year) * Prediabetes defined as HbA1c 39-47 mmol/mol (5.7-6.4%) at the time of screening (specifically for the prediabetes group, HbA1c will be repeated at the time of screening if there are no recent results within the last 3 months, in order to confirm the diagnosis of prediabetes) * Heart failure (as defined by the presence of typical signs and symptoms of heart failure with documented reduced ejection fraction (ref SIGN and ESC guidelines)) * NYHA class II-IV * LVEF ≤40% * On stable doses of ACEI, ARB or ARNI for 4 weeks prior to randomisation unless contraindicated or not tolerated. They should also be taking a beta-blocker at a stable dose for 4 weeks unless contraindicated or not tolerated * Women of childbearing potential (WOCBP) must be currently adhering to, or be willing to use, highly effective birth control methods for study treatment duration including: * Combined hormonal contraception (oestrogen and progestogen containing medication) either orally, intravaginally, or transdermally * Progesterone only hormonal contraception either orally, injected, or implanted * Intrauterine device (IUD) * Intrauterine hormone release system (IUS) * Bilateral fallopian tube occlusion * Vasectomised partner * Complete sexual abstinence where this is their preferred and usual lifestyle WOCBP comprises women who have experienced menarche and who have not undergone successful surgical sterilisation (hysterectomy, bilateral tubal ligation, or bilateral oophorectomy) or who are not post-menopausal. Post-menopausal is defined as: o Women who have had amenorrhea for ≥12 consecutive months (without another medical cause) Exclusion Criteria: * Type 1 DM * History of hospital admission with a diagnosis of diabetic ketoacidosis (DKA) * Insulin use within 1 year of diagnosis of diabetes * History of acute or chronic pancreatitis * eGFR \<30 ml/min/1.73m2 (derived using CKD EPI) * Persistent/permanent atrial fibrillation/flutter (conditions which significantly impede MRI image interpretability) * Acute coronary syndrome, stroke or surgery within 1 month (small type 2 MI in the context of acute HF does not apply) * BMI \>52 kg/m2 * Liver disease, defined by serum levels of alanine aminotransferase, aspartate aminotransferase, or alkaline phosphatase above 3 x upper limit of normal (ULN) during screening * Bariatric surgery within the past two years and other gastrointestinal surgeries that induce chronic malabsorption * Any condition outside the cardiovascular and renal disease area, such as but not limited to malignancy, with a life expectancy of less than 2 years based on investigator's clinical judgement * Active malignancy requiring treatment at the time of visit 1 (with the exception of successfully treated basal cell or treated squamous cell carcinoma, adjuvant hormonal therapy for breast cancer and hormone therapy for prostate cancer) * Blood dyscrasias or any disorders causing haemolysis or unstable red blood cells (e.g. malaria, babesiosis, haemolytic anaemia) * Treatment with systemic steroids at time of informed consent or change in dosage of thyroid hormones within 6 weeks prior to informed consent * Any uncontrolled endocrine disorder except Type 2 DM * Alcohol or drug abuse within 3 months of informed consent that would interfere with trial participation or any ongoing condition leading to decreased compliance with study procedures or study drug intake * Known hypersensitivity to the empagliflozin or excipients * Known hypersensitivity to gadolinium * Inability to give informed consent * SGLT2 inhibitor use (current or previous) * Devices or any other contraindication to MRI scans * Currently pregnant, planning pregnancy, or currently breastfeeding * History of previous lower limb amputation * Current participation in another interventional medical study or within the last 90 days * Anyone who, in the investigators' opinion, is not suitable to participate in the trial for other reasons