SLC5A2 and diabetes mellitus: SGLT2: sodium-glucose cotransporter 2; MRAs: mineralocorticoid receptor antagonists; RCT: randomized controlled trial; KCCQ-TSS: Kansas City Cardiomyopathy Questionnaire-Total Symptom Score; eGFR: estimated glomerular filtration rate; KCCQ-CSS: Kansas City Cardiomyopathy Questionnaire-Clinical Summary Score; 6MWD: six-minute walking distance; HFmrEF: heart failure with mildly reduced ejection fraction; HFpEF: heart failure with preserved ejection fraction; NYHA: New York Heart Association; LVF: left ventricular function; T2DM: type 2 diabetes mellitus