In the Normal/mild-AKI vs. Moderate-severe-AKI group, heart failure impairs cardiac pumping, reducing renal perfusion, triggering renal vasoconstriction, and activating the renin-angiotensin-aldosterone system (RAAS) to induce/worsen AKI (43), making these patients more prone to moderate-severe AKI. The gene discussed is REN; the disease is heart failure.