Loss of functioning nephrons impacts the 1-hydroxylase negatively and affects the ability to generate 1,25(OH)2D. [22, 23] On the other hand, experimental models have shown that vitamin D depletion contributes to AKI development due to several mechanisms, including upregulation of the renin–angiotensin–aldosterone system, increased expression of renal vascular renin and dysregulation of the immune system. Here, REN is linked to acute kidney injury.