PPIG and diabetic retinopathy: A second CYP enzyme of interest is CYP46A1, which converts cholesterol to 24-hydroxycholesterol, as retinas from Cyp46a1−/− mice exhibit venous beading and tortuosity, microglia/macrophage activation, and increased vascular permeability, features commonly associated with diabetic retinopathy (Saadane et al., 2019).