SIRT2 and non-proliferative diabetic retinopathy: In different subtypes of DR, we found that PC (18:0_20:4) could exert a protective effect against NPDR through the mediating effects of β‐NGF and SIRT2, whereas in PDR PC (16:0_20:2) and SE (27:1/14:0) exerted a protective effect through the mediating effects of TNFB and LAP TGF‐β, respectively.