B2M and non-proliferative diabetic retinopathy: Based on our proteomics data, the B2M level was significantly increased in NPDR+DKD plasma (P=0.0120), the IGIH3 level was significantly elevated in NPDR+DKD patients (p=0.0017), PSMA7 was significantly upregulated in the NPDR+DKD group (p=0.0159), and the VIM level was also significantly increased in NPDR+DKD samples.