INS and proliferative diabetic retinopathy: Adjusted for age, sex, duration of diabetes, the presence of proliferative diabetic retinopathy, smoking status, the use of insulin, renin–angiotensin system inhibitors, antiplatelet agents, and statins, hemoglobin, uric acid, eGFR, urinary ACR at baseline, BMI, SBP and DBP, triglycerides, HDL-C and LDL-C levels