RBP4 and Insulin resistance: Alterations in fasting blood glucose (FPG), glycated hemoglobin (HbA1c), fasting serum insulin (FINS), homeostatic model assessment for insulin resistance (HOMA-IR), serum retinol-binding protein 4 (RBP4), serum cystatin C (CysC), and nesfatin-1 of all eligible participants were analyzed, and the occurrence of complications was recorded.