RESUMO
This research was conducted to investigate two main aims; the first aim was to find if there is a relationship between insulin resistance (IR) and retinol binding protein 4 (RBP4). The second aim was to use berberis vulgaris extract and vitamin A as protective and/or curative agents against insulin resistance. IR was developed by feeding the female rats a high fat diet (HFD) for six weeks then treating or protecting them with b. vulgaris extract (0.2 g/Kg body weight) or vitamin A (12.8µg/Kg/day) for two weeks. HFD intake elevated insulin level and RBP4 expression that associated with hyperglycemia and hyperlipidemia. Co-administration of vitamin A and B. vulgaris extracts reduced blood glucose level, insulin, body weight and RBP4 expression before, during and after HFD. Furthermore, vitamin A reduced the blood glucose, triglycerides (TG) and cholesterol levels. IR syndrome associated with the RBP 4 alteration that gives high indication about the role of RBP4 expression in the IR progression and development. Furthermore, the treatment with vitamin A and/or b. vulgaris alleviated the IR syndrome through the action on RBP4 and Insulin secretion. On the other hand, vitamin A must be avoided for the predisposed IR and prediabetic patients.