Association of retinol binding protein 4 and insulin resistance: a review on molecular mechanisms

Retinol (ROH) and its derivatives named vitamin A are substantial for several cells’ functions. Retinol Binding Protein 4 (RBP4) is known as the career for vitamin A in blood. The main receptor for RBP4 is Stimulated by retinoid acid gene 6 (STRA6). RBP4 circulates in bound with Transports Thyroxine and Retinol (TTR) to form ternary ROH-RBP-TTR complex. Recently, RBP4 implicated in insulin resistance which may exerts its functions through inflammatory pathways. Although studies indicated that RBP4 may have role in inflammation as an adipocytokine. the cellular and molecular mechanisms including the interaction between Holo- or Apo-RBP4 and their receptor to induce inflammation is controversial. In this review, we focus on molecular structure of RBP4, STRA6, and their interaction to induce inflammation and insulin resistance to illustrate the potential conflicts in this area.