RBP4 and type 2 diabetes mellitus: In the current study, we aimed to assess the comparative effect of chiglitazar and sitagliptin on the levels of RBP-4 and insulin resistance in patients with T2DM who had insufficient glycaemic control and to further investigate the significance of the changes in the levels of RBP-4, which is identified as a potential metabolic health biomarker and outcome for the evaluation of islet function.