This protein belongs to the lipocalin family and is the specific carrier for retinol (vitamin A), delivering retinol from the liver stores to the peripheral tissues. The RBP4-retinol complex interacts with transthyretin and prealbumin, which increases the serum half-life of RBP4. RBP4 promotes hyperglycemia through downregulation of the glucose transporter GLUT4 in adipocytes, upregulation of PEPCK, and attenuation of insulin receptor signaling in skeletal muscle. Serum RBP4 levels are elevated in type 2 diabetes and obesity, due primarily to increased production by visceral and liver adipocytes. Elevated levels have also been associated with pancreatic cancer.
Novel Biomarkers for Change in Renal Function in People With Dysglycemia. (2019) Gerstein HC, Pare G, McQueen MJ, Lee SF, Bangdiwala SI, Kannt A, Hess A, ORIGIN Trial Investigators Diabetes Care
Exploring hepsin functional genetic variation association with disease specific protein expression in bipolar disorder: Applications of a proteomic informed genomic approach (2017) Nassan M, Jia Y, Jenkins G, Colby C, Feeder S, Choi D, Veldic M, McElroy SL, Bond DJ, Weinshilboum R, Biernacka JM, Frye MA J Psychiatr Res
Feasibility of investigating differential proteomic expression in depression: implications for biomarker development in mood disorders (2015) Frye MA, Nassan M, Jenkins GD, Kung S, Veldic M, Palmer BA, Feeder SE, Tye SJ, Choi DS and Biernacka HM Translational Psychiatry