 In addition to the liver, RBP4 is also secreted by adipocytes of the fat tissue in a smaller portion and acts as a signal to surrounding cells, when there is a decrease in plasma glucose concentration.It is suspected that an elevated level of RBP4 attracts macrophages to the fat tissue, causes local inflammation, and leads to insulin resistance.Mutations in the RBP4 gene have recently been linked to a form of autosomal dominant microphthalmia, anophthalmia, and coloboma (MAC) disease.