Retinol-binding protein 4 has recently been described as an adipokine that contributes to insulin resistance in the AG4KO mouse model. It is secreted by adipocytes，and can act as a signal to other cells，when there is a decrease in plasma glucose concentration. Mutations in the RBP4 gene have recently been linked to a form of autosomal dominant microphthalmia，anophthalmia，and coloboma (MAC) disease.
