The contribution of retinol binding protein 4 (RBP4) in obesity and IR was first discovered in adipose-Glut4−/− mice5, after which the results of a human study showed that elevated serum RBP4 levels were correlated with the magnitude of IR and metabolic risk factors in lean, obese, and diabetic subjects6. The gene discussed is RBP4; the disease is obesity due to melanocortin 4 receptor deficiency.