RBP4 and Impaired glucose tolerance: Previous work employing SWATH-MS to study biomarkers in patients with impaired glucose tolerance who lost weight in response to a diet and exercise programme and in whom HbA1c resolved identified the following major differentiating proteins: Insulin-like growth factor 2 (IGF-II), Retinol binding protein 4 (RBP4), Fetuin-A (FetA) -Zinc-α2- glycoprotein (ZA2G), Visfatin (NAMPT), fatty acid synthase (FAS) and vitamin D binding protein (VDR) [26].