RBP4 and type 2 diabetes mellitus: Another study investigated 867 non-obese Chinese patients with NGT [16] and showed that serum RBP4 correlated with glucose-stimulated insulin secretion, assessed by ΔI30/ΔG30 (increment in plasma insulin concentration plasma glucose concentration 30 min after the oral administration of 75 g glucose) and the total area under the curve for insulin over 180 min (AUC-I), in NGT non-visceral obesity subjects, but not in NGT visceral obesity subjects and T2DM patients.