The protein nucleobindin-2 (NUCB2) has been recently identified as a novel satiety regulator. However, its pathophysiological role in humans remains unknown. The aims of the present study are to explore whether plasma NUCB2-1 and NUCB2 transcription activity are increased in newly diagnosed Type 2 diabetes mellitus (nT2DM) and, if so, whether changing NUCB2-1 level is a physiologic response or a compensatory mechanism for impaired insulin action. The nT2DM, impaired glucose tolerance (IGT), and healthy people (NGT, normal glucose tolerance) groups were enrolled in this study. The peripheral and hepatic insulin actions in rats with intracerebroventricular (ICV) NUCB2-1 administration were examined by euglycemic-hyperinsulinemic clamps. Plasma NUCB2-1 levels were elevated in subjects with both nT2DM and IGT compared with normal controls. NUCB2 mRNA and protein contents of muscle and adipose tissues in T2DM patients were also significantly increased compared to controls. ICV NUCB2-1 infusion in rats inhibited hepatic phosphoenolpyruvate carboxykinase (PEPCK) activity, and this was sufficient to induce insulin sensitivity in the liver and peripheral tissues during euglycemic-hyperinsulinemic clamps. In T2DM patients, there were increases in plasma NUCB2-1 levels and increases in NUCB2 mRNA and protein contents in muscle and adipose tissues. These increases are presumably a compensatory response to defective insulin action.