Disclosed herein are methods for treating type 2 diabetes, limiting development of type 2 diabetes, and treating a pre-diabetic state by administering to a subject in need thereof a GPBP inhibitor. Also disclosed herein are methods for diagnosing a pre-diabetic state and for diagnosing a propensity to develop type 2 diabetes by determining an amount of GPBP in a sample from a subject and comparing to control.