According to an article published in the November 2013 issue of the medical journal, Nature, glucose regulation is only 50% related to the action of insulin. The other 50% is regulated through a mechanism called "glucose effectiveness" that originates in the hypothalamus of the brain. Glucose effectiveness is an unrelated separate mechanism from insulin that controls blood sugar levels.
Normal glucose control is a partnership between the action of insulin and glucose effectiveness. The development of type 2 diabetes requires failure of both systems. Most often failure of the hypothalamus precedes failure of pancreatic secretion of insulin. Managing blood sugar levels by regulating insulin secretion with drugs or insulin is only treating the symptoms of diabetes, not the cause.