A new test of peripheral insulin sensitivity in vivo using artificial beta cell.

A new in vivo test of insulin sensitivity is described. It utilizes closed-loop insulin delivery device (GCIIS, Biostator) capable of infusing glucose and insulin according to preselected algorithms. In euglycemic patients, insulin was infused by GCIIS to maintain euglycemia in the face of challenges with gradually increasing doses on intravenously administered glucose. Under the described experimental conditions, the endogenous insulin release was minimized as evidenced by serum C-peptide levels of less than 2 ng/ml, and thus the peripheral disposal of glucose should have depended entirely on the exogenous insulin. The amount of the insulin infused was considered to be a measure of peripheral insulin sensitivity. The test was applied to normal and non diabetic obese individuals, and to diabetics, both insulin dependent and independent. Significant insulin resistance was demonstrated in the obese and diabetic patients. In two obese females, the test was repeated after a prolonged period of starvation, and showed marked increase in insulin sensitivity. In two poorly controlled insulin dependent diabetics, marked increase in insulin sensitivity was also observed, here following a prolonged period of euglycemia (48 hours). It is concluded that the GCIIS controlled insulin sensitivity test is a simple, reliable test of peripheral insulin sensitivity, most convenient for clinical and experimental studies in vivo.