Insulin-like Activity in Serum of Normal and Diabetic Subjects: Results Obtained with Dual Assay Measuring Conversion of C-14 Glucose to CO2 and to Lipid in Rat Adipose Tissue

Abstract

Epididymal fat pad assays of insulin-like activity in plasma of normal and diabetic subjects have been carried out. When conversion of l-C-14 glucose to C-14-O2 was used as a measure of ILA, diabetics revealed elevated fasting levels, and adult diabetics showed an exaggerated ILA response to glucose loads. Juvenile-type diabetics had lower levels of ILA than the adult diabetics and responded less well to glucose. When the measure was the conversion of 6-C-14 glucose to lipid, no elevation in fasting ILA was found in diabetics. Evidence was obtained indicating that elevated levels of NEFA may inhibit the effect of insulin on adipose tissue with respect to fat synthesis from glucose and not CO2 production. Possible explanations for the discrepancy in the two ILA parameters are discussed.