Mobilization of Free Fatty Acids from Adipose Tissue from Normal and Diabetic Subjects: Influence of Glucose and Insulin

Abstract

The quantity of free fatty acids (FFA) released from epididymal fat pads in vitro and their concentration within the tissue were determined. These quantities paralleled one another and were low in the case of tissue from fed animals, but were both increased with tissue from 24- to 72-hour starved normal and alloxan diabetic animals. The addition of glucose had little effect on their levels in the former but decreased them very considerably in the case of starved rats and to a lesser extent in the diabetic animals. The additional presence of insulin increased the uptake of glucose both by normal and by diabetic tissue, but in neither case did it cause any further reduction in the quantity of FFA. The findings suggested that the rate of cellular utilization of glucose in vitro had an important controlling effect on the release of FFA, and that the extent of the inhibitory action of glucose on the release was largely a manifestation of its activity in decreasing the concentration of FFA within the cells. The predominant effect of glucose was to increase the rate of esterification of FFA, but insulin appeared to have little effect on this. Inadequate esterification could account for the increased mobilization of FFA during starvation and seemed to be the major factor controlling it, whereas in diabetic animals it was likely that in addition an increased rate of lipolysis was also partly responsible.