Alterations in insulin action by endotoxin in vitro.

Fat cells isolated from epididymal fat pads of Sprague-Dawley rats were exposed to E coli endotoxin in vitro, and after washing the ensuing alterations in glucose oxidation and antilipolysis were studied. Although endotoxin (500 microgram/ml) exhibited an insulin-like effect on basal glucose oxidation, it diminished insulin stimulation of glucose oxidation, seemingly inducing an insulin-resistant state. On the other hand, identical doses of insulin elicited significantly greater antilipolytic effects in endotoxin-treated cells, than in untreated cells. Thus, endotoxin exposure (in a range of 0.05-200 microgram/0.5 ml cell suspension) rendered adipocytes more sensitive to the antilipolytic effect of insulin. Results of this study indicate that the different physiologic actions of insulin on adipocytes are not affected in a uniform manner by endotoxin exposure in vitro.