In vitro effect of endotoxin on lipolysis and lipoprotein lipase activity in adipocytes from lean, obese and obese diabetic Zucker rats

Endotoxemia and sepsis in non diabetic rats are associated with alterations in adipose tissue metabolism evidenced by an increase in lipolysis and decrease in lipoprotein lipase (LPL) activity. The purpose of this study was to determine the in vitro effect of endotoxin (LPS) on lipolysis and the activities of LPL in epididymal adipocytes isolated from 11-12-week-old obese diabetic, obese, and lean rats. Epinephrine-stimulated lipolysis was higher in the adipocytes from obese diabetic and obese rats than lean rats. Maximal lipolytic response for all groups occurred with 10-5 M of epinephrine. LPS increased the lipolytic rate in adipocytes from the obese and obese diabetic rats by 58% and 97%, respectively, in comparison to the lean rats. Heparin-releasable and extractable LPL activities were suppressed in LPS-treated adipocytes from lean rats; heparin-releasable, but not extractable LPL activity, was depressed in adipocytes from obese rats. The LPS-induced depression in LPL activities did not occur in adipocytes from obese diabetic rats. Since LPL is not altered, adipose tissue from the obese diabetic rats may not become depleted when challenged with endotoxin as is the case for the normal endotoxin-treated lean rat with diminished LPL activity.