Endotoxin inhibits catabolism of low density lipoproteins in vivo: an experimental study in the rat

Abstract

Hyperlipidaemia frequently accompanies infectious diseases and may be due to an increase in lipoprotein production or a decrease of lipoprotein clearance. The administration of endotoxin has been used to mimic infection and previous studies have demonstrated that endotoxin induces an increase in low density lipoprotein (LDL) levels. In the present study in rats, the dose of endotoxin (055:B5, 50 μg 100 g body weight⁻¹) induced hyperlipidaemia without shock and death. The dearance of ¹²⁵I-LDL was measured after simultaneous injection of 100 μg LDL protein with endotoxin or without endotoxin (control). Endotoxin sidcantly inhibited the clearance of ¹²⁵I-LDL from blood at all time intervals between 1 and 24 h. The total ¹²⁵I and trichloroacetic acid-(TCA)precipitable ¹²⁵I in the liver was higher in endotoxin-treated animals than in controls after 0.5, 4 and 24 h. An increased tissue radioactivity was also seen in several other tissues at various time intervals in the endotoxin treated group. The increase in plasma triglyceride induced by endotoxin reached a maximum after 8 h. Endotoxin thus causes a rapid inhibition of both the LDL disappearance from blood and of the LDL degradation after the uptake by the liver. This effect precedes the increase in triglyceride levels. The inhibition of the LDL catabolism may contribute to the rise in LDL levels in endotoxin induced hyperlipidaemia.

Key Words:

• Endotoxin
• lipoproteins
• metabolism
• in vivo