Effect of interleukin-1 alpha on lipoprotein lipids in cynomolgus monkeys: comparison to tumor necrosis factor

Acute inflammation is associated with changes in lipoprotein metabolism. Cytokines are thought to mediate the metabolic effects of the inflammatory process. This study was undertaken to compare the effects of interleukin-1 alpha (IL-1 alpha) to tumor necrosis factor (TNF) on lipoprotein metabolism in non-human primates. Recombinant human IL-1 alpha (100 micrograms/kg), TNF alpha (20 micrograms/kg) and lipopolysaccharide (20 micrograms/kg) were injected into cynomolgus monkeys. Lipoprotein concentrations, plasma activities of post-heparin lipase (PHLA) and lecithin:cholesterol acyltransferase (LCAT) were measured prior to and 24 and 48 h after, injection. All three injections caused afebrile response in the animals. Interleukin-1 alpha had no effect on plasma lipoprotein concentrations, composition of lipoproteins or enzyme activity. In contrast, injection of TNF caused significant changes in lipoprotein concentrations. There was a 38% increase in plasma triacylglycerol and 30% decrease in plasma cholesterol at 48 h after injection. Concentrations of apolipoproteins A-I and B were decreased 20% and 44%, respectively, at 48 h. Compositional analyses of lipoprotein particles after TNF injection showed that both the LDL and HDL particles had decreased content of cholesterol ester and increased triacylglycerol after injection, and plasma activities of PHLA and LCAT were decreased. These changes were qualitatively similar to those seen after LPS injection. These data suggest that, unlike TNF, IL-1 alpha is not an important mediator of the inflammatory process on lipoprotein metabolism in cynomolgus monkeys.