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Interleukin-6 causes hypocholesterolemia in middle-aged and old rhesus monkeys
W H Ettinger1, W H Sun, N Binkley
1Department of Internal Medicine, Bowman Gray School of Medicine, Winston-Salem, North Carolina, USA.
Background:
Hypocholesterolemia is a risk factor for morbidity and mortality in older people. We have hypothesized that hypocholesterolemia in older people is due to the chronic effect of proinflammatory cytokines on lipoprotein metabolism.
Methods:
To test the effects of the chronic administration of interleukin-6 (IL-6) on lipoprotein levels in middle-aged and old rhesus monkeys, five middle-aged and five old rhesus monkeys received a subcutaneous injection of recombinant human IL-6 (15 micrograms/kg) for 28 days. Lipid, apolipoprotein, and albumin levels were measured at 0, 28, and 42 days after injection.
Results:
Total and HDL cholesterol levels fell by 16 and 23%, respectively, after IL-6 injections. The concentrations of apolipoproteins A1 and B also decreased. The changes in lipoprotein levels were accompanied by a decrease in albumin levels and body weight. Levels of lipids and plasma proteins returned toward normal 2 weeks after injections were stopped. There was no difference in response between middle-aged and older animals.
Conclusions:
Chronic IL-6 injections cause acquired hypocholesterolemia, hypoalbuminemia, and weight loss in nonhuman primates. These changes are similar to those seen in older persons with acquired hypocholesterolemia.