Journal of Lipid Research, Vol 35, 633-643, Copyright © 1994 by Lipid Research, Inc.
Metabolic mechanisms for responses to dietary cholesterol and fat in high and low LDL responding baboons (Papio sp.)
RS Kushwaha, CA Reardon, GS Getz, DS Lewis, KS Rice, KD Carey and HC McGill Jr
Department of Physiology, Southwest Foundation for Biomedical Research, San Antonio, TX 78228-0147.
These studies were conducted to determine how plasma low density
lipoprotein (LDL) cholesterol levels respond to dietary cholesterol, fed in
increasing amounts with either corn oil or coconut oil diets, in high as
compared to low LDL responding baboons; and to determine how apolipoprotein
(apo) B transcription levels are modulated in response to dietary lipids.
Eight high and eight low LDL responding pedigreed adult baboons, balanced
for sire, age, sex, and weight, were challenged for successive 7-week
periods with increasing levels of dietary cholesterol combined with either
coconut oil or corn oil. At the end of each dietary period, plasma and
lipoprotein lipids, apoB, apoA-I, and hepatic mRNA levels for
apolipoproteins were measured. As dietary cholesterol increased, plasma
cholesterol concentrations (mostly LDL cholesterol) increased in both
phenotypes and with both types of fat, but phenotypic differences were
greater with coconut oil. There was not a consistent dose-response
relationship of plasma or LDL cholesterol levels to increasing intakes of
dietary cholesterol. Neither dietary cholesterol, type of dietary fat, nor
LDL phenotype affected hepatic apoB or apoE mRNA levels. In a second
experiment to resolve the inconsistent dose-response to dietary
cholesterol, we fed the animals varying levels of dietary cholesterol
combined with coconut oil, and separated the challenge periods with
intervening 12-week chow periods. Plasma and LDL cholesterol and apoB
concentrations rose consistently with increasing dietary cholesterol, and
the slope of the increase diminished at the higher doses. The results
suggest that genetic differences in the initial response of LDL cholesterol
to dietary cholesterol and saturated fatty acids are not due to the
differences in hepatic transcription of apoB, and that the preceding
dietary intake of cholesterol and saturated fatty acids is a major
determinant of the response of plasma lipids and the associated metabolic
processes to a dietary challenge. The response of baboon plasma LDL
cholesterol concentrations to dietary cholesterol, when fed with saturated
fatty acids, is similar to that of humans.