Journal of Lipid Research, Vol 26, 1079-1088, Copyright © 1985 by Lipid Research, Inc.
Relationship of the parameters of body cholesterol metabolism with plasma levels of HDL cholesterol and the major HDL apoproteins
CB Blum, RB Dell, RH Palmer, R Ramakrishnan, AH Seplowitz and DS Goodman
The inverse relationship between plasma levels of high density lipoprotein
(HDL) and coronary heart disease rates has suggested that HDL might
influence body stores of cholesterol. Therefore, we have investigated
potential relationships between the parameters of body cholesterol
metabolism and the plasma levels of HDL cholesterol and the major HDL
apoproteins. The study involved 55 human subjects who underwent long-term
cholesterol turnover studies, as well as plasma lipoprotein and
apolipoprotein assays. In order to maximize the likelihood of detecting
existing relationships, the subjects were selected to span a wide range of
plasma levels of lipids, lipoproteins, and apolipoproteins. Single
univariate correlation analyses suggested weak but statistically
significant inverse relationships of HDL cholesterol and apoA-I levels with
the following model parameters: production rate (PR), the mass of rapidly
exchanging body cholesterol (M1), the minimum estimate of the mass of
slowly exchanging body cholesterol (M3min), and of the mass of total
exchangeable body cholesterol (Mtotmin). These correlations, however, were
quantitatively quite small (/r/ = 0.28-0.42) in comparison to the strength
of the univariate relationships between body weight and PR (r = 0.76), M1
(r = 0.61), M3min (r = 0.58), and Mtotmin (r = 0.78). Correlations for
apoA- II and apoE levels were even smaller than those for apoA-I and HDL
cholesterol. In additional analyses using multivariate approaches, HDL
cholesterol, apoA-I, apoA-II, and apoE levels were all found not to be
independent determinants of the parameters of body cholesterol metabolism
(/partial r/ less than 0.17, P greater than 0.3 in all cases). Thus the
weak univariate correlations reflect relationships of HDL cholesterol and
apoA-I levels with physiological variables, such as body size, which are
primarily related to the model parameters. We conclude that plasma levels
of HDL cholesterol and apoproteins A-I, A- II, and E are not quantitatively
important independent determinants of the mass of slowly exchanging body
cholesterol or of other parameters of long-term cholesterol turnover in
humans. These studies give no support to the hypothesis that the inverse
relationship between HDL cholesterol levels and coronary heart disease
rates is mediated via an influence of HDL on body stores of cholesterol.