Relationships Between Metabolism of Cholesterol and the Turnover of Plasma Lipoproteins

Abstract

While there is some literature on the correlations between the metabolism of plasma triglycerides and the metabolism of plasma lipoproteins, the metabolism of endogenous cholesterol has not, in general, been related to the metabolism of lipoproteins. Studies done in our laboratories indicated to us that synthesis and catabolism of endogenous cholesterol as well as the esterification of plasmafree cholesterol were signficantly greater in hypertriglyceridemic patients than in those with normal plasma triglycerides and comparable levels of plasma cholesterol (Sodhi and Kudchodkar, 1973a, 1973b; Sodhi 1974; Kudchodkar and Sodhi, 1976). Since plasma triglycerides by themselves are unlikely to cause these changes in cholesterol metabolism (Sodhi and Kudchodkar, 1974a), we reasoned that the observed correlations in man must be mediated through the state of lipoprotein metabolism associated with hypertriglyceridemia (Sodhi and Kudchodkar, 1973c). The bulk of available evidence indicated that hypertriglyceridemia in man was generally associated with increased synthesis and turnover of plasma very lowdensity lipoproteins (VLDL). (Reaven et al., 1965; Nestel and Whyte, 1968; Nikkila und Kekki, 1971; Brunzell et al., 1973; Kaye and Galton, 1975; Sigurdsson et al., 1976; Kudchodkar and Sodhi, 1976; Nestel, 1976). We should, however, recognize that the method used in the laboratories of Havel (Havel et al., 1970) and of Carlson (Boberg et al., 1972) produced data which did not fully agree with the results obtained by most other methods.