A New Perspective on Cholesterol Metabolism in Man

Eur J Clin Investigation

1976

Studies on plasma cholesteryl esters were made in 32 normal and hyperlipidaemic subjects in an attempt to elucidate further the metabolic relationships between cholesterol and other plasma lipids and lipoproteins. Fractional and net turnover rates of plasma cholesteryl esters were measured using two independent (in vivo and in vitro) methods, both of which determined the prevailing activity of plasma lecithin: cholesterol acyltransferase in the ambiance of the patients own plasma. The results obtained by the two methods were in excellent agreement. The turnover rates of plasma cholesteryl esters in hypertriglyceridaemic patients were significantly greater than in patients with only hypercholesterolaemia and in those with normal plasma lipids. In agreement with these observations, the esterified to free cholesterol ratios in hypertriglyceridaemic patients were significantly greater than in those with normal plasma triglycerides. Patients who had only hypercholesterolaemia had normal esterified to free cholesterol ratios. The rates of esterification of plasma free cholesterol correlated well with triglyceride concentrations as well as with the net turnover of plasma triglycerides and also with the turnover or synthesis of endogenous cholesterol. Since the turnover of plasma triglycerides in most patients with modest to moderate hypertriglyceridaemia reflects the turnover of their plasma very low density lipoproteins, it is suggested that it is the turnover of these lipoproteins which correlates with the hepatic synthesis of cholesterol and with the esterification of plasma cholesteryl esters.

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Section: The Plasma Lcat Activity (Determined I N V I T R O ) In Hysupporting

confidence: 89%

Section: Ns -Not Significantmentioning

confidence: 96%

Section: Ns -Not Significantmentioning

confidence: 99%

Section: The Plasma Lcat Activity (Determined I N V I T R O ) In Hymentioning

confidence: 99%

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Turnover of Plasma Cholesteryl Esters and its Relationship to Other Parameters of Lipid Metabolism in Man¹

Eur J Clin Investigation

1976

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“…29 In steady-state conditions (i.e., in absence of mobilization of tissue cholesterol) the synthetic rate of cholesterol equals the fecal losses of neutral and acidic metabolites of endogenous cholestero!. The cholesterol which is catabolized in the Iiver is partitioned into biliary cholesterol and biliary bile acids , the ratios of which remain more or less the same in steady-state conditions.P According to our model for cholesterol metabolism, 25,32 areduction in the endogenous synthesis of cholesterol would be reflected in proportionate decrease in biliary excretion of both cholesterol and bile acids. If there is any mobilization of tissue cholesterol, it will be reflected primarily as an increase in biliary cholesterol.…”

Section: Discussionmentioning

confidence: 98%

Effects of clofibrate on cholesterol metabolism

Clin Pharma and Therapeutics

Horlick

et al. 1977

Self Cite

The effects of clofibrate on cholesterol metabolism were studied in one normolipidemic and 5 hyperlipidemic patients by sterol balance methods. In 2 patients, the effects of discontinuation of treatment were also assessed. Clofibrate reduced all classes of plasma lipids. The percentage reduction in triglycerides correlated weil (r = 0.99) with pretreatment levels. On the other hand, percentage reductions in plasma cholesterol, free fatty acids, and phospholipids did not correlate with pretreatment levels but correlated significantly with the fall in plasma triglycerides. In 3 patients, in whom plasma cholesterol was labeled by intravenous infusion of radioactive cholesterol, the specific activity (SA) of plasma cholesterol was determined at frequent intervals. Clofibrate reduced the rate offall ofplasma cholesterol SA while discontinuation of clofibrate increased rate of decline of plasma cholesterol SA. Since clofibrate did not affect the absorption of dietary cholesterol, the changes in plasma cholesterol SA were in all probability related to changes in endogenous synthesis of cholesterol. In addition to the above changes in the specific activity slopes, there were acute increases in plasma cholesterol specific activity which could be explained only by mobilization of tissue cholesterol from the slowly exchangeable pool immediately after the beginning of treatment. The effect of clofibrate on the excretion of fecal neutral and acidic steroids was variable and was probably dependent on the balance of its effect on the turnover of plasma lipoproteins on one hand and the mobilization of tissue cholesterol on the other.

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Effects of Caloric Restriction on Cholesterol Metabolism in Hyperlipemic Obese Subjects

1977

Atherosclerosis