Studies on low-density lipoprotein turnover in relation to atromid therapy

A small series of cases of idiopathic hyperlipaemia (here defined as an increase predominantly of S f 20– 400 lipoproteins) and of idiopathic hypercholesterolaemia (here defined as a predominant increase of S f 0-20 lipoproteins) have been treated with Atromid, and the responses of serum cholesterol and lipoproteins have been evaluated at monthly intervals. Selected cases have also,been subjected to turnover studies of isotopically labelled low-density lipoproteins before and after treatment. A marked and persistent response of the serum lipids to treatment was found in cases of hyperlipaemia. A seasonal fluctuation of serum cholesterol and lipoproteins was observed in hypercholesterolaemia and this made the evaluation of response to Atromid difficult; but even where initial falls in serum lipids occurred in this condition, escape of serum cholesterol and lipoprotein levels was observed in spite of continued treatment. Studies of turnover of low-density lipoproteins in normal subjects and patients with idiopathic hyperlipaemia or hypercholesterolaemia showed that in the latter conditions the biological half-life of the protein moiety of the low-density lipoproteins was unaltered but the total exchangeable pool of lipoprotein and its catabolic rate were greatly increased. Treatment with Atromid left the biological half-life of the protein unaltered but in hyperlipaemia the total exchangeable pool and the catabolic rate of the protein decreased. From a consideration of the results obtained in this study it is suggested that the mechanism of action of Atromid does not affect lipoprotein metabolism directly by suppressing the synthesis of the protein moiety, but indirectly, possibly by decreasing liver triglyceride formation. Un nombre restreint de cas d'hyperlipidémie idiopathique (définie ici comme une augmentation prédominante de lipoprotéines S f 20-400) et d'hypercholestérolémie idiopathique (définie ici comme une augmentation prédominante de lipoprotéines S f 0-20) ont été traités par l'Atromide; les réponses du cholestérol et des lipoprotéines sériques ont ensuite été evaluées à des intervalles d'un mois. Des cas sélectionnés ont de plus été soumis avant et après le traitement à des études du cycle métabolique des lipoprotéines marquées de basse densité. Une réponse accusée et persistente des lipides sériques au traitement a été constatée dans les cas d'hyperlipidémie. Une variation saisonniére du cholestérol et des lipoprotéines sériques a été observée