Influence of Essential Phospholipids on Serum Lipids and Lipid Metabolism in the Aortic Wall

Abstract

A deficiency of essential fatty acids in the atherosclerotic artery leads to the formation of saturated cholesterol esters which are sclerogenic. The presence of essential phospholipids (EPL) within the arterial wall should favor the formation of non-sclerogenic polyunsaturated cholesterol esters which are readily removed from the vessel wall. Therefore, the effects of EPL (40 mg/kg/day) in the cholesterol-fed rabbit on serum and aortic lipids in vivo, and on the arterial lipid synthesis in tissue cultures of arteries of the same animals were investigated. The EPL was intravenously injected 3 times weekly in parallel to the cholesterol diet; the control animals received a corresponding injection of saline. Blood samples were taken after 4 and 8 weeks of treatment, then the aortas were removed and placed into a tissue culture. The explants were pulse-labelled during a 24 h incubation either with ³H-EPL, ¹⁴C-acetate and ³²P-phoshate or with ³H-oleic and ¹⁴(C-linoleic acid, respectively. After this pulse label incubation the explants were removed, one third of them were used for uptake studies and two thirds of them were reincubated in a non-radioactive medium to determine the labelled lipids released from the explants. — After 4 and 8 weeks the ratio of linoleic:oleic acids in serum phospholipids and serum triglycerides in the EPL treated animals differred significantly from the controls. The LCAT activity was lower in the EPL treated group. — No significant differences in the arterial lipid composition were observed. The incorporation of ³H-EPL into cholesterol esters was significantly higher in the atherosclerotic artery. ³H-EPL cholesterol esters were removed from arterial tissues after 8 weeks of EPL treatment. ¹⁴C-acetate, ³H-oleic and ¹⁴C-linoleic labelled cholesterol esters were also removed. The phospholipid synthesis from ¹⁴C-acetate was significantly depressed by the EPL treatment.