Effects of Dietary Polyunsaturated and Saturated Fat on the Properties of High Density Lipoproteins and the Metabolism of Apolipoprotein A-I

Abstract

A B S T R A C T In this study we have investigated, in four normal males the effects of dietary saturated and polyunsaturated fat on the chemical composition and thermotropic properties of human high density lipoproteins (HDL) and have measured the influence of the diets on the metabolism of that fraction of HDL apolipoprotein A-I (apoA-I) that undergoes exchange in vitro and accounts for approximately twothirds of the lipoprotein's apoA-I complement. When compared with the saturated fat diet, the polyunsaturated diet reduced plasma cholesterol (24%, P < 0.01) by affecting the cholesterol content in the very low density lipoprotein (125%, P < 0.02), low density lipoprotein (120%, P < 0.01), and high density lipoprotein fractions (133%, P < 0.01). Plasma triglyceride was also lowered (by 13%, P < 0.01). Furthermore, polyunsaturated fat ingestion caused a significant fall in the palmitate and stearate content of HDL triglyceride (41 and 37%, respectively), cholesteryl esters (29 and 35%), and phospholipids (17 and 9%) with a concomitant increase in the linoleate content of these moieties (157, 28, and 29%, respectively). The polyunsaturated diet also produced reciprocal changes in the percentage protein (19%, P <0.02) and phospholipid (411.5%, P < 0.01) in HDL. These compositional changes were associated with an increase in the microscopic fluidity of the polyunsaturated HDL, although both diets had little effect on the fluidity parameters of HDL at body temperature. Rate zonal ultracentrifugation indicated that the HDLJHDL3 ratio fell by 28% (P < 0.05) on the polyunsaturated fat diet. In addition to the above,

Triglyceride-lowering effect of marine polyunsaturates in patients with hypertriglyceridemia.

“…Shepherd et al 25 noted a reduction in total HDL cholesterol and a decrease in the ratio of HDLj/HDLj in normal subjects when the intake of polyunsaturated/saturated fat was increased from 0.25 to 4.0. In that study, the polyunsaturated fat was of vegetable origin.…”

Polyunsaturated fatty acids, hyperlipidemia, and thrombosis.

“…Substitution of polyunsaturated fatty acids for saturates decreased the synthesis of apo A-l, the major apoprotein in HDL, by 26%. 59 No change in the fractional catabolic rate of apo A-l was noted.…”

Effect of Various Dietary Fatty Acid Ethyl Esters on Plasma Cholesterol and Lipoprotein Metabolism in Rats.

“…In rats, a PUFA-rich fat diet has been shown to lower [2], raise [3,4], or have no effect on plasma cholesterol [5,6], while high-density lipoprotein cholesterol (HDL-C) is lowered [7,8]. Although monounsaturated fatty acid (MUFA) of oleic fatty acid-rich fat has been found to decrease plasma cholesterol levels in humans [9][10][11], this hypocholesterolemic response has not been demonstrated in animal models.…”