DIETARY POLYUNSATURATED FAT DECREASES INTERACTION BETWEEN LOW-DENSITYLIPOPROTEINS AND ARTERIAL PROTEOGLYCANS

Polyunsaturated dietary fat (n-3 and n-6) results in less atherosclero sis in monkeys compared to lard (Parks, J.S., Kaduck-Sawyer, J., Bullo ck, B.C., and Rudel, L.L., Arteriosclerosis 10, 1102-1112; Rudel, L.L. , Parks, J.S., Johnson, F.L., and Babiak, J., J. Lipid Res. 27, 465-47 4, 1986). We hypothesized that this was due, in part, to a decreased r eactivity of low density lipoproteins (LDL) with arterial proteoglycan s (PG). To test this hypothesis, cynomolgus monkeys were fed diets con taining lard, safflower oil (n-6 polyunsaturated; Poly), menhanden fis h oil (FO), or oleic acid-rich safflower oil (oleinate; Mono) for 14 m on, and plasma LDL were isolated and characterized. Several properties of LDL thought to be important in the interaction of LDL with arteria l PG were measured including LDL particle size, chemical composition, sialic acid content, density distribution, apolipoprotein E (apoE) con tent and cholesteryl ester transition temperature. Plasma LDL choleste rol concentrations (mg/dL) after 14 mon of diet consumption averaged ( mean +/- SEM): FO (366 +/- 45), Lard (352 +/- 27), Poly (279 +/- 24), and Mono (230 +/- 43). The composition of LDL was similar among diet g roups except that FO LDL were relatively depleted of cholesteryl ester and enriched in protein and were smaller in size. LDL sialic acid con tent was similar among diet groups (4.5-5.0 mu g/mg LDL protein). The LDL apoE/B molar ratio, a measure of the apoE content per LDL particle averaged: Mono (3.0 +/- 1.0), Poly (2.0 +/- 0.1), Lard (1.8 +/- 0.5), and FO (1.0 +/- 0.2). The FO group had a lower proportion (13%) of th e apoE enriched d = 1.015-1.025 g/mL subfraction of LDL than did the o ther diet groups (31-45%), The transition temperature of the LDL chole steryl esters was below body temperature for the FO and Poly groups (3 6 degrees C) and above for the Lard and Mono groups (40-44 degrees C). The percentage of LDL cholesterol that formed insoluble complexes wit h arterial chondroitin sulfate PG; averaged: Mono (29 +/- 4%), Lard (1 8 +/- 3%), Poly (14 +/- 3%), and FO (7 +/- 2%). Among all diet groups, there was a significant positive correlation (r = 0.54) between LDL-P G complex formation and LDL apoE/B molar ratio. We conclude that dieta ry FO and Poly result in LDL that are less reactive with arterial PG c ompared to Lard or Mono fats. While FO appears to decrease PG binding by decreasing the apoE content and amount of the largest LDL subfracti on, Poly fat appears to affect LDL-PG interactions by other mechanisms . Decreased LDL-PG interactions may lead to decreased atherosclerosis in animals fed polyunsaturated dietary fat.