Effects of saturated and polyunsaturated dietary fat on the concentrations of HDL subpopulations in African green monkeys.

Abstract

The effect of the type of dietary fat on the concentrations and compositions of high density llpoproteln (HDL) subpopulations was studied In groups of African green monkeys consuming 40% of calories as fat supplied as saturated fat (P/S = 0.3) or polyunsaturated fat (P/S = 2.2) In the presence of either 0.8 mg or 0.03 mg cholesterol/kcal. Plasma HDL cholesterol concentrations were lower In polyunsaturated fat-fed animals. The distribution of mass among HDL subtractions was assessed by analytic ultracentrrfugatlon (AnUC), density gradient ultracentrlfugatlon (DGUC), and polyacrylamlde gradient gel electrophoresls (GGE). This made It possible to characterize and quantltate the HDL subpopulations HDL^,, HDLj,, HDL3., HDL^, and HDLy. (arranged In order of decreasing particle size and decreasing cholesterol content). Polyunsaturated fat-fed animals had lower concentrations of the large, cholesterol-rich subpopulatlon, as well as higher concentrations of Intermediate size HDL z.HDL3. on the high cholesterol diet; HDL^ and HDLj,, on the low cholesterol diet). Consistent with the observed fat-related redistribution of HDL mass, the saturated fat-fed monkeys had higher apo A-l/apo A-ll ratios. The larger HDL often contained detectable apo E; however, the concentration of apo E In HDL was low In both saturated and polyunsaturated fat-fed animals. Thus, compared to saturated fat, dietary polyunsaturated fat Induced the formation of smaller size HDL subpopulations and, therefore, an overall lower cholesterol content per particle for plasma HDL. 3 The effect of dietary fat on plasma HDL concentrations has been examined by many investigators 4 " 8 who wish to learn the relationship between diet and this lipoprotein risk factor for atherosclerosis. A frequent finding in these studies is that polyunsaturated fat feeding results in lower HDL cholesterol concentrations. This result is paradoxical because a diet rich in polyunsaturated fat has been shown to induce less severe atherosclerosis in the coronary arteries of African green monkeys than a diet rich in saturated fat, 9 ' 10 even though the former diet results in lower HDL concentrations. One possible explanation is that, in addition to affecting the total amount of HDL cholesterol, the type of dietary fat affects the distribution of mass among plasma HDL subpopulations, and the concentrations of specific HDL subpopulations may be better indicators than total HDL cholesterol of atherogenic risk. The particle heterogeneity of plasma HDL has been well documented in humans and nonhuman primates, 11 " 14 but few studies have examined the effect of dietary fat on individual HDL subpopulations. Studies in humans 5 and baboons 7 have demonstrated by analytic urtracentrifugation that polyunsaturated fat feeding results in decreased plasma concentrations of total HDL as well as HDLa,, the largest in particle size and most cholesterol-rich subpopulation of normal plasma HDL. These diet-related differences in the concentration of HDLa, are difficult to interpret because it has also be...

Childhood consumption of dietary polyunsaturated fat lowers risk for coronary artery atherosclerosis in African green monkeys.

“…On the basis of the caloric content of rhesus monkey breast milk, 38 the cholesterol intake of the nursing animals averaged 0.2 and 0.3 mg/kcal for saturated and polyunsaturated fat groups, respectively. In both diet groups the cholesterol intake from breast milk was lower than that consumed in experimental diets (0.8 mg/kcal 21 ). Triglyceride fatty acid composition of breast milk was found to differ significantly between the two dietary fat groups.…”

“…Both semipurified diets 21 were designed to mimic the consumption of dietary fat by North Americans, with approximately 40% of calories from fat, 40% of calories from carbohydrate, and 20% of calories from protein. The substitution of safflower oil for lard in the polyunsaturated fat diet resulted in diets with differing fatty acid patterns 20 and a polyunsaturated-to-saturated fatty acid ratio of 0.3 for saturated fat-and 2.5 for polyunsaturated fat-enriched diets.…”

Species, diet, and gender differences in plasma postheparin lipolytic activities in nonhuman primates. Relationships with plasma lipids and high density lipoproteins.

“…11 For the analyses of HDL subtractions, the procedure followed was that described by Babiak et al 8 Briefly, the density of plasma was adjusted to 1.225 g/ml with solid KBr, and the plasma was centrifuged in a Beckman L5-50 ultracentrifuge in a 70.1 Ti rotor for 24 hours at 50 000 rpm. The top layer containing all of the lipoproteins was removed, and an aliquot was mixed with bromophenol blue tracking dye.…”

“…Percentages of HDLs,, HDLaj, and HDUc were summed and termed HDL 3 for the purposes of this article. The standardization of the densitometry has been described 8 ; repeat analysis of the same sample generally yields agreement within 5%.…”

“…This hypothesis was based on the idea that HTGL functions to regulate the interconversion of HDU to HDI-3-6 ' 7 Several observations stimulated us to compare the relative activities of HTGL in nonhuman primates. Babiak et al 8 have found that animals fed polyunsaturated fat have lower concentrations of the larger HDL subtractions (HDLaO than animals fed saturated fat, but have higher concentrations of the intermediate HDL subtractions (HDL3.). African green monkeys have been found to have higher HDL concentrations than cynomolgus monkeys," and the former also have more of the larger HDL subtractions (Rudel, unpublished observations).…”