Larry M. Davidson

Influence of native and randomized peanut oil on lipid metabolism and aortic sudanophilia in the vervet monkey

Vervet monkeys (Cercopithecus aethiops pygerethrus) were fed cholesterol-free, semipurified diets containing 40% sucrose, 25% casein, 15% cellulose and 14% peanut oil (PNO), randomized peanut oil (RPNO) or corn oil (CO). After 4 months, serum cholesterol and triglyceride levels, serum lecithin-cholesterol acyl transferase (LCAT) activity and plasma lipoprotein lipase (LPL) activity were similar in all groups. Livers of monkeys fed CO converted 156% more acetate and 24% more mevalonate to cholesterol than those of monkeys fed RPNO. Cholesterogenesis in RPNO-fed monkeys was enhanced compared to PNO (68% from acetate; 62% from mevalonate). Incidence of atherosclerosis was 33% in monkeys fed RPNO, 80% in those fed CO and 90% in those fed PNO. Extent of sudanophilia was lowest in aortas of monkeys fed RPNO. Incidence of arteriosclerosis was 40% in monkeys fed CO, 56% in those fed RPNO and 70% in those fed PNO. Extent of aortic surface showing arteriosclerosis was highest in monkeys fed RPNO.

Effect of trans-unsaturated fats on experimental atherosclerosis in vervet monkeys

Vervet monkeys ( Ceropithecus aethiops pygerethrus ) were placed on semipurified diets containing 14% fat of which 3.2 or 6.0% was present as trans-unsaturated fatty acid (t-FA). Two groups were fed the high and low levels of t-FA for a year and two others were fed t-FA for 6 months and then returned to the control diet for 6 months more. One other group was fed the control diet for a year. The control diet contained 14% fat which was a mixture of 72% olive oil and 28% corn oil. There were no significant differences in weight gain. Monkeys fed 6% t-FA or control diets for one year had lowest liver weights. Serum cholesterol and triglycerides in monkeys fed 3.2% t-FA for one year were 134 and 55 mg/dl, respectively; in monkeys returned to control diet after 6 months on 6% t-FA the values were 146 and 50 g/dl. Serum and triglyceride levels for the other 3 groups were 166 +/- 2 and 70 +/- 2 mg/dl. Liver cholesterol levels ranged from 4.0 mg/g (3.2% t-FA) to 4.7 mg/g (control) and 4.8 mg/g (6% t-FA). Lecithin:cholesterol acyltransferase (LCAT) activity was 59.0 microM/h for controls and ranged from 52.4 microM/h (3.2% t-FA) to 73.4 microM/h (6% t-FA). Cholesterol synthesis by liver slices was not affected by diet when the substrate was acetate. When mevalonate was used, the monkeys fed either level of t-FA for 12 months exhibited greatly reduced (about 80%) cholesterogenesis. The levels of t-FA in serum and liver reflected the amount in the diet. After being returned to control diet levels of t-FA in serum and liver of monkeys (fed 3.2% t-FA) fell by 97 and 94%, respectively, and those in serum and liver of monkeys fed 6% t-FA fell by 65 and 91%. There were no significant differences in aortic atherosclerosis or arteriosclerosis.(ABSTRACT TRUNCATED AT 400 WORDS)

Serum and liver lipids of rats fed cocoa butter, corn oil, palm kernel oil, coconut oil and cholesterol.

Abstract Male Wistar rats were fed semipurified diets containing 10% fat and 0.4% cholesterol for three weeks. The fats were cocoa butter, corn oil, palm kernel oil and coconut oil. Rats fed corn oil gained more weight than those fed the other fats. Serum cholesterol levels of rats fed cocoa butter or corn oil were similar and significantly lower than those of rats fed palm kernel or coconut oils whose cholesterol levels were also similar. Rats fed cocoa butter had lower liver cholesterol (39–52%) and triglyceride (28–67%) levels than rats fed the other fats. Serum and liver fatty acid spectra resembled those of the dietary fats except for the high levels of arachidonic acid in livers of rats fed cocoa butter. Despite its low iodine value cocoa butter does not exhibit hyperlipidemic properties.

Experimental atherosclerosis in rabbits fed cholesterol-free diets 13. Interaction of proteins and fat

The atherogenic and cholesterolemic effects of animal protein vis-a-vis plant protein are well documented. Virtually all the studies were carried out using diets high in saturated fat, such as coconut oil. In order to determine if the same effects were seen with less saturated fat, we have compared atherogenic effects of an animal protein (casein) with those of a plant protein (soybean protein isolate) fed with partially hydrogenated soybean oil (PHS) (iodine value 72) or soybean oil (iodine value 134) as part of a cholesterol-free semipurified diet. After 6 months only rabbits fed casein-PHS exhibited elevated levels of plasma and liver cholesterol and triglycerides and atherosclerosis. Rabbits fed soy protein-PHS had slightly higher plasma cholesterol and triglycerides than did those fed soy protein and soybean oil, but values in both groups were in the normal range. The different effects of animal and plant protein on lipidemia and atherosclerosis can be influenced by dietary fat and appear to be dependent on fat saturation.

Influence of Dietary Fiber on Aortic Sudanophilia in Vervet Monkeys

Vervet monkeys were fed a cholesterol-free, semipurified diet containing 40% sucrose, 25% casein, 14% coconut oil and 15% fiber for 23 weeks. The fibers used were cellulose, wheat straw or alfalfa. Serum lipid and lipoprotein levels were highest in the monkeys fed the cellulose-containing diet. Liver lipids were slightly higher in the cellulose-fed monkeys. The ratio of endogenous to exogenous cholesterol was estimated using isotopically labeled sterol and sterol precursor and found to be similar in all three groups. The levels of endogenous or exogenous cholesterol in the serum and liver of alfalfa-fed monkeys were lower than the levels in the other two groups, which were similar. The ratio of exogenous to endogenous cholesterol in the feces was highest in the monkeys fed alfalfa. Monkeys fed alfalfa exhibited the lowest lithogenic index. Cholesterol 7α-hydroxylase activity was highest in livers of monkeys fed wheat straw. The data suggest that alfalfa inhibits absorption and reabsorption of cholesterol more than wheat straw or cellulose. Monkeys fed cellulose exhibited more severe aortic sudanophilia than those fed the other two fibers.

Cholesterol absorption in primates as determined by the Zilversmit isotope ratio method

Summary The Zilversmit isotope ratio method for measuring cholesterol absorption has been applied to baboons (Papio ursinus) and vervet monkeys (cercopithecus aethiops pygerethrus) and found to compare well with the more complicated method involving fecal excretion. Cholesterol absorption in the baboon was found to be 26.3% by the Zilversmit method and 22.2% by the fecal excretion method. In vervet monkeys the Zilversmit method showed 26.9% absorption as compared with 29.1% by the other. Sitosterol degradation (which is used to assay degradation) was found to be 64.1 and 69.3% in monkeys and baboons, respectively. Sitosterol degradation is about 5% in rats (1) and 23–27% in man (8). The correction for sterol degradation must, therefore, be determined for each species (and possibly in each experiment).

Effects of dietary fiber in Vervet monkeys fed “Western” diets

Male Vervet monkeys (7/treatment) were fed a “Western” diet containing 46.2% calories as fat, 39.8% as carbohydrate and 14.0% as protein. The diet was augmented with 10% cellulose or 10% pectin. A third (control) group of seven monkeys was fed a commercial ration augmented with fruit and bread. After 34 weeks, serum cholesterol levels were elevated significantly in the two test groups compared with the controls but there was no difference between the two fiber-fed groups. Serum triglycerides were unaffected. Liver cholesterol levels were the same in all three groups but liver triglyceride levels were lower in the monkeys fed cellulose. Biliary lipids were similar in all three groups as were the calculated lithogenic indices. The average aortic sudanophilia (percent of total area) in the three groups was cellulose, 10.6±2.5; pectin, 8.1±2.5; and control, 1.1±0.4. One animal in each of the groups fed “Western” diet exhibited an atherosclerotic plaque. The results indicate that there is no difference between pectin and cellulose with regard to their effects on either lipidemia or aortic sudanophilia in Vervet monkeys fed a Western-type diet.

Identification of acidic steroids in feces of monkeys fed β-sitosterol

Vervet monkeys were fed a suspension of β-sitosterol in corn oil Acidic steroids, were separated from a 4-day pool of feces and subjected, after fraction, to gas liquid chromatography and mass spectrometry. Evidence for the presence of derivatives of 27-carboxysitosterol, 27-carboxysitostanol and 7-hydroxy, 27-carboxysitostanol is adduced.

Quantitative recovery of lipids from aortas stained with Sudan IV

The separation of Sudan IV from lipid extracts of stained aortas can be accomplished by thin layer or column chromatography, but the most convenient method involves adsorption of the dye to activated carbon. The aortic lipids are thus recovered quantitatively.

Seasonal variation of serum lipids in the Vervet monkey

Seasonal variation of serum lipids has been observed in man, primates and other species. We are presenting data on serum lipid variation in Vervet monkeys (Cercopithecus aethiops). The monkeys (54 males, 33 females) were fed control diets (commercial pellets, fruit, vegetables) and data were pooled and grouped by season. Data having been obtained in South Africa, the seasons were: summer (December, January, February); fall (March, April, May); winter (June, July, August); and spring (September, October, November). Data presented are based on multiple samplings. Total serum cholesterol (mg/dl) and beta-lipoprotein cholesterol (mg/dl) varied significantly with season, peak values being observed in the fall months. Triglyceride and alpha-lipoprotein cholesterol levels showed seasonal variation which was not statistically significant. However, when data were analyzed by weight group (less than 3.3 kg; 3.3-4.3 kg; 4.4-5.3 kg; greater than 5.4 kg) only triglyceride and alpha-lipoprotein levels varied significantly with season. Significant interactions between diet, sex, weight, and season have also been observed. These observations can be used in planning future studies.