Robert J. Nicolosi

Rice bran oil consumption and plasma lipid levels in moderately hypercholesterolemic humans.

The effect of rice bran oil, and oil not commonly consumed in the United States, on plasma lipid and apolipoprotein concentrations was studied within the context of a National Cholesterol Education Panel (NCEP) Step 2 diet and compared with the effects of canola, corn, and olive oils. The study subjects were 15 middle-aged and elderly subjects (8 postmenopausal women and 7 men; age range, 44 to 78 years) with elevated low-density lipoprotein (LDL) cholesterol (C) concentrations (range, 133 to 219 mg/dL). Diets enriched in each of the test oils were consumed by each subject for 32-day periods in a double-blind fashion and were ordered in a Latin square design. All food and drink were provided by the metabolic research unit. Diet components were identical (17% of calories as protein, 53% as carbohydrate, 30% as fat [< 7% as saturated fat], and 80 mg cholesterol/1000 kcal) except that two thirds of the fat in each diet was contributed by rice bran, canola, corn, or olive oil. Mean +/- SD plasma total cholesterol concentrations were 192 +/- 19, 194 +/- 20, 194 +/- 19, and 205 +/- 19 mg/dL, and LDL-C concentrations were 109 +/- 30, 109 +/- 26, 108 +/- 31, and 112 +/- 29 mg/dL after consumption of the rice bran, canola, corn, and olive oil-enriched diets, respectively. Plasma cholesterol and LDL-C concentrations were similar and statistically indistinguishable when the subjects consumed the rice bran, canola, and corn oil-enriched diets and lower than when they consumed the olive oil-enriched diet.(ABSTRACT TRUNCATED AT 250 WORDS)

Effect of dietary fat saturation on plasma lipoproteins and high density lipoprotein metabolism of the rhesus monkey.

Rhesus monkeys were fed corn or coconut oil-based diets for 3-6 mo to determine effects on the composition of all lipoprotein classes and on the metabolism of high density lipoproteins (HDL). Major findings included the following. Coconut oil feeding increased concentrations of all classes of plasma lipoproteins without altering lipoprotein size, suggesting an increase in particle number. The percentage of saturated fatty acids in the cholesteryl esters (CE) of low density lipoproteins (LDL) and HDL reached 40% with coconut oil feeding. This value probably constitutes a minimum estimate of the CE which were of intracellular rather than intraplasmic origin. The CE in LDL and HDL were nearly identical suggesting virtually complete equilibration by the core lipid transfer reaction. The CE in very low density lipoproteins, in contrast, were significantly more saturated than those in LDL and HDL irrespective of diet. Lower HDL levels on the corn oil diet were associated with higher fractional catabolic rates for both apolipoprotein A-I (0.42 vs. 0.31 d-1) and apolipoprotein A-II (0.45 vs. 0.30 d-1).

Comparative cholesterol lowering properties of vegetable oils: beyond fatty acids.

Objective: Our laboratory has previously reported that the hypolipidemic effect of rice bran oil (RBO) is not entirely explained by its fatty acid composition. Although RBO has up to three times more serum cholesterol-raising saturated fatty acids (SATS) than some unsaturated vegetable oils, we hypothesized that its greater content of the unsaponifiables would compensate for its high SATS and yield comparable cholesterol-lowering properties to other vegetable oils with less SATS. Methods: To study the comparative effects of different unsaturated vegetable oils on serum lipoprotein levels, nine cynomologus monkeys (Macaca fascicularis) were fed diets, for four weeks, in a Latin square design, containing rice bran, canola or corn oils (as 20% of energy) in a basal mixture of other fats to yield a final dietary fat concentration of 30% of energy. All animals were fed a baseline diet containing 36% of energy as fat with 15% SATS, 15% monounsaturated fatty acids (MONOS) and 6% polyunsaturated fatty acids (POLYS). Results: Despite the lower SATS and higher MONOS content of canola oil and the higher POLYS content of corn oil, RBO produced similar reductions in serum total cholesterol (TC) (−25%) and low density lipoprotein cholesterol (LDL-C) (−30%). In addition, as compared to the baseline diet, the reduction in serum TC and LDL-C cholesterol with RBO was not accompanied by reductions in high density lipoprotein cholesterol (HDL-C) which occurred with the other two dietary oils. Using predictive equations developed from data gathered from several studies with non-human primates, we noted that the observed serum TC and LDL-C lowering capabilities of the RBO diet were in excess of those predicted based on the fatty acid composition of RBO. Conclusions: These studies suggest that non-fatty acid components (unsaponifiables) of RBO can contribute significantly to its cholesterol-lowering capability.

Rapid clearance of serum amyloid A from high-density lipoproteins

The serum amyloid A proteins (SAA) occur in plasma in six polymorphic forms that are associated with the high-density lipoproteins (HDL). We studied two of the SAA proteins, SAA1 and SAA4, which have the same amino- and carboxy-terminal residues but different solution properties and electrophoretic mobilities, to determine whether they are interconverted in plasma in vivo. They were radioiodinated in vitro, incorporated into HDL, and administered to cynomolgus monkeys. Both remained associated with HDL for at least 6 h, had similar plasma die-away curves, and retained their characteristic electrophoretic mobilities, suggesting they are not related as precursor and product. The plasma clearance of the most prevalent SAA species, SAA4, was also simultaneously compared with the human A-I and C-III-2 apolipoproteins. Human apolipoprotein A-I decayed from plasma at a rate comparable to that of monkey HDL proteins. Apolipoprotein C-III-2 was cleared more rapidly and SAA4 at an even greater rate. These findings suggest that SAA are either dissociated from HDL before clearance from plasma or that SAA are contained in an HDL subspecies with metabolic fate different from that of most HDL particles.

Densitometric quantitation of neutral lipids on ammonium sulfate impregnated thin-layer chromatograms.

A procedure is described which extends the densitometric quantitation of phospholipids on ammonium sulfate impregnated thin-layer chromatograms by Gluck et al. to include total lipid, free and esterified cholesterol, free fatty acid and triglyceride. Lipids separated on thin-layer plates containing silica gel G impregnated with ammonium sulfate were charred upon heating and absorbance was measured densitometrically. Thus, the necessity of spraying or submersing in a charring agent was eliminated, uniform charring became possible, and quantitation over a wider range of sample sizes than most densitometric procedures was obtained. One linear relationship existed for concentrations of standards over the range of 0.0-3.0 mug and another line from 4.0-50.0 mug. Both accuracy and precision of the method were highly reliable.

Lecithin influence on hyperlipemia in rhesus monkeys.

Previous studies in humans have shown that the ingestion of lecithin can alter plasma cholesterol and triglyceride concentrations by mechanism(s) that remain to be elucidated. To further explore this response to lecithin, hyperlipemic rhesus monkeys were selected from a group of animals fed a semipurified diet containing corn oil, casein, sucrose and cholesterol (120 mg/100 Kcal) for 10 years. Soybean lecithin (92% phosphatidylcholine) was supplemented in the diet (0.5 g/100 Kcal) of these monkeys. Measurements of plasma cholesterol, triglycerides and phospholipid were made prior to, during and following 7 wk of lecithin supplementation. In addition, determinations of triglyceride secretion rates following administration of Triton WR1339, triglyceride clearance after intravenous infusion of Intralipid® and plasma lecithin:cholesterol acyl transferase enzyme (LCAT) activity were assessed at the same time intervals. As in other studies, manipulation of lecithin intake elicited a highly variable response, but significant changes were observed in plasma cholesterol and triglycerides as a consequence of supplementing or removing lecithin from the diet. Lecithin had no influence on the absolute plasma phospholipid level or LCAT activity. However, lecithin significantly reduced total lipids, increased the relative concentration of phospholipid and tended to increase the phospholipid/free cholesterol (PL/FC) concentration. While lecithin did not significantly affect triglyceride secretion rates, all animals were able to clear Intralipid® (triglyceride) more efficiently while fed lecithin. These data are interpreted to mean that the reduction in plasma lipids associated with lecithin ingestion may have been mediated via enhanced clearance of lipids transported in lipoproteins of lower density, whereas the rebound following lecithin removal reflected reduced clearance of these lipids.

Nutrition and Metabolism of the Squirrel Monkey

Feeding and foraging occupy a large percentage of time for the squirrel monkey. Animals have been reported to consume a variety of natural foods, including nuts, fruits, seeds, leaves, and insects. These data have been collected from visual observation of materials that enter the animal’s mouth, from studying the stomach contents of primates that have been collected, from identification of damage done to surrounding fauna and flora, and from studying the contents of fecal material left from the animals (Brodie and Marshall, 1963a,b; Fooden, 1964; Thorington, 1968, 1970). With these techniques, however, it is difficult to quantitate the nutrient intakes over long periods of time and it is impossible to make estimates of the mean calorie, protein, vitamin, and mineral intakes of these animals.

Characteristics of the aortic intima in young and old cebus and squirrel monkeys.

To document naturally occurring aortic intimal changes with age in squirrel and Cebus monkeys, the aortic lipid class composition, histology, and fine structure were quantitatively compared in the two species at birth and in old age. The aortic intima plus inner media in the young squirrel monkey contained more lipid, particularly in the phospholipid and cholesterol ester fractions than the young Cebus. The lipid class composition of the old Cebus monkey aorta resembled that of the young Cebus. In the old squirrel monkey aorta, cholesteryl ester, and to a lesser extent, free cholesterol were increased over young levels, while the phospholipid concentration tended to be lower. The aortic cholesteryl esterphospholipid ratio increased with age in both species, but the old Cebus monkey aorta maintained the ratio below unity at 0.3, whereas the old squirrel monkey aorta ratio was 2.5. The abdominal aorta of the old squirrel monkey tended to have more lipid in each class than the thoracic segment. Morphologically, the old Cebus monkey aortic intima was similar to the young Cebus in terms of the intima:media ratio, intimal cellularity, and the distribution of intimal components determined by points in electron micrographs. In both age groups the Cebus monkey aorta was characterized by diffuse intimal thickening without lipid deposits. In contrast, the old squirrel monkey aorta had a much greater intima:media ratio, especially in the abdominal aorta, and a greater intimal cellularity than the young squirrel monkey. The distribution of intimal components in electron micrographs of the old squirrel monkey aorta shifted to a predominance of extracellular lipid, smooth muscle cells, and collagen. Deposits of small dense granules, presumably the products of cellular breakdown, were observed in aortic intimas and medias of both species in old age. Thus, differences between Cebus and squirrel monkey aortic intimas were evident at birth. By old age, the Cebus monkey aortic intima remodeled without accumulating lipid, whereas the squirrel monkey developed aortic intimal lesions resembling human atherosclerosis.

The effect of semipurified diets containing two levels (20% and 40%) of either casein or soybean protein isolate and concentrate on plasma lipids in hamsters

Abstract Six groups of 10 F 1 B hamsters were fed cholesterol-enriched (0.1%) semipurified diets containing two levels (20% and 40%) of casein, soybean protein isolate, and soybean protein concentrate. The hamsters fed the 20% casein diet had higher plasma cholesterol levels (7.05±1.38 mmol/L, Mean± SD, n=10) than those fed the 20% soybean protein isolate (5.73±0.64 mmol/L) or the 20% soybean protein concentrate (5.39±0.63 mmol/L). Increasing the proportion of dietary casein, soybean protein isolate, and soybean protein concentrate from 20% to 40% increase dthe plasma cholesterol concentrations, irrespective of the type of protein in the diet; however, the hamsters fed the 40% casein diets had higher plasma cholesterol concentrations (10.47±4.55 mmol/L) than those fed the 40% soybean protein isolate (7.12±0.88 mmol/L) and 40% soybean protein concentrate (6.34±0.74 mmol/L). Differences in plasma cholesterol levels between the various groups were reflected in differences in very low density and low density lipoprotein (VLDL+LDL) cholesterol levels, and there were no significant differences between the high density lipoprotein (HDL) cholesterol concentrations. Thus, the results of these studies (a) confirm the differential cholesterolemic effect of dietary casein and soybean protein in the hamster and show in addition (b) that increasing the proportion of protein in the diet increased the plasma cholesterol levels, irrespective of the type of protein.

Composition of plasma and nascent very low density lipoprotein from perfused livers of hypercholesterolemic squirrel monkeys

The composition of circulating very low density lipoprotein (VLDL) was compared with the composition and secretion of nascent VLDL from perfused livers of squirrel monkeys that were fed unsaturated or saturated fat diets to elicit different degrees of plasma hypercholesterolemia. All squirrel monkeys studied had cholesteryl ester-rich plasma VLDL, although greater enrichment occurred in hypercholesterolemic animals fed saturated fat. Livers from hypercholesterolemic animals were capable of secreting VLDL particles enriched in cholesteryl ester, suggesting hepatic origin for a portion of this circulating lipid moiety. Total VLDL lipid, but not protein output by perfused livers of hypercholesterolemic monkeys, was greater than that by livers from hypocholesterolemic animals. These results indicate that saturated fat-induced hypercholesterolemia is associated with changes in the composition of hepatic VLDL in the squirrel monkey.