Alteration of serum lipoprotein metabolism by polychlorinated biphenyls and methionine in rats fed a soybean protein diet

The effects of dietary supplementation of methionine to a 20% soybean protein isolate diet on serum lipoprotein profiles and secretion rate of VLDL in rats receiving polychlorinated biphenyls (PCB) were investigated. Serum cholesterol levels were higher in rats fed PCB or a methionine supplement than in controls. The effects of PCB and methionine were synergistic. The feeding of PCB resulted in more cholesterol in all fractions of serum lipoproteins tested, especially HDL (HDL1 and HDL2). Dietary supplementation of methionine primarily increased HDL cholesterol. The elevation of serum lipoprotein cholesterol due to PCB and/or methionine was significant in HDL1, which showed alpha-mobility. These results showed that methionine and PCB significantly influenced HDL metabolism. The secretion rate of VLDL was higher in rats fed PCB than in controls, but the addition of methionine to diets did not affect the secretion rate of VLDL cholesterol. This implies that PCB increased serum cholesterol partly through the stimulation of VLDL cholesterol secretion.     

The effect of dietary fat saturation on plasma and hepatic lipoproteins in the rat

Semipurified diets containing 10% kilocalories from either safflower oil (SO), corn oil (CO), olive oil (OO) or palm oil (PO) were fed to weanling male rats for 2 weeks. The effects of dietary fat saturation on plasma lipids and lipoproteins were: 1) Nonfasted plasma cholesterol concentration was higher in rats fed OO (mean +/- SEM = 81.0 +/- 2.9 mg/dl) vs. CO (67.5 +/- 2.9); 2) plasma chylomicron cholesterol concentration was higher in rats fed OO vs. SO and CO, with PO values in between; and 3) the cholesterol concentration of plasma very low density lipoprotein (VLDL), low density lipoprotein (LDL) and high density lipoprotein (HDL) did not differ among groups. The effects of dietary fat saturation on hepatic lipoproteins (determined by liver perfusion techniques) were: 1) hepatic higher density lipoprotein (d = 1.006-1.21 g/ml) cholesterol production was greater in rats fed SO and CO vs. PO [19.1 +/- 1.2, 17.2 +/- 0.8 and 13.7 +/- 1.6 micrograms/(g liver X 1.5 hour), respectively]; 2) there was no difference in hepatic VLDL cholesterol production among groups; and 3) the ratio of cholesterol to protein of hepatic VLDL and the higher density lipoprotein fraction was higher in rats fed diets rich in polyunsaturated fatty acids versus saturated fatty acids. Dietary fat saturation had no effect on carcass and liver cholesterol concentrations. Since differences in hepatic lipoprotein production were not reflected in plasma lipoprotein patterns, these results suggest that extrahepatic lipoprotein metabolism differs in rats fed diets containing fatty acids of varying saturation.     

ApoE distribution among lipoproteins of rhesus monkeys is modulated by dietary fat and cholesterol

The effect of dietary saturated fat and cholesterol on plasma cholesterol and apolipoprotein E (apoE) distribution among lipoproteins was studied in rhesus monkeys. Two groups of four monkeys had been fed diets containing 31% energy as either corn oil or coconut oil for 5 yr from birth. Each group was then fed short-term their respective diet with a 0.2% cholesterol supplement, the opposite fat without cholesterol, the opposite fat +0.2% cholesterol, followed by their original fat without cholesterol for 5 to 8 wk periods. Plasma was assayed for total cholesterol, total triglyclerides, and the distribution of apoE within lipoproteins (VLDL, IDL, LDL, HDL) separated by gradient-density electrophoresis. When coconut oil was fed, plasma cholesterol and triglyceride concentrations were 134% and 157%, respectively, of the levels when corn oil was fed. Cholesterol supplementation of corn oil also elevated the plasma cholesterol (141%), whereas cholesterol supplementation of coconut oil appeared to induce a synergistic increase (198%). Both groups of monkeys responded similarly to a given diet. The distribution of apoE in lipoproteins differed according to dietary treatment, with cholesterol feeding causing a major shift from HDL to IDL, whereas coconut oil caused a modest shift from HDL to VLDL. The relative amount of apoE in LDL was unchanged by diet. We conclude that dietary saturated fat or cholesterol can modulate the apoE distribution within lipoproteins in rhesus monkeys in conjunction with the previously noted expansion of the cholesteryl ester pool in VLDL and IDL.     

Lipoprotein lipases, lipoproteins and tissue lipids in rats fed fish oil or coconut oil

The effect of fish oil and coconut oil on plasma lipoproteins and lipoprotein-catabolizing enzymes [lipoprotein lipase (LPL) and hepatic endothelial lipase (HL)] was studied in rats. Male rats were fed for 4 wk purified diets containing equienergetic, amounts of either coconut oil (group A), coconut oil:fish oil, 50:50 (group B) or fish oil (group C). Whole plasma triacylglycerol, cholesterol and phospholipid concentrations were appreciably lower in group C than in group A, mainly due to a fall in very low density lipoprotein (VLDL) and subgroup 2 of high density lipoprotein (HDL2), with less consistent changes in LDL and HDL3. VLDL components of group B were also considerably lower than corresponding ones in group A. LPL and HL activities were about 50% lower in groups B and C than in group A. Increased hepatic triacylglycerol and cholesterol concentrations were observed in groups B and C. It is suggested that the decrease in LPL and HL activity of fish oil-fed rats may be an adaptive response to the low concentration of the substrate (triacylglycerols) for these enzymes.     

The contrasting effect of dietary phosphatidylethanolamine and phosphatidylcholine on serum lipoproteins and liver lipids in rats

The effect of dietary phosphatidylethanolamine (PE) and phosphatidylcholine (PC) added to cholesterol-free semipurified diet on serum lipoprotein and hepatic and fecal lipids was compared to the effect on rats fed soybean oil (controls). The dietary PE, but not PC, caused a decrease in serum cholesterol, phospholipid, apolipoprotein A-I (apoA-I) and apoE and an increase in high molecular weight apoB. The simultaneous addition of PC and ethanolamine also decreased serum apoA-I and cholesterol. The distribution patterns of phospholipid subclasses in the liver and fatty acid composition of hepatic and plasma phospholipids were also altered by dietary PE. Both PE and PC increased to a similar extent the excretion of fecal neutral steroids and hepatic 3-hydroxy-3-methylglutaryl-coenzyme A reductase activity compared to the controls. The present study, therefore, demonstrated for the first time that the PE in the soybean phospholipid preparation is responsible for the alterations of profiles of serum lipids and apoproteins in rats.     

Rapid induction of essential fatty acid deficiency by intragastric infusion of triolein-supplemented total parenteral nutrition solutions: evidence of increased hepatic cholesterol esterification in the rat

Rats were fed linoleic acid from a safflower oil emulsion or triolein-supplemented total parenteral nutrition solutions by continuous intragastric infusion for 7 and 14 d. Biochemical signs of essential fatty acid deficiency (EFAD) developed in rats supplemented with triolein compared with those receiving linoleic acid, and the relationship between hepatic cholesterol esterification and the distribution of free cholesterol in plasma lipoproteins was investigated in the EFAD and control animals. Results indicate that hepatic triglyceride (TG) and cholesterol ester content are greater and plasma levels of TG and cholesterol are lower in triolein-supplemented groups. Hepatic accumulation of cholesterol esters is associated with an increase in hepatic acyl-CoA:cholesterol acyltransferase activity and also with plasma very low density lipoprotein (VLDL) and high-density lipoprotein (HDL), which contain a greater proportion of cholesterol esters. These data suggest that EFAD can be rapidly induced with continuous intragastric feeding and that hepatic accumulation of cholesterol esters and enrichment of VLDL and HDL with cholesterol esters are early indicators of EFAD in the rat.     

大豆蛋白对大鼠血浆胆固醇影响及作用机制

目的探讨膳食大豆蛋白对高胆固醇模型大鼠血浆胆固醇及其相关血脂指标的影响及可能的作用机制。方法4周龄断乳雄性Wistar大鼠，诱导高胆固醇模型28d后，按体重和血浆总胆固醇浓度均衡分为2组，分别喂饲含酪蛋白和大豆蛋白的纯合成高脂饲料56d。结果酪蛋白组和大豆蛋白组大鼠TC、甘油三酯（TG）、载脂蛋白B（apoB）含量显著降低，粪胆汁酸排泄量增高。但对高密度脂蛋白胆固醇（鼢L—C），载脂蛋白AⅠ（apoA—Ⅰ）zk平无影响；同时可见，大豆蛋白可以增强大鼠肝脏3-羟基-3-甲酰基CoA（HMG—CoA）还原酶及低密度脂蛋白受体（LDL—R）基因的表达。结论大豆蛋白可通过影响apoB、HMG—CoA还原酶及LDL—R基因的表达来改变血浆胆固醇水平，其作用机制还需进一步探讨。     

酸化豆粉对大鼠降血脂和抗氧化作用的影响

目的研究酸化豆粉对大鼠降血脂和抗氧化作用的影响。方法将SD雄性大鼠根据体重和血胆固醇水平分为3组,普通饲料对照组、高脂饲料组及10%酸化豆粉组,饲养6周后,测定大鼠空腹血脂、载脂蛋白及抗氧化指标水平的变化。结果酸化豆粉可显著降低大鼠血清低密度脂蛋白胆固醇、总胆固醇、甘油三脂及血清载脂蛋白B浓度,增高高密度脂蛋白胆固醇及血清载脂蛋白A水平,同时增高载脂蛋白A/载脂蛋白B比值;酸化豆粉组大鼠血清超氧化物歧化酶、谷胱甘肽过氧化物酶及血清硒水平显著升高,脂质过氧化产物水平显著降低。结论酸化豆粉预防大鼠高血脂及抗氧化作用明显,提示酸化豆粉有成为心血管保健食品的潜力和意义。     

Dietary grape seed tannins affect lipoproteins, lipoprotein lipases and tissue lipids in rats fed hypercholesterolemic diets

The effects of monomeric and polymeric grape seed tannins on rat plasma lipoproteins, lipoprotein lipase, hepatic lipase and aortic and hepatic lipid concentration were studied. Male Sprague-Dawley rats received either a normal diet (with no added cholesterol and no tannins), a control diet (hypercholesterolemic diet) or hypercholesterolemic diets supplemented with 2% tannin monomers or 2% polymers 3 or 9 wk. Plasma total cholesterol, triacylglycerol, LDL cholesterol and VLDL concentrations were significantly higher and the HDL cholesterol concentration lower in controls and in rats fed the diet supplemented with monomers compared with rats fed polymeric tannins at both time points. Lipoprotein lipase and hepatic lipase activities were significantly higher in control and in monomer-fed groups than in the polymer-fed group. Hepatic and aortic cholesterol and triacylglycerol concentrations were significantly higher in control rats and those fed monomers than in the polymer-fed group. Moreover, plasma HDL cholesterol and hepatic lipase activity were closely associated with low aortic cholesterol and triacylglycerol in rats fed polymeric tannins. These rats also exhibited greater fecal excretion of cholesterol and especially bile acids than the control or monomer-fed groups. Thus dietary grape seed tannins have a pronounced anti-hypercholesterolemic effect by enhancing reverse cholesterol transport and also by reducing intestinal cholesterol absorption and increasing bile acid excretion.     

Effects of diets rich in fermentable carbohydrates on plasma lipoprotein levels and on lipoprotein catabolism in rats

This study was conducted to examine the effects of a combination of several dietary fibers (5% guar gum, 5% apple pectin, 15% wheat bran, 22% soybean fiber) and crude potato starch (23%) on plasma lipids and lipoproteins and on liver lipid concentration in rats fed a diet containing either 15% lard or 5% oil with or without dietary cholesterol/cholic acid. Male Wistar rats ate the test diets for 3 wk. The incorporation of fiber and crude potato starch into the diet resulted in a significant enlargement of the cecum; it also increased the concentration of volatile fatty acids and the pool of acetate, propionate and butyrate. Feeding this fermentable carbohydrate decreased plasma cholesterol and triglyceride levels in rats given a low fat diet and prevented the expected rise in plasma cholesterol and triglycerides in rats fed cholesterol/cholic acid or lard. Further studies of high density lipoprotein (HDL) composition, 3-hydroxy-3-methyl-glutaryl coenzyme A reductase (HMG-CoA reductase) activity and 125I-labeled human low density lipoprotein (LDL) turnover were done in the group fed the low fat diet without added cholesterol/cholic acid. The study of the HDL fraction in rats fed a diet rich in fermentable carbohydrates demonstrated a decrease in the HDL1 subpopulation and in the proportion of apolipoprotein E. Plasma clearance of intravenously injected 125I-labeled LDL was faster in rats fed this diet than in rats fed the fiber-free diet. In the liver, cholesterol and triglyceride levels were depressed whereas the activity of HMG-CoA reductase was increased.(ABSTRACT TRUNCATED AT 250 WORDS)     

Changes in serum and lipoprotein fatty acids of growing rats fed protein-deficient diets with low or adequate linolenic acid concentrations.

The effects of a protein-deficient diet associated with sunflower oil [adequate in 18:2(n-6), poor in 18:3(n-3)] or soybean oil [adequate in both 18:2(n-6) and 18:3(n-3)] on lipid serum and lipoprotein compositions were studied in growing rats. Four groups of rats were fed different diets: SFC (20% casein + 5% sunflower oil); SFd (2% casein + 5% sunflower oil); SC (20% casein + 5% soybean oil); Sd (2% casein + 5% soybean oil). After 28 d, both protein-deficient groups exhibited low concentrations of protein, phospholipid, triacylglycerol and total cholesterol in serum and VLDL. Compared with rats fed 20% casein diets, those fed low protein diets had lower 18:2(n-6) and 20:4(n-6) in phospholipids of serum, VLDL and HDL2-3, and the 20:4(n-6)/18:2(n-6) ratio was twofold higher in triacylglycerols of serum and VLDL. In the SFd-fed group, 22:5(n-6) was higher than in the SFC-fed group for both triacylglycerols and phospholipids in overall lipoprotein fractions studied. In addition, the 20:3(n-9)/20:4(n-6) ratio was 0.1 in HDL2-3 phospholipids of the SFd-fed group. Sunflower oil-fed rats compared with soybean oil-fed rats had greater monounsaturated fatty acids and lower total (n-3) fatty acids in both triacylglycerols and phospholipids of serum, VLDL and HDL2-3, as well as lower total (n-6) fatty acids in serum and VLDL triacylglycerols. Apolipoproteins (apo) of VLDL were drastically depressed in rats fed protein-deficient diets, whereas apo-AI of HDL2-3 showed a particular resistance. Likewise, sunflower oil-fed rats had enhanced apo-B48 of VLDL and apo-C, apo-AII and apo-AIV of HDL2-3. The present findings show that some effects of protein malnutrition were enhanced by alpha-linolenic acid deficiency, in particular reduced (n-6) and (n-3) fatty acid bioavailability.     

Arterial deepvenous difference of lipoproteins in skeletal muscle of patients in postoperative state: effects of medium chain triglyceride emulsion

The effect of fat infusion with medium chain triglycerides (MCT) and long chain triglycerides (LCT) on serum lipoproteins before and after passage through the skeletal muscle was investigated with the forearm technic in eight patients after abdominal operation. All lipoprotein fractions were enriched with triglycerides and phospholipids from infused artificial fat particles with the consequence of significantly increased ratios of TG/PL and TG/apo B in VLDL, of TG/apo B in LDL and TG/apo A-I in HDL. Uptake and release of lipoprotein components by skeletal muscle are given by arterial-deepvenous differences considering the blood flow rates. The positive arterial-deepvenous difference of VLDL triglycerides after 4-hr infusion is interpreted as cleavage and uptake of infused MCT by the muscle. The release of LDL is more pronounced after the fat infusion than before, suggesting a degradation and enhanced catabolism of artificial fat particles. HDL release may be also a consequence of catabolism of artificial TG/PL-particles. These results indicate an uptake of MCT/LCT emulsion by the skeletal muscle.     

Plasma lipids, lipoproteins, and fecal excretion of neutral sterols and bile acids in rats fed various high fat diets or a low fat/high sucrose diet

The effect of feeding various diets on plasma lipids and lipoproteins and on fecal excretion of neutral sterols and bile acids was studied in rats fed for 7 wk diets containing 42% of energy as either coconut oil (CO), sunflower seed oil (SO), fish body oil (FBO), cod liver oil (CLO), or a low fat/high sucrose diet (SU). Triacylglycerols (TG) in whole plasma and VLDL + LDL were lower in rats fed high amounts of polyunsaturated fatty acids (PUFA) than in those fed the CO diet. Plasma HDL2 components in FBO and CLO groups were generally lower than in the other groups. Percentages of liver and heart linoleic and arachidonic acid were higher in the SO group, but lower in groups fed marine oils, than in the CO group. There was a high relative amount of eicosapentaenoic and docosahexaenoic acid in liver and heart of rats fed marine oils. Fecal excretion of bile acids was lower in the PUFA groups than in the CO group, whereas the sum of neutral sterols was similar in all groups. Plasma HDL2 (and VLDL + LDL) correlated positively, but HDL3 negatively, with fecal bile acid excretion. Accordingly, increased bile acid excretion does not seem to account for hypolipemia following intake of PUFA diets.     

Dietary fish protein modulates high density lipoprotein cholesterol and lipoprotein lipase activity in rabbits.

To explore the pathways by which fish protein feeding influences HDL metabolism, postheparin plasma lipoprotein lipase and hepatic triglyceride lipase activities were measured in rabbits fed fish protein or soybean protein combined with corn oil or coconut oil in a 2 x 2 factorial arrangement. In addition to greater serum total and LDL-cholesterol concentrations, the elevated HDL cholesterol concentration caused by feeding fish protein, compared with soybean protein, was accompanied by lower VLDL triglycerides and parallel higher lipoprotein lipase activity in fish protein-fed rabbits. These results suggest an enhanced assembly of circulating HDL through promoted lipoprotein lipase activity in rabbits fed fish protein. Moreover, dietary proteins and lipids interacted with one another to alter HDL triglycerides and liver cholesterol concentrations. Diet-induced changes in lipoprotein lipase activity were, however, not related to insulinemia, which was unaltered by purified diet feeding. The present results suggest that fish protein may affect HDL metabolism through the modulation of lipoprotein lipase activity in rabbits.     

单纯性肥胖症儿童血脂、载脂蛋白A1、B100的研究

通过对单纯性肥胖儿童血脂,载脂蛋白Ａ１,Ｂ１００的研究,以初步了解其脂质代谢紊乱的状况,并探讨其动脉粥样硬硬化危险性增加的可能机制。对筛选出的肥胖儿童及其正常儿童各４９名,测定其血清甘油三酯（ＴＧ）,总胆固醇（ＴＣ）,高密度脂蛋胆固醇（ＨＤＬ－ｃｈ）,低密度脂蛋白胆固醇（ＬＤＬ－ｃｈ）,极低密度脂蛋白胆固醇（ＶＬＤＬ－ｃｈ）,载脂蛋白Ａｌ（ａｐｏＡ１）;载脂蛋白Ｂ１００（ａｐｏＢ１００）。     

Dietary fatty acids and cholesterol differentially modulate HDL cholesterol metabolism in Golden-Syrian hamsters

Dietary fatty acids alter HDL cholesterol concentrations, presumably through mechanisms related to reverse cholesterol transport. The effect of dietary fats (coconut oil, butter, traditional stick margarine, soybean oil, canola oil) differing in fatty acid profile on this antiatherogenic process was assessed with respect to plasma lipids; exogenous and endogenous lecithin-cholesterol acyltransferase (LCAT), cholesterol ester transfer protein (CETP), phospholipid transfer protein (PLTP) activities; and LCAT, apolipoprotein (apo) A-I and scavenger receptor B class-1 (SR-B1) mRNA abundance. Golden-Syrian hamsters were fed a nonpurified (6.25 g/100 g fat) diet containing an additional 10 g/100 g experimental fat and 0.1 g/100 g cholesterol for 6 wk. Canola and soybean oils significantly lowered serum HDL cholesterol concentrations relative to butter. Canola oil, relative to butter, resulted in higher exogenous LCAT activity, and both soybean and canola oils significantly increased hepatic apo A-I and SR-B1 mRNA abundance. Butter, relative to margarine, coconut and soybean oils, significantly increased serum non-HDL cholesterol concentrations. Endogenous and exogenous LCAT, CETP, and PLTP activities did not differ in hamsters fed margarine or saturated fat diets, despite lower hepatic LCAT, apo A-I, and SR-B1 mRNA abundance, suggesting that changes in available substrate and/or modification to the LCAT protein may have been involved in lipoprotein changes. These results suggest that lower HDL cholesterol concentrations, as a result of canola and soybean oil feeding, may not be detrimental due to increases in components involved in the reverse cholesterol transport process in these hamsters and may retard the progression of atherosclerosis.     

Lipoprotein lipid and protein responses to dietary fat and diabetes in rats

Dietary and insulin-deficiency types of hyperlipidemia were compared in adult normal and streptozotocin-induced diabetic male breeder rats. High beef tallow, high corn oil or low fat diets (BT, CO and LF, respectively) were fed ad libitum for 2 months. Glucose and insulin were measured in plasma and total cholesterol, free cholesterol, cholesteryl ester, triglycerides and apoproteins in very low density, low density and high density lipoproteins (VLDL, LDL and HDL, respectively). Diet did not affect plasma glucose or insulin levels. LDL-triglycerides were higher in BT and diabetic than in CO and LF rats. HDL-free cholesterol levels were higher in CO- and LF-than in BT-fed rats. Diabetes resulted in a decrease in HDL-cholesterol. Diabetic animals had higher HDL-apoA-I (apolipoprotein A-I) levels than did CO- and LF- but not BT-fed rats. VLDL-triglycerides were higher in diabetic than in normal rats, with no dietary differences in normal rats. In LDL, apoB levels were lower and apoE levels were higher in LF-fed rats than in animals fed high fat diets. Diabetes resulted in an increase in LDL-apoB but a decrease in LDL-apoE. HDL-apoE levels were higher, although HDL-apoA-I levels were lower in LF than in high fat-fed rats. The results related to lipoprotein composition supported the hypothesis that excess intake of a diet high in saturated fat may contribute to a metabolic pattern that resembles that of a diabetic state.     

Hepatic steatosis and serum very low density lipoproteins during two types of protein malnutrition followed by balanced refeeding

The relation of serum very low density lipoproteins (VLDL) to hepatic steatosis was studied during protein malnutrition followed by refeeding of a balanced diet in growing rats. A control group was fed a balanced diet containing 15% casein for 42 days. Two depleted groups were fed low protein diets containing 2% casein (group C) or 5% gluten (group GI) (protein malnutrition phase) for 28 days and then were fed the balanced diet for 14 days (refeeding phase). The concentrations of phospholipids and proteins in both liver and serum VLDL were decreased during protein malnutrition, whereas triacylglycerols, unesterified cholesterol, and cholesteryl esters were higher in the liver and lower in the serum VLDL in the C and GI groups compared with the control group. There was a significant inverse relation between serum VLDL apolipoproteins and liver triacylglycerols on the one hand and between serum VLDL triacylglycerols and liver triacylglycerols on the other hand, in both depleted groups, although this relation was less important in the GI group. The major fatty acid levels of liver triacylglycerols were negatively correlated with those of serum VLDL during protein malnutrition. Our results show that in spite of a similar fatty acid intake, protein malnutrition involved an important decrease in essential fatty acids in VLDL triacylglycerols and phospholipids. Moreover, triacylglycerol accumulation was accompanied by increases in unesterfied cholesterol and cholesteryl esters in the liver of rats fed low protein diets, especially with 5% gluten. Hence, the hepatic steatosis was not entirely attributable to impaired transport of triacylglycerols by VLDL.     

Interrelationship of plasma triglycerides and HDL size and composition in rats fed different dietary saturated fats

We investigated the relative effects of different dietary saturated fats on the size distribution, apolipoprotein (apo) and chemical composition of HDL in fasted rats. Male Sprague-Dawley rats (174 +/- 2 g) were fed diets containing 0.035% cholesterol and 16% fat (wt/wt) from corn oil (CO diet) or from 2% CO plus 14% butterfat (BF diet), beef tallow (BT diet), palm oil (PO diet) or coconut oil (CN diet) for 6 wk. Apparent lipid digestibility was significantly lower with the PO and BT diets vs. the CO, BF and CN diets. Plasma total cholesterol levels were significantly higher in rats fed the PO and BT diets than in rats fed the BF and CN diets but were not different among the PO-, BT- and CO-fed groups. Nondenaturing gradient gel electrophoresis immunoblot analysis indicated that HDL apo A-I and E resided on particles with significantly smaller modal diameters in rats fed all saturated fats compared with those fed the CO diet. Chemical analyses indicated that HDL generally contained proportionately less protein and more triglyceride, free cholesterol and apo E with saturated fat feeding than with CO diet feeding. Significantly higher plasma and VLDL triglyceride levels were noted with ingestion of the BT, PO or CN diet than with the CO diet. Butterfat feeding resulted in lower plasma triglycerides and HDL-esterified cholesterol than did feeding the other saturated fats. Very low density lipoprotein triglyceride concentrations were inversely correlated with HDL modal diameter of apo E containing lipoproteins (P less than 0.005). These data provide further evidence of the interrelationship of triglyceride and HDL metabolism and suggest that mechanisms independent of cholesterol ester transfer protein may mediate this response in rats.     

Relative effects of dietary oleic- and linoleic-rich oils on plasma lipoprotein composition in rats

Plasma lipoprotein composition and hepatic lipid content were investigated in male Sprague-Dawley rats (104 +/- 2 g) fed diets containing 12% olive oil [OO, 70% 18:1(n-9)], 12% high oleic safflower oil [SO, 70% 18:(ln-9)] or 12% high linoleic safflower oil [SL, 73% 18:2(n-6)] for periods of up to 10 wk. Fasting plasma triglycerides were significantly higher after feeding oleic-rich diets than after feeding SL for 3, 5 and 6 wk. At 6 wk VLDL triglycerides were two- to threefold higher in rats fed OO or SO than in those fed SL, but by 10 wk both plasma and VLDL triglycerides were similar. A greater proportion of HDL2 (diameter 8.0-12.1 nm), a lower proportion of HDL1 (diameter 12.2-17.0 nm) and lower HDL apo E content occurred in rats fed OO and SO than in those fed SL at both 6 and 10 wk. LDL and HDL protein and cholesterol concentrations were not different with feeding SO or SL. After 10 wk of feeding the experimental diets, rats fed OO had significantly lower HDL protein, cholesterol and apo E concentrations and significantly higher hepatic triglyceride content compared to rats fed SO or SL, P less than 0.05. These data suggest that HDL and hepatic lipid content are determined by some property of the dietary oil other than its oleic acid content.