Dietary fat and cholesterol modulate the plasma lipoprotein distribution and production of pigment or cholesterol gallstones in hamsters.

To evaluate the impact of key dietary factors on plasma lipoproteins and gallstone induction, male Syrian hamsters were fed either cholesterol and fat-supplemented purified diets containing glucose or lactose, or cholesterol and fat-free diets with or without fiber, for 13 wk. Fat-supplemented hamsters were hyperlipidemic in comparison to those fed fat-free diets. The former group revealed a greatly expanded VLDL fraction, whereas a normal HDL2 pool predominated in the latter group. Plasma fatty acids indicated that hamsters fed the fat-free diet were essential fatty acid deficient whilst the hamsters fed the fat-supplemented diet were subnormal in essential fatty acids. Ninety-three percent of the hamsters fed the fat-supplemented diet had gallstones (mostly cholesterol), whereas 62% of hamsters fed the fat-free diet had gallstones (almost all pigmented). Lactose increased cecal weight and prevented pigment stone formation in the fat-supplemented hamsters, whereas adding fiber to the fat-free diet contributed essential fatty acids, eliminated cholesterol stones and enhanced pigment stone formation. Thus, diets containing casein, rice flour, glucose and fiber with minimal essential fatty acids but no cholesterol promoted pigment stones (associated with a normal lipoprotein profile); a low fat diet limited in essential fatty acids but containing cholesterol and lactose, promoted cholesterol gallstones (associated with an expanded VLDL pool).     

Dose-response relationships between dietary (n-3) fatty acids and plasma and tissue lipids, steroid excretion and urinary malondialdehyde in rats.

For a 28-d experimental period, rats were fed a nonpurified, cereal-based diet containing 9.1% supplemental beef tallow or fish oil or one of the following beef tallow:fish oil blends: 95:5; 90:10; 80:20 and 50:50. All diets provided between 21.3 and 22.7 g linoleic acid/kg. Higher fish oil intake was paralleled by elevated incorporation of long-chain (n-3) fatty acids in plasma total lipid, mainly at the expense of arachidonic acid. Significant inverse relationships were found between plasma total (n-3) fatty acid concentration and plasma triglyceride, cholesterol or free fatty acid concentrations. Fish oil intake did not lead to a shift of triglycerides or cholesterol from the plasma to the tissues (liver, heart, kidneys). Reduced plasma cholesterol concentrations in the fish oil-fed rats could not be explained by higher fecal excretion of neutral sterols and bile acids. In vivo lipid peroxidation, assessed by urinary malondialdehyde excretion, was enhanced when diets containing greater than 1.8% fish oil were fed.     

Effect of dietary lipid composition on rat liver microsomal phosphatidylcholine synthesis

Effects of dietary lipid on microsomal membrane fatty acid composition and phosphatidylcholine synthesis were examined with respect to the degree of saturation and chain length of dietary fatty acids. Diets containing 20% fat (wt/wt), primarily in the form of coconut oil, beef tallow, or soybean oil were fed to weanling rats for 28 d. All diets were adequate in essential fatty acids. Feeding the coconut oil diet, containing more than 50% saturated medium-chain fatty acids, increased the long-chain omega 3 fatty acid levels and altered the ratio of omega 6 to omega 3 fatty acids in membrane phosphatidylcholine and phosphatidylethanolamine compared to that in animals fed diets containing a saturated tallow or polyunsaturated soybean oil diet. Change in membrane fatty acid composition in response to the coconut oil diet was accompanied by decreased synthesis of phosphatidylcholine via the cytidine diphosphate choline (CDP-choline) pathway, and increased synthesis via the phosphatidylethanolamine methyltransferase (PEMT) pathway. An overall decrease in phosphatidylcholine production was reflected in a lower ratio of phosphatidylcholine to phosphatidylethanolamine in the membrane. Modulation of hepatic phosphatidylcholine synthesis during early growth thus appears to be in response to the ratio of long-chain omega 6 fatty acids to omega 3 fatty acids in membrane phospholipid rather than levels of specific fatty acids or the relative degree of saturation of fatty acids in the diet.     

Regulation of plasma and liver total cholesterol levels by dietary oleic acid in rats fed a high-cholesterol diet.

The effects of diets containing fats and oils or fatty acids on the lipid metabolism were investigated in male rats of the Wistar strain fed hypercholesterolemic diets, especially focusing our attention on the correlation between dietary oleic acid (OLE) contents and the levels of plasma and liver total cholesterol (T-CHOL) or the fatty acid profiles in plasma and liver CHOL-ester. In the rats fed the free (FR)-type fatty acids, the concentrations of plasma and liver T-CHOL were high and the amounts of neutral steroids excreted into the feces were low when compared with those of rats given the triacylglycerol (TG)-type fatty acids, showing that TG-type fatty acids suppress the intestinal CHOL absorption more than the FR-type fatty acids do. The concentrations of plasma T-CHOL were highest in rats fed the oleic acid (OLE)-rich diets, followed in order by rats supplied with the palmitic acid (PAL)-rich diets, the hydrogenated coconut oil (HCO) diet, and the linoleic acid (LIN)-rich diets; the lowest was in rats given tristearin (TSTE) and linseed oil (LIS) diets. A positive correlation was obtained between the dietary OLE contents and the levels of plasma and liver T-CHOL or OLE in the plasma and liver CHOL-ester, and an inverse correlation between dietary OLE contents and the amounts of excreted neutral steroids. These results suggest that the dietary OLE contents regulate the levels of plasma and liver T-CHOL in CHOL-loaded rats.     

Influence of dietary ascorbic acid on plasma lipid levels in the rainbow trout

Rainbow trout maintained on ascorbic acid deficient and three grades of ascorbic acid supplemented diets (160--1280 mg ascorbic acid pr kg feed) for a period of 53 weeks, were studied for effects on plasma lipid levels. Fish fed the diet with no ascorbic acid manifested lethargy, lordosis, scoliosis, internal hemorrhages and low body weight. With regard to blood properties, ascorbic acid deficient fish had low hematocrit and high plasma levels of triglycerides and cholesterol but low level of free fatty acids. Plasma level of free fatty acids was low also in fish fed the diet containing the highest amount of ascorbic acid.     

Effect of dietary n-3 fatty acids on weight gain and liver polar lipid fatty acid composition of fingerling channel catfish

A 10-wk experiment was conducted to determine the effect of supplementing a 5% tristearin basal diet with linoleic acid [18:2(n-6)], linolenic acid [18:3(n-3)], an n-3 highly unsaturated fatty acid (n-3 HUFA) mixture, cod liver oil, corn oil or linseed oil on growth and fatty acid composition of the liver polar lipid fraction of fingerling channel catfish (Ictalurus punctatus). The lowest weight gain was observed in fish fed the basal diet. Weight gain was improved by certain levels of supplemental n-3 fatty acids. Fish fed a diet containing 2% 18:3(n-3) grew at the same rate as fish fed a diet containing 2.5% cod liver oil plus 2.5% corn oil. The best growth rate was observed in fish fed diets containing either 5% cod liver oil or 5% linseed oil. Growth rate was depressed by supplementation with 4% 18:3(n-3) or 1.25% n-3 HUFA mix. No improvement in growth rate was observed with dietary 18:2(n-6). Dietary linolenate was converted to docosahexaenoic acid [22:6(n-3)]. The ratio of 20:3(n-9) to 22:6(n-3) of the fish showing good growth was less than 0.4. The data obtained in this experiment indicate that n-3 fatty acids are essential for channel catfish and that the 18:3(n-3) or n-3 HUFA dietary requirement is 1.0-2.0% or 0.5-0.75%, respectively.     

Dietary conjugated linoleic acids and lipid source alter fatty acid composition of juvenile yellow perch, Perca flavescens

A study was conducted to examine the effects of dietary conjugated linoleic acids (CLA; 0, 0.5 or 1.0 g/100 g total CLA) and lipid source (menhaden oil, soybean oil or a 1:1 mixture of menhaden:soybean oil) on growth rates and fatty acid composition of yellow perch. Dietary treatments were fed to apparent satiation to triplicate groups of fish initially weighing 37.9 g/fish. At the end of the 9-wk feeding trial, no significant differences were detected in weight gain or feed intake among fish fed any of the dietary treatments. Dietary CLA, lipid source and/or their interaction significantly affected feed efficiency, total liver lipid concentration, and muscle and liver fatty acid concentrations. Feed efficiency (g gain/g feed) was significantly lower in fish fed diets containing soybean oil (0.51) compared with fish fed menhaden oil (0.58) or menhaden:soybean oil (0.60). Liver total lipid concentrations were significantly reduced in fish fed 0.5 and 1.0 g/100 g CLA compared with fish fed the diets containing no CLA and in fish fed menhaden oil compared with those fed soybean oil or a 1:1 mixture of menhaden:soybean oil. Total CLA levels increased in both liver and muscle as dietary CLA concentration increased, irrespective of lipid source. However, total CLA concentrations were significantly lower in liver and muscle of fish fed soybean oil. Total muscle CLA concentrations were 0, 1.26 and 2.92 g/100 g fatty acids in fish fed diets containing menhaden oil and 0, 0.5 and 1.0 g/100 g CLA, respectively. Mono- and polyunsaturated fatty acid (PUFA) concentrations were significantly lower in muscle and liver of fish fed CLA compared with fish fed the diets containing no CLA. In contrast, liver concentrations of saturated fatty acids, 14:0, 16:0 and 18:0, were significantly higher in fish fed 1.0 g/100 g CLA.     

High propionic acid fermentations and mineral accumulation in the cecum of rats adapted to different levels of inulin

The digestive and metabolic effects of inulin (from chicory) were studied in rats adapted to semipurified diets containing 0, 5, 10 or 20% inulin (wt/wt). Moderate levels of inulin (5-10%) did not significantly affect food intake or body weight gain. Dietary inulin resulted in considerably greater cecal fermentation and a significantly greater intraluminal concentration of propionate (peaking at 58.4 mmol/L). A lower concentration of acetate (42.6 mmol/L) was observed in rats fed 20% inulin. Lactic fermentations were observed in rats fed the 10 or 20% inulin diets. The cecal pool of volatile fatty acids tended to reach a plateau in rats fed diets containing more than 10% inulin (up to 600-700 mumol), but volatile fatty acid absorption was a slightly hyperbolic function of the dietary inulin level. Butyrate absorption was proportionally lower than that of propionate. Inulin-containing diets induced an enlargement of the cecal pool of calcium, phosphate and (to a lesser extent) magnesium. There was also an enhanced absorption of these divalent cations. The cecal pool of bile acids was greater in rats fed inulin, and this oligosaccharide displayed a slight hypocholesterolemic effect, even in rats fed the 5% inulin diet. However, plasma triglycerides were depressed only in rats fed the 20% inulin diet. In conclusion, inulin seems very effective in promoting propionic fermentation and in enhancing the calcium content of the large intestine. However, high levels of inulin (greater than 10%) may affect growth in rats and lead to acidic (pH 5.65) cecal fermentation.     

Digestibility of cocoa butter and corn oil and their influence on fatty acid distribution in rats

The comparative bioavailability of cocoa butter (a predominantly saturated fat) and corn oil (a predominantly unsaturated fat) was determined in male Sprague-Dawley rats by analysis of total fecal lipids following ad libitum feeding of purified diets containing 5, 10 and 20% cocoa butter or corn oil for 2 wk. Fecal lipid elimination was significantly increased (P less than 0.05) in each cocoa butter group when compared with the corresponding corn oil group, resulting in lower digestibility coefficients for cocoa butter (59-72%) than for corn oil (93-97%). Body weight gain and food intake data were similar among all treatment groups. Fecal fatty acid profiles in rats fed corn oil diets consisted primarily of 27-34% palmitic acid (16:0), 22-32% stearic acid (18:0) and 25-37% oleic acid (18:1). Palmitic, oleic and linoleic acids were also the primary fatty acids stored in epididymal fat tissue from corn oil-fed rats. In contrast, fecal fatty acids in animals fed cocoa butter diets consisted of 31-37% palmitic acid and 58-64% stearic acid; oleic acid was the major fatty acid stored in epididymal fat tissue. These results indicate that the decreased digestibility of cocoa butter is largely a result of its fatty acid composition. This reduced bioavailability of cocoa butter may be at least partially responsible for its previously described neutral effect on serum cholesterol.     

Dietary (n-3) fatty acids affect rat heart, liver and aorta protective enzyme activities and lipid peroxidation

In a 16-wk study, weanling Wistar rats (32 males and 32 females) were fed a modified AIN-76 diet containing 20% fat with various (n-3) fatty acids. All dietary fats provided the same amount of saturates, monounsaturates, and total essential fatty acids [(n-6) + (n-3)]. The control diet contained lard/corn oil (L/CO). The other diets contained (n-3) fatty acids from linseed oil (LSO), from linseed oil + menhaden oil (LSO + MO) or from menhaden oil (MO). The (n-3) diets reduced total and HDL-cholesterol, particularly in rats fed the MO diet. Platelet thromboxane levels were equally depressed by the LSO and MO diets. Dietary (n-3) fatty acids significantly elevated docosahexaenoic acid in livers and hearts of male and female rats, with females reaching higher levels. This increase was accompanied by reduced arachidonic acid, except for hearts of females in which the major decrease was in linoleic acid. Overall, enzyme activities in the MO-fed group were decreased to the following levels (relative to the activity in the control group): heart Mn superoxide dismutase (SOD), 28%; liver CuZnSOD, 82%; aorta CuZnSOD, 32%. Greater reductions in these enzyme activities were seen in the female rats fed the MO diet compared with male rats. Lipid peroxidation, assessed by urinary, heart and liver thiobarbituric acid reactants, was increased by dietary (n-3) fatty acids (MO greater than LSO + MO greater than LSO greater than L/CO) and was higher in females than in males. These results indicate that enhanced lipid peroxidation occurs with the increased oxidative stress of elevated tissue (n-3) fatty acids accompanied by reduced SOD activity.     

合成油的营养评价 (一)合成油饲料对正常大鼠的生长、血脂水平、肝脂与体脂脂肪酸组成的影响

本文研究了由石油副产品尿素蜡中提炼出辛酸(8:0)和癸酸(10:0),酯化后作为日常食用油的可能性。 (1)用含12％不同油酯(合成油,豆汕,不同比例配合的合成油与豆油,和奇数碳脂肪酸的合成油等)的饲料,分别饲养断乳大鼠12周,每组16只大鼠,雌雄各半,观察其生长、脏体比、血脂与肝脂水平、肝脂与体脂的脂肪酸组成、和体脂碘价的改变。 (2)用12％合成油饲料喂养大鼠的12周内,动物生长良好,未见必需脂肪酸缺乏的典型症状。在饲养期的前8周内,各组动物的体重增长近似,在后4周内,凡掺有含偶数碳脂肪酸的合成油饲料组动物,其体重增加值皆显著较少。 (3)合成油饲料和豆油饲料比较,对大鼠血清胆固醇水平无影响,但显著使血清甘油三酯含量增高。 (4)合成油饲料不影响动物的体成分(水份、蛋白质、脂肪),其体脂含量较豆油饲料组的略低(0.05相似文献   

Dietary linoleic acid modulates liver plasma membrane unsaturated fatty acid composition,phosphatidylcholine and cholesterol content,as well as glucagon stimulated adenylate cyclase activity

Male Sprague-Dawley rats were fed diets containing 20% (w/w) fat in which linoleic acid was substituted for saturated fatty acids. High or low levels of dietary linoleic acid were fed for 24 days. Liver plasma membranes were isolated for analysis of lipid composition and glucagon stimulated adenylate cyclase activity. Dietary saturated fatty acid content did not affect the saturated fatty acid composition of membrane phospholipids. Increase in dietary linoleic acid increased content of linoleic acid homologues in phosphatidylcholine. Diets low in linoleic acid increased total phosphatidylcholine and cholesterol levels in the plasma membrane, increasing glucagon stimulated and fluoride stimulated adenylate cyclase activity. These observations imply that change in glucagon stimulated adenylate cyclase activity resulted from transitions in membrane phospholipid content of linoleic acid and its homologous fatty acids or from associated changes in membrane phospholipid class content.     

Effects of Japanese torreya (Torreya nucifera) seed oil on lipid metabolism in rats

OBJECTIVE: We investigated effects of Japanese torreya (Torreya nucifera) seed oil containing non-methylene-interrupted polyunsaturated fatty acid of all-cis-5,11,14-eicosatrienoic acid (sciadonic acid) on rat lipid metabolism. METHODS: Male Sprague-Dawley rats were fed the experimental diets based on AIN-93 containing 10% corn, soybean, or torreya oil for 4 wk. Blood and tissues were recovered from each rat, and concentrations of triacylglycerol, cholesterol, and phospholipid in plasma and liver were determined by enzymatic assays. Moreover, fatty acid composition was analyzed for triacylglycerol, cholesterol ester, and phospholipid isolated from plasma and liver lipids by gas liquid chromatography. RESULTS: Plasma triacylglycerol level in rats fed torreya oil was lower than that in rats fed corn or soybean oil, although there were no significant differences in plasma cholesterol and phospholipid levels in all rats. Liver triacylglycerol level was also lower in rats fed torreya oil, whereas liver cholesterol and phospholipid levers were same for all rats. omega-3 Polyunsaturated fatty acids such as 22:6 (omega-3) were lower in plasma and liver lipids of torreya and corn oil groups, whereas omega-6 polyunsaturated fatty acids such as 22:4 (omega-6) and 22:5 (omega-6) were higher. Considerable amounts of sciadonic acid were detected in cholesterol ester, triacylglycerol, and phospholipid in plasma and liver of rats fed torreya oil. CONCLUSION: These observations suggest that torreya seed oil can modify lipid metabolism, resulting in lower triacylglycerol levels in plasma and liver of rats.     

GROWTH AND CEREBRAL LIPID COMPOSITION DURING MATURATION OF RATS FED VARYING LEVELS OF LINOLEATE AND LINOLENATE

Rats were fed diets containing 3.0, 0.75 or 0.07 percent of the calories as essential fatty acids (EFA) for three generations. In general, growth and fatty acid composition were very similar at the two higher intakes of EFA. The pattern of linoleate series fatty acids in cerebral phosphatidylethanolamine was very similar with all three groups. The increase in linolenate series fatty acids depended on the level of dietary linolenate, was much slower and continued to increase with age.     

Influence of Dietary Fats Upon Systolic Blood Pressure in the Rat

Studies were performed to determine whether feeding diets with differing fatty acid content and composition had an influence on systolic blood pressure in the rat. Weanling male rats were fed standard laboratory chow (2.9% fat in total), or synthetic diets (10% fat in total) containing fish oil, butter, coconut oil or corn oil, for 5 weeks. Coconut oil and butter diets were rich in saturated fatty acids, whilst fish oil and corn oil were rich in the n-3 and n-6 unsaturated fatty acids respectively. Systolic blood pressure was measured using an indirect tail-cuff method at the end of the feeding period, and compared to a group of weanling rats.

Feeding the different diets did not alter the growth of the rats, so all animals were of similar weights at the time of blood pressure determination. Control (chow fed) animals, at nine weeks of age, had higher systolic blood pressures than the weanling, baseline control group. Fish oil fed rats had similar pressures to the chow fed rats. Corn oil fed rats had significantly lower systolic pressures than the controls. The rats fed the diets rich in saturated fatty acids (butter and coconut oil) had significantly higher blood pressures than all other groups. Systolic blood pressure was found to be significantly related to the dietary intakes of saturated and unsaturated fatty acids. The dietary intake of linoleic acid was significantly higher in corn oil fed rats than in other groups. Systolic blood pressure was inversely related to linoleic acid intake. Feeding a diet rich in saturated fatty acids significantly increases blood pressure in the rat. A high intake of n-6 fatty acids, and in particular linoleic acid, appears to have a hypotensive effect. Prenatal exposure of the rats to a maternal low protein diet, abolished the hypertensive effects of the coconut oil diet and the hypotensive effect of the corn oil diet upon young adult females. The intrauterine environment may, therefore, be an important determinant of the effects of these fatty acids on blood pressure in later life.     

Tissue distribution, uptake, and requirement for alpha-tocopherol of rainbow trout (Salmo gairdneri) fed diets with a minimal content of unsaturated fatty acids

The metabolism of and requirements for alpha-tocopherol in rainbow trout fed diets containing 1% linolenic acid as sole source of unsaturated fat and graded levels of tocopherol (0.06-10 mg/100 g) were examined. Fish grew 5-fold over a 16-week period. In liver, tocopherol was concentrated in mitochondria with little in cytosol. Orally administered [3H]-tocopherol was rapidly taken up by plasma and liver but uptake into erythrocytes and white muscle was much slower; in most tissues radioactivity reached a plateau after about 3 days but in red muscle radioactivity increased over a 10-day period. Activities of enzymes that prevent free radical initiated tissue damage did not change in tocopherol deficiency. Tocopherol-deficient trout had no gross or subcellular pathologies even though liver and muscle were severely depleted of the vitamin. Ascorbic acid-stimulated lipid peroxidation in liver organelles indicated a tocopherol requirement of 2-3 mg/100 g diet; the molar ratios of polyunsaturated fatty acids to tocopherol in livers of trout fed diets lacking or supplemented with tocopherol (100 mg/100 g) were 980 and 170, respectively.     

Differential effects of diets that provide different lipid sources on hepatic lipogenic activities in rats under ad libitum or restricted feeding

This work was designed to study the effect of different lipid sources on hepatic lipogenic enzyme activity in rats fed ad libitum or energy-controlled diets. Male Wistar rats were fed diets containing 40% of energy as fat (olive oil, sunflower oil, palm oil, or beef tallow) for 4 wk. In experiment 1 rats had free access to food, and in experiment 2 rats were fed a controlled amount of food. In both experiments, rats fed the olive oil diets had higher activities of glucose-6-phosphate dehydrogenase, malic enzyme, fatty acid synthase, and acetyl-CoA carboxylase (P < 0.05) than rats fed the other fats. It is unlikely that this effect could be attributed to the stimulation by insulin or triiodothyronine because serum values did not differ among the groups. Enzymatic activities were positively and significantly correlated with liver triacylglycerol content, but not with serum triacylglycerol levels. No interaction between lipid source and feeding protocol was found. Oleic acid and components in olive oil other than fatty acids, such as phytosterols, may account for the effects of dietary fat on lipogenic enzyme activity.     

Dietary long-chain polyunsaturated fatty acids from different sources affect fat and fatty acid excretions in rats.

Several sources of long-chain polyunsaturated fatty acids (LCP) have been evaluated for infant-formula supplementation. These sources differ in their chemical structure [triglyceride (TG) or phospholipid (PL)], arrangement of fatty acids on the TG or PL backbone, fatty acid composition and presence of other lipid components. All of these characteristics influence fat digestion, may affect fat and fatty acid absorption, and hence, LCP bioavailability and metabolism in infancy. The main objective of this work was to establish the influence of different dietary LCP sources on overall fat and LCP absorption in early life. We compared fat and fatty acid excretions at weaning in rats fed control diets or diets supplemented with LCP as TG or PL. Two separate experiments were conducted. In Experiment 1, weanling rats were fed for 3 wk a control diet (C1), a diet with TG from tuna and fungal oils (TF-TG) or a diet with PL from pig brain concentrate (PB-PL). In Experiment 2, weanling rats were fed for 3 wk a control diet (C2), a diet containing egg-TG (EG-TG) or a diet containing egg-PL (EG-PL). Fat, mineral and saturated fatty acid excretions in feces were higher in rats fed PB-PL compared with those fed TF-TG diet. In Experiment 2, groups did not differ in fat and mineral excretions. However, the EG-PL group had lower fecal excretions of saturated fatty acids than the C2 and EG-TG groups. The 16:1(n-7), 18:1(n-9), 18:2(n-6) and 22:6(n-3) levels in feces were higher in the EG-TG group than in the EG-PL group. In summary, total fat and LCP excretions differed among rats fed diets supplemented with LCP from different sources.