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.     

Exocrine pancreatic secretion is stimulated in piglets fed fish oil compared with those fed coconut oil or lard.

An experiment was conducted to study the effect of feeding diets containing fat sources with different fatty acid composition (fish oil, coconut oil or lard, 10 g/100 g diet) on exocrine pancreatic secretion in piglets after weaning. A total of 16 barrows were weaned at 4 wk of age; 3 d later, they were surgically fitted with a catheter in the pancreatic duct for continuous collection of pancreatic juice. Collections of pancreatic juice were made every other day starting 4 d postsurgically. Piglets fed the fish oil diet secreted a significantly greater volume of pancreatic juice than piglets fed the coconut oil or lard diets. The output [U/(h. kg(0.75))] of lipase was higher in piglets fed fish oil than in piglets fed lard or coconut oil. The output of colipase was greater in piglets fed fish oil and coconut oil than in those fed lard. The dietary treatments did not affect the output of carboxylester hydrolase. The output of trypsin was significantly lower in piglets fed lard than in piglets fed fish oil or coconut oil diets and the output of carboxypeptidase B was greater in those fed the fish oil diet. Protein, chymotrypsin, carboxypeptidase A, elastase and amylase outputs did not differ among the dietary treatment groups. The apparent digestibilities of nutrients and energy were measured in feces and did not differ among groups. Thus, the greater output of lipase in fish oil-fed piglets did not result in a greater digestibility of fat in this diet.     

Fetal growth and fetal lung phospholipid content in rats fed safflower oil, menhaden oil, or hydrogenated coconut oil

The objective was to determine if dietary fish oil decreased the degree of fatty acid saturation in rat lung phosphatidylcholine (PC). A diet containing 12% of its energy as fat was fed for 3 wk to growing male Sprague-Dawley rats (trial I) or to pregnant rats for days 8-21 of gestation (trial II). The dietary fat treatments in trial I were safflower oil (SO), menhaden oil (MO), or hydrogenated coconut oil (HCO) and in trial II were SO, MO, HCO, or SO-MO (75%:25%). Polyunsaturated fatty acids reduced (p less than 0.05) hepatic fatty acid synthetase (MO greater than SO) in growing rats but the dietary lipids had no effect on lung palmitate content. Maternal consumption of MO vs SO reduced (p less than 0.05) fetal body weight and lung weight but not lung:body wt ratio. Dietary MO and SO-MO increased (p less than 0.05) disaturated PC content of fetal lungs. The fetal lung data indicate that maternal ingestion of fish oil improve fetal lung maturation.     

Digestion of fat does not differ in growing pigs fed diets containing fish oil, rapeseed oil or coconut oil

We studied the digestion of fat and fatty acids in diets containing oils with different fatty acid composition. Four barrows (initial weight 35 kg) were fitted with a simple T-cannula at the terminal ileum. Three wheat starch and fish meal-based diets were formulated to contain either 150 g fish oil, rapeseed oil or coconut oil/kg. A basal diet, which did not contain oil, was also prepared. The diets were fed according to a 4 x 4 Latin square design. Each experimental period comprised 5 d adaptation to the diets, 3 d fecal collection and 2 d digesta collection. The apparent ileal and fecal digestibilities of fat were relatively high (88 - 93%). The ileal digestibilities of total, saturated and monounsaturated fatty acids did not differ among the diets. However, the digestibilities of polyunsaturated fatty acids (PUFA) in the fish and rapeseed oil diets were higher (P < 0.05) than in the coconut oil diet. The ileal digestibilities of 18:1, 18:2 and 18:3 in the rapeseed oil diet ranged from 94 to 97%. The ileal digestion of the unsaturated long-chain fatty acids 20:5(n-3) and 22:6(n-3) in the fish oil diet was nearly complete (97 - 98%). Apparent fecal digestibilities of saturated fatty acids (76 - 89%) were lower than apparent ileal digestibilities (89 - 94%). The digestibilities of fat and fatty acids were relatively high when pigs were fed diets containing fish oil, rapeseed oil or coconut oil. There were few differences in the digestibilities of saturated, monounsaturated and PUFA in the fish oil, rapeseed oil or coconut oil diets.     

Mammary tumor lipids and plasma lipoproteins in DMBA-intubated rats fed olive or safflower oils

The effects of feeding olive and safflower oils on lipid and fatty acid composition of mammary tumors, plasma lipids and lipoproteins, and the nuclear magnetic resonance (NMR) spectra of plasma were investigated in rats. 7-12-Dimethylbenz[a]anthracene (DMBA)- and placebo-intubated male Sprague-Dawley rats were fed 20% fat diets containing 18:2n-6 (wt/wt) from either high-linoleic safflower oil (SL, 14.6% 18:2n-6), high oleic safflower oil (SO, 3.4% 18:2n-6), olive oil (OO, 1.1% 18:2n-6), or olive oil supplemented with 18:2n-6 (OL, 3.4% 18:2n-6) for 16 weeks. Our result indicated that tumor composition of 18:1n-9 and 18:2n-6 reflected the diet, but tumor neutral lipid (NL) was more reflective of diet than was tumor phospholipid (PL). The 20:4n-6 content of tumor PL was constant in all of the dietary groups despite threefold higher levels of 18:2n-6 in tumor PL from animals fed SL than from those fed SO, OO, or OL diets. This suggests a possible feedback inhibition of delta 6-desaturase by the higher content of 18:2n-6 associated with SL feeding No diet effects were obtained for tumor total lipid, NL, PL, cholesterol, and triglyceride contents. Plasma lipoprotein changes were more reflective of diet than tumorigenesis except for apolipoprotein-E, which was lower, and for very low-density lipoprotein cholesterol and low-density lipo protein, which were higher in tumor-bearing rats. Plasma NMR analysis indicated no difference in the average line widths of the methyl and methylene resonances for tumor-bearing and nontumor-bearing rats fed any of the diets.     

Plasma lipids and lipoproteins in hypercholesterolemic men fed a lipid-lowering diet containing lean beef,lean fish,or poultry

BACKGROUND: To reach desirable lipid and lipoprotein concentrations, patients with hypercholesterolemia are often told to replace the consumption of beef with that of fish and poultry. OBJECTIVE: The objective of this study was to compare the effects on lipoprotein profiles in hypercholesterolemic men of the incorporation of lean beef, poultry (without skin), and lean fish into an American Heart Association diet with a high polyunsaturated-to-saturated fatty acid ratio and a high fiber content. DESIGN: Three groups of subjects each rotated in a crossover design through 3 experimental periods that lasted 26 d each. The diets were planned to provide 11 713 kJ/d, of which 18% came from protein, 53% from carbohydrate, and 30% from lipids (polyunsaturated-to-monounsaturated-to-saturated fatty acid ratio: 1.0:1.1:1.0); 268 mg cholesterol/d; and 29 g fiber/d. RESULTS: The lean beef, lean fish, and poultry diets reduced plasma total and LDL cholesterol by 5-9%, LDL apolipoprotein B by 16-19%, VLDL triacylglycerols by 22-31%, and the ratio of total cholesterol to HDL cholesterol by 6-11%; they also increased the ratio of LDL cholesterol to apolipoprotein B by 18-28%. No significant difference was found in these lipid variables between the 3 experimental diets. However, the lean fish diet increased HDL(2) cholesterol significantly more (P < 0.05) than did the lean beef diet and the ratio of HDL(2) to HDL(3) cholesterol significantly more (P < 0.05) than did the lean beef and poultry diets. CONCLUSION: The results indicate that an American Heart Association diet with a high polyunsaturated-to-saturated fatty acid ratio and high fiber content induced numerous favorable changes in coronary artery disease risk factors in hypercholesterolemic men, regardless of the protein source.     

Taurine prevents hypercholesterolemia in ovariectomized rats fed corn oil but not in those fed coconut oil

We studied whether the type of dietary fatty acid influences the preventive effect of taurine on the ovarian hormone deficiency-induced increase in plasma cholesterol concentration in 6-mo-old ovariectomized rats. Rats were fed one of the following four diets for 28 d: purified diets based on corn oil, which is rich in linoleic acid, with or with out taurine (50 g/kg) or purified diets based on coconut oil, which is rich in lauric and myristic acids, with or without taurine. Body mass gain, food intake, liver weight and plasma apolipoprotein (apo) A-I, apo B, LDL and VLDL concentrations were not affected by the diets. On the other hand, taurine lowered the plasma total cholesterol concentration (P < 0.02) in rats fed corn oil, but not in those fed coconut oil. In rats fed both types of oils, taurine increased the LDL receptor mRNA level (P < 0.01), hepatic cholesterol 7alpha-hydroxylase activity (P < 0.01) and fecal bile acid excretion (P < 0.01). Taurine increased the HMG-CoA reductase mRNA level (P < 0.02) in the liver of rats fed coconut oil, but not in those fed corn oil. Taurine increased liver total lipid (P < 0.05) and triglyceride (P < 0.05) concentrations in rats fed corn oil, but not in those fed coconut oil. These results indicate that the effect of taurine on ovarian hormone deficiency-induced changes in cholesterol metabolism is influenced by the type of dietary fatty acids.     

Lipid metabolism responses in rats fed beef tallow, native or randomized fish oil and native or randomized peanut oil

In experiments with male Wistar rats, we measured the effects of nonpurified diets containing 9.1% added fat (beef tallow, native or randomized fish oil, native or randomized peanut oil) on apparent digestibility of total fat and individual fatty acids. We also investigated the effects of the diets on plasma contents of triglyceride, cholesterolesters and free and total cholesterol as well as on the fatty acid profiles of plasma and liver phospholipids. Randomization of fish oil or peanut oil had no significant effect on any of the lipid measurements. Fat digestibility was significantly lower in the rats fed beef tallow. Apparent absorption of 18:1(n-9) and polyunsaturated fatty acids was not dependent on the fatty acid profile of the dietary fat. Apparent absorption of 16:1(n-7) and saturated fatty acids was generally highest in the rats fed fish oil. Intake of fish oil or peanut oil significantly decreased plasma triglyceride content. Intake of fish oil resulted in substantially decreased contents of total cholesterol and cholesterolesters in plasma, but intake of peanut oil did not. Efficiency of conversion of 18:2(n-6) into 20:4(n-6) was inhibited by long-chain (n-3) fatty acids.     

Beneficial effect of wheat germ on circulating lipoproteins and tissue lipids in rats fed a high fat, cholesterol-containing diet

Adult male rats were fed for 7 wk either a low fat diet (3% fat) or a high fat-cholesterol diet (20% fat, 0.5% cholesterol) containing 7% wheat germ or not. Body weights and food intakes were unchanged by adding wheat germ to the control low fat or high fat diets. Adding wheat germ to the high fat-cholesterol diet significantly increased high density lipoprotein (HDL) cholesterol and the HDL-serum cholesterol ratio and lowered the very low density lipoprotein (VLDL) triglycerides. Thus the lipoprotein pattern was comparable to that obtained with the low fat diet, but the VLDL lipid composition remained altered. At the same time, triglyceride and cholesterol accumulation in the liver and the triglyceride content in skin were significantly decreased. When wheat germ was added to the low fat diet, cholesterol and triglycerides were not significantly modified. No adaptative change in lipase and colipase contents was observed in the pancreas of rats fed the wheat germ-supplemented diets, whereas the high fat diet increased these values. The results show a beneficial effect of wheat germ added to a high fat-cholesterol diet on the lipid status of rats; the implicated mechanisms are yet to be elucidated.     

Effect of exercise on tissue lipids and serum lipoproteins of rats fed two levels of fat.

Adult rats were fed a low fat (4%) or a high fat (40%) diet, and groups of other rats selected for good running were fed these two diets and were treadmill exercised 5 days a week for 6 weeks. The serum triglycerides were significantly lower in exercised rats fed the low fat diet, but not in those fed the high fat diet, as compared with corresponding controls. The liver lipids were vastly elevated in sedentary rats fed the high fat diet as compared with those fed the low fat diet. An interesting effect of exercise was reflected by the near normal liver lipid levels in rats fed the high fat diet and exercised. However, in these animals, the muscle concentration of cholesterol was significantly higher than that in all other groups. The very low density lipoproteins tended to be lower while the low density lipoproteins tended to be greater in exercised as compared with sedentary rats. It was suggested that the decline in very low density lipoproteins was due to decreased synthesis resulting from adaptive changes in the exercised animal. It was further postulated that the increase in low density lipoproteins was possibly due to increased synthesis necessitated by the need to enhance the catabolism and excretion of cholesterol in exercised animals.     

Effect of pectin, wheat bran and cellulose on serum lipids and lipoproteins in rats fed on a low- or high-fat diet

1. Four groups of adult male Sprague-Dawley rats were fed for 6 weeks on a diet with a low-fat content (50 g/kg) and another four groups were given a diet rich in fat (250 g/kg) and cholesterol (12 g/kg). In both cases, the basal diets were either fibre-depleted or supplemented with cellulose (60 g/kg), wheat bran (100 g/kg) or low-methoxyl pectin (100 g/kg). 2. Low-methoxyl pectin displayed the most hypocholesterolaemic effect and decreased the cholesterol content of the very-low-density lipoproteins (VLDL) and low-density lipoproteins (LDL), when the low-fat diet was given. When rats were fed on the high-fat diet, pectin no longer had a hypocholesterolaemic effect but still decreased the VLDL-cholesterol content. Pectin lowered serum triglyceride and VLDL-triglyceride levels only when the low-fat diet was given. 3. Wheat bran exerted no hypocholesterolaemic effect in rats fed on the low- and high-fat diets, but decreased the cholesterol content of VLDL and lowered serum triglycerides and VLDL-triglycerides when the high-fat diet was given. 4. Purified cellulose had no significant effect on plasma lipids. 5. As shown by multivariance analysis, low-methoxyl pectin and wheat bran both beneficially modified the serum triglyceride and cholesterol variables except VLDL-triglycerides. However, the magnitude of the effect of each individual type of fibre was dependent on the fat and cholesterol content of the diet, suggesting the existence of different mechanisms of action.     

Blood lipids, lipoproteins, apoproteins, and uric acid in men fed diets containing fructose or high-amylose cornstarch

Ten hyperinsulinemic and 11 nonhyperinsulinemic men consumed for 5 wk each in a cross-over design a diet, similar to one currently consumed in the United States, with 20% of the kilocalories from either fructose or high-amylose cornstarch to determine the effects of the two diets on various blood metabolites considered to be risk factors associated with heart disease. In the hyperinsulinemic men the intake of fructose as compared with cornstarch significantly increased total triglycerides and their lipoprotein distribution; total and very-low-density lipoprotein cholesterol; apoproteins B-100, C-II, C-III; and uric acid. In the nonhyperinsulinemic men total triglycerides, total and low-density lipoprotein cholesterol and uric acid were significantly greater after the consumption of fructose than after cornstarch. The results indicate that in a diet high in saturated fatty acids and cholesterol, fructose increases the levels of risk factors associated with heart disease, especially in hyperinsulinemic men.     

橄榄油和鱼油对大鼠血脂和脂质过氧化的影响

为观察橄榄油和鱼油对大鼠血脂水平及脂质过氧化的影响 ,将 44只Wistar大鼠随机分成 4组 ,分别接受正常饲料、高脂饲料、高脂饲料加橄榄油灌胃 (4ml·kg- 1 ·d- 1 )和高脂饲料加鱼油灌胃 (4ml·kg- 1 ·d- 1 )处理。实验期 6周。结果显示 ,橄榄油和鱼油均能降低大鼠血清总胆固醇和甘油三酯水平 ,并且鱼油的效果较橄榄油好 ,鱼油能够显著提高高密度脂蛋白胆固醇 ;橄榄油和鱼油均可降低高脂饲料引起的肝 体比值增大 ,而且鱼油可以明显减少肾脏和睾丸周围脂肪。橄榄油组和鱼油组大鼠的血清丙二醛水平均明显下降 ;而且红细胞超氧化物歧化酶活性有所提高 ,表明橄榄油和鱼油对进食高脂饲料引起的体内过氧化物水平升高具有拮抗作用。结果提示橄榄油和鱼油对高血胆固醇、甘油三酯有降低作用 ,并能改善高脂所致体内过氧化状态异常 ,减轻对机体的过氧化损伤 ,鱼油的效果优于橄榄油     

Catabolism of newly formed triglyceride-rich lipoproteins and serum high density lipoproteins in rats fed soybean phospholipid and soybean oil

Previous research has shown that serum cholesterol and apolipoprotein (apo) A-I were lower and serum apoB was higher in rats fed soybean phospholipid (PL) than in rats fed soybean oil. Secretion of cholesterol and apoA-I, but not apoB, from the liver and intestine was lower in rats fed soybean PL. In the present study catabolism of newly formed triglyceride (TG)-rich lipoproteins, from the liver and intestine, and of serum high density lipoproteins (HDL) were compared in rats fed soybean PL and in rats fed soybean oil. The following results were seen: Feeding of soybean PL was related to more TG and less cholesterol in intestinal lymph chylomicrons (CM) and hepatic very low density lipoproteins (VLDL) than was feeding of soybean oil. A lesser amount of the TG, labeled with [3H]oleate in CM and hepatic VLDL, was incorporated into the adipose tissue and muscle in vivo. The clearance of CM-TG from plasma was higher, but that of VLDL-TG and apoB labeled with [3H]lysine was lower. The catabolism of 125I-labeled HDL from the plasma was lower while hepatic uptake of 125I-labeled HDL, in vivo and in vitro, was higher. These results indicate that soybean PL modifies the catabolism of the respective serum lipoproteins. Therefore, we suggest that changes in both the catabolism and secretion of lipoproteins are responsible for the altered serum lipid and apolipoprotein patterns found in rats fed soybean PL.     

Effect of thioacetamide and dexamethasone on serum lipids in rats fed on high-fat sunflower or olive oil diets.

We have previously reported that high-fat diets develop hepatic steatosis and, depending on the fat quality, affect serum lipid levels differently (J Nutr Sci Vitaminol, 1997, 43, 155-160). The aim of this work is to study the influence of high-fat diets (14% sunflower or olive oils) on serum lipids in a model of hepatic acute damage induced by thioacetamide, and their influence when dexamethasone is administered before thioacetamide injection. Serum lipids and hepatic collagen have been evaluated using biochemical methods, and the steatotic process by histological staining. The results showed that hepatic steatosis and fibrosis are developed either by high-fat diets or thioacetamide injection. Pretreatment with dexamethasone did not decrease the hepatic collagen content. Thioacetamide injection alone or pretreatment with dexamethasone produced increase in serum tryglicerides (TG), total cholesterol (TC) and LDL-C in both high-fat diet groups, and a HDL-C increase in the olive-oil group, even though the atherogenic indices (HDL/TC and HDL/TG) were different depending on the enriched diet. The administration of high-fat diets to study the influence of the fat quality on health and disease should be interpreted carefully due to the ability of the diets themselves to cause hepatic damage.     

Metabolic effects of coconut, safflower, or menhaden oil feeding in lean and obese Zucker rats.

The aim of the present investigation was to study the effects of fish oil feeding in obese Zucker rats to establish its suitability as an animal model of hyperlipidaemia, and to understand the possible mechanism of fish oil-induced perturbations in cell metabolism. Lean and obese Zucker rats were fed on diets containing 180 g coconut, safflower, or menhaden oil/kg for 10 weeks. Body-weights and food intakes of lean coconut (LC), safflower (LS), and menhaden (LM) groups were similar. Obese menhaden (OM) rats had lower food intakes and body-weights compared with obese coconut (OC) and obese safflower (OS) groups, but values for all obese rats were higher than those for lean rats. Liver weights were higher in obese compared with lean rats, but on a percentage body-weight basis menhaden oil rats had higher values within genotype. Serum cholesterol and triacylglycerol levels were lower in the OM group compared with the OC and OS groups, and in the LM group compared with the LC group. Glucose and insulin levels were highest in OS rats followed by OC and OM rats and then the lean rats. Serum triiodothyronine and thyroxine were lower in OM rats compared with OC and OS rats. Liver mitochondrial state 3 rates with glutamate-malate and succinate were lower; mitochondrial beta-oxidation was unaffected and peroxisomal beta-oxidation was higher in menhaden oil rats compared with both coconut and safflower oil rats. In general, consumption of menhaden oil lowered hepatic malic enzyme (EC 1.1.1.38, 1.1.1.40), glucose-6-phosphate dehydrogenase (EC 1.1.1.49) and glutathione peroxidase (EC 1.11.1.9) activities and elevated long-chain fatty acyl-CoA hydrolase (EC 3.1.2.2) activity when compared with the two other diets. It is concluded that obese Zucker rats do respond like human subjects to fish oil feeding but not to vegetable oils. The hypolipidaemic effect of fish oil appears to be mediated through a lowering of lipogenic enzymes, glucose-6-phosphate dehydrogenase and malic enzyme.     

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.