Growth and lipid metabolism responses in rats fed different dietary fat sources

An experiment with male albino rats was conducted to examine the effect of dietary fat sources on growth performance and apparent digestibility of total fat and fatty acids. The effect on plasma and organ cholesterol concentrations as well as lipoproteins cholesterol and fatty acid profile of hepatic phospholipids was also examined. Forty 3 week old rats were fed purified diets containing 0.041% cholesterol and 7% fat (wt/wt) from soy oil (SO), or cow ghee (GH), or 25% fish oil (FO) plus soy oil (SF) or 25% fish oil plus 75% ghee (GF), or 50% soy oil plus 50% ghee (SG) for a period of 35 days. Final body weight, weight gain, organ weights and feed efficiency ratio showed no significant differences (P < 0.05) among the dietary treatments. The apparent digestibility of total dietary fat and saturated fatty acids in the animals fed diet containing cow ghee only or in combination with fish oil or soy oil was significantly lower than the other dietary groups. Consumption of ghee with combination of fish oil or soy oil lead to significant improvement in the fat apparent digestibility of dietary fat. Total cholesterol and triglyceride concentrations of plasma and organs as well as lipoprotein cholesterol levels were higher in animals fed diets containing ghee. For rats fed diet containing cow ghee in combination with fish oil or soy oil, the cholesterol content of total plasma, lipoprotein fractions (VLDL, LDL and HDL) and organs was decreased significantly. Furthermore, dietary fats altered the fatty acids composition of hepatic phospholipid fatty acids composition. Feeding dietary fish oil reduced arachidonic acid (20:4) and increased linoleic acid (18:2) and eicosapentaenoic acid (20:5) contents. The reduction in the arachidonic acid was being more pronounced in animals fed dietary ghee with combination of fish oil.     

Growth and lipid metabolism responses in rats fed different dietary fat sources

An experiment with male albino rats was conducted to examine the effect of dietary fat sources on growth performance and apparent digestibility of total fat and fatty acids. The effect on plasma and organ cholesterol concentrations as well as lipoproteins cholesterol and fatty acid profile of hepatic phospholipids was also examined. Forty 3 week old rats were fed purified diets containing 0.041% cholesterol and 7% fat (wt/wt) from soy oil (SO), or cow ghee (GH), or 25% fish oil (FO) plus soy oil (SF) or 25% fish oil plus 75% ghee (GF), or 50% soy oil plus 50% ghee (SG) for a period of 35 days. Final body weight, weight gain, organ weights and feed efficiency ratio showed no significant differences (P < 0.05) among the dietary treatments. The apparent digestibility of total dietary fat and saturated fatty acids in the animals fed diet containing cow ghee only or in combination with fish oil or soy oil was significantly lower than the other dietary groups. Consumption of ghee with combination of fish oil or soy oil lead to significant improvement in the fat apparent digestibility of dietary fat. Total cholesterol and triglyceride concentrations of plasma and organs as well as lipoprotein cholesterol levels were higher in animals fed diets containing ghee. For rats fed diet containing cow ghee in combination with fish oil or soy oil, the cholesterol content of total plasma, lipoprotein fractions (VLDL, LDL and HDL) and organs was decreased significantly. Furthermore, dietary fats altered the fatty acids composition of hepatic phosphlipid fatty acids composition. Feeding dietary fish oil reduced arachidonic acid (20:4) and increased linoleic acid (18:2) and eicosapentaenoic acid (20:5) contents. The reduction in the arachidonic acid was being more pronounced in animals fed dietary ghee with combination of fish oil.     

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   

Interrelated effects of the type of dietary fat and carbohydrate on cholesterol metabolism in rats

Rats were fed semipurified diets, differing in the amount of cholesterol and the sources of fat (corn oil or coconut fat) and carbohydrate (sucrose or starch). After 21 days dietary corn oil had induced higher serum cholesterol concentrations than did coconut fat, except for on diets with a high-cholesterol, high-sucrose background. On high-cholesterol diets containing coconut fat, dietary sucrose increased serum cholesterol, when compared with starch; with corn oil sucrose tended to lower serum cholesterol. Such a tendency was not seen on cholesterol-free diets. Cholesterol feeding caused a dramatic increase in liver cholesterol with all dietary carbohydrate-fat combinations. Liver cholesterol was higher in rats fed corn oil than in those fed coconut fat. The influence of the type of dietary carbohydrate on liver cholesterol was dependent on the type of fat and the amount of cholesterol in the diet. Thus effects of a single dietary component on serum and liver cholesterol in rats are strongly influenced by the background of the diet. This implies that published results of experiments on diet and cholesterol metabolism in rats cannot be compared readily.     

Linoleate enrichment of diet and prostaglandin metabolism in rats.

Evidence that biosynthesis of prostaglandins (PG) in tissues of animals deficient in essential fatty acids is dependent on the availability of their precursors has been demonstrated. The purpose of this study was to determine the following: (1) effects of dietary linoleate enrichment on PG biosynthesis in rats; (2) effects of exogenous PGE2 and dietary linoleate on plasma free fatty acids and serum cholesterol in fed and fasted rats. Rats were fed three different concentrations of dietary linoleate as beef tallow, hydrogenated vegetable fat, or corn oil. The concentrations of PGE1 and PGF2a measured by radioimmunoassay were higher in rats fed the fed the beef tallow diet independent of energy status. A decrease in the concentration of PG between fasted and fed rats receiving hydrogenated vegetable fat is discussed in respect to the possible influence of trans isomers of unsaturated fatty acids on the biosynthesis of PG. There were significant effects of fasting on serum cholesterol concentration regardless of diet and significant interactions among effects of PGE2, fasting, and diet, suggesting regulatory effects of PGE2 on serum cholesterol concentration. The increase in plasma free fatty acids associated with fasting was prevented by PGE2 for all diets, but had the most marked effect on rats fed hydrogenated vegetable fat.     

Regulation of hepatic microsomal cytochrome P450IIE1 level by dietary lipids and carbohydrates in rats

The present work tests the hypothesis that high fat/low carbohydrate diets elevate the level of liver microsomal cytochrome P450IIE1. Male Sprague-Dawley rats were fed liquid diets containing varied ratios of corn oil/carbohydrate for 4 d. Rats fed diets with higher fat/carbohydrate ratios produced higher serum acetone levels and higher hepatic microsomal P450IIE1 content and N-nitrosodimethylamine demethylase activity than those fed diets with lower fat/carbohydrate ratios. This dietary fat/carbohydrate effect on P450IIE1 also was observed with modified semipurified AIN-76A diets. In addition, both the quantity and the extent of unsaturation of dietary lipids affected P450IIE1 regulation. At moderate fat levels (5 and 20% diet), rats fed corn oil and menhaden oil diets produced higher P450IIE1 activity than those fed lard and olive oil diets. Rats fed a diet containing 20% corn oil or an amount of linoleic acid equivalent to the 20% corn oil diet showed twofold to threefold increases in the level of P450IIE1 over those fed a fat-free diet. Rats fed a 25% corn oil diet showed twofold higher enflurane metabolism in vivo than those fed a 0.5% corn oil diet. The present results suggest that the constitutive P450 enzyme level is regulated by dietary fat/carbohydrate ratios.     

Serum and liver lipids in rats and chicks fed with diets containing different oils

OBJECTIVES: Because dietary fat composition is determinant for serum cholesterol level, which is related to cardiovascular disease, we evaluated the effects of diets containing saturated (coconut oil) or polyunsaturated fatty acids (soybean oil) supplemented or not with dietary cholesterol on serum and liver lipid composition in two animal species. METHODS: Male Wistar rats (21 d old) were assigned to one of seven groups and fed with commercial diet or diets containing 5% or 20% soybean oil or 20% coconut oil with or without 1% cholesterol. Chicks were assigned to one of four groups and fed with diets containing 15% soybean oil or 15% coconut oil with or without 1% cholesterol. RESULTS: In rats, the accumulations of hepatic cholesterol and triacylglycerols were higher in the group fed 20% soybean oil and 1% cholesterol than in the group fed 20% coconut fat and 1% cholesterol. The highest serum levels of cholesterol and triacylglycerols were observed in the group fed coconut oil and cholesterol, compared with the group fed soybean oil and cholesterol. Triacylglycerol, high-density lipoprotein, and total cholesterol serum levels increased with diet containing coconut oil and cholesterol. In chicks, the highest hepatic cholesterol accumulation occurred in the group fed 15% coconut fat and 1% cholesterol. Total and high-density lipoprotein cholesterol levels increased with diet containing coconut oil and cholesterol, although none of these diets modified serum triacylglycerol levels. CONCLUSIONS: The type of experimental animal model and the diet composition influence lipid metabolism.     

Detrimental effects of a high fat diet in early renal injury are ameliorated by fish oil in Han:SPRD-cy rats

Dietary fish oils containing (n-3) fatty acids can modulate renal inflammatory injury. We previously demonstrated that a high fat (HF) diet worsens early renal disease progression in the Han:SPRD-cy rat model of polycystic kidney disease (PKD). Therefore, using HF (20 g/100 g diet) and low fat (LF; 5 g/100 g diet) diets, we compared the effects of menhaden oil (MO), soybean oil (SO) and cottonseed oil (CO) on renal function and histology in male Han:SPRD-cy rats fed the diets for 6 wk in the early stages of renal disease. Overall, rats fed HF compared with those fed LF diets had larger kidneys, more renal fibrosis and lower creatinine clearance (main effects of fat level).Rats fed MO rather than CO and SO diets had significantly lower kidney weights, kidney water content, cyst volumes and serum cholesterol and triglyceride concentrations (main effects of fat type). Rats fed MO diets also had less renal fibrosis than those fed CO diets, but the least fibrosis was in rats fed SO diets. Analysis of simple effects (due to interactions between fat level and type) revealed that HF diets increased renal inflammation in rats fed CO diets, but reduced inflammation was present in those fed SO and MO diets; HF diets also increased compared with LF diets serum urea nitrogen concentrations in rats fed the MO and CO diets, but not the SO diet. These results confirm that high dietary fat worsens early disease progression in this model of renal disease, and further demonstrate that diets with oils containing (n-3) fatty acids ameliorate some of the detrimental effects of a high fat diet.     

合成油的营养评价——(二)合成油饲料对实验性高胆固醇血症大鼠体重、血脂和肝脂成分的影响

在88g基础饲料中加入12g不同种类的油脂(合成油、猪油和豆油)和1％胆固醇喂养大鼠5周以诱导动物产生高脂血症,并以不加入胆固醇的豆油饲料作为正常对照。比较各组动物在实验期内的生长、血清脂质、肝脏脂质和某些内脏器官重量的改变。结果如下: (1)大鼠摄食含不同油脂的致高胆固醇血症饲料5周后,各组雄鼠的体重增加无明显的不同,雌鼠的体重增加则有显著的差别,即合成油组动物的增重显著较猪油组和对照组的为低。 (2)在各种油脂饲料中加入胆固醇都可使动物的肝重增大。猪油组和豆油组动物的肝脏有明显的脂肪肝病变。肝脂含量增加,肝胆固醇和甘油三酯大量积存(分别约为对照组的9-10倍和2-3倍)。而合成油组动物的肝脏外观表现正常,肝脂含量、肝胆固醇和甘油三酯水平则接近对照组的正常水平。 (3)在各种油脂饲料中加入胆固醇喂养大鼠,对雄鼠血清胆固醇水平的影响不明显,但引起雌鼠血清胆固醇的改变和对照组比较,猪油饲料使动物的血清胆固醇含量明显增高,豆 油和合成油饲料则可维持动物的血胆固醇含量于正常水平。血清甘油三酯水平则以合成油饲料组动物的为最高。 (4)在各种饲料中加入胆固醇除增大肝脏重量外,也使雌鼠的主动脉重量增高,但饲料油脂种类对其重量的影响不明显。 上述结果表明,当饲料中含有高水?     

Health benefits of dietary fat reduction by a novel fat replacer: Mimix

The primary goals of this study were to identify any health benefits of the replacement of dietary fat with a novel fat replacer, Mimix, and to assure that the consumption of this fat replacer did not convey any deleterious health effects. Male, weanling, Fischer 344 rats were fed one of six diets containing between 5 and 20% w/w as fat for 8 weeks. These diets included two high fat diets (safflower oil or lard), a low fat diet and three diets where 15% of the fat in the high fat diets was replaced with various amounts of Mimix. When animals were fed a diet rich in saturated fat they consumed significantly more energy than other diet groups. When 15% saturated fat (lard) was replaced with safflower oil animals adjusted their food intake so that no difference in energy intake was observed between the high safflower diet and the low fat and Mimix diets. When the various Mimix fat replacements were compared to animals fed a high fat lard diet there was incomplete compensation of energy intake. Animals fed the high fat lard diet also had higher glucose and total serum cholesterol than their low fat and fat replacement counterparts. Feeding a high fat safflower oil diet to rats resulted in a significantly lower total serum cholesterol and serum triglyceride than all other diets. Replacement of dietary fat with Mimix demonstrated no deleterious effects on the heart, liver and intestinal tract that were all of normal weight, morphology and colour compared to other diet groups. Body composition analysis demonstrated that animals fed high fat diets had higher body fat mass at the expense of lean body mass. This was most obvious for animals fed high fat lard diets who had heavier epididymal fat pads. These data demonstrate that the replacement of dietary fat with the novel fat replacer Mimix can convey a number of health benefits in the absence of any deleterious effects.     

Influence of dietary fats and vitamin e on plasma and hepatic vitamin a and β‐carotene levels in rats fed excess β‐carotene

Effects of different dietary lipids and excess vitamin E on plasma and hepatic concentrations of β‐carotene were evaluated in rats fed diets containing a large excess (0.2%) of β‐carotene. Male weanling Wistar Kyoto rats were fed β‐carotene‐supplemented diets containing various dietary lipids as follows: Group I, a saturated fat (coconut oil); Group II, a monounsaturated fat (olive oil); Group III, a polyunsaturated fat rich in ω‐6 fatty acids (safflower oil); Group IV, same as Group III plus vitamin E; and Group V, a polyunsaturated fat rich in ω‐3 fatty acids (menhaden oil). All diets contained 2% saf flower oil to provide sufficient amounts of linoleic acid (an essential fatty acid). Rats were killed after six weeks of feeding the various diets, and the concentrations of Q‐carotene and vitamin A were determined in plasma and liver. Plasma vitamin A levels were not altered by any of the dietary lipids or by an excess of vitamin E. The concentrations of β‐carotene in plasma were the lowest in rats fed the diet containing menhaden oil. The feeding of the diet containing an excess of vitamin E also resulted in a significant decrease in plasma β‐carotene concentration. Similarly, the hepatic β‐carotene concentration was also reduced to about one‐half in rats fed the diet containing an excess of vitamin E. Liver β‐carotene concentration was higher in Groups II and III than in the other three dietary groups. Hepatic vitamin A concentrations were also affected by the type of dietary fat. The highest levels were observed in rats fed the coconut oil diet; the lowest level of vitamin A was in rats fed menhaden oil (Group V). The results of this study suggest that the type of dietary fat and an excess of vitamin E can have a significant effect on 0‐carotene and vitamin A stores in liver and on β‐carotene content of plasma.     

Health benefits of dietary fat reduction by a novel fat replacer: Mimix

The primary goals of this study were to identify any health benefits of the replacement of dietary fat with a novel fat replacer, Mimix, and to assure that the consumption of this fat replacer did not convey any deleterious health effects. Male, weanling, Fischer 344 rats were fed one of six diets containing between 5 and 20% w/w as fat for 8 weeks. These diets included two high fat diets (safflower oil or lard), a low fat diet and three diets where 15% of the fat in the high fat diets was replaced with various amounts of Mimix. When animals were fed a diet rich in saturated fat they consumed significantly more energy than other diet groups. When 15% saturated fat (lard) was replaced with safflower oil animals adjusted their food intake so that no difference in energy intake was observed between the high safflower diet and the low fat and Mimix diets. When the various Mimix fat replacements were compared to animals fed a high fat lard diet there was incomplete compensation of energy intake. Animals fed the high fat lard diet also had higher glucose and total serum cholesterol than their low fat and fat replacement counterparts. Feeding a high fat safflower oil diet to rats resulted in a significantly lower total serum cholesterol and serum triglyceride than all other diets. Replacement of dietary fat with Mimix demonstrated no deleterious effects on the heart, liver and intestinal tract that were all of normal weight, morphology and colour compared to other diet groups. Body composition analysis demonstrated that animals fed high fat diets had higher body fat mass at the expense of lean body mass. This was most obvious for animals fed high fat lard diets who had heavier epididymal fat pads. These data demonstrate that the replacement of dietary fat with the novel fat replacer Mimix can convey a number of health benefits in the absence of any deleterious effects.     

Reversal of the arrhythmogenic effects of long-term saturated fatty acid intake by dietary n-3 and n-6 polyunsaturated fatty acids

This study investigated whether the adverse influences of dietary saturated animal fatty acids (SF) on vulnerability to cardiac arrhythmias in rats could be modified by crossover in maturity to diets rich in polyunsaturated fatty acids (PUFAs). The arrhythmia model was coronary artery occlusion and reperfusion under anesthesia. Animals were fed commercial stock diet (4% fat wt:wt) supplemented (12% wt:wt) with fat (final diets, 35% energy as fat). Of rats fed the SF diet for 9 and 18 mo, ventricular fibrillation (VF) occurred in 71% during occlusion and in 86% on reperfusion. Mortality from VF was 0% after 9 mo on the SF diet but 67% after 18 mo. Dietary crossover to n-3 (tuna-fish oil) or n-6 (sunflower-seed oil) PUFA-supplemented diets at 9 mo reduced arrhythmias (VF incidence less than 30% in occlusion and reperfusion) and mortality (0%). The n-3 PUFAs were most effective. Dietary interventions can be effective even when introduced in mature, high-risk animals and may be of benefit in reducing risk of sudden cardiac death.     

Effects of dietary trans-fatty acids on reproductive performance of Wistar rats

1. Wistar rats were fed for three successive generations on a semi-purified diet, in which the fat was provided by butter, sunflower oil, rapeseed oil or hydrogenated vegetable fat, differing in the content of cis,cis-18:2 and trans-18:1 fatty acids. Effects of these fats on the composition of adipose tissue and reproductive performance were studied. Fatty acids were analysed using high-performance liquid chromatography. 2. The fatty acid pattern of adipose tissue was closely related to dietary fat composition and, established in the first generation, did not change significantly in successive generations of rats. 3. Hydrogenated fat adversely affected litter size, sperm morphology and regularity of oestrous cycle, and prolonged the period of gestation in experimental animals. Differences observed between the generations were not significant. 4. Hydrogenated fat decreased the level of serum testosterone in males, but the differences observed in levels of serum progesterone in females were not apparently related to the dietary trans-fatty acids.     

Influence of dietary fats and vitamin E on plasma and hepatic vitamin A and beta-carotene levels in rats fed excess beta-carotene

Effects of different dietary lipids and excess vitamin E on plasma and hepatic concentrations of beta-carotene were evaluated in rats fed diets containing a large excess (0.2%) of beta-carotene. Male weanling Wistar Kyoto rats were fed beta-carotene-supplemented diets containing various dietary lipids as follows: Group I, a saturated fat (coconut oil); Group II, a monounsaturated fat (olive oil); Group III, a polyunsaturated fat rich in omega-6 fatty acids (safflower oil); Group IV, same as Group III plus vitamin E; and Group V, a polyunsaturated fat rich in omega-3 fatty acids (menhaden oil). All diets contained 2% safflower oil to provide sufficient amounts of linoleic acid (an essential fatty acid). Rats were killed after six weeks of feeding the various diets, and the concentrations of beta-carotene and vitamin A were determined in plasma and liver. Plasma vitamin A levels were not altered by any of the dietary lipids or by an excess of vitamin E. The concentrations of beta-carotene in plasma were the lowest in rats fed the diet containing menhaden oil. The feeding of the diet containing an excess of vitamin E also resulted in a significant decrease in plasma beta-carotene concentration. Similarly, the hepatic beta-carotene concentration was also reduced to about one-half in rats fed the diet containing an excess of vitamin E. Liver beta-carotene concentration was higher in Groups II and III than in the other three dietary groups. Hepatic vitamin A concentrations were also affected by the type of dietary fat.(ABSTRACT TRUNCATED AT 250 WORDS)     

Body fat accumulation is greater in rats fed a beef tallow diet than in rats fed a safflower or soybean oil diet

The effects of dietary fats , consisting of different fatty acids, on body fat accumulation and uncoupling protein (UCP) in interscapular brown adipose tissue were studied in rats. Metabolisable energy in experimental diets based on safflower oil, soybean oil or beef tallow was measured strictly (experiment 1). Male Wistar rats were then meal-fed an isoenergetic diet for 8 weeks (experiment 2). Each group of rats showed the same weight gain during the 8-week experimental period. Carcass fat content was greater in rats fed the beef tallow diet than in those fed the with the safflower or soybean oil diets, whereas the weight of abdominal adipose tissue was the same for all three dietary groups. Gene expression of UCP1 and the UCP content of the interscapular brown adipose tissue was lower in the beef tallow diet group than in the other dietary groups. A negative correlation was observed between carcass fat content and n-6 unsaturated fatty acid content in dietary fats. These results suggest that the greater body fat accumulation in rats fed the beef tallow diet results from lower expression of UCP1 mRNA and lower UCP content in brown adipose tissue. n-6 Polyunsaturated fatty acids may be the most effective fatty acids in limiting body fat.     

Dietary ratio of (n-6)/(n-3) polyunsaturated fatty acids alters the fatty acid composition of bone compartments and biomarkers of bone formation in rats

The effects of dietary polyunsaturated fatty acids (PUFA) on ex vivo bone prostaglandin E(2) (PGE(2)) production and bone formation rate were evaluated in rats. Weanling male Sprague-Dawley rats were fed AIN-93G diet containing 70 g/kg of added fat for 42 d. The dietary lipid treatments were formulated with safflower oil and menhaden oil to provide the following ratios of (n-6)/(n-3) fatty acids: 23.8 (SMI), 9.8 (SMII), 2.6 (SMIII), and 1.2 (SMIV). Ex vivo PGE(2) production in liver homogenates and bone organ cultures (right femur and tibia) were significantly lower in rats fed diets with a lower dietary ratio of (n-6)/(n-3) fatty acids than in those fed diets with a higher dietary ratio. Regression analysis revealed a significant positive correlation between bone PGE(2) and the ratio of arachidonic acid (AA)/eicosapentaenoic acid (EPA), but significant negative correlations between bone formation rate and either the ratio of AA/EPA or PGE(2) in bone. Activities of serum alkaline phosphatase isoenzymes, including the bone-specific isoenzyme (BALP), were greater in rats fed a diet high in (n-3) or a low ratio of (n-6)/(n-3), further supporting the positive action of (n-3) fatty acids on bone formation. These results demonstrated that the dietary ratio of (n-6)/(n-3) modulates bone PGE(2) production and the activity of serum BALP in growing rats.     

Consumption of a solid fat rich in lauric acid results in a more favorable serum lipid profile in healthy men and women than consumption of a solid fat rich in trans-fatty acids

Solid fats are used in food manufacturing to provide texture and firmness to foods. Such fats are rich in either saturated or trans-fatty acids, both of which increase the risk of coronary heart disease. Epidemiological and experimental studies suggest that trans-fatty acids increase risk more than do saturates because they lower serum high density lipoprotein (HDL) cholesterol. However, there appear to be differences between saturates in their effect on HDL cholesterol. We investigated whether the consumption of a solid fat rich in lauric acid (C12:0) would result in a more favorable blood lipid profile than the consumption of a solid fat rich in trans-fatty acids. We fed 32 healthy men and women two controlled diets in a 2 x 4-wk randomized crossover design. The diets consisted of a background diet supplemented with margarines. In the trans-diet, 9.2% of energy was provided by trans-fatty acids and 12.9% by saturated fatty acids. In the Sat-diet, energy intake was 0% from trans-fatty acids and 22.9% from saturated fatty acids. Lauric acid composed one third of all saturates in the Sat-diet. Serum HDL cholesterol was 0.36 mmol/L lower at the end of the trans-diet than at the end of the Sat-diet (95% confidence interval, -0.46 to -0.26), whereas serum low density lipoprotein cholesterol and triglyceride concentrations remained stable. Serum total cholesterol was 0.31 mmol/L (95% confidence interval, -0.48 to -0.14) lower at the end of the trans-diet than at the end of the Sat-diet. Consumption of a solid fat rich in lauric acid gives a more favorable serum lipoprotein pattern than consumption of partially hydrogenated soybean oil rich in trans-fatty acids. Thus, solid fats rich in lauric acids, such as tropical fats, appear to be preferable to trans-fats in food manufacturing, where hard fats are indispensable.     

Physiological response of mature rats to replacement of dietary fat with a fat substitute

The effects of replacing dietary fat with a fat substitute on food intake, body composition and lipid metabolism were examined in rats. Female Sprague-Dawley rats (250 g) were fed diets containing between 2 and 63% of energy as fat for 64 d. Inclusion of a substitute resulted in diets of different fat content but similar texture. When 10% corn oil (21% kJ-fat diet) was replaced with the substitute supplemented with linoleic acid (2% kJ-fat diet), rats increased food intake so that there was no effect on energy intake, body weight, body composition or serum lipid profile. Rats fed a diet containing 10% corn oil and 30% Crisco vegetable shortening (63% kJ-fat diet) became obese and hyperinsulinemic. When half (51% kJ-fat diet) or all (30% kJ-fat diet) of the Crisco was replaced with the fat substitute, the rats increased food intake and were fatter than controls but less obese than rats fed the 63% kJ-fat diet. Hepatic lipid oxidation and ketone synthesis were proportional to the percentage of dietary energy as fat. Adipocyte de novo lipid synthesis was inhibited by 51% kJ-fat and 63% kJ-fat diets. Partial or total replacement of Crisco prevented the hyperinsulinemia observed in 63% kJ-fat rats, suggesting a protective effect against the development of insulin resistance with diet-induced obesity.     

The influence of dietary medium and long chain triglycerides on growth performances and fat deposition in growing rats.

The present study was undertaken to investigate the effects of dietary medium and long chain triglycerides (MCT and LCT) on fat deposition and fatty acid composition of adipose tissues of rats. Twenty-seven Wistar strain male rats were divided into three groups and fed semisynthetic experimental diets: Basal (AIN 76), MCT (basal+C8:0 10%), LCT (basal+corn oil 10%). Feed intake was measured every day and body weight was measured once a week. At the beginning, 4th and 8th week of experimental feeding, 3, 12, 12 rats were slaughtered, respectively. Liver, perirenal and epididymal adipose tissue pads were weighted and their fatty acid composition was determined. Chemical composition of wholebody carcass was measured. Body weight gain was greater in rats fed the LCT diet than in rats fed the basal and MCT diets. Feed intakes were decreased in rats fed the MCT and LCT diets compared to that of the basal group. Subsequently, when compared to the basal group rats, feed efficiencies in rats fed the MCT and LCT diets were improved at the level of 6 and 14% for 4 weeks, and then 17 and 24% for 8 weeks, respectively. The weight of perirenal and epididymal adipose tissue pads tended to be larger in rats fed the MCT and LCT diets than in the basal group, although not significant. There were not significant differences in wholebody composition among the three groups. But it appeared that in rats fed the MCT diet, moisture content tended to be decreased and crude protein content increased compared to the LCT group rats. Fatty acid composition of the rats fed the LCT diet showed a good reflection of dietary fatty acid composition. Unlike LCT, little of medium chain fatty acid (MCFA) itself were incorporated into liver or adipose tissues. However, it seems that fat deposition of the MCT group was accomplished not by incorporation of dietary fatty acids but by de novo fatty acids synthesis.