Dietary effect of eicosapentaenoic acid (EPA) containing soyphospholipid

In this study, we evaluated on a comparative basis the dietary effect between eicosapentaenoic acid (C20:5, EPA)- containing soyphospholipid and soyphospholipid without EPA when added at 5% or 10% level by weight in soybean oil as the dietary oil on the proportions of lipid components in serum of rats. Rats were taken in five groups. One group was fed 20% soybean oil. Two groups received soybean oil containing 5% and 10% soyphospholipid by weight, respectively. Two other groups were fed soybean oil containing 5% and 10% EPA- containing soyphospholipid by weight, respectively. The other dietary components remained same for all the groups. The feeding experiment was conducted for 4 weeks. After the feeding period there was no significant change in weight gain, food intake and food efficiency ratio (FER). No significant change was observed in serum lipid profiles between the rats fed soybean oil and soybean oil with 5% or 10% soyphospholipid. There was significant decrease in serum triglyceride (TG) level in the rats fed soybean oil blended with EPA containing soyphospholipid at 5% level. The contents of total cholesterol (TC), TG, very low density lipoprotein (VLDL)-cholesterol and low density lipoprotein (LDL)-cholesterol decreased significantly while high density lipoprotein (HDL)-cholesterol increased compared to the soyphospholipid group at 10% level.     

Borage or primrose oil added to standardized diets are equivalent sources for γ-linolenic acid in rats

The aim of this study was to evaluate the effect of different doses and sources of dietary γ-linolenic acid (GLA) on the tissue phospholipid fatty acid composition. Rats fed four different levels of GLA (2.3, 4.6, 6.4 and 16.2 g of GLA/kg diet) in the form of either borage oil or evening primrose oil during 6 wk were compared with animals fed corn oil. The levels of dihomo-γ-linolenic acid (DHLA) and GLA showed a significant dose-related increase in liver, erythrocyte and aorta phospholipids. Moreover, the arachidonic acid/DHLA ratios in tissues decreased with increasing intake of dietary GLA. There was no significant difference in tissue GLA and DHLA levels within groups given equal amounts of dietary GLA either as borage oil or evening primrose oil. The amount of dietary GLA administered did not significantly influence prostaglandin E₂ production in stimulated aortic rings and thromboxane B₂ levels in serum; however, an increase in prostaglandin E₁ derived from DHLA was observed in the supernatants of stimulated aorta.     

Effect of dietary fats on some membrane-bound enzyme activities,membrane lipid composition and fatty acid profiles of rat heart sarcolemma

The effect of various dietary fats on membrane lipid composition, fatty acid profiles and membrane-bound enzyme activities of rat cardiac sarcolemma was assessed. Four groups of male weanling Charles Foster Young rats were fed diets containing 20% of groundnut, coconut, safflower or mustard oil for 16 weeks. Cardiac sarcolemma was prepared from each group and the activities of Na⁺,K⁺-ATPase, 5′-nucleotidase, Ca²⁺-ATPase and acetylcholinesterase were examined. ATPase activities were similar in all groups except the one fed coconut oil, which had the highest activities. Acetylcholinesterase activity was also similar in all the groups, however, it was significantly higher in the group fed mustard oil. No significant changes were observed among the groups in 5′-nucleotidase activity, in the cholesterol-to-phospholipid molar ratio and in sialic acid content. The coconut, safflower and mustard oil diets significantly increased cholesterol and phospholipid contents and the lipid-to-protein ratio of cardiac sarcolemma as compared to feeding the groundnut oil diet. The fatty acid composition of membrane lipids was quite different among the various groups, reflecting the type of dietary fat given. The total unsaturated-to-saturated fatty acid ratio was not different among the various groups; however, the levels of some major fatty acids such as palmitic (16∶0), oleic (18∶1) and linoleic (18∶2) acids were significantly different. Cardiac sarcolemma of the group fed safflower oil had the highest polyunsaturated fatty acid content. The results suggest that dietary fats induce changes not only in the fatty acid composition of the component lipids but also in the activities of sarcolemmal enzymes involved in the regulation of cardiac function.     

Metabolism of erucic acid in perfused rat liver: Increased chain shortening after feeding partially hydrogenated marine oil and rapeseed oil

The metabolism of [14-¹⁴C] erucic acid was studied in perfused livers from rats fed on diets containing partially hydrogenated marine oil or rapeseed oil for three days or three weeks. Control rats were given groundnut oil. Chain-shortening of erucic acid, mainly to 18∶1, was found in all dietary groups. In the marine oil and rapeseed oil groups, the percentage of chain-shortened fatty acids in very low density lipoproteins-triacylglycerols (VLDL-TG) exported from the liver increased after prolonged feeding. A similar increase was found in liver TG only with partially hydrogenated marine oil. This oil, rich intrans fatty acids, thus seemed to be more effective in promoting chain-shortening. The fatty acid composition of the secreted and stored TG differed both with respect to total fatty acids and radioactively labeled fatty acids, indicating that at least 2 different pools of TG exist in the liver. The lack of lipidosis in livers from rats fed dietary oils rich in 22∶1 fatty acids is discussed in relation to these findings. In conclusion, a discussion is presented expressing the view that the reversal of the acute lipidosis in the hearts of rats fed rapeseed oil or partially hydrogenated marine oils is, to a large extent, derived from the increased chain-shortening capacity of erucic acid in liver.     

Enrichment of γ-linolenic acid from evening primrose oil and borage oilvia lipase-catalyzed hydrolysis

Lipase-catalyzed selective partial hydrolysis of evening primrose (Oenothera biennis L.) seed oil and borage (Borago officinalis L.) seed oil led to an increase in the level of γ-linolenic acid (GLA; 18∶3n−6) in the unhydrolyzed acylglycerols. Thus, in evening primrose oil, the GLA level could be raised from 9.4% in the starting material to 46.5% in the unhydrolyzed acylglycerols by means of a lipase fromCandida cylindracea. Selective hydrolysis of borage oil with Pancreatin led to an increase in the GLA content from 20.4% in the oil to 33.5% in the unhydrolyzed acylglycerols. Partial hydrolysis of borage oil with lipase fromC. cylindracea raised the GLA content of the acylglycerols to 47.8%.     

Comparative hypocholesterolemic effects of six dietary oils in cholesterol-fed rats after long-term feeding

Rats (8 wk of age) fed a conventional diet were shifted to diets containing 10% Oenothera biennis Linn oil (OBLO, linoleic acid +γ-linolenic acid) from a wild plant, evening primrose oil (EPO, linoleic acid +γ-linolenic acid) from a cultivated plant, bio-γ-linolenic acid oil from mold (BIO, palmitic acid+oleic acid+linoleic acid+γ-linolenic acid), safflower oil (linoleic acid), palm oil (PLO, palmitic acid+oleic acid+linoleic acid), or soybean oil (linoleic acid+α-linolenic acid) with 0.5% cholesterol for 13 wk. Though there were no significant differences in the food intake among the groups, the body weight gain of the OBLO group was significantly lower than that of other groups except for the BIO and PLO groups, and that of the EPO and SPO groups were the highest among the groups. The liver weight of the OBLO group was significantly lower than that of other groups, and that of the PLO group was the highest among the groups. The serum total cholesterol and very low density lipoprotein (VLDL)+intermediate density lipoprotein (IDL)+low density lipoprotein (LDL) cholesterol concentrations of the OBLO and EPO groups were consistently lower than those in the other groups. However, those of the BIO group were higher than those in the OBLO and EPO groups. The liver cholesterol concentration of the PLO group was the highest among all groups except for the EPO group. The fecal neutral sterol and bile acid extraction of the BIO group tended to increase compared to other groups. The results of this study demonstrate that OBLO and EPO inhibit the increasing of serum total cholesterol and VLDL+IDL+LDL-cholesterol concentrations in the presence of excess cholesterol in the diet compared with the other dietary oils.     

Effects of diets enriched in n−6 or n−3 fatty acids on cholesterol metabolism in older rats chronically fed a cholesterol-enriched diet

Hypocholesterolemic effects in older animals after long-term feeding are unknown. Therefore, aged rats (24 wk of age) fed a conventional diet were shifted to diets containing 10% perilla oil [PEO; oleic acid+linoleic acid+α-linolenic acid; n−6/n−3, 0.3; polyunsaturated fatty acid/saturated fatty acid (P/S), 9.6], borage oil [oleic acid+linoleic acid+α-linolenic acid; n−6/n−3, 15.1; P/S, 5.3], evening primrose oil (FPO; linoleic acid+γ-linolenic acid; P/S, 10.5), mixed oil (MIO; oleic acid+linoleic acid+γ-linolenic acid+α-linolenic acid; n−6/n−3, 1.7; P/S, 6.7), or palm oil (PLO; palmitic acid+oleic acid+linoleic acid; n−6/n−3, 25.3; P/S, 0.2) with 0.5% cholesterol for 15 wk in this experiment. There were no significant differences in the food intake and body weight gain among the groups. The liver weight in the PEO (n−6/n−3, 0.3) group was significantly higher than those of other groups in aged rats. The serum total cholesterol and very low density lipoprotein (VLDL) +intermediate density lipoprotein (IDL)+low density lipoprotein (LDL)-cholesterol concentrations of the PLO (25.3) group were consistently higher than those in the other groups. The serum high density lipoprotein cholesterol concentrations of the PEO (0.3) and EPO groups were significantly lower than in the other groups at the end of the 15-wk feeding period. The liver cholesterol concentration of the PLO (25.3) group was significantly higher than those of other groups. There were no significant differences in the hepatic LDL receptor mRNA level among the groups. Hepatic apolipoprotein (apo) B mRNA levels were not affected by the experimental conditions. The fecal neutral steroid excretion of the PLO (25.3) group tended to be low compared to the other groups. The results of this study demonstrate that both n\t-6 fatty acid and n\t-3 fatty acids such as \gg-linolenic acid and \ga-linolenic acid inhibit the increase of serum total cholesterol and VLDL+IDL+LDL-cholesterol concentrations of aged rats in the presence of excess cholesterol in the diet compared with dietary saturated fatty acid.     

Interaction between dietary protein and fat in triglyceride metabolism in the rat: Effects of soy protein and menhaden oil

The objective of the present study was to determine the mechanisms by which dietary proteins interact with dietary lipids in the regulation of triglyceridemia in rats. Male Sprague-Dawley rats (n=56) were subjected to 28-d experimental diets containing different combinations of proteins (20% w/w) and lipid sources (14% w/w): (i) casein-menhaden oil, (ii) casein-beef tallow, (iii) soy protein-menhaden oil, and (iv) soy protein-beef tallow. Significant protein-lipid interactions were observed on triglyceridemia and hepatic cholesterol in fasted rats. The combination of casein and beef tallow was associated with high plasma TG and hepatic cholesterol concentrations, which were reduced by substitution either of soy for casein or of menhaden oil for beef tallow. Therefore, triglyceridemia and liver cholesterol remained low with soy protein feeding, independently of the lipid source, as well as with menhaden oil feeding, regardless of the protein source. The menhaden oil diets reduced plasma cholesterol, hepatic TG, and TG secretion compared with beef tallow diets independently of the dietary protein source. Modifying the source of dietary proteins and lipids had no effect on post-heparin plasma lipoprotein lipase activity. These results demonstrate that soy protein can lower rat triglyceridemia relative to casein when associated with beef tallow consumption, whereas menhaden oil can attenuate hypertriglyceridemia when rats are fed casein. The data further suggest that part of the hypotriglyceridemic effect of soy protein in the rat may be mediated by reduced hepatic lipid synthesis, as is the case for menhaden oil.     

Gamma linolenic acid (GLA) content of encapsulated evening primrose oil products

The fatty acid composition of 16 brands of evening primrose oil (EPO) capsules was determined by capillary gas chromatography. Fourteen of these EPO brands contained γ-linolenic acid (GLA) levels between 7% and 10% (mean, 8.7; range, 1.9–10.5%) and there was generally good agreement between the level of GLA claimed by the manufacturer and the level determined by analysis. Low levels of the monoenes 22∶1 and 24∶1 found in some brands may indicate contamination of EPO with borage oil.     

Essential fatty acids alter the activity of manganese-superoxide dismutase in rat heart

The effects of oil-derived dietary essential fatty acids on the activities of mitchondrial Mn-SOD (manganese-superoxide dismutase) and cytosolic cupric zinc-superoxide dismutase (Cu/Zn-SOD) were investigated in rat heart. A control group of rats was fed a stock diet for 29 d, and a second group was fed on a fat-free diet. Three other groups were fed fat-free diets that were supplemented with (i) borage oil, which is rich in linoleic (18∶2n−6) and γ-linolenic (18∶3n−6) acids, (ii) fungal oil, which is rich in γ-linolenic, but low in linoleic acid, or (iii) evening primrose oil, which is rich in linoleic acid and low in γ-linolenic acid. An increase in the percentage composition of arachidonic acid (20∶4n−6) in both the choline and ethanolamine phospholipids, together with a decrease in linoleic acid in ethanolamine phospholipids, were found in heart membranes after feeding the rats with diets containing borage oil or fungal oil as compared to those fed the stock diet. The respective activities of Mn-SOD in rats fed the borage or fungal oil diets were also significantly higher than in rats fed the stock diet alone. No change in cytosolic Cn/Zn-SOD activity was observed. Dietary supply of linoleic acid-rich evening primrose oil resulted in an increased proportion of choline phospholipid linoleic acid without any changes in arachidonic acid content or in the activity of Mn-SOD. By contrast, a reduction in the activity of Mn-SOD was detected in rats fed a fat-free diet. These results show that the activity of heart mitochondrial Mn-SOD is influenced by dietary essential fatty acids, whereas the activity of cytosolic Cu/Zn-SOD remained unaffected.     

Purification of GLA-Triglycerides from Evening Primrose Oil by Gravimetric Column Chromatography

Gravimetric normal-phase silver ion–silica gel column chromatography has been used for the novel application of purification of GLA-containing triglycerides (GLA-TGs) from evening primrose seed oil (EPO). Gradient elution with increasing polarity enabled separation of valuable TG species containing γ-linolenic acid (GLA, 18:3n-6). Enzymatic hydrolysis revealed the distribution of fatty acids (FAs) in the isolated TG species, with GLA in the sn-2 position in different percentages, depending on the degree of unsaturation. A novelty of this work was the successful use of the procedure to improve the purification of raw GLA species from EPO up to preparative scale, thus enabling use of this methodology for industrial purposes.     

Interaction between dietary proteins and lipids in the regulation of serum and liver lipids in the rabbit. Effect of fish protein

Purified diets varying in dietary protein, namely casein (CA), soy protein (SP), fish protein (FP), and lipid origin (corn oil (CN), coconut oil (CO)) were fed to rabbits to evaluate the effects of protein and fat source, as well as protein-lipid interactions, on serum total, lipoprotein and hepatic lipid levels. Dietary proteins and lipids exerted a separate effect on serum total cholesterol (C), very low-density lipoprotein cholesterol (VLDL-C), and low-density lipoprotein cholesterol to high density lipoprotein cholesterol (LDL-C/HDL-C) ratio. Hence, CA increased serum cholesterol compared to SP, while coconut oil enhanced serum and VLDL-C, and decreased LDL-C/HDL-C compared to corn oil. Dietary proteins interacted with dietary lipids to modulate HDL-C levels. Thus, FP maintained a high level of HDL-C regardless of lipid origin, compared to CA and SP whose HDL-C levels were decreased by corn oil, compared to coconut oil. A dietary protein-lipid interaction was also observed in the regulation of liver cholesterol levels. Coconut oil, compared to corn oil, decreased liver cholesterol in rabbits fed FP, whereas hepatic cholesterol concentration was unaltered by dietary lipid source in CA- and SP-fed rabbits. These results demonstrate that dietary proteins act synergistically with dietary lipids to regulate cholesterol metabolism in the rabbit. This work was presented in part at the 74th Annual FASEB meeting held in Washington, D.C., April 1–5, 1990.     

Effect of Dietary Replacement of Soybean Oil with Different Sources of Gamma‐Linolenic Acid on Fatty Acid Composition of Nile Tilapia

Gamma‐linolenic acid (GLA) plays an important role in the prevention and/or treatment of certain diseases. In this work, we investigate the incorporation of GLA from supplemented feed diets with borage oil (BO) and evening primrose oil (EPO) as substitutes for soybean oil (SO) into the composition of tilapia fillet lipids. High contents of PUFA and n‐6 fatty acids were quantified in fish fillet after 30 days of treatment with SO, BO, and EPO. Feed diets containing BO and EPO were efficient in the incorporation of GLA into fish. Compared to the initial day of the experiment, the increase of GLA was significant (from 6.43 to 13.99 and 15.12 mg g^?1, in lipids of fish treated for 30 days with BO and EPO, respectively). The increase of GLA was also observed in fish which were fed with SO diet (6.43–11.43 mg g^?1). Principal component analysis (PCA) allowed the separation of the treatments and discriminated BO and EPO in a group of fish that received the GLA supplemented diet. In addition to GLA, n‐3 fatty acids were important in the characterization of SO diet and affected the separation of BO and EPO from SO in the PCA score plot.     

γ-Linolenic acid concentrates from borage and evening primrose oil fatty acidsvia lipase-catalyzed esterification

γ-Linolenic acid (GLA, all-cis 6,9,12-octadecatrienoic acid) has been enriched from fatty acids of borage (Borago officinalis L.) seed oil to 93% from the initial concentration of 20% by lipase-catalyzed selective esterification of the fatty acids withn-butanol in the presence ofn-hexane as solvent. The immobilized fungal lipase preparation, Lipozyme, used as biocatalyst, preferentially esterified palmitic, stearic, oleic and linoleic acids and discriminated against GLA, which was thus concentrated in the unesterified fatty acids fraction. In the absence of hexane, concentrate containing about 70% GLA was obtained. When the reaction conditions, optimized for borage oil fatty acids, were applied to fatty acids of evening primrose (Oenothera biennis L.) oil, concentrates containing 75% GLA were obtained. From both oils, GLA concentrates were prepared efficiently in short reaction times (1–3 h) at 30–60°C. The process can be applied for the production of GLA concentrates for dietetic purposes.     

Separate effects of dietary protein and fat on serum cholesterol levels: another view of amino acid content of proteins

Casein or soy protein with vegetable or animal fat were used to determine the dietary protein or fat effects and their possible interaction on serum cholesterol levels. Young, male New Zealand white rabbits with a mean weight of 2.1 kg were divided into groups of six and fed one of four different diets containing 20% of the calories as protein, 30% as fat (according to dietary guidelines for the United States) and 50% as carbohydrate. The diets contained casein or soy (lysine/arginine ratio = 2.2 or 0.9, respectively) as the protein sources with fat from either almond oil or butter. There was no significant difference in weight gain among the diet groups. Total serum cholesterol level was highest among animals fed the diet containing butter with casein (177 +/- 25 mg/dl) or soy protein (189 +/- 50 mg/dl), it was intermediate in animals fed the vegetable oil with casein (121 +/- 14 mg/dl), and lowest in the soy protein with vegetable oil group (58 +/- 12 mg/dl). There was a significant difference in serum cholesterol levels due to the protein effect when vegetable oil was used (p less than 0.05) but not with butter. There was also a significant fat effect on serum cholesterol when the diet contained soy protein (p less than 0.005) but not when the protein was casein. No significant interaction was observed between the dietary fat and protein sources on serum cholesterol levels, which suggests that dietary protein and fat independently affect the levels of serum cholesterol. Thus, dietary protein has a significant effect on serum cholesterol levels and may be a factor in the low levels of serum cholesterol observed among vegetarians and in humans of Third World countries where the diets is primarily of vegetable origin.     

Effect of marine oil and rapessee oil on composition of fatty acids in lipoprotein triacylglycerols from rat blood plasma and liver perfusate

The fatty acid patterns of triacylglycerols (TG) from very low density lipoprotein (VLDL) in blood plasma and liver-perfusate from rats fed partially hydrogenated marine oil or rapeseed oil were determined. In the plasma from rats fed rapeseed oil for three days and three weeks, there was a small but significant decrease in the percentage of 22∶1 fatty acid from 17.2 to 11.2% with length of feeding. In liver-perfusate, the comparable decrease with dietary rapeseed oil was from 18.5 to 5.2%, and with dietary marine oil from 13.4 to 8.0%. In contrast to the liver-perfusate, the remaining liver had only a very low 22∶1 composition (ca 2%) independent of feeding period or diet. The results indicated that the liver exported the very long chain fatty acids and that an adaptation took place after three days feeding with rapeseed oil or marine oil. This adaptation in the liver could possibly explain why TG accumulation in hearts, which appears after three days' feeding with rapeseed oil or marine oil, disappears after an extended feeding period.     

Relationship between erucic acid and myocardial changes in male rats

The back and belly fat of pigs fed a diet containing 20% by wt rapeseed oil (22% erucic acid) for 16 weeks was rendered into oil. This rendered pig fat, which contained 5.6% erucic acid, was fed to male rats in three separate experiments at 20% by wt of the diet for 16 weeks. In experiment I rendered pig fat was compared only toBrassica campestris var. Span rapeseed oil containing 4.8% erucic acid. In experiments II and III, rendered pig fat was compared to commerical lard containing 0.2% docosenoic acid, commercial lard to which 5.4% free erucic acid was added, and Span rapessed oil. There was no significant (P<0.01) differences observed in the level of erucic acid in the hearts of rats fed diets of rendered pig fat, Span rapeseed oil, or commercial lard plus erucic acid. However, the incidence (P<0.001) and severity (P<0.01) of cardiac lesions were significantly higher in Span rapeseed oil fed rats compared to rats fed control diets. The number of rats affected or the severity of lesions in the rendered pig fat fed group was not significantly different from controls. The results of this study indicate that the myocardial lesions associated with feeding 20% rapeseed oil diets are not related to the content of erucic acid per se. The possible reasons why rapeseed oil causes cardiac lesions in rats are discussed. It is suggested that a triglyceride imbalance in the oil might play an important role in causing these lesions in rats. Contribution No. 585, Animal Research Institute, Agriculture Canada, Ottawa, Canada, K1A 0C6.     

Serum cholesterol,triglycerides and total lipid fatty acids of rats in response to okra(hibiscus escuientus) seed oil

Tender pods of okra are commonly consumed vegetables in India. Okra seed kernel, like soybean, is a rich source of protein and fat. Its fat, with its appreciable linoleic acid content (>42%), prompted us to look into its metabolic utility in comparison with commonly consumed groundnut oil. Serum lipid profiles, with respect to cholesterol, triglycerides and total lipid fatty acids were determined in rats receiving okra seed oil at a level of 10% in the casein based diet which was adequate with respect to vitamins, minerals, etc. The control group received a casein based diet in which groundnut oil was the source of fat. Serum lipid profiles in this group were similarly monitored. The feeding trial was carried out for a period of 90 days. Results showed that serum cholesterol content of rats receiving okra seed oil was significantly lower compared to those consuming groundnut oil. A decreasing trend in total lipids as well as triglycerides was also evident in animals fed okra seed oil. Serum fatty acid profiles showed a relatively higher proportion of long chain and polyunsaturated fatty acids in this group as compared to the group receiving groundnut oil. These results indicate that okra seed oil consumption has a potential hypocholesterolemic effect. To whom correspondence to be addressed. ¹Part of this work was presented at 45th Annual Meeting of Oil Technologists Association of India, New Delhi-Feb. 9–10, 1990.     

Atherogenesis in swine fed several types of lipid-cholesterol diets

Eighteen-month-old Nebraska strain minipigs were fed diets containing 2% cholesterol and 20% corn oil, lard, or coconut oil for 12 to 18 months. Concentrations of serum total lipid, total cholesterol, and total phospholipid increased 200 to 300% with each diet. Changes in serum concentrations of S_f 20+ and S_f 0–20 lipoproteins varied with diets fed. Serum concentration of high density lipoprotein was increased in all cases. Intima concentration of S_f 0–20 lipoprotein fraction was elevated by feeding the corn oil diet. There was no development of atherosclerosis as a result of feeding the corn oil-cholesterol diet, but there was an increase in atherosclerosis as a result of feeding the lard or coconut oil diet. There were no correlations between fatty acid patterns of several lipid fractions from serum and corresponding lipid fractions from aortic intima of corn oil fed animals. Deceased.     

Dietary α-linolenic acid lowers postprandial lipid levels with increase of eicosapentaenoic and docosahexaenoic acid contents in rat hepatic membrane

This study was designed to examine the effects of dietary n−3 and n−6 polyunsaturated fatty acids (PUFA) on postprandial lipid levels and fatty acid composition of hepatic membranes. Male Sprague-Dawley rats were trained for a 3−h feeding protocol and fed one of five semipurified diets: one fat-free diet or one of four diets supplemented with 10% (by weight) each of corn oil, beef tallow, perilla oil, and fish oil. Two separate experiments were performed, 4-wk long-term and 4-d short-term feeding models, to compare the effects of feeding periods. Postprandial plasma lipid was affected by dietary fats. Triacylglycerol (TG) and total cholesterol levels were decreased in rats fed perilla oil and fish oil diets compared with corn oil and beef tallow diets. Hepatic TG and total cholesterol levels were also reduced by fish oil and perilla oil diets. Fatty acid composition of hepatic microsomal fraction reflected dietary fatty acids and their metabolic conversion. The major fatty acids of rats fed the beef tallow diet were palmitic, stearic, and oleic. Similarly, linoleic acid (LA) and arachidonic acid in the corn oil group, α-linolenic acid (ALA) and eicosapentaenoic acid (EPA) in the perilla oil group, and palmitic acid and docosahexaenoic acid (DHA) in the fish oil group were detected in high proportions. Both long- and short-term feeding experiments showed similar results. In addition, microsomal DHA content was negatively correlated with plasma lipid levels. Hepatic lipid levels were also negatively correlated with EPA and DHA contents. These results suggest that n−3 ALA has more of a hypolipidemic effect than n−6 LA and that the hypolipidemic effect of n−3 PUFA may be partly related to the increase of EPA and DHA in hepatic membrane.