Fatty liver of growing rats fed excess lysine and its prevention by adenine or allopurinol

Weanling male Sprague-Dawley rats were fed ad libitum 15% casein diets with and without 5.0% lysine-HCl, 0.25% adenine sulfate or 0.1% allopurinol for 2 weeks. Addition of lysine alone depressed 2-week growth from 94 to 65 g, increased average daily urinary orotic acid excretion from 0.39 to 1.77 mg and increased the percentage of total liver lipids from 3.6 to 11.2. Adenine or allopurinol did not change growth but markedly enhanced lysine-induced orotic aciduria and completely prevented lysine-induced fatty livers. Reports by others show that adenine and allopurinol also prevent fatty livers of rats fed arginine-free diets or excess orotic acid. The authors conclude that lysine-induced orotic aciduria results from arginine deficiency caused by antagonism of arginine function by lysine, and that lysine-induced fatty liver probably results from a lesion identifical to that produced by feeding excess orotic acid.     

Effect of continuous enteral medium-chain fatty acid infusion on lipid metabolism in rats

This study compared (i) the relative effects of long-chain triglycerides (LCT) and medium-chain triglycerides (MCT), (ii) the influence of amount of MCT, and (iii) the impact of medium-chain fatty acid position, on plasma and lymphatic triglycerides and portal vein free fatty acids. The animals were fed approximately at 250 kcal/kg · day for 20h. The lymph from lymphatic duct and blood from portal vein and systemic circulation were collected. The results showed that feeding 100% MCT for 20h was sufficiently long to reduce significantly the level of linoleic acid in portal vein fatty acids and plasma and lymph triglycerides. However, this alteration induced by MCT feeding was partially prevented by adding LCT to the diet. The level of arachidonic acid was significantly reduced in plasma triglycerides by any of the diets containing medium-chain fatty acids compared to 100% LCT. When feeding MCT only, palmitoleic acid, presumably reflecting de novo lipogenesis, was increased in lymphatic triglycerides and portal vein fatty acids. Total saturated fatty acids as a total percentage of total fatty acids were also significantly increased in plasma and lymphatic triglycerides and portal vein fatty acids. Thus, when linoleic acid is limiting, the conversion of MCT into long-chain fatty acids by de novo lipogenesis is likely to be an important metabolic route. Providing LCT with MCT or 2-monodecanoin appears to limit this pathway.     

Composition and dietary effects of the fish oil from "mandi" (Pinelodus clarias)

A study was carried out to determine the chemical composition and dietary effects of the oil from "mandi" (Pimelodus clarias). Findings revealed that it had a low proportion of essential C18:2 fatty acids and a high percentage of oleic acid (20.93%), as well as polyunsaturated fatty acids with more than 18 carbon atoms. Of the long-chain fatty acids, C22:6 was present in the highest percentage (1.94%). When rats were fed a diet the lipid source of which was the oil of mandi, they showed a reduced growth rate as compared to animals receiving the control diet (corn oil). The fatty acid composition of the liver and heart of rats from the experimental group was modified. The greatest variation occurred in the percentage of C22:6 in the heart muscle, wherein a five-fold increase was observed. Reduction of growth and alteration in the polyunsaturated fatty acids levels may be due to a deficiency in C18:2-w6, or to a possible imbalance between C18:2-w6 and C18:3-w3.     

Intestinal versus hepatic contribution to circulating triglyceride levels

Using intravenous injected [2-³H] glycerol, measurements wee made of the kinetics of appearance and disappearance of circulating [³H] labeled triglyceride in rats fed a fat free diet containing either no orotic acid (controls) or 2% orotic acid. Following injection of [³H] glycerol, more time is required for the initial appearance of [³H] triglyceride in the circulation of orotic acid treated rats than controls. The sustained entry of triglyceride into the circulation of orotic acid fed rats was only one-half times as rapid as that seen for control rats. Ca. 10% as much [³H] triglyceride entered the circulation of the orotic acid treated rats as compared with controls. However, the clearance of [³H] triglyceride from the circulation of the orotic acid fed rat was only ca. one-half times as rapid as that of the control rat. This apparently is due to differences between the lipoproteins produced by the intestines and liver, rather than to changes in the ability of the orotic acid fed animal to clear lipoprotein-triglyceride from the circulation. Labeled lipoproteins taken from controls and injected into orotic acid treated rats were cleared from the circulation more than twice as rapidly as those taken from orotic acid fed rats and injected into controls. Considering the measured levels of plasma triglyceride synthesis and the slower turnover of the triglycerides produced by the orotic acid fed rat, the findings of this study indicate that the intestines supply 20% or more of the total plasma triglyceride in the absence of dietary fat.     

Untersuchungen über die Eignung von Leindotterpreßkuchen als Futtermittel 1. Mitteilung: Futterwert und Einsatzgrenzen bei der Fütterung von Schweinen

Studies on the suitability of false flax expeller as feedstuff. 1st Communication: Feeding value and incorporation limits for pigs. To evaluate the feeding value of false flax expeller (FFE) for pigs, nutrients (crude nutrients, amino acids and fatty acids) were analyzed and their digestibility was determined with 6 growing pigs, by means of difference technique. Additionally, a feeding trial followed by slaughter investigations was performed with a total of 60 pigs (25–120 kg liveweight) to study the influence of increasing levels of FFE in diet (0%, 5%, 10%) on growth rate, slaughter performance and meat quality. The FFE used in these experiments was found to have 287 g digestible crude protein and 13.9 MJ ME per kg dry matter. Results of the feeding trial show depression of growth rate, when the percentage of FFE exceeds 5% in diets. Average daily liveweight gain decreased from 758 g (controls) to 725 g (10% FFE) and costs of metabolizable energy increased from 38.9 MJ to 39.7 MJ per kg live-weight gain. Additionally, metabolic burdens, indicated as increased liverweights, up to 16% were observed. Due to the high polyenic fatty acid contents of FFE oil consistancy of carcass fat deteriorated with increasing FFE consumption. The percentage of polyenic fatty acids in total fatty acids of back fat increased from 11.5% (controls) to 14.7% (10% FFE). The taste of meat was negatively influenced as well. The percentage of meat samples tasting atypically increased from 3% (controls) to 18% (5% FFE) and to 36% (10% FFE).     

Response of urinary malondialdehyde to factors that stimulate lipid peroxidation in vivo

Malondialdehyde (MDA) derivatives occur as normal constituents of rat and human urine. In a previous study, it was found that MDA excretion in rats is responsive to MDA intake and to certain factors that increase lipid peroxidation in vivo: vitamin E deficiency, iron administration and a high concentration of cod liver oil (CLO) fatty acids in the tissues. In the present study, the effect on MDA excretion of several additional dietary and endogeneous factors was evaluated. The composition of dietary fatty acids had a major influence on MDA excretion in fed animals, being highest for animals fed n−3 fatty acids (20∶5 and 22∶6) from CLO, intermediate for those fed n−6 (18∶2) acids from corn oil (CO) and lowest for those fed saturated acids from hydrogenated coconut oil (HCO). Diet was the main source of urinary MDA in all groups. Fasting produced a marked increase in urinary MDA, which tended to be higher in rats previously fed CLO. Fasting MDA excretion was not affected by the level of CO in the diet (5, 10 or 15%), indicating that feeding n−6 acids does not increase lipid peroxidation in vivo. Adrenocorticotropic hormone and epinephrine administration increased urinary MDA, further indicating that lipolysis either releases fatty acid peroxides from the tissues or increases the susceptibility of mobilized fatty acids to peroxidation. A decrease in fasting MDA excretion was observed in rats previously fed a high level of antioxidants (vitamin E+BHT+vitamin C) vs a normal level of vitamin E. MDA excretion increased following adriamycin and CCl₄ administration. No increase was observed following short-term feeding of a choline-methionine-deficient diet, which has been reported to increase peroxidation of rat liver nuclear lipids. This study provides further evidience that urinary MDA can serve as a useful indicator of lipid peroxidation in vivo when peroxidation of dietary lipids is precluded. This research was performed in partial fulfillment of the requirements for the M.Sc. degree in Nutritional Sciences     

The influence of storage on the fatty acid content of cod liver oil

Summary A study has been made of the change of fatty acid content of cod liver oils during storage. Thirty oils varying in acid content from 0.38% to 20.88% were procured in the open market. They represented three types of oils—medicinal, animal feeding and industrial oils. The samples of oil were stored at room temperature, in the dark, in three-fourths filled, four-ounce, amber, cork-stoppered bottles. The acid content was determined twelve times during a period of forty-two months. The acid content of each oil increased. The amount of increase varied from 7.42% for a sample of industrial oil with an initial acid content of 16.45% to 84.80% for a sample of animal feeding oil with an initial acid content of 0.99%. In general, the cod liver oils with initial high acid content showed a lower percentage increase in free fatty acids than oils with a low initial free fatty acid content.     

Influence of medium-chain triglycerides on lipid metabolism in the chick

The effect of corn oil, coconut oil, and medium-chain triglyceride (MCT, a glyceride mixture consisting almost exclusively of fatty acids of 8 and 10 carbons in length) ingestion on lipid metabolism was studied in chicks. In chicks fed cholesterol-free diets, MCT ingestion elevated plasma total lipids and cholesterol and depressed liver total lipids and cholesterol when compared to chicks receiving the corn oil diet. As a consequence of the opposite effects of MCT ingestion on plasma and liver cholesterol and total lipids, the plasma-liver cholesterol pool was not altered. When cholesterol was included in the diets, dietary MCT depressed liver and plasma total lipids and cholesterol as compared with corn oil, consequently also lowered the plasmaliver cholesterol pool. The in vitro cholesterol and fatty acid synthesis from acetate-1-¹⁴C was higher in liver slices from chicks fed MCT than in those from chicks fed corn oil. The percentage of radioactivity from acetate-1-¹⁴C incorporated into the carboxyl carbon of fatty acids by liver slices was not altered by MCT feeding, indicating that the increased acetate incorporation represented de novo fatty acid synthesis. The conversion of palmitate-1-¹⁴C to C₁₈ acids was increased in liver of chicks fed MCT, implying that fatty acid chain elongating activity was also increased. Studies on the conversion of stearate-2-¹⁴C to mono- and di-unsaturated C₁₈ acids showed that hepatic fatty acid desaturation activity was enhanced by MCT feeding. Data are presented on the plasma and liver fatty acid composition of chicks fed MCT-, corn oil-, or coconut oil-supplemented diets. The principles of laboratory animal care, as promulgated by the National Society for Medical Research, were observed.     

The influence of dietary fat on the lipogenic activity and fatty acid composition of rat white adipose tissue

The in vivo fatty acid synthesis rate, selected enzyme activities and fatty acid composition of rat white adipose tissue from animals fed semisynthetic diets of differing fat type and content were studied. All animals were starved for 48 hr and then refed a fat-free (FF) diet for 48 hr. They were then divided into three groups. One group was continued on the FF diet for 48 hr. Another group was fed a diet containing 44% of calories from corn oil (CO). The final group was fed a diet containing 44% of calories from completely hydrogenated soybean oil (HSO). The animals on the FF diet had a marked increase in adipose tissue fatty acid synthesis during the 96-hr feeding peroid (as measured by³H incorporation into adipose fatty acids). Addition of either CO or HSO to the diets did not significantly inhibit fatty acid synthesis in dorsal or epididymal adipose tissue. The activities of the enzymes' fatty acid synthetase, ATP-citrate lyase and glucose-6-phosphate dehydrogenase increased on the FF diet and generally were not inhibited significantly by the addition of either fat to the diets. Linoleic acid was the major polyunsaturated fatty acid (ca. 22%) in adipose tissue. Monounsaturated fatty acids (palmitoleic, oleic,cis-vaccenic) made up ca 38% of the total adipose fatty acids, while saturated fatty acids accounted for about 32% (myristic, palmitic and stearic). White adipose tissue in mature male rats was a major depot for n−3 fatty acids. There were differences in the fatty acid composition of epididymal and dorsal adipose tissue, particularly in their content of long chain, polyunsaturated fatty acids with epididymal tissue containing more of these compounds than dorsal fat. The fatty acid composition of the white adipose tissue did not change significantly during fasting or 96 hr of refeeding the FF diets. The addition of HSO to the diet for 48 hr had little influence on the adipose tissue fatty acid composition, but the addition of CO to the diet caused a 7% increase in the dorsal adipose tissue linoleate content (as percentage of total dorsal adipose tissue fatty acids) within 48 hr compared to animals fed the stock diet and those starved for 48 hr. The fatty acid synthesis data indicated that adipose tissue in the rat can continue to be a source of de novo fatty acid synthesis in animals consuming high-fat diets.     

Effects of zinc deficiency and castration on fatty acid composition and desaturation in rats

The effects of zinc deficiency and testosterone on fatty acid composition of plasma lipids and microsomes of liver, intestine and testes were studied. The activities of fatty acid desaturase (Δ6 and Δ5) in rat liver and testes were also measured. A significant decrease in the level of arachidonic acid was observed in plasma of normal rats fed the zinc-deficient diet. Castration significantly decreased arachidonic acid but increased 20∶3 fatty acid, which is negligible in normal rats. Testosterone and zinc administration restored arachidonic acid to normal values. Zinc deficiency does not significantly change the fatty acid profile in liver, but castration decreased both arachidonic and 22∶6 fatty acid. Intestinal mucosal microsomes showed that the predominant fatty acid in this tissue, palmitic acid, is independent of zinc status, whereas polyunsaturated fatty acids 18∶2 and 20∶4 were decreased by zinc-deficient diet or castration. Zinc deficiency sharply decreased 22∶5 fatty acid and to some extent, other polyunsaturated fatty acids in testis microsomes. These changes in fatty acids are in agreement with increased Δ9 desaturation and decreased Δ5 desaturase activity. In testes, both Δ6 and Δ5 desaturase activities are decreased in zinc deficiency. It appears that zinc influences the conversion of linoleic to arachidonic acid, whereas testosterone influences Δ6 desaturase activity. The data suggest that zinc deficiency may be one of the important factors in the causation of polyunsaturated fatty acid deficiency, which in turn, may induce serum hypertriglyceridemia.     

Antioxidant efficacy of amino acids in methyl linoleate at different relative humidities

Antioxidant efficacy of the amino acids methionine, tryptophan, aspartic acid, serine, alanine and arginine in methyl linoleate were compared to a methyl linoleate control at 2,50 or 79% relative humidity (RH) at 37°C. Antioxidant efficacy varied with RH and the individual amino acids. Arginine had the highest antioxidant efficacy at all RH values compared to the control. The efficacy of alanine was equal to that of arginine at RHs of 50 and 79% but was lower at 2% RH. The presence of aliphatic, alkaline amino, hydroxyl or thiol groups in the side chain of the amino acids increased the antioxidant efficacy at high RHs.     

Effects of dietarytrans acids on the biosynthesis of arachidonic acid in rat liver microsomes

Effects of dietarytrans acids on the interconversion of linoleic acid was studied using the liver microsomal fraction of rats fed a semipurified diet containing fat supplements of safflower oil (SAFF), hydrogenated coconut oil (HCO) at 5 and 20% levels or a 5% level of a supplement containing 50.3% linolelaidic and 24.3% elaidic acids devoid ofcis,cis-linoleic acid (TRANS). Growth rate was suppressed to a greater extent with the animals fed the 20% than the 5% level of the HCO-supplemented diets and still further by the TRANS diet compared to the groups fed the SAFF diets. Food intake was greater in the groups fed the HCO than the SAFF-supplemented diets, demonstrating the marked effect of an essential fatty acid (EFA) deficiency on feed efficiency. In contrast to an EFA deficiency produced by the HCO supplement, which stimulated the in vitro liver microsomal biosynthesis of arachidonic acid, diets containing the TRANS supplement exacerabated the EFA deficiency and depressed 6-desaturase activity of the liver microsomal fraction. The liver microsomal fraction of the animals receiving this supplement also was more sensitive to fatty acid inhibition of the desaturation of linoleic acid than those obtained from animals fed either the SAFF or HCO diets. It is suggested that dietarytrans acids alter the physical properties of the 6-desaturase enzyme system, suppressing its activity, which increases the saturation of the tissue lipids and, in turn, the requirement for EFA or polyunsaturated fatty acids.     

The effect of dietary sterculic acid on the hepatic lipids of rainbow trout

Groups of young rainbow trout (5 g) were fed a basal diet containing 9% salmon oil and 1% tristearin with 0, 100 or 200 ppm methyl sterculate. Liver lipids were separated into polar and nonpolar fractions and the fatty acids quantitatively analyzed. Significant elevations of the stearic-oleic and the palmiticpalmitoleic ratios were found in liver fatty acid composition 10 days after the feeding trial began. Liver triglycerides of fish fed methyl sterculate for 87 days contained only 2–3% docosahexenoic acid as compared to 10.69% in control trout, suggesting an effect on the biosynthesis of long chain polyunsaturates. Dietary cyclopropenoid fatty acids (CPFA) suppressed growth rate during the first part of the 200 day feeding trial. After 90 days no differences in the rate of weight gain were observed between the control and CPFA groups. A seven day feeding trial with 0, 5, 20, 50 and 100 ppm CPFA resulted in a maximum change in the stearic-oleic ratio at 50 and 100 ppm levels. All levels of CPFA increased this ratio and caused marked alterations in the cellular morphology of the liver. Presented in part at the annual meeting of the Federation of American Societies for Experimental Biology, Atlantic City, New Jersey, April, 1968. Technical Paper No. 2565, Oregon Agricultural Experimental Station.     

Altered fatty acid desaturation and microsomal fatty acid composition in the streptozotocin diabetic rat

Streptozotocin diabetes in the rat diminishes the synthesis of both monounsaturated and polyunsaturated fatty acids. Rat liver microsomal fatty acid composition and fatty acid desaturation were studied in the streptozotocin diabetic rat. The major alterations in fatty acid composition found in the diabetic rat were decreased proportions of palmitoleic, oleic and arachidonic acids and an increased proportion of linoleic and docosahexaeneoic acids. These findings, other than the increased docosahexaeneoic acid, probably result from the diminished liver microscomal δ9 and δ6 desaturase activities found in these animals. These changes are not due to the diminished weight gain of the diabetic animals since restricting food intake of control animals to achieve a similar weight gain failed to reproduce either the changes in fatty acid composition or the decrease in fatty acid desaturation. The increased food intake of the diabetic animal may contribute to the altered proportions of linleic and arachidonic acids since limiting food intake in diabetic animals to that of normal controls diminished the magnitude of these changes. Insulin therapy for 2 days not only reverses and overcorrects the diminished desaturase activities, but likewise reverses and overcorrects the altered fatty acid composition, with the exception of the diminished arachidonic aicd levels which are further decreased following insulin therapy. These findings strongly suggest that most of the changes in fatty acid composition in the diabetic rat are indeed caused by the diminished fatty acid desaturase activities.     

Studies on the metabolism of linoelaidic acid in the essential fatty acid-deficient rat

Male weanling rats of the Sprague-Dawley strain were made essential fatty acid (EFA)-deficient by feeding them a fat-free diet for five months. The animals were then fed a supple-ment of methyltrans-9,trans-12-octadecadienoate (methyl linoelaidate), as 5% of the dietary calo-ries (approximately 400 mg/animal/day) for 19 days, and killed by exsanguination. The com-position of the liver, kidney, epididymal and plasma lipids was determined and compared with that obtained from EPA-deficient rats given oral supplements of methylcis-9,cis-12-octadeca-dienoate (linoleate) and methylcis-9,trans-12- octadecadienoate. Linoelaidic acid was depos-ited in the phospholipids, sterol esters and tri-glycerides in all of the tissues examined. Iso-lation analysis of the fatty acids showed no evidence that linoelaidic acid was converted to higher polyunsaturated fatty acids in the EFA-deficient rat. Supported in part by U. S. Public Health Service Grant No. AM 04942.     

Daily variations of the biosynthesis and composition of fatty acids in rats fed on complete and fat-free diets

This report describes the daily changes in fatty acid composition and fatty acid desaturation in rats feeding on a complete diet and a fat-free diet successively. Rats on a complete diet showed a good homeostasis in the percentage of fatty acid in plasma, with a possible palmitic acid rhythm, but the fat-free diet initiated an essential fatty acid-deficient pattern in a few hours. The light-dark period in animals feeding on a complete diet motivates a feeding rhythm that causes changes in linoleic and arachidonic acids in the whole liver and microsomes that are related to Δ6 and Δ5 desaturase activities. The patterns of Δ6 and Δ5 desaturase changes were different. Linoleic acid intake during the dark periods (complete diet feeding) caused a decrease of Δ6 desaturase activity and the activation of Δ5 desaturation that led to an increase of arachidonic acid biosynthesis. The feeding of a fat-free diet eliminated the rhythm observed in linoleic and arachidonic acid composition in the liver and changed the desaturase rhythms. The Δ9 desaturase activity in the liver also showed a daily rhythm in the complete-diet period that disappeared with the change to a fat-free diet, while the activity increased markedly. A negative correlation existed between the percentage of linoleic acid in the liver and the Δ9 desaturase activity. However, no correlation was found between Δ9 desaturase activity and the percentage of 16∶1 and 18∶1 in the complete-diet period.     

Die Veränderung der freien Fettsäuren nach Verabreichung von Orotsäure

Change in Free Fatty acids after Ingestion of Orotic Acid The level of free fatty acids in blood-serum of rats after per os and intraperitoneal ingestion of orotic acid was studied. High doses of perorally administered orotic acid was without any action, whereas parenteral application led to a considerable lowering of the free fatty acid level already after 30 min. The latter was proportional to orotic acid concentration in serum. The smallest amount leading to a statistically significant reduction was about 100 mg orotic acid/kg, which was present in orotic acid containing compounds.     

The effect of dietary partially hydrogenated marine oils on desaturation of fatty acids in rat liver microsomes

The influence of dietary partially hydrogenated marine oils on distribution of phospholipid fatty acids in rat liver microsomes was studied with particular reference to the metabolism of linoleic acid. Five groups of weanling rats were fed diets containing 20% (w/w) peanut oil (PO), partially hydrogenated peanut oil (HPO), partially hydrogenated Norwegian capelin oil (HCO), partially hydrogenated herring oil (HHO), and rapeseed oil (RSO) for 10 weeks. The partially hydrogenated oils were supplemented with linoleic acid corresponding to 4.6 cal % in the diets. Accumulation of linoleic acid and reduced amount of total linoleic acid metabolites were observed in liver microsomal phospholipids from rats fed partially hydrogenated oils as compared to PO feeding. The most striking effects on the distribution of ω6-polyunsaturated fatty acids was obtained after feeding HHO, a marine oil with a moderate content oftrans fatty acids in comparison with HPO but rich in isomers of eicosenoic and docosenoic acids. Liver microsomal Δ⁶-as well as Δ⁶-desaturase activities as measured in vitro were reduced in rats kept on HHO as compared to PO dietary treatment. The results obtained suggest that the dietary influence of partially hydrogenated marine oils on the metabolism of linoleic acid might be better related to the intake of isomeric eicosenoic and docosenoic acids than to the total intake oftrans fatty acids.     

Stearoyl-CoA desaturase activity in adipose tissue and liver of the cardiomyopathic hamster

Stearoyl-CoA desaturase activity and the fatty acid composition of lipids of adipose tissue and liver were determined in 35- and 180-day-old cardiomyopathic hamsters and age-matched normal controls. Enzyme activity was unchanged in the adipose tissue of 35-day-old animals but was significantly depressed in the 180-day-old cardiomyopathic hamsters. In the liver, stearoyl-CoA desaturase activity was significantly lower in the 35-day-old disease animals but was unchanged in the 180-day-old animals. The analysis of the fatty acid composition of the lipids isolated from adipose tissue showed an increase in the relative percentage of saturated fatty acids accompanied by a decrease in the relative percentage of unsaturated fatty acids in both age groups of the cardiomyopathic hamsters. However, linoleic acid content was increased in the diseased animals. Similar changes in fatty acid composition of lipids from the livers of 35-day-old cardiomyopathic hamsters were observed, but no significant differences in the fatty acid composition between 180-day-old cardiomyopathic hamsters and normal controls were observed. The changes in the fatty acid composition appear to be related to the observed changes in desaturase activity. In is concluded that such changes in desaturase activity and fatty acid composition could affect the normal structure and functions of membranes and membrane-related processes.     

Dietary conjugated linoleic acid reciprocally modifies ketogenesis and lipid secretion by the rat liver

The effects of dietary conjugated linoleic acid (CLA) and linoleic acid (LA) on ketone body production and lipid secretion were compared in isolated perfused rat liver. After feeding the 1% CLA diet for 2 wk, the concentration of post-perfused liver cholesterol was significantly reduced by CLA feeding, whereas that of triacylglycerol remained unchanged. Livers from CLA-fed rats produced significantly more ketone bodies; and the ratio of β-hydroxybutyrate to acetoacetate, an index of mitochondrial redox potential, tended to be consistently higher in the liver perfusate. Conversely, cumulative secretions of triacylglycerol and cholesterol were consistently lower in the livers of rats fed CLA, and the reduction in the latter was statistically significant. Thus dietary CLA appeared to exert its hypolipidemic effect at least in part through an enhanced β-oxidation of fatty acids at the expense of esterification of fatty acid in the liver.