Effect of dietary fat upon aflatoxicosis in rats fed torula yeast containing diet

This study was designed to study the possible interrelationships between Torula yeast, vitamin E, and the dietary fat source on aflatoxin-induced tumors. Rats were fed Torula yeast-containing basal diets which included 1.7 ppm aflatoxin B₁ with either lard, corn oil or no fat, and with or without vitamin E supplements for 3 months. Thereafter, the respective diets without aflatoxin were fed for ca. 9 months. Animals receiving the vitamin E-deficient diets had a high mortality. Although the vitamin E-deficient, aflatoxin-treated rats had lower wt gains than did the vitamin E-deficient controls, they lived twice as long. In addition, regardless of the dietary fat source, the kidneys and adrenals of these vitamin E-deficient, aflatoxin-supplemented rats were found to be significantly heavier than the controls, and plasma cholesterol levels were elevated. Increased amounts of liver lipid were observed in response to aflatoxin in both corn oil-fed and fat-deficient rats. No such differences were observed in the responses of the vitamin E-supplemented groups to aflatoxin. On the corn oil diet, aflatoxin administration resulted in an increased deposition of polyunsaturated fatty acids in cholesteryl ester and phospholipid fractions in livers of vitamin E-deficient rats and the phospholipid fraction of vitamin E-sufficient rats. The vitamin E-deficient rats exhibited necrosis of the liver, which was alleviated when aflatoxin was included in the diet, and calcification of the kidneys, which was potentiated by the dietary aflatoxin. No tumors were observed in these animals. In animals maintained on vitamin E-sufficient diets for 1 year, growth was depressed as a result of aflatoxin administration with the greatest depression occurring in the group fed corn oil. Spleen wt were decreased in all groups given aflatoxin. However, there were no changes in either plasma or liver cholesterol or total liver lipids which could be attributed to aflatoxin administration. When aflatoxin was fed with lard, the cholesteryl ester, triglyceride, and free fatty acid fractions of plasma had decreased amounts of the C20:4 acid. In the cholesteryl ester fraction only, this change was accompanied by increased levels of C16:0, C18:0, and C18:1 acids. In the liver phospholipids, there were increased levels of mono- and polyunsaturated fatty acids and decreases in the saturated fatty acids. All of the animals receiving aflatoxin exhibited severe necrosis and tumor formation in the kidneys; the animals fed lard had the highest level of involvement and those in the fat-free group the least. Liver pathology was the least marked among the rats fed the fat-free diet. Since aflatoxin-induced tumors are rich in lipids, the fat-free diet may be protective to the animal.     

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

Lipid metabolism was studied in rats fed diets containing corn oil, coconut oil, or medium-chain triglyceride (MCT), a glyceride mixture containing fatty acids of 8 and 10 carbons in length. The ingestion of MCT-supplemented, cholesterolfree diets depressed plasma and liver total lipids and cholesterol as compared with corn oil-supplemented diets. In rats fed cholesterol-containing diets, plasma cholesterol levels were not influenced by dietary MCT, but liver cholesterol levels were significantly lower than in animals fed corn oil. In vitro cholesterol synthesis from acetate-1-¹⁴C was lower in liver slices of rats that consumed MCT than in similar preparations from corn oil-fed rats. Studies of fatty acid carboxyl labeling from acetate-1-¹⁴C and the conversion of palmitate-1-¹⁴C to C₁₈ acids by liver slices showed that chain-lengthening activity is greater in the liver tissue of rats fed MCT than in the liver of animals fed corn oil. The hepatic fatty acid desaturation mechanisms, evaluated by measuring the conversion of stearate-2-¹⁴C to oleate, was also enhanced by feeding MCT. Adipose tissue of rats fed MCT converts acetate-1-¹⁴C to fatty acids at a much faster rate than does tissue from animals fed corn oil. Evidence is presented to show that the enhanced incorporation of acetate into fatty acids by the adipose tissue of rats fed MCT represents de novo synthesis of fatty acids and not chain-lengthening activity. Data are also presented on the fatty acid composition of plasma, liver, and adipose tissue lipids of rats fed the different fats under study.     

Effects of dietary vitamin E,selenium, and polyunsaturated fats on in vivo lipid peroxidation in the rat as measured by pentane production

Starting at 21 days of age, groups of six rats each were fed a basal Torula yeast diet supplemented with 0,4% L-methionine and varying amounts of vitamin E as dl-alpha tocopherol acetate, selenium as sodium selenite, and with either 10% stripped corn oil, stripped lard, or coconut oil. By 7 wk, pentane production by rats fed a corn oil diet deficient in both vitamin E and selenium was twice that by rats fed 0.1 or 1 mg of selenium per kg of the same basal diet. Blood glutathione peroxidase activity after 7 wk was proportional to the logarithm of dietary selenium. Groups of rats fed the vitamin E- and selenium-deficient diets with lard or coconut oil had one-half the pentane production of rats fed the vitamin E- and selenium-deficient corn oil diets. The plasma level of linoleic plus arachidonic acid was 1.8 times greater on a wt % basis in rats fed corn oil than in rats fed lard or coconut oil as the fat source. Pentane production by rats fed 40 i.u. dl-alpha tocopherol acetate per kg of the selenium-deficient corn oil diet was one-sixth of that by rats fed the same diet without vitamin E; the plasma of the rats fed the vitamin E-supplemented corn oil diet had a level of vitamin E that was about six times greater than that of the rats fed the vitamin E-deficient corn oil diet.     

Changes in lipid composition of liver microsomes and fatty acyl-CoA desaturase activities induced by medium chain triglyceride feeding

Changes in fatty acid composition, microsomal Δ⁹- and Δ⁶-desaturase activities and liver contents of cholesterol and phospholipids were studied in rats fed medium chain triglyceride-supplemented diets. Weanling rats were divided into four groups and fed for three weeks a basal diet with different 10%-fat supplements: corn oil, medium chain triglyceride-corn oil, olive oil and medium chain triglyceride-olive oil. The highest relative content of saturated fatty acids corresponded to corn oil-fed animals. Both monounsaturated fatty acid content and Δ⁹-desaturase activity were higher in the animals fed olive oil diets than in corn oil-fed rats. The long chain polyunsaturated fatty acids of the n−3 series were increased in the olive oil and medium chain triglyceride-olive oil-fed groups probably due to the lower linoleic/α-linolenic ratios found in these two diets. The cholesterol/phospholipid molar ratio was unaffected by diet and the unsaturation index was only slightly changed in the four groups. Thus, some mechanism may be operative under these conditions to maintain the homeostasis of the membrane.     

Ratios of polyunsaturated fatty acids to α-tocopherol in tissues of rats fed corn or soybean oils

This study was part of a larger experiment designed to assess the vitamin E adequacy of corn and soybean oils in relation to their polyunsaturated fatty acids (PUFA). Young male rats were fed a semipurified diet containing 20% corn or soybean oil and adequate selenium. After 8 and 12 weeks, animals were sacrificed, and 7 tissues analyzed for α- and γ-tocopherols and for fatty acids. Calculations were made of the molar ratios of total polyunsaturated fatty acids/α-tocopherol, and also of all polyunsaturated fatty acids, except linoleate, designated polyunsaturated fatty acids>18∶2, to α-tocopherol. It is proposed that the latter ratio may have more significance, physiologically, than when linoleic acid also is considered. Tissues from rats fed corn oil had slightly more favorable (lower) ratios than did tissues from rats fed soybean oil. In both groups, the molar polyunsaturated fatty acids>18∶2/α-tocopherol ratio was lowest for heart and lung, intermediate for muscle and testis, and highest for liver, kidney, and adipose tissue. Since both corn and soybean oils provide adequate vitamin E as determined by several biochemical and physiological parameters, adequate molar ratios of polyunsaturated fatty acids>18∶2/α-tocopherol were: lung, 400; heart and leg muscles, 700; testis, 1100; liver and kidney, 1500–2000; and adipose tissue, 2000.     

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 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.     

1-14C-Linoleic acid distribution in various tissue lipids of guinea pigs following an oral dose

A recent study on the metabolism of 1-¹⁴C-α-linolenic acid in the guinea pig revealed that the fur had the highest specific activity of all tissues examined, 48 h after dosing. The present study investigated the pattern of tissue lipid labeling following an oral dose of 1-¹⁴C-linoleic acid after the animals had been dosed for the same time as above. Guinea pigs were fed one of two diets with a constant linoleic acid content (18% total fatty acids) and a different content of α-linolenic acid (0.3 or 17.3%) from weaning for 3 wk and 1-¹⁴C-linoleic acid was given orally to each animal for 48 h prior to sacrifice. The most highly labeled tissues (dpm/mg of linoleic acid) were liver, followed by brain, lung and spleen, heart, kidney and adrenal and intestines, in both diet groups. The liver had almost a three-fold higher specific activity than skin and fur which was more extensively labeled than the adipose and carcass. Approximately two-thirds of the label in skin plus fur was found in the fur which, because of a low lipid mass, would indicate that the fur was highly labeled. All tissues derived from animals on the diet with the low α-linolenic acid level were significantly more labeled than the tissues from the animals on the high α-linolenic acid diet, by a factor of 1.5 to 3. The phospholipid fraction was the most highly labeled fraction in the liver, free fatty acids were the most labeled fraction in skin & fur, while triacyglycerols were the most labeled in the carcass and adipose tissue. In these tissues, more than 90% of the radioactivity was found in fatty acids with 2-double bonds in the tissue lipids. These data indicate that the majority of label found in guinea pig tissues 48 h after dosing was still associated with a fatty acid fraction with 2-double bonds, which suggests there was little metabolism of linoleic acid to more highly unsaturated fatty acids in this time frame. In this study, the labeling of guinea pig tissues with linoleic acid, 48 h after dosing, was quite different from the labeling with α-linolenic acid reported previously. The retention of the administered radioactivity from ¹⁴C-linoleic acid in the whole body lipids was 1.6 times higher in the group fed the low α-linolenic acid diet (diet contained a total of 1.8 g PUFA/100 g diet)compared with the group fed the high α-linolenic acid diet (diet contained 3.6 g PUFA/100 g diet). The lack of retention of ¹⁴C-labeled lipids in the whole body would be consistent with an increased rate of β-oxidation of the labeled fatty acid on the diet rich in PUFA, a result supported by other studies using direct measurement of labeled carbon dioxide.     

The effects of fat-free,saturated and polyunsaturated fat diets on rat liver and plasma lipids

The liver and plasma lipids and fatty acid composition of rats fed synthetic diets of differing fat type and content were studied. All animals were starved for 48 hr and then refed a high carbohydrate, fat-free diet for 48 hr. They were then divided into three groups and fed for an additional 48 hrs the following: group 1, the fat-free diet; group 2, a diet containing 44% of calories from corn oil; and group 3, a diet containing 44% calories from completely hydrogenated soybean oil. The total lipid concentration of the liver in the animals on the fat-free diet was elevated at 72 and 96 hr. The addition of either saturated or unsaturated fat in the diet at 48 hr prevented this accumulation. The total phospholipid and cholesterol concentrations of the liver were relatively uninfluenced by any diet in this study. Plasma total fatty acid concentration was elevated at 72 hr in the animals on a fat-free diet compared to those fed the stock diet, starved for 48 hr or fed the fat-containing diets. By 96 hr, however plasma fatty acid concentrations in all groups were similar to those in animals fed only the stock diet. The release of de novo synthesized fatty acids into plasma from the liver was strongly inhibited by dietary fat, either saturated or polyunsaturated. With the fat-free diet there was a significant increase in the saturated and monounsaturated fatty acids in both liver and plasma. The addition of corn oil to the diet facilitated a reversion of the fatty acid composition in liver and plasma to that found in the animals fed the stock diet ad libitum, but saturated fat did not. No effect of diet on the fatty acid composition of the red cells was observed during the course of this study. Exogenous saturated fatty acids, although similar chemically to the fatty acids synthesized by the liver, may have physiological actions that differ from endogenously synthesized fat.     

Cardiac lipids in rats and gerbils fed oils containing C22 fatty acids

Docosenoic acid from rapeseed oil or herring oil in the diet of the young rat promoted an accumulation of cardiac lipid. The triglyceride fraction accounted for most of the deposited fat and contained a high concentration of the docosenoic acid. Liquid rapeseed oil, partially hydrogenated rapeseed oil or partially hydrogenated herring oil increased the amount of cardiac fatty acids at 1 week and led to the development of degenerative lesions at 16 weeks. Whale or seal oils low in C₂₂ fatty acids produced little effect on the amount of lipids in the heart of rats or gerbils. The latter species receiving 20% rapeseed oil in the diet showed a peak in cardiac lipid deposition at 4 days with similar levels of total fatty acids to that of rats, but with a lower concentration of erucic acid. Oil fromLimnanthes douglasii and hydrogenated herring oil also increased the amount of cardiac fatty acids in gerbils. A high intake of docosenoic acid was common to the animals displaying the cardiac alterations. Presented at the AOCS Meeting, Atlantic City, October 1971.     

Effect of dietary palm oil and its fractions on rat plasma and high density lipoprotein lipids

Male Sprague Dawley rats were fed semipurified diets containing 20% fat for 15 weeks. The dietary fats were corn oil, soybean oil, palm oil, palm olein and palm stearin. No differences in the body and organ weights of rats fed the various diets were evident. Plasma cholesterol levels of rats fed soybean oil were significantly lower than those of rats fed corn oil, palm oil, palm olein or palm stearin. Significant differences between the plasma cholesterol content of rats fed corn oil and rats fed the three palm oils were not evident. HDL cholesterol was raised in rats fed the three palm oil diets compared to the rats fed either corn oil or soybean oil. The cholesterol-phospholipid molar ratio of rat platelets was not influenced by the dietary fat type. The formation of 6-keto-PGF_1α was significantly enhanced in palm oil-fed rats compared to all other dietary treatments. Fatty acid compositional changes in the plasma cholesterol esters and plasma triglycerides were diet regulated with significant differences between rats fed the polyunsaturated corn and soybean oil compared to the three palm oils.     

Effects of dietary corn oil and salmon oil on lipids and prostaglandin E2 in rat gastric mucosa

Three groups of male rats were fed either a corn oilenriched diet (17%, w/w), a salmon oil-enriched diet (12.5%) supplemented with corn oil (4.5%) or a low-fat diet (4.4%) for eight wk to investigate the possible relationships between dietary fatty acids and lipid composition, and prostaglandin E₂ level and phospholipase A₂ activity in the rat gastric mucosa. High-fat diets induced no important variation in total protein, phospholipid and cholesterol contents of gastric mucosa. Compared with a low-fat diet, corn oil produced a higher n−6/n−3 ratio in mucosal lipids, whereas this ratio was markedly lowered by a fish oil diet. In comparison with the low-fat diet, the production of prostaglandin E₂(PGE₂) in gastric mucosa of rats fed salmon oil was significantly, decreased by a factor of 2.8. In the corn oil group, PGE₂ production tended to decrease, but not significantly. In comparison with the low-fat diet, both specific and total gastric mucosal phospholipase A₂ activities were increased (+18 and 23%, respectively) in the salmon oil group; they were unchanged in the corn oil group. It is suggested that the decrease of gastric PGE₂ in rats fed fish oil is not provoked by a decrease in phospholipase A₂ activity but may be the result of the substitution of arachidonic acid by n−3 PUFA or activation of PGE₂ catabolism.     

The n−3 polyunsaturated fatty acid levels in rat tissue lipids increase in response to dietary olive oil relative to sunflower oil

In the present study, changes in phospholipid compositions of liver microsomes, erythrocyte membranes, platelets, aorta, cardiac muscle and brain of rats fed olive oil were compared with those of rats fed sunflower oil. Four groups of rats starting at weaning were fed for four weeks a basal diet containing 5 or 25% olive oil or sunflower oil. We found that oleic acid was higher and linoleic acid was lower in membrane phospholipids of olive oil fed rats compared to sunflower oil fed rats. Polyunsaturated fatty acids of the n−3 series were markedly elevated in all tissues of rats on the olive oil diets relative to those on the sunflower oil diets. The results are consistent with a lower linoleic/linolenic acid ratio induced by the olive oil diets, suggesting a positive correlation between olive oil ingestion and n−3 polyunsaturated fatty acid levels in cell and tissue lipids. The study suggests that an adequate intake of olive oil may enhance the conversion of n−3 fatty acids.     

The effect of a moderately thermoxidized dietary fat on the vitamin E status,the fatty acid composition of tissue lipids,and the susceptibility of low-density lipoproteins to lipid peroxidation in rats

Several studies demonstrated that dietary oxidized oils markedly affect the vitamin E status and alter the fatty acid composition of tissue lipids in animals. It must however be emphasized that highly oxidized oils reduce the feed intake of animals, which makes it difficult to interpret the results. Therefore, the present study used a moderately thermoxidized soybean oil (peroxide value: 75 mEq O₂/kg), having a similar fatty acid composition as fresh soybean oil (peroxide value: 9.5 mEq O₂/kg) which was used as control. Moreover, according to a bifactorial design, two different vitamin E supplementary levels (11 vs. 511 mg α-to-copherol equivalents per kg diet) were used. The experiment was conducted with male Sprague-Dawley rats. The feeding period lasted for 40 days. In order to assess the vitamin E status, the vitamin E concentrations in plasma, liver, heart, kidney, and adipose tissue were determined. The vitamin E supply had a pronounced effect on the vitamin E concentrations of those tissues whereas the type of fat had only a slight effect. The fatty acid composition of total lipids from liver, erythrocytes, and low-density lipoproteins was also only slightly influenced by the oxidized fat. The osmotic fragility of erythrocytes was even reduced by feeding the oxidized oil. With a low vitamin E supply, the in vitro susceptibility of low-density lipoproteins to lipid peroxidation was slightly increased by feeding the oxidized oil. In contrast, with a high vitamin E supply, there was no adverse effect of the dietary oxidized oil on the susceptibility of low-density lipoproteins to lipid peroxidation. Feeding the oxidized oil, however, increased the concentrations of malondialdehyde in low-density lipoproteins suggesting an increased in vivo lipid peroxidation. Therefore, it cannot be ruled out that moderately oxidized dietary fats increase the atherogenicity of low-density lipoproteins. In contrast, a moderately oxidized oil scarcely affected the vitamin E status and the fatty acid composition of tissue lipids.     

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.     

Fatty acids of adipose tissue,plasma, muscle and duodenal ingesta of steers fed extruded soybeans

Effects of feeding a high-energy diet that contained extruded soybeans on fatty acid composition of lipids of adipose tissue, skeletal muscle and plasma were determined for 18 Angus steers. Steers weighing an average of 309 kg were fed either a control diet or a diet containing 14.3% extruded soybeans and 6% fat until they weighed 474 kg. A third group was fed the control diet for the first half of the experiment and the soybean-containing diet for the rest of the experiment. Samples of blood, muscle (M. trapezius) and subcutaneous adipose tissue were obtained at 309, 368 and 427 kg of body weight; steers were slaughtered at 474 kg body weight, and samples of subcutaneous and perirenal adipose tissues,M. longissimus and blood were obtained. The lipids of subcutaneous adipose tissue taken at slaughter of all steers fed full-fat, extruded soybeans contained 24% more 18:2 and 18:3 than did those of steers fed the control diet. Extruded soybeans also caused an increase in 18:3 but only a slight increase in 18:2 in perirenal adipose tissue. The proportion of unsaturated fatty acids of lipids inM. trapezius increased slightly with dietary soybeans, whereas that ofM. longissimus was not affected. Lipids of blood plasma of soybean-fed steers contained a greater proportion of 18:2 and 18:3 and concomitantly less 14:0, 15:0, 16:1 and 17:0. Results indicate that feeding steers enough extruded soybeans to raise the fat content of the diet to 6% increases the proportion of polyunsaturated fatty acids of tissue lipids of cattle, and that this altered composition results from an increased amount of these fatty acids being available for absorption by the small intestine.     

Effects of oxidized soybean oil on the vitamin A nutrition of the rat

Three lots of cold-pressed soybean oil were treated with bubbling oxygen for 70, 80, and 180 hrs. at 70°C. and fed to rats at a level of 18% in diets which were nutritionally adequate but devoid of vitamin A. Untreated soybean oil was fed in similar control diets. Subgroups of 15 weanling rats each were given graded injections of vitamin A acetate intramuscularly each week. Diarrhea developed in the rats fed the diets containing oxidized oil. This condition soon subsided in the groups receiving vitamin A injections but not in the vitamin A-free group. Diarrhea was not noted in the rats receiving the untreated soybean oil, without respect to the amount of vitamin A they received. The rats on the vitamin A-free diets developed deficiency more rapidly when the diet contained oxidized rather than the untreated oil. The food efficiencies of the groups fed the oxidized oils were lower than the controls. The intestines of the groups receiving the oxidized oils were distended with fluid and were hemorrhagic. Enlarged kidneys were noted in the vitamin A-deficient control as well as in test rats. The retroperitoneal lipids of the groups on the oxidized oil were less unsaturated, had lower refractive indices, higher peroxide values, and higher carbonyl values than comparable groups fed the control oil. Vitamin A deficiency decreased the unsaturation of the kidney and liver lipids but increased that of the retroperitoneal lipids. Injections of increasing amounts of vitamin A produced increases in the unsaturation of the body lipids. The kidney lipids of the groups on the oxidized oil diets were less unsaturated and contained more peroxidic compounds than the controls. Vitamin A deficiency increased the peroxidic compounds in the kidney and liver lipids, even in rats fed the control oil. The liver lipids of the groups fed oxidized oil were less unsaturated, lower in vitamin A content, and higher in peroxide compounds than the controls. The vitamin A content of the whole blood varied in relation to the amounts injected. The content of tocopherol in the tissues were not affected significantly by the oxidized oil in the diet. The evidence indicates that severely oxidized oil may destroy vitamin A in the tissue of the rat, thereby hastening the development of deficiency on vitamin A-free diets, reducing the storage of injected vitamin A, and increasing the vitamin A requirement. These effects are with abused oil and should not be interpreted to mean that the mildly oxidized oils and fats, such as those in the diets of human beings in this country are toxic. 1 Read in part at the 36th Fall meeting. American Oil Chemists' society, Chicago, October 20–22, 1958. 2 Assisted by a grant from the Roche Anniversary, Fund, Hoffmann LaRoche Inc. 3 Contribution No. 414 from the Department of Nutrition. Food Science and Technology, Massachusetts Institute of Technology, Cambridge, Mass.     

Effects of dietary antioxidants on in vivo lipid peroxidation in the rat as measured by pentane production

The hypothesis that pentane is an in vivo product of lipid peroxidation was confirmed by a study of the effects of a nonbiological antioxidant on pentane production in rats fed a diet deficient in vitamin E and supplemented with 0.01% N,N′-diphenyl-p-phenylenediamine (DPPD). Seven rats were fed a vitamin E-deficient diet starting at 3 wk of age. After 5 wk, 0.01% DPPD was added to the diets of three rats (group DPPD) while the diet of the other four rats remained unchanged (group OE). Within 2 wk of the diet change, rats in group DPPD exhaled 65% less pentane than rats of the same age in group OE. After 5 wk of being fed the DPPD-supplemented diet, rats in group DPPD were again fed the basal vitamin E-deficient diet; within 3 wk, these rats produced pentane levels similar to those of rats in group OE. The effects of vitamin E depletion and repletion on in vivo lipid peroxidation in rats were also studied. Three groups of three rats each were initially fed a vitamin E-deficient diet starting at 3 wk of age. After 8, 8, and 5 wk of being fed this diet, the three groups were fed diets supplemented with 3.3 (group 0→3.3E), 11 (group 0→11 E), and 200 (group 200E) i.u. vitamin E acetate/kg diet, respectively. Another group of three rats (group 11 E) was fed a diet supplemented with 11 i.u. vitamin E/kg starting at 3 wk of age for the duration of the study. There were significant decreases in pentane production by rat groups 0→3.3E, 0→11E, and 200E within 2 wk of the change to the vitamin E-supplemented diets. After about 5 wk of being fed their respective vitamin E-supplemented diets, pentane breath levels had stabilized. Breath pentane levels were inversely proportional to the log of dietary vitamin E concentration.     

Hydroxystearic acid deposition and metabolism in rats fed hydrogenated castor oil

Groups of rats were fed diets containing corn oil, 1% hydrogenated castor oil (principal constituent: 12-hydroxystearic acid) or 10% hydrogenated castor oil. Rats were sacrificed after 4, 8, 12 and 16 weeks for determination of hydroxy fatty acids in excised abdominal adipose tissue or in lipid extracted from lyophilized carcass. Maximum content of hydroxystearic acid was 4.4% in adipose tissue of rats four weeks on the 10% hydrogenated castor oil diet. When rats on hydrogenated castor oil diets were switched to the corn oil diet, hydroxystearic acid was depleted from their tissues. 10-Hydroxypalmitic and 9-hydroxymyristic acids were characterized as metabolites of 12-hydroxystearic acid. No adverse effects of diets were observed except reduced growth in rats given 10% hydrogenated castor oil diet. Presented at the AOCS Meeting, New York, October, 1968. Western Utiliz. Res. & Dev. Div., ARS, USDA.     

Lung surfactant and fatty acid composition of lung tissue and lavage of rats fed diets containing different lipids

Two nutritional models, essential fatty acid (EFA) deficiency and the feeding of saturated vs unsaturated fats, were used to determine the effects of dietary lipids on the fatty acid composition of rat lung and lavage. Semipurified diets containing 7% corn oil, 7% hydrogenated coconut oil (EFA-deficient), 10% butter or 10% safflower oil were fed to dams during lactation and thereafter to their offspring for a total of 24 weeks. Lipids were extracted from the lung lavage and lung tissue and their fatty acid composition was determined. The content of dipalmitoylphosphatidylcholine (DPPC), the main surfactant in the lungs, was also determined. The results show that the levels of DPPC in the lungs of rats fed 10% butter decreased although the decrease in the EFA-deficient rats was greater. Comparing rats fed butter with those fed corn oil, there were also modifications in the fatty acid composition of the total lipids and phospholipids of lung tissue and lavage as well as in phosphatidylcholine, phosphatidylethanolamine and phosphatidylinositol +phosphatidylserine fractions isolated from the lung tissue. The changes in fatty acid composition were somewhat fewer in rats fed butter then in those fed an EFA-deficient diet. The results suggest that a marginal EFA deficiency produced in rats by long-term feeding of 10% butter may account for the reduction in DPPC levels and in the changes in fatty acid composition in the lung tissue and lavage.