The effect of clofibrate on heart and plasma lipids in rats fed a diet containing rapeseed oil

The effect of clofibrate on heart and plasma lipids in rats fed a diet containing 30% of the calories as peanut oil (PO) or rapeseed oil (RSO) (42.7% erucic acid and 0.5% eicosenoic acid) was studied. A decrease of erucic acid content to one-third and concomitant increase in the content of 18∶1, 16∶1 and 16∶0 fatty acids in plasma triacylglycerols were observed after administration of clofibrate to rats fed the RSO-diet. It is suggested that these changes reflect the increased capacity of the liver to chainshorten very long chain length fatty acids. The extent of lipidosis in the heart of rats fed the RSO-diet was decreased by 50% by clofibrate. However, the concentration of erucic acid in heart triacylglycerols decreased much less (30%) than the concentration of all other fatty acids (50–65%). It is concluded that the clofibrate administration increased the oxidative capacity of the heart mitochondria and that the heart cell does not have an efficient system to handle very long chain length monounsaturated fatty acids as does the liver.     

Effects of coconut oil on heart lipids and on fatty acid utilization in rapeseed oil

Male adult Sprague-Dawley rats were fed diets containing 15% by weight of sunflower oil, coconut oil, rapeseed oil or combinations of these oils for 5 or 60 days. The digestibility of erucic acid (22∶1), lauric acid (12∶0) and linoleic acid (18∶2) was measured and found to be decreased for erucic acid at both time intervals, and for lauric acid after 60 days when coconut oil and rapeseed oil were blended. The cardiac lipodosis was proportional to the content of erucic acid in the diet. At 60 days, the high level of 22∶6 in the cardiac phospholipids of rats fed rapeseed oil was reduced by the addition of sunflower oil but not by coconut oil. Thus, the blending of rapeseed oil with coconut oil apparently is less desirable than that of rapeseed oil and sunflower oil.     

The effect of dietary erucic acid on cardiac triglycerides and free fatty acid levels in rats

Male Sprague-Dawley rats, 3 weeks of age, were fed semisynthetic diets containing test oils at 20% by weight for 3 days, 1 week, and 16 weeks. The test oils contained up to 22.3% erucic acid. Growth retardation was evident in rats fed rapeseed oil high in erucic acid, and soybean oil and Tower rapeseed oil diets containing about 5% erucic acid. Cardiac triglyceride accumulation was found in rats fed diets containing about 5% erucic acid but not in rats fed Tower rapeseed oil which contains 0.2% of this acid. The cardiac free fatty acid levels were low, 50–100 μg/g of wet heart tissue, and were not affected by feeding diets containing about 5% erucic acid. Feeding a diet containing a high erucic acid rapeseed oil did result in higher free fatty acid levels but only at 3 days and 1 week; the level at 16 weeks was similar to the other oils. The fatty acid analysis of cardiac triglycerides and free fatty acids showed high percentages of erucic acid at 3 days and 1 week; at 16 weeks these levels had declined significantly. The results indicate that the accumulated erucic and eicosenoic acids, at 3 days and 1 week, accounted for the increase in cardiac free fatty acids when rats were fed the high erucic acid rapeseed oil. There appears to be no evidence that the early cardiac triglyceride or free fatty acid accumulation is related to the formation of the long term myocardial lesions. Contribution No. 739 Animal Research Institute.     

Changes in rat heart phospholipid composition after rapeseed oil feeding

The influence of long duration rapeseed oil feeding with high or low levels of erucic acid has been investigated on rat heart phospholipids. The rats treated for 20 wk with rapeseed oil containing 46.2% erucic acid showed a twofold increase in the sphingomyelin content of the heart. Treatment with primor rapeseed oil (3.7% erucic acid) for 20 wk did not modify phospholipid composition of rat heart. The fatty acid patterns of phosphatidylethanolamine and phosphatidylcholine were slightly influenced by the high erucic rapeseed oil; eicosenoic acid was incorporated preferentially into position one, but erucic acid showed a random distribution in both. After high erucic rapeseed oil feeding, 22∶1 was incorporated into cardiolipin (5.6%) and sphingomyelin (10.5%). The incorporation of 22∶1 into sphingomyelin was associated with an increase of the percentage of 24∶1 (14.6%) and a decrease of saturated long chain fatty acid (22∶0, 24∶0) percentages. Primor rapeseed oil caused a slight increase of 24∶1 and a decrease of 22∶0 and 24∶0 in rat heart sphingomyelin. As cardiolipin is localized in the inner membrane of mitochondria and sphingomyelin in plasma and microsomal membranes, the acyl-moiety alterations of both phospholipids might be correlated to the pathological lesions of rat heart after a long duration of rapeseed oil feeding.     

The effect of dietary fatty acid balance on myocardial lesions in male rats

Three hundred (experiment I) and 350 (experiment II) weanling, 3-week-old male Sprague-Dawley rats weighing between 40–50 g were randomly assigned two per cage and 50 per dietary treatment to study the effect of dietary fatty acid balance on myocardial lesions. The following oils were tested: Experiment I.Brassica napus var. Tower rapeseed oil [Tower RSO, 1974 cultivar and 1975 cultivar, each containing 0.3% erucic (22∶1) acid];B. napus var. Zephyr RSO containing 0.9% 22∶1; corn oil; olive oil; and soybean oil. Experiment II.B. napus var. Tower RSO (1974 cultivar), olive oil, soybean oil, and the following oils to which was added the indicated level of free 22∶1; Tower +0.5% 22∶1; Tower +5.6% 22∶1; olive oil +4.4% 22∶1; soybean oil +5.7% 22∶1. In each case the oils were incorporated in a semisynthetic diet at a level of 20% by weight. Heart and heart lipid weights of rats fed the different oils did not differ statistically from each other. Fatty acid analyses of heart lipids revealed that the fatty acid composition of the cardiac lipids reflected that of the diet fed. In experiment I, there was a definite but significantly lower incidence (P<0.01) and severity (P<0.01) of heart lesions in rats fed control oils (corn, olive, soybean) than in rats fed rapeseed oils. Also, in experiment II, a definite but lower incidence and severity of heart lesions occurred in rats fed control oils (soybean, olive) compared to rats fed Tower RSO or this oil with added free 22∶1. Adding 22∶1 to an oil naturally high in 18∶3 (soybean) did not alter the incidence of heart lesions, whereas adding 22∶1 to an oil naturally high in 18∶1 (olive) increased significantly (P<0.01) both the incidence and severity of heart lesions. Thus, it appears that the background incidence of heart lesions that are found in the rat in any case, and which are increased by rapeseed oil feeding, is caused by the imbalanced fatty acid composition of the oil for the growing rat, i.e. high monoenes (18∶1, 20∶1, and 22∶1) and high 18∶3 and is not only due to the presence of excess 18∶3. Contribution No. 706, Animal Research Institute.     

Composition of fatty acids and structure of triglycerides in medium and low erucic acid rapeseed

Total triglycerides in medium (MEAR) and low (LEAR) erucic acid cultivars of rapeseed were fractionated by argentation chromatography into twelve and ten fractions, respectively. Gas liquid chromatography of the fatty acids in the triglyceride fractions and their 2-monoglycerides was used to evaluate the structural characteristics of the individual fractions. Fractionation occurred on the basis of degree of unsaturation, molecular weight and positional characteristics. The most mobile fractions contained 34–50% of saturated fatty acids while the less mobile had 59–65% of polyunsaturated fatty acids. In the medium erucic acid oil, long chain fatty acids (C20–C22) were found in all fractions, but four fractions of low erucic acid oil were essentially free of long chain acids. Two of these fractions in the latter oil, which represented 44% of the total triglycerides, were glycerol trioleate and dioleoyllinoleoylglycerol. The majority of the 2-positions were occupied by unsaturated C18 fatty acids, generally in the order of linoleic ≥linolenic> oleic acids. The saturated and long chain fatty acids occurred predominantly in the 1-and 3-positions. The various fractions of medium and low erucic acid oils were similar in structural composition except that eicosenoic and erucic acids substituted for oleic acid in some external positions. Erucic acid did not appear to substitute directly for oleic acid in the 2-position.     

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.     

The effects of partially hydrogenated marine oils on the mitochondrial function and membrane phospholipid fatty acids in rat heart

The influence of dietary partially hydrogenated marine oils containing docosenoic acid on rat heart mitochondrial membrane phospholipid fatty acid composition was studied with particular reference to cardiolipin and oxidative phosphorylation. Five groups of male 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. All the cardiac phospholipids investigated were influenced by the experimental diets. An increased amount of arachidonic acid observed in phosphatidylethanolamine (PE) after feeding partially hydrogenated oils suggests a changed regulation of the arachidonic acid metabolism in comparison with PO treatment. 22∶1 originating from the dietary oils was incorporated only to a small extent into phosphatidylcholine (PC) and PE. A selective incorporation of 18∶1 isomers into the 1- and 2-positions of PC and PE with respect to geometry and position of the double bond was observed. Large amounts of 18∶1trans were incorporated into the 1-position of PC and PE, irrespective of the amount of 18∶2 supplemented to the diets, replacing a considerable proportion of stearic acid in this position. After feeding HHO and RSO, the content of 22∶1 in mitochondrial cardiolipin of rat heart was found to be 3% (mainly cetoleic acid) and 10% (mainly erucic acid), respectively, indicating a high affinity forcis isomers of 22∶1, but also a considerable resistance against incorporation oftrans isomers was observed. The ability of rat cardiac mitochondria to oxidize palmitoylcarnitine and to synthesize ATP was depressed after feeding HHO and RSO. Dietarycis isomers of 22∶1 seem to have a specific ability to interfere with cardiac ATP synthesis and also to alter the fatty acid composition of cardiolipin of rat heart.     

Effects of rapeseed oil on fatty acid oxidation and lipid levels in rat heart and liver

The comparative rates of oxidation of erucic and oleic acids and of their CoA esters were studied in heart and liver mitochondria of rats fed a standard diet or semisynthetic diets containing 25% of the calories as either rapeseed oil (46.6% erucic and 10.4% eicosenoic acid) or olive oil, for a period of 5 months. The long exposure to the diet containing 25% rapeseed oil did not alter the oxidative activity of mitochondria and did not induce morphological changes in the heart. It is confirmed that erucic acid is oxidized in mitochondria at lower rates than other long chain fatty acids and that its activation as CoA derivative may be one of the rate limiting steps of the overall oxidation process. Total lipids and triglycerides do not significantly change in the heart whereas they increase in the liver of rats fed the diet containing rapeseed oil.     

Changes in fatty acid composition of cardiac mitochondrial phospholipids in rats fed rapeseed oil

Male Wistar rats were fed rapeseed oil containing high or low levels or erucic acid for 20 weeks, and changes in the fatty acid composition of cardiac mitochondrial phospholipids were studied. Treatment with rapeseed oil containing 46.2% erucic acid showed incorporation of 22∶1 (5.6%) into isolated cardiolipin from heart mitochondria. After high or low (3.7%) erucic rapeseed oil feeding, linoleic acid was slightly incorporated into cardiolipin. Moreover, both of these rapeseed oils induced a significant increase of linoleate-arachidonate ratio in phosphatidylethanolamine and phosphatidylcholine. This ratio was also significantly increased in fatty acids esterified to the β-position of these phospholipids. On the basis of such results, we have to consider the role of linolenic acid which is present at a high level in the different rapeseed oils used, as a possible inhibitor of heart microsomal enzymes involved in linoleate arachidonate conversion. Such alterations might account for mitochondrial fragility and myocardial lesions obtained in long term rapeseed oil feeding experiments. ERA-CNRS n^o 070497     

Composition of seeds of cruciferous oil crops

Several species of the Cruciferae family are presently used as oilseed crops, viz.,Brassica campestris (turnip rape and sarson),B. juncea (brown or yellow mustard),B. napus (rape),Crambe abyssinica (crambe), andSinapis alba (white or yellow mustard). Seed oils of these species are characterized by variable but generally large amounts of erucic acid (22:1) in the triacylglycerols, which make up 95–98% of the total lipids of high quality, viable seeds. In addition to erucic acid, the major fatty acids are oleic (typically 10–25%), linoleic (10–20%), linolenic (7–11%) and eicosenoic (5–10%). However cultivars of rapeseed lacking erucic acid and having about 55–60% oleic, 20–25% linoleic and ca. 10% linolenic acid have been developed. The eicosenoic and erucic acids are located exclusively at the 1 and 3 positions of the triacylglycerol. As a consequence, major triacylglycerol types have carbon numbers 54, 56, 58, 60 and 62. The phospholipids of rapeseed are essentially devoid of erucic acid and have palmitic, oleic and linoleic acids as major fatty acids. Sterols generally amount to about 0.5% of the oil with β-sitosterol, campesterol and brassicasterol as major constituents (about 55%, 25% and 15%, respectively, of the total sterols). A few per cent of the total sterol fractions is cholesterol. The tocopherol content of rapeseed oil is about 800 ppm with α- and γ-tocopherol as major components. Cruciferous seeds contain a fairly large number of storage proteins. Thus approximately 50 components have been detected in alkaline extracts ofBrassica napus, a major portion of which are in the molecular weight range 120–150,000. The protein spectrum ofB. napus (rape) is more complex than that ofB. campestris (turnip rape) since the former species is an allotetraploid withB. oleracea (kale, cabbage, etc.) andB. campestris as parents. Approximately 5% of the fat free seed meal is composed of glucosinolates, which are split upon enzymatic hydrolysis to antinutritional factors: isothiocyanates, oxazolidinethiones and nitriles. The different crucifers discussed have both qualitative and quantitative differences with respect to glucosinolate content. One of nine papers presented at the Symposium, “Cruciferous Oilseeds,” ISF-AOCS World Congress, Chicago, September 1970.     

Comparison of lipid status in the hearts of piglets and rats on short term feeding of marine oils and rapeseed oils

A series of 4 experiments with piglets and one experiment with rats has been conducted to establish the cardiac lipid status of weanling (3 weeks old) male animals fed fats with different contents of docosenoic fatty acids. Experimental fats were rapeseed oil (RSO) (48.0% 22∶1), refined fish oil (RFO) (14.6% 22∶1), partially hydrogenated fish oil (PHFO) (14.3% 22∶1) and lard (0% 22∶1) combined with sunflower seed oil (SFO) in different proportions in diets with 21% total fat. Lipidosis could not be detected in piglets as increased heart weights, by chemical assay for myocardial contents of triglycerides, or by accumulation of docosenoic fatty acids or nonesterified fatty acids (NEFA). In rats, diets with RSO at a level of 16% increased myocardial triglyceride and docosenoic fatty acid contents about 7 times while the effect on cardiac NEFA was inconsistent. Histological examinations of the hearts revealed stainable intracellular fat droplets in some piglets fed 16% RSO for 8 to 13 days, but not after 2,4 and 6 and 16, 19 and 22 days of feeding. After 10 days of feeding, mild to moderate histological lipidosis was found in piglets fed diets containing 2% or more of 22∶1 fatty acids, with no significant difference between RSO, RFO and PHFO in this respect. The same diets in rats gave about 5 times more histological lipidosis than in piglets. This is attributed to a difference in species response, the rat reacting in a more pronounced manner than the piglet. The cardiac lipidosis no-effect level in piglets corresponded to a daily intake of docosenoic fatty acids of 0.4 g per kg body weight. Mild lipidosis was also found in a few animals on docosenoic acid-free diets.     

Influence of elaidate and erucate on heart mitochondria

Male, weanling rats were fed, for up to six weeks, corn oil (CO), rapeseed oil (RSO), partially hydrogenated fat (HF), or a mixture of partially hydrogenated fat and corn oil (HF+CO). The respiratory activity of their isolated heart mitochondria, their hormone-sensitive lipase activity, and the fatty acid compositions of the phospholipids of the mitochondria were determined. The results indicated that heart mitochondria isolated from rats which had been fed corn oil (CO) had a higher rate of oxygen uptake, showed higher respiratory control ratios, higher ADP/0 ratios and a higher rate of ATP synthesis than the heart mitochondria isolated from those fed rapeseed oil or hydrogenated fats. The oxygen uptake rates of the rat heart mitochondria isolated from each dietary group of rats was in order: oleyl carnitine ≫ erucyl carnitine > elaidyl carnitine. The decreased capacity to oxidize substrate by heart mitochondria which had been isolated from the hearts of rats fed rapeseed or hydrogenated soybean oil as compared with those fed corn oil as a sole source of dietary fat seemed related to the mitochondria lipid composition. The type of dietary fat fed had a pronounced influence on the mitochondrial fatty acid compositions of phosphatidylcholine, phosphatidylethanolamine, and cardiolipin. The lipase activity of the RSO-fed group did not show any increment with either epinephrine or supplemental ATP treatment. The substrate preference for lipase activity in myocardium was corn oil-triglycerides > trierucin > trielaidin > tripalmitin. However, cardiac lipid accumulation did not seem related to lipase activity in the myocardium. Taken from a thesis submitted by Chi Ming Lee Hsu in partial fulfillment of the Ph.D. degree in Food Science, University of Illinois at Urbana-Champaign.     

The effect of long-chain monoenes on prostaglandin E2 synthesis by rat skin

In order to ascertain whether the dermal lesions observed in male rats fed rapeseed oils are due to impaired prostaglandin biosynthesis, endogenous levels of prostaglandin E₂ (PGE₂) in skin and the capacity of this tissue to synthesize PGE₂ from arachidonic acid was investigated. Male Sprague-Dawley rats were fed from weaning for 8 weeks either a standard rat diet (chow) or semisynthetic diets containing 20% by weight of the following fat sources: corn oil; commercial lard; commercial lard to which was added 5.4% free erucic acid; rendered pig fat; or the following rapeseed oils:Brassica napus var. Zephyr;B. campestris var. Span;B. campestris var. Arlo (15%) and var. Echo (85%) designated HEAR (high erucic acid rapeseed). The long-chain monoene content (18∶1, 20∶1, and 22∶1) of the diets fed ranged from 30 to 71 mole % and that of skin from 27 to 74 mole %. A significant (P<0.01) correlation was found between the level of 18∶2n−6 in the diet and the endogenous PGE₂ levels in skin and the capacity of this tissue to synthesize PGE₂. No relationship was found between these two PGE₂ parameters and the level of erucic acid in the diet. The rate of turnover of PGE₂ appeared to be lower in rats fed rapeseed oil as evidenced by the relatively high endogenous PGE₂ levels when these oils were fed (96 to 105 μg/g). On the other hand, the lowest capacity for PGE₂ synthesis was found with skin from rats fed Zephyr rapeseed oil, rats which also had the most severe incidence of hair loss and dermal lesions. Significant (P<0.01) negative correlations were observed between the level of monoenes and specifically the level of oleic (18∶1n−9) acid in the diets and PGE₂ synthesis capacity of skin, possibly confirming the known inhibitory effect of 18∶1n−9 on the prostaglandin synthesizing enzyme system. Contribution No. 687, Animal Research Institute.     

Effects of dietary saturated fat on erucic acid induced myocardial lipidosis in rats

Male Sprague-Dawley rats were fed for one week diets containing 20% by weight fat/oil mixtures with different levels of erucic acid (22∶1n−9) (∼2.5 or 9%) and total saturated fatty acids (∼8 or 35%). Corn oil and high erucic acid rapeseed (HEAR) oil were fed as controls. The same hearts were evaluated histologically using oil red O staining and chemically for cardiac triacylglycerol (TAG) and 22∶1n−9 content in cardiac TAG to compare the three methods for assessing lipid accumulation in rat hearts. Rats fed corn oil showed trace myocardial lipidosis by staining, and a cardiac TAG content of 3.6 mg/g wet weight in the absence of dietary 22∶1n−9. An increase in dietary 22∶1n−9 resulted in significantly increased myocardial lipidosis as assessed histologically and by an accumulation of 22∶1n−9 in heart lipids; there was no increase in cardiac TAG except when HEAR oil was fed. An increase in saturated fatty acids showed no changes in myocardial lipid content assessed histologically, the content of cardiac TAG or the 22∶1n−9 content of TAG at either 2.5 or 9% dietary 22∶1n−9. The histological staining method was more significantly correlated to 22∶1n−9 in cardiac TAG (r=0.49;P<0.001) than to total cardiac TAG (r=0.40;P<0.05). The 22∶1n−9 content was highest in cardiac TAG and free fatty acids. Among the cardiac phospholipids, the highest incorporation was observed into phosphatidylserine, followed by sphingomyelin. With the addition of saturated fat, the fatty acid composition showed decreased accumulation of 22∶1n−9 and increased levels of arachidonic and docosahexaenoic acids in most cardiac phospholipids, despite decreased dietary concentrations of their precursor fatty acids, linoleic and linolenic acids.     

Myocardial changes in newborn piglets fed sow milk or milk replacer diets containing different levels of erucic acid

This study was undertaken to determine whether the neonate was more susceptible to the effects of dietary erucic acid (22∶1n−9) than the adult. Newborn piglets were used to assess the safety of different levels of 22∶1n−9 on lipid and histological changes in the heart. Newborn piglets showed no myocardial lipidosis as assessed by oil red 0 staining, but lipidosis appeared with consumption of sow milk and disappeared by seven days of age. Milk replacer diets containing soybean oil, or rapeseed oil mixtures with up to 5% 22∶1n−9 in the oil, or 1.25% in the diet, gave trace myocardial lipidosis. Rapeseed oil mixtures with 7 to 42.9% 22∶1n−9 showed definite myocardial lipidosis in newborn piglets, which correlated to dietary 22∶1n−9, showing a maximum after one week on diet. The severity of the lipidosis was greater than observed previously with weaned pigs. There were no significant differences among diets in cardiac lipid classes except for triacylglycerol (TAG), which increased in piglets fed a repeseed oil with 42.9% 22∶1n−9. TAG showed the highest incorporation of 22∶1n−9, the concentration of 22∶1n−9 in TAG was similar to that present in the dietary oil. Among the cardiac phospholipids, sphingomyelin and phosphatidylserine had the highest, and diphosphatidylglycerol (DPG) the lowest level of 22∶1n−9. The low content of 22∶1n−9 in DPG of newborn piglets is not observed in weaned pigs and rats fed high erucic acid rapeseed oil. The relative concentration of saturated fatty acids was lowered in all cardiac phospholipids of piglets fed rapeseed oils, possibly due to the low content of saturated fatty acids in rapeseed oils. The results suggest that piglets fed up to 750 mg 22∶1n−9/kg body weight/day showed no adverse nutritional or cardiac effects.     

Nutritional and toxicological evaluation of rubber seed oil

Rubber (Hevea brasiliensis) seed oil (RSO) is available in India (Ca. 4500 tons per year) and is used mainly as a drying oil. The oil does not contain any unusual fatty acids, and it is a rich source of essential fatty acids C_18∶2 and C_18∶3 that make up 52% of its total fatty acid composition. Acute toxic potential in rats and the systemic effects and nutritional quality were assessed in a 13 week feeding study in weanling albino rats using a diet containing RSO or groundnut oil (GNO) (as the control) at a 10% level as the sole source of dietary fat. RSO did not manifest any acute toxic potential. Food consumption, growth rate and feed efficiency ratio of rats fed RSO were similar to those fed GNO. The digestibility of this oil was found to be 97%, as compared to 94% for GNO. There were no macroscopic or microscopic lesions in any of the organs which could be ascribed to the RSO incroporation in the diet. Thus the current data show that RSO could be used for edible purposes. However, it will be necessary to process the oil to achieve deodorization and to remove free fatty acids to make it organoleptically acceptable.     

Genetic control of fatty acid biosynthesis in rapeseed (Brassica napus L.)

Isolation of rapeseed plants containing no erucic acid in their seed oil gave simultaneous selection for low eicosenoic acid. Genetic analy-sis of populations segregating for erucic acid content indicated that the synthesis of these fatty acids was controlled, in the developing embryo, by two genes which displayed no domi-nance and acted in an additive manner. As the genetic capacity for erucic acid synthesis de-creased, there was an increase in percentage of oleic acid with no corresponding decrease in total oil content. The percentage of eicosenoic acid re-mained relatively constant with decreasing erucic acid except in the zero erucic acid genotype where only 1% eicosenoic was detected instead of approx 12%. These observations were in-terpreted to mean that eicosenoic and erucic acids were formed by a genetically controlled carbon chain lengthening system operating by the addi-tion of acetate molecules to the carboxyl end of oleic acid. This hypothesis was supported by data obtained from the injection of radioactive sodium acetate into immature rapeseed pods. In the monoene fraction of the oil, eicosenoate had three times the specific activity of oleate and erucate had twice the activity of eicosenoate. On oxidation, the monocarboxylic fragments of these three acids had low and similar specific activities while in the dicarboxylic acids, where chain elongation has presumably taken place, activity increased in the ratio of 1:5:19. AOCS Bond Award, Fall 1963.     

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.     

Effect of very long chain fatty acids on peroxisomal β-oxidation in primary rat hepatocyte cultures

Previous studies have demonstrated that certain high fat diets can induce peroxisomal fatty acid β-oxidation in rodent liver and that this may be due to their content oftrans 22∶1 fatty acids. In this study we have examined the effects ofcis andtrans 22∶1 fatty acids (erucic and brassidic) and oleic acid (18∶1) on palmitoyl-CoA oxidation, carnitine acetyltransferase and carnitine palmitoyltransferase activities in primary rat hepatocyte cultures. Brassidic and erucic acid and, to a lesser extent, oleic acid were cytotoxic to rat hepatocytes. However, at a concentration of 0.1 mM, brassidic acid produced small increases in palmitoyl-CoA oxidation and carnitine acetyltransferase activities in hepatocytes cultured 70 hr. Treatment of cells with 0.1 and 0.3 mM of either erucic or oleic acid had no effect on any of the enzymes measured.