Monoethylenic isomers in cardiac lipids of rats fed partially hydrogenated herring oil

Compositional studies have been carried out to compare the monoethylenic fatty acid isomers of a partially hydrogenated herring oil with those found in the cardiac lipid of young rats fed this oil for 1 or 16 weeks. In general, all geometrical and positional isomers with chain lengths C₁₆, C₁₈, C₂₀ and C₂₂ found in the hydrogenated oil were also observed in cardiac lipid. Evidence was also obtained for the occurrence of β-oxidation in the catabolism of thecis andtrans isomers of these long chain acids. Presented at the AOCS Meeting, Ottawa, September 1972.     

Myocardial alterations resulting from feeding partially hydrogenated marine oils and peanut oil to rats

Myocardial alterations were observed in 5 groups of rats fed diets containing 20% fat for 16 weeks. The incidence was comparable to that from other studies and uniform at 6/20 in hearts from rats fed: partially hydrogenated herring oil to give dietary levels of either 16.7% or 4.6% 22∶1; partially hydrogenated redfish/flatfish oil to give 4.5% 22∶1 in the dietary fat; and peanut oil (of unknown origin) containing 0.1% 22∶1. The incidence was 9/20 in the hearts of rats fed an unrefined and unprocessed redfish oil at a dietary level of 16.0% 22∶1 in fatty acids.     

Hydrocarbons of dogfish and cod livers and herring oil

Dogfish and cod liver oils and the oil from the whole herring were saponified and the hydrocarbons concentrated by chromatography of the unsaponifiable portion over alumina followed by silica gel treatment of the resulting fractions. Temperature programmed gas chromatography employing a 3% SE-30 packing was applied to the analysis of hydrocarbons of C₁₄ to C_32.5. The paraffins comprised two or more groups. Dogfish liver oil gave rise to 7.62% unsaponifiables and pristane, other saturated types, squalene and an additional group, high in unsaturated components, were 193, 325, 308 and 200 mg% in this portion or 15.7, 24.8, 23.5 and 15.3 mg%, respectively, in the oil. Cod liver oil yielded 1.0% unsaponifiables of which the above hydrocarbons in the order stated amounted to 0.30%, 1.15%, 3.29% and 2.27% or 3.0, 11.5, 32.9 and 22.7 mg% in the liver oil. The unsaponifiable material of herring oil (1.35%) was prominent in paraffinic hydrocarbons, the levels of the above specified components being 16.34%, 3.51%, 0.99% and 1.41% as stated or 221, 47.4, 13.4 and 19.1 mg% in the oil. The sterol and alcoholic contents were ascertained for the three marine oils and the glyceryl ether levels found to be highest for dogfish liver oil.     

Sterol metabolism studies in rats: Effects of taurodeoxycholic acid feeding on sterol metabolism

Sterol metabolism studies using isotopic and chromatographic techniques were carried out in: (a) control rats fed stock chow +0.1% cholesterol (control group), and (b) rats fed stock chow +0.1% cholesterol and supplemented with 0.5% sodium taurodeoxycholate (taurodeoxycholate group). Feeding the bile acid enriched diet led to decreased acidic steroid synthesis, decreased cholesterol turnover, and cholesterol balance compared to nonsupplemented controls. There were no significant differences in fecal neutral sterol output, endogenous neutral sterol output, or cholesterol absorption between bile acid fed animals and controls. Tissue cholesterol levels (liver, plasma, and bile) in the two groups were also similar.     

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.     

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.     

Effect of chitosan feeding on intestinal bile acid metabolism in rats

The effect of chitosan feeding (for 21 days) on intestinal bile acids was studied in male rats. Serum cholesterol levels in rats fed a commercial diet low in cholesterol were decreased by chitosan supplementation. Chitosan inhibited the transformation of cholesterol to coprostanol without causing a qualitative change in fecal excretion of these neutral sterols. Increased fiber consumption did not increase fecal excretion of bile acids, but caused a marked change in fecal bile acid composition. Litcholic acid increased sigificantly, deoxycholic acid increased to a leasser extent, whereas hyodeoxycholic acid and the 6β-isomer and 5-epimeric 3α-hydroxy-6-keto-cholanoic acid(s) decreased. The pH in the cecum and colon became elevated by chitosan feeding which affected the conversion of primary bile acids to secondary bile acids in the large intestine. In the cecum, chitosan feeding increased the concentration of α-,β-, and ω-muricholic acids, and lithocholic acid. However, the levels of hyodeoxycholic acid and its 6β-isomer, of monohydroxy-monoketo-cholanoic acids, and of 3α, 6ξ, 7ξ-trihydroxy-cholanoic acid decreased. The data suggest that chitosan feeding affects the metabolism of intestinal bile acids in rats.     

Cold acclimation or grapeseed oil feeding affects phospholipid composition and mitochondrial function in duckling skeletal muscle

The phospholipid fatty acid (FA) composition and functional properties of skeletal muscle and liver mitochondria were examined in cold-acclimated (CA, 4°C) ducklings. Phospholipid FA of isolated muscle mitochondria from CA birds were longer and more unsaturated than those from thermoneutral (TN, 25°C) reared ducklings. The rise in long-chain and polyunsaturated FA (PUFA, mainly 20∶4n-6) was associated with a higher State 4 respiration rate and a lower respiratory control ratio (RCR). Hepatic mitochondria, by contrast, were much less affected by cold acclimation. The cold-induced changes in phospholipid FA profile and functional properties of muscle mitochondria were reproduced by giving TN ducklings a diet enriched in grapeseed oil (GO, rich in n-6 FA), suggesting a causal relationship between the membrane structure and mitochondrial functional parameters. However, hepatic mitochondria from ducklings fed the GO diet also showed an enrichment in long-chain PUFA but opposite changes in their biochemical characteristics (lower State 4, higher RCR). It is suggested that the differential modulation of mitochondrial functional properties by membrane lipid composition between skeletal muscle and liver may depend on muscle-specific factors possibly interacting with long-chain PUFA and affecting the proton leakiness of mitochondrial membranes.     

Studies on phospholipids with particular reference to cardiolipin of rat heart after feeding rapeseed oil

The influence of dietary rapeseed oil on the lipid classes and fatty acid pattern of rat heart homogenate and mitochondria has been investigated after feeding a diet with 9.8% by wt erucic acid for 10 days and 1.4% and 2.6% erucic acid for 28 days. The rats treated with 9.8% erucic acid showed a significant increase in the triglycerides of the heart mitochondria. This tendency was much less pronounced in rats treated with 1.4 and 2.6% erucic acid, respectively. In all experiments, the triglycerides of the heart mitochondria showed a high content of erucic acid. The fatty acids of phosphatidylcholine, phosphatidylethanolamine, and cardiolipin were all influenced by the dietary rapeseed oil, but the erucic acid seemed to have a specific affinity to cardiolipin. Cardiolipin of rat heart mitochondria was isolated and identified with gas chromatography and mass spectrometry. The isolated cardiolipin was found to contain 12% erucic acid after feeding 9.8% erucic acid as rapeseed oil for 10 days. Similar results were obtained after feeding glyceryl trierucate for 5 days to rats. The incorporation of erucic acid into cardiolipin was followed by a corresponding decrease of linoleic acid. This observation is of great interest because the molecular structure of fatty acids in lipid molecules has a profound influence on the packing of these molecules in a bilayer. Since cardiolipin is a component of the inner membrane of mitochondria its high affinity for erucic acid might influence the normal function of the inner membrane of heart mitochondria.     

Effects of cholesterol feeding to maternal rats on metabolism of cholesterol and bile acids in the dams and their offspring

The influence of feeding cholesterol to rats during pregnancy and postpartum (from the 11th day of gestation to the third day after delivery) on the serum and hepatic cholesterol levels and on the bile acid composition in the pool and in the liver in relationship to the dams and their pups was examined. The hepatic content of cholesterol in both dam and offspring increased during cholesterol feeding without any changes in serum cholesterol level. In the dams, mainly the esterified cholesterol was increased; in the pups, mainly the free cholesterol was increased. Cholesterol feeding led to a pronounced increase in the pool of β-muricholic acid and a relative decrease in the lithocholic acid concentration in pregnant rats. In fetal rats, the chenodeoxycholic acid pool was increased by cholesterol intake. The lithocholic acid pool was larger in the postpartum rats fed cholesterol than in the controls, while the concentration of α- and β-muricholic acids was decreased. The neonates of cholesterol-fed dams had a larger pool of chenodeoxycholic acid but a smaller pool of β-muricholic acid. These results suggest that the metabolism of cholesterol and of bile acids in dams and their offspring respond differently to cholesterol intake.     

Effects of feeding chenodeoxycholic acid on metabolism of cholesterol and bile acids in germ-free rats

The aim of this investigation was to study the influence of chenodeoxycholic acid administration on cholesterol and bile acid synthesis in germ-free rats. Seven rats were fed a basal diet and 2 groups of 4 rats received the same diet supplemented with 0.4 and 1% chenodeoxycholic acid, respectively. After 6 weeks, feces were collected in one 3- and one 4-day pool for analysis of cholesterol and bile acids. When the sampling period was finished, the rats were killed and the liver microsomal fractions isolated. The activities of HMG CoA reductase and cholesterol 7α-hydroxylase were determined, the 7α-hydroxylase by a mass fragmentographic method. The 2 dominating bile acids in the untreated rats were cholic acid and β-muricholic acid. During treatment with chenodeoxycholic acid, 60–70% of this bile acid was converted into α- and β-muricholic acid, indicating a high activity of the 6β-hydroxylase. The excretion of cholic acid was almost completely inhibited and the 7α-hydroxylase activity was decreased ca 75% in the rats fed 1% chenodeoxycholic acid. The activity of the hepatic HMG CoA reductase was unchanged. The fecal excretion of cholesterol increased 2–3 times. An accumulation of cholesterol was seen in the rats treated with 1% chenodeoxycholic acid, which was probably a result of the decreased catabolism of cholesterol to bile acids.     

The effects of a dietary oxidized oil on lipid metabolism in rats

This study was carried out to investigate the effects of a dietary oxidized oil on lipid metabolism in rats, particularly the desaturation of fatty acids. Two groups of rats were fed initially for a period of 35 d diets containing 10% of either fresh oil or thermally treated oil (150°C, 6d). The dietary fats used were markedly different for lipid peroxidation products (peroxide value: 94.5 vs. 3.1 meq O₂/kg; thiobarbituric acid-reactive substances: 230 vs. 7 μmol/kg) but were equalized for their fatty acid composition by using different mixtures of lard and safflower oil and for tocopherol concentrations by individual supplementation with dl-α-tocopherol acetate. In the second period which lasted 16 d, the same diets were supplemented with 10% linseed oil to study the effect of the oxidized oil on the desaturation of α-linolenic acid. During the whole period, all the rats were fed identical quantities of diet by a restrictive feeding system in order to avoid a reduced food intake in the rats fed the oxidized oil. Body weight gains and food conversion rates were only slightly lower in the rats fed the oxidized oil compared to the rats fed the fresh oil. Hence, the effects of lipid peroxidation products could be studied without a distortion by a marked reduced food intake and growth. To assess the rate of fatty acid desaturation, the fatty acid composition of liver and heart total lipids and phospholipids was determined and ratios between product and precursor of individual desaturation reactions were calculated. Rats fed the oxidized oil had reduced ratios of 20∶4n−6/18∶2n−6, 20∶5n−3/18∶3n−3, 20∶4n−6/20∶3n−6, and 22∶6n−3/22∶5n−3 in liver phospholipids and reduced ratios of 20∶4n−6/18∶2n−6, 22∶5n−3/18∶3n−3, and 22∶6n−3/18∶3n−3 in heart phospholipids. Those results suggest a reduced rate of desaturation of linoleic acid and α-linolenic acid by microsomal Δ4-, Δ5-, and Δ6-desaturases. Furthermore, liver total lipids of rats fed the oxidized oil exhibited a reduced ratio between total monounsaturated fatty acids and total saturated fatty acids, suggesting a reduced Δ9-desaturation. Besides those effects, the study observed a slightly increased liver weight, markedly reduced tocopherol concentrations in liver and plasma, reduced lipid concentrations in plasma, and an increased ratio between phospholipids and cholesterol in the liver. Thus, the study demonstrates that feeding an oxidized oil causes several alterations of lipid and fatty acid metabolism which might be of great physiologic relevance.     

Feeding rats with liposomes or fish oil differently affects their lipid metabolism

Two n‐3 polyunsaturated fatty acid (PUFA)‐rich diets differing in their chemical and physical forms were given to rats during 2 wk. Liposomes [phospholipids (PL) organized in bilayer structures] made from a natural marine lipid extract or a mixture of fats containing fish oil [similar fatty acids esterified in triacylglycerols (TAG)] were used. The influence of n‐3 PUFA dietary sources on plasma parameters, i.e. TAG, cholesterol and PL concentrations, was investigated. A similar hypotriglyceridemic effect of n‐3 PUFA from liposomes or fish oil was observed. In contrast, feeding rats with liposomes led to different PL and cholesterol patterns. In the plasma of rats fed liposomes, total cholesterol amounts were positively correlated with PL levels. Liposome and fish oil feedings caused a marked increase in the amounts of n‐3 PUFA, which occurred mainly at the expense of n‐6 PUFA. However, the enrichment in n‐3 PUFA in the different plasma lipid classes differed substantially when ingested in the form of fish oil or liposomes. These results were interpreted in terms of different lipid bioavailability and metabolic fate during the digestive steps and in the liver, with the dietary source.     

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     

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.     

Effects of dietary triolein and sunflower oil on insulin release and lipid metabolism in zucker rats

Obese and lean male Zucker rats were fed ad libitum on diets containing either 50 (L) or 200 (H) g/kg diet of either triolein (T) or sunflowerseed oil (S). The specific activity of the hepatic microsomal Δ9 desaturase enzyme was depressed in both lean and obese rats fed the HS diet compared with the other three diets. The fatty acid composition of liver and subcutaneous white adipose tissue lipids were consistent with a lower Δ9 desaturation activity in rats fed the H diets, particularly for the HS diet. In both genotypes, microsomal Δ9 desaturase activity and the ratio of 16∶1/(16∶0+16∶1) fatty acids in liver lipids were inversely related to the proportion of 18∶2 in liver lipid. Plasma insulin concentrations and rates of glucose-stimulated insulin release in vivo were higher in obese rats compared with lean rats, and plasma insulin levels were higher in rats fed S compared with T. There was no relationship between Δ9 desaturase activity and either plasma insulin concentration or rates of insulin release in vitro. These findings suggest that hepatic Δ9 desaturase activity of Zucker rats is responsive to changes in the proportion of 18∶2 in liver lipids but is not affected by changes in insulin secretion.     

Cardiopathogenicity of soybean oil and tower rapessed oil triglycerides when fed to male rats

The triglycerides of soybean oil were purified by molecular distillation and those of Tower rapeseed oil by molecular distillation and adsorption chromatography. The original oils and the purified triglycerides were incorporated in semisynthetic diets at 20% by weight and fed for 16 weeks to weanling male Sprague-Dawley rats to compare the nutritional and pathological effects of the oils and their triglyceride fractions on rats. The study was carried out at two independent laboratories. No significant differences were observed between the results of the two establishments. The incidence of myocardial lesions was significantly higher in rats fed Tower rapeseed oil than in those fed soybean oil. Purification of the triglycerides by molecular distillation and adsorption chromatography appeared to have no major effect on the incidence of myocardial lesions. This supports our previous findings that the cardiopathogenicity of the test oils to rats resides in the triglycerides of these oils. Contribution No. 832 from Animal Research Institute and No. I-78 from Engineering and Statistical Research Institute.     

Effect of fish oil on cancer cachexia and host liver metabolism in rats with prostate tumors

The aim of this study was to investigate whether tumor-induced cachexia and aberrations in host liver metabolism, induced by the MAT-LyLu variant of the Dunning prostate tumor, could be prevented by ω3 fatty acids from fish oil. On day 0, adult Copenhagen-Fisher rats fed normal chowad libitum were inoculated with 10⁶ MAT-LyLu cells (n=14) or saline (n=9). On day 7, when tumors were palpable, four tumor-bearing (TB) and four nontumorbearing (NTB) rats were put on isocaloric diets with 50% of total energy as fish oil. The introduction of fish oil-enriched diets caused a reduction in energy intake to less than half of the energy intake by animals fed normal diets during days 7–14 (difference by dietary group: NTB,P<0.001; TB,P<0.001). During days 14–21, energy intake in fish oil-fed animals returned to approximately 75% of energy intake by animals fed normal diets (difference by dietary group: NTB,P<0.003; TB,P=0.001). Carcass weight of animals on day 21, when the study was terminated, was significantly related to initial weight (P=0.05) and mean food intake during the study (P=0.01). When data were adjusted for these variables using analysis of covariance, with NTB animals on normal diets being the reference group, significant loss of carcass weight was observed in TB animals on normal diets only (mean ±SEM 58±10 g loss,P<0.001), but not in TB animals on fish oil diets (8±18 g loss,P=0.67). This positive effect of fish oil diets on carcass weight in TB animals was statistically significant (50±19 g,P<0.02), implicating that the fish oil enriched diet inhibited tumor-induced weight loss by more than 85%. No effect of fish oil diets on tumor growth was detected. In all TB animals, regardless of diet, hepatic [P_i]/adenosine triphosphate] ratios measured by³¹P magnetic resonance spectroscopy (MRS)in vivo andin vitro were elevated, and absolute concentrations of phosphocholine, glycerophosphocho-line, glycerophosphoethanolamine and glucose-6-phosphate as determined by³¹P MRSin vitro were reduced. Ultrastructural studies of liver tissue revealed increased numbers of mitochondria and increased amounts of endoplasmic reticulum in the host liver of TB animals, without differences between dietary group. In conclusion, fish oil supplementation partially inhibited MAT-LyLu tumor-induced cachexia, but did not prevent the majority of³¹P MRS-detectable alterations in host liver metabolism.     

The metabolism of 20- and 22-carbon unsaturated acids in rat heart and myocytes as mediated by feeding fish oil

When rats were fed 5% corn oil, the heart phospholipids contained large amounts of 22-carbon (n−6) acids. When half of the corn oil was replaced with fish oil, the reduced level of arachidonate and 22-carbon (n−6) acids in phospholipids was accompanied by increases in the levels of 22-carbon (n−3) acids while only small amounts of 20∶5(n−3) were acylated. Heart myocytes readily took up and acylated [1-¹⁴C]-labeled 20∶4(n−6), 20∶5(n−3) and 22∶6(n−3) into phospholipids. The uptake and acylation of 20∶4(n−6) was greater than for 20∶5(n−3) but the intracellular labeling profiles were similar. Uptake and acylation of 22∶6(n−3) was somewhat lower. In addition the intracellular labeling profile differed in that more 22∶6(n−3) was incorporated into the ethanolamine-containing phospholipids than when 20∶4(n−6) or 20∶5(n−3) were the substrates. Neither 20∶4(n−6) nor 20∶5(n−3) was chain elongated. When [3-¹⁴C]-labeled 22∶4(n−6) and 22∶5(n−3) were the substrates, it was not possible to detect radioactive 22∶5(n−6) or 22∶6(n−3). Both [3-¹⁴]-labeled substrates were acylated into phospholipids and retroconverted with the subsequent esterification of radioactive 20∶4(n−6) and 20∶5(n−3) into triglycerides and phospholipids. These studies show that cardiomyocytes lack the ability to make 22-carbon acids from 20-carbon precursors but they retroconvert 22-carbon acids to 20-carbon acids. The high levels of 22-carbon polyunsaturated acids in total heart lipids thus cannot be attributed to the synthetic capacities of cardiomyocytes.