Production of prostaglandins in homogenates of kidney medullae and cortices of spontaneously hypertensive rats fed menhaden oil

Menhaden oil (MO), whose polyunsaturated fatty acids consist mainly of (n−3) fatty acids, was fed to spontaneously hypertensive rats to determine the effect of (n−3) fatty acid on the in vitro production of prostaglandins produced from arachidonic acid (20∶4[n−6]). Capacity to form PGE₂ and PGF_2α was impaired in homogenates of kidney medullae and cortices from rats fed the MO diet compared to rats fed the control diet. The lower amounts of diene prostaglandins produced corresponded to the decrease in the amount of 20∶4 (n−6) in the tissue. Possibly changes produced in tissue lipids by dietary fatty acids affect prostaglandin production by reducing the availability of substrate in tissue lipids.     

Myocardial lipids and nucleotides of rats fed olive oil or rapeseed oil

After 1 week, the level of myocardial fatty acids was 4 times greater in young rats fed high erucic rapessed oil than in those fed olive oil. The proportion of erucic acid was 5.6% in the mitochondrial fraction, 15.1% in the microsomal fraction, and 34.8% in the floating fat fraction. This incorporation of erucic acid into triglycerides of the floating fat was evidence of esterification. The changes in the mitochondrial lipids did not alter the content of adenine nucleotides of the myocardium nor its apparent capacity to oxidize substrates.     

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.     

Membrane physical properties do not explain increased cyclic AMP production in hepatocytes from rats fed menhaden oil

To study the effect of altering plasma membrane fatty acid composition on the glucagon signal transduction pathway, cAMP accumulation was measured in hepatocytes from rats fed diets containing either menhaden oil (MO) or coconut oil (CO). Hepatocytes from MO-fed animals produced significantly more cAMP in response to glucagon and forskolin compared to CO-fed animals. Glucagon receptor number and affinity were similar in MO- and CO-fed rats. Liver plasma membranes from MO-fed animals were enriched in long-chain n-3 fatty acids and contained significantly lower amounts of saturated C₁₀−C₁₆ and 18∶1n−9 than CO-fed animals. Membrane physical properties were examined using both Fourier transform infrared spectroscopy (FTIR) and the fluorescent probe 1,6-diphenyl-1,3,5-hexatriene (DPH). FTIR analysis revealed that below 34°C, CO membranes were more ordered than MO membranes. However, as assay temperature approached 37°C, MO and CO membranes became similarly ordered. DPH polarization values indicated no differences in membrane order at 37°C, whereas membrane order was decreased in CO-fed animals at 25°C. These data indicate the importance of assay temperature in assessing the influence of membrane physical properties on the activity of signal transduction pathways. Whereas increased signal transduction activity has been correlated to reduced membrane order in MO-fed animals, these data indicate that at physiological temperatures membrane order did not vary between groups. Enhanced cAMP accumulation in response to forskolin indicates that adenylate cyclase activity or content may be elevated in MO-vs. CO-fed rats. Enhanced adenylate cyclase activity may result, in part, from changes in specific fatty acids in hepatocyte plasma membranes without demonstrable changes in membrane physical properties.     

Eicosanoid synthesis in 7,12-dimethylbenz(a)anthracene-induced mammary carcinomas in Sprague-Dawley rats fed primrose oil,menhaden oil or corn oil diet

The comparative effects of high-fat diets (20%, w/w) on eicosanoid synthesis during mammary tumor promotion in 7,12-dimethylbenz(a)anthracene (DMBA)-induced rats were studied using diets containing 20% primrose oil (PO), 20% menhaden oil (MO) or 20% corn oil (CO). Sprague-Dawley rats fed the PO or MO diet had 21% or 24% fewer adenocarcinomas, respectively, than rats fed the CO diet. Histologically (i.e., mitotic figures, inflammatory cell infiltration and necrosis), the CO-fed rats exhibited the highest frequency of changes within tumors. Plasma fatty acid composition was significantly altered by diet, reflecting the composition of the oils which were being fed. Only the plasma of PO-fed rats contained detectable levels of gamma-linolenic acid (GLA). Arachidonic acid (AA) levels were significantly higher (p<0.05) in PO-fed than in CO- or MO-fed rats. MO-fed rats had significantly higher levels of plasma palmitic acid, while palmitoleic, eicosapentaenoic (EPA) and docosahexaenoic (DHA) acids were detected only in MO-fed rats. As expected, linoleic acid (LA) and AA levels were lower (p<0.05) in the MO-fed rats than in PO- or CO-fed groups. The plasma of the CO-fed rats contained significantly higher levels of oleic acid. Eicosanoid synthesis in mammary carcinomas of rats fed the 20%-fat diets was 2–10 times higher than in mammary fat pads of control rats. The synthesis of PGE₁ and LTB₄ was significantly (p<0.05) higher in PO-fed rats than in CO-fed or MO-fed rats, although PGE values were significantly (p<0.05) higher in CO-fed rats than in Mo or PO groups. The synthesis of eicosanoids in both mammary fat pads and mammary carcinomas of MO-fed rats was lower (p<0.05) than in tissues of rats fed either CO or PO diets due to less AA precursor being fed and/or to competition between n−6 and n−3 fatty acids for cyclooxygenase and lipoxygenase. The ratios of monoenoic to dienoic eicosanoids in both mammary fat pads and mammary carcinomas were higher in the PO group than in the MO or CO groups. These results suggest that inclusion of GLA (PO feeding) or EPA and DHA (MO feeding) in the diet may decrease malignancy by altering eicosanoid profiles.     

Restoration of depressed prostanoid-induced ileal contraction in spontaneously hypertensive rats by dietary fish oil

We have reported that dietary fish oil (FO) rich in n-3 PUFA modulates gut contractility. It was further demonstrated that the gut of spontaneously hypertensive rats (SHR) has a depressed contractility response to prostaglandins (PG) compared with normotensive Wistar-Kyoto (WKY) rats. We investigated whether feeding diets supplemented with n-3 PUFA increased gut contractility and restored the depressed prostanoid response in SHR gut. Thirteen-week-old SHR were fed diets containing fat at 5 g/100 g as coconut oil (CO), lard, canola oil containing 10% (w/w) n-3 FA as alpha-linolenic acid (1 8:3n-3), or FO (as HiDHA, 22:6n-3) for 12 wk. A control WKY group was fed 5 g/100 g CO in the diet. As confirmed, the SHR CO group had a significantly lower gut response to PGE2 and PGF2alpha compared with the WKY CO group. Feeding FO increased the maximal contraction response to acetylcholine in the ileum compared with all diets and in the colon compared with lard, and restored the depressed response to PGE2 and PGF2alpha in the ileum but not the colon of SHR. FO feeding also led to a significant increase in gut total phospholipid n-3 PUFA as DHA (22:6n-3) with lower n-6 PUFA as arachidonic acid (20:4n-6). Canola feeding led to a small increase in ileal EPA (20:5n-3) and DHA and in colonic DHA without affecting contractility. However, there was no change in ileal membrane muscarinic binding properties due to FO feeding. This report confirms that dietary FO increases muscarinic- and eicosanoid receptor-induced contractility in ileum and that the depressed prostanoid response in SHR ileum, but not colon, is restored by tissue incorporation of DHA as the active nutrient.     

Fractionation of menhaden oil and partially hydrogenated menhaden oil: Characterization of triacylglycerol fractions

Menhaden oil (MO) and partially hydrogenated menhaden oil (PHMO) were dry-fractionated and solvent-fractionated from acetone. After conversion to fatty acid methyl esters, the compositional distribution of saturated, monounsaturated, trans, and n−3 polyunsaturated fatty acids (PUFA) in the isolated fractions was determined by gas chromatography. Acetone fractionation of MO at −38°C significantly increased the n−3 PUFA content in the liquid fractions over that of starting MO (P<0.05). For PHMO, liquid fractions obtained by low-temperature crystallization (−38, −18, and 0°C) from acetone showed significant increases (P<0.05) in monounsaturated fatty acid (MUFA) content over that of the starting PHMO. For selected MUFA-enriched fractions, reversed-phase high-performance liquid chromatography (HPLC) was used to separate, isolate, and characterize the major triacylglycerol (TAG) molecular species present. Thermal crystallization patterns for these fractions also were determined by differential scanning calorimetry (DSC). The results demonstrated that under the appropriate conditions it is possible to dry-fractionate or solvent-fractionate MO and PHMO into various solid and liquid fractions that are enriched in either saturated, monounsaturated, polyunsaturated, or the n−3 classes of fatty acids. Moreover, characterization of these TAG fractions by reversed-phase HPLC gives insight into the compositional nature of the TAG that are concentrated into the various fractions produced by these fractionation processes. Finally, the DSC crystallization patterns for the fractions in conjunction with their fatty acid compositional data allow for the optimization of the fractionation schemes developed in this study. This information allows for the production of specific TAG fractions from MO and PHMO that are potentially useful as functional lipid products.     

Effect oftrans fatty acids on plasma lipids,platelet function and systolic blood pressure in stroke-prone spontaneously hypertensive rats

To investigate the effect oftrans fatty acids on plasma lipid levels and systolic blood pressure, hydrogenated corn oil was fed to SHRSP (stroke-prone spontaneously hypertensive rats) and WKY (Wistar-Kyoto) rats for 30 days. Significantly lower systolic blood pressure and plasma total cholesterol were observed in SHRSP rats fedtrans fatty acids when compared with rats fedcis fatty acids from olive oil. In addition, higher HDL cholesterol and lower VLDL plus chylomicron cholesterol levels were found in SHRSP rats fedtrans fatty acids. Although no significant changes of systolic blood pressure and plasma total cholesterol levels were observed in WKY rats aftertrans fatty acids treatment, WKY rats fedtrans fatty acids had lower plasma LDL cholesterol and higher HDL cholesterol levels. In addition, platelet aggregation induced by collagen was decreased in WKY rats fedtrans fatty acids. It is interesting thattrans fatty acids increased the activity of plasma lecithin:cholesterol acyltransferase (LCAT) in both SHRSP and WKY rats. The observed influence oftrans fatty acids on plasma lipid levels, systolic blood pressure and platelet aggregation suggests thattrans fatty acids might prevent thrombotic disorders in SHRSP rats.     

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.     

Serum lipids in suckling and post-weanling iron-deficient rats

Serum lipids were studied in iron-deficient and control rats during suckling and after weaning at 21, 30, and 60 days of age. Diets providing 5 or 307 ppm iron were fed to dams and their offspring during gestation, lactation, and after weaning. Rats on the deficient diet throughout the experimental period developed a hyperlipidemia characterized by elevated triglycerides, cholesterol, and phospholipids which was present at 21, 30, and 60 days. Control pups weaned to the deficient diet developed anemia at 30 days of age and hypertriglyceridemia at 60 days of age. Repletion of deficient rats with iron after weaning caused a rapid decline in serum lipid levels after only 9 days on the control diet. The hyperlipidemia of iron deficiency thus appears to be reversible with iron supplementation. The time required to develop hypertriglyceridemia in iron deficiency is longer postweaning than during suckling.     

Occurrence of geometrical isomers of eicosapentaenoic and docosahexaenoic acids in liver lipids of rats fed heated linseed oil

Monotrans geometrical isomers of 20∶5 n−3 and 22∶6 n−3 were detected in liver lipid of rats fed heated linseed oil. The isomers were identified as being 20∶5 δ5c, 8c, 11c, 14c, 17t and 22∶6 δ4c, 7c, 10c, 13c, 16c, 19t. These fatty acids were isolated as methyl esters by preparative high-performance liquid chromatography (HPLC) on reversed phase columns followed by silver nitrate thin layer chromatography (AgNO₃-TLC). The structures were identified using partial hydrazine reduction, AgNO₃-TLC of the resulting monoenes, oxidative ozonolysis of each monoene band, and gas-liquid chromatography (GLC) of the resulting dimethyl esters and monomethyl esters. Fourier-transform-infrared spectrometry confirmed thetrans geometry in isolated 20∶5 and 22∶6 isomers. The isomers of eicosapentaenoic and docosahexaenoic acids in liver lipids probably resulted from desaturation and elongation of 18∶3 δ9c, 12c, 15t, a geometrical isomer of linolenic acid present in the heated dietary oil.     

Dietary docosahexaenoic acid affects stearic acid desaturation in spontaneously hypertensive rats

Docosahexaenoic acid (DHA, 22∶6n−3) is an n−3 polyunsaturated fatty acid which attenuates the development of hypertension in spontaneously hypertensive rats (SHR). The effects of DHA on delta-9-desaturase activity in hepatic microsomes and fatty acid composition were examined in young SHR. Two groups of SHR were fed either a DHA-enriched diet or a control diet for 6 wk. Desaturase activity and fatty acid composition were determined in hepatic microsomes following the dietary treatments. Delta-9-desaturase activity was decreased by 53% in DHA-fed SHR and was accompanied by an increase in 16∶0 and a reduction in 16∶1n−7 content in hepatic microsomes. The DHA diet also increased the levels of eicosapentaenoic acid (20∶5n−3) and DHA. The n−6 fatty acid content was also affected in DHA-fed SHR as reflected by a decrease in gamma-linolenic acid (18∶3n−6), arachidonic acid (20∶5n−6), adrenic acid (22∶4n−6), and docosapentaenoic acid (22∶5n−6). A higher proportion of dihomo-gamma-linolenic acid (20∶3n−6) and a lower proportion of 20∶4n−6 is indicative of impaired delta-5-desaturase activity. The alterations in fatty acid composition and metabolism may contribute to the antihypertensive effect of DHA previously reported.     

Adsorptive bleaching and molecular distillation of menhaden oil

Some of the major barriers to wide acceptance of fish oils as sources of polyunsaturated triglycerides, fatty acids, and fatty acid derivatives have been the problems associated with color, odor, flavor, and other impurities. Adsorptive bleaching and molecular distillation were investigated as methods to obtain natural triglycerides from menhaden oil that do not have undesirable flavors and odors. Results of these studies have shown that certain activated clays will satisfactorily reduce the color of commercial menhaden oil but will not remove the odor and flavor. Molecular distillation was found to be more effective in improving the odor and flavor of the oil than adsorptive bleaching with activated clays but somewhat less effective in reducing the color. When used jointly with bleaching, molecular distillation yields menhaden oil of high quality, suitable for use both in animal and human nutrition and in medical research. Spectral data in the 400–700 mμ range were used to evaluate the success of the refining process.     

Bromine levels in tissue lipids of rats fed brominated fatty acids

Lipids - Rats have been fed diets containing either 0.8% brominated corn oil or 0.5% of the ethyl ester of 9,10-dibromostearate or 9,10,12,13-tetrabromostearate. The brominated compounds were...     

Effects of acidic polysaccharides from gastrodia rhizome on systolic blood pressure and serum lipid concentrations in spontaneously hypertensive rats fed a high-fat diet

The effects of acidic polysaccharides purified from Gastrodia rhizome on blood pressure and serum lipid levels in spontaneously hypertensive rats (SHR) fed a high-fat diet were investigated. Acidic polysaccharides were purified from crude polysaccharides by DEAE-Sepharose CL-6B. Thirty-six male SHR were randomly divided into three groups: Gastrodia rhizome crude polysaccharide (A), acidic polysaccharide (B) groups, and a control group (C). A 5-week oral administration of all treatment groups was performed daily in 3- to 8-week-old SHRs with a dose of 6 mg/kg of body weight/day. After 5 weeks of treatment, total cholesterol in the acidic polysaccharide group, at 69.7 ± 10.6 mg/dL, was lower than in the crude polysaccharide group (75.0 ± 6.0 mg/dL) and the control group (89.2 ± 7.4 mg/dL). In addition, triglyceride and low-density lipoprotein cholesterol levels in the acidic polysaccharide group were lower than in the crude polysaccharide and control groups. The atherogenic index of the acidic polysaccharide group was 46.3% lower than in the control group. Initial blood pressure after the initial three weeks on the high-fat diet averaged 195.9 ± 3.3 mmHg among all rats. Compared with the initial blood pressure, the final blood pressure in the control group was increased by 22.8 mmHg, whereas it decreased in the acidic polysaccharide group by 14.9 mmHg. These results indicate that acidic polysaccharides from Gastrodia rhizome reduce hypertension and improve serum lipid levels.     

Lipase‐catalyzed synthesis of structured lipids with fatty acids fractionated from saponified chicken fat and menhaden oil

In this study, free fatty acids (FFA) of chicken fat and menhaden oil, which were obtained by saponification, were dry‐fractionated and solvent fractionated. Using these fractionation processes, FFA fractions enriched in monounsaturated (MUFA) and polyunsaturated fatty acids were obtained. Chicken fat FFA fractions enriched in MUFA were modified further by lipase‐catalyzed esterification with the starting fat to produce structured lipids of high MUFA content.     

Liver and serum lipids and lipoproteins of rats fed 5% L-lysine

Soybean protein and casein supplemented with 1% Arg were compared for their ability to prevent fatty livers caused by excess dietary Lys. The concentrations of serum lipids and lipoproteins of rats fed 5% Lys and having vatty livers were also compared with those of rats fed the identical diet but lacking fatty livers when killed. The total liver lipids, triglycerides and cholesterol of rats fed 15% casein +5% Lys were 3.9, 12.4 and 2 times control values, respectively. Rats fed 5% Lys +1% Arg or 5% Lys with 15% soybean protein had liver lipid concentrations similar to controls fed no supplemental Lys. Serum total lipids, triglycerides, cholesterol, phospholipids and free fatty acids also did not change, and serum ketone bodies were slightly elevated with Lys feeding whether the rats had fatty livers or not. The concentrations of circulating HDL were slightly depressed in all rats fed 5% Lys while LDL were significantly elevated, particularly in rats without fatty livers. Serum VLDL did not change with 5% dietary Lys. Overall, excessive dietary Lys caused fatty livers which were prevented by varying the diet or length of feeding. Excess Lys feeding altered lipoprotein metabolism shown by decreased serum HDL and a substantial elevation in LDL. The latter was more apparent when the fat accumulation in liver was less severe or absent. The data suggest that the fatty liver from Lys excess is probably unrelated to increased fat mobilization from storage, decreased fat oxidation or to a major block in the transport of triglycerides from the liver to the circulation.     

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.     

Identification of noveltrans isomers of 20∶5n−3 in liver lipids of rats fed a heated oil

Trans polyunsaturated n−3 fatty acids are formed as a result of the heat treatment of vegetable oils. It was demonstrated previously that the 18∶3 Δ9cis, 12cis, 15trans containing acis Δ9 ethylenic bond was converted to a geometrical isomer of 20∶5n−3, the 20∶5 Δ5cis, 8cis, 11cis, 14cis, 17trans. In the present study, we have identified two new isomers of eicosapentaenoic acid, the Δ11 monotrans and the Δ11, 17 ditrans isomers in liver of rats fed a heated oil. These are formed as a result of the conversion of two of the main isomers of linolenic acid which are present in refined and frying oils, the 18∶3 Δ9trans, 12cis, 15cis and the 18∶3 Δ9trans, 12cis, 15trans.