Dietary modulation of fatty acid profiles and oxidative status of rat hepatocyte nodules: Effect of different n−6/n−3 fatty acid ratios

Male Fischer rats were fed the AIN76A diet containing varying n−6/n−3 FA ratios using sunflower oil (SFO), soybean oil (SOY), and SFO supplemented with EPA-50 and GLA-80 (GLA) as fat sources. Hepatocyte nodules, induced using diethylnitrosamine followed by 2-acetylaminofluorene/partial hepatoctomy promotion, were harvested, with surrounding and respective dietary control tissues, 3 mon after partial hepatectomy. The altered growth pattern of hepatocyte nodules in rats fed SFO is associated with a distinct lipid pattern entailing an increased concentration of PE, resulting in increased levels of 20∶4n−6. In addition, there is an accumulation of 18∶1n−9 and 18∶2n−6 and a decrease in the end products of the n−3 metabolic pathway in PC, suggesting a dysfunctional Δ-6-desaturase enzyme. The hepatocyte nodules of the SFO-fed rats exhibited a significantly reduced lipid peroxidation level that was associated with an increaser in the glutathione (GSH) concentration. The low n−6/n−3 FA ratio diets significantly decreased 20∶4n−6 in PC and PE phospholipid fractions with a concomitant increase in 20∶5n−3, 22∶5n−3, and 22∶6n−3. The resultant changes in the 20∶4/20∶5 FA ratio and the 20∶3n−6 FA level in the case of the GLA diet suggest a reduction of prostaglandin synthesis of the 2-series. The GLA diet also counteracted the increased level of 20∶4n−6 in PE by equalizing the nodule/surrounding ratio. The low n−6/n−3 ratio diets significantly increased lipid peroxidation levels in hepatocyte nodules, mimicking the level in the surrounding and control tissue while GSH was decreased. An increase in n−3 FA levels and oxidative status resulted in a reduction in the number of glutathione-S-transferase positive foci in the liver of the GLA-fed rats. Modulation of cancer development with low n−6/n−3 ratio diets containing specific dietary FA could be a promising tool in cancer intervention in the liver.     

Detergent action of rosin soaps and fatty acid — Rosin soaps

Summary A method for evaluating the detergent action of soaps has been described and applied to a series of soap solutions. The detergent action of rosin soaps, the effect of compounds present in soap or used with soap on the detergent action of a rosin soap, and the effect of rosin soap on the detergent action of tallow soap have been tested. The effect of temperature on the detergent action of some of the detergent solutions has also been determined. The results of these detergent tests on rosin, fatty acid and fatty acid-rosin soaps indicated the following: (1) Rosin soaps made from different gum rosins, produced from longleaf and slash pine gums, have equal detergent action; (2) The presence of soaps of oxidized rosin acids has no effect on detergent action of the rosin soap; (3) The detergent action of soaps made from pyroabietic acid, abietic acid and hydrogenated rosin parallels their ability to lower the surface tension of water and the amount of hydrogen present in the rosin acids; (4) The addition of builders that increase the alkalinity of the rosin soap solution improves the detergent action of the solution; (5) The blending of rosin soap with tallow soap improves the detergent action of the tallow soap in solutions having a soap concentration of 0.25 percent or more; (6) Temperature affects the detergent action of rosin and coconut oil soaps more than tallow soap.     

Δ9 desaturase activity in bovine subcutaneous adipose tissue of different fatty acid compositiondesaturase activity in bovine subcutaneous adipose tissue of different fatty acid composition

Two experiments were conducted to investigate the relationship between Δ⁹ desaturase (stearoyl-coenzyme A desaturase) activity and fatty acid composition in subcutaneous adipose tissue from cattle of different backgrounds. In Experiment 1, subcutaneous adipose tissue samples were taken from carcasses of pasture-fed cattle and feedlot cattle fed for 100, 200, or 300 d. Adipose tissue from pasture-fed cattle had significantly lower total saturated fatty acids and higher total unsaturated fatty acids than feedlot cattle. Desaturase activity correspondingly was 60–85% higher in pasture-fed cattle than in feedlot cattle. There was no difference in the fatty acid composition or desaturase activity among samples from the 100-, 200-, and 300-d feedlot cattle. In Experiment 2, adipose tissue samples were collected from carcasses of feedlot cattle fed for 180 d with either a standard feedlot ration (control group), or a ration containing rumen-protected cottonseed oil (CSO) for the last 70–80 d. Adipose tissue from the CSO-fed cattle was more saturated than that from the control group, having significantly more 18∶0 and less 16∶1 and 18∶1. Correspondingly, adipose tissue from the CSO group had significantly lower desaturase activity. The elevated 18∶2 in adipose tissue from the CSO group confirmed that unsaturated fatty acids (including cyclopropenoid fatty acids) were protected from biohydrogenation. Further studies are needed to determine whether the repression of desaturase activity results from direct inhibition by cyclopropenoic acids or by higher dietary contents of 18∶2.     

Effects of ψ-linolenic acid and docosahexaenoic acid in formulae on brain fatty acid composition in artificially reared rats

This study evaluated the effects of dietary supple-mentation with ψ-linolenic acid (GLA, 18∶3n−6) and docosahexaenoic acid (DHA, 22∶6n−3) on the fatty acid composition of the neonatal brain in gastrostomized rat pups reared artificially from days 5–18. These pups were fed rat milk substitutes containing fats that provided 10% linoleic acid and 1% α-linolenic acid (% fatty acids) and, using a 2×3 factorial design, one of two levels of DHA (0.5 and 2.5%), and one of three levels of GLA (0.5, 1.0, and 3.0%). A seventh artificially reared groups served as a reference group and was fed 0.5% DHA and 0.5% arachidonic acid (AA, 20∶4n−6); these levels are within the range of those found in rat milk. The eighth group, the suckled control group, was reared by nursing dams fed a standard American Institute of Nutrition 93M chow. The fatty acid composition of the phosphatidylethanolamine, phosphatidyl-choline, and phosphatidylserine/phosphatidylinositol membrane fractions of the forebrain on day 18 reflected the dietary composition in that high levels of dietary DHA resulted in increases in DHA but decreases in 22∶4n−6 and 22∶5n−6 in brain. High levels of GLA increased 22∶4n−6 but, in contrast to previous findings with high levels of AA, did not decrease levels of DHA. These results suggest that dietary GLA, during development, differs from high dietary levels of AA in that it does not lead to reductions in brain DHA.     

n−3 fatty acid enrichment of edible tissue of poultry: A review

There is clear evidence of the nutritional benefits of consuming long-chain n−3 PUFA, which are found predominantly in oily fish. However, oily fish consumption, particularly in the United Kingdom, is declining, as is the consumption of all meats with the exception of poultry, which has increased in consumption by 73% in the last 30 yr. This pattern, if less marked, is reflected throughout Europe, and therefore one means of increasing long-chain n−3 PUFA consumption would be to increase the long-chain n−3 PUFA content in the edible tissues of poultry. This review considers the feasibility of doing this, concentrating particularly on chickens and turkeys. It begins by summarizing the benefits to human health of consuming greater quantities of n−3 FA and the sources of n−3 PUFA in the human diet. The literature on altering the FA composition of poultry meat is then reviewed, and the factors affecting the incorporation of n−3 PUFA into edible tissues of poultry are investigated. The concentration of α-linolenic acid (ALA) in the edible tissues of poultry is readily increased by increasing the concentration of ALA in the birds' diet (particularly meat with skin, and dark meat to a greater extent than white meat). The concentration of EPA in both white and dark meat is also increased when the birds' diet is supplemented with EPA, although supplementing the diet with the precursor (ALA) does not result in a noticeable increase in EPA content in the edible tissues. Although supplementing the birds' diets with relatively high concentrations of DHA does result in an increased concentration of DHA in the tissues, the relationship between dietary and tissue concentrations of DHA is much weaker than that observed with ALA and EPA. The impact that altering the FA composition of edible poultry tissue may have on the organoleptic and storage qualities of poultry products is also considered.     

Fourier-transform infrared spectra of fatty acid salts—Kinetics of high-oleic sunflower oil saponification

Sodium, lithium, and calcium soaps obtained by saponification of high-oleic sunflower oil were studied by Fourier-transform infrared spectroscopy. Spectra of crude mixtures containing soap, glycerin, residual alkali, and triacylglycerols were compared to those of pure soaps obtained from fatty acids. The infrared spectra of crude soaps showed the same characteristic bands as pure ones. The absorption bands of asymmetric (ω₂) and symmetric (ω₁) stretching vibrations of the carboxylate group indicated that the metal-oxygen bonds of these soaps had an ionic character whose strength differed from one cationic counterion to another. Once the characteristic absorption bands of the soaps were assigned, a kinetics study of saponification was performed. Saponification by sodium, anhydrous lithium, and calcium hydroxides was an autocatalytic reaction, characterized by an S-shaped kinetics curve, whereas saponification by aqueous lithium hydroxide was stoichiometric. The structure of the metal-oxygen bond played a role in the kinetic mechanisms.     

Effect of n−3 polyunsaturated fatty acid supplementation on lipid peroxidation of rat organs

The present study was undertaken in order to reexamine the effect of n−3 polyunsaturated fatty acid (PUFA)-rich diet supplementation on lipid peroxidation and vitamin E status of rat organs. Male Wistar rats were fed a diet containing safflower or fish oil at 50 g/kg diet and an equal amount of vitamin E at 59 mg/kg diet (1.18 g/kg oil; and 1.5 g/kg PUFA in safflower oil diet, and 4.3 g/kg PUFA in fish oil diet) for 6 wk. Fatty acid composition of total lipids of brain, liver, heart, and lung of rats fed fish oil was rich in n−3 PUFA, whereas that of each organ of rats fed safflower oil was rich in n−6 PUFA. The vitamin E levels in liver, stomach, and testis of the fish oil diet group were slightly lower than those of the safflower oil diet group, but the levels in brain, heart, lung, kidney, and spleen were not different between the two diet groups. The levels of phospholipid hydroperoxides were determined by the high-performance liquid chromatography-chemiluminescence method and the levels of thiobarbituric acid-reactive substances (TBARS) were determined at pH 3.5 in the presence of butylated hydroxytoluene with or without EDTA. Levels of phospholipid hydroperoxides and TBARS in the brain, liver, heart, lung, kidney, spleen, stomach and testis of the fish oil diet group were similar to those of the safflower oil diet group. The results indicate that high fish oil intake does not induce increased levels of phospholipid hydroperoxides and TBARS in rat organs.     

High-purity γ-linolenic acid from borage oil fatty acids

High-purity γ-linolenic acid (GLA) was obtained by employing a modified low-temperature solvent crystallization process, followed by a lipase-catalyzed esterification, to borage oil fatty acid. By applying a two-stage solvent crystallization process to the borage oil fatty acid, GLA content was increased from 23.4 to 92.1% with a yield of 89.3%. After the esterification of GLA-rich fatty acid with butanol catalyzed by Lipozyme IM-60, GLA content in the fatty acid was further raised from 92.1 to 99.1%. The overall yield of the combined process was 72.8%. The effects of operation parameters on the Lipozyme IM-60 catalyzed esterification between fatty acid and alcohol were systematically investigated.     

Comparison of growth and fatty acid metabolism in rats fed diets containing equal levels of γ-linolenic acid from high γ-linolenic acid canola oil or borage oil

We have utilized transgenic technology to develop a new source of γ-linolenic acid (GLA) using the canola plant as a host. The aim of the present study was to compare the growth and fatty acid metabolism in rats fed equal amounts of GLA obtained from the transgenic canola plant relative to GLA from the borage plant. Young male Sprague-Dawley rats (n=10/group) were randomized and fed a purified AIN93G diet (10% lipid by weight) containing either a mixture of high GLA canola oil (HGCO) and corn oil or a control diet containing borage oil (BO) for 6 wk. GLA accounted for 23% of the triglyceride fatty acids in both diets. Growth and diet consumption were monitored every 2–3 d throughout the study. At study termination, the fatty acid composition of the liver and plasma phospholipids was analyzed by gas chromatography. The growth and diet consumption of the HGCO group were similar to the BO group. There were no adverse effects of either diet on the general health or appearance of the rats, or on the morphology of the major organs. There was no significant difference between the diet groups for total percentage of n−6 polyunsaturated fatty acids present in either the total or individual phospholipid fractions of liver or plasma. The relative percentage of GLA and its main metabolite, arachidonic acid, in each phospholipid fraction of liver or plasma were also similar between groups. The percentage of 18∶2n−6 in liver phosphatidylethanolamine and phosphatidylinositol/serine was higher (P<0.05) and 22∶5n−6 was lower in the HGCO group than the BO group. This finding could be attributed to the higher 18∶3n−3 content in the HGCO diet than the BO diet. Results from this long-term feeding study of rats show for the first time that a diet containing transgenically modified canola oil was well-tolerated, and had similar biological effects, i.e., growth characteristics and hepatic metabolism of n−6 fatty acids, as a diet containing borage oil.     

Comparative effects of α- and γ-linolenic acids on rat liver fatty acid oxidation

It has been reported that both n−3 and n−6 octadecatrienoic acids can increase hepatic fatty acid oxidation activity. It remains unclear, however, whether different enzymes in fatty acid oxidation show a similar response to n−3 and n−6 octadecatrienoic acids. The activity of hepatic fatty acid oxidation enzymes in rats fed an oil mixture rich in α-linolenic acid (18:3n−3) and borage oil rich in γ-linolenic acid (18:3n−6) was therefore compared to that in rats fed an oil mixture rich in linoleic acid (18:2n−6) and a saturated fat (palm oil) in this study. Linseed oil served as the source of 18:3n−3 for the oil mixture rich in this octadecatrienoic acid and contained 30.6% 18:3n−3 but not 18:3n−6. Borage oil contained 25.7% 18:3n−6 and 4.5% 18:3n−3. Groups of seven rats each were fed diets containing 15% various fats for 15 d. The oxidation rate of palmitoyl-CoA in the peroxisomes was higher in rats fed a fat mixture rich in 18:3n−3 (3.03 nmol/min/mg protein) and borage oil (2.89 nmol/min/mg protein) than in rats fed palm oil (2.08 nmol/min/mg protein) and a fat mixture rich in 18:2n−6 (2.15 nmol/min/mg protein). The mitochondrial palmitoyl-CoA oxidation rate was highest in rats fed a fat mixture rich in 18:3n−3 (1.93 nmol/min/mg protein), but no significant differences in this parameter were seen among the other groups (1.25–1.46 nmol/min/mg protein). Compared to palm oil and fat mixtures rich in 18:2n−6, a fat mixture rich in 18:3n−3 and borage oil significantly increased the hepatic activity of carnitine palmitoyl-transferase and acyl-CoA oxidase. Compared to palm oil and a fat mixture rich in 18:2n−6, a fat mixture rich in 18:3n−3, but not fats rich in 18:3n−6, significantly decreased 3-hydroxyacyl-CoA dehydrogenase activity. Compared to palm oil and a fat mixture rich in 18:2n−6, borage oil profoundly decreased mitochondrial acyl-CoA dehydrogenase activity, but a fat mixture rich in 18:3n−3 increased it. 2,4-Dienoyl-CoA reductase activity was significantly lower in rats fed palm oil than in other groups. Compared to other fats, borage oil significantly increased Δ³, Δ²-enoyl-CoA isomerase activity. Activity was also significantly higher in rats fed 18:2n−6 oil than in those fed palm oil. It was confirmed that both dietary 18:3n−6 and 18:3n−3 increased fatty acid oxidation activity in the liver. These two dietary octadecatrienoic acids differ considerably, however, in how they affect individual fatty acid oxidation enzymes.     

Changes of the transcriptional and fatty acid profiles in response to n−3 fatty acids in SH-SY5Y neuroblastoma cells

Synthesis of docosahexaenoic acid (DHA) from its metabolic precursors contributes to membrane incorporation of this FA within the central nervous system. Although cultured neural cells are able to produce DHA, the membrane DHA contents resulting from metabolic conversion do not match the high values of those resulting from supplementation with preformed DHA. We have examined whether the DHA precursors down-regulate the incorporation of newly formed DHA within human neuroblastoma cells. SH-SY5Y cells were incubated with gradual doses of alpha-linolenic acid (alpha-LNA), EPA, or docosapentaenoic acid (DPA), and the incorporation of DHA into ethanolamine glycerophospholipids was analyzed as a reflection of synthesizing activity. The incorporation of EPA, DPA, and preformed DHA followed a dose-response saturating curve, whereas that of DHA synthesized either from alpha-LNA, EPA, or DPA peaked at concentrations of precursors below 15-30 microM and sharply decreased with higher doses. The mRNA encoding for six FA metabolism genes were quantified using real-time PCR. Two enzymes of the peroxisomal beta-oxidation, L-bifunctional protein and peroxisomal acyl-CoA oxidase, were expressed at lower levels than fatty acyl-CoA ligase 3 (FACL3) and delta6-desaturase (delta6-D). The delta6-D mRNA slightly increased between 16 and 48 h of culture, and this effect was abolished in the presence of 70 microM EPA. In contrast, the EPA treatment resulted in a time-dependent increase of FACL3 mRNA. The terminal step of DHA synthesis seems to form a "metabolic bottleneck," resulting in accretion of EPA and DPA when the precursor concentration exceeds a specific threshold value. We conclude that the critical precursor- concentration window of responsiveness may originate from the low basal expression level of peroxisomal enzymes.     

Metabolism of n−3 and n−6 fatty acids in Atlantic salmon liver: Stimulation by essential fatty acid deficiency

Oxidation, esterification, desaturation, and elongation of [1-¹⁴C]18∶2n−6 and [1-¹⁴C]18∶3n−3 were studied using hepatocytes from Atlantic salmon (Salmo salar I.) maintained on diets deficient in n−3 and n−6 polyunsaturated fatty acids (PUFA) or supplemented with n−3 PUFA. For both dietary groups, radioactivity from 18∶3n−3 was incoporated into lipid fractions two to three times faster than from 18∶2n−6, and essential fatty acids (FFA) deficiency doubled the incorporation. Oxidation to CO₂ was very low and was independent of substrate or diet, whereas oxidation to acid-soluble products was stimulated by EFA deficiency. Products from 18∶2n−6 were mainly 18∶3n−6, 20∶3n−6, and 20∶4n−6, with minor amounts of 20∶2n−6 and 22∶5n−6. Products from 18∶3n−3 were mainly 18∶4n−3, 20∶5n−3, and 22∶6n−3, with small amounts of 20∶3n−3. The percentage of 22∶6n−3 in the polar lipid fraction of EFA-deficient hepatocytes was fourfold higher than in n−3 PUFA-supplemented cells. This correlated well with our other results obtained after abdominal injection of [1-¹⁴C]18∶3n−3 and [1-¹⁴C]18∶2n−6. In hepatocytes incubated with [4,5-³H]-22∶6n−3, 20∶5n−3 was the main product. This retrocon-version was increased by EFA deficiency, as was peroxisomal β-oxidation activity. This study shows that 18∶2n−6 and 18∶3n−3 can be elongated and desaturated in Atlantic salmon liver, and that this conversion and the activity of retroconversion of very long chain PUFA is markedly enhanced by FFA deficiency.     

Characterization of the ybdT gene product of Bacillus subtilis: Novel fatty acid β-hydroxylating cytochrome P450

We have characterized the gene encoding fatty acid α-hydroxylase, a cytochrome P450 (P450) enzyme, from Sphingomonas paucimobilis. A database homology search indicated that the deduced amino acid sequence of this gene product was 44% identical to that of the ybdT gene product that is a 48 kDa protein of unknown function from Bacillus subtilis. In this study, we cloned the ybdT gene and characterized this gene product using a recombinant enzyme to clarify function of the ybdT gene product. The carbon monoxide difference spectrum of the recombinant enzyme showed the characteristic one of P450. In the presence of H₂O₂, the recombinant ybdT gene product hydroxylated myristic acid to produce β-hydroxyristic acid and α-hydroxymyristic acid which were determined by high-performance liquid chromatography (HPLC) and gas chromatography-mass spectrometry. The amount of these products increased with increasing reaction period and amount of H₂O₂ in the reaction mixture. The amount of β-hydroxyl product was slightly higher than that of α-hydroxyl product at all times during the reaction. However, no reaction products were detected at any time or at any concentration of H₂O₂ when heat-inactivated enzyme was used. HPLC analysis with a chiral column showed that the β-hydroxyl product was nearly enantiomerically pure R-form. These results suggest that this P450 enzyme is involved in a novel biosynthesis of β-hydroxy fatty acid.     

Amine-cured ω-epoxy fatty acid triglycerides: Fundamental structure-property relationships

Several triacyl glycerides (2), having terminal epoxy functionalities on aliphatic residues of varying chain length, were allowed to react with either 4,4′-methylenedianiline or phthalic anhydride to give a new group of glassy network polymers with glass transition temperatures (T_gs) of 48-133 °C. Although cured 2 have substantially lower moduli than do conventional epoxy thermosets based on bisphenol A-diglycidyl ether (BADGE), the crosslinked triglycerides adhere strongly to steel and aluminum and are much more ductile and considerably tougher than commercial epoxy systems. In addition to a comparison of thermal and mechanical properties of thermosets based on 2, BADGE and common epoxidized linseed oil, reactivity differences among these epoxy resins are briefly discussed.     

Assessing fatty acid biostatus: Red blood cells or plasma?

Omega‐3 fatty acid (n‐3 FA) biostatus can be estimated using red blood cell (RBC) membranes or plasma. The sample type that exhibits the lower within‐person variability and is less affected by an acute dose of n‐3 FA is preferred in clinical practice. The experiments described here indicate that RBC‐based metrics are superior to plasma‐based for use in patient care.     

Effects of storage time and added antioxidant on fatty acid composition of red blood cells at −20°C

The stability of PUFA in venous red blood cells (RBC) of women aged 25 to 55 years (n=12) was investigated during storage at −20°C. The RBC sample from each participant was divided into seven portions: one baseline with the antioxidant BHT, another without BHT, samples without BHT stored for 2, 4, 9, or 17 wk, and samples with BHT stored for 17 wk. No difference was found in proportions of PUFA at baseline and after storage for 2 and 4 wk without BHT, and 17 wk with BHT. After 9 wk without BHT the proportion of 22∶6n−3 in RBC was lower, and after 17 wk without BHT proportions of all PUFA were lower than at baseline. High proportion of 22∶6n−3 in RBC at baseline was associated with more stable concentration of total FA in RBC without BHT during 17 wk. The findings indicate that PUFA in RBC from healthy women are stable at −20°C for 4 wk, without BHT and for at least 17 wk with BHT.     

5-Hydroxy fatty acid amides from δ-lactones and alkyl glucamines

δ-Lactones derived from unsaturated fatty acids are useful precursors to fatty amides due to their enhanced reactivity. Consequently, temperature-sensitive glucamines were easily converted to their 5-hydroxy fatty acid amides in high yield (52–97%) by reaction with C₁₈ and C₂₀ δ-lactones. High yields of amides (52–97%) were obtained with little or no solvent at 90°C in less than 24 h. C₁₈ δ-lactones were more miscible in the glucamine than the C₂₀ δ-lactones and thus increased reaction rates and yields of amides. In addition, amidation reactions run in the absence of catalyst gave good yields, whereas reactions in the presence of base catalysts completely inhibited the reaction. The 1-(N-alkyl-5-hydroxy fatty acid amido)-d-glucitols are expected to have useful properties as biodegradable components in detergents.     

Dietary fatty acids regulate cholesterol induction of liver CYP7α1 expression and bile acid production

In the present study we investigated the effects of dietary fats containing predominantly PUFA, monounsaturated FA (MUFA), or saturated FA (SFA) on lipid profile and liver cholesterol 7α-hydroxylase (CYP7α1) mRNA expression and bile acid production in C57BL/6J mice. The animals (n=75) were randomly divided into five groups and fed a basic chow diet (AIN-93G) (BC diet), a chow diet with 1g/100g of cholesterol (Chol diet), a chow diet with 1g/100g of cholesterol and 14g/100g of safflower oil (Chol+PUFA diet), a chow diet with 1g/100g of cholesterol and olive oil (Chol+MUFA diet), or a chow diet with 1g/100g of cholesterol and myristic acid (Chol+SFA diet) for 6 wk. The results showed that the Chol+SFA diet decreased CYP7α1 gene expression and bile acid pool size, resulting in increased blood and liver cholesterol levels. Addition of PUFA and MUFA to a 1% cholesterol diet increased the bile acid pool production or bile acid excretion and simultaneously decreased liver cholesterol accumulation despite decreased CYP7α1 mRNA expression. The results indicate that the decreased bile acid pool size induced by the SFA diet is related to inhibition of the liver CYP7α1 gene expression, but an increased bile acid pool size and improved cholesterol homeostasis are disassociated from the liver CYP7α1 gene expression.