Formation of genotoxic dicarbonyl compounds in dietary oils upon oxidation

Dietary oils—tuna, salmon, cod liver, soybean, olive, and corn oils—were treated with accelerated storage conditions (60°C for 3 and 7 d) and a cooking condition (200°C for 1 h). Genotoxic malonaldehyde (MA), glyoxal, and methylglyoxal formed in the oils were analyzed by GC. Salmon oil produced the greatest amount of MA (1070±77.0 ppm of oil) when it was heated at 60°C for 7 d. The highest formation of glyoxal was obtained from salmon oil heated at 60°C for 3 d. More glyoxal was found from salmon and cod liver oils when they were heated for 3 d (12.8±1.10 and 7.07±0.19 ppm, respectively) than for 7d (6.70±0.08 and 5.94±0.38 ppm, respectively), suggesting that glyoxal underwent secondary reactions during a prolonged time. The amount of methyglyoxal formed ranged from 2.03±0.13 (cod liver oil) to 2.89±0.11 ppm (tuna oil) in the fish oils heated at 60°C for 7 d. Among vegetable oils, only olive oil yielded methylglyoxal (0.61±0.03 ppm) under accelerated storage conditions. When oils were treated under cooking conditions, the aldehydes formed were comparable to those formed under accelerated storage conditions. Fish oils produced more MA, glyoxal, and methylglyoxal than did vegetable oils because the fish oils contained higher levels of long-chain PUFA, such as EPA and DHA, than did the vegetable oils. A statistically significant correlation (P<0.05) between the α-tocopherol content and the oxidation parameters was obtained from only MA and fish oils heated at 60°C for 3 d.     

Gas chromatographic analysis of malonaldehyde and 4-hydroxy-2-(E)-nonenal produced from arachidonic acid and linoleic acid in a lipid peroxidation model system

Malonaldehyde (MA) and 4-hydroxynonenal (4-HN) formed upon oxidation with Fe²⁺/H₂O₂ from arachidonic acid and linoleic acid, and their ethyl esters were analyzed by gas chromatography (GC). The MA and 4-HN produced were reacted withN-methylhydrazine (NMH) to give 1-methylpyrazole and 5(1′-hydroxyhexyl)-1-methyl-2-pyrazoline, respectively. The derivatives were analyzed by GC on a fused silica capillary column using a nitrogen-phosphorus detector. With arachidonic acid, more MA and 4-HN were formed from the ester (88 nmol/mg and 23 nmol/mg, respectively) than from the free acid (25 nmol/mg and 9 nmol/mg, respectively). In contrast, with linoleic acid, more MA and 4-HN were produced from the free acid (53 nmol/mg and 13 nmol/mg, respectively) than from the ester (39 nm/mg and 8 nmol/mg, respectively).     

Analysis of free malonaldehyde formed in lipid peroxidation systemsvia a pyrimidine derivative

A high-performance liquid chromatographic (HPLC) method for the determination of malonaldehyde (MA) in foods and biological samples was developed. MA was derivatized by reaction with urea under acidic conditions to form 2-hydroxypyrimidine, which was subsequently measured by HPLC. The highest yield (98%) of the product was obtained when 100 nmol of MA was reacted with 60 mmol of urea for 60 min at 100°C. Arachidonic acid, linolenic acid, linoleic acid and oleic acid were oxidized by a FeCl₂/H₂O₂ reagent in aqueous solution. MA formed was determined as 2-hydroxypyrimidine by HPLC. Arachidonic acid produced the highest level of MA (60 nmol/mg fatty acid), whereas oleic acid did not produce any. The formation levels of MA in microsomes upon enzymatic and nonenzymatic oxidation were 34 nmol/mL and 45 nmol/mL, respectively. Antioxidative activity of α-tocopherol was also monitored successfully by this HPLC method.     

Analysis of free malondialdehyde in photoirradiated corn oil and beef fat via a pyrazole derivative

Malondialdehyde (MA) formed in linolenic acid, linoleic acid, corn oil and beef fat upon photoirradiation was determined by gas chromatography (GC). The MA produced was reacted with methylhydrazine to give 1-methyl-pyrazole and was subsequently analyzed on a GC equipped with a nitrogen-phosphorus specific detector and a fused silica capillary column. MA values determined by this method correspond to free or unbound MA levels. Linolenic and linoleic acids produced 867 μg MA/g and 106 μg MA/g, respectively. Oleic and stearic acids did not produce detectable levels of MA upon photoirradiation. Amounts of MA produced after eight hour irradiations of corn oil and beef fat were 56.24 μg/g and 25.01 μg/g, respectively. Some photoreaction products in irradiated corn oil also were identified as methylhydrazine derivatives.     

Inhibition of malonaldehyde formation by antioxidants from ω3 polyunsaturated fatty acids

The inhibitory effect of α-tocopherol, β-carotene, 2″-O-glycosyl isovitexin (2″-O-GIV), and butylated hydroxytoluene (BHT) on malonaldehyde (MA) formation from ω3 polyunsaturated fatty acids (PUFA) was determined by gas chromatography. The levels of MA formed from 1 mg each of octadecatetraenoic acid (ODTA), eicosapentaenoic acid (EPA), and docosahexaenoic acid (DHA) upon oxidation with Fenton's reagent were 29.8±1.5, 17.2±1.5, and 22.0±0.7 nmol, respectively. BHT was most effective toward protecting all three ω3 PUFA, whereas β-carotene did not exhibit any inhibitory effect. 2″-O-GIV inhibited MA formation from EPA and DHA by 56 and 43%, respectively, showing the second greatest inhibitory activity after BHT. α-Tocopherol inhibited MA formation from ODTA and DHA by 67 and 28%, respectively, but it did not show any activity toward EPA oxidation. The naturally occurring antioxidant, 2″-O-GIV, may be useful to prevent oxidation of ω3 PUFA.     

Accumulation of Hydroxyl Lipids and 4-Hydroxy-2-Hexenal in Live Fish Infected with Fish Diseases

Hydroxy lipids (L-OH) and 4-hydroxy-2-hexenal (HHE) levels as well as other parameters such as lipid level, lipid class, fatty acid composition, and other aldehydes levels in the liver of diseased fish were investigated. Although significant differences in lipid level, lipid class, fatty acid composition, and other aldehyde levels were not always observed between normal and diseased fish, L-OH and HHE levels were significantly higher in the liver of the diseased fish than in that of the normal fish cultured with the same feeds under the same conditions. In the liver of puffer fish (Fugu rubripes) infected with Trichodina, L-OH and HHE levels significantly increased from 25.29 ± 5.04 to 47.70 ± 5.27 nmol/mg lipid and from 299.79 ± 25.25 to 1,184.40 ± 60.27 nmol/g tissue, respectively. When the levels of HHE and other aldehydes in the liver of the normal and diseased puffer fish were plotted, a linear relationship with a high correlation coefficient was observed between HHE and propanal (r ² = 0.9447). Increased L-OH and HHE levels in the liver of the diseased fish and a high correlation between HHE and propanal in the liver of the normal and diseased fish were also observed in flat fish (Paralichthys olivaceus) infected with streptococcus, yellowtail (Seriola quinqueradiata) infected with jaundice, and amberjack (S. purpurascens) infected with Photobacterium damselae subsp. piscicida.     

Optimization of the Conditions for Removing Cholesterol from Cod Liver Oil by β-Cyclodextrin Crosslinked with Adipic Acid

This study was conducted to find the optimum conditions for β-cyclodextrin (β-CD) crosslinked by adipic acid to remove cholesterol from cod liver oil. The cholesterol content of the non-treated cod liver oil was 554.51 mg/100 g oil. The different factors considered were concentrations of crosslinked β-CD, mixing temperature, ratio of cod liver oil to distilled water, mixing time, and mixing speed. The optimum conditions for cholesterol removal from cod liver oil using crosslinked β-CD were a 1:2 ratio of cod liver oil to distilled water, 25% (crosslinked β-CD/distilled water, w/v) crosslinked β-CD concentration, 20 min mixing time, 400 rpm mixing speed and 60 °C mixing temperature with about 87% cholesterol removal. In a recycling study, cholesterol removal from the cod liver oil with recycled crosslinked β-CD in the first recycling trial was 85.09%, which was slightly lower than that with new crosslinked β-CD (87.27%). Up to three time trials, more than 82% cholesterol removal was observed.     

Tocopherols and tocotrienols in Finnish foods: Oils and fats

The tocopherols and tocotrienols of vegetable oils, cod liver oil, margarines, butter and Voimariini dairy spread were analyzed by HPLC. The total tocopherol content varied from 4 (coconut oil) to 242 mg/100 g (wheat germ oil). α-tocopherol equivalents varied from 2 (coconut oil) to 225 mg/100 g (wheat germ oil). Semisoft and soft margarines had an average total tocopherol of 53 and 61 mg, and an average α-tocopherol equivalent of 17 and 27 mg/100 g, respectively. Hard margarines averaged 29 mg total tocopherol and 9 mg α-tocopherol equivalent/100 g. The average tocopherol content of butter and Voimariini was 2 and 15 mg/100 g, respectively, and the average α-tocopherol equivalent 2 and 6 mg/100 g.     

Determination of the Δ15 double bond in fatty acids of hydrogenated soybean oil

A method was developed to determine the extent of hydrogenation of the Δ15 double bond which occurs during partial catalytic hydrogenation of soybean oil. A linear relationship was found to exist between the linolenate content of commonly occurring C₁₈ unhydrogenated oils (containing no tetraene) and the propanal resulting from their ozonization reduction. The amount of propanal so produced is directly related to the amount of Δ15 double bond in these oils, as well as in hydrogenated soybean oils. Soybean oil was treated with ozone in carbon tetrachloride at —20 C and then reduced with triphenylphosphine. The ozonized-reduced sample was injected into a gas chromatograph, operated at 170C and equipped with a 12 ft × 1/4 in. column of 100/ 120 mesh porous polymer beads. The propanal peak was identified and its area used as a measure of the fatty acids containing Δ15 double bonds in unhydrogenated soybean and other oils of known linolenate content. A nearly stoichiometric amount of propanal results from ozonizing, reducing and chromatographing soybean oil as shown by comparison with a standard mixture of propanal and carbon tetrachloride. The relative standard deviation for the method is ±4.4%. We have also found this method applicable to other oils containing the omega-3 double bond. Presented at the AOCS-AACC Meeting, Washington, D.C., March, 1968. No. Utiliz, Res. Div., ARS, USDA.     

Metabolism of malonaldehyde in vivo and in vitro

The metabolism of malonaldehyde (MA) was investigated in vivo using male Wistar rats and in vitro using rat liver mitochondria. Twelve hr after intubation with [1,3-¹⁴C] MA, 60–70%, 5–15% and 9–17% of administered radioactivity was recovered in expired CO₂, feces and urine, respectively. In rats intubated with [1,2-¹⁴C] acetate, the corresponding values were 68–82%, 1–2% and 2–3%.¹⁴CO₂ evolution was initially slower after¹⁴C-MA administration than after¹⁴C-acetate administration and more radioactivity was excreted in the feces and urine. In vitro experiments using [1,3-¹⁴C] MA showed that MA is metabolized primarily in the mitochondria via reactions involving O₂ utilization and¹⁴CO₂ production. The apparent K_m and V_max were 0.5 mM and 9.3 nmol/min/mg protein for O₂ uptake, respectively, and 2.0 mM and 2.4 nmol/min/mg protein for¹⁴CO₂ production. Addition of malonic acid to mitochondrial incubates at concentrations inhibitory to succinate dehydrogenase did not affect MA-induced O₂ uptake but enhanced¹⁴CO₂ production from¹⁴C-MA.¹⁴C-Acetate appeared to be the major accumulating metabolite in rat liver mitochondrial preparations following a 120-min incubation with¹⁴C-MA. A probable biochemical route for MA metabolism involves oxidation of MA by mitochondrial aldehyde dehydrogenase followed by decarboxylation to produce CO₂ and acetate.     

Comparison of the effects of dietary fish oils with different n−3 polyunsaturated fatty acid compositions on plasma and liver lipids in rats

The effects of dietary fish oils with different n−3 polyunsaturated fatty acid compositions on plasma lipid profiles in rats have been studied. Forty-eight male rats, previously maintained on a cholesterol-free diet for 15 days, were fed for 60 days with diets supplemented with 10% fat of either marine hilsa fish (Hilsa ilisa, family clupeidae) or fresh-water chital fish (Notopterus chitala, family notopteridae). The diets had similar levels of total saturated (35–41%), monounsaturated (43–47%) and n−3 polyunsaturated (9–10%) fatty acids. Cholesterol contents of the diets were adjusted to 0.85%; γ-linolenic acid (3.3%) in chital oil and eicosapentaenoic acid (4.9%) in hilsa oil diets were the major n−3 contributors. The percentage of eicosapentaenoic acid in the chital oil diet was 0.57 times that of the hilsa oil diet, but the eicosapentaenoic (EPA) to arachidonic acid (AA) ratio in the latter (4.08) was 3.2 times that of the former (1.27). Sixty days of hilsa oil diet feeding decreased the levels of cholesterol (53.3±2.9 to 50.0±1.1 mg/dL), triacylglycerol (75.7±3.8 to 64.3±2.6 mg/dL) and phospholipid (55.8±1.5 to 51.7±3.1 mg/dL) in rat plasma. Similar treatment with chital oil diet elevated the plasma cholesterol level (53.3±2.9 to 62.3±7.6 mg/dL) while triacylglycerol and phospholipid contents remained unaltered. Both the dietary treatments decreased the levels of linoleic and arachidonic acids in liver but only under the hilsa oil diet did the eicosapentaenoic acid percentage increase markedly (0.8±0.06% to 5.5±0.06%) at the expense of arachidonic acid. This study strongly suggests that the hypolipidemic effect depends on the composition of the n−3 polyunsaturated fatty acids rather than on the total n−3 polyunsaturated fatty acid content of the dietary fish oil.     

Plasma concentrations of dihydro-vitamin K1 following dietary intake of a hydrogenated vitamin K1-rich vegetable oil

Dihydro-vitamin K₁ is a dietary form of vitamin K₁ (phylloquinone) produced during the hydrogenation of vegetable oils. To determine if dihydro-vitamin K₁ is present in plasma following dietary intake of a hydrogenated fat, eight healthy adults consumed each of two diets containing 30% of calories from fat, of which 20% was either soybean oil or a partially hydrogenated soybean oil-based stick margarine. Of the fats and oils analyzed, dihydro-vitamin K₁ was only found in the hydrogenated products. The soybean oil diet contained 180 ±12 μg (mean±SD) of vitamin K₁/day and nondetectable levels of dihydro-vitamin K₁, whereas the stick margarine diet contained 199±7 μg of vitamin K₁/day and 23±2 μg of dihydrovitamin K₁/day. After consuming each diet for five weeks, plasma dihydro-vitamin K₁ concentrations were higher (P=0.002) in all eight subjects when consuming the stick margarine diet (0.56 ±0.33 nmol/L) compared to the soybean oil diet (0.12±0.11 nmol/L). There was no significant change in plasma vitamin K₁ concentrations when the two diets were compared. In conclusion, dihydro-vitamin K₁ is detectable in plasma following dietary intake of a hydrogenated vitamin K₁-rich vegetable oil.     

Impact of lemongrass oil,an essential oil,on serum cholesterol

To test the hypothesis that non-sterol mevalonate pathway end products lower serum cholesterol levels, we asked 22 hypercholesterolemic subjects (315±9 mg cholesterol/dl) to take a daily capsule containing 140 mg of lemongrass oil, an essential oil rich in geraniol and citral. The paired difference in serum cholesterol levels of subjects completing the 90-day study approached significance (P<0.06, 2-tailed t-test). The subjects segregated into two groups, one consisting of 14 subjects resistant to the protocol and the other consisting of 8 subjects who responded. Paired differences in cholesterol level at 30, 60 and 90 d for resistant subjects were +2±6, +2±7 and −1±6 mg/dl; paired differences for the responding subjects were −25±10 (p<0.05), −33±8 (p<0.01) and −38±10 (p<0.025), respectively. The paired difference (+8±4) in the cholesterol levels of six responders 90 days after the discontinuation of lemongrass oil was not significant.     

Quantitative determination of total lipid hydroperoxides by a flow injection analysis system

A flow injection analysis (FIA) system coupled with a fluorescence detection system using diphenyl-1-pyrenylphosphine (DPPP) was developed as a highly sensitive and reproducible quantitative method of total lipid hydroperoxide analysis. Fluorescence analysis of DPPP oxide generated by the reaction of lipid hydroperoxides with DPPP enabled a quantitative determination of the total amount of lipid hydroperoxides. Use of 1-myristoyl-2-(12-((7-nitro-2-1,3-benzoxadiazol-4-yl)amino) dodecanoyl)-sn-glycero-3-phosphocholine as the internal standard improved the sensitivity and reproducibility of the analysis. Several commercially available edible oils, including soybean oil, rapeseed oil, olive oil, corn oil, canola oil, safflower oil, mixed vegetable oils, cod liver oil, and sardine oil were analyzed by the FIA system for the quantitative determination of total lipid hydroperoxides. The minimal amounts of sample oils required were 50 μg of soybean oil (PV=2.71 meq/kg) and 3 mg of sardine oil (PV=0.38 meq/kg) for a single injection. Thus, sensitivity was sufficient for the detection of a small amount and/or low concentration of hydroperoxides in common edible oils. The recovery of sample oils for the FIA system ranged between 87.2±2.6% and 102±5.1% when PV ranged between 0.38 and 58.8 meq/kg. The CV in the analyses of soybean oil (PV=3.25 meq/kg), cod liver oil (PV=6.71 meq/kg), rapeseed oil (PV=12.3 meq/kg), and sardine oil (PV=63.8 meq/kg) were 4.31, 5.66, 8.27, and 11.2%, respectively, demonstrating sufficient reproducibility of the FIA system for the determination of lipid hydroperoxides. The squared correlation (r ²) between the FIA system and the official AOCS iodometric titration method in a linear regression analysis was estimated at 0.9976 within the range of 0.35−77.8 meq/kg of PV (n=42). Thus, the FIA system provided satisfactory detection limits, recovery, and reproducibility. The FIA system was further applied to evaluate changes in the total amounts of lipid hydroperoxides in fish muscle stored on ice.     

Hepatic origin of triglycerides in fatty livers produced by the continuous intragastric infusion of an ethanol diet

Male Wistar rats were maintained for 30 days on an independent and continuous intragastric infusion of ethanol and nutritionally defined liquid diet containing only a small amount of corn oil (CO-4.9% calories). Ethanol intake was progressively increased from 32% to 40.4% of the total calories to maintain a high degree of intoxication during this period. Rats in the control group were infused with an isocaloric diet in which alcohol was replaced by dextrose. The liver triglyceride (TG) content of rats given alcohol (61.5±16.4 mg/g) was ca. 10-fold greater than that of controls (5.9±2.1 mg/g) and similar to that observed previously in rats fed an ethanol diet containing high levels of fat (35% and 43% calories). In TG of fatty liver, the level of 18∶2 was small (3%), even though CO in the diet contained a high level of this acid. Furthermore, 16∶1 and 16∶0 contents were markedly elevated (16% and 40%, respectively) despite the fact that CO did not contain 16∶1 and had only a small amount of 16∶0. Liver TG having a fatty acid (FA) composition markedly different from that of CO and the presence of high levels of 16∶1 and 16∶0 indicate that the TG accumulated in the fatty liver originated from hepatic lipogenesis rather than from dietary fat.     

Highly unsaturated fatty acid synthesis in marine fish: Cloning, functional characterization, and nutritional regulation of fatty acyl Δ6 desaturase of Atlantic cod (Gadus morhua L.)

This study reports the cloning, functional characterization, tissue expression, and nutritional regulation of a Δ6 fatty acyl desaturase of Atlantic cod (Gadus morhua). PCR primers were designed based on the sequences of conserved motifs in available fish desaturases and used to isolate a cDNA fragment from cod liver, with full-length cDNA obtained by rapid amplification of cDNA ends. The cDNA for the putative desaturase was shown to comprise 1980 bp, including a 261-bp 5′-UTR, a 375-bp 3′-UTR, and an ORF of 1344 bp that specified a protein of 447 amino acids. The protein sequence included three histidine boxes, two transmembrane regions, and an N-terminal cytochrome b₅ domain containing the heme-binding motif HPGG, all characteristic of microsomal fatty acyl desaturases. The cDNA displayed Δ6 desaturase activity in a yeast expression system. Quantitative real-time PCR assay of gene expression in cod showed that the Δ6 desaturase gene was expressed highly in brain, to a slightly lesser extent in liver, kidney, intestine, red muscle, and gill, and at much lower levels in white muscle, spleen, and heart. The expression of the Δ6 desaturase gene did not appear to be under significant nutritional regulation, with levels in liver and intestine being barely altered in fish fed a vegetable oil blend, in comparison with levels in fish fed fish oil. This was reflected in enzyme activity, as hepatocytes or enterocytes showed very little highly unsaturated FA biosynthesis activity irrespective of diet. Further studies are required to determine why the Δ6 desaturase appears to be barely functional in cod under the conditions tested.     

Pyloric ceca are significant sites of newly synthesized 22∶6n−3 in rainbow trout (<Emphasis Type="Italic">Oncorhynchus mykiss</Emphasis>)

In this pulse-chase study, rainbow trout fed a diet containing deuterated (D₅) (17,17,18,18,18)-18∶3n−3 ethyl ester accumulated D₅-22∶6n−3 in pyloric ceca to a greater extent than in liver 2 d post-dose. The ratio of newly synthesized D₅-22∶6n−3 in ceca to that in liver 2 d after feeding D₅-18∶3n−3 was 4.7±1.2 when expressed as per mg tissue and 5.2±2.4 when expressed as per mg protein. The amount of D₅-22∶6n−3 in ceca then declined whereas that in liver and blood increased, with the ratio of ceca to liver falling to 1.7 and 1.4, respectively, by day 5 and approaching unity by day 9. A crude cecal mucosa fraction contained 123±50 ng D₅-22∶6n−3/mg protein/mg D₅-18∶3n−3 eaten 2 d after feeding the tracer, compared with 35±21 ng D₅-22∶6n−3/mg protein/mg D₅-18∶3n−3 eaten in liver. Three days later the amount in cecal mucosa had fallen by one-third and that in liver had increased threefold. Most of the D₅-18∶3n−3 was catabolized very rapidly. The ratio of D₅-18∶3n−3 to 21∶4n−6 (a relatively inert FA marker) in the diet was 4.0, but this fell to 0.30 in ceca and ca. 0.8 in liver, blood, and whole carcass one day after feeding. These results indicate that ceca are active in the synthesis of 22∶6n−3 and the oxidation of 18∶3n−3.     

Chemical Characteristics and Fatty Acid Profile of Foxtail Millet Bran Oil

Chemical characteristics of a sample of foxtail millet bran and its oil, focusing on the approximate composition of foxtail millet bran and the fatty acid profile, physicochemical properties and tocopherol composition of foxtail millet bran oil, are presented in this work. The results indicate that the millet bran constituted 9.39 ± 0.17% crude oil, 12.48 ± 0.41% crude protein, and 51.69 ± 2.14% crude fiber. The specific gravity, refractive index, saponification value, and unsaponifiable matter content of millet bran oil were 0.9185 ± 0.0003 g/cm³ ( d₂₀²⁰ ) \left( {d_{20}^{20} } \right) , 1.4676 ± 0.0002 ( n_D⁴⁰ ) \left( {n_{D}^{40} } \right) , 186.29 ± 0.51 mg KOH/g, and 3.62 ± 0.19 g/100 g, respectively. The tocopherol content was 64.83 ± 0.83 mg/100 g oil, which consisted mainly of γ-tocopherol (48.79 ± 0.46 mg/100 g oil) and α-tocopherol (15.53 ± 0.31 mg/100 g oil). The millet bran oil was rich in linoleic acid (66.5%) and oleic acid (13.0%). The saturated fatty acids included palmitic acid (6.4%) and stearic acid (6.3%). The major fatty acid in the sn-2 position of the millet oil was linoleic acid (71.2%). The dominant triacylglycerols, calculated according to the 1,3-random-2-random hypothesis, were trilinoleate (LLL, 29.3%) and dilinoleoyl-monoolein (LLO, 17.2%). This work might be useful for developing applications for millet bran and its oil.     

Vitamin E. Deficiency increases the synthesis of platelet-activating factor (PAF) in rat polymorphonuclear leucocytes

Vitamin E deficiency was found to stimulate FMLP (N-formyl-L-methionyl-L-leucyl-L-phenylalanine)-induced biosynthesis of PAF (1-O-alkyl-2-acetyl-sn-glycero-3-phosphocholine) in polymorphonuclear leucocytes (PMN) from rat peritoneum. In three separate experiments each, the amounts of PAF synthesized during 6min and 12 min incubation of PMN cells from control, vitamin E-supplemented, and vitamin E-deficient rats were 129–240, 131–227 and 248–354 pmol/10⁶ cells, respectively. The activity of the acetyl-transferase, which transfers the acetyl moiety of [³H]acetyl-CoA to 2-lysoPAF (1-O-alkyl-sn-glycero-3-phosphocholine) to form [³H]PAF, was higher in PMN homogenates from vitamin E-deficient rats (2.28±0.07 nmol/min/mg protein) than in those from E-supplemented rats (1.06±0.10 nmol/min/mg protein). However, there was no difference between the two groups in the activity of acetylhydrolase (4.26±0.71 and 4.26±0.06 nmol/min/mg protein, respectively), measured as degradation of [³H]PAF to [³H]lysoPAF.In vitro addition of α-tocopherol did not inhibit the increased activity of acetyl-transferase in vitamin E-deficient rats, in-dicating that the enzyme in vitamin E-supplemented rats was not directly inhibited by α-tocopherol. The acetyltransferases of the two groups showed similar Km values for acetyl-CoA, but different Vmax values (225 μM and 6.4 nmol/min/mg protein in vitamin E-deficient rats, and 216 μM and 3.6 nmol/min/mg protein in vitamin E-supplemented rats), suggesting that the enzyme was not activated but increased in amount in vitamin E deficiency.     

Effect of n−3 fatty acid-rich fish oil supplementation on the oxidation of low density lipoproteins

This study was aimed at determining the effect of fish oil supplementation on copper-catalyzed oxidation of low density lipoproteins (LDL) from nine hypertriglyceridemic human subjects. A rapid headspace gas chromatographic method was used to measure the volatile oxidation products from LDL. Propanal and hexanal were the major volatile products formed in the oxidation of n−3 and n−6 polyunsaturated fatty acids (PUFA), respectively. Fish oil supplementation resulted in a significant increase in propanal formation from 3.7 to 13.4 nmol/mL LDL (P<0.01); it also resulted in small decreases in pentanal formation from 14.7 to 11.4 nmol/mL LDL and in hexanal formation from 138 to 108 nmol/mL LDL (P<0.05). The changes in peroxidation products paralleled the changes in LDL composition, which showed a significant increase in n−3 PUFA from 3.2 to 14.6% (P<0.01) and a decrease in n−6 PUFA from 43.7 to 35.0% (P<0.05). Propanal formation was highly and significantly correlated with n−3 PUFA content (r=0.950,P<0.001). Since total volatiles remained unchanged, this indicated that the two groups of LDL samples did not differ in overall oxidative susceptibility. Although fish oil intake did not alter the oxidative susceptibility of LDL, the chemically modified LDL particles generated a distinct pattern of volatile oxidation products that reflected changes in their fatty acid composition.