Influence of formulas with borage oil or borage oil plus fish oil on the arachidonic acid status in premature infants

Several studies have reported that feeding γ-linolenic acid (GLA) has resulted in no increase in arachidonic acid (AA) in newborns. This result was ascribed to the eicosapentaenoic acid (EPA)-rich fish oil used in these formulas. Docosahexaenoic acid (DHA) sources with only minor amounts of EPA are now available, thus the addition of GLA to infant formulas might be considered an alternative to AA supplementation. Sixty-six premature infants were randomized to feeding one of four formulas [ST: no GLA, no long-chain polyunsaturated fatty acids; BO: 0.6% GLA (borage oil); BO + FOLOW: 0.6% GLA, 0.3% DHA, 0.06% EPA; BO + FOHIGH: 0.6% GLA, 0.3% DHA, 0.2% EPA] or human milk (HM, nonrandomized) for 4 wk. Anthropometric measures and blood samples were obtained at study entry and after 14 and 28 d. There were no significant differences between groups in anthropometric measures, tocopherol, and retinol status at any of the studied time points. The AA content of plasma phospholipids was similar between groups at study start and decreased significantly until day 28 in all formulafed groups, but not in the breast-fed infants [ST: 6.6±0.2%, BO: 6.9±0.3%, BO + FOLOW: 6.9±0.4%, BO + FOHIGH: 6.7±0.2%, HM: 8.6±0.5%, where values are reported as mean ±standard error; all formulas significantly different (P≤0.05) from HM]. There was no significant influence of GLA or fish oil addition to the diet. GLA had only a very limited effect on AA status which was too small to obtain satisfactory concentrations (concentrations similar to breast-fed babies) under the circumstances tested. The effect of GLA on AA is independent of the EPA and DHA content in the diet within the dose ranges studied.     

Separation of eicosapentaenoic acid and docosahexaenoic acid in fish oil by kinetic resolution using lipase

The objective of this study was to investigate the use of lipases as catalysts for separating eicosapentaenoic acid (EPA) and docosahexaenoic acid (DHA) in fish oil by kinetic resolution. Transesterification of various fish oil triglycerides with a stoichiometric amount of ethanol by immobilized Rhizomucor miehei lipase under anhydrous solvent-free conditions resulted in a good separation. When free fatty acids from the various fish oils were directly esterified with ethanol under similar conditions, greatly improved results were obtained. By this modification, complications related to regioselectivity of the lipase and nonhomogeneous distribution of EPA and DHA into the various positions of the triglycerides were avoided. As an example, when tuna oil comprising 6% EPA and 23% DHA was transesterified with ethanol, 65% conversion into ethyl esters was obtained after 24 h. The residual glyceride mixture contained 49% DHA and 6% EPA (8:1), with 90% DHA recovery into the glyceride mixture and 60% EPA recovery into the ethyl ester product. When the corresponding tuna oil free fatty acids were directly esterified with ethanol, 68% conversion was obtained after only 8h. The residual free fatty acids comprised 74% DHA and only 3% EPA (25:1). The recovery of both DHA into the residual free fatty acid fraction and EPA into the ethyl ester product remained very high, 83 and 87%, respectively.     

Enrichment of eicosapentaenoic acid and docosahexaenoic acid in saponified menhaden oil

Eicosapentaenoic acid (EPA, 20∶5n−3) and docosahexaenoic acid (DHA, 22∶6n−3) in free fatty acids (FFA) derived from saponified menhaden oil were concentrated by the solubility differences of FFA-salts in organic solvent. FFA-salts were formed by adding NaOH to a solution containing FFA. A Buchner funnel was used to separate solid phases from liquids containing FFA-salts. FFA that are rich in EPA and DHA can be recovered from the liquid phase by the addition of 12 N HCl. The effects of reaction time, the amount of NaOH, and solvent used on the concentration of EPA and DHA were systematically investigated. With a total volume of 112 mL, made up of 1.85% 15 N NaOH, 88.1% acetone, and 10.0% FFA, a reaction temperature of 30°C, and a reaction time of 1 h, the resulting liquid phase contained 65.4 wt% EPA and DHA, with a corresponding yield of 41.5%. By replacing the acetone with a mixture of 45% acetone and 55% acetonitrile and then storing the liquid phase at −70°C overnight, the content and yield of EPA and DHA in the final liquid phase were 61.4 wt% and 66.2%, respectively.     

The preparation of concentrates of eicosapentaenoic acid and docosahexaenoic acid by lipase-catalyzed transesterification of fish oil with ethanol

The objective of this study was to investigate the use of lipases as catalysts for producing concentrates of eicosapentaenoic acid (EPA) and docosahexaenoic acid (DHA) from fish oil as an alternative to conventional chemical procedures. Transesterification of fish oil with ethanol was conducted under anhydrous solvent-free conditions with a stoichiometric amount of ethanol. Among the 17 lipases tested, the results showed that Pseudomonas lipases had the highest activity toward the saturated and monounsaturated fatty acids in the fish oil, much lower activity toward EPA and DHA and, at the same time, good tolerance toward the anhydrous alcoholic conditions. With 10 wt% of lipase, based on weight of the fish oil triacylglycerol substrate (15% EPA and 9% DHA initial content), a 50% conversion into ethyl esters was obtained in 24 h at 20°C, in which time the bulk of the saturated and monounsaturated fatty acids reacted, leaving the long-chain n-3 polyunsaturated fatty acids unreacted in the residual mixture as mono-, di-, and triacylglycerols. This mixture comprised approximately 50% EPA+DHA. Total recovery of DHA and EPA was high, over 80% for DHA and more than 90% for EPA. The observed fatty acid selectivity, favoring DHA as a substrate, was most unusual because most lipases favor EPA.     

Low doses of eicosapentaenoic acid, docosahexaenoic acid, and hypolipidemic eicosapentaenoic acid derivatives have no effect on lipid peroxidation in plasma

It was of interest to investigate the influence of both high doses of eicosapentaenoic acid (EPA) and low doses of 2-or 3-methylated EPA on the antioxidant status, as they all cause hypolipidemia, but the dose required is quite different. We fed low doses (250 mg/d/kg body wt) of different EPA derivatives or high doses (1500 mg/d/kg body wt) of EPA and DHA to rats for 5 and 7 d, respectively. The most potent hypolipidemic EPA derivative, 2,2-dimethyl-EPA, did not change the malondialdehyde content in liver or plasma. Plasma vitamin E decreased only after supplementation of those EPA derivatives that caused the greatest increase in the fatty acyl-CoA oxidase activity. Fatty acyl-CoA oxidase activity increased after administration of both EPA and DHA at high doses. High doses of EPA and DHA decreased plasma vitamin E content, whereas only DHA elevated lipid peroxidation. In liver, however, both EPA and DHA increased lipid peroxidation, but the hepatic level of vitamin E was unchanged. The glutathione-requiring enzymes and the glutathione level were unaffected, and no significant changes in the activities of xanthine oxidase and superoxide dismutase were observed in either low-or high-dose experiments. In conclusion, increased peroxisomal β-oxidation in combination with high amounts of polyunsaturated fatty acids caused elevated lipid peroxidation. At low doses of polyunsaturated fatty acids, lipid peroxidation was unchanged, in spite of increased peroxisomal β-oxidation, indicating that polyunsaturation is the most important factor for lipid peroxidation.     

Geometrical isomerisation of eicosapentaenoic and docosahexaenoic acid at high temperatures

Concentrates of eicosapentaenoic acid (EPA) and docosahexaenoic acid (DHA) were heated at 140–240 °C for 2–8 h under nitrogen. The trans isomers were analysed by gas chromatography‐mass spectrometry on a BPX‐70 cyanopropyl column. All geometrical isomers of EPA and DHA with one trans double bond were observed. The rate constants (k) for the isomerisation of the all‐cis isomers were calculated and found to be higher than previously reported for linoleic acid and α‐linolenic acid. Arrhenius plots showed a linear relationship between ln k and the reciprocal absolute temperature above 180 °C. The distribution patterns of isomers with one trans double bond are approximately constant up to a degree of isomerisation of 25%. The degree of isomerisation can therefore be estimated from selected trans peaks.     

Increased hepatic β-oxidation of docosahexaenoic acid, elongation of eicosapentaenoic acid, and acylation of lysophosphatidate in rats fed a docosahexaenoic acid-enriched diet

Rats were fed a diet supplemented with corn oil (n-3 deficient), soy oil, or a mixture containing 8% 22∶6n-3 ethyl ester for 6 wk. The hepatic capacities for the β-oxidation and synthesis of 22∶6n-3, in addition to the acylation of lysophosphatidate, were tested in vitro. In rats that were fed a 22∶6n-3-enriched diet, both the β-oxidation of 22∶6n-3 and elongation of 20∶5n-3 were enhanced compared to those in rats fed the other diets. Acylation of lysophosphatidate was also enhanced in rats fed a 22∶6n-3-enriched diet, while the rate of dephosphorylation of phosphatidate was not changed. The amount of 22∶6n-3 in the liver was much less than that consumed in a docosahexaenoic acid-enriched diet. These results suggest that a significant amount of dietary 22∶6n-3 was degraded via β-oxidation, and that a portion of the retroconverted 20∶5n-3 was recycled for the synthesis of 22∶6n-3. The recycling of 20∶5n-3 might contribute to the low level of 22∶6n-3 in rats fed an n-3-deficient diet.     

Incorporation of linolenic-1-C14 acid into eicosapentaenoic and docosahexaenoic acids in fish

Following intraperitoneal injection of methyl linolenate-1-C¹⁴ into kelp bass,Paralablax clathratus, the highly polyunsaturated fatty acids of their body fats were concentrated by low temperature crystallization from acetone, and eicosapentaenoic and docosahexaenoic acids were isolated from the concentrate by reversed-phase chromatography and hydrogenated. The resulting arachidic and behenic acids were degraded stepwise to margaric acid, and the distribution of activity was determined. The results indicate that the injected linolenic acid was converted to eicosapentaenoic acid and the latter incorporated into docosahexaenoic acid. A probable conversion pathway is linolenic acid→6,9,12,15-octadecatetraenoic acid→8,11,14,17-eicosatetraenoic acid→5,8,11,14,17-eicosapentaenoic acid→7,10,13,16,-19-docosapentaenoic acid→4,7,10,13,16,19-docosahexaenoic acid. Supported by a training grant from the National Heart Institute, Bethesda, Md. This paper based partially on work performed under Contract AT(04-1)GEN-12 between the Atomic Energy Commission and the University of California.     

Docosahexaenoic acid in developing brain and retina of piglets fed high or low α-linolenate formula with and without fish oil

Docosahexaenoic acid (22∶6n−3) can be synthesized in the liver and/or brain from α-linolenic acid (18∶3n−3) and is required in large amounts in structural membranes of developing brain and retina. The adequacy and efficacy of formulas containing 18∶3n−3 and/or fish oil in providing 22∶6n−3 for deposition was investigated in piglets fed formula from birth to 15 days. The test formulas contained high (HL) or low (LL) 18∶3n−3 (3.9 or 0.7% of the total formula fatty acids, respectively), or low 18∶3n−3 plus fish oil (LL+FO) to provide C₂₀ and C₂₂ n−3 polyunsaturated fatty acids (0.8% of total fatty acids). Fatty acid analyses of synaptic plasma membrane and retina ethanolamine phospholipids (EPL), which are especially enriched in 22∶6n−3, were compared to those of 15-day-old piglets fed sow milk (SM). Feeding LL resulted in lower 22∶6n−3 in synaptic plasma membrane. Fatty acid levels in HL and LL+FO piglets were equivalent to SM, with the exception of lower 22∶5n−3 in the synaptic plasma membrane of LL+FO and in the retina of HL and LL+FO-fed piglets. Levels of 22∶4n−6 were also lower in the retina of the LL+FO group. The results suggest formula 18∶3n−3 is at least 24% as effective as C₂₀ and C₂₂ n−3 fatty acids as a source of membrane 22∶6n−3. This study shows dietary 18∶3n−3, as the only n−3 fatty acid, can support deposition of comparable percentage of 22∶6n−3 to natural milk. Fish oil also supported tissue levels of 22∶6n−3 similar to natural milk; however, lower 22∶4n−6 may indicate possible inhibitory effects on n−6 metabolism. Recipient of the 1967 Science and Engineering Scholarship, Natural Sciences & Engineering Research Council of Canada.     

Increased docosahexaenoic acid levels in human newborn infants by administration of sardines and fish oil during pregnancy

In rhesus monkeys, maternal n-3 fatty acid deficiency during pregnancy produces infant monkeys deficient in n-3 fatty acids at birth. These results stimulated current experiments to find out if n-3 fatty acids from fish in the diets of pregnant women would influence the concentration of docosahexaenoic acid (DHA, 22:6 n-3) in the newborn human infant. Fifteen healthy pregnant women were enrolled to receive a 9-wk dietary supplementation of n-3 fatty acids from the 26th to the 35th wk of pregnancy. Sixteen pregnant women were not supplemented and served as controls. n-3 Fatty acid supplementation consisted of sardines and additional fish oil, which provided a total of 2.6 g of n-3 fatty acids per day (d) for the 9-wk period of supplementation. This included 1.01 g DHA. The end point of this study was the blood concentrations of DHA in the newborn infant. DHA in maternal red blood cells increased from 4.69% of total fatty acids to 7.15% at the end of the supplement period and at the time of delivery decreased (as expected) to 5.97% of total fatty acids. Maternal plasma showed a similar change from 2.12 to 3.51% of total fatty acids and then decreased to 2.35%. Levels of DHA in plasma and red blood cells of unsupplemented mothers did not change during the same time period. Levels of DHA in blood of newborn infants differed greatly in infants born from n-3-supplemented mothers compared with control infants. In red blood cells, DHA was 7.92% of total fatty acids compared with 5.86% (control infants). Plasma values showed a similar difference: 5.05% vs. 3.47% (controls). In n-3-supplemented infants, DHA concentrations were 35.2% higher than in control infants in red blood cells and 45.5% higher in plasma. These data indicate the importance of maternal dietary n-3 fatty acids and, in particular, maternal dietary DHA in promoting higher concentrations of DHA in the blood of the newborn infant.     

Intestinal lymph absorption of butter,corn oil,cod liver oil,menhaden oil,and eicosapentaenoic and docosahexaenoic acid ethyl esters in rats

Adult male rats were surgically given a drainage catheter in the main mesenteric lymph duct. After an overnight fast, five groups of rats received intragastrically, in one bolus, butter, corn oil (CO), cod liver oil (CLO), menhaden oil (MO), or ethyl esters of eicosapentaenoic (EPA) and docosahexaenoic (DHA) acids (K80). Intestinal lymph was collected in these conscious animals, each hour during the first 6 h and in a single sample for the next 18 h. The absorption peak appeared earlier after MO and CO than after CLO administration. The quantities of triglycerides recovered during the first 6 h were significantly lower after butter (91 mg) and K80 (54 mg) administration than for the other three oils. No difference was observed between the vegetable oil and the two marine oils (CO=173 mg, CLO=148 mg, MO=180 mg). The total triglyceride recovered in 24 h was highest after CLO (410 mg) and lowest with K80 (146 mg). An increase in the weight percentage of some characteristic fatty acids of the lipid mixtures was observed: oleic acid for butter, oleic and linoleic acids for CO, EPA and DHA for CLO, MO, and K80. Chylomicrons were the largest with CO, more numerous and smaller with CLO, and the smallest with K80. Results obtained illustrated the relation between gastrointestinal hydrolysis, enterocyte biochemical events, and lymph triglyceride absorption profiles as related to the composition and distribution of triglyceride fatty acids.     

Effect of dietary α-linolenic acid intake on incorporation of docosahexaenoic and arachidonic acids into plasma phospholipids of term infants

The fractional conversion rates of plasma phospholipid α-linolenic acid (18:3n-3) and linoleic acid (18:2n-6) to docosahexaenoic acid (22:6n-3) and arachidonic acid (20:4n-6), respectively, and the fractional rates of incorporation of 22:6n-3 and 20:4n-6 into plasma phospholipids were determined in 27 healthy 3-wk-old term infants who had received formulas with ≈16% of fat as 18:2n-6 and 0.4% (n=6), 1.0% (n=11), or 3.2% (n=10) as 18:3n-3 from birth. The infants were given a single dose of both [U-¹³C] 18:2n-6 and [U-¹³C]18:3n-3 with a feeding, and blood samples were collected 8, 12, and 24 h afterward for determination of the isotopic enrichments of the [M+18] isotopomers of plasma phospholipid fatty acids by negative chemical ionization gas chromatography/mass spectrometry. A simple precursor/product compartmental model was used to estimate fractional rates of conversion and incorporation. All infants converted 18:3n-3 to 22:6n-3 and 18:2n-6 to 20:4n-6. Although the fractional rate of conversion of 18:3n-3 to 22:6n-3 did not differ among groups, the fractional rate of incorporation of 22:6n-3 into the plasma phospholipid fraction was greater in infants who received 3.2% vs. 0.4% or 1.0% 18:3n-3 (4.1±2.2 vs 1.6±1.5 or 2.0±1.0% of the plasma phospholipid 22:6n-3 pool daily). The fractional rate of conversion of 18:2n-6 to 20:4n-6 was less in infants who received the 3.2% 18:3n-3 intake (0.4±0.3% of the plasma phospholipid 18:2n-6 pool daily vs. 1.1±0.7% and 0.8±0.5% in those who received 0.4 and 1.0% 18:3n-3, respectively). The fractional rate of incorporation of 20:4n-6 into plasma phospholipid also was less in the 3.2% vs. the 0.4 and 1.0% 18:3n-3 groups (2.7±1.4% vs. 5.9±2.6 and 4.4±1.7%, respectively, of the plasma phospholipid 20:4n-6 pool daily).     

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.     

Accumulation of eicosapentaenoic acid in plasma phospholipids of subjects fed canola oil

The metabolism of α-linolenic acid from canola oil was studied in eight normolipidemic men. The 42-day study was divided into three periods: a 6-day pre-experimental and two 18-day experimental. Approximately 75% of the dietary fat (28% of total energy) was provided by a mixture of fats during the pre-experimental period and either canola oil (CO) or sunflower oil (SO) during the experimental periods. The CO and SO diets were fed in a cross-over design. The ratios of linoleic to linolenic acid were 2.6∶1 and 73.9∶1 in the CO and SO diets, respectively. Dietary fat source had an effect on plasma phospholipid fatty acids: 18∶1n−9, 18∶3n−3 and 20∶5n−3 were higher (p<0.05), and 18∶2n−6 was lower in the phosphatidylcholine fraction; 18∶1n−9 was higher and 20∶4n−6 lower in the phosphatidyl-ethanolamine fraction; and 18∶1n−9 and 20∶5n−3 were higher and 20∶4n−6 and 22∶6n−3 were lower in the alkenylacyl-ethanolamine phospholipid fraction on the CO diet as compared to the SO diet. Consumption of the canola oil diet resulted in higher n−3 fatty acid levels and lower n−6 fatty acid levels in plasma phospholipids than consumption of the sunflower oil diet.     

Differential utilization of eicosapentaenoic acid and docosahexaenoic acid in human plasma

It has recently been shown that the ω3 fatty acid status in humans can be predicted by the concentration of eicosapentaenoic (EPA) and docosahexaenoic (DHA) acids in plasma phospholipids [Bjerve, K.S., Brubakk, A.M., Fougner, K.J., Johnsen, H., Midjthell, K., and Vik, T. (1993)Am. J. Clin. Nutr., in press]. In countries with low intake of ω3 fatty acids, the level of EPA in plasma phospholipids is often only about one-fifth the concentration of DHA. The purpose of this study was to investigate whether this difference in the concentration of these two fatty acids was due to a selective loss of EPA relative to DHA or to a lower dietary intake of EPA. Seven female volunteers ingested four grams of MaxEPA daily for 2 wk and in the following 4 wk they ate a diet almost completely devoid of the long-chain ω3 fatty acids. The concentrations of the ω3 fatty acids in the plasma cholesteryl esters, triglycerides and phospholipids and the high density lipoprotein phospholipids were examined at weekly intervals throughout the study. There was a more rapid rise in the concentration of EPA than in DHA levels in the supplementation period in all lipid fractions, but there was a disproportionate rise in DHA relative to EPA in the plasma lipids compared with the ratio in the supplement. In the depletion phase there was a rapid disappearance of EPA from all fractions, such that pre-trial levels were reached by one week post-supplementation. The disappearance of DHA was slower, particularly for the plasma phospholipids: at 4 wk post-supplementation, the DHA concentration in this fraction was still 40% above the pre-trial value. It is suggested that the low plasma EPA values relative to DHA are the result of increased β-oxidation of EPA and/or low dietary intake, rather than a rapid conversion of EPA to DHA. One practical result of this experiment is that, compared with DHA, the maintenance of increased EPA levels in plasma (and therefore tissues) would require constant inputs of EPA due to its more rapid loss from the plasma.     

Platelet and aorta arachidonic and eicosapentaenoic acid levels andin vitro eicosanoid production in rats fed high-fat diets

There is a significant interest in the interrelationship between long-chain n-3, and n-6 fatty acids due to their ability to modulate eicosanoid production. In general, the intake of arachidonic acid (AA) results in enhanced eicosanoid production, whereas n-3 polyunsaturated fatty acids (PUFA) decrease the production of eicosanoids from AA. The purpose of this study was to investigate whether the effects of dietary AA on eicosanoid production in the rat were correlated with the AA and EPA levels in platelets and aorta (eicosanoid-producing tissues). Four groups of male Sprague-Dawley rats were fed a highfat diet enriched with eicosapentaenoic acid (EPA) and docosahexaenoic acid (DHA) (approximately 100 mg/day of EPA+DHA) for 24 d. During the last 10 d, the four groups were orally supplemented with 0,30,60, and 90 mg/day of ethyl arachidonate. A further group of rats was fed a control diet (without longchain n-3 PUFA) for 24 d.In vitro aorta prostacyclin (PGI₂) production, serum thromboxane A₂ (TxA₂) production and plasma, and platelet and aorta phospholipid (PL) fatty acids were measured. Enriching the diet with n-3 PUFA resulted in significant reductions in tissue AA levels and an increase in the n-3 PUFA, particularly EPA. On this diet, the AA to EPA ratio was 1:1 in platelet PL, and it was 2:1 in the aorta PL. There were significant decreases in thein vitro PGI₂ and TxA₂ production compared with the control animals. The inclusion of AA in the diet resulted in marked increases in AA levels in the platelet and aorta PL with corresponding decreases in EPA. The lowest dose of AA (30 mg/rat) reversed the effects of 100 mg/day of n-3 PUFA on AA levels in platelet and aortic PL and onin vitro aorta PGI₂ and serum TxA₂ production. The dietary AA caused a differential (twofold) increase in TxA₂ relative to PGI₂ for all three levels of AA supplementation. There were greater changes in the levels of AA and/or EPA in platelet PL compared with the aorta PL, which might have accounted for the differential effects of these PUFA on thromboxane production compared with PGI₂ production in this study.     

Peroxisomes in mice fed a diet supplemented with low doses of fish oil

The influence of low dietary doses (0.1 and 0.8% w/w) of a commercial fish oil preparation on peroxisomes in normal mice was studied and compared to the known strong inductive effects of high (10%) fish oil diets. Low fish oil doses were chosen to supply the mice with a concentration of docosahexaenoic acid, which was beneficial to patients with a peroxisomal disease. Peroxisomes were evaluated by cytochemical, morphometric, and enzymological techniques. The 0.1% fish oil diet had no effect on peroxisomes in liver, heart, and kidney even after prolonged treatment. The 0.8% diet did not change the peroxisomal number nor the catalase (EC 1.11.1.6) activity in the liver. Hepatic peroxisomal β-oxidation, however, was increased by 50% after 14 d. This was accompanied by reduced peroxisomal size. The 0.8% diet also caused a small increase (+25%) in myocardial catalase activity. No effect was observed in kidneys. Our results indicate that in mice a low (<0.8%) dietary fish oil dose has no or only a slight effect on hepatic peroxisomal β-oxidation. This may be of particular interest to patients with a peroxisomal fatty acid β-oxidation defect and who display a severe deficiency of docosahexaenoic acid—diets supplemented with low fish oil doses will improve the docosahexaenoic acid level without adding a strong load to the disturbed fatty acid metabolism.     

Effect of dietary docosahexaenoic acid on brain composition and neural function in term infants

There is a need to determine whether there is a dietary requirement for docosahexaenoic acid (DHA, 22:6n-3) by term infants to achieve their full developmental potential. Studies of brain fatty acid composition demonstrated that infants who were breast fed had greater levels of cerebral cortex DHA than did infants who were formula fed, suggesting that DHA in the cerebrum is dependent on a supply in the diet. Some physiological studies reported that electrophysiological and behavioral assessments of visual function were improved in breast-fed infants relative to those fed formula and that this was related to the length of breast feeding. While some randomized studies of DHA supplementation of infant formula to term infants demonstrated that the visual function of formula-fed infants could be improved to breast-fed levels by adding DHA to formula, others failed to demonstrate an effect. Variations in dietary treatments and methods of assessment make comparison of the studies difficult. Further work is necessary to rigorously establish if there are long-term benefits of dietary DHA to the term infant.     

Specific susceptibility of docosahexaenoic acid and eicosapentaenoic acid to peroxidation in aqueous solution

The peroxidation of different polyunsaturated fatty acids (PUFA) after photoirradiation in aqueous solution was evaluated by measuring fatty acid loss and malonaldehyde production in medium. The oxidation rates of eicosapentaenoic acid (EPA) and docosahexaenoic acid (DHA), two highly unsaturated fatty acids of the n−3 series, were surprisingly lower (14 and 22%, respectively) than the oxidation rates of linoleic, α-linolenic, γ-linolenic, dihomo γ-linolenic, and arachidonic acids (62–90%). The quantities of malonaldehyde (MA) produced were assayed simultaneously by gas chromatography (GC) and high performance liquid chromatography (HPLC). MA production was found to be related to both the degree of unsaturation and the metabolic series of the fatty acid. The maximum value was observed with arachidonic acid (MA production from 2 mM arachidonic acid in aqueous solution was estimated at 44.9±6.0 μM by GC and 46.8 ±4.0 μM by HPLC). Eicosapentaenoic acid and docosahexaenoic acid produced lower MA quantities compared to arachidonic acid (MA production from 2 mM EPA and 2 mM DHA was estimated at 17.9±1.5 μM and 37.9±0.7 μM, respectively, by GC, and 26.3±4.9 μM and 37.3±4.2 μM, respectively, by HPLC). The MA yield, defined as the amount of MA (nmols) produced per 100 nanomoles of oxidized fatty acid, was used to express the susceptibility of individual PUFA to peroxidation. The MA yield correlated well with the degree of unsaturation, but was independent of carbon chain length and metabolic series. The study suggests that adequate assessment of lipid peroxidation cannot be achieved by measuring MA formation alone, but it also requires knowledge of the fatty acid composition of the system studied.     

Dietary docosahexaenoic acid as a source of eicosapentaenoic acid in vegetarians and omnivores

The utilization of dietary docosahexaenoic acid (DHA; 22:6n−3) as a source of eicosapentaenoic acid (EPA; 20:5n−3) via retroconversion was investigated in both vegetarians and omnivores. For this purpose, an EPA-free preparation of DHA was given as a daily supplement (1.62 g DHA) over a period of 6 wk. The dietary supplement provided for a marked increase in DHA levels in both serum phospholipid (from 2.1 to 7.1 mol% in vegetarians and 2.2 to 7.6 mol% in omnivores) and platelet phospholipid (from 1.1 to 3.4 mol% in vegetarians and 1.4 to 3.9 mol% in omnivores). EPA levels rose to a significant but much lesser extent, while 20:4n−6, 22:5n−6, and 22:5n−3 all decreased. Based on the serum phospholipid data, the retroconversion of DHA to EPA in vivo was estimated to be 9.4% overall with no significant difference between omnivores and vegetarians.