Showing papers in "Lipids in 1992"

First year growth of preterm infants fed standard compared to marine oil n-3 supplemented formula.

Abstract: Very low birth weight (VLBW) infants (748-1390 g, n = 65) were randomly assigned to receive control or marine oil-supplemented formula when they achieved intakes > 454 kJ (110 kcal)/kg/d of a formula designed for VLBW infants. Study formulas with or without marine oil were provided until 79 wk of postconceptional age (PCA), first in a formula designed for preterm infants followed by a formula designed for term infants. Infants were studied at regular intervals through 92 wk PCA. Weight, length, and head circumference were determined by standardized procedures and normalized to the National Center for Health Statistics figures for growth of infants born at term of the same age and gender. Mean normalized weight, weight-to-length, and head circumference were greatest at 48 wk and decreased thereafter. The decline in normalized weight was greater in infants fed the marine oil-supplemented formula. Beginning at 40 wk, marine oil-supplemented infants compared to controls had significantly poorer Z-scores for weight, length and head circumference. In addition, birth order (negatively) and maternal height (positively) influenced weight and length achievement in infancy as shown previously in infants born at term.

Nitric oxide, an inhibitor of lipid oxidation by lipoxygenase, cyclooxygenase and hemoglobin.

Abstract: The present study demonstrated that nitric oxide, which is an important mammalian metabolite, can inhibit oxidation by lipoxygenase, cyclooxygenase and hemoglobin. The inhibition is manifested as a lag-phase that is reversible. The inhibitory effect of nitric oxide on lipoxygenase and cyclooxygenase seems to derive from i) the capability of ·NO to reduce the ferric enzyme to the ferrous form, which is inactive; ii) competition for the iron site available for exogenous ligands; and iii) the radical scavenging ability of the nitroxide radical. Nitric oxide may act as a modulator of the arachidonic acid cascade and in the generation of oxygen-active species.

Redox cycling of iron and lipid peroxidation

Abstract: Mechanisms of iron-catalyzed lipid peroxidation depend on the presence or absence of preformed lipid hydroperoxides (LOOH). Preformed LOOH are decomposed by Fe(II) to highly reactive lipid alkoxyl radicals, which in turn promote the formation of new LOOH. However, in the absence of LOOH, both Fe2+ and Fe3+ must be available to initiate lipid peroxidation, with optimum activity occurring as the Fe2+/Fe3+ ratio approaches unity. The simultaneous availability of Fe2+ and Fe3+ can be achieved by oxidizing some Fe2+ with hydrogen peroxide or with chelators that favor autoxidation of Fe2+ by molecular oxygen. Alternatively, one can use Fe3+ and reductants like superoxide, ascorbate or thiols. In either case excess Fe2+ oxidation or Fe3+ reduction will inhibit lipid peroxidation by converting all the iron to the Fe3+ or Fe2+ form, respectively. Superoxide dismutase and catalase can affect lipid peroxidation by affecting iron reduction/oxidation and the formation of a (1:1) Fe2+/Fe3+ ratio. Hydroxyl radical scavengers can also increase or decrease lipid peroxidation by affecting the redox cycling of iron.

Incorporation of n-3 fatty acids of fish oil into tissue and serum lipids of ruminants.

Abstract: This study examines the biohydrogenation and utilization of the C20 and C22 polyenoic fatty acids in ruminants. Eicosapentaenoic (20∶5n−3) and docosahexaenoic (22∶6n−3) acids were not biohydrogenated to any significant extent by rumen microorganisms, whereas C18 polyenoic fatty acids were extensively hydrogenated. The feeding of protected fish oil increased the proportion of 20∶5 from 1% to 13–18% and 22∶6 from 2% to 7–9% in serum lipids and there were reductions in the proportion of stearic (18∶0) and linoleic (18∶2) acids. The proportion of 20∶5 in muscle phospholipids (PL) increased from 1.5% to 14.7% and 22∶6 from 1.0% to 4.2%; these acids were not incorporated into muscle or adipose tissue triacylglycerols (TAG). In the total PL of muscle, the incorporated 20∶5 and 22∶6 substituted primarily for oleic (18∶1) and/or linoleic (18∶2) acid, and there was no consistent change in the porportion of arachidonic (20∶4) acid.

Lipids of selected molds grown for production of n-3 and n-6 polyunsaturated fatty acids.

Abstract: The lipid classes and component fatty acids of seven fungi were examined. Three marine fungi,Thraustochytrium aureum, Thraustochytrium roseum andSchizochytrium aggregatum (grown at 30, 25 and 25°C, respectively), produced less than 10% lipid but contained docosahexaenoic acid (DHA) up to 30% and eicosapentaenoic acid (EPA) up to 11% of the total fatty acids.Mortierella alpinapeyron produced 38% oil containing solely n-6 polyunsaturated fatty acids (PUFA) with arachidonic acid (AA) at 11% of the total fatty acids.Conidiobolus nanodes andEntomorphthora exitalis produced 25% oil and contained both n−3 and n−6 PUFA, with AA at 16% and 18%, respectively.Saprolegnia parasitica produced 10% oil and contained AA and EPA, respectively, at 19% and 18%. The triacylglycerol fraction always represented the major component at between 44% and 68% of the total lipid. Each fungus, exceptT. aureum, had the greatest degree of fatty acid unsaturation in the phospholipid fraction. The triacylglycerol fraction ofT. aureum was the most unsaturated with DHA representing 29% (w/w) of all fatty acids present. The presence of the enzyme ATP:citrate lyase correlated with the ability of molds to accumulate more than 10% (w/w) lipid when the fungi were grown in nitrogen-limiting media. In those molds that failed to accumulate more than 10% lipid, the enzyme was absent.

Metals and lipid oxidation. Contemporary issues.

Abstract: Lipid oxidation is now recognized to be a critically important reaction in physiological and toxicological processes as well as in food products. This provides compelling reasons to understand what causes lipid oxidation in order to be able to prevent or control the reactions. Redox-active metals are major factors catalyzing lipid oxidation in biological systems. Classical mechanisms of direct electron transfer to double bonds by higher valence metals and of reduction of hydroperoxides by lower valence metals do not always account for patterns of metal catalysis of lipid oxidation in multiphasic or compartmentalized biological systems. To explain why oxidation kinetics, mechanisms, and products in molecular environments which are both chemically and physically complex often do not follow classical patterns predicted by model system studies, increased consideration must be given to five contemporary issues regarding metal catalysis of lipid oxidation: hypervalent non-heme iron or iron-oxygen complexes, heme catalysis mechanism(s), compartmentalization of reactions and lipid phase reactions of metals, effects of metals on product mixes, and factors affecting the mode of metal catalytic action.

Dietary fat and colon cancer: Animal model studies

Abstract: Since it was first suggested that high dietary fat is a risk factor in colon cancer, there have been several studies to test this hypothesis. Epidemiologic studies suggested a positive association between dietary fat and colon cancer. Laboratory animal model studies demonstrated that not only the amount of rat, but also types of fat differing in fatty acid composition are important determining factors in colon tumor development. Chemically-induced colon tumor incidence was increased in rats fed the semipurified diets containing 23% corn oil, safflower oil, lard or beef tallow (high-fat) as compared to those fed 5% corn oil, safflower oil, lard or beef tallow diets (low-fat). Diets containing 23% conconut oil, olive oil or fish oil, or high-fat diets containing varying levels oftrans fat, had no colon tumor-enhancing effect compared to their respective low fat diets. The stage at which the effect of dietary fat is exerted appears to be mostly during the post-initiation phase of colon carcinogenesis. Lack of a colon tumor enhancing effect of dietary fish oil is observed both during the initiation and postinitiation phases. The mechanisms by which various dietary fats increase colon carcinogenesis are not fully understood. In most instances, however, the high-fat diet appears to enhance tumorigenesis through elevation of agents, such as secondary bile acids, that act as promoters of tumor development. Lack of colon tumor promotion by dietary fish oil andtrans fat appears to be mediated through their effect on mucosal ornithine decarboxylase activity, colonic secondary bile acids and/or prostaglandin synthesis.

Effects of polyphenolic natural products on the lipid profiles of rats fed high fat diets

Abstract: Male Wistar rats were fed a high fat diet (HFD) containing 2.5% cholesterol and 16% lard supplemented with polyphenolic natural products namely quercetin, morin or tannic acid (100 mg/rat/day) for 4, 7 and 10 wk. Rats fed HFD without the supplements served as control. The effects of these compounds on blood lipid profiles, enzymes, liver fat and aorta of the rat were studied. In rats fed HFD containing tannic acid, plasma total cholesterol (TC), low density lipoprotein cholesterol (LDLC) and triglyceride (TG) were reduced by 33.3%, 29.6% and 65.1%, respectively, at week 10. High density lipoprotein cholesterol (HDLC) concentration was not altered. Fat deposition was also decreased in the liver of these rats. Morin significantly reduced plasma TG (65.1%) and liver fat only at week 7 while at week 10 it reduced plasma TC and LDLC by 30.9% and 29.3% respectively. The plasma HDLC concentration was increased by 47.3% at week 4 but no effect was seen at weeks 7 and 10. In the rats fed HFD containing quercetin, plasma HDLC was increased by 28.6% at week 7 but at week 10, plasma LDLC was increased by 21.2%. Quercetin did not cause any significant changes on the plasma TC, TG and liver fat at weeks 4, 7 and 10. Plasma alanine aminotransferase, alkaline phosphatase and bilirubin in control and treated groups were not significantly different. However, hepatic lipase activity in rats fed tannic acid was significantly lower. Aortae of all groups of rats showed no abnormalities. The present report indicates that tannic acid and morin are effective in reducing plasma and liver lipids when supplemented with a high fat diet in rats.

Ascorbate and phenolic antioxidant interactions in prevention of liposomal oxidation

Abstract: Efficient prevention of membrane lipid peroxidation by vitamin E (α-tocopherol) may involve its regeneration by vitamin C (ascorbate). Conceivably, the efficacy of antioxidants designed as therapeutic agents could be enhanced if a similar regeneration were favorable; thus, a model membrane system was developed which allowed assessment of interaction of phenolic antioxidants with ascorbate and ascorbyl-6-palmitate. Ascorbate alone (50–200 μM) potentiated oxidation of soybean phosphatidylcholine liposomes by Fe2+/histidine-Fe3+, an effect which was temporally related to reduction of Fe3+ generated during oxidation. Addition of 200 μM ascorbate to α-tocopherol-containing liposomes (0.1 mol%) resulted in marked, synergistic protection. Accordingly, in the presence but not absence of ascorbate, α-tocopherol levels were maintained relatively constant during Fe2+/histidine-Fe3+ exposure. Probucol (4,4′-[(1-methylethylidine)bis(thio)]bis[2,6-bis(1,1-dimethylethyl)]phenol), and antioxidant which prevents oxidation of low density lipoproteins, and its analogues MDL 27,968 (4,4′-[(1-methylethylidene)bis(thio)]-bis[2,6-dimethyl]phenol) and MDL 28,881 (2,6-bis(1,1-dimethylethyl)-4-[(3,7,11-trimethyldodecyl)thio]phenol) prevented oxidation but exhibited no synergy with ascorbate. Ascorbyl-6-palmitate itself was an effective antioxidant but did not interact synergistically with any of the phenolic antioxidants. Differential scanning calorimetry revealed significant differences among the antioxidants in their effect on the liquid-crystalline phase transition of dipalmitoyl phosphatidylcholine (DPPC) liposomes. Both α-tocopherol and MDL 27,968 significantly reduced the phase transition temperature and the enthalpy of the transition. MDL 28,881 had no effect while probucol was intermediate. The potential for ascorbate or its analogues to interact with phenolic antioxidants to provide a more effective antioxidant system appears to be dictated by structural features and by the location of the antioxidants in the membrane.

Essentiality of dietary omega 3 fatty acids for premature infants: plasma and red blood cell fatty acid composition.

Abstract: Pre-term infants, that are not breast-fed, are deprived of vital intrauterine fat accretion during late pregnancy and must rely on formula to obtain fatty acids essential for normal development, particularly of the visual system. Preterm infants (30 wk postconception) receiving human milk were compared to infants given one of the following formulae: Formula A was a commercial preterm formula with predominantly 18:2 omega 6 (24.2%) and low (0.5%) 18:3 omega 3; Formula B was based on soy oil and contained similar 18:2 omega 6 levels (20%) and high 18:3 omega 3 (2.7%); Formula C was also a soy oil-based formula (20% 18:2, 1.4% 18:3) but was supplemented with marine oil to provide omega 3 long-chain polyunsaturated fatty acids (LCP) at a level (docosahexaenoic acid, DHA, 0.35%) equivalent to human milk. At entry (10 days of age), the fatty acid composition of plasma and red blood cell (RBC) membrane lipids of the formula groups were identical. By 36 wk postconception, the DHA content in lipids of group A was significantly reduced compared to that in the human milk and marine oil formula groups. Omega-3 LCP results were further amplified by 57 wk with compensatory increases in 22:5 omega 6 in both plasma and RBC lipids. Provision of 2.7% alpha-linolenic acid in formula group B was sufficient to maintain 22:6 omega 3 levels equivalent to those in human milk-fed infants at 36 wk but not at 57 wk. Effects on the production of thiobarbituric acid reactive substances and fragility of RBC attributable to the marine oil supplementation were negligible. The results support the essentiality of omega 3 fatty acids for preterm infants to obtain fatty acid profiles comparable to infants receiving human milk. Formula for preterm infants should be supplemented with omega 3 fatty acids including LCP.

Effect of fish oil on the fatty acid composition of human milk and maternal and infant erythrocytes.

Abstract: To examine the effect of fish oil supplementation on the fatty acid (FA) composition of human milk and maternal and infant erythrocytes, five lactating women were supplemented with 6 g of fish oil daily for 21d. Usual maternal diets contained 1,147 mg of total n−3 FA, with 120 mg from very long-chain (>C18) n−3 FA. Supplementation increased dietary levels to 3,092 mg of total n−3 FA and 2,006 mg of very long-chain n−3 FA. Milk samples were collected daily, prior to fish oil ingestion, and at 4-h intervals on days 1, 7, 14 and 21. Milk n−3 FA content increased within 8 h and reached steady state levels within one week. The n−6 fatty acid content decreased. Erythrocyte eicosapentaenoic acid content increased from 0.24% to 1.4% (P<0.01) in mothers and from 0.11% to 0.70% (P<0.05) in infants. Docosapentaenoic acid increased from 1.4% to 2.2% (P<0.05) in mothers and from 0.30% to 0.78% (P<0.01) in infants. There was no significant change in docosahexaenoic acid or n−6 fatty acid content. Maternal platelet aggregation responses were variable. No differences in milk or plasma tocopherol levels were noted.

Cholestane as a digestibility marker in the absorption of polyunsaturated fatty acid ethyl esters in Atlantic salmon

Abstract: Salmonid fish require long-chain n−3 fatty acids in their diet. The digestibility of different chemical forms of fish oil fatty acids, fed as triacylglycerols, free fatty acids or ethyl esters, was examined in 300 g farmed Atlantic salmon (Salmo salar) using cholestane as an indicator of fat absorptionin lieu of the chromium oxide (Cr2O3) which is commonly used as a marker in digestibility studies. It was established that the two digestibility markers gave similar results. Conveniently, cholestane does not require a separate analysis if fatty acids are to be determined by appropriate gas-liquid chromatography. The long-chain polyunsaturated fatty acids were particularly well absorbed, the apparent digestibility being 90–98% when feeding triacylglycerols or free fatty acids. However, the digestibility of monounsaturated fatty acids (75–94%) was lower, and lower still for saturated fatty acids (50–80%). Ethyl esters of fatty acids were significantly less well absorbed (P<0.05) than were the corresponding fatty acids in free acid or triacylglycerol form. Irrespective of dietary fat type, only free fatty acids were identified in feces, indicating total hydrolysis of triacylglycerols and ethyl esters.

Studies on the transfer of tocopherol between lipoproteins.

Abstract: The net transfer of labeled alpha-tocopherol from donor to acceptor lipoproteins at physiological concentrations was investigated. Labeled lipoproteins were isolated i) following in vitro addition of [3,4-3H] all rac-alpha-tocopherol to plasma, or ii) from plasma obtained 12-16 h after ingestion by normal subjects of an oral dose (100 mg each) of 2R,4'R,8'R-alpha-[5,7-(C2H3)2]tocopheryl acetate and 2S,4'R,'R-alpha-[5-C2H3]tocopheryl acetate. A constant amount (on a protein basis) of labeled lipoprotein was incubated with an increasing amount of unlabeled acceptor lipoprotein for 2 h at 37 degrees C. No discrimination between stereoisomers of alpha-tocopherol was detected. Labeled VLDL and labeled LDL (very low and low density lipoproteins, respectively) tended to retain their labeled tocopherol. Labeled high density lipoproteins (HDL) readily transferred the labeled tocopherol to VLDL (> 60% transferred), while the transfer to LDL was dependent upon the ratio of labeled HDL/LDL with a lower net transfer at higher ratios. This dependency of the distribution of tocopherol upon the ratio of HDL/LDL was also observed in vivo. The tocopherol/mg HDL protein was measured in 11 subjects with varying HDL levels. As the % HDL in the plasma increased from 14 to 50%, the tocopherol/HDL protein also increased (r2 = 0.37, P < 0.05).

Dietary ether lipid incorporation into tissue plasmalogens of humans and rodents

Abstract: Chronic feeding of 1-O-octadecyl-sn-glycerol (batyl alcohol) to patients suffering from congenital deficiency in tissue ether glycerolipids showed an increase in the plasmalogens content of their erythrocytes However, nothing is known about the ether lipid content of other tissues in these patients Feeding 1-O-heptadecyl-sn-glycerol to young rats showed that this uncommon ether lipid was incorporated to a high extent into the plasmalogens of all tissues except brain Comparative studies with other precursors, such as 3-O-heptadecyl-sn-glycerol, heptadecanol and heptadecanoic acid, indicated a stereospecific incorporation of the dietary 1-O-alkyl-sn-glycerols into tissue plasmalogens without cleavage of the ether bond Dietary ether lipids were also shown to be transferred from mothers to suckling rats, but not from pregnant rats to fetuses The implication of these results to possible dietary ether lipid therapy for patients suffering from peroxisomal disorders is discussed

Humans, lipids and evolution.

Abstract: The genetically ordered physiology of contemporary humans was selected over eons of evolutionary experience for a nutritional pattern affording much less fat, particularly less saturated fat. Current dietary recommendations do not accord exactly with those generated by an understanding of prior hominoid/hominid evolution. Similarly, widely advocated standards for serum cholesterol values fail to match those observed in recently studied hunter-gatherers, whose experience represents the closest living approximation of “natural” human lipid metabolism. The evolutionary paradigm suggests that fats should comprise 20–25% of total energy intake, that the ratio of polyunsaturated to saturated fat should exceed 1.0, and that total serum cholesterol levels should be below 150 mg/dL (∼4 mM/L).

Changes in blood lipids and fibrinogen with a note on safety in a long term study on the effects of n-3 fatty acids in subjects receiving fish oil supplements and followed for seven years

Abstract: The present study was designed to assess the effectiveness of the n−3 fatty acids in modifying serum total, low density lipoprotein and high density lipoprotein (HDL) cholesterol, as well as serum triglycerides, over a seven-year period. Changes in plasma fibrinogen were recorded and long term safety assessed. A total of 365 subjects with ischemic heart disease (IHD), hyperlipidemia or a strong family history of IHD had their diet supplemented with MaxEPA (Seven Seas Ltd., Hull, England) fish oil containing 18–19% eicosapentaenoic acid. Venous blood samples were taken at regular intervals for lipid and fibrinogen assays and routine clinical chemistry and hematological profiling. Current medication was recorded and no further dietary modification was attempted. Triglyceride and fibrinogen were significantly reduced, whereas a significant reduction in total cholesterol occurred only in the subjects with a pre-oil level>6.5 mmol/L. HDL cholesterol significantly increased over the study period. Clinical chemistry and hematological profiles were not adversely affected, and platelet count did not change significantly. The type of lipid changes observed were those usually considered antiatherogenic. Reducing fibrinogen may result in beneficial changes in the pathological processes leading to thrombotic occlusion. The consumption of MaxEPA by our patients over a seven-year period did not indicate any adverse effects.

Inhibition of ferrous-induced lipid peroxidation by pyrimido-pyrimidine derivatives in human liver membranes

Abstract: The effects of pyrimido-pyrimidine derivatives (dipyridamole, RA-642, and RA-233) on lipid peroxidation, using d-α-tocopherol as standard, were studied in enriched membrane fractions from human and rat hepatocytes. Equimolar concentrations of ferrous sulfate and ascorbic acid were used to induce lipid peroxidation. The amount of peroxidized lipids observed in membrane fractions from human liver was smaller than in those from rat liver. In both species, however, pyrimido-pyrimidine derivatives, except for RA-233 in rat liver, inhibited lipid peroxidation dose-dependently in the following sequence: RA-642 > dipyridamole > d-α-tocopherol RA-233.

Metabolism of [1‐14C]docosahexaenoate (22∶6n−3), [1‐14C]eicosapentaenoate (20∶5n−3) and [1‐14C]linolenate (18∶3n−3) in brain cells from juvenile turbotScophthalmus maximus

Abstract: The incorporation of [1-14C]18∶3n−3, (LNA) and [1-14C]-22∶6n−3 (DHA), and the metabolismvia the desaturase/elongase pathways of [1-14C]LNA, and [1-14C]20∶5n−3 (EPA) were studied in brain cells from newly-weaned (1-month-old) and 4-month-old turbot. The rank order of the extent of net incorporation of both LNA and DHA into glycerophospholipids was total diradyl glycerophosphocholines (CPL)> total diradyl glycerophosphoethanolamines (EPL)> phosphatidylserine (PS) and phosphatidylinositol (PI) and was independent of the polyunsaturated fatty acid added, the age of the fish and the time of incubation. However, the rate of incorporation of LNA into total lipid, CPL, EPL and PS was significantly greater than the rate of incorporation of DHA, and there was a significantly greater amount of DHA incorporated into EPL than LNA. There was no significant difference between the amounts of LNA and DHA incorporated into total lipid, CPL, PS and PI. Therefore, little preferential uptake and incorporation of DHA into brain cells was apparent. In 24-h incubations, on average 1.1% and 8.5% of radioactivity from [1-14C]LNA and [1-14C]EPA, respectively, were recovered in the DHA fraction. Therefore, LNA cannot contribute significantly to brain DHA levels in the turbot but EPA can. There were no significant differences between the amounts of radioactivity from either [1-14C]LNA or [1-14C]EPA recovered in the individual products/intermediates of the desaturase pathways in brain cells from 30-day-old and 120-day-old turbot.

Comparison of sulfoquinovosyl diacylglycerol from spinach and the purple bacteriumRhodobacter sphaeroides by fast atom bombardment tandem mass spectrometry

Abstract: Isolated sulfoquinovosyl-diacylglycerol (SQD) from spinach and the purple bacteriumRhodobacter sphaeroides provide two sources of very different molecular species of SQD. We were able to demonstrate by fast atom bombardment-collisionally activated dissociation tandem mass spectrometry in the negative ion mode that the sulfoquinovosyl head group of the plant and bacterial lipids can be characterized by the common fragmentation pattern found in the spectra of both samples. Differences in the acyl functions from the two sources were also identified by this technique. SQD specific fragments are found atm/z 299, 283, 241, 225, 165 and 80 which indicate the presence of the sulfoquinovosyl moiety. The two predominant molecular species found in spinach contain palmitic and linolenic ([M−H]− atm/z 815) or two linolenic acids ([M−H]− atm/z 837) in thesn−1 andsn−2 positions, while the two major species of the bacterial lipid contain palmitic and 18∶1 (vaccenic) cids ([M−H]− atm/z 819) or stearic and 18∶1 (vaccenic) acids, ([M−H]− atm/z 847), respectively.

Effects of dietary linseed oil and marine oil on lipid peroxidation in monkey liver in vivo and in vitro

Abstract: Diets rich in linoleic acid (CO) from corn oil, or in linoleic acid and either α-linolenic acid (LO) based on linseed oil or n−3 fatty acids (MO) from menhaden oil were fed to male and female Cynomolgus monkeys for 15 wk. In the liver a 40% reduction of α-tocopherol occurred in the MO group relative to the CO and LO groups followed by increased formation of lipofuscinin vivo. A four-fold increase of α-tocopherol in the MO diet (MO+E) brought the level in the liver to that found with CO and LO. The increased peroxidation in the MO group in the liver phospholipids was associated with the replacement of 60% of the n−6 fatty acids by n−3 fatty acids from menhaden oil. Similar fatty acid profiles were found in groups fed MO and MO+E, respectively. Compared to the CO fed group, feeding α-linolenic acid only resulted in a slight incorporation of n−3 fatty acids in the liver membranes mainly due to a direct incorporation of α-linolenic acid. However, in monkeys fed menhaden oil more than 30% of the total fatty acids in the liver phospholipids were n−3 fatty acids. The various diets did not influence the activity of liver catalase (EC 1.11.1.6) nor superoxide dismutase (EC 1.15.1.1), but glutathione-peroxidase activity (EC 1.11.1.9) was higher in monkeys fed the MO diet. The catalase activity in females was 20% higher than in males. In anin vitro assay, liver microsomes from monkeys fed the MO diet or the MO diet supplemented with tocopherol produced similar amounts of thiobarbituric acid reactive substances and at a much higher rate than microsomes from the CO and LO groups. It appeared that α-tocopherol did not protect long-chain n−3 C20 and C22 fatty acids as well as n−6 fattya acids against peroxidation. The present data showed that monkeys were not fully able to compensate for increased peroxidative stress but a four-fold supplement of vitamin E to the diets reduced the oxidation.

Eicosapentaenoic acid at hypotriglyceridemic dose enhances the hepatic antioxidant defense in mice.

Abstract: The effect of oral administration of purified (95%) eicosapentaenoic acid on serum lipids, hepatic peroxisomal enzymes, antioxidant enzymes and lipid peroxidation was compared with that of palmitic acid fed mice and corresponding controls. After 10 d, a dose of 1000 mg eicosapentaenoic acid per day/kg body weight lowered serum triglycerides by 45%, while no significant change in serum cholesterol level was noted in comparison to palmitic acid fed mice and controls. Hepatic acyl-CoA oxidase and catalase activities increased by 50% and 30%, respectively, in the eicosapentaenoic acid fed group. In addition, the hepatic reduced glutathione content and the activities of glutathione transferase, glutathione peroxidase and glutathione reductase, increased significantly during eicosapentaenoic acid treatment. The levels of hepatic lipid peroxides were lower after eicosapentaenoic acid feeding, while no significant change was noted in the palmitic acid fed mice when compared to the controls. Taken together, the present data demonstrate for the first time that at hypolipidemic doses eicosapentaenoic acid feeding i) enhances the hepatic antioxidant defense, and ii) does not cause a significant differential induction of the two peroxisomal enzymes, acyl-CoA oxidase and catalase, as was noted after administration of hypolipidemic peroxisome proliferating compounds, such as clofibrate in rodents.

The dual effect of oxidation on lipid bilayer structure

Abstract: Sphingomyelin membranes were prepared with different levels of oxidative damage caused bytert-butyl hydroperoxide (TBH). Temperature-induced changes in membrane hydrocarbon chain packing (phase transitions) were monitored using infrared spectroscopy. Lipid phase transition characteristics were evaluated from thermodynamic parameters fitted to the experimental transition curve data. At temperatures below the lipid phase transition Tc, hydrocarbon chains pack in an ordered state whereas above the Tc the hydrocarbonchains pack in a disordered state. Compared to the non-oxidized control, the packing of the hydrocarbon chains of mildly oxidized sphingomyelin ( 10nmol TBH/mg lipid) were more disordered at temperatures above and below the Tc compared to the control samples. These results suggest that lipid oxidation has a dual effect on lipid order. A more ordered or disordered state may result depending on the degree of oxidation and the state of lipid order prior to oxidation. These results could be important for explaining the structural changes in oxidized membranes high in sphingomyelin such as those found in the ocular lens and liver plasma membranes.

Dietary fat, fatty acids and prostate cancer

Abstract: International comparisons suggest a relationship between prostate cancer incidence and dietary fat, an inference supported by migration studies, the changing incidence rates and levels of animal fat consumption in Japan and the results from some case-control studies. Overall, however, epidemiological studies have been inconclusive, and although prostate cancer is one of the hormone-dependent tumors, evidence of interactions between dietary fats and male endocrine function is incomplete. Laboratory experimentation has shown that n−6 fatty acids stimulate and n−3 fatty acids inhibit human prostate cancer cells in culture; also, feeding diets rich in marine oils suppresses growth of these cells as solid tumors in athymic nude mice. These growth effects of polyunsaturated fatty acids appear to involve both prostaglandins and leukotrienes and to interconnect with autocrine regulation by epidermal growth factor-related polypeptides.

High-performance liquid chromatography of human milk triacylglycerols and gas chromatography of component fatty acids.

Abstract: Human milk triacylglycerols were separated by high-performance liquid chromatography. A 5-μ Supelcosil LC-18 column (Supelco, Inc., Bellefonte, PA) was used with acetone/acetonitrile (64∶36, vol/vol) as mobile phase. Triacylglycerols were tentatively identified based on theoretical carbon number and relative retention time. Despite changes resulting from dietary fat variation, the major component triacylglycerols were those composed of palmitic, oleic and linoleic acids. Triacylglycerols with palmitic, stearic and oleic acids were present as minor components. Fatty acids were quantified by gas chromatography relative to an internal standard. Ratios of n−6/n−3 fatty acids were found to be high than previously reported.

Lipid composition of subcellular membranes from larvae and prepupae of Drosophila melanogaster.

Abstract: Subcellular membranes were analyzed for their lipid composition and protein content at two developmental points representing the third instar wandering larvae and prepupal stages of Drosophila. At both stages, phosphatidylethanolamine (PE) and phosphatidylcholine (PC) were the major constituents with phosphatidylinositol (PI), phosphatidylserine (PS), diphosphatidylglycerol (DPG) and phosphatidic acid (PA) being relatively minor components. In total homogenates and in the nuclear-enriched fraction there was no significant difference in the phospholipid composition of the wandering larvae and prepupae. In mitochondria only a significant increase in the minor component PS was observed in the prepupae. In lysosomal membranes on the other hand, the relative abundance of the major components PE and PC increased in the prepupae although the molar ratios of the two lipids remained almost constant. The fatty acid composition of the phospholipids remained virtually unchanged in all of the fractions examined, including the lysosomes, and there was no evidence of lipid peroxidation. With regard to cellular degeneration and the involvement of lysosomes, we conclude that mechanisms other than gross modification of the lipid and/or lipid/protein ratio of their membranes are involved in the liberation of the acid phosphatase contents.

α-Helical requirements for free apolipoproteins to generate HDL and to induce cellular lipid efflux

Abstract: The structural requirement has been studied for apolipoproteins in their free form to interact with cells, to generate high density lipoprotein (HDL), and to cause cellular lipid efflux (J. Biol. Chem. 266, 3080–3086, 1991). It is shown that human apolipoprotein (apo) A-IV and apolipophorin III ofManduca sexta cause cholesterol efflux from cholesterol-loaded mouse peritoneal macrophages and reduce intracellularly accumulated cholesteryl ester as a results of forming HDL-like particles with cellular lipids, as do apoA-I, A-II and E. On the other hand, similar to apoC-III, reduced-and-carboxymethylated human apoA-II had no such effect. Thus, apolipoproteins seem to require at least four amphiphilic helical segments per molecule to express this function.

Effects of aging on the content, composition and synthesis of sphingomyelin in the central nervous system

Abstract: Sphingomyelin (SPH) content and composition in different regions of the brain were analyzed in 2.5, 21.5 and 26.5-month-old rats. SPH content increased in the cerebral hemispheres, cerebellum and medulla oblongata plus pons as age increased. The highest SPH content was observed in 26.5-month-old rats, with values increasing by 1.74, 2.75 and 0.88-fold, respectively, over 2.5-month-old rats. The SPH fatty acid composition of brains from aged rats was markedly different from that of adult rats. Between 2.5 and 26.5 months of age the monoenoic/saturated fatty acid ratio increased from 0.22, 0.30 and 0.54 to 0.54, 0.68 and 1.03 in cerebral hemispheres, cerebellum and medulla oblongata plus pons, respectively. The percentage and content of fatty acids longer than 22 carbon atoms esterified to SPH increased with age from 18, 26 and 44 to 48, 52 and 62 mole % in cerebral hemispheres, cerebellum and medulla oblongata plus pons in 26.5-month-old rats. In subcortical white matter from aged rats, monoenoic 22-26 carbon atom fatty acids increased more than the saturated ones in 21.5-month-old rats relative to 2.5-month-old rats. In vitro synthesis of SPH from [3H]choline and [3H]palmitic acid in cerebral cortex and cerebellum showed no significant differences between adult rats and those 21.5 months of age. In cerebellum and in cerebral cortex, [14C]serine incorporation increased in aged rats. The results suggest that aging induces increases in both SPH content and in the monoenoic/saturated fatty acid ratio. These increases are quantitatively different in all brain regions analyzed.

Purification and characterization of an extracellular lipase from the fungusRhizopus delemar

Abstract: The complete purification and characterization of an extracellular lipase (acylglycerol acylhydrolase, EC 3.1.1.3) fromR. delemar is described. The final product was homogeneous as judged by electrophoresis in denaturing polyacrylamide gels and by isoelectric focusing, and was shown by means of an activity stain to be lipolytic. The purified enzyme had a monomer molecular weight of 30,300, an isoelectric point of 8.6, and approximately one monosaccharide moiety per molecule.N-Terminal sequence data (28 residues) and the amino acid composition of the lipase indicated that it corresponds to the product of a lipase-encoding cDNA previously isolated fromR. delemar. Optimal activity occurred between pH 8.0 and 8.5. The activity and stability of the enzyme were maximum at 30°C. Divalent cations were required for activity, with barium, calcium and manganese conferring maximum activity. Activation by calcium was maximal at and above 10 mM. The lipase was not inactivated by reducing agents, sodium fluoride or phenylmethlsufonyl fluoride. It was resistant toN-ethylmaleimide, and inactivated byp-chloromercuribenzoic acid in a manner which was not reversed by cysteine.

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

Abstract: 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.

Adipose hormone-sensitive lipase preferentially releases polyunsaturated fatty acids from triglycerides

Abstract: Rat adipose hormone-sensitive lipase-mediated release of fatty acids from triglycerides was studied in three model systems: i) cultured preadipocytes containing polyunsaturated fatty acid-enriched triglyceride; ii) perfused epididymal fat pads; and iii) in vitro incubations of crude preparations of hormone-sensitive lipase with synthetic triglyceride-analogues as substrates. We found that cultured preadipocytes challenged with 10 microM norepinephrine tended to release more omega 6 and omega 3 polyunsaturated fatty acids than saturated fatty acids. Fat pads perfused with 10 microM norepinephrine preferentially released arachidonate and alpha-linolenate but tended to retain oleate and linoleate. Finally, crude preparations of hormone-sensitive lipase released from the triglyceride-analogue substrates alpha-linolenate twice as fast as oleate. We conclude that rat adipose hormone-sensitive lipase preferentially releases polyunsaturated fatty acids from triglycerides. We suggest that this may be a mechanism by which these fatty acids are kept from being trapped in fat depots and maintained in the circulation.