Microbial biohydrogenation of oleic acid to trans isomers in vitro

Ruminant products are significant sources of dietary trans fatty acids. Trans fatty acids, including various conjugated linoleic acid isomers, have been shown to act as metabolic modifiers of lipid metabolism. Trans fatty acids originate from biohydrogenation of dietary unsaturated fatty acids by gut microbes; however, the exact synthetic pathways are unclear. It was our goal to examine the biohydrogenation pathway for oleic acid, where oleic acid is hydrogenated directly to stearic acid. Our objective in this study was to trace the time course of appearance of 13C in labeled oleic acid to determine if trans monoenes are formed from the 13C-labeled oleic acid or if the 13C appears only in stearic acid as described in reviews of earlier work. Enrichments were calculated from the mass abundance of 13C in major fatty acid fragments and expressed as a percentage of total carbon isotopomers. Significant 13C enrichment was found in stearic acid, oleic acid, trans-6, trans-7, and in all trans C18:1 in positions 9-16. We concluded that the biohydrogenation of oleic acid by mixed ruminal microbes involves the formation of several positional isomers of trans monoenes rather than only direct biohydrogenation to form stearic acid as previously described.     

Effect of dietary fats on linoleic acid metabolism. A radiolabel study in rats

Effects on the linoleic acid metabolism in vivo of three dietary fats, rich in either oleic acid, trans fatty acids or alpha-linolenic acid, and all with the same linoleic acid content, were investigated in male Wistar rats. After 6 weeks of feeding, the rats were intubated with [1-14C]linoleic acid and [3H]oleic acid. The incorporation of these radiolabels into liver, heart and serum was investigated 2, 4, 8, 24 and 48 h after intubation. The amount of 14C-labelled arachidonic acid incorporated into the liver phospholipid of the group fed the oleic acid-rich diet was significantly higher than that of the other groups. However, compared to the trans fatty acids-containing diet, the oleic acid-rich diet induced only a slightly higher arachidonic acid level in the phospholipid fraction of the tissues as determined by GLC. Dietary alpha-linolenic acid more than halved the arachidonic acid levels. Our results do not support the hypothesis that the delta 6-desaturase system actually determines the polyunsaturated fatty acid levels in tissue lipids by regulating the amount of polyunsaturated fatty acids (e.g., arachidonic acid) synthesized. The biosynthesis of polyunsaturated fatty acids only is not sufficient to explain the complicated changes in fatty acid compositions as observed after feeding different dietary fats.     

Dietary effects on brain fatty acid composition: the reversibility of n-3 fatty acid deficiency and turnover of docosahexaenoic acid in the brain, erythrocytes, and plasma of rhesus monkeys

Rhesus monkeys given pre- and postnatal diets deficient in n-3 essential fatty acids develop low levels of docosahexaenoic acid (22:6 n-3, DHA) in the cerebral cortex and retina and impaired visual function. This highly polyunsaturated fatty acid is an important component of retinal photoreceptors and brain synaptic membranes. To study the turnover of polyunsaturated fatty acids in the brain and the reversibility of n-3 fatty acid deficiency, we fed five deficient juvenile rhesus monkeys a fish oil diet rich in DHA and other n-3 fatty acids for up to 129 weeks. The results of serial biopsy samples of the cerebral cortex indicated that the changes of brain fatty acid composition began as early as 1 week after fish oil feeding and stabilized at 12 weeks. The DHA content of the phosphatidylethanolamine of the frontal cortex increased progressively from 3.9 +/- 1.2 to 28.4 +/- 1.7 percent of total fatty acids. The n-6 fatty acid, 22:5, abnormally high in the cerebral cortex of n-3 deficient monkeys, decreased reciprocally from 16.2 +/- 3.1 to 1.6 +/- 0.4%. The half-life (t 1/2) of DHA in brain phosphatidylethanolamine was estimated to be 21 days. The fatty acids of other phospholipids in the brain (phosphatidylcholine, -serine, and -inositol) showed similar changes. The DHA content of plasma and erythrocyte phospholipids also increased greatly, with estimated half-lives of 29 and 21 days, respectively. We conclude that monkey cerebral cortex with an abnormal fatty acid composition produced by dietary n-3 fatty acid deficiency has a remarkable capacity to change its fatty acid content after dietary fish oil, both to increase 22:6 n-3 and to decrease 22:5 n-6 fatty acids. The biochemical evidence of n-3 fatty acid deficiency was completely corrected. These data imply a greater lability of the fatty acids of the phospholipids of the cerebral cortex than has been hitherto appreciated.     

Arachidonate geometrical isomers generated by thiyl radicals: the relationship with trans lipids detected in biological samples

The presence of trans fatty acids in mammalians is attributed to exogenous sources; nevertheless, trans isomers could be easily formed by free radical-catalyzed isomerization processes in vivo. The isomerization of methyl arachidonate (all-cis isomer) catalyzed by thiyl radical is proposed as a methodology applicable in biochemical laboratories, which produces mono- and di-trans isomers. Carbon-13 nuclear magnetic resonance spectroscopy shows that the carbon atom in position 15 is characteristic for each mono- and di-trans isomer. Antioxidants, such as alpha-tocopherol and all-trans-retinol acetate, inhibited the isomerization process. Trans phospholipids are formed in erythrocyte membranes by exposing blood to gamma-irradiation in the presence of thiols, which is in contradiction with the known role of these compounds as radioprotectors. Trans isomers are also analyzed in tissues harvested from breast cancer patients and compared to the adipose breast tissue taken a few centimeters from the edge of the tumor from the same patient. This work is generally aimed at contributing to the debate on trans fatty acids and stimulating a reconsideration of the current view on the exclusive presence of cis double bonds in cell membranes by studying radical processes that could affect or protect this natural configuration.     

Isomerization increases the postprandial oxidation of linoleic acid but not alpha-linolenic acid in men

Human lipid intake contains various amounts of trans fatty acids. Refined vegetable and frying oils, rich in linoleic acid and/or alpha-linolenic acid, are the main dietary sources of trans-18:2 and trans-18:3 fatty acids. The aim of the present study was to compare the oxidation of linoleic acid, alpha-linolenic acid, and their major trans isomers in human volunteers. For that purpose, TG, each containing two molecules of [1-(13)C]linoleic acid, alpha-[1-(13)C]linolenic acid, [1-(13)C]-9cis,12trans-18:2, or [1-(13)C]-9cis,12cis,15trans-18:3, were synthesized. Eight healthy young men ingested labeled TG mixed with 30 g of olive oil. Total CO(2) production and (13)CO(2) excretion were determined over 48 h. The pattern of oxidation was similar for the four fatty acids, with a peak at 8 h and a return to baseline at 24 h. Cumulative oxidation over 8 h of linoleic acid, 9cis,12trans-18:2, alpha-linolenic acid, and 9cis,12cis,15trans-18:3 were, respectively, 14.0 +/- 4.1%, 24.7 +/- 6.7%, 23.6 +/- 3.3%, and 23.4 +/- 3.7% of the oral load, showing that isomerization increases the postprandial oxidation of linoleic acid but not alpha-linolenic acid in men.     

Modulation of native T-type calcium channels by omega-3 fatty acids

Low voltage-activated, rapidly inactivating T-type Ca(2+) channels are found in a variety of cells where they regulate electrical activity and Ca(2+) entry. In whole-cell patch clamp recordings from bovine adrenal zona fasciculata cells, cis-polyunsaturated omega-3 fatty acids including docosahexaenoic acid (DHA), eicosapentaenoic acid, and alpha-linolenic acid inhibited T-type Ca(2+) current (I(T-Ca)) with IC(50)s of 2.4, 6.1, and 14.4microM, respectively. Inhibition of I(T-Ca) by DHA was partially use-dependent. In the absence of stimulation, DHA (5microM) inhibited I(T-Ca) by 59.7+/-8.1% (n=5). When voltage steps to -10mV were applied at 12s intervals, block increased to 80.5+/-7.2%. Inhibition of I(T-Ca) by DHA was accompanied by a shift of -11.7mV in the voltage dependence of steady-state inactivation, and a smaller -3.3mV shift in the voltage dependence of activation. omega-3 fatty acids also selectively altered the gating kinetics of T-type Ca(2+) channels. DHA accelerated T channel recovery from inactivation by approximately 3-fold, but did not affect the kinetics of T channel activation or deactivation. Arachidonic acid, an omega-6 polyunsaturated fatty acid, also inhibited T-type Ca(2+) current at micromolar concentrations, while the trans polyunsaturated fatty acid linolelaidic acid was ineffective. These results identify cis polyunsaturated fatty acids as relatively potent, new T-type Ca(2+) channel antagonists. omega-3 fatty acids are essential dietary components that have been shown to possess remarkable neuroprotective and cardioprotective properties that are likely mediated through suppression of electrical activity and associated Ca(2+) entry. Inhibition of T-type Ca(2+) channels in neurons and cardiac myocytes could contribute significantly to their protective actions.     

The effects of trans trans methyl linoleate on the concentration of prostaglandins and their precursors in rat

Four groups of weanling male rats were fed a diet containing hydrogenated coconut oil (Treatment A); 9-trans, 12-trans linoleate (trans linoleate, Treatment B); an equal mixture of 9-cis, 12-cis linoleate (cis linoleate) and trans linoleate (Treatment C); and cis linoleate (Treatment D); respectively for 12 weeks. The level of dietary fat was 11% of calories. Only trace amount of eicosatrienoic acid (C20:3w6) was detected in tissues, (liver, platelets) of rats in Treatments A and B. The level of C20:3w6 in platelet lipids of Treatments C and D was 0.1 and 0.33% respectively. The level of arachidonic acid in rats on Treatments A, B, C and D was 2.0, 1.4, 14.1 and 17.6% for platelet lipids, respectively. The serum levels of prostaglandin PGE₁ for Treatments A, B, C and D were 1.10 ± 0.24, 0.22 ± 0.02, 3.51 ± 0.58 and 5.69 ± 0.59 ng/ml, respectively and 2.19 ± 0.85, 0.15 ± 0.03, 11.64 ± 2.63 and 24.89 ± 4.35 ng/ml for PGE₂, respectively. Thus feeding trans linoleate to rats apparently caused decreased biosynthesis of PGs resulting from decreased levels of precursor acids. This was apparently due to the inhibition of conversion of cis linoleate to longer chain polyunsaturated fatty acids. The results indicate that the availability of precursor acids is one limiting factor in PG biosynthesis in rats, and small differences in the level of precursor acids, affected by dietary trans fatty acids may cause large variations in amounts of PGs synthesized.     

The effects of trans trans methyl linoleate on the concentration of prostaglandins and their precursors in rat.

Four groups of weanling male rats were fed a diet containing hydrogenated coconut oil (Treatment A); 9-trans, 12-trans linoleate (trans linoleate, (Treatment B); an equal mixture of 9-cis, 12-cis linoleate (cis linoleate) and trans linoleate (Treatment C); and cis linoleate (Treatment D); respectively for 12 weeks. The level of dietary fat was 11% of calories. Only trace amount of eicosatrienoic acid (C20:3w6) was detected in tissues, (liver, platelets) of rats in Treatments A and B. The level of C20:3w6 in platelet lipids of Treatments C and D was 0.1 and 0.33% respectively. The level of arachidonic acid in rats on Treatments A, B, C and D was 2.0, 1.4, 14.1 and 17.6% for platelet lipids, respectively. The serum levels of prostaglandin PGE1 for Treatments A, B, C and D were 1.10 +/- 0.24, 0.22 +/- 0.02, 3.51 +/- 0.58 and 5.69 +/- 0.59 ng/ml, respectively and 2.19 +/- 0.85, 0.15 +/- 0.03, 11.64 +/- 2.63 and 24.89 +/- 4.35 ng/ml for PGE2, respectively. Thus feeding trans linoleate to rats apparently caused decreased biosynthesis of PGs resulting from decreased levels of precursor acids. This was apparently due to the inhibition of conversion of cis linoleate to longer chain polyunsaturated fatty acids. The results indicate that the availability of precursor acids is one limiting factor in PG biosynthesis in rats, and small differences in the level of precursor acids, affected by dietary trans fatty acids may cause large variations in amounts of PGs synthesized.     

Unsaturated fatty acid isomers: effects on the circadian rhythm of a fatty-acid-deficient Neurospora crassa mutant

The fatty acids oleic, linoleic, and linolenic, each of which has a cis double bond at the delta 9 position, are known to lengthen the circadian period of conidiation (spore formation) of strains of Neurospora crassa carrying the cel mutation. cel confers a partial fatty acid requirement on the organism and has been used to promote incorporation of exogenous fatty acids. To test whether a physical effect imparted by the cis double bonds, such as increased membrane fluidity, is critical for the perturbation of the rhythm, various isomers of these fatty acids were supplemented to the bd csp cel strain. Positional isomers of oleic acid, such as petroselinic (delta 6) and vaccenic (delta 11) acids, and longer-chain isomers, such as eicosenoic (delta 11) and erucic (delta 13) acids, did not lengthen the rhythm. The shorter-chain palmitoleic (delta 9) acid did not give a consistent lengthening of the rhythm; it may be elongated to vaccenic acid. In contrast, gamma-linolenic acid (delta 6,9,12) dramatically lengthened the period. Linoelaidic acid (the trans,trans isomer of linoleic acid) lengthened the period at 22 degrees C, but elaidic acid (the trans isomer of oleic acid) did not. Elaidic acid was shown to exert a lengthening effect, but only at lower temperatures. The data do not support a direct physical action as the source of the fatty acids' "chronobiotic" ability.     

The influence of dietary docosahexaenoic acid and arachidonic acid on central nervous system polyunsaturated fatty acid composition

Numerous studies on perinatal long-chain polyunsaturated fatty acid nutrition have clarified the influence of dietary docosahexaenoic acid (DHA) and arachidonic acid (ARA) on central nervous system PUFA concentrations. In humans, omnivorous primates, and piglets, DHA and ARA plasma and red blood cells concentrations rise with dietary preformed DHA and ARA. Brain and retina DHA are responsive to diet while ARA is not. DHA is at highest concentration in cells and tissues associated with high energy consumption, consistent with high DHA levels in mitochondria and synaptosomes. DHA is a substrate for docosanoids, signaling compounds of intense current interest. The high concentration in tissues with high rates of oxidative metabolism may be explained by a critical role related to oxidative metabolism.     

Dietary trans fatty acids modulate erythrocyte membrane fatty acyl composition and insulin binding in monkeys

The substitution of trans- for half of the cis-monounsaturated fatty acids in the diet of Macaca fasicularis monkeys resulted in alterations in erythrocyte fatty acid composition and insulin receptor properties but not in membrane fluidity. Both cis and trans diets contained 10% fat and similar fatty acid compositions, except that approximately 50% of the cis-octadecenoate (c-18:1) in the cis diet was replaced with trans-octadecenoate isomers (t-18:1) in the trans diet. Compared with the cis diet, the trans diet resulted in the incorporation of approximately 11% t-18:1, an approximately 50% decrease in c-18:1, an approximately 16% decrease in total saturated fatty acids, and an approximately 20% increase in 18:2(n-6) in erythrocyte membrane lipids. The increase in 18:2(n-6) may reflect on homeostatic mechanisms designed to maintain overall membrane fluidity, as no diet-related changes in fluidity were observed with diphenylhexatriene steady state fluorescence polarization. Values observed for insulin binding and insulin receptor number were higher and binding affinity was lower in monkeys fed the cis diet. In the absence of an effect on overall membrane fluidity, altered receptor activity suggests that insulin receptor activity is dynamic, requiring specific fluid membrane subdomains or highly specific fatty acid-protein interactions.     

Differential effects of cis and trans fatty acid isomers, oleic and elaidic acids, on the cholesteryl ester transfer protein activity.

In a previous publication (Lagrost, L. and Barter, P.J. (1991) Biochim. Biophys. Acta 1085, 209-216), saturated and cis unsaturated non-esterified fatty acids have been shown to modulate the rate at which cholesteryl esters are transferred from high-density lipoproteins (HDL) to low-density lipoproteins (LDL) in the presence of the human cholesteryl ester transfer protein (CETP). In the present report, the effects of cis (oleic acid) and trans (elaidic acid) monounsaturated isomers on the CETP-mediated transfer of cholesteryl esters between HDL and LDL were compared. Mixtures of human LDL and HDL3, containing or not radiolabelled cholesteryl esters, were incubated at 37 degrees C with CETP in the presence or in the absence of either stearic (18:0), oleic (18:1 cis) or elaidic (18:1 trans) acids. It was observed that oleic acid and elaidic acid had different effects on the CETP-mediated redistribution of radiolabelled cholesteryl esters as well as on the net mass transfer of cholesterol from HDL3 to LDL. In particular, at high non-esterified fatty acid/lipoprotein ratio, the transfer of cholesteryl esters was significantly inhibited by the cis isomer and increased by the trans isomer.     

Synthesis of four isomers of parinaric acid

A simple and reliable method for synthesizing four isomers of parinaric acid from alpha-linolenic acid (ALA) in high yields is described. The methylene-interrupted, cis triene system (1,4,7-octatriene) of ALA and common to other naturally occurring polyunsaturated fatty acids was transformed to a conjugated tetraene system (1,3,5,7-octatetraene). The synthesis involves bromination of ALA using 0.l M Br(2) in a saturated solution of NaBr in methanol, esterification of the fatty acid dibromides, double dehydrobromination by 1,8-diazabicyclo[5.4.0]undec-7-ene and saponification of the conjugated esters to a mixture of free conjugated acids. Addition of one molecule of bromine to the 12,13-double bond of ALA and subsequent dehydrobromination produces alpha-parinaric acid (9Z,11E,13E,15Z-octadecatetraenoic acid); addition of Br(2) to the 9,10-double bond or 15,16-double bond and then dehydrobromination and rearrangement yields 9E,11E,13E,15Z-octadecatetraenoic or 9E,11E,13E,15Z-octadecatetraenoic acids, respectively. The mixture of parinaric acid isomers is obtained in 65% yield, and the isomers can be purified by preparative HPLC; alternatively, the isomers can be converted by base catalyzed cis-trans isomerization (or by treatment with I(2)) to exclusively beta-parinaric acid (9E,11E,13E,15E-octadecatetraenoic acid). The various parinaric acid isomers were characterized by (1)H NMR, (13)C NMR, UV, GLC, HPLC and mass spectrometry.     

Influence of dietary partially hydrogenated fat high in trans fatty acids on lipid composition and function of intestinal brush border membrane in rats

The effect of dietary hydrogenated fat (Indian vanaspati) high in trans fatty acids (6 en%) on lipid composition, fluidity and function of rat intestinal brush border membrane was studied at 2 and 8 en% of linoleic acid. Three groups of weanling rats were fed rice-pulse based diet containing 10% fat over a ten week period: Group I (groundnut oil), Group II (vanaspati), Group III (vanaspati + safflower oil). The functionality of the brush border membrane was assessed by the activity of membrane bound enzymes and transport of D-glucose and L-leucine. The levels of total cholesterol and phospholipids were similar in all groups. The data on fatty acid composition of membrane phospholipids showed that, at 2 en% of linoleic acid in the diet, trans fatty acids lowered arachidonic acid and increased linoleic acid contents indicating altered polyunsaturated fatty acid metabolism. Alkaline phosphatase activity was increased while the activities of sucrase, gamma-glutamyl transpeptidase and transport of D-glucose and L-leucine were not altered by dietary trans fatty acids. However at higher intake of linoleic acid in the diet, trans fatty acids have no effect on polyunsaturated fatty acid composition and alkaline phosphatase activity of intestinal brush border membrane. These data suggest that feeding dietary fat high in trans fatty acids is associated with alteration in intestinal brush border membrane polyunsaturated fatty acid composition and alkaline phosphatase activity only when the dietary linoleic acid is low.     

Effect of radical stress and ageing on the occurrence of trans fatty acids in rats fed a trans-free diet

In a previous paper, we demonstrated that tissue trans fatty acids can not only derive from the diet but also be endogenously formed. The central focus of this study was to prove that the in vivo isomerization occurs via a radical process. Two different models of radical insult were used: CCl(4) and AAPH injection to rats fed a diet completely free of trans isomers. Following this acute radical stress, a significant increase in unnatural trans fatty acid content of erythrocyte, kidney, and heart, but not liver, was observed. These results can be mainly explained by the high content, particularly in the liver, of antioxidant vitamins A and E that exhibit also an "anti-isomerizing" effect. Since during ageing cellular components are exposed to increasing radical insults, the observation of a significant trans fatty acid accumulation in 30-month-old rats could confirm that the in vivo formation of unnatural isomers is due to a radical process. Trans fatty acids can influence the physical characteristics of bilayer microdomains, affecting membrane properties and functions; thus, knowledge of biological radical species responsible for cis/trans isomerization and their possible sources can provide protective systems for preserving lipid geometry.     

How relevant is the ratio of dietary n-6 to n-3 polyunsaturated fatty acids to cardiovascular disease risk? Evidence from the OPTILIP study

PURPOSE OF REVIEW: There has been much debate over the practical utility of the dietary ratio of n-6 to n-3 polyunsaturated fatty acids in optimizing the benefits of n-3 fatty acids (C18-C22) on cardiovascular health. This review examines the supporting evidence from the OPTILIP study within the context of the emerging consensus on the value of this dietary metric. RECENT FINDINGS: The question of whether the ratio of n-6/n-3 polyunsaturated fatty acids or total amounts of dietary polyunsaturated fatty acids is of more importance to cardiovascular health has been addressed recently in a randomly controlled trial (OPTILIP) and in a stable isotope tracer study. These two studies were independently unanimous in concluding that the ratio of n-6/n-3 polyunsaturated fatty acids is of no value in modifying cardiovascular disease risk. The latter study also showed that the absolute amounts of dietary linoleic acid and alpha-linolenic acid are of relevance to the efficiency of conversion of alpha-linolenic acid to eicosapentaenoic acid and docosahexaenoic acid. SUMMARY: This review should help to settle any outstanding controversy over the dietary ratio of n-6/n-3 polyunsaturated fatty acids. It reinforces current recommendations to increase the consumption of preformed eicosapentaenoic acid/docosahexaenoic acid in fish, and supports dietary measures to increase and decrease intakes alpha-linolenic acid and linoleic acid, respectively, to promote the endogenous synthesis of these longer chain n-3 polyunsaturated fatty acids.     

The effects of a diet rich in docosahexaenoic acid on organ and vascular fatty acid composition in spontaneously hypertensive rats

Previous research has shown that dietary docosahexaenoic acid (DHA) attenuates the development of high blood pressure in young spontaneously hypertensive rats (SHR). The purpose of this study was to investigate the effects of dietary DHA on organ and vascular fatty acid composition in SHR. Given the important structural and functional role of fatty acids in cell membranes, alterations in fatty acid composition may contribute to the antihypertensive effect of DHA. SHR were fed a purified diet containing either a corn/soybean oil mixture (CSO, control) or a DHA-enriched oil for 6 weeks. The DHA diet markedly increased the levels of DHA in the aorta, renal artery, plasma, liver, heart, kidney, and lung by 5-, 15-, 7-, 6-, 3.8-, 3.5-, and 8.8-fold (P<0.001), respectively. The levels of eicosapentaenoic acid were also increased while there was a concomitant reduction in arachidonic and adrenic acids. Therefore, dietary DHA increases the incorporation of omega-3 polyunsaturated fatty acids in specific organs and vascular tissue in SHR at the expense of omega-6 polyunsaturated fatty acids.     

Bio-availability and metabolism of n-3 fatty acid rich garden cress (Lepidium sativum) seed oil in albino rats

The ratio of fatty acids namely linoleic acid (LA, 18:2, n-6) and alpha linolenic acid (ALA, 18:3, n-3) in the diet plays an important role in enrichment of ALA in tissues and further conversion to long-chain polyunsaturated fatty acids (LC-PUFA) like eicosapentaenoic acid (EPA, 20:5, n-3) and docosahexaenoic acid (DHA, 22:6, n-3). Garden cress seed oil (GCO) is one of the richest sources of omega-3 fatty acid and contains 29-34.5% of ALA. In this study, dietary supplementation of GCO on bio-availability and metabolism of alpha-linolenic acid was investigated in growing rats. Male wistar rats were fed with semi-purified diets supplemented with 10.0% sunflower oil (SFO 10%); 2.5% GCO and 7.5% SFO (GCO 2.5%); 5% GCO and 5% SFO (GCO 5.0%); 10% GCO (GCO 10%) for a period of 8 weeks. There was no significant difference with regard to the food intake, body weight gain and organ weights of rats in different dietary groups. Rats fed with GCO showed significant increase in ALA levels in serum and tissues compared to SFO fed rats. Feeding rats with 10% GCO lowered hepatic cholesterol by 12.3% and serum triglycerides by 40.4% compared to SFO fed group. Very low density lipoprotein cholesterol (VLDL-C) and low density lipoprotein cholesterol (LDL-C) levels decreased by 9.45% in serum of 10% GCO fed rats, while HDL remained unchanged among GCO fed rats. Adipose tissue showed incorporation of 3.3-17.4% of ALA and correlated with incremental intake of ALA. Except in adipose tissue, the EPA, DHA levels increased significantly in serum, liver, heart and brain tissues in GCO fed rats. A maximum level of DHA was registered in brain (11.6%) and to lesser extent in serum and liver tissues. A significant decrease in LA and its metabolite arachidonic acid (AA) was observed in serum and liver tissue of rats fed on GCO. Significant improvement in n-6/n-3 fatty acid ratio was observed in GCO based diets compared to diet containing SFO. This is the first study to demonstrate that supplementation of GCO increases serum and liver ALA, EPA, DHA and decreases LA and AA in rats. Therefore, the GCO can be considered as a potential, alternate dietary source of ALA.     

Effects of vitamin E and selenium deficiency on the fatty acid composition of rat retinal tissues.

The fatty acid composition of retinal tissues was measured in rats maintained for 26--32 weeks on each of the following diets: a purified basal diet deficient in alpha-tocopherol and selenium, an identical control diet supplemented with alpha-tocopherol and selenium, and a commerical laboratory rat chow. Dietary deficiencies of antioxidant nutrients were found to cause a large decrease in total polyunsaturated fatty acids in the retinal pigment epithelium, a small decrease in the retinal rod outer segments, but no change in the whole retina or liver when compared to tissues from animals fed the vitamin E- and selenium-supplemented control diet. The polyunsaturated fatty acid content which we have observed for the retinal pigment epithelium from rats fed commerical lab chow is similar to that which we observed for bovine retinal pigment epithelium. Our results indicate that changes in fatty acid composition are not generalized to all tissues in severely antioxidant-deficient animals, but that changes do occur in some tissues, such as the retinal pigment epithelium, which appears to be particularly sensitive to in vivo lipid peroxidation.     

Tissue essential fatty acid composition and competitive response to dietary manipulations in white bass (Morone chrysops), striped bass (M. saxatilis) and hybrid striped bass (M. chrysopsxM. saxatilis)

The effects of wide changes in dietary levels of docosahexaenoic (DHA) or arachidonic (ArA) acids on growth, survival and fatty acid composition in body tissues of Morone larvae were examined. White bass (WB, Morone chrysops), striped bass (SB, Morone saxatilis) and sunshine hybrid bass (HSB, M. chrysopsxM. saxatilis) larvae (day 24-46) were fed Artemia nauplii enriched with algal sources of varying proportions of DHA and ArA (from 0 to over 20% of total fatty acids). WB larvae fed DHA-deficient Artemia diet retarded over 50% of their potential growth, however, increasing dietary DHA/ArA ratios were associated with a significant growth improvement. The highest proportion of polyunsaturated fatty acids was found in WB neural tissue (approx. 50% of total fatty acids), while HSB neural tissue contained the highest proportion of saturated fatty acids (approx. 35% of total fatty acids). Within the neural tissues of all Morone larvae, both DHA and ArA were generally the most dominant as well as the most responding fatty acids to dietary manipulations (except in WB fed DHA or ArA deficient diets). HSB neural tissue was particularly efficient in retaining a significant amount of DHA in the face of dietary deficiency. However, WB neural tissue was the most responsive to dietary increase in DHA, accumulating a significantly higher amount of DHA (P<0.05) than SB or HSB. Results demonstrate significant differences in fatty acid composition and growth responsiveness to dietary manipulations between Morone larvae species and within specific tissues. WB weight gain and neural tissue composition was affected most by dietary changes in both DHA and ArA whereas SB and HSB tissue compositions were generally less affected by dietary manipulations.