Linoleic Desaturation Research Articles

Exploring lipid health indices and protein quality in ninety Indian linseed varieties by comprehensive analysis of fatty acid composition, lignan content, and amino acid composition

Biochemical profiling of 90 linseed (Linum usitatissimum L.) varieties was done to have insights into their health benefits and nutritional properties. The analysis of fatty acid (FA) composition revealed 5 major FAs as α-linolenic acid (ALA), linoleic acid (LA), oleic acid (OA), palmitic acid (PA), and stearic acid (SA) ranging from 1.68% to 59.19%, 5.61–62.44%, 18.14–45.54%, 5.69–9.5%, and 3.94–10.29%, respectively. Secoisolariciresinol diglucoside (SDG) content varied significantly with a wide range of 0.02–3.60% in the seed with highest SDG content recorded so far as 3.60% in variety KL-226. Amino acid (AA) composition analysis revealed the variation in average amino acid content of essential amino acids (EAA) (His, Thr Val, Met, Trp, Phe, Ile, Leu, Lys) and non-essential amino acids (NEAA) (Asp, Glu, Ser, Gly, Arg, Ala, Tyr, Cys). Total NEAA content ranged from 3.24% to 23.69% while total EAA content ranged from 1.89% to 14.89%. Lipid heath indices such as atherogenicity index, thrombogenicity index, cholestrolemic index and peroxidisability index along with other fatty acid ratios such as n-6/n-3 ratio, UFA/SFA, PUFA/SFA were calculated to determine the stability of the varieties against auto-oxidation. It also revealed the positive effect of all varieties providing protection against atherosclerosis, coronary heart diseases, cancer and inflammatory diseases. Oleic desaturation ratio (ODR) and linoleic desaturation ratio (LDR) calculated to determine the desaturation efficiency of fatty acids, while protein efficiency ratio (PER) value calculated using amino acid composition determine the nutritional quality of protein. PER value ranged from 1.92 to 4.12 making all 90 varieties a good quality protein plant source. Principal component analysis revealed a significant variation between the fatty acid composition, amino acid composition and SDG content with a total variation of 69.95%. Hierarchical cluster analysis calculated using Pearson correlation coefficient revealed that 89 varieties are mostly similar except TL-99 variety.

Quality Evaluation Indices for Soybean Oil in Relation to Cultivar, Application of N Fertiliser and Seed Inoculation with Bradyrhizobium japonicum.

Soybean ranks second in production and consumption of vegetable oils worldwide and these are expected to continue to increase. The suitability of soybean oil for specific uses is determined by the fatty acid composition from which a number of indices and indicators can be calculated. The aim of this study was to evaluate the indices of nutritional and health-promoting fat in seeds of soybean cultivars grown in 2016–2019 under the influence of varying doses of N and inoculation with Bradyrhizobium japonicum. Omega 3 and Omega 6, unsaturated fatty acids (UFA), saturated fatty acids (SFA), polyunsaturated fatty acids (PUFA), index of desirable fatty acids (DFA), sum of hypercholesterolemic fatty acids (OFA), index of atherogenicity (AI), index of thrombogenicity (TI), oleic desaturation ratio (ODR), linoleic desaturation ratio (LDR), calculated oxidizability value (COX) and the hypocholesterolemic/hypercholesterolemic ratio (HH), saturation fat index (S/P) and ALA/LA, OL/(LA+ALA) ratios and the consumer index (CI) were included. Fat quality indices for soybean seeds were strongly determined by weather conditions. Seeds of the cv. Aldana contained higher amounts of Omega 6 and featured more favourable MUFA/PUFA and OL/(LA+ALA) ratios, while the seeds of the cv. Annushka had more favourable CI and higher ODR, COX and S/P indices. No important differences were observed regarding the effect of nitrogen dose and seed inoculation on the formation of the DFA, OFA, HH, AI, TI and CI indices. The value of the S/P index suggests that higher nitrogen rates (60 kg∙ha−1) and the lack of inoculation treatment produce seeds with a more favourable dietary fatty acid balance.

Identification of the NaCl-responsive metabolites in Citrus roots: A lipidomic and volatomic signature

ABSTRACT It is known that the first osmotic phase affects the growth rates of roots immediately upon addition of salt; thus, dissecting metabolites profiling provides an opportunity to throw light into the basis of plant tolerance by searching for altered signatures that may be associated with tolerance at this organ. This study examined the influence of salt treatment on fatty acid composition and chemical composition of the essential oil of C. aurantium roots. Results proved that, under salt treatment, an increase of double bond index and linoleic desaturation ratio was pointed out. On the other hand, the reduction of saturated fatty acids was spotted. Such treatment also induced quantitative changes in the chemical composition of the essential oils from C. aurantium roots and increased markedly the rates of monoterpenes, while the sesquiterpenes decreased significantly. Both primary and secondary metabolites were found to be significantly salt responsive, including one fatty acid (palmitoleic acid) and six volatiles (E-2-dodecenal, tetradecanal, γ-Elemene, trans-caryophyllene, α-Terpinene and germacrene D). Plasticity at the metabolic level may allow Citrus plants to acclimatize their metabolic ranges in response to changing environmental conditions.

Late season deficit irrigation for water-saving: selection of rapeseed (Brassica napus) genotypes based on quantitative and qualitative features

ABSTRACTTo select and introduce the best rapeseed genotypes under withholding irrigation, two field experiments were carried out in seasons 2015–2016 and 2016–2017 in Iran. Factorial arrangement of treatments was set up as RCBD with three replications. The experiment factors were two irrigation treatments (normal irrigation during the growing season and withholding irrigation from silique setting stage until the end of the growing season) and 17 genotypes of rapeseed. Grain yield, oil content and fatty acid contents were measured. The results revealed that oleic acid (62.15%) was the highest followed by linoleic (19.28%), linolenic (5.65%), palmitic (5.24%) and stearic acids (2.44%). ODR (oleic desaturation ratio) and LDR (linoleic desaturation ratio) were significantly affected by genotypes and irrigation treatments. The biosynthetic pathway of fatty acids affected by drought stress. This means that linoleic acid increases under withholding irrigation condition, while linolenic acid decreases in such a water deficit stress condition. The highest performance of qualitative and quantitative was detected in HL3721 genotype due to high values of grain yield (3892.45 kg ha−1), oil content (437.05 g kg−1), unsaturated fatty acids (87.63%) and low values of saturated fatty acids (7.98%), and it could be used under withholding irrigation in arid and semi-arid climates.

Fatty Acid Composition of Lipids in Picea obovata Needles in the Spring Vegetation Period

The dynamics of the fatty acid (FA) composition of total lipids in needles of Siberian spruce (Picea obovata L.) during the first half (March–July) of the 2010 vegetation season has been studied. Three maxima of the unsaturated fatty acid (UFA) content with increased levels of α-linolenic acid are revealed in the postwinter (March 10–April 6), spring (April 20–May 18), and summer (June 1–July 20) periods. During postwinter and spring vegetation, the UFA increase is accompanied by an increase in the oleic and linoleic desaturation ratios. The spring peak of the 18:3ω3 content coincides with the spring peak in chlorophylls in the light-harvesting complexes of photosynthetic units and with the onset of the net CO2 assimilation. The summer peak is characterized by the level of chlorophylls, which is the highest over the entire monitoring period. The possible ways that the FA is involved in the rearrangement of the structural and functional organization of the photosynthetic apparatus of a coniferous plant are discussed.

Distribution of (n‐9) and (n‐7) Isomers of Monounsaturated Fatty Acids in Indian Mustard (Brassica juncea)

AbstractThe seed oils of 19 Indian mustard varieties were analyzed for fatty acid composition using GC–MS, reporting the presence of n‐7 isomers of C18:1, C20:1 and C22:1 fatty acids. n‐7 isomers namely cis‐vaccenic (C18:1), 11, eicosenoic(C20:1) and 13‐cis‐docosenoic (C22:1) acids ranged from 0.61 to 1.73, 1.04 to 1.69 and 0.58 to 1.17 %, respectively. The average values of C20:1(n‐7) was highest (1.36) amongst the three acids. Nervonic acid was also reported in the range of 0.69 to 2.52 %. The ratios of (n‐7)/(n‐9) ranged from 6.22 to 14.62, 12.38 to 27.35 and 2.01 to 3.24 % for C18:1, C20:1 and C22:1 fatty acids, respectively. The variety RLM‐619 had the lowest elongation ratio (ER) as 0.44 and the highest desaturation ratio (DR) as 0.41 indicating higher efficiency of the desaturation pathway than for other varieties. The oleic desaturation ratio (ODR) values varied from 0.68 (Basanti) to 0.75 (GM‐2) with a mean value of 0.72 and linoleic desaturation ratio from 0.40 (Basanti) to 0.49 (Pusa Bold) with a mean value of 0.45. Palmitoleic acid showed positive correlation with C18:1(n‐7), C20:1(n‐7), C20:2, C22:0, C22:1(n‐7), C24:1, (n‐7)/(n‐9) ratio of C18:1 and C22:1 and a positive trend with ER but a significant negative correlation with C18:3, DR and ODR. The results indicated that palmitoleic acid is an important intermediate component in the synthesis of long chain (n‐7) fatty acids.

Effect of salt stress on growth, fatty acids and essential oils in safflower (Carthamus tinctorius L.)

This study examined the influence of salt treatment on the growth parameters (fresh and dry weights), the mineral content (K+ and Na+), total lipid contents, fatty acid composition, yields and chemical composition of the essential oil of safflower (Carthamus tinctorius L.) grown in hydroponics for 2 weeks. Results showed that the application of 50 mM NaCl reduced the fresh weight of aerial parts (shoots and leaves) while it enhanced those of the roots. The reduction of dry weight was found to be more pronounced in the aerial parts. Salt treatment increased markedly the concentrations of Na+ in both plant parts while it reduced those of K+ which resulted in a sharp reduction of K+/Na+ ratio. In response to salt treatment, total lipids contents decreased in both plant parts and great qualitative changes in the fatty acids profiles were observed. Whatever the plant parts analysed, a redirection of the lipidic metabolism towards synthesis of unsaturated fatty acids as revealed by the increase of double bond index and linoleic desaturation ratio was pointed out. The increased unsaturation index was found to be more important in roots than in aerial parts. Such treatment also reduced the essential oil yields and induced marked quantitative changes in the chemical composition of the essential oils from both plant parts. Of all the identified components, oxygenated components display a prominent salt-induced synthesis and/or accumulation in both roots and aerial parts.

Variation in Fatty Acid Composition in Indian Germplasm of Sesame

AbstractA germplasm collection of 33 entries comprising 22 sesame (Sesamum indicum L.) cultivars, 4 landraces of S. mulayanum and 7 other accessions of 4 wild species were analyzed for the fatty acid compositions of their seed oil. The entries varied widely in their fatty acid compositions. The percentage content of oleic, linoleic, palmitic and erucic acids ranged between 36.7–52.4, 30.4–51.6, 9.1–14.8 and 0.0–8.0, respectively. Linolenic and arachidonic acids were the minor constituents but varied widely in wild species. Oleic and linoleic were the major fatty acids with mean values of 45.9 and 40.5%, respectively and the mean of their combined values was 86.4%. The polyunsaturated fatty acid (PUFA) compositions ranged from 30.9 to 52.5% showing high variation in PUFA in the germplasm. Linoleic acid content was very high in one landrace (47.8) and one accession each of three wild species, S. mulayanum (49.3), S. malabaricum (48.2) and S. radiatum (51.6%). Use of fatty acid ratios to estimate the efficiency of biosynthetic pathways resulted in high oleic and low linoleic desaturation ratios and consequently high linoleic and very low linolenic acid contents in seed oil. The results of this study provided useful background information on the germplasm and also identified a few accessions having high linoleic acid which can be used for developing cultivars with desirable fatty acid compositions.

The utilization and desaturation of oleate and linoleate during glycerolipid biosynthesis in olive (Olea europaea L.) callus cultures

Callus cultures from olive (Olea europaea L.) were used to study characteristics of desaturation in this oil-rich tissue. The incorporation of [1-14C]oleate and [1-14C]linoleate into complex lipids and their further desaturation was followed in incubations of up to 48 h. Both radiolabelled fatty acids were rapidly incorporated into lipids, especially phosphatidylcholine and triacylglycerol. Radiolabelling of these two lipids peaked after 1–4 h, after which it fell. In contrast, other phosphoglycerides and the galactosylglycerides were labelled in a more sustained manner. [1-14C]Linoleate was almost exclusively found in the galactolipids. With [1-14C]linoleate as a precursor, the only significant desaturation to linolenate was in the galactolipids. Monogalactosyldiacylglycerol was the first lipid in which [1-14C]linoleate and [1-14C]linolenate appeared after incubation of the calli with [1-14C]oleate and [1-14C]linoleate, respectively. The presence of radioactivity in the plastidial lipids shows that both [1-14C]oleate and [1-14C]linoleate can freely enter the chloroplast. Two important environmental effects were also examined. Raised incubation temperatures (30–35 °C) reduced oleate desaturation and this was also reflected in the endogenous fatty acid composition. Low light also caused less oleate desaturation. The data indicate that lysophosphatidylcholine acyltransferase is important for the entry of oleate and linoleate into olive callus lipid metabolism and phospholipid:diacylglycerol acyltransferase may be involved in triacylglycerol biosynthesis. In addition, it is shown that plastid desaturases are mainly responsible for the production of polyunsaturated fatty acids. Individual fatty acid desaturases were differently susceptible to environmental stresses with FAD2 being reduced by both high temperature and low light, whereas FAD7 was only affected by high temperature.

Changes in serum lipoprotein lipids and their fatty acid compositions and lipid peroxidation in growing rats fed soybean protein versus casein with or without cholesterol*1

We compared the effects of diets based on soybean protein and casein supplemented or not supplemented with 0.1% cholesterol on plasma lipoprotein lipid amounts and their fatty acid compositions, lecithin:cholesterol acyl-transferase activity, and lipid peroxidation. The composition and concentration of lipid and apolipoprotein in different lipoprotein classes, plasma LCAT activity, and lipid peroxidation were determined in rats fed 20% highly purified soybean protein or casein with or without 0.1% cholesterol for 2 mo. Soybean protein and casein diets with or without cholesterol had similar plasma total cholesterol concentrations. Soybean protein consumption diminished very low-density lipoprotein particle number, as measured by diminished contents of very low-density lipoprotein triacylglycerol, phospholipid, and apolipoprotein-B100. Lecithin:cholesterol acyl-transferase activity was not significantly modified by either protein. The soybean protein diet decreased the linoleate desaturation index (20:4[ω-6]/18:2[ω-6]) in liver and high-density lipoprotein fraction 2–3-phospholipids but enhanced red blood cell resistance against free radical attack. Addition of cholesterol to both protein diets decreased concentrations of high-density lipoprotein fraction 2–3 cholesterol. Lecithin:cholesterol acyl-transferase activity tended to be greater after cholesterol feeding, likely due to the enhanced high-density lipoprotein fraction 2–3 apolipoprotein-AI, a cofactor activator for lecithin:cholesterol acyl-transferase. Regardless of dietary protein source, cholesterol supplementation decreased the linoleate desaturation index in liver and plasma lipoprotein lipids and red blood cell resistance to free radical attack. Our results suggest that the dietary protein origin affects lipid peroxidation and polyunsaturated fatty acid biosynthesis and distribution among liver and different lipoprotein lipid classes, but plays only a minor role in the regulation of plasma and lipoprotein cholesterol concentrations. Providing dietary cholesterol (0.1%) with casein or soybean protein attenuates the effects of these proteins, with the exception of plasma cholesterol.

Changes in serum lipoprotein lipids and their fatty acid compositions and lipid peroxidation in growing rats fed soybean protein versus casein with or without cholesterol

Objective We compared the effects of diets based on soybean protein and casein supplemented or not supplemented with 0.1% cholesterol on plasma lipoprotein lipid amounts and their fatty acid compositions, lecithin:cholesterol acyl-transferase activity, and lipid peroxidation. Methods The composition and concentration of lipid and apolipoprotein in different lipoprotein classes, plasma LCAT activity, and lipid peroxidation were determined in rats fed 20% highly purified soybean protein or casein with or without 0.1% cholesterol for 2 mo. Results Soybean protein and casein diets with or without cholesterol had similar plasma total cholesterol concentrations. Soybean protein consumption diminished very low-density lipoprotein particle number, as measured by diminished contents of very low-density lipoprotein triacylglycerol, phospholipid, and apolipoprotein-B100. Lecithin:cholesterol acyl-transferase activity was not significantly modified by either protein. The soybean protein diet decreased the linoleate desaturation index (20:4[ω-6]/18:2[ω-6]) in liver and high-density lipoprotein fraction 2–3-phospholipids but enhanced red blood cell resistance against free radical attack. Addition of cholesterol to both protein diets decreased concentrations of high-density lipoprotein fraction 2–3 cholesterol. Lecithin:cholesterol acyl-transferase activity tended to be greater after cholesterol feeding, likely due to the enhanced high-density lipoprotein fraction 2–3 apolipoprotein-AI, a cofactor activator for lecithin:cholesterol acyl-transferase. Regardless of dietary protein source, cholesterol supplementation decreased the linoleate desaturation index in liver and plasma lipoprotein lipids and red blood cell resistance to free radical attack. Conclusions Our results suggest that the dietary protein origin affects lipid peroxidation and polyunsaturated fatty acid biosynthesis and distribution among liver and different lipoprotein lipid classes, but plays only a minor role in the regulation of plasma and lipoprotein cholesterol concentrations. Providing dietary cholesterol (0.1%) with casein or soybean protein attenuates the effects of these proteins, with the exception of plasma cholesterol.

Ethyl arachidonate is the predominant fatty acid ethyl ester in the brains of alcohol-intoxicated subjects at autopsy.

The role of fatty acid ethyl esters (FAEE), the nonoxidative ethanol metabolites, as mediators of alcohol-induced organ damage is increasingly being recognized. FAEE are detectable in the blood and in liver and adipose tissue after ethanol ingestion, and on that basis, FAEE can be used as markers of ethanol intake. In this study, 10 samples of human brain were collected at autopsy at the Massachusetts Medical Examiner's Office and analyzed for FAEE. FAEE were isolated and quantified as mass per gram of wet weight. The blood ethanol level was also obtained in each case along with the other drugs detected in routine postmortem toxicology screening tests. Ethyl arachidonate was the predominant FAEE species in the brain, representing up to 77.4% of total FAEE in the brain. The percent age of ethyl arachidonate of the total FAEE in the brain was significantly higher than what has been found in all other organs and tissues previously analyzed. Linoleate, the precursor of arachidonate, was a poor substrate for FAEE synthesis, as the percentage of ethyl linoleate of the total FAEE content was extremely low. Thus, this reflects preferred incorporation of arachidonate into newly synthesized FAEE in the brain. Since arachidonate is derived from linoleate, which is depleted in FAEE while arachidonate is enriched, the synthesis of FAEE may be linked to the desaturation and elongation of linoleate to arachidonate.

Highly Purified Soybean Protein Is Not Hypocholesterolemic in Rats but Stimulates Cholesterol Synthesis and Excretion and Reduces Polyunsaturated Fatty Acid Biosynthesis

The specific effects of soybean protein on lipid metabolism were determined with highly purified soybean protein. At 5 wk of age, growing rats were fed diets containing 20% highly purified soybean protein or casein supplemented or not with 0.1% cholesterol for 2 mo. Plasma and liver lipid composition, fecal steroid excretion and several hepatic enzyme activities were measured. There were no significant dietary protein-related differences in plasma and liver cholesterol concentrations. When diets were cholesterol free, highly purified soybean protein stimulated fecal neutral and acidic steroid excretion associated with concomitantly higher hydroxy methylglutaryl CoA (HMG-CoA) reductase activity, but lower cholesterol 7α-hydroxylase activity. Soybean protein lowered the linoleate desaturation index [20:4(n-6)/18:2(n-6)] in liver microsomal lipids and phospholipids. This may have been due to the reduced microsomal Δ6(n-6) desaturase activity in rats fed soybean protein, whereas Δ5(n-6) desaturase activity did not differ between groups fed the two proteins. Cholesterol supplementation (0.1%) did not affect plasma cholesterol but increased liver cholesterol and triacylglycerol concentrations and reduced HMG-CoA reductase activity; this latter effect was greatest in rats fed soybean protein. Cholesterol 7α-hydroxylase activity, however, was diminished only in rats fed casein. Desaturase activities, and particularly Δ5(n-6) activity, were lowered by cholesterol supplementation in rats fed both protein diets, including a significantly lower 20:4(n-6)/18:2(n-6) ratio in liver microsomal lipids and liver phospholipids. Thus although dietary proteins have no effect on serum cholesterol in rats, they affect enzyme activities involved in cholesterol metabolism and fatty acid desaturation.

Induced variability for C18 unsaturated fatty acids in Ethiopian mustard

The improvement of oil composition for C18 unsaturated fatty acids is one of the most important breeding objectives for the development of high-quality Ethiopian mustard oil. The objective of this research was to induce variability for fatty acid composition in this species using chemical mutagenesis. Seeds of line C-101 were treated with 1% ethylmethane sulfonate and the progenies of 8331 M2 plants were screened for fatty acid composition of the oil with near infrared reflectance spectroscopy followed by gas liquid chromatography on selected plants. Oleic and linoleic desaturation ratios (ODR and LDR, respectively) were used to detect putative mutants with altered levels of C18 unsaturated fatty acids. Seven of these mutants were isolated and M4 lines were developed. Six lines were characterized by low ODR, showing an increase in oleic acid and a reduction in linoleic acid. Three of these lines also showed reduced levels of linolenic acid. The other mutant line showed a decrease in both LDR and linolenic acid content. Since different enzyme systems seemed to be altered, a further oil improvement for C18 unsaturated fatty acids may be achieved through recombination among mutants. Key words: Brassica carinata Braun, C18 unsaturated fatty acids, mutagenesis

Selection on pollen for linolenic acid content in rapeseed, Brassica napus L.

AbstractIn order to enhance the economic value of edible rapeseed oil, an improvement of quality is necessary. Mutagenesis of rapeseed resulted in a low linolenic acid content and a low ‘linolenic acid (CIS: 3) level to linoleic acid (CIS: 2) level’ ratio, that is, the linoleic desaturation ratio (LDR), in the seeds of the Canadian variety ‘Stellar’. As an early breeding marker for low linolenic acid content, the pollen fatty acid composition was determined on 80 doubled haploid plants derived from a single F1 hybrid obtained from a cross between ‘Stellar’ and a high CIS: 3 variety ‘Drakkar’. Fatty acid analysis on seed and pollen showed that the low CIS: 3 and the low LDR traits from the ‘Stellar’ variety were expressed in pollen and in seeds, and that a very close correlation (r = 0.88) existed between seed and pollen for these two traits. The inheritance of these traits is controlled by two major genes with additive effects, both in seed and pollen. However, minor genes also appeared to be expressed in pollen and seed. These genes may allow the production of plants with lower CIS: 3 levels than that of the low linolenic acid content parent. The efficiency of this new tool for early screening in breeding programmes is discussed.

Differences in the regulation of biosynthesis of 20- versus 22-carbon polyunsaturated fatty acids

The incorporation of (n-3) versus (n-6) fatty acids into membrane lipids is regulated by a number of different processes within the cell. It is generally accepted that a common 6-desaturase uses both linoleate and linolenate as substrates. Desaturation of linoleate and linolenate are generally considered to be the rate limiting steps in the biosynthesis of arachidonate and 20:5(n-3) respectively (1). The addition of fatty acids to the diet, beyond the rate limiting 6-desaturation step, would thus appear to be a way to increase the amount of arachidonate or 20:5(n-3) that is produced and potentially made available for esterification into membrane lipids. In order to evaluate this hypothesis, we carried out a number of feeding studies with deuterium labeled (n-6) fatty acids using the following general protocol. Male weanling Sprague-Dawley rats were maintained on a modified AIN diet that contained 3.3% fat the composition of which was 2.1% oleate, 1.0% linoleate and 0.2% linolenate. After 4 weeks on this diet, the animals were changed to one in which all of the linoleate was replaced by 17,17,18,18-d4 linoleate. After 4 days the animals were sacrificed and it was observed that 34 mol % of arachidonate esterifed in liver phospholipids was derived from the deuterium labeled linoleic acid. Another group of animals was maintained on the AIN diet that contained 1.9% oleate, 1% linoleate, 0.2% linolenate and in addition 0.2% ethyl 18:3(n-6). Again, all of the linoleate

A comparison of the specific activities of linoleate and arachidonate in liver, heart and kidney phospholipids after feeding rats ethyl linoleate-9,10,12,13- d4

In order to determine how dietary linoleate is metabolized, rats were maintained on a chemically defined diet containing 1.6% ethyl linoleate. After 5 weeks the linoleate was replaced by an equal amount of ethyl 9,10,12,13- d 4-linoleate. The animals were killed 3 days later and the molar percentage of d 4-linoleate and d 4-arachidonate were quantified in liver, heart and kidne phospholipids. In liver, 54 and 22.8 mol% respectively of the esterified linoleate and arachidonate was deuteriated. The lower specific activity of arachidonate versus linoleate suggests that desaturation of linoleate, by a 6-desaturase, is not only rate limiting for synthesis of arachidonate but that the amount of newly synthesized arachidonate is insufficient by itself to maintain steady state levels of esterified arachidonate. The molar fraction of deuteriated linoleate in heart and kidney phospholipids was respectively 35 and 37.4%. These values are lower than for liver phospholipids but it appears there is adequate dietary linoleate available in these tissues for the synthesis of arachidonate. However, of the esterified arachidonate in heart and kidney phospholipids only 4.2 and 8.6 mol% respectively was deuteriated. Our results suggest that arachidonate is made in liver and transported to heart and kidney.

Effects of Sunflowers on Lipid Metabolism in Rats

The effects of the flower lipid-saccharide complex (lipopoly-saccharide analogue) and unsaponifiable matter (1 g/kg diet) of the sunflower on various lipid parameters was studied in rats given cholesterol-enriched diets. After six weeks of feeding, there were no significant differences in the concentrations of serum cholesterol and triacylglycerol, although they tended to decrease with dietary sunflower consumption. The liver cholesterol concentration was significantly reduced with the sunflower diet. The linoleate de-saturation index, an arachidonic acid/linoleic acid ratio, in tissue phosphatidylcholine significantly increased in the unsaponifiable matter group. The fecal coprostanol and bile acid concentrations increased significantly in the lipid–saccharide complex and unsaponifiable matter groups. The fecal cholesterol concentrations also tended to increase with the dietary sunflower consumption.

Dietary Cholesterol Influences on Various Lipid Indices and Eicosanoid Production in Rats Fed Dietary Fat Desirable for the Protection of Ischemic Heart Disease.

Young male Sprague-Dawley rats were fed diets containing 10% fat with P/S and n-6/n-3 ratios of 1.2 and 5.0, respectively, and differing levels of dietary cholesterol (0.05 to 1.0% by weight) for 3 weeks, following which the tissue lipid concentration, fatty acid composition, desaturation of linoleic acid, and eicosanoid production were examined. The composition of dietary fat was that recommended for the prevention of atherosclerosis. Dietary cholesterol did not largely influence the concentration of serum cholesterol, but it markedly increased liver cholesterol in a dose-dependent manner. The delta 6-desaturase activity in liver microsomes, linoleate desaturation index in liver phosphatidylcholine, and the production of prostaglandin by the aorta and thromboxane A2 by platelets all decreased to a similar extent in relation to dietary cholesterol above 0.2%. Thus, dietary cholesterol influenced various lipid parameters characteristically even when dietary fat with a fatty acid composition desirable for the prevention of atherosclerosis was consumed simultaneously. The dietary cholesterol level of 0.2% was the point of maximum influence in rats upon the indices examined.

Effect of overnight fasting on the fatty acid composition of tissue lipids in rats fed with different proteins.

The effect of overnight fasting on the dietary protein-dependent change in the fatty acid composition of tissue lipids was studied in rats fed with casein or soybean protein (20%) diets containing 5 or 2% corn oil. The activity of the Δ6-desaturase of liver microsomes, a key enzyme of linoleate metabolism to arachidonate, was depressed significantly by overnight fasting, and the protein effect disappeared, irrespective of the level of dietary fat. The proportion of linoleate in liver phosphatidylcholine was decreased, whereas that of arachidonate was increased after overnight fasting in rats fed with a low fat diet, resulting in an elevation of the linoleate desaturation index. Although the effect of fasting became obscure on a high fat diet, the protein effects were maintained even after fasting. A similar trend was also observed in various lipid fractions. Thus, the effect of dietary protein on the polyunsaturated fatty acid profile was not modulated by overnight fasting, particularly when a minimal amo...