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.     

Kinetic profile of the cellular lipid composition in an oleaginous Yarrowia lipolytica capable of producing a cocoa-butter substitute from industrial fats

Cell growth, lipid accumulation and cellular lipid composition of Yarrowia lipolytica growing on mixtures of industrial fats containing stearic, oleic, linoleic and palmitic acid have been studied. During growth, the strain incorporated oleic and linoleic acids more rapidly than the saturated fatty acids. Relatively high lipid accumulation (up to 0.44 g of lipids per g of dry matter) was observed when stearic acid was included in the culture medium. In contrast, substrates rich in oleic acid did not favor cellular lipid accumulation. The accumulated lipids, mainly composed of triacylglycerols (45-55% w/w), demonstrated a different total fatty acid composition compared with that of the substrate; in all cases, the microorganism showed the unusual capacity to increase its cellular stearic acid level, even if this fatty acid was not found in high concentrations in the substrate. This permitted the synthesis of interesting lipid profiles with high percentages of stearic acid and non-negligible percentages of palmitic and oleic acid, with a composition resembling that of cocoa-butter.     

甘肃胡麻地方种质资源品质特性研究

对甘肃省116份胡麻地方品种的重要品质指标———粗脂肪、硬脂酸、棕榈酸、油酸、亚油酸、亚麻酸含量和碘值进行测定,并根据这些品质指标对供试品种进行聚类分析。结果显示:(1)供试品种粗脂肪含量平均值为37.48%,变异系数3.8%;硬脂酸、油酸含量平均值分别为5.32%和29.05%,变异系数分别为19.5%和11.6%;棕榈酸、亚麻酸、亚油酸含量平均值分别为5.9%、48.76%、10.95%,变异系数分别为8.4%、8%、8%;平均碘价175.60,变异系数2.76%;(2)聚类分析结果显示,116个品种聚为7大类,其中:b亚组群硬脂酸和油酸含量最高,而亚麻酸含量最低;d亚组群品种亚麻酸含量最高;e亚组群粗脂肪含量和碘价最高,油酸含量最低;f亚组群硬脂酸含量最低;g亚组群棕榈酸含量最高,碘价最低。     

Oral cavity discrimination of vapor-phase long-chain 18-carbon fatty acids

Linoleic, oleic, and stearic fatty acids, presented vapor-phase retronasally, were discriminable from blanks and each other, but the same concentrations, oral-cavity-only (OCO), were not discriminable from blanks. It remained possible that higher concentrations might be discriminable OCO. To evaluate this, participants attempted to discriminate undiluted linoleic, oleic, or stearic acids, vapor-phase OCO, from blanks. For each fatty acid, participants received 5 stimulus delivery containers (SDCs) in 2 trials; 4 SDC held blanks, the fifth, a fatty acid. As a "positive control" in 2 trials, participants received vapor-phase OCO peppermint extract and blanks. For all trials, the task was to select the 1 different SDC. It was found that the 1 different SDC was selected in 24% of stearic, 32% of linoleic, 47% of oleic acid, and in 92% of peppermint trials; discriminations (the 1 different SDC selected in both trials) occurred in 0%, 16%, 26%, and 84% of pairs, respectively. Correct selections for oleic acid differed from chance, P = 0.0004, but not for linoleic acid, P = 0.125, or stearic acid, P = 0.345, Bonferroni corrected. Vapor-phase oleic acid can be an oral cavity trigeminal stimulus, linoleic acid might be (uncorrected P = 0.0384), but vapor-phase stearic acid cannot be.     

Incorporation and metabolism of stearic, oleic, linoleic and alpha-linolenic acids in minimal deviation hepatoma 7288 C cells.

Minimal Deviation Hepatoma 7288 C cells were cultured in confluent layer with labeled stearic, oleic, linoleic and alpha-linolenic acids. The kinetics of incorporation and conversion to higher homologs was studied. The maximum amounts incorporated in nmoles per mg of cellular protein for stearic, oleic, linoleic and alpha-linolenic acids were 39, 115.6, 90 and 230 respectively. alpha-linolenic acid was converted to octadeca-6,9,12,15-tetraenoic acid (18:1), eicosa-11,14,17-trienoic acid (20:3), eicosa-8,11,14,17 and 5,11,14,17-tetraenoic acids (20:4) and eicosa-5,8,11,14,17-pentaenoic acid (20:5), and also to myristic, palmitic, palmitoleic, stearic and oleic acids. By a mathematical approach, the endogenous pool size of alpha-linolenic acid available for conversion to eicosa-5,8,11,14,17-pentaenoic acid, were calculated. Both values decreased when the cells were preincubated with unlabeled alpha-linolenic acid.     

Inhibition of chymase activity by long chain fatty acids

The activity of chymase was markedly inhibited by fatty acids with carbon chain lengths of 14-22 at doses greater than 0.02 microM, irrespective of the number of double bonds. Cis acids with a carbon chain length of 18, such as stearic acid, oleic acid, linoleic acid, and linolenic acid were potent inhibitors, whereas the trans isomer of oleic acid, elaidic acid, showed less inhibitory activity. The extent of inhibition by oleyl alcohol was almost the same as that by oleic acid, suggesting that the acid moiety itself was not necessary for the inhibition; but a fatty acid with a terminal functional amide, oleamide, showed little inhibitory activity. The inhibition was noncompetitive and was reversible, and the Ki value of oleic acid was 2.7 microM. Stearic acid and oleic acid inhibited all chymotrypsin-type serine endopeptidases tested. The ID50 values of these fatty acids for atypical mast cell protease were higher than those for the other chymotrypsin-type serine endopeptidases tested. Other proteases, such as papain, trypsin, collagenase, and carboxypeptidase A, except cathespin D, were not affected by stearic or oleic acid.     

Modification of fatty acid composition of lipid accumulating yeasts with cyclopropene fatty acid desaturase inhibitors

Summary The effect of cyclopropene fatty acids, sterculic and malvalic, on the lipids of yeasts grown under nitrogen limiting, lipid accumulating, conditions was studied. The ratio of stearic to oleic acid showed a dose response effect, with an increase in stearic acid content as the dose of cyclopropene fatty acid increased, and a corresponding reduction in oleic acid. Linoleic and linolenic acids were not affected to the same extent. These effects are shown for the yeasts Candida sp. 107, Trichosporon cutaneum, and Rhodosporidium toruloides.     

Effects of fatty acids on phosphatidylcholine biosynthesis in isolated hamster heart

The effects of stearic, oleic, and arachidonic acids on phosphatidylcholine biosynthesis in the hamster heart were investigated. When hamster hearts were perfused with labelled choline in the presence of fatty acids, biosynthesis of phosphatidylcholine was stimulated only by stearic acid. Stearic acid was found to accumulate in unesterified (free) form in the hamster heart after perfusion. The stimulation by stearic acid was mediated in vivo by an enhancement of CTP:phosphocholine cytidylyltransferase activity in the microsomal fraction of the hamster heart and the enzyme activity in the cytosolic fraction was not affected. In contrast with the observations in rat hepatocytes, cytidylyltransferase from the hamster heart was not stimulated directly by stearic acid. The selective activation of the microsomal enzyme when the heart was perfused with stearic acid suggests that activation of the enzyme was mediated via the modification of the membrane by stearic acid.     

Dietary Stearic Acid Leads to a Reduction of Visceral Adipose Tissue in Athymic Nude Mice

Stearic acid (C18:0) is a long chain dietary saturated fatty acid that has been shown to reduce metastatic tumor burden. Based on preliminary observations and the growing evidence that visceral fat is related to metastasis and decreased survival, we hypothesized that dietary stearic acid may reduce visceral fat. Athymic nude mice, which are used in models of human breast cancer metastasis, were fed a stearic acid, linoleic acid (safflower oil), or oleic acid (corn oil) enriched diet or a low fat diet ad libitum. Total body weight did not differ significantly between dietary groups over the course of the experiment. However visceral fat was reduced by ∼70% in the stearic acid fed group compared to other diets. In contrast total body fat was only slightly reduced in the stearic acid diet fed mice when measured by dual-energy x-ray absorptiometry and quantitative magnetic resonance. Lean body mass was increased in the stearic acid fed group compared to all other groups by dual-energy x-ray absorptiometry. Dietary stearic acid significantly reduced serum glucose compared to all other diets and increased monocyte chemotactic protein-1 (MCP-1) compared to the low fat control. The low fat control diet had increased serum leptin compared to all other diets. To investigate possible mechanisms whereby stearic acid reduced visceral fat we used 3T3L1 fibroblasts/preadipocytes. Stearic acid had no direct effects on the process of differentiation or on the viability of mature adipocytes. However, unlike oleic acid and linoleic acid, stearic acid caused increased apoptosis (programmed cell death) and cytotoxicity in preadipocytes. The apoptosis was, at least in part, due to increased caspase-3 activity and was associated with decreased cellular inhibitor of apoptosis protein-2 (cIAP2) and increased Bax gene expression. In conclusion, dietary stearic acid leads to dramatically reduced visceral fat likely by causing the apoptosis of preadipocytes.     

Platelet membrane fatty acids in thrombocytosis due to myeloproliferative disorders

The fatty acid composition of platelet membranes has been analysed in patients with thrombocytosis due to myeloproliferative disorders, who had not taken any drugs. A significant increase in palmitic and oleic acid, together with a decrease in stearic, linoleic and arachidonic acids was observed. The fatty acid pattern of platelet membranes was also analysed in patients during treatment with ASA (acetylsalicylic acid). ASA ingestion completely normalizes the platelet content of palmitic acid and partially that of stearic and arachidonic acid, whereas it has no effect on the level of linoleic acid and raises that of oleic acid. The altered pattern of fatty acids observed in patients may interfere with platelet function by decreasing membrane fluidity. Treatment of patients with ASA seems to act on platelet membranes by partially normalizing the fatty acid composition.     

The incorporation of long-chain fatty acids into phospholipids of respiring slices of rat cerebrum

1. Respiring slices of adult rat cerebrum have been shown to incorporate long-chain (14)C-labelled fatty acids into phospholipid. 2. Labelling was almost entirely confined to lecithin and ethanolamine phospholipid, only traces being present in serine phospholipid. 3. Palmitic acid, oleic acid and linoleic acid were incorporated more actively into lecithin than into ethanolamine phospholipid, but the converse was found with stearic acid. 4. All four acids labelled the 1- and 2-positions of both lipids; palmitic acid, oleic acid and linoleic acid were approximately evenly distributed, but stearic acid was incorporated predominantly at the 1-position. 5. It is considered that incorporation is most likely brought about through acylation of endogenously derived lysophosphatides. 6. The possible implications of this pathway of lipid metabolism in nervous tissue are discussed.     

Effects of fatty acids on lysis of Streptococcus faecalis.

Palmitic, stearic, oleic, and linoleic acids at concentrations of 200 nmol/ml all inhibited autolysin activity 80% or more in whole cells or cell-free extracts. This concentration of the saturated fatty acids palmitic acid and stearic acid had little or no effect on the growth of whole cells or protoplasts. However, the unsaturated fatty acids oleic acid and linoleic acid induced lysis in both situations. This lytic effect is apparently not related to any uncoupling activity or inhibition of energy catabolism by unsaturated fatty acids. It is concluded that unsaturated fatty acids induce cell and protoplast lysis by acting as more potent membrane destabilizers than saturated fatty acids.     

Tritium release assay for oleic acid desaturation

The “tritium release” assay for the enzymic conversion of stearic acid into oleic acid introduced by Talamo and Bloch in 1969 (1) represented a major advance in the measurement of enzymic fatty acid desaturation. By measuring the release of tritium from the 9- and 10-positions of erythro-[9,10³H₂]stearic acid into water instead of isolating the oleic acid chromatographically, the processing time can be reduced from about 2–3 hr to 5–10 min per assay. Recently, Johnson and Gurr (2) showed that the release of tritium does not represent an absolute measure of enzymic activity due to a primary kinetic isotope effect discriminating against tritium. In that paper we recorded the magnitude of the isotope effect, described the synthesis and use of threo-[9,10³H₂]stearic acid, which increases the sensitivity of the assay, and demonstrated that release of tritium from this substrate was proportional to the formation of oleic acid.     

Selective retention of n-3 and n-6 fatty acids in human milk lipids in the face of increasing proportions of medium chain-length (C10-14) fatty acids

This paper reports the results of our analysis of the impact high levels of de novo fatty acids have on the proportions of essential and non-essential fatty acids in human milk lipids. The data for seven fatty acids (linoleic, alpha-linolenic, arachidonic (AA), docosahexaenoic (DHA), palmitic, stearic and oleic) were derived from several studies conducted in Nigeria. The proportion by weight of each of these fatty acids was plotted versus the proportion of C10-14 fatty acids. As the proportion of C10-14 fatty acids increased from 15 to 65%, there was not a proportional decrease in the percentages of all seven fatty acids, but, instead, preferential incorporation of the essential fatty acids, AA and DHA into the triacylglycerol component of the milk. At the same time, the proportions of stearic and oleic acid declined by 69% and 86%, respectively. However, the proportions of linoleic acid, palmitic acid, DHA, AA and alpha-linolenic acid, in milk lipids decreased by only 44%, 40%, 39%, 28% and 2.3%, respectively. These observations indicate that as the contribution of C10-14 fatty acids increases, essential fatty acids are preferentially incorporated into milk triacylglycerols at the expense of oleic acid and stearic acid.     

Effect of oleic acid on mitochondrial oxidative phosphorylation in rat brain slices

We tested the effect of oleic acid on oxidative phosphorylation and free fatty acid composition in rat brain slices simultaneously to investigate the relationship between the change in respiratory control ratio and the uptake of oleic acid in the brain mitochondria. The uncoupling of mitochondria was observed when the ratio of oleic acid to stearic acid in the free fatty acid fraction was nearly doubled, but was not recovered even by the addition of fatty acid-free bovine serum albumin. The data suggest that the intactness of oxidative phosphorylation of brain mitochondria is maintained by the precise control of the free fatty acid composition in the mitochondrial membranes.     

Composition and synthesis of fatty acids in atherosclerotic aortas of the pigeon

The composition, synthesis, and esterification of fatty acids were studied in aortas of White Carneau and Show Racer pigeons after perfusion of the aortas with a medium containing acetate-1-(14)C. For both breeds of pigeons the principal change in aortic fatty acids, in response to an atherogenic diet, was a marked increase in the percentage of oleic acid in the cholesteryl ester fraction. In atherosclerotic aortas incorporation of acetate-1-(14)C into the phospholipid and glyceride fractions increased 2-fold, while a much greater increase (up to 10-fold) was seen in incorporation into cholesteryl esters. In those birds receiving the atherogenic diet, palmitic acid accounted for approximately 50% of the fatty acid radioactivity, compared with approximately 25% from control aortas. Calculation of fatty acid synthesis showed the major newly synthesized fatty acids to be stearic acid in the phospholipid fraction; stearic, palmitic, and oleic acids in the glycerides; and oleic acid in the cholesteryl esters. The pattern of fatty acid synthesis was closely similar to the actual fatty acid composition of the aorta. In atherosclerotic aortas an increased synthesis of all fatty acids was seen, but the greatest increase was seen in the synthesis of oleic acid and its esterification to cholesterol.     

Oleic acid prevents detrimental effects of saturated fatty acids on bovine oocyte developmental competence

Mobilization of fatty acids from adipose tissue during metabolic stress will increase the amount of free fatty acids in blood and follicular fluid and, thus, may affect oocyte quality. In this in vitro study, the three predominant fatty acids in follicular fluid (saturated palmitic and stearic acid and unsaturated oleic acid) were presented to maturing oocytes to test whether fatty acids can affect lipid storage of the oocyte and developmental competence postfertilization. Palmitic and stearic acid had a dose-dependent inhibitory effect on the amount of fat stored in lipid droplets and a concomitant detrimental effect on oocyte developmental competence. Oleic acid, in contrast, had the opposite effect, causing an increase of lipid storage in lipid droplets and an improvement of oocyte developmental competence. Remarkably, the adverse effects of palmitic and stearic acid could be counteracted by oleic acid. These results suggest that the ratio and amount of saturated and unsaturated fatty acid is relevant for lipid storage in the maturing oocyte and that this relates to the developmental competence of maturing oocytes.     

Oleic Acid Inhibits Gap Junction Permeability and Increases Glucose Uptake in Cultured Rat Astrocytes

Abstract: The role of oleic acid in the modulation of gap junction permeability was studied in cultured rat astrocytes by the scrape-loading/Lucifer yellow transfer technique. Incubation with oleic acid caused a dose-dependent inhibition of gap junction permeability by 79.5% at 50 µ M , and no further inhibition was observed by increasing the oleic acid concentration to 100 µ M . The oleic acid-mediated inhibition of gap junction permeability was reversible and was prevented by bovine serum albumin. The potency of oleic acid-related compounds in inhibiting gap junction permeability was arachidonic acid > oleic acid > oleyl alcohol > palmitoleic acid > stearic acid > octanol > caprylic acid > palmitic acid > methyloleyl ester. Oleic acid and arachidonic acid, but not methyloleyl ester, increased glucose uptake by astrocytes. Neither oleic acid nor arachidonic acid increased glucose uptake in the poorly coupled glioma C6 cells. These results support that the inhibition of gap junction permeability is associated with the increase in glucose uptake. We suggest that oleic acid may be a physiological mediator of the transduction pathway leading to the inhibition of intercellular communication.     

Lipid Metabolism of Rumen Ciliates and Bacteria: I. Uptake of Fatty Acids by Isotricha prostoma and Entodinium simplex

Washed suspensions of the ruminal ciliates, Isotricha prostoma and Entodinium simplex, concentrated C¹⁴-labeled oleic, palmitic, stearic, and linoleic acids within the cells during short incubation periods. Radioautographs demonstrated that oleic acid-1-C¹⁴ was hydrogenated to stearic acid by I. prostoma, and Warburg manometric data showed that the sodium salts of oleic, valeric, caproic, and acetic acids, and methyl myristate, methyl laurate, and the triglyceride tributyrin stimulated fermentation of I. prostoma. The total lipid and free fatty acid contents of I. prostoma were determined.