Inhibition of desaturation of stearic acid in livers of rats fed ethionine

The effect of ethionine on the conversion of stearic acid to oleic acid was studied. Rats were fed essential fatty acid (EFA) deficient diet for three weeks, after which time half the animals were fed 0.25% DL-ethionine for nine additional days. Seventeen hours prior to killing, they were fed a slurry of the diet containing 18-¹⁴C-stearic acid. Liver triglycerides and phospholipids were extracted and separated and their fatty acid composition and the distribution of radioactivity between stearic and oleic acid was determined. In the tissues studied, oleic acid was maintained at control levels in ethionine-fed rats, but eicosatrienoic acid was significantly depressed. Distribution of radioactivity and specific activity of oleic acid in the triglycerides and phospholipids were significantly reduced by the analogue. In vitro studies of desaturation and chain elongation reactions, with liver microsomes, using 18-¹⁴C-stearic and 1-¹⁴C-linoleic acids as substrates, showed that ethionine depressed the synthesis of oleic acid from stearic and γ-linolenic from linoleic acid. Elongation of linoleic adie to a 20∶2 fatty acid was unaffected by ethionine. Therefore, the results showed that ethionine inhibited desaturation of stearic to oleic acid in vivo and in vitro and probably also impaired the desaturation of oleic to octadeca-6, 9-dienoic acid. Maintenance of control levels of oleic acid in the tissues of ethionine-fed, EFA deficient rats suggested the presence of synthetic pathways for oleic acid other than via desaturation of stearic acid. Presented in part at the AOCS Meeting, San Francisco, April 1969.     

Is there an entero-hepatic circulation of the bile phospholipids?

Bile previously labeled with tritiated oleic acid (the main radioactivity was on bile phospholipids) was mixed with pure isolated phospholipids previously labeled with¹⁴C oleic acid; this mixture was perfused during 6 or 23 hr into the duodenum of test rats bearing a bile fistula. At the time of decapitation, in the small intestine a large hydrolysis of the¹⁴C phospholipids was found. In contrast no bile phospholipid hydrolysis was observed. In the collected bile samples of the test rats, no¹⁴C could be detected (this means a very large decrease of the¹⁴C fatty acids specific activities by the body fatty acids), and the tritiated fatty acids specific activities were only 2.5–12 times lower than in the perfused bile. These results can be explained, assuming that the bile phospholipids enter in an entero-hepatic circulation and are preserved from the dilution in a large pool of lipids.     

Variation in Seed Oil Content and Fatty Acid Composition of Globe Artichoke Under Different Irrigation Regimes

Seed oil content of globe artichoke and its composition were assessed under three irrigation regimes, including irrigation at 20, 50, and 80 % depletion of soil available water. Water deficit affected the phenological characteristics, amount and the quality of the oil as well as the phenolics and antioxidant activity of the leaves and capitula. The seed oil content ranged from 18.7 % in 80 % to 22.8 % in 20 % treatment. The fatty acid composition of oil was determined using gas chromatography (GC). The predominant fatty acids in the oil were linoleic (51.68 %), oleic (34.22 %), palmitic (9.94 %), and stearic (3.58 %). Water deficit leads to reduced oil content, linoleic acid, the unsaturated/saturated fatty acid ratio and the iodine value. On the other hand, some other fatty acids such as palmitic and oleic acid and also the ratio of oleic/linoleic acid were elevated due to water deficit. Higher antioxidant activity was observed in capitula (IC₅₀ = 222.6 μg ml^?1) in comparison to the leaves (IC₅₀ = 285.8 μg ml^?1). Finally, the severe drought stress condition caused to gain higher oil stability, while the highest seed oil content and unsaturated fatty acids in the oil was obtained in non‐stress condition. Moreover, high phenolics, flavonoids and antioxidant activity as well as appreciable dry matter content were obtained in the moderate water stress condition.     

Dietary linoleic, α-linolenic and oleic acids are oxidized at similar rates in rats fed a diet containing these acids in equal proportions

The objective of this study was to examine whether whole body oxidation rates of dietary linoleic, α-linolenic and oleic acids differ when the acids are provided in identical quantities. Male rats were fed for 10 wk a 15% fat (w/w) diet containing equal amounts of linoleic, α-linolenic and oleic acids (22.7, 23.0 and 23.2% of total fatty acids, respectively). At week 10, after overnight fasting, rats were intragastrically administered 20 μCi of either [1-¹⁴C]-labelled linoleic, α-linolenic or oleic acid in a 200-μL bolus of oil containing equal quantities of each fatty acid. The appearance of¹⁴CO₂ in expired air was then monitored hourly for 12h for each animal. A preliminary study had shown that growth and food consumption patterns in animals consuming the oil containing equal quantities of each of the fatty acids paralleled the patterns of animals that were self-selecting among separate diets, each of which contained one of the component oils. The appearance of¹⁴C, expressed as percent dose administered, peaked at 2–3 h post-dose for¹⁴C-labelled linoleic (5.28±0.37%/h), α-linolenic (6.92±0.51%/h) and oleic (5.98±0.44%/h) acids. Statistically these values were not significantly different. Cumulative¹⁴CO₂ excretion rates over 12 h were also similar for linoleic (27.2±0.9%), α-linolenic (26.8±1.2%) and oleic (25.9±1.2%) acids. The results suggest that the rat's capacity to oxidize 18-carbon unsaturated fatty acids is not affected by fatty acid unsaturation when these fatty acids are provided at equal dietary levels.     

The effect of protein deficiency on some rat liver lipid metabolic enzymes and CoA

Two groups of male Wistar rats were fed normal (i.e., 18%) and protein-free diets, respectively, for 7 weeks. In vivo incorporation of [1-¹⁴C] acetate into palmitic, stearic, oleic, and arachidonic acids by the liver was reduced in the protein-deficient rats. In vitro incubation of liver microsomes with labeled palmitate or linoleate revealed no change in the specific activities of chain elongating or desaturating enzymes. Protein deficiency resulted in a decrease in specific activity of short chain acyl-CoA synthetase and in total CoA, accompanied by the virtual disappearance of acyl-CoA and an increase in free CoA. Furthermore, there was less microsomal fatty acid synthetase and mitochondrial β-hydroxybutyrate dehydrogenase activity. These results are discussed in relation to fatty acid synthesis and the changes in liver fatty acid composition.     

Oil composition of pistachio nuts (Pistacia vera L.) from Turkey

The oil content, fatty acid and sterol compositions and other parameters of pistachio nut (Pistacia vera L.) samples corresponding to five different varieties, all cultivated in Turkey were determined. Mean values were 59.69 ± 1.80% for fat content, 0.9143 ± 0.006 for specific gravity of the oil, 1.4693 ± 0.004 for refractive index, 94.23 ± 1.510 for iodine value, and 188.2 ± 3.80 for saponification value. Fatty acids identified in the oil samples were palmitic, palmitoleic, stearic, oleic, and linoleic acids with oleic acid as the dominant fatty acid (68.78 ± 2.05%). Halebi variety had the highest level of oleic acid among the varieties studied. The sterols isolated from the unsaponifiable fraction were campesterol, stigmasterol, β-sitosterol, and Δ⁵-avenasterol with β-sitosterol as the major constituent (84.95 ± 2.80%). Higher levels of β-sitosterol were found in Kιrmιzι variety. The high level of oil, oleic acid and β-sitosterol content was found in all the varieties studied. Fat content, iodine value, palmitic acid and oleic acid content significantly differed between varieties.     

Characterization of chemicals mediating ovipositional host-plant finding byAmyelois transitella females

Ovipositional host-finding in the navel orangeworm,Amyelois transitella (Walker), is brought about by an in-flight response to host odors. Wind-tunnel studies of the response of gravid females to almonds showed that this response is mediated primarily by long-chain fatty acids, particularly oleic acid and linoleic acid. Evidence for the behavioral activity of fatty acids is based on the fact that: (1) behavioral activity of almond oil was concentrated in a single liquid chromatographic fraction whose composition was predominantly long-chain fatty acids, (2) behavioral activity was lost when either almond oil or the active fraction of that oil was treated with diazomethane, (3) full activity was elicited by a selective extraction of free fatty acids from crude almond oil, and (4) upwind response by females was elicited by a blend of synthetic oleic and linoleic acids, albeit at a level less than that elicited by almond oil. Five fatty acids identified from the almond oil were: myristic acid (1%), palmitic acid (16%), stearic acid (3%), oleic acid (58%), and linoleic (22%). Attraction to various combinations of synthetic acids was observed only when oleic acid was present, and oleic acid elicited upwind flights to the source when presented alone; however, short-range responses were enhanced by the addition of linoleic acid, which elicited no long-range orientation by itself. Despite significant levels of attraction to synthetic blends, the percentage of females flying to the source was lower than that flying to acidulated almond oil, the best natural attractant tested. Thus, although longrange response may be mediated primarily by a blend of oleic and linoleic acids, additional and as yet unidentified components must also play an important role. Long-range chemically modulated host finding in this and other generalist plant feeders is discussed with respect to current models of the evolution of host finding, and it is argued that suggestions that long-range host finding should be correlated with narrowness of host utilization are logically flawed and are not supported by our current understanding of specific examples of host finding.     

Influence of fatty alcohol and other fatty acid derivatives on fatty acid uptake into rat intestinal epithelial cells

We investigated the influence of various substrates on the uptake of long-chain fatty acid into IEC-6, rat intestinal epithelial cell line. The uptake of [³H]oleic acid into IEC-6 cells was a saturable function of the oleic acid concentration. Long-chain fatty acids significantly inhibited the oleic acid uptake into IEC-6 cells and shorter-chain fatty acids had little or no effect. Various fatty acid esters suppressed the oleic acid uptake into IEC-6. Fatty alcohols also inhibited oleic acid uptake into IEC-6 and the length of the carbon chain played an important role. These results suggest that long-chain fatty acid uptake was inhibited by the substrates which had a structure similar to long-chain fatty acids, especially those with a long carbon chain. At least two molecules, fatty acid translocase and fatty acid transport protein type 4, which are considered to be involved in the long-chain fatty acid transport into the cell, were expressed on IEC-6 cells, supporting the existence of the carrier-mediated system of long-chain fatty acid transport on IEC-6 cells.     

Fatty acid specificity of glyceride synthesis by homogenates of bovine mammary tissue

Fatty acid esterification by cell free preparations of bovine mammary tissue was investigated to determine if the type of long chain fatty acid supplied might influence the rate of triglyceride synthesis by that tissue. Homogenates of lactating bovine mammary tissue esterified¹⁴C-fatty acids into glycerides at rates dependent upon chain length and degree of unsaturation. Palmitic, stearic, oleic and linoleic acids were esterified at rates consistent with their concentration in milk fat. A comparison of free fatty acid concentrations of mammary tissue with levels saturating esterification suggested that supply of fatty acids does not limit glyceride synthesis. Certain combinations of fatty acids were facilitory, competitive or inhibitory to esterification. Stearic acid complimented esterification of palmitic and oleic acids. Unlabeledtrans-11-octadecenoic acid did not compete with¹⁴C-palmitate as efficiently in the esterification process as did unlabeledcis-9-octadecenoic acid, indicating that the mammary gland may preferentially esterify thecis-isomer of C-18∶1. Linoleic acid inhibited esterification of palmitic, stearic and oleic acids. Michigan Agricultural Experiment Station Journal Article No. 5100.     

Fractionation and analysis of rat liver14CH3-lecithins labeled in vivo

The¹⁴CH₃-lecithins were biosynthesized by normal adult rats injected with¹⁴CH₃-methionine. About 20% of the dose was incorporated into liver lecithins. The¹⁴CH₃-lecithins were isolated by thin-layer chromatography. Separation of lecithins on AgNO₃-treated silica gel yielded lecithins containing a saturated fatty acid in combination with mainly one unsaturated fatty acid, namely, oleic, linoleic, eicosatrienoic, or arachidonic acid. These fractions were eluted with methanolic choline chloride, which prevented elution of AgNO₃. The lecithins, after extraction into petroleum ether, were analyzed for radioactivity and for fatty acid composition. Yields were about 75%, based upon fatty acids or radioactivity applied to the plate. Specific activities differed sharply between the fractions, and arachidonoyllecithins had the highest specific activity. The sum of the activities contributed by each of the fractions agreed well with the specific activity of total lecithins, indicating the recovery of intact lecithin molecules. The recovery of intact molecules allows this procedure to be used with lecithins containing any isotopic labels. The high specific activity of arachidonoyl-lecithins relative to the other fractions indicates a high degree of specificity in the metabolic reactions which lead to the formation of rat liver lecithins.     

The biosynthesis of polyunsaturated fatty acids in plants

This paper is a review of some of the work being done at the author's laboratory. The phospholipids and glycolipids of the alga,Chlorella vulgaris, have been implicated in fatty acid transformations such as chain elongation and desaturation. Labeling studies with [¹⁴C] acetate have shown that newly synthesized galactosyl glycerides have mainly saturated fatty acids. Subsequent to de novo synthesis, a series of alterations of fatty acid structure takes place within the same glycolipid molecules. The specific incorporation of [¹⁴C] oleic acid intoChlorella phosphatidyl choline provides a convenient model system for studying the lipid dependent desaturation of oleic to linoleic acid. The inhibitor of fatty acid desaturation, sterculic acid, only inhibits the conversion of oleate into linoleate if added before the precursor fatty acid has been incorporated into a complex lipid. Studies with isomeric monoenoic fatty acids have suggested that there are two enzymes which catalyze the formation of linoleic from oleic acid. One measures the position of the second double bond from the carboxyl group, the other, from the methyl end of the chain. The latter enzyme probably requires the complex lipid substrate.     

Current advances in sunflower oil and its applications

The fatty acid and triacylglycerol composition of a vegetable oil determine its physical, chemical and nutritional properties. The applications of a specific oil depend mainly on its fatty acid composition and the way in which fatty acids are arranged in the glycerol backbone. Minor components, e. g. tocopherols, also modify oil properties such as thermo‐oxidative resistance. Sunflower seed commodity oils predominantly contain linoleic and oleic fatty acids with lower content of palmitic and stearic acids. High‐oleic sunflower oil, which can be considered as a commodity oil, has oleic acid up to around 90%. Additionally, new sunflower varieties with different fatty acids and tocopherols compositions have been selected. Due to these modifications sunflower oils possess new properties and are better adapted for direct home consumption, for the food industry, and for non‐food applications such as biolubricants and biodiesel production.     

Fatty acid composition of oleaster pulp and pit oils

Fatty acid compositions of oleaster pulp and pit oils were determined by gas chromatography in 4 samples of different varieties. Pit oils were highly unsaturated, containing >90% linoleic, oleic, and linolenic acids, as well as traces of palmitoleic acid. Saturated fatty acids consisted of palmitic and stearic acids with traces of arachidic acid. Pulp oils showed fatty acid compositions entirely different from that of pit oils. They contained 9 saturated fatty acids, C₁₂ to C₂₄, some of them with high quantities, up to 34.9%, of the total fatty acids. Unsaturated fatty acids, mainly oleic and linoleic, with low quantities of palmitoleic and linolenic acids composed about one-third of the total fatty acids.     

Circadian rhythm of fatty acid desaturation in mouse liver

A study was made of the diurnal changes in liver microsomal desaturation of labeled stearic, linoleic and α-linolenic acids to oleic, γ-linolenic and octadeca-6,9,12,15-tetraenoic acids, respectively. C3H-S mice were used and were exposed to light-dark cycles. A circadian rhythm was observed for stearic acid desaturation, and a different one for linoleic acid. Linoleic and α-linolenic desaturation had similar responses in the day cycle. This would indicate that different mechanisms control the oxidative desaturations of the fatty acids in the 9 and 6 carbons. The fatty acid composition of the whole liver and liver microsomes also showed variations. Remarkable oscillations were observed for stearic and oleic acids. Neither the total protein synthesis nor the free fatty acid concentration in the microsomes followed a rhythm parallel to the desaturation of the studied fatty acids. The injection of cycloheximide 4 hr before measuring the desaturation modified the circadian variation of both the 9 and 6 desaturations. The modification induced by cycloheximide was considered to indicate that both variations are related to the synthesis of specific proteins but not to that of a degradative or inhibitory protein.     

The cytotoxicity of fatty acid/α‐lactalbumin complexes depends on the amount and type of fatty acid

Complexes of the milk protein, α‐lactalbumin, and the fatty acid, oleic acid, have previously been shown to be cytotoxic. Complexes of α‐lactalbumin and five different fatty acids (vaccenic, linoleic, palmitoleic, stearic, and elaidic acid) were prepared and compared to those formed with oleic acid. All complexes were cytotoxic to human promyelocytic leukemia‐derived (HL‐60) cells but to different degrees depending on the fatty acid. The amount of fatty acid per α‐lactalbumin molecule was found to correlate with the cytotoxicity; the higher the number of fatty acids per protein, the more cytotoxic the complex. Importantly, all the tested fatty acids were also found to be cytotoxic on their own in a concentration dependent manner. The cytotoxic effect of complexes between α‐lactalbumin and linoleic acid, vaccenic acid, or oleic acid was further investigated using flow cytometry and found to induce cell death resembling apoptosis on Jurkat cells. Practical applications: Cytotoxic complexes of α‐lactalbumin and several different fatty acids could be produced. The cytotoxicity of all the variants is similar to that previously determined for α‐lactalbumin/oleic acid complexes.     

The differential effect of eicosapentaenoic acid and oleic acid on lipid synthesis and VLDL secretion in rabbit hepatocytes

The suppression of plasma very low density lipoprotein (VLDL) triglyceride levels by dietary fish oils rich in polyunsaturated n−3 fatty acids has been attributed to decreased hepatic VLDL secretion. To investigate the effect of n−3 fatty acids on lipid metabolism and VLDL secretion in a tissue culture system, we incubated rabbit hepatocytes with oleic acid and eicosapentaenoic acid (EPA) and examined [³H]glycerol and [¹⁴C]fatty acid incorporation into hepatocyte triglyceride and phospholipid and into media VLDL. Glycerol incorporation studies showed that EPA failed to stimulate VLDL triglyceride secretion from hepatocytes as occurred with oleic acid (P<0.05). Oleic acid preferentially enhanced hepatocyte triglyceride synthesis while EPA stimulated significantly phospholipid synthesis (P<0.01). Varying the relative concentrations of oleic acid and EPA at a constant total fatty acid concentration corroborated preferential triglyceride synthesis from oleic acid. Synthesis shifted predominantly to phospholipids with increasing concentrations of EPA and lower levels of oleic acid. Incorporation of the [¹⁴C]fatty acids (800 μM) followed similar patterns: 87% of [¹⁴C]oleic acid was incorporated into hepatocyte triglyceride and 44% of [¹⁴C]EPA was assimilated in hepatocyte phospholipid (p<0.001). Fatty acids at trace concentrations (53 nM) showed a more divergent pattern of lipid incorporation: 60% of [¹⁴C]oleic acid was incorporated into triglyceride while 91% of [¹⁴CEPA was incorporated into phospholipid (p<0.001). We conclude that in primary rabbit hepatocyte culture, which appears to be a useful model to study lipid metabolism and VLDL secretion, EPA is avidly incorporated into phospholipid while oleic acid predominantly becomes esterified in triglyceride. In addition, EPA, unlike oleic acid, fails to stimulate hepatocyte VLDL secretion. These divergent effects on hepatocyte lipid metabolism are, at least in part, likely to be responsible for fish oil induced suppression of plasma triglycerides.     

Effect of storage and grilling on fatty acids in muscle of pigs fed plant oils

The purpose of the study was to assess changes in the fatty acid composition of raw and grilled pig muscles after different storage periods. A total of 13 female and 12 castrated Pietrain×German Landrace pigs were fed a basal concentrate diet supplemented with 5% olive oil or 5% linseed oil during the growing‐finishing period. An entire cut of the pork loin with bone (15^th rib to 5^th lumbar vertebra) was stored at 5 °C for 48, 96 or 144 h. Simultaneous analyses of intramuscular fat and lipid composition were carried out on raw and grilled longissimus muscles following different storage intervals. Dietary inclusion of linolenic acid by linseed oil feeding effectively increased the long‐chain n‐3 fatty acids, whereas in the olive oil group the oleic acid in pork was higher. Mean total lipid ranged from 1.8 to 2.3% for raw and from 2.6 to 3.5% for grilled pork chops. The relative proportions of lauric acid, stearic acid and oleic acid significantly increased with storage time, while the percentages of linoleic, arachidonic, eicosapentaenoic acid and the sum of polyunsaturated fatty acids, especially n‐6 fatty acids, were decreased. Compared with raw muscle, grilling affected the relative fatty acid profile only slightly. Related to the original weight, storage and grilling increased the total fatty acid contents and the sum of saturated, monounsaturated, n‐6 and n‐3 fatty acids of loin chops, as a result of water losses.     

Tissue culture of cocoa bean (Theobroma cacao L.): Incorporation of fatty acids into lipids of cultured cells

Suspension cell cultures of cocoa bean rapidly incorporated palmitic, stearic, oleic and linoleic acids into cellular lipids. Thus, 75 and 20% of [1-¹⁴C] palmitic acid was incorporated into polar lipids and triglycerides, respectively, after 48 hr. When [1-¹⁴C] oleic and [1-¹⁴C] linoleic acid were added separately, polar lipids consistently contained most of the radioactive fatty acids. Ca. 60% of the stearic acid accumulated as unesterified fatty acid in the cells. Palmitic and stearic acid were not desaturated, but oleic acid and linoleic acid were further desaturated. The kinetics of conversion of oleic acid and linoleic acid suggested a sequential desaturation pathway of 18∶1→18∶2→18∶3 in cocoa bean cell suspensions.     

Influence of Temperature on the Fatty Acid Composition of the Oil From Sunflower Genotypes Grown in Tropical Regions

The influence of temperature on the fatty acid composition of the oils from conventional and high oleic sunflower genotypes grown in tropical regions was evaluated under various environmental conditions in Brazil (from 0° S to 23° S). The amounts of the oleic, linoleic, palmitic and stearic fatty acids from the sunflower oil were determined using gas chromatography (GC). The environment exhibited little influence on the amounts of oleic and linoleic fatty acids in high oleic genotypes of sunflower. In conventional genotypes, there was broad variation in the average amounts of these two fatty acids, mainly as a function of the minimum temperature. Depending on the temperature, especially during the maturation of the seeds, the amount of oleic acid in the oil of conventional sunflower genotypes could exceed 70 %. Higher temperatures led to average increases of up to 35 % for this fatty acid. Although the minimum temperature had the strongest effect on the fatty acid composition, locations at the same latitude with different minimum temperatures displayed similar values for both oleic acid and linoleic acid. Furthermore, minimum temperature had little influence on the amounts of palmitic and stearic fatty acids in the oil.     

Effect of dietary fats on some membrane-bound enzyme activities,membrane lipid composition and fatty acid profiles of rat heart sarcolemma

The effect of various dietary fats on membrane lipid composition, fatty acid profiles and membrane-bound enzyme activities of rat cardiac sarcolemma was assessed. Four groups of male weanling Charles Foster Young rats were fed diets containing 20% of groundnut, coconut, safflower or mustard oil for 16 weeks. Cardiac sarcolemma was prepared from each group and the activities of Na⁺,K⁺-ATPase, 5′-nucleotidase, Ca²⁺-ATPase and acetylcholinesterase were examined. ATPase activities were similar in all groups except the one fed coconut oil, which had the highest activities. Acetylcholinesterase activity was also similar in all the groups, however, it was significantly higher in the group fed mustard oil. No significant changes were observed among the groups in 5′-nucleotidase activity, in the cholesterol-to-phospholipid molar ratio and in sialic acid content. The coconut, safflower and mustard oil diets significantly increased cholesterol and phospholipid contents and the lipid-to-protein ratio of cardiac sarcolemma as compared to feeding the groundnut oil diet. The fatty acid composition of membrane lipids was quite different among the various groups, reflecting the type of dietary fat given. The total unsaturated-to-saturated fatty acid ratio was not different among the various groups; however, the levels of some major fatty acids such as palmitic (16∶0), oleic (18∶1) and linoleic (18∶2) acids were significantly different. Cardiac sarcolemma of the group fed safflower oil had the highest polyunsaturated fatty acid content. The results suggest that dietary fats induce changes not only in the fatty acid composition of the component lipids but also in the activities of sarcolemmal enzymes involved in the regulation of cardiac function.