Lipid biosynthesis, oxidative enzyme activities and cellular changes in growing olive fruit

Fruit of Olea europea L. was examined by light and electron microscopy to determine whether commencement of lipid accumulation depended upon the fruit achieving structural maturity. Maturation of fruit develops progressively from the smallest changes towards the largest in cellular structures. Important metabolic and structural changes have been observed: oil body formation, changes in the structural and reserve lipid biosynthesis and in the fatty acid of total lipid content, as well as in G6PDH and LOX activities. The labelling of fruit lipids by previously incubating the leaves with (1-14C)-acetate and (1,5-14C)-citrate or by putting the labelled substrates directly on the fruit surface, shows a 14C assimilate derived from acetate greater than that from citrate; the incorporation of the latter is higher in the methanol-water fractions. At the beginning of fruit development the lipid biosynthesis with both substrates is greater in polar lipids; on the contrary, the incorporation of 14C into neutral lipids increases during fruit maturation. Additionally, a maximum of substrate export from leaves to fruit coincides with an increase in the lipoxygenase and, above all, in the glucose-6-phosphate dehydrogenase activities. The transported 14C from leaves begins its activity before the small oil bodies close to the tonoplast can be observed in the fruit, and well before the beginning of maturation. The results suggest that structural development and some other rate controlling metabolic steps can govern the initiation of lipid accumulation in olive fruit.     

Low-temperature-induced changes in intracellular fatty acid fluxes in Dunaliella salina

Two-minute exposures to exogenous [14C]palmitic, [14C]oleic, or [14C]lauric acid differentially labeled the lipids of Dunaliella salina microsomes and chloroplasts. Changes in fatty acid desaturation and intracellular movement during a subsequent 16-h incubation in nonradioactive medium indicated a slow transfer of lipids into the chloroplast from other organelles. Since Dunaliella lacks the massive traffic of microsomally produced glycerolipids into chloroplast galactolipids that dominates chloroplast-microsome lipid relations in most plant cells, it affords a sensitive system for studying more subtle intracellular lipid fluxes. Lowering the culture temperature from 30 to 12 degrees C was more inhibitory toward glycerolipid biosynthesis in chloroplasts than in microsomes. The ability of Dunaliella chloroplasts to utilize microsomal lipids may be essential for their systematic acclimation to low temperature.     

Lipid Biosynthesis in Leaf and Fruit of Olive

A comparative study of fatty acids from total lipids, and ofthe distribution of the main lipid groups in fruit and leaf,has been accomplished in olive during the development of thefruit. Palmitic, oleic, and especially -linolenic acids arethe main fatty acids of the leaf throughout the cycle. In youngfruits this composition is similar to that of the leaf,; butthe quantity of oleic acid increases and the saturated and polyunsaturatedacids decrease with the time. The incorporation of [1-¹⁴C]acetateinto neutral lipids of fruit increases with ripening, whereasthe synthesis of glycolipids decreases. In the leaf an increaseoflabelled glycolipids in the stage of fruit maturity can beobserved, whereas the synthesis of phospholipids reaches maximain the first and last stages studied. All these events suggestthat there is little correlation between leaf and fruit in lipidbiosynthesis.     

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-(14)C]oleate and [1-(14)C]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-(14)C]Linoleate was almost exclusively found in the galactolipids. With [1-(14)C]linoleate as a precursor, the only significant desaturation to linolenate was in the galactolipids. Monogalactosyldiacylglycerol was the first lipid in which [1-(14)C]linoleate and [1-(14)C]linolenate appeared after incubation of the calli with [1-(14)C]oleate and [1-(14)C]linoleate, respectively. The presence of radioactivity in the plastidial lipids shows that both [1-(14)C]oleate and [1-(14)C]linoleate can freely enter the chloroplast. Two important environmental effects were also examined. Raised incubation temperatures (30-35 degrees 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.     

Fatty acid composition of galactolipids and phospholipids in neoplasmatic plant tissues (cecidia) and normal leaf tissue

Insect-elicited modifications of leaf cells that produce leaf galls on higher plants are concurrent with changes at the biochemical level. The neoplasmatic alterations affect the composition and concentration of membrane phospho and galactolipids. In vitro labeling of developing leaf galls from oak [induced by cympids (Hymenoptera) on L.] with [¹⁴C]-acetate and [³H]-oleate was used to study the label distribution in monogalactosyldiacylglyceride, digalactosyldiacylglyceride, phospha-tidylglycerol and phosphatidylinositol in these tissues and in the normal host organs (leaf laminae). The incorporation of both labels was higher into the leaf galactolipids than into gall galactolipids, whereas the incorporation of oleate was slightly increased in the 2 phospholipids in cynipid galls. The degree of acyl chain unsaturation of individual endogenous phosphoglycerides (phosphatidylcholine, phosphatidyletha-nolamine. phosphatidylglycerol, diphosphatidylglycerol, phosphatidylinositol) was, in most cases, higher in the gall tissues. Differences in the endogenous fatty acid composition of plant polar lipids and the molar concentrations of labeled fatty-acid precursors in galacto- and phospholipids are discussed with regard to modifications of the leaf phenotype and cecidogenesis on Quercus palustris L.     

Biosynthesis of lipids in chloroplasts isolated from jack pine needles

Suspensions of isolated pine needle chloroplasts were shown to incorporate galactose from UDP galactose-[¹⁴C] into galactolipids. The incorporation of the label among galactolipids was always considerably higher in the monogalactosyl diglycerides than in the digalactosyl diglycerides. The galactosyl incorporation into both galactolipid fractions was optimal at pH 8.0 and was inhibited by sulphydryl reagents (p-chloromercuribenzoate, N-ethyl maleimide and CdCl₂). The chloroplast preparations were also able to biosynthesize various phospholipids and galactolipids from palmitoyl-[1-¹⁴C]-CoA; the major portion of the label appeared in phosphatidyl choline. The incorporation of palmitic-[1-¹⁴C] acid into various lipids was very poor compared to that of palmitoyl-[1-¹⁴C]-CoA. However, addition of ATP and CoA markedly stimulated lipid biosynthesis from palmitic-[1-¹⁴C] acid, suggesting the presence of activating enzymes. These chloroplast suspensions did not show any de novo fatty acid synthesis.     

Sequence of prolactin effects on phospholipid synthesis in mouse mammary gland explants

In cultured mouse mammary gland explants derived from 12-14 day pregnant mice, the effect of prolactin (PRL) on the rate of incorporation of several precursors into neutral lipids and phospholipids was determined. Employing [14C]-acetate as a substrate, PRL stimulates its incorporation into a) neutral lipids by 4-6 hours, b) phosphatidyl choline (PC) and phosphatidyl inositol-phosphatidyl serine (PI-PS) by 1-2 hours, and c) phosphatidyl ethanolamine (PE) by 2-4 hours. Using [3H]-glycerol as a substrate, the temporal response to PRL for its incorporation into the neutral lipids was the same as that for [14C]-acetate, however, PRL did not enhance the rate of [3H]-glycerol incorporation into the phospholipids at any time through 16 hours. PRL similarly had no effect on the rates of [3H]-choline, [3H]-serine, [3H]-ethanolamine, or [32P]O4 incorporation into the phospholipids at hormone exposure periods of 8 hours or more. And finally, PRL had no effect on the rates of [3H]-arachidonate or [14C]-linoleate incorporation into neutral lipids or phospholipids at culture periods up to 18 hours. These data suggest that the early effect of PRL on [14C]-acetate incorporation into the phospholipids is due to either the insertion of newly synthesized fatty acids and/or the extension of fatty acids contained in the phospholipids.     

Effects of ethanol on the remodeling of neutral lipids and phospholipids in brain mitochondria and microsomes

We have analyzed the effects of ethanol in vitro on the remodeling of neutral lipids and phospholipids in mitochondria and microsomes isolated from chick brain. We used three different fatty acyl-CoAs of similar chain lengths but different degrees of unsaturation. Our results demonstrate the existence of active mechanisms for acyl-CoA transfer into neutral lipids and phospholipids in both mitochondria and microsomes. The profile of fatty acid incorporation was clearly different according to the membrane and lipid fraction in question. Thus, in mitochondrial lipids, the remodeling processes showed a clear preference for the saturated fatty acid whilst the polyunsaturated one was the preferred substrate for microsomal lipid acylation. With regard to the effects of ethanol in vitro, we were able to demonstrate that exposure of the membrane to ethanol led to an increase in the incorporation of polyunsaturated fatty acid into triacylglycerol (TG) in both mitochondria and microsomes, indicating that it directly stimulates the acylation of diacylglycerol (DG) to give TG. This effect may then contribute to the widely reported stimulation of TG biosynthesis in cases of both acute and chronic ethanol ingestion. It is noteworthy that the exposure of microsomes to ethanol in vitro also stimulated the incorporation of oleoyl-CoA into the aminophospholipids phosphatidylethanolamine (PE) and phosphatidylserine (PS). We also demonstrate that both mitochondria and microsomes synthesize fatty acid ethyl esters (FAEEs) from fatty acyl-CoA, although there is a clear difference in preference for the fatty acid used as substrate in the esterification of the alcohol. Thus, mitochondria were capable of forming FAEEs from the polyunsaturated fatty acid whilst in microsomes the saturated fatty acid was the preferred substrate. In both types of membrane, FAEE production was lowest with the monounsaturated fatty acyl-CoA.     

Ketone body utilization for energy production and lipid synthesis in isolated rat brain capillaries

Isolated brain capillaries from 2-month-old rats were incubated for 2 h in the presence of [3-14C]acetoacetate, D-3-hydroxy[3-14C]butyrate, [U-14C]glucose, [1-14C]acetate or [1-14C]butyrate. Labelled CO2 was collected as an index of oxidative metabolism and incorporation of label precursors into lipids was determined. The rate of CO2 production from glucose was slightly higher than from the other substrates. Interestingly, acetoacetate was oxidized at nearly the same rate as glucose. This shows that ketone bodies could be used as a source of energy by brain capillaries. Radiolabelled substrates were also used for the synthesis of lipids, which was suppressed by the addition of albumin. The incorporation of [U-14C]glucose in total lipids was 10-times higher than that from other precursors. However, glucose labelled almost exclusively the glycerol backbone of phospholipids, especially of phosphatidylcholine. Ketone bodies as well as glucose were incorporated mainly into phospholipids, whereas acetate and butyrate were mainly incorporated into neutral lipids. The contribution to fatty acid synthesis of various substrates was in the following order: butyrate greater than or equal to acetate greater than ketone bodies greater than or equal to glucose. All precursors except glucose were used for sterol synthesis. Glucose produced almost exclusively the glycerol backbone of phospholipids.     

Cadmium stress induces changes in the lipid composition and biosynthesis in tomato (<Emphasis Type="Italic">Lycopersicon esculentum</Emphasis> Mill.) leaves

The effects of cadmium (Cd) stress on lipid composition and biosynthesis were investigated in young leaves of ten-day-old tomato seedlings (Lycopersicon esculentum Mill. cv. Ibiza F1). Cd was found to be mainly accumulated in roots, but a severe inhibition of biomass production occurred in leaves, even at its low concentration (1.0 μM). Seven days after Cd treatment, the membrane lipids were extracted and separated on silica-gel thin layer chromatography (TLC). Fatty acid methyl esters were analyzed by FID-GC on a capillary column. Our results showed that Cd stress decreased the quantities of all lipids classes (phospholipids, galactolipids and neutral lipids). Likewise, there was also a decline in the levels of tri-unsaturated fatty acids, such as linolenic (C18:3) and hexadecatrienoic (C16:3) acids. The linolenic acid (C18:3) decreased in monogalactosyldiacylglycerol (MGDG) and all phospholipids, while hexadecatrienoinic acid (C16:3) declined mainly in MGDG. Moreover, Cd at high concentrations (25.0 and 50.0 μM) significantly enhanced the levels of lipid peroxides. Radiolabelling experiments were carried out by laying down microdroplets of [1-¹⁴C]acetate–a major precursor of lipid biosynthesis–on attached leaves of the control and Cd-treated plants. After incubation for 1, 2, 12 and 24 h, the leaves were harvested and lipids extracted and analysed. Cd stress was found to decrease the incorporation of [1-¹⁴C]acetate in total lipids. The biosynthesis of total lipids was altered with 25.0 and 50.0 μM Cd. The decline in the incorporation of [1-¹⁴C]acetate due to Cd stress was observed in all lipid classes. There was also a substantial decline in the incorporation of [1-¹⁴C]acetate in tri-unsaturated fatty acids. The results indicate that Cd treatment induces an oxidative stress by inhibiting the chloroplastic and extrachloroplastic lipid-biosynthesis pathways as well as lipid peroxidation.     

Comprehensive Analysis of Lipid Composition in Crude Palm Oil Using Multiple Lipidomic Approaches

Palm oil is currently the leading edible oil consumed worldwide. Triacylglycerol （TAG） and diacylglycerol （DAG） are the dominant lipid classes in palm oil. Other lipid classes present in crude palm oil, such as phospholipids and galactolipids, are very low in abundance. These low-abundance lipids constitute key intermediates in lipid biosynthesis. In this study, we applied multiple lipidomic approaches, including high-sensitivity and high-specificity multiple reaction monitoring, to comprehensively quantify individual lipid species in crude palm oil. We also established a new liquid chromatography-coupled mass spectrometry method that allows direct quantification of low-abundance galactolipids in palm oil without the need for sample pretreatrnent. As crude palm oil contains large amounts of neutral lipids, our direct-detection method circumvents many of the challenges encountered with conventional lipid quantification methods. This approach allows direct measurement of lipids with no hassle during sample preparation and is more accurate and precise compared with other methods.     

The effect of 3-methylindole on the rates of phospholipid and neutral lipid synthesis in cultured fibroblasts

The present study was designed to test the hypothesis that a pneumotoxin, 3-methylindole, alters the basic metabolic pathways involved in phospholipid and neutral lipid synthesis in cultured fibroblasts. Rat skin fibroblasts were obtained from day-old pups. Confluent monolayers were preincubated for up to 24 h with a range of concentrations (0-0.76 mM) of 3-methylindole. Following these treatments, the cell lipids were labelled by incubation for 6 h with [14C]glycerol. The lipids were extracted, separated by thin layer chromatography, and the radioactivity in each fraction was determined. 3-Methylindole had no effect on the total incorporation of [14C]glycerol into lipids, but significantly altered the distribution among lipid fractions. Incubation with 3-methylindole caused a decrease in the incorporation of [14C]glycerol into phosphatidylcholine, while radioactivity accumulated in the neutral lipid fraction. The other lipid fractions responded variably. Similarily, Flow 2000 human diploid lung fibroblasts were incubated for 24 h with 3-methylindole followed by treatment with [14C]glycerol, resulting in a 74% decrease in the incorporation of [14C]glycerol into phosphatidylcholine and a 50% increase in its accumulation in neutral lipid. The results indicate that 3-methylindole inhibits the synthesis of phosphatidylcholine from diacylglycerol precursors on the endoplasmic reticulum in cultured fibroblasts. This is an important observation as it shows that 3-methylindole affects the synthesis of phospholipids required for membrane turnover in cells that are not specialized for the production of phospholipids for surfactant.     

The desaturation and elongation of linolenic acid and eicosapentaenoic acid by hepatocytes and liver microsomes from rainbow trout (Oncorhynchus mykiss) fed diets containing fish oil or olive oil

The products of desaturation and elongation of [1−¹⁴C] 18:3(n − 3) and [1−¹⁴C]20:5(n − 3) were studied using hepatocytes and microsomes prepared from livers of trout maintained on diets containing either olive oil or fish oil, to establish the extent to which the formation of 22:6(n − 3) was enhanced in the absence of dietary 22:6(n − 3) and to investigate the pathway(s) of conversion of 18:3(n − 3) and 20:5(n − 3) to 22:6(n − 3). Levels of 20:5(n − 3) and 22:6(n − 3) in the total lipid of hepatocytes from trout fed olive oil were 20-fold and 10-fold, respectively, lower than in cells from trout fed fish oil. For both dietary groups, [1−¹⁴C]18:3(n − 3) was incorporated into hepatocyte lipid to a greater extent than [1−¹⁴C]20:5(n − 3). Almost 70% of the total radioactivity from [1−¹⁴C]18:3(n − 3) was recovered in hepatocyte triacylglycerols, whereas radioactivity from [1−¹⁴C]20:5(n − 3) was recovered almost equally in neutral lipids (52%) and polar lipids (48%). The products of desaturation and elongation from both labelled substrates were esterified mainly into hepatocyte polar lipids, whereas elongation products of [1−¹⁴C]18:3(n − 3) were preferentially incorporated into neutral lipids. Radioactivity recovered in the 22:6(n − 3) of polar lipids of hepatocytes from trout fed olive oil, from both ¹⁴C substrates, was approximately double that in hepatocytes from trout fed fish oil. No radioactivity from either [1−¹⁴C]18:3(n − 3) or [1−¹⁴C]20:5(n − 3) was incorporated into 22:6(n − 3) by microsomes isolated from livers from either group of fish and incubated in the presence of acetyl-CoA, malonyl-CoA, NADH, NADPH, ATP and coenzyme A. However, significant radioactivity was recovered in 24:5(n − 3) and 24:6(n − 3) from [1−¹⁴C]20:5(n − 3) and more radioactive 24:6(n − 3) accumulated in microsomes from trout fed olive oil than from trout fed fish oil. The results establish that the formation of 22:6(n − 3) from both 18:3(n − 3) and 20:5(n − 3) in hepatocytes of rainbow trout is stimulated by omitting 22:6(n − 3) from the diet and are consistent with the biosynthesis of 22:6(n − 3) in trout liver cells proceeding via 24:5(n − 3) and 24:6(n − 3) intermediates.     

The effect of cadmium on lipid and fatty acid biosynthesis in tomato leaves

This research aims to examine the effect of cadmium uptake on lipid composition and fatty acid biosynthesis, in young leaves of tomato treated seedlings (Lycopersicon esculentum cv. Ibiza F1). Results in membrane lipids investigations revealed that high cadmium concentrations affect the main lipid classes, leading to strong changes in their composition and fatty acid content. Thus, the exposure of tomato plants to cadmium caused a concentration-related decrease in the unsaturated fatty acid content, resulting in a lower degree of fatty acid unsaturation. The level of lipid peroxides was significantly enhanced at high Cd concentrations. Studies of the lipid metabolism using radioactive labelling with [1-¹⁴C]acetate as a major precursor of lipid biosynthesis, showed that levels of radioactivity incorporation in total lipids as well as in all lipid classes were lowered by Cd doses. In total lipid fatty acids, [1-¹⁴C]acetate incorporation was reduced in tri-unsaturated fatty acids (C16:3 and C18:3); While it was enhanced in the palmitic (C16:0), palmitoleic (C16:1), stearic (C18:0) and linoleic (C18:2) acids. [1-¹⁴C]acetate incorporation into C16:3 and C18:3 of galactolipids [monogalactosyldiacylglycerol (MGDG) and digalactosyldiacylglycerol (DGDG)] and some phospholipids [phosphatidylcholine (PC) and phosphatidylglycerol (PG)] was inhibited by Cd stress. Our results showed that in tomato plants, cadmium stress provoked an inhibition of polar lipid biosynthesis and reduced fatty acid desaturation process.     

Incorporation into liver microsomal lipids of linoleic and stearic acids and of their respective products of delta 6 and delta 9 desaturation, gamma-linolenic and oleic acids: effect of age and of blackcurrant seed oil.

The incorporation of [1-14C]linoleic and [1-14C]stearic acid and of their delta 6 and delta 9 desaturation products (gamma-linolenic and oleic acids, respectively) into different classes of lipids was studied in liver microsomes of rats in function of the diet (blackcurrant seed oil diet, containing gamma-linolenic acid, versus control diet) and in function of age (3, 6 and 9 months). After delta 6 desaturation, total radioactivity was distributed between phospholipids, especially phosphatidylcholine, and neutral lipids. The desaturation product, gamma-linolenic acid, was totally recovered in the phospholipid fraction. Blackcurrant seed oil, which decreased the rate of delta 6 desaturation in 6- and 9-month-old rats, also decreased the incorporation of radioactivity in total phospholipids, especially in phosphatidylcholine. At 6 months of age, after delta 9 desaturation, the majority of radioactivity was recovered in neutral lipids principally as oleic acid, the desaturation product. The precursor, stearic acid, was highly incorporated into phospholipids, especially in rats on a diet of blackcurrant seed oil.     

Effects of water stress on lipid metabolism in cotton leaves

After 2, 10 and 24 hr labelling with [1-¹⁴C] acetate, radioactivity incorporated into the lipids of cotton leaves is mainly found in phosphatidylcholine, phosphatidylglycerol and neutral lipids. Galactolipids are slowly synthesized and after 24 hr, account for only 10% of the total radioactivity. Under water stress, a marked decrease of precursor incorporation into leaf lipids occurs, particularly in phosphatidylcholine and galactolipids. Relative incorporation into neutral lipids, on the contrary, increases. Water deficits provoke an inhibition of the fatty acid desaturation, resulting in a sharp decrease of linoleic and linolenic acid biosynthesis. The decrease in unsaturated fatty acid biosynthesis occurs in all lipid classes, but is most pronounced in the galactolipid fractions. In the drought-resistant cotton variety (Mocosinho), the variations in lipid and fatty acid metabolism under water stress are less pronounced than in the drought-sensitive variety (Reba), and this attests a greater stability of the membrane system.     

Total polar lipid biosynthesis during growth of Crotalaria juncea pollen tubes

[1-¹⁴C]-Acetate incorporation into total and polar lipids was studied in the growing pollen tubes of Crotalaria juncea. Ungerminated pollen had phosphatidyl inositol, phosphatidyl serine, phosphatidyl choline, phosphatidyl ethanolamine, phosphatidyl glycerol, monogalactosyl diglyceride, digalactosyl diglyceride, sulpholipid and steryl glycosides. In the growing pollen tubes considerable [1-¹⁴C]-acetate incorporation was observed into the individual polar lipids. The exogenous carbon source significantly influenced lipid biosynthesis. Boric acid (20mg/l.) promoted both pollen tube growth and acetate incorporation into phospholipids. In comparison to 5′-adenosine monophosphate, cyclic-3′,5′-adenosine monophosphate (cAMP) promoted tube growth and also enhanced phospho-and glycolipid biosynthesis. The regulation of membrane component biosynthesis by cAMP is suggested.     

In vivo incorporation of acetate into the acyl moieties of polar lipids from etiolated leek seedlings

Seven-day-old leek seedlings actively synthesize lipids in vivo from [1-¹⁴C]acetate, both in the light and in the dark. In the dark, phospholipid synthesis is more effective than galactolipid synthesis. Whatever the time of acetate incorporation by the etiolated seedlings, very long chain fatty acids having from 20 to 26 carbon atoms are found in all the polar lipids, including the acyl-CoAs. All of the labelled very long chain fatty acids incorporated into the polar lipids are saturated. On the other hand, the labelled C₁₈-fatty acids are unsaturated in phospholipids and galactolipids and almost no label is found in the saturated or unsaturated C₁₈-fatty acids of the acyl-CoAs.     

Lipid synthesis in germinating safflower seeds and protoplasts

Galactolipids and phospholipids rapidly accumulated in a whole seed between 2 and 4 days after germination. However, the rate of incorporation of [¹⁴C] acetate into galactolipids was very low. The predominant fatty acid of galactolipids was linolenic acid, while those of phospholipids were linoleic and palmitic acids. Fatty acids of monogalactosyldiacylglycerol in germinating safflower seeds were randomly distributed between the 1 - and 2-positions of the glycerol molecule and the distribution in digalactosyldiacylglycerol was slightly non-random, while fatty acids of galactolipids in mature safflower leaves were non-randomly distributed. Triacylglycerol was synthesized in the cotyledon tissue of the germinating seeds simultaneously with its rapid degradation. In addition, lipid biosynthesis in protoplasts is described.     

The effect of dietary menhaden,olive, and coconut oil fed with three levels of vitamin E on plasma and liver lipids and plasma fatty acid composition in rats

The effect of dietary fats with varying degrees of unsaturation in the presence of different concentrations of vitamin E on tissue lipid levels was studied in rats. Rats were fed either menhaden oil, olive oil or coconut oil at 15% levels with either 0.1, 0.3 or 0.6 mg/g of vitamin E as alpha-tocopherol for four weeks. Rat serum and liver were analyzed for total cholesterol, HDL-cholesterol, triacylglycerol and phospholipids. In addition, fatty acid composition of serum lipids was also analyzed. Serum total cholesterol and triacylglycerol were significantly lower in rats fed menhaden oil than in those fed olive or coconut oil, while the HDL-cholesterol was significantly higher in serum of rats fed menhaden and olive oil than in those fed coconut oil. Levels of vitamin E in the diet had only a significant effect on serum cholesterol and liver phospholipids. The Pearson correlation coefficient showed a significant positive relationship between serum triacylglycerol and total cholesterol, and a negative correlation between triacylglycerol and HDL-cholesterol, and between total and HDL-cholesterol.In the liver, total cholesterol was significantly higher in rats fed coconut oil than in rats fed menhaden oil. Total liver phospholipids were lower in rats fed either coconut oil or olive oil compared to those fed menhaden oil, especially with higher levels of vitamin E intake. Higher levels of vitamin E in the diet appear to increase triacylglycerol and phospholipids in livers of rats fed menhaden oil. In the liver a significant negative correlation was observed between phospholipids and cholesterol. The type and degree of unsaturation (polyunsaturated fatty acids in menhaden oil, monounsaturated fatty acids in olive oil and saturated fatty acids in coconut oil) significantly affected plasma and tissue lipids.