Changes in fatty acid composition of phospholipids and triglycerides of Musca domestica resulting from choline deficiency

The fatty acid composition of the phospholipids and triglycerides extracted from housefly larvae reared on diets containing no added fatty acids but containing differing concentrations of choline has been determined. Reducing the choline content of the diet resulted in a graded reduction of the percentage of phosphatidylcholine present in the phospholipids of the larvae. This was accompanied by changes in the fatty acid composition, choline deficiency causing an increased utilization of 16-C rather than 18-C acids by the phospholipids. Changes in the fatty acid composition of the triglyceride fraction were also observed but these were associated with insects containing very low levels of phosphatidylcholine. Examination of the fatty acids in the different classes of phospholipids showed that the major change resulting from choline deficiency was in the fatty acids of the phosphatidylethanolamine fraction—the phospholipid which increased as the phosphatidylcholine decreased.Although the fatty acid composition of the different classes of phospholipids was not completely fixed, some preferential utilization of certain fatty acids by certain classes was observed, in both larval and adult insects. The fatty acid composition of the phospholipids extracted from larval gut, muscle, fat body, cuticle, trachea, nervous tissue, and haemolymph was determined. Changes resulting from choline deficiency similar to those seen in the whole larva were observed in all tissues except the nervous tissue. The effect of rearing larvae at temperatures between 24 and 35°C resulted in only minor changes in the fatty acid composition of both phospholipid and triglyceride fractions but the difference due to choline deficiency was observed at all temperatures. The possibility that the observed changes in the fatty acids of the phospholipids are compensatory to the changes in the proportion of the choline to the ethanolamine phospholipids is discussed.     

Aldosterone alters the phospholipid composition of rat colonocytes

Previous studies have shown that aldosterone treatment of amphibian epithelial cells results not only in stimulation of Na(+) absorption but also in changes in phospholipid composition which are necessary for the mineralocorticoid action of aldosterone. The present study was designed to investigate the effect of aldosterone on phospholipids of mammalian epithelia. Phospholipid and fatty acid composition was examined in colonic epithelium (mineralocorticoid target tissue) and thymus (non-mineralocorticoid but glucocorticoid target tissue) of rats which had received aldosterone or vehicle by a miniosmotic pump for 7 days. Aldosterone increased the mass of colonic phospholipids relative to cellular proteins with concomitant changes in the percentage distribution of fatty acids, whereas the relative distribution of membrane phospholipds was not changed. Phosphatidylcholine increased the content of polyunsaturated and decreased that of monounsaturated fatty acids, which predominantly reflected the accretion of arachidonic and a decrease in oleic and palmitoleic acids. Within the phosphatidylethanolamine subclass, pretreatment of rats with aldosterone decreased the content of monounsaturated fatty acids (predominantly oleic and palmitoleic acid) and of n-3 fatty acids, and increased the content of saturated fatty acids (palmitic acid). The saturated-to-nonsaturated fatty acid ratio also significantly increased after aldosterone treatment. No changes in thymic phospholipids were seen. The results are consistent with the contention that aldosterone specifically modulates phospholipid concentration and metabolism in mineralocorticoid target tissue. The changes in phospholipid content and its fatty acid composition during the fully developed effect of aldosterone may reflect a physiologically important phenomenon with long-term consequences for membrane structure and function.     

Phospholipids and protein adaptation of Pseudomonas sp. to the xenoestrogen tributyltin chloride (TBT)

A tributyltin (TBT)-resistant strain of Pseudomonas sp. isolated from an overworked car filter was tested for its adaptation to TBT. The isolate was checked for organotin degradation ability, as well as membrane lipid and cellular protein composition in the presence of TBT. The phospholipid profiles of bacteria, grown with and without increased amounts of TBT, were characterized using liquid chromatography/electrospray ionization/mass spectrometry. The strain reacted to the biocide by changing the composition of its phospholipids. TBT induced a twofold decline in the amounts of many molecular species of phosphatidylglycerol and an increase in the levels of phosphatidic acid (by 58 %) and phosphatidylethanolamine (by 70 %). An increase in the degree of saturation of phospholipid fatty acids of TBT exposed Pseudomonas sp. was observed. These changes in the phospholipid composition and concentration reflect the mechanisms which support optimal lipid ordering in the presence of toxic xenobiotic. In the presence of TBT the abundances of 16 proteins, including TonB-dependent receptors, porins and peroxidases were modified, which could indicate a contribution of some enzymes to TBT resistance.     

Differences in lipid and in fatty acid composition of taproots and lateral roots of faba bean plants (Vicia faba L.) grown in saline media

Abstract

The content and composition of lipids and fatty acids of taproots and lateral roots of Vicia faba were investigated with plants grown under saline (80 mM NaCl) and non-saline conditions. Lipids of both types of faba bean roots are constituted of ～80% phospholipids, of ～15% glycolipids and of some 5% of wax-esters. Phosphatidylethanolamine (PE) and phosphatidylcholine are the main constituents of both root types. Di-phosphatyidylglycerol and phosphatidylinositol are present in medium concentrations, whereas phosphatidylglycerol and phosphatidylserine are present only in trace amounts. The content of sulpholipids was much lower in salt-treated roots as compared with that of the controls. The content of cardiolipins and PE was higher in lateral roots than in the taproots. Roots of salt-treated plants had some 18% lower ether-soluble lipid content in the lateral roots, and approximately 28% lower than the taproots. Less than 25% of the fatty acids of the extracted phospholipids were saturated, with palmitic acid as the main constituent (13 – 18%). Linoleic acid comprised 65 – 70% of the unsaturated acids. Differences in the composition of some fatty acids were found between taproots and lateral roots of salt-treated plants. The observed differences in composition between root types suggests that the reported physiological differences between such roots could be based, at least in part, on structural or compositional differences in their lipids.     

Adaptive modification of membrane phospholipid fatty acid composition and metabolic thermosuppression of brown adipose tissue in heat-acclimated rats

Thermogenesis, especially facultative thermogenesis by brown adipose tissue (BAT), is less important in high ambient temperature and the heat-acclimated animals show a lower metabolic rate. Adaptive changes in the metabolic activity of BAT are generally found to be associated with a modification of membrane phospholipid fatty acid composition. However, the effect of heat acclimation on membrane phospholipid fatty acid composition is as yet unknown. In this study, we examined the thermogenic activity and phospholipid fatty acid composition of interscapular BAT from heat-acclimated rats (control: 25±1°C, 50% relative humidity and heat acclimation: 32±0.5°C, 50% relative humidity). Basal thermogenesis and the total thermogenic capacity after noradrenaline stimulation, as estimated by in vitro oxygen consumption of BAT (measured polarographically using about 1-mm³ tissue blocks), were smaller in the heat-acclimated group than in the control group. There was no difference in the tissue content of phospholipids between the groups when expressed per microgram of DNA. The phospholipid fatty acid composition was analyzed by a capillary gas chromatograph. The state of phospholipid unsaturation, as estimated by the number of double bonds per fatty acid molecule, was similar between the groups. The saturated fatty acid level was higher in the heat-acclimated group. Among the unsaturated fatty acids, heat acclimation decreased docosahexaenoic acid and oleic acid levels, and increased the arachidonic acid level. The tissue level of docosahexaenoic acid correlated with the basal oxygen consumption of BAT (r=0.6, P<0.01) and noradrenaline-stimulated maximum values of oxygen consumption (r=0.5, P<0.05). Our results show that heat acclimation modifies the BAT phospholipid fatty acids, especially the n-3 polyunsaturated fatty acid docosahexaenoic acid, which is possibly involved in the metabolic thermosuppression. Received: 9 August 1999 / Revised: 8 November 1999 / Accepted: 24 November 1999     

Onset of changes in phospholipid fatty acid composition and prostaglandin synthesis following dietary manipulation with n-6 and n-3 fatty acids in the rat

A synthetic diet preparation supplemented with 10% by weight of either safflower oil, hydrogenated coconut oil containing 3% safflower oil, or 'max EPA' fish oil was fed to rats over a 8-week period. Serial measurements of serum fatty acids, serum thromboxane B2 and urinary prostaglandin excretion were taken during the treatment period to assess the rate of change in fatty acid composition and prostaglandin synthesis following dietary manipulation. There was no significant change in weight gain between the dietary groups during the treatment period. Significant changes in serum fatty acids occurred within 48 h of treatment, with the 'max EPA' oil group having arachidonic acid levels reduced by 23% (P less than 0.01) compared to the coconut oil group. Conversely, rats fed safflower oil had an 18% enhancement of arachidonic acid during the same time period. Whole blood synthesis of thromboxane B2 was significantly depressed (P less than 0.01) after 48 h in rats fed 'max EPA' oil compared to the safflower oil or coconut oil groups. This suppression reached a maximum of 65% (P less than 0.001) after 7 days of dietary 'max EPA' oil treatment. The safflower oil and coconut oil-fed groups showed the same levels of serum thromboxane B2 production over the treatment period. Urinary excretion of both 6-ketoprostaglandin F1 alpha and prostaglandin E2 varied significantly (P less than 0.01) between the groups after 7 days of dietary treatment. Rats fed 'max EPA' oil had depressed urinary prostanoid excretion compared to the safflower and coconut oil groups which remained very similar to each other. After the 8-week treatment period rats were killed and the phospholipid fatty acid composition and prostaglandin-generating capacity of platelets, aorta and renal tissue was examined. Prostanoid production by kidney cortex and medulla and segments of aorta was consistently suppressed in rats fed 'max EPA' oil. These observations correlated well with changes in the phospholipid fatty acid profiles in these tissues. This study shows rapid changes in serum fatty acids and thromboxane B2 generation following dietary manipulation, while changes in urinary excretion or prostanoid metabolites occur only after a longer time period.     

Temperature-induced changes in fatty acid composition of myelinated and non-myelinated axon phospholipids

The olfactory (non-myelinated) and trigeminal (myelinated) nerve axons of garfish show changes in phospholipid fatty acid composition when these fish are acclimated to temperatures ranging from 11 to 35 degrees C. Myelinated and non-myelinated nerve axons show similar changes in the percent saturated, percent 16-carbon, percent 18-carbon, and percent 20-carbon-and-greater unsaturated fatty acids. The observed changes in phospholipid fatty acid composition fit a linear regression model suggesting a gradual change in axonal phospholipid fatty acid composition with temperature. The temperature-induced changes in garfish nerve phospholipid fatty acid composition are consistent with the general observation of increased saturated fatty acid residues in plasma membrane phospholipids of organisms acclimated to higher environmental temperatures. The garfish data are similar to data previously obtained for goldfish tissues and Tetrahymena.     

Phospholipids and the Phospholipid Fatty Acids of Germinating Hazel Seeds (Corylus avellana L.)

An analysis of the phospholipids and phospholipid fatty acidsof germinating hazel seeds has been carried out. The phospholipidcontent of the cotyledons and embryonic axes increased duringgermination. Early increases in the relative amounts of phosphatidylglycerol and decreases in the relative amounts of phosphatidylethanolamine occurred in both cotyledons and axes. The laterstages of germination were accompanied by further changes inthe phospholipid composition of the axes. Increases in the degreeof unsaturation of the C₁₈ fatty acids occurred in both tissues.     

Effects of temperature and gibberellic acid on 4-desmethylsterol composition of Avena sativa stem segments

Of the three morphological subunits of Avena sativa stem segments (node, leaf-sheath and internode) examined, internodes constituted the richest source of phospholipids and sterols, yielding almost double the concentration of lipid found in the leaf-sheath. The phospholipid compositions of nodes and internodes were similar, comprising mostly phosphatidylcholine (PC) and phosphatidylethanolamine (PE), with linoleic, linolenic and palmitic acids as the predominant component fatty acids. Leaf-sheath tissue contained mainly PE, with equally high amounts of palmitic, linoleic and linolenic acids. β-Sitosterol and cholesterol were the major 4-desmethylsterols of the internode, while β-sitosterol was predominant in the node and leaf-sheath tissues. The growth temperature of segments prior to isolation produced its major effect on the concentration of stigmasterol, which decreased markedly with temperature. The sitosterol/stigmasterol ratio increased significantly as temperature decreased. Stem segments isolated from plants treated with gibberellic acid (GA₃) for 3 weeks, showed a significant reduction in the amounts of 4-desmethyl sterols on a dry wt basis when compared with control segments. However, when stem segments were incubated with GA₃ for 20 hr, no change in 4-desmethylsterol composition or concentration was observed, even though significant growth in response to GA₃ occurred.     

Enhanced phospholipase B activity and alteration of phospholipids and neutral lipids in Saccharomyces cerevisiae exposed to N-nitrosonornicotine

A tobacco-specific nitrosamine (TSNA), N-nitrosonornicotine (NNN), is a potent carcinogen present in cigarette smoke, and chronic exposure to it can lead to pulmonary cancer. NNN causes changes in phospholipid metabolism and the mechanism is yet to be elucidated. Exposure of Saccharomyces cerevisiae to 50 μM NNN leads to a substantial decrease in phosphatidylserine (PS) by 63%, phosphatidylcholine (PC) by 42% and phosphatidylethanolamine (PE) by 36% with a concomitant increase in lysophospholipids (LPL) by 25%. The alteration in phospholipid content was dependent on increasing NNN concentration. Reduced phospholipids were accompanied with increased neutral lipid content. Here we report for the first time that NNN exposure, significantly increases phospholipase B (PLB) activity and the preferred substrate is PC, a major phospholipid responsible for a series of metabolic functions. Furthermore, NNN also promotes the alteration of fatty acid (FA) composition; it increases the long chain fatty acid (C18 series) in phospholipids specifically phosphatidylethanolamine (PE) and PS; while on the contrary it increases short chain fatty acids in cardiolipin (CL). NNN mediated degradation of phospholipids is associated with enhanced PLB activity and alteration of phospholipid composition is accompanied with acyl chain remodelling. Understanding the altered phospholipid metabolism produced by NNN exposure is a worthwhile pursuit because it will help to understand the toxicity of tobacco smoke.     

Membrane Lipids in Senescing Flower Tissue of Ipomoea tricolor

Rib segments excised from flower buds of Ipomoea tricolor Cav. pass through the same phases of senescence as the respective tissue on the intact plant. Such segments were used to correlate changes in lipid content with known symptoms of aging, such as rolling up of the ribs and ethylene formation. It was found that the level of phospholipid had already started to decline before visible signs of senescence were evident. As the segments began to roll up and to produce ethylene, the rate of phospholipid loss accelerated sharply. During the same period, the level of fatty acids esterified to phospholipids also fell by 40%. No qualitative changes in any lipid component could be detected during senescence. Labeling experiments using ³³P as marker showed that the rate at which radioactivity was lost from phospholipids during aging was parallel to the rate at which the level of total phospholipids declined. Exogenously applied ethylene accelerated the loss of phospholipid and the senescence of rib segments while benzyladenine retarded both of these processes.     

Altered lipid composition of adipose tissue in human muscular dystrophy

Lipids of subcutaneous adipose tissue from normal and dystrophic human samples were investigated with particular reference to the fatty acid composition of neutral lipids and phospholipids. The free fatty acid pattern did not show much change. Triglyceride, which together with cholesterol composed most of the neutral lipid fraction, showed significant changes in fatty acid composition by gas-liquid chromatography (GLC). There was a decrease in the total phospholipids. Analysis of the levels of individual phospholipids, however, showed an increase in sphingomyelin and ethanolamine phosphoglyceride contents. Fatty acid composition of the different phospholipid classes analyzed by GLC showed significant changes.     

Membrane lipids and ethanol tolerance in the mouse. The influence of dietary fatty acid composition

Mice of the TO Swiss strain received diets containing different amounts of saturated or unsaturated fat throughout life. These diets produced characteristic changes in cardiac phospholipid fatty acid composition, but produced no significant differences in fatty acid composition of phospholipids from a crude membrane fraction of brain. When littermates of these animals were exposed to ethanol vapour in an inhalation chamber it was observed that mice which had received a diet high in saturated fat lost the righting reflex at an estimated concentration of ethanol in blood higher than that required for mice receiving a control diet, or a diet rich in polyunsaturated fat. Analysis of the brain membrane fraction from those animals which had received ethanol revealed that mice receiving the highly saturated fat diet now had a significantly greater proportion of saturated fatty acids in brain membrane phospholipids. These results are discussed in relation to the hypothesis that brain membrane lipid composition may influence the behavioural response to ethanol.     

Decreased cytochrome oxidase activity in hepatic mitochondria after chronic ethanol consumption and the possible role of decreased cytochrome aa3 content and changes in phospholipids

In ethanol-fed baboons, hepatic mitochondrial cytochrome oxidase activity and cytochrome aa₃ content were significantly decreased by 58.3 and 50.5%, respectively, compared to their pair-fed controls. However, there was no significant correlation between the two, suggesting that other factors in addition to cytochrome aa₃ may be responsible for the depression in cytochrome oxidase activity. The total phospholipid content of the mitochondrial membranes was significantly decreased (0.24 ± 0.03 μmol of phospholipid phosphorus/mg of protein vs. 0.32 ± 0.04 in controls). This change was accounted for, in part, by the significant decrease in the levels of phosphatidylcholine and cardiolipin. In addition, the fatty acid pattern of the phospholipids was changed. There was a marked increase in the relative amounts of oleic and linoleic acid and a decrease in arachidonic acid. These changes were associated with an increase in the activity of phospholipase A₂. The reactivation rate of phospholipid-depleted cytochrome oxidase by endogenous phospholipids from ethanol-fed baboons was significantly lower than that by phospholipid from pair-fed controls, when measured at an optimal phospholipid to protein ratio. Thus, it appears that alterations in the phospholipid composition of the mitochondrial membranes are responsible, at least in part, for the depression of cytochrome oxidase activity produced by chronic ethanol consumption.     

Changes of Lipid Composition with Growth Phase of Cryptococcus neoformans

Qualitative and quantitative profiles of phospholipids, neutral lipids, and fatty acid composition in Cr. neoformans during the growth phase were investigated in relation to pyrophosphatidic acid. A marked increase of the total lipid content, which depended on the accumulation of triglyceride in yeast cells with the growth, was observed. The total phospholipid contents in yeast cells remained almostly constant during the exponential phase and slightly decreased in the stationary phase. The major phospholipids of this yeast were phosphatidylcholine, phosphatidylethanolamine, phosphatidylinositol, phosphatidylserine, and cardiolipin, the next groups being pyrophosphatidic acid, phosphatidic acid, lysophos-phatidylcholine, and unidentified components. The amounts of phosphatidylcholine, phosphatidylinositol, and cardiolipin were fairly constant throughout the growth phase, but the amount of phosphatidylethanolamine increased and that of phosphatidylserine decreased with progressive growth. The pyrophosphatidic acid contents were 0.9~0.7% for total phospholipid during the growth phase. The major fatty acids of pyrophosphatidic acid were C_16:0, C_18:1, and C_18:2 acids. The changing patterns of fatty acid composition in pyrophosphatidic acid through the growth phase closely resembled that of phosphatidic acid, which contained larger amounts of C_18:1 acid (35~45%) than C_16:0 acid (30~25%) and C_18:2 acid (30~25%). Phosphatidylserine and phosphatidylinositol contained considerable amounts of saturated fatty acid (C_16:0 acid, more than 55%). On the other hand, phosphatidylcholine, phosphatidylethanolamine, and cardiolipin contained extremely large amounts of unsaturated fatty acid (C_18:1 and C_18:2 acid, 85ç90%).     

Phospholipids and fatty acids of Neisseria gonorrhoeae.

The phospholipids and fatty acids of two strains of Neisseria gonorrhoeae of different penicillin susceptibilities were examined. The phospholipids, which comprise about 8% of the dry weight of the cells, consisted of phosphatidylethanolamine (70%) and phosphatidylglycerol (20%); small amounts of phosphatidylcholine and traces of cardiolipin were also present. Growing and stationary-phase cells were similar in content and composition of phospholipids except for phosphatidylcholine, which increased two- to fivefold in the stationary-phase cells. The fatty acids of the phospholipids were characterized by two major acids, palmitic and a C16:1, with myristic and a C18:1 acid present in smaller amounts. The fatty acids present in purified phospholipid fractions varied considerably in relative proportions from fraction to fraction. No significant difference in the composition of phospholipids from the two strains was evident. Large amounts of beta-hydroxy lauric acid were detected only after saponification of the organisms. Differences in the lipid composition between the gonococcus and other gram-negative bacteria are discussed.     

Characterisation of the wheat phospholipid fraction in the presence of nickel and/or selenium

The influence of nickel (Ni) and/or selenium (Se) on phospholipid composition was studied in shoots and roots of wheat seedlings. Phospholipid differences between samples were analysed using liquid chromatography/electrospray ionization–MS coupled. A total of 39 lipid species were identified. Individual phospholipids were then quantified using a multiple reaction monitoring method. In the roots, Ni toxicity was associated with an elevated level of phosphatidic acid species. In the shoots, the phosphatidylcholine/phosphatidylethanolamine ratio was about fivefold higher than in roots and decreased in Ni-treated samples. Additionally, the concentrations of phospholipid species containing C 18:3 fatty acid were reduced. Lipidome data were then analyzed using principal component analysis, which confirmed the compositional changes in phospholipids in response to Ni and Ni + Se. In contrast, the phospholipid profiles of wheat seedlings exposed to Se alone showed more similarities with the control. Together, our results suggested that the presence of Se, despite a considerable improvement of growth of Ni-treated wheat, did not counterbalance negative effect of Ni on the phospholipid composition in wheat roots and shoots.     

Influence of growth hormone and thyroxine on thermotropic effects of respiration and 1-anilino-8-naphthalene sulfonate fluorescence and on lipid composition of cardiac membranes

The effects of hypophysectomy and subsequent administration of growth hormone and/or L-thyroxine on thermotropic properties of State 3 respiration (ADP-induced), cholesterol, phospholipid and fatty acid composition of phospholipid fraction were examined in myocardial mitochondria of rats. Temperature-dependence of 1-anilino-8-naphthalene sulfonate fluorescence was determined in vesicles prepared from lipids of heart mitochondria. Transition temperature obtained from the Arrhenius plots of respiration occurred at 21 and 24°C for heart mitochondria of normal and hypophysectomized rats, respectively. Most notably, after hypophysectomy the rate of respiration was lower below 24°C, but was progressively higher above that temperature when compared to normal rats. The energy of activation was 148 and 36% larger below and above the transition temperature, respectively. Growth hormone restored almost completely the energy of activation and respiratory rates to normal levels. Administration of L-thyroxine, with or without growth hormone, did not significantly change the rate of respiration but decreased the transition temperature to 17.7–17.0°C. Lipid and phospholipid content, as well as percent distribution of phospholipids and their fatty acid composition were not statistically different among the different groups of rats. Only cholesterol content was increased after hypophysectomy. Administration of growth hormone and thyroxine did not significantly change the total unsaturation index of fatty acids, but growth hormone increased the content of arachidonic acid (20 : 4) by 70% but decreased the docosahexaenoic acid (22 : 6) three times which may have a beneficial effect on mitochondrial membranes. These and other results suggest that hormones exert different effects on subcellular organelles in different tissues, like heart and liver.     

Comprehensive quantitative lipidomic approach to investigate serum phospholipid alterations in breast cancer

Introduction

Globally, breast cancer is the most common cancer in women and ranks second most common cause of cancer related mortality. Although efforts are made by researchers in molecular characterization of breast cancer using “-OMIC’S” approaches, limited work has explored to understand the phospholipid alterations in breast cancer.

Objectives

This study aims to explore five classes of serum phospholipid alterations in breast cancer towards discrimination of breast cancer from benign and healthy controls.

Methods

Twenty eight each of breast cancer patients and age-matched benign and healthy control serum samples were used to identify alterations of phospholipids using liquid chromatography-multiple reaction monitoring-mass spectrometry. Both multivariate and univariate statistical analyses were applied to investigate breast cancer associated phospholipid alterations. Differentially expressed phospholipid species were further confirmed by liquid chromatography-tandem mass spectrometry (LC-MS/MS).

Results

Among the identified and quantified 200 phospholipids, 25 phospholipids were found to be statistically significant (VIP > 1.4 and ANOVA p < 0.05) in the serum of women with breast cancer when compared with benign and healthy controls. Comparison of serum phospholipids of breast cancer patients and healthy controls revealed 12 phospholipids were found to be differentially expressed in which six were up-regulated and six were down-regulated. While comparative analysis of breast cancer serum against benign showed an increased concentration of six phospholipids in breast cancer samples. Further, significantly altered phospholipids were structurally characterized by enhanced product ion scanning.

Conclusion

Our results demonstrate that some of the differentially regulated phospholipids identified in our study such as PE (14:1/16:0), PC (18:0/18:0), LPE 14:0, PE (20:0/22:2) could be a panel of potential signature which can discriminate breast cancer from benign and healthy controls. These findings also provide insight into lipidomic information that can be used for monitoring of breast cancer progression.

     

Incorporation of n-3 fatty acids into phospholipids of rat liver and white and brown adipose tissues: A time-course study during fish-oil feeding

The aim of this study was to determine the time-course incorporation of dietary n-3 polyunsaturated fatty acids into phospholipids of tissues highly involved in lipid and energy metabolism: the liver and the white (WAT) and brown (BAT) adipose tissues. Rats were fed a diet supplemented with 19% fish oil for up to 4 weeks. Minor changes in the relative proportions of tissue phospholipids were observed in the three tissues. Fish-oil feeding induced rapid and large replacements of n-6 fatty acids by n-3 fatty acids. In liver, the 22:6n-3 level increased progressively and reached a plateau after 3 (phosphatidylethanolamine and phosphatidylserine) or 7 days (phosphatidylcholine and phosphatidylinositol). In contrast, the 20:5n-3 level transiently peaked in all liver phospholipids at days 1–3 before reaching a plateau after day 7. In WAT as in BAT the level of n-3 fatty acids increased progressively and reached in all phospholipids a plateau after day 7. As a general trend, in each phospholipid class the 22:6n-3/20:5n-3 ratio was higher in liver than in the two adipose tissues. This study shows that each dietary n-3 fatty acid is incorporated very rapidly into liver, WAT, and BAT phospholipids but according to time courses and at levels that depend simultaneously on the tissue and phospholipid class considered.