Acid Composition Of Neutral Lipids Research Articles

Seasonal lipid dynamics of four Arctic bivalves: Implications for their physiological capacities to cope with future changes in coastal ecosystems.

The Arctic is exposed to unprecedented warming, at least three times higher than the global average, which induces significant melting of the cryosphere. Freshwater inputs from melting glaciers will subsequently affect coastal primary production and organic matter quality. However, due to a lack of basic knowledge on the physiology of Arctic organisms, it remains difficult to understand how these future trophic changes will threaten the long-term survival of benthic species in coastal habitats. This study aimed to gain new insights into the seasonal lipid dynamics of four dominant benthic bivalves (Astarte moerchi, Hiatella arctica, Musculus discors, and Mya truncata) collected before and after sea ice break-up in a high-Arctic fjord (Young Sound, NE Greenland). Total lipid content and fatty acid composition of digestive gland neutral lipids were analyzed to assess bivalve energy reserves while the fatty acid composition of gill polar lipids was determined as a biochemical indicator of interspecies variations in metabolic activity and temperature acclimation. Results showed a decrease in lipid reserves between May and August, suggesting that bivalves have only limited access to fresh organic matter until sea ice break-up. The lack of seasonal variation in the fatty acid composition of neutral lipids, especially essential ω3 fatty acids, indicates that no fatty acid transfer from the digestive glands to the gonads occurs between May and August, and therefore, no reproductive investment takes place during this period. Large interspecies differences in gill fatty acid composition were observed, which appear to be related to differences in species life span and metabolic strategies. Such differences in gill fatty acid composition of polar lipids, which generally influence metabolic rates and energy needs, may imply that not all benthic species will be equally sensitive to future changes in primary production and organic matter quality in Arctic coastal habitats.

α-Tocopherol-13'-Carboxychromanol Induces Cell Cycle Arrest and Cell Death by Inhibiting the SREBP1-SCD1 Axis and Causing Imbalance in Lipid Desaturation.

α-Tocopherol-13'-carboxychromanol (α-T-13'-COOH) is an endogenously formed bioactive α-tocopherol metabolite that limits inflammation and has been proposed to exert lipid metabolism-regulatory, pro-apoptotic, and anti-tumoral properties at micromolar concentrations. The mechanisms underlying these cell stress-associated responses are, however, poorly understood. Here, we show that the induction of G0/G1 cell cycle arrest and apoptosis in macrophages triggered by α-T-13'-COOH is associated with the suppressed proteolytic activation of the lipid anabolic transcription factor sterol regulatory element-binding protein (SREBP)1 and with decreased cellular levels of stearoyl-CoA desaturase (SCD)1. In turn, the fatty acid composition of neutral lipids and phospholipids shifts from monounsaturated to saturated fatty acids, and the concentration of the stress-preventive, pro-survival lipokine 1,2-dioleoyl-sn-glycero-3-phospho-(1'-myo-inositol) [PI(18:1/18:1)] decreases. The selective inhibition of SCD1 mimics the pro-apoptotic and anti-proliferative activity of α-T-13'-COOH, and the provision of the SCD1 product oleic acid (C18:1) prevents α-T-13'-COOH-induced apoptosis. We conclude that micromolar concentrations of α-T-13'-COOH trigger cell death and likely also cell cycle arrest by suppressing the SREBP1-SCD1 axis and depleting cells of monounsaturated fatty acids and PI(18:1/18:1).

The effect of dietary fat supplements on the activity of palmitic and stearic acid desaturases based on the results of a study of the fatty acid composition of neutral lipids in blood serum and liver of rats receiving a fat-free diet

Background. Desaturase enzymes are involved in the formation of monoenoic acids from saturated fatty acids. One such enzyme is stearyl-CoA-desaturase (SCD1), which converts stearic acid to oleic acid. The aim of this work was to determine the effect of edible fats with different fatty acid compositions on SCD1 activity.
 Methods. High linoleic sunflower oil (HLSO), high oleic sunflower oil (HOSO) and palm oil (PO) were used. The rats were fed for 30 days with a semi-synthetic diet that did not contain any fats (FFD) and fat diets containing 5 % of each of the above oils. In animals, lipids were extracted from serum and liver and divided into 3 fractions: neutral lipids (NL), phospholipids (PL), and free fatty acids (FFA).
 The fatty acid composition of each fraction was determined by gas chromatography. The SCD18 activity was determined by the C18:1 n-9/C18:0 ‒ ratio, and the SCD16 activity was determined by the C16:1 n-7/C16:0 ratio.
 Results. A higher activity of SCD16 and SCD18 was found in the NL fraction, and the activity of SCD18 significantly exceeds that of SCD16. A decrease in the content of C16:0, C16:1 and C18:0 in the NL fraction of the liver and blood serum was shown. The activity of SCD16 in blood serum and liver decreases in rats fed fat diets­, while the activity of SCD18 does not decrease, and even increases with the consumption of HOSO.­
 Conclusions. To determine the SCD1 activity, it is advisable to use the C18:1/C18:0 ratio in terms of the level of fatty acids in the NL fraction. Fatty diet inhibits SCD16 activity, and consumption of HOSO increases SCD18 activity.

CONTENT OF MINERAL SUBSTANCES AND SOME BIOLOGICALLY ACTIVE COMPOUNDS IN THE TISSUE OF THE SHOOTS TETRALOPHOZIA SETIFORMIS (EHRH.) SCHLJAKOV, PTILIDIUM PULCHERRIMUM (WEBER) VAIN. AND RADULA COMPLANATA (L.) DUMORT FROM THE FLORA OF THE REPUBLIC OF KOMI

The study of the chemical composition of biologically active substances (neutral lipids and their fatty acid composition, prothenogenic amino acids, alkaloids) and the content of macro- and microelements in the shoots of three types of liverworts from the flora of the Komi Republic – Tetralophosia setiformis (Ehrh.) Schljakov, Ptilidium pulcherrimum (Weber) Vain. and Radula complanata (L.) Dumort, was carried out. It is shown that the content of neutral lipids in the studied representatives lies in the lower limits typical for plants (0.3; 0.9; 0.5% of dry weight). The fatty acid composition of neutral lipids is represented by molecules with chains from C12 to C20. It was found that the main share is made up of saturated fatty acids, among which palmitic (C16:0), stearic (C18:0) and arachinic (C20:0) dominate. Unsaturated acids are mainly represented by oleic and linoleic acids. Lipids of P. pulcherrimum are characterized by a fairly high content of extremely rare unsaturated vaccenic acid in plants (3.0% of the total acid content), which is classified as an unusual fatty acid. The mass fraction of nitrogen in the dry matter of three types of liverworts ranges from 0.83 to 1.27%. Of the 17 proteinogenic acids in all liver samples, the dominant ones are aspartic and glutamic acids, which are part of the proteins of all known living organisms, as well as alanine, leucine and lysine. In addition, a fairly high content of the partially interchangeable amino acid arginine was found. In the three studied species, 13 micro- and six macronutrients were found. At the same time, T. setiformis is characterized by a higher content of trace elements of iron, aluminum and lead and the macronutrient sodium, P. pulcherrimum – manganese, potassium and phosphorus, R. complanata – trace elements of zinc, copper, barium and strontium, macronutrients of calcium and magnesium. Testing the samples for the presence of alkaloids using sedimentary reactions and UV detection of extracts gave a negative result for two species, but a positive reaction with two reagents and an intense glow during UV detection of P. pulcherrimum extracts, which requires additional more detailed study.

Effects of a juνenoid on lipid metabolism and fatty acid composition during growth of Heliothis armigera

The effect of the juvenoid ZR-619 (Zoecon Corp.) on lipid metabolism and fatty acid composition of last instar larvae, pupae and pharate adults of Heliothis armigera Hbn. (Lepidoptera, Noctuidae) were studied. Treatments at low doses with the juvenoid resulted in an increase of the body weight of larvae and affected the composition of lipids accumulated. In non-treated larvae neutral lipids represent 88.9% of the total lipids, while in treated larvae, the neutral lipids are present at a lower level (80.2%). Fatty acid composition in untreated larvae, pupae and pharate adults is characterized by large proportions of palmitic and oleic acids and higher proportions of linoleic acid than of linolenic acid. Alteration in fatty acid composition is observed in phospholipids of pupae and pharate adults, the proportions of palmitic and oleic acid being lower than in larvae. The juvenoid ZR-619 slightly affected the fatty acid composition of neutral lipids in treated larvae, while fatty acid composition of phospholipids was affected.

The Potential of Microalgae Lipids for Edible Oil Production.

The objective of this study was to evaluate the potential of oil-rich green algae, Chlorella vulgaris, Scenedesmus obliquus, and Nannochloropsis oceanica, to produce edible oil with respect to lipid and residue properties. The results showed that C. vulgaris and N. oceanica had similarly much higher lipid recovery (about 50%) in hexane extraction than that of S. obliquus (about 25%), and C. vulgaris had the highest content of neutral lipids among the three algae. The fatty acid compositions of neutral lipids from C. vulgaris and S. obliquus were mainly C16 and C18, resembling that of vegetable oils. ARA and EPA were the specific valuable fatty acids in lipids of N. oceanica, but the content of which was lower in neutral lipids. Phytol was identified as the major unsaponifiable component in lipids of the three algae. Combined with the evaluation of the ratios in SFA/MUFA/PUFA, (n-6):(n-3) and content of free fatty acids, lipids obtained from C. vulgaris displayed the great potential for edible oil production. Lipids of N. oceanica showed the highest antioxidant activity, and its residue contained the largest amounts of protein as well as the amino acid compositions were greatly beneficial to the health of human beings.

Dry‐cured loin from the native pig breed Chato murciano with high unsaturated fatty acid content undergoes intense lipolysis of neutral and polar lipids during processing

The purpose of this work was to evaluate the fatty acid levels and lipolysis of dry‐cured loins obtained from the native pig breed Chato murciano during processing to improve the processing technology. The fatty acid composition of neutral lipids (NL), polar lipids (PL), and free fatty acids (FFA) was analyzed in a gas chromatograph equipped with a flame ionization detector. The NL and PL contents decreased by 45 and 75%, respectively, confirming that PL was the fraction most affected by lipolysis. This decrease resulted in a higher level of FFA (80.26%). The concentrations of all the NL and PL fatty acids decreased and the FFA increased (except C14:0 and C20:0). The most affected were C18:2, C18:3, and C20:4, decreasing in NL and PL and increasing in FFA. The concentrations of the different groups of fatty acids depended on the lipid fraction. Thus, the concentrations of the groups of fatty acids were MUFA > SFA > PUFA in NL; SFA > PUFA = MUFA in PL, and MUFA > PUFA = SFA in FFA, at day 60 of processing. Chato murciano dry‐cured loin is characterized by a high MUFA concentration (mainly C18:1) in the NL and FFA fractions, which agrees with the findings made in other native pig breeds.Practical applications: Characterization of the Chato murciano native pig breed is essential if the processing of meat products of high commercial value is to be improved and to ensure the genuine nature of products. Besides, it is widely held that the consumption of products derived from native pig breeds should not only satisfy consumer demands, but also promote the development of areas where these breeds originate. Previous works described the sensory quality of Chato murciano dry‐cured loin and ham, while greater knowledge of fatty acid composition and lipolysis is necessary. The results obtained may help ascertain the most suitable conditions for processing. Confirmation that Chato murciano dry‐cured loin is a significant source of MUFA compared with the same products obtained from commercial crossbreed genotypes of pigs would increase the attraction of using the breed to obtain derived products.Evolution of SFA, MUFA and PUFA in neutral lipids (NL), polar lipids (PL), and free fatty acids (FFA) of Chato murciano dry‐cured loin at different days of processing.

A comparison of fatty acid profiles and lipolysis during ripening of dry-cured loins obtained from a native pig breed (ChatoMurciano) and from a modern crossbreed pig

The fatty acid composition of neutral lipids (NL), polar lipids (PL) and free fatty acids (FFA) was analysed in dry-cured loins obtained from the native pig breed Chato Murciano (CM) and from a modern crossbreed pig genotype (CG) during the ripening stage (between the 30 and 60 days of processing). Fatty acid concentrations from neutral lipids, polar lipids and free fatty acid fractions were affected by breed. With respect to ripening time, lipolysis was more intense in the CG than in CM product, resulting in a decrease in the concentrations of fatty acids in the NL and PL fractions, accompanied by a corresponding increase in FFA. Results for lipid determination provided evidence that the concentrations of the different groups of fatty acids within the lipid fractions depend on the breed. In order of abundance, the groups of fatty acids in the neutral lipid fraction were monounsaturated fatty acids (MUFA) > saturated fatty acids (SFA) > polyunsaturated fatty acids (PUFA) (59%, 37% and 4% in CM; 58%, 35% and 6% in CG) at 60 days of processing. In the polar lipid fraction, the order was SFA > PUFA > MUFA (44%, 29% and 27% in CM; 42%, 38% and 20% in CG), and in free fatty acid fraction, the order was MUFA > PUFA > SFA (40%, 30%, and 30% in CM; 39%, 32%, and 29% in CG) at 60 days of processing.

Changes of Intramuscular Fat Composition, Lipid Oxidation and Lipase Activity in Biceps femoris and Semimembranosus of Xuanwei Ham During Controlled Salting Stages

Fatty acid composition of neutral lipids (NLs), phospholipids (PLs) and free fatty acids (FFAs) from intramuscular fat (IMF), lipid oxidation and lipase activity in muscle Semimembranosus (SM) and msucle Biceps femoris (BF) of dry-cured Xuanwei ham during the 90-d salting stages were analysed. The salt content increased from 0.34 to 3.52% in BF and from 0.10 to 5.42% in SM during the 90 d salting stage, respectively. PLs of IMF in both BF and SM decreased 54.70% (P<0.001) and 34.64% (P<0.05), furthermore, the saturated fatty acids (SFA), monounsaturated fatty acids (MUFA) and polyunsaturated fatty acids (PUFA) of PLs in both muscles were hydrolysed almost isochronously. FFAs were increased from 0.46 g 100 g−1 lipids to 2.92 g 100 g−1 lipids in BF at the end of salting, which was lower than SM (from 1.29 g 100 g−1 lipids to 9.70 g 100 g−1 lipids). The activities of acid lipase, neutral lipase and acid phospholipase all remained active in the 90 d. The thiobarbituric acid reactive substances (TBARS) was slowly increased to 1.34 mg kg−1 muscle in BF and to 2.44 mg kg−1 muscle in SM during the salting stage. In conclusion, the controlled salting process prompted the hydrolysis of PLs of IMF notably and increased the lipid oxidation of muscles within some limits.

Polyunsaturated fatty acids induce modification in the lipid composition and the prostaglandin production of the conjunctival epithelium cells

This study was conducted to evaluate whether polyunsaturated fatty acids (PUFA) such as γ-linolenic acid (GLA) and eicosapentaenoic acid (EPA), as found in the diet, may affect the lipid composition of conjunctival epithelium and whether these modifications affect prostaglandin (PG) production after inflammatory stimulation. Chang and IOBA-NHC conjunctival human cells were treated with GLA and/or EPA at 5, 10, 20, 30, 40, or 50μg/ml for 72h and then were stimulated with interferon-gamma (IFN-γ) for 48h. Changes in the composition of neutral lipids and phospholipids were monitored by gas chromatography. PGE1 and PGE2 levels were measured by enzyme immunoassay. PUFA supplementations in the culture medium induced incorporation of these fatty acids and of their metabolites in neutral lipids and phospholipids of the conjunctival cells. The fatty acid composition of neutral lipids and phospholipids was not affected by stimulation with IFN-γ. The production of PGE1 and PGE2 was affected by GLA supplementation whereas it was not modified by EPA supplementation. A combined supplementation of EPA and GLA did not change the production of PGE1 but decreased the production of PGE2. These results suggest that modulation of fatty acid composition and PG production by PUFA supplementation is possible in the conjunctival epithelium, which is an important site of inflammation in dry eye syndrome.

Lipids and flavolignans from Silybum marianum

Lipids from the air-dried aerial part (AP) and seeds of Silybum marianum (L.) Gaerth. (Asteraceae) were studied. The class and fatty acid compositions of neutral lipids (AP, seeds) and glyco- and phospholipids (AP) were determined. Neutral lipids (NL) with a complicated set of lipophilic components, mainly triterpenols, sterols, and their esters predominated in the AP. The fatty acids of the AP were dominated by 16:0, 18:2 (glycolipids), and 18:3 (neutral lipids, phospholipids); of seed NL, by 18:2 and 18:1. The content and composition of flavolignans isolated from defatted seeds and the content of total protein in the meal were found.

Cheese whey as a renewable substrate for microbial lipid and biomass production by Zygomycetes

AbstractThree Zygomycetes, Mortierella isabellina, Thamnidium elegans and Mucor sp., were tested for their ability of producing biomass and lipid‐containing γ‐linolenic acid (GLA) during their cultivation on cheese whey. M. isabellina consumed all of the available lactose and a significant amount of the available protein. On the contrary, the two other fungi seemed incapable of consuming lactose after protein exhaustion. In the second series of experiments, for M. isabellina a supplementary quantity of lactose was added into the medium in order to increase the C/N ratio and hence to increase the production of fat. In the case of T. elegans and Mucor sp., a supplementary quantity of ammonium sulfate was added in order to favor the consumption of lactose and the production of biomass. Indeed, enhancement of lipid production was observed for M. isabellina and biomass production for T. elegans and Mucor sp.. Fatty acid analysis of the microbial lipid showed a composition that presented non‐negligible changes in relation with the age of the culture and the C/N molar ratio of the medium. Further analysis of the fat showed that the quantity of neutral lipids was the more abundant. The fatty acid composition of neutral lipids resembled to that of total lipids. Phospholipids were the more unsaturated fraction for Mucor sp. and M. isabellina. GLA was synthesized in all trials but its concentration presented differences related with the utilized strains and the fermentation time. Growth of M. isabellina on lactose‐supplemented whey resulted in a maximum GLA production of 301 mg/L.

Die Fettsäureverteilung in den Neutralfetten des Humanspermas

The fatty acid composition of neutral lipids of human semen was determined by gas liquid chromatography. Qualitative and quantitative differences in the fatty acid contents were not found between pooled semen from oligozoospermic and astheno- or teratozoospermic patients. The neutral lipids contained relatively high proportions of unsaturated acids.

Lipolytic and oxidative changes in Iberian dry-cured loin

This study was conducted using 61 Iberian pigs from four different genetic lines fattened under two different rearing systems. Fatty acid composition of neutral lipids (NL), polar lipids (PL) and free fatty acids (FFA) of the 61 fresh loins and their corresponding dry-cured loins and indices of lipid oxidation (hexanal, TBARS and rancid flavour) of the dry-cured loins were analyzed. Although the total amount of fatty acids from PL decreased most (89.77%), the fatty acid profile of FFA from dry-cured loin was more similar to that of NL from fresh loins. Monounsaturated fatty acids (MUFA) were the most abundant FFA type (260 mg/100 g muscle dry matter) followed by saturated fatty acid (SFA) (256 mg/100 g muscle dry matter) and polyunsaturated fatty acids (PUFA) (148 mg/100 g muscle dry matter). Neither genetic line nor rearing system showed any significant ( P > 0.05) effect on the decrease of fatty acids in the lipid fractions studied. The important decrease in PUFA from NL (43.70%) and PL (89%) was not reflected in higher oxidative indices in dry-cured loin. Neither PCA nor Pearson’s correlation showed any clear relationships between lipolytic changes and oxidative indices.

Docosahexaenoic Acid Production and Lipid-Body Formation in Schizochytrium limacinum SR21

Schizochytrium limacinum SR21, a thraustochytrid (Labyrinturomycota), is a heterotrophic marine microorganism. SR21 has attracted recent attention because of the production of docosahexaenoic acid (DHA). We obtained highly concentrated SR21 zoospores and successfully observed synchronous growth. We investigated changes of lipid content and fatty acid composition during the growth. The morphological features of the lipid bodies were also described via fluorescent and electron microscopy. The cells developed quickly after zoospore settlement. Lipid bodies developed in accordance with an increase in lipid content during the 8-h synchronous growth. The total lipid was composed mainly of triacylglycerol, sterol esters, and phosphatidylcholine. The proportion of neutral lipids (triacylglycerol and sterol esters) in the total lipid was fairly constant during growth. The fatty acid composition of neutral lipids, primary components of the lipid body, and phospholipids, primary components of the cell membranes, was nearly unchanged during the synchronous growth. However, the DHA content of the phospholipids decreased drastically after a 10-day culture. Electron micrographs prepared using a high-pressure freeze substitution technique revealed a fine structure of light- and dark-staining bands inside the lipid bodies in many stages of the cells.

Lipolysis in dry-cured ham: Influence of salt content and processing conditions

Fatty acid composition of neutral lipids (NLs), polar lipids (PLs) and free fatty acids (FFA) from the intramuscular fat of Semimembranosus and Biceps femoris muscles was analysed in 46 Iberian dry-cured hams processed with different amounts of salt (6% high salt batch – HS vs. 3% low salt batch – LS w/w) and different processing systems (traditional – T vs. modified – M). Total amounts of saturated (SFA), monounsaturated (MUFA) and polyunsaturated (PUFA) fatty acids in NLs decreased in similar proportions during processing of the hams as well as SFA, MUFA and PUFA in the PL fraction, whereas the amounts of SFA, MUFA and PUFA of FFAs significantly increased in Semimembranosus and Biceps femoris muscles. The amount of total fatty acids (TFA), from NLs and PLs, decreased in both muscles throughout the processing. Such a decline was more intense in HS hams than in LS ones, which could be a sign of a promoting effect of sodium chloride on lipolysis. However, the increase in FFA content throughout processing was not more intense in HS hams. Processing conditions studied in this work did not affect the changes in the fatty acid content of each fraction.

Evolution of fatty acids from intramuscular lipid fractions during ripening of Iberian hams as affected by α-tocopheryl acetate supplementation in diet

The influence of feeding Iberian pigs with and without α-tocopheryl acetate (α-TAc) on fatty acid composition of intramuscular lipids, throughout dry-cured ham maturation was investigated. Supranutritional levels of α-TAc (100 mg α-TAc/kg) increased α-tocopherol content in m. Semimembranosus in comparison to a basal diet containing 5 mg α-TAc/kg (Control: 6.38 vs. E-supplemented: 10.31 μg/g muscle dry matter). Fatty acid composition of lipids in the raw hams was similar whatever the level of vitamin E in the diet. Fatty acid composition of neutral lipids did not change much during ham maturation. In contrast, fatty acid content of polar lipids decreased considerably (∼90%) after 700 days of maturation. At the end of ripening (700 days), the contents of polyunsaturated fatty acids from neutral and polar lipids were significantly higher in hams from Iberian pigs fed on α-TAc-enriched diet than those fed with a basal diet. This result indicates that α-tocopherol-enriched diets maintain polyunsaturated fatty acids in neutral and polar lipid fractions of intramuscular fat in dry-cured hams from Iberian pigs.

Distribution of Novel Nonmethylene-Interrupted Fatty Acids over Neutral and Polar Lipids of Ophiuroidea (Brittle Star).

Fatty acid compositions of neutral lipids (NL) and polar lipids (PL) have been analyzed for a unique sample of Ophiuroidea (brittle star) Ophiura sarsi containing novel nonmethylene-interruped (NMI) fatty acids, 7E,13E-icosadienoic (20:2), 7E,13E,17Z-icosatrienoic (20:3), 9E,15E,19Z-docosatrienoic (22:3), and 4Z,9E,15E,19Z-docosatetraenoic (22:4) acids. All of the NMI fatty acids were concentrated in NL (mainly triacylglycerols) rather than in PL (mainly phosphatidylcholines and phosphatidylethanolamines). On the other hand, 6,9,12,15,18,21-tetracosahexaenoic acid (24:6n-3) usually observed in Ophiuroidea lipids was found in PL at higher concentration than in NL. Biological property and origin of the novel NMI fatty acids appear to be different from those of 24:6n-3.

Fatty Acid Composition of Neutral Lipid Energy Reserves in Infective Juveniles of Entomopathogenic Nematodes

The fatty acid composition of neutral lipids from infective juveniles (IJs) of Steinernema carpocapsae strain All, S. riobravis strain Biosys 355, S. feltiae strain UK76, and S. glaseri strain NC stored in distilled water at 25°C was determined. Newly emerged IJs of all four species had similar neutral lipid fatty acid profiles and of the 18 fatty acids identified, C18:1n−9 (43–49 mol %), C16:0 (18–23%), C18:2n−6 (8–14%) and C18:0 (4–8%) were the most abundant. Unsaturated fatty acids predominated, with about 50% being monoene and 14–22% polyene; the unsaturation index ranged from 91.6 in S. glaseri to 111.6 in S. carpocapsae. The fatty acid composition of the total lipid and the free fatty acid fraction mirrored that of the neutral lipids. During storage, the relative levels (%) of C16:0, C18:0, and C18:1n−9 in the neutral lipids declined significantly, suggesting they were preferentially utilised.

Incorporation of fatty acids by concanavalin A-stimulated lymphocytes and the effect on fatty acid composition and membrane fluidity

The fatty acid compositions of the neutral lipid and phospholipid fractions of rat lymph node lymphocytes were characterized. Stimulation of rat lymphocytes with the T-cell mitogen concanavalin A resulted in significant changes in the fatty acid composition of both neutral lipids and phospholipids (a decrease in the proportions of stearic, linoleic and arachidonic acids and an increase in the proportion of oleic acid). Membrane fluidity was measured using nitroxide spin-label e.s.r., and increased during culture with concanavalin A. Culturing the lymphocytes in the absence of mitogen did not affect fatty acid composition or membrane fluidity. The uptake and fate of palmitic, oleic, linoleic and arachidonic acids were studied in detail; there was a time-dependent incorporation of each fatty acid into all lipid classes but each fatty acid had a characteristic fate. Palmitic and arachidonic acids were incorporated principally into phospholipids whereas oleic and linoleic acids were incorporated in similar proportions into phospholipids and triacylglycerols. Oleic acid was incorporated mainly into phosphatidylcholine, palmitic and linoleic acids were incorporated equally into phosphatidylcholine and phosphatidylethanolamine, and arachidonic acid was incorporated mainly into phosphatidylethanolamine. Supplementation of the culture medium with particular fatty acids (myristic, palmitic, stearic, oleic, linoleic, alpha-linolenic, arachidonic, eicosapentaenoic or docosahexaenoic acid) led to enrichment of that fatty acid in both neutral lipids and phospholipids. This generated lymphocytes with phospholipids differing in saturated/unsaturated fatty acid ratio, degree of polyunsaturation, index of unsaturation and n - 6/n - 3 ratio. This method allowed the introduction into lymphocyte phospholipids of fatty acids not normally present (e.g. alpha-linolenic) or usually present in low proportions (eicosapentaenoic and docosahexaenoic). These three n - 3 polyunsaturated fatty acids replaced arachidonic acid in lymphocyte phospholipids. Fatty acid incorporation led to an alteration in lymphocyte membrane fluidity: palmitic and stearic acids decreased fluidity whereas the unsaturated fatty acids increased fluidity. It is proposed that the changes in lymphocyte phospholipid fatty acid composition and membrane fluidity brought about by culture in the presence of polyunsaturated fatty acids are responsible for the inhibition of lymphocyte functions caused by these fatty acids.