Fatty Acid Composition Of Triacylglycerols Research Articles

Accumulation of Acyl Plastoquinol and Triacylglycerol in Six Cyanobacterial Species with Different Sets of Genes Encoding Type-2 Diacylglycerol Acyltransferase-like Proteins.

Recently, acyl plastoquinol (APQ) and plastoquinone-B (PQ-B), which are fatty acid esters of plastoquinol and plastoquinone-C respectively, have been identified as the major neutral lipids in cyanobacteria. In Synechocystis sp. PCC 6803, Slr2103 having homology with the eukaryotic enzyme for triacylglycerol (TAG) synthesis, diacylglycerol acyltransferase 2 (DGAT2), was identified as responsible for the synthesis of these plastoquinone-related lipids. On the other hand, TAG synthesis in cyanobacteria remains controversial due to the low accumulation level within cyanobacterial cells together with the high contamination level from the environment. In this study, to quantify more precisely and elucidate the relationship between the accumulation of neutral lipids and the presence or absence of DGAT2-like genes, plastoquinone-related lipids and TAG were analyzed directly from total lipids of six cyanobacterial species with different sets of genes encoding DGAT2-like proteins belonging to two distinct subclades. The results showed that the synthesis of these neutral lipids is highly dependent on clade A DGAT2-like proteins under the culture conditions used in this study, although accumulation level of TAG was quite low. In contrast to APQ highly abundant in saturated fatty acids, the fatty acid composition of TAG was species-specific and partly reflected the total lipid composition. Gloeobacter violaceus PCC 7421, which lacks a DGAT2-like gene, accumulated APQ with a high proportion of C18:0, suggesting APQ synthesis by an unidentified acyltransferase.

Functional triacylglycerols from microalgae and their use in the formulation of functional foods—Review

Consumers increased demand for food products that promote health has compelled the food processing industry to develop food products that not only satiate hunger but also aid in the prevention of non-communicable diseases. Microalgae have emerged as a potential source of functional components like triacylglycerols containing essential fatty acids that could be used in the formulation of functional food products. These components help prevent non-communicable diseases due to their inherent characteristics like anti-oxidative, anti-cancer, anti-diabetic, anti-inflammatory, etc. The microalgae are concentrated sources of triacylglycerols containing essential fatty acids and are considered a potential replacer for fish oil in providing these functional ingredients also well accepted by the vegan. This review aims to cover the literature on the triacylglycerol content of microalgae with a focus on the functional triacylglycerol, the fatty acid composition of triacylglycerol extracted from different microalgal biomass, innovative extraction technologies for intensified extraction, the potential use of triacylglycerols from microalgae in the formulation of functional food products. Further, the present constraints and future prospectus in using microalgal triacylglycerol in functional food are also discussed.

Altering the fatty acid profile of Yarrowia lipolytica to mimic cocoa butter by genetic engineering of desaturases

BackgroundDemand for Cocoa butter is steadily increasing, but the supply of cocoa beans is naturally limited and under threat from global warming. One route to meeting the future demand for cocoa butter equivalent (CBE) could be to utilize microbial cell factories such as the oleaginous yeast Yarrowia lipolytica.ResultsThe main goal was to achieve triacyl-glycerol (TAG) storage lipids in Y. lipolytica mimicking cocoa butter. This was accomplished by replacing the native Δ9 fatty acid desaturase (Ole1p) with homologs from other species and changing the expression of both Ole1p and the Δ12 fatty acid desaturase (Fad2p). We thereby abolished the palmitoleic acid and reduced the linoleic acid content in TAG, while the oleic acid content was reduced to approximately 40 percent of the total fatty acids. The proportion of fatty acids in TAG changed dramatically over time during growth, and the fatty acid composition of TAG, free fatty acids and phospholipids was found to be very different.ConclusionsWe show that the fatty acid profile in the TAG of Y. lipolytica can be altered to mimic cocoa butter. We also demonstrate that a wide range of fatty acid profiles can be achieved while maintaining good growth and high lipid accumulation, which, together with the ability of Y. lipolytica to utilize a wide variety of carbon sources, opens up the path toward sustainable production of CBE and other food oils.

Seasonal effects of the fatty acid composition of phospholipid and triacylglycerol in the muscle and liver of male Salmo trutta macrostigma

The seasonal effects on the fatty acid composition of triacylglycerol (TAG) and phospholipid (PL) in the muscle and liver of male Salmo trutta macrostigma were determined using the gas chromatographic (GC) method. The fatty acid (FA) compositions of total lipid, PL and TAG fractions were determined in muscle and liver tissues of S. trutta macrostigma. The phospholipids contained a higher proportion of 16:0 compared to the TAG in the muscle tissue of S. trutta macrostigma. Docosahexaenoic acid (22:6 ω-3) and eicosapentaenoic acid (20:5 ω-3) contents were high in both muscle and liver tissues. The total lipid contents in the muscle and liver were 1.07-2.45 and 3.00-4.64%, respectively. S. trutta macrostigma is a rich source of ω-3 and ω-6, polyunsaturated fatty acids (PUFA) with numerous benefits to human health.

Triacylglycerol remodeling in Physaria fendleri indicates oil accumulation is dynamic and not a metabolic endpoint.

Oilseed plants accumulate triacylglycerol (TAG) up to 80% of seed weight with the TAG fatty acid composition determining its nutritional value or use in the biofuel or chemical industries. Two major pathways for production of diacylglycerol (DAG), the immediate precursor to TAG, have been identified in plants: de novo DAG synthesis and conversion of the membrane lipid phosphatidylcholine (PC) to DAG, with each pathway producing distinct TAG compositions. However, neither pathway fits with previous biochemical and transcriptomic results from developing Physaria fendleri seeds for accumulation of TAG containing >60% lesquerolic acid (an unusual 20 carbon hydroxylated fatty acid), which accumulates at only the sn-1 and sn-3 positions of TAG. Isotopic tracing of developing P. fendleri seed lipid metabolism identified that PC-derived DAG is utilized to initially produce TAG with only one lesquerolic acid. Subsequently a nonhydroxylated fatty acid is removed from TAG (transiently reproducing DAG) and a second lesquerolic acid is incorporated. Thus, a dynamic TAG remodeling process involving anabolic and catabolic reactions controls the final TAG fatty acid composition. Reinterpretation of P. fendleri transcriptomic data identified potential genes involved in TAG remodeling that could provide a new approach for oilseed engineering by altering oil fatty acid composition after initial TAG synthesis; and the comparison of current results to that of related Brassicaceae species in the literature suggests the possibility of TAG remodeling involved in incorporation of very long-chain fatty acids into the TAG sn-1 position in various plants.

Fatty acid compositions of triacylglycerols in flax (Linum usitatissimum L.) seeds with varied seeding dates and nitrogen fertilization in a temperate region of Japan

ABSTRACT We monitored fatty acid compositions of the triacylglycerol (TAG) fractions in flax (Linum usitatissimum L.) seeds cultivated in pots with different seeding dates and nitrogen (N) fertilizing conditions in a temperate region Wakayama, Japan. Five flax cultivars were seeded in early and late December 2017, and in late January 2018, and matured in May, June and July in the order of planting. Three types of N fertilizer were applied for plants seeded in January. Fatty acid profiles in seed TAG fractions were varied among the cultivation conditions. A cluster analysis dissected the fatty acid profiles of the same genotype with different seeding dates. Principal component analyses revealed inverse correlations between saturated and unsaturated fatty acid contents, which could be affected by temperature, N fertilization, and genotypic factors. The highest correlation was observed between α-linolenic and oleic acid contents, which showed a strong inverse relationship across genotypes (r= 0.964, n = 15). The ratio of α-linolenic acid content to that of oleic acid in seeds from plants seeded in early December were higher than those seeded on the other two dates across genotypes. We suppose that seeding date and N supply might be crucial determinants of flax lipid quality in temperate regions.

Myristate can be used as a carbon and energy source for the asymbiotic growth of arbuscular mycorrhizal fungi

Arbuscular mycorrhizal (AM) fungi, forming symbiotic associations with land plants, are obligate symbionts that cannot complete their natural life cycle without a host. The fatty acid auxotrophy of AM fungi is supported by recent studies showing that lipids synthesized by the host plants are transferred to the fungi, and that the latter lack genes encoding cytosolic fatty acid synthases. Therefore, to establish an asymbiotic cultivation system for AM fungi, we tried to identify the fatty acids that could promote biomass production. To determine whether AM fungi can grow on medium supplied with fatty acids or lipids under asymbiotic conditions, we tested eight saturated or unsaturated fatty acids (C12 to C18) and two β-monoacylglycerols. Only myristate (C14:0) led to an increase in the biomass of Rhizophagus irregularis, inducing extensive hyphal growth and formation of infection-competent secondary spores. However, such spores were smaller than those generated symbiotically. Furthermore, we demonstrated that R. irregularis can take up fatty acids in its branched hyphae and use myristate as a carbon and energy source. Myristate also promoted the growth of Rhizophagus clarus and Gigaspora margarita Finally, mixtures of myristate and palmitate accelerated fungal growth and induced a substantial change in fatty acid composition of triacylglycerol compared with single myristate application, although palmitate was not used as a carbon source for cell wall biosynthesis in this culture system. Our findings demonstrate that myristate boosts the asymbiotic growth of AM fungi and can also serve as a carbon and energy source.

NMR characterization and evaluation of antibacterial and antiobiofilm activity of organic extracts from stationary phase batch cultures of five marine microalgae (Dunaliella sp., D. salina, Chaetoceros calcitrans, C. gracilis and Tisochrysis lutea)

The chemical composition of five marine microalgae (Dunaliella sp., Dunaliella salina, Chaetoceros calcitrans, Chaetoceros gracilis and Tisochrysis lutea) was investigated through nuclear magnetic resonance (NMR) spectroscopic study of the soluble material obtained by sequential extraction with hexane, ethyl acetate (AcOEt) and methanol of biomass from stationary phase cultures. Hexane extracted the major lipids present in the microalgae during the stationary phase of growth, which correspond to storage lipids. Triacylglycerols (TGs) were the only storage lipids produced by Dunaliella and Chaetoceros. In contrast, T. lutea predominantly stored polyunsaturated long-chain alkenones, with sterols also detected as minor components of the hexane extract. The molecular structure of brassicasterol was determined in T. lutea and the presence of squalene in this sample was also unequivocally detected. Monogalactosyldiacylglycerols (MGDGs) and pigments were concentrated in the AcOEt extracts. C. calcitrans and D. salina constituted an exception due to the high amount of TGs and glycerol produced, respectively, by these two strains. Chlorophylls a and b and β-carotene were the major pigments synthesized by Dunaliella and chlorophyll a and fucoxanthin were the only pigments detected in Chaetoceros and T. lutea. Information concerning the acyl chains present in TGs and MGDGs as well as the positional distribution of acyl chains on the glycerol moiety was obtained by NMR analysis of hexane and AcOEt extracts, with results consistent with those expected for the genera studied. Fatty acid composition of TGs in the two Dunaliella strains was different, with polyunsaturated acyl chains almost absent in the storage lipids produced by D. salina. Except in C. calcitrans, the polar nature of soluble compounds was inferred through the relative extraction yield using methanol as the extraction solvent. Glycerol was the major component of this fraction for the Dunaliella strains. In T. lutea 1,4/2,5-cyclohexanetetrol (CHT) and dimethylsulfoniopropionate (DMSP) preponderated. CHT was also the major polyol present in the Chaetoceros strains in which DMSP was not detected, but prominent signals of 2,3-dihydroxypropane-1-sulfonate (DHSP) were observed in the 1H NMR spectra of methanolic extracts. The presence of DHSP confirms the production of this metabolite by diatoms. In addition, several other minor compounds (digalactosyldiacyglycerols (DGDGs), sulphoquinovosyldiacylglycerols (SQDGs), amino acids, carbohydrates, scyllo-inositol, mannitol, lactic acid and homarine) were also identified in the methanolic extracts. The antibacterial and antibiofilm activities of the extracts were tested. The AcOEt extract from C. gracilis showed a moderate antibiofilm activity.

Attenuation of oxidative stress-induced lesions in skeletal muscle in a mouse model of obesity-independent hyperlipidaemia and atherosclerosis through the inhibition of Nox2 activity

Obesity leading to hyperlipidaemia and atherosclerosis is recognised to induce morphological and metabolic changes in many tissues. However, hyperlipidaemia can occur in the absence of obesity. The impact of the latter scenario on skeletal muscle and liver is not understood sufficiently. In this regard, we used the Apolipoprotein E-deficient (ApoE-/-) mouse model, an established model of hyperlipidaemia and atherosclerosis, that does not become obese when subjected to a high-fat diet, to determine the impact of Western-type diet (WD) and ApoE deficiency on skeletal muscle morphological, metabolic and biochemical properties. To establish the potential of therapeutic targets, we further examined the impact of Nox2 pharmacological inhibition on skeletal muscle redox biology. We found ectopic lipid accumulation in skeletal muscle and the liver, and altered skeletal muscle morphology and intramuscular triacylglycerol fatty acid composition. WD and ApoE deficiency had a detrimental impact in muscle metabolome, followed by perturbed gene expression for fatty acid uptake and oxidation. Importantly, there was enhanced oxidative stress in the skeletal muscle and development of liver steatosis, inflammation and oxidative protein modifications. Pharmacological inhibition of Nox2 decreased reactive oxygen species production and protein oxidative modifications in the muscle of ApoE-/- mice subjected to a Western-type diet. This study provides key evidence to better understand the pathophysiology of skeletal muscle in the context of hyperlipidaemia and atherosclerosis and identifies Nox2 as a potential target for attenuating oxidative stress in skeletal muscle in a mouse model of obesity-independent hyperlipidaemia.

Renin-Angiotensin System Inhibition Alters Triacylglycerol Metabolism in Diabetic Kidney Disease

Lipids are essential metabolites with diverse functions impacting physiology. We recently identified several lipidomic abnormalities in diabetic kidney disease (DKD), including remodeling of triacylglycerol (TAG) fatty acid composition to increase availability of long, polyunsaturated TAGs. Using the BKS eNOS-/- db/db diabetic mouse model, we studied the effect of renin-angiotensin system (RAS) inhibition with combination treatment of lisinopril (20 mg/kg/d) and losartan (30 mg/kg/d) for 12 weeks, an intervention which ameliorates DKD in this mouse model without impacting glycemia. We examined the kidney cortical lipidome to identify lipid alterations that may be pathogenic in DKD. As expected, RAS inhibition did not significantly alter glycemic control or total plasma triglycerides or cholesterol, but decreased the 24-hour urine albumin/creatinine ratio (2564 vs. 615 μg/mg creatinine) and decreased the glomerular periodic acid-Schiff stained area by 13% (p<0.05). We performed mass-spectrometry based untargeted lipidomic profiling to quantify 635 lipids across 17 lipid classes in kidney cortex. Lisinopril/losartan treatment remodeled TAG fatty acid composition and increased conversion between TAGs and several glycerophospholipid classes, particularly medium-chain phosphatidylcholines, phosphatidylethanolamines, phosphatidylinositols and cardiolipins (p<0.05). These correlations in lipid levels were associated with changes in corresponding enzymes of lipid metabolism, suggesting increased metabolism of TAGs into glycerophospholipids, which are key components of cell membranes and precursors for signaling molecules. In addition to the known salutary effect of RAS inhibition on DKD, our results suggest a previously unrecognized role of RAS inhibition on kidney complex lipid levels through increased TAG metabolism. These findings raise the possibility that TAG metabolism might be a target for intervention aimed at decreasing DKD progression. Disclosure K. Sas: None. J. Lin: None. V. Nair: None. M. Kretzler: Research Support; Self; AstraZeneca, Novo Nordisk Inc., Boehringer Ingelheim GmbH, National Institute of Diabetes and Digestive and Kidney Diseases, Eli Lilly and Company, Gilead Sciences, Inc.. F. Brosius: None. S. Pennathur: None.

Optimization of enzymatic interesterification of coconut (<i>Cocos nucifera</i>) and Sesame (<i>Sesamum indicum</i>) oils using <i>Thermomyces lanuginosus</i> lipase by response surface methodology

Blends ofcoconut (Cocosnucifera) oil (CO) and sesame (Sesamumindicum) oil (SO) were enzymatically interesrerified using aqueous lipase derived from Thermomyceslanuginosus and the reaction conditions were optimized using Response Surface Methodology (RSM). A three-factor, three-level central composite design (facecentred cube design) was employed to optimize the reaction parameters, namely temperature (45-65°C), time (16-48 h) and mass ratio of oils (CO:SO; 70:30 - 50:50). Lipase, diluted in phosphate buffer (pH 8) was used at 0.2% (v/w) of the substrate. Degree of interesterification (DI), and the ratio of monounsaturated and polyunsaturated fatty acids (MUFA:PUFA) of triacylglycerols (TAGs)were used as response variables. Triacylglycerol (TAG) fractions of the samples were separated using Thin Layer Chromatography (TLC) and the fatty acid composition of TAGs was determined using Gas-Liquid Chromatography (GLC). Thelinear and squared effects of temperature and time were significant (p<0.05) for DI whilethe reaction conditions did not exhibit a significant (p<0.05) effect on MUFA: PUFA ratio. The optimum conditions for enzymatic interesterificationwere45°C (temperature), 40.24 h (time) and 70:30 (weight ratio of CO:SO).Under these optimized conditions, the DI was 28.98% and MUFA:PUFA was 1.50±0.06. According to the response surface regression analysis, the R2 value for DI versus reaction parameters was 91.85% and MUFA:PUFA ratio versus reaction parameters was 61.82%. Therefore it can be concluded that enzymatic interesterification can effectively be applied to develop nutritionally and functionally superior modified oilknown as structured lipids using coconut and sesame oils.

Optimization of seawater-based triacylglycerol accumulation in a freshwater green alga, Chlorella kessleri, through simultaneous imposition of lowered-temperature and enhanced-light intensity

Triacylglycerols (TG), the major components of crop oils used for the production of food oils and biodiesel fuel, accumulate in algal species under single environmental stress conditions including nitrogen-starvation. In a freshwater green alga, Chlorella kessleri, its TG content reached 24.7% in dry cell weight in 72h, on cultivation in 3-fold diluted seawater (1/3 SW), through the synergetic stimulating effects of hyperosmosis and nutrient-limitation. These observations would indicate the importance of combinatory stresses for strong induction of TG accumulation [Hirai et al. 2016]. We here searched for novel stresses in C. kessleri to elevate the seawater-based TG accumulation level through their additional actions. A higher light intensity (moderate light, ML) caused a small, but definite increase of TG, whereas a lowered growth temperature (LT) led to a large, but temporal increase of it until 48h, followed by severe degradation. The decrease of TG in LT cells was abolished on simultaneous imposition of ML. C. kessleri cells were then cultured in 1/3 SW under combinatory conditions of ML/LT, the TG content consequently increasing to as high as 48.5% in dry cells. These results indicated the validity of combinatory stresses for strong induction of algal TG accumulation. As to the fatty acid composition of TG, C. kessleri was intermediate between palm and the other three major oil crops including rapeseed. The rapid and abundant accumulation of TG with fatty acid composition suitable for industrial use demonstrated the great potential of development of the industrial algal TG production system with the use of the combinatory stresses in C. kessleri. TG of C. kessleri was also characteristic to contain C18 acids as representing 81mol% of its constituent fatty acids or 90% of fatty acids at its sn-2 position, which suggested a peculiar TG synthetic pathway in this oleaginous alga.

Neither linoleic acid nor arachidonic acid promote white adipose tissue inflammation in Fads2-/- mice fed low fat diets

Dietary n-6 polyunsaturated fatty acids (PUFA) are widely perceived to promote inflammation and contribute to the development of chronic diseases. This dogma has been recently questioned due to evidence that n-6 PUFA, specifically linoleic acid (LA, 18:2n-6) and arachidonic acid (AA, 20:4n-6), do not appear to activate inflammatory signalling pathways when consumed in moderate amounts. However, delineating the independent roles of different dietary n-6 PUFA in vivo is challenging because LA is continuously converted into AA in a pathway regulated by the fatty acid desaturase 2 (Fads2) gene. The objective of this study was to investigate the independent roles of LA and AA on white adipose tissue (WAT) inflammatory signalling pathways using Fads2-/- mice. We hypothesized that dietary LA would not induce WAT inflammation, unless it was endogenously converted into AA. Male C57BL/6 wild-type (WT) and Fads2-/- mice were fed low-fat isocaloric diets containing either 7% corn oil w/w (CD, containing ~42% LA) or 7% ARASCO oil w/w (AD, containing ~27% AA) for 9 weeks. WAT inflammatory gene expression, protein levels, as well as phospholipid (PL) and triacylglycerol (TAG) fatty acid composition, were analyzed by RT-qPCR, western blots, and gas chromatography, respectively. Fads2-/- mice fed CD had high LA, but little-to-no GLA (18:3n-6), DGLA (20:3n-6), and AA in PLs and TAGs compared to their WT counterparts. In comparison, Fads2-/- and WT mice fed AD showed minimal differences in n-6 PUFA content in serum and WAT, despite having significantly more AA than CD-fed mice. No differences in gene expression for common inflammatory adipokines (e.g. Mcp-1, Ccl5, Tnfα) or key regulators of eicosanoid production (e.g. Cox-2, Alox-12, Alox-15) were detected in WAT between any of the diet and genotype groups. Furthermore, no differences in MCP-1, and total or phosphorylated STAT3 and p38 inflammatory proteins, were observed. Collectively, these results demonstrate that neither LA nor AA promote WAT inflammation when consumed as part of a low-fat diet. Therefore, the existing dogma surrounding n-6 PUFA and inflammation needs to be reconsidered.

Biologically active components in Madia sativa seed oil.

Biologically active components in lipids (fatty acids, phospholipids, sterols and tocopherols) from three varieties of Madia sativa seeds introduced in Bulgaria (BGR 457 and BGR 458 with German origin, and BGR 459 with US origin) were investigated. Glyceride oil in the seeds was found to be 36.6, 34.2 and 35.4%, respectively. Total phospholipid content was 2.4, 1.7 and 2.6% and the main classes were phosphatidylcholine, phosphatidylinositol and phosphatidylethanolamine. The amount of sterols in the oil was 0.3% for all samples and the major component was β-sitosterol, followed by campesterol and stigmasterol. Total tocopherols in the oils were 768, 795 and 856mgkg-1, respectively and α-tocopherol predominated (more than 70.0%). Fatty acid composition of triacylglycerols and sterol esters was also established. Main fatty acids in triacylglycerols were linoleic (47.5-50.5%), oleic (30.2-32.4%) and palmitic acids (13.0-13.5%). The content of saturated fatty acids (palmitic and stearic) in sterol esters (40.1-50.9%) was significantly higher than in triacylglycerols (18.3-19.4%).

Temperature adaptation of lipids in diapausing Ostrinia nubilalis: an experimental study to distinguish environmental versus endogenous controls

Larvae of the European corn borer (Ostrinia nubilalis Hubn.) were cold acclimated during different phases of diapause to determine if changes in the fatty acid composition lipids occur as part of a programmed diapause strategy, or as a response to low temperatures during winter. Cold acclimation of fifth instar larvae of O. nubilalis during diapause had modest effects further on the readjustments in fatty acid composition of triacylglycerols and phospholipids. Overall, FA unsaturation (UFAs/SFAs ratio) was stable, with the exception of the triacylglycerols fraction after exposure to -3 and -10 °C in mid-diapause (MD) when it significantly increased. Differential scanning calorimetry (DSC) was used to examine phase transitions of total body lipid of cold-acclimated larvae in diapause. Thermal analysis indicated that changes in the melt transition temperatures of whole body total lipids were subtle, but consistent with the modest changes in the level of FA unsaturation observed. We conclude that lipid rearrangements are a function of the endogenous "diapause program" rather than a direct effect of low temperatures, which proved to have limited impact on lipid changes in diapausing larvae of O. nubilalis.

C1 Metabolism Inhibition and Nitrogen Deprivation Trigger Triacylglycerol Accumulation in Arabidopsis thaliana Cell Cultures and Highlight a Role of NPC in Phosphatidylcholine-to-Triacylglycerol Pathway.

Triacylglycerol (TAG) accumulation often occurs in growth limiting conditions such as nutrient deprivations. We analyzed and compared the lipid contents of Arabidopsis cells grown under two conditions that inhibited growth as a way to study interactions between membrane and storage lipids. In order to inhibit C1 metabolism, the first condition utilized methotrexate (MTX), a drug that inhibits methyl transfer reactions and potentially reduces Pi-choline synthesis, the polar head of phosphatidylcholine (PC). MTX-treated cells displayed a 10- to 15-fold increase in TAG compared to that found in control cells. This corresponded to a net increase of lipids as the total amount of membrane glycerolipids was minimally affected. Under this condition, PC homeostasis appeared tightly regulated and not strictly dependent on the rate of Pi-choline synthesis. The second condition we investigated involved nitrogen deprivation. Here, we observed a 40-fold increase of TAG. In these cells, the overall lipid content remained unchanged, but membrane lipids decreased by a factor of two suggesting a reduction of the membrane network and a rerouting of membrane lipids to storage lipids. Under all conditions, fatty acid (FA) analyses showed that the FA composition of TAG was comparable to that in PC, but different from that in acyl-CoA, suggesting that TAG accumulation involved PC-derived DAG moieties. In agreement, analyses by qPCR of genes coding for TAG synthesis showed a strong increase of non-specific phospholipase C (NPC) expressions, and experiments using labeled (fluorescent) PC indicated higher rates of PC-to-TAG conversion under both situations. These results highlight a role for NPC in plant cell oil production.

LA and ALA prevent glucose intolerance in obese male rats without reducing reactive lipid content, but cause tissue-specific changes in fatty acid composition.

While the cause of Type 2 diabetes remains poorly defined, the accumulation of reactive lipids within white adipose tissue, skeletal muscle, and liver have been repeatedly implicated as underlying mechanisms. The ability of polyunsaturated fatty acids (PUFAs) to prevent the development of insulin resistance has gained considerable interest in recent years; however, the mechanisms-of-action remain poorly described. Therefore, we determined the efficacy of diets supplemented with either linoleic acid (LA) or α-linolenic acid (ALA) in preventing insulin resistance and reactive lipid accumulation in key metabolic tissues of the obese Zucker rat. Obese Zucker rats displayed impaired glucose homeostasis and reduced n-3 and n-6 PUFA content in the liver and epididymal white adipose tissue (EWAT). After the 12-wk feeding intervention, both LA- and ALA-supplemented diets prevented whole body glucose and insulin intolerance; however, ALA had a more pronounced effect. These changes occurred in association with n-3 and n-6 accumulation in all tissues studied, albeit to different extents (EWAT > liver > muscle). Triacylglycerol (TAG), diacylglycerol (DAG), ceramide, and sphingolipid accumulation were not attenuated in obese animals supplemented with either LA or ALA, suggesting that preservation of glucose homeostasis occurred independent of changes in reactive lipid content. However, PUFA-supplemented diets differentially altered the fatty acid composition of TAGs, DAGs, and PLs in a tissue-specific manner, suggesting essential fatty acid metabolism differs between tissues. Together, our results indicate that remodeling of the fatty acid composition of various lipid fractions may contribute to the improved glucose tolerance observed in obese rats fed PUFA-supplemented diets.

Type I Diacylglycerol Acyltransferase (MtDGAT1) from Macadamia tetraphylla: Cloning, Characterization, and Impact of Its Heterologous Expression on Triacylglycerol Composition in Yeast.

Acyltransferase enzymes have been reported as useful biotechnological tools in order to increase oil yield and modify fatty acid composition. Macadamia species are able to accumulate unusually high levels of palmitoleic acid that besides oleic acid amounts to over 80% of monounsaturated fatty acids in the seed oil. In this work, a gene encoding a type 1 acyl-CoA:diacylglycerol acyltransferase (DGAT1) was cloned from M. tetraphylla. DGAT activity of the protein encoded by MtDGAT1 was confirmed by heterologous expression in a yeast mutant. Fatty acid composition of triacylglycerols synthesized by MtDGAT1 was compared to that of DGAT1 enzymes from Arabidopsis and Echium, with the results suggesting a substrate preference for monounsaturated over polyunsaturated fatty acids. Characteristics of MtDGAT1 may contribute to biochemical mechanisms determining the particular fatty acid composition of Macadamia oil and also indicate the possibility of using this enzyme in biotechnological approaches where a reduction of polyunsaturated fatty acids in the oil is desired.

ALTERATION OF LIPID COMPOSITION OF BLUE MUSSELS MYTILUS EDULIS L. AS A RESULT OF THEIR ACCLIMATION TO LABORATORY CONDITIONS

Organ-specific modifications and assimilation of trophic lipids, primarily of their fatty acids, were shown in the study of compensatory lipid and fatty acid composition changes in blue mussels Mytilus edulis L. as a result of acclimation to laboratory conditions using commercial plankton-based food. It was found that phospholipid fatty acid composition of mussel gills does not depend on food source, while triacylglycerol fatty acid composition exactly reflects the trophic fatty acid profile. Significant changes in the content of the main lipid fractions and their fatty acids in digestive glands of acclimated mussels were apparently caused by absence of essential phytoplankton polyene n-3 fatty acids in the feed. However, increased concentration of triacylglycerols enriched with short-chain saturated fatty acids, α-linolenic and vaccenic acids in the commercial food promoted the accumulation of these lipids in investigated mussel’s tissues.

Reprint of: Seasonal changes in the composition of storage and membrane lipids in overwintering larvae of the codling moth, Cydia pomonella

The codling moth (Cydia pomonella) is a major insect pest of apples worldwide. It overwinters as a diapausing fifth instar larva. The overwintering is often a critical part of the insect life-cycle in temperate zone. This study brings detailed analysis of seasonal changes in lipid composition and fluidity in overwintering larvae sampled in the field. Fatty acid composition of triacylglycerol (TG) depots in the fat body and relative proportions of phospholipid (PL) molecular species in biological membranes were analyzed. In addition, temperature of melting (Tm) in TG depots was assessed by using differential scanning calorimetry and the conformational order (fluidity) of PL membranes was analyzed by measuring the anisotropy of fluorescence polarization of diphenylhexatriene probe in membrane vesicles. We observed a significant increase of relative proportion of linoleic acid (C18:2n6) at the expense of palmitic acid (C16:0) in TG depots during the larval transition to diapause accompanied with decreasing melting temperature of total lipids, which might increase the accessibility of depot fats for enzymatic breakdown during overwintering. The fluidity of membranes was maintained very high irrespective of developmental mode or seasonally changing acclimation status of larvae. The seasonal changes in PL composition were relatively small. We discuss these results in light of alternative survival strategies of codling moth larvae (supercooling vs. freezing), variability and low predictability of environmental conditions, and other cold tolerance mechanisms such as extending the supercooling capacity and massive accumulation of cryoprotective metabolites.