Triacylglycerol Species Research Articles

Label-free measurement of the yeast short chain TAG lipase activity by ESI-MS after one-step esterification

Triacylglycerol (TAG) lipases hydrolyze ester bonds in TAG and release diacylglycerol (DAG), monoacylglycerol (MAG), and FA. We present a one-step chemical derivatization method for label-free quantification of a mixture of TAG, DAG, and MAG following lipase assay by ESI-MS. Because the ionization efficiencies of TAG, DAG, and MAG are not identical, lipase reaction products, DAG and MAG, are derivatized to TAG species by esterifying their hydroxyl groups using acyl chloride, whose acyl chain contains one less (or one more) -CH2 group than that of substrate TAG. This resulted in three TAG species that were separated by 14 Da from one another and exhibited similar ion responses representing their molar amounts in the mass spectra. A good linear correlation was observed between peak intensity ratios and molar ratios in calibration curve. This method enables simultaneous quantification of TAG, DAG, and MAG in lipase assay and, in turn, allows stoichiometric determination of the concentrations of FAs released from TAG and DAG separately. By applying this strategy to measure both TAG and DAG lipolytic activities of the yeast Tgl2 lipase, we demonstrated its usefulness in studying enzymatic catalysis, as lipase enzymes often show dissimilar activities toward these lipids.

UHPLC-APCI-MS Profiling of Triacylglycerols in Vegetable Oils—Application to the Analysis of Four North African Sesame Seed Varieties

Here, we describe an isocratic ultra-high performance liquid chromatography-atmospheric pressure chemical ionization mass spectrometry (UHPLC-APCI-MS) method for the characterization and the quantification of triacylglycerols (TAGs) in vegetable oils. The linearity and the precision of the method are validated, and the limits of detection are estimated. The APCI-MS detector shows a linear response from 1 to 1000 μg/mL, and the correlation coefficients (r2) obtained for standards TAGs exceed 0.995. As compared to previous methods, the proposed method is rapid, simpler, and more sensitive. The limits of detection estimated for several standard TAGs varies from 0.03 to 0.05 injected nanograms (6 to 10 μg/L). The application of the proposed method to the analysis of sesame oil allowed us to unambiguously identify 30 TAG species whereas previous methods have detected 19 TAGs, at the most. Among vegetable oils, sesame oil became an attractive target for adulteration due to its high commercial value. Most of the previous studies of TAG profiles of sesame oils had been devoted to the analysis of sesame oils originating from Asia and some Sub-Saharan countries. To the best of our knowledge, the TAG profiles of sesame oils from other origins are still unknown. The results we obtained for the four Tunisian sesame seed varieties clearly indicate that sesame oils can be classified according to their equivalent carbon number differences (ΔECN) with some rules similar to those required for olive oils.

Size Dependent Lipidomic Analysis of Urinary Exosomes from Patients with Prostate Cancer by Flow Field-Flow Fractionation and Nanoflow Liquid Chromatography-Tandem Mass Spectrometry.

Exosomes are membrane-bound extracellular vesicles involved in intercellular communication and tumor cell metastasis. In this study, flow field-flow fractionation (FlFFF) was utilized to separate urinary exosomes by size, demonstrating a significant difference in exosome sizes between healthy controls and patients with prostate cancer (PCa). Exosome fractions of different sizes were collected for microscopic analysis during an FlFFF run and evaluated with exosome marker proteins using Western blot analysis. The results indicated that exosomes of different sizes originated from different types of cells. Collected exosome fractions were further examined using nanoflow ultrahigh performance liquid chromatography-electrospray ionization-tandem mass spectrometry (nUPLC-ESI-MS/MS) for lipidomic analysis. A total of 162 lipids (from 286 identified) were quantified using a selected reaction monitoring (SRM) method. The overall amount of lipids increased by 1.5- to 2-fold in patients with PCa and degree of increase was more significant in the smaller fractions (diameter <150 nm) than in the larger ones (diameter >150 nm) some classes of lipids. In addition, neutral lipids like diacylglycerol (DAG) and triacylglycerol (TAG) decreased in all exosomes without size dependency. Moreover, a dramatic increase in 22:6/22:6-phosphatidylglycerol (PG) was observed and significant decrease in (16:0,16:0)- and (16:1, 18:1)-DAG species (nearly 5-fold) and high abundant TAG species (>2.5-fold) was observed in patients with PCa. The results of this study indicate that FlFFF can be employed for the high-speed screening of urinary exosome sizes in patients with PCa and lipidomic analysis of the fractionated exosomes has potential for developing and distinguishing biomarkers of PCa.

Covalent immobilization of lipase onto aminopropyl-functionalized hydroxyapatite-encapsulated-γ-Fe2O3 nanoparticles: A magnetic biocatalyst for interesterification of soybean oil.

Hydroxyapatite-encapsulated γ-Fe2O3 nanoparticles were prepared, and lipase from Candida rugosa was then covalently bound onto the magnetic materials via covalent linkages. The magnetic carrier and immobilized lipase were characterized by enzyme activity assays, XRD, FT-IR, TEM, VSM and N2 adsorption-desorption techniques. Results demonstrated that γ-Fe2O3 nanoparticles were coated with the hydroxyapatite, and the lipase was indeed tethered to the magnetic carriers without damage to their structure. The immobilized lipase showed a strong magnetic responsiveness and displayed high catalytic activities towards the interesterification of soybean oil. The interesterified products were evaluated for their total fatty acid (FA) composition, slip melting point (SMP), iodine value, triacylglycerols (TAGs) profile and FA composition at sn-2 position in TAGs. The FA positional distributions and TAG species significantly changed after the enzymatic interesterification. Besides this, the interesterified products showed an obvious reduction in their SMP in comparison with the physical blends.

Characterization of Coconut Oil Fractions Obtained from Solvent Fractionation Using Acetone.

This work was aimed to study the solvent fraction of coconut oil (CNO). The fatty acid and triacylglycerol compositions, solid fat content (SFC) and the crystallization properties of CNO and its solid and liquid fractions obtained from fractionation at different conditions were investigated using various techniques. CNO was dissolved in acetone (1:1 w/v) and left to crystallize isothermally at 10°C for 0.5, 1 and 2 h and at 12°C for 2, 3 and 6 h. The solid fractions contained significantly lower contents of saturated fatty acids of ≤ 10 carbon atoms but considerably higher contents of saturated fatty acids with > 12 carbon atoms with respect to those of CNO and the liquid fractions. They also contained higher contents of high-melting triacylglycerol species with carbon number ≥ 38. Because of this, the DSC crystallization onset temperatures and the crystallization peak temperatures of the solid fractions were higher than CNO and the liquid fractions. The SFC values of the solid fractions were significantly higher than CNO at all measuring temperatures before reaching 0% just below the body temperature with the fraction obtained at 12°C for 2 h exhibiting the highest SFC. On the contrary, the SFC values of the liquid fractions were lower than CNO. The crystallization duration exhibited strong influence on the solid fractions. There was no effect on the crystal polymorphic structure possibly because CNO has β'-2 as a stable polymorph. The enhanced SFC of the solid fractions would allow them to find use in food applications where a specific melting temperature is desired such as sophisticated confectionery fats, and the decreased SFC of the liquid fractions would provide them with a higher cold stability which would be useful during extended storage time.

Identification of molecular species of acylglycerols of Philippine wild edible mushroom, Ganoderma lucidum

We identified the lipid species of the solvent extract from liquid-cultured mycelium of G. lucidum NRRL66208. The molecular species of acylglycerols containing all normal fatty acids were identified. One hundred and three molecular species of acylglycerols containing all normal fatty acids were identified by the MS fragmentation involved their constituent fatty acids. The chain lengths of the constituent fatty acids were from 14 to 26 carbon atoms and the numbers of double bonds were from zero to three. The contents of the molecular species of triacylglycerols in the mushroom lipid extract in decreasing order were: OOP (2.45%), OOO (1.94%), LLP (1.92%), OLP (1.80%), LLO (1.57%), OPP (1.30%), OOL (1.09%), OOS (0.88%), and LLL (0.85%). Forty one molecular species of acylglycerols out of 103 contained fatty acids with odd numbered carbon atoms. The fatty acids with odd numbered carbon atoms were 15:0, 17:0, 17:1, 19:0, 19:1, 21:0, 23:0 and 25:0. The total content of fatty acids with odd numbered carbon atoms was about 6.6% of all of the fatty acids of the triacylglycerols containing three normal fatty acids, and contents of individual fatty acids with odd numbered carbon atoms were as: 15:0 (2.76%), 17:0 (2.13%), 17:1 (1.35%), 19:0 (0.20%), 19:1 (0.17%). The contents of fatty acids with odd numbered carbon atoms in mushroom were high compared to those in higher plants. This is the first report on the molecular species of acylglycerols in mushroom.

Reduced Triacylglycerol Mobilization during Seed Germination and Early Seedling Growth in Arabidopsis Containing Nutritionally Important Polyunsaturated Fatty Acids.

There are now several examples of plant species engineered to synthesize and accumulate nutritionally important polyunsaturated fatty acids in their seed triacylglycerols (TAG). The utilization of TAG in germinating seeds of such transgenic plants was unknown. In this study, we examined the TAG utilization efficiency during seed germination in transgenic Arabidopsis seeds containing several examples of these fatty acids. Seed TAG species with native fatty acids had higher utilization rate than the TAG species containing transgenically produced polyunsaturated fatty acids. Conversely, quantification of the fatty acid components remaining in the total TAG after early stages of seed germination revealed that the undigested TAGs tended to contain elevated levels of the engineered polyunsaturated fatty acids (PUFA). LC-MS analysis further revealed asymmetrical mobilization rates for the individual TAG species. TAGs which contained multiple PUFA fatty acids were mobilized slower than the species containing single PUFA. The mobilized engineered fatty acids were used in de novo membrane lipid synthesis during seedling development.

Determination of the triacylglycerol content for the identification and assessment of purity of shea butter fat, peanut oil, and palm kernel oil using maldi-tof/tof mass spectroscopic technique

ABSTRACTThis article reports the rapid screening and identification of the triacylglycerol content of shea butter fat, palm kernel oil, and peanut oil sold in the local Ghanaian market for their characterization and identification. Samples were dissolved in chloroform with 2,5-dihydroxybenzoic acid as the matrix. After subjecting the samples to matrix-assisted laser desorption ionization-time-of-flight/mass spectrometry, the spectra obtained showed the characteristic triacylglycerols as sodium adducts. Seven major triacylglycerol species were identified as dipalmitoyl olein, palmitoyl diolein, palmitoyl stearoyl olein, linoleoyl diolein, triolein, stearoyl diolein, and distearoyl olein in all three samples. Palmitoyl linoleoyl olein and tristearin were also identified. Oxygenated triacylglycerols and other species from the fragmentation of triacylglycerols were also obtained. The presence of the oxygenated triacylglycerols and the triacylglycerol fragments may be a result of poor handling and production processes.

Abstract 1014: The anti-Warburg agent BPM 31510 arbitrates fatty acid metabolism in eliciting an anticancer response

Abstract De-regulated lipid homeostasis is a key feature of the altered metabolic phenotype observed in cancer, particularly in the adipose-rich microenvironment of breast tumors. Mitochondria serve as a central hub for lipid metabolism through mitochondrial β-oxidation pathways and biosynthesis through production of citric acid cycle-derived citrate and the activity of ATP citrate lyase, the rate-limiting enzyme in lipid biosynthesis. We have previously demonstrated BPM 31510 ability to effectuate Warburg switch from glycolysis to mitochondrial oxidative phosphorylation resulting in activation of apoptosis in multiple cancers including triple negative breast cancer. The present investigated the role of BPM 31510 in influencing lipid metabolism in cancer cells to arbitrate its anti-cancer effect. Cell viability was assessed in MDA-MB231 and SkBr-3 breast cancer cells exposed to BPM 31510 alone or in combination with fatty metabolism inhibitors including C75, etomoxir, and trimetazidine, inhibitors of fatty acid synthase (FASN), carnitine palmitoyltransferase 1 (CPT-1), and β-oxidation, respectively, as well as a more pleiotropic fatty acid metabolism modulator, metformin. Breast cancer cells were more sensitive to BPM 31510 when treated in combination with C75, etomoxir, and trimetazidine as indicated by a left-shift in the BPM 31510 dose-response curve in both MDA-MB231 and SkBr-3 cells. In contrast, combined treatment with metformin did not alter cytotoxic responses to BPM 31510, indicating specificity for responses in fatty acid metabolism pathway modulation. Interestingly, BPM31510 treatment was associated with a dose- and time-dependent increase in mRNA expression of fatty acid metabolism gene products (FASN, CPT1, ACSL1) and accumulation of the triglyceride backbone, glycerol, in MDA-MB-231 cells. Structural lipidomic analysis used to assess the metabolic fate of BPM 31510 liposomal formulation components demonstrated that these were readily incorporated into prevalent diacyl-glyerol (DAG) and triacyl-glycerol (TAG) species along with de novo fatty acid species such as palmitate. Together, these results demonstrate that BPM 31510 alters endogenous and exogenous lipid homeostasis in breast cancer cells and rationale for potential combination with fatty acid metabolism inhibitors for anti-cancer therapy. The results expands on BPM 31510 anti-cancer mechanism, suggesting a central role in arbitrating the convergence of glycolysis, glucose and fatty acid oxidation pathways within the cancer cell metabolism network. Citation Format: Bianca Jambhekar, Tulin Dadali, Anne R. Diers, Fei Gao, Hannah Rockwell, Emily Chen, Stephane Gesta, Vivek K. Vishnudas, Michael A. Kiebish, Niven R. Narain, Rangaprasad Sarangarajan. The anti-Warburg agent BPM 31510 arbitrates fatty acid metabolism in eliciting an anticancer response. [abstract]. In: Proceedings of the 107th Annual Meeting of the American Association for Cancer Research; 2016 Apr 16-20; New Orleans, LA. Philadelphia (PA): AACR; Cancer Res 2016;76(14 Suppl):Abstract nr 1014.

ATGL and DGAT1 are involved in the turnover of newly synthesized triacylglycerols in hepatic stellate cells

Hepatic stellate cell (HSC) activation is a critical step in the development of chronic liver disease. During activation, HSCs lose their lipid droplets (LDs) containing triacylglycerol (TAG), cholesteryl esters (CEs), and retinyl esters (REs). Here we aimed to investigate which enzymes are involved in LD turnover in HSCs during activation in vitro. Targeted deletion of the Atgl gene in mice HSCs had little effect on the decrease of the overall TAG, CE, and RE levels during activation. However, ATGL-deficient HSCs specifically accumulated TAG species enriched in PUFAs and degraded new TAG species more slowly. TAG synthesis and levels of PUFA-TAGs were lowered by the diacylglycerol acyltransferase (DGAT)1 inhibitor, T863. The lipase inhibitor, Atglistatin, increased the levels of TAG in both WT and ATGL-deficient mouse HSCs. Both Atglistatin and T863 inhibited the induction of activation marker, α-smooth muscle actin, in rat HSCs, but not in mouse HSCs. Compared with mouse HSCs, rat HSCs have a higher turnover of new TAGs, and Atglistatin and the DGAT1 inhibitor, T863, were more effective. Our data suggest that ATGL preferentially degrades newly synthesized TAGs, synthesized by DGAT1, and is less involved in the breakdown of preexisting TAGs and REs in HSCs. Furthermore a large change in TAG levels has modest effect on rat HSC activation.

Sodium-Doped Gold-Assisted Laser Desorption Ionization for Enhanced Imaging Mass Spectrometry of Triacylglycerols from Thin Tissue Sections.

The deposition of sodium salts followed by a sputtered layer of gold has been demonstrated to be a power combination for the analysis of triacylglycerols (TAGs) from tissue sections by laser desorption ionization (LDI) imaging mass spectrometry (IMS). Various sodium salts were tested for their capability to ionize TAGs and their ability to produce fast drying, small crystals (≤3 μm). The spray deposition of a sodium acetate and carbonate buffer mixture at pH 10.3 on which a 28 ± 3 nm sputtered layer of gold (Au-CBS) is subsequently deposited was found to provide the most effective combination for TAG analysis by high imaging resolution IMS. Under these conditions, a 30-fold increase in TAG signal intensity was observed when compared to matrix-assisted LDI (MALDI) methods using 2,5-dihydrobenzoic acid as matrix. Furthermore, Au-CBS led to an increase in the number of detected TAG species from ∼7 with DHB to more than 25 with the novel method, while few phospholipid signals were observed. These results were derived from the IMS investigation of fresh frozen mouse liver and rabbit adrenal gland tissue sections with a range of higher spatial resolutions between 35 and 10 μm. Au-CBS-LDI MS presents a highly sensitive and specific alternative to MALDI MS for imaging of TAGs from tissue sections. This novel approach has the potential to provide new biological insights on the role of TAGs in both health and disease.

Blood triacylglycerols: a lipidomic window on diet and disease.

Although the measurement of triacylglycerols (TAGs) by clinical chemistry has been used in the diagnosis of a range of metabolic diseases, such approaches ignore the different species of TAGs that contribute to the total concentration. With the advent of LC and direct infusion forms of MS it is now possible to profile the individual TAGs in blood plasma or tissue extracts. This mini review surveys the information that is obtainable from the lipidomic profiling of TAGs in following metabolic diseases such as type2 diabetes (T2DM), cardiovascular disease (CVD) and non-alcoholic fatty liver disease, as well as the development of insulin resistance and obesity.

Characterization of type 2 diacylglycerol acyltransferases in Chlamydomonas reinhardtii reveals their distinct substrate specificities and functions in triacylglycerol biosynthesis.

Diacylglycerol acyltransferases (DGATs) catalyze a rate-limiting step of triacylglycerol (TAG) biosynthesis in higher plants and yeast. The genome of the green alga Chlamydomonas reinhardtii has multiple genes encoding type 2 DGATs (DGTTs). Here we present detailed functional and biochemical analyses of Chlamydomonas DGTTs. In vitro enzyme analysis using a radiolabel-free assay revealed distinct substrate specificities of three DGTTs: CrDGTT1 preferred polyunsaturated acyl CoAs, CrDGTT2 preferred monounsaturated acyl CoAs, and CrDGTT3 preferred C16 CoAs. When diacylglycerol was used as the substrate, CrDGTT1 preferred C16 over C18 in the sn-2 position of the glycerol backbone, but CrDGTT2 and CrDGTT3 preferred C18 over C16. In vivo knockdown of CrDGTT1, CrDGTT2 or CrDGTT3 resulted in 20-35% decreases in TAG content and a reduction of specific TAG fatty acids, in agreement with the findings of the in vitro assay and fatty acid feeding test. These results demonstrate that CrDGTT1, CrDGTT2 and CrDGTT3 possess distinct specificities toward acyl CoAs and diacylglycerols, and may work in concert spatially and temporally to synthesize diverse TAG species in C. reinhardtii. CrDGTT1 was shown to prefer prokaryotic lipid substrates and probably resides in both the endoplasmic reticulum and chloroplast envelope, indicating its role in prokaryotic and eukaryotic TAG biosynthesis. Based on these findings, we propose a working model for the role of CrDGTT1 in TAG biosynthesis. This work provides insight into TAG biosynthesis in C. reinhardtii, and paves the way for engineering microalgae for production of biofuels and high-value bioproducts.

Effects of Triacylglycerol Molecular Species on the Oxidation Behavior of Oils Containing α-Linolenic Acid.

Two kinds of oils, pure perilla oil and a blend of perilla oil with palm oil, and their enzymatically interesterified oils having the same fatty acid compositions but with different compositions of triacylglycerol (TAG) species, were studied. In particular, the effects of TAG molecular species on the oxidation resistance of oils containing α-linolenic acid (Ln) were investigated. The content of TAG binding to three Ln molecules (3Ln-TAG) was found to be different between perilla oil (38.7%) and the interesterified oils (14.5-28.9%) , which were generated using Lipozyme RM-IM(®) (regiospecificity: sn-1, 3 positional). Oils with lower 3Ln-TAG contents were more stable to oxidation as determined by the conductometric determination method (CDM; 90°C, 20 L/h) than oils with higher 3Ln-TAG contents. This result was also supported by heating oxidation tests (180°C, 7 h) using the interesterified blended oils; the residual ratio of Ln-TAGs in the oils was found to be in the order of 3Ln-TAG<2Ln-TAG<1Ln-TAG. Oxidation stability of Lipase OF(®) (regiospecificity: random)-interesterified blended oils also improved on lowering the 3Ln-TAG content. In addition, the oxidation stabilities of Lipozyme RM-IM(®)-interesterified oils were slightly higher than those of the Lipase OF(®)-interesterified oils. We found that the content of 3Ln-TAG was almost the same in both oils, and the content of unsaturated fatty acid at the sn-1, 3 positions of Lipase OF(®)-interesterified oils was higher than that of Lipozyme RM-IM(®)-interesterified oils. These results indicate that oxidation stabilities of oils containing TAG with unsaturated fatty acid such as Ln at sn-2 position were higher than those having unsaturated fatty acids at the sn-1, 3 positions. From these results, the oxidation stability of oils rich in Ln, such as perilla oil and linseed oil, can be improved not only by decreasing 3Ln-TAG but also by enzymatically reducing the unsaturated fatty acid content at the sn-1, 3 positions.

Ratios of Regioisomers of the Molecular Species of Triacylglycerols in Lesquerella (Physaria fendleri) Oil Estimated by Mass Spectrometry

AbstractThe ratios of regioisomers of 72 molecular species of triacylglycerols (TAG) in lesquerella oil were estimated using the electrospray ionization mass spectrometry of the lithium adducts of TAG in the HPLC fractions of lesquerella oil. The ratios of ion signal intensities (or relative abundances) of the fragment ions from the neutral losses of fatty acids (FA) as α‐lactones at the sn‐2 position (MS3) of the molecular species of TAG were used as the ratios of the regioisomers. The order of the preference of FA incorporation at the sn‐2 position of the molecular species of TAG in lesquerella was as: normal FA &gt; OH18 (monohydroxy FA with 18 carbon atoms) &gt; diOH18 &gt; OH20 &gt; diOH20, while in castor was as: normal FA &gt; OH18 &gt; OH20 &gt; diOH18 &gt; triOH18. Elongation (from C18 to C20) was more effective than hydroxylation in lesquerella to incorporate hydroxy FA at the sn‐1/3 positions. The block of elongation in lesquerella may be used to increase the content of hydroxy FA, e.g., ricinoleate, at the sn‐2 position of TAG and to produce triricinolein (or castor oil) for industrial uses. The content of normal FA at the sn‐2 position was about 95 %, mainly oleate (38 %), linolenate (31 %) and linoleate (23 %). This high normal FA content (95 %) at the sn‐2 position was a big space for the replacement of ricinoleate to increase the hydroxy FA content in lesquerella oil. The content of hydroxy FA at the sn‐1/3 positions was 91 % mainly lesquerolic acid (85 %) and the content of normal FA was 6.7 % at the sn‐1/3 position in lesquerella oil.

APA-style human milk fat analogue from silkworm pupae oil: Enzymatic production and improving storage stability using alkyl caffeates.

Silkworm pupae oil derived from reeling waste is a rich source of α-linolenic acid (ALA), which has multipal applications. ALAs were added in sn-1, 3 positions in a triacylglycerol (TAG) to produce an APA-human milk fat analogues (APA-HMFAs, A: α-linolenic acid, P: palmitic acid). The optimum condition is that tripalmitin to free fatty acids of 1:12 (mole ratio) at 65 °C for 48 h using lipase Lipozyme RM IM. Results show that, the major TAG species that comprised APA-HMFAs were rich in ALA and palmitic acid, which contained 64.52% total unsaturated fatty acids (UFAs) and 97.05% PA at the sn-2 position. The melting point of APA was −27.5 °C which is much lower than tripalmitin (40.5 °C) indicating more plastic character. In addition, the practical application of alkyl caffeates as liposoluble antioxidants in APA was developed. Alkyl caffeate showed a superior IC50 (1.25–1.66 μg/mL) compared to butyl hydroxy anisd (1.67 μg/mL) and L-ascorbic acid-6-palmitate (L-AP) (1.87 μg/mL) in DPPH analysis. The addition of ethyl caffeate to oil achieved a higher UFAs content (73.58%) at high temperatures. Overall, APA was obtained from silkworm pupae oil successfully, and the addition of caffeates extended storage ranges for APA-HMFAs.

Enzymatic Interesterification of High Oleic Sunflower Oil and Tripalmitin or Tristearin

AbstractThe objective of this study was to produce low saturated, zero‐trans, interesterified fats with 20 or 30 % saturated fatty acids (SFA) such as C16:0 or C18:0. Tripalmitin (TP) or tristearin (TS) was blended with high oleic sunflower oil (HOSO) at different ratios (0.1:1, 0.3:1, and 0.5:1 [w/w]). Total C16:0 and C18:0 compositions of the resulting TP/HOSO and TS/HOSO blends, respectively, were plotted against blending ratios. Linear interpolation was used to estimate blending ratios that would yield physical blends (PB) with 20 or 30 % SFA. Interesterified blends (IB) were then synthesized from the customized PB using Lipozyme TL IM as the biocatalyst. Total and sn‐2 fatty acid compositions, triacylglycerol (TAG) molecular species, thermal behavior, and oxidative stability of PB and IB were compared. The total fatty acid compositions of PB and IB were similar but fatty acid positional distributions and TAG molecular species composition differed. IB contained 5–10 % more SFA at the sn‐2 position than corresponding PB. Furthermore, interesterification generated mono‐ and disaturated TAG species which resulted in broader melting profiles for IB. However, IB had lower oxidative stability than PB. The reformulation of food products with zero‐trans interesterified fats may be advantageous to the reduction of cardiovascular disease burden in the population.

Identification and quantification of triacylglycerols containing n-3 long-chain polyunsaturated fatty acids in bovine milk

The n-3 long-chain polyunsaturated fatty acids (LC-PUFA) are low-abundance components in milk fat, but have great potential in promoting human health. A comprehensive survey on triacylglycerol (TAG) molecular species in milk that contain at least one type of n-3 LC-PUFA, namely eicosapentaenoic acid, docosahexaenoic acid, and docosapentaenoic acid, was conducted in this work using HPLC-linear trap quadrupole-Orbitrap and HPLC-triple quadrupole mass spectrometry techniques. A total of 51 TAG species that contain n-3 LC-PUFA have been identified in bovine milk and their structures assigned. The TAG species containing docosahexaenoic acid were found in much smaller number and at much lower abundance compared with the other 2 types of TAG. An HPLC-triple quadrupole mass spectrometry-based method was developed, which provides relative quantification of all these TAG species in a run of 36 min. Application of this method to the quantification of n-3 LC-PUFA-incorporated TAG in 32 individual animal milk samples allowed us to determine variation between animals, identify strong metabolic relationships between TAG species, and reveal negative effect of a grape marc supplement on the accumulation of eicosapentaenoic acid in milk.

Effect of feeding CLA on plasma and granules fatty acid composition of eggs and prepared mayonnaise quality

Eggs rich in trans, trans conjugated linoleic acid (CLA) are significantly more viscous, have more phospholipids containing linoleic acid (LA), and more saturated triacylglycerol species than control eggs. However, the fatty acid (FA) composition of yolk plasma and granule fractions are unreported. Furthermore, there are no reports of mayonnaise rheological properties or emulsion stability by using CLA-rich eggs. Therefore, the objectives were (1) compare the FA composition of CLA-rich yolk granules and plasma, relative to standard control and LA-rich control yolks, (2) compare the rheological properties of mayonnaise prepared with CLA-rich eggs to control eggs and (3) compare the emulsion stability of CLA-yolk mayonnaise. CLA-rich eggs and soy control eggs were produced by adding 10% CLA-rich soy oil or 10% of control unmodified soy oil to the hen’s diet. The eggs were used in subsequent mayonnaise preparation. CLA-yolk mayonnaise was more viscous, had greater storage modulus, resisted thinning, and was a more stable emulsion, relative to mayonnaise prepared with control yolks or soy control yolks.

Regulation of hepatic lipase activity by sphingomyelin in plasma lipoproteins

Hepatic lipase (HL) is an important enzyme in the clearance of triacylglycerol (TAG) from the circulation, and has been proposed to have pro-atherogenic as well as anti-atherogenic properties. It hydrolyzes both phospholipids and TAG of lipoproteins, and its activity is negatively correlated with HDL levels. Although it is known that HL acts preferentially on HDL lipids, the basis for this specificity is not known, since it does not require any specific apoprotein for activity. In this study, we tested the hypothesis that sphingomyelin (SM), whose concentration is much higher in VLDL and LDL compared to HDL, is an inhibitor of HL, and that this could explain the lipoprotein specificity of the enzyme. The results presented show that the depletion of SM from normal lipoproteins activated the HL roughly in proportion to their SM content. SM depletion stimulated the hydrolysis of both phosphatidylcholine (PC) and TAG, although the PC hydrolysis was stimulated more. In the native lipoproteins, HL showed specificity for PC species containing polyunsaturated fatty acids at sn-2 position, and produced more unsaturated lyso PC species. The enzyme also showed preferential hydrolysis of certain TAG species over others. SM depletion affected the specificity of the enzyme towards PC and TAG species modestly. These results show that SM is a physiological inhibitor of HL activity in lipoproteins and that the specificity of the enzyme towards HDL is at least partly due to its low SM content.