Molecular Species Composition Research Articles

Changes in the composition of molecular species of covalently bound and free ceramides [EOS], and their correlation with disease severity in atopic dermatitis.

Ceramides are major constituents of stratum corneum (SC) intercellular lipids involved in skin barrier function. The ratio of molecular species of ceramides and their correlation with disease severity was examined in patients with atopic dermatitis (AD). Thirty-eight patients with AD and 32 healthy controls (HCs) were assessed for transepidermal water loss, SC collection and clinical assessment. The ceramide content of different molecular species in the samples was quantified using high-performance liquid chromatography coupled with tandem mass spectrometry. Unsaturated acyl chains of both covalently bound and free ceramides [EOS] were higher in AD lesional skin than those in AD non-lesional or normal HC skin. The proportion of unsaturated acyl chains (C30:1, C32:1 and C34:1) was higher than other ceramide molecular species among covalently bound and free ceramides [EOS] in patients with AD. The proportion of unsaturated acyl chains in covalently bound ceramides was positively correlated with transepidermal water loss (r = 0.600) when considering the total number of non-lesional and lesional skin. Additionally, thymus and activation-regulated chemokine (TARC) showed a positive correlation with unsaturated acyl chains proportion in AD non-lesional (r = 0.676) and lesional (r = 0.503) skin. Our study is the first to show the increase in unsaturated acyl chains of both covalently bound and free ceramides [EOS] in lesional and non-lesional skin in AD for each molecular species. This increase is associated with dryness and impaired barrier function, which correlates with TARC levels, a marker for the degree of type 2 inflammation. We speculate that type 2 inflammation exacerbation leads to abnormal epidermal lipid metabolism in the skin of patients with AD.

Cardiac lipidomic profiles in mice undergo changes from fetus to adult

AimsLipids are essential cellular components with many important biological functions. Disturbed lipid biosynthesis and metabolism has been shown to cause cardiac developmental abnormality and cardiovascular diseases. In this study, we aimed to investigate the composition and the molecular profiles of lipids in mammalian hearts between embryonic and adult stages and uncover the underlying links between lipid and cardiac development and maturation. Materials and methodsWe collected mouse hearts at the embryonic day 11.5 (E11.5), E15.5, and the age of 2 months, 4 months and 10 months, and performed lipidomic analysis to determine the changes of the composition, molecular species, and relative abundance of cardiac lipids between embryonic and adult stages. Additionally, we also performed the electronic microscopy and RNA sequencing in both embryonic and adult mouse hearts. Key findingsThe relative abundances of certain phospholipids and sphingolipids including cardiolipin, phosphatidylglycerol, phosphatidylethanolamine, and ceramide, are different between embryonic and adult hearts. Such lipidomic changes are accompanied with increased densities of mitochondrial membranes and elevated expression of genes related to mitochondrial formation in adult mouse hearts. We also analyzed individual molecular species of phospholipids and sphingolipids, and revealed that the composition and distribution of lipid molecular species in hearts also change with development. SignificanceOur study provides not only a lipidomic view of mammalian hearts when developing from the embryonic to the adult stage, but also a potential pool of lipid indicators for cardiac cell development and maturation.

Acquisition of Desiccation Tolerance Unveiled: Polar Lipid Profiles of Streptophyte Algae Offer Insights.

Terrestrialization by photosynthetic eukaryotes took place in the two branches of green microalgae: Chlorophyta and Charophyta. Within the latter, the paraphyletic streptophytic algae divide into two clades. These are named Klebsormidiophyceae-Chlorokybophyceae-Mesostigmatophyceae (KCM), which is the oldest, and Zygnematophyceae-Coleochaetophyceae-Charophyceae (ZCC), which contains the closest relatives of vascular plants. Terrestrialization required the emergence of adaptations in response to new challenges, such as irradiance, temperature oscillations and water deprivation. In this study, we evaluated lipid composition in species representative of distinct phylogenetic clusters within Charophyta and Chlorophyta. We aim to study whether the inherent thylakoid lipid composition, as well as its adaptability in response to desiccation, were fundamental factors for the evolutionary history of terrestrial plants. The results showed that the lipid composition was similar to that found in flowering land plants, differing only in betaine lipids. Likewise, the largest constitutive pool of oligogalactolipids (OGL) was found only in the fully desiccation-tolerant species Klebsormidium nitens. After desiccation, the content of polar lipids decreased in all species. Conversely, the content of OGL increased, particularly trigalactosyldiacylglycerol and tetragalactosyldiacylglycerol in the ZCC clade. The analysis of the molecular species composition of the newly formed OGL may suggest a different biosynthetic route for the KCM and ZCC clades. We speculate that the appearance of a new OGL synthesis pathway, which eventually arose during the streptophyte evolutionary process, endowed algae with a much more dynamic regulation of thylakoid composition in response to stress, which ultimately contributed to the colonization of terrestrial habitats.

Mixed light photoperiod and biocide pollution affect lipid profiles of periphyton communities in freshwater ecosystems

Environmental factors, such as light intensity and exposure to contaminants, may significantly influence the lipid composition of algae in periphytic communities. In this study, we investigated the joint effects of dodecylbenzyldimethylammonium chloride (BAC 12), as biocide, and light photoperiods on the polar lipidome of a freshwater biofilm. Exposure to BAC 12 in a microcosm experiment increased the heterotrophic compartment, while phototrophic organisms were severely affected, with corresponding shifts in lipid composition. The overall decrease in polyinsaturated fatty acids suggested a significant impact of the biocide on biofilm microalgae. However, it was difficult to distinguish the influence of light from that of contamination, as there was no observable effect of photoperiod on conventional fatty acid determination. Thus, the molecular species compositions of both glycolipids and phospholipids were explored in additional multivariate analyzes. The results suggested that certain molecular species can serve as more specific markers of light duration at the biofilm scale, independently of the chemical pressure caused by other pollutants.

Lipidome of the Brown Macroalga Undaria pinnatifida: Influence of Season and Endophytic Infection.

An analysis of the lipidome of the brown alga Undaria pinnatifida (Laminariales) was performed' more than 900 molecular species were identified in 12 polar lipids and 1 neutral lipid using HPLC/MS-MS. The seasonal changes of U. pinnatifida lipidome were determined. It was shown that acclimatization to winter and spring was accompanied by an increase in the unsaturation of both polar and neutral lipids. In autumn and summer, on the contrary, the contents of more saturated molecular species of all lipid classes increased. Based on the data obtained, a scheme for the polar and neutral lipid synthesis in brown algae was proposed. In addition, the influence of infection with the brown filamentous endophyte Laminariocolax aecidioides (Ectocarpales) on U. pinnatifida lipidome was studied. It was found that infection has the most noticeable effect on the molecular species composition of triacylglycerides, phosphatidylglycerol, phosphatidylcholine, phosphatidylethanolamine, and phosphatidylhydroxyethylglycine of the host macrophyte. In infected samples of algae, changes in the composition of triacylglycerides were revealed both in areas with the presence of an endophyte and in adjacent intact tissues, which may indicate the occurrence of a secondary infection.

Component and Content of Lipid Classes and Phospholipid Molecular Species of Eggs and Body of the Vietnamese Sea Urchin Tripneustes gratilla.

Sea urchins (Tripneustes gratilla) are among the most highly prized seafood products in Vietnam because of their nutritional value and medicinal properties. In this research, lipid classes and the phospholipid (PL) molecular species compositions from the body and eggs of T. gratilla collected in Hon Tam, Nha Trang, Khanh Hoa, Vietnam, were investigated. Hydrocarbon and wax (HW), triacylglycerol (TG), mono- and diacylglycerol (MDAG), free fatty acid (FFA), sterol (ST), polar lipid (PoL), and monoalkyl-diacylglycerol are the major lipid classes. In PL, five main glycerophospholipid classes have been identified, in which 137 PL molecular species were detected in the body and eggs of T. gratilla, including 20 inositol glycerophospholipids (PI), 11 serine glycerophospholipids (PS), 22 ethanolamine glycerophospholipids (PE), 11 phosphatidic acids (PA), and 73 choline glycerophospholipids (PC). PI 18:0/20:4, PS 20:1/20:1, PE 18:1e/20:4, PA 20:1/20:1, and PC 18:0e/20:4 are the most abundant species with the highest content values of 38.65-48.19%, 42.48-44.41%, 41.21-40.03%, 52.42-52.60%, and 7.77-7.18% in each class of the body-eggs, respectively. Interestingly, PL molecules predominant in the body sample were also found in the egg sample. The molecular species with the highest content account for more than 40% of the total species in each molecular class. However, in the PC class containing 73 molecular species, the highest content species amounted to only 7.77%. For both the body and egg TL samples of the sea urchin T. gratilla, a substantial portion of C20:4n polyunsaturated fatty acid was found in PI, PE, and PC, but C16, C18, C20, and C22 saturated fatty acids were reported at low levels. The most dominant polyunsaturated fatty acid in PI, PE, and PC was tetracosapolyenoic C20, while unsaturated fatty acid C20:1 was the most dominant in PS and PA. To our knowledge, this is the first time that the chemical properties of TL and phospholipid molecular species of the PoL of Vietnamese sea urchin (T. gratilla) have been studied.

Study on lipid and phospholipid composition from the seed oil of Dalbergia tonkinensis

The content and composition of classes and molecular species of phospholipid extracted from Dalbergia tonkinensis Prain (Cây Sưa) seed oil in Viet Nam have been investigated using HPLC-HRMS and LCMS-IT-TOF. The content of phospholipid subclasses and their molecular species of D. tonkinensis seed oil have been investigated for the first time. The results showed that D. tonkinensis seed oil contains all basic classes of lipid: polar lipid, sterol, triacylglycerol, free fatty acid, diacylglycerol, hydrocarbon, and wax. In which, the content of triacylglycerol accounts for the highest percentage of 76.38 %, while polar lipid and free fatty acid also have a relatively high content. This result indicated the presence of 12 specific phospholipid subclasses of the plant, including phosphatidylethanolamine, phosphatidylcholine, and phosphatidylinositol. The "molecular forms" of phospholipids of Sua seeds lipids have been identified. The results show that the phospholipids of Sua seeds have 3 classes of substances including phosphatidylethanolamine (PE), phosphatidylcholine (PC), phosphatidylinositol (PI). In which PE has 5 molecular forms, PC has 5 molecular forms and has 2 molecular forms of PI. These are the first data was found and published in Sua seeds.

A lipidomics platform to analyze the fatty acid compositions of non-polar and polar lipid molecular species from plant tissues: Examples from developing seeds and seedlings of pennycress (Thlaspi arvense).

The lipidome comprises the total content of molecular species of each lipid class, and is measured using the analytical techniques of lipidomics. Many liquid chromatography-mass spectrometry (LC-MS) methods have previously been described to characterize the lipidome. However, many lipidomic approaches may not fully uncover the subtleties of lipid molecular species, such as the full fatty acid (FA) composition of certain lipid classes. Here, we describe a stepwise targeted lipidomics approach to characterize the polar and non-polar lipid classes using complementary LC-MS methods. Our "polar" method measures 260 molecular species across 12 polar lipid classes, and is performed using hydrophilic interaction chromatography (HILIC) on a NH2 column to separate lipid classes by their headgroup. Our "non-polar" method measures 254 molecular species across three non-polar lipid classes, separating molecular species on their FA characteristics by reverse phase (RP) chromatography on a C30 column. Five different extraction methods were compared, with an MTBE-based extraction chosen for the final lipidomics workflow. A state-of-the-art strategy to determine and relatively quantify the FA composition of triacylglycerols is also described. This lipidomics workflow was applied to developing, mature, and germinated pennycress seeds/seedlings and found unexpected changes among several lipid molecular species. During development, diacylglycerols predominantly contained long chain length FAs, which contrasted with the very long chain FAs of triacylglycerols in mature seeds. Potential metabolic explanations are discussed. The lack of very long chain fatty acids in diacylglycerols of germinating seeds may indicate very long chain FAs, such as erucic acid, are preferentially channeled into beta-oxidation for energy production.

Effect of Temperature and Light Intensity on the Polar Lipidome of Endophytic Brown Algae Streblonema corymbiferum and Streblonema sp. In Vitro.

The effect of temperature and light intensity on the polar lipidome of endophytic brown algae Streblonema corymbiferum and Streblonema sp. in vitro was investigated. More than 460 molecular species have been identified in four glycoglycerolipids classes, five phosphoglycerolipids classes and one betaine lipid class. The lipids glucuronosyldiacylglycerol and diacylglyceryl-N,N,N-trimethyl-homoserine were found in the algae of the order Ectocarpales for the first time. A decrease in cultivation temperature led to an increase in the unsaturation level in all classes of polar lipids. Thus, at low temperatures, the content of 18:4/18:4 monogalactosyldiacylglycerol (MGDG), 20:5/18:4 digalactosyldiacylglycerol (DGDG), 18:3/16:0 sulfoquinovosyldiacylglycerol (SQDG), 18:3/18:3 and 18:3/18:4 phosphatidylglycerol (PG), 20:4/20:5 and 20:5/20:5 phosphatidylethanolamine (PE), 14:0/20:5, 16:0/20:5 and 20:5/20:5 phosphatidylcholine (PC), 20:5/20:4 phosphatidylhydroxyethylglycine and 18:1/18:2 DGTS increased. At high temperatures, an increase in the content of chloroplast-derived MGDG, DGDG and PG was observed. Both low and high light intensities caused an increase in 20:5/18:3 MGDG and 18:3/16:1 PG. At low light intensity, the content of DGDG with fatty acid (FA) 18:3 increased, and at high light intensity, it was with FA 20:5. The molecular species composition of extraplastid lipids also showed a dependence on light intensity. Thus, the content of PC and PE species with C20-polyunsaturated FA at both sn-positions, 18:1/18:1 DGTS and 16:0/18:1 phosphatidylinositol increased. Low light intensity induced a significant increase in the content of chloroplast-derived 18:1/16:1 phosphatidylethanolamine.

A multimodal analytical method to simultaneously determine monoacetyldiacylglycerols, medium and long chain triglycerides in biological samples during routine lipidomics

BackgroundMonoacetyldiglycerides (MAcDG), are acetylated triglycerides (TG) and an emerging class of bioactive or functional lipid with promising nutritional, medical, and industrial applications. A major challenge exists when analyzing MAcDG from other subclasses of TG in biological matrices, limiting knowledge on their applications and metabolism.MethodsHerein a multimodal analytical method for resolution, identification, and quantitation of MAcDG in biological samples was demonstrated based on thin layer chromatography-flame ionization detection complimentary with C30-reversed phase liquid chromatography-high resolution accurate mass tandem mass spectrometry. This method was then applied to determine the MAcDG molecular species composition and quantity in E. solidaginis larvae. The statistical method for analysis of TG subclass composition and molecular species composition of E. solidaginis larvae was one-way analysis of variance (ANOVA).ResultsThe findings suggest that the proposed analytical method could simultaneously provide a fast, accurate, sensitive, high throughput analysis of MAcDG from other TG subclasses, including the fatty acids, isomers, and molecular species composition.ConclusionThis method would allow for MAcDG to be included during routine lipidomics analysis of biological samples and will have broad interests and applications in the scientific community in areas such as nutrition, climate change, medicine and biofuel innovations.Graphical abstract

Amino Acid Metabolism Controls Fatty Acid Structure in Staphylococcus aureus

Staphylococcus aureus produces a combination of branched and straight chain fatty acids to maintain membrane homeostasis. Recently, we showed that the branched:straight chain ratio in fatty acids is controlled by amino acid metabolism that supplies the branched‐chain acyl‐CoA primers for fatty acid biosynthesis. The fatty acid composition is determined when FabH catalyzes the initial condensation using the available short‐chain acyl‐CoA primers with malonyl‐acyl carrier protein. Branched‐chain ketoacid dehydrogenase (Bkd) is recognized as the primary enzyme responsible for the formation of branched‐chain acyl‐CoA primers. Most experiments with S. aureus are carried out in media with an abundant supply of branched‐chain amino acids where the Bkd pathway for the utilization of Ile dominates. However, branched‐chain fatty acids are still produced in bkd knockout strains and the enzyme(s) responsible for this alternate biosynthetic pathway is unknown. It is important to understand how S. aureus copes with limited availability of Ile because multiple laboratories conclude that isoleucine is a limiting nutrient at S. aureus infection sites that regulates metabolism and virulence.Mass tracing experiments with heavy amino acids show that Bkd is the key step in a pathway that selectively converts extracellular Ile into 2‐methyl‐butyryl‐CoA (anteiso‐C5‐CoA) that FabH uses to initiate anteiso fatty acid synthesis. The phosphatidylglycerol (PG) molecular species in wild‐type strains consists of a mixture of anteiso‐17:0 and ‐19:0 and 18:0 and 20:0 straight chain fatty acids in the 1‐position paired with anteiso‐15:0 in the 2‐position. If Ile is removed from the medium, Leu metabolism results in the introduction of iso‐15:0 into the 2‐position. Val is not significantly metabolized by the Bkd pathway. The analysis of the PG molecular species in strains lacking an active Bkd complex have a straight chain fatty acid in the 1‐position paired with either iso‐14:0 or anteiso‐15:0 in the 2‐position. This same switch in PG molecular species composition is observed when wild‐type strains are grown in defined medium lacking both Ile and Leu. Our metabolomics analyses show that C5‐CoA derived from the Bkd pathway is the most abundant acyl‐CoA primer available for FabH in wild‐type strains; however, when Ile and Leu are not present in the medium, iso‐C4‐CoA increases and anateiso‐C5‐CoA decreases. In the bkd knockout strains, the C4‐CoA pool is even more elevated, and the C5‐CoA pool is substantially lower. This means that in the absence of Bkd, a second pathway creates a supply of iso‐C4‐CoA for FabH to prime fatty acid synthesis and produce iso‐14:0 for the 2‐position. Thus, there are two pathways for the formation of branched‐chain acyl‐CoA substrates for FabH. The Bkd pathway is responsible for the utilization of extracellular Ile (and to a lesser extent, Leu) to initiate fatty acid synthesis, whereas the alternate, de novo biosynthetic pathway makes a significant contribution in wild‐type strain growth without exogenous Ile and is the only process operating in the bkd knockout strains. We are testing the hypothesis that the key enzyme in the de novo pathway to iso‐C4‐CoA is CidC, an enzyme related to pyruvate oxidase.

Lipidomic profiling reveals biosynthetic relationships between phospholipids and diacylglycerol ethers in the deep-sea soft coral Paragorgia arborea

The cold-water gorgonian coral Paragorgia arborea is considered as a foundation species of deep-sea ecosystems in the northern Atlantic and Pacific oceans. To advance lipidomic studies of deep-sea corals, molecular species compositions of diacylglycerol ethers (DAGE), which are specific storage lipids of corals, and structural glycerophospholipids (GPL) including ethanolamine, choline, inositol and serine GPL (PE, PC, PI, and PS, respectively) were analyzed in P. arborea by HPLC and tandem mass spectrometry. In DAGE molecules, alkyl groups (16:0, 14:0, and 18:1), polyunsaturated fatty acids (PUFA), and monounsaturated FA are mainly substituted the glycerol moiety at position sn-1, sn-2, and sn-3, respectively. The ether form (1-O-alkyl-2-acyl) predominates in PE and PC, while PI is comprised of the 1,2-diacyl form. Both ether and diacyl forms were observed in PS. At position sn-2, C20 PUFA are mainly attached to PC, but C24 PUFA, soft coral chemotaxonomic markers, concentrate in PS, PI, and PE. A comparison of non-polar parts of molecules has shown that DAGE, ether PE, and ether PC can originate from one set of 1-O-alkyl-2-acyl-sn-glycerols. Ether PE may be converted to ether PS by the base-exchange reaction. A diacylglycerol unit generated from phosphatidic acid can be a precursor for diacyl PS, PC, and PI. Thus, a lipidomic approach has confirmed the difference in biosynthetic origins between ether and diacyl lipids of deep-sea gorgonians.

Lipid composition and molecular species of phospholipid in oyster Crassostrea lugubris (Sowerby, 1871) from Lang Co Beach, Hue Province, Vietnam.

Oysters are widely distributed worldwide, but are mainly concentrated in tropics and subtropics. Total lipid (TL), fatty acid (FA) composition of TL and polar lipid (PoL) fractions, phospholipid (PL) class, and molecular species composition in soft tissues of Crassostrea lugubris were investigated for the first time from Vietnam. Phosphatidylglycolic acid (PGA) is the new phospholipid class first identified in marine species in general and Crassostrea lugubris in particular. Main eight classes of PL were determined in PoL fraction: diphosphatidylglycerol (DPG), phosphatidylethanolamine (PE), phosphatidylcholine (PC), phosphatidylinositol (PI), phosphatidylserine (PS), ceramide aminoethylphosphonate (CAEP), CAEP with hydroxylated FAs (CAEP‐OH), and lysophosphatidylcholine. PE and PC accounted for approximately 63% of total known PL. Polyunsaturated FAs accounted for more than 30% of TL. Ninety molecular species of glycerophospholipids, including PGA, PE, PC, PS, PI, DPG, and PG, and sphingophosphonolipids (CAEP) were identified in PoL. Alkenyl‐acyl forms of glycerophospholipids were predominated in the molecular species of PGA, PE, and PS. PGA 38:1 (p18:0/20:1), PE 40:6 (p18:0/22:6 and p18:1/22:5), PC 30:0 (14:0/16:0), PS 38:1 (p18:0/20:1), PI 40:5 (20:1/20:4), PG 32:0 (16:0/16:0), DPG 88:24 (22:6/22:6/22:6/22:6), and CAEP 34:2 (d18:2/16:0) were major molecular species.

Molecular Composition, Digestion and Absorption Characteristics of Astaxanthin in Antarctic Krill Oil

The extraction of Antarctic krill oil enrich astaxanthins using n-hexane-ethanol solvent systems was studied, taking the total astaxanthin content, phospholipid content and yield of Antarctic krill oil as the investigation indexes. Meanwhile, the molecular species composition of astaxanthins in Antarctic krill oil which extracted under the optimized conditions were characterized and analyzed. Then the digestion process and bioaccessibility of astaxanthins in Antarctic krill oil were investigated by single-dose oral gavage with different doses of Antarctic krill oil, using ICR mice as model animals. Furthermore, the bioacceptability of astaxanthin from Antarctic krill oil and Haematococcus pluvialis were compared. The results showed that the 60%(V/V) n-hexane-ethanol solution was selected as the best solvent to extract Antarctic krill oil enrich astaxanthins. The astaxanthins in krill oil were mainly present as fatty acid esters, the relative percentages of astaxanthin diesters, monoesters, and free astaxanthin were 73.5%, 24.8%, and 1.62%. The astaxanthin diesters were hydrolyzed to monoesters or free from in the gastrointestinal tract. After 24 hours of gavage, the bioaccessibility of astaxanthin in low, middle and high dose groups was not significant, and the bioaccessibility of astaxanthin in Antarctic krill oil was about 74%. In addition, the bioaccessibility of astaxanthin in Antarctic krill oil was about 1.25 times of that in Haematococcus pluvialis oil. These results could provide a scientific basis for the rational production and the evaluation of dietary nutritional of Antarctic krill oil.

Seasonal variation in the lipidome of two species of Millepora hydrocorals from Vietnam coastal waters (the South China Sea)

In shallow tropical seas, hydrocoral colonies are locally abundant and important reef-framework builders. Hydrocorals are rich in lipids, which play an essential role in their physiology, but no data on seasonal variations in lipids of hydrocorals are available to date. In the present study, the profiles of total lipids, fatty acids (FA), storage and structural lipids classes, and molecular species of structural lipids in symbiotic dinoflagellates and the host of the hydrocorals Millepora dichotoma and M. platyphylla were analyzed each month throughout the year. In both hydrocoral species, the twofold increase in total lipids in the summer coincided with the water temperature rise and was caused primarily by the considerable accumulation of storage lipids with insignificant variations in structural lipids. The FA markers confirmed the year-round hydrocorals’ predation on zooplankton and indicated that M. dichotoma can consume more diatoms than M. platyphylla during October–January. The polar lipidomes of the two Millepora species were similar. The remodeling of alkyl and sphingosine groups in three structural lipid classes rather than unsaturation degree of their FA groups may be considered as a seasonal adaptive response of host biomembranes in Millepora. The symbiotic dinoflagellates of the hydrocorals kept the galactolipid ratio stable throughout the year but significantly increased the levels of sulfoquinovosyldiacylglycerol and betaine lipid in winter. The FA markers of the symbionts correlated negatively with galactolipids, thus, indicating a higher transfer of the symbiotic FA to the host in winter. Throughout the year, symbionts controlled their lipid class composition, but their lipid molecular species composition varied in a random manner. The considerable amounts of digalactosyldiacylglycerols with C20–22 polyunsaturated FA distinguished M. platyphylla from M. dichotoma and suggested that different hydrocorals contain different symbiont species. Data on seasonal variations of the lipidomes provide new background information for future studies of ecology, physiology, and biochemistry of hydrocorals.

Overview of Lipidomic Analysis of Triglyceride Molecular Species in Biological Lipid Extracts.

Triglyceride (TG) is a class of neutral lipids, which functions as an energy storage depot and is important for cellular growth, metabolism, and function. The composition and content of TG molecular species are crucial factors for nutritional aspects in food chemistry and are directly associated with several diseases, including atherosclerosis, diabetes, obesity, stroke, etc. As a result of the complexities of aliphatic moieties and their different connections/locations to the glycerol backbone in TG molecules, accurate identification of individual TG molecular species and quantitative assessment of TG composition and content are particularly challenging, even at the current stage of lipidomics development. Herein, methods developed for analysis of TG species, such as liquid chromatography-mass spectrometry with a variety of columns and different mass spectrometric techniques, shotgun lipidomics approaches, and ion-mobility-based analysis, are reviewed. Moreover, the potential limitations of the methods are discussed. It is our sincere hope that the overviews and discussions can provide some insights for researchers to select an appropriate approach for TG analysis and can serve as the basis for those who would like to establish a methodology for TG analysis or develop a new method when novel tools become available. Biologically accurate analysis of TG species with an enabling method should lead us toward improving the nutritional quality, revealing the effects of TG on diseases, and uncovering the underlying biochemical mechanisms related to these diseases.

Spatial Analysis of Phosphatidylinositol Molecular Species in Pork Chop Tissues Using Matrix-assisted Laser Desorption/ionization-Mass Spectrometry Imaging.

Matrix-assisted laser desorption/ionization-mass spectrometry imaging (MALDI-MSI) is a powerful technique for visualizing lipids in biological tissues. Phosphatidylinositol (PI), a phospholipid in pork, is a major source of inositol in animal-derived foods believed to be protective against diseases related to pregnancy and cancer. However, the distribution of PI molecular species in pork is not well understood. Here, we performed MALDI-MSI analysis to investigate the distribution and composition of PI molecular species in pork chop comprising Longissimus thoracis et lumborum muscle (loin), intermuscular fat tissue, transparent tissue, and spinalis muscle. Twelve diacyl-PI molecular species were identified using liquid chromatography-electrospray ionization-tandem mass spectrometry (MS/MS) and MALDI-MS/MS analysis and visualized using MALDI-MSI. Spinalis muscle had the highest amount of identified PI molecular species, followed by loin, transparent tissue, and intermuscular fat tissue. The diacyl-PI molecular species containing hexadecadienoic, oleic, linoleic and eicosadienoic acids at the sn-2 position were mainly abundant in the loin and spinalis muscle, whereas those containing mead, arachidonic, docosatetraenoic, and docosapentaenoic acids at the sn-2 position were mainly abundant in both muscles as well as transparent tissues. Notably, the balance of PI molecular species differed among the tissues depending on fatty acid compositions at the sn-2 position. These results suggested that MALDI-MSI is a promising tool for assessing the association between individual pork tissues and the protective effects of PI molecular species against diseases related to pregnancy and cancer. To the best of our knowledge, this is the first report showing tissue-specific distributions of PI molecular species in pork chop using MALDI-MSI.

Analysis of Free and Esterified Sterol Content and Composition in Seeds Using GC and ESI-MS/MS.

Total sterol content and composition in plant tissues can be easily determined by gas chromatography (GC) after saponification of the total lipid extract. However, in oleogenic tissues a significant proportion of the sterol is esterified to fatty acids, with GC methodologies unable to provide information about the proportion and the molecular species composition of intact steryl esters (SEs). Here we describe an electrospray ionization-tandem mass spectrometry (ESI-MS/MS) and Multiple Reaction Monitoring (MRM) method which, in parallel with GC analysis, allows for the accurate determination of both free and esterified sterol content and composition in seeds. After extraction of seed oil with hexane, free sterols are derivatized with undecanoyl chloride, total steryl esters are then purified from triacylglycerol (TAG) by liquid chromatography, infused and ionized as ammonium adducts, with molecular species identified and quantified by fragmentation in the presence of internal standards.

Changes in compositions of galactolipids, triacylglycerols, and tocopherols of lettuce varieties (Lactuca sativa L.) with type, age, and light source

The compositions of molecular species of structural lipids and storage lipids of two types of lettuce leaves, romaine (green leaf) and Lolla Rossa (red leaf), are reported. Lettuce was harvested at two ages, three weeks (microgreens) and eight weeks (mature), and analyzed by liquid chromatography-mass spectrometry. Samples grown under natural light in a greenhouse were compared to those grown under grow lights. Compositions of molecular species of galactolipids (GALs), which are structural lipids, and triacylglycerols (TAGs) and diacylglycerols (DAGs), which are storage lipids, were examined relative to type (cultivar), age, and light source. GALs were most abundant, and the predominant molecular species were dilinolenoyl-monogalactosyldiacylglycerol (LnLn-MGDG) and dilinolenoyl-digalactosyldiacylglycerol (LnLn-DGDG), averaging 53.6 ± 1.4 % and 33.7 ± 2.3 % of galactolipids, respectively. TAGs containing linolenic acid (Ln) increased from three to eight weeks, especially LnLnL, LLLn, PLLn (P is palmitic acid and L is linoleic acid), and LnLnLn, with corresponding decreases in TAGs containing mostly linoleic acid, especially LLL, LLP, and LLO (O is oleic acid). α-Tocopherol started at similar levels in both varieties of greenhouse-grown lettuce, and it approximately tripled in Lolla Rossa, from 3.4 ± 0.3 μg/g to 9.9 ± 0.7 μg/g, by two LED lighting treatments.

Lipidomic Analysis of Plasma from Healthy Men and Women Shows Phospholipid Class and Molecular Species Differences between Sexes.

The phospholipid composition of lipoproteins is determined by the specificity of hepatic phospholipid biosynthesis. Plasma phospholipid 20:4n‐6 and 22:6n‐3 concentrations are higher in women than in men. We used this sex difference in a lipidomics analysis of the impact of endocrine factors on the phospholipid class and molecular species composition of fasting plasma from young men and women. Diester species predominated in all lipid classes measured. 20/54 Phosphatidylcholine (PtdCho) species were alkyl ester, 15/48 phosphatidylethanolamine (PtdEtn) species were alkyl ester, and 12/48 PtdEtn species were alkenyl ester. There were no significant differences between sexes in the proportions of alkyl PtdCho species. The proportion of alkyl ester PtdEtn species was greater in women than men, while the proportion of alkenyl ester PtdEtn species was greater in men than women. None of the phosphatidylinositol (PtdIns) or phosphatidylserine (PtdSer) molecular species contained ether‐linked fatty acids. The proportion of PtdCho16:0_22:6, and the proportions of PtdEtn O‐16:0_20:4 and PtdEtn O‐18:2_20:4 were greater in women than men. There were no sex differences in PtdIns and PtdSer molecular species compositions. These findings show that plasma phospholipids can be modified by sex. Such differences in lipoprotein phospholipid composition could contribute to sexual dimorphism in patterns of health and disease.