Glycerophospholipid Molecular Species Research Articles

Molecular species of some glycerophospholipid classes of soft coral \(\textit{Sinularia leptoclados}\) collected in Nha Trang, Khanh Hoa

In the soft coral Sinularia leptoclados, 30 molecular species belonged to 4 glycerophospholipid classes, including 8 ethanolamine glycerophospholipid (PE), 13 choline glycerophospholipid (PC), 3 serine glycerophospholipid (PS) and 6 inositol glycerophospholipid (PI) molecular species were identified. PE 18:1e/20:4, PC 18:0e/20:4, PS 18:0e/24:5 and PI 18:0/24:5 are the most abundant species with value of 69.94%, 45.57%, 68.55% and 68.18%, respectively. The PE, PC, and PS classes are reported to contain alkylacylphospholipid; meanwhile, a considerable level of diacylphospholipid is found in PI. A large portion of C20:4n polyunsaturated fatty acid was found in PE and PC; meanwhile, C16, C18, C22, and C24 fatty acids were reported at a minor level. The most dominant polyunsaturated fatty acid in PI and PS is tetracosapolyenoic C24. In the presence of fatty acids specific for the biosynthesis of zooxanthellae18:4n and 22:6n, PC is the most influenced class by the lipid composition of symbiotic microalgae. The PC 16:0e/18:4 and PC 18:1e/22:6 molecular species with recorded content of 1.69% and 8.05% are the evidence for lipid transportation from zooxanthellae to host corals. The PE, PS, and PI classes exhibit the lipid composition of the host coral; also, they are less affected by zooxanthellae lipids.

Differences in lipid composition of Bigeye tuna (Thunnus obesus) during storage at 0 °C and 4 °C

This study aimed to investigate the lipid oxidation and distribution in Bigeye tuna stored at 0 °C and 4 °C for 6 days. Tuna were evaluated by determining the peroxide value (POV), acid value (AV), anisidine value (AnV), polyene index, fluorescence ratio (FR), phosphatidylcholine (PC), phosphatidylethanolamine (PE), phosphatidylinositol (PI) content, and major glycerophospholipid molecular species. The value of lipid oxidation indexes (POV, AV, AnV, FR, PC, PE and PI) increased as the storage time increased. High-performance liquid chromatography-tandem mass spectrometry (HPLC-MS/MS) results indicated that the major types of lipids included diacylglycerol (DAG), monoacylglycerol (MAG), phospholipid (PL), and triacylglycerol (TAG). At least 136 PC and 64 PE molecular species were identified in Bigeye tuna. The results of the confocal laser scanning microscope analysis indicated the distribution of TAG and PL particles. In addition, principal component analysis showed that the contents of PI and TAG were positively correlated with PC, polyene index and lipid content but negatively correlated with PI, POV, FR, AOV, AnV, MAG, and DAG, which might be explained by distinguishing the lipid parameters affecting lipid oxidation. Therefore, this study may provide a novel method to evaluate lipid changes and contribute to the balanced nutritional value of aquatic foods during cold storage.

Detailed Analysis of Lipids in Edible Viscera and Muscles of Cooked Crabs Portunus trituberculatus and Portunus pelagicus

ABSTRACTThe lipid profiles, including lipid classes, phospholipid (PL) classes, fatty acid (FA) composition, and glycerophospholipid (GP) molecular species, in the two edible parts (edible viscera and muscles) of two species of cooked crabs (Portunus trituberculatus and Portunus pelagicus) were systematically characterized for the first time to reveal their nutritional values. For the muscles, PL (66.84–82.23% of total lipids) was the major component of lipids. While for the edible viscera, triacylglycerol (79.04–96.66% of total lipids) was the dominant lipid class. For all lipid samples, eicosapentaenoic acid (EPA) (3.47–22.02% of total FA) and docosahexaenoic acid (DHA) (7.30–16.52% of total FA) were the predominant FAs. Among PL from the crab muscles, phosphocholine (61.51–63.27 mol%) and phosphoethanolamine (21.58–23.43 mol%) were abundant. About 250 GP molecular species belonging to six classes, including glycerophosphocholine, lysoglycerophosphocholine, glycerophosphoethanolamine, lysoglycerophosphoethanolamine, glycerophosphoserine, and lysoglycerophosphoserine, were identified in crab muscles using direct infusion mass spectrometric method. A majority of the dominant molecular species of GP contained omega-3 polyunsaturated fatty acid, especially EPA and DHA. The useful information obtained in this study makes it possible to use crab lipid for producing higher value-added products for commercial exploitation.

Seasonal Variation of Lipid Profile of Oyster Crassostrea talienwhanensis from the Yellow Sea Area

ABSTRACTLipid profile of the oyster Crassostrea talienwhanensis from the Yellow Sea was evaluated based on the seasonal changes in lipid categories, phospholipid (PL) categories, fatty acid (FA) composition, atherogenicity index (IA), thrombogenicity index (IT), and glycerophospholipid (GP) molecular species. We observed that the samples harvested in February contained higher levels of polyunsaturated fatty acid (PUFA) (48.77% of total FAs) and PL (52.12% of total lipids) and had lower IA (0.29). In addition, more than 290 GP molecular species of glycerophosphocholine (GPCho), glycerophosphoethanolamine (GPEtn), glycerophosphoserine (GPSer), and glycerophosphoinositol (GPIns) were determined. The molecular species containing eicosapentaenoic acid (EPA) and docosahexaenoic acid (DHA) constituted 75.24% of total GPCho in the samples harvested in February. Considering the lipid profile, oyster Crassostrea talienwhanensis harvested in February had better nutritional value.

Comprehensive study of the lipid from whelk (Chlorostoma rusticum and Neverita didyma) with emphasis on characterization of phospholipid molecular species by shot-gun strategy

In the present study, an effective shot-gun lipidomic methodology was established to determine the glycerophospholipid (GP) molecular species of two species of edible marine whelks (Chlorostoma rusticum and Neverita didyma). Simultaneously, the lipid content, lipid classes, phospholipid (PL) subclasses and fatty acid compositions were also investigated. Over 210 molecular species of GP including glycerophosphocholine, lysoglycerophosphocholine, glycerophosphoethanolamine, lysoglycerophosphoethanolamine, glycerophosphoserine, lysoglycerophosphoserine, glycerophosphoinositol and lysoglycerophosphoinositol were characterized in the two abovementioned whelk species. The predominant GP molecular species contained n-3 long chain polyunsaturated fatty acid (n-3 LC-PUFA), especially docosahexaenoic acid and eicosapentaenoic acid. Meanwhile, PL (57.70-58.86% of total lipids) and PUFA (21.69-37.68% of total FA) take large proportions in whelk lipids. Among PL, phosphatidylcholine (50.58-52.41 mol%) and phosphatidylethanolamine (27.67-32.73 mol%) were dominant. Therefore, marine whelks turn out to be promising source of n-3 LC-PUFA existed in PL form and thus directly contribute to the health benefits of consumer.

Characterization of glycerophospholipid molecular species in muscles from three species of cephalopods by direct infusion-tandem mass spectrometry

More than 200 molecular species of glycerophospholipids (GP) including glycerophosphocholine (GPC), glycerophosphoethanolamine (GPE), glycerophosphoserine (GPS), lysoglycerophosphocholine (LGPC), lysoglycerophosphoethanolamine (LGPE) and lysoglycerophosphoserine (LGPS), as well as 18 kinds of sphingomyelin (SM) were characterized by using a direct infusion-tandem mass (MS/MS) spectrometry method for lipids from the muscles of cephalopods Sepiella maindroni, Octopus ocellatus and Loligo chinensis for the first time. The majority of the GP molecular species contained long-chain omega-3 polyunsaturated fatty acids (n-3 LC-PUFA), especially eicosapentaenoic acid (EPA) and docosahexaenoic acid (DHA). Therefore, cephalopods can be a good possible source of dietary GP carrying n-3 LC-PUFA. The total lipids were composed of phospholipid (PL, 72.29–83.32 wt% of total lipids), cholesterol (12.70–23.60 wt% of total lipids), triacylglycerol (1.86–2.93 wt% of total lipids), diacylglycerol (0.15–1.09 wt% of total lipids), monoacylglycerol (0.06-0.18 wt% of total lipids) and free fatty acid (0.72–1.86 wt% of total lipids). For PL, phosphatidylcholine (44.47–62.30 mol%), phosphatidylethanolamine (22.57–39.08 mol%), phosphatidylserine (6.15–10.18 mol%), phosphatidylglycerol (0.68–3.11 mol%), phosphatidylinositol (2.41–7.15 mol%) and lysophosphatidylcholine (1.84–5.24 mol%) were detected. Furthermore, the total lipids from the muscles of cephalopods Sepiella maindroni, Octopus ocellatus and Loligo chinensis contained 41.80–50.02 mol% of saturated fatty acids, 11.53–21.54 mol% of monounsaturated fatty acids and 36.67–40.82 mol% of PUFA, whilst DHA (15.25–26.71 mol%) and EPA (6.29–16.57 mol%) were found to account for the majority of the PUFA. With these data presented, cephalopod muscle can be considered as a healthy food for humans.

Impact of Frying on Changes in Clam (Ruditapes philippinarum) Lipids and Frying Oils: Compositional Changes and Oxidative Deterioration

AbstractThe current study shows the compositional changes and oxidation development of clam (Ruditapes philippinarum, R. philippinarum) lipids and frying oils when subjected to different processing conditions. Parameters measured include acid value, peroxide value (POV), thiobarbituric acid‐reactive substances (TBARS), total oxidation (TOTOX), lipid classes, fatty acid composition, phosphatidylcholine (PC), and phosphatidylethanolamine (PE) contents together with major glycerophospholipid (GP) molecular species. Deep‐fat frying increased triacylglycerol (TAG) content and decreased the contents of PC, PE, and GP molecular species in clam in a time‐dependent manner. Meanwhile, minor amounts of free fatty acids, diacylglycerols, monoacylglycerols, and polar lipids were detected in frying oils, indicating lipid migration between the clam and frying oils. The time‐dependent increase of POV, TBARS, and TOTOX in fried clams and frying oils with concurrent reduction of docosahexenoic acid and eicosapentaenoic acid indicates extensive oxidative degradation of clam lipids. Moreover, the moisture‐rich clam aggravated the deterioration of frying oils. Consequently, deep‐fat frying significantly altered the lipid profile and decreased the nutritional value of clams.

Lipidomic analysis of urinary exosomes from hereditary α-tryptasemia patients and healthy volunteers.

Exosomes are nano‐sized vesicles that are involved in various biological processes including cell differentiation, proliferation, signaling, and intercellular communication. Urinary exosomes were isolated from a cohort of hereditary α‐tryptasemia (HαT) patients and from healthy volunteers. There was a greater number of exosomes isolated from the urine in the HαT group compared to the control volunteers. Here, we investigated the differences in both lipid classes and lipid species within urinary exosomes of the two groups. Lipids were extracted from urinary exosomes and subjected to liquid chromatography mass spectrometry using a targeted approach. Various molecular species of glycerophospholipids, glycerolipids, and sterols were significantly reduced in HαT patients. Out of a possible 1127 lipids, 521 lipid species were detected, and relative quantities were calculated. Sixty‐four lipids were significantly reduced in urinary exosomes of HαT patients compared to controls. All significantly reduced sphingolipids and most of the phospholipids were saturated or mono‐unsaturated lipids. These results suggest exosome secretion is augmented in HαT patients and the lipids within these exosomes may be involved in various biological processes. The unique lipid composition of urinary exosomes from HαT patients will contribute to our understanding of the biochemistry of this disease.

Quantitative Fragmentation Model for Bottom-Up Shotgun Lipidomics.

Quantitative bottom-up shotgun lipidomics relies on molecular species-specific “signature” fragments consistently detectable in tandem mass spectra of analytes and standards. Molecular species of glycerophospholipids are typically quantified using carboxylate fragments of their fatty acid moieties produced by higher-energy collisional dissociation of their molecular anions. However, employing standards whose fatty acids moieties are similar, yet not identical, to the target lipids could severely compromise their quantification. We developed a generic and portable fragmentation model implemented in the open-source LipidXte software that harmonizes the abundances of carboxylate anion fragments originating from fatty acid moieties having different sn-1/2 positions at the glycerol backbone, length of the hydrocarbon chain, and number and location of double bonds. The postacquisition adjustment enables unbiased absolute (molar) quantification of glycerophospholipid species independent of instrument settings, collision energy, and employed internal standards.

Seasonal Variation of Proximate Composition and Lipid Nutritional Value of Two Species of Scallops (Chlamys farreri and Patinopecten yessoensis)

The scallops Chlamys farreri and Patinopecten yessoensis from the Yellow Sea are evaluated according to the seasonal changes of lipid nutritional value including lipid classes, phospholipid (PL) classes, fatty acid (FA) composition, atherogenicity index (IA), thrombogenicity index (IT), and glycerophospholipid molecular species, for the first time. More than 32 species of glycerophosphocholine (GPCho) and 42 species of glycerophosphoethanolamine (GPEtn) are determined. For samples harvested in February, the PL molecular species containing eicosapentaenoic acid (EPA) and docosahexaenoic acid (DHA) account for 48.57–50.77% and 80.45–85.50% of total molecular species, respectively, for GPCho and GPEtn. Moreover, the samples harvested in February contain higher levels of polyunsaturated fatty acid (PUFA) (58.76–59.12% of total FA) and PL (84.67–85.11% of total lipids) but lower level of cholesterol (8.77–10.10%) as well as IA (0.29–0.31) and IT (0.12–0.13) compared to samples harvested in other seasons. Therefore considering nutritional value, the lipids from scallops (C. farreri and P. yessoensis) harvested in February have better value in view of commercial exploitation.Practical Application: A systematic and in‐depth investigation on seasonal changes in basic component and lipid nutritional value in adductor muscle of C. farreri and P. yessoensis is reported in this contribution. This useful information makes it possible to use scallop lipid for producing higher value‐added products in view of commercial exploitation.Chlamys farreri and Patinopecten yessoensis from the Yellow Sea are evaluated according to the seasonal changes of lipid qualities including lipid classes, phospholipid classes, fatty acid composition, atherogenicity index, thrombogenicity index, and glycerophospholipid molecular species for the first time. Considering nutritional value, the lipids from scallops (C. farreri and P. yessoensis) harvest in February have better value in view of commercial exploitation.

Lipid Profile and Glycerophospholipid Molecular Species in Two Species of Edible Razor Clams Sinonovacula constricta and Solen gouldi.

Total lipids were extracted from razor clams Sinonovacula constricta and Solen gouldi, and the molecular species of glycerophospholipid (Gpl) including choline glycerophospholipid (ChoGpl), ethanolamine glycerophospholipid (EtnGpl), serine glycerophospholipid (SerGpl), inositol glycerophospholipid (InsGpl), lysoChoGpl, lysoEtnGpl, and lysoSerGpl were characterized using a direct-infusion tandem mass spectrometric method for the first time. Meanwhile, the lipid class composition and phospholipid (PL) class composition as well as the fatty acid (FA) composition of total lipids, triacylglycerol (TAG), and PL were also investigated. About 238 and 235 molecular species were characterized, respectively, in Sinonovacula constricta and Solen gouldi. The majority of the dominant Gpl molecular species contained n-3 long-chain polyunsaturated fatty acids (n-3 LC-PUFA), especially docosahexaenoic acid (DHA) and eicosapentaenoic acid (EPA). Also, razor clam lipids contained a high-proportioned PL (52.19-65.41% of total lipids) and PUFA (47.94-54.81 mol%). Furthermore, PL contained a higher proportion of PUFA (63.05-67.13 mol%), especially DHA (20.04-22.47 mol%) and EPA (16.27-21.46 mol%) than TAG (the corresponding values being 33.73-34.45, 11.95-12.27, and 8.13-0.8.99 mol%, respectively). Meanwhile, phosphatidylcholine (44.38-46.21 mol%) and phosphatidylethanolamine (38.84-39.95 mol%) were dominant among PL. In consideration of the high proportion of PUFA-enriched Gpl, razor clam plays a great role in promoting human health.

Characterization of Glycerophospholipid Molecular Species in Two Species of Arcidaes (Scapharca subcrenata and Scapharca broughtonii)

ABSTRACTIn this study, the molecular species of glycerophosphocholine (GPCho), glycerophosphoethanolamine (GPEtn), glycerophosphoserine (GPSer), glycerophosphatidylinositol (GPIns), lysoglycerophosphocholine (LGPCho), and lysoglycerophosphoethanolamine (LGPEtn) from arcidaes Scapharca subcrenata and Scapharca broughtonii were characterized using direct infusion-tandem mass (shotgun) method for the first time. At least 201 and 303 glycerophospholipid (GP) molecular species were characterized, respectively. Most of the predominant GP molecular species contained polyunsaturated fatty acids (PUFA), mainly eicosapentaenoic acid (EPA) and docosahexaenoic acid (DHA). Meanwhile, the arcidae lipids contained a high proportion of polar lipids (81.57–86.72% of total lipids). Among PL, phosphatidylcholine (30.53–32.04 mol%) and phosphatidylethanolamine (21.48–26.71 mol%) were dominant.

Differential composition of DHA and very-long-chain PUFAs in rod and cone photoreceptors

Long-chain PUFAs (LC-PUFAs; C20-C22; e.g., DHA and arachidonic acid) are highly enriched in vertebrate retina, where they are elongated to very-long-chain PUFAs (VLC-PUFAs; C 28) by the elongation of very-long-chain fatty acids-4 (ELOVL4) enzyme. These fatty acids play essential roles in modulating neuronal function and health. The relevance of different lipid requirements in rods and cones to disease processes, such as age-related macular degeneration, however, remains unclear. To better understand the role of LC-PUFAs and VLC-PUFAs in the retina, we investigated the lipid compositions of whole retinas or photoreceptor outer segment (OS) membranes in rodents with rod- or cone-dominant retinas. We analyzed fatty acid methyl esters and the molecular species of glycerophospholipids (phosphatidylcholine, phosphatidylethanolamine, and phosphatidylserine) by GC-MS/GC-flame ionization detection and ESI-MS/MS, respectively. We found that whole retinas and OS membranes in rod-dominant animals compared with cone-dominant animals had higher amounts of LC-PUFAs and VLC-PUFAs. Compared with those of rod-dominant animals, retinas and OS membranes from cone-dominant animals also had about 2-fold lower levels of di-DHA (22:6/22:6) molecular species of glycerophospholipids. Because PUFAs are necessary for optimal G protein-coupled receptor signaling in rods, these findings suggest that cones may not have the same lipid requirements as rods.

Hydrolysis and oxidation of lipids in mussel Mytilus edulis during cold storage

Change in quality of mussels (Mytilus edulis) meat when stored at 4 °C was evaluated by determining volatile basic nitrogen (TVB-N), peroxide value (POV), thiobarbituric acid reactive substance (TBARS), total oxidation (TOTOX), lipid class, fatty acid (FA), phosphatidylcholine (PC) and phosphatidylcholine (PE) content, and glycerophospholipid (GP) molecular species. After 4 days of storage, the percentages of triacylglycerol and polar lipid as well as the contents of PC, PE and major GP molecular species significantly decreased (P < 0.05), while the percentages of free FA and monoacylglycerol significantly increased (P < 0.05), indicating the hydrolysis of lipids. The increase in activities of phospholipase and lipase during storage suggests that they may contribute to the hydrolysis of lipids. The cold storage also resulted in significantly increased POV, TBARS and TOTOX as well as lipoxygenase activity (P < 0.05) but slightly decreased percentage of polyunsaturated FA (PUFA), indicating the occurrence of lipid oxidation.

Changes in Lipid Profiles of Dried Clams ( Mactra chinensis Philippi and Ruditapes philippinarum) during Accelerated Storage and Prediction of Shelf Life.

To predict the shelf life through an Arrhenius model and evaluate the changes in lipid profiles, two types of dried clams were stored at 50 and 65 °C and collected periodically for analysis. The predicted shelf life values of the two dried clam samples were 530 ± 14 and 487 ± 24 h (24 °C), and the relative errors between the actual and predicted values were 5.7 and 6.8%, respectively. During accelerated storage, the peroxide value, p-anisidine value, thiobarbituric acid-reactive substances value, total oxidation value, acid value, and free fatty acid content all increased, while the levels of triacylglycerol, phosphatidylcholine, phosphatidylethanolamine, major glycerophospholipid molecular species, and polyunsaturated fatty acid (PUFA) decreased. Moreover, content of phospholipid containing PUFA decreased significantly than that of triacylglycerol containing PUFA. Results indicated that the Arrhenius model was suitable for the shelf life prediction of dried clams and accelerated storage caused loss in quality of dried clams in terms of lipids.

Direct infusion mass spectrometric identification of molecular species of glycerophospholipid in three species of edible whelk from Yellow Sea

Whelk has been exploited commercially as a delicacy for a long time. Although previous studies have suggested that whelk might serve as a potential rich source of long chain omega-3 polyunsaturated fatty acids (n-3 LC-PUFA) enriched phospholipid (PL), the molecular species profile of the PL have not been reported yet. In this study, more than 220 molecular species of glycerophospholipid (GP) belonging to eight classes including glycerophosphocholine, glycerophosphoethanolamine, glycerophosphoserine, glycerophosphoinositol, lysoglycerophosphocholine, lysoglycerophosphoethanolamine, lysoglycerophosphoserine and lysoglycerophosphoinositol in three species of edible whelks (Buccinium yokomaruae, Neptunea arthritica cumingi Cosse and Volutharpa ampullaceal) were identified for the first time by using direct infusion tandem mass spectrometric method. Most of the predominant GP molecular species contained n-3 LC-PUFA, especially eicosapentaenoic acid (EPA) and docosahexaenoic acid (DHA). Meanwhile, the whelk lipids contained a high proportion of PL (32.92–55.55% of total lipids) and PUFA (30.45–41.42% of total FA). Among PL, phosphatidylcholine (44.18–65.49mol%) was dominant.

Lipid profiles in different parts of two species of scallops (Chlamys farreri and Patinopecten yessoensis)

Different classes of lipids and phospholipids (PL) as well as fatty acid (FA) compositions, and glycerophospholipid (GP) molecular species in edible parts (adductor muscles) and by-products (gonads and mantles) of scallops Patinopecten yessoensis and Chlamys farreri were characterized. The lipids contained high levels of polyunsaturated FA (PUFA) (20.44–58.81% of total FAs) and PL (54.99–78.26% of total lipids). Among PL, phosphatidylcholine (41.39–51.86 mol%) was dominant. More than 230 GP species belonging to glycerophosphocholine, glycerophosphoethanolamine, glycerophosphoserine, glycerophosphoinositol, lysoglycerophosphocholine, lysoglycerophosphoethanolamine and lysoglycerophosphoinositol were characterized. Individual GP molecular species in different body parts of scallops were also partially quantified. Most of the dominant GP species contained PUFA, especially eicosapentaenoic acid (EPA, 20:5n-3) and docosahexaenoic acid (DHA, 22:6n-3). Considering the high level of PUFA enriched GP, edible parts and by-products (gonads and mantles) of scallops Patinopecten yessoensis and Chlamys farreri provide great potential as health-promoting food for human consumption.

Characterization of lipids in three species of sea urchin

Sea urchin gonad has been regarded as a “healthy” food. Although previous studies have suggested that sea urchin gonad might serve as a potential rich source of long chain omega-3 polyunsaturated fatty acids (n-3 LC-PUFA) enriched phospholipid (PL), the molecular species profile of its PL has rarely been reported. In this study, about 200 molecular species of glycerophospholipid (GP), including glycerophosphocholine, glycerophosphoethanolamine, glycerophosphoserine, glycerophosphoinositol, lysoglycerophosphocholine and lysoglycerophosphoethanolamine, in gonads from three species of sea urchin (Glyptocidaris crenularis, Strongylocentrotus intermedius and Strongylocentrotus nudus) were characterized using tandem mass spectrometry. Most of the predominant GP molecular species contained PUFA, especially eicosapentaenoic acid (EPA). Meanwhile, the sea urchin lipids contained a high proportion of PL (39.45–50.30% of total lipids) and PUFA (34.47–46.56% of total FA). Among PL, phosphatidylcholine (67.88–72.58mol%) was dominant. Considering the high level of PUFA enriched GP, sea urchin gonads provide great potential as health-promoting food for human consumption.

Extraction and detailed characterization of phospholipid-enriched oils from six species of edible clams

Phospholipid (PL)-enriched oils were recovered from six species of edible clams, namely Cyclina sinensis, Mactra chinensis Philippi, Mactra veneriformis Reeve, Meretrix meretrix, Ruditapes phliippinarum and Saxidomus purpurata, using a mixture of ethanol and hexane (1:1, v/v). The oils contained a high proportion of polyunsaturated fatty acids (PUFA) (26.78–45.36% of total FAs), especially eicosapentaenoic acid (EPA) (8.17–10.48% of total FAs) and docosahexaenoic acid (DHA) (7.83–21.34% of total FAs). The oils also contained a high percentage of PL (39.86–74.05% of total lipids). Among PL, phosphatidylcholine (37.40–52.19mol%) and phosphatidylethanolamine (34.74–43.10mol%) were dominant. At least 435, 442, 513, 438, 433 and 437 glycerophospholipid (GP) molecular species were characterized, respectively, in lipids from Cyclina sinensis, Mactra chinensis Philippi, Mactra veneriformis Reeve, Meretrix meretrix, Ruditapes phliippinarum and Saxidomus purpurata. Most of the predominant GP molecular species contained PUFA, mainly EPA and DHA, indicating that clam is a potential resource of PUFA enriched GP.

Metabolic Heavy Isotope Labeling to Study Glycerophospholipid Homeostasis of Cultured Cells

Glycerophospholipids consist of a glycerophosphate backbone to which are esterified two acyl chains and a polar head group. The head group (e.g., choline, ethanolamine, serine or inositol) defines the glycerophospholipid class, while the acyl chains together with the head group define the glycerophospholipid molecular species. Stable heavy isotope (e.g., deuterium)-labeled head group precursors added to the culture medium incorporate efficiently into glycerophospholipids of mammalian cells, which allows one to determine the rates of synthesis, acyl chain remodeling or turnover of the individual glycerophospholipids using mass spectrometry. This protocol describes how to study the metabolism of the major mammalian glycerophospholipids i.e., phosphatidylcholines, phosphatidylethanolamines, phosphatidylserines and phosphatidylinositols with this approach.