Crabs Eriocheir japonica and Paralithodes camtschaticus Are a Rich Source of Lipid Molecular Species with High Nutritional Value.

Due to their valuable meat and hepatopancreas, the world's most famous delicacies, crabs, have become target species of commercial fisheries and aquaculture. By methods of supercritical fluid and high-performance liquid chromatography, coupled with high resolution mass spectrometry, we analyzed triacylglycerols (TG) and phospholipids (PL)-glycerophosphoethanolamines (PE), glycerophosphocholines (PC), glycerophosphoserines (PS), and glycerophosphoinositols (PI)-in the hepatopancreas and muscles of the Japanese mitten crab Eriocheir japonica and the red king crab Paralithodes camtschaticus inhabiting the Sea of Japan. TGs were the main class of lipids in the crab hepatopancreas, while they were found in trace amounts in muscle. TGs of E. japonica differed from those of P. camtschaticus by a higher content of 16:0, 16:1, 18:2, and 20:4 FA and a lower content of eicosapentaenoic and docosahexaenoic acids. The Japanese mitten crab differed from the red king crab by a lower content of molecular species with eicosapentaenoic acid in PC and PI; an increased content of arachidonic acid in PE, PS, and PI; and a lower content of molecular species with docosahexaenoic acid in PE in the hepatopancreas and muscles. The high nutritional value of the crabs E. japonica and P. camtschaticus was confirmed by a high content of molecular species of lipids with n-3 polyunsaturated fatty acids. The data of the lipid molecular species profile provide new background information for future studies on biochemistry and aquaculture of crabs.

Protective Properties of Marine Alkyl Glycerol Ethers in Chronic Stress.

In this paper we discuss the effect of alkyl glycerol ethers (AGs) from the squid Berryteuthis magister on a chronic stress model in rats. The study was performed on 32 male Wistar rats. Animals received AGs at a dose of 200 mg/kg through a gavage for six weeks (1.5 months), and were divided into four groups: group 1 (control), group 2 (animals received AGs), group 3 (stress control), group 4 (animals received AGs and were subjected to stress). Chronic immobilization stress was induced by placing each rat into an individual plexiglass cages for 2 h daily for 15 days. The serum lipid spectrum was evaluated by the content of total cholesterol, triglycerides, high-density lipoprotein cholesterol, low lipoprotein cholesterol and very low-density lipoprotein cholesterol. The atherogenic coefficient was calculated. The hematological parameters of peripheral blood were evaluated. The neutrophil-lymphocyte ratio was counted. The levels of cortisol and testosterone in blood plasma were determined. AGs at the selected dose did not have a significant effect on the body weight of rats in the preliminary period of the experiment. Under stress, the body weight gain, the concentrations of very low-density lipoprotein cholesterol and blood triglycerides decreased significantly. The neutrophil-lymphocyte ratio in animals treated with AGs shifted towards lymphocytes. A favorable increase in the percentage of lymphocytes was found in the stressed group of animals treated with AGs. So, for the first time, it was found that AGs prevent stress-induced suppression of the immune system. This confirms the benefit of AGs for the immune system under chronic stress. Our results prove the efficiency of the use of AGs for treating chronic stress, a serious social problem in modern society.

The Phospholipid Molecular Species Profile of Apostichopus japonicus Tissues Modifies through Exposure to n-3 Polyunsaturated Fatty Acid-Deficient Diet.

The sea cucumber Apostichopus japonicus, being a target species of commercial fisheries and aquaculture, is also used as a source of biologically active compounds with high pharmacological potential. By the methods of high-performance liquid chromatography with high resolution mass spectrometry, we analyzed the major structural phospholipids (PL)-glycerophosphoethanolamines (PE), glycerophosphocholines (PC), glycerophosphoserines (PS), and glycerophosphoinositols (PI)-in tissues of wild and cultured sea cucumbers. The intestines of the wild and cultured animals differed from the other tissues by an elevated content of molecular species of PE, PC, and PS with 22:6n-3 fatty acid. The respiratory trees of the studied animals contained a high level of odd-chain PI and PI with 20:4n-6. The exposure to n-3 PUFA-deficient diet resulted in substantial changes in the molecular species profile of PL of the wild and cultured animals. The cultured sea cucumbers showed a significant decrease in the 20:5n-3 content in all four studied PL classes. A replacement of 20:5n-3 by 20:4n-6 occurred in PE, PC, and PI. The decrease in the level of molecular species of PS with 20:5n-3 was compensated by an increase in the level of monounsaturated long-chain PS. The diet of cultured sea cucumbers is a crucial factor for enhancing the nutritional properties of the product obtained from them.

Coral Holobionts Possess Distinct Lipid Profiles That May Be Shaped by Symbiodiniaceae Taxonomy.

Symbiotic relationships are very important for corals. Abiotic stressors cause the acclimatization of cell membranes in symbionts, which possess different membrane acclimatization strategies. Membrane stability is determined by a unique lipid composition and, thus, the profile of thylakoid lipids can depend on coral symbiont species. We have analyzed and compared thylakoid lipidomes (mono- and digalactosyldiacylglycerols (MGDG and DGDG), sulfoquinovosyldiacylglycerols (SQDG), and phosphatidylglycerols (PG)) of crude extracts from symbiotic reef-building coral Acropora sp., the hydrocoral Millepora platyphylla, and the octocoral Sinularia flexibilis. S. flexibilis crude extracts were characterized by a very high SQDG/PG ratio, a DGDG/MGDG ratio < 1, a lower degree of galactolipid unsaturation, a higher content of SQDG with polyunsaturated fatty acids, and a thinner thylakoid membrane which may be explained by the presence of thermosensitive dinoflagellates Cladocopium C3. In contrast, crude extracts of M. platyphylla and Acropora sp. exhibited the lipidome features of thermotolerant Symbiodiniaceae. M. platyphylla and Acropora sp. colonies contained Cladocopium C3u and Cladocopium C71/C71a symbionts, respectively, and their lipidome profiles showed features that indicate thermotolerance. We suggest that an association with symbionts that exhibit the thermotolerant thylakoid lipidome features, combined with a high Symbiodiniaceae diversity, may facilitate further acclimatization/adaptation of M. platyphylla and Acropora sp. holobionts in the South China Sea.

Current Progress in Lipidomics of Marine Invertebrates.

Marine invertebrates are a paraphyletic group that comprises more than 90% of all marine animal species. Lipids form the structural basis of cell membranes, are utilized as an energy reserve by all marine invertebrates, and are, therefore, considered important indicators of their ecology and biochemistry. The nutritional value of commercial invertebrates directly depends on their lipid composition. The lipid classes and fatty acids of marine invertebrates have been studied in detail, but data on their lipidomes (the profiles of all lipid molecules) remain very limited. To date, lipidomes or their parts are known only for a few species of mollusks, coral polyps, ascidians, jellyfish, sea anemones, sponges, sea stars, sea urchins, sea cucumbers, crabs, copepods, shrimp, and squid. This paper reviews various features of the lipid molecular species of these animals. The results of the application of the lipidomic approach in ecology, embryology, physiology, lipid biosynthesis, and in studies on the nutritional value of marine invertebrates are also discussed. The possible applications of lipidomics in the study of marine invertebrates are considered.

Physiological processes and lipidome dynamics in the soft coral Sinularia heterospiculata under experimental bleaching.

Coral polyps host intracellular symbiotic dinoflagellates (SD). The loss of SD (referred as bleaching) under stressful environmental conditions is the main reason of coral reef destruction, and therefore, intensively studied over the world. Lipids are the structural base of biomembranes and energy reserve of corals and are directly involved in the coral bleaching. In order to establish a relationship between coral tissue morphology, physiological processes and lipidome dynamics during bleaching, the soft coral Sinularia heterospiculata was exposed to experimental heat stress (33 °C) for 72 h. A chlorophyll content, structure of cells, the level of reactive oxygen species (ROS), and molecular species of storage and structural lipids were analyzed. After 24 h of heat exposure, the level of ROS-positive SD cells did not increase, but the host tissues lost a significant part of SD. The removal of SD cells by exocytosis were suggested. Exocytosis was presumed to prevail at earlier stages of the soft coral bleaching. Symbiophagosomes with degenerative SD were observed in the stressed coral host cells. After 24 h, the content of phosphatidylinositols, which involved in apoptosis and autophagy, was significantly decreased. The innate immune response was triggered, and SD were digested by the coral host. After 48 h, a degradation of SD chloroplasts and a decrease in the specific monogalactosyldiacylglycerol molecular species were detected that confirmed a disruption of lipid biosynthesis in chloroplasts. At the end of coral bleaching, the appearance of oxidized phosphatidylethanolamines, indicating damage to the host membranes, and the degradation of the coral tissues were simultaneously observed. Thus, a switch between dominant mechanisms of the SD loss during bleaching of S. heterospiculata was found and proved by certain variations of the lipidomic profile. Lipidomic parameters may become indicators of physiological processes occurring in the symbiotic coral organism and may be used for assessing anthropogenic or natural destructive effects on coral reefs.

Chemical Diversity of Soft Coral Steroids and Their Pharmacological Activities.

The review is devoted to the chemical diversity of steroids produced by soft corals and their determined and potential activities. There are about 200 steroids that belong to different types of steroids such as secosteroids, spirosteroids, epoxy- and peroxy-steroids, steroid glycosides, halogenated steroids, polyoxygenated steroids and steroids containing sulfur or nitrogen heteroatoms. Of greatest interest is the pharmacological activity of these steroids. More than 40 steroids exhibit antitumor and related activity with a confidence level of over 90 percent. A group of 32 steroids shows anti-hypercholesterolemic activity with over 90 percent confidence. Ten steroids exhibit anti-inflammatory activity and 20 steroids can be classified as respiratory analeptic drugs. Several steroids exhibit rather rare and very specific activities. Steroids exhibit anti-osteoporotic properties and can be used to treat osteoporosis, as well as have strong anti-eczemic and anti-psoriatic properties and antispasmodic properties. Thus, this review is probably the first and exclusive to present the known as well as the potential pharmacological activities of 200 marine steroids.

N-Docosahexaenoylethanolamine Attenuates Neuroinflammation and Improves Hippocampal Neurogenesis in Rats with Sciatic Nerve Chronic Constriction Injury.

Chronic neuropathic pain is a condition that causes both sensory disturbances and a variety of functional disorders, indicating the involvement of various brain structures in pain pathogenesis. One of the factors underlying chronic neuropathic pain is neuroinflammation, which is accompanied by microglial activation and pro-inflammatory factor release. N-docosahexaenoylethanolamine (DHEA, synaptamide) is an endocannabinoid-like metabolite synthesized endogenously from docosahexaenoic acid. Synaptamide exhibits anti-inflammatory activity and improves neurite outgrowth, neurogenesis, and synaptogenesis within the hippocampus. This study aims to evaluate the effects of synaptamide obtained by the chemical modification of DHA, extracted from the Far Eastern raw material Berryteuthis magister on neuroinflammatory response and hippocampal neurogenesis changes during neuropathic pain. The study of microglial protein and cytokine concentrations was performed using immunohistochemistry and ELISA. The brain lipid analysis was performed using the liquid chromatography-mass spectrometry technique. Behavioral experiments showed that synaptamide prevented neuropathic pain-associated sensory and behavioral changes, such as thermal allodynia, impaired locomotor activity, working and long-term memory, and increased anxiety. Synaptamide attenuated microglial activation, release of proinflammatory cytokines, and decrease in hippocampal neurogenesis. Lipid analysis revealed changes in the brain N-acylethanolamines composition and plasmalogen concentration after synaptamide administration. In conclusion, we show here that synaptamide may have potential for use in preventing or treating neuropathic cognitive pain and emotional effects.

Protective action of alkylglycerols under stress.

The adaptogenic properties of alkylglycerols (AGs) after 1 month's treatment were investigated in a rat model of acute immobilization stress (AIS). The animals receiving AGs 157 mg/kg showed a body weight (BW) decrease in addition to a more pronounced increase in the adrenal glands index under stress conditions. Also, AGs at this dose prevented AIS-induced catalase inhibition. In addition, antiulcerative AG effects were already detected at a dose of 15 mg/kg. The data indicate that AGs promote adrenal gland activation in AIS. At the same time, AGs neutralize some of negative effects of stressful conditions, which include restoration of the oxidation-reduction balance, reduction of gastric mucosal stress lesion formation.LAY SUMMARYThe effect of alkylglycerols, ether lipids from marine organisms, was studied in stressed animals. AGs have antioxidant activity and can be useful in the complex therapy of stomach lesions.

1-O-alkylglycerols from the hepatopancreas of the crab Paralithodes camtschaticus, liver of the squid Berryteuthis magister, and liver of the skate Bathyraja parmifera, and their anticancer activity on human melanoma cells.

1-O-alkylglycerols (AKG) are a class of natural ether lipids derived from 1-O-alkyl-2,3-diacyl-sn-glycerols by deacylation. In this study, 1-O-alkylglycerol (AKG) composition was investigated in the hepatopancreas lipids of the crab Paralithodes camtschaticus and the liver lipids of the squid Berryteuthis magister and the skate  Bathyraja parmifera. One of the principal AKG in marine organisms was 1-O-hexadecyl-sn-glycerol (AKG 16:0). To assess AKG influence on melanoma, we evaluated the cytotoxicity and antiproliferative actions of natural AKG 16:0 and synthetic 1-O-octyl-sn-glycerol (AKG 8:0) on three human melanoma cell lines SK-Mel-5, SK-Mel-28, and RPMI-7951. Natural AKG 16:0 in concentration up to 20 µM was not toxic to all cell lines. AKG 8:0 showed no toxicity to cells SK-Mel-5 and SK-Mel-28 in concentrations up to 20 µM but had moderate cytotoxicity to RPMI-7951 cells with an IC50 of 13 µM. Both investigated substances inhibited the proliferation, formation, and growth of cell colonies of RPMI-7951. PRACTICAL APPLICATIONS: AKG exhibit a variety of biological activities, including anticancer effects. In this study, the liver lipids of the skate B. parmifera and the hepatopancreas lipids of crab P. camtschaticus were shown to be sources of AKG. Our data showed that AKG can be used to prevent the formation of new colonies of malignant cells in combination therapy against melanoma. The results will be useful for future studies involving marine ether lipids and the examination of their anticancer properties against malignant cells.

Adult hippocampal neurogenesis in neuropathic pain and alkyl glycerol ethers treatment.

Neuropathic pain manifested by a number of sensory symptoms is often accompanied by disorders of higher nervous activity, such as memory impairment, depression, anxiety, anhedonia, etc. This emphasizes the involvement of supraspinal structures including the hippocampus in neuropathic pain pathogenesis. In the present study, we focused on the impact of chronic neuropathic pain on hippocampal neurogenesis and microglial state. In addition, we test the effect of alkyl glycerol ethers on hippocampal neuronal and microglial plasticity as well as behavioral parameters. Neuropathic pain was induced using the model of sciatic nerve chronic constriction injury. We found an impairment of working memory and locomotor activity in animals with neuropathic pain, which was prevented by alkyl glycerol ethers treatment. Sciatic nerve ligation in mice contributed to the decrease in hippocampal neurogenesis intensity. Alkyl glycerol ethers administration significantly reduced this effect. Neuropathic pain-associated neurogenesis reduction was accompanied by an increased percentage of Iba1-labeled area in the CA1 hippocampal region on the 14th and 28th days after surgery. In addition, we observed a decrease in hippocampal pro-inflammatory microglia marker CD86 immunostaining on day 28 after surgery in alkyl glycerol ethers-treated mice with sciatic nerve ligation. These results are consistent with data on pro- and anti-inflammatory cytokines expression in the hippocampus. Alkyl glycerol ethers administration increased IL-10 and decreased IL-1ß hippocampal expression in animals with neuropathic pain. Taken together, these data suggest that neuropathic pain-behavior in rodents is accompanied by changes in microglia polarization, thereby contributing to neurogenesis impairment and cognitive disturbances. Alkyl glycerol ethers prevented M1 microglial activation, contributing to the maintenance of normal neurogenesis levels within the hippocampus and normalizing working memory.

Identification of molecular species of monoalkyldiacylglycerol from the squid Berryteuthis magister using liquid chromatography-APCI high-resolution mass spectrometry.

Monoalkyldiacylglycerol (MADAG) is an important lipid class in mollusks, corals, starfishes, and some species of zooplankton. Up to 80% of liver oils of squids and sharks are comprised of MADAG. Except for one fish species, there are no data on the composition of MADAG molecular species of marine organisms. The molecular species of MADAG obtained from digestive glands of the deep-sea squid Berryteuthis magister were identified. High-performance liquid chromatography (HPLC) and tandem high-resolution mass spectrometry (HRMS) with atmospheric pressure chemical ionization (APCI) were applied. The mass spectra of each molecular species contained positive quasi-molecular ion [M+H]+ with fragment ions [M-R'CO2]+, [M-R''CO2]+, and [M-OR''']+, as well as negative cluster ion [M+2H2OH]- without fragments. The exact masses of the negative ions allowed determination of the molecular formulas and the number of double bonds; the positive fragment ions were used to determine the location of acyl and alkyl groups in MADAG molecules. Ninety molecular species of MADAG were revealed. The regiospecific composition was identified for 72 individual molecular species. Eleven pairs of positional isomers of acyl groups were found. Four molecular ions were produced by a mixture of acyl/alkyl isomers. Most of molecular species contained 16:0e or 18:1e alkyl groups in the sn-1 position, whereas polyunsaturated fatty acids mainly esterified the sn-2 position of MADAG from B. magister. These structural features are supposed to be characteristic for biologically active MADAG.