Improvement of Blood Plasmalogens and Clinical Symptoms in Parkinson's Disease by Oral Administration of Ether Phospholipids: A Preliminary Report

The sphingosine 1-phosphate analogue, FTY720, modulates the lipidomic signature of the mouse hippocampus

The small-molecule drug, FTY720 (fingolimod), is a synthetic sphingosine 1-phosphate (S1P) analogue currently used to treat relapsing-remitting multiple sclerosis in both adults and children. FTY720 can cross the blood-brain barrier (BBB) and, over time, accumulate in lipid-rich areas of the central nervous system (CNS) by incorporating into phospholipid membranes. FTY720 has been shown to enhance cell membrane fluidity, which can modulate the functions of glial cells and neuronal populations involved in regulating behaviour. Moreover, direct modulation of S1P receptor-mediated lipid signalling by FTY720 can impact homeostatic CNS physiology, including neurotransmitter release probability, the biophysical properties of synaptic membranes, ion channel and transmembrane receptor kinetics, and synaptic plasticity mechanisms. The aim of this study was to investigate how chronic FTY720 treatment alters the lipid composition of CNS tissue in adolescent mice at a key stage of brain maturation. We focused on the hippocampus, a brain region known to be important for learning, memory, and the processing of sensory and emotional stimuli. Using mass spectrometry-based lipidomics, we discovered that FTY720 increases the fatty acid chain length of hydroxy-phosphatidylcholine (PCOH) lipids in the mouse hippocampus. It also decreases PCOH monounsaturated fatty acids (MUFAs) and increases PCOH polyunsaturated fatty acids (PUFAs). A total of 99 lipid species were up-regulated in the mouse hippocampus following 3 weeks of oral FTY720 exposure, whereas only 3 lipid species were down-regulated. FTY720 also modulated anxiety-like behaviours in young mice but did not affect spatial learning or memory formation. Our study presents a comprehensive overview of the lipid classes and lipid species that are altered in the hippocampus following chronic FTY720 exposure and provides novel insight into cellular and molecular mechanisms that may underlie the therapeutic or adverse effects of FTY720 in the central nervous system.

Chronic inflammation, neuroglial dysfunction, and plasmalogen deficiency as a new pathobiological hypothesis addressing the overlap between post-COVID-19 symptoms and myalgic encephalomyelitis/chronic fatigue syndrome

After five waves of coronavirus disease 2019 (COVID-19) outbreaks, it has been recognized that a significant portion of the affected individuals developed long-term debilitating symptoms marked by chronic fatigue, cognitive difficulties ("brain fog"), post-exertional malaise, and autonomic dysfunction. The onset, progression, and clinical presentation of this condition, generically named post-COVID-19 syndrome, overlap significantly with another enigmatic condition, referred to as myalgic encephalomyelitis/chronic fatigue syndrome (ME/CFS). Several pathobiological mechanisms have been proposed for ME/CFS, including redox imbalance, systemic and central nervous system inflammation, and mitochondrial dysfunction. Chronic inflammation and glial pathological reactivity are common hallmarks of several neurodegenerative and neuropsychiatric disorders and have been consistently associated with reduced central and peripheral levels of plasmalogens, one of the major phospholipid components of cell membranes with several homeostatic functions. Of great interest, recent evidence revealed a significant reduction of plasmalogen contents, biosynthesis, and metabolism in ME/CFS and acute COVID-19, with a strong association to symptom severity and other relevant clinical outcomes. These bioactive lipids have increasingly attracted attention due to their reduced levels representing a common pathophysiological manifestation between several disorders associated with aging and chronic inflammation. However, alterations in plasmalogen levels or their lipidic metabolism have not yet been examined in individuals suffering from post-COVID-19 symptoms. Here, we proposed a pathobiological model for post-COVID-19 and ME/CFS based on their common inflammation and dysfunctional glial reactivity, and highlighted the emerging implications of plasmalogen deficiency in the underlying mechanisms. Along with the promising outcomes of plasmalogen replacement therapy (PRT) for various neurodegenerative/neuropsychiatric disorders, we sought to propose PRT as a simple, effective, and safe strategy for the potential relief of the debilitating symptoms associated with ME/CFS and post-COVID-19 syndrome.

Ethanolamine plasmalogens derived from whale brain stimulate both follicle-stimulating hormone and luteinizing hormone secretion by bovine gonadotrophs

Ethanolamine plasmalogens (EPls) are the only known ligands of a novel receptor, G protein-coupled receptor 61, and bovine brain EPls stimulate follicle-stimulating hormone (FSH) but not luteinizing hormone (LH), secreted by bovine gonadotrophs. We hypothesized that the brain EPls of whales (Balaenoptera edeni), another Cetartiodactyla with at least twice the lifespan of bovines, could stimulate FSH secretion by gonadotrophs. To test this hypothesis, bovine gonadotrophs (from approximately 2-year-old Japanese Black heifers) were cultured for 3.5 days and treated with increasing concentrations of brain EP1s from whales (approximately 22 years old). FSH and LH secretion was stimulated by all tested concentrations of whale EPls (p < 0.05). To clarify the important differences between bovine and whale EPls, we utilized two-dimensional liquid chromatography-mass spectrometry, which revealed 35 peaks. Among them, we observed significant differences between 12 EPl molecular species. Additionally, we identified differentially expressed genes for enzymes involved in EPl synthesis or degradation in the hypothalamus of young heifers and old cows (approximately 10 years old) as compared to whales (approximately 28 years old) via deep sequencing of the transcriptome. We conclude that whale brains contain unique EPls that stimulate both FSH and LH secretion by bovine gonadotrophs.

Plasmalogens inhibit neuroinflammation and promote cognitive function

Neuroinflammation (NF) is defined as the activation of brain glial cells that are found in neurodegenerative diseases including Alzheimer's disease (AD). It has been known that an increase in NF could reduce the memory process in the brain but the key factors, associated with NF, behind the dysregulation of memory remained elusive. We previously reported that the NF and aging processes reduced the special phospholipids, plasmalogens (Pls), in the murine brain by a mechanism dependent on the activation of transcription factors, NF-kB and c-MYC. A similar mechanism has also been found in postmortem human brain tissues with AD pathologies and in the AD model mice. Recent evidence showed that these phospholipids enhanced memory and reduced neuro-inflammation in the murine brain. Pls can stimulate the cellular signaling molecules, ERK and Akt, by activating the membrane-bound G protein-coupled receptors (GPCRs). Therefore, recent findings suggest that plasmalogens could be one of the key phospholipids in the brain to enhance memory and inhibit NF.

The physiological functions of human peroxisomes

Peroxisomes are subcellular organelles that play a central role in human physiology by catalyzing a range of unique metabolic functions. The importance of peroxisomes for human health is exemplified by the existence of a group of usually severe diseases caused by an impairment in one or more peroxisomal functions. Among others these include the Zellweger spectrum disorders, X-linked adrenoleukodystrophy, and Refsum disease. To fulfill their role in metabolism, peroxisomes require continued interaction with other subcellular organelles including lipid droplets, lysosomes, the endoplasmic reticulum, and mitochondria. In recent years it has become clear that the metabolic alliance between peroxisomes and other organelles requires the active participation of tethering proteins to bring the organelles physically closer together, thereby achieving efficient transfer of metabolites. This review intends to describe the current state of knowledge about the metabolic role of peroxisomes in humans, with particular emphasis on the metabolic partnership between peroxisomes and other organelles and the consequences of genetic defects in these processes. We also describe the biogenesis of peroxisomes and the consequences of the multiple genetic defects therein. In addition, we discuss the functional role of peroxisomes in different organs and tissues and include relevant information derived from model systems, notably peroxisomal mouse models. Finally, we pay particular attention to a hitherto underrated role of peroxisomes in viral infections.

Transient Ca2+ entry by plasmalogen-mediated activation of receptor potential cation channel promotes AMPK activity

Ethanolamine-containing alkenyl ether glycerophospholipids, plasmalogens, are major cell membrane components of mammalian cells that activate membrane protein receptors such as ion transporters and G-protein coupled receptors. However, the mechanism by which plasmalogens modulate receptor function is unknown. Here, we found that exogenously added plasmalogens activate transient receptor potential cation channel subfamily C member 4 (TRPC4) to increase Ca²⁺ influx, followed by calcium/calmodulin-dependent protein kinase 2-mediated phosphorylation of AMP-activated protein kinase (AMPK). Upon topical application of plasmalogens to the skin of mice, AMPK activation was observed in TRPC4-expressing hair bulbs and hair follicles. Here, TRPC4 was co-localized with the leucine-rich repeat containing G protein-coupled receptor 5, a marker of hair-follicle stem cells, leading to hair growth. Collectively, this study indicates that plasmalogens could function as gate openers for TRPC4, followed by activating AMPK, which likely accelerates hair growth in mice.

Protective Effects of Fish (Alaska Pollock) Protein Intake against Short-Term Memory Decline in Senescence-Accelerated Mice

Dietary fish intake has proven to have health benefits in humans. n-3 polyunsaturated fatty acids (PUFAs) in fish oil (FO), especially, may provide protection against age-related cognitive disorders. Owing to the unique benefits of n-3 PUFAs, other nutrients, such as fish protein (FP), have not been well studied. To clarify the effects of FO and FP on brain function, we investigated whether FO or FP feeding can prevent age-related cognitive dysfunction in senescence-accelerated mouse-prone 10 (SAMP10) mice. The FP group maintained a better working memory compared to the control and FO groups in the Y-maze test, but not episodic memory in the novel object recognition test. To evaluate demyelination levels, we measured neurofilament H (NfH) and myelin basic protein (MBP) immunoreactivity in the hippocampus (Hipp). Axon morphology was maintained in the FP group, but not in the control and FO groups. Additionally, the percentage of positive area for double-staining with NfH/MPB was significantly higher in the Hipp of FP-fed mice than in the control (p < 0.05). These results suggest that FP intake prevents age-related cognitive dysfunction by maintaining axonal morphology in the Hipp of SAMP10 mice.

Vitamin B12 Attenuates Changes in Phospholipid Levels Related to Oxidative Stress in SH-SY5Y Cells

Oxidative stress is closely linked to Alzheimer’s disease (AD), and is detected peripherally as well as in AD-vulnerable brain regions. Oxidative stress results from an imbalance between the generation and degradation of reactive oxidative species (ROS), leading to the oxidation of proteins, nucleic acids, and lipids. Extensive lipid changes have been found in post mortem AD brain tissue; these changes include the levels of total phospholipids, sphingomyelin, and ceramide, as well as plasmalogens, which are highly susceptible to oxidation because of their vinyl ether bond at the sn-1 position of the glycerol-backbone. Several lines of evidence indicate that a deficiency in the neurotropic vitamin B12 is linked with AD. In the present study, treatment of the neuroblastoma cell line SH-SY5Y with vitamin B12 resulted in elevated levels of phosphatidylcholine, phosphatidylethanolamine, sphingomyelin, and plasmalogens. Vitamin B12 also protected plasmalogens from hydrogen peroxide (H₂O₂)-induced oxidative stress due to an elevated expression of the ROS-degrading enzymes superoxide-dismutase (SOD) and catalase (CAT). Furthermore, vitamin B12 elevates plasmalogen synthesis by increasing the expression of alkylglycerone phosphate synthase (AGPS) and choline phosphotransferase 1 (CHPT1) in SH-SY5Y cells exposed to H₂O₂-induced oxidative stress.

NADPH and Mitochondrial Quality Control as Targets for a Circadian-Based Fasting and Exercise Therapy for the Treatment of Parkinson's Disease

Dysfunctional mitochondrial quality control (MQC) is implicated in the pathogenesis of Parkinson's disease (PD). The improper selection of mitochondria for mitophagy increases reactive oxygen species (ROS) levels and lowers ATP levels. The downstream effects include oxidative damage, failure to maintain proteostasis and ion gradients, and decreased NAD⁺ and NADPH levels, resulting in insufficient energy metabolism and neurotransmitter synthesis. A ketosis-based metabolic therapy that increases the levels of (R)-3-hydroxybutyrate (BHB) may reverse the dysfunctional MQC by partially replacing glucose as an energy source, by stimulating mitophagy, and by decreasing inflammation. Fasting can potentially raise cytoplasmic NADPH levels by increasing the mitochondrial export and cytoplasmic metabolism of ketone body-derived citrate that increases flux through isocitrate dehydrogenase 1 (IDH1). NADPH is an essential cofactor for nitric oxide synthase, and the nitric oxide synthesized can diffuse into the mitochondrial matrix and react with electron transport chain-synthesized superoxide to form peroxynitrite. Excessive superoxide and peroxynitrite production can cause the opening of the mitochondrial permeability transition pore (mPTP) to depolarize the mitochondria and activate PINK1-dependent mitophagy. Both fasting and exercise increase ketogenesis and increase the cellular NAD⁺/NADH ratio, both of which are beneficial for neuronal metabolism. In addition, both fasting and exercise engage the adaptive cellular stress response signaling pathways that protect neurons against the oxidative and proteotoxic stress implicated in PD. Here, we discuss how intermittent fasting from the evening meal through to the next-day lunch together with morning exercise, when circadian NAD⁺/NADH is most oxidized, circadian NADP⁺/NADPH is most reduced, and circadian mitophagy gene expression is high, may slow the progression of PD.

Orally Administered Plasmalogens Alleviate Negative Mood States and Enhance Mental Concentration: A Randomized, Double-Blind, Placebo-Controlled Trial

Background: Plasmalogens have been shown to improve neurodegenerative pathology and cognitive function. We hypothesized that plasmalogens work in small amounts as a kind of hormone interacting with a G protein-coupled receptor, and then explored the effects of scallop-derived purified plasmalogens on psychobehavioral conditions in a randomized placebo-controlled trial of college athletes in Japan.

Methods and materials: Eligible participants were male students aged 18–22 years who belonged to university athletic clubs. They were randomly allocated to either plasmalogen (2 mg per day) or placebo treatment of 4 weeks’ duration. The primary outcome was the T-score of the Profile of Mood States (POMS) 2–Adult Short, and the secondary outcomes included the seven individual scales of the POMS 2, other psychobehavioral measures, physical performance, and laboratory measurements. The trial was registered at the Japan Registry of Clinical Trials (jRCTs071190028).

Results: Forty participants (20 in the plasmalogen group and 20 in the placebo group) completed the 4-week treatment. The Total Mood Disturbance (TMD) score of the plasmalogen group showed a greater decrease at 4 weeks than that of the placebo group while the between-group difference was marginally significant (p = 0.07). The anger-hostility and fatigue-inertia scores of the POMS 2 decreased significantly in the plasmalogen group, but not in the placebo group, at 4 weeks. Between-group differences in those scores were highly significant (p = 0.003 for anger-hostility and p = 0.005 for fatigue-inertia). The plasmalogen group showed a slight decrease in the Athens Insomnia Scale at 2 weeks, and the between-group difference was near-significant (p = 0.07). The elapsed time in minute patterns on the Uchida-Kraepelin test, which is a marker of mental concentration, revealed significantly greater performance in the plasmalogen group than in the placebo group. There were no between-group differences in physical and laboratory measurements.

Conclusion: It is suggested that orally administered plasmalogens alleviate negative mood states and sleep problems, and also enhance mental concentration.

Ether Lipids in Obesity: From Cells to Population Studies

Ether lipids are a unique class of glycero- and glycerophospho-lipid that carry an ether or vinyl ether linked fatty alcohol at the sn-1 position of the glycerol backbone. These specialised lipids are important endogenous anti-oxidants with additional roles in regulating membrane fluidity and dynamics, intracellular signalling, immunomodulation and cholesterol metabolism. Lipidomic profiling of human population cohorts has identified new associations between reduced circulatory plasmalogen levels, an abundant and biologically active sub-class of ether lipids, with obesity and body-mass index. These findings align with the growing body of work exploring novel roles for ether lipids within adipose tissue. In this regard, ether lipids have now been linked to facilitating lipid droplet formation, regulating thermogenesis and mediating beiging of white adipose tissue in early life. This review will assess recent findings in both population studies and studies using cell and animal models to delineate the functional and protective roles of ether lipids in the setting of obesity. We will also discuss the therapeutic potential of ether lipid supplementation to attenuate diet-induced obesity.

Plasmalogens Eliminate Aging-Associated Synaptic Defects and Microglia-Mediated Neuroinflammation in Mice

Neurodegeneration is a pathological condition in which nervous system or neuron losses its structure, function, or both leading to progressive neural degeneration. Growing evidence strongly suggests that reduction of plasmalogens (Pls), one of the key brain lipids, might be associated with multiple neurodegenerative diseases, including Alzheimer’s disease (AD). Plasmalogens are abundant members of ether-phospholipids. Approximately 1 in 5 phospholipids are plasmalogens in human tissue where they are particularly enriched in brain, heart and immune cells. In this study, we employed a scheme of 2-months Pls intragastric administration to aged female C57BL/6J mice, starting at the age of 16 months old. Noticeably, the aged Pls-fed mice exhibited a better cognitive performance, thicker and glossier body hair in appearance than that of aged control mice. The transmission electron microscopic (TEM) data showed that 2-months Pls supplementations surprisingly alleviate age-associated hippocampal synaptic loss and also promote synaptogenesis and synaptic vesicles formation in aged murine brain. Further RNA-sequencing, immunoblotting and immunofluorescence analyses confirmed that plasmalogens remarkably enhanced both the synaptic plasticity and neurogenesis in aged murine hippocampus. In addition, we have demonstrated that Pls treatment inhibited the age-related microglia activation and attenuated the neuroinflammation in the murine brain. These findings suggest for the first time that Pls administration might be a potential intervention strategy for halting neurodegeneration and promoting neuroregeneration.

Dietary Ethanolamine Plasmalogen Alleviates DSS-Induced Colitis by Enhancing Colon Mucosa Integrity, Antioxidative Stress, and Anti-inflammatory Responses via Increased Ethanolamine Plasmalogen Molecular Species: Protective Role of Vinyl Ether Linkages

Dietary ethanolamine plasmalogen (PlsEtn) has been reported to have several health benefits; however, its functional role during colon pathophysiology remains elusive. The present study investigated the anticolitis effect of dietary ethanolamine glycerophospholipids (EtnGpls) with high PlsEtn from ascidian muscle (86.2 mol %) and low PlsEtn from porcine liver (7.7 mol %) in dextran sulfate sodium (DSS)-induced colitis in mice. Dietary EtnGpls lowered myeloperoxidase activity, thiobarbituric acid-reactive substances, proinflammatory cytokines and proapoptosis-related protein levels in colon mucosa after 16 days of DSS treatment, with ascidian muscle (0.1% EtnGpl in diet) showing higher suppression than porcine liver (0.1% EtnGpl in diet). Moreover, dietary EtnGpls suppressed DSS symptoms after 38 days of DSS treatment as evidenced by increased body weight, colon length, and ameliorated colon mucosa integrity. Additionally, dietary EtnGpls elevated short-chain fatty acid production in DSS-treated mice. Altogether, these results indicate the potential of utilizing diets with abundant PlsEtn for the prevention of colon inflammation-related disorders.

Plasmalogens and Chronic Inflammatory Diseases

It is becoming widely acknowledged that lipids play key roles in cellular function, regulating a variety of biological processes. Lately, a subclass of glycerophospholipids, namely plasmalogens, has received increased attention due to their association with several degenerative and metabolic disorders as well as aging. All these pathophysiological conditions involve chronic inflammatory processes, which have been linked with decreased levels of plasmalogens. Currently, there is a lack of full understanding of the molecular mechanisms governing the association of plasmalogens with inflammation. However, it has been shown that in inflammatory processes, plasmalogens could trigger either an anti- or pro-inflammation response. While the anti-inflammatory response seems to be linked to the entire plasmalogen molecule, its pro-inflammatory response seems to be associated with plasmalogen hydrolysis, i.e., the release of arachidonic acid, which, in turn, serves as a precursor to produce pro-inflammatory lipid mediators. Moreover, as plasmalogens comprise a large fraction of the total lipids in humans, changes in their levels have been shown to change membrane properties and, therefore, signaling pathways involved in the inflammatory cascade. Restoring plasmalogen levels by use of plasmalogen replacement therapy has been shown to be a successful anti-inflammatory strategy as well as ameliorating several pathological hallmarks of these diseases. The purpose of this review is to highlight the emerging role of plasmalogens in chronic inflammatory disorders as well as the promising role of plasmalogen replacement therapy in the treatment of these pathologies.

Plasmalogen Replacement Therapy

Plasmalogens, a subclass of glycerophospholipids containing a vinyl-ether bond, are one of the major components of biological membranes. Changes in plasmalogen content and molecular species have been reported in a variety of pathological conditions ranging from inherited to metabolic and degenerative diseases. Most of these diseases have no treatment, and attempts to develop a therapy have been focusing primarily on protein/nucleic acid molecular targets. However, recent studies have shifted attention to lipids as the basis of a therapeutic strategy. In these pathological conditions, the use of plasmalogen replacement therapy (PRT) has been shown to be a successful way to restore plasmalogen levels as well as to ameliorate the disease phenotype in different clinical settings. Here, the current state of PRT will be reviewed as well as a discussion of future perspectives in PRT. It is proposed that the use of PRT provides a modern and innovative molecular medicine approach aiming at improving health outcomes in different conditions with clinically unmet needs.

Lipidomics Approach in High-Fat-Diet-Induced Atherosclerosis Dyslipidemia Hamsters: Alleviation Using Ether-Phospholipids in Sea Urchin

Ether-phospholipids (ether-PLs) in sea urchins, especially eicosapentaenoic-acid-enriched plasmenyl phosphatidylethanolamine (PE-P) and plasmanyl phosphatidylcholine (PC-O), exhibit potential lipid-regulating effects. However, their underlying regulatory mechanisms have not yet been elucidated. Herein, we integrated an untargeted lipidomics strategy and biochemical analysis to investigate these mechanisms in high-fat-induced atherosclerotic hamsters. Dietary supplementation with PE-P and PC-O decreased total cholesterol and low-density lipoprotein cholesterol concentrations in serum. The lipid regulatory effects of PE-P were superior to those of PC-O. Additionally, 20 lipid molecular species, including phosphatidylethanolamine, cholesteryl ester, triacylglycerol, and phosphatidylinositol, were identified as potential lipid biomarkers in the serum of hamsters with PC-O and PE-P treatment (95% confidence interval; p < 0.05). The variations of lipids may be attributed to downregulation of adipogenesis genes and upregulation of lipid β-oxidation genes and bile acid biosynthesis genes. The improved lipid homeostasis by ether-PLs in sea urchins might be a key pathway underlying the antiatherosclerosis effect.

Plasmalogen-Based Liquid Crystalline Multiphase Structures Involving Docosapentaenoyl Derivatives Inspired by Biological Cubic Membranes

Structural properties of plasmenyl-glycerophospholipids (plasmalogens) have been scarcely studied for plasmalogens with long polyunsaturated fatty acid (PUFA) chains, despite of their significance for the organization and functions of the cellular membranes. Elaboration of supramolecular assemblies involving PUFA-chain plasmalogens in nanostructured mixtures with lyotropic lipids may accelerate the development of nanomedicines for certain severe pathologies (e.g., peroxisomal disorders, cardiometabolic impairments, and neurodegenerative Alzheimer's and Parkinson's diseases). Here, we investigate the spontaneous self-assembly of bioinspired, custom-produced docosapentaenoyl (DPA) plasmenyl (ether) and ester phospholipids in aqueous environment (pH 7) by synchrotron small-angle X-ray scattering (SAXS) and cryogenic transmission electron microscopy (cryo-TEM). A coexistence of a liquid crystalline primitive cubic Im3m phase and an inverted hexagonal (H_II) phase is observed for the DPA-ethanolamine plasmalogen (C16:1p-22:5n6 PE) derivative. A double-diamond cubic Pn3m phase is formed in mixed assemblies of the phosphoethanolamine plasmalogen (C16:1p-22:5n6 PE) and monoolein (MO), whereas a coexistence of cubic and lamellar liquid crystalline phases is established for the DPA-plasmenyl phosphocholine (C16:1p-22:5n6 PC)/MO mixture at ambient temperature. The DPA-diacyl phosphoinositol (22:5n6-22:5n6 PI) ester lipid displays a propensity for a lamellar phase formation. Double membrane vesicles and multilamellar onion topologies with inhomogeneous distribution of interfacial curvature are formed upon incorporation of the phosphoethanolamine plasmalogen (C16:1p-22:5n6 PE) into dioleoylphosphocholine (DOPC) bilayers. Nanoparticulate formulations of plasmalogen-loaded cubosomes, hexosomes, and various multiphase cubosome- and hexosome-derived architectures and mixed type nano-objects (e.g., oil droplet-embedding vesicles or core-shell particles with soft corona) are produced with PUFA-chain phospholipids and lipophilic antioxidant-containing membrane compositions that are characterized by synchrotron SAXS and cryo-TEM imaging. The obtained multiphase nanostructures reflect the changes in the membrane curvature induced by the inclusion of DPA-based PE and PC plasmalogens, as well as DPA-PI ester derivative, and open new opportunities for exploration of these bioinspired nanoassemblies.

Ethanolamine Plasmalogen Suppresses Apoptosis in Human Intestinal Tract Cells in Vitro by Attenuating Induced Inflammatory Stress

Ethanolamine plasmalogen (PlsEtn) is a subtype of ethanolamine glycerophospholipids (EtnGpl). Recently, PlsEtn has attracted increasing research interest due to its beneficial effects in health and disease; however, its functional role in colonic health has not been well established. This study was conducted to determine the mechanism underlying the antiapoptotic effect of PlsEtn in human intestinal tract cells under induced inflammatory stress. Lipopolysaccharide induced apoptosis of differentiated Caco-2 cells, which was suppressed by EtnGpl in a dose-dependent manner. Cells treated with ascidian muscle EtnGpl containing high levels of PlsEtn demonstrated a lower degree of apoptosis, and downregulated TNF-α and apoptosis-related proteins compared to those treated with porcine liver EtnGpl containing low PlsEtn. This indicates that PlsEtn exerted the observed effects, which provided protection against induced inflammatory stress. Overall, our results suggest that PlsEtn with abundant vinyl ether linkages is potentially beneficial in preventing the initiation of inflammatory bowel disease and colon cancer.

Therapeutic Efficacy of Plasmalogens for Alzheimer's Disease, Mild Cognitive Impairment, and Parkinson's Disease in Conjunction with a New Hypothesis for the Etiology of Alzheimer's Disease

It has been reported in recent years that blood levels of plasmalogens (Pls) are decreased in various diseases. None of those reports, however, conducted any clinical trials to examine the effect of Pls on those diseases. This article describes our recent report on a therapeutic efficacy of orally administered Pls in mild cognitive impairment (MCI), mild to severe Alzheimer's disease (AD), and Parkinson's disease (PD). A 24-week, multicenter, randomized, double-blind, placebo-controlled trial was performed in patients with MCI (n = 178) and mild AD (n = 98). The study design for moderate AD (n = 57) and severe AD (n = 18) was 12-week open-labeled, and the design for patients with PD (n = 10) was 24-week open-labeled. They showed a significant improvement in cognitive function and other clinical symptoms with elevation of the blood Pls levels. No adverse events were reported. The baseline levels of plasma ethanolamine plasmalogen and erythrocyte ethanolamine plasmalogen in MCI, AD, and PD were significantly lower than those of normal aged. The degree of reduction in the blood Pls levels was in the order of MCI ≺ mild AD ≺ moderate AD ≺ severe AD ≺ PD. The findings suggest that the blood levels of Pls may be a beneficial biomarker for assessing AD severity. Based on these results, we have proposed a new hypothesis for the etiology of AD and other neuropsychiatric disorders.

Plasmalogens, platelet-activating factor and beyond - Ether lipids in signaling and neurodegeneration

Glycerol-based ether lipids including ether phospholipids form a specialized branch of lipids that in mammals require peroxisomes for their biosynthesis. They are major components of biological membranes and one particular subgroup, the plasmalogens, is widely regarded as a cellular antioxidant. Their vast potential to influence signal transduction pathways is less well known. Here, we summarize the literature showing associations with essential signaling cascades for a wide variety of ether lipids, including platelet-activating factor, alkylglycerols, ether-linked lysophosphatidic acid and plasmalogen-derived polyunsaturated fatty acids. The available experimental evidence demonstrates links to several common players like protein kinase C, peroxisome proliferator-activated receptors or mitogen-activated protein kinases. Furthermore, ether lipid levels have repeatedly been connected to some of the most abundant neurological diseases, particularly Alzheimer's disease and more recently also neurodevelopmental disorders like autism. Thus, we critically discuss the potential role of these compounds in the etiology and pathophysiology of these diseases with an emphasis on signaling processes. Finally, we review the emerging interest in plasmalogens as treatment target in neurological diseases, assessing available data and highlighting future perspectives. Although many aspects of ether lipid involvement in cellular signaling identified in vitro still have to be confirmed in vivo, the compiled data show many intriguing properties and contributions of these lipids to health and disease that will trigger further research.