Protective effect of scallop-derived plasmalogen against vascular dysfunction, via the pSTAT3/PIM1/NFATc1 axis, in a novel mouse model of Alzheimer's disease with cerebral hypoperfusion

A strong relationship between Alzheimer's disease (AD) and vascular dysfunction has been the focus of increasing attention in aging societies. In the present study, we examined the long-term effect of scallop-derived plasmalogen (sPlas) on vascular remodeling-related proteins in the brain of an AD with cerebral hypoperfusion (HP) mouse model. We demonstrated, for the first time, that cerebral HP activated the axis of the receptor for advanced glycation endproducts (RAGE)/phosphorylated signal transducer and activator of transcription 3 (pSTAT3)/provirus integration site for Moloney murine leukemia virus 1 (PIM1)/nuclear factor of activated T cells 1 (NFATc1), accounting for such cerebral vascular remodeling. Moreover, we also found that cerebral HP accelerated pSTAT3-mediated astrogliosis and activation of the nucleotide-binding domain and leucine-rich repeat protein 3 (NLRP3) inflammasome, probably leading to cognitive decline. On the other hand, sPlas treatment attenuated the activation of the pSTAT3/PIM1/NFATc1 axis independent of RAGE and significantly suppressed NLRP3 inflammasome activation, demonstrating the beneficial effect on AD.

Integrative brain omics approach reveals key role for sn-1 lysophosphatidylethanolamine in Alzheimer's dementia

The biology of individual lipid species and their relevance in Alzheimer's disease (AD) remains incompletely understood. We utilized non-targeted mass spectrometry to examine brain lipids variations across 316 post-mortem brains from participants in the Religious Orders Study (ROS) or Rush Memory and Aging Project (MAP) cohorts classified as either control, asymptomatic AD (AAD), or symptomatic AD (SAD) and integrated the lipidomics data with untargeted proteomic characterization on the same individuals. Lipid enrichment analysis and analysis of variance identified significantly lower abundance of lysophosphatidylethanolamine (LPE) and lysophosphatidylcholine (LPC) species in SAD than controls or AAD. Lipid-protein co-expression network analyses revealed that lipid modules consisting of LPE and LPC exhibited a significant association to protein modules associated with MAPK/metabolism, post-synaptic density, and Cell-ECM interaction pathways and were associated with better antemortem cognition and with neuropathological changes seen in AD. Particularly, LPE 22:6 [sn-1] levels are significantly decreased across AD cases (SAD) and show the most influence on protein changes compared to other lysophospholipid species. LPE 22:6 may be a lipid signature for AD and could be leveraged as potential therapeutic or dietary targets for AD.

Mapping the lipidome in mitochondria-associated membranes (MAMs) in an in vitro model of Alzheimer's disease

The disruption of mitochondria-associated endoplasmic reticulum (ER) membranes (MAMs) plays a relevant role in Alzheimer's disease (AD). MAMs have been implicated in neuronal dysfunction and death since it is associated with impairment of functions regulated in this subcellular domain, including lipid synthesis and trafficking, mitochondria dysfunction, ER stress-induced unfolded protein response (UPR), apoptosis, and inflammation. Since MAMs play an important role in lipid metabolism, in this study we characterized and investigated the lipidome alterations at MAMs in comparison with other subcellular fractions, namely microsomes and mitochondria, using an in vitro model of AD, namely the mouse neuroblastoma cell line (N2A) over-expressing the APP familial Swedish mutation (APPswe) and the respective control (WT) cells. Phospholipids (PLs) and fatty acids (FAs) were isolated from the different subcellular fractions and analyzed by HILIC-LC-MS/MS and GC-MS, respectively. In this in vitro AD model, we observed a down-regulation in relative abundance of some phosphatidylcholine (PC), lysophosphatidylcholine (LPC), and lysophosphatidylethanolamine (LPE) species with PUFA and few PC with saturated and long-chain FA. We also found an up-regulation of CL, and antioxidant alkyl acyl PL. Moreover, multivariate analysis indicated that each organelle has a specific lipid profile adaptation in N2A APPswe cells. In the FAs profile, we found an up-regulation of C16:0 in all subcellular fractions, a decrease of C18:0 levels in total fraction (TF) and microsomes fraction, and a down-regulation of 9-C18:1 was also found in mitochondria fraction in the AD model. Together, these results suggest that the over-expression of the familial APP Swedish mutation affects lipid homeostasis in MAMs and other subcellular fractions and supports the important role of lipids in AD physiopathology.

Unlocking the Molecular Variations of a Micron-Scale Amyloid Plaque in an Early Stage Alzheimer's Disease by a Cellular-Resolution Mass Spectrometry Imaging Platform

Uncovering the molecular changes at the site where Aβ is deposited plays a critical role in advancing the diagnosis and treatment of Alzheimer's disease. However, there is currently a lack of a suitable label-free imaging method with a high spatial resolution for brain tissue analysis. In this study, we propose a modified desorption electrospray ionization (DESI) mass spectrometry imaging (MSI) method, called segmented temperature-controlled DESI (STC-DESI), to achieve high-resolution and high-sensitivity spatial metabolomics observation by precisely controlling desorption and ionization temperatures. By concentrating the spray plume and accelerating solvent evaporation at different temperatures, we achieved an impressive spatial resolution of 20 μm that enables direct observation of the heterogeneity around a single cell or an individual Aβ plaque and an exciting sensitivity that allows a variety of low-abundance metabolites and less ionizable neutral lipids to be detected. We applied this STC-DESI method to analyze the brains of transgenic AD mice and identified molecular changes associated with individual Aβ aggregates. More importantly, our study provides the first evidence that carnosine is significantly depleted and 5-caffeoylquinic acid (5-CQA) levels rise sharply around Aβ deposits. These observations highlight the potential of carnosine as a sensitive molecular probe for clinical magnetic resonance imaging diagnosis and the potential of 5-CQA as an efficient therapeutic strategy for Aβ clearance in the early AD stage. Overall, our findings demonstrate the effectiveness of our STC-DESI method and shed light on the potential roles of these molecules in AD pathology, specifically in cellular endocytosis, gray matter network disruption, and paravascular Aβ clearance.

Marine Plasmalogens: A Gift from the Sea with Benefits for Age-Associated Diseases

Aging increases oxidative and inflammatory stress caused by a reduction in metabolism and clearance, thus leading to the development of age-associated diseases. The quality of our daily diet and exercise is important for the prevention of these diseases. Marine resources contain various valuable nutrients, and unique glycerophospholipid plasmalogens are found abundantly in some marine invertebrates, including ascidians. One of the major classes, the ethanolamine class (PlsEtn), exists in a high ratio to phospholipids in the brain and blood, while decreased levels have been reported in patients with age-associated diseases, including Alzheimer's disease. Animal studies have shown that the administration of marine PlsEtn prepared from marine invertebrates improved PlsEtn levels in the body and alleviated inflammation. Animal and human studies have reported that marine PlsEtn ameliorates cognitive impairment. In this review, we highlight the biological significance, relationships with age-associated diseases, food functions, and healthcare materials of plasmalogens based on recent knowledge and discuss the contribution of marine plasmalogens to health maintenance in aging.

Plasmalogen Improves Memory Function by Regulating Neurogenesis in a Mouse Model of Alzheimer's Diseases

Adult hippocampal neurogenesis (AHN) is associated with hippocampus-dependent cognitive function, and its initiation is attributed to neural stem cells (NSCs). Dysregulated AHN has been identified in Alzheimer's disease (AD) and may underlie impaired cognitive function in AD. Modulating the function of NSCs and stimulating AHN are potential ways to manipulate AD. Plasmalogen (PLA) are a class of cell membrane glycerophospholipids which exhibit neuroprotective properties. However, the effect of PLA on altered AHN in AD has not been investigated. In our study, PLA(10μg/mL) -attenuated Aβ (1-42) (5μM) induced a decrease in NSC viability and neuronal differentiation of NSCs, partially through regulating the Wnt/β-catenin pathway. Additionally, AD mice were supplemented with PLA (67mg/kg/day) for 6 weeks. PLA treatment improved the impaired AHN in AD mice, including increasing the number of neural stem cells (NSCs) and newly generated neurons. The memory function of AD mice was also enhanced after PLA administration. Therefore, it was summarized that PLA could regulate NSC differentiation by activating the Wnt/β-catenin pathway and ameliorate AD-related memory impairment through up-regulating AHN.

Modifiable Innate Biology within the Gut–Brain Axis for Alzheimer’s Disease

Alzheimer’s disease (AD) is a prototypical inflammation-associated loss of cognitive function, with approximately 90% of the AD burden associated with invading myeloid cells controlling the function of the resident microglia. This indicates that the immune microenvironment has a pivotal role in the pathogenesis of the disease. Multiple peripheral stimuli, conditioned by complex and varied interactions between signals that stem at the intestinal level and neuroimmune processes, are involved in the progression and severity of AD. Conceivably, the targeting of critical innate immune signals and cells is achievable, influencing immune and metabolic health within the gut–brain axis. Considerable progress has been made, modulating many different metabolic and immune alterations that can drive AD development. However, non-pharmacological strategies targeting immunometabolic processes affecting neuroinflammation in AD treatment remain general and, at this point, are applied to all patients regardless of disease features. Despite these possibilities, improved knowledge of the relative contribution of the different innate immune cells and molecules comprising the chronically inflamed brain network to AD pathogenesis, and elucidation of the network hierarchy, are needed for planning potent preventive and/or therapeutic interventions. Moreover, an integrative perspective addressing transdisciplinary fields can significantly contribute to molecular pathological epidemiology, improving the health and quality of life of AD patients. This review is intended to gather modifiable immunometabolic processes based on their importance in the prevention and management of AD.

Liposome based drug delivery as a potential treatment option for Alzheimer's disease

Alzheimer's disease is a neurodegenerative condition leading to atrophy of the brain and robbing nearly 5.8 million individuals in the United States age 65 and older of their cognitive functions. Alzheimer's disease is associated with dementia and a progressive decline in memory, thinking, and social skills, eventually leading to a point that the individual can no longer perform daily activities independently. Currently available drugs on the market temporarily alleviate the symptoms, however, they are not successful in slowing down the progression of Alzheimer's disease. Treatment and cures have been constricted due to the difficulty of drug delivery to the blood-brain barrier. Several studies have led to identification of vesicles to transport the necessary drugs through the blood-brain barrier that would typically not achieve the targeted area through systemic delivered medications. Recently, liposomes have emerged as a viable drug delivery agent to transport drugs that are not able to cross the blood-brain barrier. Liposomes are being used as a component of nanoparticle drug delivery; due to their biocompatible nature; and possessing the capability to carry both lipophilic and hydrophilic therapeutic agents across the blood brain barrier into the brain cells. Studies indicate the importance of liposomal based drug delivery in treatment of neurodegenerative disorders. The idea is to encapsulate the drugs inside the properly engineered liposome to generate a response of treatment. Liposomes are engineered to target specific diseased moieties and also several surface modifications of liposomes are under research to create a clinical path to the management of Alzheimer's disease. This review deals with Alzheimer's disease and emphasize on challenges associated with drug delivery to the brain, and how liposomal drug delivery can play an important role as a drug delivery method for the treatment of Alzheimer's disease. This review also sheds some light on variation of liposomes. Additionally, it emphasizes on the liposomal formulations which are currently researched or used for treatment of Alzheimer's disease and also discusses the future prospect of liposomal based drug delivery in Alzheimer's disease.

Clinical and Pathological Benefits of Scallop-Derived Plasmalogen in a Novel Mouse Model of Alzheimer’s Disease with Chronic Cerebral Hypoperfusion

Background: The oral ingestion of scallop-derived plasmalogen (sPlas) significantly improved cognitive function in Alzheimer’s disease (AD) patients. Objective: However, the effects and mechanisms of sPlas on AD with chronic cerebral hypoperfusion (CCH), a class of mixed dementia contributing to 20–30% among the dementia society, were still elusive. Methods: In the present study, we applied a novel mouse model of AD with CCH to investigate the potential effects of sPlas on AD with CCH. Results: The present study demonstrated that sPlas significantly recovered cerebral blood flow, improved motor and cognitive deficits, reduced amyloid-β pathology, regulated neuroinflammation, ameliorated neural oxidative stress, and inhibited neuronal loss in AD with CCH mice at 12 M. Conclusion: These findings suggest that sPlas possesses clinical and pathological benefits for AD with CCH in the novel model mice. Furthermore, sPlas could have promising prevention and therapeutic effects on patients of AD with CCH.

Bioactive Lipids and Their Derivatives in Biomedical Applications

Lipids, which along with carbohydrates and proteins are among the most important nutrients for the living organism, have a variety of biological functions that can be applied widely in biomedicine. A fatty acid, the most fundamental biological lipid, may be classified by length of its aliphatic chain, and the short-, medium-, and long-chain fatty acids and each have distinct biological activities with therapeutic relevance. For example, short-chain fatty acids have immune regulatory activities and could be useful against autoimmune disease; medium-chain fatty acids generate ketogenic metabolites and may be used to control seizure; and some metabolites oxidized from long-chain fatty acids could be used to treat metabolic disorders. Glycerolipids play important roles in pathological environments, such as those of cancers or metabolic disorders, and thus are regarded as a potential therapeutic target. Phospholipids represent the main building unit of the plasma membrane of cells, and play key roles in cellular signaling. Due to their physical properties, glycerophospholipids are frequently used as pharmaceutical ingredients, in addition to being potential novel drug targets for treating disease. Sphingolipids, which comprise another component of the plasma membrane, have their own distinct biological functions and have been investigated in nanotechnological applications such as drug delivery systems. Saccharolipids, which are derived from bacteria, have endotoxin effects that stimulate the immune system. Chemically modified saccharolipids might be useful for cancer immunotherapy or as vaccine adjuvants. This review will address the important biological function of several key lipids and offer critical insights into their potential therapeutic applications.

Plasmalogen attenuates the development of hepatic steatosis and cognitive deficit through mechanism involving p75NTR inhibition

Emerging evidence suggests that the reduction of ethanolamine plasmalogen (PlsEtn) is associated with in Alzheimer's disease and metabolic diseases. However, the mechanistic bases for PlsEtn on the these diseases are not well understood. Plasmalogens are primarily synthesized in the liver and enriched in brain. To this end, the present study sought to investigate the potential role of PlsEtn on steatohepatitis and memory impairments and its underlying mechanism. Here we show that peroxisome dysfunction and impairment of PlsEtn synthesis pathway occurs in both of hippocampus and liver, resulting in the decrease of PlsEtn level in APP/PS1 mice and HFD-fed mice. shGNPAT induced PlsEtn deficiency in hepatocytes induces p75NTR enhancement leading to decreased lipolysis activity, thereby exacerbating steatosis. Moreover, in the brain, PlsEtn administration appears to not only improve steatosis but also prevent Alzheimer's disease through restoration of TrkA/p75NTR balance. Together, our findings reveal a molecular mechanistic insight into the preventive role of plasmalogen modulation against steatosis and memory impairments via p75NTR inhibition.

•

Peroxisome dysfunction and impairment of plasmalogen synthesis pathway resulted in the decrease of plasmalogen level.

•

Plasmalogen deficiency in hepatocytes induces p75NTR enhancement leading to decreased lipolysis activity.

•

Ethanolamine plasmalogen administration improves memory impairments by restoration of TrkA/p75NTR balance.

•

Ethanolamine plasmalogen administration attenuates neurodegeneration and neuronal death, and mitigates oxidative stress.

Advances in the Biosynthetic Pathways and Application Potential of Plasmalogens in Medicine

Plasmalogens are a special class of polar glycerolipids containing a vinyl-ether bond and an ester bond at sn-1 and sn-2 positions of the glycerol backbone, respectively. In animals, impaired biosynthesis and regulation of plasmalogens may lead to certain neurological and metabolic diseases. Plasmalogens deficiency was proposed to be strongly associated with neurodegenerative and metabolic diseases, such as Alzheimer's disease (AD) and Parkinson's disease (PD), and appropriate supplement of plasmalogens could help to prevent and possibly provide therapy of these diseases. Plasmalogens evolved first in anaerobic bacteria with an anaerobic biosynthetic pathway. Later, an oxygen-dependent biosynthesis of plasmalogens appeared in animal cells. This review summarizes and updates current knowledge of anaerobic and aerobic pathways of plasmalogens biosynthesis, including the enzymes involved, steps and aspects of the regulation of these processes. Strategies for increasing the expression of plasmalogen synthetic genes using synthetic biology techniques under specific conditions are discussed. Deep understanding of plasmalogens biosynthesis will provide the bases for the use of plasmalogens and their precursors as potential therapeutic regimens for age-related degenerative and metabolic diseases.

The TMEM189 gene encodes plasmanylethanolamine desaturase which introduces the characteristic vinyl ether double bond into plasmalogens

A significant fraction of the glycerophospholipids in the human body is composed of plasmalogens, particularly in the brain, cardiac, and immune cell membranes. A decline in these lipids has been observed in such diseases as Alzheimer's and chronic obstructive pulmonary disease. Plasmalogens contain a characteristic 1-O-alk-1'-enyl ether (vinyl ether) double bond that confers special biophysical, biochemical, and chemical properties to these lipids. However, the genetics of their biosynthesis is not fully understood, since no gene has been identified that encodes plasmanylethanolamine desaturase (E.C. 1.14.99.19), the enzyme introducing the crucial alk-1'-enyl ether double bond. The present work identifies this gene as transmembrane protein 189 (TMEM189). Inactivation of the TMEM189 gene in human HAP1 cells led to a total loss of plasmanylethanolamine desaturase activity, strongly decreased plasmalogen levels, and accumulation of plasmanylethanolamine substrates and resulted in an inability of these cells to form labeled plasmalogens from labeled alkylglycerols. Transient expression of TMEM189 protein, but not of other selected desaturases, recovered this deficit. TMEM189 proteins contain a conserved protein motif (pfam10520) with eight conserved histidines that is shared by an alternative type of plant desaturase but not by other mammalian proteins. Each of these histidines is essential for plasmanylethanolamine desaturase activity. Mice homozygous for an inactivated Tmem189 gene lacked plasmanylethanolamine desaturase activity and had dramatically lowered plasmalogen levels in their tissues. These results assign the TMEM189 gene to plasmanylethanolamine desaturase and suggest that the previously characterized phenotype of Tmem189-deficient mice may be caused by a lack of plasmalogens.

Lipids and Alzheimer's Disease

Lipids, as the basic component of cell membranes, play an important role in human health as well as brain function. The brain is highly enriched in lipids, and disruption of lipid homeostasis is related to neurologic disorders as well as neurodegenerative diseases such as Alzheimer’s disease (AD). Aging is associated with changes in lipid composition. Alterations of fatty acids at the level of lipid rafts and cerebral lipid peroxidation were found in the early stage of AD. Genetic and environmental factors such as apolipoprotein and lipid transporter carrying status and dietary lipid content are associated with AD. Insight into the connection between lipids and AD is crucial to unraveling the metabolic aspects of this puzzling disease. Recent advances in lipid analytical methodology have led us to gain an in-depth understanding on lipids. As a result, lipidomics have becoming a hot topic of investigation in AD, in order to find biomarkers for disease prediction, diagnosis, and prevention, with the ultimate goal of discovering novel therapeutics.

Identification of plasmalogens in Bifidobacterium longum, but not in Bifidobacterium animalis

Plasmalogens are glycerophospholipids that contain a vinyl ether bond at the sn-1 position of glycerol backbone instead of an ester bond. Plasmalogens are indicated to have many important functions in mammalian cells. On the other hand, it is suggested that some gut microbiota plays many probiotic functions to human health. Presence of plasmalogens in Clostridium strains in gut microbiota is well-known, but presence of plasmalogens in Bifidobacterium longum (B. longum) strain, one of the most important probiotic gut microbiota, has not been reported. We identified plasmalogens in lipid extract from some B. longum species, but not from Bifidobacterium animalis (B. animalis) species which are another important strain of probiotic bifidobacteria. Major phospholipid classes of plasmalogens in B. longum species were cardiolipin, phosphatidylglycerol and phosphatidic acid. Almost all of the phospholipids from B. longum examined were indicated to be plasmalogens. Although major phospholipid classes of plasmalogens in human brain and major phospholipid classes of plasmalogens in B. longum are different, it is interesting to note that many reported functions of microbiota-gut-brain axis on human neurodegenerative diseases and those functions of plasmalogens on neurodegenerative diseases are overlapped. The presence of plasmalogens in B. longum species may play important roles for many probiotic effects of B. longum to human health.

Marine omega-3 (n-3) phospholipids: A comprehensive review of their properties, sources, bioavailability, and relation to brain health

For several decades, there has been considerable interest in marine-derived long chain n-3 fatty acids (n-3 LCPUFAs) due to their outstanding health benefits. n-3 LCPUFAs can be found in nature either in triglycerides (TAGs) or in phospholipid (PL) form. From brain health point of view, PL n-3 is more bioavailable and potent compared to n-3 in TAG form, as only PL n-3 is able to cross the blood-brain barrier and can be involved in brain biochemical reactions. However, PL n-3 has been ignored in the fish oil industry and frequently removed as an impurity during degumming processes. As a result, PL products derived from marine sources are very limited compared to TAG products. Commercially, PLs are being used in pharmaceutical industries as drug carriers, in food manufacturing as emulsifiers and in cosmetic industries as skin care agents, but most of the PLs used in these applications are produced from vegetable sources that contain less (without EPA, DPA, and DHA) or sometimes no n-3 LCPUFAs. This review provides a comprehensive account of the properties, structures, and major sources of marine PLs, and provides focussed discussion of their relationship to brain health. Epidemiological, laboratory, and clinical studies on n-3 LCPUFAs enriched PLs using different model systems in relation to brain and mental health that have been published over the past few years are discussed in detail.

Plasmalogens and Alzheimer's disease: a review

Growing evidence suggests that ethanolamine plasmalogens (PlsEtns), a subtype of phospholipids, have a close association with Alzheimer’s disease (AD). Decreased levels of PlsEtns have been commonly found in AD patients, and were correlated with cognition deficit and severity of disease. Limited studies showed positive therapeutic outcomes with plasmalogens interventions in AD subjects and in rodents. The potential mechanisms underlying the beneficial effects of PlsEtns on AD may be related to the reduction of γ–secretase activity, an enzyme that catalyzes the synthesis of β-amyloid (Aβ), a hallmark of AD. Emerging in vitro evidence also showed that PlsEtns prevented neuronal cell death by enhancing phosphorylation of AKT and ERK signaling through the activation of orphan G-protein coupled receptor (GPCR) proteins. In addition, PlsEtns have been found to suppress the death of primary mouse hippocampal neuronal cells through the inhibition of caspase-9 and caspase-3 cleavages. Further in-depth investigations are required to determine the signature molecular species of PlsEtns associated with AD, hence their potential role as biomarkers. Clinical intervention with plasmalogens is still in its infancy but may have the potential to be explored for a novel therapeutic approach to correct AD pathology and neural function.

Serum Metabolomic Alterations Associated with Proteinuria in CKD

BACKGROUND AND OBJECTIVES

Data are scarce on blood metabolite associations with proteinuria, a strong risk factor for adverse kidney outcomes. We sought to investigate associations of proteinuria with serum metabolites identified using untargeted profiling in populations with CKD.

DESIGN, SETTING, PARTICIPANTS, & MEASUREMENTS

Using stored serum samples from the African American Study of Kidney Disease and Hypertension (AASK; n=962) and the Modification of Diet in Renal Disease (MDRD) study (n=620), two rigorously conducted clinical trials with per-protocol measures of 24-hour proteinuria and GFR, we evaluated cross-sectional associations between urine protein-to-creatinine ratio and 637 known, nondrug metabolites, adjusting for key clinical covariables. Metabolites significantly associated with proteinuria were tested for associations with CKD progression.

RESULTS

In the AASK and the MDRD study, respectively, the median urine protein-to-creatinine ratio was 80 (interquartile range [IQR], 28-359) and 188 (IQR, 54-894) mg/g, mean age was 56 and 52 years, 39% and 38% were women, 100% and 7% were black, and median measured GFR was 48 (IQR, 35-57) and 28 (IQR, 18-39) ml/min per 1.73 m2. Linear regression identified 66 serum metabolites associated with proteinuria in one or both studies after Bonferroni correction (P<7.8×10-5), 58 of which were statistically significant in a meta-analysis (P<7.8×10-4). The metabolites with the lowest P values (P<10-27) were 4-hydroxychlorthalonil and 1,5-anhydroglucitol; all six quantified metabolites in the phosphatidylethanolamine pathway were also significant. Of the 58 metabolites associated with proteinuria, four were associated with ESKD in both the AASK and the MDRD study.

CONCLUSIONS

We identified 58 serum metabolites with cross-sectional associations with proteinuria, some of which were also associated with CKD progression.

PODCAST

This article contains a podcast at https://www.asn-online.org/media/podcast/CJASN/2019_02_07_CJASNPodcast_19_03_.mp3.

Shedding Light on the Molecular Pathology of Amyloid Plaques in Transgenic Alzheimer's Disease Mice Using Multimodal MALDI Imaging Mass Spectrometry

Senile plaques formed by aggregated amyloid β peptides are one of the major pathological hallmarks of Alzheimer's disease (AD) which have been suggested to be the primary influence triggering the AD pathogenesis and the rest of the disease process. However, neurotoxic Aβ aggregation and progression are associated with a wide range of enigmatic biochemical, biophysical and genetic processes. MALDI imaging mass spectrometry (IMS) is a label-free method to elucidate the spatial distribution patterns of intact molecules in biological tissue sections. In this communication, we utilized multimodal MALDI-IMS analysis on 18 month old transgenic AD mice (tgArcSwe) brain tissue sections to enhance molecular information correlated to individual amyloid aggregates on the very same tissue section. Dual polarity MALDI-IMS analysis of lipids on the same pixel points revealed high throughput lipid molecular information including sphingolipids, phospholipids, and lysophospholipids which can be correlated to the ion images of individual amyloid β peptide isoforms at high spatial resolutions (10 μm). Further, multivariate image analysis was applied in order to probe the multimodal MALDI-IMS data in an unbiased way which verified the correlative accumulations of lipid species with dual polarity and Aβ peptides. This was followed by the lipid fragmentation obtained directly on plaque aggregates at higher laser pulse energies which provided tandem MS information useful for structural elucidation of several lipid species. Majority of the amyloid plaque-associated alterations of lipid species are for the first time reported here. The significance of this technique is that it allows correlating the biological discussion of all detected plaque-associated molecules to the very same individual amyloid plaques which can give novel insights into the molecular pathology of even a single amyloid plaque microenvironment in a specific brain region. Therefore, this allowed us to interpret the possible roles of lipids and amyloid peptides in amyloid plaque-associated pathological events such as focal demyelination, autophagic/lysosomal dysfunction, astrogliosis, inflammation, oxidative stress, and cell death.

Plasmalogen lipids: functional mechanism and their involvement in gastrointestinal cancer

The plasmalogens are a class of glycerophospholipids which contain a vinyl-ether and an ester bond at the sn-1 and sn-2 positions, respectively, in the glycerol backbone. They constitute 10 mol% of the total mass of phospholipids in humans, mainly as membrane structure components. Plasmalogens are important for the organization and stability of lipid raft microdomains and cholesterol-rich membrane regions involved in cellular signaling. In addition to their structural roles, a subset of ether lipids are thought to function as endogenous antioxidants and emerging studies suggest that they are involved in cell differentiation and signaling pathways. Although the clinical significance of plasmalogens is linked to peroxisomal disorders, the pathophysiological roles and their possible metabolic pathways are not fully understood since they present unique structural attributes for the different tissue types. Studies suggest that changes in plasmalogen metabolism may contribute to the development of various types of cancer. Here, we review the molecular characteristics of plasmalogens in order to significantly increase our understanding of the plasmalogen molecule and its involvement in gastrointestinal cancers as well as other types of cancers.

Omega-3 fatty acids, lipids, and apoE lipidation in Alzheimer's disease: a rationale for multi-nutrient dementia prevention

In the last decade, it has become obvious that Alzheimer's disease (AD) is closely linked to changes in lipids or lipid metabolism. One of the main pathological hallmarks of AD is amyloid-β (Aβ) deposition. Aβ is derived from sequential proteolytic processing of the amyloid precursor protein (APP). Interestingly, both, the APP and all APP secretases are transmembrane proteins that cleave APP close to and in the lipid bilayer. Moreover, apoE4 has been identified as the most prevalent genetic risk factor for AD. ApoE is the main lipoprotein in the brain, which has an abundant role in the transport of lipids and brain lipid metabolism. Several lipidomic approaches revealed changes in the lipid levels of cerebrospinal fluid or in post mortem AD brains. Here, we review the impact of apoE and lipids in AD, focusing on the major brain lipid classes, sphingomyelin, plasmalogens, gangliosides, sulfatides, DHA, and EPA, as well as on lipid signaling molecules, like ceramide and sphingosine-1-phosphate. As nutritional approaches showed limited beneficial effects in clinical studies, the opportunities of combining different supplements in multi-nutritional approaches are discussed and summarized.

Early-Onset Alzheimer Disease and Candidate Risk Genes Involved in Endolysosomal Transport

Importance

Mutations in APP, PSEN1, and PSEN2 lead to early-onset Alzheimer disease (EOAD) but account for only approximately 11% of EOAD overall, leaving most of the genetic risk for the most severe form of Alzheimer disease unexplained. This extreme phenotype likely harbors highly penetrant risk variants, making it primed for discovery of novel risk genes and pathways for AD.

Objective

To search for rare variants contributing to the risk for EOAD.

Design, Setting, and Participants

In this case-control study, whole-exome sequencing (WES) was performed in 51 non-Hispanic white (NHW) patients with EOAD (age at onset <65 years) and 19 Caribbean Hispanic families previously screened as negative for established APP, PSEN1, and PSEN2 causal variants. Participants were recruited from John P. Hussman Institute for Human Genomics, Case Western Reserve University, and Columbia University. Rare, deleterious, nonsynonymous, or loss-of-function variants were filtered to identify variants in known and suspected AD genes, variants in multiple unrelated NHW patients, variants present in 19 Hispanic EOAD WES families, and genes with variants in multiple unrelated NHW patients. These variants/genes were tested for association in an independent cohort of 1524 patients with EOAD, 7046 patients with late-onset AD (LOAD), and 7001 cognitively intact controls (age at examination, >65 years) from the Alzheimer's Disease Genetics Consortium. The study was conducted from January 21, 2013, to October 13, 2016.

Main Outcomes and Measures

Alzheimer disease diagnosed according to standard National Institute of Neurological and Communicative Disorders and Stroke and the Alzheimer Disease and Related Disorders Association criteria. Association between Alzheimer disease and genetic variants and genes was measured using logistic regression and sequence kernel association test-optimal gene tests, respectively.

Results

Of the 1524 NHW patients with EOAD, 765 (50.2%) were women and mean (SD) age was 60.0 (4.9) years; of the 7046 NHW patients with LOAD, 4171 (59.2%) were women and mean (SD) age was 77.4 (8.6) years; and of the 7001 NHW controls, 4215 (60.2%) were women and mean (SD) age was 77.4 (8.6) years. The gene PSD2, for which multiple unrelated NHW cases had rare missense variants, was significantly associated with EOAD (P = 2.05 × 10-6; Bonferroni-corrected P value [BP] = 1.3 × 10-3) and LOAD (P = 6.22 × 10-6; BP = 4.1 × 10-3). A missense variant in TCIRG1, present in a NHW patient and segregating in 3 cases of a Hispanic family, was more frequent in EOAD cases (odds ratio [OR], 2.13; 95% CI, 0.99-4.55; P = .06; BP = 0.413), and significantly associated with LOAD (OR, 2.23; 95% CI, 1.37-3.62; P = 7.2 × 10-4; BP = 5.0 × 10-3). A missense variant in the LOAD risk gene RIN3 showed suggestive evidence of association with EOAD after Bonferroni correction (OR, 4.56; 95% CI, 1.26-16.48; P = .02, BP = 0.091). In addition, a missense variant in RUFY1 identified in 2 NHW EOAD cases showed suggestive evidence of an association with EOAD as well (OR, 18.63; 95% CI, 1.62-213.45; P = .003; BP = 0.129).

Conclusions and Relevance

The genes PSD2, TCIRG1, RIN3, and RUFY1 all may be involved in endolysosomal transport-a process known to be important to development of AD. Furthermore, this study identified shared risk genes between EOAD and LOAD similar to previously reported genes, such as SORL1, PSEN2, and TREM2.

APP Function and Lipids: A Bidirectional Link

Extracellular neuritic plaques, composed of aggregated amyloid-β (Aβ) peptides, are one of the major histopathological hallmarks of Alzheimer's disease (AD), a progressive, irreversible neurodegenerative disorder and the most common cause of dementia in the elderly. One of the most prominent risk factor for sporadic AD, carrying one or two aberrant copies of the apolipoprotein E (ApoE) ε4 alleles, closely links AD to lipids. Further, several lipid classes and fatty acids have been reported to be changed in the brain of AD-affected individuals. Interestingly, the observed lipid changes in the brain seem not only to be a consequence of the disease but also modulate Aβ generation. In line with these observations, protective lipids being able to decrease Aβ generation and also potential negative lipids in respect to AD were identified. Mechanistically, Aβ peptides are generated by sequential proteolytic processing of the amyloid precursor protein (APP) by β- and γ-secretase. The α-secretase appears to compete with β-secretase for the initial cleavage of APP, preventing Aβ production. All APP-cleaving secretases as well as APP are transmembrane proteins, further illustrating the impact of lipids on Aβ generation. Beside the pathological impact of Aβ, accumulating evidence suggests that Aβ and the APP intracellular domain (AICD) play an important role in regulating lipid homeostasis, either by direct effects or by affecting gene expression or protein stability of enzymes involved in the de novo synthesis of different lipid classes. This review summarizes the current literature addressing the complex bidirectional link between lipids and AD and APP processing including lipid alterations found in AD post mortem brains, lipids that alter APP processing and the physiological functions of Aβ and AICD in the regulation of several lipid metabolism pathways.

Efficacy and Blood Plasmalogen Changes by Oral Administration of Plasmalogen in Patients with Mild Alzheimer's Disease and Mild Cognitive Impairment: A Multicenter, Randomized, Double-blind, Placebo-controlled Trial

Background

Plasmalogens (Pls) reportedly decreased in postmortem brain and in the blood of patients with Alzheimer's disease (AD). Recently we showed that intraperitoneal administration of Pls improved cognitive function in experimental animals. In the present trial, we tested the efficacy of oral administration of scallop-derived purified Pls with respect to cognitive function and blood Pls changes in patients with mild AD and mild cognitive impairment (MCI).

Methods

The study was a multicenter, randomized, double-blind, placebo-controlled trial of 24 weeks. Participants were 328 patients aged 60 to 85 years who had 20 to 27 points in Mini Mental State Examination-Japanese (MMSE-J) score and five or less points in Geriatric Depression Scale-Short Version-Japanese (GDS-S-J). They were randomized to receive either 1 mg/day of Pls purified from scallop or placebo. The patients and study physicians were masked to the assignment. The primary outcome was MMSE-J. The secondary outcomes included Wechsler Memory Scale-Revised (WMS-R), GDS-S-J and concentration of phosphatidyl ethanolamine plasmalogens (PlsPE) in erythrocyte membrane and plasma. This trial is registered with the University Hospital Medical Information Network, number UMIN000014945.

Findings

Of 328 patients enrolled, 276 patients completed the trial (140 in the treatment group and 136 in the placebo group). In an intention-to-treat analysis including both mild AD (20 ≤ MMSE-J ≤ 23) and MCI (24 ≤ MMSE-J ≤ 27), no significant difference was shown between the treatment and placebo groups in the primary and secondary outcomes, with no severe adverse events in either group. In mild AD patients, WMS-R improved significantly in the treatment group, and the between group difference was nearly significant (P = 0.067). In a subgroup analysis of mild AD patients, WMS-R significantly improved among females and those aged below 77 years in the treatment group, and the between-group differences were statistically significant in females (P = 0.017) and in those aged below 77 years (P = 0.029). Patients with mild AD showed a significantly greater decrease in plasma PlsPE in the placebo group than in the treatment group.

Interpretation

Oral administration of scallop-derived purified Pls may improve cognitive functions of mild AD.

Funding

The Japanese Plasmalogen Society.

•

Plasmalogens (Pls), a kind of phospholipid, are reduced in the brain and blood of patients with Alzheimer’s disease (AD).

•

Scallop-derived purified Pls were orally administered to patients with mild AD and mild cognitive impairment by RCT.

•

Oral administration of scallop-derived purified Pls may improve cognitive functions of mild AD.

It is well known that Plasmalogens (Pls), a special class of glycerophospholipid, are decreased in the brain and blood of patients with Alzheimer’s disease (AD), and inhibit γ-secretase activity. Our recent studies showed that intraperitoneal administration of purified Pls improved cognitive function in the animal model of AD. We tested the efficacy of Pls for Alzheimer’s disease by a multicenter, randomized, double-blind, placebo-controlled trial and showed that oral administration of scallop-derived purified Pls may improve cognitive functions of patients with mild AD.

Extrinsic plasmalogens suppress neuronal apoptosis in mouse neuroblastoma Neuro-2A cells: importance of plasmalogen molecular species

Plasmalogen, especially those having 22:6, suppressed neuronal apoptosisviadeath receptor and mitochondrial pathways. These mechanisms of action of plasmalogen may be responsible for regulation of membrane functions and second messenger production.