Brain arachidonic and docosahexaenoic acid cascades are selectively altered by drugs, diet and disease

Revisiting the role of phospholipases in alzheimer's: crosstalk with processed food

Phospholipases such as phospholipase-A, phospholipase-B, phospholipase-C and phospholipase-D are important functional enzymes of the cell membrane responsible for a variety of functions such as signal transduction, production of lipid mediators, metabolite digestion and playing a pathological role in central nervous system diseases. Phospholipases have shown an association with Alzheimer's disease and these enzymes have found a correlation with several metabolic pathways that can lead to the activation of inflammatory signals via astrocytes and microglial cells. We also highlighted unhealthy practices like smoking and consuming processed foods, rich in nitroso compounds and phosphatidic acid, which contribute to neuronal damage in AD through phospholipases. A few therapeutic approaches such as the use of inhibitors of phospholipase-D,phospholipase A2 as well as autophagy-mediated inhibition have been discussed to control the onset of AD. This paper serves as a crosstalk between phospholipases and their role in neurodegenerative pathways as well as their influence on other biomolecules of lipid membranes, which are acquired through unhealthy diets and possible methods to treat these anomalies occurring due to their metabolic disorder involving phospholipases acting as major signaling molecules.

Bacteroides Fragilis in the gut microbiomes of Alzheimer's disease activates microglia and triggers pathogenesis in neuronal C/EBPβ transgenic mice

Gut dysbiosis contributes to Alzheimer's disease (AD) pathogenesis, and Bacteroides strains are selectively elevated in AD gut microbiota. However, it remains unknown which Bacteroides species and how their metabolites trigger AD pathologies. Here we show that Bacteroides fragilis and their metabolites 12-hydroxy-heptadecatrienoic acid (12-HHTrE) and Prostaglandin E2 (PGE2) activate microglia and induce AD pathogenesis in neuronal C/EBPβ transgenic mice. Recolonization of antibiotics cocktail-pretreated Thy1-C/EBPβ transgenic mice with AD patient fecal samples elicits AD pathologies, associated with C/EBPβ/Asparaginyl endopeptidase (AEP) pathway upregulation, microglia activation, and cognitive disorders compared to mice receiving healthy donors' fecal microbiota transplantation (FMT). Microbial 16S rRNA sequencing analysis shows higher abundance of proinflammatory Bacteroides fragilis in AD-FMT mice. Active components characterization from the sera and brains of the transplanted mice revealed that both 12-HHTrE and PGE2 activate primary microglia, fitting with poly-unsaturated fatty acid (PUFA) metabolites enrichment identified by metabolomics. Strikingly, recolonization with live but not dead Bacteroides fragilis elicited AD pathologies in Thy1-C/EBPβ transgenic mice, so did 12-HHTrE or PGE2 treatment alone. Collectively, our findings support a causal role for Bacteroides fragilis and the PUFA metabolites in activating microglia and inducing AD pathologies in Thy1- C/EBPβ transgenic mice.

Adolescent kratom exposure affects cognitive behaviours and brain metabolite profiles in Sprague-Dawley rats

Adolescence is a critical developmental period during which exposure to psychoactive substances like kratom (Mitragyna speciosa) can cause long-lasting deleterious effects. Here, we evaluated the effects of mitragynine, the main alkaloid of kratom, and lyophilised kratom decoction (LKD) on cognitive behaviours and brain metabolite profiles in adolescent rats. Male Sprague-Dawley rats (Postnatal day, PND31) were given vehicle, morphine (5 mg/kg), mitragynine (3, 10, or 30 mg/kg), or LKD (equivalent dose of 30 mg/kg mitragynine) for 15 consecutive days. Later, a battery of behavioural testing was conducted, brain was extracted and metabolomic analysis was performed using LCMS-QTOF. The results showed that mitragynine did not affect the recognition memory in the novel object recognition task. In the social interaction task, morphine, mitragynine, and LKD caused a marked deficit in social behaviour, while in Morris water maze task, mitragynine and LKD only affected reference memory. Metabolomic analysis revealed distinct metabolite profiles of animals with different treatments. Several pathways that may be involved in the effects of kratom exposure include arachidonic acid, pantothenate and CoA, and tryptophan pathways, with several potential biomarkers identified. These findings suggest that adolescent kratom exposure can cause cognitive behavioural deficits that may be associated with changes in the brain metabolite profiles.

Cyclooxygenase Inhibition Safety and Efficacy in Inflammation-Based Psychiatric Disorders

According to the World Health Organization, the major psychiatric and neurodevelopmental disorders include major depression, bipolar disorder, schizophrenia, and autism spectrum disorder. The potential role of inflammation in the onset and progression of these disorders is increasingly being studied. The use of non-steroidal anti-inflammatory drugs (NSAIDs), well-known cyclooxygenase (COX) inhibitors, combined with first-choice specific drugs have been long investigated. The adjunctive administration of COX inhibitors to classic clinical treatments seems to improve the prognosis of people who suffer from psychiatric disorders. In this review, a broad overview of the use of COX inhibitors in the treatment of inflammation-based psychiatric disorders is provided. For this purpose, a critical analysis of the use of COX inhibitors in the last ten years of clinical trials of the major psychiatric disorders was carried out.

The effect of insomnia on development of Alzheimer's disease

Alzheimer's disease (AD) is the most common type of dementia and a neurodegenerative disorder characterized by memory deficits especially forgetting recent information, recall ability impairment, and loss of time tracking, problem-solving, language, and recognition difficulties. AD is also a globally important health issue but despite all scientific efforts, the treatment of AD is still a challenge. Sleep has important roles in learning and memory consolidation. Studies have shown that sleep deprivation (SD) and insomnia are associated with the pathogenesis of Alzheimer's disease and may have an impact on the symptoms and development. Thus, sleep disorders have decisive effects on AD; this association deserves more attention in research, diagnostics, and treatment, and knowing this relation also can help to prevent AD through screening and proper management of sleep disorders. This study aimed to show the potential role of SD and insomnia in the pathogenesis and progression of AD.

The role of lipids in the central nervous system and their pathological implications in amyotrophic lateral sclerosis

Lipids play an important role in the central nervous system (CNS). They contribute to the structural integrity and physical characteristics of cell and organelle membranes, act as bioactive signalling molecules, and are utilised as fuel sources for mitochondrial metabolism. The intricate homeostatic mechanisms underpinning lipid handling and metabolism across two major CNS cell types; neurons and astrocytes, are integral for cellular health and maintenance. Here, we explore the various roles of lipids in these two cell types. Given that changes in lipid metabolism have been identified in a number of neurodegenerative diseases, we also discuss changes in lipid handling and utilisation in the context of amyotrophic lateral sclerosis (ALS), in order to identify key cellular processes affected by the disease, and inform future areas of research.

Potential Enzymatic Targets in Alzheimer's: A Comprehensive Review

Alzheimer's, a degenerative cause of the brain cells, is called as a progressive neurodegenerative disease and appears to have a heterogeneous etiology with main emphasis on amyloid-cascade and hyperphosphorylated tau-cascade hypotheses, that are directly linked with macromolecules called enzymes such as β- & γ-secretases, colinesterases, transglutaminases, and glycogen synthase kinase (GSK-3), cyclin-dependent kinase (cdk-5), microtubule affinity-regulating kinase (MARK). The catalytic activity of the above enzymes is the result of cognitive deficits, memory impairment and synaptic dysfunction and loss, and ultimately neuronal death. However, some other enzymes also lead to these dysfunctional events when reduced to their normal activities and levels in the brain, such as α- secretase, protein kinase C, phosphatases etc; metabolized to neurotransmitters, enzymes like monoamine oxidase (MAO), catechol-O-methyltransferase (COMT) etc. or these abnormalities can occur when enzymes act by other mechanisms such as phosphodiesterase reduces brain nucleotides (cGMP and cAMP) levels, phospholipase A2: PLA2 is associated with reactive oxygen species (ROS) production etc. On therapeutic fronts, several significant clinical trials are underway by targeting different enzymes for development of new therapeutics to treat Alzheimer's, such as inhibitors for β-secretase, GSK-3, MAO, phosphodiesterase, PLA2, cholinesterases etc, modulators of α- & γ-secretase activities and activators for protein kinase C, sirtuins etc. The last decades have perceived an increasing focus on findings and search for new putative and novel enzymatic targets for Alzheimer's. Here, we review the functions, pathological roles, and worth of almost all the Alzheimer's associated enzymes that address to therapeutic strategies and preventive approaches for treatment of Alzheimer's.

Dietary N-3 PUFA deficiency affects sleep-wake activity in basal condition and in response to an inflammatory challenge in mice

Essential polyunsaturated fatty acids (PUFA) from the n-3 and n-6 series constitute the building blocks of brain cell membranes where they regulate most aspects of cell physiology. They are either biosynthesized from their dietary precursors or can be directly sourced from the diet. An overall increase in the dietary n-6/n-3 PUFA ratio, as observed in the Western diet, leads to reduced n-3 PUFAs in tissues that include the brain. Some clinical studies have shown a positive correlation between dietary n-3 PUFA intake and sleep quantity, yet evidence is still sparse. We here used a preclinical model of dietary n-3 PUFA deficiency to assess the precise relationship between dietary PUFA intake and sleep/wake activity. Using electroencephalography (EEG)/electromyography (EMG) recordings on n-3 PUFA deficient or sufficient mice, we showed that dietary PUFA deficiency affects the architecture of sleep-wake activity and the oscillatory activity of cortical neurons during sleep. In a second part of the study, and since PUFAs are a potent modulator of inflammation, we assessed the effect of dietary n-3 PUFA deficiency on the sleep response to an inflammatory stimulus known to modulate sleep/wake activity. We injected mice with the endotoxin lipopolysaccharide (LPS) and quantified the sleep response across the following 12 h. Our results revealed that n-3 PUFA deficiency affects the sleep response in basal condition and after a peripheral immune challenge. More studies are now required aimed at deciphering the molecular mechanisms underlying the intimate relationship between n-3 PUFAs and sleep/wake activity.

Novel CB1-ligands maintain homeostasis of the endocannabinoid system in ω3- and ω6-long-chain-PUFA deficiency

Mammalian ω3- and ω6-PUFAs are synthesized from essential fatty acids (EFAs) or supplied by the diet. PUFAs are constitutive elements of membrane architecture and precursors of lipid signaling molecules. EFAs and long-chain (LC)-PUFAs are precursors in the synthesis of endocannabinoid ligands of G_i/o protein-coupled cannabinoid receptor (CB)1 and CB2 in the endocannabinoid system, which critically regulate energy homeostasis as the metabolic signaling system in hypothalamic neuronal circuits and behavioral parameters. We utilized the auxotrophic fatty acid desaturase 2-deficient (fads2^−/−) mouse, deficient in LC-PUFA synthesis, to follow the age-dependent dynamics of the PUFA pattern in the CNS-phospholipidome in unbiased dietary studies of three cohorts on sustained LC-PUFA-free ω6-arachidonic acid- and DHA-supplemented diets and their impact on the precursor pool of CB1 ligands. We discovered the transformation of eicosa-all cis-5,11,14-trienoic acid, uncommon in mammalian lipidomes, into two novel endocannabinoids, 20:3^5,11,14-ethanolamide and 2-20:3^5,11,14-glycerol. Their function as ligands of CB1 has been characterized in HEK293 cells. Labeling experiments excluded Δ8-desaturase activity and proved the position specificity of FADS2. The fads2^−/− mutant might serve as an unbiased model in vivo in the development of novel CB1 agonists and antagonists.

Are Polyunsaturated Fatty Acids Implicated in Histaminergic Dysregulation in Bipolar Disorder?: AN HYPOTHESIS

Bipolar disorder (BD) is an extremely disabling psychiatric disease, characterized by alternate states of mania (or hypomania) and depression with euthymic states in between. Currently, patients receive pharmacological treatment with mood stabilizers, antipsychotics, and antidepressants. Unfortunately, not all patients respond well to this type of treatment. Bipolar patients are also more prone to heart and metabolic diseases as well as a higher risk of suicide compared to the healthy population. For a correct brain function is indispensable a right protein and lipids (e.g., fatty acids) balance. In particular, the amount of fatty acids in the brain corresponds to a 50–70% of the dry weight. It has been reported that in specific brain regions of BD patients there is a reduction in the content of unsaturated n-3 fatty acids. Accordingly, a diet rich in n-3 fatty acids has beneficial effects in BD patients, while their absence or high levels of saturated fatty acids in the diet are correlated to the risk of developing the disease. On the other hand, the histamine system is likely to be involved in the pathophysiology of several psychiatric diseases such as BD. Histamine is a neuromodulator involved in arousal, motivation, and energy balance; drugs acting on the histamine receptor H3 have shown potential as antidepressants and antipsychotics. The histaminergic system as other neurotransmission systems can be altered by fatty acid membrane composition. The purpose of this review is to explore how polyunsaturated fatty acids content alterations are related to the histaminergic system modulation and their impact in BD pathophysiology.

Anti-Inflammatory Effects of Omega-3 Fatty Acids in the Brain: Physiological Mechanisms and Relevance to Pharmacology

Classically, polyunsaturated fatty acids (PUFA) were largely thought to be relatively inert structural components of brain, largely important for the formation of cellular membranes. Over the past 10 years, a host of bioactive lipid mediators that are enzymatically derived from arachidonic acid, the main n-6 PUFA, and docosahexaenoic acid, the main n-3 PUFA in the brain, known to regulate peripheral immune function, have been detected in the brain and shown to regulate microglia activation. Recent advances have focused on how PUFA regulate the molecular signaling of microglia, especially in the context of neuroinflammation and behavior. Several active drugs regulate brain lipid signaling and provide proof of concept for targeting the brain. Because brain lipid metabolism relies on a complex integration of diet, peripheral metabolism, including the liver and blood, which supply the brain with PUFAs that can be altered by genetics, sex, and aging, there are many pathways that can be disrupted, leading to altered brain lipid homeostasis. Brain lipid signaling pathways are altered in neurologic disorders and may be viable targets for the development of novel therapeutics. In this study, we discuss in particular how n-3 PUFAs and their metabolites regulate microglia phenotype and function to exert their anti-inflammatory and proresolving activities in the brain.

Therapeutic potential of omega-3 fatty acid-derived epoxyeicosanoids in cardiovascular and inflammatory diseases

Numerous benefits have been attributed to dietary long-chain omega-3 polyunsaturated fatty acids (n-3 LC-PUFAs), including protection against cardiac arrhythmia, triglyceride-lowering, amelioration of inflammatory, and neurodegenerative disorders. This review covers recent findings indicating that a variety of these beneficial effects are mediated by "omega-3 epoxyeicosanoids", a class of novel n-3 LC-PUFA-derived lipid mediators, which are generated via the cytochrome P450 (CYP) epoxygenase pathway. CYP enzymes, previously identified as arachidonic acid (20:4n-6; AA) epoxygenases, accept eicosapentaenoic acid (20:5n-3; EPA) and docosahexaenoic acid (22:6n-3; DHA), the major fish oil n-3 LC-PUFAs, as efficient alternative substrates. In humans and rodents, dietary EPA/DHA supplementation causes a profound shift of the endogenous CYP-eicosanoid profile from AA- to EPA- and DHA-derived metabolites, increasing, in particular, the plasma and tissue levels of 17,18-epoxyeicosatetraenoic acid (17,18-EEQ) and 19,20-epoxydocosapentaenoic acid (19,20-EDP). Based on preclinical studies, these omega-3 epoxyeicosanoids display cardioprotective, vasodilatory, anti-inflammatory, and anti-allergic properties that contribute to the beneficial effects of n-3 LC-PUFAs in diverse disease conditions ranging from cardiac disease, bronchial disorders, and intraocular neovascularization, to allergic intestinal inflammation and inflammatory pain. Increasing evidence also suggests that background nutrition as well as genetic and disease state-related factors could limit the response to EPA/DHA-supplementation by reducing the formation and/or enhancing the degradation of omega-3 epoxyeicosanoids. Recently, metabolically robust synthetic analogs mimicking the biological activities of 17,18-EEQ have been developed. These drug candidates may overcome limitations of dietary EPA/DHA supplementation and provide novel options for the treatment of cardiovascular and inflammatory diseases.

Blocking of carnitine palmitoyl transferase 1 potently reduces stress-induced depression in rat highlighting a pivotal role of lipid metabolism

Major depressive disorder is a complex and common mental disease, for which the pathology has not been elucidated. The purpose of this study is to provide knowledge about the importance of mitochondrial dysfunction, dysregulated lipid metabolism and inflammation. Mitochondrial carnitine palmitoyl transferase 1a (CPT1a) is a key molecule involved in lipid metabolism and mutations in CPT1a causing reduced function is hypothesized to have a protective role in the development of depression. Moreover, CPT1a is found to be upregulated in suicide patients with history of depression. Therefore, we hypothesized that inhibition of CPT1a activity can be developed as an innovative treatment strategy for depression. Stress exposure combined with different pharmacological treatment regimens; Etomoxir, CPT1 blocker, and Escitalopram, a favoured antidepressant drug, was applied in state-of-the-art chronic mild stress model. Etomoxir treatment induced statistical significant reduction of anhedonic behavior compared to vehicle treatment (p < 0.0001) and reversed depression-like phenotype in 90% of the rats (p = 0.0007), whereas Escitalopram only proved 57% efficacy. Moreover, Etomoxir revealed downregulation of interferon-γ, interleukin-17α and tumor necrosis factor-α. This indicate that alteration in metabolism is pivotal in the pathogenesis of depression, since CPT1 blockage is highly efficient in treating anhedonia and inflammation, thereby opening up for a novel class of antidepressant medication.

Reconsidering Dietary Polyunsaturated Fatty Acids in Bipolar Disorder: A Translational Picture

Inflammation is an important mediator of pathophysiology in bipolar disorder. The omega-3 (n-3) and omega-6 (n-6) polyunsaturated fatty acid (PUFA) metabolic pathways participate in several inflammatory processes and have been linked through epidemiologic and clinical studies to bipolar disorder and its response to treatment. We review the proposed role of PUFA metabolism in neuroinflammation, modulation of brain PUFA metabolism by antimanic medications in rodent models, and anti-inflammatory pharmacotherapy in bipolar disorder and in major depressive disorder (MDD). Although the convergence of findings between preclinical and postmortem clinical data is compelling, we investigate why human trials of PUFA as treatment are mixed. We view the biomarker and treatment study findings in light of the evidence for the hypothesis that arachidonic acid hypermetabolism contributes to bipolar disorder pathophysiology and propose that a combined high n-3 plus low n-6 diet should be tested as an adjunct to current medication in future trials.

Lowering dietary n-6 polyunsaturated fatty acids: interaction with brain arachidonic and docosahexaenoic acids

PURPOSE OF REVIEW

Arachidonic (ARA) and docosahexaenoic (DHA) acids are the most abundant polyunsaturated fatty acids (PUFA) in the brain, where they have many biological effects, including on inflammation, cell-signaling, appetite regulation, and blood flow. The Western diet contains a high ratio of n-6: n-3 PUFA. Although interest in lowering this ratio has largely focused on increasing intake of n-3 PUFA, few studies have examined lowering dietary n-6 PUFA. This review will evaluate the effect of lowering dietary n-6 PUFA on levels and metabolism of ARA and DHA in animal models and in humans, with a primary focus on the brain.

RECENT FINDINGS

In animal models, lowering dietary ARA or linoleic acid generally lowers levels of brain ARA and raises DHA. Lowering dietary n-6 PUFA can also modulate the levels of ARA and DHA metabolizing enzymes, as well as their associated bioactive mediators. Human studies examining changes in plasma fatty acid composition following n-6 PUFA lowering demonstrate no changes in levels of ARA and DHA, though there is evidence of alterations in their respective bioactive mediators.

SUMMARY

Lowering dietary n-6 PUFA, in animal models, can alter the levels and metabolism of ARA and DHA in the brain, but it remains to be determined whether these changes are clinically meaningful.

Gut microbiota regulates key modulators of social behavior

Social behavior plays a pivotal role in the mental well-being of an individual. Continuous efforts in the past have led to advancements in the area of how the brain regulates emotion and cognition, while the understanding of human social behavior still remains eluded. A major breakthrough in understanding the etiology of neurological disorders is the recent insight on the role of the gut microbiota (GM). Human GM also referred to as the "forgotten organ" is home to 10(13-14) microorganisms, which is 10 times the number of cells present in the human body. In addition, the gut microbiome (total genome of GM) is 150 times greater as compared to the human genome. An emerging concept gaining worldwide focus and acceptance is that, this much big genome can potentially control human behavior and other biological functions. Herein we hypothesize on the basis of GM's ability to modify brain and behavior and that it can directly or indirectly control social behavior. This review focuses on the association of GM with various domains of social behavior like stress, cognition and anxiety.

Low unesterified:esterified eicosapentaenoic acid (EPA) plasma concentration ratio is associated with bipolar disorder episodes, and omega-3 plasma concentrations are altered by treatment

OBJECTIVES

Omega (n)-3 and n-6 polyunsaturated fatty acids (PUFAs) are molecular modulators of neurotransmission and inflammation. We hypothesized that plasma concentrations of n-3 PUFAs would be lower and those of n-6 PUFAs higher in subjects with bipolar disorder (BD) compared to healthy controls (HCs), and would correlate with symptom severity in subjects with BD, and that effective treatment would correlate with increased n-3 but lower n-6 PUFA levels. Additionally, we explored clinical correlations and group differences in plasma levels of saturated and monounsaturated fatty acids.

METHODS

This observational, parallel group study compared biomarkers between HCs (n = 31) and symptomatic subjects with BD (n = 27) when ill and after symptomatic recovery (follow-up). Plasma concentrations of five PUFAs [linoleic acid (LA), arachidonic acid (AA), alpha-linolenic acid (ALA), docosahexaenoic acid (DHA), and eicosapentaenoic acid (EPA)], two saturated fatty acids (palmitic acid and stearic acid) and two monounsaturated fatty acids (palmitoleic acid and oleic acid) were measured in esterified (E) and unesterified (UE) forms. Calculated ratios included UE:E for the five PUFAs, ratios of n-3 PUFAs (DHA:ALA, EPA:ALA and EPA:DHA), and the ratio of n-6:n-3 AA:EPA. Comparisons of plasma fatty acid levels and ratios between BD and HC groups were made with Student t-tests, and between the BD group at baseline and follow-up using paired t-tests. Comparison of categorical variables was performed using chi-square tests. Pearson's r was used for bivariate correlations with clinical variables, including depressive and manic symptoms, current panic attacks, and psychosis.

RESULTS

UE EPA was lower in subjects with BD than in HCs, with a large effect size (Cohen's d = 0.86, p < 0.002); however, it was not statistically significant after correction for multiple comparisons. No statistically significant difference was seen in any plasma PUFA concentration between the BD and HC groups after Bonferroni correction for 40 comparisons, at p < 0.001. Neither depressive severity nor mania severity was correlated significantly with any PUFA concentration. Exploratory comparison showed lower UE:E EPA in the BD than the HC group (p < 0.0001). At follow-up in the BD group, UE, E DHA:ALA, and UE EPA:ALA were decreased (p < 0.002). Exploratory correlations of clinical variables revealed that mania severity and suicidality were positively correlated with UE:E EPA ratio, and that several plasma levels and ratios correlated with panic disorder and psychosis. Depressive severity was not correlated with any ratio. No plasma fatty acid level or ratio correlated with self-reported n-3 PUFA intake or use of medication by class.

CONCLUSIONS

A large effect size of reduced UE EPA, and a lower plasma UE:E concentration ratio of EPA in the symptomatic BD state may be important factors in vulnerability to a mood state. Altered n-3 PUFA ratios could indicate changes in PUFA metabolism concurrent with symptom improvement. Our findings are consistent with preclinical and postmortem data and suggest testing interventions that increase n-3 and decrease n-6 dietary PUFA intake.

Transient postnatal fluoxetine decreases brain concentrations of 20-HETE and 15-epi-LXA4, arachidonic acid metabolites in adult mice

BACKGROUND

Transient postnatal exposure of rodents to the selective serotonin (5-HT) reuptake inhibitor (SSRI) fluoxetine alters behavior and brain 5-HT neurotransmission during adulthood, and also reduces brain arachidonic (ARA) metabolic consumption and protein level of the ARA metabolizing enzyme, cytochrome P4504A (CYP4A).

HYPOTHESIS

Brain 20-hydroxyeicosatetraenoic acid (20-HETE), converted by CYP4A from ARA, will be reduced in adult mice treated transiently and postnatally with fluoxetine.

METHODS

Male mice pups were injected i.p. daily with fluoxetine (10mg/kg) or saline during P4-P21. At P90 their brain was high-energy microwaved and analyzed for 20-HETE and six other ARA metabolites by enzyme immunoassay.

RESULTS

Postnatal fluoxetine vs. saline significantly decreased brain concentrations of 20-HETE (-70.3%) and 15-epi-lipoxin A4 (-60%) in adult mice, but did not change other eicosanoid concentrations.

CONCLUSIONS

Behavioral changes in adult mice treated postnatally with fluoxetine may be related to reduced brain ARA metabolism involving CYP4A and 20-HETE formation.

Coordinated Expression of Phosphoinositide Metabolic Genes during Development and Aging of Human Dorsolateral Prefrontal Cortex

Background

Phosphoinositides, lipid-signaling molecules, participate in diverse brain processes within a wide metabolic cascade.

Hypothesis

Gene transcriptional networks coordinately regulate the phosphoinositide cascade during human brain Development and Aging.

Methods

We used the public BrainCloud database for human dorsolateral prefrontal cortex to examine age-related expression levels of 49 phosphoinositide metabolic genes during Development (0 to 20+ years) and Aging (21+ years).

Results

We identified three groups of partially overlapping genes in each of the two intervals, with similar intergroup correlations despite marked phenotypic differences between Aging and Development. In each interval, ITPKB, PLCD1, PIK3R3, ISYNA1, IMPA2, INPPL1, PI4KB, and AKT1 are in Group 1, PIK3CB, PTEN, PIK3CA, and IMPA1 in Group 2, and SACM1L, PI3KR4, INPP5A, SYNJ1, and PLCB1 in Group 3. Ten of the genes change expression nonlinearly during Development, suggesting involvement in rapidly changing neuronal, glial and myelination events. Correlated transcription for some gene pairs likely is facilitated by colocalization on the same chromosome band.

Conclusions

Stable coordinated gene transcriptional networks regulate brain phosphoinositide metabolic pathways during human Development and Aging.

Lithium an emerging contaminant: bioavailability, effects on protein expression, and homeostasis disruption in short-term exposure of rainbow trout

Worldwide production of lithium (Li) has increased dramatically during the past decade, driven by the demand for high charge density batteries. Information about Li in the aquatic environment is limited. The present study was designed to explore the effects of Li in rainbow trout (Oncorhynchus mykiss). Juvenile trout were exposed to a nominal concentration of 1.0mg Li/L in three separate exposures. Major ion concentrations were measured in brain and plasma by ion chromatography. Plasma proteins and fatty acids were measured by HPLC-MS/MS. Lithium accumulated in the brain and plasma. Arachidonic acid was elevated in plasma after 48h. Elevated concentrations of Li in brain were associated with depressed concentrations of sodium, magnesium, potassium and ammonium relative to the control. In plasma, sodium and calcium were also depressed. Several changes occurred to plasma proteins corresponding to Li exposure: inhibition of prostaglandin synthase (Ptgs2), increased expression of copper transporting ATP synthases, and Na(+)/K(+) ATPase. To our knowledge, ours is the first study to demonstrate elevated Li concentrations in fish brain, with associated effects on ion regulation.

Chronic SSRI stimulation of astrocytic 5-HT2B receptors change multiple gene expressions/editings and metabolism of glutamate, glucose and glycogen: a potential paradigm shift

It is firmly believed that the mechanism of action of SSRIs in major depression is to inhibit the serotonin transporter, SERT, and increase extracellular concentration of serotonin. However, this undisputed observation does not prove that SERT inhibition is the mechanism, let alone the only mechanism, by which SSRI's exert their therapeutic effects. It has recently been demonstrated that 5-HT2B receptor stimulation is needed for the antidepressant effect of fluoxetine in vivo. The ability of all five currently used SSRIs to stimulate the 5-HT2B receptor equipotentially in cultured astrocytes has been known for several years, and increasing evidence has shown the importance of astrocytes and astrocyte-neuronal interactions for neuroplasticity and complex brain activity. This paper reviews acute and chronic effects of 5-HT2B receptor stimulation in cultured astrocytes and in astrocytes freshly isolated from brains of mice treated with fluoxetine for 14 days together with effects of anti-depressant therapy on turnover of glutamate and GABA and metabolism of glucose and glycogen. It is suggested that these events are causally related to the mechanism of action of SSRIs and of interest for development of newer antidepressant drugs.

Chronic dietary n-6 PUFA deprivation leads to conservation of arachidonic acid and more rapid loss of DHA in rat brain phospholipids

To determine how the level of dietary n-6 PUFA affects the rate of loss of arachidonic acid (ARA) and DHA in brain phospholipids, male rats were fed either a deprived or adequate n-6 PUFA diet for 15 weeks postweaning, and then subjected to an intracerebroventricular infusion of (3)H-ARA or (3)H-DHA. Brains were collected at fixed times over 128 days to determine half-lives and the rates of loss from brain phospholipids (J out). Compared with the adequate n-6 PUFA rats, the deprived n-6-PUFA rats had a 15% lower concentration of ARA and an 18% higher concentration of DHA in their brain total phospholipids. Loss half-lives of ARA in brain total phospholipids and fractions (except phosphatidylserine) were longer in the deprived n-6 PUFA rats, whereas the J out was decreased. In the deprived versus adequate n-6 PUFA rats, the J out of DHA was higher. In conclusion, chronic n-6 PUFA deprivation decreases the rate of loss of ARA and increases the rate of loss of DHA in brain phospholipids. Thus, a low n-6 PUFA diet can be used to target brain ARA and DHA metabolism.

Linoleic and docosahexaenoic acids in human milk have opposite relationships with cognitive test performance in a sample of 28 countries

Polyunsaturated fatty acids play critical roles in brain development and function, and their levels in human breast milk closely reflect the long-term diet. The fatty acid contents of human milk samples from 28 countries were used to predict averaged 2009 and 2012 test scores in mathematics, reading, and science from the Program for International Student Assessment. All test scores were positively related to milk docosahexaenoic acid (r=0.48 to 0.55), and negatively related to linoleic acid (r=-0.28 to -0.56). Together, these two human milk fatty acids explained 46% to 48% of the variance in scores, with no improvement in predictive power when socioeconomic variables were added to the regression. The (log) ratio of linoleic to arachidonic acid was negatively related to scores (r=-0.45 to -0.48). Statistical effects were similar for the two sexes. In a separate US sample, estimated dietary linoleic was negatively related to the levels of all long-chain n-3 and n-6 plasma fatty acids. High levels of dietary linoleic may impair cognition by decreasing both docosahexaenoic and arachidonic acids in the brain.

Fluoxetine and all other SSRIs are 5-HT2B Agonists - Importance for their Therapeutic Effects

Fluoxetine and other serotonin-specific re-uptake inhibitors (SSRIs) are generally thought to owe their therapeutic potency to inhibition of the serotonin transporter (SERT). However, research in our laboratory showed that it affects, with relatively high affinity the 5-HT2B receptor in cultured astrocytes; this finding was confirmed by independent observations showing that fluoxetine loses its ability to elicit SSRI-like responses in behavioral assays in mice in which the 5-HT2B receptor was knocked-out genetically or inhibited pharmacologically. All clinically used SSRIs are approximately equipotent towards 5-HT2B receptors and exert their effect on cultured astrocytes at concentrations similar to those used clinically, a substantial difference from their effect on SERT. We have demonstrated up-regulation and editing of astrocytic genes for ADAR2, the kainate receptor GluK2, cPLA2 and the 5-HT2B receptor itself after chronic treatment of cultures, which do not express SERT and after treatment of mice (expressing SERT) for 2 weeks with fluoxetine, followed by isolation of astrocytic and neuronal cell fractionation. Affected genes were identical in both experimental paradigms. Fluoxetine treatment also altered Ca(2+) homeostatic cascades, in a specific way that differs from that seen after treatment with the anti-bipolar drugs carbamazepine, lithium, or valproic acid. All changes occurred after a lag period similar to what is seen for fluoxetine's clinical effects, and some of the genes were altered in the opposite direction by mild chronic inescapable stress, known to cause anhedonia, a component of major depression. In the anhedonic mice these changes were reversed by treatment with SSRIs.

Coordination of gene expression of arachidonic and docosahexaenoic acid cascade enzymes during human brain development and aging

Background

The polyunsaturated arachidonic and docosahexaenoic acids (AA and DHA) participate in cell membrane synthesis during neurodevelopment, neuroplasticity, and neurotransmission throughout life. Each is metabolized via coupled enzymatic reactions within separate but interacting metabolic cascades.

Hypothesis

AA and DHA pathway genes are coordinately expressed and underlie cascade interactions during human brain development and aging.

Methods

The BrainCloud database for human non-pathological prefrontal cortex gene expression was used to quantify postnatal age changes in mRNA expression of 34 genes involved in AA and DHA metabolism.

Results

Expression patterns were split into Development (0 to 20 years) and Aging (21 to 78 years) intervals. Expression of genes for cytosolic phospholipases A₂ (cPLA₂), cyclooxygenases (COX)-1 and -2, and other AA cascade enzymes, correlated closely with age during Development, less so during Aging. Expression of DHA cascade enzymes was less inter-correlated in each period, but often changed in the opposite direction to expression of AA cascade genes. Except for the PLA2G4A (cPLA₂ IVA) and PTGS2 (COX-2) genes at 1q25, highly inter-correlated genes were at distant chromosomal loci.

Conclusions

Coordinated age-related gene expression during the brain Development and Aging intervals likely underlies coupled changes in enzymes of the AA and DHA cascades and largely occur through distant transcriptional regulation. Healthy brain aging does not show upregulation of PLA2G4 or PTGS2 expression, which was found in Alzheimer's disease.

Lithium and the other mood stabilizers effective in bipolar disorder target the rat brain arachidonic acid cascade

This Review evaluates the arachidonic acid (AA, 20:4n-6) cascade hypothesis for the actions of lithium and other FDA-approved mood stabilizers in bipolar disorder (BD). The hypothesis is based on evidence in unanesthetized rats that chronically administered lithium, carbamazepine, valproate, or lamotrigine each downregulated brain AA metabolism, and it is consistent with reported upregulated AA cascade markers in post-mortem BD brain. In the rats, each mood stabilizer reduced AA turnover in brain phospholipids, cyclooxygenase-2 expression, and prostaglandin E2 concentration. Lithium and carbamazepine also reduced expression of cytosolic phospholipase A2 (cPLA2) IVA, which releases AA from membrane phospholipids, whereas valproate uncompetitively inhibited in vitro acyl-CoA synthetase-4, which recycles AA into phospholipid. Topiramate and gabapentin, proven ineffective in BD, changed rat brain AA metabolism minimally. On the other hand, the atypical antipsychotics olanzapine and clozapine, which show efficacy in BD, decreased rat brain AA metabolism by reducing plasma AA availability. Each of the four approved mood stabilizers also dampened brain AA signaling during glutamatergic NMDA and dopaminergic D2 receptor activation, while lithium enhanced the signal during cholinergic muscarinic receptor activation. In BD patients, such signaling effects might normalize the neurotransmission imbalance proposed to cause disease symptoms. Additionally, the antidepressants fluoxetine and imipramine, which tend to switch BD depression to mania, each increased AA turnover and cPLA2 IVA expression in rat brain, suggesting that brain AA metabolism is higher in BD mania than depression. The AA hypothesis for mood stabilizer action is consistent with reports that low-dose aspirin reduced morbidity in patients taking lithium, and that high n-3 and/or low n-6 polyunsaturated fatty acid diets, which in rats reduce brain AA metabolism, were effective in BD and migraine patients.

iPLA2β knockout mouse, a genetic model for progressive human motor disorders, develops age-related neuropathology

Calcium-independent phospholipase A2 group VIa (iPLA2β) preferentially releases docosahexaenoic acid (DHA) from the sn-2 position of phospholipids. Mutations of its gene, PLA2G6, are found in patients with several progressive motor disorders, including Parkinson disease. At 4 months, PLA2G6 knockout mice (iPLA2β(-/-)) show minimal neuropathology but altered brain DHA metabolism. By 1 year, they develop motor disturbances, cerebellar neuronal loss, and striatal α-synuclein accumulation. We hypothesized that older iPLA2β(-/-) mice also would exhibit inflammatory and other neuropathological changes. Real-time polymerase chain reaction and Western blotting were performed on whole brain homogenate from 15 to 20-month old male iPLA2β(-/-) or wild-type (WT) mice. These older iPLA2β(-/-) mice compared with WT showed molecular evidence of microglial (CD-11b, iNOS) and astrocytic (glial fibrillary acidic protein) activation, disturbed expression of enzymes involved in arachidonic acid metabolism, loss of neuroprotective brain derived neurotrophic factor, and accumulation of cytokine TNF-α messenger ribonucleic acid, consistent with neuroinflammatory pathology. There was no evidence of synaptic loss, of reduced expression of dopamine active reuptake transporter, or of accumulation of the Parkinson disease markers Parkin or Pink1. iPLA2γ expression was unchanged. iPLA2β deficient mice show evidence of neuroinflammation and associated neuropathology with motor dysfunction in later life. These pathological biomarkers could be used to assess efficacy of dietary intervention, antioxidants or other therapies on disease progression in this mouse model of progressive human motor diseases associated with a PLA2G6 mutation.

Transient postnatal fluoxetine leads to decreased brain arachidonic acid metabolism and cytochrome P450 4A in adult mice

Fetal and perinatal exposure to selective serotonin (5-HT) reuptake inhibitors (SSRIs) has been reported to alter childhood behavior, while transient early exposure in rodents is reported to alter their behavior and decrease brain extracellular 5-HT in adulthood. Since 5-HT2A/2C receptor-mediated neurotransmission can involve G-protein coupled activation of cytosolic phospholipase A2 (cPLA2), releasing arachidonic acid (ARA) from synaptic membrane phospholipid, we hypothesized that transient postnatal exposure to fluoxetine would alter brain ARA metabolism in adult mice. Brain ARA incorporation coefficients k* and rates Jin were quantitatively imaged following intravenous [1-(14)C]ARA infusion of unanesthetized adult mice that had been injected daily with fluoxetine (10mg/kg i.p.) or saline during postnatal days P4-P21. Expression of brain ARA metabolic enzymes and other relevant markers also was measured. On neuroimaging, k* and Jin was decreased widely in early fluoxetine- compared to saline-treated adult mice. Of the enzymes measured, cPLA2 activity was unchanged, while Ca(2+)-independent iPLA2 activity was increased. There was a significant 74% reduced protein level of cytochrome P450 (CYP) 4A, which can convert ARA to 20-HETE. Reduced brain ARA metabolism in adult mice transiently exposed to postnatal fluoxetine, and a 74% reduction in CYP4A protein, suggest long-term effects independent of drug presence in brain ARA metabolism, and in CYP4A metabolites. These changes might contribute to reported altered behavior following early SSRI in rodents.

Plasma metabolite profiles of Alzheimer's disease and mild cognitive impairment

Previous studies have demonstrated altered metabolites in samples of Alzheimer's disease (AD) patients. However, the sample size from many of them is relatively small and the metabolites are relatively limited. Here we applied a comprehensive platform using ultraperformance liquid chromatography-time-of-flight mass spectrometry and gas chromatography-time-of-flight mass spectrometry to analyze plasma samples from AD patients, amnestic mild cognitive impairment (aMCI) patients, and normal controls. A biomarker panel consisting of six plasma metabolites (arachidonic acid, N,N-dimethylglycine, thymine, glutamine, glutamic acid, and cytidine) was identified to discriminate AD patients from normal control. Another panel of five plasma metabolites (thymine, arachidonic acid, 2-aminoadipic acid, N,N-dimethylglycine, and 5,8-tetradecadienoic acid) was able to differentiate aMCI patients from control subjects. Both biomarker panels had good agreements with clinical diagnosis. The 2 panels of metabolite markers were all involved in fatty acid metabolism, one-carbon metabolism, amino acid metabolism, and nucleic acid metabolism. Additionally, no altered metabolites were found among the patients at different stages, as well as among those on anticholinesterase medication and those without anticholinesterase medication. These findings provide a comprehensive global plasma metabolite profiling and may contribute to making early diagnosis as well as understanding the pathogenic mechanism of AD and aMCI.

Transfer of omega-3 fatty acids across the blood-brain barrier after dietary supplementation with a docosahexaenoic acid-rich omega-3 fatty acid preparation in patients with Alzheimer's disease: the OmegAD study

OBJECTIVE

Little is known about the transfer of essential fatty acids (FAs) across the human blood-brain barrier (BBB) in adulthood. In this study, we investigated whether oral supplementation with omega-3 (n-3) FAs would change the FA profile of the cerebrospinal fluid (CSF).

METHODS

A total of 33 patients (18 receiving the n-3 FA supplement and 15 receiving placebo) were included in the study. These patients were participants in the double-blind, placebo-controlled randomized OmegAD study in which 204 patients with mild Alzheimer's disease (AD) received 2.3 g n-3 FA [high in docosahexaenoic acid (DHA)] or placebo daily for 6 months. CSF FA levels were related to changes in plasma FA and to CSF biomarkers of AD and inflammation.

RESULTS

At 6 months, the n-3 FA supplement group displayed significant increases in CSF (and plasma) eicosapentaenoic acid (EPA), DHA and total n-3 FA levels (P < 0.01), whereas no changes were observed in the placebo group. Changes in CSF and plasma levels of EPA and n-3 docosapentaenoic acid were strongly correlated, in contrast to those of DHA. Changes in DHA levels in CSF were inversely correlated with CSF levels of total and phosphorylated tau, and directly correlated with soluble interleukin-1 receptor type II. Thus, the more DHA increased in CSF, the greater the change in CSF AD/inflammatory biomarkers.

CONCLUSIONS

Oral supplementation with n-3 FAs conferred changes in the n-3 FA profile in CSF, suggesting transfer of these FAs across the BBB in adults.

Effectiveness and tolerance of anti-inflammatory drugs' add-on therapy in major mental disorders: a systematic qualitative review

OBJECTIVE

To provide a systematic review of the literature regarding the efficacy of anti-inflammatory drugs in three major mental disorders [major depressive disorder (MDD), schizophrenia and bipolar disorders].

METHOD

Four databases were explored, without any year or language restrictions. The baseline search paradigm was limited to open-labelled clinical and randomized controlled trials (RCTs).

RESULTS

Four major classes of anti-inflammatory drugs were identified, namely polyunsaturated fatty acids (PUFAs), cyclooxygenase (COX) inhibitors, anti-TNFalpha and minocycline. Effectiveness and benefit/risk ratio of each class in MDD, bipolar disorders and schizophrenia was detailed when data were available. Several meta-analyses indicated effectiveness of PUFAs in MDD with a good tolerance profile. One meta-analysis indicated that COX-2 specific inhibitors showed effectiveness in schizophrenia. Anti-TNFalpha showed important effectiveness in resistant MDD with blood inflammatory abnormalities. Minocycline showed effectiveness in schizophrenia.

CONCLUSION

Polyunsaturated fatty acids seem to have the best benefit/risk ratio profile but proved their effectiveness only in MDD. A number of anti-inflammatory drugs are available as adjunct treatment for treatment-resistant patients with MDD, schizophrenia and bipolar disorder. If used with caution regarding their possible side-effects, they may be reasonable therapeutic alternatives for resistant symptomatology.

Signal Transduction in Astrocytes during Chronic or Acute Treatment with Drugs (SSRIs, Antibipolar Drugs, GABA-ergic Drugs, and Benzodiazepines) Ameliorating Mood Disorders

Chronic treatment with fluoxetine or other so-called serotonin-specific reuptake inhibitor antidepressants (SSRIs) or with a lithium salt “lithium”, carbamazepine, or valproic acid, the three classical antibipolar drugs, exerts a multitude of effects on astrocytes, which in turn modulate astrocyte-neuronal interactions and brain function. In the case of the SSRIs, they are to a large extent due to 5-HT_2B-mediated upregulation and editing of genes. These alterations induce alteration in effects of cPLA₂, GluK2, and the 5-HT_2B receptor, probably including increases in both glucose metabolism and glycogen turnover, which in combination have therapeutic effect on major depression. The ability of increased levels of extracellular K⁺ to increase [Ca²⁺]_i is increased as a sign of increased K⁺-induced excitability in astrocytes. Acute anxiolytic drug treatment with benzodiazepines or GABA_A receptor stimulation has similar glycogenolysis-enhancing effects. The antibipolar drugs induce intracellular alkalinization in astrocytes with lithium acting on one acid extruder and carbamazepine and valproic acid on a different acid extruder. They inhibit K⁺-induced and transmitter-induced increase of astrocytic [Ca²⁺]_i and thereby probably excitability. In several cases, they exert different changes in gene expression than SSRIs, determined both in cultured astrocytes and in freshly isolated astrocytes from drug-treated animals.

Kinetics of eicosapentaenoic acid in brain, heart and liver of conscious rats fed a high n-3 PUFA containing diet

Eicosapentaenoic acid (EPA, 20:5n-3), a precursor of docosahexaenoic acid (DHA), may benefit cardiovascular and brain health. Quantifying EPA's in vivo kinetics might elucidate these effects. [1-(14)C]EPA was infused i.v. for 5min in unanesthetized male rats fed a standard EPA-DHA diet. Plasma and microwaved tissue were analyzed. Kinetic parameters were calculated using our compartmental model. At 5min, 31-48% of labeled EPA in brain and heart was oxidized, 7% in liver. EPA incorporation rates from brain and liver precursor EPA-CoA pools into lipids, mainly phospholipids, were 36 and 2529nmol/s/g×10(-4), insignificant for heart. Deacylation-reacylation half-lives were 22h and 38-128min. Conversion rates to DHA equaled 0.65 and 25.1nmol/s/g×10(-4), respectively. The low brain concentration and incorporation rate and high oxidation of EPA suggest that, if EPA has a beneficial effect in brain, it might result from its suppression of peripheral inflammation and hepatic conversion to bioactive DHA.

Propylisopropylacetic acid (PIA), a constitutional isomer of valproic acid, uncompetitively inhibits arachidonic acid acylation by rat acyl-CoA synthetase 4: a potential drug for bipolar disorder

BACKGROUND

Mood stabilizers used for treating bipolar disorder (BD) selectively downregulate arachidonic acid (AA) turnover (deacylation-reacylation) in brain phospholipids, when given chronically to rats. In vitro studies suggest that one of these, valproic acid (VPA), which is teratogenic, reduces AA turnover by inhibiting the brain long-chain acyl-CoA synthetase (Acsl)4 mediated acylation of AA to AA-CoA. We tested whether non-teratogenic VPA analogues might also inhibit Acsl4 catalyzed acylation, and thus have a potential anti-BD action.

METHODS

Rat Acsl4-flag protein was expressed in Escherichia coli, and the ability of three VPA analogues, propylisopropylacetic acid (PIA), propylisopropylacetamide (PID) and N-methyl-2,2,3,3-tetramethylcyclopropanecarboxamide (MTMCD), and of sodium butyrate, to inhibit conversion of AA to AA-CoA by Acsl4 was quantified using Michaelis-Menten kinetics.

RESULTS

Acsl4-mediated conversion of AA to AA-CoA in vitro was inhibited uncompetitively by PIA, with a Ki of 11.4mM compared to a published Ki of 25mM for VPA, while PID, MTMCD and sodium butyrate had no inhibitory effect.

CONCLUSIONS

PIA's ability to inhibit conversion of AA to AA-CoA by Acsl4 in vitro suggests that, like VPA, PIA may reduce AA turnover in brain phospholipids in unanesthetized rats, and if so, may be effective as a non-teratogenic mood stabilizer in BD patients.

Elevated immune-inflammatory signaling in mood disorders: a new therapeutic target?

Converging translational evidence has implicated elevated immune-inflammatory signaling activity in the pathoetiology of mood disorders, including major depressive disorder and bipolar disorder. This is supported in part by cross-sectional evidence for increased levels of proinflammatory eicosanoids, cytokines and acute-phase proteins during mood episodes, and prospective longitudinal evidence for the emergence of mood symptoms in response to chronic immune-inflammatory activation. In addition, mood-stabilizer and atypical antipsychotic medications downregulate initial components of the immune-inflammatory signaling pathway, and adjunctive treatment with anti-inflammatory agents augment the therapeutic efficacy of antidepressant, mood stabilizer and atypical antipsychotic medications. Potential pathogenic mechanisms linked with elevated immune-inflammatory signaling include perturbations in central serotonin neurotransmission and progressive white matter pathology. Both heritable genetic factors and environmental factors including dietary fatty-acid composition may act in concert to sustain elevated immune-inflammatory signaling. Collectively, these data suggest that elevated immune-inflammatory signaling is a mechanism that is relevant to the pathoetiology of mood disorders, and may therefore represent a new therapeutic target for the development of more effective treatments.

Dietary omega-3 polyunsaturated fatty acids improve the neurolipidome and restore the DHA status while promoting functional recovery after experimental spinal cord injury

Omega-3 polyunsaturated fatty acids (ω-3 PUFAs) confer multiple health benefits and decrease the risk of neurological disorders. Studies are needed, however, to identify promising cellular targets and to assess their prophylactic value against neurodegeneration. The present study (1) examined the efficacy of a preventive diet enriched with ω-3 PUFAs to reduce dysfunction in a well-established spinal cord injury (SCI) animal model and (2) used a novel metabolomics data analysis to identify potential neurolipidomic targets. Rats were fed with either control chow or chow enriched with ω-3 PUFAs (750 mg/kg/day) for 8 weeks before being subjected to a sham or a contusion SCI operation. We report new evidence showing that rats subjected to SCI after being pre-treated with a diet enriched with ω-3 PUFAs exhibit significantly better functional outcomes. Pre-treated animals exhibited lower sensory deficits, autonomic bladder recovery, and early improvements in locomotion that persisted for at least 8 weeks after trauma. We found that SCI triggers a robust alteration in the cord PUFA neurolipidome, which was characterized by a marked docosahexaenoic acid (DHA) deficiency. This DHA deficiency was associated with dysfunction and corrected with the ω-3 PUFA-enriched diet. Multivariate data analyses revealed that the spinal cord of animals consuming the ω-3 PUFA-enriched diet had a fundamentally distinct neurolipidome, particularly increasing the levels of essential and long chain ω-3 fatty acids and lysolipids at the expense of ω-6 fatty acids and its metabolites. Altogether, dietary ω-3 PUFAs prophylaxis confers resiliency to SCI mediated, at least in part, by generating a neuroprotective and restorative neurolipidome.

Chronic clozapine reduces rat brain arachidonic acid metabolism by reducing plasma arachidonic acid availability

Chronic administration of mood stabilizers to rats down-regulates the brain arachidonic acid (AA) cascade. This down-regulation may explain their efficacy against bipolar disorder (BD), in which brain AA cascade markers are elevated. The atypical antipsychotics, olanzapine (OLZ) and clozapine (CLZ), also act against BD. When given to rats, both reduce brain cyclooxygenase activity and prostaglandin E(2) concentration; OLZ also reduces rat plasma unesterified and esterified AA concentrations, and AA incorporation and turnover in brain phospholipid. To test whether CLZ produces similar changes, we used our in vivo fatty acid method in rats given 10 mg/kg/day i.p. CLZ, or vehicle, for 30 days; or 1 day after CLZ washout. [1-(14) C]AA was infused intravenously for 5 min, arterial plasma was collected and high-energy microwaved brain was analyzed. CLZ increased incorporation coefficients ki * and decreased [corrected] rates J(in,i) of plasma unesterified AA into brain phospholipids. [corrected]. These effects disappeared after washout. Thus, CLZ and OLZ similarly down-regulated kinetics and cyclooxygenase expression of the brain AA cascade, likely by reducing plasma unesterified AA availability. Atypical antipsychotics and mood stabilizers may be therapeutic in BD by down-regulating, indirectly or directly respectively, the elevated brain AA cascade of that disease.

Translational studies on regulation of brain docosahexaenoic acid (DHA) metabolism in vivo

One goal in the field of brain polyunsaturated fatty acid (PUFA) metabolism is to translate the many studies that have been conducted in vitro and in animal models to the clinical setting. Doing so should elucidate the role of PUFAs in the human brain, and effects of diet, drugs, disease and genetics on this role. This review discusses new in vivo radiotracer kinetic and neuroimaging techniques that allow us to do this, with a focus on docosahexaenoic acid (DHA). We illustrate how brain PUFA metabolism is influenced by graded reductions in dietary n-3 PUFA content in unanesthetized rats. We also show how kinetic tracer techniques in rodents have helped to identify mechanisms of action of mood stabilizers used in bipolar disorder, how DHA participates in neurotransmission, and how brain DHA metabolism is regulated by calcium-independent iPLA₂β. In humans, regional rates of brain DHA metabolism can be quantitatively imaged with positron emission tomography following intravenous injection of [1-¹¹C]DHA.

Mind-altering microorganisms: the impact of the gut microbiota on brain and behaviour

Recent years have witnessed the rise of the gut microbiota as a major topic of research interest in biology. Studies are revealing how variations and changes in the composition of the gut microbiota influence normal physiology and contribute to diseases ranging from inflammation to obesity. Accumulating data now indicate that the gut microbiota also communicates with the CNS--possibly through neural, endocrine and immune pathways--and thereby influences brain function and behaviour. Studies in germ-free animals and in animals exposed to pathogenic bacterial infections, probiotic bacteria or antibiotic drugs suggest a role for the gut microbiota in the regulation of anxiety, mood, cognition and pain. Thus, the emerging concept of a microbiota-gut-brain axis suggests that modulation of the gut microbiota may be a tractable strategy for developing novel therapeutics for complex CNS disorders.

Long term adequate n-3 polyunsaturated fatty acid diet protects from depressive-like behavior but not from working memory disruption and brain cytokine expression in aged mice

Converging epidemiological studies suggest that dietary essential n-3 polyunsaturated fatty acid (PUFA) are likely to be involved in the pathogenesis of mood and cognitive disorders linked to aging. The question arises as to whether the decreased prevalence of these symptoms in the elderly with high n-3 PUFA consumption is also associated with improved central inflammation, i.e. cytokine activation, in the brain. To answer this, we measured memory performance and emotional behavior as well as cytokine synthesis and PUFA level in the spleen and the cortex of adult and aged mice submitted to a diet with an adequate supply of n-3 PUFA in form of α-linolenic acid (α-LNA) or a n-3 deficient diet. Our results show that docosahexaenoic acid (DHA), the main n-3 PUFA in the brain, was higher in the spleen and cortex of n-3 adequate mice relative to n-3 deficient mice and this difference was maintained throughout life. Interestingly, high level of brain DHA was associated with a decrease in depressive-like symptoms throughout aging. On the opposite, spatial memory was maintained in adult but not in aged n-3 adequate mice relative to n-3 deficient mice. Furthermore, increased interleukin-6 (IL-6) and decreased IL-10 expression were found in the cortex of aged mice independently of the diets. All together, our results suggest that n-3 PUFA dietary supply in the form of α-LNA is sufficient to protect from deficits in emotional behavior but not from memory disruption and brain proinflammatory cytokine expression linked to age.

Short-term long chain omega3 diet protects from neuroinflammatory processes and memory impairment in aged mice

Regular consumption of food enriched in omega3 polyunsaturated fatty acids (ω3 PUFAs) has been shown to reduce risk of cognitive decline in elderly, and possibly development of Alzheimer's disease. Docosahexaenoic acid (DHA) and eicosapentaenoic acid (EPA) are the most likely active components of ω3-rich PUFAs diets in the brain. We therefore hypothesized that exposing mice to a DHA and EPA enriched diet may reduce neuroinflammation and protect against memory impairment in aged mice. For this purpose, mice were exposed to a control diet throughout life and were further submitted to a diet enriched in EPA and DHA during 2 additional months. Cytokine expression together with a thorough analysis of astrocytes morphology assessed by a 3D reconstruction was measured in the hippocampus of young (3-month-old) and aged (22-month-old) mice. In addition, the effects of EPA and DHA on spatial memory and associated Fos activation in the hippocampus were assessed. We showed that a 2-month EPA/DHA treatment increased these long-chain ω3 PUFAs in the brain, prevented cytokines expression and astrocytes morphology changes in the hippocampus and restored spatial memory deficits and Fos-associated activation in the hippocampus of aged mice. Collectively, these data indicated that diet-induced accumulation of EPA and DHA in the brain protects against neuroinflammation and cognitive impairment linked to aging, further reinforcing the idea that increased EPA and DHA intake may provide protection to the brain of aged subjects.

Dose-dependent changes in neuroinflammatory and arachidonic acid cascade markers with synaptic marker loss in rat lipopolysaccharide infusion model of neuroinflammation

Background

Neuroinflammation, caused by six days of intracerebroventricular infusion of bacterial lipopolysaccharide (LPS), stimulates rat brain arachidonic acid (AA) metabolism. The molecular changes associated with increased AA metabolism are not clear. We examined effects of a six-day infusion of a low-dose (0.5 ng/h) and a high-dose (250 ng/h) of LPS on neuroinflammatory, AA cascade, and pre- and post-synaptic markers in rat brain. We used artificial cerebrospinal fluid-infused brains as controls.

Results

Infusion of low- or high-dose LPS increased brain protein levels of TNFα, and iNOS, without significantly changing GFAP. High-dose LPS infusion upregulated brain protein and mRNA levels of AA cascade markers (cytosolic cPLA₂-IVA, secretory sPLA₂-V, cyclooxygenase-2 and 5-lipoxygenase), and of transcription factor NF-κB p50 DNA binding activity. Both LPS doses increased cPLA₂ and p38 mitogen-activated protein kinase levels, while reducing protein levels of the pre-synaptic marker, synaptophysin. Post-synaptic markers drebrin and PSD95 protein levels were decreased with high- but not low-dose LPS.

Conclusions

Chronic LPS infusion has differential effects, depending on dose, on inflammatory, AA and synaptic markers in rat brain. Neuroinflammation associated with upregulated brain AA metabolism can lead to synaptic dysfunction.

Dietary n-6 polyunsaturated fatty acid deprivation increases docosahexaenoic acid metabolism in rat brain

Dietary n-6 polyunsaturated fatty acid (PUFA) deprivation in rodents reduces brain arachidonic acid (20:4n-6) concentration and 20:4n-6-preferring cytosolic phospholipase A(2) (cPLA(2) -IVA) and cyclooxygenase (COX)-2 expression, while increasing brain docosahexaenoic acid (DHA, 22:6n-3) concentration and DHA-selective calcium-independent phospholipase A(2) (iPLA(2) )-VIA expression. We hypothesized that these changes are accompanied by up-regulated brain DHA metabolic rates. Using a fatty acid model, brain DHA concentrations and kinetics were measured in unanesthetized male rats fed, for 15 weeks post-weaning, an n-6 PUFA 'adequate' (31.4 wt% linoleic acid) or 'deficient' (2.7 wt% linoleic acid) diet, each lacking 20:4n-6 and DHA. [1-(14) C]DHA was infused intravenously, arterial blood was sampled, and the brain was microwaved at 5 min and analyzed. Rats fed the n-6 PUFA deficient compared with adequate diet had significantly reduced n-6 PUFA concentrations in brain phospholipids but increased eicosapentaenoic acid (EPA, 20:5n-3), docosapentaenoic acid n-3 (DPAn-3, 22:5n-3), and DHA (by 9.4%) concentrations, particularly in ethanolamine glycerophospholipid (EtnGpl). Incorporation rates of unesterified DHA from plasma, which represent DHA metabolic loss from brain, were increased 45% in brain phospholipids, as was DHA turnover. Increased DHA metabolism following dietary n-6 PUFA deprivation may increase brain concentrations of antiinflammatory DHA metabolites, which with a reduced brain n-6 PUFA content, likely promotes neuroprotection and alters neurotransmission.

Imaging brain signal transduction and metabolism via arachidonic and docosahexaenoic acid in animals and humans

The polyunsaturated fatty acids (PUFAs), arachidonic acid (AA, 20:4n-6) and docosahexaenoic acid (DHA, 22:6n-3), important second messengers in brain, are released from membrane phospholipid following receptor-mediated activation of specific phospholipase A(2) (PLA(2)) enzymes. We developed an in vivo method in rodents using quantitative autoradiography to image PUFA incorporation into brain from plasma, and showed that their incorporation rates equal their rates of metabolic consumption by brain. Thus, quantitative imaging of unesterified plasma AA or DHA incorporation into brain can be used as a biomarker of brain PUFA metabolism and neurotransmission. We have employed our method to image and quantify effects of mood stabilizers on brain AA/DHA incorporation during neurotransmission by muscarinic M(1,3,5), serotonergic 5-HT(2A/2C), dopaminergic D(2)-like (D(2), D(3), D(4)) or glutamatergic N-methyl-d-aspartic acid (NMDA) receptors, and effects of inhibition of acetylcholinesterase, of selective serotonin and dopamine reuptake transporter inhibitors, of neuroinflammation (HIV-1 and lipopolysaccharide) and excitotoxicity, and in genetically modified rodents. The method has been extended for the use with positron emission tomography (PET), and can be employed to determine how human brain AA/DHA signaling and consumption are influenced by diet, aging, disease and genetics.

Regulation of rat brain polyunsaturated fatty acid (PUFA) metabolism during graded dietary n-3 PUFA deprivation

Knowing threshold changes in brain lipids and lipid enzymes during dietary n-3 polyunsaturated fatty acid deprivation may elucidate dietary regulation of brain lipid metabolism. To determine thresholds, rats were fed for 15 weeks DHA-free diets having graded reductions of α-linolenic acid (α-LNA). Compared with control diet (4.6% α-LNA), plasma DHA fell significantly at 1.7% dietary α-LNA while brain DHA remained unchanged down to 0.8% α-LNA, when plasma and brain docosapentaenoic acid (DPAn-6) were increased and DHA-selective iPLA(2) and COX-1 activities were downregulated. Brain AA was unchanged by deprivation, but AA selective-cPLA(2), sPLA(2) and COX-2 activities were increased at or below 0.8% dietary α-LNA, possibly in response to elevated brain DPAn-6. In summary, homeostatic mechanisms appear to maintain a control brain DHA concentration down to 0.8% dietary DHA despite reduced plasma DHA, when DPAn-6 replaces DHA. At extreme deprivation, decreased brain iPLA(2) and COX-1 activities may reduce brain DHA loss.

Fatty acid transport into the brain: of fatty acid fables and lipid tails

The blood-brain barrier formed by the brain capillary endothelial cells provides a protective barrier between the systemic blood and the extracellular environment of the central nervous system. Brain capillaries are a continuous layer of endothelial cells with highly developed tight junctional complexes and a lack of fenestrations. The presence of these tight junctions in the cerebral microvessel endothelial cells aids in the restriction of movement of molecules and solutes into the brain. Fatty acids are important components of biological membranes, are precursors for the biosynthesis of phospholipids and sphingolipids and are utilized for mitochondrial β-oxidation. The brain is capable of synthesizing only a few fatty acids. Hence, most fatty acids must enter into the brain from the blood. Here we review current mechanisms of transport of free fatty acids into cells and describe how free fatty acids move from the blood into the brain. We discuss both diffusional as well as protein-mediated movement of fatty acids across biological membranes.