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

Increasing membrane polyunsaturated fatty acids sensitizes non-small cell lung cancer to anti-PD-1/PD-L1 immunotherapy

Immune checkpoints inhibitors (ICIs) as anti-PD-1/anti-PD-L1 have been approved as first-line treatment in patients with non-small cell lung cancer (NSCLC), but only 25 % of patients achieve durable response. We previously unveiled that estrogen receptor α transcriptionally up-regulates PD-L1 and aromatase inhibitors such as letrozole increase the efficacy of pembrolizumab. Here we investigated if letrozole may have additional immune-sensitizing mechanisms. We found that higher the level of PD-L1 in NSCLC, higher the activation of SREBP1c that transcriptionally increases fatty acid synthase and stearoyl-CoA desaturase enzymes, increasing the amount of polyunsaturated fatty acids (PUFAs). Letrozole further up-regulated SREBP1c-mediated transcription of lipogenic genes, and increased the amount of PUFAs, thereby leading to greater membrane fluidity and reduced binding between PD-L1 and PD-1. The same effects were observed upon supplementation with ω3-PUFA docosahexaenoic acid (DHA) that enhanced the efficacy of pembrolizumab in humanized NSCLC immune-xenografts. We suggest that PUFA enrichment in membrane phospholipids improves the efficacy of ICIs. We propose to repurpose letrozole or DHA as new immune-sensitizing agents in NSCLC.

Effects of APOE4 on omega-3 brain metabolism across the lifespan

Omega-3 (n-3) polyunsaturated fatty acids (PUFAs), such as docosahexaenoic acid (DHA), have important roles in human nutrition and brain health by promoting neuronal functions, maintaining inflammatory homeostasis, and providing structural integrity. As Alzheimer's disease (AD) pathology progresses, DHA metabolism in the brain becomes dysregulated, the timing and extent of which may be influenced by the apolipoprotein E ε4 (APOE4) allele. Here, we discuss how maintaining adequate DHA intake early in life may slow the progression to AD dementia in cognitively normal individuals with APOE4, how recent advances in DHA brain imaging could offer insights leading to more personalized preventive strategies, and how alternative strategies targeting PUFA metabolism pathways may be more effective in mitigating disease progression in patients with existing AD dementia.

Effects of Omega-3 Polyunsaturated Fatty Acids, Docosahexaenoic Acid and Eicosapentaenoic Acid, on Post-Surgical Complications in Surgical Trauma Patients: Mechanisms, Nutrition, and Challenges

This paper aims to provide an in-depth review of the specific outcomes associated with omega-3 polyunsaturated fatty acids (PUFAs), focusing on their purported effects on post-surgical complications in trauma patients. A comprehensive investigation of omega-3 polyunsaturated fatty acids was conducted until February 2023 using the PubMed database. Surgical trauma is characterized by a disruption in immune response post surgery, known to induce systemic inflammation. Omega-3 PUFAs are believed to offer potential improvements in multiple post-surgical complications because of their anti-inflammatory and antioxidant properties. Inconsistent findings have emerged in the context of cardiac surgeries, with the route of administration playing a mediating role in these outcomes. The effects of omega-3 PUFAs on post-operative atrial fibrillation have exhibited variability across various studies. Omega-3 PUFAs have demonstrated positive effects in liver surgery outcomes and in patients with acute respiratory distress syndrome. Omega-3 is suggested to offer potential benefits, particularly in the perioperative care of patients undergoing traumatic procedures. Incorporating omega-3 in such cases is hypothesized to contribute to a reduction in certain surgical outcomes, such as hospitalization duration and length of stay in the intensive care unit. Therefore, comprehensive assessments of adverse effects can aid in identifying the presence of subtle or inconspicuous side effects associated with omega-3.

The Conventional and Breakthrough Tool for the Study of L-Glutamate Transporters

In our recent report, we clarified the direct interaction between the excitatory amino acid transporter (EAAT) 1/2 and polyunsaturated fatty acids (PUFAs) by applying electrophysiological and molecular biological techniques to Xenopus oocytes. Xenopus oocytes have a long history of use in the scientific field, but they are still attractive experimental systems for neuropharmacological studies. We will therefore summarize the pharmacological significance, advantages (especially in the study of EAAT2), and experimental techniques that can be applied to Xenopus oocytes; our new findings concerning L-glutamate (L-Glu) transporters and PUFAs; and the significant outcomes of our data. The data obtained from electrophysiological and molecular biological studies of Xenopus oocytes have provided us with further important questions, such as whether or not some PUFAs can modulate EAATs as allosteric modulators and to what extent docosahexaenoic acid (DHA) affects neurotransmission and thereby affects brain functions. Xenopus oocytes have great advantages in the studies about the interactions between molecules and functional proteins, especially in the case when the expression levels of the proteins are small in cell culture systems without transfections. These are also proper to study the mechanisms underlying the interactions. Based on the data collected in Xenopus oocyte experiments, we can proceed to the next step, i.e., the physiological roles of the compounds and their significances. In the case of EAAT2, the effects on the neurotransmission should be examined by electrophysiological approach using acute brain slices. For new drug development, pharmacokinetics pharmacodynamics (PKPD) data and blood brain barrier (BBB) penetration data are also necessary. In order not to miss the promising candidate compounds at the primary stages of drug development, we should reconsider using Xenopus oocytes in the early phase of drug development.

Erythrocyte Membrane Fatty Acid Composition as a Potential Biomarker for Depression

BACKGROUND

Major depressive disorders is a chronic and severe psychiatric disorder with poor prognosis and quality of life. Abnormal erythrocyte fatty acid (FA) composition in depressed patients were found in our previous study, but the relationship between erythrocyte membrane FA levels and different severity of depressive and anxiety symptoms remains to be explored.

METHODS

This cross-sectional study included 139 patients with first-diagnosed, drug-naïve depression and 55 healthy controls whose erythrocyte FA composition was analyzed. Patients with depression were divided into severe depression and mild to moderate depression or depression with severe anxiety and mild to moderate anxiety. Then the differences of FA levels among different groups were analyzed. Finally, the receiver operating characteristic curve analysis was applied to identify potential biomarkers in distinguishing the severity of depressive symptoms.

RESULTS

Levels of erythrocyte membrane FAs were elevated among patients with severe depression compared with healthy controls or patients with mild to moderate depression of almost all kinds. While C18:1n9t (elaidic acid), C20:3n6 (eicosatrienoic acid), C20:4n6 (arachidonic acid), C22:5n3 (docosapentaenoic acid), total fatty acids (FAs), and total monounsaturated FAs were elevated in patients with severe anxiety compared with patients with mild to moderate anxiety. Furthermore, the level of arachidonic acid, C22:4n6 (docosatetraenoic acid), elaidic acid, and the combination of all 3 were associated with the severity of depressive symptoms.

CONCLUSIONS

The results suggested that erythrocyte membrane FA levels have the potential to be the biological indicator of clinical characteristics for depression, such as depressive symptoms and anxiety. In the future, more research is needed to explore the causal association between FA metabolism and depression.

Brain fatty acid and transcriptome profiles of pig fed diets with different levels of soybean oil

BACKGROUND

The high similarity in anatomical and neurophysiological processes between pigs and humans make pigs an excellent model for metabolic diseases and neurological disorders. Lipids are essential for brain structure and function, and the polyunsaturated fatty acids (PUFA) have anti-inflammatory and positive effects against cognitive dysfunction in neurodegenerative diseases. Nutrigenomics studies involving pigs and fatty acids (FA) may help us in better understanding important biological processes. In this study, the main goal was to evaluate the effect of different levels of dietary soybean oil on the lipid profile and transcriptome in pigs' brain tissue.

RESULTS

Thirty-six male Large White pigs were used in a 98-day study using two experimental diets corn-soybean meal diet containing 1.5% soybean oil (SOY1.5) and corn-soybean meal diet containing 3.0% soybean oil (SOY3.0). No differences were found for the brain total lipid content and FA profile between the different levels of soybean oil. For differential expression analysis, using the DESeq2 statistical package, a total of 34 differentially expressed genes (DEG, FDR-corrected p-value < 0.05) were identified. Of these 34 DEG, 25 are known-genes, of which 11 were up-regulated (log2 fold change ranging from + 0.25 to + 2.93) and 14 were down-regulated (log2 fold change ranging from - 3.43 to -0.36) for the SOY1.5 group compared to SOY3.0. For the functional enrichment analysis performed using MetaCore with the 34 DEG, four pathway maps were identified (p-value < 0.05), related to the ALOX15B (log2 fold change - 1.489), CALB1 (log2 fold change - 3.431) and CAST (log2 fold change + 0.421) genes. A "calcium transport" network (p-value = 2.303e-2), related to the CAST and CALB1 genes, was also identified.

CONCLUSION

The results found in this study contribute to understanding the pathways and networks associated with processes involved in intracellular calcium, lipid metabolism, and oxidative processes in the brain tissue. Moreover, these results may help a better comprehension of the modulating effects of soybean oil and its FA composition on processes and diseases affecting the brain tissue.

Uncovering mechanisms of brain inflammation in Alzheimer's disease with APOE4: Application of single cell-type lipidomics

A chronic state of unresolved inflammation in Alzheimer's disease (AD) is intrinsically involved with the remodeling of brain lipids. This review highlights the effect of carrying the apolipoprotein E ε4 allele (APOE4) on various brain cell types in promoting an unresolved inflammatory state. Among its pleotropic effects on brain lipids, we focus on APOE4's activation of Ca²⁺ -dependent phospholipase A2 (cPLA2) and its effects on arachidonic acid, eicosapentaenoic acid, and docosahexaenoic acid signaling cascades in the brain. During the process of neurodegeneration, various brain cell types, such as astrocytes, microglia, and neurons, together with the neurovascular unit, develop distinct inflammatory phenotypes that impact their functions and have characteristic lipidomic fingerprints. We propose that lipidomic phenotyping of single cell-types harvested from brains differing by age, sex, disease severity stage, and dietary and genetic backgrounds can be employed to probe mechanisms of neurodegeneration. A better understanding of the brain cellular inflammatory/lipidomic response promises to guide the development of nutritional and drug interventions for AD dementia.

Longitudinal investigation of the relationship between omega-3 polyunsaturated fatty acids and neuropsychological functioning in recent-onset psychosis: A randomized clinical trial

Alterations in polyunsaturated fatty acids (PUFAs), including omega-3 and omega-6, have been implicated in the pathophysiology of psychotic disorders, but little is known about their associations with neuropsychological functioning. The present study includes 46 recent-onset psychosis patients who participated in a larger (n = 50) double blind, placebo-controlled randomized clinical trial comparing 16 weeks of treatment with either risperidone + fish oil (FO) (EPA 740 mg and DHA 400 mg daily) or risperidone + placebo and completed neuropsychological assessments at the baseline timepoint. We investigated the relationship between baseline omega-3 (i.e., eicosapentaenoic acid, EPA; docosapentaenoic acid, DPA and docosahexaenoic acid, DHA) and omega-6 (i.e., arachidonic acid, AA) PUFA with baseline MATRICS Consensus Cognitive Battery (MCCB) and Brief Psychiatric Rating Scale (BPRS) scores. Twenty-five patients had neuropsychological data available at 16 weeks following participation in the clinical trial, which included 12 patients assigned to risperidone + FO and 13 patients assigned to risperidone + placebo. At baseline both higher DHA and EPA correlated significantly with better social cognition after controlling for functioning on other neuropsychological domains, total BPRS score, AA level and substance use. Also, at baseline higher AA correlated significantly with hostility/uncooperativeness after controlling for DHA + EPA + DPA, overall neuropsychological functioning and substance use. Patients treated with risperidone + FO demonstrated a significant longitudinal increase in social cognition that was significantly higher at 16 weeks compared to patients treated with risperidone + placebo. DHA also correlated significantly with social cognition at the 16-week timepoint. This study provides novel evidence for a differential role of omega-3 vs. omega-6 PUFA in neuropsychological deficits and symptoms in recent-onset psychosis and its treatment.

Beneficial effects of omega-3 fatty acid supplementation in schizophrenia: possible mechanisms

BACKGROUND

Schizophrenia is a serious long-term psychotic disorder marked by positive and negative symptoms, severe behavioral problems and cognitive function deficits. The cause of this disorder is not completely clear, but is suggested to be multifactorial, involving both inherited and environmental factors. Since human brain regulates all behaviour, studies have focused on identifying changes in neurobiology and biochemistry of brain in schizophrenia. Brain is the most lipid rich organ (approximately 50% of brain dry weight). Total brain lipids is constituted of more than 60% of phospholipids, in which docosahexaenoic acid (DHA, 22:6n-3) is the most abundant (more than 40%) polyunsaturated fatty acid (PUFA) in brain membrane phospholipids. Results from numerous studies have shown significant decreases of PUFAs, in particular, DHA in peripheral blood (plasma and erythrocyte membranes) as well as brain of schizophrenia patients at different developmental phases of the disorder. PUFA deficiency has been associated to psychotic symptoms and cognitive deficits in schizophrenia. These findings have led to a number of clinical trials examining whether dietary omega-3 fatty acid supplementation could improve the course of illness in patients with schizophrenia. Results are inconsistent. Some report beneficial whereas others show not effective. The discrepancy can be attributed to the heterogeneity of patient population.

METHODS

In this review, results from recent experimental and clinical studies, which focus on illustrating the role of PUFAs in the development of schizophrenia were examined. The rationale why omega-3 supplementation was beneficial on symptoms (presented by subscales of the positive and negative symptom scale (PANSS), and cognitive functions in certain patients but not others was reviewed. The potential mechanisms underlying the beneficial effects were discussed.

RESULTS

Omega-3 fatty acid supplementation reduced the conversion rate to psychosis and improved both positive and negative symptoms and global functions in adolescents at ultra-high risk for psychosis. Omega-3 fatty acid supplementation could also improve negative symptoms and global functions in the first-episode patients with schizophrenia, but improve mainly total or general PANSS subscales in chronic patients. Patients with low PUFA (particularly DHA) baseline in blood were more responsive to the omega-3 fatty acid intervention.

CONCLUSION

Omega-3 supplementation is more effective in reducing psychotic symptom severity in young adults or adolescents in the prodromal phase of schizophrenia who have low omega-3 baseline. Omega-3 supplementation was more effective in patients with low PUFA baseline. It suggests that patients with predefined lipid levels might benefit from lipid treatments, but more controlled clinical trials are warranted.

Effects of controlled cortical impact and docosahexaenoic acid on rat pup fatty acid profiles

Traumatic brain injury (TBI) is the leading cause of acquired neurologic disability in children, particularly in those under four years old. During this period, rapid brain growth demands higher Docosahexaenoic Acid (DHA) intake. DHA is an essential fatty acid and brain cell component derived almost entirely from the diet. DHA improved neurologic outcomes and decreased inflammation after controlled cortical impact (CCI) in 17-day old (P17) rats, our established model of pediatric TBI. In adult rodents, TBI decreases brain DHA. We hypothesized that CCI would decrease rat brain DHA at post injury day (PID) 60, blunted by 0.1% DHA diet. We quantitated fatty acids using Gas Chromatography-Mass Spectrometry. We provided 0.1% DHA before CCI to ensure high DHA in dam milk. We compared brain DHA in rats after 60 days of regular (REG) or DHA diet to SHAM pups on REG diet. Brain DHA decreased in REGCCI, not in DHACCI, relative to SHAMREG. In a subsequent experiment, we gave rat pups DHA or vehicle intraperitoneally after CCI followed by DHA or REG diet for 60 days. REG increased brain Docosapentaenoic Acid (n-6 DPA, a brain DHA deficiency marker) relative to SHAMDHA and DHACCI pups (p < 0.001, diet effect). DHA diet nearly doubled DHA and decreased n-6 DPA in blood but did not increase brain DHA content (p < 0.0001, diet effect). We concluded that CCI or craniotomy alone induces a mild DHA deficit as shown by increased brain DPA.

The migration of docosahexenoic acid (DHA) to the developing ovary of female zebrafish (Danio rerio)

Fish selectively reserves docosahexenoic acid (DHA) in ovary during gonadal development. However, no direct proof supports this. The present study tried to elucidate the DHA migration to the developing ovary of female zebrafish. An injection study of ¹³C-labeled DHA for DHA tracing was conducted, and another injection study of unlabeled-DHA (DHA-injected group) and BSA-saline (control group) was conducted for lipid and DHA content detection, related gene expression analyses, and histological observation. The results showed that the rapid absorption of lipid occurred at stage III with a constant accumulation of DHA in the ovary. The proportion of oocytes at stage III on day 7 and 21, and at stage IV on day 3 and 21 in DHA-injected group was significantly higher than that in control group, respectively (P < .05). The injected ¹³C-labeled DHA was accumulated twice in the ovary respectively on day 1 and 7, and remained at a relatively high level. In DHA-injected group, the fatp4 expression was significantly higher in ovary on day 3, 5 and 7 (P < .05), and significantly lower (P < .05) in liver on day 5, 14 and in muscle on day 1, 5 and 7 than that in control group. In conclusion, the present study suggested a migration of DHA from the liver and muscle to the gonads when necessary.

Dietary Omega-3 Polyunsaturated Fatty Acid Deprivation Does Not Alter Seizure Thresholds but May Prevent the Anti-seizure Effects of Injected Docosahexaenoic Acid in Rats

Background: Brain concentrations of omega-3 docosahexaenoic acid (DHA, 22:6n-3) have been reported to positively correlate with seizure thresholds in rodent seizure models. It is not known whether brain DHA depletion, achieved by chronic dietary omega-3 polyunsaturated fatty acid (PUFA) deficiency, lowers seizure thresholds in rats.

Objective: The present study tested the hypothesis that lowering brain DHA concentration with chronic dietary n-3 PUFA deprivation in rats will reduce seizure thresholds, and that compared to injected oleic acid (OA), injected DHA will raise seizure thresholds in rats maintained on n-3 PUFA adequate and deficient diets.

Methods: Rats (60 days old) were surgically implanted with electrodes in the amygdala, and subsequently randomized to the AIN-93G diet containing adequate levels of n-3 PUFA derived from soybean oil or an n-3 PUFA-deficient diet derived from coconut and safflower oil. The rats were maintained on the diets for 37 weeks. Afterdischarge seizure thresholds (ADTs) were measured every 4–6 weeks by electrically stimulating the amygdala. Between weeks 35 and 37, ADTs were assessed within 1 h of subcutaneous OA or DHA injection (600 mg/kg). Seizure thresholds were also measured in a parallel group of non-implanted rats subjected to the maximal pentylenetetrazol (PTZ, 110 mg/kg) seizure test. PUFA composition was measured in the pyriform-amygdala complex of another group of non-implanted rats sacrificed at 16 and 32 weeks.

Results: Dietary n-3 PUFA deprivation did not significantly alter amygdaloid seizure thresholds or latency to PTZ-induced seizures. Acute injection of OA did not alter amygdaloid ADTs of rats on the n-3 PUFA adequate or deficient diets, whereas acute injection of DHA significantly increased amygdaloid ADTs in rats on the n-3 PUFA adequate control diet as compared to rats on the n-3 PUFA deficient diet (P < 0.05). Pyriform-amygdala DHA percent composition did not significantly differ between the groups, while n-6 docosapentaenoic acid, a marker of n-3 PUFA deficiency, was significantly increased by 2.9-fold at 32 weeks.

Conclusion: Chronic dietary n-3 PUFA deficiency does not alter seizure thresholds in rats, but may prevent the anti-seizure effects of DHA.

Selectivity of phospholipid hydrolysis by phospholipase A2 enzymes in activated cells leading to polyunsaturated fatty acid mobilization

Phospholipase A₂s are enzymes that hydrolyze the fatty acid at the sn-2 position of the glycerol backbone of membrane glycerophospholipids. Given the asymmetric distribution of fatty acids within phospholipids, where saturated fatty acids tend to be present at the sn-1 position, and polyunsaturated fatty acids such as those of the omega-3 and omega-6 series overwhelmingly localize in the sn-2 position, the phospholipase A₂ reaction is of utmost importance as a regulatory checkpoint for the mobilization of these fatty acids and the subsequent synthesis of proinflammatory omega-6-derived eicosanoids on one hand, and omega-3-derived specialized pro-resolving mediators on the other. The great variety of phospholipase A₂s, their differential substrate selectivity under a variety of pathophysiological conditions, as well as the different compartmentalization of each enzyme and accessibility to substrate, render this class of enzymes also key to membrane phospholipid remodeling reactions, and the generation of specific lipid mediators not related with canonical metabolites of omega-6 or omega-3 fatty acids. This review highlights novel findings regarding the selective hydrolysis of phospholipids by phospholipase A₂s and the influence this may have on the ability of these enzymes to generate distinct lipid mediators with essential functions in biological processes. This brings a new understanding of the cellular roles of these enzymes depending upon activation conditions.

Estrogen Interactions With Lipid Rafts Related to Neuroprotection. Impact of Brain Ageing and Menopause

Estrogens (E2) exert a plethora of neuroprotective actions against aged-associated brain diseases, including Alzheimer's disease (AD). Part of these actions takes place through binding to estrogen receptors (ER) embedded in signalosomes, where numerous signaling proteins are clustered. Signalosomes are preferentially located in lipid rafts which are dynamic membrane microstructures characterized by a peculiar lipid composition enriched in gangliosides, saturated fatty acids, cholesterol, and sphingolipids. Rapid E2 interactions with ER-related signalosomes appear to trigger intracellular signaling ultimately leading to the activation of molecular mechanisms against AD. We have previously observed that the reduction of E2 blood levels occurring during menopause induced disruption of ER-signalosomes at frontal cortical brain areas. These molecular changes may reduce neuronal protection activities, as similar ER signalosome derangements were observed in AD brains. The molecular impairments may be associated with changes in the lipid composition of lipid rafts observed in neurons during menopause and AD. These evidences indicate that the changes in lipid raft structure during aging may be at the basis of alterations in the activity of ER and other neuroprotective proteins integrated in these membrane microstructures. Moreover, E2 is a homeostatic modulator of lipid rafts. Recent work has pointed to this relevant aspect of E2 activity to preserve brain integrity, through mechanisms affecting lipid uptake and local biosynthesis in the brain. Some evidences have demonstrated that estrogens and the docosahexaenoic acid (DHA) exert synergistic effects to stabilize brain lipid matrix. DHA is essential to enhance molecular fluidity at the plasma membrane, promoting functional macromolecular interactions in signaling platforms. In support of this, DHA detriment in neuronal lipid rafts has been associated with the most common age-associated neuropathologies, namely AD and Parkinson disease. Altogether, these findings indicate that E2 may participate in brain preservation through a dual membrane-related mechanism. On the one hand, E2 interacting with ER related signalosomes may protect against neurotoxic insults. On the other hand, E2 may exert lipostatic actions to preserve lipid balance in neuronal membrane microdomains. The different aspects of the emerging multifunctional role of estrogens in membrane-related signalosomes will be discussed in this review.

Does Fatty Acid Composition in Subcutaneous Adipose Tissue Differ between Patients with Alzheimer's Disease and Cohabiting Proxies?

Low tissue levels of the major marine ω3 fatty acids (FAs) DHA and EPA are found in Alzheimer's disease (AD). We investigated if healthy proxies to AD patients have higher levels of these ω3 FAs. We observed lower levels of EPA and DHA in subcutaneous adipose tissue biopsies from 64 AD patients compared with 16 cognitively healthy proxies. No significant difference was observed when pairwise comparisons were made between a subset of 16 AD patients and their co-habiting proxies. Larger studies are needed to replicate these findings and to determine if they could depend on FA intake or differences in metabolism.

Dietary DHA, bioaccessibility, and neurobehavioral development in children

Docosahexaenoic acid (DHA) is a key nutritional n-3 polyunsaturated fatty acid and needs to be supplied by the human diet. High levels of DHA intake appear to reduce the risk of depression, bipolar disorder, and mood disorders. On the basis of these connections between DHA and neurological health, this paper reviews what is currently known about DHA and children neurodevelopment as well as the benefits of DHA intake to prevention of autism and behavior disorders through a selective and representative revision of different papers ranging from pure observational studies to randomized controlled trials (RCTs). This review also highlights the issue of DHA bioaccessibility and its implications to the performance of studies. As main conclusions, it can be mentioned that high DHA intake may prevent autism disorder. However, more studies are required to strengthen the connection between autism and dietary DHA. Regarding behavioral disorders, the evidence is also contradictory, thereby raising the need of further studies. From all screened studies on autism, attention deficit/hyperactivity disorder, and other disorders, it can be concluded that study samples should be larger for greater statistical significance and RCTs should be more carefully designed.

Role of prefrontal cortical calcium-independent phospholipase A2 in antinociceptive effect of the norepinephrine reuptake inhibitor antidepresssant maprotiline

The prefrontal cortex is essential for executive functions such as decision-making and planning. There is also accumulating evidence that it is important for the modulation of pain. In this study, we investigated a possible role of prefrontal cortical calcium-independent phospholipase A₂ (iPLA₂) in antinociception induced by the norepinephrine reuptake inhibitor (NRI) and tetracyclic (tricyclic) antidepressant, maprotiline. Intraperitoneal injections of maprotiline increased iPLA₂ mRNA and protein expression in the prefrontal cortex. This treatment also reduced grooming responses to von-Frey hair stimulation of the face after facial carrageenan injection, indicating decreased sensitivity to pain. The antinociceptive effect of maprotiline was abrogated by iPLA₂ antisense oligonucleotide injection to the prefrontal cortex, indicating a role of this enzyme in antinociception. In contrast, injection of iPLA₂ antisense oligonucleotide to the somatosensory cortex did not reduce the antinociceptive effect of maprotiline. Lipidomic analysis of the prefrontal cortex showed decrease in phosphatidylcholine species, but increase in lysophosphatidylcholine species, indicating increased PLA2 activity, and release of docosahexaenoic acid (DHA) and eicosapentaenoic acid (EPA) after maprotiline treatment. Differences in sphingomyelin/ceramide were also detected. These changes were not observed in maprotiline-treated mice that received iPLA₂ antisense oligonucleotide to the prefrontal cortex. Metabolites of DHA and EPA may help to strengthen a known supraspinal antinociceptive pathway from the prefrontal cortex to the periaqueductal gray. Together, results indicate a role of prefrontal cortical iPLA₂ and its enzymatic products in the antinociceptive effect of maprotiline.

Docosahexaenoic Acid Conjugation Enhances Distribution and Safety of siRNA upon Local Administration in Mouse Brain

The use of siRNA-based therapies for the treatment of neurodegenerative disease requires efficient, nontoxic distribution to the affected brain parenchyma, notably the striatum and cortex. Here, we describe the synthesis and activity of a fully chemically modified siRNA that is directly conjugated to docosahexaenoic acid (DHA), the most abundant polyunsaturated fatty acid in the mammalian brain. DHA conjugation enables enhanced siRNA retention throughout both the ipsilateral striatum and cortex following a single, intrastriatal injection (ranging from 6–60 μg). Within these tissues, DHA conjugation promotes internalization by both neurons and astrocytes. We demonstrate efficient and specific silencing of Huntingtin mRNA expression in both the ipsilateral striatum (up to 73%) and cortex (up to 51%) after 1 week. Moreover, following a bilateral intrastriatal injection (60 μg), we achieve up to 80% silencing of a secondary target, Cyclophilin B, at both the mRNA and protein level. Importantly, DHA-hsiRNAs do not induce neural cell death or measurable innate immune activation following administration of concentrations over 20 times above the efficacious dose. Thus, DHA conjugation is a novel strategy for improving siRNA activity in mouse brain, with potential to act as a new therapeutic platform for the treatment of neurodegenerative disorders.

The effect of APOE genotype on the delivery of DHA to cerebrospinal fluid in Alzheimer's disease

Background

Apolipoprotein E (APOE) ɛ4 and low cerebrospinal fluid (CSF) amyloid-β42 (Aβ42) levels are predictors for developing Alzheimer’s disease (AD). The results of several studies indicate an interaction between docosahexaenoic acid (DHA) consumption and cognitive outcomes by APOE genotype. Our objective in the present study was to examine whether APOE ɛ4 genotype and low CSF Aβ42 levels were associated with reduced delivery of DHA to CSF in the Alzheimer’s Disease Cooperative Study-sponsored DHA clinical trial.

Methods

Phospholipid DHA was assayed in the plasma of 384 participants and CSF of 70 participants at baseline. Forty-four of the 70 participants completed the 18-month follow-up visit after allocation to placebo (n = 15) or DHA (n = 29). Plasma and CSF DHA levels, CSF Aβ42, Tau, and phosphorylated Tau were measured at baseline and after the 18-month intervention. Participants were divided into tertiles based on baseline Aβ42 CSF levels. To assess DHA delivery across the blood-brain barrier, the ratio of CSF to plasma DHA levels was calculated.

Results

At baseline, there were no significant differences between CSF or plasma phospholipid DHA levels by CSF Aβ42 tertiles or ɛ4 status. After 18 months of DHA supplementation, participants at the lowest Aβ42 tertile had significantly lower CSF DHA levels (p = 0.01) and lower CSF-to-plasma DHA ratios (p = 0.05) compared to the other tertiles. Baseline CSF Aβ42 levels were significantly lower in ɛ4 carriers than in ɛ4 noncarriers (p = 0.01). Participants carrying the ɛ4 allele (n = 25) demonstrated a less pronounced increase in CSF DHA level compared with noncarriers (n = 4), with a possible interaction effect between treatment and APOE genotype (p = 0.07).

Conclusions

APOE ɛ4 allele and lower CSF Aβ42 levels were associated with less transport of DHA to CSF. Brain amyloid pathology may limit the delivery of DHA to the brain in AD.

Trial Registration

Clinicaltrials.gov identifier: NCT00440050. Registered on 22 Feb 2007.

Fatty acids and their therapeutic potential in neurological disorders

There is little doubt that we are what we eat. Fatty acid supplementation and diets rich in fatty acids are being promoted as ways to a healthier brain. Short chain fatty acids are a product of intestinal microbiota metabolism of dietary fibre; and their derivatives are used as an anti-convulstant. They demonstrated therapeutic potential in neurodegenerative conditions as HDAC inhibitors; and while the mechanism is not well understood, have been shown to lower amyloid β in Alzheimer's Disease in preclinical studies. Medium chain fatty acids consumed as a mixture in dietary oils can induce ketogenesis without the need for a ketogentic diet. Hence, this has the potential to provide an alternative energy source to prevent neuronal cell death due to lack of glucose. Long chain fatty acids are commonly found in the diet as omega fatty acids. They act as an anti-oxidant protecting neuronal cell membranes from oxidative damage and as an anti-inflammatory mediator in the brain. We review which agents, from each fatty acid class, have the most therapeutic potential for neurological disorders (primarily Alzheimer's disease, Parkinson's disease, Autism Spectrum Disorder as well as possible applications to traumatic brain injury), by discussing what is known about their biological mechanisms from preclinical studies.

Association between polymorphisms in phospholipase A2 genes and the plasma triglyceride response to an n-3 PUFA supplementation: a clinical trial

BACKGROUND

Fish oil-derived long-chain omega-3 (n-3) polyunsaturated fatty acids (PUFAs), including eicosapentaenoic acid (EPA) and docosahexaenoic acid (DHA), reduce plasma triglyceride (TG) levels. Genetic factors such as single-nucleotide polymorphisms (SNPs) found in genes involved in metabolic pathways of n-3 PUFA could be responsible for well-recognized heterogeneity in plasma TG response to n-3 PUFA supplementation. Previous studies have shown that genes in the glycerophospholipid metabolism such as phospholipase A2 (PLA2) group II, IV, and VI, demonstrate changes in their expression levels in peripheral blood mononuclear cells (PBMCs) after n-3 PUFA supplementation.

METHODS

A total of 208 subjects consumed 3 g/day of n-3 PUFA for 6 weeks. Plasma lipids were measured before and after the supplementation period. Five SNPs in PLA2G2A, six in PLA2G2C, eight in PLA2G2D, six in PLA2G2F, 22 in PLA2G4A, five in PLA2G6, and nine in PLA2G7 were genotyped. The MIXED Procedure for repeated measures adjusted for age, sex, BMI, and energy intake was used in order to test whether the genotype, supplementation or interaction (genotype by supplementation) were associated with plasma TG levels.

RESULTS

The n-3 PUFA supplementation had an independent effect on plasma TG levels. Genotype effects on plasma TG levels were observed for rs2301475 in PLA2G2C, rs818571 in PLA2G2F, and rs1569480 in PLA2G4A. Genotype x supplementation interaction effects on plasma TG levels were observed for rs1805018 in PLA2G7 as well as for rs10752979, rs10737277, rs7540602, and rs3820185 in PLA2G4A.

CONCLUSION

These results suggest that, SNPs in PLA2 genes may influence plasma TG levels during a supplementation with n-3 PUFA. This trial was registered at clinicaltrials.gov as NCT01343342.

Pathways of polyunsaturated fatty acid utilization: implications for brain function in neuropsychiatric health and disease

Essential polyunsaturated fatty acids (PUFAs) have profound effects on brain development and function. Abnormalities of PUFA status have been implicated in neuropsychiatric diseases such as major depression, bipolar disorder, schizophrenia, Alzheimer's disease, and attention deficit hyperactivity disorder. Pathophysiologic mechanisms could involve not only suboptimal PUFA intake, but also metabolic and genetic abnormalities, defective hepatic metabolism, and problems with diffusion and transport. This article provides an overview of physiologic factors regulating PUFA utilization, highlighting their relevance to neuropsychiatric disease.

Polyunsaturated fatty acids and their metabolites in brain function and disease

The brain is highly enriched with fatty acids. These include the polyunsaturated fatty acids (PUFAs) arachidonic acid and docosahexaenoic acid, which are largely esterified to the phospholipid cell membrane. Once PUFAs are released from the membrane, they can participate in signal transduction, either directly or after enzymatic conversion to a variety of bioactive derivatives ('mediators'). PUFAs and their mediators regulate several processes within the brain, such as neurotransmission, cell survival and neuroinflammation, and thereby mood and cognition. PUFA levels and the signalling pathways that they regulate are altered in various neurological disorders, including Alzheimer's disease and major depression. Diet and drugs targeting PUFAs may lead to novel therapeutic approaches for the prevention and treatment of brain disorders.

Erythrocyte DHA level as a biomarker of DHA status in specific brain regions of n-3 long-chain PUFA-supplemented aged rats

n-3 Long-chain PUFA (n-3 LC-PUFA), particularly EPA and DHA, play a key role in the maintenance of brain functions such as learning and memory that are impaired during ageing. Ageing is also associated with changes in the DHA content of brain membranes that could contribute to memory impairment. Limited studies have investigated the effects of ageing and n-3 LC-PUFA supplementation on both blood and brain fatty acid compositions. Therefore, we assessed the relationship between fatty acid contents in plasma and erythrocyte membranes and those in the hippocampus, striatum and cerebral cortex during ageing, and after a 5-month period of EPA/DHA supplementation in rats. In the blood, ageing was associated with an increase in plasma DHA content, whereas the DHA content remained stable in erythrocyte membranes. In the brain, ageing was associated with a decrease in DHA content, which was both region-specific and phospholipid class-specific. In EPA/DHA-supplemented aged rats, DHA contents were increased both in the blood and brain compared with the control rats. The present results demonstrated that n-3 LC-PUFA level in the plasma was not an accurate biomarker of brain DHA status during ageing. Moreover, we highlighted a positive relationship between the DHA levels in erythrocyte phosphatidylethanolamine (PE) and those in the hippocampus and prefrontal cortex in EPA/DHA-supplemented aged rats. Within the framework of preventive dietary supplementation to delay brain ageing, these results suggest the possibility of using erythrocyte PE DHA content as a reliable biomarker of DHA status in specific brain regions.

Role of constitutive calcium-independent phospholipase A2 beta in hippocampo-prefrontal cortical long term potentiation and spatial working memory

Calcium independent phospholipase A2 (iPLA2) is an 85 kDa protein that catalyzes the hydrolysis of the sn-2 acyl ester bond of glycerophospholipids to liberate free fatty acids and lysophospholipids. In this study, we determined the role of constitutive iPLA2β in long term potentiation (LTP) of the hippocampo-prefrontal cortical pathway in vivo. We also examined the effect of iPLA2β knockdown using the rewarded alternation in T-maze task, a test of spatial working memory which is dependent on this pathway. Intracortical injection of an inhibitor to iPLA2, bromoenol lactone (BEL) or antisense oligonucleotide to iPLA2β in the prefrontal cortex abolished induction of hippocampo-prefrontal cortical LTP. Moreover, iPLA2 inhibition and antisense knockdown resulted in increased errors in the rewarded alternation in T-maze task, indicating negative effects on spatial working memory. BEL or antisense injection did not produce DNA fragmentation in the cortex as demonstrated by TUNEL assay. Results confirm a role of constitutive iPLA2β in hippocampo-prefrontal cortical synaptic plasticity in vivo, and add to previous observations of a role of iPLA2 in hippocampal LTP in vitro, and long-term memory retrieval. They may be relevant in Alzheimer's disease, and other neurodegenerative conditions that are associated with changes in iPLA2.

Does consumption of LC omega-3 PUFA enhance cognitive performance in healthy school-aged children and throughout adulthood? Evidence from clinical trials

Long-chain (LC) omega-3 PUFA derived from marine sources may play an important role in cognitive performance throughout all life stages. Docosahexaenoic acid (DHA), the dominant omega-3 in the brain, is a major component of neuronal cell membranes and affects various neurological pathways and processess. Despite its critical role in brain function, human’s capacity to synthesize DHA de novo is limited and its consumption through the diet is important. However, many individuals do not or rarely consume seafood. The aim of this review is to critically evaluate the current evidence from randomised controlled trials (RCT) in healthy school-aged children, younger and older adults to determine whether consumption of LC omega-3 PUFA improves cognitive performance and to make recommendations for future research. Current evidence suggests that consumption of LC omega-3 PUFA, particularly DHA, may enhance cognitive performance relating to learning, cognitive development, memory and speed of performing cognitive tasks. Those who habitually consume diets low in DHA, children with low literacy ability and malnourished and older adults with age-related cognitive decline and mild cognitive impairment seem to benefit most. However, study design limitations in many RCTs hamper firm conclusions. The measurement of a uniform biomarker, e.g., % DHA in red blood cells, is essential to establish baseline DHA-status, to determine targets for cognitive performance and to facilitate dosage recommendations. It is recommended that future studies be at least 16 weeks in duration, account for potential interaction effects of gender, age and apolipoprotein E genotype, include vegan/vegetarian populations, include measures of speed of cognitive performance and include brain imaging technologies as supportive information on working mechanisms of LC omega-3 PUFA.

n-3 LCPUFA improves cognition: the young, the old and the sick

Due to the implication of docosahexaenoic acid (DHA) in neurogenesis, synaptogenesis, neurite outgrowth and to its high incorporation into the brain, this n-3 long chain polyunsaturated fatty acid (LCPUFA) is considered as crucial in the development and maintenance of the learning memory performance throughout life. In the present chapter we aimed at reviewing data investigating the relation between DHA and cognition during the perinatal period, young adult- and adulthood and neurodegenerative diseases such as Alzheimer disease (AD). In Humans, dietary DHA supplementation from the perinatal period to adulthood does not reveal a clear and consistent memory improvement whereas it is the case in animal studies. The positive effects observed in animal models may have been enhanced by using n-3 PUFA deficient animal models as controls. In animal models of AD, a general consensus on the beneficial effects of n-3 LCPUFA in attenuating cognitive impairment was established. These studies make DHA a potential suitable micronutrient for the maintenance of cognitive performance at all periods of life.

Role of cytosolic phospholipase A2 in oxidative and inflammatory signaling pathways in different cell types in the central nervous system

Phospholipases A(2) (PLA(2)s) are important enzymes for the metabolism of fatty acids in membrane phospholipids. Among the three major classes of PLA(2)s in the mammalian system, the group IV calcium-dependent cytosolic PLA(2) alpha (cPLA(2)α) has received the most attention because it is widely expressed in nearly all mammalian cells and its active participation in cell metabolism. Besides Ca(2+) binding to its C2 domain, this enzyme can undergo a number of cell-specific post-translational modifications, including phosphorylation by protein kinases, S-nitrosylation through interaction with nitric oxide (NO), as well as interaction with other proteins and lipid molecules. Hydrolysis of phospholipids by cPLA(2) yields two important lipid mediators, arachidonic acid (AA) and lysophospholipids. While AA is known to serve as a substrate for cyclooxygenases and lipoxygenases, which are enzymes for the synthesis of eicosanoids and leukotrienes, lysophospholipids are known to possess detergent-like properties capable of altering microdomains of cell membranes. An important feature of cPLA(2) is its link to cell surface receptors that stimulate signaling pathways associated with activation of protein kinases and production of reactive oxygen species (ROS). In the central nervous system (CNS), cPLA(2) activation has been implicated in neuronal excitation, synaptic secretion, apoptosis, cell-cell interaction, cognitive and behavioral function, oxidative-nitrosative stress, and inflammatory responses that underline the pathogenesis of a number of neurodegenerative diseases. However, the types of extracellular agonists that target intracellular signaling pathways leading to cPLA(2) activation among different cell types and under different physiological and pathological conditions have not been investigated in detail. In this review, special emphasis is given to metabolic events linking cPLA(2) to activation in neurons, astrocytes, microglial cells, and cerebrovascular cells. Understanding the molecular mechanism(s) for regulation of this enzyme is deemed important in the development of new therapeutic targets for the treatment and prevention of neurodegenerative diseases.

Alpha linolenic acid (ALA) from Rosa canina, sacha inchi and chia oils may increase ALA accretion and its conversion into n-3 LCPUFA in diverse tissues of the rat

Alpha-linolenic acid (ALA) is an essentialn-3 PUFA; itsn-3 LCPUFA derivatives EPA and DHA, which have diverse beneficial effects, are scarce in the human diet.

Novel n-3 immunoresolvents: structures and actions

Resolution of inflammation is now held to be an active process where autacoids promote homeostasis. Using functional-metabololipidomics and in vivo systems, herein we report that endogenous n-3 docosapentaenoic (DPA) acid is converted during inflammation-resolution in mice and by human leukocytes to novel n-3 products congenerous to D-series resolvins (Rv), protectins (PD) and maresins (MaR), termed specialized pro-resolving mediators (SPM). The new n-3 DPA structures include 7,8,17-trihydroxy-9,11,13,15E,19Z-docosapentaenoic acid (RvD1_{n-3 DPA}), 7,14-dihydroxy-8,10,12,16Z,19Z-docosapentaenoic acid (MaR1_{n-3 DPA}) and related bioactive products. Each n-3 DPA-SPM displayed protective actions from second organ injury and reduced systemic inflammation in ischemia-reperfusion. The n-3 DPA-SPM, including RvD1_{n-3 DPA} and MaR1_{n-3 DPA}, each exerted potent leukocyte directed actions in vivo. With human leukocytes each n-3 DPA-SPM reduced neutrophil chemotaxis, adhesion and enhanced macrophage phagocytosis. Together, these findings demonstrate that n-3 DPA is converted to novel immunoresolvents with actions comparable to resolvins and are likely produced in humans when n-3 DPA is elevated.

Current evidence for the clinical use of long-chain polyunsaturated n-3 fatty acids to prevent age-related cognitive decline and Alzheimer's disease

An NIH State of the Science Conference panel concluded in 2010 that insufficient evidence is available to recommend the use of any primary prevention therapy for Alzheimer's disease or cognitive decline with age. Despite the insufficient evidence, candidate therapies with varying levels of evidence for safety and efficacy are taken by the public and discussed in the media. One example is the long-chain n-3 (omega-3) polyunsaturated fatty acids (n-3 LC-PUFA), DHA and EPA, found in some fish and dietary supplements. With this report, we seek to provide a practical overview and rating of the level and type of available evidence that n-3 LC-PUFA supplements are safe and protective against cognitive aging and Alzheimer's disease, with additional discussion of the evidence for effects on quality of life, vascular aging, and the rate of aging. We discuss available sources, dose, bioavailability, and variables that may impact the response to n-3 LC-PUFA treatment such as baseline n-3 LC-PUFA status, APOE ε4 genotype, depression, and background diet. Lastly, we list ongoing clinical trials and propose next research steps to validate these fatty acids for primary prevention of cognitive aging and dementia. Of particular relevance, epidemiology indicates a higher risk of cognitive decline in people in the lower quartile of n-3 LC-PUFA intake or blood levels but these populations have not been specifically targeted by RCTs.