Fatty acids and brain peptides

Hepatic transcriptome of the euryhaline teleost Japanese seabass (Lateolabrax japonicus) fed diets characterized by α-linolenic acid or linoleic acid

To investigate the different effects of dietary α-linolenic acid (ALA) and linoleic acid (LA) on the euryhaline fish Japanese seabass, a feeding trial followed by hepatic transcriptome assay was conducted. Two experimental diets containing 10% LA-rich sunflower seed oil (diet LA) or 10% ALA-rich perilla oil (diet ALA) were used in the feeding trial. LA and ALA in diets were characteristically incorporated into fish tissues while no significant difference was observed in growth performance and body proximate composition between groups LA and ALA. Compared to LA, ALA up-regulated transcription of 49 unigenes and down-regulated those of 311 unigenes. Quantitative RT-PCR studies on eight lipid metabolism-related genes and seven randomly selected genes were conducted to validate the transcriptomic results. Lipid metabolism-related genes ApoA1, ApoA4, ApoE, FABP1, FABP3, FABP4, FATP6, and DGAT1, as well as ribosomal proteins L9e, L13e, and S4e, were transcriptionally down-regulated by ALA. The differentially expressed genes (DEGs) were primarily enriched in Gene Ontology terms such as Lipid transport, Protein metabolic process, and Ribosome biogenesis, as well as in KEGG pathways such as Complement and coagulation cascades and Ribosome. The Protein-Protein Interaction (PPI) network based on the peptide biosynthesis-related DEGs showed that ribosomal proteins such as SAe, L4e, S4e, L15e, L9e, and L13Ae had high betweenness centrality in the dietary regulation of peptide biosynthetic processes. In conclusion, under the present experimental conditions, a high level of dietary α-linolenic acid tended to suppress lipid transport and protein biosynthetic processes in the liver of Japanese seabass at the gene expression level.

Regional changes in CNS and retinal glycerophospholipid profiles with age: a molecular blueprint

We present here a quantitative molecular blueprint of the three major glycerophospholipid (GPL) classes, phosphatidylcholine (PC), phosphatidylserine (PS), and phosphatidylethanolamine (PE), in retina and six regions of the brain in C57Bl6 mice at 2, 10, and 26 months of age. We found an age-related increase in molecular species containing saturated and monoenoic FAs and an overall decrease in the longer-chain PUFA molecular species across brain regions, with loss of DHA-containing molecular species as the most consistent and dramatic finding. Although we found very-long-chain PUFAs (VLC-PUFAs) (C28) in PC in the retina, no detectable levels were found in any brain region at any of the ages examined. All brain regions (except hippocampus and retina) showed a significant increase with age in PE plasmalogens. All three retina GPLs had di-PUFA molecular species (predominantly 44:12), which were most abundant in PS (∼30%). In contrast, low levels of di-PUFA GPL (1-2%) were found in all regions of the brain. This study provides a regional and age-related assessment of the brain's lipidome with a level of detail, inclusion, and quantification that has not heretofore been published.

The Role of Essential Fatty Acids in Anorexia Nervosa and Obesity

The two basic questions in food intake study are what we eat, and how much do we eat. Most research is directed toward the control of how much is eaten. This is likely the result of the increased number of individuals with eating disorders in the Western world. Feeding behavior is highly complex, and is controlled by many psychological, physiological, biochemical, and immunological factors. The aim of this review is to clarify the involvement of fatty acids in eating disorders such as anorexia and binge eating disorder. The review will describe the modified fatty acid profile observed in individuals with anorexia or binge eating disorder, and discuss on what factors fatty acids can exert beneficial effects. In addition, the differences and similarities between anorexia and binge eating disorder will be discussed. We suggest that beneficial effects of essential fatty acids on both anorexia and binge eating disorder can be explained by the stabilizing effect of those fatty acids on the neuronal membrane fluidity index.

The importance of n-6/n-3 fatty acids ratio in the major depressive disorder

This review aims to clarify the relation between the ratio of omega-6 to omega-3 fatty acids and the development of depression. It is explained how these fatty acids are involved in the production of eicosanoids and how these fatty acids can affect the membrane fluidity, by their incorporation into membrane phospholipids. In addition, it is described how omega-3 derivatives are shown to regulate gene transcription. In view of the pathophysiology of depression, the mechanisms of how an altered ratio of omega-6 to omega-3 could be involved in depression are discussed. Possible mechanisms could include an increased production of pro-inflammatory cytokines, which can activate the HPA axis and a changed membrane fluidity, which potentially affects membrane bound enzymes, ion channels, receptor activity and neurotransmitter binding. In view of clinical trials, it is also discussed whether omega-3 supplementation could have a beneficial effect in the treatment of depressive patient. There are strong indications that an increased ratio of membrane omega-6 to omega-3 is involved in the pathogenesis of depression and so far, omega-3 supplementation has shown positive effects in clinical trials.

Relationship between fatty acids and the endocrine and neuroendocrine system

Significant interactions exist between fatty acids and the endocrine system. Dietary fatty acids alter both hormone and neuropeptide concentrations and also their receptors. In addition, hormones affect the metabolism of fatty acids and the fatty acid composition of tissue lipids. The principal hormones involved in lipid metabolism are insulin, glucagon, catecholamines, cortisol and growth hormone. The concentrations of these hormones are altered in chronic degenerative conditions such as diabetes and cardiovascular disease, which in turn leads to alterations in tissue lipids. Lipogenesis and lipolysis, which modulate fatty acid concentrations in plasma and tissues, are under hormonal control. Neuropeptides are also involved in lipid metabolism in brain and other tissues. Polyunsaturated fatty acids are also precursors for eicosanoids including prostaglandins, leucotrienes, and thromboxanes, which have hormone-like activities. Fatty acids in turn affect the endocrine system. Saturated and trans fatty acids decrease insulin concentration leading to insulin resistance. In contrast, polyunsaturated fatty acids increase plasma insulin concentration and decrease insulin resistance. In humans, omega3 polyunsaturated fatty acids alter the levels of opioid peptides in plasma. Free fatty acids have been reported to inhibit glucagon release. Fatty acids also affect receptors for hormones and neuropeptides.

Omega 3 polyunsaturated fatty acid improves spatial learning and hippocampal peroxisome proliferator activated receptors (PPARα and PPARγ) gene expression in rats

Background

This study examined the effects of dietary polyunsaturated fatty acids (PUFA) as different n-6: n-3 ratios on spatial learning and gene expression of peroxisome- proliferator-activated receptors (PPARs) in the hippocampus of rats. Thirty male Sprague–Dawley rats were randomly allotted into 3 groups of ten animals each and received experimental diets with different n-6: n-3 PUFA ratios of either 65:1, 22:1 or 4.5:1. After 10 weeks, the spatial memory of the animals was assessed using the Morris Water Maze test. The expression of PPARα and PPARγ genes were determined using real-time PCR.

Results

Decreasing dietary n-6: n-3 PUFA ratios improved the cognitive performance of animals in the Morris water maze test along with the upregulation of PPARα and PPARγ gene expression. The animals with the lowest dietary n-6: n-3 PUFA ratio presented the highest spatial learning improvement and PPAR gene expression.

Conclusion

It can be concluded that modulation of n-6: n-3 PUFA ratios in the diet may lead to increased hippocampal PPAR gene expression and consequently improved spatial learning and memory in rats.

Effects of large doses of arachidonic acid added to docosahexaenoic acid on social impairment in individuals with autism spectrum disorders: a double-blind, placebo-controlled, randomized trial

Autism spectrum disorders are a neurodevelopmental disorders with reduced cortical functional connectivity relating to social cognition. Polyunsaturated fatty acids arachidonic acid (ARA) and docosahexaenoic acid (DHA) may have key role in brain network maturation. In particularly, ARA is important in signal transduction related to neuronal maturation. Supplementation with larger ARA doses added to DHA may therefore mitigate social impairment. In a 16-week, double-blind, randomized, placebo-controlled trial, we evaluated the efficacy of supplementation with large doses of ARA added to DHA (n = 7) or placebo (n = 6) in 13 participants (mean age, 14.6 [SD, 5.9] years). To examine underlying mechanisms underlying the effect of our supplementation regimen, we examined plasma levels of antioxidants transferrin and superoxide dismutase, which are useful markers of signal transduction. The outcome measures were the Social Responsiveness Scale and the Aberrant Behavior Checklist-Community. Repeated-measures analysis of variance revealed that our supplementation regimen significantly improved Aberrant Behavior Checklist-Community-measured social withdrawal and Social Responsiveness Scale-measured communication. Treatment effect sizes were more favorable for the treatment group compared with the placebo group (communication: treatment groups, 0.87 vs, placebo, 0.44; social withdrawal: treatment groups, 0.88, vs placebo, 0.54). There was a significant difference in the change in plasma transferrin levels and a trend toward a significant difference in the change in plasma superoxide dismutase levels between the 2 groups. This preliminary study suggests that supplementation with larger ARA doses added to DHA improves impaired social interaction in individuals with autism spectrum disorder by up-regulating signal transduction.

Omega-3 fatty acid augmentation of citalopram treatment for patients with major depressive disorder

OBJECTIVE

The objective of this study was to explore the efficacy of combination therapy with citalopram plus omega-3 fatty acids versus citalopram plus placebo (olive oil) in the initial treatment of individuals with major depressive disorder (MDD). We hypothesized that combination therapy would lead not only to greater efficacy but also to a more rapid onset of therapeutic response.

METHODS

Forty-two subjects participated in this 9-week randomized, masked, placebo-controlled study of combination therapy (two 1 g capsules containing a blend of 900 mg of eicosapentaenoic acid, 200 mg of and docosahexaenoic acid, and 100 mg of other omega-3 fatty acids twice daily plus citalopram) versus monotherapy (two 1 g capsules of olive oil per day plus citalopram) treatment of MDD.

RESULTS

The combination therapy demonstrated significantly greater improvement in Hamilton Depression Rating scale scores over time (F = 7.32; df 1,177; P = 0.008) beginning at week 4 (t = -2.48; df 177; P = 0.014).

CONCLUSIONS

Combination therapy was more effective than monotherapy in decreasing signs and symptoms of MDD during the 8 weeks of active treatment; however, combination therapy did not seem to enhance the speed of the initial antidepressant response. These findings suggest that there may be an advantage to combining omega-3 fatty acids with a selective serotonin uptake inhibitor in the initial treatment of individuals with MDD. A larger definitive study is warranted.

Potentiation of omega-3 fatty acid antidepressant-like effects with low non-antidepressant doses of fluoxetine and mirtazapine

Despite the advances in psychopharmacology, the treatment of depressive disorders is still not satisfactory. Side effects and resistance to antidepressant drugs are the greatest complications during treatment. Based on recent evidence, omega-3 fatty acids may influence vulnerability and outcome in depressive disorders. The aim of this study was to further characterize the omega-3 antidepressant-like effect in rats in terms of its behavioral features in the depression model forced swimming test either alone or in combination with antidepressants fluoxetine or mirtazapine. Ultimately, we prompted to determine the lowest dose at which omega-3 fatty acids and antidepressant drugs may still represent a pharmacological advantage when employed in combined treatments. Chronic diet supplementation with omega-3 fatty acids produced concentration-dependent antidepressant-like effects in the forced swimming test displaying a behavioral profile similar to fluoxetine but different from mirtazapine. Fluoxetine or mirtazapine at antidepressant doses (10 and 20 mg/kg/day, respectively) rendered additive effects in combination with omega-3 fatty acid supplementation (720 mg/kg/day). Beneficial effects of combined treatment were also observed at sub-effective doses (1 mg/kg/day) of fluoxetine or mirtazapine, since in combination with omega-3 fatty acids (720 mg/kg/day), antidepressants potentiated omega-3 antidepressant-like effects. The antidepressant-like effects occurred in the absence of changes in brain phospholipid classes. The therapeutic approach of combining omega-3 fatty acids with low ineffective doses of antidepressants might represent benefits in the treatment of depression, especially in patients with depression resistant to conventional treatments and even may contribute to patient compliance by decreasing the magnitude of some antidepressant dose-dependent side effects.

Arachidonic acid inhibition of L-type calcium (CaV1.3b) channels varies with accessory CaVbeta subunits

Arachidonic acid (AA) inhibits the activity of several different voltage-gated Ca²⁺ channels by an unknown mechanism at an unknown site. The Ca²⁺ channel pore-forming subunit (Ca_Vα₁) is a candidate for the site of AA inhibition because T-type Ca²⁺ channels, which do not require accessory subunits for expression, are inhibited by AA. Here, we report the unanticipated role of accessory Ca_Vβ subunits on the inhibition of Ca_V1.3b L-type (L-) current by AA. Whole cell Ba²⁺ currents were measured from recombinant channels expressed in human embryonic kidney 293 cells at a test potential of −10 mV from a holding potential of −90 mV. A one-minute exposure to 10 µM AA inhibited currents with β_1b, β₃, or β₄ 58, 51, or 44%, respectively, but with β_2a only 31%. At a more depolarized holding potential of −60 mV, currents were inhibited to a lesser degree. These data are best explained by a simple model where AA stabilizes Ca_V1.3b in a deep closed-channel conformation, resulting in current inhibition. Consistent with this hypothesis, inhibition by AA occurred in the absence of test pulses, indicating that channels do not need to open to become inhibited. AA had no effect on the voltage dependence of holding potential–dependent inactivation or on recovery from inactivation regardless of Ca_Vβ subunit. Unexpectedly, kinetic analysis revealed evidence for two populations of L-channels that exhibit willing and reluctant gating previously described for Ca_V2 channels. AA preferentially inhibited reluctant gating channels, revealing the accelerated kinetics of willing channels. Additionally, we discovered that the palmitoyl groups of β_2a interfere with inhibition by AA. Our novel findings that the Ca_Vβ subunit alters kinetic changes and magnitude of inhibition by AA suggest that Ca_Vβ expression may regulate how AA modulates Ca²⁺-dependent processes that rely on L-channels, such as gene expression, enzyme activation, secretion, and membrane excitability.

Oiling the brain: a review of randomized controlled trials of omega-3 fatty acids in psychopathology across the lifespan

Around one in four people suffer from mental illness at some stage in their lifetime. There is increasing awareness of the importance of nutrition, particularly omega-3 polyunsaturated fatty acids (n-3 PUFA), for optimal brain development and function. Hence in recent decades, researchers have explored effects of n-3 PUFA on mental health problems over the lifespan, from developmental disorders in childhood, to depression, aggression, and schizophrenia in adulthood, and cognitive decline, dementia and Alzheimer's disease in late adulthood. This review provides an updated overview of the published and the registered clinical trials that investigate effects of n-3 PUFA supplementation on mental health and behavior, highlighting methodological differences and issues.

Project DyAdd: Fatty acids and cognition in adults with dyslexia, ADHD, or both

Both attention deficit hyperactivity disorder (ADHD) and dyslexia are suggested to co-occur with altered fatty acid (FA) metabolism, but it is unknown how FAs are associated with the cognitive domains that characterize these disorders. In the project DyAdd, we investigated the associations between FAs in serum phospholipids and phonological processing, reading, spelling, arithmetic, executive functions, and attention. Healthy controls (n=36), adults with ADHD (n=26), dyslexia (n=36), or both (n=9) were included in the study. FAs included saturated, monounsaturated, total polyunsaturated, n-3, and n-6 FAs, together with n-6/n-3, AA/EPA, and LA/ALA ratios. When all the study subjects were included in the analyses, especially polyunsaturated FAs (PUFAs) were positively associated with cognition, but reading was least associated with FAs. These associations were modulated by gender, intelligence, n-3 PUFA intake, and group. Accordingly, within the ADHD group, only few associations emerged with PUFAs, n-6 PUFAs, and cognitive domains, whereas in the dyslexia group the more prevalent associations appeared with PUFAs and n-3 PUFAs.

Omega-3 fatty acids as a treatment for perinatal depression: randomized double-blind placebo-controlled trial

OBJECTIVE

Epidemiological, biological marker and treatment studies, as well as neuroscientific theories, indicate a possible link between omega-3 fatty acids and perinatal depression (PND). Hence the aim of the present study was to assess whether omega-3 fatty acid treatment is superior to placebo in the treatment of PND.

METHOD

A double-blind randomized placebo-controlled trial was undertaken. Women with major depression during the perinatal period received either fish oil or placebo for six weeks. Changes in depression scores were recorded weekly.

RESULTS

A total of 26 subjects were recruited and there was no significant difference in depression scores between those receiving fish oil and those receiving the placebo.

CONCLUSIONS

This is formally a negative study, suggesting that there is no benefit for omega-3 fatty acids over placebo in treating PND. The reason could be that the study was underpowered due to recruitment difficulties and therefore we suggest that it may be unwise to interpret this result as conclusive. Omega-3 is a natural product that is a safe and well-tolerated treatment. Further research is therefore needed in this area to establish whether omega-3 fatty acids are an effective treatment for PND.

Physical fatty acid deficiency signs in children with ADHD symptoms

Fatty acid deficiency symptoms (FADS) of dry hair and skin, frequent thirst and urination have been observed to be higher in children with attention deficit hyperactivity disorder (ADHD). Two studies investigated FADS in 7-12-year-old children; Study 1 in a general population (N=347) and Study 2 in children with ADHD symptoms (N=104). Correlations between FADS and ADHD-related symptoms were found at baseline in Study 1 but not Study 2. FADS did not improve after supplementation with omega-3 and omega-6 polyunsaturated fatty acids (PUFA) versus placebo after 15 weeks in Study 2, and were not related to improvements in ADHD symptoms in the PUFA groups. However, FADS did improve in all groups, possibly attributable to the linoleic acid present in both the PUFA and placebo (palm oil) supplements. FADS are not a reliable selection criterion for children with ADHD who might benefit from omega-3 PUFA supplementation.

Changes in cerebral blood volume and amyloid pathology in aged Alzheimer APP/PS1 mice on a docosahexaenoic acid (DHA) diet or cholesterol enriched Typical Western Diet (TWD)

High dietary cholesterol and low dietary docosahexaenoic acid (DHA) intake are risk factors for Alzheimer's disease (AD). However, it is unclear how these components influence the course of the disease. We investigated the effects of dietary lipids on beta-amyloid deposition and blood circulation in the brains of 18-month-old APP/PS1 mice. Starting at 6 months of age, mice were fed a regular rodent chow, a Typical Western Diet (TWD) containing 1% cholesterol, or a diet with a high (0.5%) level of DHA for 12 months. Relative cerebral blood volume (rCBV) and flow (CBF) were determined with (2)H MR spectroscopy and gradient echo contrast enhanced MRI. Deposition of beta-amyloid was visualized in fixed brain tissue with immunohistochemistry. The TWD diet increased plaque burden in the dentate gyrus of the hippocampus, but did not significantly reduce rCBV. In contrast, the DHA-enriched diet increased rCBV without changing blood flow indicating a larger circulation in the brain probably due to vasodilatation and decreased the amount of vascular beta-amyloid deposition. Together, our results indicate that the long-term intake of dietary lipids can impact both brain circulation and beta-amyloid deposition, and support the involvement of hemodynamic changes in the development of AD.

Effect of supplementation with polyunsaturated fatty acids and micronutrients on learning and behavior problems associated with child ADHD

METHODS

Various developmental problems including attention-deficit/hyperactivity disorder (ADHD) have been linked to biological deficiencies in polyunsaturated fatty acids (PUFAs). Additionally, there is evidence that symptoms may be reduced with PUFA supplementation. This study investigated effects of supplementation with PUFAs on symptoms typically associated with ADHD. Because nutrients work synergistically, additional effects of micronutrient supplementation were also investigated. A total of 132 Australian children aged 7 to 12 years with scores > or = 2 SD above the population average on the Conners ADHD Index participated in a randomized, placebo-controlled, double-blind intervention over 15 weeks, taking PUFAs alone, PUFAs + micronutrients, or placebo. Due to unreturned questionnaires, data were only available for 104 children.

RESULTS

Significant medium to strong positive treatment effects were found on parent ratings of core ADHD symptoms, inattention, hyperactivity/impulsivity, on the Conners Parent Rating Scale (CPRS) in both PUFA treatment groups compared with the placebo group; no additional effects were found with the micronutrients. After a one-way crossover to active supplements in all groups for a further 15 weeks, these results were replicated in the placebo group, and the treatment groups continued to show significant improvements on CPRS core symptoms. No significant effects were found on Conners Teacher Rating Scales.

CONCLUSION

These results add to preliminary findings that ADHD-related problems with inattention, hyperactivity, and impulsivity might respond to treatment with PUFAs and that improvements may continue with supplementation extending to 30 weeks.

Plasma phospholipid fatty acids are influenced by a ketogenic diet enriched with n-3 fatty acids in children with epilepsy

The ketogenic diet (KD) is used to treat medically refractory epilepsy in children. Alterations of fatty acid (FA) levels may reflect one mechanism of action. We examined the influence of the KD on FA levels and seizure control. The levels of 17 FAs in plasma phospholipids were determined before and 1, 3, 6, and 12 months after initiation of the KD in 25 children (mean age 6.3 years) with intractable epilepsy. Fluid omega-3 FA was supplemented in the diet after one month. Highly significant changes of the levels of several FAs were found. Linoleic acid (LA) and eicosapentaenoic acid (EPA) increased, whereas arachidonic acid (AA) and Mead acid (20:3 n-9) decreased. Docosahexaenoic acid (DHA) increased insignificantly. However, no correlation of changes in FA levels with seizure response was found. The ratio of omega-6 to omega-3 gradually decreased from 7.0 before to 4.9 at 12 months after starting the diet, presumably a cardiovascular benefit. The composition of the KD differs as to FA content and type between different treating centers but, still, the efficacy reports are very similar. This study demonstrates the possibility of composing the KD in such a way that the FA profile is kept within a normal range, which may reduce cardiovascular risks.

Dietary supplementation of arachidonic and docosahexaenoic acids improves cognitive dysfunction

Age-dependent increase of peroxidation of membrane fatty acids such as arachidonic acid (ARA) and docosahexaenoic acid (DHA) in neurons was reported to cause a decline of the hippocampal long-term potentiation (LTP) and cognitive dysfunction in rodents. Although supplementation of ARA and DHA can improve LTP and cognitive function in rodents, their effects in humans are unknown. The present work was undertaken to study whether ARA and DHA have beneficial effects in human amnesic patients. The subjects were 21 mild cognitive dysfunction (12 MCI-A with supplementation and 9 MIC-P with placebo), 10 organic brain lesions (organic), and 8 Alzheimer's disease (AD). The cognitive functions were evaluated using Japanese version of repeatable battery for assessment of neuropsychological status (RBANS) at two time points: before and 90 days after the supplementation of 240 mg/day ARA and DHA, or 240 mg/day of olive oil, respectively. MCI-A group showed a significant improvement of the immediate memory and attention score. In addition, organic group showed a significant improvement of immediate and delayed memories. However, there were no significant improvements of each score in AD and MCI-P groups. It is suggested from these data that ARA and DHA supplementation can improve the cognitive dysfunction due to organic brain damages or aging.

Essential fatty acids and the brain: from infancy to aging

The major effects of essential fatty acids (EFA) on brain structure and functions are reviewed. EFA determine the fluidity of neuronal membrane and control the physiological functions of the brain. EFA is also involved in synthesis and functions of brain neurotransmitters, and in the molecules of the immune system. Since they must be supplied from the diet, a decreased bioavailability is bound to induce major disturbances. While the brain needs a continuous supply during the life span, there are two particularly sensitive periods-infancy and aging. EFA deficiency during infancy delays brain development, and in aging will accelerate deterioration of brain functions. In discussing the role of EFA two issues must be considered-the blood-brain barrier, which determines the bioavailability, and the myelination process, which determines the efficiency of brain and retinal functions.

Beta oxidation in the brain is required for the effects of non-esterified fatty acids on glucose-induced insulin secretion in rats

AIMS/HYPOTHESIS

NEFA play a key role in the setting of insulin resistance and hyperinsulinaemia, which are both features of the prediabetic state. In addition to the direct effects on pancreas and peripheral tissues, NEFA have been reported to act via changes in autonomic nervous system activity. The present study was aimed at studying the effects of a local increase in NEFA in the brain on glucose-induced insulin secretion (GIIS) and on insulin action. We hypothesised that cerebral NEFA beta oxidation is a prerequisite for these central effects.

METHODS

Male Wistar rats were infused with Intralipid/heparin for 24 h through the carotid artery towards the brain (IL rats), after which we performed the GIIS test, a euglycaemic-hyperinsulinaemic clamp and c-fos immunochemistry. In another series of experiments, Intralipid/heparin infusion was coupled with lateral ventricular infusion of etomoxir, a CPT1 inhibitor, which was initiated 5 days previously.

RESULTS

During the infusion period, there were no changes in plasma NEFA, insulin or glucose concentrations. IL rats displayed an increased GIIS compared with control rats (C rats) infused with saline/heparin, and their liver insulin sensitivity was decreased. Furthermore, lipid infusion induced a significant decrease in c-fos-like immunoreactive neurons in medial hypothalamic nuclei, and an increase in lateral hypothalamus. Neuronal activation profile was almost normalised in IL rats infused with etomoxir, and GIIS was strongly decreased, possibly because of the concomitant normalisation of hepatic glucose output.

CONCLUSIONS/INTERPRETATION

These results strongly suggest that beta oxidation is required for the central effects of NEFA on GIIS.

Astrocytes in culture require docosahexaenoic acid to restore the n-3/n-6 polyunsaturated fatty acid balance in their membrane phospholipids

Docosahexaenoic acid (DHA), the main n-3 polyunsaturated fatty acid (PUFA) in membranes, is particularly abundant in brain cells. Decreased cerebral concentrations of DHA, resulting from dietary n-3 deficiency, are associated with impaired cognitive function. Because the cellular causes of this impairment are still unknown, we need in vitro models that mimic the variations in n-3/n-6 PUFA seen in vivo. We have compared the PUFA profiles of hamster astrocytes cultured in medium supplemented with long-chain PUFA [DHA and/or arachidonic acid (AA)] with those of brain tissue from hamsters fed an n-6/n-3 PUFA-balanced diet or one lacking n-3 PUFA. Astrocytes were obtained from the brain cortex of newborn hamsters and cultured in minimum essential medium + 5% fetal calf serum (FCS) supplemented with DHA and/or AA for 10 days. The astrocytes cultured in medium + FCS had low n-3 PUFA contents, comparable to those of brain tissue from hamsters fed an n-3-deficient diet. We have shown that astrocytes grown in medium supplemented with DHA and/or AA, plus alpha-tocopherol to prevent lipid peroxidation, incorporated large amounts of these long-chain PUFA, so that the n-6/n-3 PUFA compositions of the phosphatidylethanolamine and phosphatidylcholine, the two main classes of membrane phospholipids, were greatly altered. Astrocytes cultured in medium plus DHA had a more physiological n-3 status, grew better, and retained their astrocyte phenotype. Thus astrocytes in culture are likely to be physiologically relevant only when provided with adequate DHA. This reliable method of altering membrane phospholipid composition promises to be useful for studying the influence of n-6/n-3 imbalance on astrocyte function.

Dietary long chain PUFAs differentially affect hippocampal muscarinic 1 and serotonergic 1A receptors in experimental cerebral hypoperfusion

The chronic dietary intake of essential polyunsaturated fatty acids (PUFAs) can modulate learning and memory by being incorporated into neuronal plasma membranes. Representatives of two PUFA families, the n-3 and n-6 types become integrated into membrane phospholipids, where the actual (n-6)/(n-3) ratio can determine membrane fluidity and thus the function of membrane-bound proteins. In the present experiment we studied hippocampal neurotransmitter receptors after chronic administration of n-3 PUFA enriched diets in a brain hypoperfusion model, which mimics decreased cerebral perfusion as it occurs in ageing and dementia. Male Wistar rats received experimental diets with a decreased (n-6)/(n-3) ratio from weaning on. Chronic experimental cerebral hypoperfusion was imposed by a permanent, bilateral occlusion of the common carotid arteries (2VO) at the age of 4 months. The experiment was terminated when the rats were 7 months old. Three receptor types, the muscarinic 1, serotonergic 1A and the glutaminergic NMDA receptors were labeled in hippocampal slices by autoradiographic methods. Image analysis demonstrated that 2VO increased muscarinic 1 and NMDA receptor density, specifically in the dentate gyrus and the CA3 region, respectively. The increased ratio of n-3 fatty acids in combination with additional dietary supplements enhanced the density of the serotonergic 1A and muscarinic 1 receptors, while n-3 fatty acids alone increased binding only to the muscarinic 1 receptors. Since the examined receptor types reacted differently to the diets, we concluded that besides changes in membrane fluidity, the biochemical regulation of receptor sensitivity might also play a role in increasing hippocampal receptor density.

Possible anti-Parkinson properties of N-(alpha-linolenoyl) tyrosine: a new molecule

Tyrosine is unable to cross the blood-brain barrier and is therefore unable to improve the status of brain dopamine (DA) and to provide relief for patients with Parkinson's disease (PD) or other DA-insufficient disorders. We report the creation of an amide bond molecule [N-(alpha-linolenoyl)tyrosine (NLT)] that combines tyrosine with a fatty acid mixture. NLT significantly improves the rotational behavior of rats [following unilateral striatal lesions (as a model for Parkinson's)] and overcomes the exaggerated eye-blinking induced by a potent DA-depleting agent (as a model for essential blepharospasm). These results are supported by the finding that NLT's mode of action, in striatum, is the same as the mode of action of D-amphetamine. They both induce an increase in the DA level, DA turnover and release.

Alzheimer's disease through the eye of a mouse. Acceptance lecture for the 2001 Gayle A. Olson and Richard D. Olson prize

There is now ample evidence that beta-amyloid proteins decrease memory. The SAMP8 mouse (P8) develops an early decline in the ability to learn and to retain new information. The studies reviewed here suggest that this is due to overproduction of beta-amyloid. Both antibodies to beta-amyloid and specific antisense to the amyloid precursor protein reverse these deficits in the P8 mouse. This antisense can cross the blood brain barrier. It is hypothesized that the overproduction of beta-amyloid leads to a decline in Delta(9) desaturase activity with an alteration in membrane fatty acids. This results in altered membrane mobility leading to a decline in neurotransmitter activity and a decreased release of acetylcholine. This decreased cholinergic activity results in a decreased ability of the P8 mouse to learn and retain new information.

Differential effects of dietary cholesterol on aminopeptidase A, B and M in the frontal cortex of male and female mice

Although hypercholesterolemia and hypertension have been extensively associated, the regulatory mechanism underlying this relationship is poorly understood. Systemic and local renin-angiotensin systems are involved in the control of blood-pressure. Angiotensin II has been considered as the main effector peptide of renin-angiotensin system. However, other peptides derived from the metabolism of angiotensin II, as angiotensins III and IV have been shown to play significant roles. The aim of this study is to analyse the effect of dietary cholesterol on the activity of the enzymes involved in the metabolism of angiotensins II and III. Soluble and membrane-bound aminopeptidase A (aspartyl- and glutamyl-aminopeptidases), B (arginyl-aminopeptidase) and M (alanyl-aminopeptidase) activities were measured in the frontal cortex of male and female mice fed a cholesterol enriched-diet (1% cholesterol; 0.5 cholic acid). Soluble and membrane-bound aminopeptidases B and M did not change in male or female cholesterol groups. Significant increases were observed in membrane-bound aspartyl- and glutamyl-aminopeptidase activities in both cholesterol groups. Soluble aspartyl- and glutamylaminopeptidases did not change in male cholesterol group, but significant decreases were detected in female cholesterol group. Our results may indicate that the metabolism of angiotensin II to angiotensin III by aminopeptidase A is increased, but angiotensin III metabolism by aminopeptidases B and M is not modified after cholesterol intake; so cholesterol may enhance the effects of angiotensin III, at least, at the cortical level.

Pituitary aminopeptidase activities involved in blood-pressure regulation are modified by dietary cholesterol: sex differences

Given that the existence of a local renin-angiotensin system (RAS) in the pituitary and its participation in the regulation of blood pressure and other biological functions are widely accepted, the aim of this work is to analyze the influence of dietary cholesterol on the activity of the enzymes involved in the metabolism of the effector peptides of the renin-angiotensin system (angiotensin II and III) and vasopressin, in the pituitary of male and female mice fed on a cholesterol-enriched diet (1% cholesterol and 0.5% cholic acid). Soluble and membrane-bound pituitary aminopeptidase A (aspartyl- and glutamyl-aminopeptidase), aminopeptidase M (alanyl-aminopeptidase), aminopeptidase B (arginyl-aminopeptidase) and cystinyl-aminopeptidase activities were fluorimetrically measured. In female mice, cholesterol-enriched diet produced a significant increase in soluble aspartyl- and membrane-bound aspartyl- and glutamyl-aminopeptidase activities, and a significant decrease in membrane-bound alanyl-, arginyl- and cystinyl-aminopeptidase activities. In male mice, after feeding the diet, a significant increase in soluble glutamyl- and membrane-bound arginyl-aminopeptidase activities was observed. Our results indicate differential effects of dietary cholesterol on the metabolism of angiotensin II and III and vasopressin in the pituitary of male and female mice.

Glucose-induced insulin hypersecretion in lipid-infused healthy subjects is associated with a decrease in plasma norepinephrine concentration and urinary excretion

We investigated the effect of a 48 h triglyceride infusion on the subsequent insulin secretion in response to glucose in healthy men. We measured the variations in plasma concentration and urinary excretion of catecholamines as an indirect estimation of sympathetic tone. For 48 h, 20 volunteers received a triglyceride/heparin or a saline solution, separated by a 1-month interval. At time 48 h, insulin secretion in response to glucose was investigated by a single iv glucose injection (0.5 g/kg(-1)) followed by an hyperglycemic clamp (10 mg.kg(-1).min(-1), during 50 min). The triglyceride infusion resulted in a 3-fold elevation in plasma free fatty acids and an increase in insulin and C-peptide plasma concentrations (1.5- and 2.5-fold, respectively, P < 0.05), compared with saline. At time 48 h of lipid infusion, plasma norepinephrine (NE) concentration and urinary excretion levels were lowered compared with saline (plasma NE: 0.65 +/- 0.08 vs. 0.42 +/- 0.06 ng/ml, P < 0.05; urinary excretion: 800 +/- 70 vs. 620 +/- 25 nmol/24 h, P < 0.05). In response to glucose loading, insulin and C-peptide plasma concentrations were higher in lipid compared with saline infusion (plasma insulin: 600 +/- 98 vs. 310 +/- 45 pM, P < 0.05; plasma C-peptide 3.5 +/- 0.2 vs. 1.7 +/- 0.2 nM, P < 0.05). In conclusion, in healthy subjects, a 48-h lipid infusion induces basal hyperinsulinemia and exaggerated insulin secretion in response to glucose which may be partly related to a decrease in sympathetic tone.

The relationship between age and the fatty acid composition of cerebral cortex and erythrocytes in human subjects

The important role that neural tissue fatty acid composition plays in neurodevelopment and various pathological states is increasingly recognized. However, there are limited data regarding the fatty acid composition of normal human brain at various ages. The purpose of this study was to describe human cerebral cortex fatty acid composition from ages 2 to 88 years. The relationship between cerebral cortex and erythrocyte fatty acid composition was also investigated. Samples of frontal cerebral cortex and of erythrocytes were obtained from 58 human subjects on whom autopsies were performed. The mean age of subjects was 40 +/- 29 years, with a range of 2 to 88 years. The fatty acid composition of tissues was determined, and linear regression models were used to describe the relationship between age and the fatty acid composition of cerebral cortex and erythrocytes. The data were bilinear, with changes occurring after the approximate age of 18 years. Therefore, the cohort was divided into subjects with ages < or =18 and >18 years. In the younger group, the polyunsaturated fatty acids generally decreased with age, with the exception of 22:6n3, which demonstrated a significant increase. The level of mono-unsaturated fatty acids, in contrast, generally increased to the age of 18 years. Several of the polyunsaturated fatty acids also decreased with age in the older cohort, particularly 20:4n6. The levels of 18:2n6, however, increased significantly with age in the older cohort. Among subjects < or =18 years of age, there was no significant relationship between cerebral cortex and erythrocyte fatty acid levels. In the older cohort, there was a significant relationship between brain and erythrocyte levels for several fatty acids, particularly 16:0. These data demonstrate that levels of cerebral cortex fatty acids change from early childhood through late adulthood, and indicate that the levels of several erythrocyte fatty acids may be useful in predicting brain fatty acid levels in adults.

Polyunsaturated fatty acids and cerebral function: focus on monoaminergic neurotransmission

More and more reports in recent years have shown that the intake of polyunsaturated fatty acids (PUFA) constitutes an environmental factor able to act on the central nervous system (CNS) function. We recently demonstrated that the effects of PUFA on behavior can be mediated through effects on the monoaminergic neurotransmission processes. Supporting this proposal, we showed that chronic dietary deficiency in alpha-linolenic acid in rats induces abnormalities in several parameters of the mesocortical and mesolimbic dopaminergic systems. In both systems, the pool of dopamine stored in presynaptic vesicles is strongly decreased. This may be due to a decrease in the number of vesicles. In addition, several other factors of dopaminergic neurotransmission are modified according to the system affected. The mesocortical system seems to be hypofunctional overall [e.g., decreased basal release of dopamine (DA) and reduced levels of dopamine D2 (DAD2) receptors]. In contrast, the mesolimbic system seems to be hyperfunctional overall (e.g., increased basal release of DA and increased levels of DAD2 receptors). These neurochemical changes are in agreement with modifications of behavior already described with this deficiency. The precise mechanisms explaining the effects of PUFA on neurotransmission remain to be clarified. For example, modifications of physical properties of the neuronal membrane, effects on proteins (receptors, transporters) enclosed in the membrane, and effects on gene expression and/or transcription might occur. Whatever the mechanism, it is therefore assumed that interactions exist among PUFA, neurotransmission, and behavior. This might be related to clinical findings. Indeed, deficits in the peripheral amounts of PUFA have been described in subjects suffering from neurological and psychiatric disorders. Involvement of the monoaminergic neurotransmission function has been demonstrated or hypothesized in several of these diseases. It can therefore be proposed that functional links exist among PUFA status, neurotransmission processes, and behavioral disorders in humans. Animal models are tools of choice for the understanding of such links. Improved prevention and complementary treatment of neurological and psychiatric diseases can be expected from these studies.

Significantly reduced docosahexaenoic and docosapentaenoic acid concentrations in erythrocyte membranes from schizophrenic patients compared with a carefully matched control group

BACKGROUND

Fatty acid research in schizophrenia has demonstrated an altered cell membrane phospholipid metabolism. Erythrocyte membrane phospholipid composition closest reflects that of neuronal membranes.

METHODS

(Poly)(un)saturated fatty acid concentrations were measured in the erythrocyte membranes of 19, consecutively admitted, medicated young schizophrenic patients and then compared with matched control subjects. Psychiatric symptomatology was rated with the Positive and Negative Symptom Scale and Montgomery-Asberg Depression Rating Scale. Because diet, hormones, and cannabis influence fatty acid metabolism, we included these factors in our study.

RESULTS

The most distinctive findings concerned the omega-3 series: C22:5 omega-3, C22:6 omega-3 (docosahexaenoic acid), and the sum of omega-3 fatty acids were significantly decreased. Interestingly, C20:4 omega-6 (arachidonic acid) was not lowered. In the omega-9 series, higher levels of C22:1 omega-9 and lower levels its elongation product, C24:1 omega-9 (nervonic acid), were found. Interestingly, the other arm of the desaturation-elongation sequence of C18:1 omega-9, C20:3 omega-9, was lower in patients. The total omega-9 fatty acid levels were also lower in patients.

CONCLUSIONS

Significant differences in erythrocyte fatty acid composition were found. The differences were not due to diet or hormonal status and could not be explained by the medication or cannabis use. No consistent pattern emerged from the different fatty acid abnormalities and the clinical symptom scores.

Fatty acid mixture counters stress changes in cortisol, cholesterol, and impair learning

A mixture of linoleic and alpha-linolenic acids (free non-esterified unsaturated fatty acids) administered for 3 weeks prior to injection of cortisol (10 mg/kg), or prior to immersion of rats in a 10 degree C saline bath, prevented elevation of blood levels of cortisol and cholesterol and deficits in Morris water maze spatial learning that usually accompany such stressful conditions. Differences from controls on all behavioural and biochemical measures were statistically significant (P < .05). It is proposed that induction of intense stress, and the associated increase in cortisol, cholesterol and other corticosteroids may damage hippocampal structures and help account for the cognitive decline witnessed in Alzheimer's disease and other age-related conditions. The modulation of these consequences by the fatty acid mixture may provide an alternative strategy for the study of stress markers and for the development of other intervention options in humans.

A frontal variant of Alzheimer's disease exhibits decreased calcium-independent phospholipase A2 activity in the prefrontal cortex

A frontal variant of Alzheimer's disease (AD) has recently been identified on neuropathological and neuropsychological grounds (Johnson, J.K., Head, E., Kim, R., Starr, A., Cotman, C.W., 1999. Clinical and pathological evidence for a frontal variant of Alzheimer Disease. Arch. Neurol. 56, 1233-1239). Frontal AD differs strikingly from typical AD by the occurrence of neurofibrillary tangle densities in the frontal cortex as high or higher than in the entorhinal cortex. Since cerebrocortical membranes are commonly abnormal in Alzheimer's disease (AD), we assayed frontal AD cases for enzymes regulating membrane phospholipid composition. We specifically measured activity of phospholipase A2s (PLA2s) in dorsolateral prefrontal and lateral temporal cortices of frontal AD cases (n=12), which have respectively high and low densities of neurofibrillary tangles. In neither cortical area was Ca(2+)-dependent PLA2 activity abnormal compared to controls (n=12). In contrast, a significant 42% decrease in Ca(2+)-independent PLA2 activity was found in the dorsolateral prefrontal, but not the lateral temporal, cortex of the frontal AD cases. Similarly, the dorsolateral prefrontal cortex, but not the lateral temporal cortex of the frontal AD cases suffered a 42% decrease in total free fatty acid content, though neither that decrease nor those in any one species of free fatty acid was significant. The observed biochemical changes probably occurred in neurons given (a) our finding that PLA2 activity of cultured human NT2 neurons is virtually all Ca(2+)-independent and (b) the finding of others that nearly all Ca(2+)-independent PLA2 in brain gray matter is neuronal. The decrease in Ca(2+)-independent PLA2 activity is not readily attributable to Group VI or VIII iPLA2s since neither NT2N neurons nor our brain homogenates were greatly inhibited by drugs potently suppressing those iPLA2s. Decreased Ca(2+)-independent PLA2 activity in frontal AD may reflect a compensatory response to pathologically accelerated phospholipid metabolism early in the disorder. That could cause an early elevation of prefrontal free fatty acids, which can stimulate polymerization of tau and thus promote the prefrontal neurofibrillary tangle formation characteristic of frontal AD.

Correlates of sleep and waking in Drosophila melanogaster

Drosophila exhibits a circadian rest-activity cycle, but it is not known whether fly rest constitutes sleep or is mere inactivity. It is shown here that, like mammalian sleep, rest in Drosophila is characterized by an increased arousal threshold and is homeostatically regulated independently of the circadian clock. As in mammals, rest is abundant in young flies, is reduced in older flies, and is modulated by stimulants and hypnotics. Several molecular markers modulated by sleep and waking in mammals are modulated by rest and activity in Drosophila, including cytochrome oxidase C, the endoplasmic reticulum chaperone protein BiP, and enzymes implicated in the catabolism of monoamines. Flies lacking one such enzyme, arylalkylamine N-acetyltransferase, show increased rest after rest deprivation. These results implicate the catabolism of monoamines in the regulation of sleep and waking in the fly and suggest that Drosophila may serve as a model system for the genetic dissection of sleep.

Relationship between fatty acids and the endocrine system

Significant interactions exist between fatty acids and the endocrine system. Hormones affect the metabolism of fatty acids and the fatty acid composition of tissue lipids. The principal hormones involved in lipid metabolism are insulin, glucagon, catecholamines, cortisol and growth hormone. The concentrations of these hormones are altered in chronic degenerative conditions such as diabetes and cardiovascular disease, which in turn lead to alterations in tissue lipids. Lipogenesis and lipolysis, which modulate fatty acid concentrations in plasma and tissues, are under hormonal control. Neuropeptides are involved in lipid metabolism in brain and other tissues. Polyunsaturated fatty acids (PUFA) are also precursors for eicosanoids including prostaglandins, leukotrienes, and thromboxanes, which have hormone-like activities. Fatty acids in turn alter both hormone and neuropeptide concentrations and their receptors. Saturated and trans fatty acids (TFA) decrease insulin concentration leading to insulin resistance. In contrast, PUFA increase plasma insulin concentration and decrease insulin resistance. In humans, omega-3 PUFA alter the levels of opioid peptides in plasma.

Essential fatty acids are mediators of brain biochemistry and cognitive functions

Major advances have been made in understanding the biochemistry of essential fatty acids (FA) and their interactions with metabolic pathways leading to the production of longer and more complex fatty acids and lipids. Less understood are the roles played by FA which are known to affect neurotransmitters, peptides, releasing factors, hormones, and a variety of physiological and cognitive processes. Based on empirical findings we propose that (a) FA exert a controlling function in the modulation of neuronal membrane fluidity, and (b) the critical factor in FA action and efficacy is not absolute level but rather the ratio between various groups of FA. This approach unifies the biochemical and cognitive results obtained from many different and unrelated fields of research.

Treatment with a polyunsaturated fatty acid prevents deleterious effects of Ro4-1284

Ro4-1284 (2-Ethyl-1,3,4,6,7,11b-hexahydro-3-isobutyl-9,10-dimethoxy-2H-benzo[a] quinolizin-2-ol hydrochloride), a benzoquinolizine, is a potent dopamine depletion agent whose acute and chronic administration results in a (1) deterioration of learning in the Morris Water Maze and passive avoidance tasks, (2) decrease in locomotion and rearing, (3) intense hypothermia, and (4) decrease in the percentage of polyunsaturated fatty acids and an increase in the level of cholesterol in neuronal membranes. Pretreatment with a specific mixture of free polyunsaturated fatty acids prevents most of the behavioral, physiological, and biochemical effects of Ro4-1284 except for rearing. We propose that the dopamine-mediated functions tested in this study are dependent on the interaction of intact dopamine D1 and D2 receptors. Rearing, which is controlled only by dopamine D1 receptors, remained, therefore, unaffected. Our hypothesis is that SR-3 exerts its beneficial effects by normalizing the structure and function of the neuronal membrane and by restoring dopamine D2 receptor functions.