Effects of docosahexaenoic acid on in vitro amyloid beta peptide 25–35 fibrillation

Esterification of Docosahexaenoic Acid Enhances Its Transport to the Brain and Its Potential Therapeutic Use in Brain Diseases

Docosahexaenoic acid-containing lysophosphatidylcholine (DHA-LysoPC) is presented as the main transporter of DHA from blood plasma to the brain. This is related to the major facilitator superfamily domain-containing protein 2A (Mfsd2a) symporter expression in the blood-brain barrier that recognizes the various lyso-phospholipids that have choline in their polar head. In order to stabilize the DHA moiety at the sn-2 position of LysoPC, the sn-1 position was esterified by the shortest acetyl chain, creating the structural phospholipid 1-acetyl,2-docosahexaenoyl-glycerophosphocholine (AceDoPC). This small structure modification allows the maintaining of the preferential brain uptake of DHA over non-esterified DHA. Additional properties were found for AceDoPC, such as antioxidant properties, especially due to the aspirin-like acetyl moiety, as well as the capacity to generate acetylcholine in response to the phospholipase D cleavage of the polar head. Esterification of DHA within DHA-LysoPC or AceDoPC could elicit more potent neuroprotective effects against neurological diseases.

A Synergistic Combination of DHA, Luteolin, and Urolithin A Against Alzheimer’s Disease

Alzheimer’s disease (AD) is a devastating neurodegenerative disorder and the most common form of dementia worldwide. The classical AD brain is characterized by extracellular deposition of amyloid-β (Aβ) protein aggregates as senile plaques and intracellular neurofibrillary tangles (NFTs), composed of hyper-phosphorylated forms of the microtubule-associated protein Tau. There has been limited success in clinical trials for some proposed therapies for AD, so attention has been drawn toward using alternative approaches, including prevention strategies. As a result, nutraceuticals have become attractive compounds for their potential neuroprotective capabilities. The objective of the present study was to derive a synergistic nutraceutical combination in vitro that may act as a potential preventative therapy for AD. The compounds of interest were docosahexaenoic acid (DHA), luteolin (LUT), and urolithin A (UA). The cell viability and cytotoxicity assays MTS and LDH were used to evaluate the compounds individually and in two-compound combinations, for their ability to inhibit Aβ1–42-induced toxicity in human neuroblastoma BE(2)-M17 cells. The LDH-derived% protection values were used in the program CompuSyn v.1.0 to calculate the combination index (CI) of the two-compound combinations. The software-predicted potentially synergistic (CI < 1) two-compound combinations were validated using CellTiter Glo assay. Finally, a three-compound combination was predicted (D5L5U5) and shown to be the most effective at inhibiting Aβ1–42-induced toxicity. The synergistic combination, D5L5U5 warrants further research for its mechanism of action; however, it can serve as a basis to develop an advanced functional food for the prevention or co-treatment of AD.

Why Have the Benefits of DHA Not Been Borne Out in the Treatment and Prevention of Alzheimer's Disease? A Narrative Review Focused on DHA Metabolism and Adipose Tissue

Docosahexaenoic acid (DHA), an omega-3 fatty acid rich in seafood, is linked to Alzheimer's Disease via strong epidemiological and pre-clinical evidence, yet fish oil or other DHA supplementation has not consistently shown benefit to the prevention or treatment of Alzheimer's Disease. Furthermore, autopsy studies of Alzheimer's Disease brain show variable DHA status, demonstrating that the relationship between DHA and neurodegeneration is complex and not fully understood. Recently, it has been suggested that the forms of DHA in the diet and plasma have specific metabolic fates that may affect brain uptake; however, the effect of DHA form on brain uptake is less pronounced in studies of longer duration. One major confounder of studies relating dietary DHA and Alzheimer's Disease may be that adipose tissue acts as a long-term depot of DHA for the brain, but this is poorly understood in the context of neurodegeneration. Future work is required to develop biomarkers of brain DHA and better understand DHA-based therapies in the setting of altered brain DHA uptake to help determine whether brain DHA should remain an important target in the prevention of Alzheimer's Disease.

Curcumin and Homotaurine Suppress Amyloid-β25-35 Aggregation in Synthetic Brain Membranes

Amyloid-β (Aβ) peptides spontaneously aggregate into β- and cross-β-sheets in model brain membranes. These nanometer sized can fuse into larger micrometer sized clusters and become extracellular and serve as nuclei for further plaque and fibril growth. Curcumin and homotaurine represent two different types of Aβ aggregation inhibitors. While homotaurine is a peptic antiaggregant that binds to amyloid peptides, curcumin is a nonpeptic molecule that can inhibit aggregation by changing membrane properties. By using optical and fluorescent microscopy, X-ray diffraction, and UV-vis spectroscopy, we study the effect of curcumin and homotaurine on Aβ_25-35 aggregates in synthetic brain membranes. Both molecules partition spontaneously and uniformly in membranes and do not lead to observable membrane defects or disruption in our experiments. Both curcumin and homotaurine were found to significantly reduce the number of small, nanoscopic Aβ aggregates and the corresponding β- and cross-β-sheet signals. While a number of research projects focus on potential drug candidates that target Aβ peptides directly, membrane-lipid therapy explores membrane-mediated pathways to suppress peptide aggregation. Based on the results obtained, we conclude that membrane active drugs can be as efficient as peptide targeting drugs in inhibiting amyloid aggregation in vitro.

Phytol loaded PLGA nanoparticles regulate the expression of Alzheimer's related genes and neuronal apoptosis against amyloid-β induced toxicity in Neuro-2a cells and transgenic Caenorhabditis elegans

Amyloid β (Aβ) induced neurotoxicity has been postulated to initiate synaptic loss and subsequent neuronal degeneration in Alzheimer's disease (AD). The nanoparticles based drug carrier system is considered as a promising therapeutic strategy to combat this incurable disease. It was also found to inhibit cholinesterase activity and apoptosis mediated cell death in Neuro-2a cells. The in vivo study further revealed that the Phytol and Phytol-PLGA NPs (Poly Lactic-co-Glycolic Acid Nanoparticles) was found to increase the lifespan, chemotaxis behavior and decrease Aβ deposition & ROS (Reactive oxygen species) production in transgenic Caenorhabditis elegans models of AD (CL2006, CL4176). Phytol and Phytol-PLGA NPs treatment downregulated the expression of AD associated genes viz Aβ, ace-1 and hsp-4 and upregulated the gene involved in the longevity to nematodes (dnj-14) and it also reduced the expression of Aβ peptide at the protein level. Our results of in vitro and in vivo studies suggest that Phytol and Phytol-PLGA NPs hold promising neuroprotective efficacy and targets multiple neurotoxic mechanisms involved in the AD progression.

Omega-3 Docosahexaenoic Acid Is a Mediator of Fate-Decision of Adult Neural Stem Cells

The mammalian brain is enriched with lipids that serve as energy catalyzers or secondary messengers of essential signaling pathways. Docosahexaenoic acid (DHA) is an omega-3 fatty acid synthesized de novo at low levels in humans, an endogenous supply from its precursors, and is mainly incorporated from nutrition, an exogeneous supply. Decreased levels of DHA have been reported in the brains of patients with neurodegenerative diseases. Preventing this decrease or supplementing the brain with DHA has been considered as a therapy for the DHA brain deficiency that could be linked with neuronal death or neurodegeneration. The mammalian brain has, however, a mechanism of compensation for loss of neurons in the brain: neurogenesis, the birth of neurons from neural stem cells. In adulthood, neurogenesis is still present, although at a slower rate and with low efficiency, where most of the newly born neurons die. Neural stem/progenitor cells (NSPCs) have been shown to require lipids for proper metabolism for proliferation maintenance and neurogenesis induction. Recent studies have focused on the effects of these essential lipids on the neurobiology of NSPCs. This review aimed to introduce the possible use of DHA to impact NSPC fate-decision as a therapy for neurodegenerative diseases.

Effect of Varying Concentrations of Docosahexaenoic Acid on Amyloid Beta (1⁻42) Aggregation: An Atomic Force Microscopy Study

Healthcare has advanced significantly, bringing with it longer life expectancies and a growing population of elders who suffer from dementia, specifically Alzheimer’s disease (AD). The amyloid beta (Aβ) peptide has been implicated in the cause of AD, where the peptides undergo a conformational change and form neurotoxic amyloid oligomers which cause neuronal cell death. While AD has no cure, preventative measures are being designed to either slow down or stop the progression of this neurodegenerative disease. One of these measures involves dietary supplements with polyunsaturated fatty acids such as docosahexaenoic acid (DHA). This omega-3 fatty acid is a key component of brain development and has been suggested to reduce the progression of cognitive decline. However, different studies have yielded different results as to whether DHA has positive, negative, or no effects on Aβ fibril formation. We believe that these discrepancies can be explained with varying concentrations of DHA. Here, we test the inhibitory effect of different concentrations of DHA on amyloid fibril formation using atomic force microscopy. Our results show that DHA has a strong inhibitory effect on Aβ_1–42 fibril formation at lower concentrations (50% reduction in fibril length) than higher concentrations above its critical micelle concentration (70% increase in fibril length and three times the length of those at lower concentrations). We provide evidence that various concentrations of DHA can play a role in the inhibitory effects of amyloid fibril formation in vitro and help explain the discrepancies observed in previous studies.

Membrane-Modulating Drugs can Affect the Size of Amyloid-β25-35 Aggregates in Anionic Membranes

The formation of amyloid-β plaques is one of the hallmarks of Alzheimer's disease. The presence of an amphiphatic cell membrane can accelerate the formation of amyloid-β aggregates, making it a potential druggable target to delay the progression of Alzheimer's disease. We have prepared unsaturated anionic membranes made of 1-palmitoyl-2-oleoyl-sn-glycero-3-phosphocholine (POPC) and 1,2-dimyristoyl-sn-glycero-3-phospho-L-serine (DMPS) and added the trans-membrane segment Aβ_25-35. Peptide plaques spontaneously form in these membranes at high peptide concentrations of 20 mol%, which show the characteristic cross-β motif (concentrations are relative to the number of membrane lipids and indicate the peptide-to-lipid ratio). We used atomic force microscopy, fluorescence microscopy, x-ray microscopy, x-ray diffraction, UV-vis spectroscopy and Molecular Dynamics (MD) simulations to study three membrane-active molecules which have been speculated to have an effect in Alzheimer's disease: melatonin, acetylsalicyclic acid (ASA) and curcumin at concentrations of 5 mol% (drug-to-peptide ratio). Melatonin did not change the structural parameters of the membranes and did not impact the size or extent of peptide clusters. While ASA led to a membrane thickening and stiffening, curcumin made membranes softer and thinner. As a result, ASA was found to lead to the formation of larger peptide aggregates, whereas curcumin reduced the volume fraction of cross-β sheets by ~70%. We speculate that the interface between membrane and peptide cluster becomes less favorable in thick and stiff membranes, which favors the formation of larger aggregates, while the corresponding energy mismatch is reduced in soft and thin membranes. Our results present evidence that cross-β sheets of Aβ_25-35 in anionic unsaturated lipid membranes can be re-dissolved by changing membrane properties to reduce domain mismatch.

Alpha-Linolenic Acid from Perilla frutescens var. japonica Oil Protects Aβ-Induced Cognitive Impairment through Regulation of APP Processing and Aβ Degradation

Alzheimer's disease (AD) is characterized by progressive cognitive and memory impairment. The major pathological hallmark of AD is the accumulation of amyloid beta (Aβ), which is produced from the amyloid precursor protein (APP) through cleavage of β- and γ-secretase. Recently, dietary plant oil containing ω-3 polyunsaturated fatty acid has become an attractive alternative source to fish oil containing eicosapentaenoic acid or docosahexaenoic acid (DHA). We investigated whether ALA isolated from perilla oil has direct effects on improvement of cognitive ability and molecular mechanisms in APP processing in comparison with DHA. In the present study, ICR mice were treated orally with ALA or DHA (100 mg/kg/day) for 14 days after i.c.v. injection of Aβ_25-35. Administration of ALA resulted in a prevention of learning and memory deficit in Aβ_25-35-injected mice compared with the control group, as observed in T-maze, novel object recognition, and Morris water maze tests. ALA supplementation also markedly ameliorated the Aβ_25-35-induced oxidative stress by inhibition of lipid peroxidation and nitric oxide overproduction in the mouse brain, liver, and kidney, almost down to the levels in DHA-administered group. These effects of ALA on protective mechanisms were related to the regulation of APP processing via promoting nonamyloidogenic pathway such as up-regulation of soluble APP alpha, C-terminal fragment alpha/beta ratio, and A disintegrin and metalloprotease10 protein expressions. Furthermore, ALA inhibited the amyloidogenic pathway through the down-regulation of β-site APP-cleaving enzyme and presenilin2. ALA also enhanced Aβ degradation enzyme, insulin-degrading enzyme. In conclusion, the present study indicated a beneficial effect of ALA in improving the cognitive ability against Aβ_25-35, and these effects were comparable to those exerted by DHA. Its neuroprotective effects are mediated, in part, by regulation of APP processing and Aβ degradation, and thus, ALA might be a potential candidate for prevention or treatment of neurodegenerative diseases such as AD.

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

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

The pleiotropic effects of omega-3 docosahexaenoic acid on the hallmarks of Alzheimer's disease

Among omega-3 polyunsaturated fatty acids (PUFAs), docosahexaenoic acid (DHA, 22:6n-3) is important for adequate brain development and cognition. DHA is highly concentrated in the brain and plays an essential role in brain functioning. DHA, one of the major constituents in fish fats, readily crosses the blood-brain barrier from blood to the brain. Its critical role was further supported by its reduced levels in the brain of Alzheimer's disease (AD) patients. This agrees with a potential role of DHA in memory, learning and cognitive processes. Since there is yet no cure for dementia such as AD, there is growing interest in the role of DHA-supplemented diet in the prevention of AD pathogenesis. Accordingly, animal, epidemiological, preclinical and clinical studies indicated that DHA has neuroprotective effects in a number of neurodegenerative conditions including AD. The beneficial effects of this key omega-3 fatty acid supplementation may depend on the stage of disease progression, other dietary mediators and the apolipoprotein ApoE genotype. Herein, our review investigates, from animal and cell culture studies, the molecular mechanisms involved in the neuroprotective potential of DHA with emphasis on AD.

Dietary DHA supplementation in an APP/PS1 transgenic rat model of AD reduces behavioral and Aβ pathology and modulates Aβ oligomerization

Increased dietary consumption of docosahexaenoic acid (DHA) is associated with decreased risk for Alzheimer's disease (AD). These effects have been postulated to arise from DHA's pleiotropic effects on AD pathophysiology, including its effects on β-amyloid (Aβ) production, aggregation, and toxicity. While in vitro studies suggest that DHA may inhibit and reverse the formation of toxic Aβ oligomers, it remains uncertain whether these mechanisms operate in vivo at the physiological concentrations of DHA attainable through dietary supplementation. We sought to clarify the effects of dietary DHA supplementation on Aβ indices in a transgenic APP/PS1 rat model of AD. Animals maintained on a DHA-supplemented diet exhibited reductions in hippocampal Aβ plaque density and modest improvements on behavioral testing relative to those maintained on a DHA-depleted diet. However, DHA supplementation also increased overall soluble Aβ oligomer levels in the hippocampus. Further quantification of specific conformational populations of Aβ oligomers indicated that DHA supplementation increased fibrillar (i.e. putatively less toxic) Aβ oligomers and decreased prefibrillar (i.e. putatively more toxic) Aβ oligomers. These results provide in vivo evidence suggesting that DHA can modulate Aβ aggregation by stabilizing soluble fibrillar Aβ oligomers and thus reduce the formation of both Aβ plaques and prefibrillar Aβ oligomers. However, since fibrillar Aβ oligomers still retain inherent neurotoxicity, DHA may need to be combined with other interventions that can additionally reduce fibrillar Aβ oligomer levels for more effective prevention of AD in clinical settings.

Assessment of anti-amyloidogenic activity of marine red alga G. acerosa against Alzheimer's beta-amyloid peptide 25-35

OBJECTIVE

The amyloid hypothesis stimulates the discovery of compounds, which promotes beta-amyloid peptide (Aβ) clearance, thereby altering the underlying pathophysiology of Alzheimer's disease (AD). Hence, the present study aims at the evaluation of anti-amyloidogenic potential of Gelidiella acerosa.

METHODS

Prevention of Aβ 25-35 aggregate formation and disaggregation of pre-formed fibrils by G. acerosa was evaluated in three phases by thioflavin T spectrophotometric assay. The results were further validated by confocal microscopic analysis. The conformational changes in the aggregated and non-aggregated Aβ in the presence of G. acerosa were analyzed by Fourier transform infrared (FTIR) spectroscopic analysis.

RESULTS

Phase-I study shows that G. acerosa reverts (4.56 ± 0.35 AU at 96 hours) the increase in fluorescence intensity of aggregated Aβ (18.76 ± 0.99 AU) significantly (P < 0.05) as that of non-aggregated peptides, which suggests that G. acerosa prevents the formation of oligomers from monomers. The seaweed also prevents the fibril formation even after the aggregation process was initiated at 20 hours, which was verified by the significant (P < 0.05) decrease in the fluorescence intensity (2.94 ± 0.0721 AU) at 36 hours (Phase II). In addition, G. acerosa promotes fibrillar destabilization (Phase III), which was further substantiated by confocal microscopic analysis. Fourier transform infrared spectroscopy reveals that alteration in amide I and amide II band spectrum, which occurs due to Aβ 25-35 aggregation was restored upon co-treatment with G. acerosa benzene extract.

CONCLUSION

Overall, the results suggest that G. acerosa might have direct interaction with the aggregated peptide, thereby preventing oligomerization and fibrillation of Aβ 25-35.

Effects of Krill-derived phospholipid-enriched n-3 fatty acids on Ca(2+) regulation system in cerebral arteries from ovariectomized rats

AIMS

To investigate the effects of n-3 polyunsaturated fatty acids on cerebral circulation, ovariectomized (OVX) rats were administered with phospholipids in krill oil (KPL) or triglycerides in fish oil (FTG); effects on the Ca(2+) regulating system in their basilar artery (BA) were then analyzed.

MAIN METHODS

The rats were divided into 4 groups: control, OVX, OVX given KPL (OVXP), and OVX given FTG (OVXT) orally, daily for 2weeks. Time dependent relaxation (TDR) of contractile response to 5HT in BA was determined myographically, Na(+)/Ca(2+) exchanger (NCX) 1 mRNA expression was determined by real time PCR, and nucleotides were analyzed by HPLC.

KEY FINDINGS

The level of TDR in OVX that was significantly lower in the control was inhibited by l-NAME and indomethacin; TEA inhibited TDR totally in the control but only partly in OVXP and OVXT. Relaxation induced by the addition of 5mM KCl to the BA pre-contracted with 5-HT was inhibited by TEA in the controls, OVXP and OVXT, but not in OVX. Overexpression of NCX1 mRNA in the BA from OVX was significantly inhibited by FTG. The ratio of ADP/ATP in cerebral arteries from OVX was significantly inhibited by KPL and FTG. Levels of triglyceride and arachidonic acid in the plasma of OVX increased, but were significantly inhibited by KPL and FTG.

SIGNIFICANCE

Ovarian dysfunction affects Ca(2+) activated-, ATP-sensitive-K(+) channels and NCX1, which play crucial roles in the autoregulation of cerebral blood flow. Also, KPL may become as good a supplement as FTG for postmenopausal women.

Influence of the physiochemical properties of superparamagnetic iron oxide nanoparticles on amyloid β protein fibrillation in solution

Superparamagnetic iron oxide nanoparticles (SPIONs) are recognized as promising nanodiagnostic materials due to their biocompatibility, unique magnetic properties, and their application as multimodal contrast agents. As coated SPIONs have potential use in the diagnosis and treatment of various brain diseases such as Alzheimer's, a comprehensive understanding of their interactions with Aβ and other amyloidogenic proteins is essential prior to their clinical application. Here we demonstrate the effect of thickness and surface charge of the coating layer of SPIONs on the kinetics of fibrillation of Aβ in aqueous solution. A size and surface area dependent "dual" effect on Aβ fibrillation was observed. While lower concentrations of SPIONs inhibited fibrillation, higher concentrations increased the rate of Aβ fibrillation. With respect to coating charge, it is evident that the positively charged SPIONs are capable of promoting fibrillation at significantly lower particle concentrations compared with negatively charged or uncharged SPIONs. This suggests that in addition to the presence of particles, which affect the concentration of monomeric protein in solution (and thereby the nucleation time), there are also effects of binding on the protein conformation.

Docosahexaenoic acid withstands the Aβ(25-35)-induced neurotoxicity in SH-SY5Y cells

BACKGROUND

Docosahexaenoic acid (DHA, C22:6, n-3) ameliorates the memory-related learning deficits of Alzheimer's disease (AD), which is characterized by fibrillar amyloid deposits in the affected brains. Here, we have investigated whether DHA-induced inhibition of Amyloid β-peptide(25-35) (Aβ(25-35)) fibrillation limits or deteriorates the toxicity of the human neuroblastoma cells (SH-SY5Y).

EXPERIMENTAL METHODS

In vitro fibrillation of Aβ(25-35) was performed in the absence or presence of DHA. Afterwards, SH-SY5Y cells were incubated with Aβ(25-35) in absence or presence 20 μM DHA to evaluate its effect on the Aβ(25-35)-induced neurotoxicity by MTT [3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide)]-redox and TUNEL (TdT-mediated dUTP-biotin nick end-labeling) assay and immunohistochemistry. The level of Aβ(25-35)-induced lipid peroxide (LPO) was determined in the absence or presence of oligomer-specific antibody. Fatty acid profile was estimated by gas chromatography.

RESULTS

DHA significantly reduced the Aβ(25-35) in vitro fibrillation, as indicated by fluorospectroscopy and transmission electron microscopy. Aβ(25-35) decreased the MTT-redox activity and increased the apoptotic damage and levels of LPO when compared with those of the controls. However, when the SH-SY5Y cells were treated with Aβ(25-35) in the presence of DHA, MTT redox potential significantly increased and the levels LPO decreased, suggesting an inhibition of the Aβ(25-35)-induced neurotoxicity. DHA improved the Aβ(25-35) induced DNA damage and axodendritic loss, with a concomitant increase in the cellular level of DHA, suggesting DHA protects the cell from neurotoxic degeneration.

CONCLUSION

DHA not only inhibits the in vitro fibrillation but also resists the Aβ(25-35)-induced toxicity in the neuronal cells. This might be the basis of the DHA-induced amelioration of Aβ-induced neurodegeneration and related cognitive deficits.

Are omega-3 fatty acids options for prevention and treatment of cognitive decline and dementia?

PURPOSE OF REVIEW

To report recent data on the potential role of omega-3 fatty acids (n-3 FA) found in oily fish, especially docosahexaenoic acid (DHA), to prevent and treat cognitive decline and Alzheimer's disease.

RECENT FINDINGS

Observational studies still provide conflicting results, in which the majority indicate beneficial effects on cognition, both when assessed as a continuous variable or as incident dementia, mainly Alzheimer's disease. Experimental studies have demonstrated potentially ameliorating effects of eicosapentaenoic acid (EPA) and DHA on amyloid fragment formation, signal transduction including upregulation of the apolipoprotein receptor SorLA, as well as on angiogenesis. The role of EPA and DHA metabolites on Alzheimer's disease pathology is under investigation. Recently, three randomized intervention studies, with duration up to 6 months have been reported. In contrast to a small study from Taiwan, no positive overall effects were reported from the Swedish OmegAD Study or from a Dutch study, although post hoc analyses indicate that selected individuals with mild forms of Alzheimer's disease or cognitive decline may respond to treatment.

SUMMARY

No firm conclusions can be drawn. Based on epidemiological data, fish including oily fish could be advised as part of a balanced diet for public health purpose, although the evidence for better cognition is only fairly consistent. It is unlikely that n-3 FA will emerge as a treatment option in general for improving cognitive function in patients with Alzheimer's disease. n-3 FA, especially DHA, may turn out as an adjuvant therapy in selected cases. Further long-term intervention studies on individuals with mild cognitive reductions are awaited.