Biological Role of Omega – 6 Fatty Acid in Ad:

The Mechanistic Insights:

The Core mechanism of AD can be well explored by the many authors and address their findings such as accumulation of amyloid and tau pathology coupled with cholinergic dysfunction, leading to cognitive decline, despite understanding these complex mechanisms and utilizing advanced biomarkers for diagnosis, effective disease-modifying treatments currently remain difficult to find^16,17.

Omega-6 fatty acids particularly Arachidonic acid and Linoleic acid play crucial role in brain development and brain function. Among those AA is highly enriched in brain tissues and also serve as a signalling molecule. The metabolic conversion of linoleic acid to arachidonic acid is a crucial biosynthetic pathway composed of alternating desaturation and elongation steps, the initial step of this pathway is by the Δ6 -desaturase enzyme it converts linoleic acid to gamma linoleic acid, Subsequent elongation and desaturation produce the ARA which is the key signalling and membrane component¹⁸.

In addition to AA, Linoleic acid and its isomer, Conjugated Linoleic Acid has a neuroprotective and anti-inflammatory action. LA decreases apoptotic neuronal signal and neurodegeneration markers while, mitigating the neuroinflammation by reducing the activation of astrocytes and microglial cells -example in Parkinson disease, CLA isomer decrease neuroinflammation in BV-2 microglial cells by suppressing pro-inflammatory signalling notably through the upregulation of Peroxisomal Beta Oxidation, suppression of SCD1 and enhanced the production of anti-inflammatory lipid mediators^19,20. In the context of Alzheimer’s disease, the ARA and linoleic acid produce pro-inflammatory mediators and the anti-inflammatory mediators through the various mechanism. Among all those omega-6 fatty acids AA has the critical role on neuroinflammation, Oxidative stress, synaptic dysfunction and amyloid dysfunction. The mechanism of arachidonic acid in Alzheimer’s disease involves three main components such as enzymatic release of ARA, oxidative stress and impairment of microglial function. By the activation of phospholipase A2, the enzyme specifically cytosolic PLA2 initiates the arachidonic acid cascade and liberate the free fatty acid AA, from the membrane, the elevated cPLA2 accumulated in the cerebral cortex and result in active inflammatory process in AD, it accelerates the metabolism of this free AA through key enzymatic pathways and release the eicosanoid such as prostaglandins and leukotrienes it, contributes to neuroinflammation, AA highly vulnerable to oxidation by reactive oxygen species, it produces toxic lipid peroxidase and it accumulate in the early Alzheimer’s disease and around the Aβ plaques which leads to oxidative stress and lipid peroxide production, The excessive release of ARA combined with reduction of ARA-containing phospholipids result in enhanced ARA mobilization which leads to the microglial impairment^21–23. Another mechanism linking ARA to the pathology relevant to AD is highly susceptible to non-enzymatic auto-oxidation and peroxidation which is driven by oxidative stress generated during mitochondrial fatty acid β oxidation, by inhibiting the mitochondrial β-oxidation significantly reduced the levels of nonenzymatic auto-oxidative PUFA metabolite, because it responsible for the oxidative stress and generated β-oxidation increases the peroxidation of PUFA, including ARA²⁴.

In addition to, arachidonic acid another important omega-6 fatty acid such as linoleic acid and its derivative gamma linoleic acid has contribute to the Alzheimer’s disease mechanism. Linoleic acid decreases the expression of inducible nitric oxide synthase, the enzyme responsible for the production of nitric oxide in microglia and help to prevent the excessive microglial activation as well as neuroinflammation²⁵ROS production may disrupt the mitochondrial function and contribute to the which LA contributes to reduced bioenergetic function in AD²⁶. Linoleic acid derivative gamma linolic acid inhibit the activation of nuclear factor- kappa B, the key transcription factor involved in neuroinflammation by inhibiting the NF-kB, it decreases the pro-inflammatory cytokines such as TNFα- and PGE2 elevated in the Alzheimer’s pathology, additionally it also reduces the activity of MAPK signalling and contributes to the anti-inflammatory effects, beyond all those effects it also decreases the reactive oxygen species and product the neurons from the amyloid β induced toxicity²⁷. Another mechanistic insight is tau pathology; some article addresses the role of tau in AD as the Neurofibrillary tangles are obtained by hyperphosphorylation and the treatment focus on the Aβ for the potent molecular target for the prevention of AD^28,29. The isomer of linoleic acid such as conjugated linoleic acid decreases the amyloid β levels in the hippocampus of AD and thus decrease tau phosphorylati¹⁴. The author Dhinakaran et al 2019 reviews that main targets for the AD are Ach esterase, β secretase and tau proteins³⁰.

While free Arachidonic acid is contributing to the pro-inflammatory cascade and its parent LA, derivative GLA, isomer CLA has the anti-inflammatory and neuroprotective action by inhibiting inflammatory signals like NF-kB. With this dual role of omega-6 fatty acids, its mechanism conclude that AD is not caused by omega-6 fatty acid, but by a critical dysregulation of metabolic pathway. This sets the stage for considering how modulating omega-6 levels or pathways might serve as a therapeutic strategy.

Therapeutic Insights and Potential Roles of Omega-6 in Ad:

Despite its pro-inflammatory effect of Arachidonic Acid, other omega-6 fatty acids like GLA, CLA and its derivatives provides anti-inflammatory and neuroprotective action. This dual role of omega-6 fatty acid is a critical therapeutic target for Alzheimer’s disease, the mechanistic evidence suggests that beyond its pro-inflammatory action, some of its derivatives have anti-inflammatory action. Therefore, therapeutic strategies are moving beyond the simple dietary interventions, to focus on metabolic imbalance. This section will discuss on its therapeutical role. As we discussed the mechanism in the previous section, the AA cause the pro-inflammatory action. Therefore, inhibiting its conversion to inflammatory mediators is beneficial for the treatment. Targeting the inhibition of cPLA2, the enzyme releases the AA from membrane phospholipid. AA released by cPLA2 oxidized by COX or LOX enzyme to prostaglandins and leukotrienes the potent mediators of inflammation and increases leukotriene B4, its higher level contributes to oxidative stress and neuroinflammation. By using pyrrophenone (cPLA2 inhibitors) inhibit the cPLA2 and reduce the inflammatory markers protect against synaptic loss and memory deficit especially in the APOE4 human brain³¹. By inhibiting the cPLA2 enzyme the AA release cannot be occurred and it can be beneficial for the anti-inflammatory effect for Alzheimer’s disease. While, inhibiting the cPLA2, upstream blockage and prevent the initial release of Arachidonic Acid next targeting the downstream enzyme which convert to metabolite AA such as Lipoxygenase.Evidence from pre-clinical studies reported that the 5-Lipoxygenase enzyme responsible for the conversion of AA to 5-hydroxyperoxy eicosatetraenoic acid which metabolized to the various leukotrienes. The treatment with Zileuton (5LO inhibitor) inhibits the 5LO activity in the brain of mouse model 3×Tg mice which reduce the leukotriene B4 levels and Aβ deposition as well as tau hyperphosphorylation, by inhibiting the 5LO it prevents the conversion of Arachidonic acid and suggesting that it is a viable therapeutic target ³²..Along with 5LO pathway, Cyclooxygenase pathway contribute to the AA metabolism which convert into prostaglandins and responsible for neuroinflammation. To address these recent therapeutical findings on COX has been developed, which primarily focusing on inhibiting the COX-2 enzyme, because it is responsible for the production of Prostaglandins from the Arachidonic acid cascade. The treatment with NS398, a specific COX-2 inhibitor blocks the effects of TNF-α and ZnSO4 which induce the COX-2 expression and decrease the phosphorylation of tau, the presence of impairment of learning ability in the TauP301S Tg mice ³³. Overall, these studies address that strong rationale for the inhibition of AA cascade whether by an upstream cPLA2 or by a downstream COX and LOX inhibitor and mitigating the AD pathology of Aβ deposition and tau phosphorylation.

The group IV isoform of phospholipase A2 was identified as a potential target for AD as GIVA-PLA2 has been elevated in the hAPP mice, leads to AD risk and its therapeutic outcomes are complete or partial genetic removal of GIVA-PLA2 protected against Aβ dependent deficits in learning and memory in in vivo and in in-vitro studies address that inhibition of GIVA-PLA2 diminished Aβ-induced neurotoxicity, inhibitor of GIVA-PLA2 AACOCF3 reduced the Aβ1-42 induced cell death³⁴. Conversely, some studies have reported that AA has the beneficial effect on AD pathology rather than producing the pro-inflammatory eicasoinds and highlighting its therapeutical strategy for the neuroprotection action. Findings from human studies shows that higher circulating levels of arachidonic acid were associated with better cognitive outcomes, it is an prospective cohort study conducted within the larger cardiovascular health study and the investigation was measurement of Plasma phospholipid fatty acid taken at three point, it is an long term exposure study, this study findings address that higher plasma phospholipid ARA experienced a slower rate of cognitive decline over decades and significantly lower risk of developing dementia and participants in the top quintile ARA had roughly a 0.5 point slower annual 3MSE decline and 47% reduced hazard of dementia compared to the bottom quintile and notably, association grew stronger with longer follow-up, suggesting a potential long term protective effect of ARA⁹.AA acts as a potential inhibitor of Propyl Endopeptidase, the enzyme elevated in the postmortem brains of AD and simultaneously is essential for the cognitive function and balancing its overall diet omega-6 fatty acids may be a therapeutic strategy for reducing neuroinflammation^9,35.

As we have established the both neuroprotective and neuroinflammatory role of AA, its parent Linoleic acid major component of modern diet has gained a positive therapeutic role on neuroinflammation. Some studies address the findings on linoleic acid as that participants include individual with AD and asymptomatic individuals with AD pathology, the brain region studies for this are middle frontal gyrus, inferior temporal gyrus and cerebellum which in vulnerable to the AD pathology and the metabolite detection were made, it suggests that decreased in the linoleic acid were seen in the AD patients, Furthermore decreased linoleic acid were contribute to the slower cognitive function and higher tau and amyloid deposition suggesting that depletion level may contribute to the disease Progression, these findings suggest that maintaining the linoleic acid could be a therapeutic relevance and hence these mechanism not be clearly addressed, it need further investigation ³⁶.Investigation in Walnut oil had been reported that it is enhanced by the presence of linoleic acid and treatment with this walnut oil reduce the Aβ levels and promote neurite growth, also LA is important for the mitochondrial membrane and contributes to the neuronal benefit³⁷.Another study is from the primrose oil and fish oil which contain the linoleic acid along with oleic acid have contribute the anti-inflammatory effect, LA was reported to protect against the pro-inflammatory effect of lipid, while oleic acid possessed a cardioprotective effect, These actions might collectively alleviate the risk of cardiovascular disease hence, mechanism contributes to the subsequent reduction of Alzheimer’s disease progression in rats³⁸.

The study targeting the influence of omega-6 fatty acids as the anti-inflammatory effect. The humanized APOE model (EFAD mice) were used for the study it primarily focuses on the linoleic acid and its long chain metabolite docosapentanoic acid, by administering high dietary linoleic acid suppress the release of pro-inflammatory cytokines and increase the activation of anti-inflammatory cytokines such as IL-10,suppress the cox-2 mRNA expression in the mice model and it releases its metabolite DPAn-6 which has the neuroprotective effect by suppressing the cytokine receptor, inhibit COX-1 gene expression, lower apoptosis markers, enhances neurotropic/synaptic support and produce the neuroprotective action in the late stage AD models, therefore it could be potential treatment for the AD like pathology¹³.

In addition to Linoleic Acid, its isomer Conjugated Linoleic Acid have also gained a therapeutic implication in neuroprotection. Preclinical study using mouse model address that dietary intake cis-9 tans -11 CLA was decrease the Aβ accumulation and enhancing anti-inflammatory effects by reducing the Aβ42 and Aβ40 levels in the hippocampus which decrease the Aβ deposition and tau phosphorylation the decrease effect result in upregulation of anti-inflammatory cytokines, increase in IL-10 or IL-19 suggest that feeding with CLA leads to the suppression of inflammation and also CLA can increase the total number of microglia in both the cortex and hippocampus, thus it promote the Aβ clearance¹⁴.Another study using the animal model of 5×FAD mice has been treated with the Nano- PSO and the result is decrease in the intracellular and extracellular amyloid -beta levels, reduction in the amyloid plaque burden beyond that it also contribute to the restoration of the mitochondrial function and prevent oxidative damage, suggest that it may prevent or delay the progression of neurodegenerative disorder such as AD³⁹.

Beyond, the isomer CLA, Linoleic acid’s direct metabolite, Gamma Linoleic Acid has an anti-inflammatory action. The study using rat model was carried out and it state that advanced glycation end products which is involved in the development of age related cognitive decline and Alzheimer’s disease, by treatment with the GLA it has the anti-glycation effect, reduced the formation of AGE in vitro studies as well as in in- vivo studies rats are feed with high fructose to accelerate the aging process in the rat and after administration with the GLA it reverse the rise in glycosylated haemoglobin levels particularly at low levels, therefore it inhibit the AGE formation in invitro and reverse the memory impairment, rise in HBA1c levels are occur at the low doses of GLA,Hence low doses of GLA is considered as the therapeutic candidate for the memory impairment⁴⁰.

On the other hand, omega-6/omega-3 balance appears critical, particularly in genetically susceptible individuals. The work of Abdullah et al. (2017) underscores that an excess of omega-6 relative to omega-3 can be harmful in the context of APOE ε4 genotype. In their study, cognitively normal ε4 carriers who later progressed to MCI/AD had strikingly higher serum AA:DHA ratios than those who remained healthy, in fact an elevated AA/DHA ratio predicted conversion to AD with over 90% accuracy in their sample, this suggest that omega-6 fatty acids are not inherently ‘bad’ but need to be balanced with omega-3s.APOE ε4 known to impair DHA delivery to the brain and is association with lipid dysregulation; in such individuals, an abundance of ARA without sufficient DHA might exacerbate inflammation or fail to resolve it.Importantly,fish oil supplementation was associated with lower AA/DHA ratios even in 4 carriers, hinting that increasing omega-3 intake could counteract an omega-6 imbalance, thus one therapeutic insight is that dietary interventions in APOE4 individuals may need to emphasize omega-3 enrichment to restore a healthy PUFA equilibrium. It’s not simply a matter of ‘more omega-6 cause AD’-rather the context (counteract omega-3 levels, genetics, disease stage) determines omega-6’s impact¹².The study of Alfred et al. (2020) finds that association of omega-6 fatty acid with Alzheimer’s disease pathology and suggest therapeutic implications by examined in the n-6 PUFA composition in CSF in that four PUFA were identified in the AD participants while N-6 PUFA are precursors to lipid mediators of inflammation that are known to be altered in AD, its therapeutic and preventive implications are the maintain balance of n-3 to n-6,this findings address that dietary interventions should favour pro-resolving fatty acids(n-3) to inflammatory fatty acids(n-6) to enhance cognitive function⁴¹.

In conclusion, the dual role of omega-6 fatty acids has been discussed, the pro-inflammatory effect of AA and neuroprotective effect of LA, CLA, GLA shows that omega-6 fatty acid plays a vital role in Alzheimer’s disease. By targeting the cPLA2, COX, LOX enzymes and inhibiting them can reduce the release off AA, prevent inflammation and its anti-inflammatory effect can be produced by other omega-6 fatty acids LA, CLA and GLA. In the prodromal or preclinical stage, ensuring a healthy omega-6/omega-3 balance-possibly via diet or supplementation-may help maintain cognitive resilience, especially for high -risk APOE4 individuals ¹². The central target is not omega-6 fatty acids themselves but the metabolic pathways, hence further investigation need for its therapeutic action.

Limitations of Current Research:

Despite recent advancements, significant knowledge gaps still exist concerning omega-6 fatty acids and Alzheimer's disease. Most of the human data are observational (observed exposure and outcome with no intervention), which limits the causal inferences and also exposes study investigators to confounding variables. Findings may vary and not only reflect the effects of unexamined disease stages. Preclinical models warrant their own challenges as they include accelerated, brief studies that cannot verify long-term purpose or safety. Lastly, there are also metabolic differences between humans and rodents. A conceptual flaw is that omega-6 is not separable from omega-3 - these two classes of fatty acids compete for the same enzymes and there is substantial evidence suggesting the omega-6/omega-3 ratio (i.e., AA: DHA), perhaps particularly in APOE ε4 carriers, is more relevant than absolute omega-6 levels themselves. In a related note, the literature more generally tends to combine all omega-6 FAs without consideration for specific metabolite functions (e.g. LA, ARA or DPAn-6), which we now understand can have unique and possibly opposing functional characteristics. Monthly review of the literature with recognition of many significant translational barriers to normative clinical care suggest that, where a result does emerge, any future intervention is likely to have to be a multi-therapy combination.

Future Directions:

Future studies should focus on establishing the causal effect of omega-6 fatty acids in humans, particularly among individuals at high risk (i.e., carriers of specific alleles of APOE). Randomized controlled trials should be conducted to assess the effects of modulating the omega-6/omega-3 (AA: DHA) ratio and possibly supplementing with arachidonic acid (ARA), to resolve the inconsistencies regarding the protective effect. To understand the mechanisms involved, an important area is to go beyond fatty acid classes and characterize specialized metabolites (e.g., DPAn-6 in reducing inflammation) as potential biomarkers and therapeutics. This area could also include screening for newly developed drug candidates that target key regulatory enzymes (e.g., cPLA₂, LPCAT3) to modulate the ARA cascade with greater resolution.

Longitudinal -omic studies (lipidomics, for example) are crucial to trace the dynamics of the "omega-6 lipidome" throughout the progression of AD and to discover new potential biomarkers, as well as guidance for intervention timing. This information will contribute to consequent personalized nutrition recommendations, wherein dietary PUFA recommendations are based on the individual’s genetic make-up as well as specific lipid profile. In the near term, real-world evidence can begin to be captured now through the integration of optimized n-6: n-3 ratios into multi-domain lifestyle intervention trials. Finally, future work should extend beyond amyloid and inflammation to establish the poorly understood relationship between omega-6 modulation and tau pathology.

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Received on 28.11.2025 Revised on 15.12.2025

Accepted on 30.12.2025 Published on 12.02.2026

Available online from February 14, 2026

Res.J. Pharmacology and Pharmacodynamics.2026;18(1):73-80.

DOI: 10.52711/2321-5836.2026.00009

This work is licensed under a Creative Commons Attribution-NonCommercial-ShareAlike 4.0 International License. Creative Commons License.

Author/year	Subject/Model	Omega 6 Focus	Key findings
De Oliveira Otta et al⁹2023	3,564 Participants from Cardiovascular Health Study aged of ≥ 65 years old (Prospective cohort Study). The study Observation period was 23 years.	Plasma phospholipid fatty acids (AA, Linoleic acid)	Higher level of Arachidonic acid in blood leads to slower cognitive decline and also helps to low the risk of dementia& Alzheimer disease. Linoleic acid can quickly slow down the dementia risk although, not consistent association was observed with LA.
Pablo Galeano et al¹¹. 2023	MCgill-R-Thy1-APP is a transgenic rat for early-stage AD. 5 × FAD transgenic mice for late-stage AD.	High Fat diet-Corn oil rich in omega-6 Fatty acids.	Transgenic animal model was treated with Corn oil (omega- 6 fatty acid) combined with the omega -3 fatty acids (25:1) study there is did not increase in the hippocampal Aβ deposition. On the other hand, in rat study high fatty acid promote microglial activation and thus enhances the neuronal inflammation. This study suggests that high PUFA (omega -6 with omega-3) may not worsen the AD pathology, however the diet rich in omega-6 fatty acids can cause the neuroinflammation in Early-stage AD.
Abdullah et al¹². 2017	195 participants (Cognitive free adults) from ADAPT-3 years follow -up and the subject used in this study was mice model which expressing APOEε4 isoforms.	Blood sample of phospholipid composition ratio of AA: DHA (omega -6: omega- 3).	In mice model which expressing human APOE especially E4FAD has increase in omega 6 fatty acids (AA) decrease in omega 3 fatty acids (DHA) in the brain, these may promote the inflammatory effect and leads to AA/DHA imbalance, therefore it may contribute to AD risk. Followed by human study of 23 individual with APOE4 carriers found that serum levels of AA:DHA ratio has been higher in 3 years followed up study, which could be function as the biomarker for early detection of AD.
Ma et al ¹³. 2020	E3FAD AND E4FAD mice (experimental model) which genetically modify to carry APOE3 and APOE4.These mice contain 5 × FAD transgenes (Overproduce human amyloid -beta). Invitro (BV2) microglial cell culture used to assess the cellular inflammation response.	Linoleic acid (Omega -6 fatty acids) and its metabolite docosapentaenoic acid (DPAn-6).	LA reduce the COX-1 and expression of COX-2 miRNA genes and also IL-1β, IL-6(Pro-inflammatory cytokines) and its metabolite DPAn-5×6 fold increases the IL-10(anti-inflammatory) in E3FAD and E4FAD mice. This study suggests that Linoleic acid and its metabolite DPAn-6 reduce the neuroinflammation and improvement of neurodegeneration in AD models.
Fujita et al ¹⁴. 2021	Transgenic hAPPS Wind(J20) mice which overexpress the human amyloid precursor protein	Cis 9-trans 11 CLA (omega -6 linoleic acid isomer).	Conjugated Linoleic acid decreases the Aβ40 & Aβ42 levels (amyloid β-protein) in the hippocampus and increase the numbers of microglia (CD45+ and CD206+) as well as astrocytes expressing IL-10 & IL-19 (anti-inflammatory cytokines) increase in the hippocampus. This study concludes that Cis 9-trans 11 CLA increases the anti-inflammatory effect and reduce inflammation, Aβ clearance by the activation PPARγ.
Youn et al¹⁵. 2018	Rat Pheochromocytoma (PC12) Cells as a cellular model for neurotoxicity.	Gamma Linoleic Acid (omega -6 fatty acids)	GLA protect the PC12 cells against the Aβ25-35 -induced cytotoxicity and decrease the excessive generation Reactive Oxygen Species. By inhibiting the proinflammatory cytokines (TNF-a) and by supressing inflammatory prostaglandin (E2 and Nitic Oxide), it blocks the key inflammatory signalling pathway such as NF-KB and MAPK pathway.