Plasma polyunsaturated fatty acids and mental disorders in adolescence and early adulthood: cross-sectional and longitudinal associations in a general population cohort

Omega-3 fatty acids and major depression: a Mendelian randomization study

Omega-3 fatty acids have been implicated in the aetiology of depressive disorders, though trials supplementing omega-3 to prevent major depressive disorder (MDD) have so far been unsuccessful. Whether this association is causal remains unclear. We used two sample Mendelian randomization (MR) to investigate causality. Genetic variants associated with circulating omega-3 and omega-6 fatty acids in UK Biobank (UKBB, n = 115,078) were selected as exposures. The Psychiatric Genomics Consortium (PGC) genome-wide association studies (GWAS) of MDD (n = 430,775; cases = 116,209; controls = 314,566) and recurrent depression (rMDD, n = 80,933; cases = 17,451; controls = 62,482), were used as outcomes. Multivariable MR (MVMR) models were used to account for biologically correlated lipids, such as high- and low-density cholesterol and triglycerides, and to explore the relative importance of longer-chain omega-3 fatty acids eicosapentaenoic acid (EPA) and docosahexaenoic acid (DHA) using data from the Cohorts for Heart and Aging Research in Genomic Epidemiology (CHARGE, n = 8866). Genetic colocalization analyses were used to explore the presence of a shared underlying causal variant between traits. Genetically predicted total omega-3 fatty acids reduced the odds of MDD (ORIVW 0.96 per standard deviation (SD, i.e. 0.22 mmol/l) (95% CIs 0.93-0.98, p = 0.003)). The largest point estimates were observed for eicosapentaenoic acid (EPA), a long-chain omega-3 fatty acid (OREPA 0.92; 95% CI 0.88-0.96; p = 0.0002). The effect of omega-3 fatty acids was robust to MVMR models accounting for biologically correlated lipids. 'Leave-one-out' analyses highlighted the FADS gene cluster as a key driver of the effect. Colocalization analyses suggested a shared causal variant using the primary outcome sample, but genomic confounding could not be fully excluded. This study supports a role for omega-3 fatty acids, particularly EPA, in the aetiology of depression, although pleiotropic mechanisms cannot be ruled out. The findings support guidelines highlighting the importance of EPA dose and ratio for MDD and question whether targeted interventions may be superior to universal prevention trials, as modest effect sizes will limit statistical power.

Plasma fatty acids and attention deficit hyperactivity disorder: a Mendelian randomization investigation

Background

Attention deficit hyperactivity disorder (ADHD) is the most common neurodevelopmental disorder of childhood, and pathogenesis is not fully understood. Observational studies suggest an association between fatty acids abnormalities and ADHD, but there are contradictions and differences between these findings. To address this uncertainty, we employed a two-sample bidirectional Mendelian Randomization (MR) analysis to investigate the causal relationship between fatty acids and ADHD.

Methods

We conducted a two-sample Mendelian Randomization (MR) study, selecting single nucleotide polymorphisms (SNPs) highly correlated with fatty acid levels from the CHARGE Consortium as our instruments. The outcome data were sourced from the Psychiatric Genomics Consortium (PGC) dataset on ADHD, comprising 225,534 individuals, with 162,384 cases and 65,693 controls. Inverse variance weighting, MR-Egger, and weighted median methods were employed to estimate the causal relationship between fatty acids and ADHD. Cochran's Q-test was used to quantify heterogeneity of instrumental variables. Sensitivity analyses included MR-Egger intercept tests, leave-one-out analyses, and funnel plots.

Results

The MR analysis revealed no significant associations between genetically predicted levels of various saturated, monounsaturated, and polyunsaturated fatty acids (including omega-3 and omega-6) and ADHD risk in the CHARGE and PGC cohorts. Notably, an initial association with Dihomo-gamma-linolenic acid (DGLA) (OR = 1.009, p = 0.032 by IVW) did not persist after correction for multiple testing (adjusted p-value = 0.286). Sensitivity analysis supported our findings, indicating robustness. Moreover, there was a lack of evidence supporting a causal link from ADHD to fatty acids.

Conclusion

While our study on the basis of genetic data does not provide evidence to support the causal role of fatty acids in ADHD, it does not preclude their potential involvement in reducing the risk of ADHD. Further research is needed to explore this possibility.

Longitudinal Trajectories of Plasma Polyunsaturated Fatty Acids and Associations With Psychosis Spectrum Outcomes in Early Adulthood

BACKGROUND

Evidence supports associations between polyunsaturated fatty acids such as docosahexaenoic acid (DHA) and psychosis. However, polyunsaturated fatty acid trajectories in the general population have not been characterized, and associations with psychosis spectrum outcomes in early adulthood are unknown.

METHODS

Plasma omega-6 to omega-3 ratio and DHA (expressed as percentage of total fatty acids) were measured by nuclear magnetic spectroscopy at 7, 15, 17, and 24 years of age in participants of ALSPAC (Avon Longitudinal Study of Parents and Children). Curvilinear growth mixture modeling evaluated body mass index-adjusted trajectories of both measures. Outcomes were assessed at 24 years. Psychotic experiences (PEs), at-risk mental state status, psychotic disorder, and number of PEs were assessed using the Psychosis-Like Symptoms interview (n = 3635; 2247 [61.8%] female). Negative symptoms score was measured using the Community Assessment of Psychic Experiences (n = 3484; 2161 [62.0%] female). Associations were adjusted for sex, ethnicity, parental social class, and cumulative smoking and alcohol use.

RESULTS

Relative to stable average, the persistently high omega-6 to omega-3 ratio trajectory was associated with increased odds of PEs and psychotic disorder, but attenuated on adjustment for covariates (PEs adjusted odds ratio [aOR] = 1.63, 95% CI = 0.92-2.89; psychotic disorder aOR = 1.69, 95% CI = 0.71-4.07). This was also the case for persistently low DHA (PEs aOR = 1.42, 95% CI = 0.84-2.37; psychotic disorder aOR = 1.14, 95% CI = 0.49-2.67). Following adjustment, persistently high omega-6 to omega-3 ratio was associated with increased number of PEs (β = 0.41, 95% CI = 0.05-0.78) and negative symptoms score (β = 0.43, 95% CI = 0.14-0.72), as was persistently low DHA (number of PEs β = 0.45, 95% CI = 0.14-0.76; negative symptoms β = 0.35, 95% CI = 0.12-0.58).

CONCLUSIONS

Optimization of polyunsaturated fatty acid status during development warrants further investigation in relation to psychotic symptoms in early adulthood.

Lipids in Psychiatric Disorders: Functional and Potential Diagnostic Role as Blood Biomarkers

Lipids are a crucial component of the human brain, serving important structural and functional roles. They are involved in cell function, myelination of neuronal projections, neurotransmission, neural plasticity, energy metabolism, and neuroinflammation. Despite their significance, the role of lipids in the development of mental disorders has not been well understood. This review focused on the potential use of lipids as blood biomarkers for common mental illnesses, such as major depressive disorder, anxiety disorders, bipolar disorder, and schizophrenia. This review also discussed the impact of commonly used psychiatric medications, such as neuroleptics and antidepressants, on lipid metabolism. The obtained data suggested that lipid biomarkers could be useful for diagnosing psychiatric diseases, but further research is needed to better understand the associations between blood lipids and mental disorders and to identify specific biomarker combinations for each disease.

Prognostic models predicting transition to psychotic disorder using blood-based biomarkers: a systematic review and critical appraisal

Accumulating evidence suggests individuals with psychotic disorder show abnormalities in metabolic and inflammatory processes. Recently, several studies have employed blood-based predictors in models predicting transition to psychotic disorder in risk-enriched populations. A systematic review of the performance and methodology of prognostic models using blood-based biomarkers in the prediction of psychotic disorder from risk-enriched populations is warranted. Databases (PubMed, EMBASE and PsycINFO) were searched for eligible texts from 1998 to 15/05/2023, which detailed model development or validation studies. The checklist for Critical Appraisal and Data Extraction for Systematic Reviews of Prediction Modelling Studies (CHARMS) was used to guide data extraction from eligible texts and the Prediction Model Risk of Bias Assessment Tool (PROBAST) was used to assess the risk of bias and applicability of the studies. A narrative synthesis of the included studies was performed. Seventeen eligible studies were identified: 16 eligible model development studies and one eligible model validation study. A wide range of biomarkers were assessed, including nucleic acids, proteins, metabolites, and lipids. The range of C-index (area under the curve) estimates reported for the models was 0.67-1.00. No studies assessed model calibration. According to PROBAST criteria, all studies were at high risk of bias in the analysis domain. While a wide range of potentially predictive biomarkers were identified in the included studies, most studies did not account for overfitting in model performance estimates, no studies assessed calibration, and all models were at high risk of bias according to PROBAST criteria. External validation of the models is needed to provide more accurate estimates of their performance. Future studies which follow the latest available methodological and reporting guidelines and adopt strategies to accommodate required sample sizes for model development or validation will clarify the value of including blood-based biomarkers in models predicting psychosis.

A Preliminary Comparison of Plasma Tryptophan Metabolites and Medium- and Long-Chain Fatty Acids in Adult Patients with Major Depressive Disorder and Schizophrenia

Background and Objectives: Disturbance of tryptophan (Trp) and fatty acid (FA) metabolism plays a role in the pathogenesis of psychiatric disorders. However, quantitative analysis and comparison of plasma Trp metabolites and medium- and long-chain fatty acids (MCFAs and LCFAs) in adult patients with major depressive disorder (MDD) and schizophrenia (SCH) are limited. Materials and Methods: Clinical symptoms were assessed and the level of Trp metabolites and MCFAs and LCFAs for plasma samples from patients with MDD (n = 24) or SCH (n = 22) and healthy controls (HC, n = 23) were obtained and analyzed. Results: We observed changes in Trp metabolites and MCFAs and LCFAs with MDD and SCH and found that Trp and its metabolites, such as N-formyl-kynurenine (NKY), 5-hydroxyindole-3-acetic acid (5-HIAA), and indole, as well as omega-3 polyunsaturated fatty acids (N3) and the ratio of N3 to omega-6 polyunsaturated fatty acids (N3: N6), decreased in both MDD and SCH patients. Meanwhile, levels of saturated fatty acids (SFA) and monounsaturated fatty acids (MUFA) decreased in SCH patients, and there was a significant difference in the composition of MCFAs and LCFAs between MDD and SCH patients. Moreover, the top 10 differential molecules could distinguish the two groups of diseases from HC and each other with high reliability. Conclusions: This study provides a further understanding of dysfunctional Trp and FA metabolism in adult patients with SCH or MDD and might develop combinatorial classifiers to distinguish between these disorders.

Destabilization of Aβ fibrils by omega-3 polyunsaturated fatty acids: a molecular dynamics study

The senile plaques of neurotoxic aggregates of Aβ protein, deposited extraneuronally, mark the pathological hallmark of Alzheimer's disease (AD). The natural compounds such as omega-3 (ω-3) polyunsaturated fatty acids (PUFAs), which can access blood-brain barrier, are believed to be potential disruptors of preformed Aβ fibrils to cure AD with unknown mechanism. Herein, we present the destabilization potential of three ω-3 PUFAs, viz. Eicosapentaenoic acid (EPA), Docosahexaenoic acid (HXA), and α-linolenic acid (LNL) by molecular dynamics simulation. After an initial testing of 300 ns, EPA and HXA have been considered further for extended production run time, 500 ns. The increased value of root mean square deviation (RMSD), radius of gyration, and solvent-accessible surface area (SASA), the reduced number of H-bonds and β-sheet content, and disruption of salt bridges and hydrophobic contacts establish the binding of these ligands to Aβ fibril leading to destabilization. The polar head was found to interact with positively charged lysine (K28) residue in the fibril. However, the hydrophobicity of the long aliphatic tail competes with the intrinsic hydrophobic interactions of Aβ fibril. This amphiphilic nature of EPA and HXA led to the breaking of inherent hydrophobic contacts and formation of new bonds between the tail of PUFA and hydrophobic residues of Aβ fibril, leading to the destabilization of fibril. The Molecular Mechanics Poisson-Boltzmann Surface Area (MM-PBSA) results explain the binding of EPA and HXA to Aβ fibril by interacting with different residues. The destabilization potential of EPA and HXA establishes them as promising drug leads to cure AD, and encourages prospecting of other fatty acids for therapeutic intervention in AD.Communicated by Ramaswamy H. Sarma.

Abnormal erythrocyte fatty acid composition in first-diagnosed, drug-naïve patients with depression

BACKGROUND & AIMS

The correlation between fatty acids (FAs) and depression is not yet conclusive. This study examined the relationship of FAs composition with the presence and clinical characteristics of first-diagnosed, drug-naïve patients with depression.

METHODS

A total of 139 first-diagnosed, drug-naïve patients with depression and 55 healthy controls (HCs) were included in the cross-sectional study. The levels of erythrocyte membrane FAs were compared and then the correlation between clinical symptoms and fatty acid levels in depression was investigated.

RESULTS

Compared to HCs, patients with depression had higher C18:1n9t (z = -2.033, p = 0.042), C20:4n6 (z = -2.104, p = 0.035), C20:3n6 (z = -2.104, p = 0.035) and n-6 polyunsaturated fatty acids (PUFAs) (z = -2.127, p = 0.033), whereas the levels of C18:1n9c (z = -3.348, p = 0.001) were significantly lower. Higher C20:3n6, C20:4n6, C18:1n9t and n-6 PUFAs levels were associated with higher severity of depressive and anxiety symptoms in patients with depression, and the correlation remained after adjusting for the related confounding factors (p < 0.05).

CONCLUSIONS

Patients with first-diagnosed, drug-naïve depression show abnormal erythrocyte fatty acid composition. Trans fatty acids (TFAs) and n-6 PUFAs levels are closely related to clinical characteristics of depression. This study indicated that increased n-6 PUFAs and TFAs are characteristic changes of first-diagnosed, drug-naïve depression.

Exercise and Dietary Factors Mediate Neural Plasticity Through Modulation of BDNF Signaling

The term “neural plasticity” was first used to describe non-pathological changes in neuronal structure. Today, it is generally accepted that the brain is a dynamic system whose morphology and function is influenced by a variety of factors including stress, diet, and exercise. Neural plasticity involves learning and memory, the synthesis of new neurons, the repair of damaged connections, and several other compensatory mechanisms. It is altered in neurodegenerative disorders and following damage to the central or peripheral nervous system. Understanding the mechanisms that regulate neural plasticity in both healthy and diseased states is of significant importance to promote cognition and develop rehabilitation techniques for functional recovery after injury. In this minireview, we will discuss the mechanisms by which environmental factors promote neural plasticity with a focus on exercise- and diet-induced factors. We will highlight the known circulatory factors that are released in response to exercise and discuss how all factors activate pathways that converge in part on the activation of BDNF signaling. We propose to harness the therapeutic potential of exercise by using BDNF as a biomarker to identify novel endogenous factors that promote neural plasticity. We also discuss the importance of combining exercise factors with dietary factors to develop a lifestyle pill for patients afflicted by CNS disorders.

Transdiagnostic inflammatory subgroups among psychiatric disorders and their relevance to role functioning: a nested case-control study of the ALSPAC cohort

Individuals with psychotic disorders and depressive disorder exhibit altered concentrations of peripheral inflammatory markers. It has been suggested that clinical trials of anti-inflammatory therapies for psychiatric disorders should stratify patients by their inflammatory profile. Hence, we investigated whether different subgroups of individuals exist across psychiatric disorders, based on their inflammatory biomarker signatures. We measured the plasma concentrations of 17 inflammatory markers and receptors in 380 participants with psychotic disorder, depressive disorder or generalised anxiety disorder and 399 controls without psychiatric symptoms from the ALSPAC cohort at age 24. We employed a semi-supervised clustering algorithm, which discriminates multiple clusters of psychiatric disorder cases from controls. The best fit was for a two-cluster model of participants with psychiatric disorders (Adjusted Rand Index (ARI) = 0.52 ± 0.01) based on the inflammatory markers. Permutation analysis indicated the stability of the clustering solution performed better than chance (ARI = 0.43 ± 0.11; p < 0.001), and the clusters explained the inflammatory marker data better than a Gaussian distribution (p = 0.021). Cluster 2 exhibited marked increases in sTNFR1/2, suPAR, sCD93 and sIL-2RA, compared to cluster 1. Participants in the cluster exhibiting higher inflammation were less likely to be in employment, education or training, indicating poorer role functioning. This study found evidence for a novel pattern of inflammatory markers specific to psychiatric disorders and strongly associated with a transdiagnostic measure of illness severity. sTNFR1/2, suPAR, sCD93 and sIL-2RA could be used to stratify clinical trials of anti-inflammatory therapies for psychiatric disorders.

Machine learning based prediction and the influence of complement - Coagulation pathway proteins on clinical outcome: Results from the NEURAPRO trial

BACKGROUND

Functional outcomes are important measures in the overall clinical course of psychosis and individuals at clinical high-risk (CHR), however, prediction of functional outcome remains difficult based on clinical information alone. In the first part of this study, we evaluated whether a combination of biological and clinical variables could predict future functional outcome in CHR individuals. The complement and coagulation pathways have previously been identified as being of relevance to the pathophysiology of psychosis and have been found to contribute to the prediction of clinical outcome in CHR participants. Hence, in the second part we extended the analysis to evaluate specifically the relationship of complement and coagulation proteins with psychotic symptoms and functional outcome in CHR.

MATERIALS AND METHODS

We carried out plasma proteomics and measured plasma cytokine levels, and erythrocyte membrane fatty acid levels in a sub-sample (n = 158) from the NEURAPRO clinical trial at baseline and 6 months follow up. Functional outcome was measured using Social and Occupational Functional assessment Score (SOFAS) scale. Firstly, we used support vector machine learning techniques to develop predictive models for functional outcome at 12 months. Secondly, we developed linear regression models to understand the association between 6-month follow-up levels of complement and coagulation proteins with 6-month follow-up measures of positive symptoms summary (PSS) scores and functional outcome.

RESULTS AND CONCLUSION

A prediction model based on clinical and biological data including the plasma proteome, erythrocyte fatty acids and cytokines, poorly predicted functional outcome at 12 months follow-up in CHR participants. In linear regression models, four complement and coagulation proteins (coagulation protein X, Complement C1r subcomponent like protein, Complement C4A & Complement C5) indicated a significant association with functional outcome; and two proteins (coagulation factor IX and complement C5) positively associated with the PSS score. Our study does not provide support for the utility of cytokines, proteomic or fatty acid data for prediction of functional outcomes in individuals at high-risk for psychosis. However, the association of complement protein levels with clinical outcome suggests a role for the complement system and the activity of its related pathway in the functional impairment and positive symptom severity of CHR patients.

Effect of High Ratio of n-6/n-3 PUFAs on Depression: A Meta-Analysis of Prospective Studies

Objective

The aim of this systematic review and meta-analysis was to examine the association between high ratio of n-6/n-3 polyunsaturated fatty acids (PUFAs) and depression.

Methods

The authors conducted a meta-analysis of research articles on the association of high ratio of n-6/n-3 PUFAs with the risk of depression published in the online article database on PubMed, Embase, Cochrane library as of December 2021. Pooled odds ratios (OR) were calculated using random effects models. Publication bias was assessed visually by funnel plots and statistically by the Egger’s and Begg’s tests.

Results

Finally, 12 studies included in this systematic review and meta-analysis with a total of 66,317 participants (including 4,173 individuals with depression condition). The pooled results showed that high ratio of n-6/n-3 PUFAs might be positively associated with depression [OR = 1.21, 95% confidence intervals (CIs): 1.04∼1.41]. The I² test indicated that there was a substantial statistical heterogeneity across the included studies (I² = 54.38%, P = 0.01). Subgroup analysis showed that high ratio of n-6/n-3 PUFAs in blood had no significant association with depression (OR = 1.15, 95%CI: 0.88∼1.50), while high ratio of n-6/n-3 PUFAs in dietary supplements was positively associated with depression (OR = 1.32, 95%CI: 1.16∼1.51).

Conclusion

This meta-analysis confirmed the association between high ratio of n-6/n-3 PUFAs and the risk of depression. High ratio of n-6/n-3 PUFAs in dietary supplementation was positively associated with depression, but had no significant association in the blood. This study suggested that lowering the dietary intake of the ratio of n-6/n-3 PUFAs would be beneficial in the prevention of depression.

Soluble Epoxide Hydrolase as a Therapeutic Target for Neuropsychiatric Disorders

It has been found that soluble epoxide hydrolase (sEH; encoded by the EPHX2 gene) in the metabolism of polyunsaturated fatty acids (PUFAs) plays a key role in inflammation, which, in turn, plays a part in the pathogenesis of neuropsychiatric disorders. Meanwhile, epoxy fatty acids such as epoxyeicosatrienoic acids (EETs), epoxyeicosatetraenoic acids (EEQs), and epoxyeicosapentaenoic acids (EDPs) have been found to exert neuroprotective effects in animal models of neuropsychiatric disorders through potent anti-inflammatory actions. Soluble expoxide hydrolase, an enzyme present in all living organisms, metabolizes epoxy fatty acids into the corresponding dihydroxy fatty acids, which are less active than the precursors. In this regard, preclinical findings using sEH inhibitors or Ephx2 knock-out (KO) mice have indicated that the inhibition or deficiency of sEH can have beneficial effects in several models of neuropsychiatric disorders. Thus, this review discusses the current findings of the role of sEH in neuropsychiatric disorders, including depression, autism spectrum disorder (ASD), schizophrenia, Parkinson’s disease (PD), and stroke, as well as the potential mechanisms underlying the therapeutic effects of sEH inhibitors.

The association of plasma inflammatory markers with omega-3 fatty acids and their mediating role in psychotic symptoms and functioning: An analysis of the NEURAPRO clinical trial

There is increasing evidence that dysregulation of polyunsaturated fatty acids (FAs) mediated membrane function plays a role in the pathophysiology of schizophrenia. Even though preclinical findings have supported the anti-inflammatory properties of omega-3 FAs on brain health, their biological roles as anti-inflammatory agents and their therapeutic role on clinical symptoms of psychosis risk are not well understood. In the current study, we investigated the relationship of erythrocyte omega-3 FAs with plasma immune markers in a clinical high risk for psychosis (CHR) sample. In addition, a mediation analysis was performed to examine whether previously reported associations between omega-3 FAs and clinical outcomes were mediated via plasma immune markers. Clinical outcomes for CHR participants in the NEURAPRO clinical trial were measured using the Brief Psychiatric Rating Scale (BPRS), Schedule for the Scale of Assessment of Negative Symptoms (SANS) and Social and Occupational Functioning Assessment Scale (SOFAS) scales. The erythrocyte omega-3 index [eicosapentaenoic acid (EPA) + docosahexaenoic acid (DHA)] and plasma concentrations of inflammatory markers were quantified at baseline (n = 268) and 6 month follow-up (n = 146) by gas chromatography and multiplex immunoassay, respectively. In linear regression models, the baseline plasma concentrations of Interleukin (IL)-15, Intercellular adhesion molecule (ICAM)-1 and Vascular cell adhesion molecule (VCAM)-1 were negatively associated with baseline omega-3 index. In addition, 6-month change in IL-12p40 and TNF-α showed a negative association with change in omega-3 index. In longitudinal analyses, the baseline and 6 month change in omega-3 index was negatively associated with VCAM-1 and TNF-α respectively at follow-up. Mediation analyses provided little evidence for mediating effects of plasma immune markers on the relationship between omega-3 FAs and clinical outcomes (psychotic symptoms and functioning) in CHR participants. Our results indicate a predominantly anti-inflammatory relationship of omega-3 FAs on plasma inflammatory status in CHR individuals, but this did not appear to convey clinical benefits at 6 month and 12 month follow-up. Both immune and non-immune biological effects of omega-3 FAs would be resourceful in understanding the clinical benefits of omega-3 FAs in CHR papulation.