Disentangling the Molecular Mechanisms of the Antidepressant Activity of Omega-3 Polyunsaturated Fatty Acid: A Comprehensive Review of the Literature

Dietary fatty acid composition drives neuroinflammation and impaired behavior in obesity

Nutrient composition in obesogenic diets may influence the severity of disorders associated with obesity such as insulin-resistance and chronic inflammation. Here we hypothesized that obesogenic diets rich in fat and varying in fatty acid composition, particularly in omega 6 (ω6) to omega 3 (ω3) ratio, have various effects on energy metabolism, neuroinflammation and behavior. Mice were fed either a control diet or a high fat diet (HFD) containing either low (LO), medium (ME) or high (HI) ω6/ω3 ratio. Mice from the HFD-LO group consumed less calories and exhibited less body weight gain compared to other HFD groups. Both HFD-ME and HFD-HI impaired glucose metabolism while HFD-LO partly prevented insulin intolerance and was associated with normal leptin levels despite higher subcutaneous and perigonadal adiposity. Only HFD-HI increased anxiety and impaired spatial memory, together with increased inflammation in the hypothalamus and hippocampus. Our results show that impaired glucose metabolism and neuroinflammation are uncoupled, and support that diets with a high ω6/ω3 ratio are associated with neuroinflammation and the behavioral deterioration coupled with the consumption of diets rich in fat.

Key structural factors and intermolecular interactions underlying the formation, functional properties and behaviour in the gastrointestinal tract in vitro of the liposomal form of nutraceuticals coated with whey proteins and chitosan

The aim of this study was to gain a better understanding of the key structural factors and intermolecular interactions underlying the formation, functionality, and in vitro gastrointestinal behaviour of the liposomal form of nutraceuticals coated with whey proteins (WPI) and chitosan (CHIT). Phosphatidylcholine (PC) liposomes were used to encapsulate a combination of hydrophobic and hydrophilic nutraceuticals. The hydrophobic constituents were long-chain (LC) n-3 PUFAs (DHA and EPA) from fish oil (FO), vitamin D3, and clove essential oil (CEO), while the hydrophilic component was γ-aminobutyric acid (GABA). A combination of physicochemical methods was used to achieve this goal, including electron paramagnetic resonance spectroscopy (EPRS), laser light scattering in dynamic, static, and electrophoretic modes, transmission electron microscopy, spectrophotometry and tensiometry. The efficiency of encapsulating the nutraceuticals in PC liposomes simultaneously was as follows: 100 ± 1% for both FO triglycerides and CEO, 82 ± 2% for vitamin D3, and 50 ± 1% for GABA. According to EPRS data, encapsulating LC PUFA reduced microviscosity at a depth of 20 Å in the PC bilayer. The co-encapsulation of other nutraceuticals in PC liposomes at selected concentrations did not alter this effect. The upper part (8 Å) of PC liposome bilayers showed an increase in rigidity parameter S, indicating the presence of D3, CEO, and partially GABA. The liposome layer-by-layer encapsulation efficiency (EE%) was achieved by using WPI to form the binary complex [WPI-(PC-FO-D3-GABA-CEO)] (EE = 50% at pH 7.0 and I = 0.001 M), followed by coating with chitosan to form the ternary complex [WPI-(PC-FO-D3-GABA-CEO)]-CHIT (EE = 80% at pH 5.1 and I = 0.001 M). The biopolymer-coated liposomes displayed high water solubility owing to their submicron sizes, thermodynamic affinity for the aqueous medium, and 20 mV ζ-potential values. The chitosan shell regulated the release of liposomes from the ternary complex during in vitro gastrointestinal digestion. In the stomach, the hydrolysis of chitosan by pepsin resulted in a 40% release of liposomes. In the small intestine, chitosan was separated from the WPI-liposome core, facilitatig its hydrolysis and resulting in a 60% release of liposomes. The bioavailability of nutraceuticals encapsulated in PC liposomes in the small intestine may be enhanced by the interactions of both non-hydrolysed and hydrolysed liposomes with bile salts and mucin.

Association between serum omega-3 PUFAs levels and cognitive impairment in never medically treated first-episode patients with geriatric depression: A cross-sectional study

BACKGROUND

Geriatric depression increases the public health burden and health care costs, reduces quality of life. Studies have shown the association between ω-3 PUFAs levels and inflammatory markers levels and depression, but few have explored the relationship between omega-3 PUFAs, inflammatory markers, and cognitive function in geriatric depression. This study aimed to compare the differences in ω-3 PUFAs levels and inflammatory markers between geriatric depression with cognitive impairment (CI) and those without CI.

METHODS

A total of three hundred and five elderly patients were recruited. In addition to collecting basic information, their blood specimens were collected to detect serum EPA, DHA, AA, TC, LDL-C, IL-6, TNF-α, and hs-CRP levels. The Hamilton depression scale (HAMD), Hamilton anxiety scale (HAMA), and The Montreal cognitive assessment (MoCA) were used to assess their depression, anxiety, and cognitive function, respectively.

RESULTS

Compared to those without CI, geriatric depression patients with CI had higher serum TC, LDL-C levels, lower EPA, DHA, and AA levels, and more elevated IL-6, TNF-α, and hs-CRP levels (all P < 0.05). Further linear regression analysis showed that EPA, DHA, and TNF-α, hs-CRP levels were significantly associated with the occurrence and the severity of CI.

LIMITATIONS

No causal relationship could be drawn due to the cross-sectional design.

CONCLUSIONS

Omega-3 PUFAs and inflammatory factors levels may predict CI in elderly patients with MDD in the future. Our findings suggest that ω-3 PUFAs (EPA and DHA) and inflammatory factors (TNF-α and CRP) may predict the occurrence and the severity of CI among elderly MDD patients.

Nutritional Criminology: Why the Emerging Research on Ultra-Processed Food Matters to Health and Justice

There is mounting concern over the potential harms associated with ultra-processed foods, including poor mental health and antisocial behavior. Cutting-edge research provides an enhanced understanding of biophysiological mechanisms, including microbiome pathways, and invites a historical reexamination of earlier work that investigated the relationship between nutrition and criminal behavior. Here, in this perspective article, we explore how this emergent research casts new light and greater significance on previous key observations. Despite expanding interest in the field dubbed 'nutritional psychiatry', there has been relatively little attention paid to its relevancy within criminology and the criminal justice system. Since public health practitioners, allied mental health professionals, and policymakers play key roles throughout criminal justice systems, a holistic perspective on both historical and emergent research is critical. While there are many questions to be resolved, the available evidence suggests that nutrition might be an underappreciated factor in prevention and treatment along the criminal justice spectrum. The intersection of nutrition and biopsychosocial health requires transdisciplinary discussions of power structures, industry influence, and marketing issues associated with widespread food and social inequalities. Some of these discussions are already occurring under the banner of 'food crime'. Given the vast societal implications, it is our contention that the subject of nutrition in the multidisciplinary field of criminology-referred to here as nutritional criminology-deserves increased scrutiny. Through combining historical findings and cutting-edge research, we aim to increase awareness of this topic among the broad readership of the journal, with the hopes of generating new hypotheses and collaborations.

Associations of n-3 polyunsaturated fatty acid status and intake with paediatric major depressive disorder in Swiss adolescents: A case-control study

BACKGROUND

Observational studies suggest a link between n-3 polyunsaturated fatty acid (PUFA) intake, n-3 PUFA status, and depression in adults, but studies in adolescents are scarce. This study aimed to determine associations of n-3 PUFA status and intake with paediatric major depressive disorder (pMDD) in Swiss adolescents.

METHODS

We conducted a matched case-control study in 95 adolescents diagnosed with pMDD and 95 healthy controls aged 13 to <18 years. We analysed red blood cell (RBC) fatty acid (FA) composition (% of total FA). n-3 PUFA intake was assessed using a focused food frequency questionnaire and depression severity was assessed by the Children's Depression Rating Scale-Revised (CDRS-R).

RESULTS

Mean RBC eicosapentaenoic acid (EPA) and docosahexaenoic acid (DHA) were lower in cases than controls (EPA: 0.41 ± 0.11 vs 0.46 ± 0.12, p < 0.001; DHA: 4.07 ± 1.04 vs 4.73 ± 1.04, p < 0.001). Subsequently, the mean RBC n-3 index was lower (4.51 ± 1.10 vs 5.20 ± 1.11, p < 0.001) and the n-6/n-3 PUFA ratio higher (5.51 ± 1.25 vs 4.96 ± 1.08, p < 0.001) in cases than controls. Adolescents with a higher n-3 index had lower odds for depression (OR = 0.49 [95% CI: 0.32-0.71]). In contrast, the n-6/n-3 PUFA ratio was associated with higher odds for depression (OR = 1.58 [95% CI: 1.14-2.25]). Intake of alpha-linolenic acid, EPA and DHA did not differ between cases and controls.

CONCLUSION

Our results suggest that a higher RBC n-3 PUFA status during adolescence is associated with a lower risk for pMDD, whereas a higher n-6/n-3 PUFA ratio is associated with a higher risk for pMDD. Differences in n-3 PUFA intake did not explain the observed differences in n-3 PUFA status.

The Effects of Early-Life Stress on Liver Transcriptomics and the Protective Role of EPA in a Mouse Model of Early-Life-Stress-Induced Adolescent Depression

Early-life stress (ELS) was found to increase the risk of adolescent depression, and clinical evidence indicated that eicosapentaenoic acid (EPA) was decreased in patients with adolescent depression, but the underlying mechanisms are unclear. Here, we utilized an ELS model of maternal separation with early weaning to explore the protective role of EPA in adolescent depression. We found that that ELS induced depression-like behavior rather than anxiety-like behavior in adolescent mice. RNA-sequencing results showed that ELS changed the transcription pattern in the liver, including 863 upregulated genes and 971 downregulated genes, especially those related to the biosynthesis of unsaturated fatty acids metabolism in the liver. Moreover, ELS decreased the expression of the rate-limiting enzymes, fatty acid desaturases 1/2 (FADS1/2), involved in the biosynthesis of EPA in the liver. Additionally, ELS reduced the levels of EPA in the liver, serum, and hippocampus, and EPA administration improved depression-like behavior-induced by ELS. Our results provide transcriptomic evidence that ELS increases the risk of adolescent depression by reducing the synthesis of unsaturated fatty acids in the liver, especially EPA, and suggest that supplementation with EPA should be investigated as a potential treatment for adolescent depression.

Modulatory effect of n-3 polyunsaturated fatty acids on depressive-like behaviors in rats with chronic sleep deprivation: potential involvement of melatonin receptor pathway and brain lipidome

Clinical evidence suggests that a bidirectional relationship is present between sleep loss and psychiatric disorders. Both melatonin receptor agonist ramelteon (RMT) and n-3 polyunsaturated fatty acids (n-3 PUFAs) exhibit antidepressant effects, while their underlying molecular mechanisms might be different. Thus, the present study aims to investigate the add-on effects and possible mechanisms of how RMT and different n-3 PUFAs modulate the melatonin receptor pathway as well as brain lipidome to ameliorate the neuropsychiatric behaviors displayed in rats under chronic sleep deprivation. Thirty-one 6-week-old male Wistar rats were divided into five groups: control (C), sleep deprivation (S), sleep deprivation treated with RMT (SR), sleep deprivation treated with RMT and eicosapentaenoic acid (C20:5n-3, EPA) (SRE), and sleep deprivation treated with RMT and docosahexaenoic acid (C22:6n-3, DHA) (SRD) groups. The results reveal that RMT plus EPA alleviated depressive-like behavior when the rats were subjected to the forced swimming test, whereas RMT plus DHA alleviated anxiety-like behavior when the rats were subjected to the elevated plus maze test. The results of a western blot analysis further revealed that compared with the rats in the S group, those in the SRE and SRD groups exhibited a significantly increased expression of MT₂ in the prefrontal cortex, with greater benefits observed in the SRE group. In addition, decreased BDNF and TrkB expression levels were upregulated only in the SRE group. Lipidomic analysis further revealed possible involvement of aberrant lipid metabolism and neuropsychiatric behaviors. RMT plus EPA demonstrated promise as having the effects of reversing the levels of the potential biomarkers of depressive-like behaviors. RMT plus EPA or DHA could ameliorate depressive- and anxiety-like behaviors in sleep-deprived rats through the alteration of the lipidome and MT₂ receptor pathway in the brain, whereas EPA and DHA exerted a differential effect.

Improvement of retinal function in Alzheimer disease-associated retinopathy by dietary lysophosphatidylcholine-EPA/DHA

Alzheimer disease (AD) is the most prevalent cause of dementia in the elderly. Although impaired cognition and memory are the most prominent features of AD, abnormalities in visual functions often precede them, and are increasingly being used as diagnostic and prognostic markers for the disease. Retina contains the highest concentration of the essential fatty acid docosahexaenoic acid (DHA) in the body, and its deficiency is associated with several retinal diseases including diabetic retinopathy and age related macular degeneration. In this study, we tested the hypothesis that enriching retinal DHA through a novel dietary approach could ameliorate symptoms of retinopathy in 5XFAD mice, a widely employed model of AD. The results show that 5XFAD mice have significantly lower retinal DHA compared to their wild type littermates, and feeding the lysophosphatidylcholine (LPC) form of DHA and eicosapentaenoic acid (EPA) rapidly normalizes the DHA levels, and increases retinal EPA by several-fold. On the other hand, feeding similar amounts of DHA and EPA in the form of triacylglycerol had only modest effects on retinal DHA and EPA. Electroretinography measurements after 2 months of feeding the experimental diets showed a significant improvement in a-wave and b-wave functions by the LPC-diet, whereas the TAG-diet had only a modest benefit. Retinal amyloid β levels were decreased by about 50% by the LPC-DHA/EPA diet, and by about 17% with the TAG-DHA/EPA diet. These results show that enriching retinal DHA and EPA through dietary LPC could potentially improve visual abnormalities associated with AD.

Dietary Nutrient Deficiencies and Risk of Depression (Review Article 2018-2023)

Depression is classified as one of the most common mental disorders. Its prevalence has recently increased, becoming a growing public health threat. This review focuses on clarifying the role and importance of individual nutrients in the diet and the impact of nutrient deficiencies on the risk of depression. Deficiencies in nutrients such as protein, B vitamins, vitamin D, magnesium, zinc, selenium, iron, calcium, and omega-3 fatty acids have a significant impact on brain and nervous system function, which can affect the appearance of depressive symptoms. However, it is important to remember that diet in itself is not the only factor influencing the risk of or helping to treat depression. There are many other aspects, such as physical activity, sleep, stress management, and social support, that also play an important role in maintaining mental health. The data review observed that most of the available analyses are based on cross-sectional studies. Further studies, including prospective cohort, case-control studies, are recommended to draw more reliable conclusions.

Effects of polyunsaturated fatty acid supplementation on plasma and follicular fluid resolvin D1 concentration and mRNA abundance in granulosa cells in ewes

The aim of this experiment was to evaluate the effect of increasing dietary omega-3 (n-3) polyunsaturated fatty acid (PUFA) supplementation on plasma and follicular fluid resolvin D1 (RvD1) concentration and the mRNA expression of genes related to RvD1 production, inflammatory response, oxidative stress, hormone receptors and production, and free fatty acid receptors in the granulosa cells of ewes. Dorset × Hampshire ewes (n = 24) aged 2 to 4 yr and with an initial body weight (BW) of 84.08 ± 13.18 kg were blocked by body condition score (BCS) and BW, and randomly assigned to 12 pens. Each pen within each block was randomly assigned to one of three treatments: 1) diet without fatty acid supplementation (control), 2) diet with 0.5% n-3 PUFA supplementation (PUFA0.5), and 3) diet with 1% n-3 PUFA supplementation (PUFA1). BW, BCS, and blood samples were obtained on day 1 and every 21 d for 3 mo. Ewes were then synchronized, superstimulated, and ovariectomized. Antral follicles were aspirated to evaluate RvD1 concentration in follicular fluid, and granulosa cells were used to determine mRNA abundance. Data were analyzed as a randomized complete block design using a mixed model (MIXED or GLIMMIX with log as a link function when data presented a nonnormal distribution). A polynomial effect of treatments was used to analyze RvD1 concentration and mRNA expression when there was no interaction. In addition, the correlation between plasma and follicular fluid RvD1 concentration was evaluated. We found no differences in BW (P = 0.28) and BCS (P = 0.29) between treatments. The concentration of RvD1 in plasma and follicular fluid linearly increased (P = 0.03) and tended to increase (P = 0.06) concomitantly to increasing PUFA supplementation. Plasma and follicular fluid RvD1 concentrations were positively correlated (r = 0.61; P < 0.01). The abundance of GPX1 and GPR32 mRNA tended to increase linearly with increasing PUFA supplementation (P = 0.06). In addition, PUFA supplementation linearly decreased and tended to decrease IL-1β and COX-2 mRNA abundance (P = 0.01 and P = 0.06, respectively). In conclusion, the correlation between plasma and follicular fluid RvD1 concentration indicates a relationship between both compartments. Also, the decrease of IL-1β and the increase of GPX1 mRNA abundance after PUFA supplementation could have beneficial effects on follicle development.

Biological Role of Nutrients, Food and Dietary Patterns in the Prevention and Clinical Management of Major Depressive Disorder

Major Depressive Disorder (MDD) is a growing disabling condition affecting around 280 million people worldwide. This complex entity is the result of the interplay between biological, psychological, and sociocultural factors, and compelling evidence suggests that MDD can be considered a disease that occurs as a consequence of an evolutionary mismatch and unhealthy lifestyle habits. In this context, diet is one of the core pillars of health, influencing multiple biological processes in the brain and the entire body. It seems that there is a bidirectional relationship between MDD and malnutrition, and depressed individuals often lack certain critical nutrients along with an aberrant dietary pattern. Thus, dietary interventions are one of the most promising tools to explore in the field of MDD, as there are a specific group of nutrients (i.e., omega 3, vitamins, polyphenols, and caffeine), foods (fish, nuts, seeds fruits, vegetables, coffee/tea, and fermented products) or dietary supplements (such as S-adenosylmethionine, acetyl carnitine, creatine, amino acids, etc.), which are being currently studied. Likewise, the entire nutritional context and the dietary pattern seem to be another potential area of study, and some strategies such as the Mediterranean diet have demonstrated some relevant benefits in patients with MDD; although, further efforts are still needed. In the present work, we will explore the state-of-the-art diet in the prevention and clinical support of MDD, focusing on the biological properties of its main nutrients, foods, and dietary patterns and their possible implications for these patients.

Omega-3 polyunsaturated fatty acid biomarkers and risk of type 2 diabetes, cardiovascular disease, cancer, and mortality

BACKGROUND & AIMS

Considerable attention has focused on the role of omega-3 polyunsaturated fatty acids (PUFA) in the prevention of cardiometabolic diseases, which has led to dietary recommendations to increase omega-3 fatty acid intake. A meta-analysis was conducted to summarize evidence from prospective studies regarding associations between omega-3 PUFA biomarkers and risk of developing major chronic diseases.

METHODS

Four electronic databases were searched for articles from inception to March 1, 2022. Random-effects model was used to estimate the pooled relative risk (RR) and 95% confidence intervals (CIs) for the association of omega-3 PUFAs, including α-linolenic acid (ALA), eicosapentaenoic acid (EPA), docosapentaenoic acid (DPA), and docosahexaenoic acid (DHA), with risk of developing type 2 diabetes (T2D), cardiovascular disease (CVD), including coronary heart disease (CHD) and stroke, cancer, and mortality. The Grades of Recommendation, Assessment, Development and Evaluation assessment tool was used to rates the confidence in estimates.

RESULTS

A total of 67 prospective studies comprised of 310,955 participants were identified. Individual omega-3 PUFAs showed divergent associations with the study outcomes of interest. A significant inverse association with T2D risk was observed across categories of ALA (relative risk [RR]: 0.89, 95% confidence interval [CI]: 0.82-0.96), EPA (RR: 0.85, 95% CI: 0.72-0.99) and DPA (RR: 0.84, 95% CI: 0.73-0.96) biomarkers. The marine-origin omega-3 fatty acids biomarkers but not ALA was significantly associated with lower risks of total CVD, CHD, and overall mortality, with RRs ranging from 0.70 for DHA-CHD association to 0.85 for EPA-CHD association. A lower risk of colorectal cancer was observed at higher levels of DPA (RR: 0.76, 95% CI: 0.59-0.98) and DHA (RR: 0.80; 95% CI: 0.65-0.99), whereas no association was noted for other outcomes. In addition, a dose-response relationship was observed between an increasing level of EPA, DPA, or DHA biomarker and lower risk of CVD.

CONCLUSIONS

Higher concentrations of marine-derived omega-3 PUFA biomarkers were associated with a significantly reduced risk of total CVD, CHD, and total mortality. Levels of ALA were inversely associated with a lower risk of T2D but not CVD-related outcomes. These data support the dietary recommendations advocating the role of omega-3 PUFAs in maintaining an overall lower risk of developing cardiovascular disease and premature deaths.

Fish and human health: an umbrella review of observational studies

Fish represents one of the most important dietary sources of omega-3 polyunsaturated fatty acids, which are known to be associated with various health benefits. This study aimed to systematically review existing meta-analyses of observational studies exploring the association between fish intake and various health outcomes. A systematic search of electronic databases was conducted to retrieve a total of 63 studies. Evidence was deemed as possible for the association between higher fish intake and decreased risk of the acute coronary syndrome, liver cancer, and depression, and limited for other outcomes (including age-related macular degeneration, Alzheimer's disease, heart failure, all-cause and coronary heart disease mortality, total and ischaemic stroke) due to heterogeneity between results and potential otherwise inexplicable confounding factors. In conclusion, results from epidemiological studies support the mechanistic effects associated with omega-3 fatty acids from high fish consumption, but evidence needs to be further corroborated with more reliable results.

Potential Suicide Prophylactic Activity by the Fish Oil Metabolite, 4-Hydroxyhexenal

Low levels of n-3 poly-unsaturated fatty acids (n-3 PUFAs) and high levels of n-6 PUFAs in the blood circulation are associated with an increased risk for suicide. Clinical studies indicate that docosahexaenoic acid (DHA, a n-3 PUFA found in fish-oil) displays protective effects against suicide. It has recently been proposed that the activation of the transcription factor NRF2 might be the pharmacological activity that is common to current anti-suicidal medications. Oxidation products from fish oil, including those from DHA, are electrophiles that reversibly bind to a protein ‘KEAP1’, which acts as the molecular inhibitor of NRF2 and so indirectly promotes NRF2-transcriptional activity. In the majority of publications, the NRF2-stimulant effect of DHA is ascribed to the metabolite 4-hydroxyhexenal (4HHE). It is suggested to investigate whether 4HHE will display a therapeutically useful anti-suicidal efficacy.

Non-targeted metabolomics and associations with per- and polyfluoroalkyl substances (PFAS) exposure in humans: A scoping review

OBJECTIVE

To summarize the application of non-targeted metabolomics in epidemiological studies that assessed metabolite and metabolic pathway alterations associated with per- and polyfluoroalkyl substances (PFAS) exposure.

RECENT FINDINGS

Eleven human studies published before April 1st, 2021 were identified through database searches (PubMed, Dimensions, Web of Science Core Collection, Embase, Scopus), and citation chaining (Citationchaser). The sample sizes of these studies ranged from 40 to 965, involving children and adolescents (n = 3), non-pregnant adults (n = 5), or pregnant women (n = 3). High-resolution liquid chromatography-mass spectrometry was the primary analytical platform to measure both PFAS and metabolome. PFAS were measured in either plasma (n = 6) or serum (n = 5), while metabolomic profiles were assessed using plasma (n = 6), serum (n = 4), or urine (n = 1). Four types of PFAS (perfluorooctane sulfonate(n = 11), perfluorooctanoic acid (n = 10), perfluorohexane sulfonate (n = 9), perfluorononanoic acid (n = 5)) and PFAS mixtures (n = 7) were the most studied. We found that alterations to tryptophan metabolism and the urea cycle were most reported PFAS-associated metabolomic signatures. Numerous lipid metabolites were also suggested to be associated with PFAS exposure, especially key metabolites in glycerophospholipid metabolism which is critical for biological membrane functions, and fatty acids and carnitines which are relevant to the energy supply pathway of fatty acid oxidation. Other important metabolome changes reported included the tricarboxylic acid (TCA) cycle regarding energy generation, and purine and pyrimidine metabolism in cellular energy systems.

CONCLUSIONS

There is growing interest in using non-targeted metabolomics to study the human physiological changes associated with PFAS exposure. Multiple PFAS were reported to be associated with alterations in amino acid and lipid metabolism, but these results are driven by one predominant type of pathway analysis thus require further confirmation. Standardizing research methods and reporting are recommended to facilitate result comparison. Future studies should consider potential differences in study methodology, use of prospective design, and influence from confounding bias and measurement errors.

Review of the Midbrain Ascending Arousal Network Nuclei and Implications for Myalgic Encephalomyelitis/Chronic Fatigue Syndrome (ME/CFS), Gulf War Illness (GWI) and Postexertional Malaise (PEM)

Myalgic Encephalomyelitis/Chronic Fatigue Syndrome (ME/CFS and Gulf War Illness (GWI) share features of post-exertional malaise (PEM), exertional exhaustion, or postexertional symptom exacerbation. In a two-day model of PEM, submaximal exercise induced significant changes in activation of the dorsal midbrain during a high cognitive load working memory task (Washington 2020) (Baraniuk this issue). Controls had no net change. However, ME/CFS had increased activity after exercise, while GWI had significantly reduced activity indicating differential responses to exercise and pathological mechanisms. These data plus findings of the midbrain and brainstem atrophy in GWI inspired a review of the anatomy and physiology of the dorsal midbrain and isthmus nuclei in order to infer dysfunctional mechanisms that may contribute to disease pathogenesis and postexertional malaise. The nuclei of the ascending arousal network were addressed. Midbrain and isthmus nuclei participate in threat assessment, awareness, attention, mood, cognition, pain, tenderness, sleep, thermoregulation, light and sound sensitivity, orthostatic symptoms, and autonomic dysfunction and are likely to contribute to the symptoms of postexertional malaise in ME/CFS and GWI.

Possible antidepressant mechanisms of omega-3 polyunsaturated fatty acids acting on the central nervous system

Omega-3 polyunsaturated fatty acids (PUFAs) can play important roles in maintaining mental health and resistance to stress, and omega-3 PUFAs supplementation can display beneficial effects on both the prevention and treatment of depressive disorders. Although the underlying mechanisms are still unclear, accumulated evidence indicates that omega-3 PUFAs can exhibit pleiotropic effects on the neural structure and function. Thus, they play fundamental roles in brain activities involved in the mood regulation. Since depressive symptoms have been assumed to be of central origin, this review aims to summarize the recently published studies to identify the potential neurobiological mechanisms underlying the anti-depressant effects of omega-3 PUFAs. These include that of (1) anti-neuroinflammatory; (2) hypothalamus-pituitary-adrenal (HPA) axis; (3) anti-oxidative stress; (4) anti-neurodegeneration; (5) neuroplasticity and synaptic plasticity; and (6) modulation of neurotransmitter systems. Despite many lines of evidence have hinted that these mechanisms may co-exist and work in concert to produce anti-depressive effects, the potentially multiple sites of action of omega-3 PUFAs need to be fully established. We also discussed the limitations of current studies and suggest future directions for preclinical and translational research in this field.

Omega-3 fatty acids for depression in adults

BACKGROUND

Major depressive disorder (MDD) is highly debilitating, difficult to treat, has a high rate of recurrence, and negatively impacts the individual and society as a whole. One potential treatment for MDD is n-3 polyunsaturated fatty acids (n-3PUFAs), also known as omega-3 oils, naturally found in fatty fish, some other seafood, and some nuts and seeds. Various lines of evidence suggest a role for n-3PUFAs in MDD, but the evidence is far from conclusive. Reviews and meta-analyses clearly demonstrate heterogeneity between studies. Investigations of heterogeneity suggest different effects of n-3PUFAs, depending on the severity of depressive symptoms, where no effects of n-3PUFAs are found in studies of individuals with mild depressive symptomology, but possible benefit may be suggested in studies of individuals with more severe depressive symptomology. Hence it is important to establish their effectiveness in treating MDD. This review updates and incorporates an earlier review with the same research objective (Appleton 2015).

OBJECTIVES

To assess the effects of n-3 polyunsaturated fatty acids (also known as omega-3 fatty acids) versus a comparator (e.g. placebo, antidepressant treatment, standard care, no treatment, wait-list control) for major depressive disorder (MDD) in adults.

SEARCH METHODS

We searched the Cochrane Central Register of Controlled trials (CENTRAL), Ovid MEDLINE, Embase and PsycINFO together with trial registries and grey literature sources (to 9 January 2021). We checked reference lists and contacted authors of included studies for additional information when necessary.

SELECTION CRITERIA

We included studies in the review if they: used a randomised controlled trial design; provided n-3PUFAs as an intervention; used a comparator; measured depressive symptomology as an outcome; and were conducted in adults with MDD. Primary outcomes were depressive symptomology (continuous data collected using a validated rating scale) and adverse events. Secondary outcomes were depressive symptomology (dichotomous data on remission and response), quality of life, and non-completion of studies.

DATA COLLECTION AND ANALYSIS

We used standard methodological procedures as expected by Cochrane. We assessed the certainty of the evidence using GRADE criteria.

MAIN RESULTS

The review includes 35 relevant studies: 34 studies involving a total of 1924 participants investigated the impact of n-3PUFA supplementation compared to placebo, and one study involving 40 participants investigated the impact of n-3PUFA supplementation compared to antidepressant treatment. For the placebo comparison, n-3PUFA supplementation resulted in a small to modest benefit for depressive symptomology, compared to placebo: standardised mean difference (SMD) (random-effects model) -0.40 (95% confidence interval (CI) -0.64 to -0.16; 33 studies, 1848 participants; very low-certainty evidence), but this effect is unlikely to be clinically meaningful. An SMD of 0.40 represents a difference between groups in scores on the HDRS (17-item) of approximately 2.5 points (95% CI 1.0 to 4.0), where the minimal clinically important change score on this scale is 3.0 points. The confidence intervals include both a possible clinically important effect and a possible negligible effect, and there is considerable heterogeneity between studies. Sensitivity analyses, funnel plot inspection and comparison of our results with those of large well-conducted trials also suggest that this effect estimate may be biased towards a positive finding for n-3PUFAs. Although the numbers of individuals experiencing adverse events were similar in intervention and placebo groups (odds ratio (OR) 1.27, 95% CI 0.99 to 1.64; 24 studies, 1503 participants; very low-certainty evidence), the confidence intervals include a small decrease to a modest increase in adverse events with n-3PUFAs. There was no evidence for a difference between n-3PUFA and placebo groups in remission rates (OR 1.13, 95% CI 0.74 to 1.72; 8 studies, 609 participants, low-certainty evidence), response rates (OR 1.20, 95% CI 0.80 to 1.79; 17 studies, 794 participants; low-certainty evidence), quality of life (SMD -0.38 (95% CI -0.82 to 0.06), 12 studies, 476 participants, very low-certainty evidence), or trial non-completion (OR 0.92, 95% CI 0.70 to 1.22; 29 studies, 1777 participants, very low-certainty evidence). The evidence on which these results are based was also very limited, highly heterogeneous, and potentially biased. Only one study, involving 40 participants, was available for the antidepressant comparison. This study found no differences between treatment with n-3PUFAs and treatment with antidepressants in depressive symptomology (mean difference (MD) -0.70, 95% CI -5.88 to 4.48), rates of response to treatment (OR 1.23, 95% CI 0.35 to 4.31), or trial non-completion (OR 1.00, 95% CI 0.21 to 4.71). Confidence intervals are however very wide in all analyses, and do not rule out important beneficial or detrimental effects of n-3PUFAs compared to antidepressants. Adverse events were not reported in a manner suitable for analysis, and rates of depression remission and quality of life were not reported.

AUTHORS' CONCLUSIONS

At present, we do not have sufficient high-certainty evidence to determine the effects of n-3PUFAs as a treatment for MDD. Our primary analyses may suggest a small-to-modest, non-clinically beneficial effect of n-3PUFAs on depressive symptomology compared to placebo; however the estimate is imprecise, and we judged the certainty of the evidence on which this result is based to be low to very low. Our data may also suggest similar rates of adverse events and trial non-completion in n-3PUFA and placebo groups, but again our estimates are very imprecise. Effects of n-3PUFAs compared to antidepressants are very imprecise and uncertain. More complete evidence is required for both the potential positive and negative effects of n-3PUFAs for MDD.

Exploring the Role of Nutraceuticals in Major Depressive Disorder (MDD): Rationale, State of the Art and Future Prospects

Major depressive disorder (MDD) is a complex and common disorder, with many factors involved in its onset and development. The clinical management of this condition is frequently based on the use of some pharmacological antidepressant agents, together with psychotherapy and other alternatives in most severe cases. However, an important percentage of depressed patients fail to respond to the use of conventional therapies. This has created the urgency of finding novel approaches to help in the clinical management of those individuals. Nutraceuticals are natural compounds contained in food with proven benefits either in health promotion or disease prevention and therapy. A growing interest and economical sources are being placed in the development and understanding of multiple nutraceutical products. Here, we summarize some of the most relevant nutraceutical agents evaluated in preclinical and clinical models of depression. In addition, we will also explore less frequent but interest nutraceutical products which are starting to be tested, also evaluating future roads to cover in order to maximize the benefits of nutraceuticals in MDD.

Antarctic Thraustochytrids as Sources of Carotenoids and High-Value Fatty Acids

Eicosapentaenoic acid (EPA), docosahexaenoic acid (DHA), and carotenoids are needed as human dietary supplements and are essential components in commercial feeds for the production of aquacultured seafood. Microorganisms such as thraustochytrids are potential natural sources of these compounds. This research reports on the lipid and carotenoid production capacity of thraustochytrids that were isolated from coastal waters of Antarctica. Of the 22 isolates, 21 produced lipids containing EPA+DHA, and the amount of these fatty acids exceeded 20% of the total fatty acids in 12 isolates. Ten isolates were shown to produce carotenoids (27.4-63.9 μg/g dry biomass). The isolate RT2316-16, identified as Thraustochytrium sp., was the best producer of biomass (7.2 g/L in five days) rich in carotenoids (63.9 μg/g) and, therefore, became the focus of this investigation. The main carotenoids in RT2316-16 were β-carotene and canthaxanthin. The content of EPA+DHA in the total lipids (34 ± 3% w/w in dry biomass) depended on the stage of growth of RT2316-16. Lipid and carotenoid content of the biomass and its concentration could be enhanced by modifying the composition of the culture medium. The estimated genome size of RT2316-16 was 44 Mb. Of the 5656 genes predicted from the genome, 4559 were annotated. These included genes of most of the enzymes in the elongation and desaturation pathway of synthesis of ω-3 polyunsaturated fatty acids. Carotenoid precursors in RT2316-16 were synthesized through the mevalonate pathway. A β-carotene synthase gene, with a different domain organization compared to the gene in other thraustochytrids, explained the carotenoid profile of RT2316-16.