Administration of docosahexaenoic acid influences behavior and plasma catecholamine levels at times of psychological stress

Antidepressant-like effect of flaxseed in rats exposed to chronic unpredictable stress

INTRODUCTION

Depression is a serious mental illness. However, a significant proportion of patients with depression fail to achieve remission with antidepressant therapies. This study was conducted to explore the antidepressant-like effect of flaxseed oil and flour in an animal model with depression-like behaviors induced by chronic unpredictable stress (CUS).

METHODS

Rats were randomly divided into five groups: normal control (Sham-Sham), CUS plus saline (S-SN), CUS plus escitalopram (S-Esc), CUS plus flaxseeds oil (S-FO), and CUS plus flaxseed flour (S-FF). Behaviors were tested using sucrose preference test and forced swimming test. The serum BDNF concentration, hippocampal BDNF mRNA, and protein expression were measured by enzyme-linked immunosorbent assay, real-time PCR, and Western blot, respectively.

RESULTS

The sucrose preference rate was significantly higher in S-FO and S-FF rats than in S-SN and S-Esc rats (p < .01), and lower in S-Esc rats than in Sham-Sham rats (p < .01). The immobility time was significantly shorter in S-FO and S-FF rats than in S-SN rats (p < .01), and shorter in S-Esc rats than in S-SN rats (p < .01). Plasma BDNF concentrations were significantly lower in S-FO, S-FF, and S-Esc rats than in Sham-Sham rats (p < .01); BDNF was lower in S-FO, S-FF, and S-SN rats than in S-Esc rats. The hippocampal BDNF protein expression was significantly higher in S-Esc rats than in S-SN rats (p < .05). The hippocampal BDNF mRNA expression was significantly higher in S-Esc rats than in S-SN rats (p < .01). The BDNF gene expression in plasma and the hippocampus negatively correlated with the immobility time (p < .05), but BDNF gene expression in the hippocampus positively correlated with the sucrose preference rate (p < .05).

CONCLUSION

Flaxseed oil and flaxseed flour exert antidepressant-like effect in rats exposed to chronic stress. Flaxseed may have a therapeutic effect on depression.

Docosahexaenoic Acid Helps to Lessen Extinction Memory in Rats

Abstract: Memory extinction is referred to as a learning process in which a conditioned response (CR) progressively reduces over time as an animal learns to uncouple a response from a stimulus. Extinction occurs when the rat is placed into a context without shock after training. Docosahexaenoic acid (DHA, C22:6, n-3) is implicated in memory formation in mammalian brains. In a two-way active shuttle-avoidance apparatus, we examined whether DHA affects the extinction memory and the expression of brain cognition-related proteins, including gastrin-releasing peptide receptor (GRPR), brain-derived neurotrophic factor receptor (BDNFR) tyrosine kinase receptor B (TrKB), and N-methyl-d-aspartate receptor (NMDAR) subunits NR2A and NR2B. Also, the protein levels of GRP, BDNF, postsynaptic density protein-95 (PSD-95), and vesicular acetylcholine transporter (VAChT), and the antioxidative potentials, in terms of lipid peroxide (LPO) and reactive oxygen species (ROS), were examined in the hippocampus. During the acquisition phase, the rats received a conditioned stimulus (CS-tone) paired with an unconditioned stimulus (UCS foot shock) for three consecutive days (Sessions S1, S2, and S3, each consisting of 30-trials) after 12 weeks of oral administration of DHA. After a three-day interval, the rats were re-subjected to two extinction sessions (S4, S5), each comprising 30 trials of CS alone. During the acquisition training in S1, the shock-related avoidance frequency (acquisition memory) was significantly higher in the DHA-administered rats compared with the control rats. The avoidance frequency, however, decreased with successive acquisition trainings in sessions S2 and S3. When the rats were subjected to the extinction sessions after a break for consolidation, the conditioned response (CR) was also significantly higher in the DHA-administered rats. Interestingly, the freezing responses (frequency and time) also significantly decreased in the DHA-administered rats, thus suggesting that a higher coping capacity was present during fear stress in the DHA-administered rats. DHA treatments increased the mRNA levels of GRPR, BDNF receptor TrKB, and NMDAR subunit NR2B. DHA also increased the protein levels of GRP, BDNF, PSD-95, and VAChT, and the antioxidative potentials in the hippocampus. These results suggest the usefulness of DHA for treating stress disorders.

The Role of Lipid Biomarkers in Major Depression

In the UK, the lifetime-documented prevalence of major depressive disorder (MDD) is currently 10%. Despite its increasing prevalence and devastating impact on quality of life, the pathophysiological mechanisms underpinning MDD remain to be fully elucidated. Current theories of neurobiological components remain incomplete and protein-centric, rendering pharmacological treatment options suboptimal. In this review, we highlight the pivotal role of lipids in intra- and inter-neuronal functioning, emphasising the potential use of lipids as biomarkers for MDD. The latter has significant implications for improving our understanding of MDD at the cellular and circuit level. There is particular focus on cholesterol (high and low density lipoprotein), omega-3, and omega-6 polyunsaturated fatty acids due to established evidence in the literature of a link between atherosclerotic disease and major depression. We argue that there is significant potential scope for the use of such peripheral biomarkers in the diagnosis, stratification and treatment of MDD.

Lipids and polyunsaturated fatty acid levels in deliberate self-harm: a 10-year follow-up study

OBJECTIVES

To evaluate if n-3 polyunsaturated fatty acids (PUFAs) and lipid levels are associated with episodes of self-harm or depression over a 10-year period.

METHODS

We included 40 individuals who self-harmed and 40 controls. Episodes of self-harm and depression were ascertained and levels of depression, impulsivity, suicidal ideation and plasma lipid levels measured at baseline and at 10-year follow-up.

RESULTS

Further episode(s) of self-harm occurred in 26% of cases. Omega-3 PUFAs or lipids were not predictive of depressive or self-harm episodes. Baseline eicosapentaenoic acid levels were modestly correlated with suicidal ideation at follow-up and dihomo-γ-linolenic acid and arachidonic acid were modestly correlated with motor impulsivity at follow-up in cases.

CONCLUSIONS

Despite significant negative correlations at baseline between plasma lipids, n-3 PUFAs and psychopathology, these levels were not predictive of clinical outcome over a 10-year period. Further research however is required due to the relatively low sample size and the risk of selection bias due to loss to follow-up in this study.

Role of monoaminergic system in the etiology of olive oil induced antidepressant and anxiolytic effects in rats

Olive oil is the major component of the Mediterranean diet and has rich history of nutritional and medicinal uses. In the present study, the antidepressant and anxiolytic effects and their neurochemical basis following repeated administration of extravirgin olive oil were monitored. Male albino Wistar rats were used during study. Animals of test group were given olive oil orally at the dose of 0.25 mL/kg daily for 4 weeks. Control rats received equal volume of water. Elevated-plus maze (EPM) test and forced swim test (FST) were performed for the assessment of anxiety and depression like symptoms. An increase in time spent in open arm in EPM and increased struggling time in FST following long-term administration of olive oil indicate that olive oil has anxiolytic and antidepressant properties. Neurochemical results showed that repeated administration of olive oil decreased the levels of brain 5-HT (5-hydroxytryptamine), 5-HIAA (5-hydroxyindoleacetic acid), and levels of DA (dopamine); however, levels of DA metabolite HVA (homovalinic acid) were increased. Hence, present findings suggest that olive oil has neuroprotective effects. It reduces behavioral deficits via altering 5-HT and DA metabolism. So it could be used as a therapeutic substance for the treatment of depression and anxiety.

Effects of marine-derived omega-3 fatty acids on systemic hemodynamics at rest and during stress: a dose-response study

BACKGROUND

Omega-3 fatty acids reduced heart rate (HR) and blood pressure (BP) in some studies, but dose-response studies are rare, and little is known about underlying mechanisms.

PURPOSE

We examined effects of 0.85 g/day eicosapentaenoic acid (EPA) + docosahexaenoic acid (DHA) (low dose) and 3.4 g/day EPA + DHA (high dose) on HR and systemic hemodynamics during rest, speech, and foot cold pressor tasks.

METHODS

This was a dose-response, placebo-controlled, double-blind, randomized, crossover trial (8-week treatment, 6-week washout) in 26 adults.

RESULTS

Throughout the testing sessions, HR was reduced in a dose-dependent manner. The high dose reduced BP and stroke volume and increased pre-ejection period. Reductions in BP were associated with increases in erythrocyte omega-3 fatty acids.

CONCLUSIONS

High-dose long-chain omega-3 fatty acids can reduce BP and HR, at rest and during stress. These findings suggest that at-risk populations may achieve benefits with increased omega-3 intake. The trial was registered on ClinicalTrials.gov (NCT00504309).

Effects of a diet integration with an oily emulsion of DHA-phospholipids containing melatonin and tryptophan in elderly patients suffering from mild cognitive impairment

Age-related changes in nutritional status can play an important role in brain functioning. Specific nutrient deficiencies in the elderly may exacerbate pathological processes in the brain. Consequently, the potential of nutritional intervention to prevent or delay cognitive impairment and the development of dementia is an important topic. A randomized, double-blind, placebo-controlled trial has been performed in 25 elderly subjects (86 ± 6 years, 20 females, 5 males) with mild cognitive impairment (MCI). These subjects were randomly assigned to supplement their diet with either an oily emulsion of docosahexaenoic acid (DHA)-phospholipids containing melatonin and tryptophan (11 subjects) or a placebo (14-matched subjects) for 12 weeks. The main aim of this study was to evaluate the efficacy of the dietary supplement on cognition, by the assessment at the start and after 12 weeks of: (1) Orientation and other cognitive functions: Mini-Mental State Examination (MMSE); (2) Short-term memory: digit, verbal, and spatial span (digit span; verbal span; Corsi's test); (3) Long-term memory: Rey's auditory-verbal learning test; 'short story' test; Rey-Osterrieth complex figure (recall); (4) Attentional abilities: attentive matrices; (5) Executive functions: Weigl's sorting test; phonological fluency 'FAS'; (6) Visuo-constructional and visuo-spatial abilities: copy of simple drawings; Rey-Osterrieth complex figure (copy); (7) Language: semantic fluency; (8) Mood: Geriatric Depression Scale (GDS). Moreover, Sniffin' Sticks olfaction test and Mini Nutritional Assessment (MNA) have been performed. After 12 weeks, a significant treatment effect for the MMSE (P < 0.001) and a positive trend for the semantic verbal fluency was found in the supplement group (P < 0.06). A significant treatment effect was found out for the olfactory sensitivity assessment (P < 0.009). As regards the nutrition evaluation, after 12 weeks of treatment the supplemented group showed an improvement in the MNA score with a significant difference relative to placebo (P < 0.005). Older adults with MCI had significant improvements in several measures of cognitive function when supplemented with an oily emulsion of DHA-phospholipids containing melatonin and tryptophan for 12 weeks, compared with the placebo.

Are the Adaptogenic Effects of Omega 3 Fatty Acids Mediated via Inhibition of Proinflammatory Cytokines?

The study was undertaken to estimate the size of the impact of n-3 fatty acids in psychological stress and the extent to which it is mediated via proinflammatory cytokines. Structural equation modeling (SEM) was used to analyze data from 194 healthy Australians. Biomarkers used were erythrocyte polyunsaturated fatty acids (docosahexaenoic acid (DHA) and arachidonic acid (AA)), ex-vivo stimulated secretion of proinflammatory cytokines (interleukins (IL-1 and IL-6), and tumor necrosis factor (TNF)). Stress was measured with the perceived stress scale (PSS-10), found to comprise three factors: Coping (items 4, 7, 5), Overwhelm (2, 10, 6 and 8), and Emotional (1, 9 and 3). This modeling demonstrated that the effects of DHA on coping are largely direct effects (0.26, t = 2.05) and were not significantly mediated via the suppression of proinflammatory cytokines. Future modeling should explore whether adding EPA to the model would increase the significance of the mediation pathways.

Docosahexaenoic acid (DHA): an ancient nutrient for the modern human brain

Modern humans have evolved with a staple source of preformed docosahexaenoic acid (DHA) in the diet. An important turning point in human evolution was the discovery of high-quality, easily digested nutrients from coastal seafood and inland freshwater sources. Multi-generational exploitation of seafood by shore-based dwellers coincided with the rapid expansion of grey matter in the cerebral cortex, which characterizes the modern human brain. The DHA molecule has unique structural properties that appear to provide optimal conditions for a wide range of cell membrane functions. This has particular implications for grey matter, which is membrane-rich tissue. An important metabolic role for DHA has recently been identified as the precursor for resolvins and protectins. The rudimentary source of DHA is marine algae; therefore it is found concentrated in fish and marine oils. Unlike the photosynthetic cells in algae and higher plants, mammalian cells lack the specific enzymes required for the de novo synthesis of alpha-linolenic acid (ALA), the precursor for all omega-3 fatty acid syntheses. Endogenous synthesis of DHA from ALA in humans is much lower and more limited than previously assumed. The excessive consumption of omega-6 fatty acids in the modern Western diet further displaces DHA from membrane phospholipids. An emerging body of research is exploring a unique role for DHA in neurodevelopment and the prevention of neuropsychiatric and neurodegenerative disorders. DHA is increasingly being added back into the food supply as fish oil or algal oil supplementation.

Serum omega-3 fatty acids are associated with variation in mood, personality and behavior in hypercholesterolemic community volunteers

Low dietary intake of omega-3 polyunsaturated fatty acids has been linked to several features of psychiatric symptomatology, including depression, disorders of impulse control, and hostility. Preliminary intervention trials of omega-3 fatty acid supplementation for clinical depression and other disorders have reported benefit. However, few studies have investigated the relationships between these fatty acids and normative variability in mood, behavior and personality. Participants were 105 hypercholesterolemic, but otherwise healthy, non-smoking adults. Fasting serum alpha-linolenic (alpha-LNA), eicosapentaenoic (EPA) and docosahexaenoic acid (DHA) were assayed with gas chromatography. Participants completed the Beck Depression Inventory (BDI), the NEO Five Factor Personality Inventory (NEO-FFI) and the Barratt Impulsiveness Scale (BIS). In multivariate analyses, higher levels of the long chain omega-3 PUFAs, EPA and DHA, were associated with significantly reduced odds of scoring >or=10 on the BDI. Similarly, DHA and EPA covaried inversely with NEO-Neuroticism scores, whereas DHA was positively associated with NEO-Agreeableness. On the BIS, DHA was inversely related to cognitive impulsivity and alpha-LNA was inversely related to motor and total impulsivity. These findings suggest that omega-3 fatty acid status is associated with variability in affect regulation, personality and impulse control.

From homicide to happiness--a commentary on omega-3 fatty acids in human society. Cleave Award Lecture

The field of omega-3 fatty acid deficiencies as reversible risk factors in major psychiatric disorders has flourished in the last decade. Treatment recommendations of the American Psychiatric Association may be considered for application to more normative states of psychiatric health. Considered here is the proposition that an increased risk of personality disorders, and an increased sense of despair in normative populations, might be considered as symptoms of deficiencies of omega-3 fatty acids. The major changes in the essential fatty acid composition of the food supply, including increased availability of the omega-6 linoleic acid, may be correlated not only with increased risks of homicide, but also increased risks of suicide and suboptimal social cohesion.

Mediation of cognitive function by high fat diet following stress and inflammation

In addition to commonly advertised hazards of obesity contributed by excess dietary fat, evidence of alterations in brain chemistry and structure are well documented. This brief review examines the role of nutrients, minerals and certain lipids, primarily the essential fatty acids (FA), that are beneficial to the maintenance of good health and that may offer therapeutic options by dietary supplementation. The review also considers the damaging effects of stress, especially in pre-existing conditions of obesity and diabetes, as studied in both animals and humans. The main focus of this brief review is to examine the effects of a high fat diet on stress and the immune system with particular emphasis on brain and cognitive function.

One generation of n-3 polyunsaturated fatty acid deprivation increases depression and aggression test scores in rats

Male rat pups at weaning (21 days of age) were subjected to a diet deficient or adequate in n-3 polyunsaturated fatty acids (n-3 PUFAs) for 15 weeks. Performance on tests of locomotor activity, depression, and aggression was measured in that order during the ensuing 3 weeks, after which brain lipid composition was determined. In the n-3 PUFA-deprived rats, compared with n-3 PUFA-adequate rats, docosahexaenoic acid (22:6n-3) in brain phospholipid was reduced by 36% and docosapentaenoic acid (22:5n-6) was elevated by 90%, whereas brain phospholipid concentrations were unchanged. N-3 PUFA-deprived rats had a significantly increased (P = 0.03) score on the Porsolt forced-swim test for depression, and increased blocking time (P = 0.03) and blocking number (P = 0.04) scores (uncorrected for multiple comparisons) on the isolation-induced resident-intruder test for aggression. Large effect sizes (d > 0.8) were found on the depression score and on the blocking time score of the aggression test. Scores on the open-field test for locomotor activity did not differ significantly between groups, and had only small to medium effect sizes. This single-generational n-3 PUFA-deprived rat model, which demonstrated significant changes in brain lipid composition and in test scores for depression and aggression, may be useful for elucidating the contribution of disturbed brain PUFA metabolism to human depression, aggression, and bipolar disorder.

An adaptogenic role for omega-3 fatty acids in stress; a randomised placebo controlled double blind intervention study (pilot) [ISRCTN22569553]

Background

There is evidence for an adaptive role of the omega -3 fatty acid, docosahexaenoic acid (DHA) during stress. Mechanisms of action may involve regulation of stress mediators, such as the catecholamines and proinflammatory cytokines. Prevention of stress-induced aggression and hostility were demonstrated in a series of clinical trials. This study investigates whether perceived stress is ameliorated by DHA in stressed university staff.

Methods

Subjects that scored ≥ 17 on the Perceived Stress Scale were randomised into a 6-week pilot intervention study. The diet reactive group was supplemented with 6 g of fish oil containing 1.5 g per day DHA, while the placebo group was supplemented with 6 g a day of olive oil. The groups were compared with each other and a wider cross sectional study population that did not receive either active or placebo intervention.

Results

There was a significant reduction in perceived stress in both the fish oil and the placebo group from baseline. There was also a significant between-group difference between the fish oil group and the no-treatment controls in the rate of stress reduction (p < 0.05). However, there was not a significant between-group difference between the fish oil and the placebo group, nor the placebo group and the control group.

These results are discussed in the context of several methodological limitations. The significant stress reductions in both the fish oil and the placebo group are considered in view of statistical regression, an effect likely to have been exaggerated by the time course of the study, a large placebo effect and the possibility of an active effect from the placebo.

Conclusion

There were significant differences (p < 0.05) in the fish oil group compared with no-treatment controls. This effect was not demonstrated in the placebo group. As a pilot study, it was not sufficiently powered to find the difference between the fish oil group and the placebo group significant. Further work needs to be undertaken to conclusively demonstrate these data trends. However, the findings from this research support the literature in finding a protective or 'adaptogenic' role for omega-3 fatty acids in stress.

Relationship between stress, inflammation and metabolism

PURPOSE OF REVIEW

Various threatening stimuli, such as pain, low blood pressure, or infection, elicit a set of neuroendocrine responses that include an increased secretion of catecholamines and glucocorticoid from the adrenal gland and activation of the sympathetic nervous system. These hormonal secretions allow a "fight or flight" response by mobilizing endogenous substrate. They also exert anti-insulin actions, and may in the long term induce a state of insulin resistance. In addition, stress stimulates inflammatory mediators in mononuclear cells. Given the possible role of low-grade inflammation in chronic metabolic disorders, this suggests that stress may be a factor in the development of insulin resistance and the metabolic syndrome.

RECENT FINDINGS

Studies reviewed in this article cover: (1) the metabolic and haemodynamic effects of stress in healthy and insulin-resistant individuals; (2) the relationship between stress and inflammation and the role of the autonomic nervous system; and (3) some factors known to modulate the neuroendocrine responses to stress. Future perspectives, together with some hints regarding the role of neurotrophins such as brain-derived neurotrophic factor, are delineated.

SUMMARY

Recent work performed in the field has indicated that stress may be a significant factor in the pathogenesis of metabolic disorders. Nutritional intervention or pharmacological agents targeted at modulating stress should be investigated.

Dietary ethyl-eicosapentaenoic acid but not soybean oil reverses central interleukin-1-induced changes in behavior, corticosterone and immune response in rats

Omega (n)-3 and n-6 fatty acids are important membrane components of neurons and immune cells, and related to psychiatric and inflammatory diseases. Increased ratio of n-6/n-3 in the blood has been reported in depressed patients and in students following stress exposure. The n-3 fatty acid, eicosapentaenoic acid (ethyl-EPA) suppresses inflammation and has antidepressant properties. Interleukin (IL)-1beta can stimulate corticosterone secretion, induce anxiety and stress-like behavior and inflammatory responses. This study was to evaluate the effect of diets enriched with coconut oil, ethyl-EPA and soybean oil on central IL-1beta induced stress and anxiety-like behavior, induced changes in the concentration of prostaglandin (PG) E2 and corticosterone and the release of IL-10. Groups of rats were fed with either 5% coconut oil (as control diet), 0.2% EPA with 4.8% coconut oil or 1% EPA with 4% coconut oil and 5% soybean oil for 7 weeks. The central administration of IL-1beta induced sickness, stress and anxiety-like behavior as indicated by a reduction in body weight, decreased time spent, and the number of entries, into the open arms of the elevated plus maze and decreased exploration and entry into the central zone of the "open field" apparatus. IL-1beta also increased PGE2 and corticosterone concentrations and decreased the release of IL-10 from leucocytes. Food enriched with ethyl-EPA but not soybean oil, significantly attenuated most of these changes. These results demonstrate that ethyl-EPA has anti-inflammatory, anti-stress and anti-anxiety effects in rats.

Polyunsaturated fatty acids in the blood of spontaneously or induced muricidal male Wistar rats

Serum levels of several n-6 and n-3 polyunsaturated fatty acids were compared in male Wistar muricidal (Mu) and non-Mu rats. The Mu behavior was either spontaneous or induced by long-term isolation, feeding with a starch-enriched polyunsaturated fatty acid diet (PUFA+S), water restriction, or adrenalectomy (ADX). Arachidonic acid (ARA) levels were lower in diet-induced (PUFA+S) Mu rats than in their non-Mu controls. Total n-6 fatty acid levels were also lower in spontaneously Mu rats than in spontaneously non-Mu rats. Docosahexaenoic acid (DHA) and total n-3 fatty acids levels were lower in rats with isolation-induced Mu behavior. The n-3/n-6 ratio was higher in spontaneously Mu rats than in spontaneously non-Mu rats. The changes in ARA levels were greater than those in DHA levels, possibly due to the higher blood-brain barrier passage of arachidonic acid. The results were analyzed in the light of recent results showing a role of PUFAs in human and animal behavior.

Possible regulatory mechanism of DHA-induced anti-stress reaction in rats

To determine whether docosahexaenoic acid (DHA) affects stress responses in rats, we investigated its influence on several behavioral tests. Female rats were fed a diet deficient in (n-3) fatty acid from mating through pregnancy and lactation. Male pups fed the same diet as their dams were used for experiments. The effects of dietary (n-3) fatty acid deficiency and supplementation with DHA on psychological stress and conditioned-fear stress were investigated. The effect of DHA on psychological stress was examined by an elevated plus-maze test. The (n-3) deficient rats spent significantly (P<0.05) less time in the open arms; after 1 week of supplementation with DHA, they showed a significant (P<0.01) improvement. We then examined the paired effects of DHA and CRH on stress manifestations by an intracerebroventricular (i.c.v.) cannulation and behavior testing. An i.c.v. infusion of CRH (500 pmol) under resting conditions was shown to have stress-inducing effects on behavior such as decreases of rearing, smelling and feeding, and increases of face washing; the supplementation of DHA significantly improved these distress behaviors. Finally, conditioned fear was induced by 40 min forced exposure to a cage in which the rat had experienced footshocks (30 x 1 mA x 1 s) 1 day before. Freezing behavior was dramatically suppressed by the supplementation of DHA, even 48 h after the conditioning treatment. Furthermore, the effect of DHA on the conditioned fear stress response is maintained over a long-term period. The i.c.v. pre-treatment of rats with bicuculline, a GABA(A) receptor antagonist, enhanced the conditioned-fear-induced freezing time in a dose-dependent fashion in the (n-3) fatty acid deficient animals. Significantly, the DHA supplemented group was not affected by the pre-treatment with bicuculline. From these findings, it is concluded that the involvement of DHA in stress responses may act via a GABA(A) receptor-mediated mechanism.