Brain docosahexaenoic acid status and learning in young rats submitted to dietary long-chain polyunsaturated fatty acid deficiency and supplementation limited to lactation

Unraveling the effects of maternal breastfeeding duration and exclusive breast milk on children's cognitive abilities in early childhood

Background

This study investigated the putative associations between mothers' use of exclusive breast milk and the duration of breastfeeding with child cognitive development.

Methods

This study is based on 2,210 Canadian families with children assessed longitudinally from age 4 to 7 years on their memory-span and math skills. These cognitive abilities were measured with standardized tasks. Breastfeeding practices were collected via maternal reports. We applied propensity scores to control the social selection bias for breastfeeding.

Results

Results adjusted for propensity scores and sample weight revealed no significant differences between non-breastfed children with those being non-exclusively breastfed for 5 months or less, and with children being exclusively breastfed for 9.2 months on average, on their early math skills and memory-span. We found that children who were non-exclusively breastfed for 6.8 months on average had a slightly higher levels of memory-span at age 4 than children who were never breastfed, and this small but significant difference lasted up to age 7.

Conclusion

Our findings suggest no significant differences between children being exclusively breastfed and those fed with formula on their early math skills and memory-span. The encouragement of breastfeeding to promote child cognitive school readiness may, in some case (non-exclusive breastfeeding for more than 5 months), show a small but long-lasting advantage in early memory-span.

Role of functional fatty acids in modulation of reproductive potential in livestock

Fatty acids are not only widely known as energy sources, but also play important roles in many metabolic pathways. The significance of fatty acids in modulating the reproductive potential of livestock has received greater recognition in recent years. Functional fatty acids and their metabolites improve follicular development, oocyte maturation and embryo development, as well as endometrial receptivity and placental vascular development, through enhancing energy supply and precursors for the synthesis of their productive hormones, such as steroid hormones and prostaglandins. However, many studies are focused on the impacts of individual functional fatty acids in the reproductive cycle, lacking studies involved in deeper mechanisms and optimal fatty acid requirements for specific physiological stages. Therefore, an overall consideration of the combination and synergy of functional fatty acids and the establishment of optimal fatty acid requirement for specific stages is needed to improve reproductive potential in livestock.

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.

Age Drives Distortion of Brain Metabolic, Vascular and Cognitive Functions, and the Gut Microbiome

Advancing age is the top risk factor for the development of neurodegenerative disorders, including Alzheimer's disease (AD). However, the contribution of aging processes to AD etiology remains unclear. Emerging evidence shows that reduced brain metabolic and vascular functions occur decades before the onset of cognitive impairments, and these reductions are highly associated with low-grade, chronic inflammation developed in the brain over time. Interestingly, recent findings suggest that the gut microbiota may also play a critical role in modulating immune responses in the brain via the brain-gut axis. In this study, our goal was to identify associations between deleterious changes in brain metabolism, cerebral blood flow (CBF), gut microbiome and cognition in aging, and potential implications for AD development. We conducted our study with a group of young mice (5-6 months of age) and compared those to old mice (18-20 months of age) by utilizing metabolic profiling, neuroimaging, gut microbiome analysis, behavioral assessments and biochemical assays. We found that compared to young mice, old mice had significantly increased levels of numerous amino acids and fatty acids that are highly associated with inflammation and AD biomarkers. In the gut microbiome analyses, we found that old mice had increased Firmicutes/Bacteroidetes ratio and alpha diversity. We also found impaired blood-brain barrier (BBB) function and reduced CBF as well as compromised learning and memory and increased anxiety, clinical symptoms often seen in AD patients, in old mice. Our study suggests that the aging process involves deleterious changes in brain metabolic, vascular and cognitive functions, and gut microbiome structure and diversity, all which may lead to inflammation and thus increase the risk for AD. Future studies conducting comprehensive and integrative characterization of brain aging, including crosstalk with peripheral systems and factors, will be necessary to define the mechanisms underlying the shift from normal aging to pathological processes in the etiology of AD.

Effects of iron supplementation on growth, gut microbiota, metabolomics and cognitive development of rat pups

BACKGROUND

Iron deficiency is common during infancy and therefore iron supplementation is recommended. Recent reports suggest that iron supplementation in already iron replete infants may adversely affect growth, cognitive development, and morbidity.

METHODS

Normal and growth restricted rat pups were given iron daily (30 or 150 μg/d) from birth to postnatal day (PD) 20, and followed to PD56. At PD20, hematology, tissue iron, and the hepatic metabolome were measured. The plasma metabolome and colonic microbial ecology were assessed at PD20 and PD56. T-maze (PD35) and passive avoidance (PD40) tests were used to evaluate cognitive development.

RESULTS

Iron supplementation increased iron status in a dose-dependent manner in both groups, but no significant effect of iron on growth was observed. Passive avoidance was significantly lower only in normal rats given high iron compared with controls. In plasma and liver of normal and growth-restricted rats, excess iron increased 3-hydroxybutyrate and decreased several amino acids, urea and myo-inositol. While a profound difference in gut microbiota of normal and growth-restricted rats was observed, with iron supplementation differences in the abundance of strict anaerobes were observed.

CONCLUSION

Excess iron adversely affects cognitive development, which may be a consequence of altered metabolism and/or shifts in gut microbiota.

Breastfeeding, Cognitive and Noncognitive Development in Early Childhood: A Population Study

BACKGROUND AND OBJECTIVES

There is mixed evidence from correlational studies that breastfeeding impacts children's development. Propensity score matching with large samples can be an effective tool to remove potential bias from observed confounders in correlational studies. The aim of this study was to investigate the impact of breastfeeding on children's cognitive and noncognitive development at 3 and 5 years of age.

METHODS

Participants included ∼8000 families from the Growing Up in Ireland longitudinal infant cohort, who were identified from the Child Benefit Register and randomly selected to participate. Parent and teacher reports and standardized assessments were used to collect information on children's problem behaviors, expressive vocabulary, and cognitive abilities at age 3 and 5 years. Breastfeeding information was collected via maternal report. Propensity score matching was used to compare the average treatment effects on those who were breastfed.

RESULTS

Before matching, breastfeeding was associated with better development on almost every outcome. After matching and adjustment for multiple testing, only 1 of the 13 outcomes remained statistically significant: children's hyperactivity (difference score, -0.84; 95% confidence interval, -1.33 to -0.35) at age 3 years for children who were breastfed for at least 6 months. No statistically significant differences were observed postmatching on any outcome at age 5 years.

CONCLUSIONS

Although 1 positive benefit of breastfeeding was found by using propensity score matching, the effect size was modest in practical terms. No support was found for statistically significant gains at age 5 years, suggesting that the earlier observed benefit from breastfeeding may not be maintained once children enter school.

N-3 Polyunsaturated Fatty Acids through the Lifespan: Implication for Psychopathology

OBJECTIVE

The impact of lifetime dietary habits and their role in physical, mental, and social well-being has been the focus of considerable recent research. Omega-3 polyunsaturated fatty acids as a dietary constituent have been under the spotlight for decades. Omega-3 polyunsaturated fatty acids constitute key regulating factors of neurotransmission, neurogenesis, and neuroinflammation and are thereby fundamental for development, functioning, and aging of the CNS. Of note is the fact that these processes are altered in various psychiatric disorders, including attention deficit hyperactivity disorder, depression, and Alzheimer's disease.

DESIGN

Relevant literature was identified through a search of MEDLINE via PubMed using the following words, "n-3 PUFAs," "EPA," and "DHA" in combination with "stress," "cognition," "ADHD," "anxiety," "depression," "bipolar disorder," "schizophrenia," and "Alzheimer." The principal focus was on the role of omega-3 polyunsaturated fatty acids throughout the lifespan and their implication for psychopathologies. Recommendations for future investigation on the potential clinical value of omega-3 polyunsaturated fatty acids were examined.

RESULTS

The inconsistent and inconclusive results from randomized clinical trials limits the usage of omega-3 polyunsaturated fatty acids in clinical practice. However, a body of literature demonstrates an inverse correlation between omega-3 polyunsaturated fatty acid levels and quality of life/ psychiatric diseases. Specifically, older healthy adults showing low habitual intake of omega-3 polyunsaturated fatty acids benefit most from consuming them, showing improved age-related cognitive decline.

CONCLUSIONS

Although further studies are required, there is an exciting and growing body of research suggesting that omega-3 polyunsaturated fatty acids may have a potential clinical value in the prevention and treatment of psychopathologies.

Reducing dietary intake of linoleic acid of mouse dams during lactation increases offspring brain n-3 LCPUFA content

Omega (n-)3 and n-6 long chain polyunsaturated fatty acids (LCPUFA) accumulation in the infant brain after birth is strongly driven by dietary supply of n-3 and n-6 LCPUFAs and their C18 precursors through breast milk or infant formula. n-3 LCPUFA accretion is associated with positive effects on neurodevelopmental outcome whereas high n-6 LCPUFA accumulation is considered disadvantageous. Maternal diet is crucial for breast milk fatty acid composition. Unfortunately, global increases in linoleic acid (C18:2n-6; LA) intake have dramatically increased n-6 LCPUFA and reduced n-3 LCPUFA availability for breastfed infants. We investigated the effects of reducing maternal dietary LA, or increasing n-3 LCPUFA, during lactation on milk and offspring brain fatty acids in mice. Offspring brain n-3 LCPUFA was higher following both interventions, although effects were mediated by different mechanisms. Because of competitive interactions between n-3 and n-6 fatty acids, lowering maternal LA intake may support neurodevelopment in breastfed infants.

Repeated systemic administration of the nutraceutical alpha-linolenic acid exerts neuroprotective efficacy, an antidepressant effect and improves cognitive performance when given after soman exposure

Exposure to nerve agents results in severe seizures or status epilepticus caused by the inhibition of acetylcholinesterase, a critical enzyme that breaks down acetylcholine to terminate neurotransmission. Prolonged seizures cause brain damage and can lead to long-term consequences. Current countermeasures are only modestly effective against the brain damage supporting interest in the evaluation of new and efficacious therapies. The nutraceutical alpha-linolenic acid (LIN) is an essential omega-3 polyunsaturated fatty acid that has a wide safety margin. Previous work showed that a single intravenous injection of alpha-linolenic acid (500 nmol/kg) administered before or after soman significantly protected against soman-induced brain damage when analyzed 24h after exposure. Here, we show that administration of three intravenous injections of alpha-linolenic acid over a 7 day period after soman significantly improved motor performance on the rotarod, enhanced memory retention, exerted an anti-depressant-like activity and increased animal survival. This dosing schedule significantly reduced soman-induced neuronal degeneration in four major vulnerable brain regions up to 21 days. Taken together, alpha-linolenic acid reduces the profound behavioral deficits induced by soman possibly by decreasing neuronal cell death, and increases animal survival.

Curcumin boosts DHA in the brain: Implications for the prevention of anxiety disorders

Dietary deficiency of docosahexaenoic acid (C22:6 n-3; DHA) is linked to the neuropathology of several cognitive disorders, including anxiety. DHA, which is essential for brain development and protection, is primarily obtained through the diet or synthesized from dietary precursors, however the conversion efficiency is low. Curcumin (diferuloylmethane), which is a principal component of the spice turmeric, complements the action of DHA in the brain, and this study was performed to determine molecular mechanisms involved. We report that curcumin enhances the synthesis of DHA from its precursor, α-linolenic acid (C18:3 n-3; ALA) and elevates levels of enzymes involved in the synthesis of DHA such as FADS2 and elongase 2 in both liver and brain tissues. Furthermore, in vivo treatment with curcumin and ALA reduced anxiety-like behavior in rodents. Taken together, these data suggest that curcumin enhances DHA synthesis, resulting in elevated brain DHA content. These findings have important implications for human health and the prevention of cognitive disease, particularly for populations eating a plant-based diet or who do not consume fish, a primary source of DHA, since DHA is essential for brain function and its deficiency is implicated in many types of neurological disorders.

Linoleic and docosahexaenoic acids in human milk have opposite relationships with cognitive test performance in a sample of 28 countries

Polyunsaturated fatty acids play critical roles in brain development and function, and their levels in human breast milk closely reflect the long-term diet. The fatty acid contents of human milk samples from 28 countries were used to predict averaged 2009 and 2012 test scores in mathematics, reading, and science from the Program for International Student Assessment. All test scores were positively related to milk docosahexaenoic acid (r=0.48 to 0.55), and negatively related to linoleic acid (r=-0.28 to -0.56). Together, these two human milk fatty acids explained 46% to 48% of the variance in scores, with no improvement in predictive power when socioeconomic variables were added to the regression. The (log) ratio of linoleic to arachidonic acid was negatively related to scores (r=-0.45 to -0.48). Statistical effects were similar for the two sexes. In a separate US sample, estimated dietary linoleic was negatively related to the levels of all long-chain n-3 and n-6 plasma fatty acids. High levels of dietary linoleic may impair cognition by decreasing both docosahexaenoic and arachidonic acids in the brain.

Nutritional n-3 PUFAs deficiency during perinatal periods alters brain innate immune system and neuronal plasticity-associated genes

Low dietary intake of the n-3 polyunsaturated fatty acids (PUFAs) is a causative factor of neurodevelopmental disorders. However the mechanisms linking n-3 PUFAs low dietary intake and neurodevelopmental disorders are poorly understood. Microglia, known mainly for their immune function in the injured or infected brain, have recently been demonstrated to play a pivotal role in regulating maturation of neuronal circuits during normal brain development. Disruption of this role during the perinatal period therefore could significantly contribute to psychopathologies with a neurodevelopmental neurodevelopmental component. N-3 PUFAs, essential lipids and key structural components of neuronal membrane phospholipids, are highly incorporated in cell membranes during the gestation and lactation phase. We previously showed that in a context of perinatal n-3 PUFAs deficiency, accretion of these latter is decreased and this is correlated to an alteration of endotoxin-induced inflammatory response. We thus postulated that dietary n-3 PUFAs imbalance alters the activity of microglia in the developing brain, leading to abnormal formation of neuronal networks. We first confirmed that mice fed with a n-3 PUFAs deficient diet displayed decreased n-3 PUFAs levels in the brain at post-natal days (PND)0 and PND21. We then demonstrated that n-3 PUFAs deficiency altered microglia phenotype and motility in the post-natal developing brain. This was paralleled by an increase in pro-inflammatory cytokines expression at PND21 and to modification of neuronal plasticity-related genes expression. Overall, our findings show for the first time that a dietary n-3 PUFAs deficiency from the first day of gestation leads to the development of a pro-inflammatory condition in the central nervous system that may contribute to neurodevelopmental alterations.

Dissociable effects of dorsal and ventral hippocampal DHA content on spatial learning and anxiety-like behavior

Chronic deficiency of dietary docosahexaenoic acid (DHA) during critical developmental windows results in severe deficits in spatial learning, anxiety and hippocampal neuroplasticity that parallel a variety of neuropsychiatric disorders. However, little is known regarding the influence of long-term, multigenerational exposure to dietary DHA enrichment on these same traits. To characterize the potential benefits of multigenerational DHA enrichment, mice were fed a purified 10:1 omega-6/omega-3 diet supplemented with either 0.1% preformed DHA/kg feed weight or 1.0% preformed DHA/kg feed weight through three generations. General locomotor activity, spatial learning, and anxiety-like behavior were assessed in adult male offspring of the third generation. Following behavioral assessments, ventral and dorsal hippocampus was collected for DHA and arachidonic acid (AA) analysis. Animals consuming the 0.1% and 1.0% DHA diet did not differ from control animals for locomotor activity or on performance during acquisition learning, but made fewer errors and showed more stable across-day performance during reversal learning on the spatial task and showed less anxiety-like behavior. Consumption of the DHA-enriched diets increased DHA content in the ventral and dorsal hippocampus in a region-specific manner. DHA content in the dorsal hippocampus predicted performance on the reversal training task. DHA content in the ventral hippocampus was correlated with anxiety-like behavior, but AA content in the dorsal hippocampus was a stronger predictor of this behavior. These results suggest that long-term, multigenerational DHA administration improves performance on some aspects of complex spatial learning, decreases anxiety-like behavior, and that modulation of DHA content in sub-regions of the hippocampus predicts which behaviors are likely to be affected.

Omega-3 fatty acid and nutrient deficits in adverse neurodevelopment and childhood behaviors

Nutritional insufficiencies of omega-3 highly unsaturated fatty acids (HUFAs) may have adverse effects on brain development and neurodevelopmental outcomes. A recent meta-analysis reported a small to modest effect size for the efficacy of omega-3 in youth. Several controlled trials of omega-3 HUFAs combined with micronutrients show sizable reductions in aggressive, antisocial, and violent behavior in youth and young adult prisoners. Studies of HUFAs in youth, however, remain lacking. As the evidence base for omega-3 HUFAs as potential psychiatric treatment develops, dietary adjustments to increase omega-3 and reduce omega-6 HUFA consumption are sensible recommendations based on general health considerations.

n-3 LCPUFA improves cognition: the young, the old and the sick

Due to the implication of docosahexaenoic acid (DHA) in neurogenesis, synaptogenesis, neurite outgrowth and to its high incorporation into the brain, this n-3 long chain polyunsaturated fatty acid (LCPUFA) is considered as crucial in the development and maintenance of the learning memory performance throughout life. In the present chapter we aimed at reviewing data investigating the relation between DHA and cognition during the perinatal period, young adult- and adulthood and neurodegenerative diseases such as Alzheimer disease (AD). In Humans, dietary DHA supplementation from the perinatal period to adulthood does not reveal a clear and consistent memory improvement whereas it is the case in animal studies. The positive effects observed in animal models may have been enhanced by using n-3 PUFA deficient animal models as controls. In animal models of AD, a general consensus on the beneficial effects of n-3 LCPUFA in attenuating cognitive impairment was established. These studies make DHA a potential suitable micronutrient for the maintenance of cognitive performance at all periods of life.

Dietary omega-3 deficiency reduces BDNF content and activation NMDA receptor and Fyn in dorsal hippocampus: implications on persistence of long-term memory in rats

Omega-3 (n-3) fatty acids are important for adequate brain function and cognition. The aim of the present study was to evaluate how n-3 fatty acids influence the persistence of long-term memory (LTM) in an aversive memory task and to explore the putative mechanism involved. Female rats received isocaloric diets that included n-3 (n-3 group) or not (D group). The adult litters were subjected to an inhibitory avoidance task (0.7 mA, 1.0 seconds foot shock) to elicit persistent LTM. Twelve hours after the training session, the fatty acid profile and the brain derived neurotrophic factor (BDNF) content of the dorsal hippocampus were assessed. In addition, we measured the activation of the NR2B subunit of the N-methyl-d-aspartate (NMDA) receptor and the SRC family protein Fyn. Despite pronounced learning in both groups, the persistence of LTM was abolished in the D group 7 days after the training session. We also observed that the D group presented reductions in hippocampal DHA (22:6 n-3) and BDNF content. Twelve hours after the training session, the D group showed decreased NR2B and Fyn phosphorylation in the dorsal hippocampus, with no change in the total content of these proteins. Further, there was a decrease in the interaction of Fyn with NR2B in the D group, as observed by co-immunoprecipitation. Taken together, these data suggest that n-3 fatty acids influence the persistence of LTM by maintaining adequate levels of DHA and BDNF as well as by influencing the activation of NR2B and Fyn during the period of memory formation.

Long-chain omega-3 fatty acids: time to establish a dietary reference intake

The beneficial effects of consuming omega-3 polyunsaturated fatty acids (n-3 PUFAs), specifically eicosapentaenoic acid (EPA) and docosahexaenoic acid (DHA), on cardiovascular health have been studied extensively. To date, there is no dietary reference intake (DRI) for EPA and DHA, although many international authorities and expert groups have issued dietary recommendations for them. Given the substantial new evidence published since the last Institute of Medicine (IOM) report on energy and macronutrients, released in 2002, there is a pressing need to establish a DRI for EPA and DHA. In order to set a DRI, however, more information is needed to define the intakes of EPA and DHA required to reduce the burden of chronic disease. Information about potential gender- or race-based differences in requirements is also needed. Given the many health benefits of EPA and DHA that have been described since the 2002 IOM report, there is now a strong justification for establishing a DRI for these fatty acids.

Maternal long-chain PUFA supplementation during protein deficiency improves brain fatty acid accretion in rat pups by altering the milk fatty acid composition of the dam

Long-chain PUFA (LC-PUFA) are important for fetal and neonatal brain development. However, their accretion in the brain is compromised during maternal protein restriction. Hence, we investigated the effect of maternal supplementation with n-3 DHA plus n-6 arachidonic acid (ARA) at a low protein level (9 %) on offspring brain fatty acid accretion using Wistar rats (nine rats per group) randomly fed a control (C), a low-protein (LP) or a low-protein DHA + ARA-supplemented (LPS) diet during gestation and lactation. At birth, pups from the LPS group had the highest brain DHA and n-3 fatty acid levels (P = 0·001), whereas pups from the LP group had the highest MUFA (P = 0·05) but the lowest DHA and total n-3 PUFA levels (P = 0·000). During lactation, pups from the LPS group accrued significantly more α-linolenic acid (P = 0·003), EPA (P = 0·02) and DHA (P = 0·000) in brain lipids than pups from the LP group, whereas brain lipids of pups from the LP group had markedly increased levels of the n-3 deficiency marker docosapentaenoic acid and n-6:n-3 ratio (P = 0·000). Owing to supplementation, milk from LPS dams had the highest DHA and ARA, but lower SCFA and medium-chain fatty acids as compared with milk from C and LP dams during early lactation, but normalised by mid-lactation. To conclude, adverse effects of restricted maternal protein intake on LC-PUFA accretion in the brain of offspring were ameliorated by alterations in maternal milk fatty acid profile due to supplementation. Results underscore the importance of LC-PUFA for protein-deficient mothers during gestation as well as lactation to achieve the optimum brain LC-PUFA status of progeny.

Cognitive enhancement by omega-3 fatty acids from child-hood to old age: findings from animal and clinical studies

Omega-(n)-3 polyunsaturated fatty acids (PUFAs), including docosahexaenoic acid (DHA) and eicosapentaenoic acid (EPA) are major components of neuronal membranes and have a wide range of functions, from modulating synaptic plasticity and neurochemistry, to neuroimmune-modulation and neuroprotection. Thus, it is not surprising that n-3 PUFA are widely acknowledged to have cognitive-enhancing effects. Although clinical evidence is somewhat conflicting, probably in large part due to methodological issues, animal studies have consistently demonstrated that n-3 PUFA are indispensable for proper brain development, may enhance cognitive function in healthy, adult individuals and attenuate cognitive impairment in aging and age-related disorders, such as dementia. This review discusses and integrates up to date evidence from clinical and animal studies investigating the cognitive-enhancing effects of n-3 PUFA during development, child- and adult-hood, as well as old-age with associated neurodegenerative diseases, such as Alzheimer's disease. Furthermore, we cover the major underlying biochemical and neurophysiological mechanisms by which n-3 PUFA mediate these effects on cognition. This article is part of a Special Issue entitled 'Cognitive Enhancers'.

Sex differences in the relationship of dietary Fatty acids to cognitive measures in american children

Because the first neurons evolved in an environment high in the n−3 (omega-3) fatty acid docosahexaenoic acid (DHA), this fatty acid became a major component of neural structure and function and makes up 10% of the dry weight of the human brain. Since n−3 fatty acids must come from the diet, this suggests a possible positive role for dietary n−3 fatty acids in cognition and a possible negative role for n−6 fatty acids, which compete with n−3 for access to critical enzymes. Because human females must provide DHA for the growth of the unusually large brains of their offspring from maternal fat stored during childhood, their need for DHA is especially great. We used stepwise regression to determine whether particular dietary fatty acids and other nutrients were related to cognitive performance in over 4000 American children aged 6–16 from the Third National Health and Nutrition Examination Survey; a variety of possible biological, social, and environmental risk factors were statistically controlled. In this context the only dietary factors related to cognitive performance were n−3 and n−6 fatty acids. Dietary n−3 fatty acids were positively related to cognitive test scores in male and female children, while n−6 showed the reverse relationship, significantly so in females. In female children the positive effects of n−3 intake were twice as strong as in males and exceeded the negative effects of lead exposure. This suggests that increasing dietary intake of n−3 and decreasing n−6 fatty acids may have cognitive benefits in children, especially in females.

Dietary n-3 polyunsaturated fatty acid deprivation together with early maternal separation increases anxiety and vulnerability to stress in adult rats

Low concentrations of n-3 polyunsaturated fatty acid (PUFA) and chronic stress are implicated in susceptibility to mood disorders. We have investigated the combined effects of chronic n-3 PUFA dietary deficiency and early maternal separation (MS) stress on the reactivity to stressful situations of rats as adults. Pups fed a control or an n-3 PUFA deficient diet were daily separated for two weeks before weaning They were all tested at 3 month-old to determine their anxiety, and their ability to learn two aversive tasks differing in the control they could exert on the situation: auditory fear conditioning and brightness avoidance discrimination. Neither the n-3 PUFA-deficient diet nor MS alone significantly affected behavior. But n-3 PUFA-deficient rats that had been separated were more anxious and fearful in inescapable situations, while their ability to cope with an aversive avoidance task remained unaffected. These results support the notion that PUFA-unbalanced diet, together with stress, may be a determinant risk factor in emotional disorders.

Towards establishing dietary reference intakes for eicosapentaenoic and docosahexaenoic acids

There is considerable interest in the impact of (n-3) long-chain PUFA in mitigating the morbidity and mortality caused by chronic diseases. In 2002, the Institute of Medicine concluded that insufficient data were available to define Dietary Reference Intakes (DRI) for eicosapentaenoic acid (EPA) or docosahexaenoic acid (DHA), noting only that EPA and DHA could contribute up to 10% toward meeting the Adequate Intake for alpha-linolenic acid. Since then, substantial new evidence has emerged supporting the need to reassess this recommendation. Therefore, the Technical Committee on Dietary Lipids of the International Life Sciences Institute North America sponsored a workshop on 4-5 June 2008 to consider whether the body of evidence specific to the major chronic diseases in the United States--coronary heart disease (CHD), cancer, and cognitive decline--had evolved sufficiently to justify reconsideration of DRI for EPA+DHA. The workshop participants arrived at these conclusions: 1) consistent evidence from multiple research paradigms demonstrates a clear, inverse relation between EPA+DHA intake and risk of fatal (and possibly nonfatal) CHD, providing evidence that supports a nutritionally achievable DRI for EPA+DHA between 250 and 500 mg/d; 2) because of the demonstrated low conversion from dietary ALA, protective tissue levels of EPA+DHA can be achieved only through direct consumption of these fatty acids; 3) evidence of beneficial effects of EPA+DHA on cognitive decline are emerging but are not yet sufficient to support an intake level different from that needed to achieve CHD risk reduction; 4) EPA+DHA do not appear to reduce risk for cancer; and 5) there is no evidence that intakes of EPA+DHA in these recommended ranges are harmful.

An n-3 fatty acid deficient diet affects mouse spatial learning in the Barnes circular maze

Deficiency in n-3 fatty acids has been accomplished through the use of an artificial rearing method in which ICR mouse pups were hand fed a deficient diet starting from the 2nd day of life. There was a 51% loss of total brain DHA in mice with an n-3 fatty acid-deficient diet relative to those with a diet sufficient in n-3 fatty acids. n-3 fatty acid adequate and deficient mice did not differ in terms of locomotor activity in the open field test or in anxiety-related behavior in the elevated plus maze. The n-3 fatty acid-deficient mice demonstrated impaired learning in the reference-memory version of the Barnes circular maze as they spent more time and made more errors in search of an escape tunnel. No difference in performance between all dietary groups in the cued and working memory version of the Barnes maze was observed. This indicated that motivational, motor and sensory factors did not contribute to the reference memory impairment.

Essential fatty acid deficiency profile in patients with nephrotic-range proteinuria

Plasma free fatty acids are bound to albumin, filtered through the glomeruli, and reabsorbed at the proximal nephron. The aim of the present investigation was to determine if urinary loss of fatty acids results in essential fatty acid (EFA) deficiency in patients with nephrotic-range proteinuria. We studied 12 patients aged 9 months to 23 years (eight male, four female) four suffering from congenital nephrotic syndrome (NS) and eight from different renal diseases. Six patients were studied postrenal transplantation. Proteinuria ranged between 41 and 829 mg/m2/h. Results were compared with data obtained in 83 healthy children. The patients had significantly lower values for plasma arachidonic acid content and EFA index (omega3 + omega6/omega7 + omega9). Deficiency in polyunsaturated fatty acids (PUFA) was especially manifest in infants with congenital NS. Plasma content of arachidonic and docosahexaenoic acids related negatively with the degree of proteinuria. In the lineal regression model, the degree of proteinuria explained 60% of the variability of plasma values of those fatty acids. We conclude that plasma fatty acid status should be regularly monitored in patients with nephrotic-range proteinuria, especially in young infants with congenital NS, who represent a population at special risk with regard to neurological development.

Has an aquatic diet been necessary for hominin brain evolution and functional development?

A number of authors have argued that only an aquatic-based diet can provide the necessary quantity of DHA to support the human brain, and that a switch to such a diet early in hominin evolution was critical to human brain evolution. This paper identifies the premises behind this hypothesis and critiques them on the basis of clinical literature. Both tissue levels and certain functions of the developing infant brain are sensitive to extreme variations in the supply of DHA in artificial feeding, and it can be shown that levels in human milk reflect maternal diet. However, both the maternal and infant bodies have mechanisms to store and buffer the supply of DHA, so that functional deficits are generally resolved without compensatory diets. There is no evidence that human diets based on terrestrial food chains with traditional nursing practices fail to provide adequate levels of DHA or other n-3 fatty acids. Consequently, the hypothesis that DHA has been a limiting resource in human brain evolution must be considered to be unsupported.

Mice raised on milk transgenically enriched with n-3 PUFA have increased brain docosahexaenoic acid

The brain contains high levels of the long-chain n-3 FA DHA (22:6n-3), mainly in the gray matter and synaptosomes. Adequate intake of DHA is crucial for optimal nervous system function, particularly in infants. Supplementation of infant formulas with DHA at levels similar to human breast milk is recommended for biochemical and functional benefits to neonates. We generated transgenic mice that produce elevated levels of n-3 PUFA in their milk by expressing the Caenorhabditis elegans n-3 FA desaturase under the control of a lactation-induced goat beta-casein promoter. To examine the postnatal effects of consuming the n-3-enriched milk, we compared the growth and brain and plasma FA composition of mouse pups raised on milk from transgenic dams with those observed for pups raised on milk from nontransgenic dams. A significant decrease in arachidonic acid (ARA, 20:4n-6) and concomitant increases in n-3 PUFA were observed in the phospholipid fraction of transgenic mouse milk. The n-6:n-3 FA ratios were 4.7 and 34.5 for the transgenic and control milk phospholipid fractions, respectively. DHA and DPA (22:5n-6) comprised 15.1% and 2.8% of brain FA from weanling mice nursed on transgenic dams, as compared with 6.9% and 9.2% for weanling mice nursed on control dams, respectively. This transgenic mouse model offers a unique approach to disassociate the effects and fetal programming resulting from a high n-6:n-3 FA ratio gestational environment from the postnatal nutritional effects of providing milk with differing n-6:n-3 FA ratios.

Essential fatty acids: biochemistry, physiology and pathology

Essential fatty acids (EFAs), linoleic acid (LA), and alpha-linolenic acid (ALA) are essential for humans, and are freely available in the diet. Hence, EFA deficiency is extremely rare in humans. To derive the full benefits of EFAs, they need to be metabolized to their respective long-chain metabolites, i.e., dihomo-gamma-linolenic acid (DGLA), and arachidonic acid (AA) from LA; and eicosapentaenoic acid (EPA) and docosahexaenoic acid (DHA) from ALA. Some of these long-chain metabolites not only form precursors to respective prostaglandins (PGs), thromboxanes (TXs), and leukotrienes (LTs), but also give rise to lipoxins (LXs) and resolvins that have potent anti-inflammatory actions. Furthermore, EFAs and their metabolites may function as endogenous angiotensin-converting enzyme and 3-hdroxy-3-methylglutaryl coenzyme A reductase inhibitors, nitric oxide (NO) enhancers, anti-hypertensives, and anti-atherosclerotic molecules. Recent studies revealed that EFAs react with NO to yield respective nitroalkene derivatives that exert cell-signaling actions via ligation and activation of peroxisome proliferator-activated receptors. The metabolism of EFAs is altered in several diseases such as obesity, hypertension, diabetes mellitus, coronary heart disease, schizophrenia, Alzheimer's disease, atherosclerosis, and cancer. Thus, EFAs and their derivatives have varied biological actions and seem to be involved in several physiological and pathological processes.

Omega-3 fatty acids and rodent behavior

This paper reviews the role of the n-3 fatty acids in the regulation of cognitive functions, locomotor and exploratory activity and emotional status in rodents. There are disparate data on the performance of n-3 fatty acid deficient animals in the open field test and elevated plus maze. Results obtained in our laboratory indicated slower habituation to the open field in deficient mice, which affects total locomotor and exploratory parameters. We also observed no change in plus maze performance of deficient mice under low-stress but elevated anxiety under high-stress conditions. There is some evidence of elevated aggression and increased immobility time in the forced swimming test caused by n-3 fatty acid deficiency in rodents. Effects of n-3 fatty acid deficiency and supplementation on learning in several tests such as the Morris water maze, two odor olfactory discriminations, radial arm maze performance and avoidance tasks are reviewed in detail. There is some evidence of an enhanced vulnerability to stress of n-3 fatty acid deficient animals and this factor can influence performance in a variety of tests. Thus, behavioral tasks that involve a higher level of stress may better differentiate behavioral effects related to brain docosahexaenoic acid (DHA) status. It is suggested that a fruitful area for future investigations of functional alterations related to brain DHA status will be the delineation of the factors underlying changes in performance in behavioral tasks. The possible role of non-cognitive factors like emotionality and attention in the impaired performance of n-3 fatty acid deficient animals also requires further investigation.