ArticlePDF AvailableLiterature Review

Docosahexaenoic acid,22:6n-3: Its roles in the structure and function of the brain

DOI:10.1016/j.ijdevneu.2019.10.004

Authors:

Rahul Mallick

University of Eastern Finland

Sanjay Basak

National Institute of Nutrition, Indian Council of Medical Research

Asim K Duttaroy

University of Oslo

Docosahexaenoic acid,22:6n-3 (DHA) and its metabolites are vital for the structure and functional brain development of the fetus and infants, and also for maintenance of healthy brain function of adults. DHA is thought to be an essential nutrient required throughout the life cycle for the maintenance of overall brain health. The mode of actions of DHA and its derivatives at both cellular and molecular levels in the brain are emerging. DHA is the major prevalent fatty acid in the brain membrane. The brain maintains its fatty acid levels mainly via the uptake of plasma free fatty acids. Therefore, circulating plasma DHA is significantly related to cognitive abilities during ageing and is inversely associated with cognitive decline. The signaling pathways of DHA and its metabolites are involved in neurogenesis, antinociceptive effects, anti-apoptotic effect, synaptic plasticity, Ca2+ homeostasis in brain diseases, and the functioning of nigrostriatal activities. Mechanisms of action of DHA metabolites on various processes in the brain are not yet well known. Epidemiological studies support a link between low habitual intake of DHA and a higher risk of brain disorders. A diet characterized by higher intakes of foods containing high in n-3 fatty acids, and/or lower intake of n-6 fatty acids was strongly associated with a lower Alzheimer's Disease and other brain disorders. Supplementation of DHA improves some behaviors associated with attention deficit hyperactivity disorder, bipolar disorder, schizophrenia, and impulsive behavior, as well as cognition. Nevertheless, the outcomes of trials with DHA supplementation have been controversial. Many intervention studies with DHA have shown an apparent benefit in brain function. However, clinical trials are needed for definitive conclusions. Dietary deficiency of n-3 fatty acids during fetal development in utero and the postnatal state has detrimental effects on cognitive abilities. Further research in humans is required to assess a variety of clinical outcomes, including quality of life and mental status, by supplementation of DHA.

DHA synthesis in the body. The plant source provides us ALA is converted to EPA and DHA. The desaturations and elongations occur in the endoplasmic reticulum, and the β-oxidation occurs in the peroxisome, to where 24-carbon PUFA are transferred. The animal source provides us with EPA and DHA without the need of conversion process. The enzyme delta 6 desaturase is required to begin the conversion of ALA.

…

Schematic representation of fatty acid transport mediated by fatty acid binding/transport proteins. The family of FATPs, FAT, FABPpm and MFSD2A facilitate the uptake of fatty acids into tissues. However, the FATPs also possess ACSL activity and facilitate the flux of fatty acids across membranes secondary to metabolic effects. After uptake, fatty acids are bound by cytoplasmic FABPs. Fatty acids can undergo a number of metabolic fates. Fatty acid transport proteins modulate cognition by influencing brain fatty acid transport and therefore by modulating the supply of the needed fatty acids to the brain.

…

DHA metabolites formation and function in the brain. DHA is converted into maresin 1(MaR1), neuroprotectin D1(NPD1) and resolvins by human 12-LOX, 15-LOX and CYP or aspirin-treated COX-2 enzymatically. These metabolites have multiple functions in the brain, which have been mentioned in the upper and lower boxes. DHA is metabolised by P450 system, cyclooxygenase, and lipoxygenase enzymes under different metabolic conditions.

…

Functions of DHA metabolites.

…

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Contents lists available at ScienceDirect

International Journal of Developmental Neuroscience

journal homepage: www.elsevier.com/locate/ijdevneu

Review

Docosahexaenoic acid,22:6n-3: Its roles in the structure and function of the

brain

Rahul Mallick

, Sanjay Basak

, Asim K. Duttaroy

c,⁎

Department of Biotechnology and Molecular Medicine, A.I. Virtanen Institute for Molecular Sciences, University of Eastern Finland, Finland

ICMR-National Institute of Nutrition, Hyderabad, India

Department of Nutrition, Institute of Basic Medical Sciences, Faculty of Medicine, University of Oslo, Norway

ARTICLE INFO

Keywords:

Docosahexaenoic acid,22:6n-3

Cognitive

Brain development

Endocannabinoid system

Marine oil

Neurogenesis

Resolvins

Clinical trials

DHA uptake

FABPs

Brain disorders

ABSTRACT

Docosahexaenoic acid,22:6n-3 (DHA) and its metabolites are vital for the structure and functional brain de-

velopment of the fetus and infants, and also for maintenance of healthy brain function of adults. DHA is thought

to be an essential nutrient required throughout the life cycle for the maintenance of overall brain health. The

mode of actions of DHA and its derivatives at both cellular and molecular levels in the brain are emerging. DHA

is the major prevalent fatty acid in the brain membrane. The brain maintains its fatty acid levels mainly via the

uptake of plasma free fatty acids. Therefore, circulating plasma DHA is signiﬁcantly related to cognitive abilities

during ageing and is inversely associated with cognitive decline. The signaling pathways of DHA and its me-

tabolites are involved in neurogenesis, antinociceptive eﬀects, anti‐apoptotic eﬀect, synaptic plasticity, Ca

homeostasis in brain diseases, and the functioning of nigrostriatal activities. Mechanisms of action of DHA

metabolites on various processes in the brain are not yet well known. Epidemiological studies support a link

between low habitual intake of DHA and a higher risk of brain disorders. A diet characterized by higher intakes

of foods containing high in n‐3 fatty acids, and/or lower intake of n‐6 fatty acids was strongly associated with a

lower Alzheimer's Disease and other brain disorders. Supplementation of DHA improves some behaviors asso-

ciated with attention deﬁcit hyperactivity disorder, bipolar disorder, schizophrenia, and impulsive behavior, as

well as cognition. Nevertheless, the outcomes of trials with DHA supplementation have been controversial. Many

intervention studies with DHA have shown an apparent beneﬁt in brain function. However, clinical trials are

needed for deﬁnitive conclusions. Dietary deﬁciency of n‐3 fatty acids during fetal development in utero and the

postnatal state has detrimental eﬀects on cognitive abilities. Further research in humans is required to assess a

variety of clinical outcomes, including quality of life and mental status, by supplementation of DHA.

1. Introduction

α-Linolenic acid,18;3n-3 (ALA) and linoleic acid, 18:2n-6 (LA) are

the two essential fatty acids for human health. ALA is available in plant

oils, e.g., walnut, edible seeds (hemp, chia), canola, kukui, ﬂaxseed oil

and hemp oil whereas its long-chain polyunsaturated fatty acids

(LCPUFAs) eicosapentaenoic acid,20:5n-3 (EPA) and docosahexaenoic

acid, 22:6n-3 (DHA) are obtained from marine ﬁsh and oils. In healthy

young adults, consumed ALA from the diet can be converted into EPA

and DHA in little amount (Burdge and Wootton, 2002), but with age,

the conversion capability is reduced (Bradbury, 2011). DHA is, there-

fore, a conditionally essential fatty acid for human health. DHA inﬂu-

ences numerous processes in the body, e.g., signal transduction, mem-

brane structure and function, cellular proliferation, inﬂammation,

https://doi.org/10.1016/j.ijdevneu.2019.10.004

Received 22 August 2019; Received in revised form 10 October 2019; Accepted 11 October 2019

Abbreviations: AA, arachidonic acid; AD, Alzheimers disease; ADHD, attention deﬁcit hyperactivity disorder; ALA, α-linolenic acid, 183n-3; APOE, apolipoprotein E;

B-FABP, brain-fatty acid-binding proteins; COX, cyclooxygenase; CYP, cytochrome P450; DHA, docosahexaenoic acid,226n-3; EDPs, epoxydocosapentaenoic acids;

EPA, eicosapentaenoic acid,205n-3; EFOX, electrophilic oxo-derivatives; FABP, fatty acid-binding proteins; FAHFA, fatty acid esters of hydroxy fatty acids; FADS2,

delta 6 desaturase enzyme; GPRs, G-protein coupled receptors; H-FABP, heart-fatty acid-binding proteins; HPA, hypothalamus-pituitary-adrenal; HDoHE, hydro-

xydocosahexaenoic acids; HpDHA, DHA hydroperoxides; LCPUFA, long-chain polyunsaturated fatty acids; MaR1, maresin 1; NPD1, neuroprotectin D1; LOX, li-

poxygenases; NO, nitric oxide; PEMT, phosphatidyl ethanolamine–N–methyltransferase; p-FABPpm, placental plasma membrane fatty acid-binding protein; PPAR,

peroxisome proliferator-activated receptor; PPAR-α, peroxisome proliferator-activated receptor α; PPAR-γ, peroxisome proliferator-activated receptor gamma;

PUFAs, polyunsaturated fatty acids; RXR, retinoid X receptor specialized pro-resolving mediators

⁎

Corresponding author at: Faculty of Medicine, University of Oslo, P.O.B. 1046 Blindern, N-0316, Oslo, Norway.

E-mail address: a.k.duttaroy@medisin.uio.no (A.K. Duttaroy).

International Journal of Developmental Neuroscience 79 (2019) 21–31

Available online 17 October 2019

angiogenesis and host of other processes aﬀecting health and disease

(Basak et al., 2013;Bradbury, 2011;Quinn et al., 2010b). DHA meta-

bolites also play a signiﬁcant role in diﬀerent biological and cellular

processes. Risk of inﬂammatory disorders, cognitive disorders, in-

suﬃcient brain growth and development may occur due to low intake

of DHA and its precursor EPA (Quinn et al., 2010b). DHA is also re-

commended to treat cardiovascular disease (CVD) risk factors such as

hypercholesterolemia, hypertriglyceridemia, and hypertension (Mori

et al., 2000a,b). Higher intake of DHA is usually recommended to

prevent CVD. EPA is mostly involved in cell signalling, whereas DHA is

mainly used for cell membrane structure and function (Bradbury, 2011;

Innis, 2008). However, recently several studies demonstrated the sig-

nalling pathways of DHA metabolites in the brain. A signiﬁcant number

of reviews are available on DHA and human brain (Bradbury, 2011;

Brenna and Carlson, 2014;Salem and Eggersdorfer, 2015;Sun et al.,

2018). This review describes the roles of DHA and its metabolites in the

structure and function of the human brain.

2. DHA uptake and metabolism in human

DHA is mostly deposited in the brain and retina, whereas its dis-

tribution in other tissues such as heart, liver, skeletal muscle, adipose

tissue, blood cell is low. The most signiﬁcant n-3 fatty acid present in

the brain is DHA, whereas EPA and ALA are present in very small

amounts. DHA constitutes over 90% of the n-3 PUFAs in the brain and

constitutes 10%–20% of its total lipids (Brenna and Carlson, 2014).

DHA is especially found in the grey matter (Suzuki et al., 1997). In a

cellular context, DHA is esteriﬁed into the cell membrane phospholipids

mostly in phosphatidylethanolamine and phosphatidylserine and other

complex lipids (Calder, 2016). Following insertion into the cell mem-

brane, DHA interacts with cholesterol that inﬂuences the membrane

phospholipid width by packing constraints and conformation of ad-

jacent phospholipid acyl chains (Sherratt and Mason, 2018). Physical

nature of DHA increases electron density in the phospholipid head

group region within the cell membrane, which attributes rapid con-

formational changes. Owing to the unique structure, DHA is capable of

providing a wide range of cell membrane structure and functions. Thus,

DHA aﬀects diﬀerent biophysical characteristics and physiological

processes such as membrane ﬂuidity, lipid raft function, neuro-

transmitter release, membrane receptors, gene expression, signaling

pathways, myelination, inﬂammation, and cell growth and diﬀer-

entiation (Duttaroy, 2016;O’Brien and Sampson, 1965;Sun et al.,

2018;Suzuki et al., 1997). Depending on the maternal supply of ALA,

EPA or DHA, DHA accumulates in the fetal brain during the last period

of pregnancy. The brain’s frontal lobes are more responsive to DHA

supply in adolescent and older adults for executive and higher-order

cognitive activities (Goustard-Langelier et al., 1999).

EPA plays a dominant role in inhibiting delta-5-desaturase enzyme-

mediated production of the arachidonic acid,20:4n-6(AA). Therefore,

the AA derived pro-inﬂammatory eicosanoids (prostaglandins, throm-

boxanes, leukotrienes) are inhibited by EPA intake in the diet. Also,

EPA competes with AA for phospholipase A

enzyme. These are unique

roles of EPA whereas DHA neither ﬁts the catalytic site of delta-5-de-

saturase enzyme nor competes with AA for phospholipase A

enzyme

due to its massive spatial structure. Unlike DHA, EPA level is not high

enough in the brain to contribute to neurological function. EPA is re-

ported to be rapidly oxidized in the brain (Chen et al., 2009).

While EPA inhibits the delta-5-desaturase enzyme that directly in-

hibits AA, DHA inhibits another role-playing enzyme delta-6-desaturase

enzyme that involves in LA metabolism (Sato et al., 2001). Due to more

massive spatial structure, DHA sweeps out a higher volume of ﬂuid in

the membrane than EPA which increases in membrane ﬂuidity for

critical synaptic vesicles and the retina to transmit signals from the

surface of the membrane to the interior of the nerve cells. DHA may also

involve in the breakup of lipid rafts in membranes due to its continuous

sweeping motion (Chapkin et al., 2008). As a result, cancer cells cannot

survive, and inﬂammatory cytokines struggle to initiate signaling re-

sponses (Li et al., 2005). The spatial characteristics of DHA cause an

increase in the LDL particle sizes comparatively, which reduces the

entry of LDL particles into arterial muscle cells to develop athero-

sclerosis lesions (Mori et al., 2000a).

3. Dietary and metabolic sources of DHA and its worldwide

consumption

DHA and EPA are present together ubiquitously in marine mammals

and plant plankton, whereas all terrestrial plants contain ALA. DHA and

EPA are present in marine sources as triacylglycerols and phospholi-

pids. Usually, 100 g of cooked salmon ﬁsh contains 500–1500 mg DHA.

Caviar, anchovies, mackerel, and herring are the other high sources of

DHA (Agriculture, 2005). Beef, lamb, pork, and chicken contain around

0.02 gm of DHA per 100 gm of meat (Calder, 2016). Although DHA is

mainly obtained from marine ﬁsh sources, nowadays, DHA is com-

mercially manufactured from microalgal sources such as Crypthecodi-

nium cohnii and Schizochytrium (Ulven and Holven, 2015). The meta-

bolic biosynthesis of DHA via a series of elongation, desaturation, and

beta-oxidation reactions from EPA is known as “Sprecher’s Shunt”

(Burdge et al., 2002;Burdge and Wootton, 2002). Maternal DHA sup-

plementation can contribute to brain and visual development and

function of the fetus and the infant. Maternal breast milk also contains

DHA around 0.32% of total fatty acid (Calder, 2016). N-3 LC-PUFA

dietary supplements are widely available, usually in the triacylglycerol,

non-esteriﬁed fatty acid, and ethyl ester forms. The ﬁsh oil supplements

are reported not only have n-3 LCPUFA contents well below those

claimed by labels but are also considerably oxidized(Albert et al.,

2015); however, the associated health implications of consuming oxi-

dized LCPUFAs are unclear(Myhrstad et al., 2016)

The human body converts ALA to EPA and DHA via desaturases and

elongases pathways. ALA and LA compete for the same desaturase and

elongase in order to form their respective LCPUFA metabolites (Chilton

et al., 2014;Duttaroy, 2009). Low levels of vitamin B6, magnesium,

zinc and ageing reduce the delta 6 desaturase activity. The activity of

delta-6-desaturase is also blocked by trans fats, present in hydrogenated

oils, fast foods, and many packaged foods. The delta 6 desaturase ac-

tivity is decreased in chronic alcoholism and in diabetes. Delta 5 de-

saturase is inhibited by deﬁciencies of vitamin C, niacin and zinc.

Higher intakes of LA can dominate these enzymes, especially the delta 6

desaturase enzyme (FADS2); thus biosynthesis of EPA and DHA from

ALA is reduced. So, consumption of the higher amount of ALA can in-

crease DHA level to some extent; however, this may not increase plasma

DHA in humans suﬃciently (Neﬀet al., 2010;Plourde and Cunnane,

2008). Fig. 1 shows the conversion of dietary ALA to EPA and DHA. In

order to increase the DHA level in the body, dietary supplementation of

DHA is the most preferred strategy (Cunnane et al., 2013). The synth-

esis of DHA from ALA by elevating levels of enzymes such as FADS2 and

elongase 2 by curcumin is promising. Interestingly, curcumin also en-

hances DHA absorption (Wu et al., 2015). Curcumin is widely con-

sumed as a cooking spice in Indian sub-continent; therefore, the low

intake of DHA in this population may be compensated by the curcumin

intake. Another nutraceutical, quercetin enhanced the anti-in-

ﬂammatory eﬀects of DHA on LPS-stimulated inﬂammatory response in

microglial cells (Sun et al., 2019). These studies indicate that the cer-

tain phytochemicals may enhance the synthesis, bioavailability and

functionalities of DHA; however, further work is required to promote

the role of these phytochemicals in DHA mediated human health ef-

fects.

Retro-conversion of DHA to EPA occurs in the peroxisomes via β-

oxidation to remove the double bond at position 4. Retro-conversion of

DHA is more common in non-neural cells than neural cells (Park et al.,

2016). However, recently it was shown that increased plasma level of

EPA in human following DHA supplementation did not occur via retro-

conversion rather a result of slowed metabolism and/or accumulation

R. Mallick, et al. International Journal of Developmental Neuroscience 79 (2019) 21–31

of plasma EPA (Metherel et al., 2019). During the last 30 years or so,

the increasing incidence of several metabolic diseases are thought to be

due to the results of high dietary intake of n-6 fatty acid containing

foods and oils compared with n-3 fatty acids, thus increased the ratio of

n-6:n-3 fatty acids (20:1) intake to a much higher level than the re-

commended ratio for optimal health beneﬁts (Simopoulos, 2016).

DHA intake among developed countries varies a lot. DHA intake is

the highest among the people in Iceland (793.4 mg/day). Even in the

USA, daily DHA intake is around 3.5 times lower than that of Iceland.

Among the Scandinavian countries, Danish people consume the highest

level of DHA (232.3 mg/day). The highest and lowest DHA consump-

tion levels in developing countries by the people of Maldives

(1409.3 mg/day) and Ethiopia (7.01 mg/day) respectively. Estimated

dietary intake indicate that the people from India consume only

52.1 mg DHA/day, while people from Bangladesh consume 167 mg

DHA/day through diet. Pakistanis (24 mg/day) and Nepalese (23.2 mg/

day) consume the lowest level of DHA among all South-Asian countries

(Forsyth et al., 2016). Overall, the daily intake of DHA as a per cent of

daily total energy intake (% energy) from food sources is highest in

Japan (0.152%) followed by China (0.090%), USA and Canada

(0.055%). The people from Oceania and Europe continents consume

0.052% DHA of total energy intake. However, these data had several

limitations including the fact that the data did not directly measure

food consumption but instead reﬂected the food supply in a certain

country and might not accurately reﬂect the real intake of DHA. DHA

consumption is lowest in low-income countries (Forsyth et al., 2016).

The countries having access to coastal areas consume a greater amount

of seafood, and therefore, dietary intake of DHA in these countries is

quite higher than other countries comparatively. N-3 PUFA intake of

0.5–2.0% of total energy is recommended for adults. Dietary intakes of

0.1-0.18% DHA of total energy for infants above six months old and

10–12 mg of DHA/Kg body weight for infants aged up to six months are

recommended (WHO and FAO, 2008). Pregnant or breastfeeding mo-

thers are advised to consume 200 mg of DHA, or 300–900 mg of com-

bined EPA and DHA per person per day. Vegetarians and vegans can

take microalgae supplements that contain DHA (Davis and Kris-

Etherton, 2003;Yurko-Mauro et al., 2010). The European Food Safety

Authority (EFSA) recommended a maximum dose of 5 g/day of

EPA + DHA as safe (EFSAReport, 2019).

4. DHA and its impact on the structure and function of the brain

As a crucial structural membrane component of the brain, DHA is

present in the cerebral cortex, synaptic membrane regions, retinal mi-

tochondria, and photoreceptors. Brain and retina tissues contain around

40% and 60% DHA of total PUFAs, respectively. DHA is present in high

amounts in retinal photoreceptors and is therefore essential for visual

function(Liu et al., 2011). Animal studies and human observational

studies have suggested that there is an inverse relationship between

dietary intake of n-3 LCPUFAs and the risk of developing age‐related

macular degeneration. The data from intervention trials have been

mixed, although the delayed progression of an intermediate type of

age‐related macular degeneration was reported earlier (Huang et al.,

2008). The later studies did not ﬁnd any positive eﬀect on the age-

related macular after supplementation with n-3 LCPUFAs (Souied et al.,

2015;Wu et al., 2017). The X-linked retinitis pigmentosa was shown to

be improved with DHA supplementation (Hoﬀman et al., 2004). The

recent clinical trial did not observe such improvement for X-linked re-

tinitis pigmentosa(Hoﬀman et al., 2014). However, some positive ef-

fects, such as the reduced elevation in ﬁnal dark-adapted thresholds and

slowed loss of the visual ﬁeld sensitivity, were observed (Hoﬀman et al.,

2015).

Neuronal cell membranes contain approximately 50% DHA (Calder,

2016;Singh, 2005). DHA contributes around 15% of the total fatty acid

composition in the adult prefrontal cortex. DHA is important for hip-

pocampal and cortical neurogenesis, neuronal migration, and out-

growth (Calderon and Kim, 2004;Cao et al., 2005;Kawakita et al.,

2006). DHA suppresses cell death by promoting cell-cycle exit in neuro-

progenitor cells (Insua et al., 2003;Kawakita et al., 2006). Along with

other fatty acids, DHA has a signiﬁcant role in monoaminergic and

cholinergic systems during brain development (Aïd et al., 2003;Chalon,

2006;Innis, 1991). Prenatal DHA supply has a long term eﬀect on

serotonergic and dopaminergic neurotransmission (Anderson et al.,

2005;Chalon, 2006) indicating the importance of DHA as a nutrient in

early brain development. DHA inﬂuences gene expression, neuro-

transmission, and oxidative stress (Innis, 2018). DHA is an essential

factor for neurogenesis, phospholipid synthesis, and turnover (Coti

Bertrand et al., 2006;Kawakita et al., 2006;Salem et al., 2001).

The brain is atrophied in diﬀerent neurodegenerative diseases.

Brain atrophy is also associated with age and cognitive degradation.

Various studies showed that DHA could improve learning and memory,

along with neuronal loss reduction (Weiser et al., 2016). DHA accu-

mulates during intrauterine fetal brain growth and maintains its levels

lifelong (Carver et al., 2001). DHA accumulation in the fetal brain is

highest during the third trimester of pregnancy. DHA incorporation into

brain membrane in early life solely depends on its supply via the pla-

centa, breastfeeding, and endogenous LCPUFAs production (Duttaroy,

2016;Innis, 2008;Lauritzen et al., 2016). DHA has a signiﬁcant role in

both brain and retinal development (Authority, 2011;Lauritzen et al.,

2016). Since the brain has a critical developmental window in utero as

Fig. 1. DHA synthesis in the body.

The plant source provides us ALA is converted

to EPA and DHA. The desaturations and elon-

gations occur in the endoplasmic reticulum,

and the β-oxidation occurs in the peroxisome,

to where 24-carbon PUFA are transferred. The

animal source provides us with EPA and DHA

without the need of conversion process. The

enzyme delta 6 desaturase is required to begin

the conversion of ALA.

R. Mallick, et al. International Journal of Developmental Neuroscience 79 (2019) 21–31

well as during the postnatal life, therefore, any perturbations such as

nutritional and environmental or postnatal nutrition would sig-

niﬁcantly aﬀect brain development. During critical periods of devel-

opment, any perturbation leads to profound and potentially irreversible

defects of brain maturation. A signiﬁcant linear relationship between

maternal DHA level and umbilical cord plasma phospholipid contents

are observed (Calder, 2016). Optimal placental growth and develop-

ment are crucial for the eﬀective exchange of nutrients and waste

products between the mother and the fetus (Basak et al., 2013). The

growing fetus mostly depends on the placental supply of maternal DHA

due to its limited DHA synthetic capacity (Duttaroy, 2000). Aberrant

placental development with a deranged vasculature may inﬂuence fetal

development and survival (Duttaroy, 2016). Recent studies suggested

that DHA has a role in early placentation processes along with the brain

and retinal development during the last trimester of pregnancy (Basak

et al., 2013;Duttaroy, 2000;Johnsen et al., 2011). Preferential transfer

of maternal DHA to the fetus during the last trimester of pregnancy was

suggested to be performed by the high-aﬃnity placental plasma mem-

brane fatty acid-binding protein (p-FABPpm) (Duttaroy, 2009).

Intracellular DHA is transported by FABPs (please see details on

FABP in the next section). DHA is the ligand for peroxisome pro-

liferator-activated receptor gamma (PPAR-γ), which is expressed in the

embryonic mouse brain and neural stem cells. The critical early brain

development regulator, PPAR-γheterodimerizes with the retinoid X

receptor (RXR) and regulates the transcription of target genes (Wada

et al., 2006). DHA is one of the key ligands for brain RXR (Lengqvist

et al., 2004). Along with retinoic acid receptor, RXR plays an important

role in embryonic neurogenesis, neuronal plasticity, and catecholami-

nergic neuron diﬀerentiation. RXR is highly expressed in the hippo-

campus (Lengqvist et al., 2004;Rioux and Arnold, 2005). As a free

radical scavenger, DHA protects the developing brain from peroxidative

damages of lipid and protein (Cao et al., 2004;Green et al., 2001;

Okada et al., 1996).

5. Fatty acid transport and metabolism in the human brain

It is generally assumed that the transport of fatty acids to the tissues

occurs in the form of the non-esteriﬁed pool of fatty acids (FFAs) bound

to serum albumin. The plasma FFAs is transferred across the cell via

fatty acid membrane transporters (FAT, FABPpm. FATP) and cyto-

plasmic fatty acid-binding proteins (FABPs) (Duttaroy, 2009). Fig. 2

summarises the putative roles of fatty acid-binding/transport proteins

in the uptake of free fatty acids. Recent studies showed that the

mammalian brain uniquely takes up DHA in the form of lysopho-

sphatidylcholine (LPC-DHA) (Chan et al., 2018). LPC-DHA uptake is

mediated by the major facilitator superfamily domain-containing pro-

tein 2 (Mfsd2 or Mfsd2a) present at the blood-brain barrier (Nguyen

et al., 2014). Therefore it may be necessary to increase the plasma level

of LPC-DHA for eﬃcient enrichment of brain DHA in human, however

further work is required for conﬁrmation. An essential requirement

common to both prenatal and postnatal brain development is the bio-

synthesis of a huge amount of membrane phospholipid, the origin of

which was believed to be exclusively derived from de novo biosynthesis

within cells of the brain, and acquisition of essential fatty acids from the

periphery into the developing brain. A major function of DHA during

brain development is to regulate SREBP-1 and SREBP-2 activity re-

sulting in major changes in phospholipid saturation(Huang et al.,

2017). FABP is thought to play a crucial role in the cytoplasmic fatty

acid transfer and thus help fatty acids aﬀect gene expression and

synthesis of other metabolites. There are two types of FABPs available

in the brain: (1) B-FABP, which is found in ventricular germinal and

glial cells in the embryonic brain and in the astrocytes of developing

and adult brains and (2) H-FABP, which is only available in adult brains

(Owada et al., 2006;Veerkamp and Zimmerman, 2001). DHA has a

preference for binding with B-FABP that may be necessary for early

neurogenesis or neuronal migration (Owada et al., 2006).

Fatty acid metabolism is one of the vital steps for energy require-

ment in the brain. Brain gets 20% of total energy from β-oxidation of

fatty acid in mitochondria of astrocytes. In the pre-oxidation step, fatty

acids are initially converted to fatty acyl-CoA by acyl-CoA synthases.

Besides mitochondria, peroxisome also plays a signiﬁcant role in fatty

acid metabolism. Peroxisome proliferator-activated receptor α(PPAR-

α) stimulates the expression of catabolic enzymes, such as the CPT fa-

mily, and acyl-CoA dehydrogenases in low energy status (Tracey et al.,

2018). Through the β-oxidation, very long and branched-chain fatty

acids are oxidized to shorten them. Also, α-oxidation clears a single

carbon from fatty acids that are incapable of typical β-oxidation in

peroxisome (Tracey et al., 2018). The peroxisomal β-oxidation is unable

to breakdown the full fatty acids, while mitochondria degrade the fatty

acids completely via the tricarboxylic acid pathway (Tracey et al.,

2018). However, for energy production, utilization of fatty acids is in-

creased signiﬁcantly during fasting or extreme exertion which may

damage the brain due to reactive oxygen species, speciﬁcally in the

form of superoxide (Tracey et al., 2018).

Another important pathway for the utilization of fatty acids in brain

astrocytes is the ketogenesis pathway. Ketone bodies may form from

fatty acid-derived acetyl-CoA in the hypoglycemic condition. In suitable

condition, these ketone bodies are lysed again into acetyl-CoA, which

again enter into the tricarboxylic acid cycle (Tracey et al., 2018).

6. Roles of DHA and its metabolites in brain function

As an integral component of cell membrane phospholipid, DHA

contributes to maintaining membrane ﬂuidity and lipid raft assembly

and other membrane functions. DHA inﬂuences electrical, chemical,

hormonal, or antigenic signals of the cells. One study demonstrated that

higher signal transduction mediated by two DHA molecules than no or

one DHA molecule along with other highly unsaturated fatty acids in

the phospholipid bilayer (Calder, 2016). DHA acts via cell membrane

surface and intracellular receptors. DHA promotes membrane-asso-

ciated G-protein-coupled receptor (GPR)120 mediated gene activation

to promote anti-inﬂammatory conditions (Oh et al., 2014). DHA also

activates PPARs and upregulates PPAR targeted genes to increase in-

sulin sensitivity, reduce plasma triglyceride level and inﬂammation

(Calder, 2016). Dietary intervention plays a signiﬁcant role to maintain

healthy brain function, which prevents stress, depression, and brain

degenerative disorders (McEwen, 2010;Sun et al., 2018). The bene-

ﬁcial eﬀects of DHA are mediated by the fatty acid itself (PPAR ligand)

as well as by its bioactive metabolites. DHA and its metabolites have a

wide range of actions at diﬀerent levels and sites (Diep et al., 2000;

Zúñiga et al., 2011). The DHA metabolites have a wide range of actions

at diﬀerent levels and sites. Table 1 summarizes various functions of

DHA metabolites. Bioactive DHA-derived specialized pro-resolving

mediators (SPMs), DHA epoxides, electrophilic oxo-derivatives (EFOX)

of DHA, neuroprostanes, ethanolamines, acylglycerols, docosahex-

aenoyl amides of amino acids or neurotransmitters, and branched DHA

esters of hydroxy fatty acids are the metabolic end products of DHA

(Anderson and Taylor, 2012;Robertson et al., 2013). Also, epox-

ydocosapentaenoic acids (EDPs) and 22-hydroxydocosahexaenoic acids

(22-HDoHEs) are the metabolized from DHA (Kuda, 2017;Westphal

et al., 2011). 5-, 12- and 15-lipoxygenases (LOX), COX-2 and cyto-

chrome P450 (CYP) are the responsible enzymes for DHA metabolism.

Table 2 summarizes the enzymes responsible for DHA metabolism. As

most exigent by-products of DHA, resolvins are formed by either LOX15

or CYP or aspirin-treated COX-2 stimulation (Fig. 3)(Duvall and Levy,

2016;Sun et al., 2018). Although the LOX15 treated formed resolvins

are homologous to CYP, or aspirin-treated formed resolvins (Duvall and

Levy, 2016). As the potential inﬂammation resolution mediators, re-

solvins act through a diﬀerent GPR (Duvall and Levy, 2016;Serhan,

2014).

The neuroprotectors, resolvin D1, and aspirin-triggered resolvin D1

improve brain functions and impair neuronal death by downregulating

R. Mallick, et al. International Journal of Developmental Neuroscience 79 (2019) 21–31

NF-kB, TLR4, CD200, and IL6R (Bisicchia et al., 2018;Recchiuti et al.,

2010). They induce remote functional recovery after brain damage

(Bisicchia et al., 2018). Resolvin D2 and aspirin-triggered resolvin D2

protect from cerebral ischemic injury through ERK1/2 phosphorylation

followed by stimulation of nNOS or eNOS to inhibit programmed

neuronal cell death and increase zonula occludens-1 for the main-

tenance of blood-brain barrier integrity (Zuo et al., 2018). Resolvin D3,

resolvin D5, aspirin-triggered resolvin D3, and aspirin-triggered re-

solvin D5 halt neuroinﬂammatory process (Dalli et al., 2013;Hong

et al., 2005). However, the functions of other resolvins are still not

known.

Table 3 shows the DHA-derived resolvins and their receptors with

functions.

Macrophage derived anti-inﬂammatory pro-resolving mediator;

maresins are biosynthesized from DHA in response to inﬂammation,

healing, and regeneration process (Ariel and Serhan, 2012;Stables

et al., 2011;Zhang and Spite, 2012). Maresin 1(MaR1) is the leading

subtype of maresins. Along with the reduction of LTB

production,

MaR1 stimulates macrophagic phagocytosis and eﬀerocytosis at the

inﬂammatory site (Serhan et al., 2015b,2012;Serhan et al., 2008).

MaR1 regulates stem cell diﬀerentiation to accelerate tissue repair

along with an analgesic role via TRPV1-mediated responses blockage

(Serhan et al., 2012;Yanes et al., 2010). MaR1 plays a role in the im-

provement of neurocognitive functions by regulating macrophage in-

ﬁltration, NF-κB signaling, oxidative stress, and after cytokine release

Maresin 1 attenuates neuroinﬂammation in a mouse model of perio-

perative neurocognitive disorders (Yang et al., 2019). Also, MaR1 has

shown signiﬁcant improvement of locomotive function in a post-spinal

cord injury model (Francos-Quijorna et al., 2017).

Neuroprotectin D1(NPD1) is one of the DHA derived SPMs, improve

brain cell survival, and repair in ageing and neurodegenerative diseases

(Bazan et al., 2011). Like MaR1, NPD1 also possesses anti-inﬂammatory

and neuroprotective activity (Balas and Durand, 2016). However, NPD1

has anti-apoptotic activity, which makes it unique from MaR1 (Ariel

Fig. 2. Schematic representation of fatty acid transport mediated by fatty acid binding/transport proteins.

The family of FATPs, FAT, FABPpm and MFSD2A facilitate the uptake of fatty acids into tissues. However, the FATPs also possess ACSL activity and facilitate the ﬂux

of fatty acids across membranes secondary to metabolic eﬀects. After uptake, fatty acids are bound by cytoplasmic FABPs. Fatty acids can undergo a number of

metabolic fates. Fatty acid transport proteins modulate cognition by inﬂuencing brain fatty acid transport and therefore by modulating the supply of the needed fatty

acids to the brain.

Table 1

Functions of DHA metabolites.

Types of metabolites Name of metabolites Eﬀects

Oxygenated metabolites Maresins Resolution of inﬂammation, wound healing, analgesic actions

Protectins Resolution of inﬂammation, neuroprotection

Resolvins Resolution of inﬂammation and wound healing

Electrophilic oxo-derivatives (EFOX) of DHA Anti-inﬂammatory, anti-proliferative eﬀects

Epoxides Anti-hypertensive, analgesic actions

Neuroprostanes Cardioprotection, wound healing

DHA conjugates Ethanolamines and glycerol esters Neural development, immunomodulation, metabolic eﬀects

Branched fatty acid esters of hydroxy fatty acids (FAHFA) Immunomodulation, resolution of inﬂammation

N-acyl amides Metabolic regulation, neuroprotection, neurotransmission

R. Mallick, et al. International Journal of Developmental Neuroscience 79 (2019) 21–31

et al., 2005;Serhan et al., 2015b). In response to neuroinﬂammation,

NPD1 is produced from endogenous DHA in retina and brain (Bazan,

2005;Calandria et al., 2009). Besides antiviral protection, NPD1 helps

in neurocognitive functions (García-Sastre, 2013;Morita et al., 2013;

Zhao et al., 2011). NDP1 can repress inﬂammation, oxidative stress,

and cell apoptosis induced by Ab 42 and promote neuronal survival.

NDP1 may prevent Alzheimer's disease progression through upregu-

lating PPARγ, amyloid precursor protein-α, and downregulating β-

amyloid precursor protein. Thus, the amyloid-βpeptide is reduced in

neuronal tissue (Zhao et al., 2011).

Anti-inﬂammatory signaling properties of EFOX and neuroprostanes

are beneﬁcial for diﬀerent neuroinﬂammatory disorders in association

with Parkinson’s disease, and Alzheimer’s disease (Dyall, 2015;Gladine

et al., 2014;Groeger et al., 2010). On the other hand, docosahexaenoyl

ethanolamide improves energy homoeostasis in association with mood,

pain modulation, anti-inﬂammation, hunger, and glucose uptake in the

brain through the endocannabinoid system (De Petrocellis et al., 1999;

Kim et al., 2014;Piazza et al., 2007;Soderstrom, 2004;Valenti et al.,

2005;Watanabe et al., 2003).

DHA glyceryl ester controls food intake and neuroinﬂammation in

the brain in the same fashion as docosahexaenoyl ethanolamide by

using the endocannabinoid system (D’Addario et al., 2014;Masoodi

et al., 2015). As an integral part of brain structure, the endocannabinoid

system has a signiﬁcant role in memory, cognition, and pain perception

(Wagner and Alger, 1996;Wilson and Nicoll, 2002). DHA conjugates

reduce neuroinﬂammation and cause neurogenesis by acting on can-

nabinoid receptors (Calder, 2013;Lu and MacKie, 2016).

Stress-induced hormone production via hypothalamus-pituitary-

adrenal (HPA) axis pathways can be regulated and modulated by nu-

tritional approaches (Lupien et al., 2009;Ranabir and Reetu, 2011).

The lipid is an integrated part of the brain, so fatty acid status should

have a relationship with stress (Laugero et al., 2011;O’Brien and

Sampson, 1965). Adequate dietary DHA supplementation lowers HPA

activation, corticosterone peak, and stress-induced weight loss (Chen

and Su, 2013;Hennebelle et al., 2012). Not only to alleviate short-term

stress, but DHA also has a signiﬁcant role in brain development, which

prevents anxiety and stress in later life (Robertson et al., 2013;Song

et al., 2008). Although, due to some conﬂicting precedents for asso-

ciation with PUFA supplementation and cognitive development, it has

become more critical to determine optimum DHA doses for eﬀective

neurodevelopment at diﬀerent ages (Qawasmi et al., 2012;Simmer

et al., 2011;Smithers et al., 2008). Stress stimulated TNF-alfa, and IFN-

γproduction, lipopolysaccharide (LPS) stimulated IL-6 production are

reduced by a signiﬁcantly higher level of DHA supplementation

Table 2

Enzymes responsible for DHA metabolism.

Enzymes Mode of action

5-, 12- and 15-lipoxygenases converts DHA to DHA hydroperoxides (HpDHA), which are further metabolized by hydrolases, and several members of the CYP superfamily

(Serhan et al., 2015b;Spite et al., 2014).

Cyclooxygenase-2 converts DHAinto resolvins when triggered with aspirin, EFOX (Groeger et al., 2010;Lima-Garcia et al., 2011).

CYP Epoxygenases such as CYP2C, CYP2J produce EDPs from DHA, while ω/(ω-1)-hydroxylases such as CYP4A, CYP4F produce 22-HDoHEs (Westphal

et al., 2011).

Fig. 3. DHA metabolites formation and function in the brain.

DHA is converted into maresin 1(MaR1), neuroprotectin D1(NPD1) and resolvins by human 12-LOX, 15-LOX and CYP or aspirin-treated COX-2 enzymatically. These

metabolites have multiple functions in the brain, which have been mentioned in the upper and lower boxes. DHA is metabolised by P450 system, cyclooxygenase, and

lipoxygenase enzymes under diﬀerent metabolic conditions.

R. Mallick, et al. International Journal of Developmental Neuroscience 79 (2019) 21–31

(Kiecolt-Glaser et al., 2011;Lucas et al., 2009;Maes et al., 2000;

Robertson et al., 2013).

Though stress and anxiety have a close relationship with depression,

DHA is suggested to be an important nutrient for preventing and

treating depression (Murray and Lopez, 1996;Robertson et al., 2013).

DHA has shown some beneﬁcial eﬀects in the treatment of various

psychiatric disorders, e.g., schizophrenia, unipolar and bipolar mood

disorders, anxiety disorders, obsessive-compulsive disorder, ADHD,

autism, aggression, hostility and impulsivity, borderline personality

disorder, substance abuse and anorexia nervosa (Bozzatello et al., 2016;

Sun et al., 2018). During the last decades several trials using n-3

LCPUFAs in mental diseases were performed. However, the ﬁndings of

most of the trials are controversial and inconclusive(Pusceddu et al.,

2016;Sun et al., 2018).

There is evidence that consumption of n-3 fatty acids containing

ﬁshes reduce depression (Hibbeln, 1998). However, the studies have

shown that EPA is more potent to treat depression than DHA (Bourre,

2005;Marangell et al., 2003;Peet and Horrobin, 2002). Lower pro-

inﬂammatory plasma IL-6 level and higher EPA/AA ratio have been

observed in PUFA treated depressed patients (Lin and Su, 2007).

Higher consumption of marine ﬁsh improves cognitive function

(Van Gelder et al., 2007). DHA has a signiﬁcant role in the reduction of

dementia risk (Schaefer et al., 2006). Neuroinﬂammation can be dam-

pened by DHA supplementation in the pathogenesis of Alzheimer’s

disease (Kinney et al., 2018;Trépanier et al., 2016). DHA derived anti-

inﬂammatory eicosanoids, neuroprotectins prevent Alzheimer's disease

pathogenesis (Lukiw et al., 2005). DHA regulates Alzheimer's disease-

related processes such as cholesterol and apolipoprotein E (APOE)

along with lipid raft assembly alteration and cell signalling regulation

(Boudrault et al., 2009;Hashimoto et al., 2005). Neuronal protection

against cytotoxicity, inhibition of nitrogen oxide production, calcium

inﬂux, activation of antioxidant enzymes (glutathione peroxidase and

glutathione reductase) and reduction of apoptosis are the signiﬁcant

molecular functions of DHA (Seidl et al., 2014). The second most pre-

valent neurodegenerative disease, Parkinson’sdisease is suggested to be

prevented by the neuroprotective role of DHA (Seidl et al., 2014). At-

tention deﬁcit hyperactivity disorder (ADHD) is another common

neurodevelopmental disorder among school-aged children that leads to

severe problems in social behavior. Studies showed evidence for the

successful treatment of a mild form of ADHD symptoms with DHA

supplementation (Kiliaan and Königs, 2016). Several reviews on DHA

supplementation in ADHD were published in recent years(Ramalho

et al., 2018;Sun et al., 2018). Despite the heterogeneity of the studies,

DHA may contribute to improvements in the capacity of reading,

learning, nonverbal cognitive development, perceptive visual capacity

and executive function of ADHD children. Future in depth large-scale,

well-designed randomized clinical trials are required to achieve

evidence for clinical recommendations.

Bipolar disorder of the brain is characterized by periods of depres-

sion and mania. DHA improves depressive symptoms of bipolar dis-

order by increasing N-acetyl-aspartate levels in the brain, but it has no

signiﬁcant eﬀects on the protection of mania (Bozzatello et al., 2016).

Intelligence quotient in children and cognitive function in the ageing

brain are improved by DHA supplementation (Lauritzen et al., 2016;

Weiser et al., 2016). Sun et al. (Sun et al., 2018)recently reviewed the

mechanistic relationships of brain DHA with diﬀerent mental disorders,

including autism. Interestingly the studies have been reported that EPA

in association with DHA improves outcome in cognitive function than

DHA alone. DHA can be divided into two diﬀerent types based on their

properties in brain function: lipid-bound DHA in membrane bilayer and

unesteriﬁed DHA (Innis, 2018). Lipid-bound DHA inﬂuences lipid

rafting, signal transduction, and neurotransmission (Chalon, 2006;

Grossﬁeld et al., 2006;Stillwell et al., 2005). On the other hand, reg-

ulation of gene expression and ion channel activities are related to

unesteriﬁed DHA properties (Bazan, 2006;Kitajka et al., 2002;

Vreugdenhil et al., 2002). DHA also inhibits cell migration, growth

arrest and apoptosis of brain tumor cells via activation of PPAR-γin the

nucleus (Mita et al., 2010).

7. DHA deﬁciency and human brain function

As an integral component of brain structure, fatty acids play a sig-

niﬁcant role in healthy brain function. Diﬀerent diseases/disorders,

e.g., Alzheimer's disease, Parkinson’s disease, Huntington’s disease,

schizophrenia, mood disorders, are linked due to altered membrane

fatty acid composition and their signalling in disease progression

(Bazinet and Layé, 2014;Shamim et al., 2018). The encephalopathy

“Reye syndrome”is causally associated with altered fatty acid oxidation

(Orlowski, 1999). A rare congenital peroxisome biogenesis disorder

called by "Zellweger syndrome," is linked with abnormal fatty acid

accumulation that impairs brain development (Crane, 2014). DHA de-

ﬁciency is linked with depressive disorder, bipolar disorder

(McNamara, 2010;McNamara et al., 2007).

The studies on pregnant women showed that DHA deﬁciency might

lead to poor language skill among children (Mulder et al., 2014). Even

autistic spectrum disorder or ADHD among teenagers is related to DHA

deﬁciency (Bos et al., 2015;Parellada et al., 2017). Due to DHA deﬁ-

ciency, neurocognitive functional insuﬃciency in young adults or

loneliness related memory problems in middle age has been observed

(Bauer et al., 2014;Jaremka et al., 2014). DHA deﬁciency in the third

trimester signiﬁcantly aﬀects brain development (Smith and Rouse,

2017).

Table 3

DHA-derived resolvins and their receptors with functions.

DHA-derived Resolvins Receptors Functions

Resolvin D1 •Stimulates GPR32 and FPR2 (Serhan et al., 2015a)

•Inhibits TRPV3, TRPV4 and TRPA1 (Serhan et al., 2015a)

•Anti-inﬂammatory (Qu et al., 2015)

•Analgesic (Farooqui, 2012)

Resolvin D2 •Stimulates GPR32, GRP18 and FPR2 (Lim et al., 2015;Shinohara and Serhan, 2016)

•Inhibits TRPV1 and TRPA1 (Lim et al., 2015;Shinohara and Serhan, 2016)

•Anti-inﬂammatory (Qu et al., 2015)

•Analgesic (Klein et al., 2014)

Resolvin D3 •Stimulates GPR32 (Serhan et al., 2015a)•Anti-inﬂammatory (Qu et al., 2015)

Resolvin D4 Unknown Unknown

Resolvin D5 •Stimulates GPR32 •Anti-inﬂammatory (Qu et al., 2015)

Resolvin D6 Unknown Unknown

Aspirin triggered resolvin D1 •Stimulates GPR32 and FPR2 (Lim et al., 2015;Serhan et al., 2015a) Inhibits TRPV3, TRPV4 and

TNFR (Lim et al., 2015;Serhan et al., 2015a)

•Anti-inﬂammatory (Qu et al., 2015)

•Analgesic (Farooqui, 2012)

Aspirin triggered resolvin D2 Unknown Unknown

Aspirin triggered resolvin D3 •Stimulates GPR32 (Serhan et al., 2015a)•Anti-inﬂammatory (Qu et al., 2015)

Aspirin triggered resolvin D4 Unknown Unknown

Aspirin triggered resolvin D5 Unknown Unknown

Aspirin triggered resolvin D6 Unknown Unknown

R. Mallick, et al. International Journal of Developmental Neuroscience 79 (2019) 21–31

8. Clinical trials of DHA supplementation and brain function

N-3 LCPUFAs supplementation is recommended worldwide for feto-

maternal and maternal-childhood growth and development, and cog-

nitive function of the child(Carlson et al., 2013;Julvez et al., 2016;

Koletzko et al., 2007;Parra-Cabrera et al., 2011). DHA supplementation

improved pregnancy outcome, gestation, reduction in early preterm

and very low birth weight, childhood visual and psychomotor devel-

opment (Carlson et al., 2013;Shulkin et al., 2018).

Several clinical studies were reported on n-3 LCPUFAs and mental

disorders. Some of these clinical trials and their health outcomes are

presented in Table 4. Most of the clinical studies did not show any

signiﬁcant eﬀects of DHA supplementation (Sun et al., 2018). Diﬀer-

ences in methodologies, the sample size, dietary habit, selection cri-

teria, age, choice and dosage of LCPUFAs (EPA, or DHA, or a combi-

nation of EPA + DHA) and the duration of the intervention are mostl

possibly responsible for inconclusive results(Sun et al., 2018).

9. Conclusions

The optimal structure and function of the brain are critical for

quality of life, productivity and individual growth. DHA and its meta-

bolites inﬂuence the brain’s development, structure and functions,

signaling pathways, receptor function, and enzyme activities. All these

functionalities are critical for optimum brain physiology throughout the

lifespan. In order to achieve these functionalities, sustained supply of

DHA is required well before conception, during the gestation period,

adolescence, adulthood and adult life. Therefore, maintaining optimal

levels of DHA in the brain are likely to be required throughout the

lifespan by obtaining preformed DHA via dietary or supplementation.

Several studies suggest that the consumption of DHA leads to many

inherent positive physiological and behavioral eﬀects, however further

clinical trials are required to assess diﬀerent clinical outcomes, in-

cluding mental health status and quality of life.

Declaration of Competing Interest

The authors declare no conﬂict of interest.

Acknowledgements

This study was supported by the Throne Holst Foundation and the

Faculty of Medicine, University of Oslo, Norway.

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Table 4

Various clinical studies of DHA supplementation in relation with brain function.

Study Experimental setting Observed outcome

The Kansas University DHA outcome study (KUDOS) Cognitive and behavioral development Improvement of visual attention among infants has been observed

with the reduction of preterm birth risk (Colombo et al., 2019).

DHA supplementation on developmental outcomes of

toddlers born preterm

Developmental outcomes of toddlers Daily supplementation of DHA didn’t improve cognitive function and

negative eﬀects on language development in certain subgroups of

children (Keim et al., 2018).

Eﬀect of DHA supplementation during pregnancy on

maternal depression and neurodevelopment of young

children

Neurodevelopmental outcome of children No reduction in postpartum depression in mothers nor improved

cognitive and language development in their oﬀspring during early

childhood (Makrides et al., 2009).

Neurodevelopmental outcomes of preterm infants fed high-

dose docosahexaenoic acid

Neurodevelopment at 18 months age. Did not increase Bayley mental development index scores of preterm

infants overall born earlier than 33 weeks, but improved the Bayley

mental development index scores of girls (Makrides et al., 2009)

Neurodevelopmental outcomes at 7 years' corrected age in

preterm infants who were fed high-dose DHA to term

equivalent

Cognitive outcome detected at 18 months

age

Did not show any evidence of beneﬁt (Collins et al., 2015).

Feeding preterm infants milk with a higher dose of DHA

than that used in current practice

Language or behavior in early childhood. Did not result in any clinically meaningful change to language

development or behavior when assessed in early childhood (Smithers

et al., 2008).

DHA supplementation in children with ADHD DHA supplementation for 4 months

decreases the symptoms or not

No statistically signiﬁcant improvement of ADHD symptoms(Voigt

et al., 2001)

Maternal consumption of a DHA-containing functional food

during pregnancy: memory tasks at age 9 months

Problem-solving abilities and recognition

memory

Enhancement of problem-solving

skills but not recognition skills

at 9 months of age of infants(Judge et al., 2007)

DHA supplementation slows cognitive decline in Alzheimer

disease or not

DHA supplementation in individuals with

mild to moderate Alzheimer disease

DHA supplementation led to no beneﬁcial

eﬀect on rate of cognitive and functional

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Effects of fatty acid metabolites on nocturia

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Feb 2022

Dysregulation of circadian rhythm can cause nocturia. Levels of fatty acid metabolites, such as palmitoylethanolamide (PEA), 9-hydroxy-10E,12Z-octadecadienoic acid (9-HODE), and 4-hydroxy-5E,7Z,10Z,13Z,16Z,19Z-docosahexaenoic acid (4-HDoHE), are higher in the serum of patients with nocturia; however, the reason remains unknown. Here, we investigated the circadian rhythm of fatty acid metabolites and their effect on voiding in mice. WT and Clock mutant (ClockΔ19/Δ19) mice, a model for nocturia with circadian rhythm disorder, were used. Levels of serum PEA, 9-HODE, and 4-HDoHEl were measured every 8 h using LC/MS. Voiding pattern was recorded using metabolic cages after administration of PEA, 9-HODE, and 4-HDoHE to WT mice. Levels of serum PEA and 9-HODE fluctuated with circadian rhythm in WT mice, which were lower during the light phase. In contrast, circadian PEA and 9-HODE level deteriorated or retreated in ClockΔ19/Δ19 mice. Levels of serum PEA, 9-HODE, and 4-HDoHE were higher in ClockΔ19/Δ19 than in WT mice. Voiding frequency increased in PEA- and 4-HDoHE-administered mice. Bladder capacity decreased in PEA-administered mice. The changes of these bladder functions in mice were similar to those in elderly humans with nocturia. These findings highlighted the novel effect of lipids on the pathology of nocturia. These may be used for development of biomarkers and better therapies for nocturia.

Oxidation of Polyunsaturated Fatty Acids as a Promising Area of Research in Infertility

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May 2022

In this review, the role of fatty acids (FA) in human pathological conditions, infertility in particular, was considered. FA and FA-derived metabolites modulate cell membrane composition, membrane lipid microdomains and cell signaling. Moreover, such molecules are involved in cell death, immunological responses and inflammatory processes. Human health and several pathological conditions are specifically associated with both dietary and cell membrane lipid profiles. The role of FA metabolism in human sperm and spermatogenesis has recently been investigated. Cumulative findings indicate F2 isoprostanes (oxygenated products from arachidonic acid metabolism) and resolvins (lipid mediators of resolution of inflammation) as promising biomarkers for the evaluation of semen and follicular fluid quality. Advanced knowledge in this field could lead to new scenarios in the treatment of infertility.

Metabolic and molecular evidence for long-chain PUFA biosynthesis capacity in the grass carp Ctenopharyngodon idella

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Full-text available

May 2022
COMP BIOCHEM PHYS A

There is a growing interest to understand the capacity of farmed fish species to biosynthesise the physiologically important long-chain (≥C20) n-3 and n-6 polyunsaturated fatty acids (LC-PUFAs), eicosapentaenoic acid (EPA), docosahexaenoic acid (DHA) and arachidonic acid (ARA), from their C18 PUFA precursors available in the diet. In fish, the LC-PUFA biosynthesis pathways involve sequential desaturation and elongation reactions from α-linolenic acid (ALA) and linoleic acid (LA), catalysed by fatty acyl desaturases (Fads) and elongation of very long-chain fatty acids (Elovl) proteins. Our current understanding of the grass carp (Ctenopharyngodon idella) LC-PUFA biosynthetic capacity is limited despite representing the most farmed finfish produced worldwide. To address this knowledge gap, this study first aimed at characterising molecularly and functionally three genes (fads2, elovl5 and elovl2) with putative roles in LC-PUFA biosynthesis. Using an in vitro yeast-based system, we found that grass carp Fads2 possesses ∆8 and ∆5 desaturase activities, with ∆6 ability to desaturase not only the C18 PUFA precursors (ALA and LA) but also 24:5n-3 to 24:6n-3, a key intermediate to obtain DHA through the “Sprecher pathway”. Additionally, the Elovl5 showed capacity to elongate C18 and C20 PUFA substrates, whereas Elovl2 was more active over C20 and C22. Collectively, the molecular cloning and functional characterisation of fads2, elovl5 and elovl2 demonstrated that the grass carp has all the enzymatic activities required to obtain ARA, EPA and DHA from LA and ALA. Importantly, the hepatocytes incubated with radiolabelled fatty acids confirmed the yeast-based results and demonstrated that these enzymes are functionally active.

Intranasal Administration of Nanovectorized Docosahexaenoic Acid (DHA) Improves Cognitive Function in Two Complementary Mouse Models of Alzheimer’s Disease

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Apr 2022

Polyunsaturated fatty acids (PUFAs) are a class of fatty acids that are closely associated with the development and function of the brain. The most abundant PUFA is docosahexaenoic acid (DHA, 22:6 n-3). In humans, low plasmatic concentrations of DHA have been associated with impaired cognitive function, low hippocampal volumes, and increased amyloid deposition in the brain. Several studies have reported reduced brain DHA concentrations in Alzheimer’s disease (AD) patients’ brains. Although a number of epidemiological studies suggest that dietary DHA consumption may protect the elderly from developing cognitive impairment or dementia including AD, several review articles report an inconclusive association between omega-3 PUFAs intake and cognitive decline. The source of these inconsistencies might be because DHA is highly oxidizable and its accessibility to the brain is limited by the blood–brain barrier. Thus, there is a pressing need for new strategies to improve DHA brain supply. In the present study, we show for the first time that the intranasal administration of nanovectorized DHA reduces Tau phosphorylation and restores cognitive functions in two complementary murine models of AD. These results pave the way for the development of a new approach to target the brain with DHA for the prevention or treatment of this devastating disease.

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Apr 2022
CLIN PERINATOL

Fatty acids are critical bioactives for fetal and neonatal development. Premature delivery and current nutritional strategies pose several challenges in restoring fatty acid balance in the preterm infant. The impact on fatty acid balance and outcomes using lipid emulsions, enteral nutrition, and enteral supplements are reviewed, including a summary of the most recent large clinical trials of enteral fatty acid supplementation for the preterm infant. Research gaps remain in successfully implementing nutritional strategies to optimize fatty acid status in preterm infants.

Neuroprotective effects of DHA-derived peroxidation product 4(RS)-4-F4t-neuroprostane on microglia

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Apr 2022
FREE RADICAL BIO MED

The abundance of docosahexaenoic acid (DHA) in brain membrane phospholipids has stimulated studies to explore its role in neurological functions. Upon released from phospholipids, DHA undergoes enzymatic reactions resulting in synthesis of bioactive docosanoids and prostanoids. However, these phospholipids are also prone to non-enzymatic reactions leading to more complex pattern of metabolites. A non-enzymatic oxidized product of DHA, 4(RS)-4-F4t-Neuroprostane (44FNP), has been identified in cardiac and brain tissues. In this study, we examined effects of the 44FNP on oxidative and inflammatory responses in microglial cells treated with lipopolysaccharide (LPS). The 44FNP attenuated LPS-induced production of reactive oxygen species (ROS) in both primary and immortalized microglia (BV2). It also attenuated LPS-induced inflammation through suppressing NFκB-p65 and levels of iNOS and TNFα. In addition, 44FNP also suppressed LPS-induced mitochondrial dysfunction and upregulated the Nrf2/HO-1 antioxidative pathway. In sum, these findings with microglial cells demonstrated neuroprotective effects of this 44FNP and shed light into the potential of nutraceutical therapy for neurodegenerative diseases.

Effects of glycerol and glucose on docosahexaenoic acid synthesis in Aurantiochyrium limacinum SFD-1502 by transcriptome analysis

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Mar 2022

Docosahexaenoic acid (DHA) has numerous functions in adjusting the organic health and pragmatic value in medicine and food field. In this study, we compared glycerol and glucose as the only carbon source for DHA production by Aurantiochytrium. When the glycerol concentration was 120 g/L, the maximum DHA yield was 11.08 g/L, and the DHA yield increased significantly, reaching 47.67% of the total lipid content. When the cells grew in glucose, the DHA proportion was 37.39%. Transcriptome data showed that the glycolysis pathway and tricarboxylic acid cycle in Aurantiochytrium were significantly inhibited during glycerol culture, which promoted the tricarboxylic acid transport system and was conducive to the synthesis of fatty acids by acetyl coenzyme A; glucose as substrate activated fatty acid synthesis (FAS)pathway and produced more saturated fatty acids, while glycerol as substrate activated polyketide synthase (PKS)pathway and produced more long-chain polyunsaturated fatty acids. This laid a foundation for fermentation metabolism regulation and molecular transformation.

Clinical Features, Diagnostic Evaluation, and Management of COVID-19 Patients

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Full-text available

Apr 2020
ADV EXP MED BIOL

Introduction: Severe acute respiratory syndrome-related coronavirus 2 (SARS-CoV-2)-associated coronavirus pandemic has posed a global health emergency. Methods: We focused on clinical features, diagnostic evaluation, management, infection prevention, and safe handling of deceased bodies with suspected and confirmed COVID-19. Results: The case fatality rate is estimated at around 3%. Diagnosis is by the demonstration of the virus in respiratory secretions by RT-PCR mainly. Common laboratory findings include average/low white cell counts with elevated C-reactive protein (CRP). The disease is mild in most people; in some (usually the elderly and those with comorbidities), it may progress to pneumonia, acute respiratory distress syndrome (ARDS), and multiple organ dysfunction syndromes (MODS). Conclusion: Treatment is primarily supportive; the role of antiviral agents is yet to be established. Prevention entails home isolation of suspected cases and those with mild illnesses and strict infection control measures at hospitals that include contact and droplet precautions.

Dietary Supplements in Chemotherapy-Induced Peripheral Neuropathy: A New Hope?

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Jan 2022

Chemotherapy-induced peripheral neuropathy (CIPN) is one of the main and most prevalent side effects of chemotherapy, significantly affecting the quality of life of patients and the course of chemotherapeutic treatment. Nevertheless, despite its prevalence, the management of the CIPN is considered particularly challenging, with this condition often being perceived as very difficult or even impossible to prevent with currently available agents. Therefore, it is imperative to find better options for patients diagnosed with this condition. While the search for the new agents must continue, another opportunity should be taken into consideration—repurposing of the already known medications. As proposed, acetyl-L-carnitine, vitamins (group B and E), extracts of medical plants, including goshajinkigan, curcumin and others, unsaturated fatty acids, as well as the diet composed of so-called “sirtuin-activating foods”, could change the typical way of treatment of CIPN, improve the quality of life of patients and maintain the continuity of chemotherapy. This review summarizes currently available data regarding mentioned above agents and evaluates the rationale behind future research focused on their efficacy in CIPN. View Full-Text

Integration of intestinal microbiota and metabonomic to elucidate different alleviation impacts of non-saponification and saponification astaxanthin pre-treatment on Paracetamol-induced oxidative stress in rats

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Jan 2022

Intestinal microbiota and metabonomic were integrated to investigate the efficiency of non-saponification or saponification astaxanthin (N-Asta or S-Asta) derived from Penaeus sinensis by-products on alleviating paracetamol (PCM)-induced oxidative stress. Pre-treated...

Quercetin Potentiates Docosahexaenoic Acid to Suppress Lipopolysaccharide-induced Oxidative/Inflammatory Responses, Alter Lipid Peroxidation Products, and Enhance the Adaptive Stress Pathways in BV-2 Microglial Cells

Article

Full-text available

Feb 2019
INT J MOL SCI

High levels of docosahexaenoic acid (DHA) in the phospholipids of mammalian brain have generated increasing interest in the search for its role in regulating brain functions. Recent studies have provided evidence for enhanced protective effects when DHA is administered in combination with phytochemicals, such as quercetin. DHA and quercetin can individually suppress lipopolysaccharide (LPS)–induced oxidative/inflammatory responses and enhance the antioxidative stress pathway involving nuclear factor erythroid-2 related factor 2 (Nrf2). However, studies with BV-2 microglial cells indicated rather high concentrations of DHA (IC50 in the range of 60–80 µM) were needed to produce protective effects. To determine whether quercetin combined with DHA can lower the levels of DHA needed to produce protective effects in these cells is the goal for this study. Results showed that low concentrations of quercetin (2.5 µM), in combination with DHA (10 µM), could more effectively enhance the expression of Nrf2 and heme oxygenase 1 (HO-1), and suppress LPS–induced nitric oxide, tumor necrosis factor-α, phospho-cytosolic phospholipase A2, reactive oxygen species, and 4-hydroxynonenal, as compared to the same levels of DHA or quercetin alone. These results provide evidence for the beneficial effects of quercetin in combination with DHA, and further suggest their potential as nutraceuticals for improving health.

Maresin 1 attenuates neuroinflammation in a mouse model of perioperative neurocognitive disorders

Article

Full-text available

Dec 2018

Background Resolution of inflammation is an active and dynamic process after surgery. Maresin 1 (MaR1) is one of a growing number of specialised pro-resolving lipids biosynthesised by macrophages that regulates acute inflammation. We investigated the effects of MaR1 on postoperative neuroinflammation, macrophage activity, and cognitive function in mice. Methods Adult male C57BL/6 (n=111) and Ccr2RFP/+Cx3cr1GFP/+ (n=54) mice were treated with MaR1 before undergoing anaesthesia and orthopaedic surgery. Systemic inflammatory changes, bone healing, neuroinflammation, and cognition were assessed at different time points. MaR1 protective effects were also evaluated using bone marrow derived macrophage cultures. Results MaR1 exerted potent systemic anti-inflammatory effects without impairing fracture healing. Prophylaxis with MaR1 prevented surgery-induced glial activation and opening of the blood–brain barrier. In Ccr2RFP/+Cx3cr1GFP/+ mice, fewer infiltrating macrophages were detected in the hippocampus after surgery with MaR1 prophylaxis, which resulted in improved memory function. MaR1 treatment also reduced expression of pro-inflammatory cell surface markers and cytokines by in vitro cultured macrophages. MaR1 was detectable in the cerebrospinal fluid of older adults before and after surgery. Conclusions MaR1 exerts distinct anti-inflammatory and pro-resolving effects through regulation of macrophage infiltration, NF-κB signalling, and cytokine release after surgery. Future studies on the use of pro-resolving lipid mediators may inform novel approaches to treat neuroinflammation and postoperative neurocognitive disorders.

Inflammation as a central mechanism in Alzheimer's disease

Article

Full-text available

Sep 2018

Alzheimer's disease (AD) is a progressive neurodegenerative disorder that is characterized by cognitive decline and the presence of two core pathologies, amyloid β plaques and neurofibrillary tangles. Over the last decade, the presence of a sustained immune response in the brain has emerged as a third core pathology in AD. The sustained activation of the brain's resident macrophages (microglia) and other immune cells has been demonstrated to exacerbate both amyloid and tau pathology and may serve as a link in the pathogenesis of the disorder. In the following review, we provide an overview of inflammation in AD and a detailed coverage of a number of microglia-related signaling mechanisms that have been implicated in AD. Additional information on microglia signaling and a number of cytokines in AD are also reviewed. We also review the potential connection of risk factors for AD and how they may be related to inflammatory mechanisms.

The lysolipid transporter Mfsd2a regulates lipogenesis in the developing brain

Article

Full-text available

Aug 2018
PLOS BIOL

Brain development requires a massive increase in brain lipogenesis and accretion of the essential omega-3 fatty acid docosahexaenoic acid (DHA). Brain acquisition of DHA is primarily mediated by the transporter Major Facilitator Superfamily Domain containing 2a (Mfsd2a) expressed in the endothelium of the blood-brain barrier (BBB) and other abundant cell types within the brain. Mfsd2a transports DHA and other polyunsaturated fatty acids (PUFAs) esterified to lysophosphatidylcholine (LPC-DHA). However, the function of Mfsd2a and DHA in brain development is incompletely understood. Here, we demonstrate, using vascular endothelial-specific and inducible vascular endothelial-specific deletion of Mfsd2a in mice, that Mfsd2a is uniquely required postnatally at the BBB for normal brain growth and DHA accretion, with DHA deficiency preceding the onset of microcephaly. In Mfsd2a-deficient mouse models, a lipidomic signature was identified that is indicative of increased de novo lipogenesis of PUFAs. Gene expression profiling analysis of these DHA-deficient brains indicated that sterol regulatory-element binding protein (Srebp)-1 and Srebp-2 pathways were highly elevated. Mechanistically, LPC-DHA treatment of primary neural stem cells down-regulated Srebp processing and activation in a Mfsd2a-dependent fashion, resulting in profound effects on phospholipid membrane saturation. In addition, Srebp regulated the expression of Mfsd2a. These data identify LPC-DHA transported by Mfsd2a as a physiological regulator of membrane phospholipid saturation acting in a feedback loop on Srebp activity during brain development.

Lipids: An insight into the neurodegenerative disorders

Article

Full-text available

May 2018

Brain development is a sequential anatomical process characterised by specific well-defined stages of growth and maturation. One of the fundamental and necessary events in the normal development of the central nervous system in vertebrates is the formation of a myelin sheath. This process is influenced by dietary lipids. A number of researches have indicated that the administration of a diet, deficient in essential fatty acids during development causes hypomyelination in the brain. Brain lipids determine the localization and function of proteins in the cell membrane and in doing so regulate synaptic signalling in neurons. Lipids may also function as transmitters and relay signals from the membrane to intracellular compartments or to other cells. Several experimental studies have suggested a crucial role of n-3 polyunsaturated fatty acids in membrane formation, as well as clinical role of glycerolipids, glycerophospholipids, and sphingolipids in the attenuation of depression- and anxiety-related behaviours. Hence it can be assumed that polyunsaturated fatty acids may also offer new treatment options (for example, targeted dietary supplementation or pharmacological interference with lipid-regulating enzymes). These lipids could be exploited for improved prevention and treatment. A very interesting and emerging approach in this direction is through ‘Lipidomics’ which is a relatively recent research field that has been driven by rapid advances in technologies such as mass spectrometry (MS), nuclear magnetic resonance (NMR) spectroscopy, fluorescence spectroscopy, dual polarisation interferometry and computational methods, coupled with the recognition of the role of lipids in many metabolic diseases such as obesity, atherosclerosis, stroke, hypertension and diabetes.

Resolvin D2 protects against cerebral ischemia/reperfusion injury in rats

Article

Full-text available

Dec 2018

Cerebral ischemia/reperfusion (I/R) injury is a critical factor leading to a poor prognosis for ischemic stroke patients. ω-3 fatty acid supplements taken as part of a daily diet have been shown to improve the prognosis of patients with ischemic stroke. In this study, we aimed to investigate the potential effects of resolvin D2 (RvD2), a derivative of ω-3 fatty acids, and its possible advantage on cerebral I/R injury in rats. Cerebral I/R caused by middle cerebral artery occlusion and reperfusion (MCAO/R) was established in Sprague-Dawley rats. First, in rats fed a regular diet, the MCAO/R stimulus led to a significant decrease in endogenous production of RvD2. Exogenous supply of RvD2 via intraperitoneal injection reversed MCAO/R-induced brain injury, including infarction, inflammatory response, brain edema, and neurological dysfunction. Meanwhile, RvD2 reversed the MCAO/R-induced decrease in the protein level of GPR18, which has been identified as a receptor for RvD2, especially in neurons and brain microvascular endothelial cells (BMVECs). Furthermore, RvD2 exerted rescue effects on MCAO/R-induced neuron and BMVEC death. Moreover, GPR18 antagonist O-1918 could block the rescue effects of RvD2, possibly at least partially though the GPR18-ERK1/2-NOS signaling pathway. Finally, compared with ω-3 fatty acid supplements, RvD2 treatment had a better rescue effect on cerebral infarction, which may be due to the MCAO/R-induced decrease in 5-lipoxygense phosphorylation and subsequent RvD2 generation. In conclusion, compared with ω-3 fatty acids, RvD2 may be an optimal alternative and complementary treatment for ischemic stroke patients with recanalization treatment.

Neuronal Lipid Metabolism: Multiple Pathways Driving Functional Outcomes in Health and Disease

Article

Full-text available

Jan 2018

Lipids are a fundamental class of organic molecules implicated in a wide range of biological processes related to their structural diversity, and based on this can be broadly classified into five categories; fatty acids, triacylglycerols (TAGs), phospholipids, sterol lipids and sphingolipids. Different lipid classes play major roles in neuronal cell populations; they can be used as energy substrates, act as building blocks for cellular structural machinery, serve as bioactive molecules, or a combination of each. In amyotrophic lateral sclerosis (ALS), dysfunctions in lipid metabolism and function have been identified as potential drivers of pathogenesis. In particular, aberrant lipid metabolism is proposed to underlie denervation of neuromuscular junctions, mitochondrial dysfunction, excitotoxicity, impaired neuronal transport, cytoskeletal defects, inflammation and reduced neurotransmitter release. Here we review current knowledge of the roles of lipid metabolism and function in the CNS and discuss how modulating these pathways may offer novel therapeutic options for treating ALS.

Compound-specific isotope analysis reveals no retroconversion of DHA to EPA but substantial conversion of EPA to DHA following supplementation: A randomized control trial

Article

Jun 2019
AM J CLIN NUTR

Background: It has long been believed that DHA supplementation increases plasma EPA via the retroconversion pathway in mammals. However, in rodents this increase in EPA is likely due to a slower metabolism of EPA, but this has never been tested directly in humans. Objective: The aim of this study was to use the natural variations in 13C:12C ratio (carbon-13 isotopic abundance [δ13C]) of n-3 PUFA supplements to assess n-3 PUFA metabolism following DHA or EPA supplementation in humans. Methods: Participants (aged 21.6 ± 2.2 y) were randomly assigned into 1 of 3 supplement groups for 12 wk: 1) olive oil control, 2) ∼3 g/d DHA, or 3) ∼3 g/d EPA. Blood was collected before and after the supplementation period, and concentrations and δ13C of plasma n-3 PUFA were determined. Results: DHA supplementation increased (P < 0.05) plasma EPA concentrations by 130% but did not affect plasma δ13C-EPA (-31.0 ± 0.30 to -30.8 ± 0.19, milliUrey ± SEM, P > 0.05). In addition, EPA supplementation did not change plasma DHA concentrations (P > 0.05) but did increase plasma δ13C-DHA (-27.9 ± 0.2 to -25.6 ± 0.1, P < 0.05) toward δ13C-EPA of the supplement (-23.5 ± 0.22). EPA supplementation increased plasma concentrations of EPA and docosapentaenoic acid (DPAn-3) by 880% and 200%, respectively, and increased plasma δ13C-EPA (-31.5 ± 0.2 to -25.7 ± 0.2) and δ13C-DPAn-3 (-28.9 ± 0.3 to -25.0 ± 0.1) toward δ13C-EPA of the supplement. Conclusions: In this study, we show that the increase in plasma EPA following DHA supplementation in humans does not occur via retroconversion, but instead from a slowed metabolism and/or accumulation of plasma EPA. Furthermore, substantial amounts of supplemental EPA can be converted into DHA. δ13C of n-3 PUFA in humans is a powerful and underutilized tool that can track dietary n-3 PUFA and elucidate complex metabolic questions. This trial was registered at clinicaltrials.gov as NCT03378232.

Docosahexaenoic acid supplementation for children with attention deficit hyperactivity disorder: A comprehensive review of the evidence

Article

Apr 2018

Attention deficit hyperactivity disorder (ADHD) is considered the most common behavioural disorder in school-age children. ADHD is a complex and multifactorial disorder characterised by a variety of symptoms, including concentration problems, excessive motor activity and impulsivity which interferes with execution of simple school tasks. Diagnosis has been essentially subjective, since no specific laboratory tests are available. However, ADHD remains overdiagnosed, probably due to social pressures for children to be successful in school from an early age, which leads parents to seek medical support. Although therapeutic approaches for ADHD have been essentially pharmacologic, in recent years several studies were performed to investigate the role of nutrition, especially omega 3 polyunsaturated fatty acid (omega 3-PUFA), in the development and treatment of this disorder. In this review, the authors gathered the most relevant evidence regarding omega 3-PUFA, mainly docosahexaenoic acid, as coadjutant or as a single therapy, in the management of ADHD symptoms. The authors also reviewed this disorder's current medical and therapeutic features.

Docosahexaenoic acid,22:6n-3: Its roles in the structure and function of the brain

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