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Fatty acid binding protein 7 (FABP7), abundant in the embryonic brain, binds with the highest affinity to docosahexaenoic acid (DHA) and is expressed in the early stages of embryogenesis. Here, we have examined the consequences of the exposure to different DHA levels and of the in utero depletion of FABP7 on early rat brain development. Neurodevelopment was evaluated through the contents of two proteins, connexin 43 (Cx43) and cyclin-dependent kinase 5 (CDK5), both involved in neuroblast proliferation, differentiation, and migration. The dams were fed with diets presenting different DHA contents, from deficiency to supplementation. DHA brain embryos contents already differed at embryonic day 11.5 and the differences kept increasing with time. Cx43 and CDK5 contents were positively associated with the brain DHA levels. When FABP7 was depleted in vivo by injections of siRNA in the telencephalon, the enhancement of the contents of both proteins was lost in supplemented animals, but FABP7 depletion did not modify phospholipid compositions regardless of the diets. Thus, FABP7 is a necessary mediator of the effect of DHA on these proteins synthesis, but its role in DHA uptake is not critical, although FABP7 is localized in phospholipid-rich areas. Our study shows that high contents of DHA associated with FABP7 are necessary to promote early brain development, which prompted us to recommend DHA supplementation early in pregnancy. © 2015 Wiley Periodicals, Inc. Develop Neurobiol 76: 287–297, 2016

International audience; We isolated neural stem cells/neural progenitors (NSC) from 1-day-old rat pups born to mothers fed diets that were deficient or supplemented with n-3 polyunsaturated fatty acids (PUFAs) and compared their proliferation and differentiation in vitro. The cells isolated from the n-3PUFA-deficient pups consistently proliferated more slowly than cells that were isolated from n-3PUFA-supplemented pups, despite the fact that both were cultured under the same conditions. The differences in the proliferation rates were evaluated up until 40 days of culture and were highly significant. When the cells were allowed to differentiate, the deficient cells exhibited a higher degree of neuronal maturation in response to the addition of PUFAs in the medium, as demonstrated by an increase in neurite length, whereas the neurons derived from the supplemented pups showed no change. This result was consistent, regardless of the age of the culture. The properties of the NSC were durably modified throughout the length of the culture, although the membrane phospholipid compositions were similar. We examined the differential expression of selected mRNAs and micro RNAs. We found significant differences in the gene expression of proliferating and differentiating cells, and a group of genes involved in neurogenesis was specifically modified by n-3 PUFA treatment. We conclude that n-3 PUFA levels in the maternal diet can induce persistent modifications of the proliferation and differentiation of NSCs and of their transcriptome. Therefore, the n-3 supply received in utero may condition on a long-term basis cell renewal in the brain.

The peripheral astrocyte process (PAP) preferentially associates with the synapse. The PAP, which is not found around every synapse, extends to or withdraws from it in an activity-dependent manner. Although the pre- and postsynaptic elements have been described in great molecular detail, relatively little is known about the PAP because of its difficult access for electrophysiology or light microscopy, as they are smaller than microscopic resolution. We investigated possible stimuli and mechanisms of PAP plasticity. Immunocytochemistry on rat brain sections demonstrates that the actin-binding protein ezrin and the metabotropic glutamate receptors (mGluRs) 3 and 5 are compartmentalized to the PAP but not to the GFAP-containing stem process. Further experiments applying ezrin siRNA or dominant-negative ezrin in primary astrocytes indicate that filopodia formation and motility require ezrin in the membrane/cytoskeleton bound (i.e., T567-phosphorylated) form. Glial processes around synapses in situ consistently display this ezrin form. Possible motility stimuli of perisynaptic glial processes were studied in culture, based on their similarity with filopodia. Glutamate and glutamate analogues reveal that rapid (5 min), glutamate-induced filopodia motility is mediated by mGluRs 3 and 5. Ultrastructurally, these mGluR subtypes were also localized in astrocytes in the rat hippocampus, preferentially in their fine PAPs. In vivo, changes in glutamatergic circadian activity in the hamster suprachiasmatic nucleus are accompanied by changes of ezrin immunoreactivity in the suprachiasmatic nucleus, in line with transmitter-induced perisynaptic glial motility. The data suggest that ( i ) ezrin is required for the structural plasticity of PAPs and ( ii ) mGluRs can stimulate PAP plasticity.

The conversion rate of α-linolenic acid (ALA) into docosahexaenoic acid (DHA) is determined by dietary and non-dietary factors. Higher capacity of DHA synthesis has been evidenced in females, indicating that sex factors influence the conversion pathway. To evaluate the extent to which sexual dimorphism of DHA synthesis is subordinated to nutritional handling, we measured the ω3 ∆4-desaturation index in male and female rats receiving adequate or inadequate amounts of ALA. The ω3 ∆4-desaturation index was drawn from the DHA to docosapentaenoic acid (ω3DPA) ratio in liver phospholipids. Male and female rats born to ω3-deficient dams were fed a supplemented diet supplying low, inadequate, intermediate, or adequate ALA (5, 20, 100, or 300 mg ALA/100 g diet, respectively). Control rats from both gender received the adequate diet from fetal life. Compared with control, low ALA feeding induced the ω3 ∆4-desaturation index to increase by 38 and 70% in the phosphatidylethanolamine fraction of males and females, respectively, and by 67% in phosphatidylcholine in females only. Supplementations with increased doses of ALA progressively smoothed this gender effect. Moreover, the analysis of our data from a previous study shows that ovariectomy decreased, whereas estradiol treatment increased the ω3 index to values comparable with those of diet-matched males and intact females, respectively. Females are more prone than males to increase their index of ω3 ∆4-desaturation, especially in response to low supplies in ALA. Estradiol supports the ω3 index, suggesting that this hormone plays a role in the effect of gender on DHA synthesis.

National audience; Nutritional investigations indicate that the n-3 polyunsaturated fatty acid (PUFA) content of western diets is too low to provide the brain with an optimal supply of DHA, the main n-3 PUFA in cell membranes. Insufficient brain DHA has been associated with memory impairment, emotional disturbances and altered brain processes in experimental studies. Epidemiological studies have revealed that a low n-3 PUFA is correlated with cognitive or behavioral defects during early development, adulthood and aging. Most of the DHA accumulates in the brain during the perinatal period, but its turnover in brain membranes remains elevated throughout life. Although the mechanism of action of n-3 PUFA in brain processes is not fully understood, an increasing bulk of data show the impact of DHA on brain cell activities. By influencing membrane biophysical properties, participating to lipid signaling pathways, and activating transcriptional factors, DHA is involved in the regulation of neurotransmission, neurogenesis, brain energy supply, and neuroprotection.; Le cerveau est l’un des organes les plus riches en acide docosahexaénoïque ou DHA, le principal AGPI n-3 présent dans les membranes cellulaires. Le déséquilibre des apports en acides gras polyinsaturés, AGPI n-6 et n-3, dans les populations occidentales peut compromettre l’approvisionnement du cerveau en DHA et ainsi altérer la physiologie cérébrale. Les études épidémiologiques et expérimentales ont montré qu’un défaut d’apport en AGPI n-3 est associée à des troubles cognitifs et comportementaux à la fois chez l’enfant, l’adulte et le sujet âgé. La période périnatale est déterminante pour l’incorporation du DHA dans les structures cérébrales mais le renouvellement du DHA a lieu tout au long de la vie. L’influence du DHA dans la physiologie cérébrale est multiple. En influençant les propriétés physico-chimiques des membranes, la production de médiateurs lipidiques dans les cascades de signalisation, l’activation de facteurs de transcription, le DHA intervient dans la régulation de la neurotransmission, la neurogénèse, l’énergétique cérébrale et la neuroprotection.

Polyunsaturated fatty acids (PUFA) are crucial for proper functioning of cell membranes, particularly in brain. Biologically important PUFA include docosahexaenoic acid (n-3 series) and arachidonic acid (n-6 series) which can be formed from their respective dietary essential precursors, alpha-linolenic acid (ALA) and linoleic acid (LA). Steroid hormones are thought to modulate PUFA synthesis in humans but whether they regulate PUFA status in brain and/or in neural membranes is unknown. In human neuroblastoma SH-SY5Y cells, we compared the effect of estradiol, testosterone, and progesterone on PUFA synthesis. Cells were incubated with ALA and/or LA 7 microM in combination with estradiol, testosterone, or progesterone at 10 nM without serum. The fatty acid composition was determined by gas chromatography and the mRNA expression of genes involved in PUFA metabolism by real-time RT-PCR. Estradiol affected both the n-3 and the n-6 PUFA conversion, the n-3 PUFA pathway being more sensitive to the estradiol treatment. In ALA-supplemented cells, estradiol increased while testosterone decreased the long-chain n-3 PUFA content (+17% and -15%, respectively) and the mRNA expression of the Delta5-desaturase (+11% and -9%), these two events being strongly correlated. Progesterone did not affect the PUFA composition. The positive effect of estradiol was blocked by the estrogen receptor antagonist ICI-182,780. We conclude that steroids have differential effects on PUFA synthesis and that their mode of action could involve the modulation of the Delta5-desaturase mRNA expression in neuroblastoma cells. These results help our understanding of the regulation of brain PUFA metabolism by steroid hormones.

The effectiveness of 4 dyes (methylene blue, rhodamine 6 G, chlorophyllin, riboflavine) was determinated in the photodynamic killing of Pieris brassicae larvae and Myzus persicae larvae under conditions of artificial photoperiods. Several dyes concentrations were tested at different fluence rates (from 2 to 13,4 W/m2, and at 55 and 164 W/m2), and for different photoperiods between 2 and 16 h of light/24 h. In these experimental conditions, in both species, mortality varies with dyes concentration and is dependent on parameters of photoirradiation (fluence rate and duration) and on specific susceptibility. Methylene blue and rhodamine 6 G caused the highest mortality in dye-fed light-exposed larvae; chlorophyllin was not as effective but was more effective than riboflavine. Dye-fed controls kept in constant darkness had a very low percent of mortality. A better knowledge of susceptibilities to photosensitizers in different insects is an necessary step for assessing the interest of photodynamic action as a new method of insect control. Zusammenfassung Photodynamische Wirkung auf zwei Insekten, den Grosen Kohlweisling, Pieris brassicae (L.) und die Grune Pfirsichlaus, Myzus persicae (Sulzer) Die letale Wirkung von vier Farbstoffen (Methylenblau, Rhodamin 6 G, Chlorophyllin, Riboflavin) wurde an den Larven von Pieris brassicae und an jenen von Myzus persicae, die sich in kunstlicher Photoperiode befinden, aufgezeigt. Mehrere Farbstoffkonzentrationen wurden bei verschiedenen Beleuchtungsstarken (von 2 bis 13,4 W/m2 und bei 55 und 164 W/m2) und Photoperioden — 2 bis 16 Stunden Lichteinwirkung/24 Stunden — getestet. Unter diesen Untersuchungsbedingungen variiert die Sterblichkeit bei beiden Arten mit Farbstoffkonzentration und hangt von den Parametern der Photobestrahlung (Starke und Dauer der Beleuchtung) und von der arteigen Empfindlichkeit ab. Methylenblau und Rhodamin 6 G verursachen die starkste Sterblichkeit unter den Larven, die auf gefarbtem Nahrboden ernahrt werden und dem Licht ausgesetzt sind. Chlorophyllin ist nicht ebenso wirksam, aber doch wirksamer als Riboflavin. Kontrollen, die auf kunstlichem, Farbstoffe enthaltendem Nahrboden in standiger Dunkelheit gehalten wurden, wiesen nur eine sehr geringe Sterblichkeitsrate auf. Eine bessere Kenntnis der Empfindlichkeit verschiedener Insekten gegenuber Photosensibilisatoren ist ein notwendiger Schritt fur weitere Forschungsarbeiten uber den photodynamischen Effekt im Hinblick auf eine Benutzung dieses Phanomens als neue Methode in der Insektenbekampfung.

Resume Les acides gras polyinsatures a 18 atomes de carbone des series omega-6 et omega-3 sont obligatoirement apportes par l’alimentation. Ces precurseurs essentiels sont transformes par l’organisme en derives a longue chaine necessaires au bon fonctionnement des membranes cellulaires, respectivement en acide arachidonique et en acide docosahexaenoique (DHA). Leur formation fait intervenir une succession de desaturations et d’elongations, qui se deroulent principalement dans le foie et qui mettent en jeu les voies de regulation de l’expression des genes du metabolisme lipidique. Les donnees de la litterature indiquent que le dimorphisme sexuel influe sur ces voies de regulation. Le precurseur de la serie omega-3, l’acide a-linolenique, est majoritairement oxyde en acetyl-CoA par la voie mitochondriale, tandis que seule une fraction minoritaire est convertie en DHA. Les proportions destinees a l’oxydation et a la conversion sont, respectivement, moins elevees et plus elevees chez les femmes que chez les hommes. Dans des conditions nutritionnelles equivalentes, la teneur en DHA des lipides circulants est generalement plus elevee chez les femmes et d’autant plus chez celles qui prennent des traitements estrogeniques. L’ensemble des donnees suggere que le statut en hormones steroides est l’un des acteurs de la regulation de l’expression des genes du metabolisme lipidique.

Several studies suggest that (n-3) PUFA may play a role in the regulation of cognitive functions, locomotor and exploratory activity, and affective disorders. Additionally, (n-3) PUFA affect pineal function, which is implicated in the sleep-wake rhythm. However, no studies to our knowledge have explored the role of PUFA on the circadian system. We investigated the effect of an (n-3) PUFA-deficient diet on locomotor and pineal melatonin rhythms in Syrian hamsters used as model species in circadian rhythm research. To assess the possible relationship between voluntary wheel running activity and dopaminergic neurotransmission, we also measured endogenous monoamine concentrations in the striatum. Two-month-old male hamsters, fed either an (n-3) PUFA-deficient or an (n-3) PUFA-adequate diet, were housed individually in cages equipped with run wheels. At 3 mo, cerebral structures were extracted for biochemical and cellular analysis. In (n-3) PUFA-deficient hamsters, the induced changes in the pineal PUFA membrane phospholipid composition were associated with a reduction in the nocturnal peak level of melatonin that was 52% lower than in control hamsters (P < 0.001). The (n-3) PUFA-deficient hamsters also had higher diurnal (P < 0.01) and nocturnal (P = 0.001) locomotor activity than the control hamsters, in parallel with activation of striatal dopaminergic function (P < 0.05). The (n-3) PUFA-deficient hamsters exhibited several symptoms: chronic locomotor hyperactivity, disturbance in melatonin rhythm, and striatal hyperdopaminergia. We suggest that an (n-3) PUFA-deficient diet lessens the melatonin rhythm, weakens endogenous functioning of the circadian clock, and plays a role in nocturnal sleep disturbances as described in attention deficit/hyperactivity disorder.

Docosahexaenoic acid (DHA, 22:6n-3) in membrane phospholipids originates from dietary intake of preformed DHA and from conversion of its essential precursor α-linolenic acid (ALA, 18:3n-3). Cultured cells, especially nervous cells, are increasingly used to explore the uptake, metabolism and gene transcription effects of n-3 fatty acids, raising the question of the specific metabolic fate of different fatty acids and of the physiological relevance of their concentrations in the culture medium. This paper reports experimental data that 1) compare the dose-dependent incorporation of preformed DHA into the ethanolamine phosphoglycerolipids (EPG) of neural and cerebral endothelial cells in culture with that of the developing rat brain, 2) evaluate the pathway of DHA synthesis from ALA, eicosapentaenoic acid (EPA, 20:5n-3) or n-3 docosapentaenoic acid (DPA, 22:5n-3) in a model of neuronal cells, the SH-5YSY human neuroblastoma cells, and 3) characterize in these cells the mRNA expression profile of genes involved in the fatty acid metabolism. The incorporation of preformed DHA in EPG followed, both in vivo and in vitro, a dose-response curve from which two parameters were drawn: the DHAmax, i.e. the plateau-value of the linearized dose-response curve (expressed in weight % of total fatty acids), and the DHA50, the concentration of DHA in the diet or in the culture medium corresponding to an incorporation of DHA in EPG equal to one-half the DHAmax. The ratio of DHAmax to DHA50 reflects the propensity (so-called the ‘avidity’ for DHA) of cells or tissues to incorporate the exogenous DHA. The DHAmax and the DHAmax/DHA50 ratio values of SH-SY5Y cells and of rat brain endothelial cells in culture were compared to those of the frontal cortex and hippocampus of rats chronically deficient in n-3 fatty acids and supplemented with preformed DHA. The same DHAmax/DHA50 ratio values were found in SH-SY5Y (5.2) cells and in rat brain areas (5.1-5.7) when the DHA doses were expressed in lmol DHA/liter of culture medium and in lmol DHA/10 g diet, respectively. The SH-SY5Y cells were able to produce neoformed EPA, DPA and DHA from supplemental ALA. The incorporation of neoformed EPA and DPA in EPG followed a dose-response saturating curve, while that of DHA was bell-shaped. The different pattern of neoformed DPA and neoformed DHA suggests that the conversion pathway was limited at the terminal step of DHA synthesis. The mRNA profile showed that two enzymes of the peroxisomal b-oxidation system, the L- and D-bifunctional proteins, were expressed at lower levels than those of the endoplasmic reticulum pathway (Δ6-desaturase). These data show that incorporation of preformed DHA in cultured neuroblastoma cells match physiological values, indicating that DHA uptake, acyl-CoA activation, and phospholipid acyltransferases are active. However, the synthesis and incorporation of newly formed DHA in SH-SY5Y cells responds to a critical concentration-window of precursors which could originate from the low basal expression level of peroxisomal enzymes.

L'influence des acides gras polyinsatures en omega-3 sur la sante est aujourd'hui une question qui deborde le cadre scientifique : la publicite pour des produits ou des supplements alimentaires contenant ou enrichis en ces acides gras vante leurs bienfaits reels ou supposes. Les recherches sur les acides gras en omega-3 ont commence il y a une trentaine d'annees avec la decouverte de leurs implications dans la prevention des maladies cardiovasculaires. Elles sont aujourd'hui plus actives que jamais, et se sont etendues aux aspects les plus divers de la sante. Cette revue est un bref tour d'horizon des recherches recentes sur ce theme, en privilegiant les travaux realises chez l'homme. Sur la base de revues recentes et de travaux originaux, on examinera successivement la biosynthese de ces acides gras et les consequences nutritionnelles, leur niveau de consommation en France, les besoins de la femme enceinte et allaitante et du nouveau-ne, et leurs effets averes ou possibles dans la prevention ou le traitement des maladies inflammatoires, de la resistance a l'insuline, du diabete et de l'obesite, des maladies cardiovasculaires, des cancers, des maladies mentales et des maladies neurodegeneratives.

Polyunsaturated fatty acids (PUFAs) are essential nutrients for mammals and the human species, and belong to either of two distinct and not interconvertible series, omega 6 and omega 3. The metabolic precursors of these two series, linoleic and α-linolenic acids respectively, are the dietary essential fatty acids. These two fatty acids, once absorbed, lead to the specific synthesis and incorporation in practically all cell membranes of long-chain active PUFA derivatives such as arachidonic acid for the omega 6 series and eicosapentaenoic and docosahexaenoic acids for the omega 3 series. Long-chain PUFA affect many physiological functions because they are essential factors in many cellular functions by regulating physical properties of membranes, eicosanoid signalling and gene expression of encoding enzymes of triglyceride storage and fatty acid oxidation. The consumption of omega 6 and omega 3 fatty acids in equilibrated proportions could be crucial in the regulation of cellular physiology and in the prevention of pathologies such as cardiovascular, autoimmune and inflammatory diseases, diabetes and obesity, certain neuropsychiatric affections, etc. Indeed, the dietary intake of omega 3 fatty acid (α-linolenate and also docosahexaenoate) are crucial parameters in the development of retinal and neural function in the newborn infant. On the other hand, a high ratio of omega6/omega 3 fatty acids in cell membranes due to an excessive consumption of omega 6 fatty acids and a relative omega 3 fatty acid deficiency, may promote the pathogenesis of several diseases, including cardiovascular diseases, metabolic syndrome, inflammatory disorders and obesity.

Resume Les acides gras polyinsatures (AGPI) de la serie n-3, et notamment l'acide docosahexaenoique (22:6n-3, DHA), sont des nutriments indispensables pour assurer un developpement optimal du systeme nerveux central. En effet, de par sa concentration exceptionnellement elevee dans les membranes excitables du cerveau et de la retine, le DHA exerce un role fondamental dans la physiologie de ces tissus (proprietes structurale, de precurseur de derives endoperoxydes, et regulatrice de l'activite synaptique et de l'expression de genes cibles). Chez le rongeur et le singe, la chute de la teneur membranaire en DHA, suite a une carence alimentaire en AGPI n-3, s'accompagne de la reduction des capacites d'apprentissage et de discrimination visuelle (memoire, attention, motivation). Quelques cas de carence alimentaire ont ete rapportes chez l'Homme, notamment chez des enfants nouveau-nes qui presentaient un retard dans le developpement de leur acuite visuelle. Dans l'apparition de troubles neuropsychiatriques lies a la pathologie (hyperactivite chez l'enfant, schizophrenie, depression, ...), un lien avec l'apport alimentaire en AGPI n-3 pourrait etre implique et concernerait un second acide gras de cette famille, l'acide eicosapentaenoique (20:5n-3, EPA). Enfin, la consommation de ces acides gras pourrait egalement etre benefique vis-a-vis de l'incidence des neuropathologies associees au vieillissement comme le suggerent des etudes epidemiologiques et prospectives recentes (maladie d'Alzheimer, demence senile).

BACKGROUND Functional maturation of nervous tissues depends on membrane accretion of docosahexaenoic acid (DHA). Animal studies have shown that incorporation of dietary DHA into membrane phospholipids is dose dependent. The molecular effects of DHA are commonly studied in cultured cells, but questions remain about the physiologic connection between animal and cell models. OBJECTIVE We developed a linear model for comparing the responses of rat nervous tissues to dietary DHA with the responses of human cell lines to DHA in medium. DESIGN Rats were rendered chronically deficient in n-3 fatty acids by being reared on a peanut oil diet. DHA status was replenished in the F2 generation by using increasing supplements of a microalgal oil. Human retinoblastoma and neuroblastoma cells were dosed with unesterified DHA. DHA accumulation into phospholipids was defined by the plateau of the dose-response curve (DHA(max)) and by the supplement required to produce one-half the DHA(max) (DHA(50)). RESULTS The DHA(max) values for 4 brain regions and 2 neuroblastoma lines were similar, and the value for the retinoblastoma line was similar to the retinal value. Expressing the DHA input as micro mol/10 g diet and as micro mol/L medium resulted in similar values for the ratio of DHA(max) to DHA(50) in the 4 brain regions and the 3 cell lines. The DHA(max)-DHA(50) ratios in the ethanolamine phosphoglyceride and phosphatidylcholine fractions in retinal phospholipids were 6 and 10 times, respectively, those in the brain and cultured cells. CONCLUSIONS The dose-dependent responses of cells and the brain to DHA supplements can be compared by using DHA(max)-DHA(50) ratios. We propose a counting frame that allows the comparison of the dose responses of the brain and cells to exogenous DHA.

Docosahexaenoic acid (DHA), the main n-3 polyunsaturated fatty acid (PUFA) in membranes, is particularly abundant in brain cells. Decreased cerebral concentrations of DHA, resulting from dietary n-3 deficiency, are associated with impaired cognitive function. Because the cellular causes of this impairment are still unknown, we need in vitro models that mimic the variations in n-3/n-6 PUFA seen in vivo. We have compared the PUFA profiles of hamster astrocytes cultured in medium supplemented with long-chain PUFA [DHA and/or arachidonic acid (AA)] with those of brain tissue from hamsters fed an n-6/n-3 PUFA-balanced diet or one lacking n-3 PUFA. Astrocytes were obtained from the brain cortex of newborn hamsters and cultured in minimum essential medium + 5% fetal calf serum (FCS) supplemented with DHA and/or AA for 10 days. The astrocytes cultured in medium + FCS had low n-3 PUFA contents, comparable to those of brain tissue from hamsters fed an n-3-deficient diet. We have shown that astrocytes grown in medium supplemented with DHA and/or AA, plus alpha-tocopherol to prevent lipid peroxidation, incorporated large amounts of these long-chain PUFA, so that the n-6/n-3 PUFA compositions of the phosphatidylethanolamine and phosphatidylcholine, the two main classes of membrane phospholipids, were greatly altered. Astrocytes cultured in medium plus DHA had a more physiological n-3 status, grew better, and retained their astrocyte phenotype. Thus astrocytes in culture are likely to be physiologically relevant only when provided with adequate DHA. This reliable method of altering membrane phospholipid composition promises to be useful for studying the influence of n-6/n-3 imbalance on astrocyte function.

Long-chain polyunsaturated (n-3) fatty acids have been reported to influence the efficiency of membrane receptors, transporters and enzymes. Because the brain is particularly rich in docosahexaenoic acid (DHA, 22:6 n-3), the present study addresses the question of whether the 22:6 n-3 fatty acid deficiency induces disorder in regulation of energy metabolism in the CNS. Three brain regions that share a high rate of energy metabolism were studied: fronto-parietal cortex, hippocampus and suprachiasmatic nucleus. The effect of the diet deficient in n-3 fatty acids resulted in a 30-50% decrease in DHA in membrane phospholipids. Moreover, a 30% decrease in glucose uptake and a 20-40% decrease in cytochrome oxidase activity were observed in the three brain regions. The n-3 deficient diet also altered the immunoreactivity of glucose transporters, namely GLUT1 in endothelial cells and GLUT3 in neurones. In n-3 fatty acid deficient rats, GLUT1-immunoreactivity readily detectable in microvessels became sparse, whereas the number of GLUT3 immunoreactive neurones was increased. However, western blot analysis showed no significant difference in GLUT1 and GLUT3 protein levels between rats deficient in n-3 fatty acids and control rats. The present results suggest that changes in energy metabolism induced by n-3 deficiency could result from functional alteration in glucose transporters.

The aim of the present study was to develop a quantitative method to measure the immunoreactivity of the glial fibrillary acidic protein on the suprachiasmatic nucleus of hamster. For this purpose, optical microscopy images from brain sections processed for glial fibrillary acidic protein immunostaining were digitised under different light conditions. Image treatment and immunoreactivity quantification were performed following five different methods using the program Adobe Photoshop®. The results were analysed in order to determine the ability of each method to differentiate immunoreactivity levels, and their susceptibility to the light conditions during image acquisition. Four of the five methods were found to be susceptible to the tested light conditions, while the other was not. This last method, which permits detection of differences in immunoreactivity between the different sections, was considered for further quantification of glial fibrillary acidic protein immunoreactivity on the suprachiasmatic nucleus.

International audience; Chronic stress causes the release of glucocorticoids, which greatly influence cerebral function, especially glutamatergic transmission. These stress-induced changes in neurotransmission could be counteracted by increasing the dietary intake of omega-3 polyunsaturated fatty acids (n-3 PUFAs). Numerous studies have described the capacity of n-3 PUFAs to help protect glutamatergic neurotransmission from damage induced by stress and glucocorticoids, possibly preventing the development of stress-related disorders such as depression or anxiety. The hippocampus contains glucocorticoid receptors and is involved in learning and memory. This makes it particularly sensitive to stress, which alters certain aspects of hippocampal function. In this review, the various ways in which n-3 PUFAs may prevent the harmful effects of chronic stress, particularly the alteration of glutamatergic synapses in the hippocampus, are summarized.

International audience; Epidemiological data suggest that a poor ω3 status favoured by the low ω3/ω6 polyunsaturated fatty acids ratio in western diets contributes to cognitive decline in the elderly, but mechanistic evidence is lacking. We therefore explored the impact of ω3 deficiency on the evolution of glutamatergic transmission in the CA1 of the hippocampus during aging by comparing 4 groups of rats aged 6-22 months fed ω3-deficient or ω3/ω6-balanced diets from conception to sacrifice: Young ω3 Balanced (YB) or Deficient (YD), Old ω3 Balanced (OB) or Deficient (OD) rats. ω3 Deficiency induced a 65% decrease in the amount of docosahexaenoic acid (DHA, the main ω3 in cell membranes) in brain phospholipids, but had no impact on glutamatergic transmission and astroglial function in young rats. Aging induced a 10% decrease in brain DHA, a 35% reduction of synaptic efficacy (fEPSP/PFV) due to decreased presynaptic glutamate release and a 30% decrease in the astroglial glutamate uptake associated with a marked astrogliosis (+100% GFAP). The ω3 deficiency further decreased these hallmarks of aging (OD vs. OB rats: -35% fEPSP/PFV P < 0.05, -15% astroglial glutamate uptake P < 0.001, +30% GFAP P < 0.01). This cannot be attributed to aggravation of the brain DHA deficit because the brains of OD rats had more DHA than those of YD rats. Thus, ω3 deficiency worsens the age-induced degradation of glutamatergic transmission and its associated astroglial regulation in the hippocampus.

Peroxisome proliferator-activated receptors (PPARs) are members of the nuclear receptor superfamily and function as transcription factors that regulate gene expression in numerous biological processes. Although the PPARβ/δ subtype is highly expressed in the brain, its physiological roles in neuronal function remain to be elucidated. In this study, we examined the presence of PPARβ/δ in the master circadian clock of the Syrian hamster and investigated its putative functional role in this structure. In mammals, the central circadian clock, located in the suprachiasmatic nucleus (SCN), is entrained by the light-dark (LD) cycle via photic6 signals conveyed by a direct pathway whose terminals release glutamate. Using immunocytochemical and qRT-PCR analysis, we demonstrated that the rhythmic expression of PPAR β/δ within the SCN of hamsters raised under an LD cycle was detectable only at the transcriptional level when the hamsters were maintained under constant darkness (DD). The increase in the number of immunoreactive PPARβ/δ cells observed under DD after light stimulation during the early subjective night (CT14), but not during the subjective day (CT06), demonstrated that the expression of PPARβ/δ can be up-regulated according to the photosensitive phase of the circadian clock. All of the PPARβ/δ-positive cells in the SCN also expressed the glutamate receptor NMDAR1. Moreover, we demonstrated that at the photosensitive point (CT14), the administration of L-16504, a specific agonist of PPARβ/δ, amplified the phase delay of the locomotor response induced by a light pulse. Taken together, these data suggest that PPARβ/δ activation modulates glutamate release that mediates entrainment of the circadian clock by light.

International audience; The increasing life expectancy in the populations of rich countries raises the pressing question of how the elderly can maintain their cognitive function. Cognitive decline is characterised by the loss of short-term memory due to a progressive impairment of the underlying brain cell processes. Age-related brain damage has many causes, some of which may be influenced by diet. An optimal diet may therefore be a practical way of delaying the onset of age-related cognitive decline. Nutritional investigations indicate that the ω-3 poyunsaturated fatty acid (PUFA) content of western diets is too low to provide the brain with an optimal supply of docosahexaenoic acid (DHA), the main ω-3 PUFA in cell membranes. Insufficient brain DHA has been associated with memory impairment, emotional disturbances and altered brain processes in rodents. Human studies suggest that an adequate dietary intake of ω-3 PUFA can slow the age-related cognitive decline and may also protect against the risk of senile dementia. However, despite the many studies in this domain, the beneficial impact of ω-3 PUFA on brain function has only recently been linked to specific mechanisms. This review examines the hypothesis that an optimal brain DHA status, conferred by an adequate ω-3 PUFA intake, limits age-related brain damage by optimizing endogenous brain repair mechanisms. Our analysis of the abundant literature indicates that an adequate amount of DHA in the brain may limit the impact of stress, an important age-aggravating factor, and influences the neuronal and astroglial functions that govern and protect synaptic transmission. This transmission, particularly glutamatergic neurotransmission in the hippocampus, underlies memory formation. The brain DHA status also influences neurogenesis, nested in the hippocampus, which helps maintain cognitive function throughout life. Although there are still gaps in our knowledge of the way ω-3 PUFA act, the mechanistic studies reviewed here indicate that ω-3 PUFA may be a promising tool for preventing age-related brain deterioration.

International audience; Omega-3 fatty acids are important for several neuronal and cognitive functions. Altered omega-3 fatty acid status has been implicated in reduced resistance to stress and mood disorders. We therefore evaluated the effects of repeated restraint stress (6 h/day for 21 days) on adult rats fed omega-3 deficient, control or omega-3 enriched diets from conception. We measured body weight, plasma corticosterone and hippocampus glucocorticoid receptors and correlated these data with emotional and depression-like behaviour assessed by their open-field (OF) activity, anxiety in the elevated-plus maze (EPM), the sucrose preference test and the startle response. We also determined their plasma and brain membrane lipid profiles by gas chromatography. Repeated restraint stress caused rats fed a control diet to lose weight. Their plasma corticosterone increased and they showed moderate behavioural changes, with increases only in grooming (OF test) and entries into the open arms (EPM). Rats fed the omega-3 enriched diet had a lower stress-induced weight loss and plasma corticosterone peak, and reduced grooming. Rats chronically lacking omega-3 fatty acid exhibited an increased startle response, a stress-induced decrease in locomotor activity and exaggerated grooming. The brain omega-3 fatty acids increased as the dietary omega-3 fatty acids increased; diets containing preformed long-chain omega-3 fatty acid were better than diets containing the precursor alpha-linolenic acid. However, the restraint stress reduced the amounts of omega-3 incorporated. These data showed that the response to chronic restraint stress was modulated by the omega-3 fatty acid supply, a dietary deficiency was deleterious while enrichment protecting against stress.

International audience; Converging epidemiological studies suggest that dietary essential n-3 polyunsaturated fatty acid (PUFA) are likely to be involved in the pathogenesis of mood and cognitive disorders linked to aging. The question arises as to whether the decreased prevalence of these symptoms in the elderly with high n-3 PUFA consumption is also associated with improved central inflammation, i.e. cytokine activation, in the brain. To answer this, we measured memory performance and emotional behavior as well as cytokine synthesis and PUFA level in the spleen and the cortex of adult and aged mice submitted to a diet with an adequate supply of n-3 PUFA in form of α-linolenic acid (α-LNA) or a n-3 deficient diet. Our results show that docosahexaenoic acid (DHA), the main n-3 PUFA in the brain, was higher in the spleen and cortex of n-3 adequate mice relative to n-3 deficient mice and this difference was maintained throughout life. Interestingly, high level of brain DHA was associated with a decrease in depressive-like symptoms throughout aging. On the opposite, spatial memory was maintained in adult but not in aged n-3 adequate mice relative to n-3 deficient mice. Furthermore, increased interleukin-6 (IL-6) and decreased IL-10 expression were found in the cortex of aged mice independently of the diets. All together, our results suggest that n-3 PUFA dietary supply in the form of α-LNA is sufficient to protect from deficits in emotional behavior but not from memory disruption and brain proinflammatory cytokine expression linked to age.

International audience; n-3 Polyunsaturated fatty acids (PUFA) support whole brain energy metabolism but their impact on neuroenergetics in specific brain areas and during neuronal activation is still poorly understood. We tested the effect of feeding rats as control, n-3 PUFA-deficient diet, or docosahexaenoic acid (DHA)-supplemented diet on the expression of key genes in fronto-parietal cortex and hippocampal neuroenergetics before and after neuronal stimulation (activated) by an enriched environment. Compared to control rats, n-3 deficiency specifically repressed GLUT1 gene expression in the fronto-parietal cortex in basal state and also during neuronal activation which specifically stimulated GLUT1. In contrast, in the CA1 area, n-3 deficiency improved the glutamatergic synapse function in both neuronal states (glutamate transporters, Na(+)/K(+) ATPase). DHA supplementation induced overexpression of genes encoding enzymes of the oxidative phosphorylation system and the F1F0 ATP synthase in the CA1 area. We conclude that n-3 deficiency repressed GLUT1 gene expression in the cerebral cortex, while DHA supplementation improved the mitochondrial ATP generation in the CA1 area of the hippocampus.

International audience; 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.

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Remerciements : Plate forme de Micorgénomique (Iso Cell Express), INRA Domaine de Vilvert 78352 Jouy-en-Josas; Hormonal and nutritional factors regulate the metabolism of long-chain polyunsaturated fatty acids (LC-PUFA). We aimed to determine whether ovarian hormones influence the capacity of rats to synthesize the end-products 22:6n-3 (DHA) and 22:5n-6 (n-6DPA) from their respective dietary precursors (18:3n-3 and 18:2n-6), and can regulate PUFA conversion enzymes gene transcription in brain and/or liver. Females born with a low DHA status were fed from weaning to 8 weeks of age a diet providing both essential precursors, and were concurrently submitted to sham-operated control (SOC) or ovariectomy (OVX) in combination with or without 17β-estradiol (E2) dosed at 8 or 16 μg/day. Relative to SOC, OVX increased the hepatic Δ9-, Δ6- and Δ5-desaturase transcripts and cognate transcription factors (PPARα, PPARγ, RXRα, RARα), but it did not affect LC-PUFA contents in phospholipids. In comparison with SOC and OVX groups, both E2 doses prevented the increase of transcripts, while paradoxically augmenting DHA and n-6DPA in liver phospholipids. Thus, in the liver of rats undergoing ovariectomy, changes of LC-PUFA synthesizing enzyme transcripts and of LC-PUFA proportions were not correlated. In brain, ovariectomy did not modify the transcripts of lipid metabolism genes, but it decreased DHA (-15%) and n-6DPA (-28%). In comparison with SOC and OVX groups, ovariectomized females treated with E2 preserved their status of both LC-PUFA in brain and had increased transcripts of E2 receptor β, PPARδ, RARα and LC-PUFA synthesizing enzymes. In conclusion, E2 sustained the transcription of lipid metabolism genes and proportions of neo-formed DHA and n-6DPA differently in brain and liver.

Several in vivo studies suggest that docosahexaenoic acid (22:6 n -3), the main n -3 long-chain polyunsaturated fatty acids (LC-PUFA) of brain membranes, could be an important regulator of brain energy metabolism by affecting glucose utilization and the density of the two isoforms of the glucose transporter-1 (GLUT1) (endothelial and astrocytic). This study was conducted to test the hypothesis that 22:6 n -3 in membranes may modulate glucose metabolism in brain endothelial cells. It compared the impact of 22:6 n -3 and the other two main LC-PUFA, arachidonic acid (20:4 n -6) and eicosapentaenoic acid (20:5 n -3), on fatty acid composition of membrane phospholipids, glucose uptake and expression of 55-kDa GLUT1 isoform in two models of rat brain endothelial cells (RBEC), in primary culture and in the immortalized rat brain endothelial cell line RBE4. Without PUFA supplementation, both types of cerebral endothelial cells were depleted in 22:6 n -3, RBE4 being also particularly low in 20:4 n -6. After exposure to supplemental 20:4 n -6, 20:5 n -3 or 22:6 n -3 (15 μM, i.e. a physiological dose), RBEC and RBE4 avidly incorporated these PUFA into their membrane phospholipids thereby resembling physiological conditions, i.e. the PUFA content of rat cerebral microvessels. However, RBE4 were unable to incorporate physiological level of 20:4 n -6. Basal glucose transport in RBEC (rate of [ 3 H]-3-o-methylglucose uptake) was increased after 20:5 n -3 or 22:6 n -3 supplementation by 50% and 35%, respectively, whereas it was unchanged with 20:4 n -6. This increase of glucose transport was associated with an increased GLUT1 protein, while GLUT1 mRNA was not affected. The different PUFA did not impact on glucose uptake in RBE4. Due to alterations in n -6 PUFA metabolism and weak expression of GLUT1, RBE4 seems to be less adequate than RBEC to study PUFA metabolism and glucose transport in brain endothelial cells. Physiological doses of n -3 LC-PUFA have a direct and positive effect on glucose transport and GLUT1 density in RBEC that could partly explain decreased brain glucose utilization in n -3 PUFA-deprived rats.

International audience; Biochemical evidence suggests a role for n-3 polyunsaturated fatty acids (n-3 PUFAs) in the regulation of behavioral disturbances. A number of studies have revealed an association between reduced n-3 PUFA levels and attention-deficit hyperactivity disorder or depression. Here, we summarize the main findings regarding the association between n-3 PUFA and hyperactive and emotional disorders, and discuss potential mechanisms of action. Because the basal ganglia are involved in the control of locomotion and emotion, we examined published data regarding the role of n-3 PUFA in dopamine (DA) regulation in the basal ganglia. These results are discussed in the light of recent data from our laboratory suggesting an association between the drop in melatonin in the pineal gland and the increase in DA in the striatum and nucleus accumbens of n-3 PUFA-deprived rodents.

International audience; Brain cells are especially rich in polyunsaturated fatty acids (PUFA), mainly the n-3 PUFA docosahexaenoic acid (DHA) and the n-6 PUFA arachidonic acid (AA). They are released from membranes by PLA2 during neurotransmission, and may regulate glutamate uptake by astroglia, involved in controlling glutamatergic transmission. AA has been shown to inhibit glutamate transport in several model systems, but the contribution of DHA is less clear and has not been evaluated in astrocytes. Because the high DHA content of brain membranes is essential for brain function, we investigated the role of DHA in the regulation of astroglial glutamate transport. We evaluated the actions of DHA and AA using cultured rat astrocytes and suspensions of rat brain membranes (P1 fractions). DHA reduced D-[(3)H]aspartate uptake by cultured astrocytes and cortical membrane suspensions, while AA did not. This also occurred in astrocytes enriched with alpha-tocopherol, indicating that it was not due to peroxidation products. The reduction of d-[(3)H]aspartate uptake by DHA did not involve any change in the concentrations of membrane-associated astroglial glutamate transporters (GLAST and GLT-1), suggesting that DHA reduced the activity of the transporters. In contrast with the inhibition induced by free-DHA, we found no effect of membrane-bound DHA on D-[(3)H]aspartate uptake. Indeed, the uptake was similar in astrocytes with varying amount of DHA in their membrane (induced by long-term supplementation with DHA or AA). Therefore, DHA reduces glutamate uptake through a signal-like effect but not through changes in the PUFA composition of the astrocyte membranes. Also, reactive astrocytes, induced by a medium supplement (G5), were insensitive to DHA. This suggests that DHA regulates synaptic glutamate under basal condition but does not impair glutamate scavenging under reactive conditions. These results indicate that DHA slows astroglial glutamate transport via a specific signal-like effect, and may thus be a physiological synaptic regulator.

International audience; The aim was to determine the consequences of multi-generational n-3 polyunsaturated fatty acids (PUFA) deficiency on emotional response in rats subjected to maternal separation (MS) as chronic early life stress. Pups fed a control or an n-3 PUFA deficient diet were daily separated for 2 weeks before weaning. In adult rats, reward response was assessed by sucrose consumption and reactivity to novelty using openfield test. Both n-3 PUFA deficiency and MS increased reward response and impulsivity. Moreover, nutritional deficiency and stress acted in synergy to elevate sucrose intake by 80%, compared to control conditions. n-3 PUFA deprivation induced a depletion of docosahexanoeic acid of brain membranes by 70% compensated by increase in 22:5 n-6 and arachidonic acid (AA) levels. The diet-induced AA increase was, however, significantly higher in MS rats. This suggests that n-3 PUFA deficit could be an environmental risk increasing vulnerability to depressive-like response induced by chronic stress.

International audience; Sickness behaviour is an adaptive behavioural response to the activation of the innate immune system. It is mediated by brain cytokine production and action, especially interleukin-6 (IL-6). Polyunsaturated fatty acids (PUFA) are essential fatty acids that are highly incorporated in brain cell membranes and display immunomodulating properties. We hypothesized that a decrease in n-3 (also known as omega3) PUFA brain level by dietary means impacts on lipopolysaccharide (LPS)-induced IL-6 production and sickness behaviour. Our results show that mice exposed throughout life to a diet containing n-3 PUFA (n-3/n-6 diet) display a decrease in social interaction that does not occur in mice submitted to a diet devoid of n-3 PUFA (n-6 diet). LPS induced high IL-6 plasma levels as well as expression of IL-6 mRNA in the hippocampus and cFos mRNA in the brainstem of mice fed either diet, indicating intact immune-to-brain communication. However, STAT3 and STAT1 activation, a hallmark of the IL-6 signalling pathway, was lower in the hippocampus of LPS-treated n-6 mice than n-3/n-6 mice. In addition, LPS did not reduce social interaction in IL-6-knockout (IL-6-KO) mice and failed to induce STAT3 activation in the brain of IL-6-KO mice. Altogether, these findings point to alteration in brain STAT3 as a key mechanism for the lack of effect of LPS on social interaction in mice fed with the n-6 PUFA diet. The relative deficiency of Western diets in n-3 PUFA could impact on behavioural aspects of the host response to infection.

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Whether neurosteroids regulate the synthesis of long chain polyunsaturated fatty acids in brain cells is unknown. We examined the influence of 17-beta-estradiol (E2) on the capacity of SH-SY5Y cells supplemented with alpha-linolenic acid (ALA), to produce eicosapentaenoic acid (EPA), docosapentaenoic acid (DPA) and docosahexaenoic acid (DHA). Cells were incubated for 24 or 72 h with ALA added alone or in combination with E2 (ALA + E2). Fatty acids were analyzed by gas chromatography of ethanolamine glycerophospholipids (EtnGpl) and phosphatidylcholine (PtdCho). Incubation for 24 h with ALA alone increased EPA and DPA in EtnGpl, by 330 and 430% compared to controls (P < 0.001) and DHA by only 10% (P < 0.05). Although DHA increased by 30% (P < 0.001) in ALA + E2-treated cells, the difference between the ALA and ALA + E2 treatments were not significant after 24 h (Anova-1, Fisher's test). After 72 h, EPA, DPA and DHA further increased in EtnGpl and PtdCho of cells supplemented with ALA or ALA + E2. Incubation for 72 h with ALA + E2 specifically increased EPA (+34% in EtnGpl, P < 0.001) and DPA (+15%, P < 0.001) compared to ALA alone. Thus, SH-SY5Y cells produced membrane EPA, DPA and DHA from supplemental ALA. The formation of DHA was limited, even in the presence of E2. E2 significantly favored EPA and DPA production in cells grown for 72 h. Enhanced synthesis of ALA-elongation products in neuroblastoma cells treated with E2 supports the hypothesis that neurosteroids could modulate the metabolism of PUFA.

International audience; The very high enrichment of the nervous system in the polyunsaturated fatty acids, arachidonic (AA, 20: 4n-6) and docosahexaenoic acids (DHA, 22: 6n-3), is dependant of the dietary availability of their respective precursors, linoleic (18: 2n-6) and_-linolenic acids (18: 3n-3). Inadequate amounts of DHA in brain membranes have been linked to a wide variety of abnormalities ranging from visual acuity and learning irregularities, to psychopathologies. However, the molecular mechanisms involved remain unknown. Several years ago, we hypothesized that a modification of DHA contents of neuronal membranes by dietary modulation could change the neurotransmission function and then underlie inappropriate behavioural response. We showed that, in parallel to a severe loss of brain DHA concomitant to a compensatory substitution by 22:5n-6, the dietary lack of α-linolenic acid during development induced important changes in the release of neurotransmitters (dopamine, serotonin, acetylcholine) in cerebral areas specifically involved in learning, memory and reward processes. Data suggested alteration of presynaptic storage process and dysregulations of reciprocal functional interactions between monoaminergic and cholinergic pathways. Moreover, we showed that recovery of these neurochemical changes was possible when the deficient diet was switched to a diet balanced in n-3 and n-6 PUFA before weaning. The next step is to understand the mechanism involved. Particularly, we focus on the study of the metabolic cooperation between the endothelial cell, the astrocyte and the neuron which regulate synaptic transmission.These works could contribute to the understanding of the link between some neuropsychiatric disorders and the metabolism of n-3 PUFA, through their action on neurotransmission.

International audience; Inattention, hyperactivity and impulsiveness are the main symptoms of the heterogeneous attention-deficit/hyperactivity disorder (ADHD). It has been suggested that ADHD is associated with an imbalance in polyunsaturated fatty acid (PUFA) composition, with abnormal low levels of the main n-3 PUFA, DHA (22: 6n-3). DHA is highly accumulated in nervous tissue membranes and is implicated in neural function. Animal studies have shown that diet-induced lack of DHA in the brain leads to alterations in cognitive processes, but the relationship between DHA and hyperactivity is unclear. We examined the membrane phospholipid fatty acid profile in frontal cortex of rats characterized for attention, impulsiveness and motricity in various environmental contexts to determine the relationship between brain PUFA composition and the symptoms of ADHD. The amounts of n-3 PUFA in the PE were significantly correlated with nocturnal locomotor activity and the locomotor response to novelty: hyperactive individuals had less n-3 PUFA than hypoactive ones. We conclude that spontaneous hyperactivity in rats is the symptom of ADHD that best predicts the n-3 PUFA content of the frontal cortex. This differential model in rats should help to better understand the role of PUFA in several psychopathologies in which PUFA composition is modified.

National audience; Long chain polyunsaturated fatty acids (PUFAs), particularly arachidonic acid and docosahexaenoic acid (DHA), are integral components of neural membrane phospholipids. DHA deficiency is associated with behavioural and neurophysiological disorders. A deficiency of DHA markedly affects neurotransmission, membrane-bound proteins, ion channel activities and synaptic plasticity, and the supplementation restores neurotransmission. Although the molecular mechanism of DHA involvement remains unknown, more and more data demonstrate its implication in various cellular activities contributing to regulation of neurotransmission. Since recent studies have provided evidence that n-3 deficiency altered neurogenesis in embryonic brain, the question of lasting effects on neural function can be addressed.

Background Anatomic and functional brain lateralization underlies hemisphere specialization for cognitive and motor control, and deviations from the normal patterns of asymmetry appear to be related to behavioral deficits. Studies on n-3 polyunsaturated fatty acid (PUFA) deficiency and behavioral impairments led us to postulate that a chronic lack of n-3 PUFA can lead to changes in lateralized behavior by affecting structural or neurochemical patterns of asymmetry in motor-related brain structures. Methods We compared the effects of a chronic n-3 PUFA deficient diet with a balanced diet on membrane phospholipid fatty acids composition and immunolabeling of choline acetyltransferase (ChAt), as a marker of cholinergic neurons, in left and right striatum of rats. Lateral motor behavior was assessed by rotation and paw preference. Results Control rats had an asymmetric PUFA distribution with a right behavioral preference, whereas ChAt density was symmetrical. In deficient rats, the cholinergic neuron density was 30% lower on the right side, associated with a loss of PUFA asymmetry and behavior laterality. They present higher rotation behavior, and significantly more of them failed the handedness test. Conclusion These results indicate that a lack of n-3 PUFA is linked with a lateral behavior deficit, possibly leading to cognitive disturbances.

National audience; Docosahexaenoic acid (DHA, 22:6n-3) and arachidonic acid (AA, 20:4n-6) are the major polyunsaturated fatty acids in the membranes of brain and retinal cells. Animals specifically deficient in dietary n-3 fatty acids have reduced visual acuity and impaired learning ability. Studies on human infants have shown that adding DHA and AA to milk replacer-formulas can bring their concentrations in the infant blood lipids to values as high as those produced by breast feeding. The concurrent structural impact on the CNS membranes could have transient but significant outcomes on mental development and on maturation of visual function. In older subjects, neuropsychological and neurodegenerative diseases have been associated to impaired status of blood DHA and/or AA which might lead to decreased contents in neuronal membranes. The mechanisms by which polyunsaturated fatty acids can impact on neuronal functions involve the modulation of membrane biophysical properties, the regulation of neurotransmitter release, the synthesis of oxygenated biologically-active derivatives, and the nuclear receptor-mediated transcription of lipid-responsive genes; L’acide docosahexaénoique (DHA, 22:6n-3) et l’acide arachidonique (AA, 20:4n-6) sont les principaux acides gras polyinsaturés des membranes cérébrales et rétiniennes. Les animaux spécifiquement carencés en acides gras n-3 présentent des altérations de la fonction visuelle et des capacités cognitives. Les études menées chez des enfants allaités au biberon ont montré que la supplémentation des laits de remplacement avec l’AA et le DHA permet de rehausser la teneur en ces acides gras dans le plasma et les hématies, et d’atteindre ainsi le même statut sanguin que celui produit par l’allaitement au sein. L’impact probable de cette supplémentation sur les membranes nerveuses de l’enfant est susceptible de se traduire par une amélioration transitoire mais significative du développement mental et de la maturation de la fonction visuelle. Chez l’adulte, des maladies neuropsychiatriques ou neurodégénératives ont été associées à la diminution du statut sanguin en DHA et/ou en AA, qui pourrait refléter une réduction de leurs teneurs dans les membranes nerveuses. Les effets des acides gras polyinsaturés sur les fonctions nerveuses mettent en jeu des mécanismes impliqués dans la modulation des propriétés dynamiques des membranes, la régulation du processus de libération des neurotransmetteurs, la synthèse de médiateurs oxygénés bioactifs et la transcription de gènes via l’activation de récepteurs nucléaires sensibles aux lipides

Because brain membranes contain large amounts of docosahexaenoic acid (DHA, 22:6n-3), and as (n-3) PUFA dietary deficiency can lead to impaired attention, learning, and memory performance in rodents, we have examined the influence of an (n-3) PUFA-deprived diet on the central cholinergic neurotransmission system. We have focused on several cholinergic neurochemical parameters in the frontal cortex and hippocampus of rats fed an (n-3) PUFA-deficient diet, compared with rats fed a control diet. The (n-3) PUFA deficiency resulted in changes in the membrane phospholipid compositions of both brain regions, with a dramatic loss (62–77%) of DHA. However, the cholinergic pathway was only modified in the hippocampus and not in the frontal cortex. The basal acetylcholine (ACh) release in the hippocampus of deficient rats was significantly (72%) higher than in controls, whereas the KCl-induced release was lower (34%). The (n-3) PUFA deprivation also caused a 10% reduction in muscarinic receptor binding. In contrast, acetylcholinesterase activity and the vesicular ACh transporter in both brain regions were unchanged. Thus, we evidenced that an (n-3) PUFA-deficient diet can affect cholinergic neurotransmission, probably via changes in the phospholipid PUFA composition.

International audience; The circadian clock, located in the suprachiasmatic nucleus (SCN) of the hypothalamus in mammals, exhibits astroglial plasticity indicated by GFAP expression over the 24-h period. In this study, we evaluated the role of neuronal retinal input in the observed changes. Modifications of retinal input, either by rearing animals under darkness (DD) or under constant light (LL), or by suppressing afferent input (bilateral enucleation), induced drastic changes in astroglial plasticity. In enucleated animals, a dramatic decrease in GFAP expression was evident in the area of the SCN deprived of retinal projections, whereas persistence of a rhythmic variation was in those areas still exhibiting GFAP expression. By contrast, no changes in astrocytic plasticity were detected in hamsters maintained under LL. These data suggest two fundamental roles for astrocytes within the SCN: (1) to regulate and mediate glutamate released by retinal terminals throughout the neuronal network to facilitate photic signal transmission; (2) to contribute to synchronization between suprachiasmatic neurons. GLIA 34:88 –100, 2001.

Cytochrome oxidase (CO) activity was studied over a 24-h period in the Syrian hamster suprachiasmatic nucleus (SCN) (site of the biological clock), anterior hypothalamic area (AHA), and motor cortex. The SCN CO activity was highest at the middle of the day (Zeitgeber time (ZT) 05), decreased at the end of the light period (ZT 10) and continued at a low level during the night (ZT 13, 16, 21.5 and 24). AHA and motor cortex showed a similar profile of CO activity and no changes of CO activity were found in animals maintained under darkness (DD). We propose that photic input plays a role in the SCN neuronal activity that modulates metabolic activity on this area.

Introduction et but de l’etude Les acides gras polyinsatures (AGPI) des series n-3 et n-6 sont des constituants majeurs des membranes cellulaires, notamment l’acide arachidonique (AA, 20 :4n-6) et l’acide docosahexaenoique (DHA, 22 :6n-3). L’approvisionnement en DHA de l’organisme necessite un apport en DHA preforme (poissons gras) ou la conversion de l’acide alpha-linolenique (huiles de colza, soja) en DHA. Cette voie, limitante sur le plan metabolique, est commune avec la voie de conversion des AG n-6. Des etudes cliniques recentes suggerent que les oestrogenes pourraient reguler le metabolisme des AG n-3 : la concentration plasmatique en DHA est plus importante chez les femmes que chez les homes pour des conditions nutritionnelles identiques, et elle est superieure chez les femmes prenant une contraception orale. Dans cette etude, nous comparons la capacite de restauration du statut en DHA chez des rats mâles et femelles nes de meres carencees en n-3. Materiel et methodes Les rats mâles (n = 24) et femelles (n = 24) carences en acides gras n-3 depuis l’embryogenese, sont alimentes des le sevrage (âge de 3 semaines) avec un regime contenant 6,8 % en poids d’huile de colza, soit 20 mg d’acide alpha-linolenique /100 g de regime comme seule source d’apport en acides gras n-3. Les mâles (n =6) et les femelles (n=6) sont sacrifies aux âges de 3, 5, et 8 semaines, et le cortex, l’hippocampe, le foie, et le plasma sont preleves. La composition en acides gras des phospholipides (phosphatidylcholine, phosphatidylethanolamine, et phosphatidylserine) est analysee par chromatographie en phase gazeuse. L’expression de la D-Bifunctional protein (DBP), une enzyme cle de la voie de synthese du DHA est egalement analysee par western blot. Resultats La supplementation en huile de colza induit l’augmentation du DHA et du rapport DHA/22 :5n-3 (DHA/DPA, acide docosapentaenoique) dans tous les tissus analyses. Les teneurs en DHA dans les phospholipides du plasma, du cortex, et du foie sont significativement plus elevees (+10 a + 38%) chez les femelles aux âges de 5 et 8 semaines. A l’âge de 8 semaines, le rapport DHA/ DPA est egalement de 1,3 a 2 fois plus eleve chez les femelles. L’expression de la proteine DBP dans le foie des animaux âges de 5 semaines ne presente pas de difference significative entre les mâles et les femelles. Conclusions Nous concluons que la capacite de restauration du statut en DHA est plus grande chez les femelles que chez les mâles. Cette difference metabolique est notamment illustree par la valeur plus elevee du rapport DHA/DPA, qui suggere que la derniere etape de synthese du DHA (en aval du DPA) est plus active chez les femelles. Nos resultats sont compatibles avec l’hypothese d’une regulation du metabolisme des AGPI par les oestrogenes. Leur mode d’action pourrait impliquer l’activation de l’expression de genes du metabolisme lipidique. L’etude en cours vise a quantifier l’expression de 22 genes par PCR quantitative en temps reel.