Search

The development and optimal functioning of our immune system is directly influenced by our diet. Any deficiency or excess of certain nutrients can affect the number and activity of immune cells. Among the nutrients identified, dietary fatty acids are described as having major effects on immunity. Indeed, the fatty acid composition of the membranes of immune cells seems to be easily modulated under the effect of dietary fats and the resulting rapid changes in composition are likely to generate functional effects on the reactivity and functioning of these cells within a very short period of time. Among the different mechanisms identified to explain the impact of dietary fatty acids on the immune function, the synthesis of lipid mediators from polyunsaturated fatty acids is a key one notably in the context of inflammation.

Les données de consommation en acides gras polyinsaturés (AGPI) de la femme allaitante sont rares bien qu’essentielles pour évaluer le niveau d’apport en acides gras du nourrisson et éventuellement orienter la mère vers une alimentation adaptée voire vers une supplémentation en acides gras essentiels. Les données INCA 2 concernant les femmes allaitantes ont été combinées aux données de composition nutritionnelle des aliments de la base de données Ciqual 2013 pour évaluer leurs apports en acides gras. Bien qu’il s’agisse d’un échantillon limité d’individus enquêtés il y a 12 ans, ces données restent malgré tout intéressantes à analyser et à comparer aux recommandations actuelles de l’Anses. Elles montrent que la consommation en AGPI n-3 n’est pas suffisante au regard des recommandations. Par ailleurs, il a été démontré que la composition en acides gras du lait maternel est un marqueur reconnu de la consommation des lipides alimentaires et un bon reflet du niveau de consommation des AGPI n-6 et n-3. Or, les données épidémiologiques relatives à la quantité et à la qualité des lipides consommés en France sont rares. Dans le cadre de différentes études cliniques conduites sur le lait maternel, l’ITERG a pu ainsi estimer l’évolution des habitudes alimentaires des Français depuis près de 17 ans. Un travail de synthèse a repris l’ensemble des données acquises au cours de 4 études cliniques menées entre 1997 et 2014. Cette synthèse a mis en évidence une évolution positive des proportions en AGPI n-3 en 17 ans (1997–2014). Toutefois, les proportions d’acide alpha-linolénique (ALA) et d’acide docosahexaénoïque (DHA) dans le lait maternel restent en deçà des recommandations nutritionnelles pour le nouveau-né.

A lot of studies performed in rodents revealed that n-3 polyunsaturated fatty acid (PUFA) deficient diets could induce deficits of learning capacities but the mechanisms involved are not well known. Retinoic acid (RA) and its nuclear receptors (RAR and RXR) play a central role in the maintenance of cognitive processes and synaptic plasticity via its action on target genes that are neurogranin (RC3) and neuromodulin (GAP43). Given some interferences were described between the retinoid and fatty acid signaling pathways, we investigated the effects of a _α-linolenic acid (18: 3 n-3) deficient diet on retinoic acid nuclear receptors (RAR, and RXR), on GAP43 and RC3, and on blood and brain fatty acid composition in rats at three times of diet: 3, 9 and 18 weeks. In blood and brain of these animals, we observed a severe n-3 PUFA deficit (18:3 n-3, 20:5 n-3 and particularly 22:6 n-3) associated with an increase in the n-6 PUFA content (mainly 22:5 n-6). Real-time PCR and western blot analysis allowed us to note that retinoid signaling, GAP43 and RC3 expression were affected in the striatum of the n-3 PUFA deprived rats.

We investigated the impact of increased alpha-linolenic acid (ALA) dietary levels on its plasma bioavailability and its bioconversion in n-3 long chain poly unsaturated fatty acids during a 60-d kinetics and the oxidative stress potentially associated. Rats were submitted to a normolipidic diet providing 0, 3, 10 and 24% ALA of dietary lipids for 0, 15, 30 and 60 days. The lipid peroxidation and oxidative stress (nitric oxide (NO) contents and catalase (CAT), superoxide dismutase (SOD), gluthation peroxidase (GPx) activities) were studied in the liver and plasma. When the diet was deprived in n-3 PUFAs, ALA, (eicosanoic acid) EPA and docosahexaenoic acid (DHA) levels decreased in all lipid fractions of plasma and in red blood cell (RBC) lipids. The addition of ALA in the diet linearly improves its bioavailability and its bioconversion in EPA (R²=0.98). By providing 10 to 24% ALA in dietary lipids (LA/ALA, 1·6 and 5·5 respectively), ALA and EPA were more broadly packaged in all lipid fractions (triglyceride (TAG), cholesterol ester (CE) and free fatty acids (FFA)) of plasma from 15 to 30 days timeframe. Only 3% ALA was sufficient to promote the maximal bioconversion of ALA in DHA in phospholipid (PL) and TAG fractions. Additionally, the improvement of ALA bioconversion in EPA and DHA did not impact the oxidative stress markers and limiting lipid peroxidation. To conclude, this study demonstrated that in rat, 10% ALA in the lipid diet for 15–30 days promotes its bioavailability and its bioconversion and allowed the greatest levels in plasma and RBCs. [ABSTRACT FROM AUTHOR]

Adjusted differences black squares and 95% confidence intervals (CIs) (horizontal lines) of observed and predicted retinal -3 PUFAs contents for age-related macular degeneration in donor eyes and humans patients. Interestingly, cholesteryl esters species with -3 PUFAs contributed positively to the estimation of retinal -3 PUFAs content whereas those with -6 PUFAs lowered the prediction index, which is consistent with the well-established competitive metabolism of -3 and -6 PUFAs. Current treatments for age-related macular degeneration (AMD)-the leading cause of blindness in industrialized countries-are restricted to a single form of the disease and cannot always avoid severe visual loss.1 Among emerging preventive strategies, -3 polyunsaturated fatty acids (PUFAs) are enjoying interest as they promote normal retinal structure and function, reduce incidence, and slow progression of AMD, consistently with their abundance in retinal neurons. [Extracted from the article]

n-3 Long-chain PUFA (n-3 LC-PUFA), particularly EPA and DHA, play a key role in the maintenance of brain functions such as learning and memory that are impaired during ageing. Ageing is also associated with changes in the DHA content of brain membranes that could contribute to memory impairment. Limited studies have investigated the effects of ageing and n-3 LC-PUFA supplementation on both blood and brain fatty acid compositions. Therefore, we assessed the relationship between fatty acid contents in plasma and erythrocyte membranes and those in the hippocampus, striatum and cerebral cortex during ageing, and after a 5-month period of EPA/DHA supplementation in rats. In the blood, ageing was associated with an increase in plasma DHA content, whereas the DHA content remained stable in erythrocyte membranes. In the brain, ageing was associated with a decrease in DHA content, which was both region-specific and phospholipid class-specific. In EPA/DHA-supplemented aged rats, DHA contents were increased both in the blood and brain compared with the control rats. The present results demonstrated that n-3 LC-PUFA level in the plasma was not an accurate biomarker of brain DHA status during ageing. Moreover, we highlighted a positive relationship between the DHA levels in erythrocyte phosphatidylethanolamine (PE) and those in the hippocampus and prefrontal cortex in EPA/DHA-supplemented aged rats. Within the framework of preventive dietary supplementation to delay brain ageing, these results suggest the possibility of using erythrocyte PE DHA content as a reliable biomarker of DHA status in specific brain regions. [ABSTRACT FROM PUBLISHER]

Purpose: To assess the correlation between macular pigment optical density and plasma levels of lutein, zeaxanthin, and fatty acids, especially omega-3 polyunsaturated fatty acids (PUFAs)., Methods: The PIMAVOSA study is an observational study of 107 healthy volunteers, aged 20 to 60 years and born in southwest France, without histories of ocular disease. Macular pigment optical density (MPOD) was measured using the two-wavelength autofluorescence method with a modified scanning laser ophthalmoscope. Plasma measurements (lutein, zeaxanthin, and fatty acids) were performed from fasting blood samples collected on the day of the eye examination., Results: MPOD within 6° correlated with plasma levels of lutein and zeaxanthin (r = 0.35, P < 0.001, and r = 0.30, P < 0.005, respectively). MPOD also significantly correlated with total plasma omega-3 PUFAs (r = 0.22, P < 0.05). Among the different omega-3 PUFAs, docosapentaenoic acid (DPA) had the highest correlation with MPOD (r = 0.31, P < 0.001), whereas correlation with eicosapentaenoic acid (EPA) was moderate (r = 0.21, P < 0.05) and did not reach statistical significance for docosahexaenoic acid (r = 0.14, P = 0.14)., Conclusions: In the present study, macular pigment density was associated not only with plasma lutein and zeaxanthin but also with omega-3 long-chain PUFAs, particularly with EPA and DPA. Further studies will be needed to confirm these findings and to identify the underlying mechanisms.

Epidemiologic studies suggest that intake of high energy from fat, inducing overweight, increases the risk of cancer development and promotes colon carcinogenesis. It is therefore important to understand which parameters are affected early on by a high-fat diet in order to devise and improve protective nutritional strategies. We investigated the effect of high energy/fat intake on colon mucosa of male Wistar rats induced by a single 1,2-dimethylhydrazine (DMH) injection. Aberrant crypt foci (ACF) were numbered and modifications in cyclooxygenase-2 (COX-2) and beta-catenin levels assessed. Peroxisome proliferator- and retinoic acid-activated receptors (PPAR and RAR, RXR) are key transcription factors regulating gene expression in response to nutrient-activated signals. A short-term study was designed to evaluate whether alterations in mRNA expression of nuclear receptors can be detected at the beginning of the weight gain phase induced by an appetizing hyperlipidic diet (HLD). HLD consumption induced early downregulation of PPARgamma (-33.1%) and RARbeta (-53.1%) mRNA expression concomitant with an increase in levels of COX-2 (+45.5%) and beta-catenin (+84.56%) and in the number of ACF (191.56 +/- 88.60 vs. 21.14 +/- 11.64, p < 0.05). These findings suggest that HLD increases ACF occurrence, possibly through alterations in the mRNA expression profile of nuclear receptors. Moreover, the use HLD rich in retinyl esters or supplemented with all-trans retinoic acid led to a reduction in the number of ACF. Vitamin A also prevented HLD-induced alterations and the increase in levels of COX-2 and beta-catenin. The present observations show a protective role for vitamin A against disturbances associated with HLD exposure in induced colon carcinogenesis.