Cécile Gladine

Lipid profiling following intake of the omega 3 fatty acid DHA identifies the peroxidized metabolites F4-neuroprostanes as the best predictors of atherosclerosis prevention.

Abstract The anti-atherogenic effects of omega 3 fatty acids, namely eicosapentaenoic (EPA) and docosahexaenoic acids (DHA) are well recognized but the impact of dietary intake on bioactive lipid mediator profiles remains unclear. Such a profiling effort may offer novel targets for future studies into the mechanism of action of omega 3 fatty acids. The present study aimed to determine the impact of DHA supplementation on the profiles of polyunsaturated fatty acids (PUFA) oxygenated metabolites and to investigate their contribution to atherosclerosis prevention. A special emphasis was given to the non-enzymatic metabolites knowing the high susceptibility of DHA to free radical-mediated peroxidation and the increased oxidative stress associated with plaque formation. Atherosclerosis prone mice (LDLR−/−) received increasing doses of DHA (0, 0.1, 1 or 2% of energy) during 20 weeks leading to a dose-dependent reduction of atherosclerosis (R2 = 0.97, p = 0.02), triglyceridemia (R2 = 0.97, p = 0.01) and cholesterolemia (R2 = 0.96, p<0.01). Targeted lipidomic analyses revealed that both the profiles of EPA and DHA and their corresponding oxygenated metabolites were substantially modulated in plasma and liver. Notably, the hepatic level of F4-neuroprostanes, a specific class of DHA peroxidized metabolites, was strongly correlated with the hepatic DHA level. Moreover, unbiased statistical analysis including correlation analyses, hierarchical cluster and projection to latent structure discriminate analysis revealed that the hepatic level of F4-neuroprostanes was the variable most negatively correlated with the plaque extent (p<0.001) and along with plasma EPA-derived diols was an important mathematical positive predictor of atherosclerosis prevention. Thus, oxygenated n-3 PUFAs, and F4-neuroprostanes in particular, are potential biomarkers of DHA-associated atherosclerosis prevention. While these may contribute to the anti-atherogenic effects of DHA, further in vitro investigations are needed to confirm such a contention and to decipher the molecular mechanisms of action.

DHA at nutritional doses restores insulin sensitivity in skeletal muscle by preventing lipotoxicity and inflammation

Skeletal muscle plays a major role in the control of whole body glucose disposal in response to insulin stimulus. Excessive supply of fatty acids to this tissue triggers cellular and molecular disturbances leading to lipotoxicity, inflammation, mitochondrial dysfunctions, impaired insulin response and decreased glucose uptake. This study was conducted to analyze the preventive effect of docosahexaenoic acid (DHA), a long-chain polyunsaturated n-3 fatty acid, against insulin resistance, lipotoxicity and inflammation in skeletal muscle at doses compatible with nutritional supplementation. DHA (30 μM) prevented insulin resistance in C2C12 myotubes exposed to palmitate (500 μM) by decreasing protein kinase C (PKC)-θ activation and restoring cellular acylcarnitine profile, insulin-dependent AKT phosphorylation and glucose uptake. Furthermore, DHA protected C2C12 myotubes from palmitate- or lipopolysaccharide-induced increase in Ptgs2, interleukin 6 and tumor necrosis factor-α mRNA level, probably through the inhibition of p38 MAP kinase and c-Jun amino-terminal kinase. In LDLR -/- mice fed a high-cholesterol-high-sucrose diet, supplementation with DHA reaching up to 2% of daily energy intake enhanced the insulin-dependent AKT phosphorylation and reduced the PKC-θ activation in skeletal muscle. Therefore, DHA used at physiological doses participates in the regulation of muscle lipid and glucose metabolisms by preventing lipotoxicity and inflammation.

Simultaneous quantitative profiling of 20 isoprostanoids from omega-3 and omega-6 polyunsaturated fatty acids by LC–MS/MS in various biological samples

Isoprostanoids are a group of non-enzymatic oxygenated metabolites of polyunsaturated fatty acids. It belongs to oxylipins group, which are important lipid mediators in biological processes, such as tissue repair, blood clotting, blood vessel permeability, inflammation and immunity regulation. Recently, isoprostanoids from eicosapentaenoic, docosahexaenoic, adrenic and α-linolenic namely F3-isoprostanes, F4-neuroprostanes, F2-dihomo-isoprostanes and F1-phytoprostanes, respectively have attracted attention because of their putative contribution to health. Since isoprostanoids are derived from different substrate of PUFAs and can have similar or opposing biological consequences, a total isoprostanoids profile is essential to understand the overall effect in the testing model. However, the concentration of most isoprostanoids range from picogram to nanogram, therefore a sensitive method to quantify 20 isoprostanoids simultaneously was formulated and measured by liquid chromatography-tandem mass spectrometry (LC-MS/MS). The lipid portion from various biological samples was extracted prior to LC-MS/MS evaluation. For all the isoprostanoids LOD and LOQ, and the method was validated on plasma samples for matrix effect, yield of extraction and reproducibility were determined. The methodology was further tested for the isoprostanoids profiles in brain and liver of LDLR(-/-) mice with and without docosahexaenoic acid (DHA) supplementation. Our analysis showed similar levels of total F2-isoprostanes and F4-neuroprostanes in the liver and brain of non-supplemented LDLR(-/-) mice. The distribution of different F2-isoprostane isomers varied between tissues but not for F4-neuroprostanes which were predominated by the 4(RS)-4-F4t-neuroprostane isomer. DHA supplementation to LDLR(-/-) mice concomitantly increased total F4-neuroprostanes levels compared to F2-isoprostanes but this effect was more pronounced in the liver than brain.

Increasing intake of long-chain n -3 PUFA enhances lipoperoxidation and modulates hepatic gene expression in a dose-dependent manner

Long-chain (LC) n-3 PUFA have a broad range of biological properties that can be achieved at the gene expression level. This has been well described in liver, where LC n-3 PUFA modulate the expression of genes related to lipid metabolism. However, the complexity of biological pathway modulations and the nature of bioactive molecules are still under investigation. The present study aimed to investigate the dose-response effects of LC n-3 PUFA on the production of peroxidised metabolites, as potential bioactive molecules, and on global gene expression in liver. Hypercholesterolaemic rabbits received by daily oral administration (7 weeks) either oleic acid-rich oil or a mixture of oils providing 0.1, 0.5 or 1 % (groups 1, 2 and 3 respectively) of energy as DHA. Levels of specific peroxidised metabolites, namely 4-hydroxyhexenal (4-HHE)-protein adducts, issued from LC n-3 PUFA were measured by GC/MS/MS in liver in parallel to transcription profiling. The intake of LC n-3 PUFA increased, in a dose-dependent manner, the hepatic production of 4-HHE. At the highest dose, LC n-3 PUFA provoked an accumulation of TAG in liver, which can be directly linked to increased mRNA levels of lipoprotein hepatic receptors (LDL-receptor and VLDL-receptor). In groups 1 and 2, the mRNA levels of microsomal TAG transfer protein decreased, suggesting a possible new mechanism to reduce VLDL secretion. These modulations of genes related to lipoprotein metabolism were independent of PPARα signalling but were probably linked to the activation of the farnesol X receptor pathway by LC n-3 PUFA and/or their metabolites such as HHE.

DHA-derived oxylipins, neuroprostanes and protectins, differentially and dose-dependently modulate the inflammatory response in human macrophages: Putative mechanisms through PPAR activation

ABSTRACT Whereas the anti‐inflammatory properties and mechanisms of action of long chain ω3 PUFAs have been abundantly investigated, research gaps remain regarding the respective contribution and mechanisms of action of their oxygenated metabolites collectively known as oxylipins. We conducted a dose‐dependent and comparative study in human primary macrophages aiming to compare the anti‐inflammatory activity of two types of DHA‐derived oxylipins including the well‐described protectins (NPD1 and PDX), formed through lipoxygenase pathway and the neuroprostanes (14‐A4t‐ and 4‐F4t‐NeuroP) formed through free‐radical mediated oxygenation and expected to be new anti‐inflammatory mediators. Considering the potential ability of these DHA‐derived oxylipins to bind PPARs and knowing the central role of these transcription factors in the regulation of macrophage inflammatory response, we performed transactivation assays to compare the ability of protectins and neuroprostanes to activate PPARs. All molecules significantly reduced mRNA levels of cytokines such as IL‐6 and TNF‐&agr;, however not at the same doses. NPD1 showed the most effect at 0.1 &mgr;M (−14.9%, p<0.05 for IL‐6 and −26.7%, p<0.05 for TNF‐&agr;) while the three other molecules had greater effects at 10 &mgr;M, with the strongest result due to the cyclopentenone neuroprostane, 14‐A4t‐NeuroP (−49.8%, p<0.001 and −40.8%, p<0.001, respectively). Part of the anti‐inflammatory properties of the DHA‐derived oxylipins investigated could be linked to their activation of PPARs. Indeed, all tested oxylipins significantly activated PPAR&ggr;, with 14‐A4t‐NeuroP leading to the strongest activation, and NPD1 and PDX also activated PPAR&agr;. In conclusion, our results show that neuroprostanes and more especially cyclopentenone neuroprostanes have potent anti‐inflammatory activities similar or even more pronounced than protectins supporting that neuroprostanes should be considered as important contributors to the anti‐inflammatory effects of DHA. Graphical abstract Figure. No Caption Available. HighlightsBoth Neuroprostanes and Protectins attenuate inflammatory response of macrophages.Cyclopentenone neuroprostanes have the most potent anti‐inflammatory properties.Protectin D1 is active at low dose and loses its bioactivity at high dose.Neuroprostanes and Protectins might act through PPAR activation.Neuroprostanes preferentially activate PPAR&ggr; while Protectins mainly activate PPAR&agr;.

Pulmonary arterial systolic pressure and susceptibility to high altitude pulmonary edema.

There is evidence that pulmonary arterial hypertension plays a major role in the occurrence of high altitude pulmonary edema (HAPE). We tested the hypothesis that the pulmonary arterial systolic pressure response to a challenge associated with hypoxia and mild exercise may be considered a predictive factor of HAPE. Pulmonary arterial systolic pressure was measured by Doppler echocardiography in 8 HAPE susceptible (HAPE-S) subjects and 8 HAPE resistant mountaineers (HAPE-R) during a hypoxic exercise challenge established by the French Association for Sport Medicine (Richalets test). Pulmonary arterial systolic pressure during hypoxic exercise allowed a significant discrimination between the groups, although an overlap of values was observed. When expressed as individual variations from baseline to hypoxic exercise level however, we found a highly significant difference. No overlap was observed between HAPE-R (range: 6.7-18.5 mmHg) and HAPE-S (range: 19.2-30.4 mmHg) groups, with a cut-off value at 19 mmHg. Plasma Vascular Endothelial growth factor (VEGF) and malondialdehyde (MDA) increased in response to hypoxic exercise only in HAPE-S group. Individual increases in pulmonary arterial systolic pressure during hypoxic exercise from basal resting normoxic values seem relevant to estimate HAPE susceptibility when measured during the Richalets test.

Neuroprostanes, produced by free-radical mediated peroxidation of DHA, inhibit the inflammatory response of human macrophages.

The anti-inflammatory properties of DHA have been largely demonstrated in vitro and in vivo but research gaps remain regarding the contribution of the oxygenated metabolites. Among them, we are focusing on prostaglandin-like molecules termed Neuroprostanes (NeuroPs) which are produced through free-radical-mediated peroxidation of DHA. We hypothesized that these specific molecules which are highly reactive and produced in abundance during oxidative stress and inflammation could contribute to the anti-inflammatory properties of DHA. Human peripheral blood mononuclear cells were isolated from healthy donors by Ficoll density gradient centrifugation. Monocytes were differentiated into resting macrophages (RM) for 6 days (37°C, 5% CO2). RM were exposed to 2 different types of NeuroPs (i.e. 14-A4-NeuroP and 4-F4t-NeuroP, 10µM) or ethanol (vehicle 0.15%) during 30min. Then LPS (100ng/mL) was added for 6hours to induced inflammatory response. Both types of NeuroPs (14-A4-NeuroP and 4-F4t-NeuroP) significantly decreased the mRNA levels of IL-6 (-49% and -26% respectively) and MCP-1 (-55% and -24% respectively). Secretion of TNFα and MCP-1 was also reduced when RM were exposed to 14-A4-NeuroP (-10%, ns and -34%, p<0.05) and 4-F4t-NeuroP (-12%, p<0.01 and 25%, ns). Preliminary results regarding the expression and phosphorylation of IkBa suggest that 4-F4t-NeuroP could exert its anti-inflammatory effects through the inhibition of IkBa phosphorylation. Finally, cotransfection of luciferase reporter vector with hPPARg expression vector performed on Cos-7 cells suggests that NeuroPs probably act independently of PPARg. In conclusion, these results suggest that the anti-inflammatory properties of DHA could be mediated, at least in part, by NeuroPs which corroborates the importance of oxidative stress in cell signaling.

Insight into the contribution of isoprostanoids to the health effects of omega 3 PUFAs

Omega 3 polyunsaturated fatty acids have been reported to confer beneficial health effects notably in the field of cardiovascular and inflammatory diseases. The current knowledge suggests a significant portion of the effects of omega 3 polyunsaturated fatty acids are mediated by their oxygenated metabolites. This review attempts to cover the current literature about the contribution of specific omega 3 oxygenated metabolites, namely omega 3 isoprostanoids, which are produced through free-radical mediated oxidation. A special emphasis has been given to the most biologically relevant omega 3 polyunsaturated fatty acids namely the α-linolenic, eicosapentaenoic and docosahexaenoic acids. The review includes a comprehensive description of the biosynthetic pathways, a summary of studies related to the biological significance of omega 3 isoprostanoids as well as a critical description of analytical development in the field of omega 3 isoprostanoids profiling in biological samples.

Quantification of 4-hydroxy-2-nonenal-protein adducts in the in vivo gastric digesta of mini-pigs using a GC-MS/MS method with accuracy profile validation

Hydroxyalkenals are lipid oxidation end-products resulting from the oxidation of polyunsaturated fatty acids (PUFA). This study aimed at quantifying the production of 4-hydroxy-2-nonenal-protein adducts (HNE-P) via Michael addition from n-6 PUFA oxidation in the gastric digesta of mini-pigs after the consumption of meat-based meals with different plant antioxidant contents. Using the accuracy profile procedure, we validated an extraction protocol for the quantification of HNE-P by GC-MS/MS in gastric contents. The formation of HNE-P in the gastric compartment was observed for the first time, with concentrations ranging from less than 0.52 to 1.33 nmol HNE-P per 500 mg digesta. Nevertheless, most gastric HNE-P levels were below the limit of quantification of 0.52 nmol HNE-P per 500 mg digesta. In this animal study, the protective effect of plant antioxidant sources on HNE-P formation was not evidenced contrasting with the results using TBARS as markers.

Muscle loss associated changes of oxylipin signatures during biological aging: an exploratory study from the PROOF cohort

Characterizations of the multiple mechanisms determining biological aging are required to better understand the etiology and identify early biomarkers of sarcopenia. Oxylipins refer to a large family of signaling lipids involved in the regulation of various biological processes that become dysregulated during aging. To investigate whether comprehensive oxylipin profiling could provide an integrated and fine characterization of the early phases of sarcopenia, we performed a quantitative targeted metabolomics of oxylipins in plasma of 81-year old subjects from the PROOF cohort with decreased (n = 12), stable (n = 16) or increased appendicular muscle mass (n = 14). Multivariate and univariate analyses identified significant and concordant changes of oxylipin profiles according to the muscle status. Of note, 90 % of the most discriminant oxylipins were derived from EPA and DHA and were increased in the sarcopenic subjects. The oxylipins signatures of sarcopenic subjects revealed subtle activation of inflammatory resolution pathways, coagulation processes and oxidative stress as well as the inhibition of angiogenesis. Heat maps highlighted relationships between oxylipins and the cardiometabolic health parameters which were mainly lost in sarcopenic subjects. This exploratory study supports that targeted metabolomics of oxylipins could provide relevant and subtle characterization of early disturbances associated with muscle-loss during aging.