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Peroxisomal multifunctional protein 2 deficiency perturbs lipid homeostasis in the retina causing visual dysfunction in mice

ABSTRACT: Patients lacking multifunctional protein 2, the central enzyme of the peroxisomal β-oxidation pathway, develop retinopathy. This metabolic pathway is involved in the metabolism of very long chain (VLCFAs) and polyunsaturated (PUFAs) fatty acids, which are enriched in the photoreceptor outer segments (POS). The molecular mechanisms underlying the retinopathy remain however elusive. Here, we report that Mfp2-/- mice display decreased retinal function already at the age of 3 weeks, which is accompanied by a profound shortening of the photoreceptor outer and inner segments, but with preserved photoreceptor ultrastructure. Furthermore, Mfp2-/- retinas exhibit severe changes in gene expression with downregulation of genes involved in the phototransduction pathway and upregulation of inflammation related genes. Lipid profiling of the retina of Mpf2-/- mice revealed a profound reduction of DHA-containing phospholipids. This was likely due to a hampered systemic supply and retinal traffic of this PUFA, although we cannot exclude that the local defect of peroxisomal β-oxidation contributes to this DHA decrease. Moreover, VLC-PUFAs were also reduced, except those containing ≥34 carbons that accumulated. The latter suggests that there is an uncontrollable elongation of retinal PUFAs. In conclusion, we showed that intact peroxisomal β-oxidation is indispensable for retinal integrity, most likely by maintaining PUFA homeostasis.

ORGANISM(S): Mus musculus

PROVIDER: GSE163770 | GEO | 2021/01/31

REPOSITORIES: GEO

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Project description:<p>N-3 polyunsaturated fatty acids (PUFAs) may prevent retinal vascular abnormalities observed in oxygen-induced retinopathy, a model of retinopathy of prematurity (ROP). In the OmegaROP prospective cohort study, we showed that preterm infants who will develop ROP accumulate the n-6 PUFA arachidonic acid (ARA) at the expense of the n-3 PUFA docosahexaenoic acid (DHA) in erythrocytes with advancing gestational age (GA). As mice lacking plasmalogens ―that are specific phospholipids considered as reservoirs of n-6 and n-3 PUFAs― display a ROP-like phenotype, the aim of this study was to determine whether plasmalogens are responsible for the changes observed in subjects from the OmegaROP study. Accordingly, preterm infants aged less than 29 weeks GA were recruited at birth in the Neonatal Intensive Care Unit of University Hospital Dijon, France. Blood was sampled very early after birth to avoid any nutritional influence on its lipid composition. The lipid composition of erythrocytes and the structure of phospholipids including plasmalogens were determined by global lipidomics using liquid chromatography coupled to high-resolution mass spectrometry (LC-HRMS). LC-HRMS data confirmed our previous observations by showing a negative association between the erythrocyte content in phospholipid esterified to n-6 PUFAs and GA in infants without ROP (rho = -0.485, p = 0.013 and rho = -0.477, p = 0.015 for ethanolamine and choline total phospholipids, respectively). Phosphatidylcholine (PtdCho) and phosphatidylethanolamine (PtdEtn) species with ARA, namely PtdCho16:0/20:4 (rho = -0.511, p < 0.01) and PtdEtn18:1/20:4 (rho = -0.479, p = 0.015), were the major contributors to the relationship observed. On the contrary, preterm infants developing ROP displayed negative association between PtdEtn species with n-3 PUFAs and GA (rho = -0.380, p = 0.034). They were also characterized by a positive association between GA and the ratio of ethanolamine plasmalogens (PlsEtn) with n-6 PUFA to PlsEtn with n-3 PUFAs (rho = 0.420, p = 0.029), as well as the ratio of PlsEtn with ARA to PlsEtn with DHA (rho = 0.843, p = 0.011). Altogether, these data confirm the potential accumulation of n-6 PUFAs with advancing GA in erythrocytes of infants developing ROP. These changes may be partly due to plasmalogens.</p>

Project description:Dietary polyunsaturated fatty acids (PUFA) act as potent natural hypolipidemics and are linked to many health benefits in humans and in animal models. Mice fed long-term a high fat diet, in which medium-chain alpha linoleic acid (ALA) was partially replaced by long-chain docosahexaenoic (DHA) and eicosapentaenoic (EPA) fatty acids, showed reduced accumulation of body fat and prevention of insulin resistance, besides increased mitochondrial beta-oxidation in white adipose tissue and decreased plasma lipids. ALA, EPA and DHA all belong to PUFA of n-3 series. The intestine is a gatekeeper organ for ingested lipids. To examine the potential contribution of the intestine in the beneficial effects of EPA and DHA, this study assessed gene expression changes using whole genome microarray analysis on small intestinal scrapings. The main biological process affected was lipid metabolism. Fatty acid uptake, peroxisomal and mitochondrial beta-oxidation, and omega-oxidation of fatty acids were all increased. Quantitative real time PCR and intestinal fatty acid oxidation measurements ([14C(U)]-palmitate) confirmed significant gene expression differences in a dose-dependent manner. Furthermore, no major changes in the expression of lipid metabolism genes were observed in colonic scrapings. In conclusion, we show that marine n-3 fatty acids regulate small intestinal gene expression patterns. Since this organ contributes significantly to whole organism energy use, this adaptation of the small intestine may contribute to the complex and observed beneficial physiological effects of these natural compounds under conditions that will normally lead to development of obesity and diabetes. Experiment Overall Design: Male 4-month-old C57BL/6J mice were maintained for 4 weeks on semisynthetic high-fat (20% wt/wt) diets differing in the composition of n-3 PUFA. Two isocaloric diets were used (n=12): control sHFf diet which contained flax-seed oil (rich in ALA) as the only lipid source, or the sHFf-F2 diet, which had the same composition except that 44 % of the lipids were replaced by a n-3 PUFA concentrate (EPA&DHA) containing 6 % EPA and 51 % DHA (EPAX 1050TG; EPAX AS, Lysaker, Norway). Quality control of RNA samples showed that four samples did not pass quality thresholds, and these samples were excluded from array analysis (two control small intestine samples and one EPA&DHA small intestine sample). The remaining RNA samples were pooled per tissue per diet group. Thus; the flax-seed (control) array was hybridized with RNA pooled from of 10 mice, the PUFA array was hybridized with RNA pooled from 11 mice.

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Peroxisomal multifunctional protein 2 deficiency perturbs lipid homeostasis in the retina causing visual dysfunction in mice

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