Diabetic retinopathy and age-related macular degeneration are the leading causes of blindness in Western populations. Although it is a matter of controversy, large-scale population-based studies have reported increased prevalence of age-related macular degeneration in patients with diabetes or diabetic retinopathy. We hypothesized that metabolic syndrome, one of the major risk factors for type 2 diabetes, would represent a favorable environment for the development of choroidal neovascularization, the main complication of age-related macular degeneration. The fructose-fed rat was used as a model for metabolic syndrome in which choroidal neovascularization was induced by laser photocoagulation. Male Brown Norway rats were fed for 1, 3, and 6 months with a standard equilibrated chow diet or a 60%-rich fructose diet (n = 24 per time point). The animals expectedly developed significant body adiposity (+17%), liver steatosis at 3 and 6 months, hyperleptinemia at 1 and 3 months (two-fold increase) and hyperinsulinemia at 3 and 6 months (up to two-fold increase), but remained normoglycemic and normolipemic. The fructose-fed animals exhibited partial loss of rod sensitivity to light stimulus and reduced amplitude of oscillatory potentials at 6 months. Fructose-fed rats developed significantly more choroidal neovascularization at 14 and 21 days post-laser photocoagulation after 1 and 3 months of diet compared to animals fed the control diet. These results were consistent with infiltration/activation of phagocytic cells and up-regulation of pro-angiogenic gene expression such as Vegf and Leptin in the retina. Our data therefore suggested that metabolic syndrome would exacerbate the development of choroidal neovascularization in our experimental model.

Lipid rafts play a pivotal role in physiological functions of platelets. Their isolation using nonionic mild detergents is considered as the gold standard method, but there is no consensual detergent for lipid raft studies. We aimed to investigate which detergent is the most suitable for lipid raft isolation from platelet membrane, based on lipidomics and proteomics analysis. Platelets were obtained from healthy donors. Twelve sucrose fractions were extracted by three different detergents, namely Brij 35, Lubrol WX, and Triton X100, at 0.05% and 1%. After lipidomics analysis and determination of fractions enriched in cholesterol (Ch) and sphingomyelin (SM), proteomics analysis was performed. Lipid rafts were mainly observed in 1-4 fractions, and non-rafts were distributed on 5-12 fractions. Considering the concentration of Ch and SM, Lubrol WX 1% and Triton X100 1% were more suitable detergents as they were able to isolate lipid raft fractions that were more enriched than non-raft fractions. By proteomics analysis, overall, 822 proteins were identified in platelet membrane. Lipid raft fractions isolated with Lubrol WX 0.05% and Triton X100 1% contained mainly plasma membrane proteins. However, only Lubrol WX 0.05 and 1% and Triton X100 1% were able to extract non-denaturing proteins with more than 10 transmembrane domains. Our results suggest that Triton X100 1% is the most suitable detergent for global lipid and protein studies on platelet plasma membrane. However, the detergent should be adapted if investigation of an association between specific proteins and lipid rafts is planned.

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-The retina is responsible for coding the light stimulus into a nervous signal that is transferred to the brain via the optic nerve. The retina is formed by the association of the neurosensory retina and the retinal pigment epithelium that is supported by Bruch's membrane. Both the physical and metabolic associations between these partners are crucial for the functioning of the retina, by means of nutrient intake and removal of the cell and metabolic debris from the retina. Dysequilibrium are involved in the aging processes and pathologies such as age-related macular degeneration, the leading cause of visual loss after the age of 50 years in Western countries. The retina is composed of several populations of cells including glia that is involved in cholesterol biosynthesis. Cholesterol is the main sterol in the retina. It is present as free form in cells and as esters in Bruch's membrane. Accumulation of cholesteryl esters has been associated with aging of the retina and impairment of the retinal function. Under dietary influence and in situ synthesized, the metabolism of cholesterol is regulated by cell interactions, including neurons and glia via cholesterol-24S-hydroxylase. Several pathophysiological associations with cholesterol and its metabolism can be suggested, especially in relation to glaucoma and age-related macular degeneration.Keywords: Retina / lipid / cholesterol / glaucoma / age-related macular degeneration / aging Résumé -Cholestérol et pathologies oculaires : focus sur le rôle de la cholestérol-24S-hydroxylase dans l'homéostasie du cholestérol. La rétine est le tissu neurosensoriel de l'oeil qui assure la transduction visuelle, c'est-à-dire le codage de l'information lumineuse en influx nerveux. Le terme de rétine regroupe l'association de la rétine neurale et de l'épithélium pigmentaire rétinien qui repose sur la membrane de Bruch. L'association physique de ces deux partenaires et leurs interactions métaboliques sont des éléments indispensables au bon fonctionnement de la rétine, à la fois en termes d'apport en nutriments et de maintien de l'homéostasie. Des dérèglements de ces équilibres sont associés au vieillissement et à des pathologies comme la dégénérescence maculaire liée à l'âge, première cause de malvoyance après 50 ans dans les populations occidentales. La rétine neurale est composée de plusieurs types cellulaires, incluant la glie dont le rôle est crucial pour la biosynthèse du cholestérol dans la rétine. Le cholestérol est le principal stérol de la rétine. Il y est présent dans la cellule essentiellement en tant que cholestérol libre et d'esters de cholestérol au niveau extracellulaire dans la membrane de Bruch. L'accumulation de ces esters de cholestérol à ce niveau est un marqueur du vieillissement de la rétine et de la diminution de sa fonction. Sous influence alimentaire et synthétisé localement, le cholestérol est également régulé via les interactions entre populations cellulaires de la rétine, comme entre neurones et glie, via la cholestérol-24S-hydroxylase. Plusieur...

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Purpose Diabetic retinopathy is a chronic inflammatory disease where the infiltration of plasma and neovascularization of the retina cause blindness. This disease affects millions of people in developed countries and early biological markers would better manage these patients. Methods For this purpose we purified monocytes, key players of inflammation, blood of healthy and sick people. On the surface of monocytes, there are dynamic structures called rafts membrane microdomains, which there are two subtypes: flat rafts and caveolae rafts. They correspond to dynamic assemblies and ordered cholesterol and sphingolipids. We isolated these rafts membranes of monocytes and studied protein AT2 (angiotensin receptor II) and gp91 (major membrane subunit of NADPH oxidase, producing enzyme superoxide anions), potential markers of the severity of diabetic retinopathy. Results Our results have shown a switch of cholesterol and sphingomyelin flat rafts to caveolae rafts. The analysis of the constituent proteins (flotillin and caveolin) and functional (AT2, gp91 and p47phox) have shown that these are mobile in the membrane in an inflammatory context. Subunits of NADPH oxidase seem to gather in caveolae rafts and more precisely when the enzyme is activated. Conclusion The proteins of interest and the switch composition of lipid rafts therefore would appear to be an indicator of the progression of diabetic retinopathy and it would be interesting to provide a mechanistic explanation for the evolution of this chronic vascular disease to consider potential therapeutic targets

PurposeThe catabolism of cholesterol in neurons leads to a more hydrophilic compound soluble form, the 24‐S‐hydroxycholesterol by means of an enzyme the CYP46A1.The aim of this study was to analyse the implication of 24‐S‐hydroxycholesterol (24‐S‐OHC) on Müller glial cells (MGC) membrane dynamics in the rat.MethodsMGC were grown in vitro from retinas of 10‐day‐old Long Evans rats. Cells were treated with 24‐S‐OHC (treatment) or ethanol (control) for 2 min or 6 h. From twenty millions of MGC in each group, lipid‐rafts were obtained after a 1% Lubrol lysis and an ultra centrifugation (180,000 g – 20 h – 4°C). The following proteins: caveolin, flottilin, connexin 30 and 43, CRALBP, DHAPAT, GFAP and vimentin were analysed using Western blotting on all fractions (lipid‐rafts and non‐rafts). MGC membrane fluidity was studied in vitro with two different techniques: anisotropy measurements performed with the lipophilic fluorescent probe TMA‐DPH and fluorescence recovery after photobleaching (FRAP) observed using confocal microscopy.Results24‐S‐OHC treatment on in vitro MGC increased the expression of GFAP and delocalized GFAP in the lipid‐raft fraction; 24‐S‐OHC treatment induced a delocalization of DHAPAT protein out of the lipid‐rafts fraction. Anisotropy was decreased with the 24‐S‐OHC treatment (difference: 5.1 × 10−3; p < 0.01) revealing an increase of the membrane fluidity. This increase was confirmed by the FRAP technique, which showed a shorter time of fluorescence recovery for the treated cells.ConclusionsThis study showed that 24‐S‐OHC could be a candidate leading a key role in the activation of MGC, disturbing lipid‐raft organization by changing the localization of signalization proteins and increasing membrane's fluidity.