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Aldose reductase (AR) is an enzyme implicated in the development of diabetes complications among them diabetic retinopathy. Erythrocyte AR activity was measured in control and diabetic Meriones shawi, a type-2 diabetic model. We noticed an increase of AR activity in diabetic Meriones by comparison to controls. Olive leaf aqueous extract and oleuropein were tested for their inhibitory potential on AR activity. Both exerted a partial in-vitro inhibition effect which was higher with the olive leaf extract. The ex-vivo protective effect of oleuropein was tested in photoreceptors rod and Mcône retinal cells of Meriones shawi in hyperglycaemic conditions. Mixed retinal cells were cultured at 25 mM glucose for 5 days and treated with oleuropein. Cell viability was assessed using MTT test and trypan blue exclusion dye. Rod and Mcône Photoreceptors were characterised by immuno-cytochemistry. Oleuropein protected retinal cells against the toxic effect of glucose by improving the viability of photoreceptors. [ABSTRACT FROM AUTHOR]

Astaxanthin (ATX) is a marine carotenoid known for its powerful antioxidant and neuroprotective properties. In this study, we investigated the in vitro and in vivo potential inhibitory effect of ATX on the aldose reductase (AR) activity, a key enzyme in the polyol pathway responsible for the pathogenesis of diabetic complications including diabetic retinopathy (DR). The gerbil Psammomys obesus (P. ob.), an animal model for type 2 diabetes and DR has been used. The erythrocyte and retinal AR activity of P. ob. individuals were, respectively, assessed monthly and at the 7th month during a 7‐month hypercaloric diet (HD) using a NADPH oxidation method. Meanwhile, the body weight and blood glucose of the gerbils were monitored. After 7 months, P. ob. individuals were fed with ATX (4.8 mg/kg of body weight) once a day for 1 week. The results showed that the HD‐fed animals developed significant obesity and hyperglycemia in comparison with controls. Erythrocyte AR activity showed a progressive and significant increase in the HD‐fed group compared with controls. Retinal AR activity was higher in the 7‐month HD‐fed group compared with controls. Erythrocyte AR activity was markedly decreased after ATX‐treatment in vitro and in vivo. These findings suggested that ATX inhibited the erythrocyte AR activity and could be used for DR prevention and/or early treatment. [ABSTRACT FROM AUTHOR]

Astaxanthin is a major marine carotenoid with powerful antioxidant and neuroprotective properties. The in vitro protective effect of astaxanthin in adult retinal cells of the type-2 diabetic model Psammomys obesus in hyperglycemic conditions was investigated. Primary retinal cells were cultured in normal (5 mM) or high concentrations of glucose (25 and 40 mM) for 5 days and treated with 1-20 µM astaxanthin for the last 48 h of culturing. Mitochondrial dehydrogenase activity and cell viability were assessed using MTT test and trypan blue exclusion dye. Retinal cells were characterized by immunohistochemistry. The results showed that mitochondrial function increased significantly ( P < 0.05) with 5-20 µM astaxanthin in 25-40 mM glucose. At 10 µM astaxanthin, cell viability recovered to 78.51 ± 5.81% and 54.37 ± 9.64% of control in 25 and 40 mM, respectively. Neurons and glial cells expression were enhanced in elevated glucose conditions. These finding suggest that astaxanthin exerted neuroprotection against high glucose induced- retinal damage. Practical Applications The xanthophyll astaxanthin is found in many marine food sources such as shrimp. The cytoprotective and antioxidant capacity of astaxanthin in retinal disease has been pointed out and presented as a promising therapeutic strategy. The present study shows that astaxanthin can interfere with hyperglycemia-induced retinal cell death and that primary retinal culture of Psammomys obesus may represent an effective system to explore astaxanthin antioxidant mechanisms in diabetic retinopathy. [ABSTRACT FROM AUTHOR]

Purpose: The retina contains the highest concentration of the omega 3 fatty acid, docosahexaenoic acid (DHA), in the body. Although epidemiologic studies showed an inverse correlation between the consumption of omega 3 fatty acids and the prevalence of diabetic retinopathy, there are no data showing the effect of diabetes on retinal DHA in humans. In this study, we measured the DHA content of the retina in diabetic and non-diabetic humans as well as mice and determined the effect of diabetes on retinal thickness and function in mice., Methods: Fatty acid composition was determined by gas chromatography/mass spectroscopy. Retinal thickness in mice was measured by optical coherence tomography and retinal function was measured by electroretinogram (ERG). Expression of selected genes involved in inflammation and lipid metabolism was determined by quantitative real-time PCR (qRT-PCR)., Results: We found a 40% reduction of DHA in peripheral retina and a 25% reduction in the macula of diabetic humans compared with nondiabetic controls. There was a 24% reduction in retinal DHA of type 2 diabetic mice (db/db) compared with the controls (db/+). The retinal thickness was significantly decreased in db/db mice, especially in the inner retina, and the ERG b-wave amplitudes were significantly attenuated. Increased expression of proinflammatory genes was observed in both human and mouse diabetic retinas., Conclusions: Retinal DHA is reduced in diabetic humans and mice, which is associated with a thinning of retina and functional defects in diabetic mice. Enriching retinal DHA through diet may be beneficial in the prevention and treatment of diabetic retinopathy.