Neuroprotective Effect of Hydroxytyrosol in Experimental Diabetic Retinopathy: Relationship with Cardiovascular Biomarkers.

The aim of the study was to test the neuroprotective effect of hydroxytyrosol (HT) on experimental diabetic retinopathy. Animals were divided in four groups: (1) control nondiabetic rats, (2) streptozotocin-diabetic rats (DR), (3) DR treated with 1 mg/kg/day p.o. HT, and (4) DR treated with 5 mg/kg/day p.o. HT. Treatment with HT was started 7 days before inducing diabetes and was maintained for 2 months. In the DR group, total area occupied by extracellular matrix was increased, area occupied by retinal cells was decreased; both returned to near-control values in DR rats treated with HT. The number of retinal ganglion cells in DR was significantly lower (44%) than in the control group, and this decrease was smaller after HT treatment (34% and 9.1%). Linear regression analysis showed that prostacyclin, platelet aggregation, peroxynitrites, and the dose of 5 mg/kg/day HT significantly influenced retinal ganglion cell count. In conclusion, HT exerted a neuroprotective effect on diabetic retinopathy, and this effect correlated significantly with changes in some cardiovascular biomarkers.

Effects of hydroxytyrosol on cardiovascular biomarkers in experimental diabetes mellitus.

The aim of this study was to assess the influence of hydroxytyrosol (HT) on cardiovascular biomarkers and morphometric parameters of the arterial wall in streptozotocin-diabetic rats. Seven groups of rats (N=10 per group) were studied for 2 months: nondiabetic rats (NDR), diabetic rats treated with saline (DR) and DR treated with HT (0.5, 1, 2.5, 5 and 10 mg kg-1 day-1 p.o.). DR had higher platelet aggregation values, higher thromboxane B2, plasma lipid peroxidation, 3-nitrotyrosine, oxidized LDL (oxLDL), myeloperoxidase, vascular cell adhesion molecule 1 (VCAM-1) and interleukin-1ß (IL-1ß) concentrations, and lower aortic 6-keto-prostaglandin F1α and nitric oxide production than NDR. Aortic wall area and smooth muscle cell count were also higher in DR than in NDR. HT significantly reduced both oxidative and nitrosative stress, oxLDL concentration, VCAM-1 and inflammatory mediators, platelet aggregation and thromboxane B2 production. Morphometric values in the aortic wall were reduced to values near those in NDR. In conclusion, HT influenced the major biochemical processes leading to diabetic vasculopathy, and reduced cell proliferation in the vascular wall in this experimental model.

Virgin olive oil administration improves the effect of aspirin on retinal vascular pattern in experimental diabetes mellitus.

The aim of the present study is to evaluate the possible influence of virgin olive oil (VOO) on the effect of acetylsalicylic acid (ASA) in platelet aggregation, prostanoid and NO production and retinal vascular pattern in rats with experimental type 1-like diabetes. We used 100 male Wistar rats that were distributed into five groups: (1) non-diabetic rats (NDR); (2) untreated diabetic rats (DR); (3) DR treated with ASA (2 mg/kg per d per os (p.o.)); (4) DR treated with VOO (0.5 ml/kg per d p.o.); (5) DR treated with ASA plus VOO. The duration of diabetes was 3 months, and each treatment was administered from the first day of diabetes. Variables that were quantified were platelet aggregation (I(max)), thromboxane B(2) (TxB(2)), aortic prostacyclin (6-keto-PGF(1alpha)) and NO, and the percentage of retina with horseradish peroxidase-permeable vessels (HRP-PV). Diabetic rats showed a higher I(max) (35 %) and TxB(2) (63 %) than NDR, and a lower 6-keto-PGF(1alpha), NO and HRP-PV than NDR ( - 74.6 %). ASA and VOO administration reduced these differences and prevented the percentage of HRP-PV ( - 59.7 % with ASA and - 46.7 % with VOO). The administration of ASA plus VOO showed a strong platelet inhibition (80.2 v. 23.4 % for VOO and 50.6 % for ASA+VOO, P < 0.0001), and reduced HRP-PV differences to - 31.6 % (P < 0.001 with respect to DR and P < 0.0001 with respect to DR treated with ASA). In conclusion, the administration of VOO to rats with type 1-like diabetes mellitus improves the pharmacodynamic profile of ASA, and increases its retinal anti-ischaemic effect.

Effect of virgin olive oil plus acetylsalicylic acid on brain slices damage after hypoxia-reoxygenation in rats with type 1-like diabetes mellitus.

Aspirin is the most widely used drug for the secondary prevention of ischemic stroke in patients suffering from diabetes mellitus. Moreover virgin olive oil (VOO) administration exerts a neuroprotective effect in healthy rat brain slices. The aim of the present study was to determine the possible influence of VOO administration to streptozotocin-diabetic rats (DR) on the neuroprotective effect of aspirin in rat brain. DR were treated during 3 months with saline, aspirin (2mg/kg/day p.o.), VOO (0.5 mL/kg/day p.o.) or its association; a control normoglycemic group was treated with saline. Brain slices were subjected to oxygen-glucose deprivation before a reoxygenation period. All the treatments significantly reduced lactate dehydrogenase LDH efflux after reoxygenation (-54.1% for aspirin, -51.3% for VOO and -72.9% for aspirin plus VOO). Lipid peroxides in brain slices were also reduced after the treatment with aspirin (-17.90%), VOO (-37.3%) and aspirin plus VOO (-49.2%). Production of nitric oxide after reoxygenation was inhibited by all the treatments (-46.5% for ASA, -48.2% for VOO and -75.8% for ASA plus VOO). The activity of the inducible isoform (iNOS) was inhibited by the three types of treatment (-31.8% for ASA, -29.1% for VOO and -56.0% for ASA plus VOO). The main conclusion of our study is that daily oral administration of VOO to diabetic rats may be a natural way to increase the neuroprotective effect of aspirin in diabetic animals.

Virgin olive oil polyphenol hydroxytyrosol acetate inhibits in vitro platelet aggregation in human whole blood: comparison with hydroxytyrosol and acetylsalicylic acid.

Hydroxytyrosol acetate (HT-AC) is a polyphenol present in virgin olive oil (VOO) at a proportion similar to hydroxytyrosol (HT) (160-479 micromol/kg oil). The present study was designed to measure the in vitro platelet antiaggregating activity of HT-AC in human whole blood, and compare this effect with that of HT and acetylsalicylic acid (ASA). The experiments were designed according to the standard procedure to investigate the activity of ASA. HT-AC and HT inhibited platelet aggregation induced by ADP, collagen or arachidonic acid in both whole blood and platelet-rich plasma (PRP). ASA and HT-AC had a greater effect in whole blood than in PRP when ADP or collagen was used as inducer. ASA and HT-AC had a greater effect in PRP+leucocytes than in PRP alone. All three compounds inhibited platelet thromboxane B2 and leucocyte 6-keto-prostaglandin F1alpha (6-keto-PF1 alpha) production. The thromboxane/6-keto-PGF1alpha inhibition ratio (as an indirect index of the prostanoid equilibrium) was 10.8 (SE 1) for HT-AC, 1.0 (SE 0.1) for HT and 3.3 (SE 0.2) for ASA. All three compounds stimulated nitric oxide production, although HT was a weaker effect. In our experiments only concentrations higher than 500 microm (HT) or 1 mm (HT-AC and ASA) inhibited 3-nitrotyrosine production. All three compounds inhibited the production of TNFalpha by leucocytes, with no significant differences between them. In quantitative terms HT-AC showed a greater antiplatelet aggregating activity than HT and a similar activity to that of ASA. This effect involved a decrease in platelet thromboxane synthesis and an increase in leucocyte nitric oxide production.

Neuroprotective effect of hydroxytyrosol and hydroxytyrosol acetate in rat brain slices subjected to hypoxia-reoxygenation.

Hydroxytyrosol (HT) and hydroxytyrosol acetate (HT-AC) are two well-known phenolic compounds with antioxidant properties that are present in virgin olive oil (VOO). Because VOO has shown neuroprotective effects in rats, the purpose of the present study was to investigate the possible neuroprotective effect of HT and HT-AC in a model of hypoxia-reoxygenation in rat brain slices after in vitro incubation of these compounds or after 7 days of oral treatment with 5 or 10 mg/kg per day. Lactate dehydrogenase (LDH) efflux to the incubation medium was measured as a marker of brain cell death. HT and HT-AC inhibited LDH efflux in a concentration-dependent manner, with 50% inhibitory concentrations of 77.78 and 28.18 microM, respectively. Other well-known antioxidants such as vitamin E and N-acetyl-cysteine had no neuroprotective effect in this experimental model. After 1 week of treatment, HT (5 and 10 mg/kg per day p.o.) reduced LDH efflux by 37.8% and 52.7%, respectively, and HT-AC reduced LDH efflux by 45.4% and 67.8%. These data are additional evidence of the cytoprotective effect of VOO administration, and provide a preliminary basis for further study of these polyphenols as potential neuroprotective compounds.