Influence of the hydroxytyrosol/triterpenes ratio on the neuroprotective effect of olive oil in an experimental model of diabetes mellitus

The aim of the study is to analyse the possible neuroprotective effect of two types of olive oils, one with a high content of alcoholic phenols (POO) and the other with a high content of alcoholic phenols and triterpenes (PTOO), in an experimental model of diabetes mellitus. We also aimed to assess the participation of triterpenes, alone or in association with hydroxytyrosol, in the neuroprotective effect of these olive oils. We administered 0.5 mL/kg/d of both oils to type 1 diabetic animals and performed a hypoxia-reoxygenation model in brain slices. Both oils reduced cell death in this experimental model: 38.3% with POO and 57.2% with PTOO. Both oils reduced brain oxidative stress in this model, with PTOO showing a greater effect than POO in increasing brain antioxidant variables. In in vitro experiments in the hypoxia-reoxygenation model, both hydroxytyrosol and triterpene compounds reduced cell death (IC₅₀ 17.7±0.5 µmol/L for triterpenes and 58.7±1.1 µmol/L for hydroxytyrosol. They also showed an antioxidant effect in the experimental model. When associating both types of compounds in proportion to their concentrations in POO and PTOO, a greater neuroprotective and antioxidant effect was quantified, mainly in the inhibition of lipid peroxidation and in the increase of antioxidant variables. It is concluded that the administration of PTOO exerts a greater neuroprotective effect, possibly due to a positive interaction between the content of triterpenes and alcoholic phenols present in olive oils.