0158 : Effect of polyphenols of olive oil, hydroxytyrosol and its glucuronides on the vascular reactivity in a type 2 diabetes context

Abstract

Hydroxytyrosol (HT) and Resveratrol (RES) are recognized as strong antioxidant polyphenolic compound. While RES antioxidative mechanisms are well known, those of HT are controversial because of its low intestinal absorption and its high metabolisation in glucuronides (GC), suggesting that these metabolites are susceptible to express HT biologicial activity in vivo . Our objective was to compare the vasorelaxant effect of Res, HT and GC on isolated aortic from young males Wistar rats (3months), old Wistar and GK rats (14 months), in presence or not of t -BOOH-induced oxidative stress (1mM; 30min). No vasorelaxant effect of the polyphenols was observed in young or old males Wistar rats. However, in old GK rats, Res and GC had significant vasorelaxant effect. In response to t -BOOH-induced oxidative stress, HT and RES protected the aortic rings of young Wistar rats (p < 0.05). However, different maximal relaxation was found between HT + t -BOOH, Res + t -BOOH and Control (72.5 ± 2.8%, 76.1% ± 7.7% vs 88.8 ± 0.7% ; p<0.05). The sensibility to Ach (EC50) was altered negatively in Res + t -BOOH and t -BOOH in comparison of Control (2084.6 ± 1687 nM, 2983.5 ± 1110 nM vs 66.9±10.7 nM). The protective effect of HT and RES against the acute effect of t -BOOH-induced oxidative stress in a normal context tends to confirm our results in old GK rats, highlighting an effect of these polyphenols only in a pro-oxidant context.