Extra virgin olive oil lowers postprandial glycaemia. We investigated if oleuropein, a component of extra virgin olive oil, exerts a similar effect on postprandial glycaemia and the underlying mechanism.

Twenty healthy subjects were randomly allocated in a cross‐over design to 20 mg oleuropein or placebo immediately before lunch. Postprandial glycaemia along with blood insulin, dipeptidyl‐peptidase‐4 (DPP‐4) and glucagon‐like peptide‐1 and oxidative stress, which included soluble NADPH oxidase‐derived peptide activity (sNox2‐dp), 8‐iso‐prostaglandin‐2α and platelet p47^phox phosphorylation, were analysed before and 2 h after meal.

After 2 h, subjects who assumed oleuropein had significantly lower blood glucose, DPP‐4 activity and higher insulin and glucagon‐like peptide‐1 compared to placebo. Furthermore, sNox2‐dp, 8‐iso‐PGF2α and platelet p47^phox phosphorylation were significantly lower in oleuropein‐ compared to placebo‐treated subjects. DPP‐4 significantly correlated with sNox2‐dp [Spearman's rho (Rs) = 0.615; P < 0.001], p47^phox phosphorylation (Rs = 0.435; P < 0.05) and 8‐iso‐ prostaglandin‐2α (Rs = 0.33; P < 0.05). In vitro study demonstrated that hydroxytyrosol, a metabolite of oleuropein, significantly reduced p47^phox phosphorylation and isoprostane formation.

These findings indicate that oleuropein improves postprandial glycaemic profile via hampering Nox2‐derived oxidative stress.