Nutritional Intervention Study to Evaluate the Effect of Hydroxytyrosol on Phase II Enzymes in Healthy Subjects

Hydroxytyrosol is peculiar to olives (and, hence, to olive oil) and is being exploited as a potential supplement or preservative to be employed in the nutraceutical, cosmeceutical, and food industry. One of the properties described for the hydroxytyrosol is its high antioxidant activity. Also, hydroxytyrosol is able to modulate several enzymatic activities linked to cardiovascular disease. Animal experiments confirm hydroxytyrosol retains its antioxidant activity once ingested (though the human metabolic pathway has been elucidated and shows extensive glucuronidation and subsequent urinary excretion), protects from second hand smoke-induced oxidative damage, inhibits platelet aggregation, ameliorates lipid profile and decreases atherosclerosis development, increases brain cell resistance to oxidation and mitochondrial membrane potential Several mechanisms have been proposed to explain how biologically polyphenols protect against degenerative diseases. It is now thought more likely that some phytochemicals, including polyphenols, are processed by the body as xenobiotics. They stimulate stress- related cell signalling pathways that result in increased expression of genes encoding cytoprotective genes. Nrf2 (NF-E2-related factor 2) is a transcription factor which binds to the Antioxidant Response Element (ARE) in cells and thus regulates enzymes involved in antioxidant functions or detoxification (e.g. thioredoxin reductase-1 and glutathione peroxidases). Polyphenols might increase gene transcription of Nrf2 mediated by such response elements. This provides grounds for the theory of hormesis, i.e. when mild stress triggers defense mechanisms. In the case of polyphenols it indicates how they could have an indirect antioxidant action.

That is why plans to carry this study to explore the detoxifying potential of hydroxytyrosol and its effects on Phase II enzyme expression (leading to xenobiotics detoxification in the liver). It´ll be a randomized crossover, pilot study examining the effects of two doses of hydroxytyrosol, in the form of a commercially-available raw mixture: 1) providing 5 mg/d; 2) 25 mg/d, for one week with a one-week washout period in between, during 6 weeks.

The investigators will recruit 20 healthy volunteers, from within those who participate in the Genyal Platform studies AT IMDEA-Food Institute.