Effects of the olive-derived polyphenol oleuropein on human health

Abstract

The use of the products derived from the olive tree on human health dates back centuries. In several civilizations, the olive tree had and still has a very strong cultural and religious symbolism. Notably, the official seal and emblem of the World Health Organization features the rod of Asclepius over a world map surrounded by olive tree branches, chosen as a symbol of peace and health. Recently, accumulating experimental, clinical and epidemiological data have provided support to the traditional beliefs of the beneficial effect provided by olive derivates. In particular, the polyphenols present in olive leaves, olives, virgin (unrefined) olive oil and olive mill waste are potent antioxidant and radical scavengers with anti-tumor and anti-inflammatory properties. Here, we review the positive impact on human health of oleuropein, the most prevalent polyphenol present in olives. In addition, we provide data collected in our laboratory on the role of oleuropein in counteracting lipid accumulation in a mouse model of non-alcoholic fatty liver disease.

Figure 1

Oleuropein supplementation reduces hepatic lipid accumulation in high fat diet-treated mice. C57BL/6 mice were fed with a high fat diet (HFD) for eight weeks; then, animals were randomly divided into three groups of six mice each: the first received a normocaloric diet (ND), the second HFD, the third HFD supplemented with 3% oleuropein (HFD + Ole), for a further eight weeks. Mice were sacrificed, and histology was performed on sections of liver tissue, indicating reduced lipid deposition in the HFD + Ole group. Hematoxylin and eosin stain; original magnification: 40×. All experimental procedures conformed to protocols approved by the Institutional Animal Care and Use Committee (178/2013 B, on 16 July 2013) and were performed according to the Guidelines of the Italian National Institutes of Health.

Figure 2

Oleuropein supplementation reduces body, liver and heart weights in high fat diet-treated mice. C57BL/6 mice were fed with a high fat diet (HFD) for eight weeks; then, animals were randomly divided into three groups: the first received a normocaloric diet (ND), the second high fat diet (HFD), the third HFD supplemented with 3% oleuropein (HFD + Ole) for further eight weeks. At the end of treatment, HFD + Ole mice had reduced weight gain (total body—25%, liver—50%, heart—70%) compared to HFD-fed mice. Data are expressed as the mean; error bars indicate the standard error; number of animals per group = 6. An asterisk denotes a statistically significant difference between HFD and HFD + Ole groups (p < 0.05 assessed with a two-tailed Student’s t-test for unpaired data).