Extra virgin olive oil reduced polyunsaturated fatty acid and cholesterol oxidation in rodent liver: Is this accounted by hydroxytyrosol - fatty acid conjugation?
Chem Res Toxicol. 2016 Sep 2. Epub 2016 Sep 2. PMID: 27588434
Yiu Yiu Lee
The effects of extra virgin olive oil (EVOO) and carbon tetrachloride (CCl4) induced oxidative stress in rats were determined by the generation of isoprostanoids. These are known to be the robust biomarkers to evaluate non-enzymatic and free radical related oxidation. Other oxidative stress biomarkers such hydroxyeicosatetraenoic acid products (HETEs) and cholesterol oxidation products (COPs) were also evaluated. The rodents received control diet, high-fat diet (20% w/w) composed of extra virgin olive oil (EVOO), corn oil (CO) or lard and high-fat diet with CCl4 insult throughout the experimental period. EVOO diet was found to suppress the formation of isoprostanoids and COPs compared to control. EVOO also had high total phenolic content and antioxidant activity compared to CO and lard, and may be contributed by the hydroxytyrosol component conjugated to fatty acids (HT-FA). This is the first study to identify HT-FA in EVOO, and was 4-fold higher than olive oil whereas none was found in corn oil. Furthermore, EVOO diet showed reduced liver lipid vesicles in CCl4 treated rats compared to control. However, liver toxicity measurement of AST (aspartate transaminase) and ALT (alanine transaminase) activities showed augmentation with CCl4 treatment but were not alleviated by the diets given. Our findings suggest that EVOO is a daily functional food capable to enhance the antioxidant system for liver protection; the effect is potentially attributed by the phenolic and lipophenolic (phenol conjugated to fatty acids) content.