The Mediterranean diet (MeD) is well-known to impart considerable protection against the occurrence of cardiovascular disease and cancer. In particular, the plethora of protective health benefits of the MeD including improved lipid profile and reduced inflammation has been linked largely to the high levels of fatty acid content found in extra virgin olive oil (EVOO).
However, there is still no clarity as to which components of EVOO are responsible for the regulation of genes involved in inflammatory, anti-oxidant or immune pathways.
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In addition, while there are a few human clinical studies on the acute effect of high intake of EVOO on gene expression changes, to date there are no reports on the EVOO effect on the whole transcriptome expression profile (genome and RNA).
The regulation of normal biological function at the cellular and molecular levels is through small RNA sequences known as MicroRNA (miRNA) that have been promising as therapeutic targets for certain diseases. Advances in whole genome mRNA (transcriptome) sequencing has led to comprehensive analysis of RNA transcripts in a given tissue sample.
In a recent study published in Biochim Biophys Acta, a collaborative group of researchers in Italy took advantage of transcriptome sequencing technology and investigated the health protective mechanisms of extra virgin olive oil by identifying gene expression signature after an acute consumption of EVOO in both healthy volunteers and metabolic syndrome patients.
The study involved consumption of a single dose of low- or high-polyphenol extra virgin olive oil (50ml) by healthy volunteers and patients with metabolic syndrome on different occasions. The selected EVOOs were similar in fatty acid but differed in polyphenol compositions.
The scientists found that acute polyphenol-rich EVOO effects in healthy participants led to marked improvement in insulin sensitivity and glucose metabolism, at the same time supporting miRNA and gene expression in inflammation and immune responses.
On the contrary, these biochemical and molecular effects of EVOO were largely absent in patients affected by metabolic syndrome or participants who consumed low-polyphenol EVOO suggestive of a putative role for the phenolic component.
Next, the researchers sought to determine whether such benefits of EVOO in healthy volunteers were attributed to the polyphenols or the fatty acid components of EVOO.
They found that in volunteers who consumed polyphenol-rich EVOO, there was a significant change in the expression of genes previously know to be activated by fatty acids than any other EVOO components. In contrast, the majority of gene expressions remained the same in individuals after ingestion of extra virgin olive oil low in polyphenols.
The scientists further demonstrated that the effects of EVOO high in polyphenols at the molecular level supported regulation of miRNA exerting various effects on inflammation, cancer and insulin resistance.
The key message of this study was that “the intake of EVOO containing high phenols improves insulin sensitivity and modulates different pathways in inflammatory cells of healthy subjects; most of these changes point to a beneficial role of EVOO in promoting health toward its anti-inflammatory, anti-cancer, and antioxidant properties.”