Intestinal microbiota modulation at the strain level by the olive oil polyphenols in the diet

Abstract

IntroductionPreviously we have reported a r16S gene next generation sequencing study on the effect of high fat diets in the intestinal microbiota using a murine model. However, many important microbial traits occur at strain level and, in order to detect these population changes, culture-dependent approaches need to be applied. With this goal, we decided to study a very well-known commensal genus, Enterococcus, and therefore, intestinal enterococci methodically isolated during the above-mentioned experiment were analyzed.Materials and methodsA collection of 75 distinct enterococcal strains isolated from feces of mice fed a standard diet or high-fat diets enriched with butter, refined olive oil, or extra virgin olive oil and after 0, 6 or 12 weeks of diet, were genetically and phenotypically characterized in search of virulence factors, biogenic amine production and antibiotic resistance. All strains were tested for the susceptibility in vitro to two virgin olive oil polyphenols, oleuropein (the bitter principle of olives) and hydroxytyrosol (derived from oleuropein by enzymatic hydrolysis and responsible for the high stability of olive oil).ResultsNo drastic polyphenol effect was found except at high concentrations. However, when carrying out a comparative statistical study in the 75 strains of the collection according to the different diets, we have detected significant differences between the strains isolated from mice fed with a diet enriched with virgin olive oil and the rest of the diets. EVOO strains also presented less resistance to antibiotics and a more beneficial profile overall.DiscussionThese results support the prebiotic role of polyphenols, showing how they are able to modulate the set of strains that comprises a genus in the gut, allowing them to adapt to a changing environment in the host’s intestine and possibly exerting effects on its physiology.

Oxidative Stress as a Target for Non-Pharmacological Intervention in MAFLD: Could There Be a Role for EVOO?

“…Several metabolic pathways have been advocated to explain the health benefits of EVOO. Among these are the upregulation of Nrf2 expression, causing an increase in antioxidant molecule expression [ 145 ]; reduction of NF-kB activation, with a consequent downregulation of cytokines, chemokines, adhesion molecules, and inflammatory/oxidative stress enzymes [ 146 , 147 , 148 ]; activation of phosphoinositide 3-kinase (PI3K/Akt) and mitogen-activated protein kinase (MAPK) (ERK and p38) signaling cascades, thus inducing endothelial NO synthase phosphorylation and modulating NO levels [ 149 ]; increase of both MUFA and PUFA absorption, bringing about a reduction of both TC and LDL, decreasing TC/HDL and LDL/HDL ratios [ 150 ]; and modification of gut microbiota species and modulation of their metabolism, leading to the modulation of intestinal permeability, antigen exposition, immune cell response, inflammation, and oxidative stress [ 141 , 151 , 152 , 153 ].…”

Olive Oil Waste as a Source of Functional Food Ingredients: Assessing Polyphenolic Content and Antioxidant Activity in Olive Leaves

“…Rutin and luteolin have shown hypoglycaemic and antioxidant activities, while quercetin has demonstrated anti-inflammatory and anti-tumoral effects [22]. Likewise, oleuropein, a secoiridoid compound constituting the main polyphenol in olive leaves, has shown protective effects against oxidative stress [23], anti-inflammatory activity [24], and positive effects on the control of body weight [25], glycemia [26], and intestinal microbiota [27,28]. In recent years, increased attention has also been given to hydroxytyrosol, which is the main metabolite of oleuropein.…”