Evaluación clínica de dos aceites de oliva virgen optimizados de diferentes fracciones de la aceituna comparados con un aceite de oliva virgen control
- Autores: Estefanía Sánchez Rodríguez
- Directores de la Tesis: María Dolores Mesa García (dir. tes.), Ángel Gil Hernández (dir. tes.)
- Lectura: En la Universidad de Granada ( España ) en 2018
- Idioma: español
- Tribunal Calificador de la Tesis: Jesús Rodríguez Huertas (presid.), Concepción María Aguilera García (secret.), Gabriel Beltrán Maza (voc.), Parveen Yaqoob (voc.), Oscar Daniel Rangel Huerta (voc.)
- Programa de doctorado: Programa de Doctorado en Nutrición y Ciencias de los Alimentos por la Universidad de Granada y la Universidad de las Illes Balears
- Materias:
- Enlaces
- Tesis en acceso abierto en: DIGIBUG
- Resumen
Introduction.
There is consolidated clinical evidence that the Mediterranean diet is associated with a lower risk of cardiovascular diseases, including myocardial infarction, stroke and cardiovascular death (Gardener et al. 2011). A large study in a high cardiovascular risk population has found that the Mediterranean diet supplemented with virgin olive oil protects people from vascular disease, suggesting a key role of olive oil (Martínez-González et al. 2015). A systematic review and meta-analysis have provided evidence that olive oil might exert beneficial effects on endothelial function and biomarkers of inflammation, thus representing a key ingredient contributing to the Mediterranean diet-associated cardiovascular-protective effects (Schwingshackl, Christoph, Hoffmann 2015). Olive oil is not only a source of monounsaturated fatty acids but also an important source of bioactive compounds, such as phenols and triterpenes (Covas et al. 2006a). The content of the phenolic compounds (also known as polyphenols) of an olive oil depends of the cultivar, climate, olive variety and ripeness, and the type of processing, and virgin olive oil has the highest phenolic content (Covas, de la Torre, Fitó 2015). Triterpenic acids, for example oleanolic and maslinic acids, are present mainly in the seeds and the skin of the olives. Virgin olive oil contains low amounts of triterpenic acids, that are more abundant in pomace olive oil.
Among these components from the unsaponifiable fraction that has demonstrated healthy beneficial effects stand up phenolic compounds, mainly oleuropein and hydroxytyrosol (Hohmann et al. 2015), and triterpenic acids, mainly oleanolic and maslinic acids that have also potential health benefits against cardiovascular diseases and its complications (Herrera, Rodríguez-Rodríguez, Ruíz-Gutiérrez 2006; Lou-Bonafonte et al. 2012; Sánchez-Quesada et al. 2013). Previous studies have suggested a protective effect of olive oil phenolic compounds on endothelial dysfunction (Storniolo et al. 2014), whereas olive oil triterpenes could be useful for the prevention of multiple diseases related to oxidative damage (Sánchez-Quesada et al. 2013). The potential of these olive oil triterpenic acids for use as a therapeutic strategy to improve vascular function and treating cardiovascular diseases has been recently reviewed (Rodríguez-Rodríguez 2015).
Randomized and controlled clinical studies evaluating olive oil, particularly the virgin one, rich in phenolic compounds, have reported benefits on different mechanisms key for atherosclerosis development, such as oxidative damage, inflammation, and endothelial dysfunction. In addition, a protection for hard primary endpoints such as atrial fibrillation and diabetes by virgin olive oil consumption has also been reported (Covas, de la Torre, Fitó 2015). On November 2011, the European Food Safety Authority (EFSA) released a claim concerning the benefits of the daily ingestion of olive oils rich in phenolic compounds on low density lipoproteins (LDL) oxidation (EFSA 2011), regulated by the Commission regulation (EU) nº 432/2012. This claim indicates that olive oils containing at least 5 mg of hydroxytyrosol and its derivatives (e.g. oleuropein complex and tyrosol) per 20 g of olive oil may protect LDL against oxidation. Due to the high caloric content of the olive oil, only high phenolic content olive oils can bear the claim. Therefore, to obtain high phenolic content olive oils, by optimizing the olive oil processing, is one of the current goals in terms of increasing the nutritional value of an olive oil.
However, the human health benefits of triterpenes from olive oil have not been evaluated at present. To our best knowledge, the present Thesis presents results from the first clinical trial (the NUTRAOLEUM study) performed to provide evidence of the benefits of olive triterpenic acids in healthy adults, according to EFSA requirement (EFSA 2011).
We hypothesized that an optimized virgin olive oil with a high phenolic content and a functional olive oil rich in both phenolic compounds and triterpenic acids can provide additional benefits, to those provided by a standard virgin olive oil, on risk factors for coronary heart disease in humans. According to the Evidence Based Medicine (Woolf et al. 1990), the healthy properties of optimized and functional oils must be tested in proper clinical randomized trials, vs control oils obtained by traditional procedures, for ensuring that their benefits for health are really highlighted.
Aims The aims of the present trial are to assess the benefits of the enrichment of optimized virgin olive oil with both olive oil polyphenols and triterpenes on selected biomarkers of cardiovascular diseases risk in healthy volunteers. Therefore, an optimized virgin olive oil with high phenolic content (490 ppm of phenolic compounds and 86 ppm of triterpenic acids) and a functional one, rich in both phenolic compounds (487 ppm of phenolic compounds) and triterpenic acids (389 mg/kg), have been compared with a standard virgin olive oil (124 ppm of phenolic compounds and 87 ppm of triterpenic acids).
The primary hypothesis is: The efficacy for protecting against lipid and DNA oxidation, inflammation, and endothelial dysfunction of the olive oils will be as follows: functional oil > optimized virgin olive oil > standard virgin olive oil.
Material and Methods A randomized, double-blind, crossover, controlled study has been conducted (Biel et al. 2016). Healthy volunteers (aged 20 to 50) were randomized into one of three groups of daily raw olive oil consumption: a standard virgin olive oil, an optimized virgin olive oil rich in phenolic compounds, and a functional oil rich in phenolic compounds and enriched with triterpenic acids obtained from the olive exocarp. The standard virgin olive oil was obtained after washing the optimizing virgin olive oil. Thus oils only differed on the presence of bioactive compounds, i. e. they had similar fatty acid profile and micronutrients composition except the polyphenols and triterpenic acids. Daily, 30 ml of the correspondent olive oil were consumed over 3-week periods preceded by 2-week washout ones when participants were asked to use only sunflower oil and none olive-derived product. The main outcomes of the present study were biomarkers of vascular function, oxidation and inflammation. Specific outcomes were systolic and diastolic blood pressures, in vivo and ex vivo endothelin-1, and molecules of vascular and cellular adhesion as biomarkers of vascular function in plasma; 8-hidroxy-2’-deoxyguanosine (8-OHdG) and isoprostanes in urine as biomarkers of DNA and lipid oxidation, respectively; plasma antioxidant vitamins, and interleukin 8 (IL-8) and tumor necrosis factor α (TNF-α) as biomarkers of inflammation in plasma. Compliance markers were also determined as tyrosol, hydroxytyrosol and triterpenes in urine and plasma triterpenes and fatty acids. The Trial has been registered in ClinicalTrials.gov ID: NCT02520739.
One-factor analysis of the variance (ANOVA) or Kruskal-Wallis test were used for variables to determine differences among the three olive oil interventions, in terms of baseline characteristics, nutrient intake and for the ex vivo endothelin-1 experiment. Biochemical parameters were analyzed using a linear mixed-effects model, to compare variables before and after each intervention (pre- vs post-interventions, intra-treatment effect) and to compare the results between the groups after the 3-week intervention (inter-treatment effect), adjusting for age, gender, pre-intervention and period as fixed effects and for subjects and hospital as random effects. The same model was also used to compare changes of the variables (post-intervention minus pre-intervention) without adjusting for pre-intervention. The multiple comparisons post hoc is given by the estimated means in the model (adjusted by Sidak). The effect by gender and the carryover effects were also checked (Senn 2002). In addition, Pearson or Spearman correlations were evaluated. A p<0.05 value was considered significant. Statistical Package for the Social Sciences version 20 software was used to perform the statistical analysis (SPSS Inc., Chicago, IL, USA).
Results and Discussion The benefits of rich-phenolic natural olive oils on risk factors for chronic diseases have been established in human studies (Covas, de la Torre, Fitó 2015). The PREDIMED (Prevención por Dieta Mediterránea) study reported a decrease in the atrial fibrillation in cardiovascular disease risk individuals when the Mediterranean diet was supplemented with extra virgin olive oil (Martínez-González et al. 2014). The effect of olive oils polyphenols on plasma lipids is not completely clear (EFSA 2012; Sanchez-Rodriguez et al. 2018).
The present Thesis has reported that daily intake of virgin olive oil rich in phenolic compounds during three weeks may improve plasma high density lipoproteins (HDL) cholesterol levels, one of the features of metabolic syndrome, although no differences were found at the end of the three interventions (Sánchez-Rodríguez et al. 2018). In addition, the virgin olive oil with at least 124 ppm of phenolic compounds, regardless of the triterpenes content, improved the systemic endothelin-1 (a vasoconstrictor molecule) levels in vivo and endothelin-1 secreted ex vivo when extracted blood was cultured in the presence of phytohaemagglutinin (PMA), E. coli lipopolysaccharide (LPS) and phorbol 12-myristate 13-acetate plus ionomycin (PMA+IO), while no additional effect of triterpenes was observed. These changes in endothelin-1 secretion did not modify blood pressure, suggesting that longer intervention periods would be needed to get the potential health benefits of polyphenols and triterpenic acids-rich olive oils (Sánchez-Rodríguez et al. 2018).
On the other hand, daily supplementation during 3-week with 30 ml of a functional olive oil providing 13.4 mg/d of phenolic compounds (487 ppm) and 4.7 mg/d of oleanolic acid and 6 mg/d of maslinic acid (171 and 218 ppm, respectively) may protect DNA against oxidative stress in vivo, by decreasing urinary 8-OHdG concentrations compared to the same virgin oil but without triterpenes. In this regard, in vitro (Fabiani et al. 2008; Quiles et al. 2002) and animal (Jacomelli et al. 2010) studies have reported that olive oil phenolic compounds protect DNA from oxidation, whereas in vitro studies have reported that also pentacyclic triterpenes are able to protect against oxidative DNA damage (Allouche et al. 2011). The 8-OHdG results of the present study agrees with observations made in the EUROLIVE study in which supplementation with olive oil protects DNA against oxidation after 3-week in healthy males (Machowetz et al. 2007). This effect was independent of the phenolic content and related to the monounsaturated fatty acid present in the olive oil (Machowetz et al. 2007). No additional effect was found in other oxidative stress biomarkers in this study.
The present study shows that daily supplementation during 3 weeks with 30 ml of a functional olive oil rich in phenolic compounds and enriched with olive triterpenic acids improve plasma inflammatory biomarkers, by decreasing plasma IL-8 and TNF-α concentrations, compared with the oils with less triterpenic acids. This is the first time than an “in vivo “effect of triterpenic acids from olive oil is described. The optimized oil improved the IL-8 concentration but did not modify the TNF-α. The Mediterranean diet associated with a lower incidence of chronic inflammatory diseases (Alarcón de la Lastra et al. 2001). A recent review in human studies indicates that olive oil consumption reduces TNF-α and interleukin 6 (IL-6) levels when associated with Mediterranean diet and lifestyle (Yarla, Polito, Peluso 2017). A systematic review has concluded that olive oil might exert beneficial effects on inflammatory biomarkers, such as C reactive protein and IL-6, after at least four weeks of intervention in individuals adhering to the Mediterranean diet (Schwingshackl, Christoph, Hoffmann 2015). In addition, long-term adherence to this Mediterranean diet decreases plasma concentrations of IL-6 and IL-8 related to different steps of atheroma plaque development in elderly subjects at high cardiovascular risk (Casas et al. 2017). The major anti-inflammatory components in olives are tyrosol, hydroxytyrosol, oleuropein, ligustroside, verbascoside and their derivatives (di Nunzio et al. 2018). In particular, hydroxytyrosol is considered the major anti-inflammatory compound in aqueous olive extracts (Richard et al. 2011). In agreement with our results, human studies, observed a decrease of IL-8 concentrations after an intake of 136.2 mg of oleuropein and 6.4 mg of hydroxytyrosol per day during an intervention of six weeks in pre-hypertension males (Lockyer et al. 2017).
Conclusions The controlled intake of optimized virgin olive oil, rich in polyphenols, for 3 weeks increases the plasma concentrations of HDL cholesterol in healthy adult volunteers, especially in women.
The consumption of a virgin olive oil for 3 weeks decreases the plasma concentrations of endothelin-1, which may contribute to the improvement of the endothelial functionality. However, no additional benefits of a virgin olive oil enriched in triterpenes were observed in the endothelial functionality biomarkers after 3 weeks of supplementation.
Virgin olive oil can prevent DNA oxidation in vivo. This protective capacity seems to be related to the presence of oleic acid in plasma.
The functional olive oil presents anti-inflammatory activity, decreasing some biomarkers of inflammatory state such as IL-8 and TNF-α, compared with oils that do not contain triterpenes.
Our results are useful as hypotheses to propose new clinical studies of longer duration in elderly people and particularly in those affected by metabolic syndrome and endothelial dysfunction, as well as in subjects diagnosed with cardiovascular diseases, that would allow evaluating the effects of the minor components of virgin olive oils, both polyphenols and triterpenes, on health.
