C.A. Demopoulos* [GR]
*Emeritus Professor of Biochemistry & Food Chemistry, Faculty of Chemistry, National & Kapodistrian University of Athens, Greece, member of the Scientific Society of Olive Encyclopaedists (4E), demopoulos@chem.
The beneficial effect of olive oil on various diseases has been known since ancient times. This has been confirmed to date in a scientific way. That is, with observations in populations whose diet includes significant amounts of olive oil or from nutritional interventions with olive oil or finally from in vivo experiments on experimental animals as well as from in vitro experiments. However, of all diseases, only cardiovascular diseases have directly proven the ability of olive oil to inhibit and/or regress (cure) atherosclerosis.
Studies to certify the ability of an ingredient to protect and/or treat a disease should include the following experimental approaches. To demonstrate this, information obtained from in vitro experiments with human or non-human cell cultures, from in vivo experiments with experimental animals and finally from nutritional interventions/clinical studies should be included. Of all these cases, only the studies performed with experimental animals can directly demonstrate the capacity of an ingredient to inhibit the formation of atherosclerotic plaque. In these experiments an internationally accepted experimental animal model should be used. In addition, the studied disease should be induced in the same way in both the control and the intervention groups and the clinical outcome should be clearly defined. Finally, appropriate biochemical measurements should be performed in order to clarify the biochemical mechanism that causes these phenomena. If the ingredient is a natural product, its chemical structure should have been elucidated and chemically synthesized.
Olive oil has been reported to exert beneficial effect in several pathological conditions. From all of these, only in the case of cardiovascular diseases this beneficial effect has been proven in a direct way. Specifically, our research team consisting of the Emeritus Professor of Biochemistry & Food Chemistry at the Department of Chemistry of the National & Kapodistrian University of Athens C.A. Demopoulos, and the Professor of Biochemistry at the Department of Nutrition -Dietetics of Harokopio University S. Antonopoulou, has studied and published in scientific journals the results from all the required experiments, which have been mentioned above. In the case of cardiovascular diseases, for obvious reasons, humans cannot be used, but only experimental animals since the primary clinical outcome should be based on the measurement of the thickness of the atheromatous plaques and the elasticity of the vessels, after euthanasia of the experimental animal.
At first, our group studied the phenomenon of atherosclerosis, which is the first stage of cardiovascular diseases, and we proposed a new theory, “the PAF-implicated atherogenesis theory ” that combined and complemented the existing theories of atherogenesis and proposed as a generative factor, the most potent lipoid inflammatory mediator, Platelet-Activating Factor (PAF), first characterized by Demopoulos and colleagues . This theory was published in a scientific journal  and we also proposed the biochemical mechanism that causes atherogenesis in the form of animation [YouTube/VIDEO https://www.youtube.com/watch?v=yKrWBA7l7s4]. PAF was indeed biosynthesized (by activation of its biosynthetic enzymes) and as a result, PAF levels were elevated in the internationally accepted hypercholesterolemic rabbit model that have developed atheromatous plaques after 6 weeks consumption of atherogenic diet .
By common sense, if the generative cause of atherogenesis was PAF, then PAF inhibitors would inhibit atherogenesis. The existence of PAF inhibitors was first studied in olive oil. Indeed, we found in vitro experiments that PAF inhibitors are present in olive oil and olive pomace too. These inhibitors were isolated, and their chemical structure was elucidated [4,5]. These inhibitors belong to a family of molecules with the chemical form of glyceryl-ether glycolipids. Synthetic analogues of this family inhibited the biological activity of PAF as well as activity of PAF biosynthetic enzymes. These inhibitors are contained in the polar lipid fraction of olive oil approximately in an amount of 0.5% of the olive oil components.
Our next step was to study and establish the ability of the polar lipid fraction to inhibit the production of PAF by experiments with human cell cultures . Olive oil polar lipids not only inhibit the PAF-induced human platelet reach plasma aggregation, but also in cultured human mesangial cells decrease the activation of the PAF biosynthetic enzyme (PAF-Cholinephosphotransferase, PAF-CPT) and activate the PAF degradative enzyme (PAF-Acetylhydrolase, PAF-AH) in these cells. Which means a simultaneously PAF-biosynthesis reduction and a PAF-degradation increase.
Results from morphometric analysis of experiments with experimental animals for the inhibition and regression (treatment) of atheromatous lesions. Control groups A (for inhibition) and C (for regression) were given atherogenic diet rich in cholesterol and formation of atheromatous plaques were observed in the time period shown in the figure (thickness is defined by the two red arrows). In group B (for the inhibition) an atherogenic diet with olive oil polar lipids was administered, at the intervals shown in the figure, and an inhibition of the formation of atheroma is observed. In group D (for regression), after the atherogenic diet, conventional food was co-administered, at the intervals shown in the figure, together with polar lipids of olive oil or statin, and regression of the atheromatous plaque was observed in both cases.
The in vivo studies were performed with hypercholesterolemic rabbits. In other words when animals consume an appropriate atherogenic diet, atheromatous plaques are induced in a few weeks. In these experiments, the studied component is co-administered with the atherogenic diet, and the formation of atheromatous plaques is compared to the control group. We used olive oil as well as the polar lipid fraction of olive oil or olive oil from which the polar lipid fraction had been removed. We demonstrated that both olive oil and the polar lipid fraction inhibited the formation of atheromatous plaques, while olive oil from which we had removed the polar lipid fraction had no beneficial effect . Finally, when atheromatous plaques were initially induced in experimental animals, polar lipids induced plaque regression (healing), comparable to the effect produced by a statin, known to induce regression of atherosclerotic plaques .
In human dietary intervention studies, polar lipids consumption as an enrichment in a commercial yogurt, improved cardiovascular risk factors . So, the cardioprotective action of polar lipids in humans was also confirmed (for obvious reasons) indirectly. It is pointed out that in a corresponding in vivo experiment using the model of hypercholesterolemic rabbits, it was shown that the yogurt containing polar lipids caused inhibition of atherogenesis and regression of existing atheromatous plaques .
The effect of other components of olive oil such as phenolic compounds on atherogenesis in experimental animals, has also been reported. It should point out that administration of olive oil or olive oil from which the phenolic compounds were removed, resulted in the same antiatherogenic effect. A fact that led researchers to conclude that it is not the phenolic compounds that inhibit atherogenesis but some other components , although phenolic compounds improve some cardiovascular risk factors in human studies. Despite this, the increased amounts of phenolic compounds in olive oil make it possible for the EFSA (European Food Safety Authority) to formulate a health claim for “cardioprotective action” and “protection against cardiovascular diseases” for olive oil. However, the possibility of formulating a similar health claim, based on our experimental results, can be given by EFSA [EC 1924/200. Article 13: 5.4.] for the polar lipids of olive oil, too. Soon, in fact, a food supplement with the polar lipids of olive oil in a capsule will be released in France.
We must point out that PAF inhibitors are also present in other foods of the Mediterranean diet  thus providing a biochemical explanation for its cardioprotective action known since decades.
 Forty Years Since the Structural Elucidation of Platelet-Activating Factor (PAF): Historical, Current, and Future Research Perspectives.
Molecules. 2019; 24(23)
- Lordan, A. Tsoupras, I. Zabetakis, C.A.Demopoulos.
 Platelet-activating factor—a molecular link between atherosclerosis theories.
Eur. J. Lipid Sci. Technol. 2003, 105, 705–716.
C.A. Demopoulos, H.C.Karantonis, S. Antonopoulou.
 In vivo antiatherogenic properties of olive oil and its constituent lipid classes in
Nutr Metab Cardiovasc Dis. (2006) 16, 174
H.C. Karantonis, S. Antonopoulou, D. N. Perrea, D. P. Sokolis, S. E. Theocharis, N. Kavantzas, D. G. Iliopoulos, C. A. Demopoulos
 Antithrombotic lipid minor constituents from vegetable oils. Comparison between olive oils and others.
Agric. Food Chem., (2002) 50, 1150
H.C.Karantonis, S.Antonopoulou, C.A.Demopoulos
 Bioactive polar lipids in olive oil, pomace and waste byproducts
- Food Biochem., 32, 443-459, 2008.
H.C. Karantonis, N. Tsantila, G. Stamatakis, M. Samiotaki, G. Panayotou, S. Antonopoulou, C.A. Demopoulos.
 IN VITRO PROTECTIVE EFFECTS OF OLIVE POMACE POLAR LIPIDS TOWARDS PLATELET ACTIVATING FACTOR METABOLISM IN HUMAN RENAL CELLS.
Current Topics in Nutraceutical Research . Aug2011, Vol. 9 Issue 3, p105-110. 6p.
- B. Tsoupras, E. Fragopoulou, C. Iatrou, C. A. Demopoulos.
 Atherosclerosis regression study in rabbits upon olive pomace polar lipid extract administration
Nutrition, Metabolism & Cardiovascular Diseases (2010) 20, 740-747 (doi: 10.1016/j.numecd.2009.06.008).
N.Tsantila, H.C.Karantonis, D.N.Perrea, S.E.Theocharis, D.G.Iliopoulos, C.Iatrou, S.Antonopoulou, C.A.Demopoulos
 Consumption of yogurt enriched with polar lipids from olive oil by-products reduces platelet sensitivity against platelet activating factor and inflammatory indices: A randomized, double-blind clinical trial
Human Nutrition & Metabolism, 28 (2022) 200145
Smaragdi Antonopoulou, Maria Detopoulou, Elizabeth Fragopoulou, Tzortzis
Nomikos, Αnastasia Mikellidi, Mary Yannakoulia, Adamantini Kyriacou, Evdokia
Mitsou, Demosthenes Panagiotakos, Costas Anastasiou
 Inhibition of atherogenesis in rabbits by yogurt enriched with olive mill by-product extracts
Hellenic Journal of Atherosclerosis (2012) 3,212–218
G.M. Stamatakis, H.C. Karantonis, C. Nasopoulou, V. Gkogkaki, S. Antonopoulou, D. Perrea, S.E. Theocharis, C.A. Demopoulos
 Efficacy of bioactive compounds from extra virgin olive oil to modulate atherosclerosis development
Mol. Nutr. Food Res. 2012, 56, 1043–1057 DOI 10.1002/mnfr.201100668 1043
Jose M. Lou-Bonafonte, Carmen Arnal, Maria A. Navarro, Jesus Osada
 Mediterranean diet and platelet-activating factor; a systematic review
Clin Biochem . 2018 Sep;60:1-10. doi: 10.1016/j.clinbiochem.2018.08.004. Epub 2018 Aug 22
Tzortzis Nomikos , Elizabeth Fragopoulou , Smaragdi Antonopoulou , Demosthenes B Panagiotakos