Francesco Visioli

Low density lipoprotein oxidation is inhibited in vitro by olive oil constituents

Oxidation of low density lipoproteins maybe a factor in the development of atherosclerosis. The Mediterranean diet rich in vegetables, grains, legumes, fruits, and oils, mainly olive oil, has been suggested to reduce the incidence of coronary heart disease, because of its low saturated and high monounsaturated fatty acids content. It is also possible that the natural antioxidants in the oil help to prevent lipid oxidation, e.g. that of low density lipoproteins, thus retarding the formation of atherosclerotic plaques. First-pressed, extra-virgin olive oil contains appreciable amounts of polyphenolic compounds that prevent its autoxidation and are responsible for its high stability. We tested these compounds on low density lipoprotein oxidation and found an inhibitory effect, at low concentrations, on various indexes of lipid oxidation (vitamin E content, formation of thiobarbituric acid-reacting substances, lipid peroxides, levels of polyunsaturated fatty acids, protein modification, conjugated diene formation). Our data suggest that natural antioxidants could play a role in inhibiting the formation of cytotoxic products such as lipid peroxides thus retarding the onset of the atherosclerotic damage.

Olive oil phenolics are dose‐dependently absorbed in humans

Olive oil phenolic constituents have been shown, in vitro, to be endowed with potent biological activities including, but not limited to, an antioxidant action. To date, there is no information on the absorption and disposition of such compounds in humans. We report that olive oil phenolics, namely tyrosol and hydroxytyrosol, are dose‐dependently absorbed in humans after ingestion and that they are excreted in the urine as glucuronide conjugates. Furthermore, an increase in the dose of phenolics administered increased the proportion of conjugation with glucuronide.

Biological Properties of Olive Oil Phytochemicals

Referee: Dr. Joe Vinson, Chemistry Department, University of Scranton, Scranton, PA 18510 Olive oil is the principal source of fat in the Mediterranean diet, which has been associated with a lower incidence of coronary heart disease and certain cancers. Extra-virgin olive oil contains a considerable amount of phenolic compounds, for example, hydroxytyrosol and oleuropein, that are responsible for its peculiar taste and for its high stability. Evidence is accumulating to demonstrate that olive oil phenolics are powerful antioxidants, both in vitro and in vivo; also, they exert other potent biological activities that could partially account for the observed healthful effects of the Mediterranean diet.

Oleuropein, the bitter principle of olives, enhances nitric oxide production by mouse macrophages

The Mediterranean diet, rich in fresh fruits and vegetables, has been associated with a lower incidence of cardiovascular disease and cancer, partly because of its high proportion of bioactive compounds such as vitamins, flavonoids and polyphenols. The major lipid component of such diet is the drupe-derived olive oil, that can be distinguished from other seed oils for the peculiar composition of its non-triglyceride fraction. In fact, several minor components, including polyphenols, grant the oil its particular taste and aroma. Oleuropein, the most abundant among these components, has been shown to be a potent antioxidant endowed with antiinflammatory properties. We investigated the effects of oleuropein on NO release in cell culture and its activity toward nitric oxide synthase (iNOS) expression. The results show that oleuropein dose-dependently enhance nitrite production in LPS-challenged mouse macrophages. This effect was blocked by the iNOS inhibitor L-NAME, indicating increased iNOS activity. Also, Western blot analysis of cell homogenates show that oleuropein increases iNOS expression in such cells. Taken together, our data suggest that, during endotoxin challenge, oleuropein potentiates the macrophage-mediated response, resulting in higher NO production, currently believed to be beneficial for cellular and organismal protection.

Polyunsaturated fatty acids as antioxidants.

The susceptibility of fatty acids to oxidation is thought to be directly dependent on their degree of unsaturation. However, some in vitro and in vivo studies suggest that the relation between chemical structure and susceptibility to oxidation is not as straightforward as hypothesized from theoretical viewpoints. Indeed, long chain polyunsaturated fatty acids (LC-PUFAs) might be less oxidizable than others under specific experimental conditions. We investigated the free radical-scavenging potential of PUFA and the production of reactive oxygen/nitrogen (ROS/RNS) species by human aortic endothelial cells (HAECs) supplemented with different fatty acids. Fatty acid micelles scavenged superoxide in an unsaturation-dependent manner, up to eicosapentaenoic acid, which was the most effective fatty acid. Supplementation of HAEC with polyunsaturated fatty acids of the omega 3 series resulted in lower formation of ROS, as compared with cells supplemented with saturates, monounsaturates, or polyunsaturates of the omega 6 series. This effect was maximal at concentrations of 10muM. The effects of omega 3 fatty acids on reactive species production appear to be stronger when ROS were evaluated, as a milder, albeit significant effect was observed on RNS generation. Based on in vivo data showing reduced excretion of lipid peroxidation products after omega 3 intake and our data on ROS production and direct superoxide scavenging by LC-PUFAs, notably those of the omega 3 series, we propose that this series of fatty acid might act as indirect anti- rather than pro-oxidant in vascular endothelial cells, hence diminishing inflammation and, in turn, the risk of atherosclerosis and cardiovascular disease.

Polyphenols and Human Health: A Prospectus

The lay press often heralds polyphenols as panacea for all sorts of diseases. The rationale is that their antioxidant activity would prevent free radical damage to macromolecules. However, basic and clinical science is showing that the reality is much more complex than this and that several issues, notably content in foodstuff, bioavailability, or in vivo antioxidant activity are yet to be resolved. We summarize the recent findings concerning the effects of polyphenols on human health, analyze the current limitations at pitfalls, and propose future directions for research.

Olive Phenol Hydroxytyrosol Prevents Passive Smoking–Induced Oxidative Stress

BackgroundOxidative stress is involved in the onset of several degenerative disorders, and epidemiological studies indicate that a high intake of dietary antioxidants, as in the case of the Mediterranean basin, is protective. Olive mill waste waters (OMWWs) are a byproduct of olive oil production rich in phenolic antioxidants, such as hydroxytyrosol. We tested the effects of a low dose of an OMWW extract in a model of sidestream smoke–induced oxidative stress in rats by evaluating the urinary excretion of 8-iso-prostaglandin (PG) F2&agr; (iPF2&agr;-III). Methods and ResultsAn OMWW extract (5 mg/kg, providing 414 &mgr;g/kg of hydroxytyrosol) was administered to rats daily for 4 days, during which time the animals were exposed to sidestream smoke for 20 minutes once a day. Daily urines were collected, and the urinary excretion of 8-iso-PGF2&agr; was evaluated as an index of oxidative stress–induced in vivo lipid peroxidation. The exposure of rats to passive smoking increased the urinary excretion of 8-iso-PGF2&agr; by 44±4.2% at 48 hours and by 55±10% at 96 hours. Treatment with the OMWW extract was able to completely prevent the increase at 48 hours and resulted in lower increments (34±18% versus 55±10%) of 8-iso-PGF2&agr; excretion at 96 hours. ConclusionsA low dose of hydroxytyrosol, administered through OMWW, reduces the consequences of sidestream smoke–induced oxidative stress in rats.

Ascorbic acid in Charcot-Marie-Tooth disease type 1A (CMT-TRIAAL and CMT-TRAUK): a double-blind randomised trial

Summary Background Ascorbic acid reduced the severity of neuropathy in transgenic mice overexpressing peripheral myelin protein 22 (PMP22), a model of Charcot–Marie–Tooth disease type 1A (CMT1A) associated with the PMP22 duplication. However, in three 1-year trials, ascorbic acid had no benefit in human beings. We did a multicentre 2-year trial to test the efficacy and tolerability of ascorbic acid in patients with CMT1A. Methods Adult patients (aged 18–70 years) with symptomatic CMT1A were enrolled from nine centres in Italy and the UK, and were randomly assigned (1:1 ratio) to receive 1·5 g/day oral ascorbic acid or matching placebo for 24 months. The randomisation sequence was computer generated by block randomisation, stratified by centre and disease severity, and patients were allocated to treatment by telephone. The primary outcome was change in the CMT neuropathy score (CMTNS) at 24 months. Secondary outcomes were timed 10 m walk test, nine-hole peg test, overall neuropathy limitations scale, distal maximal voluntary isometric contraction, visual analogue scales for pain and fatigue, 36-item short-form questionnaire, and electrophysiological measurements. Patients, treating physicians, and physicians assessing outcome measures were masked to treatment allocation. Analysis of the primary outcome was done on all randomised patients who received at least one dose of study drug. This study is registered, numbers ISRCTN61074476 (CMT-TRAUK) and EudraCT 2006-000032-27 (CMT-TRIAAL). Findings We enrolled and randomly assigned 277 patients, of whom six (four assigned to receive ascorbic acid) withdrew consent before receiving treatment; 138 receiving ascorbic acid and 133 receiving placebo were eligible for analysis. Treatment was well tolerated: 241 of 271 patients (89% in each group) completed the study; 20 patients (nine receiving ascorbic acid) dropped out because of adverse events. Mean CMTNS at baseline with missing data imputed was 14·7 (SD 4·8) in the ascorbic acid group and 13·9 (4·2) in the placebo group. Mean worsening of CMTNS was 0·2 (SD 2·8, 95% CI −0·3 to 0·7) in the ascorbic acid group and 0·2 (2·7, −0·2 to 0·7) in the placebo group (mean difference 0·0, 95% CI −0·6 to 0·7; p=0·93). We recorded no differences between the groups for the secondary outcomes at 24 months. 21 serious adverse events occurred in 20 patients, eight in the ascorbic acid group and 13 in the placebo group. Interpretation Ascorbic acid supplementation had no significant effect on neuropathy compared with placebo after 2 years, suggesting that no evidence is available to support treatment with ascorbic acid in adults with CMT1A. Funding Telethon-UILDM and AIFA (Italian Medicines Agency) for CMT-TRIAAL, and Muscular Dystrophy Campaign for CMT-TRAUK.

The fate of olive oil polyphenols in the gastrointestinal tract: implications of gastric and colonic microflora-dependent biotransformation.

We have conducted a detailed investigation into the absorption, metabolism and microflora-dependent transformation of hydroxytyrosol (HT), tyrosol (TYR) and their conjugated forms, such as oleuropein (OL). Conjugated forms underwent rapid hydrolysis under gastric conditions, resulting in significant increases in the amount of free HT and TYR entering the small intestine. Both HT and TYR transferred across human Caco-2 cell monolayers and rat segments of jejunum and ileum and were subject to classic phase I/II biotransformation. The major metabolites identified were an O-methylated derivative of HT, glucuronides of HT and TYR and a novel glutathionylated conjugate of HT. In contrast, there was no absorption of OL in either model. However, OL was rapidly degraded by the colonic microflora resulting in the formation of HT. Our study provides additional information regarding the breakdown of complex olive oil polyphenols in the GI tract, in particular the stomach and the large intestine.

Mitochondrial Decay in the Aging Rat Heart

Mitochondrial decay has been postulated to be a significant underlying part of the aging process. Decline in mitochondrial function may lead to cellular energy deficits, especially in times of greater energy demand, and compromise vital ATP‐dependent cellular operations, including detoxification, repair systems, DNA replication, and osmotic balance. Mitochondrial decay may also lead to enhanced oxidant production and thus render the cell more prone to oxidative insult. In particular, the heart may be especially susceptible to mitochondrial dysfunction due to myocardial dependency on β‐oxidation of fatty acids for energy and the postmitotic nature of cardiac myocytes, which would allow for greater accumulation of mitochondrial mutations and deletions. Thus, maintenance of mitochondrial function may be important to maintain overall myocardial function. Herein, we review the major age‐related changes that occur to mitochondria in the aging heart and the evidence that two such supplements, acetyl‐l‐carnitine (ALCAR) and (R)‐α‐lipoic acid, may improve myocardial bioenergetics and lower the increased oxidative stress associated with aging. We and others have shown that feeding old rats ALCAR reverses the age‐related decline in carnitine levels and improves mitochondrial β‐oxidation in a number of tissues studied. However, ALCAR supplementation does not appear to reverse the age‐related decline in cardiac antioxidant status and thus may not substantially alter indices of oxidative stress. Lipoic acid, a potent thiol antioxidant and mitochondrial metabolite, appears to increase low molecular weight antioxidant status and thereby decreases age‐associated oxidative insult. Thus, ALCAR along with lipoic acid may be effective supplemental regimens to maintain myocardial function.