Monica Deiana

Characterization of conjugated diene fatty acids in milk, dairy products, and lamb tissues

Conjugated diene isomers of linoleic acid (CLA), possess anticarcinogenic and antiatherogenic properties, but little is known about their metabolism. We have recently obtained evidence that CLA present in partially hydrogenated oil can be metabolized to conjugated linolenic and eicosatrienoic acids in rat liver. In the present study, we have investigated whether CLA are metabolized in the liver of lambs, which normally consume high levels of CLA produced in the rumen and present in their diet, consisting exclusively of milk. Conjugated linolenic, eicosatrienoic, and arachidonic acids were detected in lamb liver phospholipids showing that elongation and desaturation of CLA occur also in lamb tissues, and that all metabolites maintain the conjugated diene structure.

Inhibition of peroxynitrite dependent DNA base modification and tyrosine nitration by the extra virgin olive oil-derived antioxidant hydroxytyrosol

Hydroxytyrosol is one of the o-diphenolic compounds in extra virgin olive oil and has been suggested to be a potent antioxidant. The superoxide radical (O2*-) and nitric oxide (NO*) can react very rapidly to form peroxynitrite (ONOO ), a reactive tissue damaging species thought to be involved in the pathology of several chronic diseases. Hydroxytyrosol was highly protective against the peroxynitrite-dependent nitration of tyrosine and DNA damage by peroxynitrite in vitro. Given that extra virgin olive oil is consumed daily by many humans, hydroxytyrosol derived from this diet could conceivably provide a defense against damage by oxidants in vivo. The biological activity of hydroxytyrosol in vivo will depend on its intake, uptake and access to cellular compartments.

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.

Hydroxytyrosol inhibits the proliferation of human colon adenocarcinoma cells through inhibition of ERK1/2 and cyclin D1.

Extra virgin olive oil is rich in phenolic compounds which are believed to exert beneficial effects against many pathological processes, including the development of colon cancer. We show that one of the major polyphenolic constituents of extra virgin olive oil, hydroxytyrosol (HT), exerts strong antiproliferative effects against human colon adenocarcinoma cells via its ability to induce a cell cycle block in G2/M. These antiproliferative effects were preceded by a strong inhibition of extracellular signal-regulated kinase (ERK)1/2 phosphorylation and a downstream reduction of cyclin D1 expression, rather than by inhibition of p38 activity and cyclooxygenase-2 (COX-2) expression. These findings are of particular relevance due to the high colonic concentration of HT compared to the other olive oil polyphenols and may help explain the inverse link between colon cancer and olive oil consumption.

l-Ergothioneine modulates oxidative damage in the kidney and liver of rats in vivo: studies upon the profile of polyunsaturated fatty acids

BACKGROUND & AIMS L-ergothioneine is a fungal metabolite exhibiting antioxidant functions in cells. The aim of this study was to assess the effect of oral administration of L-ergothioneine on the oxidative damage in vivo caused by the Fenton reagent ferric-nitrilotriacetate. METHODS Rats were supplemented with L-ergo prior to the administration of acute dose of ferric-nitrilotriacetate. Kidney and liver levels of L-ergothioneine, glutathione, alpha-tocopherol, polyunsaturated fatty acids and conjugated dienes were assessed. RESULTS Oral administration of 70 mg L-ergo/kg body weight of rats for 7 days prior to the injection of ferric-nitrilotriacetate protected the fatty acids against oxidation, with notable protections directed to: 20:5 (eicosapentaenoic acid) (23%), 22:6 (docosahexaenoinic acid) (30%), 20:3 n6 (eicosatrienoic acid) (22%), 20:4 (arachidonic acid) (25%), 18:2 linoleic acid (25%) and 18:1 oleic acid (14%) in the kidney. The protection of 20:5, 20:3 n6 and 18:1 in the liver by 32%, 20% and 11%, respectively, were statistically significant. L-ergothioneine significantly reduced kidney and liver levels of conjugated dienes and conserved the concentrations of alpha-tocopherol and glutathione in the kidney and liver in the ferric-nitrilotriacetate/L-ergothioneine treated rats. CONCLUSION Supplementation with L-ergothioneine not only protects the organs against the lipid peroxidation but conserves the consumption of endogenous glutathione and alpha-tocopherol. However consumption of mushrooms may have better promise as dietary sources of L-ergothioneine to humans.

Protective effect of simple phenols from extravirgin olive oil against lipid peroxidation in intestinal Caco-2 cells

Complex polyphenols present in extravirgin olive oil are not directly absorbed, but undergo gastrointestinal biotransformation, increasing the relative amount of tyrosol (TYR) and hydroxytyrosol (HT) entering the small and large intestine. We investigated the capacity of TYR and HT to inhibit the insult of dietary lipid hydroperoxydes on the intestinal mucosa, using cultures of Caco-2, a cell line with enterocyte-like features, and studying the effect of tert-butyl hydroperoxide (TBH) treatment on specific cell membrane lipid targets. The effect of homovanillic alcohol (HVA), metabolite of HT in humans and detected as metabolite of HT in Caco-2 cells, was also evaluated. Exposure to TBH induced a significant increase of the level of MDA, the formation of fatty acid hydroperoxides and 7-ketocholesterol and the loss of α-tocopherol. Pretreatment with both HT and HVA protected Caco-2 cells from oxidative damage: there was no significant detection of oxidation products and the level of α-tocopherol was preserved. Noteworthy, TYR also exerted a protective action against fatty acids degradation. In vitro trials, where the simple phenols were tested during linoleic acid and cholesterol oxidation, gave evidence of a direct scavenging of peroxyl radicals and suggested a hydrogen atom-donating activity.

Protective effect of hydroxytyrosol and its metabolite homovanillic alcohol on H2O2 induced lipid peroxidation in renal tubular epithelial cells

We investigated the capacity of hydroxytyrosol (HT), 3,4-dihydroxyphenylethanol, and homovanillic alcohol (HVA), 4-hydroxy-3-methoxy-phenylethanol, to inhibit H(2)O(2) induced oxidative damage in LLC-PK1, a porcine kidney epithelial cell line, studying the effect of H(2)O(2) on specific cell membrane lipid targets, unsaturated fatty acids and cholesterol. Exposure to H(2)O(2) induced a significant increase of the level of MDA together with a disruption of the membrane structure, with the loss of unsaturated fatty acids, cholesterol and alpha-tocopherol, and the formation of fatty acids hydroperoxides and 7-ketocholesterol. Pretreatment with HT protected renal cells from oxidative damage: the level of membrane lipids was preserved and there was no significant detection of oxidation products. HVA exerted a comparable activity, thus both HT and HVA were able to prevent in renal cells the lipid peroxidation process that plays a central role in tubular cell injury.

Antioxidant activity of oligomeric acylphloroglucinols from Myrtus communis L

The use of myrtle (Myrtus communis L.) as a culinary spice and as a flavoring agent for alcoholic beverages is widespread in the Mediterranean area, and especially in Sardinia. Myrtle contains unique oligomeric non-prenylated acylphloroglucinols, whose antioxidant activity was investigated in various systems. Both semimyrtucommulone (1) and myrtucommulone A (2) showed powerful antioxidant properties, protecting linoleic acid against free radical attack in simple in vitro systems, inhibiting its autoxidation and its FeCl3- and EDTA-mediated oxidation. While both compounds lacked pro-oxidant activity, semimyrtucommulone was more powerful than myrtucommulone A, and was further evaluated in rat liver homogenates for activity against lipid peroxidation induced by ferric-nitrilotriacetate, and in cell cultures for cytotoxicity and the inhibition of TBH- or FeCl3-induced oxidation. The results of these studies established semimyrtucommulone as a novel dietary antioxidant lead.

Oxidative stability of polyunsaturated fatty acids: effect of squalene

The propensity of polyunsaturated fatty acids (PUFAs) to undergo oxidation plays an important role in the integrity of biological membrane and lipid containing foods. The ability of squalene (SQ), a naturally occurring dehydrotriterpene present in animal and plant tissues, to protect linoleic, linolenic, arachidonic and docosahexaenoic acids against temperature-dependent autoxidation and UVA (ultraviolet A, 320-380 nm) mediated oxidation was assessed. The oxidation of PUFAs was protected in varying degrees, with highest protection observed for linolenic, arachidonic and docosahexaenoic acids. Linoleic acid was less protected. At a molar ratio of 7:1 (PUFA:SQ) the inhibition of the oxidation process was 22% in the presence of linoleic acid and about 50% in presence of the other PUFAs tested. The different protection exerted by SQ against PUFAs with different degrees of unsaturation may be accounted for by the higher stability of octadecadienoic acid hydroperoxide isomers compared with respective PUFA hydroperoxides. Observing mild UVA-mediated oxidation and the temperature-dependent autoxidation reactions we found similarities in the oxidation pattern and the protection exerted by SQ. These findings suggest that the reaction of autoxidation is predominant and SQ acts mainly as peroxyl radical scavenger.

A Novel Approach to Study Linoleic Acid Autoxidation: Importance of Simultaneous Detection of the Substrate and its Derivative Oxidation Products

In this paper we have proposed a novel approach for studying the reaction of lipid oxidation by using the simplest chemical system available. Neat linoleic acid was incubated for 24 hours at 37 degrees C in the air. The course of lipid oxidation was followed by measuring simultaneously by HPLC with a diode array detector 1) linoleic acid decrease, 2) the products formed by radical attack, namely four hydroperoxy-octadeca-dienoic acid (HPODE) isomers, two c,t (c,t) and two trans,trans (t,t). 3) the byproducts formed by HPODE degradations, the four oxo-octadeca-dienoic acid (oxo-ODE) isomers. In HPODEs the presence of conjugated diene chromophore was confirmed by second derivative spectrophotometry. c,t HPODEs were also identified for their positional isomerism, while for t,t molecules the lack of suitable reference compound makes unfeasible the identification of their positional isomerism. As in the case of the latter two c,t and two t,t oxo-ODE isomers were characterized. This simple system appears to be useful for studying the activity exherted by lipophilic molecules that, like alpha-tocopherol, may act as antioxidants and/or as hydrogen atom donating molecules. The presence of alpha-tocopherol in different concentration for 24 hours in the reaction environment, shifts the reaction of linoleic acid autoxidation towards different byproduct formations. From the results obtained it is evident that alpha-tocopherol acts as hydrogen atom donor at all concentration tested, shifting the reaction toward a prevalent formation of c,t isomer of both HPODEs and oxo-ODEs. At concentration lower than 40 nmoles, when the ratio between alpha-tocopherol and linoleic acid was 1:100, the reaction of autoxidation is strongly inhibited, while at higher concentration alpha-tocopherol acted as a prooxidant. In these experimental conditions, alpha-tocopherylquinone was spectrophotometrically identified as the predominant oxidation product of alpha-tocopherol.