Amel Nakbi

Effects of olive oil and its fractions on oxidative stress and the liver's fatty acid composition in 2,4-Dichlorophenoxyacetic acid-treated rats

BackgroundOlive oils beneficial effects are not only related to its high content of oleic acid, but also to the antioxidant potential of its polyphenols. In this study, we assess the effects of virgin olive oil and its fractions on 2,4-D- induced oxidative damage in the liver of rats.MethodsMale Wistar rats were randomly divided into eight groups of ten each: (C) a control group, (D) group that received 2,4-D (5 mg/kg b.w.), (D/EVOO) group treated with 2,4-D plus extra virgin olive oil, (D/OOHF) group that received 2,4-D plus hydrophilic fraction, (D/OOLF) group treated with 2,4-D plus lipophilic fraction, (EVOO) group that received only extra virgin olive oil, (OOHF) group given hydrophilic fraction and (OOLF) group treated with lipophilic fraction. These components were daily administered by gavage for 4 weeks.ResultsA significant liver damage was observed in rats treated with 2,4-D via increased serum levels of transaminases and alkaline phosphatase, hepatic lipid peroxidation and decreased hepatic antioxidant enzyme activities, namely, superoxide dismutase, catalase, glutathione peroxidase, and glutathione reductase. The livers fatty acid composition was also significantly modified with 2,4-D exposure. However, extra virgin olive oil and hydrophilic fraction intake during 2,4-D treatment induced a significant increase in the antioxidant enzyme activities and a decrease in the conjugated dienes (CD) and thiobarbituric acid-reactive substances (TBARs) levels in the liver. The lipophilic fraction supplemented to 2,4-D- treated rats did not show any improvement in the liver oxidative status while a marked improvement was detected in the hepatic fatty acid composition of rats supplemented with olive oil and the two fractions.ConclusionWe concluded that the protective effect of olive oil against oxidative damage induced by 2,4-D is mainly related to the antioxidant potential of its hydrophilic fraction.

Dietary virgin olive oil protects against lipid peroxidation and improves antioxidant status in the liver of rats chronically exposed to ethanol

Excessive ethanol intake induces severe tissue damage particularly in the liver through the generation of reactive oxygen species. The aim of this study was to determine the effect of a virgin olive oil-rich diet on oxidative stress induced by chronic ethanol exposure in rats. Wistar rats were treated daily with a 35% ethanol solution for 6 weeks and fed with a standard chow or a diet containing 5% virgin olive oil. By administering ethanol to rats, a severe toxicity occurred in their liver, as assessed by the significantly elevated levels of serum transaminases. The hepatic malondialdehyde level, indicator of lipid peroxidation, was also increased in ethanol-treated rats, whereas the hepatic antioxidant enzyme activities, namely, superoxide dismutase, glutathione peroxidase, and catalase were significantly reduced. The activity of glutathione reductase remained unchanged in rats. Fatty acid composition of the liver was also significantly changed with ethanol intake. In contrast, virgin olive oil intake during ethanol treatment in rats resulted in a higher antioxidant activity and inhibited toxicity to the liver, as monitored by the reduction of transaminases levels and hepatic lipid peroxidation. Rats showed a better profile of the antioxidant system with normal glutathione peroxidase activity and ameliorated superoxide dismutase and catalase activities. In conclusion, results of this study indicate that olive oil ingestion by rats protects the liver from ethanol-induced oxidative damage by affecting the cellular redox potential.

Relationship between genetic polymorphisms of angiotensin-converting enzyme and methylenetetrahydrofolate reductase as risk factors for type 2 diabetes in Tunisian patients.

BACKGROUND/AIMS The role of methylenetetrahydrofolate reductase (MTHFR) and angiotensin-converting enzyme (ACE) gene polymorphisms as being risk factors for diabetes is still controversial. The aim was to investigate the distribution of ACE and MTHFR genotypes as well as to evaluate the role of plasmatic total homocysteine levels (tHcy) and ACE activity in Tunisian patients with type 2 diabetes mellitus (T2DM). DESIGN AND METHODS 115 T2DM patients compared to 116 healthy volunteers. RESULTS The ACE I/D polymorphism was significantly associated with diabetes (p<0.0001). The DD genotype and D allele were more frequent in patients compared to control group [DD: OR=4.93; p<0.0001; 95 % CI: 2.71-8.97; D: OR=3.08, 95% CI: 2.09-4.51 p<0.0001]. MTHFR allele and genotype frequencies did not differ between patients and controls. The susceptibility to diabetes in individuals with genotypes DD+vTT was 13.39 and in the individuals with DD+CT was 6.57 times that of the controls. However, individuals with genotypes ID+CC or II+CT have a protective effect against diabetes. The DD and TT genotypes were associated with significantly higher ACE activity and tHcy levels in diabetics. CONCLUSION Our data suggest that ACE ID polymorphism may act synergistically with MTHFR C677T polymorphism to assess diabetes risk.

Impact of packaging material and storage time on olive oil quality

Olive oil is very appreciated for its characteristic flavor and its biological and nutritional value which are strongly related to the quality. The effect of packaging materials (stainless, jar, clear polyethylenene terephthalate (PET), clear glass and dark glass bottles) on quality attributes of extra virgin olive oil (EVOO) was studied as a function of storage time (0 to 12 months). The results made it possible to highlight a light influence of time as well as type of container on the acidic composition of oils, although oleic acid slightly increased at the end of the analytical period. Indeed, the least stable oils were those stored in the jars with a progressive increase in quality attributes and the palmitic acid level. A clear reduction in the contents of antioxidants (carotenes, chlorophylls and total phenols) was observed in the oils stored in the earthenware jars and PET. Quality indexes were strongly influenced by the type of packaging material and the time of storage. Overall, the results revealed that the storage of oils in stainless and dark glass appears most adequate, thus supporting the conservation of primarily contents antioxidants with indices of quality indicating an unrefined olive oil lasting storage.

Association of homocysteine thiolactonase activity and PON1 polymorphisms with the severity of acute coronary syndrome.

INTRODUCTION Excess of total homocysteine (tHcy) and decrease of thiolactonase activities (HTase) have been proposed as risk factors for coronary artery diseases (CAD). OBJECTIVES We evaluated the relationship of tHcy and HTase with paraoxonase 1 (PON1) gene polymorphism according to CAD severity. DESIGN AND METHODS 118 healthy volunteers and 91 CAD patients were compared. RESULTS Serum levels of tHcy and oxidized LDL (ox-LDL) increased significantly by 26% and 48% in CAD patients and were associated with significantly lower levels of HDL cholesterol (p=0.02) and 42% of decrease in HTase activities (p<0.05). In these patients the HTase activity was negatively associated with tHcy and Hs CRP levels (r=-0.622, p=0.00 and r=-0.355, p=0.007 respectively) but positively associated with apoB and triglyceride levels (r=0.35, p=0.042 and r=0.308, p=0.003 respectively). HTase activity decreased inversely to the number of affected vessels and according to PON1 polymorphism. PON1 Q192R RR and PON1 L55M MM genotypes were associated with higher HTase activities. Only PON1 L55M (MM) genotype frequency was significantly higher in CAD patients than in controls (P<0.05), while its frequency was similar between the two subgroups according to CAD severity. In a multivariate analysis, tHcy levels were the only independent factor affecting the severity of cardiovascular disease (p=0.029). CONCLUSIONS High tHcy levels are associated with the severity of cardiovascular disease and may be partly explained by the diminished HTase activities in these patients.

Genotypic interactions of renin-angiotensin system genes with diabetes type 2 in a Tunisian population.

AIMS To explore the role of genetic variants of angiotensinogen (AGT M235T), angiotensin-converting enzyme (ACE I/D), and angiotensin type 1 receptor (AT1R A1166C) as predictors of diabetes risk and to examine their combined effects on type 2 diabetes mellitus (T2DM) patients. MAIN METHODS One hundred and fourteen T2DM patients were compared to 175 healthy controls with similar age and sex. KEY FINDINGS The genotypic frequencies for all three genes alone were significantly associated with increased risk of developing diabetes. Logistic regression analysis of classic coronary risk factors and the genetic polymorphisms demonstrated that hypertension and ACE DD genotype were the most significant contributors to T2DM. For the renin-angiotensin system (RAS) genes, the risk of T2DM in individuals with one risk genotype was 1.9 (95%CI: 1.1-3.0, p=0.017) higher than those with zero risk genotype. Individuals who carried two risk genotypes had a 4.0 (95%CI 1.7-9.4, p=0.001) times higher risk of T2DM than those who did not carry any risk genotypes of the RAS genes. Most interestingly, the risk of T2DM for individuals with three risk genotypes was 26.2 (95%CI: 5.8-117.9, p<0.001) higher than those with zero risk genotype. SIGNIFICANCE The results of the present study imply that genotyping of renin-angiotensin system genes could become an important part of the clinical process of risk identification for T2DM in Tunisian population.

Relationship between thiolactonase activity and hyperhomocysteinemia according to MTHFR gene polymorphism in Tunisian Behçet's disease patients.

Abstract Background: Behçets disease (BD) is a multisystemic immuno-inflammatory disorder. Inflammatory processes may cause lipid peroxidation, alteration of lipid profile and increase the risk of atherosclerosis. The aim of this study was to evaluate the association between thiolactonase (HTLase) activity and plasma homocysteine levels (tHcy) in a BD population and to investigate their association with methylenetetrahydrofolate reductase (MTHFR) 677C→T genotype. Method: A total of 35 BD patients were compared to 39 healthy volunteers. Results: Significantly higher tHcy levels associated with lower HTLase activities were found in BD patients as compared to healthy controls (p<0.001). These patients also exhibited lower values of triglycerides and high-density lipoprotein cholesterol (HDL-C). Homozygosity for the T allele of the MTHFR gene was more frequent in BD patients (14.3% vs. 7.7%). It was associated with significantly higher tHcy levels (16.9 μmol/L for n=17 vs. 13.1 μmol/L for n=18; p<0.05) and markedly lower HTLase activity (362.6±156.7 U/L vs. 414.2±180.2 U/L) for the (TT+CT) and CC genotypes, respectively. Moreover, HDL-C levels were inversely correlated with tHcy (r=–0.5; p=0.004) but positively associated with HTLase activity (r=0.374; p=0.038). These correlations were also present in several clinical manifestations, such as ocular, neurological involvement or thrombosis. Conclusions: Homozygosity of the T allele of the MTHFR gene is prevalent in BD patients. High levels of tHcy associated with low HTLase activities may be one of the causes leading to thrombosis in BD patients. Clin Chem Lab Med 2008;46:187–92.

Alteration of lipid status and lipid metabolism, induction of oxidative stress and lipid peroxidation by 2,4-dichlorophenoxyacetic herbicide in rat liver

Abstract This study aims to investigate the effects of the 2,4-dichlorophenoxyacetic herbicide (2,4-D) on plasma lipids, lipoproteins concentrations, hepatic lipid peroxidation, fatty acid composition and antioxidant enzyme activities in rats. Animals were randomly divided into four groups of 10 each: control group and three 2,4-D-treated groups G1, G2 and G3 were administered 15, 75 and 150 mg/kg/BW/d 2,4-D by gavage for 28 d, respectively. Results showed that 2,4-D caused significant negative changes in the biochemical parameters investigated. The malondialdehyde level was significantly increased in 2,4-D-treated groups. Fatty acid composition of the liver was also significantly changed with 2,4-D exposure. Furthermore, the hepatic antioxidant enzyme activities were significantly affected. Finally, 2,4-D at the studied doses modifies lipidic status, disrupt lipid metabolism and induce hepatic oxidative stress. In conclusion, at higher doses, 2,4-D may play an important role in the development of vascular disease via metabolic disorder of lipoproteins, lipid peroxidation and oxidative stress.

Biochemical and histological evaluation of kidney damage after sub-acute exposure to 2,4-dichlorophenoxyacetic herbicide in rats: involvement of oxidative stress.

The present study evaluated the effects of sub-acute exposure to different doses of 2,4-dichlorophenoxyacetic acid (2,4-D) on rat kidney. Forty animals were divided into four equal groups and treated with different doses of 2,4-D: 0, 15, 75 and 150 mg/kg body weight per day via oral gavage for 28 consecutive days. Renal function, histopathology, tissue malondialdehyde and antioxidant enzyme activities were evaluated. The results showed a significant decrease (p < 0.01) in uric acid level and an increase in plasma levels of urea and creatinine (p < 0.01) in rats administered 2,4-D at the three studied doses. The activities of catalase and superoxide dismutase were significantly affected for all treated rats, while glutathione peroxidase significantly decreased in rats exposed to 2,4-D at a dose of 150 mg/kg. Through sub-acute treatment, starting from the low to the high doses of 2,4-D, there were significant increase in kidney MDA as compared to controls. The histopathological study revealed tubular damages, glomerular alterations, vascular congestion and increased number of pyknotic nuclei in kidneys of all 2,4-D treated groups. The severity of these alterations increase in a dose-dependent manner. Our findings confirm that sub-acute exposure to 2,4-D induced oxidative renal dysfunction in rats. Therefore, at higher doses, 2,4-D may be implicated in the pathogenesis of kidney failure via lipid peroxidation and oxidative stress.

Association of the C677T MTHFR Polymorphism With Homocysteine, Ox-LDL Levels, and Thiolactonase Activities in the Severity of Coronary Syndrome

Coronary artery diseases (CAD) are influenced by multiple genes of modest effect as the methylenetetrahydrofolate reductase (MTHFR) C677T gene polymorphism, related to MTHFR activity and total plasma homocysteine (tHcy) concentration. This study was designed to evaluate tHcy, oxidized low-density lipoprotein (LDL) (ox-LDL), high-sensibility C-reactive protein (Hs CRP) levels, and homocysteine thiolactonase (HTase) activities as new risk factors for CAD and to investigate an association between MTHFR polymorphism tHcy concentrations and coronary syndrome severity. Our results showed significantly higher levels of tHcy and ox-LDL in patients associated with lower HTase activities. These levels increased proportionally to disease severity. Total plasma Hcy levels were negatively correlated to HTase activities in patients where the TT genotype was significantly more frequent. In a multivariate analysis, tHcy level was the only independent factor affecting the coronary syndrome severity. High tHcy levels are associated with coronary syndrome severity and may be explained either by the elevated prevalence of TT genotype or by the diminished HTase activities.