Role of quercetin and its in vivo metabolites in protecting H9c2 cells against oxidative stress.

The aim of this study was to investigate the potential of quercetin and two of its "in vivo" metabolites, 3'-O-methyl quercetin and 4'-O-methyl quercetin, to protect H9c2 cardiomyoblasts against H(2)O(2)-induced oxidative stress. As limited data are available regarding the potential uptake and cellular effects of quercetin and its metabolites in cardiac cells, we have evaluated the cellular association/uptake of the three compounds and their involvement in the modulation of two pro-survival signalling pathways: ERK1/2 signalling cascade and PI3K/Akt pathway. The three flavonols associated with cells to differing extents. Quercetin and its two O-methylated metabolites were able to reduce intracellular ROS production but only quercetin was able to counteract H(2)O(2) cell damage, as measured by MTT reduction assay, caspase-3 activity and DNA fragmentation assays. Furthermore, only quercetin was observed to modulate pro-survival signalling through ERK1/2 and PI3K/Akt pathway. In conclusion we have demonstrated that quercetin, but not its O-methylated metabolites, exerts protective effects against H(2)O(2) cardiotoxicity and that the mechanism of its action involves the modulation of PI3K/Akt and ERK1/2 signalling pathways.

Gamma-linolenic acid dietary supplementation can reverse the aging influence on rat liver microsome delta 6-desaturase activity.

We have recently demonstrated that in rats the process of delta 6-desaturation of linoleic and alpha-linolenic acids slows with aging. One method of counteracting the effect of slowed desaturation of linoleic acid would be to provide the 6-desaturated metabolite, gamma-linolenic acid (18:3(n-6) GLA) directly. We have here investigated the 6-desaturation of both linoleic and alpha-linolenic acids in liver microsomes of young and old rats given GLA in the form of evening primrose oil (EPO) (B diet) in comparison to animals given soy bean oil alone (A diet), monitoring also the fatty acid composition of liver microsomes and relating this to the microviscosity of the membranes. In young rats the different experimental diets did not produce any difference in delta 6-desaturase (D6D) activity on either substrate suggesting that, when D6D activity is at or near its peak, the variations in diet tested are unable to influence it. In the old animals the rate of 6-desaturation of linoleic and particularly of alpha-linolenic acid was significantly greater in the B diet fed animals than in the A diet fed. The effects of the diets on the fatty acid composition of liver microsomes were consistent with the findings with regard to 6-desaturation. Administration of GLA partially corrected the abnormalities of n-6 essential fatty acid (EFA) metabolism by raising the concentration of 20:4(n-6) and other 6-desaturated EFAs. Furthermore, the GLA rich diet also increased the levels of dihomo-gamma-linolenic acid and of 6-desaturated n-3 EFAs in the liver microsomes. The microviscosity of microsomal membranes as indicated by DPH polarization was correlated with the unsaturation index of the same membranes. There was a very strong correlation between the two. In both young and old rats the B diet reduced the microviscosity and increased the unsaturation index. However, the effect was much greater in the old animals.

Manipulation of lipid composition of rat heart myocytes aged in culture and its effect on alpha1-adrenoceptor stimulation.

The fatty acid composition of the phosphoinositides was evaluated in cultured neonatal rat cardiomyocytes during the aging-like process in vitro, comparing data obtained from control and gamma-linolenic acid supplemented cardiomyocytes. The response to alpha1 stimulation was evaluated in both control and supplemented cells to verify the relationship between the alterations of the phosphoinositide fatty acid composition concomitant to culture aging and the cell response to exogenous stimuli. Arachidonate level decreased as a function of age in all the phosphoinositides, which appeared to be more saturated as cells aged in culture. Inositol phosphate production in response to alpha1 stimulation decreased as cells aged in culture. Supplementation of culture medium with gamma-linolenic acid caused significant modifications in the fatty acid pattern of the phosphoinositides, which appeared less saturated than the corresponding fractions isolated from unsupplemented cells during the aging-like process. The modifications induced by the supplementation in the phosphoinositide fatty acid composition prevented the age-related reduction of inositol phosphate production upon stimulation. These results clearly indicate a major role for the lipid composition in determining the response to alpha1 stimulation, suggesting a nutritional approach to overcome some of the impairments of molecular events related to the process of aging.

Green tea modulation of inducible nitric oxide synthase in hypoxic/reoxygenated cardiomyocytes.

Hypoxia/reoxygenation (H/R) is one of the causes of the increased expression of inducible nitric oxide synthase (iNOS) in cardiomyocytes. Since an aberrant NOS induction has detrimental consequences, we evaluated the effect of a green tea extract (GTE) on the NOS induction and activity in H/R-cardiomyocytes to define a nutritional strategy. Cultured rat cardiomyocytes were exposed to H/R in the presence of two concentrations of a green tea extract (GTE), which is reported to inhibit NOS expression and activity in different cells. In cultured cardiomyocytes two NOS isoforms were constitutively expressed, but only iNOS was induced by H/R. GTE supplementation at the lowest concentration, comparable to that in human plasma after dietary consumption, was ineffective, while the highest, comparable to that achievable by dietary supplements, counteracted the effect of H/R on iNOS induction and activity. It is necessary to verify in humans the relationship between the modulation of NO production and green tea dietary consumption.

Effect of age and extent of dietary restriction on hepatic microsomal lipid peroxidation potential in mice.

Lipid peroxidation potential in hepatic microsomes from young and old mice following two different caloric restriction regimens was measured by a colorimetric thiobarbituric acid method under conditions where Fe2+ autoxidation and free oxygen radical production were undetectable. Peroxidation was highest in the young (3.5-month-old) slightly restricted group (caloric intake 75% of ad libitum mice) but very low in young severely restricted (caloric intake 50% of ad libitum mice) and in both old (27-month-old) slightly and severely restricted groups. Very old (45-month-old) severely restricted animals had intermediate lipid peroxidation potentials. Fatty acid composition of liver homogenates was also determined. Significant differences between groups were found for only three fatty acids. Linoleic acid (18:2(n-6)) decreased in aged slightly restricted animals while it remained stable in severely restricted animals during aging. Dihomo-gamma-linolenic acid (20:3(n-6)) was higher in very old restricted animals than in old slightly restricted animals. Docosahexaenoic acid (22:6(n-3)) decreased in old slightly restricted animals. These results indicated that the effect of diets on hepatic fatty acid composition and the potential for microsomal lipid peroxidation in mice was dependent on the degree of caloric restriction and age.

Essential fatty acid metabolism in long term primary cultures of rat cardiomyocytes: a beneficial effect of n-6:n-3 fatty acids supplementation.

In long term (21 days) primary cultures of neonatal rat cardiomyocytes, utilized as a model of in vitro senescence, we investigated the dual effect of the time length in culture and of the supplementation with n-6:n-3 fatty acid mixtures on linoleic (LA) and alpha-linolenic acid (ALA) metabolism. Cardiomyocytes were divided into groups receiving: (1) control medium; (2) control medium plus n-3 fatty acids; (3) and (4) control medium plus n-6 and n-3 fatty acids in the ratio 1:2 or 2:1, respectively. In control cells. senescence caused a reduction in the conversion of LA and ALA, and the decrease in their metabolites was bypassed by the different supplementations. The fatty acid composition of cardiomyocyte lipids was therefore affected by both senescence and supplementation, as evidenced by the n-6:n-3 fatty acid ratio and the unsaturation index (U.I.) in cellular lipids. The final result of ageing in culture and of fatty acid supplementations was in all the groups of cells but one (n-6:n-3, 2:1) an unbalance in the n-6:n-3 fatty acid ratio. All the supplementations were able to counteract the decrease in the U.I. observed with senescence, but only the n-6:n-3 (2:1) was able to do so by increasing the cellular content of the fatty acids which are precursors of anti-aggregation eicosanoids without altering the n-6:n-3 fatty acid ratio.

Influence of chronic ethanol consumption on the inositol phospholipid fatty acid composition of human peripheral blood lymphocytes.

The breakdown of inositol phospholipids is an important event after the binding of antigens to the T-cell antigen receptor. In alcoholics, changes either in early or in late steps of lymphocyte activation have been documented, however no study on the role of phosphoinositide fatty acid composition in signal transduction has been reported. We have analyzed the fatty acid pattern of phosphatidylinositol, phosphatidylinositol-4-phosphate and phosphatidylinositol-4,5-bisphosphate from peripheral blood lymphocytes of alcoholic patients and healthy controls, in order to point out the possible compositional differences which could interfere with the signal transmission responsible for the early events in lymphocyte activation. In alcoholics, the arachidonic acid relative molar content in all the inositol phospholipid (PtdIns) fractions derived from lymphocytes was lower than in controls; all PtdIns classes appeared much more saturated than the corresponding fractions from control lymphocytes. The different fatty acid pattern of PtdIns in alcoholic patients could be responsible for an altered second messenger production, above all the production of a modified diacylglycerol which, in turn, could cause a different activation pattern of protein kinase C, with a consequent alteration in cell proliferation. The decrease in arachidonic acid molar content in the phosphoinositides and particularly in the phosphatidylinositol-4,5-bisphosphate fraction of PBL of alcoholic patients could lead to a reduced synthesis of prostanoids of the (n-6) series, and, as a consequence, to an alteration in the mitogenic response of the cells.

Phosphatidylinositol metabolism in lymphocytes of chronic alcoholic patients after anti-CD3 stimulation.

The immunological alterations observed in chronic alcoholic patients may be due to alterations of signal transduction across the lymphocyte membrane. Upon binding of mitogens or antigens to specific plasma membrane receptors, the activation of phospholipase C leads to the hydrolysis of inositol phospholipids, producing inositol phosphates and diacylglycerol. One of the early events in lymphocyte activation is an increase of intracellular calcium concentration, due to both an influx from extracellular fluid and a release from intracellular stores mediated by inositol phosphates. In this study we verified whether the diminished mobilization of intracellular calcium, previously observed in alcoholics, is caused by alteration in phosphoinositide turnover. We evaluated total inositol phosphate production in peripheral blood lymphocytes after anti-CD3 stimulation, comparing control subjects and alcoholic patients. Lymphocyte activation generated inositol phosphates in both controls and alcoholics, but to a different extent, inositol phosphate production being significantly higher in controls than in alcoholics. This reduction in inositol phosphate production could be accounted either to an inhibition of PLC activity or to a modified affinity of phospholipase C for its own substrates, i.e., phosphoinositides, which fatty acid composition has been previously demonstrated to be greatly different in alcoholics in comparison to healthy subjects.

A randomized controlled study comparing elemental diet and steroid treatment in Crohn's disease.

BACKGROUND: Elemental diet is considered an effective primary treatment for active Crohn's disease, but it is usually given by a feeding tube. METHODS: Twenty-two patients (12 males, median age 30 years, range 18-60) with moderately active Crohn's disease were enrolled in a randomized study in which the efficacy of an elemental diet administered orally was compared to high-dose corticosteroids in achieving clinical and laboratory remission. Ten patients were treated by oral elemental diet (Peptamen, Clintec, USA) and 10 received corticosteroids. Both treatment regimens lasted 2 weeks. The two groups did not differ with respect to age, sex, body weight, location of disease, treatment or disease activity prior to the study. In all patients studied, simple Crohn's disease activity index, nutritional status (expressed as body mass index), percentage of ideal body weight, fat mass, fat free mass, erythrocyte sedimentation rate, interleukin-6, intestinal permeability (expressed as permeability index), prealbumin, retinol binding protein and multiskin test were evaluated before and after treatment. RESULTS: After 2 weeks of treatment, there were significant improvements in simple Crohn's disease activity index, erythrocyte sedimentation rate, permeability index, body mass index, prealbumin, retinol binding protein and multiskin test in the elemental diet group. There were significant improvements in simple Crohn's disease activity index and fat free mass in the corticosteroid group. CONCLUSIONS: These data suggest that, in the short term, an oral elemental diet is at least as effective as steroids in inducing remission of mild-moderately active Crohn's disease, but it may be more effective in improving the nutritional status of these patients, probably through a more rapid restoration of normal intestinal permeability.

Role of gamma-linolenic acid in counteracting doxorubicin-induced damage in cultured rat cardiomyocytes.

The clinical usefulness of doxorubicin is limited by cardiotoxicity. We have demonstrated that doxorubicin has a dual negative effect on myocardial lipids, acting against highly unsaturated fatty acids (HUFAs) directly and desaturating/elongating enzymes required for their biosynthesis, thus decreasing linoleic and alpha -linolenic conversion to higher metabolites. Primary cultures of rat cardiomyocytes were challenged with different doxorubicin concentrations and doxorubicin exposure was followed by a 24-h recovery period in the absence or presence of serum, and of gamma -linolenic acid. Serum in the recovery medium did not appear to be essential for the restoration of the desaturating/elongating activities, and gamma -linolenic acid supplementation influenced only alpha -linolenic acid conversion. Serum, and particularly gamma-linolenic acid, were very important in increasing HUFA levels behind the pure biosynthesis. HUFA biosynthesis plays a role in counteracting doxorubicin toxicity, but it cannot completely overcome the depletion of these fatty acids; serum and exogenous gamma-linolenate are critical in filling the decreased HUFA pool.

Kinetic analysis of delta-6-desaturation in liver microsomes: influence of gamma-linoleic acid dietary supplementation to young and old rats.

Previous experiments demonstrated the ability-of a gamma-linoleic acid (GLA) dietary supplementation (as evening primrose oil--EPO) to counteract the fall off in delta-6-desaturase (D6D) activity of linoleic acid and alpha-linoleic acid in aged rats. Kinetic parameters of the D6D were determined in order to test the possibility that there may be a significant influence of GLA administration to young and aged rats on the Vm and Km values for 6-desaturation of both the substrates. In young rats GLA supplementation did not affect the kinetic parameters, while in old rats it produced an increase of Vm values of 6-desaturation for both the substrates. Thus the administration of small doses of GLA to old rats might offer substantial protection against the loss of D6D affinity observed in aging, enhancing the capacity of the enzyme itself.

Age-related changes in essential fatty acid metabolism in cultured rat heart myocytes.

We previously demonstrated that cultured neonatal rat myocytes have the capacity to desaturate/elongate essential fatty acids, alpha-linolenic acid conversion being higher than linoleic acid conversion. The whole process of highly unsaturated fatty acid formation from linoleic and alpha-linolenic acids slows with aging. In this study we grew heart myocytes in culture for different periods of time, and we observed a decrease in the desaturating/elongating activities for both substrates as the cells aged in culture. Alpha-linolenic acid conversion into highly unsaturated fatty acids was less impaired by aging than linoleic acid conversion. These modifications are correlated to the age-dependent alterations observed in the total lipid fatty acid composition, which caused a decrease in the unsaturation index. Changes in the lipid composition that occur in aging cultures parallel those reported for several tissues upon aging in the whole animal. The data herein reported may suggest the possibility of counteracting the effects of aging on lipid metabolism by supplementing cultures with appropriate amounts of highly unsaturated fatty acids.

Green tea extracts can counteract the modification of fatty acid composition induced by doxorubicin in cultured cardiomyocytes.

Doxorubicin cardiotoxicity is associated with the generation of free radicals, and involves not only lipid peroxidation but also a decreased biosynthesis of highly unsaturated fatty acids, leading to significant modification in cardiomyocyte fatty acid composition. We have evaluated whether naturally occurring antioxidants could counteract this side-effect. Green tea is an excellent source of catechins; we supplemented cultured rat cardiomyocytes with different green tea extracts to relate their catechin content and composition to their ability in protecting cells against doxorubicin-induced damage. The determination of total lipid fatty acid composition, of conjugated diene production (indicator of lipid peroxidation), and of lactate dehydrogenase release revealed that supplementation with tea extracts could counteract significant modifications in the fatty acyl pattern due to doxorubicin exposure, although to different extents. These differences could be ascribed to the different total catechin content and to qualitative differences among the tea extracts, determined by HPLC analysis.

Dual influence of aging and vitamin B6 deficiency on delta-6-desaturation of essential fatty acids in rat liver microsomes.

Delta-6-desaturase (D6D) activity is influenced by many nutritional and non-nutritional factors, among which one of the most important is aging. D6D activity could be susceptible to the dual influence of aging itself and of nutritional deficiencies, due to the reduced intake and/or absorption of essential nutrients. Particularly, vitamin B6 deficiency might be a crucial factor for D6D activity in aged people. Using 20 month old Sprague-Dawley rats fed a diet with a subnormal level of vitamin B6, we evaluated D6D activity for linoleic acid (LA) and alpha-linolenic acid (ALA) in liver microsomes, and the fatty acid composition of microsomal total lipids. We observed a diminished D6D activity for LA and also for ALA in vitamin B6-deficient animals, being approximately 63% and 81% respectively of the corresponding activity in control rats. As a consequence, significant modifications in the relative molar content of microsomal fatty acids were observed. The content of arachidonic and docosahexaenoic acid, the main products of the conversion of LA and ALA respectively, decreased, LA content increased and a decrease in the unsaturation index was observed in liver microsomes of B6-deficient rats. The foregoing results suggest that the impairment of D6D activity by vitamin B6 deficiency might be an important factor in decreasing the synthesis of n-6 and n-3 PUFAs. This may be particularly important in aging, where D6D activity is already impaired.

Delta-6-desaturase activity of human liver microsomes from patients with different types of liver injury.

The delta-6-desaturase (D6D) activity was evaluated in microsomes from liver fragments of cholecystectomized subjects without any liver pathology and from explanted liver of patients affected by cirrhosis of different etiologies. We observed a significant decrease in D6D activity, evaluated by a radiochemical technique using 1-[14C]-linoleic acid as substrate, in cirrhotic patients with no correlation with the etiology of the cirrhosis. The D6D activity within the pathological group was quite similar. No alteration in the 20:4/18:2 ratio obtained by gas chromatographic analysis of fatty acid methyl esters of microsomal membranes was found. Liver disease seems to be the main cause of the decreased enzyme activity independent of its etiology.

Concentration- and time-dependent effects of gamma-linolenic acid supplementation to tumor cells in culture.

Gamma-linolenic acid (GLA) supplemented to neuroblastoma SK-N-BE, tubal carcinoma TG and colon carcinoma SW-620 cells was incorporated into phospholipids in all the cell lines (although to different extents), in a concentration- and time-dependent manner. All the cell lines were able to metabolize GLA to arachidonic acid, SK-N-BE being the most active. Supplementation with low GLA concentrations for short periods was not sufficient to impair cell proliferation; only higher amounts of GLA had an anti-proliferative effect also in short times. In these conditions, the antiproliferative effect of GLA is probably due to cellular dysfunction caused by fatty acid modifications.

Visual evoked potentials and dietary long chain polyunsaturated fatty acids in preterm infants.

The influence of dietary long chain polyunsaturated fatty acid (LCP) supply, and especially of docosahexaenoic acid (DHA), on evoked potential maturation, was studied in 58 healthy preterm infants using flash visual evoked potentials (VEPs), flash electroretinography (ERG), and brainstem acoustic evoked potentials (BAEPs) at 52 weeks of postconceptional age. At the same time, the fatty acid composition of red blood cell membranes was examined. The infants were fed on breast milk (n = 12), a preterm formula supplemented with LCP (PF-LCP) (n = 21), or a traditional preterm formula (PF) (n = 25). In the breast milk and PF-LCP groups the morphology and latencies of the waves that reflect the visual projecting system were similar; in the PF group the morphology was quite different and the wave latencies were significantly longer. This could mean that the maturation pattern of VEPs in preterm infants who did not receive LCP was slower. Moreover, a higher level of erythrocyte LCP, especially DHA, was found in breast milk and PF-LCP groups compared with the PF group. ERG and BAEP recordings were the same in all three groups. These results suggest that a well balanced LCP supplement in preterm formulas can positively influence the maturation of visual evoked potentials in preterm infants when breast milk is not available.

The protective role of different green tea extracts after oxidative damage is related to their catechin composition.

The antioxidant activities of three different green tea extracts were investigated and compared by two different methods. By the first method, which evaluated the direct protective effect of the green tea extracts on lipid peroxidation, the extracts were added, at different concentrations, to a lipid model system, made by refined peanut oil, freshly submitted to a further bleaching and subjected to forced oxidation at 98 degrees C, by an oxidative stability instrument. By the second method, the effectiveness of the same extracts was checked in cultures of neonatal rat cardiomyocytes exposed to a free radical-generating system by evaluating conjugated diene production and lactate dehydrogenase release. All of the extracts revealed a strong antioxidant activity by both the methods, and a particular effectiveness was demonstrated by the extracts having higher amounts of (-)-epigallocathechin-3-gallate and (-)-epigallocathechin, as analyzed by reverse-phase HPLC analysis.

Evening primrose oil (Efamol) in the treatment of children with atopic eczema.

It has been reported that essential fatty acid levels may be low and that there may be reduced levels of delta-6-desaturase metabolites of linoleic acid in patients with atopic eczema. Good therapeutic results have been reported on the use of evening primrose oil (Efamol) in adults but not in children. Efamol contains gamma-linolenic acid, the delta-6-desaturase metabolite of linoleic acid. The authors have studied 24 children with atopic eczema: 12 of them were treated with a higher dose of evening primrose oil than in previous studies and 12 with placebo olive oil. The clinical status and plasma, neutrophil and lymphocyte fatty acid composition in these children have been evaluated. After 4 weeks the eczema of essential fatty acid-treated children significantly improved in comparison with that of placebo-treated children (p less than 0.01). There were significant changes in plasma fatty acid composition between the basal values and the end of active treatment, and between the placebo and actively treated children. Neutrophil and lymphocyte fatty acid composition did not seem to be related to disease activity.

A long-term study on the use of evening primrose oil (Efamol) in atopic children.

The effect of essential fatty acids on atopic eczema is controversial. Some workers have reported that patients with atopic eczema improved following oral treatment with evening primrose oil (an oil with a high concentration of gamma-linolenic acid), but others have disputed this. This study was designed to look at the effect of evening primrose oil as a long-term oral supplementation for children with atopic eczema. Treated children dramatically improved their clinical condition after 4 weeks of therapy, and this improvement was maintained during the whole period of treatment (20 weeks). At the same time, modifications in plasma, neutrophil and lymphocyte fatty acid composition were detected.