Phospholipid fatty acid composition affects enzymatic antioxidant defenses in cultured Swiss 3T3 fibroblasts

Summary

The aim of this work was to study the adaptation of enzymatic antioxidant cell defense to the nature of the membrane polyunsaturated fatty acids (PUFA). 3T3 Swiss fibroblasts were grown for 5 days in a medium supplemented with 50 μM linoleic acid (LA) or eicosapentaenoic acid (EPA) and compared t control cells (C). The phospholipid fatty acid content was evaluated: LA were enriched in n-6 PUFA (27.8%) in comparison to C (6.7%) or EPA (5.6%); EPA were enriched in n-3 PUFA (26.2%) in comparison to LA (4.4%) or C (4.6%). The fatty acid double bond index (DBI) increased from C to LA and EPA. The activities of the three key enzymatic antioxidant defenses, SOD, GPx and GST, increased with the degree of unsaturation of the phospholipid fatty acids. In the cells with fatty acids that are very sensitive to oxidative stress, the higher activities of SOD and GPx might act to limit the initiation of lipid peroxidation and the higher activities of GST and GPx to decrease the toxic effects of the various species produced from lipid degradation.     

Enrichment of RAW264.7 macrophages with essential 18-carbon fatty acids affects both respiratory burst and production of immune modulating cytokines

Macrophages play a vital role in the innate immune system. Thereby, production of both reactive oxygen intermediates and immune modulating cytokines is crucial for successful pathogen defense. Fatty acids may interfere with immune response in several ways. In this study, we investigated the influence of essential polyunsaturated fatty acids (PUFA) on key macrophage functions. RAW264.7 macrophages were cultured in a medium supplemented with 2 or 15 μmol/L of the n-6 PUFA linoleic acid (LA) or of the n-3 PUFA α-linolenic acid (LNA), respectively. Cells were tested for incorporation of fatty acids as well as NADPH oxidase activity. Furthermore, supernatants were collected for detection of NO and cytokine release (TNF-α, IL-6, IL-10). Exposure of RAW264.7 macrophages to LA or LNA resulted in incorporation of these fatty acids and their derivatives. Thereby, supplementation with both LA and LNA caused a significant increase in NADPH oxidase activity. In contrast, synthesis of NO was not affected by PUFA supplementation. Moreover, distinct effects could be seen in the release of immune modulating cytokines. Due to enhancement of NADPH oxidase activity, PUFA presumably promote the killing of pathogens crucial in host defense. In addition, the unsaturated fatty acids tested in our study were shown to modulate cytokine release by the macrophages, thus driving immune response into an anti-inflammatory direction. Of note, distinct differences between the n-6 PUFA LA and the n-3 PUFA LNA underline the impact of PUFA family on immune response.     

Polyunsaturated fatty acid supplements modulate mast cell membrane microdomain composition

In the present study, the lipid raft composition of a canine mastocytoma cell line (C2) was analyzed. Lipid rafts were well separated from non-raft plasma membranes using a detergent-free isolation technique. To study the influence of n-3 and n-6 polyunsaturated fatty acids (PUFA) on raft fatty acid composition in comparison to non-raft cell membrane, C2 were supplemented with one of the following: α-linolenic acid, eicosapentaenoic acid, docosahexaenoic acid, linoleic acid or arachidonic acid. Enrichment of the culture medium with a specific PUFA resulted in an increase in the content of this fatty acid both in rafts and non-raft membranes. Contents of cholesterol and protein were found not to be affected by the changes in the fatty acid profiles. In conclusion, our data provide strong evidence that PUFA modulate lipid composition and physiological properties of membrane micro domains of mast cells which in turn may have effects on mast cell function.     

Antioxidant modulation of oxidant-stimulated uptake and release of arachidonic acid in eicosapentaenoic acid-supplemented human lymphoma U937 cells

Omega-3 polyunsaturated fatty acids (PUFA) are increasingly finding use as treatments for a variety of medical conditions. PUFA supplementation can, however, result in increased oxidative stress causing elevated turnover rate of membrane phospholipids, impairment of membrane integrity and increased formation of inflammatory mediators. The aim of this study was to determine which antioxidant compounds were most effective in ameliorating the stimulation of phospholipid turnover by oxidative stress. U937 cells were supplemented with eicosapentaenoic acid and either ascorbic acid, alpha-tocopherol, beta-carotene or astaxanthin prior to being challenged with oxidant. Although all antioxidants were found to be effective in decreasing oxidant-stimulated peroxide formation, only alpha-tocopherol significantly decreased oxidant-stimulated release of 3H-labeled arachidonic acid (AA), while ascorbic acid markedly increased release. All antioxidants except alpha-tocopherol decreased oxidant-stimulated 3H-AA uptake. Our data suggest that antioxidants are not equally effective in combating the effects of oxidative stress upon membrane phospholipid turnover, and that optimal protection will require mixtures of antioxidants.     

Modification of phospholipids fatty acid composition in reuber H35 hepatoma cells: effect on HMG-CoA reductase activity

There is controversy about the effect of saturated and polyunsaturated fats on 3-hydroxy-3-methylglutaryl-CoA (HMG-CoA) reductase, the main regulatory enzyme of cholesterogenic pathway. Results from dietary studies are difficult to interpret because diets normally contain a mixture of fatty acids. Therefore, we have used Reuber H35 hepatoma cells whose phospholipids were enriched in different individual fatty acids and have studied their effects on the cellular reductase activity. Lauric, myristic, eicosapentaenoic (EPA), and docosahexaenoic (DHA) acids were supplemented to the culture medium coupled to bovine serum albumin. The four fatty acids were incorporated into phospholipids from cells grown in media containing whole serum or lipoprotein-poor serum (LPPS). Reductase activity of cells cultivated in a medium with LPPS was three to four times higher than those cultivated in medium with whole serum. Saturated fatty acids increased reductase activity of cells grown in medium with whole serum, whereas n-3 polyunsaturated fatty acids (PUFA) decreased it. However, both saturated and polyunsaturated fatty acids increased reductase activity when serum lipoproteins were removed. In conclusion, this is one of the first reports demonstrating that saturated and n-3 PUFA only show differential effects on HMG-CoA reductase activity in the presence of lipoproteins.     

Polyunsaturated fatty acids do not activate AMP-activated protein kinase in mouse tissues

Stearoyl-CoA desaturase 1 (SCD1) deficiency partitions fatty acids away from lipid synthesis towards fatty acid oxidation in liver and skeletal muscle in part due to activation of AMP-activated protein kinase (AMPK) pathway. The mechanism of AMPK activation by SCD1 mutation is unknown, however since SCD1-/- animals have increased relative amounts of polyunsaturated fatty acids (PUFA), we hypothesized that the increased levels of PUFA might be responsible for the activation of AMPK in SCD1 deficient mice. Therefore, the present study was undertaken to analyze the effect of PUFA on AMPK in liver, skeletal muscle, and heart. We fed mice ad libitum for 14 days with diet supplemented with fish oil (5% fat). As expected, fish oil supplementation significantly increased n-3 PUFA content in each of the analyzed tissues. Hepatic mRNA levels of fatty acid synthase and acyl-CoA oxidase decreased by 92% and increased by 60%, respectively, consistent with known PUFA effects. However, after 14 days of PUFA feeding, we did not find any changes in AMPK phosphorylation and protein content in mouse liver, skeletal muscle, and heart. The data suggest that PUFA are not involved in AMPK activation in mouse tissues and that the increased activity of AMPK in SCD1-/- mice is probably PUFA-independent.     

Inhibition of Δ-6 desaturase reduces fatty acid re-esterification in 3T3-L1 adipocytes independent of changes in n3-PUFA cellular content

Δ-6 desaturase (D6D) is a key enzyme in the synthesis of long-chain polyunsaturated fatty acids (LC-PUFA). Evidence suggests that reduced D6D activity not only disrupts LC-PUFA production, but also impacts whole body lipid handling and body weight; however, the mechanisms remain largely unexplored. Therefore, we investigated the effect of D6D inhibition on the regulation of lipid accumulation in 3T3-L1 adipocytes with and without changes in n-3 PUFA content. 3T3-L1 cells were treated with a D6D inhibitor (SC-26196) in the presence or absence of α-linolenic acid (ALA) throughout differentiation. We found that D6D inhibition blocked the conversion of ALA to eicosapentaenoic acid (EPA) and docosapentaenoic acid (DPAn-3) when ALA was supplemented, while no changes in n-3 PUFA content were observed in cells treated with the D6D inhibitor alone. D6D inhibited cells had reduced triacylglycerol (TAG) accumulation despite an EPA/DPA deficiency. In addition, analyses of cellular protein markers, as well as non-esterified fatty acids and glycerol release in medium, suggested an increase in lipolysis and a decrease in fatty acid re-esterification in D6D-inhibited cells, independent of n-3 PUFA changes. To provide further evidence, we treated cells with the D6D inhibitor in the presence or absence of EPA and compared them with ALA-treated cells. Although EPA further reduced TAG content, the reduced markers of fatty acid re-esterification were not affected by ALA or EPA. Collectively, this study provides new insight showing that D6D inhibition reduces TAG accumulation and fatty acid re-esterification in adipocytes independent of changes in n-3 PUFA cellular content.     

UV-C irradiation-induced peroxidative degradation of microsomal fatty acids and proteins: protection by an extract of Ginkgo biloba (EGb 761).

After exposure of rat liver microsomes to UV-C irradiation, analysis of membrane fatty acids by gas chromatography confirmed that EGb 761, a drug containing a dosed and standardized extract of Ginkgo biloba, provides effective protection against free radical attack in vitro. This analysis, coupled with thiobarbituric acid (TBA) reaction, permitted qualitative and overall quantitative evaluation of radical-induced damage to polyunsaturated fatty acids (PUFA), as well as evidence of the antioxidant properties of the Ginkgo biloba extract. Assay of thiobarbituric acid reactive substances (TBARS) showed a correlation between TBARS concentration and the state of degradation of the polyunsaturated fatty acids. Mannitol (5.5 mM) did not prevent degradation of microsomal PUFA or malondialdehyde (MDA) production, nor did it prevent polymerization of membrane proteins. Low doses of EGb 761 were found to provide efficient protection of membrane PUFA regardless of individual susceptibility to peroxidation. This protection was accompanied by a decrease in the production of TBARS. EGb 761 also protected membrane proteins from the irreversible polymerization induced by these degradation products, but did not appear to prevent thiols oxidation into disulfide bonds.     

Shewanella sp. GA-22, a psychrophilic hydrocarbonoclastic antarctic bacterium producing polyunsaturated fatty acids

AIMS: The effects of different growth media and temperature on production of polyunsaturated fatty acids (PUFA) by Shewanella sp. GA-22 were investigated. The attempts to characterize the GA-22 genes, homologous to those of PUFA biosynthesis gene cluster, was performed. METHODS AND RESULTS: Physiological and phylogenetic characterization of new Antarctic isolate GA-22 was performed. Total fatty acids were isolated from the cells growing under different conditions and analysed by gas chromatography-mass spectrometry (GC-MS). Using degenerated primers derived from the conserved regions within PUFA fatty acid synthase operons, five fragments of homological genes were amplified from GA-22 DNA, and two of them corresponding to pfaA and pfaC synthase subunits were sequenced. CONCLUSIONS: Strain GA-22 was shown to be able to produce three different PUFA: linoleic, arachidonic and eicosapentaenoic acids. The PUFA production was temperature- and carbon source-dependent. The deduced gene products exhibited high similarity to corresponding fatty acid synthases PfaA and PfaC. SIGNIFICANCE AND IMPACT OF STUDY: The PUFA production was detected on media supplemented with crude oil, gasoline and n-tetradecane. The apparent conservation of PUFA genes may point to the potential utilization of designed primers as functional markers in culture-independent ecological studies, and for initial screening in biotechnological fields.     

A review of nutritional effects on fat composition of animal products with special emphasis on n-3 polyunsaturated fatty acids

The fatty acid composition of animal products (eggs, milk and meat) is the reflect of both the tissue fatty acid biosynthesis and the fatty acid composition of ingested lipids. This relationship is stronger in monogastrics (pigs, poultry and rabbits) than in ruminants, where dietary fatty acids are hydrogenated in the rumen. There is an increasing recognition of the health benefits of polyunsaturated fatty acids (PUFA), because these fatty acids are essential for humans. In addition, the ratio n-6/n-3 fatty acids in the human diet is important. This ratio by far exceeds the recommended value of 5. Therefore, inclusion of fish meals, or n-3 PUFA rich oils, or linseed in animal diets is a valid means of meeting consumer demand for animal products that are nutritionally beneficial.The studies that are undertaken on animals mainly use diets supplemented with linseed, as a source of n-3 fatty acids. The use of linseed diets generally leads to an increased n-3 fatty acid content in animal products (egg, meat, milk) in ruminants and monogastrics. Recent studies have also demonstrated that neither the processing nor the cooking affects the PUFA content of pork meat or meat products.The ability of unsaturated fatty acids, especially those with more than two double bonds, to rapidly oxidise, is important in regulating the shelf life of animal products (rancidity and colour deterioration); however, a good way to avoid such problems is to use antioxidant products (such as vitamin E) in the diet.Some studies also show that it is not necessary to feed animals with linseed-supplemented diets for a long time to have the highest increase in PUFA content of the products. So, short-term diet manipulation can be a practical reality for industry.As the market for n-3 PUFA enriched products is today limited in most countries, other studies must be undertaken to develop this kind of production.     

Flaxseed and dried tomato waste used together in laying hens diet

The aim of this study was to investigate the effects of simultaneous supplementation of laying hens with dietary sources of n-3 polyunsaturated fatty acids (PUFA) and carotenoids on egg quality, fatty acids and carotenoid profile of the egg yolk and on feed and yolk lipid peroxidation. A 6-week experiment was carried out with 53-week old laying hens (96 Tetra SL) assigned to a control and three treatment groups supplemented with 5% flaxseeds and different levels of dried tomato waste (DTW, 2.5%, 5.0% and 10.0%). Hens from the groups supplemented with 5% and 7.5% DTW had a significantly lower average daily feed intake and laying percentage as compared to the control. Increased doses of dietary DTW enhanced yolk Roche colour score in direct correlation with the enrichment of egg yolk in carotenoids but decreased their transfer efficiency from feed to egg. After 4 weeks, egg yolk from hens fed with 5% flaxseeds and 7.5% DTW had increased lutein and zeaxanthin levels (by 29% and 24%, respectively) and the colour score was 3.5 fold higher compared to the control group. As a result of the dietary supplementation with flaxseed, the n-3 fatty acid content was 3.1–3.7-fold higher in egg yolk compared with the control and the n-6/n-3 ratio decreased from 18.3 (control) to 4.1–5.4 in supplemented diets. Dietary supplementation with 5% DTW effectively prevented lipid oxidation of eggs enriched with n-3 PUFA, but the increase in DTW content depressed the absorption and deposition of n-3 PUFA in egg yolk.     

A comparison of the effects of troglitazone and vitamin E on the fatty acid composition of serum phospholipids in an experimental model of insulin resistance

The aim of this study was to investigate the effects of troglitazone (TRO)--a new insulin-sensitizing agent--on some metabolic parameters in an experimental model of hypertriglyceridemia and insulin resistance, hereditary hypertriglyceridemic rats, and to compare its effects with those of vitamin E, an antioxidant agent. Three groups of the above rats were fed diets with a high content of sucrose (70% of energy as sucrose) for four weeks. The first group was supplemented with TRO (120 mg/kg diet), the second one with vitamin E (500 mg/kg diet), and the third group served as the control. Vitamin E supplementation did not lower serum triglycerides (2.42 +/- 0.41 vs. 3.39 +/- 0.37 mmol/l, N.S.) while TRO did (1.87 +/- 0.24 vs. 3.39 +/- 0.37 mmol/l, p < 0.01). Neither TRO nor vitamin E influenced the serum levels of free fatty acids (FFA). Both drugs influenced the spectrum of fatty acids in serum phospholipids--TRO increased the levels of polyunsaturated fatty acids (PUFA) n-6 (36.04 +/- 1.61 vs. 19.65 +/- 1.56 mol %, p < 0.001), vitamin E increased the levels of PUFA n-3 (13.3 +/- 0.87 vs. 6.79 +/- 0.87 mol %, p < 0.001) and decreased the levels of saturated fatty acids (32.97 +/- 0.58 vs. 51.45 +/- 4.01 mol %, p < 0.01). In conclusion, TRO lowered the level of serum triglycerides but vitamin E did not have this effect in hypertriglyceridemic rats. Compared with TRO, vitamin E had a different effect on the spectrum of fatty acids in serum phospholipids.     

Modification of membrane phospholipid fatty acyl composition in a leukemic T cell line: effects on receptor mediated intracellular Ca2+ increase.

The effect of modifying fatty acyl composition of cellular membrane phospholipids on receptor-mediated intracellular free Ca2+ concentration ([Ca2+]i) increase was investigated in a leukemic T cell line (JURKAT). After growing for 72 h in medium supplemented with unsaturated fatty acids (UFAs) and alpha-tocopherol, the fatty acyl composition of membrane phospholipids in JURKAT cells was extensively modified. Each respective fatty acid supplemented in the culture medium was readily incorporated into phosphatidylinositol, phosphatidylserine, phosphatidylethanolamine and phosphatidylcholine in the JURKAT cells. The total n-6 fatty acyl content was markedly reduced in phosphatidylinositol and phosphatidylcholine of cells grown in the presence of n-3 fatty acids (alpha-linolenic acid, eicosapentaenoic acid and docosahexaenoic acid). Conversely, in the presence of n-6 fatty acids (linoleic acid and arachidonic acid), the total n-3 fatty acyl content was reduced in all the phospholipids examined. In n-3 and n-6 polyunsaturated fatty acid (PUFA) modified JURKAT cells, the total n-9 monounsaturated fatty acyl content in the phospholipids were markedly reduced. Changing the fatty acyl composition of membrane phospholipids in the JURKAT cells appears to have no affect on the presentation of the T cell receptor/CD3 complex or the binding of anti-CD3 antibodies (OKT3) to the CD3 complex. However, the peak increase in [Ca2+]i and the prolonged sustained phase elicited by OKT3 activation were suppressed in n-3 and n-6 PUFA but not in n-9 monounsaturated fatty acid modified cells. In Ca2+ free medium, OKT3-induced transient increase in [Ca2+]i representing Ca2+ release from the inositol 1,4,5-trisphosphate-sensitive Ca2+ stores, were similar in control and UFA modified cells. Using Mn2+ entry as an index of plasma membrane Ca2+ permeability, the rate of fura-2 fluorescence quenching as a result of Mn2+ influx stimulated by OKT3 in n-9 monounsaturated fatty acid modified cells was similar to control cells, but the rates in n-3 and n-6 PUFA modified cells were significantly lower. These results suggest that receptor-mediated Ca2+ influx in JURKAT cells is sensitive to changes in the fatty acyl composition of membrane phospholipids and monounsaturated fatty acids appears to be important for the maintenance of a functional Ca2+ influx mechanism.     

Effects of Polyunsaturated Fatty Acids in Growth Medium on Lipid Composition and on Physicochemical Surface Properties of Lactobacilli

Most probiotic lactobacilli adhere to intestinal surfaces, a phenomenon influenced by free polyunsaturated fatty acids (PUFA). The present study investigated whether free linoleic acid, γ-linolenic acid, arachidonic acid, α-linolenic acid, or docosahexaenoic acid in the growth medium alters the fatty acid composition of lactobacilli and their physical characteristics. The most abundant bacterial fatty acids identified were oleic, vaccenic, and dihydrosterculic acids. PUFA, especially conjugated linoleic acid (CLA) isomers and γ-linolenic, eicosapentaenoic, docosahexaenoic, and α-linolenic acids, also were identified in lactobacilli. When lactobacilli were cultured in MRS broth supplemented with various free PUFA, the incorporation of a given PUFA into bacterial fatty acids was clearly observed. Moreover, PUFA supplementation also resulted in PUFA-dependent changes in the proportions of other fatty acids; major interconversions were seen in octadecanoic acids (18:1), their methylenated derivatives (19:cyc), and CLA. Intermittent changes in eicosapentaenoic acid proportions also were noted. These results were paralleled by minor changes in the hydrophilic or hydrophobic characteristics of lactobacilli, suggesting that PUFA interfere with microbial adhesion to intestinal surfaces through other mechanisms. In conclusion, we have demonstrated that free PUFA in the growth medium induce changes in bacterial fatty acids in relation to the regulation of the degree of fatty acid unsaturation, cyclization, and proportions of CLA and PUFA containing 20 to 22 carbons. The potential role of lactobacilli as regulators of PUFA absorption may represent another means by which probiotics could redirect the delicate balance of inflammatory mediators derived from PUFA within the inflamed intestine.     

Effects of dietary factors on oxidation of low-density lipoprotein particles

Oxidized low-density lipoproteins (ox-LDLs) appear to play a significant role in atherogenesis. In fact, circulating ox-LDL concentrations have been recognized as a risk factor for cardiovascular disease (CVD). A higher intake of some nutrients and specific food compounds such as monounsaturated fatty acids (MUFAs), polyunsaturated fatty acids (PUFAs) and flavonoids have also been associated with a lower risk of CVD. These dietary factors could be associated to a lower risk of CVD through a reduction of the atherogenicity of LDL particles through limited oxidation. Therefore, the purpose of this article is to review human clinical studies that evaluated effects of dietary antioxidant vitamins, fatty acids (MUFA, PUFA) and specific flavonoid-rich foods on LDL particle oxidation and describe potential mechanisms by which dietary factors may prevent oxidation of LDL particles. Antioxidant vitamin supplements such as alpha-tocopherol and ascorbic acid as well as beta-carotene and fish-oil supplements have not been clearly demonstrated to prevent oxidation of LDL particles. Moreover, inconsistent documented effects of flavonoid-rich food such as olive oil, tea, red wine and soy on LDL particle oxidizability may be explained by difference in variety and quantity of flavonoid compounds used among studies. However, a healthy food pattern such as the Mediterranean diet, which includes a combination of antioxidant compounds and flavonoid-rich foods, appears effective to decrease LDL particle oxidizability, which may give some insight of the cardiovascular benefits associated with the Mediterranean diet.     

Fatty acid and peptide profiles in plasma membrane and membrane rafts of PUFA supplemented RAW264.7 macrophages

The eukaryotic cell membrane possesses numerous complex functions, which are essential for life. At this, the composition and the structure of the lipid bilayer are of particular importance. Polyunsaturated fatty acids may modulate the physical properties of biological membranes via alteration of membrane lipid composition affecting numerous physiological processes, e.g. in the immune system. In this systematic study we present fatty acid and peptide profiles of cell membrane and membrane rafts of murine macrophages that have been supplemented with saturated fatty acids as well as PUFAs from the n-3, the n-6 and the n-9 family. Using fatty acid composition analysis and mass spectrometry-based peptidome profiling we found that PUFAs from both the n-3 and the n-6 family have an impact on lipid and protein composition of plasma membrane and membrane rafts in a similar manner. In addition, we found a relation between the number of bis-allyl-methylene positions of the PUFA added and the unsaturation index of plasma membrane as well as membrane rafts of supplemented cells. With regard to the proposed significance of lipid microdomains for disease development and treatment our study will help to achieve a targeted dietary modulation of immune cell lipid bilayers.     

Long-chain acyl-CoA synthetase 6 preferentially promotes DHA metabolism

Previously we demonstrated that supplementation with the polyunsaturated fatty acids (PUFA) arachidonic acid (AA) or docosahexaenoic acid (DHA) increased neurite outgrowth of PC12 cells during differentiation, and that overexpression of rat acyl-CoA synthetase long-chain family member 6 (Acsl6, formerly ACS2) further increased PUFA-enhanced neurite outgrowth. However, whether Acsl6 overexpression enhanced the amount of PUFA accumulated in the cells or altered the partitioning of any fatty acids into phospholipids (PLs) or triacylglycerides (TAGs) was unknown. Here we show that Acsl6 overexpression specifically promotes DHA internalization, activation to DHA-CoA, and accumulation in differentiating PC12 cells. In contrast, oleic acid (OA) and AA internalization and activation to OA-CoA and AA-CoA were increased only marginally by Acsl6 overexpression. Additionally, the level of total cellular PLs was increased in Acsl6 overexpressing cells when the medium was supplemented with AA and DHA, but not with OA. Acsl6 overexpression increased the incorporation of [(14)C]-labeled OA, AA, or DHA into PLs and TAGs. These results do not support a role for Acsl6 in the specific targeting of fatty acids into PLs or TAGs. Rather, our data support the hypothesis that Acsl6 functions primarily in DHA metabolism, and that its overexpression increases DHA and AA internalization primarily during the first 24 h of neuronal differentiation to stimulate PL synthesis and enhance neurite outgrowth.     

Lipid alterations in human colon epithelial cells induced to differentiation and/or apoptosis by butyrate and polyunsaturated fatty acids

The present study highlights the important association between lipid alterations and differentiation/apoptotic responses in human colon differentiating (FHC) and nondifferentiating (HCT-116) cell lines after their treatment with short-chain fatty acid sodium butyrate (NaBt), polyunsaturated fatty acids (PUFAs), and/or their combination. Our data from GC/MS and LC/MS/MS showed an effective incorporation and metabolization of the supplemented arachidonic acid (AA) or docosahexaenoic acid (DHA), resulting in an enhanced content of the respective PUFA in individual phospholipid (PL) classes and an altered composition of the whole cellular fatty acid spectrum in both FHC and HCT-116 cells. We provide novel evidence that NaBt combined with PUFAs additionally modulated AA and DHA cellular levels and caused their shift from triacylglycerol to PL fractions. NaBt increased, while AA, DHA and their combination with NaBt decreased endogenous fatty acid synthesis in FHC but not in HCT-116 cells. Fatty acid treatment also altered membrane lipid structure, augmented cytoplasmic lipid droplet accumulation, reactive oxygen species (ROS) production and dissipation of the mitochondrial membrane potential. All these parameters were significantly enhanced by combined NaBt/PUFA treatment, but only in FHC cells was this accompanied by highly increased apoptosis and suppressed differentiation. Moreover, the most significant changes of ROS production, differentiation and apoptosis among the parameters studied, the highest effects of combined NaBt/PUFA treatment and a lower sensitivity of HCT-116 cells were confirmed using two-way ANOVA. Our results demonstrate an important role of fatty acid-induced lipid alterations in the different apoptotic/differentiation response of colon cells with various carcinogenic potential.     

Flavonoids and their oxidation products protect efficiently albumin-bound linoleic acid in a model of plasma oxidation

Although LDL esterified polyunsaturated fatty acids (PUFA) contribute largely to the pool of oxidizable lipids in plasma, they coexist with a non-negligible content of free PUFA. In some pathological conditions, the free PUFA/albumin ratio becomes abnormally elevated. Modeling was performed in a system constituted of linoleic acid bound to human serum albumin (HSA) in which oxidation was initiated by hydrophilic AAPH. Inhibition of lipid peroxidation was evaluated for various flavonoids. The accumulations of hydroperoxyoctadecadienoic acids (HPODE), hydroxyoctadecadienoic acids (HODE) and ketooctadecadienoic acids (KODE) were similarly inhibited: isoquercitrin>quercetin>catechin=isorhamnetin>kaempferol>quercetin-4'-beta-D-glucoside=quercetin-3,4'-di-beta-D-glucoside. Surprisingly, quercetin and isorhamnetin afforded a protection to linoleic acid long after their consumption. Elucidation by mass spectrometry and NMR of the quercetin oxidation products and assessment of their antioxidant capacity pointed out that 3,4-dihydroxybenzoic acid and 2-(3,4-dihydroxybenzoyl)-2,4,6-trihydroxybenzofuran-3(2H)-one are major contributors to the apparent quercetin antioxidant capacity.     

Kinetic expression for the oxidation of linoleic and arachidonic acid esters in their mixed system

Two polyunsaturated fatty acids (PUFAs) or their esters were mixed, and their oxidation processes were measured at 65 degrees C and ca. 0% relative humidity. Except when a PUFA ester was mixed with a free PUFA, the oxidation of the less-oxidative PUFA was promoted as its content in the mixture decreased, while the oxidation of the more-oxidative PUFA was delayed with a decrease in its content. A kinetic model is proposed whereby a PUFA acts as the diluent for another PUFA, and the oxidation rate of the PUFA is proportional to the product of the unoxidized PUFA concentration and the sum of the concentrations of the oxidized PUFA and the other oxidized PUFA. This model well expressed the oxidation processes of the PUFAs in their mixed system.