Conjugated linoleic acid is synthesized endogenously in lactating dairy cows by Delta(9)-desaturase.
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Conjugated linoleic acid (CLA) is a naturally occurring anticarcinogen found in milk fat and body fat of ruminants. Although CLA is an intermediate in ruminal biohydrogenation of linoleic acid, we hypothesized that its primary source was from endogenous synthesis. This would involve Delta(9)-desaturase and synthesis from trans-11 18:1, another intermediate in ruminal biohydrogenation. Our first experiment supplied lactating cows (n = 3) with trans-11 18:1 by abomasal infusion and examined the potential for endogenous synthesis by measuring changes in milk fat CLA. By d 3, infusion of trans-11 18:1 resulted in a 31% increase in concentration of cis-9, trans-11 CLA in milk fat, demonstrating that an active pathway for endogenous synthesis of CLA exists. Our second experiment examined the quantitative importance of endogenous synthesis of CLA in lactating cows (n = 3) by abomasally infusing a putative stimulator (retinol palmitate) or an inhibitor (sterculic oil) of Delta(9)-desaturase. Infusion of retinol palmitate had no influence on milk fatty acid desaturation, and yield of CLA in milk fat was not altered. However, sterculic oil infusion decreased the concentration of CLA in milk fat by 45%. Consistent with Delta(9)-desaturase inhibition, the sterculic oil treatment also altered the milk fat concentration of other Delta(9)-desaturase products as indicated by the two- to threefold increase in the ratios of 14:0 to 14:1(,) 16:0 to 16:1 and 18:0 to cis-18:1. Using changes in the ratio of 14:0 to 14:1 as an indication of the extent of Delta(9)-desaturase inhibition with the sterculic oil treatment, an estimated 64% of the CLA in milk fat was of endogenous origin. Overall, results demonstrate that endogenous synthesis of CLA from trans-11 18:1 represented the primary source of CLA in milk fat of lactating cows. (+info)
Supplementation of postmenopausal women with fish oil rich in eicosapentaenoic acid and docosahexaenoic acid is not associated with greater in vivo lipid peroxidation compared with oils rich in oleate and linoleate as assessed by plasma malondialdehyde and F(2)-isoprostanes.
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BACKGROUND: Although the replacement of dietary saturated fat with unsaturated fat has been advocated to reduce the risk of cardiovascular disease, diets high in polyunsaturated fatty acids (PUFAs) could increase lipid peroxidation, potentially contributing to the pathology of atherosclerosis. OBJECTIVE: The objective of this study was to examine indexes of in vivo lipid peroxidation, including free F(2)-isoprostanes, malondialdehyde (MDA), and thiobarbituric acid reacting substances (TBARS), in the plasma of postmenopausal women taking dietary oil supplements rich in oleate, linoleate, and both eicosapentaenoic acid and docosahexaenoic acid. DESIGN: Fifteen postmenopausal women took 15 g sunflower oil/d, providing 12.3 g oleate/d; safflower oil, providing 10.5 g linoleate/d; and fish oil, providing 2.0 g EPA/d and 1.4 g DHA/d in a 3-treatment crossover trial. RESULTS: Plasma free F(2)-isoprostane concentrations were lower after fish-oil supplementation than after sunflower-oil supplementation (P: = 0.003). When plasma free F(2)-isoprostane concentrations were normalized to plasma arachidonic acid concentrations, significant differences among the supplements were eliminated. Plasma MDA concentrations were lower after fish-oil supplementation than after sunflower-oil supplementation (P: = 0.04), whereas plasma TBARS were higher after fish-oil supplementation than after sunflower oil (P: = 0.003) and safflower oil (P: = 0.001) supplementation. When plasma MDA concentrations were normalized to plasma PUFA concentrations, significant differences were eliminated, but TBARS remained higher after fish-oil supplementation than after sunflower oil (P: = 0.01) and safflower-oil (P: = 0.0003) supplementation. CONCLUSIONS: With fish-oil supplementation, there was no evidence of increased lipid peroxidation when assessed by plasma F(2)-isoprostanes and MDA, although plasma TBARS was higher than with sunflower-oil and safflower-oil supplementation. (+info)
Cytoprotective antioxidant function of tyrosine and tryptophan residues in transmembrane proteins.
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The transmembrane domains of integral membrane proteins show an astounding accumulation of tyrosine and tryptophan residues, especially in the region of the highest lipid density. We found that these residues perform vital antioxidant functions inside lipid bilayers and protect cells from oxidative destruction. First, tyrosine- and tryptophan-containing peptides representing stretches from the transmembrane domains of different integral membrane proteins, including presenilin and the cystic fibrosis transmembrane conductance regulator, prevent oxidative lysis in clonal and primary cells. Second, long-chain acylated tyrosine and tryptophan, but not phenylalanine or short-chain acylated derivatives, are potent inhibitors of lipid peroxidation and oxidative cell death. The antioxidant functions of tyrosine and tryptophan may provide a specific explanation for (a) their unique transmembrane distribution pattern and (b) the high vulnerability of low-protein neuronal membranes to oxidative stress, as seen in neurodegenerative disorders. (+info)
Abnormal arachidonic acid content of red blood cell membranes and main lithogenic factors in stone formers.
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BACKGROUND: Increased arachidonic acid content in red blood cell membranes of stone formers (SF) has recently been reported and is hypothesized as representing the underlying causal factor for both hyperoxaluria and hypercalciuria. We performed the present study to see whether we could confirm this finding and to test whether any relationship exists between the fatty acid composition of red blood cell membranes and the main metabolic factors involved in stone formation. METHODS: In 21 SF and 40 healthy controls subjects the fatty acid composition of red blood cell membranes was assessed. In addition, the following parameters were evaluated in SF: daily and fasting urinary calcium excretion, fractional intestinal calcium absorption, 1,25-dihydroxy-vitamin D, intact parathyroid hormone, hydroxyproline in fasting urine, daily urinary excretion of oxalate, citrate, urate, electrolytes, urea, sulphate, relative supersaturation for calcium oxalate monohydrate. RESULTS: The red blood cell membrane of SF had a lower content of arachidonic acid, linoleic acid, and docosahexaenoic acid than that of control subjects. Arachidonic acid content was not correlated with any of the parameters studied. However, when patients were grouped according to the degree of oxalate excretion, hyperoxaluric SF had a higher arachidonic acid content and arachidonic/linoleic acid ratio than SF with normal oxalate excretion. CONCLUSIONS: Our results do not confirm the finding of an increased arachidonic acid content of red blood cell membrane in SF. On the contrary, reduced arachidonic acid levels were found in our patients. However, hyperoxaluric SF had a relatively higher arachidonic acid content than SF with normal urinary oxalate excretion. (+info)
This study for the first time confirmed the peroxidative role of the Amadori product derived from the glycation of phosphatidylethanolamine (PE), namely Amadori-PE. The product was synthesized from the reaction of dioleoyl PE with D-glucose, and then purified by a solid-phase extraction procedure, which was a key step in the next HPLC technique for the isolation of essentially pure Amadori-PE. When the synthetically prepared Amadori-PE was incubated with linoleic acid in the presence of Fe(3+) in micellar system, a remarkable formation of thiobarbituric acid reactive substances was observed together with increases in lipid hydroperoxides. In addition, the lipid peroxidation caused by Amadori-PE was effectively inhibited by superoxide dismutase, mannitol, catalase and metal chelator. These results indicated that Amadori-PE triggers oxidative modification of lipids via the generation of superoxide, and implied the involvement of 'lipid glycation' along with membrane lipid peroxidation in the pathogenesis of diabetes and aging. (+info)
Effects of modified tall oil versus a commercial source of conjugated linoleic acid and increasing levels of modified tall oil on growth performance and carcass characteristics of growing-finishing pigs.
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Two experiments were conducted to evaluate the effects of conjugated linoleic acid (CLA)-enriched feed additives for swine. These additives included a source of CLA that was commercially available (CLA-60) and modified tall oil (MTO). Experiment 1 used 36 barrows (initially 37.6+/-2.8 kg) to compare the effects of CLA-60 and MTO on growth performance and carcass characteristics of finishing pigs. The corn-soybean meal diets contained .50% soybean oil (control), .50% CLA-60, or .50% MTO. Pigs fed CLA-60 had less (P = .03) ADG from 37.6 to 72.6 kg than the control pigs; otherwise, pigs fed either CLA-60 or MTO had growth performance similar (P > .15) to that of the control pigs. Pigs fed MTO grew faster (P = .03) and consumed more feed (P = .10) over the duration of the experiment (37.6 to 106.4 kg) than pigs fed CLA-60. Dietary treatment did not affect (P > .15) plasma triglycerides or carcass characteristics, but pigs fed either MTO or CLA-60 had greater saturation of fatty acids in the adipose tissue at the 10th rib than pigs fed the control diet. Experiment 2 used 80 barrows (initially 33.4+/-2.2 kg) to examine the effects of increasing levels of MTO on growth performance and carcass characteristics of finishing pigs. The corn-soybean meal diet contained 1% cornstarch, which was replaced with MTO to give dietary levels of .25, .50, or 1.00% MTO. Dietary treatment did not affect (P > .15) growth performance. Feeding increasing levels of MTO quadratically decreased (P = .02) average backfat thickness and longissimus muscle drip loss (P = .04) and quadratically increased longissimus muscle area (P = .07) and percentage lean (P = .03). Feeding MTO tended to increase belly firmness (P < .10) compared with pigs fed the control diet. These traits appeared to be optimized with .50% MTO. In summary, pigs fed MTO had greater ADG, ADFI, and ending BW than pigs fed CLA-60. Feeding MTO does not appear to affect growth performance but improves carcass lean content and may additionally improve some aspects of meat quality in growing-finishing pigs. (+info)
The CCR2-mediated recruitment of monocytes into the vessel wall plays an important role in all stages of atherosclerosis. In recent studies, we have shown that lipoproteins can modulate CCR2 expression and have identified native LDL as a positive regulator. In contrast, oxidized LDL (OxLDL), which is mainly formed in the aortic intima, reduces CCR2 expression, promotes monocyte retention, and may cause pathological accumulation of monocytes in the vessel wall. We now provide evidence that OxLDL reduces monocyte CCR2 expression by activating intracellular signaling pathways that may involve peroxisome proliferator-activated receptor gamma (PPARgamma). Receptor-mediated uptake of the lipoprotein particle was required and allows for delivery of the exogenous ligand to the nuclear receptor. The suppression of CCR2 expression by OxLDL was mediated by lipid components of OxLDL, such as the oxidized linoleic acid metabolites 9-HODE and 13-HODE, known activators of PPARgamma. Modified apoB had no such effect. Consistent with a participation of the PPARgamma signaling pathway, BRL49653 reduced CCR2 expression in freshly isolated human monocytes ex vivo and in circulating mouse monocytes in vivo. These results implicate PPARgamma in the inhibition of CCR2 gene expression by oxidized lipids, which may help retain monocytes at sites of inflammation, such as the atherosclerotic lesion. (+info)
Characterization of RCI-1, a chloroplastic rice lipoxygenase whose synthesis is induced by chemical plant resistance activators.
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A full-length lipoxygenase cDNA (RCI-1) has been cloned from rice (Oryza sativa) whose corresponding transcripts accumulate in response to treatment of the plants with chemical inducers of acquired resistance such as benzo(1,2,3)thiadiazole-7-carbothioic acid S-methyl ester (BTH), 2,6-dichloroisonicotinic acid (INA), and probenazole. In contrast, RCI-1 transcript levels did not increase after inoculation with compatible and incompatible races of the rice blast fungus Magnaporthe grisea and the nonhost pathogen Pseudomonas syringae pv. syringae. RCI-1 transcript levels also increased after exogenous application of jasmonic acid, but not upon wounding. Dose-response and time course experiments revealed a similar pattern of transcript accumulation and lipoxygenase activity in BTH-treated rice leaves. Enzymatic analysis of recombinant RCI-1 protein produced in Escherichia coli revealed that 13-hydroperoxy-octadecanoic acids were the predominant reaction products when either linoleic or linolenic acid used as a substrate. The RCI-1 sequence features a putative chloroplast targeting sequence at its N-terminus. Indeed, a protein consisting of the putative chloroplast transit peptide fused to green fluorescent protein was exclusively localized in chloroplasts, indicating that RCI-1 is a chloroplastic enzyme. (+info)