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1.
Gangliosides and atherosclerosis 总被引:2,自引:0,他引:2
The ganglioside levels in atherosclerotic lesions of human aorta are considerably higher than those in unaffected areas of
aorta, and atherosclerotic patients frequently have increased concentrations of serum gangliosides. The present review summarizes
recent findings that suggest the possible involvement of aortic gangliosides in platelet activation and adhesion of platelets
to the vessel wall. The effect of gangliosides on the structure of low density lipoproteins (LDL), on the interaction of LDL
with macrophages and hepatic cells and on the LDL-regulated biosynthesis of cholesterol is also discussed.In vitro experiments have demonstrated that a major ganglioside of the intima of atherosclerotic aorta induces rapid adhesion, aggregation
and spreading of platelets. Moreover, gangliosides present in elevated amounts in the intercellular space of atherosclerotic
aortic tissue modify the surface structure and stimulate aggregation of LDL. Ganglioside-modified LDL are readily recognized
and taken up by macrophages, while preincubation of LDL with low concentrations of gangliosides inhibits LDL binding to hepatic
cells. Thus, ganglioside enrichment of LDL is likely to interfere with LDL clearancevia the hepatic cells. Thus, ganglioside enrichment of LDL is likely to interfere with LDL clearancevia the hepatic LDL receptor, and to stimulate binding of LDL to the scavenger receptor of macrophages. It is postulated that
high ganglioside levels in the aorta and serum may be an additional risk factor in atherosclerosis.
The abbreviations used for gangliosides are standard abbreviations as recommended by Svennerholm [Svennerholm, L. (1964)J. Lipid Res. 5, 145–155]. 相似文献
2.
This research was in order to follow the periodic fluctuation of lipid peroxidation by a new method in rats exposed to nitrogen
dioxide. Wistar male rats were examined for lipid peroxidation as demonstrated by ethane exhalation. In rats continuously
exposed to 10 ppm nitrogen dioxide for 2 weeks, the amount of ethane exhaled fluctuated in a complex manner during the exposure.
Ethane exhalation decreased slightly after the first day of exposure and then increased rapidly. The maximal values were observed
after the fourth day of exposure and then decreased gradually to the initial level. Furthermore, the activity of glutathione
peroxidase in lungs of rats exposed to 10 ppm nitrogen dioxide varied symmetrically against the change of ethane formation.
Similar changes in ethane exhalation were observed in rats exposed to the lower levels of nitrogen dioxide (0.4, 1.2 and 4.0
ppm) for 4 months. Compared to 10 ppm nitrogen dioxide exposure for 14 days, the characteristics in rats exposed to the low
levels (0.4–4.0 ppm) of nitrogen dioxide were: the decline of ethane formation, the delay in alterations, and the tendency
toward gradual increased during the longer period exposure. 相似文献
3.
Low density lipoprotein of synovial fluid in inflammatory joint disease is mildly oxidized 总被引:4,自引:0,他引:4
M. J. James D. van Reyk K. A. Rye R. T. Dean L. G. Cleland P. J. Barter W. Jessup 《Lipids》1998,33(11):1115-1121
Oxidatively modified low density lipoprotein (LDL) has many biological activities which could contribute to the pathology
of the atherosclerotic lesion. Because atherosclerosis has an inflammatory component, there has been much interest in the
extent to which LDL could be oxidatively modified in vivo by inflammation. The present study examined LDL present in an accessible inflammatory site, the inflamed synovial joint,
for evidence of compositional change and oxidative modification. LDL was isolated from knee joint synovial fluid (SF) from
subjects with inflammatory arthropathies and also from matched plasma samples. SF and plasma LDL had similar free cholesterol
and α-tocopherol content, but SF LDL had a lower content of esterified cholesterol. On electrophoresis, SF LDL was slightly
more electronegative than LDL from matched plasma samples, but the changes were much less than those resulting from Cu2+-treatment of LDL. Oxidized cholesterol was not detected in any samples, but cholesterol ester hydroperoxide levels were greater
in SF than in plasma LDL. When samples from three subjects were incubated with macrophages, the SF LDL did not cause significant
loading of the cells with cholesterol or cholesterol esters, in contrast to the situation with acetylated LDL. Overall, the
SF LDL displayed evidence of slightly increased oxidation by comparison with matched plasma samples. Despite their isolation
from an environment with active inflammation, changes were modest compared with those resulting from Cu2+ treatment. Thus, extensive LDL oxidation is not a necessary correlate of location in a chronic inflammatory site, even though
it is characteristic of atherosclerotic lesions. 相似文献
4.
Fitó M Covas MI Lamuela-Raventós RM Vila J Torrents L de la Torre C Marrugat J 《Lipids》2000,35(6):633-638
The protective effect of phenolic compounds from an olive oil extract, and of olive oils with (extra-virgin) and without (refined)
phenolic components, on low density lipoprotein (LDL) oxidation was investigated. When added to isolated LDL, phenolics [0.025–0.3
mg/L caffeic acid equivalents (CAE)] increased the lag time of conjugated diene formation after copper-mediated LDL oxidation
in a concentration-dependent manner. Concentrations of phenolics greater than 20 mg/L inhibited formation of thiobarbituric-acid
reactive substances after AAPH-initiated LDL oxidation. LDL isolated from plasma after preincubation with phenolics (25–160
mg/L CAE) showed a concentration-dependent increase in the lag time of conjugated diene formation after copper-mediated LDL
oxidation. Refined olive oil (0 mg/L CAE) and extra-virgin olive oil (0.1 and 0.3 mg/L CAE) added to isolated LDL caused an
increase in the lag time of conjugated diene formation after copper-mediated LDL oxidation that was related to olive oil phenolic
content. Multiple regression analysis showed that phenolics were significantly associated with the increase in lag time after
adjustment for effects of other antioxidants; α-tocopherol also achieved a statistically significant effect. These results
indicate that olive oil phenolic compounds protect LDL against peroxyl radical-dependent and metal-induced oxidation in vitro and could associate with LDL after their incubation with plasma. Both types of olive oil protect LDL from oxidation. Olive
oil containing phenolics, however, shows more antioxidant effect on LDL oxidation than refined olive oil. 相似文献
5.
The effect of γ-interferon to inhibit macrophage-high density lipoprotein interactions is reversed by Δ12,14-prostaglandin J2J2 总被引:1,自引:0,他引:1
Macrophage activation has been recognized as playing a central role in chronic inflammatory diseases in general and more specifically,
in the vascular wall during the progression of atherosclerotic lesions. Macrophage-activating factors present within the atherosclerotic
lesion include the colony-stimulating factors and gamma interferon (IFNγ). In the present study, the effects of IFNγ on macrophage binding and uptake of fluorochrome-labeled high density lipoprotein (HDL) were investigated by flow cytometry
and by measuring the amount of the type B scavenger receptors CD36 and scavenger receptor type B (SR-BI) by Northern blot
analysis. IFNγ-, but not granulocyte macrophage colony-stimulating factor (GM-CSF)-treated murine peritoneal macrophages displayed a two-
to threefold decrease in Dil-labeled HDI uptake. This effect was observed in the absence of a comparable decrease in SR-BI
meassage and protein or CD36 message. This decrease in both HDL binding and uptake was reversed by the peroxisome proliferator-activated
receptor gamma (PPARγ) agonist, Δ12,14-prostaglandin J2 (15d-PGJ2), which also inhibited the IFNγ inductin of the β2 integrin CD1 1a. Furthermore, 15d-PGJ2 increased the expression of SR-BI and CD36 message and SR-BI protein which was reflected in an increase in HDL binding and
uptake. These results suggest a role for PPARγ agonists in modulating the IFNγ-mediated macrophage effector functions relevant to atherosclerotic disease progression. 相似文献
6.
This study was conducted to develop a quantitative FTIR spectroscopy method to measure LDL lipid oxidation products and determine
the effect of oxidation on LDL lipid and protein. In vitro LDL oxidation at 37°C for 1 h produced a range of conjugated diene (CD) (0.14–0.26 mM/mg protein) and carbonyl contents (0.9–3.8
μg/g protein) that were used to produce calibration sets. Spectra were collected from the calibration set and partial least
squares regression was used to develop calibration models from spectral regions 4000-650, 3750-3000, 1720-1500, and 1180-935
cm−1 to predict CD and carbonyl contents. The optimal models were selected based on their standard error of prediction (SEP),
and the selected models were performance-tested with an additional set of LDL spectra. The best models for CD prediction were
derived from spectral regions 4000-650 and 1180-935 cm−1 with the lowest SEP of 0.013 and 0.013 mM/mg protein, respectively. The peaks at 1745 (cholesterol and TAG ester C=O stretch),
1710 (carbonyl C-O stretch), and 1621 cm−1 (peptide C=O stretch) positively correlated with LDL oxidation. FTIR and chemometrics revealed protein conformation changes
during LDL oxidation and provided a simple technique that has potential for rapidly observing structural changes in human
LDL during oxidation and for measuring primary and secondary oxidation products. 相似文献
7.
We investigated the changes in human LDL primary and secondary lipid oxidation products and modification of the apolipoprotein
B-100 (apoB-100) secondary structures during Cu2+-mediated oxidation by FTIR spectroscopy in the presence of catechin, quercetin, and α-tocopherol at physiological concentrations.
Catechin- and quercetin-containing samples had slower rates and longer lag phases for conjugated diene hydroperoxide (CD)
formation than α-tocopherol-containing samples; however, all antioxidant-treated LDL samples generated similar CD levels (P<0.05). A lower maximum (98.4 nmol/mg LDL protein) of carbonyl compounds was produced in the quercetin- and catechin-treated
samples than in α-tocopherol samples. Modification of the apoB-100 secondary structures corresponded closely to the formation
of carbonyls and was hampered by the presence of antioxidants. Physiological concentrations of catechin and quercetin offered
similar levels of protection against modification by carbonyls of the apoB-100 at advanced stages (carbonyls ∼96.0 nmol/mg
LDL protein) but not at the intermediate stages (carbonyls ∼58.0 nmol/mg LDL protein) of LDL oxidation probably owing to differences
in the protein-binding mechanisms of catechin and quercetin. Relationships between peroxide formation, carbonyl products,
and LDL protein denaturation were shown by the FTIR approach. The FTIR technique provided a simple new tool for a comprehensive
evaluation of antioxidant performance in protecting LDL during in vitro oxidation. 相似文献
8.
We identified and quantified the hydroperoxides, hydroxides, epoxides, isoprostanes, and core aldehydes of the major phospholipids
as the main components of the oxophospholipids (a total of 5–25 pmol/μmol phosphatidylcholine) in a comparative study of human
atheroma from selected stages of lesion development. The developmental stages examined included fatty streak, fibrous plaque,
necrotic core, and calcified tissue. The lipid analyses were performed by normal-phase HPLC with on-line electrospray MS using
conventional total lipid extracts. There was great variability in the proportions of the various oxidation products and a
lack of a general trend. Specifically, the early oxidation products (hydroperoxides and epoxides) of the glycerophosphocholines
were found at the advanced stages of the plaques in nearly the same relative abundance as the more advanced oxidation products
(core aldehydes and acids). The anticipated linear accumulation of the more stable oxidation products with progressive development
of the atherosclerotic plaque was not apparent. It is therefore suggested that lipid infiltration and/or local peroxidation
is a continuous process characterized by the formation and destruction of both early and advanced products of lipid oxidation
at all times. The process of lipid deposition appears to have been subject to both enzymatic and chemical modification of
the normal tissue lipids. Clearly, the appearance of new and disproportionate old lipid species excludes randomness in any
accumulation of oxidized LDL lipids in atheroma. 相似文献
9.
Atherosclerosis research typically focuses on the evolution of intermediate or advanced atherosclerotic lesions rather than on prelesional stages of atherogenesis. Yet these early events may provide decisive leads on the triggers of the pathologic process, before lesions become clinically overt. Thereby, it is mandatory to consider extracellular lipoprotein deposition at this stage as the prerequisite of foam cell formation leading to a remarkable accumulation of LDL (Low Density Lipoproteins). As progression of atherosclerosis displays the characteristic features of a chronic inflammatory process on the one hand and native LDL lacks inflammatory properties on the other hand, the lipoprotein must undergo biochemical modification to become atherogenic. During the last 25 years, evidence was accumulated in support of a different concept on atherogenesis proposing that modification of native LDL occurs through the action of ubiquitous hydrolytic enzymes (enzymatically modified LDL or eLDL) rather than oxidation and contending that the physiological events leading to macrophage uptake and reverse transport of eLDL first occur without inflammation (initiation with reversion). Preventing or reversing initial atherosclerotic lesions would avoid the later stages and therefore prevent clinical manifestations. This concept is in accordance with the response to retention hypothesis directly supporting the strategy of lowering plasma levels of atherogenic lipoproteins as the most successful therapy for atherosclerosis and its sequelae. Apart from but unquestionable closely related to this concept, there are several other hypotheses on atherosclerotic lesion initiation favoring an initiating role of the immune system (‘vascular-associated lymphoid tissue’ (VALT)), defining foam cell formation as a variant of lysosomal storage disease, relating to the concept of the inflammasome with crystalline cholesterol and/or mitochondrial DAMPs (damage-associated molecular patterns) being mandatory in driving arterial inflammation and, last but not least, pointing to miRNAs (micro RNAs) as pivotal players. However, direct anti-inflammatory therapies may prove successful as adjuvant components but will likely never be used in the absence of strategies to lower plasma levels of atherogenic lipoproteins, the key point of the perception that atherosclerosis is not simply an inevitable result of senescence. In particular, given the importance of chemical modifications for lipoprotein atherogenicity, regulation of the enzymes involved might be a tempting target for pharmacological research. 相似文献
10.
Dietary polyunsaturated fat decreases interaction between low density lipoproteins and arterial proteoglycans 总被引:2,自引:0,他引:2
James M. Manning Abraham K. Gebre Iris J. Edwards Williams D. Wagner Lawrence L. Rudel John S. Parks 《Lipids》1994,29(9):635-641
Polyunsaturated dietary fat (n−3 and n−6) results in less atherosclerosis in monkeys compared to lard (Parks, J.S., Kaduck-Sawyer,
J., Bullock, B.C., and Rudel, L.L.,Arteriosclerosis 10, 1102–1112; Rudel, L.L., Parks, J.S., Johnson, F.L., and Babiak, J.,J. Lipid Res. 27, 465–474, 1986). We hypothesized that this was due, in part, to a decreased reactivity of low density lipoproteins (LDL)
with arterial proteoglycans (PG). To test this hypothesis, cynomolgus monkeys were fed diets containing lard, safflower oil
(n−6 polyunsaturated; Poly), menhanden fish oil (FO), or oleic acid-rich safflower oil (oleinate; Mono) for 14 mon, and plasma
LDL were isolated and characterized. Several properties of LDL thought to be important in the interaction of LDL with arterial
PG were measured including LDL particle size, chemical composition, sialic acid content, density distribution, apolipoprotein
E (apoE) content and cholesteryl ester transition temperature. Plasma LDL cholesterol concentrations (mg/dL) after 14 mon
of diet consumption averaged (mean±SEM): FO (366±45), Lard (352±27), Poly (279±24), and Mono (230±43). The composition of
LDL was similar among diet groups except that FO LDL were relatively depleted of cholesteryl ester and enriched in protein
and were smaller in size. LDL sialic acid content was similar among diet groups (4.5–5.0 μg/mg LDL protein). The LDL apoE/B
molar ratio, a measure of the apoE content per LDL particle averaged: Mono (3.0±1.0), Poly (2.0±0.1), Lard (1.8±0.5), and
FO (1.0±0.2). The FO group had a lower proportion (13%) of the apoE enriched d=1.015–1.025 g/mL subfraction of LDL than did
the other diet groups (31–45%). The transition temperature of the LDL cholesteryl esters was below body temperature for the
FO and Poly groups (36°C) and above for the Lard and Mono groups (40–44°C). The percentage of LDL cholesterol that formed
insoluble complexes with arterial chondroitin sulfate PG averaged: Mono (29±4%), Lard (18±3%), Poly (14±3%), and FO (7±2%).
Among all diet groups, there was a significant positive correlation (r=0.54) between LDL-PG complex formation and LDL apoE/B
molar ratio. We conclude that dietary FO and Poly result in LDL that are less reactive with arterial PG compared to Lard or
Mono fats. While FO appears to decrease PG binding by decreasing the apoE content and amount of the largest LDL subfraction,
Poly fat appears to affect LDL-PG interactions by other mechanisms. Decreased LDL-PG interactions may lead to decreased atherosclerosis
in animals fed polyunsaturated dietary fat. 相似文献
11.
The apolipoprotein F (apoF) knockout mouse has provided an approach to the investigation of the effect of both cellular and
humoral processes on atherosclerotic lesion progression. In the present study, pharmacologic modulation of both interferon
gamma (IFNγ)-inducible macrophage effector functions, and atherosclerotic lesions in the apoE knockout mouse were investigated
using the peroxisome proliferator-activated receptor (PPAR) α,γ coagonist LY465608. LY465608 inhibited, in a concentration-dependent
manner, IFNγ induction of both nitric oxide synthesis and the β2 integrin CD11a in elicited peritoneal macrophages from apoE
knockout mice. Similar effects were observed ex vivo following 10 d of treating mice with 10 mg/kg of LY465608. Treatment of apoE knockout mice for 18 wk with LY465608 resulted
in a statistically significant 2.5-fold reduction in atherosclerotic lesion area in en face aorta preparations. These effects
were apparent in the absence of any reduction in total serum cholesterol or in lipoprotein distribution. Finally, treatment
of apoE knockout mice with established atherosclerotic disease resulted in a modest but not statistically significant decrease
in aortic lesional surface area. These results demonstrate the utility of PPAR coagonists in reducing the progression of the
atherosclerotic lesion. 相似文献
12.
Kyu-Suk Hwang Sang-Wook Park Dae-Won Park Kwang-Joong Oh Seong-Soo Kim 《Korean Journal of Chemical Engineering》2009,26(5):1383-1388
Rubidium carbonate was used as an adsorbent to capture carbon dioxide from gaseous stream of carbon dioxide, nitrogen, and
moisture in a fixed-bed to obtain the breakthrough data of CO2. Experiments were carried out at flow rates of carbon dioxide and nitrogen (5×10−6–35×10−6 m3/min), moisture (0.5×10−6–3.0×10−6 m3/h), amount of adsorbent (0.5×10−3–1.8×10−3 kg), mole fraction of carbon dioxide (0.03–0.22), and different sorption temperatures (323–353 K) at atmospheric pressure.
The deactivation model in the non-catalytic heterogeneous reaction systems was used to analyze the sorption kinetics among
carbon dioxide, carbonate, and moisture, employing the experimental breakthrough data that fit the deactivation model better
than the adsorption isotherm models in the literature. 相似文献
13.
Effect of n−3 fatty acid-rich fish oil supplementation on the oxidation of low density lipoproteins 总被引:4,自引:0,他引:4
This study was aimed at determining the effect of fish oil supplementation on copper-catalyzed oxidation of low density lipoproteins
(LDL) from nine hypertriglyceridemic human subjects. A rapid headspace gas chromatographic method was used to measure the
volatile oxidation products from LDL. Propanal and hexanal were the major volatile products formed in the oxidation of n−3
and n−6 polyunsaturated fatty acids (PUFA), respectively. Fish oil supplementation resulted in a significant increase in propanal
formation from 3.7 to 13.4 nmol/mL LDL (P<0.01); it also resulted in small decreases in pentanal formation from 14.7 to 11.4 nmol/mL LDL and in hexanal formation from
138 to 108 nmol/mL LDL (P<0.05). The changes in peroxidation products paralleled the changes in LDL composition, which showed a significant increase
in n−3 PUFA from 3.2 to 14.6% (P<0.01) and a decrease in n−6 PUFA from 43.7 to 35.0% (P<0.05). Propanal formation was highly and significantly correlated with n−3 PUFA content (r=0.950,P<0.001). Since total volatiles remained unchanged, this indicated that the two groups of LDL samples did not differ in overall
oxidative susceptibility. Although fish oil intake did not alter the oxidative susceptibility of LDL, the chemically modified
LDL particles generated a distinct pattern of volatile oxidation products that reflected changes in their fatty acid composition. 相似文献
14.
Hironori Yashima Michishige Terasaki Ami Sotokawauchi Takanori Matsui Yusaku Mori Tomomi Saito Naoya Osaka Hideki Kushima Munenori Hiromura Makoto Ohara Tomoyasu Fukui Sho-ichi Yamagishi 《International journal of molecular sciences》2020,21(23)
Advanced glycation end products (AGEs) are localized in macrophage-derived foam cells within atherosclerotic lesions, which could be associated with the increased risk of atherosclerotic cardiovascular disease under diabetic conditions. Although foam cell formation of macrophages has been shown to be enhanced by AGEs, the underlying molecular mechanism remains unclear. Since cyclin-dependent kinase 5 (Cdk5) is reported to modulate inflammatory responses in macrophages, we investigated whether Cdk5 could be involved in AGE-induced CD36 gene expression and foam cell formation of macrophages. AGEs significantly increased Dil-oxidized low-density lipoprotein (ox-LDL) uptake, and Cdk5 and CD36 gene expression in U937 human macrophages, all of which were inhibited by DNA aptamer raised against RAGE (RAGE-aptamer). Cdk5 and CD36 gene expression levels were correlated with each other. An antioxidant, N-acetyl-l-cysteine, mimicked the effects of RAGE-aptamer on AGE-exposed U937 cells. A selective inhibitor of Cdk5, (R)-DRF053, attenuated the AGE-induced Dil-ox-LDL uptake and CD36 gene expression, whereas anti-CD36 antibody inhibited the Dil-ox-LDL uptake but not Cdk5 gene expression. The present study suggests that AGEs may stimulate ox-LDL uptake into macrophages through the Cdk5–CD36 pathway via RAGE-mediated oxidative stress. 相似文献
15.
Primary cultures of rat skin fibroblasts were used as a model system to investigate the cellular uptake and oxidation of malonaldehyde
(MA). The cells were grown in a medium containing 10−5 M, 10−4 M or 10−3 M concentrations of [1,3-14C]MA. There was a limited, concentration-dependent uptake of MA by 24 hr (∼4% at all concentrations). The uptake of [1,2-14C]acetate by 24 hr was ∼24%; 83–89% of the14C in the MA taken up was oxidized to14CO2 by 24 hr and ∼5% was recovered in the major lipids. Despite its low uptake and rapid oxidation to CO2, pretreatment of the cells with 10−3 M MA for 24 hr produced a latent inhibition of [14C]glucose oxidation. Limited cellular uptake of MA may explain the tolerance of cells grown in culture to relatively high
MA concentrations. 相似文献
16.
R. Ponnampalam J. Delisle Y. Gagne J. Amiot 《Journal of the American Oil Chemists' Society》1990,67(8):531-536
Rapeseed flour was acylated to various degrees with acetic and succinic anhydrides to produce acetylated rapeseed protein
concentrates (SRPC) and succinylated rapeseed protein concentrates (SRPC), respectively. With both acylating agents, approximately
5–82% (ARPC-5 to ARPC-82) and 5–56% (SRPC-5 to SRPC-56) of ε-amino groups of lysine were acylated. Changes in functional properties
were monitored; nitrogen solubility, emulsifying properties and specific viscosity were improved by acylation. The effects
on functional properties were more pronounced with succinylation than acetylation. The nutritive value of succinylated rapeseed
protein concentrates was determined and compared with those of unmodified rapessed protein concentrate and rapessed flour.
Succinylation reduced the availability of lysine and decreased (p<0.05) the net protein ratio (NPR) and apparent digestibility
coefficient (ADC) of nitrogen in rapessed protein concentrates. Supplementation of SRPC with lysine improved the NPR compared
to that of SRPC-56. 相似文献
17.
Fenofibrate protects lipoproteins from lipid peroxidation: Synergistic interaction with α-tocopherol
Evelyne Chaput Dominique Maubrou-Sanchez François D. Bellamy Alan D. Edgar 《Lipids》1999,34(5):497-502
One of the earliest steps of atherosclerotic plaque formation is an increase of circulating apolipoprotein B-containing lipoproteins
which, after infiltrating the subendothelial space, undergo oxidative modification. Fenofibrate is an effective cholesterol-
and triglyceride-lowering agent which has been shown to be beneficial in the treatment of atherosclerosis. Vitamin E, or α-tocopherol,
is a powerful antioxidant which has been shown in a variety of studies to prevent lipoprotein peroxidation. The purpose of
the present study was to investigate the effect of fenofibrate treatment, either alone or in combination with α-tocopherol,
in reducing the susceptibility of lipoproteins to oxidative modification. Rats fed a normal diet were treated for up to 27
d with fenofibrate, either alone or in combination with equimolar doses of α-tocopherol. Combined VLDL (very low density lipoproteins)
and LDL (low density lipoproteins) isolated after fenofibrate treatment were more resistant to coppermediated oxidation, as
assessed by conjugated diene formation. Lag time was prolonged up to 3.2-fold, while the maximal rate of diene production
was significantly decreased by up to 2.2-fold. Treatment of rats with α-tocopherol alone at the selected dose had no significant
effect on lag time, while the propagation rate was slightly decreased. Coadministration of fenofibrate with α-tocopherol prolonged
the lag phase to a greater extent than fenofibrate alone, showing a synergistic interaction between the two compounds. Finally,
the combination of fenofibrate and α-tocopherol was significantly more effective in modifying lipoprotein oxidation parameters
than what was observed with α-tocopherol and bezafibrate or gemfibrozil. Thus, in addition to its well-established effects
on lipoprotein concentrations and atherogenic parameters, fenofibrate reduces the susceptibility of VLDL and LDL to oxidative
modification and exerts its action synergistically with α-tocopherol. 相似文献
18.
S. O. Soloviev 《Catalysis in Industry》2012,4(1):1-10
The catalytic properties of Ni/Al2O3 composites supported on ceramic cordierite honeycomb monoliths in oxidative methane reforming are reported. The prereduced
catalyst has been tested in a flow reactor using reaction mixtures of the following compositions: in methane oxidation, 2–6%
CH4, 2–9% O2, Ar; in carbon dioxide and oxidative carbon dioxide reforming of methane, 2–6% CH4, 6–12% CO2, and 0–4% O2, and Ar. Physicochemical studies include the monitoring of the formation and oxidation of carbon, the strength of the Ni-O
bond, and the phase composition of the catalyst. The structured Ni-Al2O3 catalysts are much more productive in the carbon dioxide reforming of methane than conventional granular catalysts. The catalysts
performance is made more stable by regulating the acid-base properties of their surface via the introduction of alkali metal
(Na, K) oxides to retard the coking of the surface. Rare-earth metal oxides with a low redox potential (La2O3, CeO2) enhance the activity and stability of Ni-Al2O3/cordierite catalysts in the deep and partial oxidation and carbon dioxide reforming of methane. The carbon dioxide reforming
of methane on the (NiO + La2O3 + Al2O3)/cordierite catalyst can be intensified by adding oxygen to the gas feed. This reduces the temperature necessary to reach
a high methane conversion and does not exert any significant effect on the selectivity with respect to H2. 相似文献
19.
Rates of turnover and oxidation of plasma free fatty acid (FFA) were determined in unanesthetized dogs during exercise, acute
cold exposure and anaphylactic shock, with the aid of a technique involving the continuous infusion of albumin-bound palmitate-1-14C and the simultaneous measurement of O2 uptake, CO2 output and the specific activities of CO2 and FFA. During exercise in normal untrained dogs, plasma FFA supplied 20–30% of the energy, whereas in trained dogs 70–90%
of the energy was derived from the FFA oxidation. In resting dogs at room temperature the plasma FFA level was 0.58 μEq/ml
with a turnover rate of 18.6 μEq/kg/min of which 22% was immeditely oxidized and contributed 29% to the exhaled CO2. These results were compared with data obtained in pancreatectomized and thyroidectomized dogs. Acute cold exposure (temperature
4–5C) increased the FFA level and turnover rate to 1.02 μEq/ml and 28.0 μEq/kg/min, respectively, of which 33% was immedaitely
oxidized, contributing 46% to the exhaled CO2. During anaphylactic shock, blood lactate increased, FFA level and turnover rate were reduced, and the fraction which was
immediately oxidized was depressed markedly, i.e., 3–9% of FFA turnover. Sodium lactate infusion, which induces a blood lactate
level comparable to that seen in anaphylaxis or nicotinic acid infusion, markedly decreased the level and turnover rate of
FFA. However the fraction of turnover oxidized remained the same as during the preinfusion period (range of 21–40%. Exercise
or the administration of norepinephrine during anaphylactic shock provided results suggesting that endogenous lactic acid
interferes with FFA oxidation, whereas exogenous, lactate had no effect on this oxidation. 相似文献
20.
The degradation of α-tocopherol and the formation of α-tocopherol and triacylglycerol oxidation products at high temperatures
(150–250°C) over a heating period (0–4h) for a model system ranging between triolein and tripalmitin were modeled by use of
an experimental design. The oxidation products of α-tocopherol formed under these conditions were α-tocopherolquinone (1.4–7.7%)
and epoxy-α-tocopherolquinones (4.3–34.8%). The results indicate a very high susceptibility of α-tocopherol to capture peroxyl
radicals upon oxidation, leading to the formation of polar tocopherol oxidation products. Both α-tocopherolquinone and epoxy-α-tocopherolquinones
were not stable upon prolonged heating and were further degraded to other unknown oxidation products. The kinetics of α-tocopherol
oxidation were significantly influenced by the triolein/tripalmitin ratio. By increasing the level of triacylglycerol unsaturation
the rate of α-tocopherol recovery after heating increased significantly from 2.2 to 44.2% whereas in the meantime triacylglycerol
polymerization increased from 0 to 3.7%. 相似文献