bluuebunny/crossref_metadata_2025_split huggingface dataset:
Intermediates and products formed during fatty acid α‐oxidation in cucumber (Cucumis sativus)
Authors: Andersen Borge Grethe I. , Vogt Gjermund , Nilsson Astrid 
Published: November 2006

AbstractFatty acid α‐oxidation is an essential metabolic pathway both in plants and in mammals which is still not completely understood. We previously described and purified an α‐oxidation enzyme in cucumber which has been used in the present investigation of the α‐oxidation reaction mechanism. Free fatty acids, and not the CoA thioesters, were found to undergo α‐oxidation in cucumber. 2‐Hydroxy‐ and 2‐oxopalmitic acids were identified as palmitic acid α‐oxidation intermediates by high‐performance liquid chromatography and gas chromatography—mass spectrometry analysis in cucumber subcellular 150,000×gmax pellets obtained by differential centrifugation. Incubation of purified α‐oxidation enzyme with [1‐14C]palmitic acid resulted in the formation of both the above‐described intermediates and the Cn−1 product, pentadecanal, and 14CO2. Besides 14CO2, 14C‐formate was identified as an α‐oxidation product from [1‐14C]palmitic acid in cucumber subcellular fractions. Fe2+ stimulated the 14CO2 and 14C‐formate production, and the addition of ascorbate and 2‐oxoglutarate together with Fe2+ resulted in optimal α‐oxidation activities, suggesting a dioxygenase reaction mechanism, as previously shown in mammals. NADPH and, to a lesser extent, NADH stimulated the total 14C‐formate plus 14CO2 production but had only slight or no effects on 14CO2 production. H2O2 showed concentration‐dependent inhibitory effects, while FAD had neither effect on 14CO2 nor 14CO2 plus 14C‐formate production. The results in the present study demonstrate that an α‐oxidation enzyme in cucumber is capable of oxidizing palmitic acid via 2‐hydroxy‐ and 2‐oxopalmitic acid to produce pentadecanal and CO2. In contrast to the subcellular 150,000×gmax fraction, the purified α‐oxidation enzyme could neither produce formate nor convert 14C‐formate into 14CO2, indicating two possible α‐oxidation routes in cucumber.
Proportion of geometrical hydroperoxide isomers generated by radical oxidation of methyl linoleate in homogeneous solution and in aqueous emulsion
Authors: Wang Xing‐Hua , Ohshima Toshiaki , Ushio Hideki , Koizumi Chiaki 
Published: November 2006

AbstractThe proportion of geometrical hydroperoxide isomers generated by aerobic oxidation of methyl linoleate (18∶2 Me) in either aqueous emulsion consisting of Tris‐HCl buffer (pH 7.4) or in a homogeneous dichloromethane solution was determined to understand the mechanism of lipid oxidation in different reaction systems. Four geometrical isomers were generated after oxidation of 18∶2 Me in dichloromethane: methyl 13‐hydroperoxy‐cis‐9,trans‐11‐octadecadienoate, methyl 13‐hydroperoxy‐trans‐9,trans‐11‐octadecadienoate, methyl 9‐hydroperoxy‐trans‐10,cis‐12‐octadecadienoate, and methyl 9‐hydroperoxy‐trans‐10,trans‐12‐octadecadienoate in the ratios of 1∶4∶1∶4, respectively. The ratios between each isomer did not change until the peroxide value (PV) increased to 58 meq/kg. Oxidation of 18∶2 Me in aqueous emulsion yielded the same geometrical isomers of hydroperoxide. However, the ratios were different: 3∶2∶3∶2 until the PV increased to 110 meq/kg. Predominant (60%) formation of trans,trans hydroperoxide isomers was obtained in the oxidation of a mixture of 18∶2 Me and methyl laurate (12∶0 Me). These results are interpreted to reflect the importance of the concentration of hydrogen atom‐donating equivalents to the kinetic preference for different products. The high effective concentration of hydrogen donors in the oxidation of 18∶2 Me in emulsions favored the formation of the less stable cis,trans isomers. The lower concentration of hydrogen donor in the dichloromethane solution effectively slowed hydrogen donation and led to the strong preference for the more stable trans,trans isomers. This interpretation was further tested by preparing emulsions of 18∶2 Me and 12∶0 Me to dilute concentration of hydrogen‐donating species using the nonhydrogen‐donating 12∶0 Me. Consistent with the proposed hypothesis, the proportion of trans,trans isomers increased as a result of 12∶0 Me addition.
19‐Azasqualene‐2,3‐epoxide and its N‐oxide: Metabolic fate and inhibitory effect on sterol biosynthesis in Saccharomyces cerevisiae
Authors: Milla Paola , Viola Franca , Ceruti Maurizio , Rocco Flavio , Cattel Luigi , Balliano Gianni 
Published: November 2006

Abstract19‐Azasqualene‐2,3‐epoxide was more inhibitory than the corresponding N‐oxide against 2,3‐oxidosqualene cyclase (OSC) solubilized from Saccharomyces cerevisiae (IC50 7±2 and 25±5 μM, respectively). Both compounds showed a reversible, noncompetitive‐type inhibition on solubilized OSC. Different inhibitory properties between the compounds were especially evident when measuring [14C]acetate incorporation into nonsaponifiable lipids extracted from treated cells. In cells treated with 19‐azasqualene‐2,3‐epoxide at 30 μM, the radioactivity associated with the oxidosqualene fraction, which was negligible in the controls, rose to over 40% of the nonsaponifiable lipids, whereas it remained at a slightly appreciable level in cells treated with the N‐oxide derivative under the same conditions. 19‐Azasqualene‐2,3‐epoxide was also more effective than the N‐oxide as a cell growth inhibitor (minimal concentration of compound needed to inhibit yeast growth: 45 and >100 μM, respectively). The two inhibitors underwent different metabolic fates in the yeast: while 19‐azasqualene‐2,3‐epoxide did not undergo any transformation, its N‐oxide was actively reduced to the corresponding amine in whole and in “ultrasonically stimulated” cells. The N‐oxide reductases responsible for this transformation appear to be largely confined within the microsomal fractions and require NADPH for their activity. A possible relationship between the inhibitory properties of the two compounds and their metabolic fates is discussed.
C2‐ceramide attenuates phenylephrine‐induced vasoconstriction and elevation in [Ca2+]i in rat aortic smooth muscle
Authors: Zheng Tao , Li Wenyan , Wang Jun , Altura Bella T. , Altura Burton M. 
Published: November 2006

AbstractIn the present study, we examined the effects of cell‐permeable C2‐ceramide on contraction of aortic smooth muscle and intracellular free Ca2+ ([Ca2+]i). C2‐ceramide (10−7 to 10−4M) alone did not elicit any significant changes in either basal tension or resting levels of [Ca2+]i in rat aortic smooth muscle. However, C2‐ceramide (10−7 to 10−4 M) attenuated phenylephrine‐induced contractions in isolated rat aortic rings in a concentration‐related manner, and inhibited elevations in [Ca2+]i in cultured rat aortic smooth muscle cells induced by phenylephrine. C2‐ceramide‐induced relaxation was found to be only slightly endothelium‐dependent. However, nitric oxide inhibitors (l‐NNA, l‐NMMA), an inhibitor of prostanoid synthesis (indomethacin), an inhibitor of opiate actions, and several inhibitors of the pharmacologic actions of various vasoactive amines all failed to interfere with the vasorelaxant responses of C2‐ceramide. Three different inhibitors of protein kinase C, when used in a wide concentration range, also failed to interfere with the ceramide‐induced relaxations. Our results suggest that the sphingomyelin‐signaling pathway may play an important regulatory role in arterial wall tone.
The effects of a dietary oxidized oil on lipid metabolism in rats
Authors: Eder Klaus 
Published: November 2006

AbstractThis study was carried out to investigate the effects of a dietary oxidized oil on lipid metabolism in rats, particularly the desaturation of fatty acids. Two groups of rats were fed initially for a period of 35 d diets containing 10% of either fresh oil or thermally treated oil (150°C, 6d). The dietary fats used were markedly different for lipid peroxidation products (peroxide value: 94.5 vs. 3.1 meq O2/kg; thiobarbituric acid‐reactive substances: 230 vs. 7 μmol/kg) but were equalized for their fatty acid composition by using different mixtures of lard and safflower oil and for tocopherol concentrations by individual supplementation with dl‐α‐tocopherol acetate. In the second period which lasted 16 d, the same diets were supplemented with 10% linseed oil to study the effect of the oxidized oil on the desaturation of α‐linolenic acid. During the whole period, all the rats were fed identical quantities of diet by a restrictive feeding system in order to avoid a reduced food intake in the rats fed the oxidized oil. Body weight gains and food conversion rates were only slightly lower in the rats fed the oxidized oil compared to the rats fed the fresh oil. Hence, the effects of lipid peroxidation products could be studied without a distortion by a marked reduced food intake and growth. To assess the rate of fatty acid desaturation, the fatty acid composition of liver and heart total lipids and phospholipids was determined and ratios between product and precursor of individual desaturation reactions were calculated. Rats fed the oxidized oil had reduced ratios of 20∶4n−6/18∶2n−6, 20∶5n−3/18∶3n−3, 20∶4n−6/20∶3n−6, and 22∶6n−3/22∶5n−3 in liver phospholipids and reduced ratios of 20∶4n−6/18∶2n−6, 22∶5n−3/18∶3n−3, and 22∶6n−3/18∶3n−3 in heart phospholipids. Those results suggest a reduced rate of desaturation of linoleic acid and α‐linolenic acid by microsomal Δ4‐, Δ5‐, and Δ6‐desaturases. Furthermore, liver total lipids of rats fed the oxidized oil exhibited a reduced ratio between total monounsaturated fatty acids and total saturated fatty acids, suggesting a reduced Δ9‐desaturation. Besides those effects, the study observed a slightly increased liver weight, markedly reduced tocopherol concentrations in liver and plasma, reduced lipid concentrations in plasma, and an increased ratio between phospholipids and cholesterol in the liver. Thus, the study demonstrates that feeding an oxidized oil causes several alterations of lipid and fatty acid metabolism which might be of great physiologic relevance.
Application of high‐resolution, two‐dimensional 1H and 13C nuclear magnetic resonance techniques to the characterization of lipid oxidation products in autoxidized linoleoyl/linolenoylglycerols
Authors: Silwood Christopher J. L. , Grootveld Martin 
Published: November 2006

AbstractSubjection of polyunsaturated fatty acid (PUFA)‐rich culinary oils to standard frying episodes generates a range of lipid oxidation products (LOP), including saturated and α,β‐unsaturated aldehydes which arise from the thermally induced fragmentation of conjugated hydroperoxydiene precursors. Since such LOP are damaging to human health, we have employed high‐resolution, two‐dimensional 1H‐1H relayed coherence transfer, 1H‐1H total correlation, 1H‐13C heteronuclear multiple quantum correlation, and 1H‐1H J‐resolved nuclear magnetic resonance (NMR) spectroscopic techniques to further elucidate the molecular structures of these components present in (i) a model linoleoylglycerol compound (1,3‐dilinolein) allowed to autoxidize at ambient temperature and (ii) PUFA‐rich culinary oils subjected to repeated frying episodes. The above techniques readily facilitate the resolution of selected vinylic and aldehydic resonances of LOP which appear as complex overlapping patterns in conventional one‐dimensional spectra, particularly when employed in combination with solvent‐induced spectral shift modifications. Hence, much useful multi‐component information regarding the identity and/or classification of glycerol‐bound conjugated hydroperoxydiene and hydroxydiene adducts, and saturated and α,β‐unsaturated aldehydes, present in autoxidized PUFA matrices is provided by these NMR methods. Such molecular information is of much value to researchers investigating the deleterious health effects of LOP available in the diet.
Increased diaphragm expression of GLUT4 in control and streptozotocin‐diabetic rats by fish oil‐supplemented diets
Authors: Girón María D. , Salto Rafael , Hortelano Paloma , Periago José L. , Vargas Alberto M. , Suárez María D. 
Published: November 2006

AbstractDietary fat intake influences plasma glucose concentration through modifying glucose uptake and utilization by adipose and skeletal muscle tissues. In this paper, we studied the effects of a low‐fat diet on diaphragm GLUT4 expression and fatty acid composition in control and streptozotocin‐induced diabetic rats. Control as well as diabetic rats were divided into three different dietary groups each. Either 5% olive oil, 5% sunflower oil, or 5% fish oil was the only fat supplied by the diet. Feeding these low‐fat diets for 5 wk induced major changes in fatty acid composition, both in control and in diabetic rats. Arachidonic acid was higher in diabetic olive and sunflower oil‐fed rats with respect to fish oil‐fed, opposite to docosahexaenoic acid which was higher in diabetic fish oil‐fed rats with respect to the other two groups. Animals receiving a fish oil diet had the lowest plasma glucose concentration. GLUT4 expression in diaphragm, as indicated by GLUT4 protein and mRNA, is modulated both by diabetes and by diet fatty acid composition. Diabetes induced a decrease in expression in all dietary groups. Plasma glucose levels correlated well with the increased amount of GLUT4 protein and mRNA found in fish oil‐fed groups. Results are discussed in terms of the influence that arachidonic and n−3 polyunsaturated fatty acids may exert on the transcriptional and translational control of the GLUT4 gene.
Effects of cholestyramine on hepatic cholesterol 7α‐hydroxylase and serum 7α‐hydroxycholesterol in the hamster
Authors: Kuroki Syoji , Naito Tokio , Chijiiwa Kazuo , Tanaka Masao 
Published: November 2006

AbstractCholestyramine increases activities of hepatic cholesterol 7α‐hydroxylase and serum levels of 7α‐hydroxycholesterol. To examine if serum 7α‐hydroxycholesterol levels parallel with enzyme activity, 0, 0.5, 1, 2, 4, and 10% of cholestyramine was administered to female golden Syrian hamsters for 28 d in the dose‐dependent study, and 2% cholestyramine for 0, 1, 3, 7, 14, 21, and 28 d in the time‐dependent study. In the dose‐dependent study, hepatic and serum cholesterol levels were significantly decreased dose‐dependently when more than 0.5% of cholestyramine was fed for 28 d. Cholestyramine increased the cholesterol 7α‐hydroxylase activity in a dose‐dependent manner, while the serum 7α‐hydroxycholesterol level was essentially unchanged. No correlation was found between the serum level and the hepatic enzyme activity. In the time‐dependent study, hepatic and serum cholesterol levels markedly decreased when 2% cholestyramine was fed for longer than 3 d. The serum triglyceride level increased significantly for the first 7 d and then decreased. Cholesterol 7α‐hydroxylase activity increased significantly as early as day 1, reached maximum activity level on day 7, and then kept the significantly high values until day 28. The serum 7α‐hydroxycholesterol level significantly increased for the first 7 d and decreased to the pretreatment level thereafter. 7α‐Hydroxycholesterol levels significantly correlated with serum cholesterol and triglyceride levels. We conclude that the serum 7α‐hydroxycholesterol level does not always reflect the activity of hepatic cholesterol 7α‐hydroxylase, when cholesterol metabolism is severely disturbed by cholestyramine.
Incorporation of [1‐13C]oleate into cellular triglycerides in differentiating 3T3L1 cells
Authors: Guo Wen , Choi Ji‐Kyung , Kirkland James L. , Corkey Barbara E. , Hamilton James A. 
Published: November 2006

AbstractOleate is one of the most abundant dietary fatty acids, and much remains to be learned about its metabolism in fat cells. We studied the incorporation of exogenous [1‐13C]‐oleate into triglycerides (TG) in differentiating 3T3L1 preadipocytes using 13C NMR spectroscopy. The quantity of oleate incorporated into TG was found to increase as preadipocytes differentiated into fat cells. The ratio of unesterified [1‐13C]oleate to total stored fatty acids was higher in less differentiated cells, and declined at later stages of differentiation as cells accumulated fatty acids through de novo synthesis. When added as the only exogenous fatty acid, oleate was largely esterified at the sn‐2 position. When equimolar unlabeled linoleate was co‐provided at the same time, the ratio of [1‐13C]oleate esterified at the sn‐1,3 position increased, implying competition between linoleate and oleate for esterification, especially at the sn‐2 position. When cells pre‐enriched with [1‐13C]oleate (esterified to TG) were treated with isoproterenol, a lipolytic agent, most of the [1‐13C]oleate was still found in TG, despite a high rate of lipolysis determined by measuring glycerol release. This implies extensive re‐esterification of the oleate released by lipolysis.
The effect of conjugated linoleic acid on the antioxidant enzyme defense system in rat hepatocytes
Authors: Cantwell H. , Devery R. , O'Shea M. , Stanton C. 
Published: November 2006

AbstractShort‐term effects of physiological concentrations of conjugated linoleic acid (CLA) on membrane integrity, metabolic function, cellular lipid composition, lipid peroxidation, and antioxidant enzymes were examined using rat hepatocyte suspension cultures. Incubation with CLA (5–20 ppm) for 3 h decreased the ability of hepatocyte plasma membranes to exclude trypan blue by approximately 25%, and caused leakage of cytosolic lactate dehydrogenase (LDH) into the medium. The significant decrease (P<0.02) in hepatocyte viability as measured by LDH leakage during cell incubation with 10 and 20 ppm CLA was not associated with significant changes in cellular ATP content. Protein synthesis in hepatocytes was elevated (P<0.05) in the presence of 5 and 10 ppm CLA, but at a higher concentration (20 ppm), protein synthesis was similar to that of control cells. Gluconeogenesis was maintained in cells incubated with lower concentrations of CLA (5 and 10 ppm) but was decreased (P<0.02) at the higher concentration. Incubation with 20 ppm CLA for 3 h did not affect the specific activity of 3‐hydroxy‐3‐methylglutaryl coenzyme A reductase, the rate‐limiting enzyme of cholesterol synthesis. Both cis‐9,trans‐11/trans‐9,cis‐11, and cis‐10,trans‐12/trans‐10,cis‐12 isomers of CLA were incorporated to a similar level into hepatocytes. Levels ranged from 3.9 to 4.1%, respectively, of total fatty acids in neutral lipids, and from 0.7 to 0.8%, respectively, of total fatty acids in phospholipids. Cellular lipid peroxidation remained unchanged in the presence of CLA (5–20 ppm), despite significant inhibition (P<0.05) of superoxide dismutase. Catalase activity was maintained near control levels in the presence of 5 and 10 ppm CLA but was significantly decreased in the presence of 20 ppm CLA. Glutathione peroxidase activity was significantly decreased in the presence of 10 ppm CLA. The apparent sensitivity of the antioxidant enzyme defense system of liver cells to CLA, coupled with the lack of effect of CLA on lipid peroxidation in cells, suggests that cytotoxic effects of CLA as described by LDH leakage and decreased gluconeogenesis were not mediated by a prooxidant action in hepatocytes.
Positional analysis of triglycerides and phospholipids rich in long‐chain polyunsaturated fatty acids
Authors: Amate L. , Ramírez M. , Gil A. 
Published: November 2006

AbstractFour sources of long‐chain polyunsaturated fatty acids (LCP) differing in their chemical structure (triglycerides or phospholipids) and in their origin (tuna triglycerides, fungal triglycerides, egg phospholipids, and pig brain phospholipids) were analyzed to determine the distribution of the component fatty acids within the molecule. Lipase and phospholipase A2 hydrolysis was performed to obtain 2‐monoacylglycerols and lysophospholipids, respectively, which allowed us to determine the distribution of fatty acids between the sn‐2 and sn‐1,3 positions of triglycerides or between the sn‐1 and sn‐2 position of phospholipids. Fatty acids in the LCP sources analyzed were not randomly distributed. In tuna triglycerides, half of the total amount of 22∶6n−3 was located at the sn‐2 position (49.52%). In fungal triglycerides, 16∶0 and 18∶0 were esterified to the sn‐1,3 (92.22% and 91.91%, respectively) 18∶1 and 18∶2 to the sn‐2 position (59.77% and 62.62%, respectively), and 45% of 20∶3n−6 and only 21.64% of 20∶4n−6 were found at the sn‐2 position. In the lipid sources containing phospholipids, LCP were mainly esterified to the phosphatidylethanolamine fraction. In egg phospholipids, most of 20∶4n−6 (5.50%, sn‐2 vs. 0.91%, sn‐1) and 22∶6n−3 (2.89 vs. 0.28%) were located at the sn‐2 position. In pig brain phospholipids, 22∶6n−3 was also esterified to the sn‐2 (13.20 vs. 0.27%), whereas 20∶4n−6 was distributed between the two positions (12.35 vs. 5.86%). These results show a different fatty acid composition and distribution of dietary LCP sources, which may affect the absorption, distribution, and tissue uptake of LCP, and should be taken into account when supplementing infant formulas.
Synthesis of 9Z,11E‐octadecadienoic and 10E,12Z‐octadecadienoic acids, the major components of conjugated linoleic acid
Authors: Chen Chien‐An , Lu Wei , Sih Charles J. 
Published: November 2006

AbstractLinoleic acid was efficiently converted into the two major components of conjugated linoleic acid, 9Z,11E‐octadecadienoic (1a) and 10E,12Z‐octadecadienoic acid (1b) using either the superbase (n‐butyllithium/potassium tert‐butoxide) or by simply refluxing with KOH in 1‐butanol. In turn, 1a and 1b were separated from each other using the lipase from Aspergillus niger via stereoselective esterification in 1‐butanol. This enzyme has a preference for the 9Z,11E isomer, 1a, and has excellent selectivity. This method has allowed the ready preparation of gram quantities of 1a and 1b in their highly purified forms, which are not readily accessible by current methods.
Lipidemic effects of an interesterified mixture of butter, medium‐chain triacylglycerol and safflower oils
Authors: Mascioli Edward A. , McLennan Christine E. , Schaefer Ernst J. , Lichtenstein Alice H. , Høy Carl‐Erik , Christensen Michael S. , Bistrian Bruce R. 
Published: November 2006

AbstractThe objective of this study was to determine if the positional structure of dietary triacylglycerol affected lipidemic responses. Thirty healthy adults (16 men and 14 postmenopausal women) with low‐density lipoprotein cholesterol (LDL‐C) concentrations >3.37 mM (130 mg/dl) enrolled in a prospective, single‐blind, cross‐over outpatient clinical trial that consisted of two 5‐wk dietary phases. After baseline screening, subjects were instructed to follow individualized meal plans (weight maintenance diets with 36% of total energy from fat, half of which was from a test oil) and randomized to receive either butter (B) or an interesterified mixture (IM) of butter, medium‐chain triacylglycerol (MCI), and safflower oils. Blood drawn during weeks 5 and 10 of feeding was analyzed for total cholesterol (TC), high density lipoprotein cholesterol (HDL‐C), LDL‐C, and triacylglycerols (TAG). Mean plasma levels of TC (B, 6.98±1.06 mM; IM, 7.09±1.20 mM), HDL‐C (B,1.30±0.35 mM; IM, 1.29±0.34 mM), and LDL‐C (B, 4.91±0.95 mM; IM, 492±1.10 mM) were not significantly different between the two dietary treatments. Mean TAG levels were higher for the interesterified B‐MCT mixture (B, 1.75±0.72 mM; IM, 1.96±0.86 mM, P<0.05). We conclude that an IM of B, MCT and safflower oils as compared to native B has no appreciable effect on plasma cholesterol concentrations but is associated with a modest rise in plasma TAG.