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PubMed2003

Effect of different lipid extraction methods on delta13C of lipid and lipid-free fractions of fish and different fish feeds.

For many ecological applications of stable carbon isotope techniques, it is necessary to separate the lipid and lipid-free fractions. The effect of different lipid extraction methods on the isotope signature of the remaining lipid-free matter as well as the lipid fraction was tested. A hot extraction form of the Soxhlet method using petrol-ether was compared with two liquid-liquid extraction methods for lipid determination described by Bligh and Dyer and Smedes. Solid samples of fish and different natural food items were subjected to extraction and the carbon isotope ratios in lipid and lipid-free matter determined by IRMS. All methods were suitable for lipid extraction from all samples analysed here and did not cause biologically relevant differences (> 1%) in carbon isotopic ratios, except the Bligh and Dyer extraction method using chloroform which caused systematic errors for delta13C when applied to diatoms.

Animal Feed↗
PubMed1980

Lipid-lipid and lipid-protein interactions in membranes.

Over the past decade spectroscopic methods (fluorescence, ESR, and NMR) have been used to provide new information about the molecular dynamics of lipid-lipid and lipid-protein interactions in membranes. The various methods of characterizing isotropic and anisotropic motion are described. Lipid bilayers are highly dynamic, with rapid acyl chain motion and rapid lateral diffusion in the plane of the membrane. In membranes where proteins penetrate through the bilayer, a large hydrophobic surface area exists in contact with the bilayer lipids. Lipids at the protein interface are in dynamic equilibrium with the remaining pools of bilayer. The protein has been shown spectroscopically to have some influence on the dynamics of the nearest neighbor lipids, leaving the rest of the bilayer relatively unperturbed. Evidence is summarized that, in some cases, the lipid composition in the interfacial region is influenced by the protein.

Chemical Phenomena↗
PubMed1997

Volatile anaesthetic effects on calcium conductance of planar lipid bilayers formed with synthetic lipids or extracted lipids from sarcoplasmic reticulum.

Volatile anaesthetics are known to increase leakage of calcium from the light fraction of skeletal sarcoplasmic reticulum (L-SR) which has no calcium release channels. To explore the role of the lipid environment, we have examined the effect of volatile anaesthetics on calcium conductance (gCa) of lipid membranes. Planar lipid bilayers were formed with a mixture of synthetic phospholipids and cholesterol, resembling the composition of SR membranes, or with lipids extracted from skeletal L-SR, gCa was estimated by calculating the calcium transference number (tCa) using diffusion potential measurements. Membranes formed with L-SR-extracted lipids had a higher gCa than membranes formed with synthetic lipids. Volatile anaesthetics increased total conductance and gCa in a dose-dependent manner, but did not affect tCa or membrane specific capacitance. In membranes formed with L-SR-extracted lipids, isoflurane induced the largest increase in gCa (1260 (SEM 304) % increase, n = 4, 0.94 mmol litre-1), followed by enflurane (264 (75)%, n = 5, 1.88 mmol litre-1) and halothane (53 (33)%, n = 5; 1.54 mmol litre-1). In membranes formed with synthetic lipids, volatile anaesthetic-induced increases in gCa followed the same trend but were larger. Volatile anaesthetics increased gCa without changing the ionic selectivity of membranes. However, the magnitude of the increase in gCa in the presence of volatile anaesthetics cannot account for the previously observed calcium leakage from L-SR vesicles. Therefore, the volatile anaesthetic-induced increase in calcium leakage in L-SR vesicles must be mediated via other pathways involving membrane proteins.

Anesthetics, Inhalation↗
PubMed1997

Structural elucidation of oxygenated storage lipids in cucumber cotyledons. Implication of lipid body lipoxygenase in lipid mobilization during germination.

At early stages of germination, a special lipoxygenase is expressed in cotyledons of cucumber and several other plants. This enzyme is localized at the lipid storage organelles and oxygenates their storage triacylglycerols. We have isolated this lipid body lipoxygenase from cucumber seedlings and found that it is capable of oxygenating in vitro di- and trilinolein to the corresponding mono-, di-, and trihydroperoxy derivatives. To investigate the in vivo activity of this enzyme during germination, lipid bodies were isolated from cucumber seedlings at different stages of germination, and the triacylglycerols were analyzed for oxygenated derivatives by a combination of high pressure liquid chromatography, gas chromatography/mass spectrometry, and nuclear magnetic resonance spectroscopy. We identified as major oxygenation products triacylglycerols that contained one, two, or three 13S-hydroperoxy-9(Z),11(E)-octadecadienoic acid residues. During germination, the amount of oxygenated lipids increased strongly, reaching a maximum after 72 h and declining afterward. The highly specific pattern of hydroperoxy lipids formed suggested the involvement of the lipid body lipoxygenase in their biosynthesis. These data suggest that this lipoxygenase may play an important role during the germination process of cucumber and other plants and support our previous hypothesis that the specific oxygenation of the storage lipids may initiate their mobilization as a carbon and energy source for the growing seedling.

Chromatography, High Pressure Liquid↗
PubMedDate not supplied

Lipid levels and use of lipid-lowering drugs for patients in pharmacist-managed lipid clinics versus usual care in 2 VA Medical Centers.

OBJECTIVE: The objective of this study was to assess the effectiveness of pharmacist- managed dyslipidemia clinics at 2 Veterans Affairs medical centers since the release of the 2001 National Cholesterol Education Panel Adult Treatment Panel III (NCEP ATP III) guideline compared with the usual care (UC) provided by other health care professionals in the same setting. METHODS: Analysis was performed through retrospective chart review of patients with a diagnosis of dyslipidemia who received care in either the Amarillo or Lubbock, Texas, pharmacist-managed lipid clinics (LCs) or UC from a primary care physician. Data from medical charts were abstracted for dates of service from July 2001 to December 2003 for 115 patients selected randomly from LC rolls matched with 115 patients with a diagnosis of dyslipidemia selected randomly from UC. All patients had to have had at least 3 visits with the LC or 3 visits in UC with a billing code of dyslipidemia; they were followed for at least 6 months after an initial visit in July 2001 or thereafter and were enrolled in the VA health care system for at least 1 year. Baseline lipid values were available for LC but not UC patients. Cholesterol target goals were determined according to NCEP ATP III guideline. RESULTS: After an average of 21.6 months of follow-up, the proportion of patients in the LC group that attained goal level increased from 45.2% at baseline to 82.6% for total cholesterol (TC) and from 36.5% at baseline to 64.3% for lowdensity lipoprotein cholesterol (LDL-C [P <0.001 for both comparisons]). There was an average 24.5 mg/dL absolute reduction (relative reduction, 19.4%) in LDL-C along with significant improvements in the other lipid levels (P <0.001 for TC and LDL-C, P = 0.007 for triglycerides [TGs]) with the exception of highdensity lipoprotein cholesterol (HDL-C), which declined from 40.0 mg/dL to 36.3 mg/dL (P <0.001). A total of 50 patients (43.5%) were on lipid-lowering pharmacotherapy at baseline versus 108 patients (93.9%) at follow-up. Compared with UC, LC patients were more likely to have achieved goal LDL-C (64.3% vs. 15.7% for UC, P <0.001) and TC (82.6% vs. 40.9%, P <0.001), but there was no difference in the proportion of patients at TG goal for LC (65.2%) compared with UC (52.2%, P = 0.061) or at HDL-C goal (23.5% for LC vs. 33.0% for UC, P = 0.143). A higher proportion of LC patients (93.9%) used lipid-lowering agents compared with UC patients (24.3%, P <0.001). Subanalysis of patients on a lipid-lowering agent found that a significantly higher proportion (85.2%) in the LC group were at goal total cholesterol compared with 60.7% for UC (P = 0.012) and at goal LDL-C (66.7% for LC vs. 39.3% for UC, P = 0.016). However, a lower proportion were at goal HDL-C for LC (21.3%) versus 42.9% for UC (P = 0.043). Overall, only 11 LC patients (9.6%) attained goal levels for all 4 serum lipid values by the end of follow-up versus 2 UC patients (1.7%, P = 0.019). CONCLUSIONS: Nearly two thirds of patients diagnosed with dyslipidemia and enrolled in a pharmacist-managed LC had LDL-C levels at or below NCEP ATP III target goal compared with 16% of dyslipidemia patients who received UC from their primary care provider. The pharmacist-managed LC patients were also twice as likely (83 vs. 41%) to have attained the TC target goal, but there was no difference between the 2 groups in the proportion of patients who attained either TG or HDL-C target goals. Only 9.6% of LC patients were at goal for all 4 individual lipid measures at the end of follow-up.

Ambulatory Care Facilities↗
PubMed2004

Lipid species profiling: a high-throughput approach to identify lipid compositional changes and determine the function of genes involved in lipid metabolism and signaling.

The development of electrospray ionization mass spectrometry has provided the foundation for the development of strategies to identify and quantify complex lipids from unfractionated extracts of small biological samples. In the 1990s, the feasibility of detailed lipid profiling was demonstrated; in the past two years, analytical strategies have been extended to include classes of lipids that are unique to plants. High-throughput lipid profiling by electrospray ionization tandem mass spectrometry, in combination with forward- or reverse-genetics approaches, has recently been utilized to identify lipid metabolic pathways that are involved in plant development and stress responses, to specify the roles of particular genes and enzymes in plant responses to environmental cues, to determine the lipid species that serve as the substrates and products of specific enzymes, and to identify lipid-metabolizing enzymes that are involved in varied plant processes.

Genes, Plant↗
PubMed2002

Interference of poly(ethylene glycol)-lipid analogues with cationic-lipid-mediated delivery of oligonucleotides; role of lipid exchangeability and non-lamellar transitions.

Cationic liposomes are applied to transfer oligonucleotides (ODNs) into cells to regulate gene expression for gene therapeutic or cell biological purposes. In vivo, poly(ethylene glycol) (PEG)-lipid derivatives are employed to stabilize and prolong the circulation lifetime of nucleic acid-containing particles, and to improve targeting strategies. In this study, we have studied the effects of PEG-lipid analogues, i.e. PEG coupled to either phosphatidylethanolamine (PE) or ceramide, on cationic-lipid-DNA complex ('lipoplex') assembly and the mechanism of cationic-lipid-mediated delivery of ODNs in vitro. Inclusion of 10 mol% PEG-PE in ODN lipoplexes inhibited their internalization in Chinese hamster ovary cells by more than 70%. The intracellular fraction remained entrapped in the endosomal/lysosomal pathway, and no release of ODNs was apparent. Similar observations were made for complexes prepared from liposomes that contained PEG-ceramides. Interestingly, delivery resumed when lipoplexes had been externally coated with PEG-ceramides. In this case, the kinetics of delivery were dependent on the length of the ceramide acyl chain, consistent with a requirement for the PEG-lipid to dissociate from the complex. Moreover, although the chemical nature of the PEG-ceramides distinctly affected the net internalization of the complexes, impediment of delivery was largely related to an inhibitory effect of the PEG-lipid on the release of ODNs from the endosomal compartment. Cryo-electron microscopy and small-angle X-ray scattering revealed that the PEG-lipids stabilize the lamellar phase of the lipoplexes, while their acyl-chain-length-dependent transfer from the complex enables adaptation of the hexagonal phase. Within the endosomal compartment, this transition appears to be instrumental in causing the dissociation and cytosolic release of the ODNs for their nuclear homing.

Animals↗
PubMed1982

Dietary cellulose, wheat bran, and fish meal in relation to hepatic lipids, serum lipids, and lipid excretion in laying hens.

Isonitrogenous diets supplemented with 10% cellulose, 10% wheat bran, or 10% fish meal were fed to White Leghorn hens from 245 to 322 days of age. Neither body weights nor egg production of the hens fed these diets differed significantly from those of controls fed a corn-soybean meal basal diet. Supplemental fish meal and wheat bran did not significantly affect liver weight or liver lipids, although serum lipids of the hens fed the diet containing fish meal were significantly lower than those of the hens fed the basal diet. The hens fed the cellulose-supplemented diet, however, exhibited significantly decreased liver weights, serum lipids, and liver lipids, which were accompanied by a significant increase in excreta lipid. It is speculated that lipid excretion may be involved in some dietary induced alterations in the hepatic lipid concentration of laying chickens.

Animals↗
PubMed2000

Expression of cucumber lipid-body lipoxygenase in transgenic tobacco: lipid-body lipoxygenase is correctly targeted to seed lipid bodies.

A particular isoform of lipoxygenase (LOX, EC 1.13.11.12) localized on lipid bodies has been shown by earlier investigations to play a role during seed germination in initiating the mobilization of triacylglycerols. On lipid bodies of germinating cucumber (Cucumis sativus L.) seedlings, the modification of linoleoyl moieties by this LOX precedes the hydrolysis of the ester bonds. We analyzed the expression and intracellular location of this particular LOX form in leaves and seeds of tobacco (Nicotiana tabacum L.) transformed with one construct coding for cucumber lipid-body LOX and one construct coding for cucumber LOX fused with a hemagglutinin epitope. In both tissues, the amount of lipid-body LOX was clearly detectable. Biochemical analysis revealed that in mature seeds the foreign LOX was targeted to lipid bodies, and the preferred location of the LOX on lipid bodies was verified by immunofluorescence microscopy. Cells of the endosperm and of the embryo exhibited fluorescence based on the immunodecoration of LOX protein whereas very weak fluorescent label was visible in seeds of untransformed control plants. Further cytochemical analysis of transformed plants showed that the LOX protein accumulated in the cytoplasm when green leaves lacking lipid bodies were analyzed. Increased LOX activity was shown in young leaves of transformed plants by an increase in the amounts of endogenous (2E)-hexenal and jasmonic acid.

Aldehydes↗
PubMed1987

Lipid shape as a determinant of lipid composition in Clostridium butyricum. The effects of incorporation of various fatty acids on the ratios of the major ether lipids.

The lipid composition of Clostridium butyricum is strongly influenced by the aliphatic chain compositions of the membrane lipids. Growth on cis-monounsaturated fatty acids in the absence of biotin was shown to affect the relative proportions of phosphatidylethanolamine, plasmenylethanolamine, and the glycerol acetal of plasmenylethanolamine most strongly, with smaller effects on the acidic lipids, phosphatidylglycerol and cardiolipin. The ratio of the glycerol acetal of plasmenylethanolamine to total phosphatidylethanolamine in cells grown on a series of fatty acids is shown to decrease in the following order; cis-vaccenic acid greater than or equal to oleic acid = C19-cyclopropane fatty acid greater than linoleic acid greater than petroselinic acid greater than elaidic acid greater than 14-methylhexadecanoic acid (anteiso-C17) greater than 12-methyltridecanoic acid (iso-C14). All fatty acids were extensively incorporated into the lipid acyl, alkenyl, and alkyl chains. There was considerable chain-elongation of the iso-C14 to iso-C16. The results are consistent with the hypothesis that the membrane lipid composition is strongly influenced by lipid shape and that the observed changes in lipid composition serve to stabilize the bilayer arrangement of the cell membrane.

Clostridium↗
PubMed2001

The rate of lipid transfer during fusion depends on the structure of fluorescent lipid probes: a new chain-labeled lipid transfer probe pair.

A number of fluorescent probes have been used to follow membrane fusion events, particularly intermixing of lipids. None of them is ideal. The most popular pair of probes is NBD-PE and Rh-PE, in which the fluorescent groups are attached to the lipid headgroups, making them sensitive to changes in the surrounding medium. Here we present a new assay for monitoring lipid transfer during membrane fusion using the acyl chain tagged fluorescent probes BODIPY500-PC and BODIPY530-PE. Like the NBD-PE/Rh-PE assay, this assay is based on fluorescence resonance energy transfer (FRET) between the donor, BODIPY500, and the acceptor, BODIPY530. The magnitude of FRET is sensitive to the probe surface concentration, allowing one to detect movement of probes from labeled to unlabeled vesicles during fusion. The high quantum yield of fluorescence, high efficiency of FRET (R(o) is estimated to be approximately 60 A), photostability, and localization in the central hydrophobic region of a bilayer all make this pair of probes quite promising for detecting fusion. We have compared this and two other lipid mixing assays for their abilities to detect the initial events of poly(ethylene glycol) (PEG)-mediated fusion of small unilamellar vesicles (SUVs). We found that the BODIPY500/530 assay showed lipid transfer rates consistent with those obtained using the DPHpPC self-quenching assay, while lipid mixing rates measured with the NBD-PE/Rh-PE RET assay were significantly slower. We speculate that the bulky labeled headgroups of NBD-PE and especially Rh-PE molecules hamper movement of probes through the stalk between fusing vesicles, and thus reduce the apparent rate of lipid mixing.

Boron Compounds↗
PubMed1995

Induction by estrogens of lipid peroxidation and lipid peroxide-derived malonaldehyde-DNA adducts in male Syrian hamsters: role of lipid peroxidation in estrogen-induced kidney carcinogenesis.

Estrogen-induced kidney carcinogenesis in male Syrian hamsters has previously been postulated to be mediated by free radicals generated by redox cycling of catecholestrogen metabolites. As part of our examination of this hypothesis, we have studied the induction of lipid peroxidation and lipid peroxide-derived malondialdehyde (MDA)-DNA adducts in kidney and liver of hamsters treated with single injections of diethylstilbestrol (DES) or with estradiol (E2) implants for various lengths of time. Treatment of hamsters with 50 and 100 mg/kg DES increased concentrations of both lipid hydroperoxides and of MDA-DNA adducts. In hamsters treated with E2 implants for up to 50 days, lipid peroxide levels in liver were double control values 3 h after hormone implantation, and then decreased to plateau values of 30% over controls. Those in kidney rose to 2- to 3-fold above controls 3 days after hormone implantation and then decreased to plateau values of 51% above controls. MDA-DNA adduct levels were two or three times higher than those of controls in liver and kidney of hamsters treated with hormone implants for 3 and 7 days. Renal lipid peroxide concentrations were raised by chronic treatment with E2, but not by weakly carcinogenic estrogens ethinylestradiol or 2-fluoroestradiol. In contrast, MDA-DNA adduct levels were raised by all three steroidal estrogens 3 days after estrogen implantation. The increases in lipid peroxides and in MDA-DNA adducts in estrogen-treated hamsters support a mechanism of carcinogenesis by free radical generation via redox cycling of catcholestrogen metabolites. Lipid peroxides are postulated to play a dual role in estrogen-induced carcinogenesis, (i) as cofactors for cytochrome P450-mediated formation of catecholestrogen metabolites and their redox cycling, and (ii) as precursors of MDA, a DNA adduct-forming endogenous electrophile.

Animals↗
PubMed2004

Lipids partition caveolin-1 from ER membranes into lipid droplets: updating the model of lipid droplet biogenesis.

Caveolin-1, a putative mediator of intracellular cholesterol transport, is generally assumed to be integrated into the cytoplasmic leaflets of all cellular membranes. Lipid droplets form by budding at the endoplasmic reticulum (ER), and caveolin-1 is thought to be transferred to the droplet surface along with the cytoplasmic leaflet of ER membranes and not to enter the droplet core. We explored how caveolin-1 accesses lipid droplets from the ER by localizing caveolin-1 in ER membranes and in lipid droplets in cultured smooth muscle cells using freeze-fracture immunocytochemistry. We detected caveolin-1 in endoplasmic leaflets of ER membranes but never in cytoplasmic leaflets. Caveolin-1 was also present in lipid droplet cores. These findings are incompatible with the current hypothesis of lipid droplet biogenesis. We suggest that the inherent high affinity of caveolin-1 for neutral lipids causes caveolin-1 molecules to be extracted from the endoplasmic leaflets of ER membranes and to be transferred into the droplet core by inundating lipids during droplet formation.

Aorta↗
PubMed1984

Effects of dietary lipids on behaviour, lipid biosynthesis and lipid composition, in rat platelets.

Rats of either sex were fed for 18 and 34 weeks respectively diets containing 40% (by weight) lipids with polyunsaturated fatty acids representing 1.34% or 13.2% of total calories. Platelet reactivity to thrombin, platelet fatty acid composition and incorporation of [14C]acetate into platelet lipids were investigated. Diets rich in saturated fatty acids markedly increased platelet sensitivity to thrombin. The concentration of 20:3 and 22:3 of the (n - 9) series and of 20:3 and 22:5 of the (n - 6) series were increased at the expense of 18:2 and 22:4 of the (n - 6) family in platelet lipids. 20:4 (n - 6) was unchanged. The fatty acid changes were more pronounced in male rats and after 34 weeks. [14C]Acetate incorporation into total platelet lipids and particularly into choline phosphoglycerides and ceramides was lower in animals fed saturated fats. This diet reduced the synthesis of 16:0 and of 22:4(n - 6) in platelet total fatty acids, while that of 22:3(n - 9) was markedly enhanced. This study showed that long-term feeding of high-saturated-low-polyunsaturated fat diets in rats induced marked changes in platelet lipid synthesis and composition, in both sexes. The lipid synthesis modification appears to be more pronounced in males than in females. The changes in the fatty acids 20:3(n - 9), 22:3(n - 9) and 22:4(n - 6) appeared to be closely related to platelet behaviour. The balance between the content and synthesis of these last fatty acids might be of significance for the effect of diet on thrombogenesis.

Acetates↗
PubMed1990

Age-related changes of lipid fractions and total fatty acids in liver lipids and heart lipids of female and male rats aged 37-1200 days (liver) and 331-1200 days (heart).

1. Total lipids and the lipid fractions cholesterol ester, triacylglycerol, free cholesterol, free fatty acids and phospholipids, as well as the fatty acid patterns of total lipids, were measured in liver homogenates of female and male rats (Wistar SPF, strain Hannover) aged 37-1213 days. 2. The same parameters were measured in the apex of the heart in female and male rats aged 331-1213 days. 3. All parameters were monitored every 49th day. Five female and five male animals were used in each experiment. 4. The lipid fractions in liver showed a positive linear regression vs age, whereas all lipids in rat heart showed a negative regression vs age in both sexes. 5. The significance of regression vs age of fatty acids was much less than that in the lipid fractions of liver and heart of these animals.

Aging↗
PubMed1979

Plasma lipid distributions in selected North American populations: the Lipid Research Clinics Program Prevalence Study. The Lipid Research Clinics Program Epidemiology Committee.

Cross-sectional age- and sex-specific plasma lipid distributions (means, medians and selected percentiles) are given for 48,431 white participants in visit 1 of the Lipid Research Clinics (LRC) Prevalence Study. This study consisted of two visits in which 10 LRCs screened participants selected from well-defined North American target populations that included a broad range of sociodemographic subgroups. These data confirm findings from earlier studies in developed countries, showing age-related differences in plasma lipid levels. However, for overall distributions, the LRC data showed slightly lower cholesterol and markedly higher triglyceride values than those previously reported for North America. Some variation in plasma lipid values was evident among the clinic populations. The large number of participants within most subgroups permitted a variety of analytic and comparative studies. For example, data from the large pediatric population revealed a drop in plasma cholesterol levels in adolescent males and females. Males aged 20--50 years had higher cholesterol levels than females in the same age group, and higher triglyceride levels between ages 20--70 years. Numbers were also sufficient for meaningful comparisons between lipid distributions of females who were taking sex hormones and those who were not: In females taking sex hormones, cholesterol and triglyceride levels were higher for subjects younger than 45 years, but slightly lower after age 45, than lipid levels in females not taking hormones.

Adolescent↗