A study on cholesterol-cholesteryl ester metabolic homeostasis and drug intervention in hyperlipidemic hamsters using UHPLC-MS/MS

Hyperlipidemia is a global metabolic disorder characterized by dysregulation of lipid metabolism. This dysregulation is closely associated with the altered homeostasis of cholesterol-cholesteryl ester (CE) metabolism in systemic circulation, and some organs. Additionally, the relationship between oxidized cholesteryl ester (oxCE) and the disease has also gained attention. Currently, there is a lack of comprehensive research on the alterations in cholesterol-CE metabolism in the context of hyperlipidemia, as well as the characteristics of lipid-lowering agents in regulating this metabolic state. Therefore, 40 oxCEs were identified in the hamster liver sample, and novel ultrahigh performance liquid chromatography-tandem mass spectrometry (UHPLC-MS/MS) methods were established for simultaneous analysis of cholesterol, 57 CEs, and 40 oxCEs in the serum, liver, adipose tissue, and intestine of hyperlipidemic hamsters. This study investigated the metabolic alterations between cholesterol-CE/oxCE in hyperlipidemic hamsters and those treated with lipid-lowering agents, including the Niemann-Pick-C1 like-1 protein (NPC1L1) inhibitor ezetimibe and the acyl coenzyme A: cholesterol acyltransferase (ACAT) inhibitor avasimibe. The study findings demonstrate metabolic disorders in cholesterol-CE/oxCE homeostasis in hyperlipidemic hamsters. Lipid-lowering agent therapy can improve the metabolic dysregulation caused by hyperlipidemia, with distinct characteristics: ezetimibe is more effective in reducing cholesterol, while avasimibe is more effective in reducing CEs/oxCEs. Eight potential biomarkers indicating the dysregulation of cholesterol-CE metabolism caused by hyperlipidemia and its improvement by lipid-lowering agents have been identified in the serum. This study offers new insights into the hyperlipidemia pathophysiology and the mechanisms of lipid-lowering agents from a novel perspective on cholesterol-CE/oxCE metabolic homeostasis.

Single-cell lipidomics with high structural specificity by mass spectrometry

Single-cell analysis is critical to revealing cell-to-cell heterogeneity that would otherwise be lost in ensemble analysis. Detailed lipidome characterization for single cells is still far from mature, especially when considering the highly complex structural diversity of lipids and the limited sample amounts available from a single cell. We report the development of a general strategy enabling single-cell lipidomic analysis with high structural specificity. Cell fixation is applied to retain lipids in the cell during batch treatments prior to single-cell analysis. In addition to tandem mass spectrometry analysis revealing the class and fatty acyl-chain for lipids, batch photochemical derivatization and single-cell droplet treatment are performed to identify the C=C locations and sn-positions of lipids, respectively. Electro-migration combined with droplet-assisted electrospray ionization enables single-cell mass spectrometry analysis with easy operation but high efficiency in sample usage. Four subtypes of human breast cancer cells are correctly classified through quantitative analysis of lipid C=C location or sn-position isomers in ~160 cells. Most importantly, the single-cell deep lipidomics strategy successfully discriminates gefitinib-resistant cells from a population of wild-type human lung cancer cells (HCC827), highlighting its unique capability to promote precision medicine.

Recent development on liquid chromatography-mass spectrometry analysis of oxidized lipids

Polyunsaturated fatty acids (PUFAs) in the cellular membrane can be oxidized by various enzymes or reactive oxygen species (ROS) to form many oxidized lipids. These metabolites are highly bioactive, participating in a variety of physiological and pathophysiological processes. Mass spectrometry (MS), coupled with Liquid Chromatography, has been increasingly recognized as an indispensable tool for the analysis of oxidized lipids due to its excellent sensitivity and selectivity. We will give an update on the understanding of the molecular mechanisms related to generation of various oxidized lipids and recent progress on the development of LC-MS in the detection of these bioactive lipids derived from fatty acids, cholesterol esters, and phospholipids. The purpose of this review is to provide an overview of the formation mechanisms and technological advances in LC-MS for the study of oxidized lipids in human diseases, and to shed new light on the potential of using oxidized lipids as biomarkers and mechanistic clues of pathogenesis related to lipid metabolism. The key technical problems associated with analysis of oxidized lipids and challenges in the field will also discussed.

Alterations in lipid metabolism of spinal cord linked to amyotrophic lateral sclerosis

Amyotrophic lateral sclerosis (ALS) is characterized by progressive loss of upper and lower motor neurons leading to muscle paralysis and death. While a link between dysregulated lipid metabolism and ALS has been proposed, lipidome alterations involved in disease progression are still understudied. Using a rodent model of ALS overexpressing mutant human Cu/Zn-superoxide dismutase gene (SOD1-G93A), we performed a comparative lipidomic analysis in motor cortex and spinal cord tissues of SOD1-G93A and WT rats at asymptomatic (~70 days) and symptomatic stages (~120 days). Interestingly, lipidome alterations in motor cortex were mostly related to age than ALS. In contrast, drastic changes were observed in spinal cord of SOD1-G93A 120d group, including decreased levels of cardiolipin and a 6-fold increase in several cholesteryl esters linked to polyunsaturated fatty acids. Consistent with previous studies, our findings suggest abnormal mitochondria in motor neurons and lipid droplets accumulation in aberrant astrocytes. Although the mechanism leading to cholesteryl esters accumulation remains to be established, we postulate a hypothetical model based on neuroprotection of polyunsaturated fatty acids into lipid droplets in response to increased oxidative stress. Implicated in the pathology of other neurodegenerative diseases, cholesteryl esters appear as attractive targets for further investigations.

Raman spectroscopy imaging reveals interplay between atherosclerosis and medial calcification in the human aorta

Medial calcification in the human aorta accumulates during aging and is known to be aggravated in several diseases. Atherosclerosis, another major cause of cardiovascular calcification, shares some common aggravators. However, the mechanisms of cardiovascular calcification remain poorly understood. To elucidate the relationship between medial aortic calcification and atherosclerosis, we characterized the cross-sectional distributions of the predominant minerals in aortic tissue, apatite and whitlockite, and the associated extracellular matrix. We also compared the cellular changes between atherosclerotic and nonatherosclerotic human aortic tissues. This was achieved through the development of Raman spectroscopy imaging methods that adapted algorithms to distinguish between the major biomolecules present within these tissues. We present a relationship between apatite, cholesterol, and triglyceride in atherosclerosis, with the relative amount of all molecules concurrently increased in the atherosclerotic plaque. Further, the increase in apatite was disproportionately large in relation to whitlockite in the aortic media directly underlying a plaque, indicating that apatite is more pathologically significant in atherosclerosis-aggravated medial calcification. We also discovered a reduction of β-carotene in the whole aortic intima, including a plaque in atherosclerotic aortic tissues compared to nonatherosclerotic tissues. This unprecedented biomolecular characterization of the aortic tissue furthers our understanding of pathological and physiological cardiovascular calcification events in humans.

Human fetal intestinal epithelial cells metabolize and incorporate branched chain fatty acids in a structure specific manner

BACKGROUND

Branched chain fatty acids (BCFA) are constituents of gastrointestinal (GI) tract in healthy newborn human infants, reduce the incidence of necrotizing enterocolitis (NEC) in a neonatal rat model, and are incorporated into small intestine cellular lipids in vivo. We hypothesize that BCFA are taken up, metabolized and incorporated into human fetal cells in vitro.

METHODS

Human H4 cells, a fetal non-transformed primary small intestine cell line, were incubated with albumin-bound non-esterified anteiso-17:0, iso-16:0, iso-18:0 and/or iso-20:0, and FA profiles in lipid fractions were analyzed.

RESULTS

All BCFA were readily incorporated as major constituents of cellular lipids. Anteiso-17:0 was preferentially taken up, and was most effective among BCFA tested in displacing normal (n-) FA. The iso BCFA were preferred in reverse order of chain length, with iso-20:0 appearing at lowest level. BCFA incorporation in phospholipids (PL) followed the same order of preference, accumulating 42% of FA as BCFA with no overt morphological signs of cell death. Though cholesterol esters (CE) are at low cellular concentration among lipid classes examined, CE had the greatest affinity for BCFA, accumulating 65% of FA as BCFA. BCFA most effectively displaced lower saturated FA. Iso-16:0, iso-18:0 and anteiso-17:0 were both elongated and chain shortened by ±C2. Iso-20:0 was chain shortened to iso-18:0 and iso-16:0 but not elongated.

CONCLUSIONS

Nontransformed human fetal intestinal epithelial cells incorporate high levels of BCFA when they are available and metabolize them in a structure specific manner. These findings imply that specific pathways for handling BCFA are present in the lumen-facing cells of the human fetal GI tract that is exposed to vernix-derived BCFA in late gestation.

High-energy collision-induced dissociation by MALDI TOF/TOF causes charge-remote fragmentation of steroid sulfates

A method for structural elucidation of biomolecules dating to the 1980s utilized high-energy collisions (~10 keV, laboratory frame) that induced charge-remote fragmentations (CRF), a class of fragmentations particularly informative for lipids, steroids, surfactants, and peptides. Unfortunately, the capability for high-energy activation has largely disappeared with the demise of magnetic sector instruments. With the latest designs of tandem time-of-flight mass spectrometers (TOF/TOF), however, this capability is now being restored to coincide with the renewed interest in metabolites and lipids, including steroid-sulfates and other steroid metabolites. For these metabolites, structure determinations are required at concentration levels below that appropriate for NMR. To meet this need, we explored CRF with TOF/TOF mass spectrometry for two groups of steroid sulfates, 3-sulfates and 21-sulfates. We demonstrated that the current generation of MALDI TOF/TOF instruments can generate charge-remote fragmentations for these materials. The resulting collision-induced dissociation (CID) spectra are useful for positional isomer differentiation and very often allow the complete structure determination of the steroid. We also propose a new nomenclature that directly indicates the cleavage sites on the steroid ring with carbon numbers.

Identification of novel regulatory cholesterol metabolite, 5-cholesten, 3β,25-diol, disulfate

Oxysterol sulfation plays an important role in regulation of lipid metabolism and inflammatory responses. In the present study, we report the discovery of a novel regulatory sulfated oxysterol in nuclei of primary rat hepatocytes after overexpression of the gene encoding mitochondrial cholesterol delivery protein (StarD1). Forty-eight hours after infection of the hepatocytes with recombinant StarD1 adenovirus, a water-soluble oxysterol product was isolated and purified by chemical extraction and reverse-phase HPLC. Tandem mass spectrometry analysis identified the oxysterol as 5-cholesten-3β, 25-diol, disulfate (25HCDS), and confirmed the structure by comparing with a chemically synthesized compound. Administration of 25HCDS to human THP-1-derived macrophages or HepG2 cells significantly inhibited cholesterol synthesis and markedly decreased lipid levels in vivo in NAFLD mouse models. RT-PCR showed that 25HCDS significantly decreased SREBP-1/2 activities by suppressing expression of their responding genes, including ACC, FAS, and HMG-CoA reductase. Analysis of lipid profiles in the liver tissues showed that administration of 25HCDS significantly decreased cholesterol, free fatty acids, and triglycerides by 30, 25, and 20%, respectively. The results suggest that 25HCDS inhibits lipid biosynthesis via blocking SREBP signaling. We conclude that 25HCDS is a potent regulator of lipid metabolism and propose its biosynthetic pathway.

Rapid approach to analyze biochemical variation in rat organs by ATR FTIR spectroscopy

ATR FTIR spectra were collected from rat tissue homogenates (myocardium, brain, liver, lung, intestine, and kidney) to analyze their biochemical content. Based on the second derivative of an average spectral profile it was possible to assign bands e.g. to triglycerides and cholesterol esters, proteins, phosphate macromolecules (DNA, RNA, phospholipids, phosphorylated proteins) and others (glycogen, lactate). Peaks in the region of 1600-1700 cm(-1) related to amide I mode revealed the secondary structure of proteins. The collected spectra do not characterize morphological structure of the investigated tissues but show their different composition. The comparison of spectral information gathered from FTIR spectra of the homogenates and those obtained previously from FTIR imaging of the tissue sections implicates that the presented here approach can be successfully employed in the investigations of biochemical variation in animal tissues. Moreover, it can be used in the pharmacological and pharmacokinetic studies to correlate the overall biochemical status of the tissue with the pathological changes it has undergone.

The spectrophotometric sulfo-phospho-vanillin assessment of total lipids in human meibomian gland secretions

Human meibomian gland secretions (meibum) are the major lipid component of the human preocular tear film. The predominant lipid classes found in meibum include waxes (WE), cholesteryl esters (CE), and varying amounts of cholesterol (Chl). The classical sulfo-phospho-vanillin assay (SPVA), adapted for a microplate reader, was used to quantitate lipids in meibum. To account for varying reactivities of different lipids in SPVA, a model meibomian lipid mixture (MMx) that approximated the WE/CE/Chl composition of meibum was developed and used to quantitate meibomian lipids. The overall SPV responses of MMx and meibum were found to be close, with similar intermediate and final reaction products for both. Saturated WE that had not been expected to be reactive were found to be SPV-positive. A reaction mechanism for these compounds in SPVA which involves the formation of alkenyl ethers is proposed and discussed. Tested proteins were non-reactive in SPVA. Thus, by comparing the results of gravimetric analyses of meibum samples with the results of a properly calibrated SPVA, it was estimated that the SPV-reactive lipid content of dry meibum in tested samples was about 78 % (w/w). The SPV method can also be adopted for analyzing other types of complex lipids secretions, such as sebum, as well as whole lipid extracts from other lipid-enriched organs and tissues, if proper standards are chosen.

Macrophage Elovl6 deficiency ameliorates foam cell formation and reduces atherosclerosis in low-density lipoprotein receptor-deficient mice

OBJECTIVE

Elovl6, a long-chain fatty acid elongase, is a rate-limiting enzyme that elongates saturated and monounsaturated fatty acids and has been shown to be related to obesity-induced insulin resistance via modification of fatty acid composition. In this study, we investigated the roles of Elovl6 in foam cell formation in macrophages and atherosclerosis in mice.

METHODS AND RESULTS

To investigate the roles of Elovl6 in macrophages in the progression of atherosclerosis, we transplanted bone marrow cells of wild-type or Elovl6(-/-) mice into irradiated LDL-R(-/-) mice that were fed a western diet. Aortic atherosclerotic lesion areas and infiltration of macrophages were significantly smaller in Elovl6(-/-) bone marrow cells-transplanted LDL-R(-/-) mice than in wild-type. Accumulation of esterified cholesterol on exposure to acetylated-LDL was less severe in peritoneal macrophages from Elovl6(-/-) mice than those from wild-type. Cholesterol efflux and expression of cholesterol efflux transporters were increased in Elovl6(-/-) macrophages, although no difference in uptake of acetylated-LDL was found between the two groups. On analysis of fatty acid composition of the esterified cholesterol fraction in macrophages, n-6 polyunsaturated fatty acids were decreased by absence of Elovl6.

CONCLUSIONS

These findings suggest that Elovl6 in macrophages may contribute to foam cell formation and progression of atherosclerosis.

Linear Response Equilibrium versus echo-planar encoding for fast high-spatial resolution 3D chemical shift imaging

In this work Linear Response Equilibrium (LRE) and Echo-planar spectroscopic imaging (EPSI) are compared in terms of sensitivity per unit time and power deposition. In addition an extended dual repetition time scheme to generate broad stopbands for improved inherent water suppression in LRE is presented. The feasibility of LRE and EPSI for assessing cholesterol esters in human carotid plaques with high spatial resolution of 1.95×1.15×1.15 mm(3) on a clinical 3T MR system is demonstrated. In simulations and phantom experiments it is shown that LRE has comparable but lower sensitivity per unit time relative to EPSI despite stronger signal generated. This relates to the lower sampling efficiency in LRE relative to EPSI as a result of limited gradient performance on clinical MR systems. At the same time, power deposition of LRE is significantly reduced compared to EPSI making it an interesting niche application for in vivo high field spectroscopic imaging of metabolites within a limited bandwidth.

Quantification and characterization of aortic cholesterol in rabbits fed a high-cholesterol diet

Determination of fat percentage of aortic intimal area stained by Sudan III is useful as an index of atherosclerosis in the rabbit animal model. However, the determination of sudanophilic area of the thoracic aorta is two-dimensional and does not measure the third dimension of depth. The objective of the present study was to quantify and characterize aortic lipids using the gas-liquid chromatographic (GLC) technique and to determine whether elevated measurements of total cholesterol and cholesteryl esters was correlated with increased measurements of sudanophilic area staining of the thoracic aorta in rabbits given either a normal chow or a 1% cholesterol diet. The GLC results showed that there was a mean accumulation of 10.9 mg of cholesterol per gram of aortic tissue in the rabbits given a cholesterol diet (mean sudanophilic area of 23.8%). In contrast, rabbits on a normal chow diet had only a deposition of 0.58 mg of cholesterol per gram of the aortic tissue diet (mean sudanophilic area of 1.4%). The present study suggests that quantification of the aortic lipids can be performed by using GLC techniques and that it could be used as an alternative to the measurement of sudanophilic area when assessing the severity of atherosclerosis.

Characterization of foam cells in experimental atherosclerosis

A series of biochemical and morphological studies has focused on the properties and origins of lipid laden foam cells in experimentally induced atherosclerosis in rabbits. Lipids inclusions present in these cells occupy half or more of the cytoplasmic volume and are of two kinds: cytoplasmic lipid droplets composed predominantly of cholesteryl esters and lysosomes in which substantial quantities of free cholesterol have accumulated. The foam cells exhibit some properties of macrophages but not others. They possess high levels of acid hydrolases and catalase and Fc membrane receptors can be detected on their surface. Only about one third of the foam cells, however, exhibit C3 receptors and few if any of the cells appear to contain or secrete lysozyme.

Development of atherosclerotic plaques

Atherosclerosis is a multifactorial disease. A unified model for the lesion development reveals many connections between the response-to-injury hypothesis and the lipid hypothesis. Various cellular uptake mechanisms for native and modified lipoproteins are discussed with respect to foam cell formation and lesion development. The role of arterial smooth muscle cells in atherogenesis is emphasized. Preliminary results of biochemical analyses from the coronary arteries of accidentally died Finnish children and adults reveal that the accumulation of plasma-derived cholesteryl esters in young children began early in childhood, long before the vessels became macroscopically affected and changes in arterial glycosaminoglycans correlated significantly with the accumulation of cholesteryl esters.

Studies on high density lipoproteins in fish eye disease

Serum high density lipoproteins (HDL) were isolated by preparative ultracentrifugation from two patients with fish eye disease (FED). Compared to HDL from control subjects the HDL particles of FED were characterized by their abnormally small size and a relative enrichment with polar lipids. No qualitative abnormalities of the HDL apolipoproteins were revealed upon polyacrylamide disc gel electrophoresis or isoelectric focusing. The plasma pool of apolipoprotein A was reduced by 90%.

Docosahexaenoic acid is a substrate for ACAT1 and inhibits cholesteryl ester formation from oleic acid in MCF-10A cells

MCF-10A breast epithelial cells treated with docosahexaenoic acid (DHA) or oleic acid (OA) accumulated cytoplasmic lipid droplets containing both triacylglycerol and cholesteryl esters (CE). Interestingly, total CE mass was reduced in cells treated with DHA compared to cells treated with OA, and the CEs were rich in n-3 fatty acids. Thus, we hypothesized that DHA may be, in addition to a substrate, an inhibitor of cholesterol esterification in MCF-10A cells. We determined that the primary isoform of acyl-CoA: cholesterol acyltransferase expressed in MCF-10A cells is ACAT1. We investigated CE formation with DHA, OA, and the combination in intact cells and isolated microsomes. In both cells and microsomes, the rate of CE formation was faster and more CE was formed with OA compared to DHA. DHA substantially reduced CE formation when given in combination with OA. These data suggest for the first time that DHA can act as a substrate for ACAT1. In the manner of a poor substrate, DHA also inhibited the activity of ACAT1, a universally expressed enzyme involved in intracellular cholesterol homeostasis, in a cell type that does not secrete lipids or express ACAT2.

Accumulation of cholesterol in the lesions of focal segmental glomerulosclerosis

Intraglomerular deposition of low-density lipoprotein (LDL) and oxidized LDL has been described in various human glomerular diseases. Yet it is not clear whether esterified cholesterol (EC) and unesterified cholesterol (UC) carried in LDL are mobilized from deposited LDL particles or accumulate in the diseased human glomeruli, particularly in the segmentally sclerotic lesions. To address this issue, frozen sections of renal biopsies were first immunostained to localize apolipoprotein B (apo B) and then oil red O (ORO) stained to colocalize neutral lipids. By using 124 ORO-positive biopsies and nine ORO-negative ones, UC was visualized directly with filipin staining, and EC was visualized after its enzymatic hydrolysis and staining with filipin. Seventy-seven biopsies (58%) showed filipin staining of accumulated EC and/or UC in the glomeruli. Of these, 11 showed heavy filipin staining for both EC and UC in the segmentally sclerotic lesions. In a group with UC deposits in the sclerotic segments, the percentage of the glomeruli affected by sclerosis and the intensity of filipin fluorescence for UC were significantly higher than biopsies with only mesangial UC deposits. Most filipin-positive biopsies showed apo B staining mainly in the mesangium. Yet in the sclerotic segments, apo B staining was rarely noted. Accumulated apo B-stained lipoprotein was not coincident with ORO-stained lipid in the diseased glomeruli. These results suggest that both EC and UC accumulate in the sclerotic glomerular segments as the glomerular lesions are advanced, and that these EC and UC appear to be derived from altered LDL with progressive loss of apo B.

NMR spectroscopic identification of cholesterol esters, plasmalogen and phenolic glycolipids as fingerprint markers of human intracranial tuberculomas

Detailed (1)H and (13)C NMR spectroscopy of lipid extracts from 12 human intracranial tuberculomas and two control brain tissue samples was performed to assess the role of lipids in the disease process. One-dimensional and two-dimensional NMR techniques were used to resolve the mixture of lipid components and make resonance assignments. The lipid components that could be identified in tuberculoma lipid extracts and not in control samples were: cholesterol ester, plasmalogen and phenolic glycolipids. It is proposed that the combined occurrence of these lipid components can be used as 'fingerprint markers' for the differentiation of intracranial tuberculoma from healthy brain tissue. Furthermore, phenolic glycolipids present in intracranial tuberculomas may have diagnostic significance in differentiating them from other disease conditions of the central nervous system such as malignant tumors.

Ultrastructural localization of intraneuronal Abeta-peptide in Alzheimer disease brains

Autopsied brain tissue from Alzheimer's disease patients and old non-demented controls was studied after immunocytochemistry with the 4G8 monoclonal antibody that recognizes amyloid-beta peptides. Intraneuronal 4G8-positive reaction product was detected in all of the studied brains. The same brain regions in the Alzheimer's disease samples consistently showed both more immunopositive neurons and more stained reaction product per neuron than those from the non-demented brains. Ultrastructurally, the immunopositive reaction product accumulated in clusters of cytoplasmic elements that had a lipofuscin-like appearance, showed a fibrogranular content and were also closely apposed to lipid droplets located either on their periphery or within them. The most strongly 4G8-immunopositive elements had diffuse limits with their fibrogranular content free in the cytoplasm, whereas elements either without or showing only light immunoreaction had a limiting membrane. All immunopositive neurons displayed a similar pattern of clumping heterochromatin. The hypothetical neurotoxic role of intraneuronal amyloid-beta peptides free in the cytoplasm is discussed as is the possible relationship between the amyloid-beta peptides recognized by the 4G8 antibody and the lipid droplets which would presumably contain esterified cholesterol.

Human stratum corneum lipid organization as observed by atomic force microscopy on Langmuir–Blodgett films

The barrier function of skin ultimately depends on the physical state and structural organisation of the stratum corneum extracellular lipid matrix. Ceramides, cholesterol and a broad distribution of saturated long-chain free fatty acids dominate the stratum corneum lipid composition. Additionally, smaller amounts of cholesterol sulfate and cholesteryl oleate may be present. A key feature determining skin barrier capacity is thought to be whether or not different lipid domains coexist laterally in the stratum corneum extracellular lipid matrix. In this study, the overall tendency for lipid domain formation in different mixtures of extracted human stratum corneum ceramides, cholesterol, free fatty acids, cholesterol sulfate and cholesteryl oleate were studied using atomic force microscopy (AFM) on Langmuir-Blodgett (LB) films on mica. It is shown that the saturated long-chain free fatty acid distribution of human stratum corneum prevents hydrocarbon chain segregation. Further, LB-films of human stratum corneum ceramides express a pattern of connected elongated domains with a granular domain interface. The dominating effect of both cholesterol and cholesterol sulfate is that of increased ceramide domain dispersion. This effect is counteracted by the presence of free fatty acids, which preferentially mix with ceramides and not with cholesterol. Cholesteryl oleate does not mix with other skin lipid components, supporting the hypothesis of an extra-endogenous origin. In the system composed of endogenous human ceramides and cholesterol plus 15 wt% stratum corneum distributed free fatty acids, i.e., the system mimicking most closely the lipid composition of the stratum corneum extracellular space, LB-films on mica express lateral domain formation.

Calculation of serum "total lipid" concentrations for the adjustment of persistent organohalogen toxicant measurements in human samples

Persistent organohalogen toxicants such as 2,3,7,8-tetrachlorodibenzo-p-dioxin or polychlorinated biphenyls measured in human serum are often expressed on a lipid weight basis, most commonly by dividing the toxicants' concentration by the weight of total lipids in the sample. Therefore, the manner in which this lipid adjustment is calculated may influence the final reported result. Gravimetric total lipid assays have been used, but they are time-consuming and sometimes may be ill-defined. Consequently, alternative methods using enzymatic assays have been developed based on summing the individual lipid species measured. Recent reports, however, have suggested that significantly different total lipid results may be obtained when using alternative formulae in a summation approach. In this report, we summarize the results obtained from lipid measurements of nearly 900 samples made as part of a study of a group of older American men (mean age 62 years), and we compare our total lipid estimates obtained by using both our standard and "short" formula (the latter based on total cholesterol and triglycerides only) with results obtained using the recently proposed alternative formulae. Our findings indicate that both our long and short formulae provide similar estimates of serum total lipid concentrations, and that differences observed in lipid estimates when using the newer alternative summation methods may reflect differences in how the term "total lipid" is defined, especially with regard to the need to include the contribution of the weight of the cholesterol ester fatty acids in the calculation.

Consumption of virgin olive oil influences membrane lipid composition and regulates intracellular signaling in elderly adults with type 2 diabetes mellitus

We aimed to define changes in membrane fatty acids and signaling proteins induced by virgin olive oil (VOO) consumption in elderly persons with type 2 diabetes (n = 16) compared to a control group (n = 28). The fatty acid composition was determined by gas chromatography and G-protein subunits and protein kinase C alpha (PKCalpha) by immunoblotting. VOO consumption increased the monounsaturated fatty acid content in phospholipids and cholesterol esters in both groups. In contrast, saturated fatty acids were decreased only in phospholipids. The levels of Galphao, Gbeta, and PKCalpha were significantly lower in diabetics than in controls. However, whereas VOO consumption reduced Galphas, Gbeta, and PKCalpha in both groups, reduction in Galphai was observed only in diabetics. These results indicate that long-term VOO consumption modifies the fatty acid composition of plasma membrane, which influences the association of G proteins and PKCalpha with the lipid bilayer. These combined effects probably account for the positive effects of VOO on glycemic homeostasis.

Knockdown of ACAT-1 reduces amyloidogenic processing of APP

Previous studies have shown that acyl-coenzyme A:cholesterol acyl transferase (ACAT), an enzyme that controls cellular equilibrium between free cholesterol and cholesteryl esters, modulates proteolytic processing of APP in cell-based and animal models of Alzheimer's disease. Here we report that ACAT-1 RNAi reduced cellular ACAT-1 protein by approximately 50% and cholesteryl ester levels by 22% while causing a slight increase in the free cholesterol content of ER membranes. This correlated with reduced proteolytic processing of APP and 40% decrease in Abeta secretion. These data show that even a modest decrease in ACAT activity can have robust suppressive effects on Abeta generation.

Identification of atherosclerotic lipid deposits by diffusion-weighted imaging

OBJECTIVES

The content and distribution of lipids is an important aspect of plaque vulnerability, but lipids are present within a heterogeneous environment, impeding detection by magnetic resonance imaging. Our goal was to achieve accurate detection of mobile lipids by a single magnetic resonance imaging sequence.

METHODS AND RESULTS

Carotid endarectomy specimens (n=23) were imaged ex vivo at a high magnetic field (11.7 T) within 24 hours after surgery. Three contrast-weighted (T1W, T2W, and diffusion-weighted imaging [DWI]) image sequences were acquired and then coregistered with histological preparations for lipids (Oil red O and polarized light microscopy) and fibrous tissue (trichrome). Contrast-to-noise ratios were measured and compared for the 3 contrast weightings. Contrast-to-noise ratio measurement in regions identified as lipid versus fibrous tissue showed greater differences by DWI (4.5+/-0.63 versus 0.64+/-0.08; P<0.05) as compared with T2W (2.83+/-0.36 versus 1.36+/-0.37; P<0.05). We validated the presence and distribution of lipids (mainly cholesteryl esters) by both histology and image-guide spectroscopy. The basis for distinguishing mobile lipid and water inside the plaque was illustrated by diffusion-weighted spectroscopy.

CONCLUSIONS

Biophysical properties of plaque lipids can confer selective identification by DWI, as opposed to standard T1W and T2W imaging sequences. Successful translation of DWI in vivo could identify of features of vulnerable plaque.

Defect in fatty acid esterification of dolichol in Niemann-Pick type C1 mouse livers in vivo

Fatty acid esterification of dolichol and cholesterol in Niemann-Pick type C1 mouse (Balb/c NIH npc1(-/-)) livers was investigated in response to treatment with peroxisomal proliferators. These inducers have hypolipidemic properties and influence the mevalonate pathway and the intracellular transport of the final products of this biosynthetic route. Such inducers are consequently interesting to use in a disease model with defective intracellular transport of lipids. In wild-type mice, the levels of dolichol and cholesterol found as free alcohols were not changed to any great extent upon treatment with the peroxisomal inducers dehydroepiandrosterone, clofibrate and diethylhexylphtalate. In contrast, the amounts of dolichyl esters increased whereas cholesteryl esters decreased by the same treatments. The rate of enzymatic esterification of dolichol in isolated microsomes was accordingly elevated after 5- to 7-day treatments with the efficient peroxisomal proliferators DEHP and PFOA, while the corresponding esterification of cholesterol was decreased. Upon peroxisomal induction in npc1(-/-) mice, the enzymatic dolichol esterification in vitro increased whereas the low concentration of dolichyl esters remained unchanged. The results thus demonstrate that the induction of fatty acid esterification of dolichol in vivo is impaired in npc1(-/-) mouse liver. It is therefore proposed that the intracellular lipid transport defect in npc1(-/-) mouse liver disables either dolichol and/or the fatty acid from reaching the site of esterification in vivo. This proposal was strengthened by the finding that the amount of dolichol was decreased in an isolated Golgi fraction from npc1(-/-) mice.

Detection of cholesteryl ester hydroperoxide isomers using gas chromatography–mass spectrometry combined with thin-layer chromatography blotting

Oxidative modification of low-density lipoprotein (LDL) has been implicated in the pathogenesis of atherosclerosis. During the oxidation of LDL, cholesteryl esters, the major lipid components in LDL, are oxidized to cholesteryl ester hydroperoxides (CEOOH). The isomers of CEOOH may reflect the reactive species that initiate the peroxidation reaction. In the current study, a novel analytical method for the determination of CEOOH isomers, especially cholesteryl linoleate hydroperoxide isomers, was developed using the combination of two chromatographic techniques: (i) thin-layer chromatography blotting with diphenyl-1-pyrenylphosphine (DPPP) fluorescent detection (DPPP-TLC blotting) and (ii) gas chromatography-electron ionization-mass spectrometry (GC-EI-MS). CEOOH was applied to DPPP-TLC blotting, the obtained DPPP-derived fluorescent spots containing cholesteryl ester hydroxides were extracted and derivatized (hydrogenation, transmethylation, and trimethylsilylation), and the formed methyl ester/trimethylsilylether derivatives of hydroxyoctadecenoic acid were then analyzed by GC-EI-MS. The CEOOH isomers were determined by selected ion monitoring of isomer-specific fragment ions originated from the alpha-cleavage of the trimethylsilyloxyl group. Using these two chromatographic techniques, we were able to detect isomeric CEOOH in the oxidized human LDL. Our results indicated that GC-EI-MS analysis combined with DPPP-TLC blot is a specific method for analyzing cholesteryl ester hydroperoxide isomers in biological samples such as oxidized LDL.

Dithiobissuccinimidyl propionate self assembled monolayer based cholesterol biosensor

A dithiobissuccinimidyl propionate (DTSP) self-assembled monolayer (SAM) prepared onto a gold (Au) surface has been utilized for covalent immobilization of cholesterol oxidase (ChOx) and cholesterol esterase (ChEt). These ChOx-ChEt/DTSP/Au bio-electrodes have been characterized using electrochemical impedance and cyclic voltammetric (CV) techniques, respectively. Differential pulse voltammetry (DPV) has been used for enzymatic assay of immobilized ChOx and ChEt onto the DTSP modified gold surface as a function of cholesterol oleate concentration. The response measurement conducted on ChOx-ChEt/DTSP/Au bio-electrode reveal the value of Michaelis-Menten constant (Km) as 0.95 mM suggesting enhanced affinity of enzymes (ChOx and ChEt). The ChOx-ChEt/DTSP/Au bio-electrodes show linearity in range of 50 to 400 mg dl(-1) of cholesterol oleate and the shelf-life of more than 50 days when stored at 4 degrees C. This biosensing electrode shows correlation coefficient of 0.9973 and standard deviation of regression as 0.859 microA.

Chlamydia pneumoniae--induced macrophage foam cell formation is mediated by Toll-like receptor 2

Chlamydia pneumoniae induces macrophage foam cell formation, a hallmark of early atherosclerosis, in the presence of low-density lipoprotein (LDL). This study examined the role that Toll-like receptor 2 (TLR2) and TLR4 may play in pathogen-induced foam cell formation. Murine macrophage RAW 264.7 cells either infected with C. pneumoniae or treated with the TLR4 ligand E. coli lipopolysaccharide (LPS) or the TLR2 ligand Pam(3)-Cys-Ala-Gly-OH (Pam) became Oil Red O-stained foam cells and showed increased cholesteryl ester (CE) content when cocultured with LDL. In macrophages from TLR2(-/-) mice, foam cells were induced by Escherichia coli LPS but not by C. pneumoniae or Pam. Conversely, C. pneumoniae or Pam, but not E. coli LPS, induced foam cells in the TLR4-deficient GG2EE macrophage cell line, suggesting that C. pneumoniae elicits foam cell formation predominantly via TLR2. Enhancing cholesterol efflux using the liver X receptor (LXR) agonist GW3965 significantly decreased the CE content of cells exposed to each of the three TLR ligands (C. pneumoniae, Pam, and E. coli LPS). Overall, our results suggest that activation of the LXR signaling pathway may affect potentially atherogenic processes modulated by the TLR ligands.

Factor analysis of fatty acids in serum lipids as a measure of dietary fat quality in relation to the metabolic syndrome in men

BACKGROUND

A specific fatty acid (FA) composition in plasma lipid esters is related to the metabolic syndrome (MetS) and may influence the development of the MetS.

OBJECTIVE

The objective was to define and study FA factors as measures of dietary fat quality and endogenous FA metabolism in relation to MetS.

DESIGN

Principal factor analysis was performed to define specific FA factors in men participating in a population-based cohort study-the Uppsala Longitudinal Study of Adult Men. The factors were generated at ages 50 (n = 2009) and 70 (n = 576) y, and relations between FA factors and MetS (National Cholesterol Education Program) were studied in cross-sectional and prospective (20 y) analyses.

RESULTS

The factor analysis generated 3 major FA factors: a low-linoleic acid (LA) factor, a dietary saturated FA factor, and an n-3 polyunsaturated FA (PUFA) factor. All factors differed between those subjects with MetS (n = 281 of 2009) and those without MetS at age 50 y; only the low-LA factor differed at age 70 y, which suggests an association between MetS and fat quality. The low-LA factor (odds ratio: 1.51; 95% CI: 1.28, 1.79; P < 0.0001) and the n-3 PUFA factor (0.76; 0.64, 0.90; P < 0.001) predicted MetS development over 20 y, independent of smoking habits, physical activity, and BMI.

CONCLUSIONS

The generated FA factors, which presumably represent dietary fat quality and endogenous FA metabolism, may be important in the development of MetS. This finding supports current dietary recommendations to increase PUFA intakes and restrict saturated FA intakes.

Effects of Japanese torreya (Torreya nucifera) seed oil on lipid metabolism in rats

OBJECTIVE

We investigated effects of Japanese torreya (Torreya nucifera) seed oil containing non-methylene-interrupted polyunsaturated fatty acid of all-cis-5,11,14-eicosatrienoic acid (sciadonic acid) on rat lipid metabolism.

METHODS

Male Sprague-Dawley rats were fed the experimental diets based on AIN-93 containing 10% corn, soybean, or torreya oil for 4 wk. Blood and tissues were recovered from each rat, and concentrations of triacylglycerol, cholesterol, and phospholipid in plasma and liver were determined by enzymatic assays. Moreover, fatty acid composition was analyzed for triacylglycerol, cholesterol ester, and phospholipid isolated from plasma and liver lipids by gas liquid chromatography.

RESULTS

Plasma triacylglycerol level in rats fed torreya oil was lower than that in rats fed corn or soybean oil, although there were no significant differences in plasma cholesterol and phospholipid levels in all rats. Liver triacylglycerol level was also lower in rats fed torreya oil, whereas liver cholesterol and phospholipid levers were same for all rats. omega-3 Polyunsaturated fatty acids such as 22:6 (omega-3) were lower in plasma and liver lipids of torreya and corn oil groups, whereas omega-6 polyunsaturated fatty acids such as 22:4 (omega-6) and 22:5 (omega-6) were higher. Considerable amounts of sciadonic acid were detected in cholesterol ester, triacylglycerol, and phospholipid in plasma and liver of rats fed torreya oil.

CONCLUSION

These observations suggest that torreya seed oil can modify lipid metabolism, resulting in lower triacylglycerol levels in plasma and liver of rats.

Di-(2-ethylhexyl)-phthalate affects lipid profiling in fetal rat brain upon maternal exposure

Lipids, especially essential fatty acids (EFAs), play critical roles in guiding proper fetal development. Exposure to xenobiotics that may alter the fetal supply of EFAs/lipids could potentially lead to fetotoxicity. In this study, we investigated the effects of the peroxisome proliferator chemical, di-(2-ethylhexyl)-phthalate (DEHP), on the lipid metabolomic profile of the rat fetal brain upon maternal exposure during gestation. Female Sprague-Dawley rats were orally gavaged with a control vehicle or DEHP (1,500 mg/kg) from gestational day (GD) 0 to GD 19 and fetal brain tissue was isolated at GD 20. The concentrations of 11 lipid classes [free fatty acid, free cholesterol (FC), cholesterol ester (CE), diacylglycerol (DAG), triacylglyceride, phosphatidylcholine, phosphatidylethanolamine, phosphatidylserine (PS), lysophosphatidylcholine (LYPC), cardiolipin, and sphingomyelin (SM)] were determined, as well as the differences in the composition of individual fatty acids. The total lipid concentration decreased with DEHP exposure, particularly for FC and SM, by 33 and 54%, respectively. The same trend was observed in the fatty acid compositions, particularly the unsaturated fatty acids, where a greater decrease was observed with longer fatty acid chain length. The compositions of docosahexaenoic acid decreased significantly in five lipid classes (P < 0.05), including CE (43%), DAG (60%), PS (33%), LYPC (35%), and SM (40%). In contrast, the most remarkable reduction of arachidonic acid presented in two lipid classes, CE and LYPC, with a decrease of up to 33%. These results suggest that in utero exposure to DEHP alters the lipid metabolome in the fetal brain, which may lead to aberrant neurodevelopment.

Permeability of the reconstructed human epidermis model Episkin in comparison to various human skin preparations

The objective of this work was to compare the barrier function of the small diameter reconstructed human epidermis model Episkin (d=12 mm) to human skin in vitro. For that purpose a modification for the Franz diffusion cell (d=15mm) had to be developed so as to allow direct comparison with the following human skin preparations: Full thickness skin (FTS), split thickness skin (STS), heat-separated epidermis (HSE), and trypsin isolated stratum corneum (TISC). Among the tested preparations, HSE appeared to be the most preferable due to its clear morphological structure and ease of preparation. The lipid profile of HSE and Episkin was analyzed and showed significant differences in terms of cholesterol, ceramides and triglycerides contents, whereas cholesterol esters and fatty acids were not different. Permeation data with HSE and Episkin were then gathered using caffeine and testosterone. Both test compounds permeated much faster through Episkin than through HSE. Moreover, opposed to Episkin, HSE differentiated between the two test compounds. In spite of the remarkable progress in developing RHEs in the past years at this time Episkin can obviously not yet fully replace human skin for in vitro permeability experiments.

Evidence of Dual Pathways for Lipid Uptake during Chylomicron Remnant-Like Particle Processing by Human Macrophages

BACKGROUND

Though it is now clear that chylomicron remnants are pro-atherogenic lipoproteins, events leading to their incorporation by macrophages are poorly understood.

METHODS

This study investigates, in human macrophages, the fate of either [(3)H]cholesteryl oleate or [(3)H]triacylglycerol carried by human apolipoprotein-E-containing chylomicron remnant-like particles (CRLP) and the influence of CRLP containing trilinolein, (18:2)CRLP, or triolein, (18:1)CRLP, on lipid accumulation, newly synthesized cholesteryl ester (CE) and triacylglycerol (TG).

RESULTS

Labelled fatty acids from TG were markedly incorporated into TG and phospholipid and, to a lesser extent, into free fatty acids and were scarcely recovered in cholesteryl esters. [(3)H]CE from CRLP accumulated in cells in a dose-dependent manner with a significant difference between concentrations of 10 and 40 microg cholesterol/ml with (18:2)CRLP. In the same concentration range, TG synthesis was enhanced by about 46 and 30% by (18:2)CRLP and (18:1)CRLP cholesterol, respectively, whereas the esterification of cholesterol, evaluated by [(3)H]oleate incorporation, was decreased by about 30% with both types of CRLP. Endocytosis inhibition did not prevent cell cholesterol and TG accumulation, whereas lipoprotein lipase inhibition reduced the TG content.

CONCLUSIONS

The results are consistent with the hypotheses that in macrophages dietary remnants may support TG and CE internalization via different mechanisms. Extracellular lipolysis seems particularly important for internalization of dietary fatty acids, whereas the entrance of CE seems attributable to a concomitant selective CE uptake mediated by scavenger receptor class B type I, since the scavenger receptor class B type I antibody induces significant inhibition (38%) of [(3)H]CE transported by CRLP, but does not affect internalization of [(3)H]TG carried by the same particles.

Leptin modulates nitric oxide production and lipid metabolism in human placenta

Leptin has significant effects on appetite, energy expenditure, lipid mobilisation and reproduction. During pregnancy, leptin is produced in the placenta, a tissue in which leptin receptors are highly expressed, suggesting autocrine/paracrine functions for this hormone. In the present study, a putative role of leptin as a regulator of nitric oxide (NO) production and lipid metabolism was evaluated in term human placenta. We demonstrated that leptin enhanced NO production in human placental explants (P < 0.01). Although leptin did not modify the placental levels of cholesteryl esters and phospholipids, leptin decreased levels of triglycerides (P < 0.01) and cholesterol (P < 0.001) in term human placenta. The effect of leptin on lipid mass seems to be independent of the modulation of de novo lipid synthesis because leptin did not modify the incorporation of (14)C-acetate into any of the lipids evaluated. We investigated the effects of leptin on placental lipid catabolism and found that in both term human placental explants and primary cultures of trophoblastic cells, leptin increased glycerol release, an index of the hydrolysis of esterified lipids, in a dose-dependent manner. In conclusion, we have shown that leptin affects NO production and lipid catabolism in human placenta, providing supportive evidence for a role of leptin in placental functions that would determine the transfer of nutrients to the developing fetus.

Acute P-407 administration to mice causes hypercholesterolemia by inducing cholesterolgenesis and down-regulating low-density lipoprotein receptor expression

PURPOSE

Poloxamer 407 (P-407) is a chemical that induces a dose-controlled dyslipidemia in mice. Our aim was to determine the acute effects of P-407 treatment on the mechanisms that influence hepatic cholesterol homeostasis.

METHODS

We measured lipid levels in plasma and liver samples from control and P-407-treated mice (24 h post-i.p. injection of 0.5 g kg(-1) of P-407 or saline for the control mice). We measured acyl-coenzyme A:cholesterol acyltransferase (ACAT) and 3-hydroxy-3-methylglutaryl coenzyme A (HMG-CoA) reductase activities in liver microsomes. The protein expression of ACAT2, scavenger receptor class B, type I (SR-BI), ATP-binding cassette transporter A1 (ABCA1), ATP-binding cassette transporter G8 (ABCG8), low-density lipoprotein receptor (LDLr), and actin was measured by immunoblot.

RESULTS

We found an increase in plasma cholesterol and triglyceride levels as well as increased hepatic cholesteryl esters (CE) in P-407-treated mice. The hepatic ACAT microsomal activity and ACAT2 protein expression were not altered by P-407. The protein expression of the LDLr was decreased in the livers of P-407-treated mice. This decrease was specific, because the expression of the SR-BI was unchanged. The P-407-induced hypercholesterolemia was accounted for by increased activity and protein expression of HMG-CoA reductase. ATP-binding cassette transporters A1 and G8 protein expression were not significantly different in P-407-treated mice compared to controls.

CONCLUSIONS

The increased hepatic CE levels, following P-407 treatment, was neither related to an up-regulation of ACAT2 nor enhanced SR-BI expression. Hypercholesterolemia was associated with an up-regulation of both the protein expression and activity of HMG-CoA reductase and decreased LDLr expression.

Attenuated corticosterone response to chronic ACTH stimulation in hepatic lipase-deficient mice: evidence for a role for hepatic lipase in adrenal physiology

Hepatic lipase (HL), a liver-expressed lipolytic enzyme, hydrolyzes triglycerides and phospholipids in lipoproteins and promotes cholesterol delivery through receptor-mediated whole particle and selective cholesterol uptake. HL activity also occurs in the adrenal glands, which utilize lipoprotein cholesterol to synthesize glucocorticoids in response to pituitary ACTH. It is likely that the role of adrenal HL is to facilitate delivery of exogenous cholesterol for glucocorticoid synthesis. On this basis, we hypothesized that HL deficiency would blunt the glucocorticoid response to ACTH. Furthermore, because exogenous cholesterol also is derived from the LDL receptor (LDLR) pathway, we hypothesized that LDLR deficiency would blunt the response to ACTH. To test these hypotheses, we compared the corticosterone response to eight daily ACTH injections in HL-deficient (hl-/-), LDLR-deficient (Ldlr-/-), and HL- and LDLR-doubly deficient (Ldlr-/- hl-/-) mice with that in wild-type (WT) mice. Plasma corticosterone levels were measured on days 2, 5, and 8. Differences in plasma corticosterone levels between genotypes were analyzed by Kruskal-Wallis one-way ANOVA on ranks and pairwise multiple comparisons by Dunn's test. Our results demonstrate a trend toward reductions in plasma corticosterone levels on day 2 and significant reductions on day 5 and day 8 in the knockout models. Thus, on day 5, plasma corticosterone levels were reduced by 57, 70, and 73% (all P < 0.05) and on day 8 by 76, 59, and 63% (all P < 0.05) in hl-/-, Ldlr-/-, and Ldlr-/- hl-/- mice, respectively. These results demonstrate that HL deficiency, like LDLR deficiency, blunts the adrenal response to chronic ACTH stimulation and suggest a novel role for HL in adrenal physiology.

Medical application of an infrared free-electron laser: selective removal of cholesterol ester in carotid artery atheromatous plaques

Object

The purpose of this study was to determine the effectiveness of infrared free-electron laser (FEL) irradiation of cholesterol esters in human carotid artery (CA) atheromas.

Methods

The degradation of cholesterol ester was estimated from changes in the infrared absorption spectra acquired using microscopic transmission Fourier transform infrared spectroscopy. An FEL emitting radiation at 5.75-μm wavelengths and a power density of 15.9 W/cm2 was used to treat intimal slices of extirpated human arterial atherosclerotic plaques.

Peak signals derived from an ester bond of cholesterol ester decreased in height as irradiation time increased and disappeared completely after 180 seconds. No other change was observed in the infrared absorption spectrum after 180 seconds of irradiation, and no histological damage was noted.

Conclusions

The authors concluded that FEL irradiation can remove cholesterol ester selectively from human atheromatous CA plaques. This novel technique differs from previous approaches involving conventional lasers.

A Novel Type of Membrane Based on Cholesteryl Phosphocholine, Cholesteryl Phosphate, or Sitosteryl Phosphate, and Dimyristoylglycerol

Mixtures of amphiphilic cholesteryl phosphate (CP), sitosteryl phosphate (SP), or cholesteryl phosphocholine (CPC) with the nonphosphoryl diacyl lipid dimyristoylglycerol (DMG) or with cholesterol give self-organized systems (giant vesicles) in a wide range of pH, as demonstrated by fluorescence microscopy, differential scanning calorimetry, and small-angle X-ray scattering. The water permeability of a 1 : 1 molar mixture of CPC and DMG was also measured by a stopped-flow/light-scattering method. The novel self-organized systems are akin to natural eukaryotic ones, the only difference being the site of the phosphate-containing head-group, located on cholesterol instead of DMG. They might be present in some organisms not yet studied for the composition of their membranes.

Measurement of gastric emptying by the13C-octanoate breath test—rationalization with scintigraphy

The (13)C-octanoate breath test has not achieved universal acceptance for the measurement of solid phase gastric emptying, largely because the results are not comparable with those from direct methods such as scintigraphy. To convert breath-test data to their scintigraphic equivalent scale corrections are applied which have been obtained from population studies, but there is no guarantee that these are applicable in all cases. We propose an alternative method applicable on an individual basis based upon a simple physiological model which does not require any change to the breath-test protocol. It is demonstrated by comparison with scintigraphy and the octanoate saliva test. Results from an existing dataset of simultaneous breath test, saliva test and scintigraphic determinations of solid phase gastric emptying from nine healthy subjects were re-analysed. The corrected breath tests gave gastric emptying curves which were shown to be not significantly different to those obtained from scintigraphy. The method provides a simple but effective way of generating gastric emptying curves from breath-test data that are directly comparable with direct measurement methods, which is advantageous since it allows the whole of the gastric emptying profile to be generated, not just values for the lag phase and half-emptying times.

High throughput quantification of cholesterol and cholesteryl ester by electrospray ionization tandem mass spectrometry (ESI-MS/MS)

Analysis of free cholesterol (FC) is not well suited for electrospray ionization (ESI); however, cholesteryl ester (CE) form ammonium adducts in positive ion mode and generate a fragment ion of m/z 369 upon collision-induced fragmentation. In order to allow parallel analysis of FC and CE using ESI tandem mass spectrometry (ESI-MS/MS), we developed an acetyl chloride derivatization method to convert FC to cholesteryl acetate (CE 2:0). Derivatization conditions were chosen to provide a quantitative conversion of FC to CE 2:0 without transesterification of naturally occurring CE species. FC and CE were analyzed by direct flow injection analysis using a fragment of m/z 369 in a combination of selected reaction monitoring (SRM) and precursor ion scan for FC and CE, respectively. Quantification was achieved using deuterated D(7)-FC and CE 17:0/CE 22:0 as internal standards as well as calibration lines generated by addition of FC and naturally occurring CE species to the respective sample matrix. The developed assay showed a precision and detection limit sufficient for routine analysis. A run time of 1.3 min and automated data analysis allow high throughput analysis. Loading of human skin fibroblast and monocyte derived macrophages with stable isotope labeled FC showed a potential application of this method in metabolism studies. Together with existing mass spectrometry methodologies for lipid analysis, the present methodology will provide a useful tool for clinical and biochemical studies and expands the lipid spectrum that can be analyzed from one lipid sample on a single instrumental platform.

Identification of cholesteryl esters in human carotid atherosclerosis by ex vivo image-guided proton MRS

Vulnerable atherosclerotic plaques may be identified by their large lipid component, particularly liquid cholesteryl ester (CE), covered by a fibrous cap. We hypothesized that image-guided 1H proton magnetic resonance spectroscopy (MRS) would identify mobile CE in discrete, preselected regions of atherosclerotic plaque. Human carotid endarterectomy specimens (n = 10) were imaged ex vivo by magnetic resonance imaging (MRI) at high field (11.7 T) utilizing standard T1- and T2-weighted spin echo protocols. MRS spectra were acquired from 1 mm3 voxels, localized to plaque regions that we judged by MRI to be lipid rich or lipid poor. The spectra revealed methyl and methylene resonances of fatty acyl chains with relative intensities and linewidths characteristic of pure CE, by comparison with lipid standards. Regions judged to be lipid rich by MRI showed much more intense CE resonances than did lipid-poor regions. The integrated intensities of lipid peaks were 5.5 +/- 2.0% (lipid-rich regions) versus 0.9 +/- 0.6% (lipid-poor regions) of the unsuppressed water peak (P < 0.0001). Lipid distribution by histology, MRS, and MRI showed strong correlation. Image-guided proton MRS accurately identified CE in selected regions of atherosclerotic plaque as small as 1 mm3 in an ex vivo setting. This procedure may permit the noninvasive detection and quantification of CE in atherosclerotic plaque in vivo.

Liver X Receptor Activation Controls Intracellular Cholesterol Trafficking and Esterification in Human Macrophages

Liver X receptors (LXRs) are nuclear receptors that regulate macrophage cholesterol efflux by inducing ATP-binding cassette transporter A1 (ABCA1) and ABCG1/ABCG4 gene expression. The Niemann-Pick C (NPC) proteins NPC1 and NPC2 are located in the late endosome, where they control cholesterol trafficking to the plasma membrane. The mobilization of cholesterol from intracellular pools to the plasma membrane is a determinant governing its availability for efflux to extracellular acceptors. Here we investigated the influence of LXR activation on intracellular cholesterol trafficking in primary human macrophages. Synthetic LXR activators increase the amount of free cholesterol in the plasma membrane by inducing NPC1 and NPC2 gene expression. Moreover, ABCA1-dependent cholesterol efflux induced by LXR activators was drastically decreased in the presence of progesterone, which blocks postlysosomal cholesterol trafficking, and reduced when NPC1 and NPC2 mRNA expression was depleted using small interfering RNA. The stimulation of cholesterol mobilization to the plasma membrane by LXRs led to a decrease in cholesteryl ester formation and Acyl-coenzyme A cholesterol acyltransferase-1 activity. These data indicate that LXR activation enhances cholesterol trafficking to the plasma membrane, where it becomes available for efflux, at the expense of esterification, thus contributing to the overall effects of LXR agonists in the control of macrophage cholesterol homeostasis.

A systematic method for the sensitive and specific determination of hair lipids in combination with chromatography

A systematic method for the sensitive, precise and accurate determination of hair lipids, including trace amounts of intrinsic endogenous cholesterol (CH), ceramide/N-palmitoyl-DL-dihydrosphingosine (CER/PDS), cholesterol sulfate (CS) and chemically bound 18-methyl eicosanoic acid (18-MEA), has been developed in combination with TLC/FID (flame ionization detection), LC/MS and GC/MS. TLC/FID was used for the simultaneous determination of squalene (SQ), wax esters (WEs), triglycerides (TGs) and free fatty acids (FFAs). Optimal conditions for LC/MS to determine CS and 18-MEA were developed using selected ion monitoring (SIM) under the negative ion mode of electrospray ionization. An alternative procedure for the determination of 18-MEA was also established using commercially available heneicosanoic acid (HEA). In GC/MS, the optimal selection of ions for SIM of trimethylsilylated CH and CER/PDS, and the use of on-column injection has enabled their simultaneous detection. This newly developed method has been used to characterize the hair lipid composition from the proximal root end to the distal tip of chemically untreated hair fibers from two different females, and specific changes of hair lipids probably due to its origin and individuals have been demonstrated for the first time. This method may be useful for clarifying the important roles of intrinsic endogenous 18-MEA, CS, CH and CERs in the function of the cell membrane complex of hair fibers.

Effects of oleic acid rich oils on aorta lipids and lipoprotein lipase activity of spontaneously hypertensive rats

Hypertension development in the spontaneously hypertensive rat (SHR) leads to vascular wall widening by smooth muscle cell proliferation. In these cells, triglycerides (TG) and cholesteryl esters (CE) can accumulate until they become foam cells. We administrated two oleic rich oils, virgin olive (VOO) and high oleic sunflower oils (HOSO), to Wistar-Kyoto rats (WKY) and SHR because these oils have been reported to reduce the risk for coronary heart disease in hypertensive patients and SHR. After 12 weeks of feeding, we analyzed the TG and CE composition and the lipolytic (lipoprotein lipase, LPL, and non-LPL) activity in aortas of these animals. HOSO increased the content of linoleic acid in CE and TG of aortas from both WKY and SHR as compared with animals fed VOO by proportionally decreasing the content of oleic acid. Conversely, VOO reduced the LPL and non-LPL lipolytic activities, hence limiting the free fatty acids available for the synthesis of TG and CE in the vascular wall.

Insulin resistance, dietary fat intake and blood pressure predict left ventricular diastolic function 20 years later

BACKGROUND AND AIMS

Our knowledge on the development of left ventricular diastolic dysfunction is scarce. Thus, we aimed to investigate the relationship between left ventricular diastolic function and a wide variety of cardiovascular risk factors, including dietary factors using both cross-sectional and longitudinal data with 20 years follow-up.

METHOD AND RESULTS

A population-based cohort of 505 50-year-old men was examined with determinations of blood pressure, insulin, glucose and fatty acid composition of serum cholesterol esters. A reinvestigation 20 years later also included hyperinsulinaemic euglycaemic clamp, 7-day diet record and Doppler echocardiography with determination of left ventricular diastolic function (early (E) and late (A) peak mitral velocities and left atrial diameter). Blood pressure both at age 50 and 70 was negatively correlated to the E/A ratio (r=-0.15, p<0.001 and r=-0.23, p<0.001) at age 70. Insulin resistance at age 50 and 70 were negatively correlated to the A-wave and left atrial diameter at follow-up. A fatty acid profile indicating a diet high in saturated fats at age 50 was correlated to an increased left atrial diameter 20 years later and the dietary intake of fat was negatively correlated to the E/A ratio (r=-0.09, p<0.05) at age 70. All findings were independent of myocardial infarction and cardiovascular medication.

CONCLUSION

Apart from blood pressure, insulin resistance and dietary fat intake predicted left ventricular diastolic function after 20 years. These findings suggest that both hemodynamic and metabolic factors may play a role for left ventricular diastolic function and disclose new possibilities for prevention of left ventricular diastolic dysfunction.

Tendon xanthomas in familial hypercholesterolemia are associated with a differential inflammatory response of macrophages to oxidized LDL

Tendon xanthomas (TX) are pathognomonic lipid deposits commonly found in familial hypercholesterolemia (FH) patients. The aim of this study was to determine whether macrophages from FH patients with TX (TX+) have higher predisposition to foam cells formation after oxidized LDL (oxLDL) overload than those from FH patients without TX (TX-), and if their differential gene expression profile could explain these different phenotypes. Total RNA pools from macrophages from FH patients TX+ and TX- were analyzed using Affymetrix oligonucleotide arrays to evaluate the gene expression profile in presence and absence of oxLDL. Also, the intracellular lipid content was measured by fluorescence flow cytometry. Results of these studies suggest that macrophages from FH subjects TX+ compared to those TX- have a differential response to oxLDL, since they show higher intracellular cholesterol ester accumulation and a differential gene expression profile. The gene array data were validated by relative quantitative real-time RT-PCR and quantitative ELISA in culture media and plasma samples. FH subjects TX+ showed increased plasma tryptase, TNF-alpha, IL-8 and IL-6 concentrations. We propose that TX formation are associated with higher intracellular lipid content, and higher inflammatory response of macrophages in response to oxLDL.

[Determination of cholesteryl palmitate in Oviductus Ranae by HPLC]

OBJECTIVE

To develop a new method for the determination of cholesteryl palmitate in Oviductus Ranae.

METHOD

A HPLC method was set up, using Zorbax Silica column and cyclohexane-diethyl ether (40:1) as mobile phase with a flow rate of 1.0 mL x min(-1), and the UV detection wavelength was 203 nm.

RESULT

The calibration curve was linear over the range of 0.60-8.92 microg (r = 0.9997), the average recovery of the method was 98.4%. RSD 1.8% (n = 6).

CONCLUSION

The results showed that method was reliable and accurate.