Impact of manufacturing processes on glycerolipid and polar lipid composition and ultrastructure in infant formula

The introduction of exogenous lipids in the production of infant formula induces significant alterations in milk lipid composition, content, and membrane structure, thus affecting the lipid digestion, absorption, and utilization. This study meticulously tracks these changes throughout the manufacturing process. Pasteurization has a significant effect on phosphatidylcholine and sphingomyelin in the outer membrane, decreasing their relative contents to total polar lipids from 12.52% and 17.34% to 7.72% and 12.59%, respectively. Subsequent processes, including bactericidal-concentration and spray-drying, demonstrate the thermal stability of sphingomyelin and ceramides, while glycerolipids with arachidonic acid/docosahexaenoic acid and glycerophospholipids, particularly phosphatidylethanolamine, diminish significantly. Polar lipids addition and freeze-drying technology significantly enhance the polar lipid content and improve microscopic morphology of infant formula. These findings reveal the diverse effects of technological processes on glycerolipid and polar lipid compositions, concentration, and ultrastructure in infant formulas, thus offering crucial insights for optimizing lipid content and structure within infant formula.

Improved Structural Characterization of Glycerophospholipids and Sphingomyelins with Real-Time Library Searching

In mass spectrometry-based lipidomics, complex lipid mixtures undergo chromatographic separation, are ionized, and are detected using tandem MS (MSn) to simultaneously quantify and structurally characterize eluting species. The reported structural granularity of these identified lipids is strongly reliant on the analytical techniques leveraged in a study. For example, lipid identifications from traditional collisionally activated data-dependent acquisition experiments are often reported at either species level or molecular species level. Structural resolution of reported lipid identifications is routinely enhanced by integrating both positive and negative mode analyses, requiring two separate runs or polarity switching during a single analysis. MS3+ can further elucidate lipid structure, but the lengthened MS duty cycle can negatively impact analysis depth. Recently, functionality has been introduced on several Orbitrap Tribrid mass spectrometry platforms to identify eluting molecular species on-the-fly. These real-time identifications can be leveraged to trigger downstream MSn to improve structural characterization with lessened impacts on analysis depth. Here, we describe a novel lipidomics real-time library search (RTLS) approach, which utilizes the lipid class of real-time identifications to trigger class-targeted MSn and to improve the structural characterization of phosphotidylcholines, phosphotidylethanolamines, phosphotidylinositols, phosphotidylglycerols, phosphotidylserine, and sphingomyelins in the positive ion mode. Our class-based RTLS method demonstrates improved selectivity compared to the current methodology of triggering MSn in the presence of characteristic ions or neutral losses.

Lactational Changes of Phospholipids Content and Composition in Chinese Breast Milk

Phospholipids are pivotal polar lipids in human milk and essential for infants’ growth and development, especially in the brain and cognitive development. Its content and composition are affected by multiple factors and there exist discrepancies in different studies. In this study, we determined five major phospholipids classes (phosphatidylethanolamine, phosphatidylinositol, phosphatidylserine, phosphatidylcholine, and sphingomyelin) in 2270 human milk samples collected from 0 to 400 days postpartum in six regions of China. The high-performance liquid chromatography coupled with an evaporative light scattering detector (HPLC-ELSD) was performed to quantify the phospholipids. Total phospholipid median (IQR) content was in a range between 170.38 ± 96.52 mg/L to 195.69 ± 81.80 mg/L during lactation and was higher concentrated in colostrum milk and later stage of lactation (after 200 days postpartum) compared with that in the samples collected between 10 to 45 days postpartum. Variations in five major sub-class phospholipids content were also observed across lactation stages (phosphatidylethanolamine: 52.61 ± 29.05 to 59.95 ± 41.74 mg/L; phosphatidylinositol: 17.65 ± 10.68 to 20.38 ± 8.55 mg/L; phosphatidylserine: 15.98 ± 9.02 to 22.77 ± 11.17 mg/L; phosphatidylcholine: 34.13 ± 25.33 to 48.64 ± 19.73 mg/L; sphingomyelin: 41.35 ± 20.31 to 54.79 ± 35.26 mg/L). Phosphatidylethanolamine (29.18–32.52%), phosphatidylcholine (19.90–25.04%) and sphingomyelin (22.39–29.17%) were the dominant sub-class phospholipids in Chinese breast milk during the whole lactation period. These results updated phospholipids data in Chinese human milk and could provide evidence for better development of secure and effective human milk surrogates for infants without access to breast milk.

Total Fatty Acid and Polar Lipid Species Composition of Human Milk

Human milk lipids are essential for infant health. However, little is known about the relationship between total milk fatty acid (FA) composition and polar lipid species composition. Therefore, we aimed to characterize the relationship between the FA and polar lipid species composition in human milk, with a focus on differences between milk with higher or lower milk fat content. From the Norwegian Human Milk Study (HUMIS, 2002–2009), a subset of 664 milk samples were analyzed for FA and polar lipid composition. Milk samples did not differ in major FA, phosphatidylcholine, or sphingomyelin species percentages between the highest and lowest quartiles of total FA concentration. However, milk in the highest FA quartile had a lower phospholipid-to-total-FA ratio and a lower sphingomyelin-to-phosphatidylcholine ratio than the lowest quartile. The only FAs associated with total phosphatidylcholine or sphingomyelin were behenic and tridecanoic acids, respectively. Milk FA and phosphatidylcholine and sphingomyelin species containing these FAs showed modest correlations. Associations of arachidonic and docosahexaenoic acids with percentages of phosphatidylcholine species carrying these FAs support the conclusion that the availability of these FAs limits the synthesis of phospholipid species containing them.

Comparative sphingolipidomic analysis reveals significant differences between doxorubicin-sensitive and -resistance MCF-7 cells

Drug resistance is responsible for the failure of many available anticancer drugs. Several studies have demonstrated the association between the alteration in sphingolipids (SPLs) and the development of drug resistance. To investigate the association between SPLs metabolism and doxorubicin (dox)-resistance in MCF-7 cells, a comparative sphingolipidomics analysis between dox-sensitive (parental) and -resistant MCF-7 cell lines along with validation by gene expression analysis were conducted. A total of 31 SPLs representing 5 subcategories were identified. The data obtained revealed that SPLs were clustered into two groups differentiating parental from dox-resistant cells. Eight SPLs were significantly altered in response to dox-resistance including SM (d18:1/16), SM (d18:1/24:2), SM (d18:1/24:0), SM (d18:1/20:0), SM (d18:1/23:1), HexCer (d18:1/24:0), SM (d18:1/15:0), DHSM (d18:0/20:0). The current study is the first to conclusively ascertain the potential involvement of dysregulated SPLs in dox-resistance in MCF-7 cells. SPLs metabolism in dox-resistant MCF-7 cells is oriented toward the downregulation of ceramides (Cer) and the concomitant increase in sphingomyelin (SM). Gene expression analysis has revealed that dox-resistant cells tend to escape from the Cer-related apoptosis by the activation of SM-Cer and GluCer-LacCer-ganglioside pathways. The enzymes that were correlated to the alteration in SPLs metabolism of dox-resistant MCF-7 cells and significantly altered in gene expression can represent potential targets that can represent a winning strategy for the future development of promising anticancer drugs.

Application of enzymatic fluorometric assays to quantify phosphatidylcholine, phosphatidylethanolamine and sphingomyelin in human plasma lipoproteins

Phosphatidylcholine (PC), phosphatidylethanolamine (PE) and sphingomyelin (SM) are important surface components of plasma lipoproteins, including very-low-density lipoproteins (VLDL), low-density lipoproteins (LDL) and high-density lipoproteins (HDL). However, the pathophysiological roles of PC, PE and SM in lipoproteins have not been well characterized owing to the difficulties in quantifying phospholipid classes in lipoproteins. In this study, we assessed the precision and accuracy of the enzymatic fluorometric assays for measuring PC, PE and SM in VLDL, LDL and HDL, which were isolated from human plasma by ultracentrifugation. The within-run coefficients of variation (CV) for the measurements of PC, PE and SM in lipoproteins were 1.5-2.8 %, 1.1-2.4 % and 0.9-2.3 %, respectively, whereas the between-run CVs for the PC, PE and SM assays were 2.7-4.7 %, 2.1-4.5 % and 1.6-3.3 %, respectively. Excellent linearity and almost complete recovery were achieved for all assays measuring PC, PE and SM in VLDL, LDL and HDL. Our preliminary results using these enzymatic fluorometric assays suggested that the phospholipid compositions were different among VLDL, LDL and HDL. In conclusion, we established high-throughput enzymatic fluorometric assays to quantify PC, PE and SM in human plasma VLDL, LDL and HDL, which will be useful for further investigation of pathophysiological roles of phospholipids in lipoproteins.

UHPLC-Q-Orbitrap HRMS-based quantitative lipidomics reveals the chemical changes of phospholipids during thermal processing methods of Tan sheep meat

Thermal processing affects the lipid compositions of meat products. The study determined the effects of boiled, steamed and roasted processing methods on the lipidomics profiles of Tan sheep meat with a validated UPLC-Q-Orbitrap HRMS combined lipid screening strategy method. Combined with sphingolipid metabolism, the boiled approach was the suitable choice for atherosclerosis patients for more losses of sphingomyelin than ceramide in meat. The similarly less losses of phosphatidylcholine and lysophosphatidylcholine showed in glycerophospholipid metabolism implied that steamed Tan sheep meat was more suitable for the populations of elderly and infants. Furthermore, a total of 90 lipids with significant difference (VIP > 1) in 6 lipid subclasses (sphingomyelin, ceramide, lysophosphatidylcholine, phosphatidylcholine, phosphatidylethanolamines, triacylglycerol,) were quantified among raw and three types of thermal processed Tan sheep meat, further providing useful information for identification of meat products with different thermal processing methods (LOD with 0.14-0.31 μg kg^-1, LOQ with 0.39-0.90 μg kg^-1).

A comparative study on the lipidome of normal knee synovial fluid from humans and horses

The current limitations in evaluating synovial fluid (SF) components in health and disease and between species are due in part to the lack of data on normal SF, because of low availability of SF from healthy articular joints. Our study aimed to quantify species-dependent differences in phospholipid (PL) profiles of normal knee SF obtained from equine and human donors. Knee SF was obtained during autopsy by arthrocentesis from 15 and 13 joint-healthy human and equine donors, respectively. PL species extracted from SF were quantitated by mass spectrometry whereas ELISA determined apolipoprotein (Apo) B-100. Wilcoxon’s rank sum test with adjustment of scores for tied values was applied followed by Holm´s method to account for multiple testing. Six lipid classes with 89 PL species were quantified, namely phosphatidylcholine, lysophosphatidylcholine, sphingomyelin, phosphatidylethanolamine, plasmalogen, and ceramide. Importantly, equine SF contains about half of the PL content determined in human SF with some characteristic changes in PL composition. Nutritional habits, decreased apolipoprotein levels and altered enzymatic activities may have caused the observed different PL profiles. Our study provides comprehensive quantitative data on PL species levels in normal human and equine knee SF so that research in joint diseases and articular lubrication can be facilitated.

Lipid Dynamics due to Muscle Atrophy Induced by Immobilization

Muscle atrophy refers to skeletal muscle loss and dysfunction that affects glucose and lipid metabolism. Moreover, muscle atrophy is manifested in cancer, diabetes, and obesity. In this study, we focused on lipid metabolism during muscle atrophy. We observed that the gastrocnemius muscle was associated with significant atrophy with 8 days of immobilization of hind limb joints and that muscle atrophy occurred regardless of the muscle fiber type. Further, we performed lipid analyses using thin layer chromatography, liquid chromatography-mass spectrometry, and mass spectrometry imaging. Total amounts of triacylglycerol, phosphatidylserine, and sphingomyelin were found to be increased in the immobilized muscle. Additionally, we found that specific molecular species of phosphatidylserine, phosphatidylcholine, and sphingomyelin were increased by immobilization. Furthermore, the expression of adipose triglyceride lipase and the activity of cyclooxygenase-2 were significantly reduced by atrophy. From these results, it was revealed that lipid accumulation and metabolic changes in specific fatty acids occur during disuse muscle atrophy. The present study holds implications in validating preventive treatment strategies for muscle atrophy.

Early Signs of Atherogenic Features in the HDL Lipidomes of Normolipidemic Patients Newly Diagnosed with Type 2 Diabetes

Cardiovascular disease (CVD) is the major cause of death in patients with type-2 diabetes mellitus (T2DM), although the factors that accelerate atherosclerosis in these patients are poorly understood. The identification of the altered quantity and quality of lipoproteins, closely related to atherogenesis, is limited in routine to a pattern of high triglycerides and low HDL-cholesterol (HDL-C) and in research as dysfunctional HDLs. We used the emerging NMR-based lipidomic technology to investigate compositional features of the HDLs of healthy individuals with normal coronary arteries, drug-naïve; recently diagnosed T2DM patients with normal coronary arteries; and patients with recent acute coronary syndrome. Patients with T2DM and normal serum lipid profiles even at diagnosis presented significant lipid alterations in HDL, characterized by higher triglycerides, lysophosphatidylcholine and saturated fatty acids; and lower cholesterol, phosphatidylcholine, phosphatidylethanolamine, sphingomyelin, plasmalogens and polyunsaturated fatty acids, an atherogenic pattern that may be involved in the pathogenesis of atherosclerosis. These changes are qualitatively similar to those found, more profoundly, in normolipidemic patients with established Coronary Heart Disease (CHD). We also conclude that NMR-based lipidomics offer a novel holistic exploratory approach for identifying and quantifying lipid species in biological matrixes in physiological processes and disease states or in disease biomarker discovery.

SERS studies on normal epithelial and cancer cells derived from clinical breast cancer specimens

Surface-enhanced Raman scattering (SERS) spectroscopy of single-cell suspensions obtained from fresh specimens of breast cancer tissue and normal breast tissue by mechanical enzymatic digestion was obtained and analysed, which is different from most Raman studies using breast cancer cell lines. Random forest classification was implemented to develop effective diagnostic algorithms for the classification of SERS of different typed cells. We first examined the SERS spectra of the primary breast cancer single cell and normal epithelial single cell obtained by flow sorting cytometry due to their biomarkers of CD326+/CD45-. Comparison analyses on their SERS spectra disclose that the nucleic acid and protein levels of the primary breast cancer single cell are higher than those of the normal epithelial single cell, while the lipids are at a relatively lower level. An important finding is that the cholesterol, palmitic acid, and sphingomyelin in the cancer cell profiles exhibit stronger than those of normal cells, while the glycans are at a relatively lower level. Furthermore, the standard deviation (SD) of the normal epithelial single cell is larger than that of the breast cancer cell, and the SD of the primary breast cancer single cell is more obvious than that of the normal epithelial cells. In addition, the prospective application of an algorithm to the dataset results in an accuracy of 78.2%, a precision of 75.5%, and a recall of 66.7%. The breast cancer diagnostic model laid a solid foundation for judgment of breast-conserving surgical margins and early diagnosis of breast cancer.

Comparative Lipidomic Study of Human Milk from Different Lactation Stages and Milk Formulas

In this report, we present a detailed comparison of the lipid composition of human milk (HM) and formula milk (FM) targeting different lactation stages and infant age range. We studied HM samples collected from 26 Polish mothers from colostrum to 19 months of lactation, along with FM from seven brands available on the Polish market (infant formula, follow-on formula and growing-up formula). Lipid extracts were analysed using liquid chromatography coupled to high-resolution mass spectrometry (LC-Q-TOF-MS). We found that the lipid composition of FM deviates significantly from the HM lipid profile in terms of qualitative and quantitative differences. FM had contrasting lipid profiles mostly across brands and accordingly to the type of fat added but not specific to the target age range. The individual differences were dominant in HM; however, differences according to the lactation stage were also observed, especially between colostrum and HM collected in other lactation stages. Biologically and nutritionally important lipids, such as long-chain polyunsaturated fatty acids (LC-PUFAs) containing lipid species, sphingomyelines or ether analogues of glycerophosphoethanoloamines were detected in HM collected in all studied lactation stages. The observed differences concerned all the major HM lipid classes and highlight the importance of the detailed compositional studies of both HM and FM.

Analysis of sphingolipid composition in human vitreous from control and diabetic individuals

OBJECTIVE

Sphingolipids have a fundamental role in many cellular processes, and they have been implicated in insulin resistance and Diabetes Mellitus (DM) and its complications, including diabetic retinopathy (DR). Little is known about how bioactive sphingolipids relate to retinopathies in human DM. In this study, we analyzed the sphingolipid composition of type 2 diabetic (T2DM) and non-diabetic human vitreous samples.

METHODS

We conducted an observational study on post-mortem human vitreous samples from non-diabetic (Controls; n = 4; age: 71.6 ± 11.0 years, mean ± SD) and type 2 diabetic (T2DM; n = 9; age: 67.0 ± 9.2 years) donors to identify changes in sphingolipid composition. Samples were analyzed by a triple quadrupole mass spectrometer and individual sphingolipid species were identified and quantified using established protocols.

RESULTS

The total quantity (pmol/mg) of ceramide (Cer), lactosylceramide (Lac-Cer), and sphingomyelin (SM) were increased in type 2 diabetic vitreous samples. Among individual species, we found a general trend of increase in the longer chain species of ceramides, hexosylceramides (Hex-Cer), Lac-Cer, and SM.

CONCLUSIONS

This study shows the presence of measurable levels of sphingolipids in human vitreous. The results indicate changes in sphingolipid composition in the vitreous due to type 2 diabetes, which could be connected to the disease pathologies of the retina, retinal vessels, vitreous and the surrounding tissues.

Metabolomic profiling reveals correlations between spermiogram parameters and the metabolites present in human spermatozoa and seminal plasma

In 50% of all infertility cases, the male is subfertile or infertile, however, the underlying mechanisms are often unknown. Even when assisted reproductive procedures such as in vitro fertilization and intracytoplasmic sperm injection are performed, the causes of male factor infertility frequently remain elusive. Since the overall activity of cells is closely linked to their metabolic capacity, we analyzed a panel of 180 metabolites in human sperm and seminal plasma and elucidated their associations with spermiogram parameters. Therefore, metabolites from a group of 20 healthy donors were investigated using a targeted LC-MS/MS approach. The correlation analyses of the amino acids, biogenic amines, acylcarnitines, lysophosphatidylcholines, phosphatidylcholines, sphingomyelins and sugars from sperm and seminal plasma with standard spermiogram parameters revealed that metabolites in sperm are closely related to sperm motility, whereas those in seminal plasma are closely related to sperm concentration and morphology. This study provides essential insights into the metabolome of human sperm and seminal plasma and its associations with sperm functions. This metabolomics technique could be a promising screening tool to detect the factors of male infertility in cases where the cause of infertility is unclear.

Reorganization of platelet membrane sphingomyelins by adenosine diphosphate and ticagrelor

Platelets are major targets for the treatment of thrombo-embolic disorders. Their plasma membrane contains specialized microdomains enriched in sphingomyelins and free cholesterol including membrane receptors. P2Y12 receptors need to be situated in these domains to be able to conduct activation signaling by adenosine diphosphate (ADP). We studied the impact of ticagrelor, a P2Y12 antagonist, and ADP on the composition and distribution of sphingomyelins in detergent-resistant membrane (DRM) of platelet membranes. Platelets were obtained from healthy donors. DRMs of platelet membranes were isolated in 4 experimental groups: control; ADP, with platelets stimulated by 20 μM ADP and 5 mM CaCl2; ticagrelor, with platelets incubated by ticagrelor 4 μM methanol dissolved; and ticagrelor + ADP, with incubation by ticagrelor followed by stimulation by ADP as above. After mass spectrometry analysis, we found 16 species of sphingomyelins in platelet membrane DRMs. We also found that treatment with ticagrelor and stimulation by ADP could induce changes in the composition, distribution and concentration of sphingomyelins in membranes of platelets. In all groups, the predominant species of sphingomyelins in platelet membrane was d18:1/16:0. Taken together, our results show that stimulation by ADP or inhibition by ticagrelor changed the level and composition of sphingomyelins in platelet membranes. These changes might be considered as reorganization or new recruitment of certain types of sphingomyelins through the membrane.

Multi-modal imaging of long-term recovery post-stroke by positron emission tomography and matrix-assisted laser desorption/ionisation mass spectrometry

RATIONALE

Stroke is a leading cause of disability worldwide. Understanding the recovery process post-stroke is essential; however, longer-term recovery studies are lacking. In vivo positron emission tomography (PET) can image biological recovery processes, but is limited by spatial resolution and its targeted nature. Untargeted mass spectrometry imaging offers high spatial resolution, providing an ideal ex vivo tool for brain recovery imaging.

METHODS

Magnetic resonance imaging (MRI) was used to image a rat brain 48 h after ischaemic stroke to locate the infarcted regions of the brain. PET was carried out 3 months post-stroke using the tracers [¹⁸ F]DPA-714 for TSPO and [¹⁸ F]IAM6067 for sigma-1 receptors to image neuroinflammation and neurodegeneration, respectively. The rat brain was flash-frozen immediately after PET scanning, and sectioned for matrix-assisted laser desorption/ionisation mass spectrometry (MALDI-MS) imaging.

RESULTS

Three months post-stroke, PET imaging shows minimal detection of neurodegeneration and neuroinflammation, indicating that the brain has stabilised. However, MALDI-MS images reveal distinct differences in lipid distributions (e.g. phosphatidylcholine and sphingomyelin) between the scar and the healthy brain, suggesting that recovery processes are still in play. It is currently not known if the altered lipids in the scar will change on a longer time scale, or if they are stabilised products of the brain post-stroke.

CONCLUSIONS

The data demonstrates the ability to combine MALD-MS with in vivo PET to image different aspects of stroke recovery.

A Comparison of Tissue Spray and Lipid Extract Direct Injection Electrospray Ionization Mass Spectrometry for the Differentiation of Eutopic and Ectopic Endometrial Tissues

Recent research revealed that tissue spray mass spectrometry enables rapid molecular profiling of biological tissues, which is of great importance for the search of disease biomarkers as well as for online surgery control. However, the payback for the high speed of analysis in tissue spray analysis is the generally lower chemical sensitivity compared with the traditional approach based on the offline chemical extraction and electrospray ionization mass spectrometry detection. In this study, high resolution mass spectrometry analysis of endometrium tissues of different localizations obtained using direct tissue spray mass spectrometry in positive ion mode is compared with the results of electrospray ionization analysis of lipid extracts. Identified features in both cases belong to three lipid classes: phosphatidylcholines, phosphoethanolamines, and sphingomyelins. Lipids coverage is validated by hydrophilic interaction liquid chromatography with mass spectrometry of lipid extracts. Multivariate analysis of data from both methods reveals satisfactory differentiation of eutopic and ectopic endometrium tissues. Overall, our results indicate that the chemical information provided by tissue spray ionization is sufficient to allow differentiation of endometrial tissues by localization with similar reliability but higher speed than in the traditional approach relying on offline extraction. Graphical Abstract ᅟ.

Quantification of glycerophospholipids and sphingomyelin in human milk and infant formula by high performance liquid chromatography coupled with mass spectrometer detector

Phospholipids and sphingomyelin have a central role in infant nutrition, phospholipid acting as a nutrient carrier of long chain polyunsaturated fatty acids and sphingomyelin having an important role in cognitive function. However, analytical methods to precisely characterize and quantify these compounds in maternal milk are needed. Phospholipids and sphingomyelin were extracted using chloroform and methanol and separated on Polaris 3 Si column 250×2.0mm from Varian and analyzed by high performance liquid chromatography (HPLC) coupled with mass spectrometer detector (MS). The analytical method was validated and repeatability, intermediate reproducibility, and recovery values were calculated. The relative standard deviation of repeatability (CV(r)) and intermediate reproducibility (CV(iR)) values ranged between 2.3 and 7.2% and 9.5 and 17.8%, respectively and the recovery values between 96 and 109%. Finally, the validated method was tested on human milk samples and on infant formula which were analysed also by HPLC coupled with evaporative light scattering detector (ELSD). In human milk, sphingomyelin (9.28mg100mL^-1) was the most abundant compound, followed by phosphatidylcholine (5.39mg100mL^-1), phosphatidylethanolamine (2.85mg100mL^-1) and phosphatidylinositol (1.82mg100mL^-1).

Planar Optical Nanoantennas Resolve Cholesterol-Dependent Nanoscale Heterogeneities in the Plasma Membrane of Living Cells

Optical nanoantennas can efficiently confine light into nanoscopic hotspots, enabling single-molecule detection sensitivity at biological relevant conditions. This innovative approach to breach the diffraction limit offers a versatile platform to investigate the dynamics of individual biomolecules in living cell membranes and their partitioning into cholesterol-dependent lipid nanodomains. Here, we present optical nanoantenna arrays with accessible surface hotspots to study the characteristic diffusion dynamics of phosphoethanolamine (PE) and sphingomyelin (SM) in the plasma membrane of living cells at the nanoscale. Fluorescence burst analysis and fluorescence correlation spectroscopy performed on nanoantennas of different gap sizes show that, unlike PE, SM is transiently trapped in cholesterol-enriched nanodomains of 10 nm diameter with short characteristic times around 100 μs. The removal of cholesterol led to the free diffusion of SM, consistent with the dispersion of nanodomains. Our results are consistent with the existence of highly transient and fluctuating nanoscale assemblies enriched by cholesterol and sphingolipids in living cell membranes, also known as lipid rafts. Quantitative data on sphingolipids partitioning into lipid rafts is crucial to understand the spatiotemporal heterogeneous organization of transient molecular complexes on the membrane of living cells at the nanoscale. The proposed technique is fully biocompatible and thus provides various opportunities for biophysics and live cell research to reveal details that remain hidden in confocal diffraction-limited measurements.

Metabolomic profiling of ascending thoracic aortic aneurysms and dissections - Implications for pathophysiology and biomarker discovery

Objective

Our basic understanding of ascending thoracic aortic aneurysm (ATAA) pathogenesis is still very limited, hampering early diagnosis, risk prediction, and development of treatment options. “Omics”-technologies, ideal to reveal tissue alterations from the normal physiological state due to disease have hardly been applied in the field. Using a metabolomic approach, with this study the authors seek to define tissue differences between controls and various forms of ATAAs.

Methods

Using a targeted FIA-MS/MS metabolomics approach, we analysed and compared the metabolic profiles of ascending thoracic aortic wall tissue of age-matched controls (n = 8), bicuspid aortic valve-associated aneurysms (BAV-A; n = 9), tricuspid aortic valve-associated aneurysms (TAV-A; n = 14), and tricuspid aortic valve-associated aortic dissections (TAV-Diss; n = 6).

Results

With sphingomyelin (SM) (OH) C22:2, SM C18:1, SM C22:1, and SM C24:1 only 4 out of 92 detectable metabolites differed significantly between controls and BAV-A samples. Between controls and TAV-Diss samples only phosphatidylcholine (PC) ae C32:1 differed. Importantly, our analyses revealed a general increase in the amount of total sphingomyelin levels in BAV-A and TAV-Diss samples compared to controls.

Conclusions

Significantly increased levels of sphingomyelins in BAV-A and TAV-Diss samples compared to controls may argue for a repression of sphingomyelinase activity and the sphingomyelinase-ceramide pathway, which may result in an inhibition of tissue regeneration; a potential basis for disease initiation and progression.

Rapid test for lung maturity, based on spectroscopy of gastric aspirate, predicted respiratory distress syndrome with high sensitivity

AIM

Respiratory distress syndrome (RDS) is a major cause of mortality and morbidity in premature infants. By the time symptoms appear, it may already be too late to prevent a severe course, with bronchopulmonary dysplasia or mortality. We aimed to develop a rapid test of lung maturity for targeting surfactant supplementation.

METHODS

Concentrations of the most surface-active lung phospholipid dipalmitoylphosphatidylcholine and sphingomyelin in gastric aspirates from premature infants were measured by mass spectrometry and expressed as the lecithin/sphingomyelin ratio (L/S). The same aspirates were analysed with mid-infrared spectroscopy. Subsequently, L/S was measured in gastric aspirates and oropharyngeal secretions from another group of premature infants using spectroscopy and the results were compared with RDS development. The 10-minute analysis required 10 μL of aspirate.

RESULTS

An L/S algorithm was developed based on 89 aspirates. Subsequently, gastric aspirates were sampled in 136 infants of 24-31 weeks of gestation and 61 (45%) developed RDS. The cut-off value of L/S was 2.2, sensitivity was 92%, and specificity was 73%. In 59 cases, the oropharyngeal secretions had less valid L/S than gastric aspirate results.

CONCLUSION

Our rapid test for lung maturity, based on spectroscopy of gastric aspirate, predicted RDS with high sensitivity.

Lipid mapping of the rat brain for models of disease

Lipids not only constitute the primary component of cellular membranes and contribute to metabolism but also serve as intracellular signaling molecules and bind to specific membrane receptors to control cell proliferation, growth and convey neuroprotection. Over the last several decades, the development of new analytical techniques, such as imaging mass spectrometry (IMS), has contributed to our understanding of their involvement in physiological and pathological conditions. IMS allows researchers to obtain a wide range of information about the spatial distribution and abundance of the different lipid molecules that is crucial to understand brain functions. The primary aim of this study was to map the spatial distribution of different lipid species in the rat central nervous system (CNS) using IMS to find a possible relationship between anatomical localization and physiology. The data obtained were subsequently applied to a model of neurological disease, the 192IgG-saporin lesion model of memory impairment. The results were obtained using a LTQ-Orbitrap XL mass spectrometer in positive and negative ionization modes and analyzed by ImageQuest and MSIReader software. A total of 176 different molecules were recorded based on the specific localization of their intensities. However, only 34 lipid species in negative mode and 51 in positive were assigned to known molecules with an error of 5ppm. These molecules were grouped by different lipid families, resulting in: Phosphatidylcholines (PC): PC (34: 1)+K⁺ and PC (32: 0)+K⁺ distributed primarily in gray matter, and PC (36: 1)+K⁺ and PC (38: 1)+Na⁺ distributed in white matter. Phosphatidic acid (PA): PA (38: 3)+K⁺ in white matter, and PA (38: 5)+K⁺ in gray matter and brain ventricles. Phosphoinositol (PI): PI (18: 0/20: 4)-H⁺ in gray matter, and PI (O-30: 1) or PI (P-30: 0)-H⁺ in white matter. Phosphatidylserines (PS): PS (34: 1)-H⁺ in gray matter, and PS (38: 1)-H⁺ in white matter. Sphingomyelin (SM) SM (d18: 1/16: 0)-H⁺ in ventricles and SM (d18: 1/18: 0)-H⁺ in gray matter. Sulfatides (ST): ST (d18: 1/24: 1)-H⁺ in white matter. The specific distribution of different lipids supports their involvement not only in structural and metabolic functions but also as intracellular effectors or specific receptor ligands and/or precursors. Moreover, the specific localization in the CNS described here will enable us to analyze lipid distribution to identify their physiological conditions in rat models of neurodegenerative pathologies, such as Alzheimer's disease. This article is part of a Special Issue entitled: Membrane Lipid Therapy: Drugs Targeting Biomembranes edited by Pablo V. Escribá.

Contribution of glycerophospholipids and sphingomyelin to the circulating NEFA

BACKGROUND

Serum nonesterified fatty acids (NEFA) are known to be associated with the development of insulin resistance. Recently, differences in the NEFA profile were found in subjects with history of gestational diabetes (postGDM) and healthy controls. Little is known about the NEFA sources in the postprandial state, which prevails most of the day in humans in modern societies. In the present study, we aimed to explore the potential contributions of glycerophospholipid (GPL) and sphingomyelin (SM) fatty acids to the circulating NEFA.

METHODS

Serum-samples of 19 postGDM women and 20 controls were obtained in fasting state (t0) and 90 minutes (t90) after an oral glucose tolerance test. Fatty acid composition of NEFA and SM were analyzed with liquid chromatography coupled to triple quadrupole mass spectrometry and GPL by gas chromatography.

RESULTS

The ratio of individual NEFA at t90 vs. t0 (t90/0-ratio) showed no difference between the two groups but increased with chain-length (7% for C16:1, 82% for C26:3). Only NEFA 10:0 was found with lower concentration at t0 and t90 in postGDM. At t90, long-chain polyunsaturated fatty acid correlated closely between NEFA and GPL in postGDM (20:5, 22:4, 22:5 and 22:6) and controls (20:3, 20:4 and 20:5). Very long-chain fatty acid 24:0 correlated significantly between NEFA and SM in postGDM and controls. Saturated and monounsaturated fatty acids correlated less between NEFA and GPL or SM.

CONCLUSIONS

The NEFA composition varied highly between fasting and fed state in both groups. GPL appeared to contribute long-chain polyunsaturated fatty acid, while SM appeared to contribute very long-chain fatty acids to the NEFA pool.

Ultrastructure and lipid composition of detergent-resistant membranes derived from mammalian sperm and two types of epithelial cells

Lipid rafts are micro-domains of ordered lipids (L_o phase) in biological membranes. The L_o phase of cellular membranes can be isolated from disordered lipids (L_d phase) after treatment with 1 % Triton  X-100 at 4 °C in which the L_o phase forms the detergent-resistant membrane (DRM) fraction. The lipid composition of DRM derived from Madin-Darby canine kidney (MDCK) cells, McArdle cells and porcine sperm is compared with that of the whole cell. Remarkably, the unsaturation and chain length degree of aliphatic chains attached to phospholipids is virtually the same between DRM and whole cells. Cholesterol and sphingomyelin were enriched in DRMs but to a cell-specific molar ratio. Sulfatides (sphingolipids from MDCK cells) were enriched in the DRM while a seminolipid (an alkylacylglycerolipid from sperm) was depleted from the DRM. Treatment with <5 mM methyl-ß-cyclodextrin (MBCD) caused cholesterol removal from the DRM without affecting the composition and amount of the phospholipid while higher levels disrupted the DRM. The substantial amount of (poly)unsaturated phospholipids in DRMs as well as a low stoichiometric amount of cholesterol suggest that lipid rafts in biological membranes are more fluid and dynamic than previously anticipated. Using negative staining, ultrastructural features of DRM were monitored and in all three cell types the DRMs appeared as multi-lamellar vesicular structures with a similar morphology. The detergent resistance is a result of protein–cholesterol and sphingolipid interactions allowing a relatively passive attraction of phospholipids to maintain the L_o phase. For this special issue, the relevance of our findings is discussed in a sperm physiological context.

Glycerophospholipid Profiles of Bats with White-Nose Syndrome

Pseudogymnoascus destructans is an ascomycetous fungus responsible for the disease dubbed white-nose syndrome (WNS) and massive mortalities of cave-dwelling bats. The fungus infects bat epidermal tissue, causing damage to integumentary cells and pilosebaceous units. Differences in epidermal lipid composition caused by P. destructans infection could have drastic consequences for a variety of physiological functions, including innate immune efficiency and water retention. While bat surface lipid and stratum corneum lipid composition have been described, the differences in epidermal lipid content between healthy tissue and P. destructans-infected tissue have not been documented. In this study, we analyzed the effect of wing damage from P. destructans infection on the epidermal polar lipid composition (glycerophospholipids [GPs] and sphingomyelin) of little brown bats (Myotis lucifugus). We hypothesized that infection would lead to lower levels of total lipid or higher oxidized lipid product proportions. Polar lipids from three damaged and three healthy wing samples were profiled by electrospray ionization tandem mass spectrometry. We found lower total broad lipid levels in damaged tissue, specifically ether-linked phospholipids, lysophospholipids, phosphatidylcholine, and phosphatidylethanolamine. Thirteen individual GP species from four broad GP classes were present in higher amounts in healthy tissue. Six unsaturated GP species were absent in damaged tissue. Our results confirm that P. destructans infection leads to altered lipid profiles. Clinical signs of WNS may include lower lipid levels and lower proportions of unsaturated lipids due to cellular and glandular damage.

High-dose simvastatin exhibits enhanced lipid-lowering effects relative to simvastatin/ezetimibe combination therapy

Statins are the frontline in cholesterol reduction therapies; however, their use in combination with agents that possess complimentary mechanisms of action may achieve further reductions in low-density lipoprotein cholesterol. Thirty-nine patients were treated with either 80 mg simvastatin (n=20) or 10 mg simvastatin plus 10 mg ezetimibe (n=19) for 6 weeks. Dosing was designed to produce comparable low-density lipoprotein cholesterol reductions, while enabling assessment of potential simvastatin-associated pleiotropic effects. Baseline and post-treatment plasma were analyzed for lipid mediators (eg, eicosanoids and endocannabinoids) and structural lipids by liquid chromatography tandem mass spectrometry. After statistical analysis and orthogonal projections to latent structures multivariate modeling, no changes were observed in lipid mediator levels, whereas global structural lipids were reduced in response to both monotherapy (R(2)Y=0.74; Q(2)=0.66; cross-validated ANOVA P=7.0×10(-8)) and combination therapy (R(2)Y=0.67; Q(2)=0.54; cross-validated ANOVA P=2.6×10(-5)). Orthogonal projections to latent structures modeling identified a subset of 12 lipids that classified the 2 treatment groups after 6 weeks (R(2)Y=0.65; Q(2)=0.61; cross-validated ANOVA P=5.4×10(-8)). Decreases in the lipid species phosphatidylcholine (15:0/18:2) and hexosyl-ceramide (d18:1/24:0) were the strongest discriminators of low-density lipoprotein cholesterol reductions for both treatment groups (q<0.00005), whereas phosphatidylethanolamine (36:3e) contributed most to distinguishing treatment groups (q=0.017). Shifts in lipid composition were similar for high-dose simvastatin and simvastatin/ezetimibe combination therapy, but the magnitude of the reduction was linked to simvastatin dosage. Simvastatin therapy did not affect circulating levels of lipid mediators, suggesting that pleiotropic effects are not associated with eicosanoid production. Only high-dose simvastatin reduced the relative proportion of sphingomyelin and ceramide to phosphatidylcholine (q=0.008), suggesting a pleiotropic effect previously associated with a reduced risk of cardiovascular disease.

[Sphingolipids in skeletal muscles of C57B1/6 mice after short-term simulated microgravity]

For the first time in skeletal muscle, the sphingolipid profile and key enzymes involved in the generation of ceramide in cells were investigated in simulated microgravity. It was found that, in C57B1/6 mice, the 4-day hindlimb unloading, in addition to reducing the mass of m. soleus, leads to the ceramide accumulation (3-fold) and the decrease of sphingomyelin content in this muscle (7.2-fold), as well as to the increase (2.7-fold) of protein level of acid sphingomyelinase. In a loaded m. biceps brachii the amount of ceramide is also enhanced, but both the amount of sphingomyelin and sphingomyelinase, as well as the muscle mass do not change, while the level of serine palmitoyltranspherase becomes significantly lower than in control mice. Taking into account the negative effects of ceramide in skeletal muscle (insulin resistance, inhibition of protein synthesis and increase of its decay) we can assume that sphingolipid mechanisms may be involved in the development of structural and functional abnormalities of skeletal muscle under conditions of weightlessness.

Altered lipid levels provide evidence for myelin dysfunction in multiple system atrophy

Multiple system atrophy (MSA) is a rapidly-progressive neurodegenerative disease characterized by parkinsonism, cerebellar ataxia and autonomic failure. A pathological hallmark of MSA is the presence of α-synuclein deposits in oligodendrocytes, the myelin-producing support cells of the brain. Brain pathology and in vitro studies indicate that myelin instability may be an early event in the pathogenesis of MSA. Lipid is a major constituent (78% w/w) of myelin and has been implicated in myelin dysfunction in MSA. However, changes, if any, in lipid level/distribution in MSA brain are unknown. Here, we undertook a comprehensive analysis of MSA myelin. We quantitatively measured three groups of lipids, sphingomyelin, sulfatide and galactosylceramide, which are all important in myelin integrity and function, in affected (under the motor cortex) and unaffected (under the visual cortex) white matter regions. For all three groups of lipids, most of the species were severely decreased (40-69%) in affected but not unaffected MSA white matter. An analysis of the distribution of lipid species showed no significant shift in fatty acid chain length/content with MSA. The decrease in lipid levels was concomitant with increased α-synuclein expression. These data indicate that the absolute levels, and not distribution, of myelin lipids are altered in MSA, and provide evidence for myelin lipid dysfunction in MSA pathology. We propose that dysregulation of myelin lipids in the course of MSA pathogenesis may trigger myelin instability.

Effect of lead on lipid peroxidation, phospholipids composition, and methylation in erythrocyte of human

Lead (Pb) is one of the most abundant heavy metals on earth considered as number one environmental persistent toxin and health hazard affecting millions of people in all age groups. After entering bloodstream, 99% of Pb is accumulated in erythrocytes and causes poisoning. Toxic Pb effects on erythrocytes membrane's composition of phosphatidyl serine (PS), phosphatidyl ethanolamine (PE), phosphatidyl choline (PC), and sphingomyelin (SM), and phospholipids transmethylation were determined. Lipid peroxidation in Pb-exposed erythrocytes was evaluated as malondialdehyde (MDA) formation in presence of Fe and vitamin E to understand severity of Pb toxicity and its mitigation. Pb (0.5-5.0 μM) degraded PS (12 to 31%, P < 0.05-0.001) and elevated SM (19-51%, P < 0.05-0.001). Composition of PC and PE were diminished (22%) and elevated (29%), respectively, with higher Pb exposure (5.0 μM, P < 0.001). Pb toxicity suppressed (P < 0.001) transmethylation of phospholipids in membranes (34, 41, and 50%, respectively, with 0.5, 2.5, and 5.0 μM). Pb-induced dose-related MDA production (P < 0.05-0.001) in erythrocytes was obtained, which was accentuated in presence of Fe (P < 0.05-0.001). The vitamin E mitigated (P < 0.05-0.01) the severity of Pb-induced lipid peroxidation. The ratio PS/SM showed maximum change of -27 (P < 0.01), -30 (P < 0.01), and -54% (P < 0.001), respectively at 0.5, 2.5, and 5.0 μM Pb exposures. Ratios PC/SM and PS/PE were at the second, whereas PE/PS at the third order. The study suggests that the mechanisms underlying distortion of compositional phospholipids, inhibition of transmethylation, and exasperated phospholipid peroxidative damage are the active phenomena of Pb toxicity in erythrocytes.

Analysis of phospholipids in infant formulas using high performance liquid chromatography-tandem mass spectrometry

Phospholipids have been used widely in the food industry as emulsifiers, but it is their biological and nutritional function that has been the focus over recent years. The recognition of the importance of phospholipids and sphingomyelin for infant development has led to an increase in the number of infant formulas claiming to contain these complex lipid components. Therefore, the ability to measure these lipids in infant formulas and dairy-derived complex lipid ingredients for fortification purposes is important. A high-performance liquid chromatography-tandem mass spectrometry method that quantifies phosphatidylcholine, phosphatidylethanolamine, phosphatidylinositol, phosphatidylserine, and sphingomyelin found in infant formulas and dairy-derived complex lipid ingredients is described. The method uses external standards of similar fatty acid profile for calibration. The recovery of phospholipids ranged from 92% to 102% with a method repeatability coefficient of variation of 6-10%. In addition to the specificity and selectivity of the method, details of the molecular species in the individual phospholipid classes are available using this method.

Liquid chromatography-tandem mass spectrometry for the determination of sphingomyelin species from calf brain, ox liver, egg yolk, and krill oil

In this study, molecular species of sphingomyelin (SM) in egg yolk, calf brain, ox liver, and krill oil were investigated. Classes of phospholipids (PLs) were purified, identified, and quantified by normal phase semipreparative high-performance liquid chromatography (HPLC) combined with evaporative light scattering detectors (ELSD). For SM molecular species identification, pure SM collected through a flow splitter was loaded to HPLC-electrospray ionization-tandem mass spectrometry (LC-ESI-MS(2)), with 100% methanol containing 5 mM ammonium formate as mobile phase. In addition to classes of PLs, the used approach allowed the determination of profiles of SM species in egg yolk, ox liver, and calf brain, whereas krill oil turned out not to contain any SM. It also allowed the separation and identification of SM subclasses, as well as tentative identification of species with the same molecular mass, including isomers. The results showed that egg yolk contained the highest proportion of (d18:1-16:0)SM (94.1%). The major SM molecular species in ox liver were (d18:1-16:0)SM (25.5%), (d18:1-23:0)SM (19.7%), (d18:1-24:0)SM (13.2%), and (d18:1-22:0)SM (12.5%). Calf brain SM was rich in species such as (d18:1-18:0)SM (40.7%), (d18:1-24:1)SM (17.1%), and (d18:1-20:0)SM (10.8%).

Improved solvent extraction procedure and high-performance liquid chromatography-evaporative light-scattering detector method for analysis of polar lipids from dairy materials

A normal-phase high-performance liquid chromatography-evaporative light-scattering detector method employing dichloromethane, methanol, and acetic acid/triethylamine buffer as the mobile phase was developed for analysis of polar lipids (PLs). This method was applicable for analysis of PLs from both dairy materials and soy lecithin. All of the PLs of interest such as glycolipids, phospholipids, and sphingomyelin were well separated with a total run time of 22.5 min and without necessitating the removal of neutral lipids beforehand. Peak retention times were stable, and the method was reproducible. In this study, a modified method of using solvents for extraction of PLs from dairy matrices was also investigated. The modified method offered higher extraction efficiency, consumed less time, and in some cases saved solvent use.

Mass spectrometric analysis of long-chain lipids

Electrospray and matrix assisted laser desorption ionization generate abundant molecular ion species from all known lipids that have long chain fatty acyl groups esterified or amidated to many different polar headgroup features. Molecular ion species include both positive ions from proton addition [M+H](+) and negative ions from proton abstraction [M-H](-) as well as positive ions from alkali metal attachment and negative ions from acetate or chloride attachment. Collisional activation of both MALDI and ESI behave very similarly in that generated molecular species yield product ions that reveal many structural features of the fatty acyl lipids that can be detected in tandem mass spectrometric experiments. For many lipid species, collision induced dissociation of the positive [M+H](+) reveals information about the polar headgroup, while collision induced dissociation of the negative [M-H](-) provides information about the fatty acyl chain. The mechanisms of formation of many of these lipid product ions have been studied in detail and many established pathways are reviewed here. Specific examples of mass spectrometric behavior of several molecular species are presented, including fatty acids, triacylglycerol, phosphatidic acid, phosphatidylcholine, phosphatidylethanolamine, phosphatidylinositol, phosphatidylserine, phosphatidylglycerol, ceramide, and sphingomeylin.

Mass spectrometric analysis of long-chain lipids

Electrospray and matrix assisted laser desorption ionization generate abundant molecular ion species from all known lipids that have long chain fatty acyl groups esterified or amidated to many different polar headgroup features. Molecular ion species include both positive ions from proton addition [M+H](+) and negative ions from proton abstraction [M-H](-) as well as positive ions from alkali metal attachment and negative ions from acetate or chloride attachment. Collisional activation of both MALDI and ESI behave very similarly in that generated molecular species yield product ions that reveal many structural features of the fatty acyl lipids that can be detected in tandem mass spectrometric experiments. For many lipid species, collision induced dissociation of the positive [M+H](+) reveals information about the polar headgroup, while collision induced dissociation of the negative [M-H](-) provides information about the fatty acyl chain. The mechanisms of formation of many of these lipid product ions have been studied in detail and many established pathways are reviewed here. Specific examples of mass spectrometric behavior of several molecular species are presented, including fatty acids, triacylglycerol, phosphatidic acid, phosphatidylcholine, phosphatidylethanolamine, phosphatidylinositol, phosphatidylserine, phosphatidylglycerol, ceramide, and sphingomeylin.

Sphingomyelin is more sensitively detectable as a negative ion than phosphatidylcholine: a matrix-assisted laser desorption/ionization time-of-flight mass spectrometric study using 9-aminoacridine (9-AA) as matrix

Phospholipids (PLs) are increasingly analyzed by matrix-assisted laser desorption/ionization time-of-flight (MALDI-TOF) mass spectrometry (MS) and imaging MS. Different classes of PLs are preferentially detectable either as positive or negative ions depending on the charges of their headgroups. Sphingomyelin (SM) and phosphatidylcholine (PC) occur in virtually all biological samples and both are assumed to be detectable with the same sensitivity (in the positive ion mode) because their headgroups are identical. We will show here that the detectabilities of PC and SM depend on the matrix used. In the presence of 2,5-dihydroxybenzoic acid (DHB) SM is more sensitively detectable in positive ion mode than PC while the use of 9-aminoacridine (9-AA) as matrix inverts the detectabilities. Our explanation is that the preferred generation of negative ions from SM if 9-AA is used as matrix results in a reduced yield of positive ions. It will also be shown that this is not only valid if a simplified model system is investigated, but also if, for instance, extracts from human erythrocytes are investigated. It will also be outlined that this finding is particularly important in the context of imaging studies where no previous separation of the lipids of interest can be performed.

[Comparative analysis of phospholipid composition in erythrocytes of mouse-like rodents of different species]

Comparative analysis of phospholipid quantitative composition of blood erythrocytes has been performed in white (laboratory mice and rats) and wild (tundra voles) mouse-like rodents. A non-characteristic of mammals low relative content of sphingomyelin is revealed in erythrocyte phospholipids in tundra voles. A hypothesis is put forward that the unique composition of erythrocyte lipids is a peculiar evolutionary developed strategy of adaptation aimed at survival under condition of constant circulation of agents of leptospirosis in populations of this species.

Composition and fatty acid distribution of bovine milk phospholipids from processed milk products

The aim of this work was to assess the accuracy of different extraction methods of phospholipids and to measure the effect that processing has on phospholipid composition. Four methods of extracting phospholipids from buttermilk powder were compared to optimize recovery of sphingomyelin. Using the optimal method, the phospholipid profile of four dairy products (raw milk, raw cream, homogenized and pasteurized milk, and buttermilk powder) was determined. A total lipid extraction by the Folch method followed by a solid-phase extraction using the Bitman method was the most efficient technique to recover milk sphingomyelin. Milk processing (churning, centrifuging, homogenization, spray-drying) affected the profile of milk phospholipids, leading to a loss of sphingomyelin and phosphatidylcholine after centrifugation for cream separation. A corresponding decrease in the saturation content of the raw cream phospholipids and a loss of phosphatidylethanolamine after spray-drying to produce buttermilk powder were also observed.

1H-14N HSQC detection of choline-containing compounds in solutions

Choline nitrogen ((14)N) has a long relaxation time (seconds) which is due to the highly symmetric chemical environments. (14)N in choline also has coupling constants with protons (0.6 Hz to methyl protons, 2.7 Hz to CH(2)O protons and 0.2 Hz to NCH(2) protons). Based on these properties, we introduce a two-dimensional NMR method to detect choline and its derivatives in solutions. This method is the (1)H-(14)N hetero-nuclear single-quantum correlation (HSQC) experiment which has been developed in solid-state NMR in recent years. Experiments have demonstrated that the (1)H-(14)N HSQC technique is a sensitive method for detection of choline-containing compounds in solutions. From 1mM choline solution in 16 min on a 500 MHz NMR spectrometer, a (1)H-(14)N HSQC spectrum has been recorded with a signal-to-noise ratio of 1700. Free choline, phosphocholine and glycerophosphocholine in milk can be well separated in (1)H-(14)N HSQC spectra. This technique would become a promising analytical approach to mixture analyses where choline-containing compounds are of interest, such as tissue extracts, body fluids and food solutions.

Membrane saturated fatty acids and disease progression in multiple sclerosis patients

The risk of developing multiple sclerosis is associated with increased dietary intake of saturated fatty acids. We determined the fatty acid composition within the different phospholipid fractions of red blood and peripheral blood mononuclear cell membranes of 31 patients diagnosed with multiple sclerosis and 30 healthy control subjects using gas chromatography. Individual saturated fatty acids were correlated with the severity of neurological outcome as measured by the Kurtzke Expanded Disability Status Scale. Significant increases were found in multiple sclerosis peripheral blood mononuclear cell membrane sphingomyelin C14:0 and phosphatidylinositol C22:0. In the peripheral blood mononuclear cell membranes, C22:0 and C24:0 showed positive correlations, while C14:0, C16:0 and C20:0 showed inverse correlations with the Functional System Scores. In conclusion, this study is in accordance with previous studies that have shown an increase in shorter long-chain SATS in MS patients. In addition, this study also showed that higher C14:0 and C16:0 reflected better disease outcome as demonstrated by the inverse correlation with the EDSS and FSS. We have also characterized the specific SATS, that is, long-chain SATS that may increase the risk of developing MS.

Imaging of lipids in atheroma by desorption electrospray ionization mass spectrometry

One of the hallmarks of atherosclerosis is the accumulation of lipoproteins within the wall of blood vessels. The lipid composition can vary among atheroma, even within a single individual, and is also dynamic, changing as the lesion progresses. One desirable characteristic of atheroma is their stability, as the rupture of unstable plaques can interfere with normal blood flow to the brain or heart, leading to stroke or heart attack. Desorption electrospray ionization mass spectrometry (DESI-MS) was used in this study for the profiling and imaging of arterial plaques. DESI-MS is an ambient ionization method in which a charged, nebulized solvent spray is directed a surface. In the positive and negative ion modes, sodium and chloride adducts, respectively, of diacyl glycerophosphocholines (GPChos), sphingomyelins (SMs), and hydrolyzed GPChos were detected. Also, cholesteryl esters were detected via adduct formation with ammonium cations. Finally, cholesterol was imaged in the atheroma by doping the charge labeling reagent betaine aldehyde directly into the DESI solvent spray, leading to in situ chemical derivatization of the otherwise nonionic cholesterol. DESI imaging experiments, in which the spatial distribution of the various chemical species is determined by scanning the DESI probe across an entire sample surface, revealed that there are lipid rich regions within the arterial walls, and the lipid rich regions seem to have one of two different lipid profiles. These lipid rich regions likely correspond to the areas of the tissue where lipoprotein particles have accumulated. It is also possible that the different lipid distributions may correlate with the stability or vulnerability of that particular region of the plaque.

Analysis of sphingomyelin in meat based on hydrophilic interaction liquid chromatography coupled to electrospray ionization-tandem mass spectrometry (HILIC-HPLC-ESI-MS/MS)

The amount of sphingomyelin in different kinds of meat was analyzed by hydrophilic interaction liquid chromatography (HILIC-HPLC) coupled with electrospray ionization-tandem mass spectrometry (ESI-MS/MS). Analysis comprised sphingomyelin species with the five different sphingoid bases dihydrosphingosine (d18:0), sphingosine (d18:1(Delta4)), 4,8-sphingadienine (d18:2(Delta4,8)), 4-hydroxysphinganine (phytosphingosine (t18:0)), and 4-hydroxy-8-sphingenine (t18:1), and fatty acids with 12-26 carbon atoms as well as their (poly)unsaturated (up to four double bonds) and monohydroxylated analogues. Most sphingolipids contained sphingosine (d18:1) as the predominant sphingoid base, while stearic acid and palmitic acid were found as prevalent fatty acids. Total amounts vary from 361-471 mg/kg, whereas the meat of the wild animals showed considerably lower amounts.

Immobilization of the influenza A M2 transmembrane peptide in virus envelope-mimetic lipid membranes: a solid-state NMR investigation

The dynamic and structural properties of membrane proteins are intimately affected by the lipid bilayer. One property of membrane proteins is uniaxial rotational diffusion, which depends on the membrane viscosity and thickness. This rotational diffusion is readily manifested in solid-state NMR spectra as characteristic line shapes and temperature-dependent line narrowing or broadening. We show here that this whole-body uniaxial diffusion is suppressed in lipid bilayers mimicking the composition of eukaryotic cell membranes, which are rich in cholesterol and sphingomyelin. We demonstrate this membrane-induced immobilization on the transmembrane peptide of the influenza A M2 (AM2-TM) proton channel protein. At physiological temperature, AM2-TM undergoes uniaxial diffusion faster than approximately 10(5) s(-1) in DLPC, DMPC, and POPC bilayers, but the motion is slowed by 2 orders of magnitude, to <10(3) s(-1), in a cholesterol-rich virus envelope-mimetic membrane ("viral membrane"). The immobilization is manifested as near rigid-limit (2)H quadrupolar couplings and (13)C-(1)H, (15)N-(1)H, and (13)C-(15)N dipolar couplings for all labeled residues. The immobilization suppresses intermediate time scale broadening of the NMR spectra, thus allowing high-sensitivity and high-resolution spectra to be measured at physiological temperature. The conformation of the protein in the viral membrane is more homogeneous than in model PC membranes, as evidenced by the narrow (15)N lines. The immobilization of the M2 helical bundle by the membrane composition change indicates the importance of studying membrane proteins in environments as native as possible. It also suggests that eukaryote-mimetic lipid membranes may greatly facilitate structure determination of membrane proteins by solid-state NMR.

The effect of clinical characteristics on the lecithin/sphingomyelin ratio and lamellar body count: a cross-sectional study

OBJECTIVES

To study the changes in the lecithin/sphingomyelin (L/S) ratio and lamellar body count (LBC) during pregnancy and to study the effect of clinical characteristics on these measurements.

METHODS

We reviewed in retrospect the amniotic fluid samples for the assessment of fetal lung maturity of consecutive women between January 1996 and December 2000. We evaluated the effect of antenatal administration of glucocorticoids, the presence of diabetes, fetal growth restriction and the amount of amniotic fluid on the L/S ratio and LBC. We then constructed normal curves, by relating the L/S ratio and LBC to gestational age in the cases without respiratory distress syndrome (RDS). Data from the literature were added to these curves.

RESULTS

From the 334 included women, 64 infants (19%) developed RDS. The LBC was lower in women with polyhydramnios (p = 0.04), and similar in women with oligohydramnios. Administration of glucocorticoids, the presence of maternal diabetes or fetal growth restriction did not affect the L/S ratio or the LBC. The median L/S ratio in cases without RDS showed a constant increase from a gestational age of 28 weeks onwards. The median LBC increased slowly between a gestational age of 28 weeks and 34 weeks, to increase more steeply thereafter.

CONCLUSIONS

The amount of amniotic fluid affects the LBC, but not the L/S ratio. Since the L/S ratio and the LBC increase with gestation, differences in gestational age should be taken into account in the interpretation of these fetal lung maturity tests.

Effect of Hemodialysis on the Content of Fatty Acids in Monolayers of Erythrocyte Membranes in Patients with Chronic Renal Failure

Lipid metabolism disorders are found in patients with chronic renal failure (CRF). Changes in the content of fatty acids of the phospholipid fraction of erythrocyte membranes can lead to changes in the rheological properties. The objective of our study was to assess the effect of hemodialysis on the composition of fatty acids in two fractions of phospholipids: sphingomyelin (SPH, representative of the external monolayer) and phosphatidylethanolamine (PE, representative of the internal monolayer). Venous blood was drawn from patient with CRF before and after the HD procedure. Lipids from the erythrocyte stroma were extracted using the Rose and Oklander method and then were separated into phospholipid fractions using thin-layer chromatography (TLC). PE and SPH fractions were extracted, and the fatty acid profile was determined using gas chromatography (Perkin Elmer 8400; RTx 2330 column; length: 105 m). In the phospholipid fractions tested, a high content of saturated FA with a medium carbon chain (C 16:0 to C 18:2) and a long carbon chain such as C 24:0, C 24:1; C 22:6; and C 26:0 was found. The HD procedure affected the FA profile in the fractions tested. The proportion of saturated and unsaturated long-chain FA (above 18 C) increased in PE. However, the content of medium-chain FA C 16:0 to C 18:1 decreased. A significant decrease in the content of the majority of long-chain FA could be noted in SPH. The ratio of unsaturated (U) to saturated (S) fatty acids in the SPH fraction increased. Hemodialysis has a significant effect on the content of fatty acids in the PE and SPH fractions of erythrocyte membranes in patients with CRF.

Lung maturation in small for gestational age fetuses from pregnancies complicated by placental insufficiency or maternal hypertension

BACKGROUND

Clinical studies suggest that respiratory outcome of infants born preterm may be influenced by placental insufficiency and hemolysis, elevated liver enzymes, low platelets (HELLP) syndrome. If so, one could expect to see differences in lung maturation indices (lecithin/sphingomyelin (L/S) ratio and lamellar body count (LBC)) in the amniotic fluid. The present study investigates lung maturation indices of preterm small for gestational age (SGA) fetuses with or without abnormal Doppler ultrasound examination and with or without maternal hypertension/HELLP syndrome.

STUDY DESIGN

Retrospective cohort study of 76 neonates born in our center between 1997 and 2003 with gestational age (GA) <34 weeks, birth weight <p10 for GA and available results from amniocentesis. All analyses were corrected for potential confounders.

RESULTS

The L/S ratio was significantly higher in the abnormal Doppler group as compared to the normal Doppler group (p=0.02). The L/S ratio was significantly lower in hypertensive pregnancies as compared to normotensive pregnancies (p=0.02). Subdivision of the maternal hypertension group showed a significantly lower L/S ratio in the HELLP syndrome group as compared to the normotension group (p=0.04).

CONCLUSION

The L/S ratio of SGA fetuses is significantly higher in cases with presumed placental insufficiency and significantly lower when pregnancies are complicated by HELLP syndrome. These observations are in line with the hypothesis that placental insufficiency accelerates lung maturation and with recent reports of poorer respiratory outcome in infants from mothers with HELLP syndrome.

Vorbeugende Behandlung des Atemnotsyndroms des Neugeborenen durch antepartale Glukokortikoidgabe (Betamethason)

Betamethason was administered to 105 patients with threatened premature labour at risk for respiratory distress syndrome (RDS) of the newborn. The most important indications were premature rupture of the membranes (30%) and premature labour (40%). The betamethason treatment was given between the 27. and 35. week of gestation. 79% of the patients delivered prior to 36 weeks of gestation, over 50% prior to 34 weeks gestation. The total incidence of RDS was 25%. Severe types of RDS (stage III and IV) were rare (7%). The mortality of RDS after betamethason treatment was 5.4%. After 32 weeks gestation the mortality from RDS was 0%. Severe types of RDS appear to occur more often in male than in female infants. The incidence of RDS was not lowered further by premature of the membranes. The lecithin/sphingomyelin(L/S)-ratio in the amniotic fluid following treatment with betamethason increased to over 2 in only 2/3 of the cases. The predictive value of the L/S ratio that respiratory distress syndrome of the newborn only occurs rarely with values over 2 was maintained after treatment with betamethason. Our rate in cases with an L/S ratio over 2 was 7.9%.

High-performance liquid chromatography method for quantifying sphingomyelin in rat brain

A rapid, reproducible and accurate high-performance liquid chromatographic (HPLC) method for the quantitative determination of sphingomyelin in rat brain was developed and validated using normal-phase silica gel column, acetonitrile-methanol-water (65:18:17 (v/v)) at a flow rate of 1 ml/min, isocratic elution, UV detection at 207 nm and 1,2-dimyristoyl-sn-glycero-3-phosphocholine as an internal standard. Total run time was 10.0 min. The calibration curve was linear over the range of 0.025-0.4 mg/ml sphingomyelin (R2>0.99). The intra-day coefficient of variation ranged from 1.4% to 2.2%. The average inter-day coefficient of variation over a period of 4 days was 3.1%. The practical limit of detection was 0.005 mg/ml with a quantification limit of 0.01 mg/ml.

Allometric dependence of the life span of mammal erythrocytes on thermal stability and sphingomyelin content of plasma membranes

Thermal stability of erythrocyte membrane is a measure for its ability to maintain permeability barrier at deleterious conditions. Hence, it could impact the resistance of erythrocytes against detrimental factors in circulation. In this study the thermostability of erythrocyte membranes was expressed by the temperature, T(go), at which the transmembrane gradient of ion concentration rapidly dissipated during transient heating. T(go) is the inducing temperature of the membrane transition that activated passive ion permeability at hyperthermia causing thermal hemolysis. A good allometric correlation of T(go) to the resistance against thermal hemolysis and the life span of erythrocytes were found for 13 mammals; sheep, cow, goat, dog, horse, man, rabbit, pig, cat, hamster, guinea pig, rat, and mouse. For the same group, the values of T(go) were strictly related to the sphingomyelin content of erythrocyte membranes. The residual ion permeability, P, was temperature activated from 38 to 57 degrees C with activation energy of 250+/-15 kJ/mol that strongly differed from that below 37 degrees C. The projected value of P at 37 degrees C was about half that of residual physiological permeability for Na+ and K+ that build ground for possible explanation of the life span vs membrane thermostability allometric correlation.

Long-term ethanol consumption impairs reverse cholesterol transport function of high-density lipoproteins by depleting high-density lipoprotein sphingomyelin both in rats and in humans

Moderate alcohol consumption has been linked to lower incidence of coronary artery disease due to increased plasma high-density lipoprotein (HDL), whereas heavy drinking has the opposite effect. Because of the crucial role of HDL in reverse cholesterol transport and positive correlation of HDL sphingomyelin (SM) content with cholesterol efflux, we have compared HDL SM content with its reverse cholesterol transport capacity both in rats fed ethanol on long-term basis and alcoholic individuals. In rats, SM HDL content was decreased in the ethanol group (-15.4%, P < .01) with a concomitant efflux decrease (-21.0%, P < .01) compared to that in controls. Similarly, HDL from the ethanol group, when compared with HDL from the control group, exhibited 13.8% (P < .05) less cholesterol uptake with control-group hepatocytes and 35.0% (P < .05) less cholesterol uptake with ethanol-group hepatocytes. Conversely, hepatocytes from the ethanol group, when compared with hepatocytes from the control group, exhibited 31.0% (P < .01) less cholesterol uptake with control-group HDL and 48.0% (P < .01) less with ethanol-group HDL. In humans, SM content in plasma HDL was also decreased in chronically alcoholic individuals without liver disease (-51.5%, P < .01) and in chronically alcoholic individuals with liver disease (-51.3%, P < .01), compared with nondrinkers. Concomitantly, in alcoholic individuals without liver disease, both efflux and uptake were decreased by 83.0% and 54.0% (P < .01), respectively, and in chronically alcoholic individuals with liver disease by 84.0% and 61.0% (P < .01), respectively, compared with nondrinkers. Based on these findings, we conclude that long-term ethanol consumption significantly impairs not only cholesterol efflux function of HDL by decreasing its SM content but also cholesterol uptake by affecting presumably hepatocyte receptors for HDL.