Sphingolipid Distribution Research Articles

Metabolome Comparison of Sichuan Dried Orange Peels (Chenpi) Aged for Different Years

Chuan chenpi is obtained by aging the peel of Citrus reticulata cv. ‘Dahongpao’, a traditional Chinese citrus variety. Chenpi has been used in traditional Chinese medicine since ancient times. It is believed that the longer the ripening period, the better the health properties. The composition of the metabolome of Chuan chenpi and how different aging periods affect it are not known. Current analysis was performed using Chuan chenpi aged for one (CR1), five (CR5) and ten (CR10) years. Initially, the total flavonoid and phenolic content were quantified, and then the global metabolomic profiles of CR1, CR5 and CR10 were studied. The total flavonoid and phenolic content increased significantly in CR5 compared to CR1 and then decreased in CR10. The metabolomic analyses led to the identification of 781 compounds belonging to more than 19 classes. Flavonoids and phenolic acids accounted for almost half (~48%) of the Chuan chenpi metabolome. Other major classes included amino acids (~8%), alkaloids (7.17%), organic acids (~7%), sugars (5.5%), nucleotides and derivatives (~5%), free fatty acids (3.33%) and other classes. The metabolite diversity of glycerol esters, terpenoids and stilbenes was constant during the three storage periods, whereas those of lignans, vitamins, coumarins, lipids and free fatty acids showed slight variations. The subclass distribution of phenylpropanoids, quinones, sphingolipids, and organic acids showed a decrease in diversity from CR1 to CR5, with CR10 showing a further decrease or remaining constant. Amino acids and derivatives, phenolic acids and flavonoids showed an increasing trend in the number of metabolites over the storage period. Compared to CR5, CR10 showed a higher number of differentially accumulated metabolites; in particular, flavonoids, phenolic acids and organic acids showed increased accumulation in CR10. In conclusion, the metabolome of Chuan chenpi is rich in flavonoids and phenols. Aging significantly affects the metabolome composition. Both CR5 and CR10 may be useful materials for health studies depending on the objectives of pharmacological use.

Arabidopsis Leaf Chloroplasts Have a Specific Sphingolipidome.

Sphingolipids are ubiquitous in eukaryotes and certain prokaryotes, where they serve as vital components of biological membranes and bioactive molecules. Chloroplasts have complex membrane structures that play crucial roles in photosynthesis, but their specific sphingolipidome remains unreported. In this study, we used liquid chromatography-mass spectrometry (LC-MS/MS) to analyze the sphingolipidome of purified Arabidopsis thaliana chloroplasts. We detected 92 chloroplast sphingolipids. The chloroplast sphingolipidome differed from total leaf (TL) samples, with a higher content of free long-chain bases and hydroxyceramides and a greater proportion of complex sphingolipids with 16C fatty acid (FA) forms. Notably, chloroplast glucosylceramides were predominantly the d18:1 h16:0 and t18:1 h16:0 forms rather than the 24C FA form found in TL and other cellular structures. Comparing the sphingolipidomes of different cellular structures underscores the inhomogeneity of the intracellular distribution of sphingolipids. This provides a robust reference for further elucidating the function of sphingolipids in plant cells.

Toward Understanding the Subcellular Distributions of Cholesterol and Sphingolipids Using High-Resolution NanoSIMS Imaging.

Characterizing the subcellular distributions of biomolecules of interest is a basic inquiry that helps inform on the potential roles of these molecules in biological functions. Presently, the functions of specific lipid species and cholesterol are not well understood, partially because cholesterol and lipid species of interest are difficult to image with high spatial resolution but without perturbing them. Because cholesterol and lipids are relatively small and their distributions are influenced by noncovalent interactions with other biomolecules, functionalizing them with relatively large labels that permit their detection may alter their distributions in membranes and between organelles. This challenge has been surmounted by exploiting rare stable isotopes as labels that may be metabolically incorporated into cholesterol and lipids without altering their chemical compositions, and the Cameca NanoSIMS 50 instrument's ability to image rare stable isotope labels with high spatial resolution. This Account covers the use of secondary ion mass spectrometry (SIMS) performed with a Cameca NanoSIMS 50 instrument for imaging cholesterol and sphingolipids in the membranes of mammalian cells. The NanoSIMS 50 detects monatomic and diatomic secondary ions ejected from the sample to map the elemental and isotopic composition at the surface of the sample with better than 50 nm lateral resolution and 5 nm depth resolution. Much effort has focused on using NanoSIMS imaging of rare isotope-labeled cholesterol and sphingolipids for testing the long-standing hypothesis that cholesterol and sphingolipids colocalize within distinct domains in the plasma membrane. By using a NanoSIMS 50 to image rare isotope-labeled cholesterol and sphingolipids in parallel with affinity-labeled proteins of interest, a hypothesis regarding the colocalization of specific membrane proteins with cholesterol and sphingolipids in distinct plasma membrane domains has been tested. NanoSIMS performed in a depth profiling mode has enabled imaging the intracellular distributions of cholesterol and sphingolipids. Important progress has also been made in developing a computational depth correction strategy for constructing more accurate three-dimensional (3D) NanoSIMS depth profiling images of intracellular component distribution without requiring additional measurements with complementary techniques or signal collection. This Account provides an overview of this exciting progress, focusing on the studies from our laboratory that shifted understanding of plasma membrane organization, and the development of enabling tools for visualizing intracellular lipids.

The nutritional functions of dietary sphingomyelin and its applications in food.

Sphingolipids are common structural components of cell membranes and are crucial for cell functions in physiological and pathophysiological conditions. Sphingomyelin and its metabolites, such as sphingoid bases, ceramide, ceramide-1-phosphate, and sphingosine-1-phosphate, play signaling roles in the regulation of human health. The diverse structures of sphingolipids elicit various functions in cellular membranes and signal transduction, which may affect cell growth, differentiation, apoptosis, and maintain biological activities. As nutrients, dietary sphingomyelin and its metabolites have wide applications in the food and pharmaceutical industry. In this review, we summarized the distribution, classifications, structures, digestion, absorption and metabolic pathways of sphingolipids, and discussed the nutritional functioning of sphingomyelin in chronic metabolic diseases. The possible implications of dietary sphingomyelin in the modern food preparations including dairy products and infant formula, skin improvement, delivery system and oil organogels are also evaluated. The production of endogenous sphingomyelin is linked to pathological changes in obesity, diabetes, and atherosclerosis. However, dietary supplementations of sphingomyelin and its metabolites have been shown to maintain cholesterol homeostasis and lipid metabolism, and to prevent or treat these diseases. This seemly paradoxical phenomenon shows that dietary sphingomyelin and its metabolites are candidates for food additives and functional food development for the prevention and treatment of chronic metabolic diseases in humans.

The key role of sphingolipid metabolism in cancer: New therapeutic targets, diagnostic and prognostic values, and anti-tumor immunotherapy resistance

Biologically active sphingolipids are closely related to the growth, differentiation, aging, and apoptosis of cancer cells. Some sphingolipids, such as ceramides, are favorable metabolites in the sphingolipid metabolic pathway, usually mediating antiproliferative responses, through inhibiting cancer cell growth and migration, as well as inducing autophagy and apoptosis. However, other sphingolipids, such as S1P, play the opposite role, which induces cancer cell transformation, migration and growth and promotes drug resistance. There are also other sphingolipids, as well as enzymes, played potentially critical roles in cancer physiology and therapeutics. This review aimed to explore the important roles of sphingolipid metabolism in cancer. In this article, we summarized the role and value of sphingolipid metabolism in cancer, including the distribution of sphingolipids, the functions, and their relevance to cancer diagnosis and prognosis. We also summarized the known and potential antitumor targets present in sphingolipid metabolism, analyzed the correlation between sphingolipid metabolism and tumor immunity, and summarize the antitumor effects of natural compounds based on sphingolipids. Through the analysis and summary of sphingolipid antitumor therapeutic targets and immune correlation, we aim to provide ideas for the development of new antitumor drugs, exploration of new therapeutic means for tumors, and study of immunotherapy resistance mechanisms.

The Glucosylceramide Synthase Inhibitor PDMP Causes Lysosomal Lipid Accumulation and mTOR Inactivation.

For many years, the biology of glycosphingolipids was elucidated with the help of glucosylceramide synthase (GCS) inhibitors such as 1-phenyl-2-decanoylamino-3-morpholino-1-propanol (PDMP). Additionally, PDMP gained interest because of its chemosensitizing effects. Several studies have successfully combined PDMP and anti-cancer drugs in the context of cancer therapy. However, the mechanism of action of PDMP is not fully understood and seems to go beyond glycolipid inhibition. Here, we used a functionalized sphingosine analogue (pacSph) to investigate the acute effects of PDMP on cellular sphingolipid distribution and found that PDMP, but not other GCS inhibitors, such as ND-DNJ (also called Miglustat), induced sphingolipid accumulation in lysosomes. This effect could be connected to defective export from lysosome, as monitored by the prolonged lysosomal staining of sphingolipids as well as by a delay in the metabolic conversion of the pacSph precursor. Additionally, other lipids such as lysobisphosphatidic acid (LBPA) and cholesterol were enriched in lysosomes upon PDMP treatment in a time-dependent manner. We could further correlate early LBPA enrichment with dissociation of the mechanistic target of rapamycin (mTOR) from lysosomes followed by nuclear translocation of its downtream target, transcription factor EB (TFEB). Altogether, we report here a timeline of lysosomal lipid accumulation events and mTOR inactivation arising from PDMP treatment.

Qualitative distribution of endogenous sphingolipids in plasma of human and rodent species by UPLC-Q-Exactive-MS

Sphingolipids (SLs) are endogenously bioactive molecules with diverse structures, and its metabolic disorders are involved in the progression of many diseases. In this study, an ultra-performance liquid chromatography quadrupole exactive mass spectrometry (UPLC-Q-Exactive-MS) method was established to comprehensively profile SLs in plasma. First, the fragment patterns of SL standards of each subclass were investigated. Then, the SL species in plasma were characterized based on the fragmentation rules. Finally, a total of 144 endogenous SL species consisting of 216 regioisomers were identified in plasma of human, golden hamster and C57BL/6 mice, which was the most comprehensive identification for SLs in plasma. In addition to the known species, 19 SL species that have never been reported were also identified. The profile of SLs in plasma of human and two rodent species was compared subsequently. It was worth noting that a total of 9 SL molecular species consisting of 11 regioisomers with low abundance were successfully identified in human plasma through comparison among species. Those findings contribute to a deeper understanding of SLs in human plasma and provide scientific basis for the selection of animal model. The established profile of SLs in plasma could be used for screening of lipid biomarkers of various diseases.

Sphingolipid Profiling Reveals Different Extent of Ceramide Accumulation in Bovine Retroperitoneal and Subcutaneous Adipose Tissues.

Sphingolipids are bioactive lipids that can modulate insulin sensitivity, cellular differentiation, and apoptosis in a tissue-specific manner. However, their comparative profiles in bovine retroperitoneal (RPAT) and subcutaneous adipose tissue (SCAT) are currently unknown. We aimed to characterize the sphingolipid profiles using a targeted lipidomics approach and to assess whether potentially related sphingolipid pathways are different between SCAT and RPAT. Holstein bulls (n = 6) were slaughtered, and SCAT and RPAT samples were collected for sphingolipid profiling. A total of 70 sphingolipid species were detected and quantified by UPLC-MS/MS in multiple reaction monitoring (MRM) mode, including ceramide (Cer), dihydroceramide (DHCer), sphingomyelin (SM), dihydrosphingomyelin (DHSM), ceramide-1-phosphate (C1P), sphingosine-1-phosphate (S1P), galactosylceramide (GalCer), glucosylceramide (GluCer), lactosylceramide (LacCer), sphinganine (DHSph), and sphingosine (Sph). Our results showed that sphingolipids of the de novo synthesis pathway, such as DHSph, DHCer, and Cer, were more concentrated in RPAT than in SCAT. Sphingolipids of the salvage pathway and the sphingomyelinase pathway, such as Sph, S1P, C1P, glycosphingolipid, and SM, were more concentrated in SCAT. Our results indicate that RPAT had a greater extent of ceramide accumulation, thereby increasing the concentration of further sphingolipid intermediates in the de novo synthesis pathway. This distinctive sphingolipid distribution pattern in RPAT and SCAT can potentially explain the tissue-specific activity in insulin sensitivity, proinflammation, and oxidative stress in RPAT and SCAT.

Sphingolipids in the Heart: From Cradle to Grave.

Cardiovascular diseases are the leading cause of mortality worldwide and this has largely been driven by the increase in metabolic disease in recent decades. Metabolic disease alters metabolism, distribution, and profiles of sphingolipids in multiple organs and tissues; as such, sphingolipid metabolism and signaling have been vigorously studied as contributors to metabolic pathophysiology in various pathological outcomes of obesity, including cardiovascular disease. Much experimental evidence suggests that targeting sphingolipid metabolism may be advantageous in the context of cardiometabolic disease. The heart, however, is a structurally and functionally complex organ where bioactive sphingolipids have been shown not only to mediate pathological processes, but also to contribute to essential functions in cardiogenesis and cardiac function. Additionally, some sphingolipids are protective in the context of ischemia/reperfusion injury. In addition to mechanistic contributions, untargeted lipidomics approaches used in recent years have identified some specific circulating sphingolipids as novel biomarkers in the context of cardiovascular disease. In this review, we summarize recent literature on both deleterious and beneficial contributions of sphingolipids to cardiogenesis and myocardial function as well as recent identification of novel sphingolipid biomarkers for cardiovascular disease risk prediction and diagnosis.

Sphingolipid distribution at mitochondria-associated membranes (MAMs) upon induction of apoptosis

The levels and composition of sphingolipids and related metabolites are altered in aging and in common disorders such as diabetes and cancers, as well as in neurodegenerative, cardiovascular, and respiratory diseases. Changes in sphingolipids have been implicated as being an essential step in mitochondria-driven cell death. However, little is known about the precise sphingolipid composition and modulation in mitochondria or related organelles. Here, we used LC-MS/MS to analyze the presence of key components of the ceramide metabolic pathway in vivo and in vitro in purified ER, mitochondria-associated membranes (MAMs), and mitochondria. Specifically, we analyzed the sphingolipids in the three pathways that generate ceramide: sphinganine in the de novo ceramide pathway, SM in the breakdown pathway, and sphingosine in the salvage pathway. We observed sphingolipid profiles in mouse liver, mouse brain, and a human glioma cell line (U251). We analyzed the quantitative and qualitative changes of these sphingolipids during staurosporine-induced apoptosis in U251 cells. Ceramide (especially C16-ceramide) levels increased during early apoptosis possibly through a conversion from mitochondrial sphinganine and SM, but sphingosine and lactosyl- and glycosyl-ceramide levels were unaffected. We also found that ceramide generation is enhanced in mitochondria when SM levels are decreased in the MAM. This decrease was associated with an increase in acid sphingomyelinase activity in MAM. We conclude that meaningful sphingolipid modifications occur in MAM, the mitochondria, and the ER during the early steps of apoptosis.

Dynamics of sphingolipids and the serine palmitoyltransferase complex in rat oligodendrocytes during myelination

Myelin is a unique lipid-rich membrane structure that accelerates neurotransmission and supports neuronal function. Sphingolipids are critical myelin components. Yet sphingolipid content and synthesis have not been well characterized in oligodendrocytes, the myelin-producing cells of the CNS. Here, using quantitative real-time PCR, LC-MS/MS-based lipid analysis, and biochemical assays, we examined sphingolipid synthesis during the peak period of myelination in the postnatal rat brain. Importantly, we characterized sphingolipid production in isolated oligodendrocytes. We analyzed sphingolipid distribution and levels of critical enzymes and regulators in the sphingolipid biosynthetic pathway, with focus on the serine palmitoyltransferase (SPT) complex, the rate-limiting step in this pathway. During myelination, levels of the major SPT subunits increased and oligodendrocyte maturation was accompanied by extensive alterations in the composition of the SPT complex. These included changes in the relative levels of two alternative catalytic subunits, SPTLC2 and -3, in the relative levels of isoforms of the small subunits, ssSPTa and -b, and in the isoform distribution of the SPT regulators, the ORMDLs. Myelination progression was accompanied by distinct changes in both the nature of the sphingoid backbone and the N-acyl chains incorporated into sphingolipids. We conclude that the distribution of these changes among sphingolipid family members is indicative of a selective channeling of the ceramide backbone toward specific downstream metabolic pathways during myelination. Our findings provide insights into myelin production in oligodendrocytes and suggest how dysregulation of the biosynthesis of this highly specialized membrane could contribute to demyelinating diseases.

Variation in Coronary Atherosclerosis Severity Related to a Distinct LDL (Low-Density Lipoprotein) Profile: Findings From a Familial Hypercholesterolemia Pig Model.

In an adult porcine model of familial hypercholesterolemia (FH), coronary plaque development was characterized. To elucidate the underlying mechanisms of the observed inter-individual variation in disease severity, detailed lipoprotein profiles were determined. Approach and Results: FH pigs (3 years old, homozygous LDLR R84C mutation) received an atherogenic diet for 12 months. Coronary atherosclerosis development was monitored using serial invasive imaging and histology. A pronounced difference was observed between mildly diseased pigs which exclusively developed early lesions (maximal plaque burden, 25% [23%-34%]; n=5) and advanced-diseased pigs (n=5) which developed human-like, lumen intruding plaques (maximal plaque burden, 69% [57%-77%]) with large necrotic cores, intraplaque hemorrhage, and calcifications. Advanced-diseased pigs and mildly diseased pigs displayed no differences in conventional risk factors. Additional plasma lipoprotein profiling by size-exclusion chromatography revealed 2 different LDL (low-density lipoprotein) subtypes: regular and larger LDL. Cholesterol, sphingosine-1-phosphate, ceramide, and sphingomyelin levels were determined in these LDL-subfractions using standard laboratory techniques and high-pressure liquid chromatography mass-spectrometry analyses, respectively. At 3 months of diet, regular LDL of advanced-diseased pigs contained relatively more cholesterol (LDL-C; regular/larger LDL-C ratio 1.7 [1.3-1.9] versus 0.8 [0.6-0.9]; P=0.008) than mildly diseased pigs, while larger LDL contained more sphingosine-1-phosphate, ceramides, and sphingomyelins. Larger and regular LDL was also found in plasma of 3 patients with homozygous FH with varying LDL-C ratios. In our adult FH pig model, inter-individual differences in atherosclerotic disease severity were directly related to the distribution of cholesterol and sphingolipids over a distinct LDL profile with regular and larger LDL shortly after the diet start. A similar LDL profile was detected in patients with homozygous FH.

Flotillin proteins recruit sphingosine to membranes and maintain cellular sphingosine-1-phosphate levels

Sphingosine-1-phosphate (S1P) is an important lipid signalling molecule. S1P is produced via intracellular phosphorylation of sphingosine (Sph). As a lipid with a single fatty alkyl chain, Sph may diffuse rapidly between cellular membranes and through the aqueous phase. Here, we show that the absence of microdomains generated by multimeric assemblies of flotillin proteins results in reduced S1P levels. Cellular phenotypes of flotillin knockout mice, including changes in histone acetylation and expression of Isg15, are recapitulated when S1P synthesis is perturbed. Flotillins bind to Sph in vitro and increase recruitment of Sph to membranes in cells. Ectopic re-localisation of flotillins within the cell causes concomitant redistribution of Sph. The data suggest that flotillins may directly or indirectly regulate cellular sphingolipid distribution and signalling.

Cholesterol is enriched in the sphingolipid patches on the substrate near nonpolarized MDCK cells, but not in the sphingolipid domains in their plasma membranes

Information about the distributions of cholesterol and sphingolipids within the plasma membranes of mammalian cells provides insight into the roles of these molecules in membrane function. In this report, high-resolution secondary ion mass spectrometry was used to image the distributions of metabolically incorporated rare isotope-labeled sphingolipids and cholesterol on the surfaces of nonpolarized epithelial cells. Sphingolipid domains that were not enriched with cholesterol were detected in the plasma membranes of subconfluent Madin-Darby canine kidney cells. Surprisingly, cholesterol-enriched sphingolipid patches were observed on the substrate adjacent to these cells. Based on the shapes of these cholesterol-enriched sphingolipid patches on the substrate and their proximity to cellular projections, we hypothesize that they are deposits of membranous particles released by the cell.

Subcellular Distribution of Cholesterol and Sphingolipids in Rat Hepatocytes

Hepatocytes are central in energy and lipid homeostasis of mammals and as such are key players in maintaining and regulating serum cholesterol levels. In addition, hepatocytes produce bile, which has detergent properties and is the main product of cholesterol metabolism. The canalicular membrane is the site of bile formation and needs protective mechanisms against the detergent properties of bile. One such mechanism could be a specific lipid composition. We therefore aimed to use a targeted lipidomics approach to determine simultaneously the cholesterol and sphingolipid composition of the organelles involved in lipid synthesis in hepatocytes. Subcellular organelles were isolated from rat liver with standard methodologies and lipids were analyzed by either electrospray ionization mass spectrometry (glycerophospholipids and sphingolipids) or gas chromatography coupled mass spectrometry (sterols). Our data indicate that there is a distinct difference in cholesterol and sphingolipid content in the organelle fractions. Highest cholesterol content is found in basolateral plasma membranes and in the Golgi fraction, while endoplasmic reticulum displays a low cholesterol content. A high proportion of sphingomyelin is present in basolateral plasma membranes, smooth endoplasmic reticulum and in the Golgi apparatus. Ceramide content is higher in basolateral membranes compared to organelles and the canalicular plasma membrane. Glucosylceramide levels are very low and are mostly found in Golgi fractions. Our preliminary data so far show a parallel distribution of cholesterol and sphingolipids in subcellular fractions of rat hepatocytes.This abstract is from the Experimental Biology 2018 Meeting. There is no full text article associated with this abstract published in The FASEB Journal.

Investigating the Transbilayer Distribution of Cholesterol in Asymmetric Unilamellar Vesicles using Small-Angle Scattering

Cholesterol is the most abundant component of eukaryotic plasma membranes (PMs), accounting for 30-50% of the total lipid. In addition to modulating the structural and mechanical properties of lipid bilayers, cholesterol promotes the formation of ordered+disordered fluid phase separation in model membranes, and may similarly contribute to microdomain or “raft” formation in the PM. A major unresolved question is how PM properties and functions are influenced by the asymmetric transbilayer distribution of lipids, including cholesterol. While the distribution of most phospholipids and sphingolipids is known, determining the average transbilayer distribution of cholesterol has been challenging due to its rapid translocation between the PM leaflets. Previous attempts to probe the cholesterol distribution in cell membranes using fluorescence-based methods have yielded conflicting results. Moreover, studies using model vesicles have been limited due to the difficulty of preparing asymmetric liposomes. Making use of recent advancements enabling the production of asymmetric large unilamellar vesicles (aLUVs) via cyclodextrin-mediated lipid exchange, we prepared cholesterol-containing aLUVs in which one leaflet was enriched in egg sphingomyelin (eSM), and the other in phosphatidylethanolamine (POPE). We then used small-angle neutron and x-ray scattering combined with isotopic labeling strategies to probe the average cholesterol location within these bilayers. An analysis of scattering data, together with complementary Molecular Dynamics simulations, provides insight into the transbilayer distribution of cholesterol in asymmetric membranes.

Sphingolipid Distribution, Content and Gene Expression during Olive-Fruit Development and Ripening.

Plant sphingolipids are involved in the building of the matrix of cell membranes and in signaling pathways of physiological processes and environmental responses. However, information regarding their role in fruit development and ripening, a plant-specific process, is unknown. The present study seeks to determine whether and, if so, how sphingolipids are involved in fleshy-fruit development and ripening in an oil-crop species such as olive (Olea europaea L. cv. Picual). Here, in the plasma-membranes of live protoplasts, we used fluorescence to examine various specific lipophilic stains in sphingolipid-enriched regions and investigated the composition of the sphingolipid long-chain bases (LCBs) as well as the expression patterns of sphingolipid-related genes, OeSPT, OeSPHK, OeACER, and OeGlcCerase, during olive-fruit development and ripening. The results demonstrate increased sphingolipid content and vesicle trafficking in olive-fruit protoplasts at the onset of ripening. Moreover, the concentration of LCB [t18:1(8Z), t18:1 (8E), t18:0, d18:2 (4E/8Z), d18:2 (4E/8E), d18:1(4E), and 1,4-anhydro-t18:1(8E)] increases during fruit development to reach a maximum at the onset of ripening, although these molecular species decreased during fruit ripening. On the other hand, OeSPT, OeSPHK, and OeGlcCerase were expressed differentially during fruit development and ripening, whereas OeACER gene expression was detected only at the fully ripe stage. The results provide novel data about sphingolipid distribution, content, and biosynthesis/turnover gene transcripts during fleshy-fruit ripening, indicating that all are highly regulated in a developmental manner.

A preliminary study of bipolar disorder type I by mass spectrometry-based serum lipidomics

The present study aimed at investigating possible alterations in the serum lipid profile of euthymic patients with bipolar disorder type I (BD) compared to healthy controls (HC). Thirty-five individuals from both genders were recruited, with 14 diagnosed and treated as BD patients (BD group) and 21 healthy subjects (HC group). Clinical assessment was based on the Structured Clinical Interview for DSM-IV Axis I Disorders (SCID-I), Young Mania Rating Scale (YMRS), and 17-items of Hamilton Depression Rating Scale (HDRS-17) data, which were used to confirm diagnosis, to verify psychiatric comorbidities, and to estimate the severity of manic and depressive symptoms. Ultra-high performance liquid chromatography (UHPLC) coupled to high resolution mass spectrometry (HRMS) was applied to analyze the lipids extracted from all serum samples from both studied groups. In this pioneer and exploratory study, we observed different serum lipid profiles for BD and HC groups, especially regarding glycerophospholipid, glycerolipid, and sphingolipid distribution. Multivariate statistical analyses indicated that 121 lipids were significantly different between BD and HC. Phosphatidylinositols were identified as the most altered lipids in BD patient sera. The results of this preliminary study reinforce the role of lipid abnormalities in BD and offer additional methodological possibilities for investigation in the field.

Localization of Sphingolipid Enriched Plasma Membrane Regions and Long-Chain Base Composition during Mature-Fruit Abscission in Olive

Sphingolipids, found in membranes of eukaryotic cells, have been demonstrated to carry out functions in various processes in plant cells. However, the roles of these lipids in fruit abscission remain to be determined in plants. Biochemical and fluorescence microscopy imaging approach has been adopted to investigate the accumulation and distribution of sphingolipids during mature-fruit abscission in olive (Olea europaea L. cv. Picual). Here, a lipid-content analysis in live protoplasts of the olive abscission zone (AZ) was made with fluorescent dyes and lipid analogs, particularly plasma membrane sphingolipid-enriched domains, and their dynamics were investigated in relation to the timing of mature-fruit abscission. In olive AZ cells, the measured proportion of both polar lipids and sphingolipids increased as well as endocytosis was stimulated during mature-fruit abscission. Likewise, mature-fruit abscission resulted in quantitative and qualitative changes in sphingolipid long-chain bases (LCBs) in the olive AZ. The total LCB increase was due essentially to the increase of t18:1(8E) LCBs, suggesting that C-4 hydroxylation and Δ8 desaturation with a preference for (E)-isomer formation were quantitatively the most important sphingolipids in olive AZ during abscission. However, our results also showed a specific association between the dihydroxylated LCB sphinganine (d18:0) and the mature-fruit abscission. These results indicate a clear correlation between the sphingolipid composition and mature-fruit abscission. Moreover, measurements of endogenous sterol levels in the olive AZ revealed that it accumulated sitosterol and campesterol with a concomitant decrease in cycloartenol during abscission. In addition, underlying the distinct sterol composition of AZ during abscission, genes for key biosynthetic enzymes for sterol synthesis, for obtusifoliol 14α-demethylase (CYP51) and C-24 sterol methyltransferase2 (SMT2), were up-regulated during mature-fruit abscission, in parallel to the increase in sitosterol content. The differences found in AZ lipid content and the relationships established between LCB and sterol composition, offer new insights about sphingolipids and sterols in abscission.

Sphingolipid Organization in the Plasma Membrane and the Mechanisms That Influence It.

Sphingolipids are structural components in the plasma membranes of eukaryotic cells. Their metabolism produces bioactive signaling molecules that modulate fundamental cellular processes. The segregation of sphingolipids into distinct membrane domains is likely essential for cellular function. This review presents the early studies of sphingolipid distribution in the plasma membranes of mammalian cells that shaped the most popular current model of plasma membrane organization. The results of traditional imaging studies of sphingolipid distribution in stimulated and resting cells are described. These data are compared with recent results obtained with advanced imaging techniques, including super-resolution fluorescence detection and high-resolution secondary ion mass spectrometry (SIMS). Emphasis is placed on the new insight into the sphingolipid organization within the plasma membrane that has resulted from the direct imaging of stable isotope-labeled lipids in actual cell membranes with high-resolution SIMS. Super-resolution fluorescence techniques have recently revealed the biophysical behaviors of sphingolipids and the unhindered diffusion of cholesterol analogs in the membranes of living cells are ultimately in contrast to the prevailing hypothetical model of plasma membrane organization. High-resolution SIMS studies also conflicted with the prevailing hypothesis, showing sphingolipids are concentrated in micrometer-scale membrane domains, but cholesterol is evenly distributed within the plasma membrane. Reductions in cellular cholesterol decreased the number of sphingolipid domains in the plasma membrane, whereas disruption of the cytoskeleton eliminated them. In addition, hemagglutinin, a transmembrane protein that is thought to be a putative raft marker, did not cluster within sphingolipid-enriched regions in the plasma membrane. Thus, sphingolipid distribution in the plasma membrane is dependent on the cytoskeleton, but not on favorable interactions with cholesterol or hemagglutinin. The alternate views of plasma membrane organization suggested by these findings are discussed.