Role Of Sphingolipid Metabolism Research Articles

Lipid-lowering drugs affect lung cancer risk via sphingolipid metabolism: a drug-target Mendelian randomization study.

Background: The causal relationship between lipid-lowering drug (LLD) use and lung cancer risk is controversial, and the role of sphingolipid metabolism in this effect remains unclear. Methods: Genome-wide association study data on low-density lipoprotein (LDL), apolipoprotein B (ApoB), and triglycerides (TG) were used to develop genetic instrumental variables (IVs) for LLDs. Two-step Mendelian randomization analyses were performed to examine the causal relationship between LLDs and lung cancer risk. The effects of ceramide, sphingosine-1-phosphate (S1P), and ceramidases on lung cancer risk were explored, and the proportions of the effects of LLDs on lung cancer risk mediated by sphingolipid metabolism were calculated. Results: APOB inhibition decreased the lung cancer risk in ever-smokers via ApoB (odds ratio [OR] 0.81, 95% confidence interval [CI] 0.70-0.92, p = 0.010), LDL (OR 0.82, 95% CI 0.71-0.96, p = 0.040), and TG (OR 0.63, 95% CI 0.46-0.83, p = 0.015) reduction by 1 standard deviation (SD), decreased small-cell lung cancer (SCLC) risk via LDL reduction by 1 SD (OR 0.71, 95% CI 0.56-0.90, p = 0.016), and decreased the plasma ceramide level and increased the neutral ceramidase level. APOC3 inhibition decreased the lung adenocarcinoma (LUAD) risk (OR 0.60, 95% CI 0.43-0.84, p = 0.039) but increased SCLC risk (OR 2.18, 95% CI 1.17-4.09, p = 0.029) via ApoB reduction by 1 SD. HMGCR inhibition increased SCLC risk via ApoB reduction by 1 SD (OR 3.04, 95% CI 1.38-6.70, p = 0.014). The LPL agonist decreased SCLC risk via ApoB (OR 0.20, 95% CI 0.07-0.58, p = 0.012) and TG reduction (OR 0.58, 95% CI 0.43-0.77, p = 0.003) while increased the plasma S1P level. PCSK9 inhibition decreased the ceramide level. Neutral ceramidase mediated 8.1% and 9.5% of the reduced lung cancer risk in ever-smokers via ApoB and TG reduction by APOB inhibition, respectively, and mediated 8.7% of the reduced LUAD risk via ApoB reduction by APOC3 inhibition. Conclusion: We elucidated the intricate interplay between LLDs, sphingolipid metabolites, and lung cancer risk. Associations of APOB, APOC3, and HMGCR inhibition and LPL agonist with distinct lung cancer risks underscore the multifaceted nature of these relationships. The observed mediation effects highlight the considerable influence of neutral ceramidase on the lung cancer risk reduction achieved by APOB and APOC3 inhibition.

Neutral sphingomyelinase blockade enhances hematopoietic stem cell fitness through an integrated stress response

AbstractHematopoietic stem and progenitor cell (HSPC) transplantation serves as a curative therapy for many benign and malignant hematopoietic disorders and as a platform for gene therapy. However, growing needs for ex vivo manipulation of HSPC-graft products are limited by barriers in maintaining critical self-renewal and quiescence properties. The role of sphingolipid metabolism in safeguarding these essential cellular properties has been recently recognized, but not yet widely explored. Here, we demonstrate that pharmacologic and genetic inhibition of neutral sphingomyelinase 2 (nSMase-2) leads to sustained improvements in long-term competitive transplantation efficiency after ex vivo culture. Mechanistically, nSMase-2 blockade activates a canonical integrated stress response (ISR) and promotes metabolic quiescence in human and murine HSPCs. These adaptations result in part from disruption in sphingolipid metabolism that impairs the release of nSMase-2–dependent extracellular vesicles (EVs). The aggregate findings link EV trafficking and the ISR as a regulatory dyad guarding HSPC homeostasis and long-term fitness. Translationally, transient nSMase-2 inhibition enables ex vivo graft manipulation with enhanced HSPC potency.

Two ways to die: Species dependent PCD modes in grapevine cells

Programmed cell death (PCD) is considered as a hallmark of strain-specific immunity. In contrast, generic basal immunity is thought to act without PCD. This classical bifurcation has been questioned during recent years. Likewise, the role of jasmonate signalling for these two modes of innate immunity has remained ambiguous. We have addressed both questions using two closely related grapevine cell lines (V. rupestris, V. vinifera cv. ‘Pinot Noir’) that contrast in their cell-death response to the bacterial elicitor harpin and the hormonal trigger methyl jasmonate (MeJA). We follow different cellular (loss of membrane integrity, mortality), molecular (induction of transcripts for phytoalexin synthesis and for metacaspases), as well as metabolic (sphingolipid profiles) responses to the two triggers in the two cell lines. The role of NADPH oxidases and induction of transcripts for the class-II metacaspases MC5 differ qualitatively between the two cell lines. We tested a possible role of sphingolipid metabolism but can rule this out. We propose a model, where V. rupestris, originating from co-evolution with several biotrophic pathogens, readily activates a hypersensitive cell death in response to harpin, while the context of MeJA-induced cell death in ‘Pinot Noir’ might not be related to immunity at all. We propose that the underlying signalling is modular, recruiting metacaspases differently depending on upstream signalling.

Deletion of ORM2 Causes Oleic Acid-Induced Growth Defects in Saccharomyces cerevisiae.

The endoplasmic reticulum (ER) resident proteins of the Orm family (Orm1p and Orm2p) play an essential regulatory role in sphingolipid metabolism and proteostasis of Saccharomyces cerevisiae. Sphingolipid metabolism and its relationship with yeast ORM1 and ORM2 have been studied widely, but its position in phospholipids and neutral lipids requires further studies. We found that the deletion of ORM2 reduced phospholipid levels, but orm1Δ had shown no significant alteration of phospholipids. On the contrary, neutral lipid levels and lipid droplet (LD) numbers were increased in both orm1∆ and orm2∆ cells. Unlike orm1Δ, free fatty acid (FFA) levels were steeply accumulated in orm2∆ cells, and deletion of ORM2 made the cells more sensitive towards oleic acid toxicity. Misregulation of fatty acids has been implicated in the causation of several lipid metabolic disorders. It is imminent to comprehend the control mechanisms of free fatty acid homeostasis and its pathophysiology. Our study has provided experimental evidence of ORM2 role in the lipid and fatty acid metabolism of yeast.

Ceramide synthase 6 impacts T-cell allogeneic response and graft-versus-host disease through regulating N-RAS/ERK pathway

Allogeneic hematopoietic cell transplantation (allo-HCT) is an effective immunotherapy for various hematologic malignancies, predominantly through potent graft-versus-leukemia (GVL) effect. However, the mortality after allo-HCT is because of relapse of primary malignancy and followed by graft-vs-host-disease (GVHD) as a major cause of transplant-related mortality. Hence, strategies to limit GVHD while preserving the GVL effect are highly desirable. Ceramide, which serves a central role in sphingolipid metabolism, is generated by ceramide synthases (CerS1-6). In this study, we found that genetic or pharmacologic targeting of CerS6 prevented and reversed chronic GVHD (cGVHD). Furthermore, specific inhibition of CerS6 with ST1072 significantly ameliorated acute GVHD (aGVHD) while preserving the GVL effect, which differed from FTY720 that attenuated aGVHD but impaired GVL activity. At the cellular level, blockade of CerS6 restrained donor T cells from migrating into GVHD target organs and preferentially reduced activation of donor CD4 T cells. At the molecular level, CerS6 was required for optimal TCR signaling, CD3/PKCθ co-localization, and subsequent N-RAS activation and ERK signaling, especially on CD4+ T cells. The current study provides rationale and means for targeting CerS6 to control GVHD and leukemia relapse, which would enhance the efficacy of allo-HCT as an immunotherapy for hematologic malignancies in the clinic.

The Role of Sphingolipid Metabolism in Bone Remodeling.

Emerging studies of bioactive lipids have made many exciting discoveries in recent years. Sphingolipids and their metabolites perform a wide variety of cellular functions beyond energy metabolism. Emerging evidence based on genetically manipulated mouse models and molecular biology allows us to obtain new insights into the role sphingolipid played on skeletal remodeling. This review summarizes studies or understandings of the crosstalk between sphingomyelin, ceramide, and sphingosine-1-phosphate (S1P) of sphingolipids family and the cells, especially osteoblasts and osteoclasts of the bone through which bone is remodeled during life constantly. This review also shows agonists and antagonists of S1P as possible therapeutic options and opportunities on bone diseases.

Ceramide Synthase 6 Maximizes p53 Function to Prevent Progeny Formation from Polyploid Giant Cancer Cells.

Simple SummaryOne mechanism that contributes to cancer recurrence is the ability of some malignant cells to temporarily halt cell division and accumulate multiple nuclei that are later released as progeny, which resume cell division. The release of progeny occurs via primitive cleavage and is highly dependent on the sphingolipid enzyme acid ceramidase but the role of sphingolipid metabolism in this process remains to be elucidated. This study highlights differences in sphingolipid metabolism between non-polyploid and polyploid cancer cells and shows that ceramide synthase 6, which preferentially generates C16-ceramide maximizes the ability of the tumor suppressor p53 to inhibit progeny formation in polyploid cancer cells. These results offer an explanation as to why non-cancerous polyploid cells, which express wildtype p53, do not generate progeny and suggest that cancer cells with deregulated p53 function pose a higher risk of evading therapy especially if enzymes that generate C16-ceramide are also dysregulated.Polyploid giant cancer cells (PGCC) constitute a transiently senescent subpopulation of cancer cells that arises in response to stress. PGCC are capable of generating progeny via a primitive, cleavage-like cell division that is dependent on the sphingolipid enzyme acid ceramidase (ASAH1). The goal of this study was to understand differences in sphingolipid metabolism between non-polyploid and polyploid cancer cells to gain an understanding of the ASAH1-dependence in the PGCC population. Steady-state and flux analysis of sphingolipids did not support our initial hypothesis that the ASAH1 product sphingosine is rapidly converted into the pro-survival lipid sphingosine-1-phosphate. Instead, our results suggest that ASAH1 activity is important for preventing the accumulation of long chain ceramides such as C16-ceramide. We therefore determined how modulation of C16-ceramide, either through CerS6 or p53, a known PGCC suppressor and enhancer of CerS6-derived C16-ceramide, affected PGCC progeny formation. Co-expression of the CerS6 and p53 abrogated the ability of PGCC to form offspring, suggesting that the two genes form a positive feedback loop. CerS6 enhanced the effect of p53 by significantly increasing protein half-life. Our results support the idea that sphingolipid metabolism is of functional importance in PGCC and that targeting this signaling pathway has potential for clinical intervention.

A circular network of coregulated sphingolipids dictates lung cancer growth and progression

BackgroundSphingolipid metabolism is among the top dysregulated pathways in non-small cell lung carcinomas (NSCLC). However, the molecular control of sphingolipid metabolic reprogramming in cancer progression remains unclear. MethodsWe first determined the correlation between sphingolipid metabolic gene expression and patient prognosis. We then carried out sphingolipidomics analysis of health individual and NSCLC patient sera as well as B3GNT5 and GAL3ST1 genetically perturbed NSCLC cell lines. We used these cell lines to perform tumorigenesis study to determine the cellular role of B3GNT5 and GAL3ST1 in cancer growth and progression. FindingsThe expression of B3GNT5 and GAL3ST1 among sphingolipid metabolic enzymes is most significantly associated with patient prognosis, whilst sphingolipidomics analysis of healthy individual and NSCLC patient sera identifies their metabolites, lacto/neolacto-series glycosphingolipid and sulfatide species, as potential biomarkers that were more effective than current clinical biomarkers for staging patients. Further network analysis of the sphingolipidomes reveals a circular network of coregulated sphingolipids, indicating that the lacto/neolacto-series glycosphingolipid/sulfatide balance functions as a checkpoint to determine sphingolipid metabolic reprograming during patient progression. Sphingolipidomics analysis of B3GNT5/GAL3ST1 genetically perturbed NSCLC cell lines confirms their key regulatory role in sphingolipid metabolism, while B3GNT5 and GAL3ST1 expression has an opposite role on tumorigenesis. InterpretationOur results provide new insights whereby B3GNT5 and GAL3ST1 differentially regulate sphingolipid metabolism in lung cancer growth and progression. FundingThis work was supported by the Natural Science Foundation of China (81872142, 81920108028); Guangzhou Science and Technology Program (201904020008); Guangdong Science and Technology Department (2020A0505100029, 2019A1515011802, 2020A1515011280, 2020B1212060018, 2020B1212030004); China Postdoctoral Science Foundation (2019M650226, 2019M650227).

Sphingolipids and Kidney Disease: Possible Role of Preeclampsia and Intrauterine Growth Restriction (IUGR).

Sphingolipids are now considered not only as constitutional components of the cellular membrane but also as essential bioactive factors regulating development and physiologic functions. Ceramide is a vital intermediate of sphingolipid metabolism, synthesized by de novo and salvage pathways, producing multiple types of sphingolipids and their metabolites. Although mutations in gene-encoding enzymes regulating sphingolipid synthesis and metabolism cause distinct diseases, an abnormal sphingolipid metabolism contributes to various pathologic conditions, including kidney diseases. Excessive accumulation of glycosphingolipids and promotion of the ceramide salvage and sphingosine-1-phosphate (S1P) pathways are found in the damaged kidney. Acceleration of the sphingosine kinase/S1P/S1P receptor (SphK/S1P/S1PR) axis plays a central role in deteriorating kidney functions. The SphK/S1P/S1PR signaling impairment is also found during pregnancy complications, such as preeclampsia and intrauterine growth restriction (IUGR). This mini-review discusses the current state of knowledge regarding the role of sphingolipid metabolism on kidney diseases, and the possible involvement of preeclampsia and IUGR conditions.

Ceramide Analysis by Multiple Linked-Scan Mass Spectrometry Using a Tandem Quadrupole Instrument.

Ceramides are a special class of sphingolipids and play a central role in sphingolipid metabolism, and have diverse structures. In this book chapter, tandem quadrupole mass spectrometric approaches applying multiple linked scannings including various constant neutral loss scan (NLS) and precursor ion scan (PIS), the unique applicable feature of a triple-stage quadrupole (TSQ) instrument for analysis of ceramides desorbedas [M-H]- and [M+Li]+ ions are described. Thesemultiple dimensional tandem mass spectrometric approaches are fully adapted to the conventional shotgun lipidomics workflow with minimal or without prior chromatographic separation to profile ceramide molecules, and thus detection of a whole class of ceramide or various specific ceramide subclasses in crude lipid extractcan be achieved. With addition of internal standard(s), semi-quantitation of ceramide in the lipid extract of biological origin is possible. Examples have shown promise in ceramide profiling of several whole lipid extracts from porcine brain, the model Dictyostelium Discoideum cells for cancer study, and skin.

Identification of the Interactions Interference Between the PH and START Domain of CERT by Limonoid and HPA Inhibitors.

The multi domain ceramide transfer protein (CERT) which contains the domains START and PH, is a protein that allows the transport of ceramide from the endoplasmic reticulum to the Golgi and so it plays a major role in sphingolipid metabolism. Recently, the crystal structure of the PH-START complex has been released, suggesting an inhibitory action of START to the binding of the PH domain to the Golgi apparatus and thus limiting the CERT activity. Our study presents a combination of docking and molecular dynamic simulations of N-(3-hydroxy-1-hydroxymethyl-3-phenylpropyl)alkanamides (HPA) analogs and limonoids compounds known to inhibit CERT. Through our computational study, we compared the binding affinity of 14 ligands at both domains (START and PH) and also at the START-PH interface, including several mutations known to play a role in the CERT’s activity. At the difference of HPA compounds, limonoids have a stronger binding affinity for the START-PH interface. Furthermore, 2 inhibitors (HPA-12 and isogedunin) were investigated through molecular dynamic (MD) simulations. 50 ns of molecular dynamic simulations have displayed the stability of isogedunin as well as keys residues in the binding of this molecule at the interface of the PH-START complex. Therefore, this study suggests a novel inhibitory mechanism of CERT for limonoid compounds involving the stabilization of the START-PH interface. This could help to develop new and potentially more selective inhibitors of this transporter, which is a potent target in cancer therapy.

Overriding sorafenib resistance via blocking lipid metabolism and Ras by sphingomyelin synthase 1 inhibition in hepatocellular carcinoma.

The survival benefit of sorafenib, the most used drug for advanced hepatocellular carcinoma (HCC), is unsatisfactory due to the development of adaptive resistance. Exploring the mechanisms underlying sorafenib resistance is important to develop sensitizing strategy. Sphingomyelin synthase (SMS) plays a critical role in sphingolipid metabolism which is involved in oncogenesis and drug resistance. SMS1 and SMS2 levels in HCC cells in response to prolonged chemotherapy were analyzed using ELISA. mRNA and protein levels of SMS in HCC and adjacent normal tissues were analyzed by ELISA and real-time PCR. The roles of SMS and its downstream targets were investigated using cellular and biochemical assays and mass spectrometry. SMS1, but not SMS2, was upregulated in HCC in response to sorafenib treatment, although HCC displayed similar RNA and protein level of SMS1 compared to adjacent normal liver tissues. Overexpression of SMS1 promoted HCC growth and migration, and alleviated sorafenib's toxicity. SMS1 inhibition via genetic and pharmacological approaches consistently resulted in inhibition of growth and migration, and apoptosis induction in sorafenib-resistance HCC cells. SMS1 inhibition also augmented the efficacy of sorafenib in sensitive HCC cells. SMS1 inhibition disrupted sphingolipid metabolism via accumulating ceramide and decreasing sphingomyelin, inducing mitochondrial dysfunction and oxidative stress, and decreasing Ras activity in resistant cells. Overexpression of constitutively active Ras reversed the inhibitory effects of SMS1 inhibition. Although SMS1 overexpression did not affect Ras expression and activity, Pearson correlation coefficient analysis of SMS1 and Ras expression demonstrated that there was positive correlation between SMS1 and RAS (NRAS, R = 0.55, p < 0.01; KRAS, R = 0.44, p < 0.01). Our work is the first to suggest that SMS1 plays a more important role in sorafenib resistance than tumorigenesis, and provides preclinical evidence to overcome sorafenib resistance with SMS1 inhibition in HCC.

A Circular Network of Coregulated Sphingolipids Dictates Lung Cancer Growth and Progression

Sphingolipid metabolism is one of the top dysregulated pathways in NSCLC. However, the molecular control of sphingolipid metabolic reprogramming in cancer progression remains unknown. Here, we first provide clinical evidence that expression of sphingolipid metabolic enzymes, B3GNT5 and GAL3ST1, but not the others, is most significantly associated with patient prognosis, whilst sphingolipidomics analysis of NSCLC patient sera identifies their metabolites, neolacto-series glycosphingolipid and sulfatide, as biomarkers that outperformed current clinical biomarkers for staging patients. Further network analysis of the sphingolipidomes reveals a circular network of coregulated sphingolipids, indicating that the neolacto-series glycosphingolipid/sulfatide balance functions as a checkpoint to determine sphingolipid metabolic reprograming during patient progression. Importantly, sphingolipidomics analysis of B3GNT5/GAL3ST1 genetically perturbed NSCLC cell lines confirms their key regulatory role in sphingolipid metabolism, while B3GNT5 and GAL3ST1 expression has an opposite role on tumorigenesis in vitro and in vivo. Overall, our results provide new insights whereby B3GNT5 and GAL3ST1 differentially regulate sphingolipid metabolism in lung cancer growth and progression. Funding Statement: This work was supported by the Natural Science Foundation of China (81920108028, 81872142); Guangzhou Science and Technology Program (201904020008); Young Teacher Foundation of Sun Yat-sen University (18ykzd07); Guangdong Science and Technology Department (2020B1212060018, 2019A1515011802, 2020A1515011280, 2020A0505100029); China Postdoctoral Science Foundation (2019M650226, 2019M650227). Declaration of Interests: No potential conflicts of interest were disclosed. Ethics Approval Statement: Serum samples were collected from healthy individuals and NSCLC patients (age-matched and body-mass index –matched) with informed consent, and the research program and all the related procedures were approved by the Ethics Committee of Sun Yat-sen Memorial Hospital (Guangzhou, China) and stored according to standard operating procedures for Good Clinical Laboratory Practice standards. All animal procedures were approved by the Institutional Animal Care and Use Committee (IACUC) of Sun Yat-Sen University.

New Insights into the Role of Sphingolipid Metabolism in Melanoma.

Cutaneous melanoma is a deadly skin cancer whose aggressiveness is directly linked to its metastatic potency. Despite remarkable breakthroughs in term of treatments with the emergence of targeted therapy and immunotherapy, the prognosis for metastatic patients remains uncertain mainly because of resistances. Better understanding the mechanisms responsible for melanoma progression is therefore essential to uncover new therapeutic targets. Interestingly, the sphingolipid metabolism is dysregulated in melanoma and is associated with melanoma progression and resistance to treatment. This review summarises the impact of the sphingolipid metabolism on melanoma from the initiation to metastatic dissemination with emphasis on melanoma plasticity, immune responses and resistance to treatments.

Sphingomyelin Synthases in Neuropsychiatric Health and Disease.

Sphingomyelin synthases (SMS) catalyze the conversion of ceramide and phosphatidylcholine to sphingomyelin and diacylglycerol and are thus crucial for the balance between synthesis and degradation of these structural and bioactive molecules. SMS thereby play an essential role in sphingolipid metabolism, cell signaling, proliferation and differentiation processes. Although tremendous progress has been made toward understanding the involvement of SMS in physiological and pathological processes, literature in the area of neuropsychiatry is still limited. In this review, we summarize the main features of SMS as well as the current methodologies and tools used for their study and provide an overview of SMS in the central nervous system and their implications in neurological as well as psychiatric disorders. This way, we aim at establishing a basis for future mechanistic as well as clinical investigations on SMS in neuropsychiatric health and diseases.

The role of sphingolipid metabolism in lifespan and healthspan extension in C. elegans

Multiple advancements in research have led to a better understanding of the aging process. However, many metabolic pathways that promote healthy aging are still unknown. Here, we investigate the bioactive sphingolipid metabolism pathway and its roles in regulating lifespan and healthspan, which is the average period of one's life in good health. Sphingolipids are involved in cellular signaling and known to promote cell proliferation, secretion, stress response and survival. The sphingolipid pathway is composed of sphingomyelin, ceramide, sphingosine and sphingosine‐1‐phosphate (S1P). Ceramide synthases (CER synthases) mediate the conversion of ceramide to sphingosine while sphingosine kinase (SPHK) converts sphingosine to S1P. Using C. elegans, we previously found that mutations in sphk‐1/SPHK and hyl‐2/CER synthase result in decreased lifespan, suggesting that sphingolipids play a role in lifespan extension. However, it is unknown whether the sphingolipid genes act in known cellular pathways that mediate aging. Therefore, we tested the genetic interactions between sphingolipid enzymes and known models of aging, including the insulin like signaling (ILS) pathway that has been linked to lifespan extension. For this, lifespan analyses were performed on daf‐16/FOXO, which has a shortened lifespan phenotype, coupled with knockdown of sphingolipid metabolism genes. DAF‐16 is a downstream transcription factor target of DAF‐2/insulin‐like growth factor receptor and has important roles in mediating the gene expression of stress response. We observed that daf‐16 is epistatic to sphingolipid mutants for lifespan phenotypes, as indicated by similar short lifespan phenotypes of double knockout of daf‐16;hyl‐2 and daf‐16;sphk‐1compared to mutants with a single knockout of daf‐16. Thus, sphingolipids may act upstream of DAF‐16 to mediate stress response genes and lifespan. Future experiments will analyze transcriptional reporters for DAF‐16, and known stress response genes SOD‐3/superoxide dismutase, to determine whether cellular stress response mechanisms occurs normally in hyl‐2 and sphk‐1mutants under induced oxidative stress. An analysis of stress response will further enhance our understanding of the interaction between sphingolipids and known pathways that promote lifespan and healthspan.Support or Funding InformationResearch reported in this publication was supported by the National Institute On Aging of the National Institutes of Health under Award Number R15AG052933.This abstract is from the Experimental Biology 2019 Meeting. There is no full text article associated with this abstract published in The FASEB Journal.

Regulation of Sphingolipid Metabolism by MicroRNAs: A Potential Approach to Alleviate Atherosclerosis.

The rapidly expanding field of bioactive lipids is exemplified by the many sphingolipids, which are structurally and functionally diverse molecules with significant physiologic functions. These sphingolipids are main constituents of cellular membranes and have been found associated with plasma lipoproteins, and their concentrations are altered in several metabolic disorders such as atherosclerosis, obesity, and diabetes. Understanding the mechanisms that regulate their biosynthesis and secretion may provide novel information that might be amenable to therapeutic targeting in the treatment of these diseases. Several sphingolipid synthesis genes have been targeted as potential therapeutics for atherosclerosis. In recent years, significant progress has been made in studying the role of microRNAs (miRNAs) in lipid metabolism. However, little effort has been made to investigate their role in sphingolipid metabolism. Sphingolipid biosynthetic pathways involve various enzymes that lead to the formation of several key molecules implicated in atherosclerosis, and the identification of miRNAs that regulate these enzymes could help us to understand these complex pathways better and may prove beneficial in alleviating atherosclerosis.

Identification of progesterone receptor membrane component-1 as an interaction partner and possible regulator of fatty acid 2-hydroxylase.

The fatty acid 2-hydroxylase (FA2H) is essential for synthesis of 2-hydroxylated fatty acids in myelinating and other cells, and deficiency of this enzyme causes a complicated form of hereditary spastic paraplegia also known as fatty acid hydroxylase-associated neurodegeneration. Despite its important role in sphingolipid metabolism, regulation of FA2H and its interaction with other proteins involved in the same or other metabolic pathways is poorly understood. To identify potential interaction partners of the enzyme, quantitative mass spectrometry using stable isotope labeling of cells was combined with formaldehyde cross-linking and proximity biotinylation, respectively. Besides other enzymes involved in sphingolipid synthesis and intermembrane transfer of ceramide, and putative redox partners of FA2H, progesterone receptor membrane component-1 (PGRMC1) and PGRMC2 were identified as putative interaction partners. These two related heme-binding proteins are known to regulate several cytochrome P450 enzymes. Bimolecular fluorescence complementation experiments confirmed the interaction of FA2H with PGRMC1. Moreover, the PGRMC1 inhibitor AG-205 significantly reduced synthesis of hydroxylated ceramide and glucosylceramide in FA2H-expressing cells. This suggests that PGRMC1 may regulate FA2H activity, possibly through its heme chaperone activity.

Metabolomic profiling suggests long chain ceramides and sphingomyelins as a possible diagnostic biomarker of epithelial ovarian cancer

IntroductionEpithelial ovarian cancer (EOC) is a disease with a poor survival rate mostly due to its discovery in late stages. The aim of this study was to investigate the metabolomic profile of ovarian cancer with the intention of identifying and describing novel biomarkers with diagnostic potential. Material and methodsTargeted serum metabolomic profiling was performed on 15 patients with ovarian cancer, 21 healthy controls and 21 patients with benign ovarian conditions, using HPLC–TQ/MS. ResultsPanel of 49 top performing biomarkers shows separation between EOC and controls with 87% specificity and 87% sensitivity with AUC of 93% (CI 90%–95%). Using only 5 top biomarkers, specificity of 80% and sensitivity of 83% was achieved on extended sample set. Most significant biomarkers belong to sphingolipid classes, especially long chain ceramides and sphingomyelins. Different concentrations of various fatty acid chain lengths ceramides and sphingomyelins are also implying their respective roles in cell proliferation and growth inhibition. ConclusionLong chain ceramides and sphingomyelins may serve as a novel biomarker for epithelial ovarian cancer detection and may also offer insight into the role of sphingolipid metabolism in cell proliferation.

Adoptive Transfer of Ceramide Synthase 6 Deficient Splenocytes Reduces the Development of Colitis

Sphingolipids regulate critical cellular processes including inflammation. Ceramide, which serves a central role in sphingolipid metabolism, is generated by six ceramide synthases (CerS) that differ in substrate specificity. CerS6 preferentially generates C16-ceramide and its mRNA is highly expressed in immune tissues. In this study we analyzed how deficiency of CerS6 impacts on the development of colitis using an adoptive transfer model. Adoptive transfer of CerS6-deficient splenocytes, which have significantly decreased levels of C16-ceramide, showed that CerS6-deficiency protected against the development of colitis. However, adoptively transferred cells isolated from the lamina propria of the large intestine from wild type or CerS6-deficient groups showed no differences in the percentages of immune-suppressive regulatory T cells, pro-inflammatory Th17 cells, or their ability to express IL-17. In vitro polarization of wild type or CerS6-deficient splenocytes also revealed no defects in the development of T cell subsets. Our data suggest that protection from colitis following adoptive transfer of CerS6-deficient splenocytes maybe related to their ability to migrate and proliferate in vivo rather than subset development or cytokine expression.