Chain length-specific properties of ceramides

Dysregulated Lipid Metabolism and Its Role in α-Synucleinopathy in Parkinson's Disease

Parkinson's disease (PD) is the second most common neurodegenerative disease, the main pathological hallmark of which is the accumulation of α-synuclein (α-syn) and the formation of filamentous aggregates called Lewy bodies in the brainstem, limbic system, and cortical areas. Lipidomics is a newly emerging field which can provide fresh insights and new answers that will enhance our capacity for early diagnosis, tracking disease progression, predicting critical endpoints, and identifying risk in pre-symptomatic persons. In recent years, lipids have been implicated in many aspects of PD pathology. Biophysical and lipidomic studies have demonstrated that α-syn binds preferentially not only to specific lipid families but also to specific molecular species and that these lipid-protein complexes enhance its interaction with synaptic membranes, influence its oligomerization and aggregation, and interfere with the catalytic activity of cytoplasmic lipid enzymes and lysosomal lipases, thereby affecting lipid metabolism. The genetic link between aberrant lipid metabolism and PD is even more direct, with mutations in GBA and SMPD1 enhancing PD risk in humans and loss of GALC function increasing α-syn aggregation and accumulation in experimental murine models. Moreover, a number of lipidomic studies have reported PD-specific lipid alterations in both patient brains and plasma, including alterations in the lipid composition of lipid rafts in the frontal cortex. A further aspect of lipid dysregulation promoting PD pathogenesis is oxidative stress and inflammation, with proinflammatory lipid mediators such as platelet activating factors (PAFs) playing key roles in arbitrating the progressive neurodegeneration seen in PD linked to α-syn intracellular trafficking. Lastly, there are a number of genetic risk factors of PD which are involved in normal lipid metabolism and function. Genes such as PLA2G6 and SCARB2, which are involved in glycerophospholipid and sphingolipid metabolism either directly or indirectly are associated with risk of PD. This review seeks to describe these facets of metabolic lipid dysregulation as they relate to PD pathology and potential pathomechanisms involved in disease progression, while highlighting incongruous findings and gaps in knowledge that necessitate further research.

Interrelations of Sphingolipid and Lysophosphatidate Signaling with Immune System in Ovarian Cancer

The sphingolipid and lysophosphatidate regulatory networks impact diverse mechanisms attributed to cancer cells and the tumor immune microenvironment. Deciphering the complexity demands implementation of a holistic approach combined with higher-resolution techniques. We implemented a multi-modular integrative approach consolidating the latest accomplishments in gene expression profiling, prognostic/predictive modeling, next generation digital pathology, and systems biology for epithelial ovarian cancer. We assessed patient-specific transcriptional profiles using the sphingolipid/lysophosphatidate/immune-associated signature. This revealed novel sphingolipid/lysophosphatidate-immune gene-gene associations and distinguished tumor subtypes with immune high/low context. These were characterized by robust differences in sphingolipid-/lysophosphatidate-related checkpoints and the drug response. The analysis also nominates novel survival models for stratification of patients with CD68, LPAR3, SMPD1, PPAP2B, and SMPD2 emerging as the most prognostically important genes. Alignment of proprietary data with curated transcriptomic data from public databases across a variety of malignancies (over 600 categories; over 21,000 arrays) showed specificity for ovarian carcinoma. Our systems approach identified novel sphingolipid-lysophosphatidate-immune checkpoints and networks underlying tumor immune heterogeneity and disease outcomes. This holds great promise for delivering novel stratifying and targeting strategies.

Association Between Fatty Acids of Blood Cell Membranes and Incidence of Coronary Heart Disease

Objective—

To examine the associations between baseline levels of fatty acids in blood cell membranes and their 1-year changes with the incidence of coronary heart disease (CHD) in older adults at high cardiovascular disease risk.

Approach and Results—

This is a case-control study nested in the PREDIMED trial (Prevención con Dieta Mediterránea), with 136 CHD cases and 272 controls (matched on age, sex, body mass index, intervention group, and time of permanence in the study to the time event). We used gas chromatography to measure the proportion of 22 fatty acids in blood cell membranes at baseline and after 1 year. Conditional logistic regression was used to estimate odds ratios (ORs) and 95% CIs. After adjustment for classical CHD risk factors and multiple testing, 1 SD increase in baseline levels of C22:0, C24:0 and the sum of individual very long chain saturated fatty acids was associated with 56% (OR, 0.44 [95% CI, 0.28–0.69]), 59% (OR, 0.41 [95% CI, 0.25–0.65]), and 55% (OR, 0.45 [95% CI, 0.29–0.70]) a decreased odds of developing CHD, respectively. Baseline C20:1n9 was associated with higher odds of CHD (OR, 1.58 [95% CI, 1.25–2.00]).

Conclusions—

Higher levels of C22:0 and C24:0 were associated with a lower CHD incidence, whereas higher levels of C20:1n9 were associated with a higher risk. This study adds to the growing body of evidence suggesting potential differences in the cardiovascular disease effects of different types of circulating saturated fatty acids.

Associations of circulating very-long-chain saturated fatty acids and incident type 2 diabetes: a pooled analysis of prospective cohort studies

BACKGROUND

Saturated fatty acids (SFAs) of different chain lengths have unique metabolic and biological effects, and a small number of recent studies suggest that higher circulating concentrations of the very-long-chain SFAs (VLSFAs) arachidic acid (20:0), behenic acid (22:0), and lignoceric acid (24:0) are associated with a lower risk of diabetes. Confirmation of these findings in a large and diverse population is needed.

OBJECTIVE

We investigated the associations of circulating VLSFAs 20:0, 22:0, and 24:0 with incident type 2 diabetes in prospective studies.

METHODS

Twelve studies that are part of the Fatty Acids and Outcomes Research Consortium participated in the analysis. Using Cox or logistic regression within studies and an inverse-variance-weighted meta-analysis across studies, we examined the associations of VLSFAs 20:0, 22:0, and 24:0 with incident diabetes among 51,431 participants.

RESULTS

There were 14,276 cases of incident diabetes across participating studies. Higher circulating concentrations of 20:0, 22:0, and 24:0 were each associated with a lower risk of incident diabetes. Pooling across cohorts, the RR (95% CI) for incident diabetes comparing the 90th percentile to the 10th percentile was 0.78 (0.70, 0.87) for 20:0, 0.84 (0.77, 0.91) for 22:0, and 0.75 (0.69, 0.83) for 24:0 after adjustment for demographic, lifestyle, adiposity, and other health factors. Results were fully attenuated in exploratory models that adjusted for circulating 16:0 and triglycerides.

CONCLUSIONS

Results from this pooled analysis indicate that higher concentrations of circulating VLSFAs 20:0, 22:0, and 24:0 are each associated with a lower risk of diabetes.

Preservation of Acyl Coenzyme A Attenuates Pathological and Metabolic Cardiac Remodeling Through Selective Lipid Trafficking

BACKGROUND

Metabolic remodeling in heart failure contributes to dysfunctional lipid trafficking and lipotoxicity. Acyl coenzyme A synthetase-1 (ACSL1) facilitates long-chain fatty acid (LCFA) uptake and activation with coenzyme A (CoA), mediating the fate of LCFA. The authors tested whether cardiac ACSL1 overexpression aids LCFA oxidation and reduces lipotoxicity under pathological stress of transverse aortic constriction (TAC).

METHODS

Mice with cardiac restricted ACSL1 overexpression (MHC-ACSL1) underwent TAC or sham surgery followed by serial in vivo echocardiography for 14 weeks. At the decompensated stage of hypertrophy, isolated hearts were perfused with ¹³C LCFA during dynamic-mode ¹³C nuclear magnetic resonance followed by in vitro nuclear magnetic resonance and mass spectrometry analysis to assess intramyocardial lipid trafficking. In parallel, acyl CoA was measured in tissue obtained from heart failure patients pre- and postleft ventricular device implantation plus matched controls.

RESULTS

TAC-induced cardiac hypertrophy and dysfunction was mitigated in MHC-ACSL1 hearts compared with nontransgenic hearts. At 14 weeks, TAC increased heart weight to tibia length by 46% in nontransgenic mice, but only 26% in MHC-ACSL1 mice, whereas ACSL1 mice retained greater ejection fraction (ACSL1 TAC: 65.8±7.5%; nontransgenic TAC: 45.9±7.3) and improvement in diastolic E/E'. Functional improvements were mediated by ACSL1 changes to cardiac LCFA trafficking. ACSL1 accelerated LCFA uptake, preventing C16 acyl CoA loss post-TAC. Long-chain acyl CoA was similarly reduced in human failing myocardium and restored to control levels by mechanical unloading. ACSL1 trafficked LCFA into ceramides without normalizing the reduced triglyceride storage in TAC. ACSL1 prevented de novo synthesis of cardiotoxic C16- and C24-, and C24:1 ceramides and increased potentially cardioprotective C20- and C22-ceramides post-TAC. ACLS1 overexpression activated AMP activated protein kinase at baseline, but during TAC, prevented the reduced LCFA oxidation in hypertrophic hearts and normalized energy state (phosphocreatine:ATP) and consequently, AMP activated protein kinase activation.

CONCLUSIONS

This is the first demonstration of reduced acyl CoA in failing hearts of humans and mice, and suggests possible mechanisms for maintaining mitochondrial oxidative energy metabolism by restoring long-chain acyl CoA through ASCL1 activation and mechanical unloading. By mitigating cardiac lipotoxicity, via redirected LCFA trafficking to ceramides, and restoring acyl CoA, ACSL1 delayed progressive cardiac remodeling and failure.

Biochemistry of very-long-chain and long-chain ceramides in cystic fibrosis and other diseases: The importance of side chain

Ceramides, the principal building blocks of all sphingolipids, have attracted the attention of many scientists around the world interested in developing treatments for cystic fibrosis, the most common genetic disease of Caucasians. Many years of fruitful research in this field have produced some fundamentally important, yet controversial results. Here, we aimed to summarize the current knowledge on the role of long- and very-long- chain ceramides, the most abundant species of ceramides in animal cells, in cystic fibrosis and other diseases. We also aim to explain the importance of the length of their side chain in the context of stability of transmembrane proteins through a concise synthesis of their biophysical chemistry, cell biology, and physiology. This review also addresses several remaining riddles in this field. Finally, we discuss the technical challenges associated with the analysis and quantification of ceramides. We provide the evaluation of the antibodies used for ceramide quantification and we demonstrate their lack of specificity. Results and discussion presented here will be of interest to anyone studying these enigmatic lipids.

Multiple Myeloma and Fatty Acid Metabolism

Multiple myeloma (MM) accounts for 13% to 15% of all blood cancers1 and is characterized by the proliferation of malignant cells within the bone marrow (BM). Despite important advances in treatment, most patients become refractory and relapse with the disease. As MM tumors grow in the BM, they disrupt hematopoiesis, create monoclonal protein spikes in the blood, initiate systemic organ and immune system shutdown,2 and induce painful osteolytic lesions caused by overactive osteoclasts and inhibited osteoblasts.3, 4 MM cells are also extremely dependent on the BM niche, and targeting the BM niche has been clinically transformative for inhibiting the positive-feedback "vicious cycle" between MM cells and osteoclasts that leads to bone resorption and tumor proliferation.5, 6, 7, 8 Bone marrow adipocytes (BMAs) are dynamic, secretory cells that have complex effects on osteoblasts and tumor cells, but their role in modifying the MM cell phenotype is relatively unexplored.9, 10, 11, 12, 13 Given their active endocrine function, capacity for direct cell-cell communication, correlation with aging and obesity (both MM risk factors), potential roles in bone disease, and physical proximity to MM cells, it appears that BMAs support MM cells.14, 15, 16, 17 This supposition is based on research from many laboratories, including our own. Therapeutically targeting the BMA may prove to be equally transformative in the clinic if the pathways through which BMAs affect MM cells can be determined. In this review, we discuss the potential for BMAs to provide free fatty acids to myeloma cells to support their growth and evolution. We highlight certain proteins in MM cells responsible for fatty acid uptake and oxidation and discuss the potential for therapeutically targeting fatty acid metabolism or BMAs from where they may be derived. © 2019 The Authors. JBMR Plus published by Wiley Periodicals, Inc. on behalf of American Society for Bone and Mineral Research.

Acid ceramidase inhibition ameliorates α-synuclein accumulation upon loss of GBA1 function

GBA1 encodes the lysosomal enzyme β-glucocerebrosidase (GCase) which converts glucosylceramide into ceramide and glucose. Mutations in GBA1 lead to Gaucher's disease and are a major risk factor for Parkinson's disease (PD) and Dementia with Lewy bodies (DLB), synucleinopathies characterized by accumulation of intracellular α-synuclein. In this study, we examined whether decreased ceramide that is observed in GCase-deficient cells contributes to α-synuclein accumulation. We demonstrated that deficiency of GCase leads to a reduction of C18-ceramide species and altered intracellular localization of Rab8a, a small GTPase implicated in secretory autophagy, that contributed to impaired secretion of α-synuclein and accumulation of intracellular α-synuclein. This secretory defect was rescued by exogenous C18-ceramide or chemical inhibition of lysosomal enzyme acid ceramidase that converts lysosomal ceramide into sphingosine. Inhibition of acid ceramidase by carmofur resulted in increased ceramide levels and decreased glucosylsphingosine levels in GCase-deficient cells, and also reduced oxidized α-synuclein and levels of ubiquitinated proteins in GBA1-PD patient-derived dopaminergic neurons. Together, these results suggest that decreased ceramide generation via the catabolic lysosomal salvage pathway in GCase mutant cells contributes to α-synuclein accumulation, potentially due to impaired secretory autophagy. We thus propose that acid ceramidase inhibition which restores ceramide levels may be a potential therapeutic strategy to target synucleinopathies linked to GBA1 mutations including PD and DLB.

Plasma lipidome reveals critical illness and recovery from human Ebola virus disease

Ebola virus disease (EVD) often leads to severe and fatal outcomes in humans with early supportive care increasing the chances of survival. Profiling the human plasma lipidome provides insight into critical illness as well as diseased states, as lipids have essential roles as membrane structural components, signaling molecules, and energy sources. Here we show that the plasma lipidomes of EVD survivors and fatalities from Sierra Leone, infected during the 2014-2016 Ebola virus outbreak, were profoundly altered. Focusing on how lipids are associated in human plasma, while factoring in the state of critical illness, we found that lipidome changes were related to EVD outcome and could identify states of disease and recovery. Specific changes in the lipidome suggested contributions from extracellular vesicles, viremia, liver dysfunction, apoptosis, autophagy, and general critical illness, and we identified possible targets for therapies enhancing EVD survival.

Changes in lipids composition and metabolism in colorectal cancer: a review

Altered metabolism of lipids is currently considered a hallmark characteristic of many malignancies, including colorectal cancer (CRC). Lipids are a large group of metabolites that differ in terms of their fatty acid composition. This review summarizes recent evidence, documenting many alterations in the content and composition of fatty acids, polar lipids, oxylipins and triacylglycerols in CRC patients' sera, tumor tissues and adipose tissue. Some of altered lipid molecules may be potential biomarkers of CRC risk, development and progression. Owing to a significant role of many lipids in cancer cell metabolism, some of lipid metabolism pathways may also constitute specific targets for anti-CRC therapy.

Imbalanced sphingolipid signaling is maintained as a core proponent of a cancerous phenotype in spite of metabolic pressure and epigenetic drift

Tumor heterogeneity may arise through genetic drift and environmentally driven clonal selection for metabolic fitness. This would promote subpopulations derived from single cancer cells that exhibit distinct phenotypes while conserving vital pro-survival pathways. We aimed to identify significant drivers of cell fitness in pancreatic adenocarcinoma (PDAC) creating subclones in different nutrient formulations to encourage differential metabolic reprogramming. The genetic and phenotypic expression profiles of each subclone were analyzed relative to a healthy control cell line (hTert-HPNE). The subclones exhibited distinct variations in protein expression and lipid metabolism. Relative to hTert-HPNE, PSN-1 subclones uniformly maintained modified sphingolipid signaling and specifically retained elevated sphingosine-1-phosphate (S1P) relative to C16 ceramide (C16 Cer) ratios. Each clone utilized a different perturbation to this pathway, but maintained this modified signaling to preserve cancerous phenotypes, such as rapid proliferation and defense against mitochondria-mediated apoptosis. Although the subclones were unique in their sensitivity, inhibition of S1P synthesis significantly reduced the ratio of S1P/C16 Cer, slowed cell proliferation, and enhanced sensitivity to apoptotic signals. This reliance on S1P signaling identifies this pathway as a promising drug-sensitizing target that may be used to eliminate cancerous cells consistently across uniquely reprogrammed PDAC clones.

Maternal obesity leads to long-term altered levels of plasma ceramides in the offspring as revealed by a longitudinal lipidomic study in children

BACKGROUND/OBJECTIVES

Maternal obesity is associated with increased risk of obesity and other symptoms of the metabolic syndrome in the offspring. Nevertheless, the molecular mechanisms and cellular factors underlying this enhanced disease susceptibility remain to be determined. Here, we aimed at identifying changes in plasma lipids in offspring of obese mothers that might underpin, and serve as early biomarkers of, their enhanced metabolic disease risk.

SUBJECTS/METHODS

We performed a longitudinal lipidomic profiling in plasma samples from normal weight, overweight, and obese pregnant women and their children that participated in the Prenatal Omega-3 Fatty Acid Supplementation, Growth, and Development trial conducted in Mexico. At recruitment women were aged between 18 and 35 years and in week 18-22 of pregnancy. Blood samples were collected at term delivery by venipuncture from mothers and from the umbilical cord of their newborns and from the same infants at 4 years old under non-fasting conditions. Lipidomic profiling was done using ultra-performance liquid chromatography high-resolution mass spectrometry.

RESULTS

Analysis of the lipidomic data showed that overweight and obese mothers exhibited a significant reduction in the total abundance of ceramides (Cer) in plasma, mainly of Cer (d18:1/20:0), Cer (d18:1/22:0), Cer (d18:1/23:0), and Cer (d18:1/24:0), compared with mothers of normal body weight. This reduction was confirmed by the direct quantification of these and other ceramide species. Similar quantitative differences in the plasma concentration of Cer (d18:1/22:0), Cer (d18:1/23:0), and Cer (d18:1/24:0), were also found between 4-year-old children of overweight and obese mothers compared with children of mothers of normal body weight. Noteworthy, children exhibited equal daily amounts of energy and food intake independently of the BMI of their mothers.

CONCLUSIONS

Maternal obesity results in long-lasting changes in plasma ceramides in the offspring suggesting that these lipids might be used as early predictors of metabolic disease risk due to maternal obesity.

Clinical signs of meibomian gland dysfunction (MGD) are associated with changes in meibum sphingolipid composition

PURPOSE

Sphingolipids (SPL) play roles in cell signaling, inflammation, and apoptosis. Changes in SPL composition have been reported in individuals with MGD, but associations between clinical signs of MGD and compositional changes in meibum SPLs have not been examined.

METHODS

Forty-three individuals underwent a tear film assessment. Groups were split into those with good or poor quality meibum. Meibum was collected then analyzed with liquid chromatography-mass spectroscopy to quantify SPL classes. Relative composition of SPL and major classes, Ceramide (Cer), Hexosyl-Ceramide (Hex-Cer), Sphingomyelin (SM), Sphingosine (Sph) and Sphingosine 1-phosphate (S1P) was calculated via mole percent.

RESULTS

22 and 21 individuals were characterized with good and poor quality meibum, respectively. Individuals with poor quality were older (60 ± 8 vs 51 ± 16 years) and more likely to be male (90% vs 64%). Relative composition analysis revealed that individuals with poor meibum quality had SPL composed of less Cer (33.36% vs 49.49%, p < 0.01), Hex-Cer (4.88% vs 9.15%, p < 0.01), and S1P (0.16% vs 0.31%, p = 0.05), and more SM (58.67% vs 38.18%, p < 0.01) and Sph (2.92% vs 2.87%, p = 0.97) compared to individuals with good quality meibum. Assessment of the ratio of Cer (pro-apoptotic) to S1P (pro-survival) showed that individuals with poor meibum quality had a relative increase in Cer (495.23 vs 282.69, p = 0.07).

CONCLUSION

Meibum quality, a clinically graded marker of MGD, is associated with compositional changes in meibum sphingolipids. Further investigation of the structural and bioactive roles of sphingolipids in MGD may provide future targets for therapy.

Patterns of adipose tissue fatty acids and the risk of atrial fibrillation: A case-cohort study

Fatty acids in adipose tissue share dietary sources and metabolic pathways and therefore occur in patterns. The aim of the present study was to investigate the association between adipose tissue fatty acid patterns identified by the data-driven dimension-reducing method treelet transform and the risk of atrial fibrillation. A total of 57,053 Danish men and women aged 50–64 years participating in the Diet, Cancer and Health cohort had an adipose tissue biopsy taken at baseline. During a median follow-up of 14.6 years, a total of 4,710 participants developed atrial fibrillation or atrial flutter. Adipose tissue biopsies were analysed for fatty acid content by gas chromatography for all cases of atrial fibrillation and for a randomly drawn subcohort (n = 3,500) representative for the entire cohort. Hazard ratios with 95% confidence intervals for atrial fibrillation according to quintiles of factor scores were determined by weighted Cox proportional hazards regression analyses for men and women separately. From the 32 fatty acids measured, 7 major factors/patterns of fatty acids were identified using treelet transform. We found that a pattern consisting of n-6 polyunsaturated fatty acids (PUFA) (except linoleic acid) was associated with a lower hazard of atrial fibrillation. Patterns consisting of marine n-3 PUFA and containing n-9 fatty acids were associated with a lower hazard of atrial fibrillation in women. In conclusion, patterns of fatty acids in adipose tissue identified by treelet transform may be differentially associated with the risk of atrial fibrillation.

Sphingolipids in neurodegeneration (with focus on ceramide and S1P)

For many decades, research on sphingolipids associated with neurodegenerative disease focused on alterations in glycosphingolipids, particularly glycosylceramides (cerebrosides), sulfatides, and gangliosides. This seemed quite natural since many of these glycolipids are constituents of myelin and accumulated in lipid storage diseases (sphingolipidoses) resulting from enzyme deficiencies in glycolipid metabolism. With the advent of recognizing ceramide and its derivative, sphingosine-1-phosphate (S1P), as key players in lipid cell signaling and regulation of cell death and survival, research focus shifted toward these two sphingolipids. Ceramide and S1P are invoked in a plethora of cell biological processes participating in neurodegeneration such as ER stress, autophagy, dysregulation of protein and lipid transport, exosome secretion and neurotoxic protein spreading, neuroinflammation, and mitochondrial dysfunction. Hence, it is timely to discuss various functions of ceramide and S1P in neurodegenerative disease and to define sphingolipid metabolism and cell signaling pathways as potential targets for therapy.

Overexpression of acid ceramidase (ASAH1) protects retinal cells (ARPE19) from oxidative stress

Over 11 million people in the United States alone have some form of age-related macular degeneration (AMD). Oxidative stress, cell death, and the degeneration of retinal pigment epithelial (RPE) cells contribute to AMD pathology. Recent evidence suggests that ceramide (Cer), a cellular sphingolipid mediator that acts as a second messenger to induce apoptosis, might play a role in RPE cell death. The lysosomal breakdown of Cer by acid ceramidase [N-acylsphingosine amidohydrolase (ASAH)1] into sphingosine (Sph) is the major source for Sph 1-phosphate production, which has an opposing role to Cer and provides cytoprotection. Here, we investigated the role of Cer in human RPE-derived ARPE19 cells under hydrogen peroxide-induced oxidative stress, and show that Cer and hexosyl-Cer levels increase in the oxidatively stressed ARPE19 cells, which can be prevented by overexpression of lysosomal ASAH1. This study demonstrates that oxidative stress generates sphingolipid death mediators in retinal cells and that induction of ASAH1 could rescue retinal cells from oxidative stress by hydrolyzing excess Cers.

Novel glucosylceramide synthase inhibitor based prodrug copolymer micelles for delivery of anticancer agents

In order to improve the efficacy of chemotherapy for cancers, we have developed a novel prodrug micellar formulation to co-deliver ceramide-generating anticancer agents and ceramide degradation inhibitor (PPMP). The prodrug nanocarrier is based on a well-defined POEG-b-PPPMP diblock copolymer. The hydrophilic block of POEG-b-PPPMP is POEG, and the hydrophobic block is composed of a number of PPMP units, which could work synergistically with loaded anticancer drugs. POEG-b-PPPMP was readily synthesized via a one-step reversible addition-fragment transfer (RAFT) polymerization from a PPMP monomer. The newly synthesized polymers were self-assembled into micelles and served as a carrier for several hydrophobic anticancer drugs including DOX, PTX and C6-ceramide. POEG-b-PPPMP prodrug polymer exhibited intrinsic antitumor activity in vitro and in vivo. In addition, POEG-b-PPPMP prodrug polymer was comparable to free PPMP in selectively enhancing the production of pro-apoptotic ceramide species as well as down-regulating the mRNA expression of GCS. DOX-loaded POEG-b-PPPMP micelles exhibited an excellent stability of 42 days at 4 °C. Moreover, DOX loaded in POEG-b-PPPMP micelles showed higher levels of cytotoxicity than DOX loaded in a pharmacologically inert polymer (POEG-b-POM) and Doxil formulation in several tumor cell lines. Consistently, in a 4T1.2 murine breast cancer model, the tumor inhibition followed the order of DOX/POEG-b-PPPMP > DOX/POEG-b-POM ≥ Doxil > POEG-b-PPPMP > POEG-b-POM. Our data suggest that POEG-b-PPPMP micelles are a promising dual-functional carrier that warrants more studies in the future.

Data set for characterization of TNF-α-inducible glycosphingolipids in vascular endothelial cells

The data presented here pertain to a research article entitled "Structural characterization and dynamics of globotetraosylceramide in vascular endothelial cells under TNF-α stimulation" (Okuda et al., 2010). The present article provides additional structural and gene expression data for the characterization of a TNF-α-inducible glycosphingolipid, globotetraosylceramide (Gb4), in vascular endothelial cells. (i) Structural details of Gb4 in lipid raft-enriched cell membranes were determined by MALDI-TOF MS. These analyses identified Gb4 with very-long-chain fatty acids as the major molecular species in this fraction, and the expression levels of whole molecular species of Gb4 with different fatty acid structures in the membrane are uniformly upregulated by TNF-α stimulation. (ii) The expression levels of genes encoding enzymes for synthesis of the ceramide portion of Gb4 were analyzed by real-time PCR. These assays revealed that TNF-α stimulation promotes transcription of the Elovl1 and Cers5 genes, which are involving in the synthesis of Gb4 with very-long-chain fatty acids. Collectively, these results indicate that TNF-α regulates glycosphingolipid synthesis and lipid raft formation in vascular endothelial cells via transcriptional up-regulation of related genes. These data thus provide new insights useful for understanding the molecular basis of inflammation-associated pathology in vascular endothelia.

Quantitative lipidomic analysis of mouse lung during postnatal development by electrospray ionization tandem mass spectrometry

Lipids play very important roles in lung biology, mainly reducing the alveolar surface tension at the air-liquid interface thereby preventing end-expiratory collapse of the alveoli. In the present study we performed an extensive quantitative lipidomic analysis of mouse lung to provide the i) total lipid quantity, ii) distribution pattern of the major lipid classes, iii) composition of individual lipid species and iv) glycerophospholipid distribution pattern according to carbon chain length (total number of carbon atoms) and degree of unsaturation (total number of double bonds). We analysed and quantified 160 glycerophospholipid species, 24 sphingolipid species, 18 cholesteryl esters and cholesterol from lungs of a) newborn (P1), b) 15-day-old (P15) and c) 12-week-old adult mice (P84) to understand the changes occurring during postnatal pulmonary development. Our results revealed an increase in total lipid quantity, correlation of lipid class distribution in lung tissue and significant changes in the individual lipid species composition during postnatal lung development. Interestingly, we observed significant stage-specific alterations during this process. Especially, P1 lungs showed high content of monounsaturated lipid species; P15 lungs exhibited myristic and palmitic acid containing lipid species, whereas adult lungs were enriched with polyunsaturated lipid species. Taken together, our study provides an extensive quantitative lipidome of the postnatal mouse lung development, which may serve as a reference for a better understanding of lipid alterations and their functions in lung development and respiratory diseases associated with lipids.

Associations of plasma very-long-chain SFA and the metabolic syndrome in adults

Plasma levels of very-long-chain SFA (VLCSFA) are associated with the metabolic syndrome (MetS). However, the associations may vary by different biological activities of individual VLCSFA or population characteristics. We aimed to examine the associations of VLCSFA and MetS risk in Chinese adults. Totally, 2008 Chinese population aged 35–59 years were recruited and followed up from 2010 to 2012. Baseline MetS status and plasma fatty acids data were available for 1729 individuals without serious diseases. Among 899 initially metabolically healthy individuals, we identified 212 incident MetS during the follow-up. Logistic regression analysis was used to estimate OR and 95 % CI. Cross-sectionally, each VLCSFA was inversely associated with MetS risk; comparing with the lowest quartile, the multivariate-adjusted OR for the highest quartile were 0·18 (95 % CI 0·13, 0·25) for C20 : 0, 0·26 (95 % CI 0·18, 0·35) for C22 : 0, 0·19 (95 % CI 0·13, 0·26) for C24 : 0 and 0·16 (0·11, 0·22) for total VLCSFA (all Pfor trend<0·001). The associations remained significant after further adjusting for C16 : 0, C18 : 0, C18 : 3n-3, C22 : 6n-3, n-6 PUFA and MUFA, respectively. Based on follow-up data, C20 : 0 or C22 : 0 was also inversely associated with incident MetS risk. Among the five individual MetS components, higher levels of VLCSFA were most strongly inversely associated with elevated TAG (≥1·7 mmol/l). Plasma levels of VLCSFA were significantly and inversely associated with MetS risk and individual MetS components, especially TAG. Further studies are warranted to confirm the findings and explore underlying mechanisms.

Ceramide Metabolism Balance, a Multifaceted Factor in Critical Steps of Breast Cancer Development

Ceramides are key lipids in energetic-metabolic pathways and signaling cascades, modulating critical physiological functions in cells. While synthesis of ceramides is performed in endoplasmic reticulum (ER), which is altered under overnutrition conditions, proteins associated with ceramide metabolism are located on membrane arrangement of mitochondria and ER (MAMs). However, ceramide accumulation in meta-inflammation, condition that associates obesity with a chronic low-grade inflammatory state, favors the deregulation of pathways such as insulin signaling, and induces structural rearrangements on mitochondrial membrane, modifying its permeability and altering the flux of ions and other molecules. Considering the wide biological processes in which sphingolipids are implicated, they have been associated with diseases that present abnormalities in their energetic metabolism, such as breast cancer. In this sense, sphingolipids could modulate various cell features, such as growth, proliferation, survival, senescence, and apoptosis in cancer progression; moreover, ceramide metabolism is associated to chemotherapy resistance, and regulation of metastasis. Cell–cell communication mediated by exosomes and lipoproteins has become relevant in the transport of several sphingolipids. Therefore, in this work we performed a comprehensive analysis of the state of the art about the multifaceted roles of ceramides, specifically the deregulation of ceramide metabolism pathways, being a key factor that could modulate neoplastic processes development. Under specific conditions, sphingolipids perform important functions in several cellular processes, and depending on the preponderant species and cellular and/or tissue status can inhibit or promote the development of metabolic and potentially breast cancer disease.

A prospective analysis of circulating saturated and monounsaturated fatty acids and risk of non-Hodgkin lymphoma

Circulating saturated (SFA) and monounsaturated fatty acids (MUFA), which are predominantly derived from endogenous metabolism, may influence non-Hodgkin lymphoma (NHL) risk by modulating inflammation or lymphocyte membrane stability. However, few biomarker studies have evaluated NHL risk associated with these fats. We conducted a prospective study of 583 incident NHL cases and 583 individually matched controls with archived pre-diagnosis red blood cell (RBC) specimens in the Nurses' Health Study (NHS) and Health Professionals Follow-Up Study (HPFS). RBC membrane fatty acid levels were measured using gas chromatography. Using multivariable logistic regression, we estimated odds ratios (OR) and 95% confidence intervals (CI) for risk of NHL and major NHL subtypes including T cell NHL (T-NHL), B cell NHL (B-NHL) and three individual B-NHLs: chronic lymphocytic leukemia/small lymphocytic lymphoma (CLL/SLL), diffuse large B-cell lymphoma (DLBCL) and follicular lymphoma. RBC SFA and MUFA levels were not associated with NHL risk overall. However, RBC very long chain SFA levels (VLCSFA; 20:0, 22:0, 23:0) were inversely associated with B-NHLs other than CLL/SLL; ORs (95% CIs) per standard deviation (SD) increase in level were 0.81 (0.70, 0.95) for 20:0, 0.82 (0.70, 0.95) for 22:0 and 0.82 (0.70, 0.96) for 23:0 VLCSFA. Also, both VLCSFA and MUFA levels were inversely associated with T-NHL [ORs (95% CIs) per SD: VLCSFA, 0.63 (0.40, 0.99); MUFA, 0.63 (0.40, 0.99)]. The findings of inverse associations for VLCSFAs with B-NHLs other than CLL/SLL and for VLCSFA and MUFA with T-NHL suggest an influence of fatty acid metabolism on lymphomagenesis.

Circulating Sphingolipids, Insulin, HOMA-IR, and HOMA-B: The Strong Heart Family Study

Experimental studies suggest ceramides may play a role in insulin resistance. However, the relationships of circulating ceramides and related sphingolipids with plasma insulin have been underexplored in humans. We measured 15 ceramide and sphingomyelin species in fasting baseline samples from the Strong Heart Family Study (SHFS), a prospective cohort of American Indians. We examined sphingolipid associations with both baseline and follow-up measures of plasma insulin, HOMA of insulin resistance (HOMA-IR), and HOMA of β-cell function (HOMA-B) after adjustment for risk factors. Among the 2,086 participants without diabetes, higher levels of plasma ceramides carrying the fatty acids 16:0 (16 carbons, 0 double bond), 18:0, 20:0, or 22:0 were associated with higher plasma insulin and higher HOMA-IR at baseline and at follow-up an average of 5.4 years later. For example, a twofold higher baseline concentration of ceramide 16:0 was associated with 14% higher baseline insulin (P < 0.0001). Associations between sphingomyelin species carrying 18:0, 20:0, 22:0, or 24:0 and insulin were modified by BMI (P < 0.003): higher levels were associated with lower fasting insulin, HOMA-IR, and HOMA-B among those with normal BMI. Our study suggests lowering circulating ceramides might be a target in prediabetes and targeting circulating sphingomyelins should take into account BMI.

Association between plasma ceramides and inducible myocardial ischemia in patients with established or suspected coronary artery disease undergoing myocardial perfusion scintigraphy

BACKGROUND

Recent studies have suggested that specific plasma ceramides are independently associated with major adverse cardiovascular events in patients with coronary artery disease (CAD), but it is currently unknown whether plasma ceramide levels are associated with stress-induced reversible myocardial ischemia.

METHODS

We measured six previously identified high-risk plasma ceramide molecules [Cer(d18:1/16:0), Cer(d18:1/18:0), Cer(d18:1/20:0), Cer(d18:1/22:0), Cer(d18:1/24:0), and Cer(d18:1/24:1)] in 167 consecutive patients with established or suspected CAD who underwent either exercise or dypiridamole myocardial perfusion scintigraphy (MPS) for various clinical indications. Plasma ceramide levels were measured by a targeted liquid chromatography-tandem mass spectrometry assay both at baseline and after MPS.

RESULTS

Seventy-eight patients had inducible myocardial ischemia on stress MPS. Women had significantly higher circulating levels of basal and post-stress Cer(d18:1/16:0) and Cer(d18:1/18:0) compared to men, whereas all other plasma ceramides did not differ between the sexes. Of the six measured plasma ceramides, basal Cer(d18:1/24:1) showed the strongest association with the presence of stress-induced myocardial perfusion defects in univariate analysis (unadjusted-odds ratio 1.48 per 1-SD increment, 95% confidence interval 1.08-2.04). Notably, after adjustment for age, sex, smoking, dyslipidemia, hypertension, diabetes, prior history of CAD, left ventricular ejection fraction, and type of stress testing (exercise vs. dypiridamole), all measured ceramides, except for plasma Cer(d18:1/24:0), were independently associated with the presence of inducible myocardial ischemia.

CONCLUSIONS

Distinct plasma ceramides are positive and independent predictors of stress-induced myocardial perfusion defects in patients with established or suspected CAD referred for clinically indicated MPS. Further research is needed to examine whether distinct plasma ceramides could be a useful therapeutic target for treatment and management of CAD.

Chemosensitivity of human colon cancer cells is influenced by a p53-dependent enhancement of ceramide synthase 5 and induction of autophagy

Resistance against chemotherapy is a life-threatening complication in colon cancer therapy. To increase response rate, new additional targets that contribute to chemoresistance are still needed to be explored. Ceramides, which belong to the group of sphingolipids, are well-known regulators of cell death and survival, respectively. Here, we show that in human wild-type (^wt) p53 HCT-116 colon cancer cells treatment with oxaliplatin or 5-fluorouracil (5-FU) leads to a strong increase in ceramide synthase 5 (CerS5) expression and C_16:0-ceramide levels, which was not shown in HCT-116 lacking p53 expression (HCT-116 p53^-/-). The increase in CerS5 expression occurs by stabilizing CerS5 mRNA at the 3'-UTR. By contrast, in the p53-deficient cells CerS2 expression and CerS2-related C_24:0- and C_24:1-ceramide levels were elevated which is possibly related to enhanced polyadenylation of the CerS2 transcript in these cells. Stable knockdown of CerS5 expression using CerS5-targeting shRNA led to an increased sensitivity of HCT-116 p53^wt cells, but not of p53^-/- cells, to oxaliplatin and 5-FU. Enhanced sensitivity was accompanied by an inhibition of autophagy and inhibition of mitochondrial respiration in these cells. However, knockdown of CerS2 had no significant effects on chemosensitivity of both cell lines. In conclusion, in p53^wt colon cancer cells chemosensitivity against oxaliplatin or 5-FU could be enhanced by downregulation of CerS5 expression leading to reduced autophagy and mitochondrial respiration.

Role of caveolin-1 in hepatocellular carcinoma arising from non-alcoholic fatty liver disease

The molecular features of hepatocellular carcinoma arising from non-alcoholic fatty liver disease (NAFLD-HCC) are not well known. In this study, we investigated the mechanism by which NAFLD-HCC survives in a fat-rich environment. We found that caveolin (CAV)-1 was overexpressed in clinical specimens from NAFLD-HCC patients. HepG2, HLE, and HuH-7 HCC cell lines showed decreased proliferation in the presence of the saturated fatty acids palmitic acid and stearic acid, although only HLE cells expressed high levels of CAV-1. HLE cells treated with oleic acid (OA) showed robust proliferation, whereas CAV-null HepG2 cells showed reduced proliferation and increased apoptosis. CAV-1 knockdown in HLE cells attenuated the OA-induced increase in proliferation and enhanced apoptosis. Liquid chromatography-tandem mass spectrometry analysis revealed that the levels of OA-containing ceramide, a pro-apoptotic factor, were higher in HepG2 and CAV-1-deficient HLE cells than in HLE cells, suggesting that CAV-1 inhibits apoptosis by decreasing the level of OA-containing ceramide. These results indicate that CAV-1 is important for NAFLD-HCC survival in fatty acid-rich environments and is a potential therapeutic target.

Traceless synthesis of ceramides in living cells reveals saturation-dependent apoptotic effects

Mammalian cells synthesize thousands of distinct lipids, yet the function of many of these lipid species is unknown. Ceramides, a class of sphingolipid, are implicated in several cell-signaling pathways but poor cell permeability and lack of selectivity in endogenous synthesis pathways have hampered direct study of their effects. Here we report a strategy that overcomes the inherent biological limitations of ceramide delivery by chemoselectively ligating lipid precursors in vivo to yield natural ceramides in a traceless manner. Using this method, we uncovered the apoptotic effects of several ceramide species and observed differences in their apoptotic activity based on acyl-chain saturation. Additionally, we demonstrate spatiotemporally controlled ceramide synthesis in live cells through photoinitiated lipid ligation. Our in situ lipid ligation approach addresses the long-standing problem of lipid-specific delivery and enables the direct study of unique ceramide species in live cells.

Programming and Regulation of Metabolic Homeostasis by HDAC11

Histone deacetylases (HDACs) are enzymes that regulate protein functions by catalyzing the removal of acetyl and acyl groups from lysine residues. They play pivotal roles in governing cell behaviors and are indispensable in numerous biological processes. HDAC11, the last identified and sole member of class IV HDACs, was reported over a decade ago. However, its physiological function remains poorly understood. Here, we report that HDAC11 knockout mice are resistant to high-fat diet-induced obesity and metabolic syndrome, suggesting that HDAC11 functions as a crucial metabolic regulator. Depletion of HDAC11 significantly enhanced insulin sensitivity and glucose tolerance, attenuated hypercholesterolemia, and decreased hepatosteatosis and liver damage. Mechanistically, HDAC11 deficiency boosts energy expenditure through promoting thermogenic capacity, which attributes to the elevation of uncoupling protein 1 (UCP1) expression and activity in brown adipose tissue. Moreover, loss of HDAC11 activates the adiponectin-AdipoR-AMPK pathway in the liver, which may contribute to a reversal in hepatosteatosis. Overall, our findings distinguish HDAC11 as a novel regulator of obesity, with potentially important implications for obesity-related disease treatment.

The Onus of Sphingolipid Enzymes in Cancer Drug Resistance

Chemotherapy resistance, inherent or acquired, represents a serious barrier to the successful treatment of cancer. Although drug efflux, conducted by plasma membrane-resident proteins, detoxification enzymes, cell death inhibition, and DNA damage repair are ensemble players in this unwanted biology, a full understanding of the many in concert molecular mechanisms driving drug resistance is lacking. Recent discoveries in sphingolipid (SL) metabolism have provided significant insight into the role of these lipids in cancer growth; however, considerably less is known with respect to SLs and the drug-resistant phenotype. One exception here is enhanced ceramide glycosylation, a hallmark of multidrug resistance that is believed responsible, in part, for diminishing ceramides tumor-suppressor potential. This chapter will review various aspects of SL biology that relate to chemotherapy resistance and extend this topic to acknowledge the role of chemotherapy selection pressure in promoting dysregulated SL metabolism, a characteristic in cancer and an exploitable target for therapy.

Differential effects of saturated fatty acids on the risk of metabolic syndrome: a matched case-control and meta-analysis study

BACKGROUND

We investigated the association between plasma saturated fatty acids (SFAs) and the risk of metabolic syndrome among ethnic Chinese adults in Taiwan who attended a health check-up center.

METHODS

A case-control study based on 1000 cases of metabolic syndrome and 1:1 matched control participants (mean age, 54.9 ± 10.7 y; 36% females) were recruited. Metabolic syndrome was defined according to the criteria of the International Diabetes Federation. Gas chromatography was used to measure the distribution of fatty acids in plasma (% of total fatty acids).

RESULTS

Even-chain SFAs, including 14:0, 16:0, and 18:0, were associated with metabolic syndrome; the adjusted odds ratio [OR] and 95% confidence interval [CI] per standard deviation [SD] difference was 3.32, [1.98-5.59]; however, very-long-chain SFAs, including 20:0, 21:0, 22:0, 23:0, and 24:0, were inversely associated with metabolic syndrome. The adjusted OR [95% CI] per SD difference was 0.67 [0.58-0.78]. The area under the receiver operative characteristic curve increased from 0.814 in the basic model to 0.815 (p = 0.54, compared with the basic model), 0.818 (p < 0.0001), and 0.820 (p < 0.0001) after adding odd-chain, even-chain, and very-long chain SFAs. A meta-analysis based on 12 studies showed that the summarized OR for type 2 diabetes mellitus was 1.16 [0.96-1.41] for the top versus bottom SFAs.

CONCLUSIONS

Different carbon numbers of SFAs have been shown to have differential effects on the status of metabolic syndrome, implying that SFAs are not homogenous for the effects.

The Physical Properties of Ceramides in Membranes

Ceramides are sphingolipids containing a sphingosine or a related base, to which a fatty acid is linked through an amide bond. When incorporated into a lipid bilayer, ceramides exhibit a number of properties not shared by almost any other membrane lipid: Ceramides ( a) are extremely hydrophobic and thus cannot exist in suspension in aqueous media; ( b) increase the molecular order (rigidity) of phospholipids in membranes; ( c) give rise to lateral phase separation and domain formation in phospholipid bilayers; ( d) possess a marked intrinsic negative curvature that facilitates formation of inverted hexagonal phases; ( e) make bilayers and cell membranes permeable to small and large (i.e., protein-size) solutes; and ( f) promote transmembrane (flip-flop) lipid motion. Unfortunately, there is hardly any link between the physical studies reviewed here and the mass of biological and clinical studies on the effects of ceramides in health and disease.

Determination of fatty acid and sphingoid base composition of eleven ceramide subclasses in stratum corneum by UHPLC/scheduled-MRM

INTRODUCTION

Ceramides play a key role in skin barrier function in homeostatic and pathological conditions and can be sampled non-invasively through stratum corneum collection.

OBJECTIVES

To develop a novel UHPLC/Scheduled MRM method for the identification and relative distribution of eleven classes of ceramides, which are separated by UHPLC and determined by their specific retention times. The precise composition of the fatty acid and sphingoid base parts of each individual ceramide is determined via mass fragmentation.

METHODS

More than 1000 human and pig ceramides were identified. Three human and minipig ceramide classes, CER[AS], CER[NS] and CER[EOS] have been investigated in depth.

RESULTS

Sphingoid bases were characterized by a prevalence of chain lengths with sizes from C16 to C22, whereas fatty acids were mainly observed in the range of C22-C26. Overall, the ceramide profiles between human and minipig stratum corneum were similar. Differences in the CER[AS] and CER[NS] classes included a more homogeneous distribution of fatty acids (16-30 carbon atoms) in minipig, whereas in human longer fatty acid chains (> 24 carbon atoms) predominated.

CONCLUSION

The method will be useful for the analysis of healthy and pathological skin in various specie, and the measurement of the relative distribution of ceramides as biomarkers for pharmacodynamic studies.

Identification of radiation responsive genes and transcriptome profiling via complete RNA sequencing in a stable radioresistant U87 glioblastoma model

The absence of major progress in the treatment of glioblastoma (GBM) is partly attributable to our poor understanding of both GBM tumor biology and the acquirement of treatment resistance in recurrent GBMs. Recurrent GBMs are characterized by their resistance to radiation. In this study, we used an established stable U87 radioresistant GBM model and total RNA sequencing to shed light on global mRNA expression changes following irradiation. We identified many genes, the expressions of which were altered in our radioresistant GBM model, that have never before been reported to be associated with the development of radioresistant GBM and should be concertedly further investigated to understand their roles in radioresistance. These genes were enriched in various biological processes such as inflammatory response, cell migration, positive regulation of epithelial to mesenchymal transition, angiogenesis, apoptosis, positive regulation of T-cell migration, positive regulation of macrophage chemotaxis, T-cell antigen processing and presentation, and microglial cell activation involved in immune response genes. These findings furnish crucial information for elucidating the molecular mechanisms associated with radioresistance in GBM. Therapeutically, with the global alterations of multiple biological pathways observed in irradiated GBM cells, an effective GBM therapy may require a cocktail carrying multiple agents targeting multiple implicated pathways in order to have a chance at making a substantial impact on improving the overall GBM survival.

Profiling of epidermal lipids in a mouse model of dermatitis: Identification of potential biomarkers

Lipids are important structural and functional components of the skin. Alterations in the lipid composition of the epidermis are associated with inflammation and can affect the barrier function of the skin. SHARPIN-deficient cpdm mice develop a chronic dermatitis with similarities to atopic dermatitis in humans. Here, we used a recently-developed approach named multiple reaction monitoring (MRM)-profiling and single ion monitoring to rapidly identify discriminative lipid ions. Shorter fatty acyl residues and increased relative amounts of sphingosine ceramides were observed in cpdm epidermis compared to wild type mice. These changes were accompanied by downregulation of the Fasn gene which encodes fatty acid synthase. A profile of diverse lipids was generated by fast screening of over 300 transitions (ion pairs). Tentative attribution of the most significant transitions was confirmed by product ion scan (MS/MS), and the MRM-profiling linear intensity response was validated with a C17-ceramide lipid standard. Relative quantification of sphingosine ceramides CerAS(d18:1/24:0)2OH, CerAS(d18:1/16:0)2OH and CerNS(d18:1/16:0) discriminated between the two groups with 100% accuracy, while the free fatty acids cerotic acid, 16-hydroxy palmitic acid, and docosahexaenoic acid (DHA) had 96.4% of accuracy. Validation by liquid chromatography tandem mass spectrometry (LC-MS/MS) of the above-mentioned ceramides was in agreement with MRM-profiling results. Identification and rapid monitoring of these lipids represent a tool to assess therapeutic outcomes in SHARPIN-deficient mice and other mouse models of dermatitis and may have diagnostic utility in atopic dermatitis.

Beta adrenoceptor blockade ameliorates impaired glucose tolerance and alterations of the cerebral ceramide metabolism in an experimental model of ischemic stroke

Background:

Sphingolipids are versatile signaling molecules derived from membrane lipids of eukaryotic cells. Ceramides regulate cellular processes such as proliferation, differentiation and apoptosis and are involved in cellular stress responses. Experimental evidence suggests a pivotal role of sphingolipids in the pathogenesis of cardiovascular diseases, including ischemic stroke. A neuroprotective effect has been shown for beta-adrenergic antagonists in rodent stroke models and supported by observational clinical data. However, the exact underlying pathophysiological mechanisms are still under investigation. We aimed to examine the influence of propranolol on the ceramide metabolism in the stroke-affected brain.

Methods:

Mice were subjected to 60 or 180 min transient middle cerebral artery occlusion (tMCAO) and infarct size, functional neurological deficits, glucose tolerance, and brain ceramide levels were assessed after 12, 24, and 72 h to evaluate whether the latter two processes occur in a similar time frame. Next, we assessed the effects of propranolol (10 mg/kg bw) at 0, 4 and 8 h after tMCAO and FTY720 (fingolimod; 1 mg/kg) on infarct size, functional outcome, immune cell counts and brain ceramide levels at 24 h after 60 min tMCAO.

Results:

We found a temporal coincidence between stroke-associated impaired glucose tolerance and brain ceramide accumulation. Whereas propranolol reduced ischemic lesion size, improved functional outcome and reduced brain ceramide accumulation without an effect on circulating immune cells, FTY720 showed the known neuroprotective effect and strong reduction of circulating immune cells without affecting brain ceramide accumulation.

Conclusions:

Propranolol ameliorates both stroke-associated impairment of glucose tolerance and brain ceramide accumulation which are temporally linked, strengthening the evidence for a role of the sympathetic nervous system in regulating post-stroke glucose metabolism and its metabolic consequences in the brain.

Molecular Targeting of Acid Ceramidase in Glioblastoma: A Review of Its Role, Potential Treatment, and Challenges

Glioblastoma is the most common, malignant primary tumor of the central nervous system. The average prognosis for life expectancy after diagnosis, with the triad of surgery, chemotherapy, and radiation therapy, is less than 1.5 years. Chemotherapy treatment is mostly limited to temozolomide. In this paper, the authors review an emerging, novel drug called acid ceramidase, which targets glioblastoma. Its role in cancer treatment in general, and more specifically, in the treatment of glioblastoma, are discussed. In addition, the authors provide insights on acid ceramidase as a potential druggable target for glioblastoma.

Low Serum Levels of (Dihydro-)Ceramides Reflect Liver Graft Dysfunction in a Real-World Cohort of Patients Post Liver Transplantation

Patients after orthopic liver transplantation (OLT) are at risk of developing graft dysfunction. Sphingolipids (SL’s) have been identified to play a pivotal role in the regulation of hepatocellular apoptosis, inflammation and immunity. We aimed to investigate the serum SL profile in a prospective real-world cohort of post-OLT patients. From October 2015 until July 2016, 149 well-characterized post-OLT patients were analyzed. SL’s were assessed in serum probes via Liquid Chromatography/Tandem Mass Spectrometry. Twenty-nine (20%) patients had a biopsy proven graft rejection with decreased C20-ceramide (Cer) (p = 0.042), C18-dihydroceramide (DHC) (p = 0.022) and C24DHC (p = 0.060) levels. Furthermore, C18DHC (p = 0.044) and C24DHC (p = 0.011) were significantly down-regulated in patients with ischemic type biliary lesions (ITBL; n = 15; 10%). One-hundred and thirty-three patients (89%) have so far received tacrolimus as the main immunosuppressive agent with observed elevations of C14Cer (p = 0.052), C18Cer (p = 0.049) and C18:1Cer (p = 0.024). Hepatocellular carcinoma (HCC) pre-OLT was associated with increases in C24:1Cer (p = 0.024) and C24:1DHC (p = 0.024). In this large prospective cross-sectional study of patients, post-OLT serum levels of (very-)long chain (dihydro-)ceramides associate with graft rejection, ITBL, tacrolimus intake and HCC pre-OLT. Hence, serum SL’s may be indicative of graft complications. Further research is necessary to identify their diverse mechanistic role in regulating immunity and inflammation in patients post-OLT.

Plasma ceramide levels are altered in low and normal birth weight men in response to short-term high-fat overfeeding

Low birth weight (LBW) individuals have an increased risk of developing insulin resistance and type 2 diabetes compared with normal birth weight (NBW) individuals. We hypothesised that LBW individuals exhibit an increased fatty acid flux into lipogenesis in non-adipose tissue with a resulting accumulation of lipotoxic lipids, including ceramides, in the blood. Therefore, we measured fasting plasma levels of 27 ceramides in 18 young, healthy, LBW men and 25 NBW controls after an isocaloric control diet and a 5-day high-fat, high-calorie diet by HPLC-HRMS. LBW men did not show elevated plasma ceramide levels after the control or high-fat, high-calorie diet. An increased fatty acid oxidation rate in these individuals during both diets may limit ceramide synthesis and thereby compensate for a likely increased fatty acid load to non-adipose tissue. Interestingly, LBW and NBW men decreased d18:0-18:1/d18:1-18:0 and d18:1-24:2/d18:2-24:1 levels and increased the d18:0-24:1a level in response to overfeeding. Plasma d18:0-24:1a and total ceramide levels were positively associated with the fasting blood glucose level and endogenous glucose production after the control diet, and the total ceramide level was in addition positively associated with hepatic insulin resistance. Further studies are needed to determine if lipotoxicity contributes to insulin resistance in LBW individuals.

Untargeted Metabolomics Reveal Lipid Alterations upon 2-Deoxyglucose Treatment in Human HaCaT Keratinocytes

The glucose analogue 2-deoxyglucose (2-DG) impedes cancer progression in animal models and is currently being assessed as an anticancer therapy, yet the mode of action of this drug of high clinical significance has not been fully delineated. In an attempt to better characterize its pharmacodynamics, an integrative UPLC-Q-Exactive-based joint metabolomic and lipidomic approach was undertaken to evaluate the metabolic perturbations induced by this drug in human HaCaT keratinocyte cells. R-XCMS data processing and subsequent multivariate pattern recognition, metabolites identification, and pathway analyses identified eight metabolites that were most significantly changed upon a 3 h 2-DG exposure. Most of these dysregulated features were emphasized in the course of lipidomic profiling and could be identified as ceramide and glucosylceramide derivatives, consistently with their involvement in cell death programming. Even though metabolomic analyses did not generally afford such clear-cut dysregulations, some alterations in phosphatidylcholine and phosphatidylethanolamine derivatives could be highlighted as well. Overall, these results support the adequacy of the proposed analytical workflow and might contribute to a better understanding of the mechanisms underlying the promising effects of 2-DG.

The carnitine system and cancer metabolic plasticity

Metabolic flexibility describes the ability of cells to respond or adapt its metabolism to support and enable rapid proliferation, continuous growth, and survival in hostile conditions. This dynamic character of the cellular metabolic network appears enhanced in cancer cells, in order to increase the adaptive phenotype and to maintain both viability and uncontrolled proliferation. Cancer cells can reprogram their metabolism to satisfy the energy as well as the biosynthetic intermediate request and to preserve their integrity from the harsh and hypoxic environment. Although several studies now recognize these reprogrammed activities as hallmarks of cancer, it remains unclear which are the pathways involved in regulating metabolic plasticity. Recent findings have suggested that carnitine system (CS) could be considered as a gridlock to finely trigger the metabolic flexibility of cancer cells. Indeed, the components of this system are involved in the bi-directional transport of acyl moieties from cytosol to mitochondria and vice versa, thus playing a fundamental role in tuning the switch between the glucose and fatty acid metabolism. Therefore, the CS regulation, at both enzymatic and epigenetic levels, plays a pivotal role in tumors, suggesting new druggable pathways for prevention and treatment of human cancer.

Sexual dimorphism in activation of placental autophagy in obese women with evidence for fetal programming from a placenta-specific mouse model

The incidence of maternal obesity and its co-morbidities (diabetes, cardiovascular disease) continues to increase at an alarming rate, with major public health implications. In utero exposure to maternal obesity has been associated with development of cardiovascular and metabolic diseases in the offspring as a result of developmental programming. The placenta regulates maternal-fetal metabolism and shows significant changes in its function with maternal obesity. Autophagy is a cell-survival process, which is responsible for the degradation of damaged organelles and misfolded proteins. Here we show an activation of autophagosomal formation and autophagosome-lysosome fusion in placentas of males but not females from overweight (OW) and obese (OB) women vs. normal weight (NW) women. However, total autophagic activity in these placentas appeared to be decreased as it showed an increase in SQSTM1/p62 and a decrease in lysosomal biogenesis. A mouse model with a targeted deletion of the essential autophagy gene Atg7 in placental tissue showed significant placental abnormalities comparable to those seen in human placenta with maternal obesity. These included a decrease in expression of mitochondrial genes and antioxidants, and decreased lysosomal biogenesis. Strikingly, the knockout mice were developmentally programmed as they showed an increased sensitivity to high-fat diet-induced obesity, hyperglycemia, hyperinsulinemia, increased adiposity, and cardiac remodeling. In summary, our results indicate a sexual dimorphism in placental autophagy in response to maternal obesity. We also show that autophagy plays an important role in placental function and that inhibition of placental autophagy programs the offspring to obesity, and to metabolic and cardiovascular diseases.

Effects of meal ingestion on intramyocellular ceramide concentrations and fractional de novo synthesis in humans

We investigated the effects of meal ingestion on intramyofibrillar (IMF) and subsarcolemmal (SS) ceramide metabolism in volunteers ranging from lean to obese. Thirty-eight women and men underwent a steady-state meal ingestion protocol that included a 6.5-h infusion of [U-¹³C]palmitate and muscle biopsies 1.5 and 6.5 h after starting the tracer infusion. We measured IMF and SS sphingolipid concentrations and the contribution of plasma palmitate to intramyocellular C16:0 ceramide by use of LC-MS-MS. In response to meal ingestion SS C24 ceramide concentrations, but not C14-C20 concentrations, increased significantly. IMF ceramide concentrations did not change. The increases in SS C24 ceramides were negatively related to parameters of insulin resistance. The fractional contribution of plasma palmitate to intramyocellular C16:0 ceramides in both IMF and SS fractions was inversely related to overweight status (β = -0.432, P = 0.0095 and β = -0.443, P = 0.0058, respectively). These data indicate that meal ingestion has differing effects on SS ceramide subspecies and suggest that the fractional de novo synthesis of intramyocellular ceramide from plasma palmitate in the postprandial condition is reduced in those who are overweight.

Ceramide Synthase 6 Deficiency Enhances Inflammation in the DSS model of Colitis

Colitis, an inflammatory disease of the digestive tract, is increasing in incidence and prevalence. Intestinal inflammation can occur as a consequence of dysfunctions in sphingolipid metabolism. In this study we used ceramide synthase 6 (CerS6) deficient mice, which have a reduced ability to generate long chain C₁₆-ceramide, to investigate the role of this enzyme in dextran sodium salt (DSS)-induced colitis. While CerS6-deficient mice are protected from T cell mediated colitis, in the T cell independent DSS model lack of CerS6 resulted in a more rapid onset of disease symptoms. CerS6-deficient mice maintained low levels of C₁₆-ceramide after DSS treatment, but the inflammatory lipid sphingosine-1-phosphate was significantly increased in colon tissue. In the absence of CerS6, DSS induced more severe pathology in the colon including enhanced neutrophil infiltration. In vivo analysis of myeloperoxidase activity, an enzyme released from neutrophils, was approximately 2.5-fold higher in CerS6-deficient mice compared to wild type. Differences in intestinal permeability did not account for the increase in neutrophils. Our study suggests that lack of CerS6 expression differentially impacts the development of colitis, depending on the model used.

Azide-tagged sphingolipids for the proteome-wide identification of C16-ceramide-binding proteins

Unknown ceramide-binding proteins can be identified by combining azide-tagged sphingolipids with MS-based proteomic profiling and protein array analysis.

Ganglioside Metabolism and Its Inherited Diseases

Gangliosides are sialic acid containing glycosphingolipids, which are abundant in mammalian brain tissue. Several fatal human diseases are caused by defects in glycolipid metabolism. Defects in their degradation lead to an accumulation of metabolites upstream of the defective reactions, whereas defects in their biosynthesis lead to diverse problems in a large number of organs.Gangliosides are primarily positioned with their ceramide anchor in the neuronal plasma membrane and the glycan head group exposed on the cell surface. Their biosynthesis starts in the endoplasmic reticulum with the formation of the ceramide anchor, followed by sequential glycosylation reactions, mainly at the luminal surface of Golgi and TGN membranes, a combinatorial process, which is catalyzed by often promiscuous membrane-bound glycosyltransferases.Thereafter, the gangliosides are transported to the plasma membrane by exocytotic membrane flow. After endocytosis, they are degraded within the endolysosomal compartments by a complex machinery of degrading enzymes, lipid-binding activator proteins, and negatively charged lipids.

Adipose tissue content of saturated fatty acids and atrial fibrillation: A case-cohort study

OBJECTIVES

The aim of this study was to investigate the association between adipose tissue content of total saturated fatty acids including myristic (C14:0), palmitic (C16:0) and stearic (C18:0) acid, as a measure of exposure to saturated fatty acids and the risk of incident atrial fibrillation.

MATERIALS AND METHODS

A total of 57 053 Danish men and women aged 50-64 years participating in the Diet, Cancer and Health cohort had an adipose tissue biopsy taken at baseline, and this was analysed for saturated fatty acids content by gas chromatography. Follow-up was registry based and in this case-cohort study we used all cases and a randomly drawn subcohort of 3500 participants representative for the entire cohort.

RESULTS

Data were analysed using weighted Cox proportional hazards regression. During a median follow-up of 14.6 years, a total of 4722 cases of incident atrial fibrillation were diagnosed. For both men and women, no association between adipose tissue content of total saturated fatty acids and the risk of atrial fibrillation could be demonstrated.

CONCLUSION

We did not find an association between adipose tissue content of total saturated fatty acids and the risk of incident atrial fibrillation.