Long-chain Ceramides Research Articles

Elongation of Very Long-Chain Fatty Acids (ELOVL) in Atopic Dermatitis and the Cutaneous Adverse Effect AGEP of Drugs.

Atopic dermatitis (AD) is a common inflammatory skin disease, in particular among infants, and is characterized, among other things, by a modification in fatty acid and ceramide composition of the skin's stratum corneum. Palmitic acid and stearic acid, along with C16-ceramide and 2-hydroxy C16-ceramide, occur strikingly in AD. They coincide with a simultaneous decrease in very long-chain ceramides and ultra-long-chain ceramides, which form the outermost lipid barrier. Ceramides originate from cellular sphingolipid/ceramide metabolism, comprising a well-orchestrated network of enzymes involving various ELOVLs and CerSs in the de novo ceramide synthesis and neutral and acid CERase in degradation. Contrasting changes in long-chain ceramides and very long-chain ceramides in AD can be more clearly explained by the compartmentalization of ceramide synthesis. According to our hypothesis, the origin of increased C16-ceramide and 2-hydroxy C16-ceramide is located in the lysosome. Conversely, the decreased ultra-long-chain and very long-chain ceramides are the result of impaired ELOVL fatty acid elongation. The suggested model's key elements include the lysosomal aCERase, which has pH-dependent long-chain C16-ceramide synthase activity (revaCERase); the NADPH-activated step-in enzyme ELOVL6 for fatty acid elongation; and the coincidence of impaired ELOVL fatty acid elongation and an elevated lysosomal pH, which is considered to be the trigger for the altered ceramide biosynthesis in the lysosome. To maintain the ELOVL6 fatty acid elongation and the supply of NADPH and ATP to the cell, the polyunsaturated PPARG activator linoleic acid is considered to be one of the most suitable compounds. In the event that the increase in lysosomal pH is triggered by lysosomotropic compounds, compounds that disrupt the transmembrane proton gradient or force the breakdown of lysosomal proton pumps, non-HLA-classified AGEP may result.

Balancing roles between phosphatidylinositols and sphingolipids in regulating immunity and ER stress responses in pi4kβ1,2.

Plant immune regulation is complex. In addition to proteins, lipid molecules play critical roles in modulating immune responses. The mutant pi4kβ1,2 is mutated in two phosphatidylinositol 4-kinases PI4Kβ1 and β2 involved in the biosynthesis of phosphatidylinositol 4-phosphate (PI4P). The mutant displays autoimmunity, short roots, aberrant root hairs, and a heightened sensitivity to ER stress. In a forward genetic screen designed to dissect pi4kβ1,2 autoimmunity, we found that Orosomucoid-like 1 (ORM1) is required for the phenotypes of pi4kβ1,2, including short root and ER stress sensitivity. The orm1 mutations lead to increased long-chain base and ceramide levels in the suppressors. We also found that the basic region/leucine Zipper motif (bZIP) 28 and 60 transcription factors, central regulators of ER stress response, are required for its autoimmunity and root defect. In comparison, the defense-related phytohormones salicylic acid (SA) and N-hydroxypipecolic acid (NHP) are required for its autoimmunity but plays a minor role in its root phenotypes. Further, we found that wild-type plants overexpressing ORM1 are autoimmune, displaying short roots and increased ceramide levels. The autoimmunity of the ORM1 overexpression lines is dependent on SA, NHP, and bZIP60. As ORM1 is a known negative regulator of sphingolipid biosynthesis, our study uncovers a balancing role between PIs and sphingolipids in regulating immunity and ER stress responses in pi4kβ1,2.

Liver tissue lipids in metabolic dysfunction-associated steatotic liver disease with diabetes and obesity

BackgroundDiabetes and obesity are associated with altered lipid metabolism and hepatic steatosis. Studies suggest that increases in lipid accumulation in these patients with metabolic dysfunction-associated steatotic liver disease (MASLD) are not uniform for all lipid components. This study evaluates this variation. MethodsA comprehensive lipidomic analysis of different lipid groups, were performed on liver tissue and plasma samples obtained at the time of histology from a well-defined cohort of 72 MASLD participants. The lipid profiles of controls were compared to those of MASLD patients with obesity, diabetes, or a combination of both. ResultsMASLD patients without obesity or diabetes exhibited distinct changes in the lipid profile of their liver tissue. The presence of diabetes or obesity further modified these lipid profiles (e.g., ceramide 47:7;4O), with positive or negative correlation (p < 0.05). A step-wise increase (long-chain fatty acids, triglycerides, and ceramides) or decrease (ultra-long fatty acids, diglycerides, and phospholipids) for lipid groups was observed compared to control among patients with MASLD without obesity or diabetes to MASLD patients with obesity as a single risk factor, and MASLD patients with obesity and diabetes. Changes in lipids observed in the plasma did not align with their corresponding liver tissue findings. ConclusionThe changes observed in the composition of lipids are not similar in patients with obesity and diabetes among those with MASLD. This highlights the different metabolic processes at play. The presence of obesity or diabetes in patients with MASLD exacerbates these lipid derangements, underscoring the potential for targeted intervention in MASLD patients.

Chronic Estrogen Treatment Promotes Human Microvascular Endothelial Dysfunction Through Sex-Specific Regulation of Ceramide Formation

Risk for cardiovascular disease (CVD) is elevated in individuals assigned female at birth and women of trans experience (assigned male at birth) undergoing long-term estrogen therapy (e.g. contraception, gender-affrmation). We have previously shown that chronic estrogen treatment induces microvascular endothelial dysfunction in human arterioles collected from those assigned male and female at birth. The mechanism via which estrogen causes microvascular damage remains unknown. Estrogen can increase expression of the ceramide-forming enzyme neutral sphingomyelinase (NSmase), and elevated ceramides promote cellular oxidative stress. Together, we hypothesize that estrogen induces microvascular endothelial dysfunction via NSmase-mediated ceramide formation. Human arterioles from otherwise healthy adults were treated with 17β-estradiol (E2; 100nM) +/- NSmase inhibitor (GW4869; 4μM, 24hrs). Vascular response to increasing flow rates was assessed using live videomicroscopy. Sex-specific human umbilical vein endothelial cells were treated with E2+/-GW4869 (48hrs), and H2O2 levels were measured using the fluorescent indicator peroxy yellow 1 (PY1). Endothelial ceramide levels were measured using liquid chromatography, tandem mass spectrometry. Exposure to estrogen impaired dilation to flow in arterioles from those assigned male and female at birth, an effect that was prevented by inhibition of NSmase (%Mean Dilation±SE; E2 vs E2+GW4869; male: 11.20±4.99% vs 48.43±7.15%, n=3 both, p=0.037; female: 1.78±1.99% vs 40.35±8.46%, n=5 both, p=0.006; two-way ANOVA). Estrogen treatment increased endothelial H2O2 production in cells from both sexes which was diminished by GW4869 treatment (%Change from control±SE; E2 vs E2+GW4869; male: 20.90±5.86% vs 2.85±1.99%, n=11 both, p=0.009*; female: 63.33±13.65%, n=10 vs 25.25±7.64%, n=9, p=0.031*, unpaired t-test*). Endothelial long-chain ceramide levels were higher in cells from biological males compared to females (pmol/nmol phosphate; male 5.90±2.19, n=4 vs female 2.18±0.86, n=5; p=0.009*). While estrogen treatment increased cellular ceramides in both sexes, ceramide accumulation was greater in cells from biological males compared to females (%change from baseline: 65.97±53.64% vs 6.08±7.86%, p=0.041*). Together, these results show that estrogen-induced microvascular endothelial dysfunction can be prevented through inhibition of NSmase-mediated ceramide formation. There is also notable sexual dimorphism in endothelial ceramide levels both at baseline and in response to estrogen. This study offers mechanistic insight into how chronic estrogen therapy may contribute to microvascular dysfunction and elevate the risk of CVD in patients. Furthermore, it presents the inhibition of NSmase as a plausible therapeutic approach to safeguard microvascular integrity during estrogen therapy. NHLBI R01HL160752 (J.K.F.), NHLBI K08HL141562 (J.K.F.), and AHA predoctoral fellowship grant 909315 (G.S.). This is the full abstract presented at the American Physiology Summit 2024 meeting and is only available in HTML format. There are no additional versions or additional content available for this abstract. Physiology was not involved in the peer review process.

Indian Gooseberry and Barley Sprout Complex Prevent Oxidative Stress and Photoaging of the Skin in Ultraviolet B-Irradiated SHK-I Mice.

This study investigated the protective effects of a complex of Indian gooseberry and barley sprout (IB complex) on oxidative stress and skin damage caused by ultraviolet B irradiation in SHK-I hairless mice. The study examined the impact of IB complex on skin hydration, wrinkle formation, and melanogenesis using enzyme-linked immunosorbent assay, real-time polymerase chain reaction, and western blot analysis. The IB complex reduced skin hydration loss and wrinkle formation, while also demonstrating enhanced antioxidant activities. The IB complex maintained skin hydration via upregulation of hyaluronic acid and ceramide synthesis, including the regulation of hyaluronic acid synthase, long-chain ceramide formation, dihydroceramide desaturase 1 activity, and type I collagen production. The IB complex prevented wrinkle formation via downregulating JNK and upregulating TGF-β pathways. Moreover, IB complex blocked melanin production via inhibition of protein kinase A, cAMP response element-binding protein, and microphthalmia-associated transcription factor pathways. These results suggest that IB complex is a potential agent to protect the skin against photodamage caused by exposure to UVB radiation. The research protocols underwent approval from the Institutional Animal Care and Use Committee of Kyung Hee University (KHGASP-21-577), ensuring compliance with ethical standards.

Plasma Ceramides and Other Sphingolipids in Relation to Incident Prediabetes in a Longitudinal Biracial Cohort.

Sphingolipids are linked to the pathogenesis of type 2 diabetes. To test the hypothesis that plasma sphingolipid profiles predict incident prediabetes. A case-control study nested in the Pathobiology of Prediabetes in a Biracial Cohort study, a 5-year follow-up study. Academic health center. Normoglycemic adults enrolled in the Pathobiology of Prediabetes in a Biracial Cohort study. Assessments included oral glucose tolerance test, insulin sensitivity, and insulin secretion. Participants with incident prediabetes were matched in age, sex, and ethnicity with nonprogressors. We assayed 58 sphingolipid species (ceramides, monohexosyl ceramides, sphingomyelins, and sphingosine) using liquid chromatography/tandem mass spectrometry in baseline plasma levels from participants and determined association with prediabetes risk. The primary outcome was progression from normoglycemia to prediabetes, defined as impaired fasting glucose or impaired glucose tolerance. The mean age of participants (N = 140; 50% Black, 50% female) was 48.1 ± 8.69 years, body mass index 30.1 ± 5.78 kg/m2, fasting plasma glucose 92.7 ± 5.84 mg/dL, and 2-hour plasma glucose 121 ± 23.3 mg/dL. Of the 58 sphingolipid species assayed, higher ratios of sphingomyelin C26:0/C26:1 (OR, 2.73 [95% CI, 1.172-4.408], P = .015) and ceramide C18:0/C18:1 (OR, 1.236 [95% CI, 1.042-1.466], P = .015) in baseline plasma specimens were significantly associated with progression to prediabetes during the 5-year follow-up period, after adjustments for age, race, sex, body mass index, fasting plasma glucose, 2-hour plasma glucose, insulin sensitivity, and insulin secretion. We conclude that the saturated-to-monounsaturated ratios of long-chain ceramide C18:0/C18:1 and very-long-chain sphingomyelin C26:0/C26:1 are potential biomarkers of prediabetes risk among individuals with parental history of type 2 diabetes.

Lipidomics reveals the significance and mechanism of the cellular ceramide metabolism for rotavirus replication.

As one of the most important causative agents of severe gastroenteritis in children, piglets, and other young animals, species A rotaviruses have adversely impacted both human health and the global swine industry. Vaccines against rotaviruses (RVs) are insufficiently effective, and no specific treatment is available. To understand the relationships between porcine RV (PoRV) infection and enterocytes in terms of the cellular lipid metabolism, we performed an untargeted liquid chromatography mass spectrometry (LC-MS) lipidomics analysis of PoRV-infected IPEC-J2 cells. Herein, a total of 451 lipids (263 upregulated lipids and 188 downregulated lipids), spanning sphingolipid, glycerolipid, and glycerophospholipids, were significantly altered compared with the mock-infected group. Interestingly, almost all the ceramides among these lipids were upregulated during PoRV infection. LC-MS analysis was used to validated the lipidomics data and demonstrated that PoRV replication increased the levels of long-chain ceramides (C16-ceramide, C18-ceramide, and C24-ceramide) in cells. Furthermore, we found that these long-chain ceramides markedly inhibited PoRV infection and that their antiviral actions were exerted in the replication stage of PoRV infection. Moreover, downregulation of endogenous ceramides with the ceramide metabolic inhibitors enhanced PoRV propagation. Increasing the levels of ceramides by the addition of C6-ceramide strikingly suppressed the replication of diverse RV strains. We further found that the treatment with an apoptotic inhibitor could reverse the antiviral activity of ceramide against PoRV replication, demonstrating that ceramide restricted RV infection by inducing apoptosis. Altogether, this study revealed that ceramides played an antiviral role against RV infection, providing potential approaches for the development of antiviral therapies.IMPORTANCERotaviruses (RVs) are among the most important zoonosis viruses, which mainly infected enterocytes of the intestinal epithelium causing diarrhea in children and the young of many mammalian and avian species. Lipids play an essential role in viral infection. A comprehensive understanding of the interaction between RV and lipid metabolism in the enterocytes will be helpful to control RV infection. Here, we mapped changes in enterocyte lipids following porcine RV (PoRV) infection using an untargeted lipidomics approach. We found that PoRV infection altered the metabolism of various lipid species, especially ceramides (derivatives of the sphingosine). We further demonstrated that PoRV infection increased the accumulation of ceramides and that ceramides exerted antiviral effects on RV replication by inducing apoptosis. Our findings fill a gap in understanding the alterations of lipid metabolism in RV-infected enterocytes and highlight the antiviral effects of ceramides on RV infection, suggesting potential approaches to control RV infection.

Topical Peroxisome Proliferator-Activated Receptor Agonist Induces Molecular Alterations Enhancing Barrier Function and Water-Holding Capacity of the Human Stratum Corneum In Vivo

The peroxisome proliferator-activated receptor (PPAR) ligands modulate a variety of skin functions but are rarely used in cosmetics. The aim of this double-blind, placebo-controlled, in vivo study was to determine the effect of a topically applied 0.1% PPAR ligand on the composition and physiological parameters of the stratum corneum (SC). By comparing verum and placebo groups post-treatment, we demonstrate (via lipidomic analysis of tape strips) an unstatistically significant trend toward an increase in long-chain triacylglycerols (C50–C56) and medium- and long-chain ceramides (C42–C50) at the superficial SC. By comparing treated and untreated skin using confocal Raman microspectroscopy, we found that the changes in lipid composition in the verum group led to a significant increase in the number of trans conformers and orthorhombic organisation of lipids at the exemplary SC depth. An increase in unfolded states in the secondary and tertiary keratin structures results in an increased ability to bind water. The concentrations of tightly and strongly bound water increase, while weakly bound and unbound water decrease in the entire SC, indicating a transformation of water mobility to a state of increased hydrogen bonding. Thus, the topical PPAR ligands improve the water-holding capacity and the barrier function of the SC.

Ceramides: a potential cardiovascular biomarker in young adult childhood cancer survivors?

The aim of this study was to investigate circulating ceramides involved in cardiovascular disease (CVD) in young adult childhood cancer survivors (CCS) and their correlations to previously reported adverse cardiovascular changes in this cohort. Fifty-seven CCS and 53 healthy controls (age 20-30 years) were studied. Plasma long-chain ceramides, known to be cardiotoxic (C16:0, C18:0, C24:0, and C24:1), were analysed by mass spectrometry. The coronary event risk test 2 (CERT2) score was calculated from the ceramide data. Cardiac and carotid artery ultrasound data and lipid data available from previous studies of this cohort were used to study partial correlations with ceramide and CERT2 score data. All four analysed ceramides were elevated in CCS compared with controls (P ≤ 0.012). The greatest difference was noted for C18:0, which was 33% higher in CCS compared with controls adjusted for sex, age, and body mass index (BMI) (P < 0.001). The CERT2 score was higher in CCS compared with controls (P < 0.001). In the CCS group, 35% had a high to very high CERT2 score (7-12) when compared with 9% in the control group (P < 0.001). The CCS subgroup with a CERT2 score ≥ 7 had higher heart rate, systolic blood pressure, and higher levels of apolipoprotein B compared with CCS with a CERT2 score < 6 (P ≤ 0.011). When adjusted for age, sex, and BMI, CERT2 score was significantly correlated with arterial stiffness, growth hormone, and cranial radiotherapy (P < 0.044). Ceramides could be important biomarkers in understanding the pathophysiology of CVD and in predicting CVD disease risk in young adult CCS.

GIMAP5 deficiency reveals a mammalian ceramide-driven longevity assurance pathway.

Preserving cells in a functional, non-senescent state is a major goal for extending human healthspans. Model organisms reveal that longevity and senescence are genetically controlled, but how genes control longevity in different mammalian tissues is unknown. Here, we report a new human genetic disease that causes cell senescence, liver and immune dysfunction, and early mortality that results from deficiency of GIMAP5, an evolutionarily conserved GTPase selectively expressed in lymphocytes and endothelial cells. We show that GIMAP5 restricts the pathological accumulation of long-chain ceramides (CERs), thereby regulating longevity. GIMAP5 controls CER abundance by interacting with protein kinase CK2 (CK2), attenuating its ability to activate CER synthases. Inhibition of CK2 and CER synthase rescues GIMAP5-deficient T cells by preventing CER overaccumulation and cell deterioration. Thus, GIMAP5 controls longevity assurance pathways crucial for immune function and healthspan in mammals.

The Role of Longevity Assurance Homolog 2/Ceramide Synthase 2 in Bladder Cancer

The human CERS2 gene encodes a ceramide synthase enzyme, known as CERS2 (ceramide synthase 2). This protein is also known as LASS2 (LAG1 longevity assurance homolog 2) and TMSG1 (tumor metastasis-suppressor gene 1). Although previously described as a tumor suppressor for different types of cancer, such as prostate or liver cancer, it has also been observed to promote tumor growth in adenocarcinoma. In this review, we focus on the influence of CERS2 in bladder cancer (BC), approaching the existing literature about its structure and activity, as well as the miRNAs regulating its expression. From a mechanistic point of view, different explanations for the role of CERS2 as an antitumor protein have been proposed, including the production of long-chain ceramides, interaction with vacuolar ATPase, and its function as inhibitor of mitochondrial fission. In addition, we reviewed the literature specifically studying the expression of this gene in both BC and biopsy-derived tumor cell lines, complementing this with an analysis of public gene expression data and its association with disease progression. We also discuss the importance of CERS2 as a biomarker and the presence of CERS2 mRNA in extracellular vesicles isolated from urine.

Recurrent Harlequin Ichthyosis in a Family: A Case Report

Introduction: Harlequin ichthyosis is a severe form of erythrodermic ichthyosis that manifests in a distinctive and distressing appearance at birth. The newborn baby is covered in thick, plate-like scales with distorted surface features, resulting in limited mobility. Fortunately, this condition is rare, with an estimated incidence of approximately 1 in 300,000 births. It is inherited in an autosomal recessive manner and is caused by a mutation in the adenosine triphosphate binding cassette subfamily A member 12 (ABCA12) gene. This mutation affects lipid transport, and the activity of ABCA12 is crucial to produce long-chain ceramides, which are essential for the development of a normal skin barrier. Methods: We present a case report of a newborn who presented with thick, firmly adherent dense plaques covering the entire body, accompanied by deep fissures that extended into the dermis. The facial features included severe ectropion, conjunctival chemosis, eclabium, tethered ears, and a rudimentary nose. In addition, there was flexion contracture of the arms, legs, and digits, along with hypoplastic nails. Results: The baby experienced respiratory difficulty, poor sucking, and a severe cutaneous infection. Unfortunately, the baby’s condition deteriorated and passed away on the 20th day after delivery. Conclusion: Previously considered universally fatal, harlequin ichthyosis now has reported cases of survivors, although it remains a challenging condition. It is crucial to provide parents and family with comprehensive information about the implications of the condition. They should be encouraged to explore all available options and receive psychological support throughout the process. It is essential for the neonatal intensive care unit staff to be trained in providing specialized care for these babies. In addition, parents should be offered the option of antenatal counseling, particularly in cases where there is a previously affected sibling or a history of consanguinity.

EXPRESSION OF DE NOVO CERAMIDE SYNTHESIS IN LOCAL HEART FAT DEPO IN PATIENTS WITH CARDIOVASCULAR DISEASES

Introduction. Ceramides are bioactive lipids that are not only structural components of cell membranes, but also second messengers in the transmission of cell signals. Ceramides are associated with risk factors for cardiovascular disease, may be independent predictors of cardiovascular events and proatherogenic mediators. However, due attention has not been paid to the problem of ceramide accumulation in the adipose tissue (AT) of the heart, while the accumulation of ceramides in adipocytes of epicardial and perivascular AT in coronary heart disease (CHD) is of particular interest, since they are localized in close proximity to the coronary vessels and the focus of the lesion. Objective: to evaluate the expression of de novo ceramide biosynthesis enzymes in the adipose tissue of the heart of various locations in patients with coronary heart disease and acquired heart defects. Materials and methods. The study included 30 patients with CAD, the comparison group consisted of 30 patients with acquired valvular disease (aortic stenosis/insufficiency) without CAD. During the operation, biopsies of subcutaneous, epicardial, perivascular adipose tissue (VT) (SAT, EAT, PVAT, respectively) were obtained. Expression of genes encoding de novo ceramide synthesis enzymes (subunits of C1 and C2 serine palmitoyltransferases: SPTLC1, SPTLC2; ceramide synthase 1-6: CERS1-6; dihydroceramide desaturase: DEGS1) was assessed by real-time quantitative polymerase chain reaction (qPCR) with primers synthesized by Evrogen (Moscow, Russia) on the ViiA 7 Real-Time PCR System (Applied Biosystems, Foster City, California, USA). Statistical analysis of the results was performed using GraphPad Prism 8 (GraphPad Software). Results. Patients with CAD were characterized by higher levels of SPTLC1 mRNA in subcutaneous and epicardial VT and SPTLC2 mRNA in EAT. DEGS1 expression was maximal in SVT and EAT. The expression of ceramide synthase genes in VT of patients with coronary artery disease had tissue-specific features. Expression of the CERS1 gene, encoding the enzyme ceramide synthase-1, which produces ceramides with a fatty acid residue in its composition of 18 carbon atoms (C18), expression of CERS5 and CERS6, encoding ceramide synthase-5 and -6, synthesizing ceramides C14-C16 was maximum in epicardial adipocytes. At the same time, CERS5 expression was higher than CERS6 expression. Gene expression of CERS2, encoding the enzyme ceramide synthase-2, which produces long-chain ceramides and attaches C20–C24 fatty acyl-CoA to the sphingoid base in ceramide, was maximal in subcutaneous adipocytes. While perivascular VT was characterized by a higher expression of the CERS4 and CERS3 genes, which synthesize very long chain ceramides C26 and higher. In the group of patients with valvular disease, VT samples did not differ in terms of SPTLC1, SPTLC2, CERS1, CERS2, CERS5, and CERS6 mRNA levels. However, high expression of CERS4 and DEGS1 was observed in EAT, while CERS3 and CERS4 were expressed in PVAT. When comparing the level of expression of genes for ceramide synthesis enzymes between the two studied groups, it was found that in patients with IHD, the mRNA level of SPTLC1 in SAT and EAT, SPTLC2 in EAT, CERS2 in all types of AT, CERS4 and CERS5 in EAT, DEGS1 in SAT and EAT was higher in compared with patients with valvular heart disease. Conclusion. Regional fat depots of the heart differed in the level of expression of de novo ceramide biosynthesis enzymes. The results obtained indicate the activation of ceramide synthesis along this pathway in adipocytes of predominantly epicardial localization in coronarogenic pathology, which may contribute to the accumulation of long-chain ceramides in the VT of this localization.

Ceramide synthase 6 (CerS6) is upregulated in alcohol-associated liver disease and exhibits sex-based differences in the regulation of energy homeostasis and lipid droplet accumulation

ObjectiveAlcohol-associated liver disease (ALD) is the leading cause of liver-related mortality worldwide. Current strategies to manage ALD focus largely on advanced stage disease, however, metabolic changes such as glucose intolerance are apparent at the earliest stage of alcoholic steatosis and increase the risk of disease progression. Ceramides impair insulin signaling and accumulate in ALD, and metabolic pathways involving ceramide synthase 6 (CerS6) are perturbed in ALD during hepatic steatosis. In this study, we aimed to investigate the role of CerS6 in ALD development and the relevance of CerS6 to human ALD. MethodsC57BL/6 WT and CerS6 KO mice of both sexes were fed either a Lieber-DeCarli control (CON) or 15% ethanol (EtOH) diet for six weeks. In vivo metabolic tests including glucose and insulin tolerance tests (GTT and ITT) and energy expenditure were performed. The mice were euthanized, and serum and liver lipids and liver histology were examined. For in vitro studies, CerS6 was deleted in human hepatocytes, VL17A and cells were incubated with EtOH and/or C16:0-ceramides. RNAseq analysis was performed in livers from mice and human patients with different stages of ALD and diseased controls. ResultsAfter six weeks on an EtOH diet, CerS6 KO mice had reduced body weight, food intake, and %fat mass compared to WT mice. Energy expenditure increased in both male and female KO mice, however, was only statistically significant in male mice. In response to EtOH, WT mice developed mild hepatic steatosis, while steatosis was ameliorated in KO mice as determined by H&E and ORO staining. KO mice showed significantly decreased long-chain ceramide species, especially C16:0-ceramides, in the serum and liver tissues compared to WT mice. CerS6 deletion decreased serum TG and NEFA only in male not female mice. CerS6 deletion improved glucose tolerance and insulin resistance in EtOH-fed mice of both sexes. RNAseq analysis revealed that 74 genes are significantly upregulated and 66 genes are downregulated by CerS6 deletion in EtOH-fed male mice, with key network pathways including TG biosynthetic process, positive regulation of lipid localization, and fat cell differentiation. Similar to RNAseq results, absence of CerS6 significantly decreased mRNA expression of lipid droplet associated proteins in EtOH-fed mice. In vitro, EtOH stimulation significantly increased PLIN2 protein expression in VL17A cells while CerS6 deletion inhibited EtOH-mediated PLIN2 upregulation. C16:0-ceramide treatment significantly increased PLIN2 protein expression compared to CON. Notably, progression of ALD in humans was associated with increased hepatic CerS6 expression. ConclusionsOur findings demonstrate that CerS6 deletion improves glucose homeostasis in alcohol-fed mice and exhibits sex-based differences in the attenuation of EtOH-induced weight gain and hepatic steatosis. Additionally, we unveil that CerS6 plays a major role as a regulator of lipid droplet biogenesis in alcohol-induced intra-hepatic lipid droplet formation, identifying it as a putative target for early ALD management.

1173-P: Maternally Supplemented PQQ Targets Ceramide Metabolism in Offspring to Blunt Developmental Programming of NAFLD

Maternal obesity is a key risk factor for pediatric nonalcoholic fatty liver disease (NAFLD). Using a mouse model of Western-style diet (WD)-induced maternal obesity, we studied effects of supplementing dams with pyrroloquinoline quinone (PQQ; a potent dietary antioxidant) during gestation and lactation on hepatic lipid metabolism and fibrosis in offspring at postnatal day (PND) 14 and at 16 wks after a 4 wk WD challenge. Maternal PQQ (mWDPQQ) decreased neonatal hepatic triglycerides (30%, P=0.0012) and altered bioactive sphingolipids in adult offspring compared with those exposed to maternal WD (mWD), with no change in weight gain. mWDPQQ increased very long chain ceramides (VLCer; 219%, P=0.0002), associated with protection from fibrosis, concomitant with decreased expression of genes promoting ceramide degradation (Asah2, P=0.0014 and Acer3, P=0.02). Expression of Scd1, a desaturase regulating triglyceride biosynthesis, was attenuated in mWDPQQ offspring at PND14 (P=0.0009) and at 16 wks (P=0.0012), while expression of Elovl3, an enzyme promoting elongation of saturated fatty acids and ceramide production, was increased (P=0.0026). Comparative pathway analysis of RNASeq data showed enrichment of pathways in fatty acid metabolism, hepatic fibrosis and, unexpectedly, signaling through the aryl hydrocarbon receptor (AHR; a ligand-activated transcription factor regulating immune function and hepatoxicity). Chromatin IP in mWDPQQ liver showed increased AHR binding to the Cyp1a1 promoter, its canonical target, as compared with mWD, suggesting AHR signaling may be activated by mWDPQQ. AHR binding to the Scd1 promoter, a known AHR target, was increased, as was binding to Asah2 and Acer3, putative new AHR targets regulating long-chain ceramide degradation. These findings suggest that maternal PQQ has both short and long-term effects on blunting steatosis/fibrosis and promoting VLCer increase through novel AHR targets, protecting offspring from NAFLD. Disclosure A.Mandala: None. A.M.Teague: None. R.Janssen: None. N.Patil: None. A.D.Joshi: None. J.E.Friedman: None. K.R.Jonscher: None. Funding National Institutes of Health (1R01DK121951)

Sex differences in plasma lipid profiles of accelerated brain aging

Lipids are essential components of brain structure and shown to affect brain function. Previous studies have shown that aging men undergo greater brain atrophy than women, but whether the associations between lipids and brain atrophy differ by sex is unclear. We examined sex differences in the associations between circulating lipids by liquid chromatography-tandem mass spectrometry and the progression of MRI-derived brain atrophy index Spatial Patterns of Atrophy for Recognition of Brain Aging (SPARE-BA) over an average of 4.7 (SD = 2.3) years in 214 men and 261 women aged 60 or older who were initially cognitively normal using multivariable linear regression, adjusted for age, race, education, and baseline SPARE-BA. We found significant sex interactions for beta-oxidation rate, short-chain acylcarnitines, long-chain ceramides, and very long-chain triglycerides. Lower beta-oxidation rate and short-chain acylcarnitines in women and higher long-chain ceramides and very long-chain triglycerides in men were associated with faster increases in SPARE-BA (accelerated brain aging). Circulating lipid profiles of accelerated brain aging are sex-specific and vary by lipid classes and structure. Mechanisms underlying these sex-specific lipid profiles of brain aging warrant further investigation.

Ceramide analog C2-cer induces a loss in insulin sensitivity in muscle cells through the salvage/recycling pathway

Ceramides have been shown to play a major role in the onset of skeletal muscle insulin resistance and therefore in the prevalence of type 2 diabetes. However, many of the studies involved in the discovery of deleterious ceramide actions used a nonphysiological, cell-permeable, short-chain ceramide analog, the C2-ceramide (C2-cer). In the present study, we determined how C2-cer promotes insulin resistance in muscle cells. We demonstrate that C2-cer enters the salvage/recycling pathway and becomes deacylated, yielding sphingosine, re-acylation of which depends on the availability of long chain fatty acids provided by the lipogenesis pathway in muscle cells. Importantly, we show these salvaged ceramides are actually responsible for the inhibition of insulin signaling induced by C2-cer. Interestingly, we also show that the exogenous and endogenous monounsaturated fatty acid oleate prevents C2-cer to be recycled into endogenous ceramide species in a diacylglycerol O-acyltransferase 1-dependent mechanism, which forces free fatty acid metabolism towards triacylglyceride production. Altogether, the study highlights for the first time that C2-cer induces a loss in insulin sensitivity through the salvage/recycling pathway in muscle cells. This study also validates C2-cer as a convenient tool to decipher mechanisms by which long-chain ceramides mediate insulin resistance in muscle cells and suggests that in addition to the de novo ceramide synthesis, recycling of ceramide could contribute to muscle insulin resistance observed in obesity and type 2 diabetes.

Alkaline ceramidase (ClAC) inhibition enhances heat stress response in Cyrtorhinus lividipennis (Reuter).

Ceramidases (CDases) are vital sphingolipid enzymes involved in organismal growth and development. They have been reported as key mediators of thermal stress response. However, whether and how CDase responds to heat stress in insects remain unclear. Herein, we identified two CDase genes, C. lividipennis alkaline ceramidase (ClAC) and neutral ceramidase (ClNC), by searching the transcriptome and genome databases of the mirid bug, Cyrtorhinus lividipennis, an important natural predator of planthoppers. Quantitative PCR (qPCR) analysis showed that both ClNC and ClAC were highly expressed in nymphs than in adults. ClAC was especially highly expressed in the head, thorax, and legs, while ClNC was widely expressed in the tested organs. Only the ClAC transcription was significantly affected by heat stress. Knocking down ClAC increased the C. lividipennis nymph survival rate under heat stress. The transcriptome and lipidomics data showed that the RNA interference-mediated suppression of ClAC significantly upregulated the transcription level of catalase (CAT) and the content of long-chain base ceramides, including C16-, C18-, C24-, and C31- ceramides. In C. lividipennis nymphs, ClAC played an important role in heat stress response, and the upregulation of nymph survival rate might be caused by variation in the ceramide levels and transcriptional changes in CDase downstream genes. This study improves our understanding of the physiological functions of insect CDase under heat stress and provides valuable insights into the nature enemy application.

Pathobionts in the tumour microbiota predict survival following resection for colorectal cancer

Background and aimsThe gut microbiota is implicated in the pathogenesis of colorectal cancer (CRC). We aimed to map the CRC mucosal microbiota and metabolome and define the influence of the tumoral microbiota on oncological outcomes.MethodsA multicentre, prospective observational study was conducted of CRC patients undergoing primary surgical resection in the UK (n = 74) and Czech Republic (n = 61). Analysis was performed using metataxonomics, ultra-performance liquid chromatography-mass spectrometry (UPLC-MS), targeted bacterial qPCR and tumour exome sequencing. Hierarchical clustering accounting for clinical and oncological covariates was performed to identify clusters of bacteria and metabolites linked to CRC. Cox proportional hazards regression was used to ascertain clusters associated with disease-free survival over median follow-up of 50 months.ResultsThirteen mucosal microbiota clusters were identified, of which five were significantly different between tumour and paired normal mucosa. Cluster 7, containing the pathobionts Fusobacterium nucleatum and Granulicatella adiacens, was strongly associated with CRC (PFDR = 0.0002). Additionally, tumoral dominance of cluster 7 independently predicted favourable disease-free survival (adjusted p = 0.031). Cluster 1, containing Faecalibacterium prausnitzii and Ruminococcus gnavus, was negatively associated with cancer (PFDR = 0.0009), and abundance was independently predictive of worse disease-free survival (adjusted p = 0.0009). UPLC-MS analysis revealed two major metabolic (Met) clusters. Met 1, composed of medium chain (MCFA), long-chain (LCFA) and very long-chain (VLCFA) fatty acid species, ceramides and lysophospholipids, was negatively associated with CRC (PFDR = 2.61 × 10−11); Met 2, composed of phosphatidylcholine species, nucleosides and amino acids, was strongly associated with CRC (PFDR = 1.30 × 10−12), but metabolite clusters were not associated with disease-free survival (p = 0.358). An association was identified between Met 1 and DNA mismatch-repair deficiency (p = 0.005). FBXW7 mutations were only found in cancers predominant in microbiota cluster 7.ConclusionsNetworks of pathobionts in the tumour mucosal niche are associated with tumour mutation and metabolic subtypes and predict favourable outcome following CRC resection.E9vQ1bxk-JdT4E6GMYGhRXVideo

GIMAP5 regulates a lymphocyte longevity assurance pathway

Abstract Elucidating the molecular mechanisms of immunodeficiency diseases is a powerful approach to discovering new immunoregulatory pathways in humans. One such previously unknown pathway is that of GIMAP5, an evolutionarily conserved GTPase expressed in T and NK lymphocytes, also known as the gene mutated in the Biobreeding diabetic rat and Sphinx lymphopenic mice. To better understand this disease association, we identified causative GIMAP5 mutations in 17 individuals of 9 kindreds with lymphopenia, liver disease, splenomegaly, thrombocytopenia, lymphadenopathy, lung infections, and lymphoma. As the mechanism of action, we now report that GIMAP5 controls the pathological accumulation of long chain ceramides. The ceramide synthase inhibitor, fumonisin B1, rescues GIMAP5-deficient T cells from ceramide overaccumulation and cell deterioration. Concordant with these findings, induction of ceramide accumulation and cell death by exogenous C6-ceramides in human T cell blasts was reduced by fumonisin B1 and GIMAP5 overexpression. Our work reveals the underlying long-chain ceramide mechanics of GIMAP5, opening new opportunities for further metabolomic studies of immunodeficiency diseases and targets for the development of therapeutics. This research was supported by NIAID by the Intramural Research Program of the NIH.