An overview of sphingolipid metabolism: from synthesis to breakdown

Ecosurveillance reveals subtle metabolic effects on the non-native cane toad (Rhinella marina) from low levels of accumulated environmental per- and polyfluoroalkyl substances

Per- and polyfluoroalkyl substances (PFAS) are synthetic chemicals that persist in the environment, bioaccumulate, and may have toxic effects. This study used non-native cane toads (Rhinella marina) to examine PFAS and metal accumulation and impacts in large terrestrial amphibians from urban and peri-urban areas. We quantified 38 PFAS compounds and 36 environmental and legacy metal(loid)s in 52 adult cane toad livers collected from six locations around Southeast Queensland, Australia, along a known PFAS gradient. Associations among PFAS, metal(loid) concentrations, and whole-organism metrics were assessed. An omics-led approach assessed biochemical responses in liver, muscle, fat and gonad/egg tissues associated with these PFAS concentrations. Liver PFAS concentrations ranged from 0.5 to 82.1 μg/kg ww, with one male outlier at 452 μg/kg ww (mean: 18 ± 21 SD μg/kg ww, excluding outlier). PFOS was the most dominant PFAS (60 ± 26 SD% of total), followed by PFDoDA (13 ± 9 SD%). The liver metal(loid)s with statistically significant variation among locations and sex were Al, As, Ca, Cu, Mn, Ni, Se, Sn, Sr and V. Total PFAS had no associations with whole-organism metrics, and body condition and relative femur length showed a weak interaction effect between PFAS and Ni. Metabolic profiling revealed sex-specific differences linked to total PFAS, with females showing a broader metabolic perturbation. The strongest metabolic signals were in glycerolipid metabolism, ether lipid metabolism, and fatty acid biosynthesis, though these effects were statistically weak. PFAS and metal(loid) levels were low compared to those previously recorded in tertiary consumers and aquatic vertebrates from contaminated areas. Despite minor metabolomic changes, the overall health impact was minimal. These findings contribute to the development of tissue PFAS guideline values for wild amphibians, but further studies on higher PFAS levels of accumulation and responses of additional amphibian species are needed.

Sphingolipids in medicinal mushrooms: structural insights, biological activities, and therapeutic potential

Edible mushrooms are well-known for their nutritional value, serving as rich sources of bioactive nutrients, mainly proteins, carbohydrates, lipids, vitamins, and minerals that are vital for human health. Lipids, integral to biological functions such as cellular structure and energy storage, play crucial roles in mushrooms' bioactivity. Sphingolipids, an important class of lipids, serve not only as structural elements in cell membranes but also act as bioactive molecules, playing key roles in cancer prevention, skin health, and infection control. Recent studies highlight their unique presence in mushrooms. Despite their relatively low abundance, sphingolipids in mushrooms are pivotal in cellular processes and offer therapeutic potential. Advances in analytical techniques have facilitated the characterization of these compounds. This review explores the structural profiles, biological activities, and therapeutic applications of sphingolipids in medicinal mushrooms, highlighting their potential in the development of functional foods and novel therapeutic agents.

Chlamydia trachomatis exploits sphingolipid metabolic pathways during infection of phagocytes

Chlamydiae are obligate intracellular pathogens that utilize host cell metabolites for catabolic and anabolic processes. The bacteria replicate in epithelial cells from which they take up sphingolipids (SL) and incorporate them into the chlamydial membrane and the vacuole (termed inclusion). SL uptake is essential for Chlamydia trachomatis (Ctr) in epithelial cells; however, they can also infect phagocytes, but the consequences for the SL metabolism have not yet been investigated in these cells. We performed a quantitative sphingolipidome analysis of infected primary neutrophils, macrophages, and immortalized fallopian tube epithelial cells. Sphingosine (Sph) levels are elevated in primary M2-like macrophages and human neutrophils infected with C. trachomatis. Human neutrophils respond to the pathogen by markedly upregulating sphingosine kinase 1 (SPHK1). We show in M2-like macrophages, by RNAseq, that two counteracting pathways involving upregulation of SPHK1, but also sphingosine-1-phosphate phosphatases 1 and 2 (SGPP1 and SGPP2) and sphingosine-1-phosphate lyase (SGPL1), maintain a steady pool of S1P. Using click chemistry, we show that exogenously added sphingomyelin (SM) and ceramide (Cer) are efficiently taken up into the chlamydial inclusion and are integrated into bacterial membranes in infected M2-like macrophages. Exogenous Sph reduces chlamydial infectivity, is transported into the inclusion lumen, and integrates into chlamydial membranes, suggesting that this particular SL species could represent a host defense mechanism. Taken together, our data indicate an important role for Sph/Sph kinase vs S1P/S1P phosphatase balance in infected phagocytes and a previously unrecognized role for sphingosine in the immune defense against chlamydial infection.IMPORTANCEChlamydia trachomatis (Ctr) is the leading cause of sexually transmitted diseases worldwide. Left untreated, it can cause severe complications such as blindness, pelvic inflammatory disease, or infertility. To date, no vaccines are available, and antibiotic treatment represents the only therapeutic approach to cure the infection. Limited access to antibiotics and displaced antibiotic intake increase the risk of developing recurring infections. Immune cells which fail to clear the infection and serve as a niche for chlamydial survival and replication, favor this outcome. Our research aims to elucidate the influence of sphingolipids (SL) during chlamydial infection, especially of phagocytic cells. Identifying relevant targets offers new strategies to develop alternative treatment methods.

A genome-wide CRISPR screen identifies GRA38 as a key regulator of lipid homeostasis during Toxoplasma gondii adaptation to lipid-rich conditions

Intracellular parasites like Toxoplasma gondii scavenge host nutrients, particularly lipids, to support their growth and survival. Although Toxoplasma is known to adjust its metabolism based on nutrient availability, the mechanisms that mediate lipid sensing and metabolic adaptation remain poorly understood. Here, we performed a genome-wide CRISPR screen under lipid-rich (10% Fetal Bovine Serum (FBS)) and lipid-limited (1% FBS) conditions to identify genes critical for lipid-responsive fitness. We identified the Toxoplasma protein GRA38 as a lipid-dependent regulator of parasite fitness. GRA38 exhibits phosphatidic acid (PA) phosphatase (PAP) activity in vitro, which is significantly reduced by mutation of its conserved DxDxT/V catalytic motif. Disruption of GRA38 led to the accumulation of PA species and widespread alterations in lipid composition, consistent with impaired PAP activity. These lipid imbalances correlated with reduced parasite virulence in mice. Our findings identify GRA38 as a metabolic regulator important for maintaining lipid homeostasis and pathogenesis in Toxoplasma gondii.

Mechanism of electrochemical algal control and its effect on metabolic pathways of algal cells

Algal blooms cause significant ecological and economic issues. Electrochemical methods inhibit algal blooms effectively, but their effects on algal cell gene expression and metabolic pathways remain underexplored, requiring further mechanistic and ecological data to elucidate these mechanisms. This study revealed the control mechanism of electrochemical methods on Microcystis aeruginosa using flow cytometry, real-time PCR and untargeted metabolomics. Results indicate that electrochemical treatment induces oxidative stress, severely damaging algal cell membranes and impairing cell activity. Gene transcription analysis reveals that •OH oxidation leads to lipid peroxidation, damaging proteins, biological macromolecules, and the photosynthetic system. Metabolomics data show disruptions in amino acid, carbohydrate, and sphingolipid metabolism, affecting the tricarboxylic acid cycle, transporter proteins, and photosynthesis. These findings elucidate the mechanisms by which electrochemical methods control cyanobacterial blooms, offering theoretical and practical insights for effective management strategies.

Intercellular sphingolipid signaling mediates aversive learning in C. elegans

Physiological stress in non-neural tissues drives aversive learning for sensory cues associated with stress. However, the identities of signals derived from non-neural tissues and the mechanisms by which these signals mediate aversive learning remain elusive. Here, we show that intercellular sphingolipid signaling contributes to aversive learning under mitochondrial stress in C. elegans. We found that stress-induced aversive learning requires sphingosine kinase, SPHK-1, the enzyme that produces sphingosine-1-phosphate (S1P). Genetic and biochemical studies revealed an intercellular signaling pathway in which intestinal or hypodermal SPHK-1 signals through the neuronal G protein-coupled receptor, SPHR-1, and modulates responses of the octopaminergic RIC neuron to promote aversive learning. We further show that SPHK-1-mediated sphingolipid signaling is required for learned aversion of Chryseobacterium indologenes, a bacterial pathogen found in the natural habitats of C. elegans, which causes mitochondrial stress. Taken together, our work reveals a sphingolipid signaling pathway that communicates from intestinal or hypodermal tissues to neurons to promote aversive learning in response to mitochondrial stress and pathogen infection.

Subclinical Atherosclerosis Risk Can Be Predicted in Female Patients With Systemic Lupus Erythematosus Using Metabolomic Signatures: An Observational Study

BACKGROUND

Cardiovascular disease (CVD) is a leading cause of death in women with systemic lupus erythematosus (SLE) due to accelerated atherosclerosis that is not predicted by established CVD risk scores. This study aimed to develop, validate, and test a female-focused predictive atherosclerosis risk signature based on serum metabolites in patients with SLE.

METHODS AND RESULTS

Female patients with SLE were assessed for the presence (SLE-P; n=18) or absence (SLE-NP; n=26) of subclinical atherosclerosis using vascular ultrasound for carotid/femoral intima-media thickness. CVD risk was assessed using QRISK3 (which includes SLE diagnosis as a risk factor) and Framingham Risk Score. Serum metabolomics (n≥250) was performed and analyzed using machine learning pipelines. Despite having subclinical atherosclerosis, 44.8% to 100% of patients with SLE-P had low CVD risk according to QRISK3/Framlingham Risk Score scores. Using a lipid-focused metabolomic analysis, an improved atherosclerosis risk predictive signature was developed comprising 35 metabolites/5 clinical traits that classified patients with SLE-P and outperformed CVD risk assessment tools, lipid profiles measured in routine care, and clinical features alone. This "atherosclerosis risk signature" was validated in a second adult female SLE cohort (n=98) that predicted plaque status with moderate accuracy (area under the receiver operating characteristic curve, 0.79). The signature was then refined into a 5-feature subclinical plaque-predictive score that not only stratified the combined SLE-P/SLE-NP cohorts (n=142; area under the receiver operating characteristic curve, 0.84) but also predicted 3-year atherosclerosis progression in female postpubertal patients with juvenile-onset SLE (n=36; area under the receiver operating characteristic curve, 0.79). Finally, the 5-feature score identified distinct high and low subclinical atherosclerosis risk subgroups in a "real-world" setting of unscanned adult patients with SLE (n=38).

CONCLUSIONS

This atherosclerosis risk score could improve CVD risk assessment/management in female patients with SLE across age. Validation in non-SLE and healthy cohorts could further substantiate these findings.

Dysregulation of sphingolipid metabolism contributes to the pathogenesis of chronic myeloid leukemia

Chronic myeloid leukemia (CML) is primarily driven by the BCR::ABL1 oncoprotein, which has potent tyrosine kinase activity. BCR::ABL1 has been shown to facilitate several metabolic processes, including glycolysis, lipid synthesis, and protein synthesis in vitro. However, the altered metabolic profile in vivo remains poorly understood. Using Scl/tTA-BCR::ABL1 mice as a model, we conducted an analysis of plasma metabolites at different stages following BCR::ABL1 induction. Metabolites involved in sphingolipid and thiamine metabolism were significantly altered at the early stage of CML, while the tricarboxylic acid (TCA) cycle metabolites were altered during disease progression. Among these metabolic changes, sphingolipid metabolism is of particular significance. Inhibition of sphingolipid metabolism had a more pronounced effect on the growth and survival fate of K562 cells compared to thiamine metabolism inhibition. Furthermore, knockdown of sphingosine kinase 1 (SPHK1) resulted in extensive metabolic remodeling, affecting lipid, energy, and heme metabolism. Pharmacological targeting of sphingolipid metabolism appeared to attenuate the development of CML. Our study also demonstrated that BCR::ABL1 triggers ERK-dependent phosphorylation of SphK1, leading to aberrant activation of sphingolipid metabolism, which in turn has a positive feedback effect on BCR/ABL expression. These findings highlight the dominant role of sphingolipid metabolism in BCR::ABL1-induced metabolic reprogramming in CML.

The Associations of Maternal Prepregnancy Body Mass Index With Human Milk Fatty Acid and Phospholipid Composition in the Observational Norwegian Human Milk Study

BACKGROUND

Human milk fat quality depends on its fatty acid (FA) and phospholipid (PL) composition. There is clear evidence that maternal diet influences human milk FA composition. However, the scientific literature concerning associations between prepregnancy body mass index (pBMI) and milk FA and PL composition remains inconclusive.

OBJECTIVES

This observational study aimed to identify the associations between maternal pBMI and the milk FA and choline-containing PL species composition, considering study confounders, including fish intake as a proxy for n3 long-chain polyunsaturated FA (n3-LCPUFA).

METHODS

We analyzed total FA and choline-containing PL-classes (lysophosphatidylcholine, phosphatidylcholine, and sphingomyelin) in 628 milk samples from the Norwegian Human Milk Study birth-cohort using gas chromatography and flow-injection mass spectrometry, respectively. Multiple regression analysis assessed the relationship between pBMI and milk lipid metabolites (%FA, %PL) (reported as β = standardized regression coefficient with adjusted P value < 0.0005, B(95% confidence interval [CI]) = unstandardized coefficient with 95% CI).

RESULTS

Maternal pBMI showed significant association (P < 0.0005) with n3-LCPUFA [β = -0.138, B(95% CI) = -0.010 (-0.015, -0.005)], n6/n3LCPUFA ratio [β = 0.170, B(95% CI) = 0.020(0.012, 0.028)], monounsaturated FA [β = 0.207, B(95% CI) = 0.128(0.076, 0.180)], and corresponding PL species [%LysoPC16:1, β = 0.171, B(95% CI) = 0.001(0.001,0.002), %LysoPC18:1, β = 0.155, B(95%CI) = 0.005 (0.002,0.007)] adjusted with the study covariates. The percentages of variance explained by pBMI were 40% for the n6/n3 LCPUFA ratio, 34% for n3-LCPUFA, and 10% for monounsaturated FA. Conversely, analyses revealed no significant associations between pBMI and choline-containing PL classes.

CONCLUSIONS

Biological factors likely increased stearoyl-CoA desaturase activity, lower lipoprotein lipase activity, and a compensatory higher contribution of nonesterified FA from adipose tissue in mothers with pBMI ≥30 could potentially lead to the observed outcomes. Metabolic differences regarding BMI variances may influence the FA availability for mammary gland triglyceride and PL synthesis. Therefore, in addition to dietary intake, maintaining a healthy maternal pBMI may improve the nutritional quality of human milk, ultimately supporting infants' development.

Lipid-targeting antiviral strategies: Current state and future perspectives

There is an urgent need for antiviral compounds effective against currently known and future viral threats. The development of host-targeting antivirals (HTAs) appears as an alternative strategy to fight viral infections minimizing the potential of resistant mutant development and potentially leading to the identification of broad-spectrum antiviral agents. Among the host factors explored for HTA strategy, lipids constitute an attractive target as many viruses, even genetically diverse, hijack specific lipids during their lifecycle. Multiple repurposing efforts have been performed to analyze the antiviral properties of lipid-targeting compounds. These studies include the analysis of the effects of cholesterol lowering drugs such as statins, cholesterol transport inhibitors, sphingolipid modulators, de novo lipogenesis inhibitors blocking fatty acid synthesis, compounds targeting glycerophospholipids or drugs interfering with lipid droplet metabolism. This review is focused on the current status of lipid-based or lipid-targeting antiviral strategies and their potential for the development of antiviral therapies, with special emphasis on those studies that have reached advanced stages of development such as efficacy studies in animal models or clinical trials. Whereas there is still a long way to go, multiple proof-of-concept studies and clinical evidence reinforce the therapeutic potential of these strategies warranting their further development into effective antiviral therapies.

An unraveled mystery: What's the role of brain sphingolipids in neurodegenerative and psychiatric disorders

Sphingolipids are a class of lipids highly expressed in brain, especially in the myelin sheath of white matter. In recent years, with the development of lipidomics, the role of brain sphingolipids in neurological disorders have raised lots of interests due to their function in neuronal signal transduction and survival. Although not thoroughly investigated, some previous studies have indicated that sphingolipids homeostasis are closely linked to the etiology and development of some neurological disorders. For example, disrupted sphingolipids level have been found in clinic patients with neurological disorders, such as neurodegeneration and psychiatric disorders. Conversely, intervention of sphingolipids metabolism by modulating activity of related enzymes also could result in pathological deficits identified in neurological disorders. Moreover, the alteration of sphingolipids catabolic pathway in the brain could be partly represented in cerebrospinal fluid and blood tissues, which show diagnostic potential for neurological disorders. Therefore, our review aims to summarize and discuss the known contents of bioactive sphingolipid metabolism with their related studies in neurodegenerative and psychiatric disorders, to help understand the potential mechanism underlying sphingolipid regulation of neural function and provide possible directions for further study. The new perspectives in this promising field will open up new therapeutic options for neurological disorders.

The individual isoforms of ORMDL, the regulatory subunit of serine palmitoyltransferase, have distinctive sensitivities to ceramide

Sphingolipids play crucial roles in cell membrane structure and in multiple signaling pathways. Sphingolipid de novo biosynthesis is mediated by the serine palmitoyltransferase (SPT) enzyme complex. Homeostatic regulation of this complex is dependent on its regulatory subunit, the ORMDLs, of which there are three isoforms. It is well established that the ORMDLs regulate SPT activity, but it is still unclear whether the three ORMDL isoforms have distinct functions and properties. Here, we focus on understanding the physiological importance of ORMDL isoforms (ORMDL1, ORMDL2, and ORMDL3) in regulating SPT activity and sphingolipid levels. This study delves into the differential responses of the SPT complexes containing different ORMDL isoforms to cellular ceramide levels. By using the CRISPR/Cas9 gene editing tool, we have developed Hela cell lines each of which harbor only one of the three ORMDL isoforms as well as a cell line deleted for all three isoforms. Consistent with other studies, we find that deletion of all three ORMDL isoforms desensitizes SPT to ceramide and dramatically increases levels of cellular sphingolipids. In contrast, each ORMDL isoform alone is capable of regulating SPT activity and maintaining normal levels of sphingolipid. Strikingly, however, we find that each ORMDL isoform exhibits isoform-specific sensitivity to ceramide. This suggests that the inclusion of specific ORMDL isoforms into the SPT complex may accomplish a fine-tuning of sphingolipid homeostasis. The study not only emphasizes the need for further investigation into the distinct roles of ORMDL isoforms but also sheds light on their potential as therapeutic targets.

Highlights

RMDL isoforms detect varying ceramide levels to regulate SPT.HeLa cells, there is no compensation for the absence of the ORMDL isoform, neither at the total protein level nor at the mRNA level.

RBM10 deficiency promotes brain metastasis by modulating sphingolipid metabolism in a BBB model of EGFR mutant lung adenocarcinoma

BACKGROUND

Brain metastasis significantly contributes to the failure of targeted therapy in patients with epidermal growth factor receptor (EGFR)-mutated lung adenocarcinoma (LUAD). Reduced expression of RNA-binding motif protein 10 (RBM10) is associated with brain metastasis in these patients. However, the mechanism by which RBM10 affects brain metastasis in EGFR-mutated LUAD remains unclear.

METHODS

An in vitro blood-brain barrier (BBB) model and brain metastasis-prone cell lines (BrM3) were established to confirm the brain metastatic potential of tumor cells following RBM10 knockdown. The roles of RBM10 and galactosylceramidase (GALC) in LUAD brain metastases were analyzed using cellular phenotypic assays and molecular biology techniques, including the combined analysis of Nanopore sequencing and CLIP-seq, minigene assays, and others.

RESULTS

This study demonstrates that RBM10 plays a vital role in inhibiting brain metastasis from EGFR-mutated LUAD by modulating sphingolipid metabolism. When RBM10 expression is low, GALC enters the nucleus to function. RBM10 deficiency inhibits exon skipping during GALC splicing, leading to upregulated GALC expression and increased sphingosine 1-phosphate (S1P) synthesis. S1P enhances BBB permeability, thereby promoting brain metastasis. Additionally, animal experiments show that the targeted agents Fingolimod (an S1P inhibitor) and RU-SKI-43 (a potential drug for RBM10 mutation) suppress the growth of brain metastasis.

CONCLUSION

This study offers insights into the potential mechanisms of brain metastasis in LUAD and suggests a possible therapeutic target for further investigation.

Role of Galactosylceramide Metabolism in Satellite Glial Cell Dysfunction and Neuron-Glia Interactions in Painful Diabetic Peripheral Neuropathy

Diabetic peripheral neuropathy (DPN) is a prevalent and disabling complication of diabetes, with painful diabetic peripheral neuropathy (PDPN) being its most severe subtype due to chronic pain and resistance to treatment. Satellite glial cells (SGCs), critical for maintaining dorsal root ganglion (DRG) homeostasis, undergo significant structural and functional changes under pathological conditions. This study investigated the role of galactosylceramide (GalCer), a key sphingolipid, in SGC dysfunction and neuron-glia interactions during DPN progression. Using a rat model of PDPN, we employed single-cell RNA sequencing (scRNA-seq), targeted mass spectrometry, and immunofluorescence analysis. The PDPN group exhibited transcriptional activation and structural reorganization of SGCs, characterized by increased SGC abundance and glial activation, evidenced by elevated Gfap expression. Functional enrichment analyses revealed disruptions in sphingolipid metabolism, including marked reductions in GalCer levels. Subclustering identified vulnerable SGC subsets, such as Cluster a, with dysregulated lipid metabolism. The depletion of GalCer impaired SGC-neuron communication, destabilizing DRG homeostasis and amplifying neurodegeneration and neuropathic pain. These findings demonstrate that GalCer depletion is a central mediator of SGC dysfunction in PDPN, disrupting neuron-glia interactions and exacerbating neuropathic pain. This study provides novel insights into the molecular mechanisms of DPN progression and identifies GalCer metabolism as a potential therapeutic target.

Bioactive Compounds Targeting Dihydroceramide and Their Therapeutic Potential in Cancer Treatment

Dihydroceramide (dhCer) was previously considered an inactive precursor of ceramide, a well-known sphingoid base involved in regulating apoptosis and cell death. However, recent studies have shown that dhCer plays a crucial role in various important cellular responses. In this review, we summarize the latest findings on the biological functions of dhCer and the enzymes involved in its biosynthesis. We specifically focus on the emerging evidence implicating dhCer in cancer, as well as its role in regulating key processes such as cell cycle arrest, autophagy, apoptosis, ER stress, and oxidative stress. Furthermore, we discuss bioactive compounds that can modulate dhCer levels in cancer cells, highlighting their potential therapeutic applications in counteracting cancer progression. This review emphasizes the growing recognition of dhCer as a bioactive sphingolipid metabolite with significant potential for cancer therapy.

Sphingolipid signaling in kidney diseases

Sphingolipids are a family of bioactive lipids. The key components include ceramides, ceramide-1-phosphate, sphingosine, and sphingosine-1-phosphate. Sphingolipids were originally considered to be primarily structural elements of cell membranes but were later recognized as bioactive signaling molecules that play diverse roles in cellular behaviors such as cell differentiation, migration, proliferation, and death. Studies have demonstrated changes in key components of sphingolipids in the kidneys under different conditions and their important roles in the renal function and the pathogenesis of various kidney diseases. This review summarizes the most recent advances in the role of sphingolipid signaling in kidney diseases.

Small Molecules in the Treatment of Acute Severe Ulcerative Colitis: A Review of Current Evidence

Ulcerative colitis (UC) is an inflammatory bowel disease in which one-quarter of patients are at risk of developing a severe form of the disease known as acute severe UC (ASUC). This condition exposes patients to serious complications, including toxic megacolon, surgical intervention, and even death. The current therapeutic strategy relies on time-dependent, multi-step algorithms that integrate systemic corticosteroids, calcineurin inhibitors, and biologic agents (specifically infliximab) as medical therapy aimed at avoiding colectomy. Despite this approach, a significant proportion of patients fail to respond to either corticosteroids or infliximab and may require alternative therapeutic options if there is no urgent surgical necessity. These alternatives include other biologics or emerging small molecules, although the evidence supporting these treatments remains extremely low, even considering their well-documented and promising efficacy and safety in moderate-to-severe UC. Conversely, it is necessary to investigate whether infliximab can be effectively replaced or surpassed by other approved biological agents and small molecules as first-line therapy after steroid resistance. This review aims to summarise the available evidence on small molecules, specifically Janus kinase inhibitors and sphingosine-1-phosphate receptor modulators.

Pinealectomy-Induced Melatonin Deficiency Exerts Age-Specific Effects on Sphingolipid Turnover in Rats

The existing body of literature, in conjunction with our recent studies, shows that melatonin dysfunction can accelerate the aging process, with this effect depending on the specific age of the subject. The present study aims to ascertain the impact of pinealectomy on sphingolipid (SL) turnover in young adult (3-month-old), middle-aged (14-month-old), and old (18-month-old) rats. Ceramide (Cer) levels, neutral (NSMase) and acid sphingomyelinase (ASMase), acid ceramidase (ASAH1), and sphingosine-1-phosphate (S1P) levels in hippocampus and/or plasma, were evaluated by enzyme-linked immunosorbent assay. The accumulation of Cer and its metabolite second messenger S1P in the hippocampus and plasma was associated with increased levels and activity of hippocampal NSMase in the hippocampus and plasma. However, no such association was observed for hippocampal ASMase, whose levels and activity were reduced in middle-aged and old rats compared to young adult rats. Pinealectomy-induced melatonin deficiency in young adult rats showed an increase in hippocampal Cer content compared to the sham group. However, in contrast to young adult rats, pinealectomy had an inverse effect on age-related changes in hippocampal Cer, NSMase, and ASMase in middle-aged rats. Furthermore, pinealectomy exacerbated the age-related increase in S1P in the hippocampus of 18-month-old rats. Collectively, the results of the present study suggest that melatonin deficiency may influence the aging process by modulating SL turnover in an age-specific manner.

Effects of Alexandrium pacificum Exposure on Exopalaemon carinicauda: Hepatopancreas Histology, Antioxidant Enzyme Activity, and Transcriptome Analysis

Alexandrium pacificum, a dinoflagellate known for causing harmful algal blooms (HABs), has garnered significant attention due to its potential toxicity to marine ecosystems, fisheries, and human health. However, the effects of this toxin-producing alga on shrimp are not yet comprehensively understood. This study aimed to assess the hepatopancreas damage induced by A. pacificum in the economically important shrimp species E. carinicauda and to elucidate the underlying molecular mechanisms through histology, antioxidant enzyme activity, and transcriptome analysis. The shrimp were assigned to either a control group or an exposed group, with the latter involving exposure to A. pacificum at a concentration of 1.0 × 104 cells/mL for 7 days. A histological analysis subsequently revealed pathological changes in the hepatopancreas tissue of the exposed group, including lumen expansion and the separation of the basement membrane from epithelial cells, while antioxidant enzyme activity assays demonstrated that exposure to A. pacificum weakened the antioxidant defense system, as evidenced by the reduced activities of catalase, superoxide dismutase, and glutathione, along with increased malondialdehyde levels. Transcriptome analysis further identified 663 significantly upregulated genes and 1735 significantly downregulated ones in the exposed group, with these differentially expressed genes being primarily associated with pathways such as protein processing in the endoplasmic reticulum, mitophagy, glycolysis/gluconeogenesis, sphingolipid metabolism, and glycerophospholipid metabolism. This study provides novel insights into the toxicological effects of A. pacificum on aquatic organisms and enhances the current understanding of the ecotoxicological risks posed by HABs.

Phospholipids and Sphingolipids in Osteoarthritis

Many studies now emphasize the intricate relationship between lipid metabolism and osteoarthritis (OA), a leading cause of disability. This narrative review examines alterations in the levels of phospholipids (PLs) and sphingolipids (SLs) in synovial fluid (SF), plasma, serum, and articular tissues; discusses their role in joint lubrication, inflammation, and cartilage degradation; and describes their potential as diagnostic markers and therapeutic targets. Key findings include stage-dependent elevated levels of specific PLs and SLs in the SF, blood, and tissue of OA patients, implicating them as possible biomarkers of disease severity and progression. Studies suggest that beyond the involvement of these lipids in joint lubrication, individual species, such as lysophosphatidylcholine (LPC) 16:0, lysophosphatidic acid (LPA), ceramide-1-phosphate (C1P), and sphingosine-1-phosphate (S1P), contribute to pain, inflammation, and degradation of joints through various signaling pathways. Cross-species comparisons suggest that dogs and mice experience similar lipidomic changes during OA as humans, rendering them valuable models for studying lipid-related mechanisms. PLs and SLs in SF appear to originate primarily from the synovial blood capillaries through diffusion. In addition, lipids that are produced locally by fibroblast-like synoviocytes (FLSs) are influenced by cytokines and growth factors that regulate the biosynthesis of PLs for joint lubrication. Emerging research has identified genes such as UGCG and ESYT1 as regulators of lipid metabolism in OA. Further, we examine the suitability of lipids as biomarkers of OA and the potential of targeting the PL and SL pathways to treat OA, emphasizing the need for further research to translate these findings into clinical applications.

Identification of potential biomarkers for coronary slow flow using untargeted metabolomics

BACKGROUND

Coronary slow flow (CSF) is associated with poor cardiovascular prognosis. However, its pathogenesis is unclear. This study aimed to identify potential characteristic biomarkers in patients with CSF using untargeted metabolomics.

METHODS

We prospectively enrolled 30 patients with CSF, 30 with coronary artery disease (CAD), and 30 with normal coronary arteries (NCA), all of whom were age-matched, according to the results of coronary angiography. Serum metabolomics were analyzed using ultra-performance liquid chromatography tandem mass spectrometry (UPLC-MS/MS). Differentially expressed metabolites were identified through orthogonal partial least squares-discriminant analysis (OPLS-DA) combined with univariate fold-change and VIP value analysis. Pathway enrichment of these metabolites was performed using the KEGG database, and ROC curves were plotted to assess the diagnostic value of the metabolites in CSF patients.

RESULTS

Compared to the CAD and NCA groups, 256 metabolites showed specific expression in CSF, with 18 meeting stringent screening criteria (VIP > 1, FC ≥ 2, or FC ≤ 0.5, and P < 0.05). Seven metabolites demonstrated high diagnostic value for CSF: inositol 1,3,4-trisphosphate (AUC: 1.0), Cer (d24:1/18:0 (2OH)) (AUC: 0.984), Creosol (AUC: 0.976), Chaps (AUC: 0.904), Arg-Thr-Lys-Arg (AUC: 0.929), Ser-Tyr-Arg (AUC: 0.912), and Methyl Indole-3-Acetate (AUC: 0.909). Pathway analysis highlighted the HIF-1 signaling pathway as the most significant metabolic pathway.

CONCLUSIONS

We identified seven metabolites that may serve as serum biomarkers for predicting and diagnosing CSF through untargeted metabolomics. The HIF-1 signaling pathway appears to be crucial in the development of CSF.

Sphingolipid metabolites involved in the pathogenesis of atherosclerosis: perspectives on sphingolipids in atherosclerosis

Atherosclerosis, with its complex pathogenesis, is a leading underlying cause of many cardiovascular diseases, which are increasingly prevalent in the population. Sphingolipids play an important role in the development of atherosclerosis. Key metabolites and enzymes in sphingolipid metabolism influence the pathogenesis of atherosclerosis in a variety of ways, including inflammatory responses and oxidative stress. Thus, an investigation of sphingolipid metabolism-related metabolites and key enzymes may provide novel insights and treatment targets for atherosclerosis. This review discusses various mechanisms and research progress on the relationship between various sphingolipid metabolites, related enzymes, and atherosclerosis. Finally, we look into the future research direction of phytosphingolipids.

Sphingolipids modulate redox signalling during human sperm capacitation

STUDY QUESTION

What role do sphingolipids have in mediating human sperm capacitation?

SUMMARY ANSWER

Sphingosine 1-phosphate (S1P) mediates the acquisition of fertilizing competency in human spermatozoa by engaging with its Gi-coupled receptor S1PR1 and promoting production of reactive oxygen species such as nitric oxide and superoxide anion.

WHAT IS KNOWN ALREADY

Bioactive sphingolipids, such as S1P, are fundamental for regulating numerous physiological domains and processes, such as cell membranes and signalling, cell death and proliferation, cell migration and invasiveness, inflammation, and central nervous system development.

STUDY DESIGN, SIZE, DURATION

Semen samples were obtained from a cohort of 10 healthy non-smoking volunteers (18-30 years old) to investigate the role of S1P in sperm.

PARTICIPANTS/MATERIALS, SETTING, METHODS

Percoll-selected human spermatozoa were incubated at 37°C for 3.5 h in BWW media with or without foetal cord serum ultrafiltrate (FCSu), sphingosine (Sph), or ceramide (Cer). Spermatozoa were also incubated with or without pharmacological inhibitors of sphingolipid metabolism. Protein tyrosine phosphorylation was determined by immunoblotting. The acrosome reaction was determined by PSA-FTIC labelling of the acrosome and analysed using fluorescence microscopy. Intracellular nitric oxide (NO•) production was determined using a DAF-2DA probe. Immunocytochemistry was performed to localize and assess the functional relationship of key components of lipid signalling in spermatozoa. Sperm viability and motility of the samples were evaluated by the hypo-osmotic swelling (HOS) test and computer-aided sperm analysis (CASA). Statistical differences between groups were determined using ANOVA and Tukey's test. Normal distribution of the data and variance homogeneity were assessed using Shapiro-Wilk and Levene's test, respectively. A difference was considered significant when the P-value was ≤0.05.

MAIN RESULTS AND THE ROLE OF CHANCE

S1P mediates the acquisition of fertilizing competency in human spermatozoa by engaging with its Gi-coupled receptor S1PR1. We found that S1PR1 redistributes to the post-acrosomal region upon induction of capacitation. S1P signalling promotes the activation of the PI3K-AKT pathway, leading to NO• production during sperm capacitation. L-NAME, an nitric oxide synthase inhibitor, impaired the Sph- and Cer-dependent capacitation. Additionally, Sph and Cer promote superoxide anion (O2•-) production, and the extracellular addition of superoxide dismutase (SOD) prevented Sph- and Cer-dependent capacitation, suggesting that Sph and Cer stimulate O2•- production during sperm capacitation. Protein kinase type R (PKR), ceramide kinase (CERK), and protein kinase C (PKC) are responsible for translocating and activating sphingosine kinase 1 (SphK1), which is necessary to promote S1P production for sperm capacitation.

LARGE SCALE DATA

N/A.

LIMITATIONS, REASONS FOR CAUTION

The utilization and actions of sphingolipids may differ in spermatozoa of different species.

WIDER IMPLICATIONS OF THE FINDINGS

Sphingolipid metabolites such as Sph, Cer, S1P, and ceramide 1-phosphate (C1P) play a crucial role in inducing human sperm capacitation. Our research has provided new insights into fundamental sphingolipid processes in human sperm, including the importance of C1P in translocating and activating SphK1 as well as the S1P signalling to regulate the PI3K/AKT/NOS pathway to generate NO• for sperm capacitation. We are the first to identify the presence of PKR in human spermatozoa and its role in the phosphorylation activities of SphK1 with the subsequent activation of S1P signalling. Furthermore, our study has identified that S1PR1 and S1PR3 are involved in capacitation and the acrosome reaction, respectively. These findings shed light on a novel mechanism by which sphingolipids drive capacitation in human sperm and pave the way for further exploration of the role of bioactive sphingolipid metabolites in this process. Lastly, our studies lay the foundation for examining the lipid profile of infertile males, as potential discrepancies can affect the functional capacity of spermatozoa to reach fertilizing potential.

STUDY FUNDING/COMPETING INTEREST(S)

This research was funded by the Canadian Institutes of Health Research (CIHR), grant number PJT-165962 to C.O.F. S.S. was awarded a Research Institute-MUHC Desjardins Studentship. There are no competing interests to report.

Regulatory role of S1P and its receptors in sepsis-induced liver injury

As an immune and metabolic organ, the liver affects the progression and prognosis of sepsis. Despite the severe adverse effects of sepsis liver injury on the body, treatment options remain limited. Sphingosine-1-phosphate (S1P) is a widely distributed lipid signaling molecule that binds to five sphingosine-1-phosphate receptors (S1PR) to regulate downstream signaling pathways involved in the pathophysiological processes of sepsis, including endothelial permeability, cytokine release, and vascular tone. This review summarizes current research on the role of S1P in normal liver biology and describes the mechanisms by which changes in S1P/S1PR affect the development of liver-related diseases. At the same time, the pathological processes underlying liver injury, as evidenced by clinical manifestations during sepsis, were comprehensively reviewed. This paper focused on the mechanistic pathways through which S1P and its receptors modulate immunity, bile acid metabolism, and liver-intestinal circulation in septic liver injury. Finally, the relationships between S1P and its receptors with liver inflammation and metabolism and the use of related drugs for the treatment of liver injury were examined. By elucidating the role of S1P and its receptor in the pathogenesis of sepsis liver injury, this review established a molecular targeting framework, providing novel insights into clinical and drug development.

Metabolomic Profiling and Characterization of a Novel 3D Culture System for Studying Chondrocyte Mechanotransduction

Background/Objective

Articular chondrocytes synthesize and maintain the avascular and aneural articular cartilage. In vivo these cells are surrounded by a 3D pericellular matrix (PCM) containing predominantly collagen VI. The PCM protects chondrocytes and facilitates mechanotransduction. PCM stiffness is critical in transmitting biomechanical signals to chondrocytes. Various culture systems with different hydrogels are used to encapsulate chondrocytes for 3D culture, but many lack either the PCM or the in vivo stiffness of the cartilage matrix. This study aimed at establishing a culture system to investigate a) if chondrocytes cultured in alginate will develop a PCM and b) study mechanotransduction via metabolic changes induced in 3D agarose-embedded chondrocytes upon mechanical stimulation.

Methods

We cultured primary human and bovine chondrocytes in monolayers or as alginate encapsulated cells in media containing sodium L-ascorbate. PCM expression was analyzed by immunofluorescence and western blots. We further characterized the response of chondrocytes embedded in physiologically stiff agarose to dynamic compression through metabolomic profiling.

Results

We found that primary human and bovine chondrocytes, when cultured in alginate beads with addition of sodium L-ascorbate for 7 days, had a pronounced PCM, retained their phenotype, and synthesized both collagens VI and II. This novel culture system enables alginate-encapsulated chondrocytes to develop a robust PCM thereby creating a model system to study mechanotransduction in the presence of an endogenous PCM. We also observed distinct compression-induced changes in metabolomic profiles between the monolayer-agarose and alginate-released agarose-embedded chondrocytes indicating physiological changes in cell metabolism.

Conclusion/Significance

These data show that 3D preculture of chondrocytes in alginate before encapsulation in physiologically stiff agarose leads to pronounced development of pericellular matrix that is sustained in the presence of ascorbate. This model can be useful in studying the mechanism by which chondrocytes respond to cyclical compression and other types of loading simulating in vivo physiological conditions.

Anti-ceramide antibody and sphingosine-1-phosphate as potential biomarkers of unresectable non-small cell lung cancer

Objectives

Spingosine-1-phosphate (S1P) and ceramides are bioactive sphingolipids that influence cancer cell fate. Anti-ceramide antibodies might inhibit the effects of ceramide. The aim of this study was to assess the potential role of circulating S1P and anti-ceramide antibody as biomarkers in non-small cell lung cancer (NSCLC).

Methods

We recruited 66 subjects (34 controls and 32 patients with NSCLC). Patient history and clinical variables were taken from all participants. Venous blood samples were collected to evaluate plasma biomarkers. If bronchoscopy was performed, bronchial washing fluid (BWF) was also analyzed. We measured the levels of S1P and anti-ceramide antibody with ELISA.

Results

S1P levels were significantly higher in the NSCLC group (3770.99 ± 762.29 ng/mL vs. 366.53 ± 249.38 ng/mL, patients with NSCLC vs. controls, respectively, p < 0.001). Anti-ceramide antibody levels were significantly elevated in the NSCLC group (278.70 ± 19.26 ng/mL vs. 178.60 ± 18 ng/mL, patients with NSCLC vs. controls, respectively, p = 0.007). Age or BMI had no significant effect on anti-ceramide antibody or S1P levels. BWF samples had higher levels of anti-ceramide antibody (155.29 ± 27.58 ng/mL vs. 105.87 ± 9.99 ng/mL, patients with NSCLC vs. controls, respectively, p < 0.001). Overall survival (OS) was 13.36 months. OS was not affected by anti-ceramide antibody or S1P levels.

Conclusion

Higher levels of S1P and anti-ceramide antibody were associated with active cancer. These results suggest that sphingolipid alterations might be important features of NSCLC.

Lipotoxicity-driven metabolic dysfunction-associated steatotic liver disease (MASLD)

Metabolic dysfunction-associated steatotic liver disease (MASLD) encompasses a spectrum of liver lesions, ranging from simple steatosis to metabolic dysfunction-associated steatohepatitis (MASH), that may further progress to cirrhosis. MASLD is estimated to affect more than one third of the general population and it represents a risk factor for end-stage liver failure and liver cancer, substantially contributing to liver-related morbidity and mortality. Although the pathogenesis of MASLD is incompletely understood, it is known to consist of a multifactorial process influenced by extrinsic and intrinsic factors such as metabolic, environmental and demographic features, gut microbiota and genetics. Dysregulation of both extracellular and intracellular lipid composition is known to promote the generation of toxic lipid species, thereby triggering lipotoxicity and cellular stress. These events ultimately lead to the activation of distinct cell death pathways, resulting in inflammation, fibrogenesis and, eventually, carcinogenesis. In this manuscript, we provide a comprehensive review of the role of lipotoxicity during MASLD pathogenesis, discussing the most relevant lipid species and related molecular mechanisms, summarizing the cell type-specific effects and highlighting the most promising putative therapeutic strategies for modulating lipotoxicity and lipid metabolism in MASLD.

Diet-Induced Obesity in the Rat Impairs Sphingolipid Metabolism in the Brain and This Metabolic Dysfunction Is Transmitted to the Offspring via Both the Maternal and the Paternal Lineage

Obesity leads to a number of health problems, including learning and memory deficits that can be passed on to the offspring via a developmental programming process. However, the mechanisms involved in the deleterious effects of obesity on cognition remain largely unknown. This study aimed to assess the impact of obesity on the production of sphingolipids (ceramides and sphingomyelins) in the brain and its relationship with the learning deficits displayed by obese individuals. We also sought to determine whether the effects of obesity on brain sphingolipid synthesis could be passed on to the offspring. Learning abilities and brain concentration of sphingolipids in male and female control and obese founder rats (F0) and their offspring (F1) were evaluated, respectively, by the novel object recognition test and by ultra-performance liquid chromatography tandem mass spectrometry. In addition, a global lipidome profiling of the cerebral cortex and hippocampus was performed. Both male and female F0 rats showed impaired learning and increased concentrations of ceramides and sphingomyelins in the hippocampus and frontal cortex compared to their control counterparts. However, the overall lipidome profile of these brain regions did not change with obesity. Remarkably, the alterations in brain sphingolipid synthesis, as well as the cognitive impairment induced by obesity, were also present in adult F1 male rats born to obese mothers or sired by obese fathers and were associated with enhanced expression of mRNAs coding for enzymes involved in the de novo synthesis of ceramides. These results show that the cognitive deficits and impaired sphingolipid metabolism induced by obesity can be transmitted to the offspring through both the maternal and paternal lineages and suggest that an increase in the brain concentration of sphingolipids could play a causal role in the cognitive deficits associated with obesity.

Altered sphingolipid profile in response to skeletal muscle injury in a mouse model of type 1 diabetes mellitus

A complication of type 1 diabetes mellitus (T1DM) is diabetic myopathy that includes reduced regenerative capacity of skeletal muscle. Sphingolipids are a diverse family of lipids with roles in skeletal muscle regeneration. Some studies have found changes in sphingolipid species levels in T1DM, however, the effect of T1DM on a sphingolipid panel in regenerating skeletal muscle has not been examined. Wild-type (WT) and diabetic Ins2Akita+/- (Akita) mice received cardiotoxin-induced muscle injury in their left quadriceps, gastrocnemius-plantaris-soleus, and tibialis anterior muscles with the contralateral muscles serving as uninjured controls. Muscles were collected at 1, 3, 5, or 7 days postinjury. In regenerating muscle from Akita mice, lipid staining with BODIPY 493/503 revealed increased intramyocellular and total lipids and perilipin-1-positive cell numbers as compared with WT. Liquid chromatography-mass spectrometry of quadriceps was used to identify sphingolipid levels in skeletal muscle. The C22:0 and C24:0 ceramides were significantly elevated in uninjured Akita, whereas ceramide C24:1 was decreased in injured Akita compared with WT. Ceramide-1-phosphate was increased in Akita compared with WT regardless of injury, whereas sphingosine-1-phosphate (S1P) was elevated with injury in WT but this response was muted in Akita mice. Western blotting of key enzymes involved in sphingolipid metabolism revealed S1P lyase, the enzyme that degrades S1P irreversibly, was significantly elevated in the injured muscle in Akita mice during regeneration, in accordance with lower S1P levels. This mouse model of T1DM demonstrates sphingolipidomic changes that may contribute to delayed muscle regeneration.NEW & NOTEWORTHY Muscle lipids become elevated, and the sphingolipid profile is altered by T1DM in skeletal muscle regeneration. A loss of S1P is accompanied by greater expression of sphingosine-1-phosphate lyase (SPL) in response to injury in Akita mice, suggesting a role for sphingolipids in the attenuated repair of skeletal muscle in T1DM rodent models. Although ceramide-1-phosphate (C1P) is increased with T1DM, there was no increase in ceramide kinase (CerK) suggesting an alternative route of ceramide phosphorylation in skeletal muscle.

Role of dietary and nutritional interventions in ceramide-associated diseases

Ceramides are important intermediates in sphingolipid metabolism and serve as signaling molecules with independent biological significance. Elevated cellular and circulating ceramide levels are consistently associated with pathological conditions including cardiometabolic diseases, neurological diseases, autoimmune diseases, and cancers. Although pharmacological inhibition of ceramide formation often protects against these diseases in animal models, pharmacological modulation of ceramides in humans remains impractical. Dietary interventions including the Mediterranean diet, lacto-ovo-vegetarian diet, calorie-restricted diet, restriction of dairy product consumption, and dietary supplementation with polyunsaturated fatty acids, dietary fibers, and polyphenols, all have beneficial effects on modulating ceramide levels. Mechanistic insights into these interventions are discussed. This article reviews the relationships between ceramides and disease pathogenesis, with a focus on dietary intervention as a viable strategy for lowering the concentration of circulating ceramides.

The role of sphingolipid rheostat in the adult-type diffuse glioma pathogenesis

Gliomas are highly aggressive primary brain tumors, with glioblastoma multiforme being the most severe and the most common one. Aberrations in sphingolipid metabolism are a hallmark of glioma cells. The sphingolipid rheostat represents the balance between the pro-apoptotic ceramide and pro-survival sphingosine-1-phosphate (S1P), and in gliomas it is shifted toward cell survival and proliferation, promoting gliomas' aggressiveness, cellular migration, metastasis, and invasiveness. The sphingolipid rheostat can be altered by targeting enzymes that directly or indirectly affect the ratio of ceramide to S1P, leading to increased ceramide or decreased S1P levels. Targeting the sphingolipid rheostat offers a potential therapeutic pathway for glioma treatment which can be considered through reducing S1P levels or modulating S1P receptors to reduce cell proliferation, as well as through increasing ceramide levels to induce apoptosis in glioma cells. Although the practical translation into clinical therapy is still missing, sphingolipid rheostat targeting in gliomas has been of great research interest in recent years with several interesting achievements in the glioma therapy approach, offering hope for patients suffering from these vicious malignancies.

Genomic Effects of Biomechanical Loading in Adolescent Human Growth Plate Cartilage: A Pilot Study

OBJECTIVE

The genomic effects of biomechanical loading on human growth plate cartilage are unknown so far. To address this, we used rare human growth plate biopsies obtained from children undergoing epiphysiodesis and exposed them to precisely controlled mechanical loading using a microloading device. The biopsies were cultured 24 hours after mechanical loading, followed by RNA-sequencing analyses to decipher the genomic regulation.

DESIGN

We conducted RNA-seq analysis of human growth plate cartilage obtained from three patients cultured ex vivo and subjected to cyclical mechanical loading with peak 0.4 N with frequency 0.77 Hz during a 30-second duration, using a specialized microloading device.

RESULTS

Gene ontology analysis revealed novel data showing three significantly upregulated signaling pathways, including notch, oxytocin, and tight junction, and three significantly downregulated signaling pathways, including lysosome, sphingolipid metabolism, and peroxisome proliferator-activated receptor (PPAR) in human growth plate cartilage. Moreover, we found 15 significantly regulated genes within these signaling pathways from all three patients. These genes included PSEN2, HEY1, and NCOR2 from the notch signaling; CACNB1 and PPP3R2 from the oxytocin signaling; ACTR3C, WHAMM, and ARHGEF18 from the tight junction signaling; ARSA, SMPD1, and CD68 from the lysosome signaling; ARSA and SMPD1 from the sphingolipid metabolism signaling; and SLC27A4 and AQP7 from the PPAR signaling pathway. In addition, 20 significantly upregulated genes and six significantly downregulated genes shared between two patient samples were identified.

CONCLUSION

Our study provides the first-ever transcriptomic data of mechanical loading of human growth plate cartilage. These findings can potentially provide genetic targets for future investigations in physiological and pathological bone growth conditions.

Sphingosine phosphate lyase insufficiency syndrome as a primary immunodeficiency state

Sphingosine phosphate lyase insufficiency syndrome (SPLIS) is a genetic disease associated with renal, endocrine, neurological, skin and immune defects. SPLIS is caused by inactivating mutations in SGPL1, which encodes sphingosine phosphate lyase (SPL). SPL catalyzes the irreversible degradation of the bioactive sphingolipid sphingosine-1-phosphate (S1P), a key regulator of lymphocyte egress. The SPL reaction represents the only exit point of sphingolipid metabolism, and SPL insufficiency causes widespread sphingolipid derangements that could additionally contribute to immunodeficiency. Herein, we review SPLIS, the sphingolipid metabolic pathway, and various roles sphingolipids play in immunity. We then explore SPLIS-related immunodeficiency by analyzing data available in the published literature supplemented by medical record reviews in ten SPLIS children. We found 93% of evaluable SPLIS patients had documented evidence of immunodeficiency. Many of the remainder of cases were unevaluable due to lack of available immunological data. Most commonly, SPLIS patients exhibited lymphopenia and T cell-specific lymphopenia, consistent with the established role of the S1P/S1P1/SPL axis in lymphocyte egress. However, low B and NK cell counts, hypogammaglobulinemia, and opportunistic infections with bacterial, viral and fungal pathogens were observed. Diminished responses to childhood vaccinations were less frequently observed. Screening blood tests quantifying recent thymic emigrants identified some lymphopenic SPLIS patients in the newborn period. Lymphopenia has been reported to improve after cofactor supplementation in some SPLIS patients, indicating upregulation of SPL activity. A variety of treatments including immunoglobulin replacement, prophylactic antimicrobials and special preparation of blood products prior to transfusion have been employed in SPLIS. The diverse immune consequences in SPLIS patients suggest that aberrant S1P signaling may not fully explain the extent of immunodeficiency. Further study will be required to fully elucidate the complex mechanisms underlying SPLIS immunodeficiency and determine the most effective prophylaxis against infection.

Hyperbaric Oxygen Therapy Reduces the Traumatic Brain Injury-Mediated Neuroinflammation Through Enrichment of Prevotella Copri in the Gut of Male Rats

BACKGROUND

Gastrointestinal dysfunction frequently occurs following traumatic brain injury (TBI) and significantly increases posttraumatic complications. TBI can lead to alterations in gut microbiota. The neuroprotective effects of hyperbaric oxygen (HBO) have not been well recognized after TBI. The study''s aim was to investigate the impact of HBO on TBI-induced dysbiosis in the gut and the pathological changes in the brain following TBI.

METHODS

Anesthetized male Sprague-Dawley rats were randomly assigned to three groups: sham surgery plus normobaric air (21% oxygen at 1 atmospheres absolute), TBI (2.0 atm) plus normobaric air, and TBI (2.0 atm) plus HBO (100% oxygen at 2.0 atmospheres absolute) for 60 min immediately after TBI, 24 h later, and 48 h later. The brain injury volume, tumor necrosis factor-α expression in microglia and astrocytes, and neuronal apoptosis in the brain were subsequently determined. The V3-V4 regions of 16S ribosomal rRNA in the fecal samples were sequenced, and alterations in the gut microbiome were statistically analyzed. All parameters were evaluated on the 3rd day after TBI.

RESULTS

Our results demonstrated that HBO improved TBI-induced neuroinflammation, brain injury volume, and neuronal apoptosis. HBO appeared to increase the abundance of aerobic bacteria while inhibiting anaerobic bacteria. Intriguingly, HBO reversed the TBI-mediated decrease in Prevotella copri and Deinococcus spp., both of which were negatively correlated with neuroinflammation and brain injury volume. TBI increased the abundance of these gut bacteria in relation to NOD-lik0065 receptor signaling and the proteasome pathway, which also exhibited a positive correlation trend with neuro inflammation and apoptosis. The abundance of Prevotella copri was negatively correlated with NOD-like receptor signaling and the Proteasome pathway.

CONCLUSIONS

Our study demonstrated how the neuroprotective effects of HBO after acute TBI might act through reshaping the TBI-induced gut dysbiosis and reversing the TBI-mediated decrease of Prevotella copri.

Myelin Lipid Alterations in Neurodegenerative Diseases: Landscape and Pathogenic Implications

Significance: Lipids, which constitute the highest portion (over 50%) of brain dry mass, are crucial for brain integrity, energy homeostasis, and signaling regulation. Emerging evidence revealed that lipid profile alterations and abnormal lipid metabolism occur during normal aging and in different forms of neurodegenerative diseases. Moreover, increasing genome-wide association studies have validated new targets on lipid-associated pathways involved in disease development. Myelin, the protective sheath surrounding axons, is crucial for efficient neural signaling transduction. As the primary site enriched with lipids, impairments of myelin are increasingly recognized as playing significant and complex roles in various neurodegenerative diseases, beyond simply being secondary effects of neuronal loss. Recent Advances: With advances in the lipidomics field, myelin lipid alterations and their roles in contributing to or reflecting the progression of diseases, including Alzheimer's disease, Parkinson's disease, Huntington's disease, amyotrophic lateral sclerosis, multiple sclerosis, and others, have recently caught great attention. Critical Issues: This review summarizes recent findings of myelin lipid alterations in the five most common neurodegenerative diseases and discusses their implications in disease pathogenesis. Future Directions: By highlighting myelin lipid abnormalities in neurodegenerative diseases, this review aims to encourage further research focused on lipids and the development of new lipid-oriented therapeutic approaches in this area. Antioxid. Redox Signal. 00, 000-000.

The Role of Vitamin E Isoforms and Metabolites in Cancer Prevention: Mechanistic Insights into Sphingolipid Metabolism Modulation

Natural forms of vitamin E include four tocopherols and four tocotrienols (α, β, γ, and δ), which are essential as lipophilic antioxidants. Among these eight isoforms, α-tocopherol (αT), the predominant form of vitamin E found in tissues, has traditionally received the most attention in disease prevention research due to its robust antioxidant activity. However, recent studies suggest that other forms of vitamin E exhibit distinct and potentially more potent beneficial activities in disease prevention and treatment. These non-αT forms of vitamin E are metabolized in vivo, producing various metabolites, including 13'-carboxychromanol, though their biological roles remain largely unknown. Notably, sphingolipids, known for their significant roles in cancer biology, may be involved in the anticancer effects of vitamin E through the modulation of sphingolipid metabolism. This review focuses on the diverse biological activities of different vitamin E forms and their metabolites, particularly their anticancer effects, while highlighting the underlying mechanisms, including their novel impact on regulating sphingolipid pathways. By elucidating these interactions, we aim to provide a deeper understanding on the multifaceted roles of vitamin E in cancer prevention and therapy.

Engineering of Saccharomyces cerevisiae as a platform strain for microbial production of sphingosine-1-phosphate

BACKGROUND

Sphingosine-1-phosphate (S1P) is a multifunctional sphingolipid that has been implicated in regulating cellular activities in mammalian cells. Due to its therapeutic potential, there is a growing interest in developing efficient methods for S1P production. To date, the production of S1P has been achieved through chemical synthesis or blood extraction, but these processes have limitations such as complexity and cost. In this study, we generated an S1P-producing Saccharomyces cerevisiae strain by using metabolic engineering and introducing a heterologous sphingolipid biosynthetic pathway to demonstrate the possibility of microbial S1P production.

RESULTS

To construct the sphingosine-producing S. cerevisiae strain, both the sphingolipid delta 4 desaturase gene (DES1) and the alkaline ceramidase gene (ACER1) derived from Homo sapiens were introduced into the genome of S. cerevisiae by deleting the dihydrosphingosine phosphate lyase gene (DPL1) and the sphingoid long-chain base kinase gene (LCB5) to prevent S1P degradation and byproduct formation, respectively. The sphingosine-producing strain, DDLA, produced sphingolipids containing sphingosine. In flask fed-batch fermentation, the DDLA strain showed a higher production level of sphingosine under aerobic conditions with high initial cell density. The S1P-producing strain was generated by expressing the human sphingosine kinase gene (SPHK1) under the control of the inducible promoter, while deleting the ORM1 gene involved in the regulation of sphingolipid biosynthesis. The S1P-producing strain, DDLAOgS, exhibited the highest sphingosine production level under fed-batch fermentation in a bioreactor, achieving a 2.6-fold increase compared to flask fermentation. S1P biosynthesis in the DDLAOgS strain was verified by qualitative analysis using electrospray ionization mass spectrometry (ESI-MS).

CONCLUSIONS

We successfully developed a metabolically engineered S. cerevisiae as a platform strain for microbial production of S1P by introducing an exogenous pathway of sphingolipids metabolism. The engineered yeast strains showed significant capabilities for sphingolipid production, including S1P. To our knowledge, this is the first report demonstrating that engineered S. cerevisiae can be a major platform strain for producing microbial S1P.

Unraveling the glycosphingolipid metabolism by leveraging transcriptome-weighted network analysis on neuroblastic tumors

BACKGROUND

Glycosphingolipids (GSLs) are membrane lipids composed of a ceramide backbone linked to a glycan moiety. Ganglioside biosynthesis is a part of the GSL metabolism, which involves sequential reactions catalyzed by specific enzymes that in part have a poor substrate specificity. GSLs are deregulated in cancer, thus playing a role as potential biomarkers for personalized therapy or subtype classification. However, the analysis of GSL profiles is complex and requires dedicated technologies, that are currently not included in the commonly utilized high-throughput assays adopted in contexts such as molecular tumor boards.

METHODS

In this study, we developed a method to discriminate the enzyme activity among the four series of the ganglioside metabolism pathway by incorporating transcriptome data and topological information of the metabolic network. We introduced three adjustment options for reaction activity scores (RAS) and demonstrated their application in both exploratory and comparative analyses by applying the method on neuroblastic tumors (NTs), encompassing neuroblastoma (NB), ganglioneuroblastoma (GNB), and ganglioneuroma (GN). Furthermore, we interpreted the results in the context of earlier published GSL measurements in the same tumors.

RESULTS

By adjusting RAS values using a weighting scheme based on network topology and transition probabilities (TPs), the individual series of ganglioside metabolism can be differentiated, enabling a refined analysis of the GSL profile in NT entities. Notably, the adjustment method we propose reveals the differential engagement of the ganglioside series between NB and GNB. Moreover, MYCN gene expression, a well-known prognostic marker in NTs, appears to correlate with the expression of therapeutically relevant gangliosides, such as GD2. Using unsupervised learning, we identified subclusters within NB based on altered GSL metabolism.

CONCLUSION

Our study demonstrates the utility of adjusting RAS values in discriminating ganglioside metabolism subtypes, highlighting the potential for identifying novel cancer subgroups based on sphingolipid profiles. These findings contribute to a better understanding of ganglioside dysregulation in NT and may have implications for stratification and targeted therapeutic strategies in these tumors and other tumor entities with a deregulated GSL metabolism.

Serum metabolite signature of the modified Mediterranean-DASH intervention for neurodegenerative delay (MIND) diet

INTRODUCTION

There is a lack of biomarkers of clinically important diets, such as the Mediterranean-DASH Intervention for Neurodegenerative Delay (MIND) diet.

OBJECTIVES

Our study explored serum metabolites associated with adherence to the MIND diet.

METHODS

In 3,908 Atherosclerosis Risk in Communities (ARIC) study participants, we calculated a modified MIND diet score based on a 66-item self-reported food frequency questionnaire (FFQ). The modified score did not include berries and olive oil, as these items were not assessed in the FFQ. We used multivariable linear regression models in 2 subgroups of ARIC study participants and meta-analyzed results using fixed effects regression to identify significant metabolites after Bonferroni correction. We also examined associations between these metabolites and food components of the modified MIND diet. C-statistics evaluated the prediction of high modified MIND diet adherence using significant metabolites beyond participant characteristics.

RESULTS

Of 360 metabolites analyzed, 27 metabolites (15 positive, 12 negative) were significantly associated with the modified MIND diet score (lipids, n = 13; amino acids, n = 5; xenobiotics, n = 3; cofactors and vitamins, n = 3; carbohydrates n = 2; nucleotide n = 1). The top 4 metabolites that improved the prediction of high dietary adherence to the modified MIND diet were 7-methylxanthine, theobromine, docosahexaenoate (DHA), and 3-carboxy-4-methyl-5-propyl-2-furanpropanoate (CMPF).

CONCLUSION

Twenty-seven metabolomic markers were correlated with the modified MIND diet. The biomarkers, if further validated, could be useful to objectively assess adherence to the MIND diet.

Dietary Regulation of Lipid Metabolism in Gestational Diabetes Mellitus: Implications for Fetal Macrosomia

The primary therapeutic approach for managing hyperglycemia today is diet therapy. Lipids are not only a source of nutrients but also play a role in initiating adipocyte differentiation in the fetus, which may explain the development of fetal macrosomia and future metabolic disorders in children born to mothers with gestational diabetes mellitus (GDM). Alterations in the maternal blood lipid profile, influenced by adherence to a healthy diet in mothers with GDM and the occurrence of fetal macrosomia, represent a complex and not fully understood process. The aim of this study was to examine the characteristics of the blood plasma lipid profile in pregnant women with GDM across all trimesters based on adherence to diet therapy. The clinical part of the study followed a case-control design, including 110 women: 80 in the control group, 20 in a GDM group adhering to the diet, and 10 in a GDM group not adhering to the diet. The laboratory part was conducted as a longitudinal dynamic study, with venous blood samples collected at three time points: 11-13, 24-26, and 30-32 weeks of pregnancy. A significant impact of diet therapy on the composition of blood lipids throughout pregnancy was demonstrated, starting as early as the first trimester. ROC analysis indicated high effectiveness of the models developed, with an AUC of 0.98 for the 30- to 32-week model and sensitivity and specificity values of 1 and 0.9, respectively. An association was found between dietary habits, maternal blood lipid composition at 32 weeks, and newborn weight. The changes in lipid profiles during macrosomia development and under diet therapy were found to be diametrically opposed, confirming at the molecular level that diet therapy can normalize not only carbohydrate metabolism but also lipid metabolism in both the mother and fetus. Based on the data obtained, it is suggested that after further validation, the developed models could be used to improve the prognosis of macrosomia by analyzing blood plasma lipid profiles at various stages of pregnancy.

Signaling roles of sphingolipids in the ischemic brain and their potential utility as therapeutic targets

Sphingolipids comprise a class of lipids, which are composed of a sphingoid base backbone and are essential structural components of cell membranes. Beyond their role in maintaining cellular integrity, several sphingolipids are pivotally involved in signaling pathways controlling cell proliferation, differentiation, and death. The brain exhibits a particularly high concentration of sphingolipids and dysregulation of the sphingolipid metabolism due to ischemic injury is implicated in consecutive pathological events. Experimental stroke studies revealed that the stress sphingolipid ceramide accumulates in the ischemic brain post-stroke. Specifically, counteracting ceramide accumulation protects against ischemic damage and promotes brain remodeling, which translates into improved behavioral outcome. Sphingomyelin substantially influences cell membrane fluidity and thereby controls the release of extracellular vesicles, which are important vehicles in cellular communication. By modulating sphingomyelin content, these vesicles were shown to contribute to behavioral recovery in experimental stroke studies. Another important sphingolipid that influences stroke pathology is sphingosine-1-phosphate, which has been attributed a pro-angiogenic function, that is presumably mediated by its effect on endothelial function and/or immune cell trafficking. In experimental and clinical studies, sphingosine-1-phosphate receptor modulators allowed to modify clinically significant stroke recovery. Due to their pivotal roles in cell signaling, pharmacological compounds modulating sphingolipids, their enzymes or receptors hold promise as therapeutics in human stroke patients.

Effects of regulating gut microbiota by electroacupuncture in the chronic unpredictable mild stress rat model

OBJECTIVE

This study aims to investigate the effect of electroacupuncture (EA) treatment on depression, and the potential molecular mechanism of EA in depression-like behaviors rats.

METHODS

A total of 40 male Sprague Dawley rats were divided into three groups: normal control, chronic unpredictable mild stress (CUMS), and EA (CUMS + EA). The rats in CUMS and EA groups underwent chronic stress for 10 weeks, and EA group rats received EA treatment for 4 weeks starting from week 7. Body weight and behavioral tests, including the sucrose preference test (SPT), the forced swimming test (FST), and the open field test (OFT) were monitored. Gut microbiota composition was assessed via 16S rDNA sequencing, and lipid metabolism was analyzed by using UPLC-Q-TOF/MS technology.

RESULTS

In comparison to CUMS group, EA could improve the behavior including bodyweight, immovability time, sucrose preference index, crossing piece index and rearing times index. After 4 weeks of EA treatment, 5-HT in hippocampus, serum and colon of depressive rats were simultaneously increased, indicating a potential alleviation of depression-like behaviors. In future studies revealed that EA could regulate the distribution and functions of gut microbiota, and improve the intestinal barrier function of CUMS rats. The regulation of intestinal microbial homeostasis by EA may further affect lipid metabolism in CUMS rats, and thus play an antidepressant role.

CONCLUSION

This study suggested that EA has potential antidepressant effects by regulating gut microbiota composition and abundance, subsequently affecting lipid metabolism.

Epidermal RORα Maintains Barrier Integrity and Prevents Allergic Inflammation by Regulating Late Differentiation and Lipid Metabolism

The skin epidermis provides a barrier that is imperative for preventing transepidermal water loss (TEWL) and protecting against environmental stimuli. The underlying molecular mechanisms for regulating barrier functions and sustaining its integrity remain unclear. RORα is a nuclear receptor highly expressed in the epidermis of normal skin. Clinical studies showed that the epidermal RORα expression is significantly reduced in the lesions of multiple inflammatory skin diseases. In this study, we investigate the central roles of RORα in stabilizing skin barrier function using mice with an epidermis-specific Rora gene deletion (RoraEKO). While lacking spontaneous skin lesions or dermatitis, RoraEKO mice exhibited an elevated TEWL rate and skin characteristics of barrier dysfunction. Immunostaining and Western blot analysis revealed low levels of cornified envelope proteins in the RoraEKO epidermis, suggesting disturbed late epidermal differentiation. In addition, an RNA-seq analysis showed the altered expression of genes related to "keratinization" and "lipid metabolism" in RORα deficient epidermis. A lipidomic analysis further uncovered an aberrant ceramide composition in the RoraEKO epidermis. Importantly, epidermal Rora ablation greatly exaggerated percutaneous allergic inflammatory responses to oxazolone in an allergic contact dermatitis (ACD) mouse model. Our results substantiate the essence of epidermal RORα in maintaining late keratinocyte differentiation and normal barrier function while suppressing cutaneous inflammation.

Determination of Initial Rates of Lipopolysaccharide Transport

Nonvesicular lipid trafficking pathways are an important process in every domain of life. The mechanisms of these processes are poorly understood in part due to the difficulty in kinetic characterization. One important class of glycolipids, lipopolysaccharides (LPS), are the primary lipidic component of the outer membrane of Gram-negative bacteria. LPS are synthesized in the inner membrane and then trafficked to the cell surface by the lipopolysaccharide transport proteins, LptB2FGCADE. By characterizing the interaction of a fluorescent probe and LPS, we establish a quantitative assay to monitor the flux of LPS between proteoliposomes on the time scale of seconds. We then incorporate photocaged ATP into this system, which allows for light-based control of the initiation of LPS transport. This control allows us to measure the initial rate of LPS transport (3.0 min-1 per LptDE). We also find that the rate of LPS transport by the Lpt complex is independent of the structure of LPS. In contrast, we find the rate of LPS transport is dependent on the proper function of the LptDE complex. Mutants of the outer membrane Lpt components, LptDE, that cause defective LPS assembly in live cells display attenuated transport rates and slower ATP hydrolysis compared to wild type proteins. Analysis of these mutants reveals that the rates of ATP hydrolysis and LPS transport are correlated such that 1.2 ± 0.2 ATP are hydrolyzed for each LPS transported. This correlation suggests a model where the outer membrane components ensure the coupling of ATP hydrolysis and LPS transport by stabilizing a transport-active state of the Lpt bridge.

The sphingosine kinase 2 inhibitors ABC294640 and K145 elevate (dihydro)sphingosine 1-phosphate levels in various cells

Sphingosine kinases (SphKs), enzymes that produce the bioactive lipids dihydrosphingosine 1-phosphate (dhS1P) and sphingosine 1-phosphate (S1P), are associated with various diseases, including cancer and infections. For this reason, a number of SphK inhibitors have been developed. Although off-target effects have been described for selected agents, SphK inhibitors are mostly used in research without monitoring the effects on the sphingolipidome. We have now investigated the effects of seven commonly used SphK inhibitors (5c, ABC294640 (opaganib), N,N-dimethylsphingosine, K145, PF-543, SLM6031434, and SKI-II) on profiles of selected sphingolipids in Chang, HepG2, and human umbilical vein endothelial cells. While we observed the expected (dh)S1P reduction for N,N-dimethylsphingosine, PF-543, SKI-II, and SLM6031434, 5c showed hardly any effect. Remarkably, for K145 and ABC294640, both reported to be specific for SphK2, we observed dose-dependent strong increases in dhS1P and S1P across cell lines. Compensatory effects of SphK1 could be excluded, as this observation was also made in SphK1-deficient HK-2 cells. Furthermore, we observed effects on dihydroceramide desaturase activity for all inhibitors tested, as has been previously noted for ABC294640 and SKI-II. In additional mechanistic studies, we investigated the massive increase of dhS1P and S1P after short-term cell treatment with ABC294640 and K145 in more detail. We found that both compounds affect sphingolipid de novo synthesis, with 3-ketodihydrosphingosine reductase and dihydroceramide desaturase as their targets. Our study indicates that none of the seven SphK inhibitors tested was free of unexpected on-target and/or off-target effects. Therefore, it is important to monitor cellular sphingolipid profiles when SphK inhibitors are used in mechanistic studies.

Differential roles of lysosomal cholesterol transporters in the development of C. elegans NMJs

Cholesterol homeostasis in neurons is critical for synapse formation and maintenance. Neurons with impaired cholesterol uptake undergo progressive synapse loss and eventual degeneration. To investigate the molecular mechanisms of neuronal cholesterol homeostasis and its role during synapse development, we studied motor neurons of Caenorhabditis elegans because these neurons rely on dietary cholesterol. Combining lipidomic analysis, we discovered that NCR-1, a lysosomal cholesterol transporter, promotes cholesterol absorption and synapse development. Loss of ncr-1 causes smaller synapses, and low cholesterol exacerbates the deficits. Moreover, NCR-1 deficiency hinders the increase in synapses under high cholesterol. Unexpectedly, NCR-2, the NCR-1 homolog, increases the use of cholesterol and sphingomyelins and impedes synapse formation. NCR-2 deficiency causes an increase in synapses regardless of cholesterol concentration. Inhibiting the degradation or synthesis of sphingomyelins can induce or suppress the synaptic phenotypes in ncr-2 mutants. Our findings indicate that neuronal cholesterol homeostasis is differentially controlled by two lysosomal cholesterol transporters and highlight the importance of neuronal cholesterol homeostasis in synapse development.

Emerging Roles for Sphingolipids in Cardiometabolic Disease: A Rational Therapeutic Target?

Cardiovascular disease is a leading cause of morbidity and mortality. New research elucidates increasingly complex relationships between cardiac and metabolic health, giving rise to new possible therapeutic targets. Sphingolipids are a heterogeneous class of bioactive lipids with critical roles in normal human physiology. They have also been shown to play both protective and deleterious roles in the pathogenesis of cardiovascular disease. Ceramides are implicated in dysregulating insulin signalling, vascular endothelial function, inflammation, oxidative stress, and lipoprotein aggregation, thereby promoting atherosclerosis and vascular disease. Ceramides also advance myocardial disease by enhancing pathological cardiac remodelling and cardiomyocyte death. Glucosylceramides similarly contribute to insulin resistance and vascular inflammation, thus playing a role in atherogenesis and cardiometabolic dysfunction. Sphingosing-1-phosphate, on the other hand, may ameliorate some of the pathological functions of ceramide by protecting endothelial barrier integrity and promoting cell survival. Sphingosine-1-phosphate is, however, implicated in the development of cardiac fibrosis. This review will explore the roles of sphingolipids in vascular, cardiac, and metabolic pathologies and will evaluate the therapeutic potential in targeting sphingolipids with the aim of prevention and reversal of cardiovascular disease in order to improve long-term cardiovascular outcomes.

The Effect of FTY720 on Sphingolipid Imbalance and Cognitive Decline in Aged EFAD Mice

Background

During Alzheimer's disease (AD) progression, there is a decline in the bioactive sphingolipid sphingosine-1-phosphate (S1P). Previous research showed that FTY720, an S1P mimetic, prevented cognitive decline and reduced ceramide levels in transgenic mice with familial AD carrying the human APOE4 gene (E4FAD) at 6-7 months of age.

Objective

The objective of this study is to explore the protective effects of FTY720 at late-stage AD.

Methods

Male mice aged 9.5 to 10.5 months were orally administered FTY720 (0.1 mg/kg) via oral gavage for 6 weeks. A pre-test of water maze was used for evaluating the pathological status. After 4 weeks of administration, memory, locomotion, and anxiety were assessed. Cortex samples were analyzed for amyloid-β (Aβ) and sphingolipid levels.

Results

Compared with APOE3 mice, APOE4, E3FAD and E4FAD mice exhibited significant memory deficits. After 6 weeks administration, FTY720 did not alleviate memory deficits in EFAD mice. Lipid analysis revealed that S1P was significantly reduced in EFAD mice (E3FAD or E4FAD) compared to controls (APOE3 and APOE4). Ceramide level alterations were predominantly dependent on APOE isoforms rather than AD transgenes. Interestingly, Cer (d18 : 1/22 : 1) was elevated in APOE4 mice compared to APOE3, and FTY720 reduced it.

Conclusions

E4FAD and APOE4 mice exhibited significant spatial memory deficits and higher ceramide concentrations compared to APOE3 mice. FTY720 did not reverse memory deficits in E4FAD and APOE4 mice but reduced specific ceramide species. This study provides insights into the association between sphingolipids and APOE4 in advanced AD stages, exploring potential therapeutic targeting of sphingolipid metabolism.

Deciphering the role of sphingolipid metabolism in the immune microenvironment and prognosis of esophageal cancer via single-cell sequencing and bulk data analysis

BACKGROUND

Esophageal squamous cell carcinoma (ESCC) stands as a significant global health challenge, distinguished by its aggressive progression from the esophageal epithelium. Central to this malignancy is sphingolipid metabolism, a critical pathway that governs key cellular processes, including apoptosis and immune regulation, thereby influencing tumor behavior. The advent of single-cell and transcriptome sequencing technologies has catalyzed significant advancements in oncology research, offering unprecedented insights into the molecular underpinnings of cancer.

METHODS

We explored sphingolipid metabolism-related genes in ESCC using scRNA-seq data from GEO and transcriptome data from TCGA. We assessed 97 genes in epithelial cells with AUCell, UCell, and singscore algorithms, followed by bulk RNA-seq and differential analysis to identify prognosis-related genes. Immune infiltration and potential immunotherapeutic strategies were also investigated, and tumor gene mutations and drug treatment strategies were analyzed.

RESULT

Our study identified distinct gene expression patterns, highlighting ARSD, CTSA, DEGS1, and PPTQ's roles in later cellular stages. We identified seven independent prognostic genes and created a precise nomogram for prognosis.

CONCLUSION

This study integrates single-cell and transcriptomic data to provide a reliable prognostic model associated with sphingolipid metabolism and to inform immunotherapy and pharmacotherapy for ESCC at the genetic level. The findings have significant implications for precision therapy in esophageal cancer.

Lipid remodeling in acrosome exocytosis: unraveling key players in the human sperm

It has long been thought that exocytosis was driven exclusively by well-studied fusion proteins. Some decades ago, the role of lipids became evident and escalated interest in the field. Our laboratory chose a particular cell to face this issue: the human sperm. What makes this cell special? Sperm, as terminal cells, are characterized by their scarcity of organelles and the complete absence of transcriptional and translational activities. They are specialized for a singular membrane fusion occurrence: the exocytosis of the acrosome. This unique trait makes them invaluable for the study of exocytosis in isolation. We will discuss the lipids' role in human sperm acrosome exocytosis from various perspectives, with a primary emphasis on our contributions to the field. Sperm cells have a unique lipid composition, very rare and not observed in many cell types, comprising a high content of plasmalogens, long-chain, and very-long-chain polyunsaturated fatty acids that are particular constituents of some sphingolipids. This review endeavors to unravel the impact of membrane lipid composition on the proper functioning of the exocytic pathway in human sperm and how this lipid dynamic influences its fertilizing capability. Evidence from our and other laboratories allowed unveiling the role and importance of multiple lipids that drive exocytosis. This review highlights the role of cholesterol, diacylglycerol, and particular phospholipids like phosphatidic acid, phosphatidylinositol 4,5-bisphosphate, and sphingolipids in driving sperm acrosome exocytosis. Furthermore, we provide a comprehensive overview of the factors and enzymes that regulate lipid turnover during the exocytic course. A more thorough grasp of the role played by lipids transferred from sperm can provide insights into certain causes of male infertility. It may lead to enhancements in diagnosing infertility and techniques like assisted reproductive technology (ART).