Sphingolipid metabolites as potential circulating biomarkers for sarcopenia in men.

BACKGROUND: Sarcopenia is an age-related progressive loss of muscle mass and function. Sarcopenia is a multifactorial disorder, including metabolic disturbance; therefore, metabolites may be used as circulating biomarkers for sarcopenia. We aimed to investigate potential biomarkers of sarcopenia using metabolomics. METHODS: After non-targeted metabolome profiling of plasma from mice of an aging mouse model of sarcopenia, sphingolipid metabolites and muscle cells from the animal model were evaluated using targeted metabolome profiling. The associations between sphingolipid metabolites identified from mouse and cell studies and sarcopenia status were assessed in men in an age-matched discovery (72 cases and 72 controls) and validation (36 cases and 128 controls) cohort; women with sarcopenia (36 cases and 36 controls) were also included as a discovery cohort. RESULTS: Both non-targeted and targeted metabolome profiling in the experimental studies showed an association between sphingolipid metabolites, including ceramides (CERs) and sphingomyelins (SMs), and sarcopenia. Plasma SM (16:0), CER (24:1), and SM (24:1) levels in men with sarcopenia were significantly higher in the discovery cohort than in the controls (all P < 0.05). There were no significant differences in plasma sphingolipid levels for women with or without sarcopenia. In men in the discovery cohort, an area under the receiver-operating characteristic curve (AUROC) of SM (16:0) for low muscle strength and low muscle mass was 0.600 (95% confidence interval [CI]: 0.501-0.699) and 0.647 (95% CI: 0.557-0.737). The AUROC (95% CI) of CER (24:1) and SM (24:1) for low muscle mass in men was 0.669 (95% CI: 0.581-0.757) and 0.670 (95% CI: 0.582-0.759), respectively. Using a regression equation combining CER (24:1) and SM (16:0) levels, a sphingolipid (SphL) score was calculated; an AUROC of the SphL score for sarcopenia was 0.712 (95% CI: 0.626-0.798). The addition of the SphL score to HGS significantly improved the AUC from 0.646 (95% CI: 0.575-0.717; HGS only) to 0.751 (95% CI: 0.671-0.831, P = 0.002; HGS + SphL) in the discovery cohort. The predictive ability of the SphL score for sarcopenia was confirmed in the validation cohort (AUROC = 0.695, 95% CI: 0.591-0.799). CONCLUSIONS: SM (16:0), reflecting low muscle strength, and CER (24:1) and SM (16:0), reflecting low muscle mass, are potential circulating biomarkers for sarcopenia in men. Further research on sphingolipid metabolites is required to confirm these results and provide additional insights into the metabolomic changes relevant to the pathogenesis and diagnosis of sarcopenia.

Integrative analysis of bulk and single-cell RNA sequencing reveals sphingolipid metabolism and immune landscape in clear cell renal cell carcinoma.

Clear cell renal cell carcinoma (ccRCC) is characterized by its aggressive behavior and complex molecular heterogeneity, posing significant challenges for treatment and prognostication. This study offers a comprehensive analysis of ccRCC by leveraging both bulk and single-cell RNA sequencing data, with a specific aim to unravel the complexities of sphingolipid metabolism and the intricate dynamics within the tumor microenvironment (TME). By examining ccRCC samples sourced from public databases, our investigation delves deep into the genetic and transcriptomic landscape of this cancer type. Employing advanced analytical techniques, we have identified pivotal patterns in gene expression and cellular heterogeneity, with a special focus on the roles and interactions of various immune cells within the TME. Significantly, our research has unearthed insights into the dynamics of sphingolipid metabolism in ccRCC, shedding light on its potential implications for tumor progression and strategies for immune evasion. A novel aspect of this study is the development of a risk score model designed to enhance prognostic predictions for ccRCC patients, which is currently pending external validation to ascertain its clinical utility. Despite its contributions, the study is mindful of its limitations, including a reliance on observational data from public sources and a primary focus on RNA sequencing data, which may constrain the depth and generalizability of the findings. The study does not encompass critical aspects, such as protein expression, posttranslational modifications, and comprehensive metabolic profiles. Moreover, its retrospective design underscores the necessity for future prospective studies to solidify these preliminary conclusions. Our findings illuminate the intricate interplay between genetic alterations, sphingolipid metabolism, and immune responses in ccRCC. This research not only enhances our understanding of the molecular foundations of ccRCC but also paves the way for the development of targeted therapies and personalized treatment modalities. The study underlines the importance of cautious interpretation of results and champions ongoing research using diverse methodologies to thoroughly comprehend and effectively combat this formidable cancer type.

The relationship between sphingomyelin and ceramide levels and soft neurological signs in ADHD.

Attention deficit hyperactivity disorder (ADHD), characterized by attention deficit, hyperactivity, and impulsivity, has recently been associated with lipid metabolism. In particular, the roles of sphingomyelin, ceramide, andgalactosylceramidase in the pathophysiology of ADHD are being investigated. This study aims to explore the relationship between sphingolipid metabolism markers and soft neurological signs (SNS) in children diagnosed with ADHD who are not undergoing medication treatment. A cross-sectional analysis was conducted on 41 children and adolescents aged 7-12 years diagnosed with ADHD and 39 neurotypically developing controls. Plasma levels of ceramide, sphingomyelin, and galactosylceramidase were measuredusing Enzyme-Linked Immunosorbent Assay (ELISA). SNS were assessed using the Physical and Neurological Examination for Soft Signs (PANESS). Statistical analyses included Student's t-tests, Mann-Whitney U tests, and Multivariate Analysis ofCovariance (MANCOVA), along with logistic regression analysis. Plasma levels of ceramide and sphingomyelin in children with ADHD showed significant differences compared to the neurotypically developing control group; however, there were no significant differences in galactosylceramidase levels between the two groups. Positive correlations were found between plasma levels of ceramide and sphingomyelin and the PANESS subscales F1 (Total Gait and Station) and F3 (Total Dysrhythmia). Additionally, logistic regression analysis indicated that high ceramide levels were positively associated with ADHD. This study underscores a significant association between alterations in sphingolipid metabolism (specifically increased levels of ceramide and sphingomyelin) and the presence of SNS in children with ADHD. These findings elucidate the potential role of sphingolipid metabolism in the pathophysiology of ADHD and provide suggestions for future therapeutic research targeting sphingolipid metabolism in the treatment of ADHD.

Crossing the membrane - what does it take to flip a phospholipid? Structural and biochemical advances on P4-ATPase flippases.

Membrane asymmetry is critical for maintenance of several different processes such as cell signalling, apoptosis, and vesicular transport in various eukaryotic systems. Flippases of the P4-ATPase family are associated with flipping phospholipids from the luminal or exoplasmic leaflet to the cytosolic leaflet. P4-ATPases belong to the P-type ATPase family, which are activated by phosphorylation and couple ATPase activity to substrate translocation. These proteins possess a transmembrane domain responsible for substrate transport, while the cytosolic machinery perform the necessary ATP hydrolysis for this process. Several high-resolution structures of human or yeast P4-ATPases have recently been resolved, but a comprehensive overview of the changes for reaction cycle in different members was crucial for future research. In this review, we have compiled available data reflecting the reaction cycle-associated changes in conformation of P4-ATPases. Together, this will provide an improved understanding of the similarities and differences between these members, which will drive further structural, functional and computational studies to understand the mechanisms of these flippases.

Functional Insights into the Sphingolipids C1P, S1P, and SPC in Human Fibroblast-like Synoviocytes by Proteomic Analysis.

The (patho)physiological function of the sphingolipids ceramide-1-phosphate (C1P), sphingosine-1-phosphate (S1P), and sphingosylphosphorylcholine (SPC) in articular joints during osteoarthritis (OA) is largely unknown. Therefore, we investigated the influence of these lipids on protein expression by fibroblast-like synoviocytes (FLSs) from OA knees. Cultured human FLSs (n = 7) were treated with 1 of 3 lipid species-C1P, S1P, or SPC-IL-1ß, or with vehicle. The expression of individual proteins was determined by tandem mass tag peptide labeling followed by high-resolution electrospray ionization (ESI) mass spectrometry after liquid chromatographic separation (LC-MS/MS/MS). The mRNA levels of selected proteins were analyzed using RT-PCR. The 3sphingolipids were quantified in the SF of 18 OA patients using LC-MS/MS. A total of 4930 proteins were determined using multiplex MS, of which 136, 9, 1, and 0 were regulated both reproducibly and significantly by IL-1ß, C1P, S1P, and SPC, respectively. In the presence of IL-1ß, all 3 sphingolipids exerted ancillary effects. Only low SF levels of C1P and SPC were found. In conclusion, the 3 lipid species regulated proteins that have not been described in OA. Our results indicate that charged multivesicular body protein 1b, metal cation symporter ZIP14, glutamine-fructose-6-P transaminase, metallothionein-1F and -2A, ferritin, and prosaposin are particularly interesting proteins due to their potential to affect inflammatory, anabolic, catabolic, and apoptotic mechanisms.

Fine-tuned protein-lipid interactions in biological membranes: exploration and implications of the ORMDL-ceramide negative feedback loop in the endoplasmic reticulum.

Biological membranes consist of a lipid bilayer in which integral membrane proteins are embedded. Based on the compositional complexity of the lipid species found in membranes, and on their specific and selective interactions with membrane proteins, we recently suggested that membrane bilayers can be best described as "finely-tuned molecular machines." We now discuss one such set of lipid-protein interactions by describing a negative feedback mechanism operating in the de novo sphingolipid biosynthetic pathway, which occurs in the membrane of the endoplasmic reticulum, and describe the atomic interactions between the first enzyme in the pathway, namely serine palmitoyl transferase, and the product of the fourth enzyme in the pathway, ceramide. We explore how hydrogen-bonding and hydrophobic interactions formed between Asn13 and Phe63 in the serine palmitoyl transferase complex and ceramide can influence the ceramide content of the endoplasmic reticulum. This example of finely-tuned biochemical interactions raises intriguing mechanistic questions about how sphingolipids and their biosynthetic enzymes could have evolved, particularly in light of their metabolic co-dependence.

Involvement of lipid-translocating exporter family proteins in determination of myriocin sensitivity in budding yeast.

Myriocin is an inhibitor of serine palmitoyltransferase involved in the initial biosynthetic step for sphingolipids, and causes potent growth inhibition in eukaryotic cells. In budding yeast, Rsb1, Rta1, Pug1, and Ylr046c are known as the Lipid-Translocating Exporter (LTE) family and believed to contribute to export of various cytotoxic lipophilic compounds. It was reported that Rsb1 is a transporter responsible for export of intracellularly accumulated long-chain bases, which alleviate the cytotoxicity. In this study, it was found that LTE family genes are involved in determination of myriocin sensitivity in yeast. Analyses of effects of deletion and overexpression of LTE family genes suggested that all LTEs contribute to suppression of cytotoxicity of myriocin. It was confirmed that RSB1 overexpression suppressed reduction in complex sphingolipid levels caused by myriocin treatment, possibly exporting myriocin to outside of the cell. These results suggested that LTE family genes function as a defense mechanism against myriocin.

Functional characterization of two survival factor 1 genes in Mucor lusitanicus.

Survival factor 1 (Svf1) protein has been described in some ascomycetous fungi where it was found to be contributing to several essential physiological processes, such as response to osmotic, oxidative and cold stresses, sphingolipid biosynthesis, morphogenesis, sporulation, antifungal resistance, and pathogenicity. It was also suggested that it can be a novel central regulator affecting the expression of various genes. In the present study, function of this protein and the encoding genes is described for the first time in a fungus (i.e., in Mucor lusitanicus) belonging to the order Mucorales. M. lusitanicus has two putative svf1 genes named svf1a and svf1b. Expression of both genes was proven. Although the expression of svf1a was affected by several environmental stresses and knocking out the gene affected adaptation to low temperatures and the sporulation ability, the main survival factor functions, such as participation in the maintenance of the viability, the response to oxidative and cold stresses, and the sphingolipid biosynthesis, could be associated with Svf1b, suggesting a central regulatory role to this protein. Interestingly, knockout of both genes affected the pathogenicity of the fungus in a Drosophila model. IMPORTANCE: Mucor lusitanicus is a widely used model organism to study various biological processes in the basal fungal group Mucorales. Several members of this group can be agents of mucormycosis, an opportunistic fungal infection, which is associated with high mortality, rapid progression, and wide resistance to the commonly used antifungal agents. Svf1 proteins have so far only been identified in fungi, where they have been involved in pathogenicity and resistance to antifungal agents in many cases. Only a limited number of factors affecting the stress response, antifungal resistance, and virulence of Mucorales fungi have been revealed. Elucidating the function of a fungus-specific protein that may regulate these processes may bring us closer to understanding the pathogenesis of these fungi.

Thyroid hormone receptor-beta agonist HSK31679 alleviates MASLD by modulating gut microbial sphingolipids.

BACKGROUND & AIMS: As the first approved medication for metabolic dysfunction-associated steatohepatitis (MASH), thyroid hormone receptor-beta (THR-ß) agonist MGL-3196 (Resmetirom) is highly spotlighted as the liver-directed, bioactive oral drug. However, it was also identified with remarkable heterogeneity of individual clinical efficacy and its interference with gut microbiota in host hepatoenteral circulation was still undocumented. METHODS: We compared MASH attenuation by MGL-3196 and its derivative drug HSK31679 between germ-free (GF) and specific-pathogen free (SPF) mice to evaluate the role of gut microbiota. Then cross-omics analyses of microbial metagenome, metabolome and single-cell RNA-sequencing were applied into the randomized, double-blind, placebo-controlled multiple-ascending-dose (MAD) cohort of HSK31679 treatment (n = 40), to comprehensively investigate the altered gut microbiota metabolism and circulating immune signatures. RESULTS: HSK31679 outperformed MGL-3196 in ameliorating MASH diet-induced steatohepatitis of SPF mice but not GF mice. In the MAD cohort of HSK31679, relative abundance of B. thetaiotaomicron was significantly enriched to impair glucosylceramide synthase (GCS)-catalyzed monoglucosylation of microbial Cer(d18:1/16:0) and Cer(d18:1/24:1). In stark contrast to the non-inferiority MASH resolution between MGL-3196 and HSK31679 for GFBTΔGCS mice, HSK31679 manifested superior steatohepatitis alleviation than MGL-3196 for GFBTWT mice, due to its steric hindrance with R123 and Y401 of gut microbial GCS. For participants with high fecal GCS activity, the administration of 160 mg HSK31679 induced a shift in peripheral compartments towards an immunosuppressive niche, characterized by decreased CD8α+ dendritic cells and MINCLE+ macrophages. CONCLUSIONS: This study provided novel insights into the indispensable gut microbiota for HSK31679 treatment, which revealed microbial GCS may serve as its prognostic biomarker of MASH treatment, as well as the new target for further strategies of microbiota-based MASH therapeutics. IMPACT AND IMPLICATIONS: Remarkable heterogeneity of individual clinical efficacy of THR-ß agonists and their interferences with microbiome in host hepatoenteral circulation are poorly understood. In our current germ-free mice models and randomized, double-blind multiple-dose cohort study, we identified microbial GCS as the prognostic biomarker of HSK31679 treatment, as well as the new target for further strategies of microbiota-based MASLD therapeutics.

Leech Poecilobdella manillensis protein extract ameliorated hyperuricemia by restoring gut microbiota dysregulation and affecting serum metabolites.

BACKGROUND: Hyperuricemia (HUA) is a public health concern that needs to be solved urgently. The lyophilized powder of Poecilobdella manillensis has been shown to significantly alleviate HUA; however, its underlying metabolic regulation remains unclear. AIM: To explore the underlying mechanisms of Poecilobdella manillensis in HUA based on modulation of the gut microbiota and host metabolism. METHODS: A mouse model of rapid HUA was established using a high-purine diet and potassium oxonate injections. The mice received oral drugs or saline. Additionally, 16S rRNA sequencing and ultra-high performance liquid chromatography with quadrupole time-of-flight mass spectrometry-based untargeted metabolomics were performed to identify changes in the microbiome and host metabolome, respectively. The levels of uric acid transporters and epithelial tight junction proteins in the renal and intestinal tissues were analyzed using an enzyme-linked immunosorbent assay. RESULTS: The protein extract of Poecilobdella manillensis lyophilized powder (49 mg/kg) showed an enhanced anti-trioxypurine ability than that of allopurinol (5 mg/kg) (P < 0.05). A total of nine bacterial genera were identified to be closely related to the anti-trioxypurine activity of Poecilobdella manillensis powder, which included the genera of Prevotella, Delftia, Dialister, Akkermansia, Lactococcus, Escherichia_Shigella, Enterococcus, and Bacteroides. Furthermore, 22 metabolites in the serum were found to be closely related to the anti-trioxypurine activity of Poecilobdella manillensis powder, which correlated to the Kyoto Encyclopedia of Genes and Genomes pathways of cysteine and methionine metabolism, sphingolipid metabolism, galactose metabolism, and phenylalanine, tyrosine, and tryptophan biosynthesis. Correlation analysis found that changes in the gut microbiota were significantly related to these metabolites. CONCLUSION: The proteins in Poecilobdella manillensis powder were effective for HUA. Mechanistically, they are associated with improvements in gut microbiota dysbiosis and the regulation of sphingolipid and galactose metabolism.

Concomitant targeting of FLT3 and SPHK1 exerts synergistic cytotoxicity in FLT3-ITD+ acute myeloid leukemia by inhibiting ß-catenin activity via the PP2A-GSK3ß axis.

BACKGROUND: Approximately 25-30% of patients with acute myeloid leukemia (AML) have FMS-like receptor tyrosine kinase-3 (FLT3) mutations that contribute to disease progression and poor prognosis. Prolonged exposure to FLT3 tyrosine kinase inhibitors (TKIs) often results in limited clinical responses due to diverse compensatory survival signals. Therefore, there is an urgent need to elucidate the mechanisms underlying FLT3 TKI resistance. Dysregulated sphingolipid metabolism frequently contributes to cancer progression and a poor therapeutic response. However, its relationship with TKI sensitivity in FLT3-mutated AML remains unknown. Thus, we aimed to assess mechanisms of FLT3 TKI resistance in AML. METHODS: We performed lipidomics profiling, RNA-seq, qRT-PCR, and enzyme-linked immunosorbent assays to determine potential drivers of sorafenib resistance. FLT3 signaling was inhibited by sorafenib or quizartinib, and SPHK1 was inhibited by using an antagonist or via knockdown. Cell growth and apoptosis were assessed in FLT3-mutated and wild-type AML cell lines via Cell counting kit-8, PI staining, and Annexin-V/7AAD assays. Western blotting and immunofluorescence assays were employed to explore the underlying molecular mechanisms through rescue experiments using SPHK1 overexpression and exogenous S1P, as well as inhibitors of S1P2, ß-catenin, PP2A, and GSK3ß. Xenograft murine model, patient samples, and publicly available data were analyzed to corroborate our in vitro results. RESULTS: We demonstrate that long-term sorafenib treatment upregulates SPHK1/sphingosine-1-phosphate (S1P) signaling, which in turn positively modulates ß-catenin signaling to counteract TKI-mediated suppression of FLT3-mutated AML cells via the S1P2 receptor. Genetic or pharmacological inhibition of SPHK1 potently enhanced the TKI-mediated inhibition of proliferation and apoptosis induction in FLT3-mutated AML cells in vitro. SPHK1 knockdown enhanced sorafenib efficacy and improved survival of AML-xenografted mice. Mechanistically, targeting the SPHK1/S1P/S1P2 signaling synergizes with FLT3 TKIs to inhibit ß-catenin activity by activating the protein phosphatase 2 A (PP2A)-glycogen synthase kinase 3ß (GSK3ß) pathway. CONCLUSIONS: These findings establish the sphingolipid metabolic enzyme SPHK1 as a regulator of TKI sensitivity and suggest that combining SPHK1 inhibition with TKIs could be an effective approach for treating FLT3-mutated AML.

Sphingosine Kinase 2 Regulates Aryl Hydrocarbon Receptor Nuclear Translocation and Target Gene Activation.

Sphingolipids play vital roles in metabolism and regulation. Previously, the aryl hydrocarbon receptor (AHR), a ligand-activated transcription factor, was reported to directly regulate ceramide synthesis genes by binding to their promoters. Herein, sphingosine kinase 2 (SPHK2), responsible for producing sphingosine-1-phosphate (S1P), was found to interact with AHR through LXXLL motifs, influencing AHR nuclear localization. Through mutagenesis and co-transfection studies, AHR activation and subsequent nuclear translocation was hindered by SPHK2 LXXLL mutants or SPHK2 lacking a nuclear localization signal (NLS). Similarly, an NLS-deficient AHR mutant impaired SPHK2 nuclear translocation. Silencing SPHK2 reduced AHR expression and its target gene CYP1A1, while SPHK2 overexpression enhanced AHR activity. SPHK2 was found enriched on the CYP1A1 promoter, underscoring its role in AHR target gene activation. Additionally, S1P rapidly increased AHR expression at both the mRNA and protein levels and promoted AHR recruitment to the CYP1A1 promoter. Using mouse models, AHR deficiency compromised SPHK2 nuclear translocation, illustrating a critical interaction where SPHK2 facilitates AHR nuclear localization and supports a positive feedback loop between AHR and sphingolipid enzyme activity in the nucleus. These findings highlight a novel function of SPHK2 in regulating AHR activity and gene expression.

Transcriptomics pave the way into mechanisms of cobalt and nickel toxicity: Nrf2-mediated cellular responses in liver carcinoma cells.

Cobalt (Co) and Nickel (Ni) are used nowadays in various industrial applications like lithium-ion batteries, raising concerns about their environmental release and public health threats. Both metals are potentially carcinogenic and may cause neurological and cardiovascular dysfunctions, though underlying toxicity mechanisms have to be further elucidated. This study employs untargeted transcriptomics to analyze downstream cellular effects of individual and combined Co and Ni toxicity in human liver carcinoma cells (HepG2). The results reveal a synergistic effect of Co and Ni, leading to significantly higher number of differentially expressed genes (DEGs) compared to individual exposure. There was a clear enrichment of Nrf2 regulated genes linked to pathways such as glycolysis, iron and glutathione metabolism, and sphingolipid metabolism, confirmed by targeted analysis. Co and Ni exposure alone and combined caused nuclear Nrf2 translocation, while only combined exposure significantly affects iron and glutathione metabolism, evidenced by upregulation of HMOX-1 and iron storage protein FTL. Both metals impact sphingolipid metabolism, increasing dihydroceramide levels and decreasing ceramides, sphingosine and lactosylceramides, along with diacylglycerol accumulation. By combining transcriptomics and analytical methods, this study provides valuable insights into molecular mechanisms of Co and Ni toxicity, paving the way for further understanding of metal stress.

Heavy Metal Exposure-Mediated Dysregulation of Sphingolipid Metabolism.

Exposure to heavy metals (HMs) is often associated with inflammation and cell death, exacerbating respiratory diseases including asthma. Most inhaled particulate HM exposures result in the deposition of HM-bound fine particulate matter, PM2.5, in pulmonary cell populations. While localized high concentrations of HMs may be a causative factor, existing studies have mostly evaluated the effects of systemic or low-dose chronic HM exposures. This report investigates the impact of local high concentrations of specific HMs (NaAsO2, MnCl2, and CdCl2) on sphingolipid homeostasis and oxidative stress, as both play a role in mediating responses to HM exposure and have been implicated in asthma. Utilizing an in vitro model system and three-dimensional ex vivo human tissue models, we evaluated the expression of enzymatic regulators of the salvage, recycling, and de novo synthesis pathways of sphingolipid metabolism, and observed differential modulation in these enzymes between HM exposures. Sphingolipidomic analyses of specific HM-exposed cells showed increased levels of anti-apoptotic sphingolipids and reduced pro-apoptotic sphingolipids, suggesting activation of the salvage and de novo synthesis pathways. Differential sphingolipid regulation was observed within HM-exposed lung tissues, with CdCl2 exposure and NaAsO2 exposure activating the salvage and de novo synthesis pathway, respectively. Additionally, using spatial transcriptomics and quantitative real-time PCR, we identified HM exposure-induced transcriptomic signatures of oxidative stress in epithelial cells and human lung tissues.

Identifying distinct markers in two Sorghum varieties for baijiu fermentation using untargeted metabolomics and molecular network approaches.

The quality of strong-flavor Baijiu, a prominent Chinese liquor, is intricately tied to the choice of sorghum variety used in fermentation. However, a significant gap remains in our understanding of how glutinous and non-glutinous sorghum varieties comprehensively impact Baijiu flavor formation through fermentation metabolites. This study employed untargeted metabolomics combined with feature-based molecular networking (FBMN) to explore the unique metabolic characteristics of these two sorghum varieties during fermentation. FBMN analysis revealed 267 metabolites within both types of fermented sorghum (Zaopei) in the cellar. Further multidimensional statistical analyses highlighted sphingolipids, 2,5-diketopiperazines, and methionine derivatives as critical markers for quality control. These findings represent a significant advancement in our understanding and provide valuable insights for regulating the quality of Baijiu flavors.

Circulating sphingolipids in relation to cognitive decline and incident dementia: The Cardiovascular Health Study.

INTRODUCTION: Whether circulating levels of sphingolipids are prospectively associated with cognitive decline and dementia risk is uncertain. METHODS: We measured 14 sphingolipid species in plasma samples from 4488 participants (mean age 76.2 years; 40% male; and 25% apolipoprotein E (APOE) ε4 allele carriers). Cognitive decline was assessed annually across 6 years using modified Mini-Mental State Examination (3MSE) and Digital Symbol Substitution Test (DSST). Additionally, a subset of 3050 participants were followed for clinically adjudicated dementia. RESULTS: Higher plasma levels of sphingomyelin-d18:1/16:0 (SM-16) were associated with a faster cognitive decline measured with 3MSE, in contrast, higher levels of sphingomyelin-d18:1/22:0 (SM-22) were associated with slower decline in cognition measured with DSST. In Cox regression, higher levels of SM-16 (hazard ration [HR] = 1.24 [95% confidence interval [CI]: 1.08-1.44]) and ceramide-d18:1/16:0 (Cer-16) (HR = 1.26 [95% CI: 1.10-1.45]) were associated with higher risk of incident dementia. DISCUSSION: Several sphingolipid species appear to be involved in cognitive decline and dementia risk. Highlights: Plasma levels of sphingolipids were associated with cognitive decline and dementia risk.Ceramides and sphingomyelins with palmitic acid were associated with faster annual cognitive decline and increased risk of dementia.The direction of association depended on the covalently bound saturated fatty acid chain length in analysis of cognitive decline.

Glutamate, Gangliosides, and the Synapse: Electrostatics at Work in the Brain.

The synapse is a piece of information transfer machinery replacing the electrical conduction of nerve impulses at the end of the neuron. Like many biological mechanisms, its functioning is heavily affected by time constraints. The solution selected by evolution is based on chemical communication that, in theory, cannot compete with the speed of nerve conduction. Nevertheless, biochemical and biophysical compensation mechanisms mitigate this intrinsic weakness: (i) through the high concentrations of neurotransmitters inside the synaptic vesicles; (ii) through the concentration of neurotransmitter receptors in lipid rafts, which are signaling platforms; indeed, the presence of raft lipids, such as gangliosides and cholesterol, allows a fine tuning of synaptic receptors by these lipids; (iii) through the negative electrical charges of the gangliosides, which generate an attractive (for cationic neurotransmitters, such as serotonin) or repulsive (for anionic neurotransmitters, such as glutamate) electric field. This electric field controls the flow of glutamate in the tripartite synapse involving pre- and post-synaptic neurons and the astrocyte. Changes in the expression of brain gangliosides can disrupt the functioning of the glutamatergic synapse, causing fatal diseases, such as Rett syndrome. In this review, we propose an in-depth analysis of the role of gangliosides in the glutamatergic synapse, highlighting the primordial and generally overlooked role played by the electric field of synaptic gangliosides.

Multi-omic validation of the cuproptosis-sphingolipid metabolism network: modulating the immune landscape in osteosarcoma.

Background: The current understanding of the mechanisms by which metal ion metabolism promotes the progression and drug resistance of osteosarcoma remains incomplete. This study aims to elucidate the key roles and mechanisms of genes involved in cuproptosis-related sphingolipid metabolism (cuproptosis-SPGs) in regulating the immune landscape, tumor metastasis, and drug resistance in osteosarcoma cells. Methods: This study employed multi-omics approaches to assess the impact of cuproptosis-SPGs on the prognosis of osteosarcoma patients. Lasso regression analysis was utilized to construct a prognostic model, while multivariate regression analysis was applied to identify key core genes and generate risk coefficients for these genes, thereby calculating a risk score for each osteosarcoma patient. Patients were then stratified into high-risk and low-risk groups based on their risk scores. The ESTIMATE and CIBERSORT algorithms were used to analyze the level of immune cell infiltration within these risk groups to construct the immune landscape. Single-cell analysis was conducted to provide a more precise depiction of the expression patterns of cuproptosis-SPGs among immune cell subtypes. Finally, experiments on osteosarcoma cells were performed to validate the role of the cuproptosis-sphingolipid signaling network in regulating cell migration and apoptosis. Results: In this study, seven cuproptosis-SPGs were identified and used to construct a prognostic model for osteosarcoma patients. In addition to predicting survival, the model also demonstrated reliability in forecasting the response to chemotherapy drugs. The results showed that a high cuproptosis-sphingolipid metabolism score was closely associated with reduced CD8 T cell infiltration and indicated poor prognosis in osteosarcoma patients. Cellular functional assays revealed that cuproptosis-SPGs regulated the LC3B/ERK signaling pathway, thereby triggering cell death and impairing migration capabilities in osteosarcoma cells. Conclusion: The impact of cuproptosis-related sphingolipid metabolism on the survival and migration of osteosarcoma cells, as well as on CD8 T cell infiltration, highlights the potential of targeting copper ion metabolism as a promising strategy for osteosarcoma patients.

Analysis of Lipid GPCR Molecular Interactions by Proximity Labeling.

G-protein-coupled receptors (GPCRs) are hepta-helical transmembrane proteins that mediate various intracellular signaling events in response to their specific ligands including many lipid mediators. Although analyses of GPCR molecular interactions are pivotal to understanding diverse intracellular signaling events, affinity purification of interacting proteins by a conventional co-immunoprecipitation method is challenging due to the hydrophobic nature of GPCRs and their dynamic molecular interactions. Proximity labeling catalyzed by a TurboID system is a powerful technique for defining the molecular interactions of target proteins in living cells. TurboID and miniTurbo (a modified version of TurboID) are engineered biotin ligases that biotinylate neighboring proteins in a promiscuous manner. When fused with a target protein and expressed in living cells, TurboID or miniTurbo mediates the biotin labeling of the proteins with close proximity to the target protein, allowing efficient purification of the biotinylated proteins followed by a shot-gun proteomic analysis. In this chapter, we describe a step-by-step protocol for the labeling of GPCR neighboring proteins by TurboID or miniTurbo, purification of the biotin-labeled proteins, and subsequent sample preparation for proteomic analysis. We utilized S1PR1 as a model GPCR, a receptor for a bioactive lipid molecule sphingosine 1-phosphate (S1P) that plays various roles in physiological and pathological conditions. This analysis pipeline enables the mapping of interacting proteins of lipid GPCRs in living cells.

Comprehensive metabolic modulations of sphingolipids are promising severity indicators in COVID-19.

The COVID-19 pandemic, caused by SARS-CoV-2, has had a significant worldwide impact, affecting millions of people. COVID-19 is characterized by a heterogenous clinical phenotype, potentially involving hyperinflammation and prolonged tissue damage, although the exact underlying mechanisms are yet to be fully understood. Sphingolipid metabolites, which govern cell survival and proliferation, have emerged as key players in inflammatory signaling and cytokine responses. Given the complex metabolic pathway of sphingolipids, this study aimed to understand their potential role in the pathogenesis of COVID-19. We conducted a comprehensive examination of sphingolipid modulations across groups classified based on disease severity, incorporating a time-course in serum and urine samples. Several sphingolipids, including sphingosine, lactosylceramide, and hexosylceramide, emerged as promising indicators of COVID-19 severity, as validated by correlation analyses conducted on both serum and urine samples. Other sphingolipids, such as sphingosine 1-phosphate, ceramides, and deoxy-dihydroceramides, decreased in both COVID-19 patients and individuals with non-COVID infectious diseases. This suggests that these sphingolipids are not specifically associated with COVID-19 but rather with pathological conditions caused by infectious diseases. Our analysis of urine samples revealed elevated levels of various sphingolipids, with changes dependent on disease severity, potentially highlighting the acute kidney injury associated with COVID-19. This study illuminates the intricate relationship between disturbed sphingolipid metabolism, COVID-19 severity, and clinical factors. These findings provide valuable insights into the broader landscape of inflammatory diseases.