Ceramide biogenesis is required for radiation-induced apoptosis in the germ line of C. elegans

Moderate static magnetic field modulated lipid metabolism abnormalities induced by continuous artificial light in Caenorhabditis elegans: Role of iron ions

Excessive use of artificial light sources has led to a significant increase in light pollution, which has raised serious concerns due to its serious adverse effects on lipid metabolism. Although moderate static magnetic fields (SMFs) have shown potential in health intervention and treatment as non-invasive and highly permeable physical field, the influence of SMFs on lipid metabolic disturbance induced by lights remains largely unknown. In this study, we explored the lipid metabolism of Caenorhabditis elegans (C. elegans) under varying wavelengths of light ranging from 395 nm to 635 nm, both in the presence and absence of a 0.5 T SMF, and elucidated their underlying mechanisms. Exposure of C. elegans to artificial light at 200 lux resulted in a shortened lifespan while significantly increasing fat accumulation in a wavelength-dependent manner. The presence of 0.5 T SMF significantly extended the lifespan and reduced the size of fat droplets, as well as the content of triglyceride in light exposed worms. These effects were achieved by upregulating the expression of genes related to lipolysis and downregulating the expression of genes related to lipid synthesis. Moreover, the 0.5 T SMF alleviated abnormalities in lipid metabolism caused by light through the regulation of iron ions. Our findings provided clear evidence that moderate SMFs have significant protective effects on lipid metabolism abnormalities induced by artificial light via mediating iron homeostasis, which might contribute to a better understanding of the combined photomagnetic effects in living organisms.

Causal role of plasma liposome in diabetic retinopathy: mendelian randomization (MR) study

BACKGROUND

Research indicates that there may be an association between plasma lipidome levels and the incidence of diabetic retinopathy (DR) in patients. However, the potential causality of this relationship is yet to be determined. To investigate this matter further, we employed a two-sample Mendelian randomization (MR) analysis to comprehensively assess the causality between lipidome levels and DR.

METHODS

Summary statistics for lipid levels and DR were obtained from the Genome-Wide Association Studies (GWAS) Catalog database and the FinnGen Consortium, respectively. We conducted a two-sample MR analysis, and statistical analysis were performed using the inverse variance weighted (IVW) with the addition of the MR-Egger, weighted median (WM), constrained maximum likelihood and model averaging (cML-MA) to test for causal associations between lipid levels and DR. Heterogeneity was checked using Cochran's Q statistic. The MR Pleiotropy Residual Sum and Outlier (MR-PRESSO) global test and the MR-Egger regression were used to detect horizontal pleiotropy. The robustness of our findings was assessed using leave-one-out and funnel plots. To further assess the reliability of the results, linkage disequilibrium score regressions, colocalization analysis and reverse MR analysis were also performed.

RESULTS

Analysis of the pooled MR results and after correction for the false discovery rate (FDR) revealed that five lipid levels were associated with DR risk. Phosphatidylcholine (16:0_16:0) levels [OR = 0.869 (0.810 to 0.933), Pfdr = 0.006], phosphatidylcholine (16:0_20:2) levels [OR = 0.893 (0.834 to 0.956), Pfdr = 0.043] and phosphatidylethanolamine (18:0_20:4) levels [OR = 0.906 (0.863 to 0.951), Pfdr = 0.006] were protective against DR, whereas sphingomyelin (d36:1) levels [OR = 1.120 (1.061 to 1.183), Pfdr = 0.006], and sphingomyelin (d40:1) levels [OR = 1.081 (1.031 to 1.134), Pfdr = 0.043] were associated with a greater risk of DR. Further sensitivity analysis did not reveal heterogeneity or horizontal pleiotropy.

CONCLUSION

In summary, genetic evidence suggests a causal relationship between the levels of specific lipid levels and DR. These findings may provide valuable insights into the causal relationships between lipid levels and DR, potentially informing future prevention and treatment strategies.

The potential of circulating nonesterified fatty acids and sphingolipids in the biological understanding of cognitive decline and dementia

PURPOSE OF REVIEW

Cognitive decline and late-onset dementia pose significant challenges in aging societies, and many dementia cases could be prevented or delayed through modification of associated risk factors, many of which are tied to cardiovascular and metabolic dysfunction. As individuals age, the blood-brain barrier becomes more permeable, easing the exchange of molecules between the bloodstream and the brain. Consequently, blood-based biological markers (so-called biomarkers) provide a minimally invasive and accessible means of accessing molecular changes associated with aging and neurodegeneration.

RECENT FINDINGS

Circulating free fatty acids, also called nonesterified fatty acids (NEFAs), and sphingolipids are associated with cardiovascular disease, insulin resistance, and diabetes; thus, could be promising candidates as biomarkers for cognitive decline and dementia.

SUMMARY

The opportunity to study such minimally invasive biomarkers further opens up potential new avenues for improved understanding of the underlying biology of diseases of the brain.

Synergistic Co-Cu Dual-Atom Nanozyme with Promoted Catalase-like Activity for Parkinson's Disease Treatment

Neurodegenerative diseases like Parkinson's disease (PD) are intimately associated with oxidative stress due to the excessive highly reactive oxygen species (ROS), leading to the damage of dopaminergic neurons. Herein, we develop a Co-Cu dual-atom nanozyme (CoCu-DAzyme) by uniformly anchoring Co and Cu active sites onto an AlO(OH) substrate that exhibits remarkable catalase-like catalytic activity, far exceeding that of the Co or Cu single-atom counterparts. The following density functional theory calculations reveal that the Co sites efficiently enable H2O2 adsorption, while Cu sites promote charge transfer, synergistically promoting the catalytic decomposition of H2O2 into H2O and O2. Encouragingly, the developed CoCu-DAzyme notably ameliorates α-synuclein aggregation and alleviates the motor dysfunction inCaenorhabditis elegansPD models by substantively scavenging in vivo ROS. This research shows a novel therapeutic strategy for oxidative-stress-related neurodegenerative disorders by developing well-engineered nanozymes.

Environmental Temperature Variation Affects Brain Lipid Composition in Adult Zebrafish (Danio rerio)

This study delves deeper into the impact of environmental temperature variations on the nervous system in teleost fish. Previous research has demonstrated that exposing adult zebrafish (Danio rerio) to 18 °C and 34 °C for 4 or 21 days induces behavioural changes compared to fish kept at a control temperature of 26 °C, suggesting alterations in the nervous system. Subsequent studies revealed that these temperature conditions also modify brain protein expression, indicating potential neurotoxic effects. The primary aim of this work was to investigate the effects of prolonged exposure (21 days) to 18 °C or 34 °C on the brain lipidomes of adult zebrafish compared to a control temperature. Analysis of the brain lipidome highlighted significant alteration in the relative abundances of specific lipid molecules at 18 °C and 34 °C, confirming distinct effects induced by both tested temperatures. Exposure to 18 °C resulted in an increase in levels of phospholipids, such as phosphatidylethanolamine, alongside a general reduction in levels of sphingolipids, including sphingomyelin. Conversely, exposure to 34 °C produced more pronounced effects, with increases in levels of phosphatidylethanolamine and those of various sphingolipids such as ceramide, gangliosides, and sphingomyelin, alongside a reduction in levels of ether phospholipids, including lysophosphatidylethanolamine ether, phosphatidylethanolamine ether, and phosphatidylglycerol ether, as well as levels of glycolipids like monogalactosyldiacylglycerol. These results, when integrated with existing proteomic and behavioural data, offer new insights into the effects of thermal variations on the nervous system in teleost fish. Specifically, our proteomic and lipidomic findings suggest that elevated temperatures may disrupt mitochondrial function, increase neuronal susceptibility to oxidative stress and cytotoxicity, alter axonal myelination, impair nerve impulse transmission, hinder synapse function and neurotransmitter release, and potentially lead to increased neuronal death. These findings are particularly relevant in the fields of cell biology, neurobiology, and ecotoxicology, especially in the context of global warming.

Association of circulation very long chain saturated fatty acids with depression in NHANES 2011-2014

BACKGROUND

Recent studies have shown that elevated levels of medium and long chain saturated fatty acids are associated with an increased risk of depression. However, little is known about the effect of very long chain saturated fatty acids (VLSFAs) on depression. Therefore, our study aimed to examine the association between VLSFAs and depression in the US adult population.

METHODS

A total of 2706 participants with serum VLSFAs detection from NHANES 2011-2014 were included in the study. Logistic regression models were used to evaluate the association between quartile levels of serum VLSFAs (20:0, 22:0, 23:0, 24:0, and total VLSFA) and depression.

RESULTS

After adjusting for multiple variables, we found that increased circulating levels of 22:0, 23:0, 24:0 and total VLSFA were linearly associated with a reduced risk of depression (model 3, Q4 OR: 0.658, 95 % CI: 0.438-0.989, P-trend = 0.023; OR: 0.515, 95 % CI: 0.339-0.782, P-trend<0.001; OR: 0.556, 95 % CI: 0.370-0.835, P-trend = 0.003; OR: 0.652, 95 % CI: 0.435-0.976, P-trend = 0.021, respectively). Additionally, individuals with the highest serum ratios of 22:0/16:0, 23:0/16:0, 24:0/16:0 and total VLSFA/16:0 also had a lower risk of depression after adjusting for multiple variables compared to the group with the lowest serum VLSFAs/16:0 (P-trend = 0.001, <0.001, 0.001 and 0.004, respectively). Moreover, the decreasing trend of depression associated with increased VLSFAs/18:0 remained significant.

CONCLUSION

In conclusion, our findings suggest that increased circulating levels of 22:0, 23:0, 24:0 and total VLSFA may have a protective effect against the risk of depression.

Circulating Sphingolipids and All-Cause Mortality: The Strong Heart Family Study

BACKGROUND

A growing body of research indicates that associations of ceramides and sphingomyelins with mortality depend on the chain length of the fatty acid acylated to the backbone sphingoid base. We examined associations of 8 ceramide and sphingomyelin species with mortality among an American Indian population.

METHODS AND RESULTS

The analysis comprised 2688 participants from the SHFS (Strong Heart Family Study). Plasma ceramide and sphingomyelin species carrying long-chain (ie, 16:0) and very-long-chain (ie, 20:0, 22:0, 24:0) saturated fatty acids were measured by sequential liquid chromatography and mass spectroscopy using samples from 2001 to 2003. Participants were followed for 18.8 years (2001-2020). Associations of ceramides and sphingomyelins with mortality were assessed using Cox models. The mean age of participants was 40.8 years. There were 574 deaths during a median 17.4-year follow-up. Ceramides and sphingomyelins carrying fatty acid 16:0 were positively associated with mortality. Ceramides and sphingomyelins carrying longer fatty acids were inversely associated with mortality. Per SD difference in each ceramide and sphingomyelin species, hazard ratios for death were: 1.68 (95% CI, 1.44-1.96) for ceramide-16 (Cer-16), 0.82 (95% CI, 0.71-0.95) for Cer-20, 0.60 (95% CI, 0.51-0.70) for Cer-22, 0.67 (95% CI, 0.56-0.79) for Cer-24, 1.80 (95% CI-1.57, 2.05) for sphingomyelin-16 (SM-16), 0.54 (95% CI, 0.47-0.62) for SM-20, 0.50 (95% CI, 0.44-0.57) for SM-22, and 0.59 (95% CI, 0.52-0.67) for SM-24.

CONCLUSIONS

The direction/magnitude of associations of ceramides and sphingomyelins with mortality differs according to the length of the fatty acid acylated to the backbone sphingoid base.

REGISTRATION

URL: https://www.clinicatrials.gov; Unique identifier: NCT00005134.

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.

Sphingolipid profiling reveals differential functions of sphingolipid biosynthesis isozymes of Caenorhabditis elegans

Multiple isozymes are encoded in the Caenorhabditis elegans genome for the various sphingolipid biosynthesis reactions, but the contributions of individual isozymes are characterized only in part. We developed a simple but effective reversed-phase liquid chromatography-tandem mass spectrometry (RPLC-MS/MS) method that enables simultaneous identification and quantification of ceramides (Cer), glucosylceramides (GlcCer), and sphingomyelins (SM) from the same MS run. Validating this sphingolipid profiling method, we show that nearly all 47 quantifiable sphingolipid species found in young adult worms were reduced upon RNA interference (RNAi) of sptl-1 or elo-5, which are both required for synthesis of the id17:1 sphingoid base. We also confirm that HYL-1 and HYL-2, but not LAGR-1, constitute the major ceramide synthase activity with different preference for fatty acid substrates, and that CGT-3, but not CGT-1 and CGT-2, plays a major role in producing GlcCers. Deletion of sms-5 hardly affected SM levels. RNAi of sms-1, sms-2, and sms-3 all lowered the abundance of certain SMs with an odd-numbered N-acyl chains (mostly C21 and C23, with or without hydroxylation). Unexpectedly, sms-2 RNAi and sms-3 RNAi elevated a subset of SM species containing even-numbered N-acyls. This suggests that sphingolipids containing even-numbered N-acyls could be regulated separately, sometimes in opposite directions, from those containing odd-numbered N-acyls, which are presumably monomethyl branched chain fatty acyls. We also find that ceramide levels are kept in balance with those of GlcCers and SMs. These findings underscore the effectiveness of this RPLC-MS/MS method in studies of C. elegans sphingolipid biology.

Loss of the ceramide synthase HYL-2 from Caenorhabditis elegans impairs stress responses and alters sphingolipid composition

Sphingolipids, essential membrane components and signaling molecules in cells, have ceramides at the core of their metabolic pathways. Initially termed as "longevity assurance genes", the encoding genes of ceramide synthases are closely associated with individual aging and stress responses, although the mechanisms remain unclear. This study aims to explore the alterations and underlying mechanisms of three ceramide synthases, HYL-1, HYL-2, and LAGR-1, in the aging and stress responses of Caenorhabditis elegans. Our results showed the knockdown of HYL-1 extends the lifespan and enhance stress resistance in worms, whereas the loss of HYL-2 function significantly impairs tolerances to heat, oxidation, and ultraviolet stress. Stress intolerance induced by HYL-2 deficiency may result from intracellular mitochondrial dysfunction, accumulation of reactive oxygen species, and abnormal nuclear translocation of DAF-16 under stress conditions. Loss of HYL-2 led to a significant reduction of predominant ceramides (d17:1/C20∼C23) as well as corresponding complex sphingolipids. Furthermore, the N-acyl chain length composition of sphingolipids underwent dramatic modifications, characterized by a decrease in C22 sphingolipids and an increase in C24 sphingolipids. Extra d18:1-ceramides resulted in diminished stress resilience in wild-type worms, while supplementation of d18:1/C16 ceramide to HYL-2-deficient worms marginally improved stress tolerance to heat and oxidation. These findings indicate the importance of appropriate ceramide content and composition in maintaining subcellular homeostasis and nuclear-cytoplasmic signal transduction during healthy aging and stress responses.

Advances in Engineered Nanoparticles for the Treatment of Ischemic Stroke by Enhancing Angiogenesis

Angiogenesis, or the formation of new blood vessels, is a natural defensive mechanism that aids in the restoration of oxygen and nutrition delivery to injured brain tissue after an ischemic stroke. Angiogenesis, by increasing vessel development, may maintain brain perfusion, enabling neuronal survival, brain plasticity, and neurologic recovery. Induction of angiogenesis and the formation of new vessels aid in neurorepair processes such as neurogenesis and synaptogenesis. Advanced nano drug delivery systems hold promise for treatment stroke by facilitating efficient transportation across the the blood-brain barrier and maintaining optimal drug concentrations. Nanoparticle has recently been shown to greatly boost angiogenesis and decrease vascular permeability, as well as improve neuroplasticity and neurological recovery after ischemic stroke. We describe current breakthroughs in the development of nanoparticle-based treatments for better angiogenesis therapy for ischemic stroke employing polymeric nanoparticles, liposomes, inorganic nanoparticles, and biomimetic nanoparticles in this study. We outline new nanoparticles in detail, review the hurdles and strategies for conveying nanoparticle to lesions, and demonstrate the most recent advances in nanoparticle in angiogenesis for stroke treatment.

Circulating sphingolipids and subclinical brain pathology: the cardiovascular health study

Background

Sphingolipids are implicated in neurodegeneration and neuroinflammation. We assessed the potential role of circulating ceramides and sphingomyelins in subclinical brain pathology by investigating their association with brain magnetic resonance imaging (MRI) measures and circulating biomarkers of brain injury, neurofilament light chain (NfL) and glial fibrillary acidic protein (GFAP) in the Cardiovascular Health Study (CHS), a large and intensively phenotyped cohort of older adults.

Methods

Brain MRI was offered twice to CHS participants with a mean of 5 years between scans, and results were available from both time points in 2,116 participants (mean age 76 years; 40% male; and 25% APOE ε4 allele carriers). We measured 8 ceramide and sphingomyelin species in plasma samples and examined the associations with several MRI, including worsening grades of white matter hyperintensities and ventricular size, number of brain infarcts, and measures of brain atrophy in a subset with quantitative measures. We also investigated the sphingolipid associations with serum NfL and GFAP.

Results

In the fully adjusted model, higher plasma levels of ceramides and sphingomyelins with a long (16-carbon) saturated fatty acid were associated with higher blood levels of NfL [β = 0.05, false-discovery rate corrected P (PFDR) = 0.004 and β = 0.06, PFDR = < 0.001, respectively]. In contrast, sphingomyelins with very long (20- and 22-carbon) saturated fatty acids tended to have an inverse association with levels of circulating NfL. In secondary analyses, we found an interaction between ceramide d18:1/20:0 and sex (P for interaction = <0.001), such that ceramide d18:1/20:0 associated with higher odds for infarcts in women [OR = 1.26 (95%CI: 1.07, 1.49), PFDR = 0.03]. We did not observe any associations with GFAP blood levels, white matter grade, ventricular grade, mean bilateral hippocampal volume, or total brain volume.

Conclusion

Overall, our comprehensive investigation supports the evidence that ceramides and sphingomyelins are associated with increased aging brain pathology and that the direction of association depends on the fatty acid attached to the sphingosine backbone.

Ceramides and mitochondrial homeostasis

Lipotoxicity arises from the accumulation of lipid intermediates in non-adipose tissue, precipitating cellular dysfunction and death. Ceramide, a toxic byproduct of excessive free fatty acids, has been widely recognized as a primary contributor to lipotoxicity, mediating various cellular processes such as apoptosis, differentiation, senescence, migration, and adhesion. As the hub of lipid metabolism, the excessive accumulation of ceramides inevitably imposes stress on the mitochondria, leading to the disruption of mitochondrial homeostasis, which is typified by adequate ATP production, regulated oxidative stress, an optimal quantity of mitochondria, and controlled mitochondrial quality. Consequently, this review aims to collate current knowledge and facts regarding the involvement of ceramides in mitochondrial energy metabolism and quality control, thereby providing insights for future research.

Hepatocyte-specific METTL3 ablation by Alb-iCre mice (GPT), but not by Alb-Cre mice (JAX), resulted in acute liver failure (ALF) and postnatal lethality

AIM

In 2019, to examine the functions of METTL3 in liver and underlying mechanisms, we generated mice with hepatocyte-specific METTL3 homozygous knockout (METTL3Δhep) by simultaneously crossing METTL3fl/fl mice with Alb-iCre mice (GPT) or Alb-Cre mice (JAX), respectively. In this study, we explored the potential reasons why hepatocyte-specific METTL3 homozygous disruption by Alb-iCre mice (GPT), but not by Alb-Cre mice (JAX), resulted in acute liver failure (ALF) and then postnatal lethality.

MAIN METHODS

Mice with hepatocyte-specific METTL3 knockout were generated by simultaneously crossing METTL3fl/fl mice with Alb-iCre mice (GPT; Strain No. T003814) purchased from the GemPharmatech Co., Ltd., (Nanjing, China) or with Alb-Cre mice (JAX; Strain No. 003574) obtained from The Jackson Laboratory, followed by combined-phenotype analysis. The publicly available RNA-sequencing data deposited in the NCBI Gene Expression Omnibus (GEO) database under the accession No.: GSE198512 (postnatal lethality), GSE197800 (postnatal survival) and GSE176113 (postnatal survival) were mined to explore the potential reasons why hepatocyte-specific METTL3 homozygous deletion by Alb-iCre mice (GPT), but not by Alb-Cre mice (JAX), leads to ALF and then postnatal lethality.

KEY FINDINGS

Firstly, we observed that hepatocyte-specific METTL3 homozygous deficiency by Alb-iCre mice (GPT) or by Alb-Cre mice (JAX) caused liver injury, abnormal lipid accumulation and apoptosis. Secondly, we are surprised to find that hepatocyte-specific METTL3 homozygous deletion by Alb-iCre mice (GPT), but not by Alb-Cre mice (JAX), led to ALF and then postnatal lethality. Our findings clearly demonstrated that METTL3Δhep mice (GPT), which are about to die, exhibited the severe destruction of liver histological structure, suggesting that METTL3Δhep mice (GPT) nearly lose normal liver function, which subsequently contributes to ALF, followed by postnatal lethality. Finally, we unexpectedly found that as the compensatory growth responses of hepatocytes to liver injury induced by METTL3Δhep (GPT), the proliferation of METTL3Δhep hepatocytes (GPT), unlike METTL3Δhep hepatocytes (JAX), was not evidenced by the significant increase of Ki67-positive hepatocytes, not accompanied by upregulation of cell-cycle-related genes. Moreover, GO analysis revealed that upregulated genes in METTL3Δhep livers (GPT), unlike METTL3Δhep livers (JAX), are not functionally enriched in terms associated with cell cycle, cell division, mitosis, microtubule cytoskeleton organization, spindle organization, chromatin segregation and organization, and nuclear division, consistent with the loss of compensatory proliferation of METTL3Δhep hepatocytes (GPT) observed in vivo. Thus, obviously, the loss of the compensatory growth capacity of METTL3Δhep hepatocytes (GPT) in response to liver injury might contribute to, at least partially, ALF and subsequently postnatal lethality of METTL3Δhep mice (GPT).

SIGNIFICANCE

These findings from this study and other labs provide strong evidence that these phenotypes (i.e., ALF and postnatal lethality) of METTL3Δhep mice (GPT) might be not the real functions of METTL3, and closely related with Alb-iCre mice (GPT), suggesting that we should remind researchers to use Alb-iCre mice (GPT) with caution to knockout gene in hepatocytes in vivo.

Association between the circulating very long-chain saturated fatty acid and cognitive function in older adults: findings from the NHANES

BACKGROUND

Age-related cognitive decline has a significant impact on the health and longevity of older adults. Circulating very long-chain saturated fatty acids (VLSFAs) may actively contribute to the improvement of cognitive function. The objective of this study was to investigate the associations between arachidic acid (20:0), docosanoic acid (22:0), tricosanoic acid (23:0), and lignoceric acid (24:0) with cognitive function in older adults.

METHODS

This study used a dataset derived from the 2011-2014 National Health and Nutrition Examination Survey (NHANES). A total of 806 adults (≥ 60 years) were included who underwent comprehensive cognitive testing and plasma fatty acid measurements. Multivariable linear regression, restricted cubic spline (RCS), and interaction analyses were used to assess associations between VLSFAs and cognitive function. Partial Spearman' s correlation analysis was used to examine the correlations between VLSFAs and palmitic acid (16:0), high-density lipoprotein cholesterol, low-density lipoprotein cholesterol, total cholesterol, triglycerides, systemic inflammatory markers, and dietary nutrients.

RESULTS

Multivariable linear regression analysis, adjusting for sociodemographic, clinical conditions, and lifestyle factors, showed that 22:0 and 24:0 levels were positively associated with better global cognitive function (β = 0.37, 95% confidence interval [CI] = 0.01, 0.73; β = 0.73, 95% CI = 0.29, 1.2, respectively) as well as better CEARD-DR Z-score (β = 0.82, 95% CI = 0.36, 1.3 and β = 1.2, 95% CI = 0.63, 1.8, respectively). RCS analysis showed linear associations between higher 22:0 and 24:0 levels and better cognitive performance in both global cognitive function and CERAD-DR tests.

CONCLUSIONS

The study suggests that higher levels of 22:0 and 24:0 are associated with better global cognitive function in older adults. 22:0 and 24:0 may be important biomarkers for recognizing cognitive impairment, and supplementation with specific VLSFAs (22:0 and 24:0) may be an important intervention to improve cognitive function. Further studies are needed to elucidate the underlying biological mechanisms between VLSFAs and cognitive function.

A bioinformatics approach to elucidate conserved genes and pathways in C. elegans as an animal model for cardiovascular research

Cardiovascular disease (CVD) is a collective term for disorders of the heart and blood vessels. The molecular events and biochemical pathways associated with CVD are difficult to study in clinical settings on patients and in vitro conditions. Animal models play a pivotal and indispensable role in CVD research. Caenorhabditis elegans, a nematode species, has emerged as a prominent experimental organism widely utilized in various biomedical research fields. However, the specific number of CVD-related genes and pathways within the C. elegans genome remains undisclosed to date, limiting its in-depth utilization for investigations. In the present study, we conducted a comprehensive analysis of genes and pathways related to CVD within the genomes of humans and C. elegans through a systematic bioinformatic approach. A total of 1113 genes in C. elegans orthologous to the most significant CVD-related genes in humans were identified, and the GO terms and pathways were compared to study the pathways that are conserved between the two species. In order to infer the functions of CVD-related orthologous genes in C. elegans, a PPI network was constructed. Orthologous gene PPI network analysis results reveal the hubs and important KRs: pmk-1, daf-21, gpb-1, crh-1, enpl-1, eef-1G, acdh-8, hif-1, pmk-2, and aha-1 in C. elegans. Modules were identified for determining the role of the orthologous genes at various levels in the created network. We also identified 9 commonly enriched pathways between humans and C. elegans linked with CVDs that include autophagy (animal), the ErbB signaling pathway, the FoxO signaling pathway, the MAPK signaling pathway, ABC transporters, the biosynthesis of unsaturated fatty acids, fatty acid metabolism, glutathione metabolism, and metabolic pathways. This study provides the first systematic genomic approach to explore the CVD-associated genes and pathways that are present in C. elegans, supporting the use of C. elegans as a prominent animal model organism for cardiovascular diseases.

Integrating evolutionarily conserved mechanism of response to radiation for exploring novel Caenorhabditis elegans radiation-responsive genes for estimation of radiation dose associated with spaceflight

During space exploration, space radiation is widely recognized as an inescapable perilous stressor, owing to its capacity to induce genomic DNA damage and escalate the likelihood of detrimental health outcomes. Rapid and reliable estimation of space radiation dose holds paramount significance in accurately assessing the health risks associated with spaceflight. However, the identification of space radiation-responsive genes, with their potential to serve as early indicators for diagnosing radiation dose associated with spaceflight, continues to pose a significant challenge. In this study, based on the evolutionarily conserved mechanism of radiation response, an in silico analysis method of homologous comparison was performed to identify the Caenorhabditis elegans orthologues of human radiation-responsive genes with possible roles in the major processes of response to radiation, and thereby to explore the potential C. elegans radiation-responsive genes for evaluating the levels of space radiation exposure. The results showed that there were 60 known C. elegans radiation-responsive genes and 211 C. elegans orthologues of human radiation-responsive genes implicated in the major processes of response to radiation. Through an investigation of all available transcriptomic datasets obtained from space-flown C. elegans, it was observed that the expression levels of the majority of these putative C. elegans radiation-responsive genes identified in this study were notably changed across various spaceflight conditions. Furthermore, this study indicated that within the identified genes, 19 known C. elegans radiation-responsive genes and 40 newly identified C. elegans orthologues of human radiation-responsive genes exhibited a remarkable positive correlation with the duration of spaceflight. Moreover, a noteworthy presence of substantial multi-collinearity among the majority of these identified genes was observed. This observation lends support to the possibility of treating each identified gene as an independent indicator of radiation dose in space. Ultimately, a subset of 15 potential radiation-responsive genes was identified, presenting the most promising indicators for estimation of radiation dose associated with spaceflight in C. elegans.

The lipid basis of cell death and autophagy

ABBREVIATIONS

ACSL: acyl-CoA synthetase long chain family; DISC: death-inducing signaling complex; DAMPs: danger/damage-associated molecular patterns; Dtgn: dispersed trans-Golgi network; FAR1: fatty acyl-CoA reductase 1; GPX4: glutathione peroxidase 4; LPCAT3: lysophosphatidylcholine acyltransferase 3; LPS: lipopolysaccharide; MUFAs: monounsaturated fatty acids; MOMP: mitochondrial outer membrane permeabilization; MLKL, mixed lineage kinase domain like pseudokinase; oxPAPC: oxidized 1-palmitoyl-2-arachidonoyl-sn-glycero-3-phosphocholine; OxPCs: oxidized phosphatidylcholines; PUFAs: polyunsaturated fatty acids; POR: cytochrome p450 oxidoreductase; PUFAs: polyunsaturated fatty acids; RCD: regulated cell death; RIPK1: receptor interacting serine/threonine kinase 1; SPHK1: sphingosine kinase 1; SOAT1: sterol O-acyltransferase 1; SCP2: sterol carrier protein 2; SFAs: saturated fatty acids; SLC47A1: solute carrier family 47 member 1; SCD: stearoyl-CoA desaturase; VLCFA: very long chain fatty acids.

Conserved Cardiovascular Network: Bioinformatics Insights into Genes and Pathways for Establishing Caenorhabditis elegans as an Animal Model for Cardiovascular Diseases

Cardiovascular disease (CVD) is a collective term for disorders of the heart and blood vessels. The molecular events and biochemical pathways associated with CVD are difficult to study in clinical settings on patients and in vitro conditions. Animal models play a pivotal and indispensable role in cardiovascular disease (CVD) research. Caenorhabditis elegans , a nematode species, has emerged as a prominent experimental organism widely utilised in various biomedical research fields. However, the specific number of CVD-related genes and pathways within the C. elegans genome remains undisclosed to date, limiting its in-depth utilisation for investigations. In the present study, we conducted a comprehensive analysis of genes and pathways related to CVD within the genomes of humans and C. elegans through a systematic bioinformatic approach. A total of 1113 genes in C. elegans orthologous to the most significant CVD-related genes in humans were identified, and the GO terms and pathways were compared to study the pathways that are conserved between the two species. In order to infer the functions of CVD-related orthologous genes in C. elegans, a PPI network was constructed. Orthologous gene PPI network analysis results reveal the hubs and important KRs: pmk-1, daf-21, gpb-1, crh-1, enpl-1, eef-1G, acdh-8, hif-1, pmk-2, and aha-1 in C. elegans. Modules were identified for determining the role of the orthologous genes at various levels in the created network. We also identified 9 commonly enriched pathways between humans and C. elegans linked with CVDs that include autophagy (animal), the ErbB signalling pathway, the FoxO signalling pathway, the MAPK signalling pathway, ABC transporters, the biosynthesis of unsaturated fatty acids, fatty acid metabolism, glutathione metabolism, and metabolic pathways. This study provides the first systematic genomic approach to explore the CVD-associated genes and pathways that are present in C. elegans, supporting the use of C. elegans as a prominent animal model organism for cardiovascular diseases.

Acid Ceramidase Inhibitor LCL-805 Antagonizes Akt Signaling and Promotes Iron-Dependent Cell Death in Acute Myeloid Leukemia

Acute myeloid leukemia (AML) is an aggressive hematologic malignancy requiring urgent treatment advancements. Ceramide is a cell-death-promoting signaling lipid that plays a central role in therapy-induced cell death. We previously determined that acid ceramidase (AC), a ceramide-depleting enzyme, is overexpressed in AML and promotes leukemic survival and drug resistance. The ceramidase inhibitor B-13 and next-generation lysosomal-localizing derivatives termed dimethylglycine (DMG)-B-13 prodrugs have been developed but remain untested in AML. Here, we report the in vitro anti-leukemic efficacy and mechanism of DMG-B-13 prodrug LCL-805 across AML cell lines and primary patient samples. LCL-805 inhibited AC enzymatic activity, increased total ceramides, and reduced sphingosine levels. A median EC50 value of 11.7 μM was achieved for LCL-805 in cell viability assays across 32 human AML cell lines. As a single agent tested across a panel of 71 primary AML patient samples, a median EC50 value of 15.8 μM was achieved. Exogenous ceramide supplementation with C6-ceramide nanoliposomes, which is entering phase I/II clinical trial for relapsed/refractory AML, significantly enhanced LCL-805 killing. Mechanistically, LCL-805 antagonized Akt signaling and led to iron-dependent cell death distinct from canonical ferroptosis. These findings elucidated key factors involved in LCL-805 cytotoxicity and demonstrated the potency of combining AC inhibition with exogenous ceramide.

Proton Microbeam Targeted Irradiation of the Gonad Primordium Region Induces Developmental Alterations Associated with Heat Shock Responses and Cuticle Defense in Caenorhabditis elegans

We describe a methodology to manipulate Caenorhabditis elegans (C. elegans) and irradiate the stem progenitor gonad region using three MeV protons at a specific developmental stage (L1). The consequences of the targeted irradiation were first investigated by considering the organogenesis of the vulva and gonad, two well-defined and characterized developmental systems in C. elegans. In addition, we adapted high-throughput analysis protocols, using cell-sorting assays (COPAS) and whole transcriptome analysis, to the limited number of worms (>300) imposed by the selective irradiation approach. Here, the presented status report validated protocols to (i) deliver a controlled dose in specific regions of the worms; (ii) immobilize synchronized worm populations (>300); (iii) specifically target dedicated cells; (iv) study the radiation-induced developmental alterations and gene induction involved in cellular stress (heat shock protein) and cuticle injury responses that were found.

Acid Ceramidase Inhibitor LCL-805 Antagonizes Akt Signaling and Promotes Iron-Dependent Cell Death in Acute Myeloid Leukemia

Acute myeloid leukemia (AML) is an aggressive hematologic malignancy requiring urgent treatment advancements. Ceramide is a cell death-promoting signaling lipid that plays a central role in therapy-induced cell death. Acid ceramidase (AC), a ceramide-depleting enzyme, is overexpressed in AML and promotes leukemic survival and drug resistance. The ceramidase inhibitor B-13 and next-generation lysosomal-localizing derivatives termed dimethylglycine (DMG)-B-13 prodrugs have been developed but remain untested in AML. Here, we report the in vitro anti-leukemic efficacy and mechanism of DMG-B-13 prodrug, LCL-805, across AML cell lines and primary patient samples. LCL-805 inhibited AC enzymatic activity, increased total ceramides, and reduced sphingosine levels. A median EC50 value of 11.7 μM was achieved for LCL-805 in cell viability assays across 32 human AML cell lines. As a single agent tested across a panel of 71 primary AML patient samples, a median EC50 value of 15.8 μM was achieved. Exogenous ceramide supplementation with C6-ceramide nanoliposomes, which is entering phase I/II clinical trial for relapsed/refractory AML, significantly enhanced LCL-805 killing. Mechanistically, LCL-805 antagonized Akt signaling and led to iron-dependent cell death distinct from canonical ferroptosis. These findings elucidated key factors involved in LCL-805 cytotoxicity and demonstrated the potency of combining AC inhibition with exogenous ceramide.

High-Density Lipoprotein Lipidomics and Mortality in CKD

Rationale & Objective

Patients with chronic kidney disease (CKD) have dysfunctional high-density lipoprotein (HDL) particles that lack cardioprotective properties; altered lipid composition may be associated with these changes. To investigate HDL lipids as potential cardiovascular risk factors in CKD, we tested the associations of HDL ceramides, sphingomyelins, and phosphatidylcholines with mortality.

Study Design

We leveraged data from a longitudinal prospective cohort of participants with CKD.

Setting & Participants

We included participants aged greater than 21 years with CKD, excluding those on maintenance dialysis or with prior kidney transplant.

Exposure

HDL particles were isolated using density gradient ultracentrifugation. We quantified the relative abundance of HDL ceramides, sphingomyelins, and phosphatidylcholines via liquid chromatography tandem mass spectrometry (LC-MS/MS).

Outcomes

Our primary outcome was all-cause mortality.

Analytical Approach

We tested associations using Cox regressions adjusted for demographics, comorbid conditions, laboratory values, medication use, and highly correlated lipids with opposed effects, controlling for multiple comparisons with false discovery rates (FDR).

Results

There were 168 deaths over a median follow-up of 6.12 years (interquartile range, 3.71-9.32). After adjustment, relative abundance of HDL ceramides (HR, 1.22 per standard deviation; 95% CI, 1.06-1.39), sphingomyelins with long fatty acids (HR, 1.44; 95% CI, 1.05-1.98), and saturated and monounsaturated phosphatidylcholines (HR, 1.22; 95% CI, 1.06-1.41) were significantly associated with increased risk of all-cause mortality (FDR < 5%).

Limitations

We were unable to test associations with cardiovascular disease given limited power. HDL lipidomics may not reflect plasma lipidomics. LC-MS/MS is unable to differentiate between glucosylceramides and galactosylceramides. The cohort was comprised of research volunteers in the Seattle area with CKD.

Conclusions

Greater relative HDL abundance of 3 classes of lipids was associated with higher risk of all-cause mortality in CKD; sphingomyelins with very long fatty acids were associated with a lower risk. Altered lipid composition of HDL particles may be a novel cardiovascular risk factor in CKD.

Plain-Language Summary

Patients with chronic kidney disease have abnormal high-density lipoprotein (HDL) particles that lack the beneficial properties associated with these particles in patients with normal kidney function. To investigate if small lipid molecules found on the surface of HDL might be associated with these changes, we tested the associations of lipid molecules found on HDL with death among patients with chronic kidney disease. We found that several lipid molecules found on the surface of HDL were associated with increased risk of death among these patients. These findings suggest that lipid molecules may be risk factors for death among patients with chronic kidney disease.

The heat shock protein Hsp27 controls mitochondrial function by modulating ceramide generation

Sphingolipids have key functions in membrane structure and cellular signaling. Ceramide is the central molecule of the sphingolipid metabolism and is generated by ceramide synthases (CerS) in the de novo pathway. Despite their critical function, mechanisms regulating CerS remain largely unknown. Using an unbiased proteomics approach, we find that the small heat shock protein 27 (Hsp27) interacts specifically with CerS1 but not other CerS. Functionally, our data show that Hsp27 acts as an endogenous inhibitor of CerS1. Wild-type Hsp27, but not a mutant deficient in CerS1 binding, inhibits CerS1 activity. Additionally, silencing of Hsp27 enhances CerS1-generated ceramide accumulation in cells. Moreover, phosphorylation of Hsp27 modulates Hsp27-CerS1 interaction and CerS1 activity in acute stress-response conditions. Biologically, we show that Hsp27 knockdown impedes mitochondrial function and induces lethal mitophagy in a CerS1-dependent manner. Overall, we identify an important mode of CerS1 regulation and CerS1-mediated mitophagy through protein-protein interaction with Hsp27.

Evaluation of plasma sphingolipids as mediators of the relationship between kidney disease and cardiovascular events

BACKGROUND

Sphingolipids are a family of circulating lipids with regulatory and signaling roles that are strongly associated with both eGFR and cardiovascular disease. Patients with chronic kidney disease (CKD) are at high risk for cardiovascular events, and have different plasma concentrations of certain plasma sphingolipids compared to patients with normal kidney function. We hypothesize that circulating sphingolipids partially mediate the associations between eGFR and cardiovascular events.

METHODS

We measured the circulating concentrations of 8 sphingolipids, including 4 ceramides and 4 sphingomyelins with the fatty acids 16:0, 20:0, 22:0, and 24:0, in plasma from 3,463 participants in a population-based cohort (Cardiovascular Health Study) without prevalent cardiovascular disease. We tested the adjusted mediation effects by these sphingolipids of the associations between eGFR and incident cardiovascular disease via quasi-Bayesian Monte Carlo method with 2,000 simulations, using a Bonferroni correction for significance.

FINDINGS

The mean (±SD) eGFR was 70 (±16) mL/min/1.73 m2; 62% of participants were women. Lower eGFR was associated with higher plasma ceramide-16:0 and sphingomyelin-16:0, and lower ceramides and sphingomyelins-20:0 and -22:0. Lower eGFR was associated with risk of incident heart failure and ischemic stroke, but not myocardial infarction. Five of eight sphingolipids partially mediated the association between eGFR and heart failure. The sphingolipids associated with the greatest proportion mediated were ceramide-16:0 (proportion mediated 13%, 95% CI 8-22%) and sphingomyelin-16:0 (proportion mediated 10%, 95% CI 5-17%). No sphingolipids mediated the association between eGFR and ischemic stroke.

INTERPRETATION

Plasma sphingolipids partially mediated the association between lower eGFR and incident heart failure. Altered sphingolipids metabolism may be a novel mechanism for heart failure in patients with CKD.

FUNDING

This study was supported by T32 DK007467 and a KidneyCure Ben J. Lipps Research Fellowship (Dr. Lidgard). Sphingolipid measurements were supported by R01 HL128575 (Dr. Lemaitre) and R01 HL111375 (Dr. Hoofnagle) from the National Heart, Lung, and Blood Institute (NHLBI).

Ceramide Analog 5cc Overcomes TRAIL Resistance by Enhancing JNK Activation and Repressing XIAP Expression in Metastatic Colon Cancer Cells

INTRODUCTION

Tumor necrosis factor-related apoptosis-inducing ligand (TRAIL) is considered to be an effective apoptosis inducer due to its selectivity for tumor cells. However, many cancer cells, especially metastatic cancer cells, often exhibit resistance to TRAIL because their apoptotic pathway is impaired or their pro-survival pathway is overactivated. TRAIL resistance is the main obstacle to current TRAIL therapy. Nowadays, ceramide analogs represent a new class of potential anticancer agents. Therefore, we hypothesized that disrupting pro-survival signaling with ceramide analogs would increase TRAIL-mediated apoptosis.

METHODS

MTT assay and flow cytometry were conducted to evaluate the synergistic effect of ceramide analog 5cc on TRAIL in metastatic colon cancer cells. Western blot was used to detect signaling proteins affected by 5cc. RNA interference was performed to analyze the effects of specific gene on 5cc-enhanced apoptosis.

RESULTS

Ceramide analog 5cc markedly enhanced TRAIL-induced apoptosis evidenced by increased propidium iodide/annexin V double-positive cells and PARP cleavage in SW620 and LS411N cells. At the molecular level, 5cc significantly reduced the expression of anti-apoptotic protein X-linked inhibitor of apoptosis protein (XIAP) through the activation of the c-Jun n-terminal kinase (JNK) pathway which is critically involved in sensitizing tumor cells to TRAIL/5cc combination. JNK-silenced cells exhibited a significant reversal of TRAIL/5cc-mediated apoptosis.

CONCLUSION

Our data demonstrated that ceramide analog 5cc overcomes TRAIL resistance by enhancing JNK activation and repressing XIAP expression in metastatic colon cancer cells.

m6A modification-tuned sphingolipid metabolism regulates postnatal liver development in male mice

Different organs undergo distinct transcriptional, epigenetic and physiological alterations that guarantee their functional maturation after birth. However, the roles of epitranscriptomic machineries in these processes have remained elusive. Here we demonstrate that expression of RNA methyltransferase enzymes Mettl3 and Mettl14 gradually declines during postnatal liver development in male mice. Liver-specific Mettl3 deficiency causes hepatocyte hypertrophy, liver injury and growth retardation. Transcriptomic and N6-methyl-adenosine (m⁶A) profiling identify the neutral sphingomyelinase, Smpd3, as a target of Mettl3. Decreased decay of Smpd3 transcripts due to Mettl3 deficiency results in sphingolipid metabolism rewiring, characterized by toxic ceramide accumulation and leading to mitochondrial damage and elevated endoplasmic reticulum stress. Pharmacological Smpd3 inhibition, Smpd3 knockdown or Sgms1 overexpression that counteracts Smpd3 can ameliorate the abnormality of Mettl3-deficent liver. Our findings demonstrate that Mettl3-N⁶-methyl-adenosine fine-tunes sphingolipid metabolism, highlighting the pivotal role of an epitranscriptomic machinery in coordination of organ growth and the timing of functional maturation during postnatal liver development.

Phosphorylation of the LCB1 subunit of Arabidopsis serine palmitoyltransferase stimulates its activity and modulates sphingolipid biosynthesis

Sphingolipids are the structural components of membrane lipid bilayers and act as signaling molecules in many cellular processes. Serine palmitoyltransferase (SPT) is the first committed and rate-limiting enzyme in the de novo sphingolipids biosynthetic pathway. The core SPT enzyme is a heterodimer consisting of LONG-CHAIN BASE1 (LCB1) and LCB2 subunits. SPT activity is inhibited by orosomucoid proteins and stimulated by small subunits of SPT (ssSPTs). However, whether LCB1 is modified and how such modification might regulate SPT activity have to date been unclear. Here, we show that activation of MITOGEN-ACTIVATED PROTEIN KINASE 3 (MPK3) and MPK6 by upstream MKK9 and treatment with Flg22 (a pathogen-associated molecular pattern) increases SPT activity and induces the accumulation of sphingosine long-chain base t18:0 in Arabidopsis thaliana, with activated MPK3 and MPK6 phosphorylating AtLCB1. Phosphorylation of AtLCB1 strengthened its binding with AtLCB2b, promoted its binding with ssSPTs, and stimulated the formation of higher order oligomeric and active SPT complexes. Our findings therefore suggest a novel regulatory mechanism for SPT activity.

Acid sphingomyelinase promotes diabetic cardiomyopathy via NADPH oxidase 4 mediated apoptosis

BACKGROUND

Increased acid sphingomyelinase (ASMase) activity is associated with insulin resistance and cardiac dysfunction. However, the effects of ASMase on diabetic cardiomyopathy (DCM) and the molecular mechanism(s) underlying remain to be elucidated. We here investigated whether ASMase caused DCM through NADPH oxidase 4-mediated apoptosis.

METHODS AND RESULTS

We used pharmacological and genetic approaches coupled with study of murine and cell line samples to reveal the mechanisms initiated by ASMase in diabetic hearts. The protein expression and activity of ASMase were upregulated, meanwhile ceramide accumulation was increased in the myocardium of HFD mice. Inhibition of ASMase with imipramine (20 mg Kg^-1 d^-1) or siRNA reduced cardiomyocyte apoptosis, fibrosis, and mitigated cardiac hypertrophy and cardiac dysfunction in HFD mice. The similar effects were observed in cardiomyocytes treated with high glucose (HG, 30 mmol L^-1) + palmitic acid (PA, 100 μmol L^-1) or C16 ceramide (CER, 20 μmol L^-1). Interestingly, the cardioprotective effect of ASMase inhibition was not accompanied by reduced ceramide accumulation, indicating a ceramide-independent manner. The mechanism may involve activated NADPH oxidase 4 (NOX4), increased ROS generation and triggered apoptosis. Suppression of NOX4 with apocynin prevented HG + PA and CER incubation induced Nppb and Myh7 pro-hypertrophic gene expression, ROS production and apoptosis in H9c2 cells. Furthermore, cardiomyocyte-specific ASMase knockout (ASMase^Myh6KO) restored HFD-induced cardiac dysfunction, remodeling, and apoptosis, whereas NOX4 protein expression was downregulated.

CONCLUSIONS

These results demonstrated that HFD-mediated activation of cardiomyocyte ASMase could increase NOX4 expression, which may stimulate oxidative stress, apoptosis, and then cause metabolic cardiomyopathy.

A simple, highly sensitive, and facile method to quantify ceramide at the plasma membrane

The role of ceramide in biological functions is typically based on the elevation of cellular ceramide, measured by LC-MS in the total cell lysate. However, it has become increasingly appreciated that ceramide in different subcellular organelles regulates specific functions. In the plasma membrane, changes in ceramide levels might represent a small percentage of the total cellular ceramide, evading MS detection but playing a critical role in cell signaling. Importantly, there are currently no efficient techniques to quantify ceramide in the plasma membrane. Here, we developed a method to measure the mass of ceramide in the plasma membrane using a short protocol that is based on the hydrolysis of plasma membrane ceramide into sphingosine by the action of exogenously applied bacterial recombinant neutral ceramidase. Plasma membrane ceramide content can then be determined by measuring the newly generated sphingosine at a stoichiometry of 1:1. A key step of this protocol is the chemical fixation of cells to block cellular sphingolipid metabolism, especially of sphingosine to sphingosine 1-phosphate. We confirmed that chemical fixation does not disrupt the lipid composition at the plasma membrane, which remains intact during the time of the assay. We illustrate the power of the approach by applying this protocol to interrogate the effects of the chemotherapeutic compound doxorubicin. Here we distinguished two pools of ceramide, depending on the doxorubicin concentration, consolidating different reports. In summary, we have developed the first approach to quantify ceramide in the plasma membrane, allowing the study of new avenues in sphingolipid compartmentalization and function.

Transcriptomic Signature of the Simulated Microgravity Response in Caenorhabditis elegans and Comparison to Spaceflight Experiments

Given the growing interest in human exploration of space, it is crucial to identify the effects of space conditions on biological processes. Here, we analyze the transcriptomic response of Caenorhabditis elegans to simulated microgravity and observe the maintained transcriptomic response after returning to ground conditions for four, eight, and twelve days. We show that 75% of the simulated microgravity-induced changes on gene expression persist after returning to ground conditions for four days while most of these changes are reverted after twelve days. Our results from integrative RNA-seq and mass spectrometry analyses suggest that simulated microgravity affects longevity-regulating insulin/IGF-1 and sphingolipid signaling pathways. Finally, we identified 118 genes that are commonly differentially expressed in simulated microgravity- and space-exposed worms. Overall, this work provides insight into the effect of microgravity on biological systems during and after exposure.

Crosstalk between pro-survival sphingolipid metabolism and complement signaling induces inflammasome-mediated tumor metastasis

Crosstalk between metabolic and signaling events that induce tumor metastasis remains elusive. Here, we determine how oncogenic sphingosine 1-phosphate (S1P) metabolism induces intracellular C3 complement activation to enhance migration/metastasis. We demonstrate that increased S1P metabolism activates C3 complement processing through S1P receptor 1 (S1PR1). S1P/S1PR1-activated intracellular C3b-α'2 is associated with PPIL1 through glutamic acid 156 (E156) and aspartic acid 111 (D111) residues, resulting in NLRP3/inflammasome induction. Inactivation mutations of S1PR1 to prevent S1P signaling or mutations of C3b-α'2 to prevent its association with PPIL1 attenuate inflammasome activation and reduce lung colonization/metastasis in mice. Also, activation of the S1PR1/C3/PPIL1/NLRP3 axis is highly associated with human metastatic melanoma tissues and patient-derived xenografts. Moreover, targeting S1PR1/C3/PPIL1/NLRP3 signaling using molecular, genetic, and pharmacologic tools prevents lung colonization/metastasis of various murine cancer cell lines using WT and C3a-receptor1 knockout (C3aR1-/-) mice. These data provide strategies for treating high-grade/metastatic tumors by targeting the S1PR1/C3/inflammasome axis.

Balancing life and death: BCL-2 family members at diverse ER-mitochondrial contact sites

The outer mitochondrial membrane is a busy place. One essential activity for cellular survival is the regulation of membrane integrity by the BCL-2 family of proteins. Another critical facet of the outer mitochondrial membrane is its close approximation with the endoplasmic reticulum. These mitochondrial-associated membranes (MAMs) occupy a significant fraction of the mitochondrial surface and serve as key signaling hubs for multiple cellular processes. Each of these pathways may be considered as forming their own specialized MAM subtype. Interestingly, like membrane permeabilization, most of these pathways play critical roles in regulating cellular survival and death. Recently, the pro-apoptotic BCL-2 family member BOK has been found within MAMs where it plays important roles in their structure and function. This has led to a greater appreciation that multiple BCL-2 family proteins, which are known to participate in numerous functions throughout the cell, also have roles within MAMs. In this review, we evaluate several MAM subsets, their role in cellular homeostasis, and the contribution of BCL-2 family members to their functions.

H3K9me1/2 methylation limits the lifespan of daf-2 mutants in C. elegans

Histone methylation plays crucial roles in the development, gene regulation, and maintenance of stem cell pluripotency in mammals. Recent work shows that histone methylation is associated with aging, yet the underlying mechanism remains unclear. In this work, we identified a class of putative histone 3 lysine 9 mono/dimethyltransferase genes (met-2, set-6, set-19, set-20, set-21, set-32, and set-33), mutations in which induce synergistic lifespan extension in the long-lived DAF-2 (insulin growth factor 1 [IGF-1] receptor) mutant in Caenorhabditis elegans. These putative histone methyltransferase plus daf-2 double mutants not only exhibited an average lifespan nearly three times that of wild-type animals and a maximal lifespan of approximately 100 days, but also significantly increased resistance to oxidative and heat stress. Synergistic lifespan extension depends on the transcription factor DAF-16 (FOXO). mRNA-seq experiments revealed that the mRNA levels of DAF-16 Class I genes, which are activated by DAF-16, were further elevated in the daf-2;set double mutants. Among these genes, tts-1, F35E8.7, ins-35, nhr-62, sod-3, asm-2, and Y39G8B.7 are required for the lifespan extension of the daf-2;set-21 double mutant. In addition, treating daf-2 animals with the H3K9me1/2 methyltransferase G9a inhibitor also extends lifespan and increases stress resistance. Therefore, investigation of DAF-2 and H3K9me1/2 deficiency-mediated synergistic longevity will contribute to a better understanding of the molecular mechanisms of aging and therapeutic applications.

Circulating ceramides and sphingomyelins and the risk of incident cardiovascular disease among people with diabetes: the strong heart study

BACKGROUND

Plasma ceramides and sphingomyelins have been independently linked to diabetes risk, glucose and insulin levels, and the risk of several cardiovascular (CVD) outcomes. However, whether individual ceramide and sphingomyelin species contribute to CVD risk among people with type 2 diabetes is uncertain. Our goal was to evaluate associations of 4 ceramide and 4 sphingomyelin species with incident CVD in a longitudinal population-based study among American Indians with diabetes.

METHODS

This analysis included participants with prevalent type 2 diabetes from two cohorts: a prospective cohort of 597 participants in the Strong Heart Family Study (116 incident CVD cases; mean age: 49 years; average length of follow-up: 14 years), and a nested case-control sample of 267 participants in the Strong Heart Study (78 cases of CVD and 189 controls; mean age: 61 years; average time until incident CVD in cases: 3.8 years). The average onset of diabetes was 7 years prior to sphingolipid measurement. Sphingolipid species were measured using liquid chromatography and mass spectrometry. Cox regression and logistic regression were used to assess associations of sphingolipid species with incident CVD; results were combined across cohorts using inverse-variance weighted meta-analysis.

RESULTS

There were 194 cases of incident CVD in the two cohorts. In meta-analysis of the 2 cohort results, higher plasma levels of Cer-16 (ceramide with acylated palmitic acid) were associated with higher CVD risk (HR per two-fold higher Cer-16: 1.85; 95% CI 1.05-3.25), and higher plasma levels of sphingomyelin species with a very long chain saturated fatty acid were associated with lower CVD risk (HR per two-fold higher SM-22: 0.48; 95% CI 0.26-0.87), although none of the associations met our pre-specified threshold for statistical significance of p = 0.006.

CONCLUSIONS

While replication of the findings from the SHS in other populations is warranted, our findings add to a growing body of research suggesting that ceramides, in particular Cer-16, not only are associated with higher diabetes risk, but may also be associated with higher CVD risk after diabetes onset. We also find support for the hypothesis that sphingomyelins with a very long chain saturated fatty acid are associated with lower CVD risk among adults with type 2 diabetes.

Ciliogenesis requires sphingolipid-dependent membrane and axoneme interaction

Cilium formation and regeneration requires new protein synthesis, but the underlying cytosolic translational reprogramming remains largely unknown. Using ribosome footprinting, we performed global translatome profiling during cilia regeneration in Chlamydomonas and uncovered that flagellar genes undergo an early transcriptional activation but late translational repression. This pattern guided our identification of sphingolipid metabolism enzymes, including serine palmitoyltransferase (SPT), as essential regulators for ciliogenesis. Cryo-electron tomography showed that ceramide loss abnormally increased the membrane-axoneme distance and generated bulged cilia. We found that ceramides interact with intraflagellar transport (IFT) particle proteins that IFT motors transport along axoneme microtubules (MTs), suggesting that ceramide-IFT particle-IFT motor-MT interactions connect the ciliary membrane with the axoneme to form rod-shaped cilia. SPT-deficient vertebrate cells were defective in ciliogenesis, and SPT mutations from patients with hereditary sensory neuropathy disrupted cilia, which could be restored by sphingolipid supplementation. These results reveal a conserved role of sphingolipid in cilium formation and link compromised sphingolipid production with ciliopathies.

Targeting Sphingolipid Metabolism as a Therapeutic Strategy in Cancer Treatment

Sphingolipids are bioactive molecules that have key roles in regulating tumor cell death and survival through, in part, the functional roles of ceramide accumulation and sphingosine-1-phosphate (S1P) production, respectively. Mechanistic studies using cell lines, mouse models, or human tumors have revealed crucial roles of sphingolipid metabolic signaling in regulating tumor progression in response to anticancer therapy. Specifically, studies to understand ceramide and S1P production pathways with their downstream targets have provided novel therapeutic strategies for cancer treatment. In this review, we present recent evidence of the critical roles of sphingolipids and their metabolic enzymes in regulating tumor progression via mechanisms involving cell death or survival. The roles of S1P in enabling tumor growth/metastasis and conferring cancer resistance to existing therapeutics are also highlighted. Additionally, using the publicly available transcriptomic database, we assess the prognostic values of key sphingolipid enzymes on the overall survival of patients with different malignancies and present studies that highlight their clinical implications for anticancer treatment.

Acid sphingomyelinase deactivation post-ischemia promotes brain angiogenesis and remodeling by small extracellular vesicles

Antidepressants have been reported to enhance stroke recovery independent of the presence of depressive symptoms. They have recently been proposed to exert their mood-stabilizing actions by inhibition of acid sphingomyelinase (ASM), which catalyzes the hydrolysis of sphingomyelin to ceramide. Their restorative action post-ischemia/reperfusion (I/R) still had to be defined. Mice subjected to middle cerebral artery occlusion or cerebral microvascular endothelial cells exposed to oxygen-glucose deprivation were treated with vehicle or with the chemically and pharmacologically distinct antidepressants amitriptyline, fluoxetine or desipramine. Brain ASM activity significantly increased post-I/R, in line with elevated ceramide levels in microvessels. ASM inhibition by amitriptyline reduced ceramide levels, and increased microvascular length and branching point density in wildtype, but not sphingomyelinase phosphodiesterase-1 ([Smpd1]^-/-) (i.e., ASM-deficient) mice, as assessed by 3D light sheet microscopy. In cell culture, amitriptyline, fluoxetine, and desipramine increased endothelial tube formation, migration, VEGFR2 abundance and VEGF release. This effect was abolished by Smpd1 knockdown. Mechanistically, the promotion of angiogenesis by ASM inhibitors was mediated by small extracellular vesicles (sEVs) released from endothelial cells, which exhibited enhanced uptake in target cells. Proteomic analysis of sEVs revealed that ASM deactivation differentially regulated proteins implicated in protein export, focal adhesion, and extracellular matrix interaction. In vivo, the increased angiogenesis was accompanied by a profound brain remodeling response with increased blood-brain barrier integrity, reduced leukocyte infiltrates and increased neuronal survival. Antidepressive drugs potently boost angiogenesis in an ASM-dependent way. The release of sEVs by ASM inhibitors disclosed an elegant target, via which brain remodeling post-I/R can be amplified.

Circulating Ceramides and Sphingomyelins and Risk of Mortality: The Cardiovascular Health Study

BACKGROUND

Recent studies suggest that associations of ceramides (Cer) and sphingomyelins (SM) with health outcomes differ according to the fatty acid acylated to the sphingoid backbone. The purpose of this study was to assess associations of Cer and SM species with mortality.

METHODS

The study population included participants from the Cardiovascular Health Study (CHS), a community-based cohort of adults aged ≥65 years who were followed from 1992-2015 (n = 4612). Associations of plasma Cer and SM species carrying long-chain (i.e., 16:0) and very-long-chain (i.e., 20:0, 22:0, 24:0) saturated fatty acids with mortality were assessed using Cox proportional hazards models.

RESULTS

During a median follow-up of 10.2 years, 4099 deaths occurred. High concentrations of Cer and SM carrying fatty acid 16:0 were each associated with an increased risk of mortality. Conversely, high concentrations of several ceramide and sphingomyelin species carrying longer fatty acids were each associated with a decreased risk of mortality. The hazard ratios for total mortality per 2-fold difference in each Cer and SM species were: 1.89 (95% CI), 1.65-2.17 for Cer-16, 0.79 (95% CI, 0.70-0.88) for Cer-22, 0.74 (95% CI, 0.65-0.84) for Cer-24, 2.51 (95% CI, 2.01-3.14) for SM-16, 0.68 (95% CI, 0.58-0.79) for SM-20, 0.57 (95% CI, 0.49-0.67) for SM-22, and 0.66 (0.57-0.75) for SM-24. We found no association of Cer-20 with risk of death.

CONCLUSIONS

Associations of Cer and SM with the risk of death differ according to the length of their acylated saturated fatty acid. Future studies are needed to explore mechanisms underlying these relationships.

Study on Caenorhabditis Elegans as a Combined Model of Microdosimetry and Biology

Microdosimetry is a tool for the investigation of microscopic energy deposition of ionizing radiation. This work used Caenorhabditis elegans as a model to estimate the microdosimetric deposition level at the ⁶⁰Co gamma radiation. Monte Carlo software PHITS was employed to establish irradiated nematodes model. The dose deposition of the entire body and gonad irradiated to 100 Gy was calculated. The injury levels of radiation were evaluated by the detection of biological indicators. The result of microdosimetric experiment suggested that the dose of whole body of nematodes was estimated to be 99.9 ± 57.8 Gy, ranging from 19.6 to 332.2 Gy. The dose of gonad was predicted to be 129.4 ± 558.8 Gy (9.5-6597 Gy). The result of biological experiment suggested that there were little changes in the length of nematodes after irradiation. However, times of head thrash per minute and the spawning yield in 3 consecutive days decreased 27.1% and 94.7%, respectively. Nematodes in the irradiated group displayed heterogeneity. Through contour analysis, trends of behavior kinematics and reproductive capacity of irradiated nematodes proved to be consistent with the dose distribution levels estimated by microdosimetric model. Finally, C. elegans presented a suitable combined model of microdosimetry and biology for studying radiation.

DNA repair, recombination, and damage signaling

DNA must be accurately copied and propagated from one cell division to the next, and from one generation to the next. To ensure the faithful transmission of the genome, a plethora of distinct as well as overlapping DNA repair and recombination pathways have evolved. These pathways repair a large variety of lesions, including alterations to single nucleotides and DNA single and double-strand breaks, that are generated as a consequence of normal cellular function or by external DNA damaging agents. In addition to the proteins that mediate DNA repair, checkpoint pathways have also evolved to monitor the genome and coordinate the action of various repair pathways. Checkpoints facilitate repair by mediating a transient cell cycle arrest, or through initiation of cell suicide if DNA damage has overwhelmed repair capacity. In this chapter, we describe the attributes of Caenorhabditis elegans that facilitate analyses of DNA repair, recombination, and checkpoint signaling in the context of a whole animal. We review the current knowledge of C. elegans DNA repair, recombination, and DNA damage response pathways, and their role during development, growth, and in the germ line. We also discuss how the analysis of mutational signatures in C. elegans is helping to inform cancer mutational signatures in humans.

Ceramide mediates radiation-induced germ cell apoptosis via regulating mitochondria function and MAPK factors in Caenorhabditis elegans

Studies about radiation damage in vivo are very significant for healthy risk assessment as well as cancer radiotherapy. Ceramide as a second messenger has been found to be related to radiation-induced apoptosis. However, the detailed mechanisms in living systems are still not fully understood. In the present study, the effects of ceramide in gamma radiation-induced response were investigated using Caenorhabditis elegans. Our results indicated that ceramide was required for gamma radiation-induced whole-body germ cell apoptosis by the production of radical oxygen species and decrease of mitochondrial transmembrane potential. Using genetic ceramide synthase-related mutated strains and exogenous C₁₆-ceramide, we illustrated that ceramide could regulate DNA damage response (DDR) pathway to mediate radiation-induced germ cell apoptosis. Moreover, ceramide was found to function epistatic to pmk-1 and mpk-1 in MAPK pathway to promote radiation-induced apoptosis in Caenorhabditis elegans. These results demonstrated ceramide could potentially mediated gamma radiation-induced apoptosis through regulating mitochondrial function, DDR pathway and MAPK pathway.

Ceramide synthases: insights into the expression and prognosis of lung cancer

CerSs (ceramide synthases), a group of enzymes that catalyze the formation of ceramides from sphingoid base and acyl-CoA substrates. As far, six types of CerSs (CerS1-CerS6) have been found in mammals. Each of these enzymes have unique characteristics, but maybe more noteworthy is the ability of individual CerS isoform to produce a ceramide with a characteristic acyl chain distribution. As key regulators of sphingolipid metabolism, CerSs highlight their unique characteristics and have emerging roles in regulating programmed cell death, cancer and many other aspects of biology. However, the role of CerSs in lung cancer has not been fully elucidated. In this study, there was no significant change in the sequence or copy number of CerSs gene, which could explain the stability of malignant tumor development through COSMIC database. In addition, gene expression in lung cancer was examined using the Oncomine^TM database, and the prognostic value of each gene in non-small cell lung cancer (NSCLC) was analyzed by Kaplan-Meier analysis. The results showed that high mRNA expression levels of CerS2, CerS3, CerS4 and CerS5 in all NSCLC patients were associated with improved prognosis. Among them, CerS2 and CerS5 are also highly expressed in adenocarcinoma (Ade), but not in squamous cell carcinoma (SCC). In contrast, high or low expression of CerS1 and CerS6 no difference was observed in patients with NSCLC, Ade and SCC. Integrated the data of this study suggested that these CerSs may be a potential tumor markers or drug target of new research direction.

Homozygous Smpd1 deficiency aggravates brain ischemia/ reperfusion injury by mechanisms involving polymorphonuclear neutrophils, whereas heterozygous Smpd1 deficiency protects against mild focal cerebral ischemia

By cleaving sphingomyelin into ceramide, which is an essential component of plasma membrane microdomains, acid sphingomyelinase (Asm) pivotally controls cell signaling. To define how the activation of the Asm/ceramide pathway, which occurs within seconds to minutes upon stress stimuli, influences brain ischemia/reperfusion (I/R) injury, we exposed male and female wildtype mice carrying both alleles of Asm's gene sphingomyelinase phosphodiesterase-1 (Smpd1^+/+), heterozygously Asm-deficient mice (Smpd1^+/-) and homozygously Asm-deficient mice (Smpd1^-/-) of different age (8, 12 or 16 weeks) to 30, 60 or 90 min intraluminal middle cerebral artery occlusion (MCAO). For studying the contribution of brain-invading polymorphonuclear neutrophils (PMN) to I/R injury, PMNs were depleted by delivery of a PMN-specific Ly6G antibody. In male and female mice exposed to 30 min, but not 60 or 90 min MCAO, homozygous Smpd1^-/- consistently increased I/R injury, blood-brain barrier permeability and brain leukocyte and PMN infiltration, whereas heterozygous Smpd1^+/- reduced I/R injury. Increased abundance of the intercellular leukocyte adhesion molecule ICAM-1 was noted on cerebral microvessels of Smpd1^-/- mice. PMN depletion by anti-Ly6G delivery prevented the exacerbation of I/R injury in Smpd1^-/- compared with wildtype mice and reduced brain leukocyte infiltrates. Our results show that Asm tempers leukocyte entry into the reperfused ischemic brain, thereby attenuating I/R injury.

NRIP3 upregulation confers resistance to chemoradiotherapy in ESCC via RTF2 removal by accelerating ubiquitination and degradation of RTF2

Esophageal squamous cell carcinoma (ESCC) is a common malignant cancer worldwide. Despite recent improvements in surgical techniques and adjuvant therapies, the prognosis of patients with advanced ESCC remains poor. Resistance to chemoradiotherapy (CRT) remains a major cause of treatment failure for advanced ESCC patients. Here, we report that NRIP3 (nuclear receptor interacting protein 3) promotes ESCC tumor cell growth and resistance to CRT in ESCC cells by increasing and binding to DDI1 (DNA-damage inducible 1 homolog 1) and RTF2 (homologous to Schizosaccharomyces pombe Rtf2), and accelerating the removal of RTF2, which is a key determinant for the ability of cells to manage replication stress. In addition, we found that NRIP3 could increase DDI1 expression via PPARα. The NRIP3-PPARα-DDI1-RTF2 axis represents a protective molecular pathway in ESCC cells that mediates resistance to replication stress signals induced by chemoradiotherapy. In addition, elevated NRIP3 is associated with the poor clinical outcome of ESCC patients receiving radiotherapy and/or cisplatin-based chemotherapy. Our study therefore reveals that NRIP3 is a prognostic factor in ESCC and could have some predictive value to select patients who benefit from CRT treatment. A common mechanism that protects ESCC tumor cells from DNA damage induced by CRT is also revealed in this study.

Identification of Small-Molecule Inhibitors of Neutral Ceramidase (nCDase) via Target-Based High-Throughput Screening

There is interest in developing inhibitors of human neutral ceramidase (nCDase) because this enzyme plays a critical role in colon cancer. There are currently no potent or clinically effective inhibitors for nCDase reported to date, so we adapted a fluorescence-based enzyme activity method to a high-throughput screening format. We opted to use an assay whereby nCDase hydrolyzes the substrate RBM 14-16, and the addition of NaIO4 acts as an oxidant that releases umbelliferone, resulting in a fluorescent signal. As designed, test compounds that act as ceramidase inhibitors will prevent the hydrolysis of RBM 14-16, thereby decreasing fluorescence. This assay uses a 1536-well plate format with excitation in the blue spectrum of light energy, which could be a liability, so we incorporated a counterscreen that allows for rapid selection against fluorescence artifacts to minimize false-positive hits. The high-throughput screen of >650,000 small molecules found several lead series of hits. Multiple rounds of chemical optimization ensued with improved potency in terms of IC₅₀ and selectivity over counterscreen assays. This study describes the first large-scale high-throughput optical screening assay for nCDase inhibitors that has resulted in leads that are now being pursued in crystal docking studies and in vitro drug metabolism and pharmacokinetics (DMPK).

Plasma Ceramide Species Are Associated with Diabetes Risk in Participants of the Strong Heart Study

BACKGROUND

Few studies have assessed the associations of ceramides and sphingomyelins (SMs) with diabetes in humans.

OBJECTIVE

We assessed associations of 15 circulating ceramides and SM species with incident diabetes in 2 studies.

METHODS

The analysis included 435 American-Indian participants from the Strong Heart Study (nested case-control design for analyses; mean age: 57 y; 34% male; median time until diabetes 4.3 y for cases) and 1902 participants from the Strong Heart Family Study (prospective design for analyses; mean age: 37 y; 39% male; median 12.5 y of follow-up). Sphingolipid species were measured using stored plasma samples by sequential LC and MS. Using logistic regression and parametric survival models within studies, and an inverse-variance-weighted meta-analysis across studies, we examined associations of 15 ceramides and SM species with incident diabetes.

RESULTS

There were 446 cases of incident diabetes across the studies. Higher circulating concentrations of ceramides containing stearic acid (Cer-18), arachidic acid (Cer-20), and behenic acid (Cer-22) were each associated with a higher risk of diabetes. The RRs for incident diabetes per 1 SD of each log ceramide species (μM) were 1.22 (95% CI: 1.09, 1.37) for Cer-18, 1.18 (95% CI: 1.06, 1.31) for Cer-20, and 1.20 (95% CI: 1.08, 1.32) for Cer-22. Although the magnitude of the risk estimates for the association of ceramides containing lignoceric acid (Cer-24) with diabetes was similar to those for Cer-18, Cer-20, and Cer-22 (RR = 1.13; 95% CI: 1.01, 1.26), the association was not statistically significant after correction for multiple testing (P = 0.007). Ceramides carrying palmitic acid (Cer-16), SMs, glucosyl-ceramides, or a lactosyl-ceramide were not associated with diabetes risk.

CONCLUSIONS

Higher concentrations of circulating Cer-18, Cer-20, and Cer-22 were associated with a higher risk of developing diabetes in 2 studies of American-Indian adults. This trial was registered at clinicaltrials.gov as NCT00005134.

NFYB-1 regulates mitochondrial function and longevity via lysosomal prosaposin

Mitochondria are multidimensional organelles whose activities are essential to cellular vitality and organismal longevity, yet underlying regulatory mechanisms spanning these different levels of organization remain elusive^1-5. Here we show that Caenorhabditis elegans nuclear transcription factor Y, beta subunit (NFYB-1), a subunit of the NF-Y transcriptional complex^6-8, is a crucial regulator of mitochondrial function. Identified in RNA interference (RNAi) screens, NFYB-1 loss leads to perturbed mitochondrial gene expression, reduced oxygen consumption, mitochondrial fragmentation, disruption of mitochondrial stress pathways, decreased mitochondrial cardiolipin levels and abolition of organismal longevity triggered by mitochondrial impairment. Multi-omics analysis reveals that NFYB-1 is a potent repressor of lysosomal prosaposin, a regulator of glycosphingolipid metabolism. Limiting prosaposin expression unexpectedly restores cardiolipin production, mitochondrial function and longevity in the nfyb-1 background. Similarly, cardiolipin supplementation rescues nfyb-1 phenotypes. These findings suggest that the NFYB-1-prosaposin axis coordinates lysosomal to mitochondria signalling via lipid pools to enhance cellular mitochondrial function and organismal health.

Probiotic Bacillus subtilis Protects against α-Synuclein Aggregation in C. elegans

Recent discoveries have implicated the gut microbiome in the progression and severity of Parkinson's disease; however, how gut bacteria affect such neurodegenerative disorders remains unclear. Here, we report that the Bacillus subtilis probiotic strain PXN21 inhibits α-synuclein aggregation and clears preformed aggregates in an established Caenorhabditis elegans model of synucleinopathy. This protection is seen in young and aging animals and is partly mediated by DAF-16. Multiple B. subtilis strains trigger the protective effect via both spores and vegetative cells, partly due to a biofilm formation in the gut of the worms and the release of bacterial metabolites. We identify several host metabolic pathways differentially regulated in response to probiotic exposure, including sphingolipid metabolism. We further demonstrate functional roles of the sphingolipid metabolism genes lagr-1, asm-3, and sptl-3 in the anti-aggregation effect. Our findings provide a basis for exploring the disease-modifying potential of B. subtilis as a dietary supplement.

High-glucose diets induce mitochondrial dysfunction in Caenorhabditis elegans

Glucose is an important nutrient that dictates the development, fertility and lifespan of all organisms. In humans, a deficit in its homeostatic control might lead to hyperglucemia and the development of obesity and type 2 diabetes, which show a decreased ability to respond to and metabolize glucose. Previously, we have reported that high-glucose diets (HGD) induce alterations in triglyceride content, body size, progeny, and the mRNA accumulation of key regulators of carbohydrate and lipid metabolism, and longevity in Caenorhabditis elegans (PLoS ONE 13(7): e0199888). Herein, we show that increasing amounts of glucose in the diet induce the swelling of both mitochondria in germ and muscle cells. Additionally, HGD alter the enzymatic activities of the different respiratory complexes in an intricate pattern. Finally, we observed a downregulation of ceramide synthases (hyl-1 and hyl-2) and antioxidant genes (gcs-1 and gst-4), while mitophagy genes (pink-1 and dct-1) were upregulated, probably as part of a mitohormetic mechanism in response to glucose toxicity.