Ceramides and glucosylceramides are independent antagonists of insulin signaling

Determining β-Monosaccharide Head Group Composition with High-Resolution Cyclic Ion Mobility Separations Coupled to Tandem Mass Spectrometry as a First Step for Unknown Cerebroside Analysis

Cerebrosides, a class of biologically important lipids, are comprised of a monosaccharide head group along with their ceramide tail. However, their accurate characterization is challenging because of the isomerism in both the tail, from potential double bond positioning, or in the head from monosaccharide composition and αβ anomericity. In this work, we focused on tackling the identification of the β-monosaccharide head group, as either glucose or galactose, in various cerebroside isomers as well as demonstrating how our methodology could be applied to unknowns found in a porcine extract. To achieve this, we performed collision-induced dissociation prior to cyclic ion mobility separations to generate monosaccharide fragment ions from the starting cerebroside precursor ions. With this pre-cIMS CID approach, we observed that the cIMS separations of the fragment ions were diagnostic of the β-monosaccharide head group composition (i.e., glucose versus galactose), regardless of the ceramide tail length. From there, we demonstrated an example of how this methodology could also be applied to cerebrosides found in a porcine extract and a framework for how this approach could be added to existing workflows in developing collision cross section databases. Overall, we envision that our developed pre-cIMS CID-based approach will be a complementary and orthogonal tool to existing ones in glycolipidomics workflows.

Endogenous Metabolites in Metabolic Diseases: Pathophysiologic Roles and Therapeutic Implications

Breakthroughs in metabolomics technology have revealed the direct regulatory role of metabolites in physiology and disease. Recent data have highlighted the bioactive metabolites involved in the etiology and prevention and treatment of metabolic diseases such as obesity, nonalcoholic fatty liver disease, type 2 diabetes mellitus, and atherosclerosis. Numerous studies reveal that endogenous metabolites biosynthesized by host organisms or gut microflora regulate metabolic responses and disorders. Lipids, amino acids, and bile acids, as endogenous metabolic modulators, regulate energy metabolism, insulin sensitivity, and immune response through multiple pathways, such as insulin signaling cascade, chemical modifications, and metabolite-macromolecule interactions. Furthermore, the gut microbial metabolites short-chain fatty acids, as signaling regulators have a variety of beneficial impacts in regulating energy metabolic homeostasis. In this review, we will summarize information about the roles of bioactive metabolites in the pathogenesis of many metabolic diseases. Furthermore, we discuss the potential value of metabolites in the promising preventive and therapeutic perspectives of human metabolic diseases.

Targeted Lipidomics and Transcriptomics Unveil Aberrant Lipid Metabolic Remodeling in Visceral and Subcutaneous Adipose Tissue under ER Stress

Endoplasmic reticulum (ER) stress is known to impair the function of visceral adipose tissue (VAT) and subcutaneous adipose tissue (SAT), disrupting lipid metabolism. Despite the crucial role lipid plays in regulating adipose tissue function, the specific lipidomic alterations in VAT and SAT under ER stress remain unclear. In this study, ER stress was induced in VAT and SAT, and targeted lipidomic and transcriptomic approaches were used to analyze lipid metabolism and gene expression profiles. The results revealed that VAT exhibited a stronger ER stress response, characterized by a significant increase in binding immunoglobulin protein (BiP) expression and notable lipidomic disruptions, especially in glycerides and sterols. These disruptions were marked by a decrease in protective polyunsaturated fatty acyl species and the accumulation of lipotoxic molecules. In contrast, SAT displayed less severe lipidomic alterations. Transcriptomic analysis indicated that VAT was more susceptible to immune activation, inflammation, and metabolic dysfunction, while SAT primarily showed alterations in protein folding processes. These findings underscore the tissue-specific mechanisms of ER stress adaptation in VAT and SAT. In conclusion, VAT appears to be a critical target for addressing metabolic dysfunction in obesity and related disorders, with potential therapeutic implications for managing ER stress-induced metabolic diseases.

Metabolome and RNA-seq reveal discrepant metabolism and secretory metabolism profile in skeletal muscle between obese and lean pigs at different ages

Metabolites and metabolism-related gene expression profiles in skeletal muscle change dramatically under obesity, aging and metabolic disease. Since obese and lean pigs are ideal models for metabolic research. Here, we compared metabolome and transcriptome of Longissimus dorsi (LD) muscle between Taoyuan black (TB, obese) and Duroc (lean) pigs at different ages. We defined the "window phase" of intramuscular fat (IMF) deposition in TB pig, which has significantly higher IMF than Duroc pig. Our results displayed discrepant lipid composition and different expression genes (DEGs) enriched in lipid metabolism, and both metabolome and transcriptome analyses revealed stronger energy expenditure and more active amino acid and protein metabolism in Duroc pig. 10 up- and 51 down-regulated biomarker metabolites with age- and breed-specificity were identified. Potential secretory metabolites, including organic acid (fumaric acid, succinate, malic acid, and gamma-aminobutyric acid), amino acid (L-lysine, and L-glutamic acid), lipid (2-hydroxyisovaleric acid, and L-carnitine) were demonstrated a significant correlation with IMF deposition. Our research highlights the huge difference of metabolic spectrum in skeletal muscle between obese and lean model and muscle-derived secretory metabolites might act as an ambassador of intercellular communication to regulate systematic metabolism.

Sphingolipid profiling as a biomarker of type 2 diabetes risk: evidence from the MIDUS and PREDIMED studies

BACKGROUND

Type 2 diabetes (T2D) has become a worldwide pandemic. While ceramides may serve as intermediary between obesity-related lipotoxicity and T2D, the relationship with simple glycosphingolipids remains uncertain. The aim of this study was to characterize the associations between blood glycosphingolipid and ceramide species with T2D and to identify a circulating sphingolipid profile that could serve as novel biomarker for T2D risk.

METHODS

Cross-sectional relationship between sphingolipid levels, insulin resistance, and T2D prevalence were evaluated in 2,072 American adults from MIDUS cohort. Prospectively, the association between sphingolipid species and the incidence of T2D was analyzed using a case-cohort design nested within the PREDIMED trial (250 cases and a random sample of 692 participants, with 3.8 years of median follow-up). Circulating levels of sphingolipid species in both populations were measured using LC/MS. Hazard ratios were estimated with weighted Cox regression models using Barlow weights.

RESULTS

In American adults, only CER18:0 and CER22:0 were linked to insulin resistance and a higher prevalence of T2D. Conversely, three lactosylceramides (LCER 14:0, 16:0, and 24:1) showed a strong inverse relationship with both insulin resistance and T2D. These findings led to development of two sphingolipid scores. In the prospective analysis, these scores consistently predicted a reduced risk of T2D incidence in PREDIMED (HR: 0.64, 95% CI 0.44 to 0.94 and 0.58, 0.40 to 0.85 respectively) between extreme quartiles, with 5-year absolute risk differences of 9.6% (95% CI: 0.3-20.5%) and 11.4% (1.0-21.6%). They were validated in the same trial with samples obtained after 1 year of follow-up.

CONCLUSIONS

Our findings support the potential usefulness of circulating sphingolipid profiles as novel biomarkers for T2D risk. Moreover, this study opens the door for future research on the predictive value and possible protective roles of lactosylceramides in T2D.

The plasma lipidome varies with the severity of metabolic dysfunction-associated steatotic liver disease

BACKGROUND

Metabolic dysfunction-associated steatotic liver disease (MASLD) is closely associated with many aspects of disturbed metabolic health. MASLD encompasses a wide spectrum of liver diseases, ranging from isolated steatosis to metabolic dysfunction-associated steatohepatitis (MASH), up to fibrosis, cirrhosis, and ultimately hepatocellular carcinoma. Limited noninvasive diagnostic tools are currently available to distinguish the various stages of MASLD and as such liver biopsy remains the gold standard for MASLD diagnostics. We aimed to explore whether the plasma lipidome and its variations can serve as a biomarker for MASLD stages.

METHODS

We investigated the plasma lipidome of 7 MASLD-free subjects and 32 individuals with MASLD, of whom 11 had MASH based on biopsy scoring.

RESULTS

Compared with the MASLD-free subjects, individuals with MASLD had higher plasma concentrations of sphingolipids, glycerolipids, and glycerophospholipids. Only plasma concentrations of ceramide-1-phosphate C1P(d45:1) and phosphatidylcholine PC(O-36:3), PC(O-38:3), and PC(36:2) differed significantly between presence of MASH in individuals with MASLD. Of these lipids, the first three have a very low relative plasma abundance, thus only PC(36:2) might serve as a biomarker with higher plasma concentrations in MASLD individuals without MASH compared to those with MASH.

CONCLUSIONS

Plasma lipids hold promise as biomarkers of MASLD stages, whereas plasma PC(36:2) concentrations would be able to distinguish individuals with MASH from those with MASLD without MASH.

Genotype-microbiome-metabolome associations in early childhood and their link to BMI

Through the analysis of data from children aged 6 months to 8 years enrolled in the Vitamin D Antenatal Asthma Reduction Trial (VDAART), significant simultaneous associations were identified between variants in the fragile histidine triad (FHIT) gene, children's body mass index, microbiome features related to obesity, and key lipids and amino acids. These patterns represent evidence of the genotype influence in shaping the host microbiome in developing stages and new potential biomarkers for childhood obesity, insulin resistance, and type 2 diabetes.

Increased allergic inflammation and decreased lung insulin sensitivity in offspring of obese allergic mothers

Epidemiological studies demonstrate that maternal obesity and maternal allergy are major risk factors for asthma in offspring. However, the impact of maternal allergy and obesity on offspring lung insulin signaling and allergen responsiveness is not known. To evaluate this, allergic and nonallergic female mice were fed a high-fat diet or low-fat diet from 7 wk before pregnancy until weaning. Neonatal pups were allergen-sensitized and allergen-challenged and then were assessed for obesity, insulin signaling, and allergic inflammation. Compared with pups of nonobese nonallergic mothers, allergen-challenged pups of obese nonallergic mothers, nonobese allergic mothers, and obese allergic mothers had bronchoalveolar lavage (BAL) eosinophilia, with the pups of obese allergic mothers having the highest BAL eosinophilia. These pups also had lower insulin-induced lung AKT phosphorylation, indicating a decrease in lung parenchymal insulin sensitivity. In cross-fostering experiments, allergen-challenged pups exposed to both pre- and postnatal obese allergic mothers had the highest level of BAL eosinophilia. Maternal obesity or allergy increased offspring serum allergen-specific IgE and interleukin-5 that was highest when the mother was both obese and allergic. Also, allergen-challenged pups exposed to both pre- and postnatal obese allergic mothers had the highest level of interleukin-5. In summary, offspring born to obese allergic mothers have decreased lung insulin sensitivity and increased lung allergic inflammation. Interestingly, our data also demonstrate that there is both a pregnancy and postpregnancy aspect of maternal allergy and obesity that enhances allergen responsiveness in offspring.

Glycosphingolipids in Cardiovascular Disease: Insights from Molecular Mechanisms and Heart Failure Models

This review explores the crucial role of glycosphingolipids (GSLs) in the context of cardiovascular diseases (CVDs), focusing on their biosynthesis, metabolic pathways, and implications for clinical outcomes. GSLs are pivotal in regulating a myriad of cellular functions that are essential for heart health and disease progression. Highlighting findings from both human cohorts and animal models, this review emphasizes the potential of GSLs as biomarkers and therapeutic targets. We advocate for more detailed mechanistic studies to deepen our understanding of GSL functions in cardiovascular health, which could lead to innovative strategies for diagnosis, treatment, and personalized medicine in cardiovascular care.

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

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

Metabolomic and Lipidomic Analysis of Manganese-Associated Parkinsonism: a Case-Control Study in Brescia, Italy

Background and Objectives

Excessive Manganese (Mn) exposure is neurotoxic and can cause Mn-Induced Parkinsonism (MnIP), marked by cognitive and motor dysfunction. Although metabolomic and lipidomic research in Parkinsonism (PD) patients exists, it remains limited. This study hypothesizes distinct metabolomic and lipidomic profiles based on exposure status, disease diagnosis, and their interaction.

Methods

We used a case-control design with a 2×2 factorial framework to investigate the metabolomic and lipidomic alterations associated with Mn exposure and their link to PD. The study population of 97 individuals was divided into four groups: non-exposed controls (n=23), exposed controls (n=25), non-exposed with PD (n=26) and exposed with PD (n=23). Cases, defined by at least two cardinal PD features (excluding vascular, iatrogenic, and traumatic origins), were recruited from movement disorder clinics in four hospitals in Brescia, Northern Italy. Controls, free from neurological or psychiatric conditions, were selected from the same hospitals. Exposed subjects resided in metallurgic regions (Val Camonica and Bagnolo Mella) for at least 8 continuous years, while non-exposed subjects lived in low-exposure areas around Lake Garda and Brescia city. We conducted untargeted analyses of metabolites and lipids in whole blood samples using ultra-high-performance liquid chromatography (UHPLC) and mass spectrometry (MS), followed by statistical analyses including Principal Component Analysis (PCA), Partial Least Squares-Discriminant Analysis (PLS-DA), and Two-Way Analysis of Covariance (ANCOVA).

Results

Metabolomic analysis revealed modulation of alanine, aspartate, and glutamate metabolism (Impact=0.05, p=0.001) associated with disease effect; butanoate metabolism (Impact=0.03, p=0.004) with the exposure effect; and vitamin B6 metabolism (Impact=0.08, p=0.03) with the interaction effect. Differential relative abundances in 3-sulfoxy-L-Tyrosine (β=1.12, FDR p<0.001), glycocholic acid (β=0.48, FDR p=0.03), and palmitelaidic acid (β=0.30, FDR p<0.001) were linked to disease, exposure, and interaction effects, respectively. In the lipidome, ferroptosis (Pathway Lipids=11, FDR p=0.03) associated with the disease effect and sphingolipid signaling (Pathway Lipids=9, FDR p=0.04) associated with the interaction effect were significantly altered. Lipid classes triacylglycerols, ceramides, and phosphatidylethanolamines showed differential relative abundances associated with disease, exposure, and interaction effects, respectively.

Discussion

These findings suggest that PD and Mn exposure induce unique metabolomic and lipidomic changes, potentially serving as biomarkers for MnIP and warranting further study.

Sphingolipids and Chronic Kidney Disease

Sphingolipids (SLs) are bioactive signaling molecules essential for various cellular processes, including cell survival, proliferation, migration, and apoptosis. Key SLs such as ceramides, sphingosine, and their phosphorylated forms play critical roles in cellular integrity. Dysregulation of SL levels is implicated in numerous diseases, notably chronic kidney disease (CKD). This review focuses on the role of SLs in CKD, highlighting their potential as biomarkers for early detection and prognosis. SLs maintain renal function by modulating the glomerular filtration barrier, primarily through the activity of podocytes. An imbalance in SLs can lead to podocyte damage, contributing to CKD progression. SL metabolism involves complex enzyme-catalyzed pathways, with ceramide serving as a central molecule in de novo and salvage pathways. Ceramides induce apoptosis and are implicated in oxidative stress and inflammation, while sphingosine-1-phosphate (S1P) promotes cell survival and vascular health. Studies have shown that SL metabolism disorders are linked to CKD progression, diabetic kidney disease, and glomerular diseases. Targeting SL pathways could offer novel therapeutic approaches for CKD. This review synthesizes recent research on SL signaling regulation in kidney diseases, emphasizing the importance of maintaining SL balance for renal health and the potential therapeutic benefits of modulating SL pathways.

Ceramides are fuel gauges on the drive to cardiometabolic disease

Ceramides are signals of fatty acid excess that accumulate when a cell's energetic needs have been met and its nutrient storage has reached capacity. As these sphingolipids accrue, they alter the metabolism and survival of cells throughout the body including in the heart, liver, blood vessels, skeletal muscle, brain, and kidney. These ceramide actions elicit the tissue dysfunction that underlies cardiometabolic diseases such as diabetes, coronary artery disease, metabolic-associated steatohepatitis, and heart failure. Here, we review the biosynthesis and degradation pathways that maintain ceramide levels in normal physiology and discuss how the loss of ceramide homeostasis drives cardiometabolic pathologies. We highlight signaling nodes that sense small changes in ceramides and in turn reprogram cellular metabolism and stimulate apoptosis. Finally, we evaluate the emerging therapeutic utility of these unique lipids as biomarkers that forecast disease risk and as targets of ceramide-lowering interventions that ameliorate disease.

Genotype-microbiome-metabolome associations in early childhood, and their link to BMI and childhood obesity

The influence of genotype on defining the human gut microbiome has been extensively studied, but definite conclusions have not yet been found. To fill this knowledge gap, we leverage data from children enrolled in the Vitamin D Antenatal Asthma Reduction Trial (VDAART) from 6 months to 8 years old. We focus on a pool of 12 genes previously found to be associated with the gut microbiome in independent studies, establishing a Bonferroni corrected significance level of p-value < 2.29 × 10 -6 . We identified significant associations between SNPs in the FHIT gene (known to be associated with obesity and type 2 diabetes) and obesity-related microbiome features, and the children's BMI through their childhood. Based on these associations, we defined a set of SNPs of interest and a set of taxa of interest. Taking a multi-omics approach, we integrated plasma metabolome data into our analysis and found simultaneous associations among children's BMI, the SNPs of interest, and the taxa of interest, involving amino acids, lipids, nucleotides, and xenobiotics. Using our association results, we constructed a quadripartite graph where each disjoint node set represents SNPs in the FHIT gene, microbial taxa, plasma metabolites, or BMI measurements. Network analysis led to the discovery of patterns that identify several genetic variants, microbial taxa and metabolites as new potential markers for obesity, type 2 diabetes, or insulin resistance risk.

Sphingolipid metabolism in brain insulin resistance and neurological diseases

Sphingolipids, as members of the large lipid family, are important components of plasma membrane. Sphingolipids participate in biological signal transduction to regulate various important physiological processes such as cell growth, apoptosis, senescence, and differentiation. Numerous studies have demonstrated that sphingolipids are strongly associated with glucose metabolism and insulin resistance. Insulin resistance, including peripheral insulin resistance and brain insulin resistance, is closely related to the occurrence and development of many metabolic diseases. In addition to metabolic diseases, like type 2 diabetes, brain insulin resistance is also involved in the progression of neurodegenerative diseases including Alzheimer's disease and Parkinson's disease. However, the specific mechanism of sphingolipids in brain insulin resistance has not been systematically summarized. This article reviews the involvement of sphingolipids in brain insulin resistance, highlighting the role and molecular biological mechanism of sphingolipid metabolism in cognitive dysfunctions and neuropathological abnormalities of the brain.

Multiomics Approaches Identify Biomarkers for BAT Thermogenesis

Brown adipose tissue (BAT) thermogenesis confers beneficial effects on metabolic diseases such as obesity and type-2 diabetes. Nevertheless, the mechanism and lipid driving the process that evokes this response have not been investigated yet. Here, a multiomics approach of integrative transcriptomics and lipidomics is used to explore the mechanism of regulating thermogenesis in BAT and providing promising lipid biomarkers and biomarker genes for thermogenic activators as antiobesity drugs. Lipidomics analysis demonstrated that a high abundance of glycerophospholipids and sphingolipids was more significant in BAT than in WAT. Enrichment analysis of upregulated DEGs between WAT and BAT screened suggested that the differences were mainly involved in lipid metabolism. Besides, β3-adrenergic agonist stimulation reduced the levels of TAG and DAG and increased the content of PC, PE, CL, and LPC and expression of genes involved in thermogenesis, fatty acid elongation, and glycerophospholipid metabolism in BAT. In this study, based on interpreting the inherent characterization of BAT as thermogenic tissue through comparison with WAT as fat storage tissue, adrenergic stimulation-induced BAT thermogenesis further identified specific lipid biomarkers (7 TAG species, 10 PC species, 1 LPC species, and 1 CL species) and Elovl3 and Crat gene biomarkers, which may provide targets for combating obesity by boosting BAT thermogenesis.

Effects of Endurance Exercise and Vitamin D Supplementation on Insulin Resistance and Plasma Lipidome in Middle-Aged Adults with Type 2 Diabetes

(1) Background: We investigated the effects of a 12-week exercise intervention with or without vitamin D supplementation on insulin resistance and the plasma lipidome of participants with type 2 diabetes. We further explored whether the effects of the intervention on glycemic parameters could be associated with the baseline lipidome. (2) Methods: Sixty-one participants were randomly allocated to control (Con), exercise (EX), vitamin D (VD), and EX + VD groups. Multiple glycemic and anthropometric parameters were evaluated before and after intervention. The homeostasis model assessment of insulin resistance (HOMA-IR) was the primary outcome. The plasma lipidome was analyzed before, after, and at an additional 12-week follow-up. Machine learning was applied to establish prediction models for responsiveness of glycemic control. (3) Results: Our interventions failed to improve the HOMA-IR index while fasting glucose was reduced in the EX + VD group (change%, -11.9%; effect size, 0.65; p < 0.05). Both EX and VD interventions altered the plasma lipidome, with EX + VD intervention considerably affecting levels of lyso-phosphatidylcholines and triglycerols containing long-chain unsaturated fatty acids. Such effects could last until 12 weeks after intervention. Notably, there was high inter-individual variability in glycemic parameters including HOMA-IR in response to the interventions, which could be predicted with great accuracy using an optimal panel of baseline lipid predictors alone or in combination with clinical indices, as assessed by an area under the receiver operating characteristic curve value of over 0.9. (4) Conclusions: Although substantial alterations were observed in the plasma lipidome related to glycemic control, our intervention failed to improve HOMA-IR scores, which may have been predominately due to the large inter-individual variability in responses. Basal plasma lipid levels could potentially predict an individual's response to intervention, highlighting the necessity of personalized nutrition.

Effect of the Lipid Landscape on the Efficacy of Cell-Penetrating Peptides

Every cell biological textbook teaches us that the main role of the plasma membrane is to separate cells from their neighborhood to allow for a controlled composition of the intracellular space. The mostly hydrophobic nature of the cell membrane presents an impenetrable barrier for most hydrophilic molecules larger than 1 kDa. On the other hand, cell-penetrating peptides (CPPs) are capable of traversing this barrier without compromising membrane integrity, and they can do so on their own or coupled to cargos. Coupling biologically and medically relevant cargos to CPPs holds great promise of delivering membrane-impermeable drugs into cells. If the cargo is able to interact with certain cell types, uptake of the CPP-drug complex can be tailored to be cell-type-specific. Besides outlining the major membrane penetration pathways of CPPs, this review is aimed at deciphering how properties of the membrane influence the uptake mechanisms of CPPs. By summarizing an extensive body of experimental evidence, we argue that a more ordered, less flexible membrane structure, often present in the very diseases planned to be treated with CPPs, decreases their cellular uptake. These correlations are not only relevant for understanding the cellular biology of CPPs, but also for rationally improving their value in translational or clinical applications.

The association between dietary patterns, plasma lipid profiles, and inflammatory potential in a vascular dementia cohort

Background

Inflammation and altered lipid dyshomeostasis have been implicated in the pathogenesis of Alzheimer's disease and vascular dementia.

Objective

To determine if there are any associations between dietary patterns, plasma lipid profiles, and inflammatory potential in a vascular dementia cohort.

Methods

One hundred fifty participants (36 subjects with Vascular Dementia and 114 healthy controls) from two Australian teaching hospitals completed a cross-sectional survey examining their dietary and lifestyle patterns. Each participant's diet was further evaluated using the Empirical Dietary Inflammatory Index. Some participants also donated blood samples for lipidomic analysis.

Results

After adjusting for age, education, and socioeconomic status, participants with vascular dementia tend to have higher lipid profiles, do less exercise, and engage less frequently in social interaction, educational, or reading activities. They also tend to consume more deep-fried food and full-fat dairy compared to control subjects. However, there was no difference in Empirical Dietary Inflammatory Index between the two groups after adjusting for age, education, and socioeconomic status.

Conclusion

Our findings suggest a graded inverse association between healthy lifestyle factors and vascular dementia.

Associations of altered hepatic gene expression in American lifestyle-induced obesity syndrome diet-fed mice with metabolic changes during NAFLD development and progression

Non-alcoholic fatty liver disease (NAFLD) pathogenesis remains poorly understood due to the complex metabolic and inflammatory changes in the liver. This study aimed to elucidate hepatic events related to inflammation and lipid metabolism and their linkage with metabolic alterations during NAFLD in American lifestyle-induced obesity syndrome (ALIOS) diet-fed mice. Forty-eight C57BL/6J male mice were fed with ALIOS diet (n=24) or control chow diet (n=24) for 8, 12, and 16 weeks. At the end of each timepoint, eight mice were sacrificed where plasma and liver were collected. Hepatic fat accumulation was followed using magnetic resonance imaging and confirmed with histology. Further, targeted gene expression and non-targeted metabolomics analysis were conducted. Our results showed higher hepatic steatosis, body weight, energy consumption, and liver mass in ALIOS diet-fed mice compared to control mice. ALIOS diet altered expression of genes related to inflammation (Tnfa and IL-6) and lipid metabolism (Cd36, Fasn, Scd1, Cpt1a, and Ppara). Metabolomics analysis indicated decrease of lipids containing polyunsaturated fatty acids such as LPE(20:5) and LPC(20:5) with increase of other lipid species such as LPI(16:0) and LPC(16:2) and peptides such as alanyl-phenylalanine and glutamyl-arginine. We further observed novel correlations between different metabolites including sphingolipid, lysophospholipids, peptides, and bile acid with inflammation, lipid uptake and synthesis. Together with the reduction of antioxidant metabolites and gut microbiota-derived metabolites contribute to NAFLD development and progression. The combination of non-targeted metabolomics with gene expression in future studies can further identify key metabolic routes during NAFLD which could be the targets of potential novel therapeutics.

Diet-induced gut dysbiosis and inflammation: Key drivers of obesity-driven NASH

Sucrose, the primary circulating sugar in plants, contains equal amounts of fructose and glucose. The latter is the predominant circulating sugar in animals and thus the primary fuel source for various tissue and cell types in the body. Chronic excessive energy intake has, however, emerged as a major driver of obesity and associated pathologies including nonalcoholic fatty liver diseases (NAFLD) and the more severe nonalcoholic steatohepatitis (NASH). Consumption of a high-caloric, western-style diet induces gut dysbiosis and inflammation resulting in leaky gut. Translocation of gut-derived bacterial content promotes hepatic inflammation and ER stress, and when either or both of these are combined with steatosis, it can cause NASH. Here, we review the metabolic links between diet-induced changes in the gut and NASH. Furthermore, therapeutic interventions for the treatment of obesity and liver metabolic diseases are also discussed with a focus on restoring the gut-liver axis.

Metabolomics Profiling of Vitamin D Status in Relation to Dyslipidemia

Vitamin D deficiency is a global disorder associated with several chronic illnesses including dyslipidemia and metabolic syndrome. The impact of this association with both dyslipidemia and vitamin D deficiency on metabolomics profile is not yet fully understood. This study analyses the metabolomics and lipidomic signatures in relation to vitamin D status and dyslipidemia. Metabolomics data were collected from Qatar Biobank database and categorized into four groups based on vitamin D and dyslipidemia status. Metabolomics multivariate analysis was performed using the orthogonal partial least square discriminate analysis (OPLS-DA) whilst linear models were used to assess the per-metabolite association with each of the four dyslipidemia/vitamin D combination groups. Our results indicate a high prevalence of vitamin D deficiency among the younger age group, while dyslipidemia was more prominent in the older group. A significant alteration of metabolomics profile was observed among the dyslipidemic and vitamin D deficient individuals in comparison with control groups. These modifications reflected changes in some key pathways including ceramides, diacylglycerols, hemosylceramides, lysophospholipids, phosphatidylcholines, phosphatidylethanol amines, and sphingomyelins. Vitamin D deficiency and dyslipidemia have a deep impact on sphingomyelins profile. The modifications were noted at the level of ceramides and are likely to propagate through downstream pathways.

Ceramide metabolism associated with chronic dietary nutrient surplus and diminished insulin sensitivity in the liver, muscle, and adipose tissue of cattle

High dietary energy and protein supply is common practice in livestock nutrition, aiming to maximize growth and production performance. However, a chronic nutritional surplus induces obesity, promotes insulin insensitivity, and triggers low-grade inflammation. Thirty Holstein bulls were randomly assigned to two groups, low energy and protein (LEP), and high energy and protein (HEP) intake, provided from the 13th to the 20th month of life. Body weight, carcass composition, laminitis score, and circulating insulin and glucose concentrations were assessed. The expression and extent of phosphorylation of insulin signaling proteins were measured in the liver, muscle, and adipose tissue. The sphingolipid metabolome was quantified by a targeted liquid chromatography-mass spectrometry based metabolomics approach. The HEP bulls were obese, had hyperinsulinemia with euglycemia, and expressed clinical signs of chronic laminitis. In the liver, protein kinase B (PKB) phosphorylation was decreased and this was associated with a higher tissue concentration of ceramide 16:0, a sphingolipid that diminishes insulin action by dephosphorylating PKB. In the adipose tissue, insulin receptor expression was lower in HEP bulls, associated with higher concentration of hexosylceramide, which reduces the abundance of functional insulin receptors. Our findings confirm that diet-induced metabolic inflammation triggers ceramide accumulation and disturbs insulin signaling. As insulin insensitivity exacerbates metabolic inflammation, this self-reinforcing cycle could explain the deterioration of metabolic health apparent as chronic laminitis. By demonstrating molecular relationships between insulin signaling and sphingolipid metabolism in three major tissues, our data extend our mechanistic understanding of the role of ceramides in diet-induced metabolic inflammation.

The sphingolipidome of plasma, liver, and adipose tissues and its association with insulin response to oral glucose testing in Icelandic horses

Insulin dysregulation (ID) is a determinant of equine metabolic syndrome. Among the sphingolipids, ceramides contribute to the development of ID; however, the crosstalk between the liver and adipose tissue (AT) depots and the variation among AT depots in terms of ceramide metabolism are not well-understood. We aimed to characterize the sphingolipidome of plasma, liver, and AT (nuchal, NUAT; subcutaneous, SCAT; omental, OMAT; retroperitoneal, RPAT) and their associations with insulin response to oral glucose testing (OGT) in normoinsulinemic and hyperinsulinemic horses. Plasma, liver, and AT samples were collected from 12 Icelandic horses upon euthanasia and analyzed by liquid chromatography-mass spectrometry. Eighty-four targeted compounds were effectively quantified. Comparing the AT depots, greater (FDR < 0.05) ceramide, dihydroceramide, and sphingomyelin concentrations and lower glucosyl- and galactosyl-ceramides were found in RPAT and OMAT than in NUAT and SCAT. Hyperinsulinemic response to OGT was associated with sphingolipidome alterations primarily in the RPAT and OMAT, while the NUAT sphingolipidome did not show signs of ceramide accumulation, which was inconsistent with the previously proposed role of nuchal adiposity in ID. The plasma sphingolipidome was not significantly associated with the liver or AT sphingolipidomes, indicating that plasma profiles are determined by an interplay of various organs. Further, hepatic sphingolipid profiles were not correlated with the profiles of AT depots. Finally, statistically valid partial least square regression models predicting insulin response were found in the plasma (Q²= 0.58, R²= 0.98), liver (Q²= 0.64, R²= 0.74), and RPAT (Q²= 0.68, R²= 0.79) sphingolipidome, but not in the other adipose tissues.

TREM2 in the pathogenesis of AD: a lipid metabolism regulator and potential metabolic therapeutic target

Triggering receptor expressed on myeloid cells 2 (TREM2) is a single-pass transmembrane immune receptor that is mainly expressed on microglia in the brain and macrophages in the periphery. Recent studies have identified TREM2 as a risk factor for Alzheimer’s disease (AD). Increasing evidence has shown that TREM2 can affect lipid metabolism both in the central nervous system (CNS) and in the periphery. In the CNS, TREM2 affects the metabolism of cholesterol, myelin, and phospholipids and promotes the transition of microglia into a disease-associated phenotype. In the periphery, TREM2 influences lipid metabolism by regulating the onset and progression of obesity and its complications, such as hypercholesterolemia, atherosclerosis, and nonalcoholic fatty liver disease. All these altered lipid metabolism processes could influence the pathogenesis of AD through several means, including affecting inflammation, insulin resistance, and AD pathologies. Herein, we will discuss a potential pathway that TREM2 mediates lipid metabolism to influence the pathogenesis of AD in both the CNS and periphery. Moreover, we discuss the possibility that TREM2 may be a key factor that links central and peripheral lipid metabolism under disease conditions, including AD. This link may be due to impacts on the integrity of the blood–brain barrier, and we introduce potential pathways by which TREM2 affects the blood–brain barrier. Moreover, we discuss the role of lipids in TREM2-associated treatments for AD. We propose some potential therapies targeting TREM2 and discuss the prospect and limitations of these therapies.

You aren't IMMUNE to the ceramides that accumulate in cardiometabolic disease

Obesity leads to persistent increases in immune responses that contribute to cardiometabolic pathologies such as diabetes and cardiovascular disease. Pro-inflammatory macrophages infiltrate the expanding fat mass, which leads to increased production of cytokines such as tumor necrosis factor-alpha. Moreover, saturated fatty acids enhance signaling through the toll-like receptors involved in innate immunity. Herein we discuss the evidence that ceramides-which are intermediates in the biosynthetic pathway that produces sphingolipids-are essential intermediates that link these inflammatory signals to impaired tissue function. We discuss the mechanisms linking these immune insults to ceramide production and review the numerous ceramide actions that alter cellular metabolism, induce oxidative stress, and stimulate apoptosis. Lastly, we evaluate the correlation of ceramides in humans with inflammation-linked cardiometabolic disease and discuss preclinical studies which suggest that ceramide-lowering interventions may be an effective strategy to treat or prevent such maladies.

Circadian rhythm of lipid metabolism

Lipids comprise a diverse group of metabolites that are indispensable as energy storage molecules, cellular membrane components and mediators of inter- and intra-cellular signaling processes. Lipid homeostasis plays a crucial role in maintaining metabolic health in mammals including human beings. A growing body of evidence suggests that the circadian clock system ensures temporal orchestration of lipid homeostasis, and that perturbation of such diurnal regulation leads to the development of metabolic disorders comprising obesity and type 2 diabetes. In view of the emerging role of circadian regulation in maintaining lipid homeostasis, in this review, we summarize the current knowledge on lipid metabolic pathways controlled by the mammalian circadian system. Furthermore, we review the emerging connection between the development of human metabolic diseases and changes in lipid metabolites that belong to major classes of lipids. Finally, we highlight the mechanisms underlying circadian organization of lipid metabolic rhythms upon the physiological situation, and the consequences of circadian clock dysfunction for dysregulation of lipid metabolism.

Highland barley Monascus purpureus Went extract ameliorates high-fat, high-fructose, high-cholesterol diet induced nonalcoholic fatty liver disease by regulating lipid metabolism in golden hamsters

ETHNOPHARMACOLOGICAL RELEVANCE

Hepatocyte lipid accumulation is the main feature in the early stage of nonalcoholic fatty liver disease (NAFLD). Highland barley Monascus purpureus Went (HBMPW), a fermentation product of Hordeum vulgare Linn. var. nudum Hook. f. has traditionally been used as fermented foods in Tibet with the effect of reducing blood lipid in folk medicine.

AIM OF THE STUDY

This study investigated the protective effects and molecular mechanism of highland barley Monascus purpureus Went extract (HBMPWE) on NAFLD in syrian golden hamster fed with high-fat, high-fructose, high-cholesterol diet (HFFCD).

MATERIALS AND METHODS

HFFCD-induced NAFLD golden hamster model was established and treated with HBMPWE. Liver index, biochemical index, and hematoxylin and eosin (HE) staining were observed. Liver metabolomics and western blot analysis were employed.

RESULTS

Our study found that HBMPWE ameliorated HFFCD induced dyslipidemia, weight gain and elevated the liver index. In addition, HBMPWE treatment significantly attenuated lipid accumulation in the liver and modulated lipid metabolism (sphingolipid, glycerophospholipid). Our data demonstrated that HBMPWE not only regulated the expression of proteins related to fatty acid synthesis and decomposition (SREBP-1/ACC/FAS/AceS1, PPARα/ACSL/CPT1/ACOX1), but also regulated the expression of proteins related to cholesterol synthesis and clearance (HMGCR, LDLR, CYP7A1).

CONCLUSIONS

HBMPWE improved NAFLD through multiple pathways and multiple targets in body metabolism and could be used as a functional food to treat NAFLD and other lipid metabolic disorders.

Insulin resistance induced by de novo pathway–generated C16-ceramide is associated with type 2 diabetes in an obese population

Background

Obesity and diabetes are two chronic metabolic diseases whose prevalence is increasing at an alarming rate globally. A close association between obesity, diabetes, and insulin resistance has been identified, and many studies have pinpointed obesity as a causal risk factor for insulin resistance. However, the mechanism underlying this association is not entirely understood. In the past decade, ceramides have gained attention due to their accumulation in certain tissues and their suggested role in initiating insulin resistance. This study aims to determine the association of specific ceramides and their major metabolizing enzymes with obesity-associated insulin resistance.

Methods

The samples comprised subcutaneous adipose tissues collected from three cohorts: lean non-diabetic (controls; n = 20), obese-non-diabetic (n = 66), and obese-diabetic (n = 32). Ceramide levels were quantified using LC-MS/MS and mRNA expression level for different enzymes were estimated using real-time PCR-based RNA expression analysis.

Results

C16-ceramide (P = 0.023), C16-dihydro-ceramide (P < 0.005), C18-dihydro-ceramide (P = 0.009) and C24-ceramide (P = 0.040) levels were significantly increased in the obese cohort compared to the control group. However, stratification of the obese group revealed a significant increase in the C16-ceramide levels (P = 0.027) and mRNA over expression of the serine palmitoyl transferases enzyme subunit SPT1 (P < 0.005) in the obese-diabetic cohort compared to the obese-non-diabetic cohort.

Conclusions

The present study indicates that C16-ceramide plays a pivotal role in inducing insulin resistance. Overexpression of SPT1 in the obese-diabetic group and its positive correlation with C16-ceramide suggest that C16-ceramide was generated through the de novo pathway.

Dihydroceramide- and ceramide-profiling provides insights into human cardiometabolic disease etiology

Metabolic alterations precede cardiometabolic disease onset. Here we present ceramide- and dihydroceramide-profiling data from a nested case-cohort (type 2 diabetes [T2D, n = 775]; cardiovascular disease [CVD, n = 551]; random subcohort [n = 1137]) in the prospective EPIC-Potsdam study. We apply the novel NetCoupler-algorithm to link a data-driven (dihydro)ceramide network to T2D and CVD risk. Controlling for confounding by other (dihydro)ceramides, ceramides C18:0 and C22:0 and dihydroceramides C20:0 and C22:2 are associated with higher and ceramide C20:0 and dihydroceramide C26:1 with lower T2D risk. Ceramide C16:0 and dihydroceramide C22:2 are associated with higher CVD risk. Genome-wide association studies and Mendelian randomization analyses support a role of ceramide C22:0 in T2D etiology. Our results also suggest that (dh)ceramides partly mediate the putative adverse effect of high red meat consumption and benefits of coffee consumption on T2D risk. Thus, (dihydro)ceramides may play a critical role in linking genetic predisposition and dietary habits to cardiometabolic disease risk.

Feeding of cuticles from Tenebrio molitor larvae modulates the gut microbiota and attenuates hepatic steatosis in obese Zucker rats

Insect biomass obtained from large-scale mass-rearing of insect larvae has gained considerable attention in recent years as an alternative and sustainable source of food and feed. A byproduct from mass-rearing of insect larvae is the shed cuticles - the most external components of insects which are a relevant source of the polysaccharide chitin. While it has been shown that chitin modulates the gut microbiota and ameliorates lipid metabolic disorders in obese rodent models, feeding studies dealing with isolated insects' cuticles are completely lacking. Thus, the present study tested the hypothesis that dietary insects' cuticles modulate the gut microbiome and improve hepatic lipid metabolism in obese Zucker rats. To test this hypothesis, three groups of obese Zucker rats were fed a nutrient-adequate, semisynthetic basal diet which was supplemented with either 0% (group O), 1.5% (group O1.5) or 3.0% (group O3.0) Tenebrio molitor cuticles at the expense of cellulose. Oil red O-stained liver sections showed a marked lipid accumulation, but lipid accumulation was clearly less in group O3.0 than in groups O and O1.5. In line with this, hepatic lipid concentrations were 30% lower in group O3.0 than in group O (p < 0.05). No differences were observed across the obese groups regarding liver concentrations of methionine, S-adenosylmethionine and homocysteine. Analysis of cecal microbial community at the family level revealed that the relative abundances of Bifidobacteriaceae, Coriobacteriaceae Erysipelotrichaceae, Lactobacillaceae, Prevotellaceae, Sutterellaceae, unknown Deltaproteobacteria and unknown Firmicutes were higher and those of Anaeroplasmataceae, Desulfovibrionaceae, Eubacteriaceae, Ruminococcaceae, Saccharibacteria and unknown Clostridiales were lower in group O3.0 compared to group O (p < 0.05). Cecal digesta concentrations of total short-chain fatty acids, acetate and butyrate were higher in group O3.0 than in group O (p < 0.05). Targeted plasma metabolomics revealed 53 metabolites differing between groups, amongst which two indole metabolites, indole-3-propionic acid and 3-indoxylsulfate, were markedly elevated in group O3.0 compared to groups O1.5 and O. Regarding that increased abundances of bacteria of the Actinobacteria phylum and Lactobacillaceae family in the gut have been reported to be associated with antisteatotic, hepatoprotective and antiinflammatory effects, the pronounced increases of Bifidobacteriaceae and Coriobacteriaceae (both Actinobacteria), and of Lactobacillaceae in group O3.0 might have contributed to the amelioration of fatty liver.

Dataset for liver metabolomic profile of highland barley Monascus purpureus went extract-treated golden hamsters with nonalcoholic fatty liver disease

Nonalcoholic Fatty Liver Disease (NAFLD) is a serious problem endangering human health in the world. The pathogenesis of this disease is often accompanied by lipid metabolism disorder and can cause liver lipid accumulation. Highland barley Monascus purpureus Went extract (HBMPWE) can inhibit the liver lipid accumulation caused by a high-fat, high-fructose, high-cholesterol diet. However, it is not clear what changes have taken place in the process of liver lipid metabolism after HBMPWE administration. To fill this knowledge gap and to support the findings published in the companion research article entitled “Highland Barley Monascus purpureus Went Extract Ameliorates High-Fat, High-Fructose, High-Cholesterol Diet Induced Nonalcoholic Fatty Liver Disease by Regulating Lipid Metabolism in Golden Hamsters” [1], we provided important information related to the liver differential metabolites and identified twenty-one differential metabolites of liver metabolism. In the model group, the levels of lactate, linoleic acid, and malic acid increased significantly. After HBMPWE treatment, the expressions of these metabolites reduced significantly. Therefore, these liver differential metabolites could be used as biological signatures reflecting the severity of NAFLD and HBMPWE treatment outcomes.

Sphingolipid Profiling: A Promising Tool for Stratifying the Metabolic Syndrome-Associated Risk

Metabolic syndrome (MetS) is a multicomponent risk condition that reflects the clustering of individual cardiometabolic risk factors related to abdominal obesity and insulin resistance. MetS increases the risk for cardiovascular diseases (CVD) and type 2 diabetes mellitus (T2DM). However, there still is not total clinical consensus about the definition of MetS, and its pathophysiology seems to be heterogeneous. Moreover, it remains unclear whether MetS is a single syndrome or a set of diverse clinical conditions conferring different metabolic and cardiovascular risks. Indeed, traditional biomarkers alone do not explain well such heterogeneity or the risk of associated diseases. There is thus a need to identify additional biomarkers that may contribute to a better understanding of MetS, along with more accurate prognosis of its various chronic disease risks. To fulfill this need, omics technologies may offer new insights into associations between sphingolipids and cardiometabolic diseases. Particularly, ceramides –the most widely studied sphingolipid class– have been shown to play a causative role in both T2DM and CVD. However, the involvement of simple glycosphingolipids remains controversial. This review focuses on the current understanding of MetS heterogeneity and discuss recent findings to address how sphingolipid profiling can be applied to better characterize MetS-associated risks.

Dietary Supplementation with Exogenous Sea-Cucumber-Derived Ceramides and Glucosylceramides Alleviates Insulin Resistance in High-Fructose-Diet-Fed Rats by Upregulating the IRS/PI3K/Akt Signaling Pathway

Endogenous ceramide is considered to be associated with the progress of insulin resistance. However, the effects of dietary exogenous glucosylceramides and ceramides on insulin resistance are unclear. A model of fructose-induced male Sprague Dawley rats was used to compare the effects of sea-cucumber-derived glucosylceramides and ceramides on insulin resistance. Both glucosylceramides and ceramides significantly improved glucose tolerance, reduced the concentrations of serum glucose and glycosylated hemoglobin, and alleviated the accompanied hypertension. Ceramides significantly enhanced glycogen levels in skeletal muscle, whereas glucosylceramides significantly increased the hepatic glycogen levels. Moreover, glucosylceramides alleviated insulin resistance by inhibiting gluconeogenesis, promoting glycogen synthesis and insulin signal transduction in the liver; meanwhile, ceramides were mainly due to the promotion of glycogen synthesis and insulin signal transduction in skeletal muscle. Additionally, glucosylceramides and ceramides effectively attenuated inflammation in adipose tissue. These results indicate that glucosylceramides and ceramides have potential value in the prevention and alleviation of insulin resistance.

Effect of Korean Red Ginseng on Plasma Ceramide Levels in Postmenopausal Women with Hypercholesterolemia: A Pilot Randomized Controlled Trial

Cardiovascular disease (CVD) is a crucial cause of death in postmenopausal women. Plasma ceramide concentrations are correlated with the development of atherosclerosis and are significant predictors of CVD. Here, we conducted a 4-week, double-blinded, placebo-controlled clinical pilot study to investigate the effect of Korean red ginseng (KRG) on serum ceramide concentrations in 68 postmenopausal women with hypercholesterolemia. Patients were randomly assigned to two groups: the experimental group (n = 36) received KRG and the control (n = 32) group received placebo, 2 g each, once daily. Serum ceramides were measured using liquid chromatography–tandem mass spectrometry at baseline and study completion, with changes in serum ceramide levels as the primary end point. We detected significantly greater mean changes in C16 ceramide levels (d18:1/16:0: −6.4 ± 6.3 pmol/mL vs. 14.6 ± 6.8 pmol/mL, respectively, p = 0.040; d18:1/22:0: −20.8 ± 24.4 pmol/mL vs. 71.1 ± 26.2 pmol/mL, respectively, p = 0.020). Additionally, changes in the median C16 (d18:1/16:0) and C22 (d18:1/22:0) ceramide levels were significantly greater in KRG-group subjects with metabolic syndrome than those without. Therefore, we found that KRG decreases the serum levels of several ceramides in postmenopausal women with hypercholesterolemia, suggesting it may be beneficial for preventing CVD in these individuals.

A Comprehensive Review: Sphingolipid Metabolism and Implications of Disruption in Sphingolipid Homeostasis

Sphingolipids are a specialized group of lipids essential to the composition of the plasma membrane of many cell types; however, they are primarily localized within the nervous system. The amphipathic properties of sphingolipids enable their participation in a variety of intricate metabolic pathways. Sphingoid bases are the building blocks for all sphingolipid derivatives, comprising a complex class of lipids. The biosynthesis and catabolism of these lipids play an integral role in small- and large-scale body functions, including participation in membrane domains and signalling; cell proliferation, death, migration, and invasiveness; inflammation; and central nervous system development. Recently, sphingolipids have become the focus of several fields of research in the medical and biological sciences, as these bioactive lipids have been identified as potent signalling and messenger molecules. Sphingolipids are now being exploited as therapeutic targets for several pathologies. Here we present a comprehensive review of the structure and metabolism of sphingolipids and their many functional roles within the cell. In addition, we highlight the role of sphingolipids in several pathologies, including inflammatory disease, cystic fibrosis, cancer, Alzheimer’s and Parkinson’s disease, and lysosomal storage disorders.

Inflammation and Insulin Resistance as Risk Factors and Potential Therapeutic Targets for Alzheimer's Disease

Overnutrition and modern diets containing high proportions of saturated fat are among the major factors contributing to a low-grade state of inflammation, hyperglycemia and dyslipidemia. In the last decades, the global rise of type 2 diabetes and obesity prevalence has elicited a great interest in understanding how changes in metabolic function lead to an increased risk for premature brain aging and the development of neurodegenerative disorders such as Alzheimer's disease (AD). Cognitive impairment and decreased neurogenic capacity could be a consequence of metabolic disturbances. In these scenarios, the interplay between inflammation and insulin resistance could represent a potential therapeutic target to prevent or ameliorate neurodegeneration and cognitive impairment. The present review aims to provide an update on the impact of metabolic stress pathways on AD with a focus on inflammation and insulin resistance as risk factors and therapeutic targets.

In Vitro Exposure of Leukocytes to HIV Preexposure Prophylaxis Decreases Mitochondrial Function and Alters Gene Expression Profiles

The use of antiretroviral therapy (ART) as preexposure prophylaxis (PrEP) is an effective strategy for preventing HIV acquisition. The cellular consequences of PrEP exposure, however, have not been sufficiently explored to determine potential effects on health in individuals without HIV. In this study, peripheral blood mononuclear cells (PBMCs) from people without HIV were exposed to tenofovir disoproxil fumarate (TDF) or emtricitabine (FTC) overnight. Mitochondrial mass and function were measured by flow cytometry and an Agilent XFp analyzer.

The use of antiretroviral therapy (ART) as preexposure prophylaxis (PrEP) is an effective strategy for preventing HIV acquisition. The cellular consequences of PrEP exposure, however, have not been sufficiently explored to determine potential effects on health in individuals without HIV. In this study, peripheral blood mononuclear cells (PBMCs) from people without HIV were exposed to tenofovir disoproxil fumarate (TDF) or emtricitabine (FTC) overnight. Mitochondrial mass and function were measured by flow cytometry and an Agilent XFp analyzer. Monocyte-derived macrophages (MDMs) were differentiated in 20% autologous serum for 5 days in the presence or absence of TDF or FTC, and surface markers, lipid uptake, and efferocytosis were measured by flow cytometry. MDM gene expression was measured using transcriptome sequencing (RNA-seq). Plasma lipids were measured using mass spectrometry. PBMCs exposed to TDF or FTC had decreased maximal oxygen consumption rate (OCR) and reduced mitochondrial mass. Exposure to PrEP also increased reactive oxygen species (ROS) production from monocyte subsets. Compared to MDMs cultured in medium alone, cells differentiated in the presence of TDF (829 genes) or FTC (888 genes) had significant changes in gene expression. Further, PrEP-exposed MDMs had decreased mitochondrial mass and displayed increased lipid uptake and reduced efferocytosis. Plasma biomarkers and lipid levels were also altered in vivo in individuals receiving a PrEP regimen. In conclusion, exposure of leukocytes to TDF or FTC resulted in decreased mitochondrial function and altered functional and transcriptional profiles. These findings may have important implications for the metabolic and immunologic consequences of PrEP in populations at risk for HIV acquisition.

Ceramides in Metabolism: Key Lipotoxic Players

The global prevalence of metabolic diseases such as type 2 diabetes mellitus, steatohepatitis, myocardial infarction, and stroke has increased dramatically over the past two decades. These obesity-fueled disorders result, in part, from the aberrant accumulation of harmful lipid metabolites in tissues not suited for lipid storage (e.g., the liver, vasculature, heart, and pancreatic beta-cells). Among the numerous lipid subtypes that accumulate, sphingolipids such as ceramides are particularly impactful, as they elicit the selective insulin resistance, dyslipidemia, and ultimately cell death that underlie nearly all metabolic disorders. This review summarizes recent findings on the regulatory pathways controlling ceramide production, the molecular mechanisms linking the lipids to these discrete pathogenic events, and exciting attempts to develop therapeutics to reduce ceramide levels to combat metabolic disease.

Trends in Glucocerebrosides Research: A Systematic Review

Glucocerebrosides are sphingolipid components of cell membranes that intervene in numerous cell biological processes and signaling pathways and that deregulation is implicated in human diseases such as Gaucher disease and Parkinson's disease. In the present study, we conducted a systematic review using document co-citation analysis, clustering and visualization tools to explore the trends and knowledge structure of glucocerebrosides research as indexed in the Science Citation Index Expanded database (1956-present). A co-citation network of 5,324 publications related to glucocerebrosides was constructed. The analysis of emerging categories and keywords suggested a growth of research related to neurosciences over the last decade. We identified ten major areas of research (e.g., clusters) that developed over time, from the oldest (i.e., on glucocerebrosidase protein or molecular analysis of the GBA gene) to the most recent ones (i.e., on drug resistance in cancer, pharmacological chaperones, or Parkinson's disease). We provided for each cluster the most cited publications and a description of their intellectual content. We moreover identified emerging trends in glucocerebrosides research by detecting the surges in the rate of publication citations in the most recent years. In conclusion, this study helps to apprehend the most significant lines of research on glucocerebrosides. This should strengthen the connections between scientific communities studying glycosphingolipids to facilitate advances, especially for the most recent researches on cancer drug resistance and Parkinson's disease.

Metabolic Effects of Selective Deletion of Group VIA Phospholipase A2 from Macrophages or Pancreatic Islet Beta-Cells

To examine the role of group VIA phospholipase A₂ (iPLA₂β) in specific cell lineages in insulin secretion and insulin action, we prepared mice with a selective iPLA₂β deficiency in cells of myelomonocytic lineage, including macrophages (MØ-iPLA₂β-KO), or in insulin-secreting β-cells (β-Cell-iPLA₂β-KO), respectively. MØ-iPLA₂β-KO mice exhibited normal glucose tolerance when fed standard chow and better glucose tolerance than floxed-iPLA₂β control mice after consuming a high-fat diet (HFD). MØ-iPLA₂β-KO mice exhibited normal glucose-stimulated insulin secretion (GSIS) in vivo and from isolated islets ex vivo compared to controls. Male MØ-iPLA₂β-KO mice exhibited enhanced insulin responsivity vs. controls after a prolonged HFD. In contrast, β-cell-iPLA₂β-KO mice exhibited impaired glucose tolerance when fed standard chow, and glucose tolerance deteriorated further when introduced to a HFD. β-Cell-iPLA₂β-KO mice exhibited impaired GSIS in vivo and from isolated islets ex vivo vs. controls. β-Cell-iPLA₂β-KO mice also exhibited an enhanced insulin responsivity compared to controls. These findings suggest that MØ iPLA₂β participates in HFD-induced deterioration in glucose tolerance and that this mainly reflects an effect on insulin responsivity rather than on insulin secretion. In contrast, β-cell iPLA₂β plays a role in GSIS and also appears to confer some protection against deterioration in β-cell functions induced by a HFD.

Glycosphingolipids and neuroinflammation in Parkinson's disease

Parkinson's disease is a progressive neurodegenerative disease characterized by the loss of dopaminergic neurons of the nigrostriatal pathway and the formation of neuronal inclusions known as Lewy bodies. Chronic neuroinflammation, another hallmark of the disease, is thought to play an important role in the neurodegenerative process. Glycosphingolipids are a well-defined subclass of lipids that regulate crucial aspects of the brain function and recently emerged as potent regulators of the inflammatory process. Deregulation in glycosphingolipid metabolism has been reported in Parkinson's disease. However, the interrelationship between glycosphingolipids and neuroinflammation in Parkinson's disease is not well known. This review provides a thorough overview of the links between glycosphingolipid metabolism and immune-mediated mechanisms involved in neuroinflammation in Parkinson's disease. After a brief presentation of the metabolism and function of glycosphingolipids in the brain, it summarizes the evidences supporting that glycosphingolipids (i.e. glucosylceramides or specific gangliosides) are deregulated in Parkinson's disease. Then, the implications of these deregulations for neuroinflammation, based on data from human inherited lysosomal glycosphingolipid storage disorders and gene-engineered animal studies are outlined. Finally, the key molecular mechanisms by which glycosphingolipids could control neuroinflammation in Parkinson's disease are highlighted. These include inflammasome activation and secretion of pro-inflammatory cytokines, altered calcium homeostasis, changes in the blood-brain barrier permeability, recruitment of peripheral immune cells or production of autoantibodies.

Characterization of plasma lipidomics in adolescent subjects with increased risk for type 1 diabetes in the DiPiS cohort

INTRODUCTION

Type 1 diabetes (T1D) is caused by the destruction of pancreatic islet beta cells resulting in total loss of insulin production. Recent studies have suggested that the destruction may be interrelated to plasma lipids.

OBJECTIVES

Specific lipids have previously been shown to be decreased in children who develop T1D before four years of age. Disturbances of plasma lipids prior to clinical diagnosis of diabetes, if true, may provide a novel way to improve prediction, and monitor disease progression.

METHODS

A lipidomic approach was utilized to analyze plasma from 67 healthy adolescent subjects (10-15 years of age) with or without islet autoantibodies but all with increased genetic risk for T1D. The study subjects were enrolled at birth in the Diabetes Prediction in Skåne (DiPiS) study and after 10-15 years of follow-up we performed the present cross-sectional analysis. HLA-DRB345, -DRB1, -DQA1, -DQB1, -DPA1 and -DPB1 genotypes were determined using next generation sequencing. Lipidomic profiles were determined using ultra-high-performance liquid chromatography quadrupole time-of-flight mass spectrometry. Lipidomics data were analyzed according to genotype.

RESULTS

Variation in levels of several specific phospholipid species were related to level of autoimmunity but not development of T1D. Five glycosylated ceramides were increased in insulin autoantibody (IAA) positive adolescent subjects compared to adolescent subjects without this autoantibody. Additionally, HLA genotypes seemed to influence levels of long chain triacylglycerol (TG).

CONCLUSION

Lipidomic profiling of adolescent subjects in high risk of T1D may improve sub-phenotyping in this high risk population.

Diabetic photoreceptors: Mechanisms underlying changes in structure and function

Based on clinical findings, diabetic retinopathy (DR) has traditionally been defined as a retinal microvasculopathy. Retinal neuronal dysfunction is now recognized as an early event in the diabetic retina before development of overt DR. While detrimental effects of diabetes on the survival and function of inner retinal cells, such as retinal ganglion cells and amacrine cells, are widely recognized, evidence that photoreceptors in the outer retina undergo early alterations in diabetes has emerged more recently. We review data from preclinical and clinical studies demonstrating a conserved reduction of electrophysiological function in diabetic retinas, as well as evidence for photoreceptor loss. Complementing in vivo studies, we discuss the ex vivo electroretinography technique as a useful method to investigate photoreceptor function in isolated retinas from diabetic animal models. Finally, we consider the possibility that early photoreceptor pathology contributes to the progression of DR, and discuss possible mechanisms of photoreceptor damage in the diabetic retina, such as enhanced production of reactive oxygen species and other inflammatory factors whose detrimental effects may be augmented by phototransduction.

Sphingosine kinase 1 is required for myristate-induced TNFα expression in intestinal epithelial cells

Saturated fatty acids (SFA) have been known to trigger inflammatory signaling in metabolic tissues; however, the effects of specific SFAs in the intestinal epithelium have not been well studied. Several previous studies have implicated disruptions in sphingolipid metabolism by oversupply of SFAs in inflammatory process. Also, our previous studies have implicated sphingosine kinase 1 (SK1) and its product sphingosine-1-phosphate (S1P) as having key roles in the regulation of inflammatory processes in the intestinal epithelium. Therefore, to define the role for specific SFAs in inflammatory responses in intestinal epithelial cells, we examined myristate (C14:0) and palmitate (C16:0). Myristate, but not palmitate, significantly induced the pro-inflammatory cytokine tumor necrosis factor α (TNFα), and it was SK1-dependent. Interestingly, myristate-induced TNFα expression was not suppressed by inhibition of S1P receptors (S1PRs), hinting at a potential novel intracellular target of S1P. Additionally, myristate regulated the expression of TNFα via JNK activation in an SK1-dependent manner, suggesting a novel S1PR-independent target as a mediator between SK1 and JNK in response to myristate. Lastly, a myristate-enriched milk fat-based diet (MFBD) increased expression of TNFα in colon tissues and elevated the S1P to sphingosine ratio, demonstrating the potential of myristate-involved pathobiologies in intestinal tissues. Taken together our studies suggest that myristate regulates the expression of TNFα in the intestinal epithelium via regulation of SK1 and JNK.

Lipidomics insight into chronic exposure to ambient air pollution in mice

More recent evidences are supportive of air pollution exposure on diabetes risk, including worsening of whole-body insulin sensitivity, enhancement of hepatic lipogenesis and nonalcoholic fatty liver disease after fine particulate matter (PM_2.5) exposure. Therefore, we aimed to explore the lipidomics to get a comprehensive insight about ambient real-world PM_2.5 exposure on lipid metabolism in blood and liver. After ambient PM_2.5 exposure for 6 months, excess triglyceride accumulation in the liver was observed. Remarkable metabolic alterations including neutral lipids, glycerophospholipids and sphingolipids were noticed. Lipidomic signatures in liver is different from plasma in response to PM_2.5 exposure. Lipids including species of ceramide, sphingomyeline and triglyceride may become potential biomarkers of lipotoxicity contributing to PM_2.5-induced metabolic dysfunction, and the present study may serve as a reference lipid bank for further studies.

Lactosylceramide induced by elastin-derived peptides decreases adipocyte differentiation

Elastin, the major protein of the extracellular matrix, is specially found in cardiovascular tissues and contributing to 30-50% of the dry weight of blood vessels. Elastin regulates cell signalling pathways involved in morphogenesis, injury response and inflammation. The function of elastin is frequently compromised in damaged or aged elastic tissues. Indeed, elastin degradation, observed during ageing, and the resulting production of elastin-derived peptides (EDPs), have crucial impacts on cardiovascular disease (atherosclerosis, thrombosis) or on metabolism disease progressions (type 2 diabetes or non-alcoholic steatohepatitis). In the present study, we analysed the EDP effects on 3T3 preadipocyte cell differentiation. In a first part, we treated 3T3-L1 cells with EDP and visualized the lipid droplet accumulation by the oil red O staining and measured the expression of various transcription factors and adipocyte-specific mRNAs by real-time RT-PCR. We demonstrated that the elastin receptor complex, ERC, is activated by EDPs and decreased adipocyte differentiation by a modulation of crucial adipogenesis transcriptional factor particularly PPARγ. In a second part, we identified the signalling pathway implicated in EDP-reduced cell differentiation. The flow cytometry and immunocytochemistry approaches showed that ERC activated by EDP produced a second messenger, lactosylceramide (Lac-Cer). Moreover, this Lac-Cer production favoured the phosphorylation of ERK1-2 (p-ERK1-2), to decrease adipocyte differentiation by a modulation of adipogenesis transcriptional factor PPARγ. To conclude, the EDP/Lac-Cer/p-ERK1-2 signalling pathway may be studied further as a critical target for treating complications associated with adipocyte dedifferentiation such as obesity and diabetes insulin resistance.

Plasma Ceramides and Triglycerides Are Elevated during Pregnancy in Association with Markers of Insulin Resistance in Hutterite Women

Changes in maternal insulin sensitivity and circulating lipids typically occur during the metabolic transitions of pregnancy and lactation. Although ceramides can cause insulin resistance in mammals, their potential roles during pregnancy and lactation are unknown. We hypothesized that changes in lipids like ceramide and triglycerides could occur across different reproductive states and relate to insulin resistance. Our objectives were to comprehensively characterize lipids in the plasma of pregnant, lactating, and nonpregnant and nonlactating (NPNL) women, and to evaluate the relationship between ceramides and the triglyceride index, a proxy of insulin resistance. Middle-aged Hutterite women from the South Dakota Rural Bone Health Study were classified by reproductive status as nonpregnant and nonlactating (NPNL; 19 observations), pregnant (14 observations), or lactating (31 observations). Several plasma lipids were elevated in pregnancy such as ceramides, triglycerides, and total- and high-density lipoprotein cholesterol. The triglyceride index was highest during pregnancy and was positively associated with long- and very long-chain ceramides. Lipidomics revealed lipid signatures specific to reproductive state, including triglycerides, phosphatidylcholines, sphingomyelins, and cholesteryl esters, which were also related to the triglyceride index. Our data support the possibility that ceramides contribute to the development of insulin resistance during pregnancy, and reveal distinct lipid signatures associated with pregnancy and lactation.

The Ability of Quercetin and Ferulic Acid to Lower Stored Fat is Dependent on the Metabolic Background of Human Adipocytes

SCOPE

Dietary flavonoids and phenolic acids can modulate lipid metabolism, but effects on mature human adipocytes are not well characterized.

MATERIALS AND METHODS

Human adipocytes are differentiated, and contain accumulated lipids, mimicking white adipocytes. They are then cultured either under conditions of actively synthesizing and accumulating additional lipids through lipogenesis ("ongoing lipogenic state") or under conditions of maintaining but not increasing stored lipids ("lipid storage state"). Total lipid, lipidomic and transcriptomics analyses are employed to assess changes after treatment with quercetin and/or ferulic acid.

RESULTS

In the "lipid storage state," a longer-term treatment (3 doses over 72 h) with low concentrations of quercetin and ferulic acid together significantly lowered stored lipid content, modified lipid composition, and modulated genes related to lipid metabolism with a strong implication of peroxisome proliferator-activated receptor (PPARα)/retinoid X receptor (RXRα) involvement. In the "ongoing lipogenic state," the effect of quercetin and ferulic acid is markedly different, with fewer changes in gene expression and lipid composition, and no detectable involvement of PPARα/RXRα, with a tenfold higher concentration required to attenuate stored lipid content.

CONCLUSIONS

Multiple low-dose treatment of quercetin and ferulic acid modulates lipid metabolism in adipocytes, but the effect is dramatically dependent on the metabolic state of the cell.