Ceramides - Lipotoxic Inducers of Metabolic Disorders

Lipids balance as a spectroscopy marker of diabetes. Analysis of FTIR spectra by 2D correlation and machine learning analyses

The number of people suffering from type 2 diabetes has rapidly increased. Taking into account, that elevated intracellular lipid concentrations, as well as their metabolism, are correlated with diminished insulin sensitivity, in this study we would like to show lipids spectroscopy markers of diabetes. For this purpose, serum collected from rats (animal model of diabetes) was analyzed using Fourier Transformed Infrared-Attenuated Total Reflection (FTIR-ATR) spectroscopy. Analyzed spectra showed that rats with diabetes presented higher concentration of phospholipids and cholesterol in comparison with non-diabetic rats. Moreover, the analysis of second (IInd) derivative spectra showed no structural changes in lipids. Machine learning methods showed higher accuracy for IInd derivative spectra (from 65 % to 89 %) than for absorbance FTIR spectra (53-65 %). Moreover, it was possible to identify significant wavelength intervals from IInd derivative spectra using random forest-based feature selection algorithm, which further increased the accuracy of the classification (up to 92 % for phospholipid region). Moreover decision tree based on the selected features showed, that peaks at 1016 cm-1 and 2936 cm-1 can be good candidates of lipids marker of diabetes.

Decreasing the burden of non-alcoholic fatty liver disease: From therapeutic targets to drug discovery opportunities

Non-alcoholic fatty liver disease (NAFLD) presents a pervasive global pandemic, affecting approximately 25 % of the world's population. This grave health issue not only demands urgent attention but also stands as a significant economic concern on a global scale. The genesis of NAFLD can be primarily attributed to unhealthy dietary habits and a sedentary lifestyle, albeit certain genetic factors have also been recorded to contribute to its occurrence. NAFLD is characterized by fat accumulation in more than 5 % of hepatocytes according to histological analysis, or >5.6 % of lipid volume fraction in total liver weight in patients. The pathophysiology of NAFLD/non-alcoholic steatohepatitis (NASH) is multifactorial and the mechanisms underlying the progression to advanced forms remain unclear, thereby representing a challenge to disease therapy. Despite the substantial efforts from the scientific community and the large number of pre-clinical and clinical trials performed so far, only one drug was approved by the Food and Drug Administration (FDA) to treat NAFLD/NASH specifically. This review provides an overview of available information concerning emerging molecular targets and drug candidates tested in clinical studies for the treatment of NAFLD/NASH. Improving our understanding of NAFLD pathophysiology and pharmacotherapy is crucial not only to explore new molecular targets, but also to potentiate drug discovery programs to develop new therapeutic strategies. This knowledge endeavours scientific efforts to reduce the time for achieving a specific and effective drug for NAFLD or NASH management and improve patients' quality of life.

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.

Mitochondrial Dysfunction in Glycogen Storage Disorders (GSDs)

Glycogen storage disorders (GSDs) are a group of inherited metabolic disorders characterized by defects in enzymes involved in glycogen metabolism. Deficiencies in enzymes responsible for glycogen breakdown and synthesis can impair mitochondrial function. For instance, in GSD type II (Pompe disease), acid alpha-glucosidase deficiency leads to lysosomal glycogen accumulation, which secondarily impacts mitochondrial function through dysfunctional mitophagy, which disrupts mitochondrial quality control, generating oxidative stress. In GSD type III (Cori disease), the lack of the debranching enzyme causes glycogen accumulation and affects mitochondrial dynamics and biogenesis by disrupting the integrity of muscle fibers. Malfunctional glycogen metabolism can disrupt various cascades, thus causing mitochondrial and cell metabolic dysfunction through various mechanisms. These dysfunctions include altered mitochondrial morphology, impaired oxidative phosphorylation, increased production of reactive oxygen species (ROS), and defective mitophagy. The oxidative burden typical of GSDs compromises mitochondrial integrity and exacerbates the metabolic derangements observed in GSDs. The intertwining of mitochondrial dysfunction and GSDs underscores the complexity of these disorders and has significant clinical implications. GSD patients often present with multisystem manifestations, including hepatomegaly, hypoglycemia, and muscle weakness, which can be exacerbated by mitochondrial impairment. Moreover, mitochondrial dysfunction may contribute to the progression of GSD-related complications, such as cardiomyopathy and neurocognitive deficits. Targeting mitochondrial dysfunction thus represents a promising therapeutic avenue in GSDs. Potential strategies include antioxidants to mitigate oxidative stress, compounds that enhance mitochondrial biogenesis, and gene therapy to correct the underlying mitochondrial enzyme deficiencies. Mitochondrial dysfunction plays a critical role in the pathophysiology of GSDs. Recognizing and addressing this aspect can lead to more comprehensive and effective treatments, improving the quality of life of GSD patients. This review aims to elaborate on the intricate relationship between mitochondrial dysfunction and various types of GSDs. The review presents challenges and treatment options for several GSDs.

Downregulation of CerS4 Instead of CerS2 in Liver Effectively Alleviates Hepatic Insulin Resistance in HFD Male Mice

OBJECTIVE

Consumption of a high-fat diet (HFD) induces insulin resistance (IRes), significantly affecting the maintenance of normal glucose homeostasis. Nevertheless, despite decades of extensive research, the mechanisms and pathogenesis of IRes remain incomplete. Recent studies have primarily explored lipid intermediates such as diacylglycerol (DAG), given a limited knowledge about the role of ceramide (Cer), which is a potential mediator of the IRes in the liver.

METHODS

In order to investigate the role of Cer produced by CerS2 and CerS4 for the purpose of inducing the hepatic IRes, we utilized a unique in vivo model employing shRNA-mediated hydrodynamic gene delivery in the liver of HFD-fed C57BL/6J mice.

RESULTS

Downregulation of CerS4 instead of CerS2 reduced specific liver Cers, notably C18:0-Cer and C24:0-Cer, as well as acylcarnitine levels. It concurrently promoted glycogen accumulation, leading to enhanced insulin sensitivity and glucose homeostasis.

CONCLUSION

Those findings demonstrate that CerS4 downregulating lowers fasting blood glucose levels and mitigates the HFD-induced hepatic IRes. It suggests that inhibiting the CerS4-mediated C18:0-Cer synthesis holds a promise to effectively address insulin resistance in obesity.

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-Emerging Biomarkers of Lipotoxicity in Obesity, Diabetes, Cardiovascular Diseases, and Inflammation

Abnormalities in lipid homeostasis have been associated with many human diseases, and the interrelation between lipotoxicity and cellular dysfunction has received significant attention in the past two decades. Ceramides (Cers) are bioactive lipid molecules that serve as precursors of all complex sphingolipids. Besides their function as structural components in cell and mitochondrial membranes, Cers play a significant role as key mediators in cell metabolism and are involved in numerous cellular processes, such as proliferation, differentiation, inflammation, and induction of apoptosis. The accumulation of various ceramides in tissues causes metabolic and cellular disturbances. Recent studies suggest that Cer lipotoxicity has an important role in obesity, metabolic syndrome, type 2 diabetes, atherosclerosis, and cardiovascular diseases (CVDs). In humans, elevated plasma ceramide levels are associated with insulin resistance and impaired cardiovascular and metabolic health. In this review, we summarize the role of ceramides as key mediators of lipotoxicity in obesity, diabetes, cardiovascular diseases, and inflammation and their potential as a promising diagnostic tool.

Therapeutic implications for sphingolipid metabolism in metabolic dysfunction-associated steatohepatitis

The prevalence of metabolic dysfunction-associated steatotic liver disease (MASLD), a leading cause of chronic liver disease, has increased worldwide along with the epidemics of obesity and related dysmetabolic conditions characterized by impaired glucose metabolism and insulin signaling, such as type 2 diabetes mellitus (T2D). MASLD can be defined as an excessive accumulation of lipid droplets in hepatocytes that occurs when the hepatic lipid metabolism is totally surpassed. This metabolic lipid inflexibility constitutes a central node in the pathogenesis of MASLD and is frequently linked to the overproduction of lipotoxic species, increased cellular stress, and mitochondrial dysfunction. A compelling body of evidence suggests that the accumulation of lipid species derived from sphingolipid metabolism, such as ceramides, contributes significantly to the structural and functional tissue damage observed in more severe grades of MASLD by triggering inflammatory and fibrogenic mechanisms. In this context, MASLD can further progress to metabolic dysfunction-associated steatohepatitis (MASH), which represents the advanced form of MASLD, and hepatic fibrosis. In this review, we discuss the role of sphingolipid species as drivers of MASH and the mechanisms involved in the disease. In addition, given the absence of approved therapies and the limited options for treating MASH, we discuss the feasibility of therapeutic strategies to protect against MASH and other severe manifestations by modulating sphingolipid metabolism.

A, Sarma DK, Verma V, Nagpal R, Mohania D, Tiwari R, Kumar M. Deciphering the complex interplay of risk factors in type 2 diabetes mellitus: A comprehensive review

The complex and multidimensional landscape of type 2 diabetes mellitus (T2D) is a major global concern. Despite several years of extensive research, the precise underlying causes of T2D remain elusive, but evidence suggests that it is influenced by a myriad of interconnected risk factors such as epigenetics, genetics, gut microbiome, environmental factors, organelle stress, and dietary habits. The number of factors influencing the pathogenesis is increasing day by day which worsens the scenario; meanwhile, the interconnections shoot up the frame. By gaining deeper insights into the contributing factors, we may pave the way for the development of personalized medicine, which could unlock more precise and impactful treatment pathways for individuals with T2D. This review summarizes the state of knowledge about T2D pathogenesis, focusing on the interplay between various risk factors and their implications for future therapeutic strategies. Understanding these factors could lead to tailored treatments targeting specific risk factors and inform prevention efforts on a population level, ultimately improving outcomes for individuals with T2D and reducing its burden globally.

Adiponectin overexpression improves metabolic abnormalities caused by acid ceramidase deficiency but does not prolong lifespan in a mouse model of Farber Disease

Farber Disease is a debilitating and lethal childhood disease of ceramide accumulation caused by acid ceramidase deficiency. The potent induction of a ligand-gated neutral ceramidase activity promoted by adiponectin may provide sufficient lowering of ceramides to allow for the treatment of Farber Disease. In vitro, adiponectin or adiponectin receptor agonist treatments lowered total ceramide concentrations in human fibroblasts from a patient with Farber Disease. However, adiponectin overexpression in a Farber Disease mouse model did not improve lifespan or immune infiltration. Intriguingly, mice heterozygous for the Farber Disease mutation were more prone to glucose intolerance and insulin resistance when fed a high-fat diet, and adiponectin overexpression protected from these metabolic perturbations. These studies suggest that adiponectin evokes a ceramidase activity that is not reliant on the functional expression of acid ceramidase, but indicates that additional strategies are required to ameliorate outcomes of Farber Disease.

Inflammation-mediated metabolic regulation in adipose tissue

Chronic inflammation of adipose tissue is a prominent characteristic of many metabolic diseases. Lipid metabolism in adipose tissue is consistently dysregulated during inflammation, which is characterized by substantial infiltration by proinflammatory cells and high cytokine concentrations. Adipose tissue inflammation is caused by a variety of endogenous factors, such as mitochondrial dysfunction, reactive oxygen species (ROS) production, endoplasmic reticulum (ER) stress, cellular senescence, ceramides biosynthesis and mediators of lipopolysaccharides (LPS) signaling. Additionally, the gut microbiota also plays a crucial role in regulating adipose tissue inflammation. Essentially, adipose tissue inflammation arises from an imbalance in adipocyte metabolism and the regulation of immune cells. Specific inflammatory signals, including nuclear factor-κB (NF-κB) signaling, inflammasome signaling and inflammation-mediated autophagy, have been shown to be involved in the metabolic regulation. The pathogenesis of metabolic diseases characterized by chronic inflammation (obesity, insulin resistance, atherosclerosis and nonalcoholic fatty liver disease [NAFLD]) and recent research regarding potential therapeutic targets for these conditions are also discussed in this review.

Effect of an eight-week high-intensity interval training programme on circulating sphingolipid levels in middle-aged adults at elevated cardiometabolic risk (SphingoFIT)-Protocol for a randomised controlled exercise trial

INTRODUCTION

Evidence indicates that sphingolipid accumulation drives complex molecular alterations promoting cardiometabolic diseases. Clinically, it was shown that sphingolipids predict cardiometabolic risk independently of and beyond traditional biomarkers such as low-density lipoprotein cholesterol. To date, little is known about therapeutic modalities to lower sphingolipid levels. Exercise, a powerful means to prevent and treat cardiometabolic diseases, is a promising modality to mitigate sphingolipid levels in a cost-effective, safe, and patient-empowering manner.

METHODS

This randomised controlled trial will explore whether and to what extent an 8-week fitness-enhancing training programme can lower serum sphingolipid levels of middle-aged adults at elevated cardiometabolic risk (n = 98, 50% females). The exercise intervention will consist of supervised high-intensity interval training (three sessions weekly), while the control group will receive physical activity counselling based on current guidelines. Blood will be sampled early in the morning in a fasted state before and after the 8-week programme. Participants will be provided with individualised, pre-packaged meals for the two days preceding blood sampling to minimise potential confounding. An 'omic-scale sphingolipid profiling, using high-coverage reversed-phase liquid chromatography coupled to tandem mass spectrometry, will be applied to capture the circulating sphingolipidome. Maximal cardiopulmonary exercise tests will be performed before and after the 8-week programme to assess patient fitness changes. Cholesterol, triglycerides, glycated haemoglobin, the homeostatic model assessment for insulin resistance, static retinal vessel analysis, flow-mediated dilatation, and strain analysis of the heart cavities will also be assessed pre- and post-intervention. This study shall inform whether and to what extent exercise can be used as an evidence-based treatment to lower circulating sphingolipid levels.

TRIAL REGISTRATION

The trial was registered on www.clinicaltrials.gov (NCT06024291) on August 28, 2023.

Hepatic glucose metabolism in the steatotic liver

The liver is central in regulating glucose homeostasis, being the major contributor to endogenous glucose production and the greatest reserve of glucose as glycogen. It is both a target and regulator of the action of glucoregulatory hormones. Hepatic metabolic functions are altered in and contribute to the highly prevalent steatotic liver disease (SLD), including metabolic dysfunction-associated SLD (MASLD) and metabolic dysfunction-associated steatohepatitis (MASH). In this Review, we describe the dysregulation of hepatic glucose metabolism in MASLD and MASH and associated metabolic comorbidities, and how advances in techniques and models for the assessment of hepatic glucose fluxes in vivo have led to the identification of the mechanisms related to the alterations in glucose metabolism in MASLD and comorbidities. These fluxes can ultimately increase hepatic glucose production concomitantly with fat accumulation and alterations in the secretion and action of glucoregulatory hormones. No pharmacological treatment has yet been approved for MASLD or MASH, but some antihyperglycaemic drugs approved for treating type 2 diabetes have shown positive effects on hepatic glucose metabolism and hepatosteatosis. A deep understanding of how MASLD affects glucose metabolic fluxes and glucoregulatory hormones might assist in the early identification of at-risk individuals and the use or development of targeted therapies.

Adipose tissue-derived metabolite risk scores and risk for type 2 diabetes in South Asians

BACKGROUND

South Asians are at higher risk for type 2 diabetes (T2D) than many other race/ethnic groups. Ectopic adiposity, specifically hepatic steatosis and visceral fat may partially explain this. Our objective was to derive metabolite risk scores for ectopic adiposity and assess associations with incident T2D in South Asians.

METHODS

We examined 550 participants in the Mediators of Atherosclerosis in South Asians Living in America (MASALA) cohort study aged 40-84 years without known cardiovascular disease or T2D and with metabolomic data. Computed tomography scans at baseline assessed hepatic attenuation and visceral fat area, and fasting serum specimens at baseline and after 5 years assessed T2D. LC-MS-based untargeted metabolomic analysis was performed followed by targeted integration and reporting of known signals. Elastic net regularized linear regression analyses was used to derive risk scores for hepatic steatosis and visceral fat using weighted coefficients. Logistic regression models associated metabolite risk score and incident T2D, adjusting for age, gender, study site, BMI, physical activity, diet quality, energy intake and use of cholesterol-lowering medication.

RESULTS

Average age of participants was 55 years, 36% women with an average body mass index (BMI) of 25 kg/m2 and 6% prevalence of hepatic steatosis, with 47 cases of incident T2D at 5 years. There were 445 metabolites of known identity. Of these, 313 metabolites were included in the MET-Visc score and 267 in the MET-Liver score. In most fully adjusted models, MET-Liver (OR 2.04 [95% CI 1.38, 3.03]) and MET-Visc (OR 2.80 [1.75, 4.46]) were associated with higher odds of T2D. These associations remained significant after adjustment for measured adiposity.

CONCLUSIONS

Metabolite risk scores for intrahepatic fat and visceral fat were strongly related to incident T2D independent of measured adiposity. Use of these biomarkers to target risk stratification may help capture pre-clinical metabolic abnormalities.

The Association Between C24:0/C16:0 Ceramide Ratio and Cardiorespiratory Fitness is Robust to Effect Modifications by Age and Sex

Ceramides and cardiorespiratory (CR) fitness are both related to cardiovascular diseases. The associations of three blood plasma ceramides (C16:0, C22:0, and C24:0) with CR fitness in the population-based Study of Health in Pomerania (SHIP-START-1; n = 1,102; mean age 50.3 years, 51.5% women) are investigated. In addition, subgroup analysis according to age ( Collapse

Key Words

• cardiopulmonary exercise test
• cardiorespiratory fitness
• cardiovascular risk factors
• ceramides

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MESH Headings

• Humans
• Male
• Female
• Middle Aged
• Ceramides
• Cardiorespiratory Fitness
• Biomarkers
• Cardiovascular Diseases/epidemiology

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Grants

• P20 HL113444 NIH HHS
• P20 HL113444 NHLBI NIH HHS
• P30 DK020579 NIH HHS
• R33 HL155858 NHLBI NIH HHS
• P30 DK020579 NIDDK NIH HHS

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Affiliation(s)

Jule Zatloukal Dept. of Internal Medicine B, University Medicine Greifswald, 17475, Greifswald, Germany German Centre for Cardiovascular Research (DZHK), 17475, Partner-site Greifswald, Germany
Stephanie Zylla German Centre for Cardiovascular Research (DZHK), 17475, Partner-site Greifswald, Germany Institute of Clinical Chemistry and Laboratory Medicine, University Medicine Greifswald, 17475, Greifswald, Germany
Marcello R P Markus Dept. of Internal Medicine B, University Medicine Greifswald, 17475, Greifswald, Germany German Centre for Cardiovascular Research (DZHK), 17475, Partner-site Greifswald, Germany
Ralf Ewert Dept. of Internal Medicine B, University Medicine Greifswald, 17475, Greifswald, Germany
Sven Gläser Dept. of Internal Medicine B, University Medicine Greifswald, 17475, Greifswald, Germany Clinic for Internal Medicine, Vivantes Klinikum Spandau/Neukölln, 12351, Berlin, Germany
Henry Völzke German Centre for Cardiovascular Research (DZHK), 17475, Partner-site Greifswald, Germany Institute of Community Medicine, University Medicine Greifswald, 17475, Greifswald, Germany
Diana Albrecht Institute of Community Medicine, University Medicine Greifswald, 17475, Greifswald, Germany Leibniz Institute for Plasma Science and Technology, 17489, Greifswald, Germany
Nele Friedrich German Centre for Cardiovascular Research (DZHK), 17475, Partner-site Greifswald, Germany Institute of Clinical Chemistry and Laboratory Medicine, University Medicine Greifswald, 17475, Greifswald, Germany
Matthias Nauck German Centre for Cardiovascular Research (DZHK), 17475, Partner-site Greifswald, Germany Institute of Clinical Chemistry and Laboratory Medicine, University Medicine Greifswald, 17475, Greifswald, Germany
Linda R Peterson Division of Cardiology, Department of Medicine, Washington University, St Louis, MO, 63110, USA
Xuntian Jiang Division of Cardiology, Department of Medicine, Washington University, St Louis, MO, 63110, USA
Jean E Schaffer Joslin Diabetes Center, Harvard Medical School, Boston, MA, 02215, USA
Stephan B Felix Dept. of Internal Medicine B, University Medicine Greifswald, 17475, Greifswald, Germany German Centre for Cardiovascular Research (DZHK), 17475, Partner-site Greifswald, Germany
Marcus Dörr Dept. of Internal Medicine B, University Medicine Greifswald, 17475, Greifswald, Germany German Centre for Cardiovascular Research (DZHK), 17475, Partner-site Greifswald, Germany
Martin Bahls Dept. of Internal Medicine B, University Medicine Greifswald, 17475, Greifswald, Germany German Centre for Cardiovascular Research (DZHK), 17475, Partner-site Greifswald, Germany
Stefan Gross Dept. of Internal Medicine B, University Medicine Greifswald, 17475, Greifswald, Germany German Centre for Cardiovascular Research (DZHK), 17475, Partner-site Greifswald, Germany

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GT-11 impairs insulin signaling through modulation of sphingolipid metabolism in C2C12 myotubes

AIMS

Sphingolipids are involved in the regulation of insulin signaling, which is linked to the development of insulin resistance, leading to diabetes mellitus. We aimed to study whether modulation of sphingolipid levels by GT-11 may regulate insulin signaling in C2C12 myotubes.

MAIN METHODS

We investigated the effects of sphingolipid metabolism on Akt phosphorylation and glucose uptake using C2C12 myotubes. Either GT-11, an inhibitor of dihydroceramide desaturase 1 and S1P lyase, or siRNA targeting Sgpl1, the gene encoding the enzyme, was employed to determine the effect of sphingolipid metabolism modulation on insulin signaling. Western blotting and glucose uptake assays were used to evaluate the effect of treatments on insulin signaling. Sphingolipid metabolites were analyzed by high performance liquid chromatography (HPLC).

KEY FINDINGS

Treatment with GT-11 resulted in decreased Akt phosphorylation and reduced glucose uptake. Silencing the Sgpl1 gene, which encodes S1P lyase, mimicked these findings, suggesting the potential for regulating insulin signaling through S1P lyase modulation. GT-11 modulated sphingolipid metabolism, inducing the accumulation of sphingolipids. Using PF-543 and ARN14974 to inhibit sphingosine kinases and acid ceramidase, respectively, we identified a significant interplay between sphingosine, S1P lyase, and insulin signaling. Treatment with either exogenous sphingosine or palmitic acid inhibited Akt phosphorylation, and reduced S1P lyase activity.

SIGNIFICANCE

Our findings highlight the importance of close relationship between sphingolipid metabolism and insulin signaling in C2C12 myotubes, pointing to its potential therapeutic relevance for diabetes mellitus.

Leucine improves the growth performance, carcass traits, and lipid nutritional quality of pork in Shaziling pigs

Leucine is involved in promoting fatty acid oxidation and lipolysis, mediating lipid metabolism and energy homeostasis, thus it has been widely used in livestock production. However, the effects of leucine on fat deposition and nutrition in Shaziling pigs remain unclear. A total of 72 Shaziling pigs (150 days old, weight 35.00 ± 1.00 kg) were randomly divided into 2 groups and fed with basal diet (control group) or basal diet containing 1% leucine (leucine group) for 60 days. The results showed that leucine significantly increased the average daily feed intake but decreased the ratio of feed to gain (P < 0.05), increased the loin muscle area and serum glucose content (P < 0.05) of Shaziling pigs. Besides, leucine regulated the re-distribution of fatty acids from adipose tissue to muscle as it significantly increased the contents of C18:1n-9 and C22:6n-3 (DHA) in the longissimus thoracis while decreased the contents of C22:5n-3 (DPA), C20:5n-3 (EPA), and DHA in the adipose tissue of Shaziling pigs (P < 0.05). Lipidomic analysis showed that the contents of phosphatidylethanolamines (PEs), cardiolipins (CLs), and phosphatidylglycerols (PGs) in the longissimus thoracis and the contents of lysophosphatidylethanolamines (LPEs), ceramides (Cers), phosphatidylinositols (PIs) in adipose tissue of Shaziling pigs were decreased in leucine group (P < 0.05). Collectively, this study clarified that dietary addition of 1% leucine have a better effect on growth performance and the deposition of beneficial fatty acids in the muscle of Shaziling pigs, which is conductive to the production of high quality and healthy pork. In addition, leucine altered the lipid composition of muscle and fat in Shaziling pigs. The related results provide a theoretical basis and application guidance for regulating fat deposition in Shaziling pigs, which is important for the healthy breeding of Shaziling pigs.

The role of fatty acid metabolism in acute lung injury: a special focus on immunometabolism

Reputable evidence from multiple studies suggests that excessive and uncontrolled inflammation plays an indispensable role in mediating, amplifying, and protracting acute lung injury (ALI). Traditionally, immunity and energy metabolism are regarded as separate functions regulated by distinct mechanisms, but recently, more and more evidence show that immunity and energy metabolism exhibit a strong interaction which has given rise to an emerging field of immunometabolism. Mammalian lungs are organs with active fatty acid metabolism, however, during ALI, inflammation and oxidative stress lead to a series metabolic reprogramming such as impaired fatty acid oxidation, increased expression of proteins involved in fatty acid uptake and transport, enhanced synthesis of fatty acids, and accumulation of lipid droplets. In addition, obesity represents a significant risk factor for ALI/ARDS. Thus, we have further elucidated the mechanisms of obesity exacerbating ALI from the perspective of fatty acid metabolism. To sum up, this paper presents a systematical review of the relationship between extensive fatty acid metabolic pathways and acute lung injury and summarizes recent advances in understanding the involvement of fatty acid metabolism-related pathways in ALI. We hold an optimistic believe that targeting fatty acid metabolism pathway is a promising lung protection strategy, but the specific regulatory mechanisms are way too complex, necessitating further extensive and in-depth investigations in future studies.

Association between pre-diagnostic circulating lipid metabolites and colorectal cancer risk: a nested case-control study in the European Prospective Investigation into Cancer and Nutrition (EPIC)

BACKGROUND

Altered lipid metabolism is a hallmark of cancer development. However, the role of specific lipid metabolites in colorectal cancer development is uncertain.

METHODS

In a case-control study nested within the European Prospective Investigation into Cancer and Nutrition (EPIC), we examined associations between pre-diagnostic circulating concentrations of 97 lipid metabolites (acylcarnitines, glycerophospholipids and sphingolipids) and colorectal cancer risk. Circulating lipids were measured using targeted mass spectrometry in 1591 incident colorectal cancer cases (55% women) and 1591 matched controls. Multivariable conditional logistic regression was used to estimate odds ratios (ORs) and 95% confidence intervals (CIs) for associations between concentrations of individual lipid metabolites and metabolite patterns with colorectal cancer risk.

FINDINGS

Of the 97 assayed lipids, 24 were inversely associated (nominally p < 0.05) with colorectal cancer risk. Hydroxysphingomyelin (SM (OH)) C22:2 (ORper doubling 0.60, 95% CI 0.47-0.77) and acylakyl-phosphatidylcholine (PC ae) C34:3 (ORper doubling 0.71, 95% CI 0.59-0.87) remained associated after multiple comparisons correction. These associations were unaltered after excluding the first 5 years of follow-up after blood collection and were consistent according to sex, age at diagnosis, BMI, and colorectal subsite. Two lipid patterns, one including 26 phosphatidylcholines and all sphingolipids, and another 30 phosphatidylcholines, were weakly inversely associated with colorectal cancer.

INTERPRETATION

Elevated pre-diagnostic circulating levels of SM (OH) C22:2 and PC ae C34:3 and lipid patterns including phosphatidylcholines and sphingolipids were associated with lower colorectal cancer risk. This study may provide insight into potential links between specific lipids and colorectal cancer development. Additional prospective studies are needed to validate the observed associations.

FUNDING

World Cancer Research Fund (reference: 2013/1002); European Commission (FP7: BBMRI-LPC; reference: 313010).

Biomarkers in aortic dissection: Diagnostic and prognostic value from clinical research

ABSTRACT

Aortic dissection is a life-threatening condition for which diagnosis mainly relies on imaging examinations, while reliable biomarkers to detect or monitor are still under investigation. Recent advances in technologies provide an unprecedented opportunity to yield the identification of clinically valuable biomarkers, including proteins, ribonucleic acids (RNAs), and deoxyribonucleic acids (DNAs), for early detection of pathological changes in susceptible patients, rapid diagnosis at the bedside after onset, and a superior therapeutic regimen primarily within the concept of personalized and tailored endovascular therapy for aortic dissection.

Ceramide enhanced the hepatic glucagon response through regulation of CREB activity

BACKGROUND & AIMS

Hyperglycemia is associated with lipid disorders in patients with diabetes. Ceramides are metabolites involved in sphingolipid metabolism that accumulate during lipid disorders and exert deleterious effects on glucose and lipid metabolism. However, the effects of ceramide on glucagon-mediated hepatic gluconeogenesis remain largely unknown. This study was designed to investigate the impact of ceramides on gluconeogenesis in the context of the hepatic glucagon response, with the aim of finding new pharmacological interventions for hyperglycemia in diabetes.

METHODS

Liquid chromatography-mass spectrometry was used to quantify ceramide content in the serum of patients with diabetes. Primary hepatocytes were isolated from male C57BL/6J mice to study the effects of ceramide on hepatic glucose production. Immunofluorescence staining was performed to view cAMP-responsive element-binding protein (CREB)- regulated transcription co-activator 2 (CRTC2) nuclear translocation in hepatocytes. Serine palmitoyl-transferase, long chain base subunit 2 (Sptlc2) knockdown mice were generated using an adeno-associated virus containing shRNA, and hepatic glucose production was assessed glucagon tolerance and pyruvate tolerance tests in mice fed a normal chow diet and high-fat diet.

RESULTS

Increased ceramide levels were observed in the serum of patients newly diagnosed with type 2 diabetes. De novo ceramide synthesis was activated in mice with metabolic disorders. Ceramide enhanced hepatic glucose production in primary hepatocytes. In contrast, genetic silencing of Sptlc2 prevented this process. Mechanistically, ceramides de-phosphorylate CRTC2 (Ser 171) and facilitate its translocation into the nucleus for CREB activation, thereby augmenting the hepatic glucagon response. Hepatic Sptlc2 silencing blocked ceramide generation in the liver and thus restrained the hepatic glucagon response in mice fed a normal chow diet and high-fat diet.

CONCLUSIONS

These data indicate that ceramide serves as an intracellular messenger that augments hepatic glucose production by regulating CRTC2/CREB activity in the context of the hepatic glucagon response, suggesting that CRTC2 phosphorylation might be a potential node for pharmacological interventions to restrain the hyperglycemic response during fasting in diabetes.

Two novel cases of biallelic SMPD4 variants with brain structural abnormalities

Sphingomyelin phosphodiesterase 4 (SMPD4) encodes a member of the Mg2+-dependent, neutral sphingomyelinase family that catalyzes the hydrolysis of the phosphodiester bond of sphingomyelin to form phosphorylcholine and ceramide. Recent studies have revealed that biallelic loss-of-function variants of SMPD4 cause syndromic neurodevelopmental disorders characterized by microcephaly, congenital arthrogryposis, and structural brain anomalies. In this study, three novel loss-of-function SMPD4 variants were identified using exome sequencing (ES) in two independent patients with developmental delays, microcephaly, seizures, and brain structural abnormalities. Patient 1 had a homozygous c.740_741del, p.(Val247Glufs*21) variant and showed profound intellectual disability, hepatomegaly, a simplified gyral pattern, and a thin corpus callosum without congenital dysmorphic features. Patient 2 had a compound heterozygous nonsense c.2124_2125del, p.(Phe709*) variant and splice site c.1188+2dup variant. RNA analysis revealed that the c.1188+2dup variant caused exon 13 skipping, leading to a frameshift (p.Ala406Ser*6). In vitro transcription analysis using minigene system suggested that mRNA transcribed from mutant allele may be degraded by nonsense-mediated mRNA decay system. He exhibited diverse manifestations, including growth defects, muscle hypotonia, respiratory distress, arthrogryposis, insulin-dependent diabetes mellitus, sensorineural hearing loss, facial dysmorphism, and various brain abnormalities, including cerebral atrophy, hypomyelination, and cerebellar hypoplasia. Here, we review previous literatures and discuss the phenotypic diversity of SMPD4-related disorders.

Adipose Tissue Dysfunction Determines Lipotoxicity and Triggers the Metabolic Syndrome: Current Challenges and Clinical Perspectives

The adipose tissue organ is organised as distinct anatomical depots located all along the body axis, and it is constituted of three different types of adipocytes: white, beige and brown, which are integrated with vascular, immune, neural, and extracellular stroma cells. These distinct adipocytes serve different specialised functions. The main function of white adipocytes is to ensure healthy storage of excess nutrients/energy and its rapid mobilisation to supply the demand of energy imposed by physiological cues in other organs, whereas brown and beige adipocytes are designed for heat production through uncoupling lipid oxidation from energy production. The concerted action of the three types of adipocytes/tissues ensures an optimal metabolic status. However, when one or several of these adipose depots become dysfunctional because of sustained lipid/nutrient overload, then insulin resistance and associated metabolic complications ensue. These metabolic alterations close a vicious cycle that negatively affects the adipose tissue functionality and compromises global metabolic homeostasis. Optimising white adipose tissue expandability and ensuring its functional metabolic flexibility and/or promoting brown/beige mediated thermogenic activity are complementary strategies that counteract obesity and its associated lipotoxic metabolic effects. However, the development of these therapeutic approaches requires a deep understanding of adipose tissue in all broad aspects. In this chapter, we will discuss the characteristics of the different adipose tissue depots with respect to origins and precursors recruitment, plasticity, cellular composition, and expandability capacity potential as well as molecular and metabolic characteristic signatures in both physiological and pathophysiological conditions. Current antilipotoxic strategies for future clinical application are also discussed in this chapter.

Lipid Metabolism in Metabolic-Associated Steatotic Liver Disease (MASLD)

Metabolic-associated steatotic liver disease (MASLD) is a cluster of pathological conditions primarily developed due to the accumulation of ectopic fat in the hepatocytes. During the severe form of the disease, i.e., metabolic-associated steatohepatitis (MASH), accumulated lipids promote lipotoxicity, resulting in cellular inflammation, oxidative stress, and hepatocellular ballooning. If left untreated, the advanced form of the disease progresses to fibrosis of the tissue, resulting in irreversible hepatic cirrhosis or the development of hepatocellular carcinoma. Although numerous mechanisms have been identified as significant contributors to the development and advancement of MASLD, altered lipid metabolism continues to stand out as a major factor contributing to the disease. This paper briefly discusses the dysregulation in lipid metabolism during various stages of MASLD.

Effects of aging on glucose and lipid metabolism in mice

Aging is accompanied by multiple molecular changes that contribute to aging-associated pathologies, such as accumulation of cellular damage and mitochondrial dysfunction. Tissue metabolism can also change with age, in part because mitochondria are central to cellular metabolism. Moreover, the co-factor NAD+, which is reported to decline across multiple tissue types during aging, plays a central role in metabolic pathways such as glycolysis, the tricarboxylic acid cycle, and the oxidative synthesis of nucleotides, amino acids, and lipids. To further characterize how tissue metabolism changes with age, we intravenously infused [U-13C]-glucose into young and old C57BL/6J, WSB/EiJ, and Diversity Outbred mice to trace glucose fate into downstream metabolites within plasma, liver, gastrocnemius muscle, and brain tissues. We found that glucose incorporation into central carbon and amino acid metabolism was robust during healthy aging across these different strains of mice. We also observed that levels of NAD+, NADH, and the NAD+/NADH ratio were unchanged in these tissues with healthy aging. However, aging tissues, particularly brain, exhibited evidence of up-regulated fatty acid and sphingolipid metabolism reactions that regenerate NAD+ from NADH. Because mitochondrial respiration, a major source of NAD+ regeneration, is reported to decline with age, our data supports a model where NAD+-generating lipid metabolism reactions may buffer against changes in NAD+/NADH during healthy aging.

Structure and mechanism of a eukaryotic ceramide synthase complex

Ceramide synthases (CerS) catalyze ceramide formation via N-acylation of a sphingoid base with a fatty acyl-CoA and are attractive drug targets for treating numerous metabolic diseases and cancers. Here, we present the cryo-EM structure of a yeast CerS complex, consisting of a catalytic Lac1 subunit and a regulatory Lip1 subunit, in complex with C26-CoA substrate. The CerS holoenzyme exists as a dimer of Lac1-Lip1 heterodimers. Lac1 contains a hydrophilic reaction chamber and a hydrophobic tunnel for binding the CoA moiety and C26-acyl chain of C26-CoA, respectively. Lip1 interacts with both the transmembrane region and the last luminal loop of Lac1 to maintain the proper acyl chain binding tunnel. A lateral opening on Lac1 serves as a potential entrance for the sphingoid base substrate. Our findings provide a template for understanding the working mechanism of eukaryotic ceramide synthases and may facilitate the development of therapeutic CerS modulators.

Ceramides Mediate Insulin-Induced Impairments in Cerebral Mitochondrial Bioenergetics in ApoE4 Mice

Alzheimer's disease (AD) is the most common form of neurodegenerative disease worldwide. A large body of work implicates insulin resistance in the development and progression of AD. Moreover, impairment in mitochondrial function, a common symptom of insulin resistance, now represents a fundamental aspect of AD pathobiology. Ceramides are a class of bioactive sphingolipids that have been hypothesized to drive insulin resistance. Here, we describe preliminary work that tests the hypothesis that hyperinsulinemia pathologically alters cerebral mitochondrial function in AD mice via accrual of the ceramides. Homozygous male and female ApoE4 mice, an oft-used model of AD research, were given chronic injections of PBS (control), insulin, myriocin (an inhibitor of ceramide biosynthesis), or insulin and myriocin over four weeks. Cerebral ceramide content was assessed using liquid chromatography-mass spectrometry. Mitochondrial oxygen consumption rates were measured with high-resolution respirometry, and H2O2 emissions were quantified via biochemical assays on brain tissue from the cerebral cortex. Significant increases in brain ceramides and impairments in brain oxygen consumption were observed in the insulin-treated group. These hyperinsulinemia-induced impairments in mitochondrial function were reversed with the administration of myriocin. Altogether, these data demonstrate a causative role for insulin in promoting brain ceramide accrual and subsequent mitochondrial impairments that may be involved in AD expression and progression.

SUMO-specific protease 2 regulates lipid droplet size through ERRα-mediated CIDEA expression in adipocytes

Lipid droplets are not only lipid storage sites but also are closely related to lipid metabolism. Lipid droplet growth increases lipid storage capacity and suppresses lipolysis via lipase associated with the lipid droplet surface. The cell death-inducing DFF45-like effector (CIDE) family of proteins mediates lipid droplet fusion, which mainly contributes to lipid droplet growth. We previously demonstrated small ubiquitin-like modifier (SUMO)-specific protease 2 (SENP2) plays important roles in lipid metabolism and induction/maintenance of adipogenesis. In this study, we determined whether SENP2 regulates lipid droplet size in adipocytes. Overexpression of SENP2 increased lipid droplet size in differentiated 3T3-L1 adipocytes and facilitated CIDEA transcription. We found SENP2 increased CIDEA expression mainly through desumoylation of estrogen-related receptor α (ERRα), which acted in coordination with peroxisome proliferator-activated receptor γ-coactivator α. In addition, palmitate treatment increased SENP2 and CIDEA mRNA levels. Specific small interfering RNA-mediated knockdown of SENP2, as well as ERRα knockdown, eliminated palmitate-induced CIDEA expression. These results suggest SENP2 enhances CIDEA expression by modulating ERRα when SENP2 is upregulated, such as after palmitate treatment, to increase lipid droplet size in adipocytes.

Preconception and developmental DEHP exposure alter liver metabolism in a sex-dependent manner in adult mouse offspring

Environmental exposure to endocrine disrupting chemicals (EDCs) during critical periods of development is associated with an increased risk of metabolic diseases, including hepatic steatosis and obesity. Di-2-ethylhexyl-phthalate (DEHP) is an EDC strongly associated with these metabolic abnormalities. DEHP developmental windows of susceptibility are unknown yet have important public health implications. The purpose of this study was to identify these windows of susceptibility and determine whether developmental DEHP exposure alters hepatic metabolism later in life. Dams were exposed to control or feed containing human exposure relevant doses of DEHP (50 μg/kg BW/d) and high dose DEHP (10 mg/kg BW/d) from preconception until weaning or only exposed to DEHP during preconception. Post-weaning, all offspring were fed a control diet throughout adulthood. Using the Metabolon Untargeted Metabolomics platform, we identified 148 significant metabolites in female adult livers that were altered by preconception-gestation-lactation DEHP exposure. We found a significant increase in the levels of acylcarnitines, diacylglycerols, sphingolipids, glutathione, purines, and pyrimidines in DEHP-exposed female livers compared to controls. These changes in fatty acid oxidation and oxidative stress-related metabolites were correlated with hepatic changes including microvesicular steatosis, hepatocyte swelling, inflammation. In contrast to females, we observed fewer metabolic alterations in male offspring, which were uniquely found in preconception-only low dose DEHP exposure group. Although we found that preconception-gestational-lactation exposure causes the most liver pathology, we surprisingly found preconception exposure linked to an abnormal liver metabolome. We also found that two doses exhibited non-monotonic DEHP-induced changes in the liver. Collectively, these findings suggest that metabolic changes in the adult liver of offspring exposed periconceptionally to DHEP depends on the timing of exposure, dose, and sex.

Resveratrol as a potential protective compound against skeletal muscle insulin resistance

The increasing prevalence of type 2 diabetes has become a major global problem. Insulin resistance has a central role in pathophysiology of type 2 diabetes. Skeletal muscle is responsible for the disposal of most of the glucose under conditions of insulin stimulation, and insulin resistance in skeletal muscle causes dysregulation of glucose homeostasis in the whole body. Despite the current pharmaceutical and non-pharmacological treatment strategies to combat diabetes, there is still a need for new therapeutic agents due to the limitations of the therapeutic agents. Meanwhile, plant polyphenols have attracted the attention of researchers for their use in the treatment of diabetes and have gained popularity. Resveratrol, a stilbenoid polyphenol, exists in various plant sources, and a growing body of evidence suggests its beneficial properties, including antidiabetic activities. The present review aimed to provide a summary of the role of resveratrol in insulin resistance in skeletal muscle and its related mechanisms. To achieve the objectives, by searching the PubMed, Scopus and Web of Science databases, we have summarized the results of all cell culture, animal, and human studies that have investigated the effects of resveratrol in different models on insulin resistance in skeletal muscle.

Metabolic syndrome accelerates epigenetic ageing in older adults: Findings from The Irish Longitudinal Study on Ageing (TILDA)

Metabolic syndrome (MetS) is a risk factor for the development of diabetes, cardiovascular disease, and all-cause mortality. It has an estimated prevalence of 40 % among older adults. Epigenetic clocks, which measure biological age based on DNA methylation (DNAm) patterns, are a candidate biomarker for ageing. GrimAge is one such clock which is based on levels of DNAm at 100 Cytosine-phosphate-Guanine (CpG) sites. This study hypothesised that those with MetS have 'accelerated ageing' (biological age greater than their chronological age) as indexed by GrimAge. This study examined MetS's association with GrimAge age acceleration (AA) using data from a subsample of 469 participants of the Irish Longitudinal Study on Ageing (TILDA). MetS was defined by National Cholesterol Education Program Third Adult Treatment Panel (ATP III) and International Diabetes Foundation (IDF) criteria, operationalised using the conventional binary cut-off, and as a count variable ranging from 0 to 5, based on the presence of individual components. This study also explored inflammation (as measured by C reactive protein) and metabolic dysfunction (as measured by adiponectin) as possible mediating factors between MetS and GrimAge AA. We found that MetS as defined by IDF criteria was associated with GrimAge AA of 0.63 years. When MetS was treated as a count, each unit increase in MetS score was associated with over 0.3 years GrimAge AA for both ATP III and IDF criteria. Inflammation mediated approximately one third of the association between MetS and GrimAge AA, suggesting that chronic subclinical inflammation observed in MetS has a relationship with DNAm changes consistent with a faster pace of ageing. Metabolic dysfunction mediated the association between MetS and GrimAge AA to a lesser extent (16 %). These data suggest that chronic subclinical inflammation observed in MetS has a relationship with DNAm changes consistent with a greater pace of ageing.

Lipin-1 restrains macrophage lipid synthesis to promote inflammation resolution

Macrophages are critical to maintaining and restoring tissue homeostasis during inflammation. The lipid metabolic state of macrophages influences their function, but a deeper understanding of how lipid metabolism is regulated in pro-resolving macrophage responses is needed. Lipin-1 is a phosphatidic acid phosphatase with a transcriptional coregulatory activity (TC) that regulates lipid metabolism. We previously demonstrated that lipin-1 supports pro-resolving macrophage responses, and here, myeloid-associated lipin-1 is required for inflammation resolution, yet how lipin-1-regulated cellular mechanisms promote macrophage pro-resolution responses is unknown. We demonstrated that the loss of lipin-1 in macrophages led to increased free fatty acid, neutral lipid, and ceramide content and increased phosphorylation of acetyl-CoA carboxylase. The inhibition of the first step of lipid synthesis and transport of citrate from the mitochondria in macrophages reduced lipid content and restored efferocytosis and inflammation resolution in lipin-1mKO macrophages and mice. Our findings suggest macrophage-associated lipin-1 restrains lipid synthesis, promoting pro-resolving macrophage function in response to pro-resolving stimuli.

Alzheimer's Disease in Diabetic Patients: A Lipidomic Prospect

Diabetes Mellitus (DM) and Alzheimer's disease (AD) have been two of the most common chronic diseases affecting people worldwide. Type 2 DM (T2DM) is a metabolic disease depicted by insulin resistance, dyslipidemia, and chronic hyperglycemia while AD is a neurodegenerative disease marked by Amyloid β (Aβ) accumulation, neurofibrillary tangles aggregation, and tau phosphorylation. Various clinical, epidemiological, and lipidomics studies have linked those diseases claiming shared pathological pathways raising the assumption that diabetic patients are at an increased risk of developing AD later in their lives. Insulin resistance is the tipping point beyond where advanced glycation end (AGE) products and free radicals are produced leading to oxidative stress and lipid peroxidation. Additionally, different types of lipids are playing a crucial role in the development and the relationship between those diseases. Lipidomics, an analysis of lipid structure, formation, and interactions, evidently exhibits these lipid changes and their direct and indirect effect on Aβ synthesis, insulin resistance, oxidative stress, and neuroinflammation. In this review, we have discussed the pathophysiology of T2DM and AD, the interconnecting pathological pathways they share, and the lipidomics where different lipids such as cholesterol, phospholipids, sphingolipids, and sulfolipids contribute to the underlying features of both diseases. Understanding their role can be beneficial for diagnostic purposes or introducing new drugs to counter AD.

Exposure to ambient oxidant pollution associated with ceramide changes and cardiometabolic responses

Evidence of impact of ambient oxidant pollution on cardiometabolic responses remains limited. We aimed to examine associations of oxidant pollutants with cardiometabolic responses, and effect modification by ceramides. During 2019-2020, 152 healthy adults were visited 4 times in Beijing, China, and indicators of ceramides, glucose homeostasis, and vascular function were measured. We found significant increases in ceramides of 13.9% (p = 0.020) to 110.1% (p = 0.005) associated with an interquartile increase in oxidant pollutants at prior 1-7 days. Exposure to oxidant pollutants was also related to elevations in insulin and reductions in adiponectin, and elevations in systolic and diastolic blood pressure. Further, stratified analyses revealed larger changes in oxidant pollutant related cardiometabolic responses among participants with higher ceramide levels compared to those with lower levels. Our findings suggested cardiometabolic effects associated with exposure to oxidant pollutants, which may be modified by ceramide levels.

A CCL2+DPP4+ subset of mesenchymal stem cells expedites aberrant formation of creeping fat in humans

Creeping fat is a typical feature of Crohn's disease. It refers to the expansion of mesenteric adipose tissue around inflamed and fibrotic intestines and is associated with stricture formation and intestinal obstruction. In this study, we characterize creeping fat as pro-adipogenic and pro-fibrotic. Lipidomics analysis of Crohn's disease patients (sixteen males, six females) and healthy controls (five males, ten females) reveals abnormal lipid metabolism in creeping fat. Through scRNA-seq analysis on mesenteric adipose tissue from patients (five males, one female) and healthy controls (two females), we identify a CCL2+DPP4+ subset of mesenchymal stem cells that expands in creeping fat and expedites adipogenic differentiation into dystrophic adipocytes in response to CCL20+CD14+ monocytes and IL-6, leading to the formation of creeping fat. Ex vivo experiments (tissues from five males, one female) confirm that both CCL20+CD14+ monocytes and IL-6 activate DPP4+ mesenchymal stem cells towards a pro-adipogenic phenotype. This study provides a comprehensive investigation of creeping fat formation and offers a conceptual framework for discovering therapeutic targets for treatment of Crohn's disease.

Circulating Sphingolipids in Insulin Resistance, Diabetes and Associated Complications

Sphingolipids play an important role in the development of diabetes, both type 1 and type 2 diabetes, as well as in the development of both micro- and macro-vascular complications. Several reviews have been published concerning the role of sphingolipids in diabetes but most of the emphasis has been on the possible mechanisms by which sphingolipids, mainly ceramides, contribute to the development of diabetes. Research on circulating levels of the different classes of sphingolipids in serum and in lipoproteins and their importance as biomarkers to predict not only the development of diabetes but also of its complications has only recently emerged and it is still in its infancy. This review summarizes the previously published literature concerning sphingolipid-mediated mechanisms involved in the development of diabetes and its complications, focusing on how circulating plasma sphingolipid levels and the relative content carried by the different lipoproteins may impact their role as possible biomarkers both in the development of diabetes and mainly in the development of diabetic complications. Further studies in this field may open new therapeutic avenues to prevent or arrest/reduce both the development of diabetes and progression of its complications.

Diet-derived and diet-related endogenously produced palmitic acid: Effects on metabolic regulation and cardiovascular disease risk

Palmitic acid is the predominant dietary saturated fatty acid (SFA) in the US diet. Plasma palmitic acid is derived from dietary fat and also endogenously from de novo lipogenesis (DNL) and lipolysis. DNL is affected by excess energy intake resulting in overweight and obesity, and the macronutrient profile of the diet. A low-fat diet (higher carbohydrate and/or protein) promotes palmitic acid synthesis in adipocytes and the liver. A high-fat diet is another source of palmitic acid that is taken up by adipose tissue, liver, heart and skeletal muscle via lipolytic mechanisms. Moreover, overweight/obesity and accompanying insulin resistance increase non-esterified fatty acid (NEFA) production. Palmitic acid may affect cardiovascular disease (CVD) risk via mechanisms beyond increasing low-density lipoprotein-cholesterol (LDL-C), notably synthesis of ceramides and possibly through branched fatty acid esters of hydroxy fatty acids (FAHFAs) from palmitic acid. Ceramides are positively associated with incident CVD, whereas the role of FAHFAs is uncertain. Given the new evidence about dietary regulation of palmitic acid metabolism there is interest in learning more about how diet modulates circulating palmitic acid concentrations and, hence, potentially CVD risk. This is important because of the heightened interest in low carbohydrate (carbohydrate controlled) and high carbohydrate (low-fat) diets coupled with the ongoing overweight/obesity epidemic, all of which can increase plasma palmitic acid levels by different mechanisms. Consequently, learning more about palmitic acid biochemistry, trafficking and how its metabolites affect CVD risk will inform future dietary guidance to further lower the burden of CVD.

Lipid remodeling of adipose tissue in metabolic health and disease

Adipose tissue is a dynamic and metabolically active organ that plays a crucial role in energy homeostasis and endocrine function. Recent advancements in lipidomics techniques have enabled the study of the complex lipid composition of adipose tissue and its role in metabolic disorders such as obesity, diabetes, and cardiovascular disease. In addition, adipose tissue lipidomics has emerged as a powerful tool for understanding the molecular mechanisms underlying these disorders and identifying bioactive lipid mediators and potential therapeutic targets. This review aims to summarize recent lipidomics studies that investigated the dynamic remodeling of adipose tissue lipids in response to specific physiological changes, pharmacological interventions, and pathological conditions. We discuss the molecular mechanisms of lipid remodeling in adipose tissue and explore the recent identification of bioactive lipid mediators generated in adipose tissue that regulate adipocytes and systemic metabolism. We propose that manipulating lipid-mediator metabolism could serve as a therapeutic approach for preventing or treating obesity-related metabolic diseases.

Washed Microbiota Transplantation Improves Patients with Overweight by the Gut Microbiota and Sphingolipid Metabolism

BACKGROUND

Overweight (OW) and obesity have become increasingly serious public health problems worldwide. The clinical impact of washed microbiota transplantation (WMT) from healthy donors in OW patients is unclear. This study aimed to investigate the effect of WMT in OW patients.

METHODS

The changes in body mass index (BMI = weight (kg)/height (m)2), blood glucose, blood lipids and other indicators before and after WMT were compared. At the same time, 16S rRNA gene amplicon sequencing was performed on fecal samples of OW patients before and after transplantation. Finally, serum samples were tested for sphingolipids targeted by lipid metabolomics.

RESULTS

A total of 166 patients were included, including 52 in the OW group and 114 in the normal weight (NOW) group. For OW patients, WMT significantly improved the comprehensive efficacy of OW. In the short term (about 1 month) and medium term (about 2 months), a significant reduction in BMI was seen. At the same time, in the short term (about 1 month), liver fat attenuation (LFA), triglyceride (TG) and fasting blood glucose (FBG) were significantly reduced. In the long term (about 5 months), total cholesterol (TC), low-density lipoprotein cholesterol (LDL-c), non-high-density lipoprotein (non-HDL-c), etc. were significantly reduced. WMT improved the gut microbiota of OW patients, and also had an improvement effect on OW patients by regulating sphingolipid metabolism.

CONCLUSION

WMT had a significant improvement effect on OW patients. WMT could restore gut microbiota homeostasis and improve OW patients by regulating sphingolipid metabolism.

Investigating the circulating sphingolipidome response to a single high-intensity interval training session within healthy females and males in their twenties (SphingoHIIT): Protocol for a randomised controlled trial

Introduction: Growing scientific evidence indicates that sphingolipids predict cardiometabolic risk, independently of and beyond traditional biomarkers such as low-density lipoprotein cholesterol. To date, it remains largely unknown if and how exercise, a simple, low-cost, and patient-empowering modality to optimise cardiometabolic health, influences sphingolipid levels. The SphingoHIIT study aims to assess the response of circulating sphingolipid species to a single session of high-intensity interval training (HIIT). Methods: This single-centre randomised controlled trial (RCT) will last 11 days per participant and aim to include 32 young and healthy individuals aged 20-29 (50% females). Participants will be randomly allocated to the HIIT (n= 16) or control groups (physical rest, n= 16). Participants will self-sample fasted dried blood spots for three consecutive days before the intervention (HIIT versus rest) to determine baseline sphingolipid levels. Dried blood spots will also be collected at five time points (2, 15, 30, 60min, and 24h) following the intervention (HIIT versus rest). To minimise the dietary influence, participants will receive a standardised diet for four days, starting 24 hours before the first dried blood sampling. For females, interventions will be timed to fall within the early follicular phase to minimise the menstrual cycle's influence on sphingolipid levels. Finally, physical activity will be monitored for the whole study duration using a wrist accelerometer. Ethics and dissemination: The Ethics Committee of Northwest and Central Switzerland approved this protocol (ID 2022-00513). Findings will be disseminated in scientific journals and meetings. Trial Registration The trial was registered on www.clinicaltrials.gov (NCT05390866, https://clinicaltrials.gov/ct2/show/NCT05390866) on May 25, 2022.

Longitudinal Lipidomic Profile of Hypertension in American Indians: Findings From the Strong Heart Family Study

BACKGROUND

Dyslipidemia is an important risk factor for hypertension and cardiovascular disease. Standard lipid panel cannot reflect the complexity of blood lipidome. The associations of individual lipid species with hypertension remain to be determined in large-scale epidemiological studies, especially in a longitudinal setting.

METHODS

Using liquid chromatography-mass spectrometry, we repeatedly measured 1542 lipid species in 3699 fasting plasma samples at 2 visits (1905 at baseline, 1794 at follow-up, ~5.5 years apart) from 1905 unique American Indians in the Strong Heart Family Study. We first identified baseline lipids associated with prevalent and incident hypertension, followed by replication of top hits in Europeans. We then conducted repeated measurement analysis to examine the associations of changes in lipid species with changes in systolic blood pressure, diastolic blood pressure, and mean arterial pressure. Network analysis was performed to identify lipid networks associated with the risk of hypertension.

RESULTS

Baseline levels of multiple lipid species, for example, glycerophospholipids, cholesterol esters, sphingomyelins, glycerolipids, and fatty acids, were significantly associated with both prevalent and incident hypertension in American Indians. Some lipids were confirmed in Europeans. Longitudinal changes in multiple lipid species, for example, acylcarnitines, phosphatidylcholines, fatty acids, and triacylglycerols, were significantly associated with changes in blood pressure measurements. Network analysis identified distinct lipidomic patterns associated with the risk of hypertension.

CONCLUSIONS

Baseline plasma lipid species and their longitudinal changes are significantly associated with hypertension development in American Indians. Our findings shed light on the role of dyslipidemia in hypertension and may offer potential opportunities for risk stratification and early prediction of hypertension.

Ceramides and other sphingolipids as predictors of incident dysglycemia (CASPID): Design, methods, and baseline characteristics

The Ceramides and other Sphingolipids as Predictors of Incident Dysglycemia (CASPID) study tests the overall hypothesis that sphingolipids are pathophysiologic mediators of transition from normal glucose regulation (NGR) to prediabetes, type 2 diabetes (T2DM), and associated complications. The CASPID study utilizes two longitudinal cohorts - the Pathobiology of Prediabetes in a Biracial Cohort (POP-ABC)/Pathobiology and Reversibility of Prediabetes in a Biracial Cohort (PROP-ABC) and the Diabetes Prevention Program (DPP)/DPP Outcomes Study (DPPOS). Normoglycemic POP-ABC/PROP-ABC were followed for 10 years for progression to prediabetes and offered lifestyle intervention to reverse prediabetes. The DPP/DPPOS participants had prediabetes at enrollment, were randomized to placebo, lifestyle intervention, or metformin treatment, and followed for 11 years for progression to T2DM. Using a case-control design, we analyze 76 targeted plasma sphingolipids as predictors of progression from NGR to prediabetes (Aim 1), prediabetes to T2DM (Aim 2), response to interventions (Aim 3), and development of diabetes complications (Aim 4). A sample size of 600 subjects provides >80% power to detect a 20% difference in sphingolipid profiles between comparison groups (alpha = 0.01). At enrollment, POP-ABC participants had a mean age of 47.7 ± 9.00 years, body mass index (BMI) 30.4 ± 6.10 kg/m2, fasting glucose 92.9 ± 6.90 mg/dL, and 2-h glucose 130 ± 28.8 mg/dL; DPP participants had a mean age of 51.9 ± 9.44 years, BMI 33.7 ± 6.33 kg/m2, fasting glucose 106 ± 7.88 mg/dL, and 2-h glucose 164 ± 16.9 mg/dL. Among normoglycemic participants, those with parental history of T2DM had significantly higher baseline levels of total sphingomyelins, and lower levels of total ceramides and sphingosine, compared with control subjects without familial diabetes history. As the first such study in longitudinal human cohorts, CASPID will elucidate the role of sphingolipids in the pathogenesis of dysglycemia and facilitate the discovery of novel predictive and prognostic biomarkers.

Integrative metabolomics science in Alzheimer's disease: Relevance and future perspectives

Alzheimer's disease (AD) is determined by various pathophysiological mechanisms starting 10-25 years before the onset of clinical symptoms. As multiple functionally interconnected molecular/cellular pathways appear disrupted in AD, the exploitation of high-throughput unbiased omics sciences is critical to elucidating the precise pathogenesis of AD. Among different omics, metabolomics is a fast-growing discipline allowing for the simultaneous detection and quantification of hundreds/thousands of perturbed metabolites in tissues or biofluids, reproducing the fluctuations of multiple networks affected by a disease. Here, we seek to critically depict the main metabolomics methodologies with the aim of identifying new potential AD biomarkers and further elucidating AD pathophysiological mechanisms. From a systems biology perspective, as metabolic alterations can occur before the development of clinical signs, metabolomics - coupled with existing accessible biomarkers used for AD screening and diagnosis - can support early disease diagnosis and help develop individualized treatment plans. Presently, the majority of metabolomic analyses emphasized that lipid metabolism is the most consistently altered pathway in AD pathogenesis. The possibility that metabolomics may reveal crucial steps in AD pathogenesis is undermined by the difficulty in discriminating between the causal or epiphenomenal or compensatory nature of metabolic findings.

Hepatic deletion of serine palmitoyl transferase 2 impairs ceramide/sphingomyelin balance, bile acids homeostasis and leads to liver damage in mice

Ceramides (Cer) have been shown as lipotoxic inducers, which disturb numerous cell-signaling pathways, leading to metabolic disorders such as type 2 diabetes. In this study, we aimed to determine the role of de novo hepatic ceramide synthesis in energy and liver homeostasis in mice. We generated mice lacking serine palmitoyltransferase 2 (Sptlc2), the rate limiting enzyme of ceramide de novo synthesis, in liver under albumin promoter. Liver function, glucose homeostasis, bile acid (BA) metabolism and hepatic sphingolipids content were assessed using metabolic tests and LC-MS. Despite lower expression of hepatic Sptlc2, we observed an increased concentration of hepatic Cer, associated with a 10-fold increase in neutral sphingomyelinase 2 (nSMase2) expression, and a decreased sphingomyelin content in the liver. Sptlc2ΔLiv mice were protected against obesity induced by high fat diet and displayed a defect in lipid absorption. In addition, an important increase in tauro-muricholic acid was associated with a downregulation of the nuclear BA receptor FXR target genes. Sptlc2 deficiency also enhanced glucose tolerance and attenuated hepatic glucose production, while the latter effect was dampened in presence of nSMase2 inhibitor. Finally, Sptlc2 disruption promoted apoptosis, inflammation and progressive development of hepatic fibrosis, worsening with age. Our data suggest a compensatory mechanism to regulate hepatic ceramides content from sphingomyelin hydrolysis, with deleterious impact on liver homeostasis. In addition, our results show the involvement of hepatic sphingolipid modulation in BA metabolism and hepatic glucose production in an insulin-independent manner, which highlight the still under-researched role of ceramides in many metabolic functions.

Effect of lard plus soybean oil on blood pressure and other cardiometabolic risk factors in healthy subjects: a randomized controlled-feeding trial

Lard has been consumed by humans for thousands of years, but its consumption has declined substantially in the last few decades, because of negative publicity about the consumption of animal-derived saturated fats. Emerging evidence highlights that lard plus soybean oil (blend oil) could be more beneficial for body weight and liver function than the individual use of the two oils. This study aimed to evaluate the effects of blend oil on cardiometabolic risk factors in healthy subjects. This was a parallel, three-arm, randomized controlled-feeding trial. 334 healthy subjects (mean age: 33.1 years, 60% women) were randomized into three isoenergetic diet groups with three different edible oils (30 g day^-1) (soybean oil, lard, and blend oil [50% lard and 50% soybean oil]) for 12 weeks. 245 (73.4%) participants completed the study. After the 12-week intervention, reductions in both systolic blood pressure (SBP) and diastolic blood pressure (DBP) were greater in the blend oil group than in the other two groups (P = 0.023 and 0.008 for the interaction between the diet group and time, respectively). Reductions of SBP and DBP in the blend oil group were more significant than those in the soybean oil group with P = 0.008 and P = 0.026 and the lard group with P < 0.001 and P < 0.001. Changes in SBP/DBP at 12 weeks were -6.0 (95% CI: -8.6 to -3.4)/0.8 (95% CI: -1.7 to 3.2) mmHg in the blend oil group, -3.3 (95% CI: -5.7 to -0.9)/1.5 (95% CI: -1.0 to 4.0) mmHg in the soybean oil group and -1.2 (95% CI: -3.7 to 1.4)/3.3 (95% CI: 0.9 to 5.8) mmHg in the lard group. Subgroup analyses showed that blend oil significantly decreased SBP and DBP compared with the other two groups in participants with BP ≥ 130/80 mmHg and body mass index ≥25. There were no significant differences in the changes in body weight, waist circumference, serum lipids, or glucose between groups. In conclusion, our findings suggest that blend oil (lard plus soybean oil) reduces BP compared with soybean oil and lard in healthy subjects.

Lipid homeostasis is essential for a maximal ER stress response

Changes in lipid metabolism are associated with aging and age-related diseases, including proteopathies. The endoplasmic reticulum (ER) is uniquely a major hub for protein and lipid synthesis, making its function essential for both protein and lipid homeostasis. However, it is less clear how lipid metabolism and protein quality may impact each other. Here, we identified let-767, a putative hydroxysteroid dehydrogenase in Caenorhabditis elegans, as an essential gene for both lipid and ER protein homeostasis. Knockdown of let-767 reduces lipid stores, alters ER morphology in a lipid-dependent manner, and blocks induction of the Unfolded Protein Response of the ER (UPRER). Interestingly, a global reduction in lipogenic pathways restores UPRER induction in animals with reduced let-767. Specifically, we find that supplementation of 3-oxoacyl, the predicted metabolite directly upstream of let-767, is sufficient to block induction of the UPRER. This study highlights a novel interaction through which changes in lipid metabolism can alter a cell's response to protein-induced stress.

Human Placental Adaptive Changes in Response to Maternal Obesity: Sex Specificities

Maternal obesity is increasingly prevalent and is associated with elevated morbidity and mortality rates in both mothers and children. At the interface between the mother and the fetus, the placenta mediates the impact of the maternal environment on fetal development. Most of the literature presents data on the effects of maternal obesity on placental functions and does not exclude potentially confounding factors such as metabolic diseases (e.g., gestational diabetes). In this context, the focus of this review mainly lies on the impact of maternal obesity (in the absence of gestational diabetes) on (i) endocrine function, (ii) morphological characteristics, (iii) nutrient exchanges and metabolism, (iv) inflammatory/immune status, (v) oxidative stress, and (vi) transcriptome. Moreover, some of those placental changes in response to maternal obesity could be supported by fetal sex. A better understanding of sex-specific placental responses to maternal obesity seems to be crucial for improving pregnancy outcomes and the health of mothers and children.

Distinct Metabolomic Profiling of Serum Samples from High-Fat-Diet-Induced Insulin-Resistant Mice

High-fat-diet (HFD)-induced obesity is associated with an elevated risk of insulin resistance (IR), which may precede the onset of type 2 diabetes mellitus and associated metabolic complications. Being a heterogeneous metabolic condition, it is pertinent to understand the metabolites and metabolic pathways that are altered during the development and progression of IR toward T2DM. Serum samples were collected from C57BL/6J mice fed with HFD or chow diet (CD) for 16 weeks. Collected samples were analyzed by gas chromatography-tandem mass spectrometry (GC-MS/MS). Data on the identified raw metabolites were evaluated using a combination of univariate and multivariate statistical methods. Mice fed with HFD had glucose and insulin intolerance associated with impairment of insulin signaling in key metabolic tissues. From the GC-MS/MS analysis of serum samples, a total of 75 common annotated metabolites were identified between HFD- and CD-fed mice. In the t-test, 22 significantly altered metabolites were identified. Out of these, 16 metabolites were up-accumulated, whereas 6 metabolites were down-accumulated. Pathway analysis identified 4 significantly altered metabolic pathways. In particular, primary bile acid biosynthesis and linoleic acid metabolism were upregulated, whereas the TCA cycle and pentose and glucuronate interconversion were downregulated in HFD-fed mice in comparison to CD-fed mice. These results show the distinct metabolic profiles associated with the onset of IR that could provide promising metabolic biomarkers for diagnostic and clinical applications.

Phytosphingosine inhibits cell proliferation by damaging DNA in human cell lines

Harmful cyanobacterial blooms have caused numerous biosecurity incidents owing to the production of hazardous secondary metabolites such as microcystin. Additionally, cyanobacteria also release many other components that have not been explored. We identified compounds of a toxic mixture exudated from a dominant, blooming species, Microcystis aeruginosa, and found that phytosphingosine (PHS) was one of the bioactive components. Since PHS exhibited toxicity and is deemed a hazardous substance by the European Chemicals Agency, we hypothesized that PHS is a potentially toxic compound in M. aeruginosa exudates. However, the mechanisms of PHS ecotoxicity remain unclear. We assessed the cytotoxicity of PHS using an in vitro cell model in eight human cell lines and observed that the nasopharyngeal carcinoma cell line CNE2 was the most sensitive. We exposed CNE2 cells to 0-25 µmol/L PHS for 24 hr to explore its toxicity and mechanism. PHS exposure resulted in abnormal nuclear morphology, micronuclei, and DNA damage. Moreover, PHS significantly inhibited cell proliferation and arrested cell cycle at S phase. The results of Western blot suggested that PHS increased the expression of DNA damage-related proteins (ATM, p-P53 and P21) and decreased the expression of S phase-related proteins (CDK2, CyclinA2 and CyclinE1), indicating the toxicological mechanism of PHS on CNE2 cells. These data provide evidence that PHS has genetic toxicity and inhibits cell proliferation by damaging DNA. Our study provides evidence that PHS inhibits cell proliferation by damaging DNA. While additional work is required, we propose that PHS been considered as a potentially toxic component in MaE in addition to other well-characterized secondary compounds.