Large-scale lipidomics identifies associations between plasma sphingolipids and T2DM incidence

Metabolomics in cardiometabolic diseases: Key biomarkers and therapeutic implications for insulin resistance and diabetes

Cardiometabolic diseases-including Type 2 diabetes and obesity-remain leading causes of global mortality. Recent advancements in metabolomics have facilitated the identification of metabolites that are integral to the development of insulin resistance, a characteristic feature of cardiometabolic disease. Key metabolites, such as branched-chain amino acids (BCAAs), ceramides, glycine, and glutamine, have emerged as valuable biomarkers for early diagnosis, risk stratification, and potential therapeutic targets. Elevated BCAAs and ceramides are strongly associated with insulin resistance and Type 2 diabetes, whereas glycine exhibits an inverse relationship with insulin resistance, making it a promising therapeutic target. Metabolites involved in energy stress, including ketone bodies, lactate, and nicotinamide adenine dinucleotide (NAD⁺), regulate insulin sensitivity and metabolic health, with ketogenic diets and NAD⁺ precursor supplementation showing potential benefits. Additionally, the novel biomarker N-lactoyl-phenylalanine further underscores the complexity of metabolic regulation and its therapeutic potential. This review underscores the potential of metabolite-based diagnostics and precision medicine, which could enhance efforts in the prevention, diagnosis, and treatment of cardiometabolic diseases, ultimately improving patient outcomes and quality of life.

Associations of Palmito-leic Acid and Nervonic Acid Hexosylceramides with Type 2 Diabetes Mellitus in a Prospective Nested Case-control Study Among Chinese Population

OBJECTIVES

We aimed to evaluate the associations of hexosylceramides (HexCers) and their ratio with incident type 2 diabetes mellitus (T2DM) and explore underlying mechanisms.

METHODS

We conducted a nested case-control study using the Suzhou chronic disease cohort including 234 T2DM cases and 468 controls, 1:2 matched on age (±2 y) and sex. HexCer(d18:1/16:1) and HexCer(d18:1/24:1) were measured by targeted UPLC-MS/MS. Multivariable conditional logistic regression was used to estimate the associations of these HexCer species and their ratio with T2DM risk.

RESULTS

After adjustment for potential confounders, compared with the lowest quartile, the highest quartile of HexCer(d18:1/24:1) was positively associated with T2DM risk (OR: 1.91; 95%CI, 1.12, 3.26; P-trend <0.05). The ratio of HexCer(d18:1/24:1) to HexCer(d18:1/16:1) showed a positive association with T2DM risk (OR: 1.89; 95%CI, 1.13, 3.18; P-trend <0.05). On the natural log scale, each SD increases in HexCer(d18:1/24:1) and its ratio to HexCer(d18:1/16:1) increased by 29% and 30%, respectively. No significant association for HexCer(d18:1/16:1) was found. Additive value of HexCer(d18:1/24:1) or HexCer(d18:1/24:1)/HexCer(d18:1/16:1) ratio for prediction of T2DM above traditional risk factors.

CONCLUSIONS

HexCer(d18:1/24:1) and its ratio to HexCer(d18:1/16:1) are positively associated with incident T2DM in a community-based Chinese population. Future studies are warranted to confirm our findings.

Establishment of MS LOC platform and its pilot application in clinical lipidomics

Lipidomics has demonstrated significant potential for disease diagnosis and prediction. The development and optimization of a robust mass spectrometry (MS) platform for lipidome analysis is critically important, as it can facilitate biomarker discovery, cohort testing, and performance evaluation in clinical lipidomics studies. In this work, we developed a high-throughput and reliable platform, termed MS Lab on a Chip (MS LOC), which integrates the MetArray chip, an automated lipidomics pretreatment protocol, and the reflectron matrix-assisted laser desorption/ionization time-of-flight mass spectrometry (MALDI-TOF-MS) instrument. The MetArray chip, produced through a mass production process, exhibited exceptional stability as an MS substrate. The integration of automated lipid pretreatment and MS detection processes ensures high throughput, stability and efficiency during sample preparation. The analysis of various lipid standards and different types of biological samples enabled comprehensive investigation of lipid features and annotation using the MS LOC. Furthermore, a small cohort study, consisting of hepatocellular carcinoma (HCC) and non-HCC groups, was conducted on this platform, providing preliminary validation of its performance and suggesting that this platform offers a comprehensive protocol for clinical lipidomics testing.

Phenotypic upregulation of hexocylceramides and ether-linked phosphocholines as markers of human extreme longevity

Centenarians and their relatives possess a notable survival advantage, with higher longevity and reduced susceptibility to major age-related diseases. To date, characteristic omics profiles of centenarians have been described, demonstrating that these individuals with exceptional longevity regulate their metabolism to adapt and incorporate more resilient biomolecules into their cells. Among these adaptations, the lipidomic profile stands out. However, it has not yet been determined whether this lipidomic profile is specific to centenarians or is the consequence of extreme longevity genetics and is also present in centenarians' offspring. This distinction is crucial for defining potential therapeutic targets that could help delay the aging process and associated pathologies. We applied mass-spectrometry-based techniques to quantify 569 lipid species in plasma samples from 39 centenarians, 63 centenarians' offspring, and 69 noncentenarians' offspring without familial connections. Based on this profile, we calculated different indexes to characterize the functional and structural properties of plasma lipidome. Our findings demonstrate that extreme longevity genetics (centenarians and centenarians' offspring) determines a specific lipidomic signature characterized by (i) an enrichment of hexosylceramides, (ii) a decrease of specific species of ceramides and sulfatides, (iii) a global increase of ether-PC and ether-LPC, and (iv) changes in the fluidity and diversity of specific lipid classes. We point out the conversion of ceramides to hexosylceramides and the maintenance of the levels of the ether-linked PC as a phenotypic trait to guarantee extreme longevity. We propose that this molecular signature is the result of an intrinsic adaptive program that preserves protective mechanisms and cellular identity.

CerS6 links ceramide metabolism to innate immune responses in diabetic kidney disease

Ectopic lipid deposition, mitochondrial injury, and inflammatory responses contribute to the development of diabetic kidney disease (DKD); however, the mechanistic link between these processes remains unclear. In this study, we demonstrate that the ceramide synthase 6 (CerS6) is primarily localized in podocytes of the glomeruli and is upregulated in two different models of diabetic mice. Podocyte-specific CerS6 knockout ameliorates glomerular injury and inflammatory responses in male diabetic mice and in male mice with adriamycin-induced nephropathy. In contrast, podocyte-specific overexpression of CerS6 sufficiently induces proteinuria. Mechanistically, CerS6-derived ceramide (d18:1/16:0) can bind to the mitochondrial channel protein VDAC1 at Glu59 residue, initiating mitochondrial DNA (mtDNA) leakage, activating the cGAS-STING signaling pathway, and ultimately promoting an immune-inflammatory response in the kidney. Importantly, CERS6 expression is increased in podocytes from kidney biopsies of patients with DKD and focal segmental glomerulosclerosis (FSGS), and the expression level of CERS6 is correlated negatively with glomerular filtration rate and positively with proteinuria. Thus, our findings suggest that targeting CerS6 may be a potential therapeutic strategy for proteinuric kidney diseases.

Elevated Very-Long-Chain Ceramides in the Vitreous Humor of Patients With Proliferative Diabetic Retinopathy

Purpose

To quantitate the levels of various ceramide species in the vitreous of patients with proliferative diabetic retinopathy (PDR) and to investigate the role of vitreal ceramides in the pathogenesis of PDR.

Study Design

A case control study.

Methods

We collected vitreous samples from 25 type 2 diabetes patients with PDR and 25 age- and sex-matched nondiabetic controls undergoing vitrectomy. The levels of ceramide species (C16:0, 18:0, 20:0, 22:0, 24:1, and 24:0) were measured by ultra-high-performance liquid chromatography-tandem mass spectrometry with positive electrospray ionization mode. The correlation of baseline characteristics, blood test data, and clinical manifestation of PDR were analyzed with vitreal ceramides levels.

Results

The total level of ceramides was substantially higher in the PDR group than the control group (18.626 ± 19.264 versus 3.524 ± 2.456 pmol/mg protein; P < 0.001). Among ceramides of various acyl chain lengths, the increases of very-long-chain (VLC) ceramides (C22-C24) were more drastic than those of long-chain ceramides (C16-C20). In the PDR group, VLC ceramide species accounted for 76.1%, whereas in the control group, C16 ceramide predominated at 40.5%. Based on the multivariate linear regression analysis, diagnosis of diabetes (β = 14.5751; P = 0.0327) and lower body mass index (β = -2.1396; P = 0.0173) were significantly associated with higher level of VLC ceramides. Intravitreal injection of anti-VEGF leads to insignificant reduction of VLC ceramides (P = 0.068).

Conclusions

Vitreal ceramide levels were elevated in diabetic subjects, especially the VLC species, which may contribute to the pathogenesis of diabetic retinopathy.

Randomised controlled trial of intermittent calorie restriction in people with multiple sclerosis

BACKGROUND

Calorie restriction (CR) ameliorates preclinical models of multiple sclerosis (MS) via multiple mechanisms. These include decreased leptin, a proinflammatory adipokine, but mechanistic studies in humans are lacking. Tests of daily and intermittent CR (iCR) in people with MS (pwMS) showed improvements in fatigue and well-being measures. This trial studied the effects of 12-week iCR on metabolic, immunological, and clinical outcomes in pwMS.

METHOD

Relapsing-remitting MS participants were randomised to iCR or a control group. Study visits were conducted at baseline, 6 and 12 weeks. The primary outcome was reduction in serum leptin levels at 12 weeks. Feasibility and safety were assessed by diet adherence and adverse events (AEs). Secondary outcomes included changes in anthropometric and body composition measures, metabolic and immunologic profiling, and clinical measures. Mixed effects linear regression models were used to evaluate outcome differences between and within groups over time.

RESULTS

Forty-two pwMS were randomised, 34 completed the study (17/group). Leptin serum levels at 12 weeks were significantly lower in the iCR versus the control group (mean decrease -6.98 µg/dL, 95% CI: -28.02 to 14.06; p=0.03). Adherence to iCR was 99.5% and 97.2% at 6 and 12 weeks, respectively, and no serious AEs were reported. An increase in blood CD45RO+ regulatory T-cell numbers was seen after 6 weeks of iCR. Exploratory cognitive testing demonstrated a significant improvement in the Symbol Digit Modality Test Score in the iCR group at 12 weeks.

CONCLUSIONS

iCR has the potential to benefit metabolic and immunologic profiles and is safe and feasible in pwMS.

TRIAL REGISTRATION NUMBER

NCT03539094 .

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.

Ten metabolites-based algorithm predicts the future development of type 2 diabetes in Chinese

INTRODUCTION

Type 2 diabetes (T2D) is a heterogeneous metabolic disease with large variations in the relative contributions of insulin resistance and β-cell dysfunction across different glucose tolerance subgroups and ethnicities. A more precise yet feasible approach to categorize risk preceding T2D onset is urgently needed. This study aimed to identify potential metabolic biomarkers that could contribute to the development of T2D and investigate whether their impact on T2D is mediated through insulin resistance and β-cell dysfunction.

METHODS

A non-targeted metabolomic analysis was performed in plasma samples of 196 incident T2D cases and 196 age- and sex-matched non-T2D controls recruited from a long-term prospective Chinese community-based cohort with a follow-up period of ∼ 16 years.

RESULTS

Metabolic profiles revealed profound perturbation of metabolomes before T2D onset. Overall metabolic shifts were strongly associated with insulin resistance rather than β-cell dysfunction. In addition, 188 out of the 578 annotated metabolites were associated with insulin resistance. Bi-directional mediation analysis revealed putative causal relationships among the metabolites, insulin resistance and T2D risk. We built a machine-learning based prediction model, integrating the conventional clinical risk factors (age, BMI, TyG index and 2hG) and 10 metabolites (acetyl-tryptophan, kynurenine, γ-glutamyl-phenylalanine, DG(18:2/22:6), DG(38:7), LPI(18:2), LPC(P-16:0), LPC(P-18:1), LPC(P-20:0) and LPE(P-20:0)) (AUROC = 0.894, 5.6% improvement comparing to the conventional clinical risk model), that successfully predicts the development of T2D.

CONCLUSIONS

Our findings support the notion that the metabolic changes resulting from insulin resistance, rather than β-cell dysfunction, are the primary drivers of T2D in Chinese adults. Metabolomes as a valuable phenotype hold potential clinical utility in the prediction of T2D.

Moderate-intensity Combined Training Induces Lipidomic Changes in Individuals With Obesity and Type 2 Diabetes

CONTEXT

Alterations in the lipid metabolism are linked to metabolic disorders such as insulin resistance (IR), obesity and type 2 diabetes (T2D). Regular exercise, particularly combined training (CT), is a well-known nonpharmacological treatment that combines aerobic (AT) and resistance (RT) training benefits. However, it is unclear whether moderate-intensity exercise without dietary intervention induces changes in lipid metabolism to promote a "healthy lipidome."

OBJECTIVE

The study aimed to investigate the effect of 16 weeks of CT on plasma and white adipose tissue in both sexes, middle-aged individuals with normal weight, obesity (OB), and T2D using an ultra-high performance liquid chromatography-mass spectrometry (UHPLC-MS) untargeted lipidomics approach.

METHODS

Body composition, maximum oxygen consumption (VO2max), strength, and biochemical markers were evaluated before and after the control/training period and correlated with lipid changes. CT consisted of 8 to 10 RT exercises, followed by 35 minutes of AT (45%-70% VO2max), 3 times a week for 16 weeks.

RESULTS

The CT significantly reduced the levels of saturated and monounsaturated fatty acid side-chains (SFA/MUFA) in sphingolipids, glycerolipids (GL) and glycerophospholipids (GP) as well as reducing fat mass, circumferences and IR. Increased levels of polyunsaturated fatty acids in GPs and GLs were also observed, along with increased fat-free mass, VO2 max, and strength (all P < .05) after training.

CONCLUSION

Our study revealed that 16 weeks of moderate-intensity CT remodeled the lipid metabolism in OB, and T2D individuals, even without dietary intervention, establishing a link between exercise-modulated lipid markers and mechanisms that reduce IR and obesity-related comorbidities.

Lipid profile alterations and biomarker identification in type 1 diabetes mellitus patients under glycemic control

BACKGROUND

Type 1 diabetes mellitus (T1DM) is well-known to trigger a disruption of lipid metabolism. This study aimed to compare lipid profile changes in T1DM patients after achieving glucose control and explore the underlying mechanisms. In addition, we seek to identify novel lipid biomarkers associated with T1DM under conditions of glycemic control.

METHODS

A total of 27 adults with T1DM (age: 34.3 ± 11.2 yrs) who had maintained glucose control for over a year, and 24 healthy controls (age: 35.1 + 5.56 yrs) were recruited. Clinical characteristics of all participants were analyzed and plasma samples were collected for untargeted lipidomic analysis using mass spectrometry.

RESULTS

We identified 594 lipid species from 13 major classes. Differential analysis of plasma lipid profiles revealed a general decline in lipid levels in T1DM patients with controlled glycemic levels, including a notable decrease in triglycerides (TAGs) and diglycerides (DAGs). Moreover, these T1DM patients exhibited lower levels of six phosphatidylcholines (PCs) and three phosphatidylethanolamines (PEs). Random forest analysis determined DAG(14:0/20:0) and PC(18:0/20:3) to be the most prominent plasma markers of T1DM under glycemic control (AUC = 0.966).

CONCLUSIONS

The levels of all metabolites from the 13 lipid classes were changed in T1DM patients under glycemic control, with TAGs, DAGs, PCs, PEs, and FFAs demonstrating the most significant decrease. This research identified DAG(14:0/20:0) and PC(18:0/20:3) as effective plasma biomarkers in T1DM patients with controled glycemic levels.

Illuminating the dark space of neutral glycosphingolipidome by selective enrichment and profiling at multi-structural levels

Glycosphingolipids (GSLs) are essential components of cell membranes, particularly enriched in the nervous system. Altered molecular distributions of GSLs are increasingly associated with human diseases, emphasizing the significance of lipidomic profiling. Traditional GSL analysis methods are hampered by matrix effect from phospholipids and the difficulty in distinguishing structural isomers. Herein, we introduce a highly sensitive workflow that harnesses magnetic TiO2 nanoparticle-based selective enrichment, charge-tagging Paternò-Büchi reaction, and liquid chromatography-tandem mass spectrometry. This approach enables mapping over 300 distinct GSLs in brain tissues by defining sugar types, long chain bases, N-acyl chains, and the locations of desaturation and hydroxylation. Relative quantitation of GSLs across multiple structural levels provides evidence of dysregulated gene and protein expressions of FA2H and CerS2 in human glioma tissue. Based on the structural features of GSLs, our method accurately differentiates human glioma with/without isocitrate dehydrogenase genetic mutation, and normal brain tissue.

Plasma metabolomic profile of adiposity and body composition in childhood: The Genetics of Glucose regulation in Gestation and Growth cohort

OBJECTIVE

This study identified metabolite modules associated with adiposity and body fat distribution in childhood using gold-standard measurements.

METHODS

We used cross-sectional data from 329 children at mid-childhood (age 5.3 ± 0.3 years; BMI 15.7 ± 1.5 kg/m2) from the Genetics of Glucose regulation in Gestation and Growth (Gen3G), a prospective pre-birth cohort. We quantified 1038 plasma metabolites and measured body composition using the gold-standard dual-energy x-ray absorptiometry (DXA), in addition to skinfold, waist circumference, and BMI. We applied weighted-correlation network analysis to identify a network of highly correlated metabolite modules. Spearman's partial correlations were applied to determine the associations of adiposity with metabolite modules and individual metabolites with false discovery rate (FDR) correction.

RESULTS

We identified a 'green' module of 120 metabolites, primarily comprised of lipids (mostly sphingomyelins and phosphatidylcholine), that showed positive correlations (all FDR p < 0.05) with DXA estimates of total and truncal fat (ρadjusted = 0.11-0.19), skinfold measures (ρadjusted = 0.09-0.26), and BMI and waist circumference (ρadjusted = 0.15 and 0.18, respectively). These correlations were similar when stratified by sex. Within this module, sphingomyelin (d18:2/14:0, d18:1/14:1)*, a sphingomyelin sub-specie that is an important component of cell membranes, showed the strongest associations.

CONCLUSIONS

A module of metabolites was associated with adiposity measures in childhood.

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.

ReTimeML: a retention time predictor that supports the LC-MS/MS analysis of sphingolipids

The analysis of ceramide (Cer) and sphingomyelin (SM) lipid species using liquid chromatography-tandem mass spectrometry (LC-MS/MS) continues to present challenges as their precursor mass and fragmentation can correspond to multiple molecular arrangements. To address this constraint, we developed ReTimeML, a freeware that automates the expected retention times (RTs) for Cer and SM lipid profiles from complex chromatograms. ReTimeML works on the principle that LC-MS/MS experiments have pre-determined RTs from internal standards, calibrators or quality controls used throughout the analysis. Employed as reference RTs, ReTimeML subsequently extrapolates the RTs of unknowns using its machine-learned regression library of mass-to-charge (m/z) versus RT profiles, which does not require model retraining for adaptability on different LC-MS/MS pipelines. We validated ReTimeML RT estimations for various Cer and SM structures across different biologicals, tissues and LC-MS/MS setups, exhibiting a mean variance between 0.23 and 2.43% compared to user annotations. ReTimeML also aided the disambiguation of SM identities from isobar distributions in paired serum-cerebrospinal fluid from healthy volunteers, allowing us to identify a series of non-canonical SMs associated between the two biofluids comprised of a polyunsaturated structure that confers increased stability against catabolic clearance.

Effects of wolfberry (Lycium barbarum) consumption on the human plasma lipidome and its association with cardiovascular disease risk factors: a randomized controlled trial of middle-aged and older adults

Background

Long-term wolfberry intake as part of a healthy dietary pattern was recognized to have beneficial vascular outcomes. Characterization of the plasma lipidome may further provide comprehensive insights into pathways underlying these cardiovascular protective effects.

Objective

We analyzed the plasma lipidome of subjects who adhered to a healthy dietary pattern either with or without wolfberry and investigated the associations between the plasma lipidomic profile and cardiovascular health-related indicators.

Methods

In this 16-week, parallel design, randomized controlled trial, middle-aged and older adults (n = 41) were provided dietary counseling and assigned to either consume or not consume 15 g of wolfberry daily. At baseline and post-intervention, plasma lipidomics was assayed, and its relationships with classical CVD risk factors, vascular health, oxidant burden, carotenoids status, body composition, and anthropometry were examined.

Results

From the plasma lipidome, 427 lipid species from 26 sub-classes were quantified. In the wolfberry and control groups, significant changes were prominent for 27 and 42 lipid species, respectively (P < 0.05 with > 0.2-fold change). Fold changes for seven lipid species were also markedly different between the two groups. Examining the relationships between the plasma lipidome and CVD-related risk factors, total cholesterol revealed a marked positive correlation with 13 ceramide species, while HDL-cholesterol which was notably increased with wolfberry consumption showed a positive correlation with 10 phosphatidylcholine species. Oxidant burden, as represented by plasma 8-isoprostanes, was also inversely associated with lipidomic triglycerides and ether-triglycerides (41 species) and directly associated with hexosylceramides (eight species) and sphingomyelins (six species). There were no differential associations with CVD risk detected between groups.

Conclusion

Characteristic alterations to the plasma lipidome were observed with healthy dietary pattern adherence and wolfberry consumption. An examination of these fluctuations suggests potential biochemical mechanisms that may mediate the antioxidant and cardiovascular protective effects of healthy dietary pattern adherence and wolfberry intake. This study was registered at clinicaltrials.gov as NCT0353584.

A review of the mechanisms of abnormal ceramide metabolism in type 2 diabetes mellitus, Alzheimer's disease, and their co-morbidities

The global prevalence of type 2 diabetes mellitus (T2DM) and Alzheimer's disease (AD) is rapidly increasing, revealing a strong association between these two diseases. Currently, there are no curative medication available for the comorbidity of T2DM and AD. Ceramides are structural components of cell membrane lipids and act as signal molecules regulating cell homeostasis. Their synthesis and degradation play crucial roles in maintaining metabolic balance in vivo, serving as important mediators in the development of neurodegenerative and metabolic disorders. Abnormal ceramide metabolism disrupts intracellular signaling, induces oxidative stress, activates inflammatory factors, and impacts glucose and lipid homeostasis in metabolism-related tissues like the liver, skeletal muscle, and adipose tissue, driving the occurrence and progression of T2DM. The connection between changes in ceramide levels in the brain, amyloid β accumulation, and tau hyper-phosphorylation is evident. Additionally, ceramide regulates cell survival and apoptosis through related signaling pathways, actively participating in the occurrence and progression of AD. Regulatory enzymes, their metabolites, and signaling pathways impact core pathological molecular mechanisms shared by T2DM and AD, such as insulin resistance and inflammatory response. Consequently, regulating ceramide metabolism may become a potential therapeutic target and intervention for the comorbidity of T2DM and AD. The paper comprehensively summarizes and discusses the role of ceramide and its metabolites in the pathogenesis of T2DM and AD, as well as the latest progress in the treatment of T2DM with AD.

Comprehensive profiling of ceramides in human serum by liquid chromatography coupled to tandem mass spectrometry combining data independent/dependent acquisition modes

Ceramides are sphingolipids with a structural function in the cell membrane and are involved in cell differentiation, proliferation and apoptosis. Recently, these chemical species have been pointed out as potential biomarkers in different diseases, due to their abnormal levels in blood. In this research, we present an overall strategy combining data-independent and dependent acquisitions (DIA and DDA, respectively) for identification, confirmation, and quantitative determination of ceramides in human serum. By application of liquid chromatography-tandem mass spectrometry (LC-MS/MS) method in DIA mode we identified 49 ceramides including d18:1, d18:0, d18:2, d16:1, d17:1 and t18:0 species. Complementary, quantitative determination of ceramides was based on a high-throughput and fully automated method consisting of solid-phase extraction on-line coupled to LC-MS/MS in DDA to improve analytical features avoiding the errors associated to sample processing. Quantitation limits were at pg mL-1 level, the intra-day and between-days variability were below 20 and 25 %, respectively; and the accuracy, expressed as bias, was always within ±25 %. The proposed method was tested with the CORDIOPREV cohort in order to obtain a qualitative and quantitative profiling of ceramides in human serum. This characterization allowed identifying d18:1 ceramides as the most concentrated with 70.8% of total concentration followed by d18:2 and d18:0 with 13.0 % and 8.8 %, respectively. Less concentrated ceramides, d16:1, d17:1 and t18:0, reported a 7.1 % of the total content. Combination of DIA and DDA LC-MS/MS analysis enabled to profile qualitative and quantitatively ceramides in human serum.

Lipidomic markers of obesity and their dynamics after bariatric surgery

Obesity is considered as a chronic progressive disease, heterogeneous in its etiology and clinical manifestations, and characterized by excess in body fat mass and its deposition in the body. The term “morbid obesity” refers to excessive deposition of adipose tissue with a body mass index (BMI) ≥40 kg / m2 or with a BMI ≥ 35 kg / m2 in the presence of serious complications associated with obesity. Along with obesity, the frequency of type 2 diabetes mellitus and cardiovascular diseases closely associated with it has increased. It results from the progression of metabolic disorders, including insulin resistance, which is inextricably linked with the accumulation of visceral fat and plays a key role in the pathogenesis of obesity-related diseases.

The study of lipidomic signatures in obesity and associated conditions is a promising branch of fundamental medicine, which makes it possible to significantly and at a new conceptual level stratify a cohort of obese patients into various phenotypes, including a metabolically healthy and metabolically unhealthy obesity phenotypes. Dynamic changes in the lipidome both in the context of diet, drug treatment, and after various bariatric surgeries are of great interest for developing personalized strategies for the treatment of this disease. Currently available studies and their results suggest that we are only at the very start of studying this promising biomedical field.

Lipidomics profiling reveals distinct patterns of plasma sphingolipid alterations in Alzheimer's disease and vascular dementia

BACKGROUND

Alzheimer's disease (AD) and vascular dementia (VaD) are two of the commonest causes of dementia in the elderly. Of the myriad biomolecules implicated in dementia pathogenesis, sphingolipids have attracted relatively scant research attention despite their known involvement in multiple pathophysiological processes. The potential utility of peripheral sphingolipids as biomarkers in dementia cohorts with high concomitance of cerebrovascular diseases is also unclear.

METHODS

Using a lipidomics platform, we performed a case-control study of plasma sphingolipids in a prospectively assessed cohort of 526 participants (non-cognitively impaired, NCI = 93, cognitively impaired = 217, AD = 166, VaD = 50) using a lipidomics platform.

RESULTS

Distinct patterns of sphingolipid alterations were found in AD and VaD, namely an upregulation of d18:1 species in AD compared to downregulation of d16:1 species in VaD. In particular, GM3 d18:1/16:0 and GM3 d18:1/24:1 showed the strongest positive associations with AD. Furthermore, evaluation of sphingolipids panels showed specific combinations with higher sensitivity and specificity for classification of AD (Cer d16:1/24:0. Cer d18:1/16:0, GM3 d16:1/22:0, GM3 d18:1/16:0, SM d16:1/22:0, HexCer d18:1/18:0) and VAD (Cer d16:1/24:0, Cer d18:1/16:0, Hex2Cer d16:1/16:0, HexCer d18:1/18:0, SM d16:1/16:0, SM d16:1/20:0, SM d18:2/22:0) compared to NCI.

CONCLUSIONS

AD and VaD are associated with distinct changes of plasma sphingolipids, warranting further studies into underlying pathophysiological mechanisms and assessments of their potential utility as dementia biomarkers and therapeutic targets.

Blood-Derived Lipid and Metabolite Biomarkers in Cardiovascular Research from Clinical Studies: A Recent Update

The primary prevention, early detection, and treatment of cardiovascular disease (CVD) have been long-standing scientific research goals worldwide. In the past decades, traditional blood lipid profiles have been routinely used in clinical practice to estimate the risk of CVDs such as atherosclerotic cardiovascular disease (ASCVD) and as treatment targets for the primary prevention of adverse cardiac events. These blood lipid panel tests often fail to fully predict all CVD risks and thus need to be improved. A comprehensive analysis of molecular species of lipids and metabolites (defined as lipidomics and metabolomics, respectively) can provide molecular insights into the pathophysiology of the disease and could serve as diagnostic and prognostic indicators of disease. Mass spectrometry (MS) and nuclear magnetic resonance (NMR)-based lipidomics and metabolomics analysis have been increasingly used to study the metabolic changes that occur during CVD pathogenesis. In this review, we provide an overview of various MS-based platforms and approaches that are commonly used in lipidomics and metabolomics workflows. This review summarizes the lipids and metabolites in human plasma/serum that have recently (from 2018 to December 2022) been identified as promising CVD biomarkers. In addition, this review describes the potential pathophysiological mechanisms associated with candidate CVD biomarkers. Future studies focused on these potential biomarkers and pathways will provide mechanistic clues of CVD pathogenesis and thus help with the risk assessment, diagnosis, and treatment of CVD.

Lipidomics analysis of impaired glucose tolerance and type 2 diabetes mellitus in overweight or obese elderly adults

Aims

Aging, obesity, and type 2 diabetes mellitus (T2DM) form a metabolic disease continuum that has a continuously increasing prevalence. Lipidomics explains the complex interactions between lipid metabolism and metabolic diseases. We aimed to systematically investigate the plasma lipidome changes induced by newly diagnosed impaired glucose tolerance (IGT) and T2DM in overweight/obese elderly individuals and to identify potential biomarkers to differentiate between the IGT, T2DM, and control groups.

Methods

Plasma samples from 148 overweight/obese elderly individuals, including 52 patients with IGT, 47 patients with T2DM, and 49 euglycemic controls, were analyzed using a high-coverage nontargeted absolute quantitative lipidomics approach.

Results

We quantified 1840 lipids from thirty-eight classes and seven lipid categories. Among overweight/obese elderly individuals, the lipidomic profiles of IGT and T2DM patients were significantly different from those of controls, while they were similar in the IGT and T2DM groups. The concentrations of diglycerides, triglycerides, phosphatidylcholines, and ceramides were obviously altered in the IGT and T2DM groups. Particularly, IGT and T2DM induced the accumulation of triglycerides with longer carbon atom numbers (C44-50) and saturated or lower double bond numbers (n (C=C) = 0-2). Furthermore, a total of 17 potential lipidic biomarkers were identified to successfully differentiate between the IGT, T2DM, and control groups.

Conclusions

In overweight/obese elderly patients, IGT and T2DM induced apparent lipidome-wide changes. This study's results may contribute to explaining the complex dysfunctional lipid metabolism in aging, obesity, and diabetes.

Plasma metabolomics supports non-fasted sampling for metabolic profiling across a spectrum of glucose tolerance in the Nile rat model for type 2 diabetes

Type 2 diabetes is a challenge in modern healthcare, and animal models are necessary to identify underlying mechanisms. The Nile rat (Arvicanthis niloticus) develops diet-induced diabetes rapidly on a conventional rodent chow diet without genetic or chemical manipulation. Unlike common laboratory models, the outbred Nile rat model is diurnal and has a wide range of overt diabetes onset and diabetes progression patterns in both sexes, better mimicking the heterogeneous diabetic phenotype in humans. While fasted blood glucose has historically been used to monitor diabetic progression, postprandial blood glucose is more sensitive to the initial stages of diabetes. However, there is a long-held assumption that ad libitum feeding in rodent models leads to increased variance, thus masking diabetes-related metabolic changes in the plasma. Here we compared repeatability within triplicates of non-fasted or fasted plasma samples and assessed metabolic changes relevant to glucose tolerance in fasted and non-fasted plasma of 8-10-week-old male Nile rats. We used liquid chromatography-mass spectrometry lipidomics and polar metabolomics to measure relative metabolite abundances in the plasma samples. We found that, compared to fasted metabolites, non-fasted plasma metabolites are not only more strongly associated with glucose tolerance on the basis of unsupervised clustering and elastic net regression model, but also have a lower replicate variance. Between the two sampling groups, we detected 66 non-fasted metabolites and 32 fasted metabolites that were associated with glucose tolerance using a combined approach with multivariable elastic net and individual metabolite linear models. Further, to test if metabolite replicate variance is affected by age and sex, we measured non-fasted replicate variance in a cohort of mature 30-week-old male and female Nile rats. Our results support using non-fasted plasma metabolomics to study glucose tolerance in Nile rats across the progression of diabetes.

Association of healthy dietary patterns and cardiorespiratory fitness in the community

AIMS

To evaluate the associations of dietary indices and quantitative cardiorespiratory fitness (CRF) measures in a large, community-based sample harnessing metabolomic profiling to interrogate shared biology.

METHODS AND RESULTS

Framingham Heart Study (FHS) participants underwent maximum effort cardiopulmonary exercise tests for CRF quantification (via peak VO2) and completed semi-quantitative food frequency questionnaires. Dietary quality was assessed by the Alternative Healthy Eating Index (AHEI) and Mediterranean-style Diet Score (MDS), and fasting blood concentrations of 201 metabolites were quantified. In 2380 FHS participants (54 ± 9 years, 54% female, body mass index 28 ± 5 kg/m2), 1 SD higher AHEI and MDS were associated with 5.2% (1.2 mL/kg/min, 95% CI 4.3-6.0%, P < 0.0001) and 4.5% (1.0 mL/kg/min, 95% CI 3.6-5.3%, P < 0.0001) greater peak VO2 in linear models adjusted for age, sex, total daily energy intake, cardiovascular risk factors, and physical activity. In participants with metabolite profiling (N = 1154), 24 metabolites were concordantly associated with both dietary indices and peak VO2 in multivariable-adjusted linear models (FDR < 5%). Metabolites that were associated with lower CRF and poorer dietary quality included C6 and C7 carnitines, C16:0 ceramide, and dimethylguanidino valeric acid, and metabolites that were positively associated with higher CRF and favourable dietary quality included C38:7 phosphatidylcholine plasmalogen and C38:7 and C40:7 phosphatidylethanolamine plasmalogens.

CONCLUSION

Higher diet quality is associated with greater CRF cross-sectionally in a middle-aged community-dwelling sample, and metabolites highlight potential shared favourable effects on cardiometabolic health.

Metabolic phenotyping of BMI to characterize cardiometabolic risk: evidence from large population-based cohorts

Obesity is a risk factor for type 2 diabetes and cardiovascular disease. However, a substantial proportion of patients with these conditions have a seemingly normal body mass index (BMI). Conversely, not all obese individuals present with metabolic disorders giving rise to the concept of "metabolically healthy obese". We use lipidomic-based models for BMI to calculate a metabolic BMI score (mBMI) as a measure of metabolic dysregulation associated with obesity. Using the difference between mBMI and BMI (mBMIΔ), we identify individuals with a similar BMI but differing in their metabolic health and disease risk profiles. Exercise and diet associate with mBMIΔ suggesting the ability to modify mBMI with lifestyle intervention. Our findings show that, the mBMI score captures information on metabolic dysregulation that is independent of the measured BMI and so provides an opportunity to assess metabolic health to identify "at risk" individuals for targeted intervention and monitoring.

Ceramides are decreased after liraglutide treatment in people with type 2 diabetes: a post hoc analysis of two randomized clinical trials

BACKGROUND

Specific ceramides have been identified as risk markers for cardiovascular disease (CVD) years before onset of disease. Treatment with the glucagon-like peptide-1 receptor agonist (GLP-1RA) liraglutide has been shown to induce beneficial changes in the lipid profile and reduce the risk of CVD. Reducing lipotoxic lipids with an antidiabetic drug therapy could be a path towards precision medicine approaches for the treatment of complications to diabetes. In this post-hoc study, an investigation was carried out on the effect of liraglutide on CVD-risk associated ceramides in two randomized clinical trials including participants with type 2 diabetes (T2D).

METHODS

This study analyzed plasma samples from two independent randomized placebo-controlled clinical trials. The first trial, Antiproteinuric Effects of Liraglutide Treatment (LirAlbu12) followed a crossover design where 27 participants were treated for 12 weeks with either liraglutide (1.8 mg/d) or placebo, followed by a four-week washout period, and then another 12 weeks of the other treatment. The second clinical trial, Effect of Liraglutide on Vascular Inflammation in Type-2 Diabetes (LiraFlame26), lasted for 26 weeks and followed a parallel design, where 102 participants were randomized 1:1 to either liraglutide or placebo. Heresix prespecified plasma ceramides were measured using liquid chromatography mass spectrometry and assessed their changes using linear mixed models. Possible confounders were assessed with mediation analyses.

RESULTS

In the LiraFlame26 trial, 26-week treatment with liraglutide resulted in a significant reduction of two ceramides associated with CVD risk, C16 Cer and C24:1 Cer (p < 0.05) compared to placebo. None of the remaining ceramides showed statistically significant changes in response to liraglutide treatment compared to placebo. Significant changes in ceramides were not found after 12-weeks of liraglutide treatment in the LirAlbu12 trial. Mediation analyses showed that weight loss did not affect ceramide reduction.

CONCLUSIONS

It was demonstrated that treatment with liraglutide resulted in a reduction in C16 Cer and C24:1 Cer after 26 weeks of treatment. These findings suggest the GLP-1RA can be used to modulate ceramides in addition to its other properties.

TRIAL REGISTRATION

Clinicaltrial.gov identifier: NCT02545738 and NCT03449654.

Hibernation and plasma lipids in free-ranging brown bears-implications for diabetes

Brown bears (Ursus arctos) prepare for winter by overeating and increasing adipose stores, before hibernating for up to six months without eating, drinking, and with minimal movement. In spring, the bears exit the den without any damage to organs or physiology. Recent clinical research has shown that specific lipids and lipid profiles are of special interest for diseases such as diabetes type 1 and 2. Furthermore, rodent experiments show that lipids such as sulfatide protects rodents against diabetes. As free-ranging bears experience fat accumulation and month-long physical inactivity without developing diabetes, they could possibly be affected by similar protective measures. In this study, we investigated whether lipid profiles of brown bears are related to protection against hibernation-induced damage. We sampled plasma from 10 free-ranging Scandinavian brown bears during winter hibernation and repeated sampling during active state in the summer period. With quantitative shotgun lipidomics and liquid chromatography-mass spectrometry, we profiled 314 lipid species from 26 lipid classes. A principal component analysis revealed that active and hibernation samples could be distinguished from each other based on their lipid profiles. Six lipid classes were significantly altered when comparing plasma from active state and hibernation: Hexosylceramide, phosphatidylglycerol, and lysophosphatidylglycerol were higher during hibernation, while phosphatidylcholine ether, phosphatidylethanolamine ether, and phosphatidylinositol were lower. Additionally, sulfatide species with shorter chain lengths were lower, while longer chain length sulfatides were higher during hibernation. Lipids that are altered in bears are described by others as relevant for and associated with diabetes, which strengthens their position as potential effectors during hibernation. From this analysis, a range of lipids are suggested as potential protectors of bear physiology, and of potential importance in diabetes.

Liraglutide reduces plasma dihydroceramide levels in patients with type 2 diabetes

BACKGROUND

Emerging evidence supports that dihydroceramides (DhCer) and ceramides (Cer) contribute to the pathophysiology of insulin resistance and liver steatosis, and that their circulating concentrations are independently associated with cardiovascular outcomes. Circulating DhCer levels are increased in patients with type 2 diabetes (T2D). On the other hand, the GLP-1 receptor agonist liraglutide reduces major adverse cardiac events, insulin resistance and liver steatosis in T2D patients. The main purpose of the present study was therefore to investigate whether liraglutide decreases circulating levels of DhCer and Cer in T2D patients, which could be a mechanism involved in its cardiometabolic benefits. The secondary purpose was to assess the relationship between liraglutide-induced changes in DhCer/Cer levels and insulin resistance and liver steatosis.

METHODS

Plasma concentrations of 11 DhCer and 15 Cer species were measured by a highly-sensitive mass spectrometry system in 35 controls and 86 T2D patients before and after 6 months of liraglutide (1.2 mg/day). Insulin resistance was estimated by the triglyceride-glucose (TyG) index. Liver fat content (LFC) was assessed in 53 patients by proton magnetic resonance spectroscopy.

RESULTS

Plasma levels of total DhCer, 7 DhCer and 7 Cer species were increased in T2D patients compared to controls. Liraglutide decreased total DhCer by 15.1% (p = 0.005), affecting 16:0 (p = 0.037), 18:0 (p < 0.0001), 18:1 (p = 0.0005), 20:0 (p = 0.0003), 23:0 (p = 0.005) and 24:1 (p = 0.04) species. Total plasma Cer did not significantly change after liraglutide (p = 0.18), but 5 Cer species decreased significantly, i.e. 18:0 and 18:1 (both p < 0.0001), 19:0 and 24:1 (both p < 0.01) and 26:1 (p = 0.04). In multivariate analysis, the reduction in DhCer after liraglutide was independently associated with the reduction in LFC (p = 0.0005) and in TyG index (p = 0.05).

CONCLUSIONS

Liraglutide reduces plasma levels of numerous DhCer and Cer species in T2D patients, which may contribute to the cardiovascular benefit observed in the LEADER trial. The independent association between the decrease in plasma DhCer level with the reduction in LFC and TyG index adds new insights regarding the relationship between DhCer, liver steatosis and insulin resistance. Trial registration ClinicalTrials.gov identifier: NCT02721888.

Advanced omics techniques shed light on CD1d-mediated lipid antigen presentation to iNKT cells

Invariant natural killer T cells (iNKT cells) can be activated through binding antigenic lipid/CD1d complexes to their TCR. Antigenic lipids are processed, loaded, and displayed in complex with CD1d by lipid antigen presenting cells (LAPCs). The mechanism of lipid antigen presentation via CD1d is highly conserved with recent work showing adipocytes are LAPCs that, besides having a role in lipid storage, can activate iNKT cells and play an important role in systemic metabolic disease. Recent studies shed light on parameters potentially dictating cytokine output and how obesity-associated metabolic disease may affect such parameters. By following a lipid antigen's journey, we identify five key areas which may dictate cytokine skew: co-stimulation, structural properties of the lipid antigen, stability of lipid antigen/CD1d complexes, intracellular and extracellular pH, and intracellular and extracellular lipid environment. Recent publications indicate that the combination of advanced omics-type approaches and machine learning may be a fruitful way to interconnect these 5 areas, with the ultimate goal to provide new insights for therapeutic exploration.

Replacement of dietary saturated with unsaturated fatty acids is associated with beneficial effects on lipidome metabolites: a secondary analysis of a randomized trial

BACKGROUND

The effects of replacing dietary saturated fatty acids (SFAs) with monounsaturated fatty acids (MUFAs) and/or polyunsaturated fatty acids (PUFAs) on the plasma lipidome in relation to the cardiometabolic disease (CMD) risk are poorly understood.

OBJECTIVES

We aimed to assess the impact of substituting dietary SFAs with unsaturated fatty acids (UFAs) on the plasma lipidome and examine the relationship between lipid metabolites modulated by diet and CMD risk.

METHODS

Plasma fatty acid (FA) concentrations among 16 lipid classes (within-class FAs) were measured in a subgroup from the Dietary Intervention and VAScular function (DIVAS) parallel randomized controlled trial (n = 113/195), which consisted of three 16-wk diets enriched in SFAs (target SFA:MUFA:n-6PUFA ratio = 17:11:4% total energy [TE]), MUFAs (9:19:4% TE), or a MUFA/PUFA mixture (9:13:10% TE). Similar lipidomics analyses were conducted in the European investigation into Cancer and Nutrition (EPIC)-Potsdam prospective cohort study (specific case/cohorts: n = 775/1886 for type 2 diabetes [T2D], n = 551/1671 for cardiovascular disease [CVD]). Multiple linear regression and multivariable Cox models identified within-class FAs sensitive to replacement of dietary SFA with UFA in DIVAS and their association with CMD risk in EPIC-Potsdam. Elastic-net regression models identified within-class FAs associated with changes in CMD risk markers post-DIVAS interventions.

RESULTS

DIVAS high-UFA interventions reduced plasma within-class FAs associated with a higher CVD risk in EPIC-Potsdam, especially SFA-containing glycerolipids and sphingolipids (e.g., diacylglycerol (20:0) z-score = -1.08; SE = 0.17; P value < 10^-8), whereas they increased those inversely associated with CVD risk. The results on T2D were less clear. Specific sphingolipids and phospholipids were associated with changes in markers of endothelial function and ambulatory blood pressure, whereas higher low-density lipoprotein cholesterol concentrations were characterized by higher plasma glycerolipids containing lauric and stearic acids.

CONCLUSIONS

These results suggest a mediating role of plasma lipid metabolites in the association between dietary fat and CMD risk. Future research combining interventional and observational findings will further our understanding of the role of dietary fat in CMD etiology. This trial was registered in ClinicalTrials.gov as NCT01478958.

The roles of dietary lipids and lipidomics in gut-brain axis in type 2 diabetes mellitus

Type 2 diabetes mellitus (T2DM), one of the main types of Noncommunicable diseases (NCDs), is a systemic inflammatory disease characterized by dysfunctional pancreatic β-cells and/or peripheral insulin resistance, resulting in impaired glucose and lipid metabolism. Genetic, metabolic, multiple lifestyle, and sociodemographic factors are known as related to high T2DM risk. Dietary lipids and lipid metabolism are significant metabolic modulators in T2DM and T2DM-related complications. Besides, accumulated evidence suggests that altered gut microbiota which plays an important role in the metabolic health of the host contributes significantly to T2DM involving impaired or improved glucose and lipid metabolism. At this point, dietary lipids may affect host physiology and health via interaction with the gut microbiota. Besides, increasing evidence in the literature suggests that lipidomics as novel parameters detected with holistic analytical techniques have important roles in the pathogenesis and progression of T2DM, through various mechanisms of action including gut-brain axis modulation. A better understanding of the roles of some nutrients and lipidomics in T2DM through gut microbiota interactions will help develop new strategies for the prevention and treatment of T2DM. However, this issue has not yet been entirely discussed in the literature. The present review provides up-to-date knowledge on the roles of dietary lipids and lipidomics in gut-brain axis in T2DM and some nutritional strategies in T2DM considering lipids- lipidomics and gut microbiota interactions are given.

Clinical lipidomics in the era of the big data

Lipidomics as a branch of metabolomics provides unique information on the complex lipid profile in biological materials. In clinically focused studies, hundreds of lipids together with available clinical information proved to be an effective tool in the discovery of biomarkers and understanding of pathobiochemistry. However, despite the introduction of lipidomics nearly twenty years ago, only dozens of big data studies using clinical lipidomics have been published to date. In this review, we discuss the lipidomics workflow, statistical tools, and the challenges of standartisation. The consequent summary divided into major clinical areas of cardiovascular disease, cancer, diabetes mellitus, neurodegenerative and liver diseases is demonstrating the importance of clinical lipidomics. In these publications, the potential of lipidomics for prediction, diagnosis or finding new targets for the treatment of selected diseases can be seen. The first of these results have already been implemented in clinical practice in the field of cardiovascular diseases, while in other areas we can expect the application of the results summarized in this review in the near future.

Plasma lipidomic profiling reveals metabolic adaptations to pregnancy and signatures of cardiometabolic risk: a preconception and longitudinal cohort study

BACKGROUND

Adaptations in lipid metabolism are essential to meet the physiological demands of pregnancy and any aberration may result in adverse outcomes for both mother and offspring. However, there is a lack of population-level studies to define the longitudinal changes of maternal circulating lipids from preconception to postpartum in relation to cardiometabolic risk factors.

METHODS

LC-MS/MS-based quantification of 689 lipid species was performed on 1595 plasma samples collected at three time points in a preconception and longitudinal cohort, Singapore PREconception Study of long-Term maternal and child Outcomes (S-PRESTO). We mapped maternal plasma lipidomic profiles at preconception (N = 976), 26-28 weeks' pregnancy (N = 337) and 3 months postpartum (N = 282) to study longitudinal lipid changes and their associations with cardiometabolic risk factors including pre-pregnancy body mass index, body weight changes and glycaemic traits.

RESULTS

Around 56% of the lipids increased and 24% decreased in concentration in pregnancy before returning to the preconception concentration at postpartum, whereas around 11% of the lipids went through significant changes in pregnancy and their concentrations did not revert to the preconception concentrations. We observed a significant association of body weight changes with lipid changes across different physiological states, and lower circulating concentrations of phospholipids and sphingomyelins in pregnant mothers with higher pre-pregnancy BMI. Fasting plasma glucose and glycated haemoglobin (HbA1c) concentrations were lower whereas the homeostatic model assessment of insulin resistance (HOMA-IR), 2-h post-load glucose and fasting insulin concentrations were higher in pregnancy as compared to both preconception and postpartum. Association studies of lipidomic profiles with these glycaemic traits revealed their respective lipid signatures at three physiological states. Assessment of glycaemic traits in relation to the circulating lipids at preconception with a large sample size (n = 936) provided an integrated view of the effects of hyperglycaemia on plasma lipidomic profiles. We observed a distinct relationship of lipidomic profiles with different measures, with the highest percentage of significant lipids associated with HOMA-IR (58.9%), followed by fasting insulin concentration (56.9%), 2-h post-load glucose concentration (41.8%), HbA1c (36.7%), impaired glucose tolerance status (31.6%) and fasting glucose concentration (30.8%).

CONCLUSIONS

We describe the longitudinal landscape of maternal circulating lipids from preconception to postpartum, and a comprehensive view of trends and magnitude of pregnancy-induced changes in lipidomic profiles. We identified lipid signatures linked with cardiometabolic risk traits with potential implications both in pregnancy and postpartum life. Our findings provide insights into the metabolic adaptations and potential biomarkers of modifiable risk factors in childbearing women that may help in better assessment of cardiometabolic health, and early intervention at the preconception period.

TRIAL REGISTRATION

ClinicalTrials.gov, NCT03531658.

Plasma Sphingoid Base Profiles of Patients Diagnosed with Intrinsic or Idiosyncratic Drug-induced Liver Injury

Sphingolipids are exceptionally diverse, comprising hundreds of unique species. The bulk of circulating sphingolipids are synthesized in the liver, thereby plasma sphingolipid profiles represent reliable surrogates of hepatic sphingolipid metabolism and content. As changes in plasma sphingolipid content have been associated to exposure to drugs inducing hepatotoxicity both in vitro and in rodents, in the present study the translatability of the preclinical data was assessed by analyzing the plasma of patients with suspected drug-induced liver injury (DILI) and control subjects. DILI patients, whether intrinsic or idiosyncratic cases, had no alterations in total sphingoid base levels and profile composition compared to controls, whereby cardiovascular disease (CVD) was a confounding factor. Upon exclusion of CVD individuals, elevation of 1-deoxysphingosine (1-deoxySO) in the DILI group emerged. Notably, 1-deoxySO values did not correlate with ALT values. While 1-deoxySO was elevated in all DILI cases, only intrinsic DILI cases concomitantly displayed reduction of select shorter chain sphingoid bases. Significant perturbation of the sphingolipid metabolism observed in this small exploratory clinical study is discussed and put into context, in the consideration that sphingolipids might contribute to the onset and progression of DILI, and that circulating sphingoid bases may function as mechanistic markers to study DILI pathophysiology.

The Dark Side of Sphingolipids: Searching for Potential Cardiovascular Biomarkers

Cardiovascular diseases (CVDs) are the leading cause of death and illness in Europe and worldwide, responsible for a staggering 47% of deaths in Europe. Over the past few years, there has been increasing evidence pointing to bioactive sphingolipids as drivers of CVDs. Among them, most studies place emphasis on the cardiovascular effect of ceramides and sphingosine-1-phosphate (S1P), reporting correlation between their aberrant expression and CVD risk factors. In experimental in vivo models, pharmacological inhibition of de novo ceramide synthesis averts the development of diabetes, atherosclerosis, hypertension and heart failure. In humans, levels of circulating sphingolipids have been suggested as prognostic indicators for a broad spectrum of diseases. This article provides a comprehensive review of sphingolipids' contribution to cardiovascular, cerebrovascular and metabolic diseases, focusing on the latest experimental and clinical findings. Cumulatively, these studies indicate that monitoring sphingolipid level alterations could allow for better assessment of cardiovascular disease progression and/or severity, and also suggest them as a potential target for future therapeutic intervention. Some approaches may include the down-regulation of specific sphingolipid species levels in the circulation, by inhibiting critical enzymes that catalyze ceramide metabolism, such as ceramidases, sphingomyelinases and sphingosine kinases. Therefore, manipulation of the sphingolipid pathway may be a promising strategy for the treatment of cardio- and cerebrovascular diseases.

Serum sphingolipid profiling as a novel biomarker for metabolic syndrome characterization

Background

Sphingolipids are components of cell membrane structure, but also circulate in serum and are essential mediators of many cellular functions. While ceramides have been proposed previously as a useful biomarker for cardiometabolic disease, the involvement of other sphingolipids is still controversial. The aim of this study was to investigate the cross-sectional association between blood sphingolipidomic profiles and metabolic syndrome (MetS) as well as other atherosclerotic risk factors in a large population-based study in the U.S.

Methods

Clinical data and serum sphingolipidomic profiling from 2,063 subjects who participated in the biomarker project of the Midlife in the United States (MIDUS) study were used.

Results

Consistent with previous reports, we found a positive association between most ceramide levels and obesity, atherogenic dyslipidemia, impaired glucose metabolism, and MetS prevalence. In contrast, most simple β-glycosphingolipids (i.e., hexosylceramides and lactosylceramides) were inversely associated with dysmetabolic biomarkers. However, this latter sphingolipid class showed a positive link with inflammatory and vascular damage-associated biomarkers in subjects with MetS. Through metabolic network analysis, we found that the relationship between ceramides and simple β-glycosphingolipids differed significantly not only according to MetS status, but also with respect to the participants' C-reactive protein levels.

Conclusion

Our findings suggest that a comprehensive sphingolipid profile is more informative about MetS than ceramides alone, and it may reveal new insights into the pathophysiology and further diabetic vs. cardiovascular risk in patients with MetS.

Glycosphingolipids in Diabetes, Oxidative Stress, and Cardiovascular Disease: Prevention in Experimental Animal Models

Diabetes contributes to about 30% morbidity and mortality world-wide and has tidal wave increases in several countries in Asia. Diabetes is a multi-factorial disease compounded by inflammation, dyslipidemia, atherosclerosis, and is sometimes accompanied with gains in body weight. Sphingolipid pathways that interplay in the enhancement of the pathology of this disease may be potential therapeutic targets. Thus, the application of advanced sphingolipidomics may help predict the progression of this disease and therapeutic outcomes in man. Pre-clinical studies using various experimental animal models of diabetes provide valuable information on the role of sphingolipid signaling networks in diabetes and the efficacy of drugs to determine the translatability of innovative discoveries to man. In this review, we discuss three major concepts regarding sphingolipids and diabetes. First, we discuss a possible involvement of a monosialodihexosylceramide (GM3) in insulin-insulin receptor interactions. Second, a potential role for ceramide (Cer) and lactosylceramide (LacCer) in apoptosis and mitochondrial dysfunction is proposed. Third, a larger role of LacCer in antioxidant status and inflammation is discussed. We also discuss how inhibitors of glycosphingolipid synthesis can ameliorate diabetes in experimental animal models.

Salvia miltiorrhiza extract may exert an anti-obesity effect in rats with high-fat diet-induced obesity by modulating gut microbiome and lipid metabolism

BACKGROUND

Studies have shown that a high-fat diet (HFD) can alter gut microbiota (GM) homeostasis and participate in lipid metabolism disorders associated with obesity. Therefore, regulating the construction of GM with the balance of lipid metabolism has become essential for treating obesity. Salvia miltiorrhiza extract (Sal), a common traditional Chinese medicine, has been proven effective against atherosclerosis, hyperlipidemia, obesity, and other dyslipidemia-related diseases.

AIM

To investigate the anti-obesity effects of Sal in rats with HFD-induced obesity, and explore the underlying mechanism by focusing on GM and lipid metabolism.

METHODS

Obesity was induced in rats with an HFD for 7 wk, and Sal (0.675 g/1.35 g/2.70 g/kg/d) was administered to treat obese rats for 8 wk. The therapeutic effect was evaluated by body weight, body fat index, waistline, and serum lipid level. Lipid factors (cAMP, PKA, and HSL) in liver and fat homogenates were analyzed by ELISA. The effect of Sal on GM and lipid metabolism was assessed by 16S rRNA-based microbiota analysis and untargeted lipidomic analysis (LC-MS/MS), respectively.

RESULTS

Sal treatment markedly reduced weight, body fat index, serum triglycerides (TG), total cholesterol (TC), low-density lipoprotein, glucose, free fatty acid, hepatic lipid accumulation, and adipocyte vacuolation, and increased serum high-density lipoprotein (HDL-C) in rats with HFD-induced obesity. These effects were associated with increased concentrations of lipid factors such as cAMP, PKA, and HSL in the liver and adipose tissues, enhanced gut integrity, and improved lipid metabolism. GM analysis revealed that Sal could reverse HFD-induced dysbacteriosis by promoting the abundance of Actinobacteriota and Proteobacteria, and decreasing the growth of Firmicutes and Desulfobacterita. Furthermore, LC-MS/MS analysis indicated that Sal decreased TGs (TG18:2/18:2/20:4, TG16:0/18:2/22:6), DGs (DG14:0/22:6, DG22:6/22:6), CL (18:2/ 18:1/18:1/20:0), and increased ceramides (Cers; Cer d16:0/21:0, Cer d16:1/24:1), (O-acyl)-ω-hydroxy fatty acids (OAHFAs; OAHFA18:0/14:0) in the feces of rats. Spearman's correlation analysis further indicated that TGs, DGs, and CL were negatively related to the abundance of Facklamia and Dubosiella, and positively correlated with Blautia and Quinella, while OAHFAs and Cers were the opposite.

CONCLUSION

Sal has an anti-obesity effect by regulating the GM and lipid metabolism.

Specific triacylglycerol, diacylglycerol, and lyso-phosphatidylcholine species for the prediction of type 2 diabetes: a ~ 16-year prospective study in Chinese

Background

Bioactive lipids play an important role in insulin secretion and sensitivity, contributing to the pathophysiology of type 2 diabetes (T2D). This study aimed to identify novel lipid species associated with incident T2D in a nested case–control study within a long-term prospective Chinese community-based cohort with a median follow-up of ~ 16 years.

Methods

Plasma samples from 196 incident T2D cases and 196 age- and sex-matched non-T2D controls recruited from the Hong Kong Cardiovascular Risk Factor Prevalence Study (CRISPS) were first analyzed using untargeted lipidomics. Potential predictive lipid species selected by the Boruta analysis were then verified by targeted lipidomics. The associations between these lipid species and incident T2D were assessed. Effects of novel lipid species on insulin secretion in mouse islets were investigated.

Results

Boruta analysis identified 16 potential lipid species. After adjustment for body mass index (BMI), triacylglycerol/high-density lipoprotein (TG/HDL) ratio and the presence of prediabetes, triacylglycerol (TG) 12:0_18:2_22:6, TG 16:0_11:1_18:2, TG 49:0, TG 51:1 and diacylglycerol (DG) 18:2_22:6 were independently associated with increased T2D risk, whereas lyso-phosphatidylcholine (LPC) O-16:0, LPC P-16:0, LPC O-18:0 and LPC 18:1 were independently associated with decreased T2D risk. Addition of the identified lipid species to the clinical prediction model, comprised of BMI, TG/HDL ratio and the presence of prediabetes, achieved a 3.8% improvement in the area under the receiver operating characteristics curve (AUROC) (p = 0.0026). Further functional study revealed that, LPC O-16:0 and LPC O-18:0 significantly potentiated glucose induced insulin secretion (GSIS) in a dose-dependent manner, whereas neither DG 18:2_22:6 nor TG 12:0_18:2_22:6 had any effect on GSIS.

Conclusions

Addition of the lipid species substantially improved the prediction of T2D beyond the model based on clinical risk factors. Decreased levels of LPC O-16:0 and LPC O-18:0 may contribute to the development of T2D via reduced insulin secretion.

Supplementary Information

The online version contains supplementary material available at 10.1186/s12933-022-01677-4.

A Comprehensive Profiling of Cellular Sphingolipids in Mammalian Endothelial and Microglial Cells Cultured in Normal and High-Glucose Conditions

Sphingolipids (SPLs) play a diverse role in maintaining cellular homeostasis. Dysregulated SPL metabolism is associated with pathological changes in stressed and diseased cells. This study investigates differences in SPL metabolism between cultured human primary retinal endothelial (HREC) and murine microglial cells (BV2) in normal conditions (normal glucose, NG, 5 mM) and under high-glucose (HG, 25 mM)-induced stress by sphingolipidomics, immunohistochemistry, biochemical, and molecular assays. Measurable differences were observed in SPL profiles between HREC and BV2 cells. High-glucose treatment caused a >2.5-fold increase in the levels of Lactosyl-ceramide (LacCer) in HREC, but in BV2 cells, it induced Hexosyl-Ceramides (HexCer) by threefold and a significant increase in Sphingosine-1-phosphate (S1P) compared to NG. Altered SPL profiles coincided with changes in transcript levels of inflammatory and vascular permeability mediators in HREC and inflammatory mediators in BV2 cells. Differences in SPL profiles and differential responses to HG stress between endothelial and microglial cells suggest that SPL metabolism and signaling differ in mammalian cell types and, therefore, their pathological association with those cell types.

Population-based plasma lipidomics reveals developmental changes in metabolism and signatures of obesity risk: a mother-offspring cohort study

BACKGROUND

Lipids play a vital role in health and disease, but changes to their circulating levels and the link with obesity remain poorly characterized in expecting mothers and their offspring in early childhood.

METHODS

LC-MS/MS-based quantitation of 480 lipid species was performed on 2491 plasma samples collected at 4 time points in the mother-offspring Asian cohort GUSTO (Growing Up in Singapore Towards healthy Outcomes). These 4 time points constituted samples collected from mothers at 26-28 weeks of gestation (n=752) and 4-5 years postpartum (n=650), and their offspring at birth (n=751) and 6 years of age (n=338). Linear regression models were used to identify the pregnancy and developmental age-specific variations in the plasma lipidomic profiles, and their association with obesity risk. An independent birth cohort (n=1935), the Barwon Infant Study (BIS), comprising mother-offspring dyads of Caucasian origin was used for validation.

RESULTS

Levels of 36% of the profiled lipids were significantly higher (absolute fold change > 1.5 and P_adj < 0.05) in antenatal maternal circulation as compared to the postnatal phase, with phosphatidylethanolamine levels changing the most. Compared to antenatal maternal lipids, cord blood showed lower concentrations of most lipid species (79%) except lysophospholipids and acylcarnitines. Changes in lipid concentrations from birth to 6 years of age were much higher in magnitude (log₂FC=-2.10 to 6.25) than the changes observed between a 6-year-old child and an adult (postnatal mother) (log₂FC=-0.68 to 1.18). Associations of cord blood lipidomic profiles with birth weight displayed distinct trends compared to the lipidomic profiles associated with child BMI at 6 years. Comparison of the results between the child and adult BMI identified similarities in association with consistent trends (R²=0.75). However, large number of lipids were associated with BMI in adults (67%) compared to the children (29%). Pre-pregnancy BMI was specifically associated with decrease in the levels of phospholipids, sphingomyelin, and several triacylglycerol species in pregnancy.

CONCLUSIONS

In summary, our study provides a detailed landscape of the in utero lipid environment provided by the gestating mother to the growing fetus, and the magnitude of changes in plasma lipidomic profiles from birth to early childhood. We identified the effects of adiposity on the circulating lipid levels in pregnant and non-pregnant women as well as offspring at birth and at 6 years of age. Additionally, the pediatric vs maternal overlap of the circulating lipid phenotype of obesity risk provides intergenerational insights and early opportunities to track and intervene the onset of metabolic adversities.

CLINICAL TRIAL REGISTRATION

This birth cohort is a prospective observational study, which was registered on 1 July 2010 under the identifier NCT01174875 .

Deep Lipidomics in Human Plasma: Cardiometabolic Disease Risk and Effect of Dietary Fat Modulation

BACKGROUND

In blood and tissues, dietary and endogenously generated fatty acids (FAs) occur in free form or as part of complex lipid molecules that collectively represent the lipidome of the respective tissue. We assessed associations of plasma lipids derived from high-resolution lipidomics with incident cardiometabolic diseases and subsequently tested if the identified risk-associated lipids were sensitive to dietary fat modification.

METHODS

The EPIC Potsdam cohort study (European Prospective Investigation into Cancer and Nutrition) comprises 27 548 participants recruited within an age range of 35 to 65 years from the general population around Potsdam, Germany. We generated 2 disease-specific case cohorts on the basis of a fixed random subsample (n=1262) and all respective cohort-wide identified incident primary cardiovascular disease (composite of fatal and nonfatal myocardial infarction and stroke; n=551) and type 2 diabetes (n=775) cases. We estimated the associations of baseline plasma concentrations of 282 class-specific FA abundances (calculated from 940 distinct molecular species across 15 lipid classes) with the outcomes in multivariable-adjusted Cox models. We tested the effect of an isoenergetic dietary fat modification on risk-associated lipids in the DIVAS randomized controlled trial (Dietary Intervention and Vascular Function; n=113). Participants consumed either a diet rich in saturated FAs (control), monounsaturated FAs, or a mixture of monounsaturated and n-6 polyunsaturated FAs for 16 weeks.

RESULTS

Sixty-nine lipids associated (false discovery rate<0.05) with at least 1 outcome (both, 8; only cardiovascular disease, 49; only type 2 diabetes, 12). In brief, several monoacylglycerols and FA16:0 and FA18:0 in diacylglycerols were associated with both outcomes; cholesteryl esters, free fatty acids, and sphingolipids were largely cardiovascular disease specific; and several (glycero)phospholipids were type 2 diabetes specific. In addition, 19 risk-associated lipids were affected (false discovery rate<0.05) by the diets rich in unsaturated dietary FAs compared with the saturated fat diet (17 in a direction consistent with a potential beneficial effect on long-term cardiometabolic risk). For example, the monounsaturated FA-rich diet decreased diacylglycerol(FA16:0) by 0.4 (95% CI, 0.5-0.3) SD units and increased triacylglycerol(FA22:1) by 0.5 (95% CI, 0.4-0.7) SD units.

CONCLUSIONS

We identified several lipids associated with cardiometabolic disease risk. A subset was beneficially altered by a dietary fat intervention that supports the substitution of dietary saturated FAs with unsaturated FAs as a potential tool for primary disease prevention.

A set of gene knockouts as a resource for global lipidomic changes

Enzyme specificity in lipid metabolic pathways often remains unresolved at the lipid species level, which is needed to link lipidomic molecular phenotypes with their protein counterparts to construct functional pathway maps. We created lipidomic profiles of 23 gene knockouts in a proof-of-concept study based on a CRISPR/Cas9 knockout screen in mammalian cells. This results in a lipidomic resource across 24 lipid classes. We highlight lipid species phenotypes of multiple knockout cell lines compared to a control, created by targeting the human safe-harbor locus AAVS1 using up to 1228 lipid species and subspecies, charting lipid metabolism at the molecular level. Lipid species changes are found in all knockout cell lines, however, some are most apparent on the lipid class level (e.g., SGMS1 and CEPT1), while others are most apparent on the fatty acid level (e.g., DECR2 and ACOT7). We find lipidomic phenotypes to be reproducible across different clones of the same knockout and we observed similar phenotypes when two enzymes that catalyze subsequent steps of the long-chain fatty acid elongation cycle were targeted.

Insulin-inducible THRSP maintains mitochondrial function and regulates sphingolipid metabolism in human adipocytes

BACKGROUND

Thyroid hormone responsive protein (THRSP) is a lipogenic nuclear protein that is highly expressed in murine adipose tissue, but its role in humans remains unknown.

METHODS

We characterized the insulin regulation of THRSP in vivo in human adipose tissue biopsies and in vitro in Simpson-Golabi-Behmel syndrome (SGBS) adipocytes. To this end, we measured whole-body insulin sensitivity using the euglycemic insulin clamp technique in 36 subjects [age 40 ± 9 years, body mass index (BMI) 27.3 ± 5.0 kg/m²]. Adipose tissue biopsies were obtained at baseline and after 180 and 360 min of euglycemic hyperinsulinemia for measurement of THRSP mRNA concentrations. To identify functions affected by THRSP, we performed a transcriptomic analysis of THRSP-silenced SGBS adipocytes. Mitochondrial function was assessed by measuring mitochondrial respiration as well as oxidation and uptake of radiolabeled oleate and glucose. Lipid composition in THRSP silencing was studied by lipidomic analysis.

RESULTS

We found insulin to increase THRSP mRNA expression 5- and 8-fold after 180 and 360 min of in vivo euglycemic hyperinsulinemia. This induction was impaired in insulin-resistant subjects, and THRSP expression was closely correlated with whole-body insulin sensitivity. In vitro, insulin increased both THRSP mRNA and protein concentrations in SGBS adipocytes in a phosphoinositide 3-kinase (PI3K)-dependent manner. A transcriptomic analysis of THRSP-silenced adipocytes showed alterations in mitochondrial functions and pathways of lipid metabolism, which were corroborated by significantly impaired mitochondrial respiration and fatty acid oxidation. A lipidomic analysis revealed decreased hexosylceramide concentrations, supported by the transcript concentrations of enzymes regulating sphingolipid metabolism.

CONCLUSIONS

THRSP is regulated by insulin both in vivo in human adipose tissue and in vitro in adipocytes, and its expression is downregulated by insulin resistance. As THRSP silencing decreases mitochondrial respiration and fatty acid oxidation, its downregulation in human adipose tissue could contribute to mitochondrial dysfunction. Furthermore, disturbed sphingolipid metabolism could add to metabolic dysfunction in obese adipose tissue.

Novel Plasma Metabolomic Markers Associated with Diabetes Progression in Older Puerto Ricans

We assessed longitudinal associations between plasma metabolites, their network-derived clusters, and type 2 diabetes (T2D) progression in Puerto Rican adults, a high-risk Hispanic subgroup with established health disparities. We used data from 1221 participants free of T2D and aged 40-75 years at baseline in the Boston Puerto Rican Health and San Juan Overweight Adult Longitudinal Studies. We used multivariable Poisson regression models to examine associations between baseline concentrations of metabolites and incident T2D and prediabetes. Cohort-specific estimates were combined using inverse-variance weighted fixed-effects meta-analyses. A cluster of 13 metabolites of branched chain amino acids (BCAA), and aromatic amino acid metabolism (pooled IRR = 1.87, 95% CI: 1.28; 2.73), and a cell membrane component metabolite cluster (pooled IRR = 1.54, 95% CI: 1.04; 2.27) were associated with a higher risk of incident T2D. When the metabolites were tested individually, in combined analysis, 5 metabolites involved in BCAA metabolism were associated with incident T2D. These findings highlight potential prognostic biomarkers to identify Puerto Rican adults who may be at high risk for diabetes. Future studies should examine whether diet and lifestyle can modify the associations between these metabolites and progression to T2D.

Metabolic Profiling of Obesity With and Without the Metabolic Syndrome: A Multisample Evaluation

CONTEXT

There is a dispute whether obesity without major metabolic derangements may represent a benign condition or not.

OBJECTIVE

We aimed to compare the plasma metabolome in obese subjects without metabolic syndrome (MetS) with normal-weight subjects without MetS and with obese subjects with MetS.

METHODS

This was a cross-sectional study at 2 academic centers in Sweden. Individuals from 3 population-based samples (EpiHealth, n = 2342, SCAPIS-Uppsala, n = 4985, and SCAPIS-Malmö, n = 3978) were divided into groups according to their body mass index (BMI) and presence/absence of MetS (National Cholesterol Education Program [NCEP]/consensus criteria). In total, 791 annotated endogenous metabolites were measured by ultra-performance liquid chromatography-tandem mass spectrometry.

RESULTS

We observed major differences in metabolite profiles (427 metabolites) between obese (BMI ≥ 30 kg/m2) and normal-weight (BMI < 25 kg/m2) subjects without MetS after adjustment for major lifestyle factors. Pathway enrichment analysis highlighted branch-chained and aromatic amino acid synthesis/metabolism, aminoacyl-tRNA biosynthesis, and sphingolipid metabolism. The same pathways, and similar metabolites, were also highlighted when obese subjects with and without MetS were compared despite adjustment for BMI and waist circumference, or when the metabolites were related to BMI and number of MetS components in a continuous fashion. Similar metabolites and pathways were also related to insulin sensitivity (Matsuda index) in a separate study (POEM, n = 501).

CONCLUSION

Our data suggest a graded derangement of the circulating metabolite profile from lean to obese to MetS, in particular for metabolites involved in amino acid synthesis/metabolism and sphingolipid metabolism. Insulin resistance is a plausible mediator of this gradual metabolic deterioration.

Implications of Sphingolipid Metabolites in Kidney Diseases

Sphingolipids, which act as a bioactive signaling molecules, are involved in several cellular processes such as cell survival, proliferation, migration and apoptosis. An imbalance in the levels of sphingolipids can be lethal to cells. Abnormalities in the levels of sphingolipids are associated with several human diseases including kidney diseases. Several studies demonstrate that sphingolipids play an important role in maintaining proper renal function. Sphingolipids can alter the glomerular filtration barrier by affecting the functioning of podocytes, which are key cellular components of the glomerular filtration barrier. This review summarizes the studies in our understanding of the regulation of sphingolipid signaling in kidney diseases, especially in glomerular and tubulointerstitial diseases, and the potential to target sphingolipid pathways in developing therapeutics for the treatment of renal diseases.

Plasma Metabolomics and Lipidomics Differentiate Obese Individuals by Peripheral Neuropathy Status

CONTEXT

Peripheral neuropathy (PN) is a frequent prediabetes and type 2 diabetes (T2D) complication. Multiple clinical studies reveal that obesity and dyslipidemia can also drive PN progression, independent of glycemia, suggesting a complex interplay of specific metabolite and/or lipid species may underlie PN.

OBJECTIVE

This work aimed to identify the plasma metabolomics and lipidomics signature that underlies PN in an observational study of a sample of individuals with average class 3 obesity.

METHODS

We performed plasma global metabolomics and targeted lipidomics on obese participants with (n = 44) and without PN (n = 44), matched for glycemic status, vs lean nonneuropathic controls (n = 43). We analyzed data by Wilcoxon, logistic regression, partial least squares-discriminant analysis, and group-lasso to identify differential metabolites and lipids by obesity and PN status. We also conducted subanalysis by prediabetes and T2D status.

RESULTS

Lean vs obese comparisons, regardless of PN status, identified the most significant differences in gamma-glutamyl and branched-chain amino acid metabolism from metabolomics analysis and triacylglycerols from lipidomics. Stratification by PN status within obese individuals identified differences in polyamine, purine biosynthesis, and benzoate metabolism. Lipidomics found diacylglycerols as the most significant subpathway distinguishing obese individuals by PN status, with additional contributions from phosphatidylcholines, sphingomyelins, ceramides, and dihydroceramides. Stratifying the obese group by glycemic status did not affect discrimination by PN status.

CONCLUSION

Obesity may be as strong a PN driver as prediabetes or T2D in a sample of individuals with average class 3 obesity, at least by plasma metabolomics and lipidomics profile. Metabolic and complex lipid pathways can differentiate obese individuals with and without PN, independent of glycemic status.

Emerging Roles of Ceramide in Cardiovascular Diseases

Ceramide is a core molecule of sphingolipid metabolism that causes selective insulin resistance and dyslipidemia. Research on its involvement in cardiovascular diseases has grown rapidly. In resting cells, ceramide levels are extremely low, while they rapidly accumulate upon encountering external stimuli. Recently, the regulation of ceramide levels under pathological conditions, including myocardial infarction, hypertension, and atherosclerosis, has drawn great attention. Increased ceramide levels are strongly associated with adverse cardiovascular risks and events while inhibiting the synthesis of ceramide or accelerating its degradation improves a variety of cardiovascular diseases. In this article, we summarize the role of ceramide in cardiovascular disease, investigate the possible application of ceramide as a new diagnostic biomarker and a therapeutic target for cardiovascular disorders, and highlight the remaining problems.

Mechanisms contributing to adverse outcomes of COVID-19 in obesity

A growing amount of epidemiological data from multiple countries indicate an increased prevalence of obesity, more importantly central obesity, among hospitalized subjects with COVID-19. This suggests that obesity is a major factor contributing to adverse outcome of the disease. As it is a metabolic disorder with dysregulated immune and endocrine function, it is logical that dysfunctional metabolism contributes to the mechanisms behind obesity being a risk factor for adverse outcome in COVID-19. Emerging data suggest that in obese subjects, (a) the molecular mechanisms of viral entry and spread mediated through ACE2 receptor, a multifunctional host cell protein which links to cellular homeostasis mechanisms, are affected. This includes perturbation of the physiological renin-angiotensin system pathway causing pro-inflammatory and pro-thrombotic challenges (b) existent metabolic overload and ER stress-induced UPR pathway make obese subjects vulnerable to severe COVID-19, (c) host cell response is altered involving reprogramming of metabolism and epigenetic mechanisms involving microRNAs in line with changes in obesity, and (d) adiposopathy with altered endocrine, adipokine, and cytokine profile contributes to altered immune cell metabolism, systemic inflammation, and vascular endothelial dysfunction, exacerbating COVID-19 pathology. In this review, we have examined the available literature on the underlying mechanisms contributing to obesity being a risk for adverse outcome in COVID-19.