Skeletal muscle and plasma lipidomic signatures of insulin resistance and overweight/obesity in humans

Multi-omics correlates of insulin resistance and circadian parameters mapped directly from human serum

While it is generally known that metabolic disorders and circadian dysfunction are intertwined, how the two systems affect each other is not well understood, nor are the genetic factors that might exacerbate this pathological interaction. Blood chemistry is profoundly changed in metabolic disorders, and we have previously shown that serum factors change cellular clock properties. To investigate if circulating factors altered in metabolic disorders have circadian modifying effects, and whether these effects are of genetic origin, we measured circadian rhythms in U2OS cell in the presence of serum collected from diabetic, obese or control subjects. We observed that circadian period lengthening in U2OS cells was associated with serum chemistry that is characteristic of insulin resistance. Characterizing the genetic variants that altered circadian period length by genome-wide association analysis, we found that one of the top variants mapped to the E3 ubiquitin ligase MARCH1 involved in insulin sensitivity. Confirming our data, the serum circadian modifying variants were also enriched in type 2 diabetes and chronotype variants identified in the UK Biobank cohort. Finally, to identify serum factors that might be involved in period lengthening, we performed detailed metabolomics and found that the circadian modifying variants are particularly associated with branched chain amino acids, whose levels are known to correlate with diabetes and insulin resistance. Overall, our multi-omics data showed comprehensively that systemic factors serve as a path through which metabolic disorders influence circadian system, and these can be examined in human populations directly by simple cellular assays in common cultured cells.

Comparison of Adiposomal Lipids between Obese and Non-Obese Individuals

Our recent findings revealed that human adipose tissues (AT)-derived extracellular vesicles (adiposomes) vary in cargo among obese and lean individuals. The main objective of this study was to investigate the adiposomal lipid profiles and their correlation with cardiometabolic risk factors. AT samples were collected from obese subjects and lean controls and analyzed for their characteristics and lipid content. In addition, we measured the correlation between adiposomal lipid profiles and body composition, glucose and lipid metabolic profiles, brachial artery vasoreactivity, AT arteriolar flow-induced dilation, and circulating markers such as IL-6, C-reactive protein, and nitric oxide (NO). Compared to lean controls, adiposomes isolated from obese subjects were higher in number after normalization to AT volume. The two major lipid classes differentially expressed were lysophosphatidylcholine/phosphatidylcholine (LPC/PC) and ceramides (Cer). All lipids in the LPC/PC class were several-fold lower in adiposomes from obese subjects compared to lean controls, on top of which were PC 18:2, PC 18:1, and PC 36:3. Most ceramides were markedly upregulated in the obese group, especially Cer d37:0, Cer d18:0, and Cer d39:0. Regression analyses revealed associations between adiposomal lipid profiles and several cardiometabolic risk factors such as body mass index (BMI), fat percentage, insulin resistance, arteriolar and brachial artery vasoreactivity, NO bioavailability, and high-density lipoproteins (HDL-C). We conclude that the ability of adiposomes from obese subjects to disrupt cardiometabolic function could be partly attributed to the dysregulated lipid cargo.

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.

Lipidomic signatures in Colombian adults with metabolic syndrome

Background and Aims

Metabolic syndrome (MetS) comprises a set of risk factors that contribute to the development of chronic and cardiovascular diseases, increasing the mortality rate. Altered lipid metabolism is associated with the development of metabolic disorders such as insulin resistance, obesity, atherosclerosis, and metabolic syndrome; however, there is a lack of knowledge about lipids compounds and the lipidic pathways associated with this condition, particularly in the Latin-American population. Innovative approaches, such as lipidomic analysis, facilitate the identification of lipid species related to these risk factors. This study aimed to assess the plasma lipidome in subjects with MetS.

Methods

This correlation study included healthy adults and adults with MetS. Blood samples were analyzed. The lipidomic profile was determined using an Agilent Technologies 1260 liquid chromatography system coupled to a Q-TOF 6545 quadrupole mass analyzer with electrospray ionization. The main differences were determined between the groups.

Results

The analyses reveal a distinct lipidomic profile between healthy adults and those with MetS, including increased concentrations of most identified glycerolipids -both triglycerides and diglycerides- and decreased levels of ether lipids and sphingolipids, especially sphingomyelins, in MetS subjects. Association between high triglycerides, waist circumference, and most differentially expressed lipids were found.

Conclusion

Our results demonstrate dysregulation of lipid metabolism in subjects with Mets, supporting the potential utility of plasma lipidome analysis for a deeper understanding of MetS pathophysiology.

Supplementary Information

The online version contains supplementary material available at 10.1007/s40200-024-01423-5.

Untargeted lipidomics analysis in women with morbid obesity and type 2 diabetes mellitus: A comprehensive study

There is a phenotype of obese individuals termed metabolically healthy obese that present a reduced cardiometabolic risk. This phenotype offers a valuable model for investigating the mechanisms connecting obesity and metabolic alterations such as Type 2 Diabetes Mellitus (T2DM). Previously, in an untargeted metabolomics analysis in a cohort of morbidly obese women, we observed a different lipid metabolite pattern between metabolically healthy morbid obese individuals and those with associated T2DM. To validate these findings, we have performed a complementary study of lipidomics. In this study, we assessed a liquid chromatography coupled to a mass spectrometer untargeted lipidomic analysis on serum samples from 209 women, 73 normal-weight women (control group) and 136 morbid obese women. From those, 65 metabolically healthy morbid obese and 71 with associated T2DM. In this work, we find elevated levels of ceramides, sphingomyelins, diacyl and triacylglycerols, fatty acids, and phosphoethanolamines in morbid obese vs normal weight. Conversely, decreased levels of acylcarnitines, bile acids, lyso-phosphatidylcholines, phosphatidylcholines (PC), phosphatidylinositols, and phosphoethanolamine PE (O-38:4) were noted. Furthermore, comparing morbid obese women with T2DM vs metabolically healthy MO, a distinct lipid profile emerged, featuring increased levels of metabolites: deoxycholic acid, diacylglycerol DG (36:2), triacylglycerols, phosphatidylcholines, phosphoethanolamines, phosphatidylinositols, and lyso-phosphatidylinositol LPI (16:0). To conclude, analysing both comparatives, we observed decreased levels of deoxycholic acid, PC (34:3), and PE (O-38:4) in morbid obese women vs normal-weight. Conversely, we found elevated levels of these lipids in morbid obese women with T2DM vs metabolically healthy MO. These profiles of metabolites could be explored for the research as potential markers of metabolic risk of T2DM in morbid obese women.

Lipidomic studies revealing serological markers associated with the occurrence of retinopathy in type 2 diabetes

PURPOSE

The duration of type 2 diabetes mellitus (T2DM) and blood glucose levels have a significant impact on the development of T2DM complications. However, currently known risk factors are not good predictors of the onset or progression of diabetic retinopathy (DR). Therefore, we aimed to investigate the differences in the serum lipid composition in patients with T2DM, without and with DR, and search for potential serological indicators associated with the development of DR.

METHODS

A total of 622 patients with T2DM hospitalized in the Department of Endocrinology of the First Affiliated Hospital of Xi'an JiaoTong University were selected as the discovery set. One-to-one case-control matching was performed according to the traditional risk factors for DR (i.e., age, duration of diabetes, HbA1c level, and hypertension). All cases with comorbid chronic kidney disease were excluded to eliminate confounding factors. A total of 42 pairs were successfully matched. T2DM patients with DR (DR group) were the case group, and T2DM patients without DR (NDR group) served as control subjects. Ultra-performance liquid chromatography-mass spectrometry (LC-MS/MS) was used for untargeted lipidomics analysis on serum, and a partial least squares discriminant analysis (PLS-DA) model was established to screen differential lipid molecules based on variable importance in the projection (VIP) > 1. An additional 531 T2DM patients were selected as the validation set. Next, 1:1 propensity score matching (PSM) was performed for the traditional risk factors for DR, and a combined 95 pairings in the NDR and DR groups were successfully matched. The screened differential lipid molecules were validated by multiple reaction monitoring (MRM) quantification based on mass spectrometry.

RESULTS

The discovery set showed no differences in traditional risk factors associated with the development of DR (i.e., age, disease duration, HbA1c, blood pressure, and glomerular filtration rate). In the DR group compared with the NDR group, the levels of three ceramides (Cer) and seven sphingomyelins (SM) were significantly lower, and one phosphatidylcholine (PC), two lysophosphatidylcholines (LPC), and two SMs were significantly higher. Furthermore, evaluation of these 15 differential lipid molecules in the validation sample set showed that three Cer and SM(d18:1/24:1) molecules were substantially lower in the DR group. After excluding other confounding factors (e.g., sex, BMI, lipid-lowering drug therapy, and lipid levels), multifactorial logistic regression analysis revealed that a lower abundance of two ceramides, i.e., Cer(d18:0/22:0) and Cer(d18:0/24:0), was an independent risk factor for the occurrence of DR in T2DM patients.

CONCLUSION

Disturbances in lipid metabolism are closely associated with the occurrence of DR in patients with T2DM, especially in ceramides. Our study revealed for the first time that Cer(d18:0/22:0) and Cer(d18:0/24:0) might be potential serological markers for the diagnosis of DR occurrence in T2DM patients, providing new ideas for the early diagnosis of DR.

Substitution of dietary monounsaturated fatty acids from olive oil for saturated fatty acids from lard increases low-density lipoprotein apolipoprotein B-100 fractional catabolic rate in subjects with dyslipidemia associated with insulin resistance: a randomized controlled trial

BACKGROUND

The substitution of monounsaturated acids (MUFAs) for saturated fatty acids (SFAs) is recommended for cardiovascular disease prevention but its impact on lipoprotein metabolism in subjects with dyslipidemia associated with insulin resistance (IR) remains largely unknown.

OBJECTIVES

This study aimed to evaluate the impact of substituting MUFAs for SFAs on the in vivo kinetics of apolipoprotein (apo)B-containing lipoproteins and on the plasma lipidomic profile in adults with IR-induced dyslipidemia.

METHODS

Males and females with dyslipidemia associated with IR (n = 18) were recruited for this crossover double-blind randomized controlled trial. Subjects consumed, in random order, a diet rich in SFAs (SFAs: 13.4%E; MUFAs: 14.4%E) and a diet rich in MUFAs (SFAs: 7.1%E; MUFAs: 20.7%E) in fully controlled feeding conditions for periods of 4 wk each, separated by a 4-wk washout. At the end of each diet, fasting plasma samples were taken together with measurements of the in vivo kinetics of apoB-containing lipoproteins.

RESULTS

Substituting MUFAs for SFAs had no impact on triglyceride-rich lipoprotein apoB-48 fractional catabolic rate (FCR) (Δ = -8.9%, P = 0.4) and production rate (Δ = 0.0%, P = 0.9), although it decreased very low-density lipoprotein apoB-100 pool size (PS) (Δ = -22.5%; P = 0.01). This substitution also reduced low-density lipoprotein cholesterol (LDL-C) (Δ = -7.0%; P = 0.01), non-high-density lipoprotein cholesterol (Δ = -2.5%; P = 0.04), and LDL apoB-100 PS (Δ = -6.0%; P = 0.05). These differences were partially attributed to an increase in LDL apoB-100 FCR (Δ = +1.6%; P = 0.05). The MUFA diet showed reduced sphingolipid concentrations and elevated glycerophospholipid levels compared with the SFA diet.

CONCLUSIONS

This study demonstrated that substituting dietary MUFAs for SFAs decreases LDL-C levels and LDL PS by increasing LDL apoB-100 FCR and results in an overall improved plasma lipidomic profile in individuals with IR-induced lipidemia.

TRIAL REGISTRATION

This trial was registered as clinicaltrials.gov as NCT03872349.

Untargeted metabolomics uncovers metabolic dysregulation and tissue sensitivity in ACE2 knockout mice

Angiotensin-converting enzyme 2 (ACE2) polymorphisms are associated with increased risk of type 2 diabetes mellitus (T2DM), obesity and dyslipidemia, which have been determined in various populations. Consistently, ACE2 knockout (ACE2 KO) mice display damaged energy metabolism in multiple tissues, especially the key metabolic tissues such as liver, skeletal muscle and epididymal white adipose tissue (eWAT) and show even more severe phenotype under high-fat diet (HFD) induced metabolic stress. However, the effects of ACE2 on global metabolomics profiling and the tissue sensitivity remain unclear. To understand how tissues independently and collectively respond to ACE2, we performed untargeted metabolomics in serum in ACE2 KO and control wild type (WT) mice both on normal diet (ND) and HFD, and in three key metabolic tissues (liver, skeletal muscle and eWAT) after HFD treatment. The results showed significant alterations in metabolic profiling in ACE2 KO mice. We identified 275 and 168 serum metabolites differing significantly between WT and ACE2 KO mice fed on ND and HFD, respectively. And the altered metabolites in the ACE2 KO group varied from 90 to 196 in liver, muscle and eWAT. The alterations in ND and HFD serum were most similar. Compared with WT mice, ACE2 KO mice showed an increase in N-phenylacetylglutamine (PAGln), methyl indole-3-acetate, 5-hydroxytryptophol, cholic acid, deoxycholic acid and 12(S)-HETE, while LPC (19:0) and LPE (16:1) decreased. Moreover, LPC (20:0), LPC (20:1) and PC (14:0e/6:0) were reduced in both ND and HFD serum, paralleling the decreases identified in HFD skeletal muscle. Interestingly, DL-tryptophan, indole and Gly-Phe decreased in both ND and HFD serum but were elevated in HFD liver of ACE2 KO mice. A low level of l-ergothioneine was observed among liver, muscle, and epididymal fat tissue of ACE2 KO mice. Pathway analysis demonstrated that different tissues exhibited different dysregulated metabolic pathways. In conclusion, these results revealed that ACE2 deficiency leads to an overall state of metabolic distress, which may provide a new insight into the underlying pathogenesis in metabolic disorders in both ACE2 KO mice and in patients with certain genetic variant of ACE2 gene.

Plasma Ceramides and Other Sphingolipids in Relation to Incident Prediabetes in a Longitudinal Biracial Cohort

CONTEXT

Sphingolipids are linked to the pathogenesis of type 2 diabetes (T2D).

OBJECTIVE

To test the hypothesis that plasma sphingolipid profiles predict incident prediabetes.

DESIGN

A case-control study nested in the Pathobiology of Prediabetes in a Biracial Cohort (POP-ABC) study, a 5-year follow-up study.

SETTING

Academic health center.

PARTICIPANTS

Normoglycemic adults enrolled in the POP-ABC study. Assessments included OGTT, insulin sensitivity and insulin secretion. Participants with incident prediabetes were matched in age, sex, and ethnicity with non-progressors.

INTERVENTIONS

We assayed 58 sphingolipid species (ceramides, monohexosyl ceramides, sphingomyelins, and sphingosine) using LC/tandem mass spectrometry in baseline plasma levels from participants and determined association with prediabetes risk.

MAIN OUTCOME MEASURE

The primary outcome was progression from normoglycemia to prediabetes, defined as impaired fasting glucose or impaired glucose tolerance.

RESULTS

The mean age of participants (N = 140; 50% Black, 50% female) was 48.1 ± 8.69 y, BMI 30.1 ± 5.78 kg/m2, fasting plasma glucose (FPG) 92.7 ± 5.84 mg/dl, and two-hour plasma glucose (2hrPG) 121 ± 23.3 mg/dl. Of the 58 sphingolipid species assayed, higher ratios of sphingomyelin C26:0/C26:1 (OR 2.73 [95% CI 1.172-4.408], P = 0.015) and ceramide C18:0/C18:1 (OR 1.236 [95% CI 1.042-1.466], P = 0.015) in baseline plasma specimens were significantly associated with progression to prediabetes during the 5-year follow-up period, after adjustments for age, race, sex, BMI, FPG, 2hPG, insulin sensitivity, and insulin secretion.

CONCLUSIONS

We conclude that the saturated-to-monounsaturated ratios of long-chain ceramide C18:0/C18:1 and very-long-chain sphingomyelin C26:0/C26:1 are potential biomarkers of prediabetes risk among individuals with parental history of T2D.

High fat diet is associated with gut microbiota dysbiosis and decreased gut microbial derived metabolites related to metabolic health in young Göttingen Minipigs

The objectives were 1) to characterize a Göttingen Minipig model of metabolic syndrome regarding its colon microbiota and circulating microbial products, and 2) to assess whether ovariectomized female and castrated male minipigs show similar phenotypes. Twenty-four nine-week-old Göttingen Minipigs were allocated to four groups based on sex and diet: ovariectomized females and castrated males fed either chow or high-fat diet (HFD) for 12 weeks. At study end, body composition and plasma biomarkers were measured, and a mixed meal tolerance test (MMT) and an intravenous glucose tolerance test (IVGTT) were performed. The HFD groups had significantly higher weight gain, fat percentage, fasting plasma insulin and glucagon compared to the chow groups. Homeostatic model assessment of insulin resistance index (HOMA-IR) was increased and glucose effectiveness derived from the IVGTT and Matsuda´s insulin sensitivity index from the MMT were decreased in the HFD groups. The HFD groups displayed dyslipidemia, with significantly increased total-, LDL- and HDL-cholesterol, and decreased HDL/non-HDL cholesterol ratio. The colon microbiota of HFD minipigs clearly differed from the lean controls (GuniFrac distance matrix). The main bacteria families driving this separation were Clostridiaceae, Fibrobacteraceae, Flavobacteriaceae and Porphyromonadaceae. Moreover, the species richness was significantly decreased by HFD. In addition, HFD decreased the circulating level of short chain fatty acids and beneficial microbial metabolites hippuric acid, xanthine and trigonelline, while increasing the level of branched chain amino acids. Six and nine metabolically relevant genes were differentially expressed between chow-fed and HFD-fed animals in liver and omental adipose tissue, respectively. The HFD-fed pigs presented with metabolic syndrome, gut microbial dysbiosis and a marked decrease in healthy gut microbial products and thus displayed marked parallels to human obesity and insulin resistance. HFD-fed Göttingen Minipig therefore represents a relevant animal model for studying host-microbiota interactions. No significant differences between the castrated and ovariectomized minipigs were observed.

Electroacupuncture at ST25 corrected gut microbial dysbiosis and SNpc lipid peroxidation in Parkinson's disease rats

Introduction

Parkinson's disease (PD) remains one kind of a complex, progressive neurodegenerative disease. Levodopa and dopamine agonists as widely utilized PD therapeutics have not shown significant positive long-term outcomes. Emerging evidences indicate that electroacupuncture (EA) have potential effects on the therapy of nervous system disorders, particularly PD, but its specific underlying mechanism(s) remains poorly understood, leading to the great challenge of clinical application and management. Previous study has shown that acupuncture ameliorates PD motor symptoms and dopaminergic neuron damage by modulating intestinal dysbiosis, but its intermediate pathway has not been sufficiently investigated.

Methods

A rat model of PD was induced using rotenone. The therapeutic effect of EA on PD was assessed using the pole and rotarod tests and immunohistostaining for tyrosine hydroxylase (TH) in the substantia nigra (SN) of brain. The role of gut microbiota was explored using 16S rRNA gene sequencing and metabonomic analysis. PICRUSt2 analysis, lipidomic analysis, LPS and inflammatory factor assays were used for subsequent exploration and validation. Correlation analysis was used to identify the key bacteria that EA regulates lipid metabolism to improve PD.

Results

The present study firstly reappeared the effects of EA on protecting motor function and dopaminergic neurons and modulation of gut microbial dysbiosis in rotenone-induced PD rat model. EA improved motor dysfunction (via the pole and rotarod tests) and protected TH+ neurons in PD rats. EA increased the abundance of beneficial bacteria such as Lactobacillus, Dubosiella and Bifidobacterium and decreased the abundance of Escherichia-Shigella and Morganella belonging to Pseudomonadota, suggesting that the modulation of gut microbiota by EA improving the symptoms of PD motility via alleviating LPS-induced inflammatory response and oxidative stress, which was also validated by various aspects such as microbial gene functional analysis, fecal metabolomics analysis, LPS and inflammatory factor assays and SNpc lipidomics analysis. Moreover, correlation analyses also verified strong correlations of Escherichia-Shigella and Morganella with motor symptoms and SNpc lipid peroxidation, explicating targets and intermediate pathways through which EA improve PD exercise symptom.

Conclusion

Our results indicate that the improvement of motor function in PD model by EA may be mediated in part by restoring the gut microbiota, which intermediate processes involve circulating endotoxins and inflammatory mediators, SNpc oxidative stress and lipid peroxidation. The gut-microbiome - brain axis may be a potential mechanism of EA treatment for the PD.

Circadian organization of lipid landscape is perturbed in type 2 diabetic patients

Lipid homeostasis in humans follows a diurnal pattern in muscle and pancreatic islets, altered upon metabolic dysregulation. We employ tandem and liquid-chromatography mass spectrometry to investigate daily regulation of lipid metabolism in subcutaneous white adipose tissue (SAT) and serum of type 2 diabetic (T2D) and non-diabetic (ND) human volunteers (n = 12). Around 8% of ≈440 lipid metabolites exhibit diurnal rhythmicity in serum and SAT from ND and T2D subjects. The spectrum of rhythmic lipids differs between ND and T2D individuals, with the most substantial changes observed early morning, as confirmed by lipidomics in an independent cohort of ND and T2D subjects (n = 32) conducted at a single morning time point. Strikingly, metabolites identified as daily rhythmic in both serum and SAT from T2D subjects exhibit phase differences. Our study reveals massive temporal and tissue-specific alterations of human lipid homeostasis in T2D, providing essential clues for the development of lipid biomarkers in a temporal manner.

A Maternal Western-Style Diet Impairs Skeletal Muscle Lipid Metabolism in Adolescent Japanese Macaques

Maternal consumption of a Western-style diet (mWD) during pregnancy alters fatty acid metabolism and reduces insulin sensitivity in fetal skeletal muscle. The long-term impact of these fetal adaptations and the pathways underlying disordered lipid metabolism are incompletely understood. Therefore, we tested whether a mWD chronically fed to lean, insulin-sensitive adult Japanese macaques throughout pregnancy and lactation would impact skeletal muscle oxidative capacity and lipid metabolism in adolescent offspring fed a postweaning (pw) Western-style diet (WD) or control diet (CD). Although body weight was not different, retroperitoneal fat mass and subscapular skinfold thickness were significantly higher in pwWD offspring consistent with elevated fasting insulin and glucose. Maximal complex I (CI)-dependent respiration in muscle was lower in mWD offspring in the presence of fatty acids, suggesting that mWD impacts muscle integration of lipid with nonlipid oxidation. Abundance of all five oxidative phosphorylation complexes and VDAC, but not ETF/ETFDH, were reduced with mWD, partially explaining the lower respiratory capacity with lipids. Muscle triglycerides increased with pwWD; however, the fold increase in lipid saturation, 1,2-diacylglycerides, and C18 ceramide compared between pwCD and pwWD was greatest in mWD offspring. Reductions in CI abundance and VDAC correlated with reduced markers of oxidative stress, suggesting that these reductions may be an early-life adaptation to mWD to mitigate excess reactive oxygen species. Altogether, mWD, independent of maternal obesity or insulin resistance, results in sustained metabolic reprogramming in offspring muscle despite a healthy diet intervention.

ARTICLE HIGHLIGHTS

In lean, active adolescent offspring, a postweaning Western-style diet (pwWD) leads to shifts in body fat distribution that are associated with poorer insulin sensitivity. Fatty acid-linked oxidative metabolism was reduced in skeletal muscles from offspring exposed to maternal Western-style diet (mWD) even when weaned to a healthy control diet for years. Reduced oxidative phosphorylation complex I-V and VDAC1 abundance partially explain decreased skeletal muscle respiration in mWD offspring. Prior exposure to mWD results in greater fold increase with pwWD in saturated lipids and bioactive lipid molecules (i.e. ceramide and sphingomyelin) associated with insulin resistance.

Chemical Profiling of Nitraria roborowskii Kom. by UPLC-Q-Orbitrap-MS and Their Hypolipidemic Effects in Vivo

The Nitraria roborowskii Kom. (NRK) berries, as fruits of the genus Nitraria of the Zygophyllceae family, have been widely used as folk medicine. Modern pharmacological research has demonstrated that Nitraria berries had hypolipidemic, hypoglycemic, and immunomodulatory effects. However, more research needs to be reported on the chemical composition and biological activity of NRK. Hence, the phenolic compounds in the NRK berries were comprehensively analyzed and characterized by Ultra Performance Liquid Chromatography-Quadruple-Orbitrap MS system (UPLC-Q-Orbitrap MS) in this study. In total, 52 phenolics were identified, and all were reported for the first time. In addition, the hypolipidemic efficacy of NRK berries extract was studied in the hyperlipidemic mouse model. After treatment, the high dose group of NRK substantially reversed total cholesterol, low-density lipoprotein cholesterol, and high-density lipoprotein cholesterol levels. Through lipidomics technology, 27 potential biomarkers were characterized. And there was a significant callback at 25 of them after NRK treatment by using statistical analysis methods. Pathway analysis results demonstrated that NRK might exert therapeutic effects by regulating glycerophospholipid and glycerolipid metabolism pathways. This study could provide firsthand information on NRK berries for their phenolic compounds and potential application in preventing and treating hyperlipidemia.

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.

Protective mechanisms of a microbial oil against hypercholesterolemia: evidence from a zebrafish model

A Western diet elevates the circulating lipoprotein and triglyceride levels which are the major risk factors in cardiovascular disease (CVD) development. Consumption of long-chain omega-3 fatty acids can stall the disease progression. Although these fatty acids can significantly impact the intestine under a hypercholesterolemic condition, the associated changes have not been studied in detail. Therefore, we investigated the alterations in the intestinal transcriptome along with the deviations in the plasma lipids and liver histomorphology of zebrafish offered DHA- and EPA-rich oil. Fish were allocated to 4 dietary treatments: a control group, a high cholesterol group and microbial oil groups with low (3.3%) and high (6.6%) inclusion levels. We quantified the total cholesterol, lipoprotein and triglyceride levels in the plasma. In addition, we assessed the liver histology, intestinal transcriptome and plasma lipidomic profiles of the study groups. The results suggested that higher levels of dietary microbial oil could control the CVD risk factor indices in zebrafish plasma. Furthermore, microbial oil-fed fish had fewer liver vacuoles and higher mRNA levels of genes involved in β-oxidation and HDL maturation. Analyses of the intestine transcriptome revealed that microbial oil supplementation could influence the expression of genes altered by a hypercholesterolemic diet. The plasma lipidomic profiles revealed that the higher level of microbial oil tested could elevate the long-chain poly-unsaturated fatty acid content of triglyceride species and lower the concentration of several lysophosphatidylcholine and diacylglycerol molecules. Our study provides insights into the effectiveness of microbial oil against dyslipidemia in zebrafish.

Metabolomic Profiles, Ideal Cardiovascular Health, and Risk of Heart Failure and Atrial Fibrillation: Insights From the Framingham Heart Study

Background The American Heart Association's framework "ideal cardiovascular health" (CVH) focuses on modifiable risk factors to reduce cardiovascular disease (CVD). Metabolomics provides important pathobiological insights into risk factors and CVD development. We hypothesized that metabolomic signatures associate with CVH status, and that metabolites, at least partially, mediate the association of CVH score with atrial fibrillation (AF) and heart failure (HF). Methods and Results We studied 3056 adults in the FHS (Framingham Heart Study) cohort to evaluate CVH score and incident outcomes of AF and HF. Metabolomics data were available in 2059 participants; mediation analysis was performed to evaluate the mediation of metabolites in the association of CVH score and incident AF and HF. In the smaller cohort (mean age, 54 years; 53% women), CVH score was associated with 144 metabolites, with 64 metabolites shared across key cardiometabolic components (body mass index, blood pressure, and fasting blood glucose) of the CVH score. In mediation analyses, 3 metabolites (glycerol, cholesterol ester 16:1, and phosphatidylcholine 32:1) mediated the association of CVH score with incident AF. Seven metabolites (glycerol, isocitrate, asparagine, glutamine, indole-3-proprionate, phosphatidylcholine C36:4, and lysophosphatidylcholine 18:2), partly mediated the association between CVH score and incident HF in multivariable-adjusted models. Conclusions Most metabolites that associated with CVH score were shared the most among 3 cardiometabolic components. Three main pathways: (1) alanine, glutamine, and glutamate metabolism; (2) citric acid cycle metabolism; and (3) glycerolipid metabolism mediated CVH score with HF. Metabolomics provides insights into how ideal CVH status contributes to the development of AF and HF.

Characterization of lipid signatures in the plasma and insulin-sensitive tissues of the C57BL/6J mice fed on obesogenic diets

Diet-induced obesity mouse models are widely utilized to investigate the underlying mechanisms of dyslipidemia, glucose intolerance, insulin resistance, hepatic steatosis, and type 2 diabetes mellitus (T2DM), as well as for screening potential drug compounds. However, there is limited knowledge regarding specific signature lipids that accurately reflect dietary disorders. In this study, we aimed to identify key lipid signatures using LC/MS-based untargeted lipidomics in the plasma, liver, adipose tissue (AT), and skeletal muscle tissues (SKM) of male C57BL/6J mice that were fed chow, LFD, or obesogenic diets (HFD, HFHF, and HFCD) for a duration of 20 weeks. Furthermore, we conducted a comprehensive lipid analysis to assess similarities and differences with human lipid profiles. The mice fed obesogenic diets exhibited weight gain, glucose intolerance, elevated BMI, glucose and insulin levels, and a fatty liver, resembling characteristics of T2DM and obesity in humans. In total, we identified approximately 368 lipids in plasma, 433 in the liver, 493 in AT, and 624 in SKM. Glycerolipids displayed distinct patterns across the tissues, differing from human findings. However, changes in sphingolipids, phospholipids, and the expression of inflammatory and fibrotic genes showed similarities to reported human findings. Significantly modulated pathways in the obesogenic diet-fed groups included ceramide de novo synthesis, sphingolipid remodeling, and the carboxylesterase pathway, while lipoprotein-mediated pathways were minimally affected.

Single-nucleus and bulk RNA sequencing reveal cellular and transcriptional mechanisms underlying lipid dynamics in high marbled pork

Pork is the most consumed meat in the world, and its quality is associated with human health. Intramuscular fat (IMF) deposition (also called marbling) is a key factor positively correlated with various quality traits and lipo-nutritional values of meat. However, the cell dynamics and transcriptional programs underlying lipid deposition in highly marbled meat are still unclear. Here, we used Laiwu pigs with high (HLW) or low (LLW) IMF contents to explore the cellular and transcriptional mechanisms underlying lipid deposition in highly-marbled pork by single-nucleus RNA sequencing (snRNA-seq) and bulk RNA sequencing. The HLW group had higher IMF contents but less drip loss than the LLW group. Lipidomics results revelled the changes of overall lipid classes composition (e.g., glycerolipids including triglycerides, diglycerides, and monoglycerides; sphingolipids including ceramides and monohexose ceramide significantly increased) between HLW and LLW groups. SnRNA-seq revealed nine distinct cell clusters, and the HLW group had a higher percentage of adipocytes (1.40% vs. 0.17%) than the LLW group. We identified 3 subpopulations of adipocytes, including PDE4D⁺/PDE7B⁺ (in HLW and LLW), DGAT2⁺/SCD⁺ (mostly in HLW) and FABP5⁺/SIAH1⁺ cells (mostly in HLW). Moreover, we showed that fibro/adipogenic progenitors could differentiate into IMF cells and contribute to 43.35% of adipocytes in mice. In addition, RNA-seq revealed different genes involved in lipid metabolism and fatty acid elongation. Our study provides new insights into the cellular and molecular signatures of marbling formation; such knowledge may facilitate the development of new strategies to increase IMF deposition and the lipo-nutritional quality of high marbled pork.

Metabolic remodeling of glycerophospholipids acts as a signature of dulaglutide and liraglutide treatment in recent-onset type 2 diabetes mellitus

Aims

As metabolic remodeling is a pathological characteristic in type 2 diabetes (T2D), we investigate the roles of newly developed long-acting glucagon-like peptide-1 receptor agonists (GLP-1RAs) such as dulaglutide and liraglutide on metabolic remodeling in patients with recent-onset T2D.

Methods

We recruited 52 cases of T2D and 28 control cases in this study. In the patient with T2D, 39 cases received treatment with dulaglutide and 13 cases received treatment with liraglutide. Using untargeted metabolomics analysis with broad-spectrum LC-MS, we tracked serum metabolic changes of the patients from the beginning to the end of follow-up (12th week).

Results

We identified 198 metabolites that were differentially expressed in the patients with T2D, compared to the control group, in which 23 metabolites were significantly associated with fasting plasma glucose. Compared to pre-treatment, a total of 46 and 45 differentially regulated metabolites were identified after treatments with dulaglutide and liraglutide, respectively, in which the most differentially regulated metabolites belong to glycerophospholipids. Furthermore, a longitudinal integration analysis concurrent with diabetes case-control status revealed that metabolic pathways, such as the insulin resistance pathway and type 2 diabetes mellitus, were enriched after dulaglutide and liraglutide treatments. Proteins such as GLP-1R, GNAS, and GCG were speculated as potential targets of dulaglutide and liraglutide.

Conclusions

In total, a metabolic change in lipids existed in the early stage of T2D was ameliorated after the treatments of GLP-1RAs. In addition to similar effects on improving glycemic control, remodeling of glycerophospholipid metabolism was identified as a signature of dulaglutide and liraglutide treatments.

Lipidomic profiling in the Strong Heart Study identified American Indians at risk of chronic kidney disease

Dyslipidemia associates with and usually precedes the onset of chronic kidney disease (CKD), but a comprehensive assessment of molecular lipid species associated with risk of CKD is lacking. Here, we sought to identify fasting plasma lipids associated with risk of CKD among American Indians in the Strong Heart Family Study, a large-scale community-dwelling of individuals, followed by replication in Mexican Americans from the San Antonio Family Heart Study and Caucasians from the Australian Diabetes, Obesity and Lifestyle Study. We also performed repeated measurement analysis to examine the temporal relationship between the change in the lipidome and change in kidney function between baseline and follow-up of about five years apart. Network analysis was conducted to identify differential lipid classes associated with risk of CKD. In the discovery cohort, we found that higher baseline level of multiple lipid species, including glycerophospholipids, glycerolipids and sphingolipids, was significantly associated with increased risk of CKD, independent of age, sex, body mass index, diabetes and hypertension. Many lipid species were replicated in at least one external cohort at the individual lipid species and/or the class level. Longitudinal change in the plasma lipidome was significantly associated with change in the estimated glomerular filtration rate after adjusting for covariates, baseline lipids and the baseline rate. Network analysis identified distinct lipidomic signatures differentiating high from low-risk groups. Thus, our results demonstrated that disturbed lipid metabolism precedes the onset of CKD. These findings shed light on the mechanisms linking dyslipidemia to CKD and provide potential novel biomarkers for identifying individuals with early impaired kidney function at preclinical stages.

Rosiglitazone Reverses Inflammation in Epididymal White Adipose Tissue in Hormone-Sensitive Lipase-Knockout Mice

Hormone-sensitive lipase (HSL) plays a crucial role in intracellular lipolysis, and loss of HSL leads to diacylglycerol (DAG) accumulation, reduced FA mobilization, and impaired PPARγ signaling. Hsl knockout mice exhibit adipose tissue inflammation, but the underlying mechanisms are still not clear. Here, we investigated if and to what extent HSL loss contributes to endoplasmic reticulum (ER) stress and adipose tissue inflammation in Hsl knockout mice. Furthermore, we were interested in how impaired PPARγ signaling affects the development of inflammation in epididymal white adipose tissue (eWAT) and inguinal white adipose tissue (iWAT) of Hsl knockout mice and if DAG and ceramide accumulation contribute to adipose tissue inflammation and ER stress. Ultrastructural analysis showed a markedly dilated ER in both eWAT and iWAT upon loss of HSL. In addition, Hsl knockout mice exhibited macrophage infiltration and increased F4/80 mRNA expression, a marker of macrophage activation, in eWAT, but not in iWAT. We show that treatment with rosiglitazone, a PPARγ agonist, attenuated macrophage infiltration and ameliorated inflammation of eWAT, but expression of ER stress markers remained unchanged, as did DAG and ceramide levels in eWAT. Taken together, we show that HSL loss promoted ER stress in both eWAT and iWAT of Hsl knockout mice, but inflammation and macrophage infiltration occurred mainly in eWAT. Also, PPARγ activation reversed inflammation but not ER stress and DAG accumulation. These data indicate that neither reduction of DAG levels nor ER stress contribute to the reversal of eWAT inflammation in Hsl knockout mice.

Effects of dietary supplementation of different levels of vitamin B12 on the liver metabolism of laying hens

BACKGROUND

Vitamin B₁₂ plays an important role in lipid, protein, carbohydrate and nucleic acid metabolism. We investigated the effect of supplementing layers' diets with different vitamin B₁₂ levels on liver metabolism using a liquid chromatography-mass spectrometry-based metabolomic approach to observe and analyse wide-target metabolomics in the liver.

RESULTS

We assigned hens to three groups, namely blank control group without vitamin B₁₂ diet (BCG), normal control group with 25 μg kg^-1 vitamin B₁₂ (NCG) and vitamin B₁₂ supplement group I with 100 μg kg^-1 vitamin (VBSG I). The VBSG I group layers had higher (P < 0.05) vitamin B₁₂ concentration than those from other groups. The egg yolk vitamin B₁₂ concentration increased (P < 0.01) with the increasing vitamin B₁₂ dietary supplemental level. Between the NCG versus BCG, VBSG I versus BCG, and VBSG I versus NCG groups, 11, 20 and 11 metabolites were significantly changed, respectively. The KEGG pathway of vitamin B₆ metabolism was significantly impacted in the NCG layers than those from BCG; seven and five pathways were significantly impacted in the VBSG I layers compared with those from BCG and NCG, including pyrimidine metabolism, vitamin B₆ metabolism, glycerophospholipid metabolism, etc. CONCLUSION: We concluded that 25 μg kg^-1 vitamin B₁₂ supplementation in corn-soybean meal-based layer diet increased the egg yolk vitamin B₁₂ concentration and impacted the vitamin B₆ metabolic pathway, and 100 μg kg^-1 of it increased the egg yolk and liver vitamin B₁₂ concentrations and impacted vitamin B₆ , lipid, nucleic acid and amino acid metabolic pathways. © 2022 Society of Chemical Industry.

Dairy Milk Casein and Whey Proteins Differentially Alter the Postprandial Lipidome in Persons with Prediabetes: A Comparative Lipidomics Study

Dairy milk, likely through its bioactive proteins, has been reported to attenuate postprandial hyperglycemia-induced oxidative stress responses implicated in cardiovascular diseases (CVDs). However, how its major proteins, whey and casein, alter metabolic excursions of the lipidome in persons with prediabetes is unclear. Therefore, the objective of this study was to examine whey or casein protein ingestion on glucose-induced alternations in lipidomic responses in adults (17 males and 6 females) with prediabetes. In this clinical study, participants consumed glucose alone, glucose + nonfat milk (NFM), or glucose with either whey (WHEY) or casein (CASEIN) protein, and plasma samples were collected at multiple time points. Lipidomics data from plasma samples was acquired using an ultra-high-performance liquid chromatography-high-resolution mass spectrometry-based platform. Our results indicated that glucose ingestion alone induced the largest number of changes in plasma lipids. WHEY showed an earlier and stronger impact to maintain the stability of the lipidome compared with CASEIN. WHEY protected against glucose-induced changes in glycerophospholipid and sphingolipid (SP) metabolism, while ether lipid metabolism and SP metabolism were the pathways most greatly impacted in CASEIN. Meanwhile, the decreased acyl carnitines and fatty acid (FA) 16:0 levels could attenuate lipid peroxidation after protein intervention to protect insulin secretory capacity. Diabetes-associated lipids, the increased phosphatidylethanolamine (PE) 34:2 and decreased phosphatidylcholine (PC) 34:3 in the NFM-T90 min, elevated PC 35:4 and decreased CE 18:1 to a CE 18:2 ratio in the WHEY-T180 min, decreased lysophosphatidylcholine (LPC) 22:6 and LPC 22:0/0:0 in the CASEIN-T90 min, and decreased PE 36:1 in the CASEIN-T180 min, indicating a decreased risk for prediabetes. Collectively, our study suggested that dairy milk proteins are responsible for the protective effect of non-fat milk on glucose-induced changes in the lipidome, which may potentially influence long-term CVD risk.

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

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

Effects of Sustained Hyperglycemia on Skeletal Muscle Lipids in Healthy Subjects

CONTEXT

Sustained increases in plasma glucose promote skeletal muscle insulin resistance independent from obesity and dyslipidemia (ie, glucotoxicity). Skeletal muscle lipids are key molecular determinants of insulin action, yet their involvement in the development of glucotoxicity is unclear.

OBJECTIVE

To explore the impact of mild physiologic hyperglycemia on skeletal muscle lipids.

DESIGN

Single group pretest-posttest.

PARTICIPANTS

Healthy males and females with normal glucose tolerance.

INTERVENTIONS

72-hour glucose infusion raising plasma glucose by ~50 mg/dL.

MAIN OUTCOME MEASURES

Skeletal muscle lipids, insulin sensitivity, lipid oxidation.

RESULTS

Despite impairing insulin-mediated glucose disposal and suppressing fasting lipid oxidation, hyperglycemia did not alter either the content or composition of skeletal muscle triglycerides, diacylglycerides, or phospholipids. Skeletal muscle ceramides decreased after glucose infusion, likely in response to a reduction in free fatty acid concentrations.

CONCLUSIONS

Our results demonstrate that the major lipid pools in skeletal muscle are unperturbed by sustained increases in glucose availability and suggest that glucotoxicity and lipotoxicity drive insulin resistance through distinct mechanistic pathways.

Contribution of specific ceramides to obesity-associated metabolic diseases

Ceramides are a heterogeneous group of bioactive membrane sphingolipids that play specialized regulatory roles in cellular metabolism depending on their characteristic fatty acyl chain lengths and subcellular distribution. As obesity progresses, certain ceramide molecular species accumulate in metabolic tissues and cause cell-type-specific lipotoxic reactions that disrupt metabolic homeostasis and lead to the development of cardiometabolic diseases. Several mechanisms for ceramide action have been inferred from studies in vitro, but only recently have we begun to better understand the acyl chain length specificity of ceramide-mediated signaling in the context of physiology and disease in vivo. New discoveries show that specific ceramides affect various metabolic pathways and that global or tissue-specific reduction in selected ceramide pools in obese rodents is sufficient to improve metabolic health. Here, we review the tissue-specific regulation and functions of ceramides in obesity, thus highlighting the emerging concept of selectively inhibiting production or action of ceramides with specific acyl chain lengths as novel therapeutic strategies to ameliorate obesity-associated diseases.

Circadian rhythm of lipid metabolism

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

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.

UCP1 Knockin Induces Lipid Dynamics and Transcriptional Programs in the Skeletal Muscles of Pigs

Uncoupling protein 1 (UCP1), the hallmark protein responsible for nonshivering thermogenesis in adipose tissue (especially brown adipose tissue) has regained researchers' attention in the context of metabolic disorders following the realization that UCP1 can be activated in adult humans and reconstituted in pigs. Both skeletal muscle and adipose tissue are highly dynamic tissues that interact at the metabolic and hormonal level in response to internal and external stress, and they coordinate in maintaining whole-body metabolic homeostasis. Here, we utilized lipidomics and transcriptomics to identify the altered lipid profiles and regulatory pathways in skeletal muscles from adipocyte-specific UCP1 knock-in (KI) pigs. UCP1 KI changed the contents of glycerophospholipids and acyl carnitines of skeletal muscles. Several metabolic regulatory pathways were more enriched in the UCP1 KI skeletal muscle. Comparison of the transcriptomes of adipose and skeletal muscle suggested that nervous system or chemokine signaling might account for the crosstalk between these two tissues in UCP1 KI pigs. Comparison of the lipid biomarkers from UCP1 KI pigs and other mammals suggested associations between UCP1 KI-induced metabolic alternations and metabolic and muscle dysfunction. Our study reveals the lipid dynamics and transcriptional programs in the skeletal muscle of UCP1 KI pigs and suggests that a network regulates metabolic homeostasis between skeletal muscle and adipose tissue.

Comparative Evaluation of the Effect of Metformin and Insulin on Gut Microbiota and Metabolome Profiles of Type 2 Diabetic Rats Induced by the Combination of Streptozotocin and High-Fat Diet

Lately, an increasing number of studies have investigated the relationship between metformin and gut microbiota, suggesting that metformin exerts part of its hypoglycemic effect through the microbes. However, its underlying mechanism remains largely undetermined. In the present study, we investigated the effects of metformin on gut microbiota and metabolome profiles in serum and compared it with insulin treatment in rats with type 2 diabetes mellitus (T2DM). Diabetic rats (DM group) were induced by a combination of streptozotocin and high-fat diet (HFD). After 7 days, DM rats were treated with metformin (MET group) or insulin (INS group) for 3 weeks. The 16S rRNA sequencing of the gut microbiota and non-targeted metabolomics analysis of serum were conducted. A total of 13 bile acids (BAs) in serum were further determined and compared among different groups. The rat model of T2DM was well established with the typical diabetic symptoms, showing significantly increased blood glucose, AUC of OGTT, HOMA-IR, TC, TG, LDL-C and TBA. Metformin or insulin treatment could ameliorate symptoms of diabetes and partly recover the abnormal biochemical indicators. Compared with DM rats, the relative abundances of 13 genera were significantly changed after metformin treatment, while only three genera were changed after insulin treatment. The metformin and insulin treatments also exhibited different serum metabolome profiles in T2DM rats. Moreover, 64 differential metabolites were identified between MET and DM groups, whereas 206 were identified between INS and DM groups. Insulin treatment showed greater influence on amino acids, glycerophospholipids/glycerolipids, and acylcarnitine compared with the metformin treatment, while metformin had an important impact on BAs. Furthermore, metformin could significantly decrease the serum levels of CA, GCA, UDCA, and GUDCA, but increase the level of TLCA in DM rats. Insulin treatment significantly decreased the levels of CA, UDCA, and CDCA. Besides, several metabolites in serum or microbiota were positively or negatively correlated with some bacteria. Collectively, our findings indicated that metformin had a stronger effect on gut microbiota than insulin, while insulin treatment showed greater influence on serum metabolites, which provided novel insights into the therapeutic effects of metformin on diabetes.

Untargeted Metabolomics Analysis of the Serum Metabolic Signature of Childhood Obesity

Obesity rates among children are growing rapidly worldwide, placing massive pressure on healthcare systems. Untargeted metabolomics can expand our understanding of the pathogenesis of obesity and elucidate mechanisms related to its symptoms. However, the metabolic signatures of obesity in children have not been thoroughly investigated. Herein, we explored metabolites associated with obesity development in childhood. Untargeted metabolomic profiling was performed on fasting serum samples from 27 obese Caucasian children and adolescents and 15 sex- and age-matched normal-weight children. Three metabolomic assays were combined and yielded 726 unique identified metabolites: gas chromatography–mass spectrometry (GC–MS), hydrophilic interaction liquid chromatography coupled to mass spectrometry (HILIC LC–MS/MS), and lipidomics. Univariate and multivariate analyses showed clear discrimination between the untargeted metabolomes of obese and normal-weight children, with 162 significantly differentially expressed metabolites between groups. Children with obesity had higher concentrations of branch-chained amino acids and various lipid metabolites, including phosphatidylcholines, cholesteryl esters, triglycerides. Thus, an early manifestation of obesity pathogenesis and its metabolic consequences in the serum metabolome are correlated with altered lipid metabolism. Obesity metabolite patterns in the adult population were very similar to the metabolic signature of childhood obesity. Identified metabolites could be potential biomarkers and used to study obesity pathomechanisms.

Lipid Metabolism Disorders in the Comorbid Course of Nonalcoholic Fatty Liver Disease and Chronic Obstructive Pulmonary Disease

Non-alcoholic fatty liver disease (NAFLD) is currently among the most common liver diseases. Unfavorable data on the epidemiology of metabolic syndrome and obesity have increased the attention of clinicians and researchers to the problem of NAFLD. The research results allow us to emphasize the systemicity and multifactoriality of the pathogenesis of liver parenchyma lesion. At the same time, many aspects of its classification, etiology, and pathogenesis remain controversial. Local and systemic metabolic disorders are also a part of the pathogenesis of chronic obstructive pulmonary disease and can influence its course. The present article analyzes the metabolic pathways mediating the links of impaired lipid metabolism in NAFLD and chronic obstructive pulmonary disease (COPD). Free fatty acids, cholesterol, and ceramides are involved in key metabolic and inflammatory pathways underlying the pathogenesis of both diseases. Moreover, inflammation and lipid metabolism demonstrate close links in the comorbid course of NAFLD and COPD.

Hepatic lipidomic remodeling in severe obesity manifests with steatosis and does not evolve with non-alcoholic steatohepatitis

BACKGROUNDS & AIMS

Obesity often leads to non-alcoholic fatty liver disease (NAFLD), which can progress from simple steatosis (non-alcoholic fatty liver (NAFL)) to non-alcoholic steatohepatitis (NASH). The accumulation of certain lipid subtypes is linked with worsening metabolic and liver disease, however, specific changes during progression from No-NAFL to NAFL then NASH are unresolved. Herein, we characterise the liver, adipose tissue and plasma lipidome of worsening NAFLD in obesity, and evaluate the utility of plasma lipids as biomarkers of NAFLD.

METHODS

Venous blood, liver, visceral and subcutaneous adipose tissue samples were obtained from 181 patients undergoing bariatric surgery. NAFLD severity was assessed histologically. Lipidomic analysis was performed using liquid chromatography-tandem mass spectrometry.

RESULTS

The liver lipidome showed substantial changes with increasing steatosis, with increased triacylglycerols, diacylglycerols and sphingolipids including ceramide, dihydroceramide, hexosyl-ceramide and GM3 ganglioside species. These lipid species were also increased in plasma with increasing hepatic steatosis and showed strong correlations with liver lipids. Adipose tissue lipidomes showed no correlation with NAFLD. There were no significant changes in liver lipids with NASH compared to NAFL. The addition of plasma lipid variables to routine markers yielded significant improvements in diagnostic accuracy for NASH (AUROC 0.667 vs. 0.785, p = 0.025).

CONCLUSION

Overall, these data provide a detailed description of the lipidomic changes with worsening NAFLD, showing significant changes with steatosis but no additional changes with NASH. Alterations in the liver lipidome are paralleled by similar changes in plasma. Further investigation is warranted into the potential utility of plasma lipids as non-invasive biomarkers of NAFLD in obesity.

LAY SUMMARY

Non-alcoholic fatty liver disease (NAFLD) is characterised by distinct changes in the liver lipidome with steatosis. The development of non-alcoholic steatohepatitis (NASH) does not result in further changes in the lipidome. Lipids within body fat do not appear to influence the lipid profile of the liver or blood. Changes in liver lipids are paralleled by changes in blood lipids. This has potential to be developed into a non-invasive biomarker for NAFLD.

CLINICAL TRIAL NUMBER

ACTRN12615000875505.

Retention dependences support highly confident identification of lipid species in human plasma by reversed-phase UHPLC/MS

Reversed-phase ultrahigh-performance liquid chromatography-mass spectrometry (RP-UHPLC/MS) method was developed with the aim to unambiguously identify a large number of lipid species from multiple lipid classes in human plasma. The optimized RP-UHPLC/MS method employed the C18 column with sub-2-μm particles with the total run time of 25 min. The chromatographic resolution was investigated with 42 standards from 18 lipid classes. The UHPLC system was coupled to high-resolution quadrupole-time-of-flight (QTOF) mass analyzer using electrospray ionization (ESI) measuring full-scan and tandem mass spectra (MS/MS) in positive- and negative-ion modes with high mass accuracy. Our identification approach was based on m/z values measured with mass accuracy within 5 ppm tolerance in the full-scan mode, characteristic fragment ions in MS/MS, and regularity in chromatographic retention dependences for individual lipid species, which provides the highest level of confidence for reported identifications of lipid species including regioisomeric and other isobaric forms. The graphs of dependences of retention times on the carbon number or on the number of double bond(s) in fatty acyl chains were constructed to support the identification of lipid species in homologous lipid series. Our list of identified lipid species is also compared with previous publications investigating human blood samples by various MS-based approaches. In total, we have reported more than 500 lipid species representing 26 polar and nonpolar lipid classes detected in NIST Standard reference material 1950 human plasma.

Multi-Omics Analysis Reveals Disturbance of Nanosecond Pulsed Electric Field in the Serum Metabolic Spectrum and Gut Microbiota

Nanosecond pulsed electric field (nsPEF) is a novel ablation technique that is based on high-intensity electric voltage to achieve tumour-killing effect in the target region, and increasingly considered for treating tumours of the liver, kidneys and other organs with rich blood supply. This study aims to observe effect of nsPFE treatment on serum metabolites and gut microbiota. The serum and faecal specimens of the pigs were collected pre- and post-treatment. The gut microbiota of pigs was sequenced by Illumina Miseq platform for analysing the diversity and alterations of gut microbiota. Liquid chromatography-mass spectrometry (LC-MS)-based metabonomic analysis and Pearson coefficient method were also used to construct the interaction system of different metabolites, metabolic pathways and flora. A total of 1,477 differential metabolites from the serum were identified by four cross-comparisons of different post-operative groups with the control group. In addition, an average of 636 OTUs per sample was detected. Correlation analysis also revealed the strong correlation between intestinal bacteria and differential metabolites. The nsPEF ablation of the liver results in a degree of liver damage that affects various metabolic pathways, mainly lipid metabolism, as well as gut microbiota. In conclusion, our study provided a good point for the safety and feasibility of applying nsPEF on liver through the integrated analysis of metabolomics and microbiomes, which is beneficial for the improvement of nsPEF in clinical use.

Serum Metabolomics in PCOS Women with Different Body Mass Index

Polycystic ovary syndrome (PCOS) is the most prevalent endocrine and metabolic disorder, affecting 5–10% of women of reproductive age. It results from complex environmental factors, genetic predisposition, hyperinsulinemia, hormonal imbalance, neuroendocrine abnormalities, chronic inflammation, and autoimmune disorders. PCOS impacts menstrual regularities, fertility, and dermatological complications, and may induce metabolic disturbances, diabetes, and coronary heart disease. Comprehensive metabolic profiling of patients with PCOS may be a big step in understanding and treating the disease. The study aimed to search for potential differences in metabolites concentrations among women with PCOS according to different body mass index (BMI) in comparison to healthy controls. We used broad-spectrum targeted metabolomics to evaluate metabolites’ serum concentrations in PCOS patients and compared them with healthy controls. The measurements were performed using high-performance liquid chromatography coupled with the triple quadrupole tandem mass spectrometry technique, which has highly selective multiple reaction monitoring modes. The main differences were found in glycerophospholipid concentrations, with no specific tendency to up-or down-regulation. Insulin resistance and elevated body weight influence acylcarnitine C2 levels more than PCOS itself. Sphingomyelin (SM) C18:1 should be more intensively observed and examined in future studies and maybe serve as one of the PCOS biomarkers. No significant correlations were observed between anthropometric and hormonal parameters and metabolome results.

Multiplatform metabolomics for an integrative exploration of metabolic syndrome in older men

BACKGROUND

Metabolic syndrome (MetS), a cluster of factors associated with risks of developing cardiovascular diseases, is a public health concern because of its growing prevalence. Considering the combination of concomitant components, their development and severity, MetS phenotypes are largely heterogeneous, inducing disparity in diagnosis.

METHODS

A case/control study was designed within the NuAge longitudinal cohort on aging. From a 3-year follow-up of 123 stable individuals, we present a deep phenotyping approach based on a multiplatform metabolomics and lipidomics untargeted strategy to better characterize metabolic perturbations in MetS and define a comprehensive MetS signature stable over time in older men.

FINDINGS

We characterize significant changes associated with MetS, involving modulations of 476 metabolites and lipids, and representing 16% of the detected serum metabolome/lipidome. These results revealed a systemic alteration of metabolism, involving various metabolic pathways (urea cycle, amino-acid, sphingo- and glycerophospholipid, and sugar metabolisms…) not only intrinsically interrelated, but also reflecting environmental factors (nutrition, microbiota, physical activity…).

INTERPRETATION

These findings allowed identifying a comprehensive MetS signature, reduced to 26 metabolites for future translation into clinical applications for better diagnosing MetS.

FUNDING

The NuAge Study was supported by a research grant from the Canadian Institutes of Health Research (CIHR; MOP-62842). The actual NuAge Database and Biobank, containing data and biologic samples of 1,753 NuAge participants (from the initial 1,793 participants), are supported by the Fonds de recherche du Québec (FRQ; 2020-VICO-279753), the Quebec Network for Research on Aging, a thematic network funded by the Fonds de Recherche du Québec - Santé (FRQS) and by the Merck-Frost Chair funded by La Fondation de l'Université de Sherbrooke. All metabolomics and lipidomics analyses were funded and performed within the metaboHUB French infrastructure (ANR-INBS-0010). All authors had full access to the full data in the study and accept responsibility to submit for publication.

A reference map of sphingolipids in murine tissues

Sphingolipids (SPs) have both a structural role in the cell membranes and a signaling function that regulates many cellular processes. The enormous structural diversity and low abundance of many SPs pose a challenge for their identification and quantification. Recent advances in lipidomics, in particular liquid chromatography (LC) coupled with mass spectrometry (MS), provide methods to detect and quantify many low-abundant SP species reliably. Here we use LC-MS to compile a "murine sphingolipid atlas," containing the qualitative and quantitative distribution of 114 SPs in 21 tissues of a widely utilized wild-type laboratory mouse strain (C57BL/6). We report tissue-specific SP fingerprints, as well as sex-specific differences in the same tissue. This is a comprehensive, quantitative sphingolipidomic map of mammalian tissues collected in a systematic fashion. It will complement other tissue compendia for interrogation into the role of SP in mammalian health and disease.

Ether lipids, sphingolipids and toxic 1-deoxyceramides as hallmarks for lean and obese type 2 diabetic patients

AIM

The worldwide increase in obesity and type 2 diabetes (T2D) represents a major health challenge. Chronically altered lipids induced by obesity further promote the development of T2D, and the accumulation of toxic lipid metabolites in serum and peripheral organs may contribute to the diabetic phenotype.

METHODS

To better understand the complex metabolic pattern of lean and obese T2D and non-T2D individuals, we analysed the lipid profile of human serum, skeletal muscle and visceral adipose tissue of two cohorts by systematic mass spectrometry-based lipid analysis.

RESULTS

Lipid homeostasis was strongly altered in a disease- and tissue-specific manner, allowing us to define T2D signatures associated with obesity from those that were obesity independent. Lipid changes encompassed lyso-, diacyl- and ether-phospholipids. Moreover, strong changes in sphingolipids included cytotoxic 1-deoxyceramide accumulation in a disease-specific manner in serum and visceral adipose tissue. The high amounts of non-canonical 1-deoxyceramide present in human adipose tissue most likely come from cell-autonomous synthesis because 1-deoxyceramide production increased upon differentiation to adipocytes in mouse cell culture experiments.

CONCLUSION

Taken together, the observed lipidome changes in obesity and T2D will facilitate the identification of T2D patient subgroups and represent an important step towards personalized medicine in diabetes.

Macronutrient Determinants of Obesity, Insulin Resistance and Metabolic Health

Obesity caused by the overconsumption of calories has increased to epidemic proportions. Insulin resistance is often associated with an increased adiposity and is a precipitating factor in the development of cardiovascular disease, type 2 diabetes, and altered metabolic health. Of the various factors contributing to metabolic impairments, nutrition is the major modifiable factor that can be targeted to counter the rising prevalence of obesity and metabolic diseases. However, the macronutrient composition of a nutritionally balanced "healthy diet" are unclear, and so far, no tested dietary intervention has been successful in achieving long-term compliance and reductions in body weight and associated beneficial health outcomes. In the current review, we briefly describe the role of the three major macronutrients, carbohydrates, fats, and proteins, and their role in metabolic health, and provide mechanistic insights. We also discuss how an integrated multi-dimensional approach to nutritional science could help in reconciling apparently conflicting findings.

Reduced membrane cholesterol content in skeletal muscle is not essential for greater insulin-stimulated glucose uptake after acute exercise by rats

One exercise session can elevate insulin-stimulated glucose uptake (GU) by skeletal muscle, but it is uncertain if this effect is accompanied by altered membrane cholesterol content, which is reportedly inversely related to insulin-stimulated GU. Muscles from sedentary (SED) or exercised 3 h post-exercise (3hPEX) rats were evaluated for GU, membrane cholesterol, and phosphorylation of cholesterol regulatory proteins (pHMCGR^Ser872 and pABCA1^Ser2054). Insulin-stimulated GU for 3hPEX exceeded SED. Membrane cholesterol, pHMCGR^Ser872 and pABCA1^Ser2054 did not differ between groups. Novelty: Alterations in membrane cholesterol and phosphorylation of proteins that regulate muscle cholesterol are not essential for elevated insulin-stimulated GU in skeletal muscle after acute exercise.

Methylome and transcriptome profiling revealed epigenetic silencing of LPCAT1 and PCYT1A associated with lipidome alterations in polycystic ovary syndrome

Polycystic ovary syndrome (PCOS) is the most common endocrine diseases of fertile women and a major cause of infertility. The regulatory effects of DNA methylation on gene transcription and downstream lipid metabolism have not been explored in PCOS. In this study, MBD-seq and RNA-seq were performed on ovarian granulosa cells of PCOS patients and controls, and methylation specific PCR and quantitative polymerase chain reaction were used to validate the results. Then lipidomic profiling was conducted on serum of PCOS patients and controls using UPLC-MS. We identified 73 genes with differently methylated promoters and 830 differently expressed genes. The promoter regions of LPCAT1 and PCYT1A were hypermethylated, accompanied by downregulation of their messenger RNA expression, which may be involved in the regulation of PCOS through downstream glycerophospholipid metabolism and phosphatidylcholine synthesis. The lipid profiling results showed significant changes in 21 lipids, which demonstrated the disturbance in glycerophospholipid metabolism and glycerolipid metabolism pathways. Furthermore, the metabolites-genes interaction network was constructed to illustrate the association of aberrant methylome and transcriptome with lipidome alterations in glycerolipid and glycerophospholipid metabolism pathways. Our study suggested that the methylation silencing of LPCAT1 and PCYT1A may promote glycerophospholipids metabolism dysregulation, which provided a novel genetic and lipometabolic basis for the pathogenesis of PCOS.

The Role of Lipidomics in Autism Spectrum Disorder

Autism spectrum disorder (ASD) is a complex neurodevelopmental syndrome commonly diagnosed in early childhood; it is usually characterized by impairment in reciprocal communication and speech, repetitive behaviors, and social withdrawal with loss in communication skills. Its development may be affected by a variety of environmental and genetic factors. Trained physicians diagnose and evaluate the severity of ASD based on clinical evaluations of observed behaviors. As such, this approach is inevitably dependent on the expertise and subjective assessment of those administering the clinical evaluations. There is a need to identify objective biological markers associated with diagnosis or clinical severity of the disorder. Several important issues and concerns exist regarding the diagnostic competence of the many abnormal plasma metabolites produced in the different biochemical pathways evaluated in individuals with ASD. The search for high-performing bio-analytes to diagnose and follow-up ASD development is still a major target in medicine. Dysregulation in the oxidative stress response and proinflammatory processes are major etiological causes of ASD pathogenesis. Furthermore, dicarboxylic acid metabolites, cholesterol-related metabolites, phospholipid-related metabolites, and lipid transporters and mediators are impaired in different pathological conditions that have a role in the ASD etiology. A mechanism may exist by which pro-oxidant environmental stressors and abnormal metabolites regulate clinical manifestations and development of ASD.

Differential Lipidomic Characteristics of Children Born to Women with Polycystic Ovary Syndrome

OBJECTIVE

To describe the lipidomic characteristics of offspring born to polycystic ovary syndrome (PCOS) women (PCOS-off) and assess the associations between differential lipids and clinical phenotypes.

METHODS

Ultra performance liquid chromatography and mass spectrometry were performed on plasma samples from 70 PCOS-off and 71 healthy controls. The associations of differential metabolites with clinical phenotypes were examined by multiple linear regression.

RESULTS

Forty-four metabolites were significantly altered in PCOS-off, including 8 increased and 36 decreased. After stratification according to sex, 44 metabolites (13 increased and 31 decreased) were expressed differently in girls born to PCOS women (PCOS-g), most of which were glycerolipids. Furthermore, 46 metabolites (9 increased and 35 decreased) were expressed differently in boys born to PCOS women (PCOS-b), most of which were glycerophospholipids. Significant associations of metabolites with weight Z-score and high density lipoprotein cholesterol were found in PCOS-off. Triglycerides, low density lipoprotein cholesterol, and thyroid-stimulating hormone were separately correlated with some lipids in PCOS-g and PCOS-b.

CONCLUSIONS

PCOS-off showed specific lipid profile alterations. The abnormal level of glycerophospholipids and sphingomyelin indicated the risk of glucose metabolism and cardiovascular diseases in PCOS-off. Some lipids, such as phosphatidylcholines, lysophosphatidylcholine and sphingomyelin, may be the potential markers. The results broadened our understanding of PCOS-offs' cardiometabolic status and emphasized more specific and detailed monitoring and management in this population.

Sphingolipids as a Culprit of Mitochondrial Dysfunction in Insulin Resistance and Type 2 Diabetes

Insulin resistance is defined as a complex pathological condition of abnormal cellular and metabolic response to insulin. Obesity and consumption of high-fat diet lead to ectopic accumulation of bioactive lipids in insulin-sensitive tissues. Intracellular lipid accumulation is regarded as one of the major factors in the induction of insulin resistance and type 2 diabetes (T2D). A significant number of studies have described the involvement of ceramides and other sphingolipids in the inhibition of insulin-signaling pathway in both skeletal muscles and the liver. Adverse effects of sphingolipid accumulation have recently been linked to the activation of protein kinase Cζ (PKCζ) and protein phosphatase 2A (PP2A), which, in turn, negatively affect phosphorylation of serine/threonine kinase Akt [also known as protein kinase B (PKB)], leading to decreased glucose uptake in skeletal muscles as well as increased gluconeogenesis and glycogenolysis in the liver. Sphingolipids, in addition to their direct impact on the insulin signaling pathway, may be responsible for other negative aspects of diabetes, namely mitochondrial dysfunction and deficiency. Mitochondrial health, which is characterized by appropriate mitochondrial quantity, oxidative capacity, controlled oxidative stress, undisturbed respiratory chain function, adenosine triphosphate (ATP) production and mitochondrial proliferation through fission and fusion, is impaired in the skeletal muscles and liver of T2D subjects. Recent findings suggest that impaired mitochondrial function may play a key role in the development of insulin resistance. Mitochondria stay in contact with the endoplasmic reticulum (ER), Golgi membranes and mitochondria-associated membranes (MAM) that are the main places of sphingolipid synthesis. Moreover, mitochondria are capable of synthesizing ceramide though ceramide synthase (CerS) activity. Recently, ceramides have been demonstrated to negatively affect mitochondrial respiratory chain function and fission/fusion activity, which is also a hallmark of T2D. Despite a significant correlation between sphingolipids, mitochondrial dysfunction, insulin resistance and T2D, this subject has not received much attention compared to the direct effect of sphingolipids on the insulin signaling pathway. In this review, we focus on the current state of scientific knowledge regarding the involvement of sphingolipids in the induction of insulin resistance by inhibiting mitochondrial function.

Circulating Ceramides- Are Origins Important for Sphingolipid Biomarkers and Treatments?

Biomarkers are important tools for describing the adequacy or inadequacy of biological processes (to allow for the early and accurate diagnosis) and monitoring the biological effects of intervention strategies (to identify and develop optimal dose and treatment strategies). A number of lipid biomarkers are implicated in metabolic disease and the circulating levels of these biomarkers are used in clinical settings to predict and monitor disease severity. There is convincing evidence that specific circulating ceramide species can be used as biological predictors and markers of cardiovascular disease, atherosclerosis and type 2 diabetes mellitus. Here, we review the existing literature that investigated sphingolipids as biomarkers for metabolic disease prediction. What are the advantages and disadvantages? Are circulating ceramides predominantly produced in the liver? Will hepatic sphingolipid inhibitors be able to completely prevent and treat metabolic disease? As sphingolipids are being employed as biomarkers and potential metabolic disease treatments, we explore what is currently known and what still needs to be discovered.