Plasma Sphingolipids Research Articles

Plasma sphingolipids and depressive symptoms in coronary artery disease.

BackgroundDepression is highly prevalent in individuals with coronary artery disease (CAD) and increases the risk of future cardiac events and mortality. Sphingolipids have been implicated in the pathophysiology of both CAD and depression. This study assessed the association between plasma sphingolipid concentrations and depressive symptoms in CAD subjects.MethodsDepressive symptoms were measured using the depression subscale of the self‐reported Hospital Anxiety and Depression Scale (HADS). Sphingolipid concentrations were measured from fasting plasma samples using high‐performance liquid chromatography‐coupled electrospray ionization tandem mass spectrometry (LC/MS/MS). Linear regression models were used to assess associations between log‐transformed concentrations of plasma sphingolipids and depressive symptoms.ResultsA total of 111 CAD patients (mean (SD) age = 63.6 ± 6.4, 84.7% male) were included. In linear regression analyses, higher plasma concentrations of ceramides C16:0 (β = 0.204, p = .026) and C18:0 (β = 0.209, p = .023) and sphingomyelin SM18:1 (β = 0.210, p = .024) were significantly associated with higher HADS depression subscale score after adjusting for covariates.ConclusionSphingolipids, in particular the ceramide species C16:0 and C18:0 and the sphingomyelin species SM18:1, may be implicated in the pathophysiology of depression in CAD. The association between plasma sphingolipid concentrations and depression should be further examined in CAD patients and in other populations.

Serum lipid alterations in GBA-associated Parkinson's disease

IntroductionMutations in the GBA gene, encoding for the lysosomal enzyme glucocerebrosidase, are associated with Gaucher disease. Alterations in plasma sphingolipids have been reported in Gaucher, and similarly in brain extracts in Lewy body disease. As GBA mutations are prevalent risk factors for Parkinson's disease and overlap of molecular pathways are presumable, here we assessed the lipid profiles in Parkinson's patients with and without GBA mutations. MethodsWe sequenced all GBA exons in 415 Parkinson's patients, previously genotyped for LRRK2. 64 patients (29 GBA positive vs. 35 non-GBA-carriers including 18 LRRK2 positive and 17 non-mutated) were analyzed for chitotriosidase activity and for the concentration of 40 lipid classes using HPLC-MS. Results29/415 patients (6.9%) carried 8 different GBA mutations associated with Gaucher or Parkinson's, including one novel mutation. Chitotriosidase activity was similar across the genetic groups, while the levels of key lipids were altered in GBA mutation carriers: Monohexosylceramide, Ceramide and Sphingomyelin were elevated; while Phosphatidic acid (PA), Phosphatidylethanolamine (PE), Plasmalogen phosphatidylethanolamine (PEp) and Acyl Phosphatidylglycerol (AcylPG) were decreased. ConclusionThe results suggest an important role for these lipids in GBA mediated Parkinson's disease and assist in the identification of common pathways between Gaucher and Parkinson's. Ultimately, our findings may lead to the identification of novel biomarkers for individuals at increased risk of developing Parkinson's disease.

Plasma and ovarian tissue sphingolipids profiling in patients with advanced ovarian cancer.

The role of lipids in carcinogenesis through induction of abnormal cell lines in the human body is currently undisputable. Based on the literature, bioactive sphingolipids play an essential role in the development and progression of cancer and are involved in the metastatic process. The aim of this study was to determine the concentration of selected sphingolipids in patients with advanced ovarian cancer (AOC, FIGO III/IV, high grade ovarian cancer). Seventy-four patients with ovarian cancer were enrolled. Plasma concentrations of C16-Cer, C18:1-Cer and C18-Cer were assessed by LC/MS/MS. The content of tissue sphingolipids was measured using a UHPLC/MS/MS. Plasma concentration of 3 ceramides: C16-Cer, C18:1-Cer and C18-Cer was significantly elevated in women with advanced ovarian cancer compared to control group (P=0.031; 0.022; 0.020; respectively). There were increases in concentration of 5 ceramides: C16-Cer, C18:1-Cer, C18-Cer, C24:1-Cer, C24-Cer (P=0.025; 0.049; 0.032; 0.005; 0.013, respectively) and S1P (P=0.004) in ovarian tissue of women with advanced ovarian cancer compared to healthy individuals. Importantly, significantly higher risk of ovarian cancer when the plasma concentration of C16-Cer>311.88ng/100μl (AUC: 0.76, P=0.0261); C18:1-Cer>4.75ng/100μl (AUC: 0.77, P=0.0160) and C18-Cer>100.76ng/100μl (AUC:0.77, P=0.0136) was noticed. Bioactive sphingolipids play an essential role in the development and progression of cancer and they also take part in the process of metastasizing. This study suggests that some sphingolipids can be used as potential biomarkers of advanced ovarian cancer and that they can play an important role in the pathogenesis of this disease.

Plasma Sphingolipids are Associated With Gait Parameters in the Mayo Clinic Study of Aging.

Disrupted gait has been associated with an increased risk of frailty, disability, and death, but the causal molecular pathways are not well understood. Sphingolipids, including ceramides, are associated with multiple age-related diseases. Ceramides promote atrophy, necrosis, and proteolysis in cellular and animal models, and ceramide C16:0 levels are negatively correlated with muscle mass in men. However, there is a paucity of evidence examining sphingolipids and physical function. We examined the cross-sectional association between plasma ceramides, sphingosine-1-phosphate (S1P), and ceramide/S1P ratios and gait, a robust measure of physical function, in 340 clinically normal participants aged 70 years and older enrolled in the Mayo Clinic Study of Aging. GAITRite® instrumentation was used to measure gait speed, cadence, step width, double support time, and intra-individual stride time variability. Based on previous studies, we hypothesized that higher plasma levels of ceramide C16:0 would be associated with worse gait. Multivariable adjusted linear regression models revealed that higher levels of ceramide C16:0 were associated with slower gait speed, decreased cadence, and increased double support time. These results suggest an association between plasma ceramide C16:0 and physical function. Longitudinal studies are needed to determine whether elevated ceramide C16:0 can be utilized as a prognostic marker for functional decline.

Vitamin D Supplementation Enhances C18(dihydro)ceramide Levels in Type 2 Diabetes Patients.

Sphingolipids are characterized by a broad range of bioactive properties. Particularly, the development of insulin resistance, a major pathophysiological hallmark of Type 2 Diabetes mellitus (T2D), has been linked to ceramide signaling. Since vitamin D supplementation may slow down T2D progression by improving glucose concentrations and insulin sensitivity, we investigated whether vitamin D supplementation impacts on plasma sphingolipid levels in T2D patients. Thus, plasma samples of 59 patients with non-insulin-requiring T2D from a placebo-controlled, randomized, and double-blind study were retrospectively analyzed. Once per week, patients received either 20 drops of Vigantol oil, corresponding to a daily dose of 1904 IU/d vitamin D (verum: n = 31), or a placebo oil consisting of medium chain triglycerides (placebo: n = 28). Blood samples were taken from all of the participants at three different time points: 1) at the beginning of the study (baseline), 2) after 6 months supplementation, and 3) after an additional 6 months of follow-up. Plasma sphingolipids were measured by high-performance liquid chromatography tandem mass spectrometry. At baseline and 6 months follow-up, no significant differences in plasma sphingolipid species were detected between the placebo and verum groups. After 6 months, vitamin D supplementation significantly enhanced plasma C18dihydroceramide (dhCer; N-stearoyl-sphinganine (d18:0/18:0)) and C18ceramide (Cer; N-stearoyl-sphingosine (d18:1/18:0)) levels were observed in the verum group compared to the placebo group. This was accompanied by significantly higher 25-hydroxyvitamin D3 (25(OH)D3) blood levels in patients receiving vitamin D compared to the placebo group. Taken together, vitamin D supplementation induced changes of the C18 chain-length-specific dhCer and Cer plasma levels in patients with T2D. The regulation of sphingolipid signaling by vitamin D may thus unravel a novel mechanism by which vitamin D can influence glucose utilization and insulin action. Whether this acts favorably or unfavorably for the progression of T2D needs to be clarified.

Sphingolipids Profiling of Plasma in Patients with Diabetes Mellitus Associated with Atherosclerosis by a Novel Normal-Phase UPLC-QToF MS Method

A novel normal-phase UPLC-QToF MS method was developed for sphingolipids analysis, which was then applied to separate and identify seven classes of sphingolipids in plasma. The time-consuming of this novel method was much shorter than previous 2D LC–MS method, while the sensitivity, repeatability and resolution for sphingolipids analysis were better or comparable. Besides, the differences of lipids in human plasma among diabetes mellitus patients, diabetes mellitus associated with atherosclerosis patients and control subjects were also compared. Finally, 12 sphingolipids species were identified as the amounts of which in diabetes mellitus associated with atherosclerosis patients were significantly higher than them in diabetes mellitus patients (VIP >1.0, p value 1.5). As the isomers of GalCs and GluCs were successfully separated, it was found that five GluCs, rather than GalCs, were included in these 12 potential biomarkers. These results suggest the need to separate GalCs from GluCs, and also indicated that there may be some extra activation pathways of diabetes mellitus associated with atherosclerosis, different from the atherosclerosis pathway and the diabetes mellitus pathway, causing cardiovascular disease.

Low level of the plasma sphingolipid, glucosylceramide, is associated with thrombotic diseases

Unlabelled Box BackgroundOne previous pilot study suggested the association of low plasma glucosylceramide (GlcCer) levels with venous thrombosis (VTE) risk. ObjectiveWe aimed to confirm and evaluate the association of low plasma GlcCer levels with VTE and myocardial infarction (MI) occurrence, respectively. Patients and MethodsWe evaluated the association of GlcCer in two independent case‐control studies of Caucasian VTE populations (N=210 and 636) and one case‐control study of Caucasian MI patients (N=345). ResultPlasma GlcCer levels in VTE patients were lower compared to controls in two independent VTE populations (5.0 vs 5.8 μg/mL, P=.003 for the Scripps registry, and 5.6 vs 6.0 μg/mL, P=.001 for the Valencia registry, respectively). A low plasma GlcCer level (below tenth percentile of controls) was associated with increased VTE occurrence (odds ratio [OR]=3.7 [95% CI, 1.8‐7.9] for Scripps registry and OR=2.1 [95% CI, 1.3‐3.3] for Valencia registry, respectively). For the MI study, the median GlcCer plasma level was lower in MI patients than in controls (4.3 vs 5.6 μg/mL, P<.001), and a low level of GlcCer (below tenth percentile of control) was associated with higher MI occurrence (OR=7.7, [95% CI, 4.3‐13.8]). ConclusionLower concentration of GlcCer was associated with VTE occurrence in 2 independent studies and also with MI occurrence in 1 study.

A LIPIDOMICS APPROACH TO ASSESS PLASMA SPHINGOLIPIDS AS PREDICTORS OF VERBAL MEMORY PERFORMANCE IN CORONARY ARTERY DISEASE PATIENTS UNDERTAKING CARDIAC REHABILITATION: A C18:0 SIGNATURE FOR COGNITIVE RESPONSE TO EXERCISE

Early subtle deficits in verbal memory, which may indicate early neural risk, are common in those with coronary artery disease (CAD). Accordingly, CAD is associated with increased risks of mild cognitive impairment and Alzheimer's disease. While cognition may be improved by exercise interventions, cognitive response to exercise is heterogeneous. Altered lipid metabolism, a common feature of the clinical presentation of CAD, may be a fundamental mechanism underlying neural risk in CAD. In particular, sphingolipids have been associated with the development and progression of CAD, and suggested to play a role in impairing neural adaptation to exercise and inducing neurodegeneration. In this study, plasma concentrations of sphingolipids were assessed as predictors of verbal memory performance and performance in other cognitive domains in CAD subjects undertaking a 6-month cardiac rehabilitation (CR) program using a lipidomics approach. Verbal memory, visuospatial memory, processing speed, executive function and global cognition were assessed at entry into CR and at 3- and 6-months and Z-scores based on age, gender and education were calculated. Z-scores of related tests were summed into composite Z-scores to reflect performance in a cognitive domain. Plasma sphingolipid concentrations were measured at each time point from fasting blood samples using high performance liquid chromatography coupled electrospray ionization tandem mass spectrometry (LC/MS/MS). Bivariate associations using mixed models were used to identify sphingolipids that were significantly associated with performance in verbal memory and other cognitive domains over CR. Multivariate mixed models were used to assess the sphingolipid profile associated with change in cognitive performance over CR controlling for potential confounders. In patients with CAD (n=120, mean age=64±6 years, 84% male, years of education=16±3 years), an increase in fitness was associated with significant improvement in processing speed over CR (b[SE] = 0.02 [0.009], p=0.05). Lower ceramide C18:0 concentrations significantly predicted improvement in verbal memory performance (b[SE]=-0.55 [0.25], p=0.03), visuospatial memory (b[SE]=-0.44 [0.22], p=0.05), processing speed (b[SE]=-0.89 [0.32], p=0.006) and global cognition (b[SE]=-1.47 [0.59], p=0.01) over CR. Plasma ceramide C18:0 concentrations may be a sensitive marker of cognitive response to exercise in an at-risk population such as those with CAD.

Plasma Phospholipids and Sphingolipids Identify Stent Restenosis After Percutaneous Coronary Intervention

ObjectivesThe aim of this study was to evaluate the diagnostic utility of plasma metabolomic biomarkers for in-stent restenosis (ISR). BackgroundISR remains an issue for patients after percutaneous coronary intervention. Identification of biomarkers to predict ISR could be invaluable for patient care. MethodsNext-generation metabolomic profiling was performed in the discovery phase from the plasma of 400 patients undergoing percutaneous coronary intervention. In the validation phase, targeted analysis was conducted using stable isotope dilution–multiple reaction monitoring mass spectrometry in another independent group of 500 participants. ResultsA set of 6 plasma metabolites was discovered and validated for the diagnosis of ISR as early as 1 month after percutaneous coronary intervention. This biomarker panel classified patients with ISR and control subjects with sensitivity of 91% and specificity of 90% in the discovery phase. The diagnostic accuracy in the independent validation phase was 90% (95% confidence interval: 87% to 100%). The defined 6 metabolites all belong to sphingolipid and phospholipid metabolism, including phosphatidylcholine diacyl C36:0, phosphatidylcholine diacyl C34:2, phosphatidylinositol diacyl C36:4, phosphatidic acid C34:1, ceramide, and sphingomyelin diacyl 18:1/20:1. These biomarkers play essential roles in cell signaling that regulates the proliferation and migration of vascular smooth muscle cells. ConclusionsNext-generation metabolomics demonstrates powerful diagnostic value in estimating ISR-related metabolic disturbance. The defined plasma biomarkers provide better early diagnostic value compared with conventional imaging techniques.

Sphingolipids as a new factor in the pathomechanism of preeclampsia - Mass spectrometry analysis.

Objective(s) and designThe aim of the study was to analyse a panel of 11 sphingolipids in plasma and three blood fractions (platelet-poor plasma, platelets and red blood cells) of women with mild preeclampsia.Materials and methodsWe recruited 21 women between 25–40 weeks gestation with diagnosed mild preeclampsia to the study group and 36 healthy women with uncomplicated pregnancies, who corresponded with the study group according to gestational age, to the control group. To assess the concentration of 11 sphingolipids in the blood plasma and blood fractions, we used ultra-high performance liquid chromatography coupled with triple quadrupole mass spectrometry (UHPLC/MS/MS).ResultsWe showed a significant increase in the concentration of eight sphingolipids in the plasma of women with preeclampsia in comparison to the control group: Sph (p = 0.0032), S1P (p = 0.0289), C20-Cer (p < 0.0001), C18-Cer (p < 0.0001), C16-Cer (p = 0.012), C18:1-Cer (p = 0.003), C22-Cer (p = 0.0071), and C24:1-Cer (p = 0.0085).ConclusionWe showed that selected sphingolipids, especially C20-Cer and C18-Cer, are totally new factors in the pathomechanism of PE and that these bioactive lipids may play an important role in apoptosis and autophagy.

Temporal changes in sphingolipids and systemic insulin sensitivity during the transition from gestation to lactation.

Reduced insulin action develops naturally during the peripartum to ensure maternal nutrient delivery to the fetus and neonate. However, increased insulin resistance can facilitate excessive lipolysis which in turn promotes metabolic disease in overweight dairy cattle. Increased fatty acid availability favors the accumulation of the sphingolipid ceramide and is implicated in the pathogenesis of insulin resistance, however, the relationship between sphingolipid metabolism and insulin resistance during the peripartum remains largely unknown. Our objectives were to characterize temporal responses in plasma and tissue sphingolipids in lean and overweight peripartal cows and to establish the relationships between sphingolipid supply and lipolysis, hepatic lipid deposition, and systemic insulin action. Twenty-one multiparous lean and overweight Holstein cows were enrolled in a longitudinal study spanning the transition from gestation to lactation (d -21 to 21, relative to parturition). Plasma, liver, and skeletal muscle samples were obtained, and sphingolipids were profiled using LC/MS/MS. Insulin sensitivity was assessed utilizing intravenous insulin and glucose challenges. Our results demonstrated the following: first, insulin resistance develops postpartum concurrently with increased lipolysis and hepatic lipid accumulation; second, ceramides and glycosylated ceramides accumulate during the transition from gestation to lactation and are further elevated in overweight cows; third, ceramide accrual is associated with lipolysis and liver lipid accumulation, and C16:0- and C24:0-ceramide are inversely associated with systemic insulin sensitivity postpartum; fourth, plasma sphingomyelin, a potential source of ceramides reaches a nadir at parturition and is closely associated with feed intake; fifth, select sphingomyelins are lower in the plasma of overweight cows during the peripartal period. Our results demonstrate that dynamic changes occur in peripartal sphingolipids that are influenced by adiposity, and are associated with the onset of peripartal insulin resistance. These observations are in agreement with a putative potential role for sphingolipids in facilitating the physiological adaptations of peripartum.

Plasma cross-gestational sphingolipidomic analyses reveal potential first trimester biomarkers of preeclampsia.

IntroductionPreeclampsia (PE) is a gestational disorder, manifested in the second half of pregnancy by maternal hypertension, proteinuria and generalized edema. PE is a major cause of maternal and fetal morbidity and mortality, accounting for nearly 40% of all premature births worldwide. Bioactive sphingolipids are emerging as key molecules involved in etiopathogenesis of PE, characterized by maternal angiogenic imbalance and symptoms of metabolic syndrome. The aim of this study was to compare the cross-gestational profile of circulating bioactive sphingolipids in maternal plasma from preeclamptic (PE) versus normotensive control (CTL) subjects with the goal of identifying sphingolipids as candidate first trimester biomarkers of PE for early prediction of the disease.MethodsA prospective cohort of patients was sampled at the first, second and third trimester of pregnancy for each patient (11–14, 22–24, and 32–36 weeks´ gestation). A retrospective stratified study design was used to quantify different classes of sphingolipids in maternal plasma. We used a reverse-phase high-performance liquid chromatography-tandem mass spectrometry (HPLC-ESI-MS/MS) approach for determining different sphingolipid molecular species (sphingosine-1-phosphate (S1P), dihydro-sphingosine-1-phosphate (DH-S1P), sphingomyelins (SM) and ceramides (Cer)) in cross-gestational samples of human plasma from PE (n = 7, 21 plasma samples across pregnancy) and CTL (n = 7, 21 plasma samples across pregnancy) patients.ResultsPlasma levels of angiogenic S1P did not change significantly in control and in preeclamptic patients´ group across gestation. DH-S1P was significantly decreased in second trimester plasma of PE patients in comparison to their first trimester, which could contribute to reduced endothelial barrier observed in PE. The major ceramide species (Cer 16:0 and Cer 24:0) tended to be up-regulated in plasma of control and PE subjects across gestation. The levels of a less abundant plasma ceramide species (Cer 14:0) were significantly lower in first trimester plasma of PE patients when compared with their gestational-matched control samples (p = 0.009). Major plasma sphingomyelin species (SM 16:0, SM 18:1 and SM 24:0) tended to be higher in control pregnancies across gestation. However, in PE patients, SM 16:0, SM 18:0 and SM 18:1 showed significant up-regulation across gestation, pointing to atherogenic properties of the sphingomyelins and particularly the potential contribution of SM 18:0 to the disease development. In addition, two major sphingomyelins, SM 16:0 and SM 18:0, were significantly lower in first trimester plasma of PE patients versus first trimester samples of respective controls (p = 0.007 and p = 0.002, respectively).ConclusionsCross-gestational analysis of maternal plasma of preeclamptic and normotensive women identifies differences in the biochemical profile of major sphingolipids (DH-S1P, sphingomyelins and ceramides) between these two groups. In addition, first trimester maternal plasma sphingolipids (Cer 14:0, SM 16:0 and SM 18:0) may serve in the future as early biomarkers of PE occurrence and development.

Effects of Blood Cholesterol Levels and Dietary Fatty Acids on Sphingolipid Profiles in Plasma, Liver and Adipose Tissue

ObjectivesSphingolipids are bioactive lipid compounds that are involved in many cellular pathways. Ceramides, in particular ceramide C16, have been implicated as mediators of metabolic syndrome including weight gain, glucose intolerance and susceptibility to diet‐induced metabolic dysfunction. Increased ceramide C24 has been associated with protection against high‐fat diet induced obesity and glucose intolerance. Elevated blood cholesterol is a risk factor for atherosclerosis. We have showed that replacement of saturated fats (SAT) by n‐3 fatty acids (n‐3 FAs) in high‐fat, high‐cholesterol diets reduced elevated plasma lipid levels and atherosclerosis in LDL receptor knock‐out (LDLR−/−) mice. Elevated plasma free FAs or high‐fat diets have been shown to increase ceramides associated with diabetes and cardiovascular disease. We questioned whether increased blood cholesterol affects sphingolipid profiles in blood and tissues and then evaluated the effects of SAT and n‐3 FA on modulating sphingolipid composition in both wild type (WT) and LDLR−/− mice.MethodsC57BL/6 WT and LDLR−/− mice were fed a regular rodent chow diet or a custom‐made eucaloric high‐fat (40% of fat) diet enriched in either SAT or n‐3 FA for 12 weeks. Mouse plasma, hepatic and white adipose tissue (WAT) sphingolipid profiles were determined by liquid chromatography coupled to electrospray ionization triple quad tandem mass spectrometry (ESI LC‐MS/MS). Assayed molecular species and their relative location in the sphingolipid metabolic pathway are summarized in Figure.ResultsCompared to WT, LDLR deletion increased plasma dihydroceramides (DHs), C24 ceramides (p&lt;0.0003) and sphingomyelins (SMs) (p&lt;0.001), WAT DHs (p&lt;0.0001) and WAT total ceramides (p&lt;0.0002). LDLR deletion did not affect ceramide C16 levels in plasma, WAT or liver sphingolipid profiles. Comparison of high‐fat diets show that compared to SAT, n‐3 diet markedly decreased plasma total DHs (p&lt;0.005), ceramides (C16, C20, C24, C24:1) (p&lt;0.0002) in WT and LDLR−/−. n‐3 diet decreased total plasma SMs in WT (p&lt;0.006) but increased total plasma SMs in LDLR−/−(p&lt;0.018). In contrast to an overall decrease in plasma sphingolipids mediated by n‐3 FA in LDLR−/− mice, major ceramides (C16, C18, C20 and C22) were decreased in WAT in n‐3 fed LDLR−/− mice. n‐3 FA also reduced hepatic DHs and SMs in both WT (~ 2 fold, p&lt;0.023) and LDLR−/−(~50%, p=0.056). Ratios of DH/ceramide C16 to C24/C24:1 were markedly improved by n‐3 FA feeding in liver and WAT in both WT and LDLR−/− mice. Our previously published data show that n‐3 FA did not affect plasma cholesterol in WT, but led to &gt; 2/3 decrease in hypercholesterolemic LDLR−/− mice (p&lt;0.05).ConclusionOur results demonstrate that LDLR deletion and diet content of n‐3 FA modulate plasma sphingolipid levels in blood and major tissue components. We suggest one mechanism whereby n‐3 FA ameliorating metabolic dysfunction is through changes in ratios of C16/C24 in tissues, such as liver or adipose tissue, that are important in pathways related to metabolic and cardiovascular diseases.

Plasma sphingolipids in HIV-associated chronic obstructive pulmonary disease

IntroductionChronic obstructive pulmonary disease (COPD) is a significant cause of morbidity in persons living with HIV (PLWH) and HIV appears to uniquely cause COPD, independent of smoking. The mechanisms by...

Dysregulations in circulating sphingolipids associate with disease activity indices in female patients with systemic lupus erythematosus: a cross-sectional study

Objective The objective of this study was to investigate the association of clinical and renal disease activity with circulating sphingolipids in patients with systemic lupus erythematosus. Methods We used liquid chromatography tandem mass spectrometry to measure the levels of 27 sphingolipids in plasma from 107 female systemic lupus erythematosus patients and 23 controls selected using a design of experiment approach. We investigated the associations between sphingolipids and two disease activity indices, the Systemic Lupus Activity Measurement and the Systemic Lupus Erythematosus Disease Activity Index. Damage was scored according to the Systemic Lupus International Collaborating Clinics damage index. Renal activity was evaluated with the British Island Lupus Activity Group index. The effects of immunosuppressive treatment on sphingolipid levels were evaluated before and after treatment in 22 female systemic lupus erythematosus patients with active disease. Results Circulating sphingolipids from the ceramide and hexosylceramide families were increased, and sphingoid bases were decreased, in systemic lupus erythematosus patients compared to controls. The ratio of C16:0-ceramide to sphingosine-1-phosphate was the best discriminator between patients and controls, with an area under the receiver-operating curve of 0.77. The C16:0-ceramide to sphingosine-1-phosphate ratio was associated with ongoing disease activity according to the Systemic Lupus Activity Measurement and the Systemic Lupus Erythematosus Disease Activity Index, but not with accumulated damage according to the Systemic Lupus International Collaborating Clinics Damage Index. Levels of C16:0- and C24:1-hexosylceramides were able to discriminate patients with current versus inactive/no renal involvement. All dysregulated sphingolipids were normalized after immunosuppressive treatment. Conclusion We provide evidence that sphingolipids are dysregulated in systemic lupus erythematosus and associated with disease activity. This study demonstrates the utility of simultaneously targeting multiple components of a pathway to establish disease associations.

New insights into the effects of onion consumption on lipid mediators using a diet-induced model of hypercholesterolemia

The levels and roles of lipid mediators can be modified in response to nutritional stimuli. The aim of this study was to investigate shifts in oxylipin and sphingolipid profiles stimulated by a hypercholesterolemic (HC) diet along with the modulating effects of onion introduced as an antioxidant functional ingredient characterized in the diet (HCO). Oxylipin and sphingolipid profiles were determined in plasma and tissues from Wistar rats using LC-MS/MS. Plasma ω-3 and ω-6 PUFA-derived oxylipins decreased in rats after 7 weeks of HC feeding, but did not evidence a further shift with HCO diet. Onion ingredient supplementation modulated the hepatic concentrations of prostaglandins and enhanced ω-3 oxylipins in the liver of HCO-fed rats relative to the HC group. The HC diet induced shifts in plasma sphingolipids, increasing sphingoid bases, dihydroceramides and ceramides, whilst the sphingomyelin, hexosylceramide and lactosylceramide families decreased. The HCO diet modified some HC diet-induced changes in sphingolipids in liver and spleen tissue. Onion supplementation effected changes in lipid mediator levels in diet-induced hypercholesterolemic Wistar rats. The potential of onion as regulator of pro-inflammatory mediators, and possible enhancer of pro-resolution pathways, warrants further study of the interaction of functional ingredients with bioactive lipid mediators and their potential impact on inflammation, oxidative stress and organ dysfunction.

Efficient replacement of plasma membrane outer leaflet phospholipids and sphingolipids in cells with exogenous lipids

Our understanding of membranes and membrane lipid function has lagged far behind that of nucleic acids and proteins, largely because it is difficult to manipulate cellular membrane lipid composition. To help solve this problem, we show that methyl-α-cyclodextrin (MαCD)-catalyzed lipid exchange can be used to maximally replace the sphingolipids and phospholipids in the outer leaflet of the plasma membrane of living mammalian cells with exogenous lipids, including unnatural lipids. In addition, lipid exchange experiments revealed that 70-80% of cell sphingomyelin resided in the plasma membrane outer leaflet; the asymmetry of metabolically active cells was similar to that previously defined for erythrocytes, as judged by outer leaflet lipid composition; and plasma membrane outer leaflet phosphatidylcholine had a significantly lower level of unsaturation than phosphatidylcholine in the remainder of the cell. The data also provided a rough estimate for the total cellular lipids residing in the plasma membrane (about half). In addition to such lipidomics applications, the exchange method should have wide potential for investigations of lipid function and modification of cellular behavior by modification of lipids.

Palmitic acid feeding increases ceramide supply in association with increased milk yield, circulating nonesterified fatty acids, and adipose tissue responsiveness to a glucose challenge.

Reduced insulin action is a key adaptation that facilitates glucose partitioning to the mammary gland for milk synthesis and enhances adipose tissue lipolysis during early lactation. The progressive recovery of insulin sensitivity as cows advance toward late lactation is accompanied by reductions in circulating nonesterified fatty acids (NEFA) and milk yield. Because palmitic acid can promote insulin resistance in monogastrics through sphingolipid ceramide-dependent mechanisms, palmitic acid (C16:0) feeding may enhance milk production by restoring homeorhetic responses. We hypothesized that feeding C16:0 to mid-lactation cows would enhance ceramide supply and ceramide would be positively associated with milk yield. Twenty multiparous mid-lactation Holstein cows were enrolled in a study consisting of a 5-d covariate, 49-d treatment, and 14-d posttreatment period. All cows were randomly assigned to a sorghum silage-based diet containing no supplemental fat (control; n=10; 138±45 d in milk) or C16:0 at 4% of ration dry matter (PALM; 98% C16:0; n=10; 136±44 d in milk). Blood and milk were collected at routine intervals. Liver and skeletal muscle tissue were biopsied at d 47 of treatment. Intravenous glucose tolerance tests (300mg/kg of body weight) were performed at d -1, 24, and 49 relative to start of treatment. The plasma and tissue concentrations of ceramide and glycosylated ceramide were determined using liquid chromatography coupled with tandem mass spectrometry. Data were analyzed as repeated measures using a mixed model with fixed effects of treatment and time, and milk yield served as a covariate. The PALM treatment increased milk yield, energy-corrected milk, and milk fat yield. The most abundant plasma and tissue sphingolipids detected were C24:0-ceramide, C24:0-monohexosylceramide (GlcCer), and C16:0-lactosylceramide. Plasma concentrations of total ceramide and GlcCer decreased as lactation advanced, and ceramide and GlcCer were elevated in cows fed PALM. Palmitic acid feeding increased hepatic ceramide levels, a response not observed in skeletal muscle tissue. Plasma ceramides (e.g., C24:0-ceramide) were positively correlated with plasma NEFA and milk yield, and positively correlated with NEFA levels following a glucose challenge. Our data demonstrate a remodeled plasma and hepatic sphingolipidome in mid-lactation dairy cows fed PALM. The potential involvement in ceramide in homeorhetic nutrient partitioning to support lactation requires further consideration.

Up-regulation of Plasma Hexosylceramide (d18: 1/18: 1) Contributes to Genotype 2 Virus Replication in Chronic Hepatitis C: A 20-Year Cohort Study.

The aim of the present study was to explore the relationship between plasma sphingolipids and hepatitis C virus (HCV) replication in chronic hepatitis C (CHC) patients.A cohort of 120 treatment-naïve CHC patients was included. Liver biopsies and the Scheuer scoring system were used to assess hepatic inflammatory activity. Blood biochemical indicators, HCV-RNA load, and immunological markers were also measured. Forty-four plasma sphingolipids were identified and quantified using high-performance liquid chromatography-tandem mass spectrometry.The hexosylceramide (HexCer) (d18:1/18:1) level was significantly different between patients with a low HCV load (<10 IU/mL) and a high HCV load (≥10 IU/mL), and it was positively correlated with the HCV-RNA load (r = 0.337, P = 0.001) in CHC patients. Additionally, the plasma HexCer (d18:1/18:1) level (odds ratio 1.302, 95% confidence interval 1.129-1.502) was an independent factor for a high HCV-RNA load. For patients with hepatic inflammation grade ≤2 or HCV genotype 2, HexCer (d18:1/18:1) was independently related to a high HCV-RNA load.Plasma HexCer (d18:1/18:1) might be involved in the high viral replication level in chronic HCV infection, especially for CHC patients with genotype 2.

Peripheral sphingolipids are associated with variation in white matter microstructure in older adults

Sphingolipids serve important structural and functional roles in cellular membranes and myelin sheaths. Plasma sphingolipids have been shown to predict cognitive decline and Alzheimer's disease. However, the association between plasma sphingolipid levels and brain white matter (WM) microstructure has not been examined. We investigated whether plasma sphingolipids (ceramides and sphingomyelins) were associated with magnetic resonance imaging-based diffusion measures, fractional anisotropy (FA), and mean diffusivity, 10.5 years later in 17 WM regions of 150 cognitively normal adults (mean age 67.2). Elevated ceramide species (C20:0, C22:0, C22:1, and C24:1) were associated with lower FA in multiple WM regions, including total cerebral WM, anterior corona radiata, and the cingulum of the cingulate gyrus. Higher sphingomyelins (C18:1 and C20:1) were associated with lower FA in regions such as the anterior corona radiata and body of the corpus callosum. Furthermore, lower sphingomyelin to ceramide ratios (C22:0, C24:0, and C24:1) were associated with lower FA or higher mean diffusivity in regions including the superior and posterior corona radiata. However, although these associations were significant at the a priori p < 0.05, only associations with some regional diffusion measures for ceramide C22:0 and sphingomyelin C18:1 survived correction for multiple comparisons. These findings suggest plasma sphingolipids are associated with variation in WM microstructure in cognitively normal aging.