Serum Ceramides Research Articles

Serum ceramides and type 2 diabetes are mutually independent predictors of cardiovascular events in patients with peripheral artery disease

Abstract Introduction: Ceramides are enriched in atherosclerotic plaques, and a set of circulating ceramides including Cer(d18:1/16:0), Cer(d18:1/18:0), Cer(d18:1/24:1), and Cer(d18:1/24:0) has recently emerged as predictors of cardiovascular outcomes in coronary artery disease patients. Hypothesis: We hypothesize that they have the power to predict cardiovascular events in patients with peripheral artery disease (PAD). Methods: We measured the serum concentrations of the above mentioned ceramides in a cohort of 380 patients with sonographically proven PAD, of whom 107 had type 2 diabetes (T2DM). Prospectively, we recorded 221 cardiovascular events over a mean follow-up time of 6.3±2.3 years. Results: Cardiovascular event risk was higher in T2DM patients than in those who did not have diabetes (69 vs. 52%, p=0.001). The ceramides Cer(18:1/16:0) and Cer(18:1/24:1) and the respective ratios Cer(18:1/16:0) / Cer(18:1/24:0) and Cer(18:1/24:1) / Cer(18:1/24:0) were significant predictors of cardiovascular events both univariately and after multivariate adjustment including the presence of T2DM (figure). Conversely, T2DM predicted cardiovascular events independently from the investigated ceramides (adjusted HR 1.76 [1.31-2.35], p<0.001). Conclusions: We conclude that the investigated ceramides and T2DM are mutually independent predictors of cardiovascular events in PAD patients.

Effect of conjugated estrogens and bazedoxifene on glucose, energy and lipid metabolism in obese postmenopausal women.

Combining conjugated estrogens (CE) with the selective estrogen receptor modulator bazedoxifene (BZA) is a novel, orally administered menopausal therapy. We investigated the effect of CE/BZA on insulin sensitivity, energy metabolism, and serum metabolome in postmenopausal women with obesity. Randomized, double-blind, crossover pilot trial with washout was conducted at Pennington Biomedical Research Center. Eight postmenopausal women (age 50-60 years, BMI 30-40 kg/m2) were randomized to 8 weeks CE/BZA or placebo. Primary outcome was insulin sensitivity (hyperinsulinemic-euglycemic clamp). Secondary outcomes included body composition (DXA); resting metabolic rate (RMR); substrate oxidation (indirect calorimetry); ectopic lipids (1H-MRS); fat cell size, adipose and skeletal muscle gene expression (biopsies); serum inflammatory markers; and serum metabolome (LC/MS). CE/BZA treatment produced no detectable effect on insulin sensitivity, body composition, ectopic fat, fat cell size, or substrate oxidation, but resulted in a non-significant increase in RMR (basal: P = 0.06; high-dose clamp: P = 0.08) compared to placebo. CE/BZA increased serum high-density lipoprotein (HDL)-cholesterol. CE/BZA also increased serum diacylglycerol (DAG) and triacylglycerol (TAG) species containing long-chain saturated, mono- and polyunsaturated fatty acids (FAs) and decreased long-chain acylcarnitines, possibly reflecting increased hepatic de novo FA synthesis and esterification into TAGs for export into very low-density lipoproteins, as well as decreased FA oxidation, respectively (P < 0.05). CE/BZA increased serum phosphatidylcholines, phosphatidylethanolamines, ceramides, and sphingomyelins, possibly reflecting the increase in serum lipoproteins (P < 0.05). A short treatment of obese postmenopausal women with CE/BZA does not alter insulin action or ectopic fat but increases serum markers of hepatic de novo lipogenesis and TAG production.

Ceramides and Ceramide Scores: Clinical Applications for Cardiometabolic Risk Stratification.

Ceramides are bioactive lipids that have an important role in many cellular functions such as apoptosis and inflammation. During the past decade emerging clinical data have shown that ceramides are not only of great biochemical interest but may also have diagnostic utility. Ceramides have shown independent predictive value for negative cardiovascular outcomes as well as for the onset of type 2 diabetes. Based on abundant published data, risk score using the concentrations of circulating ceramides have been developed and adapted for routine clinical practice. Currently serum ceramides are used clinically as efficient risk stratifiers for primary and secondary prevention of atherosclerotic cardiovascular disease (CVD). A direct cause-effect relationship between CVD and ceramide has not been established to date. As ceramide-specific medications are being developed, conventional strategies such as lipid lowering agents and lifestyle interventions can be used to reduce overall risk. Ceramides can identify a very high-risk coronary heart disease category of patients in need for more intense medical attention, specifically those patients at higher risk as highlighted in the 2019 European Society of Cardiology guidelines for stable chronic coronary syndrome patients. In addition, the ceramide risk score may be used as a decision-making tool in primary prevention patients with moderate CVD risk. Finally, the ceramide risk score may have a unique utility as a motivational tool to increase patient's adherence to medical therapy and lifestyle changes.

Too Much of a Good Thing? An Evolutionary Theory to Explain the Role of Ceramides in NAFLD.

Non-alcoholic fatty liver disease (NAFLD), which ranges from the relatively benign and reversible fatty liver (NAFL) to the more advanced and deadly steatohepatitis (NASH), affects a remarkably high percentage of adults in the population. Depending upon severity, NAFLD can increase one's risk for diabetes, cardiovascular disease, and hepatocellular carcinoma. Though the dominant histological feature of all forms of the disease is the accumulation of liver triglycerides, these molecules are likely not pathogenic, but rather serve to protect the liver from the damaging consequences of overnutrition. We propose herein that the less abundant ceramides, through evolutionarily-conserved actions intended to help organisms adapt to nutrient excess, drive the cellular events that define NAFL/NASH. In early stages of the disease process, they promote lipid uptake and storage, whilst inhibiting utilization of glucose. In later stages, they stimulate hepatocyte apoptosis and fibrosis. In rodents, blocking ceramide synthesis ameliorates all stages of NAFLD. In humans, serum and liver ceramides correlate with the severity of NAFLD and its comorbidities diabetes and heart disease. These studies identify key roles for ceramides in these hepatic manifestations of the metabolic syndrome.

1886-P: Serum Dihydroceramides Predict Insulin Sensitivity in Humans and Cause Insulin Resistance In Vitro

Serum ceramides are related to insulin resistance, decrease after insulin sensitizing lifestyle interventions, and are linked to CVD risk in humans. To what extent other serum sphingolipids may serve to regulate insulin sensitivity remains unknown. We performed this study to quantify a broad range of serum sphingolipids in individuals spanning the physiologic range of insulin sensitivity, and to determine if specific sphingolipid species promote insulin resistance in vitro. We evaluated serum sphingolipid content in lean (n=15), endurance trained athletes (n=16), obese (n=15), and people with type 2 diabetes (T2D; n=12). Insulin sensitivity was assessed by hyperinsulinemic-euglycemic clamps and serum sphingolipids measured using targeted lipidomics. Quantitative sphingolipid analysis revealed no differences between sphinganine, sphingosine, glucosyl- and lactosyl-ceramides, gangliosides, sphingomyelins, and sulfatides. Total serum ceramides were significantly increased in obese compared to lean individuals (p=0.01), with significant inverse relationships between C18:0 (p=0.002), C20:0 (p=0.02), and C22:0 (p-0.009) species and insulin sensitivity. Total serum dihydroceramides (p=0.0007) and most individual species were significantly greater in obese and T2D compared to lean and athletes, with C18:0 dihydroceramide showing the strongest inverse relationship to insulin sensitivity (p=0.002). We administered C18:0 dihydroceramide in liposomes to primary cultured myocytes and found that it significantly decreased insulin sensitivity in vitro by 36 +/- 6% (p=0.002), measured by insulin-stimulated glycogen synthesis. These data extend what is known regarding ceramides and insulin resistance and show a novel potential role for serum dihydroceramides, especially C18:0 species, in predicting and promoting insulin resistance in humans. Disclosure S. Zarini: None. J.T. Brozinick: Employee; Self; Eli Lilly and Company. L. Perreault: Advisory Panel; Self; Novo Nordisk Inc., Sanofi. Speaker’s Bureau; Self; AstraZeneca, Boehringer Ingelheim Pharmaceuticals, Inc., Janssen Pharmaceuticals, Inc., Merck &amp; Co., Inc., Novo Nordisk Inc. S.A. Newsom: None. D.E. Kahn: None. A. Kerege: None. K.A. Harrison: None. B.C. Bergman: Consultant; Spouse/Partner; Novo Nordisk Inc., Sanofi US. Research Support; Self; Eli Lilly and Company. Speaker’s Bureau; Spouse/Partner; AstraZeneca, Boehringer Ingelheim Pharmaceuticals, Inc., Janssen Pharmaceuticals, Inc., Merck &amp; Co., Inc. Funding National Institutes of Health (R01DK089170, T32DK07658, P30DK048520, RR-00036)

Increased Level of Serum Ceramides Correlate with Liver Steatosis, Hba1c and Cholesterol in Obese Patients

Objective: Sphingolipids including ceramides are biological active components of all cell membranes. They play a great role in cell interconnections in the process of proliferation, maturation, cell apoptosis and any fluctuations of their level can lead to development of metabolic diseases such as type 2 diabetes (T2D) and nonalcoholic fatty liver disease. Nevertheless, there is lack of information about what type of ceramides play a role in aforementioned diseases. Here we investigated the relationship between the serum level of some type of ceramides and parameters of metabolic syndrome that is commonly present in obese patients. Design: We performed cross-sectional study in two groups. One of them was control group – lean healthy people (n=10, body mass index, BMI 21, 2±1, 89) and the second group included patients with the obesity (n=24, BMI 33, 9±3, 1). We quantified the levels of serum ceramide by liquid chromatography-mass spectrometry, analyzed the parameters for insulin resistance, liver function and lipid metabolism by biochemical blood test. Results: The subjects with obesity had elevated level of ceramide C16:0, C18:0, C24:0 comparing with control group (p&lt;0,001). As results of our study, we found correlation of the level ceramide C16:0, C18:0, C24:0 with the results of steatometry and some metabolic parameters (glycosylated hemoglobin (Hb A1C), cholesterol). Conclusion: These results demonstrate that obese subjects had increased level of ceramide C16:0, C18:0, C24:0 that correlated with some metabolic parameters supposedly recognizing them as new biomarkers of metabolic syndrome.

Increased Level of Serum Ceramides Correlate with Liver Steatosis, Hba1c and Cholesterol in Obese Patients

Objective: Sphingolipids including ceramides are biological active components of all cell membranes. They play a great role in cell interconnections in the process of proliferation, maturation, cell apoptosis and any fluctuations of their level can lead to development of metabolic diseases such as type 2 diabetes (T2D) and nonalcoholic fatty liver disease. Nevertheless, there is lack of information about what type of ceramides play a role in aforementioned diseases. Here we investigated the relationship between the serum level of some type of ceramides and parameters of metabolic syndrome that is commonly present in obese patients. Design: We performed cross-sectional study in two groups. One of them was control group – lean healthy people (n=10, body mass index, BMI 21, 2±1, 89) and the second group included patients with the obesity (n=24, BMI 33, 9±3, 1). We quantified the levels of serum ceramide by liquid chromatography-mass spectrometry, analyzed the parameters for insulin resistance, liver function and lipid metabolism by biochemical blood test. Results: The subjects with obesity had elevated level of ceramide C16:0, C18:0, C24:0 comparing with control group (p&lt;0,001). As results of our study, we found correlation of the level ceramide C16:0, C18:0, C24:0 with the results of steatometry and some metabolic parameters (glycosylated hemoglobin (Hb A1C), cholesterol). Conclusion: These results demonstrate that obese subjects had increased level of ceramide C16:0, C18:0, C24:0 that correlated with some metabolic parameters supposedly recognizing them as new biomarkers of metabolic syndrome.

Serum Ceramides Level in Systemic Lupus Erythematosus (SLE) Patients as a Novel Marker for Renal Impairment

Serum Ceramides Level in Systemic Lupus Erythematosus (SLE) Patients as a Novel Marker for Renal Impairment

Abstract WP208: Lower Fractional Anisotropy in White Matter Tracts is Associated With Decreased Manipulative Manual Dexterity Higher Circulating Ceramide Levels in Healthy High-Risk Middle-Aged Individuals

Introduction: We previously reported impaired manipulative manual dexterity measured by grooved peg-board test (GPBT) in healthypeople with increased total brain ischemic white matter hyperintensities. We hypothesized that preclinical white matter tract damage (WMTD), measured as lower regional fractional anisotropy (rFA), is associated with functional decrements measured with GPBT, and with a biomarker of white matter disease, serum ceramides. Methods: Participants were recruited from the GeneSTAR study in families with a history of coronary artery disease. Diffusion tensor imaging was acquired on a Phillips 3T MRI and rFA was calculated using the 181 Eve segmented atlas. 48 susceptible regions for WMTD were analyzed.Liquid chromatography was used to measure ceramides (C). Spearman’s rank correlation (SRC) was used to test statistical associations and Bonferroni method was used to correct for multiple comparisons. Multivariate analysis (GEE) adjusting for age, sex, race and education was performed for associations that were significant in the univariate analyses. Result: Subjects (n=112) were 49±11 years; 49% male and 39% African American. rFA was correlated with decrements on GPBT in the left (L) anterior corona radiata, L genu of the corpus callosum (LGCC), L external capsule, and L &amp; right fornix (RF) (P=0.0009, 0.0008, 0.0002, 0.0003 and 8.2E-07, respectively). Additionally, rFA was negatively correlated with C18:0 in the RF and LGCC (P=1.27E-05 and 2.58E-05, respectively) and C20:0 in RF (P=6.09E-06). C18:0 was correlated with decrements on GPBT (P=0.0025). GEE showed associations between decremental GPBT and rFA in the RF (B = -0.52, 95% CI -1 - 0.03, p= 0.037), between rFA in the RF and Ceramide (C18:0, B= -0.03, 95% CI -0.046--0.0073, p=0.007, C20:0, B=-0.0002, 95%CI -0.0003-0, P= 0.018), as well as rFA in LGCC and Ceramide (C18:0, B=-0.0097, 95% CI -0.019--0.006, P=0.037). GBPT and ceramides were not associated when adjusted for rFA (B = 0.0002 95% CI -0.052 - 0.052 P= 0.99). Conclusion: These analyses support our hypothesis that preclinical WMTD represented by reduced rFA, may undermine neural networks affecting manipulative manual dexterity, with concomitant elevation in serum ceramides in healthy high risk people.

Diesel Exhaust Particle Exposure Compromises Alveolar Macrophage Mitochondrial Bioenergetics

Diesel exhaust particles (DEPs) are known pathogenic pollutants that constitute a significant quantity of air pollution. Given the ubiquitous presence of macrophages throughout the body, including the lungs, as well as their critical role in tissue and organismal metabolic function, we sought to determine the effect of DEP exposure on macrophage mitochondrial function. Following daily DEP exposure in mice, pulmonary macrophages were isolated for mitochondrial analyses, revealing reduced respiration rates and dramatically elevated H2O2 levels. Serum ceramides and inflammatory cytokines were increased. To determine the degree to which the changes in mitochondrial function in macrophages were not dependent on any cross-cell communication, primary pulmonary murine macrophages were used to replicate the DEP exposure in a cell culture model. We observed similar changes as seen in pulmonary macrophages, namely diminished mitochondrial respiration, but increased H2O2 production. Interestingly, when treated with myriocin to inhibit ceramide biosynthesis, these DEP-induced mitochondrial changes were mitigated. Altogether, these data suggest that DEP exposure may compromise macrophage mitochondrial and whole-body function via pathologic alterations in macrophage ceramide metabolism.

Elevated serum ceramides are linked with obesity-associated gut dysbiosis and impaired glucose metabolism.

Low gut microbiome richness is associated with dyslipidemia and insulin resistance, and ceramides and other sphingolipids are implicated in the development of diabetes. Determine whether circulating sphingolipids, particularly ceramides, are associated with alterations in the gut microbiome among obese patients with increased diabetes risk. This was a cross-sectional and longitudinal retrospective analysis of a dietary/weight loss intervention. Fasted serum was collected from 49 participants (41 women) and analyzed by HPLC-MS/MS to quantify 45 sphingolipids. Shotgun metagenomic sequencing of stool was performed to profile the gut microbiome. Confirming the link to deteriorated glucose homeostasis, serum ceramides were positively correlated with fasting glucose, but inversely correlated with fasting and OGTT-derived measures of insulin sensitivity and β-cell function. Significant associations with gut dysbiosis were demonstrated, with SM and ceramides being inversely correlated with gene richness. Ceramides with fatty acid chain lengths of 20-24 carbons were the most associated with low richness. Diet-induced weight loss, which improved gene richness, decreased most sphingolipids. Thirty-one MGS, mostly corresponding to unidentified bacteria species, were inversely correlated with ceramides, including a number of Bifidobacterium and Methanobrevibacter smithii. Higher ceramide levels were also associated with increased metagenomic modules for lipopolysaccharide synthesis and flagellan synthesis, two pathogen-associated molecular patterns, and decreased enrichment of genes involved in methanogenesis and bile acid metabolism. This study identifies an association between gut microbiota richness, ceramides, and diabetes risk in overweight/obese humans, and suggests that the gut microbiota may contribute to dysregulation of lipid metabolism in metabolic disorders.

Withaferin A Improves Nonalcoholic Steatohepatitis in Mice.

Nonalcoholic steatohepatitis (NASH) is the progressive stage of nonalcoholic fatty liver disease that highly increases the risk of cirrhosis and liver cancer, and there are few therapeutic options available in the clinic. Withaferin A (WA), extracted from the ayurvedic medicine Withania somnifera, has a wide range of pharmacological activities; however, little is known about its effects on NASH. To explore the role of WA in treating NASH, two well defined NASH models were used, the methionine-choline-deficient diet and the 40 kcal% high-fat diet (HFD). In both NASH models, WA treatment or control vehicle was administered to evaluate its hepatoprotective effects. As assessed by biochemical and histologic analyses, WA prevented and therapeutically improved liver injury in both models, as revealed by lower serum aminotransaminases, hepatic steatosis, liver inflammation, and fibrosis. In the HFD-induced NASH model, both elevated serum ceramides and increased hepatic oxidative stress were decreased in the WA-treated group compared with the control vehicle-treated group. To further explore whether WA has an anti-NASH effect independent of its known action in leptin signaling associated with obesity, leptin signaling-deficient ob/ob mice maintained on an HFD were used to induce NASH. WA therapeutically reduced NASH in HFD-treated leptin-deficient ob/ob mice, thus demonstrating a leptin-independent hepatoprotective effect. This study revealed that WA treatment could be an option for NASH treatment.

Overeating Saturated Fat Promotes Fatty Liver and Ceramides Compared With Polyunsaturated Fat: A Randomized Trial.

ContextSaturated fatty acid (SFA) vs polyunsaturated fatty acid (PUFA) may promote nonalcoholic fatty liver disease by yet unclear mechanisms.ObjectiveTo investigate if overeating SFA- and PUFA-enriched diets lead to differential liver fat accumulation in overweight and obese humans.DesignDouble-blind randomized trial (LIPOGAIN-2). Overfeeding SFA vs PUFA for 8 weeks, followed by 4 weeks of caloric restriction.SettingGeneral community.ParticipantsMen and women who are overweight or have obesity (n = 61).InterventionMuffins, high in either palm (SFA) or sunflower oil (PUFA), were added to the habitual diet.Main Outcome MeasuresLean tissue mass (not reported here). Secondary and exploratory outcomes included liver and ectopic fat depots.ResultsBy design, body weight gain was similar in SFA (2.31 ± 1.38 kg) and PUFA (2.01 ± 1.90 kg) groups, P = 0.50. SFA markedly induced liver fat content (50% relative increase) along with liver enzymes and atherogenic serum lipids. In contrast, despite similar weight gain, PUFA did not increase liver fat or liver enzymes or cause any adverse effects on blood lipids. SFA had no differential effect on the accumulation of visceral fat, pancreas fat, or total body fat compared with PUFA. SFA consistently increased, whereas PUFA reduced circulating ceramides, changes that were moderately associated with liver fat changes and proposed markers of hepatic lipogenesis. The adverse metabolic effects of SFA were reversed by calorie restriction.ConclusionsSFA markedly induces liver fat and serum ceramides, whereas dietary PUFA prevents liver fat accumulation and reduces ceramides and hyperlipidemia during excess energy intake and weight gain in overweight individuals.

433-P: Serum Ceramides and Type 2 Diabetes Are Mutually Independent Predictors of Cardiovascular Events in Patients with Peripheral Artery Disease

Ceramides are enriched in atherosclerotic plaques, and a set of circulating ceramides including Cer(d18:1/16:0), Cer(d18:1/18:0), Cer(d18:1/24:1), and Cer(d18:1/24:0) has recently emerged as predictors of cardiovascular outcomes in coronary artery disease patients. However, their power to predict cardiovascular events in patients with peripheral artery disease (PAD) is unknown and is addressed in the present study. We measured the serum concentrations of the above mentioned ceramides in a cohort of 380 patients with sonographically proven PAD, of whom 107 had type 2 diabetes (T2DM). Prospectively, we recorded 221 cardiovascular events over a mean follow-up time of 6.3±2.3 years. Cardiovascular event risk was higher in T2DM patients than in those who did not have diabetes (69 vs. 52%, p=0.001). The ceramides Cer(18:1/16:0) and Cer(18:1/24:1) and the respective ratios Cer(18:1/16:0)/Cer(18:1/24:0) and Cer(18:1/24:1)/Cer(18:1/24:0) were significant predictors of cardiovascular events both univariately and after multivariate adjustment including the presence of T2DM (Figure). Conversely, T2DM predicted cardiovascular events independently from the investigated ceramides (adjusted HR 1.76 [1.31-2.35], p&amp;lt;0.001). We conclude that the investigated ceramides and T2DM are mutually independent predictors of cardiovascular events in PAD patients. Disclosure A. Leiherer: None. A. Muendlein: None. C.H. Saely: None. R. Laaksonen: None. M. Laaperi: None. A. Vonbank: None. B. Larcher: None. A. Mader: None. P. Fraunberger: None. I. Baumgartner: None. H. Drexel: None. J.F. Dopheide: None.

Associations of Adiposity and Diet Quality with Serum Ceramides in Middle-Aged Adults with Cardiovascular Risk Factors.

Rates of adverse cardiovascular events have increased among middle-aged adults. Elevated ceramides have been proposed as a risk factor for cardiovascular events. Diet quality and weight status are inversely associated with several traditional risk factors; however, the relationship to ceramides is less clear. This study aimed to determine associations of adiposity and diet quality with circulating ceramides in middle-aged adults (n = 96). Diet quality was estimated using the Healthy Eating Index 2015 (HEI-2015). Serum ceramide concentrations were determined by liquid chromatography–mass spectrometry. A ceramide risk score was determined based on ceramides C16:0, C18:0, and C24:1 and their ratios to C24:0. Participants who were classified as at ‘moderate risk’ compared to ‘lower-risk’ based on a ceramide risk score had significantly higher body mass index (BMI) values, as well as higher rates of elevated fibrinogen levels, metabolic syndrome, and former smoking status. BMI was positively associated with the ceramide C18:0 (R2 = 0.31, p < 0.0001), the ratio between C18:0/C24:0 ceramides (R2 = 0.30, p < 0.0001), and the ceramide risk score (R2 = 0.11, p < 0.009). Total HEI-2015 scores (R2 = 0.42, p = 0.02), higher intakes of vegetables (R2 = 0.44, p = 0.02) and whole grains (R2 = 0.43, p = 0.03), and lower intakes of saturated fats (R2 = 0.43, p = 0.04) and added sugar (R2 = 0.44, p = 0.01) were associated with lower C22:0 values. These findings suggest that circulating ceramides are more strongly related to adiposity than overall diet quality. Studies are needed to determine if improvements in weight status result in lower ceramides and ceramide risk scores.

Sterol 12α-Hydroxylase Aggravates Dyslipidemia by Activating the Ceramide/mTORC1/SREBP-1C Pathway via FGF21 and FGF15.

Sterol 12α-hydroxylase (CYP8B1) is required for the synthesis of cholic acid in the classic bile acid synthesis pathway and plays a role in dyslipidemia and insulin resistance. However, the mechanism of the involvement of Cyp8b1 in dyslipidemia and insulin resistance is not known. CYP8B1 mRNA and protein expression are elevated in diabetic and obese (db/db) mouse liver. In this study adenovirus-mediated transduction of CYP8B1 was used to study the effect of Cyp8b1 on lipid metabolism in mice. Results show that Ad-Cyp8b1 increased 12α-hydroxylated bile acids and induced sterol regulatory element-binding protein 1c (Srebp-1c)-mediated lipogenic gene expression. Interestingly, Ad-Cyp8b1 increased ceramide synthesis and activated hepatic mechanistic target of rapamycin complex 1 (mTORC1)-p70S6K signaling cascade and inhibited AKT/insulin signaling in mice. Ad-Cyp8b1 increased free fatty acid uptake into mouse primary hepatocytes. Ceramides stimulated S6K phosphorylation in both mouse and human primary hepatocytes. In high-fat diet-fed mice, Ad-Cyp8b1 reduced fibroblast growth factor 21 (FGF21), activated intestinal farnesoid X receptor (FXR) target gene expression, increased serum ceramides, VLDL secretion, and LDL cholesterol. In high-fat diet-induced obese (DIO) mice, Cyp8b1 ablation by adenovirus-mediated shRNA improved oral glucose tolerance, increased FGF21, and reduced liver triglycerides, inflammatory cytokine expression, nuclear localization of Srebp-1c and phosphorylation of S6K. In conclusion, this study unveiled a novel mechanism linking CYP8B1 to ceramide synthesis and mTORC1 signaling in dyslipidemia and insulin resistance, via intestinal FXR-mediated induction of FGF15 and liver FGF21. Reducing cholic acid synthesis may be a potential therapeutic strategy to treat dyslipidemia and nonalcoholic fatty liver disease.

Rheumatoid arthritis reprograms circadian output pathways

ObjectiveWe applied systems biology approaches to investigate circadian rhythmicity in rheumatoid arthritis (RA).MethodsWe recruited adults (age 16–80 years old) with a clinical diagnosis of RA (active disease [DAS28 > 3.2]). Sleep profiles were determined before inpatient measurements of saliva, serum, and peripheral blood mononuclear leukocytes (PBML). Transcriptome and proteome analyses were carried out by RNA-SEQ and LC-MS/MS. Serum samples were analysed by targeted lipidomics, along with serum from mouse collagen induced-arthritis (CIA). Bioinformatic analysis identified RA-specific gene networks and rhythmic processes differing between healthy and RA.ResultsRA caused greater time-of-day variation in PBML gene expression, and ex vivo stimulation identified a time-of-day-specific RA transcriptome. We found increased phospho-STAT3 in RA patients, and some targets, including phospho-ATF2, acquired time-of-day variation in RA. Serum ceramides also gained circadian rhythmicity in RA, which was also seen in mouse experimental arthritis, resulting from gain in circadian rhythmicity of hepatic ceramide synthases.ConclusionRA drives a gain in circadian rhythmicity, both in immune cells, and systemically. The coupling of distant timing information to ceramide synthesis and joint inflammation points to a systemic re-wiring of the circadian repertoire. Circadian reprogramming in response to chronic inflammation has implications for inflammatory co-morbidities and time-of-day therapeutics.

Mediterranean Diet is Negatively Associated with Serum Ceramides in Middle-Aged Adults at Risk for Cardiovascular Disease

Mediterranean Diet is Negatively Associated with Serum Ceramides in Middle-Aged Adults at Risk for Cardiovascular Disease

Increased serum concentration of ceramides in obese children with nonalcoholic fatty liver disease

BackgroundHepatic lipid accumulation is closely related to the development of insulin resistance, which is regarded as one of the most significant risk factors of nonalcoholic fatty liver disease (NAFLD). Although the exact molecular pathway leading to impaired insulin signaling has not been definitively established, ceramides are suspected mediators of lipid induced hepatic insulin resistance. Therefore, the aim of the study was to evaluate the serum ceramides concentration in obese children with NAFLD.MethodsThe prospective study included 80 obese children (aged 7–17 years, median 12 years) admitted to our Department to diagnose initially suspected liver disease. Patients with viral hepatitis (HCV, HBV, CMV), autoimmune (AIH), toxic and metabolic (Wilson’s disease, alfa-1–antitrypsin deficiency) liver diseases and celiac disease were excluded. NAFLD was diagnosed based on pediatric diagnostic criteria in obese children with liver steatosis in ultrasound (US) as well as elevated alanine transaminase (ALT) serum activity after exclusion of other major liver diseases listed before. Ultrasonography was used as a screening method and for qualitative assessment of the steatosis degree (graded according to Saverymuttu scale). Advanced steatosis was defined as a score > 1. The total intrahepatic lipid content (TILC) was assessed by magnetic resonance proton spectroscopy (1HMRS) which is the most accurate technique for assessment of ectopic fat accumulation. Fasting serum concentration of ceramides was measured in 62 children.ResultsNAFLD was diagnosed in 31 children. Significant, positive correlation was found between total serum concentration of ceramides and insulin (r = 0.3, p = 0.02) and HOMA-IR (r = 0.28, p = 0.03). Total ceramide concentration as well as specific fatty acid-ceramides (FA-ceramides) concentrations, namely: myristic, palmitic, palmitoleic, stearic, oleic, behenic and lignoceric were significantly higher (p = 0.004, p = 0.003, p = 0.007, p < 0.001, p = 0.035, p = 0.008, p = 0.003, p = 0.006, respectively) in children with NAFLD compared to controls (n = 14). Moreover, children with NAFLD had significantly higher activity of ALT (p < 0.001) and GGT (p < 0.001), HOMA-IR (p = 0.04), BMI (p = 0.046), waist circumference (p = 0.01) steatosis grade in ultrasound (p < 0.001) and TILC in 1HMRS (p < 0.001) compared to children without NAFLD. We did not find significant differences in total and FA-ceramide species concentrations between children with mild (grade 1) and advanced liver steatosis in ultrasonography (grade 2–3).ConclusionElevated ceramide concentrations in obese patients together with their significant correlation with insulin resistance parameters suggest their association with molecular pathways involved in insulin signaling impairment known to be strongly linked to pathogenesis of non-alcoholic fatty liver disease.

Strong Heart, Low Ceramides.

Serum ceramides have emerged as potential biomarkers of insulin resistance, diabetes, and heart disease. In this issue of Diabetes , Lemaitre et al. (1) report the largest longitudinal study to date correlating sphingolipids with insulin resistance, profiling a cohort of 2,086 American Indians at high risk for diabetes. With the analytical power that derives from profiling such a large number of samples obtained at two visits, 5 years apart, the data from the Strong Heart Family Study (SHFS) revealed that several ceramide species correlated with hyperinsulinemia and the HOMA of insulin resistance (HOMA-IR) in this at-risk population. Here, we summarize these results in the context of other preclinical and clinical studies investigating roles for ceramides as drivers of cardiometabolic dysfunction. Ceramides are central intermediates in the biosynthetic pathway that produces the large family of sphingolipids, which includes more than 4,000 distinct molecular entities. Much of the complexity in the cellular sphingolipid pool derives from the large number of acyl chains that can be incorporated into the ceramide scaffold. Over the past 20 years, a large number of studies in preclinical models suggest that ceramides may be among the most pathogenic nutrient metabolites that accumulate in obesity, linking overnutrition to insulin resistance and its sequelae of comorbidities. In cultured cells or isolated tissues, ceramides inhibit insulin signaling and action and inhibit lipid oxidation (2). In rodents, numerous ceramide-lowering interventions have been shown to improve insulin sensitivity and ameliorate diabetes and cardiovascular pathologies (2). Because of these data, a handful of companies have started to develop ceramide-reducing interventions in hopes of producing insulin-sensitizing therapeutics. Despite the strongly consistent findings obtained in preclinical models, the role of ceramides in human cardiometabolic pathologies has been controversial. The debate stems largely from discordance in …