Alexander Sigruener

Glycerophospholipid and Sphingolipid Species and Mortality: The Ludwigshafen Risk and Cardiovascular Health (LURIC) Study

Vascular and metabolic diseases cause half of total mortality in Europe. New prognostic markers would provide a valuable tool to improve outcome. First evidence supports the usefulness of plasma lipid species as easily accessible markers for certain diseases. Here we analyzed association of plasma lipid species with mortality in the Ludwigshafen Risk and Cardiovascular Health (LURIC) study. Plasma lipid species were quantified by electrospray ionization tandem mass spectrometry and Cox proportional hazards regression was applied to assess their association with total and cardiovascular mortality. Overall no differences were detected between total and cardiovascular mortality. Highly polyunsaturated phosphatidylcholine species together with lysophosphatidylcholine species and long chain saturated sphingomyelin and ceramide species seem to be associated with a protective effect. The predominantly circulating phosphatidylcholine-based as well as phosphatidylethanolamine-based ether species and phosphatidylethanolamine species were positively associated with total and cardiovascular mortality. Saturated and monounsaturated phosphatidylcholine species, especially phosphatidylcholine 32∶0 (most probably dipalmitoyl-phosphatidylcholine) and palmitate containing sphingomyelin and ceramide species showed together with 24∶1 containing sphingomyelin and ceramide species strongest positive association with mortality. A quotient of the sums of the six most protective species and the six species with the strongest positive mortality association indicated an almost 3-fold increased risk of mortality, which was higher than the hazard ratio for known risk factors in our cohort. Plasma lipid species levels and especially ratios of certain species may be valuable prognostic marker for cardiovascular and total mortality.

Alterations of plasma lysophosphatidylcholine species in obesity and weight loss.

Background Obesity and related diseases of the metabolic syndrome contribute to the major health problems in industrialized countries. Alterations in the metabolism of lipid classes and lipid species may significantly be involved in these metabolic overload diseases. However, little is known about specific lipid species in this syndrome and existing data are contradictive. Methods In this study, we quantified plasma lipid species by electrospray ionization tandem mass spectrometry (ESI-MS/MS) in obese subjects before and after 3 month weight loss as well as in a control group. Results The comparison of obese subjects with control subjects before weight loss revealed significantly lower lysophosphatidylcholine (LPC) concentrations in obesity. LPC concentrations did not significantly increase during the observed period in the weight loss group. Analysis of LPC species revealed a decrease of most species in obesity and negative correlations with C-reactive protein (CRP) and body mass index (BMI). Correlating BMI ratio before and after weight loss with the ratio of total LPC and individual LPC species revealed significant negative relationships of LPC ratios with BMI ratio. Conclusions Our findings contribute to the contradictive discussion of the role of LPC in obesity and related chronic inflammation strongly supporting pre-existing data in the literature that show a decrease of LPC species in plasma of obese and a potentially anti-inflammatory role in these subjects.

Interleukin-15 and Soluble Interleukin-15 Receptor α in Coronary Artery Disease Patients: Association with Epicardial Fat and Indices of Adipose Tissue Distribution

Interleukin-15 (IL-15) is a pro-inflammatory cytokine which signals via a specific alpha receptor subunit (IL-15Rα). Increased IL-15 level has been observed in cardiovascular patients and IL-15 immunoreactivity has been detected at vulnerable atherosclerotic plaques. Due to the association between adipose tissue distribution, inflammation and coronary artery disease (CAD), we quantified IL-15 and IL-15Rα in CAD patients with different adiposity and adipose tissue distribution and we evaluated whether epicardial adipose tissue (EAT), a visceral fat depot surrounding and infiltrating myocardium, may be a source of both molecules. IL-15 and IL-15Rα proteins were quantified by enzyme-linked immunosorbent assays. Gene expression of IL-15 and IL-15Rα in EAT depots was evaluated by one colour microarray platform. EAT thickness was measured by echocardiography. Plasmatic IL-15 and IL-15Rα levels were higher in CAD than non-CAD patients. After classification according to adipose tissue distribution, IL-15 was higher in CAD patients with increased abdominal adiposity. Increased level of IL-15Rα was observed both in CAD and non-CAD patients with increased abdominal fat. EAT was a source of IL-15 and IL-15Rα and their expression was higher in CAD patients with increased EAT thickness. In conclusion, our data suggest that circulating levels of IL-15 and IL-15Rα seem to reflect visceral distribution of adipose tissue and that EAT may be a potential source of both IL-15 and IL-15Rα. Future studies on the relationship between IL-15, visceral fat and characteristics of atherosclerotic plaques could help to better understand the complex biology of this cytokine.

Epicardial adipose tissue inflammation is related to vitamin D deficiency in patients affected by coronary artery disease

BACKGROUND AND AIMS Alterations in epicardial adipose tissue (EAT) biology (i.e. increased fat thickness and inflammation) have been described in coronary artery disease (CAD) patients. In addition to its classic role in the regulation of calcium-phosphate homeostasis, vitamin D may exert immune-regulatory and anti-inflammatory effects. Whether EAT inflammation may be linked to vitamin D deficiency is still unknown. In the present study we evaluated plasma 25-hydroxycholecalciferol (25OHD) level in CAD patients and its relationship with EAT ability to locally metabolize vitamin D, EAT expression of inflammation-related molecules and EAT thickness. METHODS AND RESULTS Plasma 25OHD level was quantified by an immunoluminometric assay. EAT expression of inflammation-related molecules (MCP-1, PTX3, TNFα, IL-6, adiponectin), vitamin D receptor (VDR), CYP27B1 (25OHD-activating enzyme) and CYP24A1 (1,25-dihydroxycholecalciferol-metabolizing enzyme) was performed by microarray. EAT thickness was quantified by echocardiography. Median plasma 25OHD level was 10.85 ng/mL and 83% of CAD patients displayed 25OHD level below 20 ng/mL. At decreasing plasma 25OHD concentration, we observed a down-regulation in CYP27B1 and CYP24A1 level and an increased expression of VDR and pro-inflammatory cytokines (MCP-1, PTX3, TNFα, IL-6) at EAT level. No correlation was observed between plasma 25OHD level and EAT thickness. CONCLUSION Our data suggest an increased activation of inflammatory pathways at EAT level possibly related to systemic and local vitamin D deficiency in CAD patients. Whether maintaining an optimal vitamin D status may be helpful to reduce EAT inflammation and to prevent CAD and its progression needs further investigation.

Novel hepatic microRNAs upregulated in human nonalcoholic fatty liver disease

MicroRNAs (miRNAs) control gene expression by reducing mRNA stability and translation. We aimed to identify alterations in human liver miRNA expression/function in nonalcoholic fatty liver disease (NAFLD). Subjects with the highest (median liver fat 30%, n = 15) and lowest (0%, n = 15) liver fat content were selected from >100 obese patients for miRNA profiling of liver biopsies on microarrays carrying probes for 1438 human miRNAs (a cross‐sectional study). Target mRNAs and pathways were predicted for the miRNAs most significantly upregulated in NAFLD, their cell‐type‐specific expression was investigated by quantitative PCR (qPCR), and the transcriptome of immortalized human hepatocytes (IHH) transfected with the miRNA with the highest number of predicted targets, miR‐576‐5p, was studied. The screen revealed 42 miRNAs up‐ and two downregulated in the NAFLD as compared to non‐NAFLD liver. The miRNAs differing most significantly between the groups, miR‐103a‐2*, miR‐106b, miR‐576‐5p, miRPlus‐I137*, miR‐892a, miR‐1282, miR‐3663‐5p, and miR‐3924, were all upregulated in NAFLD liver. Target pathways predicted for these miRNAs included ones involved in cancer, metabolic regulation, insulin signaling, and inflammation. Consistent transcriptome changes were observed in IHH transfected with miR‐576‐5p, and western analysis revealed a marked reduction of the RAC1 protein belonging to several miR‐576‐5p target pathways. To conclude, we identified 44 miRNAs differentially expressed in NAFLD versus non‐NAFLD liver, 42 of these being novel in the context of NAFLD. The study demonstrates that by applying a novel study set‐up and a broad‐coverage array platform one can reveal a wealth of previously undiscovered miRNA dysregulation in metabolic disease.

Effects of sphingoid bases on the sphingolipidome in early keratinocyte differentiation

Keratinocyte sphingolipids are structural elements of epidermal permeability barrier and potential regulators of epidermal functions. We tested the influence of sphingoid bases sphinganine, sphingosine and phytosphingosine on in vitro keratinocyte differentiation. Lipidomic and transcriptomic analysis after treatment emphasizes sphinganine and phytosphingosine as potent modulators of keratinocyte differentiation and lipid metabolism. Sphinganine treatment regulated differentiation and sphingolipid metabolism‐related genes, and also increased all major ceramide species. Sphingosine treatment increased ceramide and phytoceramide pools without changes in dihydroceramides. Phytosphingosine treatment markedly increased phytoceramide pools without raising ceramide or dihydroceramide levels. Sphinganine treatment increased specifically very long chain ceramides essential for intact barrier function. In summary, sphingoid bases, especially sphinganine, promote differentiation and ceramide production in keratinocytes. Free sphinganine may serve as a dermatological and cosmetic agent by enhancing formation and maintenance of an intact epidermal lipid barrier, with beneficial effects for skin and hair care applications.

Ceramide and polyunsaturated phospholipids are strongly reduced in human hepatocellular carcinoma

Lipid composition affects membrane function, cell proliferation and cell death and is changed in cancer tissues. Hepatocellular carcinoma (HCC) is an aggressive cancer and this study aimed at a comprehensive characterization of hepatic and serum lipids in human HCC. Cholesteryl ester were higher in tumorous tissues (TT) compared to adjacent non-tumorous tissues (NT). Free cholesterol exerting cytotoxic effects was not changed. Phosphatidylethanolamine, -serine (PS) and -inositol but not phosphatidylcholine (PC) and lysophosphatidylcholine (LPC) were reduced in HCC tissues. Saturated species mostly increased and polyunsaturated species were diminished in all of these phospholipids. Ceramide (Cer) was markedly reduced in HCC tissues and higher levels of sphingomyelin suggest impaired sphingomyelinase activity as one of the underlying mechanisms. Importantly, ceramide in NT increased in HCC stage T3. Ceramide released from hepatocytes attracts immune cells and a positive association of the macrophage specific receptor CD163 with NT ceramide was identified. HCC associated lipid changes did not differ in patients suffering from type 2 diabetes. Protein levels of p53 were induced in TT and negatively correlated with Cer d18:1/16:0 and PS 36:1. Of the lipid species changed in HCC tissues only TT Cer d18:1/16:0, Cer d18:1/24:1, PC 38:6 and LPC 22:6 correlated with the respective serum levels. Our study demonstrates a considerably altered hepatic lipidome in HCC tissues. Ceramide was markedly reduced in HCC tissues, and therefore, raising ceramide levels specifically in the tumor represents a reasonable therapeutic approach for the treatment of this malignancy.

IL-18 level in patients undergoing coronary artery bypass grafting surgery or valve replacement: which link with epicardial fat depot?

Interleukin-18 (IL-18) is a member of the interleukin-1 family of cytokines produced constitutively by different cell types and by adipose tissue. Due to the link between obesity, inflammation and cardiovascular diseases, we aimed to measure IL-18 circulating level in patients undergoing open-heart surgery both for elective coronary artery bypass grafting (CABG) or for valve replacement (VR), and we also evaluated whether epicardial adipose tissue (EAT) depot may be a potential source of IL-18. Circulating IL-18 protein was quantified by enzyme-linked immunosorbent assay. IL-18, IL-18 receptor 1 (IL-18 Rl) and IL-18 receptor accessory protein (IL-18-RAP) gene expression in EAT depot were evaluated by one colour microarray platform. EAT thickness was measured by echocardiography. In this study we found that all cardiovascular patients (CABG and VR) have increased circulating IL-18 level compared to healthy control subjects (p < 0.0001), but no statistical significant difference was observed between CABG and VR groups (p = 0.35). A great increase in the gene expression of IL-18 (p < 0.05), IL-18 R1 (p < 0.01) and IL-18 RAP (p < 0.001) was observed in EAT samples obtained from CABG vs VR patients. In conclusion, CABG and VR patients had similar increased level of circulating IL-18 protein, but in EAT depots isolated from CABG gene expression of IL-18, IL-18 R1 and IL-18-RAP resulted higher than in VR patients. Future investigation on local IL-18 protein production, its autocrine-paracrine effect and its correlation with plasmatic IL-18 level could give more information on the relationship between IL-18 and coronary artery disease.

Transcriptomic profiling of platelet senescence and platelet extracellular vesicles

Platelets (PLTs) are derived from megakaryocytes during PLT shedding. Senescent or activated PLTs are expanded in vascular and neurological diseases and release PLT extracellular vesicles (PL‐EVs). A systematic analysis of regular messenger RNA (mRNA) and small RNA composition in PLTs and PL‐EVs during in vitro PLT senescence has not yet been published.

Lipidomic and metabolic changes in the P4-type ATPase ATP10D deficient C57BL/6J wild type mice upon rescue of ATP10D function

Background Sequence variants near the human gene for P4-type ATPase, class V, type 10D (ATP10D) were shown to significantly associate with circulating hexosylceramide d18:1/16:0 and d18:1/24:1 levels, obesity, insulin resistance, plasma high density lipoprotein (HDL), coronary stenotic index and intracranial atherosclerotic index. In mice Atp10d is associated with HDL modulation and C57BL/6 mice expressing a truncated, non-functional form of ATP10D easily develop obesity and insulin resistance on high-fat diet. Results We analyzed metabolic differences of ATP10D deficient C57BL/6J wild type and ATP10D transgenic C57BL/6J BAC129 mice. ATP10D transgenic mice gain 25% less weight on high-fat diet concomitant with a reduced increase in fat cell mass but independent of adipocyte size change. ATP10D transgenic mice also had 26% lower triacylglycerol levels with approximately 76% bound to very low density lipoprotein while in ATP10D deficient wild type mice 57% are bound to low density lipoprotein. Furthermore increased oxygen consumption and CO2 production, 38% lower glucose and 69% lower insulin levels and better insulin sensitivity were observed in ATP10D transgenic mice. Besides decreased hexosylceramide species levels were detected. Part of these effects may be due to reduced hepatic stearoyl-CoA desaturase 1 (SCD1) expression in ATP10D transgenic mice, which was reflected by altered fatty acid and lipid species patterns. There was a significant decrease in the hepatic 18:1 to 18:0 free fatty acid ratio in transgenic mice. The ratio of 16:1 to 16:0 was not significantly different. Interestingly both ratios were significantly reduced in plasma total fatty acids. Summary In summary we found that ATP10D reduces high-fat diet induced obesity and improves insulin sensitivity. ATP10D transgenic mice showed altered hepatic expression of lipid-metabolism associated genes, including Scd1, along with changes in hepatic and plasma lipid species and plasma lipoprotein pattern.