TY - JOUR A1 - Wigger, Dominik A1 - Schumacher, Fabian A1 - Schneider-Schaulies, Sibylle A1 - Kleuser, Burkhard T1 - Sphingosine 1-phosphate metabolism and insulin signaling JF - Cellular signalling N2 - Insulin is the main anabolic hormone secreted by 13-cells of the pancreas stimulating the assimilation and storage of glucose in muscle and fat cells. It modulates the postprandial balance of carbohydrates, lipids and proteins via enhancing lipogenesis, glycogen and protein synthesis and suppressing glucose generation and its release from the liver. Resistance to insulin is a severe metabolic disorder related to a diminished response of peripheral tissues to the insulin action and signaling. This leads to a disturbed glucose homeostasis that precedes the onset of type 2 diabetes (T2D), a disease reaching epidemic proportions. A large number of studies reported an association between elevated circulating fatty acids and the development of insulin resistance. The increased fatty acid lipid flux results in the accumulation of lipid droplets in a variety of tissues. However, lipid intermediates such as diacylglycerols and ceramides are also formed in response to elevated fatty acid levels. These bioactive lipids have been associated with the pathogenesis of insulin resistance. More recently, sphingosine 1-phosphate (S1P), another bioactive sphingolipid derivative, has also been shown to increase in T2D and obesity. Although many studies propose a protective role of S1P metabolism on insulin signaling in peripheral tissues, other studies suggest a causal role of S1P on insulin resistance. In this review, we critically summarize the current state of knowledge of S1P metabolism and its modulating role on insulin resistance. A particular emphasis is placed on S1P and insulin signaling in hepatocytes, skeletal muscle cells, adipocytes and pancreatic 13-cells. In particular, modulation of receptors and enzymes that regulate S1P metabolism can be considered as a new therapeutic option for the treatment of insulin resistance and T2D. KW - Insulin resistance KW - Type 2 diabetes KW - Sphingolipids KW - Hepatocytes KW - Adipocytes KW - Skeletal muscle cells Y1 - 2021 U6 - https://doi.org/10.1016/j.cellsig.2021.109959 SN - 0898-6568 SN - 1873-3913 VL - 82 PB - Elsevier Science CY - Amsterdam [u.a.] ER - TY - JOUR A1 - Gohlke, Sabrina A1 - Zagoriy, Vyacheslav A1 - Inostroza, Alvaro Cuadros A1 - Meret, Michael A1 - Mancini, Carola A1 - Japtok, Lukasz A1 - Schumacher, Fabian A1 - Kuhlow, Doreen A1 - Graja, Antonia A1 - Stephanowitz, Heike A1 - Jähnert, Markus A1 - Krause, Eberhard A1 - Wernitz, Andreas A1 - Petzke, Klaus-Juergen A1 - Schürmann, Annette A1 - Kleuser, Burkhard A1 - Schulz, Tim Julius T1 - Identification of functional lipid metabolism biomarkers of brown adipose tissue aging JF - Molecular Metabolism N2 - Objective: Aging is accompanied by loss of brown adipocytes and a decline in their thermogenic potential, which may exacerbate the development of adiposity and other metabolic disorders. Presently, only limited evidence exists describing the molecular alterations leading to impaired brown adipogenesis with aging and the contribution of these processes to changes of systemic energy metabolism. Methods: Samples of young and aged murine brown and white adipose tissue were used to compare age-related changes of brown adipogenic gene expression and thermogenesis-related lipid mobilization. To identify potential markers of brown adipose tissue aging, non-targeted proteomic and metabolomic as well as targeted lipid analyses were conducted on young and aged tissue samples. Subsequently, the effects of several candidate lipid classes on brown adipocyte function were examined. Results: Corroborating previous reports of reduced expression of uncoupling protein-1, we observe impaired signaling required for lipid mobilization in aged brown fat after adrenergic stimulation. Omics analyses additionally confirm the age-related impairment of lipid homeostasis and reveal the accumulation of specific lipid classes, including certain sphingolipids, ceramides, and dolichols in aged brown fat. While ceramides as well as enzymes of dolichol metabolism inhibit brown adipogenesis, inhibition of sphingosine 1-phosphate receptor 2 induces brown adipocyte differentiation. Conclusions: Our functional analyses show that changes in specific lipid species, as observed during aging, may contribute to reduced thermogenic potential. They thus uncover potential biomarkers of aging as well as molecular mechanisms that could contribute to the degradation of brown adipocytes, thereby providing potential treatment strategies of age-related metabolic conditions. KW - Brown adipose tissue KW - Aging KW - Ceramides KW - Sphingolipids KW - Dolichol lipids Y1 - 2019 U6 - https://doi.org/10.1016/j.molmet.2019.03.011 SN - 2212-8778 VL - 24 SP - 1 EP - 17 PB - Elsevier CY - Amsterdam ER - TY - JOUR A1 - Morris, Mackenzie C. A1 - Kassam, Farzaan A1 - Bercz, Aron A1 - Beckmann, Nadine A1 - Schumacher, Fabian A1 - Gulbins, Erich A1 - Makley, Amy T. A1 - Goodman, Michael D. T1 - The Role of Chemoprophylactic Agents in Modulating Platelet Aggregability After Traumatic Brain Injury JF - Journal of surgical research N2 - Background: The pathophysiology behind the subacute but persistent hypercoagulable state after traumatic brain injury (TBI) is poorly understood but contributes to morbidity induced by venous thromboembolism. Because platelets and their microvesicles have been hypothesized to play a role in post-traumatic hypercoagulability, administration of commonly used agents may ameliorate this coagulability. We hypothesized that utilization of aspirin, ketorolac, amitriptyline, unfractionated heparin, or enoxaparin would modulate the platelet aggregation response after TBI. Methods: Concussive TBI was induced by weight drop. Mice were then randomized to receive aspirin, ketorolac, amitriptyline, heparin, enoxaparin, or saline control at 2 and 8 h after TBI. Mice were sacrificed at 6 or 24 h after injury to determine coagulability by rotational thromboelastometry (ROTEM), platelet function testing with impedance aggregometry, and microvesicle enumeration. Platelet sphingolipid metabolites were analyzed by mass spectrometry. Results: ROTEM demonstrated increased platelet contribution to maximum clot firmness at 6 h after TBI in mice that received aspirin or amitriptyline, but this did not persist at 24 h. By contrast, adenosine diphosphate- and arachidonic acid-induced platelet aggregation at 6 h was significantly lower in mice receiving ketorolac, aspirin, and amitriptyline compared with mice receiving saline at 6 h after injury and only arachidonic acid-initiated platelet aggregation was decreased by aspirin at 24 h. There were no differences in microvesicle production at either time point. Platelet sphingosine-1-phosphate levels were decreased at 6 h in the group receiving amitriptyline and increased at 24 h along with platelet ceramide levels at 24 h in the amitriptyline group. Conclusion: After TBI, amitriptyline decreased platelet aggregability and increased contribution to clot in a manner similar to aspirin. The amitriptyline effects on platelet function and sphingolipid metabolites may represent a possible role of the acid sphingomyelinase in the hypercoagulability observed after injury. In addition, inhibition of platelet reactivity may be an underappreciated benefit of low molecular weight heparins, such as enoxaparin. (C) 2019 Elsevier Inc. All rights reserved. KW - Trauma KW - Traumatic brain injury KW - Venous thromboembolism KW - Chemoprophylaxis KW - Sphingolipids Y1 - 2019 U6 - https://doi.org/10.1016/j.jss.2019.06.022 SN - 0022-4804 SN - 1095-8673 VL - 244 SP - 1 EP - 8 PB - Elsevier CY - San Diego ER - TY - JOUR A1 - Nojima, Hiroyuki A1 - Freeman, Christopher M. A1 - Schuster, Rebecca M. A1 - Japtok, Lukasz A1 - Kleuser, Burkhard A1 - Edwards, Michael J. A1 - Gulbins, Erich A1 - Lentsch, Alex B. T1 - Hepatocyte exosomes mediate liver repair and regeneration via sphingosine-1-phosphate JF - Journal of hepatology N2 - Background & Aims: Exosomes are small membrane vesicles involved in intercellular communication. Hepatocytes are known to release exosomes, but little is known about their biological function. We sought to determine if exosomes derived from hepatocytes contribute to liver repair and regeneration after injury. Methods: Exosomes derived from primary murine hepatocytes were isolated and characterized biochemically and biophysically. Using cultures of primary hepatocytes, we tested whether hepatocyte exosomes induced proliferation of hepatocytes in vitro. Using models of ischemia/reperfusion injury and partial hepatectomy, we evaluated whether hepatocyte exosomes promote hepatocyte proliferation and liver regeneration in vivo. Results: Hepatocyte exosomes, but not exosomes from other liver cell types, induce dose-dependent hepatocyte proliferation in vitro and in vivo. Mechanistically, hepatocyte exosomes directly fuse with target hepatocytes and transfer neutral ceramidase and sphingosine kinase 2 (SK2) causing increased synthesis of sphingosine-1-phosphate (S1P) within target hepatocytes. Ablation of exosomal SK prevents the proliferative effect of exosomes. After ischemia/reperfusion injury, the number of circulating exosomes with proliferative effects increases. Conclusions: Our data shows that hepatocyte-derived exosomes deliver the synthetic machinery to form S1P in target hepatocytes resulting in cell proliferation and liver regeneration after ischemia/reperfusion injury or partial hepatectomy. These findings represent a potentially novel new contributing mechanism of liver regeneration and have important implications for new therapeutic approaches to acute and chronic liver disease. (C) 2015 European Association for the Study of the Liver. Published by Elsevier B.V. All rights reserved. KW - Liver injury KW - Sphingolipids KW - Sphingosine kinase KW - Ischemia/reperfusion KW - Transplantation Y1 - 2016 U6 - https://doi.org/10.1016/j.jhep.2015.07.030 SN - 0168-8278 SN - 1600-0641 VL - 64 SP - 60 EP - 68 PB - Elsevier CY - Amsterdam ER - TY - JOUR A1 - Reichel, Martin A1 - Hoenig, Stefanie A1 - Liebisch, Gerhard A1 - Lüth, Anja A1 - Kleuser, Burkhard A1 - Gulbins, Erich A1 - Schmitz, Gerd A1 - Kornhuber, Johannes T1 - Alterations of plasma glycerophospholipid and sphingolipid species in male alcohol-dependent patients JF - Biochimica et biophysica acta : Molecular and cell biology of lipids N2 - Background: Alcohol abuse is a major risk factor for somatic and neuropsychiatric diseases. Despite their potential clinical importance, little is known about the alterations of plasma glycerophospholipid (GPL) and sphingolipid (SPL) species associated with alcohol abuse. Methods: Plasma GPL and SPL species were quantified using electrospray ionization tandem mass spectrometry in samples from 23 male alcohol-dependent patients before and after detoxification, as well as from 20 healthy male controls. Results: A comparison of alcohol-dependent patients with controls revealed higher phosphatidylcholine (PC; P-value = 0.008) and phosphatidylinositol (PI; P-value = 0.001) concentrations in patients before detoxification, and higher PI (P-value = 0.001) and phosphatidylethanolamine (PE)-based plasmalogen (PEP; P-value = 0.003) concentrations after detoxification. Lysophosphatidylcholines (LPC) were increased by acute intoxication (P-value = 0.002). Sphingomyelin (SM) concentration increased during detoxification (P-value = 0.011). The concentration of SM 23:0 was lower in patients (P-value = 2.79 x 10(-5)), and the concentrations of ceramide Cer d18:1/16:0 and Cer d18:1/18:0 were higher in patients (P-value = 2.45 x 10(-5) and 3.73 x 10(-5)). Activity of lysosomal acid sphingomyelinase (ASM) in patients correlated positively with the concentrations of eight LPC species, while activity of secreted ASM was inversely correlated with several PE, PI and PC species, and positively correlated with the molar ratio of PC to SM (Pearson's r = 0.432; P-value = 0.039). Conclusion: Plasma concentrations of numerous GPL and SPL species were altered in alcohol-dependent patients. These molecules might serve as potential biomarkers to improve the diagnosis of patients and to indicate health risks associated with alcohol abuse. Our study further indicates that there are strong interactions between plasma GPL concentrations and SPL metabolism. (C) 2015 Elsevier B.V. All rights reserved. KW - Acid sphingomyelinase KW - Alcohol dependence KW - Anxiety KW - Cardiovascular KW - Case-control study KW - Ceramide KW - Clinical KW - Depression KW - Diagnostic KW - Disease KW - Glycerophospholipids KW - Lysophosphatidylcholines KW - Mass spectrometry KW - Phosphatidylcholines KW - Phosphatidylinositols KW - Plasma KW - Plasmalogens KW - Sphingolipids KW - Sphingomyelin KW - Tandem mass spectrometry Y1 - 2015 U6 - https://doi.org/10.1016/j.bbalip.2015.08.005 SN - 1388-1981 SN - 0006-3002 VL - 1851 IS - 11 SP - 1501 EP - 1510 PB - Elsevier CY - Amsterdam ER - TY - JOUR A1 - Fayyaz, Susann A1 - Henkel, Janin A1 - Japtok, Lukasz A1 - Krämer, Stephanie A1 - Damm, Georg A1 - Seehofer, Daniel A1 - Püschel, Gerhard Paul A1 - Kleuser, Burkhard T1 - Involvement of sphingosine 1-phosphate in palmitate-induced insulin resistance of hepatocytes via the S1P(2) receptor subtype JF - Diabetologia : journal of the European Association for the Study of Diabetes (EASD) N2 - Enhanced plasma levels of NEFA have been shown to induce hepatic insulin resistance, which contributes to the development of type 2 diabetes. Indeed, sphingolipids can be formed via a de novo pathway from the saturated fatty acid palmitate and the amino acid serine. Besides ceramides, sphingosine 1-phosphate (S1P) has been identified as a major bioactive lipid mediator. Therefore, our aim was to investigate the generation and function of S1P in hepatic insulin resistance. The incorporation of palmitate into sphingolipids was performed by rapid-resolution liquid chromatography-MS/MS in primary human and rat hepatocytes. The influence of S1P and the involvement of S1P receptors in hepatic insulin resistance was examined in human and rat hepatocytes, as well as in New Zealand obese (NZO) mice. Palmitate induced an impressive formation of extra- and intracellular S1P in rat and human hepatocytes. An elevation of hepatic S1P levels was observed in NZO mice fed a high-fat diet. Once generated, S1P was able, similarly to palmitate, to counteract insulin signalling. The inhibitory effect of S1P was abolished in the presence of the S1P(2) receptor antagonist JTE-013 both in vitro and in vivo. In agreement with this, the immunomodulator FTY720-phosphate, which binds to all S1P receptors except S1P(2), was not able to inhibit insulin signalling. These data indicate that palmitate is metabolised by hepatocytes to S1P, which acts via stimulation of the S1P(2) receptor to impair insulin signalling. In particular, S1P(2) inhibition could be considered as a novel therapeutic target for the treatment of insulin resistance. KW - FTY720 KW - Insulin signalling KW - Palmitate KW - S1P receptors KW - Sphingolipids KW - Sphingosine 1-phosphate Y1 - 2014 U6 - https://doi.org/10.1007/s00125-013-3123-6 SN - 0012-186X SN - 1432-0428 VL - 57 IS - 2 SP - 373 EP - 382 PB - Springer CY - New York ER - TY - JOUR A1 - Schmitz, Elisabeth I. A1 - Potteck, Henrik A1 - Schüppel, Melanie A1 - Manggau, Marianti A1 - Wahydin, Elly A1 - Kleuser, Burkhard T1 - Sphingosine 1-phosphate protects primary human keratinocytes from apoptosis via nitric oxide formation through the receptor subtype S1P(3) JF - Molecular and cellular biochemistry : an international journal for chemical biology in health and disease N2 - Although the lipid mediator sphingosine 1-phosphate (S1P) has been identified to induce cell growth arrest of human keratinocytes, the sphingolipid effectively protects these epidermal cells from apoptosis. The molecular mechanism of the anti-apoptotic action induced by S1P is less characterized. Apart from S1P, endogenously produced nitric oxide (NOaEuro cent) has been recognized as a potent modulator of apoptosis in keratinocytes. Therefore, it was of great interest to elucidate whether S1P protects human keratinocytes via a NOaEuro cent-dependent signalling pathway. Indeed, S1P induced an activation of endothelial nitric oxide synthase (eNOS) in human keratinocytes leading to an enhanced formation of NOaEuro cent. Most interestingly, the cell protective effect of S1P was almost completely abolished in the presence of the eNOS inhibitor L-NAME as well as in eNOS-deficient keratinocytes indicating that the sphingolipid metabolite S1P protects human keratinocytes from apoptosis via eNOS activation and subsequent production of protective amounts of NOaEuro cent. It is well established that most of the known actions of S1P are mediated by a family of five specific G protein-coupled receptors. Therefore, the involvement of S1P-receptor subtypes in S1P-mediated eNOS activation has been examined. Indeed, this study clearly shows that the S1P(3) is the exclusive receptor subtype in human keratinocytes which mediates eNOS activation and NOaEuro cent formation in response to S1P. In congruence, when the S1P(3) receptor subtype is abrogated, S1P almost completely lost its ability to protect human keratinocytes from apoptosis. KW - Keratinocytes KW - Sphingolipids KW - Sphingosine 1-phosphate KW - S1P-receptors KW - Nitric oxide KW - Endothelial nitric oxide synthase KW - Apoptosis Y1 - 2012 U6 - https://doi.org/10.1007/s11010-012-1433-5 SN - 0300-8177 VL - 371 IS - 1-2 SP - 165 EP - 176 PB - Springer CY - Dordrecht ER - TY - JOUR A1 - Bhabak, Krishna P. A1 - Kleuser, Burkhard A1 - Huwiler, Andrea A1 - Arenz, Christoph T1 - Effective inhibition of acid and neutral ceramidases by novel B-13 and LCL-464 analogues JF - Bioorganic & medicinal chemistry : a Tetrahedron publication for the rapid dissemination of full original research papers and critical reviews on biomolecular chemistry, medicinal chemistry and related disciplines N2 - Induction of apoptosis mediated by the inhibition of ceramidases has been shown to enhance the efficacy of conventional chemotherapy in several cancer models. Among the inhibitors of ceramidases reported in the literature, B-13 is considered as a lead compound having good in vitro potency towards acid ceramidase. Furthermore, owing to the poor activity of B-13 on lysosoamal acid ceramidase in living cells, LCL-464 a modified derivative of B-13 containing a basic omega-amino group at the fatty acid was reported to have higher potency towards lysosomal acid ceramidase in living cells. In a search for more potent inhibitors of ceramidases, we have designed a series of compounds with structural modifications of B-13 and LCL-464. In this study, we show that the efficacy of B-13 in vitro as well as in intact cells can be enhanced by suitable modification of functional groups. Furthermore, a detailed SAR investigation on LCL-464 analogues revealed novel promising inhibitors of aCDase and nCDase. In cell culture studies using the breast cancer cell line MDA-MB-231, some of the newly developed compounds elevated endogenous ceramide levels and in parallel, also induced apoptotic cell death. In summary, this study shows that structural modification of the known ceramidase inhibitors B-13 and LCL-464 generates more potent ceramidase inhibitors that are active in intact cells and not only elevates the cellular ceramide levels, but also enhances cell death. KW - Sphingolipids KW - Ceramide KW - Ceramidase inhibitors KW - Structure-activity-relationship Y1 - 2013 U6 - https://doi.org/10.1016/j.bmc.2012.12.014 SN - 0968-0896 VL - 21 IS - 4 SP - 874 EP - 882 PB - Elsevier CY - Oxford ER -