sphingosine-1-phosphate and Dyslipidemias

To better define the metabolism of sphingosine-1-phosphate (S1P), its transport in plasma and its interactions with S1P receptors on vascular cells, and to evaluate the effect of statin treatment on the subnormal plasma levels of high-density lipoprotein (HDL)-bound S1P characteristic of the atherogenic dyslipidemia of metabolic syndrome (MetS).. Neither clinical intervention trials targeted to raising high-density lipoprotein-cholesterol (HDL-C) levels nor human genome-wide association studies (GWAS) studies have provided evidence to support an atheroprotective role of HDL. Recently however a large monogenic univariable Mendelian randomization on the N396S mutation in the gene encoding endothelial lipase revealed a causal protective effect of elevated HDL-C on coronary artery disease conferred by reduced enzyme activity. Given the complexity of the HDL lipidome and proteome, components of HDL other than cholesterol may in all likelihood contribute to such a protective effect. Among HDL lipids, S1P is a bioactive sphingolipid present in a small proportion of HDL particles (about 5%); indeed, S1P is preferentially enriched in small dense HDL3. As S1P is bound to apolipoprotein (apo) M in HDL, such enrichment is consistent with the elevated apoM concentration in HDL3. When HDL/apoM-bound S1P acts on S1P1 or S1P3 receptors in endothelial cells, potent antiatherogenic and vasculoprotective effects are exerted; those exerted by albumin-bound S1P at these receptors are typically weaker. When HDL/apoM-bound S1P binds to S1P2 receptors, proatherogenic effects may potentially be induced. Subnormal plasma levels of HDL-associated S1P are typical of dyslipidemic individuals at high cardiovascular risk and in patients with coronary heart disease. International Guidelines recommend statin treatment as first-line lipid lowering therapy in these groups. The cardiovascular benefits of statin therapy are derived primarily from reduction in low-density lipoprotein (LDL)-cholesterol, although minor contributions from pleiotropic actions cannot be excluded. Might statin treatment therefore normalize, directly or indirectly, the subnormal levels of S1P in dyslipidemic subjects at high cardiovascular risk? Our unpublished findings in the CAPITAIN study (ClinicalTrials.gov: NCT01595828), involving a cohort of obese, hypertriglyceridemic subjects (n = 12) exhibiting the MetS, showed that pitavastatin calcium (4 mg/day) treatment for 180days was without effect on either total plasma or HDL-associated S1P levels, suggesting that statin-mediated improvement of endothelial function is not due to normalization of HDL-bound S1P. Statins may however induce the expression of S1P1 receptors in endothelial cells, thereby potentiating increase in endothelial nitric oxide synthase response to HDL-bound S1P, with beneficial downstrea. Current evidence indicates that S1P in small dense HDL3 containing apoM exerts antiatherogenic effects and that statins exert vasculoprotective effects through activation of endothelial cell S1P1 receptors in response to HDL/apoM-bound S1P.

Topics: Apolipoproteins M; Cholesterol; Dyslipidemias; Endothelial Cells; Genome-Wide Association Study; Humans; Hydroxymethylglutaryl-CoA Reductase Inhibitors; Lipoproteins, HDL; Lysophospholipids; Sphingosine

Metabolic disorders are associated with an increased risk of cardiovascular disease (CVD), and are commonly characterized by a low plasma level of high-density lipoprotein cholesterol (HDL-C). Although cholesterol lowering medications reduce CVD risk in these patients, they often remain at increased risk of CVD. Therapeutic strategies that raise HDL-C levels and improve HDL function are a potential treatment option for reducing residual CVD risk in these individuals. Over the past decade, understanding of the metabolism and cardioprotective functions of HDLs has improved, with preclinical and clinical studies both indicating that the ability of HDLs to mediate reverse cholesterol transport, inhibit inflammation and reduce oxidation is impaired in metabolic disorders. These cardioprotective effects of HDLs are supported by the outcomes of epidemiological, cell and animal studies, but have not been confirmed in several recent clinical outcome trials of HDL-raising agents. Recent studies suggest that HDL function may be clinically more important than plasma levels of HDL-C. However, at least some of the cardioprotective functions of HDLs are lost in acute coronary syndrome and stable coronary artery disease patients. HDL dysfunction is also associated with metabolic abnormalities. This review is concerned with the impact of metabolic abnormalities, including dyslipidemia, obesity and Type 2 diabetes, on the metabolism and cardioprotective functions of HDLs.

Topics: Animals; Anthropometry; Diabetes Mellitus, Type 2; Dyslipidemias; Humans; Hyperglycemia; Inflammation; Insulin Resistance; Lipoproteins, HDL; Lysophospholipids; Metabolic Syndrome; Obesity; Oxidative Stress; Sphingosine

Population-wide reductions in cardiovascular disease (CVD) have not been equally shared in the African American community due to a higher burden of CVD risk factors such as metabolic disorders and obesity. Differential concentrations of sphingolipids such as ceramide, sphingosine, and sphingosine 1-phosphate (S1P) has been associated with the development of CVD, metabolic disorders (MetD), and obesity. Whether African Americans have disparate expression levels of sphingolipids that explain higher burdens of CVD remains unknown.. A cross sectional analysis of plasma concentrations of ceramides, sphingosine, and S1P were measured from 8 whites and 7 African Americans without metabolic disorders and 7 whites and 8 African Americans with metabolic disorders using high performance liquid chromatography/tandem mass spectrometry methodology (HPLC/MS-MS). Subjects were stratified by both race and metabolic status. Subjects with one or more of the following physician confirmed diagnosis: diabetes, hypertension, hypercholesterolemia, or dyslipidemia were classified as having metabolic disease (MetD). Data was analyzed using a Two-Way ANOVA and Tukey's post hoc test.. Total ceramide levels were increased in African Americans compared to African Americans with MetD. Ceramide C16 levels were higher in whites with MetD compared to African Americans with MetD (p<0.05). Ceramide C20 levels were higher in whites with MetD compared to whites. Ceramide C20 levels were higher in African Americans compared to African Americans with MetD. Furthermore, whites with MetD had higher levels of C20 compared to African Americans with MetD (p<0.0001). Ceramide C24:0 and C24:1 in African Americans was higher compared to African Americans with MetD (p<0.05). The plasma concentration of Sph-1P ceramide was higher in African Americans vs whites (p = 0.01). Lastly, ceramide C20 negatively correlated with hemoglobin A1c (HbA1c) levels in our study cohort.. Plasma ceramide concentration patterns are distinct in African Americans with MetD. Further research with larger samples sizes are needed to confirm these findings and to understand whether racial disparities in sphingolipid concentrations have potential therapeutic implications for CVD-related health outcomes.

Topics: Adult; Aged; Black or African American; Ceramides; Chromatography, High Pressure Liquid; Cross-Sectional Studies; Diabetes Mellitus; Dyslipidemias; Female; Gas Chromatography-Mass Spectrometry; Humans; Hypercholesterolemia; Hypertension; Lysophospholipids; Male; Middle Aged; Risk Factors; Sphingosine; White People

The dyslipidemia of type 2 diabetes mellitus has multiple etiologies and impairs lipoprotein functionality, thereby increasing risk for cardiovascular disease. High-density lipoproteins (HDLs) have several beneficial effects, notably protecting the heart from myocardial ischemia. We hypothesized that glycation of HDL could compromise this cardioprotective effect.. We used in vitro (cardiomyocytes) and ex vivo (whole heart) models subjected to oxidative stress together with HDL isolated from diabetic patients and nondiabetic HDL glycated in vitro (methylglyoxal). Diabetic and in vitro glycated HDL were less effective (P<0.05) than control HDL in protecting from oxidative stress. Protection was significantly, inversely correlated with the degree of in vitro glycation (P<0.001) and the levels of hemoglobin A1c in diabetic patients (P<0.007). The ability to activate protective, intracellular survival pathways involving Akt, Stat3, and Erk1/2 was significantly reduced (P<0.05) using glycated HDL. Glycation reduced the sphingosine-1-phosphate (S1P) content of HDL, whereas the S1P concentrations of diabetic HDL were inversely correlated with hemoglobin A1c (P<0.005). The S1P contents of in vitro glycated and diabetic HDL were significantly, positively correlated (both <0.01) with cardiomyocyte survival during oxidative stress. Adding S1P to diabetic HDL increased its S1P content and restored its cardioprotective function.. Our data demonstrate that glycation can reduce the S1P content of HDL, leading to increased cardiomyocyte cell death because of less effective activation of intracellular survival pathways. It has important implications for the functionality of HDL in diabetes mellitus because HDL-S1P has several beneficial effects on the vasculature.

Topics: Animals; Animals, Newborn; Case-Control Studies; Cell Survival; Cells, Cultured; Diabetes Mellitus, Type 2; Diabetic Cardiomyopathies; Dyslipidemias; Genotype; Glycated Hemoglobin; Glycosylation; Humans; Isolated Heart Preparation; Lipoproteins, HDL; Lysophospholipids; Male; Mice, Inbred C57BL; Mice, Knockout; Myocardial Reperfusion Injury; Myocytes, Cardiac; Oxidative Stress; Phenotype; Rats, Wistar; RNA Interference; Scavenger Receptors, Class B; Sphingosine; Time Factors; Transfection

Dyslipidemia is a risk factor for intimal hyperplasia (IH). Key to IH is vascular smooth muscle cell (VSMC) migration. Thrombospondin-1 (TSP-1) is a matricellular protein that stimulates VSMC migration.. HDL will inhibit and LDL will augment TSP-1-induced VSMC chemotaxis. VSMC chemotaxis will be inhibited by the HDL moiety, S1P, through the S1PR1 receptor, and augmented by the LDL component, LPA, through the LPAR1 receptor. The goal of this study was to determine the effect of HDL and LDL and their receptors on TSP-1-induced VSMC chemotaxis. For VSMC chemotaxis to TSP-1 cells received the following pretreatments: low (25 µg/ml) or optimal (75 µg/ml) concentration of HDL, S1P, optimal (75 µg/ml) or high (175 µg/ml) concentration of LDL, or LPA. For the receptor studies, VSMCs were transfected with siRNA to S1PR1, S1PR3, LPAR1, LPAR2, LPAR3, or a S1PR2 receptor antagonist. The TSP-1-induced chemotaxis results were (1) HDL (25 µg/ml) or LDL (75 µg/ml) exhibited no effect on chemotaxis; (2) HDL (75 µg/ml) inhibited chemotaxis by 50.9 ± 8 % and S1P by 43.4 ± 11.6 %; (3) LDL (175 µg/ml) augmented chemotaxis by 30 ± 10.4 % and LPA by 25.6 ± 12.3 %; (4) S1PR1 and S1PR3 knockdown and S1PR2 antagonist-treated cells augmented chemotaxis; and (5) LPAR1 and LPAR2 knockdown inhibited and LPAR3 knockdown had no effect on chemotaxis. In conclusion, HDL/S1P inhibits, while LDL/LPA stimulates TSP-1-induced VSMC chemotaxis. The HDL/S1P effect is mediated by the S1PR1-3 receptors. The LDL/LPA effects are mediated by the LPAR1 and LPAR2 receptors, but not LPAR3. Therefore, lipids have significant effects on TSP-1-induced VSMC chemotaxis.

Topics: Cells, Cultured; Chemotaxis; Dyslipidemias; Humans; Lipoproteins, HDL; Lipoproteins, LDL; Lysophospholipids; Muscle, Smooth, Vascular; Myocytes, Smooth Muscle; Receptors, Lysophosphatidic Acid; Receptors, Lysosphingolipid; RNA Interference; Signal Transduction; Sphingosine; Sphingosine-1-Phosphate Receptors; Thrombospondin 1; Time Factors; Transfection

The pro-fibrotic connective tissue growth factor (CTGF) has been linked to the development and progression of diabetic vascular and renal disease. We recently reported that low-density lipoproteins (LDL) induced expression of CTGF in aortic endothelial cells. However, the molecular mechanisms are not fully defined. Here, we have studied the mechanism by which LDL regulates CTGF expression in renal mesangial cells. In these cells, treatment with pertussis toxin abolished LDL-stimulated activation of ERK1/2 and c-Jun N-terminal kinase (JNK), indicating the involvement of heterotrimeric G proteins in LDL signaling. Treatment with LDL promoted activation and translocation of endogenous sphingosine kinase 1 (SK1) from the cytosol to the plasma membrane concomitant with production of sphingosine-1-phosphate (S1P). Pretreating cells with SK inhibitor, dimethylsphinogsine or down-regulation of SK1 and SK2 revealed that LDL-dependent activation of ERK1/2 and JNK is mediated by SK1. Using a green fluorescent protein-tagged S1P₁ receptor as a biological sensor for the generation of physiologically relevant S1P levels, we found that LDL induced S1P receptor activation. Pretreating cells with S1P₁/S1P₃ receptor antagonist VPC23019 significantly inhibited activation of ERK1/2 and JNK by LDL, suggesting that LDL elicits G protein-dependent activation of ERK1/2 and JNK by stimulating SK1-dependent transactivation of S1P receptors. Furthermore, S1P stimulation induced expression of CTGF in a dose-dependent manner that was markedly inhibited by blocking the ERK1/2 and JNK signaling pathways. LDL-induced CTGF expression was pertussis toxin sensitive and inhibited by dimethylsphinogsine down-regulation of SK1 and VPC23019 treatment. Our data suggest that SK1-dependent S1P receptor transactivation is upstream of ERK1/2 and JNK and that all three steps are required for LDL-regulated expression of CTGF in mesangial cells.

Topics: Animals; Cell Membrane; Cells, Cultured; Connective Tissue Growth Factor; Diabetic Nephropathies; Dyslipidemias; Gene Silencing; Humans; Lipoproteins, LDL; Lysophospholipids; MAP Kinase Signaling System; Mesangial Cells; Phosphotransferases (Alcohol Group Acceptor); Protein Isoforms; Protein Transport; Rats; Receptors, Lysosphingolipid; Recombinant Fusion Proteins; RNA, Messenger; RNA, Small Interfering; Sphingosine; Sphingosine-1-Phosphate Receptors; Transcriptional Activation; Up-Regulation

The purpose of this study was to define heterogeneity in the molecular profile of lipids, including sphingomyelin and sphingosine-1-phosphate, among physicochemically-defined HDL subpopulations and potential relevance to antiatherogenic biological activities of dense HDL3.. The molecular profile of lipids (cholesteryl esters, phospholipids, sphingomyelin, and sphingosine-1-phosphate) in physicochemically-defined normolipidemic HDL subpopulations was determined by high-performance liquid chromatography and gas chromatography. As HDL particle size and molecular weight decreased with increment in density, molar lipid content diminished concomitantly. On a % basis, sphingomyelin abundance diminished in parallel with progressive increase in HDL density from HDL2b (12.8%) to HDL3c (6.2%; P<0.001); in contrast, sphingosine-1-phosphate was preferentially enriched in small HDL3 (40 to 50 mmol/mol HDL) versus large HDL2 (15 to 20 mmol/mol HDL; P<0.01). Small HDL3c was equally enriched in LpA-I particles relative to LpA-I:A-II. The sphingosine-1-phosphate/sphingomyelin ratio correlated positively with the capacities of HDL subspecies to attenuate apoptosis in endothelial cells (r=0.73, P<0.001) and to retard LDL oxidation (r=0.58, P<0.01).. An elevated sphingosine-1-phosphate/sphingomyelin ratio is an integral feature of small dense HDL3, reflecting enrichment in sphingosine-1-phosphate, a key antiapoptotic molecule, and depletion of sphingomyelin, a structural lipid with negative impact on surface fluidity and LCAT activity. These findings further distinguish the structure and antiatherogenic activities of small, dense HDL.

Topics: Antioxidants; Apoptosis; Cholesterol Esters; Cholesterol, HDL; Cholesterol, LDL; Dyslipidemias; Enzyme Activation; Humans; Lipoproteins, HDL3; Lysophospholipids; Oxidation-Reduction; Oxidative Stress; Particle Size; Probability; Reference Values; Sensitivity and Specificity; Sphingomyelins; Sphingosine