The Arg82Cys Polymorphism of the Protein Nepmucin Implies a Role in HDL Metabolism.

Context: Blood lipid levels are linked to the risk of cardiovascular disease and regulated by genetic factors. A low-frequency polymorphism Arg82Cys (rs72836561) in the membrane protein nepmucin, encoded by CD300LG, is associated with lower fasting concentration of high-density lipoprotein cholesterol (HDLc) and higher fasting triglycerides. However, whether the variant is linked to postprandial lipids and glycemic status remains elusive. Objective: Here, we augment the genetic effect of Arg82Cys on fasting plasma concentrations of HDL subclasses, postprandial lipemia after a standardized high-fat meal, and glycemic status to further untangle its role in HDL metabolism. Methods: We elucidated fasting associations with HDL subclasses in a population-based cohort study (Oxford BioBank, OBB), including 4522 healthy men and women. We investigated fasting and postprandial consequences on HDL metabolism in recall-by-genotype (RbG) studies (fasting: 20 carrier/20 noncarrier; postprandial: 7 carrier/17 noncarrier), and shed light on the synergistic interaction with glycemic status. Results: A lower fasting plasma concentration of cholesterol in large HDL particles was found in healthy male carriers of the Cys82 polymorphism compared to noncarriers, both in the OBB (P = .004) and RbG studies (P = .005). In addition, the Cys82 polymorphism was associated with low fasting plasma concentrations of ApoA1 (P = .008) in the OBB cohort. On the contrary, we did not find differences in postprandial lipemia or 2-hour plasma glucose levels. Conclusion: Taken together, our results indicate an association between the Arg82Cys variant and a lower concentration of HDL particles and HDLc, especially in larger HDL subclasses, suggesting a link between nepmucin and HDLc metabolism or maturation.

Prehospital emergency medical technicians can perform ultrasonography and blood analysis in prehospital evaluation of patients with chronic obstructive pulmonary disease: a feasibility study.

INTRODUCTION: Crowding of the emergency departments is an increasing problem. Many patients with an exacerbation of chronic obstructive pulmonary disease (COPD) are often treated in the emergency departments for a very short period before discharged to their homes. It is possible that this treatment could take place in the patients' homes with sufficient diagnostics supporting the treatment. In an effort to keep the diagnostics and treatment of some of these patients in their homes and thus to reduce the patient load at the emergency departments, we implemented a prehospital treat-and-release strategy based on ultrasonography and blood testing performed by emergency medical technicians (EMT) or paramedics (PM) in patients with acute exacerbation of COPD. METHOD: EMTs and PMs were enrolled in a six-hour educational program covering ultrasonography of the lungs and point of care blood tests. During the seasonal peak of COPD exacerbations (October 2018 - May 2019) all patients who were treated by the ambulance crews for respiratory insufficiency were screened in the ambulances. If the patient had uncomplicated COPD not requiring immediate transport to the hospital, ultrasonographic examination of the lungs, measurements of C-reactive protein and venous blood gases analyses were performed. The response to the initial treatment and the results obtained were discussed via telemedical consultation with a prehospital anaesthesiologist who then decided to either release the patient at the scene or to have the patient transported to the hospital. The primary outcome was strategy feasibility. RESULTS: We included 100 EMTs and PMs in the study. During the study period, 771 patients with respiratory insufficiency were screened. Uncomplicated COPD was rare as only 41patients were treated according to the treat-and-release strategy. Twenty of these patients (49%) were released at the scene. In further ten patients, technical problems were encountered hindering release at the scene. CONCLUSION: In a few selected patients with suspected acute exacerbations of COPD, it was technically and organisationally feasible for EMTs and PMs to perform prehospital POCT-ultrasound and laboratory testing and release the patients following treatment. None of the patients released at the scene requested a secondary ambulance within the first 48 h following the intervention.

Apolipoprotein M and Risk of Type 2 Diabetes.

CONTEXT: Recent studies have discovered a role of apolipoprotein M (apoM) in energy metabolism, and observational analyses in humans suggest an association with type 2 diabetes. The causal relationship remains however elusive. OBJECTIVE: To investigate whether reduced plasma apoM concentrations are causally linked to increased risk of type 2 diabetes. DESIGN: Prospective study design analyzed by Mendelian randomization. SETTING AND PARTICIPANTS: Two cohorts reflecting the Danish general population: the Copenhagen City Heart Study (CCHS, n = 8589) and the Copenhagen General Population Study (CGPS; n = 93 857). Observational analyses included a subset of participants from the CCHS with available plasma apoM (n = 725). Genetic analyses included the complete cohorts (n = 102 446). During a median follow-up of 16 years (CCHS) and 8 years (CGPS), 563 and 2132 participants developed type 2 diabetes. MAIN OUTCOME MEASURES: Plasma apoM concentration, genetic variants in APOM, and type 2 diabetes. RESULTS: First, we identified an inverse correlation between plasma apoM and risk of type 2 diabetes in a subset of participants from the CCHS (hazard ratio between highest vs lowest quartile (reference) = 0.32; 95% confidence interval = 0.1-1.01; P for trend = .02). Second, genotyping of specific single nucleotide polymorphisms in APOM further revealed a 10.8% (P = 6.2 × 10-5) reduced plasma apoM concentration in participants with variant rs1266078. Third, a meta-analysis including data from 599 451 individuals showed no association between rs1266078 and risk of type 2 diabetes. CONCLUSIONS: The present study does not appear to support a causal association between plasma apoM and risk of type 2 diabetes.

Aging Suppresses Sphingosine-1-Phosphate Chaperone ApoM in Circulation Resulting in Maladaptive Organ Repair.

Here, we show that the liver-derived apolipoprotein M (ApoM) protects the lung and kidney from pro-fibrotic insults and that this circulating factor is attenuated in aged mice. Aged mouse hepatocytes exhibit transcriptional suppression of ApoM. This leads to reduced sphingosine-1-phosphate (S1P) signaling via the S1P receptor 1 (S1PR1) in the vascular endothelial cells of lung and kidney. Suboptimal S1PR1 angiocrine signaling causes reduced resistance to injury-induced vascular leak and leads to organ fibrosis. Plasma transfusion from Apom transgenic mice but not Apom knockout mice blocked fibrosis in the lung. Similarly, infusion of recombinant therapeutics, ApoM-Fc fusion protein enhanced kidney and lung regeneration and attenuated fibrosis in aged mouse after injury. Furthermore, we identified that aging alters Sirtuin-1-hepatic nuclear factor 4α circuit in hepatocytes to downregulate ApoM. These data reveal an integrative organ adaptation that involves circulating S1P chaperone ApoM+ high density lipoprotein (HDL), which signals via endothelial niche S1PR1 to spur regeneration over fibrosis.

The prognostic effect of smoking status on intensively treated acute myeloid leukaemia - A Danish nationwide cohort study.

With rising life expectancy, the importance of patient-related prognostic factors and how to integrate such data into clinical decision-making becomes increasingly important. The aim of this study was to evaluate the prognostic impact of smoking status in patients with acute myeloid leukaemia (AML) treated with intensive chemotherapy. We conducted a nationwide cohort study based on data obtained from the Danish National Leukaemia Registry (DNLR). The study comprised Danish patients aged 18-75 years, diagnosed with AML between 1 January 2000 and 31 December 2012. Medical records were reviewed and data on smoking status were collected. A total of 1040 patients (median age 59 years) were included, and 602 patients (58·9%) were categorised as ever-smokers and the remaining as never-smokers. Kaplan-Meier survival estimates revealed that ever-smokers had a significant shorter median overall survival (OS) at 17·2 months [95% CI (14·9;19·1)] compared to never-smokers at 24·5 months (95% CI [19·2;30·7]). Multivariate analysis revealed smoking status as a significant prognostic factor for inferior OS with a hazard ratio (HR) of 1·22 [95% CI (1·04;1·44)]. In conclusion, smoking status was found to be associated with inferior OS in intensively treated AML patients.

Acute intramyocardial lipid accumulation in rats does not slow cardiac conduction per se.

Diabetic patients suffer from both cardiac lipid accumulation and an increased risk of arrhythmias and sudden cardiac death. This correlation suggests a link between diabetes induced cardiac steatosis and electrical abnormalities, however, the underlying mechanism remains unknown. We previously showed that cardiac conduction velocity slows in Zucker diabetic fatty rats and in fructose-fat fed rats, models that both exhibit prominent cardiac steatosis. The aim of this study was to investigate whether acute cardiac lipid accumulation reduces conduction velocity per se. Cardiac lipid accumulation was induced acutely by perfusing isolated rat hearts with palmitate-glucose buffer, or subacutely by fasting rats overnight. Subsequently, longitudinal cardiac conduction velocity was measured in right ventricular tissue strips, and intramyocardial triglyceride and lipid droplet content was determined by thin layer chromatography and BODIPY staining, respectively. Perfusion with palmitate-glucose buffer significantly increased intramyocardial triglyceride levels compared to perfusion with glucose (2.16 ± 0.17 (n = 10) vs. 0.92 ± 0.33 nmol/mg WW (n = 9), P < 0.01), but the number of lipid droplets was very low in both groups. Fasting of rats, however, resulted in both significantly elevated intramyocardial triglyceride levels compared to fed rats (3.27 ± 0.43 (n = 10) vs. 1.45 ± 0.24 nmol/mg WW (n = 10)), as well as a larger volume of lipid droplets (0.60 ± 0.13 (n = 10) vs. 0.21 ± 0.06% (n = 10), P < 0.05). There was no significant difference in longitudinal conduction velocity between palmitate-glucose perfused and control hearts (0.77 ± 0.025 (n = 10) vs. 0.75 m/sec ± 0.029 (n = 9)), or between fed and fasted rats (0.75 ± 0.042 m/sec (n = 10) vs. 0.79 ± 0.047 (n = 10)). In conclusion, intramyocardial lipid accumulation does not slow cardiac longitudinal conduction velocity per se. This is true for both increased intramyocardial triglyceride content, induced by palmitate-glucose perfusion, and increased intramyocardial triglyceride and lipid droplet content, generated by fasting.

Effect of menopause and exercise training on plasma apolipoprotein M and sphingosine-1-phosphate.

The axis of apolipoprotein M (apoM) and sphingosine-1-phosphate (S1P) is of importance to plasma lipid levels, endothelial function, and development of atherosclerosis. Menopause is accompanied by dyslipidemia and an increased risk of atherosclerosis, which can be lowered by exercise training. The aim of this study was to explore if effects of menopause and training are paralleled by changes in the apoM/S1P axis. Healthy, late premenopausal [ n = 38, age 49.2 (SD 2)] and recent postmenopausal [ n = 37, age 53.3 (SD 3)] women from the Copenhagen Women Study participated in a 3-mo, aerobic high-intensity exercise intervention. Before training, plasma apoM was higher in postmenopausal [1.08 µmol/l (SD 0.2)] compared with premenopausal [0.82 µmol/l (SD 0.2)] women ( P < 0.0001). Plasma S1P was similar in the two groups [0.44 µmol/l (SD 0.1) and 0.46 µmol/l (SD 0.1), respectively]. Thus, the pretraining S1P/apoM ratio was 26% lower in postmenopausal than premenopausal women ( P < 0.0001). After the training program, plasma apoM increased from 0.82 µmol/l (SD 0.2) to 0.90 µmol/l (SD 0.3) in premenopausal women and from 1.08 µmol/l (SD 0.2) to 1.16 µmol/l (SD 0.3) in postmenopausal women ( P < 0.05). Plasma S1P increased from 0.44 µmol/l (SD 0.1) to 0.47 µmol/l (SD 0.1) in premenopausal women and from 0.46 µmol/l (SD 0.1) to 0.48 µmol/l (SD 0.1) in postmenopausal women ( P < 0.05). The results suggest that menopause is accompanied by higher plasma apoM but not S1P concentrations and that exercise training increases plasma apoM and S1P in healthy middle-aged women irrespective of menopausal status. NEW & NOTEWORTHY The apolipoprotein M/sphingosine-1-phosphate (apoM/S1P) complex is involved in maintaining a healthy endothelial barrier function. Our study is the first, to our knowledge, to show how menopause affects the apoM/S1P axis. The results suggest that menopause is accompanied by higher plasma apoM but not S1P concentrations. Second, to our knowledge the study is also the first to show that exercise training increases both apoM/S1P in women irrespective of menopausal status.

High doses of ANP and BNP exacerbate lipolysis in humans and the lipolytic effect of BNP is associated with cardiac triglyceride content in pigs.

Drugs facilitating the cardioprotective effects of natriuretic peptides are introduced in heart failure treatment. ANP and BNP also stimulate lipolysis and increase circulating concentrations of free fatty acids (FFAs); an aspect, however, thought to be confined to primates. We examined the lipolytic effect of natriuretic peptide infusion in healthy young men and evaluated the effect in a porcine model of myocardial ischemia and reperfusion. Six young healthy normotensive men underwent infusion with ANP, BNP, or CNP for 20 min. Blood samples were collected before, during, and after infusion for measurement of FFAs. In a porcine model of myocardial ischemia and reperfusion, animals were infused for 3 h with either BNP (n = 7) or saline (n = 5). Blood samples were collected throughout the infusion period, and cardiac tissue was obtained after infusion for lipid analysis. In humans, ANP infusion dose-dependently increased the FFA concentration in plasma 2.5-10-fold (baseline vs. 0.05 µg/kg/min P < 0.002) and with BNP 1.6-3.5-fold (P = 0.001, baseline vs. 0.02 µg/kg/min) 30 min after initiation of infusion. Infusion of CNP did not affect plasma FFA. In pigs, BNP infusion induced a 3.5-fold increase in plasma FFA (P < 0.0001), which remained elevated throughout the infusion period. Triglyceride content in porcine right cardiac ventricle tissue increased ∼5.5 fold in animals infused with BNP (P = 0.02). Natriuretic peptide infusion has similar lipolytic activity in human and pig. Our data suggest that short-term infusion increases the cardiac lipid content, and that the pig is a suitable model for studies of long-term effects mediated by natriuretic peptides.

Imiquimod-Induced Psoriasis-Like Skin Lesions Do Not Accelerate Atherosclerosis in Low-Density Lipoprotein Receptor-Deficient Mice.

Psoriasis is a chronic inflammatory skin disorder associated with several comorbidities, including atherosclerosis. Disease mechanisms that may affect both psoriasis and atherosclerosis include activation of T helper 1 and T helper 17 cells. Imiquimod application is an established mouse model of psoriasis-like skin inflammation. The cardiac glycoside digoxin inhibits the master transcription factor of T helper 17 differentiation, retinoid acid receptor-related orphan nuclear receptor γt, and attenuates IL-17-dependent pathologies in mice. We investigated whether cyclic imiquimod-induced psoriasis-like skin inflammation affects atherosclerosis in low-density lipoprotein receptor-deficient mice and whether digoxin modifies either disease. Topical imiquimod application increased ear thickness, keratinocyte proliferation, and accumulation of CD3+ T cells in the skin of low-density lipoprotein receptor-deficient mice. Also, imiquimod affected the mice systemically with induction of splenomegaly as well as increased plasma levels of IL-17A and serum amyloid A. Overall, imiquimod reduced atherosclerosis in the aortic arch en face, but it did not affect atherosclerosis in the aortic root. Digoxin significantly reduced the imiquimod-induced ear thickening, had divergent effects on imiquimod-induced systemic inflammation, and did not affect atherosclerosis. In conclusion, cyclic imiquimod applications can be used for long-term induction of psoriasis-like skin lesions, but they attenuate atherosclerosis in low-density lipoprotein-deficient mice. In this model, digoxin reduces skin inflammation, but it has no effect on atherosclerosis.

The Apolipoprotein M/S1P Axis Controls Triglyceride Metabolism and Brown Fat Activity.

Apolipoprotein M (apoM) is the carrier of sphingosine-1-phosphate (S1P) in plasma high-density lipoproteins. S1P is a bioactive lipid interacting with five receptors (S1P1-5). We show that lack of apoM in mice increases the amount of brown adipose tissue (BAT), accelerates the clearance of postprandial triglycerides, and protects against diet-induced obesity (i.e., a phenotype similar to that induced by cold exposure or ß3-adrenergic stimulation). Moreover, the data suggest that the phenotype of apoM-deficient mice is S1P dependent and reflects diminished S1P1 stimulation. The results reveal a link between the apoM/S1P axis and energy metabolism.

Apolipoprotein M mediates sphingosine-1-phosphate efflux from erythrocytes.

Sphingosine-1-phosphate (S1P) is a bioactive lipid implicated in e.g. angiogenesis, lymphocyte trafficking, and endothelial barrier function. Erythrocytes are a main source of plasma S1P together with platelets and endothelial cells. Apolipoprotein M (apoM) in HDL carries 70% of plasma S1P, whereas 30% is carried by albumin. The current aim was to investigate the role of apoM in export of S1P from human erythrocytes. Erythrocytes exported S1P more efficiently to HDL than to albumin, particularly when apoM was present in HDL. In contrast, export of sphingosine to HDL was unaffected by the presence of apoM. The specific ability of apoM to promote export of S1P was independent of apoM being bound in HDL particles. Treatment with MK-571, an inhibitor of the ABCC1 transporter, effectively reduced export of S1P from human erythrocytes to apoM, whereas the export was unaffected by inhibitors of ABCB1 or ATPase. Thus, ABCC1 could be involved in export of S1P from erythrocytes to apoM.

Uremia does not affect neointima formation in mice.

Atherosclerotic cardiovascular disease is a major complication of chronic kidney disease (CKD). CKD leads to uremia, which modulates the phenotype of aortic smooth muscle cells (SMCs). Phenotypic modulation of SMCs plays a key role in accelerating atherosclerosis. We investigated the hypothesis that uremia potentiates neointima formation in response to vascular injury in mice. Carotid wire injury was performed on C57BL/6 wt and apolipoprotein E knockout (Apoe -/-) mice two weeks after induction of uremia by 5/6 nephrectomy. Wire injury led to neointima formation and downregulation of genes encoding classical SMC markers (i.e., myocardin, α-smooth muscle actin, SM22-alpha, and smooth muscle myosin heavy chain) in both wt and Apoe -/- mice. Contrary to our expectations, uremia did not potentiate neointima formation, nor did it affect intimal lesion composition as judged from magnetic resonance imaging and histological analyses. Also, there was no effect of uremia on SMC marker gene expression in the injured carotid arteries, suggesting that there may be different effects of uremia on SMCs in different vascular beds. In conclusion, uremia does not accelerate neointima formation in response to wire injury of the carotid artery in mice.

ApoB and apoM - New aspects of lipoprotein biology in uremia-induced atherosclerosis.

Chronic kidney disease affects as much as 13% of the population, and is associated with a markedly increased risk of developing cardiovascular disease. One of the underlying reasons is accelerated development of atherosclerosis. This can be ascribed both to increased occurrence of traditional cardiovascular risk factors, and to risk factors that may be unique to patients with chronic kidney disease. The latter is reflected in the observation that the current treatment modalities, mainly directed against traditional risk factors, are insufficient to prevent cardiovascular disease in the patient with chronic kidney disease. This review discusses mechanisms accelerating uremic atherosclerosis with a specific focus on the putative roles of apolipoprotein(apo)s B and M that may be particularly important in patients with chronic kidney disease.

Uremia modulates the phenotype of aortic smooth muscle cells.

BACKGROUND AND AIMS: Chronic kidney disease leads to uremia and markedly accelerates atherosclerosis. Phenotypic modulation of smooth muscle cells (SMCs) in the arterial media plays a key role in accelerating atherogenesis. The aim of this study was to investigate whether uremia per se modulates the phenotype of aortic SMCs in vivo. METHODS: Moderate uremia was induced by 5/6 nephrectomy in apolipoprotein E knockout (ApoE-/-) and wildtype C57Bl/6 mice. Plasma analysis, gene expression, histology, and myography were used to determine uremia-mediated changes in the arterial wall. RESULTS: Induction of moderate uremia in ApoE-/- mice increased atherosclerosis in the aortic arch en face 1.6 fold (p = 0.04) and induced systemic inflammation. Based on histological analyses of aortic root sections, uremia increased the medial area, while there was no difference in the content of elastic fibers or collagen in the aortic media. In the aortic arch, mRNA and miRNA expression patterns were consistent with a uremia-mediated phenotypic modulation of SMCs; e.g. downregulation of myocardin, α-smooth muscle actin, and transgelin; and upregulation of miR146a. Notably, these expression patterns were observed after acute (2 weeks) and chronic (19 and 30 weeks) uremia, both under normo- and hypercholesterolemic settings. Functionally, aortic constriction was decreased in uremic as compared to non-uremic aorta segments, as measured by myography. CONCLUSIONS: Uremia modulates the phenotype of aortic SMCs as determined by mRNA/miRNA expression, an increased medial area, and decreased aortic contractility. We propose that this phenotypic modulation of SMCs precedes the acceleration of atherosclerosis observed in uremic mice.

Liraglutide Reduces Both Atherosclerosis and Kidney Inflammation in Moderately Uremic LDLr-/- Mice.

Chronic kidney disease (CKD) leads to uremia. CKD is characterized by a gradual increase in kidney fibrosis and loss of kidney function, which is associated with a progressive increase in risk of atherosclerosis and cardiovascular death. To prevent progression of both kidney fibrosis and atherosclerosis in uremic settings, insight into new treatment options with effects on both parameters is warranted. The GLP-1 analogue liraglutide improves glucose homeostasis, and is approved for treatment of type 2 diabetes. Animal studies suggest that GLP-1 also dampens inflammation and atherosclerosis. Our aim was to examine effects of liraglutide on kidney fibrosis and atherosclerosis in a mouse model of moderate uremia (5/6 nephrectomy (NX)). Uremic (n = 29) and sham-operated (n = 14) atherosclerosis-prone low density lipoprotein receptor knockout mice were treated with liraglutide (1000 µg/kg, s.c. once daily) or vehicle for 13 weeks. As expected, uremia increased aortic atherosclerosis. In the remnant kidneys from NX mice, flow cytometry revealed an increase in the number of monocyte-like cells (CD68+F4/80-), CD4+, and CD8+ T-cells, suggesting that moderate uremia induced kidney inflammation. Furthermore, markers of fibrosis (i.e. Col1a1 and Col3a1) were upregulated, and histological examinations showed increased glomerular diameter in NX mice. Importantly, liraglutide treatment attenuated atherosclerosis (~40%, p < 0.05) and reduced kidney inflammation in NX mice. There was no effect of liraglutide on expression of fibrosis markers and/or kidney histology. This study suggests that liraglutide has beneficial effects in a mouse model of moderate uremia by reducing atherosclerosis and attenuating kidney inflammation.

Hypoxia-Inducible Factor-1α Expression in Macrophages Promotes Development of Atherosclerosis.

OBJECTIVE: Atherosclerotic lesions contain hypoxic areas, but the pathophysiological importance of hypoxia is unknown. Hypoxia-inducible factor-1α (HIF-1α) is a key transcription factor in cellular responses to hypoxia. We investigated the hypothesis that HIF-1α has effects on macrophage biology that promotes atherogenesis in mice. APPROACH AND RESULTS: Studies with molecular probes, immunostaining, and laser microdissection of aortas revealed abundant hypoxic, HIF-1α-expressing macrophages in murine atherosclerotic lesions. To investigate the significance of macrophage HIF-1α, Ldlr(-/-) mice were transplanted with bone marrow from mice with HIF-1α deficiency in the myeloid cells or control bone marrow. The HIF-1α deficiency in myeloid cells reduced atherosclerosis in aorta of the Ldlr(-/-) recipient mice by ≈72% (P=0.006).In vitro, HIF-1α-deficient macrophages displayed decreased differentiation to proinflammatory M1 macrophages and reduced expression of inflammatory genes. HIF-1α deficiency also affected glucose uptake, apoptosis, and migratory abilities of the macrophages. CONCLUSIONS: HIF-1α expression in macrophages affects their intrinsic inflammatory profile and promotes development of atherosclerosis.

Impaired endothelial barrier function in apolipoprotein M-deficient mice is dependent on sphingosine-1-phosphate receptor 1.

Apolipoprotein M (ApoM) transports sphingosine-1-phosphate (S1P) in plasma, and ApoM-deficient mice (Apom(-/-)) have ∼50% reduced plasma S1P levels. There are 5 known S1P receptors, and S1P induces adherens junction formation between endothelial cells through the S1P1 receptor, which in turn suppresses vascular leak. Increased vascular permeability is a hallmark of inflammation. The purpose of this study was to explore the relationships between vascular leakage in ApoM deficiency and S1P1 function in normal physiology and in inflammation. Vascular permeability in the lungs was assessed by accumulation of dextran molecules (70 kDa) and was increased ∼40% in Apom(-/-) mice compared to WT (C57Bl6/j) mice. Reconstitution of plasma ApoM/S1P or treatment with an S1P1 receptor agonist (SEW2871) rapidly reversed the vascular leakage to a level similar to that in WT mice, suggesting that it is caused by decreased plasma levels of S1P and reduced S1P1 stimulation. In a carrageenan-induced model of inflammation, Apom(-/-) mice had increased vascular leakage compared with that in WT mice. Adenoviral overexpression of ApoM in Apom(-/-) mice decreased the vascular leakage compared to adenoviral overexpression of green fluorescent protein. The study suggests that vascular leakage of albumin-sized particles in ApoM deficiency is S1P- and S1P1-dependent and this dependency exacerbates the response to inflammatory stimuli.-Christensen, P. M., Liu, C. H., Swendeman, S. L., Obinata, H., Qvortrup, K., Nielsen, L B., Hla, T., Di Lorenzo, A., Christoffersen, C. Impaired endothelial barrier function in apolipoprotein M-deficient mice is dependent on sphingosine-1-phosphate receptor 1.

Sphingosine-1-phosphate reduces ischaemia-reperfusion injury by phosphorylating the gap junction protein Connexin43.

AIM: Increasing evidence points to lipoprotein composition rather than reverse cholesterol transport in the cardioprotective properties of high-density lipoproteins (HDLs). HDL binding to receptors at the surface of cardiomyocytes activates signalling pathways promoting survival, but downstream targets are largely unknown. Here, we investigate the pathways by which the sphingosine-1-phosphate (S1P) constituent of HDL limits cell death induced by cardiac ischaemia-reperfusion (I/R). METHODS AND RESULTS: Apolipoprotein M (ApoM) transgenic (Apom-Tg) mice, in which plasma S1P is increased by 296%, and wild-type (WT) mice were subjected to in vivo I/R. Infarct size, neutrophil infiltration into the infarcted area, and serum Troponin I were less pronounced in Apom-Tg mice. In vitro experiments suggest that this cardioprotection depends on direct effects of S1P on cardiomyocytes, whereas leucocyte recruitment seems only indirectly affected. Importantly, short-term S1P treatment at the onset of reperfusion was sufficient to reduce I/R injury in isolated perfused hearts. Mechanistic in vitro and ex vivo studies revealed that 5 min of S1P treatment induced phosphorylation of the gap junction protein Connexin43 (Cx43) on Serine368 (S368), which was mediated by S1P2 and S1P3, but not by S1P1, receptors in cardiomyocytes. Finally, S1P-induced reduction of infarct size after ex vivo I/R was lost in hearts of mice with a truncated C-terminus of Cx43 (Cx43(K258/KO)) or in which the S368 is mutated to a non-phosphorylatable alanine (Cx43(S368A/S368A)). CONCLUSION: Our study reveals an important molecular pathway by which modulating the apoM/S1P axis has a therapeutic potential in the fight against I/R injury in the heart.

Plasma ADAMTS-13 protein is not associated with portal hypertension or hemodynamic changes in patients with cirrhosis.

BACKGROUND: Activated hepatic stellate cells synthesize the matrix metalloprotease ADAMTS13, which may be involved in the development of liver cirrhosis and portal hypertension. Plasma ADAMTS13 activity has been reported as both increased and decreased in cirrhosis, but ADAMTS13 protein has not previously been examined. AIM: To evaluate ADAMTS13 protein in the hepatic circulation and the relation to disease severity, portal pressure, and systemic hemodynamics in cirrhotic patients. METHODS: Sixty-one cirrhotic patients (Child class: A=22; B=21; C=18) and nine healthy controls underwent a liver vein catheterization with measurement of splanchnic and systemic hemodynamics, and plasma ADAMTS13 protein concentration in a hepatic vein and the femoral artery. RESULTS: ADAMTS13 protein concentrations were increased in cirrhotic patients compared with controls (774ng/ml [IQR: 585-955] vs. 538ng/ml [IQR: 484-631], p<0.03). There were no significant correlations to MELD score, Child Pugh score, portal pressure, nor systemic vascular resistance or cardiac output. CONCLUSIONS: The increased concentration of ADAMTS13 protein in the hepatic circulation may reflect an increased number of active hepatic stellate cells in cirrhosis. However, ADAMTS13 was unrelated to portal hypertension and systemic hemodynamics. In conclusion, ADAMTS13 does not appear to be associated to disease severity or the hemodynamic derangement in patients with cirrhosis.

Altered metabolism of LDL in the arterial wall precedes atherosclerosis regression.

RATIONALE: Plasma cholesterol lowering is beneficial in patients with atherosclerosis. However, it is unknown how it affects entry and degradation of low-density lipoprotein (LDL) particles in the lesioned arterial wall. OBJECTIVE: We studied the effect of lipid-lowering therapy on LDL permeability and degradation of LDL particles in atherosclerotic aortas of mice by measuring the accumulation of iodinated LDL particles in the arterial wall. METHODS AND RESULTS: Cholesterol-fed, LDL receptor-deficient mice were treated with either an anti-Apob antisense oligonucleotide or a mismatch control antisense oligonucleotide once a week for 1 or 4 weeks before injection with preparations of iodinated LDL particles. The anti-Apob antisense oligonucleotide reduced plasma cholesterol by ≈90%. The aortic LDL permeability and degradation rates of newly entered LDL particles were reduced by ≈50% and ≈85% already after 1 week of treatment despite an unchanged pool size of aortic iodinated LDL particles. In contrast, the size, foam cell content, and aortic pool size of iodinated LDL particles of aortic atherosclerotic plaques were not reduced until after 4 weeks of treatment with the anti-Apob antisense oligonucleotide. CONCLUSIONS: Improved endothelial barrier function toward the entry of plasma LDL particles and diminished aortic degradation of the newly entered LDL particles precede plaque regression.