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Van Klinken J.B.,Einthoven Laboratory for Experimental Vascular Medicine | Willems Van Dijk K.,Einthoven Laboratory for Experimental Vascular Medicine
Bioinformatics | Year: 2016

Elementary flux mode (EFM) analysis is a powerful technique for determining the metabolic capacities and robustness of stoichiometric networks. Recently, several improvements have been made to the algorithm for enumerating the EFMs, making the study of large models possible. However, currently these tools require high performance workstations to perform large-scale EFM computations, thus limiting their applicability. We developed a more time and memory efficient implementation of the algorithm for EFM enumeration in MATLAB, called FluxModeCalculator, which enables large-scale EFM computation on ordinary desktop computers. © 2015 The Author. All rights reserved.


Lips M.A.,Leiden University | Van Klinken J.B.,Leiden University | Van Harmelen V.,Leiden University | Dharuri H.K.,Leiden University | And 17 more authors.
Diabetes Care | Year: 2014

OBJECTIVE: Obesity and type 2 diabetes mellitus (T2DM) have been associated with increased levels of circulating branched-chain amino acids (BCAAs) that may be involved in the pathogenesis of insulin resistance. However, weight loss has not been consistently associated with the reduction of BCAA levels. RESEARCH DESIGN AND METHODS: We included 30 obese normal glucose-tolerant (NGT) subjects, 32 obese subjects with T2DM, and 12 lean female subjects. Obese subjects underwent either a restrictive procedure (gastric banding [GB], a very low-calorie diet [VLCD]), or a restrictive/bypass procedure (Roux-en-Y gastric bypass [RYGB] surgery). Fasting blood samples were taken for the determination of amine group containing metabolites 4 weeks before, as well as 3 weeks and 3 months after the intervention. RESULTS: BCAA levelswere higher in T2DM subjects, but not in NGT subjects, compared with lean subjects. Principal component (PC) analysis revealed a concise PC consisting of all BCAAs, which showed a correlation with measures of insulin sensitivity and glucose tolerance. Only after the RYGB procedure, and at both 3 weeks and 3 months, were circulating BCAA levels reduced. CONCLUSIONS: Our data confirm an association between deregulation of BCAA metabolism in plasma and insulin resistance and glucose in tolerance. Three weeks after undergoing RYGB surgery, a significant decrease in BCAAs in both NGT as well as T2DM subjects was observed. After 3 months, despite inducing significant weight loss, neither GB nor VLCD induced a reduction in BCAA levels. Our results indicate that the bypass procedure of RYGB surgery, independent of weight loss or the presence of T2DM, reduces BCAA levels in obese subjects. © 2014 by the American Diabetes Association.


Arslan F.,University Utrecht | Arslan F.,Netherlands Heart Institute | Smeets M.B.,University Utrecht | Riem Vis P.W.,University Utrecht | And 12 more authors.
Circulation Research | Year: 2011

Rationale: The extracellular matrix may induce detrimental inflammatory responses on degradation, causing adverse cardiac remodeling and heart failure. The extracellular matrix protein fibronectin-EDA-/- (EIIIA; EDA) is upregulated after tissue injury and may act as a "danger signal" for leukocytes to cause adverse cardiac remodeling after infarction. Objective: In the present study, we evaluated the role of EDA-/- in regulation of postinfarct inflammation and repair after myocardial infarction. Methods and Results: Wild-type and EDA-/- mice underwent permanent ligation of the left anterior coronary artery. Despite equal infarct size between groups (38.2±4.6% versus 38.2±2.9% of left ventricle; P=0.985), EDA -/- mice exhibited less left ventricular dilatation and enhanced systolic performance compared with wild-type mice as assessed by serial cardiac MRI measurements. In addition, EDA-/- mice exhibited reduced fibrosis of the remote area without affecting collagen production, cross-linking, and deposition in the infarct area. Subsequently, ventricular contractility and relaxation was preserved in EDA-/-. At tissue level, EDA -/- mice showed reduced inflammation, metalloproteINase 2 and 9 activity, and myofibroblast transdifferentiation. Bone marrow transplantation experiments revealed that myocardium-induced EDA-/- and not EDA-/- from circulating cells regulates postinfarct remodeling. FINally, the absence of EDA-/- reduced monocyte recruitment as well as monocytic Toll-like receptor 2 and CD49d expression after infarction. Conclusions: Our study demonstrated that parenchymal fn-EDA-/- plays a critical role in adverse cardiac remodeling after infarction. Absence of fn-EDA-/- enhances survival and cardiac performance by modulating matrix turnover and inflammation via leukocytes and fibroblasts after infarction. © 2011 American Heart Association, Inc.


Kuhnast S.,TNO | Kuhnast S.,Einthoven Laboratory for Experimental Vascular Medicine | Fiocco M.,LUMC | Fiocco M.,Leiden University | And 4 more authors.
European Journal of Pharmacology | Year: 2015

Non-HDL-cholesterol is well recognised as a primary causal risk factor in cardiovascular disease. However, despite consistent epidemiological evidence for an inverse association between HDL-C and coronary heart disease, clinical trials aimed at raising HDL-C (AIM-HIGH, HPS2-THRIVE, dal-OUTCOMES) failed to meet their primary goals. This systematic review and meta-analysis investigated the effects of established and novel treatment strategies, specifically targeting HDL, on inhibition of atherosclerosis in cholesteryl ester transfer protein-expressing animals, and the prevention of clinical events in randomised controlled trials. Linear regression analyses using data from preclinical studies revealed associations for TC and non-HDL-C and lesion area (R2=0.258, P=0.045; R2=0.760, P<0.001), but not for HDL-C (R2=0.030, P=0.556). In clinical trials, non-fatal myocardial infarction risk was significantly less in the treatment group with pooled odd ratios of 0.87 [0.81; 0.94] for all trials and 0.85 [0.78; 0.93] after excluding some trials due to off-target adverse events, whereas all-cause mortality was not affected (OR 1.05 [0.99-1.10]). Meta-regression analyses revealed a trend towards an association between between-group differences in absolute change from baseline in LDL-C and non-fatal myocardial infarction (P=0.066), whereas no correlation was found for HDL-C (P=0.955). We conclude that the protective role of lowering LDL-C and non-HDL-C is well-established. The contribution of raising HDL-C on inhibition of atherosclerosis and the prevention of cardiovascular disease remains undefined and may be dependent on the mode of action of HDL-C-modification. Nonetheless, treatment strategies aimed at improving HDL function and raising apolipoprotein A-I may be worth exploring. © 2015 Elsevier B.V. All rights reserved.


Verschuren J.J.W.,Leiden University | Ocak G.,Leiden University | Dekker F.W.,Leiden University | Rabelink T.J.,Leiden University | And 6 more authors.
Clinical Journal of the American Society of Nephrology | Year: 2013

Background and objectives Arteriovenous fistula (AVF) failure remains an important cause of morbidity in hemodialysis patients. The exact underlying mechanisms responsible forAVF failure are unknown but processes like proliferation, inflammation, vascular remodeling, and thrombosis are thought to be involved. The current objective was to investigate the association between AVF failure and single nucleotide polymorphisms (SNPs) in genes related to these pathophysiologic processes in a large population of incident hemodialysis patients. Design, setting, participants, & measurements A total of 479 incident hemodialysis patients were included between January 1997 and April 2004. Follow-up lasted 2 years or until AVF failure, defined as surgery, percutaneous endovascular intervention, or abandonment of the vascular access. Forty-three SNPs in 26 genes, related to proliferation, inflammation, endothelial function, vascular remodeling, coagulation, and calcium/ phosphate metabolism, were genotyped. Relations were analyzed using Cox regression analysis. Results In total, 207 (43.2%) patients developed AVF failure. After adjustment, two SNPs were significantly associated with an increased risk of AVF failure. The hazard ratio (95% confidence interval) of LRP1 rs1466535 was 1.75 (1.15 to 2.66) and patients with factor V Leiden had a hazard ratio of 2.54 (1.41 to 4.56) to develop AVF failure. The other SNPs were not associated with AVF failure. Conclusions In this large cohort of hemodialysis patients, only 2 of the 43 candidate SNPs were associated with an increased risk of AVF failure. Whether other factors, like local hemodynamic circumstances, are more important or other SNPs play a role in AVF failure remains to be elucidated. © 2013 by the American Society of Nephrology.


Van Solingen C.,LUMC | Van Solingen C.,Einthoven Laboratory for Experimental Vascular Medicine | De Boer H.C.,LUMC | De Boer H.C.,Einthoven Laboratory for Experimental Vascular Medicine | And 14 more authors.
Cardiovascular Research | Year: 2011

Aims MicroRNA-126 (miR-126), which is enriched in endothelial cells, plays a role in angiogenesis. Based on the seed sequence, miR-126 can also be predicted to regulate vasculogenesis by modulating the endothelial expression of stromal cell-derived factor-1 (SDF-1).Methods and resultsUsing miR-reporter constructs, we first validated that miR-126 inhibits SDF-1 expression in endothelial cells in vitro. Next, we investigated the potential relevance of this observation with respect to the mobilization of progenitor cells. For this, we studied the migration of human CD34 progenitor cells towards chemotactic factors present in endothelial cell-conditioned medium. Antagomir-induced silencing of miR-126 elevated SDF-1 expression by human umbilical vein endothelial cells and enhanced migration of the CD34 cells. In a murine model of hind limb ischaemia, a striking increase in the number of circulating Sca-1+/Lin- progenitor cells in antagomir-126-treated mice was observed when compared with scramblemir-treated controls. Immunohistochemical staining of capillaries in the post-ischaemic gastrocnemius muscle of miR-126-silenced mice revealed elevated SDF-1 expressing CD31-positive capillaries, whereas a mobilizing effect of miR-126 inhibition was not detected in healthy control animals.ConclusionmiR-126 can regulate the expression of SDF-1 in endothelial cells. In the context of an ischaemic event, systemic silencing of miR-126 leads to the mobilization of Sca-1+/Lin - progenitor cells into the peripheral circulation, potentially in response to elevated SDF-1 expression by endothelial cells present in the ischaemic tissue. © 2011 The Author.


Ewing M.M.,Leiden University | Ewing M.M.,Einthoven Laboratory for Experimental Vascular Medicine | Karper J.C.,Einthoven Laboratory for Experimental Vascular Medicine | Abdul S.,Einthoven Laboratory for Experimental Vascular Medicine | And 10 more authors.
International Journal of Cardiology | Year: 2013

Objective T-cells are central to the immune response responsible for native atherosclerosis. The objective of this study is to investigate T-cell contribution to post-interventional accelerated atherosclerosis development, as well as the role of the CD28-CD80/86 co-stimulatory and Cytotoxic T-Lymphocyte Antigen (CTLA)-4 co-inhibitory pathways controlling T-cell activation status in this process. Methods and results The role of T-cells and the CD28-CD80/86 co-stimulatory and CTLA-4 co-inhibitory pathways were investigated in a femoral artery cuff mouse model for post-interventional remodeling, with notable intravascular CTLA-4 + T-cell infiltration. Reduced intimal lesions developed in CD4-/- and CD80-/-CD86-/- mice compared to normal C57Bl/6J controls. Systemic abatacept-treatment, a soluble CTLA-4Ig fusion protein that prevents CD28-CD80/86 co-stimulatory T-cell activation, prevented intimal thickening by 58.5% (p = 0.029). Next, hypercholesterolemic ApoE3*Leiden mice received abatacept-treatment which reduced accelerated atherosclerosis development by 78.1% (p = 0.040) and prevented CD4 T-cell activation, indicated by reduced splenic fractions of activated KLRG1 +, PD1 +, CD69 + and CTLA-4 + T-cells. This correlated with reduced plasma interferon-γ and elevated interleukin-10 levels. The role of CTLA-4 was confirmed using CTLA-4 blocking antibodies, which strongly increased vascular lesion size by 66.7% (p = 0.008), compared to isotype-treated controls. Conclusions T-cell CD28-CD80/86 co-stimulation is vital for post-interventional accelerated atherosclerosis development and is regulated by CTLA-4 co-inhibition, indicating promising clinical potential for prevention of post-interventional remodeling by abatacept. © 2013 Elsevier Ireland Ltd. All rights reserved.


De Vries M.R.,Einthoven Laboratory for Experimental Vascular Medicine | De Vries M.R.,Leiden University | Wezel A.,Leiden University | Schepers A.,Leiden University | And 8 more authors.
Cardiovascular Research | Year: 2013

AimsFailure of vein graft conduits due to vein graft thickening, accelerated atherosclerosis, and subsequent plaque rupture is applicable to 50% of all vein grafts within 10 years. New potential therapeutic targets to treat vein graft disease may be found in components of the innate immune system, such as mast cells and complement factors, which are known to be involved in atherosclerosis and plaque destabilization. Interestingly, mast cells can be activated by complement factor C5a and, therefore, a direct role for C5a-mediated mast cell activation in vein graft disease is anticipated. We hypothesize that C5a-mediated mast cell activation is involved in the development and destabilization of vein graft lesions.Methods and resultsMast cells accumulated in time in murine vein graft lesions, and C5a and C5a-receptor (CD88) expression was up-regulated during vein graft disease in apolipoprotein E-deficient mice. Mast cell activation with dinitrophenyl resulted in a profound increase in vein graft thickening and in the number of plaque disruptions. C5a application enhanced vein graft lesion formation, while treatment with a C5a-receptor antagonist resulted in decreased vein graft disease. C5a most likely exerts its function via mast cell activation since the mast cell inhibitor cromolyn totally blocked C5a-enhanced vein graft disease. ConclusionThese data provide evidence that complement factor C5a-induced mast cell activation is highly involved in vein graft disease, which identifies new targets to prevent vein graft disease. © 2013 The Author.


De Boer H.C.,Leiden University | De Boer H.C.,Einthoven Laboratory for Experimental Vascular Medicine | Hovens M.M.,General Internal Medicine and Endocrinology | Hovens M.M.,Rijnstate Hospital | And 10 more authors.
Arteriosclerosis, Thrombosis, and Vascular Biology | Year: 2011

Objective-: The presence of kinase-insert domain-containing receptor (KDR) on circulating CD34 cells is assumed to be indicative for the potential of these cells to support vascular maintenance and repair. However, in bone marrow and in granulocyte colony-stimulating factor (G-CSF)-mobilized peripheral blood, less than 0.5% of CD34 cells co-express KDR. Therefore, we studied whether CD34+/KDR+ cells are generated in the peripheral circulation. Methods and results-: Using an ex vivo flow model, we show that activated platelets enable CD34+ cells to home to sites of vascular injury and that upon immobilization, KDR+ is translocated from an endosomal compartment to the cell-surface within 15 minutes. In patients with diabetes mellitus type 2, the percentage of circulating CD34+ co-expressing KDR was significantly elevated compared to age-matched controls. When treated with aspirin, the patients showed a 49% reduction in the generation of CD34+/KDR+ cells, indicating that the level of circulating CD34+/KDR+ cells also relates to in vivo platelet activation. Conclusion-: Circulating CD34+/KDR+ are not mobilized from bone marrow as a predestined endothelial progenitor cell population but are mostly generated from circulating multipotent CD34 + cells at sites of vascular injury. Therefore, the number of circulating CD34+/KDR+ cells may serve as a marker for vascular injury. © 2011 American Heart Association, Inc.


Roach R.E.J.,Leiden University | Lijfering W.M.,Leiden University | Lijfering W.M.,Einthoven Laboratory for Experimental Vascular Medicine | Rosendaal F.R.,Leiden University | And 5 more authors.
Circulation | Year: 2014

BACKGROUND-: The risk of recurrent venous thrombosis is 2-fold higher in men than in women. In contrast, no such sex difference in the risk of first venous thrombosis has been reported. We hypothesized that, for a first event, a risk difference between the sexes is masked by female exposure to reproductive factors (oral contraception, pregnancy/puerperium, and postmenopausal hormone therapy). METHODS AND RESULTS-: From the Multiple Environmental and Genetic Assessment of Risk Factors for Venous Thrombosis (MEGA) study, a population-based case-control study on risk factors for venous thrombosis, 2915 patients with a first venous thrombosis and their partners as control subjects were included. Odds ratios and 95% confidence intervals for first venous thrombosis were assessed in men compared with women without reproductive risk factors by use of conditional logistic regression. Analyses were stratified in 10-year age categories to account for the variation in exposure to reproductive risk factors over different age groups and adjusted for body mass index and smoking. Overall, men had a 2.1-fold (95% confidence interval, 1.9-2.4) increased risk of first venous thrombosis compared with women without reproductive risk factors. Similar results were found when 10-year age categories were viewed separately. Adjustment for body mass index and smoking and exclusion of cancer patients did not materially affect the results. CONCLUSIONS-: When female reproductive risk factors are taken into account, the risk of a first venous thrombosis is twice as high in men as in women. These findings are in line with previous studies on recurrent venous thrombosis and may have implications for future treatment and prevention strategies. © 2013 American Heart Association, Inc.

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