Michiel E Stegenga

Academisch Medisch Centrum Universiteit van Amsterdam, Amsterdam, North Holland, Netherlands

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Publications (11)56.39 Total impact

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    ABSTRACT: In diabetes mellitus and sepsis, low erythrocyte glutathione (GSH) concentrations are found. Whether this is caused by lowered GSH production has not been clarified. To obtain insight in the relationship between erythrocyte GSH concentrations and GSH production, GSH kinetics were measured in healthy male volunteers during 4 different clamps (low-dose or medium-dose insulin [100 or 400 pmol/L] and euglycemia or hyperglycemia [5 or 12 mmol/L]) in a control setting (n = 6; all 4 clamps in the same subject) or after systemic administration of lipopolysaccharide (to mimic sepsis) (4 groups of n = 6; each clamp in a different subject). Hyperinsulinemia decreased erythrocyte GSH concentration (P = .042), but did not affect fractional synthetic rate (FSR) of GSH. Hyperglycemia did not affect erythrocyte GSH concentration, but decreased FSR of GSH (P = .025). Lipopolysaccharide decreased erythrocyte GSH concentration (P < .001), but increased FSR of erythrocyte GSH (P = .035). Depending on the metabolic circumstances, we found either stable GSH concentrations with lower production rates or decreased levels with either no change or an increase in production rate. Based upon these data, it seems inappropriate to infer conclusions about changes in synthesis rate of GSH from changes in its concentration.
    Metabolism: clinical and experimental 01/2011; 60(1):99-106. · 3.10 Impact Factor
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    ABSTRACT: Thiazolidinediones (TZDs) are synthetic agonists for the peroxisome proliferator-activating receptor-gamma receptor and are currently in use as oral glucose-lowering drugs. TZDs have immune-modulating effects in vitro and in vivo. Because patients with type 2 diabetes have an increased risk for pneumonia, we evaluated the influence of ciglitazone, a TZD, on markers of inflammation and outcome during pneumonia caused by Streptococcus pneumoniae. In vivo animal study and in vitro study. University research laboratory. Female C57Bl/6 mice and murine alveolar macrophage-like MH-S cells. C57Bl/6 mice were inoculated with 10 colony-forming units of S. pneumoniae intranasally. The following interventions were studied: 1) vehicle at t = 0; 2) ciglitazone 5 mg/kg intraperitoneally at t = 0; and 3) ciglitazone 5 mg/kg intraperitoneally at t = 0 and 24 hours. Mice were killed at either 24 or 48 hours after infection. Additionally, phagocytosis and killing of S. pneumoniae by MH-S cells were assessed in vitro. Single treatment with ciglitazone reduced bacterial loads at 24 hours but not at 48 hours, whereas repeated ciglitazone treatment did diminish bacterial loads at 48 hours. After 24 hours, cytokine levels in lung homogenate were lower in single-dose ciglitazone-treated mice; however, after 48 hours, there was no difference in lung cytokines between any of the experimental groups. Repeated ciglitazone treatment was associated with less pulmonary inflammation, as judged by histologic examination. On both time points, there was no difference in plasma cytokine levels or lung myeloperoxidase levels between experimental groups. In an additional experiment, ciglitazone treatment (given once daily) tended to reduce mortality. Ciglitazone did not influence phagocytosis or killing of S. pneumoniae by murine alveolar macrophages. Ciglitazone reduces bacterial outgrowth and local inflammation at least during the early stage of S. pneumoniae pneumonia in mice.
    Critical care medicine 01/2010; 37(2):614-8. · 6.37 Impact Factor
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    ABSTRACT: Diabetes patients have an increased risk of sepsis. Several inflammatory and coagulant pathways that are activated during sepsis are also up-regulated in diabetes patients. We tested our a priori hypothesis that the presence of diabetes adversely affects the outcome of sepsis. Retrospective analysis of a previously published study. Intensive care units of 164 centers in 11 countries. Eight hundred thirty severe sepsis patients who were admitted to the intensive care unit and who received standard critical care treatment. Patients were stratified into diabetic and nondiabetic patient groups. Mortality was assessed after 28 and 90 days, causative microorganisms were evaluated, and markers of coagulation, fibrinolysis, and inflammation were measured at several time points. Diabetes was present in 22.7% of all sepsis patients. Throughout the study, plasma glucose levels were higher in diabetic patients. Mortality was equal in diabetic and nondiabetic patients (31.4% vs. 30.5% after 28 days). Markers of coagulation, fibrinolysis, and inflammation were generally equal in diabetic and nondiabetic patients, although on admission diabetic patients had slightly higher levels of anticoagulation markers. Interestingly, nondiabetic patients with admission hyperglycemia (>11.1 mmol/L; 200 mg/dL) had a higher mortality rate compared to those without admission hyperglycemia (43.0% vs. 27.2%). Although diabetes is a risk factor for sepsis, once established, the outcome of severe sepsis does not appear to be significantly influenced by the presence of diabetes. In nondiabetic patients, however, admission hyperglycemia is associated with an increased mortality.
    Critical care medicine 10/2009; 38(2):539-45. · 6.37 Impact Factor
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    ABSTRACT: Sepsis-induced hypoglycemia is a well known, but rare, event of unknown origin. The aim of the study was to obtain insight into the mechanism of sepsis-induced hypoglycemia, focusing on glucose kinetics and insulin sensitivity measured with stable isotopes by using the model of human endotoxemia. Glucose metabolism was measured during two hyperinsulinemic [insulin levels of 100 pmol/liter (low-dose clamp) and 400 pmol/liter (medium-dose clamp)] euglycemic (5 mmol/liter) clamps on two occasions: without or with lipopolysaccharide (LPS). The study was conducted at the Academic Medical Center, Metabolic and Clinical Research Unit (Amsterdam, The Netherlands). Eighteen healthy male volunteers participated in the study. A hyperinsulinemic euglycemic (5 mmol/liter) clamp with LPS (two groups of six subjects; insulin infusion at rates of either 10 or 40 mU.m(-2).min(-1)) or without LPS (n = 6; both insulin infusions in same subjects). We measured hepatic and peripheral insulin sensitivity. Hepatic insulin sensitivity, defined as a decrease in endogenous glucose production during hyperinsulinemia (100 pmol/liter), was higher in the LPS group compared to the control group (P = 0.010). Insulin-stimulated peripheral glucose uptake was higher in both clamps after LPS compared to the control setting (P = 0.006 and 0.010), despite a significant increase in the plasma concentrations of norepinephrine and cytokines in the LPS group during both clamps. These data indicate that shortly (2 h) after administration of LPS, peripheral and hepatic insulin sensitivity increase. This may contribute to the hypoglycemia occurring in some patients with critical illness, especially in the setting of intensive insulin therapy.
    Journal of Clinical Endocrinology &amp Metabolism 12/2008; 94(2):463-8. · 6.43 Impact Factor
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    ABSTRACT: Type 2 diabetes is associated with altered immune and hemostatic responses. We investigated the selective effects of hyperglycemia and hyperinsulinemia on innate immune, coagulation, and fibrinolytic responses during systemic inflammation. Twenty-four healthy humans were studied for 8 hours during clamp experiments in which either plasma glucose, insulin, both, or none was increased, depending on randomization. Target plasma concentrations were 5 versus 12 mM for glucose, and 100 versus 400 pmol/L for insulin. After 3 hours, 4 ng/kg Escherichia coli endotoxin was injected intravenously to induce a systemic inflammatory and procoagulant response. Endotoxin administration induced cytokine release, activation of neutrophils, endothelium and coagulation, and inhibition of fibrinolysis. Hyperglycemia reduced neutrophil degranulation (plasma elastase levels, P < .001) and exaggerated coagulation (plasma concentrations of thrombin-antithrombin complexes and soluble tissue factor, both P < .001). Hyperinsulinemia attenuated fibrinolytic activity due to elevated plasminogen activator-inhibitor-1 levels (P < .001). Endothelial cell activation markers and cytokine concentrations did not differ between clamps. We conclude that in humans with systemic inflammation induced by intravenous endotoxin administration hyperglycemia impairs neutrophil degranulation and potentiates coagulation, whereas hyperinsulinemia inhibits fibrinolysis. These data suggest that type 2 diabetes patients may be especially vulnerable to prothrombotic events during inflammatory states.
    Blood 08/2008; 112(1):82-9. · 9.78 Impact Factor
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    ABSTRACT: Adiponectin is a fat-derived hormone with insulin-sensitizing properties. In patients with type 2 diabetes plasma adiponectin levels are decreased. Since these patients are characterized by high plasma insulin and glucose concentrations, hyperinsulinemia and hyperglycemia could be responsible for the downregulation of adiponectin. Insulin decreases adiponectin levels in humans. The effect of hyperglycemia is unknown. To determine the selective effects of insulin, glucose, or their combination on plasma adiponectin, clamps were performed in six healthy males on four occasions in a crossover design: 1) lower insulinemic-euglycemic clamp (100 pmol/l insulin, 5 mmol/l glucose) (reference clamp); 2) hyperinsulinemic-euglycemic clamp (400 pmol/l insulin, 5 mmol/l glucose); 3) lower insulinemic-hyperglycemic clamp (100 pmol/l insulin, 12 mmol/l glucose); and 4) hyperinsulinemic-hyperglycemic clamp (400 pmol/l insulin, 12 mmol/l glucose). Adiponectin concentrations and high-molecular-weight (HMW)-to-total adiponectin ratio were measured at the start and end of the 6-h clamps. After the 6-h study period, total plasma adiponectin levels were significantly (P = 0.045) decreased by 0.63 microg/ml in the lower insulinemic-euglycemic clamp (clamp 1). In both euglycemic groups (clamps 1 and 2) adiponectin concentrations significantly declined (P = 0.016) over time by 0.56 microg/ml, whereas there was no change in both hyperglycemic groups (clamps 3 and 4) (P = 0.420). In none of the clamps did the ratio of HMW to total adiponectin change. We conclude that insulin suppresses plasma adiponectin levels already at a plasma insulin concentration of 100 pmol/l. Hyperglycemia prevents the suppressive effect of insulin. This suggests that, in contrast to glucose, insulin could be involved in the downregulation of plasma adiponectin in insulin-resistant patients.
    AJP Endocrinology and Metabolism 07/2008; 295(3):E613-7. · 4.51 Impact Factor
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    ABSTRACT: Severe pneumonia is associated with a local inhibition of fibrinolysis in the lung as reflected by strongly reduced pulmonary plasminogen activator activity.Objectives: To study the effect of elevation of local plasminogen activator activity during pneumonia caused by the common respiratory pathogen Klebsiella pneumoniae. Female C57Bl/6 mice were inoculated intranasally with a replication-defective adenoviral vector expressing human tissue-type plasminogen activator or a control vector 24 h before intranasal infection with K. pneumoniae. Mice infected with Klebsiella via the airways developed overt pneumonia, which was accompanied by a downregulation of pulmonary tissue-type plasminogen activator levels at protein and mRNA levels. Pulmonary overexpression of human tissue-type plasminogen activator resulted in increased fibrinolytic activity in the lungs during pneumonia, as indicated by higher D-dimer levels and reduced fibrin deposition. Interestingly, overexpression of tissue-type plasminogen activator markedly improved host defense against pneumonia: mice treated with the tissue-type plasminogen activator vector displayed less bacterial growth and dissemination, attenuated distant organ injury and a reduced mortality. These data demonstrate that local elevation of plasminogen activator activity in the lungs improves host defense against severe gram-negative pneumonia and sepsis.
    Journal of Thrombosis and Haemostasis 05/2008; 6(4):660-8. · 6.08 Impact Factor
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    ABSTRACT: Type 2 diabetes is frequently associated with infectious complications. Swift activation of leucocytes is important for an adequate immune response. We determined the selective effects of hyperglycaemia and hyperinsulinaemia on lipopolysaccharide (LPS)-induced proinflammatory gene expression and cytokine production in leucocytes and on neutrophil functions. Six healthy humans were studied on four occasions for 6 h during: (i) lower insulinaemic euglycaemic clamp, (ii) lower insulinaemic hyperglycaemic clamp, (iii) hyperinsulinaemic euglycaemic clamp, and (iv) hyperinsulinaemic hyperglycaemic clamp. Target levels of plasma glucose were 12.0 mmol/l (hyperglycaemic clamps) or 5.0 mmol/l (euglycaemic clamps). Target plasma insulin levels were 400 pmol/l (hyperinsulinaemic clamps) or 100 pmol/l (lower insulinaemic clamps). Hyperglycaemia reduced LPS-induced mRNA expression of nuclear factor of kappa light polypeptide gene enhancer in B cells inhibitor alpha (NFKBIA), interleukin-1 alpha (IL1A) and chemokine (C-C motif) ligand 3 (CCL3), whereas during hyperinsulinaemia enhanced mRNA levels occurred in six out of eight measured inflammation-related genes, irrespective of plasma glucose levels. Combined hyperglycaemia and hyperinsulinaemia led to enhanced IL1A, interleukin-1 beta (IL1B) and CCL3 mRNA levels upon LPS stimulation. Neither hyperglycaemia nor hyperinsulinaemia altered cytokine protein production, neutrophil migration, phagocytic capacity or oxidative burst activity. These results suggest that short-term hyperglycaemia and hyperinsulinaemia influence the expression of several inflammatory genes in an opposite direction, that the acute effects of hyperinsulinaemia on inflammatory mRNA levels may be stronger than those of hyperglycaemia, and that the effects of insulin, in particular, may be relevant in the concurrent presence of hyperglycaemia.
    Diabetic Medicine 03/2008; 25(2):157-64. · 3.24 Impact Factor
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    ABSTRACT: Type 2 diabetes and insulin resistance syndromes are associated with an increased risk for cardiovascular and thrombotic complications. A disturbed balance between coagulation and fibrinolysis has been implicated in the pathogenesis hereof. To determine the selective effects of hyperglycemia and hyperinsulinemia on coagulation and fibrinolysis, six healthy humans were studied on four occasions for 6 h: 1) lower insulinemic-euglycemic clamp, 2) lower insulinemic-hyperglycemic clamp, 3) hyperinsulinemic-euglycemic clamp, and 4) hyperinsulinemic-hyperglycemic clamp. In the hyperglycemic clamps, target levels of plasma glucose were 12 versus 5 mmol/l in the normoglycemic clamps. In the hyperinsulinemic clamps, target plasma insulin levels were 400 versus 100 pmol/l in the lower insulinemic clamps. Hyperglycemia exerted a procoagulant effect irrespective of insulin levels, as reflected by mean twofold rises in thrombin-antithrombin complexes and soluble tissue factor, whereas hyperinsulinemia inhibited fibrinolysis irrespective of glucose levels, as reflected by a decrease in plasminogen activator activity levels due to a mean 2.5-fold rise in plasminogen activator inhibitor type 1. The differential effects of hyperglycemia and hyperinsulinemia suggest that patients with hyperglycemia due to insulin resistance are especially susceptible to thrombotic events by a concurrent insulin-driven impairment of fibrinolysis and a glucose-driven activation of coagulation.
    Diabetes 07/2006; 55(6):1807-12. · 7.90 Impact Factor
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    ABSTRACT: Leptin is a pleiotrophic protein mainly produced by adipocytes that has been implicated as a link between nutritional status and immune function. Severe bacterial infection is associated with elevated plasma levels of leptin. To determine the role of leptin in the host response to bacterial pneumonia leptin deficient ob/ob mice and normal wild-type (WT) mice were intranasally infected with different doses of the Gram-positive pathogen Streptococcus (S.) pneumoniae or the Gram-negative bacterium Klebsiella (K.) pneumoniae. After infection with lower doses of either pathogen ob/ob mice displayed lower pulmonary levels of proinflammatory cytokines, in particular tumor necrosis factor-alpha and chemokines. However, after infection with a higher dose of S. pneumoniae or K. pneumoniae the lung concentrations of these inflammatory mediators did not differ between ob/ob and WT mice. In addition, the extent and severity of lung inflammation, as assessed by semi-quantitative histopathology scores, were similar in both mouse strains. Finally, leptin deficiency did not impact on the bacterial outgrowth in the lungs during either Gram-positive or Gram-negative pneumonia irrespective of the infective dose. These data suggest that although leptin may play a modest role in the regulation of inflammation during bacterial pneumonia, it does not contribute to host defense mechanisms that act to limit the outgrowth of S. pneumoniae or K. pneumoniae in the lower airways.
    Shock 05/2006; 25(4):414-9. · 2.61 Impact Factor
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    M. E. Stegenga