Erythrocyte glutathione concentration and production during hyperinsulinemia, hyperglycemia, and endotoxemia in healthy humans.

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.

Aortic cross-clamping and reperfusion in pigs reduces microvascular oxygenation by altered systemic and regional blood flow distribution.

BACKGROUND: In this study, we tested the hypothesis that aortic cross-clamping (ACC) and reperfusion cause distributive alterations of oxygenation and perfusion in the microcirculation of the gut and kidneys despite normal systemic hemodynamics and oxygenation. METHODS: Fifteen anesthetized pigs were randomized between an ACC group (n = 10), undergoing 45 minutes of aortic clamping above the superior mesenteric artery, and a time-matched sham surgery control group (n = 5). Systemic, intestinal, and renal hemodynamics and oxygenation variables were monitored during 4 hours of reperfusion. Microvascular oxygen partial pressure (microPo(2)) was measured in the intestinal serosa and mucosa and the renal cortex, using the Pd-porphyrin phosphorescence technique. Intestinal luminal Pco(2) was determined by air tonometry and the serosal microvascular flow by orthogonal polarization spectral imaging. RESULTS: Organ blood flow and renal and intestinal microPo(2) decreased significantly during ACC, whereas the intestinal oxygen extraction and Pco(2) gap increased. The intestinal response to reperfusion after ACC was a sustained reactive hyperemia but no such effect was seen in the kidney. Despite a sustained high intestinal O(2) delivery, serosal microPo(2) (median [range], 49 mm Hg [41-67 mm Hg] versus 37 mm Hg [27-41 mm Hg]; P < 0.05 baseline versus 4 hours reperfusion) and the absolute number of perfused microvessels decreased along with an increased intestinal Pco(2) gap (17 mm Hg [10-19 mm Hg] versus 23 mm Hg [19-30 mm Hg]; P < 0.05). In contrast, the kidney showed a progressive O(2) delivery decrease accompanied by a decrease in renal cortex oxygenation (70 mm Hg [52-93 mm Hg] versus 57 mm Hg [33-64 mm Hg]; P < 0.05). CONCLUSION: Increased systemic and regional blood flow and oxygen supply after ACC does not ensure adequate regional blood flow and microcirculatory oxygenation in all organs.

Diabetes does not alter mortality or hemostatic and inflammatory responses in patients with severe sepsis.

OBJECTIVE: 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. DESIGN: Retrospective analysis of a previously published study. SETTING: Intensive care units of 164 centers in 11 countries. PATIENTS: Eight hundred thirty severe sepsis patients who were admitted to the intensive care unit and who received standard critical care treatment. INTERVENTIONS: 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. MEASUREMENTS AND MAIN RESULTS: 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%). CONCLUSIONS: 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.

Early endotoxemia increases peripheral and hepatic insulin sensitivity in healthy humans.

CONTEXT: Sepsis-induced hypoglycemia is a well known, but rare, event of unknown origin. OBJECTIVE: 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. DESIGN: 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). SETTING: The study was conducted at the Academic Medical Center, Metabolic and Clinical Research Unit (Amsterdam, The Netherlands). PARTICIPANTS: Eighteen healthy male volunteers participated in the study. INTERVENTION: 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). MAIN OUTCOME MEASURE: We measured hepatic and peripheral insulin sensitivity. RESULTS: 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. CONCLUSIONS: 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.

The thiazolidinedione ciglitazone reduces bacterial outgrowth and early inflammation during Streptococcus pneumoniae pneumonia in mice.

OBJECTIVE: 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. DESIGN: In vivo animal study and in vitro study. SETTING: University research laboratory. SUBJECTS: Female C57Bl/6 mice and murine alveolar macrophage-like MH-S cells. INTERVENTIONS: 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. MEASUREMENTS AND MAIN RESULTS: 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. CONCLUSIONS: Ciglitazone reduces bacterial outgrowth and local inflammation at least during the early stage of S. pneumoniae pneumonia in mice.

Hyperglycemia prevents the suppressive effect of hyperinsulinemia on plasma adiponectin levels in healthy humans.

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.

Hyperglycemia enhances coagulation and reduces neutrophil degranulation, whereas hyperinsulinemia inhibits fibrinolysis during human endotoxemia.

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.

Hyperglycemia stimulates coagulation, whereas hyperinsulinemia impairs fibrinolysis in healthy humans.

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.

Leptin and host defense against Gram-positive and Gram-negative pneumonia in mice.

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.