[Repercussions and management of perioperative hyperglycemia in cardiac surgery]

Surgery produces a neuroendocrine stress response that affects resistance to insulin, reduces insulin secretion, and increases the release of glucose from the liver. This situation can trigger hyperglycemia in both diabetics and nondiabetics. Hyperglycemia has been linked to an increase in the morbidity and mortality among patients who undergo cardiac surgery, and the benefits of correcting hyperglycemia in this setting by means of intensive insulin therapy are well documented. This review discusses various aspects of hyperglycemia, particularly the evidence supporting stricter control of this condition in patients undergoing cardiac surgery. Furthermore, based on the available data and recommendations, and our clinical experience, we suggest therapeutic strategies to improve the control of hyperglycemia in these patients.

Characteristics of the antibodies of two patients who developed daytime hyperglycemia and morning hypoglycemia because of insulin antibodies

We encountered two patients who developed daytime hyperglycemia and early morning hypoglycemia because of insulin antibody (IA) that the affinity was extremely lower and the capacity extremely higher than those of IA in the insulin autoimmune syndrome, after their insulin treatment were changed from human insulin to analog insulin.

[AGE-RAGE: a hypothesis or a mechanism?]

Acausal relation between hyperglycemia and accelerated atherosclerosis has been recently suggested. The AGE-RAGE interaction is a potential mechanism underlying the accelerated atherosclerosis. Hyperglycemia causes via nonenzymatic glycation the formation of AGEs (advanced glycation endproducts). AGEs as well as other ligands like S100/Calgranulin and Amphoterin mediate receptor-independent and -dependent (via the interaction with RAGE) effects. The ligand-RAGE-interaction results in an activation of NF-kappaB, increased expression of cytokines, chemokines, and adhesion molecules and induces oxidative stress. A relevant role of the ligand-RAGE-interaction has been demonstrated in in vivo studies, both for the accelerated atherosclerosis and increased neointima formation in diabetes mellitus. Recent data analysing atherosclerotic lesions of diabetic patients provide further evidence for the pathogenetic role of the RAGE-ligand-interaction. In addition, new experimental data established that AGEs interact with other receptors than RAGE, while RAGE interacts with a diverse group of ligands. Thus, further studies are needed for the characterization of the ligand-RAGE-interaction. These studies will provide a rationale for the development of new therapeutic approaches for accelerated atherosclerosis in diabetes mellitus.

[Immunosuppressive mechanisms in diabetes mellitus]

Infectious diseases are common and serious complication of diabetes mellitus (DM) and hyperglycemia. The increase of infections in patients with DM is known to depend upon an immunosuppressive condition which is brought about by impaired innate immunity and acquired immunity. For instance, functions of neutrophils such as phagocyte, chemotaxis and cytokine-production are decreased in DM model mouse and hyperglycemia and a Th2-axis shift which reduces Th1-dependent immunity are observed in DM patients. However, the majority of results concerning interaction of hyperglycemia and immune function are controversial and relevance of hyperglycemia and/or hyperinsulinemia to immunosuppressive mechanisms remains unclear.

Macropinocytosis is decreased in diabetic mouse macrophages and is regulated by AMPK

BACKGROUND

Macrophages (MPhis) utilize macropinocytosis to integrate immune and metabolic signals in order to initiate an effective immune response. Diabetes is characterized by metabolic abnormalities and altered immune function. Here we examine the influence of diabetes on macropinocytosis in primary mouse macrophages and in an in vitro diabetes model.

RESULTS

The data demonstrate that peritoneal MPhis from diabetic (db/db) mice had reduced macropinocytosis when compared to MPhis from non-diabetic (db/+) mice. Additionally, MPhis cultured in hyperglycemic conditions were less adept at macropinocytosis than those cultured in low glucose. Notably, AMP-activated protein kinase (AMPK) activity was decreased in MPhis cultured in hyperglycemic conditions. Activation of AMPK with leptin or 5-aminoimidazole-4-carboxamide-1-beta-riboside (AICAR) increased macropinocytosis and inhibition of AMPK with compound C decreased macropinocytosis.

CONCLUSION

Taken together, these findings indicate that MPhis from diabetic mice have decreased macropinocytosis. This decrease appears dependent on reduced AMPK activity. These results demonstrate a previously unrealized role for AMPK in MPhis and suggest that increasing AMPK activity in diabetic MPhis could improve innate immunity and decrease susceptibility to infection.

[Polimorphonuclear leukocytes and diabetes mellitus]

Diabetic subjects have a higher infective risk than healthy people, with more frequent and severe infections. This predisposition to infections is determined by hyperglycemia, microangiopathy and altered immune system. In particular, there is a polymorphonuclear leukocytes disfunction including chemotaxis, phagocytosis, bacterial killing and cellular activation by infective stimulus. These alterations are due to abnormal properties of polymorphonuclear leukocytes (PMN) in diabetic patients. Several parameters like phagocytosis of bacterial cells, chemiluminescence during oxidative burst and cell membrane deformability are related to glycaemia and glycated hemoglobin. Recent acquisitions show an altered integrin pattern on diabetics PMN, at baseline and after in vitro stimulation with soluble stimulus like fMLP or PMA. This could influence the interactions between PMN and endothelial cells and the diapedesis. Receptorial alterations on PMN surface may be ascribed to the abnormalities of the cytoscheleton, of the endocytosis and of the transduction mechanism, due to hyperglycemia.

Infections in Diabetes Mellitus and Hyperglycemia

Infections in diabetes mellitus are relatively more common and serious. Diabetic patients run the risk of acute metabolic decompensation during infections, and conversely patients with metabolic decompensation are at higher risk of certain invasive infections. Tight glycemic control is of paramount importance during acute infected or high stress state. Infections in diabetic patients result in extended hospital stays and additional financial burden. Given the risks of not alleviating the metabolic dysregulation and the benefits of decent glycemic control, it is necessary that besides antimicrobial therapy, equal emphasis be placed on intensified glycemic control.

Midkine is involved in tubulointerstitial inflammation associated with diabetic nephropathy

The concept that inflammation plays a crucial role in the pathogenesis of diabetic nephropathy has been recently emerging, although the principal pathology of diabetic nephropathy comprises glomerular sclerosis and associated changes in nephrons. Here, we identified the growth factor midkine (MK) as a novel key molecule involved in inflammation associated with Streptozotocin-induced diabetic nephropathy. The tubulointerstitial damage, as assessed as morphological changes, osteopontin expression, collagen I deposition and macrophage infiltration, were strikingly less in MK-deficient (Mdk(-/-)) mice than in Mdk(+/+) mice. Monocyte chemoattractant protein (MCP)-1 expression, but not that of intercellular adhesion molecule-1, was also lower in Mdk(-/-) mice. High glucose upregulated MK expression in primary-cultured tubular epithelial cells, and induced MCP-1 to a larger extent in Mdk(+/+) cells than in Mdk(-/-) cells. Correspondingly, the combination of exogenous MK and high glucose enhanced MCP-1 expression in Mdk(-/-) cells. Furthermore, high glucose and oxidant stress enhanced MK expression in macrophages. Consistent with the findings in the mouse model, MK expression was detected in the glomeruli, tubular epithelium and interstitium of kidneys from patients with diabetic nephropathy. Our data indicate that MK plays a critical role in the tubulointerstitial inflammation associated with diabetic nephropathy through activation of the MCP-1 pathway.

Bone marrow is a preferential homing site for autoreactive T-cells in type 1 diabetes

OBJECTIVE

The pancreatic microenvironment is considered to be the primary location of autoreactive T-cells in type 1 diabetes. Diabetogenic T-cells have also been detected in the spleens of NOD mice. However, it is not known whether bone marrow also contains T-cells specific for self-antigens in hosts with autoimmunity. In this study, we investigated whether autoreactive diabetogenic T-cells are present in the bone marrow of NOD mice.

RESEARCH DESIGN AND METHODS

Bone marrow and splenic T-cells of female NOD mice were purified and tested for their cytokine secretion and proliferation in response to stimulation with immunodominant peptides of pancreatic beta-cells. The diabetogenic nature and homing properties of purified bone marrow T-cells were compared with those of splenic T-cells in NOD-Scid and wild-type mice.

RESULTS

The bone marrow T-cells from both hyperglycemic and young euglycemic mice demonstrated profoundly higher proliferation and cytokine production in response to stimulation with beta-cell antigens than T-cells from spleen. Bone marrow T-cells showed rapid expansion and aggressive infiltration into pancreatic islets in NOD-Scid mice and induced hyperglycemia earlier than splenic T-cells. Adoptive transfer of bone marrow T-cells resulted in their trafficking predominantly to bone marrow and pancreatic lymph nodes.

CONCLUSIONS

Our study demonstrates that a large number of diabetogenic T-cells are present in the bone marrow of female NOD mice and that these autoreactive T-cells can be detected long before clinical onset of the disease.

Interleukin-8 production from human umbilical vein endothelial cells during brief hyperglycemia: the effect of tumor necrotic factor-alpha

BACKGROUND

This study evaluated the changes in chemokine interleukin (IL)-8 production from endothelial cells under various hyperglycemic conditions and investigated whether the hyperglycemia associated with the acute inflammatory response could enhance the IL-8 production from the endothelial cells.

MATERIALS AND METHODS

Human umbilical endothelial cells (HUVECs) were seeded at a concentration of 1 x 10(5) cells/well and cultured. The culture medium was replaced with Medium 199 containing various concentrations of glucose (final glucose concentration of culture medium was 100, 200, 300, 400, 500 mg/dL; n = 7 each) with or without 100 ng of tumor necrosis factor-alpha (TNF-alpha). After 12 or 24 h at 37 degrees C, the supernatants were collected from the cultures and stored at -80 degrees C until cytokine assay. IL-8 levels of the samples from the supernatants were quantified using a commercially available enzyme-linked immunosorbent assay kit.

RESULTS

The IL-8 production by the HUVECs was significantly higher in the high glucose culture than in the control culture (glucose concentration of 100 mg/dL) (P < 0.05). Moreover, the hyperglycemia associated with elevated TNF-alpha was found to enhance the level of IL-8 production by the HUVECs cultured at all glucose concentrations and over both time courses, compared to the control (P < 0.05).

CONCLUSIONS

In this study we observed a significant augmentation of IL-8 production by endothelial cells during short-term hyperglycemia, and a similar but significantly stronger augmentation was obtained through TNF treatment. These findings suggest that the hyperglycemia associated with acute inflammatory response after trauma may put the patients at high risk for secondary tissue damage.

Altered B:9–23 Insulin, When Administered Intranasally with Cholera Toxin Adjuvant, Suppresses the Expression of Insulin Autoantibodies and Prevents Diabetes

Insulin peptide B:9-23 is a major autoantigen in type 1 diabetes that contains two distinct CD4 epitopes (B:9-16 and B:13-23). One of the two epitopes, B:13-23, overlaps with a CTL epitope (B:15-23). In this study, we report that the elimination of the CTL epitope from the B:9-23 peptide by amino acid substitution (with alanine) at positions B:16 and 19 (A16,19 altered peptide ligand) or truncation of the C-terminal amino acids from the peptide (B:9-21), neither of which stimulated the proliferation of insulin B:15-23 reactive CD8 T cells, provided significant intranasally induced suppression of diabetes when coadministered with a potent mucosal adjuvant cholera toxin (CT). Intranasal treatment with A16,19 resulted in the elimination of spontaneous insulin autoantibodies, significant inhibition of insulitis and remission from hyperglycemia, and prevented the progression to diabetes. Intranasal administration of native B:9-23/CT or B:11-23/CT resulted in a significant enhancement of insulin autoantibody expression and severity of insulitis and failed to prevent diabetes. Our present study indicates that elimination of the CTL epitope from the B:9-23 peptide was critically important for mucosally induced diabetes prevention. The A16,19 altered peptide ligand, but not other native insulin peptides, suppresses insulin autoantibodies associated with protection from and remission of diabetes.

LPS-dependent suppression of social exploration is augmented in type 1 diabetic mice

We have previously shown that type 2 diabetes (T2D) in the mouse is associated with increased responsivity to innate immune challenge. Here we demonstrate that in a mouse model of type 1 diabetes (T1D) LPS-dependent suppression of social exploration (SE) is augmented and dependent on hyperglycemia. T1D was induced in mice with intraperitoneal (i.p.) streptozotocin (STZ). After 4d, STZ treated mice had blood glucose levels of 417+/-34mg/dl compared to 160+/-11mg/dl in non-STZ treated mice. When these diabetic mice were challenged with i.p. lipopolysaccharide (LPS), LPS-induced depression of SE was nearly 2.7-fold greater in diabetic mice at 2h than in non-diabetic mice. Examination of peritoneal proinflammatory cytokine levels 2h after LPS administration showed that diabetic mice had 4-, 2.5- and 3.6-fold greater concentrations of IL-1beta, IL-6 and TNF-alpha, respectively, when compared to non-diabetic mice. Control of blood glucose levels with injected insulin in diabetic mice improved 2h post LPS-induced loss of SE by 3.9-fold. Interestingly, insulin given intracerebroventricularly to diabetic mice did not impact LPS-induced loss of SE but did increase basal SE 8, 12 and 24h later. Finally, administration of STZ to hyperglycemic/hyperinsulinemic db/db mice did not alter LPS-induced loss of SE. Taken together these findings indicate that mice with T1D have augmented loss of SE in response to LPS and this is due to hyperglycemia and not to insulin.

Increased Fructose 2,6-bisphosphate in peripheral blood mononuclear cells of patients with diabetes

Fructose 2,6-bisphosphate (F2,6BP) is a powerful allosteric activator of 6-phosphofructo-1-kinase, which is the rate-limiting enzyme for glycolysis. Mitogenic stimulation of lymphocytes is related to an enhanced rate of glucose utilization and F2,6BP mediated activation of glycolysis. To determine the effect of hyperglycemia on intracellular glycolysis of lymphocytes, we measured intracellular F2,6BP content in peripheral blood mononuclear cells obtained from patients with diabetes and normal subjects. A total of 62 subjects participated in the present study. Venous blood samples were collected and peripheral blood mononuclear cells were separated by Ficoll gradients. Intracellular F2,6BP levels in peripheral blood mononuclear cells from normal control subjects were significantly lower than age-matched diabetic subjects. We observed a significant positive correlation between intracellular F2,6BP levels and long term glycemic control, as assessed by HbA1c. These data suggest that hyperglycemia increases intracellular F2,6BP in immune cells. These findings may help to clarify the impaired function in immune cells in patients with diabetes.

Cytokine production and hospital mortality in patients with sepsis-induced stress hyperglycemia

OBJECTIVES

To investigate whether stress hyperglycemia affects the production of the main pro- and anti-inflammatory cytokines and the 28-day hospital mortality in patients with severe sepsis.

METHODS

The study included 62 patients with severe sepsis, divided in three groups according to their glycemic profile within 24h after admission: patients with stress hyperglycemia (group SH, n=16), diabetes mellitus type II (group DM, n=27), and normal glucose levels (group NG, n=19). The serum levels of the cytokines TNF-alpha, IL-6, IL-10 and TGFbeta-1 were measured within 24h after admission.

RESULTS

A higher percentage of septic patients with stress hyperglycemia died compared to diabetic patients (43.7 vs. 14.8%) and group NG (43.7 vs. 5.2%). Group SH had higher SOFA score and levels of IL-6 and IL-10 than group DM and group NG. It also had higher levels of TNF-alpha than group DM but not group NG. There was no difference in the levels of TGFbeta-1 among the three groups. Non-survivors had higher levels of IL-10, no difference was detected for IL-6, TNF-alpha, IL-10/TNF-alpha ratio and TGFbeta-1. Interleukin-10 values, mean fasting glucose values and age were found as prognostic factors associated with outcome.

CONCLUSIONS

Stress hyperglycemia is associated with increased cytokine production and an adverse clinical outcome in patients with severe sepsis.

Suppression of hyperglycemia in NOD mice after inoculation with recombinant vaccinia viruses

In autoimmune (type 1) diabetes, autoreactive lymphocytes destroy pancreatic beta-cells responsible for insulin synthesis. To assess the feasibility of gene therapy for type 1 diabetes, recombinant vaccinia virus (rVV) vectors were constructed expressing pancreatic islet autoantigens proinsulin (INS) and a 55-kDa immunogenic peptide from glutamic acid decarboxylase (GAD), and the immunomodulatory cytokine interleukin (IL)-10. To augment the beneficial effects of recombinant virus therapy, the INS and GAD genes were fused to the C terminus of the cholera toxin B subunit (CTB). Five-week-old non-obese diabetic (NOD) mice were injected once with rVV. Humoral antibody immune responses and hyperglycemia in the infected mice were analyzed. Only 20% of the mice inoculated with rVV expressing the CTB::INS fusion protein developed hyperglycemia, in comparison to 70% of the mice in the uninoculated animal group. Islets from pancreatic tissues isolated from euglycemic mice from this animal group showed no sign of inflammatory lymphocyte invasion. Inoculation with rVV producing CTB::GAD or IL-10 was somewhat less effective in reducing diabetes. Humoral antibody isotypes of hyperglycemic and euglycemic mice from all treated groups possessed similar IgG1/IgG2c antibody titer ratios from 19 to 32 wk after virus inoculation. In comparison with uninoculated mice, 11-wk-old NOD mice injected with virus expressing CTB::INS were delayed in diabetes onset by more than 4 wk. The experimental results demonstrate the feasibility of using rVV expressing CTB::INS fusion protein to generate significant protection and therapy against type 1 diabetes onset and progression.

Functional deficiencies of granulocyte-macrophage colony stimulating factor and interleukin-3 contribute to insulitis and destruction of beta cells

The pathogenesis of type 1 diabetes (T1D) involves the immune-mediated destruction of insulin-producing beta cells in the pancreatic islets of Langerhans. Genetic analysis of families with a high incidence of T1D and nonobese diabetic (NOD) mice, a prototypical model of the disorder, uncovered multiple susceptibility loci, although most of the underlying immune defects remain to be delineated. Here we report that aged mice doubly deficient in granulocyte-macrophage colony-stimulating factor (GM-CSF) and interleukin-3 (IL-3) manifest insulitis, destruction of insulin-producing beta cells, and compromised glucose homeostasis. Macrophages from mutant mice produce increased levels of p40 after LPS stimulation, whereas concurrent ablation of interferon-gamma (IFN-gamma) ameliorates the disease. The administration of antibodies that block cytotoxic T lymphocyte associated antigen-4 (CTLA-4) to young mutant mice precipitates the onset of insulitis and hyperglycemia. These results, together with previous reports of impaired hematopoietic responses to GM-CSF and IL-3 in patients with T1D and in NOD mice, indicate that functional deficiencies of these cytokines contribute to diabetes.

Induction of monocyte chemoattractant protein-1 expression by angiotensin II in the pancreatic islets and beta-cells

Angiotensin II (AngII), the principal hormone of the renin-angiotensin system, is actively generated in the pancreas and has been suggested as a key mediator of inflammation. Monocyte chemoattractant protein-1 (MCP-1) is a chemokine that plays an important role in the recruitment of mononuclear cells into the pancreatic islets. In this study, we investigated the potential molecular basis for the role of AngII in islet inflammation through studying its effect on MCP-1. AngII significantly increased the expression of MCP-1 mRNA and protein in the RINm5F beta-cell line and activated MCP-1 promoter. AngII-MCP-1 mRNA induction was inhibited by an AngII type 1 receptor antagonist but was unchanged by an AngII type 2 receptor antagonist. AngII-MCP-1 induction was inhibited by the tyrosine kinase inhibitor genistein, suggesting a MAPK signaling mechanism. AngII activated the phosphorylation of ERK1/2 but not p38 or c-Jun NH(2)-terminal MAPKs. Inhibition of ERK1/2 activation reduced the AngII-induced MCP-1 synthesis. In nonobese diabetic mice pancreata, the temporal pattern of angiotensin-converting enzyme expression correlated well with progression of insulitis and beta-cell destruction. Immunostaining of pancreatic serial sections show colocalization of angiotensin-converting enzyme with MCP-1 in beta-cells in the islets. In freshly isolated islets from normoglycemic mice, AngII alone and in combination with IL-1beta elicited an inflammatory response by stimulation of MCP-1. Our data suggest a positive autocrine/paracrine action for the local pancreatic AngII-generating system during insulitis and provide the first insight into an AngII-initiated signal transduction pathway that regulates MCP-1 as a possible inflammatory mechanism in the islets.

Type B insulin resistance syndrome associated with systemic lupus erythematosus

OBJECTIVE

To document a case of type B insulin resistance syndrome associated with systemic lupus erythematosus.

METHODS

We present the clinical course of a female patient with type B insulin resistance syndrome, from the onset, diagnosis, and empiric treatment until remission of her disease.

RESULTS

A 40-year-old African American woman with systemic lupus erythematosus presented with a relatively acute onset of severe hyperglycemia in January 2004. Her hyperglycemia was resistant to treatment with high doses of insulin (up to an equivalent dose of regular insulin of 4,500 units daily). The diagnosis of type B insulin resistance syndrome was confirmed after her insulin receptor antibody was found to be strongly positive. The patient's hemoglobin Ale level improved substantially after she had been treated with azathioprine for 3 months. By November 2004, she was able to discontinue insulin therapy. Repeated insulin receptor antibody testing in February 2005 revealed that her insulin receptor antibody had become negative. The patient's fasting glucose level became normal, and only occasional mild postprandial hyperglycemic episodes have been noted.

CONCLUSION

Immunosuppressive therapy with azathioprine seems to be responsible for our patient's remission of type B insulin resistance, although the possibility of the occurrence of a spontaneous remission cannot be completely excluded.

High glucose concentrations impair the activation of K+ channels and proteases in undifferentiated THP-1 monocytes

Transient alkalization caused by activation of the BK(Ca) channels has been reported to be essential for the activation of proteolytic enzymes and bacterial killing in the leukocytic phagosomes. We investigated the effects of high glucose concentrations on these processes in THP-1 cells. While E. coli transiently raised the pH of the phagosomes in THP-1 monocytes, high glucose concentrations impaired the transient rise of pH in a dose-and time-dependent manner. Electrophysiological studies confirmed that the bacteria elicited a transient K+ current, and that a high glucose concentration diminished the current. High glucose concentrations also inhibited the activation of cathepsin G in the THP-1 cells. NS1619, a BK(Ca) channel opener, accentuated the transient alkalization induced by the bacteria, and reversed the inhibitory effect of high concentrations of glucose. However, electrophysiological study revealed that the membrane current differed from the BK(Ca) current. Our findings indicate that high glucose concentrations impair K+ channel activation and the subsequent activation of proteolytic enzymes in THP-1 monocytes. The precise identity of the K+ channel remains unclear, although it dose not appear to be the BK(Ca). Suppression of the transient alkalization and activation of proteases may be one of the mechanisms for bacterial killing by phagocytes in diabetic patients.

Pro-Atherogenic Alterations in T-Lymphocyte Subpopulations Related to Acute Hyperglycaemia in Type 2 Diabetic Patients

BACKGROUND

T cells are among the earliest cells to infiltrate the arterial intima during the initial stages of atherosclerosis. Alterations in the peripheral blood lymphocyte distribution might be associated with intensive lymphocytes extravasation and stimulation of atherosclerotic plaque development. Epidemiological data reveal that short-term postprandial hyperglycemia is a significant risk factor for coronary heart disease. Using a parameter that indicates recently-past acute hyperglycemia, 1,5-anhydro-D-glucitol (1,5-AG), the aim of the present study was to elucidate which alterations in peripheral blood T-lymphocytes, if any, are associated with acute hyperglycemia in patients with type 2 diabetes mellitus (DM) and, thus, might be involved in the progression of atherosclerosis.

METHODS AND RESULTS

Measurement of fasting glucose level, glycated hemoglobin A(1c), 1,5-AG, lipid profile and lymphocyte receptors expression (CD3+, CD4+, CD8+, CD8+28+, CD+28 -) was performed in 97 patients with type 2 DM, 23 patients with coronary heart disease, and 15 healthy controls. The mean CD3+, CD4+, CD8+28 - and CD8+28+ lymphocyte counts were significantly higher in the DM patients than in both control groups. Multiple regression analysis revealed that CD4+ and CD8+28- lymphocyte counts primarily were dependent on 1,5-anhydro-D-glucitol plasma levels.

CONCLUSIONS

These results suggest that acute hyperglycemia results in the progression of atherosclerosis in type 2 DM, at least in part through changes in CD4+ and CD8+28- lymphocyte subsets.

The metabolic syndrome sensitizes leukocytes for glucose-induced immune gene expression

Definitions of the metabolic syndrome (MetS) include obesity, dyslipidemia, elevated levels of fasting blood glucose, and blood pressure as criteria, but it is also known that the MetS is associated with chronic, subclinical inflammation. Hyperglycemia (fasting and postprandial) may be important in exacerbating this proinflammatory state. We aimed to assess the impact of oral glucose challenge and in vitro glucose-stimulation on gene expression and secretion of inflammatory parameters in peripheral blood leukocytes and to investigate whether presence of the MetS could "prime" leukocytes to up-regulate proinflammatory markers in response to glucose. Using quantitative real-time PCR, we could show that the expression of intercellular adhesion molecule 1 (ICAM-1), tumor necrosis factor alpha (TNF-alpha), and interleukin 6 (IL-6) significantly increased in peripheral blood leukocytes from "MetS" subjects (n=39) compared to "no MetS" subjects (n=35) 2 h after an oral glucose tolerance test (ICAM-1 +52%, TNF-alpha +107%, and IL-6 +38%) and also in vitro after 72 h cultivation in high-glucose medium (ICAM-1 +74%, TNF-alpha +71%, and IL-6 +44%). Using ELISA and Luminex technique, we further observed a trend towards increased immune mediator concentrations in the corresponding cell culture supernatants from MetS patients (ICAM-1 +21%, TNF-alpha +31%, and IL-6 +175%). Thus, the MetS may support peripheral inflammation by sensitizing leukocytes to up-regulate proinflammatory markers in response to glucose, which in turn increases the risk for type-2 diabetes mellitus and cardiovascular disease.

Activation of RAGE induces elevated O2- generation by mononuclear phagocytes in diabetes

Oxidative stress has been found to play a role in the pathogenesis of diabetic complications. The aim of this study was to define the oxidative burst of diabetic monocytes to characterize the phenotype associated with poor diabetic control. Superoxide (O(2)(-)) is the first molecule generated during the respiratory burst of phagocytes by NADPH oxidase, and its generation by monocytes from 26 controls and 34 diabetic subjects was evaluated in this study. Under resting states or stimulation by PMA or opsonized zymosan, diabetic monocytes produce significantly more O(2)(-) than nondiabetic cells. The increased O(2)(-) generation was found to be correlated with glycemic control (glycated hemoglobin) of patients. To clarify the effects of hyperglycemia on O(2)(-) generation, normal human monocytes were treated with receptor for advanced glycation endproducts (RAGE) ligands (AGE protein and S100B) or high glucose media before stimulation. RAGE ligands and high glucose concentration increased O(2)(-) generation from human mononuclear phagocytes. RAGE ligands, specifically and potently, increased O(2)(-) generation from mononuclear phagocytes, and high-glucose effects were associated with correspondingly increased osmotic pressure. Differentiated THP-1 cells, from a human monocytic cell line, were used as a model of human monocytes to study the effects of S100B, the RAGE ligand. It was confirmed that RAGE is involved in the priming of O(2)(-) generation by S100B. This study demonstrates that RAGE ligands can contribute significantly to the hyper-responsive phenotype of diabetic monocytes, which might be reversible by blocking the RAGE or controlling the presence of RAGE ligands by controlling hyperglycemia.

Effects of hyperglycemia, hyperinsulinemia, and hyperosmolarity on neutrophil apoptosis

BACKGROUND

Hyperglycemia is an independent risk factor for increased mortality of critically ill surgical patients, but despite the recognized clinical benefits of early insulin treatment, there is a lack of understanding of the cellular and molecular mechanisms behind this phenomenon. We hypothesized that polymorphonuclear neutrophils, the first line of the innate immune defense system, suffer from altered apoptotic turnover when exposed to hyperglycemic conditions, ultimately decreasing the number of viable cells active at a site of infection.

METHODS

Venous blood samples were drawn from 10 volunteers and incubated for 0.5 or 24 h in a 1:10 dilution with RPMI 1640 medium at various glucose and insulin concentrations. Mannitol was used to control for increased osmolarity. In addition, all samples were incubated either with low-dose lipopolysaccharide (LPS) (1 ng/mL) or without LPS. Neutrophils were extracted using Ficoll-Hypaque density centrifugation and stained with annexin V and propidium iodide. Fluorescence was detected by flow cytometry and analyzed using CellQuest software.

RESULTS

The mean percentage of apoptotic neutrophils after 24 h of incubation at physiologic glucose concentrations (100 mg/dL) was 42.2 +/- 4.1%; exposure to low-dose LPS decreased this number to 18.4 +/- 2.5% (p < 0.01). Neither the exposure to low (10 mg/dL) nor increasingly high (200 or 400 mg/dL) glucose concentrations altered these percentages significantly. Exposing whole blood to increasing osmolarity (addition of 5.5 mM and 16.5 mM mannitol to simulate 200 and 400 mg/dL glucose) led to a mean absolute reduction of the percentage of apoptotic neutrophils to 34.6 +/- 3.6% (+5.5 mOsm; p < 0.05) and 32.3 +/- 4.5% (16.5 mOsm; p < 0.01), respectively.

CONCLUSIONS

The ability of neutrophils to enter their apoptotic program in cultured whole blood withstands short-term changes in glucose and insulin concentrations. Neither hyperglycemia nor hypoglycemia led to a significant alteration of the apoptotic turnover of these cells, suggesting that the increased rate of infectious complications in short-term hyperglycemic critically ill patients may not be traced to increased apoptosis of neutrophils. However, isolated hyperosmolarity reduces neutrophil apoptosis, an observation that may warrant future investigation.

Diabetes-induced decrease of adenosine kinase expression impairs the proliferation potential of diabetic rat T lymphocytes

The proliferative response of T lymphocytes is a crucial step in cell-mediated immunity. This study was undertaken to investigate the mechanisms leading to the impaired proliferative response of diabetic T lymphocytes. T cells that had been isolated from the spleen of normal rats and cultured in medium containing 20 mm glucose and no insulin displayed the same degree of proliferative impairment as cells isolated from diabetic rats. The rate of T-cell proliferation, when induced with concanavalin A or anti-CD3 and anti-CD28 antibodies, was not affected by the inhibition of nucleoside transporters. T cells cultured at high glucose concentrations in the absence of insulin displayed decreased expression of adenosine kinase, and released measurable extracellular quantities of adenosine. Under resting conditions, the level of cAMP was 5.9-fold higher in these cells compared to cells grown in low glucose and in the presence of insulin. Experiments with specific adenosine receptor agonists and antagonists showed that adenosine-induced suppression of diabetic T cell proliferation was mediated by the A2A adenosine receptor, but not by the A2B receptor. Treatment of diabetic T cells with 10 microm H-89, a specific protein kinase A inhibitor, restored T-cell proliferation. These results show that suppressed proliferation of diabetic T lymphocytes is evoked by the decreased expression of adenosine kinase, leading to the outflow of adenosine from the cell. Extracellular adenosine then stimulates the A2A receptor and induces cAMP production, leading to the activation of protein kinase A, and suppression of T-cell proliferation.

Short-term hyperglycemia in surgical patients and a study of related cellular mechanisms

OBJECTIVE

To examine cellular mechanisms by which short-term elevations of glucose or insulin impair leukocyte functions and to assess the occurrence of perioperative hyperglycemia in surgical patients.

SUMMARY BACKGROUND DATA

A major factor in the contemporary management of the critically ill surgical patient is the progressively exact control of blood glucose. However, the separate role of insulin and underlying immunologic mechanisms are not well understood.

METHODS

Venous blood samples of 20 healthy volunteers were exposed for 24 hours to various glucose and insulin concentrations. Lipopolysaccharide (LPS) was added at 1 ng/mL for up to 16 hours and the monocytes' ability to express CD14 and HLA-DR assessed as an index of the monocyte's capability to present antigen. To evaluate the clinical importance of the observed experimental results, a prospective evaluation of perioperative blood glucose values in 5285 surgical patients in Kentucky was performed.

RESULTS

Both exposure to high glucose (400 mg/dL) and insulin (100 muU/mL) led to an independent and additive impairment of monocyte HLA-DR expression after 24 hours (P < 0.01). Perioperative blood glucose exceeded 200 mg/dL in 21% of all cardiothoracic patients and in 31% of diabetic patients undergoing common major operations.

CONCLUSIONS

Both short-term hyperglycemia and hyperinsulinemia are associated with significantly decreased monocyte HLA-DR expression, a parameter correlating with infectious complications and patient mortality. This may provide a mechanism by which high glucose and insulin impair innate immunity. It also appears that perioperative maintenance of normoglycemia will become a valid performance measure for practicing surgical specialists.