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

Diabetes and the fabkin complex: A dual-edged sword

The Fabkin complex, composed of FABP4, ADK, and NDPKs, emerges as a novel regulator of insulin-producing beta cells, offering promising prospects for diabetes treatment. Our approach, which combines literature review and database analysis, sets the stage for future research. These findings hold significant implications for both diabetes treatment and research, as they present potential therapeutic targets for personalized treatment, leading to enhanced patient outcomes and a deeper comprehension of the disease. The multifaceted role of the Fabkin complex in glucose metabolism, insulin resistance, anti-inflammation, beta cell proliferation, and vascular function underscores its therapeutic potential, reshaping diabetes management and propelling advancements in the field.

Anti-tumor effects of anti-programmed cell death-1 antibody treatment are attenuated in streptozotocin-induced diabetic mice

Hyperglycemia impairs immune response; however, it remains unknown whether the anti-tumor effects of anti-programmed cell death-1 antibody (PD-1-Ab) treatment are changed in hyperglycemic conditions. We analyzed the effect of PD-1-Ab on tumor growth in streptozotocin-induced diabetic mice (STZ-mice) subcutaneously inoculated with MC38 (a colon carcinoma cell line). Furthermore, we assessed the expression of chemokines by polymerase chain reaction (PCR) array in tumor-draining lymph nodes (dLNs) of these mice and MC38 cells cultured in different glucose concentrations. The suppressive effect of PD-1-Ab on tumor growth was attenuated. This was accompanied by fewer tumor-infiltrating CD8⁺ T cells, and STZ-mice had fewer tumor-infiltrating CD11c⁺ dendritic cells (DCs) than normoglycemic mice. mRNA expression levels of CXCL9, a chemokine recruiting CD8⁺ T cells, were lower in dLNs of STZ-mice than in normoglycemic mice after PD-1-Ab treatment, and its protein was expressed in DCs. In MC38 cells cultured with 25 mM glucose, mRNA expression of CCL7, a chemokine recruiting DCs, was decreased compared to cells cultured with 5 mM glucose. These results suggest that the STZ-induced hyperglycemia impairs the effect of PD-1-Ab treatment on MC38 tumor growth, and is accompanied by reduced infiltration of DCs and CD8⁺ T cells and decreased expression of CCL7 and CXCL9.

Risk factors for cardiac implantable electronic device infections: a nationwide Danish study

AIMS

Cardiac implantable electronic device (CIED) infection is a severe complication to modern management of cardiac arrhythmias. The CIED type and the type of surgery are recognized as risk factors for CIED infections, but knowledge of patient-related risk factors is scarce. This study aimed to identify lifelong patient-related risk factors for CIED infections.

METHODS AND RESULTS

Consecutive Danish patients undergoing a CIED implantation or reoperation between January 1996 and April 2018 were included. The cohort consisted of 84 429 patients undergoing 108 494 CIED surgeries with a combined follow-up of 458 257 CIED-years. A total of 1556 CIED explantations were classified as either pocket (n = 1022) or systemic CIED infection (n = 534). Data were cross-linked with records from the Danish National Patient Registry and the Danish National Prescription Registry. Using multiple-record and multiple-event per subject proportional hazard analysis, specific patient-related risk factors were identified but with several variations amongst the subtypes of CIED infection. CIED reoperations were associated with the highest risk of pocket CIED infection but also CIED type, young age, and prior valvular surgery [hazard ratio (HR): 1.62, 95% confidence interval (CI): 1.29-2.04]. Severe renal insufficiency/dialysis (HR: 2.40, 95% CI: 1.65-3.49), dermatitis (HR: 2.80, 95% CI: 1.92-4.05), and prior valvular surgery (HR: 2.09, 95% CI: 1.59-2.75) were associated with the highest risk of systemic CIED infections. Congestive heart failure, ischaemic heart disease, malignancy, chronic obstructive pulmonary disease, and temporary pacing were not significant at multivariate analysis.

CONCLUSION

Specific comorbidities and surgical procedures were associated with a higher risk of CIED infections but with variations amongst pocket and systemic CIED infection. Pocket CIED infections were associated with CIED reoperations, young age and more complex type of CIED, whereas systemic CIED infections were associated with risk factors predisposing to bacteraemia.

Melatonin attenuates diabetes-induced oxidative stress in spleen and suppression of splenocyte proliferation in laboratory mice

Hyperglycaemic condition induced oxidative stress in diabetic individuals caused oxidative damages of internal organs, including immune organ spleen. We studied the effects of low doses of melatonin (25, 50, and 100 µg/100g. B.wt./day) on histoarchitecture, oxidative stress, and splenocyte proliferation in streptozotocin-induced diabetic mice. Melatonin significantly resisted the increase in blood glucose levels and showed a dose-dependent effect on circulatory melatonin, body weight, and relative spleen weight in diabetic mice. Exogenous melatonin suppressed the diabetes-induced lipid peroxidation and increased the activity of the antioxidant enzymes and antioxidant GSH in the spleen tissue of diabetic mice in a dose-dependent manner. Melatonin improved the reactivity of Nrf-2 and HO-1 in the spleen of diabetic mice. Melatonin treatment normalised the splenic cellularity and increased the splenocyte proliferation in a dose-dependent manner. The present study may suggest the dose-dependent effect of melatonin in attenuation of oxidative stress and suppression of splenocyte proliferation in diabetic mice.

Endangered Lymphocytes: The Effects of Alloxan and Streptozotocin on Immune Cells in Type 1 Induced Diabetes

Alloxan (ALX) and streptozotocin (STZ) are extensively used to induce type 1 diabetes (T1D) in animal models. This study is aimed at evaluating the differences in immune parameters caused by ALX and STZ. T1D was induced either with ALX or with STZ, and the animals were followed for up to 180 days. Both ALX and STZ induced a decrease in the total number of circulating leukocytes and lymphocytes, with an increase in granulocytes when compared to control mice (CT). STZ-treated mice also exhibited an increase in neutrophils and a reduction in the lymphocyte percentage in the bone marrow. In addition, while the STZ-treated group showed a decrease in total CD3+, CD4-CD8+, and CD4+CD8+ T lymphocytes in the thymus and CD19+ B lymphocytes in the pancreas and spleen, the ALX group showed an increase in CD4-CD8+ and CD19+ only in the thymus. Basal levels of splenic interleukin- (IL-) 1β and pancreatic IL-6 in the STZ group were decreased. Both diabetic groups showed atrophy of the thymic medulla and degeneration of pancreatic islets of Langerhans composed of inflammatory infiltration and hyperemia with vasodilation. ALX-treated mice showed a decrease in reticuloendothelial cells, enhanced lymphocyte/thymocyte cell death, and increased number of Hassall's corpuscles. Reduced in vitro activation of splenic lymphocytes was found in the STZ-treated group. Furthermore, mice immunized with ovalbumin (OVA) showed a more intense antigen-specific paw edema response in the STZ-treated group, while production of anti-OVA IgG1 antibodies was similar in both groups. Thereby, important changes in immune cell parameters in vivo and in vitro were found at an early stage of T1D in the STZ-treated group, whereas alterations in the ALX-treated group were mostly found in the chronic phase of T1D, including increased mortality rates. These findings suggest that the effects of ALX and STZ influenced, at different times, lymphoid organs and their cell populations.

Hyperglycemia results in decreased immune cell infiltration and increased viral load in the lung in a mouse model of RSV infection

Respiratory Syncytial virus (RSV) infection is a feared disease in vulnerable populations with impaired immune responses. There is currently no vaccine against RSV and young children along with elderly people are at increased risk of severe or sometimes life-threatening RSV infection. Hyperglycemia with immunomodulatory patterns can impact on infectious disease outcomes and immune system responses in diabetic patients. Even though research continues to uncover the complex mechanisms underlying RSV immunopathogenesis and diabetes mellitus disease separately, limited information is available about interaction between these two phenomena. Here, we evaluated the influence of hyperglycemia as the hallmark of diabetes mellitus disease on the pathogenesis and immunopathogenesis of RSV in a mouse model. In this experiment, hyperglycemia was induced by intraperitoneal injection of Streptozotocin (STZ), and after diabetes confirmation, mice were infected with RSV-A2, and the immune responses were followed for 5 days until the mice were sacrificed. Analyses on airway immune cell influx, T-Lymphocyte subtypes, cytokines secretion, lung histopathology, and viral load were conducted. Our results showed that hyperglycemia resulted in reduced lung immune cells infiltration totally and it was associated with decreased pathological damage of the lung. Following RSV infection in hyperglycemic mice, the ratio of CD4/CD8 T-Lymphocytes due to CD8+ depletion, increased. Furthermore, the level of IFN-γ and IL-17A cytokines decreased, whereas IL-10 showed an upward trend and the viral load increased in hyperglycemic mice compared with normoglycemic mice. In conclusion, these findings indicate that hyperglycemia can ameliorate and downregulate RSV-induced inflammatory and antiviral responses, and result in increment of viral load.

The Genotoxic and Pro-Apoptotic Activities of Advanced Glycation End-Products (MAGE) Measured with Micronuclei Assay Are Inhibited by Their Low Molecular Mass Counterparts

An association between the cancer invasive activities of cells and their exposure to advanced glycation end-products (AGEs) was described early in some reports. An incubation of cells with BSA-AGE (bovine serum albumin-AGE), BSA-carboxymethyllysine and BSA-methylglyoxal (BSA-MG) resulted in a significant increase in DNA damage. We examined the genotoxic activity of new products synthesized under nonaqueous conditions. These were high molecular mass MAGEs (HMW-MAGEs) formed from protein and melibiose and low molecular mass MAGEs (LMW-MAGEs) obtained from the melibiose and N-α-acetyllysine and N-α-acetylarginine. We have observed by measuring of micronuclei in human lymphocytes in vitro that the studied HMW-MAGEs expressed the genotoxicity. The number of micronuclei (MN) in lymphocytes reached 40.22 ± 5.34 promille (MN/1000CBL), compared to 28.80 ± 6.50 MN/1000 CBL for the reference BSA-MG, whereas a control value was 20.66 ± 1.39 MN/1000CBL. However, the LMW-MAGE fractions did not induce micronuclei formation in the culture of lymphocytes and partially protected DNA against damage in the cells irradiated with X-ray. Human melanoma and all other studied cells, such as bronchial epithelial cells, lung cancer cells and colorectal cancer cells, are susceptible to the genotoxic effects of HMW-MAGEs. The LMW-MAGEs are not genotoxic, while they inhibit HMW-MAGE genotoxic activity. With regard to apoptosis, it is induced with the HMW-MAGE compounds, in the p53 independent way, whereas the low molecular mass product inhibits the apoptosis induction. Further investigations will potentially indicate beneficial apoptotic effect on cancer cells.

Adenosine kinase: An epigenetic modulator in development and disease

Adenosine kinase (ADK) is the key regulator of adenosine and catalyzes the metabolism of adenosine to 5'-adenosine monophosphate. The enzyme exists in two isoforms: a long isoform (ADK-long, ADK-L) and a short isoform (ADK-short, ADK-S). The two isoforms are developmentally regulated and are differentially expressed in distinct subcellular compartments with ADK-L localized in the nucleus and ADK-S localized in the cytoplasm. The nuclear localization of ADK-L and its biochemical link to the transmethylation pathway suggest a specific role for gene regulation via epigenetic mechanisms. Recent evidence reveals an adenosine receptor-independent role of ADK in determining the global methylation status of DNA and thereby contributing to epigenomic regulation. Here we summarize recent progress in understanding the biochemical interactions between adenosine metabolism by ADK-L and epigenetic modifications linked to transmethylation reactions. This review will provide a comprehensive overview of ADK-associated changes in DNA methylation in developmental, as well as in pathological conditions including brain injury, epilepsy, vascular diseases, cancer, and diabetes. Challenges in investigating the epigenetic role of ADK for therapeutic gains are briefly discussed.

Local and Systemic Immune Dysregulation Alters Glioma Growth in Hyperglycemic Mice

PURPOSE

Unlike most cancers, no clear epidemiological correlation between diabetes (Db) and malignant glioma progression exists. Because hyperglycemia activates proinflammatory pathways through the receptor for advanced glycation endproducts (RAGE), we hypothesized that Db can also promote malignant glioma progression.

EXPERIMENTAL DESIGN

We compared the growth of two phenotypically diverse syngeneic glioma models in control and diabetic mice. Tumor growth and antitumor immune responses were evaluated in orthotopic and heterotopic models and correlated to RAGE and RAGE ligand expression.

RESULTS

Irrespective of tumor implantation site, growth of a "classical" glioma model, GL261, increased in hyperglycemic mice and was mediated by upregulation of RAGE and its ligand, HMGB1. However, growth of a "mesenchymal" glioma subtype, K-Luc, depended on tumor implantation site. Whereas heterotopic K-Luc tumors progressed rapidly in Db mice, intracranial K-Luc tumors grew slower. We further showed that hyperglycemia inhibited the innate antitumor inflammatory responses in both models. Although this contributed to the accelerated growth of heterotopic tumors, suppression of tumor inflammatory responses dampened the growth of orthotopic K-Luc gliomas.

CONCLUSIONS

Hyperglycemia may enhance glioma growth through promotion of RAGE expression and suppression of antitumor immune responses. However, abrogation of the proinflammatory milieu in tumors may also dampen the growth of inflammatory glioma subtypes in the brains of diabetic mice. This dichotomy in glioma growth response to hyperglycemia may partly explain why conflicting epidemiological studies show both an increased risk and a protective effect of Db in patients with malignant gliomas.

Diabetes mellitus is associated with unfavorable pathologic features, increased postoperative mortality, and worse long-term survival in resected pancreatic cancer

BACKGROUND

The risk of pancreatic ductal adenocarcinoma (PDAC) is increased in patients with diabetes mellitus (DM), particularly in those with new-onset DM. However, the impact of DM on outcomes following pancreatic surgery is not fully understood. We sought to explore the effects of DM on post-resection outcomes in patients undergoing either upfront resection or following neoadjuvant treatment (NAT).

METHODS

Resections for PDAC between 2007 and 2016 were identified from a prospectively-maintained database. Data on demographics, pathology, and perioperative outcomes were compared between patients with or without DM. Survival analysis was performed using Kaplan-Meier curves and adjusted for confounders by a Cox-proportional hazards model.

RESULTS

662 patients were identified, of whom 277 (41.8%) had DM. Diabetics were more likely to be male, had higher BMI, and higher ASA-scores. At pathology, DM was associated with larger tumors (30 vs. 26 mm; p = 0.041), higher rates of lymph-node involvement (69% vs. 59%; p = 0.031) and perineural invasion (88% vs. 82%; p = 0.026). Despite having similar rates of complications, diabetics experienced higher 30-day mortality (3.2% vs. 0.8%; p = 0.019). Median overall survival was worse in diabetic patients (18 vs. 34 months; p < 0.001); this effect was more pronounced in patients with NAT (18 vs. 54 months; p < 0.001). At multivariate analysis, DM was confirmed as an independent predictor of post-resection survival.

CONCLUSION

DM is a common comorbidity in PDAC and is associated with unfavorable pathology, as well as worse postoperative and oncologic outcomes. The blunted effect on survival is more pronounced in patients who undergo resection following NAT.

Targeting Adenosine in Cancer Immunotherapy to Enhance T-Cell Function

T cells play a critical role in cancer control, but a range of potent immunosuppressive mechanisms can be upregulated in the tumor microenvironment (TME) to abrogate their activity. While various immunotherapies (IMTs) aiming at re-invigorating the T-cell-mediated anti-tumor response, such as immune checkpoint blockade (ICB), and the adoptive cell transfer (ACT) of natural or gene-engineered ex vivo expanded tumor-specific T cells, have led to unprecedented clinical responses, only a small proportion of cancer patients benefit from these treatments. Important research efforts are thus underway to identify biomarkers of response, as well as to develop personalized combinatorial approaches that can target other inhibitory mechanisms at play in the TME. In recent years, adenosinergic signaling has emerged as a powerful immuno-metabolic checkpoint in tumors. Like several other barriers in the TME, such as the PD-1/PDL-1 axis, CTLA-4, and indoleamine 2,3-dioxygenase (IDO-1), adenosine plays important physiologic roles, but has been co-opted by tumors to promote their growth and impair immunity. Several agents counteracting the adenosine axis have been developed, and pre-clinical studies have demonstrated important anti-tumor activity, alone and in combination with other IMTs including ICB and ACT. Here we review the regulation of adenosine levels and mechanisms by which it promotes tumor growth and broadly suppresses protective immunity, with extra focus on the attenuation of T cell function. Finally, we present an overview of promising pre-clinical and clinical approaches being explored for blocking the adenosine axis for enhanced control of solid tumors.

Adenosine kinase and cardiovascular fetal programming in gestational diabetes mellitus

Gestational diabetes mellitus (GDM) is a detrimental condition for human pregnancy associated with endothelial dysfunction and endothelial inflammation in the fetoplacental vasculature and leads to increased cardio-metabolic risk in the offspring. In the fetoplacental vasculature, GDM is associated with altered adenosine metabolism. Adenosine is an important vasoactive molecule and is an intermediary and final product of transmethylation reactions in the cell. Adenosine kinase is the major regulator of adenosine levels. Disruption of this enzyme is associated with alterations in methylation-dependent gene expression regulation mechanisms, which are associated with the fetal programming phenomenon. Here we propose that cellular and molecular alterations associated with GDM can dysregulate adenosine kinase leading to fetal programming in the fetoplacental vasculature. This can contribute to the cardio-metabolic long-term consequences observed in offspring after exposure to GDM.

A rapid and sensitive colorimetric assay for the determination of adenosine kinase activity

Adenosine kinase (ADK) plays an important role in the growth and development of organisms. A convenient, quick, reliable, sensitive and low-cost assay for ADK activity is of great significance. Here, we found the reaction system with bromothymol blue as the pH indicator had a maximum absorption peak at 614 nm. The absorbance change in 614 nm was positively correlated with the generated hydrogen ions in the reaction catalyzed by ADK. Then, we demonstrated this assay was feasible for ADK activity. Further, we analyzed the effects of buffer, bromothymol blue concentrations on the sensitivity of the assay, and investigated the sensitivity of ADK contents and adenosine concentration on the assay. Finally, we calculated the K_m and Vmax of ADK from Bombyx mori with this assay. Our results suggested this assay was quick, convenient, reliable, sensitive and economic for the activity of ADK. It is an excellent alternative for the conventional ADK assays.

Diagnostic Value of Adenosine Deaminase and Its Isoforms in Type II Diabetes Mellitus

Background and Aims. In the present study, we have investigated the activity of adenosine deaminase (ADA) as a diagnostic marker in type 2 (or II) diabetes mellitus (T2DM). Design and Methods. The deaminase activity of ADA1 and ADA2 was determined in serum from 33 patients with type 2 (or II) diabetes mellitus and 35 healthy controls. We also determined the proportion of glycated hemoglobin (HbA1c). Results. Our results showed significant differences between total serum ADA (tADA) and ADA2 activities in the diabetic groups with HbA1c < 8 (%) and HbA1c ≥ 8 (%) with respect to the values in healthy individuals (p < 0.001). ADA2 activity in patients with high HbA1c was found to be much higher than that in patients with low HbA1c (p = 0.0001). In addition, total ADA activity showed a significant correlation with HbA1c (r = 0.6, p < 0.0001). Conclusions. Total serum ADA activity, specially that due to ADA2, could be useful test for the diagnosis of type 2 (or II) diabetes mellitus.

Dynamic Regulation of the Adenosine Kinase Gene during Early Postnatal Brain Development and Maturation

The ubiquitous metabolic intermediary and nucleoside adenosine is a “master regulator” in all living systems. Under baseline conditions adenosine kinase (ADK) is the primary enzyme for the metabolic clearance of adenosine. By regulating the availability of adenosine, ADK is a critical upstream regulator of complex homeostatic and metabolic networks. Not surprisingly, ADK dysfunction is involved in several pathologies, including diabetes, epilepsy, and cancer. ADK protein exists in the two isoforms nuclear ADK-L, and cytoplasmic ADK-S, which are subject to dynamic expression changes during brain development and in response to brain injury; however, gene expression changes of the Adk gene as well as regulatory mechanisms that direct the cell-type and isoform specific expression of ADK have never been investigated. Here we analyzed potential gene regulatory mechanisms that may influence Adk expression including DNA promoter methylation, histone modifications and transcription factor binding. Our data suggest binding of transcription factor SP1 to the Adk promoter influences the regulation of Adk expression.

Immunotoxicological effects of streptozotocin and alloxan: in vitro and in vivo studies

Streptozotocin (STZ) and alloxan (ALX), widely used to induce diabetes in experimental animals, have different structures and mechanisms of action. We investigated those effects of these drugs on the immune system that might influence engraftment efficiency and graft survival in transplantation models, and their cytotoxicity on hematopoietic cell lines. We used the minimum dose to induce diabetes in a mouse, i.e. 180 mg/kg i.v. STZ and 75 mg/kg i.v. ALX. Both groups exhibited significant decrease in body weight during 4 days post-treatment as compared to controls. We found that blood glucose in ALX-injected mice increased faster than in STZ-injected mice. The total number of recovered splenocytes was lower in STZ-injected animals than in ALX-injected animals. The survival periods of rat islet grafts in recipient mice were longer and more diverse in STZ-injected recipients (7-24 days) compared to ALX-injected recipients (6-7 days). The in vitro study showed that ALX was less cytotoxic in cell lines with IC50 values of 2809, 3679 and >4000 μg/ml for HL60, K562 and C1498 cells respectively. STZ was more toxic, especially in HL60 cells, with IC50 values of 11.7, 904 and 1024 μg/ml for HL60, K562 and C1498 cells respectively. Furthermore, in response to concanavalin A (Con-A), splenocytes from STZ-injected mice produced higher amounts of interferon-gamma (IFN-γ) than those from ALX-injected mice. In conclusion, STZ was more cytotoxic than ALX in vitro and in vivo. STZ caused lymphocytopenia, which may result in longer graft survival in STZ-treated animals than in ALX-treated animals.

Impact of hyperglycemia on survival and infection-related adverse events in patients with metastatic colorectal cancer who were receiving palliative chemotherapy

PURPOSE

Non-metastatic colorectal cancer patients with diabetes have poor overall survival than those without diabetes. However, the effect of hyperglycemia on survival after diagnosis of metastatic colorectal cancer (CRC) has not been assessed. Therefore, we assessed the impact of hyperglycemia on the survival and infection-related adverse events (AEs) in patients with metastatic CRC.

MATERIALS AND METHODS

We reviewed the records of 206 patients with newly diagnosed metastatic CRC who were treated with palliative chemotherapy from March 2000 to December 2012 at Chungbuk National University Hospital. The mean glucose level of each patient was calculated using all available glucose results.

RESULTS

The mean glucose levels ranged between 76.8 and 303.5 mg/dL, and patients were categorized into quartiles in accordance to their mean glucose level: group 1 (< 106.7 mg/dL), group 2 (106.7-117.2 mg/dL), group 3 (117.3-142.6 mg/dL), and group 4 (> 142.6 mg/dL). The median overall survival for patients in groups 1, 2, 3, and 4 were 22.6, 20.1, 18.9, and 17.9 months, respectively; however, this difference was not statistically significant (p=0.643). Compared with patients in group 1, those in groups 2, 3, and 4 were at a higher risk of infection-related AEs, according to a multivariate analysis (p=0.002).

CONCLUSION

Hyperglycemia was not associated with shorter survival; however, it was associated with infection-related AEs in patients with newly diagnosed metastatic CRC receiving palliative chemotherapy.

Deletion of CD73 promotes dyslipidemia and intramyocellular lipid accumulation in muscle of mice

CONTEXT

CD73 converts extracellular AMP to adenosine which is well known to inhibit lipolysis. It is unknown, however, whether adenosine formed directly by CD73 is functionally relevant in this process.

OBJECTIVE

We therefore explored the effect of CD73-derived adenosine on body fat of aged mice.

RESULTS

In lean mice, extracellular adenosine formation by adipocytes is dependent on CD73. High fat diet down-regulates the expression of CD73 in wildtype mice similar to ob/ob mice. Transgenic mice chronically lacking CD73 (CD73(-/-)) gain significantly less body weight and show decreased superficial white fat content as well as increased serum free fatty acids and triglycerides. In addition, intramyocellular lipid levels are significantly increased. This phenotype is accompanied by an increase in blood glucose and serum insulin levels although insulin secretion and the level of insulin degrading enzyme are unaltered. Additionally, insulin-induced Akt phosphorylation is reduced in skeletal muscle of CD73(-/-) mice.

CONCLUSION

CD73-derived adenosine is functionally involved in body fat homeostasis.

Adenosine kinase: exploitation for therapeutic gain

Adenosine kinase (ADK; EC 2.7.1.20) is an evolutionarily conserved phosphotransferase that converts the purine ribonucleoside adenosine into 5'-adenosine-monophosphate. This enzymatic reaction plays a fundamental role in determining the tone of adenosine, which fulfills essential functions as a homeostatic and metabolic regulator in all living systems. Adenosine not only activates specific signaling pathways by activation of four types of adenosine receptors but it is also a primordial metabolite and regulator of biochemical enzyme reactions that couple to bioenergetic and epigenetic functions. By regulating adenosine, ADK can thus be identified as an upstream regulator of complex homeostatic and metabolic networks. Not surprisingly, ADK dysfunction is involved in several pathologies, including diabetes, epilepsy, and cancer. Consequently, ADK emerges as a rational therapeutic target, and adenosine-regulating drugs have been tested extensively. In recent attempts to improve specificity of treatment, localized therapies have been developed to augment adenosine signaling at sites of injury or pathology; those approaches include transplantation of stem cells with deletions of ADK or the use of gene therapy vectors to downregulate ADK expression. More recently, the first human mutations in ADK have been described, and novel findings suggest an unexpected role of ADK in a wider range of pathologies. ADK-regulating strategies thus represent innovative therapeutic opportunities to reconstruct network homeostasis in a multitude of conditions. This review will provide a comprehensive overview of the genetics, biochemistry, and pharmacology of ADK and will then focus on pathologies and therapeutic interventions. Challenges to translate ADK-based therapies into clinical use will be discussed critically.

Differential effect of hyperglycaemia on the immune response in an experimental model of diabetes in BALB/cByJ and C57Bl/6J mice: participation of oxidative stress

Diabetes is associated with an increased risk of death from infectious disease. Hyperglycaemia has been identified as the main factor contributing to the development of diseases associated with diabetes mellitus. However, experimental evidence indicates individual susceptibility to develop complications of diabetes. In this context, the aim of this work was to study the immune response in a streptozotocin-induced type 1 diabetes in two mouse strains: BALB/cByJ and C57Bl/6J. The participation of hyperglycaemia and oxidative stress was also analysed. Diabetic BALB/cByJ mice showed a decrease in both the in-vivo and in-vitro immune responses, whereas diabetic C57Bl/6J mice had higher blood glucose but exhibited no impairment of the immune response. The influence of hyperglycaemia over the immune response was evaluated by preincubation of lymphocytes from normal mice in a high glucose-containing medium. T and B cells from BALB/cByJ mice showed a decrease in cell viability and mitogen-stimulated proliferation and an increase in apoptosis induction. An increase in oxidative stress was implicated in this deleterious effect. These parameters were not affected in the T and B lymphocytes from C57Bl/6J mice. In conclusion, BALB/cByJ mice were sensitive to the deleterious effect of hyperglycaemia, while C57BL/6J were resistant. Although an extrapolation of these results to clinical conditions must be handled with caution, these results highlight the need to contemplate the genetic background to establish models to study the deleterious effect of diabetes in order to understand phenotypical variations that are of clinical importance in the treatment of patients.

Hyperglycemia increases the complicated infection and mortality rates during induction therapy in adult acute leukemia patients

OBJECTIVE

To determine the prevalence of hyperglycemia during induction therapy in adult patients with acute leukemia and its effect on complicated infections and mortality during the first 30 days of treatment.

METHODS

An analysis was performed in a retrospective cohort of 280 adult patients aged 18 to 60 years with previously untreated acute leukemia who received induction chemotherapy from January 2000 to December 2009 at the Hemocentro de Pernambuco (HEMOPE), Brazil. Hyperglycemia was defined as the finding of at least one fasting glucose measurement > 100 mg/dL observed one week prior to induction therapy until 30 days after. The association between hyperglycemia and complicated infections, mortality and complete remission was evaluated using the Chi-square or Fisher's exact tests by the Statistical Package for Social Sciences (SPSS) in the R software package version 2.9.0.

RESULTS

One hundred and eighty-eight patients (67.1%) presented hyperglycemia at some moment during induction therapy. Eighty-two patients (29.3%) developed complicated infections. Infection-related mortality during the neutropenia period was 20.7% (58 patients). Mortality from other causes during the first 30 days after induction was 2.8%. Hyperglycemia increased the risk of complicated infections (OR 3.97; 95% confidence interval: 2.08 - 7.57; p-value < 0.001) and death (OR 3.55; 95% confidence interval: 1.77-7.12; p-value < 0.001) but did not increase the risk of fungal infections or decrease the probability of achieving complete remission.

CONCLUSION

This study demonstrates an association between the presence of hyperglycemia and the development of complicated infections and death in adult patients during induction therapy for acute leukemia.

The immunosuppressive role of adenosine A2A receptors in ischemia reperfusion injury and islet transplantation

Activation of adenosine A2A receptors (A2AR) reduces inflammation by generally inhibiting the activation of pro-inflammatory cells, decreasing endothelial adhesion molecule expression and reducing the release of proinflammatory cytokine mediators. Numerous preclinical studies using selective A2AR agonists, antagonists, A2AR knockout as well as chimeric mice have suggested the therapeutic potential of A2AR agonists for the treatment of ischemia reperfusion injury (IRI) and autoimmune diseases. This review summarizes the immunosuppressive actions of A2AR agonists in murine IRI models of liver, kidney, heart, lung and CNS, and gives details on the cellular effects of A2AR activation in neutrophils, macrophages, dendritic cells, natural killer cells, NKT cells, T effector cells and CD4+CD25+FoxP3+ T regulatory cells. This is discussed in the context of cytokine mediators involved in inflammatory cascades. Whilst the role of adenosine receptor agonists in various models of autoimmune disease has been well-documented, very little information is available regarding the role of A2AR activation in type 1 diabetes mellitus (T1DM). An overview of the pathogenesis of T1DM as well as early islet graft rejection in the immediate peri-transplantation period offers insight regarding the use of A2AR agonists as a beneficial intervention in clinical islet transplantation, promoting islet graft survival, minimizing early islet loss and reducing the number of islets required for successful transplantation, thereby increasing the availability of this procedure to a greater number of recipients. In summary, the use of A2AR agonists as a clinical intervention in IRI and as an adjunct to clinical immunesuppressive regimen in islet transplantation is highlighted.

Immunomodulatory effects of black seeds and garlic on alloxan-induced Diabetes in albino rat

BACKGROUND

Alteration in the proliferation capacity of leukocytes and in the level of some cytokines, such as TNF-α, IL-4 and IL-8 have been suggested to associate with Diabetes mellitus in alloxan-induced diabetic rats given the potential immunomodulatory effects of black seeds and garlic.

AIM OF THE WORK

The aim of this study was to test the effects of these agents on the immune cells in alloxan-induced diabetic rats.

METHODS

To this end, Diabetes was induced in albino rats by a single intraperitoneal injection of alloxan monohydrate (120mg/kg of body weight). Diabetic rats were then fed normal diet or diet with black seeds or garlic for 28 days.

RESULTS

The results showed significant increase in the numbers of monocytes and granulocytes, but with significant decreases in lymphocyte proliferation and the TNF-α, interleukin (IL)-4 and IL-8 levels in the diabetic group. Treatment of diabetic rats with black seeds or garlic induced significant amelioration in the numbers of monocytes and granulocytes, with significant increase in lymphocytes numbers and the TNF-α, IL-4 and IL-8 levels.

CONCLUSIONS

These results indicate the potential beneficial effects of black seeds and garlic as adjuvant treatment during treatment of Diabetes.

High glucose concentration impairs ATP outflow and immunoglobulin production by human peripheral B lymphocytes: involvement of P2X7 receptor

AIMS/HYPOTHESIS

Patients with diabetes are more prone to bacterial infections mostly due to hyperglycemia-induced suppression of immune cells function. B lymphocytes by secreting antibodies inhibit microbial replication, but the impact of high glucose concentration on humoral immune response is not fully resolved. The aim of this work was to investigate the effect of high glucose concentration on B cells response to stimulation with a bacterial antigen and autocrine regulation.

METHODS

Purified human peripheral blood B cells were cultured at different glucose concentrations and stimulated in vitro with Staphylococcus aureus Cowan I (SAC) plus IL-2. B cells proliferation, differentiation and IgM expression were analyzed by flow cytometry. B cell ATP release and involvement of P2 purinergic receptors in regulation of IgM secretion was assessed.

RESULTS

B cells cultured at 25 mM glucose in response to SAC stimulation released significantly less (≈ 55%) IgM comparing to cells maintained in 5mM glucose. Under resting and stimulatory conditions B cells released significant quantities of ATP to the culture media, but ATP level decreased when B cells were maintain in high glucose. SAC-induced B cell IgM release was totally blocked by highly selective antagonist (Az11645373) of P2X7 receptor. IgM secretion increased in the presence of potent P2X7 receptor agonist (BzATP), but this effect was abolished by high glucose concentration.

CONCLUSIONS/INTERPRETATION

High glucose concentration impairs B cell function by suppression of P2X7 receptor-dependent IgM release in response to in vitro bacterial antigen stimulation. This alteration may greatly contribute to the impaired humoral immune response in diabetics.

Differential response of Drosophila cell lines to extracellular adenosine

Adenosine (Ado) is a crucial metabolite that affects a wide range of physiological processes. Key proteins regulating Ado signaling, transport and metabolism are conserved among vertebrates and invertebrates. It is well known that Ado influences proliferation of several vertebrate and invertebrate cells. Here we show that Ado negatively influences viability, changes morphology and mitochondrial polarity of the Drosophila imaginal disc cell line (Cl.8+) via a mechanism exclusively dependent on cellular Ado uptake. High transport of Ado is followed by phosphorylation and ATP production as a part of Ado salvation, which at higher concentrations may interfere with cellular homeostasis. In contrast, hematopoietic cell line Mbn2, which grows well in high Ado concentration, preferentially uses adenosine deaminase as a part of the purine catabolic pathway. Our results show that different types of Drosophila cell lines use different pathways for Ado conversion and suggest that such differences may be an important part of complex mechanisms maintaining energy homeostasis in the body.

Antihypertriglyceridemia and anti-inflammatory activities of monascus-fermented dioscorea in streptozotocin-induced diabetic rats

The rice fermented by Monascus, called red mold rice (RMR), and has a long tradition in East Asia as a dietary staple. Monascus-fermented dioscorea called red mold dioscorea (RMD) contains various metabolites to perform the ability of reducing oxidative stress and anti-inflammatory response. We used Wistar rats and induced diabetes by injecting streptozotocin (STZ, 65 mg/kg i.p.). RMD was administered daily starting six weeks after disease onset. Throughout the experimental period, significantly (P < .05) lowered plasma glucose, triglyceride, cholesterol, free fatty acid and low density lipoprotein levels were observed in the RMD-treated groups. The RMD-treated diabetic rats showed higher activities of glutathione disulfide reductase, glutathione reductase, catalase and superoxide dismutase (P < .05) in the pancreas compared with the diabetic control rats. RMD also inhibited diabetes-induced elevation in the levels of interleukin (IL)-1β, IL-6, interferon-γ and tumor necrosis factor-α. Pancreatic β-cells damaged by STZ in the RMD supplemented groups were ameliorated. The results of this study clearly demonstrated that RMD possesses several treatment-oriented properties, including the control of hyperglycemia, antioxidant effects, pancreatic β-cell protection and anti-inflammatory effects. Considering these observations, it appears that RMD may be a useful supplement to delay the development of diabetes and its complications.

Links between insulin resistance, adenosine A2B receptors, and inflammatory markers in mice and humans

OBJECTIVE

To determine the mechanisms by which blockade of adenosine A(2B) receptors (A(2B)Rs) reduces insulin resistance.

RESEARCH DESIGN AND METHODS

We investigated the effects of deleting or blocking the A(2B)R on insulin sensitivity using glucose tolerance tests (GTTs) and hyperinsulinemic-euglycemic clamps in mouse models of type 2 diabetes. The effects of diabetes on A(2B)R transcription and signaling were measured in human and mouse macrophages and mouse endothelial cells. In addition, tag single nucleotide polymorphisms (SNPs) in ~42 kb encompassing the A(2B)R gene, ADORA2B, were evaluated for associations with markers of diabetes and inflammation.

RESULTS

Treatment of mice with the nonselective adenosine receptor agonist 5'-N-ethylcarboxamidoadensoine (NECA) increased fasting blood glucose and slowed glucose disposal during GTTs. These responses were inhibited by A(2B)R deletion or blockade and minimally affected by deletion of A(1)Rs or A(2A)Rs. During hyperinsulinemic-euglycemic clamp of diabetic KKA(Y) mice, A(2B)R antagonism increased glucose infusion rate, reduced hepatic glucose production, and increased glucose uptake into skeletal muscle and brown adipose tissue. Diabetes caused a four- to sixfold increase in A(2B)R mRNA in endothelial cells and macrophages and resulted in enhanced interleukin (IL)-6 production in response to NECA due to activation of protein kinases A and C. Five consecutive tag SNPs in ADORA2B were highly correlated with IL-6 and C-reactive protein (CRP). Diabetes had a highly significant independent effect on variation in inflammatory markers. The strength of associations between several ADORA2B SNPs and inflammatory markers was increased when accounting for diabetes status.

CONCLUSIONS

Diabetes affects the production of adenosine and the expression of A(2B)Rs that stimulate IL-6 and CRP production, insulin resistance, and the association between ADORA2B SNPs and inflammatory markers. We hypothesize that increased A(2B)R signaling in diabetes increases insulin resistance in part by elevating proinflammatory mediators. Selective A(2B)R blockers may be useful to treat insulin resistance.

Experimental diabetes attenuates calcium mobilization and proliferative response in splenic lymphocytes from mice

The present study was conducted to investigate the effects of the diabetic condition on cytosolic free Ca(2+) concentration, [Ca(2+)](i), and the proliferation of splenic lymphocytes from mice. Diabetes was induced in mice by intraperitoneal injection of alloxan. [Ca(2+)](i) and the proliferation ex vivo of splenic lymphocytes isolated from mice were examined using fura-2 and 3-(4,5-dimethyl-2-thiazolyl)-2,5-diphenyl-2H-tetrazolium bromide, respectively. Diabetes caused a significant increase in resting [Ca(2+)](i) and significantly reduced the ability of concanavalin A (Con A; a T-lymphocyte-selective mitogen) to increase [Ca(2+)](i), but not that of lipopolysaccharide (LPS; a B-lymphocyte-selective mitogen). In addition, diabetes significantly reduced Con A-stimulated but not LPS-stimulated lymphocyte proliferation. Verapamil (an L-type Ca(2+) channel blocker) inhibited Con A-induced increases in [Ca(2+)](i) and proliferation in lymphocytes from control and diabetic mice to a similar extent, respectively. These results suggest that diabetes attenuates Con A-stimulated T-lymphocyte proliferation by decreasing [Ca(2+)](i) via reduction of Ca(2+) entry through L-type Ca(2+) channels.

Regulation of adenosine receptors expression in rat B lymphocytes by insulin

Development of diabetes is associated with altered expression of adenosine receptors (ARs). Some of these alterations might be attributed to changes in insulin concentration. This study was undertaken to investigate the possible insulin effect on ARs level, and to determine the signaling pathway utilized by insulin to regulate the expression of ARs in rat B lymphocytes. Western blot analysis of B lymphocytes protein extracts indicated that all four ARs were present at detectable levels in the cells cultured for 24 h without insulin (<or=10(-11) M), although the protein band of A(2A)-AR was barely visible. Inclusion of insulin (10(-8) M) in the culture medium resulted in an increase of A(1)-AR and A(2A)-AR protein levels and a significant decrease of A(2B)-AR protein, whereas the protein level of A(3)-AR remained unchanged. Alterations in the ARs protein content were accompanied by changes in the ARs mRNA levels. Increase of the insulin concentration from 10(-11) to 10(-8) M resulted in 50% decrease of A(2B)-AR mRNA level and two-, and threefold increase of A(1)-AR and A(2A)-AR mRNA levels, respectively. Pretreatment of B cells with cycloheximide completely blocked the insulin action on A(1)-AR and A(2A)-AR mRNA, but not on A(2B)-AR expression. Detailed pharmacological analysis demonstrated that insulin-induced A(1)-AR and A(2A)-AR mRNA expression through the Ras/Raf-1/MEK/ERK pathway. The insulin effect on A(2B)-AR expression was blocked by p38 MAP kinase inhibitor (SB 203580). Concluding, elevated insulin concentration differentially affects the expression of ARs in B lymphocytes in a fashion that might enhance the various immunomodulatory effects of adenosine.

Dysglycemia following glucocorticoid therapy for acute graft-versus-host disease adversely affects transplantation outcomes

Disordered glucose metabolism is a common complication of glucocorticoid therapy for acute graft-versus-host disease (aGVHD) after allogeneic hematopoietic cell transplantation (HCT). We aimed to examine the impact of dysglycemia on outcomes in 173 recipients of HCT treated with glucocorticoids for aGVHD. A total of 147 of these patients contributed data to a landmark analysis performed at 12 weeks post-HCT. Median aGVHD onset was 21 days (range: 5-79) after transplant. Median duration of glucocorticoid therapy was 381 days (range: 15-1632). Glucose values were obtained from glucocorticoid initiation date to death or last follow-up, resulting in 11,588 total values. The median (range) for each parameter were: maximum 292 mg/dL (128-694), minimum 75 mg/dL (34-142), average 142 mg/dL (86-327), and standard deviation 46 mg/dL (12-108). Baseline diabetes mellitus predicted significantly greater maximum, mean, and standard deviation. With median follow-up of 20 months (range: 3-55), median overall survival (OS) was 33.7 months (95% confidence interval [CI] 16.4-not reached). On multivariable analysis, maximum, average, or standard deviation of glucose values predicted OS and maximum or average glucose values predicted nonrelapse mortality (NRM). Minimum glucose values of (0-60 mg/dL) were associated with worsened OS and increased NRM. Those patients treated with insulin or oral agents suffered significantly worse OS and increased NRM compared to patients who did not need therapy. Finally, those with sustained maximum values >200 mg/dL despite treatment suffered worse OS and increased NRM. These data suggest an independent adverse effect of dysglycemia in patients treated with glucocorticoids for aGVHD, and argue for stringent glycemic control in this setting.

Methylglyoxal modulates immune responses: relevance to diabetes

Increased methylglyoxal (MG) concentrations and formation of advanced glycation end-products (AGEs) are major pathways of glycaemic damage in diabetes, leading to vascular and neuronal complications. Diabetes patients also suffer increased susceptibility to many common infections, the underlying causes of which remain elusive. We hypothesized that immune glycation damage may account for this increased susceptibility. We previously showed that the reaction mixture (RM) for MG glycation of peptide blocks up regulation of CD83 in myeloid cells and inhibits primary stimulation of T cells. Here, we continue to investigate immune glycation damage, assessing surface and intracellular cytokine protein expression by flow cytometry, T-cell proliferation using a carboxyfluorescein succinimidyl ester assay, and mRNA levels by RT-PCR. We show that the immunomodulatory component of this RM was MG itself, with MG alone causing equivalent block of CD83 and loss of primary stimulation. Block of CD83 expression could be reversed by MG scavenger N-acetyl cysteine. Further, MG within RM inhibited stimulated production of interleukin (IL)-10 protein from myeloid cells plus interferon (IFN)-gamma and tumour necrosis factor (TNF)-alpha from T cells. Loss of IL-10 and IFN-gamma was confirmed by RT-PCR analysis of mRNA, while TNF-alpha message was raised. Loss of TNF-alpha protein was also shown by ELISA of culture supernatants. In addition, MG reduced major histocompatibility complex (MHC) class I expression on the surface of myeloid cells and increased their propensity to apoptose. We conclude that MG is a potent suppressor of myeloid and T-cell immune function and may be a major player in diabetes-associated susceptibility to infection.

Association of exogenous insulin or sulphonylurea treatment with an increased incidence of hepatoma in patients with hepatitis C virus infection

BACKGROUND

Diabetes mellitus is frequently seen in hepatitis C patients and is often treated with antidiabetic agents that increase serum insulin levels. Because insulin is a growth-promoting hormone, antidiabetic agents could pose a risk for hepatocellular carcinoma (HCC).

AIM

The aim of this study was to investigate an association between antidiabetic therapies and the incidence of HCC in hepatitis C patients with diabetes mellitus.

METHODS

A nested case-control study was conducted. Participants were recruited from a cohort study, in which patients with hepatitis C were consecutively registered. Participants were assigned to an HCC group (n=138) or a non-HCC group (n=103). To identify independent factors, variables including use of antidiabetic agents were analysed by logistic regression analysis.

RESULTS

Besides ageing, being male, cirrhosis and hypoalbuminaemia, use of exogenous insulin and a second-generation sulphonylurea were significant independent factors associated with an incidence of HCC [odds ratio (OR) 2.969, 95% confidence interval (CI) 1.293-6.819, P<0.0103 and OR 6.831, 95% CI 1.954-23.881, P<0.0026 respectively). In stratified analyses, the impact of these antidiabetic agents was more evident in patients who were non-cirrhotic than in those who were cirrhotic.

CONCLUSIONS

Exogenous insulin and a second-generation sulphonylurea were independent variables associated with an incidence of HCC in hepatitis C patients with diabetes mellitus. This association was evident in patients who were non-cirrhotic. To verify a causal relationship between these antidiabetic agents and the development of HCC, a prospective cohort study is required.

Deciphering ligand dependent degree of binding site closure and its implication in inhibitor design: A modeling study on human adenosine kinase

Protein flexibility plays a significant role in drug research due to its effect on accurate prediction of ligand binding mode and activity. Adenosine kinase (AK) represents a highly flexible binding site and is known to exhibit large conformational changes as a result of substrate or inhibitor binding. Here we propose a semi-open conformation for ligand binding in human AK, in addition to the known closed and open forms. The modeling study illustrates the necessity of thorough understanding of the conformational states of protein for docking and binding mode prediction. It has been shown that predicting activity in the context of correct binding mode can improve the insight into conserved interactions and mechanism of action for inhibition of AK. Integrating the knowledge about the binding modes of ligands in different conformational states of the protein, separate pharmacophore models were generated and used for virtual screening to explore potential novel hits. In addition, 2D descriptor based clustering was done to differentiate the ligands, binding to closed, semi-open and open conformations of human AK. The results indicated that binding of all AK inhibitors cannot be described by same rules, instead, they represent a rule based preference for inhibition. This inference about tubercidins binding to semi-open conformation of human AK may facilitate in finding much extensive space for AK inhibitors.

Methylglyoxal: possible link between hyperglycaemia and immune suppression?

No matter the cause of diabetes, the result is always hyperglycaemia. This excess glucose metabolism drives several damage pathways and raises concentrations of the reactive dicarbonyl, methylglyoxal (MG). MG can modify the structure and function of target molecules by forming advanced glycation end-products (AGEs) that act through their receptor (RAGE) to perpetuate vascular and neuronal injury responsible for long-term complications of diabetes. Diabetes patients also suffer lower resistance to many common infections, although the cause(s) for this lower resistance remains elusive. Here, we review recent evidence concerning immune suppression in diabetes and discuss the effects of MG on components of the immune system. We suggest that MG could be a missing link between hyperglycaemia and immune suppression in diabetes.

Ursolic acid enhances the cellular immune system and pancreatic beta-cell function in streptozotocin-induced diabetic mice fed a high-fat diet

This study investigated the effects of ursolic acid on immunoregulation and pancreatic beta-cell function in type 1 diabetes fed a high-fat diet for 4 weeks. Male mice were divided into non-diabetic, diabetic control, and diabetic-ursolic acid (0.05%, w/w) groups, which were fed a high-fat (37% calories from fat). Diabetes was induced by injection of streptozotocin (200 mg/kg B.W., i.p.). Ursolic acid significantly improved blood glucose levels, glucose intolerance, and insulin sensitivity compared to the diabetic group. The plasma insulin and C-peptide concentrations were significantly higher in the diabetic-ursolic acid group than in the diabetic group. Ursolic acid significantly elevated the insulin levels with preservation of insulin staining of beta-cells in the pancreas. In splenocytes, concanavalin (Con) A-induced T-cell proliferation was significantly higher in the diabetic-ursolic acid group compared to the diabetic group, but liposaccharide (LPS)-induced B-cell proliferation did not differ between groups. Ursolic acid enhanced IL-2 and IFN-gamma production in response to Con A stimulation, whereas it inhibited TNF-alpha production in response to LPS stimulation. In this study, neither streptozotocin nor ursolic acid had effects on lymphocyte subsets. These results indicate that ursolic acid exhibits potential anti-diabetic and immunomodulatory properties by increasing insulin levels with preservation of pancreatic beta-cells and modulating blood glucose levels, T-cell proliferation and cytokines production by lymphocytes in type 1 diabetic mice fed a high-fat diet.

Antecedent hyperglycemia is associated with an increased risk of neutropenic infections during bone marrow transplantation

OBJECTIVE

To use bone marrow transplantation (BMT) as a model for testing the association between hyperglycemia and infection.

RESEARCH DESIGN AND METHODS

This cohort study included 382 adults (6.5% with diabetes) who had no evidence of infection before neutropenia during BMT. Mean glucose was calculated from central laboratory and bedside measurements taken before neutropenia; the primary outcome was neutropenic infections.

RESULTS

Eighty-four patients (22%) developed at least one neutropenic infection, including 51 patients (13%) with bloodstream infections. In patients who did not receive glucocorticoids during neutropenia, each 10 mg/dl increase in mean preneutropenia glucose was associated with an odds ratio of 1.08 (95% CI 0.98-1.19) (P = 0.14) for any infection and 1.15 (1.03-1.28) (P = 0.01) for bloodstream infections, after adjusting for age, sex, race, year, cancer diagnosis, transplant type, and total glucocorticoid dose before neutropenia. In those who received glucocorticoids during neutropenia (n = 71), the adjusted odds ratio associated with a 10 mg/dl increase in mean glucose was 1.21 (1.09-1.34) (P < 0.0001) for any infection and 1.24 (1.11-1.38) (P < 0.0001) for bloodstream infections. There was no association between mean glycemia and long length of hospital stay, critical status designation, or mortality.

CONCLUSIONS

In a BMT population highly susceptible to infection, there was a continuous positive association between mean antecedent glycemia and later infection risk, particularly in patients who received glucocorticoids while neutropenic. Tight glycemic control during BMT and glucocorticoid treatment may reduce infections.

Impaired immune responses in streptozotocin-induced type I diabetes in mice. Involvement of high glucose

Diabetes is widely believed to predispose to serious infections. However, the mechanisms linking diabetes and immunosuppression are not well defined. One potential mediator of the altered defence mechanisms is hyperglycaemia. It has been identified as the main factor contributing to the development of diseases associated with diabetes mellitus. In this study we analyse the immune response in diabetes and the direct effect of hyperglycaemia on T and B lymphocyte reactivity. Diabetes induced an early decrease in IgG levels in the secondary response. However, both primary responses against a T-cell-dependent or independent antigen were affected after 6 months of diabetes induction. T- and B- cell proliferation was only decreased at this time. To gain insight into the potential mechanisms involved, we evaluated the influence of hyperglycaemia over the immune response. Pre-incubation of lymph node and spleen cells in a high glucose (HG) containing medium led to a significant time- and dose-dependent decrease in T- and B-cell proliferation. This effect was associated with the presence of HG-derived supernatants. Still viable cells after HG exposition were able to improve their proliferative response when cultured with the mitogen in a fresh standard medium. HG diminished cell viability, increased apoptosis and induced oxidative stress in lymphocytes. These results indicate that HG concentrations can directly affect lymphoid cell growth. An increase in oxidative stress would be implicated in this deleterious effect. The possibility that prolonged exposure to pathologically HG concentrations would result in the immunosuppressive state observed in diabetes is also discussed.