Nano-scale encapsulation enhances allograft survival and function of islets transplanted in a mouse model of diabetes

AIMS/HYPOTHESIS

The success of islet transplantation as a treatment for type 1 diabetes is currently hampered by post-transplantation loss of functional islets through adverse immune and non-immune reactions. We aimed to test whether early islet loss can be limited and transplant survival improved by the application of conformal nano-coating layers to islets.

METHODS

Our novel coating protocol used alternate layers of phosphorylcholine-derived polysaccharides (chitosan or chondroitin-4-sulphate) and alginate as coating materials, with the binding based on electrostatic complexation. The in vitro function of encapsulated mouse islets was studied by analysing islet secretory function and cell viability. The in vivo function was evaluated using syngeneic and allogeneic transplantation in the streptozotocin-induced mouse model of diabetes.

RESULTS

Nano-scale encapsulated islets retained appropriate islet secretory function in vitro and were less susceptible to complement- and cytokine-induced apoptosis than non-encapsulated control islets. In in vivo experiments using a syngeneic mouse transplantation model, no deleterious responses to the coatings were observed in host animals, and the encapsulated islet grafts were effective in reversing hyperglycaemia. Allo-transplantation of the nano-coated islets resulted in preserved islet function post-implantation in five of seven mice throughout the 1 month monitoring period.

CONCLUSIONS/INTERPRETATION

Nano-scale encapsulation offers localised immune protection for implanted islets, and may be able to limit early allograft loss and extend survival of transplanted islets. This versatile coating scheme has the potential to be integrated with tolerance induction mechanisms, thereby achieving long-term success in islet transplantation.

Clinical, biochemical, and immunological characteristics of newly diagnosed nonobese diabetic patients aged 18-45 years in China

BACKGROUND

The purpose was to characterize the clinical, biochemical, and immunological features of newly diagnosed adult-onset nonobese diabetic patients in China.

METHODS

Newly diagnosed diabetic patients aged 18-45 years with body mass index<23 kg/m(2) were included. Excluding one mitochondrial diabetes patient, there were 102 diabetic patients enrolled in this study. Clinical and biochemical data were collected and analyzed. Radioimmunoassay was used to detect islet autoantibodies.

RESULTS

Among the 102 study participants, 68.6% had type 1 diabetes (T1DM), 20.6% had type 2 diabetes (T2DM), and 10.8% had latent autoimmune diabetes in adults (LADA). About 92% of the T1DM patients presented hyperglycemic symptoms. The corresponding number in T2DM and LADA patients was 13% and 38%, respectively (P<.01). C-peptide in T2DM patients (1.4±0.7 ng/ml) was significantly higher than that in T1DM (0.4±0.3 ng/ml) and LADA (0.4±0.2 ng/ml) patients (P<.01). The prevalence of glutamic acid decarboxylase antibody (GADA) (64.3%) in T1DM patients was higher than that of insulin autoantibody (17.1%) (P<.05). GADA and islet cell antibody (ICA) combination was positive in 75.7% of T1DM patients.

CONCLUSION

T1DM patients accounted for majority of the study sample. In addition, the clinical symptoms of T1DM patients were more severe compared with T2DM patients. GADA is the most sensitive autoantibody marker for adult-onset T1DM and LADA. GADA and ICA are the best test combination for adult-onset autoimmune diabetes. Specific types of diabetes should be in mind when diabetes presents itself with special transmission mode or with other extrapancreatic manifestations.

The role of hyperglycemia in mechanisms of exacerbated inflammatory responses within the oral cavity

Immune modulating factors are necessary for pathogen clearance, but also contribute to host tissues damage, as those seen in periodontal diseases. Many of these responses can be exacerbated by host conditions including type 2 diabetes [T2D], where toll-like receptor 4 [TLR4] and the receptor for advanced glycated end products [RAGE] play a significant role. Here we investigate causality associated with the increase in inflammatory markers observed in periodontally diseased patients with T2D using multi-variant correlation analysis. Inflammation associated with periodontal diseases, characterized by elevated pro-inflammatory cytokines, innate immune receptor expression, and cellular infiltrate was exacerbated in patients with T2D. In addition, a feed forward loop regulated by poor glycemic control was associated with a loss of mucosal barrier integrity and accumulation of innate immune receptor ligands resulting in an exacerbation of ongoing inflammation, where RAGE and TLR4 cooperated to induce responses in oral epithelial cells, which were exacerbated by hyperglycemia.

Impaired interleukin-1beta expression by monocytes stimulated with Staphylococcus aureus in diabetes

Diabetic patients with poorly controlled blood glucose have frequent and persistent bacterial infections particularly those infecting the skin, such as Staphylococcus aureus and S. epidermidis. The function of phagocytes of diabetic patients is believed to be impaired due to hyperglycemia, leading to suboptimal immune response to clear acute infection. The present study investigated interleukin (IL)-1beta expression by diabetic patients' monocytes (n = 22) experimentally infected with S. aureus compared with that from healthy subjects (n = 30). In addition, the in vitro effect of hyperglycemia on IL-1beta expression by monocytes from normal subjects (n = 18) stimulated with S. aureus and S. epidermidis was investigated. Monocytes from diabetic patients, stimulated or not with S. aureus, express significantly lower levels of IL-1beta than those from healthy subjects. In vitro hyperglycemia did not affect IL-1beta expression by unstimulated monocytes. However, at the same levels of glucose normal monocytes stimulated with S. aureus produce significantly higher IL-1beta than those stimulated with S. epidermidis. These findings suggest that diabetic patients have abnormally lower IL-1beta expression and hyperglycemia is related to abnormal expression of IL-1beta by monocytes, which could lead to enhanced susceptibility to infection by the more virulent bacteria.

Effects of lipopolysaccharides on TLR4 expression in INS-1 rat insulinoma cells

The aim of the study was to obtain insight into the mechanism of sepsis-induced hyperglycemia, to explore the expression of Toll-like receptor 4 (TLR4) on INS-1 cells, the effects of lipopolysaccharide (LPS) on TLR4 expression and cell viability. The expression of TLR4 on INS-1 was detected by both RT-PCR and Western blot assays. After being intervened by LPS of various concentrations (0.01, 0.1, 1, 5, 10mg/L) for a certain time, the effects of LPS on TLR4 expression and cell viability were detected by quantitative real-time reverse-transcriptase polymerase chain reaction, western blotting and CCK-8 assay. Then INS-1 cells were stimulated by LPS (0.1, 1mg/L) together with anti-TLR4 antibody, cell viability and TLR4 expression were detected again. TLR4 expressed in INS-1 cell line. Its expression was up-regulated by the stimulation of LPS higher than 0.1mg/L for 12h (P<0.05). However, there was a little down-regulation of TLR4 between the LPS treated groups and controls with further LPS treatment for 24 and 48 h (P>0.05). In certain concentrations(0.1~10mg/L), viability of INS-1 cells was inhibited by LPS in a dose dependent manner (P<0.05) These effects could be blocked by anti-TLR4 antibody partially. These results suggest that LPS may act directly on the pancreatic β cells via TLR4 on the β-cell membrane. LPS increased TLR4 expression in the early short period of time and caused injury to INS-1 cells after a certain time. It could be one of the mechanisms that hyperglycemia occurs in the early stage of sepsis.

Hyperglycemic myocardial damage is mediated by proinflammatory cytokine: macrophage migration inhibitory factor

Background

Diabetes has been regarded as an inflammatory condition which is associated with left ventricular diastolic dysfunction (LVDD). The purpose of this study was to examine the expression levels of macrophage migration inhibitory factor (MIF) and G protein-coupled receptor kinase 2 (GRK2) in patients with early diabetic cardiomyopathy, and to investigate the mechanisms involved in MIF expression and GRK2 activation.

Methods

83 patients in the age range of 30-64 years with type 2 diabetes and 30 matched healthy men were recruited. Left ventricular diastolic function was evaluated by cardiac Doppler echocardiography. Plasma MIF levels were determined by ELISA. To confirm the clinical observation, we also studied MIF expression in prediabetic rats with impaired glucose tolerance (IGT) and relationship between MIF and GRK2 expression in H9C2 cardiomyoblasts exposed to high glucose.

Results

Compared with healthy subjects, patients with diabetes have significantly increased levels of plasma MIF which was further increased in diabetic patients with Left ventricular diastolic dysfunction (LVDD). The increased plasma MIF levels in diabetic patients correlated with plasma glucose, glycosylated hemoglobin and urine albumin levels. We observed a significant number of TUNEL-positive cells in the myocardium of IGT-rats but not in the control rats. Moreover, we found higher MIF expression in the heart of IGT with cardiac dysfunction compared to that of the controls. In H9C2 cardiomyoblast cells, MIF and GRK2 expression was significantly increased in a glucose concentration-dependant manner. Furthermore, GRK2 expression was abolished by siRNA knockdown of MIF and by the inhibition of CXCR4 in H9C2 cells.

Conclusions

Our findings indicate that hyperglycemia is a causal factor for increased levels of pro-inflammatory cytokine MIF which plays a role in the development of cardiomyopathy occurring in patients with type 2 diabetes. The elevated levels of MIF are associated with cardiac dysfunction in diabetic patients, and the MIF effects are mediated by GRK2.

Is plasma 25(OH) D related to adipokines, inflammatory cytokines and insulin resistance in both a healthy and morbidly obese population?

To analyse in a cohort of healthy subjects and in a group of morbidly obese patients, we studied the association amongst 25(OH) D and plasma concentrations of adipocytokines, inflammatory cytokines and insulin resistance. We also aimed to determine whether vitamin D-deficient patients showed a greater inflammatory profile. In the observational study that the authors conducted, plasma concentrations of 25(OH) D, leptin, resistin, adiponectin and interleukine-18 were determined in 134 healthy men and 127 women. In the population consisting of 44 patients with morbid obesity, plasma concentrations of 25(OH) D, leptin, resistin, adiponectin, interleukine-18, soluble tumor necrosis factor receptors 1 and 2 and C-reactive protein were analysed. In the healthy population, plasma 25(OH) D showed a negative correlation with body mass index, body fat, waist, hip circumference and with leptin. However, no significant associations were found amongst 25(OH) D and plasma concentrations of resistin, adiponectin or interleukine-18. Patients with vitamin D deficiency showed higher body mass index, fat mass percentage and higher leptin concentrations compared with subjects with normal 25(OH) D concentrations. In the morbidly obese subjects, 25(OH) D did not correlate with leptin, resistin, adiponectin, interleukine-18, soluble tumor necrosis factor receptors 1 and 2 or with C-reactive protein. In patients with morbid obesity, no differences were found in adipokines and inflammatory cytokines concentrations regarding 25(OH) D status. No associations were found either between 25(OH) D and plasma glucose and insulin resistance or with lipid profile. Plasma 25(OH) D concentrations are associated with adiposity markers but not with adipocytokines implicated in inflammation. This lack of association does not support a major role of 25(OH) D in the pro-inflammatory environment observed in morbidly obese subjects. In addition, subjects with vitamin D deficiency are not characterized by a greater inflammatory state.

Vascular cellular adhesion molecule-1 (VCAM-1) expression in mice retinal vessels is affected by both hyperglycemia and hyperlipidemia

Background

Inflammation has been proposed to be important in the pathogenesis of diabetic retinopathy. An early feature of inflammation is the release of cytokines leading to increased expression of endothelial activation markers such as vascular cellular adhesion molecule-1 (VCAM-1). Here we investigated the impact of diabetes and dyslipidemia on VCAM-1 expression in mouse retinal vessels, as well as the potential role of tumor necrosis factor-α (TNFα).

Methodology/Principal Findings

Expression of VCAM-1 was examined by confocal immunofluorescence microscopy in vessels of wild type (wt), hyperlipidemic (ApoE^−/−) and TNFα deficient (TNFα^−/−, ApoE^−/−/TNFα^−/−) mice. Eight weeks of streptozotocin-induced diabetes resulted in increased VCAM-1 in wt mice, predominantly in small vessels (<10 µm). Diabetic wt mice had higher total retinal TNFα, IL-6 and IL-1β mRNA than controls; as well as higher soluble VCAM-1 (sVCAM-1) in plasma. Lack of TNFα increased higher basal VCAM-1 protein and sVCAM-1, but failed to up-regulate IL-6 and IL-1β mRNA and VCAM-1 protein in response to diabetes. Basal VCAM-1 expression was higher in ApoE^−/− than in wt mice and both VCAM-1 mRNA and protein levels were further increased by high fat diet. These changes correlated to plasma cholesterol, LDL- and HDL-cholesterol, but not to triglycerides levels. Diabetes, despite further increasing plasma cholesterol in ApoE^−/− mice, had no effects on VCAM-1 protein expression or on sVCAM-1. However, it increased ICAM-1 mRNA expression in retinal vessels, which correlated to plasma triglycerides.

Conclusions/Significance

Hyperglycemia triggers an inflammatory response in the retina of normolipidemic mice and up-regulation of VCAM-1 in retinal vessels. Hypercholesterolemia effectively promotes VCAM-1 expression without evident stimulation of inflammation. Diabetes-induced endothelial activation in ApoE^−/− mice seems driven by elevated plasma triglycerides but not by cholesterol. Results also suggest a complex role for TNFα in the regulation of VCAM-1 expression, being protective under basal conditions but pro-inflammatory in response to diabetes.

Increased levels of CRP and MCP-1 are associated with previously unknown abnormal glucose regulation in patients with acute STEMI: a cohort study

BACKGROUND

Inflammation plays an important role in the pathophysiology of both atherosclerosis and type 2 diabetes and some inflammatory markers may also predict the risk of developing type 2 diabetes. The aims of the present study were to assess a potential association between circulating levels of inflammatory markers and hyperglycaemia measured during an acute ST-elevation myocardial infarction (STEMI) in patients without known diabetes, and to determine whether circulating levels of inflammatory markers measured early after an acute STEMI, were associated with the presence of abnormal glucose regulation classified by an oral glucose tolerance test (OGTT) at three-month follow-up in the same cohort.

METHODS

Inflammatory markers were measured in fasting blood samples from 201 stable patients at a median time of 16.5 hours after a primary percutaneous coronary intervention (PCI). Three months later the patients performed a standardised OGTT. The term abnormal glucose regulation was defined as the sum of the three pathological glucose categories classified according to the WHO criteria (patients with abnormal glucose regulation, n = 50).

RESULTS

No association was found between inflammatory markers and hyperglycaemia measured during the acute STEMI. However, the levels of C-reactive protein (CRP) and monocyte chemoattractant protein-1 (MCP-1) measured in-hospital were higher in patients classified three months later as having abnormal compared to normal glucose regulation (p = 0.031 and p = 0.016, respectively). High levels of CRP (≥ 75 percentiles (33.13 mg/L)) and MCP-1 (≥ 25 percentiles (190 ug/mL)) were associated with abnormal glucose regulation with an adjusted OR of 3.2 (95% CI 1.5, 6.8) and 7.6 (95% CI 1.7, 34.2), respectively.

CONCLUSION

Elevated levels of CRP and MCP-1 measured in patients early after an acute STEMI were associated with abnormal glucose regulation classified by an OGTT at three-month follow-up. No significant associations were observed between inflammatory markers and hyperglycaemia measured during the acute STEMI.

Autoantigens plus interleukin-10 suppress diabetes autoimmunity

BACKGROUND

Recombinant vaccinia virus (rVV) strains expressing the immunomodulatory cholera toxin B subunit (CTB) fused to the autoantigen glutamic acid decarboxylase (GAD) or the immunosuppressive cytokine interleukin-10 (IL-10) were independently able to generate only low levels of immune suppression of type 1 diabetes mellitus (T1DM). Here we suggest that a vaccinia virus (VV)-mediated combination of CTB::GAD fusion and IL-10 proteins promises a effective and durable immunotherapeutic strategy for T1DM.

METHODS

To explore this hypothesis, a CTB::GAD fusion gene was co-delivered with a gene encoding IL-10 by rVV infection (rVV-CTB::GAD + rVV-IL10) into 5-7-week-old non-obese diabetic (NOD) mice. The mice were assessed for vaccine protection against development of hyperglycemia from 12 to 64 weeks of age by assessment of pancreatic inflammation (insulitis) and splenocyte-secreted interferon-gamma and IL-10 cytokine levels.

RESULTS

By 36 weeks of age, from 54% to 80% of the mice in the negative control animal groups (either mock-infected or inoculated with unrelated plasmid or VV) had developed hyperglycemia. Similarly, no statistically significant improvement in protection against diabetes onset was achieved by inoculation with VV expressing CTB::GAD or IL-10 independently. Surprisingly, only 20% of mice co-inoculated with rVV-CTB::GAD + rVV-IL10 developed hyperglycemia by 28 weeks of age. Other treatment groups developed hyperglycemia by 32-36 weeks. After 36 weeks, diabetes incidence no longer increased in any groups until the end of experiment at 64 weeks of age. Histological analysis of pancreatic tissues of hyperglycemic mice revealed high levels of intra-islet insulitis. Analysis of insulitis at termination of the experiment showed that euglycemic mice co-inoculated with VV expressing CTB::GAD and IL-10 had more effectively reduced inflammation in comparison with the other groups.

CONCLUSIONS

A combinatorial vaccination strategy based on VV co-delivery of genes encoding the immunoenhanced autoantigen CTB::GAD and the anti-inflammatory cytokine IL-10 can maintain effective and durable euglycemia and immunological homeostasis in NOD mice with prediabetes.

Treatment of type B insulin resistance: a novel approach to reduce insulin receptor autoantibodies

BACKGROUND

Type B insulin resistance belongs to a class of diseases caused by an autoantibody to a cell surface receptor. Blockade of insulin action results in hyperglycemia, hypercatabolism, severe acanthosis nigricans, and hyperandrogenism in women. This rare autoimmune disorder has been treated with various forms of immunosuppression with mixed success.

METHODS

We describe 14 patients with type B insulin resistance referred to the National Institutes of Health, adding to an existing cohort of 24 patients. This report focuses on seven patients who were treated with an intensive combination protocol of rituximab, cyclophosphamide, and pulse corticosteroids aimed at control of pathogenic autoantibody production. Hematological, metabolic, and endocrine parameters, including fasting glucose, glycated hemoglobin, insulin dose, lipids, and testosterone, were monitored before and after treatment.

RESULTS

All seven treated patients achieved remission, defined as amelioration of hyperglycemia, discontinuation of insulin therapy, and resolution of hyperandrogenism. Glycated hemoglobin has normalized in all seven treated patients. Remission was achieved on average in 8 months from initiation of treatment. The medication regimen was well tolerated, with no serious adverse events.

CONCLUSIONS

In seven patients with type B insulin resistance, standardized treatment with rituximab, cyclophosphamide, and pulse steroids results in remission of the disease. Future studies will determine whether this treatment protocol can be applied to other autoantibody/cell surface receptor disease states.

trans-resveratrol inhibits hyperglycemia-induced inflammation and connexin downregulation in retinal pigment epithelial cells

The purpose of this study was to determine the inhibitory activity of trans-resveratrol against hyperglycemia-induced inflammation and degradation of gap junction intercellular communication in retinal pigment epithelial cells. Retinal (ARPE-19) cells were incubated with 5.5 mM glucose, 5.5 mM glucose and 10 microM resveratrol, 33 mM glucose, or 33 mM glucose and 0-10 microM trans-resveratrol at 37 degrees C and 5% CO(2) for 9 days. Cell viability was determined by the crystal violet assay. The levels of low-grade inflammation biomarkers interleukin-6 and interleukin-8 (IL-6 and IL-8), angiogenic factors, and vascular endothelial growth factor (VEGF) were determined by the enzyme-linked immunosorbent assay (ELISA). Gap junction intercellular communication (GJIC) was determined by the scrape-load/dye transfer method. The expression levels of protein kinase Cbeta (PKCbeta), connexin 43 (Cx43), transforming growth factor-beta1 (TGF-beta1), and cyclooxygenase-2 (COX-2) were determined by Western blot. Incubation of retinal cells with 10 microM trans-resveratrol in the presence of 5.5 mM glucose did not affect any of the biomarkers investigated. Incubation of ARPE-19 cells with 33 mM glucose for 9 days significantly induced the accumulation of VEGF, IL-6, IL-8, TGF-beta, and COX-2, activation of PKCbeta, and reduction of Cx43 and GJIC. Incubation of ARPE-19 cells with 33 mM glucose in the presence of 0-10 microM trans-resveratrol dose-dependently inhibited VEGF, TGF-beta1, COX-2, IL-6, and IL-8 accumulation, PKCbeta activation, and Cx43 degradation and enhanced GJIC. These data suggest that trans-resveratrol can protect the retinal pigment epithelial cells against hyperglycemia-induced low-grade inflammation and GJIC degradation.

Interleukin-6 autoantibodies are involved in the pathogenesis of a subset of type 2 diabetes

Interleukin-6 (IL6) is critically involved in inflammation and metabolism. About 1% of people produce IL6 autoantibodies (aAb-IL6) that impair IL6 signaling in vivo. We tested the hypothesis that the prevalence of such aAb-IL6 is increased in type 2 diabetic patients and that aAb-IL6 plays a direct role in causing hyperglycemia. In humans, the prevalence of circulating high-affinity neutralizing aAb-IL6 was 2.5% in the type 2 diabetic patients and 1% in the controls (odds ratio 2.5, 95% confidence interval 1.2-4.9, P=0.01). To test for the role of aAb-IL6 in causing hyperglycemia, such aAb-IL6 were induced in mice by a validated vaccination procedure. Mice with plasma levels of aAb-IL6 similar to the 2.5% type 2 diabetic patients developed obesity and impaired glucose tolerance (area under the curve (AUC) glucose, 2056+/-62 vs 1793+/-62, P=0.05) as compared with sham-vaccinated mice, when challenged with a high-fat diet. Mice with very high plasma levels of aAb-IL6 developed elevated fasting plasma glucose (mM, 4.8+/-0.4 vs 3.3+/-0.1, P<0.001) and impaired glucose tolerance (AUC glucose, 1340+/-38 vs 916+/-25, P<0.001) as compared with sham-control mice on normal chow. In conclusion, the prevalence of plasma aAb-IL6 at levels known to impair IL6 signaling in vivo is increased 2.5-fold in people with type 2 diabetes. In mice, matching levels of aAb-IL6 cause obesity and hyperglycemia. These data suggest that a small subset of type 2 diabetes may in part evolve from an autoimmune attack against IL6.

Progression to diabetes in relatives of type 1 diabetic patients: mechanisms and mode of onset

OBJECTIVE

Relatives of type 1 diabetic patients are at enhanced risk of developing diabetes. We investigated the mode of onset of hyperglycemia and how insulin sensitivity and beta-cell function contribute to the progression to the disease.

RESEARCH DESIGN AND METHODS

In 328 islet cell autoantibody-positive, nondiabetic relatives from the observational arms of the Diabetes Prevention Trial-1 Study (median age 11 years [interquartile range 8], sequential OGTTs (2,143 in total) were performed at baseline, every 6 months, and 2.7 years [2.7] later, when 115 subjects became diabetic. Beta-cell glucose sensitivity (slope of the insulin-secretion/plasma glucose dose-response function) and insulin sensitivity were obtained by mathematical modeling of the OGTT glucose/C-peptide responses.

RESULTS

In progressors, baseline insulin sensitivity, fasting insulin secretion, and total postglucose insulin output were similar to those of nonprogressors, whereas beta-cell glucose sensitivity was impaired (median 48 pmol/min per m2 per mmol/l [interquartile range 36] vs. 87 pmol/min per m2 per mmol/l [67]; P < 0.0001) and predicted incident diabetes (P < 0.0001) independently of sex, age, BMI, and clinical risk. In progressors, 2-h glucose levels changed little until 0.78 years before diagnosis, when they started to rise rapidly (approximately 13 mmol x l(-1) x year(-1)); glucose sensitivity began to decline significantly (P < 0.0001) earlier (1.45 years before diagnosis) than the plasma glucose surge. During this anticipation phase, both insulin secretion and insulin sensitivity were essentially stable.

CONCLUSIONS

In high-risk relatives, beta-cell glucose sensitivity is impaired and is a strong predictor of diabetes progression. The time trajectories of plasma glucose are frequently biphasic, with a slow linear increase followed by a rapid surge, and are anticipated by a further deterioration of beta-cell glucose sensitivity.

Comparison of lymphomononuclear cell energy metabolism between healthy, impaired glucose intolerance and type 2 diabetes mellitus patients

Diabetes mellitus (DM) is a complex disease that affects many systems. The most important cells of the immune system are lymphomononuclear (LMN) cells. Here, we aimed to evaluate the energy metabolism of LMN cells in patients with diabetes and impaired glucose tolerance. We measured LMN cell energy metabolism in patients with type 2 diabetes mellitus, impaired glucose tolerance (IGT) and healthy subjects. Cells were freshly isolated from peripheral blood and the subgroups were determined by flow cytometric method. Lactate production and glycogen utilization were significantly increased in the LMN cells of patients with type 2 DM and IGT when compared with healthy volunteers. No statistical difference was observed between the patients with type 2 DM and IGT. There was a significant correlation between fasting plasma glucose and lactate production in LMN cells. LMN cells changed their energy pathway in a diabetic state and preferred anaerobic glycolysis. Prediabetic range also affected energy metabolism in LMN cells. This abnormal energy production might cause dysfunction in LMN cells and the immune system in diabetic and prediabetic patients. In conclusion, we concluded that impaired glucose metabolism could change energy metabolism.

Naturally occurring flavonoids attenuate high glucose-induced expression of proinflammatory cytokines in human monocytic THP-1 cells

Activation of circulating monocytes by hyperglycemia is bound to play a role in inflammatory and atherosclerosis. In this study, we examined whether flavonoids (catechin, EGCG, luteolin, quercetin, rutin) - phytochemicals that may possible belong to a new class of advanced glycation end products (AGEs) inhibitors - can attenuate high glucose (15 mmol/L, HG)-induced inflammation in human monocytes. Our results show that all flavonoids significantly inhibited HG-induced expression of proinflammatory genes and proteins, including TNF-alpha, interleukin-1beta (IL-1beta), and cyclooxygenase (COX)-2, at a concentration of 20 microM. Flavonoids also prevented oxidative stress in activated monocytes, as demonstrated by their inhibitory effects on intracellular reactive oxygen species (ROS) and N(epsilon)-(carboxymethyl)lysine formation caused by HG. These inhibitory effects may involve inhibition of nuclear factor-kappaB activation and may be supported by downregulation of the following: i) PKC-dependent NADPH oxidase pathway; ii) phosphorylation of p38 mitogen-activated protein kinase and extracellular signal-regulated protein kinase, and iii) mRNA expression of receptor of AGEs. In addition, we found for the first time that lower levels of Bcl-2 protein under HG conditions could be countered by the action of flavonoids. Our data suggest that, along with their antioxidant activities, flavonoids possess anti-inflammatory properties and might therefore have additional protective effects against glycotoxin-related inflammation.

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.

Glucose control in the hospitalized elderly--a concern not just for patients with diabetes

Hyperglycemia is commonly noted yet undertreated among hospitalized patients. Older adults are particularly susceptible to the adverse effects of elevated glucose because of hyperglycemia-induced immune defects coupled with age-associated immune senescence. Although the American Diabetes Association (ADA) recommends maintaining fasting blood glucose (FBG) levels below 126 mg/dL and random glucose levels below 200 mg/dL in patients on general medical wards, there is limited evidence to support these targets since the recommendations are not based on randomized, controlled trials. We discuss the limitations of the current literature and present evidence from medical intensive-care studies that other glucose targets may lead to better outcomes. Furthermore, a study we conducted demonstrates that mild FBG elevations (100 to 126 mg/dL) were associated with increased morbidity among elderly patients on general medical wards. We advocate that all hospitalized patients be screened for hyperglycemia, and treatment should follow current ADA recommendations while studies are being completed to evaluate optimal targets.

[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.