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Background: Diabetic foot ulcer (DFU) is a severe complication that occurs in patients with diabetes and is a primary factor that necessitates amputation. Therefore, the occurrence and progression of DFU must be predicted at an early stage to improve patient prognosis and outcomes. In this regard, emerging evidence suggests that inflammation-related markers play a significant role in DFU. One such potential marker, the monocyte-lymphocyte ratio (MLR), has not been extensively studied in relation to DFU. This study aimed to define a connection between MLR and DFU. Methods: A cross-sectional study was conducted using National Health and Nutrition Examination Survey (NHANES) data from 1999 to 2004. DFU was defined based on survey questionnaires assessing the presence of nonhealing ulcers in the lower extremities for more than 4 weeks in diabetes patients. The MLR was calculated as the ratio of the monocyte count to the lymphocyte count, which was directly obtained from laboratory data files. Logistic regression analysis was performed to assess the relationship between the MLR and DFU. Stratified analysis according to age, sex, body mass index, blood glucose, hemoglobin, and glycated hemoglobin categories was conducted, and multiple imputations were applied to missing data. Results: In total, 1246 participants were included; the prevalence of DFU was 9.4% (117/1246). A multivariable regression model revealed a significant association between DFU and a 0.1 unit increase in MLR after adjusting for all covariates (adjusted odds ratio=1.16, 95% confidence interval: 1.02-1.33). Subgroup analyses revealed consistent findings regarding the impact of MLR on the presence of DFU (p > 0.05). Conclusion: MLR is significantly associated with DFU in diabetes patients, and can be used as one of the indicators for predicting the occurrence of DFU. MLR assessment may be a valuable component in the follow-up of patients with diabetes. [ABSTRACT FROM AUTHOR]

These reports of new-onset diabetes in the post-acute phase would fall within the WHO definition of long-COVID if the diabetes were a direct consequence of COVID-19. Keywords: COVID-19; hyperglycemia; obesity; diabetes; metabolism; public health; mucormycosis EN COVID-19 hyperglycemia obesity diabetes metabolism public health mucormycosis 1 6 6 05/02/22 20220428 NES 220428 Introduction Endocrinologist are well aware of the many adverse health issues consequent to the global pandemic of metabolic disturbances, such as obesity and diabetes, in which hyperglycemia plays a central role. COVID-19, hyperglycemia, obesity, diabetes, metabolism, public health, mucormycosis This common mechanism for cell invasion provides a link explaining the importance of hyperglycemia in both the COVID-19 and mucormycosis pandemics ([51]-[53]) and demonstrates the broader implications of the AI generated insights into how hyperglycemia affects the internal milieu ([5]). [Extracted from the article]

The β-cell response to injury may be as critical for the development of diabetes as the specific insult. In the current study, we used streptozotocin (S TZ) to injure the β-cell in order to study the response with a focus on NFκB. MIN6 cells were exposed to STZ (0.5-8 mM, 0-24h) ±TNFα (100 ng/mL) and ±IκBβ siRNA to lower the threshold to NFκB activation. Cell viability was determined by trypan blue exclusion. NFκB activation was determined by the expression of the target genes Nos2 and Cxcl10, localization of the NFκB proteins p65 and p50, and expression and localization of the NFκB inhibitors, IκBβ and IκBa. There was no NFκB activation in MIN6 cell exposed to STZ (2 mM) alone. However, knocking down IκBβ expression using siRNA resulted in STZ-induced expression of NFκB target genes and increased cell death, while co-incubation with STZ and TNFα enhanced cell death compared to either exposure alone. Adult male IκBβ-/- and WT mice were exposed to STZ and monitored for diabetes. The IκBβ-/- mice developed hyperglycemia and diabetes more frequently than contr ols following STZ exposure. Based on these results we conclude that STZ exposure alone does not induce NFκB activity. However, lowering the threshold to NFκB activation by co-incubation with TNFα or lowering IκBβ levels by siRNA sensitizes the NFκB response to STZ and results in a higher likelihood of developing diabetes in vivo. Therefore, increasing the threshold to NFκB activation through stabilizing NFκB inhibitory proteins may prevent β-cell injury and the development of diabetes. [ABSTRACT FROM AUTHOR]

Background: Diabetes mellitus (DM) has been demonstrated to be linked to atrial fibrillation (AF). However, the underlying mechanisms of the DM-associated increase in AF susceptibility and the potential effects of DM on atrial remodeling remain unclear. Methods and Results: Twenty-five C57BL/6 mice were randomly assigned to the normal/control group (Con, n=10) and model group (n=15). Mice in the model group were administered a high-fat diet combined with multiple injections of low-dose streptozocin (STZ) (35 mg/kg). Eleven mice were ultimately included in DM group. Left atrial tissue structural and inflammatory alterations were assessed. In our study, the atrial weights of DM mice were markedly heavier than those of mice in the Con group. DM mice exhibited significantly increased fasting plasma glucose, fasting insulin, and dyslipidaemia. Furthermore, H&E and Masson's staining revealed broadened interstitial spaces, myocyte disarray and atrial fibrosis in DM mice. The expression levels of the atrial inflammation-associated factor nuclear factor κB (NF-κB) and its pathway were significantly altered in the atria of DM mice. Conclusion: DM could induce atrial structural remodeling and inflammation in mice. [ABSTRACT FROM AUTHOR]

Copyright of Viral Hepatitis Journal / Viral Hepatit Dergisi is the property of Galenos Yayinevi Tic. LTD. STI and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

Background: Diabetes mellitus is a chronic disease caused by inherited and /or acquired deficiency in the production of insulin or ineffectiveness of the insulin. This life-long disease has been a source of concern since it affects mostly individuals in their reproductive age (45-64 years) and high risk of cardiovascular disease, blindness, kidney failure, lower limb amputation, nerve disease and fetal organ damage during pregnancy. Although, several agents are available for managing diabetes, there is absence of adequate information on the strategies for preventing, managing and treating the disease. Discussion: Herein, we gave an account of different strategies that can be adopted to prevent and manage diabetes mellitus. We indicated that strategies for preventing and managing diabetes include life style modifications, antioxidants, phytotherapy, pharmacological approach, reducing inflammatory mediators, targeting key carbohydrate metabolizing enzymes and gene therapy. Conclusion: These strategies can be adopted to reduce the high prevalence of diabetes and associated complications. [ABSTRACT FROM AUTHOR]

The death of cardiomyocytes is a precursor for the cascade of hypertrophic and fibrotic remodeling that leads to cardiomyopathy. In diabetes mellitus (DM), the metabolic environment of hyperglycemia, hyperlipidemia, and oxidative stress causes cardiomyocyte cell death, leading to diabetic cardiomyopathy (DMCM), an independent cause of heart failure. Understanding the roles of the cell death signaling pathways involved in the development of cardiomyopathies is crucial to the discovery of novel targeted therapeutics and biomarkers for DMCM. Recent evidence suggests that hydrogen sulfide (H2S), an endogenous gaseous molecule, has cardioprotective effects against cell death. However, very little is known about signaling by which H2S and its downstream targets regulate myocardial cell death in the DM heart. This review focuses on H2S in the signaling of apoptotic, autophagic, necroptotic, and pyroptotic cell death in DMCM and other cardiomyopathies, abnormalities in H2S synthesis in DM, and potential H2S-based therapeutic strategies to mitigate myocardial cell death to ameliorate DMCM. [ABSTRACT FROM AUTHOR]

Introduction: During pregnancy, the female's body undergoes many adaptations, including changes in the number and survival of White Blood Cells (WBCs). Programmed deaths of the cells are an important regulatory process that happens under a variety of physiological and pathological conditions. Aim: To measure the percentage of apoptosis of lymphocytes in peripheral blood of pregnant females and healthy non pregnant females, and to compare lymphocytes apoptosis between them in term of blood pressure and blood sugar. Also, to relate this apoptosis to blood sugar levels and blood lead levels. Materials and Methods: Fourty two pregnant females in their third trimester had been enrolled in the prospective study and were considered as the patients group. They were recruited from the labour room of the Baghdad Teaching Hospital, Baghdad, Iraq. The control group consisted of 15 healthy non pregnant women with matched age. Blood samples were collected from both groups and subjected to lymphocytes apoptosis estimation; blood sugar level and blood lead level measurements. Blood lead level was measured using blood lead analyser kit. Lymphocytes examination and separation was done. Data analysis was done using SPSS version 20.0. ANOVA test, Independent sample t-test and Pearson correlation test were also used. Results: There was no significant difference in age and blood lead level between patients and control groups. Lymphocyte apoptosis was significantly higher in the patients group than the control group (3.50±2.24 vs. 1.49±0.66). Lead level correlated positively and significantly with lymphocyte apoptosis in both groups. Apoptosis level was not significantly higher in hypertensive patients however, it was significantly higher in diabetic patients. Conclusion: Lymphocytes apoptosis is significantly higher in third trimester of pregnancy and it is higher in diabetic and hypertensive pregnant women than healthy non pregnant women. The increase in blood lead level may cause a significant increase in lymphocytes apoptosis in pregnant and non pregnant women. [ABSTRACT FROM AUTHOR]

Background: An impaired leukocytes function is the factor causing the susceptibility of patients with diabetes mellitus to infections. The outmost importance for the understanding of the immunological processes involved in diabetes pathogenesis is to give the characteritics of the immunological profile and changes therein, during the course of desease. Long-used in folk medicine to treat diabetes Galega officinalis L. has been chosen for the correction of the immune system dysfunction. Methods: The experiments were conducted on male Wistar rats. Fractionation of bone marrow cells suspension was performed in a three-layer ficoll--sodium amidotrizoate density gradient. The lymphocytic-granulocytic cells proliferative activity was studied using enzyme immunoassay with 5-bromo-2'-deoxyuridine (BrdU). For staining of bone marrow preparations May-Gruenwald-Romanowsky-Giemsa (Pappenheim) method was used. To evaluate the content of cationic proteins and myeloperoxidase in neutrophilic leukocytes cytochemical studies were performed. Content of tumor necrosis factor alpha was carried out by immuno-enzymatic analysis. Lymphocytes apoptosis was examined by fluorescent analysis using annexin V. Results: Diabetes mellitus development was accompanied with violation of neutrophils and lymphocytes proliferation, increased activity of myeloperoxidase and enhanced apoptosis process. Administration of Galega officinalis extract under the condition of diabetes promotes the restoration of neutrophils bone marrow pool and the reduction of lymphoblasts number and causes inhibition of the lymphocytes apoptosis process. Conclusions: Investigated medicine has a pronounced immunocorrective effect under the conditions of diabetes mellitus and can become the basis for creating a new generation of antidiabetic drugs. [ABSTRACT FROM AUTHOR]

Sepsis develops when an infection surpasses local tissue containment. A series of dysregulated physiological responses are generated, leading to organ dysfunction and a 10% mortality risk. When patients with sepsis demonstrate elevated serum lactates and require vasopressor therapy to maintain adequate blood pressure in the absence of hypovolemia, they are in septic shock with an in-hospital mortality rate >40%. With improvements in intensive care treatment strategies, overall sepsis mortality has diminished to ~20% at 30 days; however, mortality continues to steadily climb after recovery from the acute event. Traditionally, it was thought that the complex interplay between inflammatory and anti-inflammatory responses led to sepsis-induced organ dysfunction and mortality. However, a closer examination of those who die long after sepsis subsides reveals that many initial survivors succumb to recurrent, nosocomial, and secondary infections. The comorbidly challenged, physiologically frail diabetic individuals suffer the highest infection rates. Recent reports suggest that even after clinical "recovery" from sepsis, persistent alterations in innate and adaptive immune responses exists resulting in chronic inflammation, immune suppression, and bacterial persistence. As sepsis-associated immune defects are associated with increased mortality long-term, a potential exists for immune modulatory therapy to improve patient outcomes. We propose that diabetes causes a functional immune deficiency that directly reduces immune cell function. As a result, patients display diminished bactericidal clearance, increased infectious complications, and protracted sepsis mortality. Considering the substantial expansion of the elderly and obese population, global adoption of a Western diet and lifestyle, and multidrug resistant bacterial emergence and persistence, diabetic mortality from sepsis is predicted to rise dramatically over the next two decades. A better understanding of the underlying diabetic-induced immune cell defects that persist following sepsis are crucial to identify potential therapeutic targets to bolster innate and adaptive immune function, prevent infectious complications, and provide more durable diabetic survival. [ABSTRACT FROM AUTHOR]

Diabetes is a risk factor for heart failure and cardiovascular mortality with specific changes to myocardial metabolism, energetics, structure, and function. The gradual impairment of insulin production and signalling in diabetes is associated with elevated plasma fatty acids and increased myocardial free fatty acid uptake and activation of the transcription factor PPARβ. The increased free fatty acid uptake results in accumulation of toxic metabolites, such as ceramide and diacylglycerol, activation of protein kinase C, and elevation of uncoupling protein-3. Insulin signalling and glucose uptake/oxidation become further impaired, and mitochondrial function and ATP production become compromised. Increased oxidative stress also impairs mitochondrial function and disrupts metabolic pathways. The diabetic heart relies on free fatty acids (FFA) as the major substrate for oxidative phosphorylation and is unable to increase glucose oxidation during ischaemia or hypoxia, thereby increasing myocardial injury, especially in ageing female diabetic animals. Pharmacological activation of PPARγ in adipose tissue may lower plasma FFA and improve recovery from myocardial ischaemic injury in diabetes. Not only is the diabetic heart energeticallyimpaired, it also has early diastolic dysfunction and concentric remodelling. The contractile function of the diabetic myocardium negatively correlates with epicardial adipose tissue, which secretes proinflammatory cytokines, resulting in interstitial fibrosis. Novel pharmacological strategies targeting oxidative stress seem promising in preventing progression of diabetic cardiomyopathy, although clinical evidence is lacking. Metabolic agents that lower plasma FFA or glucose, including PPARγ agonism and SGLT2 inhibition, may therefore be promising options. [ABSTRACT FROM AUTHOR]

Purpose: The optimal target blood glucose concentration for acute glycemic control remains unclear because few studies have directly compared 144-180 with 110-144 or >180 mg/dL. Accordingly, we performed a network meta-analysis to compare four different target blood glucose levels (<110, 110-144, 144-180, and >180 mg/dL) in terms of the benefit and risk of insulin therapy.Methods: We included all of the studies from three systematic reviews and searched the PubMed and Cochrane databases for other studies investigating glucose targets among critically ill patients. The primary outcome was hospital mortality, and the secondary outcomes were sepsis or bloodstream infection and the risk of hypoglycemia. Network meta-analysis to identify an optimal target glucose concentration.Results: The network meta-analysis included 18,098 patients from 35 studies. There were no significant differences in the risk of mortality and infection among the four blood glucose ranges overall or in subgroup analysis. Conversely, target concentrations of <110 and 110-144 mg/dL were associated with a four to ninefold increase in the risk of hypoglycemia compared with 144-180 and >180 mg/dL. However, there were no significant differences between the target concentrations of 144-180 and >180 mg/dL.Conclusions: This network meta-analysis found no significant difference in the risk of mortality and infection among four target blood glucose ranges in critically ill patients, but indicated that target blood glucose levels of <110 and 110-144 mg/dL were associated with a higher risk of hypoglycemia than target levels of 144-180 and >180 mg/dL. Further studies are required to refute or confirm our findings. [ABSTRACT FROM AUTHOR]

Aims: People with type 2 diabetes mellitus (T2DM) have abnormal peripheral and central haemodynamics at rest and during exercise, probably due to metabolic perturbations, but mechanisms are unknown. We used untargeted metabolomics to determine the relationships between metabolic perturbations and haemodynamics (peripheral and central) measured at rest and during exercise. Methods: Serum samples from 39 participants with T2DM (62 ± 9 years; 46 % male) and 39 controls (52 ± 10 years; 51 % male) were analysed by liquid chromatography-mass spectrometry, nuclear magnetic resonance spectroscopy and principal component analysis. Scores on principal components (PC) were used to assess relationships with haemodynamics including peripheral and central BP, central augmentation index (AIx) and central augmentation pressure (AP). Results: Participants with T2DM had higher resting and exercise haemodynamics (peripheral and central BP, central AIx and central AP) compared to controls ( p < 0.05). PC that comprised of a signature metabolic pattern of T2DM was independently associated with resting and exercise central AIx and central AP ( p < 0.05). Conclusions: Serum metabolic profile was associated with central, but not peripheral, haemodynamics in T2DM participants, suggesting that metabolic irregularities may explain abnormal central haemodynamics in T2DM patients. [ABSTRACT FROM AUTHOR]

Although the precise pathogenesis of diabetic cardiac damage remains unclear, potential mechanisms include increased oxidative stress, autonomic nervous dysfunction, and altered cardiac metabolism. Thioredoxin-interacting protein (Txnip) was initially identified as an inhibitor of the antioxidant thioredoxin but is now recognized as a member of the arrestin superfamily of adaptor proteins that classically regulate G protein-coupled receptor signaling. Here we show that Txnip plays a key role in diabetic cardiomyopathy. High glucose levels induced Txnip expression in rat cardiomyocytes in vitro and in the myocardium of streptozotocin-induced diabetic mice in vivo. While hyperglycemia did not induce cardiac dysfunction at baseline, β-adrenergic challenge revealed a blunted myocardial inotropic response in diabetic animals (24-wk-old male and female C57BL/6; 129Sv mice). Interestingly, diabetic mice with cardiomyocyte-specific deletion of Txnip retained a greater cardiac response to β-adrenergic stimulation than wild-type mice. This benefit in Txnip-knockout hearts was not related to the level of thioredoxin activity or oxidative stress. Unlike the β-arrestins, Txnip did not interact with β-adrenergic receptors to desensitize downstream signaling. However, our proteomic and functional analyses demonstrated that Txnip inhibits glucose transport through direct binding to glucose transporter 1 (GLUT1). An ex vivo analysis of perfused hearts further demonstrated that the enhanced functional reserve afforded by deletion of Txnip was associated with myocardial glucose utilization during β-adrenergic stimulation. These data provide novel evidence that hyperglycemia-induced Txnip is responsible for impaired cardiac inotropic reserve by direct regulation of insulin-independent glucose uptake through GLUT1 and plays a role in the development of diabetic cardiomyopathy. [ABSTRACT FROM AUTHOR]

Increased risk of cerebrovascular accident in diabetes cannot be fully explained by traditional risk factors. Epidemiological studies show that postprandial hyperglycemia is strongly associated with cerebrovascular events and cerebrovascular-associated mortality. Postprandial hyperglycemia contributes to vascular damage by several mechanisms such as endothelial dysfunction, arthrosclerosis, oxidative stress, inflammation, and hypercoagulability. Hyperglycemia has deleterious effects on the vascular endothelium and leads to the development of cerebrovascular disease. Thus, an important strategy to reduce cerebrovascular risk in patients with diabetes is to reduce postprandial hyperglycemia. Glucagonlike peptide-1 receptor agonists, dipeptidyl peptidase-4 inhibitors, and α-glucosidase inhibitors predominantly reduce postprandial plasma glucose levels. Among all of these, ?-glucosidase inhibitors reduces postprandial hyperglycemia by delaying carbohydrate absorption from the intestine and this mechanism provides glycemic control without exacerbating coexisting cerebrovascular risk factors. Good glycemic control is proven to reduce the risk of cardiovascular complications, but equivalent evidence for cerebrovascular risk reduction is lacking. This review examines the evidences that postprandial hyperglycemia plays a major role in vascular damage, along with the complex interplay between hyperglycemia and coexisting risk factors. Furthermore, the mechanism by which α-glucosidase inhibitors may prevent this vascular damage as well as risk of hypoglycemia with α-glucosidase inhibitors are examined. Thus, this review suggests that α-glucosidase inhibitors are useful in reducing the risk of cerebrovascular events in patients with diabetes. [ABSTRACT FROM AUTHOR]

Diabetes and its complications are hyperglycemic toxicity diseases. Many metabolic pathways in this array of diseases become aberrant, which is accompanied with a variety of posttranslational protein modifications that in turn reflect diabetic glucotoxicity. In this review, we summarize some of the most widely studied protein modifications in diabetes and its complications. These modifications include glycation, carbonylation, nitration, cysteine S-nitrosylation, acetylation, sumoylation, ADP-ribosylation, O-GlcNAcylation, and succination. All these posttranslational modifications can be significantly attributed to oxidative stress and/or carbon stress induced by diabetic redox imbalance that is driven by activation of pathways, such as the polyol pathway and the ADP-ribosylation pathway. Exploring the nature of these modifications should facilitate our understanding of the pathological mechanisms of diabetes and its associated complications. [ABSTRACT FROM AUTHOR]

ABSTRACT Diabetes has been the subject of recent research by increase susceptibility to infections, thus the aim of this study was to evaluate in animal model of diabetes induced by alloxan (ALX) and subjected to sepsis the parameters of oxidative stress on the brain. Diabetes was induced in Wistar rats by ALX (150 mg/kg), and 15 days after, sepsis was induced by cecal ligation and puncture (CLP). The myeloperoxidase activity (MPO), nitrite/nitrate, oxidative damage parameters, and the activity of superoxide dismutase (SOD) and catalase (CAT) were measured in the cerebellum, hippocampus, striatum, prefrontal, and cortex in 6, 12, and 24 h after CLP. The results showed the potentiation of diabetes with sepsis. We verified these potentiation on MPO levels in the cerebellum, hippocampus, and prefrontal and an increase of the nitrite/nitrate concentration in the hippocampus, striatum, prefrontal, and cortex in 24 h after sepsis surgery. To oxidative damage, we verified in 6 h an increase on lipid and protein damage parameters in the striatum and hippocampus in 24 h. When we associate sepsis and diabetes, the SOD and CAT activity not were altered. Thus, diabetes associated with sepsis exacerbates brain damage resulting from inflammation and oxidative stress in brain. Synapse, 2014. © 2014 Wiley Periodicals, Inc. [ABSTRACT FROM AUTHOR]

Background: Few studies about long-term glucose homeostasis in bariatric patients are available. In a prospective protocol that included retrospective information, outcome of patients with both impaired and normal fasting blood glucose (FBG) was monitored to assess frequencies and correlates. Methods: Patients submitted to Roux-en-Y gastric bypass were classified as group I, elevated FBG, and group II, normal controls. Those in group I with improvement in FBG were defined as responsive and the others as refractory. Group II participants progressing to new-onset diabetes (NOD) or prediabetes represented NOD cases; the remaining were listed as stable controls. FBG was the main endpoint, but HbA1c results were considered, along with diet composition and general biochemical profile. Results: Among 97 selected patients, 51 belonged to group I (52.4 ± 10.5 years, 29.6 % males, initial body mass index (BMI) 58.4 ± 13.4, current BMI 35.1 ± 8.4 kg/m) and 46 to group II (48.2 ± 10.5 years, 19.6 % males, initial BMI 55.5 ± 8.8, current BMI 33.9 ± 6.9 kg/m). Follow-up was 7-9 years, and 31.4 % (16/51) of group I were classified as refractory, whereas 15.2 % (7/46) of the controls converted to NOD. Multivariate analysis pointed out higher current BMI, older age, consumption of antidiabetic drugs, and male gender as features of refractory cases, whereas NOD participants were not significantly different from non-progressing controls. Conclusions: This is the first investigation, to the best of our knowledge, to underscore the correlates of refractory and NOD within the bariatric context. Further studies are recommended as such information could be valuable for patient selection, prognostic scoring, and outcome monitoring. [ABSTRACT FROM AUTHOR]

The activities of the antioxidant enzymes superoxide dismutase (SOD), catalase (CAT) and glutathione S-transferase (GST), the incidence of DNA damage, the activation of poly (ADP-ribose) polymerase-1 (PARP-1), a marker of DNA repair, and connective tissue growth factor (CTGF), a marker of tissue fibrosis, were examined in the hearts of rats for 16 weeks after diabetes induction by streptozotocin (STZ) administration. A 150% increase in CAT activity was detected at the end of the 2nd week post-STZ administration, and CAT activity remained 80% above the control level throughout 16 weeks. While total SOD and CuZn-SOD exhibited progressively decreasing activities, those of Mn-SOD and GST were elevated. Neither DNA strand breaks (apoptosis or necrosis) nor changes in PARP-1 activity and in CTGF levels (fibrosis) were observed in the diabetic heart. The absence of cardiomyopathy is accompanied with increased activities of CAT, MnSOD and GST. [ABSTRACT FROM AUTHOR]

We hypothesized that the administration of the superoxide dismutase (SOD) mimetic Tempol (4-hydroxy-2, 2, 6, 6-tetramethylpiperidine 1-oxyl) may reverse diabetes-induced erectile dysfunction. To test this hypothesis, reactive oxygen species-related genes (SOD1, SOD2, GP × 1, CAT, NOS2, NOS3) were tested, erectile functional studies and immunohistochemical analysis were carried out in diabetic rats treated with or without Tempol. Thirty Sprague–Dawley (3–4months old) rats were divided into three groups (n=10 each), 20 with diabetes (diabetic control and Tempol treatment) and 10 healthy controls. At 12 weeks after the induction of diabetes by streptozotocin and Tempol treatment, all groups underwent in vivo cavernous nerve stimulation. Rat crura were harvested and the expression of antioxidative defense enzymes were examined by semi-quantitative reverse transcriptase PCR (RT–PCR). To confirm the RT–PCR results, we carried out immunohistochemistry (IHC) for catalase (CAT) and iNOS (NOS2). Nitration of tyrosine groups in proteins was also examined by IHC. Mean intracavernous pressure in the diabetic group was significantly lower than in the healthy controls (P <0.001) and was reversed by Tempol treatment (P <0.0108). NOS2 protein expression was significantly increased in diabetic animals compared with healthy controls and Tempol restored NOS2 protein level. Nitrotyrosine was also higher in diabetic animals and although Tempol treatment decreased its formation, it remained higher than that found in healthy controls. This study suggests that Tempol treatment increased erectile function through modulating oxidative stress-related genes in diabetic rats. This is the first report about the relationship between diabetes-induced erectile dysfunction and oxidative stress, and antioxidative therapy using the superoxide dismutase mimetic, Tempol, to restore erectile function. [ABSTRACT FROM AUTHOR]

In this study, we investigated the effect of the xanthine oxidase (XO) inhibitor, allopurinol (ALP), on cardiac dysfunction, oxidative-nitrosative stress, apoptosis, poly(ADP-ribose) polymerase (PARP) activity and fibrosis associated with diabetic cardiomyopathy in mice. Diabetes was induced in C57/BL6 mice by injection of streptozotocin. Control and diabetic animals were treated with ALP or placebo. Left ventricular systolic and diastolic functions were measured by pressure–volume system 10 weeks after established diabetes. Myocardial XO, p22phox, p40phox, p47phox, gp91phox, iNOS, eNOS mRNA and/or protein levels, ROS and nitrotyrosine (NT) formation, caspase3/7 and PARP activity, chromatin fragmentation and various markers of fibrosis (collagen-1, TGF-β, CTGF, fibronectin) were measured using molecular biology and biochemistry methods or immunohistochemistry. Diabetes was characterized by increased myocardial, liver and serum XO activity (but not expression), increased myocardial ROS generation, p22phox, p40phox, p47phox, p91phox mRNA expression, iNOS (but not eNOS) expression, NT generation, caspase 3/7 and PARP activity/expression, chromatin fragmentation and fibrosis (enhanced accumulation of collagen, TGF-β, CTGF and fibronectin), and declined systolic and diastolic myocardial performance. ALP attenuated the diabetes-induced increased myocardial, liver and serum XO activity, myocardial ROS, NT generation, iNOS expression, apoptosis, PARP activity and fibrosis, which were accompanied by improved systolic (measured by the evaluation of both load-dependent and independent indices of myocardial contractility) and diastolic performance of the hearts of treated diabetic animals. Thus, XO inhibition with ALP improves type 1 diabetes-induced cardiac dysfunction by decreasing oxidative/nitrosative stress and fibrosis, which may have important clinical implications for the treatment and prevention of diabetic cardiomyopathy and vascular dysfunction. [ABSTRACT FROM AUTHOR]

Postpandrial hyperglycaemia is a significant risk factor for the development of macrovascular diseases. There is no clear agreement in the field whether these alterations result from hyperglycaemic episodes or from exaggerated alterations (‘glycaemic swings’) in blood glucose. We compared the effect of stable high glucose with a model of poorly maintained insulin-controlled diabetes (on average lower glucose, but with large glycaemic swings) on the development of endothelial dysfunction in rats. Intermediate- or long-acting insulin was used to reduce mean blood glucose levels. One group of animals had stable low glucose levels, while animals in the other group exhibited rapid changes (‘swings’) in their blood glucose concentration. Acetylcholine-induced endothelium-dependent vascular relaxation of the thoracic aorta was measured. Immunohistochemistry, western blot analysis and flow cytometry were used to determine nitrotyrosine formation and poly(ADP-ribose) accumulation in the aorta, in circulating leucocytes and in bone marrow cells. Steady normalisation of blood glucose levels (a model of well-controlled diabetes) protected against the development of endothelial dysfunction, poly(ADP-ribose) polymerase (PARP) activation and nitrotyrosine production. However, impairment of endothelium-dependent relaxation was found in the animals undergoing glycaemic swings, even though the fructosamine levels in these animals were lower than in the untreated diabetic rats. This was associated with elevated PARP activation in the aorta and in bone marrow cells that was similar to or even more pronounced than that seen in the untreated diabetic animals. Large glycaemic swings exert deleterious cardiovascular effects in diabetes mellitus, in part via enhanced activation of the PARP pathway. [ABSTRACT FROM AUTHOR]

The present study investigated whether combination of resveratrol and 4-amino 1,8 naphthalimide (4-ANI) is effective in the development of diabetic neuropathy (DN). After 6 weeks of diabetes induction, rats were treated for 2 weeks with resveratrol and 4-amino 1,8 naphthalimide (4-ANI) either alone or in combination. Experimental end points included functional, behavioural and biochemical parameters along with PAR immunohistochemistry and were performed at the end of treatment. Combination of resveratrol (10 mg/kg) and 4-ANI (3 mg/kg) attenuated conduction and nerve blood flow deficits and resulted in amelioration of diabetic neuropathic pain. Significant reversal of biochemical alterations (peroxynitrite, MDA and NAD levels) were also observed, as well as PAR accumulation in the sciatic nerve. This study suggests the beneficial effect of combining resveratrol and 4-ANI in experimental diabetic neuropathy. [ABSTRACT FROM AUTHOR]

BACKGROUND: Peroxynitrite plays an important role in the pathogenesis of diabetic complications. Nitrosylated protein expression in peripheral blood monocytes reflects intracellular peroxynitrite injury, and thus could be a marker of higher diagnostic and prognostic value than plasma nitrotyrosine level. The purpose of this pilot study was to assess if peripheral blood monocytes of diabetic subjects accumulate nitrosylated proteins, and if nitrosylated protein expression correlates with blood glucose control, variables of lipid profile, C-reactive protein concentration (a marker of inflammation), and differs in patients with and without diabetic macrovascular and microvascular complications. METHODS: Nitrosylated protein expression in peripheral blood monocytes (Western blot analysis) was assessed in 31 subjects with diabetes mellitus (29 Type 2, 2 Type 1; 20 males, 11 females; mean age 66 years). The presence of microangiopathy was defined by retinopathy, albumin excretion, and/or neuropathy, and macroangiopathy by carotid plaques, a history of myocardial infarction, and/or stroke. RESULTS: Diabetic subjects accumulated significant amounts of nitrosylated proteins in peripheral blood monocytes. Nitrosylated protein expression positively correlated with body weight, blood glucose, HbA 1C, and plasma C-reactive protein concentrations in the whole cohort as well as in subjects with diabetic macroangiopathy. CONCLUSIONS: Monocyte nitrosylated protein expression is a new biomarker of metabolic control and inflammation in diabetic subjects with macroangiopathy. A more detailed assessment of diabetic microvascular complications in a larger group of patients is needed to determine if this variable can be employed as a biomarker of the presence, severity, and progression of diabetic neuropathy, retinopathy, and nephropathy. [ABSTRACT FROM AUTHOR]

Abstract. Objective:  To investigate the allergic reaction in neonatal streptozotocin (nSTZ)-induced diabetes mellitus. Material:  Male newborn Wistar rats were made diabetic by the injection of streptozotocin (160 mg/kg, i. p.) and used 8 weeks thereafter. Treatment:   Animals were sensitized against ovalbumin (OA, 50 μg and Al(OH)3, 5 mg, s. c.) and challenged 14 or 21 days thereafter. Methods:  OA-induced airway inflammation and OA-induced pleurisy models were used to investigate leukocyte migration (total and differential leukocyte counts) and lung vascular permeability (Evans blue dye extravasation). Results:  nSTZ-diabetic rats presented glucose intolerance and insulin resistance. Relative to controls, nSTZ rats exhibited a 30% to 50% reduction in lung vascular permeability. Leukocyte infiltration in both models of allergen-induced inflammation, and number of pleural mast cells did not differ between groups. Conclusions:  Data suggest that the reduction of allergic inflammatory reactions in nSTZ rats is restricted to microvascular dysfunctions and associated, probably, with insulin resistance in lung microvascular endothelium. [ABSTRACT FROM AUTHOR]

Interventions targeting the treatment of diabetic complications have not been nearly as successful as initially estimated, despite a marked improvement in therapeutic options for diabetes. The need for understanding why some very promising interventions have failed demands a closer look at the pathomechanisms of the complications. Great strides have been made in understanding the pathology, and several important hypotheses have emerged in recent years. On this basis, Brownlee and coworkers suggested a unifying hypothesis integrating various mechanisms discussed in past years with an overproduction of reactive oxygen species as an initiating cause. This hypothesis and further hypotheses, as well as mechanisms, are highlighted in this article. The field of pathomechanisms of diabetic complications is very wide, and any attempt to completely cover it within a single article is unrealistic. Therefore, our purpose is to present the most relevant concepts underlying diabetic complications in an attempt to contribute to a better understanding and pinpoint areas that warrant further research. [ABSTRACT FROM AUTHOR]

1. Arginase is the focal enzyme of the urea cycle hydrolysingl-arginine to urea andl-ornithine. Emerging studies have identified arginase in the vasculature and have implicated this enzyme in the regulation of nitric oxide (NO) synthesis and the development of vascular disease. 2. Arginase inhibits the production of NO via several potential mechanisms, including competition with NO synthase (NOS) for the substratel-arginine, uncoupling of NOS resulting in the generation of the NO scavenger, superoxide and peroxynitrite, repression of the translation and stability of inducible NOS protein, inhibition of inducible NOS activity via the generation of urea and by sensitization of NOS to its endogenous inhibitor asymmetric dimethyl-l-arginine. 3. Upregulation of arginase inhibits endothelial NOS-mediated NO synthesis and may contribute to endothelial dysfunction in hypertension, ageing, ischaemia–reperfusion and diabetes. 4. Arginase also redirects the metabolism ofl-arginine tol-ornithine and the formation of polyamines andl-proline, which are essential for smooth muscle cell growth and collagen synthesis. Therefore, the induction of arginase may also promote aberrant vessel wall remodelling and neointima formation. 5. Arginase represents a promising novel therapeutic target that may reverse endothelial and smooth muscle cell dysfunction and prevent vascular disease. [ABSTRACT FROM AUTHOR]

Accumulating evidence suggests that the reactive oxygen and nitrogen species are generated in cardiomyocytes and endothelial cells during myocardial ischemia/reperfusion injury, various forms of heart failure or cardiomyopathies, circulatory shock, cardiovascular aging, diabetic complications, myocardial hypertrophy, atherosclerosis, and vascular remodeling following injury. These reactive species induce oxidative DNA damage and consequent activation of the nuclear enzyme poly(ADP-ribose) polymerase 1 (PARP-1), the most abundant isoform of the PARP enzyme family. PARP overactivation, on the one hand, depletes its substrate, NAD+, slowing the rate of glycolysis, electron transport, and ATP formation, eventually leading to the functional impairment or death of the endothelial cells and cardiomyocytes. On the other hand, PARP activation modulates important inflammatory pathways, and PARP-1 activity can also be modulated by several endogenous factors such as various kinases, purines, vitamin D, thyroid hormones, polyamines, and estrogens, just to mention a few. Recent studies have demonstrated that pharmacological inhibition of PARP provides significant benefits in animal models of cardiovascular disorders, and novel PARP inhibitors have entered clinical development for various cardiovascular indications. Because PARP inhibitors can enhance the effect of anticancer drugs and decrease angiogenesis, their therapeutic potential is also being explored for cancer treatment. This review discusses the therapeutic effects of PARP inhibitors in myocardial ischemia/reperfusion injury, various forms of heart failure, cardiomyopathies, circulatory shock, cardiovascular aging, diabetic cardiovascular complications, myocardial hypertrophy, atherosclerosis, vascular remodeling following injury, angiogenesis, and also summarizes our knowledge obtained from the use of PARP-1 knockout mice in the various preclinical models of cardiovascular diseases. [ABSTRACT FROM AUTHOR]

Atorvastatin exerts beneficial vascular effects in diabetes, but the underlying mechanisms are yet to be elucidated. The aim of the present study was to determine whether Rac-1 is involved in the effect of atorvastatin on oxidative stress and vascular dysfunction. Using human aortic endothelial cells (HAECs) we evaluated the effect of high glucose levels on peroxide production by dihydrodichlorofluorescein and on Rac-1 activity using immunocytochemistry to detect Rac-1 translocation to the membrane. We evaluated vascular function, peroxide production by dihydroethidium and NADPH oxidase activity in vessels from atorvastatin-treated mice. Rac-1 activity was also assessed, both by immunoprecipitation of the Rac–p21-activated kinase complex and by analysis of Rac-1 translocation to the membrane. These experiments were also conducted in vessels infected with an adenoviral vector carrying a constitutively active mutant of Rac-1. In HAECs exposed to high glucose levels, atorvastatin prevented oxidative stress, and this protection was associated with impaired Rac-1 activation. This effect was also observed in a murine model of diabetes mellitus. More importantly, the addition of geranylgeranyl pyrophosphate (GGPP) blocked the effects of atorvastatin in both glucose-exposed HAECs and diabetic vessels. Atorvastatin failed to afford protection against vascular abnormalities in the presence of a constitutively active mutant of Rac-1. The results of this study demonstrate that the vascular antioxidant effect of atorvastatin in diabetes is mediated through inhibition of Rac-1 via a reduction in GGPP. Thus, selective Rac-1 inhibition should be considered in the design of novel pharmacological strategies to reduce the impact of diabetes mellitus on vascular function. [ABSTRACT FROM AUTHOR]

Background: Diabetes is associated with a cardiomyopathy that is independent of coronary artery disease or hypertension. In the present study we used in vivo magnetic resonance imaging (MRI) and echocardiographic techniques to examine and characterize early changes in myocardial function in a mouse model of type 1 diabetes. Methods: Diabetes was induced in 8-week old C57BL/6 mice with two intraperitoneal injections of streptozotocin. The blood glucose levels were maintained at 19-25 mmol/l using intermittent low dosages of long acting insulin glargine. MRI and echocardiography were performed at 4 weeks of diabetes (age of 12 weeks) in diabetic mice and age-matched controls. Results: After 4 weeks of hyperglycemia one marker of mitochondrial function, NADH oxidase activity, was decreased to 50% of control animals. MRI studies of diabetic mice at 4 weeks demonstrated significant deficits in myocardial morphology and functionality including: a decreased left ventricular (LV) wall thickness, an increased LV end-systolic diameter and volume, a diminished LV ejection fraction and cardiac output, a decreased LV circumferential shortening, and decreased LV peak ejection and filling rates. M-mode echocardiographic and Doppler flow studies of diabetic mice at 4 weeks showed a decreased wall thickening and increased E/A ratio, supporting both systolic and diastolic dysfunction. Conclusion: Our study demonstrates that MRI interrogation can identify the onset of diabetic cardiomyopathy in mice with its impaired functional capacity and altered morphology. The MRI technique will lend itself to repetitive study of early changes in cardiac function in small animal models of diabetic cardiomyopathy. [ABSTRACT FROM AUTHOR]

In patients with diabetes, an increased risk of symptomatic heart failure usually develops in the presence of hypertension or ischemic heart disease. However, a predisposition to heart failure might also reflect the effects of underlying abnormalities in diastolic function that can occur in asymptomatic patients with diabetes alone (termed diabetic cardiomyopathy). Evidence of cardiomyopathy has also been demonstrated in animal models of both Type 1 (streptozotocin-induced diabetes) and Type 2 diabetes (Zucker diabetic fatty rats and ob/ob or db/db mice). During insulin resistance or diabetes, the heart rapidly modifies its energy metabolism, resulting in augmented fatty acid and decreased glucose consumption. Accumulating evidence suggests that this alteration of cardiac metabolism plays an important role in the development of cardiomyopathy. Hence, a better understanding of this dysregulation in cardiac substrate utilization during insulin resistance and diabetes could provide information as to potential targets for the treatment of cardiomyopathy. This review is focused on evaluating the acute and chronic regulation and dysregulation of cardiac metabolism in normal and insulin- resistant/diabetic hearts and how these changes could contribute toward the development of cardiomyopathy. [ABSTRACT FROM AUTHOR]

Diabetes mellitus leads to the development of endothelial dysfunction which finally contributes to diabetic angiopathy. We investigated the effects of hyperglycaemia on nitric oxide (NO) liberation and a possible influence of L-arginine supplementation. Porcine endothelial aortic cells (PAEC) were cultured in Medium 199 containing 0.33 mmol/l L-arginine. During the entire third culture passage (= 4 days) cells were either exposed to 5 or 20 mmol/l D-glucose with or without additional 3 mmol/l L-arginine. For osmotic control, cells were exposed to 15 mmol/l mannitol. NO liberation was measured under basal conditions and after stimulation with 1 mmol/l ATP using the spectrophotometrical methemoglobin assay. Cells released 35 ± 8 pmol NO/1 × 106 cells/10 min under basal conditions while hyperglycaemia led to a significant reduction in NO release to 16 ± 6 pmol/1 × 106 cells/10 min. In osmotic control, NO release was unchanged (37 ± 10 pmol/1 × 106 cells/10 min). Stimulation with 1 mmol/l ATP led to a significant increase in NO release to 103 ± 11 pmol/1 × 106 cells/10 min (normoglycaemia) which was unchanged in osmotic controls. Under normoglycaemic conditions, additional L-arginine supplementation did not influence NO release from PAEC. In hyperglycaemia (0.33 mmol/l L-arginine) ATP stimulated NO release was reduced (48 ± 8 pmol/1 × 106 cells/10 min, p < 0.05), which was completely prevented by 3 mmol/l L-arginine treatment (98 ± 15 pmol/ 1 × 106 cells/10 min). Hyperglycaemia (but not enhanced osmotic pressure) leads to endothelial dysfunction with reduced NO release which is completely prevented by L-arginine. L-Arginine utilisation may be impaired in hyperglycaemia and L-arginine supplementation might be an interesting additional therapeutic tool in diabetic patients. Copyright © 2006 S. Karger AG, Basel [ABSTRACT FROM AUTHOR]

Poly(ADP-ribose)polymerase (PARP-1), a nuclear enzyme activated by DNA strand breaks, is involved in DNA repair, aging, inflammation, and neoplastic transformation. In diabetes, reactive oxygen and nitrogen species occurring in response to hyperglycemia cause DNA damages and PARP-1 activation. Because circulating mononuclear cells (MNCs) are involved in inflammation mechanisms, these cells were chosen as the experimental model to evaluate PARP-1 levels and activity in patients with type 2 diabetes. MNCs were isolated from 25 diabetic patients (18 M, 7 F, age, 63.5 ± 10.2 years, disease duration 17.7 ± 8.2 years) and 11 age and sex matched healthy controls. PARP-1 expression and activity were analyzed by semi-quantitative PCR, Western and activity blot, and immunofluorescence microscopy. PARP-1-mRNA expression was increased in MNCs from all diabetic patients versus controls (P < 0.01), whereas PARP-1 content and activity were significantly lower in diabetic patients (P < 0.0001). To verify whether low PARP-1 levels and activity were due to a proteolytic effect of caspase-3 like, the latter activation was measured by a fluorimetric assay. Caspase-3 activity in MNCs was significantly higher in diabetic patients versus control subjects (P < 0.0001). The different PARP-1 behavior in MNCs from patients with type 2 diabetes could therefore be responsible for the abnormal inflammation and infection responses in diabetes. © 2005 Wiley-Liss, Inc. [ABSTRACT FROM AUTHOR]

Aims/hypothesis: Impaired nitric oxide (NO) bioactivity and increased superoxide (SO) production are characteristics of vascular endothelial dysfunction in diabetes. The underlying mechanisms remain unknown. In this regard, we investigated the role of tetrahydrobiopterin (BH4) bioavailability in regulating endothelial nitric oxide synthase (eNOS) activity, dimerisation and SO production in streptozotocin-induced diabetic mice. Methods: Mouse aortas were used for assays of the following: (1) aortic function by isometric tension; (2) NO by electronic paramagnetic resonance; (3) SO by lucigenin-enhanced chemiluminescence and dihydroethidine fluorescence; (4) total biopterin and BH4 by high-performance liquid chromatography; and (5) eNOS protein expression and dimerisation by immunoblotting. Results: In diabetic mouse aortas, relaxations to acetylcholine and NO levels were significantly decreased, but SO production was increased, in association with reductions in total biopterins and BH4. Although total eNOS levels were increased in diabetes, the protein mainly existed in monomeric form. Conversely, specifically augmented BH4 in diabetic endothelium preserved eNOS dimerisation, but the expression remained unchanged. Conclusions/interpretation: Our results demonstrate that BH4 plays an important role in regulating eNOS activity and its functional protein structure, suggesting that increasing endothelial BH4 and/or protecting it from oxidation may be a rational therapeutic strategy to restore eNOS function in diabetes. [ABSTRACT FROM AUTHOR]

Aims/hypothesis: Hyperglycaemia in diabetes is associated with increased glycation, oxidative stress and nitrosative stress. Proteins modified consequently contain glycation, oxidation and nitration adduct residues, and undergo cellular proteolysis with release of corresponding free adducts. These free adducts leak into blood plasma for eventual renal excretion. The aim of this study was to perform a comprehensive quantitative analysis of protein glycation, oxidation and nitration adduct residues in plasma protein and haemoglobin as well as of free adducts in plasma and urine to quantify increased protein damage and flux of proteolytic degradation products in diabetes. Methods: Type 1 diabetic patients (n=21) and normal healthy control subjects (n=12) were studied. Venous blood samples, with heparin anticoagulant, and 24-h urine samples were taken. Samples were analysed for protein glycation, oxidation and nitration adducts by a quantitative comprehensive screening method using liquid chromatography with triple quadrupole mass spectrometric detection. Results: In type 1 diabetic patients, the concentrations of protein glycation, oxidation and nitration adduct residues increased up to three-fold in plasma protein and up to one-fold in haemoglobin, except for decreases in pentosidine and 3-nitrotyrosine residues in haemoglobin when compared with normal control subjects. In contrast, the concentrations of protein glycation and oxidation free adducts increased up to ten-fold in blood plasma, and urinary excretion increased up to 15-fold in diabetic patients. Conclusions/interpretation: We conclude that there are profound increases in proteolytic products of glycated and oxidised proteins in diabetic patients, concurrent with much lower increases in protein glycation and oxidation adduct residues. [ABSTRACT FROM AUTHOR]

Somatic DNA damage has been linked to coronary artery disease (CAD). However, whether genetic instability is linked to CAD per se or to concomitant potentially genotoxic metabolic and pharmacological factors remains still unclear. The aim of this study was to evaluate the determinants of somatic DNA damage in a large population of patients undergoing coronary angiography. A total of 278 in-hospital patients (215 men, age 61.8±0.7 years) were studied by using micronucleus assay (MN) in human lymphocytes, which is one of the most commonly used biomarker for somatic DNA damage. Significant CAD (>50% diameter stenosis) was present in 210 patients (179 men, age 62.3±0.7 years). Normal coronary arteries were observed in 68 patients (35 men, age 60.2±1.7 years). There were no significant differences between patients with and without CAD, but patients with multivessel disease had the highest MN levels (P=0.01). MN frequency was also found significantly higher in presence of type 2 diabetes (P<0.0001), dyslipidemia (P=0.048) and nitrate therapy (P=0.0002). A significant additive effect was also observed between diabetes and nitrate therapy (P=0.02). On multivariate logistic regression analysis, diabetes [odds ratio =6.8 (95% confidence interval, 3.2-14.5),P<0.0001] and nitrate therapy [odds ratio =2.4 (95% confidence interval, 1.3-4.7),P=0.01] remained the only significant determinants for the 50th percentile of MN (>12‰). These results indicated that diabetes and, to a lesser extent, chronic nitrate therapy are major determinants of somatic DNA instability in patients with CAD. DNA damage might represent an additional pathogenetic dimension and a possible therapeutic target in the still challenging management of coronary artery disease concerning diabetics. [ABSTRACT FROM AUTHOR]

Cardiovascular complications, characterized by endothelial dysfunction and accelerated atherosclerosis, are the leading cause of morbidity and mortality associated with diabetes. There is growing evidence that excess generation of highly reactive free radicals, largely due to hyperglycemia, causes oxidative stress, which further exacerbates the development and progression of diabetes and its complications. Overproduction and/or insufficient removal of these free radicals result in vascular dysfunction, damage to cellular proteins, membrane lipids and nucleic acids. Despite overwhelming evidence on the damaging consequences of oxidative stress and its role in experimental diabetes, large scale clinical trials with classic antioxidants failed to demonstrate any benefit for diabetic patients. As our understanding of the mechanisms of free radical generation evolves, it is becoming clear that rather than merely scavenging reactive radicals, a more comprehensive approach aimed at preventing the generation of these reactive species as well as scavenging may prove more beneficial. Therefore, new strategies with classic as well as new antioxidants should be implemented in the treatment of diabetes. [ABSTRACT FROM AUTHOR]

This study evaluated the effects of aldose reductase inhibition on diabetes-induced oxidative-nitrosative stress and poly(ADP-ribose) polymerase (PARP) activation. In animal experiments, control and streptozotocin-induced diabetic rats were treated with or without the aldose reductase inhibitor (ARI) fidarestat (16 mg . kg(-1) . day(-1)) for 6 weeks starting from induction of diabetes. Sorbitol pathway intermediate, but not glucose, accumulation in sciatic nerve and retina was completely prevented in diabetic rats treated with fidarestat. Sciatic motor nerve conduction velocity, hindlimb digital sensory nerve conduction velocity, and sciatic nerve concentrations of two major nonenzymatic antioxidants, glutathione and ascorbate, were reduced in diabetic versus control rats, and these changes were prevented in diabetic rats treated with fidarestat. Fidarestat prevented the diabetes-induced increase in nitrotyrosine (a marker of peroxynitrite-induced injury) and poly(ADP-ribose) immunoreactivities in sciatic nerve and retina. Fidarestat counteracted increased superoxide formation in aorta and epineurial vessels and in in vitro studies using hyperglycemia-exposed endothelial cells, and the DCF test/flow cytometry confirmed the endothelial origin of this phenomenon. Fidarestat did not cause direct inhibition of PARP activity in a cell-free system containing PARP and NAD(+) but did counteract high-glucose-induced PARP activation in Schwann cells. In conclusion, aldose reductase inhibition counteracts diabetes-induced nitrosative stress and PARP activation in sciatic nerve and retina. These findings reveal the new beneficial properties of fidarestat, thus further justifying the ongoing clinical trials of this specific, potent, and low-toxic ARI. [ABSTRACT FROM AUTHOR]

Functional damage to microvascular endothelial cells by hyperglycemia is thought to be one of the critical risk factors in the impaired wound healing seen with diabetes mellitus. It is also thought that free radical stress plays a significant role in this endothelial cell dysfunction. In the present study, the effect of a free radical scavenger, MCI 186, on the endothelial cell dysfunction of cultured cells induced by high-glucose conditions was studied. Human dermal microvascular endothelial cells were cultured with high-glucose medium (50 mM) with or without MCI-18 6 (10μM) for 7 days. Fifty mM mannitol was used as an osmotic control in this study. After this treatment, cell proliferation, activation of mitogen-activated protein kinase (MAPK), the level of apoptosis, and caspase-3 activation induced by removal of growth factors or tumor necrosis factor-α treatment were studied. High-glucose conditions significantly decreased cell proliferation and increased apoptosis levels with the activation of caspase-3 induced by growth factor removal. The high-glucose condition significantly activated MAPK. MCI-186 treatment improved cellular proliferation and reduced apoptosis and caspase-3 activation induced by high-glucose conditions. MCI-186 also inhibited the activation of MAPK. On the other hand, MCI-186 did not alter the level of apoptosis and caspase-3 activation induced by TNF-α treatment. In conclusion, we suggest that MCI-186 may be beneficial for improving the endothelial cell dysfunction induced by hyperglycemia. [ABSTRACT FROM AUTHOR]

The current study investigated the role of poly(ADP-ribose) polymerase (PARP) in the development of diabetic retinopathy. Activity of PARP was increased in whole retina and in endothelial cells and pericytes of diabetic rats. Administration of PJ-34 (a potent PARP inhibitor) for 9 months to diabetic rats significantly inhibited the diabetes-induced death of retinal microvascular cells and the development of early lesions of diabetic retinopathy, including acellular capillaries and pericyte ghosts. To further investigate how PARP activation leads to cell death in diabetes, we investigated the possibility that PARP acts as a coactivator of nuclear factor-kappaB (NF-kappaB) in the retinal cells. In bovine retinal endothelial cells (BRECs), PARP interacted directly with both subunits of NF-kappaB (p50 and p65). More PARP was complexed to the p50 subunit in elevated glucose concentration (25 mmol/l) than at 5 mmol/l glucose. PJ-34 blocked the hyperglycemia-induced increase in NF-kappaB activation in BRECs. PJ-34 also inhibited diabetes-induced increase expression of intercellular adhesion molecule-1, a product of NF-kappaB-dependent transcription in retina, and subsequent leukostasis. Inhibition of PARP or NF-kappaB inhibited the hyperglycemia (25 mmol/l glucose)-induced cell death in retinal endothelial cells. Thus, PARP activation plays an important role in the diabetes-induced death of retinal capillary cells, at least in part via its regulation of NF-kappaB. [ABSTRACT FROM AUTHOR]

The homeostatic control of beta-cell mass in normal and pathological conditions is based on the balance of proliferation, differentiation, and death of the insulin-secreting cells. A considerable body of evidence, accumulated during the last decade, has emphasized the significance of the disregulation of the mechnanisms regulating the apoptosis of beta-cells in the sequence of events that lead to the development of diabetes. The identification of agents capable of interfering with this process needs to be based on a better understanding of the beta-cell specific pathways that are activated during apoptosis. The aim of this article is fivefold: (1) a review of the evidence for beta-cell apoptosis in Type I diabetes, Type II diabetes, and islet transplantation, (2) to review the common stimuli and their mechanisms in pancreatic beta-cell apoptosis, (3) to review the role of caspases and their activation pathway in beta-cell apoptosis, (4) to review the caspase cascade and morphological cellular changes in apoptotic beta-cells, and (5) to highlight the putative strategies for preventing pancreatic beta-cells from apoptosis. © 2004 Wiley-Liss, Inc. [ABSTRACT FROM AUTHOR]

Purpose. Oxidative and nitrosative stress and activation of poly(ADP ribose) polymerase (PARP) play a role in the pathogenesis of diabetic complications. We evaluated the effectiveness of the peroxynitrite decomposition catalyst, PP 15, and the PARP inhibitor, PJ34, in the treatment of leukocyte entrapment in the retinal microcirculation of diabetic rats. Methods. Diabetes was induced in rats by intraperitoneal injection of 60mg/kg of streptozotocin. Rats were divided into four groups: controls; untreated diabetes; diabetes treated with PP 15 (10 mg/kg oral gavage twice daily) and diabetes treated with PJ34 (10mg/kg oral gavage twice daily). All experiments were performed 4 weeks after initiation of treatment. Leukocyte entrapment in the retinal microcirculation was quantitatively evaluated in vivo with acridine orange digital fluorography. Results, The density of leukocytes trapped in the retinal microcirculation 30 minutes after dye injection was significantly greater in untreated diabetes (32.1 ± 4.7 cells/mm²) than in controls (11.3 ± 4.5 cells/mm²) (p <0.05). Compared with untreated diabetes, the density of trapped leukocytes significantly decreased in diabetes treated with FP15 (14.5 ± 5.1 cells/mm²) (p <0.0001) and diabetes treated with PJ34 (24.1 ± 4.2 cells/mm²) (p <0.05). Conclusions. Treatment with FP15 and PJ34 decreased enhanced leukocyte entrapment in the retinal microcirculation during the early diabetic period. The current study suggests a role for peroxynitrite production and for PARP activation in the pathogenesis of retinal microvascular leukostasis in early diabetes. [ABSTRACT FROM AUTHOR]

Pressure-induced vasodilation (PIV) is a mechanism whereby skin blood flow increases in response to progressive locally applied pressure. Skin blood flow in response to applied pressure decreased early in diabetic patients as a result of vascular and/or neural impairment. This study was designed to determine the effect of vascular changes on PIV in 1-week streptozotocin-induced diabetic mice. We assessed cutaneous microvascular response to local increasing pressure application measured by laser Doppler flowmetry (LDF) and endothelium-dependent and -independent vasodilation by iontophoretic delivery of acetylcholine and sodium nitroprusside and sciatic motor nerve conduction velocity and morphometry. In control mice, LDF increased 34% from baseline to 0.2 kPa external pressure, showing PIV response. In contrast, diabetic mice had no LDF increase in response to progressive external pressure. Moreover, after iontophoretic delivery of acetylcholine, endothelium-dependent vasodilation was largely attenuated in diabetic mice (25%) compared with control mice (81%), whereas vasodilation to sodium nitroprusside was not different between groups. Nerve function as assessed by sciatic nerve conduction velocity and morphometry did not differ between groups. These findings suggest that endothelial impairment is sufficient to severely alter PIV response, which seems to be highly sensitive to endothelial nitric oxide levels. PIV suppression could favor diabetes complications such as diabetic foot ulcers. [ABSTRACT FROM AUTHOR]

It has been proposed that low activities of antioxidant enzymes in pancreatic beta cells may increase their susceptibility to autoimmune attack. We have therefore used the spontaneously diabetic BB/S rat model of type 1 diabetes to compare islet catalase and superoxide dismutase activities in diabetes-prone and diabetes-resistant animals. In parallel studies, we employed the RINm5F beta cell line as a model system (previously validated) to investigate whether regulation of antioxidant enzyme activity by inflammatory mediators (cytokines, nitric oxide) occurs at the gene or protein expression level. Diabetes-prone rat islets had high insulin content at the age used (58–65 days) but showed increased amounts of DNA damage when subjected to cytokine or hydrogen peroxide treatments. There was clear evidence of oxidative damage in freshly isolated rat islets from diabetes-prone animals and significantly lower catalase and superoxide dismutase activities than in islets from age-matched diabetes-resistant BB/S and control Wistar rats. The mRNA expression of antioxidant enzymes in islets from diabetes-prone and diabetes-resistant BB/S rats and in RINm5F cells, treated with a combination of cytokines or a nitric oxide donor, DETA-NO, was analysed semi-quantitatively by real time PCR. The mRNA expression of catalase was lower, whereas MnSOD expression was higher, in diabetes-prone compared to diabetes-resistant BB/S rat islets, suggesting regulation at the level of gene expression as well as of the activities of these enzymes in diabetes. The protein expression of catalase, CuZnSOD and MnSOD was assessed by Western blotting and found to be unchanged in DETA-NO treated cells. Protein expression of MnSOD was increased by cytokines in RINm5F cells whereas the expression of CuZnSOD was slightly decreased and the level of catalase protein was unchanged. We conclude that there are some changes, mostly upregulation, in protein expression but no decreases in the mRNA expression of catalase, CuZnSOD or MnSOD enzymes in beta cells treated with either cytokines or DETA-NO. The lower antioxidant enzyme activities observed in islets from diabetes-prone BB/S rats could be a factor in the development of disease and in susceptibility to DNA damage in vitro and could reflect islet alterations prior to immune attack or inherent differences in the islets of diabetes-prone animals, but are not likely to result from cytokine or nitric oxide exposure in vivo at that stage. [ABSTRACT FROM AUTHOR]

Aims/hypothesis. Increased angiogenesis of fetoplacental vessels is a feature of pregnancies complicated by Type 1 diabetes mellitus, but the underlying molecular mechanisms are unknown. This investigation tests whether the diabetic maternal environment alters the phenotypic expression of placental vascular endothelial cadherin and β-catenin, which have been implicated as key molecules in barrier formation and angiogenesis in the endothelium. Methods. Term placental microvessels from normal pregnancies (n=8) and from those complicated by Type 1 diabetes (n=8) were perfused with 76-Mr dextran tracers (1 mg/ml) and subjected to immunocytochemistry, immunoblotting and microscopy. Junctional integrity, localisation and phosphorylation were investigated along with total protein levels of vascular endothelial cadherin, β-catenin and vascular endothelial growth factor. Stereological sampling and estimation tools were used to quantify aspects of angiogenesis and endothelial proliferation. Results. In the Type 1 diabetic placentae, junctional localisations of vascular endothelial cadherin and β-catenin altered significantly, with more than 50% of microvessels showing complete loss of immunoreactivity and with no overall loss of total protein. Tracer leakage was associated with these vessels. There was a two- to three-fold increase in vessels showing junctional phospho-tyrosine immunoreactivity and hyperphosphorylated β-catenin. Vascular endothelial growth factor levels were higher in these placentae. A four-fold increase in endothelial proliferation was observed, along with an increase in total length of capillaries without any change in luminal diameter. Conclusions/interpretation. Molecular perturbations of vascular endothelial cadherin and β-catenin occur in fetoplacental vessels of pregnancies complicated by Type 1 diabetes. Phosphorylation and loss of these molecules from the adherens junctional domains may be influenced in part by the elevated levels of vascular endothelial growth factor in the placenta. Perturbations of the junctional proteins may explain the observed breach in barrier integrity and may contribute to the mechanisms that drive proliferation and increases in capillary length. [ABSTRACT FROM AUTHOR]

Oxidative and nitrosative stress play a key role in the pathogenesis of diabetic neuropathy, but the mechanisms remain unidentified. Here we provide evidence that poly(ADP-ribose) polymerase (PARP) activation, a downstream effector of oxidant-induced DNA damage, is an obligatory step in functional and metabolic changes in the diabetic nerve. PARP-deficient (PARP(-/-)) mice were protected from both diabetic and galactose-induced motor and sensory nerve conduction slowing and nerve energy failure that were clearly manifest in the wild-type (PARP(+/+)) diabetic or galactose-fed mice. Two structurally unrelated PARP inhibitors, 3-aminobenzamide and 1,5-isoquinolinediol, reversed established nerve blood flow and conduction deficits and energy failure in streptozotocin-induced diabetic rats. Sciatic nerve immunohistochemistry revealed enhanced poly(ADP-ribosyl)ation in all experimental groups manifesting neuropathic changes. Poly(ADP-ribose) accumulation was localized in both endothelial and Schwann cells. Thus, the current work identifies PARP activation as an important mechanism in diabetic neuropathy and provides the first evidence for the potential therapeutic value of PARP inhibitors in this devastating complication of diabetes. [ABSTRACT FROM AUTHOR]

Increasing evidence in both experimental and clinical studies suggests that there is a close link between hy-perglycemia, oxidative stress and diabetic complica-tions. High blood glucose level determines overpro-duction of reactive oxygen species (ROS) by the mitochondria electron transport chain. High reactivity of ROS determines chemical changes in virtually all cel-lular components, leading to DNA and protein modifi-cation and lipid peroxidation. Measurement of bio-markers such 8-hydroxy-2'deoxyguanosine (8-OHdG), isoprostanes, malondialdehyde (MDA) and nitrotyro-sine is a useful tool to assess the oxidative stress of the organism. Knowledge of the mechanisms of ROS dam-age of is the first step for development of new thera-peutic molecules and for rationalizing the use of exist-ing drugs. [ABSTRACT FROM AUTHOR]

Poly(ADP-ribose) polymerase-1 (PARP-1) is a nuclear enzyme that consumes NAD in response to DNA strand breaks. Its excessive activation seems particularly deleterious to pancreatic beta-cells, as exemplified by the complete resistance of PARP-1-deficient mice to the toxic diabetes induced by streptozotocin. Because of the possible implication of this enzyme in type 1 diabetes, many human trials using nicotinamide, an inhibitor of PARP-1, have been conducted either in patients recently diagnosed or in subjects highly predisposed to this disease. To analyze the role of this enzyme in murine type 1 diabetes, we introgressed a disrupted PARP-1 allele onto the autoimmune diabetes-prone nonobese diabetic (NOD) mouse strain. We showed that these mice were protected neither from spontaneous nor from cyclophosphamide-accelerated diabetes. Surprisingly they were also highly sensitive to the diabetes induced by a single high dose of streptozotocin, standing in sharp contrast with C57BL/6 mice that bear the same inactivated PARP-1 allele. Our results suggest that NOD mice are characterized not only by their immune dysfunction but also by a peculiarity of their islets leading to a PARP-1-independent mechanism of streptozotocin-induced beta-cell death. [ABSTRACT FROM AUTHOR]

Patients with diabetes exhibit a high incidence of diabetic cardiomyopathy and vascular complications, which underlie the development of retinopathy, nephropathy, and neuropathy and increase the risk of hypertension, stroke, and myocardial infarction. There is emerging evidence that the activation of the nuclear enzyme poly(ADP-ribose) polymerase (PARP) importantly contributes to the development of endothelial dysfunction in a streptozotocin-induced model of diabetes. We investigated the role of PARP activation in the pathogenesis of cardiac dysfunction in streptozotocin-induced and genetic (nonobese diabetic) models of diabetes in rats and mice. Development of diabetes was accompanied by hyperglycemia, cardiac PARP activation, a selective loss of endothelium-dependent vasodilation in the thoracic aorta, and an early diastolic dysfunction of the heart. Treatment with a novel potent phenanthridinone-based PARP inhibitor, PJ34, starting 1 week after the onset of diabetes, restored normal vascular responsiveness and significantly improved cardiac dysfunction, despite the persistence of severe hyperglycemia. The beneficial effect of PARP inhibition persisted even after several weeks of discontinuation of the treatment. Thus, PARP activation plays a central role in the pathogenesis of diabetic cardiovascular (cardiac as well as endothelial) dysfunction. PARP inhibitors may exert beneficial effects against the development of cardiovascular complications in diabetes. [ABSTRACT FROM AUTHOR]

Diabetes mellitus is a major cause of peripheral neuropathy, commonly manifested as distal symmetrical polyneuropathy. This review examines evidence for the importance of vascular factors and their metabolic substrate from human and animal studies. Diabetic neuropathy is associated with risk factors for macrovascular disease and with other microvascular complications such as poor metabolic control, dyslipidaemia, body mass index, smoking, microalbuminuria and retinopathy. Studies in human and animal models have shown reduced nerve perfusion and endoneurial hypoxia. Investigations on biopsy material from patients with mild to severe neuropathy show graded structural changes in nerve microvasculature including basement membrane thickening, pericyte degeneration and endothelial cell hyperplasia. Arterio-venous shunting also contributes to reduced endoneurial perfusion. These vascular changes strongly correlate with clinical defects and nerve pathology. Vasodilator treatment in patients and animals improves nerve function. Early vasa nervorum functional changes are caused by the metabolic insults of diabetes, the balance between vasodilation and vasoconstriction is altered. Vascular endothelium is particularly vulnerable, with deficits in the major endothelial vasodilators, nitric oxide, endothelium-derived hyperpolarising factor and prostacyclin. Hyperglycaemia and dyslipidaemia driven oxidative stress is a major contributor, enhanced by advanced glycation end product formation and polyol pathway activation. These are coupled to protein kinase C activation and ω-6 essential fatty acid dysmetabolism. Together, this complex of interacting metabolic factors accounts for endothelial dysfunction, reduced nerve perfusion and function. Thus, the evidence emphasises the importance of vascular dysfunction, driven by metabolic change, as a cause of diabetic neuropathy, and highlights potential therapeutic approaches. [Diabetologia (2001) 44: 1973–1988] [ABSTRACT FROM AUTHOR]