The roles of hyperglycaemia and oxidative stress in the rise and collapse of the natural protective mechanism against vascular endothelial cell dysfunction in diabetes

Exosomes: current knowledge and future perspectives

Exosomes are membrane-bound micro-vesicles that possess endless therapeutic potential for treatment of numerous pathologies including autoimmune, cardiovascular, ocular, and nervous disorders. Despite considerable knowledge about exosome biogenesis and secretion, still, there is a lack of information regarding exosome uptake by cell types and internal signaling pathways through which these exosomes process cellular response. Exosomes are key components of cell signaling and intercellular communication. In central nervous system (CNS), exosomes can penetrate BBB and maintain homeostasis by myelin sheath regulation and the waste products elimination. Therefore, the current review summarizes role of exosomes and their use as biomarkers in cardiovascular, nervous and ocular disorders. This aspect of exosomes provides positive hope to monitor disease development and enable early diagnosis and treatment optimization. In this review, we have summarized recent findings on physiological and therapeutic effects of exosomes and also attempt to provide insights about stress-preconditioned exosomes and stem cell-derived exosomes.

Unraveling the Intricate Roles of Exosomes in Cardiovascular Diseases: A Comprehensive Review of Physiological Significance and Pathological Implications

Exosomes, as potent intercellular communication tools, have garnered significant attention due to their unique cargo-carrying capabilities, which enable them to influence diverse physiological and pathological functions. Extensive research has illuminated the biogenesis, secretion, and functions of exosomes. These vesicles are secreted by cells in different states, exerting either protective or harmful biological functions. Emerging evidence highlights their role in cardiovascular disease (CVD) by mediating comprehensive interactions among diverse cell types. This review delves into the significant impacts of exosomes on CVD under stress and disease conditions, including coronary artery disease (CAD), myocardial infarction, heart failure, and other cardiomyopathies. Focusing on the cellular signaling and mechanisms, we explore how exosomes mediate multifaceted interactions, particularly contributing to endothelial dysfunction, oxidative stress, and apoptosis in CVD pathogenesis. Additionally, exosomes show great promise as biomarkers, reflecting differential expressions of NcRNAs (miRNAs, lncRNAs, and circRNAs), and as therapeutic carriers for targeted CVD treatment. However, the specific regulatory mechanisms governing exosomes in CVD remain incomplete, necessitating further exploration of their characteristics and roles in various CVD-related contexts. This comprehensive review aims to provide novel insights into the biological implications of exosomes in CVD and offer innovative perspectives on the diagnosis and treatment of CVD.

Prognostic Impact of Plasma Glucose on Patients With Cardiogenic Shock With or Without Diabetes Mellitus from the SMART RESCUE Trial

Although the presence of hyperglycemia has been shown to affect the clinical outcome of patients with cardiogenic shock, the extent of hyperglycemia and its association with prognosis have not been fully addressed in a large population. A total of 1,177 consecutive patients with cardiogenic shock were enrolled from January 2014 to December 2018 at 12 hospitals in South Korea. The primary outcome was in-hospital mortality. Patients were divided into 4 groups according to their initial plasma glucose level in patients with diabetes mellitus (DM) (n = 752) and patients without DM (n=425); group 1 (≤8 mmol/L or 144 mg/100 ml), group 2 (8 to 12 mmol/L or 144 to 216 mg/100 ml), group 3 (12 to 16 mmol/L or 216 to 288 mg/100 ml), and group 4 (≥16 mmol/L or 288 mg/100 ml). The groups with higher admission plasma glucose were associated with lower systolic blood pressure and higher lactic acid levels in patients with and without DM. In-hospital mortality increased in groups with higher admission plasma glucose level in patients without DM (group 1:24.2%, group 2: 28.6%, group 3: 38.1%, group 4: 49.0%, p <0.01), whereas in patients with DM, mortality and admission plasma glucose level showed no significant association (group 1: 45%, group 2: 35.4%, group 3: 33.3%, group 4: 43.1%, p = 0.26). Even after multivariate analysis, high plasma glucose was an independent predictor of in-hospital mortality in patients without DM. In patients with cardiogenic shock, plasma glucose obtained at admission was associated with in-hospital mortality in patients without DM.

The Effect of High and Variable Glucose on the Viability of Endothelial Cells Co-Cultured with Smooth Muscle Cells

Diabetes mellitus causes endothelial dysfunction. The aim of this study was to investigate the effect of normal (5 mmol/L), high (20 mmol/L), and fluctuating (5 and 20 mmol/L changed every day) glucose concentration in the culture medium on the viability of human umbilical vein endothelial cells (HUVECs) co-cultured with human umbilical artery smooth muscle cells (HUASMCs). The cultures were conducted on semi-permeable flat polysulfone (PSU) fibronectin-coated membranes immobilized in self-made inserts. The insert contained either HUVECs on a single membrane or HUASMCs and HUVECs on two membranes close to each other. Cultures were conducted for 7 or 14 days. Apoptosis, mitochondrial potential, and the production of reactive oxygen species and lactate by HUVECs were investigated. The results indicate that fluctuations in glucose concentration have a stronger negative effect on HUVECs viability than constant high glucose concentration. High and fluctuating glucose concentrations slow down cell proliferation compared to the culture carried out in the medium with normal glucose concentration. In conclusion, HUASMCs affect the viability of HUVECs when both types of cells are co-cultured in medium with normal or variable glucose concentration.

Exosomes in Cardiovascular Diseases: Pathological Potential of Nano-Messenger

Cardiovascular diseases (CVDs) represent a major global health problem, due to their continued high incidences and mortality. The last few decades have witnessed new advances in clinical research which led to increased survival and recovery in CVD patients. Nevertheless, elusive and multifactorial pathophysiological mechanisms of CVD development perplexed researchers in identifying efficacious therapeutic interventions. Search for novel and effective strategies for diagnosis, prevention, and intervention for CVD has shifted research focus on extracellular vesicles (EVs) in recent years. By transporting molecular cargo from donor to recipient cells, EVs modulate gene expression and influence the phenotype of recipient cells, thus EVs prove to be an imperative component of intercellular signaling. Elucidation of the role of EVs in intercellular communications under physiological conditions implied the enormous potential of EVs in monitoring and treatment of CVD. The EVs secreted from the myriad of cells in the cardiovascular system such as cardiomyocytes, cardiac fibroblasts, cardiac progenitor cells, endothelial cells, inflammatory cells may facilitate the communication in physiological and pathological conditions. Understanding EVs-mediated cellular communication may delineate the mechanism of origin and progression of cardiovascular diseases. The current review summarizes exosome-mediated paracrine signaling leading to cardiovascular disease. The mechanistic role of exosomes in cardiovascular disease will provide novel avenues in designing diagnosis and therapeutic interventions.

Guidance for the Management of Patients with Vascular Disease or Cardiovascular Risk Factors and COVID-19: Position Paper from VAS-European Independent Foundation in Angiology/Vascular Medicine

COVID-19 is also manifested with hypercoagulability, pulmonary intravascular coagulation, microangiopathy, and venous thromboembolism (VTE) or arterial thrombosis. Predisposing risk factors to severe COVID-19 are male sex, underlying cardiovascular disease, or cardiovascular risk factors including noncontrolled diabetes mellitus or arterial hypertension, obesity, and advanced age. The VAS-European Independent Foundation in Angiology/Vascular Medicine draws attention to patients with vascular disease (VD) and presents an integral strategy for the management of patients with VD or cardiovascular risk factors (VD-CVR) and COVID-19. VAS recommends (1) a COVID-19-oriented primary health care network for patients with VD-CVR for identification of patients with VD-CVR in the community and patients' education for disease symptoms, use of eHealth technology, adherence to the antithrombotic and vascular regulating treatments, and (2) close medical follow-up for efficacious control of VD progression and prompt application of physical and social distancing measures in case of new epidemic waves. For patients with VD-CVR who receive home treatment for COVID-19, VAS recommends assessment for (1) disease worsening risk and prioritized hospitalization of those at high risk and (2) VTE risk assessment and thromboprophylaxis with rivaroxaban, betrixaban, or low-molecular-weight heparin (LMWH) for those at high risk. For hospitalized patients with VD-CVR and COVID-19, VAS recommends (1) routine thromboprophylaxis with weight-adjusted intermediate doses of LMWH (unless contraindication); (2) LMWH as the drug of choice over unfractionated heparin or direct oral anticoagulants for the treatment of VTE or hypercoagulability; (3) careful evaluation of the risk for disease worsening and prompt application of targeted antiviral or convalescence treatments; (4) monitoring of D-dimer for optimization of the antithrombotic treatment; and (5) evaluation of the risk of VTE before hospital discharge using the IMPROVE-D-dimer score and prolonged post-discharge thromboprophylaxis with rivaroxaban, betrixaban, or LMWH.

A review of the putative causal mechanisms associated with lower macular pigment in diabetes mellitus

Macular pigment (MP) confers potent antioxidant and anti-inflammatory effects at the macula, and may therefore protect retinal tissue from the oxidative stress and inflammation associated with ocular disease and ageing. There is a body of evidence implicating oxidative damage and inflammation as underlying pathological processes in diabetic retinopathy. MP has therefore become a focus of research in diabetes, with recent evidence suggesting that individuals with diabetes, particularly type 2 diabetes, have lower MP relative to healthy controls. The present review explores the currently available evidence to illuminate the metabolic perturbations that may possibly be involved in MP's depletion. Metabolic co-morbidities commonly associated with type 2 diabetes, such as overweight/obesity, dyslipidaemia, hyperglycaemia and insulin resistance, may have related and independent relationships with MP. Increased adiposity and dyslipidaemia may adversely affect MP by compromising the availability, transport and assimilation of these dietary carotenoids in the retina. Furthermore, carotenoid intake may be compromised by the dietary deficiencies characteristic of type 2 diabetes, thereby further compromising redox homeostasis. Candidate causal mechanisms to explain the lower MP levels reported in diabetes include increased oxidative stress, inflammation, hyperglycaemia, insulin resistance, overweight/obesity and dyslipidaemia; factors that may negatively affect redox status, and the availability, transport and stabilisation of carotenoids in the retina. Further study in diabetic populations is warranted to fully elucidate these relationships.

Selective deletion of endothelial cell calpain in mice reduces diabetic cardiomyopathy by improving angiogenesis

AIMS/HYPOTHESIS

The role of non-cardiomyocytes in diabetic cardiomyopathy has not been fully addressed. This study investigated whether endothelial cell calpain plays a role in myocardial endothelial injury and microvascular rarefaction in diabetes, thereby contributing to diabetic cardiomyopathy.

METHODS

Endothelial cell-specific Capns1-knockout (KO) mice were generated. Conditions mimicking prediabetes and type 1 and type 2 diabetes were induced in these KO mice and their wild-type littermates. Myocardial function and coronary flow reserve were assessed by echocardiography. Histological analyses were performed to determine capillary density, cardiomyocyte size and fibrosis in the heart. Isolated aortas were assayed for neovascularisation. Cultured cardiac microvascular endothelial cells were stimulated with high palmitate. Angiogenesis and apoptosis were analysed.

RESULTS

Endothelial cell-specific deletion of Capns1 disrupted calpain 1 and calpain 2 in endothelial cells, reduced cardiac fibrosis and hypertrophy, and alleviated myocardial dysfunction in mouse models of diabetes without significantly affecting systemic metabolic variables. These protective effects of calpain disruption in endothelial cells were associated with an increase in myocardial capillary density (wild-type vs Capns1-KO 3646.14 ± 423.51 vs 4708.7 ± 417.93 capillary number/high-power field in prediabetes, 2999.36 ± 854.77 vs 4579.22 ± 672.56 capillary number/high-power field in type 2 diabetes and 2364.87 ± 249.57 vs 3014.63 ± 215.46 capillary number/high-power field in type 1 diabetes) and coronary flow reserve. Ex vivo analysis of neovascularisation revealed more endothelial cell sprouts from aortic rings of prediabetic and diabetic Capns1-KO mice compared with their wild-type littermates. In cultured cardiac microvascular endothelial cells, inhibition of calpain improved angiogenesis and prevented apoptosis under metabolic stress. Mechanistically, deletion of Capns1 elevated the protein levels of β-catenin in endothelial cells of Capns1-KO mice and constitutive activity of calpain 2 suppressed β-catenin protein expression in cultured endothelial cells. Upregulation of β-catenin promoted angiogenesis and inhibited apoptosis whereas knockdown of β-catenin offset the protective effects of calpain inhibition in endothelial cells under metabolic stress.

CONCLUSIONS/INTERPRETATION

These results delineate a primary role of calpain in inducing cardiac endothelial cell injury and impairing neovascularisation via suppression of β-catenin, thereby promoting diabetic cardiomyopathy, and indicate that calpain is a promising therapeutic target to prevent diabetic cardiac complications.

Prognostic Value of Admission Blood Glucose Level in Critically Ill Patients Admitted to Cardiac Intensive Care Unit according to the Presence or Absence of Diabetes Mellitus

BACKGROUND

Admission blood glucose (BG) level is a predictor of mortality in critically ill patients with various conditions. However, limited data are available regarding this relationship in critically ill patients with cardiovascular diseases according to diabetic status.

METHODS

A total of 1,780 patients (595 with diabetes) who were admitted to cardiac intensive care unit (CICU) were enrolled from a single center registry. Admission BG level was defined as maximal serum glucose level within 24 hours of admission. Patients were divided by admission BG level: group 1 (< 7.8 mmol/L), group 2 (7.8-10.9 mmol/L), group 3 (11.0-16.5 mmol/L), and group 4 (≥ 16.6 mmol/L).

RESULTS

A total of 105 patients died in CICU (62 non-diabetic patients [5.2%] and 43 diabetic patients [7.9%]; P = 0.105). The CICU mortality rate increased with admission BG level (1.7%, 4.8%, 10.3%, and 18.8% from group 1 to group 4, respectively; P < 0.001). On multivariable analysis, hypertension, mechanical ventilator, continuous renal replacement therapy, acute physiology and chronic health evaluation II (APACHE II) score, and admission BG level significantly influenced CICU mortality in non-diabetic patients (group 1 vs. group 3: hazard ratio [HR], 3.31; 95% confidence interval [CI], 1.47-7.44; P = 0.004; group 1 vs. group 4: HR, 6.56; 95% CI, 2.76-15.58; P < 0.001). However, in diabetic patients, continuous renal replacement therapy and APACHE II score influenced CICU mortality but not admission BG level.

CONCLUSION

Admission BG level was associated with increased CICU mortality in critically ill, non-diabetic patients admitted to CICU but not in diabetic patients.

Piracetam Facilitates the Anti-Amnesic but not Anti-Diabetic Activity of Metformin in Experimentally Induced Type-2 Diabetic Encephalopathic Rats

Piracetam exhibits anti-amnesic activity in several animal models of dementia. However, its anti-amnesic potential has yet to be evaluated in type-2 diabetes mellitus (T2DM)-induced encephalopathy. Therefore, in the present study, piracetam (25, 50 and 100 mg/kg) was screened for anti-amnesic and anti-diabetic activity in T2DM-induced encephalopathic male rats. Subsequently, anti-amnesic and anti-diabetic activities were evaluated for piracetam, metformin and their combination in T2DM-induced encephalopathic animals. Rats received streptozotocin (45 mg/kg) and nicotinamide (110 mg/kg) injections on day-1 (D-1) of the experimental schedule and were kept undisturbed for 35 days to exhibit T2DM-induced encephalopathy. All drug treatments were continued from D-7 to D-35 in both experiments. Piracetam (100 mg/kg) attenuated loss in learning and memory in terms of increase in escape latency on D-4 (D-34) and decrease in time spent in the target quadrant on D-5 (D-35) of Morris water maze test protocol, and spatial memory in terms of reduced spontaneous alternation behavior in Y-maze test of encephalopathic rats. Additionally, piracetam attenuated altered levels of fasting plasma glucose and insulin, HOMA-IR and HOMA-B in encephalopathic animals, comparatively lesser than metformin. In the next experiment, combination of piracetam and metformin exhibited better anti-amnesic but not anti-diabetic activity than respective monotherapies in encephalopathic rats. Further, the combination attenuated reduced acetylcholine level and increased acetylcholinesterase activity, increased glycogen synthase kinase-3β level and decreased brain-derived neurotropic factor level in hippocampus and pre-frontal cortex of encephalopathic animals. Thus, piracetam could be used as an adjuvant to metformin in the management of dementia in T2DM-induced encephalopathy.

Functional food supplements to ameliorate the secondary complications in high fructose fed diabetic rats

Poly-herbal functional food supplements inhibited high fructose induced glycation in diabetic rats and showed promise for effective management of secondary complications of diabetes such as improved lipid profile, kidney function and reduction of oxidative stress.

Usefulness of the plasma glucose concentration-to-HbA1c ratio in predicting clinical outcomes during acute illness with extreme hyperglycaemia

AIMS

To evaluate the correlation between the plasma glucose-to-glycated haemoglobin ratio (GAR) and clinical outcome during acute illness.

METHODS

This retrospective observational cohort study enrolled 661 patients who visited the emergency department of our hospital between 1 July 2008 and 30 September 2010 with plasma glucose concentrations>500mg/dL. Systolic blood pressure, heart rate, white blood cells, neutrophils, haematocrit, blood urea nitrogen, serum creatinine, liver function and plasma glucose concentration were recorded at the initial presentation to the emergency department. Data on glycated haemoglobin over the preceding 6 months were reviewed from our hospital database. The glucose-to-HbA_1c ratio (GAR) was calculated as the plasma glucose concentration divided by glycated haemoglobin.

RESULTS

The GAR of those who died was significantly higher than that of the survivors (81.0±25.9 vs 67.6±25.0; P<0.001). There was a trend towards a higher 90-day mortality rate in patients with higher GARs (log-rank test P<0.0001 for trend). On multivariate Cox regression analysis, the GAR was significantly related to 90-day mortality (hazard ratio [HR] for 1 standard deviation [SD] change: 1.41, 95% confidence interval [CI]: 1.22-1.63; P<0.001), but not to plasma glucose (HR: 0.89, 95% CI: 0.70-1.13; P=0.328). Rates of intensive care unit (ICU) admission and mechanical ventilator use were also higher in those with higher GARs.

CONCLUSION

GAR independently predicted 90-day mortality, ICU admission and use of mechanical ventilation. It was also a better predictor of patient outcomes than plasma glucose alone in patients with extremely high glucose levels.

In situ eNOS/NO up-regulation-a simple and effective therapeutic strategy for diabetic skin ulcer

Decreased nitric oxide (NO) synthesis and increased NO consumption in diabetes induces the inadequate blood flow to tissues that is primarily responsible for the pathogenesis and refractoriness of diabetic skin ulcers. The present study proposed a simple and effective therapeutic strategy for diabetic skin ulcers—in situ up-regulation of endothelial nitric oxide synthase (eNOS) expression and NO synthesis by statin-loaded tissue engineering scaffold (TES). In vitro experiments on human umbilical vein endothelial cells indicated that the statin-loaded TES relieved the high-glucose induced decrease in cell viability and promoted NO synthesis under high-glucose conditions. In a rat model of diabetes, the statin-loaded TES promoted eNOS expression and NO synthesis in/around the regenerated tissues. Subsequently, accelerated vascularization and elevated blood supply were observed, followed by rapid wound healing. These findings suggest that the in situ up-regulation of eNOS/NO by a statin-loaded TES may be a useful therapeutic method for intractable diabetic skin wounds.

Hormetic and regulatory effects of lipid peroxidation mediators in pancreatic beta cells

Nutrient sensing mechanisms of carbohydrates, amino acids and lipids operate distinct pathways that are essential for the adaptation to varying metabolic conditions. The role of nutrient-induced biosynthesis of hormones is paramount for attaining metabolic homeostasis in the organism. Nutrient overload attenuate key metabolic cellular functions and interfere with hormonal-regulated inter- and intra-organ communication, which may ultimately lead to metabolic derangements. Hyperglycemia and high levels of saturated free fatty acids induce excessive production of oxygen free radicals in tissues and cells. This phenomenon, which is accentuated in both type-1 and type-2 diabetic patients, has been associated with the development of impaired glucose tolerance and the etiology of peripheral complications. However, low levels of the same free radicals also induce hormetic responses that protect cells against deleterious effects of the same radicals. Of interest is the role of hydroxyl radicals in initiating peroxidation of polyunsaturated fatty acids (PUFA) and generation of α,β-unsaturated reactive 4-hydroxyalkenals that avidly form covalent adducts with nucleophilic moieties in proteins, phospholipids and nucleic acids. Numerous studies have linked the lipid peroxidation product 4-hydroxy-2E-nonenal (4-HNE) to different pathological and cytotoxic processes. Similarly, two other members of the family, 4-hydroxyl-2E-hexenal (4-HHE) and 4-hydroxy-2E,6Z-dodecadienal (4-HDDE), have also been identified as potential cytotoxic agents. It has been suggested that 4-HNE-induced modifications in macromolecules in cells may alter their cellular functions and modify signaling properties. Yet, it has also been acknowledged that these bioactive aldehydes also function as signaling molecules that directly modify cell functions in a hormetic fashion to enable cells adapt to various stressful stimuli. Recent studies have shown that 4-HNE and 4-HDDE, which activate peroxisome proliferator-activated receptor δ (PPARδ) in vascular endothelial cells and insulin secreting beta cells, promote such adaptive responses to ameliorate detrimental effects of high glucose and diabetes-like conditions. In addition, due to the electrophilic nature of these reactive aldehydes they form covalent adducts with electronegative moieties in proteins, phosphatidylethanolamine and nucleotides. Normally these non-enzymatic modifications are maintained below the cytotoxic range due to efficient cellular neutralization processes of 4-hydroxyalkenals. The major neutralizing enzymes include fatty aldehyde dehydrogenase (FALDH), aldose reductase (AR) and alcohol dehydrogenase (ADH), which transform the aldehyde to the corresponding carboxylic acid or alcohols, respectively, or by biding to the thiol group in glutathione (GSH) by the action of glutathione-S-transferase (GST). This review describes the hormetic and cytotoxic roles of oxygen free radicals and 4-hydroxyalkenals in beta cells exposed to nutritional challenges and the cellular mechanisms they employ to maintain their level at functional range below the cytotoxic threshold.

High glucose concentration induces endothelial cell proliferation by regulating cyclin-D2-related miR-98

Cyclin D2 is involved in the pathology of vascular complications of type 2 diabetes mellitus (T2DM). This study investigated the role of cyclin‐D2‐regulated miRNAs in endothelial cell proliferation of T2DM. Results showed that higher glucose concentration (4.5 g/l) significantly promoted the proliferation of rat aortic endothelial cells (RAOECs), and significantly increased the expression of cyclin D2 and phosphorylation of retinoblastoma 1 (p‐RB1) in RAOECs compared with those under low glucose concentration. The cyclin D2‐3′ untranslated region is targeted by miR‐98, as demonstrated by miRNA analysis software. Western blot also confirmed that cyclin D2 and p‐RB1 expression was regulated by miR‐98. The results indicated that miR‐98 treatment can induce RAOEC apoptosis. The suppression of RAOEC growth by miR‐98 might be related to regulation of Bcl‐2, Bax and Caspase 9 expression. Furthermore, the expression levels of miR‐98 decreased in 4.5 g/l glucose‐treated cells compared with those treated by low glucose concentration. Similarly, the expression of miR‐98 significantly decreased in aortas of established streptozotocin (STZ)‐induced diabetic rat model compared with that in control rats; but cyclin D2 and p‐RB1 levels remarkably increased in aortas of STZ‐induced diabetic rats compared with those in healthy control rats. In conclusion, this study demonstrated that high glucose concentration induces cyclin D2 up‐regulation and miR‐98 down‐regulation in the RAOECs. By regulating cyclin D2, miR‐98 can inhibit human endothelial cell growth, thereby providing novel therapeutic targets for vascular complication of T2DM.

Insights into the molecular mechanisms of diabetes-induced endothelial dysfunction: focus on oxidative stress and endothelial progenitor cells

Diabetes mellitus is a heterogeneous, multifactorial, chronic disease characterized by hyperglycemia owing to insulin insufficiency and insulin resistance (IR). Recent epidemiological studies showed that the diabetes epidemic affects 382 million people worldwide in 2013, and this figure is expected to be 600 million people by 2035. Diabetes is associated with microvascular and macrovascular complications resulting in accelerated endothelial dysfunction (ED), atherosclerosis, and cardiovascular disease (CVD). Unfortunately, the complex pathophysiology of diabetic cardiovascular damage is not fully understood. Therefore, there is a clear need to better understand the molecular pathophysiology of ED in diabetes, and consequently, better treatment options and novel efficacious therapies could be identified. In the light of recent extensive research, we re-investigate the association between diabetes-associated metabolic disturbances (IR, subclinical inflammation, dyslipidemia, hyperglycemia, dysregulated production of adipokines, defective incretin and gut hormones production/action, and oxidative stress) and ED, focusing on oxidative stress and endothelial progenitor cells (EPCs). In addition, we re-emphasize that oxidative stress is the final common pathway that transduces signals from other conditions-either directly or indirectly-leading to ED and CVD.

Nanomolar Caffeic Acid Decreases Glucose Uptake and the Effects of High Glucose in Endothelial Cells

Epidemiological studies suggest that moderate and prolonged consumption of coffee is associated with a reduced risk of developing type 2 diabetes but the molecular mechanisms underlying this effect are not known. In this study, we report the effects of physiological concentrations of caffeic acid, easily achievable by normal dietary habits, in endothelial cells cultured in 25 mM of glucose (high glucose, HG). In HG, the presence of 10 nM caffeic acid was associated with a decrease of glucose uptake but not to changes of GLUT-1 membrane localization or mRNA levels. Moreover, caffeic acid countered HG-induced loss of barrier integrity, reducing actin rearrangement and FITC-dextran passage. The decreased flux of glucose associated to caffeic acid affected HG induced apoptosis by down-regulating the expression of initiator (caspase 8 and 9) and effector caspases (caspase 7 and 3) and by increasing the levels of phosphorylated Bcl-2. We also observed that caffeic acid in HG condition was associated to a reduction of p65 subunit nuclear levels with respect to HG alone. NF-κB activation has been shown to lead to apoptosis in HG treated cells and the analysis of the expression of a panel of about 90 genes related to NF-κB signaling pathway revealed that caffeic acid significantly influenced gene expression changes induced by HG. In conclusion, our results suggest that caffeic acid, decreasing the metabolic stress induced by HG, allows the activation of survival mechanisms mediated by a different modulation of NF-κB-related signaling pathways and to the activation of anti-apoptotic proteins.

Hypoxia-induced increases in glucose uptake do not cause oxidative injury or advanced glycation end-product (AGE) formation in vascular endothelial cells

An increase in glucose uptake by endothelial cells exposed to hyperglycemia is the presumed initiating event that causes systemic vascular disease in individuals with diabetes. Diabetics do not develop clinically significant pulmonary vascular disease, however, despite the pulmonary circulation’s exposure to the same level of glucose. We hypothesized that pulmonary artery endothelial cells are protected from the detrimental effects of hyperglycemia because they take up less glucose than endothelial cells in the systemic circulation, either because of intrinsic differences between the two cell types or because the lower oxygen tension in the pulmonary arterial blood depresses glucose uptake. To test this hypothesis, we exposed normoglycemic and hyperglycemic bovine pulmonary artery (PAECs) and aortic endothelial cells (AECs) from the same animal to progressively lower oxygen tensions and determined glucose uptake. In contrast with our initial hypothesis, we detected no significant difference in glucose uptake between the two cell types. Furthermore, glucose uptake in both PAECs and AECs increased, not decreased, as the oxygen tension dropped; this oxygen-dependent increase in glucose uptake in endothelial cells predominated over the hyperglycemia-mediated decrease in glucose uptake that has been reported by others. Despite the increase in glucose uptake at lower oxygen tensions, we detected no corresponding increase in protein carbonylation or advanced glycation endproducts. These results demonstrate that small physiologically relevant changes in oxygen tension can have an important impact on glucose uptake in endothelial cells. These results also demonstrate that an increase in glucose uptake, by itself, is not sufficient to generate ROS-mediated protein carbonylation or increase intracellular advanced glycation endproducts in vascular endothelial cells.

Interactions between mitochondrial reactive oxygen species and cellular glucose metabolism

Mitochondrial reactive oxygen species (ROS) production and detoxification are tightly balanced. Shifting this balance enables ROS to activate intracellular signaling and/or induce cellular damage and cell death. Increased mitochondrial ROS production is observed in a number of pathological conditions characterized by mitochondrial dysfunction. One important hallmark of these diseases is enhanced glycolytic activity and low or impaired oxidative phosphorylation. This suggests that ROS is involved in glycolysis (dys)regulation and vice versa. Here we focus on the bidirectional link between ROS and the regulation of glucose metabolism. To this end, we provide a basic introduction into mitochondrial energy metabolism, ROS generation and redox homeostasis. Next, we discuss the interactions between cellular glucose metabolism and ROS. ROS-stimulated cellular glucose uptake can stimulate both ROS production and scavenging. When glucose-stimulated ROS production, leading to further glucose uptake, is not adequately counterbalanced by (glucose-stimulated) ROS scavenging systems, a toxic cycle is triggered, ultimately leading to cell death. Here we inventoried the various cellular regulatory mechanisms and negative feedback loops that prevent this cycle from occurring. It is concluded that more insight in these processes is required to understand why they are (un)able to prevent excessive ROS production during various pathological conditions in humans.

Pathologic function and therapeutic potential of exosomes in cardiovascular disease

The heart is a very complex conglomeration of organized interactions between various different cell types that all aid in facilitating myocardial function through contractility, sufficient perfusion, and cell-to-cell reception. In order to make sure that all features of the heart work effectively, it is imperative to have a well-controlled communication system among the different types of cells. One of the most important ways that the heart regulates itself is by the use of extracellular vesicles, more specifically, exosomes. Exosomes are types of nano-vesicles, naturally released from living cells. They are believed to play a critical role in intercellular communication through the means of certain mechanisms including direct cell-to-cell contact, long-range signals as well as electrical and extracellular chemical molecules. Exosomes contain many unique features like surface proteins/receptors, lipids, mRNAs, microRNAs, transcription factors and other proteins. Recent studies indicate that the exosomal contents are highly regulated by various stress and disease conditions, in turn reflective of the parent cell status. At present, exosomes are well appreciated to be involved in the process of tumor and infection disease. However, the research on cardiac exosomes is just emerging. In this review, we summarize recent findings on the pathologic effects of exosomes on cardiac remodeling under stress and disease conditions, including cardiac hypertrophy, peripartum cardiomyopathy, diabetic cardiomyopathy and sepsis-induced cardiovascular dysfunction. In addition, the cardio-protective effects of stress-preconditioned exosomes and stem cell-derived exosomes are also summarized. Finally, we discuss how to epigenetically reprogram exosome contents in host cells which makes them beneficial for the heart.

Cardiomyocytes mediate anti-angiogenesis in type 2 diabetic rats through the exosomal transfer of miR-320 into endothelial cells

Exosomes, nano-vesicles naturally released from living cells, have been well recognized to play critical roles in mediating cell-to-cell communication. Given that diabetic hearts exhibit insufficient angiogenesis, it is significant to test whether diabetic cardiomyocyte-derived exosomes possess any capacity in regulating angiogenesis. In this study, we first observed that both proliferation and migration of mouse cardiac endothelial cells (MCECs) were inhibited when co-cultured with cardiomyocytes isolated from adult Goto-Kakizaki (GK) rats, a commonly used animal model of type 2 diabetes. However, GK-myocyte-mediated anti-angiogenic effects were negated upon addition of GW4869, an inhibitor of exosome formation/release, into the co-cultures. Next, exosomes were purified from the myocyte culture supernatants by differential centrifugation. While exosomes derived from GK myocytes (GK-exosomes) displayed similar size and molecular markers (CD63 and CD81) to those originated from the control Wistar rat myocytes (WT-exosomes), their regulatory role in angiogenesis is opposite. We observed that the MCEC proliferation, migration and tube-like formation were inhibited by GK-exosomes, but were promoted by WT-exosomes. Mechanistically, we found that GK-exosomes encapsulated higher levels of miR-320 and lower levels of miR-126 compared to WT-exosomes. Furthermore, GK-exosomes were effectively taken up by MCECs and delivered miR-320. In addition, transportation of miR-320 from myocytes to MCECs could be blocked by GW4869. Importantly, the exosomal miR-320 functionally down-regulated its target genes (IGF-1, Hsp20 and Ets2) in recipient MCECs, and overexpression of miR-320 inhibited MCEC migration and tube formation. GK exosome-mediated inhibitory effects on angiogenesis were removed by knockdown of miR-320. Together, these data indicate that cardiomyocytes exert an anti-angiogenic function in type 2 diabetic rats through exosomal transfer of miR-320 into endothelial cells. Thus, our study provides a novel mechanism underlying diabetes mellitus-induced myocardial vascular deficiency which may be caused by secretion of anti-angiogenic exosomes from cardiomyocyes.

Signaling properties of 4-hydroxyalkenals formed by lipid peroxidation in diabetes

Peroxidation of polyunsaturated fatty acids is intensified in cells subjected to oxidative stress and results in the generation of various bioactive compounds, of which 4-hydroxyalkenals are prominent. During the progression of type 2 diabetes mellitus, the ensuing hyperglycemia promotes the generation of reactive oxygen species (ROS) that contribute to the development of diabetic complications. It has been suggested that ROS-induced lipid peroxidation and the resulting 4-hydroxyalkenals markedly contribute to the development and progression of these pathologies. Recent findings, however, also suggest that noncytotoxic levels of 4-hydroxyalkenals play important signaling functions in the early phase of diabetes and act as hormetic factors to induce adaptive and protective responses in cells, enabling them to function in the hyperglycemic milieu. Our studies and others' have proposed such regulatory functions for 4-hydroxynonenal and 4-hydroxydodecadienal in insulin secreting β-cells and vascular endothelial cells, respectively. This review presents and discusses the mechanisms regulating the generation of 4-hydroxyalkenals under high glucose conditions and the molecular interactions underlying the reciprocal transition from hormetic to cytotoxic agents.

Propolis protects against high glucose-induced vascular endothelial dysfunction in isolated rat aorta

While propolis is known to have abundant bioactive constituents and a variety of biological activities, it is not clear whether propolis has beneficial effects on high glucose-mediated vascular endothelial impairment. The aim of the present study was to investigate the potential protective effect of propolis extract against the acute vascular endothelial dysfunction resulting from exposure to high glucose load and to elucidate its underlying mechanism. Rat aortic rings were incubated with normal glucose (11 mM), high glucose (44 mM), or mannitol (44 mM) for 3 h with or without propolis extract (400 μg/ml). Contraction to phenylephrine (Phe, 10(-9)-10(-5) M) and relaxation to acetylcholine (ACh, 10(-9)-10(-5) M) and sodium nitroprusside (SNP, 10(-9)-10(-5) M) were measured before and after incubation. Changes in malondialdehyde (MDA), reduced glutathione (GSH), and superoxide dismutase (SOD) were also measured. Phe-induced contraction was impaired by high glucose as the E(max) decreased from 138.87 ± 11.43 to 103.65 ± 11.5 %. In addition, ACh-induced relaxation was impaired as the E(max) decreased from 99.80 ± 7.25 to 39.20 ± 6.5 %. SNP-induced relaxation was not affected. Furthermore, high glucose decreased the levels of both SOD (by 6 U/ml) and GSH (by 68 %) and increased levels of MDA (by 85 %). Propolis extract prevented high glucose-induced impairment of Phe and ACh responses and increased both SOD and GSH, leading to decreased MDA levels. In conclusion, propolis can protect against high glucose-induced vascular dysfunction by reducing oxidative stress.

A comparative study of ferulic acid on different monosaccharide-mediated protein glycation and oxidative damage in bovine serum albumin

Three dietary monosaccharides, (glucose, fructose, and ribose), have different rates of protein glycation that accelerates the production of advanced glycation end-products (AGEs). The present work was conducted to investigate the effect of ferulic acid (FA) on the three monosaccharide-mediated protein glycations and oxidation of BSA. Comparing the percentage reduction, FA (1-5 mM) reduced the level of fluorescence AGEs (F-AGEs) and N(ε)-(carboxymethyl) lysine (N(ε)-CML) in glucose-glycated BSA (F-AGEs = 12.61%-36.49%; N(ε)-CML = 33.61%-66.51%), fructose-glycated BSA (F-AGEs = 25.28%-56.42%; N(ε)-CML = 40.21%-62.91%), and ribose-glycated BSA (F-AGEs = 25.63%-51.18%; N(ε)-CML = 26.64%-64.08%). In addition, the percentages of FA reduction of fructosamine (Frc) and amyloid cross β-structure (Amy) were Frc = 20.45%-43.81%; Amy = 17.84%-34.54% in glucose-glycated BSA, Frc = 25.17%-36.92%; Amy = 27.25%-39.51% in fructose-glycated BSA, and Frc = 17.34%-29.71%; Amy = 8.26%-59.92% in ribose-glycated BSA. FA also induced a reduction in protein carbonyl content (PC) and loss of protein thiol groups (TO) in glucose-glycated BSA (PC = 37.78%-56.03%; TO = 6.75%-13.41%), fructose-glycated BSA (PC = 36.72%-52.74%; TO = 6.18%-20.08%), and ribose-glycated BSA (PC = 25.58%-33.46%; TO = 20.50%-39.07%). Interestingly, the decrease in fluorescence AGEs by FA correlated with the level of N(ε)-CML, fructosamine, amyloid cross β-structure, and protein carbonyl content. Therefore, FA could potentially be used to inhibit protein glycation and oxidative damage caused by monosaccharides, suggesting that it might prevent AGEs-mediated pathologies during diabetic complications.

Glycemic variability and glycemic control in the acutely ill cardiac patient

The mechanisms for hyperglycemia-mediated harm in the hospitalized cardiac patient are poorly understood. Potential obstacles in the inpatient management of hyperglycemia in cardiac patients include rapidly changing clinical status, frequent procedures and interruptions in carbohydrate exposure, and short hospital length of stay. A patient's preadmission regimen is rarely suitable for inpatient glycemic control. Instead, an approach to a flexible, physiologic insulin regimen is described, which is intended to minimize glycemic excursions. When diabetes or hyperglycemia is addressed early and consistently, the hospital stay can serve as a potential window of opportunity for reinforcing self-care behaviors that reduce long-term complications.

Activation of aerobic metabolism by Amaranth oil improves heart rate variability both in athletes and patients with type 2 diabetes mellitus

The aim of present research was to study the effects of Amaranth oil (AmO) supplementation on aerobic metabolism and heart rate variability (HRV) in type 2 diabetes mellitus patients and in athletes. Several parameters of aerobic metabolism and HRV were assessed. Supplementation with AmO caused mild pro-oxidant activity resulting in improved uptake of oxidative destruction products and modulation of catalase and SOD activity with subsequent development of an antioxidant effect. These findings were very distinct in athletes but less pronounced in diabetics. Redistribution of haemoglobin ligands in athletes indicates involvement of haemoproteins in free radical reactions during AmO supplementation. Improvement in HRV by daily consumption of AmO as observed in both study groups suggested increased production of endogenous oxygen and enhancement of the cardio-respiratory function. The advantage of activation of aerobic metabolism in OS-related disorders resulting in improved self-organization of the living system and hormetic reaction mechanisms are discussed.

Rosuvastatin improves endothelial function in db/db mice: role of angiotensin II type 1 receptors and oxidative stress

BACKGROUND AND PURPOSE

HMG-CoA reductase inhibitors, statins, with lipid-reducing properties combat against atherosclerosis and diabetes. The favourable modulation of endothelial function may play a significant role in this effect. The present study aimed to investigate the cellular mechanisms responsible for the therapeutic benefits of rosuvastatin in ameliorating diabetes-associated endothelial dysfunction.

EXPERIMENTAL APPROACH

Twelve-week-old db/db diabetic mice were treated with rosuvastatin at 20 mg·kg⁻¹ ·day⁻¹ p.o.for 6 weeks. Isometric force was measured in isolated aortae and renal arteries. Protein expressions including angiotensin II type 1 receptor (AT₁R), NOX4, p22(phox) , p67(phox) , Rac-1, nitrotyrosine, phospho-ERK1/2 and phospho-p38 were determined by Western blotting, while reactive oxygen species (ROS) accumulation in the vascular wall was evaluated by dihydroethidium fluorescence and lucigenin assay.

KEY RESULTS

Rosuvastatin treatment of db/db mice reversed the impaired ACh-induced endothelium-dependent dilatations in both renal arteries and aortae and prevented the exaggerated contractions to angiotensin II and phenylephrine in db/db mouse renal arteries and aortae. Rosuvastatin reduced the elevated expressions of AT₁R, p22(phox) and p67(phox) , NOX4, Rac1, nitrotyrosine and phosphorylation of ERK1/2 and p38 MAPK and inhibited ROS production in aortae from db/db mice.

CONCLUSIONS AND IMPLICATIONS

The vasoprotective effects of rosuvastatin are attributed to an increase in NO bioavailability, which is probably achieved by its inhibition of ROS production from the AT₁R-NAD(P)H oxidase cascade.

Cinnamic acid and its derivatives inhibit fructose-mediated protein glycation

Cinnamic acid and its derivatives have shown a variety of pharmacologic properties. However, little is known about the antiglycation properties of cinnamic acid and its derivatives. The present study sought to characterize the protein glycation inhibitory activity of cinnamic acid and its derivatives in a bovine serum albumin (BSA)/fructose system. The results demonstrated that cinnamic acid and its derivatives significantly inhibited the formation of advanced glycation end products (AGEs) by approximately 11.96–63.36% at a concentration of 1 mM. The strongest inhibitory activity against the formation of AGEs was shown by cinnamic acid. Furthermore, cinnamic acid and its derivatives reduced the level of fructosamine, the formation of N^ɛ-(carboxymethyl) lysine (CML), and the level of amyloid cross β-structure. Cinnamic acid and its derivatives also prevented oxidative protein damages, including effects on protein carbonyl formation and thiol oxidation of BSA. Our findings may lead to the possibility of using cinnamic acid and its derivatives for preventing AGE-mediated diabetic complications.

Hyperthermia-induced Hsp90·eNOS preserves mitochondrial respiration in hyperglycemic endothelial cells by down-regulating Glut-1 and up-regulating G6PD activity

Uncoupling of NO production from NADPH oxidation by endothelial nitric-oxide synthase (eNOS) is enhanced in hyperglycemic endothelium, potentially due to dissociation of heat shock proteins 90 (Hsp90), and cellular glucose homeostasis is enhanced by a ROS-induced positive feed back mechanism. In this study we investigated how such an uncoupling impacts oxygen metabolism and how the oxidative phosphorylation can be preserved by heat shock (42 °C for 2 h, hyperthermia) in bovine aortic endothelial cells. Normal and heat-shocked bovine aortic endothelial cells were exposed to normoglycemia (NG, 5.0 mM) or hyperglycemia (30 mM). With hyperglycemia treatment, O(2) consumption rate was reduced (from V(O(2)max) = 7.51 ± 0.54 to 2.35 ± 0.27 mm Hg/min/10(6) cells), whereas in heat-shocked cells, O(2) consumption rate remained unaltered (8.19 ± 1.01 mm Hg/min/10 × 10(6) cells). Heat shock was found to enhance Hsp90/endothelial NOS interactions and produce higher NO. Moreover, ROS generation in the hyperglycemic condition was also reduced in heat-shocked cells. Interestingly, glucose uptake was reduced in heat-shocked cells as a result of decrease in Glut-1 protein level. Glucose phosphate dehydrogenase activity that gives rise to NADPH generation was increased by hyperthermia, and mitochondrial oxidative metabolism was preserved. In conclusion, the present study provides a novel mechanism wherein the reduced oxidative stress in heat-shocked hyperglycemic cells down-regulates Glut-1 and glucose uptake, and fine-tuning of this pathway may be a potential approach to use for therapeutic benefit of diabetes mellitus.

Choline-deprivation alters crucial brain enzyme activities in a rat model of diabetic encephalopathy

Diabetic encephalopathy describes the moderate cognitive deficits, neurophysiological and structural central nervous system changes associated with untreated diabetes. It involves neurotoxic effects such as the generation of oxidative stress, the enhanced formation of advanced glycation end-products, as well as the disturbance of calcium homeostasis. Due to the direct connection of choline (Ch) with acetylcholine availability and signal transduction, a background of Ch-deficiency might be unfavorable for the pathology and subsequently for the treatment of several metabolic brain diseases, including that of diabetic encephalopathy. The aim of this study was to shed more light on the effects of adult-onset streptozotocin (STZ)-induced diabetes and/or Ch-deprivation on the activities of acetylcholinesterase (AChE) and two important adenosine triphosphatases, namely Na(+),K(+)-ATPase and Mg(2+)-ATPase. Male adult Wistar rats were divided into four main groups, as follows: control (C), diabetic (D), Ch-deprived (CD), and Ch-deprived diabetic (D+CD). Deprivation of Ch was provoked through the administration of Ch-deficient diet. Both the induction of diabetes and the beginning of dietary-mediated provoking of Ch-deprivation occurred at the same day, and rats were killed by decapitation after 30 days (1 month; groups C1, D1, CD1 and D1+CD1) and 60 days (2 months; groups C2, D2, CD2 and D2+CD2, respectively). The adult rat brain AChE activity was found to be significantly increased by both diabetes (+10%, p < 0.001 and +11%, p < 0.01) and Ch-deprivation (+19%, p < 0.001 and +14%, p < 0.001) when compared to the control group by the end of the first (C1) and the second month (C2), respectively. However, the Ch-deprived diabetic rats' brain AChE activity was significantly altered only after a 60-day period of exposure, resulting in a +27% increase (D2+CD2 vs. C2, p < 0.001). Although the only significant change recorded in the brain Na(+),K(+)-ATPase activity after the end of the first month is attributed to Ch-deprivation (+21%, p < 0.05, CD1 vs. C1), all groups of the second month exhibited a statistically significant decrease in brain Na(+),K(+)-ATPase activity (-24%, p < 0.01, D2 vs. C2; -21%, p < 0.01, CD2 vs. C2; -22%, p < 0.01, D2+CD2 vs. C2). As concerns Mg(2+)-ATPase, the enzyme's activity demonstrates no significant changes, with the sole exception of the D2+CD2 group (+21%, p < 0.05, D2+CD2 vs. C2). In addition, statistically significant time-dependent changes concerning the brain Mg(2+)-ATPase activity were recorded within the diabetic (p < 0.05, D2 vs. D1) and the Ch-deprived (p < 0.05, CD2 vs. CD1) rat groups. Our data indicate that Ch-deprivation seems to be an undesirable background for the above-mentioned enzymatic activities under untreated diabetes, in a time-evolving way. Further studies on the issue should focus on a region-specific reevaluation of these crucial enzymes' activities as well as on the possible oxidative mechanisms involved.

Regulation effects on abnormal glucose and lipid metabolism of TZQ-F, a new kind of Traditional Chinese Medicine

AIM OF THE STUDY

Based on the recipe of the traditional anti-diabetic formula TZQ, we developed TZQ-F, a new formula including 8 fractions isolated from Red Paeony root, Mulberry leaf, Lotus leaf, Danshen root and Hawthorn leaf with a good quality assurance. The study was aimed at fraction preparation and effects of the fractions on abnormal glucose and lipid metabolism.

MATERIALS AND METHODS

The active fractions were obtained by macroporous resin, ion-exchange resin and polyamide resin column chromatographies. HPLC analyses were used for quality control. In vitro mechanism study included DPPH radical scavenging, AGEs formation inhibition, alpha-glucosidase inhibition and lipase inhibition, and rats on high-fat diet were used for in vivo study.

RESULTS

In vitro mechanism study showed that among the 8 fractions, three of them had inhibition effects on intestinal disaccharase, three with inhibition effects on lipase, and five with effects of free radical scavenging. In vivo study showed that after 4 weeks of treatment, TZQ-F significantly decreased the levels of serum total cholesterol, TG, glucose, LDL-C and HDL-C in rats on high-fat diet. Consistent with the in vitro and in vivo results, histology study demonstrated that TZQ-F alleviated hepatic steatosis induced by high-fat diet.

CONCLUSIONS

TZQ-F possesses the potential regulation effects on abnormal glucose and lipid metabolism.

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

OBJECTIVE

Diabetes patients have an increased risk of sepsis. Several inflammatory and coagulant pathways that are activated during sepsis are also up-regulated in diabetes patients. We tested our a priori hypothesis that the presence of diabetes adversely affects the outcome of sepsis.

DESIGN

Retrospective analysis of a previously published study.

SETTING

Intensive care units of 164 centers in 11 countries.

PATIENTS

Eight hundred thirty severe sepsis patients who were admitted to the intensive care unit and who received standard critical care treatment.

INTERVENTIONS

Patients were stratified into diabetic and nondiabetic patient groups. Mortality was assessed after 28 and 90 days, causative microorganisms were evaluated, and markers of coagulation, fibrinolysis, and inflammation were measured at several time points.

MEASUREMENTS AND MAIN RESULTS

Diabetes was present in 22.7% of all sepsis patients. Throughout the study, plasma glucose levels were higher in diabetic patients. Mortality was equal in diabetic and nondiabetic patients (31.4% vs. 30.5% after 28 days). Markers of coagulation, fibrinolysis, and inflammation were generally equal in diabetic and nondiabetic patients, although on admission diabetic patients had slightly higher levels of anticoagulation markers. Interestingly, nondiabetic patients with admission hyperglycemia (>11.1 mmol/L; 200 mg/dL) had a higher mortality rate compared to those without admission hyperglycemia (43.0% vs. 27.2%).

CONCLUSIONS

Although diabetes is a risk factor for sepsis, once established, the outcome of severe sepsis does not appear to be significantly influenced by the presence of diabetes. In nondiabetic patients, however, admission hyperglycemia is associated with an increased mortality.

The Maillard reaction in the human body. The main discoveries and factors that affect glycation

Ever since the discovery of the Maillard reaction in 1912 and the discovery of the interaction between advanced glycation end-products and cellular receptors, impressive progress has been made in the knowledge of nonenzymatic browning of proteins in vivo. This reaction which leads to the accumulation of random damage in extracellular proteins is known to have deleterious effects on biological function, and is associated with aging and complication in chronic diseases. Despite a controlled membrane permeability and a protective regulation of the cells, intracellular proteins are also altered by the Maillard reaction. Two main factors, protein turnover and the concentration of carbonyls, are involved in the rate of formation of the Maillard products. This paper reviews the key milestones of the discovery of the Maillard reaction in vivo, better known as glycation, and the factors which are likely to affect it.

Glycemic control in the medical intensive care unit

Hyperglycemia in the critically ill is a well-known phenomenon, even in those without known diabetes. The stress response is due to a complex interplay between counter-regulatory hormones, cytokines, and changes in insulin sensitivity. Illness/infection, overfeeding, medications (e.g., corticosteroids), insufficient insulin, and/or volume depletion can be additional contributors. Acute hyperglycemia can adversely affect fluid balance (through glycosuria and dehydration), immune and endothelial function, inflammation, and outcome. While there are several insulin infusion protocols that are able to safely and effectively treat hyperglycemia, the bulk of accumulated evidence does not support a causal relationship between acute hyperglycemia and adverse outcomes in the medical intensive care unit. Meta-analysis of randomized controlled trials suggests there is no benefit to tightening glucose control to normal levels compared to a reasonable and achievable goal of 140 to 180 mg/dl. There is a significantly increased risk of hypoglycemia. Although there is some evidence that patients without known diabetes have worse outcomes than those with known diabetes, more recent evidence is conflicting. Glycemic control in critically ill patients should not be neglected, as studies have not tested tight versus no/poor control, but tight versus good control. A moderate approach to managing critical illness hyperglycemia seems most prudent at this juncture. Future research should ascertain whether there are certain subgroups of patients that would benefit from tighter glycemic goals. It also remains to be seen if tight glucose control is beneficial once hypoglycemia is minimized with technological advances such as continuous glucose monitoring systems.

Proteomic Analysis of Vascular Endothelial Cells-Effects of Laminar Shear Stress and High Glucose

This study directly measured the relative protein levels in bovine aortic endothelial cells (BAEC) that were cultured for two weeks in normal (5 mM, NG) or high (22 mM, HG) glucose and then were subjected to laminar shear stress at 0 or 15 dynes/cm(2). Membrane preparations were labeled with one of the four isobaric tagging reagents (iTRAQ), followed by LC-MS/MS analysis. The results showed that HG and/or shear stress induced alterations in various membrane associated proteins involving many signaling pathways. While shear stress induced an increase in heat shock proteins and protein ubiquitination, which remained enhanced in HG, the effects of shear stress on the mechanosensing and protein phosphorylation pathways were altered by HG. These results were validated by Western blot analysis, suggesting that HG importantly modulates shear stress-mediated endothelial function.

Rotenone partially reverses decreased BK Ca currents in cerebral artery smooth muscle cells from streptozotocin-induced diabetic mice

1. Reactive oxygen species (ROS) cause vascular complications and impair vasodilation in diabetes mellitus. Large-conductance Ca(2+)-activated potassium channels (BK(Ca)) modulate vascular tone and play an important negative feedback role in vasoconstriction. In the present study, we tested the hypothesis that ROS regulate the function of BK(Ca) in diabetic cerebral artery smooth muscle cells. 2. Diabetes was induced in male BALB/c mice by injection of streptozotocin (STZ; 180 mg/kg, i.p., dissolved in sterile saline). Control and diabetic mice were treated with 12.7 micromol/L rotenone, an inhibitor of the mitochondrial electron transport chain complex I, or placebo every other day for 5 weeks. The whole-cell patch clamp-technique and functional vasomotor methods were used to record BK(Ca) currents and myogenic tone of cerebral artery smooth muscle cells. 3. In the diabetic group, there was a significant decrease in spontaneous transient outward currents in cerebral artery smooth muscle cells compared with control. Although the currents were only moderately increased in rotenone-treated diabetic mice, they remained significantly lower than in the control group. Furthermore, the macroscopic BK(Ca) currents that were decreased in diabetic mice were partially recovered in rotenone-treated diabetic mice (P < 0.05 vs untreated diabetic group). 4. The posterior cerebral artery from diabetic mice had a significantly higher myogenic tone than the control group, but this impaired contraction was partially reversed in the rotenone-treated diabetic group (P < 0.05 vs untreated diabetic group). 5. The H(2)O(2) concentration was significantly increased in cerebral arteries from diabetic mice compared with control. This increase in H(2)O(2) was significantly blunted by rotenone treatment. 6. In conclusion, rotenone partially reverses the decreased macroscopic BK(Ca) currents in STZ-induced Type 1 diabetic mice and this reversal of BK(Ca) currents may be related to the inhibitory effects of rotenone on H(2)O(2) production. Reactive oxygen species, particularly H(2)O(2), are important regulators of BK(Ca) channels and myogenic tone in diabetic cerebral artery.

Impaired glucose transporter-1 degradation and increased glucose transport and oxidative stress in response to high glucose in chondrocytes from osteoarthritic versus normal human cartilage

Introduction

Disorders that affect glucose metabolism, namely diabetes mellitus (DM), may favor the development and/or progression of osteoarthritis (OA). Thus far, little is known regarding the ability of chondrocytes to adjust to variations in the extracellular glucose concentration, resulting from hypoglycemia and hyperglycemia episodes, and so, to avoid deleterious effects resulting from deprivation or intracellular accumulation of glucose. The aim of this study was to compare the ability of normal and OA chondrocytes to regulate their glucose transport capacity in conditions of insufficient or excessive extracellular glucose and to identify the mechanisms involved and eventual deleterious consequences, namely the production of reactive oxygen species (ROS).

Methods

Chondrocytes, isolated from normal and OA human cartilage, were maintained in high-density monolayer cultures, in media without or with 10 or 30 mM glucose. Glucose transport was measured as the uptake of 2-deoxy-D-glucose (2-DG). Glucose transporter-1 (GLUT-1) mRNA and protein content were evaluated by real-time RT-PCR and western blot, respectively. ROS production was measured with 2',7'-dichlorodihydrofluorescein diacetate.

Results

Basal and IL-1β-induced 2-DG uptake, including the affinity (1.066 ± 0.284 and 1.49 ± 0.59 mM) and maximal velocity (0.27 ± 0.08 and 0.33 ± 0.08 nmol/μg protein/hour), and GLUT-1 content were identical in normal and OA chondrocytes. Glucose deprivation increased 2-DG uptake and GLUT-1 protein both in normal and OA chondrocytes. Exposure to high glucose (30 mM) for 18 or 48 hours decreased those parameters in normal but not in OA chondrocytes. GLUT-1 mRNA levels were unaffected by high glucose, either in normal or OA chondrocytes. The high glucose-induced reduction in GLUT-1 protein in normal chondrocytes was reversed by treatment with a lysosome inhibitor. High glucose induced ROS production, which lasted significantly longer in OA than in normal chondrocytes.

Conclusions

Normal human chondrocytes adjust to variations in the extracellular glucose concentration by modulating GLUT-1 synthesis and degradation which involves the lysosome pathway. Although capable of adjusting to glucose deprivation, OA chondrocytes exposed to high glucose were unable downregulate GLUT-1, accumulating more glucose and producing more ROS. Impaired GLUT-1 downregulation may constitute an important pathogenic mechanism by which conditions characterized by hyperglycemia, like DM, can promote degenerative changes in chondrocytes that can facilitate the progression of OA.

Effects of adult-onset streptozotocin-induced diabetes on the rat brain antioxidant status and the activities of acetylcholinesterase, (Na(+),K (+))- and Mg(2+)-ATPase: modulation by L-cysteine

Uncontrolled diabetes is known to affect the nervous system. The aim of this study was to investigate the effect of the antioxidant L: -cysteine (Cys) on the changes caused by adult-onset streptozotocin (STZ)-induced diabetes on the rat brain total antioxidant status (TAS) and the activities of acetylcholinesterase (AChE), (Na(+),K(+))-ATPase and Mg(2+)-ATPase. Thirty-eight male Wistar rats were divided into six groups: C(A) (8-week-control), C(B) (8-week-control + 1-week-saline-treated), C + Cys (8-week-control + 1-week-Cys-treated), D(A) (8-week-diabetic), D(B) (8-week-diabetic + 1-week-saline-treated) and D + Cys (8-week-diabetic + 1-week-Cys-treated). All diabetic rats were once treated with an intraperitoneal (i.p.) STZ injection (50 mg/kg body weight) at the beginning of the experiment, while all Cys-treated groups received i.p. injections of Cys 7 mg/kg body weight (daily, for 1-week, during the 9th-week). Whole rat brain parameters were measured spectrophotometrically. In vitro incubation with 0.83 mM of Cys or 10 mM of STZ for 3 h was performed on brain homogenate samples from groups C(B) and D(B), in order to study the enzymes' activities. Diabetic rats exhibited a statistically significant reduction in brain TAS (-28%, D(A) vs C(A);-30%, D(B) vs C(B)) that was reversed after 1-week-Cys-administration into basal levels. Diabetes caused a significant increase in AChE activity (+27%, D(A) vs C(A); +15%, D(B) vs C(B)), that was further enhanced by Cys-administration (+57%, D + Cys vs C(B)). The C + Cys group exhibited no significant difference compared to the C(B) group in TAS (+2%), but showed a significantly increased AChE activity (+66%, C + Cys vs C(B)). Diabetic rats exhibited a significant reduction in the activity of Na(+),K(+)-ATPase (-36%, D(A) vs C(A);-48%, D(B) vs C(B)) that was not reversed after 1-week Cys administration. However, in vitro incubation with Cys partially reversed the diabetes-induced Na(+),K(+)-ATPase inhibition. Mg(2+)-ATPase activity was not affected by STZ-induced diabetes, while Cys caused a significant inhibition of the enzyme, both in vivo (-14%, C + Cys vs C(B);-17%, D + Cys vs C(B)) and in vitro (-16%, D(B) + in vitro Cys vs C(B)). In vitro incubation with STZ had no effect on the studied enzymes. The present data revealed a protective role for Cys towards the oxidative effect of diabetes on the adult rat brain. Moreover, an increase in whole brain AChE activity due to diabetes was recorded (not repeatedly established in the literature, since contradictory findings exist), that was further increased by Cys. The inhibition of Na(+),K(+)-ATPase reflects a possible mechanism through which untreated diabetes could affect neuronal excitability, metabolic energy production and certain systems of neurotransmission. As concerns the use of Cys as a neuroprotective agent against diabetes, our in vitro findings could be indicative of a possible protective role of Cys under different in vivo experimental conditions.

Stress hyperglycaemia

Results of randomised controlled trials of tight glycaemic control in hospital inpatients might vary with population and disease state. Individualised therapy for different hospital inpatient populations and identification of patients at risk of hyperglycaemia might be needed. One risk factor that has received much attention is the presence of pre-existing diabetes. So-called stress hyperglycaemia is usually defined as hyperglycaemia resolving spontaneously after dissipation of acute illness. The term generally refers to patients without known diabetes, although patients with diabetes might also develop stress hyperglycaemia-a fact overlooked in many studies comparing hospital inpatients with or without diabetes. Investigators of several studies have suggested that patients with stress hyperglycaemia are at higher risk of adverse consequences than are those with pre-existing diabetes. We describe classification of stress hyperglycaemia, mechanisms of harm, and management strategies.

Curcumin ameliorates high glucose-induced acute vascular endothelial dysfunction in rat thoracic aorta

1. The aims of the present study were to explore the protective effect of curcumin against the acute vascular endothelial dysfunction induced by high glucose and to investigate the possible role of heme oxygenase (HO)-1 in this protective action. 2. Thoracic aortic rings, with or without endothelium, obtained from male Sprague-Dawley rats were mounted in an organ bath. Isometric contraction of the rings was recorded. After completion of the organ bath studies, rings were homogenized and centrifuged (30,000 g, 4 degrees C, 15 min) and HO activity was determined in the supernatant. 3. After 2 h incubation of aortic rings in the presence of high glucose (44 mmol/L), the relaxation evoked by acetylcholine (3 x 10(-8) to 3 x 10(-5) mol/L) was significantly decreased only in rings with an intact endothelium. When rings were coincubated in the presence of curcumin (10(-13) to 10(-11) mol/L) and high glucose, curcumin reversed the vasodilator dysfunction induced by high glucose dose dependently. 4. Curcumin (10(-11) mol/L) increased HO activity in the aortic rings compared with activity in control rings (63.1 +/- 3.6 vs control 43.2 +/- 2.9 pmol/mg per h, respectively; P < 0.01). Protoporphyrin IX zinc (10(-6) mol/L), an inhibitor of HO-1, offset the protective effects of curcumin. In addition, the non-selective guanylate cyclase (GC) inhibitor methylene blue (10(-6) mol/L) completely abolished the protective effects of curcumin. 5. In conclusion, the results of the present study show that curcumin alleviates the acute endothelium-dependent vasodilator dysfunction induced by high glucose in rat aortic rings. Increased HO-1 activity and stimulation of GC may be involved in the protective effects of curcumin.

Role of nitrosative stress in the pathogenesis of diabetic vascular dysfunction

Here we overview the role of reactive nitrogen species (nitrosative stress) and associated pathways in the pathogenesis of diabetic vascular complications. Increased extracellular glucose concentration, a principal feature of diabetes mellitus, induces a dysregulation of reactive oxygen and nitrogen generating pathways. These processes lead to a loss of the vascular endothelium to produce biologically active nitric oxide (NO), which impairs vascular relaxations. Mitochondria play a crucial role in this process: endothelial cells placed in increase extracellular glucose respond with a marked increase in mitochondrial superoxide formation. Superoxide, when combining with NO generated by the endothelial cells (produced by the endothelial isoform of NO synthase), leads to the formation of peroxynitrite, a cytotoxic oxidant. Reactive oxygen and nitrogen species trigger endothelial cell dysfunction through a multitude of mechanisms including substrate depletion and uncoupling of endothelial isoform of NO synthase. Another pathomechanism involves DNA strand breakage and activation of the nuclear enzyme poly(ADP-ribose) polymerase (PARP). PARP-mediated poly(ADP-ribosyl)ation and inhibition of glyceraldehyde-3-phosphate dehydrogenase importantly contributes to the development of diabetic vascular complications: it induces activation of multiple pathways of injury including activation of nuclear factor kappa B, activation of protein kinase C and generation of intracellular advanced glycation end products. Reactive species generation and PARP play key roles in the pathogenesis of 'glucose memory' and in the development of injury in endothelial cells exposed to alternating high/low glucose concentrations.