Hyperinsulinemia enhances transcriptional activity of nuclear factor-kappaB induced by angiotensin II, hyperglycemia, and advanced glycosylation end products in vascular smooth muscle cells

Sex-specific association between triglyceride-glucose index and all-cause mortality in patients with osteoporotic fractures: a retrospective cohort study

Background

Osteoporotic fractures (OPFs) pose a considerable global health burden and are linked with an elevated mortality risk. The triglyceride-glucose index (TyG-I) is a recognized marker of insulin resistance across various populations. The association between all-cause mortality (ACM) and the TyG-I has been widely investigated in a variety of clinical settings. The potential sex-specific differences in this association among OPF patients remain uncertain.

Methods

In this retrospective cohort study, 2,307 patients ≥ 50 years old admitted to the hospital between January 2018 and August 2023 for surgical treatment of OPFs were included. The TyG-I was determined using fasting triglyceride and glucose levels measured at admission. The association between ACM and the TyG-I was evaluated by Cox proportional hazards regression, adjusting for possible confounding variables. Analyses were categorized by sex, and subgroup analyses evaluated possible interaction effects. The ACM rates among TyG-I tertiles were compared via Kaplan-Meier curves.

Results

This research study analyzed 2,307 patients, of whom 247 (10.71%) died from any cause during the follow-up period. In females, a linear association of the TyG-I with ACM was observed even after adjusting for confounders, with each unit increase in the TyG-I correlating with a 37% increased risk of death (HR: 1.37, 95% CI: 1.06-1.77, p = 0.02). However, in males, there was a non-linear correlation, where patients in the uppermost TyG-I tertile showed a substantially decreased mortality risk relative to those in the lowest tertile (HR: 0.53, 95% CI: 0.30-0.92, p = 0.02). TyG-I indicated a statistically significant relation with sex (P for interaction = 0.01).

Conclusion

In patients diagnosed with OPFs, distinct sex-specific variations were observed in the relationship between ACM and the TyG-I. Among female patients, each unit increase in the TyG-I was linked to a 37% greater risk of mortality. Conversely, male patients within the highest TyG-I tertile indicated a lower mortality risk than those in the lowest tertile. Further research is required to confirm these sex-specific associations.

Association of Glutathione Peroxidase 3 (GPx3) and miR-196a with Carbohydrate Metabolism Disorders in the Elderly

The escalating prevalence of carbohydrate metabolism disorders (CMDs) prompts the need for early diagnosis and effective markers for their prediction. Hyperglycemia, the primary indicator of CMDs including prediabetes and type 2 diabetes mellitus (T2DM), leads to overproduction of reactive oxygen species (ROS) and oxidative stress (OxS). This condition, resulting from chronic hyperglycemia and insufficient antioxidant defense, causes damage to biomolecules, triggering diabetes complications. Additionally, aging itself can serve as a source of OxS due to the weakening of antioxidant defense mechanisms. Notably, previous research indicates that miR-196a, by downregulating glutathione peroxidase 3 (GPx3), contributes to insulin resistance (IR). Additionally, a GPx3 decrease is observed in overweight/obese and insulin-resistant individuals and in the elderly population. This study investigates plasma GPx3 levels and miR-196a expression as potential CMD risk indicators. We used ELISA to measure GPx3 and qRT-PCR for miR-196a expression, supplemented by multivariate linear regression and receiver operating characteristic (ROC) analysis. Our findings included a significant GPx3 reduction in the CMD patients (n = 126), especially in the T2DM patients (n = 51), and a decreasing trend in the prediabetes group (n = 37). miR-196a expression, although higher in the CMD and T2DM groups than in the controls, was not statistically significant, potentially due to the small sample size. In the individuals with CMD, GPx3 levels exhibited a negative correlation with the mass of adipose tissue, muscle, and total body water, while miR-196a positively correlated with fat mass. In the CMD group, the analysis revealed a weak negative correlation between glucose and GPx3 levels. ROC analysis indicated a 5.2-fold increased CMD risk with GPx3 below 419.501 ng/mL. Logistic regression suggested that each 100 ng/mL GPx3 increase corresponded to a roughly 20% lower CMD risk (OR = 0.998; 95% CI: 0.996-0.999; p = 0.031). These results support the potential of GPx3 as a biomarker for CMD, particularly in T2DM, and the lack of a significant decline in GPx3 levels in prediabetic individuals suggests that it may not serve reliably as an early indicator of CMDs, warranting further large-scale validation.

Free Radicals and Obesity-Related Chronic Inflammation Contrasted by Antioxidants: A New Perspective in Coronary Artery Disease

We are surrounded by factors called free radicals (FR), which attach to the molecules our body is made of, first among them the endothelium. Even though FR are to a certain extent a normal factor, nowadays we face an escalating increase in these biologically aggressive molecules. The escalating formation of FR is linked to the increased usage of man-made chemicals for personal care (toothpaste, shampoo, bubble bath, etc.), domestic laundry and dish-washer detergents, and also an ever wider usage of drugs (both prescription and over the counter), especially if they are to be used long-term (years). In addition, tobacco smoking, processed foods, pesticides, various chronic infectious microbes, nutritional deficiencies, lack of sun exposure, and, finally, with a markedly increasing impact, electromagnetic pollution (a terribly destructive factor), can increase the risk of cancer, as well as endothelial dysfunction, owing to the increased production of FR that they cause. All these factors create endothelial damage, but the organism may be able to repair such damage thanks to the intervention of the immune system supported by antioxidants. However, one other factor can perpetuate the state of inflammation, namely obesity and metabolic syndrome with associated hyperinsulinemia. In this review, the role of FR, with a special emphasis on their origin, and of antioxidants, is explored from the perspective of their role in causing atherosclerosis, in particular at the coronary level.

A high triglyceride-glucose index associated with adverse cardiovascular events in patients with type 2 diabetes mellitus and chronic total occlusion after percutaneous coronary intervention

Triglyceride-glucose index (TyG index) is a reliable surrogate marker of insulin resistance, associated with morbidity and prognosis of cardiovascular disease. However, its predictive value for cardiovascular events in patients with type 2 diabetes mellitus (T2DM) and chronic total occlusion (CTO) after percutaneous coronary intervention (PCI) has not been studied. Here, we retrospectively enrolled 681 patients with T2DM and CTO after PCI. Patients were divided into two groups based on a median TyG index of 9.02. The TyG index was calculated as ln [fasting triglyceride (mg/dL) × fasting glucose (mg/dL)/2]. The primary observational end point was the composite of overall death, nonfatal myocardial infarction, and unplanned revascularization. The Multivariate Cox hazards regression analysis showed that the TyG index was significantly correlated with the primary end point (hazard ratio = 1.699, 95% confidence interval 1.254-2.303, p = 0.001). The addition of TyG to a baseline risk model had an incremental effect on the predictive value for the primary end point (area under the curve: TyG index vs baseline model, 0.693 vs 0.663, comparison p = 0.040; integrated discrimination improvement = 0.049, p = 0.020). The TyG index might be a predictor of adverse cardiovascular events. Moreover, adding the TyG index into a baseline risk model had a cumulative effect on the predictive potential for the primary end point.

DPP4 Activity, Hyperinsulinemia, and Atherosclerosis

CONTEXT

Obesity and type 2 diabetes are associated with chronic hyperinsulinemia, elevated plasma levels of dipeptidyl peptidase-4 (DPP4), and a pro-atherosclerotic milieu.

EVIDENCE ACQUISITION

PubMed search of the term "insulin and atherosclerosis," "hyperinsulinemia," "atherosclerosis," or "cardiovascular outcomes" cross-referenced with "DPP4." Relevant research and review articles were reviewed.

EVIDENCE SYNTHESIS

Hyperinsulinemia in the setting of insulin resistance promotes vascular inflammation, vascular smooth muscle cell growth, pathological cholesterol profile, hypertension, and recruitment of immune cells to the endothelium, all contributing to atherosclerosis. DPP4 has pleiotropic functions and its activity is elevated in obese humans. DPP4 mirrors hyperinsulinemia's atherogenic actions in the insulin resistant state, and genetic deletion of DPP4 protects rodents from developing insulin resistance and improves cardiovascular outcomes. DPP4 inhibition in pro-atherosclerotic preclinical models results in reduced inflammation and oxidative stress, improved endothelial function, and decreased atherosclerosis. Increased incretin levels may have contributed to but do not completely account for these benefits. Small clinical studies with DPP4 inhibitors demonstrate reduced carotid intimal thickening, improved endothelial function, and reduced arterial stiffness. To date, this has not been translated to cardiovascular risk reduction for individuals with type 2 diabetes with prior or exaggerated risk of cardiovascular disease.

CONCLUSION

DPP4 may represent a key link between central obesity, insulin resistance, and atherosclerosis. The gaps in knowledge in DPP4 function and discrepancy in cardiovascular outcomes observed in preclinical and large-scale randomized controlled studies with DPP4 inhibitors warrant additional research.

Insulin Resistance and Atherosclerosis: Implications for Insulin-Sensitizing Agents

Patients with type 2 diabetes mellitus (T2DM) are at high risk for macrovascular complications, which represent the major cause of mortality. Despite effective treatment of established cardiovascular (CV) risk factors (dyslipidemia, hypertension, procoagulant state), there remains a significant amount of unexplained CV risk. Insulin resistance is associated with a cluster of cardiometabolic risk factors known collectively as the insulin resistance (metabolic) syndrome (IRS). Considerable evidence, reviewed herein, suggests that insulin resistance and the IRS contribute to this unexplained CV risk in patients with T2DM. Accordingly, CV outcome trials with pioglitazone have demonstrated that this insulin-sensitizing thiazolidinedione reduces CV events in high-risk patients with T2DM. In this review the roles of insulin resistance and the IRS in the development of atherosclerotic CV disease and the impact of the insulin-sensitizing agents and of other antihyperglycemic medications on CV outcomes are discussed.

Anti-inflammatory Action of Metformin with Respect to CX3CL1/CX3CR1 Signaling in Human Placental Circulation in Normal-Glucose Versus High-Glucose Environments

Upregulation of chemokine CX3CL1 and its receptor CX3CR1 occurs in the diabetic human placenta. Metformin, an insulin-sensitizing biguanide, is used in the therapy of diabetic pregnancy. By preventing the activation of NF-κB, metformin exhibits anti-inflammatory properties. We examined the influence of hyperglycemia (25 mmol/L glucose; HG group; N = 36) on metformin-mediated effects on CX3CL1 and TNF-α production by placental lobules perfused extracorporeally. Additionally, CX3CR1 expression and contents of CX3CR1, TNF-α receptor 1 (TNFR1), and NF-κB proteins in the placental tissue were evaluated. Placentae perfused under normoglycemia (5 mmol/L glucose; NG group; N = 36) served as the control. Metformin (2.5 and 5.0 mg/L; subgroups B and C) lowered the production of CX3CL1 and TNF-α in a dose-dependent and time-dependent manner. Hyperglycemia did not weaken the strength of these metformin effects. Moreover, CX3CL1 levels after perfusion with 5.0 mg/L metformin were reduced by 33.28 and 33.83% (at 120 and 150 min, respectively) in the HG-C subgroup versus 24.98 and 23.66% in the NG-C subgroup, which indicated an augmentation of the metformin action over time in hyperglycemia. CX3CR1 expression was significantly higher in the HG-B and HG-C subgroups compared to that in the NG-B and NG-C subgroups. Increased CX3CR1 protein content in the placental lysates was observed in subgroups B and C. The two higher metformin concentrations significantly decreased the levels of NF-κBp65 protein content in both groups. However, the decrease was significantly stronger in hyperglycemia. TNFR1 upregulation in the HG group was not affected by metformin. Further studies on metformin therapy during pregnancy are needed, including safety issues.

High Glucose Level Disturbs the Resveratrol-Evoked Curtailment of CX3CL1/CX3CR1 Signaling in Human Placental Circulation

Hyperglycemia-induced hyperactivity of chemokine CX3CL1 (fractalkine) occurs in the human placenta. Anti-inflammatory/antioxidant activities of resveratrol (3,5,4'-trihydroxy-trans-stilbene) are related to the modulation of chemokine CX3CL1 and its receptor, CX3CR1, signaling pathways. We examined the influence of high glucose (25 mmol/L glucose; HG group; N = 36) on resveratrol-mediated effects on CX3CL1 and TNF-α production by the placental lobule, CX3CR1 expression and contents of CX3CR1, TNF-α receptor 1 (TNFR1), and NF-κB proteins in placental tissue. The placental lobules perfused under normoglycemic conditions formed the control NG group (N = 36). Resveratrol (50 and 100 μM; subgroups B and C) administered into the perfusion fluid lowered the production of both CX3CL1 and TNF-α. The reductions in CX3CL1 levels were more evident in the NG group. CX3CR1 expression was significantly higher in the NG subgroups B and C compared to the HG subgroups B and C (385.2 and 426.5% versus 199.3 and 282.4%, resp.). An increase in CX3CR1 protein content in placental lysates was observed in the NG subgroups B and C. Also, resveratrol significantly decreased NF-κBp65 protein content only in the NG group, not affecting hyperglycemia-elicited TNFR1 upregulation. In conclusion, euglycemia assures optimal effects of resveratrol pertaining to CX3CL1/CX3CR1 signaling in the placenta. Future studies on resveratrol are needed, especially those including maternal-fetal risk assessments.

miR-146a regulates glucose induced upregulation of inflammatory cytokines extracellular matrix proteins in the retina and kidney in diabetes

Hyperglycemic damage to the endothelial cells (ECs) leads to increased synthesis of inflammatory cytokines. We have previously shown miR-146a downregulation in ECs and in the tissues of diabetic mice. Here we investigated the role of miR-146a, in the production of specific inflammatory cytokines and extracellular matrix (ECM) proteins in retina and kidneys in diabetes. We generated an endothelial specific miR-146a overexpressing transgenic mice (TG). We investigated these mice and wild type (WT) controls with or without streptozotocin (STZ) induced diabetes. Retinal and renal cortical tissues from the mice were examined for mRNAs for specific inflammatory markers, (ECM) proteins and inflammation inducible transcription factor by real time RT-PCR. Corresponding proteins, where possible, were examined using immunofluorescence or ELISA. In parallel, we examined ECs following incubation with various levels of glucose with or without miR-146a mimic transfection. In the retina and kidneys of WT mice with diabetes, increased expression of inflammatory markers (IL-6, TNFα, IL1β) in association augmented expression of ECM proteins (collagen 1αIV, fibronectin) and NF κB-P65 were observed, compared to WT non-diabetic controls. These changes were prevented in diabetic miR-146a TG mice along with retinal and renal functional and structural changes. In vitro studies showed similar changes in the ECs exposed to high glucose. Such changes were corrected in the cells following miR-146a mimic transfection. Further analyses of renal cortical tissues showed diabetes induced significant upregulation of two regulators of NFκB, namely Interleukin-1 associated Kinase 1 and tumour necrosis factor receptor associated factor. Such changes were prevented in diabetic TG animals. These data indicate that augmented production of inflammatory cytokines and ECM proteins in the retina and kidneys in diabetes are regulated through endothelium derived miR-146a. Identification of such novel mechanisms may potentially lead to the development of novel therapies.

Latent Inflammation and Insulin Resistance in Adipose Tissue

Obesity is a growing problem in modern society and medicine. It closely associates with metabolic disorders such as type 2 diabetes mellitus (T2DM) and hepatic and cardiovascular diseases such as nonalcoholic fatty liver disease, atherosclerosis, myocarditis, and hypertension. Obesity is often associated with latent inflammation; however, the link between inflammation, obesity, T2DM, and cardiovascular diseases is still poorly understood. Insulin resistance is the earliest feature of metabolic disorders. It mostly develops as a result of dysregulated insulin signaling in insulin-sensitive cells, as compared to inactivating mutations in insulin receptor or signaling proteins that occur relatively rare. Here, we argue that inflammatory signaling provides a link between latent inflammation, obesity, insulin resistance, and metabolic disorders. We further hypothesize that insulin-activated PI3-kinase pathway and inflammatory signaling mediated by several IκB kinases may constitute negative feedback leading to insulin resistance at least in the fat tissue. Finally, we discuss perspectives for anti-inflammatory therapies in treating the metabolic diseases.

Blood glucose control using a computer-guided glucose management system in allogeneic hematopoietic cell transplant recipients

Allogeneic hematopoietic cell transplantation (HCT) is a potentially curative treatment for patients with hematological malignancies. However, is associated with substantial rates of morbidity and mortality. We and others have shown that malglycemia is associated with adverse transplant outcome. Therefore, improving glycemic control may improve transplant outcome. In this prospective study we evaluated the feasibility of using Glucommander (a Computer-Guided Glucose Management System; CGGM) in order to achieve improved glucose control in hospitalized HCT patients. Nineteen adult patients contributed 21 separate instances on CGGM. Patients were on CGGM for a median of 43 h. Median initial blood glucose (BG) on CGGM was 244 mg/dL, and patients on 20 study instances reached the study BG target of 100-140 mg/dL after a median of 6 h. After BG reached the target range, the median average BG level per patient was 124 mg/dL. Six patients had a total of 10 events of BG <70 mg/dL (0.9% of BG measurements), and no patients experienced BG level <40 mg/dL. The total estimated duration of BG <70 mg/dL was 3 h (0.2% of the total CGGM time). In conclusion, our study demonstrates that stringent BG control in HCT patients using CGGM is feasible.

The Prominent Role of P38 Mitogen-Activated Protein Kinase in Insulin-Mediated Enhancement of VCAM-1 Expression in Endothelial Cells

Insulin levels are a marker for cardiovascular events, but the link between hyperinsulinemia and atherosclerosis is poorly understood. We previously showed that insulin increases monocyte-endothelial interactions and the endothelial expression of the pro-atherogenic vascular cell adhesion molecule-1 (VCAM-1). The aim of this study is to examine molecular mechanisms involved in the effect of insulin on VCAM-1 expression. Human umbilical vein endothelial cells (HUVEC) were incubated with insulin (0–24 h) ± inhibitors of signaling pathways potentially involved. At pathophysiological concentrations (10−9-10−7 M), insulin selectively induced VCAM-1 expression. The p38mitogen activated protein(MAP) kinase inhibitors SB203580 and SB202190, and partially the c-Jun NH2-terminal kinase (JNK) inhibitor SP600127, decreased insulin effect on VCAM-1. Gene silencing by small interfering RNA significantly reduced the expression of p38MAP kinase, and this was accompanied by suppression of insulin-stimulated VCAM-1 expression. Treatment with insulin also led to the activation of NF-κB and induction of IκB-α phosphorylation, thus accounting for NF-κB translocation into the nucleus. Co-treatment of HUVEC with insulin and SB202190 strongly reverted the stimulatory effect of insulin on NF-κB activation, thus establishing a link between NF-κB activation and p38MAPkinase-mediated induction of VCAM-1 by insulin. In conclusion, pathophysiological insulin concentrations increase VCAM-1 expression and activate NF-κB. This mostly occurs through stimulation of p38MAP kinase.

Central obesity, type 2 diabetes and insulin: exploring a pathway full of thorns

The prevalence of type 2 diabetes (T2D) is rapidly increasing. This is strongly related to the contemporary lifestyle changes that have resulted in increased rates of overweight individuals and obesity. Central (intra-abdominal) obesity is observed in the majority of patients with T2D. It is associated with insulin resistance, mainly at the level of skeletal muscle, adipose tissue and liver. The discovery of macrophage infiltration in the abdominal adipose tissue and the unbalanced production of adipocyte cytokines (adipokines) was an essential step towards novel research perspectives for a better understanding of the molecular mechanisms governing the development of insulin resistance. Furthermore, in an obese state, the increased cellular uptake of non-esterified fatty acids is exacerbated without any subsequent β-oxidation. This in turn contributes to the accumulation of intermediate lipid metabolites that cause defects in the insulin signaling pathway. This paper examines the possible cellular mechanisms that connect central obesity with defects in the insulin pathway. It discusses the discrepancies observed from studies organized in cell cultures, animal models and humans. Finally, it emphasizes the need for therapeutic strategies in order to achieve weight reduction in overweight and obese patients with T2D.

Perioperative hyperglycemia and risk of adverse events among patients with and without diabetes

OBJECTIVE

To study the association between diabetes status, perioperative hyperglycemia, and adverse events in a statewide surgical cohort.

BACKGROUND

Perioperative hyperglycemia may increase the risk of adverse events more significantly in patients without diabetes (NDM) than in those with diabetes (DM).

METHODS

Using data from the Surgical Care and Outcomes Assessment Program, a cohort study (2010-2012) evaluated diabetes status, perioperative hyperglycemia, and composite adverse events in abdominal, vascular, and spine surgery at 53 hospitals in Washington State.

RESULTS

Among 40,836 patients (mean age, 54 years; 53.6% women), 19% had diabetes; 47% underwent a perioperative blood glucose (BG) test, and of those, 18% had BG ≥180 mg/dL. DM patients had a higher rate of adverse events (12% vs 9%, P < 0.001) than NDM patients. After adjustment, among NDM patients, those with hyperglycemia had an increased risk of adverse events compared with those with normal BG. Among NDM patients, there was a dose-response relationship between the level of BG and composite adverse events [odds ratio (OR), 1.3 for BG 125-180 (95% confidence interval (CI), 1.1-1.5); OR, 1.6 for BG ≥180 (95% CI, 1.3-2.1)]. Conversely, hyperglycemic DM patients did not have an increased risk of adverse events, including those with a BG 180 or more (OR, 0.8; 95% CI, 0.6-1.0). NDM patients were less likely to receive insulin at each BG level.

CONCLUSIONS

For NDM patients, but not DM patients, the risk of adverse events was linked to hyperglycemia. Underlying this paradoxical effect may be the underuse of insulin, but also that hyperglycemia indicates higher levels of stress in NDM patients than in DM patients.

Type 2 diabetes and cardiovascular disease: Have all risk factors the same strength?

Diabetes mellitus is a chronic condition that occurs when the body cannot produce enough or effectively use of insulin. Compared with individuals without diabetes, patients with type 2 diabetes mellitus have a considerably higher risk of cardiovascular morbidity and mortality, and are disproportionately affected by cardiovascular disease. Most of this excess risk is it associated with an augmented prevalence of well-known risk factors such as hypertension, dyslipidaemia and obesity in these patients. However the improved cardiovascular disease in type 2 diabetes mellitus patients can not be attributed solely to the higher prevalence of traditional risk factors. Therefore other non-traditional risk factors may be important in people with type 2 diabetes mellitus. Cardiovascular disease is increased in type 2 diabetes mellitus subjects due to a complex combination of various traditional and non-traditional risk factors that have an important role to play in the beginning and the evolution of atherosclerosis over its long natural history from endothelial function to clinical events. Many of these risk factors could be common history for both diabetes mellitus and cardiovascular disease, reinforcing the postulate that both disorders come independently from “common soil”. The objective of this review is to highlight the weight of traditional and non-traditional risk factors for cardiovascular disease in the setting of type 2 diabetes mellitus and discuss their position in the pathogenesis of the excess cardiovascular disease mortality and morbidity in these patients.

Diabetes protects from prostate cancer by downregulating androgen receptor: new insights from LNCaP cells and PAC120 mouse model

Type 2 diabetes has been associated with decreased risk of prostate cancer in observational studies, and this inverse association has been recently confirmed in several large cohort studies. However the mechanisms involved in this protective effect remain to be elucidated. The aim of the present study was to explore whether different features of type 2 diabetes (hyperinsulinemia, hyperglycemia and tumor necrosis factor alpha [TNF-α]) protect against the development of prostate cancer. For this purpose LNCaP cells were used for in vitro experiments and nude mice in which PAC120 (hormone-dependent human prostate cancer) xenografts had been implanted were used for in vivo examinations. We provide evidence that increasing glucose concentrations downregulate androgen receptor (AR) mRNA and protein levels through NF-κB activation in LNCaP cells. Moreover, there was a synergic effect of glucose and TNFα in downregulating the AR in LNCaP cells. By contrast, insulin had no effect on AR regulation. In vivo experiments showed that streptozotocin-induced diabetes (STZ-DM) produces tumor growth retardation and a significant reduction in AR expression in PAC120 prostate cancer mice. In conclusion, our results suggest that hyperglycemia and TNF-α play an important role in protecting against prostate cancer by reducing androgen receptor levels via NF-κB.

Epigenetic regulation of vascular smooth muscle cell function in atherosclerosis

Epigenetics involve heritable and acquired changes in gene transcription that occur independently of the DNA sequence. Epigenetic mechanisms constitute a hierarchic upper-level of transcriptional control through complex modifications of chromosomal components and nuclear structures. These modifications include, for example, DNA methylation or post-translational modifications of core histones; they are mediated by various chromatin-modifying enzymes; and ultimately they define the accessibility of a transcriptional complex to its target DNA. Integrating epigenetic mechanisms into the pathophysiologic concept of complex and multifactorial diseases such as atherosclerosis may significantly enhance our understanding of related mechanisms and provide promising therapeutic approaches. Although still in its infancy, intriguing scientific progress has begun to elucidate the role of epigenetic mechanisms in vascular biology, particularly in the control of smooth muscle cell phenotypes. In this review, we will summarize epigenetic pathways in smooth muscle cells, focusing on mechanisms involved in the regulation of vascular remodeling.

Effect of dietary nitrate on blood pressure, endothelial function, and insulin sensitivity in type 2 diabetes

Diets rich in green, leafy vegetables have been shown to lower blood pressure (BP) and reduce the risk of cardiovascular disease. Green, leafy vegetables and beetroot are particularly rich in inorganic nitrate. Dietary nitrate supplementation, via sequential reduction to nitrite and NO, has previously been shown to lower BP and improve endothelial function in healthy humans. We sought to determine if supplementing dietary nitrate with beetroot juice, a rich source of nitrate, will lower BP and improve endothelial function and insulin sensitivity in individuals with type 2 diabetes (T2DM). Twenty-seven patients, age 67.2±4.9 years (18 male), were recruited for a double-blind, randomized, placebo-controlled crossover trial. Participants were randomized to begin, in either order, a 2-week period of supplementation with 250ml beetroot juice daily (active) or 250ml nitrate-depleted beetroot juice (placebo). At the conclusion of each intervention period 24-h ambulatory blood pressure monitoring, tests of macro- and microvascular endothelial function, and a hyperinsulinemic isoglycemic clamp were performed. After 2 weeks administration of beetroot juice mean ambulatory systolic BP was unchanged: 134.6±8.4mmHg versus 135.1±7.8mmHg (mean±SD), placebo vs active-mean difference of -0.5mmHg (placebo-active), p=0.737 (95% CI -3.9 to 2.8). There were no changes in macrovascular or microvascular endothelial function or insulin sensitivity. Supplementation of the diet with 7.5mmol of nitrate per day for 2 weeks caused an increase in plasma nitrite and nitrate concentration, but did not lower BP, improve endothelial function, or improve insulin sensitivity in individuals with T2DM.

Safe insulin use in the hospital setting

Inpatients have a high rate of diabetes (12%-26%) and hyperglycemia (~38%). All patients should have their glycosylated hemoglobin (A1C) checked on admission to help differentiate between long-term and new-onset hyperglycemia. Good glycemic control throughout the hospital stay is associated with decreases in short- and long-term risk of mortality, inpatient complications, length of hospital stay, and health care costs. Insulin is first-line therapy for hyperglycemia; patients with hyperglycemia should be managed using either intravenous (IV) or subcutaneous (SC) insulin algorithms. A hypoglycemia management protocol should be in place at the hospital for safety purposes. For successful glycemic control, insulin algorithms should have dynamic scales, require frequent glucose monitoring, and be simple and easy to use. The algorithm should address transitioning patients from IV to SC insulin and a discharge plan. Insulin analogues are preferred for basal, mealtime, and correction doses instead of human insulins (regular and NPH) because analogues have a more predictable absorption and action profile and less pharmacokinetic fluctuation. Institutions can increase safe insulin use by utilizing insulin algorithms, preprinted order sets, and hypoglycemia protocols; by supporting patient and health care provider education; and by implementing needle-stick prevention techniques.

Motherhood, apple pie, hemoglobin A(1C), and the DCCT

OBJECTIVE

To review recent literature on the limitations of hemoglobin A(1c) (HbA(1c)) as a marker of glycemic control.

METHODS

English-language literature published between 1985 and 2011 was reviewed specific to analyses of major trials relating glycemic control to complications of diabetes mellitus, as expressed through HbA(1c) as a marker of glycemic control.

RESULTS

HbA(1c) has been accepted as the most fundamental biomarker in diabetes, if not all of medicine, as it clearly predicts risk for diabetes-related complications. What is not generally appreciated is that HbA(1c) is a crude marker of glycemia with many limitations. It is now accepted that HbA(1c) does not reflect mean glucose for many people, and even for those it does, any level could represent a wide range of glycemia. While we have learned HbA(1c) is not a perfect biomarker, we also know that in the Diabetes Control and Complications Trial, HbA(1c) could only explain 11% of the variation in retinopathy risk between the conventional and intensive therapy groups. This important finding suggests that other glycemic and nonglycemic factors may be responsible for the pathogenesis of diabetes-related complications. One candidate is glycemic variability, which must be differentiated from postprandial hyperglycemia since hypoglycemia can also result in inflammatory activation. Importantly, although it is clear that in insulin-requiring patients glycemic variability is associated with hypoglycemia, we require a definitive prospective trial to confirm glycemic variability's association with one or more vascular complications.

CONCLUSIONS

What is abundantly clear is that the HbA(1c) message, as we know it, is too simplistic. While certain wholesome concepts such as motherhood and apple pie are accepted by all, the HbA(1c) message may be more complex than originally appreciated, and it may be time to reevaluate our most basic premise in diabetes.

Rosiglitazone attenuates NF-κB-mediated Nox4 upregulation in hyperglycemia-activated endothelial cells

Vascular complications, a major cause of morbidity and mortality in diabetic patients, are related to hyperglycemia-induced oxidative stress. Previously, we reported that rosiglitazone (RSG) attenuated vascular expression and activity of NADPH oxidases in diabetic mice. The mechanisms underlying these effects remain to be elucidated. We hypothesized that RSG acts directly on endothelial cells to modulate vascular responses in diabetes. To test this hypothesis, human aortic endothelial cells (HAECs) were exposed to normal glucose (NG; 5.6 mmol/l) or high glucose (HG; 30 mmol/l) concentrations. Select HAEC monolayers were treated with RSG, caffeic acid phenethyl ester (CAPE), diphenyleneiodonium (DPI), small interfering (si)RNA (to NF-κB/p65 or Nox4), or Tempol. HG increased the expression and activity of the NADPH oxidase catalytic subunit Nox4 but not Nox1 or Nox2. RSG attenuated HG-induced NF-κB/p65 phosphorylation, nuclear translocation, and binding to the Nox4 promoter. Inhibiting NF-κB with CAPE or siNF-κB/p65 also reduced HG-induced Nox4 expression and activity. HG-induced H(2)O(2) production was attenuated by siRNA-mediated knockdown of Nox4, and HG-induced HAEC monocyte adhesion was attenuated by treatment with RSG, DPI, CAPE, or Tempol. These results indicate that HG exposure stimulates HAEC NF-κB activation, Nox4 expression, and H(2)O(2) production and that RSG attenuates HG-induced oxidative stress and subsequent monocyte-endothelial interactions by attenuating NF-κB/p65 activation and Nox4 expression. This study provides novel insights into mechanisms by which the thiazolidinedione peroxisome proliferator-activated receptor-γ ligand RSG favorably modulates endothelial responses in the diabetic vasculature.

Glycemic management in the inpatient setting

Hyperglycemia occurs frequently in hospitalized patients and affects patient outcomes, including mortality, inpatient complications, hospital length of stay, and overall hospital costs. Various degrees of glycemic control have been studied and consensus statements from the American Diabetes Association/American Association of Clinical Endocrinologists and The Endocrine Society recommend a target blood glucose range of 140 to 180 mg/dL in most hospitalized patients. Insulin is the preferred modality for treating all hospitalized patients with hyperglycemia, as it is adaptable to changing patient physiology over the course of hospitalization. Critically ill patients should receive intravenous insulin infusion, and all noncritically ill patients with hyperglycemia (individuals with and without diabetes) should be managed using a subcutaneous insulin algorithm with basal, nutritional, and correctional dose components. Hypoglycemia remains a limiting factor to achieving optimal glycemic targets. Similar to hyperglycemia, hypoglycemia is an independent risk factor for poor outcomes in hospitalized patients. Improvement in glycemic control throughout the hospital includes efforts from all health care providers. Institutions can encourage safe insulin use by using insulin algorithms, preprinted order sets, and hypoglycemia protocols, as well as by supporting patient and health care provider education.

The renin-angiotensin system: a target of and contributor to dyslipidemias, altered glucose homeostasis, and hypertension of the metabolic syndrome

The renin-angiotensin system (RAS) is an important therapeutic target in the treatment of hypertension. Obesity has emerged as a primary contributor to essential hypertension in the United States and clusters with other metabolic disorders (hyperglycemia, hypertension, high triglycerides, low HDL cholesterol) defined within the metabolic syndrome. In addition to hypertension, RAS blockade may also serve as an effective treatment strategy to control impaired glucose and insulin tolerance and dyslipidemias in patients with the metabolic syndrome. Hyperglycemia, insulin resistance, and/or specific cholesterol metabolites have been demonstrated to activate components required for the synthesis [angiotensinogen, renin, angiotensin-converting enzyme (ACE)], degradation (ACE2), or responsiveness (angiotensin II type 1 receptors, Mas receptors) to angiotensin peptides in cell types (e.g., pancreatic islet cells, adipocytes, macrophages) that mediate specific disorders of the metabolic syndrome. An activated local RAS in these cell types may contribute to dysregulated function by promoting oxidative stress, apoptosis, and inflammation. This review will discuss data demonstrating the regulation of components of the RAS by cholesterol and its metabolites, glucose, and/or insulin in cell types implicated in disorders of the metabolic syndrome. In addition, we discuss data supporting a role for an activated local RAS in dyslipidemias and glucose intolerance/insulin resistance and the development of hypertension in the metabolic syndrome. Identification of an activated RAS as a common thread contributing to several disorders of the metabolic syndrome makes the use of angiotensin receptor blockers and ACE inhibitors an intriguing and novel option for multisymptom treatment.

Insulin augments tumor necrosis factor-alpha stimulated expression of vascular cell adhesion molecule-1 in vascular endothelial cells

BACKGROUND

Atherosclerosis is an inflammatory disease that is marked by increased presence of Tumor Necrosis Factor-alpha (TNFα), increased expression of Vascular Cell Adhesion Molecule-1 (VCAM-1), increased presence of serum monocytes and activation of the canonical inflammatory molecule, Nuclear Factor Kappa-B (NFκB). Hyperinsulinemia is a hallmark of insulin resistance and may play a key role in this inflammatory process.

METHODS

Using Western blot analysis, immunocytochemistry, flow cytometry and biochemical inhibitors, we measured changes in VCAM-1 protein expression and NFκB translocation in vascular endothelial cells in the presence of TNFα and/or hyperinsulinemia and in the absence or presence of kinase pathway inhibitors.

RESULTS

We report that hyperinsulinemia augmented TNFα stimulated increases in VCAM-1 protein greater than seen with TNFα alone and decreased the time in which VCAM-1 translocated to the cell surface. We also observed that in the presence of Wortmannin, a biochemical inhibitor of phosphatidylinositol 3-kinase (a hallmark of insulin resistance), VCAM-1 expression was greater in the presence of TNFα plus insulin as compared to that seen with insulin or TNFα alone. Additionally, nuclear import of NFκB occurred sooner in the presence of insulin and TNFα together as compared to each alone, and in the presence of Wortmannin, nuclear import of NFκB was greater than that seen with insulin and TNFα alone.

CONCLUSIONS

hyperinsulinemia and insulin resistance appear to augment the inflammatory effects of TNFα on VCAM-1 expression and NFκB translocation, both of which are markers of inflammation in the vasculature.

ERK5: a novel IKKα-kinase in rat hippocampal neurons

BACKGROUND

Alzheimer's Disease (AD) is characterized in part by the increased presence of neurofibrillary tangles and amyloid beta (Aβ) plaques. Alzheimer's Disease is considered an inflammatory disease and, as such, nuclear factor-kappaB (NFκB) plays an important role in the pathophysiology of AD. Insulin acts as a neurotrophic factor. Yet, in the context of insulin resistance, concomitant hyperinsulinemia may contribute to the pathogenesis of AD.

METHODS

Rat Primmary Hippocampal Neurons (RPHN) were treated with insulin in the absence and presence of Wortmannin and ERK5 small inhibitory RNA and assayed for downstream effectors of activated ERK5.

RESULTS

Here we demonstrate that genetic inhibition of ERK5 blocks insulin stimulated (1) activation and translocation of ERK5 and NFκB, (2) phosphorylation of IKKα via association with ERK5, (3) increases in Aβ1-40 and Aβ1-42 soluble proteins 3-fold and 2.2-fold, respectively, and (4) increases in tau phosphorylation in RPHN.

CONCLUSIONS

ERK5 plays an active role in insulin signaling in neurons and may be a potential therapeutic target for neurodegenerative diseases.

Involvement of membrane type 1-matrix metalloproteinase (MT1-MMP) in RAGE activation signaling pathways

An advanced glycation end products (AGE)/a receptor for AGE (RAGE) axis plays a key role in diabetic vascular complications. Membrane type 1-matrix metalloproteinase (MT1-MMP) has been shown to function not only as a proteolytic enzyme but also as a signaling molecule. In this study, we investigated the role of MT1-MMP in the AGE/RAGE-triggered signaling pathways in cultured rabbit smooth muscle cells (SMCs) and the molecular interaction between RAGE and MT1-MMP in vitro and in vivo. In SMCs, AGE-activated Rac1 and p47(phox) within 1 min, NADPH oxidase activity and reactive oxygen species (ROS) generation within 5 min, and NF-κB phosphorylation within 15 min, thereby inducing redox-sensitive molecular expression. Silencing of RAGE by small-interfering RNA (siRNA) blocked the AGE-induced signaling pathways. AGE-induced geranylgeranyl transferase I (GGTase I) activity, Rac1·p47(phox) activation, NADPH oxidase activity, ROS generation, and molecular expression were also markedly attenuated by silencing of MT1-MMP. An inhibitor of GGTase I mimicked the effects of MT1-MMP-specific siRNA. Fluorescent immunohistochemistry revealed that MT1-MMP was partially co-localized with RAGE in SMCs, and RAGE was found to form a complex with MT1-MMP in both cultured SMCs and the aortae of diabetic rats by immunoprecipitation. Furthermore, MT1-MMP and RAGE formed a complex in the aortic atherosclerotic lesions of hyperlipidemic rabbits. We show that MT1-MMP plays a crucial role in RAGE-activated NADPH oxidase-dependent signaling pathways and forms a complex with RAGE in the vasculature, thus suggesting that MT1-MMP may be a novel therapeutic target for diabetic vascular complications.

Cellular and molecular mechanisms of vascular injury in diabetes--part I: pathways of vascular disease in diabetes

Diabetes-induced micro- and macrovascular complications are the major causes of morbidity and mortality in diabetic patients. While hyperglycemia is a key factor for the pathogenesis of diabetic microvascular complications, it is only one of the multiple factors capable of increasing the risk of macrovascular complications. Hyperglycemia induces vascular damage probably through a single common pathway - increased intracellular oxidative stress - linking four major mechanisms, namely the polyol pathway, advanced glycation end-products (AGEs) formation, the protein kinase C (PKC)-diacylglycerol (DAG) and the hexosamine pathways. In addition, in conditions of insulin resistance, i.e., preceding the onset of type 2 diabetes, the phosphatidylinositol (PI) 3-kinase (PI3K)/Akt pathway is selectively inhibited, while the mitogen activated protein (MAP)-kinase pathway remains largely unaffected, thus allowing compensatory hyperinsulinemia to elicit pro-atherogenic events in vascular smooth muscle and endothelial cells, including increased cell proliferation, and the expression of plasminogen activator inhibitor-1, as well as of proinflammatory cytokines and endothelial adhesion molecules.

Insulin resistance, lipotoxicity, type 2 diabetes and atherosclerosis: the missing links. The Claude Bernard Lecture 2009

Insulin resistance is a hallmark of type 2 diabetes mellitus and is associated with a metabolic and cardiovascular cluster of disorders (dyslipidaemia, hypertension, obesity [especially visceral], glucose intolerance, endothelial dysfunction), each of which is an independent risk factor for cardiovascular disease (CVD). Multiple prospective studies have documented an association between insulin resistance and accelerated CVD in patients with type 2 diabetes, as well as in non-diabetic individuals. The molecular causes of insulin resistance, i.e. impaired insulin signalling through the phosphoinositol-3 kinase pathway with intact signalling through the mitogen-activated protein kinase pathway, are responsible for the impairment in insulin-stimulated glucose metabolism and contribute to the accelerated rate of CVD in type 2 diabetes patients. The current epidemic of diabetes is being driven by the obesity epidemic, which represents a state of tissue fat overload. Accumulation of toxic lipid metabolites (fatty acyl CoA, diacylglycerol, ceramide) in muscle, liver, adipocytes, beta cells and arterial tissues contributes to insulin resistance, beta cell dysfunction and accelerated atherosclerosis, respectively, in type 2 diabetes. Treatment with thiazolidinediones mobilises fat out of tissues, leading to enhanced insulin sensitivity, improved beta cell function and decreased atherogenesis. Insulin resistance and lipotoxicity represent the missing links (beyond the classical cardiovascular risk factors) that help explain the accelerated rate of CVD in type 2 diabetic patients.

Metabolic memory and diabetic nephropathy: potential role for epigenetic mechanisms

Many clinical studies have shown that intensive glycemic control in patients with diabetes can reduce the incidence and progression of diabetic nephropathy and can also reduce the incidence of other complications. These beneficial effects persist after patients return to usual (often worse) glycemic control. The Diabetes Control and Complications Trial was the first to refer to this phenomenon as 'metabolic memory'. Many patients with diabetes, however, still develop diabetic nephropathy despite receiving intensified glycemic control. Preliminary work in endothelial cells has shown that transient episodes of hyperglycemia can induce changes in gene expression that are dependent on modifications to histone tails (for example, methylation), and that these changes persist after return to normoglycemia. The persistence of such modifications cannot yet be fully explained, but certain epigenetic changes, as well as biochemical mechanisms such as advanced glycation, may provide new and interesting clues towards explaining the pathogenesis of this phenomenon. Further elucidation of the molecular events that enable prior glycemic control to result in end-organ protection in diabetes may lead to the development of new approaches for reducing the burden of diabetic nephropathy.

Insulin-like growth factor-1 receptor expression masks the antiinflammatory and glucose uptake capacity of insulin in vascular smooth muscle cells

OBJECTIVE

Insulin resistance of vascular smooth muscle cells (VSMCs) has been linked to accelerated atherosclerosis in diabetes; however, the effects of insulin on VSMCs remain controversial. Most VSMC insulin receptors are sequestered into insulin-insensitive hybrids with insulin-like growth factor-1 receptors (IGF1Rs). Thus we hypothesized that regulation of IGF1R expression may impact cellular insulin sensitivity.

METHODS AND RESULTS

IGF1R expression was increased in aortas from diabetic mice. IGF1R overexpression in VSMCs impaired insulin-induced Akt phosphorylation. Conversely, IGF1R downregulation by siRNA allowed assembly of insulin holoreceptors, enhanced insulin-induced phosphorylation of its receptor, Akt, Erk1/2, and further augmented insulin-induced glucose uptake. IGF1R downregulation uncovered an insulin-induced reduction in activation of NF-kappaB and inhibition of MCP-1 upregulation in response to TNF-alpha.

CONCLUSIONS

Downregulation of IGF1R increases the fraction of insulin receptors organized in holoreceptors, which leads to enhanced insulin signaling and unmasks potential antiinflammatory properties of insulin in VSMCs. Therefore, IGF1R, which is susceptible to feedback regulation by its own ligand, may represent a novel target for interventions designed to treat insulin resistance in the vasculature.

Insulin potentiates cytokine-induced VCAM-1 expression in human endothelial cells

Hyperinsulinemia is an independent risk factor for cardiovascular events and may contribute to cardiovascular disease. Low-grade chronic inflammation has been implicated in the pathogenesis of atherosclerosis. We aimed at determining the impact of pathophysiologically high insulin concentrations on cytokine-induced endothelial activation in human umbilical vein endothelial cells (HUVEC). HUVEC were incubated with insulin (0-24 h)+/-tumor necrosis factor (TNF)-alpha or lipopolysaccharide (LPS). At pathophysiological/pharmacological concentrations (10(-9)-10(-7) mol/L), insulin selectively induced VCAM-1 expression and potentiated the effects of TNF-alpha andLPS, effects reverted by the proteasome inhibitor lactacystin. Compared with TNF-alpha alone, insulin+TNF-alpha doubled U937 cell adhesion. Insulin markedly increased TNF-alpha-induced NF-kappaB activation and induced phosphorylated IkappaB-alpha accumulation. Therefore, hyperinsulinemia enhances cytokine-induced VCAM-1 expression in endothelial cells, thus potentially contributing to detrimental effects of other inflammatory stimuli on atherogenesis.

The deleterious effect of high concentrations of D-glucose requires pro-inflammatory preconditioning

OBJECTIVES

The present study investigated whether high concentrations of D-glucose can trigger pro-inflammatory mechanisms in human aortic smooth muscle cells.

METHODS

The expression and/or the activity of inducible nitric oxide synthase (iNOS), the extracellular signal-regulated kinase (ERK) 1/2 and nuclear factor (NF)-kappaB were studied in cultured human aortic smooth muscle cells (HASMC) in response to increasing concentrations of D-glucose and/or the inflammatory cytokine interleukin (IL)-1beta.

RESULTS

Increasing D-glucose in the medium from 5.5 to 22 mmol/l had no effect on any of these parameters. However, the high concentration of D-glucose did increase iNOS expression in response to low concentrations of IL-1beta (2.5 and 5 ng/ml), as well as the IL-1beta-induced activation of both ERK 1/2 and NF-kappaB. D-glucose also enhanced, concentration-dependently, the expression and activity of iNOS induced by co-incubation with IL-1beta (10 ng/ml). Pretreatment with IL-1beta sensitized the cells to the subsequent effects of high D-glucose.

CONCLUSIONS

The results indicate that high concentrations of D-glucose exacerbate the pro-inflammatory effects of IL-1beta. We suggest that the observed association between inflammation and diabetes is the result of elevated D-glucose enhancing a pre-existing inflammatory condition, rather than a direct effect of D-glucose on the production of inflammatory mediators.

Modulation of CD36 protein expression by AGEs and insulin in aortic VSMCs from diabetic and non-diabetic rats

BACKGROUND AND AIM

In type 2 diabetes, the interplay between cells and inflammatory mediators up-regulates CD36 expression in macrophages. The aim of this work was to investigate advanced glycation end products (AGE)-induced CD36 expression and its regulation by insulin in aortic vascular smooth muscle cells (VSMCs) from Goto-Kakisaki (GK) rats, a non-obese insulin model of both insulin resistance and type 2 diabetes. The context of overexpression of CD36 in aortas was also evaluated.

METHODS AND RESULTS

VSMCs were isolated and cultured from the aortas of GK rats and non-diabetic rats. The expression of proteins was evaluated by Western blot. The aortic production of superoxide anion (O(2)(.-)) was measured by luminescence on isolated tissue. AGEs and advanced oxidation protein products (AOPPs) were determined in plasma by fluorescence spectroscopy and spectrophotometry, respectively. AGE receptor (RAGE), NF-kappaB, and CD36 protein expression as well as O(2)(.-) production were higher in GK aortas than in control aortas, and AGEs and AOPPs were higher in GK plasma. In VSMCs from non-diabetic rats, insulin was able to reduce (10 nM) or suppress (100 nM) the protein overexpression of CD36 induced by AGEs-BSA. In contrast, in VSMCs from GK rats, insulin was unable to reduce AGEs-BSA-induced CD36 overexpression.

CONCLUSIONS

The results suggest an overexpression of CD36 in VSMCs from GK rats and impaired control by insulin. In the context of increased plasma AGEs, aortic RAGE overexpression and increased oxidative stress markers, the data are compatible with an AGEs induced CD36 overexpression in diabetes.

Inpatient diabetes: review of data from the cardiac care unit

OBJECTIVE

To review prospective and retrospective studies in an effort to assess the effect of glucose control on outcomes in critically ill populations.

METHODS

Results from recent prospective and retrospective studies are presented and analyzed in detail, with an emphasis on patients with myocardial infarction.

RESULTS

Retrospective observations show that, with the routine use of percutaneous coronary interventions, hyperglycemia continues to be a risk factor for mortality. In 2 prospective studies using glucose-insulin-potassium infusion, glucose levels did not reach target, and the results of both trials were negative with regard to the primary endpoint, mortality. However, progressive hyperglycemia was a risk factor for death in both prospective studies. It is an interesting paradox that diabetes actually may be protective for myocardial infarction. Although the reasons for this are not clear, one study showed that patients with diabetes were more likely to receive insulin for any given blood glucose level.

CONCLUSION

A study using variable-rate intravenous insulin infusion should be commissioned. In the meantime, clinicians should strive to achieve the best-possible glucose control in all patients with acute myocardial infarction and hyperglycemia. While we improve our understanding of the basic roles of glucose and insulin in modulating inflammation, we must aggressively treat hyperglycemia to the national goals for this population, which would substantially improve outcomes.

Atherosclerosis in diabetes and insulin resistance

Atherosclerosis and cardiovascular disease are the major causes of morbidity and mortality in patients with diabetes and those with insulin resistance and the metabolic syndrome. Both conditions profoundly accelerate the development of atherosclerosis and increase the morbidity and mortality of cardiovascular events. The question, therefore, is what are the molecular/biochemical mechanisms that underlie the potentiating influence of diabetes, the metabolic syndrome and/or insulin resistance on the development and progression of atherosclerosis? The following review will focus on the molecular mechanism whereby hyperglycaemia and/or hyperinsulinemia either directly or indirectly promote atherosclerosis.

Effects of insulin dependence on inflammatory process, thrombotic mechanisms and endothelial function, in patients with type 2 diabetes mellitus and coronary atherosclerosis

BACKGROUND

Type 2 diabetes mellitus (T2DM) is characterized by endothelial dysfunction, increased thrombogenicity and abnormal inflammatory response.

HYPOTHESIS

We hypothesizsed that insulin dependence/exogenous insulin administration may affect thrombotic/inflammatory status and endothelial function in patients with T2DM and coronary artery disease (CAD).

METHODS

Fifty-five patients with T2DM + CAD (26 insulin-treated (INS) and 29 under oral biguanide + sulphonylurea (TABL)) were recruited. Endothelial function was assessed by gauge-strain plethysmography, and serum levels of inflammatory and thrombotic markers were determined by enzyme linked immunosorbent assay.

RESULTS

There was no significant difference in endothelium-dependent dilation (EDD) between the study groups, while EDD was correlated with fasting glucose levels in both INS (r = - 0.776, p = 0.0001) and TABL (r = - 0.702, p = 0.0001). Patients in INS group had higher levels of interleukin-6 (IL-6), tumor necrosis factor alpha (TNF-alpha), monocyte chemoattractant protein (MCP-1) and vascular cell adhesion molecule (sVCAM-1), compared to TABL. However, TNF-alpha was negatively correlated with protein C (PrtC) only in INS (r = - 0.726, p = 0.01) but not in TABL group (r = - 0.066, p = 0.738). Similarly, sVCAM-1 was correlated with PrtC only among INS patients (r = - 0.451, p = 0.046) but not in TABL (r = 0.069, p = 0.727). In multivariate analysis, insulin dependence was a predictor of IL-6, TNF-alpha, MCP-1 and sVCAM-1 levels independently from the patients' demographic characteristics, the angiographic extend of CAD or the duration of diabetes.

CONCLUSIONS

Insulin treatment in patients with type 2 diabetes mellitus affects the expression of inflammatory cytokines and subsequently modifies the thrombotic mechanisms in patients with coronary atherosclerosis, independently from the duration of diabetes and the extend of coronary artery disease.

Angiotensin II type 1 receptor blockade improves hyperglycemia-induced endothelial dysfunction and reduces proinflammatory cytokine release from leukocytes

Angiotensin II and glucose share components of their intracellular redox signaling pathways in endothelial and inflammatory cells. We hypothesized that valsartan, an angiotensin II blocker, attenuates hyperglycemia-induced endothelial dysfunction and downregulates release of proinflammatory cytokines from leukocytes. A sustained hyperglycemic clamp (12 mmol/L) to induce endothelial dysfunction was performed in healthy volunteers before and after 4 weeks of treatment with 160 mg of valsartan. Brachial artery flow-mediated vasodilation (FMD), lipopolysaccharide-induced release of interleukin-6 and TNF-alpha from peripheral blood leukocytes ex vivo, and circulating proinflammatory cytokines were determined before and during the clamp. The hyperglycemic clamp induced a decrease in FMD from 9.2 +/- 0.8 (t = 0 hr) to 4.4+/- 0.5 (t = 2 hr), 3.8 +/- 0.5 (t = 4 hr), and 4.8 +/- 0.5% (t = 22 hr) during the clamp. Valsartan attenuated endothelial dysfunction [FMD 7.0 +/- 0.7 (t = 2 hr), 6.1 +/- 0.7 (t = 4 hr), 6.2 +/- 0.6% (t = 22 hr); P < 0.005] and decreased the release of interleukin-6 and TNF-alpha from leukocytes both before and during the clamp (P < 0.05). Valsartan improves hyperglycemia-induced endothelial dysfunction and reduces the cytokine response to an inflammatory stimulus. A pathophysiological link between the effects of hyperglycemia and the renin-angiotensin system on endothelium and peripheral blood leukocytes may underlie the beneficial effects of inhibitors of the renin-angiotensin system on cardiovascular outcome in patients with diabetes mellitus.

[Insulin and angiotensin II signaling pathways cross-talk: implications with the association between diabetes mellitus, arterial hypertension and cardiovascular disease]

Insulin (Ins) and angiotensin II (AII) play pivotal roles in the control of two vital and closely related systems: the metabolic and the circulatory, respectively. A failure in the proper action of each of these hormones results, to a variable degree, in the development of two highly prevalent and commonly overlapping diseases--diabetes mellitus (DM) and hypertension (AH). In recent years, a series of studies has revealed a tight connection between the signal transduction pathways that mediate Ins and AII actions in target tissues. This molecular cross-talk occurs at multiple levels and plays an important role in phenomena that range from the action of anti-hypertensive drugs to cardiac hypertrophy and energy acquisition by the heart. At the extracellular level, the angiotensin-converting enzyme controls AII synthesis but also interferes with Ins signaling through the proper regulation of AII and the accumulation of bradykinin. At an early intracellular level, AII, acting through JAK-2/IRS-1/PI3-kinase, JNK and ERK, may induce the serine phosphorylation and inhibition of key elements of the Ins-signaling pathway. Finally, by inducing the expression of the regulatory protein SOCS-3, AII may impose a late control on the Ins signal. This review will focus on the main advances obtained in this field and will discuss the implications of this molecular cross-talk in the common clinical association between DM and AH.

Achieving durable glucose control in the intensive care unit without hypoglycaemia: a new practical IV insulin protocol

BACKGROUND

Hyperglycaemia occurs in a substantial portion of critically ill patients in our intensive care units. Near normalization of elevated blood glucose levels with IV insulin may improve outcome. However, currently published IV insulin protocol are not ideal; most are relatively complex and often result in hypoglycaemia. We designed a protocol that would be practical to use while incorporating the necessary complexities required to achieve good glucose control, coupled with a low incidence hypoglycaemia.

METHODS

The essential part of the protocol is a matrix specifying the amount by which an insulin flow rate is to be changed. The intersection of the current and the previous blood glucose values on the matrix locates the appropriate cell containing the required change in insulin flow rate. No additional calculations or tables are required.

RESULTS

The initial glucose level obtained by blood glucose meter (BGM) averaged 253.5 +/- 95.6 mg/dL and fell below 140 within 9.3 h on the protocol. The average BGM on the protocol was 133.5 +/- 43.9 mg/dL. Only 0.09% of all glucose values were <40 mg/dL and insulin had to be held only 2.2% of the time on the protocol. Physician input was not required and nursing accuracy in applying the protocol was greater than 94%. This protocol has been adopted as the default IV insulin protocol for the NorthShore-LIJ Health System and several other medical centers.

CONCLUSION

A practical IV insulin protocol that has been extensively tested is presented. The protocol has been implemented at multiple institutions indicating its ease of use and excellent results.

Monocyte chemoattractant protein-1--a major contributor to the inflammatory process associated with diabetes

There is evidence that strongly suggests that inflammation plays an important role in diabetes and cardiovascular diseases. The high glucose-induced inflammatory process is characterised by the cooperation of a complex network of inflammatory molecules such as cytokines, adhesion molecules, growth factors, and chemokines. Among the chemokine family, monocyte chemoattractant protein (MCP-1) is a potent chemotactic factor, which is upregulated at sites of inflammation being in control of leukocytes trafficking. Here, we review the current knowledge on MCP-1 and its regulation by high glucose level in vascular cells involved in diabetes-induced accelerated atherosclerosis. The signalling pathways involved in MCP-1 modulation by high glucose, the proximal signalling events that stimulate downstream effects and the role of this chemokine in the pathophysiology of diabetes and its complications, are discussed.

Percutaneous coronary revascularization in diabetics: from balloon angioplasty to drug-eluting stents

Diabetic patients may have aggressive coronary disease with an excessive rate of restenosis and accelerated atherosclerotic progression. This article reviews the different modalities of percutaneous treatment and their results in the diabetic population, from the early days of balloon angioplasty to the current implementation of drug-eluting stents. As restenosis may be virtually eradicated in the near future, plaque progression remains the cornerstone for interventional cardiologists and the medical community. In this regard, attempts to modify life habits, and a more accurate control of the components of the metabolic syndrome should be the main therapeutic objective.

The role of insulin therapy in critically ill patients

Protracted critically ill patients have a seriously deranged metabolism, characterized by severe hyperglycemia, a disturbed serum lipid profile, and protein hypercatabolism. The severity of stress-induced hyperglycemia and insulin resistance in critically ill patients reflect the risk of death. A large, prospective, randomized, controlled study showed that maintaining normoglycemia with intensive insulin therapy reduces morbidity and mortality of surgical intensive care patients. These results were recently confirmed by two studies: one randomized controlled study of surgical intensive care patients and a prospective observational study of a heterogeneous patient population admitted to a mixed medical/surgical intensive care unit. The clinical benefits of intensive insulin therapy appear to be related both to prevention of glucose toxicity and to other direct insulin actions that are independent of glycemic control. Prevention of the toxic effects of high circulating glucose levels protected the ultrastructure and function of hepatocyte mitochondria. Benefits of the non-glycemic effects of insulin included partial correction of the deranged serum lipid profile and possibly counteraction of the catabolic state. In addition to its metabolic effects, intensive insulin therapy also prevented excessive inflammation and improved immune function.

The multi-faceted cross-talk between the insulin and angiotensin II signaling systems

Insulin and angiotensin II are hormones that play pivotal roles in the control of two vital and closely related systems, the metabolic and the circulatory systems, respectively. A failure in the proper action of each of these hormones results, to a variable degree, in the development of two highly prevalent and commonly overlapping diseases-diabetes mellitus and hypertension. In recent years, a series of studies has revealed a tight connection between the signal transduction pathways that mediate insulin and angiotensin II actions in target tissues. This molecular cross-talk occurs at multiple levels and plays an important role in phenomena that range from the action of anti-hypertensive drugs to cardiac hypertrophy and energy acquisition by the heart. At the extracellular level, the angiotensin-converting enzyme controls angiotensin II synthesis but also interferes with insulin signaling through the proper regulation of angiotensin II and through the accumulation of bradykinin. At an early intracellular level, angiotensin II, acting through JAK-2/IRS-1/PI3-kinase, JNK and ERK, may induce the serine phosphorylation and inhibition of key elements of the insulin-signaling pathway. Finally, by inducing the expression of the regulatory protein SOCS-3, angiotensin II may impose a late control on the insulin signal. This review will focus on the main advances obtained in this field and will discuss the implications of this molecular cross-talk in the common clinical association between diabetes mellitus and hypertension.

[Endothelial dysfunction in patients with diabetes: identification, pathogenesis and treatment]

Cardiovascular diseases are the leading cause of morbidity and mortality in people with diabetes. Vascular abnormalities can be observed long before atherosclerosis develops and in sites not usually prone to atherosclerosis. These vascular abnormalities are known to be due to endothelial dysfunctions, one of the most frequent of which is depressed endothelium-dependent dilation. In patients with diabetes, this is mainly linked to decreased bioavailability of nitric oxide. Although inactivation of tetrahydrobiopterin, a co-factor of NO-synthase, may depress nitric oxide production, the latter is more likely due to the inactivation of nitric oxide by superoxide anions: enhanced oxidative stress increases their production in people with diabetes. Moreover, hyperglycemia directly activates oxidative stress, which in turn depresses endothelium-dependent vasodilation. Glycemia and oxidative stress are positively correlated in people with diabetes. However, while depression of endothelium-dependent dilation may be a visible functional manifestation of oxidative stress, the oxidative stress itself is mainly responsible for the cascade of endothelial events that play a key role in development of vascular atherosclerosis and its complications. Especially important among these events are the activation of NF-kappaB and the oxidation of LDL-cholesterol. Although antioxidants provide short-term improvement of endothelial function in humans, all studies of the effectiveness of preventive antioxidant therapy have been disappointing. Control of hyperglycemia thus remains the best way to improve endothelial function and to prevent atherosclerosis and other cardiovascular complications of diabetes.

Growth factor receptor-protein bound 2 (GRB2) upregulation in the placenta in preeclampsia implies a possible role for ras signalling

OBJECTIVES

To screen for genes with altered expression in placentas from pregnancies complicated by preeclampsia.

STUDY DESIGN

To corroborate gene expression profile of preeclamptic and normal placentas (ATLAS Clontech), by dot blot, Northern blot analysis and RT-PCR for growth factor receptor bound-protein 2 (GRB2), using immunohistochemistry to localize its expression in the placenta.

RESULTS

Increased expression of GRB2 upregulated in the microarrays was found in preeclampsia by Dot blot and Northern blot analysis. RT-PCR performed with primers specific for GRB2 and its alternatively spliced isoform GRB3-3 showed that most of the cDNA represented in the array was GRB2. The protein was localized to the smooth muscle wall of stem vessels by immunohistochemistry.

CONCLUSION

The ras signalling activated by placental receptor tyrosine kinases may play a role in the segmental thickening of the stem vascular wall in preeclamptic placentas, resulting in reduced blood flow to the developing fetus.

Insulin alters nuclear factor-κB and peroxisome proliferator-activated receptor-γ protein expression induced by glycated bovine serum albumin in vascular smooth-muscle cells

In both type 2 diabetes and insulin-resistance syndromes, hyperglycemia and advanced glycation end products (AGEs) activate the transcription factor nuclear factor-kappaB (NF-kappaB) through a mechanism that partly involves the generation of reactive oxygen species (ROS). The contribution of hyperinsulinemia in this sequence has not been completely elucidated. In this work we investigated the actions of insulin and PPAR-gamma on the stimulation by AGEs of NF-kappaB protein expression in cultured aortic vascular smooth-muscle cells (VSMCs) from non-insulin-dependent diabetic rats and nondiabetic rats. The expression of proteins was evaluated with the use of Western immunoblotting. Incubations (24 hours) of VSMCs with 10 to 100 microg/mL glycated bovine serum albumin (AGE- BSA) increased NF-kappaB protein expression in both models. PPAR-gamma protein expression was only enhanced at concentrations of 500 to 1000 microg/mL (AGE-BSA). In the presence of insulin (10-100 nmol/L), the stimulation of NF-kappaB protein expression by AGE-BSA (100 microg/mL) was decreased, whereas the expression of PPAR-gamma, protein was enhanced. 15-Deoxyprostaglandin J2, a direct activator of PPAR-gamma, decreased AGE-BSA-stimulated NF-kappaB expression. These findings suggest that insulin decreases the incidence of alterations in VSMCs induced by AGEs through the reduction of NF-kappaB and an increase in PPAR-gamma protein expression (as far as the model could be extrapolated to in vivo situations). These data may help justify current therapeutic approaches involving the use of insulin and PPAR-gamma agonists.