Diabetes-related Atherosclerosis Research Articles

Whole-body insulin resistance leads to accelerated atherosclerosis: role for Nox2 NADPH oxidase.

Insulin resistance underpins the progression of type 2 diabetes mellitus and leads to a collection of risk factors for the development of atherosclerosis. Whether or not insulin resistance at a whole-body level per se leads to accelerated atherosclerosis is unclear. To answer this question, we generated atherosclerosis-prone mice with whole-body insulin resistance secondary to haploinsufficiency of the insulin receptor (IR+/-) deficient in ApoE-/- (IR+/-/ApoE-/-). IR+/-/ApoE-/- and ApoE-/- littermates had similar weight, lipids, and glucose tolerance at baseline. After 12 weeks of Western high-cholesterol diet, IR+/-/ApoE-/- had significantly more atherosclerosis in the thoracoabdominal aorta and at the level of the aortic sinus than ApoE-/- littermates. Excess Nox2 NADPH oxidase (Nox2) derived superoxide has been suggested to underpin diabetes-related atherosclerosis. In IR+/-/ApoE-/- we examined the effect of inhibiting Nox2 using genetic or pharmacological approaches on the development of atherosclerosis. To genetically delete Nox2, we generated IR+/-/ApoE-/-/Nox2-/y and to inhibit Nox2 pharmacologically, we treated IR+/-/ApoE-/- with the peptide Nox2 inhibitor gp91dstat. IR+/-/ApoE-/-/Nox2-/y had significant disruption of the aortic wall with increased thoracoabdominal atherosclerosis when compared to IR+/-/ApoE-/-/Nox2+/y littermates. Inhibition of Nox2 using gp91dstat reduced atherosclerosis in the thoracoabdominal aorta of IR+/-/ApoE-/-. Whole-body insulin resistance accelerates the development of atherosclerosis. Genetic inhibition of Nox2 leads to disruption of the aortic wall in IR+/-/ApoE-/- mice with accelerated atherosclerosis, whereas pharmacological Nox2 inhibition reduces atherosclerosis in IR+/-/ApoE-/- without disruption of the arterial wall.

NRF2-HIF2α Signaling Attenuates Endothelial Cell Senescence and Maintains Intercellular Junctions in Diabetes.

In the context of diabetes, endothelial cells frequently exhibit compromised intercellular junctions and accelerated cellular senescence simultaneously. The precise mechanisms underlying these issues and the identification of effective treatments remain largely undefined. Our findings reveal that human umbilical vein endothelial cells (HUVECs) can counteract senescence and uphold the integrity of intercellular junctions under mildly to moderately elevated glucose levels (10 mM and 15 mM) via two primary mechanisms: i) The acetylation of NRF2 at lysine residues K56, K68, and K52 prevents its ubiquitination, enhancing the transcription of antioxidant genes GST, SOD1, and GPX1. This activity diminishes cytoplasmic oxidative stress, thereby mitigating endothelial cell senescence. ii) The interaction between the Neh2 domain of NRF2 and the PAS-B domain of HIF-2α within the nucleus curtails the attachment of HIF-2α to the NOX4/p22phox promoter. This action lessens oxidative stress near the cell membrane, maintaining intercellular junctions by safeguarding the disulfide bonds in occludin and E-cadherin from disruption. However, these protective strategies prove insufficient under severe hyperglycemic conditions (25 mM). Further investigation has identified Oltipraz, an activator of NRF2, as also promoting the degradation of HIF-2α. Through its simultaneous modulation of NRF2 and HIF-2α, Oltipraz significantly reduces cellular senescence and prevents the deterioration of intercellular junctions in HUVECs subjected to high glucose concentrations (25 mM). Our research positions Oltipraz as a promising therapeutic candidate for mitigating diabetes-induced vascular endothelial damage, potentially offering benefits against diabetes-related atherosclerosis and valvular calcification.

AGEs induce high expression of Dll4 via endoplasmic reticulum stress PERK signaling-mediated internal ribosomal entry site mechanism in macrophages

Background and aimAdvanced glycation end products (AGEs)- exposed macrophages was characterized by Delta-like ligand 4 (Dll4) high expressed and has been shown to participate in diabetes-related atherosclerosis. This study was aimed to investigate the translational regulatory mechanism of Dll4 high expression in macrophages exposed to AGEs. MethodsHuman Dll4 5′ untranslated region (5′UTR) sequence was cloned and inserted into a bicistronic reporter plasmid. Human THP-1 macrophages transfected with the bicistronic reporter plasmids were exposed to AGEs. Dual-luciferase assay was used to detect internal ribosome entry site (IRES) activity contained in Dll4 5′UTR. Small interference RNA transfection was used to knock-down specific gene expression. Localization of protein was analyzed. ResultsAGEs exposure significantly induced IRES activity in Dll4 5′ UTR in human macrophages. Internal potential promoter and ribosome read-through mechanisms were excluded. Inhibition of endoplasmic reticulum stress and specific silencing of protein kinase R-like endoplasmic reticulum kinase (PERK)/eukaryotic initiation factor 2α (eIF2α) signaling pathway activation reduced IRES activity in Dll4 5′ UTR in human macrophages. Dll4 5′ UTR IRES activity was also inhibited by targeted silencing of heterogeneous nuclear ribonucleoprotein A1 (hnRNPA1). Moreover, specific inhibition of PERK/eIF2α signaling pathway led to deactivation of hnRNPA1, resulting to reduction of AGEs- induced Dll4 5’ UTR IRES activity in human macrophages. ConclusionsAGEs induced Dll4 5′ UTR IRES activity in human macrophages which was dependent on endoplasmic reticulum stress PERK/eIF2α signaling pathway. hnRNPA1 acted the role as an ITAF was also indispensable for AGEs-induced Dll4 5′UTR IRES activity in human macrophages.

Guidelines on models of diabetic heart disease.

Diabetes is a major risk factor for cardiovascular diseases, including diabetic cardiomyopathy, atherosclerosis, myocardial infarction, and heart failure. As cardiovascular disease represents the number one cause of death in people with diabetes, there has been a major emphasis on understanding the mechanisms by which diabetes promotes cardiovascular disease, and how antidiabetic therapies impact diabetic heart disease. With a wide array of models to study diabetes (both type 1 and type 2), the field has made major progress in answering these questions. However, each model has its own inherent limitations. Therefore, the purpose of this guidelines document is to provide the field with information on which aspects of cardiovascular disease in the human diabetic population are most accurately reproduced by the available models. This review aims to emphasize the advantages and disadvantages of each model, and to highlight the practical challenges and technical considerations involved. We will review the preclinical animal models of diabetes (based on their method of induction), appraise models of diabetes-related atherosclerosis and heart failure, and discuss in vitro models of diabetic heart disease. These guidelines will allow researchers to select the appropriate model of diabetic heart disease, depending on the specific research question being addressed.

The AGP-PPARγ axis promotes oxidative stress and diabetic endothelial cell dysfunction.

Alkyl-glycerophosphate (AGP) accumulates in atherogenic oxidized-LDL and human atherosclerotic plaques and is a potent agonist of peroxisome-proliferator-activated receptor-gamma (PPARγ). Recent studies suggest a potential regulatory role for PPARγ in endothelial nitric oxide synthase (eNOS) expression/activation and nitrogen oxide (NO) generation in the vascular endothelium. Importantly, eNOS-induced NO and advanced glycation end-products (AGEs) are involved in blood-vessel damage, and diabetic patients exhibit high serum NO and AGE levels; however, the effect of AGP on NO- and AGE-mediated endothelium dysfunction remains unknown. Investigation of the AGP-specific effects on NO- and AGE-mediated dysfunction and the underlying molecular mechanisms revealed that AGP upregulated eNOS expression and NO production, and that eNOS silencing and PPARγ antagonism inhibited AGP-mediated eNOS upregulation and NO production. Moreover, AGP-PPARγ-axis-mediated NO production promoted the generation of reactive oxygen species and AGE formation. These results suggested that AGP plays a significant role in the initiation/progression of diabetes-related atherosclerosis through PPARγ activation.

Current views on neuropeptide Y and diabetes-related atherosclerosis.

Diabetes-induced atherosclerotic cardiovascular disease is the leading cause of death of diabetic patients. Neuronal regulation plays a critical role in glucose metabolism and cardiovascular function under physiological and pathological conditions, among which, neurotransmitter neuropeptide Y has been shown to be closely involved in these two processes. Elevated central neuropeptide Y level promotes food intake and reduces energy expenditure, thereby increasing adiposity. Neuropeptide Y is co-localized with noradrenaline in central and sympathetic nervous systems. As a major peripheral vascular contractive neurotransmitter, through interactions with its receptors, neuropeptide Y has been implicated in the pathology and progression of diabetes, by promoting the proliferation of endothelial cells and vascular fibrosis, which may contribute to diabetes-induced cardiovascular disease. Neuropeptide Y also participates in the pathogenesis of atherosclerosis, the major form of cardiovascular disease, via aggravating endothelial dysfunction, growth of vascular smooth muscle cells, formation of foam cells and platelets aggregation. This review highlights the causal role of neuropeptide Y and its receptor system in the development of diabetes mellitus and one of its complications: atherosclerotic cardiovascular disease. The information from this review provides both critical insights onto the mechanisms underlying the pathogenesis of atherosclerosis and evidence for the development of therapeutic strategies.

Activated Status and Altered Functions of Neutrophils in Poorly Controlled Diabetes

Objectives. This study aimed to investigate the association of hyperglycemia and AGE on the phenotypes and biological functions of neutrophils to understand their roles in diabetes-related atherosclerosis. Methodology. Healthy subjects (HS) (n=5) and type 2 diabetic patients grouped according to glycemic control [good control, HbA1c 7% or less, n=6 (well controlled diabetic, WCD); poor control, HbA1c more than 9%, n=6 (poorly controlled diabetic, PCD)] were included in the study. Neutrophils were isolated from peripheral venous blood samples. To determine in vitro effects of high glucose and AGE, neutrophils derived from HS were exposed to 5 mM glucose, 25 mM glucose, 100 μg/mL BSA and AGE-BSA. We determined basal and PMA-stimulated production of ROS, expression of CD11b and CD66b, release of MPO, cell migration to IL-8 and adhesion to an endothelial cell layer. Results. In diabetic subjects, cells from WCD produced significantly higher basal and PMA-stimulated ROS ( p =0.014), while cells from PCD showed significantly increased expression of CD11b, CD66b and MPO production (p=0.021, 0.034, 0.05, respectively). The release of MPO was significantly increased after PMA stimulation in cells incubated in AGE-BSA, compared to those incubated in unmodified BSA. We observed significantly enhanced migration towards IL-8 and adherence to endothelial cells in neutrophils exposed to high glucose. Conclusions. Our findings indicate the activated status of neutrophils from diabetic patients. Neutrophils from healthy subjects exposed to conditions simulating hyperglycemia showed increased adhesive capacity. We made the novel finding of enhanced neutrophil migration toward IL-8 and adherence to endothelial cells upon exposure to high glucose conditions. These altered neutrophil functions may lead to the development and progression of atherosclerosis in diabetes.

Cigarette smoking and albuminuria are associated with impaired arterial smooth muscle function in patients with type 2 diabetes mellitus: a FIELD substudy

AimImpaired arterial function has been implicated in diabetes-related atherosclerosis, but its determinants in high-risk adults have not been well characterised. We investigated factors associated with impaired arterial function in adults with type 2 diabetes. MethodsFlow-mediated dilatation (a marker of endothelial function) and dilator response to glyceryl trinitrate (to assess smooth muscle function) of the brachial artery were assessed at baseline in 193 patients with type 2 diabetes from the Fenofibrate Intervention and Event Lowering in Diabetes (FIELD) study. Traditional risk factors were assessed and a multivariable model was constructed to identify factors independently associated with impaired arterial function. ResultsMedian age was 64 years (interquartile range, 58–69; 61% male) and duration of diabetes was 4 years (interquartile range, 2–9). Flow-mediated dilatation (3.06±0.25%, mean±SEM) was severely impaired but not significantly associated with other risk factors. Dilator responses to glyceryl trinitrate (10.56±0.52%) were significantly and independently impaired in past and present cigarette smokers (P=0.005) and in subjects with increased urinary albumin/creatinine ratio (P=0.01). ConclusionsIn adults with type 2 diabetes and known or suspected atherosclerosis, arterial smooth muscle-dependent dilatation was shown to be significantly impaired in cigarette smokers and those with elevated urinary albumin levels.

Increased circulating RANTES in type 2 diabetes.

The pro-atherogenic role of RANTES, a chemokine expressing pleiotropic activities, in the course of type 2 diabetes-related atherosclerosis has been well documented. However, it is not known which of the diabetes-related factors primarily influence serum RANTES levels in patients with type 2 diabetes. Our aim was to investigate relationships between several factors known to be related to an increased risk of atherosclerosis and serum RANTES levels in type 2 diabetic patients. A total of 168 subjects were examined, which included 138 patients with type 2 diabetes and 30 non-diabetic controls. Measurements of venous, fasting, plasma glucose, HbA1c, lipid profile, 1,5-anhydro-D-glucitol (1,5-AG) plasma levels, homocysteine and the fasting, serum C-peptide levels were performed. Serum concentrations of RANTES were assayed using BD(TM) Cytometric Bead Array tests. Peripheral insulin resistance was expressed according to a new index defined by Ohkura et al. RANTES levels in type 2 diabetic patients correlated with 1,5-AG, fasting glycaemia, HbA1c and the Ohkura index. Multivariate regression analysis was performed taking into consideration several factors related to the inflammatory process and atherosclerosis, namely the patient's age, diabetes duration, waist circumference, 1,5-AG, HbA1c, lipid profile parameters, serum homocysteine levels and Ohkura index, as independent variables potentially influencing serum RANTES levels in type 2 diabetic patients. It is shown that RANTES concentrations in the serum is primarily dependent upon 1,5-AG plasma levels. Our results suggest that increased serum levels of RANTES in type 2 diabetic patients are closely related to postprandial (acute) hyperglycaemia.

Response to Comment on: Sukumar et al. Nox2 NADPH Oxidase Has a Critical Role in Insulin Resistance–Related Endothelial Cell Dysfunction. Diabetes 2013;62:2130–2134

We would like to thank Drs. Jandeleit-Dahm and Schmidt (1) for their interesting comments regarding our study examining the role of the Nox2 isoform of NADPH oxidase in insulin resistance–related endothelial cell dysfunction (2). We would also like to congratulate them on their own elegant and comprehensive piece of work examining the role of the Nox isoforms Nox1, Nox2, and Nox4 in the development of advanced type 1 diabetes–related atherosclerosis (3). Based on their findings that Nox1 may be more important in diabetes-related atherosclerosis than other isoforms of NADPH oxidase, the authors raise concerns regarding our conclusions that Nox2 has a critical …

Reduction in carotid intima-media thickness after pancreatic islet transplantation in patients with type 1 diabetes.

OBJECTIVEDetermine the impact of islet transplantation on carotid intima-media thickness (CIMT), a marker for atherosclerosis, in type 1 diabetes without kidney disease.RESEARCH DESIGN AND METHODSConsecutive case series of 15 adults (mean age [SD], 49 years [10 years]; 87% female) with type 1 diabetes for ≥5 years (mean duration [SD], 30 years [12 years]; mean HbA1c [SD], 7.2% [0.9%]), without kidney disease, presenting with severe hypoglycemic unawareness to undergo allogeneic pancreatic islet transplant(s) (one to three each) in a phase 1/2 and 3 clinical trial. Current follow-up ranges from 1 to 5 years (2005–2011). CIMT of the common and internal carotid arteries was measured before and every 12–16 months after the first transplant (two to six CIMTs each) by one ultrasonographer and one blinded reader. CIMT was analyzed as change from baseline to 12- and 50-month follow-up; a combined CIMT score was calculated as the sum of the standardized IMT scores (SD units [SDs]) of both arteries.RESULTSAll patients achieved insulin independence after one to three transplants. CIMT decreased at 12 months (n = 15) for the common carotid (−0.058 mm; P = 0.006) and combined score (−1.28 SDs; P = 0.004). In those with 50-month follow-up (n = 7), the decrease in the combined score continued from 12 (−1.59 SDs; P = 0.04) to 50 months (−0.77 SDs; P = 0.04). During follow-up, the decreasing slope of change in CIMT was associated with decreasing slopes of change in HbA1c, lipoproteins, and cardiovascular/inflammatory markers.CONCLUSIONSIslet transplantation may ameliorate diabetes-related atherosclerosis through improved glycemic control consequent to restoring endogenous insulin secretion, and optimal lipid management posttransplant also contributes.

Insulin promotes macrophage foam cell formation: potential implications in diabetes-related atherosclerosis

The prevalence of atherosclerotic cardiovascular disease is higher in patients with type 2 diabetes, a disorder characterized by hyperinsulinemia and insulin resistance. The role of hyperinsulinemia as an independent participant in the atherogenic process has been controversial. In the current study, we tested the effect of insulin and the insulin sensitizer, adiponectin, on human macrophage foam cell formation. We found that both insulin and adiponectin increased the expression of the type 2 scavenger receptor CD36 by approximately twofold and decreased the expression of the ATP-binding cassette transporter ABCA1 by >80%. In both cases regulation was post-transcriptional. As a consequence of these changes, we found that oxidized LDL (oxLDL) uptake was increased by 80% and cholesterol efflux to apolipoprotein A1 (apoA1) was decreased by ∼25%. This led to two- to threefold more cholesterol accumulation over a 16-h period. As reported previously in studies of murine systems, scavenger receptor-A (SR-A) expression on human macrophages was downregulated by insulin and adiponectin. Insulin and adiponectin did not affect oxLDL-induced secretion of monocyte attractant protein-1 (MCP-1) and interleukin-6 (IL-6). These studies suggest that hyperinsulinemia could promote macrophage foam cell formation and thus may contribute to atherosclerosis in patients with type 2 diabetes.

Antiatherosclerotic and Renoprotective Effects of Ebselen in the Diabetic Apolipoprotein E/GPx1-Double Knockout Mouse

OBJECTIVETo investigate the effect of the GPx1-mimetic ebselen on diabetes-associated atherosclerosis and renal injury in a model of increased oxidative stress.RESEARCH DESIGN AND METHODSThe study was performed using diabetic apolipoprotein E/GPx1 (ApoE−/−GPx1−/−)-double knockout (dKO) mice, a model combining hyperlipidemia and hyperglycemia with increased oxidative stress. Mice were randomized into two groups, one injected with streptozotocin, the other with vehicle, at 8 weeks of age. Groups were further randomized to receive either ebselen or no treatment for 20 weeks.RESULTSEbselen reduced diabetes-associated atherosclerosis in most aortic regions, with the exception of the aortic sinus, and protected dKO mice from renal structural and functional injury. The protective effects of ebselen were associated with a reduction in oxidative stress (hydroperoxides in plasma, 8-isoprostane in urine, nitrotyrosine in the kidney, and 4-hydroxynonenal in the aorta) as well as a reduction in VEGF, CTGF, VCAM-1, MCP-1, and Nox2 after 10 weeks of diabetes in the dKO aorta. Ebselen also significantly reduced the expression of proteins implicated in fibrosis and inflammation in the kidney as well as reducing related key intracellular signaling pathways.CONCLUSIONSEbselen has an antiatherosclerotic and renoprotective effect in a model of accelerated diabetic complications in the setting of enhanced oxidative stress. Our data suggest that ebselen effectively repletes the lack of GPx1, and indicate that ebselen may be an effective therapeutic for the treatment of diabetes-related atherosclerosis and nephropathy. Furthermore, this study highlights the feasibility of addressing two diabetic complications with one treatment regimen through the unifying approach of targeted antioxidant therapy.

Targeting the endothelium to prevent diabetes-related atherosclerosis

Targeting the endothelium to prevent diabetes-related atherosclerosis

Gestational Diabetes, Pregnancy Hypertension, and Late Vascular Disease

The complexity of the several pathogenic pathways that cause hypertension and vascular disease and the prolonged interval that appears to predate clinical morbidity have hindered inquiry into the association between GDM and vascular disorders. As a forme fruste of later type 2 diabetes, GDM-affected gravidas are identified as at risk of diabetes-related atherosclerosis, glomerular disruption, and pathogenic retinal angio-genesis. That GDM is evidence for underlying chronic conditions such as dysregulation of innate immune response that, independent of the diabetic state, produces vascular disease is difficult state, produces vascular disease is difficult to assert with the present published literature. Cross-sectional studies of patients with established gestational hypertension or preeclampsia are ambiguous as to the possible pathogenic effect of insulin resistance. Cohort studies initiated in early and mid-pregnancy show evidence that both gestational hypertension and preeclampsia may be more prevalent in gravidas with greater insulin resistance. The association of gestational glucose intolerance with gestational hypertension appears to be independent of obesity and ambient glycemia but explained in part by insulin resistance. Late pregnancy preeclampsia is associated with elevated mid-pregnancy BMI, blood pressure, fasting glucose and insulin, urate, and C-reactive protein, suggestive of metabolic and immune dysregulation. GDM appears to be associated with overexpressed innate immune response, which, in turn, is associated with vascular dysfunction and vascular disease. Among women with GDM, markers of insulin resistance do not appear to correlate with hypertension in short-term cohort studies. However, when non-GDM subjects are compared with subjects with GDM, postpregnancy studies do show an associated with vascular dysfunction and vascular disease. Among women with GDM, markers of insulin resistance do not appear to correlate with hypertension in short-term cohort studies. However, when non-GDM subjects are compared with subjects with GDM, postpregnancy studies do show an association of insulin resistance with both inflammatory dysregulation and vascular dysfunction. Cohort studies that have used population-based pregnancy databases consistently identify a clinically significant association of both gestational hypertension and preeclampsia with later hypertensive disorders. Associations with coronary artery disease or stroke are less consistent, requiring further investigation. Preventing the evolution of diabetes and lipid and immune dysregulation of the metabolic syndrome has become a silent public health issue because of the epidemic of childhood and early adulthood obesity and the opportunity at hand to treat insulin resistance by behavioral and pharmacological interventions. However, limited available literature highlights the need for long-term cohort studies of women with well-characterized metabolic and vascular profiles during pregnancy and decades later. Our present knowledge suggests that screening for GDM provides an opportunity of pregnancy outcome improvement. Limited studies of diabetes prevention in at-risk patient groups suggest that we may have the opportunity to reduce the risk of later diabetes. Additional investigation is required to determine if interventions that prevent or postpone diabetes also delay the onset of vascular disease.

New in vitro model to study high glucose-dependent endothelial dysfunctions

Several thrombogenic abnormalities are associated with diabetes. Since endothelial dysfunction occurs at early stages of disease, it may reflect pathophysiological changes that are responsible for alterations in vascular structure, growth and modifications of adhesivity to platelets and leukocytes, leading to atherosclerosis and thrombosis. Predisposing factors of vascular diseases, such as diabetes, are also associated with endothelial dysfunction. Restoration or replacement of endothelium-related factors like nitric oxide impede the progression of vascular thrombogenic diseases, and prevent the action of vasoconstrictor factors such as endothelin or other prothrombotic factors such as plasminogen-activator inhibitor-1. Since high glucose concentration in blood is the hallmark of diabetes and because the vascular lesions of atherosclerosis are localized in large artheries, we have cultured endothelial cells from the human aorta. Two endothelial cell strains from the same aortic tract that show different characteristics and behavior in high glucose were isolated. Such findings reflect the importance to have well characterized and standardized cell culture systems to carry out experiments to study the glucose-dependent atherosclerotic process in vitro. Our cell strains may represent a useful in vitro model to study the complex pathophysiology of diabetes-related atherosclerosis.

Minerals in cardiovascular disease

Reviewed here are the relationships between soft-water regions and total cardiovascular disease, between cadmium and sodium on the one hand and hypertension on the other, and finally between chromium and diabetes-related atherosclerosis