Amir Aziz

Insulin Resistance Impairs Circulating Angiogenic Progenitor Cell Function and Delays Endothelial Regeneration

OBJECTIVE Circulating angiogenic progenitor cells (APCs) participate in endothelial repair after arterial injury. Type 2 diabetes is associated with fewer circulating APCs, APC dysfunction, and impaired endothelial repair. We set out to determine whether insulin resistance adversely affects APCs and endothelial regeneration. RESEARCH DESIGN AND METHODS We quantified APCs and assessed APC mobilization and function in mice hemizygous for knockout of the insulin receptor (IRKO) and wild-type (WT) littermate controls. Endothelial regeneration after femoral artery wire injury was also quantified after APC transfusion. RESULTS IRKO mice, although glucose tolerant, had fewer circulating Sca-1+/Flk-1+ APCs than WT mice. Culture of mononuclear cells demonstrated that IRKO mice had fewer APCs in peripheral blood, but not in bone marrow or spleen, suggestive of a mobilization defect. Defective vascular endothelial growth factor–stimulated APC mobilization was confirmed in IRKO mice, consistent with reduced endothelial nitric oxide synthase (eNOS) expression in bone marrow and impaired vascular eNOS activity. Paracrine angiogenic activity of APCs from IRKO mice was impaired compared with those from WT animals. Endothelial regeneration of the femoral artery after denuding wire injury was delayed in IRKO mice compared with WT. Transfusion of mononuclear cells from WT mice normalized the impaired endothelial regeneration in IRKO mice. Transfusion of c-kit+ bone marrow cells from WT mice also restored endothelial regeneration in IRKO mice. However, transfusion of c-kit+ cells from IRKO mice was less effective at improving endothelial repair. CONCLUSIONS Insulin resistance impairs APC function and delays endothelial regeneration after arterial injury. These findings support the hypothesis that insulin resistance per se is sufficient to jeopardize endogenous vascular repair. Defective endothelial repair may be normalized by transfusion of APCs from insulin-sensitive animals but not from insulin-resistant animals.

Increasing Circulating IGFBP1 Levels Improves Insulin Sensitivity, Promotes Nitric Oxide Production, Lowers Blood Pressure, and Protects Against Atherosclerosis

Low concentrations of insulin-like growth factor (IGF) binding protein-1 (IGFBP1) are associated with insulin resistance, diabetes, and cardiovascular disease. We investigated whether increasing IGFBP1 levels can prevent the development of these disorders. Metabolic and vascular phenotype were examined in response to human IGFBP1 overexpression in mice with diet-induced obesity, mice heterozygous for deletion of insulin receptors (IR+/−), and ApoE−/− mice. Direct effects of human (h)IGFBP1 on nitric oxide (NO) generation and cellular signaling were studied in isolated vessels and in human endothelial cells. IGFBP1 circulating levels were markedly suppressed in dietary-induced obese mice. Overexpression of hIGFBP1 in obese mice reduced blood pressure, improved insulin sensitivity, and increased insulin-stimulated NO generation. In nonobese IR+/− mice, overexpression of hIGFBP1 reduced blood pressure and improved insulin-stimulated NO generation. hIGFBP1 induced vasodilatation independently of IGF and increased endothelial NO synthase (eNOS) activity in arterial segments ex vivo, while in endothelial cells, hIGFBP1 increased eNOS Ser1177 phosphorylation via phosphatidylinositol 3-kinase signaling. Finally, in ApoE−/− mice, overexpression of hIGFBP1 reduced atherosclerosis. These favorable effects of hIGFBP1 on insulin sensitivity, blood pressure, NO production, and atherosclerosis suggest that increasing IGFBP1 concentration may be a novel approach to prevent cardiovascular disease in the setting of insulin resistance and diabetes.

Association of diabetes with increased all-cause mortality following primary percutaneous coronary intervention for ST-segment elevation myocardial infarction in the contemporary era

Background: We investigated the association between diabetes mellitus (DM) and all-cause mortality in a large cohort of consecutive patients treated with primary percutaneous coronary intervention (PPCI) in the contemporary era. Methods: We conducted a retrospective analysis of a single-centre registry of patients undergoing PPCI for ST-segment elevation myocardial infarction (STEMI) at a large regional PCI centre between 2005 and 2009. All-cause mortality in relation to patient and procedural characteristics was compared between patients with and without DM. Results: Of 2586 patients undergoing PPCI, 310 (12%) had DM. Patients with DM had a higher prevalence of multi-vessel coronary disease (p<0.001) and prior myocardial infarction (p<0.001). Patients with DM were less commonly admitted directly to the interventional centre (p=0.002). Symptom-to-balloon (p<0.001) and door-to-balloon time (p=0.002) were longer in patients with DM. Final infarct-related-artery TIMI-flow grade was lower in patients with DM (p=0.031). All-cause mortality at 30 days (p=0.0025) and 1 year (p<0.0001) was higher in patients with DM. DM was independently associated with increased mortality after multivariate adjustment for potential confounders. Conclusions: Mortality remains substantially higher in patients with DM following reperfusion for STEMI in comparison with those without diabetes, despite contemporary management with PPCI. Greater co-morbidity, delayed presentation, longer times-to-reperfusion, and less optimal reperfusion may contribute to adverse outcomes.

Length of hospital stay is shorter in South Asian patients with myocardial infarction

a Pennine Acute Hospitals NHS Foundation Trust, Manchester, UK b Division of Cardiovascular and Diabetes Research, University of Leeds, Leeds, UK c Department of Psychiatry of Learning Disability, Brooklands Hospital, Birmingham, UK d Training Programme Director, Acute Medicine, North Western Deanery, UK e ACALM Study Unit in partnership with School of Medical Sciences, Aston University, Birmingham, UK

Insulin resistance in Type 2 diabetes and obesity: implications for endothelial function.

Recent changes in human lifestyle and nutrition have led to a dramatic increase in the prevalence of obesity and Type 2 diabetes mellitus (T2DM). By the year 2030, it is estimated that over 439 million people worldwide will have T2DM [1]. Approximately 80% of patients with T2DM will die from CVD, resulting in an increased risk of death equivalent to 15 years of aging [2]. Obesity itself, is associated with an increased risk of first acute myocardial infarction equivalent to over 10 years of aging [3]. Insulin resistance, the key metabolic perturbation underpinning T2DM and obesity, is closely related with an increased risk of CVD [4], and is now thought to play a pathological role in atherosclerotic disease. Insulin resistance is characterized by the inability of insulin to activate its tyrosine kinase receptor and downstream signaling pathways in target tissues. In canonical target tissues (skeletal muscle, liver and adipocyte) insulin resistance, followed by progressive failure of pancreatic insulin secretion, is responsible for the metabolic deregulation leading to diabetes. However, altered insulin signaling in cells involved in atherosclerosis, in particular in endothelial cells, has emerged as an important mechanism for the increased susceptibility to CVD in these individuals [5]. The endothelium comprises a monolayer of cells covering the inner surface of blood vessels that modulates the function of neighboring cells within the vessel wall and lumen. Endothelial cells secrete a portfolio of locally-acting factors, which maintain vessel health by regulating tone, inflammation, platelet aggregation and thrombosis [6]. Endothelial dysfunction, characterized by an altered balance of secreted molecules and upregulation of proinflammatory surface proteins, is one of the earliest steps in the evolution of atherosclerosis. Decreased bioavailability of nitric oxide, a classical manifestation of endothelial dysfunction, predicts the development of future cardiovascular events [7].

The role of angioplasty in patients with acute coronary syndrome and previous coronary artery bypass grafting

INTRODUCTION Angioplasty has changed the management of acute coronary syndrome (ACS). However, in patients with previous coronary artery bypass grafting (CABG), the role of angioplasty in the management of ACS is widely debated. Lack of clear guidelines leads to subjective and often stereotypical assessments based on clinician preferences. We sought to investigate if angioplasty affected all cause mortality in ACS patients with previous CABG. METHODS Completely anonymous information on patients with ACS with a background of previous CABG, co-morbidities and procedures attending three multi-ethnic general hospitals in the North West of England, United Kingdom in the period 2000-2012 was traced using the ACALM (Algorithm for Comorbidities, Associations, Length of stay and Mortality) study protocol using ICD-10 and OPCS-4 coding systems. Predictors of mortality and survival analyses were performed using SPSS version 20.0. RESULTS Out of 12,227 patients with ACS, there were 1172 (19.0%) cases of ACS in patients with previous coronary artery bypass grafting. Of these 83 (7.1%) patients underwent angioplasty. Multi-nominal logistic regression, accounting for differences in age and co-morbidities, revealed that having angioplasty conferred a 7.96 times improvement in mortality (2.36-26.83 95% CI) compared to not having angioplasty in this patient group. CONCLUSIONS We have shown that angioplasty confers significantly improved all cause mortality in the management of ACS in patients with previous CABG. The findings of this study highlight the need for clinicians to conscientiously think about the individual benefits and risks of angioplasty for every patient rather than confining to age related stereotypes.

Haploinsufficiency of the Insulin-Like Growth Factor-1 Receptor Enhances Endothelial Repair and Favorably Modifies Angiogenic Progenitor Cell Phenotype

Objectives— Defective endothelial regeneration predisposes to adverse arterial remodeling and is thought to contribute to cardiovascular disease in type 2 diabetes mellitus. We recently demonstrated that the type 1 insulin-like growth factor receptor (IGF1R) is a negative regulator of insulin sensitivity and nitric oxide bioavailability. In this report, we examined partial deletion of the IGF1R as a potential strategy to enhance endothelial repair. Approach and Results— We assessed endothelial regeneration after wire injury in mice and abundance and function of angiogenic progenitor cells in mice with haploinsufficiency of the IGF1R (IGF1R+/−). Endothelial regeneration after arterial injury was accelerated in IGF1R+/− mice. Although the yield of angiogenic progenitor cells was lower in IGF1R+/− mice, these angiogenic progenitor cells displayed enhanced adhesion, increased secretion of insulin-like growth factor-1, and enhanced angiogenic capacity. To examine the relevance of IGF1R manipulation to cell-based therapy, we transfused IGF1R+/− bone marrow–derived CD117+ cells into wild-type mice. IGF1R+/− cells accelerated endothelial regeneration after arterial injury compared with wild-type cells and did not alter atherosclerotic lesion formation. Conclusions— Haploinsufficiency of the IGF1R is associated with accelerated endothelial regeneration in vivo and enhanced tube forming and adhesive potential of angiogenic progenitor cells in vitro. Partial deletion of IGF1R in transfused bone marrow–derived CD117+ cells enhanced their capacity to promote endothelial regeneration without altering atherosclerosis. Our data suggest that manipulation of the IGF1R could be exploited as novel therapeutic approach to enhance repair of the arterial wall after injury.

Co-morbidities and mortality associated with intracranial bleeds and ischaemic stroke

Stroke is a leading cause of mortality and acquired disability; however, there has been no comprehensive comparison of co-morbid risk factors between different stroke subtypes. The aim of this study was to compare risk factors and mortality for subdural haematoma (SDH), subarachnoid haemorrhage (SAH) and ischaemic and haemorrhagic stroke. We compiled a database of all patients admitted with these conditions to a large teaching hospital in Birmingham, United Kingdom during the period 2000–2007 using the International Classification of Disease (ICD) 10th revision codes. Generalised linear models were constructed to calculate relative risks (RRs) associated with co-morbidities. In total, 4804 patients were admitted with diagnoses of SDH (1004), SAH (807), ischaemic stroke (2579) and haemorrhagic stroke (414). Patients with SDH were less likely to have pneumonia (0.492, 95% CI, 0.330–0.734; p < 0.001), whereas alcohol abuse (4.21, 95% CI, 2.82–6.28; p < 0.001) was more common. In SAH, ischaemic heart disease (0.56, 95% CI, 0.40–0.79; p < 0.001) was less common. As expected, a range of cardiovascular risk factors were associated with ischaemic stroke. Epilepsy was positively associated with ischaemic stroke (1.94, 95% CI, 1.36–2.76; p < 0.001), indicating a role for targeted primary prevention in patients with epilepsy. Five-year survival was lower in ischaemic and haemorrhagic strokes (41% and 40% respectively, vs. 73% in SDH and 64% in SAH; p < 0.001). These findings may guide clinical risk stratification, and improve the prognostic information given to patients.

Insulinlike growth factor – binding protein-1 improves vascular endothelial repair in male mice in the setting of insulin resistance

Insulin resistance is associated with impaired endothelial regeneration in response to mechanical injury. We recently demonstrated that insulinlike growth factor-binding protein-1 (IGFBP1) ameliorated insulin resistance and increased nitric oxide generation in the endothelium. In this study, we hypothesized that IGFBP1 would improve endothelial regeneration and restore endothelial reparative functions in the setting of insulin resistance. In male mice heterozygous for deletion of insulin receptors, endothelial regeneration after femoral artery wire injury was enhanced by transgenic expression of human IGFBP1 (hIGFBP1). This was not explained by altered abundance of circulating myeloid angiogenic cells. Incubation of human endothelial cells with hIGFBP1 increased integrin expression and enhanced their ability to adhere to and repopulate denuded human saphenous vein ex vivo. In vitro, induction of insulin resistance by tumor necrosis factor α (TNFα) significantly inhibited endothelial cell migration and proliferation. Coincubation with hIGFBP1 restored endothelial migratory and proliferative capacity. At the molecular level, hIGFBP1 induced phosphorylation of focal adhesion kinase, activated RhoA and modulated TNFα-induced actin fiber anisotropy. Collectively, the effects of hIGFBP1 on endothelial cell responses and acceleration of endothelial regeneration in mice indicate that manipulating IGFBP1 could be exploited as a putative strategy to improve endothelial repair in the setting of insulin resistance.

139 Endothelial specific insulin resistance promotes the development of atherosclerosis

Background Global insulin resistance and endothelial dysfunction have been identified as predisposing factors for atherosclerosis. However, it is unclear whether selective insulin resistance in endothelial cells alone, is sufficient to promote atherosclerosis. Here we addressed this question by crossing Endothelial Specific Mutant Insulin Receptor Over-expressing (ESMIRO) mice with ApoE null mice. ESMIRO mice over-express a human insulin receptor with Ala-Thr1134 mutation in the tyrosine kinase domain (which disrupts insulin signalling) selectively in endothelial cells under the control of the tie-2 promoter/enhancer. Methods Male ApoE−/−ESMIRO mice were compared with sex-matched littermate ApoE−/− mice (both on a C57Bl6 background) after feeding a Western-style diet for 12 weeks. Results ApoE−/−ESMIRO mice were morphologically indistinguishable from ApoE−/− control littermates, with normal development and no difference between groups in body mass. Heart rate, systolic blood pressure, glucose tolerance, insulin sensitivity and fasting glucose levels were similar in ApoE-/-ESMIRO and ApoE−/− mice. Aortic lipid deposition, assessed by en-face oil red O staining, was similar in ApoE−/−ESMIRO and ApoE−/− mice (6.4%±0.5% vs 5.8%±0.5%; p=0.39). However, atherosclerotic lesion area in cross sections of aortic sinus was significantly increased in ApoE−/−ESMIRO mice compared to ApoE−/− controls (24.8%±2.4% vs 16.6%±2.4%; p=0.02). Absolute plaque size was also significantly increased in ApoE−/−ESMIRO mice compared to ApoE controls (226 448.9±16 154 μm2 vs 149 424.41±24 221 μm2; p=0.01). Conclusions Endothelial specific insulin resistance is sufficient to promote atherosclerosis and increase lesion area in ApoE null mice. This suggests that enhancing endothelial insulin sensitivity may be an appropriate target to prevent atherosclerosis in insulin-resistant conditions.