Stephan Schiekofer

Disruption of coordinated cardiac hypertrophy and angiogenesis contributes to the transition to heart failure

Although increased external load initially induces cardiac hypertrophy with preserved contractility, sustained overload eventually leads to heart failure through poorly understood mechanisms. Here we describe a conditional transgenic system in mice characterized by the sequential development of adaptive cardiac hypertrophy with preserved contractility in the acute phase and dilated cardiomyopathy in the chronic phase following the induction of an activated Akt1 gene in the heart. Coronary angiogenesis was enhanced during the acute phase of adaptive cardiac growth but reduced as hearts underwent pathological remodeling. Enhanced angiogenesis in the acute phase was associated with mammalian target of rapamycin-dependent induction of myocardial VEGF and angiopoietin-2 expression. Inhibition of angiogenesis by a decoy VEGF receptor in the acute phase led to decreased capillary density, contractile dysfunction, and impaired cardiac growth. Thus, both heart size and cardiac function are angiogenesis dependent, and disruption of coordinated tissue growth and angiogenesis in the heart contributes to the progression from adaptive cardiac hypertrophy to heart failure.

Adiponectin-mediated modulation of hypertrophic signals in the heart.

Patients with diabetes and other obesity-linked conditions have increased susceptibility to cardiovascular disorders. The adipocytokine adiponectin is decreased in patients with obesity-linked diseases. Here, we found that pressure overload in adiponectin-deficient mice resulted in enhanced concentric cardiac hypertrophy and increased mortality that was associated with increased extracellular signal-regulated kinase (ERK) and diminished AMP-activated protein kinase (AMPK) signaling in the myocardium. Adenovirus-mediated supplemention of adiponectin attenuated cardiac hypertrophy in response to pressure overload in adiponectin-deficient, wild-type and diabetic db/db mice. In cultures of cardiac myocytes, adiponectin activated AMPK and inhibited agonist-stimulated hypertrophy and ERK activation. Transduction with a dominant-negative form of AMPK reversed these effects, suggesting that adiponectin inhibits hypertrophic signaling in the myocardium through activation of AMPK signaling. Adiponectin may have utility for the treatment of hypertrophic cardiomyopathy associated with diabetes and other obesity-related diseases.

Loss of pain perception in diabetes is dependent on a receptor of the immunoglobulin superfamily

Molecular events that result in loss of pain perception are poorly understood in diabetic neuropathy. Our results show that the receptor for advanced glycation end products (RAGE), a receptor associated with sustained NF-kappaB activation in the diabetic microenvironment, has a central role in sensory neuronal dysfunction. In sural nerve biopsies, ligands of RAGE, the receptor itself, activated NF-kappaBp65, and IL-6 colocalized in the microvasculature of patients with diabetic neuropathy. Activation of NF-kappaB and NF-kappaB-dependent gene expression was upregulated in peripheral nerves of diabetic mice, induced by advanced glycation end products, and prevented by RAGE blockade. NF-kappaB activation was blunted in RAGE-null (RAGE(-/-)) mice compared with robust enhancement in strain-matched controls, even 6 months after diabetes induction. Loss of pain perception, indicative of long-standing diabetic neuropathy, was reversed in WT mice treated with soluble RAGE. Most importantly, loss of pain perception was largely prevented in RAGE(-/-) mice, although they were not protected from diabetes-induced loss of PGP9.5-positive plantar nerve fibers. These data demonstrate, for the first time to our knowledge, that the RAGE-NF-kappaB axis operates in diabetic neuropathy, by mediating functional sensory deficits, and that its inhibition may provide new therapeutic approaches.

Insufficient Glycemic Control Increases Nuclear Factor-κB Binding Activity in Peripheral Blood Mononuclear Cells Isolated From Patients With Type 1 Diabetes

OBJECTIVE The redox-sensitive transcription factor nuclear factor-kB (NF-kB) is believed to contribute to late diabetic complications. It is unknown whether NF-kB is influenced by glycemic control. RESEARCH DESIGN AND METHODS To determine whether NF-kB is activated in patients with insufficient glycemic control (HbA1c > 10%), we developed a tissue culture-independent electrophoretic mobility shift assay (EMSA)-based semiquantitative detection system that allowed us to determine NF-kB activation in ex vivo-isolated peripheral blood mononuclear cells (PBMCs). We included 43 patients with type 1 diabetes in this cross-sectional study. 10 of those received the antioxidant thioctic acid (600 mg/day p.o.) for 2 weeks. RESULTS Monocytes of patients with HbA1c levels > 10% demonstrated significantly higher NF-kB binding activity in an EMSA and a stronger NF-kB staining in immunohistochemistry than monocytes of patients with HbA1c levels of 6–8%. The increase in NF-kB activation correlated with an increase in plasmatic markers of lipid peroxidation. Treatment with the antioxidant thioctic acid decreased NF-kB binding activity. CONCLUSIONS Hyperglycemia induces activation of the transcription factor NF-kB in ex vivo-isolated PBMCs of patients with type 1 diabetes. NF-kB activation is at least partially dependent on oxidative stress, since the antioxidant thioctic acid significantly lowered the extent of NF-kB binding activity.

Impaired Angiogenesis in Glutathione Peroxidase-1–Deficient Mice Is Associated With Endothelial Progenitor Cell Dysfunction

Several vascular disease are characterized by elevated levels of reactive oxygen species (ROS). Vascular endothelium is protected from oxidant stress by expressing enzymes such as glutathione peroxidase type 1 (GPx-1). In this study, we investigated the effect of vascular oxidant stress on ischemia-induced neovascularization in a murine model of homozygous deficiency of GPx-1. GPx-1–deficient mice showed impaired revascularization following hindlimb ischemic surgery based on laser Doppler measurements of blood flow and capillary density in adductor muscle. GPx-1–deficient mice also showed an impaired ability to increase endothelial progenitor cell (EPC) levels in response to ischemic injury or subcutaneous administration of vascular endothelial growth factor protein. EPCs isolated from GPx-1–deficient mice showed a reduced ability to neutralize oxidative stress in vitro, which was associated with impaired migration toward vascular endothelial growth factor and increased sensitivity to ROS-induced apoptosis. EPCs isolated from GPx-1–deficient mice were impaired in their ability to promote angiogenesis in wild-type mice, whereas wild-type EPCs were effective in stimulating angiogenesis in GPx-1–deficient mice. These data suggest that EPC dysfunction is a mechanism by which elevated levels of ROS can contribute to vascular disease.

Impaired Revascularization in a Mouse Model of Type 2 Diabetes Is Associated With Dysregulation of a Complex Angiogenic-Regulatory Network

Objective—Diabetes is a risk factor for the development of cardiovascular diseases associated with impaired angiogenesis or increased endothelial cell apoptosis. Methods and Results—Here it is shown that angiogenic repair of ischemic hindlimbs was impaired in Leprdb/db mice, a leptin receptor–deficient model of diabetes, compared with wild-type (WT) C57BL/6 mice, as evaluated by laser Doppler flow and capillary density analyses. To identify molecular targets associated with this disease process, hindlimb cDNA expression profiles were created from adductor muscle of Leprdb/db and WT mice before and after hindlimb ischemia using Affymetrix GeneChip Mouse Expression Set microarrays. The expression patterns of numerous angiogenesis-related proteins were altered in Leprdb/db versus WT mice after ischemic injury. These transcripts included neuropilin-1, vascular endothelial growth factor-A, placental growth factor, elastin, and matrix metalloproteinases implicated in blood vessel growth and maintenance of vessel wall integrity. Conclusion—These data illustrate that impaired ischemia-induced neovascularization in type 2 diabetes is associated with the dysregulation of a complex angiogenesis-regulatory network.

No-Reflow Phenomenon Pathophysiology, Diagnosis, Prevention, and Treatment. A Review of the Current Literature and Future Perspectives

No-reflow is responsible for 40% of the primary percutaneous coronary intervention without complete myocardial reperfusion despite successful reopening of the infarct-related artery. This review describes the main pathophysiological mechanisms of no-reflow, its clinical manifestation, including the strong association with increased in-hospital mortality, malignant arrhythmias, and cardiac failure as well as the diagnostic methods. The latter ranges from simple angiographic thrombolysis in myocardial infarction grade score to more complex angiographic indexes, imaging techniques such as myocardial contrast echo or cardiac magnetic resonance, and surrogate clinical end points such as ST-segment resolution. This review also summarizes the strategies of prevention and treatment of no-reflow, considering the most recent studies results regarding medical therapy and devices.

Short-Term Akt Activation in Cardiac Muscle Cells Improves Contractile Function in Failing Hearts

Akt is a serine/threonine protein kinase that is activated by a variety of growth factors or cytokines in a phosphatidylinositol 3-kinase-dependent manner. By using a conditional transgenic system in which Akt signaling can be turned on or off in the adult heart, we previously showed that short-term Akt activation induces a physiological form of cardiac hypertrophy with enhanced coronary angiogenesis and maintained contractility. Here we tested the hypothesis that induction of physiological hypertrophy by short-term Akt activation might improve contractile function in failing hearts. When Akt signaling transiently was activated in murine hearts with impaired contractility, induced by pressure overload or doxorubicin treatment, contractile dysfunction was attenuated in both cases. Importantly, improvement of contractility was observed before the development of cardiac hypertrophy, indicating that Akt activation improves contractile function independently of its growth-promoting effects. To gain mechanistic insights into Akt-mediated positive inotropic effects, transcriptional profiles in the heart were determined in a pressure overload-induced heart failure model. Biological network analysis of differentially expressed transcripts revealed significant alterations in the expression of genes associated with cell death, and these alterations were reversed by short-term Akt activation. Thus, short-term Akt activation improves contractile function in failing hearts. This beneficial effect of Akt on contractility is hypertrophy-independent and may be mediated in part by inhibition of cell death associated with heart failure.

Glimepiride reduces mononuclear activation of the redox‐sensitive transcription factor nuclear factor‐kappa B

Aims:  Glimepiride has the lowest ratio of insulin release to glucose decrease compared with other sulphonylureas. This prompted us to study in vitro and in vivo in a placebo‐controlled study the effect of glimepiride on the redox‐sensitive transcription factor nuclear factor‐kappa B (NF‐κB).

Glucose control with insulin results in reduction of NF‐κB‐binding activity in mononuclear blood cells of patients with recently manifested type 1 diabetes

Aim:  Chronic elevated blood glucose levels are associated with the formation of advanced glycation endproducts (AGEs). Hyperglycaemia and AGEs have been shown to induce activation of the redox‐sensitive transcription factor nuclear factor‐κB (NF‐κB). To validate the hypothesis that the maintenance of normal glucose levels results in the reduction of NF‐κB‐binding activity in vivo, the redox‐sensitive transcription factor NF‐κB was used as marker of hyperglycaemia‐induced mononuclear cell activation in patients who recently developed type 1 diabetes.