Troglitazone reduces neointimal tissue proliferation after coronary stent implantation in patients with non-insulin dependent diabetes mellitus: a serial intravascular ultrasound study

Control of diabetes mellitus and the risk of neointimal hyperplasia after percutaneous coronary intervention: Post-hoc analysis from the BLADE-PCI trial

BACKGROUND AND AIMS

Diabetes-mellitus (DM) is associated with increased risk of neointimal hyperplasia (NIH) and restenosis after percutaneous coronary intervention (PCI). We examined a possible association of DM severity at the time of PCI with the development of NIH.

METHODS

This post-hoc analysis from the BLADE-PCI randomized, multi-center trial included only patients with DM and baseline data of HbA1c within 14 days prior to the index PCI. All patients were treated with zotarolimus-eluting stents. The primary endpoint was percent of NIH volume at 9 months as evaluated by optical coherence tomography. This endpoint was compared between patients with uncontrolled DM (HbA1c ≥ 7.5%) and controlled DM (HbA1c <7.5%) at the index PCI.

RESULTS

The mean percentages of NIH volume were 16.5% ± 9.9 and 12.75% ± 7.9 among patients with baseline HbA1c ≥ 7.5% (n = 74) and <7.5% (n = 102), respectively (p < 0.05). In multivariable analysis, HbA1c ≥ 7.5% was not associated with higher risk of NIH development [95% CI; 2.2 (-0.8, 5.3; p = 0.15)]. Higher HbA1c was not associated with increased risk of NIH at the minimum lumen area site [95% CI; 0.9 (-5.0, 6.7); p = 0.77) or percent stent strut coverage [95% CI; -0.3 (-1.3, 0.6); p = 0.45]. Secondary clinical endpoints including major adverse cardiac and cerebrovascular events, target lesion failure and death were similar between patients with worse and better DM control.

CONCLUSIONS

Uncontrolled DM at the time of PCI performed with contemporary drug-eluting stents was not associated with an increased risk of NIH development.

Pioglitazone Attenuates Injury-Induced Neointima Formation in Mouse Femoral Artery Partially through the Activation of AMP-Activated Protein Kinase

BACKGROUND/AIMS

Pioglitazone (PIO), an antidiabetic drug, has been shown to attenuate vascular smooth muscle cell (VSMC) proliferation, which is a major event in atherosclerosis and restenosis after angioplasty. Till date, the likely contributory role of AMP-activated protein kinase (AMPK) toward PIO inhibition of VSMC proliferation has not been examined in vivo. This study is aimed at determining whether pharmacological inhibition of AMPK would prevent the inhibitory effect of PIO on neointima formation in a mouse model of arterial injury.

METHODS

Male CJ57BL/6J mice were subjected to femoral artery injury using guidewire. PIO (20 mg/kg/day) was administered orally 1 day before surgery and for 3 weeks until sacrifice in the absence or presence of compound C (an AMPK inhibitor). Injured femoral arteries were used for morphometric analysis of neointima formation. Aortic tissue lysates were used for immunoblot analysis of phosphorylated AMPK.

RESULTS

PIO treatment resulted in a significant decrease in intima-to-media ratio by ∼50.3% (p < 0.05, compared with vehicle control; n = 6), which was accompanied by enhanced phosphorylation of AMPK by ∼85% in the vessel wall. Compound C treatment led to a marked reduction in PIO-mediated inhibition of neointima formation.

CONCLUSION

PIO attenuates injury-induced neointima formation, in part, through the activation of AMPK.

Impaired glucose tolerance: do pharmacological therapies correct the underlying metabolic disturbance?

Lifestyle intervention prevents or delays the conversion from impaired glucose tolerance (IGT) to type 2 diabetes. However, many subjects fail to achieve and/or maintain long-term weight loss and to follow a regular exercise regimen may require pharmacologic therapy. Insulin resistance in liver, muscle and fat, along with impaired beta-cell function, plays a central role in the pathogenesis of type 2 diabetes. Insulin sensitising drugs, including metformin and the thiazolidinediones, have significantly reduced the conversion rate of IGT to type 2 diabetes in subjects in several large, well designed clinical trials. Insulin-sensitising drugs are likely to play an important role in future strategies for diabetes prevention.

The clinical significance of PPARα and γ agonism

The thiazolidinediones are synthetic ligands for nuclear peroxisome proliferator activated receptors (PPARs). PPARγ is a transcription factor, which in adipose tissue promotes adipocyte differentiation and also induces apoptosis of terminally differentiated insulin-resistant adipocytes. This promotes the appearance of smaller insulin-sensitive cells. PPARγ ctivation also stimulates the genes controlling triglyceride lipolysis, fatty acid uptake and storage in adipose tissue. It induces a diversion of fatty acids away from muscle and influences the expression of adipocytokines leading to improved insulin signalling in muscle and liver. It may also regulate genes involved in insulin signalling. These all result in an increase in insulin sensitivity. PPARγ s also expressed in atherosclerotic lesion foam cells and its activation may exert anti-inflammatory actions and stimulate expression of genes involved in the reverse cholesterol transport pathway. Thiazolidinediones also improve lipoprotein metabolism and this activity is most pronounced for agents that activate PPARα such as may be the case for pioglitazone.

Differential Effects of Peroxisome Proliferator Activator Receptor-α and γ Ligands on Intimal Hyperplasia After Balloon Catheter-Induced Vascular Injury in Zucker Rats

Background: Patients with type 2 diabetes mellitus have a higher rate of restenosis following angioplasty. Peroxisome proliferator activator receptor-x (PPAR) and y ligands such as fenofibrate and rosiglitazone, respectively, have been shown to have protective effects on the vessel wall. We studied the effect of fenofibrate and rosiglitazone on intimal hyperplasia in the Zucker rat, a model for insulin resistance and type 2 diabetes mellitus, following balloon catheter-induced injury.

Methods and Results: Three groups of 13-week-old female fatty Zucker rats were administered an aqueous suspension of either 3 mg/kg/d rosiglitazone (n = 7) or 150 mg/kg/d fenofibrate (n = 6) by gavage, or served as controls (n = 9). In addition, two groups of 13-week-old female lean Zucker rats were either administered 3 mg/kg/d rosiglitazone (n = 6) or served as controls (n = 6). Carotid balloon injury was induced 1 week after the drugs were started. The drug administration was continued for 3 weeks. A 2-mm balloon catheter was introduced through the femoral artery to the left carotid. The balloon was inflated to 4 atmospheres for 20 seconds and then was deflated to 2 atmospheres and dragged down to the aorta. The rats were killed 3 weeks after the injury. The carotid intima/media ratio was calculated. Intimal hyperplasia after carotid balloon-induced injury in the fatty Zucker rats was significantly reduced in the group treated with rosiglitazone (0.18 ± 0.29) compared with the untreated group (0.97 ± 0.13; P < .01). Plasma glucose, triglyceride, and insulin levels were elevated, indicative of the presence of insulin resistance; rosiglitazone treatment significantly reduced insulin and triglyceride levels without decreasing glucose. Rosiglitazone treatment also reduced, but to a lesser extent, the intimal hyperplasia in the lean Zucker rats (0.57 ± 0.10 vs 1.06 ± 0.12 treated and untreated, respectively; P < .01); however, it had no effect on insulin, triglyceride, or glucose levels in this group. The intimal hyperplasia in the fatty Zucker rats treated with fenofibrate was not reduced compared with controls (0.84 ± 0.26 vs 0.97 ± 0.13, respectively); fenofibrate reduced insulin and triglyceride, but not glucose levels, in these animals.

Conclusions: The PPAR-y ligand rosiglitazone, but not the PPAR-x ligand fenofibrate, decreases intimal hyperplasia following balloon injury in both fatty and lean Zucker rats. This effect of the PPAR-y ligand was independent of glycemia, insulin, and lipid levels, and was more pronounced in insulin-resistant rats.

Coronary artery disease and diabetes mellitus

Diabetes mellitus (DM) is a major risk factor for cardiovascular disease. Near-normal glycemic control does not reduce cardiovascular events. For many patients with 1- or 2-vessel coronary artery disease, there is little benefit from any revascularization procedure over optimal medical therapy. For multivessel coronary disease, randomized trials demonstrated the superiority of coronary artery bypass grafting over multivessel percutaneous coronary intervention in patients with treated DM. However, selection of the optimal myocardial revascularization strategy requires a multidisciplinary team approach ('heart team'). This review summarizes the current evidence regarding the effectiveness of various medical therapies and revascularization strategies in patients with DM.

Nanoparticle drug- and gene-eluting stents for the prevention and treatment of coronary restenosis

Percutaneous coronary intervention (PCI) has become the most common revascularization procedure for coronary artery disease. The use of stents has reduced the rate of restenosis by preventing elastic recoil and negative remodeling. However, in-stent restenosis remains one of the major drawbacks of this procedure. Drug-eluting stents (DESs) have proven to be effective in reducing the risk of late restenosis, but the use of currently marketed DESs presents safety concerns, including the non-specificity of therapeutics, incomplete endothelialization leading to late thrombosis, the need for long-term anti-platelet agents, and local hypersensitivity to polymer delivery matrices. In addition, the current DESs lack the capacity for adjustment of the drug dose and release kinetics appropriate to the disease status of the treated vessel. The development of efficacious therapeutic strategies to prevent and inhibit restenosis after PCI is critical for the treatment of coronary artery disease. The administration of drugs using biodegradable polymer nanoparticles as carriers has generated immense interest due to their excellent biocompatibility and ability to facilitate prolonged drug release. Despite the potential benefits of nanoparticles as smart drug delivery and diagnostic systems, much research is still required to evaluate potential toxicity issues related to the chemical properties of nanoparticle materials, as well as to their size and shape. This review describes the molecular mechanism of coronary restenosis, the use of DESs, and progress in nanoparticle drug- or gene-eluting stents for the prevention and treatment of coronary restenosis.

Effects of low dose pioglitazone on restenosis and coronary atherosclerosis in diabetic patients undergoing drug eluting stent implantation

PURPOSE

Thiazolidinediones are insulin-sensitizing agents that reduce neointimal proliferation and the adverse clinical outcomes associated with percutaneous coronary intervention (PCI) in patients with diabetes mellitus (DM). There is little data on whether or not low dose pioglitazone reduces adverse clinical outcomes.

MATERIALS AND METHODS

The study population included 121 DM patients with coronary artery disease and they were randomly assigned to 60 patients taking 15 mg of pioglitazone daily in addition to their diabetic medications and 61 patients with placebo after the index procedure with drug-eluting stents (DESs). The primary end points were rate of in-stent restenosis (ISR) and change in atheroma volume and in-stent neointimal volume. The secondary end points were all-cause death, myocardial infarction (MI), stent thrombosis and re-PCI.

RESULTS

There were no statistical differences in the clinical outcomes and the rate of ISR between the two groups [all-cause death; n=0 (0%) in the pioglitazone group vs. n=1 (1.6%) in the control group, p=0.504, MI; n=2 (3.3%) vs. n=1 (1.6%), p=0.465, re-PCI; n=6 (10.0%) vs. n=6 (9.8%), p=0.652, ISR; n=4 (9.3%) vs. n=4 (7.5%), p=1.000, respectively]. There were no differences in changes in neointimal volume, percent neointimal volume, total plaque volume and percent plaque volume between the two groups on intravascular ultrasonography (IVUS) study.

CONCLUSION

Our study demonstrated that low dose pioglitazone does not reduce rate of ISR, neointimal volume nor atheroma volume in DM patients who have undergone PCI with DESs, despite the limitations of the study.

Peroxisome proliferator-activated receptor-γ and the endothelium: implications in cardiovascular disease

Peroxisome proliferator-activated receptors-γ (PPARγs) are ligand-activated transcription factors that play a crucial regulatory role in the transcription of a large number of genes involved in lipid metabolism and inflammation. In addition to physiological ligands, synthetic ligands (the thiazoledinediones) have been developed. In spite of the much publicized adverse cardiovascular effects of one such thiazoledinedione (rosiglitazone), PPARγ activation may have beneficial cardiovascular effects. In this article we review the effects of PPARγ activation on the endothelium with special emphasis on the possible implications in cardiovascular disease. We discuss its possible role in inflammation, vasomotor function, thrombosis, angiogenesis, vascular aging and vascular rhythm. We also briefly review the clinical implications of these lines of research.

The role of peroxisome proliferator-activated receptors in pulmonary vascular disease

Peroxisome proliferator-activated receptors (PPARs) are ligand-activated transcription factors belonging to the nuclear hormone receptor superfamily that regulate diverse physiological processes ranging from lipogenesis to inflammation. Recent evidence has established potential roles of PPARs in both systemic and pulmonary vascular disease and function. Existing treatment strategies for pulmonary hypertension, the most common manifestation of pulmonary vascular disease, are limited by an incomplete understanding of the underlying disease pathogenesis and lack of efficacy indicating an urgent need for new approaches to treat this disorder. Derangements in pulmonary endothelial-derived mediators and endothelial dysfunction have been shown to play a pivotal role in pulmonary hypertension pathogenesis. Therefore, the following review will focus on selected mediators implicated in pulmonary vascular dysfunction and evidence that PPARs, in particular PPARγ, participate in their regulation and may provide a potential novel therapeutic target for the treatment of pulmonary hypertension.

Transcriptional Control of Vascular Smooth Muscle Cell Proliferation by Peroxisome Proliferator-Activated Receptor-gamma: Therapeutic Implications for Cardiovascular Diseases

Proliferation of vascular smooth muscle cells (SMCs) is a critical process for the development of atherosclerosis and complications of procedures used to treat atherosclerotic diseases, including postangioplasty restenosis, vein graft failure, and transplant vasculopathy. Peroxisome proliferator-activated receptor (PPAR) gamma is a member of the nuclear hormone receptor superfamily and the molecular target for the thiazolidinediones (TZD), used clinically to treat insulin resistance in patients with type 2 diabetes. In addition to their efficacy to improve insulin sensitivity, TZD exert a broad spectrum of pleiotropic beneficial effects on vascular gene expression programs. In SMCs, PPARgamma is prominently upregulated during neointima formation and suppresses the proliferative response to injury of the arterial wall. Among the molecular target genes regulated by PPARgamma in SMCs are genes encoding proteins involved in the regulation of cell-cycle progression, cellular senescence, and apoptosis. This inhibition of SMC proliferation is likely to contribute to the prevention of atherosclerosis and postangioplasty restenosis observed in animal models and proof-of-concept clinical studies. This review will summarize the transcriptional target genes regulated by PPARgamma in SMCs and outline the therapeutic implications of PPARgamma activation for the treatment and prevention of atherosclerosis and its complications.

Treatment of diabetic vasculopathy with rosiglitazone and ramipril: Hype or hope?

Cardiovascular diseases are responsible for increased morbidity and mortality in people with diabetes. Diabetic macrovasculopathy is associated with structural and functional changes in large arteries, which causes endothelial dysfunction, increased arterial stiffness, or decreased arterial distensability. Diabetic complications can be controlled and avoided by strict glycemic control, maintaining normal lipid profiles, regular physical exercise, adopting a healthy lifestyle and pharmacological interventions. Treatment goals for patients with type 2 diabetes specify targets for glycemia and other cardiometabolic risk factors, for example, hypertension and dyslipidemia. In recent years, special attention has been devoted to both thiazolidindiones (TZDs) and angiotensin converting enzyme (ACE) inhibitors as clinical trials revealed that these drugs may reduce the rate of progression to diabetes or delay the onset of diabetes, regression of impaired glucose tolerance (IGT) to normoglycemia and reduces the composite of all-cause mortality, nonfatal myocardial infarction and stroke in patients with diabetes. This review focuses on the potential roles of rosiglitazone, a member of TZD class of antidiabetic agents, and ramipril, an ACE inhibitor, in preventing the preclinical macrovasculopathy in diabetes and IGT population.

Add-on rosiglitazone therapy improves plasminogen activity and high-density lipoprotein cholesterol in type 2 diabetes mellitus

Rosiglitazone is an oral hypoglycaemic agent of the thiazolidinedione group. This study aimed to assess changes in the diabetic prothrombotic state via plasminogen activity and changes in surrogate markers of atherosclerotic burden via ankle-brachial pressure index (ABPI) measurements after rosiglitazone was added to a pre-existing type 2 diabetes mellitus treatment regime. A nonblinded interventional study was designed. Fifty-nine patients were enrolled. Rosiglitazone-naïve patients were prescribed oral rosiglitazone 4 mg daily for 10 weeks. ABPI, plasminogen activity, glycosylated haemoglobin (HbA1c) and fasting lipid profile were measured pretreatment and post-treatment. Forty-eight patients completed the study. At the end of this study, mean plasminogen activity improvement was nearly 16% (P<0.05), mean ABPI improvement was 0.01 (P=0.439), mean HbA1c reduction was 0.51% (P<0.05), mean total cholesterol (TC) increase was 0.36 mmol/l (P<0.05), mean high-density lipoprotein cholesterol (HDL-C) increase was 0.15 mmol/l (P<0.05) and mean low-density lipoprotein cholesterol increased by 0.19 mmol/l (P=0.098). Rosiglitazone significantly improved plasminogen activity. There was also significant HbA1c reduction, and rise in both TC and HDL-C. Thus, rosiglitazone potentially improves the atherosclerotic burden and prothrombotic state. In future, more studies are needed to confirm the relationship between rosiglitazone, fibrinolytic system and atheromatous reduction in type 2 diabetes mellitus.

The PPAR-RXR Transcriptional Complex in the Vasculature

The peroxisome proliferator-activated receptors (PPARs) and the retinoid X receptors (RXRs) are ligand-activated transcription factors that coordinately regulate gene expression. This PPAR-RXR transcriptional complex plays a critical role in energy balance, including triglyceride metabolism, fatty acid handling and storage, and glucose homeostasis: processes whose dysregulation characterize obesity, diabetes, and atherosclerosis. PPARs and RXRs are also involved directly in inflammatory and vascular responses in endothelial and vascular smooth muscle cells. New insights into fundamental aspects of PPAR and RXR biology, and their actions in the vasculature, continue to appear. Although RXRs are obligate heterodimeric partners for PPAR action, the part that RXRs, and their endogenous retinoid mediators, exert in the vessel wall is less well understood. Biological insights into PPAR-RXRs may help inform interpretation of clinical trials with synthetic PPAR agonists and prospects for future PPAR therapeutics. Importantly, the extensive data establishing a key role for PPARs and RXRs in energy balance, inflammation, and vascular biology stands separately from the clinical experience with any given synthetic PPAR agonist. Both the basic science data and the clinical experience with PPAR agonists identify the need to better understand these important transcriptional regulators.

Revascularization for coronary artery disease in diabetes mellitus: angioplasty, stents and coronary artery bypass grafting

Patients with diabetes mellitus (DM) are prone to a diffuse and rapidly progressive form of atherosclerosis, which increases their likelihood of requiring revascularization. However, the unique pathophysiology of atherosclerosis in patients with DM modifies the response to arterial injury, with profound clinical consequences for patients undergoing percutaneous coronary intervention (PCI). Multiple studies have shown that DM is a strong risk factor for restenosis following successful balloon angioplasty or coronary stenting, with greater need for repeat revascularization and inferior clinical outcomes. Early data suggest that drug eluting stents reduce restenosis rates and the need for repeat revascularization irrespective of the diabetic state and with no significant reduction in hard clinical endpoints such as myocardial infarction and mortality. For many patients with 1- or 2-vessel coronary artery disease, there is little prognostic benefit from any intervention over optimal medical therapy. PCI with drug-eluting or bare metal stents is appropriate for patients who remain symptomatic with medical therapy. However, selection of the optimal myocardial revascularization strategy for patients with DM and multivessel coronary artery disease is crucial. Randomized trials comparing multivessel PCI with balloon angioplasty or bare metal stents to coronary artery bypass grafting (CABG) consistently demonstrated the superiority of CABG in patients with treated DM. In the setting of diabetes CABG had greater survival, fewer recurrent infarctions or need for re-intervention. Limited data suggests that CABG is superior to multivessel PCI even when drug-eluting stents are used. Several ongoing randomized trials are evaluating the long-term comparative efficacy of PCI with drug-eluting stents and CABG in patients with DM. Only further study will continue to unravel the mechanisms at play and optimal therapy in the face of the profoundly virulent atherosclerotic potential that accompanies diabetes mellitus.

Cardiovascular manifestations of insulin resistance

Data from the Centers for Disease Control and Prevention indicate that the prevalence of diabetes is increasing steadily and is coupled with a rise in obesity. Studies such as the Nurses' Health Study show that even slight glucose abnormalities, namely insulin resistance, increase the risk of myocardial infarctions, strokes, other cardiovascular disease, and mortality. Insulin resistance was found to accelerate atherosclerosis, inflammation, the onset of diabetes, cardiovascular disease, obesity, hypertension, chronic kidney disease, and dyslipidemia. Adiponectin was found to have potent antiinflammatory and antiatherosclerotic effects. Similarly, studies indicate that peroxisome proliferators-activated receptor agonists have the potential to treat obesity, diabetes, and atherosclerosis. From a preventive standpoint, it was shown that intensive glucose control reduces long-term cardiovascular risk. This intensive control approach included the use of thiazolidinediones (TZDs; troglitazone, pioglitazone, and rosiglitazone), which were demonstrated to have vascular and nonglycemic effects beyond glucose-lowering. A drawback of using TZDs is peripheral fluid retention. The DREAM study showed that participants with impaired fasting glucose or impaired glucose tolerance who are free from cardiovascular disease benefited significantly from taking 8 mg rosiglitazone per day. The ADOPT study provided evidence that rosiglitazone is more efficient at controlling glycemic loss and maintaining low glycosylated hemoglobin levels than metformin and glyburide. Data from the CHICAGO study indicate that the progression of carotid artery intima-media thickness, a marker of atherosclerosis and a surrogate end point for cardiovascular disease, was slowed more with pioglitazone than glimepiride in a racially diverse population of men and women with diabetes mellitus type 2. Overall, investigators have shifted from a focus on hyperglycemia to a multifactorial approach to risk management in diabetes. This multifactorial approach includes intensive glycemic control, lifestyle intervention, and intensive management of comorbid (dyslipidemia, hypertension, early renal disease) conditions. The implementation of a regular, rigorous exercise and diet program greatly decreased insulin resistance and allowed far more patients to reach their glycosylated hemoglobin goals. Studies with atrovastatin show significant improvement in cardiovascular risk factors in patients with diabetes and hypertension. Short-term studies provide support for the administration of a combination of TZD + sulfonylureas in patients with diabetes mellitus type 2. Likewise, studies have shown that a combination of TZDs + metformin reduced the risk of myocardial infarction. Finally, dipeptidyl peptidase-IV inhibitors and glycolipoprotein-1 analogs show potential for helping prevent the deterioration of glucose metabolism in early diabetes mellitus type 2.

Disruption of endothelial peroxisome proliferator-activated receptor-gamma reduces vascular nitric oxide production

Vascular endothelial cells express the ligand-activated transcription factor, peroxisome proliferator-activated receptor-gamma (PPARgamma), which participates in the regulation of metabolism, cell proliferation, and inflammation. PPARgamma ligands attenuate, whereas the loss of function mutations in PPARgamma stimulate, endothelial dysfunction, suggesting that PPARgamma may regulate vascular endothelial nitric oxide production. To explore the role of endothelial PPARgamma in the regulation of vascular nitric oxide production in vivo, mice expressing Cre recombinase driven by an endothelial-specific promoter were crossed with mice carrying a floxed PPARgamma gene to produce endothelial PPARgamma null mice (ePPARgamma(-/-)). When compared with littermate controls, ePPARgamma(-/-) animals were hypertensive at baseline and demonstrated comparable increases in systolic blood pressure in response to angiotensin II infusion. When compared with those of control animals, aortic ring relaxation responses to acetylcholine were impaired, whereas relaxation responses to sodium nitroprusside were unaffected in ePPARgamma(-/-) mice. Similarly, intact aortic segments from ePPARgamma(-/-) mice released less nitric oxide than those from controls, whereas endothelial nitric oxide synthase expression was similar in control and ePPARgamma(-/-) aortas. Reduced nitric oxide production in ePPARgamma(-/-) aortas was associated with an increase in the parameters of oxidative stress in the blood and the activation of nuclear factor-kappaB in aortic homogenates. These findings demonstrate that endothelial PPARgamma regulates vascular nitric oxide production and that the disruption of endothelial PPARgamma contributes to endothelial dysfunction in vivo.

Reassessing the cardiovascular risks and benefits of thiazolidinediones

This article is designed for the general cardiologist, endocrinologist, and internist caring for patients with diabetes and coronary artery disease. Despite the burden of coronary disease in diabetics, little is known about the impact of commonly used oral hypoglycemic agents on cardiovascular outcomes. As the untoward effects of insulin resistance (IR) are increasingly recognized, there is interest in targeting this defect. Insulin resistance contributes to dyslipidemia, hypertension, inflammation, hypercoagulability, and endothelial dysfunction. The aggregate impact of this process is progression of systemic atherosclerosis and an increased risk of adverse cardiovascular outcomes. As such, much attention has been paid to the peroxisome-proliferator-activated receptor gamma (PPARg) agonists rosiglitazone and pioglitazone (thiazolidinediones [TZDs]). Many studies have demonstrated a beneficial effect on the atherosclerotic process; specifically, these agents have been shown to reduce markers of inflammation, retard progression of carotid intimal thickness, prevent restenosis after coronary stenting, and prevent cardiovascular death and myocardial infarction in 1 large trial. Such benefits come at the risk of fluid retention and heart failure (HF) exacerbation, and the net effect on plasma lipids is still poorly understood. Thus, the aggregate risk-benefit ratio is poorly defined. A recent meta-analysis has raised significant concerns regarding the overall cardiovascular safety of 1 particular PPARg agonist (rosiglitazone), prompting international debate and regulatory changes. This review scrutinizes the clinical evidence regarding the cardiovascular risks and benefits of PPARg agonists. Future studies of PPARg agonists, and other emerging drugs that treat IR and diabetes, must be designed to look at cardiovascular outcomes.

Use of rosiglitazone before and after vascular injury in hypercholesterolemic rabbits: Assessment of neointimal formation

Objectives

To analyse the effects of rosiglitazone administered at different times on neointimal formation in hypercholesterolemic rabbits following vascular injury.

Methods

Thirty-nine rabbits on a hypercholesterolemic diet were included. The animals underwent balloon catheter injury to the right iliac artery on day 14. They were divided into three groups as follows: control group, 13 rabbits without rosiglitazone; group I, 13 rabbits treated with rosiglitazone (3 mg/Kg body weight/day) for 28 days after the vascular injury; and group II, 13 rabbits treated with rosiglitazone (3 mg/Kg body weight/day) during all the experiment (42 days). Histological analysis was done by an experienced pathologist who was unaware of the rosiglitazone treatment. Histomorphometric parameters were performed by calculation of the luminal and intimal layer area, and intima/media layer area ratio (the area of the intimal layer divided by the area of the medial layer).

Results

Intimal area was significantly lower in group II vs. CG (p = 0.024) and group I (p = 0.006). Luminal layer area was higher in group II vs. CG (p < 0.0001) and group I (p < 0.0001). Intima/media layer area ratio was equal between CG and group I. Intima/media layer ratio area was significantly lower in group II vs. control group (p < 0.021) and group I (p < 0.003). There was a significant reduction of 65% and 71% in intima/media layer area ratio in group II vs. control group and group I, respectively.

Conclusion

Pretreatment with rosiglitazone in hypercholesterolemic rabbits submitted to vascular injury significantly reduces neointimal formation.

Rosiglitazone improves aortic arginine transport, through inhibition of PKCα, in uremic rats

Peroxisome proliferator-activated receptor (PPAR) agonists were shown to inhibit atherosclerosis through augmentation of endothelial nitric oxide synthase (eNOS) activity. In addition, rosiglitazone exerts a beneficial effect in chronic renal failure (CRF). Since l-arginine transport by CAT-1 (the specific arginine transporter for eNOS) is inhibited in uremia, we aimed to explore the effect of rosiglitazone on arginine transport in CRF. Arginine uptake by aortic rings was studied in control animals, rats, 6 wk following 5/6 nephrectomy (CRF) and rats with CRF treated with rosiglitazone. The decrease of arginine transport in CRF was prevented by rosiglitazone. Immunobloting revealed that CAT-1 protein was decreased in CRF but remained unchanged following rosiglitazone administration. Protein content of the membrane fraction of PKCα and phosphorylated CAT-1 increased significantly in CRF, effects that were prevented by rosiglitazone. PKCα phosphorylation was unchanged but significantly attenuated by rosiglitazone in CRF. Ex vivo administration of phorbol-12-myristate-13-acetate to rosiglitazone-treated CRF rats significantly attenuated the effect of rosiglitazone on arginine uptake. The decrease in cGMP response to carbamyl-choline (eNOS agonist) was significantly attenuated by rosiglitazone in CRF. Western blotting and immunohistochemistry analysis revealed that protein nitration was intensified in the endothelium of CRF rats and this was attenuated by rosiglitazone. In conclusion, rosiglitazone prevents the decrease in arginine uptake in CRF through both depletion and inactivation of PKCα. These findings are associated with restoration of eNO generation and attenuation of protein nitration and therefore may serve as a novel mechanism to explain the beneficial effects of rosiglitazone on endothelial function in uremia.

[Adjuvant drug treatment in diabetic patients undergoing percutaneous coronary intervention]

The authors describe the adjuvant drug treatment during and after percutaneous coronary intervention in order to obtain the reduction of major cardiovascular events, focusing in diabetic patients. In the clinical follow-up of diabetic patients after PCI, special attention to the control measures of cardiovascular risk factors should be observed. Among those measures, a normal glycemic level is fundamental, which can be achieved with usual clinical care. Antiplatelet therapy is a controversy issue until know. Although combined antiplatelet therapy with aspirin and a thienopyridynic is well supported by a number of clinical trials, adding GPIIb/IIIa agents as adjuvants in diabetic patients should not be irrestrictive as suggested by some authors; they should be restricted to patients with a significative thrombotic burden.

Effect of thiazolidinediones on in-stent restenosis in patients after coronary stenting: a meta-analysis of randomized controlled trials

BACKGROUND

Recent experimental studies have demonstrated that thiazolidinediones (TZDs) therapy inhibits proliferation and migration of vascular smooth muscle cells, accelerates endothelium reparation and attenuates neointimal hyperplasia. It implies that TZDs therapy may have beneficial effects on in-stent restenosis (ISR). Several small-sample clinical trials have evaluated the effect of TZDs therapy on ISR, however, the results were inconsistent across trials.

METHODS AND RESULTS

We performed a meta-analysis of all relevant randomized controlled trials to evaluate the effect of TZDs therapy on in-stent restenosis in patients undergoing coronary stenting. Eight trials involving 366 patients were included in this study. TZDs therapy was associated with a significant reduction in the risk of ISR in both diabetic (RR 0.37, 95% CI 0.23-0.59; P<0.0001) and non-diabetic patients (RR 0.16, 95% CI 0.05-0.45; P=0.0006). TZDs therapy was associated with a significant reduction in late lumen loss (WMD -0.54 mm, 95% CI -0.87 mm, -0.22 mm; P=0.001), percent diameter stenosis (WMD -15.7%, 95% CI -19.4%, -12.0%; P<0.00001), neointimal area/volume (SMD -0.76, 95% CI -1.13, -0.39; P<0.0001) and target lesion revascularization (RR 0.32, 95% CI 0.18-0.57; P=0.0001).

CONCLUSIONS

Our study suggests that TZDs therapy is an effective strategy in preventing ISR in both diabetic and non-diabetic patients undergoing coronary stenting. More studies, especially large multi-centre RCTs, are still warranted to further clarify the anti-restenotic effect of TZDs therapy.

Diabetes mellitus, insulin resistance, hyperglycemia, and stroke

It is well established that diabetes is associated with an increased risk of stroke. Once a stroke has occurred, patients with diabetes experience poorer outcomes (functional status, mortality). Convincing data now support aggressive glucose control and comprehensive cardiovascular risk factor management to prevent stroke in patients with diabetes. However, there remains a distinct paucity of information concerning secondary stroke prevention. Hyperglycemia in the acute stroke setting is a marker for poor outcomes, but it remains unclear whether intensive in-hospital lowering of blood glucose levels improves clinical outcomes. Targeting insulin resistance as a modifiable risk factor for stroke is a novel strategy currently under investigation.

A cardiologist view of vascular disease in diabetes

Diabetes mellitus is a potent risk factor for the development of a wide spectrum of cardiovascular (CV) complications. The complex metabolic milieu accompanying diabetes alters blood rheology, the structure of arteries and disrupts the homeostatic functions of the endothelium. These changes act as the substrate for end-organ damage and the occurrence of CV events. In those who develop acute coronary syndromes, patients with diabetes are more likely to die, both in the acute phase and during follow-up. Patients with diabetes are also more likely to suffer from chronic cardiac failure, independently of the presence of large vessel disease, and also more likely to develop stroke, renal failure and peripheral vascular disease. Preventing vascular events is the primary goal of therapy. Optimal cardiac care for the patient with diabetes should focus on aggressive management of traditional CV risk factors to optimize blood glucose, lipid and blood pressure control. Targeting medical therapy to improve plaque stability and diminish platelet hyper-responsiveness reduces the frequency of events associated with atherosclerotic plaque burden. In patients with critical lesions, revascularization strategies, either percutaneous or surgical, will often be necessary to improve symptoms and prevent vascular events. Improved understanding of the vascular biology will be crucial for the development of new therapeutic agents to prevent CV events and improve outcomes in patients with diabetes.

Effects of the thiazolidinedione medications on micro- and macrovascular complications in patients with diabetes--update 2008

INTRODUCTION

The thiazolidinedione (TZD) drugs, including pioglitazone (Actos) and rosiglitazone (Avandia), are commonly prescribed in patients with type 2 diabetes mellitus (T2DM), largely due to their favorable effects on hyperglycemia, insulin sensitivity, and cardiometabolic profile. However, the data are sparse assessing the effects of TZDs on micro- and macrovascular disease risk.

DISCUSSION

Although no studies have been published on microvascular clinical outcomes, both TZDs significantly reduce the urine albumin-to-creatinine ratio. TZDs have consistently been associated with favorable effects on atherosclerosis and cardiovascular disease (CVD) risk. Only one study has been published to date specifically designed to assess the effects of a TZD (pioglitazone) on macrovascular outcomes, the PROactive trial. In this trial, pioglitazone versus placebo was associated with a non-significant 10% reduction in the combined primary endpoint of mortality, coronary and peripheral vascular events, and revascularizations. No individual trial has been published specifically assessing the CVD effects of rosiglitazone, but several meta-analyses and a published interim report from an ongoing trial (RECORD) point to safety concerns regarding rosiglitazone use and the risk of myocardial infarctions (MI), leading to amplified warnings in the product labeling for rosiglitazone to reflect these concerns.

CONCLUSION

All published trials and meta-analyses of TZDs have consistently shown increased risk of heart failure (HF) with both TZDs, though the actual placebo-subtracted incidence of HF is low (<0.5% per year). The initiation of either TZD is contraindicated in patients with NHYA class III or IV HF, and cautions exist for their use in any patient with heart failure. Much uncertainty remains regarding the aggregate CVD effects of the TZDs, and several trials are presently underway to further address these issues.

Effect of cilostazol on in-stent neointimal hyperplasia after coronary artery stenting: a quantative coronary angiography and volumetric intravascular ultrasound study

BACKGROUND

This study was designed to investigate the efficacy of cilostazol on the prevention of in-stent neointimal hyperplasia as measured by both quantitative coronary angiography (CAG) and volumetric intravascular ultrasound (IVUS).

METHODS AND RESULTS

Fifty-nine patients (39 men, age 62 years) undergoing elective coronary stenting were randomly assigned to receive aspirin plus clopidogrel or ticlopidine (Group I, n=28, 30 lesions) or aspirin plus clopidogrel or ticlopidine plus cilostazol (Group II, n=31, 35 lesions). CAG and IVUS were performed and repeated at 6 months to assess the primary endpoints of minimal luminal diameter (MLD) and in-stent neointimal hyperplasia volume. Follow-up CAG was performed on all patients and follow-up IVUS study was available for 50 lesions in 48 patients (24 lesions in Group I, 26 in Group II). There were no significant differences in the baseline angiographic data between the 2 groups. At 6 months follow-up, in-stent MLD was 1.90+/-0.76 mm in Group I and 2.41+/-0.85 mm in Group II (p=0.006). Volumetric IVUS at 6 months demonstrated that in-stent intimal hyperplasia volume per stent length was 2.2+/-1.4 mm3/mm in Group I and 1.0+/-0.5 mm3/mm in Group II (p=0.001).

CONCLUSIONS

Triple antiplatelet therapy including cilostazol seems to be more effective at preventing in-stent neointimal hyperplasia than a dual antiplatelet regimen.

The Role of PPARgamma in pulmonary vascular disease

The peroxisome proliferator-activated receptor (PPAR) gamma is a member of the nuclear hormone receptor superfamily of ligand-activated transcription factors. Thiazolidinediones, pharmacological ligands for PPARgamma, are currently used in the management of type 2 diabetes. Peroxisome proliferator-activated receptor gamma is expressed in the lung and pulmonary vasculature, and its expression is reduced in the vascular lesions of patients with pulmonary hypertension. Furthermore, thiazolidinedione PPARgamma ligands reduced pulmonary hypertension and vascular remodeling in several experimental models of pulmonary hypertension. This report reviews current evidence that PPARgamma may represent a novel therapeutic target in pulmonary hypertension and examines studies that have begun to elucidate mechanisms that underlie these potential therapeutic effects.

Angiographic and clinical outcomes of rosiglitazone in patients with type 2 diabetes mellitus after percutaneous coronary interventions: a single center experience

A beneficial effect of thiazolidinediones includes the reduction of intermediate markers, suggesting a potential for reducing atherosclerosis and restenosis. The objective of this study was to determine if rosiglitazone (RSG) reduced the odds of restenosis and if RSG improved the odds of clinical outcomes after percutaneous coronary intervention (PCI) in type 2 diabetes mellitus (DM) patients. A total of 609 patients with 734 lesions were selected from the period between January 1, 2001 and January 31, 2004. These patients were divided into 2 groups: a "control" group representing patients seen between January 1, 2001 and September 2002 when RSG was not available in our hospital and a "RSG treatment" group representing patients seen between September 2002 and January 31, 2004 when RSG was available in our hospital. Thus, 213 patients with 253 lesions (1.19 L/P) were placed in the RSG group and 396 patients with 481 lesions (1.21 L/P) were placed in the control group. Subgroup analysis based on the PCI received had 88 patients in the RSG arm receiving balloon angioplasty and 125 patients receiving coronary stenting; the control group had 187 and 209 patients, respectively, in the subgroups. Primary endpoint was angiographic restenosis at 6 months, and secondary endpoints were death, myocardial infarction, and target lesion revascularization. More patients in the control group were insulin-requiring, had poorer left ventricular function, but had a larger preprocedural minimal lumen diameter (pre-MLD). At 6 months, restenosis and reocclusion rates were lower in the RSG group (P = .014 and P = .006, respectively). Twenty-nine patients died in the control group versus 1 in the RSG group (P <or= .001). RSG (P = .019), stenting (P = .005), preprocedural reference vessel diameter (P = .017), metformin (P = .022), pre-MLD (P < .001), hyperlipidemia (P = .016), and combined RSG and metformin (P = .020) were predictors of restenosis, while RSG (P = .016) and metformin (P = .029) were predictors of survival. In conclusion, RSG was found safe and well tolerated and was associated with reduced odds of restenosis, reocclusion, and mortality rates in type 2 DM patients independent of glycemic control and PCI performed.

[Care of patients after coronary stent implantation: what is important in practice?]

The introduction of Drug Eluting Stents was an important step to reduce restenosis rate after coronary stent implantation. Unfortunately, reduction of restenosis was paid off by the price of potential increased late (>30 days) stent thrombosis. However, current data are not completely conclusive with respect to extent and duration of stent thrombosis and cardiovascular risk after drug eluting stent implantation. Until now, especially for patients at risk for stent thrombosis a prolonged (12 instead of 6 months) dual antiplatelet therapy with aspirin and clopidogrel is recommended. Thereby, the quality of physician instructions is predictive for patient's compliance. Premature termination of dual antiplatelet therapy should be avoided; many small surgical interventions (e.g. tooth extraction) can be performed under dual antiplatelet therapy. Patients with "triple therapy" (aspirin, clopidogrel and coumarin derivate) should be monitored carefully, since they have an excessive bleeding risk. An elective coronary angiography after coronary stent implantation is not routinely necessary. However in selected high-risk patients (e.g. left main or multivessel stent implantation) control angiography may be useful. Medical therapy of risk factors (hyperlipidemia, hypertension, and diabetes mellitus) is essential also after coronary stent implantation. It is important to screen patients for diabetes mellitus, since approximately 1/3 of patients after coronary intervention have an otherwise unrecognized diabetes mellitus or glucose tolerance disturbance.

Anti-proliferative activity of oral anti-hyperglycemic agents on human vascular smooth muscle cells: thiazolidinediones (glitazones) have enhanced activity under high glucose conditions

Background

Inhibition of vascular smooth muscle cell (vSMC) proliferation by oral anti-hyperglycemic agents may have a role to play in the amelioration of vascular disease in diabetes. Thiazolidinediones (TZDs) inhibit vSMC proliferation but it has been reported that they anomalously stimulate [³H]-thymidine incorporation. We investigated three TZDs, two biguanides and two sulfonylureas for their ability of inhibit vSMC proliferation. People with diabetes obviously have fluctuating blood glucose levels thus we determined the effect of media glucose concentration on the inhibitory activity of TZDs in a vSMC preparation that grew considerably more rapidly under high glucose conditions. We further explored the mechanisms by which TZDs increase [³H]-thymidine incorporation.

Methods

VSMC proliferation was investigated by [³H]-thymidine incorporation into DNA and cell counting. Activation and inhibition of thymidine kinase utilized short term [³H]-thymidine uptake. Cell cycle events were analyzed by FACS.

Results

VSMC cells grown for 3 days in DMEM with 5% fetal calf serum under low (5 mM glucose) and high (25 mM glucose) increased in number by 2.5 and 4.7 fold, respectively. Rosiglitazone and pioglitazone showed modest but statistically significantly greater inhibitory activity under high versus low glucose conditions (P < 0.05 and P < 0.001, respectively). We confirmed an earlier report that troglitazone (at low concentrations) causes enhanced incorporation of [³H]-thymidine into DNA but did not increase cell numbers. Troglitazone inhibited serum mediated thymidine kinase induction in a concentration dependent manner. FACS analysis showed that troglitazone and rosiglitazone but not pioglitazone placed a slightly higher percentage of cells in the S phase of a growing culture. Of the biguanides, metformin had no effect on proliferation assessed as [³H]-thymidine incorporation or cell numbers whereas phenformin was inhibitory in both assays albeit at high concentrations. The sulfonylureas chlorpropamide and gliclazide had no inhibitory effect on vSMC proliferation assessed by either [³H]-thymidine incorporation or cell numbers.

Conclusion

TZDs but not sulfonylureas nor biguanides (except phenformin at high concentrations) show favorable vascular actions assessed as inhibition of vSMC proliferation. The activity of rosiglitazone and pioglitazone is enhanced under high glucose conditions. These data provide further in vitro evidence for the potential efficacy of TZDs in preventing multiple cardiovascular diseases. However, the plethora of potentially beneficial actions of TZDs in cell and animal models have not been reflected in the results of major clinical trials and a greater understanding of these complex drugs is required to delineate their ultimate clinical utility in preventing macrovascular disease in diabetes.

Effect of thiazolidinedione therapy on restenosis after coronary stent implantation: a meta-analysis of randomized controlled trials

BACKGROUND

We sought to review the evidence from the available randomized controlled trials (RCTs) regarding the effect of thiazolidinedione therapy on in-stent restenosis after percutaneous coronary intervention.

METHODS

The studies in our meta-analysis were retrieved from search on the PubMed database and from references in relevant articles. Included studies were RCTs that provided comparative data regarding the effectiveness of 6-month pioglitazone or rosiglitazone therapy on the prevention of in-stent restenosis after coronary stent implantation as assessed by quantitative coronary angiography.

RESULTS

Five RCTs that included 235 evaluable patients who underwent coronary stent implantation and received a 6-month pioglitazone or rosiglitazone therapy were included in our meta-analysis. Restenosis rate was significantly lower in patients who received thiazolidinedione therapy in addition to standard therapy (3 RCTs, 170 patients, odds ratio 0.29, 95% CI 0.15-0.56, random effects model). Percentage diameter stenosis was significantly lower in the pioglitazone-rosiglitazone arm (3 RCTs, 170 patients, weighted difference in means 14.35, 95% CI 19.99-8.72, random effects model). Minimal lumen diameter of the target lesion was significantly higher in patients who received thiazolidinedione therapy (3 RCTs, 170 patients, weighted difference in means 0.43, 95% CI 0.21-0.65, random effects model). Patients who received thiazolidinediones were significantly less likely to undergo target lesion revascularization due to restenosis (4 RCTs, 197 patients, odds ratio 0.24, 95% CI 0.09-0.61, random effects model).

CONCLUSIONS

Our study suggests that thiazolidinedione therapy in patients undergoing coronary stent implantation may be associated with less in-stent restenosis and repeated revascularization. Decisions on clinical use of this therapy must await larger double-blind clinical trials.

Reduction of neointimal hyperplasia after coronary stenting by pioglitazone in nondiabetic patients with metabolic syndrome

BACKGROUND

This study investigates whether pioglitazone reduces neointimal hyperplasia after coronary stenting in nondiabetic patients with metabolic syndrome (MS) using intravascular ultrasound (IVUS). Pioglitazone, a novel insulin-sensitizing thiazolidinedione, has been shown to reduce neointimal hyperplasia after coronary stenting in patients with type 2 diabetes. However, the effect of pioglitazone on in-stent restenosis in nondiabetic patients with MS remains unknown.

METHODS AND RESULTS

Twenty-eight nondiabetic patients with MS after bare-metal stent implantation were randomized to 6-month treatment with or without 30 mg/d of pioglitazone (pioglitazone group [PIO] of 14 patients with 16 lesions and control group [CONT] of 14 patients with 16 lesions). At baseline and at 6-month follow-up, assessment of insulin resistance and visceral fat accumulation, quantitative coronary angiographic analysis, and IVUS measurements were performed. Pioglitazone treatment improved insulin resistance and decreased visceral fat accumulation without significant changes in plasma glucose levels, glycosylated hemoglobin A1c levels, and lipid profiles. Intimal index (intimal area/stent area) and intimal area were reduced in PIO compared with CONT (13% +/- 7% vs 21% +/- 13%, P = .033; 1.28 +/- 0.76 mm2 vs 1.90 +/- 1.16 mm2, P = .084; respectively). Binary restenosis rate was 0% in PIO versus 31% in CONT (P = .043).

CONCLUSIONS

This is the first randomized, prospective IVUS study demonstrating that pioglitazone reduces neointimal hyperplasia after coronary stenting in nondiabetic patients with MS. Our data suggest that pioglitazone treatment may represent a novel therapeutic tool to target in-stent restenosis in nondiabetic patients with MS.

A randomized trial of the effects of rosiglitazone and metformin on inflammation and subclinical atherosclerosis in patients with type 2 diabetes

BACKGROUND

Metformin and rosiglitazone both improve glycemic control in type 2 diabetes mellitus, however may possess different anti-inflammatory and anti-atherosclerotic properties. We investigated the effects of these medications on high-sensitivity C-reactive protein (hsCRP) and carotid artery intima-media thickness (CIMT) to determine their relative potential to reduce cardiovascular risk independent of their antihyperglycemic actions.

METHODS

Ninety-two subjects with suboptimally controlled diabetes mellitus (hemoglobin A1c [HbA1c] >7.0%) were assigned to therapy with either rosiglitazone 4 mg once daily or metformin 850 mg twice daily for 24 weeks. The primary end point was the change in hsCRP after 24 weeks. The change in CIMT was prespecified as a secondary end point.

RESULTS

Metformin and rosiglitazone treatment led to similar significant improvements in glycemic control (HbA1c -1.08% in the rosiglitazone group and -1.18% in the metformin group, P = nonsignificant). High-sensitivity C-reactive protein levels decreased by an average of 68% in the rosiglitazone group (5.99 +/- 0.88 to 1.91 +/- 0.28 mg/L, P < .001), compared with a nonsignificant 4% reduction in hsCRP with metformin (5.69 +/- 0.83 to 5.46 +/- 0.92 mg/L; P = nonsignificant). Maximal CIMT progressed in the metformin group (+0.084 +/- 0.038 mm), whereas regression of maximal CIMT was observed in the rosiglitazone group (-0.037 +/- 0.031 mm; P = .02 for the between group comparison). Similar changes were observed for mean CIMT. The change in hsCRP and maximal CIMT were related in a multivariable model controlling for changes in HbA1c and lipid parameters (r = .31; P = .01).

CONCLUSIONS

Rosiglitazone, compared to metformin, induced a prompt and profound reduction in hsCRP levels independent of its effect on glycemia. This change was associated with regression of CIMT after 24 weeks.

[State-of-the-art in the treatment of chronic coronariopathy in diabetic patients: evidences and controversies based in clinical trials]

Diabetes mellitus is a powerful risk factor for coronary artery disease. Diabetics demonstrate accelerated coronary atherosclerosis and worst prognosis following cardiac events. Although myocardial revascularization procedures result in more effective relieve of symptoms in patients with known coronary artery disease, there is no substantial evidence that this strategy improves outcome, except for specific situations. In addition, the benefit of myocardial revascularization is attenuated by the presence of metabolic abnormalities related to insulin resistance and other significant co-morbidities in diabetic patients. New advances recently developed for the clinical treatment of diabetes, as well as surgical and percutaneous approaches of myocardial revascularization, such as drug-eluting stents, seem to be promising therapeutical strategies for diabetic patients. Most importantly, treatment of type 2 diabetics with chronic coronary artery disease should consider the multifactorial pathogenesis of the disease and combine aggressive control of glycemic levels, strict management of all conventional risk factors, and lifestyle modification. The metabolic effects of insulin sensitizers over cardiovascular disease and mortality are under discussion. Ongoing clinical multicenter trials will probably define the real impact of new therapeutic modalities over the prognosis of diabetic patients.

Thiazolidinediones and risk of repeat target vessel revascularization following percutaneous coronary intervention: a meta-analysis

OBJECTIVE

Thiazolidinediones (TZDs) (rosiglitazone and pioglitazone) are a class of antidiabetes agents that have a high affinity for peroxisome proliferator-activated receptor-gamma. TZDs initiate a multitude of physiologic processes that may elicit benefits as systemic agents for the prevention of restenosis requiring revascularization following percutaneous coronary intervention (PCI). Numerous trials have evaluated the impact of TZDs on repeat target vessel revascularization (TVR) in patients following PCI; however, several limitations (small sample size, inconclusive results, and risk factor stratification) complicate definitive conclusions. A meta-analysis was performed to evaluate the impact of TZDs on repeat TVR following PCI.

RESEARCH DESIGN AND METHODS

Included trials met the following criteria: 1) prospective, randomized controlled trials evaluating available TZDs versus standards of care; 2) well-described protocol; 3) minimum of 6 months of follow-up; and 4) data provided on repeat TVR. Data are presented as relative risks (RRs) with 95% CIs.

RESULTS

Seven clinical trials (n = 608) met the inclusion criteria. Upon meta-analysis, the risk of repeat TVR was significantly reduced in patients who received TZD therapy compared with standards of care (RR 0.35 [95% CI 0.22-0.57]). In studies using rosiglitazone (0.45 [0.25-0.83]) and pioglitazone (0.24 [0.11-0.51]), risk of repeat TVR was significantly reduced. Risk of repeat TVR was also significantly reduced among patients with (0.34 [0.19-0.63]) and without (0.37 [0.18-0.77]) diabetes.

CONCLUSIONS

Results from this meta-analysis suggest that TZDs effectively reduce the risk of repeat TVR following PCI.

Drug-Eluting Stents

The introduction of percutaneous transluminal coronary angioplasty has revolutionized the field of cardiology by providing patients with coronary artery disease immediate and effective therapy. Overshadowing the early success of angioplasty was the high rate of angiographic restenosis and recurrent symptoms at 6 months. The use of stents reduced the incidence of restenosis; however, the rise in the number of patients undergoing percutaneous interventions produced a new problem of restenosis occurring within the stent: in-stent restenosis (ISR). Mechanical approaches, including directional and rotational atherectomy and systemic pharmacotherapy, have failed to demonstrate a reduction in ISR in randomized clinical trials. Intravascular brachytherapy is currently the only approved therapy for ISR, although this treatment has numerous unresolved questions and is not effective in a large percent of patients. Drug-eluting stents have reduced the incidence of restenosis by providing localized therapy to the targeted lesion without systemic toxicity. The purpose of this review is to synthesize data from major clinical trials involving the 2 most successful agents used in the prevention of restenosis: sirolimus and paclitaxel. The cellular and molecular mechanisms of both ISR and restenosis postangioplasty derived from animal models will be introduced. Second, an overview of 3 alternate interventions that attempt to reduce the rates of restenosis is presented. Finally, the major randomized, controlled trials involving sirolimus and paclitaxel are described, and their clinical implications and use as a possible solution in the prevention of restenosis is discussed.

The altered homeostatic theory: A hypothesis proposed to be useful in understanding and preventing ischemic heart disease, hypertension, and diabetes – including reducing the risk of age and atherosclerosis

Evidence will be presented to support the usefulness of the altered homeostatic theory in understanding basic pathogenetic mechanisms of ischemic heart disease (IHD), hypertension, and diabetes, and in improving prevention of these disorders. The theory argues that: IHD, hypertension, and diabetes share the same basic pathogenesis; risk factors favor a sympathetic homeostatic shift; preventative factors favor a parasympathetic homeostatic shift; risk and preventative factors oppose each other through a dynamic risk/prevention balance; and prevention should be based on improving the risk/prevention balance. Prevention based on improving the risk/prevention balance should be more effective, as this method is regarded as reflecting more accurately basic pathogenetic mechanisms. As example, the theory argues that the risk of supposedly nonmodifiable risk factors as age and the risk of relatively nonmodifiable atherosclerosis can be reduced significantly. The possible validity of the altered homeostatic theory was tested by a study based on multiple associations. Findings support a common pathogenesis for IHD, hypertension, and diabetes based on a sympathetic homeostatic shift, and the usefulness of prevention based on improving the risk/prevention balance by using standard pharmaceutical and lifestyle preventative measures. The same set of multiple and diverse risk factors favored IHD, hypertension, and diabetes, and the same set of multiple and diverse pharmaceutical and lifestyle preventative measures prevented these disorders. Also, the same set of preventative agents generally improved cognitive function and bone density, and reduced the incidence of Alzheimer's disease, atrial fibrillation, and cancer. Unexpectedly, evidence was developed that four major attributes of sympathetic activation represent four major risk factors; attributes of sympathetic activation are a tendency toward thrombosis and vasoconstriction, lipidemia, inflammation, and hyperglycemia, and corresponding risk factors are endothelial dysfunction (which expresses thrombosis/vasoconstriction and epitomizes this tendency), dyslipidemia, inflammation, and insulin resistance. These findings, plus other information, provide evidence that dyslipidemia acts mainly as a marker of risk of IHD, rather than being the basic mechanism of this disorder. However, prevention generally is based solely on improvement of dyslipidemia; basing prevention on dyslipidemia relatively underemphasizes the importance of other significant risk factors and, by certifying its validity, discourages alternate pathogenetic approaches. Also, development of myocardial infarction is approached differently. It seems generally accepted that dyslipidemia results rather automatically in infarction through the sequence of atherosclerosis, atherosclerotic complications, and thrombosis. In contrast, distinction is made between development of atherosclerosis and acute induction of infarction--where atherosclerosis is only one of multiple risk factors.

Peroxisome proliferator-activated receptor-gamma agonists for management and prevention of vascular disease in patients with and without diabetes mellitus

Inflammation is known to have a pathogenic role in atherosclerosis and the genesis of acute coronary syndromes. The peroxisome proliferator-activated receptor (PPAR)-gamma, which is expressed in many constituent cells of atheromatous plaques, inhibits the activation of several proinflammatory genes responsible for atheromatous plaque development and maturation. Agonists of this receptor, such as rosiglitazone and pioglitazone, are currently available for the treatment of type 2 diabetes mellitus, and several lines of evidence have shown that these drugs have antiatherogenic effects. Insulin resistance is associated with inflammation and has a key role in atherogenesis. The antiatherogenic and insulin sensitizing effects of the thiazolidinediones in patients with type 2 diabetes mellitus may be associated with this action. However, in recent years there has been growing evidence that the antiatherogenic effects of PPAR-gamma agonists are not confined to patients with diabetes mellitus. PPAR-gamma agonists have been shown to downregulate the expression of endothelial activation markers, reduce circulating platelet activity, improve flow-mediated dilatation and attenuate atheromatous plaque progression in patients without diabetes mellitus. These effects of PPAR-gamma agonists appear to result from both insulin sensitization and a direct modulation of transcriptional activity in the vessel wall. This review summarizes the current understanding of the role of PPAR-gamma agonists in atherogenesis and discusses their potential role in the treatment of coronary artery disease in patients with type 2 diabetes mellitus and in nondiabetic patients.

Peroxisome Proliferator-Activated Receptor γ Ligand Pioglitazone Alters Neointimal Composition in a Balloon-Denuded and Radiated Hypercholesterolemic Rabbit

Peroxisome proliferator-activated receptor (PPAR)-gamma activation suppresses inflammatory response, monocyte recruitment, and vascular cell proliferation. Because inflammation, deregulated growth, and migration of monocytes and vascular smooth muscle cells (VSMC) play important roles in the development of neointima, we tested the effect of pioglitazone, a high-affinity ligand, for PPAR-gamma on neointima formation in the iliac arteries of a balloon-denuded and radiated hypercholesterolemic rabbit. Rabbits were fed a 1.0% cholesterol diet for 7 days followed by denudation of endothelial layer and continued on a 0.15% cholesterol diet. On day 32, animals were divided into 2 groups. One group received a 0.15% cholesterol diet (n = 7) and the other group received a 0.15% cholesterol diet supplemented with 400 mg of pioglitazone per kilogram. On day 35, the balloon-denuded area was radiated. Four weeks after radiation, animals were sacrificed and arterial segments were processed for morphometry and immunohistochemistry. Data analysis showed that the pioglitazone group had smaller neointima (0.85 +/- 0.36 vs. 1.41 +/- 0.56, P < 0.05), with more cells positive for VSMC (23.07 +/- 6.16 vs. 18.33 +/- 5.19, P = 0.04), less for monocytes (16.01 +/- 5.33 vs. 21.29 +/- 4.33, P < 0.05), and fewer cells expressing metalloproteinase (MMP)-1 and MMP-9 (3.69 +/- 0.47 vs. 4.82 +/- 0.93, P < 0.05 and 3.24 +/- 0.71 vs. 4.29 +/- 0.74, P < 0.05, respectively). Pioglitazone reduced neointimal area and modified its composition in a balloon-denuded and radiated hypercholesterolemic rabbit model.

Thiazolidinediones and risk for atherosclerosis: pleiotropic effects of PPar gamma agonism

Despite advances in the development of anti-hyperglycaemic drugs and a greater focus on cardiovascular risk modification for patients with diabetes, cardiovascular disease remains the most common complication of type 2 diabetes. Since their initial availability in 1997, the thiazolidinediones have become one of the most commonly prescribed classes of medications for type 2 diabetes. In addition to glucose control, the thiazolidinediones have a number of pleiotropic effects on myriad traditional and non-traditional risk factors for cardiovascular disease, and hold promise with regard to modification of cardiovascular risk. In a recently reported large-scale clinical trial, pioglitazone was associated with improved cardiovascular outcomes in patients with type 2 diabetes and prevalent atherosclerotic disease. In this review, we summarise the experimental, preclinical and clinical data regarding the effects of the thiazolidinediones on cardiovascular risk factors and clinical outcomes.

Vascular effects of TZDs: New implications

The incidence of diabetes, now affecting more than 170 million individuals is growing rapidly. Type 2 diabetes, which accounts for 90% of all diabetes cases, is associated with increased cardiovascular morbidity and mortality. Thiazolidinediones (TZDs), used for the treatment of patients with type 2 diabetes improve insulin sensitivity and endothelial dysfunction and exert beneficial effects on the lipid profile by activating the peroxisome proliferator-activated receptor gamma (PPAR-gamma). Moreover, a large body of evidence indicates that TZDs exhibit antiatherogenic effects independent of their antidiabetic and lipid-lowering properties by modulating inflammatory processes. This review will focus on the role of PPAR-gamma agonists in the vessel wall and summarize their effects on C-reactive protein (CRP), plasminogen activator inhibitor type-1 (PAI-1), matrix metalloproteinase-9 (MMP-9), adiponectin and ATP-binding cassette transporter A1 (ABCA1) and their implications for treatment of advanced stages of atherosclerosis, particularly in a setting of type 2 diabetes.

Peroxisome proliferator-activated receptors in vascular biology-molecular mechanisms and clinical implications

Peroxisome proliferator-activated receptors (PPAR)alpha, gamma and beta/delta belong to the nuclear receptor family of ligand-activated transcription factors. PPARs heterodimerize with the retinoid X receptor (RXR) and then act as transcription factors to modulate the function of many target genes. PPARalpha, gamma and beta/delta subtypes have significant differences in their ligand and gene specificities. PPARalpha is activated by polyunsaturated fatty acids and by fibrate drugs (fenofibrate and gemfibrozil) and controls expression of genes involved in lipid metabolism. PPARgamma is activated by fatty acid derivatives, such as hydroxyoctadecadienoic acid (HODEs), prostaglandin derivatives, such as 15-deoxy-Delta12,14-prostaglandin J2, and thiazolidinedione (glitazone) drugs, such as pioglitazone and rosiglitazone. PPARgamma is a key regulator of glucose homeostasis and adipogenesis. PPARbeta/delta ligands include polyunsaturated fatty acids, prostaglandins and synthetic compounds and stimulate fatty acid oxidation. All PPARs are expressed in vascular cells where they exert antiatherogenic, anti-inflammatory and vasculoprotective actions. Activators of PPARalpha (fibrates) and PPARgamma (thiazolidinediones or glitazones) antagonize angiotensin II effects in vivo and in vitro and have cardiovascular antioxidant and anti-inflammatory actions. PPAR agonists slightly reduce blood pressure are cardio-protective and correct vascular structure and endothelial dysfunction in experimental models of hypertension. Because of these beneficial effects, activators of PPARs may have therapeutic potential in the prevention of cardiovascular disease beyond their actions on carbohydrate and lipid metabolism. The present chapter focuses on the role of PPARs in vascular biology and discusses the clinical implications of using PPAR agonists in the management of vascular disease.

In stent restenosis: bane of the stent era

The long term outcome of stent implantation is affected by a process called in stent restenosis (ISR). Multiple contributory factors have been identified, but clear understanding of the overall underlying mechanism remains an enigma. ISR progresses through several different phases and involves numerous cellular and molecular constituents. Platelets and macrophages play a central role via vascular smooth muscle cell migration and proliferation in the intima to produce neointimal hyperplasia, which is pathognomic of ISR. Increased extracellular matrix formation appears to form the bulk of the neointimal hyperplasia tissue. Emerging evidence of the role of inflammatory cytokines and suppressors of cytokine signalling make this an exciting and novel field of antirestenosis research. Activation of Akt pathway triggered by mechanical stretch may also be a contributory factor to ISR formation. Prevention of ISR appears to be a multipronged attack as no therapeutic "magic bullet" exists to block all the processes in one go.