Antidiabetic PPAR gamma-activator rosiglitazone reduces MMP-9 serum levels in type 2 diabetic patients with coronary artery disease

Peroxisome proliferator-activated receptors and inflammation

Peroxisome proliferator-activated receptors (PPARs) are members of the nuclear hormone receptors family. PPARs are a family of 3 ligand-activated transcription factors: PPARalpha (NR1C1), PPARbeta/delta (NUC1; NR1C2), and PPARgamma (NR1C3). PPARalpha, -beta/delta, and -gamma are encoded by different genes but show substantial amino acid similarity, especially within the DNA and ligand binding domains. All PPARs act as heterodimers with the 9-cis-retinoic acid receptors (retinoid X receptor; RXRs) and play important roles in the regulation of metabolic pathways, including those of lipid of biosynthesis and glucose metabolism, as well as in a variety of cell differentiation, proliferation, and apoptosis pathways. Recently, there has been a great deal of interest in the involvement of PPARs in inflammatory processes. PPAR ligands, in particular those of PPARalpha and PPARgamma, inhibit the activation of inflammatory gene expression and can negatively interfere with pro-inflammatory transcription factor signaling pathways in vascular and inflammatory cells. Furthermore, PPAR levels are differentially regulated in a variety of inflammatory disorders in man, where ligands appear to be promising new therapies.

Rapid Effects of Rosiglitazone Treatment on Endothelial Function and Inflammatory Biomarkers

Background— Antidiabetic thiazolidinediones (TZDs), like rosiglitazone or pioglitazone, improve endothelial function in patients with type 2 diabetes or metabolic syndrome, but it is currently unknown, whether these beneficial effects of TZDs depend on their metabolic action or may be caused by direct effects on the endothelium. Therefore, the present study examined whether short-term rosiglitazone treatment influences endothelium-dependent vasodilation as well as serum levels of vascular disease biomarkers in healthy, nondiabetic subjects.

Methods and Results— Short-term treatment (21 days) of healthy subjects (n=10) did not significantly change blood glucose levels or lipid profile. In contrast, rosiglitazone significantly increased flow-mediated, endothelium-dependent vasodilation already within the first day from 5.3±2.7% at baseline to 7.8±2.6%, further increasing it to 9.4±3.0% at day 21. In addition, the early improvement of endothelium-dependent vasodilation was paralleled by a rapid reduction of serum levels of the biomarkers C-reactive protein (CRP), serum amyloid A (SAA), and sE-selectin. Moreover, after drug withdrawal all markers remained suppressed for the whole follow-up period of 7 days. In contrast, rosiglitazone treatment did not significantly affect tumor necrosis factor (TNF)-α, interleukin (IL)-6, sICAM-1, sVCAM-1, and sCD40L levels.

Conclusions— Our study suggests a direct effect of TZD treatment on endothelial function and inflammatory biomarkers of arteriosclerosis, promoting the concept that TZDs, independent of their metabolic action, may exhibit protective effects in the vessel wall.

Thiazolidinediones Do Not Reduce Target Vessel Revascularization in Diabetic Patients Undergoing Percutaneous Coronary Intervention

BACKGROUND

Animal studies have suggested that thiazolidinediones (TZDs) have antirestenotic properties. However, human data are lacking. The goal of this single-center study was to assess the target vessel revascularization (TVR) rate following percutaneous coronary intervention (PCI) among diabetic patients according to TZD use.

METHODS

A total of 325 consecutive diabetic patients who underwent PCI between January 2000 and December 2001 were included in the analysis. Among them, 82 patients were on TZD and 243 patients were on other hypoglycemic regimens. All patients were treated with stents and platelet glycoprotein IIb/IIIa inhibitors at the time of intervention. TVR and death/myocardial infarction/TVR were assessed at 1 year.

RESULTS

TZD patients were more likely to be younger, male and have hyperlipidemia. TVR occurred in 36.6% of TZD patients compared with 23.9% of non-TZD patients (p=0.04). One-year death, myocardial infarction and TVR occurred in 41.1% of TZD patients compared with 30.8% of non-TZD patients (p=0.04).

CONCLUSION

In this retrospective analysis, TZD therapy did not decrease the need for repeat revascularization following PCI. Prospective randomized studies are warranted.

Plasma levels and zymographic activities of matrix metalloproteinases 2 and 9 in type II diabetics with peripheral arterial disease

Deregulation of matrix metalloproteinases (MMPs) is an important factor contributing to the development of vascular lesions. Plasma levels and zymographic activities of MMP-2 and MMP-9 were investigated in type II diabetics with (n = 51) or without (n = 42) peripheral artery disease (PAD) and in normal volunteers (n = 23). Plasma MMP-2 levels were higher in type II diabetics with (p < 0.01) or without (p > 0.05) PAD in comparison with normal volunteers. Similarly, type II diabetics with (p < 0.0001) or without (p > 0.05) PAD had higher plasma MMP-9 levels than normal volunteers. Plasma zymographic activities of both MMP-2 and MMP-9 were positively correlated with their plasma levels. Plasma MMP-2 zymographic activity was higher in type II diabetics with PAD than type II diabetics without PAD (p > 0.05). Plasma MMP-9 zymographic activity was higher in type II diabetics with (p < 0.0001) or without (p < 0.0001) PAD in comparision with normal volunteers. Together, these results indicate that increased plasma levels and zymographic activities of MMP-2 and MMP-9 may contribute to PAD in type II diabetics. In particular, plasma MMP-9 may be a useful marker for the development of vascular disease in type II diabetics.

Improvement of cardiovascular risk markers by pioglitazone is independent from glycemic control: results from the pioneer study

OBJECTIVES

This study was performed to assess whether the anti-inflammatory and antiatherogenic effects of pioglitazone suggested by animal experiments are reproducible in man and independent from improvements in metabolic control.

BACKGROUND

Type 2 diabetes is associated with increased cardiovascular risk.

METHODS

A total of 192 patients were enrolled into a six-month, prospective, open-label, controlled clinical study. They were randomized to receive either pioglitazone (45 mg) or glimepiride (1 to 6 mg, with the intent to optimize therapy). Biochemical and clinical markers to assess therapeutic effects included HbA1c, fasting glucose, insulin, adiponectin, lipids, high-sensitivity C-reactive protein (hsCRP), intracellular adhesion molecule, vascular cell adhesion molecule, vascular endothelial growth factor, fibrinogen, von Willebrand factor, matrix metalloproteinase (MMP)-9, monocyte chemoattractant protein (MCP)-1, soluble CD40 ligand, and carotid intima-media thickness (IMT).

RESULTS

The study was completed by 173 patients (66 female, 107 male; age [+/- SD]: 63 +/- 8 years; disease duration: 7.2 +/- 7.2 years; HbA1c: 7.5 +/- 0.9%; pioglitazone arm: 89 patients). A comparable reduction in HbA1c was seen in both groups (p < 0.001). In the pioglitazone group, reductions were observed for glucose (p < 0.001 vs. glimepiride group at end point), insulin (p < 0.001), low-density lipoprotein/high-density lipoprotein ratio (p < 0.001), hsCRP (p < 0.05), MMP-9 (p < 0.05), MCP-1 (p < 0.05), and carotid IMT (p < 0.001), and an increase was seen in high-density lipoprotein (p < 0.001) and adiponectin (p < 0.001). Spearman ranks analysis revealed only one correlation between the reduction in cardiovascular risk parameters and the improvement in the metabolic parameters (MMP-9 and fasting blood glucose, p < 0.05)

CONCLUSIONS

This prospective study gives evidence of an anti-inflammatory and antiatherogenic effect of pioglitazone versus glimepiride. This effect is independent from blood glucose control and may be attributed to peroxisome proliferator-activated receptor gamma activation.

Pioglitazone Decreases Carotid Intima-Media Thickness Independently of Glycemic Control in Patients With Type 2 Diabetes Mellitus

Background— Patients with type 2 diabetes mellitus are at high risk of cardiovascular disease. Carotid intima-media thickness (IMT) is a strong predictor of myocardial infarction and stroke.

Methods and Results— We compared the effects of pioglitazone-based therapy (45 mg/d) and glimepiride-based treatment (2.7±1.6 mg/d) for 12 and 24 weeks on metabolic control (HbA 1c ), insulin resistance (homeostasis model assessment), and carotid IMT (B-mode ultrasonography) in a randomized controlled study in 173 orally treated patients with type 2 diabetes (66 women, 107 men; mean±SD age, 62.6±7.9 years; body mass index, 31.8±4.6 kg/m 2 ; HbA 1c , 7.5±0.9%). Treatment was generally well tolerated in both groups. Despite similar improvements in metabolic control (HbA 1c ) after 24 weeks (−0.8±0.9% [pioglitazone] versus −0.6±0.8% [glimepiride]; P =NS), carotid IMT was reduced only in the pioglitazone group after 12 weeks (−0.033±0.052 versus −0.002±0.047 mm [glimepiride]; P <0.01 between groups) and 24 weeks (−0.054±0.059 versus −0.011±0.058 mm [glimepiride]; P <0.005 between groups). Insulin resistance was also improved only in the pioglitazone group (homeostasis model assessment, −2.2±3.4 versus −0.3±3.3; P <0.0001 between groups). Reduction of IMT correlated with improvement in insulin resistance ( r =0.29, P <0.0005) and was independent of improvement in glycemic control ( r =0.03, P =0.68).

Conclusions— We found a substantial regression of carotid IMT, independent of improved glycemic control, after 12 and 24 weeks of pioglitazone treatment. This finding may have important prognostic implications for patients with type 2 diabetes mellitus.

PPARs: therapeutic targets for metabolic disease

The three peroxisome-proliferator-activated receptor (PPAR) subtypes, PPAR-gamma, PPAR-alpha and PPAR-delta, are nuclear receptors that have been the focus of extensive research during the past decade. These receptors function as lipid sensors that coordinately regulate the expression of large gene arrays and, thereby, modulate important metabolic events. They are also the targets of drugs that are effective in the treatment of metabolic disorders (type 2 diabetes mellitus and atherosclerosis) that afflict industrialized societies at epidemic levels. Ongoing research indicates that modulation of PPAR activity might be an effective therapy for additional maladies associated with the metabolic syndrome, including obesity. Novel PPAR ligands are now being developed that possess broader efficacies and improved tolerability compared with currently available therapeutic agents.

Peroxisome proliferator-activated receptor-gamma agonist rosiglitazone reduces clinical inflammatory responses in type 2 diabetes with coronary artery disease after coronary angioplasty

Rosiglitazone, an agonist of peroxisome proliferator-activated receptor-gamma (PPAR gamma ), is an insulin-sensitizing antidiabetic agent and inhibits restenosis in animal blood vessels. However, its benefit for patients with type 2 diabetes and coronary artery disease (CAD) after percutaneous coronary intervention is unknown. Patients with diabetes and CAD who had undergone percutaneous coronary intervention were randomized to either receive or not receive rosiglitazone (4 mg/d) for 6 months. After 6 months of rosiglitazone treatment, the plasma levels of fasting glucose and insulin and those of hemoglobin A1C and homeostasis model assessment of insulin resistance were significantly decreased in the rosiglitazone group as compared with baseline levels and those in the control group. After 2 and 6 months of rosiglitazone treatment, the plasma level of high-density lipoprotein was significantly increased in the rosiglitazone group. In addition, plasma levels of monocyte chemoattractant protein-1 and C-reactive protein and hyperresponsiveness of low-dose lipopolysaccharide-induced monocyte chemoattractant protein-1 secretion from monocytes were reduced. Furthermore, the occurrence of coronary events was significantly decreased in the rosiglitazone group at 6-month follow-up. Our data indicate that rosiglitazone may protect the vascular wall through not only improving the features of metabolic disorders but also reducing proinflammatory responses and the occurrence of coronary events in patients with diabetes and CAD after percutaneous coronary intervention.

Peroxisome proliferator-activated receptor ligands in atherosclerosis

In this review, the effect of peroxisome proliferator-activated receptor (PPAR) ligands on atherosclerosis is examined. The PPAR-gamma agonist thiazolidinediones are currently indicated for the management of Type 2 diabetes mellitus, and the PPAR-alpha agonist fibrates are used in dyslipidaemia. Here their mechanism of action and the pre-clinical and clinical evidence for the use of these medications for the prevention and treatment of atherosclerotic disease is explored. In addition, the role of PPAR-delta and the possibilities for the role of dual-binding agonists are examined.

PPAR ligands: potential therapies for metabolic syndrome

Metabolic syndrome (MS), a condition characterized by multiple related clinical disorders including insulin resistance, central obesity, hyperlipidemia, hypertension, and heart disease, is an increasingly prevalent disease in industrialized societies. The intense research interest in the peroxisome proliferator-activated receptors (PPARs), by both the pharmaceutical industry and academia, stems largely from the well-documented therapeutic actions of their synthetic agonists in alleviating several of the maladies associated with MS. This report focuses on the current understanding of the mechanisms of action of PPAR agents and their clinical use in the context of MS.

Effect of pronounced weight loss on the nontraditional cardiovascular risk marker matrix metalloproteinase-9 in middle-aged morbidly obese women

OBJECTIVE

Obesity is associated with increased morbidity and mortality from atherosclerotic disease. Nontraditional cardiovascular risk factors such as C-reactive protein (CRP) and interleukin-6 (IL-6) are elevated in obese subjects and weight loss is associated with an attenuation of these risk factors. Matrix metalloproteinase-9 (MMP-9) has been linked to plaque rupture, and is, thus, a candidate marker of future myocardial events. The aim of this study was to determine the influence of weight loss on MMP-9 plasma concentrations.

METHODS AND RESULTS

CRP, IL-6 and MMP-9 were analyzed from samples of 45 morbidly obese, middle-aged women before gastric banding and 1 y postsurgical treatment in this prospective study. The body mass index (BMI) of subjects decreased from 42.5+/-4.9 to 32.3+/-5.3 kg/m(2) 1 y after gastric banding. In parallel, both MMP-9 and CRP were reduced by 23 and 41%, respectively. A positive relationship was found between BMI and MMP-9 (r=0.312, P<0.05), and between CRP and IL-6 (r=0.508, P<0.05), whereas no correlation was found between CRP and MMP-9.

CONCLUSIONS

We conclude that weight loss is associated with a pronounced decrease in the nontraditional cardiovascular risk markers MMP-9 and CRP, which could indicate future beneficial effects of weight loss on the cardiovascular risk in weight loosing subjects.

Dual role of matrix metalloproteinases (matrixins) in intimal thickening and atherosclerotic plaque rupture

Intimal thickening, the accumulation of cells and extracellular matrix within the inner vessel wall, is a physiological response to mechanical injury, increased wall stress, or chemical insult (e.g., atherosclerosis). If excessive, it can lead to the obstruction of blood flow and tissue ischemia. Together with expansive or constrictive remodeling, the extent of intimal expansion determines final lumen size and vessel wall thickness. Plaque rupture represents a failure of intimal remodeling, where the fibrous cap overlying an atheromatous core of lipid undergoes catastrophic mechanical breakdown. Plaque rupture promotes coronary thrombosis and myocardial infarction, the most prevalent cause of premature death in advanced societies. The matrix metalloproteinases (MMPs) can act together to degrade the major components of the vascular extracellular matrix. All cells present in the normal and diseased blood vessel wall upregulate and activate MMPs in a multistep fashion driven in part by soluble cytokines and cell-cell interactions. Activation of MMP proforms requires other MMPs or other classes of protease. MMP activation contributes to intimal growth and vessel wall remodeling in response to injury, most notably by promoting migration of vascular smooth muscle cells. A broader spectrum and/or higher level of MMP activation, especially associated with inflammation, could contribute to pathological matrix destruction and plaque rupture. Inhibiting the activity of specific MMPs or preventing their upregulation could ameliorate intimal thickening and prevent myocardial infarction.

The impact of antidiabetic therapies on cardiovascular disease

Cardiovascular disease disproportionately affects people with diabetes and is a leading cause of death. Glycemic control has so far not been conclusively shown to decrease cardiovascular events. The therapeutic agents used in treating glycemia have different effects on cardiovascular risks and, therefore, may have different effects on outcome. Insulin sensitizers impact cardiovascular risk factors, including dyslipidemia and fibrinolysis. Metformin is the only oral antidiabetic medication shown to decrease cardiovascular events independent of glycemic control. Thiazolidinediones improve insulin resistance and lower insulin concentrations, which is beneficial because hyperinsulinemia is an independent predictor of cardiovascular disease. Insulin therapy acutely reduces cardiovascular mortality and morbidity in patients with diabetes and known coronary artery disease and also in patients with hyperglycemia when critically ill, but the long-term effects are unclear. In contrast, insulin secretagogues have very little effect on both cardiovascular risk factors and outcomes.

New aspects in the pathogenesis of diabetic atherothrombosis

Diabetes mellitus is increasing worldwide, resulting from the interaction of obesity, inflammation, and hyperglycemia. Activated immunity and cytokine production lead to insulin resistance and other components of the metabolic syndrome, establishing the link between diabetes and atherosclerosis. Hyperglycemia-induced endothelial dysfunction is mediated by increased oxidative stress, a promoter of adventitial inflammation and vasa vasorum neovascularization in experimental models of diabetic atherosclerosis. Recent studies have documented increased inflammation, neovascularization, and intraplaque hemorrhage in human diabetic atherosclerosis. This inflammatory microangiopathic process is independently associated with plaque rupture, leading to coronary thrombosis. Tissue factor, the most potent trigger of the coagulation cascade, is increased in diabetic patients with poor glycemic control. Circulating tissue factor microparticles are also associated with apoptosis of plaque macrophages, closing the link among inflammation, plaque rupture, and blood thrombogenicity. High-density lipoproteins, responsible for free cholesterol removal, are reduced in patients with insulin resistance and diabetes. High-density lipoprotein therapy leads to a significant decrease in plaque macrophages and increase in smooth-muscle cells. These beneficial effects may be responsible for coronary plaque stabilization in patients treated with recombinant Apolipoprotein A-I Milano/phospholipid complex. Finally, peroxisomal proliferator-activated receptors (PPARs) are now considered the nuclear transcriptional regulators of atherosclerosis. Three subfamilies, including PPAR-alpha, -delta, and -gamma, have been identified with crucial roles in lipid metabolism, plaque inflammation, expression of adhesion molecules and cytokines, and regulation of matrix metalloproteinases. Multiple experimental studies have documented plaque stabilization with PPAR-gamma agonists, a group of medications holding great promise in the treatment of diabetes atherosclerosis.

[The place of thiazolidinediones in the treatment of type 2 diabetes]

SUPPLEMENTARY ORAL ANTIDIABETICS: Thiazolidinediones or glitazones are a new class of oral antidiabetics, the effects on blood sugar control of which are mediated by the sensitivity of the peripheral tissue to the effect of insulin. Hence, their effect is complementary to that of the insulin secreting agents and that of metformin, which acts by blocking the hepatic production of glucose. OTHER BENEFICIAL EFFECTS: Other than their effect on blood glucose, thiazolidinediones have a favorable influence upon the cardiovascular risk factors or markers such as blood pressure, C-reactive protein and metalloproteinase-9. They also appear to induce long term preservation of the beta-cell capital. Principle side effects are salt-water retention with a risk of decompensation of a pre-existing heart failure and weight gain with regard to the subcutaneous adipose tissue, without deleterious effects on blood glucose control.

Peroxisome proliferator activated receptor gamma and its activation in the treatment of insulin resistance and atherosclerosis: issues and opportunities

Atherosclerosis remains a major complication of type 2 diabetes mellitus. Increasing data suggest insulin resistance, and its associated metabolic abnormalities, may underlie many of the cardiovascular complications seen among patients with insulin resistance and/or diabetes mellitus. This insight has also suggested that therapeutic approaches targeting insulin resistance may not only improve metabolism but also limit complications like atherosclerosis and the inflammation that contributes to it. Thiazolidinediones, agonists of the nuclear receptor peroxisome proliferator activated receptor gamma, are one such insulin-sensitizing therapeutic intervention in current use among patients with type 2 diabetes mellitus. The existing data regarding thiazolidinedione effects on the cardiovascular system are reviewed and considered, along with the future prospects for this emerging drug class.

Preventative effects of rosiglitazone on restenosis after coronary stent implantation in patients with type 2 diabetes

OBJECTIVE

Despite the popularity of coronary stenting in coronary artery disease (CAD), restenosis remains a challenging clinical problem. This study evaluated the efficacy of rosiglitazone for preventing in-stent restenosis in type 2 diabetic patients.

RESEARCH DESIGN AND METHODS

We conducted a prospective, randomized, case-controlled trial involving 95 diabetic patients with CAD who were randomly assigned to either the control or rosiglitazone group (48 and 47 patients, respectively). Quantitative coronary angiography (QCA) was performed at study entry and again at 6-month follow-up. The primary end point was the restenosis rate, which was determined by QCA.

RESULTS

Eighty-three patients (45 patients with 55 lesions in the control group and 38 patients with 51 lesions in the rosiglitazone group) completed follow-up angiography. Rosiglitazone treatment for 6 months reduced fasting insulin concentration. The high-sensitivity C-reactive protein concentration was significantly reduced in the rosiglitazone group compared with that in the control group (from 2.92 +/- 1.98 to 0.62 +/- 0.44 mg/l, P < 0.001 vs. from 2.01 +/- 1.33 to 1.79 +/- 1.22 mg/l, P = NS). However, the baseline and follow-up glucose and lipid concentrations were not different between two groups. The rate of in-stent restenosis was significantly reduced in the rosiglitazone group compared with the control group (for stent lesions: 17.6 vs. 38.2%, P = 0.030). The rosiglitazone group had a significantly lower degree of diameter stenosis (23.0 +/- 23.4% vs. 40.9 +/- 31.9%, P = 0.004) compared with the control group.

CONCLUSIONS

We demonstrated that treatment with rosiglitazone significantly reduces in-stent restenosis in diabetic patients with CAD who underwent coronary stent implantation.

The 161TT genotype in the exon 6 of the peroxisome-proliferator-activated receptor γ gene is associated with premature acute myocardial infarction and increased lipid peroxidation in habitual heavy smokers

PPAR (peroxisome-proliferator-activated receptor) is a nuclear receptor. Activation of PPARγ by its ligands could modulate gene transcription, thereby leading to multiple anti-atherogenic and fibrinolytic effects. However, the association between the 161T allele in exon 6 of the PPARγ gene and premature AMI (acute myocardial infarction) is not clear. We recruited 146 patients with premature AMI (onset age ≤50 years) and 146 controls. The C161T polymorphism was examined using PCR and restriction-fragment-length polymorphism. Plasma levels of Ab-ox-LDL (antibody against oxidized low-density lipoprotein) were measured in 27 male smokers, whose genotypes have been identified. The frequency of the PPARγ TT genotype among patients with AMI was significantly higher than that in controls [13% compared with 5.5%; OR (95% CI) 2.7, (1.1–6.5), where OR and CI are odds ratio and confidence interval respectively]. This association was not observed in CC or CT genotypes. Using multivariate logistic regression analyses, we found that the homozygous TT genotype [OR (95% CI), 3.1 (1.2–7.9)], smoking [OR (95% CI), 3.5, (2.1–6.0)], hypertension [OR (95% CI), 3.6, (1.9–6.9)] and diabetes mellitus [OR (95% CI), 3.5 (1.5–8.4)] were independent risk factors for premature AMI. Plasma levels of Ab-ox-LDL were significantly higher in healthy volunteers with the TT genotype compared with those with the CC genotype (49.3±18.1 compared with 24.2±15.2 units/l respectively; P=0.02). Therefore in our study we observed an association between the PPARγ 161 TT genotype and premature AMI. Lipid peroxidation was significantly influenced by the 161T allele.

Peroxisome proliferator-activated receptors and atherogenesis: regulators of gene expression in vascular cells

A large body of data gathered over the past couple of years has identified the peroxisome proliferator-activated receptors (PPAR) alpha, gamma, and beta/delta as transcription factors exerting modulatory actions in vascular cells. PPARs, which belong to the nuclear receptor family of ligand-activated transcription factors, were originally described as gene regulators of various metabolic pathways. Although the PPARalpha, gamma, and beta/delta subtypes are approximately 60% to 80% homologous in their ligand- and DNA-binding domains, significant differences in ligand and target gene specificities are observed. PPARalpha is activated by polyunsaturated fatty acids and oxidized derivatives and by lipid-modifying drugs of the fibrate family, including fenofibrate or gemfibrozil. PPARalpha controls expression of genes implicated in lipid metabolism. PPARgamma, in contrast, is a key regulator of glucose homeostasis and adipogenesis. Ligands of PPARgamma include naturally occurring FA derivatives, such as hydroxyoctadecadienoic acids (HODEs), prostaglandin derivatives such as 15-deoxyDelta12,14-prostaglandin J2, and glitazones, insulin-sensitizing drugs presently used to treat patients with type 2 diabetes. Ligands for PPARbeta/delta are polyunsaturated fatty acids, prostaglandins, and synthetic compounds, some of which are presently in clinical development. PPARbeta/delta stimulates fatty acid oxidation predominantly acting in muscle. All PPARs are expressed in vascular cells, where they exhibit antiinflammatory and antiatherogenic properties. In addition, studies in various animal models as well as clinical data suggest that PPARalpha and PPARgamma activators can modulate atherogenesis in vivo. At present, no data are available relating to possible effects of PPARbeta/delta agonists on atherogenesis. Given the widespread use of PPARalpha and PPARgamma agonists in patients at high risk for cardiovascular disease, the understanding of their function in the vasculature is not only of basic interest but also has important clinical implications. This review will focus on the role of PPARs in the vasculature and summarize the present understanding of their effects on atherogenesis and its cardiovascular complications.

Insulin resistance and cardiovascular disease: the role of PPARgamma activators beyond their anti-diabetic action

Over the past few years it has been recognised that insulin resistance (IR) is an independent risk factor for major cardiovascular events. In addition, IR is associated with other factors such as hypertension, dyslipidaemia and endothelial dysfunction, and this cluster of metabolic disorders contributes to the cardiovascular risk of patients with IR. Given the increasing number of patients with IR, the modulation of their cardiovascular risk is a major task in diabetology and vascular medicine. This review will focus on the role of IR as a cardiovascular risk factor and on the potential of activators of the nuclear transcription factor peroxisome proliferator-activated receptor gamma (PPARgamma) to modulate these risk factors associated with IR.

Effect of pioglitazone on carotid intima-media thickness and arterial stiffness in type 2 diabetic nephropathy patients

Atherosclerosis is the major cause of morbidity and mortality in patients with type 2 diabetes, and pioglitazone has been reported to have anti-inflammatory and potential antiatherogenic effects. The aim of the present study was to determine whether pioglitazone, glibenclamide, or voglibose affects carotid intima-media thickness (IMT), pulse wave velocity (PWV), and urinary albumin excretion (UAE) in normotensive type 2 diabetic nephropathy patients. Forty-five normotensive type 2 diabetes patients with microalbuminuria were randomized to 12-month treatment with pioglitazone (30 mg/d, n = 15), glibenclamide (5 mg/d, n = 15), or voglibose (0.6 mg/d, n = 15). Pre- and posttreatment UAE, PWV, and IMT values were compared between treatment groups and a group of age-matched healthy control subjects (n = 30). Pretreatment PWV, IMT, and UAE values differed little between the 3 groups, but UAE was greater in the 45 type 2 diabetes patients (132.5 +/- 36.4 microg/min) than in the control subjects (6.2 +/- 1.8 microg/min, P < .001). IMT (0.76 +/- 0.12 mm) was significantly greater in the diabetics than in the controls (0.60 +/- 0.08 mm, P < .01). PWV (1,840 +/- 320 cm/s) was also significantly greater in the diabetics than in the controls (1,350 +/- 225 cm/s, P < .01). After 6 and 12 months, UAE, IMT, and PWV in the pioglitazone treatment group were significantly lower than those in the glibenclamide treatment group and voglibose treatment group (UAE: 6 months, P < .05 and 12 months, P < .01; IMT and PWV: 6 months, P < .05 and 12 months, P < .05). Pioglitazone, but not glibenclamide or voglibose, appears to be effective in reducing UAE, IMT, and PWV in normotensive type 2 diabetes patients with microalbuminuria.

Thiazolidinediones and congestive heart failure--exacerbation or new onset of left ventricular dysfunction?

BACKGROUND

Patients with diabetes mellitus have a high incidence of coronary heart disease and congestive heart failure (CHF). Thiazolidinediones (TZD) are a new class of pharmacological agents for the treatment of Type 2 diabetes mellitus, which have many beneficial cardiovascular effects. Peripheral oedema and weight gain have been reported in 4.8% of subjects on TZDs alone, with a higher incidence noted in those receiving combination insulin therapy (up to 15%), but there is limited data on the occurrence of CHF.

METHODS AND RESULTS

In this paper, we report on six cases of TZD-induced fluid retention with symptoms and signs of peripheral oedema and/or CHF that occurred in subjects attending our diabetic clinic. The predominant finding in all cases was of diastolic dysfunction. All subjects were obese and hypertensive, with 5/6 having the additional risk factor of LVH, 5/6 subjects had microvascular complications, whilst 3/6 were also on insulin therapy.

CONCLUSION

We suggest that obese, hypertensive diabetics may benefit from echocardiographic screening prior to commencement of TZDs, as these agents may exacerbate underlying undiagnosed left ventricular diastolic dysfunction.

Clinical interest of PPARs ligands

Cardiovascular disease is significantly increased in patients with metabolic syndrome and type 2 diabetes. Several factors such as chronic hyperglycemia, lipId abnormalities, endothelium dysfunction, inflammation, oxIdative stress, increased thrombosis and decreased fibrinolysis are likely to promote cardiovascular events in these patients. Because of positive effects on glucose homeostasis, lipId metabolism, proteins involved in all stages of atherogenesis, endothelium function, inflammation, thrombosis and fibrinolysis, PPARS alpha (fibrates) and PPARs gamma (glitazones) agonists are good candIdates to reduce cardiovascular disease, more precisely in subjects with metabolic syndrome or type 2 diabetes. PPARS alpha agonists (fibrates) are potent hypolipIdemic agents increasing plasma HDL-cholesterol and reducing free fatty acIds, triglycerIdes, LDL-cholesterol and the number of small dense LDL pArticles. Moreover, they reduce vascular inflammation and thrombosis, promote fibrinolysis and inhibit the production of the vasoconstrictor factor, endothelin-1, by the endothelium. They have been shown, in clinical trials, to reduce cardiovascular disease, more particularly in patients displaying lipId abnormalities typical of metabolic syndrome and type 2 diabetes (high triglycerIdes, low HDL-cholesterol). PPARS gamma agonists (glitazones) have not only beneficial effects on glucose homeostasis, by increasing insulin sensitivity and reducing blood glucose level but also on lipId metabolism by elevating plasma HDL-cholesterol, decreasing free fatty acIds and the number of small dense LDL pArticles, and for pioglitazone by reducing plasma triglycerIdes. Furthermore, they diminish vascular inflammation and vasoconstriction, inhibit monocyte chemotaxis, proliferation and migration of smooth muscle cells, in the vascular wall and decrease the production of adhesion molecules and metalloproteinases. PPARs gamma agonists (glitazones) have been shown to reduce the development of atherosclerotic lesions in rats. The potential clinical benefit of PPARs gamma agonists on the reduction of cardiovascular disease, in type 2 diabetic patients, will be specified by the ongoing intervention studies.

Recent advances in vascular inflammation: C-reactive protein and other inflammatory biomarkers

PURPOSE OF REVIEW

Inflammatory vascular diseases are initiated and perpetuated by the interaction of immune cells with cells of the affected vessel wall. This is directed by a network of chemical messengers, which, in a state of vascular health, exist as balanced but opposing forces. Our understanding of this highly complex process has advanced significantly in the last several decades. The detection of vascular inflammation and monitoring of this activity have long been attempted in systemic vasculitis, and, more recently, in atherosclerosis. Markers of vascular inflammation used thus far have been of limited value; few provide both adequate sensitivity and specificity for any particular disease. New insights into the pathophysiology of vascular inflammation have identified other potential markers that may improve detection and monitoring of these conditions.

RECENT FINDINGS

Immunomodulatory mediators of the inflammatory cascade have been identified, and their roles are being defined. There are recent data that implicate various cytokines, proteases, adhesion molecules, and acute phase proteins as participants in the generation of vascular inflammation.

CONCLUSION

The pursuit of highly sensitive and specific markers of vascular inflammation has produced a wealth of information that has been instrumental in advancing our comprehension of this complex process. Further studies will establish the role of these new markers in the diagnosis, monitoring, and prognostication of inflammatory vascular disease.

Peroxisome proliferator-activated receptor-gamma: therapeutic target for diseases beyond diabetes: quo vadis?

The discovery that the insulin-sensitising thiazolidinediones (TZDs), specific peroxisome proliferator-activated receptor-gamma (PPARgamma) agonists, have antiproliferative, anti-inflammatory and immunomodulatory effects has led to the evaluation of their potential use in the treatment of diabetic complications and inflammatory, proliferative diseases in non-insulin-resistant, euglycaemic individuals. Apart from improving insulin resistance, plasma lipids and systemic inflammatory markers, ameliorating atherosclerosis and preventing coronary artery restenosis in diabetic subjects, currently approved TZDs have been shown to improve psoriasis and ulcerative colitis in euglycaemic human subjects. These data imply that the activation of PPAR-gamma may improve cardiovascular risk factors and cardiovascular outcomes in both insulin-resistant diabetic and non-diabetic individuals. Through their immunomodulatory and anti-inflammatory actions, TZDs and other PPAR-gamma agonists may prove to be effective in treating diseases unrelated to insulin resistance, such as autoimmune (e.g., multiple sclerosis), atopic (e.g., asthma, atopic dermatitis) and other inflammatory diseases (e.g., psoriasis, ulcerative colitis). Newer and safer selective PPAR-gamma agonists are presently under development. Furthermore, of considerable interest is the recent discovery that a unique subset of currently prescribed antihypertensive angiotensin II Type 1 receptor antagonists has selective PPAR-gamma-modulating activity. These discoveries pave the way for the development of drugs for treating chronic multigenic cardiovascular and metabolic diseases, for which therapy is presently insufficient or non-existent. The potential utility of the currently available TZDs rosiglitazone and pioglitazone and PPAR-gamma-modulating angiotensin II Type 1 receptor antagonists in treating cardiovascular, metabolic and inflammatory diseases in insulin resistant and euglycaemic states is of immense clinical potential and should be investigated.

Endothelial function, inflammation, and prognosis in cardiovascular disease

The vascular endothelium is an active, dynamic tissue that controls many important functions, including regulation of vascular tone and maintenance of blood circulation, fluidity, coagulation, and inflammatory responses. Cardiovascular risk factors affect many of the normal functions of the endothelium. In particular, oxidized low-density lipoprotein cholesterol initiates a series of events that begin with cell activation, endothelial dysfunction, local inflammation, and a procoagulant vascular surface. These conspire to result in plaque formation and ultimately plaque rupture and cardiovascular events. Endothelial dysfunction may be evaluated by means of invasive techniques, such as coronary artery reactivity to acetylcholine, or noninvasive techniques, such as brachial artery ultrasonography. Loss of endothelium-dependent vasodilation is a characteristic feature throughout the development of atherosclerosis, and it is independently related to future adverse cardiovascular risk. Therefore, measurement of endothelial function can possibly be used to determine risk, to triage management, and to improve outcomes. At the same time, inflammation is a crucial factor in the atherosclerotic disease process. To identify and monitor the ongoing inflammatory process, markers of inflammation such as C-reactive protein (CRP) have been studied. Scientific evidence shows that elevated plasma CRP values add to the predictive ability of other established risk factors; moreover, elevated values appear to augment the Framingham Coronary Risk Score in identifying individuals who should be considered for cardioprotective treatment programs. Interestingly, thiazolidinediones (TZDs), peroxisome proliferator-activated receptor-gamma agonists that are effective in the treatment of type 2 diabetes mellitus, not only increase insulin sensitivity but can benefit endothelial function because they exhibit anti-inflammatory effects. For many individuals, including those with the metabolic syndrome and/or type 2 diabetes, endothelial dysfunction and elevated plasma CRP levels indicate increased risk of cardiovascular disease. Notably, the TZDs have been shown to reduce CRP levels and may improve endothelial function.

The vascular biology of atherosclerosis

Despite many advances in cardiology, atherosclerosis remains a major medical problem. This is especially the case for individuals with insulin resistance and type 2 diabetes mellitus. Atherosclerotic lesions can develop as early as the second decade of life and progress into clinical disease over time. Atherosclerosis is a complex disorder, involving many cell types and circulating mediators and resulting in an inflammatory state. The control of transcription of inflammatory mediators via ligands for peroxisome proliferator-activated receptor-gamma, such as thiazolidinediones (TZDs), has been raised as a possible mechanism for improving atherosclerosis. Results of studies performed in vitro and in animal models suggest that TZDs may increase cholesterol efflux from macrophages, decrease cytokine expression, and limit chemokine levels. Such effects may underlie the decreases in atherosclerosis seen in mouse models of atherosclerosis after TZD treatment. The direct actions of the TZDs on atherosclerosis may couple with their effects on metabolic parameters through increased insulin sensitivity. Ongoing clinical trials evaluating cardiovascular end points with TZD therapy should provide insight into these possibilities.

Peroxisome proliferator-activated receptor-gamma agonists in atherosclerosis: current evidence and future directions

PURPOSE OF REVIEW

The prevalence of type 2 diabetes globally is reaching epidemic proportions. Type 2 diabetes is strongly associated with increased risk of cardiovascular disease. Atherosclerosis is thought to arise as a result of a chronic inflammatory process within the arterial wall. Insulin resistance is central to the pathogenesis of type 2 diabetes and may contribute to atherogenesis, either directly or through associated risk factors. The peroxisome proliferator-activated receptor-gamma agonists, the thiazolidinediones, pioglitazone and rosiglitazone, are insulin sensitizing agents, that are licensed for the management of hyperglycaemia. Growing evidence supports an array of additional effects of thiazolidinedione therapy, both immunomodulatory and antiinflammatory, which may attenuate atherogenesis in type 2 diabetes.

RECENT FINDINGS

Studies have shown that thiazolidinedione therapy may lead to risk factor modulation in type 2 diabetes. Thiazolidinediones treatment has been shown to reduce blood pressure, modify the atherogenic lipid profile associated with type 2 diabetes, reduce microalbuminuria and ameliorate the prothrombotic diathesis. Further evidence suggests that thiazolidinediones therapy inhibits the inflammatory processes which may be involved in atherosclerotic plaque initiation, propagation and destabilization.

SUMMARY

Modification of insulin resistance by thiazolidinedione therapy in type 2 diabetes and the range of pleiotropic effects may not only impact on incident type 2 diabetes, but also on associated cardiovascular disease. Numerous large clinical endpoint studies are under way to investigate these issues.

Role of the epidermal growth factor receptor in signaling strain-dependent activation of the brain natriuretic peptide gene

The epidermal growth factor receptor (EGFR) and ectoshedding of heparin-binding epidermal growth factor (HBEGF), an EGFR ligand, have been linked to the development of cardiac myocyte hypertrophy. However, the precise role that the liganded EGFR plays in the transcriptional activation of the gene program that accompanies hypertrophy remains undefined. Utilizing the human (h) BNP gene as a model of hypertrophy-dependent gene activation, we show that activation of the EGFR plays an important role in mediating mechanical strain-dependent stimulation of the hBNP promoter. Strain promotes endothelin (ET) generation through NAD(P)H oxidase-dependent production of reactive oxygen species. ET in turn induces metalloproteinase-mediated cleavage of pro-HBEGF and ectoshedding of HBEGF, which activates the EGFR and stimulates hBNP promoter activity. HBEGF also stimulates other phenotypic markers of hypertrophy including protein synthesis and sarcomeric assembly. The antioxidant N-acetylcysteine or the NAD(P)H oxidase inhibitor, apocynin, inhibited strain-dependent activation of the ET-1 promoter, HBEGF shedding, and hBNP promoter activation. The metalloproteinase inhibitor, GM-6001, prevented the induction of HBEGF ectoshedding and the hBNP promoter response to strain, suggesting a critical role for the metalloproteinase-dependent cleavage event in signaling the strain response. These findings suggest that metalloproteinase activity as an essential step in this pathway may prove to be a relevant therapeutic target in the management of cardiac hypertrophy.

Peroxisome proliferator-activated receptor-alpha and receptor-gamma activators prevent cardiac fibrosis in mineralocorticoid-dependent hypertension

Peroxisome proliferator-activated receptor (PPAR) activation may prevent cardiac hypertrophy and inhibit production of endothelin-1 (ET-1), a hypertrophic agent. The aim of this in vivo study was to investigate the effects of PPAR activators on cardiac remodeling in DOCA-salt rats, a model overexpressing ET-1. Unilaterally nephrectomized 16-week-old Sprague-Dawley rats (Uni-Nx) were randomly divided into 4 groups: control rats, DOCA-salt, DOCA-salt+rosiglitazone (PPAR-gamma activator, 5 mg/kg per day), and DOCA-salt+fenofibrate (PPAR-alpha activator, 100 mg/kg per day). After 3 weeks of treatment, mean arterial blood pressure was significantly increased in DOCA-salt by 36 mm Hg. Mean arterial blood pressure was normalized by coadministration of rosiglitazone but not by fenofibrate. Both PPAR activators prevented cardiac fibrosis and abrogated the increase in prepro-ET-1 mRNA content in the left ventricle of DOCA-salt rats. Coadministration of rosiglitazone or fenofibrate failed to prevent thickening of left ventricle (LV) walls as measured by echocardiography and the increase in atrial natriuretic peptide mRNA levels. However, rosiglitazone and fenofibrate prevented the decrease in LV internal diameter and thus concentric remodeling of the LV found in DOCA-salt rats. Taken together, these data indicate a modulatory role of PPAR activators on cardiac remodeling in mineralocorticoid-induced hypertension, in part associated with decreased ET-1 production.

Thiazolidinediones -- some recent developments

The role of thiazolidinediones (currently rosiglitazone and pioglitazone) in the treatment of Type 2 diabetes is firmly established. The mechanism of action involves binding to the peroxisome proliferator-activated receptor-gamma, a transcription factor that regulates the expression of specific genes especially in fat cells but also other cell types such as endothelial cells, macrophages and monocytes, vascular smooth muscle cells and colonic epithelium. Thiazolidinediones have been shown to interfere with expression and release of mediators of insulin resistance originating in adipose tissue (e.g., increased free fatty acids, decreased adiponectin) in a way that results in net improvement of insulin sensitivity (i.e., in muscle and liver). A direct or indirect effect on AMP-dependent protein kinase may also be involved. Prevention of lipid accumulation in tissues critical to glycaemia such as visceral adipocytes, liver, muscle and beta-cells at the expense of lipids accumulating at the less harmful subcutaneous site may be central to their net metabolic effect. The sustained beneficial effect of troglitazone on beta-cell function in women with previous gestational diabetes in addition to the insulin-sensitising properties point to an important role of this class of drugs in the prevention of Type 2 diabetes. Original safety concerns based on animal and in vitro studies (e.g., fatty bone marrow transformation, colonic cancer, adipogenic transdifferentiation of blood cells) remain theoretical issues but become less pressing practically with prolonged uneventful clinical use. Hepatotoxicity for troglitazone and fluid retention, which can aggravate pre-existing heart failure, are the most important side effects. In summary, with the thiazolidinediones, a novel concept for the treatment of insulin resistance and possibly preservation of beta-cell function is available that could become effective in the prevention of Type 2 diabetes. Moreover, their anti-inflammatory properties also make them interesting in the prevention and treatment of atherosclerosis and possibly other inflammatory conditions (e.g., inflammatory bowel disease). Long-term data will be necessary for a final risk-benefit assessment of these substances.

Inflammation dampened by gelatinase A cleavage of monocyte chemoattractant protein-3

Tissue degradation by the matrix metalloproteinase gelatinase A is pivotal to inflammation and metastases. Recognizing the catalytic importance of substrate-binding exosites outside the catalytic domain, we screened for extracellular substrates using the gelatinase A hemopexin domain as bait in the yeast two-hybrid system. Monocyte chemoattractant protein-3 (MCP-3) was identified as a physiological substrate of gelatinase A. Cleaved MCP-3 binds to CC-chemokine receptors-1, -2, and -3, but no longer induces calcium fluxes or promotes chemotaxis, and instead acts as a general chemokine antagonist that dampens inflammation. This suggests that matrix metalloproteinases are both effectors and regulators of the inflammatory response.