Improvement by the insulin-sensitizing agent, troglitazone, of abnormal fibrinolysis in type 2 diabetes mellitus

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.

PPARγ and the Innate Immune System Mediate the Resolution of Inflammation

The resolution of inflammation is an active and dynamic process, mediated in large part by the innate immune system. Resolution represents not only an increase in anti-inflammatory actions, but also a paradigm shift in immune cell function to restore homeostasis. PPARγ, a ligand activated transcription factor, has long been studied for its anti-inflammatory actions, but an emerging body of literature is investigating the role of PPARγ and its ligands (including thiazolidinediones, prostaglandins, and oleanolic acids) in all phases of resolution. PPARγ can shift production from pro- to anti-inflammatory mediators by neutrophils, platelets, and macrophages. PPARγ and its ligands further modulate platelet and neutrophil function, decreasing trafficking, promoting neutrophil apoptosis, and preventing platelet-leukocyte interactions. PPARγ alters macrophage trafficking, increases efferocytosis and phagocytosis, and promotes alternative M2 macrophage activation. There are also roles for this receptor in the adaptive immune response, particularly regarding B cells. These effects contribute towards the attenuation of multiple disease states, including COPD, colitis, Alzheimer's disease, and obesity in animal models. Finally, novel specialized proresolving mediators-eicosanoids with critical roles in resolution-may act through PPARγ modulation to promote resolution, providing another exciting area of therapeutic potential for this receptor.

Breaking the mold: transcription factors in the anucleate platelet and platelet-derived microparticles

Platelets are small anucleate blood cells derived from megakaryocytes. In addition to their pivotal roles in hemostasis, platelets are the smallest, yet most abundant, immune cells and regulate inflammation, immunity, and disease progression. Although platelets lack DNA, and thus no functional transcriptional activities, they are nonetheless rich sources of RNAs, possess an intact spliceosome, and are thus capable of synthesizing proteins. Previously, it was thought that platelet RNAs and translational machinery were remnants from the megakaryocyte. We now know that the initial description of platelets as "cellular fragments" is an antiquated notion, as mounting evidence suggests otherwise. Therefore, it is reasonable to hypothesize that platelet transcription factors are not vestigial remnants from megakaryocytes, but have important, if only partly understood functions. Proteins play multiple cellular roles to minimize energy expenditure for maximum cellular function; thus, the same can be expected for transcription factors. In fact, numerous transcription factors have non-genomic roles, both in platelets and in nucleated cells. Our lab and others have discovered the presence and non-genomic roles of transcription factors in platelets, such as the nuclear factor kappa β (NFκB) family of proteins and peroxisome proliferator-activated receptor gamma (PPARγ). In addition to numerous roles in regulating platelet activation, functional transcription factors can be transferred to vascular and immune cells through platelet microparticles. This method of transcellular delivery of key immune molecules may be a vital mechanism by which platelet transcription factors regulate inflammation and immunity. At the very least, platelets are an ideal model cell to dissect out the non-genomic roles of transcription factors in nucleated cells. There is abundant evidence to suggest that transcription factors in platelets play key roles in regulating inflammatory and hemostatic functions.

Is peroxisome proliferator-activated receptor gamma (PPARγ) a therapeutic target for the treatment of pulmonary hypertension?

Pulmonary hypertension (PH), a progressive disorder associated with significant morbidity and mortality, is caused by complex pathways that culminate in structural and functional alterations of the pulmonary circulation and increases in pulmonary vascular resistance and pressure. Diverse genetic, pathological, or environmental triggers stimulate PH pathogenesis culminating in vasoconstriction, cell proliferation, vascular remodeling, and thrombosis. We conducted a thorough literature review by performing MEDLINE searches via PubMed to identify articles pertaining to PPARγ as a therapeutic target for the treatment of PH. This review examines basic and preclinical studies that explore PPARγ and its ability to regulate PH pathogenesis. Despite the current therapies that target specific pathways in PH pathogenesis, including prostacyclin derivatives, endothelin-receptor antagonists, and phosphodiesterase type 5 inhibitors, morbidity and mortality related to PH remain unacceptably high, indicating the need for novel therapeutic approaches. Consequently, therapeutic targets that simultaneously regulate multiple pathways involved in PH pathogenesis have gained attention. This review focuses on peroxisome proliferator-activated receptor gamma (PPARγ), a member of the nuclear hormone receptor superfamily of ligand-activated transcription factors. While the PPARγ receptor is best known as a master regulator of lipid and glucose metabolism, a growing body of literature demonstrates that activation of PPARγ exerts antiproliferative, antithrombotic, and vasodilatory effects on the vasculature, suggesting its potential efficacy as a PH therapeutic target.

Review of the pleiotropic effects of peroxisome proliferator-activated receptor gamma agonists on platelet function

The primary target receptor for thiazolidinediones (TZDs) or peroxisome proliferator-activated receptor gamma (PPARgamma) agonists is a transcription factor in the nucleus of adipocytes and other metabolically active cells, where they improve insulin sensitivity and glucose utilization. TZDs are also able to modify gene expression in macrophages, smooth muscle cells, and endothelial cells. Although PPARgamma is considered to be a nuclear receptor, enucleate platelets also highly express this receptor. The aim of this review is to present the current understanding of a direct or indirect effect of TZDs on platelet function. By means of a comprehensive literature search (January 1990-June 2006), publications were obtained that contained specific information about in vitro and in vivo effects of TZDs on platelet function. The effects were studied for different risk biochemical markers, i.e., proteins found to be elevated in the state of procoagulant inflammation and endothelial dysfunction. Improvement of platelet function was reported for all TZDs-troglitazone, pioglitazone, and rosiglitazone. The described effects included reduction of platelet aggregation, suppression of thrombin-induced protein kinase C-alpha and -beta activation, decrease in plasma P-selectin and platelet P-selectin expression, increase in nitric oxide production, inhibition of the Rho/Rho kinase pathway, and inhibition of tissue factor- and platelet-activating factor-induced morphological changes in macrophages. These findings appeared in parallel with reduction of the plasma concentrations of pro-inflammatory risk markers. TZDs seem to have a direct pleiotropic positive influence on platelet function and coagulation and may be helpful in treating the prothrombotic state observed in patients with type 2 diabetes and metabolic syndrome.

Pioglitazone: update on an oral antidiabetic drug with antiatherosclerotic effects

Pioglitazone, a member of the PPAR-gamma agonist drug family, has been demonstrated to improve both metabolic and vascular insulin resistance when applied to patients with Type 2 diabetes mellitus. The drug is well tolerated with fluid retention and weight gain being the most frequently described side effects. The observed effects (e.g., improvements in glucose and lipid metabolism, improvements of endothelial function and microcirculation, reduction of surrogate markers of atherosclerosis and inflammation and an improvement in hypertension) have made pioglitazone one of the frequently prescribed antidiabetic drugs in the US and Europe. Several trials have shown its potency to reduce carotid intima-media thickness, and outcome studies with pioglitazone have shown its potential to delay the progression of Type 2 diabetes and atherosclerosis and even reduce cardiovascular mortality. The purpose of this review is to provide an overview about recently published clinical results with pioglitazone. They underline the value of this drug when used alone or in combination with other antidiabetic drugs for a successful management of Type 2 diabetes mellitus.

Effects of pioglitazone on fasting and postprandial levels of lipid and hemostatic variables in overweight non-diabetic patients with coronary artery disease

OBJECTIVES

To evaluate the effects of pioglitazone on insulin sensitivity and levels of biomarkers associated with thrombotic risk in overweight and obese, non-diabetic subjects with coronary artery disease.

BACKGROUND

Little information is available regarding the effects of thiazolidinediones in the absence of diabetes. Further, although postprandial hyperlipemia is a risk factor for cardiovascular diseases, there is limited information about the postprandial effects.

METHODS

Twenty overweight and obese, non-diabetic patients with coronary artery disease were enrolled in a randomized, placebo-controlled, double-blind study. Subjects were on atorvastatin for the duration of the study and received either placebo or pioglitazone (45 mg day(-1)) for 12 weeks and then crossed over to the alternative therapy for an additional 12 weeks. Insulin sensitivity, fasting and postprandial levels of lipid, hemostatic, and inflammatory variables were measured, and endothelial function was assessed.

RESULTS

Insulin sensitivity improved from 0.03 micromol kg(-1) x min pM(-1) on placebo to 0.04 on pioglitazone (P = 0.0002), and there were decreases in fasting levels of factor (F) VII:C (102 +/- 17% to 92 +/- 18%, P = 0.001), FVII:Ag (68 +/- 12% to 60 +/- 14%, P = 0.01) and in von Willebrand factor (VWF) (174 +/- 94% to 142 +/- 69%, P = 0.01). Pioglitazone lowered postprandial levels of FVII:Ag, FVII:C, plasminogen activator inhibitor-1, VWF, and triglycerides, and increased high-density lipoproteins (+9%, P = 0.02).

CONCLUSIONS

Pioglitazone improves insulin sensitivity and favorably modifies fasting and postprandial lipid, hemostatic and inflammatory markers of the metabolic syndrome in overweight and obese non-diabetic patients with coronary artery disease.

Type 2 diabetes and cardiovascular disease: getting to the fat of the matterThis paper is one of a selection of papers published in this Special Issue, entitled Young Investigators' Forum

The increasing national prevalence of obesity is a major public health concern and a substantial burden on the health care resources of Canada. In addition to the direct health impact of obesity, this condition is a well-established risk factor for the development of various prevalent comorbidities including type 2 diabetes, hypertension, and cardiovascular disease. Historically, adipose tissue has been regarded primarily as an organ for energy storage. However, the discovery of leptin in the mid 1990’s revolutionized our understanding of this tissue and has focused attention on the endocrine function of adipose tissue as a source of secreted bioactive peptides. These compounds, collectively termed adipokines, regulate a number of biological functions including appetite and energy balance, insulin sensitivity, lipid metabolism, blood pressure, and inflammation. The physiological importance of adipokines has led to the hypothesis that changes in the synthesis and secretion of these compounds in the obese are a causative factor contributing to the development of obesity and obesity-related diseases in these individuals. Following from this it has been proposed that pharmacologic manipulation of adipokine levels may provide novel effective therapeutic strategies to treat and prevent obesity, type 2 diabetes, and cardiovascular disease.

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.

Diabetes treatments have differential effects on nontraditional cardiovascular risk factors

OBJECTIVE

The aim of this study was to determine the effect of basal insulin, alone or with a sensitizer, or a combination of oral agents on nontraditional risk factors for cardiovascular disease (CVD).

RESEARCH DESIGN AND METHODS

We randomized 57 patients with T2DM to either (1) continuous subcutaneous basal Lispro insulin at a single rate using an insulin pump (basal insulin) or (2) basal insulin and oral pioglitazone 30 mg daily (basal insulin +Pio) or (3) a sulfonylurea and metformin (SU+M). We measured glycosylated hemoglobin (HbA1c), plasma high-sensitivity C-reactive protein (hs-CRP), plasminogen activator inhibitor-1 (PAI-1), 8-epi-prostaglandin F2 alpha (PGF2alpha), serum lipoprotein (a) [Lp (a)], and lipoprotein profile at baseline and after 20 weeks of treatment.

RESULTS

HbA1c decreased by >or=2% (P<.001) and to comparable levels (P=NS) in all groups. Despite improved glycemia, hsCRP did not change in any group, whereas plasma PAI-1 fell with basal insulin +Pio (P<.02) and SU+M (P<.01). PGF2alpha declined with basal insulin (P<.02) and SU+M (P<.001). High-density lipoprotein cholesterol (HDL-C) increased only with basal insulin +Pio (18.2%, P<.05). Lp (a) increased with basal insulin therapy alone (P<.01). Data were pooled from all groups to determine the overall effect of glycemic control-there was a significant (P<.001) decline in HbA1c, PAI-1, and PGF2alpha and an increase in HDL-C (P<.001). There was no correlation between HbA1c reduction and changes in these parameters.

CONCLUSIONS

We conclude that excellent glycemic control per se does not impact nontraditional risk factors for CVD equally, but various diabetes medications have different effects on these risk factors. These findings may have implications for making appropriate therapeutic choices for patients with Type 2 diabetes, although larger studies with more appropriate treatment comparisons may be necessary.

Rosiglitazone improves, while Glibenclamide worsens blood pressure control in treated hypertensive diabetic and dyslipidemic subjects via modulation of insulin resistance and sympathetic activity

BACKGROUND

Type II diabetes is often associated with high blood pressure, elevated sympathetic activity, and high plasma insulin levels. Hypoglycemic agents may negatively interfere with blood pressure control, sympathetic activity, and plasma insulin level; therefore the choice of treatment in type II diabetes may be crucial. We aimed to compare the effects of two hypoglycemic drugs on blood glucose, blood pressure, sympathetic activity, and insulin levels in type II diabetic and hypertensive patients.

METHODS

Forty-eight (24M, 24F) type II diabetic, hypertensive, and hyperlipidemic subjects were enrolled and treated for 4 weeks with an ACE inhibitor (Cilazapril) and a statin (Simvastatin). They were then randomized into two groups to receive a thiazolidinedione (Rosiglitazone; ROS) or a sulfonylurea (Glibenclamide; GLB) for 8 weeks. Blood biochemistry, blood pressure, plasma insulin, endothelial function, and sympathetic skin activity were measured before and after treatment.

RESULTS

A significant drop in systolic and diastolic blood pressure by 6.1 +/- 4.1 mm Hg and 4.2 +/- 1.9 mm Hg respectively; a reduction in plasma insulin concentration by 4.3 +/- 1.9 mU/L and a decline in skin sympathetic activity were observed in the group receiving ROS. The GLB group showed an increase in systolic blood pressure by 3.1 +/- 2.5 mm Hg, no change in diastolic blood pressure, significant elevation in plasma insulin concentration by 2.3 +/- 1.4 mu/L, and augmentation of sympathetic activity. No significant changes in endothelial function were observed in either group.

CONCLUSIONS

Rosiglitazone improved both plasma glucose and blood pressure levels, probably by attenuation of hyperinsulinemia and sympathetic activity, while Glibenclamide worsened blood pressure control possibly by elevation of insulin levels and activation of the sympathetic system.

De novo synthesis of diacylglycerol in endothelium may mediate the association between PAI-1 and the insulin resistance syndrome

Increased free fatty acid flux, giving rise to increased de novo synthesis of diacylglycerol (DAG) and activation of protein kinase C (PKC) in vascular endothelium, may be largely responsible for the endotheliopathy and increased vascular risk associated with insulin resistance syndrome. This mechanism may also mediate, in large part, the increase in plasminogen activator inhibitor-1 (PAI-1) observed in this syndrome. PKC activation promotes transcription of PAI-1 in endothelial cells and other tissues, apparently by boosting the activity of Sp1 transcription factors that bind to the PAI-1 promoter. Plasma PAI-1 correlates inversely with the ability of insulin infusion to suppress free fatty acid levels. Moreover, infusion of triglycerides with heparin - inducing a marked increase in free fatty acids - has been shown to induce a rapid increase in plasma PAI-1. Alternatively, hyperinsulinemia and hypertriglyceridemia have been suggested as mediators of PAI-1 excess in insulin resistance, inasmuch as insulin and VLDL can stimulate PAI-1 production in cell cultures. However, plasma PAI-1 tends to decline in response to hyperinsulinemic clamps and insulin treatment of type 2 diabetes, and gemfibrozil treatment of hypertriglyceridemia does not decrease PAI-1 - suggesting that elevations of insulin or triglycerides are not likely to mediate PAI-1 excess in vivo. Hypertrophied adipose mass can secrete PAI-1, and is likely to contribute to the plasma PAI-1 pool in obese insulin-resistant subjects, but current evidence suggests that this is not likely to be the primary source of the elevated plasma PAI-1 in insulin resistance syndrome. Plasma PAI-1 can be decreased in insulin resistant subjects by improving adipocyte insulin sensitivity (with weight loss and thiazolidinediones), by consuming a very-low-fat diet that minimizes postprandial free fatty acid flux, and by administering activators of AMP-activated kinase (e.g., metformin), which can be expected to lessen tissue DAG synthesis.

Effect of metformin on fibrinolytic parameters in insulin-treated, type 2 diabetic patients

OBJECTIVE

In the present study, we measured fibrinolytic parameters, including PAI-1 antigen and activity in a group of type 2 diabetic patients in secondary oral anti-diabetic failure treated with insulin alone or with insulin plus metformin.

RESEARCH DESIGN AND METHODS

12 type 2 diabetic patients in secondary oral anti-diabetic failure were randomly allocated into two groups receiving insulin alone or insulin plus metformin 1000 mg twice a day; six weeks later, the treatments were swapped over. At the end of each treatment period, blood samples were withdrawn for metabolic and fibrinolytic analysis.

RESULTS

There were no significant differences in fasting blood glucose, fructosamine or fibrinogen; LDL cholesterol, PAI-1 antigen and activity, insulin needs were reduced by the inulin plus metformin regimen (LDL cholesterol: 1.59 +/- 0.62 versus 1.28 +/- 0.5 mmol/l, PAI-1 antigen: 28.3 +/- 17.4 versus 23.9 +/- 18 ng/ml, PAI-1 activity: 23.8 +/- 9.6 versus 21.9 +/- 10 IU/ml, insulin needs: 64 +/- 18 versus 52 +/- 15 U/day (p<0.05).

CONCLUSION

In type 2 diabetic patients with secondary oral treatment failure, insulin alone controlled blood glucose but had no effect on the levels of PAI-1; addition of metformin improved the fibrinolytic parameters.

The selective peroxisomal proliferator-activated receptor-gamma agonist has an additive effect on plaque regression in combination with simvastatin in experimental atherosclerosis

OBJECTIVES

We sought to investigate the anti-atherogenic effects of a selective peroxisomal proliferator-activated receptor-gamma (PPAR-gamma) agonist and simvastatin, as well as their combination, over time, in a rabbit model of experimental atherosclerosis.

BACKGROUND

The PPARs are nuclear transcription factors that control a variety of cellular functions, with the potential effects required to induce plaque regression and stabilization.

METHODS

Atherosclerosis was induced in rabbits (n = 37) by the combination of double-balloon injury and a nine-month high-cholesterol (HC) diet. The rabbits were randomized into a continued HC diet, a normal chow (NC) diet, NC plus simvastatin, NC plus PPAR-gamma agonist, and NC plus simvastatin plus PPAR-gamma agonist. All rabbits underwent magnetic resonance imaging (MRI) at randomization and after six months of treatment and were then sacrificed for histopathologic study.

RESULTS

All groups had a similar vessel wall area by MRI (8.45 +/- 0.65 mm(2), p = NS between groups) at randomization. Significant progression was seen in the HC diet group (15 +/- 4%, p < 0.01). In the NC and NC plus PPAR-gamma agonist groups, progression was abolished (-2.5 +/- 3% and -4.5 +/- 5%, respectively; p = NS). The NC plus simvastatin and NC plus simvastatin plus PPAR-gamma agonist groups had significant plaque regression (-12 +/- 4% [p < 0.05] and -22 +/- 4% [p < 0.01], respectively). Regression was independent of plasma lipid levels. All NC groups had similar lipid profiles at the end of treatment. Histopathologic analysis of the NC groups showed a decreased macrophage content and matrix metalloproteinase activity and an increased smooth muscle cell/collagen content of lesions.

CONCLUSIONS

Our data indicate that normalization of plasma lipid levels abolishes progression of atherosclerosis. Simvastatin elicits regression of atherosclerotic lesions, and the combination simvastatin plus PPAR-gamma agonist has additive regression effects on plaque. This is paralleled by structural alterations in plaque composition, which may increase plaque stability. These observations support the beneficial effects of statins on atherosclerosis and show additional anti-atherogenic benefits of combining a PPAR-gamma agonist with simvastatin.

The effects of rosiglitazone, a peroxisome proliferator-activated receptor-gamma agonist, on markers of endothelial cell activation, C-reactive protein, and fibrinogen levels in non-diabetic coronary artery disease patients

OBJECTIVES

We sought to assess the effect of rosiglitazone on markers of endothelial cell activation and acute-phase reactants in non-diabetic patients with coronary artery disease (CAD).

BACKGROUND

Inflammation plays a key role in all stages of atherosclerosis and in the genesis of acute coronary syndromes. Rosiglitazone, a peroxisome proliferator-activated receptor gamma agonist, is used in the treatment of type 2 diabetes mellitus, and previous data suggest that it may have anti-inflammatory effects on atherosclerosis.

METHODS

Patients with stable, angiographically documented CAD without diabetes mellitus were investigated. Patients were randomized in a double-blind manner to receive treatment with placebo or rosiglitazone (4 mg/day for 8 weeks followed by 8 mg/day for 4 weeks) for 12 weeks. Eighty-four patients completed the study. Fasting glucose, insulin, lipid profile, markers of endothelial activation, and inflammatory markers were measured at baseline and after 12 weeks.

RESULTS

Rosiglitazone treatment resulted in a significant reduction in E-selectin (p = 0.03), von Willebrand factor (p = 0.007), C-reactive protein (p < 0.001), fibrinogen (p = 0.003) and the homeostasis model of insulin resistance index (p = 0.02), compared with placebo. Significant elevations in low-density lipoprotein and triglyceride levels were observed in the rosiglitazone group (p < 0.01). Within the rosiglitazone-treated group, reductions in C-reactive protein and von Willebrand factor were significantly correlated with a reduction in insulin resistance.

CONCLUSIONS

Rosiglitazone significantly reduces markers of endothelial cell activation and levels of acute-phase reactants in CAD patients without diabetes. Potential underlying mechanisms include insulin sensitization and direct modification of transcription within the vessel wall.

Decrease in serum C-reactive protein levels by troglitazone is associated with pretreatment insulin resistance, but independent of its effect on glycemia, in type 2 diabetic subjects

Insulin-sensitizing thiazolidinediones (TZDs) decrease inflammatory markers such as high-sensitive C-reactive protein (hsCRP) in sera in addition to their hypoglycemic effects. However, factors associated with the decrease in serum hsCRP concentrations are unclear. In the present study, an effect of troglitazone on serum hsCRP levels was investigated and compared with its effect on glycemia. A total of 34 subjects with type 2 diabetes (17 men and 17 women, aged 54+/-2 years and body mass index (BMI) 26.7+/-0.6 kg/m(2), mean+/-S.E.) were studied. Nineteen out of the 34 subjects was treated with troglitazone 400mg daily for 12 weeks. The remaining 15 subjects were treated with metformin 750 mg daily as a control group. Baseline hsCRP levels were comparable between the two groups, and those were positively associated with fasting insulin levels. After treatment, glycemic control assessed by HbA1c and fasting glucose levels improved in both groups, whereas insulin sensitivity index estimated by homeostasis model assessment (HOMA-R) decreased only in the troglitazone-treated group. Serum levels of hsCRP significantly decreased from 916+/-210 ng/ml to 569+/-123 ng/ml (P<0.05) in the troglitazone-treated group, whereas the levels remained unchanged in the metformin-treated group (from 1087+/-248 ng/ml to 1152+/-301 ng/ml). In the troglitazone-treated group, there was no difference in the absolute and percent change in serum hsCRP levels between responders, who displayed the decrease in HbA1c greater than 0.6% (n=12), and the remaining non-responders (n=7). The decrease in serum hsCRP concentrations was negatively related to baseline levels of serum hsCRP and insulin and HOMA-R. In conclusion, troglitazone, but not metformin, reduced serum hsCRP levels in type 2 diabetic patients. The decrease in serum hsCRP concentrations by troglitazone was associated with the pretreatment levels of hsCRP and insulin resistance, but independent of the changes in glycemia.

Intramural plasminogen activator inhibitor type-1 and coronary atherosclerosis

Altered expression of plasminogen activator inhibitor type-1 in vessel walls, reviewed here, might affect coronary atherogenesis. Upregulation might exacerbate vasculopathy by potentiating thrombosis and by inhibiting vascular smooth muscle cell migration, resulting in attenuation of thickness of elaborated fibrous caps implicated in the vulnerability of atheroma to rupture.

Minireview: adiposity, inflammation, and atherogenesis

Adipose tissue is a dynamic endocrine organ that secretes a number of factors that are increasingly recognized to contribute to systemic and vascular inflammation. Several of these factors, collectively referred to as adipokines, have now been shown regulate, directly or indirectly, a number of the processes that contribute to the development of atherosclerosis, including hypertension, endothelial dysfunction, insulin resistance, and vascular remodeling. Several adipokines are preferentially expressed in visceral adipose tissue, and the secretion of proinflammatory adipokines is elevated with increasing adiposity. Not surprisingly, approaches that reduce adipose tissue depots, including surgical fat removal, exercise, and reduced caloric intake, improve proinflammatory adipokine levels and reduce the severity of their resultant pathologies. Systemic adipokine levels can also be favorably altered by treatment with several of the existing drug classes used to treat insulin resistance, hypertension, and hypercholesterolemia. Greater understanding of adipokine regulation, however, should result in the design of improved treatment strategies to control disease states associated with increase adiposity, an important outcome in view of the growing worldwide epidemic of obesity.

Regulation of plasma PAI-1 concentrations in HAART-associated lipodystrophy during rosiglitazone therapy

OBJECTIVE

Patients with highly active antiretroviral therapy-associated lipodystrophy (HAART+LD+) have high plasminogen activator inhibitor-1 (PAI-1) concentrations for unknown reasons. We determined whether (1). plasma PAI-1 antigen concentrations are related to liver fat content (LFAT) independently of the size of other fat depots and (2) rosiglitazone decreases PAI-1 and LFAT in these patients.

METHODS AND RESULTS

In the cross-sectional study, 3 groups were investigated: 30 HIV-positive patients with HAART+LD+, 13 HIV-positive patients without lipodystrophy (HAART+LD-), and 15 HIV-negative subjects (HIV-). In the treatment study, the HAART+LD+ group received either rosiglitazone (8 mg, n=15) or placebo (n=15) for 24 weeks. Plasma PAI-1 was increased in HAART+LD+ (28+/-2 ng/mL) compared with the HAART+LD- (18+/-3, P<0.02) and HIV- (10+/-3, P<0.001) groups. LFAT was higher in HAART+LD+ (7.6+/-1.7%) than in the HAART+LD- (2.1+/-1.1%, P<0.001) and HIV- (3.6+/-1.2%, P<0.05) groups. Within the HAART+LD+ group, plasma PAI-1 was correlated with LFAT (r=0.49, P<0.01) but not with subcutaneous or intra-abdominal fat or serum insulin or triglycerides. In subcutaneous adipose tissue, PAI-1 mRNA was 2- to 3-fold higher in the HAART+LD+ group than in either the HAART+LD- or HIV- group. Rosiglitazone decreased LFAT, serum insulin, and plasma PAI-1 and increased serum triglycerides but had no effect on intra-abdominal or subcutaneous fat mass or PAI-1 mRNA.

CONCLUSIONS

Plasma PAI-1 concentrations are increased in direct proportion to LFAT in HAART+LD+ patients. Rosiglitazone decreases LFAT, serum insulin, and plasma PAI-1 without changing the size of other fat depots or PAI-1 mRNA in subcutaneous fat. These data suggest that liver fat contributes to plasma PAI-1 concentrations in these patients.

Rosiglitazone reduces urinary albumin excretion in type II diabetes

This study examines the effect of rosiglitazone on urinary albumin excretion (UAE) in patients with type II diabetes. Urinary albumin: creatinine ratio (ACR) was measured in a 52-week, open-label, cardiac safety study comparing rosiglitazone and glyburide. Patients were randomised to treatment with rosiglitazone 4 mg b.i.d. or glyburide. ACR was measured at baseline and after 28 and 52 weeks of treatment. Statistically significant reductions from baseline in ACR were observed in both treatment groups at week 28. By week 52, only the rosiglitazone group showed a significant reduction from baseline. Similar results were observed for the overall study population and for the subset of patients with baseline microalbuminuria. For patients with microalbuminuria at baseline, reductions in ACR did not correlate strongly with reductions in glycosylated haemoglobin, or fasting plasma glucose, but showed strong correlation with changes in mean 24-h systolic and diastolic blood pressure for rosiglitazone-treated patients (deltaACR vs deltamean 24-h systolic blood pressure, r=0.875; deltaACR vs deltamean 24-h diastolic blood pressure, r=0.755; P < 0.05 for both). No such correlation was observed for glyburide-treated patients. In conclusion, rosiglitazone treatment was associated with a decrease in urinary albumin excretion. These findings suggest a potential beneficial effect of rosiglitazone in the treatment or prevention of renal and vascular complications of type II diabetes.

Effect of combination glipizide GITS/metformin on fibrinolytic and metabolic parameters in poorly controlled type 2 diabetic subjects

OBJECTIVE

Epidemiological studies have implicated increased plasminogen-activated inhibitor 1 (PAI-1) as a marker or predictor of accelerated coronary atherosclerotic disease in type 2 diabetes. We sought to determine whether metabolic control, independent of its oral mode of implementation, affects PAI-1 in patients with marked hyperglycemia.

RESEARCH DESIGN AND METHODS

A total of 91 subjects were screened, subjected to a 4-week drug washout, and randomized to daily treatment with glipizide GITS (maximum 20 mg, n = 46) or metformin (maximum 2,550 mg, n = 45) as monotherapy. After monotherapy, combination therapy was initiated by adding the second agent to the regimen. Plasma glucose (fasting and postprandial), HbA(1c), fructosamine, and PAI-1 were assayed before and after randomization and sequentially thereafter in all subjects; hepatic glucose output (HGO) and abdominal fat distribution were each measured in a subset of subjects.

RESULTS

Glycemic control was markedly impaired at baseline (mean HbA(1c) 10.4 +/- 0.2% glipizide GITS; 10.0 +/- 0.2% metformin) but improved comparably with each agent as monotherapy and in combination (P < 0.0001 vs. baseline), as assessed with meal tolerance studies, fructosamine values, and HGO. Body weight and abdominal fat distribution did not change significantly in either group. PAI-1 concentrations were extraordinarily high (5- to 10-fold more than normal) at baseline (202 +/- 12 ng/ml glipizide GITS; 201 +/- 13 ng/ml metformin) but declined comparably, and significantly, after treatment with either agent as monotherapy and decreased further with combination therapy.

CONCLUSIONS

When hyperglycemia is profound, increases in PAI-1 are also profound. Control of hyperglycemia with either glipizide GITS, an insulin secretagogue, or metformin as monotherapy comparably ameliorates elevated PAI-1.

Biologic aspects of vulnerable plaque

Atherosclerosis and its thrombotic complications are the major cause of morbidity and mortality in the industrialized world. The progression of atherosclerotic plaques in coronary circulation is modulated by several risk factors. It is now clear that plaque composition is a major determinant of plaque disruption and superimposed thrombosis. Plaque vulnerability, defined as the propensity of plaques to disrupt, is further determined by intrinsic and extrinsic triggering factors. After disruption, the fatty core of the plaque and its high content of tissue factor provide a powerful substrate for the activation of the coagulation cascade. Plaque disruption can be clinically silent or cause symptoms of ischemia depending on thrombus burden and the degree of vessel occlusion. In addition, plaque disruption and subsequent healing are recognized to play key roles in the rapid plaque progression. This review looks at the mechanisms underlying the development and progression of atherosclerotic plaques, factors leading to plaque rupture and subsequent thrombosis, and their clinical consequences as potential targets for future research.

Plasminogen activator inhibitor-1: physiologic role, regulation, and the influence of common pharmacologic agents

Plasminogen activator inhibitor-1 (PAI-1) is the major inhibitor of endogenous thrombolysis, thereby promoting thrombosis. PAI-1 is also a primary contributor to the development and recurrence of acute myocardial infarction. The renin angiotensin system, hypertriglyceridemia, hyperglycemia and hyperinsulinemia, and estrogen all influence the fibrinolytic system and PAI-1 in particular. Available data strongly suggest that angiotensin-converting enzyme (ACE) inhibitors and hormone replacement therapy with estrogen beneficially reduce PAI-1 production. Metformin, an agent commonly used for non-insulin-dependent diabetes mellitus (NIDDM), appears to favorably decrease PAI-1 production in NIDDM patients but not nondiabetic patients. Among the cholesterol-lowering statins, clinical literature evaluating pravastatin provides the most compelling data to support this agent's favorable effect on PAI-1. Other available statins either have not displayed an effect on PAI-1 or do not have clear data to conclusively define their effects on the fibrinolytic system.

Pleiotropic actions of peroxisome proliferator-activated receptors in lipid metabolism and atherosclerosis

Peroxisome proliferator-activated receptors (PPARs) are nuclear receptors activated by fatty acids and derivatives. Although PPARalpha mediates the hypolipidemic action of fibrates, PPARgamma is the receptor for the antidiabetic glitazones. PPARalpha is highly expressed in tissues such as liver, muscle, kidney, and heart, where it stimulates the beta-oxidative degradation of fatty acids. PPARgamma is predominantly expressed in adipose tissues, where it promotes adipocyte differentiation and lipid storage. PPARbeta/delta is expressed in a wide range of tissues, and recent findings indicate a role for this receptor in the control of adipogenesis. Pharmacological and gene-targeting studies have demonstrated a physiological role for PPARs in lipid and lipoprotein metabolism. PPARalpha controls plasma lipid transport by acting on triglyceride and fatty acid metabolism and by modulating bile acid synthesis and catabolism in the liver. All 3 PPARs regulate macrophage cholesterol homeostasis. By enhancing cholesterol efflux, they stimulate the critical steps of the reverse cholesterol transport pathway. As such, PPARs control plasma levels of cholesterol and triglycerides, which constitute major risk factors for coronary heart disease. Furthermore, PPARalpha and PPARgamma regulate the expression of key proteins involved in all stages of atherogenesis, such as monocyte and lymphocyte recruitment to the arterial wall, foam cell formation, vascular inflammation, and thrombosis. Thus, by regulating gene transcription, PPARs modulate the onset and evolution of metabolic disorders predisposing to atherosclerosis and exert direct antiatherogenic actions at the level of the vascular wall.

Treatment for the procoagulant state in type 2 diabetes

A procoagulant state has been found to exist in diabetes mellitus. There may be activation of the intrinsic coagulation system, decreased fibrinolytic activity, or alterations in platelet function. Intensive glycemic control with insulin is effective in reducing the impact of this procoagulant state by favorably affecting all three components of the system. Decreased fibrinolytic activity, as influenced by plasma PAI-1 levels, may be favorably affected by weight loss, exercise, a low-GI diet, or by metformin, thiazolidinediones, gemfibrozil, and ACE inhibitor therapy. Insulin has variable effects on plasma PAI-1 activity. Estrogens will lower the elevated PAI-1 levels seen in the menopausal state. Collaborative trial evidence supports the use of low-dose aspirin as a primary or secondary prevention strategy in diabetic persons who are at high cardiovascular risk. A recent study suggests that this category includes virtually every type 2 diabetic individual in the United States. The American Diabetes Association recommends enteric-coated aspirin, 81 to 325 mg/day, as the first choice. In the case of aspirin allergy, clopidrogel is an alternate choice. Thus, recognition of and therapy for a procoagulant state in diabetes mellitus is likely to result in a decrease in the atherothrombotic events that characterize the later stages of this disease.

Peroxisome proliferator-activated receptor gamma (PPARgamma) activation and its consequences in humans

Peroxisome proliferator-activated receptor gamma (PPARgamma) is a member of the superfamily of nuclear receptors. It binds and is activated by natural polyunsaturated fatty acids, eicosanoids, synthetic thiazolidinediones and related analogues. Biological effects exerted by PPARgamma ligands are mostly concerned with differentiation processes, sensitization to insulin and atherogenesis, and are paradigmatically ascribed to PPARgamma transactivation of PPARgamma-responsive genes. The PPARgamma paradigm and its consequences in humans are analyzed here in terms of the tissue specificity of PPARgamma, loss and gain of function mutants of PPARgamma, PPARgamma-responsive genes and clinical effects of PPARgamma ligands. Differentiation, as well as some of the atherogenic effects induced by PPARgamma ligands, does conform to the PPARgamma paradigm. However, sensitization to insulin as well as some of the antiatherogenic effects of PPARgamma ligands is not accounted for by PPARgamma activation, thus calling for an alternative target for insulin sensitizers.

SSPG titer is a diagnostic marker for adrenocortical adenoma in patients with non-functioning adrenal incidentaloma

We analyzed insulin resistance-related clinical markers as well as imaging characteristics of adrenal masses in 11 patients with incidentally discovered adrenal tumors that were diagnosed as non-functioning according to the results of the 1 mg dexamethasone suppression test and then voluntarily resected. Histologic examination of the resected tumors revealed adrenocortical adenoma in eight patients, and non-cortical tumors: a myelolipoma. an endothelioma and an adrenal vascular cyst in three patients. All eight patients with adrenocortical adenoma exhibited insulin resistance as estimated by the steady-state plasma glucose (SSPG). The mean systolic blood pressure of the patients with adrenocortical adenoma was higher than that of the patients with non-cortical tumors, even though three of eight patients were normotensive. HOMA-R, EIRI on 75 g oGTT. diastolic blood pressure and serum triglyceride were not significantly different between the patients with adrenocortical adenomas and those with non-cortical tumors. Imaging characteristic such as tumor size, shape and heterogeneity in the mass did not distinguish these two groups either. These results suggest that the presence of insulin resistance estimated by SSPG may be a diagnostic marker for adrenocortical adenoma in patients with a non-functioning incidentaloma.