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

Rosiglitazone induces the unfolded protein response, but has no significant effect on cell viability, in monocytic and vascular smooth muscle cells

Given the safety concerns expressed over negative cardiovascular outcomes resulting from the clinical use of rosiglitazone, and the view that rosiglitazone exerts PPARγ-independent effects alongside its insulin-sensitising PPARγ-dependent effects, we hypothesised that rosiglitazone may trigger Unfolded Protein Responses (UPRs) due to disruptions in [Ca(2+)](i) homeostasis within two cardiovascular cell types: monocytic (MM6) and vascular smooth muscle (A7r5) cells. In microsomal samples derived from both cell types, pre-incubation with rosiglitazone rapidly (30min) brought about concentration-dependent PPARγ-independent inhibition of Ca(2+)ATPase activity (IC(50) ∼2μM). Fluo-3 fluorimetric data demonstrated in intact cells that 1h treatment with 1 or 10μM rosiglitazone caused Ca(2+) ions to leak into the cytoplasm. Gene expression analysis showed that within 4h of rosiglitazone exposure, the UPR transcription factor XBP-1 was activated (likely due to corresponding ER Ca(2+) depletion), and the UPR target genes BiP and SERCA2b were subsequently upregulated within 24-72h. After 72h 1 or 10μM rosiglitazone treatment, microsomal Ca(2+)ATPase activity increased to >2-fold of that seen in control microsomes, while [Ca(2+)](i) returned to basal, indicating that UPR-triggered SERCA2b upregulation was responsible for enhanced enzymatic Ca(2+) sequestration within the ER. This appeared to be sufficient to replenish ER Ca(2+) stores and restore normal cell physiology, as cell viability levels were not decreased due to rosiglitazone treatment throughout a 2-week study. Thus, incubation with 1-10μM rosiglitazone triggers the UPR, but does not prove cytotoxic, in cells of the cardiovascular system. This observation provides an important contribution to the current debate over the use of rosiglitazone in the clinical treatment of Type-2 Diabetes.

Advanced glycation end product-mediated matrix metallo-proteinase-9 and apoptosis via renin-angiotensin system in type 2 diabetes

AIM

Advanced glycation end products (AGE) play a key role in diabetic vascular complications, whereas matrix metalloproteinases (MMPs) and apoptosis contribute to plaque instability. This study was conducted to investigate the association of AGE-mediated MMP-9 and apoptosis with the renin-angiotensin system (RAS). We also examined the correlation between plasma HbA1c levels and plaque parameters.

METHODS

We used autopsy specimens from the aortae and coronary arteries of patients with or without diabetes (n=11, each group) for the immunohistochemistry of AGE, MMP-9, angiotensin-converting enzyme (ACE), and the receptor for AGE (RAGE). Apoptosis was determined by TUNEL staining.

RESULTS

The proportions of AGE accumulation, MMP-9 expression and apoptosis in intimal areas of both aortic and coronary specimens of diabetics were greater than in nondiabetics. MMP-9 expression and apoptosis were correlated with AGE accumulation. RAGE expression was significantly increased in diabetic specimens compared to nondiabetes. Interestingly, the expression of ACE in diabetic specimens was increased and also correlated with AGE accumulation, RAGE expression, MMP-9 expression, and apoptosis in all specimens from diabetics and nondiabetics. Plasma levels of HbA1c were linearly correlated with AGE accumulation, MMP-9, apoptosis, and ACE expression.

CONCLUSION

The present study shows that AGE/RAGE-related MMP-9 expression and apoptosis were correlated with ACE expression in diabetic plaques and that RAS may be involved in AGE-dependent diabetic vascular complications.

Association between serum amyloid A and obesity: a meta-analysis and systematic review

BACKGROUND

Emerging evidence indicates an association of the acute-phase protein serum amyloid A (SAA) with obesity. Here we review and summarize quantitatively the available data related to this association.

METHODS

PubMed was systematically searched using the terms "serum amyloid A" and "obesity." Eighty-one relevant studies between January 1966 and July 2009 were identified. Of these, only 11 cross-sectional studies and 10 prospective studies with successful interventions met our inclusion criteria for the meta-analysis. All analyses were conducted using the Comprehensive Meta-Analysis software. Literature pertaining to the relationship between SAA and other inflammatory markers, and the association between SAA and obesity-related disorders, such as cardiovascular diseases, atherosclerosis, diabetes, and insulin resistance was also reviewed.

RESULTS

A strong association between body mass index and SAA levels was found in the 11 cross-sectional studies. The overall correlation coefficient is 0.230 (95% CI 0.160-0.297, P < 0.0005). The ten prospective studies were subsequently analyzed, and the difference in SAA levels before and after weight loss, expressed as standardized mean difference was -0.480 (95% CI -0.678 to -0.283, P < 0.0005). We discuss some potential underlying mechanisms and clinical applications for reducing SAA levels in obesity.

Peroxisome Proliferator-Activated Receptor Expression in Murine Models and Humans with Age-related Macular Degeneration

Peroxisome proliferator-activated receptors (PPARs) play a role in oxidative stress and VEGF regulation, which are closely related to age-related macular degeneration (AMD). PPAR γ expression and its downstream molecules were examined in fat-1 mice (transgenic mice that convert n-6 to n-3 fatty acids), Ccl2(-/-)/Cx3cr1(-/-) mice (an AMD model), ARPE19 cells (a human retinal pigment epithelial cell line, RPE, a cell type with a critical role in AMD), and human eyes with and without AMD. PPAR α, β, and γ, VEGF and receptors were determined by immunohistochemistry in the mice models, humans, and ARPE19 cells. Transcripts of PPARs, VEGF, MMP-9 and HO-1 were determined by RQ-PCR. PPARs were constitutively expressed in normal neuroretina and RPE of humans and mice. PPAR γ expression was increased in fat-1 and Ccl2(-/-)/Cx3cr1(-/-) mice. VEGF was decreased in fat-1 mice but increased in Ccl2(-/-)/Cx3cr1(-/-) mice. VEGF receptors were stable. VEGF, MMP9 and HO-1 transcript levels were increased in ARPE19 cells under H(2)O(2) - induced oxidative stress. Human AMD retinas exhibited higher PPAR γ. The findings of increased expression of PPAR γ and its downstream proteins (VEGF, MMP9, and HO-1) in H(2)O(2)-treated ARPE19 cells, Ccl2(-/-)/Cx3cr1(-/-) mice, and human AMD eyes, but decreased VEGF in fat-1 mice, suggest that PPAR γ may play a role in AMD.

Pioglitazone inhibits Toll-like receptor expression and activity in human monocytes and db/db mice

Toll-like receptors (TLRs) are key innate immune sensors of endogenous damage signals and play an important role in inflammatory diseases like diabetes and atherosclerosis. Pioglitazone (PIO), a peroxisome proliferator-activated receptor (PPAR)-gamma agonist, has been reported to be an antiinflammatory agent. Thus, in the present study, we examined the antiinflammatory effects of PIO on TLR2 and TLR4 expression in human monocytes exposed to Pam3CSK4 (Pam; TLR2 ligand) and purified lipopolysaccharide (LPS; TLR4 ligand) using flow cytometry and real-time RT-PCR. Monocytes were isolated from healthy human volunteers and pretreated with PIO (1 microM) followed by Pam (170 ng/ml) and LPS (160 ng/ml) challenge. PIO significantly decreased Pam- and LPS-induced TLR2 (-56%) and TLR4 (-78%) expression (P < 0.05). In addition, PIO decreased TLR ligand-induced nuclear factor-kappaB activity (-63%), IL-1beta (-50%), IL-6 (-52%), monocyte chemoattractant protein-1(-83%), and TNF-alpha (-87%) compared with control. Next, PIO-treated db/db mice (n = 6/group) showed decreased TLR2 (-60%) and TLR4 (-45%) expression in peritoneal macrophages compared with vehicle control mice (P < 0.001) with associated decrease in MyD88-dependent signaling and nuclear factor-kappaB activation. Data suggest that Pam- and LPS-induced TLR2 and TLR4 expression are inhibited by PIO in human monocytes and db/db mice. Thus, we define a novel pathway by which PIO could induce antiinflammatory effects.

Rosiglitazone reduces the development and rupture of experimental aortic aneurysms

BACKGROUND

Development and rupture of aortic aneurysms involve a combination of complex biological processes. Rosiglitazone, a peroxisome proliferator-activated receptor-gamma agonist, has been shown to have a broad spectrum of effects in vivo. The hypothesis that rosiglitazone would reduce aneurysm expansion or rupture was tested in the angiotensin II (Ang II)-induced hypercholesterolemic mouse model.

METHODS AND RESULTS

Apolipoprotein E-deficient mice, 12 months of age, were allocated to 4 groups. Three groups were infused with Ang II (1 microg . min(-1) . kg(-1)), and the fourth was infused with saline. Rosiglitazone was given 1 week before infusion and 1 week after infusion. At day 28, aortic size was measured, and tissues were collected for analyses. Both pretreatment and posttreatment with rosiglitazone inhibited the occurrence of fatal rupture (11 of 30 versus 0 of 30 versus 0 of 15; P=0.0013) and reduced maximal dilatation of the aorta (4.6+/-0.13 versus 2.4+/-0.48 versus 2.15+/-0.46 mm2; P<0.0001). Blood glucose, total cholesterol, body weight, and atherosclerosis did not differ between groups. Pretreatment with rosiglitazone inhibited the Ang II-induced expression of angiotensin type 1a Ang II receptor while having no effect on the angiotensin type 2 Ang II receptor, in addition to reducing Ang II-induced expression of E-selectin, tumor necrosis factor-alpha, and interleukin-6.

CONCLUSIONS

Pretreatment or posttreatment with RGZ reduced aortic expansion and rupture in this mouse model. Reduction of lesions in animals pretreated with rosiglitazone is concomitant with decreased expression of inflammatory mediators. Further studies are needed to elucidate the precise mechanism.

Pleiotropic effects of thiazolidinediones on traditional and non-traditional atherosclerotic risk factors

BACKGROUND

The thiazolidinediones pioglitazone and rosiglitazone have established efficacy in improving insulin sensitivity, glycaemic control, dyslipidaemia, hypertension and microalbuminuria in patients with type 2 diabetes. As specific agonists of peroxisome proliferator-activated receptor-gamma, thiazolidinediones have also demonstrated protective effects on a variety of atherosclerosis biomarkers and surrogate measures of cardiovascular disease.

AIM

This paper reviews the evidence for pleiotropic effects on a variety of non-traditional atherosclerotic risk factors.

DISCUSSION

Thiazolidinediones attenuate circulating levels of pro-inflammatory mediators in patients with type 2 diabetes, including C-reactive protein, interleukin-6, CD40L, monocyte chemoattractant protein-1 and metalloproteinase-9. These agents also increase levels of the vascular protective adipokine, adiponectin. The clinical significance of these findings is supported by evidence of improved endothelial dysfunction, reduced carotid intima media thickness and improvements in stenosis following coronary artery stent implantation in patients treated with thiazolidinediones. Limited data suggest that thiazolidinediones might also improve the circulating levels and functional activity of angiogenic endothelial progenitor cells, which independently predict the incidence of cardiovascular events and death. It should be noted that the US Food and Drug Administration and the European Medicines Agency have requested changes to the prescribing information for rosiglitazone to highlight the possibility of an increased risk with this agent in patients with ischaemic heart disease; on review, no such amendment was required for the pioglitazone prescribing information. Both agencies continue to suggest that the benefits of both thiazolidinediones outweight any possible detrimental effects. Further research remains to be conducted to elucidate the potentially differential vascular protective effects of thiazolidinediones. In the US, there are black box heart failure warnings for both agents.

CONCLUSION

In light of the established importance of reducing cardiovascular risk in patients with type 2 diabetes, current evidence continues to support the use of pioglitazone within multifactorial risk management strategies.

Potential implications of matrix metalloproteinase-9 in assessment and treatment of coronary artery disease

BACKGROUND

Matrix metalloproteinase (MMP)-9, a member of the MMP superfamily is consistently implicated in the pathophysiology of atherosclerosis and plaque rupture, the most common mechanism responsible for acute coronary syndrome (ACS).

AIM

To summarize the role of MMP-9 in atherosclerosis and its potential implications in assessment and treatment of coronary artery disease (CAD).

METHODS

We reviewed the PubMed database for relevant data regarding the role of MMP-9 in the pathophysiology of atherosclerosis. In the light of these data, we postulate potential implications of MMP-9 in the management and treatment of CAD.

RESULTS AND CONCLUSIONS

Existing data strongly support the role of MMP-9 in plaque destabilization and rupture. Based on the current knowledge, MMP-9 can potentially serve as a diagnostic biomarker in ACS and a prognostic biomarker in ACS and chronic CAD patients. MMP-9 is reduced by therapies that are associated with favourable outcome in atherosclerosis and thus may serve as a surrogate biomarker of treatment efficacy. However, large morbidity and mortality trials are still required to confirm that MMP-9 reduction is associated with improved outcome independent of the traditional risk factors (i.e. low-density lipoprotein cholesterol). Given its role in plaque rupture, inhibition of MMP-9 may promote plaque stabilization and consequently reduce cardiovascular events. Yet, the efficacy and safety of MMPs inhibitors should be first studied in preclinical models of atherosclerosis.

Arterial stiffness: methods of measurement, physiologic determinants and prediction of cardiovascular outcomes

Arterial stiffness has been shown to be a potent and independent predictor of cardiovascular risk. In this review, we outline methods for the measurement of arterial stiffness, describe the physiological mechanisms that underpin the utility of arterial stiffness as an integrative marker of cardiovascular disease, and detail the evidence examining the value of arterial stiffness for prediction of adverse cardiovascular events and mortality. The extent to which arterial stiffness may be modified by medical and lifestyle therapy is reviewed.

Non-conventional markers of atherosclerosis before and after gastric banding surgery

AIMS

Obesity and type 2 diabetes are associated with increased cardiovascular risk and elevation of traditional and non-traditional risk markers. As bariatric surgery reduces overweight and improves metabolic derangement, we examined a cluster of established and emerging cardiovascular risk factors, such as soluble CD40 ligand (sCD40L) and lipoprotein-associated phospholipase A(2) (Lp-PLA(2)), which might improve prediction of future cardiovascular events because of their more direct involvement in plaque destabilization.

METHODS AND RESULTS

Obese patients [n = 32, body mass index (BMI) 46.1 +/- 5.9 kg/m(2)] underwent clinical examinations and blood sampling for measurement of glucose and lipid parameters as well as non-traditional cardiovascular risk markers, i.e. high-sensitivity C-reactive protein, plasminogen activator inhibitor-1 (PAI-1), soluble cellular adhesion molecules (CAM), MMP-2, MMP-9, CD40L, and Lp-PLA(2) before and after 1 year following laparoscopic adjustable gastric banding (LAGB), respectively. In patients undergoing LAGB, blood pressure (P < 0.0001) and blood glucose (P = 0.02) were significantly lowered by approximately 16% as well as triglyceride levels by approximately 29% (P = 0.002). In addition to a decrease of the inflammatory and pro-thrombotic marker PAI-1 (P = 0.001), CAMs, and MMP-9 (P = 0.004) were reduced, whereas no change was observed for plasma levels of MMP-2, sCD40L, and Lp-PLA(2) after LAGB, respectively. Individual changes in (ICAM-1) intercellular adhesion molecule-1 (DeltaICAM-1) were related to changes in insulin (Deltafasting insulin) before and after LAGB (r = 0.36 and r = 0.38; both P = 0.04). E-selectin correlated positively with changes in BMI (r = 0.38; P = 0.04 and r = 0.36; P = 0.05), while Lp-PLA(2) concentration was negatively correlated with BMI (r =-0.41; P = 0.02) after 1 year. Changes were comparable in both overweight diabetic and non-diabetic subjects.

CONCLUSION

LAGB not only induced weight loss but also an improvement in the subclinical pro-inflammatory state. However, concentrations of most of the non-traditional risk factors for plaque instability, i.e. MMP-9, sCD40L, and Lp-PLA(2) remained unchanged.

Pioglitazone reduces monocyte activation in type 2 diabetes

Inflammation is involved in the pathophysiologic process of atherosclerosis, a frequent complication of type 2 diabetes. The purpose of our study was to investigate the effect of pioglitazone on systemic inflammatory markers and activation of circulating monocytes in type 2 diabetic patients through the dosage of IL-6. Twenty-four metformin-treated patients, in good glycemic control, were randomized to add pioglitazone for 8 weeks or to continue their previous treatment. Blood samples were collected before and at the end of the study to evaluate: serum levels of high sensitivity C-reactive protein (hs-CRP), interleukin (IL)-6 and leukocyte activation. IL-6 production of circulating monocytes after LPS stimulation was similar at baseline and showed a 54% reduction in pioglitazone-group at 8 weeks (9.1 pg/mL, range 0.0-24.3, P=0.04 vs. baseline) while, in controls, did not change at 8 weeks (16.9 pg/mL, range 1.5-58.8). Treatment with pioglitazone, associated with metformin, showed a reduction of IL-6 monocyte production after their in vitro activation with LPS.

The monocyte/macrophage as a therapeutic target in atherosclerosis

It is now clear that the monocyte/macrophage has a crucial role in the development of atherosclerosis. This cell appears to be involved in all stages of atherosclerotic plaque development and is increasingly seen as a candidate for therapeutic intervention and as a potential biomarker of disease progression and response to therapy. The main mechanisms related to the activity of the monocyte/macrophage that have been targeted for therapy are those that facilitate recruitment, cholesterol metabolism, inflammatory activity and oxidative stress. There is also increasing evidence that there is heterogeneity within the monocyte/macrophage population, which may have important implications for plaque development and regression. A better insight into how specific phenotypes may influence plaque progression should facilitate the development of novel methods of imaging and more refined treatments.

Thiazolidinedione use is associated with better survival in hemodialysis patients with non-insulin dependent diabetes

Cardiovascular mortality is especially high among dialysis patients with diabetes, as is morbidity due to protein energy wasting. Given that both of these factors may be decreased by thiazolidinedione treatment, we studied the effect of thiazolidinedione use on survival among chronic dialysis patients in a national cohort of 5290 incident dialysis patients with diabetes. Thiazolidinedione use was assessed according to prescription data, and the analyses were stratified based on insulin use due to observed interaction. In the primary analysis, thiazolidinedione treatment was associated with significantly lower all-cause mortality among insulin-free but not insulin-requiring subjects, with adjusted hazards ratios of 0.53 (0.31-0.89) and 0.82 (0.46-1.47) respectively. Sensitivity analyses found the findings to be robust with respect to confounding by indication, severity of the diabetes, potential reverse causality, and time varying exposure patterns. The mechanism of this decline in all-cause mortality will need to be examined after these studies are confirmed.

PPAR activators and COX inhibitors selectively block cytokine-induced COX-2 expression and activity in human aortic smooth muscle cells

Atherosclerotic complications are related to the unstable character of the plaque rather than its volume. Vulnerable plaques often contain a large lipid core, a reduced content of smooth muscle cells (SMCs), and an accumulation of inflammatory cells. Regulation of this inflammatory response is an essential element in chronic inflammatory diseases such as atherosclerosis. Nuclear receptors and particularly peroxisome proliferator-activated receptors (PPARs) have emerged as therapeutic targets with a widespread impact on the treatment of metabolic disorders because they can modulate gene expression involved in lipid and glucose homeostasis and can exert anti-inflammatory properties. However, little is known about nuclear receptor effects on SMC inflammation, which produces large amounts of IL-6 and prostanoids. The aim of this study was to evaluate anti-inflammatory properties of nuclear receptor activators in a human physiological SMC model. We show that PPAR activators, as well as liver X receptor alpha, farnesoid X receptor and retinoid X receptor alpha activators, inhibit IL-1beta-induced SMC 6-keto PGF1alpha synthesis, an index of cyclooxygenase (COX)-2 activity, with IC(50) between 1 and 69 microM. In contrast, PPARgamma activators, as exemplified by rosiglitazone and pioglitazone, were unable to inhibit cytokine-induced 6-keto PGF1alpha synthesis. We also demonstrate for the first time that the COX-2 inhibitor rofecoxib can reduce 6-keto PGF1alpha production by both enzymatic inhibition and transcriptional repression. These results show that some nuclear receptor activators have SMC anti-inflammatory properties due to COX-2 inhibition which could participate in their anti-atherosclerotic properties beyond lipid impacts.

Serum amyloid A: an acute-phase protein involved in tumour pathogenesis

The synthesis of acute-phase protein serum amyloid A (SAA) is largely regulated by inflammation- associated cytokines and a high concentration of circulating SAA may represent an ideal marker for acute and chronic inflammatory diseases. However, SAA is also synthesized in extrahepatic tissues, e.g. human carcinoma metastases and cancer cell lines. An increasing body of in vitro data supports the concept of involvement of SAA in carcinogenesis and neoplastic diseases. Accumulating evidence suggests that SAA might be included in a group of biomarkers to detect a pattern of physiological events that reflect the growth of malignancy and host response. This review is meant to provide a broad overview of the many ways that SAA could contribute to tumour development, and accelerate tumour progression and metastasis, and to gain a better understanding of this acute-phase reactant as a possible link between chronic inflammation and neoplasia.

Exercise training but not rosiglitazone improves endothelial function in prediabetic patients with coronary disease

BACKGROUND

Impaired glucose tolerance (IGT) is associated with endothelial dysfunction and upregulation of inflammatory markers, which is potentially reversible by adequate treatment. It was our aim to compare the impact of exercise training with that of rosiglitazone on endothelial function and inflammatory markers in patients with IGT and coronary artery disease (CAD).

METHODS

Patients with IGT and CAD were randomly assigned to either exercise training (n=13), rosiglitazone (8 mg; n=11), or a control group (n=10). During the first week, exercise training consisted of 6 x 15 min/d followed by three weeks of 30 min/d submaximal ergometer exercise. In addition, group exercise training of 1 h was performed twice per week.

RESULTS

After 4 weeks, triglycerides and uric acid were significantly lower in the exercise group whereas fasting glucose, HbA1c, low-density lipoprotein-cholesterol, high-density lipoprotein-cholesterol, C-reactive protein, fibrinogen, and body mass index did not differ between groups. In the exercise group, exercise capacity (123+/-33 vs. 144+/-31 W; P=0.006) and endothelium-dependent, flow-mediated vasodilatation (P<0.01) increased significantly, whereas in the rosiglitazone group and in the control group (P=n.s.) no changes were seen.

CONCLUSION

In patients with IGT and CAD, 4 weeks of exercise training exert significant and superior improvement of endothelium-dependent vasodilatation as compared with rosiglitazone therapy or usual care. This finding should be seen as an even further encouragement to recommend and, where available, prescribe exercise training to our patients.

Fibrosis in diabetes complications: pathogenic mechanisms and circulating and urinary markers

Diabetes mellitus is characterized by a lack of insulin causing elevated blood glucose, often with associated insulin resistance. Over time, especially in genetically susceptible individuals, such chronic hyperglycemia can cause tissue injury. One pathological response to tissue injury is the development of fibrosis, which involves predominant extracellular matrix (ECM) accumulation. The main factors that regulate ECM in diabetes are thought to be pro-sclerotic cytokines and protease/anti-protease systems. This review will examine the key markers and regulators of tissue fibrosis in diabetes and whether their levels in biological fluids may have clinical utility.

Therapeutical effects of PPAR agonists assessed by biomarker modulation

The metabolic syndrome is defined as the clustering of cardiovascular risk factors, such as glucose intolerance, hyperinsulinemia, dyslipidemia, coagulation disturbances and hypertension. Activators of the nuclear receptors peroxisome proliferator-activated receptors (PPARs) modulate several of the metabolic risk factors pre-disposing to atherosclerosis. Fibrates are hypolipidemic drugs operating through activation of PPARalpha, whereas glitazones are insulin sensitizers activating PPARgamma. In addition, these drugs exert pleiotropic and anti-inflammatory actions. This review will focus on the different effects of fibrates and glitazones, as measured by biomarker modulation, on the development of atherosclerosis and cardiovascular disease.

Winners and losers at the rosiglitazone gamble A meta-analytical approach at the definition of the cardiovascular risk profile of rosiglitazone

The treatment with rosiglitazone could be associated with increased risk for myocardial infarction (MI). This meta-analysis is aimed at identifying moderators of the effect of rosiglitazone on the risk of MI and chronic heart failure (CHF) in type 2 diabetic patients. The risk ratio (RR) of MI and CHF was calculated for each trial as the ratio of incidence density in rosiglitazone and comparator groups. A total of 86 trials were included. After adjusting for trial duration, RR for MI showed a significant inverse correlation with mean baseline HbA1c, triglycerides, and LDL-cholesterol (r=-0.24, -0.45, and -0.33, respectively; all p<0.05). Conversely, rosiglitazone-associated risk of MI was increased in trials with higher mean BMI or greater proportion of insulin-treated patients (r=0.26 and 0.42, respectively; p<0.05). Lower triglyceride levels were also associated with a higher rosiglitazone-induced risk of CHF (r=-0.23, p<0.05). Treatment with rosiglitazone could have divergent effects on cardiovascular risk, depending on the characteristics of the patients. Benefits could outweigh harms in patients with poor glycemic control and worse lipid profile; conversely, the drug could increase the risk of MI in obese or insulin-treated patients.

The effect of metformin on measurements of insulin sensitivity and beta cell response in 18 horses and ponies with insulin resistance

REASONS FOR PERFORMING STUDY

Laminitis in equids is a very common debilitating disease, and insulin resistance (IR) and hyperinsulinaemia are increasingly recognised as important predisposing factors. Pharmacological modification of IR and hyperinsulinaemia might reduce the risk of laminitis.

HYPOTHESIS

Metformin, a drug commonly prescribed for treatment of human IR, may also decrease IR in equids.

METHODS

Eighteen horses and ponies with IR and recurrent laminitis were treated with 15 mg/kg bwt metformin per os q. 12 h. Each animal served as its own control by comparing pre- and post treatment proxies for IR, insulin sensitivity (IS) and pancreatic beta cell function while controlling for possible dietary and managemental influences on IR.

RESULTS

Evidence of significantly improved IS and decreased pancreatic beta cell secretion was found following metformin treatment. The magnitude of effect was greater at earlier resampling (6-14 days) than at later times (23-220 days). Apparent subjective clinical benefits were good but less favourable than effects on IR.

CONCLUSIONS

Metformin is safe and appears to increase IS in equids.

POTENTIAL RELEVANCE

Metformin may be indicated as a treatment for IR in equids. Further studies are required to define appropriate selection of subjects warranting therapy, dosing schedule and pharmacokinetics.

A randomized, controlled trial of the effects of rosiglitazone on adipokines, and inflammatory and fibrinolytic markers in diabetic patients: study design and protocol

BACKGROUND

Although rosiglitazone may offer vascular benefits beyond lowering glucose, recently, concern has been raised that this drug may paradoxically increase cardiovascular risk.

OBJECTIVE

To assess the effects of rosiglitazone compared with standard oral hypoglycemic therapies on adipokines, and inflammatory and fibrinolytic markers in subjects with type 2 diabetes.

METHODS

A 12-week, randomized, open-label, parallel-group study will be conducted on 100 type 2 diabetic subjects with suboptimal glycemic control (glycosylated hemoglobin 0.075 or greater) despite management with lifestyle alone (drug-naive) or with monotherapy (either metformin or sulfonylurea). Drug-naive patients will be randomly assigned to receive either rosiglitazone (4 mg/day to 8 mg/day) or metformin (500 mg/day to 2000 mg/day). Patients on pre-existing monotherapy will be randomly assigned to the addition of rosiglitazone (4 mg/day to 8 mg/day), or to either metformin (500 mg/day to 2000 mg/day) or glyburide (5 mg/day to 20 mg/day) (depending on background treatment). The primary end point of the study is the change in adiponectin level (from baseline to 12 weeks) in the rosiglitazone versus metformin or sulfonylurea arms. Secondary end points include changes in leptin, high-sensitivity C-reactive protein, interleukin-6, tumour necrosis factor-alpha, matrix metalloproteinase-9, vascular cell adhesion molecule-1, plasminogen activator inhibitor type 1, insulin sensitivity, glycosylated hemoglobin and lipid levels. Additionally, all patients will be required to be treated with an inhibitor of the renin-angiotensin system, namely an angiotensin receptor antagonist, as per national diabetes treatment guidelines, to a target systolic blood pressure of less than 130 mmHg and a diastolic blood pressure of less than 80 mmHg, or for the optimal suppression of microalbuminuria.

The many faces of PPARgamma: anti-inflammatory by any means?

The peroxisome proliferator-activated receptor gamma (PPARgamma) is a member of the nuclear receptor superfamily, a group of transcription factors that regulate expression of their target genes upon ligand binding. As endogenous ligands, oxidized fatty acids and prostanoids can bind to and activate the receptor. Natural and synthetic PPARgamma activators have been studied extensively in many inflammatory settings and in most instances they have been shown to be anti-inflammatory. In this review we give an overview of the different molecular mechanisms how PPARgamma and its agonists exert their anti-inflammatory effects both at the cellular level and the level of the organism. The action of PPARgamma in acute and chronic inflammatory diseases and disease models will be presented.

Effects of rosiglitazone on the proliferation of vascular smooth muscle cell induced by high glucose

AIM

To investigate the effects of the sensitizer rosiglitazone on the proliferation of vascular smooth muscle cell (VSMC) induced by high glucose administration.

METHODS

VSMCs were isolated from rat thoracic aortas and cultured in 10% fetal bovine serum (FBS). VSMC proliferation was evaluated by methylthiazolyldiphenyl-tetrazolium bromide (MTT) assay and cell counting. The cell cycle was examined by flow cytometry. The protein expressions of proliferating cell nuclear antigen (PCNA) and matrix metalloproteinases-2 (MMP-2) were evaluated by Western blotting. MMP-2 mRNA expression was analyzed by reverse transcription-polymerase chain reaction (RT-PCR) and gelatinolytic activity was determined by zymography.

RESULTS

Promoted VSMC proliferation significantly increased the number of VSMCs in the S phase, the expressions of PCNA and MMP-2, and MMP-2 activity, as well as decreased the proportion of VSMCs in the G(0)/G(1) phase. Rosiglitazone at a concentration of 10 mumol/L markedly inhibited glucose-induced VSMC proliferation (1.869 +/- 0.22 vs 0.820 +/- 0.15, P < 0.01). Concomitantly, rosiglitazone inhibited PCNA expression (0.96 +/- 0.07 vs 0.75 +/- 0.06, P < 0.05) and cell cycle progression from G(0)/G(1) to S phase (the proportion of VSMCs in the G(0)/G(1) and S phase were 69.6 +/- 3.96% vs 84.3 +/- 1.73% and 25.2 +/- 1.73% vs 10.1 +/- 1.42% (P < 0.01), respectively). Furthermore, rosiglitazone significantly decreased MMP-2 mRNA expression (0.98 +/- 0.08 vs 0.71 +/- 0.05, P < 0.05), protein expression (0.80 +/- 0.04 vs 0.64 +/- 0.03, P < 0.05) and MMP-2 activity (320 +/- 25% vs 248 +/- 21%, P < 0.05).

CONCLUSION

Rosiglitazone significantly inhibited VSMC proliferation, at least in part by inhibiting high glucose-induced G(1)-->S phase transition, PCNA expression and MMP-2 synthesis.

Effects of rosiglitazone on contralateral iliac artery after vascular injury in hypercholesterolemic rabbits

Background

The objective was to evaluate the effects of rosiglitazone on iliac arteries of hypercholesterolemic rabbits undergoing balloon catheter injury in the contralateral iliac arteries.

Methods

White male rabbits were fed a hypercholesterolemic diet for 6 weeks and divided into two groups as follows: rosiglitazone group, 14 rabbits treated with rosiglitazone (3 mg/Kg body weight/day) during 6 weeks; and control group, 18 rabbits without rosiglitazone treatment. All animals underwent balloon catheter injury of the right iliac artery on the fourteenth day of the experiment.

Results

There was no significant difference in intima/media layer area ratio between the control group and the rosiglitazone group. Rosiglitazone did not reduce the probability of lesions types I, II, or III (72.73% vs. 92.31%; p = 0.30) and types IV or V (27.27% vs. 7.69%; p = 0.30). There were no differences in the extent of collagen type I and III deposition or in the percentage of animals with macrophages in the intima layer. The percentage of rabbits with smooth muscle cells in the intima layer was higher in rosiglitazone group (p = 0.011).

Conclusion

These findings demonstrate that rosiglitazone given for 6 weeks did not prevent atherogenesis at a vessel distant from the injury site.

Therapeutic Potential of PPARγ Activation in Stroke

Stroke (focal cerebral ischemia) is a leading cause of death and disability among adult population. Many pathological events including inflammation and oxidative stress during the acute period contributes to the secondary neuronal death leading the neurological dysfunction after stroke. Transcriptional regulation of genes that promote these pathophysiological mechanisms can be an effective strategy to minimize the poststroke neuronal death. Peroxisome proliferator-activated receptors (PPARs) are ligand-activated transcription factors known to be upstream to many inflammatory and antioxidant genes. The goal of this review is to discuss the therapeutic potential and putative mechanisms of neuroprotection following PPAR activation after stroke.

Thiazolidinedione insulin sensitizers and the heart: a tale of two organs?

Thiazolidinediones (TZDs) are relatively new agents for the treatment of type 2 diabetes. They act as agonists at the PPAR-gamma nuclear receptor and their therapeutic effects include decreased insulin resistance and hyperglycaemia, an improved plasma lipid, inflammation and pro-coagulant profile, and amelioration of hypertension, microalbuminuria and hepatic steatosis. The most common side effects of TZDs include weight gain and oedema, with occasional reports of congestive heart failure (CHF). This review discusses the benefit-risk profile of TZDs in treating patients with type 2 diabetes, with particular reference to the heart. To provide context, we explore briefly the epidemiology and pathophysiology of heart failure in patients with type 2 diabetes, touch on the association of heart disease and cardiovascular mortality with antihyperglycaemic treatment modalities other than TZDs, and then focus on the effects of TZDs on the heart, cardiovascular risk factors and outcomes. We describe the cluster of host factors, which seems to predispose patients with type 2 diabetes to TZD-induced or TZD-exacerbated oedema and CHF and then provide an overview of the putative mechanisms of these TZD-related side effects. We also propose that certain diuretics (amiloride and spironolactone), by targeting the distal nephron that expresses PPARgamma in collecting duct cells, might be of benefit in ameliorating the fluid retention and oedema associated with TZDs.

Pleiotrophic and anti-inflammatory effects of pioglitazone precede the metabolic activity in type 2 diabetic patients with coronary artery disease

We investigated MMP-9 levels and inflammatory markers during pioglitazone treatment in type 2 diabetic patients with cardiovascular disease. In this randomized multicenter, double blinded, placebo controlled study, 92 type 2 diabetic patients with angiographically proven CHD were randomly assigned to pioglitazone or placebo treatment. At baseline and during a 28 days observational period MMP-9, MCP1, hsCRP, IL-6, sCD40, and P-selectin were monitored. During Pioglitazone treatment, a 12% reduction in MMP-9 and a 18% reduction in hsCRP levels (p<0.05, respectively) could be observed already after 3 days. MCP-1 levels were reduced by 14% after 10 days of treatment (p<0.0001). At the end of the study, these parameters were significantly lower in the pioglitazone group as compared to the placebo group (MMP-9: 392+/-286 versus 427+/-166 ng/ml; hsCRP: 1.9+/-1.7 versus 3.1+/-2.3 ng/L; MCP-1: 413+/-115 versus 471+/-146 pg/ml; p<0.05, respectively). sCD40 levels decreased by 32.5% (p<0.05) and P-selectin decreased by 3.2% (p=0.053) in the pioglitazone group. No change could be found with regard to the other study endpoints. No changes in these parameters could be observed during placebo treatment. Even before effects on glucose metabolism could be obtained, pioglitazone exerts immediate effects on plasma markers of plaque vulnerability and inflammation.

Differential effect of atorvastatin and fenofibrate on plasma oxidized low-density lipoprotein, inflammation markers, and cell adhesion molecules in patients with type 2 diabetes mellitus

Type 2 diabetes mellitus is associated with elevated plasma triglyceride levels, low high-density lipoprotein cholesterol, and a high incidence of cardiovascular disease. Hydroxymethylglutaryl-coenzyme A reductase inhibitors and fibrates are frequently used in the treatment of diabetic dyslipidemia, but their specific impact on the inflammation processes involved in atherosclerosis remains to be fully characterized. The objective of this 2-group parallel study was to investigate the differential effects of a 6-week treatment with either atorvastatin 20 mg/d alone (n = 19) or micronized fenofibrate 200 mg/d alone (n = 19) on inflammation, cell adhesion, and oxidation markers in type 2 diabetes mellitus subjects with marked hypertriglyceridemia. In addition to the expected changes in lipid levels, atorvastatin decreased plasma levels of C-reactive protein (-26.9%, P = .004), soluble intercellular adhesion molecule 1 (-5.4%, P = .03), soluble vascular cell adhesion molecule 1 (-4.4%, P = .008), sE-selectin (-5.7%, P = .02), matrix metalloproteinase 9 (-39.6%, P = .04), secretory phospholipase A(2) (sPLA(2)) (-14.8%, P = .04), and oxidized low-density lipoprotein (-38.4%, P < .0001). On the other hand, fenofibrate had no significant effect on C-reactive protein levels and was associated with reduced plasma levels of sE-selectin only (-6.0%, P = .04) and increased plasma levels of sPLA(2) (+22.5%, P = .004). These results suggest that atorvastatin was potent to reduce inflammation, oxidation, and monocyte adhesion in type 2 diabetes mellitus subjects with marked hypertriglyceridemia, whereas fenofibrate decreased sE-selectin levels only and was associated with an elevation of sPLA(2) levels.

Beneficial effects of rosiglitazone on novel cardiovascular risk factors in patients with Type 2 diabetes mellitus

AIM

Impaired exercise capacity, adiponectin, MMPs and TIMPs have all been implicated in the development of cardiovascular disease. The aim of our study was to determine the effects of rosiglitazone on these factors in diabetic patients.

METHODS

Seventy individuals with Type 2 diabetes were assigned randomly to either a rosiglitazone group (8 mg/day, RG) or a control group (CG) for 6 months. All participants took gliclazide 160 mg plus metformin 1700 mg in stable dose. None of the individuals had diabetic complications or had previously participated in an exercise programme. Anthropometric parameters, VO2 peak, oxygen pulse, glycaemic indices, lipid profile, adiponectin, insulin resistance, blood pressure and serum MMP-9, TIMP-1, TIMP-2 levels were assessed at baseline and at the end of the study. After Bonferroni adjustment, a P-value < 0.017 was assumed to be statistically significant.

RESULTS

Rosiglitazone treatment significantly increased VO2 peak (P < 0.0001), the duration of the exercise test (P < 0.0001), oxygen pulse (P = 0.010) and TIMP-2 levels (P = 0.008) in comparison with CG. Insulin resistance, hyperglycaemia, diastolic blood pressure and MMP-9 levels were also reduced (P < 0.017). Fat mass, lipid profile, TIMP-1 levels and MMP9 : TIMP-1 ratio were unaltered after rosiglitazone treatment. There were no significant changes in these parameters in control subjects. In univariate analysis, the rosiglitazone-induced increment of VO2 peak was associated with alterations in plasma adiponectin (r = 0.691), HOMA-IR (r = -0.782) and HbA(1c) (r = -0.676) (P < 0.017). These relationships retained significance after multiple regression analysis (P = 0.005).

CONCLUSIONS

Rosiglitazone treatment increases cardiorespiratory fitness and modulates favourably serum adiponectin, MMP-9 and TIMP-2 levels. Whether these effects produce cardiovascular benefits in the long term requires further investigation.

PPAR Agonists and Cardiovascular Disease in Diabetes

Peroxisome proliferators activated receptors (PPARs) are ligand-activated nuclear transcription factors that play important roles in lipid and glucose homeostasis. To the extent that PPAR agonists improve diabetic dyslipidaemia and insulin resistance, these agents have been considered to reduce cardiovascular risk. However, data from murine models suggests that PPAR agonists also have independent anti-atherosclerotic actions, including the suppression of vascular inflammation, oxidative stress, and activation of the renin angiotensin system. Many of these potentially anti-atherosclerotic effects are thought to be mediated by transrepression of nuclear factor-kB, STAT, and activator protein-1 dependent pathways. In recent clinical trials, PPARalpha agonists have been shown to be effective in the primary prevention of cardiovascular events, while their cardiovascular benefit in patients with established cardiovascular disease remains equivocal. However, the use of PPARgamma agonists, and more recently dual PPARalpha/gamma coagonists, has been associated with an excess in cardiovascular events, possibly reflecting unrecognised fluid retention with potent agonists of the PPARgamma receptor. Newer pan agonists, which retain their anti-atherosclerotic activity without weight gain, may provide one solution to this problem. However, the complex biologic effects of the PPARs may mean that only vascular targeted agents or pure transrepressors will realise the goal of preventing atherosclerotic vascular disease.

Mechanisms of anti-inflammatory and neuroprotective actions of PPAR-gamma agonists

Peroxisome proliferator-activated receptors (PPARs) are ligand-activated transcription factors of the nuclear hormone receptor superfamily. The 3 PPAR isoforms (alpha, delta/beta and gamma) are known to control many physiological functions including glucose absorption, lipid balance, and cell growth and differentiation. Of interest, PPAR-gamma activation was recently shown to mitigate the inflammation associated with chronic and acute neurological insults. Particular attention was paid to test the therapeutic potential of PPAR agonists in acute conditions like stroke, spinal cord injury (SCI) and traumatic brain injury (TBI), in which massive inflammation plays a detrimental role. While 15d-prostaglandin J2 (15d PGJ2) is the natural ligand of PPAR-gamma, the thiazolidinediones (TZDs) are potent exogenous agonists. Due to their insulin-sensitizing properties, 2 TZDs rosiglitazone and pioglitazone are currently FDA-approved for type-2 diabetes treatment. Recent studies from our laboratory and other groups have shown that TZDs induce significant neuroprotection in animal models of focal ischemia and SCI by multiple mechanisms. The beneficial actions of TZDs were observed to be both PPAR-gamma-dependent as well as -independent. The major mechanism of TZD-induced neuroprotection seems to be prevention of microglial activation and inflammatory cytokine and chemokine expression. TZDs were also shown to prevent the activation of pro-inflammatory transcription factors at the same time promoting the anti-oxidant mechanisms in the injured CNS. This review article discusses the multiple mechanisms of TZD-induced neuroprotection in various animal models of CNS injury with an emphasis on stroke.

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

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

Insulin facilitates monocyte migration: a possible link to tissue inflammation in insulin-resistance

Mononuclear cells (MNCs) are the primary cell type involved in the pro-inflammatory state of obesity-linked insulin-resistance, and atherosclerosis. Increased serum levels of MMP-9 are reported in insulin-resistant type 2 diabetic patients. Here we demonstrate insulin facilitating human monocytic THP-1 cell chemotaxis via prolonged Erk1/2-dependent induction of MMP-9. In vivo, significantly increased serum levels of MMP-9 were found in obesity-induced hyperinsulinemic C57BL/J6 mice, which were diminished by treatment with the anti-diabetic PPARgamma-ligand pioglitazone. In line with this, pioglitazone inhibited Erk1/2-phosphorylation and subsequent insulin-dependent MMP-9 synthesis in THP-1 cells. Thus, insulin increases MMP-9 gelatinolytic activity in monocytic cells, which results in accelerated chemotaxis. Hyperinsulinemia is associated with enhanced MMP-9 serum levels, potentially facilitating monocyte migration to and infiltration of adipose tissue and the arterial wall, thereby contributing to the increased cardiovascular risk in obese, hyperinsulinemic patients.

Measuring biomarkers to assess the therapeutic effects of PPAR agonists?

The metabolic syndrome is defined as a clustering of cardiovascular risk factors with insulin resistance, including dyslipidemia, coagulation disturbances and hypertension. Activators of the peroxisome proliferator-activated receptors (PPARs) modulate several of the metabolic risk factors predisposing to atherosclerosis. Fibrates are hypolipidemic drugs acting through activation of PPARα, whereas glitazones are insulin sensitizers activating PPARγ. In addition, these drugs exert pleiotropic anti-inflammatory actions. In this review, we will focus on the effects of fibrates and glitazones on biomarker modulation and their usefulness in the treatment of cardiovascular disease.

Coronary heart disease outcomes in patients receiving antidiabetic agents

BACKGROUND

There is conflicting evidence on the reduction of cardiovascular risk in diabetic patients treated with oral antidiabetic agents.

OBJECTIVES

To compare the risk of myocardial infarction (MI) and coronary revascularization (CR) in type 2 diabetic patients treated with rosiglitazone, metformin, or sulfonylurea.

METHODS

Using data from a large US insurer, we created propensity-matched cohorts. We identified hospitalizations for MI or CR. We calculated incidence rates and 95% confidence intervals for the outcomes and estimated risks from Cox proportional hazards models.

RESULTS

We identified 26,931 initiators of monotherapy, 4,086 initiators of dual-therapy, and 2,346 initiators of combination with insulin therapy. There was no difference between the risk of the composite outcome with rosiglitazone monotherapy compared to metformin monotherapy (HR 1.07, 95% CI: 0.85, 1.34), and similarly with rosiglitazone monotherapy compared to sulfonylurea monotherapy (HR 0.82, 95% CI: 0.67, 1.02). There was no difference in the risk of outcome with rosiglitazone in combination with insulin therapy compared to other oral antidiabetic agents in combination with insulin (HR 0.88, 95% CI: 0.59, 1.32). Overall, there was little difference in the risk of the composite outcome or of the individual outcomes of MI and CR comparing rosiglitazone therapies to non-rosiglitazone therapies (HR for composite outcome 0.93, 95% CI: 0.80, 1.10).

CONCLUSIONS

The results from the monotherapy and the dual-therapy comparisons, though not individually significant, are consistent in suggesting that the risk of cardiovascular outcome events in patients using rosiglitazone may lie between the risks associated with sulfonylureas (higher incidence) and metformin (lower incidence).

Rosiglitazone reduces glucose-induced oxidative stress mediated by NAD(P)H oxidase via AMPK-dependent mechanism

OBJECTIVE

Hyperglycemia is the main determinant of long-term diabetic complications, mainly through induction of oxidative stress. NAD(P)H oxidase is a major source of glucose-induced oxidative stress. In this study, we tested the hypothesis that rosiglitazone (RSG) is able to quench oxidative stress initiated by high glucose through prevention of NAD(P)H oxidase activation.

METHODS AND RESULTS

Intracellular ROS were measured using the fluoroprobe TEMPO-9-AC in HUVECs exposed to control (5 mmol/L) and moderately high (10 mmol/L) glucose concentrations. NAD(P)H oxidase and AMPK activities were determined by Western blot. We found that 10 mmol/L glucose increased significantly ROS production in comparison with 5 mmol/L glucose, and that this effect was completely abolished by RSG. Interestingly, inhibition of AMPK, but not PPARgamma, prevented this effect of RSG. AMPK phosphorylation by RSG was necessary for its ability to hamper NAD(P)H oxidase activation, which was indispensable for glucose-induced oxidative stress. Downstream of AMPK activation, RSG exerts antioxidative effects by inhibiting PKC.

CONCLUSIONS

This study demonstrates that RSG activates AMPK which, in turn, prevents hyperactivity of NAD(P)H oxidase induced by high glucose, possibly through PKC inhibition. Therefore, RSG protects endothelial cells against glucose-induced oxidative stress with an AMPK-dependent and a PPARgamma-independent mechanism.

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.

Peroxisome proliferator-activated receptor gamma agonist improves arterial stiffness in patients with type 2 diabetes mellitus and coronary artery disease

Arterial stiffness is an independent risk factor for cardiovascular events in diabetic patients, and it can be assessed by measuring pulse wave velocity (PWV). We investigated the degree of arterial stiffness in diabetic patients with coronary artery disease (CAD) and the effect of the proliferator-activated receptor gamma (PPAR-gamma) agonist rosiglitazone on arterial stiffness in the potential mechanism of anti-arteriosclerosis in patients with type 2 diabetes mellitus and CAD. The 123 participants were divided into 3 groups: healthy controls (n = 36), diabetic patients (n = 41), and diabetic patients with CAD (n = 46). Forty-six diabetic patients with CAD were randomly divided into 2 groups: untreated diabetic patients with CAD and diabetic patients with CAD treated with 4 mg/d of rosiglitazone (n = 25) for 12 weeks. Pulse wave velocity was measured before treatment and at 12-week follow-up. Baseline PWV was significantly higher in patients with diabetes, diabetes and CAD, and diabetes and CAD with treatment as compared with the healthy control group (1,633 +/- 37.3, 1,669 +/- 53.8, 1,615 +/- 44.4, and 1,360 +/- 39.9 cm/s, respectively, P < .001). Pulse wave velocity in the rosiglitazone-treated group was significantly reduced, from 1,615 +/- 44.4 to 1,525 +/- 43.1 cm/s, after 12-week treatment, Furthermore, PWV was significantly decreased in the rosiglitazone-treated group compared with untreated group after 12 weeks (1525 +/- 43.1 and 1,670 +/- 41.3 cm/s, respectively). Pulse wave velocity in the untreated group did not differ from baseline levels after 12 weeks. In addition, plasma C-reactive protein level was decreased significantly in the rosiglitazone-treated group compared with values at baseline and for the untreated group after 12 weeks (0.73 +/- 0.09, 1.71 +/- 0.24, and 1.33 +/- 0.29 mg/L, respectively). Plasma level of monocyte chemoattractant protein 1 was decreased in the rosiglitazone group compared with the level at baseline (392 +/- 42 and 273 +/- 40 pg/mL, respectively). Moreover, the decrease in PWV was associated linearly both with improved homeostasis model assessment of insulin resistance and with decreased C-reactive protein level after PPAR-gamma agonist treatment. In conclusion, PPAR-gamma agonist rosiglitazone treatment may significantly decrease arterial stiffness in diabetic patients with CAD. Proliferator-activated receptor gamma agonists may play an important role in protecting against arteriosclerosis by normalizing the metabolic disorders and depressing chronic inflammation of the vascular system in patients with type 2 diabetes mellitus and serious vascular disease.