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J Am Coll Cardiol, 2005; 45:1925-1931, doi:10.1016/j.jacc.2005.03.041 © 2005 by the American College of Cardiology Foundation |
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* IKFEInstitute for Clinical Research and Development, Mainz, Germany
University of Applied Sciences, Rheinbach, Germany
University Hospital, Ulm, Germany
Takeda Pharma GmbH, Aachen, Germany
|| ISFInstitute for Metabolic Research, Frankfurt, Germany
Manuscript received October 12, 2004; revised manuscript received February 14, 2005, accepted March 10, 2005.
* Reprint requests and correspondence: Dr. Andreas Pfützner, Institute for Clinical Research and Development, Parcusstr. 8, D-55116 Mainz, Germany. (Email: AndreasP{at}ikfe.de).
| Abstract |
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BACKGROUND: Type 2 diabetes is associated with increased cardiovascular risk.
METHODS: A total of 192 patients were enrolled into a six-month, prospective, open-label, controlled clinical study. They were randomized to receive either pioglitazone (45 mg) or glimepiride (1 to 6 mg, with the intent to optimize therapy). Biochemical and clinical markers to assess therapeutic effects included HbA1c, fasting glucose, insulin, adiponectin, lipids, high-sensitivity C-reactive protein (hsCRP), intracellular adhesion molecule, vascular cell adhesion molecule, vascular endothelial growth factor, fibrinogen, von Willebrand factor, matrix metalloproteinase (MMP)-9, monocyte chemoattractant protein (MCP)-1, soluble CD40 ligand, and carotid intima-media thickness (IMT).
RESULTS: The study was completed by 173 patients (66 female, 107 male; age [± SD]: 63 ± 8 years; disease duration: 7.2 ± 7.2 years; HbA1c: 7.5 ± 0.9%; pioglitazone arm: 89 patients). A comparable reduction in HbA1c was seen in both groups (p < 0.001). In the pioglitazone group, reductions were observed for glucose (p < 0.001 vs. glimepiride group at end point), insulin (p < 0.001), low-density lipoprotein/high-density lipoprotein ratio (p < 0.001), hsCRP (p < 0.05), MMP-9 (p < 0.05), MCP-1 (p < 0.05), and carotid IMT (p < 0.001), and an increase was seen in high-density lipoprotein (p < 0.001) and adiponectin (p < 0.001). Spearman ranks analysis revealed only one correlation between the reduction in cardiovascular risk parameters and the improvement in the metabolic parameters (MMP-9 and fasting blood glucose, p < 0.05)
CONCLUSIONS: This prospective study gives evidence of an anti-inflammatory and antiatherogenic effect of pioglitazone versus glimepiride. This effect is independent from blood glucose control and may be attributed to peroxisome proliferator-activated receptor gamma activation.
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Recent experimental and clinical data suggest that a novel group of antidiabetic agents, thiazolidinediones (TZDs), like pioglitazone and rosiglitazone, may exhibit anti-inflammatory properties in the vessel wall (14,15). These agents act via the nuclear transcription factor peroxisome proliferator-activated receptor gamma (PPAR
) and, in addition to their metabolic action, have been shown to regulate the expression of various target genes in vascular cells in vitro and in vivo, subsequently limiting inflammatory cell activation and lesion formation during atherogenesis. Furthermore, clinical data suggest that TZDs reduce inflammatory biomarkers of arteriosclerosis, like C-reactive protein or sCD40L, in treated patients, thus potentially modulating their cardiovascular risk (1619). Still, most of these studies were placebo-controlled and, as such, did not allow the dissection of metabolic from nonmetabolic TZDs effects, because TZD treatment, compared to placebo, significantly improved glucose metabolism in all of these studies. Therefore, we performed a six-month prospective, randomized, controlled trial to compare the effect of pioglitazone and sulfonylurea treatment on inflammatory biomarkers of arteriosclerosis, attempting to achieve comparable improvement in blood glucose control in both treatment groups.
| Methods |
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Biochemical parameters. HbA1c was determined by means of high-pressure liquid chromatography (Adams TMA1c, Menarini Diagnostics, Florence, Italy). Therapy response was defined as an absolute decrease in HbA1c from baseline by at least 0.6% (normal reference range: 4.2% to 6.0%). Glucose was assessed using a standard glucose oxidase reference method (Ruhrtal Labortechnik, Mühnesee-Delecke, Germany), and lipids (total cholesterol, low-density lipoprotein [LDL], high-density lipoprotein [HDL], triglycerides) were measured by means of standard dry chemistry methods (OSR, Olympus Diagnostica, Hamburg, Germany). Insulin was measured using a chemiluminescence method (Sciema, Mainz, Germany), PAI-I by ELISA (American Diagnostica, Pfungstadt, Germany), endothelin by ELISA (Biomedica, Vienna, Austria), and adiponectin by radioimmunoassay (Linco, St. Charles, Missouri); ELISAs from R&D Systems (Wiesbaden, Germany) were used for the determination of the following parameters: ICAM, VCAM, vascular endothelial growth factor [VEGF], MMP-9, MCP-1. The sCD40L determinations were also performed by ELISA (Bender Medsystems, Vienna, Austria). Turbimetric methods were used for the following parameters: high-sensitivity C-reactive protein (hsCRP) (Olympus, Hamburg, Germany), fibrinogen (Dade Behring, Schwalbach, Germany), and von-Willebrand factor (Instrumentation Laboratory GmbH, Kirchheim, Germany).
High-sensitive C-reactive protein changes >15 mg/l during the observation period were attributed to other inflammatory processes (flu, cold, and so on) and were eliminated before analysis.
Carotid intima-media thickness (IMT). Carotid IMT was evaluated at all time points by a single operator with high-resolution B-mode ultrasound on a single machine (Caris Plus, Esaote SpA, Genoa, Italy) with a 10-MHz linear array transducer (LA 523). All recordings were performed in a standardized way, and readings were analyzed by a physician blinded to patient profile and treatment assignment as described previously (20,21).
Statistical analysis. The analysis of efficacy is based on the intention-to-treat population, which consists of all patients who were treated and provided assessment of the laboratory parameters at baseline and at end point of the study. All analyses were performed in an exploratory sense with appropriate parametrical and nonparametrical methods. Treatment groups were compared at baseline by using a Wilcoxon rank sum test for continuous variables and chi-square for categorical variables. Changes from baseline were evaluated by using analysis of covariance (ANCOVA) models with treatment groups as factor and baseline values as covariate. The difference between treatment groups was assessed by using t test statistics for the hypothesis that treatment group is a relevant factor in the model. Spearman rank correlation coefficients were calculated to test for the independence of the obtained results. All p values <0.05 were interpreted as statistically significant.
| Results |
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0.6%) and nonresponders (reduction in HbA1c <0.6%) revealed no difference in the overall results (Fig. 2). Spearman correlation analyses between cardiovascular risk parameters and glycemic control parameters resulted in only one correlation (reduction in MMP-9 and reduction in fasting glucose control, p < 0.05) among the multiple possible combinations (Table 4).
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| Discussion |
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activation. This hypothesis is supported by the fact that the observed changes were equally seen in therapy responders and nonresponders. In comparison to glimepiride, pioglitazone treatment led to a significant increase in HDL cholesterol and adiponectin, decrease in fasting glucose and insulin, significant higher reduction of triglycerides, and a significant higher reduction in the LDL/HDL ratio. These pronounced differences between pioglitazone and sulfonylurea treatment have been consistently described by several groups in the literature (2326). As one explanation for these findings, glyceroneogenesis has been recently identified as a target of TZDs in cultured adipocytes and fat tissues of Wistar rats. The activation of glyceroneogenesis by TZDs occurs mainly in visceral fat, the same fat depot that is specifically implicated in the progression of obesity to type 2 diabetes. The main role of this metabolic pathway is to allow the re-esterification of fatty acids via a futile cycle in adipocytes, thus lowering fatty acid release into the plasma (27).
Inflammation plays an important role in arteriosclerosis, and measurement of hsCRP has become a novel but emerging tool for detecting individuals at high risk for plaque rupture. A randomized placebo-controlled study with different doses of rosiglitazone resulted in a decrease of hsCRP by 26.8% (4 mg) and 21.8% (8 mg) as compared to the placebo group after 26 weeks in a Caucasian study population (28). In another recent study performed in Japanese patients, treatment with 45 mg of pioglitazone significantly reduced hsCRP by about 27% after three months of treatment, while no change occurred in the placebo comparator group. Independence from glucose metabolism was suggested by ANCOVA analysis (29). In our study, baseline values were much higher than in the Japanese study. The decrease in hsCRP by 29% during pioglitazone treatment for the first time compares directly to an equally effective antidiabetic comparator treatment that did not induce any hsCRP change.
Substantial evidence supports a causal role for MCP-1 and its receptor, CCR2, in the recruitment of monocytes from the circulation into atherosclerotic lesions. It has been shown that activation of PPAR by synthetic ligands or components of oxidized LDL reduces monocyte CCR2 expression and blocks chemotaxis mediated by MCP-1 (30). In parallel, activation of PPAR
by pioglitazone may be responsible for the observed effects in our study. While no human data has been published yet about the influence of pioglitazone on plasma MCP-1 levels, recent animal experiments have indicated and demonstrated the prevention of coronary arteriosclerosis by additional MCP-1-related anti-inflammatory effects (down-regulation of CCR2 in circulating and lesional monocytes) (16,31). In a small study without an active comparator, six weeks of treatment with 4 mg of rosiglitazone resulted in a significant improvement of plasma MCP-1 in diabetic and nondiabetic subjects (17).
While no data have been published about the influence of pioglitazone on plasma MMP-9 yet, two clinical reports describe the treatment effects of rosiglitazone on this marker. In both cases, however, the studies were only placebo-controlled, and significant differences between the treatment and comparator groups in long-term blood glucose control and HbA1c were the consequence of this design. In one study, MMP-9 decreased in a dose-dependent manner by 12.4% (4 mg dose) and 23.4% (8 mg dose) during 26 weeks of therapy as compared to placebo (28). In the other trial, 4 mg of rosiglitazone twice daily led to a significant reduction in MMP-9 by 24.1% (compared to baseline) after 12 weeks (18). In the presented study, however, the 14.5% decrease in MMP-9 under pioglitazone compares to an increase by 2.8% with a glimepiride treatment that results in the same HbA1c improvement.
No significant changes for sCD40L have been detected in our study. Reduction of this risk marker has been independently reported after treatment with rosiglitazone and troglitazone. A reduction of sCD40 by 18.4% after six weeks of treatment with rosiglitazone (4 mg twice a day) in comparison to placebo was reported by Marx et al. (19), and a mean reduction by 29% in a heterogeneous diabetic population was reported after troglitazone treatment for 12 weeks (12). However, in both study groups, the baseline values of sCD40L were about twice as high as in our study population, which may explain our inability to observe any significant differences with regard to this parameter.
No influence of pioglitazone could also be observed on PAI-1 levels. Some authors describe reduction of PAI-1 expression by TZDs (32,33), but others found no effect on PAI-1 expression at all (34). All these observations, however, have been made in vitro. Osman et al. (35) measured PAI-1 in type 2 patients with restenosis treated with rosiglitazone and could not find any changes in their study population (35).
The major clinical finding of this study is a significant reduction of carotid IMT, a strong and well described clinical predictor of cardiovascular risk and stroke (36,37), exclusively in the pioglitazone-treated study population. This finding and the parallel reduction in several biochemical risk markers including hsCRP, MCP-1, MMP-9, and the increase in adiponectin strongly suggest substantial antiarteriosclerotic actions of pioglitazone in vivo independent from metabolic control. While anti-inflammatory and antiarteriosclerotic effects of pioglitazone have been suggested after analysis of animal experiments (31), this is a first comprehensive clinical investigation of these effects in humans.
The answer to the question, whether the surrogate findings described in this study report can be translated into substantial clinical outcome improvements, is currently under investigation in the Prospective Pioglitazone Clinical Trial in Macrovascular Events (PROactive) study with 5,238 patients with type 2 diabetes. The cohort of patients enrolled in PROactive is a typical type 2 diabetic population at high risk of further macrovascular events. The primary end point is the time from randomization to occurrence of a new macrovascular event or death (38).
In conclusion, the presented study gives evidence of an anti-inflammatory and potential antiatherogenic effect of pioglitazone that is indicated by improvements in several traditional and nontraditional cardiovascular risk markers and carotid IMT, independent of an improvement in long-term glycemic control.
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