Rosiglitazone produces a greater reduction in circulating platelet activity compared with gliclazide in patients with type 2 diabetes mellitus—An effect probably mediated by direct platelet PPARγ activation

Atherosclerosis 197 (2008) 718–724

Rosiglitazone produces a greater reduction in circulating platelet activity compared with gliclazide in patients with type 2 diabetes mellitus—An effect probably mediated by direct platelet PPAR␥ activation M.P. Khanolkar a,∗ , R.H.K. Morris b , A.W. Thomas b , H. Bolusani a , A.W. Roberts a , J. Geen c , S.K. Jackson d , L.M. Evans a a

Llandough Hospital Diabetes Center, Department of Diabetes, Penarth, Cardiff, UK University of Wales Institute Cardiff, School of Applied Sciences, Llandaff, Cardiff, UK c Prince Charles Hospital, Department of Biochemistry, Gurnos, Merthyr Tydfil, UK University Hospital of Wales Diabetes Center, Department of Metabolic Medicine, Heath, Cardiff, UK b

d

Received 6 February 2007; received in revised form 26 June 2007; accepted 11 July 2007 Available online 31 August 2007

Abstract Aims: Type 2 diabetes mellitus (T2DM) is associated with enhanced platelet activation. We conducted a randomised double-blind study to compare the effects of combination metformin and rosiglitazone or metformin and gliclazide therapy on platelet function in persons with T2DM. Methods: Fifty subjects on metformin monotherapy received either rosiglitazone 4 mg or gliclazide 80 mg. HbA1c, HOMA-R, markers of platelet activation, inflammation, endothelial activation and oxidative stress were measured at baseline and after 24 weeks of treatment. Separate in vitro platelet function studies were conducted on platelets pre-incubated with rosiglitazone and gliclazide. Results: A significantly greater reduction in platelet aggregation was observed in the rosiglitazone treated group compared to gliclazide. HbA1c and markers of endothelial activation were reduced to a similar extent in both groups. A significant reduction in HOMA-R, markers of inflammation and oxidative stress was only observed with rosiglitazone. Reduction in platelet aggregation with rosiglitazone correlated with reduction in oxidative stress. In the in vitro study, rosiglitazone produced significantly greater reduction in platelet aggregation compared with gliclazide. Conclusion: Greater reduction in platelet activity observed with rosiglitazone may be related to reduced oxidative stress and a possible direct PPAR␥ mediated effect on platelet function. © 2007 Elsevier Ireland Ltd. All rights reserved. Keywords: Type 2 diabetes mellitus; Rosiglitazone; Platelets

1. Introduction Type 2 diabetes mellitus (T2DM) is considered as a cardiovascular risk equivalent [1]. Platelet dysfunction, among other mechanisms, contributes to the increased risk of ∗ Corresponding author at: Llandough Diabetes Centre, Llandough Hospital, Penarth, Cardiff, CF64 2XX, UK. Tel.: +44 2920716871; fax: +44 2920716495. E-mail address: [email protected] (M.P. Khanolkar).

0021-9150/$ – see front matter © 2007 Elsevier Ireland Ltd. All rights reserved. doi:10.1016/j.atherosclerosis.2007.07.020

atherothrombosis in patients with T2DM [2]. This altered platelet function is revealed by hypersensitivity to aggregants in in vitro studies and reduced sensitivity to the effects of anti-platelet agents such as aspirin and clopidogrel [3]. Insulin resistance (IR) is an important metabolic abnormality in T2DM, being recognised as an independent cardiovascular risk factor [4] and is also a determinant of platelet dysfunction [5]. Treatment of IR, thus, represents an important strategy in reducing cardiovascular risk. In this context, metformin, a mild insulin sensitising oral hypo-

M.P. Khanolkar et al. / Atherosclerosis 197 (2008) 718–724

glycaemic agent, with additional putative fibrinolytic and vascular effects [6], has demonstrated significant benefits on cardiovascular outcomes in overweight T2DM patients [7]. Consequently, metformin is now accepted as first line oral hypoglycaemic agent in the treatment of T2DM. Other insulin sensitizers licensed for use in T2DM include the thiazolidinedione (TZD) group of drugs such as rosiglitazone and pioglitazone. Their insulin sensitising effects are mediated by peroxisome proliferator activated receptor gamma (PPAR␥), a member of the ligand-activated nuclear receptor superfamily that enhances insulin sensitivity by controlling the expression of genes involved in glucose and lipid metabolism [8]. Independent of their hypoglycaemic action, treatment with TZDs is associated with significant improvements in surrogate markers of cardiovascular disease, including lipid profile, blood pressure and markers of inflammation and oxidative stress [9,10]. Furthermore, results from the PROACTIVE study have demonstrated the cardiovascular outcome benefits of TZD based therapy, using pioglitazone in high risk patients with T2DM [11]. Recent studies have demonstrated the presence of functional PPAR␥ receptors in platelets and although the precise role of PPAR␥ in platelets remains speculative, activation of platelet PPAR␥, via non-genomic effects, may attenuate platelet function [12]. This concept is supported by clinical data demonstrating that rosiglitazone reduces platelet activation in non-diabetic patients with coronary artery disease, independent of any metabolic effects [13]. Furthermore, rosiglitazone therapy is associated with significant reduction in post-coronary stent restenosis rates in patients with T2DM, an effect which may be partly mediated through attenuated platelet activation [14,15]. Since previous studies have demonstrated potential antiplatelet properties associated with gliclazide therapy [16], the aim of this study was to compare the effects of gliclazide and rosiglitazone on platelet function, both in vitro and in vivo in the setting of combination therapy with metformin.

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Table 1 Baseline characteristics; data is presented with 95% confidence intervals Rosiglitazone No. Age (years) Body mass index (kg/m2 ) Waist/hip ratio Mean blood pressure (mm Hg) HbA1c (%) HOMA-R Total cholesterol (mmol/l) LDL cholesterol (mmol/l) HDL cholesterol (mmol/l) Total cholesterol/HDL ratio Triglycerides (mmol/l) hs-CRP (mg/l) Platelet count (109 /l)

25 (14 male) 59 (40–71) 34.55 (31.23, 38.15) 0.92 (0.89, 0.94) 96.7 (93, 99.2) 7.33 (7.13, 7.54) 2.25 (1.64, 2.87) 4.96 (4.69, 5.22) 2.78 (2.58, 2.97) 1.09 (0.99, 1.18) 4.55 (4.37, 4.72) 1.80 (1.42, 2.18) 0.77 (0.49, 1.04) 286 (247, 324)

Gliclazidea 25 (15 male) 56 (36–67) 33.66 (30.53, 36.94) 0.89 (0.85, 0.92) 93.4 (90, 96.7) 7.08 (6.81, 7.35) 2.24 (1.17, 3.10) 5.17 (4.74, 5.57) 3.01 (2.81, 3.20) 1.05 (0.97, 1.12) 4.97 (4.68, 5.15) 2.35 (1.97, 2.63) 0.66 (0.50, 0.81) 254 (221, 286)

a Denotes no significant differences between the rosiglitazone and gliclazide treated groups at baseline.

At the time of patient recruitment for the study, routine use of aspirin for primary prevention in all subjects with T2DM was not essential. The study was fully approved by the regional ethics committee with all patients giving fully informed written consent before commencing the study. 2.1.2. Study design Consented patients taking less than 2 g/day metformin entered a metformin ‘titration’ period of up to 4 weeks. When the maximum tolerated dose of metformin was reached (up to 2 g/day), patients entered a further 4-week ‘run in’ period before being randomised to receive the study medication. Patients already taking metformin 2 g/day with capillary fasting blood glucose > 7 mmol/l entered the 4-week ‘run in’ period, continuing to take the same dose of metformin before being randomised to receive the study medication. Patients were randomised to receive either rosiglitazone 4 mg once daily or gliclazide 80 mg once daily for duration of at least 24 weeks.

2. Methods 2.1. Clinical study 2.1.1. Study patients A total of 50 persons with T2DM, with sub-optimal glycaemic control (HbA1c > 6.5%) on metformin monotherapy were recruited (Table 1). Smokers, patients with a history of overt cardiovascular disease or cardiac failure, patients with microalbuminuria, patients on anti-platelet medications (aspirin/clopidogrel/dipyridamole) or non-steroidal anti-inflammatory drugs, patients with significantly abnormal liver function tests (baseline alanine transaminase > two times the upper limit of normal) and female patients of child bearing age likely to get pregnant during or within 3 months after completion of the study were excluded.

2.1.3. Anthropometric measurements and blood sampling All patients in the study had their height, weight, waist and hip circumference measured at randomisation and on completion of the study to allow calculation of body mass index (BMI) and waist/hip ratio. Fasting morning blood samples were collected for measurement of glucose, insulin, HOMA-R, lipid profile, HbA1c, liver function tests, urea, creatinine, electrolytes, full blood count, high sensitivity c reactive protein (hs-CRP), soluble adhesion molecules (sE-selectin and sICAM-1) and markers of oxidative stress and platelet activation at baseline and at 24 weeks. All parameters were measured following a 12-h overnight fast.

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2.1.4. Soluble adhesion molecules Soluble E-selectin (sE-selectin) and soluble intercellular adhesion molecule-1 (sICAM-1) in serum were quantified using standard ELISA kits (R&D systems, USA).

incubated with rosiglitazone (2 ␮M) and gliclazide (2 ␮M) for 30 min was also studied.

2.1.5. Markers of oxidative stress Thiobarbituric acid reactive substances (TBARS) in serum were quantified as nmol/ml by a fluorimetric method [17].

SPSS software version 10 was used to perform statistical analysis. Data is presented as mean with 95% confidence intervals, except for triglycerides, which is presented as median with 95% confidence intervals. Comparisons within groups before and after intervention, involved using a paired-t-test or Wilcoxon’s test for non-parametric data. Multi-regression analysis was used to identify any significant associations between change in platelet activity and metabolic parameters. All correlations are reported as Pearson’s correlation coefficients.

2.1.6. Measures of platelet function The Chronolog platelet aggregometer (Chronolog, Coulter-Beckman, UK) was used to quantify ADP (0.2 ␮M) induced platelet aggregation. Whole blood collected in citrated vacutainer tube (Beckton Dickinson, Oxford, UK) was used for the study. Blood (0.5 ml) was diluted 1:1 with phosphate buffer saline and the studies were performed in triplicates within an hour of collection. Soluble CD40 ligand (sCD40L) in serum was measured using a standard ELISA method (R&D Systems). The effects of preincubating platelet rich plasma (PRP) with the nitric oxide (NO) donor, sodium nitroprusside (SNP) at 0, 10, 20, 50 and 100 ␮M or the NO synthase inhibitor, N (G)-monomethyl-larginine (LNMMA) at 10 ␮M on ADP induced aggregation in PRP derived from the study group subjects was also studied. 2.2. In vitro studies In order to evaluate the direct effects of gliclazide or rosiglitazone on platelet function, whole blood and PRP from healthy volunteers (n = 14) was pre-incubated with rosiglitazone (2 and 10 ␮M) and gliclazide (2 and 10 ␮M) for 30 min before quantifying ADP induced aggregation. The effect of the nitric oxide donor, SNP at varying concentrations (0, 10, 20, 50 and 100 ␮M) and of the nitric oxide synthase inhibitor, LNMMA at 10 ␮M on ADP induced aggregation in PRP, pre-

2.3. Data analysis

3. Results 3.1. Clinical study All the 50 patients enrolled, successfully completed the study. None of the patients reported any adverse effects. There were no significant differences in baseline characteristics in both the treatment groups (Table 1). In the entire study group, baseline platelet activation as measured by platelet aggregation correlated with the degree of insulin resistance (HOMA-R) (r = 0.39; p < 0.05). Following treatment, rosiglitazone produced a significantly greater reduction in ADP induced platelet aggregation and sCD40L in comparison with gliclazide (p < 0.05) (Table 2). Glycaemic control (HbA1c) improved to a similar extent in both groups, while insulin sensitivity improved in the rosiglitazone group (p < 0.05) (Table 2). No significant changes in lipid profile were observed in either group. While hs-CRP fell in the rosiglitazone group (p < 0.05), no significant change was observed in the gliclazide group

Table 2 Effect of treatment on baseline parameters; data is presented with 95% confidence intervals Rosiglitazone, baseline BMI (kg/m2 ) HOMA-R Mean BP (mm Hg) T cholesterol (mmol/l) LDL-C (mmol/l) HDL-C (mmol/l) Total cholesterol/HDL ratio Triglycerides (mmol/l) Platelet aggregation () sCD40L (ng/ml) sE-selectin (␮g/l) sICAM-1 (␮g/l) TBARS (nmoles/ml) HbA1c (%) hs-CRP (mg/l) a b

34.55 (31.23, 38.15) 2.25 (1.64, 2.87) 96.7 (93, 99.2) 4.96 (4.69, 5.22) 2.78 (2.58, 2.97) 1.09 (0.99, 1.18) 4.55 (4.37, 4.72) 1.80 (1.42, 2.18) 15.07 (13.03, 17.11) 23.43 (21.02, 25.83) 63.8 (55.9, 71.6) 382 (360, 403) 0.98 (0.79, 1.17) 7.33 (7.13, 7.54) 0.77 (0.49, 1.04)

Rosiglitazone, 24 weeks 34.90 (31.42, 38.30) 1.19 (0.91, 1.46)a,b 94.6 (90.3, 98.2) 5.12 (4.77, 5.48) 2.81 (2.54, 3.07) 1.17 (1.06, 1.27) 4.31 (4.16, 4.45) 2.04 (1.74, 2.34) 10.56 (9.42, 11.68)a,b 12.72 (11.10, 14.32)a,b 47.5 (41.6, 53.3) 347 (328, 365) 0.71 (0.56, 0.87)a,b 6.14 (5.91, 6.36)a 0.49 (0.29, 0.66)a,b

Denotes p < 0.05 post-treatment compared with baseline. Denotes p < 0.05 for rosiglitazone therapy compared with gliclazide.

Gliclazide, baseline

Gliclazide, 24 weeks

33.66 (30.53, 36.94) 2.24 (1.17, 3.10) 93.4 (90, 96.7) 5.17 (4.74, 5.57) 3.01 (2.81, 3.20) 1.05 (0.97, 1.12) 4.97 (4.68, 5.15) 2.35 (1.97, 2.63) 14.44 (12.48, 16.40) 21.16 (18.82, 23.49) 60.7 (53.4, 67.9) 398 (378, 417) 0.97 (0.82, 1.11) 7.08 (6.81, 7.35) 0.66 (0.50, 0.81)

33.61 (30.49, 36.65) 1.79 (1.10, 2.47) 94.7 (91.2, 98.1) 5.03 (4.62, 5.50) 2.99 (2.72, 3.26) 1.09 (0.99, 1.18) 4.61 (4.39, 4.83) 1.9 (1.45, 2.35) 12.85 (11.76, 13.93) 17.93 (16.06, 19.79) 54.2 (49.6, 61.7) 366 (345, 386) 0.88 (0.66, 1.09) 6.08 (5.82, 6.33)a 0.58 (0.37, 0.73)

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Fig. 1. Effect of metformin and rosiglitazone or gliclazide combination therapy for 24 weeks on platelet aggregation. PRP from patients who had received combination therapy were incubated with SNP (10 ␮M) and platelet aggregation induced with ADP. Superscript ‘a’ denotes p < 0.05 posttreatment compared to baseline and superscript ‘b’ denotes p < 0.05 with SNP treatment.

(Table 2). A significantly greater reduction in TBARS was observed in the rosiglitazone treated group in comparison to the gliclazide treated group (p < 0.05) (Table 2). Markers of endothelial activation as determined by sE-selectin and sICAM-1 were reduced to a similar extent in both groups (Table 2). Multi-regression analysis demonstrated that the reduction in platelet activation with rosiglitazone at 24 weeks, correlated with the reduction in oxidative stress (TBARS) (r = 0.32; p < 0.05). No significant correlations were observed with any of the other measured parameters investigated. In the gliclazide treated group, the reduction in platelet activation correlated with the reduction in HbA1c (r = 0.29; p < 0.05). In PRP derived from the study subjects, rosiglitazone therapy resulted in greater reduction in ADP induced aggregation compared to gliclazide therapy. This effect of rosiglitazone therapy on platelet aggregation was significantly augmented (p < 0.05) by preincubation of PRP with the NO donor, SNP (10 ␮M). However, no significant augmentation by SNP was observed in PRP derived from subjects receiving gliclazide (Fig. 1).

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Fig. 2. Effect of the nitric oxide donor, SNP at varying concentrations on platelet aggregation in platelet rich plasma pre-incubated with DMSO (control), rosiglitazone (2 ␮M) and gliclazide (2 ␮M). Superscript ‘a’ denotes p < 0.05 cf control.

observed with 10 ␮M rosiglitazone (superscript ‘a’ denotes p < 0.05 compared with baseline and superscript ‘b’ denotes p < 0.05 compared with 2 ␮M rosiglitazone)]. Preincubating PRP with 2 ␮M rosiglitazone for 30 min significantly enhanced the anti-platelet effect of the nitric oxide donor, SNP at 10, 20 and 50 ␮M concentrations (Fig. 2). However, addition of nitric oxide synthase inhibitor, LNMMA to PRP pre-incubated with 2 ␮M rosiglitazone for 30 min blunted its anti-aggregatory effects (Fig. 3). Preincubating whole blood and PRP with gliclazide (2 and 10 ␮M), unlike rosiglitazone, exerted no significant effect on platelet aggregation (Fig. 3).

3.2. Direct effects of rosiglitazone and gliclazide on platelet aggregation: In vitro studies Platelet aggregation was significantly reduced by incubating whole blood from normal subjects with rosiglitazone in a dose dependant manner [baseline platelet aggregation measured 20.42 ± 4.02 , reduced to 12.96 ± 1.95a  with 2 ␮M rosiglitazone and a further reduction to 9.85 ± 1.43ab was

Fig. 3. Effect of the nitric oxide synthase inhibitor, LNMMA (10 ␮M) on platelet aggregation in platelet rich plasma pre-incubated with rosiglitazone (2 ␮M) and gliclazide (2 ␮M). Data is the mean (±S.D.) of four separate experiments. Superscript ‘a’ denotes p < 0.05 cf control.

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4. Discussion This is the first study to demonstrate that rosiglitazone attenuates platelet activation as measured by reduced platelet aggregation and sCD40L in patients with T2DM and no overt evidence of coronary artery disease. The anti-platelet effect observed with the addition of a conventional clinical dose of rosiglitazone (4 mg) to ongoing metformin therapy, was significantly greater than that observed with the addition of a standard clinical dose of gliclazide (80 mg), with potential mechanisms involving reduced oxidative stress and enhanced platelet NO sensitivity. The findings of this study support those of Sidhu et al. [13] in which rosiglitazone reduced circulating platelet activity in patients with stable coronary artery disease without diabetes. The effects of rosiglitazone on platelet activity in our study correlated with the reduction in oxidative stress. Furthermore, this anti-platelet effect of rosiglitazone was independent of any metabolic changes and markers of both, inflammation (hs-CRP) and endothelial activation (sE-selectin and sICAM1). A mechanistic link between hyperglycaemia and platelet activation in diabetes has been well established [5]. The effect of gliclazide therapy in our study supports the findings of previous studies that improving glycaemic control can result in a reduction of platelet activation [18,16]. Previous studies suggest that gliclazide may attenuate endothelial activation via mitogen activated protein kinase dependant mechanisms [19]. Furthermore, gliclazide may also exert direct inhibitory effects on platelet aggregation possibly through free radical mediated mechanisms [16]. However, in our study the effects of gliclazide on platelet aggregation appear to be primarily related to improved glycaemic control, since no significant in vitro effects on platelet function were observed with gliclazide. Additionally, the reduction in platelet aggregation seen following 24 weeks of gliclazide therapy only correlated with the improvement in glycaemic control. By contrast, rosiglitazone therapy produced significantly greater effects on platelet activation over and above the similar reductions in glycaemic control observed in both groups. Insulin resistance is associated with enhanced platelet activation [5], potential mechanisms including prostacyclin (PGI2 ) and NO resistance [20] and direct effects of insulin signalling on platelet function [21]. The relationship between insulin resistance and platelet function is further supported by our baseline observation demonstrating a positive correlation between platelet aggregation and insulin resistance (HOMA-R) (r = 0.39; p < 0.05). The attenuation in measures of platelet activation seen following rosiglitazone may, thus, be a function of improved insulin sensitivity, although in our study this did not appear to be the primary mechanism. A potential mechanism through which PPAR␥ agonists may inhibit platelet activation is by reducing endothelial cell activation, a process that can result in release of promot-

ers of platelet activation [22]. PPAR␥ is highly expressed in endothelial cells, smooth muscle cells and macrophages within atherosclerotic plaques [23], where it inhibits activation of many pro-inflammatory genes. Indeed PPAR␥ agonists have been shown to inhibit production of numerous inflammatory cytokines [24] and since enhanced inflammation, particularly in the vicinity of atherosclerotic plaques may play a role in platelet activation [25], these antiinflammatory effects may contribute to reduced platelet activation associated with PPAR␥ agonist therapy. Although, there was a reduction in markers of endothelial activation (sE-selectin and sICAM-1) in both the treatment groups, this did not reach statistical significance. The inflammatory marker, hs-CRP fell significantly in the rosiglitazone treated group but did not correlate with markers of platelet activation. Enhanced lipid and protein oxidation is a recognised feature in T2DM and may contribute to a prothrombotic state [26]. In particular, lipid peroxidation may result in persistent platelet activation [27], while oxidised LDL can increase platelet aggregation by reducing platelet nitric oxide synthase activity [28]. TZDs appear to exert anti-oxidant properties, which may be independent of any metabolic effects [10]. These findings are further supported by our study, wherein rosiglitazone therapy resulted in a significant reduction in TBARS, independent of any metabolic effects. The antioxidant properties of rosiglitazone therapy in our study may, thus, influence platelet function by reducing lipid and LDL peroxidation. Our study, taken with the findings of Sidhu et al. [13] suggest that rosiglitazone may reduce platelet activity, through mechanisms independent of its metabolic effects. These may include a reduction in oxidative stress, resulting in increased NO bioavailability [29] as well as a potential direct effect on platelet function. The hypothesis that PPAR␥ agonists such as rosiglitazone may exert direct inhibitory effects on platelet activation is supported by our observations of a dose dependent inhibition of ADP induced platelet aggregation with rosiglitazone. A similar in vitro effect on platelet aggregation has been observed with troglitazone [30]. PPAR␥ agonists such as rosiglitazone may inhibit platelet activation pathways through a variety of potential mechanisms. Of particular interest is the l-arginine nitric oxide pathway [31]. Nitric oxide plays an important part by preventing platelet activation and platelet adhesion to vascular endothelium. Furthermore, studies on subjects with T2DM have demonstrated reduced platelet NO production, which may contribute to the platelet hyperaggregation observed in these subjects [32]. Human platelets are capable of synthesising NO through the action of constitutive nitric oxide synthase (cNOS) [33] and PPAR␥ agonists have been shown in previous studies to modulate the expression of cNOS [34–36]. In our in vitro studies, rosiglitazone enhanced platelet sensitivity to the effects of the nitric oxide donor, SNP. Furthermore, addition of the nitric oxide synthase inhibitor,

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LNMMA attenuated the anti-aggregatory effects of rosiglitazone. Thus, rosiglitazone may, at least in part, exert its effects on platelet function via NO dependent mechanisms. This influence of PPAR␥ agonists on NO metabolism and platelet function is further supported by recent studies demonstrating that reduced platelet aggregation observed in pioglitazone fed rats may be partly accounted for by an increased expression of cNOS [34]. The effects of rosiglitazone on enhancing platelet NO sensitivity are further illustrated by the observations of augmented inhibition of platelet aggregation by preincubation of PRP derived from subjects receiving rosiglitazone with the NO donor SNP, an effect which was absent in PRP derived from gliclazide treated subjects. The potential mechanisms which may account for this observation are putative and may relate to reduced oxidative stress, increased NO synthesis and direct non-genomic effects of platelet PPAR␥ receptor activation resulting in an enhanced response to the anti-aggregatory effects of NO. The concept that the effects of rosiglitazone on platelet activation may be partly mediated through non-genomic PPAR␥ dependent mechanisms is supported by the recent identification of functionally active PPAR␥ receptors on platelets, which appear capable of modulating platelet function [12]. Rosiglitazone is licensed for use as an oral hypoglycaemic agent in T2DM and this study supports its potential cardiovascular benefits, which may occur in addition to its blood glucose lowering effects. Indeed Choi et al. [15] recently demonstrated a reduced coronary restenosis rate following PTCA in T2DM patients receiving rosiglitazone, which appeared to be independent of any glycaemic or lipid effects. Since platelet activation is recognised to play a major role in the development of post-stent restenosis [14], our data may provide a potential mechanism to account for this observation and provides a clear rationale for outcome studies such as PPAR, which will assess the impact of rosiglitazone therapy on post coronary intervention morbidity and mortality. Our data may also have therapeutic implications in the management of patients with T2DM. Rosiglitazone may augment the anti-platelet effects of agents such as clopidogrel optimising the cardiovascular outcome benefits of such antiplatelet therapies. To conclude, this study shows for the first time that the introduction of rosiglitazone produces a greater reduction in platelet activity as compared to the introduction of gliclazide therapy, with equivalent changes in glycaemic control in patients with T2DM. This effect of rosiglitazone appears to be independent of its hypoglycaemic and insulin sensitising properties and may be a consequence of reduced oxidative stress, increased NO bioavailability and direct PPAR␥ effect on platelet function. While these data further support the potential cardiovascular benefits of PPAR␥ agonist therapy, the results of large outcome studies are awaited to determine the impact of this anti-platelet action on clinical outcomes in T2DM.

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