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

Effect and cardiovascular safety of adding rosiglitazone to insulin therapy in type 2 diabetes: A meta-analysis

AIMS/INTRODUCTION

Recently, the use of rosiglitazone has been limited or withdrawn from the market as a result of cardiovascular risk. However, theoretically adding rosiglitazone to insulin could help insulin to decrease the glucose level. The present meta-analysis was designed to investigate the effect and safety of adding rosiglitazone to insulin therapy in type 2 diabetes.

MATERIALS AND METHODS

We searched published and unpublished databases through to March 2012. Randomized controlled trials (RCTs) comparing rosiglitazone in combination with insulin (RSG + INS) vs insulin alone (INS) in type 2 diabetes with outcomes including glycated hemoglobin levels, insulin dose, lipid parameters, blood pressure, edema and cardiovascular adverse events were selected.

RESULTS

Nine RCTs with durations of 24-26 weeks involving 1,916 patients were included. The RSG + INS group showed significantly decreased glycated hemoglobin levels by 0.89% (P < 0.00001) with an 8.48-U reduction in daily insulin dose (P <0.00001). However, the risks of hypoglycemia and edema were more frequent in the RSG+INS group (P < 0.0001; P = 0.03, respectively). Total cholesterol level was significantly increased in the RSG+INS group (P < 0.00001), but none of the high-density lipoprotein cholesterol, low-density lipoprotein cholesterol, very low-density lipoprotein cholesterol or triglyceride levels were significantly different between groups. There were no significant differences between groups with regard to the risks of myocardial infarction, heart failure, cardiovascular death or all-cause death.

CONCLUSIONS

Rosiglitazone could help type 2 diabetes patients with poorly controlled glucose with insulin therapy to decrease glucose levels and reduce their daily insulin dose, but at the cost of increased total cholesterol level, hypoglycemia and edema risk. Compared with insulin therapy, adding rosiglitazone to insulin did not increase the risks of myocardial infarction, heart failure, cardiovascular death or all-cause death.

Advances in the treatment of type 2 diabetes mellitus

There is a rising worldwide prevalence of diabetes, especially type 2 diabetes mellitus (T2DM), which is one of the most challenging health problems in the 21st century. The associated complications of diabetes, such as cardiovascular disease, peripheral vascular disease, stroke, diabetic neuropathy, amputations, renal failure, and blindness result in increasing disability, reduced life expectancy, and enormous health costs. T2DM is a polygenic disease characterized by multiple defects in insulin action in tissues and defects in pancreatic insulin secretion, which eventually leads to loss of pancreatic insulin-secreting cells. The treatment goals for T2DM patients are effective control of blood glucose, blood pressure, and lipids (if elevated) and, ultimately, to avert the serious complications associated with sustained tissue exposure to excessively high glucose concentrations. Prevention and control of diabetes with diet, weight control, and physical activity has been difficult. Treatment of T2DM has centered on increasing insulin levels, either by direct insulin administration or oral agents that promote insulin secretion, improving sensitivity to insulin in tissues, or reducing the rate of carbohydrate absorption from the gastrointestinal tract. This review presents comprehensive and up-to-date information on the mechanism(s) of action, efficacy, pharmacokinetics, pleiotropic effects, drug interactions, and adverse effects of the newer antidiabetic drugs, including (1) peroxisome proliferator-activated-receptor-γ agonists (thiazolidinediones, pioglitazone, and rosiglitazone); (2) the incretin, glucagon-like peptide-) receptor agonists (incretin-mimetics, exenatide. and liraglutide), (3) inhibitors of dipeptidyl-peptidase-4 (incretin enhancers, sitagliptin, and vildagliptin), (4) short-acting, nonsulfonylurea secretagogue, meglitinides (repaglinide and nateglinide), (5) amylin anlog-pramlintide, (6) α-glucosidase inhibitors (miglitol and voglibose), and (7) colesevelam (a bile acid sequestrant). In addition, information is presented on drug candidates in clinical trials, experimental compounds, and some plants used in the traditional treatment of diabetes based on experimental evidence. In the opinion of this reviewer, therapy based on orally active incretins and incretin mimetics with long duration of action that will be efficacious, preserve the β-cell number/function, and block the progression of diabetes will be highly desirable. However, major changes in lifestyle factors such as diet and, especially, exercise will also be needed if the growing burden of diabetes is to be contained.

Effect of rosiglitazone on cardiac electrophysiology, infarct size and mitochondrial function in ischaemia and reperfusion of swine and rat heart

Rosiglitazone, a peroxisome proliferator-activated receptor γ agonist, has been used to treat type 2 diabetes. Despite debates regarding its cardioprotection, the effects of rosiglitazone on cardiac electrophysiology are still unclear. This study determined the effect of rosiglitazone on ventricular fibrillation (VF) incidence, VF threshold (VFT), defibrillation threshold (DFT) and mitochondrial function during ischaemia and reperfusion. Twenty-six pigs were used. In each pig, either rosiglitazone (1 mg kg(-1)) or normal saline solution was administered intravenously for 60 min. Then, the left anterior descending coronary artery was ligated for 60 min and released to promote reperfusion for 120 min. The cardiac electrophysiological parameters were determined at the beginning of the study and during the ischaemia and reperfusion periods. The heart was removed, and the area at risk and infarct size in each heart were determined. Cardiac mitochondria were isolated for determination of mitochondrial function. Rosiglitazone did not improve the DFT and VFT during the ischaemia-reperfusion period. In the rosiglitazone group, the VF incidence was increased (58 versus 10%) and the time to the first occurrence of VF was decreased (3 ± 2 versus 19 ± 1 min) in comparison to the vehicle group (P < 0.05). However, the infarct size related to the area at risk in the rosiglitazone group was significantly decreased (P < 0.05). In the cardiac mitochondria, rosiglitazone did not alter the level of production of reactive oxygen species and could not prevent mitochondrial membrane potential changes. Rosiglitazone increased the propensity for VF, and could neither increase defibrillation efficacy nor improve cardiac mitochondrial function.

Cardiovascular risk and thiazolidinediones--what do meta-analyses really tell us?

Meta-analyses of clinical trials suggest that the use of the thiazolidinedione (TZD), rosiglitazone, in patients with type 2 diabetes mellitus may increase the risk of myocardial ischaemic events by 30-40%. Although these controversial data must be interpreted with caution, in the absence of definitive prospective cardiovascular (CV) outcomes data, they represent a prominent source of evidence concerning the CV safety of rosiglitazone. The results of meta-analyses and a large randomized-controlled CV outcomes trial provide strong evidence that pioglitazone does not increase the risk of coronary events. This article clarifies the clinical significance of these meta-analytical findings alongside other sources of evidence and assesses their impact on evolving treatment guidelines and recommendations for the use of TZDs in patients with type 2 diabetes.

Pioglitazone and the risk of cardiovascular events in patients with Type 2 diabetes receiving concomitant treatment with nitrates, renin-angiotensin system blockers, or insulin: results from the PROactive study (PROactive 20)

BACKGROUND

Patients with Type 2 diabetes mellitus (T2DM) are often treated with multiple glucose-lowering and cardiovascular agents. The concomitant use of nitrates, renin-angiotensin system (RAS) blockers, or insulin has been linked to a potential increase in myocardial ischemic risk with rosiglitazone. The PROactive database provides an opportunity to investigate the effects of these medications on the potential macrovascular benefits reported with pioglitazone.

METHODS

The PROactive study was a randomized double-blind prospective trial that evaluated mortality and cardiovascular morbidity in 5238 patients with T2DM and macrovascular disease. Patients received pioglitazone or placebo in addition to their baseline glucose-lowering and cardiovascular medications. The effect of pioglitazone on composite endpoints was evaluated, including all-cause death, myocardial infarction (MI), and stroke, as well as safety events of edema and serious heart failure, in subgroups using nitrates, RAS blockers, or insulin at baseline.

RESULTS

The risk of all-cause death, MI, and stroke for pioglitazone versus placebo was similar regardless of the baseline use of nitrates, RAS blockers, or insulin, with hazard ratios ranging from 0.81 to 0.87. Similar results were obtained for the other composite endpoints analyzed. There were no significant interactions between baseline medication subgroups and treatment. The increased risk of edema and serious heart failure was consistent across the baseline medication subgroups.

CONCLUSIONS

This post hoc analysis did not reveal an increased risk of macrovascular events with pioglitazone in patients receiving nitrates, RAS blockers, or insulin. Rather, all patients realized the same trend towards benefit with pioglitazone, and adverse events of edema and heart failure were predictable.

Therapeutic Implications of PPARgamma in Cardiovascular Diseases

Peroxisome proliferator-activated receptor-γ (PPARγ) is the members of the nuclear receptor superfamily as a master transcriptional factor that promotes differentiation of preadipocytes by activating adipose-specific gene expression. Although PPARγ is expressed predominantly in adipose tissue and associated with adipocyte differentiation and glucose homeostasis, PPARγ is also present in a variety of cell types including vascular cells and cardiomyocytes. Activation of PPARγ suppresses production of inflammatory cytokines, and there is accumulating data that PPARγ ligands exert antihypertrophy of cardiomyocytes and anti-inflammatory, antioxidative, and antiproliferative effects on vascular wall cells and cardiomyocytes. In addition, activation of PPARγ is implicated in the regulation of endothelial function, proliferation and migration of vascular smooth muscle cells, and activation of macrophages. Many studies suggest that PPARγ ligands not only ameliorate insulin sensitivity, but also have pleiotropic effects on the pathophysiology of atherosclerosis, cardiac hypertrophy, ischemic heart, and myocarditis.

Type 2 diabetes: assessing the relative risks and benefits of glucose-lowering medications

The selection of appropriate pharmacologic therapy for any disease requires a careful assessment of benefit and risk. In the case of type 2 diabetes, this decision typically balances the benefits accrued from improved glycemic control with the risks inherent in glucose-lowering medications. This review is intended to assist therapeutic decision-making by carefully assessing the potential benefit from improved metabolic control relative to the potential risks of a wide array of currently prescribed glucose-lowering agents. Wherever possible, risks and benefits have been expressed in terms of absolute rates (events per 1000 patient-years) to facilitate cross-study comparisons. The review incorporates data from new studies (Action in Diabetes and Vascular Disease: Preterax and Diamicron Modified Release Controlled Evaluation, Action to Control Cardiovascular Risk in Diabetes, and the Veterans Affairs Diabetes Trial), as well as safety issues associated with newer glucose-lowering medications.

Optimising the medical management of hyperglycaemia in type 2 diabetes in the Middle East: pivotal role of metformin

AIMS

Increases in the prevalence of type 2 diabetes will likely be greater in the Middle East and other developing countries than in most other regions during the coming two decades, placing a heavy burden on regional healthcare resources.

METHODOLOGY

Medline search, examination of data from major epidemiological studies in the Middle Eastern countries.

RESULTS

The aetiology and pathophysiology of diabetes appears comparable in Middle Eastern and other populations. Lifestyle intervention is key to the management of diabetes in all type 2 diabetes patients, who should be encouraged strongly to diet and exercise. The options for pharmacologic therapy in the management of diabetes have increased recently, particularly the number of potential antidiabetic combinations. Metformin appears to be used less frequently to initiate antidiabetic therapy in the Middle East than in other countries. Available clinical evidence, supported by current guidelines, strongly favours the initiation of antidiabetic therapy with metformin in Middle Eastern type 2 diabetes patients, where no contraindications exist. This is due to its equivalent or greater efficacy relative to other oral antidiabetic treatments, its proven tolerability and safety profiles, its weight neutrality, the lack of clinically significant hypoglycaemia, the demonstration of cardiovascular protection for metformin relative to diet in the UK Prospective Diabetes Study and in observational studies, and its low cost. Additional treatments should be added to metformin and lifestyle intervention as diabetes progresses, until patients are receiving an intensive insulin regimen with or without additional oral agents.

CONCLUSIONS

The current evidence base strongly favours the initiation of antidiabetic therapy with metformin, where no contraindications exist. However, metformin may be under-prescribed in the Middle East.

Is the evidence from clinical trials for cardiovascular risk or harm for glitazones convincing?

Thiazolidinediones (TZDs), agonists of the nuclear receptor peroxisome proliferator-activated receptor-gamma, induce the expression of many genes, including several enzymes and transporters involved in glucose and lipid metabolism. Although the efficacy of TZDs on blood glucose control in type 2 diabetes is not questionable, their cardiovascular effects have been debated, with beneficial or harmful actions suggested by different authors. This article reviews the available clinical evidence on the cardiovascular effects of TZDs, discussing possible mechanisms underlying the observed effects and suggesting some directions for future research.

Glycemic targets for patients with type 2 diabetes mellitus

Cardiovascular disease is the predominant cause of death in diabetic patients, and reducing the risk of cardiovascular disease in diabetics has recently been the focus of several highly publicized large trials, including ACCORD (Action To Control Cardiovascular Risk in Diabetes), ADVANCE (Action in Diabetes and Vascular Disease: Preterax and Diamicron MR Controlled Evaluation), and VADT (Veterans Affairs Diabetes Trial). These studies randomized high-risk diabetic patients into either intensive treatment or standard treatment. The glycemic control arm of ACCORD was terminated 17 months before the planned end of the study because of a finding of significantly increased all-cause and cardiovascular mortality in the intensive treatment group. These findings were not duplicated in either ADVANCE or VADT. Multiple possible explanations have been brought forward, including a higher incidence of death from unrecognized hypoglycemia, effects due to increased exposure to particular antidiabetic medications, adverse effects of rapid correction of hyperglycemia, weight gain, and differences in baseline characteristics. None of these were validated in post hoc analyses of the trial data, and the cause of the increased mortality remains elusive. Subgroup analyses suggest that those who start off with better control of their diabetes or without preexisting cardiovascular disease may have the most to gain from tight glycemic control. Reducing the risk of macrovascular disease and death in diabetic patients requires not only attention to glucose control but also meticulous attention to control of nonglycemic risk factors, including hypertension, hyperlipidemia, smoking, lack of exercise, and unhealthy diet as well as timely prescription of medications with proven preventative benefits, such as aspirin and statins.

Adding pioglitazone to insulin containing regimens in type 2 diabetes: systematic review and meta-analysis

Background

Type 2 diabetes is treated in a stepwise manner, progressing from diet and physical activity to oral antidiabetic agents and insulin. The oral agent pioglitazone is licensed for use with insulin when metformin is contraindicated or not tolerated. This systematic review and meta-analysis investigates the extent to which adding pioglitazone to insulin-containing regimens produces benefits in terms of patient-relevant outcomes.

Methodology/Principal Findings

Medline, Embase, and the Cochrane Library were searched for randomised controlled trials comparing pioglitazone in combination with any insulin-containing regimen in comparison with the same insulin regimen alone in patients with type 2 diabetes. Outcomes investigated included HbA1c, hypoglycaemia, weight, and adverse events. Studies were selected, assessed and summarised according to standard systematic review methodology and in a meta-analysis. We included eight trials that examined the benefits of adding pioglitazone to an insulin regimen and studied a total of 3092 patients with type 2 diabetes. All studies included patients with previously inadequate glucose control. Trial duration was between 12 weeks and 34.5 months. The trials used pioglitazone doses of up to 45 mg/day. In our meta-analysis, the mean reduction in HbA1c was 0.58% (95% CI: −0.70, −0.46, p<0.00001). Hypoglycaemic episodes were slightly more frequent in the pioglitazone arms (relative risk 1.27; 95% CI: 0.99, 1.63, p = 0.06). Where reported, HDL-cholesterol tended to be increased with pioglitazone. Patients on pioglitazone tended to gain more weight than those who were not, with an average difference of almost 3 kg. Peripheral oedema was more frequent in the pioglitazone groups. None of the studies reported on fractures in women, and data on cardiovascular events were inconclusive, with most studies being too short or too small to assess these long-term outcomes.

Conclusions/Significance

When added to insulin regimens, pioglitazone confers a small advantage in terms of HbA1c in type 2 diabetes patients with previous inadequate glucose control, but at the cost of increased hypoglycaemia and weight gain. Other considerations include the risk of heart failure, fractures in women, a reduced insulin dose, and the net financial cost.