Rosiglitazone--continued uncertainty about safety

Bayesian estimation and testing in random-effects meta-analysis of rare binary events allowing for flexible group variability

Rare binary events data arise frequently in medical research. Due to lack of statistical power in individual studies involving such data, meta-analysis has become an increasingly important tool for combining results from multiple independent studies. However, traditional meta-analysis methods often report severely biased estimates in such rare-event settings. Moreover, many rely on models assuming a pre-specified direction for variability between control and treatment groups for mathematical convenience, which may be violated in practice. Based on a flexible random-effects model that removes the assumption about the direction, we propose new Bayesian procedures for estimating and testing the overall treatment effect and inter-study heterogeneity. Our Markov chain Monte Carlo algorithm employs Pólya-Gamma augmentation so that all conditionals are known distributions, greatly facilitating computational efficiency. Our simulation shows that the proposed approach generally reports less biased and more stable estimates compared to existing methods. We further illustrate our approach using two real examples, one using rosiglitazone data from 56 studies and the other using stomach ulcers data from 41 studies.

Acute carbohydrate overfeeding: a redox model of insulin action and its impact on metabolic dysfunction in humans

A role for fat overfeeding in metabolic dysfunction in humans is commonly implied in the literature. Comparatively less is known about acute carbohydrate overfeeding (COF). We tested the hypothesis that COF predisposes to oxidative stress by channeling electrons away from antioxidants to support energy storage. In a study of 24 healthy human subjects with and without obesity, COF was simulated by oral administration of excess carbohydrates; a two-step hyperinsulinemic clamp was used to evaluate insulin action. The distribution of electrons between oxidative and reductive pathways was evaluated by the changes in the reduction potentials (Eh) of cytoplasmic (lactate, pyruvate) and mitochondrial (β-hydroxybutyrate, acetoacetate) redox couples. Antioxidant redox was measured by the ratio of reduced to oxidized glutathione. We used cross-correlation analysis to evaluate the relationships between the trajectories of Eh, insulin, glucose, and respiratory exchange during COF. DDIT3 and XBP1s/u mRNA were measured as markers of endoplasmic reticulum stress (ER stress) in adipose tissue before and after COF. Here, we show that acute COF is characterized by net transfer of electrons from mitochondria to cytoplasm. Circulating glutathione is oxidized in a manner that significantly cross-correlates with increasing insulin levels and precedes the decrease in cytoplasmic Eh. This effect is more pronounced in overweight individuals (OW). Markers of ER stress in subcutaneous fat are detectable in OW within 4 h. We conclude that acute COF contributes to metabolic dysfunction through insulin-dependent pathways that promote electron transfer to the cytoplasm and decrease antioxidant capacity. Characterization of redox during overfeeding is important for understanding the pathophysiology of obesity and type 2 diabetes.NEW & NOTEWORTHY Current principles assume that conversion of thermic energy to metabolically useful energy follows fixed rules. These principles ignore the possibility of variable proton uncoupling in mitochondria. Our study shows that the net balance of electron distribution between mitochondria and cytoplasm is influenced by insulin in a manner that reduces proton leakage during overfeeding. Characterization of the effects of insulin on redox balance is important for understanding obesity and insulin resistance.

Alismatis Rhizoma Triterpenes Alleviate High-Fat Diet-Induced Insulin Resistance in Skeletal Muscle of Mice

Alismatis rhizoma (AR), which is the dried rhizome of Alisma orientale (Sam.) Juz. (Alismataceae), is an important component of many famous Chinese formulas for hypoglycemic. This study aimed to evaluate the insulin resistance (IR) alleviating effects of AR triterpenes (ART) and ART component compatibility (ARTC, the mixture of 16-oxo-alisol A, 16-oxo-alisol A 23-acetate, 16-oxo-alisol A 24-acetate, alisol C, alisol C 23-acetate, alisol L, alisol A, alisol A 23-acetate, alisol A 24-acetate, alisol L 23-acetate, alisol B, alisol B 23-acetate, 11-deoxy-alisol B and 11-deoxy-alisol B 23-acetate) in high-fat diet-induced IR mice and plamitate-treated IR C2C12 cells, respectively. A dose of 200 mg/kg of ART was orally administered to IR mice, and different doses (25, 50, and 100 μg/ml) of ARTC groups were treated to IR C2C12 cells. IPGTT, IPITT, body weight, Hb1AC, FFA, TNF-α, MCP-1, and IR-associated gene expression (p-AMPK, p-IRS-1, PI3K, p-AKT, p-JNK, and GLUT4) were measured in IR mice. Glucose uptake, TNF-α, MCP-1, and IR-associated gene expression were also measured in IR C2C12 cells. Results showed that ART alleviated high-fat diet-induced IR in the skeletal muscle of mice, and this finding was further validated by ARTC. This study demonstrated that ART presented a notable IR alleviating effect by regulating IR-associated gene expression, and triterpenes were the material basis for the IR alleviating activity of AR.

Scientific independence and objectivity: many questions linger about treatment of type 2 diabetes, such as scientific study design, optimal glucose control and the safety of injecting exogenous insulin

Whilst clinical guidelines exist for the treatment of people with type 2 diabetes, many underlying assumptions are still not qualified by convincing evidence. In this commentary, it is argued that fundamental issues still cloud clinical practice, such as biases in the design of clinical studies, the association between glucose control & clinical outcomes, and the safety of exposure to exogenous insulin and other glucose-lowering drugs. Relevant scientific evidence and alternative opinions about important issues continue to be largely ignored, and no effort has been made to resolve these questions. This may have had serious consequences, such as stifling innovation because there are no further benefits to be achieved in relation to glucose control.

Reporting bias in medical research - a narrative review

Reporting bias represents a major problem in the assessment of health care interventions. Several prominent cases have been described in the literature, for example, in the reporting of trials of antidepressants, Class I anti-arrhythmic drugs, and selective COX-2 inhibitors. The aim of this narrative review is to gain an overview of reporting bias in the medical literature, focussing on publication bias and selective outcome reporting. We explore whether these types of bias have been shown in areas beyond the well-known cases noted above, in order to gain an impression of how widespread the problem is. For this purpose, we screened relevant articles on reporting bias that had previously been obtained by the German Institute for Quality and Efficiency in Health Care in the context of its health technology assessment reports and other research work, together with the reference lists of these articles.We identified reporting bias in 40 indications comprising around 50 different pharmacological, surgical (e.g. vacuum-assisted closure therapy), diagnostic (e.g. ultrasound), and preventive (e.g. cancer vaccines) interventions. Regarding pharmacological interventions, cases of reporting bias were, for example, identified in the treatment of the following conditions: depression, bipolar disorder, schizophrenia, anxiety disorder, attention-deficit hyperactivity disorder, Alzheimer's disease, pain, migraine, cardiovascular disease, gastric ulcers, irritable bowel syndrome, urinary incontinence, atopic dermatitis, diabetes mellitus type 2, hypercholesterolaemia, thyroid disorders, menopausal symptoms, various types of cancer (e.g. ovarian cancer and melanoma), various types of infections (e.g. HIV, influenza and Hepatitis B), and acute trauma. Many cases involved the withholding of study data by manufacturers and regulatory agencies or the active attempt by manufacturers to suppress publication. The ascertained effects of reporting bias included the overestimation of efficacy and the underestimation of safety risks of interventions.In conclusion, reporting bias is a widespread phenomenon in the medical literature. Mandatory prospective registration of trials and public access to study data via results databases need to be introduced on a worldwide scale. This will allow for an independent review of research data, help fulfil ethical obligations towards patients, and ensure a basis for fully-informed decision making in the health care system.

Lack of association between thiazolidinediones and macular edema in type 2 diabetes: the ACCORD eye substudy

OBJECTIVE

To assess the cross-sectional association of thiazolidinediones with diabetic macular edema (DME).

METHODS

The cross-sectional association of DME and visual acuity with thiazolidinediones was examined by means of baseline fundus photographs and visual acuity measurements from the Action to Control Cardiovascular Risk in Diabetes (ACCORD) trial. Visual acuity was assessed in 9690 participants in the ACCORD trial, and 3473 of these participants had fundus photographs that were centrally read in a standardized fashion by masked graders to assess DME and retinopathy from October 23, 2003, to March 10, 2006.

RESULTS

Among the subsample, 695 (20.0%) people had used thiazolidinediones, whereas 217 (6.2%) people had DME. Thiazolidinedione use was not associated with DME in unadjusted (odds ratio [OR], 1.01; 95% confidence interval [CI], 0.71-1.44; P = .95) and adjusted (OR, 0.97; 95% CI, 0.67-1.40; P = .86) analyses. Significant associations with DME were found for retinopathy severity (P < .001) and age (OR, 0.97; 95% CI, 0.952-0.997; P = .03) but not for hemoglobin A(1c) (P = .06), duration of diabetes (P = .65), sex (P = .72), and ethnicity (P = .20). Thiazolidinedione use was associated with slightly greater visual acuity (0.79 letter; 95% CI, 0.20-1.38; P = .009) of uncertain clinical significance.

CONCLUSIONS

In a cross-sectional analysis of data from the largest study to date, no association was observed between thiazolidinedione exposure and DME in patients with type 2 diabetes; however, we cannot exclude a modest protective or harmful association. Trial Registration clinicaltrials.gov Identifier: NCT00542178.

Pioglitazone does not enhance the effectiveness of lifestyle modification in preventing conversion of impaired glucose tolerance to diabetes in Asian Indians: results of the Indian Diabetes Prevention Programme-2 (IDPP-2)

AIMS/HYPOTHESIS

The objective of this prevention programme was to study whether combining pioglitazone with lifestyle modification would enhance the efficacy of lifestyle modification in preventing type 2 diabetes in Asian Indians with impaired glucose tolerance.

METHODS

In a community-based, placebo-controlled 3 year prospective study, 407 participants with impaired glucose tolerance (mean age 45.3 +/- 6.2 years, mean BMI 25.9 +/- 3.3 kg/m(2)) were sequentially grouped to receive either: lifestyle modification plus pioglitazone, 30 mg (n = 204) or lifestyle modification plus placebo (n = 203). The participants and investigators were blinded to the assignment. The primary outcome was development of diabetes.

RESULTS

At baseline, both groups had similar demographic, anthropometric and biochemical characteristics. At year 3, the response rate was 90.2%. The cumulative incidence of diabetes was 29.8% with pioglitazone and 31.6% with placebo (unadjusted HR 1.084 [95% CI 0.753-1.560], p = 0.665). Normoglycaemia was achieved in 40.9% and 32.3% of participants receiving pioglitazone and placebo, respectively (p = 0.109). In pioglitazone group, two deaths and two non-fatal hospitalisations occurred due to cardiac problems; in the placebo group there were two occurrences of cardiac disease.

CONCLUSIONS/INTERPRETATION

Despite good adherence to lifestyle modification and drug therapy, no additional effect of pioglitazone was seen above that achieved with placebo. The effectiveness of the intervention in both groups was comparable with that of lifestyle modification alone, as reported from the Indian Diabetes Prevention Programme-1. The results are at variance with studies that showed significant relative risk reduction in conversion to diabetes with pioglitazone in Americans with IGT. An ethnicity-related difference in the action of pioglitazone in non-diabetic participants may be one explanation.

TRIAL REGISTRATION

ClinicalTrials.gov NCT00276497 FUNDING: This study was funded by the India Diabetes Research Foundation.

Adipokines in the treatment of diabetes mellitus and obesity

BACKGROUND

The physiology of adipose tissue plays a main role in the pathogenesis of type 2 diabetes mellitus. The secretion of adipocyte-derived hormones, in either an autocrine or a paracrine manner, has been proposed as a relevant mechanism in this process. In this sense, the administration and regulation of hormones derived from adipose tissue arises as an attractive option for treating metabolic disorders.

OBJECTIVE

To review the current understanding of the implication of adipokines in the development of obesity and insulin resistance, as well as their potential use as therapeutic agents.

METHODOLOGY

Review of scientific literature.

CONCLUSIONS

This review describes the role of adipokines in generating insulin resistance and the chronic low-grade inflammatory profile accompanying visceral obesity.

Risk of acute myocardial infarction in patients treated with thiazolidinediones or other antidiabetic medications

PURPOSE

Controversy surrounds the question whether thiazolidinediones (TZDs) increase the risk of acute myocardial infarction (AMI). This study examined risk of AMI in patients with type 2 diabetes mellitus (T2DM) who were taking TZDs or other antidiabetic medications.

METHODS

Using a nested case-control design, a cohort of patients aged 18-84 years with T2DM and use of an oral antidiabetic medication or exenatide between January 2002 and June 2006 was identified. Cases of AMI were matched with up to four controls based on age, gender, health plan, geography, and diabetes therapy regimen. Over the 1-year pre-index period, TZD exposure was compared with no TZD exposure, after adjustment for potential confounders.

RESULTS

Overall, 1681 cases were identified and matched with 6653 controls. Compared with no TZD exposure, an increased risk of AMI was not observed among TZD exposed patients (adjusted OR 1.01; 95%CI, 0.85-1.20; adjusted p = 0.98). When exposure proximity to the event was examined, the risk of AMI was significantly increased with recent rosiglitazone exposure between 1 and 60 days prior to the case date (adjusted OR 1.69; 95%CI, 1.18-2.44; adjusted p = 0.045) and was not significantly increased with current or remote rosiglitazone exposure or current, recent, or remote pioglitazone exposure.

CONCLUSION

TZD exposure did not increase the risk of AMI when exposure proximity was not considered. However, when evaluating exposure proximity to the event, the risk of AMI was increased with recent rosiglitazone exposure between 1 and 60 days prior to the case date.

PPARdelta Agonism for the Treatment of Obesity and Associated Disorders: Challenges and Opportunities

The prevalence of obesity in the USA and worldwide has reached epidemic proportions during the last two decades. Drugs currently available for the treatment of obesity provide no more than 5% placebo-adjusted weight loss and are associated with undesirable side effects. Peroxisome proliferator-activated receptor (PPAR) modulators offer potential benefits for the treatment of obesity and its associated complications but their development has been complicated by biological, technical, and regulatory challenges. Despite significant challenges, PPAR modulators are attractive targets for the treatment of obesity and could offer a viable alternative to the millions of patients who fail to lose weight following rigorous dieting and exercise protocols. In addition, PPAR modulators have the potential-added benefit of ameliorating the associated comorbidities.

Present and future drug treatments for chronic kidney diseases: evolving targets in renoprotection

At present, there are no specific cures for most of the acquired chronic kidney diseases, and renal transplantation is limited by organ shortage, therefore present efforts are concentrated on the prevention of progression of renal diseases. There is robust experimental and clinical evidence that progression of chronic nephropathies is multifactorial; however, intraglomerular haemodynamic changes and proteinuria play a key role in this process. With a focus on renoprotection, we first examine more established therapies--such as those that modulate the renin-angiotensin-aldosterone system--that can be used for the treatment of proteinuric renal diseases. We then discuss examples of novel drugs and biologics that might be used to target the inflammatory and profibrotic process, and glomerular injury, highlighting results from recent clinical trials.

Pharmacogenetics in drug discovery and development: a translational perspective

The ability to predict a patient's drug response on the basis of their genetic information is expected to decrease attrition during the development of new, innovative drugs, and reduce adverse events by being able to predict individual patients at risk. Most pharmacogenetic investigations have focused on drug-metabolism genes or candidate genes that are thought to be involved in specific diseases. However, robust new genetic tools now enable researchers to carry out multi-candidate gene-association and genome-wide studies for target discovery and drug development. Despite the expanding role of pharmacogenetics in industry, however, there is a paucity of published data. New forms of effective and efficient collaboration between industry and academia that may enhance the systematic collection of pharmacogenetic data are necessary to establish genetic profiles related to drug response, confirm pharmacogenetic associations and expedite the development of new drugs and diagnostic tests.

A problem for achieving informed choice

Most agree that, if all else is equal, patients should be provided with enough information about proposed medical therapies to allow them to make an informed decision about what, if anything, they wish to receive. This is the principle of informed choice; it is closely related to the notion of informed consent. Contemporary clinical trials are analysed according to classical statistics. This paper puts forward the argument that classical statistics does not provide the right sort of information for informing choice. The notion of probability used by classical statistics is complex and difficult to communicate. Therapeutic decisions are best informed by statistical approaches that assign probabilities to hypotheses about the benefits and harms of therapies. Bayesian approaches to statistical inference provide such probabilities.

Augmentation of nitric oxide is crucial for the time-dependent effects of rosiglitazone on blood pressure and baroreflex function in rats

OBJECTIVES

To determine the time-dependent effects of rosiglitazone (RSG) on blood pressure (MAP) and baroreflex sensitivity (BRS) and the involvement of nitric oxide (NO) in these effects.

METHODS

Male Sprague-Dawley rats were treated with RSG (8 mg/kg per day, orally) or saline for 4, 8 and 12 weeks. BRS was determined by linear regression method with bolus injections of phenylephrine (PE-BRS) or sodium nitroprusside (NP-BRS). Insulin sensitivity (M value) was determined by euglycemic hyperinsulinemic clamp study. Vascular and cardiac responsiveness to isoproterenol, acetylcholine and NP were determined after ganglionic blockade. Effects of endogenous NO were examined by Nomega-nitro-L-arginine-methyl ester (L-NAME) administration.

RESULTS

RSG treatment time-dependently decreased circulating lipids, insulin, glucose levels and insulin resistance (HOMA-IR) but increased plasma NOx levels. M values were progressively decreased in control rats, but remained unchanged in RSG-treated rats. Chronic RSG treatment progressively lowered MAP but reciprocally increased heart rate (HR). In addition, chronic RSG treatment significantly attenuated HR changes to methylatropine but enhanced HR changes to propranolol. Twelve-week RSG treatment enhanced PE-BRS which was suppressed by methylatropine but not propranolol, and attenuated NP-BRS which was sustained after methylatropine or propranolol. Moreover, 12-week RSG treatment also diminished cardiac responsiveness to isoproterenol and augmented vascular responsiveness to acetylcholine, but not to NP. L-NAME eliminated the differences in MAP and HR between groups, and reversed both RSG-induced enhanced PE-BRS and attenuated NP-BRS. Plasma NOx levels were highly correlated with RSG-mediated changes in the baseline MAP, HR and BRS.

CONCLUSION

These data suggest that RSG-induced NO production is important for the time-dependent effects of RSG on MAP and BRS in rats.

Secondary prevention of cardiovascular disease in type 2 diabetes and prediabetes: a cardiologist's perspective

Patients with type 2 diabetes mellitus (T2DM) and prediabetes have a substantially greater risk of developing cardiovascular (CV) disease than the general population. This increased risk of CV disease is due to a complex cluster of risk factors including insulin resistance, hyperglycaemia, diabetic dyslipidaemia, hypertension and systemic inflammation. As a result of this cluster of risk factors, life expectancy is reduced by up to 10 years upon diagnosis of T2DM, principally because of fatal CV events. Patients with T2DM are not only more likely to sustain a CV event, but also have a higher risk of a fatal outcome from this event. Therefore, whilst primary prevention is critical in determining the prognosis of patients newly diagnosed with T2DM, many will go on to suffer CV events and represent a high-risk group requiring intensive secondary prevention techniques. Recent data demonstrate that contemporary prevention therapies do not afford equal benefits to T2DM sufferers after acute myocardial infarction compared with their non-diabetic counterparts. This finding highlights the need for more effective secondary preventative strategies to prevent recurrent CV events in patients with T2DM and prediabetes. The cardiologist's role in the multidisciplinary management of T2DM is to improve patient outcomes by optimising use of evidence-based strategies for the prevention of recurrent CV events.

Does rosiglitazone increase cardiovascular outcomes?

Rosiglitazone is commonly used in the treatment of Type 2 diabetes. However, the cardiovascular outcomes with rosiglitazone have only been evaluated recently. Firstly, they were evaluated by meta-analysis. A total of 42 short-term trials, not designed to determine cardiovascular outcomes, were included in the meta-analysis. There were 72 myocardial infarctions in the control group of 12283 subjects (0.59%) and 86 in the rosiglitazone group of 15560 subjects (0.55%). This gave an odds ratio of 1.43 and a p-value of 0.03. As a consequence of this meta-analysis, the safety of this widely used medicine in subjects with Type 2 diabetes is being questioned. Interim analysis of the long-term RECORD (Rosiglitazone Evaluated for Cardiac Outcomes and Regulation of glycaemia in Diabetes) trial, which was designed to determine cardiovascular outcomes, showed that these occurred in 9.1% of control subjects and 9.8% of the rosiglitazone subjects, and these values were not significantly different. Both the meta-analysis and the interim analysis of RECORD have many limitations. In conclusion, it seems that it is possible that rosiglitazone may have a small harmful effect on cardiovascular outcomes. As the effect (if any) is small, this should not be cause for alarm, but rather for further review of how rosiglitazone should be used and for a larger trial to determine the unequivocal effect of rosiglitazone on cardiovascular outcomes.

Pharmacogenetics of thiazolidinedione therapy

The thiazolidinediones (TZDs) are peroxisome proliferator-activated receptor-γ agonists and have glucose-lowering, insulin-sensitizing and anti-inflammatory effects. TZDs are approved for the treatment of Type 2 diabetes, and have been studied as a diabetes-prevention strategy. Despite widespread use of TZDs, a large number of patients fail to achieve a substantial reduction in glucose, or an improvement in insulin sensitivity, following treatment. Available data suggest that polymorphisms in genes encoding TZD drug targets, effector proteins and metabolizing enzymes contribute to the observed interindividual variability in TZD response and disposition. The purpose of this review is to highlight recent developments in the field of TZD pharmacogenetics, specifically focusing on clinical studies that have investigated genetic determinants of TZD response (i.e., reduction in glycemia and improvement in insulin sensitivity), disposition (i.e., pharmacokinetics), and side effects in patients with Type 2 diabetes and patients at risk for Type 2 diabetes.