Thiazolidinediones and the risk of incident strokes in patients with type 2 diabetes: a nested case-control study

Peroxisome proliferator-activated receptor γ (PPARγ): A master gatekeeper in CNS injury and repair

Peroxisome proliferator-activated receptor γ (PPARγ) is a widely expressed ligand-modulated transcription factor that governs the expression of genes involved in inflammation, redox equilibrium, trophic factor production, insulin sensitivity, and the metabolism of lipids and glucose. Synthetic PPARγ agonists (e.g. thiazolidinediones) are used to treat Type II diabetes and have the potential to limit the risk of developing brain injuries such as stroke by mitigating the influence of comorbidities. If brain injury develops, PPARγ serves as a master gatekeeper of cytoprotective stress responses, improving the chances of cellular survival and recovery of homeostatic equilibrium. In the acute injury phase, PPARγ directly restricts tissue damage by inhibiting the NFκB pathway to mitigate inflammation and stimulating the Nrf2/ARE axis to neutralize oxidative stress. During the chronic phase of acute brain injuries, PPARγ activation in injured cells culminates in the repair of gray and white matter, preservation of the blood-brain barrier, reconstruction of the neurovascular unit, resolution of inflammation, and long-term functional recovery. Thus, PPARγ lies at the apex of cell fate decisions and exerts profound effects on the chronic progression of acute injury conditions. Here, we review the therapeutic potential of PPARγ in stroke and brain trauma and highlight the novel role of PPARγ in long-term tissue repair. We describe its structure and function and identify the genes that it targets. PPARγ regulation of inflammation, metabolism, cell fate (proliferation/differentiation/maturation/survival), and many other processes also has relevance to other neurological diseases. Therefore, PPARγ is an attractive target for therapies against a number of progressive neurological disorders.

Thiazolidinedione drugs in the treatment of type 2 diabetes mellitus: past, present and future

Thiazolidinedione (TZD) drugs used in the treatment of type 2 diabetes mellitus (T2DM) have proven effective in improving insulin sensitivity, hyperglycemia, and lipid metabolism. Though well tolerated by some patients, their mechanism of action as ligands of peroxisome proliferator-activated receptors (PPARs) results in the activation of several pathways in addition to those responsible for glycemic control and lipid homeostasis. These pathways, which include those related to inflammation, bone formation, and cell proliferation, may lead to adverse health outcomes. As treatment with TZDs has been associated with adverse hepatic, cardiovascular, osteological, and carcinogenic events in some studies, the role of TZDs in the treatment of T2DM continues to be debated. At the same time, new therapeutic roles for TZDs are being investigated, with new forms and isoforms currently in the pre-clinical phase for use in the prevention and treatment of some cancers, inflammatory diseases, and other conditions. The aims of this review are to provide an overview of the mechanism(s) of action of TZDs, a review of their safety for use in the treatment of T2DM, and a perspective on their current and future therapeutic roles.

Impact of glucose-lowering therapies on risk of stroke in type 2 diabetes

Patients with type 2 diabetes (T2D) have an increased risk of stroke compared with people without diabetes. However, the effects of glucose-lowering drugs on risk of ischaemic stroke in T2D have been less extensively investigated than in coronary heart disease. Some evidence, including the UKPDS, has suggested a reduced risk of stroke with metformin, although the number of studies is limited. Inhibition of the K_ATP channels increases ischaemic brain lesions in animals. This is in agreement with a recent meta-analysis showing an increased risk of stroke with sulphonylureas vs. various comparators as both mono- and combination therapy. Pioglitazone can prevent recurrence of stroke in patients with previous stroke, as already shown in PROactive, although results are less clear for first strokes. As for DPP-4 inhibitors, there was a non-significant trend towards benefit for stroke, whereas a possible increased risk of stroke with SGLT2 inhibitors-and in particular, empagliflozin in the EMPA-REG OUTCOME trial-has been suggested and requires clarification. Experimental results support a potential protective effect of GLP-1 receptor agonists against stroke that has, at least in part, been translated to clinical benefits in T2D patients in the LEADER and SUSTAIN-6 trials. Further interventional studies are now warranted to confirm the effects of glucose-lowering agents on risk of stroke in patients with T2D. In summary, the effects of antidiabetic drugs on risk of stroke appear to be heterogeneous, with some therapies (pioglitazone, GLP-1 receptor agonists) conferring possible protection against ischaemic stroke, other classes showing a neutral impact (DPP-4 inhibitors, insulin) and some glucose-lowering agents being associated with an increased risk of stroke (sulphonylureas, possibly SGLT2 inhibitors, high-dose insulin in the presence of insulin resistance).

Cardiovascular risk associated with the use of glitazones, metformin and sufonylureas: meta-analysis of published observational studies

BACKGROUND

The results of observational studies evaluating and comparing the cardiovascular safety of glitazones, metformin and sufonylureas are inconsistent.To conduct and evaluate heterogeneity in a meta-analysis of observational studies on the risk of acute myocardial infarction (AMI) or stroke in patients with type 2 diabetes using non-insulin blood glucose-lowering drugs (NIBGLD).

METHODS

We systematically identified and reviewed studies evaluating NIBGLD in patients with type 2 diabetes indexed in Medline, Embase, or the Cochrane Library that met prespecified criteria. The quality of included studies was assessed with the RTI item bank. Results were combined using fixed- and random-effects models, and the Higgins I(2) statistic was used to evaluate heterogeneity. Sensitivity analyses by study quality were conducted.

RESULTS

The summary relative risk (sRR) (95% CI) of AMI for rosiglitazone versus pioglitazone was 1.13 (1.04-1.24) [I(2) = 55%]. In the sensitivity analysis, heterogeneity was reduced [I(2) = 16%]. The sRR (95% CI) of stroke for rosiglitazone versus pioglitazone was 1.18 (1.02-1.36) [I(2)  = 42%]. There was strong evidence of heterogeneity related to study quality in the comparisons of rosiglitazone versus metformin and rosiglitazone versus sulfonylureas (I (2) ≥ 70%). The sRR (95% CI) of AMI for sulfonylurea versus metformin was 1.24 (1.14-1.34) [I(2) = 41%] and for pioglitazone versus metformin was 1.02 (0.75-1.38) [I(2) = 17%]. Sensitivity analyses decreased heterogeneity in most comparisons.

CONCLUSION/INTERPRETATION

Sulfonylureas increased the risk of AMI by 24% compared with metformin; an imprecise point estimate indicated no difference in risk of AMI when comparing pioglitazone with metformin. The presence of heterogeneity precluded any conclusions on the other comparisons. The quality assessment was valuable in identifying methodological problems in the individual studies and for analysing potential sources of heterogeneity.

Ginkgo biloba extract improves insulin signaling and attenuates inflammation in retroperitoneal adipose tissue depot of obese rats

Due to the high incidence and severity of obesity and its related disorders, it is highly desirable to develop new strategies to treat or even to prevent its development. We have previously described that Ginkgo biloba extract (GbE) improved insulin resistance and reduced body weight gain of obese rats. In the present study we aimed to evaluate the effect of GbE on both inflammatory cascade and insulin signaling in retroperitoneal fat depot of diet-induced obese rats. Rats were fed with high fat diet for 2 months and thereafter treated for 14 days with 500 mg/kg of GbE. Rats were then euthanized and samples from retroperitoneal fat depot were used for western blotting, RT-PCR, and ELISA experiments. The GbE treatment promoted a significant reduction on both food/energy intake and body weight gain in comparison to the nontreated obese rats. In addition, a significant increase of both Adipo R1 and IL-10 gene expressions and IR and Akt phosphorylation was also observed, while NF-κB p65 phosphorylation and TNF-α levels were significantly reduced. Our data suggest that GbE might have potential as a therapy to treat obesity-related metabolic diseases, with special interest to treat obese subjects resistant to adhere to a nutritional education program.

Observational studies of the association between glucose-lowering medications and cardiovascular outcomes: addressing methodological limitations

BACKGROUND

Recent years have witnessed a growing body of observational literature on the association between glucose-lowering treatments and cardiovascular disease. However, many of the studies are based on designs or analyses that inadequately address the methodological challenges involved.

METHODS

We reviewed recent observational literature on the association between glucose-lowering medications and cardiovascular outcomes and assessed the design and analysis methods used, with a focus on their ability to address specific methodological challenges. We describe and illustrate these methodological issues and their impact on observed associations, providing examples from the reviewed literature. We suggest approaches that may be employed to manage these methodological challenges.

RESULTS

From the evaluation of 81 publications of observational investigations assessing the association between glucose-lowering treatments and cardiovascular outcomes, we identified the following methodological challenges: 1) handling of temporality in administrative databases; 2) handling of risks that vary with time and treatment duration; 3) definitions of the exposure risk window; 4) handling of exposures that change over time; and 5) handling of confounding by indication. Most of these methodological challenges may be suitably addressed through application of appropriate methods.

CONCLUSIONS/INTERPRETATION

Observational research plays an increasingly important role in the evaluation of the clinical effects of diabetes treatment. Implementation of appropriate research methods holds the promise of reducing the potential for spurious findings and the risk that the spurious findings will mislead the medical community about risks and benefits of diabetes medications.

Risk of stroke with thiazolidinediones: a ten-year nationwide population-based cohort study

BACKGROUND

Thiazolidinediones (TZDs) - rosiglitazone and pioglitazone - a class of insulin sensitizer for treating type 2 diabetes, have been reported to exhibit neuroprotective effects in preclinical studies and have good effects in the control of blood sugar for diabetic patients with insulin resistance. However, clinical trials and observational studies have raised the possibility of higher stroke risk in patients treated with rosiglitazone. Whether pioglitazone poses similar stroke risk remains uncertain. Most of the studies on cardiovascular effects of TZDs were based on studies in the USA and Europe. The present study aimed to compare the stroke risk among diabetic patients on TZD to those on non-TZD medications in an Asian population.

METHODS

The study cohort included 15,981 patients with a diagnosis of diabetes without prior stroke, acute myocardial infarction (AMI) or heart failure who were followed from 2001 to 2010. Patients were classified by their prescriptions into rosiglitazone, pioglitazone and non-TZD groups. The study end points included ischemic and hemorrhagic stroke. In view of the reported association of heart failure and AMI with rosiglitazone, these 2 end points were also included in the present study. Cox hazard proportional models were used to estimate the risk of developing the end points. Likelihood ratio test was used to examine the age-drug interactions. Dose-response effects were evaluated by comparing the incidence rates among patients with different cumulative exposures to TZD.

RESULTS

During the 10-year follow-up, the rosiglitazone group showed significantly higher risk of ischemic stroke (multivariate adjusted hazard ratio, HR = 1.39; 95% confidence interval, CI = 1.16-1.66) and heart failure (HR = 1.59; 95% CI = 1.18-2.14) than the non-TZD group. The pioglitazone group did not show significant difference from the non-TZD group in ischemic stroke (HR = 0.97; 95% CI = 0.75-1.26) and heart failure (HR = 0.94; 95% CI = 0.59-1.50). The results also showed a significant dose-dependent effect of higher risk of ischemic stroke with increasing dosage of rosiglitazone, while there was no increased risk at any level of pioglitazone dosage.

CONCLUSIONS

This population-based cohort study shows that rosiglitazone imposes a higher risk of developing stroke or heart failure in this Asian patient population, suggesting the adverse side effects of rosiglitazone across ethnic boundaries. Pioglitazone, on the other hand, does not increase cardiovascular or stroke risk compared to the non-TZD group among diabetic patients without a history of macrovascular disease.

Risk of death and cardiovascular outcomes with thiazolidinediones: a study with the general practice research database and secondary care data

Objective

To describe the likely extent of confounding in evaluating the risks of cardiovascular (CV) events and mortality in patients using diabetes medication.

Methods

The General Practice Research Database was used to identify inception cohorts of insulin and different oral antidiabetics. An analysis of bias and incidence of mortality, acute coronary syndrome, stroke and heart failure were analysed in GPRD, Hospital Episode Statistics and death certificates.

Results

206,940 patients were identified. The bias analysis showed that past thiazolidinedione users had a lower mortality risk compared to past metformin users. There were no differences between past users of rosiglitazone and pioglitazone (adjusted RR of 1.04; 95% CI 0.93–1.18). Current rosiglitazone users had an increased risk of death (adjusted RR 1.20; 95% CI 1.08–1.34) and of hospitalisation for heart failure (adjusted RR of 1.73; 95% CI 1.19–2.51) compared to current pioglitazone users. Risk of mortality was increased two-fold shortly after starting rosiglitazone. Excess risk of death over 3 years with rosiglitazone was 0.3 per 100 in those aged 50–64 years, 2.0 aged 65–74, 3.0 aged 75–84, and 7.0 aged 85+. The cause of death with rosiglitazone was more likely to be due to a disease of the circulatory system.

Conclusions

Higher risks for death (overall and due to cardiovascular disease) and heart failure were found for rosiglitazone compared to pioglitazone. These excess risks were largest in patients aged 65 years or older. The European regulatory decision to suspend rosiglitazone is supported by this study.