Thiazolidinediones: effects on the development and progression of type 2 diabetes and associated vascular complications

Efficacy and safety of chiglitazar, a novel peroxisome proliferator-activated receptor pan-agonist, in patients with type 2 diabetes: a randomized, double-blind, placebo-controlled, phase 3 trial (CMAP)

Chiglitazar (Carfloglitazar) is a novel non-thiazolidinedione (TZD) structured peroxisome proliferator-activated receptor (PPAR) pan-agonist that has shown promising effects on glycemic control and lipid regulation in patients with type 2 diabetes in previous clinical studies. This randomized phase 3 trial aimed to compare the efficacy and safety of chiglitazar with placebo in patients with type 2 diabetes with insufficient glycemic control by strict diet and exercise alone. Eligible patients were randomly assigned to receive chiglitazar 32 mg (n = 167), chiglitazar 48 mg (n = 166), or placebo (n = 202) once daily. The primary endpoint was the change in glycosylated hemoglobin A_1c (HbA_1c) at week 24 with superiority of chiglitazar over placebo. The results showed that both chiglitazar 32 and 48 mg resulted in significant and clinically meaningful reductions in HbA_1c, and placebo-adjusted estimated treatment differences at week 24 for chiglitazar 32 and 48 mg were -0.87% (95% confidential interval (CI): -1.10 to -0.65; P < 0.0001) and -1.05% (95% CI: -1.29 to -0.81; P < 0.0001), respectively. Secondary efficacy parameters including glycemic control, insulin sensitivity and triglyceride reduction were also significantly improved in the chiglitazar groups. The overall frequency of adverse events and study discontinuation attributable to adverse events were similar among the groups. Low incidences of mild edema and body weight gain were reported in the chiglitazar dose groups. The results from this phase 3 trial demonstrated that the PPAR pan-agonist chiglitazar possesses an overall good efficacy and safety profile in patients with type 2 diabetes inadequately controlled with lifestyle interventions, thereby providing adequate supporting evidence for using this PPAR pan-agonist as a treatment option for type 2 diabetes.

Pioglitazone Is Associated with Lower Major Adverse Cardiovascular and Cerebrovascular Events than DPP4-Inhibitors in Diabetic Patients with End-Stage Renal Disease: A Taiwan Nationwide Cohort Study, 2006-2016

While pioglitazone reduces insulin resistance and hepatic gluconeogenesis effectively in patients with type 2 diabetes mellitus (T2DM), these benefits remained controversial in patients with end stage renal disease (ESRD). We compared major adverse cardiac cerebrovascular events (MACCEs) and mortality (overall, infection-related, and MACCE-related) of pioglitazone to that of dipeptidyl peptidase 4 inhibitors (DPP4-inhibitors) in patients with T2DM and ESRD. From Taiwan’s national health insurance research database (NHIRD), 647 pioglitazone users and 6080 DPP4-inhibitors users between 1 April 2006 and 31 December 2016 were followed from the 91th date after the ESRD certification until the study outcomes, independently; withdraw from the NHI program, death, or 31 December 2017, whichever came first. After weighting, risks of MACCEs (10.48% vs. 12.62% per person-years, hazard ratio (HR): 0.85, 95% (CI): 0.729–0.985) and all-cause mortality (12.86% vs. 13.22% per person-years, (HR): 0.88, 95% (CI): 0.771–0.995) are significantly lower in pioglitazone group. Subgroup analysis found lower MACCEs risk in the pioglitazone users without insulin therapy (6.44% vs. 10.04% (HR): 0.59, 95% (CI): 0.42–0.82) and lower MACCEs related death (2.76% vs. 3.84% (HR): 0.61, 95% (CI): 0.40–0.95) in the pioglitazone group with dyslipidemia, when comparing with DPP4-inhibitors users. Pioglitazone is associated with lower all-cause mortality and MACCEs in diabetic patients with ESRD, compared to DPP4-inhibitors. These benefits were even more significant in the non-insulin users and patients with dyslipidemia.

Naturally-Derived Biomaterials for Tissue Engineering Applications

Naturally-derived biomaterials have been used for decades in multiple regenerative medicine applications. From the simplest cell microcarriers made of collagen or alginate, to highly complex decellularized whole-organ scaffolds, these biomaterials represent a class of substances that is usually first in choice at the time of electing a functional and useful biomaterial. Hence, in this chapter we describe the several naturally-derived biomaterials used in tissue engineering applications and their classification, based on composition. We will also describe some of the present uses of the generated tissues like drug discovery, developmental biology, bioprinting and transplantation.

Antioxidative potential of antidiabetic agents: A possible protective mechanism against vascular complications in diabetic patients

Many vascular complications are related to exposure of tissues to elevated levels of glucose, a condition that promotes oxidative stress. The primary goal of antidiabetic medication is for normalization of blood glucose. However, antidiabetic medications may have antioxidant effects that go beyond their hypoglycemic influences. Therefore, antidiabetic drugs may be doubly beneficial in preventing diabetic complications. Vascular dysfunction due to uncontrolled diabetes is a serious complication of the disease and one which has a severe impact on quality of life. Readjustment of the oxidative balance in subjects with diabetes, and the positive effects thereof is a topic of intense interest at present. In the current review, we highlight the antioxidant effects of antidiabetic medications which may prevent or delay the onset of vascular dysfunction.

Gene expression microarray analysis of the sciatic nerve of mice with diabetic neuropathy

The present study aimed to explore novel target genes that regulate the development of diabetic neuropathy (DN) by analyzing gene expression profiles in the sciatic nerve of infected mice. The GSE11343 microarray dataset, which was downloaded from Gene Expression Omnibus, included data on 4 control samples and 5 samples from mice with diabetes induced by streptozotocin (STZ), 5 samples from normal mice treated with rosiglitazone (Rosi) and 5 samples from mice with diabetes induced by STZ and treated with Rosi. Differentially expressed genes (DEGs) between the different groups were identified using the substitution augmentation modification redefinition (SAMR) model. The Gene Ontology (GO) term and Kyoto Encyclopedia of Genes and Genomes (KEGG) pathway enrichment analyses were performed using the Database for Annotation, Visualization and Integrated Discovery (DAVID). Regulatory and protein‑protein interaction networks were searched using BioCarta and STRING, respectively. The protein structures of potential regulatory genes were predicted using the SYBYL program. Compared with the controls, 1,384 DEGs were identified in the mice with STZ-induced diabetes and 7 DEGs were identified in the mice treated with Rosi. There were 518 DEGs identified between the mice in the STZ + Rosi and STZ groups. We identified 45 GO items, and the calmodulin nerve phosphatase and chemokine signaling pathways were identified as the main pathways. Three genes [myristoylated alanine-rich protein kinase C substrate (Marcks), GLI pathogenesis-related 2 (Glipr2) and centrosomal protein 170 kDa (Cep170)] were found to be co-regulated by both STZ and Rosi, the protein structure of which was predicted and certain binding activity to Rosi was docked. Our study demonstrates that the Marcks, Glipr2 and Cep170 genes may be underlying drug targets in the treatment of DN.

A review on thiazolidinediones and bladder cancer in human studies

There is a concern of an increased risk of bladder cancer associated with the use of thiazolidinediones, a class of oral glucose-lowering drugs commonly used in patients with type 2 diabetes with a mechanism of improving insulin resistance. Human studies on related issues are reviewed, followed by a discussion on potential concerns on the causal inference in current studies. Pioglitazone and rosiglitazone are discussed separately, and findings from different geographical regions are presented. Randomized controlled trials designed for primarily answering such a cancer link are lacking, and evidence from clinical trials with available data for evaluating the association may not be informative. Observational studies have been reported with the use of population-based administrative databases, single-hospital records, drug adverse event reporting system, and case series collection. Meta-analysis has also been performed by six different groups of investigators. These studies showed a signal of higher risk of bladder cancer associated with pioglitazone, especially at a higher cumulative dose or after prolonged exposure; however, a weaker signal or null association is observed with rosiglitazone. In addition, there are some concerns on the causal inference, which may be related to the use of secondary databases, biases in sampling, differential detection, and confounding by indications. Lack of full control of smoking and potential biases related to study designs and statistical approaches such as prevalent user bias and immortal time bias may be major limitations in some studies. Overlapping populations and opposing conclusions in studies using the same databases may be of concern and weaken the reported conclusions of the studies. Because randomized controlled trials are expensive and unethical in providing an answer to this cancer issue, observational studies are expected to be the main source in providing an answer in the future. Furthermore, international comparison studies using well-designed and uniform methodology to clarify the risk in specific sexes, ethnicities, and other subgroups and to evaluate the interaction with other environmental risk factors or medications will be helpful to identify patients at risk.

PPARγ modulates vascular smooth muscle cell phenotype via a protein kinase G-dependent pathway and reduces neointimal hyperplasia after vascular injury

Vascular smooth muscle cells (VSMCs) undergo phenotypic changes in response to vascular injury such as angioplasty. Protein kinase G (PKG) has an important role in the process of VSMC phenotype switching. In this study, we examined whether rosiglitazone, a peroxisome proliferator-activated receptor (PPAR)-γ agonist, could modulate VSMC phenotype through the PKG pathway to reduce neointimal hyperplasia after angioplasty. In vitro experiments showed that rosiglitazone inhibited the phenotype change of VSMCs from a contractile to a synthetic form. The platelet-derived growth factor (PDGF)-induced reduction of PKG level was reversed by rosiglitazone treatment, resulting in increased PKG activity. This increased activity of PKG resulted in phosphorylation of vasodilator-stimulated phosphoprotein at serine 239, leading to inhibited proliferation of VSMCs. Interestingly, rosiglitazone did not change the level of nitric oxide (NO) or cyclic guanosine monophosphate (cGMP), which are upstream of PKG, suggesting that rosiglitazone influences PKG itself. Chromatin immunoprecipitation assays for the PKG promoter showed that the activation of PKG by rosiglitazone was mediated by the increased binding of Sp1 on the promoter region of PKG. In vivo experiments showed that rosiglitazone significantly inhibited neointimal formation after balloon injury. Immunohistochemistry staining for calponin and thrombospondin showed that this effect of rosiglitazone was mediated by modulating VSMC phenotype. Our findings demonstrate that rosiglitazone is a potent modulator of VSMC phenotype, which is regulated by PKG. This activation of PKG by rosiglitazone results in reduced neointimal hyperplasia after angioplasty. These results provide important mechanistic insight into the cardiovascular-protective effect of PPARγ.

Effects of pioglitazone on cardiac ion currents and action potential morphology in canine ventricular myocytes

Despite its widespread therapeutical use there is little information on the cellular cardiac effects of the antidiabetic drug pioglitazone in larger mammals. In the present study, therefore, the concentration-dependent effects of pioglitazone on ion currents and action potential configuration were studied in isolated canine ventricular myocytes using standard microelectrode, conventional whole cell patch clamp, and action potential voltage clamp techniques. Pioglitazone decreased the maximum velocity of depolarization and the amplitude of phase-1 repolarization at concentrations ≥3 μM. Action potentials were shortened by pioglitazone at concentrations ≥10 μM, which effect was accompanied with significant reduction of beat-to-beat variability of action potential duration. Several transmembrane ion currents, including the transient outward K(+) current (Ito), the L-type Ca(2+) current (ICa), the rapid and slow components of the delayed rectifier K(+) current (IKr and IKs, respectively), and the inward rectifier K(+) current (IK1) were inhibited by pioglitazone under conventional voltage clamp conditions. Ito was blocked significantly at concentrations ≥3 μM, ICa, IKr, IKs at concentrations ≥10 μM, while IK1 at concentrations ≥30 μM. Suppression of Ito, ICa, IKr, and IK1 has been confirmed also under action potential voltage clamp conditions. ATP-sensitive K(+) current, when activated by lemakalim, was effectively blocked by pioglitazone. Accordingly, action potentials were prolonged by 10 μM pioglitazone when the drug was applied in the presence of lemakalim. All these effects developed rapidly and were readily reversible upon washout. In conclusion, pioglitazone seems to be a harmless agent at usual therapeutic concentrations.

Outcomes and lessons from the PROactive study

Beyond improvement of glucose control, thiazolidinediones exert pleiotropic effects, which may contribute to some cardiovascular protection. PROactive ("PROspective pioglitAzone Clinical Trial In macroVascular Events") has provided valuable, although controversial, information on the impact of pioglitazone on cardiovascular outcomes in a high-risk population of patients with type 2 diabetes and established macrovascular disease. Since 2005, there has been much debate on the relative value of the statistically non-significant 10% reduction in the quite challenging primary composite endpoint (combining cardiovascular disease-driven and procedural events in all vascular beds) versus the statistically significant 16% decrease in the more robust and conventional main secondary endpoint (all-cause mortality, myocardial infarction, and stroke) observed with pioglitazone. Revisiting PROactive deserves much interest following the report of inconclusive results on cardiovascular efficacy and safety of rosiglitazone in RECORD, the withdrawal (limitation) of rosiglitazone because of cardiovascular safety concern, the recent publication of a statement positioning pioglitazone in type 2 diabetes and the near availability of cheaper generics of pioglitazone. Although subanalyses may have more limited value from a statistical viewpoint, they nonetheless can provide valuable information on the drug efficacy/safety profile and clinical insights into which patients might benefit most (in terms of cardiovascular outcomes) from pioglitazone therapy.

Therapeutic developments in Friedreich ataxia

Friedreich ataxia is an inherited, severe, progressive neuro- and cardiodegenerative disorder for which there currently is no approved therapy. Friedreich ataxia is caused by the decreased expression and/or function of frataxin, a mitochondrial matrix protein that binds iron and is involved in the formation of iron-sulfur clusters. Decreased frataxin function leads to decreased iron-sulfur cluster formation, mitochondrial iron accumulation, cytosolic iron depletion, oxidative stress, and mitochondrial dysfunction. Cloning of the disease gene for Friedreich ataxia and elucidation of many aspects of the biochemical defects underlying the disorder have led to several major therapeutic initiatives aimed at increasing frataxin expression, reversing mitochondrial iron accumulation, and alleviating oxidative stress. These initiatives are in preclinical and clinical development and are reviewed herein.

Can the electrophysiological action of rosiglitazone explain its cardiac side effects?

Recent large clinical trials found an association between the antidiabetic drug rosiglitazone therapy and increased risk of cardiovascular adverse events. The aim of this report is to elucidate the cardiac electrophysiological properties of rosiglitazone (R) on isolated rat and murine ventricular papillary muscle cells and canine ventricular myocytes using conventional microelectrode, whole cell voltage clamp, and action potential (AP) voltage clamp techniques. In histidine-decarboxylase knockout mice as well as in their wild types R (1-30 µM) shortened AP duration at 90% level of repolarization (APD(90)) and increased the AP amplitude (APA) in a concentration-dependent manner. In rat ventricular papillary muscle cells R (1-30 µM) caused a significant reduction of APA and maximum velocity of depolarization (V(max)) which was accompanied by lengthening of APD(90). In single canine ventricular myocytes at concentrations ≥10 µM R decreased the amplitude of phase-1 repolarization, the plateau potential and reduced V(max). R suppressed several ion currents in a concentration-dependent manner under voltage clamp conditions. The EC(50) value for this inhibition was 25.2±2.7 µM for the transient outward K(+ ) current (I(to)), 72.3±9.3 µM for the rapid delayed rectifier K(+ ) current (I(Kr)), and 82.5±9.4 µM for the L-type Ca(2+ ) current (I(Ca)) with Hill coefficients close to unity. The inward rectifier K(+ ) current (I(K1)) was not affected by R up to concentrations of 100 µM. Suppression of I(to), I(Kr), and I(Ca) has been confirmed under action potential voltage clamp conditions as well. The observed alterations in the AP morphology and densities of ion currents may predict serious proarrhythmic risk in case of intoxication with R as a consequence of overdose or decreased elimination of the drug, particularly in patients having multiple cardiovascular risk factors, such as elderly diabetic patients.

Effects of rosiglitazone on the configuration of action potentials and ion currents in canine ventricular cells

BACKGROUND AND PURPOSE

In spite of its widespread clinical application, there is little information on the cellular cardiac effects of the antidiabetic drug rosiglitazone in larger experimental animals. In the present study therefore concentration-dependent effects of rosiglitazone on action potential morphology and the underlying ion currents were studied in dog hearts.

EXPERIMENTAL APPROACH

Standard microelectrode techniques, conventional whole cell patch clamp and action potential voltage clamp techniques were applied in enzymatically dispersed ventricular cells from dog hearts.

KEY RESULTS

At concentrations ≥10 µM rosiglitazone decreased the amplitude of phase-1 repolarization, reduced the maximum velocity of depolarization and caused depression of the plateau potential. These effects developed rapidly and were readily reversible upon washout. Rosiglitazone suppressed several transmembrane ion currents, concentration-dependently, under conventional voltage clamp conditions and altered their kinetic properties. The EC(50) value for this inhibition was 25.2 ± 2.7 µM for the transient outward K(+) current (I(to)), 72.3 ± 9.3 µM for the rapid delayed rectifier K(+) current (I(Kr)) and 82.5 ± 9.4 µM for the L-type Ca(2+) current (I(Ca) ) with Hill coefficients close to unity. The inward rectifier K(+) current (I(K1)) was not affected by rosiglitazone up to concentrations of 100 µM. Suppression of I(to), I(Kr), and I(Ca) was confirmed also under action potential voltage clamp conditions.

CONCLUSIONS AND IMPLICATIONS

Alterations in the densities and kinetic properties of ion currents may carry serious pro-arrhythmic risk in case of overdose with rosiglitazone, especially in patients having multiple cardiovascular risk factors, like elderly diabetic patients.

Opposite effects of pioglitazone and rosiglitazone on mitochondrial respiration in skeletal muscle of patients with type 2 diabetes

AIM

Skeletal muscle insulin resistance has been linked to mitochondrial dysfunction. We examined how improvements in muscular insulin sensitivity following rosiglitazone (ROSI) or pioglitazone (PIO) treatment would affect muscle mitochondrial function in patients with type 2 diabetes mellitus (T2DM).

METHODS

Muscle biopsies were obtained from 21 patients with T2DM before and after 12 weeks on either ROSI (4 mg once daily) [n = 12; age, 59.2 +/- 2.2 years; body mass index (BMI), 29.6 +/- 0.7 kg/m(2)] or PIO (30 mg once daily) (n = 9; age, 56.3 +/- 2.4 years; BMI, 29.5 +/- 1.5 kg/m(2)). An age- and BMI-matched control group was also included (n = 8; age, 61.8 +/- 2.3 years; BMI, 28.4 +/- 0.6 kg/m(2)). Insulin sensitivity, citrate synthase- and beta-hydroxyacyl-CoA-dehydrogenase (HAD) activity, intramuscular triglyceride (IMTG) and protein content of complexes I-IV were measured, while mitochondrial respiration per milligram muscle was measured in saponin-treated skinned muscle fibres using high-resolution respirometry.

RESULTS

Mitochondrial respiration per milligram muscle was lower in T2DM compared to controls at baseline and decreased during ROSI treatment but increased during PIO treatment. Citrate synthase activity and average protein content of complexes I-IV were unchanged in the ROSI group, but protein content of complexes II and III increased during PIO treatment. Insulin sensitivity improved in all patients, but IMTG levels were unchanged.

CONCLUSIONS

We show opposite effects of ROSI and PIO on mitochondrial respiration, and also show that insulin sensitivity can be improved independently of changes in mitochondrial respiration. We confirm that mitochondrial respiration is reduced in T2DM compared to age- and BMI-matched control subjects.

Baseline characteristic differences between patients prescribed sitagliptin vs. other oral antihyperglycemic agents: analysis of a US electronic medical record database

AIMS

This study examined the relationship of baseline characteristics and medication use in patients with type 2 diabetes who were prescribed sitagliptin versus other oral antihyperglycemic agents in clinical practice settings in the United States.

METHODS

The General Electric Healthcare's Clinical Data Services electronic medical record (EMR) database, covering 12 million US patients of all ages from 49 states, was used to identify patients with type 2 diabetes, aged >or=30 years, who received their first sitagliptin, metformin, sulfonylurea, or thiazolidinedione prescription between October 2006 and June 2008 (index period) as part of new mono-, dual, or triple therapy regimens. Patient demographics, diagnoses, prescriptions, and laboratory results were extracted for the 12-month period (baseline) prior to the index date (i.e., date of first prescription). Data were stratified by mono-, dual, or triple therapy and compared between sitagliptin regimens and non-sitagliptin regimens with other oral agents (metformin, sulfonylureas, or thiazolidinediones). Adjusted logistic regression analyses were used to estimate odds ratios (OR) associated with prescribing sitagliptin versus other oral monotherapy in relation to patient baseline characteristics.

RESULTS

Among 41,836 patients new to oral monotherapy, 876 (2.1%) received sitagliptin. Compared to patients initiating non-sitagliptin monotherapy, patients on sitagliptin monotherapy were older (64 vs. 60 years) and had lower body mass index (33 kg/m(2) vs. 34 kg/m(2)), higher serum creatinine (1.2 vs. 1.0 mg/dL), higher prevalence of chronic renal disease (7.2% vs. 1.9%), greater use of lipid-lowering agents (42% vs. 38%), and higher prevalence of cardiovascular conditions (CVD: 12.7% vs. 8.3%) and microvascular complications (MVD: 13.4% vs. 5.8%) (all p < 0.05). Of 22,683 patients new to dual therapy, 1885 (8.3%) were on sitagliptin regimens. Relative to patients on non-sitagliptin dual therapy regimens, patients prescribed sitagliptin as part of dual therapy regimens were older and had higher serum creatinine, higher prevalence of CVD, MVD, or chronic renal disease, and greater use of lipid-lowering and antihypertensive agents (all p < 0.05). Among 9967 patients new to triple therapy, 2828 (28.4%) were on triple therapy regimens with sitagliptin. Relative to patients on non-sitagliptin triple therapy regimens, patients on sitagliptin as part of triple therapy regimens were older, and had higher serum creatinine and greater use of antihypertensive or lipid-lowering agents (all p < 0.05). Adjusted logistic regression showed that significant predictors of being prescribed sitagliptin monotherapy were older age (OR 1.01, 95% CI 1.00, 1.02), higher HbA(1c) level (OR 1.10, 95% CI 1.04, 1.17), higher serum creatinine level (OR 1.22, 95% CI 1.08, 1.39), presence of MVD (OR 1.50, 95% CI 1.08, 2.09), and presence of chronic renal disease (OR 2.22, 95% CI 1.41, 3.49).

LIMITATIONS

Diabetes care delivered by non-participating physicians is not captured in the GE CDS EMR database and, therefore, the prevalence of the diseases identified based on ICD-9 diagnosis/procedure and CPT codes provided in the Appendix may be underestimated. Duration of diabetes was not consistently recorded and some measures were not available.

CONCLUSION

Patients with type 2 diabetes who were prescribed sitagliptin regimens in clinical practice were older and more likely to have pre-existing co-morbid conditions compared to patients receiving non-sitagliptin regimens with other common oral antihyperglycemic agents. These findings have important implications for observational studies in that estimated clinical and health outcome measures may be biased due to channeling of patients to different therapies based on different baseline characteristics.