Peroxisome proliferator-activated receptor agonists and bladder cancer: lessons from animal studies

Thiazolidinedione Use Is Associated with a Borderline Lower Risk of Multiple Myeloma and a Significantly Lower Risk of Death in Patients with Type 2 Diabetes Mellitus in Taiwan

BACKGROUND

Thiazolidinedione (TZD) exerts anti-proliferative effects on multiple myeloma (MM) cells. However, there has not been any human study investigating the risk of MM associated with TZD use.

METHODS

We used Taiwan's National Health Insurance database to identify 423,949 patients who had been newly diagnosed with diabetes mellitus between 1999 and 2005. After excluding ineligible patients, 86,999 pairs of patients with and without the use of TZD (rosiglitazone or pioglitazone) that had been matched based on propensity score were selected for a follow-up for MM until 31 December 2011. The hazard ratios for MM were estimated using Cox regression and weighted using a propensity score.

RESULTS

After a median follow-up of 4.6 years and 4.7 years in ever users and never users of TZD, 32 and 47 cases were diagnosed with MM, respectively. A 35% lower risk (though not statistically significant) was observed among ever users (hazard ratio 0.652, 95% confidence interval: 0.416-1.023, p = 0.0625). When ever users were divided by the median (15 months) cumulative duration of TZD therapy, the hazard ratios (95% confidence interval) for the lower and upper medians were 0.706 (0.394-1.264) and 0.603 (0.346-1.051), respectively. When treated as a continuous variable, the hazard ratio for every 1-month increment of the cumulative duration was 0.980 (95% confidence interval: 0.963-0.997, p = 0.0185). In the age subgroup analysis, a significantly lower risk could be seen in the older age subgroup of ≥65 years (hazard ratio 0.550, 95% confidence interval: 0.305-0.992, p = 0.0468). Additional analyses suggested that there were no interactions between TZD and some medications and between TZD and some clinical diagnoses, and that the use of TZD as a preventive drug for MM might not be cost-effective because a number-needed-to-treat of 5800 was too large. Survival analyses suggested that ever users had a significantly lower risk of death when all patients were analyzed (hazard ratio: 0.84, 95% confidence interval: 0.81-0.87, p < 0.0001 via a log-rank test) or when patients who developed MM were analyzed (hazard ratio: 0.40, 95% confidence interval: 0.19-0.86, p = 0.0153 via a log-rank test).

CONCLUSIONS

In Taiwanese patients with type 2 diabetes mellitus, TZD use is associated with a borderline lower risk of MM, which is more remarkable in patients aged ≥65 years. Because of the low incidence of MM, the use of TZD for the prevention of MM may not be cost-effective. Patients who have been treated with TZD may have a survival advantage. Future research is required to confirm the findings.

Rosiglitazone Does Not Affect the Risk of Inflammatory Bowel Disease: A Retrospective Cohort Study in Taiwanese Type 2 Diabetes Patients

Human studies on the effect of rosiglitazone on inflammatory bowel disease (IBD) are still lacking. We investigated whether rosiglitazone might affect IBD risk by using the reimbursement database of Taiwan's National Health Insurance to enroll a propensity-score-matched cohort of ever users and never users of rosiglitazone. The patients should have been newly diagnosed with diabetes mellitus between 1999 and 2006 and should have been alive on 1 January 2007. We then started to follow the patients from 1 January 2007 until 31 December 2011 for a new diagnosis of IBD. Propensity-score-weighted hazard ratios were estimated with regards to rosiglitazone exposure in terms of ever users versus never users and in terms of cumulative duration and cumulative dose of rosiglitazone therapy for dose-response analyses. The joint effects and interactions between rosiglitazone and risk factors of psoriasis/arthropathies, dorsopathies, and chronic obstructive pulmonary disease/tobacco abuse and the use of metformin were estimated by Cox regression after adjustment for all covariates. A total of 6226 ever users and 6226 never users were identified and the respective numbers of incident IBD were 95 and 111. When we compared the risk of IBD in ever users to that of the never users, the estimated hazard ratio (0.870, 95% confidence interval: 0.661-1.144) was not statistically significant. When cumulative duration and cumulative dose of rosiglitazone therapy were categorized by tertiles and hazard ratios were estimated by comparing the tertiles of rosiglitazone exposure to the never users, none of the hazard ratios reached statistical significance. In secondary analyses, rosiglitazone has a null association with Crohn's disease, but a potential benefit on ulcerative colitis (UC) could not be excluded. However, because of the low incidence of UC, we were not able to perform detailed dose-response analyses for UC. In the joint effect analyses, only the subgroup of psoriasis/arthropathies (-)/rosiglitazone (-) showed a significantly lower risk in comparison to the subgroup of psoriasis/arthropathies (+)/rosiglitazone (-). No interactions between rosiglitazone and the major risk factors or metformin use were observed. We concluded that rosiglitazone has a null effect on the risk of IBD, but the potential benefit on UC awaits further investigation.

Pioglitazone and breast cancer risk in female patients with type 2 diabetes mellitus: a retrospective cohort analysis

Background

Whether pioglitazone may affect breast cancer risk in female diabetes patients is not conclusive and has not been investigated in the Asian populations.

Methods

The reimbursement database of Taiwan’s National Health Insurance was used to enroll an unmatched cohort and a propensity score-matched cohort of ever users and never users of pioglitazone in female patients with newly diagnosed type 2 diabetes during 1999–2008. The patients were alive on January 1, 2009 and were followed up for breast cancer incidence until December 31, 2011. Cox regression was used to estimate hazard ratios for ever users and tertiles of cumulative duration of pioglitazone therapy versus never users, and for cumulative duration of pioglitazone therapy treated as a continuous variable. Three models were created for the unmatched cohort and the matched cohort, respectively: 1) without adjustment for covariates; 2) after adjustment for covariates that differed with statistical significance (P-value < 0.05) between ever users and never users; and 3) after adjustment for all covariates.

Results

There were 174,233 never users and 6926 ever users in the unmatched cohort; and 6926 never users and 6926 ever users in the matched cohort. After a median follow-up of 2.8 years, the numbers of incident breast cancer were 1044 in never users and 35 in ever users in the unmatched cohort and were 41 and 35, respectively, in the matched cohort. Hazard ratios suggested a null association between pioglitazone and breast cancer in all three models in either the unmatched cohort or the matched cohort. The overall hazard ratio after adjustment for all covariates was 0.758 (95% confidence interval: 0.539–1.065) in the unmatched cohort and was 0.824 (95% confidence interval: 0.524–1.296) in the matched cohort. None of the hazard ratios for the tertiles of cumulative duration of pioglitazone therapy and for the cumulative duration being treated as a continuous variable were statistically significant.

Conclusions

This study suggests a null association between pioglitazone and breast cancer risk in female patients with type 2 diabetes mellitus. However, because of the small breast cancer cases and the limited follow-up time, further studies are warranted to confirm our findings.

Pioglitazone, Bladder Cancer and the Presumption of Innocence

BACKGROUND

Thiazolidinediones are potent exogenous agonists of PPAR-γ, which augment the effects of insulin to its cellular targets and mainly at the level of adipose tissue. Pioglitazone, the main thiazolidinedione in clinical practice, has shown cardiovascular and renal benefits in patients with type 2 diabetes, durable reduction of glycated hemoglobulin levels, important improvements of several components of the metabolic syndrome and beneficial effects of non-alcoholic fatty liver disease.

OBJECTIVE

Despite all of its established advantages, the controversy for an increased risk of developing bladder cancer, combined with the advent of newer drug classes that achieved major cardiorenal effects have significantly limited its use spreading a persistent shadow of doubt for its future role.

METHODS

Pubmed, Google and Scope databases have been thoroughly searched and relevant studies were selected.

RESULTS

This paper explores thoroughly both in vitro and in vivo (animal models and humans) studies that investigated the possible association of pioglitazone with bladder cancer.

CONCLUSION

Currently the association of pioglitazone with bladder cancer cannot be based on solid evidence. This evidence cannot justify its low clinical administration, especially in the present era of individualised treatment strategies. Definite clarification of this issue is imperative and urgently anticipated from future high quality and rigorous pharmacoepidemiologic research, keeping in mind its unique mechanism of action and its significant pleiotropic effects.

Pioglitazone and Risk of Chronic Obstructive Pulmonary Disease in Patients with Type 2 Diabetes Mellitus: A Retrospective Cohort Study

Background

Pioglitazone’s effect on chronic obstructive pulmonary disease (COPD) has rarely been studied.

Purpose

This retrospective observational study investigated whether the use of pioglitazone would affect the risk of COPD in patients with type 2 diabetes mellitus.

Patients and Methods

The Taiwan’s National Health Insurance database was used to enroll 9487 matched pairs of ever users and never users of pioglitazone based on propensity score from a cohort of 350,536 patients. The enrolled patients had a new diagnosis of type 2 diabetes mellitus between 1999 and 2008 and were not having a diagnosis of COPD before January 1, 2009. They were then followed up for COPD, starting from January 1, 2009 until December 31, 2011. Diagnosis of COPD was based on the codes of 491 for chronic bronchitis and 492 for emphysema based on the International Classification of Diseases, Ninth Revision, Clinical Modification. Cox regression was used to estimate hazard ratios. The interactions between pioglitazone and COPD risk factors including pneumonia, pulmonary tuberculosis and tobacco abuse were also investigated.

Results

In 9487 never users and 9487 ever users of pioglitazone, the case numbers of incident COPD were 359 and 295, respectively. The respective incidence rates of COPD were 1484.73 and 1167.61 per 100,000 person-years. The overall hazard ratio (95% confidence interval) for COPD that compared ever to never users was 0.778 (0.667–0.908). The hazard ratios for the tertiles of cumulative duration of pioglitazone therapy (cutoffs: <11.0, 11.0–19.6 and >19.6 months) to never users were 0.904 (0.729–1.121), 0.727 (0.578–0.914) and 0.715 (0.570–0.896), respectively. No interactions between pioglitazone and COPD risk factors including pneumonia, pulmonary tuberculosis and tobacco abuse were noted.

Conclusion

Pioglitazone use is associated with a significantly lower risk of COPD.

Lobeglitazone: A Novel Thiazolidinedione for the Management of Type 2 Diabetes Mellitus

Type 2 diabetes mellitus (T2DM) is characterized by insulin resistance and β-cell dysfunction. Among available oral antidiabetic agents, only the thiazolidinediones (TZDs) primarily target insulin resistance. TZDs improve insulin sensitivity by activating peroxisome proliferator-activated receptor γ. Rosiglitazone and pioglitazone have been used widely for T2DM treatment due to their potent glycemic efficacy and low risk of hypoglycemia. However, their use has decreased because of side effects and safety issues, such as cardiovascular concerns and bladder cancer. Lobeglitazone (Chong Kun Dang Pharmaceutical Corporation), a novel TZD, was developed to meet the demands for an effective and safe TZD. Lobeglitazone shows similar glycemic efficacy to pioglitazone, with a lower effective dose, and favorable safety results. It also showed pleiotropic effects in preclinical and clinical studies. In this article, we summarize the pharmacologic, pharmacokinetic, and clinical characteristics of lobeglitazone.

A Contemporary Overview of PPARα/γ Dual Agonists for the Management of Diabetic Dyslipidemia

Background:

Diabetes mellitus and concomitant dyslipidemia, being referred to as ‘diabetic dyslipidemia’, are the foremost detrimental factors documented to play a pivotal role in cardiovascular illness. Diabetic dyslipidemia is associated with insulin resistance, high plasma triglyceride levels, low HDL-cholesterol concentration and elevated small dense LDL-cholesterol particles. Maintaining an optimal glucose and lipid levels in patients afflicted with diabetic dyslipidemia could be a major task that might require a well-planned diet-management system and regular physical activity, or otherwise an intake of combined antidiabetic and antihyperlipidemic medications. Synchronized treatment which efficiently controls insulin resistance-associated diabetes mellitus and co-existing dyslipidemia could indeed be a fascinating therapeutic option in the management of diabetic dyslipidemia. Peroxisome proliferator-activated receptors α/γ (PPARα/γ) dual agonists are such kind of drugs which possess therapeutic potentials to treat diabetic dyslipidemia. Nevertheless, PPARα/γ dual agonists like muraglitazar, naveglitazar, tesaglitazar, ragaglitazar and aleglitazar have been reported to have undesirable adverse effects, and their developments have been halted at various stages. On the other hand, a recently introduced PPARα/γ dual agonist, saroglitazar is an emerging therapeutic agent of glitazar class approved in India for the management of diabetic dyslipidemia, and its treatment has been reported to be generally safe and well tolerated.

Conclusion:

Some additional and new compounds, at initial and preclinical stages, have been recently reported to possess PPARα/γ dual agonistic potentials with considerable therapeutic efficacy and reduced adverse profile. This review sheds light on the current status of various PPARα/γ dual agonists for the management of diabetic dyslipidemia.

DHCR24 predicts poor clinicopathological features of patients with bladder cancer: A STROBE-compliant study

To investigate the prognostic value of DHCR24 for patients with bladder cancer (BC). We used public bladder cancer microarray studies to evaluate the expression of DHCR24 between normal bladder tissues and BC cells, to investigate the relationship between the expression of DHCR24 and the clinical features of BC patients. Survival analysis was performed to investigate the correlation between DHCR24 expression and the survivals of BC patients. Gene set enrichment analysis was conducted to identify relevant mechanisms. The results showed that DHCR24 was up-regulated in BC cells compared with that in normal bladder tissues (P = .0389). Results of chi-square test suggested that BC patients in DHCR24 low expression group were proved to have better clinical characteristics (including tumor grade, disease progression, T staging, and N staging) as compared with those in DHCR24 low expression group (P < .0001, P = .002, P = .005, and P = .002, respectively). BC patients in DHCR24 low expression group were associated with better cancer-specific survival and overall survival (P < .0001 and P = .0008, respectively). DHCR24 might promote the proliferation of BC cells through several oncogenesis-associated biological processes (estrogen response, heme metabolism, P53 pathway, cholesterol homeostasis, mTORC1 signaling, peroxisome, xenobiotic metabolism, glycolysis, and protein secretion). Thus, DHCR24 might be a therapeutic target for patients with BC.

Opposite Interplay Between the Canonical WNT/β-Catenin Pathway and PPAR Gamma: A Potential Therapeutic Target in Gliomas

In gliomas, the canonical Wingless/Int (WNT)/β-catenin pathway is increased while peroxisome proliferator-activated receptor gamma (PPAR-γ) is downregulated. The two systems act in an opposite manner. This review focuses on the interplay between WNT/β-catenin signaling and PPAR-γ and their metabolic implications as potential therapeutic target in gliomas. Activation of the WNT/β-catenin pathway stimulates the transcription of genes involved in proliferation, invasion, nucleotide synthesis, tumor growth, and angiogenesis. Activation of PPAR-γ agonists inhibits various signaling pathways such as the JAK/STAT, WNT/β-catenin, and PI3K/Akt pathways, which reduces tumor growth, cell proliferation, cell invasiveness, and angiogenesis. Nonsteroidal anti-inflammatory drugs, curcumin, antipsychotic drugs, adiponectin, and sulforaphane downregulate the WNT/β-catenin pathway through the upregulation of PPAR-γ and thus appear to provide an interesting therapeutic approach for gliomas. Temozolomide (TMZ) is an antiangiogenic agent. The downstream action of this opposite interplay may explain the TMZ-resistance often reported in gliomas.

Rosiglitazone reduces breast cancer risk in Taiwanese female patients with type 2 diabetes mellitus

This study investigated whether rosiglitazone may affect breast cancer risk in female patients with type 2 diabetes mellitus in Taiwan. The reimbursement database of all female patients with type 2 diabetes mellitus under oral antidiabetic agents or insulin from 1996 to 2009 was retrieved from the National Health Insurance. An entry date was set on 1 January 2006 and a total of 431447 patients were followed up for breast cancer incidence till the end of 2009. Incidences for ever users, never users and subgroups of rosiglitazone dose-response parameters (tertile cutoffs of cumulative duration and cumulative dose) were calculated and hazard ratios estimated by Cox regression. There were 53029 ever users and 378418 never users, respective numbers of incident breast cancer 410 (0.77%) and 3292 (0.87%), and respective incidence 217.53 and 249.12 per 100000 person-years. The overall hazard ratio was 0.889 (95% confidence interval: 0.797−0.992) in the fully adjusted model. Significantly lower risk was observed for the third tertiles of cumulative duration (> 14 months) and cumulative dose (> 1792 mg) while compared to never users, with respective adjusted hazard ratio of 0.815 (95% confidence interval: 0.682−0.973) and 0.815 (95% confidence interval: 0.682−0.974). Additionally, a significant interaction between metformin and rosiglitazone was observed. The lowest risk was seen in patients who used both drugs (hazard ratio 0.812, 95% confidence interval: 0.705−0.934). In conclusion, rosiglitazone reduces breast cancer risk in female patients with type 2 diabetes mellitus, which shows a significant interaction with metformin.

Sitagliptin may reduce prostate cancer risk in male patients with type 2 diabetes

This retrospective cohort study evaluated the risk of prostate cancer associated with sitagliptin use in Taiwanese male patients with type 2 diabetes mellitus by using the reimbursement databases of the National Health Insurance. Male patients with newly diagnosed type 2 diabetes mellitus at an age ≥25 years between 1999 and 2010 were recruited. A total of 37,924 ever users of sitagliptin and 426,276 never users were followed until December 31, 2011. The treatment effect of sitagliptin (for ever versus never users, and for tertiles of cumulative duration of therapy) was estimated by Cox regression incorporated with the inverse probability of treatment weighting using propensity score. Analyses were also conducted in a 1:1 matched pair cohort based on 8 digits of propensity score. Results showed that during follow-up, 84 ever users and 2,549 never users were diagnosed of prostate cancer, representing an incidence of 140.74 and 240.17 per 100,000 person-years, respectively. The hazard ratio (95% confidence intervals) for ever users versus never users was 0.613 (0.493-0.763). The respective hazard ratio for the first, second, and third tertile of cumulative duration of sitagliptin use <5.9, 5.9-12.7 and >12.7 months was 0.853 (0.601-1.210), 0.840 (0.598-1.179) and 0.304 (0.191-0.483), respectively; and was 0.856 (0.603-1.214), 0.695 (0.475-1.016) and 0.410 (0.277-0.608) for cumulative dose <15,000, 15,000-33,600 and >33,600 mg, respectively. Findings were supported by analyses in the matched cohort. In conclusion, sitagliptin significantly reduces the risk of prostate cancer, especially when the cumulative duration is >12.7 months or the cumulative dose >33,600 mg.

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.

Peroxisome proliferator-activated receptor (PPAR) α and δ activators induce ICAM-1 expression in quiescent non stimulated endothelial cells

Background

Peroxisome proliferator-activated receptors (PPARs) are ligand-activated transcription factors that are implicated in the regulation of lipid and glucose homeostasis. PPAR agonists have been shown to control inflammatory processes, in part by inhibiting the expression of distinct proinflammatory genes such as vascular cell adhesion molecule-1 (VCAM-1), IL-8, and intercellular adhesion molecule-1 (ICAM-1). ICAM-1 is an important endothelial membrane receptor that facilitates the transmigration of leukocytes across the endothelium. To date, the influence of PPARα and δ activators on the expression of ICAM-1 in non-induced, quiescent endothelial cells has been unclear. Therefore, we examined the effects of various PPARα and δ agonists on the expression of ICAM-1 in non-stimulated primary human endothelial cells.

Results

We found that PPARα and PPARδ agonists significantly induced ICAM-1 surface, intracellular protein, and mRNA expression in a time and concentration-dependent manner. The PPARδ induced ICAM-1 expression could be paralleled with a significantly increased T-cell adherence to the endothelial cells whereas PPARα failed to do so. Transcriptional activity studies using an ICAM-1 reporter gene constructs revealed that PPARδ, but not PPARα agonists induced gene expression by stimulating ICAM-1 promoter activity via an Sp1 transcription factor binding site and inhibit the binding of the transcription factors Sp1 and Sp3. Furthermore, we performed mRNA stability assays and found that PPARα and PPARδ agonists increased ICAM-1 mRNA stability.

Conclusion

Therefore, our data provide the first evidence that PPARα and PPARδ agonists induce ICAM-1 expression in non-stimulated endothelial cells via transcriptional and posttranscriptional mechanisms.

Pioglitazone does not increase the risk of type II diabetes in patients with bladder cancer: A retrospective study

The aim of the retrospective study was to analyze the effect of pioglitazone on the expression of tumor tissue inflammation factor interleukin (IL)-8, macrophage colony-stimulating factor (M-CSF) and vascular endothelial growth factor (VEGF) of type II diabetes in bladder cancer patients. In addition, whether there was a correlation between pioglitazone and the occurrence of male bladder cancer was also investigated. In total, 42 male cases diagnosed with type II diabetes secondary to bladder cancer were selected. Forty male cases, with simplex type II diabetes but not with bladder cancer, served as the control. Tumor biopsy specimens were collected to detect the expression levels of IL-8, M-CSF and VEGF. The results showed that the expression of IL-8, M-CSF and VEGF of the simplex diabetes group was significantly lower than that of the secondary to tumor group (P<0.05). The comparison of the two groups in terms of daily dose and time of oral pioglitazone, duration of diabetes, average fasting blood sugar and glycated hemoglobin levels, was not statistically significant. Multivariable logistic regression analysis revealed that the expression levels of IL-8, M-CSF and VEGF were independent risk factors for the occurrence of bladder cancer (P<0.05), but were not associated with daily dose and time of oral pioglitazone (P>0.05). In conclusion, oral pioglitazone may not increase the risk of type II diabetes patients with bladder cancer. However, the occurrence of bladder cancer be associated with the increasing expression levels of IL-8, M-CSF and VEGF.

Assessing Bladder Cancer Risk in Type 2 Diabetes Clinical Trials: the Dapagliflozin Drug Development Program as a 'Case Study'

INTRODUCTION

Dapagliflozin, a sodium-glucose co-transporter 2 inhibitor, decreases plasma glucose levels by suppressing renal glucose reabsorption and increasing urinary glucose excretion. Previously published pre-clinical data suggest that dapagliflozin lacks carcinogenic potential. This article reviews data on bladder cancer with dapagliflozin to illustrate the challenges in assessing bladder cancer in drug development programs in patients with type 2 diabetes mellitus (T2DM).

METHODS

Clinical cases of bladder cancer were analyzed in a pooled population of >9000 patients in 21 phase 2b/3 dapagliflozin clinical trials of up to 208 weeks' duration.

RESULTS

In the 21-study pool, demographic and baseline characteristics were generally consistent between dapagliflozin and comparator groups. The overall incidence of malignancies was also balanced between the treatment groups, with an incidence rate ratio (IRR) of 1.035 [95% confidence interval (CI): 0.724, 1.481]. Nine of 5936 dapagliflozin-treated patients and 1 of 3403 comparator-treated patients reported bladder cancer, with an IRR of 5.168 (95% CI: 0.677, 233.55). All of these patients had clinical attributes typical of bladder cancer in the general population (≥60-year-old males; 8 of the 10 patients were current/former smokers). All cases of bladder cancer were reported within 2 years of starting study treatment. There was an absence of detailed workup of hematuria prior to randomization, and no hematuria workup data were collected proactively in the dapagliflozin trials, which is typical of clinical practice. Failure to exclude bladder cancer prior to randomization increases the chance of recruiting patients with pre-existing bladder cancer in clinical trials and may delay the final diagnosis. Of the nine dapagliflozin-treated patients with bladder cancer, eight had microscopic hematuria prior to start of treatment or within 6 months of initiating study treatment.

CONCLUSION

The assessment of bladder cancer data illustrates the challenges of characterizing cancer risk in T2DM drug development programs. The totality of evidence to date does not suggest a causal relationship between dapagliflozin and bladder cancer.

FUNDING

AstraZeneca.

Polemics of pioglitazone: an appraisal in 2015

Pioglitazone is an inexpensive and effective oral drug for the treatment of Type 2 diabetes. It addresses insulin resistance, one of the core pathophysiological defects in Type 2 diabetes, at both the adipose tissue and skeletal muscle level. As a majority of Type 2 diabetics classically exhibit higher insulin resistance, pioglitazone may strike exactly at the Achilles heel in this core pathogenesis. However, with the emerging association of bladder cancer with pioglitazone, French and German regulators were the first to ban or restrict pioglitazone use in 2011. The Indian regulators also suspended pioglitazone, although this ban was revoked within a month. Recently, a 10-year longitudinal study commissioned by US FDA found no association between bladder cancer and pioglitazone. Nevertheless, this controversy created a huge outcry in the medical fraternity. This review article is an overview of the development of this topic and an attempt to provide perspective on this contemporary issue.

Antiproliferative effects and molecular mechanisms of troglitazone in human cervical cancer in vitro

We investigated the effects of troglitazone on human cervical cancer SiHa cells and its mechanisms of action. SiHa cells were incubated with different concentrations of troglitazone (100, 200, or 400 μg/mL) for 24, 48, and 72 hours. Cell viability was measured by 3-(4,5-dimethylthiazol-2-yl) 2,5-diphenyltetrazolium bromide (MTT) assay; cell cycle and apoptosis were detected by flow cytometry; and morphology of SiHa cells was observed under an inverted microscope. pcDNA3.1 and pcDNA3.1-Skp2 plasmids were constructed and then transfected into SiHa cells. Protein expression was analyzed by Western blotting. Troglitazone inhibited the proliferation of SiHa cells in a time- and concentration-dependent manner. Troglitazone caused G0/1 phase arrest but failed to reduce apoptosis in SiHa cells. Troglitazone significantly increased expression of p27 but decreased Skp2 expression. Skp2 overexpression inhibited the role of troglitazone in increasing expression of p27, and the cell cycle inhibitory effect of troglitazone. Troglitazone can inhibit SiHa cell viability by affecting cell cycle distribution but not apoptosis, and Skp2 and p27 may play a critical role.

Neuroprotective and anti-inflammatory properties of a novel non-thiazolidinedione PPARγ agonist in vitro and in MPTP-treated mice

Peroxisome proliferator-activated receptor (PPAR)γ is a potential pharmacological target for disease-modification in Parkinson's disease (PD), mainly acting by modulating the neuroinflammatory response. However, currently available agonists thiazolidinediones (TZDs) present limitations due to safety concerns. We evaluated a novel thiobarbituric-like compound MDG548, which acts as a functional PPARγ agonist displaying higher and selective binding affinity as compared to TZDs. Neuroprotection by MDG548 was tested in vitro and in a mouse MPTP model of PD, and neuroinflammation was investigated as a putative underlying mechanism. Viability assay on rat cortical neurons showed lack of cytotoxic effect in the dose-range of 100 nM-10 μM, which was therefore used for testing in vitro protection against H2O2 and MPP+ neurotoxicity. MDG548 dose-dependently increased cell viability of rat cortical neurons co-treated with H2O2 or pre-exposed to MDG548 prior to H2O2. Moreover, MDG548 induced neuroprotection in MPP+-treated PC12 cells. NF-kB activation was investigated to assess anti-inflammatory activity. MDG548 dose-dependently decreased NF-kB activation induced by LPS (100 ng/100ml) in HEK-Blue-hTLR4 cells. Given the supposed cancer risk of other PPARγ agonists, Ames test for genotoxicity was performed in Salmonella typhimurium TA100 and TA98 strains, showing that MDG548 was not genotoxic. In vivo, BL/6J mice were treated with MPTP (20mg/kg i.p. once/day for 4 days) in association with saline or MDG548 (2, 5, 10 mg/kg i.p.). Stereological counting showed that MDG548 prevented the MPTP-induced reduction in TH-positive cells in the substantia nigra compacta (SNc) at all doses tested. Moreover, MDG548 reduced reactive microglia and iNOS induction in the SNc. MDG548, being a non-TZD compound with high PPARγ affinity, void of genotoxicity, and with in vitro as well as in vivo neuroprotective properties, provides a promising alternative in the search for safer PPARγ agonists to be tested as potential disease-modifying drugs in PD.

Rosiglitazone may reduce non-melanoma skin cancer risk in Taiwanese

Background

Whether rosiglitazone may affect the risk of non-melanoma skin cancer (NMSC) has not been investigated.

Methods

The reimbursement databases of all Taiwanese diabetic patients from 1996 to 2009 were retrieved from the National Health Insurance. An entry date was set at 1 January 2006 and a total of 886418 patients with type 2 diabetes were followed up for NMSC incidence until the end of 2009. Incidences for ever-users, never-users and subgroups of rosiglitazone exposure (using tertile cutoffs of duration of therapy and cumulative dose) were calculated and hazard ratios estimated by Cox regression. Additional models were created as sensitivity analyses.

Results

There were 103097 ever-users and 783321 never-users, respective numbers of incident NMSC 250 (0.24%) and 2084 (0.27%), and respective incidence 68.90 and 76.77 per 100000 person-years. Although the overall hazard ratio was not significant in the unadjusted, age-sex-adjusted or fully adjusted model, the risk was significantly lower in the third tertile of duration of therapy and cumulative dose, with significant P for trends. The fully adjusted hazard ratio (95% confidence interval) for a duration of therapy >13.77 months and a cumulative dose of >1752 mg was 0.723 (0.566, 0.923) and 0.783 (0.618, 0.993), respectively. The findings were supported by various sensitivity analyses.

Conclusions

Rosiglitazone may reduce the risk of NMSC, but further confirmation is required.

An updated review on cancer risk associated with incretin mimetics and enhancers

Incretin-based therapies, including the use of incretin mimetics of glucagon-like peptide-1 receptor (GLP-1R) agonists and incretin enhancers of dipeptidyl-peptidase 4 (DPP-4) inhibitors, are widely used by clinicians for glucose lowering in patients with type 2 diabetes mellitus. These agents have benefits of a lower risk of hypoglycemia, being neutral for body weight for DPP-4 inhibitors and having a potential for weight reduction with GLP-1R agonists. They may also have a neutral or beneficial cardiovascular effect. Despite these benefits, an increased risk of cancer (especially pancreatic cancer and thyroid cancer) associated with incretin-based therapies has been reported. In this article, we reviewed related literature of experimental animal and observational human studies, clinical trials, and meta-analyses published until December 15, 2014. Current studies suggested a probable role of GLP-1R activation on the development of pancreatic cancer and thyroid cancer in rodents, but such an effect in humans is not remarkable due to the lower or lack of expression of GLP-1R on human pancreatic ductal cells and thyroid tissues. Findings in human studies are controversial and inconclusive. In the analyses of the US Food and Drug Administration adverse events reporting system, a significantly higher risk of pancreatic cancer was observed for GLP-1R agonists and DPP-4 inhibitors, but a significantly higher risk of thyroid cancer was only observed for GLP-1R agonists. Such a higher risk of pancreatic cancer or thyroid cancer could not be similarly demonstrated in other human observational studies or analyses of data from clinical trials. With regards to cancers other than pancreatic cancer and thyroid cancer, available studies supported a neutral association in humans. Some preliminary studies even suggested a potentially beneficial effect on the development of other cancers with the use of incretins. Based on current evidence, continuous monitoring of the cancer issues related to incretin-based therapies is required, even though the benefits may outweigh the potential cancer risk in the general patients with type 2 diabetes mellitus.

Metformin reduces thyroid cancer risk in Taiwanese patients with type 2 diabetes

Background

Whether metformin may affect thyroid cancer risk has not been studied. This study investigated the association between metformin use and thyroid cancer risk in Taiwanese patients with type 2 diabetes mellitus.

Methods

The reimbursement databases of all diabetic patients from 1996 to 2009 were retrieved from the National Health Insurance. An entry date was set at 1 January 2006 and 1,414,723 patients with type 2 diabetes were followed for thyroid cancer incidence until the end of 2009. Incidences for ever-users, never-users and subgroups of metformin exposure using tertile cutoffs for cumulative duration of therapy and cumulative dose were calculated and adjusted hazard ratios were estimated by Cox regression. Additional sensitivity analyses were conducted.

Results

There were 795,321 ever-users and 619,402 never-users, with respective numbers of incident thyroid cancer of 683 (0.09%) and 1,614 (0.26%), and respective incidence of 24.09 and 87.33 per 100,000 person-years. The overall fully adjusted hazard ratio (95% confidence interval) was 0.683 (0.598–0.780), and all categories of the dose-response parameters showed significantly lower risk with P-trends <0.0001. The protective effect of metformin on thyroid cancer incidence was also supported by sensitivity analyses, disregarding age (<50 or ≥50 years) and sex; and was not affected by excluding users of insulin, sulfonylurea, and insulin and/or sulfonylurea respectively, by previous diagnosis of other cancers or by potential detection examinations that might lead to differential diagnosis of thyroid cancer.

Conclusions

This study provides evidence for the first time that metformin use in patients with type 2 diabetes may reduce the risk of thyroid cancer.

Thiazolidinediones and the promise of insulin sensitization in type 2 diabetes

Type 2 diabetes is caused by insulin resistance coupled with an inability to produce enough insulin to control blood glucose, and thiazolidinediones (TZDs) are the only current antidiabetic agents that function primarily by increasing insulin sensitivity. However, despite clear benefits in glycemic control, this class of drugs has recently fallen into disuse due to concerns over side effects and adverse events. Here we review the clinical data and attempt to balance the benefits and risks of TZD therapy. We also examine potential mechanisms of action for the beneficial and harmful effects of TZDs, mainly via agonism of the nuclear receptor PPARγ. Based on critical appraisal of both preclinical and clinical studies, we discuss the prospect of harnessing the insulin sensitizing effects of PPARγ for more effective, safe, and potentially personalized treatments of type 2 diabetes.

Thiazolidinediones under preclinical and early clinical development for the treatment of Parkinson's disease

INTRODUCTION

Current treatment of Parkinson's disease (PD) is limited to symptomatic dopaminergic therapy, while no interventions have been shown to slow down disease progression.

AREAS COVERED

The following article highlights a group of PPAR-γ agonists called thiazolidinediones (TZDs), which are currently being tested for a putative disease-modifying benefit in PD, using pioglitazone as a prototypic compound. PPAR-γ is highly expressed in neurons of the substantia nigra and CNS immune cells. Preclinical data in rodent and primate support an effect of TZDs in preventing and/or arresting neurodegeneration and development of motor symptoms. Although no data on the neuroprotective effect of TZDs is currently available, a clinical trial is ongoing where the primary objective is to assess pioglitazone's impact on the progression of PD. The trial is also evaluating the drug's safety concerns.

EXPERT OPINION

The efficacy data from clinical trials must be carefully weighed against the safety concerns. However, given the solid preclinical data, and since the safety data are not yet fully conclusive and limited to the diabetic population, PPAR-γ research in PD can continue with caution. Ideally, drug discovery and development efforts will lead to the identification of new compounds with reduced risk of peripheral side effects.

Pioglitazone does not affect the risk of kidney cancer in patients with type 2 diabetes

OBJECTIVE

To investigate whether pioglitazone treatment of patients with type 2 diabetes mellitus was associated with an increased risk of kidney cancer.

METHODS

The reimbursement databases of all Taiwanese patients with type 2 diabetes who received oral anti-diabetic agents or insulin from 1996 to 2009 were retrieved from the National Health Insurance. An entry date was set at 1 January 2006, and a total of 1,093,675 patients with type 2 diabetes were followed up for kidney cancer incidence until the end of 2009. The incidences of kidney cancer among patients who had and had not received pioglitazone, as well as among subgroups of those treated with pioglitazone (sorted by time since starting pioglitazone, duration of treatment and cumulative dose) were calculated and hazard ratios (HRs) estimated by Cox regression analysis.

RESULTS

Of the 1,093,675 patients, 58,172 (5.3%) had and 1,035,503 (94.7%) had not received pioglitazone, with incident kidney cancer developing in 208 (0.36%) and 3304 (0.32%) patients, respectively, and a respective incidence of 97.7 and 90.5 per 100,000 person-years. Pioglitazone and kidney cancer were not significantly associated in unadjusted (HR 1.04; 95% confidence interval (CI), 0.90-1.20), age-sex-adjusted (HR 1.09; 95% CI, 0.95-1.25), and fully adjusted (HR 1.09; 95% CI, 0.94-1.26) models. None of the dose-response parameters showed a significant trend of risk association, with all P-trends >0.10.

CONCLUSIONS

Pioglitazone does not affect the risk of kidney cancer.

Biomimetic urothelial tissue models for the in vitro evaluation of barrier physiology and bladder drug efficacy

The bladder is an important tissue in which to evaluate xenobiotic drug interactions and toxicities due to the concentration of parent drug and hepatic/enteric-derived metabolites in the urine as a result of renal excretion. Breaching of the barrier provided by the bladder epithelial lining (the urothelium) can expose the underlying tissues to urine and cause harmful effects (e.g., cystitis or cancer). Human urothelium is most commonly represented in vitro as immortalized or established cancer-derived cell lines, but the compromised ability of such cells to undergo differentiation and barrier formation means that nonimmortalized, normal human urothelial (NHU) cells provide a more relevant cell culture system. The impressive capacity for urothelial self-renewal in vivo can be harnessed in vitro to generate experimentally-useful quantities of NHU cells, which can subsequently be differentiated to form a functional or "biomimetic" urothelium. When seeded onto permeable membranes, these barrier-forming human urothelial tissue models enable the modeling of serum and luminal (intravesical) exposure to drugs and metabolites, thus supporting efficacy/toxicity assessments. Biomimetic human urothelial constructs provide a potential step along the preclinical trail and may support the extrapolation from rodent in vivo data to determine human relevance. Early evidence is beginning to demonstrate that human urothelium in vitro can provide information that supersedes conventional rodent studies, but further validation is needed to support widespread adoption.

Metformin may reduce bladder cancer risk in Taiwanese patients with type 2 diabetes

Whether metformin therapy affects bladder cancer risk in patients with type 2 diabetes mellitus (T2DM) has not been extensively investigated. The reimbursement databases of all Taiwanese patients with a new diagnosis of T2DM between 1998 and 2002 (n = 940,708) were retrieved from the National Health Insurance for follow-up of bladder cancer up to the end of 2009. Metformin was treated as a time-dependent variable, and of these patients, 532,519 were never-users and 408,189 were ever-users of metformin. A time-dependent approach was applied in the calculation of bladder cancer incidence and in the estimation of hazard ratios by Cox regression for ever-users, never-users, and subgroups of metformin exposure (using tertile cutoffs of cumulative duration of therapy and cumulative dose). During the study period, 1,847 (0.45%) metformin ever-users and 6,213 (1.17%) metformin never-users developed bladder cancer, representing an incidence of 72.03 and 189.22 per 100,000 person-years, respectively. The age-sex-adjusted and multivariable-adjusted hazard ratios (95% confidence intervals) for ever- versus never-users were 0.382 (0.360-0.405) and 0.600 (0.564-0.638), respectively. The multivariable-adjusted hazard ratios for the first, second, and third tertiles of cumulative duration of metformin therapy were 1.034 (0.954-1.120), 0.696 (0.632-0.766), and 0.258 (0.229-0.291), respectively (P trend <0.0001). Similarly, the multivariable-adjusted hazard ratios for the first, second, and third tertiles of cumulative dose of metformin were 0.997 (0.920-1.080), 0.615 (0.559-0.677), and 0.285 (0.253-0.321), respectively (P trend <0.0001). This study suggests that metformin use is associated with a decreased risk of bladder cancer in patients with T2DM.

Biological Rationale for the Use of PPARγ Agonists in Glioblastoma

Glioblastoma multiforme (GBM) is the most common primary intrinsic central nervous system tumor and has an extremely poor overall survival with only 10% patients being alive after 5 years. There has been interesting preliminary evidence suggesting that diabetic patients receiving peroxisome proliferator-activated receptor gamma (PPARγ) agonists, a group of anti-diabetic, thiazolidinedione drugs, have an increased median survival for glioblastoma. Although thiazolidinediones are effective oral medications for type 2 diabetes, certain agonists carry the risk for congestive heart failure, myocardial infarction, cardiovascular disease, bone loss, weight gain, and fluid retention as side-effects. The nuclear receptor transcription factor PPARγ has been found to be expressed in high grade gliomas, and its activation has been shown to have several antineoplastic effects on human and rat glioma cell lines, and in some instances an additional protective increase in antioxidant enzymes has been observed in normal astrocytes. At present, no clinical trials are underway with regards to treating glioma patients using PPARγ agonists. This review presents the case for evaluating the potential of PPARγ agonists as novel adjuvants in the treatment of refractory high grade glioma.

Diabetes and gastric cancer: The potential links

This article reviews the epidemiological evidence linking diabetes and gastric cancer and discusses some of the potential mechanisms, confounders and biases in the evaluation of such an association. Findings from four meta-analyses published from 2011 to 2013 suggest a positive link, which may be more remarkable in females and in the Asian populations. Putative mechanisms may involve shared risk factors, hyperglycemia, Helicobacter pylori (H. pylori) infection, high salt intake, medications and comorbidities. Diabetes may increase the risk of gastric cancer through shared risk factors including obesity, insulin resistance, hyperinsulinemia and smoking. Hyperglycemia, even before the clinical diagnosis of diabetes, may predict gastric cancer in some epidemiological studies, which is supported by in vitro, and in vivo studies. Patients with diabetes may also have a higher risk of gastric cancer through the higher infection rate, lower eradication rate and higher reinfection rate of H. pylori. High salt intake can act synergistically with H. pylori infection in the induction of gastric cancer. Whether a higher risk of gastric cancer in patients with diabetes may be ascribed to a higher intake of salt due to the loss of taste sensation awaits further investigation. The use of medications such as insulin, metformin, sulfonylureas, aspirin, statins and antibiotics may also influence the risk of gastric cancer, but most of them have not been extensively studied. Comorbidities may affect the development of gastric cancer through the use of medications and changes in lifestyle, dietary intake, and the metabolism of drugs. Finally, a potential detection bias related to gastrointestinal symptoms more commonly seen in patients with diabetes and with multiple comorbidities should be pointed out. Taking into account the inconsistent findings and the potential confounders and detection bias in previous epidemiological studies, it is expected that there are still more to be explored for the clarification of the association between diabetes and gastric cancer.

Human insulin does not increase bladder cancer risk

Background

Whether human insulin can induce bladder cancer is rarely studied.

Methods

The reimbursement databases of all Taiwanese diabetic patients from 1996 to 2009 were retrieved from the National Health Insurance. An entry date was set at 1 January 2004 and a total of 785,234 patients with type 2 diabetes were followed up for bladder cancer incidence until the end of 2009. Users of pioglitazone were excluded and the period since the initiation of insulin glargine (marketed after the entry date in Taiwan) was not included in the calculation of follow-up. Incidences for ever-users, never-users and subgroups of human insulin exposure (using tertile cutoffs of time since starting insulin, duration of therapy and cumulative dose) were calculated and the hazard ratios were estimated by Cox regression.

Results

There were 87,940 ever-users and 697,294 never-users, with respective numbers of incident bladder cancer of 454 (0.52%) and 3,330 (0.48%), and respective incidence of 120.49 and 94.74 per 100,000 person-years. The overall hazard ratios (95% confidence intervals) indicated a significant association with insulin in the age-sex-adjusted models [1.238 (1.122–1.366)], but not in the model adjusted for all covariates [1.063 (0.951–1.187)]. There was also a significant trend for the hazard ratios for the different categories of the dose-response parameters in the age-sex-adjusted models, which became insignificant when all covariates were adjusted.

Conclusions

This study relieves the concern of a bladder cancer risk associated with human insulin. Appropriate adjustment for confounders is important in the evaluation of cancer risk associated with a medication.

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.

Rosiglitazone may reduce thyroid cancer risk in patients with type 2 diabetes

BACKGROUND

Whether rosiglitazone use in patients with type 2 diabetes may affect thyroid cancer risk has not been investigated.

METHODS

The reimbursement databases of all diabetic patients under oral anti-diabetic agents or insulin from 1996 to 2009 were retrieved from the National Health Insurance of Taiwan. An entry date was set at 1 January 2006, and 887,665 patients with type 2 diabetes were followed for thyroid cancer incidence until the end of 2009 for ever-users, never-users, and subgroups of rosiglitazone exposure using tertile cut-offs for time since starting rosiglitazone, duration of therapy, and cumulative dose. Hazard ratios were estimated by Cox regression.

RESULTS

There were 103,224 ever-users and 784,441 never-users, with respective numbers of incident thyroid cancer of 84 (0.08%) and 764 (0.10%), and respective incidence of 23.12 and 28.09 per 100,000 person-years. The overall multivariable-adjusted hazard ratio was not significant. However, in dose-response analyses, the adjusted hazard ratios (95% confidence intervals) were significant for the third tertile of duration of therapy (≥ 14 months) and cumulative dose (≥ 1,800 mg) for age ≥ 50 years: 0.53 (0.31-0.89) and 0.50 (0.29-0.87), respectively.

CONCLUSIONS

This study suggests that rosiglitazone use in patients with type 2 diabetes may reduce the risk of thyroid cancer.

Diabetes, insulin use, smoking, and pancreatic cancer mortality in Taiwan

The aim of the study was to evaluate the link between diabetes and pancreatic cancer (PC) mortality and the joint effect of smoking and insulin use on PC mortality. A total of 39,988 men and 46,909 women with type 2 diabetes, aged ≥25 years and recruited in 1995-1998, were followed to 2006 for PC mortality. Age-sex-specific mortality rate ratios for diabetic patients versus the general population were calculated. Cox regression was used to evaluate hazard ratios for PC mortality for covariates including age, sex, diabetes duration, body mass index, smoking, insulin use, and area of residence. The interaction and joint effect of smoking and insulin use were also evaluated. A total of 89 men and 63 women died of PC. The mortality rate ratios (95 % CI) showed a significantly higher risk in diabetic patients with a magnitude most remarkable at the youngest age: 1.51 (1.15, 1.98), 2.02 (1.35, 3.03), and 8.36 (5.39, 12.98) for ≥65, 55-64, and 25-54 years old, respectively, for men; and 1.16 (0.84, 1.59), 2.12 (1.39, 3.23) and 3.33 (1.14, 9.68), respectively, for women. In multivariable Cox regression analysis, only age was significantly predictive for PC mortality. Although smoking and insulin use might be associated with a 50 % higher risk when analyzed as individual risk factors, they did not reach statistical significance. The interaction term of smoking and insulin use was also not statistically significant in additional modeling. However, smoking and insulin use jointly increased the risk with an adjusted hazard ratio (95 % CI) of 3.04 (1.37, 6.73) when compared to patients who did not smoke and did not use insulin. Diabetic patients have a significantly higher risk of PC mortality. In patients with type 2 diabetes, smoking and insulin use may jointly increase the risk by threefold.

Insulin use and smoking jointly increase the risk of bladder cancer mortality in patients with type 2 diabetes

BACKGROUND

Whether insulin use predicts bladder cancer mortality has not been investigated. Furthermore, it is not known whether insulin use and smoking jointly influence the risk.

MATERIALS AND METHODS

A total of 86,939 patients (40,014 men, 46,925 women) with type 2 diabetes mellitus (T2DM) and aged ≥ 25 years in a nationally representative cohort were followed prospectively from 1995 to 2006 for bladder cancer mortality. Cox regression was used considering the following independent variables: age, sex, diabetes duration, body mass index, smoking, insulin use, and area of residence. The models were created for patients aged ≥ 25 and ≥ 65 years, separately; and sensitivity analyses were conducted after excluding (1) patients with duration between onset of diabetes and bladder cancer mortality < 5 years, and (2) patients with diabetes duration at recruitment < 3 years. The joint effect of insulin use and smoking was evaluated.

RESULTS

Patients who died of bladder cancer were characterized by older age, male predominance, longer diabetes duration, smoking, and insulin use. In multivariable Cox models, age, male sex, and insulin use were consistently predictive for bladder cancer mortality in all analyses, whereas the other variables were not. The adjusted hazard ratios for bladder cancer mortality for insulin users vs. nonusers ranged from 1.877 to 2.502 in different models (all P values < .05). Insulin use and smoking jointly increased the adjusted hazard ratio to 3.120 (95% confidence interval, 1.329-7.322).

CONCLUSIONS

Insulin use is significantly predictive for bladder cancer mortality in patients with T2DM. Insulin use and smoking jointly increase the risk.