Dose effect of thiazolidinedione on cancer risk in type 2 diabetes mellitus patients: a six-year population-based cohort study

WHAT IS KNOWN AND OBJECTIVE

Prior studies found that thiazolidinediones (TZDs) might have tumour-suppressor activity mediated through cell-cycle arrest, induction of apoptosis and inhibition of cell invasion. The main objective of this study was to investigate the effects of TZDs on the risk of cancer among patients with type 2 diabetes mellitus (DM).

METHODS

Patients diagnosed with DM between 1 January 1998 and 31 December 2002 were identified from the Longitudinal Health Insurance Database (LHID) within the Taiwan National Health Insurance (NHI) programme. Using Cox regression models, we assessed the association between prescribed TZDs and cancer risk, TZDs' dose effect and the association between TZDs and specific cancer types. Hazard ratios (HR) were adjusted for potential confounders (age, gender, income, Charlson score index, metformin and insulin use).

RESULTS AND DISCUSSION

The adjusted HRs for those prescribed TZD were 0·74 (95% CI 0·43-1·26, P = 0·27), 0·39 (95% CI 0·33-0·45, P < 0·001) and 0·49 (95% CI 0·27-0·89, P = 0·02), respectively, relative to non-DM patients, DM patients prescribed other anti-DM drugs besides TZDs and DM patients not prescribed any anti-DM drugs. In addition, the effects of TZDs were shown to be significantly dose dependent (P for trend < 0·001). The risk of breast, brain, colorectal, ear-nose-throat, kidney, liver, lung, lymphatic, prostate, stomach, and uterus cancer was significantly lower in those prescribed TZDs.

WHAT IS NEW AND CONCLUSIONS

The results showed a decrease in cancer risk in diabetic patients using TZD, and the association was dose dependent.

Gender-specific effects of oral hypoglycaemic agents on cancer risk in type 2 diabetes mellitus

AIMS

To analyse the association between cancer incidence and oral diabetes therapy (biguanide, sulphonylurea, thiazolidinedione and meglitinide) in men and women with type 2 diabetes mellitus.

METHODS

A retrospective analysis of the electronic health record-based Cleveland Clinic Diabetes Registry (25 613 patients) was cross-indexed with the histology-based tumour registry (48 051 cancer occurrences) over an 8-year period (1998-2006). Multiple imputations were used to account for missing data. Cox regression with propensity scores was used to model time for the development of incident cancer in each of the imputed datasets and the results were pooled.

RESULTS

During 51 994 person follow-up years, 892 incident cancer cases were identified; prostate (14.5%) and breast (11.7%) malignancies were most frequent. In women, thiazolidinedione use was associated with a 32% decreased cancer risk compared with sulphonylurea use [hazard ratio (HR) 0.68; 95% confidence interval (CI) 0.48-0.97, in the adjusted analysis]. Comparison of insulin secretagogues (sulphonylurea and meglitinide) versus insulin sensitizers (biguanide and thiazolidinedione) demonstrated a 21% decreased cancer risk in insulin sensitizers [HR 0.79 (95% CI 0.64-0.98) in the adjusted analysis]. Oral diabetes therapy showed no significant difference in men. Adjustments were made for age, body mass index (BMI), low-density lipoprotein (LDL), high-density lipoprotein (HDL), triglycerides, coronary heart disease (CHD), diabetes oral monotherapy, race, gender, haemoglobin A1c, statin use, income, insulin use, glomerular filtration rate (GFR), new diabetes status, prior cancer, prior cerebrovascular accident (stroke or transient ischaemic event), systolic/diastolic blood pressure, tobacco use (ever/never) and the propensity score for receiving a biguanide.

CONCLUSIONS

Oral insulin sensitizers, particularly thiazolidinedione, are associated with decreased malignancy risk in women with type 2 diabetes mellitus.

Association of Weight Loss and Medication Adherence Among Adults With Type 2 Diabetes Mellitus: SHIELD (Study to Help Improve Early evaluation and management of risk factors Leading to Diabetes)

BACKGROUND

Adherence to prescribed diabetes medications is suboptimal, which can lead to poor glycemic control and diabetic complications. Treatment-related weight gain is a side effect of some oral antidiabetic agents and insulin, which may negatively affect adherence to therapy.

OBJECTIVE

This study investigated whether adults with type 2 diabetes mellitus (T2DM) who lost weight had better medication adherence than those who gained weight.

METHODS

Weight change over 1 year (2007 to 2008) was assessed among respondents in the US Study to Help Improve Early evaluation and management of risk factors Leading to Diabetes (SHIELD). Weight loss of >1.0%, ≥3%, and ≥5% of weight was compared with weight gain of ≥1.0%. Medication adherence was assessed using the Morisky 4-item questionnaire for medication-taking behavior, with lower scores representing better adherence.

RESULTS

There were 746 T2DM respondents who lost >1.0%, 483 who lost ≥3%, 310 who lost ≥5%, and 670 who gained ≥1.0% of weight. Each weight-loss group had significantly lower Morisky scores than the weight-gain group; mean scores of 0.389 versus 0.473 (P = 0.050) for the >1.0% weight-loss group, 0.365 versus 0.473 (P = 0.026) for the ≥3% weight-loss group, and 0.334 versus 0.473 (P = 0.014) for the ≥5% weight-loss group. Significantly fewer respondents who lost weight had received insulin, sulfonylurea, or thiazolidinedione therapy (57%) compared with respondents who gained weight (64%) (P = 0.002). Demographics, exercise habits, and dieting were similar between weight-loss and weight-gain groups.

CONCLUSIONS

T2DM respondents with weight loss had significantly better medication adherence and were less likely to be on treatment regimens that increase weight than T2DM respondents with weight gain. These findings suggest that strategies that lead to weight loss, including use of diabetes medications associated with weight loss, may improve medication adherence.

Thiazolidinediones improve hepatic fibrosis in rats with non-alcoholic steatohepatitis by activating the adenosine monophosphate-activated protein kinase signalling pathway

Thiazolidinediones (TZDs) markedly reduce hepatic steatosis in both rodents and humans. However, the effects and mechanisms of action of TZDs on hepatic fibrosis remain unclear. The aim of the present study was to determine the effects of TZDs on histological changes in the liver and on the modulation by adiponectin via the AMP-activated protein kinase (AMPK) signalling pathway in rats with non-alcoholic steatohepatitis (NASH). Forty rats were divided into normal control, high-fat diet (HFD), pioglitazone control and pioglitazone intervention groups. After 24 weeks treatment with pioglitazone (10 mg/kg per day by gavage), changes in liver histology, serum aminotransaminase, triglyceride (TG), free fatty acid (FFA), glucose, insulin, adiponectin and transforming growth factor (TGF)-β1 concentrations and hepatic adiponectin, AMPK, α-smooth muscle actin (α-SMA) and collagen I expression were evaluated. The degree of hepatic steatosis and fibrosis was significantly higher in HFD-induced NASH rats compared with normal controls, as were serum concentrations of aminotransaminase, TG, FFA, glucose, insulin and TGF-β1 and hepatic expression of α-SMA and collagen I protein. Serum adiponectin concentrations and hepatic expression of adiponectin mRNA and AMPK protein were significantly lower in the HFD-induced NASH rats compared with the normal control. Pioglitazone significantly reduced the degree of hepatic steatosis and fibrosis, as well as serum concentrations of aminotransaminase, TG, FFA, glucose, insulin and TGF-β1 and hepatic expression of α-SMA and collagen I protein. In addition, pioglitazone significantly increased serum adiponectin concentrations and hepatic expression of adiponectin mRNA and AMPK protein. In conclusion, the TZD pioglitazone improved hepatic fibrosis in rats with NASH by upregulating adiponectin expression and activating AMPK, thus subsequently inhibiting the activation of hepatic stellate cells and the overproduction of extracellular matrix.

Regulation of energy metabolism by long-chain fatty acids

In mammals, excess energy is stored primarily as triglycerides, which are mobilized when energy demands arise. This review mainly focuses on the role of long chain fatty acids (LCFAs) in regulating energy metabolism as ligands of peroxisome proliferator-activated receptors (PPARs). PPAR-alpha expressed primarily in liver is essential for metabolic adaptation to starvation by inducing genes for beta-oxidation and ketogenesis and by downregulating energy expenditure through fibroblast growth factor 21. PPAR-delta is highly expressed in skeletal muscle and induces genes for LCFA oxidation during fasting and endurance exercise. PPAR-delta also regulates glucose metabolism and mitochondrial biogenesis by inducing FOXO1 and PGC1-alpha. Genes targeted by PPAR-gamma in adipocytes suggest that PPAR-gamma senses incoming non-esterified LCFAs and induces the pathways to store LCFAs as triglycerides. Adiponectin, another important target of PPAR-gamma may act as a spacer between adipocytes to maintain their metabolic activity and insulin sensitivity. Another topic of this review is effects of skin LCFAs on energy metabolism. Specific LCFAs are required for the synthesis of skin lipids, which are essential for water barrier and thermal insulation functions of the skin. Disturbance of skin lipid metabolism often causes apparent resistance to developing obesity at the expense of normal skin function.

Effect of pioglitazone on the course of new-onset type 1 diabetes mellitus

OBJECTIVE

Type 1 diabetes mellitus (T1DM) is caused by insulin deficiency resulting from progressive destruction of β cells. The histological hallmark of the diabetic islet is mononuclear cell infiltration. Thiazolidinediones (TZDs) activate PPARg and enhance the actions of insulin. Studies in non-obese diabetic and streptocotozin-treated mouse models demonstrated that pretreatment with TZDs prevented the development of T1DM. The purpose of this study was to examine whether pioglitazone, given with insulin, preserved β cell function in patients with new-onset T1DM.

METHODS

This was a randomized, double-blind, placebo-controlled 24-week study. Subjects received pioglitazone or placebo. Blood sugar, glycated hemoglobin (HbA1c), C-peptide, and liver enzymes were measured at baseline. Boost© stimulated C-peptide responses were measured at baseline and at 24 weeks. Blood sugar, insulin dose, height, weight, and liver enzymes were monitored at each visit. HbA1c was performed every 12 weeks.

RESULTS

Of the 15 patients, 8 received pioglitazone, and 7 - placebo. There was no clinical improvement in HbA1c between or within groups at the completion of the study. Mean peak C-peptide values were similar between groups at baseline. Mean peak C-peptide level was slightly higher at 24 weeks in the pioglitazone group compared to the placebo (1.8 vs. 1.5 ng/mL) which was considered as clinically insignificant. The interaction of HbA1c and insulin dose (HbA1c* insulin/kg/day), which combines degree of diabetic control and dose of insulin required to achieve this control, showed transient improvement in the pioglitazone group at 12 weeks but was not sustained at 24 weeks.

CONCLUSION

In this pilot study, pioglitazone did not preserve β cell function when compared to placebo.

A quantitative LC-MS/MS method for determination of thiazolidinedione mitoNEET ligand NL-1 in mouse serum suitable for pharmacokinetic studies

Thiazolidinedione (TZD) compounds have shown promise as antidiabetic, antibiotics, antifungal and neuroprotective agents. The mitochondrial effect of a novel mitoNEET ligand, NL-1 {5-[(3,5-di-tert-butyl-4-hydroxyphenyl)methyl]-1,3-thiazolidine-2,4-dione}, and other TZD compounds, is a newly proposed mechanism for the neuroprotective action of these TZD compounds. In this work, a sensitive LC-MS/MS assay has been developed and validated for quantification of NL-1 in mouse serum. Sample preparation involved an acetonitrile protein precipitation procedure with addition of an internal standard NL-2 {5-[(4-hydroxy-3,5-dimethyl-phenyl)methyl]thiazolidine-2,4-dione}. LC-MS/MS analysis utilized a Columbus C-18 HPLC column (2mm×50mm, 5μm). Chromatography employed a multiple step gradient program that featured a steep linear gradient (25-95% in 0.5min) of 15μM ammonium acetate (additive for eliminating carry-over) in 2% methanol mixing with increasing proportions of 100% methanol. The HPLC was interfaced to a QTrap 5500 mass spectrometer (AB Sciex) equipped with an electrospray ionization source used in a negative ionization mode. Multiple reaction monitoring (MRM) of m/z 334→263 for NL-1 and m/z 250→179 for NL-2 was done. The method had a linear range of at least 1-100ng/mL in serum. The intra-assay and inter-assay percent coefficient of variation (%CV) were less than 4% and accuracies (%RE) ranged from -2.7% to 2.0%. The analytical procedure gave 96-115% absolute extraction recovery of NL-1. The relative matrix effect was measured and found to be insignificant. The analyte in serum was confirmed to be stable during storage and treatment. The method is suitable for pharmacokinetic (PK) studies of the parent drug NL-1 based on the preliminary serum results from dosed NL-1 mouse studies.

Current clinical evidence on pioglitazone pharmacogenomics

Pioglitazone is the most widely used thiazolidinedione and acts as an insulin-sensitizer through activation of the Peroxisome Proliferator-Activated Receptor-γ (PPARγ). Pioglitazone is approved for use in the management of type 2 diabetes mellitus (T2DM), but its use in other therapeutic areas is increasing due to pleiotropic effects. In this hypothesis article, the current clinical evidence on pioglitazone pharmacogenomics is summarized and related to variability in pioglitazone response. How genetic variation in the human genome affects the pharmacokinetics and pharmacodynamics of pioglitazone was examined. For pharmacodynamic effects, hypoglycemic and anti-atherosclerotic effects, risks of fracture or edema, and the increase in body mass index in response to pioglitazone based on genotype were examined. The genes CYP2C8 and PPARG are the most extensively studied to date and selected polymorphisms contribute to respective variability in pioglitazone pharmacokinetics and pharmacodynamics. We hypothesized that genetic variation in pioglitazone pathway genes contributes meaningfully to the clinically observed variability in drug response. To test the hypothesis that genetic variation in PPARG associates with variability in pioglitazone response, we conducted a meta-analysis to synthesize the currently available data on the PPARG p.Pro12Ala polymorphism. The results showed that PPARG 12Ala carriers had a more favorable change in fasting blood glucose from baseline as compared to patients with the wild-type Pro12Pro genotype (p = 0.018). Unfortunately, findings for many other genes lack replication in independent cohorts to confirm association; further studies are needed. Also, the biological functionality of these polymorphisms is unknown. Based on current evidence, we propose that pharmacogenomics may provide an important tool to individualize pioglitazone therapy and better optimize therapy in patients with T2DM or other conditions for which pioglitazone is being used.

Pre-transplant signal induction for vascularisation in human islets

Human islet transplant success is partially impaired by slow revascularisation. Our study investigated the potential for rotational cell culture (RC) of human islets combined with thiazolidinedione (TZD) stimulation of peroxisome proliferator-activated receptor gamma (PPARγ) to upregulate vascular endothelial growth factor (VEGF) expression in the islets. Four groups of human islets were studied: static culture (SC) with and without 25 mmol/L TZD and RC with and without 25 mmol/L TZD. These were assessed for insulin secretion and soluble VEGF-A release. Both proteins were quantified by enzyme-linked immunosorbent assay (ELISA), supported with qualitative immunofluorescence staining. RC + TZD increased insulin secretion by >20% (p < 0.05-0.001) in response to 16.7 mmol/L glucose and 16.7 mmol/L glucose + 10 mmol/L theophylline (G + T). This effect was seen at all time intervals compared with SC and without addition of TZD. Soluble VEGF-A release was significantly augmented by RC and TZD exposure with an increased effect of >30% (p < 0.001) at 72 h under both SC and RC conditions. RC supplemented with a TZD enhances and prolongs the release of insulin and soluble VEGF-A by isolated human islets.

Bone loss in the oestrogen-depleted rat is not exacerbated by sitagliptin, either alone or in combination with a thiazolidinedione

Antihyperglycaemic therapy on bone was evaluated in the ovariectomized (OVX), non-diabetic adult rat. Animals were treated daily for 12 weeks with various doses of sitagliptin, pioglitazone, rosiglitazone, combinations of sitagliptin with pioglitazone or vehicle alone. Sitagliptin target engagement was confirmed by assessing inhibition of plasma dipeptidyl peptidase-4 (DPP-4) and oral glucose tolerance. Parameters related to bone health were evaluated in femur and vertebrae by dual-energy X-ray absorptiometry and histomorphometry. Bone mineral density (BMD) generally did not differ significantly between OVX-sitagliptin-treated animals and OVX-vehicle controls. In lumbar vertebrae, however, there was significantly less BMD loss with increasing sitagliptin dose. Thiazolidinedione (TZD) treatment generally resulted in lower BMD; OVX-TZD-treated (but not OVX-sitagliptin-treated) animals also had lessened cortical thickness in central femur and profoundly greater bone marrow adiposity in lumbar vertebrae. These findings support prior findings with TZDs and suggest a neutral or beneficial impact of DPP-4 inhibition on bone health.

Intensive glycemic control and thiazolidinedione use: effects on cortical and trabecular bone at the radius and tibia

Factors that contribute to bone fragility in type 2 diabetes are not well understood. We assessed the effects of intensive glycemic control, thiazolidinediones (TZDs), and A1C levels on bone geometry and strength at the radius and tibia. In a substudy of the Action to Control Cardiovascular Risk in Diabetes trial, peripheral quantitative computed tomographic (pQCT) scans of the radius and tibia were obtained 2 years after randomization on 73 participants (intensive n = 35, standard n = 38). TZD use and A1C levels were measured every 4 months during the trial. Effects of intervention assignment, TZD use, and A1C on pQCT parameters were assessed in linear regression models. Intensive, compared with standard, glycemic control was associated with 1.3 % lower cortical volumetric BMD at the tibia in men (p = 0.02) but not with other pQCT parameters. In women, but not men, each additional year of TZD use was associated with an 11 % lower polar strength strain index (SSIp) at the radius (p = 0.04) and tibia (p = 0.002) in models adjusted for A1C levels. In women, each additional 1 % increase in A1C was associated with an 18 % lower SSIp at the ultradistal radius (p = 0.04) in models adjusted for TZD use. There was no consistent evidence of an effect of intensive, compared with standard, glycemic control on bone strength at the radius or tibia. In women, TZD use may reduce bone strength at these sites. Higher A1C may also be associated with lower bone strength at the radius, but not tibia, in women.

Effects of age on noninvasive assessments of vascular function in nonhuman primates: implications for translational drug discovery

BACKGROUND

Endothelium-dependent flow mediated dilation (FMD) and pulse-wave velocity (PWV), are used as measures of vascular health and predictors of cardiovascular risk in clinical studies, and both are age-dependent. Numbers of circulating endothelial microparticles (EMPs) and endothelial progenitor cells (EPCs) are also associated with cardiovascular risk, but independent of age in humans. The use of these measurements for pre-clinical assessment of drug cardiovascular safety and efficacy in non-human primates (NHPs) may promote the translation of drug-induced effects on vascular function to clinic outcomes. However, in NHPs, the age effects on the non-invasive measurements of FMD and PWV and the relationship of EMPs/EPCs with FMD are unknown.

METHODS

A non-invasive, clinically-relevant approach to assess FMD and PWV was used to examine their relationship with age and with EMPs/EPCs in NHPs. The effects on FMD of nicotine and rosiglitazone were evaluated in senescent primates in an effort to validate our FMD method for pre-clinical assessment of vascular function.

RESULTS

FMD and PWV methods were established in a colony (n = 25) of metabolically healthy, cynomolgus monkeys ranging in age from 6 to 26 years. FMD, defined as the percent change, at 1 min of cuff release, from baseline vascular diameter (0.15 ± 0.03 cm), had a strong, negative correlation with age (r = -0.892, p < 0.0001), ranging from 6% to 33%. PWV positively correlated with age (r = 0.622, p < 0.002) in the same healthy monkeys. Nicotine and rosiglitazone, were evaluated in subsets of senescent primates (mean age 16.3 ± 1.5[SEM] years). Rosiglitazone significantly improved FMD (21.0 ± 1.6% vs. vehicle 16.3 ± 1.6%, p < 0.01) without changing baseline diameters, and coincided with a significant increase in circulating numbers of endothelial progenitor cells (CD45-CD31 + CD34 + VEGFR2+ 7.1 ± 1.3 vs. 4.8 ± 1.1 counts/μl) and a decrease in endothelial microparticles (CD45-CD42a-CD54+ 26.7 ± 11.1 vs. 62.2 ± 9.8 counts/μl)(p < 0.05). Conversely, FMD was significantly reduced with nicotine (8.7 ± 1.4% vs. vehicle 20.1 ± 2.2%, p < 0.05).

CONCLUSIONS

Adult NHPs demonstrate the characteristic linear relationship between age and vascular function using the non-invasive clinically-related measurements of FMD and PWV. However, numbers of circulating EMPs and EPCs did not correlate with age. Endothelial function assessed with FMD, together with EMPs/EPCs assessment, may serve as a novel approach for translational research and therapeutic discovery. Age should be considered in the study design or data analyses when FMD or PWV is used in NHPs.

Peroxisome proliferator-activated receptor-γ as a therapeutic target for hepatic fibrosis: from bench to bedside

Hepatic fibrosis is a dynamic chronic liver disease occurring as a consequence of wound-healing responses to various hepatic injuries. This disorder is one of primary predictors for liver-associated morbidity and mortality worldwide. To date, no pharmacological agent has been approved for hepatic fibrosis or could be recommended for routine use in clinical context. Cellular and molecular understanding of hepatic fibrosis has revealed that peroxisome proliferator-activated receptor-γ (PPARγ), the functioning receptor for antidiabetic thiazolidinediones, plays a pivotal role in the pathobiology of hepatic stellate cells (HSCs), whose activation is the central event in the pathogenesis of hepatic fibrosis. Activation of PPARγ inhibits HSC collagen production and modulates HSC adipogenic phenotype at transcriptional and epigenetic levels. These molecular insights indicate PPARγ as a promising drug target for antifibrotic chemotherapy. Intensive animal studies have demonstrated that stimulation of PPARγ regulatory system through gene therapy approaches and PPARγ ligands has therapeutic promise for hepatic fibrosis induced by a variety of etiologies. At the same time, thiazolidinedione agents have been investigated for their clinical benefits primarily in patients with nonalcoholic steatohepatitis, a common metabolic liver disorder with high potential to progress to fibrosis and liver-related death. Although some studies have shown initial promise, none has established long-term efficacy in well-controlled randomized clinical trials. This comprehensive review covers the 10-year discoveries of the molecular basis for PPARγ regulation of HSC pathophysiology and then focuses on the animal investigations and clinical trials of various therapeutic modalities targeting PPARγ for hepatic fibrosis.

Changing prescribing patterns of type 2 diabetes medications from 2002-2010: an electronic health record-based evaluation

BACKGROUND

The implementation of electronic health records (EHRs) may support evaluations of health care delivery, such as the prescription of newly approved medications, to adults with diabetes. We aimed to evaluate prescribing patterns of thiazolidinediones and novel glucose-lowering drug classes using electronic prescribing data contained in an outpatient EHR from 2002-2010.

METHODS

We identified adults with type 2 diabetes seen from 2002-2010 who were newly prescribed rosiglitazone (ROSI), pioglitazone (PIO), or a novel glucose-lowering drug class (other). The annual number of new prescriptions and their relative percentages (per 1000 patients) were calculated.

RESULTS

From 2002-2010, 6209 patients with type 2 diabetes were newly prescribed 8858 eligible medications. In 2006, ROSI and PIO accounted for 44% and 37% of new prescriptions, respectively. After 2007, the relative percentage of new ROSI prescriptions declined more rapidly than PIO prescriptions, falling to 7% and 47% of peak levels, respectively, by 2010. By 2010, the relative percentages of new ROSI, PIO, and other prescriptions were 2%, 18%, and 80%, respectively.

CONCLUSIONS

Evaluations of EHR data represent a cost-effective method for evaluating diabetes medications with new Food and Drug Administration warnings or indications. Validation of demographic and clinical data will expand the scope of EHR-based evaluations of health care delivery and outcomes for adults with diabetes.

Hospitalised hip fracture risk with rosiglitazone and pioglitazone use compared with other glucose-lowering drugs

AIMS/HYPOTHESIS

Current drug labels for thiazolidinediones (TZDs) warn of increased fractures, predominantly for distal fractures in women. We examined whether exposure to TZDs affects hip fracture in women and men and compared the risk to that found with other drugs used in diabetes.

METHODS

Using a nationwide database of prescriptions, hospital admissions and deaths in those with type 2 diabetes in Scotland we calculated TZD exposure among 206,672 individuals. Discrete-time failure analysis was used to model the effect of cumulative drug exposure on hip fracture during 1999-2008.

RESULTS

There were 176 hip fractures among 37,479 exposed individuals. Hip fracture risk increased with cumulative exposure to TZD: OR per year of exposure 1.18 (95% CI 1.09, 1.28; p = 3 × 10(-5)), adjusted for age, sex and calendar month. Hip fracture increased with cumulative exposure in both men (OR 1.20; 95% CI 1.03, 1.41) and women (OR 1.18; 95% CI 1.07, 1.29) and risks were similar for pioglitazone (OR 1.18) and rosiglitazone (OR 1.16). The association was similar when adjusted for exposure to other drugs for diabetes and for other potential confounders. There was no association of hip fracture with cumulative exposure to sulfonylureas, metformin or insulin in this analysis. The 90-day mortality associated with hip fractures was similar in ever-users of TZD (15%) and in never-users (13%).

CONCLUSIONS/INTERPRETATION

Hip fracture is a severe adverse effect with TZDs, affecting both sexes; labels should be changed to warn of this. The excess mortality is at least as much as expected from the reported association of pioglitazone with bladder cancer.

Pioglitazone adjunctive therapy for moderate-to-severe major depressive disorder: randomized double-blind placebo-controlled trial

Thiazolidinediones have shown antidepressant effect in animal studies, as well as in some uncontrolled studies evaluating human subjects with concurrent major depressive disorder (MDD) and metabolic syndrome. Although these drugs are insulin sensitizers, they also have important anti-inflammatory, neuroprotective, and anti-excitotoxic properties. Thus, we hypothesized that they would show antidepressant effect in patients with MDD even if it was not accompanied by metabolic disturbances. In this double-blind placebo-controlled study, 40 patients with MDD (DSM-IV-TR) and Hamilton depression rating scale-17 (Ham-D) score ≥ 22 were randomized to citalopram plus pioglitazone (15 mg every 12 h) (n=20) or citalopram plus placebo (n=20) for 6 weeks. Patients were evaluated using Ham-D (weeks 0, 2, 4, 6). Repeated-measure analysis of variance (ANOVA) and analysis of covariance were used for comparison of scores between the two groups. Treatment response (≥ 50% reduction in Ham-D score), remission (Ham-D score ≤ 7), and early improvement (≥ 20% reduction in Ham-D score within the first 2 weeks) were compared between the two groups using Fisher's exact test. Pioglitazone showed superiority over placebo during the course of the trial (F(1, 38)=9.483, p=0.004). Patients in the pioglitazone group had significantly lower scores at all time points than the placebo group (P<0.01). Frequency of early improvement, response (week 6), and remission was significantly higher in the pioglitazone group (95%, 95%, 45%, respectively) than in the placebo (30%, 40%, 15% respectively) group (P<0.001, <0.001, 0.04, respectively). Frequency of side effects was similar between the two groups. Pioglitazone is a safe and effective adjunctive short-term treatment in patients with moderate-to-severe MDD even in the absence of metabolic syndrome and diabetes.

Risk of fracture with thiazolidinediones: disease or drugs?

The use of thiazolidinediones (TZDs) has been associated with an increased fracture risk. In addition, type 2 diabetes mellitus (T2DM) has been linked with fracture. We evaluated to what extent the association between TZD use and fracture risk is related to the drug or to the underlying disease. We conducted a population-based cohort study using the Danish National Health Registers (1996-2007), which link pharmacy data to the national hospital registry. Oral antidiabetic users (n = 180,049) were matched 1:3 by year of birth and sex to nonusers. Cox proportional hazards models were used to estimate hazard ratios (HRs) of fracture. Time-dependent adjustments were made for age, comorbidity, and drug use. We created a proxy indicator for the severity of disease. The first stage was defined as current use of either a biguanide or a sulfonyluerum, the second stage as current use of a biguanide and a sulfonyluerum at the same time, the third stage as patients using TZDs, and the fourth stage as patients using insulin. The risk of osteoporotic fracture was increased 1.3-fold for stages 3 and 4 compared with controls. Risk with current TZD use (stage 3 HR = 1.27, 95 % CI 1.06-1.52) and risk with current use of insulin (stage 4 HR = 1.25, 95 % CI 1.20-1.31) were similar. In the first (HR = 1.15, 95 % CI 1.13-1.18) and second (HR = 1.00, 95 % CI 0.96-1.04) stages risks were lower. Risk of osteoporotic fracture was similar for TZD users and insulin users. When studying fracture risk with TZDs, the underlying T2DM should be taken into account.

Selective PPARγ modulator INT131 normalizes insulin signaling defects and improves bone mass in diet-induced obese mice

INT131 is a potent non-thiazolidinedione (TZD)-selective peroxisome proliferator-activated receptor-γ modulator being developed for the treatment of type 2 diabetes. In preclinical studies and a phase II clinical trial, INT131 has been shown to lower glucose levels and ameliorate insulin resistance without typical TZD side effects. To determine whether the insulin-sensitizing action of INT131 is mediated by effects on insulin-mediated glucose homeostasis and insulin signaling, high-fat diet-induced obese (DIO) insulin-resistant mice treated with INT131 were studied. INT131's effects on bone density were also investigated. Treatment with INT131 enhanced systemic insulin sensitivity, as revealed by lower insulin levels in the fasted state and an increase in the area above the curve during an insulin tolerance test. These effects were independent of changes in adiposity. Insulin-stimulated PI3K activity in skeletal muscle and adipose tissue of DIO mice was significantly reduced ∼50-65%, but this was restored completely by INT131 therapy. The INT131 effects on PI3K activity are most likely due to increased IRS-1 tyrosine phosphorylation. Concurrently, insulin-mediated Akt phosphorylation also increased after INT131 treatment in DIO mice. Importantly, INT131 therapy caused a significant increase in bone mineral density without alteration in circulating osteocalcin in these mice. These data suggest that a newly developed insulin-sensitizing agent, INT131, normalizes obesity-related defects in insulin action on PI3K signaling in insulin target tissues by a mechanism involved in glycemic control. If these data are confirmed in humans, INT131 could be used for treating type 2 diabetes without loss in bone mass.

Enhanced glycemic control with combination therapy for type 2 diabetes in primary care

Type 2 diabetes mellitus is an increasingly common medical problem for primary care clinicians to address. Treatment of diabetes has evolved from simple replacement of insulin (directly or through insulin secretagogs) through capture of mechanisms such as insulin sensitizers, alpha-glucosidase inhibitors, and incretins. Only very recently has recognition of the critical role of the gastrointestinal system as a major culprit in glucose dysregulation been established. Since glycated hemoglobin A(1c) reductions provide meaningful risk reduction as well as improved quality of life, it is worthwhile to explore evolving paths for more efficient use of the currently available pharmacotherapies. Because diabetes is a progressive disease, even transiently successful treatment will likely require augmentation as the disorder progresses. Pharmacotherapies with complementary mechanisms of action will be necessary to achieve glycemic goals. Hence, clinicians need to be well informed about the various noninsulin alternatives that have been shown to be successful in glycemic goal attainment. This article reviews the benefits of glucose control, the current status of diabetes control, pertinent pathophysiology, available pharmacological classes for combination, limitations of current therapies, and suggestions for appropriate combination therapies, including specific suggestions for thresholds at which different strategies might be most effectively utilized by primary care clinicians.

Multi-tissue, selective PPARγ modulation of insulin sensitivity and metabolic pathways in obese rats

Peroxisome proliferator-activated receptor-γ (PPARγ) ligands, including the insulin-sensitizing thiazolidinedione drugs, transcriptionally regulate hundreds of genes. Little is known about the relationship between PPARγ ligand-specific modulation of cellular mechanisms and insulin sensitization. We characterized the insulin sensitivity and multitissue gene expression profiles of lean and insulin-resistant, obese Zucker rats untreated or treated with one of four PPARγ ligands (pioglitazone, rosiglitazone, troglitazone, and AG-035029). We analyzed the transcriptional profiles of adipose tissue, skeletal muscle, and liver from the rats and determined whether ligand treatment insulin-sensitizing potency was related to ligand treatment-induced alteration of functional pathways. Ligand treatments improved insulin sensitivity in obese rats to varying degrees. Adipose tissue profiles revealed ligand treatment-selective modulation of inflammatory and branched-chain amino acid (BCAA) metabolic pathways, which correlated with ligand treatment-specific insulin-sensitizing potency. Skeletal muscle profiles showed that obese rats exhibited elevated expression of adipocyte and slow-twitch fiber markers, which further increased after ligand treatment, but the magnitude of the treatment-induced changes was not correlated with insulin sensitization. Although PPARγ ligand treatments heterogeneously improved dysregulated expression of cholesterol and fatty acid biosynthetic pathways in obese rat liver, these alterations were not correlated with ligand insulin-sensitizing potency. PPARγ ligand treatment-specific insulin-sensitizing potency correlated with modulation of adipose tissue inflammatory and BCAA metabolic pathways, suggesting a functional relationship between these pathways and whole body insulin sensitivity. Other PPARγ ligand treatment-induced functional pathway changes were detected in adipose tissue, skeletal muscle, and liver profiles but were not related to degree of insulin sensitization.

Clinical overview of saxagliptin for Type 2 diabetes management

Saxagliptin (Onglyza™, Bristol-Myers Squibb, NJ, USA and AstraZeneca, DE, USA) is a potent, orally active, once-daily dipeptidyl peptidase-4 inhibitor that is indicated as an adjunct to diet and exercise alone, or in combination with metformin, a thiazolidinedione or a sulfonylurea to improve glycemic control in adults with Type 2 diabetes mellitus. By inhibiting dipeptidyl peptidase-4, saxagliptin increases concentrations of the intact forms of the incretin hormones, glucagon-like peptide-1 and glucose-dependent insulinotropic polypeptide, prolonging their effects. Saxagliptin also improves β-cell function, increases postprandial insulin secretion and reduces postprandial glucagon secretion. Saxagliptin is generally well tolerated with weight-neutral effects and a low incidence of hypoglycemia. Multicenter randomized trials have shown that saxagliptin as monotherapy, as initial therapy with metformin or as add-on therapy with metformin, a sulfonylurea or a thiazolidinedione leads to significant decreases in glycated hemoglobin levels, fasting and postprandial plasma glucose levels and higher percentages of patients attaining target glycated hemoglobin of less than 7% compared with controls.

Increased fracture risk in patients treated with thiazolidinediones: the role of abnormal bone turnover

Evaluation of: Zinman B, Haffner SM, Herman WH et al. Effect of rosiglitazone, metformin, and glyburide on bone biomarkers in patients with Type 2 diabetes. J. Clin. Endocrinol. Metab. 95(1), 134-142 (2010). Until recently, patients with Type 2 diabetes were thought to be relatively protected against osteoporosis by their high BMI. However, recent epidemiological data suggest that fracture risk is increased in diabetic patients. Additionally, use of thiazolidinedione antidiabetic medications (rosiglitazone and pioglitazone) was unexpectedly found to be associated with an increased risk of fractures. The paper under evaluation in this article examines changes in biochemical markers of bone turnover in subjects within the clinical trial that first raised the issue of fractures. The main finding was a significant increase in bone resorption with rosiglitazone. This conclusion conflicts with other studies examining the effects of thiozolidinediones on bone and, by itself, is unlikely to fully explain the increased fracture risk seen with these drugs.

Peroxisome-proliferator activator receptor-gamma activation decreases attachment of endometrial cells to peritoneal mesothelial cells in an in vitro model of the early endometriotic lesion

The aim of this study was to investigate whether peroxisome proliferator-activated receptor (PPAR)-gamma activation has an effect on the attachment of endometrial cells to peritoneal mesothelial cells in a well-established in vitro model of the early endometriotic lesion. The endometrial epithelial cell line EM42 and mesothelial cell line LP9 were used for this study. EM42 cells, LP9 cells or both were treated with the PPAR-gamma agonist ciglitazone (CTZ) at varying concentrations (10, 20 and 40 microM) x 48 h with subsequent co-culture of EM42 and LP9 cells. The rate of EM42 attachment and invasion through LP9 cells was then assessed and compared with control (EM42 and LP9 cells co-cultured without prior treatment with CTZ). Next, attachment of CTZ-treated and untreated EM42 cells to hyaluronic acid (HA), a cell adhesion molecule (CAM) on peritoneal mesothelial cells, were assessed. Although there was no difference in EM42 attachment when LP9 cells alone were treated with CTZ, treatment of EM42 cells with 40 microM CTZ decreased EM42 attachment to LP9 cells by 27% (P < 0.01). Treatment of both EM42 and LP9 cells with 40 microM CTZ decreased EM42 attachment to LP9 by 37% (P < 0.01). Treatment of EM42 cells with 40 microM CTZ decreased attachment to HA by 66% (P = 0.056). CTZ did not decrease invasion of EM42 cells through the LP9 monolayer. CTZ may inhibit EM42 cell proliferation. In conclusion, CTZ significantly decreased EM42 attachment to LP9 cells and HA in an in vitro model of the early endometriotic lesion.

Selective regulation of cellular and secreted multimeric adiponectin by antidiabetic therapies in humans

Adiponectin, an insulin-sensitizing factor secreted from adipose tissue, is decreased in individuals with type 2 diabetes (T2D) and increased in response to thiazolidinedione (TZD) therapy. Changes in its secretion and assembly into higher-order forms affect insulin sensitivity. To determine the relative potency of TZDs on intra-adipocyte multimerization and secretion of adiponectin, we assessed the impact of in vivo low- or high-dose rosiglitazone treatment alone or combined with metformin in subjects with T2D. T2D subjects received high-dose rosiglitazone (8 mg/day), high-dose metformin (2,000 mg/day), or low-dose combination rosiglitazone-metformin therapy (4 mg + 1,000 mg/day) for 4 mo. All subjects were then switched to high-dose rosiglitazone-metformin combination therapy (8 mg + 2,000 mg/day) for another 4 mo. Low-dose rosiglitazone increased serum adiponectin, whereas the high dose increased both adipocyte content and serum adiponectin levels. TZDs selectively increased the percentage of circulating adiponectin in the potent, high-molecular-weight (HMW) form. No TZD effects were evident on multimer distribution in the cell. Expression of the chaperone protein ERp44, which retains adiponectin within the cell, was decreased by TZD treatment. No changes occurred in Ero1-Lalpha expression. Metformin had no effect on any of these measures. Increases in adiponectin correlated with improvements in insulin sensitivity. In vivo, TZDs have apparent dose-dependent effects on cellular and secreted adiponectin. TZD-mediated improvements in whole body insulin sensitivity are associated with increases in circulating but not cellular levels of the HMW adiponectin multimer. Finally, TZDs promote the selective secretion of HMW adiponectin, potentially, in part, through decreasing the expression of the adiponectin-retaining protein ERp44.

Liraglutide, a once-daily human GLP-1 analogue, added to a sulphonylurea over 26 weeks produces greater improvements in glycaemic and weight control compared with adding rosiglitazone or placebo in subjects with Type 2 diabetes (LEAD-1 SU)

AIM

To compare the effects of combining liraglutide (0.6, 1.2 or 1.8 mg/day) or rosiglitazone 4 mg/day (all n >or= 228) or placebo (n = 114) with glimepiride (2-4 mg/day) on glycaemic control, body weight and safety in Type 2 diabetes.

METHODS

In total, 1041 adults (mean +/- sd), age 56 +/- 10 years, weight 82 +/- 17 kg and glycated haemoglobin (HbA(1c)) 8.4 +/- 1.0% at 116 sites in 21 countries were stratified based on previous oral glucose-lowering mono : combination therapies (30 : 70%) to participate in a five-arm, 26-week, double-dummy, randomized study.

RESULTS

Liraglutide (1.2 or 1.8 mg) produced greater reductions in HbA(1c) from baseline, (-1.1%, baseline 8.5%) compared with placebo (+0.2%, P < 0.0001, baseline 8.4%) or rosiglitazone (-0.4%, P < 0.0001, baseline 8.4%) when added to glimepiride. Liraglutide 0.6 mg was less effective (-0.6%, baseline 8.4%). Fasting plasma glucose decreased by week 2, with a 1.6 mmol/l decrease from baseline at week 26 with liraglutide 1.2 mg (baseline 9.8 mmol/l) or 1.8 mg (baseline 9.7 mmol/l) compared with a 0.9 mmol/l increase (placebo, P < 0.0001, baseline 9.5 mmol/l) or 1.0 mmol/l decrease (rosiglitazone, P < 0.006, baseline 9.9 mmol/l). Decreases in postprandial plasma glucose from baseline were greater with liraglutide 1.2 or 1.8 mg [-2.5 to -2.7 mmol/l (baseline 12.9 mmol/l for both)] compared with placebo (-0.4 mmol/l, P < 0.0001, baseline 12.7 mmol/l) or rosiglitazone (-1.8 mmol/l, P < 0.05, baseline 13.0 mmol/l). Changes in body weight with liraglutide 1.8 mg (-0.2 kg, baseline 83.0 kg), 1.2 mg (+0.3 kg, baseline 80.0 kg) or placebo (-0.1 kg, baseline 81.9 kg) were less than with rosiglitazone (+2.1 kg, P < 0.0001, baseline 80.6 kg). Main adverse events for all treatments were minor hypoglycaemia (< 10%), nausea (< 11%), vomiting (< 5%) and diarrhoea (< 8%).

CONCLUSIONS

Liraglutide added to glimepiride was well tolerated and provided improved glycaemic control and favourable weight profile.

Pioglitazone versus vitamin E versus placebo for the treatment of non-diabetic patients with non-alcoholic steatohepatitis: PIVENS trial design

BACKGROUND

Non-alcoholic steatohepatitis (NASH) is a common liver disease associated with obesity and diabetes. NASH is a progressive disorder that can lead to cirrhosis and liver failure. Insulin resistance and oxidative stress are thought to play important roles in its pathogenesis. There is no definitive treatment for NASH.

OBJECTIVES

PIVENS is conducted to test the hypotheses that treatment with pioglitazone, a thiazolidinedione insulin sensitizer, or vitamin E, a naturally available antioxidant, will lead to improvement in hepatic histology in non-diabetic adults with biopsy proven NASH.

DESIGN

PIVENS is a randomized, multicenter, double-masked, placebo-controlled trial to evaluate whether 96 weeks of treatment with pioglitazone or vitamin E improves hepatic histology in non-diabetic adults with NASH compared to treatment with placebo. Before and post-treatment liver biopsies are read centrally in a masked fashion for an assessment of steatohepatitis and a NAFLD Activity Score (NAS) consisting of steatosis, lobular inflammation, and hepatocyte ballooning. The primary outcome measure is defined as either an improvement in NAS by 2 or more in at least two NAS features, or a post-treatment NAS of 3 or less, and improvement in hepatocyte ballooning by 1 or more, and no worsening of fibrosis.

METHODS

PIVENS enrollment started in January 2005 and ended in January 2007 with 247 patients randomized to receive either pioglitazone (30 mg q.d.), vitamin E (800 IU q.d.), or placebo for 96 weeks. Participants will be followed for an additional 24 weeks after stopping the treatment. The study protocol incorporates the use of several validated questionnaires and specimen banking. This protocol was approved by all participating center Institutional Review Boards (IRBs) and an independent Data and Safety Monitoring Board (DSMB) which was established for monitoring the accumulated interim data as the trial progresses to ensure patient safety and to review efficacy as well as the quality of data collection and overall study management. (ClinicalTrials.gov number, NCT00063622).

PPARgamma agonists as therapeutics for the treatment of Alzheimer's disease

Alzheimer's disease (AD) is characterized by the deposition of beta-amyloid within the brain parenchyma and is accompanied by the impairment of neuronal metabolism and function, leading to extensive neuronal loss. The disease involves the perturbation of synaptic function, energy, and lipid metabolism. The development of amyloid plaques results in the induction of a microglial-mediated inflammatory response. The nuclear receptor peroxisome proliferator-activated receptor gamma (PPARgamma) is a ligand-activated transcription factor whose biological actions are to regulate glucose and lipid metabolism and suppress inflammatory gene expression. Thus, agonists of this receptor represent an attractive therapeutic target for AD. There is now an extensive body of evidence that has demonstrated the efficacy of PPARgamma agonists in ameliorating disease-related pathology and improved learning and memory in animal models of AD. Recent clinical trials of the PPARgamma agonist rosiglitazone have shown significant improvement in memory and cognition in AD patients. Thus, PPARgamma represents an important new therapeutic target in treating AD.

Thiazolidinedione drugs block cardiac KATP channels and may increase propensity for ischaemic ventricular fibrillation in pigs

AIMS/HYPOTHESIS

Opening of ATP-sensitive potassium (K(ATP)) channels during myocardial ischaemia shortens action potential duration and is believed to be an adaptive, energy-sparing response. Thiazolidinedione drugs block K(ATP) channels in non-cardiac cells in vitro. This study determined whether thiazolidinedione drugs block cardiac K(ATP) channels in vivo.

METHODS

Experiments in 68 anaesthetised pigs determined: (1) effects of inert vehicle, troglitazone (10 mg/kg i.v.) or rosiglitazone (0.1 or 1.0 mg/kg i.v.) on epicardial monophasic action potential (MAP) during 90 min low-flow ischaemia; (2) effects of troglitazone, rosiglitazone or pioglitazone (1 mg/kg i.v.) on response of MAP to intracoronary infusion of a K(ATP) channel opener, levcromakalim; and (3) effects of inert vehicle, rosiglitazone (1 mg/kg i.v.) or the sarcolemmal K(ATP) blocker HMR-1098 on time to onset of ventricular fibrillation following complete coronary occlusion.

RESULTS

With vehicle, epicardial MAP shortened by 44+/-9 ms during ischaemia. This effect was attenuated to 12+/-8 ms with troglitazone and 6+/-6 ms with rosiglitazone (p<0.01 for both vs vehicle), suggesting K(ATP) blockade. Intracoronary levcromakalim shortened MAP by 38+/-10 ms, an effect attenuated to 12+/-8, 13+/-4 and 9+/-5 ms during co-treatment with troglitazone, rosiglitazone or pioglitazone (p<0.05 for each), confirming K(ATP) blockade. During coronary occlusion, median time to ventricular fibrillation was 29 min in pigs treated with vehicle and 6 min in pigs treated with rosiglitazone or HMR-1098 (p<0.05 for both vs vehicle), indicating that K(ATP) blockade promotes ischaemic ventricular fibrillation in this model.

CONCLUSIONS/INTERPRETATION

Thiazolidinedione drugs block cardiac K(ATP) channels at clinically relevant doses and promote onset of ventricular fibrillation during severe ischaemia.

Fatty acid-induced mitochondrial uncoupling in adipocytes as a key protective factor against insulin resistance and beta cell dysfunction: a new concept in the pathogenesis of obesity-associated type 2 diabetes mellitus

Type 2 diabetes is associated with excessive food intake and a sedentary lifestyle. Local inflammation of white adipose tissue induces cytokine-mediated insulin resistance of adipocytes. This results in enhanced lipolysis within these cells. The fatty acids that are released into the cytosol can be removed by mitochondrial beta-oxidation. The flux through this pathway is normally limited by the rate of ADP supply, which in turn is determined by the metabolic activity of the adipocyte. It is expected that the latter does not adapt to an increased rate of lipolysis. We propose that elevated fatty acid concentrations in the cytosol of adipocytes induce mitochondrial uncoupling and thereby allow mitochondria to remove much larger amounts of fatty acids. By this, release of fatty acids out of adipocytes into the circulation is prevented. When the rate of fatty acid release into the cytosol exceeds the beta-oxidation capacity, cytosolic fatty acid concentrations increase and induce mitochondrial toxicity. This results in a decrease in beta-oxidation capacity and the entry of fatty acids into the circulation. Unless these released fatty acids are removed by mitochondrial oxidation in active muscles, these fatty acids result in ectopic triacylglycerol deposits, induction of insulin resistance, beta cell damage and diabetes. Thiazolidinediones improve mitochondrial function within adipocytes and may in this way alleviate the burden imposed by the excessive fat accumulation associated with the metabolic syndrome. Thus, the number and activity of mitochondria within adipocytes contribute to the threshold at which fatty acids are released into the circulation, leading to insulin resistance and type 2 diabetes.

Insulin sensitizing pharmacology of thiazolidinediones correlates with mitochondrial gene expression rather than activation of PPAR gamma

Insulin sensitizing thiazolidinediones (TZDs) are generally considered to work as agonists for the nuclear receptor peroxisome proliferative activated receptor-gamma (PPAR gamma). However, TZDs also have acute, non-genomic metabolic effects and it is unclear which actions are responsible for the beneficial pharmacology of these compounds. We have taken advantage of an analog, based on the metabolism of pioglitazone, which has much reduced ability to activate PPAR gamma. This analog (PNU-91325) was compared to rosiglitazone, the most potent PPAR gamma activator approved for human use, in a variety of studies both in vitro and in vivo. The data demonstrate that PNU-91325 is indeed much less effective than rosiglitazone at activating PPAR gamma both in vitro and in vivo. In contrast, both compounds bound similarly to a mitochondrial binding site and acutely activated PI-3 kinase-directed phosphorylation of AKT, an action that was not affected by elimination of PPAR gamma activation. The two compounds were then compared in vivo in both normal C57 mice and diabetic KKAy mice to determine whether their pharmacology correlated with biomarkers of PPAR gamma activation or with the expression of other gene transcripts. As expected from previous studies, both compounds improved insulin sensitivity in the diabetic mice, and this occurred in spite of the fact that there was little increase in expression of the classic PPAR gamma target biomarker adipocyte binding protein-2 (aP2) with PNU-91325 under these conditions. An examination of transcriptional profiling of key target tissues from mice treated for one week with both compounds demonstrated that the relative pharmacology of the two thiazolidinediones correlated best with an increased expression of an array of mitochondrial proteins and with expression of PPAR gamma coactivator 1-alpha (PGC1 alpha), the master regulator of mitochondrial biogenesis. Thus, important pharmacology of the insulin sensitizing TZDs may involve acute actions, perhaps on the mitochondria, that are independent of direct activation of the nuclear receptor PPAR gamma. These findings suggest a potential alternative route to the discovery of novel insulin sensitizing drugs.

MitoNEET is a uniquely folded 2Fe 2S outer mitochondrial membrane protein stabilized by pioglitazone

Iron-sulfur (Fe-S) proteins are key players in vital processes involving energy homeostasis and metabolism from the simplest to most complex organisms. We report a 1.5 A x-ray crystal structure of the first identified outer mitochondrial membrane Fe-S protein, mitoNEET. Two protomers intertwine to form a unique dimeric structure that constitutes a new fold to not only the approximately 650 reported Fe-S protein structures but also to all known proteins. We name this motif the NEET fold. The protomers form a two-domain structure: a beta-cap domain and a cluster-binding domain that coordinates two acid-labile 2Fe-2S clusters. Binding of pioglitazone, an insulin-sensitizing thiazolidinedione used in the treatment of type 2 diabetes, stabilizes the protein against 2Fe-2S cluster release. The biophysical properties of mitoNEET suggest that it may participate in a redox-sensitive signaling and/or in Fe-S cluster transfer.

Treatment options for type 2 diabetes in adolescents and youth: a study of the comparative efficacy of metformin alone or in combination with rosiglitazone or lifestyle intervention in adolescents with type 2 diabetes

Despite the increased prevalence of type 2 diabetes mellitus (T2DM) in the pediatric population, there is limited information about the relative effectiveness of treatment approaches. This article describes the rationale and design of a National Institutes of Health-sponsored multi-site, randomized, parallel group clinical trial designed to test the hypothesis that aggressive reduction in insulin resistance early in the course of T2DM is beneficial for prolongation of glycemic control, as well as improvement in associated abnormalities and risk factors. Specifically, the trial compares treatment with metformin with two alternate approaches, one pharmacologic (combining metformin treatment with rosiglitazone) and one combining metformin with an intensive lifestyle intervention program. The Treatment Options for Type 2 Diabetes in Adolescents and Youth (TODAY) study recruits 800 patients over a 4-yr period and follows them for a minimum of 2 yr and maximum of 6 yr. Patients are 10-17 yr of age, within 2 yr of diagnosis of diabetes at the time of randomization, lack evidence of autoimmunity, and have sustained C-peptide secretion. The primary outcome is time to loss of glycemic control, defined as a hemoglobin A1c >8% for 6 consecutive months. Secondary outcomes include the effect of the alternative treatments on insulin secretion and resistance, body composition, nutrition, physical activity and fitness, cardiovascular risk monitoring, microvascular complications, quality of life, depression, eating pathology, and resource utilization. TODAY is the first large-scale, systematic study of treatment effectiveness for T2DM in youth. When successfully completed, this study will provide critical new information regarding the natural history of T2DM in youth, the benefits of initiating early aggressive treatment in these patients, and the efficacy of delivering an intensive and sustained lifestyle intervention to children with T2DM.

Thiazolidinedione use and bone loss in older diabetic adults

CONTEXT

Activation of peroxisome proliferator-activated receptor-gamma by thiazolidinediones (TZDs) results in lower bone mass in mice.

OBJECTIVE

The objective of the study was to determine whether TZD use is associated with changes in bone mineral density (BMD) in older adults with type 2 diabetes.

DESIGN

We analyzed 4-yr follow-up data from the Health, Aging, and Body Composition observational study.

SETTING

The study was conducted in a general community.

PATIENTS

White and black, physically able men and women, aged 70-79 yr at baseline with diabetes defined by self-report, use of hypoglycemic medication, elevated fasting glucose (>/=126 mg/dl), or elevated 2-h glucose tolerance test (>/=200 mg/dl) participated in the study.

MAIN OUTCOME MEASURES

Whole-body, lumbar spine (derived from whole body), and hip BMD were measured by dual-energy x-ray absorptiometry at 2-yr intervals.

RESULTS

Of 666 diabetic participants, 69 reported TZD use at an annual visit, including troglitazone (n = 22), pioglitazone (n = 30), and/or rosiglitazone (n = 31). Those with TZD use had higher baseline hemoglobin A(1c) and less weight loss over 4 yr but similar baseline BMD and weight than others with diabetes. In repeated-measures models adjusted for potential confounders associated with TZD use and BMD, each year of TZD use was associated with greater bone loss at the whole body [additional loss of -0.61% per year; 95% confidence interval (CI) -1.02, -0.21% per year], lumbar spine (-1.23% per year; 95% CI -2.06, -0.40% per year), and trochanter (-0.65% per year; 95% CI -1.18, -0.12% per year) in women, but not men, with diabetes.

CONCLUSION

These observational results suggest that TZDs may cause bone loss in older women. These results need to be tested in a randomized trial.

Chronic treatment with the thiazolidinedione, MCC-555, is associated with reductions in nitric oxide synthase activity and beta-cell apoptosis in the pancreas of the Zucker Diabetic Fatty rat

The Zucker Diabetic Fatty (ZDF) rat is a model of impaired insulin sensitivity arising from hyperphagia owing to a mutation in the leptin receptor. In time, young ZDF rats, which are not initially diabetic, develop impaired pancreatic beta-cell function leading to apoptotic cell death. This results in an inability to fully compensate for the reduction in insulin sensitivity with hypersecretion of insulin. Young, pre-diabetic ZDF rats were treated, over a 4-week period, with the thiazolidinedione compound MCC-555, and the islet morphology studied in comparison to ZDF rats not given MCC-555. In particular, changes in the apoptotic incidence, as measured using TUNEL staining to localize apoptotic cells, were studied over the 4-week period. Changes in the induction of nitric oxide synthase and in the accumulation of nitrate/nitrite within the pancreas were also studied during the time course of administration of MCC-555. The study has demonstrated that the administration of MCC-555 significantly decreases the apoptotic incidence in the islets of Langerhans of pre-diabetic ZDF rats given the compound, as compared to those not given MCC-555, as well as decreasing the accumulation of nitrate/nitrite within the pancreas.

Differences in troglitazone action on glucose metabolism in freshly isolated vs long-term incubated rat skeletal muscle

1. Exposure of isolated skeletal muscle to troglitazone has resulted in inconsistent findings ranging from inhibition to stimulation of fuel oxidation and the glycogenic pathway. To better understand such variation in outcome, the present study used isolated rat soleus muscle strips to examine the interdependent influences of prolonged maintenance in vitro and of troglitazone exposure. 2. If freshly isolated muscle strips were exposed to troglitazone (1 micro mol l(-1)) for 24 h, glucose oxidation was markedly reduced (-26+/-1%, P<0.0001), whereas glycogen synthesis remained unaffected (+9+/-7%, n.s.). 3. In contrast, extended exposure to troglitazone for 72 h increased both glucose oxidation (+65+/-28%, P<0.05) and glycogen synthesis (+46+/-11%, P<0.005), and a similar stimulatory effect was also observed in muscles exposed to troglitazone only during the last 24 h of their 72 h preincubation period (glucose oxidation: +61+/-15%, P<0.001; glycogen synthesis: +43+/-15%, P<0.01). 4. Troglitazone thus stimulated glucose utilization in long-term incubated muscle independent of the duration of exposure (24 or 72 h), whereas it inhibited glucose utilization in freshly isolated muscle. 5. The observed differences in troglitazone action on freshly isolated vs long-term incubated muscle suggest that findings on muscle tissue subject to prolonged maintenance in vitro cannot be extrapolated to native muscle in vivo.

Ca(2+)-sensitizing effect is involved in the positive inotropic effect of troglitazone

1. Troglitazone, an insulin sensitizing agent, has a direct positive inotropic effect. However, the mechanism of this effect remains unclear. Thus, we examined the inotropic effect of troglitazone while focusing on intracellular Ca2+ handling. 2. Troglitazone significantly increased peak isovolumic left ventricular pressure (LVP(max)), peak rate of rise of LVP (dP/dt(max)), peak rate of fall of LVP (dP/dt(min)) in isolated rat hearts perfused at a constant coronary flow and heart rate. This inotropic effect of troglitazone was not inhibited by pretreatment with carbachol (muscarine receptor agonist), H89 (protein kinase A inhibitor), U73122 (phospholipase C inhibitor), H7 (protein kinase C inhibitor), verapamil (L-type Ca2+ channel antagonist), thapsigargin (Ca(2+)-adenosine triphosphatase inhibitor) or ryanodine (ryanodine receptor opener). 3. Radioimmunoassay showed that the cyclic adenosine monophosphate concentration in the left ventricle was not increased by troglitazone. 4. Whole-cell patch clamp analysis revealed that troglitazone had no effect on inward Ca2+ currents in cardiomyocytes. 5. In fura-2 loaded perfused rat hearts, troglitazone exerted its positive inotropic effect without increasing Ca2+ concentration. 6. These results suggest that neither the inward Ca2+ currents nor Ca2+ handling in the sarcoplasmic reticulum was involved in the inotropic effect of troglitazone. Furthermore, troglitazone exerted its positive inotropic effect without affecting the intracellular concentration of Ca2+. 7. In conclusion, the positive inotropic effect of troglitazone is mediated by a sensitization of Ca2+.

Chronic and acute effects of thiazolidinediones BM13.1258 and BM15.2054 on rat skeletal muscle glucose metabolism

1 New thiazolidinediones BM13.1258 and BM15.2054 were studied with regard to their PPARgamma-agonistic activities and to their acute and chronic effects on glucose metabolism in soleus muscle strips from lean and genetically obese rats. 2 Both BM13.1258 and BM15.2054 revealed to be potent PPARgamma-activators in transient transfection assays in vitro. 3 In insulin-resistant obese rats, but not in lean rats, 10 days of oral treatment with either compound increased the stimulatory effect of insulin on muscle glycogen synthesis to a similar extent (insulin-induced increment in micromol glucose incorporated into glycogen g-1 h-1: control, +1.19+/-0.28; BM13.1258, +2.50+/-0.20; BM15.2054, +2.55+/-0.46; P<0.05 vs control each). 4 In parallel to insulin sensitization, mean glucose oxidation increased insulin-independently in response to BM13.1258 (to 191 and 183% of control in the absence and presence of insulin, respectively; P<0.01 each), which was hardly seen in response to BM15.2054 (to 137 and 124% of control, respectively; ns). 5 Comparable effects on PPARgamma activation and on amelioration of insulin resistance by BM13.1258 and BM15.2054 were therefore opposed by different effects on glucose oxidation. 6 In contrast to chronic oral treatment, acute exposure of muscles to BM13.1258 or BM15.2054 in vitro elicited a distinct catabolic response of glucose metabolism in specimens from both lean and obese rats. 7 The results provide evidence that BM13.1258 and BM15.2054 can affect muscle glucose metabolism via more than one mechanism of action. 8 Further efforts are required to clarify, to what extent other mechanisms besides insulin sensitization via the activation of PPARgamma are involved in the antidiabetic actions of thiazolidinediones.

Improved metabolic status and insulin sensitivity in obese fatty (fa/fa) Zucker rats and Zucker Diabetic Fatty (ZDF) rats treated with the thiazolidinedione, MCC-555

1. We examined the effect of chronic (21 days) oral treatment with the thiazolidinedione, MCC-555 ((+)-5-[[6-(2-fluorbenzyl)-oxy-2-naphy]methyl]-2,4-thiazo lid inedione) on metabolic status and insulin sensitivity in obese (fa/fa) Zucker rats and Zucker Diabetic Fatty (ZDF) rats which display an impaired glucose tolerance (IGT) or overt diabetic symptoms, respectively. 2. MCC-555 treatment to obese Zucker rats (10 and 30 mg kg(-1)) and diabetic ZDF rats (10 mg kg(-1)) reduced non-esterified fatty acid concentrations in both rat strains and reduced plasma glucose and triglyceride concentrations in the obese Zucker rats. Liver glycogen concentrations were significantly increased by chronic MCC-555 treatment in both obese Zucker rats (30 mg kg(-1) day(-1)) and diabetic ZDF rats (10 mg kg(-1) day(-1)), as compared with vehicle-treated lean and obese rats and there was a significant increase in hepatic glycogen synthase activity in MCC-555-treated diabetic ZDF rats as compared to vehicle-treated controls. 3. During a euglycaemic hyperinsulinaemic clamp, MCC-555-treated obese Zucker rats and diabetic ZDF rats required significantly higher glucose infusion rates to maintain stable glucose concentrations (2.01+/-0.19 mg min(-1) and 6.42+/-1.03 mg min(-1), respectively) than vehicle-treated obese controls (0.71+/-0.17 mg min(-1) and 2.09+/-0.71 mg min(-1); P<0.05), demonstrating improved insulin sensitivity in both Zucker and ZDF rats. MCC-555 treatment also enhanced insulin-induced suppression of hepatic glucose production in ZDF rats as measured using infusions of [6-3H]-glucose under clamp conditions. 4. In conclusion, we have demonstrated that MCC-555 improves metabolic status and insulin sensitivity in obese Zucker and diabetic ZDF rats. MCC-555 may prove a useful compound for alleviating the metabolic disturbances and IGT associated with insulin resistance in man.

Actions of novel antidiabetic thiazolidinedione, T-174, in animal models of non-insulin-dependent diabetes mellitus (NIDDM) and in cultured muscle cells

1. The antihyperglycaemic effect and the possible mechanism of action of T-174, a novel thiazolidinedione derivative, was determined in vivo and in vitro. 2. Oral administration of T-174 markedly improved hyperglycaemia, hyperinsulinaemia, hyperlipidaemia, and glucose intolerance in genetically obese and diabetic yellow KK (KK-Ay) mice (0.2-15.5 mg kg(-1) day(-1), for 7 days) and Zucker fatty rats (1.4-11.4 mg kg(-1) day(-1), for 6 days). The ED50 values for the glucose lowering action of T-174 and pioglitazone, another thiazolidinedione antidiabetic, were 1.8 and 29 mg kg(-1) day(-1), respectively in KK-Ay mice; T-174 was about 16 times more potent than pioglitazone. 3. The hypoglycaemic effect of exogenous insulin in KK-Ay mice was enhanced after the administration of T-174. A hyperinsulinaemic euglycaemic clamp study in Zucker fatty rats showed an amelioration of whole-body insulin resistance by the T-174 treatment. 4. Insulin-stimulated glucose metabolism was enhanced in adipocytes from KK-Ay mice treated with T-174. The insulin receptor number of the adipocytes was increased without a change in the affinity of the receptor. 5. The hypomagnesaemia in KK-Ay mice was completely restored by T-174. 6. In cultured L6 myotubes, glucose consumption and [3H]-2-deoxy-glucose transport were enhanced by T-174 (EC50; 6 and 4 microM, respectively). Combination of insulin with T-174 was additive to stimulate glucose disposal. 7. These results suggest that the antihyperglycaemic effect of T-174 was mediated by enhanced insulin action. This was associated with amelioration of the hypomagnesaemia and T-174 directly increased basal and insulin-stimulated glucose utilization by cultured muscle cells.

Increased feeding in fatty Zucker rats by the thiazolidinedione BRL 49653 (rosiglitazone) and the possible involvement of leptin and hypothalamic neuropeptide Y

1. The thiazolidinedione BRL 49653 (rosiglitazone) induces hyperphagia and weight gain in obese, insulin-resistant fatty Zucker rats but not in lean insulin-sensitive rats. We investigated whether these responses might involve neuropeptide Y (NPY), leptin and insulin. 2. BRL 49653 (1 mg kg(-1) day(-1), orally) was given for 7 or 20 days to fatty and lean Zucker and Wistar rats. 3. In lean rats of either strain, BRL 49653 had no effect on food intake, body weight, plasma insulin and corticosterone, NPY or NPY mRNA levels. 4. Fatty rats given BRL 49653 showed a 30% increase in food intake and accelerated body weight gain (both P<0.01) after 7 and 20 days, but without significant changes in regional hypothalamic NPY or NPY mRNA levels. 5. Plasma leptin levels were twice as high in untreated fatty Zucker rats as in lean rats (P<0.01), but were unaffected by BRL 49653 given for 20 days. However, BRL 49653 reduced insulin levels by 42% and increased corticosterone levels by 124% in fatty rats (both P<0.01). 6. Hyperphagia induced in fatty Zucker rats by BRL 49653 does not appear to be mediated by either a fall in circulating leptin levels or increased activity of hypothalamic NPYergic neurones. The fall in plasma insulin and/or rise in corticosterone levels during BRL 49653 treatment may be involved, consistent with the postulated role of these hormones in the control of food intake.

Effect of englitazone on KATP and calcium-activated non-selective cation channels in CRI-G1 insulin-secreting cells

1. The effects of englitazone sodium, an antidiabetic agent, on ion channel activity in the CRI-G1 insulin secreting cell line was examined by use of the patch clamp technique. 2. Application of englitazone to the outside of CRI-G1 cells in the whole-cell recording configuration produced concentration-dependent inhibition of KATP currents with an IC50 value of 8 microM. The inhibition of the K+ current was not affected by the removal of Mg2+ ions from or the addition of trypsin to the solution bathing the intracellular surface of the cell membrane. 3. Englitazone also inhibited KATP channel activity in recordings from inside out excise membrane patches. The concentration-dependence of inhibition was identical to that observed in whole-cell recordings and was voltage-independent. Single channel recordings confirmed that neither the absence or presence of Mg2+ ions nor the addition of trypsin at the intracellular surface of the membrane influenced the inhibition of KATP channels by englitazone. 4. Englitazone also inhibited Ca(2+)-activated non-selective cation (NSCa) channels in inside-out patches in a concentration-dependent and voltage-independent manner with an IC50 value of 10 microM. In comparison, the non-sulphonylurea KATP channel blocker ciclazindol produced a slight voltage-dependent inhibition of the NSCa channel at a concentration of 20 microM. 5. In whole-cell recordings englitazone, at a relatively high concentration (50 microM) in comparison with that required to block KATP and NSCa channels, inhibited voltage-activated Ca2+ currents by 33% but did not inhibit voltage-activated K+ and Na+ currents. 6. It is concluded that englitazone is a novel blocker of NSCa and KATP channels. The inhibition of KATP channels occurs following procedures that dissociate sulphonylurea receptor coupling to the channel. The equipotent and voltage-independent inhibition of NSCa and KATP channels by englitazone may indicate a common mechanism of block.