Thiazolidinediones

Generation of affinity maps for thiazolidinediones with human serum albumin using affinity microcolumns. I. Studies of effects by glycation on multisite drug binding

Human serum albumin (HSA) is known to undergo modifications by glucose during diabetes. This process produces glycated HSA that can have altered binding to some drugs. In this study, high-performance affinity microcolumns and competition studies were used to see how glycation affects the binding by two thiazolidinedione-class drugs (i.e., pioglitazone and rosiglitazone) at specific regions of HSA. These regions included Sudlow sites I and II, the tamoxifen and digitoxin sites, and a drug-binding site located in subdomain IB. At Sudlow site II, the association equilibrium constants (or binding constants) for pioglitazone and rosiglitazone with normal HSA were 1.7 × 105 M-1 and 2.0 × 105 M-1 at pH 7.4 and 37 °C, with values that changed by up to 5.7-fold for glycated HSA. Sudlow site I of normal HSA had binding constants for pioglitazone and rosiglitazone of 3.4 × 105 M-1 and 4.6 × 105 M-1, with these values changing by up to 1.5-fold for glycated HSA. Rosiglitazone was found to also bind a second region that had a positive allosteric effect on Sudlow site I for all the tested preparations of HSA (binding affinity, 1.1-3.2 × 105 M-1; coupling constant for Sudlow site I, 1.20-1.34). Both drugs had a strong positive allosteric effect on the tamoxifen site of HSA (coupling constants, 13.7-19.9 for pioglitazone and 3.7-11.5 for rosiglitazone). Rosiglitazone also had weak interactions at a site in subdomain IB, with a binding constant of 1.4 × 103 M-1 for normal HSA and a value that was altered by up to 6.8-fold with glycated HSA. Neither of the tested drugs had any significant binding at the digitoxin site. The results were used to produce affinity maps that described binding by these thiazolidinediones with HSA and the effects of glycation on these interactions during diabetes.

Comparison of SGLT1, SGLT2, and Dual Inhibitor biological activity in treating Type 2 Diabetes Mellitus

Diabetes Mellitus Type 2 (T2D) is an emerging health burden in the USand worldwide, impacting approximately 15% of Americans. Current front-line therapeutics for T2D patients include sulfonylureas that act to reduce A1C and/or fasting blood glucose levels, or Metformin that antagonizes the action of glucagon to reduce hepatic glucose production. Next generation glucomodulatory therapeutics target members of the high-affinity glucose transporter Sodium-Glucose-Linked-Transporter (SGLT) family. SGLT1 is primarily expressed in intestinal epithelium, whose inhibition reduces dietary glucose uptake, whilst SGLT2 is highly expressed in kidney - regulating glucose reabsorption. A number of SGLT2 inhibitors are FDA approved whilst SGLT1 and dual SGLT1 & 2 inhibitor are currently in clinical trials. Here, we discuss and compare SGLT2, SGLT1, and dual inhibitors' biochemical mechanism and physiological effects.

Exploring plant-based alpha-glucosidase inhibitors: promising contenders for combatting type-2 diabetes

Objective: This systematic review aimed to provide comprehensive details on the α-G inhibitory potential of various bioactive compounds derived from natural sources.Methods: A comprehensive literature search was conducted using various databases and search engines, including Science Direct, Google Scholar, SciFinder, Web of Science, and PubMed until May, 2023.Results and conclusions: The enzyme alpha-glucosidase (α-G) is found in the brush border epithelium of the small intestine and consists of duplicated glycoside hydrolase (GH31) domain. It involves the conversion of disaccharides and oligosaccharides into monosaccharides by acting on alpha (1 → 4) and (1 → 6) linked glucose residue. Once absorbed, glucose enters the bloodstream and elevates postprandial glucose, which is associated with the development of type 2 Diabetes (T2D). Epidemic obesity, cardiovascular disease, and nephropathy are linked to T2D. Traditional medicinal plants with α-G inhibitory potential are commonly used to treat T2D due to the adverse effects of currently used α-G inhibitors miglitol, acarbose, and voglibose. Various bioactive compounds derived from natural sources, including lupenone, Wilforlide A, Baicalein, Betulinic acid, Ursolic acid, Oleanolic acid, Katononic acid, Carnosol, Hypericin, Astilbin, lupeol, betulonic acid, Fagomine, Lactucaxanthin, Erythritol, GP90-1B, Procyanidins, Galangin, and vomifoliol retain α-G inhibitory potential for regulating hyperglycaemia.

Assessment of Early Markers of Cardiovascular Risk in Polycystic Ovary Syndrome

Polycystic ovary syndrome (PCOS) is a heterogeneous syndrome, with long-term sequelae from birth to senescence. The long-term effects of PCOS are attributed to several metabolic aberrations ensuing the syndrome. In a systematic review of literature regarding the cardiovascular risk factors that accompany PCOS, we found that macrovascular function has been assessed by flow-mediated dilatation (FMD), microvascular function by venous occlusion plethysmography (VOP), and arterial structure by ultrasonographic assessment of intima-media thickness (IMT) usually of the carotid artery. Contradictory results have been reported; however, in most studies, endothelial dysfunction, an early marker of atherosclerosis assessed either by haemodynamic methods such as FMD or by biochemical methods such as endothelin-1 levels, was found to be impaired. VOP is a less-studied method, with few indices altered. IMT was found to be altered in most of the included studies, but the population was more heterogeneous. Inflammatory markers, including C-reactive protein, were also found to be altered in most studies. On the other hand, a number of interventions have been shown beneficial for the markers of cardiovascular risk, in the context of insulin-sensitizers. However, other interventions such as oral contraceptive pills or statins did not consistently show a similar beneficial effect. In summary, the early identification and eventual treatment of cardiovascular clinical and biochemical risk factors may be used in clinical practice to prevent potential 'silent' triggers of cardiovascular disease.

Assessment of Early Markers of Cardiovascular Risk in Polycystic Ovary Syndrome

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Sixty Years of Drug Discovery for Type 2 Diabetes: Where Are We Now?

Today, excluding insulin, there are eight classes of anti-diabetic medicines that have been added to the pharmacy since the introduction of metformin in the mid-1950s; the sulfonylureas, biguanides, thiazolidinediones, α-glucosidase inhibitors, meglitinides, incretins, and sodium glucose transport 2 inhibitors. Does the fact that metformin is still first-line treatment suggest that our drug discovery efforts over the past 60 years have not been good enough? Or does it suggest that diabetes is such a complex disorder that no single treatment, other than gastric bypass surgery, can affect true normalization of not only blood sugar but also the underlying pathologies? Our understanding of the disease has most definitely improved which may bring hope for the future in terms of science, but for it to be beneficial, this science has to be translated into better drug treatments for the disease. In this review, I have examined the eight classes of anti-diabetes drugs from a drug discovery perspective.

Anti-Inflammatory Effects of Rosiglitazone in Obesity-Impaired Wound Healing Depend on Adipocyte Differentiation

Combined diabetes-obesity syndromes severely impair regeneration of acute skin wounds in mouse models. This study assessed the contribution of subcutaneous adipose tissue to exacerbated wound inflammatory conditions. Genetically obese (ob/ob) mice showed an increased expression of positive transcriptional effectors of adipocyte differentiation such as Krüppel-like factor (KLF)-5 and peroxisome proliferator-activated receptor (PPAR)-γ and an associated expression of leptin and fatty acid-binding protein (FABP)-4, but also CXCL2 in isolated subcutaneous fat. This observation in obese mice is in keeping with differentially elevated levels of KLF-5, PPAR-γ, leptin, FABP-4 and CXCL2 in in vitro-differentiated 3T3-L1 adipocytes. Notably, CXCL2 expression restrictively appeared upon cytokine (IL-1β/TNF-α) stimulation only in mature, but not immature 3T3-L1 adipocytes. Of importance, the critical regulator of adipocyte maturation, PPAR-γ, was merely expressed in the final phase of in-vitro induced adipocyte differentiation from 3T3-L1 pre-adipocytes. Consistently, the PPAR-γ agonist rosiglitazone suppressed cytokine-induced CXCL2 release from mature adipocytes, but not from early 3T3-L1 adipocyte stages. The inhibitory effect of PPAR-γ activation on CXCL2 release appeared to be a general anti-inflammatory effect in mature adipocytes, as cytokine-induced cyclooxygenase (Cox)-2 was simultaneously repressed by rosiglitazone. In accordance with these findings, oral administration of rosiglitazone to wounded obese mice significantly changed subcutaneous adipocyte morphology, reduced wound CXCL2 and Cox-2 expression and improved tissue regeneration. Thus, our data suggest that PPAR-γ might provide a target to suppress inflammatory signals from mature adipocytes, which add to the prolonged wound inflammation observed in diabetes-obesity conditions.

Management of Polycystic Ovary Syndrome

Polycystic ovary syndrome is a common endocrinological problem in women of reproductive age. Polycystic ovary syndrome is a heterogenous disorder and patients may attend different clinics depending on the main complaint. The exact pathophysiology of polycystic ovary syndrome remains obscure, although there have been insights that have thrown light on this condition. Consensus on the definition of the syndrome has only been recently achieved. The management of polycystic ovary syndrome poses a challenge to the physician as responses to the different treatment regimes have proved to be inconsistent. Diet and lifestyle advice, restoration of menstrual cycle regularity, treatment of hyperandrogenism, treatment of infertility and prevention of long-term consequences form the basis of polycystic ovary syndrome management. This review aims to provide the reader with the latest evidence in the treatment of polycystic ovary syndrome, as well as focus on some of the controversies surrounding its management.

The Effects of Rosiglitazone Treatment on the Fibrinolytic System in Patients with Type 2 Diabetes Mellitus

Patients with type 2 diabetes mellitus (DM) are at risk for the development of cardiovascular diseases, which can in part be explained by disturbances in the hemostatic and fibrinolytic systems. The effects of rosiglitazone treatment on the fibrinolytic system and insulin sensitivity in patients with type 2 DM were assessed. Twenty-four patients with type 2 DM and 28 healthy subjects were enrolled in the study. Plasma global fibrinolytic capacity (GFC), tissue plasminogen activator (t-PA), and plasminogen activator inhibitor-1 (PAI-1) levels were measured. Insulin resistance was calculated by hoemostasis model assessment. Patients with type 2 DM then were placed on rosiglitazone (4 mg/day, for 12 weeks) in addition coexistent medication, and baseline tests were repeated. There was no difference between mean t-PA levels of the two groups. PAI-1 levels were higher in diabetic patients than control subjects (p < 0.01). Diabetic patients had lower GFC and t-PA/PAI-1 levels than control subjects (p < 0.05, p < 0.05). PAI-1 levels were positively correlated with waist circumference in diabetic group (r = 0.4, p < 0.05). After rosiglitazone treatment, there was no difference in mean plasma levels of GFC, t-PA, PAI-1 and t-PA/PAI-1 in diabetics. Insulin sensitivity significantly improved after the addition of rosiglitazone treatment in diabetic patients (p < 0.01). The short-term and low-dose treatment with rosiglitazone in type 2 diabetic patients has no effects on the fibrinolytic system, although it improves insulin sensitivity.

Atherosclerosis in Type 2 Diabetes Mellitus: The Role of Insulin Resistance

Type 2 diabetes mellitus is associated with a marked increase in the risk of atherosclerotic diseases, including coronary heart disease, peripheral arterial disease, and cerebrovascular disease. Insulin resistance is a key factor in the pathogenesis of type 2 diabetes mellitus. Insulin resistance and its attendant metabolic abnormalities may cause much of the increased cardiovascular risk of type 2 diabetes mellitus. Among the abnormalities associated with insulin resistance are dyslipidemia, hypertension, systemic inflammation, and a prothrombotic state. This review discusses the role that each of these disorders plays in the cardiovascular risk of type 2 diabetes mellitus.

Update on Safety Issues Related to Antihyperglycemic Therapy

The American Diabetes Association emphasizes the importance of individualized patient care in the management of diabetes. One of the important considerations in choosing an antihyperglycemic agent is its side-effect and safety profile. This article reviews the common and clinically significant side effects of each class of agents, including ways to prevent and overcome their occurrence.

Expression of obesity markers and Persistent Organic Pollutants levels in adipose tissue of obese patients: reinforcing the obesogen hypothesis?

Introduction

Persistent Organic Pollutants (POPs) accumulate in adipose tissue and some are described to possess endocrine disrupting capacities. Therefore, it is important to evaluate their effects on key endocrine pathways in adipose tissue (AT), to further evaluate their potential role in metabolic pathologies such as obesity.

Objectives

The aim is twofold: (i) evaluate gene expression levels of obesity marker genes, i.e. the adipokines leptin (LEP), adiponectin (ADIPOQ) and Tumor Necrosis Factor α (TNFα) and the nuclear receptor, Peroxisome Proliferator Activated Receptor γ (PPARγ) in paired subcutaneous (SAT) and visceral (VAT) AT of obese subjects (n = 50) and to relate these values to serum concentrations of LEP and ADIPOQ (ii) evaluate the association of expression levels of marker genes in AT and serum with POP concentrations in AT.

Results and Conclusions

Leptin and adiponectin levels in serum were positively correlated to respectively expression levels of leptin in SAT and adiponectin in VAT. Our study shows more significant correlations between gene expression of obesity marker genes and POP concentrations in VAT compared to SAT. Since VAT is more important than SAT in pathologies associated with obesity, this suggests that POPs are able to influence the association between obesity and the development of associated pathologies. Moreover, this finding reveals the importance of VAT when investigating the obesogen hypothesis. Concerning PPARγ expression in VAT, negative correlations with polychlorinated biphenyls (PCBs) concentrations were found in non T2D patients. LEP serum concentrations correlated with several PCBs in women whereas in men no correlations were found. This strengthens the potential importance of gender differences in obesity and within the obesogen hypothesis.

Rosiglitazone suppresses glioma cell growth and cell cycle by blocking the transforming growth factor-beta mediated pathway

Glioma is one of the most malignant tumors in the central nervous system. As a peroxisome proliferator-activated receptor γ (PPAR-γ) activator, the thiazolidinediones (TZDs) induce growth arrest and cell death in a broad spectrum of tumor cells. In this study, we investigated the role of rosiglitazone in glioma cells. We found that rosiglitazone, a member of TZDs, suppresses growth of human glioma cell lines U87 and U251. Rosiglitazone also induces cell cycle arrest and apoptosis, which may be the mechanism of its anti-proliferation effect. Next, we found that rosiglitazone suppresses the expression of TGF-beta and its receptor TGF-betaR2, and suppresses phosphorylation of Smad3. Rosiglitazone also inhibits formation of the Smad3/Smad4 complex. Furthermore, Rosiglitazone affects the expression of Smad3/Smad4 associated regulators of gene expression, including p21 and c-Myc. These results suggest that rosiglitazone suppresses growth and cell cycle of human glioma cells by blocking the TGF-beta mediated pathway.

Comprehensive evidence-based assessment and prioritization of potential antidiabetic medicinal plants: a case study from canadian eastern james bay cree traditional medicine

Canadian Aboriginals, like others globally, suffer from disproportionately high rates of diabetes. A comprehensive evidence-based approach was therefore developed to study potential antidiabetic medicinal plants stemming from Canadian Aboriginal Traditional Medicine to provide culturally adapted complementary and alternative treatment options. Key elements of pathophysiology of diabetes and of related contemporary drug therapy are presented to highlight relevant cellular and molecular targets for medicinal plants. Potential antidiabetic plants were identified using a novel ethnobotanical method based on a set of diabetes symptoms. The most promising species were screened for primary (glucose-lowering) and secondary (toxicity, drug interactions, complications) antidiabetic activity by using a comprehensive platform of in vitro cell-based and cell-free bioassays. The most active species were studied further for their mechanism of action and their active principles identified though bioassay-guided fractionation. Biological activity of key species was confirmed in animal models of diabetes. These in vitro and in vivo findings are the basis for evidence-based prioritization of antidiabetic plants. In parallel, plants were also prioritized by Cree Elders and healers according to their Traditional Medicine paradigm. This case study highlights the convergence of modern science and Traditional Medicine while providing a model that can be adapted to other Aboriginal realities worldwide.

PPAR-gamma Thiazolidinedione Agonists and Immunotherapy in the Treatment of Brain Tumors

Thiazolidinediones (TZDs) are selective agonists of the peroxisome proliferator-activated receptor (PPAR) gamma, a transcription factor belonging to the superfamily of nuclear hormone receptors. Although activation of PPARγ by TZDs has been best characterized by its ability to regulate expression of genes associated with lipid metabolism, PPARγ agonists have other physiological effects including modulating pro- and anti-inflammatory gene expression and inducing apoptosis in several cell types including glioma cells and cell lines. Immunotherapeutic approaches to reducing brain tumors are focused on means to reduce the immunosuppressive responses of tumors which dampen the ability of cytotoxic T-lymphocytes to kill tumors. Initial studies from our lab show that combination of an immunotherapeutic strategy with TZD treatment provides synergistic benefit in animals with implanted tumors. The potential of this combined approach for treatment of brain tumors is reviewed in this report.

Drug-induced hypoglycaemia: an update

Drugs are the most frequent cause of hypoglycaemia in adults. Although hypoglycaemia is a well known adverse effect of antidiabetic agents, it may occasionally develop in the course of treatment with drugs used in everyday clinical practice, including NSAIDs, analgesics, antibacterials, antimalarials, antiarrhythmics, antidepressants and other miscellaneous agents. They induce hypoglycaemia by stimulating insulin release, reducing insulin clearance or interfering with glucose metabolism. Several drugs may also potentiate the hypoglycaemic effect of antidiabetic agents. Administration of these agents to individuals with diabetes mellitus is of most concern. Many of these drugs, and depending on clinical setting, may also induce hyperglycaemia. Drug-induced hepatotoxicity and nephrotoxicity may lead in certain circumstances to hypoglycaemia. Some drugs may also induce hypoglycaemia by causing pancreatitis. Drug-induced hypoglycaemia is usually mild but may be severe. Effective clinical management can be handled through awareness of this drug-induced adverse effect on blood glucose levels. Herein, we review pertinent clinical information on the incidence of drug-induced hypoglycaemia and discuss the underlying pathophysiological mechanisms, and prevention and management.

Discovery and development of selective PPAR gamma modulators as safe and effective antidiabetic agents

IMPORTANCE OF THE FIELD

PPARgamma full agonists (pioglitazone and rosiglitazone) are the mainstay drugs for the treatment of type 2 diabetes; however, mechanism-based side effects have limited their full therapeutic potential. In recent years, much progress has been achieved in the discovery and development of selective PPARgamma modulators (SPPARgammaMs) as safer alternatives to PPARgamma full agonists.

AREAS COVERED IN THIS REVIEW

This review focuses on the preclinical and clinical data of all the SPPARgammaMs discovered so far, retrieved by searching PubMed, Prous Integrity database and company news updates from 1999 to date.

WHAT THE READER WILL GAIN

Here we thoroughly discuss SPPARgammaMs' mode of action, briefly examine new ways to identify superior SPPARgammaMs, and finally, compare and contrast the pharmacological and safety profile of various agents.

TAKE HOME MESSAGE

The preclinical and clinical findings clearly suggest that selective PPARgamma modulators have the potential to become the next generation of PPARgamma agonists: effective insulin sensitizers with a superior safety profile to that of PPARgamma full agonists.

Effects of rosiglitazone on bone mineral density and remodelling parameters in Postmenopausal diabetic women: a 2-year follow-up study

OBJECTIVE

To evaluate the effect of rosiglitazone on bone metabolism and bone density.

DESIGN

An open-label, randomized, controlled trial of 24-month duration. Patients and measurements Obese, postmenopausal women with newly diagnosed diabetes were studied. Before and after the intervention, metabolic bone markers and bone density were assessed.

RESULTS

Twenty-six patients received rosiglitazone (4 mg/day), and 23 remained on diet alone. Serum bone-specific alkaline phosphatase and osteocalcin levels decreased by 17% (P < 0.001 vs control group) and 26% (P < 0.01 vs control group), respectively, in the rosiglitazone group. There were no significant changes in the deoxypyridinoline levels between the two groups. Annual bone loss at the trochanter and at the lumbar spine associated with each year of rosiglitazone use was 2.56% (P = 0.01 vs control group) and 2.18% (P < 0.01 vs control group), respectively. Femoral neck and total hip bone density declined significantly in both groups (P < 0.01, and P = 0.01, respectively) but was not significantly different between the two groups.

CONCLUSIONS

Rosiglitazone treatment adversely affects bone formation over a 2-year period. It increases bone loss at the lumbar spine and trochanter in postmenopausal, type 2 diabetic women. However, bone loss at the total hip did not differ with use of this agent.

Smoking status is associated with serum high molecular adiponectin levels in community-dwelling Japanese men

AIM

Serum high molecular weight (HMW) adiponectin improves insulin sensitivity, and a decreased level has been reported as a risk factor for the development of diabetes and coronary heart disease. This association may be further confounded by smoking, which is involved in the development of insulin resistance. The aim of this study was to determine whether smoking status is associated with serum HMW adiponectin levels in community-dwelling males.

METHODS

The cross-sectional study was carried out in 2002. Study participants without a clinical history of diabetes (724 men aged 60+/-14 (mean+/-standard deviation) (range, 20-89) years) were randomly recruited from a single community at an annual physical examination. They were classified into never-smokers, ex-smokers, light-smokers (<30 pack x year), and heavy-smokers (>or=30 pack x year).

RESULTS

Mean serum HMW adiponectin levels were significantly lower in the current smokers than in the never- and ex-smokers but showed no significant difference between the light and heavy-smokers. Multiple linear regression analyses revealed that smoking status was significantly associated with HMW adiponectin levels, as were age, BMI, alcohol consumption, triglycerides, and high-density lipoprotein cholesterol. Multivariate-adjusted mean serum HMW adiponectin levels were lowest in the heavy-smokers, and significantly decreased in heavy-smokers compared with never-smokers and ex-smokers of an age >or=60 years, BMI >or=22 kg/m(2), alcohol consumption >or=22.9 g of ethanol/day, and HOMA-IR >or=1.6.

CONCLUSION

Smoking status is associated with serum HMW adiponectin levels in community-dwelling Japanese men.

Use of insulin-sensitizing agents in the treatment of polycystic ovary syndrome

The role of insulin sensitizing agents is discussed at length in this Committee Opinion.

Keratinocyte-derived vascular endothelial growth factor biosynthesis represents a pleiotropic side effect of peroxisome proliferator-activated receptor-gamma agonist troglitazone but not rosiglitazone and involves activation of p38 mitogen-activated protein kinase: implications for diabetes-impaired skin repair

The peroxisome proliferator-activated receptors (PPARs) represent pharmacological target molecules to improve insulin resistance in type 2 diabetes mellitus. Here we assessed a functional connection between pharmacological activation of PPAR and vascular endothelial growth factor (VEGF) expression in keratinocytes and during diabetes-impaired acute skin repair in obese/obese (ob/ob) mice. PPARbeta/delta agonist 4-[3-[4-acetyl-3-hydroxy-2-propylphenoxy)propoxy]phenoxy]acetic acid (L165,041) and PPARgamma agonists ciglitazone and troglitazone, but not rosiglitazone, potently induced VEGF mRNA and protein expression from cultured keratinocytes. Inhibitor studies revealed a strong functional dependence of troglitazone- and L165,041-induced VEGF expression on p38 and p42/44 mitogen-activated protein kinase (MAPK) activation in keratinocytes. Rosiglitazone also induced activation of p38 MAPK but failed to mediate the activation of p42/44 MAPK in the cells. Functional ablation of PPARbeta/delta and PPARgamma from keratinocytes by small interfering RNA did not abrogate L165,041- and troglitazone-induced VEGF biosynthesis and suggested VEGF induction as a pleiotropic, PPAR-independent effect of both drugs in the cells. In accordance with the in vitro situation, we found activated p38 MAPK in wound keratinocytes from acute wounds of rosiglitazone- and troglitazone-treated diabetic obese/obese mice, whereas keratinocyte-specific VEGF protein signals were only prominent upon troglitazone treatment. In summary, our data from cell culture and wound healing experiments suggested p38 MAPK activation as a side effect of thiazolidinediones; however, only troglitazone, but not rosiglitazone, seemed to translate p38 MAPK activation into a PPARgamma-independent induction of VEGF from keratinocytes.

Late-Onset Rosiglitazone-Associated Acute Liver Failure in a Patient with Hodgkin's Lymphoma

Objective:

To report a case of rosiglilazone-associated hepatotoxicity in a patient with Hodgkin's lymphoma.

Case Summary:

A 52-year-old man presented with low-grade fever and fatigue that had been present for 4 months. He had been receiving insulin for 5 years and rosiglitazone 4 mg/day for 11 months for control of type 2 diabetes; he was receiving no other drug therapy. During hospitalization, hepatotoxicity was shown, with abnormal liver function test results including alanine aminotransferase 488 U/L, aspartate aminotransferase 344 U/L, alkaline phosphatase B32 U/L, total bilirubin 4.61 mg/dL, and direct bilirubin 3.63 mg/dL. Rosiglitazone was discontinued after further elevation of bilirubin (total 14.67 mg/dL, direct 12.10 mg/dL) occurred. Other causes for hepatotoxicity were ruled out, Hodgkin's lymphoma was diagnosed during the workup; however, liver imaging and biopsy also excluded this as the direct cause of acute liver failure. Despite discontinuation of rosiglitazone, the bilirubin level continued to increase to 49.29 mg/dL (direct >20 mg/dL). The patient died 3 months after admission.

Discussion:

Rosiglitazone maleate is a thiazolidinedione approved for treatment of type 2 diabetes mellitus. The first member of this drug class, troglitazone, was withdrawn from the market due to reports of acute liver failure. Rosiglitazone has been shown to be much safer than troglitazone, despite some reported cases of early-onset nonfatal hepatotoxicity. Use of the Naranjo probability scale indicated that rosiglitazone was the probable cause of acute liver failure in our patient.

Conclusions:

We conclude that rosiglitazone may be associated with late-onset acute liver failure. Clinicians should be aware of such a complication and monitor liver function in patients receiving the drug.

Rosiglitazone decreases serum bone-specific alkaline phosphatase activity in postmenopausal diabetic women

OBJECTIVES

Our objectives were to evaluate the effect of rosiglitazone on bone metabolism and to assess the association between changes in bone turnover parameters and plasma cytokine levels in postmenopausal diabetic women.

DESIGN

This was a 12-wk open-label randomized-controlled trial.

PATIENTS OR OTHER PARTICIPANTS

A total of 56 obese postmenopausal women with newly diagnosed diabetes and 26 nondiabetic healthy controls matched for age and body mass index were included in the study.

INTERVENTIONS

The subjects were instructed to follow a weight-maintenance diet. Half were randomly assigned to receive rosiglitazone 4 mg/d, and the other half remained on diet alone.

MAIN OUTCOME MEASURES

Before and after the interventions, metabolic bone markers and serum cytokine levels were assessed.

RESULTS

Serum total alkaline phosphatase (ALP) and bone-specific ALP levels were statistically significantly lower 12 wk after initiation of rosiglitazone treatment. There were no statistically significant changes in osteocalcin levels among the three groups or in deoxypyridinoline levels in the rosiglitazone group. At the end of 12 wk, all patients had statistically significantly decreased IL-1beta and TNF-alpha levels compared with baseline. Changes in bone-specific ALP levels showed a moderate negative correlation with the changes in the TNF-alpha levels after rosiglitazone treatment and after diet in the diabetic control group.

CONCLUSIONS

Rosiglitazone use is associated with reduced bone formation at earlier stages in postmenopausal diabetic women. The cytokine-lowering effects of rosiglitazone and lifestyle changes could reverse the early inhibitory effect of rosiglitazone therapy on bone formation. Further studies will clarify the long-term effects of rosiglitazone therapy on bone loss and fracture.

Effect of pinitol on glucose metabolism and adipocytokines in uncontrolled type 2 diabetes

Pinitol (3-O-methyl-D-chiro-inositol) was identified in putative insulin mediator fractions that have hypoglycemic activity, and appears to mimic the act effects of insulin by acting downstream in the insulin signaling pathway. We evaluated the effect of pinitol therapy in type 2 diabetic patients who were poorly controlled with hypoglycemic drugs, such as sulfonylurea, metformin and/or insulin. Twenty type 2 diabetic patients were enrolled in our study. Fasting glucose, fasting c-peptide, total cholesterol, triglyceride, and HDL- and LDL-cholesterol were checked before and after a 12-week pinitol treatment (20 mg kg(-1)day(-1)). All subjects continued their current medications during the study. Adipocytokines, such as adiponectin, leptin, free fatty acids, and c-reactive protein (CRP) were checked before and after pinitol treatment. After pinitol treatment, fasting glucose, post-prandial glucose levels, and hemoglobin A1c were significantly decreased (P<0.05). Fasting serum adiponectin, leptin, free fatty acid, and CRP levels did not change after pinitol treatment. In the unresponsive group, serum c-peptide levels were higher than in the responsive group. Twelve weeks of pinitol treatment altered glucose metabolism, but not lipid profiles or adipocytokine levels, in type 2 diabetic patients. Additional research is needed to define the physiological and potential therapeutic effects of pinitol administration.

Prolonged survival of mice with established intracerebral glioma receiving combined treatment with peroxisome proliferator-activated receptor-gamma thiazolidinedione agonists and interleukin-2-secreting syngeneic/allogeneic fibroblasts

OBJECT

In this study the authors explored the benefits of treating C57B1/6 mice with an established intracerebral glioma by combining immunotherapy with interleukin (IL)-2-secreting syngeneic/allogeneic fibroblasts administered into the tumor bed along with the chemotherapeutic agent pioglitazone, a thiazolidinedione (TZD). The TZDs are agonists of the peroxisome proliferator-activated receptor-gamma. They have been found to exert antiproliferative effects on several transformed cell lines. Data from prior studies by these authors have revealed the immunotherapeutic properties of the IL-2-secreting fibroblasts in treating intracerebral gliomas in mice.

METHODS

The sensitivity of GL261 glioma cells and primary astrocytes to pioglitazone was determined in vitro by incubating the cells with increasing amounts of the drug. Viability was assessed by measuring lactate dehydrogenase release, and effects on metabolism were determined by measuring superoxide production and levels of superoxide dismutase. The GL261 cells were injected intracerebrally into C57B1/6 mice, followed by treatment with pioglitazone either orally or intracerebrally into the tumor bed. The effect of the combined therapy was determined by injecting C57B1/6 mice with an established intracerebral GL261 glioma with IL-2-secreting allogeneic fibroblasts and pioglitazone directly into the tumor bed through a unique cannula system. Pioglitazone was found to induce cell death in GL261 glioma cells grown in vitro while causing only modest damage to astrocytes. The application of pioglitazone also resulted in a significantly greater induction of cellular superoxide in glioma cells than in astrocytes, which can activate apoptotic pathways. Pioglitazone administered intracerebrally (p < 0.05) but not orally was found to prolong survival in mice harboring an intracerebral glioma. Synergistic effects of combination therapy on prolonging survival were found in mice receiving both pioglitazone and IL-2-secreting fibroblasts (p < 0.005, compared with untreated animals). Pioglitazone induces metabolic and oxidative stresses that are tolerated by astrocytes but not glioma cells, which could account for selective vulnerability and increased sensitivity to IL-2, suggesting potential for the use of this Food and Drug Administration-approved drug in the treatment of brain tumors.

CONCLUSIONS

The data indicate the beneficial effects of combination therapy using pioglitazone and immunotherapy in mice harboring intracerebral glioma.

Beneficial effects of thiazolidinediones on diabetic nephropathy in OLETF rats

PURPOSE

Diabetic nephropathy is the most serious of complications in diabetes mellitus. Thiazolidinedione (TZD) is thought to ameliorate diabetic nephropathy; however, the mechanism underlying this effect has not been elucidated. We hypothesized that the vascular endothelial growth factor (VEGF) participates in the pathogenesis of diabetic nephropathy and that TZD may be beneficial for the treatment of diabetic nephropathy because of the effect it has on VEGF.

MATERIALS AND METHODS

23 Otsuka- Long-Evans-Tokushima-Fatty (OLETF) rats and eight control Long-Evans-Tokushima-Otsuka (LETO) rats were divided into the following four groups: LETO group, control OLETF group, pioglitazone treated group (10mg/ kg/day), and rosiglitazone treated group (3mg/kg/day).

RESULTS

A progressive increase in urinary protein excretion was observed in the diabetic rats. Glomerular VEGF expression in the control OLETF rats was significantly higher than in the control LETO rats. However, there was a significant reduction in both the glomerular VEGF expression and the VEGF mRNA levels after treatment with pioglitazone and rosiglitazone. The twenty-four hour urine protein levels were significantly decreased in both groups of the treated OLETF rats.

CONCLUSION

These results suggest that TZD may have beneficial effects on diabetic nephropathy by reducing the VEGF expression.

The mushroom Agaricus Blazei Murill in combination with metformin and gliclazide improves insulin resistance in type 2 diabetes: a randomized, double-blinded, and placebo-controlled clinical trial

BACKGROUND

Complementary and alternative medicine use in adults with type 2 diabetes is popular. Although most of the herbs and supplements appear to be safe, there is still insufficient evidence that demonstrates their definitive beneficial effects. This study was done to determine whether the supplement of Agaricus blazei Murill extract improves insulin resistance in type 2 diabetes.

MATERIALS AND METHODS

This study was a clinical randomized, double-blind, placebo-controlled trial. Of a population of 536 registered diabetes patients with 72 subjects (1) aged between 20 and 75 years, (2) being Chinese, (3) having type 2 diabetes for more than 1 year, and (4) having been taking gliclazide and metformin for more than 6 months were enrolled in this study. The enrolled patients were randomly assigned to either receiving supplement of Agaricus blazei Murill (ABM) extract or placebo (cellulose) 1500 mg daily for 12 weeks. Homeostasis model assessment for insulin resistance (HOMA-IR) was used as the major outcome measurement.

RESULTS

At the end of the study, subjects who received supplement of ABM extract (n = 29) showed significantly lower HOMA-IR index (3.6[standard deviation, 2.5] versus 6.6[standard deviation, 7.4], p = 0.04) than the control group (n = 31). The plasma adiponectin concentration increased 20.0(standard deviation, 40.7)% in the ABM group after 12 weeks of treatment, but decreased 12.0(20.0)% among those taking the placebo (p < 0.001).

CONCLUSIONS

Supplement of ABM extract improves insulin resistance among subjects with type 2 diabetes. The increase in adiponectin concentration after taking AMB extract for 12 weeks might be the mechanism that brings the beneficial effect. Studies with longer periods of follow-up should be conducted in the future.

Differential effects of PPARγ agonists on the metabolic properties of gliomas and astrocytes

Recent studies show that thiazolinediones (TZDs), agonists of the peroxisome proliferator-activated receptor gamma (PPARgamma), induce apoptosis in glioma and glioblastoma cells. Here we compared the effects of troglitazone (Trog), a TZD with low affinity for binding to PPARgamma but with potent metabolic effects, on survival and metabolism in GL261 glioma cells versus primary astrocytes. Trog dose-dependently induced cell death in GL261 cells (with over 90% death at 30 microM) but did not cause any toxicity in astrocytes at the same doses. Measurements of glucose and lactate levels after incubation with Trog (30 microM) indicated an overall increase of glucose consumption and lactate production in both cell types. In astrocytes the ratio of lactate produced to glucose utilized was not significantly altered by Trog, while in glioma cells this ratio was decreased by about 40%. Trog dose-dependently reduced mitochondrial membrane potential (DeltaPsi(m)) in both cell types; and the loss of DeltaPsi(m) was greater in the tumor cells (90% loss at 20 microM) than in astrocytes (70% loss at 20 microM). These results suggest that differences in metabolic responses could contribute to the selective resistance of astrocytes to cytotoxic effects of Trog. TZDs such as Trog should therefore be considered for testing in treatment of gliomas.

Rosiglitazone: safety and efficacy in combination with insulin in poorly controlled type 2 diabetes mellitus patients treated with insulin alone

AIMS

To assess the safety and efficacy of rosiglitazone and insulin treatment in combination in poorly controlled insulin-treated type 2 diabetes mellitus (T2DM) patient.

METHOD

In this prospective, open-labelled, nonrandomised study, rosiglitazone was added to the insulin therapy in T2DM patients with baseline HbA1c>or=7.5%. Patients were followed for 12 months. Insulin dosage was adjusted as necessary.

RESULTS

Insulin and rosiglitazone combination was used in 53 patients (29 male, 24 female) for 12 months. Baseline vs. 12-month results shown as mean+/-S.D.: HbA1c reduction 1.53% (9.82+/-1.12 vs. 8.29+/-1.45, P=.0001), insulin dosage reduction 10 U (74+/-34 vs. 64+/-34 U), percentage insulin dose reduction 13.53%, and weight gain 1.0 kg only (84+/-19.93 vs. 85+/-25.73 kg, P=.1). Systolic blood pressure 144+/-22.9 vs. 134+/-15.8 mm Hg (P=.03), total cholesterol 6.18+/-4.15 vs. 4.75+/-2.71 micromol/L, triglyceride 2.62+/-1.49 vs. 2.07+/-1.44 micromol/L, and HDL cholesterol 1.43+/-0.71 vs. 1.63+/-0.36 micromol/L (P=.02). Alanine transaminase actually reduced significantly from 26+/-22 to 19+/-9 IU/L (P=.001). Improved glycaemic control was associated with favourable reduction in cardiovascular risk factors. Rosiglitazone was discontinued only in nine patients (weight gain-4, no improvement noticed-4, ankle swelling-1). No hepatotoxicity was observed.

CONCLUSION

Rosiglitazone+insulin combination is safe and effective in inadequately controlled insulin-treated T2DM patients.

Pioglitazone limits cyclosporine nephrotoxicity in rats

Chronic cyclosporine (CsA) nephrotoxicity is a relevant factor in the pathogenesis of chronic allograft nephropathy. Pioglitazone is an agonist of PPARgamma, capable of reducing chronic inflammation. We investigated the capacity of pioglitazone in preventing renal dysfunction. Adult male Wistar rats were assigned to: Vehicle (olive oil 1 ml/kg/day), CsA (10 mg/kg/day) alone and with pioglitazone (5 or 10 mg/kg/day). The animals were sacrificed at 28 days, where blood (serum creatinine ratio, CR) and kidney samples (arteriolopathy analyses) were collected. The mRNA transcripts of TGF-beta1, PAI-1, Smad3 and 7 were evaluated by real-time PCR. As expected, CsA treatment significantly decreased renal function that peaked at day 28, compared with vehicle (CR=1.29+/-0.03 vs. 0.95+/-0.14, p<0.05). In contrast, the administration of pioglitazone 5 or 10 mg/kg combined with CsA resulted in better renal function (CR=1.09+/-0.05 and 1.14+/-0.14, respectively, p<0.05). Animals treated with CSA showed relevant arteriolopathy (49.5+/-2.86%) and pioglitazone administration significantly limited it (37.0+/-3.59% and 36.6+/-1.72%, respectively, 5 or 10 mg/kg, p<0.05). In CsA-treated animals (alone and with pioglitazone), TGF-beta1 and Smad3 increased significantly. In animals treated with CsA and pioglitazone (5 mg/kg), PAI-1 was significantly lower than CsA alone (3.96+/-0.92 vs. 7.53+/-1.38, p<0.05). Interestingly, the administration of pioglitazone 5 or 10 mg/kg was associated with an increase in Smad7 (1.79+/-0.25 and 1.75+/-0.19, respectively), compared to vehicle and to CsA-treated groups (1.08+/-0.17 and 1.17+/-0.19, respectively, p<0.05). These data provide evidence that pioglitazone acts through down regulation of pro-fibrotic cytokine PAI-1 and overexpression of the regulatory Smad7.

Solid-phase extraction coupled with liquid chromatography–tandem mass spectrometry for determination of trace rosiglitazone in urine

This project evaluated solid-phase extraction (SPE) combined with liquid chromatography-tandem mass spectrometry (LC-MS/MS) to determine the trace amount of rosiglitazone in human urine. The analytical performance of four modes of LC-MS and tandem MS operation (atmospheric pressure chemical ionization (APCI), electrospray ionization (ESI), positive and negative ionization) was compared for two mass spectrometers, a triple-quadrupole and a quadrupole ion trap instrument. Rosiglitazone was extracted from urine using a SPE cartridge of 50mg C8 sorbent and acetonitrile used as the eluting solvent. Samples were then separated on a RP18 column interfaced with a tandem mass spectrometer. The recovery of rosiglitazone was greater than 91.2%. The urine assay combining SPE and LC-APCI-MS/MS of triple-quadrupole was proved a very selective and sensitive method for determination of trace rosiglitazone. The assay was linear over a wide range, with a lower limit of quantification of 0.1 ng/mL using 1 mL of urine. The intra- and inter-day precisions were <9.8% and <7.9%, respectively, and the accuracies were in the range 91.0-103.6%. The rosiglitazone concentration profile in human urine was also determined. The results of this study reveal the adequacy of SPE-LC-APCI-MS/MS method for analyzing rosiglitazone from diabetic patients' urines. The concentrations of rosiglitazone were detected to range from 760 to 164 pg/mL.

FK-614, a selective peroxisome proliferator-activated receptor gamma agonist, improves peripheral glucose utilization while decreasing hepatic insulin extraction in alloxan-induced diabetic dogs

This is the first report of the effects of a nonthiazolidinedione activator of peroxisome proliferator-activated receptor (PPAR) gamma, that is, FK-614 (a benzimidazole derivative), on glucose metabolism in vivo. To investigate the effect of FK-614 on peripheral and hepatic insulin action, we performed hyperinsulinemic-hyperglycemic clamp studies combined with the triple-catheter technique and a double-tracer approach in alloxan-diabetic dogs with (n=5) or without (n=6) treatment with FK-614 (0.32 mg/kg per day orally for 10 days). Throughout the experiment, insulin was infused intraportally at 18 pmol/kg per minute and hyperglycemia (approximately 11 mmol/L) was maintained by a peripheral glucose infusion. After a 45-minute basal period (period I), a portal infusion of glucose labeled with [U-14C]-glucose, was administered for 120 minutes (period II) to measure hepatic glucose uptake. This was followed by 90-minute recovery (period III). FK-614 marginally improved peripheral insulin sensitivity, did not affect hepatic glucose uptake, and surprisingly increased tracer-determined hepatic glucose production (19.0+/-5.0 vs 10.6+/-1.7 mumol/kg per minute, P<.001). Hepatic insulin extraction was decreased by FK-614 (47.8%+/-1.6% vs 55.9%+/-3.4%, P<.01), which led to greater peripheral insulin levels and glucose utilization. FK-614 treatment also decreased the daily insulin requirements (regular insulin, 0.18+/-0.01 vs 0.32+/-0.01 U/kg per day; and NPH insulin, 0.53+/-0.02 vs 0.89+/-0.04 U/kg per day; P<.001) to maintain fasting plasma glucose at approximately 10 mmol/L for 7 days before the experiments. We conclude that FK-614 treatment, at the dose used, improves peripheral glucose utilization because of an improvement in peripheral insulin sensitivity and a decrease in insulin clearance, but impairs hepatic insulin action in alloxan-induced diabetic dogs. The reason for the effects of FK-614 on hepatic glucose and insulin metabolism is unclear but they are both consistent with reports of hepatic steatosis by PPARgamma activation when unopposed by concomitant activation of PPARalpha.

PPAR gamma, 10 years later

It is now over 10 years since the discovery of peroxisome proliferator activated receptor gamma (PPAR gamma) and its unique role in adipogenesis. The subsequent identification of PPAR gamma as the target of insulin sensitizing drugs certified this ligand-regulated transcription factor as an exciting link between adipocyte biology and peripheral insulin resistance. Here, I summarize the great progress that has been made over the past decade in elucidating the biology of PPAR gamma and its role in adipogenesis and glucose metabolism. Prospects for future research leading to new therapies for obesity and diabetes are also discussed.

Drug bioactivation, covalent binding to target proteins and toxicity relevance

A number of therapeutic drugs with different structures and mechanisms of action have been reported to undergo metabolic activation by Phase I or Phase II drug-metabolizing enzymes. The bioactivation gives rise to reactive metabolites/intermediates, which readily confer covalent binding to various target proteins by nucleophilic substitution and/or Schiff's base mechanism. These drugs include analgesics (e.g., acetaminophen), antibacterial agents (e.g., sulfonamides and macrolide antibiotics), anticancer drugs (e.g., irinotecan), antiepileptic drugs (e.g., carbamazepine), anti-HIV agents (e.g., ritonavir), antipsychotics (e.g., clozapine), cardiovascular drugs (e.g., procainamide and hydralazine), immunosupressants (e.g., cyclosporine A), inhalational anesthetics (e.g., halothane), nonsteroidal anti-inflammatory drugs (NSAIDSs) (e.g., diclofenac), and steroids and their receptor modulators (e.g., estrogens and tamoxifen). Some herbal and dietary constituents are also bioactivated to reactive metabolites capable of binding covalently and inactivating cytochrome P450s (CYPs). A number of important target proteins of drugs have been identified by mass spectrometric techniques and proteomic approaches. The covalent binding and formation of drug-protein adducts are generally considered to be related to drug toxicity, and selective protein covalent binding by drug metabolites may lead to selective organ toxicity. However, the mechanisms involved in the protein adduct-induced toxicity are largely undefined, although it has been suggested that drug-protein adducts may cause toxicity either through impairing physiological functions of the modified proteins or through immune-mediated mechanisms. In addition, mechanism-based inhibition of CYPs may result in toxic drug-drug interactions. The clinical consequences of drug bioactivation and covalent binding to proteins are unpredictable, depending on many factors that are associated with the administered drugs and patients. Further studies using proteomic and genomic approaches with high throughput capacity are needed to identify the protein targets of reactive drug metabolites, and to elucidate the structure-activity relationships of drug's covalent binding to proteins and their clinical outcomes.