Hepatocellular injury in a patient receiving rosiglitazone. A case report

Dose-response technique combined with stable isotope tracing for drug metabolite profiling by using high-resolution mass spectrometry

Background: Mass spectrometry metabolomics-based data-processing approaches have been developed for drug metabolite profiling. However, existing approaches cannot be used to comprehensively identify drug metabolites with high efficacy. Methods: Herein, we propose a two-stage data-processing approach for effective and comprehensive drug metabolite identification. The approach combines dose-response experiments with stable isotope tracing (SIT). Rosiglitazone (ROS), commonly used to treat type 2 diabetes, was employed as a model drug. Results: In the first stage of data processing, 1,071 features exhibited a dose-response relationship among 22,597 features investigated. In the second stage, these 1,071 features were screened for isotope pairs, and 200 features with isotope pairs were identified. In time-course experiments, a large proportion of the identified features (69.5%: 137 out of 200 features) were confirmed to be possible ROS metabolites. We compared the validated features identified using our approach with those identified using a previously reported approach [the mass defect filter (MDF) combined with SIT] and discovered that most of the validated features (37 out of 42) identified using the MDF-SIT combination were also successfully identified using our approach. Of the 143 validated features identified by both approaches, 74 had a proposed structure of an ROS-structure-related metabolite; the other 34 features that contained a specific fragment of ROS metabolites were considered possible ROS metabolites. Interestingly, numerous ROS-structure-related metabolites were identified in this study, most of which were novel. Conclusion: The results reveal that the proposed approach can effectively and comprehensively identify ROS metabolites.

Dietary regulation of peroxisome proliferator-activated receptors in metabolic syndrome

BACKGROUND

Peroxisome proliferator-activated receptors (PPARs) are a class of ligand-activated nuclear transcription factors, members of the type nuclear receptor superfamily, with three subtypes, namely PPARα, PPARβ/δ, and PPARγ, which play a key role in the metabolic syndrome. In the past decades, a large number of studies have shown that natural products can act by regulating metabolic pathways mediated by PPARs.

PURPOSE

This work summarizes the physiological importance and clinical significance of PPARs and reviews the experimental evidence that natural products mediate metabolic syndrome via PPARs.

METHODS

This study reviews relevant literature on clinical trials, epidemiology, animals, and cell cultures published in NCBI PubMed, Scopus, Web of Science, Google Scholar, and other databases from 2001 to October 2022. Search keywords were "natural product" OR "botanical" OR "phytochemical" AND "PPAR" as well as free text words.

RESULTS

The modulatory involvement of PPARs in the metabolic syndrome has been supported by prior research. It has been observed that many natural products can treat metabolic syndrome by altering PPARs. The majority of currently described natural compounds are mild PPAR-selective agonists with therapeutic effects that are equivalent to synthetic medicines but less harmful adverse effects.

CONCLUSION

PPAR agonists can be combined with natural products to treat and prevent metabolic syndrome. Further human investigations are required because it is unknown how natural products cause harm and how they might have negative impacts.

A new insight into the treatment of diabetes by means of pan PPAR agonists

PPARs stand for 'peroxisome proliferator-activated receptors' and are ligand-activated transcription factors of nuclear hormone receptor superfamily. A list of the most commonly used single receptor PPAR agonists, that is α (alpha) PPAR agonists, β/δ(beta/delta) PPAR agonists, γ(gamma) PPAR agonists, along with pan PPAR agents, that are being researched on, are marketed, are in clinical trials or are being studied for further derivative findings, has been listed. Type 2 diabetes constitutes about 90% of total diabetes cases. Pan PPAR ligands could very well pave the foundation for a new class of agents, that can act on all 3 PPAR receptors, and produce better effects in general, than the individual receptor-acting ligands or dual combination ligands (α/ γ). In this review paper, we have detailed various pan PPAR agonists that can be used to treat type 2 diabetes, which can generate potential derivatives as well.

Cheonggukjang-Specific Component 1,3-Diphenyl-2-Propanone as a Novel PPARα/γ Dual Agonist: An In Vitro and In Silico Study

Background: Cheonggukjang is a traditional fermented soybean paste that is mostly consumed in Korea. However, the biological activities of Cheonggukjang specific compounds have not been studied. Thus, we aimed to discover a novel dual agonist for PPARα/γ from dietary sources such as Cheonggukjang specific volatile compounds and explore the potential role of PPARα/γ dual agonists using in vitro and in silico tools. Methods: A total of 35 compounds were selected from non-fermented and fermented soybean products cultured with Bacillus subtilis, namely Cheonggukjang, for analysis by in vitro and in silico studies. Results: Molecular docking results showed that 1,3-diphenyl-2-propanone (DPP) had the lowest docking score for activating PPARα (1K7L) and PPARγ (3DZY) with non-toxic effects. Moreover, DPP significantly increased the transcriptional activities of both PPARα and PPARγ and highly activated its expression in Ac2F liver cells, in vitro. Here, we demonstrated for the first time that DPP can act as a dual agonist of PPARα/γ using in vitro and in silico tools. Conclusions: The Cheonggukjang-specific compound DPP could be a novel PPARα/γ dual agonist and it is warranted to determine the therapeutic potential of PPARα/γ activation by dietary intervention and/or supplementation in the treatment of metabolic disorders without causing any adverse effects.

PPARγ: Potential Therapeutic Target for Ailments Beyond Diabetes and its Natural Agonism

Intense research interests have been observed in establishing PPAR gamma as a therapeutic target for diabetes. However, PPARγ is also emerging as an important therapeutic target for varied disease states other than type 2 diabetes like neurodegenerative disorders, cancer, spinal cord injury, asthma, and cardiovascular problems. Furthermore, glitazones, the synthetic thiazolidinediones, also known as insulin sensitizers, are the largely studied PPARγ agonists and the only ones approved for the treatment of type 2 diabetes. However, they are loaded with side effects like fluid retention, obesity, hepatic failure, bone fractures, and cardiac failure; which restrict their clinical application. Medicinal plants used traditionally are the sources of bioactive compounds to be used for the development of successful drugs and many structurally diverse natural molecules are already established as PPARγ agonists. These natural partial agonists when compared to full agonist synthetic thiazolidinediones led to weaker PPARγ activation with lesser side effects but are not thoroughly investigated. Their thorough characterization and elucidation of mechanistic activity might prove beneficial for counteracting diseases by modulating PPARγ activity through dietary changes. We aim to review the therapeutic significance of PPARγ for ailments other than diabetes and highlight natural molecules with potential PPARγ agonistic activity.

In vitro drug metabolism and pharmacokinetics of a novel thiazolidinedione derivative, a potential anticancer compound

Thiazolidinediones are known for their activity against Type 2 diabetes and are currently being repurposed for their potent anti-cancer activity. In the present study, we have assessed in vitro metabolic properties and in vivo pharmacokinetic parameters of a novel thiazolidinedione derivative, BIT-15-67, a potential anticancer compound. BIT-15-67 showed low solubility in aqueous buffers at different pH values. The permeability was determined across the Caco-2 monolayer and BIT-15-67 showed high permeability and an efflux ratio of less than 2 suggesting that it is not a substrate of the efflux transporters (P-gp & BCRP). The plasma protein binding was evaluated by equilibrium dialysis and the compound exhibited moderate binding to mouse and rat plasma proteins. BIT-15-67 was stable (half-life > 30 min.) in mouse, rat, dog and human liver microsomes and unstable (half-life <15 min.) in rat hepatocytes suggesting possible Phase II metabolism. Liquid chromatography-tandem mass spectrometry was used to identify Phase I and Phase II metabolites. One of each Phase I and Phase II metabolites have been identified in rat hepatocytes samples. The BIT-15-67 is not an inhibitor of CYP1A2, CYP2C9, CYP2C19, CYP2D6 and CYP3A4. The PK parameters were determined in both male and female Wistar rats after single intravenous dose administration of BIT-15-67. In rats, the mean plasma clearance of BIT-15-67 was higher in males than in females and the terminal plasma elimination half-life was shorter in males than in females. The compound was highly distributed in the tissues. Overall, the absolute oral bioavailability was 5-fold higher in females (38 %) than in males (7 %). In female nude mice with tumors, BIT-15-67 was well distributed among the collected tissues with the highest concentration in the liver. The ratio of the concentrations in tumor vs. the plasma was 0.5 which could be an important attribute in the development of the compound for anti-cancer research.

Drug-induced liver injury in obesity and nonalcoholic fatty liver disease

Obesity is commonly associated with nonalcoholic fatty liver (NAFL), a benign condition characterized by hepatic lipid accumulation. However, NAFL can progress in some patients to nonalcoholic steatohepatitis (NASH) and then to severe liver lesions including extensive fibrosis, cirrhosis and hepatocellular carcinoma. The entire spectrum of these hepatic lesions is referred to as nonalcoholic fatty liver disease (NAFLD). The transition of simple fatty liver to NASH seems to be favored by several genetic and environmental factors. Different experimental and clinical investigations showed or suggested that obesity and NAFLD are able to increase the risk of hepatotoxicity of different drugs. Some of these drugs may cause more severe and/or more frequent acute liver injury in obese individuals whereas others may trigger the transition of simple fatty liver to NASH or may worsen hepatic lipid accumulation, necroinflammation and fibrosis. This review presents the available information regarding drugs that may cause a specific risk in the context of obesity and NAFLD. These drugs, which belong to different pharmacological classes, include acetaminophen, halothane, methotrexate, rosiglitazone and tamoxifen. For some of these drugs, experimental investigations confirmed the clinical observations and unveiled different pathophysiological mechanisms which may explain why these pharmaceuticals are particularly hepatotoxic in obesity and NAFLD. Because obese people often take several drugs for the treatment of different obesity-related diseases, there is an urgent need to identify the main pharmaceuticals that may cause acute liver injury on a fatty liver background or that may enhance the risk of severe chronic liver disease.

Management of diabetes mellitus in patients undergoing liver transplantation

Diabetes is a common feature in cirrhotic individuals both before and after liver transplantation and negatively affects prognosis. Certain aetiological agents of chronic liver disease and loss of liver function per se favour the occurrence of pre-transplant diabetes in susceptible individuals, whereas immunosuppressant treatment, changes in lifestyle habits, and donor- and procedure-related factors contribute to diabetes development/persistence after transplantation. Challenges in the management of pre-transplant diabetes include the profound nutritional alterations characterizing cirrhotic individuals and the limitations to the use of drugs with liver metabolism. Special issues in the management of post-transplant diabetes include the diabetogenic potential of immunosuppressant drugs and the increased cardiovascular risk characterizing solid organ transplant survivors. Overall, the pharmacological management of cirrhotic patients undergoing liver transplantation is complicated by the lack of specific guidelines reflecting the paucity of data on the impact of glycaemic control and the safety and efficacy of anti-hyperglycaemic agents in these individuals.

New Pioglitazone Metabolites and Absence of Opened-Ring Metabolites in New N-Substituted Thiazolidinedione

Thiazolidinediones (TZDs) are drugs used to treat type 2 diabetes mellitus; however, several safety concerns remain regarding the available drugs in this class. Therefore, the search for new TZD candidates is ongoing; metabolism studies play a crucial step in the development of new candidates. Pioglitazone, one of the most commonly used TZDs, and GQ-11, a new N-substituted TZD, were investigated in terms of their metabolic activity in rat and human liver microsomes to assess their metabolic stability and investigate their metabolites. Methods for preparation of samples were based on liquid-liquid extraction and protein precipitation. Quantitation was performed using liquid chromatography (LC)-tandem mass spectrometry, and the metabolite investigation was performed using ultraperformance LC coupled to a hybrid quadrupole-time of flight mass spectrometer. The predicted intrinsic clearance of GQ-11 was 70.3 and 46.1 ml/kg per minute for rats and humans, respectively. The predicted intrinsic clearance of pioglitazone was 24.1 and 15.9 ml/kg per minute for rats and humans, respectively. The pioglitazone metabolite investigation revealed two unpublished metabolites (M-D and M-A). M-A is a hydration product and may be related to the mechanism of ring opening and the toxicity of pioglitazone. The metabolites of GQ-11 are products of oxidation; no ring-opening metabolite was observed for GQ-11. In conclusion, under the same experimental conditions, a ring-opening metabolite was observed only for pioglitazone. The resistance of GQ-11 to the ring opening is probably related to N-substitution in the TZD ring.

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

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

Targeting Peroxisome Proliferator-Activated Receptors Using Thiazolidinediones: Strategy for Design of Novel Antidiabetic Drugs

Thiazolidinediones are a class of well-established antidiabetic drugs, also named as glitazones. Thiazolidinedione structure has been an important structural domain of research, involving design and development of new drugs for the treatment of type 2 diabetes. Extensive research on the mechanism of action and the structural requirements has revealed that the intended antidiabetic activity in type 2 diabetes is due to their agonistic effect on peroxisome proliferator-activated receptor (PPAR) belonging to the nuclear receptor super family. Glitazones have specific affinity to PPARγ, one of the subtypes of PPARs. Certain compounds under development have dual PPARα/γ agonistic activity which might be beneficial in obesity and diabetic cardiomyopathy. Interesting array of hybrid compounds of thiazolidinedione PPARγ agonists exhibited therapeutic potential beyond antidiabetic activity. Pharmacology and chemistry of thiazolidinediones as PPARγ agonists and the potential of newer analogues as dual agonists of PPARs and other emerging targets for the therapy of type 2 diabetes are presented. This review highlights the possible modifications of the structural components in the general frame work of thiazolidinediones with respect to their binding efficacy, potency, and selectivity which would guide the future research in design of novel thiazolidinedione derivatives for the management of type 2 diabetes.

Role of nonalcoholic fatty liver disease as risk factor for drug-induced hepatotoxicity

BACKGROUND

Obesity is often associated with nonalcoholic fatty liver disease (NAFLD), which refers to a large spectrum of hepatic lesions including fatty liver, nonalcoholic steatohepatitis (NASH) and cirrhosis. Different investigations showed or suggested that obesity and NAFLD are able to increase the risk of hepatotoxicity of different drugs. Some of these drugs could induce more frequently an acute hepatitis in obese individuals whereas others could worsen pre-existing NAFLD.

AIM

The main objective of the present review was to collect the available information regarding the role of NAFLD as risk factor for drug-induced hepatotoxicity. For this purpose, we performed a data-mining analysis using different queries including drug-induced liver injury (or DILI), drug-induced hepatotoxicity, fatty liver, nonalcoholic fatty liver disease (or NAFLD), steatosis and obesity. The main data from the collected articles are reported in this review and when available, some pathophysiological hypotheses are put forward.

RELEVANCE FOR PATIENTS

Drugs that could pose a potential risk in obese patients include compounds belonging to different pharmacological classes such as acetaminophen, halothane, methotrexate, rosiglitazone, stavudine and tamoxifen. For some of these drugs, experimental investigations in obese rodents confirmed the clinical observations and unveiled different pathophysiological mechanisms which could explain why these pharmaceuticals are particularly hepatotoxic in obesity and NAFLD. Other drugs such as pentoxifylline, phenobarbital and omeprazole might also pose a risk but more investigations are required to determine whether this risk is significant or not. Because obese people often take several drugs for the treatment of different obesity-related diseases such as type 2 diabetes, hyperlipidemia and coronary heart disease, it is urgent to identify the main pharmaceuticals that can cause acute hepatitis on a fatty liver background or induce NAFLD worsening.

Multiparametric assay using HepaRG cells for predicting drug-induced liver injury

The utility of HepaRG cells as an in vitro cell-based assay system for assessing drug-induced liver injury (DILI) risk was investigated. Seventeen DILI-positive and 15 DILI-negative drugs were selected for the assay. HepaRG cells were treated with each drug for 24h at concentrations that were 1.6-, 6.3-, 25-, and 100-fold the therapeutic maximum plasma concentration (Cmax). After treatment, the cell viability, glutathione content, caspase 3/7 activity, lipid accumulation, leakage of lactate dehydrogenase, and albumin secretion were measured. The sensitivity and specificity were calculated to assess the ability of the assay to predict DILI. Our multiparametric assay using HepaRG cells exhibited a 67% sensitivity and 73% specificity at a 100-fold concentration of Cmax and a 41% sensitivity and 87% specificity at a 25-fold concentration of Cmax. When a 25-fold Cmax cut-off was applied, approximately 70% of drugs exhibiting positive responses were classified into the high DILI risk category. HepaRG cells distinguished relatively safe drugs from their high-risk analogs. Our study indicates that HepaRG cells may be of use to (1) prioritize drug analogs, (2) analyze the mechanism of DILI, and (3) assess the risk for DILI in the early drug discovery stage.

Diabetes and Hepatitis C: A Two-Way Association

Diabetes and hepatitis C infection are both prevalent diseases worldwide, and are associated with increased morbidity and mortality. Most studies, but not all, have shown that patients with chronic hepatitis C are more prone to develop type 2 diabetes (T2D) compared to healthy controls, as well as when compared to patients with other liver diseases, including hepatitis B. Furthermore, epidemiological studies have revealed that patients with T2D may also be at higher risk for worse outcomes of their hepatitis C infection, including reduced rate of sustained virological response, progression to fibrosis and cirrhosis, and higher risk for development of hepatocellular carcinoma. Moreover, hepatitis C infection and mainly its treatment, interferon α, can trigger the development of type 1 diabetes. In this review, we discuss the existing data on this two-way association between diabetes and hepatitis C infection with emphasis on possible mechanisms. It remains to be determined whether the new curative therapies for chronic hepatitis C will improve outcomes in diabetic hepatitis C patients, and conversely whether treatment with Metformin will reduce complications from hepatitis C virus infection. We propose an algorithm for diabetes screening and follow-up in hepatitis C patients.

Natural product agonists of peroxisome proliferator-activated receptor gamma (PPARγ): a review

Agonists of the nuclear receptor PPARγ are therapeutically used to combat hyperglycaemia associated with the metabolic syndrome and type 2 diabetes. In spite of being effective in normalization of blood glucose levels, the currently used PPARγ agonists from the thiazolidinedione type have serious side effects, making the discovery of novel ligands highly relevant. Natural products have proven historically to be a promising pool of structures for drug discovery, and a significant research effort has recently been undertaken to explore the PPARγ-activating potential of a wide range of natural products originating from traditionally used medicinal plants or dietary sources. The majority of identified compounds are selective PPARγ modulators (SPPARMs), transactivating the expression of PPARγ-dependent reporter genes as partial agonists. Those natural PPARγ ligands have different binding modes to the receptor in comparison to the full thiazolidinedione agonists, and on some occasions activate in addition PPARα (e.g. genistein, biochanin A, sargaquinoic acid, sargahydroquinoic acid, resveratrol, amorphastilbol) or the PPARγ-dimer partner retinoid X receptor (RXR; e.g. the neolignans magnolol and honokiol). A number of in vivo studies suggest that some of the natural product activators of PPARγ (e.g. honokiol, amorfrutin 1, amorfrutin B, amorphastilbol) improve metabolic parameters in diabetic animal models, partly with reduced side effects in comparison to full thiazolidinedione agonists. The bioactivity pattern as well as the dietary use of several of the identified active compounds and plant extracts warrants future research regarding their therapeutic potential and the possibility to modulate PPARγ activation by dietary interventions or food supplements.

Effect of rosiglitazone on liver structure and function in genetically diabetic Akita mice

Genetically diabetic Akita mice, kept on a high-fat and high-cholesterol diet, and treated with the peroxisome proliferator-activated receptor-γ agonist rosiglitazone (10 mg/kg per day during 4 months), displayed rosiglitazone-induced side effects, similar to those observed in patients, including weight and fat gain and early signs of hypertrophic cardiomyopathy. As several cases of hepatotoxicity were reported in patients receiving rosiglitazone treatment, this study evaluated whether rosiglitazone also induced hepatotoxicity in these diabetic animals. Liver structure and function was analysed in wild-type and rosiglitazone-treated and untreated Akita mice, kept for 4 months on the high-fat and high-cholesterol diet. Decreased circulating levels of the liver enzymes aspartate and alanine aminotransferase and increased levels of alkaline phosphatases were observed upon rosiglitazone treatment, whereas liver weight was markedly increased. Rosiglitazone administration was associated with liver steatosis, as demonstrated by triglyceride accumulation. However, gene expression of steatosis markers in liver tissue was not markedly affected by rosiglitazone treatment, while expression of fatty acid transport protein was reduced by rosiglitazone treatment, suggesting an impairment of the fatty acid β-oxidation pathway. mRNA expression of pro- and anti-oxidant enzymes and liver 3-nitrotyrosine content was not affected. Furthermore, gene and protein expression of macrophage markers and of cell adhesion molecules did not indicate progression to steatohepatitis, whereas an unaltered collagen deposition did not suggest steatofibrosis. In conclusion, rosiglitazone treatment of diabetic Akita mice induced liver steatosis without, however, progression to more advanced stages of liver disease.

Improvement of abnormal liver enzymes after rosiglitazone treatment in Chinese type 2 diabetes

Objectives:

Insulin resistance is one of the important underlying abnormalities of type 2 diabetes. The effect of thiazolidinedione on liver functions has been controversial in different studies. In this study, we evaluated the effect of rosiglitazone on liver enzymes in subjects with type 2 diabetes with and without abnormal liver function.

Materials and Methods:

Seventy-three patients with type 2 diabetes taking rosiglitazone 4 mg daily were enrolled in this 3-month study. Forty-two of them had normal liver function (NLF), and 31 had abnormal liver function (ABLF). Blood biochemistries were collected monthly during the treatment period.

Results:

At baseline, other than age and liver enzymes, there were no differences in body mass index, fasting plasma glucose, hemoglobin A1c (HbA1c), and lipid profiles between the NLF and ABLF groups. At the end of the treatment, HbA1c was lowered in both groups, but only significantly in the ABLF group (P = 0.027). More importantly, serum concentrations of both aspartate aminotransferase (AST) and alanine aminotransferase (ALT) in the ABLF group decreased significantly (AST: 57.8 ± 26.5 to 47.5 ± 20.2 U/L, P = 0.006; ALT 66.6 ± 35.0 to 51.9 ± 23.5 UL, P = 0.004), while in the NLF group, a similar change was not found.

Conclusion:

After 3-month rosiglitazone treatment in subjects with type 2 diabetes with mildly elevated liver enzymes, significant improvement in AST and ALT were observed. Our study provides some hints that rosiglitazone might not be contraindicated in subjects with diabetes with abnormal liver function as previously thought, but further well-designed studies are necessary to clarify this issue.

Citrus unshiu peel extract ameliorates hyperglycemia and hepatic steatosis by altering inflammation and hepatic glucose- and lipid-regulating enzymes in db/db mice

Insulin resistance in Type 2 diabetes leads to hepatic steatosis that can accompanied by progressive inflammation of the liver. Citrus unshiu peel is a rich source of citrus flavonoids that possess anti-inflammatory, anti-diabetic and lipid-lowering effects. However, the ability of citrus unshiu peel ethanol extract (CPE) to improve hyperglycemia, adiposity and hepatic steatosis in Type 2 diabetes is unknown. Thus, we evaluated the effects of CPE on markers for glucose, lipid metabolism and inflammation in Type 2 diabetic mice. Male C57BL/KsJ-db/db mice were fed a normal diet with CPE (2 g/100 g diet) or rosiglitazone (0.001 g/100 g diet) for 6 weeks. Mice supplemented with the CPE showed a significant decrease in body weight gain, body fat mass and blood glucose level. The antihyperglycemic effect of CPE appeared to be partially mediated through the inhibition of hepatic gluconeogenic phosphoenolpyruvate carboxykinase mRNA expression and its activity and through the induction of insulin/glucagon secretion. CPE also ameliorated hepatic steatosis and hypertriglyceridemia via the inhibition of gene expression and activities of the lipogenic enzymes and the activation of fatty acid oxidation in the liver. These beneficial effects of CPE may be related to increased levels of anti-inflammatory adiponectin and interleukin (IL)-10, and decreased levels of pro-inflammatory markers (IL-6, monocyte chemotactic protein-1, interferon-γ and tumor necrosis factor-α) in the plasma or liver. Taken together, we suggest that CPE has the potential to improve both hyperglycemia and hepatic steatosis in Type 2 diabetes.

Study on the hypoglycemic activities and metabolism of alcohol extract of Alismatis Rhizoma

The Alisma rhizoma is widely used in the therapy of diabetes in traditional folk medicine of China. Compositional analysis of the alcohol extract of Alismatis Rhizoma (AEA) revealed that the eight compounds gotten from AEA are all belonging to protostane-type triterpenes. The AEA and compounds were incubated with 3T3-L1 preadipocytes, glucose level in the 3T3-L1 adipocytes culture medium and lipid content in 3T3-L1 adipocytes were measured, and analysis of alpha-glucosidase inhibition of AEA and compounds. At the same time, the uptake of AEA by 3T3-L1 adipocytes and the metabolism of AEA in SD rats were analyzed by HPLC-ESI/MS. As result, AEA increased glucose uptake in 3T3-L1 adipocyte model, not increase adipogenesis; AEA inhibited alpha-glucosidase activity; alisol A-24-aceate (8) was absorbed by 3T3-L1 adipocytes; and two compounds were detected in blood and three were detected in urine in SD rats. So AEA had protostane-type triterpenes, these type compounds in AEA may have hypoglycemic activity via inhibition of alpha-glucosidase activity and promotion of glucose uptake. In contrast to the anti-diabetic drug thiazolidinediones, they did not induce adipogenesis, avoiding the displeased effects of rosiglitazone.

The role of insulin-sensitizing agents in the treatment of nonalcoholic steatohepatitis

Nonalcoholic fatty liver disease (NAFLD) is the hepatic manifestation of the metabolic syndrome, which includes dyslipidemia, central obesity, hypertension, and insulin resistance. These diseases collectively and individually increase the risk of cardiovascular disease. Nonalcoholic steatohepatitis (NASH) is a subset of NAFLD that can progress to cirrhosis in up to 30% of patients and lead to decompensated liver disease requiring liver transplantation in many patients. Insulin resistance is the pathophysiological hallmark of NASH and addressing insulin resistance is an important aspect of NASH management. Lifestyle modifications with diet and exercise improve insulin sensitivity and are the cornerstone of therapy, but are often difficult to maintain long term. Not surprisingly, insulin-sensitizing agents have been a focus of pharmacologic investigation in NASH. Insulin sensitizers such as the thiazolidinediones, biguanides, glucagon-like peptide-1 receptor agonists, and the dipeptidyl peptidase IV inhibitors, also known as incretins, will be discussed with respect to their mechanism of action and how these drugs might target aspects of NASH pathophysiology. Finally, we will summarize the available clinical data and review both the risks and benefits of insulin sensitizers in the treatment of NASH.

The safety of thiazolidinediones

INTRODUCTION

The prevalence of type 2 diabetes mellitus (T2DM) has reached epidemic proportions. Many new therapies have emerged, including thiazolidinediones (TZDs), selective agonists of PPAR-γ, now used as both primary and add-on therapies. Given that T2DM is a lifetime disease, there is a need for assurance that new drugs are both safe and effective. Recent concern about the cardiovascular safety of one of the new drugs, rosiglitazone, is the stimulus for this review.

AREAS COVERED

The safety of pioglitazone and rosiglitazone under the headings of liver safety, cardiovascular safety, fluid retention, weight gain and bone fractures is reviewed based on a PubMed search of the years 1997 through June 2010. This review also describes the magnitude of the risks of the TZDs and provides a recommendation on the use of TZDs.

EXPERT OPINION

Liver safety is no longer an issue with the TZDs. There are no significant differences between rosiglitazone and pioglitazone in fluid retention, weight gain and bone fractures. However, pioglitazone tends to be cardioprotective while rosiglitazone is cardiotoxic. There is no current justification for prescribing rosiglitazone.

Rosiglitazone promotes fatty acyl CoA accumulation and excessive glycogen storage in livers of mice without adiponectin

BACKGROUND & AIMS

The beneficial effects of rosiglitazone on non-alcoholic fatty liver disease (NAFLD) have been reported. Rosiglitazone treatment stimulates the production of adiponectin, an insulin-sensitizing adipokine with hepatoprotective functions. The present study aims to investigate the hepatic actions of rosiglitazone in mice without adiponectin.

METHODS

NAFLD was induced in wild type and adiponectin knockout (AKO) mice by high-fat diet feeding. After rosiglitazone treatment, mice were subjected to evaluations on systemic insulin sensitivity, lipid profiles, hepatic steatosis, and inflammation, as well as the expression and activity of key molecules involved in energy metabolism and mitochondrial functions.

RESULTS

Rosiglitazone treatment prevented hepatic inflammation and reduced the expression of pro-inflammatory cytokines in livers of wild type mice. In contrast, in livers of AKO mice, the same treatment induced severe hepatomegaly and microvesicular hepatosteatosis, and caused abnormal accumulation of fatty acyl CoA, glycogen, and their intermediate metabolites. Compared to wild type littermates, the anti-inflammatory and the mitochondria-stimulatory activity of rosiglitazone were largely attenuated in AKO mice. Replenishment with either adiponectin or uncoupling protein 2 (UCP2) significantly reduced fatty acyl CoA accumulation and increased mitochondrial activities in livers of rosiglitazone-treated AKO mice. In addition, adiponectin, but not UCP2, promoted the activation of glycogen synthase kinase 3beta (GSK3beta), a key molecule involved in regulating glycogen homeostasis.

CONCLUSIONS

Rosiglitazone elicits its protective functions against NAFLD largely through the induction of adiponectin, which prevents mitochondria stresses by promoting GSK3beta activation and UCP2 upregulation, two pathways coordinating the glucose and lipid metabolism in liver.

A nonthiazolidinedione peroxisome proliferator-activated receptor α/γ dual agonist CG301360 alleviates insulin resistance and lipid dysregulation in db/db mice

Activation of peroxisome proliferator-activated receptors (PPARs) have been implicated in the treatment of metabolic disorders with different mechanisms; PPARα agonists promote fatty acid oxidation and reduce hyperlipidemia, whereas PPARγ agonists regulate lipid redistribution from visceral fat to subcutaneous fat and enhance insulin sensitivity. To achieve combined benefits from activated PPARs on lipid metabolism and insulin sensitivity, a number of PPARα/γ dual agonists have been developed. However, several adverse effects such as weight gain and organ failure of PPARα/γ dual agonists have been reported. By use of virtual ligand screening, we identified and characterized a novel PPARα/γ dual agonist, (R)-1-(4-(2-(5-methyl-2-p-tolyloxazol-4-yl)ethoxy)benzyl)piperidine-2-carboxylic acid (CG301360), exhibiting the improvement in insulin sensitivity and lipid metabolism. CG301360 selectively stimulated transcriptional activities of PPARα and PPARγ and induced expression of their target genes in a PPARα- and PPARγ-dependent manner. In cultured cells, CG301360 enhanced fatty acid oxidation and glucose uptake and it reduced pro-inflammatory gene expression. In db/db mice, CG301360 also restored insulin sensitivity and lipid homeostasis. Collectively, these data suggest that CG301360 would be a novel PPARα/γ agonist, which might be a potential lead compound to develop against insulin resistance and hyperlipidemia.

Important elements for the diagnosis of drug-induced liver injury

BACKGROUND & AIMS

Drug-induced liver disease is the leading cause of acute liver failure in the United States. Accurate reporting of drug-induced liver injury is essential for early detection of hepatotoxicity and for developing reliable, interpretable literature. We assessed the extent to which published case reports of drug-induced liver disease include sufficient clinical data for interpreting the cause of toxicity.

METHODS

We developed a list of 42 predetermined, specific minimal elements necessary in evaluating causality of drug-induced liver injury. We then analyzed 97 published case reports or series studies of hepatotoxicity from 6 drugs (from 3 classes): amoxicillin/clavulanic acid (n = 35), troglitazone (n = 32), rosiglitazone (n = 10), pioglitazone (n = 8), zafirlukast (n = 8), and montelukast (n = 4).

RESULTS

Patient age, sex, primary disease, and drug name were reported in most, if not all, published case reports. However, many elements were underreported; some publications did not mention initial bilirubin levels (12%), many did not provide initial alkaline phosphatase levels (58%), and others provided vague descriptions of how certain diagnoses were excluded, that is, tests for hepatitis A, B, and C were negative. Data on abnormal results from serial liver tests frequently were absent. Exclusions of competing viral etiologies were reported in less than 50% of the studies.

CONCLUSIONS

Reports of drug-induced liver diseases often do not provide the data needed to determine the causes of the adverse effects. Efforts to promote and include a list of essential diagnostic elements in research articles could increase the quality and clinical utility of published case reports of drug toxicity.

Insulin releasing and alpha-glucosidase inhibitory activity of ethyl acetate fraction of Acorus calamus in vitro and in vivo

ETHNOPHARMACOLOGICAL RELEVANCE

The radix of Acorus calamus L. (AC) is widely used in the therapy of diabetes in traditional folk medicine of America and Indonesia, and we previously reported the insulin sensitizing activity of the ethyl acetate fraction of AC (ACE).

AIM OF THE STUDY

To investigate the insulin releasing and alpha-glucosidase inhibitory activity of ACE in vitro and in vivo.

MATERIALS AND METHODS

Insulin releasing and alpha-glucosidase inhibitory effects of different fractions from AC were detected in vitro using HIT-T15 cell line and alpha-glucosidase enzyme. Furthermore, effects of ACE orally on serum glucose were detected in fasted and glucose/amylum challenged normal mice.

RESULTS

AC and ACE increased insulin secretion in HIT-T15 cells as gliclazide did. As in vivo results, ACE (400 and 800 mg/kg) significantly decreased fasting serum glucose, and suppressed the increase of blood glucose levels after 2g/kg glucose loading in normal mice. In addition, ACE as a mixed-type inhibitor inhibited alpha-glucosidase activity in vitro with an IC(50) of 0.41 microg/ml, and 100mg/kg of it clearly reduced the increase of blood glucose levels after 5 g/kg amylum loading in normal mice.

CONCLUSIONS

Apart from its insulin sensitizing effect, ACE may have hypoglycemic effects via mechanisms of insulin releasing and alpha-glucosidase inhibition, and thus improves postprandial hyperglycemia and cardiovascular complications.

Metabolism of troglitazone in hepatocytes isolated from experimentally induced diabetic rats

Troglitazone (TGZ), the prototype 2,4-thiazolidinedione antidiabetic agent, is associated with hepa-totoxicity in patients with Type 2 diabetes. Although the mechanism of toxicity has not been established, alterations in the clearance of TGZ from in-vitro hepatocyte cultures through metabolic conjugation reactions are believed to modulate the toxicity of the compound. In this study, the metabolism of TGZ in freshly isolated hepatocytes from the fat-fed streptozotocin-treated rat model of Type 2 diabetes is described. Biochemical parameters such as cellular reduced glutathione content, content of cytochromes P450 and b5, and the expression of glutathione-S-transferase α (subunits Ya and Yc2) were not affected by the induced diabetes. TGZ was metabolized primarily to a sulfonate, a quinone and a glucuronide in both control and experimentally diabetic animals. However, metabolism after induction of diabetes was characterized by a moderate increase in sulfation, a decrease in the elimination half-life of TGZ and the absence of the minor metabolites of TGZ, notably the glutathione adduct of the putative reactive intermediate (m/z = 747 (M + H)+; m/z = 745 (M — H)−).

Case series of liver failure associated with rosiglitazone and pioglitazone

PURPOSE

The thiazolidinedione drugs rosiglitazone and pioglitazone are not widely known to be hepatotoxic. We evaluated the FDA Adverse Event Reporting System (AERS) to determine the number of reported cases of liver failure associated with rosiglitazone and pioglitazone between 1997 and 2006, and described their clinical characteristics.

METHODS

Adverse event reports spontaneously submitted to the FDA AERS from 1997 to 2006 were examined. Liver failure associated with rosiglitazone or pioglitazone was defined as liver injury accompanied by hepatic encephalopathy, liver transplantation, placement on a liver transplant list, or death in which all other likely etiologies were excluded. Using prescribing data, the number of reported cases of liver failure per million patient-years of exposure was calculated for each drug.

RESULTS

Twenty-one cases met our case definition. Clinical characteristics, outcomes, and pathologic data were similar between cases of liver failure associated with rosiglitazone and with pioglitazone. The median duration of therapy was 9 weeks and 85% of cases were acute, defined as symptom onset to liver failure in less than 26 weeks. The case-fatality rate was 81% (17/21), and only 14% (3/21) spontaneously recovered. Accounting for underreporting, the number needed to harm (NNH) for each case of liver failure was 44 000 patient-years of exposure for rosiglitazone and 52 000 patient-years of exposure for pioglitazone.

CONCLUSIONS

This is the largest case series of liver failure associated with rosiglitazone or pioglitazone reported to date, strengthening the evidence that these drugs can cause severe hepatotoxicity.

Drug-induced liver injury

Many drugs and environmental chemicals are capable of evoking some degree of liver injury. The liver represents a primary target for adverse drug reactions due to its central role in biotransformation and excretion of foreign compounds, its portal location within the circulation exposing it to a wide variety of substances, and its anatomic and physiologic structure. Drug-induced liver injury (DILI) remains the single most common adverse indication leading to drug candidate failure or withdrawal from the market. However, the absolute incidence of DILI is low, and this presents a challenge to mechanistic studies. DILI remains unpredictable making prevention very difficult. In this chapter, we focus on the current understanding of DILI. We begin with an overview regarding the significance and epidemiology of DILI and then examine the clinical presentation and susceptibility factors related to DILI. This is followed by a review of the current literature regarding the proposed pathogenesis of DILI, which involves the participation of a drug, or most often a reactive metabolite of the drug, that either directly affects cellular function or elicits an immune response. It is our hope that this chapter will shed light on the major problems associated with DILI in regards to the pharmaceutical industry, drug regulatory agencies, physicians and pharmacists, and patients.

Triple verses glimepiride plus metformin therapy on cardiovascular risk biomarkers and diabetic cardiomyopathy in insulin resistance type 2 diabetes mellitus rats

IRtype2DM patients are often treated with a combination of antidiabetic agents. Drugs with different complementary mechanisms of action frequently used in daily clinical practice but glycemic control with monotherapeutic attempts fail in the long run. To date, biomarkers for cardiovascular risk and insulin sensitivity with combination of triple oral hypoglycemic therapies are not fully revelled in view of additional cardiovascular risk reduction. In the present study, IRtype2DM induced by administering streptozotocin (90 mg/kg, i.p.) in neonatal rat model. IRtype2DM rats were selected by determining FPI [>60 pmol/l]; HOMA-IR & Hyperinsulinemic euglycemic clamp technique at 6 weeks and then treated for 8 weeks with (i) Metformin (120 mg/kg, o.d.)+Glimepiride (1mg/kg, o.d.), (ii) Metformin (265 mg/kg, o.d.)+Rosiglitazone (1mg/kg, o.d.)+Glimepiride (0.7 mg/kg, o.d.). At the end cardiovascular risk parameters evaluated by ELISA kits and insulin sensitivity were determined by HOMA-IR. In conclusion, triple oral hypoglycemic therapy improves glycemic control, insulin sensitivity, retards diabetic cardiomyopathy and does not increased body weight; decrease more detrimental inflammatory markers, increase interleukin-10 and adiponectin in neonatal streptozotocin-induced IRtype2DM Wistar Albino Rats. Triple therapy showed a synergistic effect and was promising in insulin resistance, better in additional cardiovascular risk reduction and those nonresponders to metformin add on glimepiride therapy.

Drug-induced hepatotoxicity or drug-induced liver injury

Drug-induced hepatotoxicity is underreported and underestimated in the United States. It is an important cause of acute liver failure. Common classes of drugs causing drug-induced hepatotoxicity include antibiotics, lipid lowering agents, oral hypoglycemics, psychotropics, antiretrovirals, acetaminophen, and complementary and alternative medications. Hepatotoxic drugs often have a signature or pattern of liver injury including patterns of liver test abnormalities, latency of symptom onset, presence or absence of immune hypersensitivity, and the course of the reaction after drug withdrawal.

Practical guidelines for diagnosis and early management of drug-induced liver injury

The spectrum of drug-induced liver injury (DILI) is both diverse and complex. The first step in diagnosis is a suspicion of DILI based on careful consideration of recent comprehensive reports on the disease. There are some situations in which the suspicion of DILI is particularly strong. Exclusion of other possible etiologies according to the pattern of liver injury is essential for the diagnosis. In patients with suspected DILI, diagnostic scales, such as the Councils for International Organizations of Medical Sciences/Roussel Uclaf Causality Assessment Method (CIOMS/RUCAM) scale, may be helpful for the final diagnosis. Early management of DILI involves prompt withdrawal of the drug suspected of being responsible, according to serum levels of alanine aminotransferase (ALT), alkaline phosphatase (ALP), and total bilirubin (T-Bil). However, as DILI patients may show resolution of liver injury without discontinuation of the drug, it should be carefully evaluated whether the suspected drug should be discontinued immediately with adequate consideration of the importance of the medication.

Treating type 2 diabetes: how safe are current therapeutic agents?

Sulphonylureas (SUs) and biguanides (metformin) are the current mainstays in the treatment of type 2 diabetes (T2DM) and represent the most commonly used oral hypoglycaemic agents (OHAs). In recent years, a variety of new OHAs have become available, including thiazolidinediones, glinides, alpha-glucosidase inhibitors, glucagon-like peptide-1 agonists, amylin analogues and dipeptidyl peptidase-IV inhibitors, providing physicians with a larger therapeutic catalogue than ever before. The traditional drugs metformin and SUs have an established safety profile through long-term use. However, long-term clinical trials and routine use are lacking for many of the new agents, and some potentially serious side effects have been reported with several of these compounds. Until adequate data is obtained, it is difficult to assess the risk-benefit ratio of these agents in relation to the traditional drugs. Until that becomes fully documented, it may be wise to start pharmacologic treatment of patients on an individual basis, weighing the benefits and costs of each medication. Thus, there remains a place for well-established drugs that have a proven safety record and are supported by years of clinical use for the treatment of T2DM.

Practical guidelines for diagnosis and early management of drug-induced liver injury

The spectrum of drug-induced liver injury (DILI) is both diverse and complex. The first step in diagnosis is a suspicion of DILI based on careful consideration of recent comprehensive reports on the disease. There are some situations in which the suspicion of DILI is particularly strong. Exclusion of other possible etiologies according to the pattern of liver injury is essential for the diagnosis. In patients with suspected DILI, diagnostic scales, such as the Councils for International Organizations of Medical Sciences/Roussel Uclaf Causality Assessment Method (CIOMS/RUCAM) scale, may be helpful for the final diagnosis. Early management of DILI involves prompt withdrawal of the drug suspected of being responsible, according to serum levels of alanine aminotransferase (ALT), alkaline phosphatase (ALP), and total bilirubin (T-Bil). However, as DILI patients may show resolution of liver injury without discontinuation of the drug, it should be carefully evaluated whether the suspected drug should be discontinued immediately with adequate consideration of the importance of the medication.

Practical guidelines for diagnosis and early management of drug-induced liver injury

The spectrum of drug-induced liver injury (DILI) is both diverse and complex. The first step in diagnosis is a suspicion of DILI based on careful consideration of recent comprehensive reports on the disease. There are some situations in which the suspicion of DILI is particularly strong. Exclusion of other possible etiologies according to the pattern of liver injury is essential for the diagnosis. In patients with suspected DILI, diagnostic scales, such as the Councils for International Organizations of Medical Sciences/Roussel Uclaf Causality Assessment Method (CIOMS/RUCAM) scale, may be helpful for the final diagnosis. Early management of DILI involves prompt withdrawal of the drug suspected of being responsible, according to serum levels of alanine aminotransferase (ALT), alkaline phosphatase (ALP), and total bilirubin (T-Bil). However, as DILI patients may show resolution of liver injury without discontinuation of the drug, it should be carefully evaluated whether the suspected drug should be discontinued immediately with adequate consideration of the importance of the medication.

Mitochondrial dysfunction and delayed hepatotoxicity: another lesson from troglitazone

AIMS/HYPOTHESIS

Troglitazone was approved for treatment of type 2 diabetes mellitus, but by 2000 it had been removed from all world markets due to severe drug-induced liver injury. Even today, we still do not know how many patients sustained a long-term liver injury. No system is in place to acquire that knowledge. Regarding toxicity mechanisms, controversy persists as to which ones are class effects of thiazolidinediones (TZDs) and which are unique to troglitazone. This study aims to provide long-term outcome data and new insights on mechanisms of troglitazone-induced liver injury.

METHODS

This case series reports the liver injuries sustained by eleven type 2 diabetic patients treated with troglitazone between 1997 and 2000. Exhaustive review of medical records was performed for all patients. Long-term outcomes were available for all the non-fatal cases. A comprehensive literature review was also performed.

RESULTS

Long-term liver injury progressing to cirrhosis was identified in seven patients. All eleven cases had liver injury patterns consistent with troglitazone toxicity. Analysis of these cases and of the experimental troglitazone toxicity data points to mitochondrial toxicity as a central factor. The general clinical patterns of mitochondrial hepatotoxic events are reviewed, as are the implications for other members of the TZD family.

CONCLUSIONS/INTERPRETATION

This analysis enables the liver injury induced by troglitazone to be better understood. In future cases of delayed drug-induced liver injury that progresses after discontinuation, the possibility of mitochondrial toxicity should be considered. When appropriate, this can then be evaluated experimentally. Such proactive investigation may anticipate clinical risk before a large-scale therapeutic misadventure occurs. Drug-induced liver injury due to mitochondrial hepatotoxins may be less unpredictable than has previously been surmised.

Use of insulin sensitizers in NASH

This article briefly discusses nonalcoholic fatty liver disease (NAFLD) and its association with the metabolic syndrome, its pathogenesis and natural history. It then presents a detailed discussion on the efficacy and safety of different insulin sensitizers in patients who have NASH.

Mechanisms and outcomes of drug- and toxicant-induced liver toxicity in diabetes

Increase dincidences of hepatotoxicity have been observed in diabetic patients receiving drug therapies. Neither the mechanisms nor the predisposing factors underlying hepatotoxicity in diabetics are clearly understood. Animal studies designed to examine the mechanisms of diabetes-modulated hepatotoxicity have traditionally focused only on bioactivation/detoxification of drugs and toxicants. It is becoming clear that once injury is initiated, additional events determine the final outcome of liver injury. Foremost among them are two leading mechanisms: first, biochemical mechanisms that lead to progression or regression of injury; and second, whether or not timely and adequate liver tissue repair occurs to mitigate injury and restore liver function. The liver has a remarkable ability to repair and restore its structure and function after physical or chemical-induced damage. The dynamic interaction between biotransformation-based liver injury and compensatory tissue repair plays a pivotal role in determining the ultimate outcome of hepatotoxicity initiated by drugs or toxicants. In this review, mechanisms underlying altered hepatotoxicity in diabetes with emphasis on both altered bioactivation and liver tissue repair are discussed. Animal models of both marked sensitivity (diabetic rats) and equally marked protection (diabetic mice) from drug-induced hepatotoxicity are described. These examples represent a remarkable species difference. Availability of the rodent diabetic models offers a unique opportunity to uncover mechanisms of clinical interest in averting human diabetic sensitivity to drug-induced hepatotoxicities. While the rat diabetic models appear to be suitable, the diabetic mouse models might not be suitable in preclinical testing for potential hepatotoxic effects of drugs or toxicants, because regardless of type 1 or type2 diabetes, mice are resistant to acute drug-or toxicant-induced toxicities.

Effect of rosiglitazone/ramipril on preclinical vasculopathy in newly diagnosed, untreated diabetes and IGT patients: 1-year randomised, double-blind, placebo-controlled study

OBJECTIVE

To investigate whether pharmacological interventions with rosiglitazone/ramipril can reverse preclinical vasculopathy in newly diagnosed untreated patients with type 2 diabetes (T2DM) and impaired glucose tolerance (IGT).

METHODS

In this randomised, double-blind, placebo-controlled study, 33 T2DM and 33 IGT patients were randomised to 4 mg rosiglitazone or 5 mg ramipril or placebo for 1 year. The subjects were newly diagnosed, untreated, normotensive, nonobese, nonsmoker, and nonhyperlipidaemic. Haemodynamic variables were measured at three treatment phases and pulse wave velocity (PWV) and augmentation index (AI) were measured throughout the treatment period.

RESULTS

Rosiglitazone showed a significant reduction in PWV (p=0.039) and AI (p=0.031) and ramipril demonstrated a significant reduction of AI (p=0.025) in IGT in comparison to placebo on the 12th month of treatment. No significant difference was observed in PWV and AI in T2DM with rosiglitazone/ramipril in comparison to placebo during overall treatment period.

CONCLUSIONS

Rosiglitazone significantly reversed preclinical vasculopathy in IGT as evident by significant decrease in PWV and AI after 1 year of treatment. Ramipril also reduced large artery stiffness as shown by significant decrease of AI after 1 year of treatment in IGT. Further trials are needed for a longer period of time, maybe with higher doses, to show whether rosiglitazone/ramipril can reverse preclinical vasculopathy in T2DM.

Effect of thiazolidinediones on bile acid transport in rat liver

The thiazolidinedione derivatives, troglitazone, rosiglitazone, and pioglitazone, are novel insulin-sensitizing drugs that are useful in the treatment of type 2 diabetes. However, hepatotoxicity associated with troglitazone led to its withdrawal from the market in March 2000. In view of case reports of hepatotoxicity from rosiglitazone and pioglitazone, it is unclear whether thiazolidinediones as a class are associated with hepatotoxicity. Although the mechanism of troglitazone-associated hepatotoxicity has not been elucidated, troglitazone and its major metabolite, troglitazone sulfate, competitively inhibit adenosine triphosphate (ATP)-dependent taurocholate transport in isolated rat canalicular liver plasma membrane vesicles mediated by the canalicular bile salt export pump (Bsep). These results suggest that cholestasis may be a factor in troglitazone-associated hepatotoxicity. To determine whether this effect is 1) limited to canalicular bile acid transport and 2) is specific to troglitazone, the effect of troglitazone, rosiglitazone, and ciglitazone on bile acid transport was examined in rat basolateral (blLPM) and canalicular (cLPM) liver plasma membrane vesicles. In cLPM vesicles, troglitazone, rosiglitazone, and ciglitazone (100 microM) all significantly inhibited ATP-dependent taurocholate transport. In blLPM vesicles, these three thiazolidinediones also significantly inhibited Na(+)-dependent taurocholate transport. Inhibition of bile acid transport was concentration dependent and competitive in both cLPM and blLPM vesicles. In conclusion, these findings are consistent with a class effect by thiazolidinediones on hepatic bile acid transport. If hepatotoxicity is associated with this effect, then hepatotoxicity is not limited to troglitazone. Alternatively, if hepatotoxicity is limited to troglitazone, other mechanisms are responsible for its reported hepatotoxicity.

The Toxicology of Ligands for Peroxisome Proliferator-Activated Receptors (PPAR)

Peroxisome proliferator-activated receptors (PPARs) are ligand activated transcription factors that modulate target gene expression in response to endogenous and exogenous ligands. Ligands for the PPARs have been widely developed for the treatment of various diseases including dyslipidemias and diabetes. While targeting selective receptor activation is an established therapeutic approach for the treatment of various diseases, a variety of toxicities are known to occur in response to ligand administration. Whether PPAR ligands produce toxicity via a receptor-dependent and/or off-target-mediated mechanism(s) is not always known. Extrapolation of data derived from animal models and/or in vitro models, to humans, is also questionable. The different toxicities and mechanisms associated with administration of ligands for the three PPARs will be discussed, and important data gaps that could increase our current understanding of how PPAR ligands lead to toxicity will be highlighted.

Review article: the treatment of non-alcoholic steatohepatitis with thiazolidinediones

It is generally accepted that non-alcoholic fatty liver disease will be the most frequent liver disease in the near future and that the management of patients with non-alcoholic fatty liver disease will be a challenge for hepatologists in the next decades. Non-alcoholic fatty liver disease is considered the hepatic manifestation of the metabolic syndrome, in which insulin resistance plays a crucial role. Although steatosis will often not progress to severe liver disease, in some patients, it results in cirrhosis and even hepatocellular carcinoma. Therefore, it is important to identify those patients at risk for developing fibrosis. Age, diabetes, obesity and hypertriglyceridaemia are independent risk factors for fibrosis in patients with elevated serum alanine aminotransferase levels and steatosis on ultrasound. The presence of multiple metabolic disorders increases the risk. Apart from diet, exercise and correction of underlying metabolic abnormalities, no specific treatment is available at the moment. Theoretically, thiazolidinediones are an attractive way to treat non-alcoholic fatty liver disease, because they improve insulin resistance. Some preliminary studies with thiazolidinediones were encouraging, as steatosis, inflammation and fibrosis improved in a substantial number of patients. Although no serious side effects occurred in the pilot studies, we should look vigilantly for hepatotoxicity, as the first generation thiazolidinediones proved to be toxic for the liver.

Combination therapy using metformin or thiazolidinediones and insulin in the treatment of diabetes mellitus

The biguanide, metformin, sensitizes the liver to the effect of insulin, suppressing hepatic glucose output. Thiazolidinediones such as rosiglitazone and pioglitazone enhance insulin-mediated glucose disposal, leading to reduced plasma insulin concentrations. These classes of drugs may also have varying beneficial effects on features of insulin resistance such as lipid levels, blood pressure and body weight. Metformin in combination with insulin has been shown to significantly improve blood glucose levels while lowering total daily insulin dose and body weight. The thiazolidinediones in combination with insulin have also been effective in lowering blood glucose levels and total daily insulin dose. Triple combination therapy using insulin, metformin and a thiazolidinedione improves glycaemic control to a greater degree than dual therapy using insulin and metformin or insulin and a thiazolidinedione. There is insufficient evidence to recommend the use of metformin or thiazolidinediones in type 1 diabetic patients. Although these agents are largely well tolerated, some subjects experience significant gastrointestinal problems while using metformin. Metformin is associated with a low risk of lactic acidosis, but should not be used in patients with elevated serum creatinine or those being treated for congestive heart failure. The thiazolidinediones are associated with an increase in body weight, although this can be avoided with careful lifestyle management. Thiazolidinediones may also lead to oedema and are associated with a low incidence of hepatocellular injury. Thiazolidinediones are contraindicated in patients with underlying heart disease who are at risk of congestive heart failure and in patients who have abnormal hepatic function. The desired blood glucose-lowering effect and adverse event profiles of these agents should be considered when recommending these agents to diabetic patients. The potential for metformin or the thiazolidinediones to impact long-term cardiovascular outcomes remains under investigation.

Hepatic injury in a patient taking rosiglitazone

We describe a 52-year-old man with type 2 diabetes mellitus who developed cholestatic hepatitis in association with rosiglitazone use. Liver biopsy findings included dilated canaliculi, inspissated bile, intrahepatocellular bile pigment deposits, and enlarged xanthomatous Kupffer cells. The form of liver injury reported in this case differs markedly from those reported previously for rosiglitazone.

Effect of rosiglitazone on serum liver biochemistries in diabetic patients with normal and elevated baseline liver enzymes

OBJECTIVES

Thiazolidinediones (TZD) are recommended to be used cautiously in diabetics with mild elevations in liver enzymes and not to be used in those with alanine aminotransferase>2.5 upper limit normal (ULN). However, studies are not adequate that evaluated the risk of TZD hepatotoxicity in diabetics with elevated liver enzymes. We conducted a study to test if diabetics with elevated liver enzymes have increased risk for hepatotoxicity from rosiglitazone (only TZD available on our formulary).

METHODS

This study consisted of two cohorts of patients prescribed rosiglitazone since January 2000. Cohort 1: 210 diabetics with elevated baseline liver enzymes (aspartate aminotransferase (AST)>40 IU/L and/or alanine aminotransferase (ALT)>35 IU/L) who received rosiglitazone, and cohort 2:628 diabetics with normal liver enzymes who received rosiglitazone. Elevations in liver biochemistries over a 12-month period after initiating rosiglitazone were characterized into mild to moderate or severe elevations and into "Hy's rule" based on published criteria.

RESULTS

Compared to cohort 2, patients in cohort 1 did not have higher incidence of mild to moderate (10% vs 6.6%, p=0.2) or severe elevations (0.9% vs 0.6%, p=0.9) in liver biochemistries. Similarly, the incidence of liver biochemistry abnormalities meeting the Hy's Rule was statistically not different between the two cohorts (0% vs 0.3%, p=0.9). The frequency of discontinuing rosiglitazone therapy during the follow-up was similar between cohorts 1 and 2 (8.6% vs 8.1%, p=1.0).

CONCLUSIONS

These results suggest that diabetics with elevated baseline liver enzymes do not have a higher risk of hepatotoxicity from rosiglitazone than those with normal enzymes.

Tratamiento médico de la hepatopatía grasa no alcohólica primaria

The need for an effective and safe medical treatment of nonalcoholic fatty liver disease is urgent due to its high prevalence and progressive character. At the moment, therapeutic strategies are largely empirical and based on the control of associated clinical conditions (especially obesity, type 2 diabetes mellitus, and hypertriglyceridemia) and the use of some specific drugs (insulin sensitizing agents, cytoprotectives, antioxidants, and anticytokines) as an attempt to counteract known elements of the pathogenesis. None of these specifics measures have been found to display enough evidence to recommend their clinical use. It is indispensable to join efforts in coordinated networks to define, as soon as possible, the best treatment and the best time to start it.

The role of thiazolidinediones in the treatment of patients with type 2 diabetes mellitus

Diabetes mellitus is a significant and growing health concern worldwide. Unfortunately, type 2 diabetes mellitus is generally under-managed, and this may explain the increasing prevalence of diabetic complications throughout the world. The introduction of newer classes of antihyperglycemic agents should enhance the ability of clinicians to achieve optimal blood glucose control. One recent addition to the pharmacologic armamentarium is the thiazolidinedione class. The main effect of thiazolidinediones is amelioration of insulin resistance. These agents may also preserve beta-cell function, although evidence in favor of this effect is still inconclusive. The mechanism of action of thiazolidinediones is not completely understood. Similarly, the current state of knowledge cannot explain the differences in the lipid effects of pioglitazone and rosiglitazone. Thiazolidinediones are commonly used as add-on therapy for those requiring large daily doses of insulin therapy, or in addition to sulfonylurea agents and metformin for those reluctant to start insulin therapy. The potential role of thiazolidinediones as first-line therapy is now emerging. It is possible that in certain subgroups, particularly patients with renal failure, elderly individuals or those with corticosteroid-induced diabetes mellitus, the use of thiazolidinediones as a first-line therapy is justifiable. However, the lack of a long-term safety record, and the cost, would limit the widespread acceptance of this class of agents as first-line therapy.

Hepatotoxicity of thiazolidinediones

Thiazolidinediones are insulin sensitisers now widely used for the treatment of Type 2 diabetes mellitus. The initial marketed drug in this class, troglitazone, was removed from the market worldwide after approximately 3 years of use due to rare but severe hepatotoxicity, which sometimes resulted in liver failure leading to the need for liver transplantation, or even death. The unpredictability of such liver toxicity made the use of troglitazone highly problematic. Fortunately, the two newer drugs in this class, rosiglitazone and pioglitazone, have a much larger margin of safety for liver toxicity. Very rare reports of liver toxicity, usually milder and reversible, have been seen with these drugs. Therefore, whilst pharmacovigilance for hepatotoxicity is probably still warranted, the practitioner and patient can be fairly confident that these drugs are safe from a liver standpoint. Finally, recent work would suggest that these agents may prove useful to reduce hepatic fat in patients with non-alcoholic steatohepatitis, and may possibly protect against adverse metabolic consequences and the ultimate development of cirrhosis in patients with fatty livers.

Thiazolidinediones and Insulin

The range of therapeutic modalities to treat type 2 diabetes mellitus has broadened in recent years. Biguanides and thiazolidinediones are the two currently available classes of anti-hyperglycemic agents with insulin-sensitizing properties. Thiazolidinediones, in particular, have received much attention, not only for the well documented hepatotoxicity of troglitazone that led to its removal from the market in 2000, but also for the emerging data that support the beneficial effects of the thiazolidinedione class of drugs on beta-cell rejuvenation and cardiovascular risk reduction. In the US, thiazolidinediones are indicated either as monotherapy or in combination with a sulfonylurea, metformin, or insulin in cases where diet, exercise, and a single drug fail. In contrast, the UK National Institute for Clinical Excellence included in its re-appraisal of 'glitazones' in August 2003 the continued exclusion from licensed use in the UK of combination therapy with thiazolidinediones and insulin. When added to insulin therapy, thiazolidinediones appear to effectively lower glucose levels and reduce insulin dosage in clinical trials involving individuals with poorly controlled type 2 diabetes. However, weight gain, hypoglycemia, and fluid retention pose problems in certain patients. The fluid retention may exacerbate or even precipitate congestive heart failure, which usually necessitates discontinuation of the drug. Risk stratification and careful management of patients at risk for heart failure, including those taking insulin concomitantly, allow healthcare providers to safely administer combination therapy with thiazolidinediones in patients with type 2 diabetes. Hepatic toxicity with currently available thiazolidinediones has been found to be minimal overall.