Rosiglitazone and hepatic failure

Rosiglitazone promotes glucose metabolism of GIFT tilapia based on the PI3K/Akt signaling pathway

The study aimed to explore the effects of rosiglitazone on glucose metabolism of GIFT tilapia based on the PI3K/Akt signaling pathway. The experiment was divided into five groups: normal starch group (32%, LC), high starch group (53%, HC), high starch +rosiglitazone group 1 (10 mg/kg, R1), high starch + rosiglitazone group 2 (20 mg/kg, R2), and high starch + rosiglitazone group 3 (30 mg/kg, R3). The results showed that a high starch diet supplemented with 10-20 mg/kg rosiglitazone had a better specific growth rate and protein efficiency that was beneficial for the growth of the tilapia. Rosiglitazone had no significant effect on the contents of crude lipid, crude protein, crude ash, and moisture of the whole fish body (p > 0.05). The contents of triglycerides and total cholesterol in the R1, R2, and R3 groups were lower than those in the HC group. The levels of glutamic oxaloacetic transaminase (GOT) and glutamic pyruvic transaminase (GPT) in R1 and R2 groups were significantly lower than those in the HC groups (p < 0.05). However, the GOT and GPT levels in the R3 groups were significantly higher than those in the R1 and R2 groups (p < 0.05). With an increase in the rosiglitazone concentration, the contents of serum glucose, insulin, and hepatic glycogen in the R1, R2, and R3 groups decreased gradually. Meanwhile, the muscle glycogen content in the R1, R2, and R3 groups increased gradually. The mRNA expression of the IRS-1, PI3K, GLUT-4, and Akt proteins in the R1, R2, and R3 groups was significantly higher than that in the HC group (p < 0.05). Compared with the HC group, the expression of the GSK-3 mRNA in the R1, R2, and R3 groups was significantly reduced (p < 0.05). The protein expression of p-Akt in the R1 and R2 groups was higher than that in the HC group (p > 0.05). The protein expression of p-GSK-3β in the R1 and R2 groups was significantly higher than that in the HC group (p < 0.05). In conclusion, a high starch diet supplemented with rosiglitazone can improve growth, enhance the serum biochemical indices, and increase the muscle glycogen content in the GIFT tilapia. It benefits in upregulating the IRS-1, PI3K, and GLUT-4 mRNA levels in the skeletal muscle and promotes glucose uptake. Meanwhile, the phosphorylation of Akt and GSK-3β increased significantly and resulted in the inactivation of GSK-3β and alleviation of insulin resistance.

Therapeutic Effects of Targeted PPARɣ Activation on Inflamed High-Risk Plaques Assessed by Serial Optical Imaging In Vivo

Rationale: Atherosclerotic plaque is a chronic inflammatory disorder involving lipid accumulation within arterial walls. In particular, macrophages mediate plaque progression and rupture. While PPARγ agonist is known to have favorable pleiotropic effects on atherogenesis, its clinical application has been very limited due to undesirable systemic effects. We hypothesized that the specific delivery of a PPARγ agonist to inflamed plaques could reduce plaque burden and inflammation without systemic adverse effects.

Methods: Herein, we newly developed a macrophage mannose receptor (MMR)-targeted biocompatible nanocarrier loaded with lobeglitazone (MMR-Lobe), which is able to specifically activate PPARγ pathways within inflamed high-risk plaques, and investigated its anti-atherogenic and anti-inflammatory effects both in in vitro and in vivo experiments.

Results: MMR-Lobe had a high affinity to macrophage foam cells, and it could efficiently promote cholesterol efflux via LXRα-, ABCA1, and ABCG1 dependent pathways, and inhibit plaque protease expression. Using in vivo serial optical imaging of carotid artery, MMR-Lobe markedly reduced both plaque burden and inflammation in atherogenic mice without undesirable systemic effects. Comprehensive analysis of en face aorta by ex vivo imaging and immunostaining well corroborated the in vivo findings.

Conclusion: MMR-Lobe was able to activate PPARγ pathways within high-risk plaques and effectively reduce both plaque burden and inflammation. This novel targetable PPARγ activation in macrophages could be a promising therapeutic strategy for high-risk plaques.

Examining the safety of PPAR agonists - current trends and future prospects

INTRODUCTION

The peroxisome proliferator-activated receptor (PPAR)-α and -γ agonists, fibrates and glitazones, are effective treatments for dyslipidemia and type 2 diabetes mellitus, respectively, but exhibit class-related, as well as compound-specific safety characteristics.

AREAS COVERED

This article reviews the profiles of PPAR-α, PPAR-γ, and dual PPAR-α/γ agonists with regard to class-related and compound-specific efficacy and adverse effects. We explore how learnings from first-generation drugs are being applied to develop safer PPAR-targeted therapies.

EXPERT OPINION

The finding that rosiglitazone may increase risk for cardiovascular events has led to regulatory guidelines requiring demonstration of cardiovascular safety in appropriate outcome trials for new type 2 diabetes mellitus drugs. The emerging data on the possibly increased risk of bladder cancer with pioglitazone may prompt the need for post-approval safety studies for new drugs. Since PPAR-α and -γ affect key cardiometabolic risk factors (diabetic dyslipidemia, insulin resistance, hyperglycemia, and inflammation) in a complementary fashion, combining their benefits has emerged as a particularly attractive option. New PPAR-targeted therapies that balance the relative potency and/or activity toward PPAR-α and -γ have shown promise in retaining efficacy while reducing potential side effects.

Troglitazone

Troglitazone was the first thiazolidinedione antidiabetic agent approved for clinical use in 1997, but it was withdrawn from the market in 2000 due to serious idiosyncratic hepatotoxicity. Troglitazone contains the structure of a unique chroman ring of vitamin E, and this structure has the potential to undergo metabolic biotransformation to form quinone metabolites, phenoxy radical intermediate, and epoxide species. Although troglitazone has been shown to induce apoptosis in various hepatic and nonhepatic cells, the involvement of reactive metabolites in the troglitazone cytotoxicity is controversial. Numerous toxicological tests, both in vivo and in vitro, have been used to try to predict the toxicity, but no direct mechanism has been demonstrated that can explain the hepatotoxicity that occurred in some individuals. This chapter summarizes the proposed mechanisms of troglitazone hepatotoxicity based in vivo and in vitro studies. Many factors have been proposed to contribute to the mechanism underlying this idiosyncratic toxicity.

Causality assessment of drug-induced hepatotoxicity: promises and pitfalls

Drug-induced liver injury is the leading cause of acute liver failure in the United States, but the ability to ascribe hepatic injury confidently to a specific drug remains a challenging and often difficult pursuit. This article explores the ongoing challenges inherent in what is currently a clinical process of elimination made in the attempt of assigning causality in drug-induced liver injury. In particular, it points out the shortcomings and pitfalls that often limit the applicability of the causality-assessment methodologies currently in use.

Dephosphorylation of ribosomal protein P0 in response to troglitazone-induced cytotoxicity

Troglitazone (TRO)-induced cytotoxicity was investigated in HepG2 cells. The cells were exposed to TRO as well as rosiglitazone (RSG) at concentrations of 0, 25, 50 and 75 microM for 48 h. Total proteins were separated by two-dimensional electrophoresis and visualized by silver staining. We focused on a protein spot at an approximate molecular weight of 35 kDa and isoelectric point (pI) of 5.7, which appeared only with the cytotoxic concentrations (50 and 75 microM) of TRO, but not with the low concentration (25 microM) of TRO or any concentrations of RSG. This protein spot was subjected to amino acid sequence analysis and identified as ribosomal protein P0 (P0). Interestingly, without any significant induction of its protein and mRNA, P0 was dephosphorylated depending on the concentration- and time-dependent manner of TRO-induced cytotoxicity. Pretreatment with a general caspase inhibitor, Z-VAD.fmk, prevented cleavage of caspase-3 but demonstrated a slight improvement of cytotoxicity induced by TRO. Thus, these effects could not prevent the dephosphorylation of P0. Our results strongly suggest that a post-translational modification, dephosphorylation, of P0 is associated with TRO-induced cytotoxicity.

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.

Second-generation thiazolidinediones and hepatotoxicity

OBJECTIVE

To report a case of hepatotoxicity probably caused by pioglitazone, summarize case reports of hepatotoxicity induced by rosiglitazone or pioglitazone, and make recommendations regarding routine liver enzyme measurement in patients taking these agents.

CASE SUMMARY

A 39-year-old black woman with type 2 diabetes mellitus, hypertension, and congestive heart failure presented to a pharmacist-staffed diabetes comanagement service. She reported fatigue, dark brown urine, nausea, itching, and loss of appetite. Pioglitazone was promptly discontinued because her symptoms were consistent with those of hepatic dysfunction and pioglitazone was identified as a potential cause. The patient was referred to her physician. Liver enzyme levels were checked 13 days after initial presentation and found to be abnormal: alanine aminotransferase 490 U/L, aspartate aminotransferase 360 U/L, alkaline phosphatase 851 U/L, total bilirubin 3.1 mg/dL, direct bilirubin 2.0 mg/dL, and indirect bilirubin 1.1 mg/dL. Within 2(1/2) months of discontinuing pioglitazone, the patient's symptoms resolved and liver enzyme levels returned to normal.

DISCUSSION

Troglitazone, a thiazolidinedione (TZD), was removed from the market because of hepatotoxicity. Reported cases involving the newer TZDs, rosiglitazone and pioglitazone, have been few in number and less severe in consequence. Six cases of rosiglitazone-induced hepatotoxicity and 5 of pioglitazone-induced hepatotoxicity have been reported. Most patients improved symptomatically 2-4 weeks following discontinuation of the offending TZD, with normalization of liver enzyme levels in 2 weeks to 6 months following TZD discontinuation.

CONCLUSIONS

Although the timeline and extent of liver enzyme elevation in this case are unclear, the Naranjo probability scale suggests that a causal relationship between pioglitazone and liver disease is probable. Patients with previous TZD-induced hepatotoxicity should not be rechallenged. Cases of hepatotoxicity with second generation TZDs, although clearly linked, have been few in number and less severe in consequence when compared to troglitazone. We agree with current package labeling that requires baseline and then periodic measurement of liver enzymes in patients taking pioglitazone or rosiglitazone.

Rosiglitazone: a review of its use in the management of type 2 diabetes mellitus

Rosiglitazone, a thiazolidinedione with a different side chain from those of troglitazone and pioglitazone, reduces plasma glucose levels and glucose production and increases glucose clearance in patients with type 2 diabetes mellitus. Insulin sensitivity, pancreatic beta-cell function and surrogate markers of cardiovascular risk factors are significantly improved by rosiglitazone. Double-blind trials of 8 to 26 weeks of rosiglitazone 4 or 8 mg/day monotherapy indicate significant decreases in fasting plasma glucose (-2 to -3 mmol/L with 8 mg/day) and glycosylated haemoglobin levels [HbA(1c); -0.6 to -0.7% (-0.8 to -1.1% in drug-naive patients) with 8 mg/day]. Significant decreases in hyperglycaemic markers occurred when rosiglitazone was combined with metformin (HbA(1c) -0.8 to -1.0%), a sulphonylurea (-1.4%) or insulin (-1.2%) for 26 weeks versus little change with active comparator monotherapy. Efficacy was maintained in trials of < or = 2 years, and was also apparent in various ethnic subgroups, elderly patients, and both obese and nonobese patients. Rosiglitazone is currently not indicated in combination with injected insulin. It should be administered in conjunction with diet and exercise regimens. Rosiglitazone is generally well tolerated. Despite rare individual reports of liver function abnormalities in rosiglitazone recipients, the incidence of these in clinical trials (< or = 2 years' duration) was similar to that in placebo and active comparator groups. Fluid retention associated with rosiglitazone may be the cause of the increased incidence of anaemia in clinical trials, and also means that patients should be monitored for signs of heart failure during therapy. Although bodyweight is increased overall with rosiglitazone therapy, increases are in subcutaneous, not visceral, fat; hepatic fat is decreased. The pharmacokinetic profile of rosiglitazone is not substantially altered by age or renal impairment, nor are there important drug interactions. Rosiglitazone is not indicated in patients with active liver disease or increased liver enzymes.

CONCLUSIONS

Oral rosiglitazone 4 or 8 mg/day provides significant antihyperglycaemic efficacy and is generally well tolerated, both as monotherapy and in combination with other antihyperglycaemic agents, in patients with type 2 diabetes mellitus who do not have active liver disease. Long-term data are required before conclusions can be drawn about the clinical significance of positive changes to surrogate markers of cardiovascular disease risk and improvements to pancreatic beta-cell function. Rosiglitazone significantly improves insulin sensitivity and, as such, is a welcome addition to the treatment options for patients with type 2 diabetes mellitus.

Hepatotoxicity with thiazolidinediones: is it a class effect?

Decreased insulin sensitivity plays a major role in various human diseases. particularly type 2 diabetes mellitus, and is associated with a higher risk of atherosclerosis and cardiovascular complications. Thiazolidinediones, more commonly termed glitazones, are the first drugs to specifically target muscular insulin resistance. They have proven efficacy for reducing plasma glucose levels in patients with type 2 diabetes mellitus treated with diet alone, sulphonylureas, metformin or insulin. In addition, they are associated with some improvement of the cardiovascular risk profile. However, troglitazone, the first compound approved by the Food and Drug Administration in the US, proved to be hepatotoxic and was withdrawn from the market after the report of several dozen deaths or cases of severe hepatic failure requiring liver transplantation. It remains unclear whether or not hepatotoxicity is a class effect or is related to unique properties of troglitazone. Rosiglitazone and pioglitazone, two other glitazones, appear to have similar efficacy with regard to blood glucose control in patients with type 2 diabetes mellitus as compared with troglitazone. In controlled clinical trials, the incidence of significant (> or =3 x upper limit of normal) increases in liver enzyme levels (ALT in particular) was similar with rosiglitazone or pioglitazone as compared with placebo, whereas troglitazone was associated with a 3-fold greater incidence. In contrast to the numerous case reports of acute liver failure in patients receiving troglitzone, only a few case reports of hepatotoxicity have been reported in patients treated with rosiglitazone until now, with a causal relationship remaining uncertain. Furthermore, no single case of severe hepatotoxicity has been reported yet with pioglitazone. It should be mentioned that troglitazone, unlike pioglitazone and rosiglitazone, induces the cytochrome P450 isoform 3A4, which is partly responsible for its metabolism, and may be prone to drug interactions. Importantly enough, obesity, insulin resistance and type 2 diabetes mellitus are associated with liver abnormalities, especially non-alcoholic steatohepatitis, independent of any pharmacological treatment. This association obviously complicates the selection of patients who are good candidates for a treatment with glitazones as well as the monitoring of liver tests after initiation of therapy with any thiazolidinedione compound. While regular monitoring of liver enzymes is still recommended and more long term data are desirable, current evidence from clinical trials and postmarketing experience in the US supports the conclusion that rosiglitazone and pioglitazone do not share the hepatotoxic profile of troglitazone.

Effects of pioglitazone and rosiglitazone on blood lipid levels and glycemic control in patients with type 2 diabetes mellitus: a retrospective review of randomly selected medical records

BACKGROUND

The antihyperglycemic effects of pioglitazone hydrochloride and rosiglitazone maleate are well documented. The results of clinical trials and observational studies have suggested, however, that there are individual differences in the effects of these drugs on blood lipid levels.

OBJECTIVE

The present study evaluated the effects of pioglitazone and rosiglitazone on blood lipid levels and glycemic control in patients with type 2 diabetes mellitus.

METHODS

This was a retrospective review of randomly selected medical records from 605 primary care practices in the United States in which adults with type 2 diabetes received pioglitazone or rosiglitazone between August 1, 1999, and August 31, 2000. The outcome measures were mean changes in serum concentrations of triglycerides (TG), total cholesterol (TC), high-density lipoprotein cholesterol (HDL-C), low-density lipoprotein cholesterol (LDL-C), and glycosylated hemoglobin (HbA1c) values.

RESULTS

Treatment with pioglitazone was associated with a reduction in mean TG of 55.17 mg/dL, a reduction in TC of 8.45 mg/dL, an increase in HDL-C of 2.65 mg/dL, and a reduction in LDL-C of 5.05 mg/dL. Treatment with rosiglitazone was associated with a reduction in mean TG of 13.34 mg/dL, an increase in TC of 4.81 mg/dL, a reduction in HDL-C of 0.12 mg/dL, and an increase in LDL-C of 3.56 mg/dL. With the exception of HDL-C, the differences in mean changes in lipid parameters between treatment groups were statistically significant (P < 0.001, pioglitazone vs rosiglitazone). Reductions in HbA1c were statistically equivalent between treatments (1.04% pioglitazone, 1.18% rosiglitazone).

CONCLUSIONS

Treatment with pioglitazone was associated with greater beneficial effects on blood lipid levels than treatment with rosiglitazone, whereas glycemic control was equivalent between the 2 treatments.

Management of rosiglitazone-induced edema: two case reports and a review of the literature

The thiazolidinediones are an important class of insulin-sensitizing agents used for the treatment of type 2 diabetes. Similar to other antidiabetic agents, use of the thiazolidinediones is limited by adverse drug reactions. Specifically, use of the thiazolidinediones is associated with a triad of fluid retention, edema, and weight gain. In premarketing clinical trials, edema was reported to occur infrequently with minimal severity. However, several published cases from postmarketing data demonstrate that thiazolidinedione-induced fluid retention, exhibited by the initial onset of peripheral edema and weight gain, can progress to a more severe form of pulmonary edema that is refractory to diuretic therapy with resolution of symptoms only through discontinuation of the offending thiazolidinedione. In clinical practice, the occurrence of edema secondary to a thiazolidinedione drug may occur more frequently than reported. Two cases presented in this report illustrate a different outpatient management approach that enables both desired glycemic control and minimal fluid retention while using the thiazolidinediones.

A review of rosiglitazone in type 2 diabetes mellitus

The thiazolidinedione rosiglitazone maleate works primarily to improve insulin sensitivity in muscle and adipose tissue. It may have additional pharmacologic effects, however, as its main target is peroxisome proliferator-activated receptor-gamma. Data using the homeostasis model assessment and proinsulin:insulin ratio in patients with type 2 diabetes mellitus suggest that rosiglitazone may have the potential to sustain or improve beta-cell function. In these patients the drug reduces fasting plasma glucose, glycosylated hemoglobin, insulin, and C-peptide. In clinical trials, rosiglitazone monotherapy significantly reduced glycosylated hemoglobin by 1.5% compared with placebo and led to significant improvements in glycemic control when given in combination with metformin, sulfonylureas, or insulin. A dosage of 4 mg twice/day significantly reduced fasting plasma glucose levels and produced comparable reductions in glycosylated hemoglobin compared with glyburide. Rosiglitazone has a low risk of gastrointestinal side effects and hypoglycemia, reduced insulin demand, potential sparing effects on beta-cells, and favorable drug interaction profile. Adverse events of clinical significance are edema, anemia, and weight gain. Premarketing data indicate no significant difference in liver enzyme elevations for rosiglitazone, placebo, or active controls. Another drug in the thiazolidinedione class, troglitazone, was associated with idiosyncratic hepatotoxicity and was removed from the market. Therefore, until long-term data are available for rosiglitazone, liver enzyme monitoring is recommended.

Oral agents for the treatment of type 2 diabetes mellitus: pharmacology, toxicity, and treatment

Currently available oral agents for the treatment of type 2 diabetes mellitus include a variety of compounds from 5 different pharmacologic classes with differing mechanisms of action, adverse effect profiles, and toxicities. The oral antidiabetic drugs can be classified as either hypoglycemic agents (sulfonylureas and benzoic acid derivatives) or antihyperglycemic agents (biguanides, alpha-glucosidase inhibitors, and thiazolidinediones). In this review, a brief discussion of the pharmacology of these agents is followed by an examination of the adverse effects, drug-drug interactions, and toxicities. Finally, treatment of sulfonylurea-induced hypoglycemia is described, including general supportive care and the management of pediatric sulfonylurea ingestions. The adjunctive roles of glucagon, diazoxide, and octreotide for refractory hypoglycemia are also discussed.

Drug-induced liver disease

This year's review is divided into several sections: the first describes drug withdrawals and new general reviews of drug-induced liver disease (DILD), including a review of a classification of drug injury. We review agents newly described as causing DILD, and new reports of DILD from established agents appearing in the year 2000. New aspects regarding the treatment of acetaminophen toxicity are included, and in the final section we deal with prevention of DILD as well as issues surrounding the use of potentially hepatotoxic medications in patients with underlying chronic disease.

Factors associated with the risk of liver enzyme elevation in patients with type 2 diabetes treated with a thiazolidinedione

STUDY OBJECTIVE

To characterize frequency of liver enzyme elevation in patients with type 2 diabetes mellitus receiving troglitazone.

DESIGN

Retrospective study.

SETTING

Hospital-affiliated medical center.

PATIENTS

Two hundred ninety-one patients with type 2 diabetes mellitus.

INTERVENTION

Data from patients with an average troglitazone exposure of 412.7 +/- 255.6 days were studied.

MEASUREMENTS AND MAIN RESULTS

Enzyme elevations more than 1.5 times the upper limit of normal (ULN) occurred in 17 patients (5.8%) and more than 3-fold elevations in 6 (2.1%). The relationship among enzyme elevation events, demographic factors, duration of troglitazone exposure, frequency of monitoring, and concurrent drugs (limited to glucose and lipid-lowering agents) was assessed by multiple logistic regression. Age was an independent predictor of risk (p=0.009), and concurrent insulin therapy approached statistical significance (p=0.051) for 1.5-fold ULN elevation in liver enzymes. Age and concurrent therapy with 3-hydroxy-3-methylglutaryl coenzyme A reductase inhibitors were the only significant predictors of 3-fold ULN elevations (p=0.03 and p=0.04, respectively).

CONCLUSION

Several factors appear to increase the risk of enzyme elevation events in patients treated with troglitazone.

Disorders of glucose metabolism in patients infected with human immunodeficiency virus

New-onset diabetes mellitus, clinically similar to type 2 diabetes, will affect a small proportion (1%-6%) of patients infected with human immunodeficiency virus (HIV) who are treated with HIV-1 protease inhibitors (PIs). However, insulin resistance and impaired glucose tolerance will develop during PI treatment in a considerable proportion of patients. Dyslipidemia, abdominal obesity, and loss of peripheral fat frequently coexist with insulin resistance, but it is not clear whether all of these result from a common pathogenic mechanism. Recent data suggest that insulin resistance may also be associated with HIV infection in patients not receiving PI therapy. The long-term consequences of insulin resistance in this population are not known. The effect of switching to other antiretroviral therapies has not been fully determined. Treatment of established diabetes mellitus should generally follow existing guidelines. There is no clinically useful screening test that will determine the existence and degree of insulin resistance in individual patients. It is therefore reasonable to recommend general measures to increase insulin sensitivity in all patients infected with HIV, such as weight reduction for obese persons and regular aerobic exercise.

Pathophysiology and pharmacological treatment of insulin resistance

Diabetes mellitus type 2 is a world-wide growing health problem affecting more than 150 million people at the beginning of the new millennium. It is believed that this number will double in the next 25 yr. The pathophysiological hallmarks of type 2 diabetes mellitus consist of insulin resistance, pancreatic beta-cell dysfunction, and increased endogenous glucose production. To reduce the marked increase of cardiovascular mortality of type 2 diabetic subjects, optimal treatment aims at normalization of body weight, glycemia, blood pressure, and lipidemia. This review focuses on the pathophysiology and molecular pathogenesis of insulin resistance and on the capability of antihyperglycemic pharmacological agents to treat insulin resistance, i.e., a-glucosidase inhibitors, biguanides, thiazolidinediones, sulfonylureas, and insulin. Finally, a rational treatment approach is proposed based on the dynamic pathophysiological abnormalities of this highly heterogeneous and progressive disease.

Rosiglitazone in the treatment of type 2 diabetes mellitus: a critical review

OBJECTIVE

This article reviews the pharmacology, pharmacokinetics, clinical efficacy, adverse effects, drug interactions, and dosing of rosiglitazone, the second thiazolidinedione approved for the treatment of type 2 diabetes mellitus.

METHODS

Background information for this article was obtained from searches of MEDLINE , Iowa Drug Information Service, and International Pharmaceutical Abstracts, as well as from data on file with the manufacturer of rosiglitazone.

RESULTS

Rosiglitazone is indicated for use alone or in combination with metformin or sulfonylureas for the maintenance of glycemic control in patients with type 2 diabetes mellitus. Rather than stimulation of insulin secretion, rosiglitazone's primary mechanism of action is sensitization of tissues to insulin through activation of the peroxisome proliferator-activated receptor gamma and increasing expression of the glucose transporter-4 receptor. Rosiglitazone is administered orally, is absorbed almost completely, and is 99.8% bound to plasma proteins. The majority of a dose is metabolized by the cytochrome P-450 2C8 isozyme, with the inactive metabolites excreted primarily in the urine. Four to 8 mg/d of rosiglitazone given alone or in combination with metformin, sulfonylureas, or insulin has produced reductions in baseline fasting plasma glucose and glycosylated hemoglobin in studies of up to 1 year's duration. Common adverse effects (occurring in > or = 5.0% of patients) include upper respiratory tract infection, injury, and headache. Edema, weight gain, and increased low-density lipoprotein cholesterol concentrations have also been observed. It is recommended that rosiglitazone be avoided in patients with alanine aminotransferase levels >2.5 times normal. No clinically relevant drug interactions have been documented with rosiglitazone to date. The initial starting daily dose of rosiglitazone is 4 mg in single or divided doses, without regard to meals, to a maximum of 8 mg.

CONCLUSIONS

No direct comparative trials of the efficacy and safety of rosiglitazone versus those of the other available thiazolidinedione, pioglitazone, have yet been performed. The role of rosiglitazone as a single agent and in combination with other antidiabetic agents remains to be clarified as additional comparative and long-term data become available.

Drug-induced liver disease

The incidence of drug-induced liver disease appears to be increasing, reflecting the increasing number of new agents that have been introduced into clinical use over the past several decades. Among the topics covered, the author discusses incidence, diagnosis, risk factors, clinical presentations, hepatitis, and vascular injury. The author also reviews the hepatic injury seen with commonly prescribed drugs, emphasizing newer developments in the field and recent publications and reports.

Management of Type 2 Diabetes in the Geriatric Patient

Type 2 diabetes is prevalent in the elderly population. In the past five years, there has been an increased number of drugs with unique mechanisms of action which have become available for the treatment of type 2 diabetes. Recent studies have shown that attaining optimal glycemic control in patients with type 2 diabetes will prevent or delay the complications associated with this disease. This article will review the management of type 2 diabetes.

Thiazolidinediones: an update

Thiazolidinediones, which are being developed for the treatment of insulin resistance and type 2 diabetes mellitus, bind and activate peroxisome proliferator-activated receptor gamma, a nuclear receptor that regulates the expression of several genes involved in metabolism. This receptor controls adipocyte differentation, lipid storage, and insulin sensitisation. Besides metabolic activities, thiazolidinediones have effects as diverse as the control of host defence, cell proliferation, and tumorigenesis.

Thiazolidinediones: a comparative review of approved uses

Thiazolidinediones are a powerful and clinically important new class of oral antidiabetic agents that act by improving insulin sensitivity. Troglitazone is the prototype drug in this class but was withdrawn from the market in March 2000 due to its association with idiosyncratic hepatotoxicity. Currently two thiazolidinediones, rosiglitazone and pioglitazone, are U.S. Food and Drug Administration (FDA) approved for treatment of type 2 diabetes. These agents bind to and activate peroxisome proliferator-activator receptor gamma (PPAR-gamma) and work by altering the expression of genes involved in glucose uptake, glucose disposal, and lipid metabolism. The drugs differ in receptor binding and potency due to differences in their side chain moieties. These agents are rapidly absorbed from the gastrointestinal tract and are metabolized mainly in the liver. Rosiglitazone is FDA approved for monotherapy and for use in combination therapy with metformin or sulfonylureas. Pioglitazone is FDA approved for monotherapy as well as for use in combination therapy with metformin, insulin, or sulfonylureas. These drugs may also cause significant changes in plasma lipid concentrations, and improved insulin sensitivity may improve ovulatory function and fertility in women with polycystic ovary syndrome. The most serious side effect of the thiazolidinediones is hepatotoxicity. Although rosiglitazone and pioglitazone were not associated with hepatotoxicity in premarketing clinical trials, there were two recent case reports of idiosyncratic hepatotoxicity in patients treated with rosiglitazone. In addition, these agents may be associated with edema and some hematological changes. The purpose of this review is to provide an overview of the two currently approved thiazolidinediones and to suggest an approach for their safe and rational use.