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

Drug-induced liver steatosis in patients with HIV infection

Drug-induced liver injury (DILI) due to the use of prescription and non-prescription medication by HIV-positive and HIV-negative patients is one of the main causes of acute liver failure and transplantation in Western countries and, although rare, has to be considered a serious problem because of its unforeseeable nature and possibly fatal course. Drug-induced steatosis (DIS) and steatohepatitis (DISH) are infrequent but well-documented types of DILI. Although a number of commonly used drugs are associated with steatosis, it is not always easy to identify them as causative agents because of the weak temporal relationship between the administration of the drug and the clinical event, the lack of a confirmatory re-challenge, and the high prevalence of non-alcoholic fatty liver disease (NAFLD) in the general population, which often makes it difficult to make a differential diagnosis of DIS and DISH. The scenario is even more complex in HIV-positive patients not only because of the underlying disease, but also because the various anti-retroviral regimens have different effects on liver steatosis. Given the high prevalence of liver steatosis in HIV-positive patients and the increasing use of drugs associated with a potential steatotic risk, the identification of clinical signs suggesting liver damage should help to avoid the possible misdiagnosis of "primary" NAFLD in a patient with DIS or DISH. This review will therefore initially concentrate on the current diagnostic criteria for DIS/DISH and their differential diagnosis from NAFLD. Subsequently, it will consider the different clinical manifestations of iatrogenic liver steatosis in detail, with specific reference to HIV-positive patients. Finally, the last part of the review will be dedicated to the possible effects of liver steatosis on the bioavailability of antiretroviral and other drugs.

Consensus: guidelines: best practices for detection, assessment and management of suspected acute drug-induced liver injury during clinical trials in patients with nonalcoholic steatohepatitis

BACKGROUND

The last decade has seen a rapid growth in the number of clinical trials enrolling patients with nonalcoholic fatty liver disease and nonalcoholic steatohepatitis (NASH). Due to the underlying chronic liver disease, patients with NASH often require different approaches to the assessment and management of suspected drug-induced liver injury (DILI) compared to patients with healthy livers. However, currently no regulatory guidelines or position papers systematically address best practices pertaining to DILI in NASH clinical trials.

AIMS

This publication focuses on best practices concerning the detection, monitoring, diagnosis and management of suspected acute DILI during clinical trials in patients with NASH.

METHODS

This is one of several papers developed by the IQ DILI Initiative, comprised of members from 15 pharmaceutical companies, in collaboration with DILI experts from academia and regulatory agencies. This paper is based on extensive literature review, and discussions between industry members with expertise in drug safety and DILI experts from outside industry to achieve consensus on common questions related to this topic.

RESULTS

Recommended best practices are outlined pertaining to hepatic inclusion and exclusion criteria, monitoring of liver tests, DILI detection, approach to a suspected DILI signal, causality assessment and hepatic discontinuation rules.

CONCLUSIONS

This paper provides a framework for the approach to assessment and management of suspected acute DILI during clinical trials in patients with NASH.

Diagnosis and Management of Drug-Induced Liver Injury (DILI) in Patients with Pre-Existing Liver Disease

The relationship between drugs and pre-existing liver disease is complex, particularly when increased liver tests (LTs) or new symptoms emerge in patients with pre-existing liver disease during drug therapy. This requires two strategies to assess whether these changes are due to drug-induced liver injury (DILI) as a new event or due to flares of the underlying liver disease. Lacking a valid diagnostic biomarker, DILI is a diagnosis of exclusion and requires causality assessment by RUCAM, the Roussel Uclaf Causality Assessment Method, to establish an individual causality grading of the suspected drug(s). Flares of pre-existing liver disease can reliably be assessed in some hepatotropic virus infections by polymerase chain reaction (PCR) and antibody titers at the beginning and in the clinical course to ascertain flares during the natural course of the disease. Unfortunately, flares cannot be verified in many other liver diseases such as alcoholic liver disease, since specific tests are unavailable. However, such a diagnostic approach using RUCAM applied to suspected DILI cases includes clinical and biological markers of pre-existing liver diseases and would determine whether drugs or underlying liver diseases caused the LT abnormalities or the new symptoms. More importantly, a clear diagnosis is essential to ensure effective disease management by drug cessation or specific treatment of the flare up due to the underlying disease.

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.

Utilizing an integrated infrastructure for outcomes research: a systematic review

OBJECTIVE

To explore the ability of an integrated health information infrastructure to support outcomes research.

METHODS

A systematic review of articles published from 1983 to 2012 by Regenstrief Institute investigators using data from an integrated electronic health record infrastructure involving multiple provider organisations was performed. Articles were independently assessed and classified by study design, disease and other metadata including bibliometrics.

RESULTS

A total of 190 articles were identified. Diseases included cognitive, (16) cardiovascular, (16) infectious, (15) chronic illness (14) and cancer (12). Publications grew steadily (26 in the first decade vs. 100 in the last) as did the number of investigators (from 15 in 1983 to 62 in 2012). The proportion of articles involving non-Regenstrief authors also expanded from 54% in the first decade to 72% in the last decade. During this period, the infrastructure grew from a single health system into a health information exchange network covering more than 6 million patients. Analysis of journal and article metrics reveals high impact for clinical trials and comparative effectiveness research studies that utilised data available in the integrated infrastructure.

DISCUSSION

Integrated information infrastructures support growth in high quality observational studies and diverse collaboration consistent with the goals for the learning health system. More recent publications demonstrate growing external collaborations facilitated by greater access to the infrastructure and improved opportunities to study broader disease and health outcomes.

CONCLUSIONS

Integrated information infrastructures can stimulate learning from electronic data captured during routine clinical care but require time and collaboration to reach full potential.

Pioglitazone treatment increases survival and prevents body weight loss in tumor-bearing animals: possible anti-cachectic effect

Cachexia is a multifactorial syndrome characterized by profound involuntary weight loss, fat depletion, skeletal muscle wasting, and asthenia; all symptoms are not entirely attributable to inadequate nutritional intake. Adipose tissue and skeletal muscle loss during cancer cachexia development has been described systematically. The former was proposed to precede and be more rapid than the latter, which presents a means for the early detection of cachexia in cancer patients. Recently, pioglitazone (PGZ) was proposed to exhibit anti-cancer properties, including a reduction in insulin resistance and adipose tissue loss; nevertheless, few studies have evaluated its effect on survival. For greater insight into a potential anti-cachectic effect due to PGZ, 8-week-old male Wistar rats were subcutaneously inoculated with 1 mL (2×10⁷) of Walker 256 tumor cells. The animals were randomly assigned to two experimental groups: TC (tumor + saline-control) and TP5 (tumor + PGZ/5 mg). Body weight, food ingestion and tumor growth were measured at baseline and after removal of tumor on days 7, 14 and 26. Samples from different visceral adipose tissue (AT) depots were collected on days 7 and 14 and stored at -80o C (5 to 7 animals per day/group). The PGZ treatment showed an increase in the survival average of 27.3% (P< 0.01) when compared to TC. It was also associated with enhanced body mass preservation (40.7 and 56.3%, p< 0.01) on day 14 and 26 compared with the TC group. The treatment also reduced the final tumor mass (53.4%, p<0.05) and anorexia compared with the TC group during late-stage cachexia. The retroperitoneal AT (RPAT) mass was preserved on day 7 compared with the TC group during the same experimental period. Such effect also demonstrates inverse relationship with tumor growth, on day 14. Gene expression of PPAR-γ, adiponectin, LPL and C/EBP-α from cachectic rats was upregulated after PGZ. Glucose uptake from adipocyte cells (RPAT) was entirely re-established due to PGZ treatment. Taken together, the results demonstrate beneficial effects of PGZ treatment at both the early and final stages of cachexia.

Using patient-reported outcomes to improve the management of co-infection with HIV and HCV: the ANRS CO13 HEPAVIH cohort

The management of co-infection with HIV and hepatitis C virus (HCV) is complicated by viral and drug-drug interactions, treatment-related side effects, and the poor response to therapy of certain HCV genotypes. Current or past drug use may also have a negative impact. HEPAVIH (ANRS CO13) is an ongoing French cohort study of co-infected individuals which combines medical and socio-behavioral follow-up. This cohort study aims at analyzing the course of HCV infection and access to HCV treatment in HIV-HCV co-infected patients, using both clinical and patient-reported outcomes. This article documents the main lessons learned to date from the HEPAVIH data and published literature, while describing research prospects and needs requiring further investigation in the field of patient-reported outcomes.

Association between elevated coffee consumption and daily chocolate intake with normal liver enzymes in HIV-HCV infected individuals: results from the ANRS CO13 HEPAVIH cohort study

BACKGROUND & AIMS

We used longitudinal data from the ANRS CO13 HEPAVIH cohort study of HIV-HCV co-infected individuals to investigate whether polyphenol rich food intake through coffee and/or daily chocolate consumption could play a role in reducing liver enzymes levels.

METHODS

Longitudinal data collection included self-administered questionnaires and medical data (aspartate aminotransferase (AST) and alanine aminotransferase (ALT) liver enzymes). Two analyses were performed to assess the association between coffee (≥3 cups a day) and daily chocolate intake and abnormal values of AST and ALT (AST or ALT >2.5 × upper normal limit (UNL)) (N=990) over time, after adjustment for known correlates. Logistic regression models based on generalized estimating equations were used to take into account the correlations between repeated measures and estimate adjusted odds ratio.

RESULTS

After adjustment, patients reporting elevated coffee consumption and daily chocolate intake were less likely to present abnormal ALT (OR=0.65; p=0.04 and OR=0.57; p=0.04, for coffee and chocolate respectively), while only patients reporting elevated coffee consumption were less likely to have abnormal AST values (p=0.05). Nevertheless, the combined indicator of coffee and chocolate intake was most significantly associated with approximately 40% reduced risk of abnormal liver enzymes (p=0.003 for AST; p=0.002 for ALT).

CONCLUSIONS

Elevated coffee consumption and daily chocolate intake appear to be associated with reduced levels of liver enzymes in HIV-HCV co-infected patients. Further experimental and observational research is needed to better understand the role that polyphenol intake or supplementation can play on liver disease and liver injury.

A review of methods used in assessing non-serious adverse drug events in observational studies among type 2 diabetes mellitus patients

Clinical drug trials are often conducted in selective patient populations, with relatively small numbers of patients, and a short duration of follow-up. Observational studies are therefore important for collecting additional information on adverse drug events (ADEs). Currently, there is no guidance regarding the methodology for measuring ADEs in such studies. Our aim was to evaluate whether the methodology used to assess non-serious ADEs in observational studies is adequate for detecting these ADEs, and for addressing limitations from clinical trials in patients with type 2 diabetes mellitus. We systematically searched MEDLINE and EMBASE for observational studies reporting non-serious ADEs (1999-2008). Methods to assess ADEs were classified as: 1) medical record review; 2) surveillance by health care professionals (HCP); 3) patient survey; 4) administrative data; 5) laboratory/clinical values; 6) not specified. We compared the range of ADEs identified, number and selection of patients included, and duration of follow-up. Out of 10,125 publications, 68 studies met our inclusion criteria. The most common methods were based on laboratory/clinical values (n = 25) and medical record review (n = 18). Solicited surveillance by HCP (n = 17) revealed the largest diversity of ADEs. Patient surveys (n = 15) focused mostly on hypoglycaemia and gastrointestinal ADEs, laboratory values based studies on hepatic and metabolic ADEs, and administrative database studies (n = 5) on cardiovascular ADEs. Four studies presented ADEs that were identified with the use of more than one method. The patient population was restricted to a lower risk population in 19% of the studies. Less than one third of the studies exceeded pre-approval regulatory requirements for sample size and duration of follow-up. We conclude that the current assessment of ADEs is hampered by the choice of methods. Many observational studies rely on methods that are inadequate for identifying all possible ADEs. Patient-reported outcomes and combinations of methods are underutilized. Furthermore, while observational studies often include unselective patient populations, many do not adequately address other limitations of pre-approval trials. This implies that these studies will not provide sufficient information about ADEs to clinicians and patients. Better protocols are needed on how to assess adverse drug events not only in clinical trials but also in observational studies.

Mechanisms of drug-induced liver injury: from bedside to bench

The low incidence of idiosyncratic drug-induced liver injury (DILI), together with the lack of a reliable diagnostic biomarker and robust preclinical and in vitro toxicology test systems for the condition have limited our ability to define the mechanisms of DILI. A notable exception is acetaminophen hepatotoxicity, which is associated with the formation of a well-characterized and highly reactive intermediate metabolite, N-acetyl-p-benzoquinone imine. However, studies have also suggested a role for the host immune response and variation in the expression of the lymphocyte CD44 gene in the pathogenesis of acetaminophen hepatotoxicity. A careful review of the laboratory, clinical and histological phenotype of patients with DILI can provide potential clues to the mechanisms of disease pathogenesis, as observed with fialuridine and valproate hepatotoxicity. In addition, the use of transcriptomic and genomic approaches in patients with well-characterized DILI has provided important insights into the involvement of the host immune response in the pathogenesis of hepatotoxicity associated with the administration of flucloxacillin, lumiracoxib or ximelagatran. This Review highlights new developments regarding the potential role of reactive metabolites, mitochondrial toxicity, host immune-response pathways and biliary transporters in the etiopathogenesis of DILI. Going forward, a bedside-to-bench approach could improve our understanding of the mechanisms and risk factors for DILI.

Liver safety in patients with type 2 diabetes treated with pioglitazone: results from a 3-year, randomized, comparator-controlled study in the US

BACKGROUND/AIMS

Non-alcoholic fatty liver disease (NAFLD), the major hepatic manifestation of type 2 diabetes mellitus, is the most common liver disease in the US. Thiazolidinediones, a commonly used drug class for the treatment of type 2 diabetes, have emerged as a potentially useful treatment for NAFLD. There are, however, lingering concerns about their potential toxicity as well as emerging concerns about how to monitor for and assess hepatotoxicity. We conducted a randomized, long-term, double-blind, hepatic safety study at 171 centres in the US in which 2097 patients with type 2 diabetes received either pioglitazone or glibenclamide (glyburide).

METHODS

Patients were randomized to receive either pioglitazone (15-45 mg once daily) or glibenclamide (5-15 mg once daily) for 3 years. The primary objective was to evaluate drug-induced liver injury manifested by liver enzyme elevations, measured every 8 weeks for the first year and every 12 weeks thereafter. The primary endpoint was a confirmed ALT greater than three times the upper limit of normal (>3 x ULN) with a secondary endpoint of 8 x ULN.

MAIN RESULTS

The intent-to-treat population included 1051 pioglitazone-treated and 1046 glibenclamide-treated patients; of these, 411 pioglitazone patients and 413 glibenclamide patients completed the study. The incidence of hepatocellular injury was 0 with pioglitazone and 4 (0.38%) with glibenclamide (p = 0.0617). Analyses of the secondary endpoints revealed no ALT >8 x ULN for pioglitazone versus 1 with glibenclamide (p = 0.4988); no ALT >3 x ULN + total bilirubin 2 x ULN with pioglitazone versus 1 with glibenclamide (p = 0.4988); and fewer ALT >3 x ULN single elevations with pioglitazone (n = 3) than with glibenclamide (n = 9; p = 0.0907). Significantly (p < or = 0.05) fewer cases of ALT >1.5 x ULN, aspartate aminotransferase >1.5 x ULN and gamma-glutamyl transpeptidase >1.5 x ULN were seen with pioglitazone compared with glibenclamide. No case of hepatic dysfunction or hepatic failure was reported in either treatment group; two cases of hepatic cirrhosis with glibenclamide were reported.

CONCLUSION

This study demonstrates an hepatic safety profile of pioglitazone similar to that of glibenclamide in long-term use in patients with poorly controlled type 2 diabetes. Trial registration number (clinicaltrials.gov): NCT00494312.

[Treatment of fatty liver disease]

Nonalcoholic fatty liver disease (NAFLD) is considered to be a hepatic manifestation of metabolic syndrome. The clinicopathologic spectrum ranges from simple steatosis to nonalcoholic steatohepatitis (NASH). Simple steatosis has a relatively benign clinical course, but NASH can progress to cirrhosis and hepatocellular carcinoma. As yet there is no convincingly effective treatment for NAFLD and the best option for these patients might be a multimodal treatment plan targeting obesity, insulin resistance, diabetes mellitus, hyperlipidemia and hypertension.

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

Objective:

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

Case Summary:

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

Discussion:

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

Conclusions:

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

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.

Review article: drug hepatotoxicity

BACKGROUND

Drug toxicity is the leading cause of acute liver failure in the United States. Further understanding of hepatotoxicity is becoming increasingly important as more drugs come to market.

AIMS

(i) To provide an update on recent advances in our understanding of hepatotoxicity of select commonly used drug classes. (ii) To assess the safety of these medications in patients with pre-existing liver disease and in the post-liver transplant setting. (iii) To review relevant advances in toxicogenomics which contribute to the current understanding of hepatotoxic drugs.

METHODS

A Medline search was performed to identify relevant literature using search terms including 'drug toxicity, hepatotoxicity, statins, thiazolidinediones, antibiotics, antiretroviral drugs and toxicogenomics'.

RESULTS

Amoxicillin-clavulanic acid is one of the most frequently implicated causes of drug-induced liver injury worldwide. Statins rarely cause clinically significant liver injury, even in patients with underlying liver disease. Newer thiazolidinediones are not associated with the degree of liver toxicity observed with troglitazone. Careful monitoring for liver toxicity is warranted in patients who are taking antiretrovirals, especially patients who are co-infected with hepatitis B and C. Genetic polymorphisms among enzymes involved in drug metabolism and HLA types may account for some of the differences in individual susceptibility to drug hepatotoxicity.

CONCLUSIONS

Drug-induced hepatotoxicity will remain a problem that carries both clinical and regulatory significance as long as new drugs continue to enter the market. Future results from ongoing multicentre collaborative efforts may help contribute to our current understanding of hepatotoxicity associated with drugs.

Rosiglitazone in diabetes control in hemodialysis patients with and without viral hepatitis infection: effectiveness and side effects

OBJECTIVE

Thiazolidinedione (TZD) may provide an additional benefit of cardiovascular protection in diabetic patients through targeting of insulin resistance. However, use of a TZD is hampered by possible effects of fluid retention and hepatotoxicity. In this study we aimed to determine whether the risk of TZD-induced fluid retention or hepatic injury is higher in hemodialysis patients with persistent viral hepatitis infection.

RESEARCH DESIGN AND METHODS

This was a prospective, cohort study on hemodialysis patients. Type 2 diabetic patients with A1C levels of >8% were followed for at least 12 months. Rosiglitazone was initiated at 2-4 mg/day. The primary outcome was the target A1C (<7%) achieved and dosages of rosiglitazone. Secondary outcomes included changes in lipid profile and inflammatory biomarkers. Safety evaluations were number of hypoglycemic episodes, changes in liver transaminase levels, cardiothoracic ratio (CTR), fluid status control during dialysis, and events of symptomatic heart failure.

RESULTS

A total of 78 patients, including 15.4% (n = 12) hepatitis B surface antigen-positive and 16.7% (n = 13) anti-hepatis C virus (HCV)-positive patients, were enrolled. The mean follow-up period was 15.4 +/- 3.8 months. The diabetic response rate (A1C <7%) to rosiglitazone was 86.1%. The serum triglyceride level was reduced (194 +/- 112.5 to 168 +/- 88 mg/dl, P = 0.037) more significantly than the total cholesterol level (178 +/- 42.1 to 174 +/- 46.5 mg/dl, P = 0.13). High-dose rosiglitazone (8 mg/day) reduced the serum level of C-reactive protein and increased the serum adiponectin level significantly. After rosiglitazone, interdialysis weight gain (2.07 +/- 1.6 to 3.2 +/- 1.2 kg, P < 0.01) and mean CTR (48.2 +/- 5.6 to 50.4 +/- 6.2%, P = 0.0213) of individuals increased significantly. Nevertheless, liver aminotransferase (aspartate aminotransferase and alanine aminotransferase) levels did not show a tendency to increase in patients (n = 25) with viral hepatitis B or C infections.

CONCLUSIONS

Among regular hemodialysis patients with chronic viral hepatitis infections, rosiglitazone may be safely used for diabetes control. However, one must be aware that a possible effect of its use is a deterioration in cardiovascular reserve.

Drug-induced liver disease

PURPOSE OF REVIEW

To summarize the pertinent case reports, case series and clinical studies that described clinical, histological, epidemiological and mechanistic features of drug-induced liver disease in 2005.

RECENT FINDINGS

Acetaminophen, highly active antiretroviral therapy and drugs for tuberculosis retained their preeminent position as the most commonly reported agents causing drug-induced liver disease, with acetaminophen continuing to be the leading cause of acute liver failure in the USA. While the frequency of drug-induced liver disease remains low, a large case-series of acute drug-induced liver disease from Spain and Sweden supported the observation that acute hepatocellular jaundice from a drug is associated with death or the need for transplant in at least 10% (known as Hy's Law). With respect to using potentially hepatotoxic medications in patients with underlying liver disease, statins and second-generation thiazolidinediones were shown to be safe when used in patients with elevated baseline alanine aminotransferase or aspartate aminotransferase levels.

SUMMARY

Drug-induced liver disease remains an important cause of acute liver failure, and research efforts by the National Institutes of Health and others are underway to better determine the risk factors and other host susceptibilities that will allow for the safer use of drugs in the future.

Review article: Drug therapy for non-alcoholic fatty liver disease

Non-alcoholic fatty liver disease represents a spectrum of liver diseases, characterized mainly by macrovesicular steatosis in the absence of significant alcohol ingestion. Non-alcoholic fatty liver disease includes both non-alcoholic fatty liver and non-alcoholic steatohepatitis. Non-alcoholic steatohepatitis once considered a benign process is now known to lead to progressive fibrosis and cirrhosis. Histologically indistinguishable from alcoholic liver disease, the exact aetiology of non-alcoholic fatty liver disease remains unknown, but the fundamental pathophysiological process appears to be insulin resistance and oxidative stress related to the metabolic syndrome. Therapy has focused on risk factors, weight reduction and pharmacological intervention. Promising pharmacological treatments have been demonstrated with antioxidants, insulin sensitizers, hepatoprotectants and lipid-lowering agents. However, without larger randomized studies, no pharmacological treatments can be recommended at this time.

Peroxisome proliferator-activated receptor gamma as a drug target in the pathogenesis of insulin resistance

Peroxisome proliferator-activated receptors (PPARs) are ligand-activated transcription factors that belong to the nuclear hormone receptor superfamily. The activation of PPAR-gamma, an isotype of PPARs, can either increase or decrease the transcription of target genes. The genes controlled by this form of PPAR have been shown to encode proteins or peptides that participate in the pathogenesis of insulin resistance. Insulin resistance is defined as a state of reduced responsiveness to normal circulating concentrations of insulin and it often co-exists with central obesity, hypertension, dyslipidemia, and atherosclerosis. There is substantial evidence that links obesity with insulin resistance and type-2 diabetes. The early phase of obesity-related insulin resistance has 2 components: (a) interruption of lipid homeostasis leading to the increased plasma concentration of fatty acids that is normally suppressed by the activation of PPAR-gamma, and (b) activation of factors such as cytokines depressed by PPAR-gamma that cause insulin resistance. Therefore, it is logical to suggest that activation of PPAR-gamma may partially reverse the state of insulin resistance. Evidently, activation of the nuclear receptor, PPAR-gamma, by thiazolidinediones has been reported to ameliorate insulin resistance. Although hepatotoxity and possibility to induce congestive heart failure (CHF) limit the widely use of thiazolodinediones, they are still powerful weapon to fight against insulin resistance and type-2 diabetes if use properly. This article reviews the physiology of PPAR-gamma and insulin-signaling transduction, the pathogenesis of insulin resistance in obesity-related type-2 diabetes, the pharmacological role of PPAR-gamma in insulin resistance, and additional effects of thiazolidinediones.