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

Review article: vascular effects of PPARs in the context of NASH

BACKGROUND

Peroxisome proliferator-activated receptors (PPARs) are ligand-activated transcription factors known to regulate glucose and fatty acid metabolism, inflammation, endothelial function and fibrosis. PPAR isoforms have been extensively studied in metabolic diseases, including type 2 diabetes and cardiovascular diseases. Recent data extend the key role of PPARs to liver diseases coursing with vascular dysfunction, including nonalcoholic fatty liver disease (NAFLD) and nonalcoholic steatohepatitis (NASH).

AIM

This review summarises and discusses the pathobiological role of PPARs in cardiovascular diseases with a special focus on their impact and therapeutic potential in NAFLD and NASH.

RESULTS AND CONCLUSIONS

PPARs may be attractive for the treatment of NASH due to their liver-specific effects but also because of their efficacy in improving cardiovascular outcomes, which may later impact liver disease. Assessment of cardiovascular disease in the context of NASH trials is, therefore, of the utmost importance, both from a safety and efficacy perspective.

Peroxisome Proliferator-Activated Receptor Gamma Agonist Attenuates Liver Fibrosis by Several Fibrogenic Pathways in an Animal Model of Cholestatic Fibrosis

PURPOSE

Peroxisome proliferator-activated receptor gamma (PPAR-γ) has a key role in hepatic fibrogenesis by virtue of its effect on the hepatic stellate cells (HSCs). Although many studies have shown that PPAR-γ agonists inhibit liver fibrosis, the mechanism remains largely unclear, especially regarding the cross-talk between PPAR-γ and other potent fibrogenic factors.

METHODS

This experimental study involved 25 male Wistar rats. Twenty rats were subjected to bile duct ligation (BDL) to induce liver fibrosis, further divided into an untreated group (BDL; n=10) and a group treated with the PPAR-γ agonist thiazolidinedione (TZD), at 14 days post-operation (BDL+TZD; n=10). The remaining 5 rats had a sham operation (sham; n=5). The effect of PPAR-γ agonist on liver fibrosis was evaluated by histopathology, protein immunohistochemistry, and mRNA expression quantitative polymerase chain reaction.

RESULTS

Histology and immunostaining showed markedly reduced collagen deposition, bile duct proliferation, and HSCs in the BDL+TZD group compared to those in the BDL group (p<0.001). Similarly, significantly lower mRNA expression of collagen α-1(I), matrix metalloproteinase-2, platelet-derived growth factor (PDGF)-B chain, and connective tissue growth factor (CTGF) were evident in the BDL+TZD group compared to those in the BDL group (p=0.0002, p<0.035, p<0.0001, and p=0.0123 respectively). Moreover, expression of the transforming growth factor beta1 (TGF-β1) was also downregulated in the BDL+TZD group (p=0.0087).

CONCLUSION

The PPAR-γ agonist inhibits HSC activation in vivo and attenuates liver fibrosis through several fibrogenic pathways. Potent fibrogenic factors such as PDGF, CTGF, and TGF-β1 were downregulated by the PPAR-γ agonist. Targeting PPAR-γ activity may be a potential strategy to control liver fibrosis.

NASH in Nondiabetic Endocrine Disorders

Nonalcoholic fatty liver disease (NAFLD) encompasses a spectrum of disease, including hepatic steatosis, inflammation, and fibrosis. NAFLD carries the risk of progression to cirrhosis with its associated complications and hepatocellular carcinoma. It is now the most common liver disease in the Western world and its prevalence is increasing. While the association between NAFLD and type 2 diabetes has been well documented, there is significantly less understanding of the pathophysiology and progression of NAFLD in patients with other endocrine disorders affecting metabolism in various ways. Some of the more common endocrine disorders such as polycystic ovarian syndrome, growth hormone deficiency, hypothyroidism, and hypogonadism are known in clinical practice to be associated with NAFLD. Medications that alter the endocrine system such as tamoxifen and adrenal steroids have also been attributed to significant NAFLD. The key to management of NAFLD at this time are dietary changes and exercise to achieve weight loss. Unfortunately, a large proportion of the patients with these endocrine disorders are unable to achieve either. This review aims to examine and summarize the current published literature that have evaluated the association between NAFLD and the above endocrine disorders and potential therapeutic interventions in each case.

Unraveling the complex relationship triad between lipids, obesity, and inflammation

Obesity today stands at the intersection between inflammation and metabolic disorders causing an aberration of immune activity, and resulting in increased risk for diabetes, atherosclerosis, fatty liver, and pulmonary inflammation to name a few. Increases in mortality and morbidity in obesity related inflammation have initiated studies to explore different lipid mediated molecular pathways of attempting resolution that uncover newer therapeutic opportunities of anti-inflammatory components. Majorly the thromboxanes, prostaglandins, leukotrienes, lipoxins, and so forth form the group of lipid mediators influencing inflammation. Of special mention are the omega-6 and omega-3 fatty acids that regulate inflammatory mediators of interest in hepatocytes and adipocytes via the cyclooxygenase and lipoxygenase pathways. They also exhibit profound effects on eicosanoid production. The inflammatory cyclooxygenase pathway arising from arachidonic acid is a critical step in the progression of inflammatory responses. New oxygenated products of omega-3 metabolism, namely, resolvins and protectins, behave as endogenous mediators exhibiting powerful anti-inflammatory and immune-regulatory actions via the peroxisome proliferator-activated receptors (PPARs) and G protein coupled receptors (GPCRs). In this review we attempt to discuss the complex pathways and links between obesity and inflammation particularly in relation to different lipid mediators.

Drug disposition in pathophysiological conditions

Expression and activity of several key drug metabolizing enzymes (DMEs) and transporters are altered in various pathophysiological conditions, leading to altered drug metabolism and disposition. This can have profound impact on the pharmacotherapy of widely used clinically relevant medications in terms of safety and efficacy by causing inter-individual variabilities in drug responses. This review article highlights altered drug disposition in inflammation and infectious diseases, and commonly encountered disorders such as cancer, obesity/diabetes, fatty liver diseases, cardiovascular diseases and rheumatoid arthritis. Many of the clinically relevant drugs have a narrow therapeutic index. Thus any changes in the disposition of these drugs may lead to reduced efficacy and increased toxicity. The implications of changes in DMEs and transporters on the pharmacokinetics/pharmacodynamics of clinically-relevant medications are also discussed. Inflammation-mediated release of pro-inflammatory cytokines and activation of toll-like receptors (TLRs) are known to play a major role in down-regulation of DMEs and transporters. Although the mechanism by which this occurs is unclear, several studies have shown that inflammation-associated cell-signaling pathway and its interaction with basal transcription factors and nuclear receptors in regulation of DMEs and transporters play a significant role in altered drug metabolism. Altered regulation of DMEs and transporters in a multitude of disease states will contribute towards future development of powerful in vitro and in vivo tools in predicting the drug response and opt for better drug design and development. The goal is to facilitate a better understanding of the mechanistic details underlying the regulation of DMEs and transporters in pathophysiological conditions.

Review article: is non-alcoholic fatty liver disease a spectrum, or are steatosis and non-alcoholic steatohepatitis distinct conditions?

BACKGROUND

Non-alcoholic fatty liver disease (NAFLD) is currently conceptualised as a clinical spectrum that results from a ‘multiple-hit’ process which begins with simple steatosis and subsequently renders the hepatocytes susceptible to a variety of insults. Ultimately, more serious liver injuries like non-alcoholic steatohepatitis (NASH) and cirrhosis may develop. Although the metabolic syndrome is considered the crucial player in the pathogenesis of NAFLD, recent studies have highlighted novel pathophysiological mechanisms in this clinical entity.

AIM

To discuss the pathophysiology of NAFLD based on the hypothesis that simple steatosis and NASH are discrete entities rather than two points on a spectrum.

METHODS

A literature search was conducted in August 2012 on PubMed, Ovid Embase, Ovid Medline and Scopus using the following search terms: steatosis, non-alcoholic steatohepatitis, pathophysiology, fatty liver, natural history and genetics.

RESULTS

Simple steatosis and NASH appear as two distinct pathophysiological entities and progression from pure fatty liver to NASH appears to be so rare as to warrant publication. The possible pathogenetic pathways specifically related to NASH are highlighted.

CONCLUSIONS

Although simple steatosis and non-alcoholic steatohepatitis are currently viewed as two histological subtypes of the unique spectrum of non-alcoholic fatty liver disease, the two conditions are likely distinct not only from a histological but also from a pathophysiological standpoint. Efforts to distinguish simple steatosis from non-alcoholic steatohepatitis using non-invasive modalities should be informed by the current pathophysiology of these two clinical entities.

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.

The current state of knowledge of hepatic ischemia-reperfusion injury based on its study in experimental models

The present review focuses on the numerous experimental models used to study the complexity of hepatic ischemia/reperfusion (I/R) injury. Although experimental models of hepatic I/R injury represent a compromise between the clinical reality and experimental simplification, the clinical transfer of experimental results is problematic because of anatomical and physiological differences and the inevitable simplification of experimental work. In this review, the strengths and limitations of the various models of hepatic I/R are discussed. Several strategies to protect the liver from I/R injury have been developed in animal models and, some of these, might find their way into clinical practice. We also attempt to highlight the fact that the mechanisms responsible for hepatic I/R injury depend on the experimental model used, and therefore the therapeutic strategies also differ according to the model used. Thus, the choice of model must therefore be adapted to the clinical question being answered.

Nonalcoholic Fatty Liver Disease

Nonalcoholic fatty liver disease (NAFLD) is an accumulation of extra fat in the liver cells not caused by alcohol consumption. This disease is an increasingly common condition and the most common cause of abnormal liver function tests among adults. NAFLD is an array of liver diseases ranging from simple hepatic steatosis (fatty liver) to nonalcoholic steatohepatitis (NASH). A liver biopsy is the gold standard for determining hepatic fat content and staging fibrosis. However, the invasiveness of this approach can be a contraindication in certain patients. Noninvasive imaging modalities such as ultrasound, computed tomography (CT), and magnetic resonance (MR) can also detect hepatic fat content.

Mechanisms and implications of age-related changes in the liver: nonalcoholic Fatty liver disease in the elderly

Nonalcoholic fatty liver disease (NAFLD) is hepatic steatosis associated with metabolic abnormalities such as overweight/central obesity, insulin resistance, type 2 diabetes (T2D), and dyslipidemia. NAFLD is becoming the most common liver disease in contemporary society, with the highest prevalence in those over 60 years. NAFLD pathology ranges from simple steatosis to a necroinflammatory fibrosing disorder called steatohepatitis (SH), the latter associated with high risk of developing cirrhosis, often occuring in the seventh to ninth decades of life. While the main health implications of NAFLD are increased risk of developing T2D, cardiovascular diseases, and common cancers, there is substantantially increased standardized mortality, and deaths from decompensated cirrhosis and hepatocellular carcinoma (HCC). Little is known about the interactive effects of ageing and NAFLD, with most studies focusing on the younger population. This paper summarises the epidemiology, pathogenesis, and clinical course of NAFLD, with particular attention to persons over age 60 years. An approach to the management of NASH and its complications in the elderly, will also be presented here.

PPARs, Obesity, and Inflammation

The worldwide prevalence of obesity and related metabolic disorders is rising rapidly, increasing the burden on our healthcare system. Obesity is often accompanied by excess fat storage in tissues other than adipose tissue, including liver and skeletal muscle, which may lead to local insulin resistance and may stimulate inflammation, as in steatohepatitis. In addition, obesity changes the morphology and composition of adipose tissue, leading to changes in protein production and secretion. Some of these secreted proteins, including several proinflammatory mediators, may be produced by macrophages resident in the adipose tissue. The changes in inflammatory status of adipose tissue and liver with obesity feed a growing recognition that obesity represents a state of chronic low-level inflammation. Various molecular mechanisms have been implicated in obesity-induced inflammation, some of which are modulated by the peroxisome proliferator-activated receptors (PPARs). PPARs are ligand-activated transcription factors involved in the regulation of numerous biological processes, including lipid and glucose metabolism, and overall energy homeostasis. Importantly, PPARs also modulate the inflammatory response, which makes them an interesting therapeutic target to mitigate obesity-induced inflammation and its consequences. This review will address the role of PPARs in obesity-induced inflammation specifically in adipose tissue, liver, and the vascular wall.

Drug metabolism alterations in nonalcoholic fatty liver disease

Drug-metabolizing enzymes play a vital role in the elimination of the majority of therapeutic drugs. The major organ involved in drug metabolism is the liver. Chronic liver diseases have been identified as a potential source of significant interindividual variation in metabolism. Nonalcoholic fatty liver disease (NAFLD) is the most common chronic liver disease in the United States, affecting between 60 and 90 million Americans, yet the vast majority of NAFLD patients are undiagnosed. NAFLD encompasses a spectrum of pathologies, ranging from steatosis to nonalcoholic steatohepatitis and fibrosis. Numerous animal studies have investigated the effects of NAFLD on hepatic gene expression, observing significant alterations in mRNA, protein, and activity levels. Information on the effects of NAFLD in human patients is limited, though several significant investigations have recently been published. Significant alterations in the activity of drug-metabolizing enzymes may affect the clearance of therapeutic drugs, with the potential to result in adverse drug reactions. With the enormous prevalence of NAFLD, it is conceivable that every drug currently on the market is being given to patients with NAFLD. The current review is intended to present the results from both animal models and human patients, summarizing the observed alterations in the expression and activity of the phase I and II drug-metabolizing enzymes.

Experimental non-alcoholic fatty liver disease results in decreased hepatic uptake transporter expression and function in rats

Non-alcoholic fatty liver disease (NAFLD) encompasses a spectrum of diagnoses ranging from simple fatty liver (SFL), to non-alcoholic steatohepatitis (NASH). This study aimed to determine the effect of moderate and severe NAFLD on hepatic transporter expression and function in vivo. Rats were fed a high-fat diet (SFL model) or a methionine-choline-deficient diet (NASH model) for eight weeks. Hepatic uptake transporter function was determined by bromosulfophthalein (BSP) disposition. Transporter expression was determined by branched DNA signal amplification assay and western blotting; inflammation was identified by immunostaining of liver slices for interleukin 1 beta (IL-1beta). MC- rats showed significant retention of BSP in the plasma when compared to control rats. Hepatic NTCP, OATP1a1, 1a4, 1b2 and 2b1; and OAT 2 and 3 mRNA levels were significantly decreased in high-fat and MC- diet rats when compared to control. Protein expression of OATP1a1 was significantly decreased in high-fat animals, while OATP1a1 and OATP1b2 expressions were significantly lower in MC- rats when compared to control. Liver tissue from high-fat and MC- rats stained positive for IL-1beta, a pro-inflammatory cytokine known to decrease expression of NTCP, OATP and OAT transporters, suggesting a plausible mechanism for the observed transporter alterations. These data suggest that different stages of NAFLD result in altered hepatic uptake transporter expression that can lead to a functional impairment of xenobiotic uptake from the blood. Furthermore, NAFLD may alter the plasma retention time of clinically relevant drugs that are reliant on these transporters and may increase the potential drug toxicity.

Drug metabolizing enzyme induction pathways in experimental non-alcoholic steatohepatitis

Non-alcoholic steatohepatitis (NASH) is a disease that compromises hepatic function and the capacity to metabolize numerous drugs. Aryl hydrocarbon receptor (AhR), constitutive androstane receptor (CAR), pregnane X receptor (PXR), peroxisome proliferator-activated receptor alpha (PPARalpha), and nuclear factor-E2 related factor 2 (Nrf2) are xenobiotic activated transcription factors that regulate induction of a number of drug metabolizing enzymes (DMEs). The purpose of the current study was to determine whether experimental NASH alters the xenobiotic activation of these transcription factors and induction of downstream DME targets Cyp1A1, Cyp2B10, Cyp3A11, Cyp4A14 and NAD(P)H:quinone oxidoreductase 1 (Nqo1), respectively. Mice fed normal rodent chow or methionine-choline-deficient (MCD) diet for 8 weeks were then treated with microsomal enzyme inducers beta-naphoflavone (BNF), 1,4-bis-[2-(3,5-dichloropyridyloxy)] benzene (TCPOBOP), pregnenolone-16alpha-carbonitrile (PCN), clofibrate (CFB) or oltipraz (OPZ), known activators of AhR, CAR, PXR, PPARalpha and Nrf2, respectively. Results of this study show that (1) Hepatic PXR mRNA levels were significantly increased (1.4-fold) in mice fed MCD diet, while AhR, CAR, PPARalpha and Nrf2 were not affected. (2) The MCD diet did not alter hepatic inducibility of Cyp1A1, Cyp2B10, Cyp3A11 mRNA levels by their respective microsomal inducers. (3) Constitutive levels of Cyp4A14 mRNA were significantly increased in mice fed the MCD diet, yet further induction by clofibrate was not observed. (4) Hepatic Nqo1 mRNA levels were significantly increased by the MCD diet; however, additional induction of Nqo1 was still achievable following treatment with the Nrf2 activator OPZ.

Weight loss, dietary advice and statin therapy in non-alcoholic fatty liver disease: a retrospective study

BACKGROUND

Studies have shown that weight loss can have a favourable effect upon non-alcoholic fatty liver disease (NAFLD). However, the most effective means of achieving weight loss and safety profile of lipid-lowering drugs in the presence of NAFLD is unknown.

AIM

To investigate the effect of dietary advice and lipid-lowering drugs, particularly statins, on patients with NAFLD and dyslipidaemia.

DESIGN

Observational records based study.

METHODS

We studied 71 patients with NAFLD and dyslipidaemia diagnosed and treated between 1996 and 2002 at University Hospital Lewisham. Some were referred to a dietician for weight loss advice as part of their management. After treatment all patients were assessed for changes in weight, serum alanine transaminase (ALT) and serum lipids including serum cholesterol, serum high density lipoprotein (HDL) and serum triglycerides.

RESULTS

Thirty-seven male and 34 female patients with NAFLD and dyslipidaemia were followed up for a mean period of 440 +/- 374 days (median 335). Regression analysis revealed a significant association between changes in weight and changes in serum ALT (p < 0.039). Dietary advice failed to reduce body weight but significantly lowered the serum cholesterol to HDL ratio (p = 0.05). Only 15.4% of patients taking statins experienced a rise in serum ALT > or = 40 U/l, and in each case the rise was transient, returning near baseline or below without discontinuation of statin treatment.

CONCLUSIONS

Weight loss appears to improve NAFLD, and dietary advice and lipid-lowering drugs may be beneficial for patients with NAFLD and dyslipidaemia even if weight loss is not achieved. Statins appear to be safe and efficacious in this group.

Peroxisome proliferator-activated receptor-gamma protects against hepatic ischemia/reperfusion injury in mice

The function of peroxisome proliferator-activated receptor-gamma (PPARgamma) in hepatic inflammation and injury is unclear. In this study, we sought to determine the role of PPARgamma in hepatic ischemia/reperfusion injury in mice. Male mice were subjected to 90 minutes of partial hepatic ischemia followed by up to 8 hours of reperfusion. PPARgamma was found to be constitutively activated in hepatocytes but not in nonparenchymal cells. Upon induction of ischemia, hepatic PPARgamma activation rapidly decreased and remained suppressed throughout the 8-hour reperfusion period. This reduced activation was not a result of decreased protein availability as hepatic nuclear PPARgamma, retinoid X receptor-alpha (RXRalpha), and PPARgamma/RXRalpha heterodimer expression was maintained. Accompanying the decrease in PPARgamma activation was a decrease in the expression of the natural ligand 15-deoxy-Delta(12,14)-prostaglandin J(2). This was associated with reduced interaction of PPARgamma and the coactivator, p300. To determine whether PPARgamma activation is hepatoprotective during hepatic ischemia/reperfusion injury, mice were treated with the PPARgamma agonists, rosiglitazone and connecting peptide. These treatments increased PPARgamma activation and reduced liver injury compared to untreated mice. Furthermore, PPARgamma-deficient mice had more liver injury after ischemia/reperfusion than their wild-type counterparts.

CONCLUSION

These data suggest that PPARgamma is an important endogenous regulator of, and potential therapeutic target for, ischemic liver injury.

Treating nonalcoholic fatty liver disease

Nonalcoholic fatty liver disease (NAFLD) is a chronic illness with multiple consequences. The spectrum of disease ranges from simple steatosis, with benign prognosis, to a potentially progressive form, nonalcoholic steatohepatitis, which may lead to liver fibrosis and cirrhosis, leading to an increase in morbidity and mortality. Furthermore, hepatocellular carcinoma incidence in NAFLD is comparable with that observed in hepatitis C-infected patients once cirrhosis is established. Current therapy is limited to lifestyle changes and control of associated metabolic disorders; however, new treatments are on the way from basic research to bedside. A review of the current literature on treatment of nonalcoholic fatty liver disease is presented in this article.

Evaluation and management of obesity-related nonalcoholic fatty liver disease

The clinicopathologic spectrum of nonalcoholic fatty liver disease (NAFLD) 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. NAFLD occurs in the absence of significant alcohol use and is considered to be the hepatic manifestation of metabolic syndrome. NAFLD affects approximately 30% of the US population and the incidence seems to be rising as the obesity epidemic continues. At present, the most accurate modality for the diagnosis of NASH is liver biopsy; however, many patients do not have a liver biopsy, and in the absence of more-accurate imaging technologies and serum markers, the diagnosis is frequently one of exclusion. As yet there is no convincingly effective treatment for NAFLD--a multimodal treatment plan that targets obesity, insulin resistance, hyperlipidemia and hypertension might be the best option for these patients.

A growing burden: the pathogenesis, investigation and management of non-alcoholic fatty liver disease

Non-alcoholic fatty liver disease (NAFLD) is the most common hepatic disorder in western countries, and its incidence is increasing. This review outlines the significant health burden posed by NAFLD and discusses what is presently known about its pathogenesis, including the roles of the metabolic syndrome, obesity, insulin resistance, hepatic steatosis, reactive oxygen species, inflammatory cytokines and adipocytokines. The way in which NAFLD is clinically diagnosed is described, and areas of uncertainty surrounding its investigation are identified, before discussing the relative merits of the limited treatment options available and looking ahead to potential therapeutic strategies for the future.

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.

Pioglitazone: a review of its use in type 2 diabetes mellitus

Pioglitazone is an antihyperglycaemic agent that, in the presence of insulin resistance, increases hepatic and peripheral insulin sensitivity, thereby inhibiting hepatic gluconeogenesis and increasing peripheral and splanchnic glucose uptake. Pioglitazone is generally well tolerated, weight gain and oedema are the most common emergent adverse events, and there are no known drug interactions between pioglitazone and other drugs. In clinical trials in patients with type 2 diabetes mellitus, pioglitazone as monotherapy, or in combination with metformin, repaglinide, insulin or a sulphonylurea, induced both long- and short-term improvements in glycaemic control and serum lipid profiles. Pioglitazone was also effective in reducing some measures of cardiovascular risk and arteriosclerosis. Pioglitazone thus offers an effective treatment option for the management of patients with type 2 diabetes.

Peroxisome Proliferator-Activated Receptor-??

Insulin resistance and obesity is a common health problem in the industrialized world. As a result of the availability of high-calorie food and a reduction in energy expenditure, maladaptive metabolic processes may interfere with the action of insulin and increase susceptibility for the development of atherosclerotic cardiovascular diseases. With the advent of peroxisome proliferator-activated receptors (PPARs), the mechanisms of this maladaptation and its relationship to insulin resistance syndrome components have become less obscure, promising new therapeutic approaches for this common problem. In this review we first focus on the molecular structure and cellular mechanisms of action of these receptors and then discuss how PPAR-gamma, a PPAR isoform, provides a link between adiposity, insulin resistance, and atherosclerosis.

Severity of liver echogenicity is correlated to serum c-peptide levels in type 2 diabetic patients

AIM

To investigate the correlation between liver echogenicity and serum C-peptide levels in type 2 diabetic patients treated with oral hypoglycaemic agents.

PATIENTS AND METHODS

The study included 231 type 2 diabetic patients (114 men) with a mean age of 64.3 +/- 6.9 years and a mean diabetes duration of 8.5 +/- 3.2 years. Liver echogenicity was graded by ultrasound examination as follows: Grade 0 (normal liver texture), grade 1 (slight increase of liver echogenicity), grade 2 (moderate increase of liver echogenicity with impaired visualization of intrahepatic vessels and right hemi-diaphragm), grade 3 (marked increase of liver echogenicity with very poor visualization or non-visualization of intrahepatic vessels and right hemi-diaphragm). Serum C-peptide was measured both in fasting state (Fasting C-peptide, FCP) and after glucagon administration (Glucagon-stimulated C-peptide, GCP).

RESULTS

FCP (median; interquartile range) showed a significant difference (p=0.041) between patients with grade 0 (1.9 ng/dl; 1.1-2.7 ng/dl),grade 1 (2.7 ng/dl; 1.9-3.7 ng/dl), grade 2 (4.1 ng/dl; 2.6-5.1 ng/dl) and grade 3 (6.2 ng/dl; 4.6-7.5 ng/dl) liver echogenicity. GCP (median; interquartile range) also differed significantly (p=0.04) between patients with grade 0 (2.6 ng/dl; 1.8-3.3 ng/dl), grade 1 (4.3 ng/dl; 3.3-5 ng/dl), grade 2 (5.8 ng/dl; 4.6-6.9 ng/dl) and grade 3 (8.3 ng/dl; 6.6-9.5 ng/dl) liver echogenicity. In multiple regression analysis, both FCP and GCP showed significant (p < 0.05) positive correlations with waist circumference, triglycerides, WHR and liver echogenicity.

CONCLUSIONS

In type 2 diabetic patients treated with oral hypoglycaemic agents, liver echogenicity shows a significant positive correlation with serum C-peptide levels, both in fasting state and after glucagon administration.