Effect of vitamin E or metformin for treatment of nonalcoholic fatty liver disease in children and adolescents: the TONIC randomized controlled trial

Farnesoid X receptor targeting to treat nonalcoholic steatohepatitis

Nonalcoholic fatty liver disease (NAFLD) is a highly prevalent chronic liver condition evolving in a proportion of patients into nonalcoholic steatohepatitis (NASH), an aggressive form of NAFLD associated with increased cardiovascular mortality and significant risk of progressive liver disease, including fibrosis, cirrhosis and hepatocellular carcinoma. At present, no specific therapies for NASH exist. In this review, we examine the evidence supporting activation of the farnesoid X receptor (FXR), a nuclear hormone receptor regulated by bile acids (BAs), for the treatment of NASH. We also discuss the potential of the semi-synthetic BA derivative obeticholic acid (OCA), a first-in-class FXR agonist, as a safe and effective drug to address this significant unmet medical need.

Nonalcoholic fatty liver disease in pediatric patients

Nonalcoholic fatty liver disease is a spectrum of liver disease ranging from simple hepatic steatosis to steatohepatitis, hepatic fibrosis, and cirrhosis. It is highly associated with obesity and insulin resistance, and with the dramatic increase in childhood and adolescent obesity, it has become the most common form of chronic liver disease in these age groups. Genetic and environmental factors both appear to play a role in the development of nonalcoholic fatty liver disease. There is currently no established effective therapy, and decreasing the prevalence of this disorder will require a reduction in the current obesity epidemic.

Nonalcoholic fatty liver disease

As the hepatic manifestation of the metabolic syndrome, nonalcoholic fatty liver disease (NAFLD) has become the most common cause of asymptomatic liver enzyme elevations in Western nations. Although it is easy to diagnose NAFLD, a liver biopsy is currently required to diagnose nonalcoholic steatohepatitis (NASH). Patients with NASH are those at greatest risk of progression to cirrhosis and, thus, treatment efforts are targeted to these individuals. Although currently there are no FDA-approved treatments for NASH, a multidisciplinary approach that addresses comorbid conditions and promotes modest weight loss comprises the backbone of therapy.

Impact of current treatments on liver disease, glucose metabolism and cardiovascular risk in non-alcoholic fatty liver disease (NAFLD): a systematic review and meta-analysis of randomised trials

AIMS/HYPOTHESIS

Non-alcoholic fatty liver disease (NAFLD) encompasses a spectrum ranging from simple steatosis to non-alcoholic steatohepatitis (NASH): NAFLD causes an increased risk of cardiovascular disease, diabetes and liver-related complications (the latter confined to NASH). The effect of proposed treatments on liver disease, glucose metabolism and cardiovascular risk in NAFLD is unknown. We reviewed the evidence for the management of liver disease and cardio-metabolic risk in NAFLD.

METHODS

Publications through November 2011 were systematically reviewed by two authors. Outcomes evaluated though standard methods were: histological/radiological/biochemical features of NAFLD, variables of glucose metabolism and cardiovascular risk factors. Seventy-eight randomised trials were included (38 in NASH, 40 in NAFLD): 41% assessed post-treatment histology, 71% assessed glucose metabolism and 88% assessed cardiovascular risk factors. Lifestyle intervention, thiazolidinediones, metformin and antioxidants were most extensively evaluated.

RESULTS

Lifestyle-induced weight loss was safe and improved cardio-metabolic risk profile; a weight loss ≥7% improved histological disease activity, but was achieved by <50% patients. Statins and polyunsaturated fatty acids improved steatosis, but their effects on liver histology are unknown. Thiazolidinediones improved histological disease activity, glucose, lipid and inflammatory variables and delayed fibrosis progression. Pioglitazone also improved blood pressure. Weight gain (up to 4.8%) was common. Antioxidants yielded mixed histological results: vitamin E improved histological disease activity when administered for 2 years, but increased insulin resistance and plasma triacylglycerols.

CONCLUSIONS/INTERPRETATION

Weight loss is safe, and improves liver histology and cardio-metabolic profile. For patients not responding to lifestyle intervention, pioglitazone improves histological disease activity, slows fibrosis progression and extensively ameliorates cardio-metabolic endpoints. Further randomised controlled trials (RCTs) of adequate size and duration will assess long-term safety and efficacy of proposed treatments on clinical outcomes.

The TONIC trial: a step forward in treating pediatric nonalcoholic fatty liver disease

Lavine JE, Schwimmer JB, Van Natta ML, Molleston JP, Murray KF, Rosenthal P, Abrams SH, et al. Effect of vitamin E or metformin for treatment of nonalcoholic fatty liver disease in children and adolescents: the TONIC randomized controlled trial. JAMA 2011;305:1659–1668. (Reprinted with permission).

CONTEXT

Nonalcoholic fatty liver disease (NAFLD) is the most common chronic liver disease in US children and adolescents and can present with advanced fibrosis or nonalcoholic steatohepatitis (NASH). No treatment has been established.

OBJECTIVE

To determine whether children with NAFLD would improve from therapeutic intervention with vitamin E or metformin.

DESIGN, SETTING, AND PATIENTS

Randomized, double-blind, double-dummy, placebo-controlled clinical trial conducted at 10 university clinical research centers in 173 patients (aged 8–17 years) with biopsy-confirmed NAFLD conducted between September 2005 and March 2010. Interventions Daily dosing of 800 IU of vitamin E (58 patients), 1000 mg of metformin (57 patients), or placebo (58 patients) for 96 weeks.

MAIN OUTCOME MEASURES

The primary outcome was sustained reduction in alanine aminotransferase (ALT) defined as 50% or less of the baseline level or 40 U/L or less at visits every 12 weeks from 48 to 96 weeks of treatment. Improvements in histological features of NAFLD and resolution of NASH were secondary outcome measures.

RESULTS

Sustained reduction in ALT level was similar to placebo (10/58; 17%; 95% CI, 9% to 29%) in both the vitamin E (15/58; 26%; 95% CI, 15% to 39%; P = .26) and metformin treatment groups (9/57; 16%; 95% CI, 7% to 28%; P = .83). The mean change in ALT level from baseline to 96 weeks was −35.2 U/L (95% CI, −56.9 to −13.5) with placebo vs −48.3 U/L (95% CI, −66.8 to −29.8) with vitamin E (P = .07) and −41.7 U/L (95% CI, −62.9 to −20.5) with metformin (P = .40). The mean change at 96 weeks in hepatocellular ballooning scores was 0.1 with placebo (95% CI, −0.2 to 0.3) vs −0.5 with vitamin E (95% CI, −0.8 to −0.3; P = .006) and −0.3 with metformin (95% CI, −0.6 to −0.0; P = .04); and in NAFLD activity score, −0.7 with placebo (95% CI, −1.3 to −0.2) vs −1.8 with vitamin E (95% CI, −2.4 to −1.2; P = .02) and −1.1 with metformin (95% CI, −1.7 to −0.5; P = .25). Among children with NASH, the proportion who resolved at 96 weeks was 28% with placebo (95% CI, 15% to 45%; 11/39) vs 58% with vitamin E (95% CI, 42% to 73%; 25/43; P = .006) and 41% with metformin (95% CI, 26% to 58%; 16/39; P = .23). Compared with placebo, neither therapy demonstrated significant improvements in other histological features.

CONCLUSION

Neither vitamin E nor metformin was superior to placebo in attaining the primary outcome of sustained reduction in ALT level in patients with pediatric NAFLD. TRIAL REGISTRATION: clinicaltrials.gov Identifier: NCT00063635.

Choline intake in a large cohort of patients with nonalcoholic fatty liver disease

BACKGROUND

There is significant histologic and biochemical overlap between nonalcoholic fatty liver disease (NAFLD) and steatohepatitis associated with choline deficiency.

OBJECTIVE

We sought to determine whether subjects with biopsy-proven NAFLD and evidence of an inadequate intake of choline had more severe histologic features.

DESIGN

We performed a cross-sectional analysis of 664 subjects enrolled in the multicenter, prospective Nonalcoholic Steatohepatitis Clinical Research Network (NASH CRN) with baseline data on diet composition (from a recall-based food-frequency questionnaire) within 6 mo of a liver biopsy. Food questionnaires were analyzed with proprietary software to estimate daily intakes of choline. Liver biopsies were centrally read, and consensus was scored with the NASH CRN-developed scoring system. Because choline needs vary by age, sex, and menopausal status, participants were segregated into corresponding categories (children 9-13 y old, males ≥14 y old, premenopausal women ≥19 y old, and postmenopausal women) on the basis of the Institute of Medicine's definition of adequate intake (AI) for choline. Deficient intake was defined as <50% AI.

RESULTS

Postmenopausal women with deficient choline intake had worse fibrosis (P = 0.002) once factors associated with NAFLD (age, race-ethnicity, obesity, elevated triglycerides, diabetes, alcohol use, and steroid use) were considered in multiple ordinal logistic regression models. Choline intake was not identified as a contributor to disease severity in children, men, or premenopausal women.

CONCLUSION

Decreased choline intake is significantly associated with increased fibrosis in postmenopausal women with NAFLD. The Pioglitazone vs Vitamin E vs Placebo for Treatment of Non-Diabetic Patients With Nonalcoholic Steatohepatitis trial was registered at clinicaltrials.gov as NCT00063622, and the Treatment of Nonalcoholic Fatty Liver Disease in Children trial was registered at clinicaltrials.gov as NCT00063635.

Role of obesity and lipotoxicity in the development of nonalcoholic steatohepatitis: pathophysiology and clinical implications

As obesity reaches epidemic proportions, nonalcoholic fatty liver disease (NAFLD) is becoming a frequent cause of patient referral to gastroenterologists. There is a close link between dysfunctional adipose tissue in NAFLD and common conditions such as metabolic syndrome, type 2 diabetes mellitus, and cardiovascular disease. This review focuses on the pathophysiology of interactions between adipose tissue and target organs in obesity and the resulting clinical implications for the management of nonalcoholic steatohepatitis. The release of fatty acids from dysfunctional and insulin-resistant adipocytes results in lipotoxicity, caused by the accumulation of triglyceride-derived toxic metabolites in ectopic tissues (liver, muscle, pancreatic beta cells) and subsequent activation of inflammatory pathways, cellular dysfunction, and lipoapoptosis. The cross talk between dysfunctional adipocytes and the liver involves multiple cell populations, including macrophages and other immune cells, that in concert promote the development of lipotoxic liver disease, a term that more accurately describes the pathophysiology of nonalcoholic steatohepatitis. At the clinical level, adipose tissue insulin resistance contributes to type 2 diabetes mellitus and cardiovascular disease. Treatments that rescue the liver from lipotoxicity by restoring adipose tissue insulin sensitivity (eg, significant weight loss, exercise, thiazolidinediones) or preventing activation of inflammatory pathways and oxidative stress (ie, vitamin E, thiazolidinediones) hold promise in the treatment of NAFLD, although their long-term safety and efficacy remain to be established. Better understanding of pathways that link dysregulated adipose tissue, metabolic dysfunction, and liver lipotoxicity will result in improvements in the clinical management of these challenging patients.

Non-alcoholic fatty liver disease in children now: lifestyle changes and pharmacologic treatments

Over the past decade, non-alcoholic fatty liver disease (NAFLD) has become one of most common chronic liver diseases in children. A greater understanding about the risk factors and molecular pathogenesis of NAFLD suggests that lifestyle interventions aiming to decrease obesity/body mass index and metabolic derangement are the first line of treatments adopted in children affected by this disease. However, because these therapeutic options are often at the beginning misjudged by the patients and their parents, the use of pharmacologic agents may help to protect the liver and other organs from further irreversible tissue damage. Pharmacologic therapies against one or more specific factors and/or molecules involved in the development of NAFLD (i.e., insulin resistance, free fatty acid lipid toxicity, and oxidative stress) also might slow the progression of this increasingly prevalent pediatric disorder. On this basis, insulin sensitizers, antioxidants, cytoprotective agents, and dietary supplementations have been evaluated in pediatric clinical trials. In this review, we discuss the efficacy of the dietary approaches, possibly coupled with regular exercise, on decreasing the metabolic and histologic damage in pediatric NAFLD. We also emphasize several advantages of the pharmacologic treatments adopted or adoptable in combination with lifestyle interventions in children with NAFLD.

Pathophysiology guided treatment of nonalcoholic steatohepatitis

Nonalcoholic fatty liver disease is a spectrum that ranges from benign steatosis to steatohepatitis. It has become the most common cause of chronic liver disease, and yet there continues to be a lack of effective therapeutic options. This article reviews current concepts underlying the pathophysiological basis of nonalcoholic steatohepatitis from development of insulin resistance to the establishment of fibrosis. Then using a physiology-based approach, specific targeted therapeutics are reviewed along with their drawbacks. The evidence behind current therapies is based predominantly on small trials and, thus, no recommendations can be made until larger randomized trials are conducted.

Emodin prevents intrahepatic fat accumulation, inflammation and redox status imbalance during diet-induced hepatosteatosis in rats

High-fat and/or high-carbohydrate diets may predispose to several metabolic disturbances including liver fatty infiltration (hepatosteatosis) or be associated with necro-inflammation and fibrosis (steatohepatitis). Several studies have emphasized the hepatoprotective effect of some natural agents. In this study, we investigated the potential therapeutic effects of the treatment with emodin, an anthraquinone derivative with anti-oxidant and anti-cancer abilities, in rats developing diet-induced hepatosteatosis and steatohepatitis. Sprague-Dawley rats were fed a standard diet (SD) for 15 weeks, or a high-fat/high-fructose diet (HFD/HF). After 5 weeks, emodin was added to the drinking water of some of the SD and HFD/HF rats. The experiment ended after an additional 10 weeks. Emodin-treated HFD/HF rats were protected from hepatosteatosis and metabolic derangements usually observed in HFD/HF animals. Furthermore, emodin exerted anti-inflammatory activity by inhibiting the HFD/HF-induced increase of tumor necrosis factor (TNF)-α. Emodin also affected the hepatocytes glutathione homeostasis and levels of the HFD/HF-induced increase of glutathionylated/phosphorylated phosphatase and tensin homolog (PTEN). In conclusion, we demonstrated that a natural agent such as emodin can prevent hepatosteatosis, preserving liver from pro-inflammatory and pro-oxidant damage caused by HFD/HF diet. These findings are promising, proposing emodin as a possible hindrance to progression of hepatosteatosis into steatohepatitis.

The efficacy of licorice root extract in decreasing transaminase activities in non-alcoholic fatty liver disease: a randomized controlled clinical trial

This study was performed to investigate the effects of licorice on non-alcoholic fatty liver disease (NAFLD). In this double blind randomized clinical trial, 66 patients were divided into case and control groups. All patients had elevated liver enzymes and had increased liver echogenicity (lipid accumulation) on sonography. The case group was treated with one capsule containing 2 g aqueous licorice root extract per day for 2 months while the control group was treated in the same manner with a placebo. Weight, body mass index (BMI) and liver transaminase levels were measured for each patient before and after the study. In the case group, the mean alanine aminotransferase (ALT) level decreased from 64.09 to 51.27 IU/mL and the aspartate aminotransferase (AST) level decreased from 58.18 to 49.45 IU/mL, which were statistically significant (p < 0.001 and p < 0.001). But in the control group, a drop in the ALT and AST levels was not statistically significant. The BMI difference before and after the study was not statistically significant in both groups. Despite the significant drop in liver enzymes following administration of licorice root extract, it is recommended that further studies that include histological examination are necessary.

Pediatric nonalcoholic fatty liver disease: a multidisciplinary approach

Nonalcoholic fatty liver disease (NAFLD) is a multifactorial condition, ranging from simple steatosis to nonalcoholic steatohepatitis (NASH) with or without fibrosis. NAFLD affects both adults and children who present with particular risk factors, including obesity, sedentary lifestyle and/or a predisposing genetic background. The escalation of the prevalence of NAFLD in children worldwide is a worrying phenomenon because this disease is closely associated with the development of both cirrhosis and cardiometabolic syndrome in adulthood. The etiopathogenesis of primary NAFLD in children is unknown; however, considerable knowledge about the mechanisms of liver damage that occur during disease progression has been gathered over the past 30 years. Understanding the pathogenetic mechanisms, together with the histological pattern, provide the basis to characterize potential early predictors of the disease, suitable noninvasive diagnostic tools and design novel specific treatments and possible management strategies. Despite a few clinical trials on the use of antioxidants combined with lifestyle intervention for NAFLD that showed encouraging results, to date, no treatment guidelines exist for children with NAFLD. In this Review, we provide an overview of current concepts in epidemiology, histological features, etiopathogenesis, diagnosis and treatment of NAFLD in children and adolescents.

Correlation of vitamin E, uric acid, and diet composition with histologic features of pediatric NAFLD

OBJECTIVES

Nonalcoholic fatty liver disease (NAFLD) is the most common chronic liver disease in children in the United States. Although changes in diet are often recommended to improve NAFLD, little is known regarding the influence of diet on histologic features of the disease.

SUBJECTS AND METHODS

This was a prospective, cross-sectional registry-based study. Children (n = 149) enrolled in the multicenter nonalcoholic steatohepatitis (NASH) Clinical Research Network had demographic, anthropometric, clinical, laboratory, and histology data obtained, including the Block Brief Food Questionnaire. Subjects were grouped by presence or absence of steatohepatitis and grades of histologic features according to NASH Clinical Research Network criteria.

RESULTS

No significant differences were found between children with steatosis compared with steatohepatitis for fraction of energy from fat, carbohydrates, and protein. Sugar-sweetened beverage consumption was low and did not correlate with histologic features, although uric acid, a surrogate marker for fructose intake, was significantly increased in those with definite NASH (P = 0.008). For all groups, vitamin E consumption was insufficient compared with the recommended daily allowance. Median consumption of vitamin E was lower in children with higher grade of steatosis (8.4 vs 6.1 vs 6.9 for grades I, II, and III, respectively, P = 0.05). Those consuming less vitamin C had increased ballooning degeneration (P = 0.05).

CONCLUSIONS

Children with NAFLD have a diet that is insufficient in vitamin E and this may contribute to the pathophysiology of NAFLD. In children with NAFLD, reported sugar-sweetened beverage consumption is low; however, uric acid, which may reflect total fructose consumption, was significantly associated with NASH and should be further evaluated.

Non-alcoholic steatohepatitis: the therapeutic challenge of a global epidemic

Non-alcoholic fatty liver disease (NAFLD) is the most common liver disease worldwide. Nonalcoholic steatohepatitis (NASH) reflects severe liver disease within the NAFLD spectrum and can progress to end-stage liver disease. Within this manuscript we review the available evidence for the treatment of NASH as well as the newer therapeutic agents that are currently being investigated.

Serum ferritin is an independent predictor of histologic severity and advanced fibrosis in patients with nonalcoholic fatty liver disease

Serum ferritin (SF) levels are commonly elevated in patients with nonalcoholic fatty liver disease (NAFLD) because of systemic inflammation, increased iron stores, or both. The aim of this study was to examine the relationship between elevated SF and NAFLD severity. Demographic, clinical, histologic, laboratory, and anthropometric data were analyzed in 628 adult patients with NAFLD (age, ≥ 18 years) with biopsy-proven NAFLD and an SF measurement within 6 months of their liver biopsy. A threshold SF >1.5 × upper limit of normal (ULN) (i.e., >300 ng/mL in women and >450 ng/mL in men) was significantly associated with male sex, elevated serum alanine aminotransferase, aspartate aminotransferase, iron, transferrin-iron saturation, iron stain grade, and decreased platelets (P < 0.01). Histologic features of NAFLD were more severe among patients with SF >1.5 × ULN, including steatosis, fibrosis, hepatocellular ballooning, and diagnosis of NASH (P < 0.026). On multiple regression analysis, SF >1.5 × ULN was independently associated with advanced hepatic fibrosis (odds ratio [OR], 1.66; 95% confidence interval [CI], 1.05-2.62; P = 0.028) and increased NAFLD Activity Score (NAS) (OR, 1.99; 95% CI, 1.06-3.75; P = 0.033).

CONCLUSIONS

A SF >1.5 × ULN is associated with hepatic iron deposition, a diagnosis of NASH, and worsened histologic activity and is an independent predictor of advanced hepatic fibrosis among patients with NAFLD. Furthermore, elevated SF is independently associated with higher NAS, even among patients without hepatic iron deposition. We conclude that SF is useful to identify NAFLD patients at risk for NASH and advanced fibrosis.

Treatment of nonalcoholic fatty liver disease in adults and children: a closer look at the arsenal

Nonalcoholic fatty liver disease encompasses a spectrum of disease from asymptomatic steatosis, with or without elevated aminotransferases, to cirrhosis with relative complications and hepatocellular carcinoma. Owing to the increasing prevalence of nonalcoholic fatty liver disease and the potential for nonalcoholic steatohepatitis to progress to cirrhosis and liver-related mortality, more research has been focused on therapy of this important liver disease over the last two decades. To date, weight loss and physical activity represent the cornerstone of treatment, with interventions being limited to subjects at risk of disease progression, but the type of treatment remains a matter of debate. A few medications have shown promising results in preliminary pilot studies, but few agents have been tested rigorously. Today, multiple therapeutic approaches are considered the way to go in treating nonalcoholic steatohepatitis patients. In this paper we review the status of current and emerging therapeutic strategies for children and adult patients with nonalcoholic steatohepatitis.

Nonalcoholic steatohepatitis: the therapeutic challenge of a global epidemic

PURPOSE OF REVIEW

Nonalcoholic fatty liver (NAFL) and especially its inflammatory variant nonalcoholic steatohepatitis (NASH) have become a major challenge to healthcare systems worldwide because of the increasing prevalence of its major risk factors obesity and type 2 diabetes, which are closely linked to overeating, physical inactivity, and the metabolic syndrome.

RECENT FINDINGS

Between 10 and 20% of patients with NAFL develop NASH, which can progress to cirrhosis, end-stage liver disease, and hepatocellular carcinoma. The overall mortality in these patients is significantly increased because of both cardiovascular and liver-related complications. Sustained weight loss by diet and exercise, which is the most effective therapeutic measure, is only achieved by a minority of patients, having led to a great yet unmet need for medical therapies of NASH.

SUMMARY

Pharmacological therapies should target the underlying pathophysiology that involves insulin resistance, enhanced peripheral lipolysis and release of free fatty acids, oxidative stress, accumulation of toxic lipids, adipose tissue inflammation, sensitization of hepatocytes toward apoptotic cell death, and fibrogenesis. However, pharmacological therapy that is well tolerated, cost-effective, and poses an acceptable risk-to-benefit ratio has still to be identified. This review summarizes the current and promising treatment options and their implications for future research and clinical practice.

Advances in pediatric nonalcoholic fatty liver disease

Nonalcoholic fatty liver disease (NAFLD) has emerged as the most common cause of pediatric liver disease in the developed world. Children have a form of NAFLD that is pathologically distinct from adults. Although NAFLD remains a pathologic diagnosis, biomarkers and imaging studies hold promise as noninvasive means of both establishing the diagnosis and following the disease course. Significant advancements have recently been made in genetics, pathophysiology, and the treatment of NAFLD. The purpose of this article is to provide a clinically relevant review of pediatric NAFLD with an emphasis on recent developments in the field.

Cholesterol-lowering therapy for the treatment of nonalcoholic fatty liver disease: an update

PURPOSE OF REVIEW

To review recent human trials assessing cholesterol-lowering agents in nonalcoholic fatty liver disease (NAFLD).

RECENT FINDINGS

Four randomized controlled trials (RCTs) assessed statins in NAFLD. In the only RCT with post-treatment biopsy, simvastatin did not change liver histology. In the remaining RCTs, atorvastatin was well tolerated, significantly improved radiological/biochemical markers of steatosis and plasma lipids, with neutral effects on glucose metabolism; in the Greek Atorvastatin and Coronary Heart Disease Evaluation (GREACE) study, atorvastatin reduced incident cardiovascular disease compared with both untreated NAFLD patients and with statin-treated patients without NAFLD. Ezetimibe was evaluated in two uncontrolled trials and two RCTs, consistently improving liver histology and plasma lipids, whereas glucose metabolism was generally unaffected; however, HbA1c increased with ezetimibe in one RCT.

SUMMARY

From the analysis of available trials, it emerges that cholesterol-lowering agents may considerably benefit NAFLD patients. Statins are well tolerated, and atorvastatin improved surrogate markers of liver disease, whereas their effect on liver histology is unknown. Furthermore, the GREACE study was the first trial to show clinical benefit from the use of a pharmacological agent in NAFLD. Ezetimibe improved liver histology. The benefit of combination therapy, as well as the safety on glucose metabolism, need further evaluation.

Roles of PPARs in NAFLD: potential therapeutic targets

Non-alcoholic fatty liver disease (NAFLD) is a liver pathology with increasing prevalence due to the obesity epidemic. Hence, NAFLD represents a rising threat to public health. Currently, no effective treatments are available to treat NAFLD and its complications such as cirrhosis and liver cancer. Peroxisome proliferator-activated receptors (PPARs) are ligand-activated nuclear receptors which regulate lipid and glucose metabolism as well as inflammation. Here we review recent findings on the pathophysiological role of PPARs in the different stages of NAFLD, from steatosis development to steatohepatitis and fibrosis, as well as the preclinical and clinical evidence for potential therapeutical use of PPAR agonists in the treatment of NAFLD. PPARs play a role in modulating hepatic triglyceride accumulation, a hallmark of the development of NAFLD. Moreover, PPARs may also influence the evolution of reversible steatosis toward irreversible, more advanced lesions. Presently, large controlled trials of long duration are needed to assess the long-term clinical benefits of PPAR agonists in humans. This article is part of a Special Issue entitled Triglyceride Metabolism and Disease.

An Endocrine Perspective of Nonalcoholic Fatty Liver Disease (NAFLD)

Endocrinologists are encountering patients with obesity-related complications such as metabolic syndrome (MetS) and type 2 diabetes mellitus (T2DM) on a daily basis. Nonalcoholic fatty liver disease (NAFLD) is a liver condition characterized by insulin resistance, hepatic steatosis and frequently T2DM. This is now the most common chronic liver condition in adults and is present in the majority of obese subjects. Liver fat accumulation may range from simple steatosis to severe steatohepatitis with hepatocyte necroinflammation (or nonalcoholic steatohepatitis [NASH]). Although the natural history is incompletely understood, NAFLD may lead to serious medical consequences ranging from cirrhosis and hepatocellular carcinoma to earlier onset of T2DM and cardiovascular disease (CVD). The diagnosis of NAFLD may be challenging because signs and symptoms are frequently absent or nonspecific, and thus easily missed. Liver aminotransferases may be helpful if elevated, but most times are normal in the presence of the disease. Liver imaging may assist in the diagnosis (ultrasound or MRI and spectroscopy) but a definitive diagnosis of NASH still requires a liver biopsy. This may change in the near future as novel biomarkers become available. Treatment of NAFLD includes aggressive management of associated cardiovascular risk factors and many times control of T2DM. Pioglitazone and vitamin E appear promising for patients with NASH, although long-term studies are unavailable. In summary, this review hopes to address the common clinical dilemmas that endocrinologists face in the diagnosis and management of NAFLD and increase awareness of a potentially serious medical condition.

Treatment of atherogenic liver based on the pathogenesis of nonalcoholic fatty liver disease: a novel approach to reduce cardiovascular risk?

Nonalcoholic fatty liver disease (NAFLD), which spans a spectrum of conditions ranging from simple steatosis to progressive nonalcoholic steatohepatitis (NASH), is the most common chronic liver disease and a relevant public health issue. The prevalence of NAFLD depends on adiposity, age, gender and ethnicity. The natural history of liver disease in those with NAFLD critically depends on liver histological changes. However, cardiovascular mortality is increased in NAFLD, particularly in middle-aged adults. Against such a background, this review consists of three sections. First, data on NAFLD as a novel mechanism of increased cardiovascular risk via hyperinsulinism, pro-thrombotic potential, and subclinical inflammation are summarized. Next, the role of atherogenic liver in the development of manifestations of oxidative stress and atherosclerosis is emphasized. Finally, whether and how treating NAFLD will mechanistically result in reduced cardiovascular risk through ameliorated metabolic syndrome is discussed.

Mechanisms of lipotoxicity in NAFLD and clinical implications

With the epidemic of childhood obesity, nonalcoholic fatty liver disease (NAFLD) has become the most common cause of chronic liver disease in pediatrics. NAFLD is strongly associated with insulin resistance and increased level of serum free fatty acids (FFAs). FFAs have direct hepatotoxicity through the induction of an endoplasmic reticulum stress response and subsequently activation of the mitochondrial pathway of cell death. FFAs may also result in lysosomal dysfunction and alter death receptor gene expression. Lipoapoptosis is a key pathogenic process in NAFLD, and correlates with progressive inflammation, and fibrosis. Accumulation of triglyceride in the liver results from uptake and esterification of FFAs by the hepatocyte, and is less likely to be hepatotoxic per se. To date, there are no proven effective therapies that halt NAFLD progression or unfortunately improve prognosis in children. The cellular mechanisms of lipotoxicity are complex but provide potential therapeutic targets for NAFLD. In this review we discuss several potential therapeutic opportunities in detail including inhibition of apoptosis, c-Jun-N-terminal kinase, and endoplasmic reticulum stress pathways.

Pediatric nonalcoholic fatty liver disease, metabolic syndrome and cardiovascular risk

Nonalcoholic fatty liver disease (NAFLD) encompasses a range of liver histology severity and outcomes in the absence of chronic alcohol use. The mildest form is simple steatosis in which triglycerides accumulate within hepatocytes. A more advanced form of NAFLD, non-alcoholic steatohepatitis, includes inflammation and liver cell injury, progressive to cryptogenic cirrhosis. NAFLD has become the most common cause of chronic liver disease in children and adolescents. The recent rise in the prevalence rates of overweight and obesity likely explains the NAFLD epidemic worldwide. NAFLD is strongly associated with abdominal obesity, type 2 diabetes, and dyslipidemia, and most patients have evidence of insulin resistance. Thus, NAFLD shares many features of the metabolic syndrome (MetS), a highly atherogenic condition, and this has stimulated interest in the possible role of NAFLD in the development of atherosclerosis. Accumulating evidence suggests that NAFLD is associated with a significantly greater overall mortality than in the general population, as well as with increased prevalence of cardiovascular disease (CVD), independently of classical atherosclerotic risk factors. Yet, several studies including the pediatric population have reported independent associations between NAFLD and impaired flow-mediated vasodilatation and increased carotid artery intimal medial thickness-two reliable markers of subclinical atherosclerosis-after adjusting for cardiovascular risk factors and MetS. Therefore, the rising prevalence of obesity-related MetS and NAFLD in childhood may lead to a parallel increase in adverse cardiovascular outcomes. In children, the cardiovascular system remains plastic and damage-reversible if early and appropriate interventions are established effectively. Therapeutic goals for NAFLD should address nutrition, physical activity, and avoidance of smoking to prevent not only end-stage liver disease but also CVD.

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

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

Atherogenic dyslipidemia and cardiovascular risk in children with nonalcoholic fatty liver disease

Nonalcoholic fatty liver disease is now regarded as the most common form of chronic liver disease in adults and children. The close association between nonalcoholic fatty liver disease (NAFLD) and the metabolic syndrome has been extensively described. Moreover, a growing body of evidence suggest that NAFLD by itself confers a substantial cardiovascular risk independent of the other components of the metabolic syndrome. Given the significant potential for morbidity and mortality in these patients, and the large proportion of both pediatric and adult population affected, it is important that we clearly define the overall risk, identify early predictors for cardiovascular disease progression, and establish management strategies. In this article, we will focus on current data linking NAFLD and the severity of liver damage present in children with cardiovascular risk.