Republished: Non-alcoholic fatty liver disease: non-invasive investigation and risk stratification

Nonalcoholic fatty liver disease and diabetes

Nonalcoholic fatty liver disease (NAFLD) is the most prevalent chronic liver disease in the world and represents a clinical-histopathologic entity where the steatosis component may vary in degree and may or may not have fibrotic progression. The key concept of NAFLD pathogenesis is excessive triglyceride hepatic accumulation because of an imbalance between free fatty acid influx and efflux. Strong epidemiological, biochemical, and therapeutic evidence supports the premise that the primary pathophysiological derangement in most patients with NAFLD is insulin resistance; thus the association between diabetes and NAFLD is widely recognized in the literature. Since NAFLD is the hepatic manifestation of a metabolic disease, it is also associated with a higher cardio-vascular risk. Conventional B-mode ultrasound is widely adopted as a first-line imaging modality for hepatic steatosis, although magnetic resonance imaging represents the gold standard noninvasive modality for quantifying the amount of fat in these patients. Treatment of NAFLD patients depends on the disease severity, ranging from a more benign condition of nonalcoholic fatty liver to nonalcoholic steatohepatitis. Abstinence from alcohol, a Mediterranean diet, and modification of risk factors are recommended for patients suffering from NAFLD to avoid major cardiovascular events, as per all diabetic patients. In addition, weight loss induced by bariatric surgery seems to also be effective in improving liver features, together with the benefits for diabetes control or resolution, dyslipidemia, and hypertension. Finally, liver transplantation represents the ultimate treatment for severe nonalcoholic fatty liver disease and is growing rapidly as a main indication in Western countries. This review offers a comprehensive multidisciplinary approach to NAFLD, highlighting its connection with diabetes.

What's New in Hepatic Steatosis

Hepatic steatosis can lead to liver cancer, cirrhosis, and portal hypertension. There are two main types, non-alcoholic fatty liver disease (NAFLD) and alcoholic liver disease. The detection and quantification of hepatic steatosis with lifestyle changes can slow the evolution from NAFLD to steatohepatitis. Currently, the gold standard for the quantification of fat in the liver is biopsy, has some limitations. Hepatic steatosis is frequently detected during cross sectional imaging. Ultrasound (US), Computed Tomography (CT), and Magnetic Resonance Imaging (MRI) provide noninvasive assessment of liver parenchyma and can detect fat infiltration in the liver. However, the non-invasive quantification of hepatic steatosis by imaging has been challenging. Recent MRI techniques show great promise in the detection and quantification of liver fat. The aim of this article is to review the utilization of non-invasive imaging modalities for the detection and quantification of hepatic steatosis, to evaluate their advantages and limitations.

Mitochondrial haplogroup G is associated with nonalcoholic fatty liver disease, while haplogroup A mitigates the effects of PNPLA3

Objectives

Mitochondrial dysfunction plays a pivotal role in the pathogenesis of nonalcoholic fatty liver disease (NAFLD). We hypothesized that mitochondrial DNA (mtDNA) haplogroups affect the risk of NAFLD in Han Chinese patients and interact with PNPLA3 genotypes.

Design

NAFLD and control patients were recruited from a tertiary care centre. The mitochondrial genome was amplified in overlapping segments and sequenced. Mitochondrial haplogroups were determined using Mitomaster. PNPLA3 rs738409 genotyping was performed using restriction fragment length polymorphism analysis.

Patients

We enrolled 655 NAFLD patients and 504 controls.

Results

More NAFLD patients encoded haplogroup G; odds ratio (OR) 1.85 (95% confidence interval [CI] 1.16, 2.80). Subhaplogroup G3 was present more frequently in NAFLD patients (25.8% vs 6.5%). The PNPLA3 CG genotype resulted in an OR of 1.66 (95% CI 1.25, 2.21), and the GG genotype resulted in an OR of 2.33 (95% CI 1.72, 3.17) for NAFLD. Patients with mitochondrial haplogroup A had a significantly higher frequency of genotype GG. Among patients with haplogroup A, no PNPLA3 genotype was associated with increased NAFLD risk (CG: OR 1.17, 95% CI 0.55, 2.34; GG: OR 1.04 95% CI 0.66, 2.65). Excluding haplogroup A, the OR for CG was 1.58 (95% CI 1.18, 2.12), and the OR for GG was 1.81 (95% CI 1.30, 2.51).

Conclusion

Haplogroup G was associated with an increased risk of NAFLD PNPLA3 GG genotype was overrepresented among patients encoding haplogroup A and was not associated with NAFLD risk among haplogroup A patients. Mitochondrial genetics influence NAFLD risk and interact with PNPLA3 genotypes.

Advances in Imaging of Diffuse Parenchymal Liver Disease

There are >1.5 billion people with chronic liver disease worldwide, causing liver diseases to be a significant global health issue. Diffuse parenchymal liver diseases, including hepatic steatosis, fibrosis, metabolic diseases, and hepatitis cause chronic liver injury and may progress to fibrosis and eventually hepatocellular carcinoma. As early diagnosis and treatment of these diseases impact the progression and outcome, the need for assessment of the liver parenchyma has increased. While the current gold standard for evaluation of the hepatic parenchymal tissue, biopsy has disadvantages and limitations. Consequently, noninvasive methods have been developed based on serum biomarkers and imaging techniques. Conventional imaging modalities such as ultrasound, computed tomography scan, and magnetic resonance imaging provide noninvasive options for assessment of liver tissue. However, several recent advances in liver imaging techniques have been introduced. This review article focuses on the current status of imaging methods for diffuse parenchymal liver diseases assessment including their diagnostic accuracy, advantages and disadvantages, and comparison between different techniques.

Current status of imaging in nonalcoholic fatty liver disease

Non-alcoholic fatty liver disease (NAFLD) is the most common diffuse liver disease, with a worldwide prevalence of 20% to 46%. NAFLD can be subdivided into simple steatosis and nonalcoholic steatohepatitis. Most cases of simple steatosis are non-progressive, whereas nonalcoholic steatohepatitis may result in chronic liver injury and progressive fibrosis in a significant minority. Effective risk stratification and management of NAFLD requires evaluation of hepatic parenchymal fat, fibrosis, and inflammation. Liver biopsy remains the current gold standard; however, non-invasive imaging methods are rapidly evolving and may replace biopsy in some circumstances. These methods include well-established techniques, such as conventional ultrasonography, computed tomography, and magnetic resonance imaging and newer imaging technologies, such as ultrasound elastography, quantitative ultrasound techniques, magnetic resonance elastography, and magnetic resonance-based fat quantitation techniques. The aim of this article is to review the current status of imaging methods for NAFLD risk stratification and management, including their diagnostic accuracy, limitations, and practical applicability.

Pharmacological management of nonalcoholic fatty liver disease in type 2 diabetes

INTRODUCTION

The prevalence of nonalcoholic fatty liver disease (NAFLD) in patients with type 2 diabetes (T2D) is high and it is associated with poor prognosis. Hepatic steatosis results as a consequence of excessive hepatic lipid accumulation which correlates with insulin resistance and lipotoxicity, with subsequent oxidative stress, inflammation, apoptosis and fibrosis. Areas covered: This article presents the main pathophysiologic mechanisms and currently available drugs evaluated for their therapeutic effects on NAFLD/nonalcoholic steatohepatitis (NASH) and drugs under development that target relevant pathogenetic pathways. However, to date there is no particular drug approved for treatment of NAFLD in patients with T2D. Expert commentary: Early recognition and intervention are essential to ameliorate disease progression. Specific recommendations are still needed for NAFLD/NASH screening and diagnosis and therapeutic algorithm in patients with T2D. Lifestyle optimization with significant weight loss is a key intervention in patients with NAFLD and T2D. Pioglitazone, liraglutide, vitamin E, OCA and pentoxifylline have proven some histological improvements in NASH and omega 3-PUFAs were shown to decrease liver fat, but no specific recommendation can be made for treatment of NASH. Perhaps a combination of agents that target different pathogenic pathways are needed to better control disease progression, but more robust evidence for these agents is still needed.

An overview of the genetics, mechanisms and management of NAFLD and ALD

Alcoholic liver disease (ALD) and, increasingly, non-alcoholic fatty liver disease (NAFLD) are common causes of advanced liver disease in many developed countries including the UK. Both diseases share parallel natural histories, progressing from steatosis, to steatohepatitis and fibrosis/cirrhosis; and are characterised by substantial interindividual variation in disease outcome. This article will provide an overview of disease mechanisms, genetic modifiers and management, focusing principally on NAFLD, while drawing parallels between the two conditions where appropriate.