Spectrum, Screening, and Diagnosis of Alcohol-related Liver Disease

From Shadows to Spotlight: Exploring the Escalating Burden of Alcohol-Associated Liver Disease and Alcohol Use Disorder in Young Women

INTRODUCTION

The burden of alcohol-related complications is considerable, particularly alcohol-associated liver disease and alcohol use disorder (AUD). However, there are deficiencies in comprehensive epidemiological research focusing on these issues, especially among young women who display higher susceptibility to such complications compared with their male counterparts. We thus aimed to determine the global burden of these conditions in this vulnerable group.

METHODS

Leveraging data from the Global Burden of Disease Study 2019, we analyzed the prevalence, mortality, and disability-adjusted life years of alcohol-associated cirrhosis (AC), liver cancer from alcohol, and AUD in young women. The findings were categorized by region, nation, and sociodemographic index.

RESULTS

The highest age-standardized prevalence rates were observed in AUD (895.96 [95% uncertainty interval (UI) 722.6-1,103.58]), followed by AC (65.33 [95% UI 48.37-86.49]) and liver cancer from alcohol (0.13 [95% UI 0.09-0.19]) per 100,000 people. The highest age-standardized mortality rates were observed in AC (0.75 [95% UI 0.55-0.97]), followed by AUD (0.48 [95% UI 0.43-0.53]) and liver cancer from alcohol (0.06 [95% UI 0.04-0.09]). The highest burdens of AC and AUD were observed in Central Europe, whereas the high-income Asia Pacific had the highest burden of liver cancer from alcohol.

DISCUSSION

Throughout the past decade, the trend of AUD varied among regions while the impact of alcohol-associated liver disease has increased, requiring urgent public health strategy to mitigate these complications, particularly in female patients in Europe and the Asia-Pacific region.

Alcohol-related liver disease: A global perspective

Alcohol-associated liver disease (ALD) represents one of the deadliest yet preventable consequences of excessive alcohol use. It represents 5.1 % of the global burden of disease, mainly involving the productive-age population (15-44 years) and leading to an increased mortality risk from traffic road injuries, suicide, violence, cardiovascular disease, neoplasms, and liver disease, among others, accounting for 5.3 % of global deaths. Daily alcohol consumption, binge drinking (BD), and heavy episodic drinking (HED) are the patterns associated with a higher risk of developing ALD. The escalating global burden of ALD, even exceeding what was predicted, is the result of a complex interaction between the lack of public policies that regulate alcohol consumption, low awareness of the scope of the disease, late referral to specialists, underuse of available medications, insufficient funds allocated to ALD research, and non-predictable events such as the COVID-19 pandemic, where increases of up to 477 % in online alcohol sales were registered in the United States. Early diagnosis, referral, and treatment are pivotal to achieving the therapeutic goal in patients with alcohol use disorder (AUD) and ALD, where complete alcohol abstinence and prevention of alcohol relapse are expected to enhance overall survival. This can be achieved through a combination of cognitive behavioral, motivational enhancement and pharmacological therapy. Furthermore, the appropriate use of available pharmacological therapy and implementation of public policies that comprehensively address this disease will make a real difference.

Multiomics Analysis of PCB126's Effect on a Mouse Chronic-Binge Alcohol Feeding Model

BACKGROUND

Environmental pollutants, including polychlorinated biphenyls (PCBs) have been implicated in the pathogenesis of liver disease. Our group recently demonstrated that PCB126 promoted steatosis, hepatomegaly, and modulated intermediary metabolism in a rodent model of alcohol-associated liver disease (ALD).

OBJECTIVE

To better understand how PCB126 promoted ALD in our previous model, the current study adopts multiple omics approaches to elucidate potential mechanistic hypotheses.

METHODS

Briefly, male C57BL/6J mice were exposed to 0.2 mg / kg polychlorinated biphenyl (PCB) 126 or corn oil vehicle prior to ethanol (EtOH) or control diet feeding in the chronic-binge alcohol feeding model. Liver tissues were collected and prepared for mRNA sequencing, phosphoproteomics, and inductively coupled plasma mass spectrometry for metals quantification.

RESULTS

Principal component analysis showed that PCB126 uniquely modified the transcriptome in EtOH-fed mice. EtOH feeding alone resulted in > 4,000 differentially expressed genes (DEGs), and PCB126 exposure resulted in more DEGs in the EtOH-fed group (907 DEGs) in comparison with the pair-fed group (503 DEGs). Top 20 significant gene ontology (GO) biological processes included "peptidyl tyrosine modifications," whereas top 25 significantly decreasing GO molecular functions included "metal/ion/zinc binding." Quantitative, label-free phosphoproteomics and western blot analysis revealed no major significant PCB126 effects on total phosphorylated tyrosine residues in EtOH-fed mice. Quantified hepatic essential metal levels were primarily significantly lower in EtOH-fed mice. PCB126-exposed mice had significantly lower magnesium, cobalt, and zinc levels in EtOH-fed mice.

DISCUSSION

Previous work has demonstrated that PCB126 is a modifying factor in metabolic dysfunction-associated steatotic liver disease (MASLD), and our current work suggests that pollutants also modify ALD. PCB126 may, in part, be contributing to the malnutrition aspect of ALD, where metal deficiency is known to contribute and worsen prognosis. https://doi.org/10.1289/EHP14132.

Contributing roles of mitochondrial dysfunction and hepatocyte apoptosis in liver diseases through oxidative stress, post-translational modifications, inflammation, and intestinal barrier dysfunction

This review provides an update on recent findings from basic, translational, and clinical studies on the molecular mechanisms of mitochondrial dysfunction and apoptosis of hepatocytes in multiple liver diseases, including but not limited to alcohol-associated liver disease (ALD), metabolic dysfunction-associated steatotic liver disease (MASLD), and drug-induced liver injury (DILI). While the ethanol-inducible cytochrome P450-2E1 (CYP2E1) is mainly responsible for oxidizing binge alcohol via the microsomal ethanol oxidizing system, it is also responsible for metabolizing many xenobiotics, including pollutants, chemicals, drugs, and specific diets abundant in n-6 fatty acids, into toxic metabolites in many organs, including the liver, causing pathological insults through organelles such as mitochondria and endoplasmic reticula. Oxidative imbalances (oxidative stress) in mitochondria promote the covalent modifications of lipids, proteins, and nucleic acids through enzymatic and non-enzymatic mechanisms. Excessive changes stimulate various post-translational modifications (PTMs) of mitochondrial proteins, transcription factors, and histones. Increased PTMs of mitochondrial proteins inactivate many enzymes involved in the reduction of oxidative species, fatty acid metabolism, and mitophagy pathways, leading to mitochondrial dysfunction, energy depletion, and apoptosis. Unique from other organelles, mitochondria control many signaling cascades involved in bioenergetics (fat metabolism), inflammation, and apoptosis/necrosis of hepatocytes. When mitochondrial homeostasis is shifted, these pathways become altered or shut down, likely contributing to the death of hepatocytes with activation of inflammation and hepatic stellate cells, causing liver fibrosis and cirrhosis. This review will encapsulate how mitochondrial dysfunction contributes to hepatocyte apoptosis in several types of liver diseases in order to provide recommendations for targeted therapeutics.

Alcohol-associated liver disease: Epidemiology and management

Alcohol is the leading cause of preventable liver morbidity and mortality worldwide, as it is also the most frequent cause of advanced liver disease. Alcohol-associated liver disease (ALD) covers different phenotypes ranging from steatosis to the development of inflammation (steatohepatitis), fibrosis and ultimately, in a proportion of patients, the development of liver cirrhosis and its associated complications. ALD has a complex pathogenesis that includes the interplay of both genetic and environmental factors, yet the precise mechanisms are largely unknown. Alcohol-associated hepatitis (AH) is a severe clinical presentation of ALD, which is characterized by abrupt jaundice and clinical decompensations of liver disease. AH occurs in a percentage of patients with underlying ALD and active alcohol consumption. Currently, there are no approved targeted therapies able to interfere in the pathogenesis of ALD and halt the progression of the disease, therefore alcohol abstinence is the most effective measure to improve prognosis in this patient population. In this regard, alcohol cessation remains the first-line treatment in all stages of alcohol disease. In patients with advanced ALD nonresponding to medical therapy, liver transplantation is the only approach that improves prognosis, and it should be considered in patients with decompensated cirrhosis. In the last years, AH has emerged as a new indication of early liver transplantation in non-responders to medical therapy, with promising results in highly selected patients. In this review, we provide an update on the epidemiology, risk factors, natural history, diagnosis, pathogenesis, and current treatments for ALD, taking into account the importance of assessing and managing alcohol consumption as the etiological factor and the main driver of prognosis in patients with ALD.

Giant mitochondria in human liver disease

This thematic review aims to provide an overview of the current state of knowledge about the occurrence of giant mitochondria or megamitochondria in liver parenchymal cells. Their presence and accumulation are considered to be a major pathological hallmark of the health and fate of liver parenchymal cells that leads to overall tissue deterioration and eventually results in organ failure. The first description on giant mitochondria dates back to the 1960s, coinciding with the availability of the first generation of electron microscopes in clinical diagnostic laboratories. Detailed accounts on their ultrastructure have mostly been described in patients suffering from alcoholic liver disease, chronic hepatitis, hepatocellular carcinoma and non-alcoholic fatty liver disease. Interestingly, from this extensive literature survey, it became apparent that giant mitochondria or megamitochondria present themselves with or without highly organised crystal-like intramitochondrial inclusions. The origin, formation and potential role of giant mitochondria remain to-date largely unanswered. Likewise, the biochemical composition of the well-organised crystal-like inclusions and their possible impact on mitochondrial function is unclear. Herein, concepts about the possible mechanism of their formation and three-dimensional architecture will be approached. We will furthermore discuss their importance in diagnostics, including future research outlooks and potential therapeutic interventions to cure liver disease where giant mitochondria are implemented.

Post-translational modifications of histone and non-histone proteins in epigenetic regulation and translational applications in alcohol-associated liver disease: Challenges and research opportunities

Epigenetic regulation is a process that takes place through adaptive cellular pathways influenced by environmental factors and metabolic changes to modulate gene activity with heritable phenotypic variations without altering the DNA sequences of many target genes. Epigenetic regulation can be facilitated by diverse mechanisms: many different types of post-translational modifications (PTMs) of histone and non-histone nuclear proteins, DNA methylation, altered levels of noncoding RNAs, incorporation of histone variants, nucleosomal positioning, chromatin remodeling, etc. These factors modulate chromatin structure and stability with or without the involvement of metabolic products, depending on the cellular context of target cells or environmental stimuli, such as intake of alcohol (ethanol) or Western-style high-fat diets. Alterations of epigenetics have been actively studied, since they are frequently associated with multiple disease states. Consequently, explorations of epigenetic regulation have recently shed light on the pathogenesis and progression of alcohol-associated disorders. In this review, we highlight the roles of various types of PTMs, including less-characterized modifications of nuclear histone and non-histone proteins, in the epigenetic regulation of alcohol-associated liver disease (ALD) and other disorders. We also describe challenges in characterizing specific PTMs and suggest future opportunities for basic and translational research to prevent or treat ALD and many other disease states.

Zonal expression of StARD1 and oxidative stress in alcoholic-related liver disease

Alcoholic-related liver disease (ALD) is one of the leading causes of chronic liver disease and morbidity. Unfortunately, the pathogenesis of ALD is still incompletely understood. StARD1 has emerged as a key player in other etiologies of chronic liver disease, and alcohol-induced liver injury exhibits zonal distribution. Here, we report that StARD1 is predominantly expressed in perivenous (PV) zone of liver sections from mice-fed chronic and acute-on-chronic ALD models compared to periportal (PP) area and is observed as early as 10 days of alcohol feeding. Ethanol and chemical hypoxia induced the expression of StARD1 in isolated primary mouse hepatocytes. The zonal-dependent expression of StARD1 resulted in the accumulation of cholesterol in mitochondria and increased lipid peroxidation in PV hepatocytes compared to PP hepatocytes, effects that were abrogated in PV hepatocytes upon hepatocyte-specific Stard1 KO mice. Transmission electron microscopy indicated differential glycogen and lipid droplets content between PP and PV areas, and alcohol feeding decreased glycogen content in both areas while increased lipid droplets content preferentially in PV zone. Moreover, transmission electron microscopy revealed that mitochondria from PV zone exhibited reduced length with respect to PP area, and alcohol feeding increased mitochondrial number, particularly, in PV zone. Extracellular flux analysis indicated lower maximal respiration and spared respiratory capacity in control PV hepatocytes that were reversed upon alcohol feeding. These findings reveal a differential morphology and functional activity of mitochondria between PP and PV hepatocytes following alcohol feeding and that StARD1 may play a key role in the zonal-dependent liver injury characteristic of ALD.

Fatty Liver Disease, Metabolism and Alcohol Interplay: A Comprehensive Review

Non-alcoholic fatty liver disease (NAFLD) is the most common cause of chronic liver disease worldwide, and its incidence has been increasing in recent years because of the high prevalence of obesity and metabolic syndrome in the Western population. Alcohol-related liver disease (ArLD) is the most common cause of cirrhosis and constitutes the leading cause of cirrhosis-related deaths worldwide. Both NAFLD and ArLD constitute well-known causes of liver damage, with some similarities in their pathophysiology. For this reason, they can lead to the progression of liver disease, being responsible for a high proportion of liver-related events and liver-related deaths. Whether ArLD impacts the prognosis and progression of liver damage in patients with NAFLD is still a matter of debate. Nowadays, the synergistic deleterious effect of obesity and diabetes is clearly established in patients with ArLD and heavy alcohol consumption. However, it is still unknown whether low to moderate amounts of alcohol are good or bad for liver health. The measurement and identification of the possible synergistic deleterious effect of alcohol consumption in the assessment of patients with NAFLD is crucial for clinicians, since early intervention, advising abstinence and controlling cardiovascular risk factors would improve the prognosis of patients with both comorbidities. This article seeks to perform a comprehensive review of the pathophysiology of both disorders and measure the impact of alcohol consumption in patients with NAFLD.