Genome-wide DNA methylation profiling in nonalcoholic fatty liver reveals predictive aberrant methylation in PRKCE and SEC14L3 promoters

Role of Folate in Liver Diseases

Folate is a water-soluble B vitamin involved in the synthesis of purines and pyrimidines and is one of the essential vitamins for human growth and reproduction. Folate deficiency due to low dietary intake, poor absorption of folate, and alterations in folate metabolism due to genetic defects or drug interactions significantly increases the risk of diseases such as neural tube defects, cardiovascular disease, cancer, and cognitive dysfunction. Recent studies have shown that folate deficiency can cause hyperhomocysteinemia, which increases the risk of hypertension and cardiovascular disease, and that high homocysteine levels are an independent risk factor for liver fibrosis and cirrhosis. In addition, folate deficiency results in increased secretion of pro-inflammatory factors and impaired lipid metabolism in the liver, leading to lipid accumulation in hepatocytes and fibrosis. There is substantial evidence that folate deficiency contributes to the development and progression of a variety of liver diseases, including non-alcoholic fatty liver disease (NAFLD), non-alcoholic steatohepatitis (NASH), alcoholic liver disease (ALD), viral hepatitis, hepatic fibrosis, and liver cancer. Here we review key studies on the role of folate in the pathophysiology of liver diseases, summarize the current status of studies on folate in the treatment of liver diseases, and speculate that folate may be a potential therapeutic target for liver diseases.

A crosstalk between epigenetic modulations and non-alcoholic fatty liver disease progression

Non-alcoholic fatty liver disease (NAFLD) has recently emerged as a major public health concern worldwide due to its rapidly rising prevalence and its potential to progress into end-stage liver disease. While the precise pathophysiology underlying NAFLD remains incompletely understood, it is strongly associated with various environmental triggers and other metabolic disorders. Epigenetics examines changes in gene expression that are not caused by alterations in the DNA sequence itself. There is accumulating evidence that epigenetics plays a key role in linking environmental cues to the onset and progression of NAFLD. Our understanding of how epigenetic mechanisms contribute to NAFLD pathophysiology has expanded considerably in recent years as research on the epigenetics of NAFLD has developed. This review summarizes recent insights into major epigenetic processes that have been implicated in NAFLD pathogenesis including DNA methylation, histone acetylation, and microRNAs that have emerged as promising targets for further investigation. Elucidating epigenetic mechanisms in NAFLD may uncover novel diagnostic biomarkers and therapeutic targets for this disease. However, many questions have remained unanswered regarding how epigenetics promotes NAFLD onset and progression. Additional studies are needed to further characterize the epigenetic landscape of NAFLD and validate the potential of epigenetic markers as clinical tools. Nevertheless, an enhanced understanding of the epigenetic underpinnings of NAFLD promises to provide key insights into disease mechanisms and pave the way for novel prognostic and therapeutic approaches.

Whole-genome DNA methylation and gene expression profiling in the livers of mice with nonalcoholic steatohepatitis

AIMS

Non-alcoholic fatty liver disease (NAFLD) has emerged as one of the major causes of liver-related morbidity and mortality. It ranges simple steatosis to non-alcoholic steatohepatitis (NASH). Previous studies have shown that epigenetic factors, such as DNA methylation, can contribute to the development and progression of simple steatosis. However, the profiling of whole-genome DNA methylation remains poorly characterized in NASH.

MAIN METHODS

In this study, we established a mouse model of diet-induced NASH, by maintaining male mice on a high-fructose-high-cholesterol diet (HFHC), to generate hepatic steatosis, inflammation and injury. We profiled hepatic gene expression by RNA-Sequencing and locus-specific 5-methylcytosine level, using Whole Genome Bisulfite Sequencing (WGBS).

KEY FINDINGS

We identified >1000 differentially methylated regions in NASH versus control group, indicating that NASH diet could modulate the liver methylome. Furthermore, integrated analysis of methylome and transcriptome identified certain key methylated genes and pathways, which may be involved in steroid metabolism and inflammation response. The liver methylation levels of key genes especially Tgfb, Msn, Iqgap1, Cyba, Fcgr1 decreased, and their consequent increased expression may lead to NASH development.

SIGNIFICANCE

We found that HFHC diet-induced NASH could induces genome-wide differential DNA methylation changes. Thus, we proposed that DNA methylation profiles of genomes may be a useful signature of gene transcription and may play an important role in the development of NASH. We also screened and validated the changes of key genes, which may provide new perspectives for the mechanistic study of NASH in future.

Alcohol Dependence Modulates Amygdalar mTORC2 and PKCε Expression in a Rodent Model

Multiple alcohol use disorder (AUD)-related behavioral alterations are governed by protein kinase C epsilon (PKCε), particularly in the amygdala. Protein kinase C (PKC) is readily phosphorylated at Ser729 before activation by the mTORC2 protein complex. In keeping with this, the current study was conducted to assess the variations in mTORC2 and PKCε during different ethanol exposure stages. The following groups of rats were employed: control, acute, chronic, ethanol withdrawal (EW), and EW + ethanol (EtOH). Ethanol-containing and non-ethanol-containing modified liquid diets (MLDs) were administered for 27 days. On day 28, either saline or ethanol (2.5 g/kg, 20% v/v) was intraperitoneally administered, followed by bilateral amygdala extraction. PKCε mRNA levels were noticeably increased in the amygdala of the EW + EtOH and EW groups. Following chronic ethanol consumption, the stress-activated map kinase-interacting protein 1 (Sin1) gene expression was markedly decreased. In the EW, EW + EtOH, and chronic ethanol groups, there was a profound increase in the protein expression of mTOR, Sin1, PKCε, and phosphorylated PKCε (Ser729). The PKCε gene and protein expressions showed a statistically significant moderate association, according to a correlation analysis. Our results suggest that an elevated PKCε protein expression in the amygdala during EW and EW + EtOH occurred at the transcriptional level. However, an elevation in the PKCε protein expression, but not its mRNA, after chronic ethanol intake warrants further investigation to fully understand the signaling pathways during different episodes of AUD.

Insights into the role of nucleotide methylation in metabolic-associated fatty liver disease

Metabolic-associated fatty liver disease (MAFLD) is a chronic liver disease characterized by fatty infiltration of the liver. In recent years, the MAFLD incidence rate has risen and emerged as a serious public health concern. MAFLD typically progresses from the initial hepatocyte steatosis to steatohepatitis and then gradually advances to liver fibrosis, which may ultimately lead to cirrhosis and carcinogenesis. However, the potential evolutionary mechanisms still need to be clarified. Recent studies have shown that nucleotide methylation, which was directly associated with MAFLD's inflammatory grading, lipid synthesis, and oxidative stress, plays a crucial role in the occurrence and progression of MAFLD. In this review, we highlight the regulatory function and associated mechanisms of nucleotide methylation modification in the progress of MAFLD, with a particular emphasis on its regulatory role in the inflammation of MAFLD, including the regulation of inflammation-related immune and metabolic microenvironment. Additionally, we summarize the potential value of nucleotide methylation in the diagnosis and treatment of MAFLD, intending to provide references for the future investigation of MAFLD.

Epigenetics and mitochondrial dysfunction insights into the impact of the progression of non-alcoholic fatty liver disease

A metabolic problem occurs when regular functions of the body are disrupted due to an undesirable imbalance. Nonalcoholic fatty liver disease (NAFLD) is considered as one of the most common in this category. NAFLD is subclassified and progresses from lipid accumulation to cirrhosis before advancing to hepatocellular cancer. In spite of being a critical concern, the standard treatment is inadequate. Metformin, silymarin, and other nonspecific medications are used in the management of NAFLD. Aside from this available medicine, maintaining a healthy lifestyle has been emphasized as a means of combating this. Epigenetics, which has been attributed to NAFLD, is another essential feature of this disease that has emerged as a result of several sorts of research. The mechanisms by which DNA methylation, noncoding RNA, and histone modification promote NAFLD have been extensively researched. Another organelle, mitochondria, which play a pivotal role in biological processes, contributes to the global threat. Individuals with NAFLD have been documented to have a multitude of alterations and malfunctioning. Mitochondria are mainly concerned with the process of energy production and regulation of the signaling pathway on which the fate of a cell relies. Modulation of mitochondria leads to elevated lipid deposition in the liver. Further, changes in oxidation states result in an impaired balance between the antioxidant system and reactive oxygen species directly linked to mitochondria. Hence mitochondria have a definite role in potentiating NAFLD. In this regard, it is essential to consider the role of epigenetics as well as mitochondrial contribution while developing a medication or therapy with the desired accuracy.

Deciphering the role of aberrant DNA methylation in NAFLD and NASH

The global incidence of nonalcoholic fatty liver disease (NAFLD) is mounting incessantly, and it is emerging as the most frequent cause of chronic and end stage liver disorders. It is the starting point for a range of conditions from simple steatosis to more progressive nonalcoholic steatohepatitis (NASH) and associated hepatocellular carcinoma (HCC). Dysregulation of insulin secretion and dyslipidemia due to obesity and other lifestyle variables are the primary contributors to establishment of NAFLD. Onset and progression of NAFLD is orchestrated by an interplay of metabolic environment with genetic and epigenetic factors. An incompletely understood mechanism of NAFLD progression has greatly hampered the progress in identification of novel prognostic and therapeutic strategies. Emerging evidence suggests altered DNA methylation pattern as a key determinant of NAFLD pathogenesis. Environmental and lifestyle factors can manipulate DNA methylation patterns in a reversible manner, which manifests as changes in gene expression. In this review we attempt to highlight the importance of DNA methylation in establishment and progression of NAFLD. Development of novel diagnostic, prognostic and therapeutic strategies centered around DNA methylation signatures and modifiers has also been explored.

An Update in Epigenetics in Metabolic-Associated Fatty Liver Disease

Metabolic-associated fatty liver disease (MAFLD) is characterized by hepatic steatosis accompanied by one of three features: overweight or obesity, T2DM, or lean or normal weight with evidence of metabolic dysregulation. It is distinguished by excessive fat accumulation in hepatocytes, and a decrease in the liver's ability to oxidize fats, the accumulation of ectopic fat, and the activation of proinflammatory pathways. Chronic damage will keep this pathophysiologic cycle active causing progression from hepatic steatosis to cirrhosis and eventually, hepatocarcinoma. Epigenetics affecting gene expression without altering DNA sequence allows us to study MAFLD pathophysiology from a different perspective, in which DNA methylation processes, histone modifications, and miRNAs expression have been closely associated with MAFLD progression. However, these considerations also faced us with the circumstance that modifying those epigenetics patterns might lead to MAFLD regression. Currently, epigenetics is an area of great interest because it could provide new insights in therapeutic targets and non-invasive biomarkers. This review comprises an update on the role of epigenetic patterns, as well as innovative therapeutic targets and biomarkers in MAFLD.