Dysregulated Epigenetic Modifications in the Pathogenesis of NAFLD-HCC

Past, present, and future of chemically induced hepatocarcinogenesis rodent models: Perspectives concerning classic and new cancer hallmarks

Hepatocellular carcinoma (HCC), the main primary liver cancer, accounts for 5 % of all incident cases and 8.4 % of all cancer-related deaths worldwide. HCC displays a spectrum of environmental risk factors (viral chronic infections, aflatoxin exposure, alcoholic- and nonalcoholic fatty liver diseases) that result in molecular complexity and heterogeneity, contributing to a rising epidemiological burden, poor prognosis, and non-satisfactory treatment options. The emergence of HCC (i.e., hepatocarcinogenesis) is a multistep and complex process that addresses many (epi)genetic alterations and phenotypic traits, the so-called cancer hallmarks. "Polymorphic microbiomes", "epigenetic reprogramming", "senescent cells" and "unlocking phenotypic plasticity" are trending hallmarks/enabling features in cancer biology. As the main molecular drivers of HCC are still undruggable, chemically induced in vivo models of hepatocarcinogenesis are useful tools in preclinical research. Thus, this narrative review aimed at recapitulating the basic features of chemically induced rodent models of hepatocarcinogenesis, eliciting their permanent translational value regarding the "classic" and the "new" cancer hallmarks/enabling features. We gathered state-of-art preclinical evidence on non-cirrhotic, inflammation-, alcoholic liver disease- and nonalcoholic fatty liver-associated HCC models, demonstrating that these bioassays indeed express the recently added hallmarks, as well as reflect the interplay between classical and new cancer traits. Our review demonstrated that these protocols remain valuable for translational preclinical application, as they recapitulate trending features of cancer science. Further "omics-based" approaches are warranted while multimodel investigations are encouraged in order to avoid "model-biased" responses.

Non-alcoholic fatty liver disease establishment and progression: genetics and epigenetics as relevant modulators of the pathology

BACKGROUND

Non-alcoholic fatty liver disease (NAFLD) results from metabolic dysfunctions that affect more than one-third of the world population. Over the last decades, scientific investigations have clarified many details on the pathology establishment and development; however, effective therapeutics approaches are still evasive. In addition, studies demonstrated that NAFLD establishment and progression are related to several etiologies. Recently, genetics and epigenetics backgrounds have emerged as relevant elements to the pathology onset, and, hence, deserve deep investigation to clarify molecular details on NAFLD signaling, which may be correlated with population behavior. Thus, to minimize the global problem, public health and public policies should take advantage of studies on NAFLD over the next following decades.

METHODS

In this context, we have performed a selective literature review focusing on biochemistry of lipid metabolism, genetics, epigenetics, and the ethnicity as strong elements that drive NAFLD establishment.

RESULTS

Considering the etiological agents that acts on NAFLD development and progression, the genetics and the epigenetics emerged as relevant factors. Genetics acts as a powerful element in the establishment and progression of the NAFLD. Over the last decades, details concerning genes and their polymorphisms, as well as epigenetics, have been considered relevant elements in the systems biology of diseases, and their effects on NAFLD should be considered in-depth, as well as the ethnicity, clarifying whether people are susceptible to liver diseases. Moreover, the endemicity and social problems of hepatic disfunction are far to be solved, which require a combined effort of various sectors of society.

CONCLUSION

Hence, the elements presented and discussed in this short review demonstrated their relevance to the physiological control of NAFLD, opening perspectives for research to develop new strategy to treat fatty liver diseases.

Nonalcoholic Fatty Liver Disease (NAFLD) Name Change: Requiem or Reveille?

Nonalcoholic fatty liver disease (NAFLD) affects about a quarter of the world's population and poses a major health and economic burden globally. Recently, there have been hasty attempts to rename NAFLD to metabolic-associated fatty liver disease (MAFLD) despite the fact that there is no scientific rationale for this. Quest for a "positive criterion" to diagnose the disease and destigmatizing the disease have been the main reasons put forth for the name change. A close scrutiny of the pathogenesis of NAFLD would make it clear that NAFLD is a heterogeneous disorder, involving different pathogenic mechanisms of which metabolic dysfunction-driven hepatic steatosis is only one. Replacing NAFLD with MAFLD would neither enhance the legitimacy of clinical practice and clinical trials, nor improve clinical care or move NAFLD research forward. Rather than changing the nomenclature without a strong scientific backing to support such a change, efforts should be directed at understanding NAFLD pathogenesis across diverse populations and ethnicities which could potentially help develop newer therapeutic options.

Developmental programming: Prenatal testosterone-induced changes in epigenetic modulators and gene expression in metabolic tissues of female sheep

Prenatal testosterone (T)-treated female sheep manifest peripheral insulin resistance and tissue-specific changes in insulin sensitivity with liver and muscle manifesting insulin resistance accompanied by inflammatory, oxidative and lipotoxic state. In contrast, visceral (VAT) and subcutaneous (SAT) adipose tissues are insulin sensitive in spite of VAT manifesting changes in inflammatory and oxidative state. We hypothesized that prenatal T-induced changes in tissue-specific insulin resistance arise from disrupted lipid storage and metabolism gene expression driven by changes in DNA and histone modifying enzymes. Changes in gene expression were assessed in liver, muscle and 4 adipose (VAT, SAT, epicardiac [ECAT] and perirenal [PRAT]) depots collected from control and prenatal T-treated female sheep. Prenatal T-treatment increased lipid droplet and metabolism genes PPARA and PLIN1 in liver, SREBF and PLIN1 in muscle and showed a trend for decrease in PLIN2 in PRAT. Among epigenetic modifying enzymes, prenatal T-treatment increased expression of 1) DNMT1 in liver and DNMT3A in VAT, PRAT, muscle and liver; 2) HDAC1 in ECAT, HDAC2 in muscle with decrease in HDAC3 in VAT; 3) EP300 in VAT and ECAT; and 4) KDM1A in VAT with increases in liver histone acetylation. Increased lipid storage and metabolism genes in liver and muscle are consistent with lipotoxicity in these tissues with increased histone acetylation likely contributing to increased liver PPARA. These findings are suggestive that metabolic defects in prenatal T-treated sheep may arise from changes in key genes mediated, in part, by tissue-specific changes in epigenetic-modifying enzymes.

Genetics and epigenetics purpose in nonalcoholic fatty liver disease

INTRODUCTION

nonalcoholic fatty liver disease (NAFLD) comprises a broad spectrum of diseases, which can progress from benign steatosis to nonalcoholic steatohepatitis, liver cirrhosis and hepatocellular carcinoma. NAFLD is the most common chronic liver disease in developed countries, affecting approximately 25% of the general population. Insulin resistance, adipose tissue dysfunction, mitochondrial and endoplasmic reticulum stress, chronic inflammation, genetic and epigenetic factors are NAFLD triggers that control the disease susceptibility and progression.

AREAS COVERED

In recent years a large number of investigations have been carried out to elucidate genetic and epigenetic factors in the disease pathogenesis, as well as the search for diagnostic markers and therapeutic targets. This paper objective is to report the most studied genetic and epigenetic variants around NAFLD.

EXPERT OPINION

NAFLD lead to various comorbidities, which have a considerable impact on the patient wellness and life quality, as well as on the costs they generate for the country's health services. It is essential to continue with molecular research, since it could be used as a clinical tool for prognosis and disease severity. Specifically, in the field of hepatology, plasma miRNAs could provide a novel tool in liver diseases diagnosis and monitoring, representing an alternative to invasive diagnostic procedures.

A Role for the Biological Clock in Liver Cancer

The biological clock controls at the molecular level several aspects of mammalian physiology, by regulating daily oscillations of crucial biological processes such as nutrient metabolism in the liver. Disruption of the circadian clock circuitry has recently been identified as an independent risk factor for cancer and classified as a potential group 2A carcinogen to humans. Hepatocellular carcinoma (HCC) is the prevailing histological type of primary liver cancer, one of the most important causes of cancer-related death worldwide. HCC onset and progression is related to B and C viral hepatitis, alcoholic and especially non-alcoholic fatty liver disease (NAFLD)-related milieu of fibrosis, cirrhosis, and chronic inflammation. In this review, we recapitulate the state-of-the-art knowledge on the interplay between the biological clock and the oncogenic pathways and mechanisms involved in hepatocarcinogenesis. Finally, we propose how a deeper understanding of circadian clock circuitry–cancer pathways’ crosstalk is promising for developing new strategies for HCC prevention and management.