Gene-Environmental Interactions as Metabolic Drivers of Nonalcoholic Steatohepatitis

Fibrosis and Hepatocarcinogenesis: Role of Gene-Environment Interactions in Liver Disease Progression

The liver is a complex organ that performs vital functions in the body. Despite its extraordinary regenerative capacity compared to other organs, exposure to chemical, infectious, metabolic and immunologic insults and toxins renders the liver vulnerable to inflammation, degeneration and fibrosis. Abnormal wound healing response mediated by aberrant signaling pathways causes chronic activation of hepatic stellate cells (HSCs) and excessive accumulation of extracellular matrix (ECM), leading to hepatic fibrosis and cirrhosis. Fibrosis plays a key role in liver carcinogenesis. Once thought to be irreversible, recent clinical studies show that hepatic fibrosis can be reversed, even in the advanced stage. Experimental evidence shows that removal of the insult or injury can inactivate HSCs and reduce the inflammatory response, eventually leading to activation of fibrolysis and degradation of ECM. Thus, it is critical to understand the role of gene-environment interactions in the context of liver fibrosis progression and regression in order to identify specific therapeutic targets for optimized treatment to induce fibrosis regression, prevent HCC development and, ultimately, improve the clinical outcome.

The Interplay between Endocrine-Disrupting Chemicals and the Epigenome towards Metabolic Dysfunction-Associated Steatotic Liver Disease: A Comprehensive Review

Metabolic dysfunction-associated steatotic liver disease (MASLD), described as the most prominent cause of chronic liver disease worldwide, has emerged as a significant public health issue, posing a considerable challenge for most countries. Endocrine-disrupting chemicals (EDCs), commonly found in daily use items and foods, are able to interfere with nuclear receptors (NRs) and disturb hormonal signaling and mitochondrial function, leading, among other metabolic disorders, to MASLD. EDCs have also been proposed to cause transgenerationally inherited alterations leading to increased disease susceptibility. In this review, we are focusing on the most prominent linking pathways between EDCs and MASLD, their role in the induction of epigenetic transgenerational inheritance of the disease as well as up-to-date practices aimed at reducing their impact.

Exploring the role of genetic variations in NAFLD: implications for disease pathogenesis and precision medicine approaches

Non-alcoholic fatty liver disease (NAFLD) is one of the leading causes of chronic liver diseases, affecting more than one-quarter of people worldwide. Hepatic steatosis can progress to more severe forms of NAFLD, including NASH and cirrhosis. It also may develop secondary diseases such as diabetes and cardiovascular disease. Genetic and environmental factors regulate NAFLD incidence and progression, making it a complex disease. The contribution of various environmental risk factors, such as type 2 diabetes, obesity, hyperlipidemia, diet, and sedentary lifestyle, to the exacerbation of liver injury is highly understood. Nevertheless, the underlying mechanisms of genetic variations in the NAFLD occurrence or its deterioration still need to be clarified. Hence, understanding the genetic susceptibility to NAFLD is essential for controlling the course of the disease. The current review discusses genetics' role in the pathological pathways of NAFLD, including lipid and glucose metabolism, insulin resistance, cellular stresses, and immune responses. Additionally, it explains the role of the genetic components in the induction and progression of NAFLD in lean individuals. Finally, it highlights the utility of genetic knowledge in precision medicine for the early diagnosis and treatment of NAFLD patients.

Whole-Exome Sequencing (WES) Reveals Novel Sex-Specific Gene Variants in Non-Alcoholic Steatohepatitis (MASH)

Non-alcoholic steatohepatitis (NASH, also known as MASH) is a severe form of non-alcoholic fatty liver disease (NAFLD, also known as MASLD). Emerging data indicate that the progression of the disease to MASH is higher in postmenopausal women and that genetic susceptibility increases the risk of MASH-related cirrhosis. This study aimed to investigate the association between genetic polymorphisms in MASH and sexual dimorphism. We applied whole-exome sequencing (WES) to identify gene variants in 8 age-adjusted matched pairs of livers from both male and female patients. Sequencing alignment, variant calling, and annotation were performed using standard methods. Polymerase chain reaction (PCR) coupled with Sanger sequencing and immunoblot analysis were used to validate specific gene variants. cBioPortal and Gene Set Enrichment Analysis (GSEA) were used for actionable target analysis. We identified 148,881 gene variants, representing 57,121 and 50,150 variants in the female and male cohorts, respectively, of which 251 were highly significant and MASH sex-specific (p < 0.0286). Polymorphisms in CAPN14, SLC37A3, BAZ1A, SRP54, MYH11, ABCC1, and RNFT1 were highly expressed in male liver samples. In female samples, Polymorphisms in RGSL1, SLC17A2, HFE, NLRC5, ACTN4, SBF1, and ALPK2 were identified. A heterozygous variant 1151G>T located on 18q21.32 for ALPK2 (rs3809983) was validated by Sanger sequencing and expressed only in female samples. Immunoblot analysis confirmed that the protein level of β-catenin in female samples was 2-fold higher than normal, whereas ALPK2 expression was 0.5-fold lower than normal. No changes in the protein levels of either ALPK2 or β-catenin were observed in male samples. Our study suggests that the perturbation of canonical Wnt/β-catenin signaling observed in postmenopausal women with MASH could be the result of polymorphisms in ALPK2.

The application of organoid models in research into metabolic diseases

Metabolic diseases have become a major threat to human health worldwide as a result of changing lifestyles. The exploration of the underlying molecular mechanisms of metabolic diseases and the development of improved therapeutic methods have been hindered by the lack of appropriate human experimental models. Organoids are three-dimensional in vitro models of self-renewing cells that spontaneously self-organize into structures similar to the corresponding in vivo tissues, recapitulating the original tissue function. Off-body organoid technology has been successfully applied to disease modelling, developmental biology, regenerative medicine, and tumour precision medicine. This new generation of biological models has received widespread attention. This article focuses on the construction process and research progress with regard to organoids related to metabolic diseases in recent years, and looks forward to their prospective applications.

Familial coaggregation of MASLD with hepatocellular carcinoma and adverse liver outcomes: Nationwide multigenerational cohort study

BACKGROUND & AIMS

Metabolic dysfunction-associated steatotic liver disease (MASLD; formerly NAFLD) is the fastest growing cause of hepatocellular carcinoma (HCC) worldwide. However, whether family members of individuals with MASLD also share an increased risk of developing HCC is unknown.

METHODS

This nationwide multigenerational cohort study involved family members of all Swedish adults diagnosed with biopsy-proven MASLD (1969-2017), and matched general population comparators. Using the Swedish Multi-generation Register, we identified 38,018 first-degree relatives (FDRs: parents, siblings, offspring) and 9,381 spouses of patients with MASLD, as well as 197,303 comparator FDRs and 47,572 comparator spouses. We used Cox proportional hazards models to calculate adjusted hazard ratios (aHRs) for HCC, major adverse liver outcomes (cirrhosis, decompensated liver disease or liver transplantation), liver-related mortality, extrahepatic cancer, and non-liver-related mortality.

RESULTS

Over a median of 17.6 years, the rate of the primary outcome HCC was higher in MASLD FDRs vs. comparator FDRs (13 vs. 8/100,000 person-years [PY]; aHR 1.80, 95% CI 1.36-2.37). The HCC risk was further increased in FDRs of individuals with liver fibrosis/cirrhosis (aHR 2.14, 95% CI 1.07-4.27; PHeterogeneity = 0.03). MASLD FDRs also had higher rates of major adverse liver outcomes (73 vs. 51/100,000 PY; aHR 1.52, 95% CI 1.36-1.69) and liver-related mortality (20 vs. 11/100,000 PY; aHR 2.14, 95% CI 1.67-2.74). MASLD FDRs with any concomitant chronic liver condition experienced accelerated progression of liver disease (aHR 1.47, 95% CI 1.29-1.67). MASLD spouses were at higher risks of major adverse liver outcomes (86 vs. 74/100,000 PY; aHR 1.23, 95% CI 1.01-1.51) and liver-related mortality (25 vs. 19/100,000 PY; aHR 1.93, 95% CI 1.15-3.23), but not of HCC (aHR 1.43, 95% CI 0.87-2.35).

CONCLUSIONS

There is distinct familial clustering of adverse liver-related outcomes in families of individuals with biopsy-proven MASLD, with higher relative risks of HCC, progressive liver disease, and liver-related mortality, but absolute risks are low.

IMPACT AND IMPLICATIONS

Metabolic dysfunction-associated steatotic liver disease (MASLD; formerly termed NAFLD) clusters in families with high genetic susceptibility and shared environmental risk factors, but the risks of developing hepatocellular carcinoma and other major liver-related outcomes in family members of individuals with MASLD are largely unknown. This large nationwide multigenerational cohort study involving family members (first-degree relatives and spouses) of individuals with biopsy-proven MASLD and of matched general population comparators found slightly increased risks of hepatocellular carcinoma in first-degree relatives, and of developing cirrhosis and liver-related mortality in all family members of individuals with biopsy-proven MASLD. The findings of this study provide large-scale evidence to inform clinical practice guidelines for recommendations on the early identification of individuals at higher risk of liver-related morbidity and mortality.

Modeling Liver Development and Disease in a Dish

Historically, biological research has relied primarily on animal models. While this led to the understanding of numerous human biological processes, inherent species-specific differences make it difficult to answer certain liver-related developmental and disease-specific questions. The advent of 3D organoid models that are either derived from pluripotent stem cells or generated from healthy or diseased tissue-derived stem cells have made it possible to recapitulate the biological aspects of human organs. Organoid technology has been instrumental in understanding the disease mechanism and complements animal models. This review underscores the advances in organoid technology and specifically how liver organoids are used to better understand human-specific biological processes in development and disease. We also discuss advances made in the application of organoid models in drug screening and personalized medicine.

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.

Non-alcoholic Steatohepatitis in Asians: Current Perspectives and Future Directions

Non-alcoholic steatohepatitis (NASH) is a subset of non-alcoholic fatty liver disease (NAFLD), which, apart from excess fat in the liver, may be characterised by some level of inflammatory infiltration and fibrogenesis, occasionally progressing to liver cirrhosis or hepatocellular carcinoma (HCC). The objective of the current review is to elucidate the rising prevalence, the role of microbiome and genetics in pathogenesis, diagnostic challenges, and novel treatment alternatives for NASH. Newer diagnostic techniques are being developed since using liver biopsy in a larger population is not a reasonable option and is primarily restricted to clinical research, at least in developing countries. Besides these technical challenges, another important factor leading to deviation from guideline practice is the lack of health insurance coverage in countries like India. It leads to reluctance on the part of physicians and patients to delay required tests to curb out-of-pocket expenditure. There is no cure for NASH, with liver transplantation remaining the last option for those who progress to end-stage liver disease (ESLD) or are detected with early-stage HCC. Thus, lifestyle modification remains the only viable option for many, but compliance and long-term adherence remain major challenges. In obese individuals, bariatric surgery and weight reduction have shown favourable results. In patients with less severe obesity, endoscopic bariatric metabolic therapies (EBMT) are rapidly emerging as less invasive therapies. However, access and acceptability remain poor for these weight reduction methods. Therefore, intense research is being conducted for potential newer drug classes with several agents currently in phase II or III of clinical development. Some of these have demonstrated promising results, such as a reduction in hepatic fat content, and attenuation of fibrosis with an acceptable tolerability profile in phase II studies. The developments in the management of NASH have been fairly encouraging. Further well-designed long-term prospective studies should be undertaken to generate evidence with definitive results.

The Role of Choline, Soy Isoflavones, and Probiotics as Adjuvant Treatments in the Prevention and Management of NAFLD in Postmenopausal Women

Nonalcoholic fatty liver disease (NAFLD) is a prevalent condition among postmenopausal women that can lead to severe liver dysfunction and increased mortality. In recent years, research has focused on identifying potential lifestyle dietary interventions that may prevent or treat NAFLD in this population. Due to the complex and multifactorial nature of NAFLD in postmenopausal women, the disease can present as different subtypes, with varying levels of clinical presentation and variable treatment responses. By recognizing the significant heterogeneity of NAFLD in postmenopausal women, it may be possible to identify specific subsets of individuals who may benefit from targeted nutritional interventions. The purpose of this review was to examine the current evidence supporting the role of three specific nutritional factors-choline, soy isoflavones, and probiotics-as potential nutritional adjuvants in the prevention and treatment of NAFLD in postmenopausal women. There is promising evidence supporting the potential benefits of these nutritional factors for NAFLD prevention and treatment, particularly in postmenopausal women, and further research is warranted to confirm their effectiveness in alleviating hepatic steatosis in this population.

CD24 Gene Expression as a Risk Factor for Non-Alcoholic Fatty Liver Disease

In light of increasing NAFLD prevalence, early detection and diagnosis are needed for decision-making in clinical practice and could be helpful in the management of patients with NAFLD. The goal of this study was to evaluate the diagnostic accuracy of CD24 gene expression as a non-invasive tool to detect hepatic steatosis for diagnosis of NAFLD at early stage. These findings will aid in the creation of a viable diagnostic approach.

METHODS

This study enrolled eighty individuals divided into two groups; a study group included forty cases with bright liver and a group of healthy subjects with normal liver. Steatosis was quantified by CAP. Fibrosis assessment was performed by FIB-4, NFS, Fast-score, and Fibroscan. Liver enzymes, lipid profile, and CBC were evaluated. Utilizing RNA extracted from whole blood, the CD24 gene expression was detected using real-time PCR technique.

RESULTS

It was detected that expression of CD24 was significantly higher in patients with NAFLD than healthy controls. The median fold change was 6.56 higher in NAFLD cases compared to control subjects. Additionally, CD24 expression was higher in cases with fibrosis stage F1 compared to those with fibrosis stage F0, as the mean expression level of CD24 was 7.19 in F0 cases as compared to 8.65 in F1 patients but without significant difference (p = 0.588). ROC curve analysis showed that CD24 ∆CT had significant diagnostic accuracy in the diagnosis of NAFLD (p = 0.034). The optimum cutoff for CD24 was 1.83 for distinguishing patients with NAFLD from healthy control with sensitivity 55% and specificity 74.4%; and an area under the ROC curve (AUROC) of 0.638 (95% CI: 0.514-0.763) was determined.

CONCLUSION

In the present study, CD24 gene expression was up-regulated in fatty liver. Further studies are required to confer its diagnostic and prognostic value in the detection of NAFLD, clarify its role in the progression of hepatocyte steatosis, and to elucidate the mechanism of this biomarker in the progression of disease.

Hepatocyte Smoothened Activity Controls Susceptibility to Insulin Resistance and Nonalcoholic Fatty Liver Disease

BACKGROUND & AIMS

Nonalcoholic steatohepatitis (NASH), a leading cause of cirrhosis, strongly associates with the metabolic syndrome, an insulin-resistant proinflammatory state that disrupts energy balance and promotes progressive liver degeneration. We aimed to define the role of Smoothened (Smo), an obligatory component of the Hedgehog signaling pathway, in controlling hepatocyte metabolic homeostasis and, thereby, susceptibility to NASH.

METHODS

We conditionally deleted Smo in hepatocytes of healthy chow-fed mice and performed metabolic phenotyping, coupled with single-cell RNA sequencing (RNA-seq), to characterize the role of hepatocyte Smo in regulating basal hepatic and systemic metabolic homeostasis. Liver RNA-seq datasets from 2 large human cohorts were also analyzed to define the relationship between Smo and NASH susceptibility in people.

RESULTS

Hepatocyte Smo deletion inhibited the Hedgehog pathway and promoted fatty liver, hyperinsulinemia, and insulin resistance. We identified a plausible mechanism whereby inactivation of Smo stimulated the mTORC1-SREBP1c signaling axis, which promoted lipogenesis while inhibiting the hepatic insulin cascade. Transcriptomics of bulk and single Smo-deficient hepatocytes supported suppression of insulin signaling and also revealed molecular abnormalities associated with oxidative stress and mitochondrial dysfunction. Analysis of human bulk RNA-seq data revealed that Smo expression was (1) highest in healthy livers, (2) lower in livers with NASH than in those with simple steatosis, (3) negatively correlated with markers of insulin resistance and liver injury, and (4) declined progressively as fibrosis severity worsened.

CONCLUSIONS

The Hedgehog pathway controls insulin sensitivity and energy homeostasis in adult livers. Loss of hepatocyte Hedgehog activity induces hepatic and systemic metabolic stress and enhances susceptibility to NASH by promoting hepatic lipoxicity and insulin resistance.

Metabolic reprogramming of the intestinal microbiome with functional bile acid changes underlie the development of NAFLD

BACKGROUND AND AIMS

Bile acids are hepatic metabolites and have many properties considered to be relevant to the pathophysiology of NAFLD. Circulating levels of the intestinal microbiome-modified bile acid deoxycholate are increased in cirrhosis.

APPROACH AND RESULTS

To further elucidate the role of bile acids and intestinal microbiota linked to bile acids in progressively severe NAFLD, a multiomic study of feces including 16S rRNA sequencing, microbial transcriptomics and metabolomics was performed in a cohort with varying phenotypes of NAFLD. Several bile acids of microbial origin derived from deoxycholic acid (DCA) (glycodeoxycholate, 7-ketodeoxycholic acid, dehydrocholic acid) increased with disease activity and fibrosis stage. These were linked to increased expression of microbial bile salt hydrolase, bile acid operon (BaiCD) and hydroxysteroid dehydrogenases (hdhA) required for DCA and downstream metabolite synthesis providing a mechanistic basis for altered bile acid profiles with disease progression. Bacteroidetes and several genera of Lachnospiraceae family containing DCA generating genes increased with increasing disease severity, whereas several potentially beneficial microbes sensitive to antibacterial effects of DCA e.g., Ruminococcaceae were decreased. The clinical relevance of these data was confirmed in an independent cohort enrolled in a clinical trial for NASH where at entry DCA and its conjugates were associated with advanced fibrosis. In patients treated with placebo, DCA declined in those with fibrosis regression and increased in those with fibrosis progression. DCA rose further in those with compensated cirrhosis when they experienced decompensation.

CONCLUSIONS

These findings demonstrate a role for bile acids and the bile acid dependent microbiome in the development and progression of NAFLD and set the stage to leverage these findings for NASH biomarker development and for therapeutics.

Modelling metabolic diseases and drug response using stem cells and organoids

Metabolic diseases, including obesity, diabetes mellitus and cardiovascular disease, are a major threat to health in the modern world, but efforts to understand the underlying mechanisms and develop rational treatments are limited by the lack of appropriate human model systems. Notably, advances in stem cell and organoid technology allow the generation of cellular models that replicate the histological, molecular and physiological properties of human organs. Combined with marked improvements in gene editing tools, human stem cells and organoids provide unprecedented systems for studying mechanisms of metabolic diseases. Here, we review progress made over the past decade in the generation and use of stem cell-derived metabolic cell types and organoids in metabolic disease research, especially obesity and liver diseases. In particular, we discuss the limitations of animal models and the advantages of stem cells and organoids, including their application to metabolic diseases. We also discuss mechanisms of drug action, understanding the efficacy and toxicity of existing therapies, screening for new treatments and pursuing personalized therapies. We highlight the potential of combining stem cell-derived organoids with gene editing and functional genomics to revolutionize the approach to finding treatments for metabolic diseases.

Association of blood manganese, selenium with steatosis, fibrosis in the National Health and Nutrition Examination Survey, 2017-18

BACKGROUND & AIMS

Chronic liver disease is a growing health burden worldwide. Chronic metal exposures may be associated with non-alcoholic fatty liver disease (NAFLD). We aimed to evaluate the association of blood cadmium (Cd), mercury (Hg), lead (Pb), manganese (Mn), and selenium (Se) with two hallmark features of NAFLD: liver steatosis and fibrosis in the general U.S.

METHODS

We analyzed transient liver elastography data from participants of the National Health and Nutrition Examination Survey (NHANES) 2017-18, using ordinal logistic regression analyses to evaluate the cross-sectional association between blood metal concentrations and clinical stages of steatosis and fibrosis. We applied survey weights, strata, and primary sampling units and analyses were conducted using the R survey package.

RESULTS

4,154 participants were included. Median (IQR) for blood Mn and blood Se were 9.28 (7.48-11.39) and 191.08 (176.55-207.16) μg/L, respectively. Per interquartile range increase of natural log transformed blood Mn, the adjusted odds ratio (OR) (95% CI) was 1.59 (1.13-2.23) for a higher grade of steatosis and 1.16 (0.67-2.00) for liver fibrosis. The corresponding OR for steatosis was 2.00 (1.24-3.24) and 2.14 (1.04-4.42) in Black and Mexican American participants, respectively. The corresponding OR for liver fibrosis was 2.96 (1.42-6.17) for females. Per interquartile range increase of natural log transformed blood Se, the adjusted OR was 2.25 (1.30-3.89) for steatosis but 0.31 (0.13-0.72) for liver fibrosis. The inverse association of blood Se with liver fibrosis was also observed in males and White participants. Blood Cd, Hg, and Pb were not associated with liver steatosis and fibrosis in fully-adjusted models overall.

CONCLUSIONS

In NHANES 2017-18, higher blood Mn was positively associated with liver steatosis, and higher Se was positively associated with liver steatosis but negatively associated with liver fibrosis. Longitudinal studies are needed to examine the association of Mn and Se with fibrosis progression.

Procyanidin B2 Alleviates Palmitic Acid-Induced Injury in HepG2 Cells via Endoplasmic Reticulum Stress Pathway

Nonalcoholic fatty liver disease (NAFLD) is the hepatic manifestation of the metabolic syndrome featuring ectopic lipid accumulation in hepatocytes. NAFLD has been a severe threat to humans with a global prevalence of over 25% yet no approved drugs for the treatment to date. Previous studies showed that procyanidin B2 (PCB2), an active ingredient from herbal cinnamon, has an excellent hepatoprotective effect; however, the mechanism remains inconclusive. The present study aimed to investigate the protective effect and underlying mechanism of PCB2 on PA-induced cellular injury in human hepatoma HepG2 cells. Our results showed that PA-induced oxidative stress, calcium disequilibrium, and subsequent endoplasmic reticulum stress (ERS) mediated cellular injury, with elevated protein levels of GRP78, GRP94, CHOP, and hyperphosphorylation of PERK and IRE1α as well as the increased ratio of Bax/Bcl-2, which was restored by PCB2 in a concentration-dependent manner, proving the excellent antiapoptosis effect. In addition, 4-phenylbutyric acid (4-PBA), the ER stress inhibitor, increased cell viability and decreased protein levels of GRP78 and CHOP, which is similar to PCB2, and thapsigargin (TG), the ER stress agonist, exhibited conversely meanwhile partly counteracted the hepatic protection of PCB2. What is more, upregulated protein expression of p-IKKα/β, p-NF-κB p65, NLRP3, cleaved caspase 1, and mature IL-1β occurred in HepG2 cells in response to PA stress while rescued with the PCB2 intervention. In conclusion, our study demonstrated that PA induces ERS in HepG2 cells and subsequently activates downstream NLRP3 inflammasome-mediated cellular injury, while PCB2 inhibits NLRP3/caspase 1/IL-1β pathway, inflammation, and apoptosis with the presence of ERS, thereby promoting cell survival, which may provide pharmacological evidence for clinical approaches on NAFLD.