A Genetic and Metabolic Staging System for Predicting the Outcome of Nonalcoholic Fatty Liver Disease

Are we ready for genetic testing in metabolic dysfunction-associated steatotic liver disease?

Metabolic dysfunction-associated steatotic liver disease (MASLD), with its steadily increasing prevalence, represents now a major problem in public health. A proper referral could benefit from tools allowing more precise risk stratification. To this end, in recent decades, several genetic variants that may help predict and refine the risk of development and progression of MASLD have been investigated. In this review, we aim to discuss the role genetics in MASLD plays in everyday clinical practice. We performed a comprehensive literature search of PubMed for relevant publications. Available evidence highlights the emergence of genetic-based noninvasive algorithms for diagnosing fatty liver, metabolic dysfunction-associated steatohepatitis, fibrosis progression and occurrence of liver-related outcomes including hepatocellular carcinoma. Nevertheless, their accuracy is not optimal and application in everyday clinical practice remains challenging. Furthermore, susceptible genetic markers have recently become subjects of great scientific interest as therapeutic targets in precision medicine. In conclusion, decisional algorithms based on genetic testing in MASLD to facilitate the clinician decisions on management and treatment are under growing investigation and could benefit from artificial intelligence methodology.

The PD-1/PD-L1 Axis in the Biology of MASLD

Metabolic Dysfunction-Associated Steatotic Liver (MASL), previously named nonalcoholic fatty liver (NAFL), is a multifactorial disease in which metabolic, genetic, and environmental risk factors play a predominant role. Obesity and type 2 diabetes act as triggers of the inflammatory response, which contributes to the progression of MASL to Metabolic Dysfunction-Associated Steatohepatitis and the development of hepatocellular carcinoma. In the liver, several parenchymal, nonparenchymal, and immune cells maintain immunological homeostasis, and different regulatory pathways balance the activation of the innate and adaptative immune system. PD-1/PD-L1 signaling acts, in the maintenance of the balance between the immune responses and the tissue immune homeostasis, promoting self-tolerance through the modulation of activated T cells. Recently, PD-1 has received much attention for its roles in inducing an exhausted T cells phenotype, promoting the tumor escape from immune responses. Indeed, in MASLD, the excessive fat accumulation dysregulates the immune system, increasing cytotoxic lymphocytes and decreasing their cytolytic activity. In this context, T cells exacerbate liver damage and promote tumor progression. The aim of this review is to illustrate the main pathogenetic mechanisms by which the immune system promotes the progression of MASLD and the transition to HCC, as well as to discuss the possible therapeutic applications of PD-1/PD-L1 target therapy to activate T cells and reinvigorate immune surveillance against cancer.

Impact of PNPLA3 rs738409 Polymorphism on the Development of Liver-Related Events in Patients With Nonalcoholic Fatty Liver Disease

BACKGROUND AND AIMS

Nonalcoholic fatty liver disease (NAFLD) is a complex disease, resulting from the interplay between environmental determinants and genetic variations. Single nucleotide polymorphism rs738409 C>G in the PNPLA3 gene is associated with hepatic fibrosis and with higher risk of developing hepatocellular carcinoma. Here, we analyzed a longitudinal cohort of biopsy-proven NAFLD subjects with the aim to identify individuals in whom genetics may have a stronger impact on disease progression.

METHODS

We retrospectively analyzed 756 consecutive, prospectively enrolled biopsy-proven NAFLD subjects from Italy, United Kingdom, and Spain who were followed for a median of 84 months (interquartile range, 65-109 months). We stratified the study cohort according to sex, body mass index (BMI)

RESULTS

Overall, the median age was 48 years and most individuals were men (64.7%). The PNPLA3 rs738409 genotype was CC in 235 (31.1%), CG in 328 (43.4%), and GG in 193 (25.5%) patients. At univariate analysis, the PNPLA3 GG risk genotype was associated with female sex and inversely related to BMI (odds ratio, 1.6; 95% confidence interval, 1.1-2.2; P = .006; and odds ratio, 0.97; 95% confidence interval, 0.94-0.99; P = .043, respectively). Specifically, PNPLA3 GG risk homozygosis was more prevalent in female vs male individuals (31.5% vs 22.3%; P = .006) and in nonobese compared with obese NAFLD subjects (50.0% vs 44.2%; P = .011). Following stratification for age, sex, and BMI, we observed an increased incidence of liver-related events in the subgroup of nonobese women older than 50 years of age carrying the PNPLA3 GG risk genotype (log-rank test, P = .0047).

CONCLUSIONS

Nonobese female patients with NAFLD 50 years of age and older, and carrying the PNPLA3 GG risk genotype, are at higher risk of developing liver-related events compared with those with the wild-type allele (CC/CG). This finding may have implications in clinical practice for risk stratification and personalized medicine.

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Key Words

• Liver-Related Outcomes
• NAFLD
• NASH
• PNPLA3

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MESH Headings

• Humans
• Female
• Male
• Middle Aged
• Non-alcoholic Fatty Liver Disease/complications
• Non-alcoholic Fatty Liver Disease/genetics
• Non-alcoholic Fatty Liver Disease/epidemiology
• Carcinoma, Hepatocellular/epidemiology
• Carcinoma, Hepatocellular/genetics
• Carcinoma, Hepatocellular/complications
• Retrospective Studies
• Esophageal and Gastric Varices/complications
• Gastrointestinal Hemorrhage/complications
• Genotype
• Polymorphism, Single Nucleotide
• Liver Neoplasms/epidemiology
• Liver Neoplasms/genetics
• Liver Neoplasms/complications
• Genetic Predisposition to Disease

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Affiliation(s)

Chiara Rosso Division of Gastroenterology and Hepatology, Department of Medical Sciences, University of Turin, Turin, Italy
Gian Paolo Caviglia Division of Gastroenterology and Hepatology, Department of Medical Sciences, University of Turin, Turin, Italy
Giovanni Birolo Division of Gastroenterology and Hepatology, Department of Medical Sciences, University of Turin, Turin, Italy
Angelo Armandi Division of Gastroenterology and Hepatology, Department of Medical Sciences, University of Turin, Turin, Italy; Metabolic Liver Disease Research Program, I. Department of Medicine, University Medical Center of the Johannes Gutenberg-University, Mainz, Germany
Grazia Pennisi Sezione di Gastroenterologia, PROMISE, Università di Palermo, Palermo, Italy
Serena Pelusi Precision Medicine, Department of Transfusion Medicine, Fondazione IRCCS Ca' Granda Ospedale Maggiore Policlinico, Milan, Italy
Ramy Younes Boehringer Ingelheim International, GmbH, Ingelheim, Germany
Antonio Liguori Dipartimento Universitario Medicina e Chirurgia Traslazionale, Università Cattolica del Sacro Cuore, Rome, Italy
Nuria Perez-Diaz-Del-Campo Division of Gastroenterology and Hepatology, Department of Medical Sciences, University of Turin, Turin, Italy
Aurora Nicolosi Division of Gastroenterology and Hepatology, Department of Medical Sciences, University of Turin, Turin, Italy
Olivier Govaere Newcastle Liver Research Group, Translational & Clinical Research Institute, Faculty of Medical Sciences, Newcastle University, Newcastle upon Tyne, United Kingdom
Gabriele Castelnuovo Division of Gastroenterology and Hepatology, Department of Medical Sciences, University of Turin, Turin, Italy
Antonella Olivero Division of Gastroenterology and Hepatology, Department of Medical Sciences, University of Turin, Turin, Italy
Maria Lorena Abate Division of Gastroenterology and Hepatology, Department of Medical Sciences, University of Turin, Turin, Italy
Davide Giuseppe Ribaldone Division of Gastroenterology and Hepatology, Department of Medical Sciences, University of Turin, Turin, Italy
Piero Fariselli Division of Gastroenterology and Hepatology, Department of Medical Sciences, University of Turin, Turin, Italy
Luca Valenti Precision Medicine, Department of Transfusion Medicine, Fondazione IRCCS Ca' Granda Ospedale Maggiore Policlinico, Milan, Italy; Department of Pathophysiology and Transplantation, University of Milan, Milan, Italy
Luca Miele Dipartimento Universitario Medicina e Chirurgia Traslazionale, Università Cattolica del Sacro Cuore, Rome, Italy; Dipartimento di Scienze Mediche e Chirurgiche, Fondazione Policlinico Gemelli IRCCS, Rome, Italy
Salvatore Petta Sezione di Gastroenterologia, PROMISE, Università di Palermo, Palermo, Italy
Manuel Romero-Gomez UCM Digestive Diseases and SeLiver Group, Virgen del Rocío University Hospital, Institute of Biomedicine of Seville, University of Seville, Seville, Spain
Quentin M Anstee Newcastle Liver Research Group, Translational & Clinical Research Institute, Faculty of Medical Sciences, Newcastle University, Newcastle upon Tyne, United Kingdom; Newcastle NIHR Biomedical Research Centre, Newcastle upon Tyne Hospitals NHS Trust, Newcastle upon Tyne, United Kingdom
Elisabetta Bugianesi Division of Gastroenterology and Hepatology, Department of Medical Sciences, University of Turin, Turin, Italy.

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The greater impact of PNPLA3 polymorphism on liver-related events in Japanese non-alcoholic fatty liver disease patients: A multicentre cohort study

BACKGROUND & AIMS

PNPLA3 rs738409 has been associated with an increased risk of liver-related events in patients with non-alcoholic fatty liver disease (NAFLD). In this study, we investigated the epidemiology of NAFLD and the impact of PNPLA3 on prognosis in Japan.

METHODS

A longitudinal multicentre cohort study, the JAGUAR study, includes 1550 patients with biopsy-proven NAFLD in Japan. We performed genetic testing and evaluated outcomes from this cohort. Liver-related events were defined as hepatocellular carcinoma (HCC) and decompensated liver cirrhosis events.

RESULTS

During follow-up (median [range], 7.1 [1.0-24.0] years), 80 patients developed HCC, 104 developed liver-related events, and 59 died of any cause. The 5-year rate of liver-related events for each single-nucleotide polymorphism was 0.5% for CC, 3.8% for CG, and 5.8% for GG. Liver-related deaths were the most common (n = 28); only three deaths were due to cardiovascular disease. Multivariate analysis identified carriage of PNPLA3 CG/GG (hazard ratio [HR] 16.04, p = .006) and FIB-4 index >2.67 (HR 10.70, p < .01) as predictors of liver-related event development. No HCC or liver-related death was found among patients with PNPLA3 CC. There was a significantly increased risk of HCC, liver-related events, and mortality for CG/GG versus CC, but no difference between the CG and GG genotypes.

CONCLUSIONS

In Japanese individuals, the main cause of death from NAFLD is liver-related death. The greater risk of liver-related events incurred by PNPLA3 G allele was shown in Japan. Risk stratification for NAFLD in Japan is best accomplished by integrating PNPLA3 with the FIB-4 index.

Programmed cell death 1 genetic variant and liver damage in nonalcoholic fatty liver disease

BACKGROUND AND AIMS

Programmed cell death 1/programmed cell death-ligand 1 (PD-1/PDL-1) axis has been reported to modulate liver inflammation and progression to hepatocellular carcinoma (HCC) in patients with nonalcoholic fatty liver disease (NAFLD). Here, we examined whether the PDCD1 variation is associated with NAFLD severity in individuals with liver biopsy.

METHODS

We examined the impact of PDCD1 gene variants on HCC, as robust severe liver disease phenotype in UK Biobank participants. The strongest genetic association with the rs13023138 G>C variation was subsequently tested for association with liver damage in 2889 individuals who underwent liver biopsy for suspected nonalcoholic steatohepatitis (NASH). Hepatic transcriptome was examined by RNA-Seq in a subset of NAFLD individuals (n = 121). Transcriptomic and deconvolution analyses were performed to identify biological pathways modulated by the risk allele.

RESULTS

The rs13023138 C>G showed the most robust association with HCC in UK Biobank (p = 5.28E-4, OR = 1.32, 95% CI [1.1, 1.5]). In the liver biopsy cohort, rs13023138 G allele was independently associated with severe steatosis (OR 1.17, 95% CI 1.02-1.34; p = .01), NASH (OR 1.22, 95% CI 1.09-1.37; p < .001) and advanced fibrosis (OR 1.26, 95% CI 1.06-1.50; p = .007). At deconvolution analysis, rs13023138 G>C allele was linked to higher hepatic representation of M1 macrophages, paralleled by upregulation of pathways related to inflammation and higher expression of CXCR6.

CONCLUSIONS

The PDCD1 rs13023138 G allele was associated with HCC development in the general population and with liver disease severity in patients at high risk of NASH.

Nonalcoholic liver disease: Epidemiology, risk factors, natural history, and management strategies

Nonalcoholic fatty liver disease (NAFLD) is now the most common chronic liver disease worldwide and a leading indication for liver transplantation in the United States. NAFLD encompasses a heterogeneous clinicopathologic spectrum, ranging from nonalcoholic fatty liver (NAFL) to nonalcoholic steatohepatitis, and progressive fibrosis, which can lead to end-stage liver disease including cirrhosis and hepatocellular cancer. Predictive models suggest that over 100 million adults in the United States will have NAFLD by 2030, representing over a third of the population. In this manuscript, we provide an overview of NAFLD risk factors, natural history (including hepatic and extra-hepatic outcomes), diagnosis, and current management strategies.

Risk stratification and early detection biomarkers for precision HCC screening

Hepatocellular carcinoma (HCC) mortality remains high primarily due to late diagnosis as a consequence of failed early detection. Professional societies recommend semi-annual HCC screening in at-risk patients with chronic liver disease to increase the likelihood of curative treatment receipt and improve survival. However, recent dynamic shift of HCC etiologies from viral to metabolic liver diseases has significantly increased the potential target population for the screening, whereas annual incidence rate has become substantially lower. Thus, with the contemporary HCC etiologies, the traditional screening approach might not be practical and cost-effective. HCC screening consists of (i) definition of rational at-risk population, and subsequent (ii) repeated application of early detection tests to the population at regular intervals. The suboptimal performance of the currently available HCC screening tests highlights an urgent need for new modalities and strategies to improve early HCC detection. In this review, we overview recent developments of clinical, molecular, and imaging-based tools to address the current challenge, and discuss conceptual framework and approaches of their clinical translation and implementation. These encouraging progresses are expected to transform the current "one-size-fits-all" HCC screening into individualized precision approaches to early HCC detection and ultimately improve the poor HCC prognosis in the foreseeable future.

The additive effect of genetic and metabolic factors in the pathogenesis of nonalcoholic fatty liver disease

Both genetic and metabolic factors influence the pathology of nonalcoholic fatty liver disease (NAFLD). The aim of this retrospective study was to evaluate the impact of these factors at each stage of disease. We analysed the impact of obesity, diabetes mellitus and genetic risk factors (alleles of PNPLA3 or HSD17B13) on nonalcoholic steatohepatitis (NASH), significant fibrosis (stage ≥ 2) and advanced fibrosis (stage ≥ 3) in 346 patients. Genetic high risk was defined as having at least 2 risk alleles. The median age was 59 years, median body mass index was 27.1 kg/m², and 46.8% had diabetes mellitus. Obesity was a risk factor for NASH, significant fibrosis, and advanced fibrosis. Diabetes mellitus increased the risk of NASH. Genetic risk increased the risk of significant and advanced fibrosis. Odds ratios for NASH, significant fibrosis and advanced fibrosis increased with the number of genetic and metabolic risk factors. The patients with both metabolic and genetic risks had an odds ratio of 12.30 for NASH, 5.50 for significant fibrosis, and 6.25 for advanced fibrosis. Factors strongly impact on the pathology of NAFLD differed according to the fibrosis stages. Synergistic effects were observed between genetic and metabolic factors at all stages.