PNPLA3 I148M and response to treatment for hepatic steatosis: A systematic review

Global Epidemiology and Implications of PNPLA3 I148M Variant in Metabolic Dysfunction-Associated Steatotic Liver Disease: A Systematic Review and Meta-analysis

BACKGROUND & AIMS

PNPLA3 rs738409 variant is a risk factor for onset and progression of metabolic dysfunction-associated steatotic liver disease (MASLD). We aimed to assess its global prevalence, clinical and histological characteristics, and long-term outcomes in patients with MASLD.

METHODS

PubMed and Embase databases were searched until December 30, 2023, for observational studies on PNPLA3 genotyped adults with MASLD. Proportions were pooled using a generalized linear mixed model with Clopper-Pearson intervals. Continuous and dichotomous variables were analyzed using the DerSimonian-Laird method. International Prospective Register of Systematic Reviews registration number: CRD42023449838.

RESULTS

A total of 109 studies involving 118,302 individuals with MASLD were identified. The overall minor allele frequency of the G allele [MAF(G)] at PNPLA3 was 0.45 (95% confidence interval [CI]: 0.43; 0.48) with high heterogeneity (I2 = 98%). The highest MAF(G) was found in Latin America (0.63) and the lowest in Europe (0.38). No African countries were identified. Carriers of the PNPLA3 variant had reduced adiposity, altered fat metabolism, and worse liver damage/histology than noncarriers. There was significant heterogeneity in the clinical/histological analyses (I2 > 50%). Only the PNPLA3 GG genotype was associated with higher mortality and liver-related events with no heterogeneity (I2 = 0%). Metaregressions showed the influence of adiposity, age, diabetes mellitus, and glucose on some PNPLA3 expression parameters. Overall, there was a moderate risk of bias in the included studies.

CONCLUSIONS

This study reveals the global pattern of PNPLA3 and its clinical, histological, and outcome implications in MASLD. Patients with MASLD and PNPLA3 variant have different clinical features and worse liver severity, and only PNPLA3 GG has a higher risk of mortality and liver outcomes. Our findings highlight the importance of PNPLA3 genotyping in clinical trials and advocate for personalized medicine approaches.

The importance of patient engagement in the multimodal treatment of MASLD

Metabolic dysfunction-associated steatotic liver disease (MASLD) is often regarded in society as a disease caused by personal lifestyle and dietary choices. Healthcare providers who have empathy and are able to explain the disease trajectory can better engage with people with MASLD and actively work with them to improve their metabolic health on a sustainable basis. Non-invasive tests can assist in this process, but healthcare providers must ensure they explain their advantages and limitations. Discussing and setting lifestyle goals are priorities before initiating specific pharmacological treatment, since living a healthy lifestyle will remain the backbone of the multimodal management of MASLD. In this review, we discuss challenges and opportunities to actively engage with people living with MASLD in a multimodal treatment framework as a healthcare provider.

Gene-based therapies for steatotic liver disease

Advances in nucleic acid delivery have positioned the liver as a key target for gene therapy, with adeno-associated virus vectors showing long-term effectiveness in treating hemophilia. Steatotic liver disease (SLD), the most common liver condition globally, primarily results from metabolic dysfunction-associated and alcohol-associated liver diseases. In some individuals, SLD progresses from simple steatosis to steatohepatitis, cirrhosis, and eventually hepatocellular carcinoma, driven by a complex interplay of genetic, metabolic, and environmental factors. Genetic variations in various lipid metabolism-related genes, such as patatin-like phospholipase domain-containing protein 3 (PNPLA3), 17β-hydroxysteroid dehydrogenase type 13 (HSD17B13), and mitochondrial amidoxime-reducing component 1 (MTARC1), impact the progression of SLD and offer promising therapeutic targets. This review largely focuses on genes identified through clinical association studies, as they are more likely to be effective and safe for therapeutic intervention. While preclinical research continues to deepen our understanding of genetic factors, early-stage clinical trials involving gene-based SLD therapies, including transient antisense and small-molecule approaches, are helping prioritize therapeutic targets. Meanwhile, hepatocyte gene editing technologies are advancing rapidly, offering alternatives to transient methods. As such, gene-based therapies show significant potential for preventing the progression of SLD and enhancing long-term liver health.

Representation of Sex, Race and Ethnicity in MASH Randomised Controlled Trials: A Systematic Review and Meta-Analysis

BACKGROUND AND AIMS

Randomised controlled trials (RCTs) have historically underrepresented female, racial and ethnic minorities across various fields. This systematic review and meta-analysis aims to examine the global distribution, reporting and participation of diverse groups based on sex, race and ethnicity in trials focused on metabolic dysfunction-associated steatohepatitis (MASH).

METHODS

PubMed and Cochrane Library databases were systematically searched for MASH RCTs (through December 13, 2024) that included any pharmacotherapy as an intervention arm. RCTs were qualitatively reviewed to assess their global distribution and reporting of populations. A meta-analysis of proportions was performed using a generalised linear mixed model.

RESULTS

One hudred and nine studies were identified, reporting data from 112 RCTs and 19 516 MASH participants. Of the 49 countries that conducted trials, 34 were high-income countries (69.4%). Sex, race and ethnicity were reported in 111 (99.1%), 69 (61.6%) and 56 (50.0%) of the 112 RCTs, respectively, with reporting improving in recent years. We found no reporting of sexual and gender minorities. The pooled proportions of female, White, Asian, Black and Hispanic/Latino groups were 54.23% (95% confidence interval [CI]: 51.31-57.12), 87.63% (95% CI: 85.37-89.58), 4.95% (95% CI: 3.42-7.10), 2.27% (95% CI: 1.89-2.71) and 31.42% (95% CI: 26.61-36.66), respectively. Meta-regressions showed a trend toward more female, White and Hispanic/Latino participants in RCTs over time.

CONCLUSIONS

Although female and Hispanic/Latino representation has increased over time, racial minorities are underrepresented in MASH trials. These data provide an overview of participant representation in MASH trials and call for collaborative efforts among researchers, sponsors, regulators and other relevant stakeholders to improve diversity in these trials.

Human genetics of metabolic dysfunction-associated steatotic liver disease: from variants to cause to precision treatment

Metabolic dysfunction-associated steatotic liver disease (MASLD) is characterized by increased hepatic steatosis with cardiometabolic disease and is a leading cause of advanced liver disease. We review here the genetic basis of MASLD. The genetic variants most consistently associated with hepatic steatosis implicate genes involved in lipoprotein input or output, glucose metabolism, adiposity/fat distribution, insulin resistance, or mitochondrial/ER biology. The distinct mechanisms by which these variants promote hepatic steatosis result in distinct effects on cardiometabolic disease that may be best suited to precision medicine. Recent work on gene-environment interactions has shown that genetic risk is not fixed and may be exacerbated or attenuated by modifiable (diet, exercise, alcohol intake) and nonmodifiable environmental risk factors. Some steatosis-associated variants, notably those in patatin-like phospholipase domain-containing 3 (PNPLA3) and transmembrane 6 superfamily member 2 (TM6SF2), are associated with risk of developing adverse liver-related outcomes and provide information beyond clinical risk stratification tools, especially in individuals at intermediate to high risk for disease. Future work to better characterize disease heterogeneity by combining genetics with clinical risk factors to holistically predict risk and develop therapies based on genetic risk is required.

Unraveling Mechanisms of Genetic Risks in Metabolic Dysfunction-Associated Steatotic Liver Diseases: A Pathway to Precision Medicine

Metabolic dysfunction-associated steatotic liver disease (MASLD) is a growing global health problem, affecting ∼1 billion people. This condition is well established to have a heritable component with strong familial clustering. With the extraordinary breakthroughs in genetic research techniques coupled with their application to large-scale biobanks, the field of genetics in MASLD has expanded rapidly. In this review, we summarize evidence regarding genetic predisposition to MASLD drawn from family and twin studies. Significantly, we delve into detailed genetic variations associated with diverse pathogenic mechanisms driving MASLD. We highlight the interplay between these genetic variants and their connections with metabolic factors, the gut microbiome, and metabolites, which collectively influence MASLD progression. These discoveries are paving the way for precise medicine, including noninvasive diagnostics and therapies. The promising landscape of novel genetically informed drug targets such as RNA interference is explored. Many of these therapies are currently under clinical validation, raising hopes for more effective MASLD treatment.

Recent advances in MASLD genetics: Insights into disease mechanisms and the next frontiers in clinical application

Metabolic dysfunction-associated steatotic liver disease (MASLD) is the most common chronic liver disease in the world and a growing cause of liver-related morbidity and mortality. Yet, at the same time, our understanding of the pathophysiology and genetic underpinnings of this increasingly common yet heterogeneous disease has increased dramatically over the last 2 decades, with the potential to lead to meaningful clinical interventions for patients. We have now seen the first pharmacologic therapy approved for the treatment of MASLD, and multiple other potential treatments are currently under investigation-including gene-targeted RNA therapies that directly extend from advances in MASLD genetics. Here we review recent advances in MASLD genetics, some of the key pathophysiologic insights that human genetics has provided, and the ways in which human genetics may inform our clinical practice in the field of MASLD in the near future.

The Role of Exercise in Steatotic Liver Diseases: An Updated Perspective

BACKGROUND

The increasing prevalence of metabolic dysfunction-associated steatotic liver disease (MASLD), formerly known as non-alcoholic fatty liver disease (NAFLD), parallels the rise in sedentary lifestyles. MASLD is the most common form of steatotic liver disease (SLD), which represents the umbrella beneath which the vast majority of chronic liver diseases fall, including alcohol-related liver disease and their overlap. These conditions are the leading contributors to chronic liver disease, significantly impacting global morbidity and mortality. Despite the emergence of new pharmacotherapies, exercise represents the foundation of MASLD treatment.

OBJECTIVE

This review aims to provide an updated perspective on the role of exercise in the management of SLD, highlight its molecular and clinical benefits, and explore its benefits and safety in the stage of cirrhosis.

METHODS

Evidence from pre-clinical and clinical studies was reviewed to evaluate the impact of exercise on SLD (mainly MASLD), advanced chronic liver disease stages, and its relevance in the context of evolving therapies such as Resmetirom and incretin-based anti-obesity medications.

CONCLUSION

Exercise remains a cornerstone intervention in the management of MASLD, with suggested benefits even for patients who have progressed to cirrhosis. Personalized exercise regimens should be prioritized for all patients, including those receiving pharmacotherapy. Further research is needed to refine exercise protocols and investigate their impact on histologic and clinical outcomes, as well as their potential synergistic effects with emerging treatments.

Guidance and Position of RINN22 regarding Precision Nutrition and Nutriomics

BACKGROUND

Precision nutrition is based on the integration of individual's phenotypical and biological characteristics including genetic variants, epigenetic marks, gut microbiota profiles, and metabolite fingerprints as well as medical history, lifestyle practices, and environmental and cultural factors. Thus, nutriomics areas including nutrigenomics, nutrigenetics, nutriepigenetics, nutrimetabolomics, and nutrimetagenomics have emerged to comprehensively understand the complex interactions between nutrients, diet, and the human body's molecular processes through precision nutrition.

SUMMARY

This document from the Ibero-American Network of Nutriomics and Precision Nutrition (RINN22; https://rinn22.com/) provides a comprehensive overview of the concepts of precision nutrition approaches to guide their application in clinical and public health as well as establish the position of RINN22 regarding the current and future state of precision nutrition.

KEY MESSAGES

The progress and participation of nutriomics to precision nutrition is an essential pillar for addressing diet-related diseases and developing innovative managing strategies, which will be promoted by advances in bioinformatics, machine learning, and integrative software, as well as the description of specific novel biomarkers. In this context, synthesizing and critically evaluating the latest developments, potential applications, and future needs in the field of nutrition is necessary with a holistic perspective, incorporating progress in omics technologies aimed at precision nutrition interventions. This approach must address and confront healthy, social, food security, physically active lifestyle, sanitation, and sustainability challenges with preventive, participatory, and predictive strategies of personalized, population, and planetary nutrition for a precision tailored health.

Genetics of Metabolic Dysfunction-associated Steatotic Liver Disease: The State of the Art Update

Recent advances in the genetics of metabolic dysfunction-associated steatotic liver disease (MASLD) are gradually revealing the mechanisms underlying the heterogeneity of the disease and have shown promising results in patient stratification. Genetic characterization of the disease has been rapidly developed using genome-wide association studies, exome-wide association studies, phenome-wide association studies, and whole exome sequencing. These advances have been powered by the increase in computational power, the development of new analytical algorithms, including some based on artificial intelligence, and the recruitment of large and well-phenotyped cohorts. This review presents an update on genetic studies that emphasize new biological insights from next-generation sequencing approaches. Additionally, we discuss innovative methods for discovering new genetic loci for MASLD, including rare variants. To comprehensively manage MASLD, it is important to stratify risks. Therefore, we present an update on phenome-wide association study associations, including extreme phenotypes. Additionally, we discuss whether polygenic risk scores and targeted sequencing are ready for clinical use. With particular focus on precision medicine, we introduce concepts such as the interplay between genetics and the environment in modulating genetic risk with lifestyle or standard therapies. A special chapter is dedicated to gene-based therapeutics. The limitations of approved pharmacological approaches are discussed, and the potential of gene-related mechanisms in therapeutic development is reviewed, including the decision to perform genetic testing in patients with MASLD.

Insulin resistance is an integral feature of MASLD even in the presence of PNPLA3 variants

Background & Aims

It has been postulated that carriers of PNPLA3 I148M (CG [Ile/Met] or GG [Met/Met]) develop metabolic dysfunction-associated steatotic liver disease (MASLD) in the absence of insulin resistance or metabolic syndrome. However, the relationship between insulin resistance and MASLD according to the PNPLA3 allele has not been carefully assessed.

Methods

A total of 204 participants were recruited and underwent PNPLA3 genotyping, an oral glucose tolerance test, liver proton magnetic resonance spectroscopy and percutaneous liver biopsy if diagnosed with MASLD. A subgroup of patients (n = 55) had an euglycemic hyperinsulinemic clamp with glucose tracer infusion.

Results

As expected, patients with the CG/GG genotype had worse intrahepatic triglyceride content and worse liver histology. However, regardless of PNPLA3 genotype, patients with a diagnosis of MASLD had severe whole-body insulin resistance (Matsuda index, an estimation of insulin resistance in glucose metabolic pathways) and fasting and postprandial adipose tissue insulin resistance (Adipo-IR index and free fatty acid suppression during the oral glucose tolerance test, respectively, as measures of insulin resistance in lipolytic metabolic pathways) compared to patients without MASLD. Moreover, for the same amount of liver fat accumulation, insulin resistance was similar in patients with genotypes CC vs. CG/GG. In multiple regression analyses, A1c and Adipo-IR were associated with the presence of MASLD and advanced liver fibrosis, independently of PNPLA3 genotype.

Conclusions

PNPLA3 variant carriers with MASLD are equally insulin resistant as non-carriers with MASLD at the level of the liver, muscle, and adipose tissue. This calls for reframing "PNPLA3 MASLD" as an insulin-resistant condition associated with increased hepatic susceptibility to metabolic insults, such as obesity or diabetes, wherein early identification and aggressive intervention are warranted to reverse metabolic dysfunction and prevent disease progression.

Impact and implications

It has been proposed that the PNPLA3 G allele is associated with the presence of metabolic dysfunction-associated steatotic liver disease (MASLD) in the absence of insulin resistance. However, our results suggest that regardless of PNPLA3 alleles, the presence of insulin resistance is necessary for the development of MASLD. This calls for reframing patients with "PNPLA3 MASLD" not as insulin sensitive, but on the contrary, as an insulin-resistant population with increased hepatic susceptibility to metabolic insults, such as obesity or diabetes.

Genetics of liver disease in adults

Chronic liver disease stands as a significant global health problem with an estimated 2 million annual deaths across the globe. Combining the use of next-generation sequencing technologies with evolving knowledge in the interpretation of genetic variation across the human genome is propelling our understanding, diagnosis, and management of both rare and common liver diseases. Here, we review the contribution of risk and protective alleles to common forms of liver disease, the rising number of monogenic diseases affecting the liver, and the role of somatic genetic variants in the onset and progression of oncological and non-oncological liver diseases. The incorporation of genomic information in the diagnosis and management of patients with liver disease is driving the beginning of a new era of genomics-informed clinical hepatology practice, facilitating personalized medicine, and improving patient care.

PROTACs: Emerging Targeted Protein Degradation Approaches for Advanced Druggable Strategies

A potential therapeutic strategy to treat conditions brought on by the aberrant production of a disease-causing protein is emerging for targeted protein breakdown using the PROTACs technology. Few medications now in use are tiny, component-based and utilize occupancy-driven pharmacology (MOA), which inhibits protein function for a short period of time to temporarily alter it. By utilizing an event-driven MOA, the proteolysis-targeting chimeras (PROTACs) technology introduces a revolutionary tactic. Small-molecule-based heterobifunctional PROTACs hijack the ubiquitin-proteasome system to trigger the degradation of the target protein. The main challenge PROTAC's development facing now is to find potent, tissue- and cell-specific PROTAC compounds with favorable drug-likeness and standard safety measures. The ways to increase the efficacy and selectivity of PROTACs are the main focus of this review. In this review, we have highlighted the most important discoveries related to the degradation of proteins by PROTACs, new targeted approaches to boost proteolysis' effectiveness and development, and promising future directions in medicine.