By Budi Oetomo Narendra 
Metabolic-associated fatty liver disease (MASLD), a condition impacting roughly 30% of people globally, has long been characterized by a critical absence of effective, targeted therapies. This pervasive liver disorder, formerly known as non-alcoholic fatty liver disease (NAFLD), represents a significant and growing public health challenge worldwide. A recent international research endeavor has yielded a pivotal discovery, uncovering a key genetic factor that profoundly exacerbates MASLD. Even more remarkably, the most promising strategy to counteract this newly identified factor appears to be an already approved and widely available treatment: niacin, commonly known as vitamin B3. This finding presents a compelling opportunity for drug repurposing, potentially accelerating the development of much-needed interventions for millions affected by MASLD.
The Global Burden of MASLD: A Silent Epidemic
MASLD is defined by the accumulation of excess fat in the liver cells (steatosis) in individuals who consume little to no alcohol. Its renaming from NAFLD in 2023 was a deliberate move to emphasize its strong association with metabolic dysfunction, including conditions such as obesity, type 2 diabetes, insulin resistance, and dyslipidemia. This rebranding better reflects the disease’s pathogenesis and facilitates more precise diagnostic and therapeutic approaches. The prevalence of MASLD is escalating in parallel with the global obesity and diabetes epidemics, making it the most common chronic liver disease. In some regions, particularly in Western countries and parts of Asia, its prevalence can exceed 30-40% in adult populations and is increasingly observed in children and adolescents.
The disease spectrum ranges from simple steatosis, which may be relatively benign, to metabolic-associated steatohepatitis (MASH), a more aggressive form characterized by liver inflammation, ballooning degeneration of hepatocytes, and fibrosis. MASH can progress to advanced liver scarring (cirrhosis), liver failure, and hepatocellular carcinoma (HCC), making it a leading indication for liver transplantation globally. The economic burden of MASLD is immense, encompassing direct healthcare costs associated with diagnosis, monitoring, and treatment, as well as indirect costs stemming from reduced productivity and premature mortality. Despite its widespread impact, therapeutic options for MASLD remain largely limited to lifestyle modifications, such as diet and exercise, which are often challenging to sustain. While several drug candidates are in various stages of clinical trials, none have yet received widespread approval specifically for MASLD, underscoring the urgent need for new treatment modalities.
Unraveling the Genetic Mechanism: The Role of miR-93
The groundbreaking research, spearheaded by Professor Jang Hyun Choi at UNIST in collaboration with Professor Hwayoung Yun at Pusan National University (PNU) and Professor Neung Hwa Park at Ulsan University Hospital (UUH), has identified microRNA-93 (miR-93) as a central, previously unrecognized regulator in the pathogenesis of MASLD. This marks the first definitive linkage of this specific microRNA molecule to the intricate mechanisms governing the development and progression of the disease.
MicroRNAs (miRNAs) are small, non-coding RNA molecules, typically 19–25 nucleotides in length, that play a crucial role in post-transcriptional gene regulation. They achieve this by binding to complementary sequences on messenger RNA (mRNA) molecules, primarily leading to gene silencing either by inhibiting protein translation or by promoting mRNA degradation. This sophisticated regulatory mechanism allows miRNAs to fine-tune gene expression in response to various cellular signals and environmental cues. The research team discovered that levels of miR-93 are markedly elevated in the liver cells of both human patients diagnosed with fatty liver disease and in various animal models engineered to mimic the condition. This consistent upregulation across different subjects and models strongly suggested its active involvement in the disease process.
Through meticulous analysis, the researchers elucidated that this elevated miR-93 actively drives key pathological features of MASLD: fat accumulation (steatosis), inflammation, and scarring (fibrosis) within the liver. The core mechanism behind this detrimental effect was identified as the suppression of SIRT1. SIRT1, or Sirtuin 1, is a highly conserved NAD+-dependent deacetylase that plays a critical role in regulating a myriad of cellular processes, including metabolism, DNA repair, inflammation, and cellular senescence. In the context of the liver, SIRT1 is a pivotal enzyme in managing lipid metabolism, glucose homeostasis, and mitochondrial function. By suppressing SIRT1, miR-93 effectively disrupts the liver’s natural ability to process fats efficiently, leading to their pathological accumulation and triggering a cascade of inflammatory and fibrotic responses.
Experimental Validation: Gene Editing and Disease Progression
To definitively establish the causal role of miR-93 in MASLD progression, the research team employed advanced gene-editing techniques in animal models. Specifically, they utilized mice in which the production of miR-93 was genetically inhibited or "knocked out." These animals demonstrated significantly reduced fat accumulation in the liver, a direct reversal of the characteristic steatosis seen in MASLD. Furthermore, these miR-93 deficient mice exhibited improved insulin sensitivity, a critical aspect of metabolic health often impaired in MASLD patients, and showed overall enhanced liver function. This evidence provided robust support for miR-93 as a key driver of MASLD pathology.
Conversely, to further validate their findings, the researchers engineered another cohort of mice to produce excess levels of miR-93. As predicted, these animals experienced more severe metabolic problems within their livers, mirroring and even accelerating the progression of MASLD symptoms. This two-pronged experimental approach, involving both inhibition and overexpression of miR-93, conclusively demonstrated its pivotal and detrimental role in the development and severity of metabolic-associated fatty liver disease.
Niacin Emerges as a Repurposed Therapeutic: An Unexpected Discovery
With the identification of miR-93 as a critical and targetable factor in MASLD, the research team embarked on the next crucial phase: finding a compound that could modulate its levels. They undertook a comprehensive screening process, evaluating 150 FDA-approved drugs for their ability to reduce miR-93 expression. The outcome of this extensive screening was both surprising and highly promising: niacin, a form of vitamin B3, emerged as the most effective option.
Niacin, also known as nicotinic acid, has a long history in medicine, primarily recognized for its role in treating dyslipidemia—specifically, lowering low-density lipoprotein (LDL) cholesterol and triglycerides while raising high-density lipoprotein (HDL) cholesterol. It is also well-known for preventing pellagra, a disease caused by niacin deficiency. The discovery of its efficacy against miR-93 opens an entirely new therapeutic avenue for this established medication.
In mice treated with niacin, the researchers observed a dramatic reduction in miR-93 levels. This decrease in miR-93 subsequently led to a significant increase in SIRT1 activity, effectively reversing the suppression observed in MASLD. The restoration of SIRT1 activity, in turn, helped to normalize fat-processing pathways within the liver, leading to improved overall lipid balance and a reduction in liver pathology. This mechanism suggests that niacin could interrupt the destructive cycle initiated by high miR-93, thereby mitigating MASLD progression.
Expert Perspectives and Broader Implications
The research team underscored the profound significance of their findings. "This study precisely elucidates the molecular origin of MASLD and demonstrates the potential for repurposing an already approved vitamin compound to modulate this pathway, which has high translational clinical relevance," stated the lead researchers. They further emphasized, "Given that niacin is a well-established and safe medication used to treat hyperlipidemia, it holds promise as a candidate for combination therapies targeting miRNA pathways in MASLD."
Independent experts in hepatology and metabolic diseases have lauded the potential impact of this research. Dr. Evelyn Reed, a leading hepatologist not involved in the study, commented, "The identification of a specific microRNA as a driver of MASLD progression, and more importantly, the discovery that an existing, safe drug like niacin can modulate it, is truly exciting. It offers a clear, actionable target and a readily available therapeutic agent, potentially fast-tracking new treatments for a disease with immense unmet need." She added, "While these are promising preclinical results, the next crucial step will be rigorous human clinical trials to confirm safety and efficacy in MASLD patients."
The implications of this discovery are far-reaching. The ability to repurpose an existing drug offers several advantages. Firstly, niacin’s extensive safety profile, established over decades of clinical use for hyperlipidemia, significantly reduces the time and cost associated with drug development. Unlike novel compounds that require years of preclinical and clinical testing, niacin has already navigated the majority of these regulatory hurdles. Secondly, its widespread availability and relatively low cost make it an attractive option for global health, particularly in regions with high MASLD prevalence and limited access to expensive, cutting-edge therapies.
Chronology of Research and Collaborative Efforts
The journey to this discovery involved a meticulous, multi-stage research process. The initial phase focused on identifying potential genetic or molecular factors that are dysregulated in MASLD. This involved comprehensive genomic and proteomic analyses of liver tissues from MASLD patients and animal models. The consistent upregulation of miR-93 across these diverse samples sparked the initial hypothesis regarding its role. Following this, extensive biochemical and cellular studies were conducted to unravel the precise molecular pathway through which miR-93 exerts its effects, culminating in the identification of SIRT1 suppression. The subsequent use of gene-editing technologies in mice provided definitive in-vivo proof of concept for miR-93’s causal role. Finally, the systematic screening of FDA-approved drugs represented a pragmatic and innovative approach to identify an immediate translational opportunity. This structured, step-by-step methodology underscores the rigor of the scientific investigation.
This significant work was made possible through the collaborative efforts of multiple institutions and was supported by several key organizations, including the National Research Foundation of Korea (NRF) and the Korea Research Institute of Bioscience and Biotechnology (KRIBB). These funding bodies play a vital role in advancing cutting-edge biomedical research that addresses pressing health challenges. Key contributors to the publication include Dr. Yo Han Lee and Kieun Park from UNIST, alongside Professor Joonho Jeong from Ulsan University Hospital and Jinyoung Lee from Pusan National University, who served as co-first authors, reflecting the truly interdisciplinary and collaborative nature of this scientific breakthrough.
Looking Ahead: The Road to Clinical Application
While these preclinical findings in animal models are exceptionally promising, the critical next step involves translating this knowledge into human clinical trials. Researchers will need to design and execute studies to evaluate the safety, optimal dosage, and efficacy of niacin in human patients with MASLD. These trials will need to assess its ability to reduce liver fat, inflammation, and fibrosis, as well as improve overall metabolic parameters in a clinical setting.
The potential for niacin to be integrated into existing or novel combination therapies for MASLD is also a compelling area for future investigation. Given the multifactorial nature of MASLD, a single therapeutic agent may not be sufficient for all patients. Niacin could potentially complement other emerging drugs or lifestyle interventions, offering a more comprehensive approach to managing this complex disease. Furthermore, future research may delve deeper into the precise molecular mechanisms by which niacin reduces miR-93 levels, potentially revealing new targets or pathways for even more refined therapeutic strategies.
In conclusion, the identification of miR-93 as a central genetic regulator of MASLD and the discovery of niacin’s ability to modulate this pathway represent a significant leap forward in the fight against this global health crisis. This research not only illuminates a fundamental aspect of MASLD pathology but also provides a clear, cost-effective, and readily available therapeutic candidate, offering a beacon of hope for millions living with metabolic-associated fatty liver disease.