MicroRNA-122 (miR-122) is the most abundant liver-specific microRNA, comprising approximately 70% of the hepatic miRNA pool. The molecule functions as a central regulator across multiple biological processes relevant to liver health and disease, including lipid metabolism, inflammatory signaling, fibrogenesis, viral replication control, and pathways implicated in hepatocarcinogenesis. This review synthesizes available experimental, clinical, and molecular evidence on the role of miR-122 across a broad spectrum of liver disorders.
Mechanistically, miR-122 influences hepatic lipid homeostasis by acting through the Sirt1/LKB1/AMPK signaling axis, thereby governing lipogenesis. Inflammatory modulation is mediated in part by effects on the LPS/TLR-4/FoxO3 pathway. Beyond these metabolic and immune-related roles, miR-122 exerts tumor-suppressive and antiviral effects via several downstream targets and pathways, including Cyclin G1/p53, HO-1, NDRG3, GALNT10, PEG10, and NEGR1. These multiple points of interaction explain the broad phenotypic consequences of altered miR-122 expression in the liver.
The evidence links miR-122 to metabolic dysfunction-associated fatty liver disease (MAFLD) and metabolic dysfunction-associated steatohepatitis (MASH). Changes in miR-122 expression contribute to dysregulated lipogenesis and inflammatory responses that underlie these conditions. In drug-induced acute liver injury, experimental data indicate that manipulation of miR-122 can influence injury severity; for example, knockdown studies have been associated with protection against acetaminophen-mediated injury through targets such as NDRG3, as reported in the literature cited by the review.
miR-122 regulation shows etiology-specific behavior in viral hepatitis. The review highlights divergent mechanisms in hepatitis B virus (HBV) versus hepatitis C virus (HCV)-associated disease. In HBV-related disease, epigenetic silencing mechanisms contribute to altered miR-122 expression, whereas in HCV infection interferon-linked mechanisms are implicated. These distinctions have implications for both pathogenesis and the design of miR-122-directed interventions in viral hepatitis.
Loss of hepatic miR-122 expression correlates with suppression of the differentiated hepatic phenotype and acquisition of metastatic properties, linking reduced miR-122 to hepatocellular carcinoma (HCC) development and progression. The review also addresses miR-122's role in colorectal cancer liver metastasis. Through its tumor-suppressive effects on targets such as Cyclin G1/p53 and other mediators, miR-122 influences cell-cycle regulation, apoptosis, and metastatic behavior.
A recurring and clinically important theme is the compartment- and stage-dependent behavior of miR-122. Hepatic expression of miR-122 typically declines as liver disease progresses, whereas circulating levels of miR-122 rise in association with hepatocyte injury. This pattern reconciles apparently contradictory reports in the literature and emphasizes that biomarker interpretation depends critically on specimen source (liver tissue versus blood) and disease stage. Practically, the clinical utility of miR-122 as a minimally invasive biomarker requires attention to these contextual factors.
The review critically appraises efforts to translate anti-miR-122 therapeutics into clinical use. Two example agents, miravirsen and RG-101, are discussed as failed clinical translation attempts. Key obstacles identified include the emergence of viral resistance, safety liabilities observed in development, and a fundamental tumor-suppressor paradox: inhibiting a molecule with tumor-suppressive roles in the liver creates a therapeutic risk that constrains inhibition-based strategies. These factors collectively illustrate why targeting miR-122 therapeutically remains challenging despite its biological relevance.
Collectively, the assembled evidence positions miR-122 as both a biologically informative regulator of hepatic physiology and pathology and as a promising minimally invasive biomarker for various liver diseases. However, the therapeutic tractability of miR-122 is limited by etiology-specific regulation, safety concerns, resistance mechanisms in viral settings, and the tumor-suppressor paradox. Accurate clinical application—whether for diagnostics, prognosis, or therapeutic targeting—requires careful consideration of specimen source, disease stage, and disease etiology. The review underscores the need for context-aware use of miR-122 measurements and cautions that therapeutic modulation demands strategies that reconcile antiviral or metabolic benefits with oncologic safety concerns.
Note: Specific experimental details, quantitative effect sizes, and trial outcomes referenced in the review are reported in the original article and associated citations; those granular data points were not reproduced in full in the abstract and therefore are not included here.