Excess and sustained endoplasmic reticulum (ER) stress, paired with a failure of initial adaptive responses, acts as a critical trigger of nonalcoholic fatty liver disease (NAFLD) progression. Unfortunately, there is no drug currently approved for treatment, and the molecular basis of pathogenesis by ER stress remains poorly understood. Classical ER stress pathway molecules have distinct but inter-connected functions and complicated effects at each phase of the disease. Identification of the specific molecular signal mediators of the ER stress-mediated pathogenesis is, therefore, a crucial step in the development of new treatments. These signaling nodes may be specific to the cell type and/or the phase of disease progression. In this review, we highlight the recent advancements in knowledge concerning signaling nodes associated with ER stress and NAFLD progression in various types of liver cells.

Chronic liver injury due to various hepatotoxic stimuli commonly leads to fibrosis, which is a crucial factor contributing to liver disease-related mortality. Despite the potential benefits of Suaeda glauca (S. glauca) as a natural product, its biological and therapeutic effects are barely known. This study investigated the effects of S. glauca extract (SGE), obtained from a smart farming system utilizing LED lamps, on the activation of hepatic stellate cells (HSCs) and the development of liver fibrosis. C57BL/6 mice received oral administration of either vehicle or SGE (30 or 100 mg/kg) during CCl₄ treatment for 6 weeks. The supplementation of SGE significantly reduced liver fibrosis induced by CCl₄ in mice as evidenced by histological changes and a decrease in collagen accumulation. SGE treatment also led to a reduction in markers of HSC activation and inflammation as well as an improvement in blood biochemical parameters. Furthermore, SGE administration diminished fibrotic responses following acute liver injury. Mechanistically, SGE treatment prevented HSC activation and inhibited the phosphorylation and nuclear translocation of Smad2/3, which are induced by transforming growth factor (TGF)-β1 in HSCs. Our findings indicate that SGE exhibits anti-fibrotic effects by inhibiting TGFβ1-Smad2/3 signaling in HSCs.

Iron overload has emerged as a significant risk factor for metabolic dysfunction–associated steatotic liver disease (MASLD), a growing global health concern. Despite this association, the precise mechanisms by which hepatic iron and its regulatory genes connect liver pathology to systemic metabolic dysfunction remain elusive. Here, we demonstrate that humoral signals originating from iron-overloaded hepatocytes acted as critical mediators driving systemic metabolic dysfunction in MASLD. Ferroportin (FPN, SLC40A1), the sole cellular iron exporter, exhibited markedly reduced expression in hepatocytes of both patients with MASLD and mouse models of the disease, concomitant with hepatic iron accumulation. Functionally, hepatocyte-specific FPN deletion significantly exacerbated diet-induced obesity and insulin resistance, with these metabolic perturbations accompanied by decreased energy expenditure and impaired thermogenic capacity. Mechanistically, we establish that hepatic iron accumulation resulting from FPN deficiency enhanced the production of 2 specific hepatokines, fetuin-A and LECT2, through activation of the transcription factor FoxO1. Notably, therapeutic interventions — including genetic silencing of these hepatokines, hepatocyte-specific FPN overexpression, or oral iron chelation — effectively reversed the metabolic dysfunction phenotypes. These findings provide critical insights into the pathophysiological mechanisms linking MASLD to systemic metabolic disorders and highlight promising therapeutic strategies to combat these diseases.