ACMSD inhibition corrects fibrosis, inflammation, and DNA damage in MASLD/MASH.

Recent findings reveal the importance of tryptophan-initiated de novo nicotinamide adenine dinucleotide (NAD+) synthesis in the liver, a process previously considered secondary to biosynthesis from nicotinamide. The enzyme α-amino-β-carboxymuconate-ε-semialdehyde decarboxylase (ACMSD), primarily expressed in the liver and kidney, acts as a modulator of de novo NAD+ synthesis. Boosting NAD+ levels has previously demonstrated remarkable metabolic benefits in mouse models. In this study, we aimed to investigate the therapeutic implications of ACMSD inhibition in the treatment of metabolic dysfunction-associated steatotic liver disease/steatohepatitis (MASLD/MASH). In vitro experiments were conducted in primary rodent hepatocytes, Huh7 human liver carcinoma cells and induced pluripotent stem cell-derived human liver organoids (HLOs). C57BL/6J male mice were fed a western-style diet and housed at thermoneutrality to recapitulate key aspects of MASLD/MASH. Pharmacological ACMSD inhibition was given therapeutically, following disease onset. HLO models of steatohepatitis were used to assess the DNA damage responses to ACMSD inhibition in human contexts. Inhibiting ACMSD with a novel specific pharmacological inhibitor promotes de novo NAD+ synthesis and reduces DNA damage ex vivo, in vivo, and in HLO models. In mouse models of MASLD/MASH, de novo NAD+ biosynthesis is suppressed, and transcriptomic DNA damage signatures correlate with disease severity; in humans, Mendelian randomization-based genetic analysis suggests a notable impact of genomic stress on liver disease susceptibility. Therapeutic inhibition of ACMSD in mice increases liver NAD+ and reverses MASLD/MASH, mitigating fibrosis, inflammation, and DNA damage, as observed in HLO models of steatohepatitis. Our findings highlight the benefits of ACMSD inhibition in enhancing hepatic NAD+ levels and enabling genomic protection, underscoring its therapeutic potential in MASLD/MASH. Enhancing NAD+ levels has been shown to induce remarkable health benefits in mouse models of metabolic dysfunction-associated steatotic liver disease/steatohepatitis (MASLD/MASH), yet liver-specific NAD+ boosting strategies remain underexplored. Here, we present a novel pharmacological approach to enhance de novo synthesis of NAD+ in the liver by inhibiting α-amino-β-carboxymuconate-ε-semialdehyde decarboxylase (ACMSD), an enzyme highly expressed in the liver. Inhibiting ACMSD increases NAD+ levels, enhances mitochondrial respiration, and maintains genomic stability in hepatocytes ex vivo and in vivo. These molecular benefits prevent disease progression in both mouse and human liver organoid models of steatohepatitis. Our preclinical study identifies ACMSD as a promising target for MASLD/MASH management and lays the groundwork for developing ACMSD inhibitors as a clinical treatment.

Liu YJ ，Kimura M ，Li X ，Sulc J ，Wang Q ，Rodríguez-López S ，Scantlebery AML ，Strotjohann K ，Gallart-Ayala H ，Vijayakumar A ，Myers RP ，Ivanisevic J ，Houtkooper RH ，Subramanian GM ，Takebe T ，Auwerx J ... -  《-》

Inhibition of ATGL alleviates MASH via impaired PPARα signalling that favours hydrophilic bile acid composition in mice.

Adipose triglyceride lipase (ATGL) is an attractive therapeutic target in insulin resistance and metabolic dysfunction-associated steatotic liver disease (MASLD). This study investigated the effects of pharmacological ATGL inhibition on the development of metabolic dysfunction-associated steatohepatitis (MASH) and fibrosis in mice. Streptozotocin-injected male mice were fed a high-fat diet to induce MASH. Mice receiving the ATGL inhibitor atglistatin (ATGLi) were compared to controls using liver histology, lipidomics, metabolomics, 16s rRNA, and RNA sequencing. Human ileal organoids, HepG2 cells, and Caco2 cells treated with the human ATGL inhibitor NG-497, HepG2 ATGL knockdown cells, gel-shift, and luciferase assays were analysed for mechanistic insights. We validated the benefits of ATGLi on steatohepatitis and fibrosis in a low-methionine choline-deficient mouse model. ATGLi improved serum liver enzymes, hepatic lipid content, and histological liver injury. Mechanistically, ATGLi attenuated PPARα signalling, favouring hydrophilic bile acid (BA) synthesis with increased Cyp7a1, Cyp27a1, Cyp2c70, and reduced Cyp8b1 expression. Additionally, reduced intestinal Cd36 and Abca1, along with increased Abcg5 expression, were consistent with reduced levels of hepatic triacylglycerol species containing polyunsaturated fatty acids, like linoleic acid, as well as reduced cholesterol levels in the liver and plasma. Similar changes in gene expression associated with PPARα signalling and intestinal lipid transport were observed in ileal organoids treated with NG-497. Furthermore, HepG2 ATGL knockdown cells revealed reduced expression of PPARα target genes and upregulation of genes involved in hydrophilic BA synthesis, consistent with reduced PPARα binding and luciferase activity in the presence of the ATGL inhibitors. Inhibition of ATGL attenuates PPARα signalling, translating into hydrophilic BA composition, interfering with dietary lipid absorption, and improving metabolic disturbances. Validation with NG-497 opens a new therapeutic perspective for MASLD. Despite the recent approval of drugs novel mechanistic insights and pathophysiology-oriented therapeutic options for MASLD (metabolic dysfunction-associated steatotic liver disease) are still urgently needed. Herein, we show that pharmacological inhibition of ATGL, the key enzyme in lipid hydrolysis, using atglistatin (ATGLi), improves MASH (metabolic dysfunction-associated steatohepatitis), fibrosis, and key features of metabolic dysfunction in mouse models of MASH and liver fibrosis. Mechanistically, we demonstrated that attenuation of PPARα signalling in the liver and gut favours hydrophilic bile acid composition, ultimately interfering with dietary lipid absorption. One of the drawbacks of ATGLi is its lack of efficacy against human ATGL, thus limiting its clinical applicability. Against this backdrop, we could show that ATGL inhibition using the human inhibitor NG-497 in human primary ileum-derived organoids, Caco2 cells, and HepG2 cells translated into therapeutic mechanisms similar to ATGLi. Collectively, these findings reveal a possible new avenue for MASLD treatment.

Dixon ED ，Claudel T ，Nardo AD ，Riva A ，Fuchs CD ，Mlitz V ，Busslinger G ，Scharnagl H ，Stojakovic T ，Senéca J ，Hinteregger H ，Grabner GF ，Kratky D ，Verkade H ，Zimmermann R ，Haemmerle G ，Trauner M ... -  《-》

Targeting PYK2 with heterobifunctional T6BP helps mitigate MASLD and MASH-HCC progression.

The mechanisms underlying the regulation of hepatocyte non-receptor tyrosine kinases in metabolic dysfunction-associated steatohepatitis (MASH) remain largely unclear. Hepatocyte-specific overexpression or deletion and anti-protein tyrosine kinase 2 beta (PYK2) or anti-TRAF6-binding protein (T6BP) crosslinking were utilised to study fatty liver protection by T6BP. P-PTC, a peptide-proteolysis targeting chimaera, degrades PYK2 to block MASH progression. Since PYK2 activation is promoter signalling in steatohepatitis development, we find that T6BP is a novel and critical suppressor of PYK2 that reduces hepatic lipid accumulation, pro-inflammatory factor release, and pro-fibrosis production by ubiquitin ligase CBL to degrade PYK2. Mechanistic evidence suggests that T6BP directly targets PYK2 and prevents its N-terminal FERM domain-triggered dimerization, disrupting downstream PYK2-JNK signalling hyperactivation. Additionally, T6BP favourably recruits CBL, a particular E3 ubiquitin ligase targeting PYK2, to form a complex and degrade PYK2. T6BP (F1), a core fragment of T6BP, directly blocks N-terminal FERM domain-associated dimerization of PYK2, followed by T6BP-recruiting CBL-mediated PYK2 degradation in a typical T6BP-dependent manner when the tiny fragment is specifically expressed using thyroxine binding globulin (TBG)-ground vectors. This inhibits the progression of MASH, metabolic dysfunction-associated steatotic liver disease (MASLD)-related HCC (MASH-HCC), and metabolic syndrome in dietary rodent models. First-ever peptide-proteolysis targeting chimaera (P-PTC) based on the core segment of T6BP as a ligand for targeted recruitment of CBL targeting metabolic disorders like MASH has been devised and validated in animal models. Our study revealed a previously unknown mechanism: identification of T6BP as a key eliminator of fatty liver strongly contributes to the development of promising therapeutic targets, and the discovery of crucial fragments of T6BP-based pharmacon that interrupt PYK2 dimerization are novel and viable treatments for fatty liver and its advanced symptoms and complications. Excessive high-energy diet ingestion is critical in driving steatohepatitis via regulation of hepatocyte non-receptor tyrosine kinases. The mechanisms under lying the regulation of hepatocyte PYK2 in metabolic dysfunction-associated steatohepatitis (MASH) remain largely unclear. Here, we found that T6BP as a critical fatty liver eliminator has a significant impact on the development of promising therapeutic targets. Additionally, vital T6BP-based pharmacon fragments that impede PYK2 dimerization have been found, offering new and effective treatments for advanced fatty liver symptoms and complications.

Xu M ，Zhao J ，Zhu L ，Ge C ，Sun Y ，Wang R ，Li Y ，Dai X ，Kuang Q ，Hu L ，Luo J ，Kuang G ，Ren Y ，Wang B ，Tan J ，Shi S ... -  《-》

Hinokitiol ameliorates MASH in mice by therapeutic targeting of hepatic Nrf2 and inhibiting hepatocyte ferroptosis.

Metabolic dysfunction-associated steatohepatitis (MASH), an advanced stage of metabolic dysfunction-associated steatotic liver disease (MASLD), still lacks approved effective clinical drugs. Ferroptosis, a form of regulated cell death driven by excessive iron accumulation and uncontrollable lipid peroxidation, has been proven to be a trigger of inflammation and initiation of steatohepatitis. The pathogenic interplay is modulated by oxidative stress, while the Nrf2-mediated antioxidant response plays a regulatory role in ferroptosis. Phytochemical hinokitiol (Hino) has demonstrated positive efficacy in hepatocellular carcinoma (HCC) in the reported work, but it remains unknown whether its therapeutic effect attributes to delaying the progress of steatohepatitis to HCC. This work aimed to systemically investigate the significance of ferroptosis in the pathogenesis of MASH and to demonstrate that Hino, a bioactive monoterpene compound, attenuates the primary pathological characteristics of MASH via promotion of Nrf2/GPX4 signaling. In this work, a MASH model was established using the high-fat/high-cholesterol (HFHC) diet-fed in vivo and palmitic acid/oleic acid (PO)-stimulated hepatocytes in vitro. Biochemical indexes, pathological analysis, western blot, PCR assay, energy metabolic phenotype, molecular docking, and confirmatory assays were performed comprehensively to reveal the key link between the Nrf2/GPX4 axis and the treatment of MASH. Under MASH conditions with increased oxidative stress, we show that Nrf2 was remarkable downregulated in HFHC diet-fed mice and PO-managed hepatocytes. Mechanistically, hepatic upregulation of Nrf2 through phytochemical Hino supplementation inhibited ferroptosis, enhanced lipid metabolism, and thereby alleviated hepatic steatosis, inflammation, and fibrosis. Conversely, silencing Nrf2 in hepatocytes further promoted the accumulation of key markers of ferroptosis and aggravated MASH phenotypes. Increased ferroptosis promoted steatosis which further drove inflammation and hepatic fibrosis. Our results suggested the significance of Nrf2 in ameliorating MASH, which was regulated through Hino. Thus, targeted inhibition of ferroptosis through Hino administration is a feasible and effective approach for treating MASH.

Yin X ，Liu Z ，Li C ，Wang J ... -  《-》

Fibroblast growth factor 21 is a hepatokine involved in MASLD progression.

Gallego-Durán R ，Ampuero J ，Maya-Miles D ，Pastor-Ramírez H ，Montero-Vallejo R ，Rivera-Esteban J ，Álvarez-Amor L ，Pareja MJ ，Rico MC ，Millán R ，Robles-Frías MJ ，Aller R ，Rojas Á ，Muñoz-Hernández R ，Gil-Gómez A ，Gato S ，García-Lozano M ，Arias-Loste MT ，Abad J ，Calleja JL ，Andrade RJ ，Crespo J ，González-Rodríguez Á ，García-Monzón C ，Andreola F ，Pericás JM ，Jalan R ，Martín-Bermudo F ，Romero-Gómez M ... -  《-》