Metabolic disorders

Abstract 

Loss of HCF-1 results in severe liver injury, causing hallmark features of NAFLD, including steatosis, inflammation, fibrosis, and mitochondrial dysfunction. Following injury, hepatocytes typically re-enter the cell cycle to replenish lost cells. However, in the absence of HCF-1, hepatocytes fail to proliferate leading to a progressive decline in liver function. Even upon 2/3 PH, HCF-1-deficient hepatocytes remain arrested in the cell cycle, further exacerbating disease severity and preventing tissue regeneration. RNA-seq analyses revealed significant downregulation of genes involved in cell cycle progression, metabolism, and mitochondrial structure and function including those regulating oxidative phosphorylation. ChIP-seq data showed altered H3K4me3 patterns at promoter and enhancer regions of key hepatic genes. These findings indicate that HCF-1 is essential for maintaining transcriptional and epigenetic landscapes necessary for hepatocyte proliferation and regeneration. 

Abstract 

Host cell factor-1 (HCF-1) is a transcriptional coregulator essential for maintaining liver function and cellular metabolism. O-linked N-acetylglucosamine transferase (OGT) is a key nutrient-sensing enzyme that catalyzes protein O-GlcNAcylation, a critical post-translational modification regulating metabolic pathways. This study investigates the role of hepatocyte-specific depletion of HCF-1 in regulating OGT stability, activity, and cellular localization in hepatocytes. Using a transgenic mouse model with hepatocyte-specific HCF-1 deletion, we assessed the impact of HCF-1 loss on OGT expression and O-GlcNAcylation activity. OGT protein levels, mRNA expression, and cellular localization were evaluated using molecular and histological techniques. Comparisons were made with control mice and hepatocytes under nutrient-starved conditions. Hepatocyte-specific HCF-1 deletion led to progressive loss of HCF-1 protein and a concomitant decrease in OGT levels and global O-GlcNAcylation. Loss of HCF-1 did not alter OGT mRNA levels, suggesting post-translational regulation. Immunofluorescence revealed reduced nuclear OGT and O-GlcNAcylation, mimicking changes observed under fasting conditions. Isolated HCF-1-deficient hepatocytes showed impaired adhesion, further underscoring HCF-1's role in hepatocyte function. Notably, in heterozygous Hcfc1hepKO/ + females, HCF-1-negative hepatocytes displayed cytoplasmic O-GlcNAcylation, while HCF-1-positive cells maintained nuclear localization. HCF-1 is crucial for regulating OGT stability, activity, and nuclear localization in hepatocytes. These findings establish a mechanistic link between HCF-1 and OGT, highlighting their coordinated role in hepatic nutrient sensing and metabolic regulation. 

Abstract 

Metabolic Dysfunction-Associated Fatty Liver Disease (MAFLD) is a major global health issue, affecting millions, yet its underlying molecular mechanisms remain poorly understood. Here, we propose a novel diet-induced zebrafish model to investigate pathophysiology of MAFLD. To validate the model, we performed comprehensive histological analysis and molecular assessments, including RNA-sequencing, to characterize the disease progression. These approaches enabled us to examine the molecular alterations underlying MAFLD and identify key genes and pathways involved in its development. Our results demonstrate that zebrafish subjected to a high-fat diet exhibit significant weight gain and show prominent fat accumulation in the liver, as confirmed by Oil Red O and BODIPY staining. Quantitative PCR analysis reveals upregulation of key lipogenic genes, including acc, fasn, hmgcs1, and hmgcra, indicating enhanced lipid synthesis. Immunoblotting also shows increased expression of several proteins (SIRT1, SREBP-1c, CEBPA and PGC-1α) involved in lipogenesis and glucose metabolism. Additionally, we observe increased expression of genes associated with endoplasmic reticulum stress, such as atf6, xbp1, gadd45a, and ddit3, along with activation of the mitochondrial unfolded protein response and inflammatory pathways, as indicated by elevated levels of hspd1, hspa9, clpp, lonp1, il1β and il8. These findings point to mitochondrial dysfunction, further supported by the dysregulation of genes involved in oxidative phosphorylation, including uqcrc2, cox4i1, sdha, nd1, and atp5f1b at both mRNA and protein levels. Transcriptomic profiling identifies new candidate markers such as inha, gck, ces2a, id3 and highlights dysregulated pathways involved in metabolism, insulin signaling, and cellular stress, offering insights into MAFLD progression. This study establishes a zebrafish model that recapitulates key features of MAFLD, including histopathological and metabolic alterations. Through transcriptomic and protein analysis, we identify novel biomarkers and pathways, providing new insights into MAFLD pathogenesis and highlighting potential therapeutic targets.