Discovery of Novel Binders to Sterol Regulatory Element-Binding Protein-1 by High-Throughput Screening.

Sterol regulatory element-binding protein-1 (SREBP-1) is a transcription factor that regulates the expression of genes related to fatty acid biosynthesis. Its high expression and activation in obesity and associated metabolic diseases make it a potential therapeutic target. However, the role of SREBP-1 in the development and exacerbation of these diseases remains unclear, partly because of the impossibility of inhibiting its function because of the lack of specific inhibitors. Here, we aimed to identify small-molecule compounds that directly bind to SREBP-1 using the recombinant N-terminal region of SREBP-1a, which is required for its transcriptional activity. A high-throughput screening campaign was conducted using a thermal shift assay and surface plasmon resonance assay to evaluate the compound affinity and specificity, which resulted in the identification of two compounds. Future analysis of their structure-activity relationships may lead to the development of specific SREBP-1 inhibitors, thereby potentially validating SREBP-1 as a therapeutic target for obesity and resultant atherosclerotic diseases.

Establishment of a cell culture platform for human liver organoids and its application for lipid metabolism research.

Human liver organoids (HLOs) are reliable tools to represent physiological human liver biology. However, their use is limited especially in basic sciences. One of the reasons for this would be the insufficient systematic methodology to handle HLOs, including culture system, functional assessment, and gene transduction. Here, we generated and characterized mouse L cells stably and simultaneously overexpressing R-spondin1, hepatocyte growth factor, fibroblast growth factor (FGF) 7, and FGF10 via lentiviral transduction. The conditioned medium of the cells contributed to HLO growth as a replacement of commercially available recombinant proteins, which leads to a significant reduction of their culture cost. Proliferative and maturation phases of the cells were controlled by switching the medium to facilitate the evaluation of hepatocyte function, including insulin responsiveness and intracellular lipid accumulation. Gene expression analysis revealed that HLOs highly expressed genes involved in lipid metabolism. Importantly, HLOs secreted physiologically matured very low-density lipoprotein, which is rarely observed in mice and in established cell lines. Efficient gene transduction into HLOs was achieved via a transient 2-dimensional culture during viral infection. This study provides an invaluable platform for utilizing HLOs in various research fields, such as molecular biology, pharmacology, toxicology, and regenerative medicine.