Targeting Intracellular Cholesterol Distribution: Mechanisms and Therapeutic Strategies for Metabolic dysfunction-associated steatotic liver disease (MASLD) - PROJECT SUMMARY: Metabolic dysfunction-associated steatotic liver disease (MASLD) is a significant public health concern, affecting up to 25% of the U.S. population. While cholesterol homeostasis is known to influence MASLD pathogenesis, the precise mechanisms by which excess cholesterol exacerbates hepatic lipid accumulation remain unclear. Our laboratory has identified the Aster family of proteins (Aster-A, -B, and -C) as critical mediators of cholesterol transport from the plasma membrane (PM) to the endoplasmic reticulum (ER). Notably, Aster-C is selectively expressed in hepatocytes, the primary cell type responsible for lipid accumulation in MASLD. Our preliminary studies demonstrate that loss of Aster-C in hepatocytes protects against diet-induced hepatic steatosis by reducing lipid accumulation, normalizing liver enzyme levels, and decreasing inflammation-related gene expression. Based on new preliminary data and reviewer feedback, this revised application specifically investigates the role of Aster-C in cholesterol-mediated MASLD progression and evaluates the therapeutic potential of Aster-C inhibition. We hypothesize that Aster-C ablation mitigates hepatic steatosis by reducing ER cholesterol accumulation, which suppresses fatty acid uptake and de novo lipogenesis (DNL) through distinct molecular mechanisms. To test this hypothesis, we propose three aims: Aim 1 will determine how Aster-C loss reduces fatty acid uptake in hepatocytes by modulating the Nrf1/Nfe2L1-CD36 pathway. Aim 2 will investigate the impact of Aster-C loss on oxysterol synthesis and LXR-SREBP1c-mediated DNL. Aim 3 will evaluate the therapeutic potential of newly identified Aster-C-specific inhibitors in diet-induced MASLD models through pharmacokinetic and efficacy studies. These studies will elucidate the molecular mechanisms linking intracellular cholesterol transport to MASLD progression and establish Aster-C as a potential therapeutic target for MASLD.
