Hepatocyte-specific PPARγ Deletion Uncovers Role of an Antagonistic PPARγ–HNF4α Transcriptional Axis in MASLD Progression

Systemic PPARγ agonist therapies have been investigated for clinical use in MASLD. Previous studies, however, have shown that PPARγ activation in hepatocytes worsens MASLD. Overall, the precise molecular mechanisms regulated by PPARγ in hepatocyte during MASLD remain incompletely defined. Hepatocyte-specific PPARγ knockout mice were fed a clinically-relevant fast-food diet (FFD) for 2 or 5-months to characterize the role of PPARγ in MASLD progression. PPARγ expression and activity were increased in murine FFD-model and in hepatocytes of human MASLD/MASH patients, based on single-nucleus RNA-sequencing analysis. PPARγ-deletion conferred protection against diet-induced steatosis, fibrosis, and liver injury by suppressing lipogenic, inflammatory, and fibrogenic signaling. Although de-novo fatty-acid synthesis was only modestly affected and compensated with disease progression, enhancement of lipolysis and suppression of lipid droplet stabilization machinery was persistent. PPARγ-deletion robustly inhibited expression and signaling-activity of TGFβ1, a master regulator of hepatic fibrosis, throughout the progression of MASLD. Importantly, a novel PPARγ-HNF4α regulatory axis in MASLD was identified, with increased HNF4α mRNA/protein expression and activation of its downstream metabolic networks in PPARγ-deficient livers. Further, integration of ChIP-seq and transcriptomic analysis revealed that HNF4α might be co-regulating a major fraction (>70%) of genes under direct control of PPARγ during MASLD. This study provides a comprehensive temporal framework for hepatocyte PPARγ function in MASLD, revealing an antagonistic PPARγ-HNF4α transcriptional network that governs hepatic metabolic fate.