MASLD protection by STAT5-regulated transcription factors - Summary/Abstract Metabolic dysfunction-associated steatotic liver disease (MASLD) predisposes the liver to cirrhosis and hepatocellular carcinoma and is a leading cause for chronic liver disease and liver transplantation. Importantly, pre- but not post-menopausal women show a lower prevalence of MASLD than men. Clinical and experimental studies indicate that growth hormone (GH) protects the liver from steatosis and MASLD progression, but the underlying molecular and regulatory mechanisms are largely unknown. Prior work by our research groups using a mouse model of adult-onset, hepatocyte-specific GH receptor knockdown indicates the protection afforded females against MASLD can in part be explained by the sexually-dimorphic temporal pattern of pituitary GH secretion, and consequently, sex-dependent GH-activation of hepatic Stat5 activity (persistent in females vs. pulsatile in males); this, in turn, regulates the sex-dependent liver transcriptome, including expression of key sex-dependent liver transcription factors (TFs). The work proposed builds on these prior research findings and supports two central hypotheses: 1) integrative crosstalk between sex-biased TFs controls the female-dependent actions of GH and Stat5 on the hepatocyte transcriptome to confer protection from steatosis; and 2) persistent Stat5 signaling, as occurs in female liver, maintains hepatocyte-specific programs that go beyond controlling steatosis, and interact with liver non-parenchymal cells to reduce fibrosis and slow MASLD disease progression. To address these hypotheses, Aim 1 will use adult-onset, hepatocyte- specific knockdown technology to elucidate contributions of two female-biased hepatocyte TFs to GH/Stat5- signaling in sustaining female-biased gene expression and protection from steatosis. Aim 1 will also determine the potential for one of these TFs, Cux2, to feminize the male liver transcriptome and prevent steatosis. In Aim 2, mice will be fed a translationally relevant diet that induces MASLD to elucidate the hepatoprotective actions of persistent hepatocyte Stat5 activity on liver-specific disease progression. Single nucleus RNA-seq will be used to elucidate how sex-dependent, hepatocyte-specific signaling downstream of Stat5 alters expression of genes critical for controlling hepatocyte regeneration, senescence, stress and death, and their impact on cell- cell communication with liver non-parenchymal cells key to MASLD pathology. Together, this work is expected to shift current research paradigms on the hormonal control of sex-differences in liver disease, which are largely focused on gonadal steroids, to elucidate how persistent, plasma GH pattern-determined hepatic Stat5 activity and its downstream sex-dependent liver TFs protect females across the spectrum of MASLD to slow disease progression. Fundamental new knowledge will be gained in the fields of GH signaling and action, sex differences in liver biology, and MASLD development, and is expected to have real potential to unveil novel therapeutic strategies and druggable targets to treat this devastating disease and leading cause of liver failure.
