SUN-690 RSK2 Drives Estrogen Linked De Novo Lipogenesis in the Liver

Abstract Disclosure: A. Preminger: None. Female mice lacking RSK2, a serine/threonine kinase, exhibit 40% reduced fertility compared to wildtype (WT) mice, despite maintaining a normal estrus cycle. Given the tight connection between fertility and metabolism, particularly the regulation of lipid levels during pregnancy for fetal health and viability, we investigated the role of RSK2 in the liver, the central hub for metabolism, as a potential explanation for the reduced fertility observed in RSK2 knockout (KO) mice. This led us to find that RSK2 is necessary for estrogen associated upregulation of genes essential for de novo lipogenesis in the liver. Building upon previous reports linking RSK2 to estrogen signaling, we performed RNA sequencing on bulk liver samples and found that RSK2 KO mice had a reduced estrogen response based on cumulative expression of estrogen-linked genes (p=0.0003). Furthermore, transcriptome pathway analysis identified cholesterol and fatty acid synthesis and metabolism gene sets as significantly enriched in WT compared to RSK2 KO mice in estrus. To determine the physiological relevance of these transcriptional changes, we used gas chromatography to analyze liver samples and identified reduced levels of triglycerides containing the tightly regulated saturated fatty acids palmitate (p=0.0321) and stearate (p=0.0489), in RSK2 KO mice. Palmitate is the primary product of de novo lipogenesis, and its reduced presence indicated a potential dysregulation of this process. This theory is supported by qRT-PCR analysis, which demonstrated significantly reduced expression (1.8-3.2 fold change) of rate-limiting enzymes involved in de novo lipogenesis, including ACLY (p<0.0001), ACC (p=0.0104), FASN (p=0.0104), and ELOVL6 (p=0.0245), in RSK2 KO mice compared to WT mice in estrus. Additionally, serum triglyceride levels were 20% lower in RSK2 KO mice compared to WT mice (p=0.0041) indicating further dysregulation of lipid metabolism. Finally, HepG2 cells were serum starved overnight before being treated with a RSK1/2 specific inhibitor for 24 hours, and a 2-fold reduction in ACLY was observed in line with in vivo observations. In this study, we have identified RSK2 as an important effector of metabolism in homeostasis and specifically estrogen-associated lipid synthesis in the liver. Moreover, these findings support the hypothesis that RSK2 plays an important role in lipid metabolism and that it potentially impacts fertility through its regulation of the estrogen response across multiple tissues. Presentation: Sunday, July 13, 2025