Lipid Droplet Remodeling Safeguards Redox Balance through the DGAT1-PANK2-NRF2 Axis in Mammalian Oocytes and Drives Age-Associated Decline

Abstract

How lipid droplets (LDs) buffer metabolic stress and redox imbalance in aging oocytes remains poorly understood. Here, we identify de novo LD remodeling as a metabolic capacitor that couples lipid storage to mitochondrial fitness and oxidative resilience in mammalian oocytes. Live imaging revealed pronounced LD dynamics, with LD number peaking at metaphase I and declining by metaphase II, while LD area shifted inversely. Despite stable triacylglyceride and free fatty acid pools, {beta}-oxidation increased sharply, indicating elevated lipid turnover during meiotic progression. Spatial mapping and fatty-acid tracing demonstrated that newly synthesized lipids are actively incorporated into LDs, which arise primarily from the endoplasmic reticulum and engage with lysosomes and mitochondria. Acute inhibition of DGAT1, the rate-limiting enzyme of LD biogenesis, disrupted meiotic maturation and triggered oxidative stress, mitochondrial aggregation, and ultrastructural damage. Proteomic profiling revealed robust PANK2 upregulation and suppression of NRF2-linked antioxidant pathways. Mechanistic analyses showed that {beta}-oxidation blockade, PANK2 inhibition, antioxidant supplementation, or NRF2 activation each partially rescued DGAT1-dependent defects, and genetic validation in NRF2-null oocytes confirmed pathway dependence. Notably, aged oocytes exhibited reduced de novo LD biogenesis and impaired DGAT1-ER organization despite increased LD accumulation, resulting in smaller, metabolically inert droplets and a mismatch between lipid formation and utilization. Inhibiting PANK2 alleviated oxidative stress in aged oocytes, further implicating the DGAT1-PANK2-NRF2 axis in redox control and oocyte quality. Together, these findings establish LD biogenesis as a core metabolic capacitor safeguarding mitochondrial and organelle integrity during meiosis and reveal dysfunction of the DGAT1-PANK2-NRF2 axis as a mechanistic driver of reproductive aging.