Lipidomic Remodeling by HILPDA in Granulosa Cells Impairs Ovarian Reserve Through Disruption of Mitochondrial and Endoplasmic Reticulum Homeostasis.

Diminished ovarian reserve (DOR) is characterized by a decline in oocyte quantity and/or quality and represents a growing cause of female infertility, particularly among young women, yet its pathogenesis remains incompletely understood. Disordered lipid metabolism impairs folliculogenesis and steroidogenesis, thereby contributing to the pathological changes of DOR. Here, we identify hypoxia-inducible lipid droplet-associated protein (HILPDA), a regulator of lipid droplet biogenesis, as a potential contributor to DOR. We found that HILPDA was significantly upregulated in granulosa cells (GCs) from DOR patients and that its expression levels correlated with reduced ovarian reserve indicators and adverse assisted reproductive technology (ART) outcomes. Ovarian overexpression of HILPDA in mice promoted follicular atresia and disrupted the estrous cycle. In KGN cells, HILPDA overexpression suppressed proliferation and induced apoptosis. Mechanistically, HILPDA overexpression promoted excessive accumulation of triglyceride-rich lipid droplets, accompanied by depletion of phospholipids, cholesteryl esters, and mitochondrial cardiolipin species. This lipid remodeling was associated with impaired estradiol biosynthesis, mitochondrial dysfunction, and endoplasmic reticulum stress activation. Genetic restoration of lipolysis via adipose triglyceride lipase (ATGL) overexpression or pharmacological inhibition of excessive lipid droplet formation alleviated HILPDA-associated lipotoxicity and cellular dysfunction. Collectively, these findings suggest that HILPDA may play an important role in GC dysfunction in DOR through reprogramming lipid metabolism and indicate that targeting this pathway may represent a potential therapeutic strategy for DOR.