(314) Neonatal Overfeeding in Mice Alters Periovarian Adipose Tissue Development and Disrupts Ovarian Immune and ECM Signaling

In rodents, the neonatal period is a critical window for ovarian development, encompassing both the formation of the primordial follicle pool and the first wave of follicle activation. Disruption of these gonadotropin-independent events can lead to long-term reproductive consequences, including premature ovarian insufficiency. While ovarian local cytokines and growth factors regulate early folliculogenesis, adipose tissue (AT) also secretes adipokines and cytokines known to influence follicle growth and maturation.

As the body’s largest endocrine organ, dysfunctional AT can impair the physiology of neighboring tissues, including the ovary. Periovarian adipose tissue (POAT), a fat depot surrounding the ovary, regulates folliculogenesis and steroidogenesis in pubertal and adult mice, yet its role during the neonatal period remains unknown. Childhood obesity, which disrupts adipokine balance and promotes chronic inflammation, has been linked to precocious puberty and increased infertility risk, but the impact of neonatal overnutrition on POAT and early ovarian development has not been studied. Our study aims to characterize the developmental and secretory dynamics of POAT and evaluate its physiological impact on ovarian function during the neonatal period under normal and overfed conditions. We hypothesize that POAT-produced factors regulate prepubertal ovarian development and that neonatal overnutrition can disrupt POAT function, affecting ovarian physiology.

Using a litter size manipulation model to induce neonatal overfeeding, we investigated the developmental trajectory and function of POAT. Anatomical imaging and histological analysis revealed that POAT transitions from a connective tissue-like structure at postnatal day (PND) 7 to a maturing adipose depot by PND 12, with further maturation by PND 21. Pups from small litters (SL) exhibited increased body weight and significantly greater POAT mass by PND 12 compared to normal litter (NL) controls, suggesting early adipose expansion in response to overnutrition.

Mass spectrometry-based proteomic analysis revealed that SL POAT upregulated proteins involved in metabolism, proteolysis, and lipid localization, while proteins related to transporter activity and protein folding were downregulated. In the ovary, upregulated proteins were enriched in binding and catalytic activity, whereas downregulated proteins were associated with immune function. Notably, the adipokine resistin (RETN) was elevated in SL POAT, accompanied by increased expression of HSD17B1 in the ovary, a steroidogenic enzyme previously shown to be induced by RETN. Conversely, oocyte structural markers ZP1, ZP2, and ZP3 were downregulated in SL ovaries, suggesting compromised oocyte growth.

Transcriptomic profiling of the ovary further revealed that neonatal overfeeding upregulates genes associated with extracellular matrix (ECM) organization, including multiple collagens. Given the critical role of ECM composition and stiffness in follicle growth and primordial follicle activation, these changes may impair the ovarian reserve. Concurrently, immune-related genes were downregulated in SL ovaries. As immune signaling modulates early follicle activation, and Ccr2 loss (a gene reduced in SL ovaries) is known to preserve the primordial follicle pool, these changes likely impact follicle fate. RT-qPCR also revealed increased expression of key folliculogenic regulators (Amh, Kit, Bmp15) and decreased expression of Lepr, indicating altered adipokine responsiveness.

Altogether, these findings demonstrate that neonatal overfeeding disrupts the transcriptional and proteomic landscape of both POAT and the ovary, enhancing metabolic signaling while impairing immune regulation and oocyte growth. This study provides the first developmental and functional characterization of neonatal POAT and highlights its emerging role as a key modulator of early ovarian physiology in the context of early-life nutritional excess.