Optimization and verification of high-fat diet formulation for establishing a rat model of obesity-related precocious...

Childhood obesity is closely linked to the rising incidence of precocious puberty (PP), yet valid preclinical models of obesity-related PP remain lacking. High-fat diets (HFD) are widely used for obesity models, but the suitability of different HFD formulations for inducing PP is unknown. Female Sprague-Dawley (SD) rats were randomized to control, 45% HFD, or 60% HFD groups at postnatal day (PND) 21. Body weight and daily caloric intake were monitored; vaginal opening (VO) was recorded from PND 35. At study termination, serum levels of estradiol (E2), luteinizing hormone (LH), follicle-stimulating hormone (FSH), gonadotropin-releasing hormone (GnRH), leptin, and adiponectin were measured. Ovarian histology and vaginal cytology were assessed. In vitro, GT1-7 cells were treated with recombinant mouse leptin for 24 h, and GnRH secretion was quantified. Compared to controls and the 60% HFD group, rats fed 45% HFD exhibited significantly increased body weight, earlier VO onset, and elevated weights of organs. The 45% HFD group also had higher serum E2, LH, FSH, GnRH, and leptin levels, alongside reduced adiponectin; ovarian histology showed advanced follicular development, and vaginal smears displayed estrus-stage cytology. In contrast, the 60% HFD group had no significant changes in body weight or hormonal parameters, and limited ovarian development. In vitro, leptin treatment significantly upregulated GnRH secretion in GT1-7 cells. The 45% HFD formulation is optimal for constructing a juvenile rat model of obesity-related PP, as it recapitulates key phenotypic, histological, and endocrine features of the disease.