Background/Objectives: Ejiao, a macromolecular protein complex derived from donkey hide, is a traditional Chinese medicine with clinically demonstrated efficacy against ulcerative colitis (UC). Due to its large molecular size and poor absorbability, its therapeutic effects are presumed to depend on gut microbiota. We hypothesized that specific gut bacteria capable of degrading Ejiao might also mediate its biological functions. Methods: To test this hypothesis, a systematic investigation was conducted by integrating culturomics, proteomics, metabolomics, 16S rRNA gene amplicon high-throughput sequencing, and animal disease models. Results: A total of 134 human gut bacterial strains capable of utilizing Ejiao as a nutrient source were isolated. Among them, Ligilactobacillus salivarius D3-8 exhibited the strongest growth in Ejiao-based medium. Genomic analysis identified 63 protease/peptidase genes, and peptidomic profiling confirmed its degradation activity, which released 50 novel peptides. Notably, administration of L. salivarius D3-8 alone significantly alleviated dextran sodium sulfate (DSS)-induced colitis, concurrently increasing the abundance of beneficial bacterium Dubosiella newyorkensis and elevating the anti-inflammatory metabolite indole-3-carbinol via upregulated tryptophan metabolism. Conclusions: Our findings identify L. salivarius D3-8 as both a dedicated Ejiao-degrader and a protective probiotic against colitis. This work provides direct evidence that gut bacteria can utilize Ejiao and proposes a potential novel mechanistic framework in which the biological effects of Ejiao may be mediated through its interaction with specific, functionally potent degraders such as L. salivarius D3-8.

Background: Premature ovarian insufficiency (POI) is an intractable reproductive endocrine disease characterized by accelerated ovarian aging, accelerated follicle depletion and hormonal disorders, leading to secondary bone metabolic dysfunction and impaired long-term female health. Conventional hormone replacement therapy is the guideline-recommended first-line therapy for young women with POI, yet its long-term safety must be individualized; natural nutritional interventions are best viewed as complementary strategies. Donkey-hide gelatin (Ejiao), a natural food rich in bioactive collagen and amino acids, is commonly used for female reproductive care. Nevertheless, its systematic efficacy and molecular mechanisms against POI and related bone complications remain poorly defined. Methods: This study established a tripterygium glycosides (TG)-induced POI mouse model. Mice received low-dose (1.5 g/kg) and high-dose (3.0 g/kg) Ejiao treatment for 30 consecutive days. Reproductive organ morphology, estrous cycle, serum hormone levels, ovarian histopathology, bone microarchitecture and ovarian proteomic profiles were assessed. Results: Ejiao remarkably restored ovarian index and tended to improve uterine index (non-significant), corrected estrous cycle disturbance, and partially corrected the endocrine profile (E2, AMH, GnRH). It upregulated the ovarian reserve markers E2 and AMH and downregulated GnRH. Histological examination verified improved follicular development and reduced atresia. Furthermore, Ejiao alleviated POI-induced bone loss, optimized trabecular microstructure and rescued abnormal RANKL/OPG ratio to stabilize bone metabolism. Proteomic analysis revealed 313 differentially expressed proteins (DEPs) between Ejiao-treated and model groups, with enrichment in calcium signaling, cAMP, cGMP-PKG, and TGF-β/Smad pathways. Conclusions: As a natural bioactive food, Ejiao exerts dual protective effects against POI and concurrent bone metabolic dysfunction associated with modulation of multiple core signaling pathways and functional proteins (suggesting involvement of these pathways in its effects).