Isorhynchophylline Mitigates Bone Loss in OVX Mice by Modulating Inflammatory Responses, Oxidative Stress, Gut Microbiota Composition and SCFAs Production.

Osteoporosis (OP) is a systemic skeletal disorder characterized by reduced bone mass and deteriorated bone architecture. Isorhynchophylline (IRN), an active alkaloid derived from the plant Uncaria rhynchophylla, is known for its significant anti-inflammatory and antioxidant properties. However, its potential role in mitigating bone loss has not been investigated. This study examines the protective effects of IRN against bone loss in ovariectomized (OVX) mice, with a focus on its regulation of inflammatory responses, oxidative stress, gut microbiota composition, the production of short-chain fatty acids (SCFAs) and the intestinal barrier. The research methods include network pharmacology, molecular docking, and in vivo experiment. Network pharmacology analysis identified 50 intersecting targets between IRN and OP, with molecular docking demonstrating strong binding affinities of IRN to EGFR and GSK3B. GO and KEGG enrichment analyses revealed that IRN is involved in many key pathways related to cell survival, inflammation, and oxidative stress, such as the PI3K-Akt signaling pathway. In vivo assessment showed that IRN treatment reduced serum levels of the inflammatory cytokines, such as TNF-α, IL-1β and IL-6, while increasing serum levels of the anti-inflammatory cytokine IL-10 in OVX mice. IRN effectively managed the oxidative stress in the OVX model, characterized by lowered serum levels of NO, iNOS, and ROS. Combination of 16S rRNA sequencing and GC-MS analysis found that IRN modulated the gut microbiota composition, reducing the abundance of Campylobacterota and Helicobacter, and increasing the level of butanoic acid. Additionally, immunohistochemical analysis indicates that IRN repaired the compromised intestinal barrier in OVX mice by upregulating the expression of tight junction proteins, including ZO-1, Claudin-1, and Occludin. These results suggest that IRN, through its anti-inflammatory and antioxidant properties, modulation of gut microbiota composition, enhancement of SCFAs production, and protection of the intestinal barrier, provides a new therapeutic approach for natural products to alleviate bone loss.