Network pharmacology analysis uncovers the mechanism of Shudihuang-Shanzhuyu herb pair in prevention and treatment of diabetic osteoporosis via PI3K/AKT pathway.

ETHNOPHARMACOLOGICAL RELEVANCE: Diabetic osteoporosis (DOP) is a complication of diabetes characterized by reduced bone mass and increased fracture risk. Shudihuang (Rehmanniae Radix Praeparata, RR) and Shanzhuyu (Corni Fructus, CF) form a classical herb pair known as RR-CF in traditional Chinese medicine (TCM) for nourishing Yin and tonifying the kidney, and have long been used for the treatment of diabetes and OP in TCM clinical practise. However, the potential mechanism underlying the preventive and therapeutic effects of RR-CF on DOP has not been clarified.

AIM OF THE STUDY: This study aimed to explore the protective effects of RR-CF on bone loss caused by diabetes and elucidate the underlying action mechanism.

METHODS: The chemical constituents in RR-CF were detected using UPLC-Q-Exactive-MS. Type 1 diabetes mellitus (T1DM) was induced in rats by injecting streptozotocin, followed by administration of RR-CF extracts for 10 weeks. Bone mineral density, morphometric bone parameters, and serum and urine biochemical markers were analyzed using Micro-CT and ELISA kits. An in vitro osteoblastic injury model was constructed by subjecting MC3T3-E1 cells to high glucose and used to evaluate the effects of the RR-CF on osteoblastic bone formation. The anti-DOP mechanism of RR-CF was explored by network pharmacologic analysis and then verified in osteoblasts damaged by high glucose.

RESULTS: A total of 56 compounds were identified in RR-CF. Treatment with RR-CF extracts improved the bone microstructure and mineral density in the T1DM rats, and decreased the level of urine deoxypyridinoline and serum carboxyl terminal peptide of type I procollagen. The network pharmacology analysis identified cornuside, hydroxygenkwanin, acteoside, catalpol and echinacoside as the potential active components of RR-CF against DOP by interacting with the key node genes such as AKT1, EGFR, TNF, MMP9 and HSP90α. Further GO and KEGG enrichment analysis suggested that the therapeutic effects of RR, CF and RR-CF seemed to be related to the regulation of hormones, inflammation and metabolism, as well as signaling transductions of PI3K-AKT, IL-17, TNF, MAPK and estrogen signaling pathways. RR-CF promoted osteoblast differentiation and bone formation in the MC3T3-E1 cells by regulating PI3K-AKT signaling pathway.

CONCLUSION: RR-CF herb pair inhibits bone loss caused by high glucose by regulating the PI3K-AKT signaling pathways.