Abstract:

Metformin (MET) is a well-known first-line drug used to treat diabetes. However, its therapeutic effect and the underlying mechanism in treatment of skeletal diseases are still unclear. In this study, we used the zebrafish osteoporosis model to explore the function and mechanism of metformin in zebrafish bone development and damage repair through fluorescence observation, bone staining, semi-quantitative PCR, in situ hybridization and ELISA assays. Firstly, the working concentration of MET was determined to be 0.1% through embryonic lethality, bone mineralization and calcification. At this concentration, MET enhanced the bone development of zebrafish embryos and juveniles through up-regulation of bone regulatory factors at the mRNA and protein levels. Furthermore, we used ferric ammonium citrate (FAC) and NTR/MTZ system to build zebrafish osteoporosis models in vitro and in vivo, followed by MET treatment, and the experimental results showed that MET can restore the osteoporotic phenotypes, such as the decreased bone mineralization area, reduced spine calcification, and weakened osteogenic differentiation induced by FAC or MTZ, and it functioned through promoting osteoblast regeneration, enhancing the expression of osteoblast markers (sp7, ALP), and inhibiting the activities of osteoclast markers (ctsk, mmp9, TRAP). Finally, we detected the expression levels of Bmp signaling components, and our preliminary data showed that MET can not only enhance the transcriptional and protein expression levels of Bmp, but also promote zebrafish bone development and damage repair by activating Bmp downstream signaling. Taken together, our results show that in addition to treating diabetes, MET can also promote zebrafish bone development and has a significant repair effect on osteoporosis, which will provide new research directions and experimental support for the new applications of old drugs.

Key words: metformin (MET), zebrafish, osteoporosis, damage rapair, Bmp