Osteoporosis and Leptin: A Systematic Review.

Background: Leptin has a great effect on bone through direct or indirect involvement in bone remodeling. Considering the ambiguities that exist regarding the effect of leptin on bone and bone-related diseases including osteoporosis, in this study, we aimed to conduct a systematic review of various studies on the effect of leptin on osteoporosis, which may find an answer to the existing ambiguities. Methods: The search was performed to review studies on the effects of leptin on osteoporosis by using several databases including Scopus, PubMed, Web of Science, and Google Scholar. Electronic searches were conducted on 5 Jan 2023. There was no limit on the publication date of the articles. The risk of bias for the animal study was assessed with the CAMARADES checklist, and the study quality assessment was also assessed based on the guidelines for in vivo experiments (ARRIVE). In this study, the risk of bias (quality) of human studies was assessed using the quality assessment checklists by NHLBI. Results: Overall, 34 articles were included for data extraction and quality assessment. Overall, 27 human studies and seven animal studies were included in the article. The results of most of the studies conducted in this study showed that leptin has a physiological role in maintaining bone mass and better bone quality and reduces bone marrow adipogenesis and increases bone mineral density (BMD). As plasma leptin levels increased, BMD values or bone formation biomarkers increased. Conclusion: Leptin has an inhibitory role against bone resorption and increasing osteoprotegerin (OPG) levels, which, as a result, maintains bone density and reduces osteoclast activity, and has a positive relationship with increasing osteocalcin.