4. Discussion
This study systematically evaluated the causal relationships between four fitness-related metabolites and myasthenia gravis (MG) and its subtype, limb-girdle myasthenia gravis (LOMG), using a two-sample bidirectional Mendelian randomization approach. The results indicated that glutamine exhibits a robust protective effect on LOMG, while citrulline and testosterone show protective signals for LOMG and MG, respectively, although these findings require cautious interpretation. Additionally, lactate was identified as a potential risk factor for MG. These findings suggest that fitness-related metabolites may influence the risk of developing MG and its subtypes through mechanisms such as immune regulation and metabolic support.
Notably, both glutamine and citrulline are common oral fitness supplements, and testosterone can be supplemented through high-intensity resistance training or steroid injections. In recent years, the use of fitness supplements has become increasingly widespread in the general population. Many common fitness supplements not only participate in skeletal muscle energy metabolism and protein synthesis but also help to suppress immune system dysregulation (DOI: 10.1111/j.1753-4887.2008.00038.x). Based on this, we speculate that oral administration of corresponding fitness supplements, which can increase the circulating levels of these substances in the body, may indirectly affect the risk of developing MG and LOMG.