Dissecting the compatible mechanisms of pharmacological and toxicological effects of cinnabar in Guilingji by gut microbiome and metabolomics

Guilingji (GLJ) is a well-known prescription in China, and has great advantages in the treatment of frailty syndrome, accompanied by good safety profile and outcomes. Cinnabar is one of the traditional Chinese medicines in GLJ, and has been used in China for more than 2000 years in many Chinese medicine prescription. Controversially, cinnabar is reported to have many potential side effects, including brain damage, hepatotoxicity and nephrotoxicity. This study investigated the therapeutical efficacy and toxicity of cinnabar in the case that GLJ treated aging rats to explore the rationality of the application of cinnabar in GLJ. GLJ displayed the therapeutical efficacy of improving brain aging, bone aging and muscle aging, in which cinnabar contributed to the anti-aging efficacy of GLJ against muscle by increasing the levels of intestinal androgens. Meanwhile, cinnabar in a dose, equivalent to its therapeutic dose in GLJ, individually showed a certain toxicity to the liver, kidney and brain of aging rats after long exposure, whereas GLJ didn’t not. Mechanistically, cinnabar free GLJ reversed the effect that cinnabar increased the abundance of mercury methylating microbiota and reduced the abundance of mercury demethylating microbiota in gut. Furthermore, cinnabar free GLJ significantly changed the gut microbiota composition of aging rats, while GLJ reprogrammed gut microbiota composition of aging rats into that of health rats via depending on cinnabar. This research provides an efficient way to understand the compatibility of pharmacological and toxicological effects of cinnabar in TCM prescriptions.