ZeXieYin Formula alleviates TMAO-induced cognitive impairment by restoring synaptic plasticity damage

Abstract

Ethnopharmacological relevance: Treating cognitive impairment is a challenging and necessary research topic. ZeXieYin Formula (ZXYF), is a traditional herbal formula documented in the book of HuangDiNeiJing. Our previous studies demonstrated the ameliorative effects of ZXYF on atherosclerosis by reducing the plasma trimethylamine oxide (TMAO) level. TMAO is a metabolite of gut microorganisms, our recent research found that the increasing level of TMAO may have adverse effects on cognitive functions.

Aim of the study: Our study mainly focused on the therapeutic effects of ZXYF on TMAO-induced cognitive impairment in mice and explored its underlying mechanism.

Materials and methods: After the TMAO-induced cognitive impairment mice models were established, we applied behavioral tests to estimate the learning and memory ability of the ZXYF intervention mice. Liquid chromatography-mass spectrometry (LC-MS) was used to quantify the TMAO levels in plasma and the brain. The effects of ZXYF on the hippocampal synaptic structure and the neurons were observed by transmission electron microscopy (TEM) and Nissl staining. In addition, western-blotting (WB) and immunohistochemical (IHC) staining were used to detect the level of related proteins in the synaptic structure and further verify the changes in synaptic plasticity and the mTOR pathway after ZXYF administration.

Results: Behavioral tests showed that the learning and memory ability of mice impaired after a period of TMAO intervention and ZXYF could alleviate these changes. A series of results showed that ZXYF partly restored the damage of hippocampal synapse and neurons in TMAO-induced mice, at the same time, the expression of synapse-related proteins and mTOR pathway-related proteins were significantly regulated compared with the damage caused by TMAO.

Conclusion: ZXYF could alleviate TMAO-induced cognitive impairment by improving synaptic function, reducing neuronal damage, regulating synapse-associated proteins, and regulating the mTOR signaling pathway.

Keywords: Cognitive impairment; Synaptic plasticity; Trimethylamine oxide (TMAO); ZeXieYin Formula (ZXYF); mTOR pathway.