Interestingly, one species whose abundance increased the most with Hehuanhua treatment was Agathobaculum butyriciproducens (Figure 5C) and it has also been shown to be neuroprotective in Alzheimer’s and Parkinson’s disease models via Nrf2-induced expression of Ho-1 (Go et al., 2021; Lee et al., 2022). This evidence concerns the gene HMOX1 and Parkinson disease.