For example, Zifan et al. showed that gut microbiota metabolites are important factors in CNS homeostasis, and they found that supplementation of propionic acid from differential gut microbiota metabolites to Alzheimer’s disease (AD) model mice contributed to the maintenance of in vivo and in vitro mitochondrial homeostasis through the enhancement of PINK1/Parkin-mediated mitophagy in the pathophysiology of AD [122]. The gene discussed is PRKN; the disease is early-onset autosomal dominant Alzheimer disease.