Studies have shown that SCFAs can enhance the expression of proteins associated with synaptic plasticity (Tan et al., 2014) and can act as a broad-spectrum histone deacetylase (HDAC) inhibitor, which can be utilized to modulate HDAC in AD, enhance gene expression, attenuate pathological changes in patients with AD, and improve cognitive function (Govindarajan et al., 2011). The gene discussed is HDAC9; the disease is Alzheimer disease.