TNF and memory impairment: A study aimed at intervening in memory impairment by enhancing gut health found that oral administration of s_Lactobacillus johnsonii strains increased the abundance of g_Lactobacillus in the gut and decreased the gene copy number of f_Enterobacteriaceae to balance gut ecology, maintained the gut barrier by increasing the mRNA expression of tight junction proteins in the jejunum and ileum, and simultaneously downregulated the levels of TNF-α and hippocampal apoptosis and upregulated the expression level of BNDF, thereby reducing memory impairment [71].