Probiotics modulate the microbiota-gut-brain axis and improve memory deficits in aged SAMP8 mice

ProBiotic-4 is a probiotic preparation composed of Bifidobacterium lactis,Lactobacillus casei,Bifidobacterium bifidum,and Lactobacillus acidophilus.This study aims to investigate the effects of ProBiotic-4 on the microbiota-gut-brain axis and cognitive deficits,and to explore the underlying molecular mechanism using senescence-accelerated mouse prone 8(SAMP8) mice.ProBiotic-4 was orally administered to 9-month-old SAMP8 mice for 12 weeks.We observed that ProBiotic-4 significantly improved the memory deficits,cerebral neuronal and synaptic injuries,glial activation,and microbiota composition in the feces and brains of aged SAMP8 mice.ProBiotic-4 substantially attenuated aging-related disruption of the intestinal barrier and blood-brain barrier,decreased interleukin-6 and tumor necrosis factor-α at both mRNA and protein levels,reduced plasma and cerebral lipopolysaccharide(LPS) concentration,toll-like receptor 4(TLR4) expression,and nuclear factor-κB(NF-κB) nuclear translocation in the brain.In addition,not only did ProBiotic-4 significantly decreased the levels of γ-H2 AX,8-hydroxydesoxyguanosine,and retinoic-acid-inducible gene-I(RIG-I),it also abrogated RIG-I multimerization in the brain.These findings suggest that targeting gut microbiota with probiotics may have a therapeutic potential for the deficits of the microbiota-gut-brain axis and cognitive function in aging,and that its mechanism is associated with inhibition of both TLR4-and RIG-I-mediated NF-κB signaling pathway and inflammatory responses.