Oral Administration of Okara Soybean By-Product Attenuates Cognitive Impairment in a Mouse Model of Accelerated Aging.

The microbiota-gut-brain axis has attracted increasing attention in the last decade. Here, we investigated whether okara, a soybean by-product rich in dietary fiber, can attenuate cognitive impairment in senescence-accelerated mouse prone 8 (SAMP8) mice by altering gut microbial composition. Mice were fed either a standard diet, or a diet containing okara (7.5% or 15%, w/w) for 26 weeks. In the memory test, the 7.5% okara-fed mice showed a longer step-through latency and the 15% okara-fed mice had a short escape latency compared with control mice. The 15% okara-fed mice displayed decreased body weight, increased fecal weight, and altered cecal microbiota composition compared with the control group; however, there was no significant difference in the serum lactic acid and butyric acid levels among these mice groups. The 7.5% okara-fed mice had significantly higher NeuN intensity in the hippocampus compared with control mice. Furthermore, a decrease in inflammatory cytokine TNF- and an increase in brain-derived neurotrophic factor (BDNF) was observed in the 7.5% okara-fed group. The expression of synthesizing enzyme of acetylcholine was increased by the okara diets, and the acetylcholine level in the brain was higher in the 7.5% okara-fed group than in the control. These suggest that oral administration of okara could delay cognitive decline without drastically changing gut microbiota.

Long-Term Diet Supplementation with Lactobacillus paracasei K71 Prevents Age-Related Cognitive Decline in Senescence-Accelerated Mouse Prone 8.

This study aimed to assess the suppressive effect of long-term diet supplementation with Lactobacillus strains on cognitive decline in the senescence-accelerated mouse prone 8 (SAMP8) model. For 43 weeks, fourteen-week-old female SAMP8 mice were fed a standard diet containing 0.05% (w/w) Lactobacillus casei subsp. casei 327 (L. 327) or Lactobacillusparacasei K71 (L. K71) derived from rice grains and sake lees, respectively. SAMP8 mice that were fed a L. K71-supplemented diet had better cognitive performance compared with the control and L. 327 groups in the Barnes maze and passive avoidance tests. An ELISA analysis revealed that the levels of serotonin were elevated in the serum and brain tissue of L. K71-fed mice. The protein expression levels of brain-derived neurotrophic factor (BDNF), cAMP response element binding protein (CREB), and phosphorylated CREB were evaluated using western blot. Long-term administration of L. K71 resulted in increased protein expression of BDNF and CREB phosphorylation in the hippocampus. These results suggest that prolonged intake of a diet supplemented with a Lactobacillus strain derived from sake lees may prevent age-dependent cognitive decline by upregulating BDNF expression in the hippocampus.