Secoisolariciresinol diglucoside attenuates neuroinflammation and cognitive impairment in female Alzheimer's disease mice via modulating gut microbiota metabolism and GPER/CREB/BDNF pathway.

BACKGROUND: Gender is a significant risk factor for late-onset Alzheimer's disease (AD), often attributed to the decline of estrogen. The plant estrogen secoisolariciresinol diglucoside (SDG) has demonstrated anti-inflammatory and neuroprotective effects. However, the protective effects and mechanisms of SDG in female AD remain unclear. METHODS: Ten-month-old female APPswe/PSEN1dE9 (APP/PS1) transgenic mice were treated with SDG to assess its potential ameliorative effects on cognitive impairments in a female AD model through a series of behavioral and biochemical experiments. Serum levels of gut microbial metabolites enterodiol (END) and enterolactone (ENL) were quantified using HPLC-MS. Correlation analysis and broad-spectrum antibiotic cocktail (ABx) treatment were employed to demonstrate the involvement of END and ENL in SDG's cognitive improvement effects in female APP/PS1 mice. Additionally, an acute neuroinflammation model was constructed in three-month-old C57BL/6J mice treated with lipopolysaccharide (LPS) and subjected to i.c.v. injection of G15, an inhibitor of G protein-coupled estrogen receptor (GPER), to investigate the mediating role of the estrogen receptor GPER in the cognitive benefits conferred by SDG. RESULTS: SDG administration resulted in significant improvements in spatial, recognition, and working memory in female APP/PS1 mice. Neuroprotective effects were observed, including enhanced expression of CREB/BDNF and PSD-95, reduced ß-amyloid (Aß) deposition, and decreased levels of TNF-α, IL-6, and IL-10. SDG also altered gut microbiota composition, increasing serum levels of END and ENL. Correlation analysis indicated significant associations between END, ENL, cognitive performance, hippocampal Aß-related protein mRNA expression, and cortical neuroinflammatory cytokine levels. The removal of gut microbiota inhibited END and ENL production and eliminated the neuroprotective effects of SDG. Furthermore, GPER was found to mediate the inhibitory effects of SDG on neuroinflammatory responses. CONCLUSION: These findings suggest that SDG promotes the production of gut microbial metabolites END and ENL, which inhibit cerebral ß-amyloid deposition, activate GPER to enhance CREB/BDNF signaling pathways, and suppress neuroinflammatory responses. Consequently, SDG exerts neuroprotective effects and ameliorates cognitive impairments associated with AD in female mice.

Fabrication and characterization of low-fat Pickering emulsion gels stabilized by zein/phytic acid complex nanoparticles.

Pickering emulsion gels (PKEGs) are being explored as solid fat substitutes and delivery systems due to their semi-solid textures and high stabilities. However, these PKEGs have relatively high-fat content, which is undesirable for nutritional and cost reasons. Therefore, in this study, low-fat PKEGs (10 % oil content) were successfully fabricated using zein/phytic acid (ZPA) complex nanoparticles with zein to phytic acid mass ratio of 1:0.006. These nanoparticles have a mean diameter of around 161 nm and wettability of around 89°. The formation of PKEGs were confirmed by the results of dynamic rheology (G' > G″). Confocal laser scanning microscope showed that the complex nanoparticles formed a dense barrier on the surface of the oil droplets, which prevented the oil droplets against coalescence. The chemical stability of curcumin was greatly improved by encapsulation in the PKEGs. The low-fat PKEGs developed in this study may be effective delivery systems for hydrophobic bioactive substances.