(P09-031-25) Resistant Starch Supplementation Promotes Brain Health in Estrogen Deficient Mice by Modulating Gut-Derived Enzyme and Metabolites

Objectives: This study investigated the effects of two types of resistant starch (RS), retrograded (RS3) and chemically modified (RS4), on neuronal genes, gut microbial β-glucuronidase (gmGUS) activity, and metabolites affecting brain health in a mouse model of estrogen deficiency.

Methods: 3-mo-old female C57BL/6 mice were injected (ip) daily for 30 d with 4-vinylcyclohexene diepoxide (VCD, 160 mg/kg bw in sesame oil), or vehicle (Veh) to induce estrogen deficiency. Mice were then divided into three dietary groups (n=15/group) in a 2x3 factorial design: control (AIN-93M), 5% (wt/wt) RS3 or RS4 for 16 wks. Fecal gmGUS activity, involved in deconjugating estrogen and neurotransmitters, was measured. Serum tryptophan and its metabolites (kynurenine, 3-hydroxykynurenine, quinolinic and kynurenic acids), important for immune and nervous system function, were analyzed using liquid chromatography-tandem mass spectrometry (LC-MS/MS). Hippocampal RNA-seq was performed to assess genes important in brain health. Data were analyzed using two-way ANOVA with estrogen status (VCD/Veh) and diet as factors, followed by Tukey's post-hoc tests when P < 0.05.

Results: Estrogen deficiency tended (P=0.056) to decrease relative brain weight, while there was a main effect of diet with RS3 (P=0.022) and RS4 (P=0.069) decreasing brain weight compared to the control. Estrogen status had no significant effect on gmGUS activity; however, there was a main effect of diet, with RS4 increasing (P=0.048) enzyme activity compared to the control. VCD significantly reduced serum kynurenine and 3-hydroxykynurenine concentrations (Padj < 0.005), while diet tended (P=0.065) to affect only kynurenine. RNA-seq data revealed differential expression of genes involved in cognitive function. In the Veh group, both RS significantly increased Pax7 expression. In the VCD group, RS3 upregulated Thoc2 and Paxbp1, while both RS treatments increased Pura expression. In estrogen-deficient mice, Clptm1 and Vdac1, genes linked to Alzheimer's disease, were downregulated by RS3 and RS4, respectively.

Conclusions: This study provides evidence that VCD has a negative effect on tryptophan metabolites, while RS3 and RS4 improve gut derived enzyme and neuronal genes to promote brain health in estrogen deficient mice.

Funding Sources: NIH-NIA/NICCH (3R15AT011962-01S1) and Williams Professorship