Agarose oligosaccharides balance intestinal stem cell homeostasis in aging D. melanogaster by regulating the Acetobacter persici-acetic acid-JAK/STAT signaling axis.

<h4>Background</h4>Intestinal aging manifests as the decline in gut function and structure, affecting nutrient absorption and overall health. Agarose oligosaccharides (AOS) exhibit considerable anti-aging effects, but their mechanism of action remains unclear.<h4>Results</h4>Here, aging male Drosophila melanogaster (D. melanogaster) were employed to evaluate the effects of AOS on the proliferation and differentiation of intestinal stem cell (ISC) and its underlying mechanism. Our findings revealed that supplementation with AOS significantly extended mean and maximum lifespan, reduced oxidative stress, and alleviated intestinal epithelial barrier dysfunction. Notably, AOS supplementation reduced the mean fluorescence intensity of esg⁺ cells and enteroblasts (EB), leading to an improvement in ISC homeostasis, with potential mechanisms associated with activation of the PERK and JAK/STAT signaling pathways, as demonstrated by RNA interference. Integrated 16S rRNA sequencing, strain isolation, and short-chain fatty acids (SCFAs) analysis revealed that AOS was beneficial for intestinal microflora and its metabolites, evidenced by the significant increase in Acetobacter persici and acetic acid contents. Importantly, further experiments demonstrated that Acetobacter persici and acetic acid treatment could significantly decrease the esg⁺ ISC count and downregulate the expression levels of PERK, STAT, and Hsp70Bbb, suggesting that AOS can increase production of Acetobacter persici and its metabolite acetic acid, thereby modulating JAK/STAT signaling to improve ISC steady-state.<h4>Conclusions</h4>The homeostasis of ISC in aging D. melanogaster is balanced by AOS via the acetic acid-JAK/STAT axis mediated by Acetobacter persici. This axis counters age-related ISC dysregulation by balancing proliferative signals with redox homeostasis, positioning AOS as a microbiota-targeted intervention for age-associated intestinal decline.