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Figure 1. Changes in microorganisms and their metabolites with host aging. Under exposure to multiple risk factors, microbial diversity declines in aging individuals, and the alterations in bacterial genera vary across individuals. Meanwhile, the levels of short-chain fatty acids (SCFAs) and the activity of bile acid (BA)-related metabolic enzymes decrease, whereas phenylalanine-derived metabolite levels increase, eliciting multiple biological effects. (Created in BioRender. Raitasi, E. (2026) https://BioRender.com/dbhuh23). F: Firmicute;






