Health Adults

This observational follow-up study extends a previously completed 15-day intensive longitudinal study (WeF) of the gut microbiome in healthy adults. The objective of WeF2 is to characterize the long-term stability and dynamics of the gut and oral microbiota in the same cohort across multiple timescales, and to determine whether the day-to-day variability patterns observed at baseline persist over months and years. Participants who completed the WeF baseline protocol will be invited to attend periodic follow-up visits for low-frequency biospecimen collection and to repeat the original 15-day high-frequency sampling protocol at planned intervals, beginning approximately six months after the WeF baseline and continuing at extended intervals thereafter. By combining sparse routine sampling with recurring high-density sampling windows, the study aims to distinguish the stable core microbiome from transient and seasonal fluctuations, to track gradual community shifts under free-living conditions, and to further explore relationships among microbiome dynamics, dietary intake, and host glycemic regulation over an extended observation period.

This intensive longitudinal study investigates the day-to-day stability and natural fluctuations of the gut microbiome in healthy adults over a 15-day period. While the human gut microbiome is a complex ecosystem, its baseline stability in the absence of disease or medical intervention remains insufficiently characterized due to low sampling frequency in prior research. By recruiting healthy volunteers for continuous daily sampling, this study aims to map temporal community structures and evaluate the stability of core microbiota. Additionally, the research utilizes Continuous Glucose Monitoring (CGM) to explore the potential relationships between microbiome dynamics, daily dietary intake, and host glycemic stability.

The goal of this clinical trial is to validate if temporal interference brain stimulation (TIBS) is safe in healthy volunteers aged 20 to 65. The main questions it aims to answer are: * Is it safe to apply TIBS intervention to the left hippocampus in healthy participants? * Is it safe to apply TIBS intervention to the left insula in healthy participants? * Is it safe to apply TIBS intervention to the left anterior cingulate cortex in healthy participants? * Is it safe to apply TIBS intervention to the right inferior frontal cortex in healthy participants? Participants will: * Be Randomly allocated to either sham-first group or treat first-group, stratified by stimulated brain region, following a crossover-controlled experimental design * Complete baseline cognitive evaluations and mental status assessments, and undergo a baseline MRI scan on the same day * Receive stimulation for 5 consecutive days, followed by a 2-days washout period, then complete the remaining 5 days of stimulation. * Complete post-intervention cognitive evaluations and mental status assessments, and undergo a post-intervention MRI scan on the same day