Hypothesis\n\nChronic arterial stiffness alters endothelial shear stress patterns, triggering a shift in endothelial extracellular vesicle (EV) cargo that accelerates neurodegeneration biomarkers independent of amyloid pathology.\n\n## Mechanistic Rationale\n\n- Endothelial dysfunction is the earliest hallmark of vascular aging, driven by reduced NO bioavailability, oxidative stress, and inflammation [1].\n- Arterial stiffness (PWV >11 m/s) predicts mortality and correlates with plasma p‑tau217, GFAP, and NfL in cognitively unimpaired older adults [2][5].\n- Stiffness creates oscillatory and low‑magnitude shear stress, which activates endothelial NF‑κB and the NLRP3 inflammasome, promoting a senescence‑associated secretory phenotype (SASP) [3].\n- Senescent endothelial cells release EVs enriched in pro‑inflammatory miRNAs (e.g., miR‑155, miR‑21) and depleted of protective miR‑126, a key regulator of vascular repair and NO signaling [4].\n- These EVs disseminate systemically, reaching the brain where they can modulate microglial activation and tau phosphorylation, thereby elevating plasma p‑tau217 and GFAP [5].\n\nThus, arterial stiffness → altered shear stress → endothelial senescence/EV remodeling → neurodegeneration biomarker rise.\n\n## Testable Predictions\n\n1. In adults aged 40‑70 with elevated baseline PWV (>10 m/s), a 6‑month intervention known to reduce PWV (e.g., supervised aerobic exercise + NOVOS‑type multi‑target supplementation) will increase circulating endothelial EV miR‑126 levels by ≥20 % and decrease plasma p‑tau217 by ≥15 % relative to placebo.\n2. The magnitude of EV miR‑126 increase will mediate the relationship between PWV reduction and p‑tau217 decline (statistical mediation analysis).\n3. If arterial stiffness is lowered but EV miR‑126 does not increase, plasma p‑tau217 will not improve, falsifying the mechanistic link.\n\n## Potential Experimental Design\n\n- Population: 200 participants, stratified by PWV, randomized to intervention (moderate‑intensity cycling 3×/week + NOVOS‑like supplement) or placebo (stretching + iso‑caloric control).\n- Baseline & 6‑month measures: PWV (applanation tonometry), plasma EV isolation (size‑exclusion chromatography), EV miR‑126 quantification (RT‑qPCR normalized to spike‑in), plasma p‑tau217, GFAP, NfL (SIMOA), endothelial function (flow‑mediated dilation), inflammatory cytokines (IL‑6, TNF‑α).\n- Analysis: ANCOVA adjusting for baseline values, mediation analysis (PROCESS macro), correction for multiple comparisons.\n\n## Falsifiability\n\nIf the intervention reduces PWV but fails to alter EV miR‑126 or p‑tau217, or if changes in EV miR‑126 do not predict p‑tau217 trajectories, the hypothesis that endothelial EV miRNA remodeling mediates the stiffness‑neurodegeneration link would be refuted.\n\n## Broader Implications\n\nConfirming this mechanism would reposition endothelial EVs as an accessible biomarker and therapeutic target, bridging vascular aging and early neurodegenerative processes beyond amyloid‑centric models.\n\nReferences\n[1]\n[2]\n[3]\n[4]\n[5]\n[6]