OCLN and serum lipopolysaccharide activity: Hydroxytyrosol intervention dose-dependently restored tight junction protein expression (ZO-1: H50 35.17% ± 8.40%; occludin: H50 80.62% ± 6.27%; p < 0.05 vs. model), demonstrating HT’s capacity to preserve intestinal barrier function, reduce endotoxemia, and indirectly attenuate skin aging through gut-skin axis modulation.