Effects of oral administration of galacto-oligosaccharides (GOS) on photoaging via gut microbiota modulation and oxidative stress regulation in UVB-irradiated mice

• GOS alleviated UVB-induced wrinkle formation and improved skin hydration in mice. • GOS reduced ROS levels and suppressed UVB-induced skin inflammation. • GOS upregulated COL1a1, FLG, and AQP3 gene expression in photoaged skin. • GOS altered gut microbiota, increasing Adlercreutzia Mediterraneibacter and Paramuribaculum abundance. • GOS may act as a gut-skin axis modulator to prevent UVB-induced photoaging. This study examined the effects of galacto-oligosaccharide (GOS) on ultraviolet B (UVB)-induced skin photoaging in hairless mice. GOS was orally administered at a low dose (OL, 200 mg/kg) and a high dose (OH, 400 mg/kg) and its impact on skin parameters and wrinkle formation was assessed. qRT-PCR and western blotting were performed to analyze skin-related genes and inflammatory factors, along with cecal microbiome analysis. The OH group showed significant improvements in skin moisture retention, skin thickness, erythema, and transepidermal water loss, as well as a reduction in wrinkle formation. Additionally, OH increased hyaluronic acid content in skin tissue and upregulated the mRNA expression of collagen type I alpha 1 chain, filaggrin, and aquaporin 3. Furthermore, OH treatment significantly reduced reactive oxygen species (ROS) levels, suppressed the expression of inflammatory factors, and decreased IκB phosphorylation, indicating its role in regulating oxidative stress and inflammation. Notably, the gut microbiota composition in OH showed a significant difference from that of UVB-C, with a marked increase in Adlercreutzia, Mediterraneibacter , and Paramuribaculum . In conclusion, our findings suggest that GOS may alleviate UVB-induced photoaging by modulating gut microbiota and inhibiting ROS production, highlighting its potential as a gut-skin axis modulator for skin health and photoaging prevention.