L-Theanine mitigates skin aging in rats via modulation of the AGEs-RAGE pathway, enhancement of antioxidant defense, and attenuation of inflammation.

This study aimed to evaluate the anti-aging effects of L-theanine in a D-galactose-induced aging model in rats and to elucidate its underlying molecular mechanisms. Aging was induced via subcutaneous administration of D-galactose, while L-theanine was delivered orally for eight weeks. Skin aging was induced in rats by daily subcutaneous injection of D-galactose. L-theanine was administered orally for eight weeks. Skin condition was assessed through by macroscopic observation and histological examination. Enzyme-linked immunosorbent assays were conducted to measure oxidative stress parameters, inflammatory cytokines, and AGEs/RAGE expression levels. L-theanine administration significantly improved skin integrity, maintained epidermal thickness and collagen architecture, administration significantly preserved skin integrity, maintaining epidermal thickness and collagen architecture. It reduced AGEs and receptor for advanced glycation end products (RAGE) expression, enhanced antioxidant enzyme activities (SOD, CAT, GSH-Px, T-AOC), and downregulated reduced the accumulation of AGEs and the expression of RAGE, increased activities of antioxidant enzymes (SOD, CAT, GSH-Px, T-AOC), and decreased levels of pro-inflammatory cytokines (TNF-α, IL-1β, IL-6) in a dose-dependent manner. L-theanine effectively delays delayed skin aging in rats by inhibiting the AGEs-RAGE signaling cascade signaling pathway, thereby modulating attenuating oxidative stress and inflammatory responses.