Wrinkles, one of the characteristics of chronic sun-damaged and/or aged skin, are associated with psychological distress. Apart from the deterioration of collagen and elastic fibers in the dermis, which induces the loss of skin elasticity, it has been recently proposed that decreased flexibility or elasticity of the stratum corneum (SC) is also correlated with wrinkle formation. The elasticity of the SC has been shown to be regulated, at least in part, by the amounts and types of amino acids. To evaluate the ability of our newly developed amino acid-derivative (1-carbamimidoyl-L-proline; CLP), which recovers the elastic properties of the SC ex vivo, to improve wrinkles, a clinical test was performed with 126 Japanese female subjects aged 32-50 years who had crow's feet lines on their faces. Three eligible dermatologists evaluated the study according to authorized grades by the Japanese Cosmetic Science Society and scored the subjects who were much improved or improved as 29.7% and 57.8% of all CLP-treated subjects at 4 and 8 weeks, respectively. In contrast, only 1.5% and 8.1% of subjects improved with the placebo lotion at 4 and 8 weeks, respectively. These results suggest a significant efficacy of CLP to improve wrinkles. In parallel with the dermatologists' assessments, skin surface roughness in the CLP-treated group was significantly reduced after treatment with CLP for 4 and 8 weeks compared to the placebo-treated group. The sum of these data suggests that CLP is a promising and useful ingredient for the improvement of wrinkles through its ability to enhance the elasticity of the SC.
Keywords: 1-carbamimidoyl-L-proline; amino acids; skin aging; stratum corneum; wrinkles.