Effects of topical application of alpha-D-glucosylglycerol on dermal levels of insulin-like growth factor-i in mice and on facial skin elasticity in humans.

Sensory neurons release calcitonin-gene related peptide (CGRP) on stimulation. We have reported that topical application of capsaicin increases facial skin elasticity by increasing the production of dermal insulin-like growth factor-I (IGF-I) through stimulation of sensory neurons in mice and humans. In this study, we examined whether topical application of alpha-D-glucosylglycerol (GG), a compound found in Japanese traditional brewed foods such as sake (Japanese rice wine), increases the dermal production of IGF-I in mice and increases the facial skin elasticity in females. GG increased CGRP release and cAMP levels in dorsal root ganglion (DRG) neurons isolated from wild-type mice. Pretreatment with capsazepine, an inhibitor of vanilloid receptor-1 activation, and with KT5720, an inhibitor of protein kinase A, reversed GG-induced increases in CGRP release from DRG neurons. Topical application of GG increased dermal levels of IGF-I, IGF-I mRNA, and collagen in wild-type mice, but not in CGRP-knockout mice. Topical application of GG increased cheek-skin elasticity in 13 female volunteers. These observations strongly suggest that GG increases the production of IGF-I in the skin through sensory neuron stimulation, thereby increasing skin elasticity.