Paramylon extracted from Euglena gracilis EOD-1 augmented the expression of SIRT1

Euglena gracilis, a type of microalgae, contains several nutrients and accumulates paramylon, a β-1,3-glucan. In recent studies, paramylon has shown to exhibit various activities including immunomoduratory and hepatoprotective effects. In the present study, using an in vitro cell culture system, we aimed to determine whether paramylon derived from the E. gracilis EOD-1 strain, which produces large amounts of paramylon, can augment SIRT1 expression in epidermal cells via activating gut–skin interactions. Results showed that paramylon augmented the expression of SIRT1 in Caco-2 cells, a human intestinal cell line. Furthermore, microarray analysis of Caco-2 cells treated with paramylon showed that paramylon activates epidermal cells through inducing the secretion of factors from intestinal cells. Then, we focused on skin cells as target cells of paramylon-activated intestinal cells. Results showed that secretory factors from Caco-2 cells treated with paramylon augmented the expression of SIRT1 in HaCaT cells, a human keratinocyte cell line, and that expression level of genes related to the growth and maintenance of epidermal cells were significantly changed in Caco-2 cells treated with paramylon as evidenced by microarray analysis. All these results suggest that paramylon can activate epidermal cells by inducing the production of secretory factors from intestinal cells.