Yukio Yoneda
Kanazawa University, Japan
Title: Stimulation of embryonic and adult neurogenesis by the green tea amino acid theanine
Biography
Biography: Yukio Yoneda
Abstract
Theanine is an exogenous amino acid in the green tea, rather than black tea and oolong tea, with a chemical structure analogous to several neuroactive endogenous amino acids such as glutamine and glutamate. We have been studying pharmacological profiles of this green tea amino acid featuring higher relevancy to glutamine than glutamate in neural progenitor cells capable of proliferating for self-replication and differentiating into neuronal, astroglial and oligodendroglial lineages in embryonic, developing and adult brains. Significant amelioration was found in cognition ability scores determined by double-blinded expert physicians in healthy elderly age-matched people given capsules of powdered green tea enriched of theanine compared to those with normal green tea powder capsules after daily oral intake for 7 to 12 consecutive months. In cultured neural progenitor cells isolated from embryonic rat and mouse neocortex, theanine promoted both proliferation and subsequent neuronal differentiation in a concentration-dependent manner, along with deteriorated astroglial differentiation. In cultured progenitor cells from the hippocampus of adult nestin-GFP mice, moreover, theanine increased the size of neurospheres composed of clustered proliferating cells after sustained exposure. In murine embryonic carcinoma P19 cells, similar promotion was seen in proliferation and neuronal differentiation after exposure to theanine. Exposure to theanine for a rather long time up-regulated the glutamine transporter Slc38a1 transcript expression in rat and mouse progenitors, whereas theanine failed to further promote both proliferation and neuronal differentiation activities already facilitated in P19 cells stably overexpressing Slc38a1. Theanine would be thus endowed to promote embryonic and adult neurogenesis through acting at neural progenitor cells in a manner related to upregulation of the glutamine transporter Slc38a1 in rodent brains. We have made several dietary supplement products enriched of theanine supposed to be beneficial for the prophylaxis of particular abnormalities in brain functions as a return of research benefit to the community.