Theanine, the Main Amino Acid in Tea, Prevents Stress-Induced Brain Atrophy by Modifying Early Stress Responses

• Main Authors: Keiko Unno, Akira Sumiyoshi, Tomokazu Konishi, Michiko Hayashi, Kyoko Taguchi, Yoshio Muguruma, Koichi Inoue, Kazuaki Iguchi, Hiroi Nonaka, Ryuta Kawashima, Sanae Hasegawa-Ishii, Atsuyoshi Shimada, Yoriyuki Nakamura
• Format: Article
• Language: English
• Published: MDPI AG 2020-01-01
• Series: Nutrients
• Subjects: brain atrophy; chronic stress; hippocampus; mri analysis; prefrontal cortex; theanine; samp10
• Online Access: https://www.mdpi.com/2072-6643/12/1/174

Chronic stress can impair the health of human brains. An important strategy that may prevent the accumulation of stress may be the consumption of functional foods. When senescence-accelerated mice prone 10 (SAMP10), a stress-sensitive strain, were loaded with stress using imposed male mouse territoriality, brain volume decreased. However, in mice that ingested theanine (6 mg/kg), the main amino acid in tea leaves, brain atrophy was suppressed, even under stress. On the other hand, brain atrophy was not clearly observed in a mouse strain that aged normally (Slc:ddY). The expression level of the transcription factor <i>Npas4</i> (neuronal PAS domain protein 4), which regulates the formation and maintenance of inhibitory synapses in response to excitatory synaptic activity, decreased in the hippocampus and prefrontal cortex of stressed SAMP10 mice, but increased in mice that ingested theanine. Lipocalin 2 (<i>Lcn2)</i>, the expression of which increased in response to stress, was significantly high in the hippocampus and prefrontal cortex of stressed SAMP10 mice, but not in mice that ingested theanine. These data suggest that <i>Npas4</i> and <i>Lcn2</i> are involved in the brain atrophy and stress vulnerability of SAMP10 mice, which are prevented by the consumption of theanine, causing changes in the expression of these genes.