Insulinotropic and Cytoprotective Effect of L-theanine: An In vitro Dose Dependent Study

Background: L‑theanine is a natural bioactive amino acid present in tea (Camellia sinensis [L.] O. Kuntze) and consumed worldwide through tea decoction. Objective: The present work aims at evaluation of the insulin secretion and cytoprotective efficacy of L‑theanine, a bioactive amino acid present in tea, on pancreatic β‑cell line, RIN‑m5F. Methods: RIN m5F cell were treated with L-theanine alone or prior to hydrogen peroxide (200 um) treatment and subsequently cell viability, cellular morphology, insulin secretion and insulin gene expression were analyzed. Results: Studies have shown that L‑theanine dose dependently (0–300 µm) increases the β‑cell mass as well as increases insulin production by RIN‑m5F cell. It was also observed that pretreatment of the cell with L‑theanine partially protected the oxidative stress of β‑cells that were evident from cell viability, cellular morphology, and restoration of insulin‑secreting ability. Conclusion: Results suggest that L theanine is an insulinotropic agent as well as effective in giving partial protection to pancreatic β-cells in oxidatively stressed condition. L-theanine can be used in the prevention or treatment of diabetes.