Glutamic Acid Has a Liver-Protective Effect through the Suppression of Inducible Nitric Oxide Synthase in Primary Cultured Rat Hepatocytes

Background: Theanine, which is hydrolyzed into glutamic acid (Glu), excerts beneficial effects on organ metabolism. However, there is little scientific evidence that Glu influences inflammatory mediator such as tumor necrosis factor (TNF)-α and nitric oxide (NO).In inflamed liver, proinflammatory cytokines stimulate liver cells, followed by the induction of inducible NO synthase (iNOS). Excessive NO produced by iNOS has been implicated as one of the factors in liver injury. Thus it is essential to inhibit iNOS induction for the prevention of liver injury. In this study, we examined interleukin (IL)-1β-stimulated hepatocytes as a simple “in vitro injury model” to investigate liver protective effects of Glu.