Fermented date residue extract mix containing gamma-aminobutyric acid augments the immune function of mouse splenocytes.

An extract of date (fruit of a palm tree) residue plus food-grade glutamate, acetic acid, and yeast extract (date residue extract mix, DREM) has been successfully fermented with using Lactobacillus brevis JCM 1059T to produce gamma-aminobutyric acid (GABA). Here, mouse splenocytes were found to be viable when supplemented with DREM and fermented DREM containing GABA (fDREM). The addition of DREM and fDREM resulted in the secretion of tumor necrosis factor (TNF)-α from the splenocytes, fDREM being more effective than DREM. The TNF-α secretion with DREM was elevated by exogenous addition of GABA and that with fDREM was in part mediated via A-type GABA receptors. Contrary to general understanding of the suppressive effects of GABA on various biological functions, our findings suggest that GABA-containing fDREM arguments the immune function as a food and pharmaceutical material.