Gamma aminobutyric acid increases erythropoietin overexpression of hypoxia inducible factors in rats

Erythropoietin (EPO) is the primary regulator of erythropoiesis in the mammalian fetus and the adult through interaction with erythropoietin receptor (EPOR). Deficiency of EPO induces anemia that is a major cause of death in patients with chronic kidney disease. Thus, development of safe treatment for anemia is an urgent issue. In this study, we investigated the effect of γ-aminobutyric acid (GABA) on serum EPO level and erythropoiesis, and its mechanism was elucidated in rat. GABA significantly (P < 0.05) increased EPO level in serum and expression levels of EPO and EPOR in a dose dependent manner. GABA increased the expression levels of HIF-1 and HIF-2 in a dose dependent manner compared with the negative control; while GABA did not affect the expression of prolyl-hydroxylase domain protein-2α (PHD-2α) gene, an oxygen sensor. GABA supplementation alters energy production pathway resulted in hypoxic condition, which increases EPO level in rat through overexpression of HIF-1 and HIF-2. This study shows a new physiological role of GABA in EPO production and thus GABA could contribute to the prevention of anemia by using alone or in combination with other anemia treating drugs. Sprague-Dawley rats (5 weeks old, male) were purchased from Koatech (Pyungtaek, Korea). Animals were acclimated for 1 week under 12 h light and 12 h dark conditions in a room with constant temperature (20 ± 2 °C) and humidity (50 ± 5%) and a Standard diet (Harlan Diet 2018S, Harlan Laboratories, Madison, WI, USA), and drinking water were provided freely. All experimental procedures were approved by the Korea University Institutional Animal Care and Use Committee (Approval No.: KUIACUC-2016-148) and animals were maintained in accordance with the Guide for the Care and Use of Laboratory Animals (NIH Publication No. 85-23, 1996). After a week of adaptation, the rats were randomly divided into two groups (n = 3 per group), and the groups treated with 200 ppm γ-aminobutyric acid (GABA) (Sigma-Aldrich, St. Louis, Mo, USA) were designated G200. GABA was supplied via water containing 200 ppm.