Gamma-aminobutyric acid improves oxidative stress and function of the thyroid in high-fat diet fed mice

Redox status and thyroid functions of diet-induced obesity (DIO) and DIO-resistant (DIO-R) mice from 20-week high-fat diet-fed (HFD) mice were studied (study I). Whether antiobesity action of gamma-aminobutyric acid (GABA) in HFD mice was related to its antioxidative action or improvement in thyroid function was also examined (study II) by GABA in drinking water (0.2, 0.12 and 0.06%). In DIO mice, thyroid stimulating hormone (TSH) remarkably increased, free thyroid hormones (THs) decreased, thyroid structures deformed and expressions of THs synthesis-specific and thyroid antioxidative markers, THs receptors β and deiodinases in hypothalamus and liver decreased. DIO-R mice showed normalized TSH, increased THs and its functions. Three GABA treatments normalized TSH, while 0.2% and 0.12% GABA treatments restored redox status, raised THs excretions and functions. Consequently, Down-regulated thyroid and THs functions in DIO mice accounted for obesity. GABA could prevent obesity by ameliorating oxidative stress and HFD-disrupted functions of thyroid and THs.