Effects and Mechanisms of Exogenous GABA Against Oxidative Stress in Piglets

The purpose of this paper is to study the effect of exogenous γ-aminobutyric acid against oxidative stress in piglets, and the possible mediating role of hippocampal neuron γ-aminobutyric acid receptors regulating apoptosis signaling pathways in it, which will provide scientific basis for the application of γ-aminobutyric acid as animal stress regulator.

Based on the successful establishment of oxidative stress model in piglet and rat hippocampal neurons, the effects of exogenous GABA on piglets under oxidative stress, including oxidative / antioxidant related indexes, growth performance related indexes and GABA receptor in serum and hippocampus, along with the GABA receptor and apoptosis signal pathway related indexes in hippocampal neurons were investigated.

The serum MDA levels of piglets in the low, medium, and high concentration GABA feeding groups (LD+OS; MD+OS; HD+OS) were extremely significantly lower than those in the oxidative stress (OS) group (P<0.01), the GSH level was extremely significantly higher than that in the OS group (P<0.01), and the T-AOC level in the HD+OS group was extremely significantly higher than that in the OS group and control group (P<0.01). And the high concentration (100 mg·kg^-1 BW) of GABA more decreased the MDA level and more increased the GSH level in serum of piglets than those of the low concentration (20 mg·kg^-1 BW) and middle concentration (60 mg·kg^-1 BW) of GABA. Therefore, the follow-up study only investigated the anti-oxidative stress effect and mechanism of 100 mg·kg^-1 BW. The daily gains of piglets at 0-7 days, 8-14 days and 0-28 days in the OS group were extremely significantly lower than those in the control group (P<0.01), the daily gains of piglets at 0-7 days, 8-14 days and 0-28 days in the HD+OS group were extremely significantly higher than those in the OS group (P<0.01), the daily gain of piglets aged 15-28 days in the OS group was significantly lower than that in the control group (P<0.05), the daily gain of piglets aged 15-28 days in the HD+OS group was extremely significantly higher than that in the OS group (P<0.01). The above results showed that the 100 mg·kg^-1 BW GABA feeding extremely significantly increased the daily gain of piglets. There was no significant difference in the diarrhea rate of the control group, OS group and HD+OS group in the first, middle and late stages (P>0.05). The MDA level of hippocampus in the OS group was significantly higher than that of the control group and HD+OS group (P<0.01), the T-AOC and GSH levels were extremely significantly lower than the other two groups (P<0.01), which showed that GABA feeding would improve the antioxidant capacity of hippocampus. The levels of GABA_A and GABA_B receptors in the hippocampus of the HD+OS group were extremely significantly higher than those in the control group and the OS group (P<0.01), which showed that GABA feeding increased the levels of GABA_A and GABA_B in hippocampus. The Bcl-2 level in the hippocampus of the OS group was significantly lower than that of the control group (P<0.05), and the Bax and Caspase-3 levels were extremely significantly higher than those of the control group (P<0.01). The Bcl-2 level of the HD+OS group was extremely significantly higher than that of the OS group (P<0.01), the Bax level was extremely significantly lower than that of the OS group (P<0.01), and the Caspase-3 level was significantly lower than that of the OS group (P<0.05). Consistent with this, the Bax and Caspase-3 levels in hippocampal neurons of rats in the OS group, GABA+OS+Picrotoxin group and GABA+OS+CGP54626 group were significantly higher than those in the control group and GABA group (P<0.05), which indicated that GABA alleviated the damage of hippocampal neurons under oxidative stress, and the addition of GABA receptor inhibitors blocked the anti-stress damage effect of GABA.

GABA reduced the level of oxidative stress in the hippocampus of piglets. The anti-stress mechanism of GABA could be related to the decrease of the expression of apoptotic protein gene, while GABA_A and GABA_B receptors mediated this process.