Enhancing resilience to chronic ammonia stress in crucian carp ( Carassius carassius) ) through dietary gamma-aminobutyric acid (GABA) supplementation: Effects on growth performance, immune function, hepatotoxicity, and apoptosis

This study investigated the potential of gamma-aminobutyric acid (GABA), a potent bioactive compound and inhibitory neurotransmitter, in mitigating chronic ammonia stress-induced liver toxicity in crucian carp (Carassius carassius). GABA is known for its role in alleviating stress responses and enhancing antioxidant defense. In this study, experimental fishes (weighing 20.51 f 0.39 g) underwent 56 days of chronic ammonia stress (10 f 0.053 mg/L), with or without supplemented with GABA (100 mg/kg) in the diet. Serum ammonia (152.14 f 2.94, CK-95.82 f 0.81 mu mol/L), serum MDA content (3.41 f 1.24, CK-1.25 f 0.08 mu mol/L), and liver MDA content (1.98 f 1.72, CK-0.84 f 0.02 mu mol/g prot) were significantly increased in the ammonia exposure group compared with the CK group. GABA supplementation effectively alleviates the detrimental effects of chronic ammonia stress, specifically on growth parameters, serum ammonia levels, and malondialdehyde content. GABA supplementation elevated the expressions of antioxidant genes (zu/cu sod, cat), promoted the expressions of nrf2, and reduced the expression of keap1. Moreover, GABA significantly alleviated liver injury and reduced gene expression of three types of transmembrane proteins (perk, ire1, and atf6). GABA further regulated the expression of downstream apoptotic target genes (upregulation of bcl2; downregulation of bax, caspase3, and caspase9) through endoplasmic reticulum stress (ERS) pathways. This finding indicated the multifaceted benefits of GABA in combating chronic ammonia stress in crucian carp, providing valuable insights for the development of sustainable aquaculture practices.