Dietary nucleotides supplementation affect the physicochemical properties, amino acid and fatty acid constituents, apoptosis and antioxidant mechanisms in grass carp (Ctenopharyngodon idellus) muscle

A 60 days feeding trial was conducted to investigate the effects of dietary nucleotides levels on growth performance, proximate composition, physicochemical properties, amino acids constituents, fatty acids composition, apoptosis and antioxidant status related mechanism of grass carp (Ctenophatyngodon idella) (initial weight 200.00 +/- 1.00 g). Six graded levels of dietary nucleotides were designed as 0, 200.0, 400.0, 600.0, 800.0 and 1000.0 mg/kg, respectively. The results showed that, compared with control group, dietary nucleotides supplementation increased the growth of grass carp with higher final body weight, percentage weight gain and specific growth rate, decreased moisture but increased protein and lipid in muscle. However, dietary nucleotides had no effect on ash, calcium and phosphorus in fish fillets (P > .05). Dietary nucleotides supplementation increased the content of umami and sweetness-associated amino acids, flavor nucleotide (inosine mono-phosphate), healthcare n-3 PUFAs (EPA and DHA) and the ratio of n-3/n6 in fish muscle. Meanwhile, dietary nucleotides increased water holding capacity, tenderness and pH to enhance flesh quality, which were partly related to inhibited apoptosis with regulation of apoptosis-related gene expression, decreased hydroxyproline with increase of cathepsins activities and decreased lactate in muscle, respectively. In addition, dietary nucleotides enhanced flesh quality of grass carp fillets concerning increasing antioxidant enzymes activities and its gene expression, which were modulated by signaling molecules (TOR and Nrf2) gene and protein expression in grass carp muscle. In summary, dietary nucleotides supplementation increased growth performance, flavor characteristics, healthy fatty acid contents, physicochemical properties (water holding capacity, tenderness and pH), anti-apoptotic ability and antioxidant capacity in fish. This study demonstrated that nucleotides was a promising feed additives to enhance flesh quality in fish.