Glutamate ameliorates copper-induced oxidative injury by regulating antioxidant defences in fish intestine

Abstract

The objective of this study was to determine the protective effect of glutamate (Glu) in Cu-induced oxidative injury in fish intestine in vivo and enterocytes in vitro. The results indicated that exposure to 6 mg/l Cu for 72 h induced the production of reactive oxygen species, thereby increasing protein oxidation and lipid peroxidation in enterocytes of grass carp in vitro. Cells exposed to Cu alone resulted in a significant increase in lactate dehydrogenase release, which is accompanied by depletions of antioxidants, including total superoxide dismutase (T-SOD), glutathione S-transferase (GST), glutathione reductase (GR), anti-superoxide anion (ASA), anti-hydroxy radical (AHR) activities and GSH content. Pre-treatment with Glu remarkably prevented the toxic effects of Cu on the T-SOD, GST, GR, AHR, and ASA activities and GSH content in enterocytes. However, Cu induced an adaptive increase in the activities of catalase and glutathione peroxidase (GPx). Glu supplementation further increased GPx activity in enterocytes. Interestingly, the experiment in vivo showed that Glu pre-supplementation significantly elevated SOD, GPx, GST, GR, ASA and AHR activities, as well as GSH content. Further results showed that pre-treatment with Glu could alleviate Cu-induced oxidative injury by elevating antioxidant enzyme activities through regulating the expression of NF-E2-related nuclear factor 2 (Nrf2) mRNA. Together, these results indicated that Glu could attenuate Cu-induced cellular oxidative damage in fish intestine, likely mediated through Nrf2 signalling pathways regulating mRNA expressions of antioxidant enzyme genes and synthesis of GSH.

Effects of fishmeal replacement with cottonseed protein concentrate on growth, digestive proteinase, intestinal morphology and microflora in pearl gentian grouper (♀ Epinephelus fuscoguttatus × ♂ Epinephelus lanceolatu )

“…In the early stage of growth, amino acids in diets are mainly used to synthesize growth proteins. Marine fish, especially marine carnivorous fish, are very sensitive to the change in amino acid composition with the replacement of FM with plant protein (Jiang et al, 2016). The intestinal morphology growth of fish will be largely limited by the lack of amino acids, if dietary amino acid composition becomes different.…”

Effect of dietary threonine on growth performance and muscle growth, protein synthesis and antioxidant-related signalling pathways of hybrid catfishPelteobagrus vachelli♀ ×Leiocassis longirostris♂

“…These findings suggest that, as in mammals, the Thr could activate the PI3K/ AKT/TOR signalling pathways via IGF-I and contribute to muscle protein synthesis and growth in fish. In fish, PC and MDA contents are widely used as markers for protein oxidation and lipid peroxidation, respectively (76) . Increasing evidence indicates that the efficiency of myogenic differentiation is reduced by oxidative damage (27,77,78) .…”

“…Similar results are found in the intestine of grass carp (24) . Antioxidant enzyme activities were closely related to their mRNA levels in fish (76) . The present study indicated that dietary Thr increased mRNA levels of CAT and GST in muscle, which showed the same trend to their enzyme activities.…”

Dietary isoleucine improved flesh quality, muscle antioxidant capacity, and muscle growth associated with AKT/TOR/S6K1 and AKT/FOXO3a signaling in hybrid bagrid catfish (Pelteobagrus vachelli ♀ × Leiocassis longirostris♂)

“…Meanwhile, from the right sides of the same sh, muscle samples were obtained determination of physiochemical-and antioxidant-related parameters. The muscle samples from the left sides of another 6 sh were frozen in liquid nitrogen, and then stored at -80 °C for biochemical parameters and molecular analysis [49]. The muscle from the right sides of same 4 sh were cut into two parts of 1×1×1 cm 3 muscle blocks using a mold, which were used for the determination of texture parameters [6].…”

“…The supernatant was collected for enzyme activity analysis. The contents of protein, MDA, PC, GSH and the activities of T-SOD, CAT, GPX, GST, GR, ASA, and AHR were measured using commercial kits [49]. The ROS contents were measured as decreased by LeBel et al [52].…”