Evaluation of the dietary L-valine on fish growth and intestinal health after infection with Aeromonas veronii

Abstract

Endoplasmic reticulum stress and subsequent apoptosis play a pivotal role in bacterial infection in intestine. The objective of this study was to assess the influence of dietary L-valine (Val) on growth, antioxidant capacity, and endoplasmic reticulum stress-mediated apoptosis in the intestine of juvenile largemouth bass Micropterus punctulatus following an Aeromonas veronii infection. A total of 720 fish were randomly assigned to six groups and provided with varying levels of Val for 77 days. Subsequently, they were challenged with A. veronii. Our results revealed that dietary Val: (1) increased percent weight gain (PWG), specific growth rate (SGR), feed intake (FI), feed efficiency (FE), protein efficiency ratio (PER), protein production value (PPV), lipid production value (LPV), ash production value (APV) and survival rate (SR). Additionally, it alleviated A. veronii-induced intestinal injury; (2) improved intestinal antioxidant capacity by enhancing the mRNA levels of superoxide dismutase 1 (SOD1), catalase (CAT), glutathione-S-transferase (GST), glutathione peroxidase (GPx), glutathione reductase (GR), and glutamate-cysteine ligase catalytic subunit (GCLC) via the nuclear factor erythroid 2-related factor 2 (Nrf2) signaling pathway; (3) reduced intestinal DNA fragments and down-regulated glucose-regulated protein 78 (GRP78), activating transcription factor 6 (ATF6), inositol-requiring enzyme 1 (IRE1), protein kinase-like ER kinase (PERK), eukaryotic Initiation Factor 2 (eIF2α), activating transcription factor 4 (ATF4), C/EBP homologous protein (CHOP), caspase 9, and caspase 3 mRNA levels through modulating the PERK/eIF2α signaling pathway. These findings suggest that optimal dietary Val enhances the growth performance, antioxidant capacity, and mitigates A. veronii-induced intestinal injury. Finally, the mitigates optimal Val requirement of largemouth bass (37.99–162.92 g) is 21.50 g/kg diet, corresponding to 46.64 g/kg protein.