Dietary chromium picolinate alleviates hypoxia-induced liver inflammation in juvenile grass carp (Ctenopharyngodon idella): Involving the synergistic regulation of ion homeostasis and mitochondrial DNA integrity.

Abstract

Hypoxia often induces inflammatory in fish, likely due to disrupted ion homeostasis and DNA damage. Chromium (Cr), as an essential trace element for animals, aids DNA repair and regulates ion homeostasis. However, whether Crcould alleviate hypoxia-induced liver inflammation by regulating ion homeostasis or reducing DNA damage is unknown, which is the purpose of this study. A total of 2160 juvenile grass carp (10.98&#xa0;&#xb1;&#xa0;0.01&#xa0;g) were randomized to 6 treatments. The fish were fed diets containing Crat concentrations of 0.25 (basal diet), 0.67, 1.08, 1.63, 2.08, and 2.65&#xa0;mg/kg for 70&#xa0;d. Then, 96 fish were selected, randomized to control (n&#xa0;=&#xa0;48) or hypoxia (n&#xa0;=&#xa0;48) groups, and subjected to hypoxia stress for 96&#xa0;h. The results showed that: (1) In the hypoxia group, Crinhibited the gene expression of pro-inflammatory cytokines and pyroptosis-related factors, while it enhanced the gene expression of anti-inflammatory cytokines. This indicated that Cralleviated hypoxia-induced liver inflammatory responses. (2) Crreduced the relative content of mitochondrial DNA (mtDNA) in the cytoplasm of the hypoxia group (P&#xa0;<&#xa0;0.05), which suggested that Crhad a potential benefit in alleviating DNA damage. (3) In the hypoxia group, Crsuppressed the expression of proteins associated with Kand Clefflux and promoted the expression of proteins related to Kand Clinflux, thereby contributing to ion homeostasis. In summary, Crlikely maintained ion homeostasis and preserved mtDNA integrity, thereby suppressing liver inflammatory responses, which may provide a novel nutritional regulation strategy for enhancing hypoxia stress resistance in fish.