Inhibition of fatty acid oxidation induced by up-regulation of miR-124 and miR-205 during exposure of largemouth bass (Micropterus salmoides) to acute hypoxia

Abstract

With increased breeding density, the possibility of hypoxia increases. This study simulated the hypoxic environment (1.2 ± 0.2 mg / L) that may occur within 24 h of aquaculture to stress largemouth bass (Micropterus salmoides). The effects of this environment on related enzymes and genes were examined to explore the effects of hypoxia on lipid metabolism in the liver. Hypoxic stress increased liver triglyceride and non-esterified fatty acid content, and increased lipase (LPS) and lipoprotein lipase (LPL) activities related to fat mobilization. Hypoxia stress also significantly increased the expression levels of genes involved in fatty acid activation and fatty acid transport, including hormone-sensitive triglyceride lipase (HSL), solute carrier family member 27 member 6 (SLC27A6), peroxisomal proliferation activated receptor alpha (PPARA,) and acyl-CoA synthase long-chain family 4 (ACSL4). However, hypoxia stress significantly reduced the expression level of the carnitine palmitoyltransferase 1 (CPT-1) gene, with a downward trend of enzyme activity. The decreased level of CPT-1 was explained by negative regulation by miR-124 and miR-205, as measured by quantitative polymerase chain reaction and dual-luciferase reporter assays. Overall, acute hypoxic stress enhanced lipid mobilization, fatty acid activation, and fatty acid transport, but inhibited fatty acid oxidation by miR-124 and miR-205 down-regulation of CPT-1 expression. These findings provide new insights into the regulation of lipid metabolism in fish under hypoxic stress.