The improved energy metabolism and blood oxygen-carrying capacity for pufferfish, Takifugu fasciatus, against acute hypoxia under the regulation of oxygen sensors
Abstract
Hypoxia frequently occurs in aquatic ecosystem, which is influenced by salinity, water temperature, weather, and surface water runoff. In order to shed further light on the evolutionary and adaptive mechanisms in fish under hypoxic condition, the impact of acute hypoxia (1.63 ± 0.2 mg/L) and reoxygenation (7.0 ± 0.3 mg/L) on oxygen sensors, energy metabolism, and hematological indices was evaluated in Takifugu fasciatus. Data from transcriptional level analysis show that the expressions of genes related to oxygen sensors (HIF-1α, PHD2, and VHL) were upregulated in the brain and liver under hypoxia and recovered under reoxygenation. The upregulation of GLUT2, VEGF-A, and EPO in conjugation with VEGF-A protein and hematological indices conferred the rapid adjustments of cellular glucose uptake and blood oxygen-carrying capacities in pufferfish. Higher levels of glycolysis-related mRNAs (HK, PGK1, and PGAM2), HK activity, and proteins (PGK1 and PGAM2) were detected in the brain and liver under hypoxic condition compared with control. Interestingly, the expression of MDH1 at the mRNA, enzyme activity, and protein levels was significantly increased in the brain at 0 or 2 h and in the liver at 8 h under hypoxic condition. In addition, although the enzyme activity and mRNA expression of LDH in the brain were not significantly changed, a persistent upregulation was observed in the liver during hypoxia exposure. This study demonstrated that pufferfish could counterpoise the energetic demands and hematological functional properties evoked by oxygen sensors after hypoxia. Our findings provided new insights into the molecular regulatory mechanism of hypoxia in pufferfish.
Keywords
Hypoxia Energy metabolism Hematological indices Oxygen sensors Takifugu fasciatusNotes
Authors’ contributions
S.W.Y., T.W., X.R.L., and G.S.Z. conceived this study and designed and supervised the experiments; X.R.L., D.W., and W.X.Z. performed the experiments; and X.R.L., X.W., and H.Y.Z. conducted the data analysis and prepared the figures and tables. X.R.L., T.W., and Q.Q.C. wrote the manuscript. All of the authors reviewed and approved the manuscript.
Funding information
The authors are grateful to the National Natural Science Foundation of China (No. 31800436), The National Finance Projects of Agro-technical popularization (TG15-003), and the Project Foundation of the Academic Program Development of Jiangsu Higher Education Institution (PAPD) and for the financial support of the National Spark Program of China (2015GA690040).
Compliance with ethical standards
Conflict of interest
The authors declare that they have no conflict of interest.
Copyright © 2017 Li, Wang, Yin, Zhang, Cao, Wen, Zhang, Wang, and Zhu. This is an open-access article distributed under the terms of the Creative Commons Attribution License (CC BY). The use, distribution, or reproduction in other forums is permitted, provided the original author(s) or licensor is credited and that the original publication in this journal is cited, in accordance with accepted academic practice. No use, distribution, or reproduction is permitted which does not comply with these terms.
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