Elsevier

Aquaculture Reports

Volume 18, November 2020, 100427
Aquaculture Reports

Regulation of glucose and lipid metabolism by insulin and glucagon in vivo and in vitro in common carp Cyprinus carpio L.

https://doi.org/10.1016/j.aqrep.2020.100427Get rights and content
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Highlights

  • Insulin induced hypoglycemia by up-regulating glycolysis and down-regulating gluconeogenesis.

  • Insulin administration enhanced lipogenesis and reduced lipolysis.

  • Glucagon regulated blood glucose by affecting glucose metabolism.

  • Glucagon significantly increased the activity of PEPCK and LPL.

Abstract

Our objective is to study the low metabolic utilization of dietary carbohydrates in fish. The regulation of key enzymes involved in glucose and lipid metabolism in the common carp (Cyprinus carpio L.), known to be relatively tolerant to dietary carbohydrates, were assessed. We performed intraperitoneal (i.p.) administration of insulin and glucagon to common carp and also subjected common carp primary hepatocytes to insulin or glucagon. The results showed that insulin administration induced hypoglycaemia through up-regulation of the expression of the glycolysis genes glucokinase (GK) and hexose kinase (HK), coupled with increased gene expression of fatty acid synthase (FAS), acetyl-CoA carboxylase-1 (ACC-1), sterol-regulator element-binding protein-1 (SREBP-1). Insulin also limited the expression of the gluconeogenesis genes phosphoenolpyruvate carboxykinase (PEPCK) and glucose-6-phosphatase (G6Pase), coupled with decreased gene expression of lipoprotein lipase (LPL) and carnitine palmitoyl transferase I (CPT-1). However, glucagon had the opposite effect. The results showed that glucagon induced hyperglycemia with increased expression of PEPCK and G6Pase and increased lipolytic capacity as indicated by lower mRNA levels of SREBP-1. Glucagon (i.p.) significantly increased the activity of PEPCK and LPL in hepatopancreas. In addition, the mRNA expression of HK showed an up-regulated trend and the mRNA expression of PEPCK and G6Pase showed a down-regulated trend in the group of glucose (i.p.). This study demonstrates that insulin and glucagon possess the intrinsic ability to regulate hepatic energy metabolism in common carp, the regulation of which seems to be similar to that of the mammals at least at the molecular level.

Abbreviations

ACC-1
acetyl-CoA carboxylase-1
CPT-1
carnitine palmitoyl transferase 1
FAS
fatty acid synthase
FBPase
fructose-1,6-bisphosphatase
GK
glucokinase
G6Pase
glucose-6-phosphatase
HK
hexose kinase
i.p.
intraperitoneal injection
LPL
lipoprotein lipase
PBS
phosphate-buffered saline
PEPCK
phosphoenolpyruvate carboxykinase
SREBP-1
sterol-regulator element-binding protein-1
VLDL
very low density lipoprotein

Keywords

Cyprinus carpio L.
Insulin
Glucagon
Glucose metabolism
Lipid metabolism

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These authors should be considered joint first author.