Abstract
The carnitine palmitoyltransferase (CPT) family includes CPT 1 and CPT 2 that transport long-chain fatty acids into the mitochondrial compartment for β-oxidation. In this study, three isoforms (CPT 1α, CPT 1β and CPT 2) of the CPT family were cloned from Chinese mitten crab (Eriocheir sinensis) and their complete coding sequences (CDS) were obtained. Sequence analysis revealed deduced amino acid sequences of 915, 775 and 683 amino acids, respectively. Gene expression analysis revealed a broad tissue distribution for all three isoforms, with high CPT 1α and CPT 2 mRNA levels in the hepatopancreas of males and females. In males, CPT 1β was highly expressed in gill, heart, brain ganglia and muscle, while in females, CPT 1β-mRNA levels were relatively high in muscle, hepatopancreas and ovary tissue. The effects of dietary fish oil replacement on the expression of the three CPT isoforms in the hepatopancreas during gonadal development were investigated using five experimental diets formulated with replacement of 0, 25, 50, 75 and 100% fish oil by 1:1 rapeseed oil: soybean oil. The results showed that Diets 2# and 5# yielded higher CPT 1α and CPT 2 mRNA expression in males (P < 0.05), while in females, expression of all three CPT isoforms increased then declined in the hepatopancreas with increasing dietary fish oil replacement. The observed changes in CPT gene expression varied in different isoforms and gender, suggesting the three CPT genes might play different roles in fatty acid β-oxidation in E. sinensis.
Highlights
Mitochondrial β-oxidation of fatty acids is central to the provision of energy in most organisms, but long-chain fatty acids (LC-FA) cannot cross the mitochondrial inner membrane directly in animals [1, 2]
The hepatopancreas is a major site for lipolysis, and our results suggest that carnitine palmitoyltransferase (CPT) 1α might be a major player in the degradation of fatty acids in E. sinensis
In male E. sinensis, the results of the present study showed that CPT 1α and CPT 2 expression levels in the hepatopancreas first increased decreased with increasing dietary Fish oil (FO) replacement
Summary
Mitochondrial β-oxidation of fatty acids is central to the provision of energy in most organisms, but long-chain fatty acids (LC-FA) cannot cross the mitochondrial inner membrane directly in animals [1, 2]. Carnitine palmitoyltransferase 1 (CPT 1) and CPT 2 form a mitochondrial carnitine palmitoyltransferase system that mediates the uptake of LC-FA into mitochondria and plays an important role in the control and regulation of mitochondrial βoxidation [3, 4]. CPT 1 (EC 2.3.1.21), located in the outer membranes of mitochondria, catalyses the carnitine-dependent esterification of coenzyme A to form acylcarnitine, and is a ratelimiting enzyme in fatty acid oxidation [5, 6]. CPT 2, located on the inner mitochondrial membrane, catalyses a reconversion to generate acyl-CoA and carnitine within the mitochondrial matrix, and carnitine acylcarnitine translocase transfers acylcarnitine from the outer to the inner mitochondrial membrane [7]. CPT 1α is widely expressed in most tissues including liver, intestine and heart, while CPT 1β is mainly expressed in muscle, adipose tissue and heart. CPT 1γ expression is restricted to the central nervous system where it functions in the control of whole-body glucose homeostasis [3, 9, 12]
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