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. 2017 Jan 19:7:40815.
doi: 10.1038/srep40815.

Systemic regulation of L-carnitine in nutritional metabolism in zebrafish, Danio rerio

Jia-Min Li  1 , Ling-Yu Li  1 , Xuan Qin  2 , Li-Jun Ning  1 , Dong-Liang Lu  1 , Dong-Liang Li  1 , Mei-Ling Zhang  1 , Xin Wang  2 , Zhen-Yu Du  1
Affiliations

Systemic regulation of L-carnitine in nutritional metabolism in zebrafish, Danio rerio

Jia-Min Li et al. Sci Rep. .

Erratum in

Abstract

Excess fat accumulation has been observed widely in farmed fish; therefore, efficient lipid-lowering factors have obtained high attention in the current fish nutrition studies. Dietary L-carnitine can increase fatty acid β-oxidation in mammals, but has produced contradictory results in different fish species. To date, the mechanisms of metabolic regulation of L-carnitine in fish have not been fully determined. The present study used zebrafish to investigate the systemic regulation of nutrient metabolism by dietary L-carnitine supplementation. L-carnitine significantly decreased the lipid content in liver and muscle, accompanied by increased concentrations of total and free carnitine in tissues. Meanwhile, L-carnitine enhanced mitochondrial β-oxidation activities and the expression of carnitine palmitoyltransferase 1 mRNA significantly, whereas it depressed the mRNA expression of adipogenesis-related genes. In addition, L-carnitine caused higher glycogen deposition in the fasting state, and increased and decreased the mRNA expressions of gluconeogenesis-related and glycolysis-related genes, respectively. L-carnitine also increased the hepatic expression of mTOR in the feeding state. Taken together, dietary L-carnitine supplementation decreased lipid deposition by increasing mitochondrial fatty acid β-oxidation, and is likely to promote protein synthesis. However, the L-carnitine-enhanced lipid catabolism would cause a decrease in glucose utilization. Therefore, L-carnitine has comprehensive effects on nutrient metabolism in fish.

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Figures

Figure 1
Figure 1. Effect of the dietary L-carnitine on the carnitine concentration, gene of carnitine synthesis and triglyceride in tissues of zebrafish.
(A) Free carnitine; (B) Total canitine; (C) The relative mRNA abundance of carnitine synthesis (gamma-butyrobetaine hydroxylase 1, BBOX1); (D) The crude lipid content of whole fish; (E) TG content of liver, muscle, viscera. All values are means ± SEM (n = 6). Values with *,**statistically differ at P < 0.05, P < 0.01.
Figure 2
Figure 2. Effect of the dietary L-carnitine on mitochondrial and peroxisomal β-oxidation capability of zebrafish.
(A) The mitochondrial β-oxidation capability; (B) The peroxisomal β-oxidation capability; (C) The total β-oxidation capability. All values are means ± SEM (n = 4). Values with *,**statistically differ at P < 0.05, P < 0.01.
Figure 3
Figure 3. The effect of the dietary L-carnitine on mRNA expression of genes of lipid metabolism.
All values are means ± SEM (n = 6). Values with *,**statistically differ at P < 0.05, P < 0.01.
Figure 4
Figure 4. The effect of the dietary L-carnitine on glycogen and mRNA expression of the genes related to glucose metabolism.
All values are means ± SEM (n = 6). Values with *,**statistically differ at P < 0.05, P < 0.01.
Figure 5
Figure 5. The effect of the dietary L-carnitine on protein and mRNA expression of the genes related to protein metabolism.
All values are means ± SEM (n = 6). Values with *,**statistically differ at P < 0.05, P < 0.01.
Figure 6
Figure 6. The effect of the dietary L-carnitine on mRNA expression of the genes related to inflammation.
All values are means ± SEM (n = 6). Values with *,**statistically differ at P < 0.05, P < 0.01.
Figure 7
Figure 7. Systemic regulation of L-carnitine in nutritional metabolism of zebrafish.
(A) The regulation of L-carnitine in feeding state. (B) The regulation of L-carnitine in fasting state. ACS, acyl-CoA synthetase. CACT, carnitine/acylcarnitine translocase.
Figure 8
Figure 8. The possible mechanism of the L-carnitine on protein synthesis.
Figure 9
Figure 9. The design and the protocol of the present experiment.
See this image and copyright information in PMC

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