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

• Published in: Scientific reports Vol. 7; no. 1; p. 40815
• Main Authors: Li, Jia-Min, Li, Ling-Yu, Qin, Xuan, Ning, Li-Jun, Lu, Dong-Liang, Li, Dong-Liang, Zhang, Mei-Ling, Wang, Xin, Du, Zhen-Yu
• Format: Journal Article
• Language: English
• Published: England Nature Publishing Group 19.01.2017
• Subjects: Adipogenesis; Carnitine; Carnitine palmitoyltransferase; Dietary supplements; Fasting; Fatty acids; Gene expression; Gluconeogenesis; Glucose metabolism; Glycogen; Glycolysis; Lipid metabolism; Lipids; Liver; Metabolism; Mitochondria; Oxidation; Palmitoyltransferase; Protein biosynthesis; TOR protein; Zebrafish
• ISSN: 2045-2322; 2045-2322
• DOI: 10.1038/srep40815

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.