Oxidative effect of l-carnitine on energy metabolism in diploid and triploid rainbow trout (Oncorhynchus mykiss): impact on metabolites

Abstract

L-Carnitine plays a key role in the regulation of energy metabolism and growth in fish. The aim of this study was to determine the effects of dietary L-carnitine levels on carnitine homeostasis and energy metabolism in diploid and triploid trout (Oncorhynchus mykiss). Diploid and triploid trout (29.5 ± 0.6 and 31.8 ± 0.5 g, respectively) were fed with three diets supplemented with 15, 200 or 530 mg L-carnitine/kg, respectively, for 56 days. Compared to 15 mg L-carnitine, total carnitine content increased in the liver by 182% in diploid and by 154% in triploid trout fed 530 mg L-carnitine. In muscle, total carnitine content increased by 60 and 73% in diploid and by 34 and 75% in triploid with the increase in dietary L-carnitine levels. L-Carnitine caused no significant change in the plasma concentrations of metabolites like proteins (ammonia, urea and protein), lipid (triglycerides), carbohydrate (glucose, lactate) and enzyme activities (lipase, lactate, alanine transaminase, lactic acid dehydrogenase). Triploid trout had significantly lower plasma ammonia (P = 0.003), lipase (P = 0.005) and triiodothyronine (T 3 ; P = 0.003) levels than diploid trout. In conclusion, ploidy significantly affected the energy metabolism in rainbow trout, dietary L-carnitine levels altered the L-carnitine homeostasis, but not influence nutritional metabolism.

Metabolic differentiation of diploid and triploid European sea bass juveniles

“…The cells and nucleus of triploids are larger in size than those of their diploid counterparts (Benfey 1999;Maxime 2008), but the total volume of some organs may remain unchanged, possibly through the reduction in the number of cells. Ploidy can affect the energy metabolism of growing fish (Gonçalves et al 2018) and their tolerance to poor water quality (Benfey 1999) indicating reduced tolerance to hypoxic conditions and the aerobic metabolism of triploid fish. Increased size of cells may result in reduced surface-to-volume ratio reduced intracellular diffusion of oxygen and exchange of metabolic molecules.…”