Effects of exercise onl-carnitine and lipid metabolism in African catfish (Clarias gariepinus) fed different dietaryl-carnitine and lipid levels

Abstract

African catfish (Clarias gariepinus) were fed four isonitrogenous diets (34 % crude protein), each containing one of two lipid (100 or 180 g/kg) and two L-carnitine (15 or 1000 mg/kg) levels. After 81 d of feeding, thirty-two fish (body weight 32 g) from each dietary group were randomly selected, sixteen fish were induced to a 3-h swim (speed of 1·5 body length (BL)/s), while the other sixteen fish were kept under resting condition. Fish fed 1000 mg L-carnitine accumulated 3·5 and 5 times more L-carnitine in plasma and muscle, respectively, than fish fed the 15 mg L-carnitine. Muscle L-carnitine content was significantly lower in exercised fish than in rested fish. High dietary lipid level (fish oil) led to an increase in muscle n-3 PUFA content and a decrease in SFA and MUFA content. In liver, the increase in dietary lipid level resulted in an increased levels of both n-6 and n-3 PUFA. L-carnitine supplementation significantly decreased n-3 PUFA content. Exercise decreased n-3 PUFA in both muscle and liver. Plasma lactate and lactate dehydrogenase, normally associated with increased glycolytic processes, were positively correlated with exercise and inversely correlated with dietary L-carnitine level. L-carnitine supplementation reduced significantly the RQ from 0·72 to 0·63, and an interaction between dietary L-carnitine and lipid was observed (P, 0·03). Our results indicate that an increase in fatty acids (FA) intake may promote FA oxidation, and both carnitine and exercise might influence the regulation of FA oxidation selectivity.African catfish: L-carnitine metabolism: Lipid metabolism: Exercise Fish are subjected to many changes in energy demand throughout their lifespan. As the lipid content of their diet increases so does the optimal dietary level of L-carnitine (1 -3) , a multi-physiological, bioactive additive compound, synthesised from two essential amino acids, protein-bound lysine and methionine. It is not entirely understood whether animals require exogenous L-carnitine, and over the past 20 years, the scientific discussion regarding this subject continued with ambiguous arguments.L-Carnitine plays several important physiological roles like shuttling the long-chain fatty acid (FA) across the inner mitochondrial membrane for ATP production (4,5) and inhibition of superoxide radical formation (6) . According to Heo et al. (2,7) , L-carnitine biosynthesis might be sufficient to maintain growth of 20-kg pigs during optimum husbandry conditions. Nevertheless, extra dietary L-carnitine is efficiently retained in body tissues, playing a role in nutrient utilisation and thus on growth performance and body composition. The rate of lipid oxidation is determined by the energy requirements of working muscles and by the availability of free L-carnitine delivery to muscle mitochondria (8,9) .Since exogenous L-carnitine may influence energy utilisation efficiency, several studies using birds and mammals as animal models tested the effect of dietary L-carnitine supplementation on the exercise performance and on l...

Effects of supplemental dietary l-carnitine and ractopamine on the performance of juvenile rainbow trout, Oncorhynchus mykiss

“…Total n‐3 poly unsaturated fatty acids (n‐3 PUFA) were reduced by l ‐carnitine supplementation. Slight effects of dietary l ‐carnitine upon muscle n‐3 and n‐6 long‐chain PUFAs were also reported by Ozório (2001). On the other hand, results reported by Chatzifotis, Takeuchi and Seikai (1996) showed some reduction of only the EPA level in muscle of red sea bream fed l ‐carnitine‐supplemented feed.…”

“…2005). It is noteworthy that there are cases where l ‐carnitine does not improve growth but only accumulates in fish (Ozório 2001).…”

“…This might be due to the fact that supplementation of l ‐carnitine results in an acceleration of fatty acid oxidation and improved nitrogen retention (Ji, Bradley & Tremblay 1996). Furthermore, Ozório (2001) indicated that 1 g kg −1 l ‐carnitine supplementation in the diet of African catfish raised the concentration of some amino acids in muscle tissue and concluded that l ‐carnitine increased fatty acid oxidation and decreased amino acid combustion for energy. Our results are in close agreement with Ji et al .…”

“…There was a significant l ‐carnitine and ractopamine interaction effect on blood glucose, resulting in hyperglycaemia in fish fed by ractopamine when supplemented with 1 g kg −1 l ‐carnitine in the diet. According to the available literature, β agonists stimulated glycogenolysis and inhibited glycolysis (Wright, Perry & Moon 1989; Reid, Moon & Perry 1992) and l ‐carnitine increased fatty acid oxidation (Ozório 2001; Bacurau, Navarro, Bassin, Meneguello, Santos, Almeida & Costa Rosa 2003), hence producing a sparing effect on blood glucose level.…”

Separate and combined effects of cyclic fasting and l-carnitine supplementation in red porgy (Pagrus pagrus, L. 1758)

“…Commonly, fish undergoing a period of starvation satisfy the energy requirements by utilizing lipid stores (Weatherley & Gill 1987). Because the liver is the first storage site where lipid and glycogen are depleted in fish (Ozório, Van Ginneken, Bessa, Verstegen, Verreth & Huisman 2010), we expected to observe a relationship between fasting and liver lipid content.…”