Selective utilization of fatty acids in rainbow trout (Oncorhynchus mykiss Walbaum) red muscle mitochondria

Abstract

This study was undertaken to establish whether fatty acids are generally oxidized at the same rate or if a pattern of oxidation rates exists to protect certain fatty acids from degradation for ATP formation. Beta-oxidation was studied in red muscle mitochondria of 10 major fatty acids that are acquired in the diet and occur in the fat depots of rainbow trout (Oncorhynchus mykiss Walbaum). The mitochondria were isolated by fractional centrifugation and the fatty acids were added as coenzyme A esters in the presence of carnitine. The fatty acids could be separated into roughly three groups in relation to their oxidation rates. Two fatty acids (14:0 and 16:0) were oxidized as rapidly as pyruvate. Another six acids (16:1 n − 7, 18:0, 18:1 n − 9, 20:1 n − 9, 22:1 n − 9 and 22:6 n − 3) were oxidized at about three-quarters to one-half the rate of pyruvate. The two essential fatty acids (18:2 n − 6 and 18:3 n − 3) had a slow oxidation rate, about one-fifth of that of pyruvate. The liver mitochondria from rainbow trout oxidized 18:0, 18:1, 18:2, and 18:3 at the same rate, 70–80% of that of pyruvate. These results show that rainbow trout red muscle discriminates between fatty acids used in energy production and essential fatty acid precursors, as indicated by the low β-oxidation rate of the latter acids.

Differential Effects of Dietary Lipids on Growth Performance, Digestibility, Fatty Acid Composition and Histology of African Catfish (Heterobranchus longifilis) Fingerlings

“…The synthesis and degradation of FA occurred mainly in the liver, and several enzymes regulating these pathways show varying affinities for the different fatty acids available in the organ [38], thus imbalance in the dietary fatty acids could modify the functioning and morphology of this organ. In addition, liver function as a main energy reservoir, frequently in the form of triacylglycerols (TG), in certain species such as cod [39], sea bream or sea bass [40].…”

Nutritional and environmental regulation of the synthesis of highly unsaturated fatty acids and of fatty-acid oxidation in Atlantic salmon (Salmo salar L.) enterocytes and hepatocytes

“…With the importance of lipid as an energy source in most fish species, particularly salmonids and marine fish, there have been several studies on fatty acid oxidation in fish (Crockett and Sidell 1993;Kiessling and Kiessling 1993;Frøyland et al 1998Frøyland et al , 2000Fjermestad et al 2000;Torstensen et al 2000;Nanton et al 2003;Vegusdal et al 2004;Oxley et al 2005;Stubhaug et al 2005aStubhaug et al ,b,c, 2006.…”

“…Higher β-oxidation activity in the FO group may, at least partly, be related to the long-chain monoene fatty acids levels of the diets, as the FO diet contained more than twice the amount of longchain monoenes compared to the VO diet. This is based on studies measuring β-oxidation capacity using subcellular fractions, in which long-chain monenes were preferred over PUFA as substrates in fish (Henderson and Sargent 1985;Kiessling and Kiessling 1993;Henderson 1996;Frøyland et al 2000). However, recent intact cell studies, which measure relative fates of fatty acids taken up by the cells, have suggested that PUFA can be relatively more oxidized than 18:1n-9 in salmonid hepatocytes or enterocytes (Oxley et al 2005;Stubhaug et al 2005c).…”

Effect of dietary conjugated linoleic acid (CLA) on growth performance, body composition and hepatic intermediary metabolism in juvenile yellow catfish Pelteobagrus fulvidraco

“…In fish, liver is attributed preferentially to a sensitive organ reflecting dietary lipid change and plays a central role in lipid metabolism including fatty acid synthesis and degradation through enzyme regulation (Likimani and Wilson, 1982;Kiessling and Kiessling, 1993). Despite the fact that the major biochemical and metabolic pathways have been identified in fish (Cowey and Walton, 1989), effects of dietary CLA on hepatic intermediary metabolism are still poorly understood.…”