The objective of the present experiment was to investigate the effect of dietary methionine (Met) concentration and alternating feeding strategies in methionine delivery, on the mRNA transcript levels of genes involved in Met resynthesis (betainehomocysteine methyltransferase, BHMT; S-adenosylhomocysteine hydrolase, SAAH) and net Met loss (taurine synthesis) (cystathionine beta-synthase, CBS) in Atlantic salmon (Salmo salar) liver. Salmon alevins (265±3 mg) were randomly distributed into 24 tanks at a density of 50 fish per tank (3 replicates) in a semi-recirculation system. Water temperature was maintained between 15 to 19°C. The experimental diets were supplemented with L-methionine at levels of 0, 1.9, 5.8, and 17.4 g/kg (M0, M1/3, M1, and M3, respectively). The M3 diet without glycine was additionally prepared to examine Met toxicity (M3-G). These diets were provided to the fish following the ‘mono-feeding strategy’ meaning fish were fed a designated single diet during the entire feeding experiment. This experiment also included three alternative feeding groups with ‘duo-feeding’ strategy: AF1 (fish that were sequentially fed M0 for 2 days followed by M1 for 1 day), AF2 (fish that were fed M0 for 2 days followed by M3 for 1 day), and AF3 (fish that were fed two meals of M0 followed by one meal of M3). The results showed that salmon alevins fed M0 diet had smaller weight compared to all other groups. There was no significant effect of alternative feeding on the growth of salmon except with the M0 group. The highest expression of CBS gene was found in the M0, M1/3, and AF-1 groups compared to M3 and M3-G groups. The expression of CBS gene in the M1 group was lower compared to the AF-1 group but not different than M0 or M1/3 groups. The expression of SAAH gene was the highest in the M3 group compared to M1, M1/3, and AF-3 groups but there was no difference between the M0, M3, and M3-G groups. The highest expression of BHMT gene was found in the M0, M1/3, and AF-1 groups indicating enhanced re-methylation of homocysteine by betaine to Met. The lowest BHMT expression in M1, M3, M3-G, AF-2, and AF-3 groups compared to other treatments can be indicative of downregulation of remethylation in the liver
Dietary methionine in salmonid fish feed alters the expression of genes involved in methionine metabolism.
TEROVA, GENCIANA;BOSSI, ELENA;SAROGLIA, MARCO;
2014-01-01
Abstract
The objective of the present experiment was to investigate the effect of dietary methionine (Met) concentration and alternating feeding strategies in methionine delivery, on the mRNA transcript levels of genes involved in Met resynthesis (betainehomocysteine methyltransferase, BHMT; S-adenosylhomocysteine hydrolase, SAAH) and net Met loss (taurine synthesis) (cystathionine beta-synthase, CBS) in Atlantic salmon (Salmo salar) liver. Salmon alevins (265±3 mg) were randomly distributed into 24 tanks at a density of 50 fish per tank (3 replicates) in a semi-recirculation system. Water temperature was maintained between 15 to 19°C. The experimental diets were supplemented with L-methionine at levels of 0, 1.9, 5.8, and 17.4 g/kg (M0, M1/3, M1, and M3, respectively). The M3 diet without glycine was additionally prepared to examine Met toxicity (M3-G). These diets were provided to the fish following the ‘mono-feeding strategy’ meaning fish were fed a designated single diet during the entire feeding experiment. This experiment also included three alternative feeding groups with ‘duo-feeding’ strategy: AF1 (fish that were sequentially fed M0 for 2 days followed by M1 for 1 day), AF2 (fish that were fed M0 for 2 days followed by M3 for 1 day), and AF3 (fish that were fed two meals of M0 followed by one meal of M3). The results showed that salmon alevins fed M0 diet had smaller weight compared to all other groups. There was no significant effect of alternative feeding on the growth of salmon except with the M0 group. The highest expression of CBS gene was found in the M0, M1/3, and AF-1 groups compared to M3 and M3-G groups. The expression of CBS gene in the M1 group was lower compared to the AF-1 group but not different than M0 or M1/3 groups. The expression of SAAH gene was the highest in the M3 group compared to M1, M1/3, and AF-3 groups but there was no difference between the M0, M3, and M3-G groups. The highest expression of BHMT gene was found in the M0, M1/3, and AF-1 groups indicating enhanced re-methylation of homocysteine by betaine to Met. The lowest BHMT expression in M1, M3, M3-G, AF-2, and AF-3 groups compared to other treatments can be indicative of downregulation of remethylation in the liver
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