The effects of branched-chain amino acid interactions on growth performance, blood metabolites, enzyme kinetics and transcriptomics in weaned pigs
MK Wiltafsky, MW Pfaffl and FX Roth, 2010. British Journal of Nutrition, 103:964-976.
05-Jul-2010 (15 years 11 months 2 days ago)Interactions among the branched-chain amino acids (BCAA), such as the performance depressing effects of excess dietary leucine (Leu), are known in several species. The impact of high dietary Leu levels needs to be elucidated in order to make correct estimates of adequate supplies and requirements for isoleucine (Ile) and valine (Val).
The impact of excess dietary Leu was studied in two growth experimental trials with pigs (8–25 kg). In each trial, forty-eight pigs were allotted to one of six dietary groups. The dietary Leu supply increased from treatment L100 to L200 (three increments). To guarantee that interactions between the branched-chain amino acids (BCAA) were not cushioned either surpluses of isoleucine (Ile, expt 1) or valine (Val; expt 2) were avoided. In the fifth treatment, the effects of a simultaneous excess of Leu and Val (expt 1), or of Leu and Ile (expt 2) were investigated. The sixth treatment was a positive control.
An increase in dietary Leu decreased growth performance, and increased plasma Leu and serum a-keto-isocaproate levels in a linear, dose-dependent manner. Levels of plasma Ile and Val, and of serum a-keto-b-methylvalerate and a-keto-isovalerate, indicated increased catabolism. Linear increases in the activity of basal branched-chain a-keto acid dehydrogenase in the liver confirmed these findings. No major alterations occurred in the mRNA of branched-chain amino acid catabolism genes. In liver tissue from expt 2, however, the mRNA levels of growth hormone receptor, insulin-like growth factor acid labile subunit and insulin-like growth factor 1 decreased significantly (P<0.05) with increasing dietary Leu.
In conclusion, excess dietary Leu increased the catabolism of BCAA mainly through post-transcriptional mechanisms. The impact of excess Leu on the growth hormone–insulin-like growth factor-1 axis requires further investigation.
The impact of excess dietary Leu was studied in two growth experimental trials with pigs (8–25 kg). In each trial, forty-eight pigs were allotted to one of six dietary groups. The dietary Leu supply increased from treatment L100 to L200 (three increments). To guarantee that interactions between the branched-chain amino acids (BCAA) were not cushioned either surpluses of isoleucine (Ile, expt 1) or valine (Val; expt 2) were avoided. In the fifth treatment, the effects of a simultaneous excess of Leu and Val (expt 1), or of Leu and Ile (expt 2) were investigated. The sixth treatment was a positive control.
An increase in dietary Leu decreased growth performance, and increased plasma Leu and serum a-keto-isocaproate levels in a linear, dose-dependent manner. Levels of plasma Ile and Val, and of serum a-keto-b-methylvalerate and a-keto-isovalerate, indicated increased catabolism. Linear increases in the activity of basal branched-chain a-keto acid dehydrogenase in the liver confirmed these findings. No major alterations occurred in the mRNA of branched-chain amino acid catabolism genes. In liver tissue from expt 2, however, the mRNA levels of growth hormone receptor, insulin-like growth factor acid labile subunit and insulin-like growth factor 1 decreased significantly (P<0.05) with increasing dietary Leu.
In conclusion, excess dietary Leu increased the catabolism of BCAA mainly through post-transcriptional mechanisms. The impact of excess Leu on the growth hormone–insulin-like growth factor-1 axis requires further investigation.