leucine

Dietary supplementation of valine, isoleucine, and tryptophan may overcome the negative effects of excess leucine in diets for weanling pigs containing corn fermented protein

Mallea, Andrea P., Charmaine D. Espinosa, Su A Lee, Minoy A. Cristobal, Leidy J. Torrez‑Mendoza, Hans H. Stein. 2024. Dietary supplementation of valine, isoleucine, and tryptophan may overcome the negative effects of excess leucine in diets  for weanling pigs containing corn fermented protein.    J. Anim. Sci.

Effects of excess dietary leucine in corn protein diets

Malea, A. P., and H. H. Stein. 2023. Effects of excess dietary leucine in corn protein diets. National Hog Farmer, On-line edition. November 14, 2023.

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Supplementation of Valine, Isoleucine, and Tryptophan may overcome the negative effects of dietary excess Leucine in corn protein when fed to weanling pigs

High protein corn protein (HPCP) is a corn co-product derived from the ethanol industry that contains between 40 and 50% crude protein, and therefore, may be used in diets for pigs as a source of amino acids (AA). However, such diets will contain more than twice as much Leu as recommended and there is a negative relationship between dietary Leu and brain synthesis of serotonin, which results in reduced feed intake of pigs fed diets containing excess Leu. There is also a reduced protein synthesis because of increased Val and Ile metabolism due to excess dietary Leu. As a consequence, pigs often have reduced growth performance if fed diets with high concentrations of HPCP. However, it may be possible to counteract the negative effects of the high Leu concentrations in corn co-products by adding crystalline sources of Trp, Val, and Ile to the diets and it may, therefore, be possible that HPCP can be used in diets without influencing growth performance or intestinal health of weanling pigs. Therefore, the hypothesis that HPCP may be used as the primary source of AA in diets for weanling pigs if diets are fortified with crystalline AA was tested. 

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Effects of dietary leucine and tryptophan on serotonin metabolism and growth performance of growing pigs

Kwon, Woong B., Jose A. Soto, and Hans H. Stein. 2022. Effects of dietary leucine and tryptophan on serotonin metabolism and growth performance of growing pigs. J. Anim. Sci. 100, 1–10. doi.org/10.1093/jas/skab356. Link to full text. 

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Effects of Dietary Valine, Isoleucine, and Tryptophan Supplementations to Diets Containing Excess Leucine from Corn Protein on Growth Performance of Growing Pigs

Kwon, W. B., J. A. Soto, and H. H. Stein. 2021. Effects of Dietary Valine, Isoleucine, and Tryptophan Supplementations to Diets Containing Excess Leucine from Corn Protein on Growth Performance of Growing Pigs. J. Anim. Sci. 99(Suppl. 1): 61–62. doi.org/10.1093/jas/skab054.103. Link to Abstract.

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Effects of Dietary Valine, Isoleucine, and Tryptophan Supplementations to Diets Containing Excess Leucine on Nitrogen Balance of Growing Pigs

Kwon, W. B., J. A. Soto, and H. H. Stein. 2021. Effects of Dietary Valine, Isoleucine, and Tryptophan Supplementations to Diets Containing Excess Leucine on Nitrogen Balance of Growing Pigs. J. Anim. Sci. 99(Suppl. 1): 61. doi.org/10.1093/jas/skab054.102. Link to Abstract.

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Effects on nitrogen balance and metabolism of branched-chain amino acids by growing pigs of supplementing isoleucine and valine to diets with adequate or excess concentrations of dietary leucine

Kwon, Woong B., Jose A. Soto, and Hans H. Stein. 2020. Effects on nitrogen balance and metabolism of branched-chain amino acids by growing pigs of supplementing isoleucine and valine to diets with adequate or excess concentrations of dietary leucine. Journal of Animal Science, 2020, Vol. 98, No. 11, 1–10. doi:10.1093/jas/skaa346.

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Effects of dietary isoleucine and valine supplementation to excess or low leucine diets on nitrogen balance and metabolism of branched-chain amino acids in growing pigs

Leucine is a key regulator that stimulates catabolism of branched-chain AA (BCAA; i.e., Leu, Ile, and Val) in skeletal muscle and liver. If diets fed to pigs contain excess Leu, catabolism of all 3 BCAA may increase because of the stimulating effect of the Leu metabolite, α-keto isocaproate, on the branched-chain α-keto acid dehydrogenase enzyme complex, which is responsible for degradation of the 3 branched-chain α-keto acids that originate from metabolism of the 3 BCAA. Serum Ile and Val concentrations were reduced by excess dietary Leu in growing pigs, and high dietary Leu reduces feed intake and growth performance in pigs, which may be a result of the imbalanced supply of BCAA that result from increased metabolism of Val and Ile. Recent data confirmed that excess dietary Leu reduced growth performance and tended to reduce protein synthesis, which is likely a result of reduced availability of Val and Ile.

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Tryptophan can partially overcome negative effects of leucine in pig diets

Kwon, W. B., and H. H. Stein. 2020. Tryptophan can partially overcome negative effects of leucine in pig diets. National Hog Farmer, Online edition. Jan.

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Excess dietary leucine in diets for growing pigs reduces growth performance, biological value of protein, protein retention, and serotonin synthesis

Kwon, Woong B., Kevin J. Touchette, Aude Simongiovanni, Kostas Syriopoulos, Anna Wessels, and Hans H. Stein. 2019. Excess dietary leucine in diets for growing pigs reduces growth performance, biological value of protein, protein retention, and serotonin synthesis. Journal of Animal Science, 2019, 4282–4292. Link to full text.

Effects of dietary leucine and tryptophan supplementation on serotonin metabolism and growth performance of growing pigs

Tryptophan is an indispensable AA that is often limiting for growth in pigs fed corn-soybean meal-based diets. Tryptophan may act as a regulator of feed intake by enhancing serotonin signaling in the brain, because Trp is a precursor for serotonin. High Trp intake increases feed intake, and this is partly attributed to increased serotonin synthesis. Availability of dietary Trp in the brain is considered the rate-limiting step in hypothalamic serotonin synthesis. However, to be transported into the brain, Trp competes with other large neutral AA such as Val, Leu, Ile, Tyr, and Phe for a common transporter (L-type AA transporter 1) to cross the blood-brain barrier.

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Excess leucine reduces nitrogen retention, growth performance in pigs.

Kwon, W. B., and H. H. Stein. 2019. Excess leucine reduces nitrogen retention, growth performance in pigs. July 29, 2019. Link to ful text.

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Effects of dietary leucine concentration on branched-chain amino acid metabolism in growing pigs

Leucine, Val, and Ile are categorized as the branched-chain AA (BCAA) because of the structural similarity of their side chains. All 3 BCAA share the enzymes that are involved in the first 2 steps of their catabolic pathway. The first step is a transamination step catalyzed by BCAA transaminase (BCAT) and producing branched-chain α-keto acids (BCKA). The second step is an irreversible degradation step catalyzed by branched-chain α-keto acid dehydrogenase (BCKDH). In the second step, Leu has been considered a key regulator as its BCKA metabolite (α-keto isocaproate) stimulates activation of the BCKDH complex in the liver. When excess Leu in diets is offered to pigs, degradation of all 3 BCAA may increase because of increased activity of BCAT and BCKDH. Leucine and Trp are both categorized as large neutral AA, and they share a common uptake pathway across the blood-brain barrier. Therefore, it is possible that excessive Leu may result in reduced Trp uptake into the brain due to competition for transporters, resulting in reduced serotonin synthesis.

 

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