Branched-chain Amino Acids L-valine Research Articles

Effects of L-valine supplementation on performance parameters of weaned piglets

T branched-chain amino acid L-valine is typically the fifth-limiting amino acid in practical feed formulation in European pig diets. Current recommendations for the optimal valine:lysine ratio in piglet feed vary between different organizations indicating the need of further research. A trial was performed to evaluate the effects of graded levels of L-valine on the performance of piglets. 200 weaned piglets weighing 8.7±1.1 kg were randomly allocated to 5 dietary treatments. The treatments consisted of two basal diets (pre-starter and starter) providing valine:lysine ratios of 0.59 and 0.57 on a standardized ileal digestible basis and increasing supplemental valine providing valine:lysine ratios of 0.63, 0.67, 0.71 and 0.75 during the pre-starter phase and 0.62, 0.66, 0.70 and 0.75 during the starter phase. Throughout the experiment, the supplementation of L-valine to the basal diets resulted in a significant increase in weight gain and feed intake (p<0.05). The benefits of additional L-valine were observed to occur in a dose-response relationship totaling a 17% higher weight gain in the groups provided a valine:lysine ratio of 0.75 compared to the basal diet. It can be concluded that the supplementation of valine deficient piglet diets with L-valine improves weight gain and feed intake and that a valine:lysine ratio of 0.70 can be suggested as the requirement of piglets in the body weight range of 8-30 kg.

Application of metabolic engineering for the biotechnological production of L-valine.

The branched chain amino acid L-valine is an essential nutrient for higher organisms, such as animals and humans. Besides the pharmaceutical application in parenteral nutrition and as synthon for the chemical synthesis of e.g. herbicides or anti-viral drugs, L-valine is now emerging into the feed market, and significant increase of sales and world production is expected. In accordance, well-known microbial production bacteria, such as Escherichia coli and Corynebacterium glutamicum strains, have recently been metabolically engineered for efficient L-valine production under aerobic or anaerobic conditions, and the respective cultivation and production conditions have been optimized. This review summarizes the state of the art in L-valine biosynthesis and its regulation in E. coli and C. glutamicum with respect to optimal metabolic network for microbial L-valine production, genetic strain engineering and bioprocess development for L-valine production, and finally, it will shed light on emerging technologies that have the potential to accelerate strain and bioprocess engineering in the near future.

Lrp of Corynebacterium glutamicum controls expression of the brnFE operon encoding the export system for l-methionine and branched-chain amino acids

Corynebacterium glutamicum possesses export systems for various amino acids including BrnFE, a two-component export system for L-methionine and the branched-chain amino acids L-valine, L-isoleucine and L-leucine. A gene for a putative transcriptional regulator of the Lrp family is transcribed divergently to the brnFE operon and is required for L-isoleucine export. By comparing global gene expression changes due to L-isoleucine addition we revealed increased brnFE expression in response to L-isoleucine in C. glutamicum wild type but not in an lrp deletion mutant. ChIP-to-chip analysis, band shift experiments and DNAse footprint analysis demonstrated that Lrp binds to the intergenic region between lrp and brnF. Expression analysis of transcriptional fusions with the lrp and brnFE promoters indicated that branched-chain amino acids and L-methionine when added to the growth medium stimulated brnFE expression in the order L-leucine > L-methionine > L-isoleucine > L-valine and that Lrp was required for activation of brnFE expression. Thus, regulation of brnFE by Lrp ensures that BrnFE is synthesized only if its substrate amino acids accumulate in cells which is commensurate with its role to counteract such situations of metabolic imbalance.

Soy Peptide Ingestion Increases Neuroactive Amino Acids in the Adult Brain of Wild-Type and Genetically Engineered Serine-Deficient Mice

The aim of this study was to assess the neurochemical effects produced by short-term dietary soy peptide ingestion in C57BL/6 wild-type mice and in serine-deficient mice that were created as a genetic serine-deficiency disease model. D, L-Amino acid analysis demonstrated that overnight oral ingestion of a 35% (w/v) soy peptide solution significantly increased the hippocampal tissue content of certain neuroactive amino acids in both genotype groups of mice. These amino acids included the neurotransmitter l-glutamate, its precursor L-glutamine, the neuromodulator d-aspartate, and branched-chain amino acids l-valine, l-leucine, and l-isoleucine. Soy peptide ingestion caused similar increases in contents of L-glutamine and branched chain amino acids in the cerebral cortex. Oral ingestion of a 150 mM L-serine solution did not alter contents of these amino acids in the hippocampus and the cerebral cortex in both genotype groups. The present findings indicate that the short-term oral intake of soy peptide positively modulates the levels of certain neuroactive amino acids in the adult brain.

Plasma catecholamines in hepatic coma and liver cirrhosis: role of octopamine.

Plasma levels of adrenaline, noradrenaline and octopamine were estimated by a radioenzymatic method in nine cirrhotic outpatients with encephalopathy and in ten patients with hepatic coma (coma grade III–IV). In the cirrhotic outpatients normal as well as elevated plasma levels of noradrenaline were found. Octopamine could not be detected in the plasma of these patients as well as of ten healthy volunteers. Elevated noradrenaline levels were present in all patients with hepatic coma. Plasma noradrenaline remained elevated or even further increased during the course of hepatic coma, whereas adrenaline was elevated less frequently. In eight of the ten patients with hepatic coma octopamine was again not detectable in plasma. Only in two patients high levels of octopamine up to 59.5 ng/ml could be found in addition to increased noradrenaline concentrations. The infusion of the branched chain amino acid L-valine had no influence on the plasma level of either noradrenaline or octopamine. The data indicate that the sympathetic nervous system is activated during the course of hepatic coma. An accumulation of octopamine is not a common finding in chronic liver disease and hepatic coma. Since in the two patients with elevated octopamine levels the rise in octopamine occured concomitantly with a rise in noradrenaline, a displacement of noradrenaline by the false neurotransmitter octopamine in the noradrenergic neuron of the peripheral sympathetic nervous system seems unlikely. The results indicate that the development of hypotension in the course of liver cirrhosis and hepatic coma cannot be related to a deficiency of noradrenaline.

Oral and parenteral nutrition with L-Valine: mode of action.

The intravenous application of the branched chain amino acid L-valine to patients with hepatic coma resulted in a specific drop of tryptophan, serotonin and 5-hydroxyindole acetic acid. Clinical improvement of hepatic encephalopathy and of the underlying neurotransmitter (serotonin) and ammonia derangements by administration of L-valine suggest a possible role of this competitive amino acid on intermediary metabolism and ammonia detoxification.