Large neutral amino acids: dietary effects on brain neurochemistry and function

Abstract

The ingestion of large neutral amino acids (LNAA), notably tryptophan, tyrosine and the branched-chain amino acids (BCAA), modifies tryptophan and tyrosine uptake into brain and their conversion to serotonin and catecholamines, respectively. The particular effect reflects the competitive nature of the transporter for LNAA at the blood-brain barrier. For example, raising blood tryptophan or tyrosine levels raises their uptake into brain, while raising blood BCAA levels lowers tryptophan and tyrosine uptake; serotonin and catecholamine synthesis in brain parallel the tryptophan and tyrosine changes. By changing blood LNAA levels, the ingestion of particular proteins causes surprisingly large variations in brain tryptophan uptake and serotonin synthesis, with minimal effects on tyrosine uptake and catecholamine synthesis. Such variations elicit predictable effects on mood, cognition and hormone secretion (prolactin, cortisol). The ingestion of mixtures of LNAA, particularly BCAA, lowers brain tryptophan uptake and serotonin synthesis. Though argued to improve physical performance by reducing serotonin function, such effects are generally considered modest at best. However, BCAA ingestion also lowers tyrosine uptake, and dopamine synthesis in brain. Increasing dopamine function in brain improves performance, suggesting that BCAA may fail to increase performance because dopamine is reduced. Conceivably, BCAA administered with tyrosine could prevent the decline in dopamine, while still eliciting a drop in serotonin. Such an LNAA mixture might thus prove an effective enhancer of physical performance. The thoughtful development and application of dietary proteins and LNAA mixtures may thus produce treatments with predictable and useful functional effects.

Biochemical correlates of neuropsychiatric illness in maple syrup urine disease

“…With longer survival, our focus has shifted to the more subtle, chronic neurological sequelae of MSUD. Evidence suggests that, over the life span of an MSUD patient, at least 3 mechanisms threaten brain structure and function: (a) cerebral essential amino acid deficiencies due to unbalanced blood-to-brain transport (2,9,18,19); (b) depletion of neurotransmitters (2,(8)(9)(10)(20)(21)(22); and (c) inhibition of mitochondrial enzymes and the respiratory chain ( Figure 5 and refs. 9,[23][24][25][26].…”

Functional amino acids in nutrition and health

“…Emerging evidence shows a crucial role for glutamate in chemical sensing in the gastrointestinal tract (San Gabriel and Uneyama 2012) and possibly in other tissues (Gallinetti et al 2013). Furthermore, these AA, along with glycine, tryptophan, tyrosine and D-amino acids (e.g., D-alanine, D-aspartate, and D-serine), regulate neurological development and function (Fernstrom 2012;Friedman and Levin 2012;Hou et al 2012a, b;Wang et al 2013). Moreover, leucine activates the mammalian target of rapamycin to stimulate protein synthesis and inhibit intracellular proteolysis (Dillon 2012;Li et al 2011b), whereas methionine is the major donor of the methyl group to affect DNA and protein methylation in cells (Wang et al 2012).…”

The challenge of diabetes in Asia

“…Specifi c attention has been given to the effects on infant growth and development due to changes in infant feeding (Heine, 1999;Heine et al, 1996;Jackson et al, 2002;Lien, 2003;Lien et al, 2002;Markus et al, 2000;Markus et al, 2002) and the precursor roles of specifi c amino acid such as tryptophan in regards to serotonin (Borbély and Youmbi-Balderer, 1987;Fernstrom, 2012;Fernstrom, 2013;Fernstrom and Fernstrom, 1995;Fernstrom et al, 2013;Sharp et al, 1992;Yogman et al, 1982) and tyrosine in regards to adrenaline and noradrenaline. Moreover, the evidence produced over the past decade indicates that improved linear growth is associated with lower risk of death during childhood and to enhance educational performance and labour productivity later in life.…”