Soy peptide ingestion augments the synthesis and metabolism of noradrenaline in the mouse brain

To examine whether edible peptide intake affects neurotransmitter metabolism in the brain, we evaluated the effect of peptides derived from soy proteins or fish collagen on free amino acids and monoamines in the mouse brain. Ingestion of soy peptides led to markedly higher levels of tyrosine, a catecholamine precursor, in the serum, and cerebral cortex compared to those following ingestion of vehicle alone or collagen peptides. Soy peptide ingestion also effectively increased 3-methoxy-4-hydroxyphenylethyleneglycol and normetanephrine, the principal metabolites of noradrenaline, in the cerebral cortex, hippocampus, and brainstem, whereas collagen peptides did not exert such effects. Further, soy peptide ingestion led to a significant increase in noradrenaline itself in the brainstem, where noradrenergic neurons are present. Noradrenergic turnover was also markedly stimulated in these regions after soy peptide ingestion. These <i>in vivo</i> observations suggest that soy peptide ingestion can maintain and promote the synthesis and metabolism of noradrenaline in the brain. Soy peptide ingestion promotes the synthesis and metabolism of noradrenaline in the brain via increased Tyr availability.

为探究可食用肽摄入对大脑神经递质代谢的影响，我们评估了大豆蛋白衍生肽与鱼胶原蛋白衍生肽对小鼠大脑内游离氨基酸及单胺类物质的作用。相较于仅摄入赋形剂（vehicle）或鱼胶原蛋白肽的组别，摄入大豆肽可使血清与大脑皮层内的酪氨酸——一种儿茶酚胺前体——的水平显著升高。此外，摄入大豆肽还可有效提升大脑皮层、海马体与脑干内去甲肾上腺素（noradrenaline）的主要代谢产物——3-甲氧基-4-羟基苯乙二醇与去甲变肾上腺素——的水平，而鱼胶原蛋白肽未产生此类作用。进一步研究显示，摄入大豆肽可使存在去甲肾上腺素能神经元的脑干内的去甲肾上腺素水平显著升高，且上述区域的去甲肾上腺素能代谢周转也显著增强。这些体内（in vivo）实验观察结果表明，摄入大豆肽可维持并促进大脑内去甲肾上腺素的合成与代谢。摄入大豆肽可通过提升酪氨酸（Tyr）的可利用性，促进大脑内去甲肾上腺素的合成与代谢。