Shibata Katsumi, Imai Shoko, Nakata Chifumi, Fukuwatari Tsutomu
Department of Nutrition, School of Human Cultures, The University of Shiga Prefecture.
J Nutr Sci Vitaminol (Tokyo). 2013;59(6):533-40. doi: 10.3177/jnsv.59.533.
Nicotinamide and serotonin are synthesized from L-tryptophan in mammals. It is important to know the nutritional factors affecting the synthesis of nicotinamide and serotonin. We investigated the effects of amino acid composition. Young adult rats were fed ad libitum for 21 d a low-protein (9% casein) diet([1] control), or one of the low protein diets supplemented with following amino acids: [2] glycine, L-threonine, and L-cystine, [3] L-threonine and L-cystine, [4] glycine and L-cystine, and [5] glycine and L-threonine. The amounts of glycine, L-threonine and L-cystine supplementations were 2%, 0.078%, and 0.2%, respectively, and the amino acid contents of all diet were adjusted with supplementation of L-glutamic acid. The body weight gain, food efficiency ratio, and the amino acid nutrition biomarker, which is the urinary excretion ratio of (N(1)-methyl-2-pyridone-5-carboxamide+N(1)-methyl-4-pyridone-3-carboxamide)/N(1)-methylnicotinamide, improved by adding the amino acids glycine, L-threonine and L-cystine to a 9% casein diet. The conversion percentage of L-tryptophan to nicotinamide decreased with the addition of the amino acids glycine, L-threonine and L-cystine to a 9% casein diet, while the concentrations of serotonin in the brain, stomach and small intestine were not affected at all. The effects of each amino acid on body weight gain and the conversion ratios were also investigated. Glycine did not affect these variables. L-Cystine improved the body weight gain, the food efficiency ratio and the urine ratio, and decreased the conversion percentage. L-Threonine did not affect body weight gain or food efficiency ratio; however, it improved the urine ratio and decreased the conversion percentage.
在哺乳动物中，烟酰胺和5-羟色胺由L-色氨酸合成。了解影响烟酰胺和5-羟色胺合成的营养因素很重要。我们研究了氨基酸组成的影响。将成年幼鼠随意喂食低蛋白（9%酪蛋白）饮食（[1]对照组），或喂食补充了以下氨基酸的低蛋白饮食之一：[2]甘氨酸、L-苏氨酸和L-胱氨酸，[3]L-苏氨酸和L-胱氨酸，[4]甘氨酸和L-胱氨酸，以及[5]甘氨酸和L-苏氨酸。甘氨酸、L-苏氨酸和L-胱氨酸的补充量分别为2%、0.078%和0.2%，所有饮食中的氨基酸含量通过补充L-谷氨酸进行调整。通过在9%酪蛋白饮食中添加甘氨酸、L-苏氨酸和L-胱氨酸，体重增加、食物效率比以及氨基酸营养生物标志物（即（N(1)-甲基-2-吡啶酮-5-甲酰胺+N(1)-甲基-4-吡啶酮-3-甲酰胺）/N(1)-甲基烟酰胺的尿排泄率）得到改善。在9%酪蛋白饮食中添加甘氨酸、L-苏氨酸和L-胱氨酸后，L-色氨酸向烟酰胺的转化率降低，而大脑、胃和小肠中5-羟色胺的浓度完全不受影响。还研究了每种氨基酸对体重增加和转化率的影响。甘氨酸对这些变量没有影响。L-胱氨酸改善了体重增加、食物效率比和尿比率，并降低了转化率。L-苏氨酸对体重增加或食物效率比没有影响；然而，它改善了尿比率并降低了转化率。
