Johnston J L, Romsos D R, Bergen W G
J Nutr. 1986 Mar;116(3):435-45. doi: 10.1093/jn/116.3.435.
Five-week-old female lean and obese (ob/ob) mice were fed a 20% protein diet (1.1% tyrosine) or a 20% protein diet supplemented with tyrosine (4% tyrosine). On d 4 of supplementation, brain norepinephrine (NE) synthesis rate and brain efflux of 3-methoxy-4-hydroxyphenylethyleneglycol (MHPG), a major metabolite of NE in mouse brain, were measured after administration of the monoamine oxidase inhibitor pargyline. Control obese mice had a lower rate of NE synthesis and a lower MHPG efflux than lean controls. Tyrosine supplementation elevated brain tyrosine concentration twofold, but had no effect on NE synthesis rate or MHPG efflux in either group. Likewise, tyrosine supplementation for up to 1 mo had no effect on food intake, oxygen consumption or body weight in obese mice and only a transient effect in lean mice, in which oxygen consumption was higher on d 2 and 3 and food intake was higher on d 3 and 4 compared with nonsupplemented lean mice. We conclude that tyrosine availability is not a limiting factor in the reduced brain noradrenergic activity of obese mice.
给5周龄的雌性瘦小鼠和肥胖（ob/ob）小鼠喂食20%蛋白质饮食（1.1%酪氨酸）或补充酪氨酸（4%酪氨酸）的20%蛋白质饮食。在补充的第4天，在给予单胺氧化酶抑制剂帕吉林后，测量脑去甲肾上腺素（NE）合成率以及3-甲氧基-4-羟基苯乙二醇（MHPG，小鼠脑中NE的主要代谢产物）的脑外流。对照肥胖小鼠的NE合成率和MHPG外流低于瘦对照小鼠。补充酪氨酸使脑酪氨酸浓度提高了两倍，但对两组的NE合成率或MHPG外流均无影响。同样，补充酪氨酸长达1个月对肥胖小鼠的食物摄入量、耗氧量或体重没有影响，对瘦小鼠只有短暂影响，与未补充酪氨酸的瘦小鼠相比，补充酪氨酸的瘦小鼠在第2天和第3天耗氧量较高，在第3天和第4天食物摄入量较高。我们得出结论，酪氨酸的可利用性不是肥胖小鼠脑去甲肾上腺素能活性降低的限制因素。
