4. 肉碱的化学名称为β-羟基-γ-三甲胺基丁酸，是B族维生素类似物，其主要功能是作为活性脂肪酸进入线粒体进行β-氧化的载体，它通过肉碱脂酰转移酶系统把脂肪酸以脂酰肉碱的形式从线粒体膜外转运到膜内，从而促进了长链脂肪酸的氧化。肉碱可调节脂酰－COA／COA-SH的比值，来抑制糖的异生作用，加速脂类的氧化过程。Santulli等(1988)在海鲈、Rumsey(1991)在斑点叉尾鮰中发现，饲料中添加肉碱可促进生长，降低肝脏中脂肪的含量，提高饲料转化率，改变由于投喂高脂饲料而造成的肝脂沉积，防止脂肪肝的发生。Chatzifotis等(l996)发现，饲料中添加肉碱可提高真鲷肝脏中长链脂肪酸氧化的速度，降低肝脏中脂肪的含量。左旋肉碱具有显著促进脂肪代谢、减少脂肪在体内积累的作用，而右旋肉碱作用不明显，或具有相反的作用。所以在水产饲料中要认清标志，注意添加左旋肉碱，添加量一般为80～120g/吨。
5. 蛋氨酸和赖氨酸都是鱼类的必需氨基酸，可参加蛋白质的合成，并可作为甲基供体，也是合成脂蛋白所必需的。蛋氨酸供应不足，不仅影响鱼类的生长，而且也妨碍脂蛋白的合成，影响脂肪代谢。Wilson等(1978)认为，蛋氨酸不仅参与直接的转甲基反应，而且给磷脂酰乙醇氨提供三个活性的基团。Rumsey(1991)发现，虹鳟饲料中添加蛋氨酸可节约饲料中的胆碱用量。Dunn(1981)研究表明，肉碱在鱼体肝脏中可由赖氨酸和蛋氨酸合成，肉碱的碳和氮原子来自赖氨酸，而N-甲基来自蛋氨酸。Rebouche(1991)指出，游离赖氨酸不能合成肉碱，只有肽结合的赖氨酸才能合成肉碱。Burtle(1994)认为，赖氨酸可降低斑点叉尾鮰的肝脂含量。
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The cause of fatty liver of cultured fish and the anti-fatty liver factor
Lin J
ianbin
(Fujian Provincial Institute of Freshwater Fisheries, Fuzhou 350002,China)
Abstract:This article reviews the cause of fatty liver of cultured fish and the characteristic of the anti-fatty liver factor.
2007121061024249.pdf
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