Ronden J E, Drittij-Reijnders M J, Vermeer C, Thijssen H H
Department of Biochemistry, Cardiovascular Research Institute Maastricht, Maastricht University, The Netherlands.
Biochim Biophys Acta. 1998 Jan 8;1379(1):69-75. doi: 10.1016/s0304-4165(97)00089-5.
To elucidate the role of intestinal bacteria in the conversion of phylloquinone into menaquinone-4 (MK-4) we investigated the tissue distribution of vitamin K in germ-free rats. The rats were made vitamin K deficient by feeding a vitamin K-free diet for 13 days. In a subsequent period of 6 days, phylloquinone and menadione were supplied via the drinking water in concentrations of 10 and 50 micromol l(-1). Menadione supplementation led to high levels of tissue MK-4, particularly in extrahepatic tissues like pancreas, aorta, fat and brain. Liver and serum were low in MK-4. Phylloquinone supplementation resulted in higher phylloquinone levels in all tissues when compared with vitamin K-deficient values. The main target organs were liver, heart and fat. Remarkably, tissue MK-4 levels were also higher after the phylloquinone supplementation. The MK-4 tissue distribution pattern after phylloquinone intake was comparable with that found after menadione intake. Our results demonstrate that the conversion of phylloquinone into MK-4 in extrahepatic tissues may occur in the absence of an intestinal bacterial population and is tissue specific. A specific function for extrahepatic MK-4 or a reason for this biochemical conversion of phylloquinone into MK-4 remains unclear thus far.
为阐明肠道细菌在叶绿醌转化为甲基萘醌-4（MK-4）过程中的作用，我们研究了无菌大鼠体内维生素K的组织分布情况。通过给大鼠喂食不含维生素K的饲料13天，使其维生素K缺乏。在随后的6天里，通过饮用水分别提供浓度为10和50微摩尔/升的叶绿醌和甲萘醌。补充甲萘醌导致组织中MK-4水平升高，尤其是在胰腺、主动脉、脂肪和脑等肝外组织中。肝脏和血清中的MK-4含量较低。与维生素K缺乏时的值相比，补充叶绿醌后所有组织中的叶绿醌水平均升高。主要靶器官是肝脏、心脏和脂肪。值得注意的是，补充叶绿醌后组织中的MK-4水平也升高。摄入叶绿醌后MK-4的组织分布模式与摄入甲萘醌后相似。我们的结果表明，在没有肠道菌群的情况下，肝外组织中叶绿醌可转化为MK-4，且具有组织特异性。目前尚不清楚肝外MK-4的具体功能或叶绿醌转化为MK-4这种生化转化的原因。
