Clarification of a novel physiological function of menaquinone-4 (vitamin K2), a postulated active form of vitamin K in various tissues

叶绿醌（维生素K1=VK1）和甲基萘醌（MK-n，或维生素K2=VK2）是维生素k的天然存在形式。大多数甲基萘醌是由微生物合成的，但我们已经报道过MK-4通常是通过口服摄入的VK1或甲基萘醌（=VK3）在缺乏肠道微生物群的无菌大鼠和小鼠的主要组织中合成的。这一结果否定了Martius关于肠道菌群细菌酶参与这一转化的理论。近年来，MK-4因其对破骨细胞和白血病细胞的凋亡活性等特殊生理作用而引起了研究者的关注，有利于维持我们健康的生活质量。因此，我们认为MK-4除了在肝脏中具有凝血作用和在其他组织中具有所有维生素k类似物所具有的与gla蛋白相关的作用外，还可能在动物的各种组织中具有特定的新功能。为了进一步阐明这一假说，我们试图找出在VK缺乏条件下表达上调或下调的基因。DNA微阵列技术是同时观察基因表达谱的有力工具。两组无菌大鼠分别饲喂缺乏VK和补充VK1的饲料8 d，处死，并取血和组织标本。凝血时间（凝血酶原时间和活化部分凝血活酶时间）和各组织VK水平的测定结果均支持缺食大鼠表现出更为严重的VK缺乏症状。肝脏、脑和睾丸的基因表达谱显示，维生素K缺乏会影响多种基因的表达。在VK缺陷肝中显著上调的一系列基因属于一组特殊的蛋白，即急性期蛋白。这一结果与我们之前的观察结果一致，即VK缺陷无菌小鼠在肝脏和肌肉中有急性组织学变化。饮食中的VK1在体内LPS（脂多糖）刺激系统中具有抗炎作用，可能通过其转化为MK-4，因为我们观察到，在原代培养的脾脏中，在培养基中添加MK-4而不是VK1，可以显著抑制LPS刺激的IL-6表达。总之，任何一种被认为在各种组织中转化为MK-4的膳食VK在啮齿动物中都具有抗炎作用，可能在人类中也是如此，尽管MK-4作用的详细机制还有待进一步阐明。少

Phylloquinone (vitamin K1=VK1) and the menaquinones (MK-n, or vitamin K2=VK2) are naturally occurring forms of vitamin K. Most of the menaquinones are synthesized by micro-organisms, but we have reported that MK-4 is usual in being synthesized by the conversion of orally ingested VK1 or menadione (=VK3) in the major tissues of germfree rats and mice which lack their intestinal microflora. This result denies Martius' theory that described the participation of bacterial enzyme of the intestinal flora to this conversion. Recently MK-4 has been attracted the attention of researchers due to its specific physiological action such as apoptotic activity on osteoclast cells and leukemia cells, etc. that is beneficial for the maintainance of our healthy quality of life. Therefore, we considered that MK-4 may have a specific novel function in various tissues of animals besides of coagulation in the liver and Gla-protein related action in the other tissues which all analogues of vitamin Ks have.In … More order to elucidate this hypothesis, we tried to identify genes of which expression is up-or down-regulated under VK deficient condition. DNA microarray technique is a very powerful tool to see the pofile of gene expression simultaneously. Two groups of germfree rats fed VK deficient or VK1 supplemented diet for eight days were sacrificed, and blood and tissue samples were deprived. The results of blood coagulation time (prothrombin time and activated-partial thromboplastin time) and the measurement of VK levels in various tissues supported that rats fed deficient diet showed much more sevefe VK deficient symptoms.The profile of gene expression in the liver, brain, and testis showed that the expression of diverse genes was affected under vitamin K deficiency. The series of genes which were markedly up-regulated in VK deficient liver belonged to a particular group of protein, i.e., acute phase proteins. This result was consistent with our previoous observations that VK deficient germfree mice had acute histological changes in the liver and muscle. Dietary VK1 has an anti-inflammatory effect in the LPS (lipopolysaccharide)-stimulated system in vivo, probably through its conversion to MK-4, because we observed that LPS-stimulated IL-6 expression in the primary cultured spleen was significantly inhibited by the addition of MK-4 to the culture medium rather than VK1. In conclusion, any kind of dietary VK that is considered to convert to MK-4 in various tissues has an anti-inflammatory role in the rodents and probably in humans, though detailed mechanisms involved in the effect of MK-4 should be clarified further. Less