Menaquinone-4 enhances testosterone production in rats and testis-derived tumor cells.
Menaquinone-4 enhances testosterone production in rats and testis-derived tumor cells.
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DOI：
10.1186/1476-511x-10-158
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发表时间：
2011-09-13
影响因子：
4.5
通讯作者：
Komai M
中科院分区：
文献类型：
--
作者：
Ito A;Shirakawa H;Takumi N;Minegishi Y;Ohashi A;Howlader ZH;Ohsaki Y;Sato T;Goto T;Komai M
维生素K对各种Gla蛋白的翻译后修饰至关重要。虽然它广泛存在于包括睾丸在内的几个器官中，但维生素K在这些器官中的功能尚未得到很好的表征。在这项研究中，我们研究了维生素K在睾丸中的功能，并分析了其在类固醇合成中的作用。8周龄雄性Wistar大鼠喂食补充有甲基萘醌-4（MK-4，75 mg/kg饮食）的饮食5周，甲基萘醌-4是睾丸中存在的主要K2维生素之一。通过酶联免疫吸附试验测定大鼠血浆和睾丸的体内睾酮水平，并在几个时间点用MK-4（0 - 100 μM）处理后，测定维持在含10%胎牛血清的Ham's F-10培养基中的睾丸源性肿瘤细胞（I-10细胞）的体外睾酮水平。分析了睾酮和细胞蛋白水平对类固醇生成的影响。与对照组大鼠相比，MK-4喂养大鼠血浆和睾丸中的睾酮水平显著升高，血浆促黄体激素水平无明显差异。从I-10细胞分泌的睾酮水平升高MK-4，但不是由维生素K1，在一个独立的cAMP治疗剂量依赖性的方式。蛋白质印迹分析表明，CYP 11 A，类固醇生成的限速酶，蛋白激酶A（PKA）和cAMP反应元件结合蛋白的磷酸化水平的表达都刺激MK-4的存在。PKA的特异性抑制剂H89可抑制睾酮生成的增加，而γ-谷氨酰羧化的抑制剂华法林则无此作用。MK-4通过激活PKA刺激大鼠和睾丸源性肿瘤细胞中的睾酮产生。MK-4可能参与睾丸类固醇生成，补充MK-4可逆转老年人睾酮生成的下调。
Vitamin K is essential for the posttranslational modification of various Gla proteins. Although it is widespread in several organs, including the testis, the function of vitamin K in these organs is not well characterized. In this study, we investigated the function of vitamin K in the testis and analyzed its role in steroidogenesis. Eight-week-old male Wistar rats were fed a diet supplemented with menaquinone-4 (MK-4, 75 mg/kg diet), one of the predominant K2 vitamins present in the testis, for 5 weeks. In vivo testosterone levels of the rats' plasma and testes were measured by enzyme-linked immunosorbent assay, and in vitro testosterone levels of testis-derived tumor cells (I-10 cells) maintained in Ham's F-10 medium with 10% fetal bovine serum were measured following treatment with MK-4 (0 to 100 μM) at several time points. Testosterone and cellular protein levels were analyzed with respect to their effects on steroidogenesis. Testosterone levels in the plasma and testes of MK-4-fed rats were significantly increased compared to those of control rats, with no obvious differences in plasma luteinizing hormone levels. Secreted testosterone levels from I-10 cells were elevated by MK-4, but not by vitamin K1, in a dose-dependent manner independent of cAMP treatment. Western blot analysis revealed that expression of CYP11A, the rate-limiting enzyme in steroidogenesis, and phosphorylation levels of protein kinase A (PKA) and the cAMP response element-binding protein were all stimulated by the presence of MK-4. Enhancement of testosterone production was inhibited by H89, a specific inhibitor of PKA, but not by warfarin, an inhibitor of γ-glutamylcarboxylation. MK-4 stimulates testosterone production in rats and testis-derived tumor cells via activation of PKA. MK-4 may be involved in steroidogenesis in the testis, and its supplementation could reverse the downregulation of testosterone production in elders.