Department of Food and Nutrition, Japan Women's University, Tokyo, Japan.
Bone. 2011 May 1;48(5):1036-42. doi: 10.1016/j.bone.2011.01.020. Epub 2011 Feb 2.
Vitamin K is a cofactor for γ-glutamyl carboxylase, which is an essential enzyme for the γ-carboxylation of vitamin K-dependent proteins such as osteocalcin and matrix Gla protein. Although it has been suggested that vitamin K plays an important role in the improvement of bone metabolism, the relationship between dietary vitamin K intake and bone metabolism has not been thoroughly investigated. Moreover, vitamin K is thought to have other actions beyond influencing the γ-carboxylation status. In the present study, we examined the effects of the long-term addition of phylloquinone (PK) or menaquinone-4 (MK-4) to a control diet on bone mineral density, bone strength, body composition, and serum parameters in rats. A total of 23 female Sprague-Dawley strain rats (6 weeks old) were divided into three groups: basic control diet group, PK diet (PK: 600mg/kg diet) group, and MK diet (MK-4: 600mg/kg diet) group. Three months after starting the experimental diet, the addition of PK to the basic control diet significantly increased the bone mineral density (BMD) of the femur (p<0.05). In the MK group, there was no significant difference in the BMD of the femur. However, two types of bone strength parameter: the minimum cross-sectional moment of inertia and the polar moment of inertia, were significantly higher in the MK group than in the control (p<0.05, respectively). Furthermore, the femoral bone parameters (the width, dry weight and ash weight, and cortical, cancellous, trabecular, and total bone mineral contents) in the MK group were increased significantly compared with the control. Interestingly, the addition of PK or MK-4 significantly decreased the total fat accumulation (p<0.01 and p<0.05, respectively), and serum triglycerides were reduced by 48% in the PK group and 29% in the MK group compared with the control. There were no significant differences in the levels of serum calcium, phosphorus, alkaline phosphatase, growth hormone, insulin-like growth hormone-1, insulin-like growth hormone binding protein-3, and cross-linked N-teleopeptide of type I collagen among the three groups. This is the first study to demonstrate the effect of the long-term addition of PK or MK-4 to the control diet on body composition and serum parameters in an in vivo system using rats. Further studies on the mechanism of vitamin K supplementation in the regulation of bone metabolism would provide valuable data on the prevention of lifestyle-related disorders, including osteoporosis.
维生素 K 是 γ-谷氨酰羧化酶的辅助因子，γ-谷氨酰羧化酶是维生素 K 依赖蛋白如骨钙素和基质 Gla 蛋白 γ-羧化所必需的酶。虽然已经有人提出维生素 K 在改善骨代谢方面发挥着重要作用，但膳食中维生素 K 摄入与骨代谢之间的关系尚未得到彻底研究。此外，维生素 K 除了影响 γ-羧化状态之外，还有其他作用。在本研究中，我们研究了长期添加叶绿醌 (PK) 或甲萘醌-4 (MK-4) 对控制饮食对大鼠骨矿物质密度、骨强度、身体成分和血清参数的影响。将 23 只 6 周龄雌性 Sprague-Dawley 大鼠分为三组：基础对照饮食组、PK 饮食 (PK：600mg/kg 饮食) 组和 MK 饮食 (MK-4：600mg/kg 饮食) 组。在开始实验饮食 3 个月后，在基础对照饮食中添加 PK 可显著增加股骨的骨矿物质密度 (BMD)(p<0.05)。在 MK 组中，股骨的 BMD 没有显著差异。然而，两种类型的骨强度参数：最小横截面积惯性矩和极惯性矩，在 MK 组中明显高于对照组 (p<0.05，分别)。此外，MK 组的股骨参数 (宽度、干重和灰重，以及皮质骨、松质骨、小梁骨和总骨矿物质含量) 明显高于对照组。有趣的是，添加 PK 或 MK-4 可显著减少总脂肪堆积 (p<0.01 和 p<0.05，分别)，与对照组相比，PK 组血清甘油三酯降低了 48%，MK 组降低了 29%。三组间血清钙、磷、碱性磷酸酶、生长激素、胰岛素样生长激素-1、胰岛素样生长激素结合蛋白-3 和 I 型胶原交联 N-端肽水平无显著差异。这是第一项在体内系统中使用大鼠研究长期添加 PK 或 MK-4 对控制饮食的身体成分和血清参数影响的研究。关于维生素 K 补充剂在调节骨代谢中的作用机制的进一步研究将为预防与生活方式相关的疾病，包括骨质疏松症，提供有价值的数据。
