Vitamin K status of healthy Japanese women : age-related vitamin K requirement for γ-carboxylation of osteocalcin

• Published in: The American journal of clinical nutrition 2006-02, Vol.83 (2), p.380-386
• Main Authors: TSUGAWA, Naoko, SHIRAKI, Masataka, SUHARA, Yoshitomo, KAMAO, Maya, TANAKA, Kiyoshi, OKANO, Toshio
• Format: Article
• Language: English
• Subjects: Adult; Age; Age Factors; Aged; Aged, 80 and over; Aging - blood; Aging - physiology; Asian people; Biological and medical sciences; Biomarkers - blood; Bone and Bones - metabolism; Bone Density - physiology; Bones; Carboxylic Acids - metabolism; Feeding. Feeding behavior; Female; Fractures, Bone - epidemiology; Fractures, Bone - etiology; Fundamental and applied biological sciences. Psychology; Humans; Japan; Metabolism; Middle Aged; Nutritional Requirements; Nutritional Status; Older people; Osteocalcin - metabolism; Risk Factors; Vertebrates: anatomy and physiology, studies on body, several organs or systems; Vitamin K - blood; Vitamin K - metabolism; Vitamin K 1 - blood; Vitamin K 2 - analogs & derivatives; Vitamin K 2 - blood; Vitamin K Deficiency - complications; Vitamins; Vitamins - blood; Women
• ISSN: 0002-9165; 1938-3207
• DOI: 10.1093/ajcn/83.2.380

Vitamin K deficiency is associated with low bone mineral density and increased risk of bone fracture. Phylloquinone (K1) and menaquinone 4 (MK-4) and 7 (MK-7) are generally observed in human plasma; however, data are limited on their circulating concentrations and their associations with bone metabolism or with gamma-carboxylation of the osteocalcin molecule. The objectives were to measure the circulating concentrations of K1, MK-4, and MK-7 in women and to ascertain whether each form of vitamin K is significantly associated with bone metabolism. Plasma concentrations of K1, MK-4, MK-7, undercarboxylated osteocalcin (ucOC; measured by using the new electrochemiluminescence immunoassay), intact osteocalcin (iOC), calcium, and phosphorus; bone-derived alkaline phosphatase activity; and concentrations of urinary creatinine, N-terminal telopeptide, and deoxypyridinoline were measured in healthy women (n = 396). On average, MK-7 and MK-4 were the highest and lowest, respectively, of the 3 vitamers in all age groups. K1 and MK-7 correlated inversely with ucOC, but associations between nutritional basal concentration of MK-4 and ucOC were not observed. Multiple regression analysis indicated that not only K1 and MK-7 concentrations but also age were independently correlated with ucOC concentration and the ratio of ucOC to iOC. The plasma K1 or MK-7 concentration required to minimize the ucOC concentration was highest in the group aged > or =70 y, and it decreased progressively for each of the younger age groups. The definite role of ucOC remains unclear. However, if submaximal gamma-carboxylation is related to the prevention of fracture or bone mineral loss, circulating vitamin K concentrations in elderly people should be kept higher than those in young people.