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


OBJECTIVE
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.


METHODS
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).


RESULTS
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.


CONCLUSIONS
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.
Tsugawa
Naoko
N
Department of Hygienic Sciences, Kobe Pharmaceutical University, Kobe, Japan.
Shiraki
Masataka
M
Suhara
Yoshitomo
Y
Kamao
Maya
M
Tanaka
Kiyoshi
K
Okano
Toshio
T
D000328:Adult; D000367:Age Factors; D000368:Aged; D000369:Aged, 80 and over; D000375:Aging / Q000097:blood* / Q000502:physiology; D015415:Biomarkers / Q000097:blood; D015519:Bone Density / Q000502:physiology*; D001842:Bone and Bones / Q000378:metabolism*; D002264:Carboxylic Acids / Q000378:metabolism; D005260:Female; D050723:Fractures, Bone / Q000453:epidemiology / Q000209:etiology; D006801:Humans; D007564:Japan; D008875:Middle Aged; D009751:Nutritional Requirements; D009752:Nutritional Status; D015675:Osteocalcin / Q000378:metabolism*; D012307:Risk Factors; D014812:Vitamin K / Q000097:blood* / Q000378:metabolism; D010837:Vitamin K 1 / Q000097:blood; D024482:Vitamin K 2 / Q000031:analogs & derivatives / Q000097:blood; D014813:Vitamin K Deficiency / Q000150:complications; D014815:Vitamins / Q000097:blood
D015415:Biomarkers; D002264:Carboxylic Acids; D014815:Vitamins; D015675:Osteocalcin; D024482:Vitamin K 2; D014812:Vitamin K; C030814:menatetrenone; D010837:Vitamin K 1; C062629:menaquinone 7