Abstract
BackgroundMenaquinone-4 is a type of vitamin K that has a physiological function in maintaining bone quality via γ-carboxylation of osteocalcin. However, little is known about the beneficial effect of intake of dosages below1500 μg/day.FindingsFifteen healthy males aged 25.0 years (median) participated in a non-placebo-controlled dose-examination study. They received menaquinone-4 daily for 5 weeks at 0, 300, 600, 900, and 1500 μg/day in weeks 1, 2, 3, 4, and 5, respectively. Compared with baseline, serum γ-carboxylated osteocalcin levels were significantly greater at an intake of 900 μg/day or more; serum undercarboxylated osteocalcin levels and the ratio of serum undercarboxylated osteocalcin to γ-carboxylated osteocalcin were significantly lower than baseline at doses of 600 μg/day or more.ConclusionsThis preliminary graded-dose study suggested that menaquinone-4 supplementation at 600 μg/day or more is likely to be important in terms of vitamin K requirements for bone health.
Highlights
There are two major forms of dietary vitamin K: phylloquinone and menaquinone
This preliminary graded-dose study suggested that menaquinone-4 supplementation at 600 μg/day or more is likely to be important in terms of vitamin K requirements for bone health
Serum γ-carboxylated osteocalcin (Gla-OC) is used as a marker of bone formation, whereas serum undercarboxylated osteocalcin (ucOC) is used as a marker of vitamin K deficiency and as a predictor of hip fracture risk independently of femoral neck bone mineral density [2]; the cut-off value of 4.5 ng/mL for ucOC has been validated [3] and is generally accepted in the selection of Japanese patients for medication for osteoporosis
Summary
Vitamin K plays an important role in coagulation and bone homeostasis as a coenzyme that mediates γ-carboxylation of glutamate residues into γ-carboxylated proteins such as coagulation factors, osteocalcin, and matrix Gla-protein. The precise role of osteocalcin is not known, but it is known that γ-carboxylated osteocalcin (Gla-OC) is a bone protein that attracts Ca2+ and incorporates it into hydroxyapatite crystals. Absolute Gla-OC or ucOC levels are not indicative of the overall vitamin K status in the bone metabolism. The ratio of ucOC to Gla-OC (UGR) is used as a sensitive marker of the vitamin K status of bone [4]. Vitamin K supplementation controls bone homeostasis by increasing Gla-OC levels and decreasing ucOC levels and the UGR. Menaquinone-4 is a type of vitamin K that has a physiological function in maintaining bone quality via γ-carboxylation of osteocalcin. Little is known about the beneficial effect of intake of dosages below1500 μg/day
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