The effect of vitamin K2 supplementation on cardiovascular risk markers.

Vitamin K was mainly known for its function in blood coagulation, but recently
its function in bone metabolism and vascular calcification became apparent.
Vitamin K is a fat-soluble vitamin present in green vegetables in the form of
vitamin K1 (phylloquinone) and as vitamin K2 (menaquinone) in animal products
(meat, cheese). Vitamin K acts as a co-factor in the carboxylation of clotting
factors, but also of other proteins in bone, osteocalcin (OC), and the vessel
wall, matrix Gla-protein (MGP). MGP is a potent inhibitor of vascular
calcification. Vitamin K can thus reduce vascular calcification and eventually
cardiovascular disease (CVD) by carboxylation of MGP. Observational studies
from our group have shown that a high vitamin K2 intake is associated with
reduced coronary calcification and a reduced risk of coronary heart disease.
These effects have been confirmed in randomized controlled trials among healthy
volunteers. The effects of vitamin K2 are thought to be mediated by increased
carboxylation of MGP. However, because conformation-specific analyses of MGP
have not been available, the effect of vitamin K2 supplementation on
carboxylation of MGP has not been examined. This study will investigate whether
and at what dose vitamin K2 carboxylates MGP, using a novel ELISA assay to
measure conformation-specific MGP. Preliminary studies have shown that vitamin
K2 may also affect other cardiovascular risk factors such as blood lipid
profile, inflammatory factors and insulin sensitivity. The effect of vitamin K2
supplementation on these markers will therefore be investigated as a secondary
objective.

The main objective is to investigate whether and at what dose vitamin K2
increases carboxylation of MGP. Secondary objective is to investigate the
effect of vitamin K2 on markers of CVD (osteocalcin, blood lipids, inflammatory
factors and insulin sensitivity).

Double-blind, placebo-controlled, randomized trial (parallel design)

The intervention period is 12 weeks.
Intervention group one receives a daily dose of 180 µg vitamin K2 (1 MK-7
capsule of 180 µg + one placebo)
Intervention group two receives a daily dose of 360 µg vitamin K2 (2 MK-7
capsules of 180 µg)
the placebo group receives daily a placebo (2 placebo capsules).

All participants will have to fill out small questionnaires at the start,
during, and at the end of the study. They will fill in a 3-day food diary.
There will be 3 site visits. During these visits we will take blood samples 35
ml each time). Further, participants have to take 2 capsules every day during
12 weeks.