Temporal variations in plasma vitamin K and lipid concentrations and clotting factor activity in humans

There is no information available on temporal variability in plasma vitamin K concentrations and its relationship to coagulation processes. We investi gated the possible existence of temporal changes in plasma vitamin K and li pid concentrations and activity of clotting factors II, VII, IX, and X and relationships between these variables. Plasma vitamin K and lipid concentra tions and clotting factor activity were measured at four-hour intervals for 28 hours in a group of healthy volunteers. Temporal variations existed in plasma vitamin K concentrations, with a mean maximum at 22:00 hr and a mean minimum (32% of the maximum) at 10:00 hr. Plasma triglycerol concentration s mirrored the changes in vitamin K concentrations. Mean factor Vil activit y was positively correlated with mean total plasma cholesterol concentratio ns (r = 0.714; P < 0.0001) and with mean plasma low density lipoprotein (LD L) cholesterol concentrations (r = 0.461; P < 0.0001). No distinct correlat ions were found between plasma vitamin K concentrations and either high den sity lipoprotein (HDL) or LDL cholesterol concentrations, or between trigly cerol, HDL, or LDL cholesterol concentrations and functional activity of fa ctors II, IX, and X. Plasma vitamin K concentrations did not correlate with the functional activity of any of the clotting factors. The presence of a correlation between plasma cholesterol concentrations and factor VII activi ty for blood samples collected at four-hour intervals suggests that plasma cholesterol concentrations may have a more acute effect on factor VII activ ity. Temporal variations in plasma vitamin K concentrations indicate that a single time point measurement may be an inappropriate method of establishi ng vitamin K status in an individual. (C) 2001 Wiley-Liss, Inc.