Menatetrenone (
INN), also known as menaquinone-4 (MK-4), is one of the nine forms of
vitamin K2.
Biology
MK-4 is the major form of Vitamin K in vertebrate animals, including humans and common forms of meat animals. It is produced via conversion of vitamin K1 in the body, specifically in the testes, pancreas and arterial walls.[2] The conversion is not dependent on gut bacteria, occurring in germ-free rats[3][4] and in parenterally-administered K1 in rats.[5][6] Tissues that accumulate high amounts of MK-4 have a capacity to convert up to 90% of the available K1 into MK-4.[3][4][dubious –
discuss]
Attachment of GGPP tail to form menaquinol-4, the reduced form of MK-4 (
UBIAD1)
The second and third steps are known to happen in target tissue. The first step is proposed to happen mainly in the intestines.[7]
As a medication
Menatetrenone is approved in Japan for second-line treatment of
postmenopausal osteoporosis. Evidence is restricted to small-scale RCTs; the minimum effective dose (for bone mass parameters) is 45 mg, much higher than the
Daily Value for vitamin K (80 μg).[8]
Bioavailbility and dose
420 μg of oral MK-4, in a single-dose or spread out over 7 days, does not cause detectable changes in serum MK-4 level in healthy women, whereas MK-7 produces the expected increases in MK-7 levels.[1]
The minimum effective oral dose to change serum
osteocalcin levels is 1500 μg/d, where as oral MK-7 is effective on this parameter at 45 μg/d, a level more in line with nutritional intake. In addition, rat studies show that oral MK-7 is better at increasing extrahepatic tissue levels of MK-4 than oral MK-4.[1]
^
abRonden JE, Drittij-Reijnders MJ, Vermeer C, Thijssen HH (January 1998). "Intestinal flora is not an intermediate in the phylloquinone-menaquinone-4 conversion in the rat". Biochimica et Biophysica Acta (BBA) - General Subjects. 1379 (1): 69–75.
doi:
10.1016/S0304-4165(97)00089-5.
PMID9468334.
^Iwamoto J (May 2014).
"Vitamin K2 therapy for postmenopausal osteoporosis". Nutrients. 6 (5): 1971–80.
doi:10.3390/nu6051971.
PMC4042573.
PMID24841104. administered daily doses of 15, 45, 90, and 135 mg revealed that 45 mg was the minimum effective dose for improving bone mass parameters evaluated by microdensitometry and/or single photon absorptiometry in postmenopausal women with osteoporosis
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