Abstract
Vitamin K is involved many biological processes, such as the regulation of blood coagulation, prevention of vascular calcification, bone metabolism and modulation of cell proliferation. Menaquinones (MK) and phylloquinone vary in biological activity, showing different bioavailability, half-life and transport mechanisms. Vitamin K1 and MK-4 remain present in the plasma for 8–24 h, whereas long-chain menaquinones can be detected up to 96 h after administration. Geometric structure is also an important factor that conditions their properties. Cis-phylloquinone shows nearly no biological activity. An equivalent study for menaquinone is not available. The effective dose to decrease uncarboxylated osteocalcin was six times lower for MK-7 than for MK-4. Similarly, MK-7 affected blood coagulation system at dose three to four times lower than vitamin K1. Both vitamin K1 and MK-7 inhibited the decline in bone mineral density, however benefits for the occurrence of cardiovascular diseases have been observed only for long-chain menaquinones. There are currently no guidelines for the recommended doses and forms of vitamin K in the prevention of osteoporosis, atherosclerosis and other cardiovascular disorders. Due to the presence of isomers with unknown biological properties in some dietary supplements, quality and safety of that products may be questioned.
Highlights
Vitamin K is a fat-soluble vitamin characterised by the presence of a 2-methyl-1, 4-naphthoquinone ring
The Vitamin K group (Figure 1) owe their biological activity to the presence of the naphthoquinone ring. It serves as a cofactor for an enzyme that activates vitamin-Kdependent proteins (VKDP), that are involved in processes such as regulation of blood coagulation, prevention of vascular calcification, bone metabolism and modulation of cell
Studies in rats revealed that the cis vitamin K1 isomer had practically no biological activity, but the tissue distribution of cis-phylloquinone was similar to the distribution of the trans form
Summary
Vitamin K is a fat-soluble vitamin characterised by the presence of a 2-methyl-1, 4-naphthoquinone ring. The Vitamin K group (Figure 1) owe their biological activity to the presence of the naphthoquinone ring. It serves as a cofactor for an enzyme that activates vitamin-Kdependent proteins (VKDP), that are involved in processes such as regulation of blood coagulation, prevention of vascular calcification, bone metabolism and modulation of cell 2 o. Foods 2021, 10, x FOR PEER REVIEWsymptoms such as premature osteoporosis, midfacial hypoplasia and mineralisation of skin that leads to pseudoxanthoma-elasticum-like disorder These diseases stem from deficiency of osteocalcin (OC) and matrix Gla protein (MGP) [21,22,23]. One group includes proteins such as OC, MGP and growth arrest-s tein (Gas6) which are produced extrahepatically and are not related to the b. OC and MGP (ucOC and ucMGP) and those produced in the liver—prothrombin (PIVK II, protein induced by vitamin K absence II) [37]
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