Dr. Muhammad Torequl Islam :
Vitamin K, a group of structurally similar fat-soluble vitamins that are found in foods and in dietary supplements are of two forms:
(i) K1 (phylloquinone) mainly found in green vegetables, and
(ii) K2 (including different menaquinones, MKs) derived from intestinal bacteria and fermented food (e.g., cheeses and “natty”, a Japanese soybean product).
Liver is also a rich source of menaquinones. We know about more than 12 different types of MKs, from MK-4 to MK-15, among them the most common MKs in humans are the short-chain MK-4. It is the only MK produced by systemic conversion of phylloquinone to menaquinones.
Generally, our diets contain sufficient amount of vitamin K, therefore, deficiency in healthy adults is rare. However, newborn infants may be deficient in this vitamin as their serum levels depend on the body vitamin K levels of their mothers. Vitamin K deficiency is seen in the patients, especially those who suffer from liver damage or disease (e.g., alcoholics), cystic fibrosis, inflammatory bowel diseases, bulimia, chronic kidney disease, patients receiving anticoagulants (e.g., warferin) for a long time, or kidney transplantion patients. Drugs associated with vitamin K deficiency are – salicylates, barbiturates, and cefamandole.
Vitamin K deficiency has been evident to associate with coagulopathy (a bleeding disorder) as it helps to introduce carboxyl groups into glutamic acid residues in blood coagulation factors (e.g., II, VII, IX, X). Vitamin K1 deficiency is seen in anemia and heavy menstrual bleeding in women, while K2 is evident to cause osteoporosis and coronary heart disease. It should be mentioned that high mortality rates in novel coronavirus disease 2019 (COVID-19) patients have been seen in patients with coagulopathy and coronary heart disease.
COVID-19 causes blood clotting and leads to the degradation of elastic fibres in the lungs. We need vitamin K for a complete synthesis of certain proteins that are needed for blood coagulation or for controlling binding of calcium in bones and other tissues. It can protect against lung disease. In the Netherlands, some COVID-19 patients (>100) have been reported to have deficiencies in vitamin K. The MGP (matrix glutamic carboxyl protein) is a vitamin-K dependent protein. It makes sure minerals (e.g., calcium) stay in bones than the blood vessels, which inhibits atherosclerosis. Without vitamin K the MGP does not work properly.
Moreover, MGP protects the elasticity (due to elastin protein) of connective tissue, including lung against mineralization. Stiffness of elastin impairs our pulmonary function as it results harder to breathe and exchange oxygen.
However, due to the hydrophobic nature, after intestinal absorption, vitamin K is solubilized by bile salt and pancreatic juice. Then it is packaged into chylomicrons, which are secreted into the lymphatic system. For this reason, lipids, in particular triglycerides, interfere with vitamin K measurement during diagnosis.
(Dr. Muhammad Torequl Islam is Assistant Professor, Department of Pharmacy, Life Science Faculty, Bangabandhu Sheikh Mujibur Rahman Science and Technology University. E-mail: [email protected])
