Vitamin K Flashcards
What are the two natural forms of vitamin K?
- K1 (Phylloquinone) - plant sources
- K2 (Menaquinone) - animal sources and synthesized by GI bacteria
What is the plant-based source of vitamin K?
Phylloquinone, K1 (MAJORITY)
What is the animal-based source of vitamin K?
Menaquinones, K2
What is the average adult intake of phylloquinones a day?
~70 to 80 micrograms
(TRUE/FALSE)
Intakes of vitamin K are going to vary greatly on what types of vegetables are consumed.
TRUE
Individuals who consume large amounts of green leafy vegetables (collards, spinach, broccoli), legumes, and some vegetable oils have a much larger intake of vitamin K
What is the EAR for vitamin K?
The FNB did not find sufficient data to establish an EAR; they established AIs
Where is the phylloquinone mainly absorbed? How much?
Jejunum
~15-20% of dietary phylloquinone is absorbed
(TRUE/FALSE)
Most of the vitamin K is still on the chylomicron remnant.
TRUE
What happens to the vitamin K that is on the chylomicron remnant?
It will be brought to the liver and repackaged into VLDL, which is similar to what we talked about with vitamin E
(TRUE/FALSE)
VLDL, LDL, and HDL deliver vitamin K to tissue
TRUE
What tissue contains the most concentrated amount of vitamin K?
Liver; however, it has a short-half life, so VERY LITTLE long-term storage takes place in this organ.
Where do we find the extrahepatic tissue storage of vitamin K?
Adrenal glands
Lungs
Bone marrow
Kidneys
Lymph nodes
What is the most important function of vitamin K?
It is required for blood clotting and stopping bleeding.
There are 13 total blood clotting proteins/factors that are involved in this process, and vitamin K is required as a coenzyme for 4 of them to be activated
What 4 blood clotting factors require vitamin K?
Factors II or prothrombin
Factor VII (7)
Factor IX (9)
Factor X (10)
Gamma glutamyl carboxylase
An enzyme that requires vitamin K as a coenzyme.
What type of residues do the 4 blood clotting factors have?
They contain several glutamic acid residues, which MUST be carboxylated for these proteins to become “activated,” which occurs via GAMMA GLUTAMYL CARBOXYLASE ***
The carboxylation of the 4 blood clotting factors activates the factor by doing what?
Gamma glutamyl carboxylase (vitamin K dependent) will add a carboxyl group, allowing for CALCIUM to bind, activating the peptide, allowing it to participate in the blood clotting process
Which vitamin K-dependent blood clotting factors are present in the intrinsic pathway?
Factors II, X, XI
(All except for Factor VII)
Intrinsic pathway = in the blood
How is a blood clot formed?
The cross-linking of fibrin
What blood clotting factor is in the extrinsic pathway?
Factor VII
Factor X
Factor II / prothrombin
Extrinsic pathway = occurs within the tissue AND has TISSUE FACTOR
Tissue Factor
Released in abundance from tissues like lungs and intestine; within the EXTRINSIC pathway
Dependent on Factor VII
SKIP VITAMIN K CYCLE - - MAKE MANUAL CARDS TO MEMORIZE THE STEPS OF THE REACTIONS
What interferes with vitamin K by preventing the conversion of vitamin K to its active coenzyme form?
Anticoagulants like warfarin
Specifically, what enzymes does warfarin interfere with?
Quinone reductase
Epoxide reductase
Besides blood clotting, what is another function of vitamin K?
Formation and mineralization of bones
What 2 proteins require vitamin K that are identified in bones?
BGP (Bone Gla protein)
MGP (Matrix Gla protein)
*Vitamin K acts as a coenzyme for gamma-glutamyl carboxylase when the above proteins are carboxylated within the bone, this will allow them to BIND UP CALCIUM
What causes bone hardening and increases bone mineral density?
BGP and MGP proteins are carboxylated within the bone, allowing them to bind additional calcium
Where are BGP and MGP mostly secreted from?
The osteoblasts
BGP and MGP contain what percent of non-collagen protein in the bone?
15-20%
(TRUE/FALSE)
BGP and MGP pull calcium out of the blood and into the bone.
TRUE
What happens if additional calcium cannot be taken up into bone via BGP and MGP?
High blood calcium will be deposited into soft tissues, and it will result in low bone density
(TRUE/FALSE)
Vitamin K deficiency is extremely unlikely in healthy individuals.
TRUE
What populations are at risk for vitamin K deficiency?
Newborn infants
Severe GI malabsorptive disorders
Chronic antibiotic consumption
Why are newborn infants at risk for vitamin K deficiency?
Breast milk is very LOW in vitamin K
Stores are low d/t poor placental transfer
Intestinal tract bacteria are not populated
In the US, this is one of the first injections they get (0.5 to 1 mg vitamin K via IM, so they are not at risk for bleeding)
What is the best assessment of vitamin K status?
Plasma prothrombin concentration
Normal: 80 to 120 micrograms/mL
