Vitamin K Flashcards
List the dietary and non-dietary forms of vitamin K.
Vitamin K1,
phylloquinone
- is synthezied in plants and is the predominant form in the diet
Vitamin K2
menaquinones
- come from animal sources and synthesis of intestinal bacteria
- includes a range of forms designated menaquinone-n (MK-n)
Menadione
- synthetic form of vit K
List the reasons why adequate amounts of vitamin K are usually present in the body?
1) vitamin K is widespread in foods
2) the vitamin K cycle conserves vitamin K
3) bacteria in the large intestine synthesize menaquinones (vit K2)
For what category of enzyme does vitamin K act as a cofactor?
vitamin K is a cofactor for an emzyme that catalyzes the
carboxylation of glutamic acid (an amino acid)
converting it to gamma-carboxyglutamic acid (Gla)
which is critical to the calcium binding function of these proteins
necessary for blood clotting and bone mineralization
Vitamin-K dependent modification of proteins such as the clotting factors affects the binding of which mineral ion by those proteins?
calcium
Name the anticoagulants that antagonize vitamin K action.
warfarin (Coumadin)
interferes with vit K recycling
Name the 3 bone proteins that depend upon vitamin K for their production.
1) osteocalcin (function unclear, thought to be bone mineralization, bone remodeling, or calcium mobilization)
2) matrix Gla protein (MGP)
(found in bone, cartilage, and soft tissue. thought to prevent calcification of soft tissue and cartilage
3) protein S
anticoagulant protein is also synthesized by osteoblasts. Its role in bone metabolism is unclear.
What role may vitamin K play in the health of soft tissue structures?
Prevents calcification
The vit K dependent protein MGP (Matrix Gla protein) has been found to prevent the calcification of soft tissues and cartilage while facilitating normal bone growth and development.
MGP messenger RNA has been found in brain, heart, liver, lung, and spleen
Lack of MGP in knockout mice has been associated with extensive arterial calcification
MGp may function to prevent calcium precipitation.
What population groups and clinical situations are associated with increased risk for vitamin K deficiency?
Adults taking vit K antagonist anticoagulants (coumadin or warfarin)
Adults with liver disease
Adults with disorders of fat metabolism
Adults being treated chronically with antibiotics
Newborns who are exclusively breast feed (human milk is low in vit K, gut bateria may not be producing vit K yet, vit K not easily transported across placenta, vit K cycle may not be fully developed. Vit K injection recommended for all new borns.)
Deficiency is unlikely i. Healthy adults
Name the blood disorder associated with a vitamin K deficiency.
In infants: vitamin K deficiency bleeding (VKDB) of the newborn
In adults: bleeding or hemorrhage caused by prolonged prothrombon time
List the methods for determining vitamin K status.
Plasma or serum phylloquinone concentrations (reflect recent intake, last 24 hours)
Whole blood clotting time
Prothrombin clotting time
(measures time to clot to form whe Ca added to plasma. greater than 25 seconds may indicate vit K deficiency. This test insensitive because plasma prothrombin levels must decrease significantly as much as 50%, before prothrombin time effected)
Measure undercarboxylated vit K-dependent proteins
such as prothrombin and osteocalcin
Which form of vitamin K has toxic potential?
The synthetic form menadione
Can cause liver damage when ingested in large amounts
What are the two major functions of vit K dependent proteins in the body?
- Blood clotting
- Bone mineralization
What are the vitamin K dependent blood clotting proteins (4) and anticoagulant proteins (3)?
Blood clotting proteins:
1. Prothrombin (factor II)
2. VII
3. IX
4. X
(memory que: 2 + 7 = 9 and one more = 10)
Anticoagulant proteins
1. C
2. S
3. Z
(memory que: CS me, Z backwards S)
What are good food sources of vit K?
Phylloquinone (main dietary source)
1. Green vegetables (broccoli, kale, chard)
2. Oils and margerine (soy and canola oils high)
Menaquinones
Synthesized by gut bacteria
Small amounts found in
Liver
Fermented cheeses
Soybean products
What is the RDA for vit K?
Adults 19 and over
Male 120 mcg
female 90 mcg
Pregnancy 90
Lactation 90
