Nutrition in Hematopoiesis Flashcards
Why does DNA synthesis require V12 and Folate?
Vitamin B12 and Folate are used to methylate dUMP
dUMP –> dUTP
Importance of Folate
Source of methyl groups
B12: co-enzyme for recycling folate
In absence of B12 or Folate RBCs cause
DNA synthesis impairment
Cell division is defective
Cytoplasm matures more rapidly than the nucleus
Megoblastic Anemia RBCs
Megoblastic Anemia
multilobed PMNs and macrocytic RBCs
nuclei of precursors mature more slowly than the cytoplasm because of DNA impairment
Folate Sources
Natural and Fortified
Natural: Polyglutamate conjugated, poor chemical stability, reduced bioavailability
Fortified: Folic Acid, synthetic, good stability, enhanced bioavailability
Causes of Folate Deficiency
Reduced intake: Alcohol, poverty, overcooking food
Increased Demands on utilization: Needed for cell division, anemias due to RBC destruction
Folate Deficiency Symptoms and Blood smear
Symptoms of anemia, neural tube defects
Smear: anemia/ pancytopenia
macrocytes and multilobed PMNs
B12 Reactions
B12 has cobalt center
B12 important for conversion of homocsyteine to methione and then SAM
SAM can methylate many things and is important for myelination of nerves
B12 also used to convert MM-CoA to sucinyl CoA for fatty acid synthesis
Sources of B12
Made by bacteria and found in meats/ animal by products
Absorption of B12
Mouth: B12 bound to protein stims production of heptocorrin
Stomach: parietal cells make IF, high acidity makes heptoccorin bind to B12
Duodenum: Dissociation of B12 from heptocorrin by pancreatic enzymes, B12 binds to IF
Ileum: uptake of B12/IF complex by ileal cells with cubilin receptor
Colon: bacteria produce b12 that we cannot use :(
Where is B12 stored?
vitamin B12 is stored in the liver, where we normally years worth of storage.
Loss of IF occurs
IF produced in stomach, IF associates with B12 in the duodenum and is taken up in the ilium.
Loss occurs with gastritis, partial gastrectomy
Pernicious Anemia
Achlorhydria
Loss of Intrinsic factor by making antibodies against parietal cells or intrinsic factor
Achlorhydria: not enough acid is being produced in the stomach due to age / drugs (doesn’t allow haptocorrin to associate with B12)
Vitamin B12 symptoms / Blood Smear
Symptoms of anemia as well as NEUROLOGICAL abnormalities
Blood smear: anemia/pancytopenia, macrocytes and multilobed PMNs
Folate is absorbed in the ______ while Vit B12 is absorbed in the ______.
Folate in the duodenum, jejunum
Vitamin B12 in the ileum
