17 – Hematopoietic Nutrients

Question 1

What are some of the hematopoietic vitamins and minerals?

Answer 1

• Folic acid
• Vitamin B12
• Fe
• (others we won’t cover)
• *both vitamins involved in single carbon transfers as catalysts)

Question 2

What is iron involved in?

Answer 2

• Oxidation reduction reactions
• Heavily involved in RBC metabolism
  o *key component of Hg and Mg
  o *aerobic metabolism would be impossible without Fe in Hg
• Other important proteins are heme-proteins

Question 3

Vitamin B12: cyanocobalamin

Answer 3

• Consists of a complex ring structure that includes a cobalt ion at its center
• Only metabolic function of cobalt
• *exception to most rules about B vitamins for absorption, storage, transport, etc
• *synthesized by bacteria and yeast
  o Absent in plant products

Question 4

Vit B12 required for methionine synthase

Answer 4

• Conversion of homocysteine to methionine requires B12 and folate
• Reactions reduces folate so it can be recycled
  o If B12 is deficient=breaks the folate cycle
  o (B12 allows the re-use of folate)

Question 5

Folate and Vit B12 deficiencies look similar: how can you tell them apart?

Answer 5

• Tell difference by administering folate
• If folate deficiency was cause=animal will be better
• If B12 was the problem=folate can’t be recycled and symptoms persist

Question 6

B12 deficiency

Answer 6

• Results in pernicious or megaloblastic anemia (large, immature RBCs in blood)
• Occurs as a heritable condition: Sprue in humans (caused by lack of intrinsic factor)
• *ruminants benefit from cobalt supplementation so that rumen microbes can synthesize B12

Question 7

Folic acid

Answer 7

• Vitamin B9
• Required for methionine and DNA synthesis
• Abundant in plant sources (including forages)
• Absorption, transport, storage and excretion are the same for Thiamin, etc.

Question 8

Folate deficiency

Answer 8

• Megaloblastic anemia
• Most common B-vitamin deficiency in humans in NA
• In early pregnancy in humans=can result in neural tube defects (spina bifida)
• In animals: anemia, stunted growth, weight loss, increased clotting time

Question 9

What is the biochemistry of Fe dominated by?

Answer 9

• Low solubility
• Redox characteristics
• *aqueous aerobic environment: Fe3+
• *physiological conditions: Fe3+ and Fe2+
• Iron easily and reversibly undergoes the reaction: Fe2+ and e-

Question 10

What are some important hemoproteins/what are they involved in?

Answer 10

• Oxygen transport: Hg and Mg
• Electron transfer (cytochromes need for ATP production)
• Metabolism of O2 and peroxides: cytochrome P450 and catalase
• Redox enzymes

Question 11

Iron handling in animals

Answer 11

• Iron reduced to Fe2+ in acid environment of stomach
• Intestinal absorption is poor (2-5%)
• Fe2+ is released to ferritin in cell and transported to basolateral membrane
• Feroportin transports Fe2+ across the basolateral membrane
• Transferrin transports iron in plasma
  o Ferritin stores iron in liver, spleen and bone marrow cells
• NO excretion mechanism other than losses

Question 12

Excess iron

Answer 12

• Saturated binding proteins=will precipitate in cells (HEMOSIDERIN)

Question 13

Intestinal absorption of iron

Answer 13

• Requires divalent metal transporter 1 (DMT1)
• Can only be absorbed as Fe2+
• Phytates and other dietary factors can decrease absorption
• Vitamin C or chelated forms of Fe increase absorption

Question 14

What are the two functions of lactoferrin?

Answer 14

1. Excreted in milk to bind iron in gut of neonates
2. Prevent bacterial infections

Question 15

During an infection, lactoferrin is secreted by liver

Answer 15

• Binds iron in body and returns it to the liver where it is stored as ferritin
• Reduces availability of Fe to bacteria
• *competition between host and bacteria for Fe

Question 16

Competition between host and bacteria for Fe

Answer 16

• Free Fe is rare in the body
• Always associated with carrier proteins
• To obtain iron, bacteria produce siderophores-iron binding proteins
• To combat: animals withhold Fe from bacteria via lactoferrin
• *lactoferrin also possess direct anti-microbial and anti-inflammatory properties

Question 17

Iron overload is rare in animals: what might be seen?

Answer 17

• Anorexia
• Weight loss
• Decreases serum albumin
• Hepatic dysfunction
• Hemosiderosis

Question 18

What is hemochromatosis?

Answer 18

• Genetic disease in humans
• *Iron is over-absorbed from diet
  o Joint pain
  o Liver disease
  o Heart abnormalities
  o Abnormal pigmentation of skin (gray or bronze)
• *treatment=bleeding

Question 19

Where do you get iron in the diet?

Answer 19

• *blood meal
• Oilseeds and pulses=higher
• Forage=unavailable
• *animal source is highly available
• MILK is not a great source in iron

Question 20

Iodine

Answer 20

• Absorbed by SI by passive diffusion
• Highest concentration of iodine=in thyroid
• Sources in feed are highly variable and depend on soil iodine levels

Question 21

What are the functions of iodine?

Answer 21

• Component of T3 and T4 which control basal metabolism
  o Thermoregulation
  o Intermediary metabolism
  o Reproduction
  o Growth
  o Development

Question 22

Iodine deficiency

Answer 22

• Classical iodine deficiency=goiter
  o Still common in many areas
  o Iodized salt is used to prevent goiter in human and animal diets (brown salt)

Question 23

Brassicas and Goitrogens

Answer 23

• Cabbage, broccoli, mustard, canola
  o *these contain glucosinolates and myrosinase
• Myrosinase: converts glucosinolates to compounds with goitrogenic properties
• *goitrin prevents oxidation of iodine that blocks formation of T3 and T4
• *low glucosinolate varieties of rapeseed developed at U of S (called CANOLA)