Niacin (B3)

Question 1

Tryptophan

Answer 1

60 mg tryptophan = 1 mg niacin

Niacin equivalent (NE)

Creates NAD+ in liver

Question 2

Excretion

Answer 2

NMN (n methyl nicotinamide)

Liver catalyzes the hydrolysis of nicotinamide with glycohydrolase.

Question 3

NAD

Answer 3

Oxidation rxns

Question 4

NADPH

Answer 4

Reduction rxns

Question 5

Deficiency: pellagra

Answer 5

3 D’s: dermatitis, diarrhea, dementia, (death)

Can be caused by deficiency in B6, riboflavin, and iron.

Caused by poor tryptophan diet.
Bound niacin not available (corn). Lime treatment.
Malabsorption, alcoholism, cancer drugs, TB.

Question 6

RDA

Answer 6

16 NE men
14 NE women

1 NE = 1 mg niacin/ 60 mg tryptophan

Question 7

Assessment

Answer 7

Urinary excretion of niacin metabolite NMN
>1 mg/d desirable

Plasma not good indicator b/c concentrations of niacin are low in healthy individuals who are assessed.

Question 8

Functions:
Electron transport (NAD)
Biosynthesis pathways (NADPH)

Answer 8

NAD: glycolysis, oxidative decarboxylation pyruvate, oxidation of acetyl CoA, beta oxidation

NADPH: fatty acid synthesis, regenerates glutathione and vitamin C, folic acid metabolism

Question 9

Niacin and Vitamin C

Answer 9

Reduces glutathione
Glutathione recycles vitamin C
Vitamin c regenerates/ reduces vitamin E

Question 10

UL 35 mg

Answer 10

Vasodilation due to increased histamine

Question 11

Megadosing

Answer 11

6 g nicotinic acid NOT nicotinamide to treat hypercholsterolemia

Low LDL
High HDL

Question 12

Sources

Answer 12

Meats especially chicken and tuna.
Fortified cereal.
Milk products.

100% absorption up to 3-4 g dose

Question 13

Pregnancy

Answer 13

Trp dioxygenase enzyme activity increases.
Prevents fetus for being rejected.

Drives immunological tolerance of fetus.