Exam #1: Water Soluble Vitamins

Question 1

What are the two major types of vitamins?

Answer 1

Water-soluble

Fat soluble

Question 2

What form of vitamins has a higher risk for toxicity? Why?

Answer 2

• Fat soluble b/c they are stored unlike water-soluble vitamins

**Note that water soluble vitamins wash-out from the body EXCEPT B12 & Folate, which are stored in the liver

Question 3

What is the DRI?

Answer 3

Dietary Reference Intake

- Set of reference values to plan and assess nutrient intake of healthy people

Question 4

What is the RDA?

Answer 4

Recommended Dietary Allowance

- Average daily level of intake for nearly all healthy people

Question 5

What is the AI?

Answer 5

Adequate Intake

- Established when insufficient evidence for RDA- assumed to ensure nutritional adequacy

Question 6

What is the EAR?

Answer 6

Estimated Average Requirement

- Expected to satisfy the needs of 50% of people in that age group

Question 7

How does the DRI vary with age and gender?

Answer 7

General increase with age & gender

Question 8

What is the TUL?

Answer 8

Tolerable Upper Limit

- Max daily intake unlikely to have harmful consequences

Question 9

What are the two major classes of water soluble vitamins?

Answer 9

Vitamin C

Vitamin B

Question 10

List the major functions of Vitamin C.

Answer 10

1) Antioxidant
2) Reduces iron AND necessary for absorption of non-heme iron
3) Hydroxylates proline and lysine= COLLAGEN SYNTHESIS
4) Dopamine Beta-Hydroxylase

Question 11

What is unique about Vitamin C?

Answer 11

Not a coenzyme

Question 12

How are B Vitamins involved in energy production?

Answer 12

• Involved in metabolism of energy-yielding nutrients
• Coenzymes

**NOT involved in rate-limiting steps

Question 13

List the hematopoietic B Vitamins.

Answer 13

• B6, PLP
• B9, Folic acid
• B12, Cobalamin

Question 14

What is the function of Vitamin B6 (PLP)?

Answer 14

1) Transamination
2) Decarboxylation
3) Cystathione Synthase
4) Heme synthesis
5) Niacin synthesis from Tryptophan (W)

Question 15

What is the function of B1 (Thamine)?

Answer 15

Thiamine is a cofactor for dehydrogenase enzyme reactions that produce ATP:

1) Branched chain amino acid dehydrogenase
2) Pyruvate dehydrogenase
3) A-ketoglutarate dehydrogenase
4) Transketolase

Deficiency leads to severe ATP depletion that affects aerobic tissues first, i.e. brain and heart.
- Worsened by glucose infusion.

Question 16

What is the function of folic acid?

Answer 16

• Folate is converted to THF, a coenzyme for 1-C transfer/methylation rxn

Important for DNA & RNA synthesis

Question 17

What are the four general functions of B12? What are the two specific enzymes it is a cofactor for?

Answer 17

1) DNA synthesis
2) FA synthesis
3) Energy production
4) Myelin sheath production

• Cofactor for methionine synthase (homocystine to methionine) and methylmalonyl-CoA mutase (methylmalonyl CoA to succinyl-CoA

Question 18

What is the function of Niacin?

Answer 18

• Niacin is a constituent of NAD+ and NADP+ that are used in redox reactions
• Therapeutically, Niacin is used to treat dyslipidemia

Question 19

What is the function of the Folate/B12 one carbon metabolism pathway?

Answer 19

Generally, Folate and B12 generate and transfer one carbon groups necessary for the methylation of DNA

Specifically, B12:

• Regenerates THF from MTHF
• Methyl-B12 donates it’s methyl group to homocysteine, forming methionine
• Is important for odd chain FA synthesis (crucial to myelin production)

Question 20

What does a B12 deficiency lead to?

Answer 20

1) Macrocytic megaloblastic anemia
2) Hypersegmented neutrophils
3) Neurologic deficits
- Posterior columns
- Lateral corticospinal tracts
- Spinocerebellar tracts
4) “Methyl trap” in methylation pathway i.e. methyl trapped as MTHF

Question 21

What does a folate deficiency result in?

Answer 21

• Macrocytic megaloblastic anemia

- Neural tube defects

Question 22

Draw the Folate/ B12 methylation pathway.

Answer 22

N/A

Question 23

List the important structural features of B12 (Cobalamin).

Answer 23

• Cobalt ion complexed in ring structure

- R group attaches to methyl group to yield “methylcobalamin”

Question 24

Where does B12 come from?

Answer 24

Animal sources ONLY

Question 25

Outline the six major steps of B12 metabolism.

Answer 25

1) Oral= R proteins needed for absorption 2) Gastric - Low pH releases B12 from dietary protein to bind R proteins - Parietal cells release intrinsic factor (IF) 3) Luminal= pancreatic proteases degrade R proteins so B12 can bind IF 4) Mucosal= B12-IF complex binds receptor in terminal ileum 5) Transport= transported in blood bound to “transcobalamin” 6) Excretion= - Excreted into bile - Most rebinds IF for recycling

Question 26

What are the causes of B12 deficiency?

Answer 26

1) Pernicious anemia 2) Gastrectomy/ bariatric surgery 3) Malabsorption syndrome 4) Celiac sprue 5) Enteritis 6) Chron's Disease 7) Diphylobothrium Latum

Question 27

What is the Schilling test? What is the purpose of this test?

Answer 27

Measures B12 & IF deficiency

Question 28

What is the difference between the presentation of folate and cobalamin deficiency?

Answer 28

B12 is associated with cognitive impairment and neurologic deficits

Question 29

What does folate deficiency in the 1st trimester lead to an increased risk of?

Answer 29

NTDs

Question 30

What is Dry Beriberi? What are the symptoms?

Answer 30

Thiamine deficiency typically in older adults from low carb & energy intake that is characterized by: 1) Muscle wasting 2) Symmetric polyneuritis w/ - Wrist/ foot drop - Loss of tendon reflexes - Paresthesias

Question 31

What is Wet Beriberi? What are the symptoms?

Answer 31

Thamine deficiency associated with higher carb intake & physical activity that is characterized by: - Dilated cardiomyopathy - Edema

Question 32

What is Infantile Beriberi

Answer 32

Thiamine deficiency in infant from breastfeeding mother with low thiamine intake that causes: - Dyspnea - Cyanosis - Heart failure

Question 33

What is Wernicke - Korsakoff Syndrome?

Answer 33

Thiamine (B1) deficiency associated with alcoholism. Wernike= 1) Confusion 2) Opthalmoplegia 3) Ataxia Korsakoff= 1) Confabulation 2) Personality change 3) Memory loss BOTH have damage to the medial dorsal nucleus and mammillary bodies of the hypothalamus

Question 34

What patient populations are at risk for scurvy today?

Answer 34

Surgical and burn patients

Question 35

What is Scurvy? What are the four H's of scurvy?

Answer 35

Scurvy is a Vitamin C deficiency that leads to: 1) Bleeding/ swollen gums 2) Bruising 3) Impaired wound healing 4) Hemarthrosis 5) Perifollicular hemorrhages The so called, "4-H's of Scurvy" include: 1) Hemorrhage 2) Hyperkeratosis 3) Hypochondriasis 4) Hematologic abnormalities

Question 36

What are the two major causes of Biotin deficiency?

Answer 36

1) Raw egg ingestion 2) Chronic antibiotic therapy *Remember “AVIDin in egg whites AVIDly binds biotin”

Question 37

What are the symptoms of biotin deficiency?

Answer 37

- Dermatitis - Alopecia - Enteritis

Question 38

A deficiency in what vitamin leads to "Burning Feet Syndrome?"

Answer 38

Pantothenic Acid (B5)

Question 39

What does Riboflavin deficiency mimic?

Answer 39

Pellagra *****Also remember, deficiency= 2x C’s of B2 o Cheilosis o Corneal vascularization

Question 40

What are the three common causes of Niacin deficiency?

Answer 40

o Hartnup Disease (decreased tryptophan absorption) o Malignant carcinoid syndrome (increased tryptophan metabolism) o Isoniazid admin. (decreased B6) *****Recall, Niacin is derived from tryptophan & requires B2 & B6 for synthesis

Question 41

What disease is caused by a Niacin deficiency?

Answer 41

Pellagra

Question 42

What are the four D's of Pellagra?

Answer 42

Dermatitis Dementia Diarrhea Death

Question 43

What are the two common causes of B6 deficiency?

Answer 43

1) Isoniazid | 2) Oral contraceptives

Question 44

What are the symptoms of B6 deficiency?

Answer 44

1) Seizures 2) Hyper-irritability 3) Peripheral neuropathy 4) Sideroblastic anemia