Flashcards in Exam #1: Water Soluble Vitamins Deck (44):
What are the two major types of vitamins?
What form of vitamins has a higher risk for toxicity? Why?
- 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
What is the DRI?
Dietary Reference Intake
- Set of reference values to plan and assess nutrient intake of healthy people
What is the RDA?
Recommended Dietary Allowance
- Average daily level of intake for nearly all healthy people
What is the AI?
- Established when insufficient evidence for RDA- assumed to ensure nutritional adequacy
What is the EAR?
Estimated Average Requirement
- Expected to satisfy the needs of 50% of people in that age group
How does the DRI vary with age and gender?
General increase with age & gender
What is the TUL?
Tolerable Upper Limit
- Max daily intake unlikely to have harmful consequences
What are the two major classes of water soluble vitamins?
List the major functions of Vitamin C.
2) Reduces iron AND necessary for absorption of non-heme iron
3) Hydroxylates proline and lysine= COLLAGEN SYNTHESIS
4) Dopamine Beta-Hydroxylase
What is unique about Vitamin C?
Not a coenzyme
How are B Vitamins involved in energy production?
- Involved in metabolism of energy-yielding nutrients
****NOT involved in rate-limiting steps
List the hematopoietic B Vitamins.
- B6, PLP
- B9, Folic acid
- B12, Cobalamin
What is the function of Vitamin B6 (PLP)?
3) Cystathione Synthase
4) Heme synthesis
5) Niacin synthesis from Tryptophan (W)
What is the function of B1 (Thamine)?
Thiamine is a cofactor for dehydrogenase enzyme reactions that produce ATP:
1) Branched chain amino acid dehydrogenase
2) Pyruvate dehydrogenase
3) A-ketoglutarate dehydrogenase
Deficiency leads to severe ATP depletion that affects aerobic tissues first, i.e. brain and heart.
- Worsened by glucose infusion.
What is the function of folic acid?
- Folate is converted to THF, a coenzyme for 1-C transfer/methylation rxn
*****Important for DNA & RNA synthesis*****
What are the four general functions of B12? What are the two specific enzymes it is a cofactor for?
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
What is the function of Niacin?
- Niacin is a constituent of NAD+ and NADP+ that are used in redox reactions
- Therapeutically, Niacin is used to treat dyslipidemia
What is the function of the Folate/B12 one carbon metabolism pathway?
Generally, Folate and B12 generate and transfer one carbon groups necessary for the methylation of DNA
- 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)
What does a B12 deficiency lead to?
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
What does a folate deficiency result in?
- Macrocytic megaloblastic anemia
- Neural tube defects
Draw the Folate/ B12 methylation pathway.
List the important structural features of B12 (Cobalamin).
- Cobalt ion complexed in ring structure
- R group attaches to methyl group to yield "methylcobalamin"
Where does B12 come from?
Animal sources ONLY
Outline the six major steps of B12 metabolism.
1) Oral= R proteins needed for absorption
- 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”
- Excreted into bile
- Most rebinds IF for recycling
What are the causes of B12 deficiency?
1) Pernicious anemia
2) Gastrectomy/ bariatric surgery
3) Malabsorption syndrome
4) Celiac sprue
6) Chron's Disease
7) Diphylobothrium Latum
What is the Schilling test? What is the purpose of this test?
Measures B12 & IF deficiency
What is the difference between the presentation of folate and cobalamin deficiency?
B12 is associated with cognitive impairment and neurologic deficits
What does folate deficiency in the 1st trimester lead to an increased risk of?
What is Dry Beriberi? What are the symptoms?
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
What is Wet Beriberi? What are the symptoms?
Thamine deficiency associated with higher carb intake & physical activity that is characterized by:
- Dilated cardiomyopathy
What is Infantile Beriberi
Thiamine deficiency in infant from breastfeeding mother with low thiamine intake that causes:
- Heart failure
What is Wernicke - Korsakoff Syndrome?
Thiamine (B1) deficiency associated with alcoholism.
2) Personality change
3) Memory loss
BOTH have damage to the medial dorsal nucleus and mammillary bodies of the hypothalamus
What patient populations are at risk for scurvy today?
Surgical and burn patients
What is Scurvy? What are the four H's of scurvy?
Scurvy is a Vitamin C deficiency that leads to:
1) Bleeding/ swollen gums
3) Impaired wound healing
5) Perifollicular hemorrhages
The so called, "4-H's of Scurvy" include:
4) Hematologic abnormalities
What are the two major causes of Biotin deficiency?
1) Raw egg ingestion
2) Chronic antibiotic therapy
*Remember “AVIDin in egg whites AVIDly binds biotin”
What are the symptoms of biotin deficiency?
A deficiency in what vitamin leads to "Burning Feet Syndrome?"
Pantothenic Acid (B5)
What does Riboflavin deficiency mimic?
*****Also remember, deficiency= 2x C’s of B2
o Corneal vascularization
What are the three common causes of Niacin deficiency?
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
What disease is caused by a Niacin deficiency?
What are the four D's of Pellagra?
What are the two common causes of B6 deficiency?
2) Oral contraceptives