Vitamins I and II Flashcards
Which vitamins are fat soluble?
KADE
Name 3 vitamins that are made endogenously
D, K, niacin
T/F- fat soluble vitamins are more easily stored long term than water soluble?
true
What two things are important for absorption of fat soluble vitamins?
bile, pancreatic enzymes
List fat malabsorption syndromes.
abetalipoproteinemia celiac disease cholestasis inflammatory bowel disease cystic fibrosis gastric bypass surgery Also: use of bile acids or mineral oil
T/F- vitamin A is a name given to a group of related compounds, some of which act as hormones
true (retinol, retinal, retinoic acid)
Name dietary sources of vit A
animal: liver, fish, eggs, milk
plant (carotenoids): 6-carotene, yellow/green vegetables
where is B-carotene converted to retinol?
intestine
Where are more than 90% of vitamin A reserves?
liver
Name 4 biological roles of vitamin A
- vision
- cell growth/differentiation (epithelial/keratin)
- metabolic effects of retinoids (bind to nuclear hormone receptors)
- Resistance to infection (mucocilliary/intestinal tract cell differentiation and retinoid immune effects)
Earliest manifestation of vitamin A deficiency?
reduced night vision
Five effects of chronic vitamin A deficiency?
- xeropthalmia (dry eye)
- xerosis conjuntivae
- bitot spots (keratin deposits)
- keratomalacia (drying/clouding of cornea)
- blindness
Name 3 therapeutic uses of retinoids
- severe acne
- psoriasis
- acute promyelocytic leukemia
T/F- retinoids aren’t teratogens
FAlse. They are! also restrictions on donating blood when taking these because of possibility of getting into a pregnant woman.
What is the most common fat-soluble vitamin poisoning in the united states?
Vit A
Symptoms of vitamin A poisoning?
- desquamation
- headache/dizziness/vomiting
- pseudotumor cerebri
Chronic excessive vitamin A results in bone resorption and fractures. T/F
True
T/F- vit D only affects a limited number of organ systems
False, it affects nearly every organ system
What receptor does it D act on?
vitamin D receptor (nuclear hormone receptor)
Where does vitamin D2 (ergocalciferol) come from?
-plants, fungi, invertebrates
where does vitamin D3 (cholecalciferol) come from?
endogenous vitamin D in animals
What is the main storage form of vitamin D and is best for assessing vitamin D nutritional status?
25-hydroxyvitamin D (calcidiol)
What is the most biologically active form of vitamin D?
1,25 dihydroxyvitamin D (calcitriol)
T/F- calcitriol controls expresssion of 200 genes, is expressed in the brain, prostate, breast, colon and other tissues, and some cancers can convert calcidiol to calcitriol
true
T/F- vitamin D cannot be used for psoriasis or auto-immune diseases
False, it can be
What role does sunlight play in endogenous synthesis of vit D?
UVB converts 7-dehydrocholesterol to previtamin D3, which rapidly converts to D3.
Not active if UV index less than 3
Can you get vit D toxicity from too much sun?
no, excess previtamin D3 destroyed by sunlight
What are some exogenous sources of vitamin D?
oily fish, eggs, milk, dietary supplements
Where is vitamin D metabolized to 25-OH?
liver
where is 25 OH converted to 1,25 dihydroxy vit D?
kidney
what regulates conversion to 1,25 dihydroxy vitamin D3?
PTH, serum Ca, phosphate
T/F- vitamin D increases absorption of intestinal Ca and Phosphorus as well as renal Ca absorption
true
What is a problem with renal failure regarding vit D?
decreased conversion to 1,25 dihydroxy vit d
T/F- vit d deficiency is rare
False, it is common and increases risk of fractures, osteomalacia, rickets etc.
Vitamin D deficiency is associated with what cancers?
colon, pancreas, breast, ovary, Hodgkins lymphoma
T/F- 1,25 dihydroxy is a potent immunomodulator
true. For example, monocytes/macrophages up regulate VDR in response to tuberculosis infection
T/F- increased 25-OH vit D is associated with lower multiple sclerosis risk
true
Name 7 causes of Vit D deficiency
Sunscreen, aging (reduced 7-dehydrocholesterol), skin damage (burns), poor diet (remember that human breast milk contains very low vitamin D!), liver failure (can’t make 25-OH), renal failure, heritable disorders
How do you treat vitamin D deficiency?
- 200 IU children and adults <50 yrs
- 1000 IU/day if no sun exposure
- 50,000 IU as a bolus injection
- sunlight/UV radiation
Should you check 1,25 dihydroxy vit D levels for nutritional status?
no
What are 3 debates for vitamin D in healthcare?
- payors not reimbursing vitamin D testing in many populations
- concerns of over aggressive supplementation
- where to set reference ranges
At UIHC, what age group gets most vitamin D testing?
around 60, more commonly females
What is the major form of vitamin E?
alpha-tocapherol
What are dietary sources of vitamin E?
vegetable oils, peanuts
What is a common reason for deficiency?
diet deficient in leafy green vegetables
What is the main biological function of vitamin E?
anti-oxidant (also thought to preserve neurological function)
Is vitamin E deficiency common or rare in U.S.?
rare
What conditions can lead to vitamin E deficiency?
cholestasis, pancreatitis, cystic fibrosis, abetalipoproteinemia
What are signs of vitamin E deficiency?
neurologic (ataxia, neuropathy), hemolytic anemia (infants)
Is vitamin E toxicity a common problem?
no, its rare
What are complications of vitamin E toxicity?
coagulopathy, decreased wound healing. infants given too much vit E have higher incidence of sepsis and necrotizing entercolitis
Where is vitamin K1 (phylloquinone) found?
plants! cabbage, cauliflower, spinach. also in pork, liver, soybeans, vegetable oils. Low amounts in breast milk
Where is vitamin K2 found or produced?
produced in intestinal tract by gram positive bacteria
Is k3 (synthetic) still used in the united states?
no
What lipid soluble vitamin does the body hold the shortest reserve of? How long is it?
vitamin K, 3 week reserve
Name 2 biological functions f vitamin K
- required for gamma-carboxylation of glutamate side chains of some clotting factors (II, VII, IX, X, C, S)
- modified glutamic acid residues (gamma-carboxyglutamic acid binds calcium, allowing cross-bridge with phospholipids
Symptom of vitamin K
deficiency?
usually hemorrhage (ecchymosis, epistaxis, intestinal bleeding)
What age group is at particularly high risk and routinely given vit K?
infants (intestinal flora not developed to make vitamin K2, breast milk low in vitamin K)
Warfarin blocks what enzyme?
VKOR (mutations in VKOR can cause resistance)
What is an overdose of warfarin treated with?
vitamin K and/or fresh frozen plasma (provides clotting factors)
T/F- vitamin K toxicity is rare but associated with hemolytic anemia in infants
true
T/F- cystic fibrosis is likely associated with combined deficiency of vitamins ADEK?
true
What would be an appropriate indication for 1,25 dihydroxy vitamin D plasma level test?
renal failure with persistent hypocalcemia
Is vitamin C synthesized endogenously in humans?
no
Name 3 biological functions of vitamin C
anti-oxidant, improves absorption of non-heme dietary iron, and involved in multiple biochemical pathways
(involved in hydroxylation of pro collagen to collagen)
Is vitamin C deficiency rare or common in USA?
rare (scurvy)
What populations are at risk for vitamin C deficiency?
elderly, those on restricted diets, alcoholics
Symptoms of scurvy?
- perifollicular hemorrhage
- coiled body hairs
- ecchymoses
- xerosis (dry skin)
- poor wound healing
- gum abnormalities
Problems with vitamin C toxicity?
high doses acidify urine and promote iron overload in pts with thalassemia and hematochromatosis. DOES NOT CAUSE KIDNEY STONES
What is another name for vitamin B1?
thiamine
Is B1 water soluble?
yes
What foods is B1 found in?
yeast, grains, peas, potatoes, vegetables
T/F- B1 is leached out of food after being washed or boiled
true
T/F- B1 is transported in plasma as thiamine and phosphorylated in tissue
true
What is the purpose of Thiamine triphosphate (TTP)?
involved in nerve conduction (Na+ channels)
What is the purpose of thiamine pyrophosphate (TPP)?
carbohydrate pathways, branched chain amino acids
Name the symptoms of thiamine deficiency in infants
dyspnea, cyanosis, diarrhea, vomiting, wasting
What populations is thiamine deficiency common in? What does this cause?
- Elderly and alcoholics
- Dry beriberi: poor appetite, fatigue, peripheral neuritis
- Wet beriberi: edema and cardiac failure
What populations is Wernicke Korsakoff syndrome common in?
alcohoilics, AIDS
-exacerbated by magnesium deficiency
Compare wernicke encephalopathy to korsakoff syndrome
- wernicke encephalopathy: confusion, ataxia, opthalmoplegia
- Korsakoff syndrome: short term memory loss, confabulation (spontaneous narration of events that never happened.
Is thiamine toxicity common?
No but it can cause headache, convulsions, cardiac arrhythmias, and neuromuscular collapse when it does happen
What is vitamin B2 known as?
riboflavin
What are the cofactor forms of B2 (riboflavin)?
flavin mononucleotide (FMN) and flavin adenine nucleotide (FAD)
What foods are high in B2?
milk, liver, eggs, vegetables
Is B2 stable to heat?
yes
Does B2 degrade in milk if exposed to light?
yes
What are the biological functions of riboflavin (B2)?
- cofactors for large group of flavoproteins
- flavoproteins funciton in redox rxns (respiratory enzymes, iron metabolism, pyridoxine metabolism, folate metabolism, xenobiotic detoxification)
What two factors put people at risk for riboflavin (B2) deficiency?
poverty and poor diet
What are symptoms of riboflavin deficiency?
angular stomatitis, glossitis, photophobia, blepharospasm, dermatological changes, neurological changes (behavior, neuropathy, EEG changes)
Is riboflavin toxicity common?
NO, very rare, little evidence for distinct overdose syndrome
What is vitamin B3 also known as?
niacin
B3 (niacin) is a derivative of what?
pyridine
B3 deficiency is associated with what?
poor diet
What are the active cofactor forms of B3?
NAD and NADP
Can NAD and NADP be made from anything beside B3?
yes, tryptophan
Name the 3 D’s associated with Niacin deficiency (pellagra)?
-diarrhea, dermatitis (+glossitis, stomatitis), dementia
T/F- carcinoid tumors can predispose to niacin deficiency due to accelerate tryptophan metabolism
true
T/F- gram doses of niacin used for lipid disorders can cause flushing, wheezing, headache, GI discomfort, liver toxicity
true (can premedicate with aspirin/NSAIDs to prevent these effects)
What enzymes should you monitor for someone on high dose niacin therapy?
liver enzymes
What is B6 also known as?
pyridoxine
What are dietary sources of B6?
meats, vegetables
What two liver enzymes is B6 important for synthesizing?
ALT/AST
T/F- B6 is needed for the conversion of tryptophan to serotonin or to niacin
true
Symptoms of vitamin B6 deficiency in infants?
-irritability, seizure, anemia, vomiting, ataxia, abdominal pain
Symptoms of B6 deficiency in adults? Predisposing factors?
- Sx: facial seborrhea, peripheral neuropathy
- Predisposing factors: celiac disease, ulcerative colitis, lactation, alcoholism
T/F- pyridoxine deficiency in pregnant women associated with poor birth outcomes?
true
What drugs antagonize pyridoxine?
isoniazid, corticosteroids, penicillamine
Symptoms of B6 toxicity?
RARE-tachypnea and neuropathy
Name 2 therapeutic uses of B6
- hyperemesis gravidarum (nausea and vomiting in pregnancy)
- seizure control in early childhood (only vitamin deficiency linked to seizures)
What is B12 also called?
cobalamin
Dietary sources of cobalamin?
meat (liver), dairy
T/F- B12 deficiency is rare in vegetarians
False. 2/3 of vegetarians have deficiency
What is pernicious anemia?
autoimmune disorder with gastric atrophy and decreased/absent intrinsic factor
Where does B12/IF absorption occur?
ileum
What is b12 carried in the plasma by?
transcobalamins
What 2 biochemical reactions require B12?
- conversion of methylTHF to TFH
- >secondarily converts homocysteine to methionine - methylmalonyl-CoA to Succinyl-CoA
How long to become deficient in B12?
2-4 years
Does B12 have low or high toxicity?
very low toxicity
Folic acid is vitamin precursor to what?
tetrahydrofolate
Source of folate in diet?
liver and green vegetables, breads and grains now supplemented
Are folates absorbed as mono or polyglutamates?
converted to monoglutamates in the gut and absorbed in the ileum then converted to polyglutamates in tissues
Functional activation of folic acid requires what?
B12
Examples of folate antagonists?
trimethoprim and methotrexate
What do folate antagonists inhibit?
TFH reductase
Who should be supplemented with folate?
pregnant women, premature infants, and patients with chronic hemolysis
T/F- cyanocobalamin (B12) can only be given separately as intramuscular injection
true
What is a caution about multivitamins?
possibility of vitamin A toxicity and on patients with warfarin (vitamin K reduces effectiveness)
Most common vitamin deficiency in a strict vegetarian who doesn’t eat eggs?
B12
