vitamins/nutrition Flashcards
fat soluble vitamins
DEAK.
absorption depends on gut (ILEUM) and pancreas.
why is toxicity with fat soluble vitamins MORE COMMON than for water-soluble vitamins?
DEAK accumulate in fat
what causes fat soluble vitamin deficiencies?
- malabsorption syndromes with steatorrhea (CF, sprue).
2. mineral oil intake.
water soluble vitamins
B1 thiamine. B2 riboflavin. B3 niacin. B5 pantothenic acid. B6 pyridoxine. B12 cobalamin. C ascorbic acid. biotin. folate.
all water soluble vitamins wash out EASILY from body EXCEPT??
B12 and folate - stored in LIVER
B complex deficiencies often result in?
dermatitis.
glossitis.
diarrhea.
vitamin A (retinol)
- antioxidant.
- visual pigments (retinal).
- normal differentiation of epith cells into specialized tissue (pancreatic. mucus-secreting.)
- prevent squamous metaplasia.
vitamin A is used as TX for…
- measles.
2. AML, subtype M3.
vitamin A found in…
liver and leafy vegetables (carotene)
vitamin A deficiency
- night blindness (nyctalopia).
- dry skin.
- infx (esp measles).
vitamin A excess
- arthralgias.
- fatigue.
- headache.
- skin changes
- alopecia.
- sore throat.
- teratogenic.
vitamin A teratogenicity
cleft palate, cardiac abn.
preg test must be done before isotretinoin prescribed for severe acne.
vitamin B1 (thiamine)
part of thiamine pyrophosphate (TPP), a cofactor for decarboxylation rxns:
- Pyruvate dehydrogenase (glycolysis).
- Alpha-ketoglutarate dehydrogenase (TCA).
- Transketolase (HMP).
- branched chain AA dehydrogenase.
“A, T, P needed for ATP synth”
vitamin B1 deficiency
impaired glucose breakdown = ATP depletion.
- Wernicke-Korsakoff syndrome.
- beriberi.
what can worsen vitamin B1 deficiency?
glucose infusion (already ATP-depleted)
which organs are affected first by vitamin B1 deficiency
highly aerobic tissues - BRAIN, HEART
vitamin B1 deficiency is seen in?
- malnutrition.
2. alcoholism (second to malnutrition and malabsorption).
Wernicke-Korsakoff
TRIAD:
- confusion.
- ophthalmoplegia.
- ataxia.
+ confabulation, personality change, memory loss (permanent)
brain damage in Wernicke-Korsakoff
medial dorsal nucleus of thalamus
and mammillary bodies
dry beriberi
polyneuritis.
symmetrical muscle wasting.
wet beriberi
high-output cardiac failure (dilated CM).
edema.
neuropathy.
vitamin B2 (riboflavin)
cofactor in oxidation and reduction (FAD, FMN)
vitamin B2: FAD
electron carrier/donor involved in electron transport chain
vitamin B2: FMN
part of complex I in ETC
vitamin B2 deficiency
Cheilosis: inflamm of lips, scaling and fissures at corners of mouth.
Corneal vascularization.
“2 C’s of B2”
vitamin B3 (niacin)
constituent of NAD+ and NADP+ used in redox runs.
what is vitamin B3 derived from?
tryptophan
what does synth of vitamin B3 require?
vitamin B6
vitamin B3 deficiency
glossitis
SEVERE vitamin B3 deficiency
PELLAGRA:
Diarrhea,
Dermatitis,
Dementia
causes of pellagra
- Hartnup disease: decreased tryptophan absorp.
- malignant carcinoid syndrome: increased tryptophan metab.
- isoniazid tx: decrease vit B6.
vitamin B3 excess
facial flushing - due to pharmacologic doses for tx of hyperlipidemia
vitamin B5 (pantothenate)
essential component of:
- coenzyme A (cofactor for acyl transfers)
- fatty acid synthase
vitamin B5 deficiency
dermatitis. enteritis. alopecia. adrenal insuff. burning feet syndrome.
vitamin B6 (pyridoxine)
converted to pyridoxal phosphate: cofactor in transamination, decarboxylation, glycogen phosphorylase
vitamin B6 needed in synth of ….?
cystathione. heme. niacin. GABA. histamine.
vitamin B6 deficiency
convulsions.
hyperirritability.
peripheral neuropathy.
sideroblastic anemias*
what drugs can induce vitamin B6 deficiency?
isoniazid (B6 analog).
oral contraceptives.
pathogenesis of sideroblastic anemia in vitamin B6 deficiency
due to impaired Hb synth and Fe excess
vitamin B12 (cobalamin)
cofactor for:
1. homocysteine methyltransferase: transfer CH3 group as methylcobalamin.
- methylmalonyl-CoA mutase.
source of vitamin B12
animal products.
can be synthesized only by microorganisms.
vitamin B12 deficiency
macrocytic megaloblastic anemia.
hypersegmented PMNs.
neuro sx: paresthesias. subacute combined degeneration. *due to abn myelin
prolonged vitamin B12 deficiency leads to…?
IRREVERSIBLE nervous system damage
why does vitamin B12 deficiency takes YEARS to develop?
very large reserve pool stored in LIVER
causes of vitamin B12 def
- malabsorption: sprue, enteritis, pancreatic insuff, Diphyllobothrium latum.
- lack of intrinsic factor: pernicious anemia, gastric bypass.
- absence of terminal ileum: Crohn’s dz.
etiology of vitamin B12 def determined with..?
Schilling test
normal urinary (radiolabeled) B12 excretion in Schilling test indicates?
dietary deficiency
low excretion in Schilling test needs to be followed with?
repeat test with addition of intrinsic factor- if excretion is then corrected, deficiency is due to pernicious anema/atrophic gastritis.
if excretion still low- deficiency due to malabsorption.
where is B12 normally absorbed?
terminal ileum (binds IF in duodenum)
TX of B12 def
parental B12
*oral only effective in dietary def
folic acid
converted to THF, a coenzyme for 1-carbon transfer/methylation rxns.
important for synth of nitrogenous bases in DNA and RNA.
source of folic acid
green leaves
folic acid storage
small reserve pool stored in liver.
lasts 3-4 months beyond dietary def.
folic acid def
macrocytic megaloblastic anemia.
NO NEURO SX.
what is the most common vit deficiency in US?
folic acid
folic acid def common in what conditions?
alcoholism.
pregnancy.
supplemental folic acid in preg reduces…?
neural tube defects
drugs that cause folic acid def
phenytoin.
sulfonamide.
MTX.
etc.
what drugs inhibit conversion of folic acid to THF?
via inhibition of DHFR:
trimethoprim.
MTX.
pyrimethamine.
S-adenosyl-methionine (SAM)
formed from ATP + methionine.
transfers methyl groups.
regeneration of SAM is dependent on ?
vit B12 and folate - (regeneration of methionine)
SAM is required for?
conversion of NE to epinephrine
biotin
cofactor for carboxylation enzymes, which add 1-carbon group.
- pyruvate carboxylase.
- acetyl CoA carboxylase.
- propionyl CoA carboxylase.
- beta-methylcrotonyl CoA carboxylase.
biotin deficiency
relatively rare.
caused by Abx or excessive ingestion of raw egg whites.
dermatitis.
enteritis.
alopecia.
vitamin C (ascorbic acid)
- antioxidant.
- keeps iron in Fe2+ reduced state for absorption.
- hydroxylation of proline and lysine in collagen synth.
- dopamine beta-hydroxylase (dopamine to NE).
source of vitamin C
fruits and vegetables
vitamin C def
SCURVY: swollen gums. bruising. hemarthrosis. anemia. poor wound healing.
weakened imm response.
pathogenesis of scurvy
vit C def causes collagen synth defect
vitamin C excess
nausea. vomiting. diarrhea. fatigue. sleep problems.
vitamin C excess increases risk of iron toxicity in…?
predisposed individuals - transfusions, hereditary hemochromatosis
vitamin D2
ergocalciferol: ingested from plants
vitamin D3
cholecalciferol: consumed in milk, formed in sun-exposed skin
storage form of vitamin D
25-OH D3
active form of vitamin D
1,25-(OH2) D3 aka calcitriol
vitamin D is different from all other vitamins because…?
it can be made in human body
vitamin D function
- increase intestinal absorption of calcium and phosphate.
2. increase bone mineralization.
vitamin D def
kids: rickets (bending bones).
adults: osteomalacia (soft bones).
hypocalcemic tetany.
skeletal deformities.
bone pain.
muscle weakness.
vitamin D in breast milk
not adequate.
supplement in dark-skinned pts.
vitamin D excess
hypercalcemia.
hypercalciuria.
loss of appetite.
stupor.
what systemic disease is assoc with vitamin D excess?
sarcoidosis:
increased activation of vitamin D by epithelioid macrophages.
*seen in other granulomatous diseases too
vitamin E (tocopherols)
ANTIOXIDANT: protects Erythrocytes and membranes from free radical damage.
*RBCs and neurons
vitamin E def
increase RBC fragility - hemolytic anemia.
muscle weakness.
dorsal (posterior) column
and spinocerebellar tract demyelination
(aka subacute combined degeneration of SC).
SX: loss of proprioception, vibration. ataxia.
vitamin K
catalyzes gamma-carboxylation of glutamic acid residues on certain proteins concerned with BLOOD CLOTTING
vitamin K synthesized by?
intestinal flora
which clotting factors require vitamin K?
II, VII, IX, X.
proteins C and S.
what drug is a vitamin K antagonist?
warfarin
vitamin K def
neonatal hemorrhage with increased PT and increased PTT but NORMAL bleeding time.
SX: tendency to bleed.
skin, umbilicus, viscera, brain.
why are neonates prone to vitamin K def?
sterile intestines - unable to synthesize vitamin K
causes of vitamin K def in adults
prolonged use of broad-spectrum Abx.
malabsorption syndromes.
generalized liver disease.
where do neonates get vitamin K when born?
injection given at birth to prevent hemorrhage.
vitamin K not present in breast milk.
zinc
essential for activity of 100+ enzymes.
part of zinc fingers (transcription factor motif).
zinc def
delayed wound healing. hypogonadism. decreased adult hair. anosmia (lack of smell). dysgeusia (abn taste).
zinc def may predispose to ?
alcoholic cirrhosis
which vitamins are antioxidants?
A, C, E
