Vitamins Flashcards
Vitamin A function
Antioxidant
Part of visual pigment retinal
Differentiation of epithelial cells (pancreatic cc or mucus-secreting cc)
Prevents squamous metaplasia
Treat measles and acute promyelocytic leukemia
Topical tx for wrinkles and acne
Found in liver and leafy veggies
PO isotretinoin for severe cystic acne
ATRA for APML
Vitamin A deficiency
Night blindness (nyctalopia); dry, scaly skin (xerosis cutis), corneal degeneration (keratomalacia), bitot spots on conjunctiva, immunosuppression
Vitamin A toxicity
Acute: nausea/vomiting, vertigo, blurred vision
Chronic: alopecia, dry skin, hepatotoxicity and enlargement, arthralgias, pseudotumor cerebri
Teratogen: cleft palate/ cardiac abnormalities; required pregnancy test before isotretinoin Rx
Vitamin B1 (thiamine) function
A part of thiamine pyrophosphate (TPP), a cofactor for:
Pyruvate dehydrogenase (links glycolysis to TCA cycle)
alpha-ketoglutarate dehydrogenase (TCA cycle)
Transketolase (HMP shunt)
Branch-chain ketoacid dehydrogenase
Vitamin B1 (thiamine) deficiency
Impaired glucose breakdown, low ATP worsened by glucose infusion, aerobic tissue affected first
In alcoholic patients gives thiamine before dextrose to stop precipitating Wernicke’s encephalophathy
Dg: increased transketolase activity in RBCs post B1 administration
Vitamin B1 (thiamine) diseases
Wernicke-Korsakoff syndrome: confusion, ophthalmoplegia, ataxia with confabulation, personality changes, damage to medial dorsal nucleus of thalamus, mammillary bodies
Dry beriberi- polyneuritis and symmetrical muscle wasting
Wet beriberi- HFpEF (DCM), edema
Vitamin B2 (riboflavin) function
Part of flavins (FAD and FMN) cofactors in redox reactions (eg succinate dehydrogenase in TCA cycle)
Vitamin B2 (riboflavin) deficiency
Cheilosis (inflammation of lips, scaling and fissures at corners of mouth), corneal vascularization
Vitamin B3 (niacin) function
Part of NAD+, NADP+ (redox), derived from tryptophan and synthesis requires B2 and B6
Treats dyslipidemia: lowers VLDL and raises HDL
Vitamin B3 (niacin) deficiency
Glossitis
Severe leads to pellagra (can also be caused by Hartnup disease, malignant carcinoid sy (increased tryptophan metabolism) and isoniazid (decreased B6))
Pellagra: diarrhea, dementia, dermatitis (dermatomal), hyperpigmentation of exposed skin
Vitamin B3 (niacin) deficiency- Hartnup disease
AR deficiency of neutral amino acid transporters in PCT and on enterocytes (neutral aminoaciduria) so less tryptophan for conversion to niacin
Tx: high protein diet, and nicotinic acid
Vitamin B3 (niacin) excess
Facial flushing (PGs) avoid by taking ASA with niacin, hyperglycemia, hyperuricemia
Vitamin B5 (pantothenic acid) function
Essential for CoA (acyl transfers) and fatty acid synthase
Vitamin B5 (pantothenic acid) deficiency
Dermatitis, enteritis, alopecia, adrenal insuff.
Vitamin B6 (pyridoxine) function
Converted to pyridoxal phosphate (PLP) cofactor in transamination (ALT and AST), decarboxylaton, glycogen phosphorylase
Needed to make: cystathionine, heme, niacin, histamine, NTs (serotonin, epi, norepi, DA and GABA)
Vitamin B6 (pyridoxine) deficiency
Convulsions, irritability, peripheral neuropathy (inducible by iNH and OCPs), sideroblasitic anemia due to impaired Hgb synth and iron excess
Vitamin B7 (biotin) function
Cofactor for carboxylation (add 1C) Pyruvate carboxylase (pyruvate to oxaloacetate) AcetylCoA carboxylase (acetylCoA to malonyl CoA) PropionylCoA carboxylase (PropionylCoA to methylmalonylCoA)
Avidin in eggwhites can bind biotin and cause deficiency
Vitamin B7 (biotin) deficiency
Dermatitis, alopecia, enteritis
Caused by Abx or eggwhites
Vitamin B9 (folate) function
Converted to THF (coenzyme for 1-carbon transfer/methylation reactions)
Synthesis of nitrogenous vases for DNA and RNA
Found in leafy green veggies, absorbed in jejunum, stored in liver
Vitamin B9 (folate) deficiency
Macrocytic megaloblastic anemia; hypersegmented PMNs, glossitis, NO NEURO
Labs: elevated homocysteine, nl methylmalonic acid
Assoc with alcoholism in pregnancy
Drugs can cause: phenytoin, sulfonamides, methotrexate
Supplement at least 1 mo prior to conception and during preg to prevent neural tube defects
Vitamin B12 (cobalamin) function
Cofactor for methionine synthase (transfers methyl group as methycobalamin) AND methylmalonyl-CoA mutase. Important in DNA synthesis.
Found in animal products, reserve for years in liver
Vitamin B12 (cobalamin) deficiency
Macrocytic megaloblastic anemia; hypersegmented PMNs, glossitis, paresthesias, subacute combined degeneration (dorsal columns, lateral corticospinal tracts and spinocerebellar tracts) due to abnl myelin; can lead to irrev. nerve damage
Causes: malabsorption (ileum) from sprue, enteritis, tape worm, lack of IF (bypass, pernicious anemia), lack of ileum (surgery, CD), veganism
Labs: elevated homocysteine, methylmalonic acid and 2˚ folate deficiency
Vitamin C (ascorbic acid) function
Antioxidant; facilitates Fe absorption by reducing to Fe2+; necessary for hydroxylation of pro and lys residues in preprocollagen; necessary for dopamine-beta-hydroxylase which converts DA to NE
Found in fruits and veggies
Ancillary tx for methemoglobinemia for reducing Fe to Fe2+
Vitamin C (ascorbic acid) deficiency
Scurvy- swollen gums, bruising, petechiae, hemarthrosis, anemia, poor wound healing, perifollicular and subperiosteal hemorrhages, corckscrew hair
Weakened immune response
Vitamin C (ascorbic acid) excess
Nausea, vomiting, diarrhea, fatigue, Ca oxalate stones, increased risk of iron tox. in transfused or ppl with hemochromatosis
Vitamin D forms
D2- ergocalciferol- ingested from plants
D3- cholecalciferol- consumed in milk, formed in sun exposed stratum basale
25-OH D3 - storage form
1,25-(OH)2D3 - calcitriol (active form)
Vitamin D function
Intestinal absorption of Ca and phosphate, increased bone mineralization at low levels, bone resorption at high levels
Vitamin D deficiency
Rickets in kids (varum bow legs); osteomalacia in adults (bone pain and muscle weakness), hypocalcemic tetany; breastfed infants need oral vit D. Deficiency is exacerbated by sun exposure, pigmented skin, prematurity
Vitamin D excess
Hypercalcemia, hypercalciuria, loss of appetite, stupor
Seen in granulomatous disease (increased D activation by epithelioid histocytes)
Vitamin E (tocopherol/tocotrienol) function
Antioxidant- protects RBC and membranes from free radical damage
HD supplementation may alter vitamin K metabolism to enhance warfarin anticoagulation
Vitamin E (tocopherol/tocotrienol) deficiency
Hemolytic anemia, acanthoytosis, muscle weakness, posterior column and spinocerebellar tract demyelination
May look like B12 deficiency; without megaloblastic anemia or hypersegmented neutrophils or methylmalonic acid
Vitamin K (phytomenadione, phylloquinone, phytonadione) function
Activated by epoxide reductase to reduced form which is a cofactor for gamma-carboxylation of glutamic acid residues on factors II, VII, IX and X + proteins C and S
Found in plants
Warfarin inhibits K-dep synth of above factors
Vitamin K (phytomenadione, phylloquinone, phytonadione) deficiency
Neonatal hemorrhage with elevated PT and aPTT; nl bleeding time, because can’t synth K due to sterile intestines; also post-prolonged Abx
Not in breast milk, give vit. K injection at birth
Zinc function
essential for many enzymes especially transcription factors
Zink deficiency
Delayed would healing, hypogonadism, lose of adult hair, dysgeusia, anosmia, acrodermatits enteropathica; predispose to alcoholic cirrhosis
