Vitamins Flashcards
Fat soluble vitamins
Vitamins A, D, E, K
Water Soluble Vitamins
Vitamins C, B1, B2, B6, B12, folate, biotin, pantothenic acid
niacin
Vitamin A function
fat soluble vitamin
binds to cell nuclear receptors
provitamin A (carotene) - structure equivalent of 2 vitamin A molecules
processing of Vitamin A
Beta-carotene into retinal & then to retinol (active form) & retinoic acid
transport for Vitamin A
retinal binding protein
active form of vitamin A
retinol (OH group on the end)
toxic level of vitamin A
anything over 100 ug/dl
importance of vitamin A
growth, reproduction, immune system
cell differentiation - maintains epithelial integrity
vision- part of rhodopsin
Vitamin A role in vision
retinol is oxidized in rods of eye retina to retinal
the complexed w/ opsin to form Rhodopsin
sight in dim light
Vitamin A deficiency
lead to night-blindness- seen in malabsorption, liver impairment, premature infant loss of hair joint pain headaches drowsiness vomiting
Hypervitaminosis A
vitamin A toxicity > 140 ug/dl in plasma
measured by HPLC
Vitamin E
(alpha-tocopherol); anti-oxidant - primary defense against oxidation of unsaturated lipids & cells
Vitamin E metabolism
40% absorbed from GI, attaches to chylomicrons for transport to liver
then transported via VLDL to cells
excreted through feces
deficiency of vitamin E
shows hemolytic anemia
can see in premature infants, fat malabsorption in adults
measured by HPLC
Vitamin K function
(napthoquinone); essential for coagulation factors
Vitamin K dependent coagulation factors
II, VII, IX, X also protein C & S
source of vitamin K
50% diet & 50% gut bacteria
absorbed into body via bile salts
lack of vitamin K
leads to hemorrhagic crisis
usually related to GI malabsorption & antibiotics
testing for vitamin K
use Prothrombin time (PT) -extended time
liver disease will also show low coag proteins but may not be vit K related
vitamin K toxicity
usually not seen in adults
children with vit K supplement at birth can see increase in bilirbuin
supplements rich in vit K : garlic, gingko, & ginseing
Vitamin D function
1,25 DHCC facilitates calcium (& phosphorus) absorption
D2
ergocalciferol - not naturally occurring
D3
cholecalciferol
can make from sunshine on 7-dehydro-cholesterol
vitamin D absorption
absorb from gut; attaches to chylomicrons for transport to liver
stored in liver
excreted in bile
vitamin D stimulates
ca2+ absorption along w/ phosphorus from intestine
w/ PTH- increases mobilization of ca2+ from bone to circulation
has apoptotic effect - cancerous cells/ loses growth regulation
vitamin D deficiencies
children- ricketts
osteomalacia- softening of the bone
AED- hinder vit D absorption
any malabsorption condition or renal issue
vitamin D toxicity
children hyperparathryoidism hypophosphatemia pregnancy excess vitD leading to excess calcium deposits in heart & kidneys (damage can be irreversible)
laboratory testing for vitamin D
calcium testing - PTH, serum Ca2+, urine Ca2+
assay 25-OH-cholecalciferol or 25-OH vit D3 by immunassay or HPLC
vitamin B1 (thiamine)
used to make thiamine pyrophosphate TPP - important coenzyme
needed for decarboxylase subunits of dehydrogenase complexes
vitamin B1 metabolism
absorbed through GI
excreted through the kidney; out the urine
chronic deficiency of vitamin B1
beri beri -wet & dry
seen in underdeveloped countries & alcoholics
lab assays for vitamin B1
looks at RBC transketolase enzyme activity or ETK before & after thiamine pyrophosphate addition (TPP)
if see >25% increase in ETK after adding TPP, then patient is thiamine deficient
vitamin B2 (riboflavin)
used to make flavin mononucleotide or FMN & flavin adenine dinucleotide or FAD
coenzymes used in oxidation-reduction reactions (krebs cycle)
vitamin B2 absorption
absorbed from GI small intestine
stored for 5 months in healthy person
excreted through kidney
vitamin B2 toxicity
no known toxicity
vitamin B2 deficiency
seen in alcoholics, chronic diarrhea, malabsorption, drugs: phenothiazine, oral BCP, TCAs
redness & sores
lab assays for vitamin B2
when glutathione reductase activity is decreased by 40% this indicates riboflavin (b2) deficiency
vitamin B6 forms
pyridoxine (plant source)
pyridox-amine
pyridoxal (animal sources)
all get converted to PYRIDOXAL-5’-PHOSPHATE
vitamin b6 absorption
absorbed through the GI tract & excreted through the urine
vitamin b6 function
used for synthesis, catabolism, & interconversion of amino acids
reactions for metabolism of proteins, lipids, & CHOs
COENZYME FOR AST & ALT!!!
lab measure for vitamin b6
measures function changes to protein
often looks at homocysteine (!!) in blood & urine
vitamin b6 deficiency
usually not alone - other b complex vitamins also deficient uremic patients (elevated BUN), liver disease,malabsorption, malignancies, alcoholics associated w/ hyperhomocysteinemia
vitamin b6 associated anemia
see normo, micro
SIDEROBLASTIC ANEMIA
niacin source
made from tryptophan as well as dietary intake
hard to be deficient in niacin
niacin function
combination of nicotinic acid & nicotinamide ; both needed to make NAD & NADP
need these coenzymes for respiration, lipid metabolism, fatty acid metabolism, & glycolysis
lab measure of niacin
measure NAD & NADP (end products of niacin)
niacin absorption
absorbed via GI & small intestine
metabolized form out the urine
niacin deficiency
not usually seen
Pellagra (4Ds) & alcoholics
4Ds= diarrhea, dementia, dermatitis, death
niacin toxicity
very low, excess niacin leads to decreased lipids, increased flushing, & blood vessel vasodilation
Folic acid/folate function
necessary for 1-carbon transfers
increased folate needs in pregnancy - helps reduce neural tube defect
folic acid/folate absorption
closely linked to vit b12
folate absorbed in jejunum w/ intrinsic factor
excess excreted through kidney & out feces
large amount of folate made by colon bacteria & absorbed
folate deficiency
MEGALOBLASTIC ANEMIA
alcoholism, malabsorption, carcinoma, chronic hemodialysis, hemolytic & sideroblastic anemia
drugs: sulfasalazine, isoniazid, cycloserine, phenytoin, alcohol, oral BCP, methotrexate
lab analysis of folate
look at serum folate & RBC folate (RBC folate tells about folate stores)
look for increase in serum homocysteine as indicator for folate deficiency
vitamin b12 (cobalamin) absorption
absorbed from ileum using INTRINSIC FACTOR from stomach, absorbed through mucosal cells, released, bound to new transport protein, goes into plasma to be taken to liver, BM, or tissues for deposit
vitamin b12 carrier protein
needs a carrier protein bc it is so large even though it is water soluble transcobalamin hydroxycobalamin methyl cobalamin deoxyadenosyl-cobalamin
vitamin b12 function
coenzyme in reactions for hematopoiesis & fatty acid metabolism
active form of vit b12
methyl cobalamin & dexoyadenosyl-cobalamin
vit b12 deficiency
increases w/ age PERNICIOUS ANEMIA vegans FISH TAPE WORM (D. lateum) malabsorption antibody to vit b12 -IF complex
vit b12 toxicity
none known, stays in liver for a decent amount of time (days-months)
lab test for vit b12
Schilling’s test- radioactive b12
measure serum & urine for radio b12
micro test w/ Lactobacillus leischmanii
immunoassay for vit b12
Biotin function
role in gluconeogenesis, lipogenesis, fatty acid synthesis role in # of carboxylation reactions: pyruvate decarboxylasse acetyl CoA carboxylase etc etc
biotin absorption
absorbed from small intestine & synthesized by gut bacteria (!)
lab assay for biotin
chemilumenescent or spectrophotometric methods
biotin deficiencies
affect the enzymes leading to adverse effects on the skin, pallor, mood & GI
depression & vomiting
biotin toxicity
not seen
pantothenic acid
converted to 4’-phosphopantotheinyl moiety which is covalently bound to either serum actyl carrier protein or coenzyme A
pantothenic acid source
found in many foods making deficiencies extremely rare
pantothenic acid deficiency
rare - see irritability, constipation, numbness, anorexia, tingling in hands & feet
pantothenic acid toxicity
not seen
pantothenic acid lab analysis
lactobacillus plantarium
Pediococcus acidilactici
RIA, GC, HPLC
give PA load & look for metabolite: acetylated-p-aminobenzoic acid in urine
vitamin C (ascorbic acid) function
strong reducing agent(!!)
important for hydroxylation reactions of proline & lysine to cross link (COLLAGEN SYNTHESIS) & for the conversion of tyrosine to catecholamines (!!!)
vitamin C deficiency
‘scurvy’/ limey’s disease
hemorrhagic tissues - bleeding gums, impaired wound healing & anemia
vitamin C absorption
absorbed through GI, distributes in water, excreted via urine
NOT STORED IN BODY
lab assays for vitamin C
colorimetric method
HPLC- newer
