Vitamins Flashcards
Vitamin Deficiencies
result from inadequate supply
Vitamin Insufficiencies or vitamin Dependencies result from
result from abnormal
metabolism with an adequate supply
Vitamin toxicity ( Fat soluble) can result if
can result if over-ingested
Vitamins physiological functions
- Serve primarily as cofactors of enzymatic
reactions in body - Some function as hormones (Vit A & D)
- Some function as transcription regulators (Vit A)
** Must be obtained from external sources
Vitamins that serve as transcription factors
Vitamin A
Vitamins that serve as hormones
Vit A and D
Vitamins metabolism
1.Reduced serum levels may not indicate a
deficiency that interrupts cellular function
2.Normal values may not reflect adequate function
2A) Clinical expression of Vit abnormalities
2B) Clinical symptoms of Vit deficiencies: nonspecific
in early as well as in mild chronic stages
➡ Deficiencies difficult to diagnose initially
Fat soluble vitamins
A, E, D, K
Water soluble vitamins
B vitamins: thiamine, riboflavin,
niacin, B6, B12,
folate, pyridoxine,
pantothenic acid &
others
➢Biotin
➢Vitamin C
➢Carnitine
Laboratory measurements of vitamins
➢ vitamin precursors
➢ vitamin
➢ vitamin metabolites
➢ some biochemical function with and
without vitamin (Schilling, etc.)
Blood (serum/plasma) or urine
* Immunoassay, HPLC, CPB
- RIA, MEIA, and FPIA
Immunoassays of vitamins
HPLC, CPB
RIA, MEIA, FPIA
FAT soluble vitamins
types
Absorbed as part of
what must be present for Absorption
what conditions are they deficient
-A,D,E,K
-Absorbed as part of the chylomicron
* Fat must be present for absorption
* Chronic malabsorptive states
Fat soluble Vitamins come from what sources and where are they stored
Dietary sources
animal & plant products—varies with
vitamin
Stored in liver and fat tissue
Deficiencies of fat soluble vitamins
Vitamin A, E, and D+K storage
May be difficult to
Deficiencies: develop slowly
- Vit A storage: 1 year
- Vit E storage: several months
- Vit D & K: storage days or weeks
may be difficult to diagnose; vague symptoms
Fat soluble vitamins disorders
Bile and pancreatic function,
bowel mucosa
mpaired bile flow,
* Pancreatic disease
* Chronic bowel inflammatory conditions
* Fistula
* Small bowel obstruction
* Alcohol liver disease
* Cryptosporidium infection
New acquired form of lipid soluble vit deficiency
- A,D,E,K
✴ Lipase inhibitor: Xenical
✴ Ingestion of non-bioavailable fat substitutes: Olester
✴ Patient after bilopancreatic diversion for obesity
Water soluble vitamins
At least how many water soluble vitamins
Moderate excess intake is
Most are stored for
Deficiencies develop more rapid then
- At least 9 water soluble vitamins
- Moderate excess intake is almost immediately excreted in the urine
- Most are stored for <2 months
➢Deficiencies develop more rapidly than fat soluble vitamin
deficiencies
Exceptions is vitamin
-B-12
-can be stored in the liver for up to 12 months.
Vitamin A
has how many active forms and what are there names
* Derived from dietary carotenoids (β-carotene)
Three biologically active forms
➢Retinol, Retinal, Retinoic acid
Vitamin A dietary source
➢animal and plant
➢butter, al-livcream, whole milk, whole milk
cheeses, egg yolk
➢dark green leafy vegetables, yellow vegetables,
yellow fruit & fortified margarine
Retinol is carried by
Chylomicrons in the lymphatics to the liver where retinol binds to RBP and pre-Albumin
Retinol + RBP/ Pre-albumin attaches to RBP-receptor and allows Retinol + cRBP into the cell.
Functions of vitamin A
➢Vision (most clearly defined role)
➢Growth
➢Reproduction
➢Mucus secretion
➢Immune system functions
➢Epithelial cell development, differentiation,
regulation.
Vitamin E: Tocopherol has several isomers but
a form is most studied
Vitamin E: Tocopherol dietary sources
➢Vegetables oils
➢Wheat germ, rice germ,
➢Leafy green vegetables,
➢Legumes & nuts
* Transported: w/ chylomicrons &
VLDL (aTTP)
* Stored primarily in adipose tissue
Vitamin E: Tocopherol functions
➢Antioxidant
➢Protects cell membrane (RBC) from
oxidation of lipids in the membrane.
➢Therapeutically to prevent hemolytic
anemia. (premature newborns)
➢Anti-aging, cardio and neuro protection
Vitamin K: hydroquinone
has several structures and they are
K1, K2, K3
Vitamin K Dietary sources
➢cabbage, cauliflower, green leaves of
alfalfa, spinach, liver, soy beans and
vegetable oil.
➢Intestinal bacteria
–> 50% from each source
*Absorption is with chylomicrons
Vitamin K (hydroquinone) functions
- Normal coagulation
➢Required for synthesis of Factor II, VII, IX,
X, protein C & S
✓Acts as a cofactor in Vit-K dependent
carboxylation of glutamic acid
Vitamin K1 is
Phylloquinone
Vitamin K2
Menaquinone-4
Vitamin K3
Menadione
Two forms of Vit D
Vitamin D3= cholecalciferol
Vitamin D2= Calciferol
Vitamin D3
➢Produced in skin from UV
activation of 7-dehydrocholesterol
➢Prohormone converted by liver to calcidiol
à hydroxylated to calcitriol (active form
Vitamin D2
*Vit D 2 : calciferol (dietary form)
➢Hydroxylated to calcitriol in the same way as D
Dietary sources of Vitamin D
➢Fish liver oil
➢Fortified milk
➢Irradiated foods
( Ionizing Radiation)
➢Smaller amounts in butter, egg yolk, liver, certain fish (esp. salmon and sardin
Vitamin D functions
➢Calcitriol enhances Ca2+ uptake from the GI and increases the release of Ca2+ from
bone into blood
Vitamin A deficiency lead to
Decreased vision and Decreased Immune system function
Vitamin A toxicity
—> upon what
symptoms
Upon overdose
❑ Symptoms:
* Dermatologic disorders
* Bone pain
* Renal disorders
* Intracranial
hypertension
* Hemorrhage
* Teratogen
Total Vitamin A assay
Retinol(RBP) assay
B-Carotene
- Total Vit A:
➡Fluorometry or HPLC - Retinol (RBP):
➡Immunoassay - β-Carotene:
➡Extraction of β-carotene, - measure directly @ 450 nm
** Light sensitive
Vitamin E Deficiency
- Rare
- Neurological signs
- Ataxia
- Peripheral neuropathy - Macrocytic megaloblastic Anemia
Vitamin E Assay
- HPLC
- GC-IDMS
- Photometry or Fluorimetry
- TLCG
à separate tocopherols &
tocotrienols.
Vitamin E assay reaction
Tocopherol + FeCl3
—–> Tocopheryl quinine + Fe2+ + a,a-dipyridyl [ Red].
Vitamin K deficiency
- ~ 3 weeks to develop
- Hemorrhage secondary to reduced
prothrombin and other coagulation factors - ecchymoses, epitaxis, intestinal
hemorrhage
Vitamin K Assay
- Seldom measured directly
- PT & APTT
à Both will be prolonged in a deficiency,
but thrombin time will be normal - Direct measurement:
immunoassay or HPLC (rare)
Vitamin D deficiency
- bone malformations
–> à Rickets in children and osteomalacia in adults
Vitamin D Assays
- Immunoassay
- HPLC
- LC with Mass Spec (LCMS)
** Normal values still being debated - <50 nmol/L considered low
water soluble vitamins
Vitamin C and B
Vitamin C
-Distributed throughout what
- Deficiency may take several blank to
- High concentrations in
- Excreted in urine as blank
- Distributed throughout tissues
- Deficiency may take several months to develop symptoms
- High concentration in CSF
- Excreted in urine as oxalate
Plasma Vitamin C concentration is lower then
CSF
Oxalate is the metabolite of
Oxalate is the metabolite of Vitamin C –~50% of urinary oxalate is from
Vitamin C
Ascorbic Acid dietary sources
-Found primarily in citrus fruits & vegetables: oranges, lemons, limes,
tomatoes, grapefruit
- Other vegetables and fruits: green peppers, broccoli, leafy green vegetables, potatoes,
strawberries
-Heat and oxygen labile
Vitamin C is high in what foods
found primarily in citrus fruits & vegetables: oranges, lemons, limes,
tomatoes, grapefruit
Highest in those foods when they are fresh & uncooked
Many plants and animals can synthesize what but humans cant
Plants and many other animals can synthesize Vitamin C, but humans cannot—
must be ingested.
Protein and glucose ?
Vitamin C- Functions
- Functions as an electron transfer molecule for enzymes involved in
collagen formation and stabilization - Antioxidant
- Involved in catecholamine synthesis
- Cholesterol metabolism
- Synthesis: Carnitine, Steroid
- Uptake of non-heme iron
Vitamin C function in Collagen and formation and stabilization
via hydroxylation of proline & lysine which are required to allow the formation of the triple helix and
the cross linking of the collagen chains). (Most well-described function and clinically demonstrated
in the Scurvy which is a disease of impaired cllagen synthesi
Vitamin C roll in Catecholamine synthesis and what type of vitamin C is involved
tyrosine conversion to the catecholamines
via dopamine β-hydroxylase. Adrenal
(medulla) have much higher concentration
of Vit C
Vitamin C involvement in Uptake of non-heme iron
in the gut is facilitated by asobic acid through the
nonenzymatic reduction of Fe 3+ to Fe2+
Vitamin C- Deficiency
It may take how many months to develop
Vitamin C is distributed throughout tissues, a deficiency may take several months to exhibit
symptoms.
Vitamin C deficiency can result in
Deficiency results in SCURVY
Impaired collagen synthesis
Breakdown of connective tissues
-Gum and tooth
disease
-Bone disease
-Poor wound healing
Vitamin C symptoms
- weakness, irritability, pains in joints/muscles
- Bleeding into skin, GI tract & urinary tract