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MBC - Lecture 47

Lipid Soluble Vitamins I (Mock)

Lecture 47 Lipid Soluble Vitamins I
Vitamin A is ___ soluble. lipid
Vitamin B is very complex and ___ soluble. water
Vitamin K is involved in ___. coagulation
Fat soluble vitamin deficiencies are most often found in ___ or ___. liver cholestasis or fat malabsoprtion
Fat soluble vitamins tend to be fat soluble due to repeating saturated or unsaturated ___ units. isoprene
Retinol Form of vitamin A, hydroxyl group on the end
Vitamin A cannot be ___ in the human body. synthesized
Sources of vitamin A are from ___ in plants or animals that have consumed plants. β-carotene
β-Carotene Dioxygenase Catalyzes formation of retinaldehyde from β-carotene present in the intestinal mucosae, activated by bile salts
Source of carotene are “___” vegetables. “yellow” (I.e. carrots)
Source of vitamin A esters is ___. beef liver (also egg yolks and fish)
Retinaldehyde Reductase Catalyzes reduction of retinaldehyde to retinol, uses NADPH
Retinaldehyde can be oxidized to ___ by a NAD/FAD-dependent oxidoreductase. retinoic acid
Retinal can be converted to ___, used in glycoprotein synthesis. retinyl phosphate
Retinal Isomerase Catalyzes isomerization of trans-retinal to cis-retinal
Cis-retinal combines with opsin to form ___. rhodopsin
Stimulation of rhodopsin causes conversion to trans-retinal with release of ___ and ___. opsin and nerve impulse (for color/vision)
Retinol-Binding Protein (RBP) Responsible for plasma transport, also associated with transthyretin (TTR)
Transthyretin (TTR) Responsible for transporting thyroid hormones
Cellular Retinoid-Binding Protein (CRBP) CRBP I through IV, CBRP II involved in intestinal absorption
Cellular Retinoic Acid Binding Protein (CRABP) CRABP I & II involved in embryogenesis
Nuclear Retinoid Receptors (RAR/RXR) Nuclear TF’s found in the nucleus, “nicely behaved” TF’s (domains for vitamin A binding, dimeraztion, DNA binding, transcription activation)
Nuclear Retinoid Receptors (Retinoic Acid Receptors) RARα, RARβ, RARγ, RXRα, RXRβ, RXRγ
RARE/RXRE (Retinoic Acid Response Elements) Specific DNA nucleotide sequence which RAR/RXR binds to
Acute Promyelocytic Leukemia Translocation of chromosomes 15 & 17, fusion of RARα receptor gene to the PML gene defeating normal regulation, responds to retinoic acid (vitamin A) therapy
Promyelocytic Leukemia (PML) Responsible for promoting immature myeloid cells to differentiate into mature cells
___ is expressed in connective tissue, skin, and embryo at critical development stages. RARγ
Cells dependent on vitamin A (retinol and retinoic acid) decrease ___. keratinization
Deficiency of vitamin A leads to increased keratinization in the ___, ___, and ___, and for proper function of ___. skin, cornea, and trachea, immunocytes
___ is a build of keratin and early sign of vitamin A deficiency. Bitot’s spots
Xeropthalmia Dryness of the conjunctiva, usually a result of severe vitamin A deficiency
Keratomalacia Irreversible blindness, can be a result of prolonged xeropthalmia, most common cause of blindness in 3rd worlds
Vitamin A is involved in transferrin ___. synthesis
Transferrin Transports iron (Fe) to bone marrow
Vitamin A/Transferrin deficiency: microcytic hypochromic anemia, resembles Fe deficiency anemia, “Fe resistant”, consider lead poisoning/Pica
Hypervitaminosis A Only from vitamin A overdose and not carotene, liver damage (toxic to the liver)/hemorrhage/coma/death
Teratogenesis Relating to or causing malformations of an embryo
Vitamin A Teratogenesis (13-cis-Retinoic Acid) Associated with >20% rate of spontaneous abortions and birth defects in the first trimester
Vitamin A Anti-Carcinogenic Properties Decreased incidence of cancer, but cannot be reproduced by direct dietary supplements of vitamin A
Role of vitamin D is to maintain ___ and ___. plasma calcium and phosphorous concentrations
Vitamin D enhances ___ and ___ absorption from the small intestine and mobilization from bone. calcium and phosphate
Dietary vitamin D3 (animals) and vitamin D2 (plants) are absorbed ___ into ___ then into the ___ via the lymph. passively into micelles then into the chylomicrons
Vitamin D3 and D2 bind ___ in the ___ and is stored. D-binding protein (DBP) in the liver
Photosynthesis of ___ can produce vitamin D3 in the skin. 7-dehydroxycholesterol (provitamin D3)
Vitamin D is released from the liver after ___. 25-hydroxylation
Assessment of patient vitamin D status is by ___ level. 25-hydroxy vitamin D [25(OH)D3]
In the kidney, 25(OH)D3 is hydroxylated by 1-α-hydroxylase to ___. 1,25-dihydroxy vitamin D3
1,25-dihydroxy vitamin D3 is the ___ form. active
___ is the inactive form and cleared from the system. 24,25-dihydroxy vitamin D3
Parathyroid gland senses ___ levels and secretes parathyroid hormone . calcium
PTH ___ the hydroxylation of 25(OH)D3 to 1,25(OH)D3. stimulates/increases
Short term calcium regulation by vitamin D is by ___ Ca2+ release from the bone. increased
Long term calcium regulation by vitamin D is by ___ Ca2+/K+ absorption in the gut. increased
Low Serum Calcium (PTH/1,25(OH)D3) PTH stimulates 1,25(OH)D3 production and decrease calcium in urine, 1,25(OH)D3 increases dietary Ca2+/K+, and PTH & 1,25(OH)D3 immediately increase serum calcium from bone
1,25(OH)D3 interacts with ___ receptors in target tissue. nuclear
Rapid action of 1,25(OH)D3 is through ___, ___, and ___. intracellular calcium, phosphatidyl inositol, and cyclic GMP
VDR codes for ___, a nuclear transcription factor. vitamin D receptor
VDR forms heterodimer with ___. RXR
VDR/RXR heterodimer binds to ___. vitamin D responsive elements
Target tissues of vitamin D are: intestine (increase absorption), bone (increase mobilization), ubiquitous
Type I Vitamin D Resistant Rickets (Vitamin D Dependent Rickets), caused by 1-α-hydroxalase deficiency
Type II Vitamin D Resistant Rickets Caused by VDR deficiency
Individuals with cholestatic liver disease have decreased ___. bone mineralization
High Serum Calcium (PTH) Parathyroid senses hypercalcemia decreases PTH increases calcitonin, calcitonin increases urine calcium decreases mobilization of calcium from bone, decreased PTH inhibits 1,25(OH)D stimulates 24,25(OH)D synthesis, decreased 1,25(OH)D decreases absorption
Bowed legs is ___ in children learning to walk. normal
Rickets can be treated with ___ supplement. vitamin D
Lack of sunlight can lead to ___. Rickets (vitamin D deficiency)
Excess Vitamin D Produces hypercalcemia by excess absorption of dietary calcium and excess mobilization of calcium from bone, body responds by PTH mechanisms (calcitonin)
Toxicity of Vitamin D Only function of vitamin D is mineral homeostasis, intakes as low as 400 IU/d are adequate, intakes higher than 2000 IU/d are toxic, sun exposure is deleterious
Vitamin D Intake Recommended adult intake 200-600 IU/d up to 2000 IU/d, 10-15 min in peak summer sun can generate 20,000 IU, US approach is 50,000 IU/month
Source of vitamin E is ___. vegetable oil
Vitamin E absorption requires ___, ___, ___, and ___. bile salt, pancreatic lipases, mixed micelles, and chylomicrons
Vitamin E is a ___ in lipid peroxyl radical chain reaction . radical quencher
Vitamin E forms ___ in the process of quenching the radical. vitamin E radical
If vitamin E is radicalized multiple times, the vitamin E is ___. lost
___ quenches vitamin E radicals, regenerating vitamin E. Vitamin C
Vitamin E deficiency leads to accumulative deficiency of ___ functions. peripheral nerve
α-Tocopherol Transfer Protein Deficiency Isolated vitamin E deficiency leading to progressive neurological disorder
Homozygous Hypobetalipoproteinemia Defective apo B leading to fat malabsorption, vitamin E deficiency, retinitis pigmentosa (acquired), and progressive neurological disorder
Abetalipoproteinemia Defective microsomal triglyceride transfer protein leading to fat malabsorption, retinitis pigmentosa, and progressive neurologic disorder
Created by: emyang



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