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Water soluble vitamine
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- B1 (thiamine:TPP)
- B2 (riboflavin: FAD, FMN)
- B3 (niacin:NAD+)
- B5 (Pantothenic acid: CoA)
- B6 (pyridoxine: PLP)
- B12 (cobalamin)
- Biotin
- C (ascorbic acid)
B12 and folate are the only two stored in liver
B-complex deficiencies often result in dermatitis, glossitis, and diarrhea
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Vitamin A (retinol)
- 1. antioxidant
- 2. constituent of visual pigments (retinal)
- 3. essential for normal differentiation of epithelial cells into specialized tissue (pancreatic cells, mucus-secreting cells)
- 4. prevents squamous metaplasia
- 5. used to treat measles and AML, subtype M3; wrinkles and acne
- 6. found in liver and leafy vegetables
Deficiency: Night blindness, dry skin
Excess: Arthralgias, fatigue, headaches, skin changes, sore throat, alopecia. Tertogenic (cleft palate, cardiac abnormalities), so a pregnancy test must be done before isotretinoin is prescribed for severe acne
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Vitamin B1 (thiamine)
Thiamine pyrophosphate (TPP)
Ber1 Ber1
Wernicke- Korsakoff (triad)
- Decarboxylation reactions:
- 1. pyruvate dehydrogenase
- 2. alpha-ketoglutarate dehydrogenase (TCA cycle)
- 3. Transketolase (HMP shunt)
- 4. Branched-chain AA dehydrogenase
- Deficiency: impaired glucose breakdown; brain and heart affected first;
- Triad: confusion, ophthalmoplegia, ataxia + confabulation, personality change, memory loss (permanent). Damage to medial dorsal nucleus of thalamus, mammillary bodies
- Dry beriberi- polyneuritis, symmetrical muscle wasting
- Wet beriberi- high-output cardiac failure (dilated cardiomyopathy), edema
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Vitamin B2 (riboflavin)
B2= 2ATP
cofactor in oxidation and reduction (FADH2)
Deficiency: Cheilosis (inflammation of lips, scaling and fissures at the corners of the mouth), Corneal vascularization
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Vitamin B3 (niacin)
B3= 3 ATP
3 D's= diarrhea, dermatitis, dementia
- Constituent of NAD+, NADP+
- Derived from tryptophan
- synthesis requires B6
Deficiency: Glossitis. Severe deficiency leads to pellagra: caused by Hartnup disease (dec tryptophan absorption), malignant carcinoid syndrome (inc tryptophan metabolism), and INH (dec vit B6)
Excess: Facial flushing (due to pharmacologic doses for treatment of hyperlipidemia)
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Vitamin B5 (pantothenate)
Essential component of CoA (a cofactor for acyl transfers) and fatty acid synthase
Deficiency: dermatitis, enteritis, alopecia, adrenal insufficiency
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Vitamin B6 (pyridoxine)
converted to pyridoxal phosphate, a cofactor used in transamination decarboxylation reaction, glycogen phosphorylase. Synthesis of cystathionine, heme, niacin and GABA
Deficiency: convulsions, hyperirritability, peripheral neuropathy (deficiency inducible by INH and oral contraceptives), sideroblastic anemias due to impaired Hb synthesis and Fe excess
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Vitamin B12 (cobalamin)
cofactor for homocysteine methyltransferase and methylmalonyl-CoA mutase (Odd #C fatty acids)
Deficiency: Macrocytic, megaloblastic anemia, hypersegmented PMNs, neurologic symptoms (paresthesias, subacute combined degeneration) due to abnormal myelin. Prolonged deficiency leads to irreversible nervous system damage
- Found in animal products
- synthesized only by microorganisms.
- Deficiency is usually caused by malabsorption (sprue, enteritis, Diphyllobothrium latum), lack of intrinsic factor (pernicious anemia, gastric bypass surgery), or absence of terminal ileum (Crohn's disease)
- Use Schilling test to detect the etiology of the deficiency.
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Folic Acid
- Converted to tetrahydrofolate (THF)
- important for the synthesis of nitrogenous bases in DNA and RNA
Deficiency: most common seen in alcoholism and pregnancy; macrocytic, megaloblastic anemia. caused by several drugs (eg phenytoin, sulfonamides, MTX)
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S-adenosyl-methionine (SAM)
- ATP + methionine --> SAM
- transfers methyl units- required fro the conversion of NE to epinephrine
- regeneration of methionine (thus SAM) is dependent on vitamin B12 and folate
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Biotin
- cofactor for carboxylation enzymes
- 1. pyruvate carboxylase: pyruvate (3 C) --> oxaloacetate
- 2. Acetyl-CoA carboxylase: acetyl-CoA (2 C)--> malonyl-CoA
- 3. Propionyl-CoA Carboxylase: propionyl-CoA (3C) --> methylmalonyl-CoA
Deficiency: Rare caused by antibiotic (biotin synthesized by GI bacteria) use or excessive ingestion of raw eggs (egg whites). Dermatitis, alopecia, enteritis
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Vitamin C (ascorbic acid)
Found in fruits and vegetables
- 1. facilitates iron absorption by keeping iron in Fe2+ reduced state
- 2. necessary for hydroxylation of proline and lysine in collagen synthesis
- 3. necessary for dopamine b-hydroxylase, which coverts dopamine to NE
Deficiency: scurvy- swollen gums, bruising, hemarthrosis, anemia, poor wound healing; weakened immune response.
Excess: nausea, vomiting, diarrhea, fatigue, sleep problems. Can inc risk of iron toxicity in predisposed individuals (transfusions, hereditary hemochromatosis)
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Vitamin D
- 7 alpha-dehydrocholesterol in skin
- D2= ergocalciferol- ingested from plants
- D3= cholecalciferol- consumed in milk, formed in sun-exposed skin
- 25-OH D3= storage form
- 1,25 (OH)2 D3 (calcitriol)= active form
Deficiency: hyopcalcemic tetany, breast milk has dec vit D
Excess: loss of appetite, stupor, seen in sarcoidosis (inc activation of vit D by epithelioid macrophages)
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Vitamin E
Antioxidant (protects erythrocytes and membranes from free-radical damage)
Deficiency: inc fragility of erythrocytes (hemolytic anemia), muscle weakness (necrotizing myopathy), posterior column and spinocerebellar tract demyelination (similar to B12 deficiency)
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Vitamin K
- catalyzes gamma-carboxylation of glutamic acid (II, VII, IX, X, protein C and S)
- synthesized by intestinal flora
- also activate osteocalcin (inhibits calcification of arteries & cartilage)
Deficiency: neonatal hemorrhages w/ inc PT and inc PTT but normal bleeding time (neonates have sterile intestine and are unable to synthesize vit K). Chondrodysplasia punctate: leads to aberrant calcification (early or excessive)
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Zinc
essential for the activity of 100+ enzymes. Imp in the formation of zinc fingers (transcription factor motif)
Deficiency: delayed wound healing, hypogonadism, dec adullt hair (axillary, facial, pubic), dysgeusia (no taste buds), anosmia (inability to perceive odor). May predispose to alcoholic cirrhosis
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