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FirstAid: Biochem Vitamins
Terms in this set (49)
Vitamin B1 (thiamine): Function
In thiamine pyrophosphate (TPP), a cofactor for several dehydrogenase enzyme reactions:
1. Pyruvate dehydrogenase (links glycolysis to TCA cycle)
2. α-ketoglutarate dehydrogenase (TCA cycle)
3. Transketolase (HMP shunt)
4. Branched-chain ketoacid dehydrogenase
Note: Think ATP: α-ketoglutarate dehydrogenase, Transketolase, and Pyruvate dehydrogenase.
Vitamin B1 (thiamine) deficiency: Sx
1. Wernicke-Korsakoff syndrome: Confusion, ophthalmoplegia, ataxia (classic triad) + confabulation, personality change, memory loss (permanent). Damage to medial dorsal nucleus of thalamus, mammillary bodies.
2. Dry beriberi: Polyneuritis, symmetrical muscle wasting.
3. Wet beriberi: Dilated cardiomyopathy (high output cardiac failure)
Vitamin B1 (thiamine) deficiency: Effect on metabolism
Impaired glucose breakdown ATP depletion worsened by glucose infusion; highly aerobic tissues (eg, brain, heart) are affected first.
Vitamin B1 (thiamine) deficiency: Dx
Increase in RBC transketolase activity following vitamin B1 administration.
Vitamin B2 (Riboflavin): Function, Sx of deficiency
1. Function: FAD and FMN
2. Sx: Cheilosis and corneal vascularization (2 C's of B2)
Note: Cheilosis is inflammation of lips, scaling and fissures at the corners of the mouth
Vitamin B3 (Niacin): Function, derived from, synthesis requires, use
1. Constituent of NAD+ and NADP+ (used in redox reactions).
2. Derived from tryptophan.
3. Synthesis requires vitamins B2 and B6
4. Used to treat dyslipidemia; lowers levels of VLDL and raises levels of HDL
Vitamin B3 deficiency: Sx
The 3 D's of B3:
2. Dementia (also hallucinations)
3. Dermatitis (C3/C4 dermatome circumferential "broad collar" rash [Casal necklace], hyperpigmentation of sun- exposed limbs)
Note: Also glossitis
Vitamin B3 excess: Sx
1. Facial flushing (Tx with aspirin, facial flushing due to prostaglandins)
Vitamin B3 deficiency: Causes
1. Hartnup disease (Tryptophan loss)
2. Malignant carcinoid syndrome (Tryptophan use)
3. Isoniazid (Decreased vitamin B6) (Tryptophan conversion)
Hartnup disease: Pathophysiology
1. Deficiency of neutral amino acid (tryptophan) transporters in proximal renal tubular cells and on enterocytes
2. Decreased absorption and aminoaciduria
3. Decreased tryptophan
4. Pellagra-like sx
Hartnup disease: Tx
High protein diet and nicotinic acid
Vitamin A (retinol): Function (4)
2. Eyes: Constituent of visual pigments (retinal)
(A) Used to treat cystic acne (isotretinoin) and wrinkles (Retinol): Essential for normal differentiation of epithelial cells into specialized tissue (pancreatic cells, mucus-secreting cells)
(B) Prevents squamous metaplasia
4. Immune system: Tx for Measles and AML subtype M3 (all-trans retinoic acid)
Vitamin A (retinol) deficiency: Sx
1. Eye: Night blindness (nyctalopia), corneal degeneration (keratomalacia), bitot spots on conjunctiva
2. Dry, scaly skin (xerosis cutis)
Vitamin A toxicity: Sx (Acute, chronic, teratogenic effects)
1. Acute toxicity: Nausea, vomiting, vertigo, and blurred vision.
2. Chronic toxicity: Alopecia,
(eg, scaliness), hepatic toxicity and enlargement,
3. Teratogenic (
cleft palate, cardiac abnormalities
), therefore a ⊝ pregnancy test and two forms of contraception are required before isotretinoin (vitamin A derivative) is prescribed.
Vitamin B5 (Pantothenic acid): Function, Sx of deficiency
1. Function: Essential component of coenzyme A (CoA, a cofactor for acyl transfers) and fatty acid synthase
2. Sx: Dermatitis, enteritis, alopecia, adrenal insufficiency
Vitamin B6 (Pyridoxine): Function
1. Converted to pyridoxal phosphate (PLP), a cofactor used in:
(A) Transamination (eg, ALT and AST) (
(B) Decarboxylation reactions
(C) Glycogen phosphorylase
2. Synthesis of cystathionine, heme, niacin, histamine
3. Synthesis of neurotransmitters: Serotonin, epinephrine, norepinephrine (NE), dopamine, and GABA
Vitamin B6 (Pyridoxine) deficiency: Sx
3. Peripheral neuropathy (deficiency inducible by isoniazid and oral contraceptives)
4. Sideroblastic anemias due to impaired hemoglobin synthesis and iron excess.
Vitamin B7 (biotin): Function
Cofactor for carboxylation enzymes (which add a 1-carbon group):
1. Pyruvate carboxylase: Converts pyruvate (3C) to oxaloacetate (4C)
2. Acetyl-CoA carboxylase: Converts acetyl-CoA (2C) to malonyl-CoA (3C)
3. Propionyl-CoA carboxylase: Converts propionyl-CoA (3C) to methylmalonyl-CoA (4C)
Vitamin B7 (Biotin) deficiency: Caused by, Sx
1. Caused by: Excessive ingestion of raw egg whites
2. Sx: Dermatitis, alopecia, enteritis (Same as B6 deficiency except no adrenal insufficiency)
Vitamin B9 (Folate): Function
1. Converted to tetrahydrofolic acid (THF), a coenzyme for 1-carbon transfer/methylation reactions.
2. Synthesis of nitrogenous bases in DNA and RNA.
Vitamin B9 (Folate): Dietary source? Where in the GI tract is it absorbed? How large is the reserve pool? Where is the reserve pool?
1. Dietary source: Green leafy vegetables
2. Absorbed in: Jejunum
3. Small reserve pool in liver
Vitamin B9 (Folate) deficiency: Labs, due to
1. Labs: Increased homocysteine, normal methylmalonic acid
2. Due to: Alcoholism, pregnancy drugs (phenytoin, sufonamides, MTX)
What can you give people that have a folate deficiency in order to prevent erythrocyte apoptosis? (assume you cannot give folate)
Vitamin B12 (cobalamin): Function
Cofactor for: 1. Methionine synthase (transfers CH3 groups as methylcobalamin) 2. methylmalonyl-CoA mutase.
Vitamin B12 deficiency: Sx
1. Macrocytic megaloblastic anemia
2. Hypersegmented PMNs
3. Paresthesia and subacute combined degeneration (degeneration of dorsal columns, lateral corticospinal tracts, and spinocerebellar tracts) due to abnormal myelin
Note: 1 and 2 are present in folate deficiency. 3 is only present in B12 deficiency. Prolonged deficiency causes irreversible nerve damage.
Vitamin B12 deficiency: Labs
1. Increased homocysteine
2. Increased methylmalonic acid levels
Vitamin B12: Source, reserve pool, storage site
1. Source: Synthesized by microorganisms
2. Reserve pool: Very large
3. Storage site: Liver
Vitamin B12 deficiency: Causes
1. Malabsorption (Sprue, enteritis, Diphyllobothrium latum)
2. Lack of intrinsic factor (pernicious anemia, gastric bypass surgery)
3. Absence of terminal ileum (surgical resection for Crohn disease)
4. Veganism (Insufficient intake)
Vitamin C (ascorbic acid): Function
2. Facilitates Fe absorption (Reduces it to Fe2+)
3. Hydroxylation of proline and lysine in collagen synthesis
4. Converts dopamine to NE (Necessary for dopamine β-hydroxylase)
Vitamin C (ascorbic acid): Use
Ancillary treatment for methemoglobinemia by
reducing Fe3+ to Fe2+.
Vitamin C (ascorbic acid) deficiency: Sx
1. Scurvy: Swollen gums, bruising, petechiae, hemarthrosis, anemia, poor wound healing, perifollicular and subperiosteal hemorrhages, "corkscrew" hair.
2. Weakened immune response
Vitamin C (ascorbic acid) toxicity: Sx
1. Nonspecific: Nausea, vomiting, diarrhea, fatigue
2. Calcium oxalate nephrolithiasis.
3. Can increase risk of iron toxicity in predisposed individuals (eg, those with transfusions, hereditary hemochromatosis).
Vitamin D: Forms (4)
D2 = ergocalciferol—ingested from plants.
D3 = cholecalciferol—consumed in milk, formed in sun-exposed skin (stratum basale).
25-OH D3 = storage form.
1,25-(OH)2 D3 (calcitriol) = active form.
Vitamin D: Function
1. Intestinal absorption of calcium and phosphate
2. Increased bone mineralization at low levels
3. Bone resorption at higher levels.
Vitamin D deficiency: Sx
1. Rickets in children (bone pain and deformity)
2. Osteomalacia in adults (bone pain and muscle weakness)
3. Hypocalcemic and tetany
Vitamin D deficiency: Prevention in infants
Breastfed infants should receive oral vitamin D.
Vitamin D deficiency: What is deficiency exacerbated by?
Deficiency is exacerbated by low sun exposure, pigmented skin, prematurity.
Vitamin D toxicity: Sx (3)
2. Loss of appetite
Vitamin D toxicity: Seen in what disease?
Granulomatous disease (Increased activation of vitamin D by epithelioid macrophages)
Vitamin E (tocopherol/tocotrienol): Function, what drug can it interact with?
1. Antioxidant (protects RBCs and membranes from free radical damage)
2. Can enhance anticoagulant effects of warfarin
Vitamin E (tocopherol/tocotrienol) deficiency: Sx
1. Hemolytic anemia
(A) Muscle weakness
(B) Posterior column and spinocerebellar tract demyelination (Neurologic presentation may appear similar to vitamin B12 deficiency, but without megaloblastic anemia, hypersegmented neutrophils, or increased serum methylmalonic acid levels)
Vitamin K (phytomenadione, phylloquinone, phytonadione): Function, synthesized by
1. Cofactor for the γ-carboxylation of glutamic acid residues on various proteins required for blood clotting
2. Synthesized by intestinal flora.
Vitamin K deficiency: Labs
1. Increased PT
2. Increased PTT
3. Normal bleeding time
What vitamin are neonates given at birth to prevent hemorrhagic disease of the newborn? Why?
1. Neonates given: Vitamin K injection
2. Vitamin K is not present in breast milk
1. Mineral essential for the activity of 100+ enzymes
2. Important in the formation of zinc fingers (transcription factor motif).
Zinc deficiency: Sx
1. Delayed wound healing
3. Adult hair (axillary, facial, pubic)
6. Acrodermatitis enteropathica
7. May predispose to alcoholic cirrhosis
Two type of malnutrition
Kwashiorkor: Due to, Sx
1. Due to: Protein malnutrition
(D) Liver (fatty)
Marasmus: Due to, Sx
1. Due to: Total calorie malnutrition resulting in emaciation
2. Sx: Tissue and muscle wasting, loss of subcutaneous fat); +/- edema.
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