Antioxidant; constituent of visual pigments (retinal); essential for normal differentiation of epithelial cells into specialized tissue (pancreatic cells, mucus-secreting cells); prevents squamous metaplasia.
Used to treat measles, severe cystic acne, and acute promyelocytic leukemia (APL).
Found in liver and leafy vegetables.
Deficiency: Night blindness (nyctalopia); dry, scaly
skin (xerosis cutis); corneal degeneration (keratomalacia); Bitot spots on conjunctiva; immunosuppression.
Acute toxicity—N/V, vertigo, and blurred vision.
Chronic toxicity—alopecia, dry skin (eg, scaliness), hepatic toxicity and enlargement, arthralgias, and pseudotumor cerebri.
Teratogenic (cleft palate, cardiac abnormalities)
A negative pregnancy test and two forms of contraception are required before isotretinoin (vitamin A derivative) is prescribed.
Niacin Function: Niacin → NAD (B*3* ≈ 33acin* Function: Niacin → NAD (B*3* ≈ *3* ATP)
Constituent of NAD+, NADP+ (redox reactions). Derived from tryptophan. Synthesis requires vitamins B2 and B6.
Treats dyslipidemia; ↓ VLDL and ↑ HDL
Glossitis. Hartnup disease, malignant carcinoid syndrome (↑ tryptophan metabolism), and isoniazid (↓ vitamin B6) → Severe deficiency → pellagra.
Pellagra 3 D's of B3: *D*iarrhea, *D*ementia (+ hallucinations), Dermatitis (C3/C4 dermatome circumferential "broad Dlagra *3 D*'s of B*3*: *D*iarrhea, *D*ementia (+ hallucinations), Dermatitis (C3/C4 dermatome circumferential "broad collar" rash [Casal necklace], hyperpigmentation of sun- exposed limbs).
Facial flushing (prostaglandin, not histamine), hyperglycemia, hyperuricemia
Avoid Niacin flush by taking aspirin with niacin
Converted to pyridoxal phosphate (PLP), a cofactor used in transamination (eg, ALT and AST), decarboxylation reactions, glycogen phosphorylase. Synthesis of cystathionine, heme, niacin, histamine, and neurotransmitters including serotonin, epinephrine, norepinephrine (NE), dopamine, and GABA.
Convulsions, hyperirritability, peripheral neuropathy (deficiency inducible by isoniazid and oral contraceptives)
↓ hemoglobin synthesis & iron excess → sideroblastic anemias
Ascorbic acid Function: Antioxidant.
Facilitates iron absorption by reducing to Fe2+ state. Necessary for hydroxylation in collagen synthesis - proline → lysine.
Necessary for dopamine β-hydroxylase (dopamine → NE).
Found in fruits and vegetables.
Ancillary treatment for methemoglobinemia (Fe3+ to Fe2+)
Deficiency: Scurvy—swollen gums, bruising, petechiae, hemarthrosis, anemia, poor wound healing, perifollicular and subperiosteal hemorrhages, "corkscrew" hairr*.
Weakened immune response.
Vitamin *C* deficiency causes sCCamin *C* deficiency causes s*C*urvy due to a
Collagen synthesis defect.
Excess: N/V, diarrhea, fatigue, calcium oxalate nephrolithiasis. ↑ risk of iron toxicity in predisposed individuals (transfusions, hemochromatosis).
Phytomenadione, phylloquinone, phytonadione
Function: Activated by epoxide reductase to reduced form, a cofactor for γ-carboxylation of glutamic acid residues on various proteins required for blood clotting. Synthesized by intestinal flora.
*K* is for Koagulation. Necessary for maturation of clotting factors *II, VII, IX, X, and proK is for *K*oagulation. Necessary for maturation of clotting factors II, VII, IX, X, and proteins C and S
Deficiency: Neonatal hemorrhage with ↑ PT and ↑ aPTT but normal bleeding time (neonates unable to synthesize vitamin K).
Not in breast milk; neonates given vitamin K injection at birth to prevent hemorrhagic dz of newborn
Function: Essential for activity of 100+ enzymes. Zinc fingers (transcription factor motif).
Deficiency: Delayed wound healing, hypogonadism, ↓ adult hair (axillary, facial, pubic), dysgeusia (foul, salty, rancid, or metallic taste sensation persists in mouth))*, anosmia, acrodermatitis enteropathica. Predisposes to alcoholic cirrhosis.
Mitochondria: Fatty acid oxidation (β-oxidation), acetyl-CoA production, TCA cycle, oxidative phosphorylation, ketogenesis.
Cytoplasm: Glycolysis, HMP shunt, and synthesis of steroids (SER), proteins (ribosomes, RER), fatty acids, cholesterol, and nucleotides.
Both: Heme synthesis, Urea cycle, Gluconeogenesis.
HUGs take two (ie, both).