Vitamins Flashcards
B1 functions (think ATP)
Thiamine pyrophosphate used as cofactor for:
Alpha ketoglutarate dehydrogenase
Transketolase
Pyruvate dehydrogenase
B1 deficiency causes:
- Impaired glucose breakdown –> ATP depletion worsened by glucose infusion (highly aerobic tissues affected first) –> Wernicke Korsakoff syndrome and beriberi
B2 functions
Riboflavin used in dehydrogenase reactions
Component of flavors FAD and FMN used in redox reactions (Succinate dehydrogenase reaction in TCA cycle)
B2 Deficiency
Cheilosis (inflammation of lips, mouth)
Corneal vascularization
B3 functions
Niacin –> constituent of NAD+, NADP+
Used to treat dyslipidemia –> lowers levels of VLDL and raises levels of HDL
What is Niacin derived from?
Tryptophan
Synthesis of Niacin (B3) requires what?
Vitamins B2 (Riboflavin) and B6 (Pyridoxine)
B3 deficiency
Pellagra (dermatitis, dementia, diarrhea)
Can be caused by Hartnup disease (no tryptophan absorption), malignant carcinoid syndrome (increased tryptophan metabolism) or Isoniazid (decreases vitamin B6)
Which conditions/drugs should Niacin be used with caution?
Hypertensives –> Niacin has vasodilatory effects that potentiate anti-HTN drugs
Associated with insulin resistance (Diabetics)
Increases serum uric acid (Gout)
Niacin toxicity
Facial flushing (from prostaglandin –> take aspirin to avoid)
Hyperglycemia
Hyperuricemia
Function of B5
Pantothenic acid –> essential component of coenzyme A (Acetylation reactions) and fatty acid synthase
Deficiency of B5
Dermatitis, enteritis, alopecia, adrenal insufficiency
Vitamin B6 function
Pyridoxine –> cofactor used in transamination, decarboxylation reactions, glycogen phosphorylase
Synthesis of cystathionine, heme, niacin, histamine, serotonin, epinephrine, norepinephrine, dopamine, GABA
B6 deficiency
Convulsions, hyper irritability, peripheral neuropathy (inducible by isoniazid and oral contraceptives), sideroblastic anemia due to impaired hemoglobin synthesis and iron excess
What can induce B6 deficiency?
Isoniazid and contraceptives
B7 function
Biotin –> cofactor for carboxyation enzymes (CO2 carrier) –> pyruvate carboxylase, acetyl coA carboxylase, propionyl coA carboxylase
Which reactions use B7 as cofactor?
Pyruvate carboyxlase: pyruvate –> oxaloacetate
Acetyl CoA carboxylase: acetyl coA –> malonyl coA
Propionyl CoA carboxylase: propionylCoA —> methylmalonyl coA
Causes of B7 deficiency
Excessive egg white ingestion
Antibiotics
B9 function
Converted to tetrahydrofolic acid, a coenzyme for 1 carbon transfer/metylation reactions
Important for the synthesis of nitrogenous bases in DNA and RNA
B9 deficiency
Macrocytic, megaloblastic anemia, glossitis
Labs in B9 deficiency
Increased homocysteine
Normal methylmalonic acid levels
Drugs that cause folate deficiency
Methotrexate
Sulfonamides
Phenytoin
Function of B12
Cofactor for homocysteine methyltransferase that transfers CH3 groups as methylcobalamin (makes homocysteine into methionine)
Cofactor for methylmalonyl coA mutase (methylmalonyl coA –> succinyl coA)
Functions of Vitamin C
Antioxidant
Facilitates iron absorption by reducing it to Fe2+
Hydroxylation of proline and lysine in collagen synthesis
Necessary for dopamine Beta hydroxylase
Vitamin C can increase toxicity of what?
Can increase risk of iron toxicity so it should be avoided in those with transfusions and hereditary hemochromatosis
Which form of Vitamin D is formed in sun exposed skin?
D3; cholecalciferol is formed in the stratum basale
Why is vitamin D excess seen in granulomatous diseases?
Epithelial macrophages cause increased activation of Vitamin D
Tocopherol/Tocotrienol
Vitamin E
Tocopherol function
Antioxidant that protects RBCs and membranes from free radical damage
Vitamin E deficiency
Hemolytic anemia
Acanthocytosis
Muscle weakness
Posterior column and spinocerebellar tract demyelination
What can be given with Warfarin to enhance anticoagulant effects?
Vitamin E (Tocopherol)
Differential of posterior column and spinocerebellar tract demyelination
Vitamin E deficiency - WITHOUT megaloblastic anemia, hypersegmented neutrophils or increased methylmalonic acid levels
Vitamin B12 deficiency - Megaloblastic anemia, hypersegmented neutrophils and increased methylmalonic acid
Phytomenadione, Phylloquinone, Phytonadione
Vitamin K
Function of Vitamin K
Cofactor for gamma carboxylation of glutamic acid resides on proteins required for blood clotting
Where is Vitamin K synthesized?
Made by intestinal flora
Vitamin K deficiency
Neonatal hemorrhage with increased PT and PTT but normal bleeding time (or after prolonged use of broad spectrum Abx or Phenytoin)
Zinc function
Essential for MANY enzymes
Zinc deficiency
Delayed wound healing Hypogonadism Decreased adult hair Dysgeusia Anosmia Acrodermatitis enteropathica
Fomepizole
Inhibits alcohol dehydrogenase
Antidote for ethylene glycol or methanol poisoning
(Normally ethylene glycol –> oxalic acid, methanol –> formaldehyde)
Disulfiram
Inhibits aldehyde dehydrogenase (hangover symptoms)
Which drugs cause Disulfiram like reaction?
Metronidazole
Procarbazine
Cephalosporins
Ethanol effects at cellular level
Increases NADH/NAD ratio in liver, causing:
- Pyruvate –> lactate (lactic acidosis)
- Oxaloacetate –> malate (prevents gluconeogenesis –> fasting hypoglycemia)
- Dihydroxyacetone phosphate –> glycerol 3 phosphate (hepatosteatosis)
