Vitamins Flashcards
Absorption dependent on (terminal) ileum, bile and pancreas
Toxicity(not readily excredible) more common- ⬆️ intake leads to eventual storage in fatty tissues
Affected by Malabsorption Syndromes:
- cystic fibrosis
- celiac sprue
- mineral oil intake
Fat-soluble vitamins
Fat-soluble vitamins
Vitamin A
Vitamin D
Vitamin E
Vitamin K
3 forms of VITAMIN A
Retinol (vitamin A alcohol) ➡️ gametogenesis
Retinal (vitamin A aldehyde) ➡️ vision
Retinoic acid (vitamin A acid) ➡️ growth regulators in epithelium
Promote epithelial cell proliferation and differentiation
Storage form: retinyl esters
Transport form: retinol-binding protein (RBP)
Vitamin A
Vitamin A deficiency
Nyctalopia (night blindness) earliest manifestation
Xerophthalmia: eye and corneal dryness
Impotence
Growth retardation
Toxicity of vitamin A (hypervitaminosis A)
Hyperkeratosis
Hepatomegaly
Pseudotumor cerebri (h ICP)
Increased fractures
Teratogenic
Derived cholesterol
Precursor: 7-DEHYDROCHOLESTEROL
Storage: 25-(OH) vitamin D3
Active form: 1,25-(OH)2 vitamin D3
Function: responds to hypocalcemia and PTH
End goal: ⬆️ calcium and ⬆️ PO4
- ⬆️ intestinal absorption of calcium
- ⬆️ bone resorption
- ⬆️ kidney reabsorption
Vitamin D
3 forms of Vitamin D
Ergocalciferol: Vitamin D2, milk, plant sources
Cholecalciferol: Vitamin D3, skin, animal sources
Calcitriol: 1,25-(OH)2 Vitamin D3
Hydroxylations of VITAMIN D
Vitamin D3 must be hydroxylated to become the active form. It undergoes a series of 2 hydroxylations:
1st- 25 hydroxylation ➡️ in the liver
2nd- 1 hydroxylation ➡️ in the kidney
(Anticipate vitamin D deficiency in CKD)
Vitamin D deficiency
Rickets: in children only, before growth plate closes
Osteomalacia: in adults only, after growth plate closes
Toxicity of Vitamin D (Hypervitaminosis D)
Most toxic vitamin
Hypercalcemia
Anorexia and nausea
Thirst
Stupor
Effects of hypocalcemia (vitamin D)
Tetany and seizures
Chvostek’s sign
Trosseau’s sign
Long QT
Effects of hypercalcemia (vitamin D)
Stones (urolithiasis)
Bones (pain, osteoporosis)
Abdominal groans (constipation, PUD, pancreatitis)
Psychic overtones (depression, anxiety, psc)
Short QT
Antioxidant in the lipid phase
Protects membrane lipids from peroxidation
Prevents oxidation of LDL - ⬇️ atherogenesis
LEAST TOXIC
membrane stabilization prevents atherosclerosis prone to hemolysis - ⬇️ vitamin E
Vitamin E
Vitamin E deficiency
RBC fragility
Neurological dysfunction (neuropathy)
3 forms of Vitamin K
Phylloquinone - Vitamin K1
Menaquinone - Vitamin K2
Menadione - Synthetic
Vitamin K deficiency
Rare, because vitamin K can be produced by bacteria in the GIT
Hemorrhagic Disease of the Newborn (HDN)
- presents as bleeding (including intracranial bleeds)
- neonates at risk because of sterile GIT and low vitamin K content of breast milk
Vitamin K toxicity
Jaundice + hemolytic anemia
Water-soluble Vitamins
Vitamin B1 (thiamine)
Vitamin B2 (riboflavin: FAD, FMN)
Vitamin B3 (niacin: NAD+)
Vitamin B5 (Pantothenic acid: CoA)
Vitamin B6 (Pyridoxine: pyridoxal phosphate)
Vitamin B12 (Cobalamin)
Vitamin C (Ascorbic acid)
Biotin
Folate
Generally non-toxic compared to the oil-solubles
- excesses just wash out of the body in the urine
- exceptions: VITAMIN B6 and B12
Water-soluble Vitamins
Active form: THIAMINE PYROPHOSPHATE (TPP)
( used as a cofactor in:
Pyruvate, a-ketoglutarate, and branched chain AA dehydrogenase
Transketolase reactions in the HMP shunt)
Vitamin B1 (Thiamine)
Vitamin B1 deficiency
Beriberi (dry and wet)
- dry beriberi: dry = no heart failure (Polyneuritis, symmetrical muscle wasting)
- wet beriberi: wet = with heart failure (High-output cardiac failure ▶️ dilated cardiomyopathy)
Wernicke-Korsakoff syndrome
Confusion
Loss of muscle coordination (ataxia)
- leg tremor
Vision changes
- abnormal eye movements (back and forth movement) NYSTAGMUS
double vision
Eye drooping
Wernicke’s encephalopathy
Inability to form new memories
Loss of memory can be severe
Making up stories (confabulation)
Seeing or hearing things that aren’t really there (hallucinations)
Korsakoff syndrome
Active form: FLAVIN MONONUCLEOTIDE (FMN), FLAVIN ADENINE DINUCLEOTIDE (FAD)
(used as cofactors in redox reactions, as electron carrier)
Vitamin B2 (Riboflavin)
Vitamin B2 deficiency
No deficiency state but with signs and symptoms
- stomatitis (inflammation of oral mucosa)
- cheilosis (inflammation of lips and angle of mouth)
- dermatitis
- corneal vascularization
Active forms: NICOTINAMIDE ADENINE DINUCLEOTIDE phosphate (NAD+ and NADP+)
(Used as coenzyme in redox reactions, as ➡️ electron carrier; may be derived from tryptophan using Vitamin B6)
Vitamin B3 (Niacin)
Vitamin B3 deficiency
Pellagra = 3Ds (diarrhea, dermatitis, dementia)
- Hartnup Disease absorption (⬇️ tryptophan)
- Carcinoid Syndrome metabolism (⬆️ tryptophan)
- Isoniazid use (⬇️ vitamin B6=⬇️ vitamin B3)
Active form: constituent of Coenzyme A (fatty acid)
used as cofactor for acyl transfers; component of fatty acid synthase
Vitamin B5 (Pantothenate)
Vitamin B5 deficiency
No deficiency state but with signs and symptoms:
- dermatitis
- enteritis
- alopecia
- adrenal insufficiency
Active form: PYRIDOXAL PHOSPHATE
- Used as coenzyme in AA transamination
- used as coenzyme for: glycogen phosphorylase (glycogenolysis), cystathionine synthase, ALA synthase, synthesis of niacin from tryptophan
Vitamin B6 (Pyridoxine)
Vitamin B6 deficiency
Isoniazid toxicity
- INH + pyridoxal phosphate = inactive derivative
- peripheral neuropathy
Vitamin B6 toxicity
Intake of >2g/day
Gait problems and CNS toxicity
Structure: cobalt in center of corrin ring
- Methylcobalamin ➡️ contains methyl group
- Cyanocobalamin ➡️ contains CN
Needs intrinsic factor for absorption
- IF produced by stomach parietal cels
- absorbed in terminal ileum
Active forms:
- 5-DEOXYADENOSYLCOBALAMIN: used for methionine synthesis (homocysteine+N-methyl THG -> methionine+THF
- Methylcobalamin: used for isomerization reactions (methylmalonyl CoA -> succinyl CoA {methylmalonyl mutase}
Vitamin B12 (Cobalamin)
Vitamin B12 deficiency
Pernicious Anemia
- autoimmune destruction of parietal cells leading to ⬇️ IF secretion and ⬇️ vitamin B12 absorption
- early SSX: Megaloblastic anemia
- late SSX: neuropsychiatric
Dx: Schilling Test, Vitamin B12 and anti-IF
Other causes: malabsorption or absence of terminal ileum
Structure: PTERIN RING + PARA-AMINOBENZOIC ACID (PABA) + GLUTAMATE RESIDUES
- humans cannot synthesize PABA and add glutamate, therefore humans cannot synthesize folate
- should be provided from diet
Active form: TETRAHYDROFOLATE (THF)
PABA ➡️ dihydrofolate (DHF) ➡️ tetrahydrofolate (THF) dihydropteroate synthetase dihydrofolate reductase
- used as coenzyme for 1-carbon transfer
- Methylation reactions, like synthesis of purines and thymine
Folic acid
Folic acid deficiency
Megaloblastic anemia with no neurological symptoms
- hypersegmentation of neutrophils (earliest manifestation)
- macrocytic anemia
Neural tube defects
- pregnant mothers must be given 400mcg (x10) folate daily
Used a cofactor for carboxylation reactions:
pyruvate carboxylase (pyruvate➡️oxaloacetate)
Acetyl CoA carboxylase (acetyl CoA➡️malonyl CoA)
Propionyl CoA carboxylase (propionyl CoA➡️methylmalonyl CoA)
Biotin
Biotin deficiency
Induced by avidin in egg whites
Dermatitis
Enteritis
Used as a cofactor in:
- Hydroxylation of proline and lysine (collagen synthesis)
- Dopamine B-hydroxylase (dopamine to norepinephrine)
Reduces Fe3 to Fe2 in stomach to ⬆️Fe absorption (Ferric ➡️ Ferrous)
Vitamin C (Ascorbic Acid)
Vitamin C deficiency
Scurvy
- loose teeth and sore guns
- swollen joints
- fragile vessels
- anemia
