Biochemistry: Nutrition Flashcards
What vitamins are fat soluble?
A/D/E/K
Absorption is 100% dependent on ileum and the pancreas (disorders in either can cause fat soluble vitamin deficiencies)
Toxicity is less common than water soluble toxicity
What vitamins are water soluble?
Thiamine (B1)
Riboflavin (B2)
Niacin (B3)
Pantothenic acid (B5)
Pyridoxine (B6)
Biotin (B7)
Folate (B9)
Cobalamin (B12)
Ascorbic acid (vitamin C)
Easier to gain toxicity of OD
- all wash out of system easily (can reverse toxicity easily) EXCEPT folate and cobalamin*
- folate stays in liver for 3-4 months
- cobalamin stays in liver 3-4 years
vitamin A (retinol/retinoic acid) function
Antioxidant
Generates retinol (helps with eye pigmentation and ability to see)
Prevents squamous cell metaplasia (cancer)
Helps epithelial tissue differentiate into mucus secreting cells
- excess is used in treatment for APL and measles*
- topical vitamin a (retinol) is used for acne sometimes*
Vitamin A (retinol/retinoic acid) deficiency effects
Night blindness
Dry scaly skin (xerosis cutis)
Bitot spots (keratin debris on conjunctiva)
Corneal degeneration
Immunosuppression
Vitamin A toxicity effects
Acute:
- nausea/vomiting/ blurry vision
Chronic
- alopecia
- dry skin
- hepatic toxicity
- intercranial HTN
is teratogenic (develops cleft palate and cardiac disfigurements)
Vitamin B1 (thiamine) function
Acts a cofactor for the following dehydrogenase reactions/enzymes:
- Branched-chained ketoacid dehydrogenase
- A-ketoglutarate dehydrogenase
- Pyruvate dehydrogenase
- Transketolase (HMP shunt pathway)
“Be APT”
Vitamin B1 (thiamine) deficiency
Impaired glucose breakdown and ATP formation
- gets worse with glucose infusion unless given thiamine first
Damages heart, brain, liver and kidney tissues first
diagnosis is made by increased RBC transketolase activity after administration of thiamine
Wet vs dry beriberi
both are precipitated via thiamine (vitamin B1) deficiencies
Dry:
- polyneuropathy
- symmetric muscle wasting
Wet:
- cardiac damage
- edema
- heart failure
Wernicke’s encephalopathy
Acute life threatning condition brought on by thiamine deficiency
- made worse if giving glucose/sugar to patients with thiamine deficiency before the thiamine injection
Symtpoms:
- neurologic issues
- classic triad of:
1) general confusion
2) opthalmoplegia (paralysis of eye muscles)
3) ataxia - treated via thiamine and glucose injections. If not treated, leads to korsakoff syndrome*
What is ataxia?
Neurological symptom that mimics drunken behaviors:
- slurred speech
- incoordination
- shuffling/staggered gate
- falling over/ poor balance
Korsakoff syndrome
Chronic thiamine deficiency syndrome often proceeded by alcoholism
- is the evolved from of wernicke’s ( however you do not always need to get wernicke’s first to have korsakoff. Just all untreated cases of wernicke’s degrades to korsakoff)
Symptoms:
- all symptoms of wernickes encephalopathy
- confabulation (making up memories that didn’t actually happen)
- personality changes
- permanent memory loss
- sometimes is called wernicke-korsakoff syndrome when the medial dorsal nucleus of the thalamus is damaged*
Vitamin B2 (riboflavin) function
Helps generate FAD and FMN molecules which are used in redox (reduction-oxidation) reactions
- “B2 generates 2 ATP”
Vitamin B2 (riboflavin) deficiency
Cheilosis (inflammation and scarring of the lips and corners of the mouth)
Corneal vascularization (chronic blood shot eyes)
“2 Cs of B2”
Vitamin B3 (niacin/nicotinic acid) function
Generates NAD/NADP molecules used in redox reactions
Naturally derived from tryptophan
requires B2 and B6 to generate naturally
often used in hyper-cholesterol (dyslipidemia) since it lowers VLDL and raises HDL
Vitamin B3 (niacin/nicotinic acid) deficiency
Glossitis (inflammation of the tongue)
Also generates pellagra which is the following three symptoms
- Diarrhea
- Dementia
- Dermatitis (around the C3/C4 dermatome)
“3D’s of vitamin B3”
* also hyperpigmentation of sun exposed limbs
Hartnup disease
Autosomal recessive disorder that results in a natural deficiency of tryptophan transporters in PCTs of renal system and enterocytes
- causes decreased reabsorption of vitamin B3 and natural conversation of tryptophan -> niacin
Generates pellagra symptoms
Treatment:
- high protein diet
- nicotinic acid supplements
Vitamin B3 toxicity
Leads to:
- facial flushing
- hyperglycemia
- hyperuricemia
- this is the only other time other than gout that podagra can form*
Vitamin B5 (Pantothenic acid) function
Essential to CoA production and FA synthesis
- CoA can not be produced without vitamin B5
Vitamin B5 deficiency
Diffuse dermatitis
Enteritis
Alopecia
Adrenal insufficiency syndrome
Vitamin B6 (pyridoxine) function
Functions to:
- generate PLP cofactor for liver enzyme production and maintenance (ALT/AST)
- synthesis of glutathione, histamine, and Heme groups
- synthesis of neurotransmitters (NE/epinephrine/serotonin/dopamine/GABA)
Vitamin B6 deficiency
- can be triggered by over use of isoniazid and oral contraceptives*
Symptoms:
- convulsions
- hyper irritability
- peripheral neuropathy
- Sideroblastic anemia
Vitamin B7 (biotin) function
Cofactor for most carboxylation enzymes/reactions
Vitamin B7 (biotin) deficiency
often caused by overconsumption of raw eggs (contains avidin which irreversibly binds biotin) and chronic use of antibiotics
Symptoms:
- dermatitis
- enteritis
- alopecia
“Avidin avidly binds biotin”
Vitamin B9 (folate) function
Synthesizes THF (tetrahydrofolate acid) which is a cofactor in methylation/carbon transfer reactions
Very important in synthesis of purines and pyrimidines found in DNA/RNA
Vitamin B9 (folate) deficiency
Macrocytic and/or megaloblastic anemia
Hypersegmented PMN cells*
increased serum methylmalonic acid levels
Glossitis
Teratogenic (increases chances of neural tube defects) MUST give supplements to mother 1 month prior to contraception and during pregnancy (first 9 months)
NO neurological symptoms
- B12 has the same symptoms, but shows neurological symptoms
Vitamin B12 (cobalamin) function
Cofactor for methionine synthase and methylation of DNA synthesis
Vitamin B12 (cobalamin) deficiency
- usually only occurs in the presence of malabsorption or lack of the terminal ileum. Can also be alcoholic or having gastric bypass surgery*
Symptoms:
- exact same hematologists issues as vitamin B 9 deficiency*
- paresthesia and subacute degeneration of dorsal medial lateral lemniscus pathway
- degeneration fo spinocerebellar tracts
- chronic deficiency = diffuse irreversible nerve damage
- increased serum methylmalonic acid levels
folate supplements can mask hematological issues, but not the neurological issues
Vitamin C (ascorbic acid) function
Antioxidant that also facilitates iron absorption by reducing iron to ferrous (Fe2+) state. (ferric is Fe3+)
Needed for hydroxylation reactions of proline and lysine in collagen synthesis as well
Needed for dopamine -> NE conversion as well
as an ancillary treatment for methemoglobinemia, give vitamin C supplements
Vitamin C (ascorbic acid) deficiency
Scurvy
- swollen gums
- easy brushing
- diffuse petechiae
- hemarthrosis
- anemia
- corkscrew-like hair
weakened immune systems
Vitamin C (ascorbic acid) excess
Nausea/vomiting
Fatigue
Calcium oxalate neprholithiasis
- Increased iron toxicity if occurring in conjunction*
- especially in hemachromotosis patients
Vitamin D function
can be D3 (version found in sunlight, Milk and fish) or D2 ( from plants and yeasts). Irrelevant though since both are converted into 1,25-OH (calcitriol)
Increased intestinal absorption Of calcium and phosphate ( for bone growth)
Increases bone resorption and mineralization
How is vitamin D levels regulated?
PTH and parathyroid glands
1,25-OH natural feedback loop
Vitamin D deficiency
Rickets (Bow-legs)= children
Osteomalacia = adults
- generalized bone pain and muscle weakness
Hypocalcemia tetany
- causes are usually malabsorption, decreased sun exposure, poor diet, chronic kidney disease and liver disease*
- the deficiency is exacerbated in premature births as well
Vitamin D excess
Hypercalcemia and Uria
Loss of appetite
Stupor
common in granulomatosis diseases
Vitamin E (tocopherol/tocotrienol) function
Antioxidant for RBCs and membranes
Vitamin E (tocopherol/tocotrienol) deficiency
Same neurological issues as B12 deficiency (demyelination of posterior columns), but does NOT show hematolgocial disorders seen in B9/12 (segmented PMNs, megaloblastic/sideroblastic anemia)
Acanthocytosis (spur-like cells)
Generalized muscle weakness
There is NO increase in serum methylmalonic acid
Vitamin E (tocopherol/tocotrienol) excess
Enterocolitis in infants
- really the only issue associated, doesnt really hurt adults directly
- can induce malabsorption of vitamin K and its metabolism*
- this exacerbates warfarin’s effect, so must monitor in patients with warfarin
Vitamin K (adione/quinone) function
Activates epoxide reductase which acts as a cofactor for gamma-carboxylation of glutamic acid residues on factors 1/7/9/10 and proteins C/S
- used for proper blood clotting
- is naturally synthesized in gut flora*
Vitamin K (adione/quinone) deficiency
Lowers ability to clot.
- in infants the bleeding time is NOT increased but PTT and PT times are (neonates do not have sterile intestines so they cannot naturally synthesis vitamin K)
- often occurs after prolonged use of broad-spectrum antibiotics
is not in breast milk so neonates are often given vitamin K injections at birth to prevent neonate hemorrhages as a complication of birth
Zinc function
Found in almost all enzymes and is required for them to work
Especially useful in the immune system and formation of transcription factor motif
Zinc deficiency
Delayed wound healing
Suppressed immunity
Male hypogodanism
Decreases male adult facial hair
Dysgeusia (impaired or inability to taste)
Anosmia (impaired or inability to smell)
increases chances of alcoholic cirrhosis of the liver
Very common natural in patients with Acrodermatitis enteropathica*
Acrodermatitis enteropathica
Autosomal recessive disorder that causes defective proteins used in binding zinc properly
- leads to malabsorption and weakened resorption of zinc
Symptoms:
- periorificial dermatitis (dermatitis around the anus, eyes and mouth)
- alopecia
- diarrhea
Treatment:
- give zinc supplements
- use drug Diodoquin (iodoquinol) to treat alopecia and dermatitis
Kwashiorkor syndrome
Protein malnutrition that results in:
- skin lesions and diffuse edema (due to low plasma oncotic pressure)
- liver malfunction and fatty liver
- swollen abdomen
- anemia
“Kwashiorkor results from proteins deficient MEALS”
- Malnutiriton
- Edema
- Anemia
- Liver is fatty
- Skin lesions
Marasmus syndrome
Caloric malnutrition disorder
- all nutrient levels are above deficency levels
Symptoms:
- wide spread muscle wasting
- weight loss
- chronic diarrhea
- sunken eyes
- poor fetal growth/development
- ribs are clearly seen through skin
