BIOCHEM--Nutrition Flashcards
Which vitamins are fat soluble?
A
D
E
K
absorption of fat soluble vitamins depend on ___ and ___
gut and pancreas
Toxicity is more common in fat or water soluble vitamins? why?
fat soluble bc they accumulate and stick around in fat
what can cause fat-soluble vitamin deficiencies?
malabsorption syndromes w/ steatorrha (eg. CF and celiac disease) or mineral oil intake
Other name for B1
thiamine
Other name for B2
riboflavin
Other name for B3
Niacin
Other name for B5
pantothenic acid
“pento”thenic acid
Other name for B6
pyridoxine
Other name for B7
biotin
Other name for B9
folate
Other name for B12
cobalamin
Other name for Vit C
ascorbic acid
all water soluble vitamins are easily washed out of the body except for ___ and ___
B12 and B9
B12 is stored in the ___ for ___
liver for ~3-4 years
B9 is stored in the ___ for ___
liver for ~3-4 months
B complex deficiencies result in ___, ___, and ___
dermatitis, glossitis, and diarrhea
other name for vitamin A
retinol
Functions of Vit A (4)
- antioxidant
- part of visual pigments
- Needed for normal differentiation of epithelial cells into specialized tissues
- Prevents squamous metaplasia
Manifestations of Vit A deficiency (5)
- Night blindness (nyctalpia)
- Dry, scaly skin (xerosis cutis)
- Corneal degeneration (keratomalacia)
- Bitot spots (foamy appearance) on conjunctiva
- Immune suppression
Manifestations of Acute Vit A toxicity (4)
nausea
vomiting
vertigo
blurred vision
Manifestations fo Chronic Vit A toxicity (4)
alopecia
dry skin
hepatic toxicity/enlargement
pseudotumor cerebri
What is required before isoretinoin can be prescribed? why?
- negative pregnancy test
- 2 forms of contraception
BC isoretinoin is teratogenic (cleft palate, cardiac abnormalities)
4 clinical applications of Vit A
- tx measles
- all-trans retinoic acid to tx acute promyelocytic leukemia
- oral isoretinoin to tx severe cystic acne
- topical retinol for wrinkles
food sources of Vit A
liver
leafy veggies
B1: what is the cofactor form?
Thiamine pyrophosphate (TPP)
What general type of enzyme is TPP a cofactor for?
dehydrogenase
Which 4 enzymes is TPP a cofactor for? and what are these enzymes involved in?
- pyruvate dehydrogenase (link glycolysis to TCA cycle)
- 𝝰-ketoglutarate dehydrogenase (TCA cycle)
- transketolase (HMP shunt)
- branched chain keto acid dehydrogenase
“Think ATP: 𝝰-ketoglutarate, Transkeltolase, Pyruvate dehydrogenase”
What is the function of thiamine?
to be a cofactor
what happens if an individual is deficient in Vit B1?
- Impaired glucose breakdown → ATP depletion, worsened by glucose infusion
- highly aerobic tissues (brain, heart) affected first
If you suspect Thiamine deficiency in an alcoholic pt, what must you do first? why?
GIVE THIAMINE before dextrose to decrease risk of Wernicke encephalopathy
How do you diagnose B1 deficiency?
↑ in RBC transketolase activity s/p B1 administration
Which 3 syndromes can B1 deficiency cause?
- Wernicke-Korsakoff Syndrome
- Dry Beriberi
- Wet Beriberi
“Spell Ber1Ber1 to remember Vit B1”
Wernicke-Korsakoff Syndrome: manifestations
Classic Triad of confusion, opthalmoplegia, ataxia + confabulation, personality change, permanent memory loss
What part of the brain is damaged in Wernicke-Korsakoff Syndrome?
medial dorsal. nucleus of thalamus, mammillary bodies
Dry Berberi: manifestations
polyneuropathy
symmetrical muscle wasting
Wet Beriberi: Manifestations
high-output cardiac failure (dilated cardiomyopathy)
edema
What is the function of B2
components used as cofactors in redox reactions
succinate dehydrogenase reaction in TCA
What are the cofactor forms of B2
- FAD and FMN
- “FAD and FMN are derived from riboFlavin (B2 = 2ATP)”
Manifestations of B2 deficiency
- Cheilosis: inflammation of lips, scaling and fissures at corners of mouth
- Corneal vascularization
B3: functions
- Constituent of NAD+ and NADP+ (used in redox reactions)
- Derived from tryptophan
- Synthesis requires B2 and B6
- “NAD derived from Niacin”
- “B3 = 3 ATP”
B3: deficiency manifestations
- glossitits
2. pellagra, if severe
What is Pellagra?
- Diarrhea
- Dementia (also hallucinations)
- Dermatitis: C3/C4 dermatologists circumferential “broad collar” rash [casal necklace] and hyper pigmentation of sun exposed limbs
B3: excess manifestations
- Facial flushing
- hyperglycemia
- Hyperuricemia (podagra/gout)
What causes the facial flushing that presents in B3 excess?
How can you avoid it?
induced by prostaglandin; avoid by taking aspirin w/ niacin
B3: clinical application
used to tx dyslipidemia; lowers VLDL and raises HDL
What else can cause pellagra?
- Hartnup Disease
- malignant carcinoid syndrome
- isoniazid
Hartnup Disease:
- inheritance
- problem
- sx
- tx
- AR
- Deficiency of neutral amino acid transporters in proximal renal tubule cells and enterocytes → neutral aminoaciduria and ↓absorption from gut→↓tryptophan for conversion to niacin
- Pellagra: Diarrhea, Dementia, Dermatitis
- High protein diet and Nicotinic acid
B5: function
Essential component of coenzyme A (CoA) and fatty acid synthase
What is CoA?
CoA is a cofactor for acyl transfers
B5: deficiency manifestations
Dermatitis
Enteritis
alopecia
Adrenal insufficiency
B6: functions
1. needed for synthesis of:
Cystathionine
Heme
Niacin
Histamine
Serotonin
Epinephrine
Norepinephrine
Dopamine
GABA
2. converted to pyridoxal phosphate (PLP)What is PLP and what is it used for?
a cofactor used in:
- Transamination (eg, ALT and AST)
- Decarboxylation reactions
- Glycogen phosphorylase
Manifestations of B6 deficiency
convulsions
hyperirritability
Peripheral neuropathy: deficiency inducible by isoniazid and OCP
Sideroblastic anemias: due to impaired hemoglobin synthesis and iron excess
Function of B7
Cofactor for carboxylation enzymes that add a 1-carbon group
Which 3 specific enzymes need B7 as a cofactor?
Pyruvate carboxylase
Acetyl-CoA carboxylase
Propionyl-CoA carboxylase
True or False: B7 deficiency is relatively rare.
true
Manifestations fo B7 deficiency
Dermatitis
Enteritis
Alopecia
What can cause B7 deficiency?
Caused by antibiotic use or excessive ingestion of raw egg whites
“Avidin in egg whites avidly binds biotin”
Functions of B9
- Important for synthesis of nitrogenous bases in DNA and RNA
- Converted to tetrahydrofolic acid (THF)
What is tetrahydrofolic acid (THF)?
coenzyme for 1-carbon transfer/methylation reactions
What 2 conditions can cause B9 deficiency?
- alcoholism
2. pregnancy
What are examples (3) of drugs that can cause B9 deficiency?
phenytoin
sulfonamides
methotrexate
What are the manifestations of B9 Deficiency?
- Hypersegmented polymorphonuclear cells
- glossitis
- macrocytic, megaloblastic anemia
- NO neuro symptoms
What labs will you find in B9 deficiency?
↑ homocysteine
normal methylmalonic acid
sources of B9
Leafy green veggies
“FOLate from FOLiage”
where is B9 absorbed in GI
Jejunum
where is the small reserve pool of B9?
liver
Clinical application of B9
Supplemental material folic acid atlas 1 month prior to conception and during preg to ↓ risk of neural tube defects
Function of B12
- Cofactor for Methylmalonyl Co-A mutase and methionine synthase
- Important for DNA synthesis
What is the function of methionine synthase
transfers CH3 groups as methylcobalamin
What can cause B12 Deficiency?
malabsorption,
lack of intrinsic factor,
absence of terminal ileum,
insufficient intake
Source of B12
Animal products,
Synthesized only by microorganisms
Manifestations of B12 deficiency
- Macrocytic, megaloblastic anemia
- Hypersegmented PMNs
- Paresthesias and subacute combined degeneration (degeneration of dorsal columns, lateral corticospinal tracts, and spinocerebellar tracts) due to abnormal myelin
- ↑ serum homocysteine and methylmalonic acid levels
- Secondary folate deficiency
- If prolonged → irreversible nerve damage
4 functions of ascorbic acid
- Antioxidant
- Facilitates iron absorption by reducing it to Fe2+ state
- Necessary for hydroxylation of proline and lysine in collagen synthesis
- Necessary for dopamine β-hydroxylase (converts dopamine to NE)
Manifestations of Vit C deficiency
- scurvy
2. weakened immune response
what are some symptoms of scurvy
Swollen gums Bruising Petechiae anemia Poor wound healing Perifollicular and subperiosteal hemorrhages “corkscrew hair”
Manifestations of Vit C excess
- N/V/D
- Fatigue
- Calcium oxalate nephrolithiasis
- ↑ iron toxicity in predisposed individuals by ↑ dietary iron absorption
Source of Vit C
fruits and veggies
Clinical applications of Ascorbic acid
Ancillary tx for m methemoglobinemia by reducing Fe3+ to Fe2+
What are the 4 forms of Vit D, and how do we get them?
- D3: cholecalciferol; from being in the sun
- D2: ergocalciferol; from eating plants
- 25-OH D3 (storage form); made from conversion of D3 and D2 in the liver
- 1,25-(OH)2 D3 (calcitriol): active form s/p conversion in the kidney
Functions of Vit D
↑ intestinal absorb of Ca2+ and phosphate
↑bone mineralization at low levels
↑increase bone resorption at higher levels
What causes Vit D deficiency?
Caused by malabsorption, ↓ sun exposure, poor diet, CKD
What exacerbates Vit D deficiency?
pigmented skin and premature birth
Manifestations of Vit D deficiency
Rickets in children
Osteomalacia in adults
Hypocalcemia tetany
Manifestations of Vit D excess
Hypercalcemia
Hypercalciuria
Loss of appetite
Stupor
Why might you see Vit D excess in granulomatous disease?
↑activation of vit D by epithelioid macrophages)
Clinical applications of Vit D?
Give oral vit D to breastfeeding babies
Two other names for Vit E
Tocopherol
Tocotrienol
Function of Vit E
Antioxidant: protests RBCs and membranes from free radical damage
What can High-dose supplementation of Vit E cause?
altered metabolism of vitamin K→enhanced anticoagulation effects of warfarin
Manifestations of vit E deficiency
- Hemolytic anemia
- Acanthocytosis
- Muscle weakness
- Posterior column and spinocerebellar tract demyelination
Neuro presentation of vit E deficiency is similar to what other deficiency?
What are the differences?
Neuro presentation can look like B12 deficiency, but w/o megaloblastic anemia, hypersegmented PMN, or ↑ methylomalonic acid levels
Risk of ___ in ___ if excess of vit E
Risk of enterocolitis in infants
4 other names that may be used to refer to Vit K
Phytomenadione
Phylloquinone
Phytonadione
Menaquinone
the active form of vit K is the ___ form.
which enzyme activates vit K?
the active form of vit K is the reduced form.
vit K reduced by epoxide reductase
activated vit K is the cofactor for what process?
Reduced form is a cofactor for the ɣ-carboxylation of glutamic acid residues on various proteins needed for blood clotting
Vit K is necessary for what?
Necessary for the maturation of clotting factors II, VII, IX, X, proteins C and S
Which drug blocks the vit K-dependent synthesis of clotting factors?
Warfarin
how might a deficiency of vit K present? why?
- Neonatal hemorrhage w/ ↑ PT and ↑aPTT, but normal bleeding time.
- Neonates have sterile intestines and cannot synthesize vitamin K
- can also occur after prolonged use of broad-spectrum antibiotics
what is the source of Vit K?
synthesized by intestinal flora
Clinical application of Vit K
injections given to neonate at brith to prevent hemorrhagic event.
Breast milk is supposed to be super cool and awesome, but it is missing a nutrient. Which one?
Vit K
what do we even need zinc for?
- essential for the activity of 100+ enzymes
2. Important in the formation of zinc fingers (a transcription factor motif)
manifestations of zinc deficiency
Delayed wound healing Suppressed immunity hypogonadism ↓ adult hair (armpit, bear, pubes) dysgeusia (distortion of the sense of taste) Anosmia (loss of sense of smell) Acrodermatitis enteropathica
zinc deficiency may predispose individuals to what?
alcoholic cirrhosis
what is the difference between the deficiencies in Kwashiorkor and Marasmus?
Kwashiorkor: protein malnutrition
Marasmus: Complete malnutrition: deficient in calories, but no nutrients are entirely absent
what would a child w/ Kwashiorkor look like?
emaciated limbs, but a swollen abdomen
Why do kids w/ Kwashiorkor look the way they do?
skin lesions and abdominal edema are due to ↓ plasma oncotic pressure, and liver malfunction
What causes the liver malfunction in kwashiorkor?
fatty change bc ↓apolipoprotein synthesis
pneumonic:
“Kwashiorkor results from protein deficient MEALS”
Malnutrition Edema Anemia Liver (fatty) Skin lesions (hyperkeratosis, dyspigmentation)
Marasmus results in ___ ___
Muscle wasting
True or False: Marasmus causes edema
false
