3.02 Vitamins Flashcards by Sarah B

General role of vitamins?

Coenzymes
Hormones
Electron donors

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The active form of thiamine in our cells?

TPP thiamine pyrophosphate

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TPP is an essential cofactor for what enzymes?

PDH - pyruvate dehydrogenase
AKDGH - alpha KG dehydrogenase (TCA Cycle)
BCKD - branched chain a KG dehydrogenase
Transketolase

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Hypoglycemia with moderate fasting, apathy, muscle weakness (2-3 weeks) are acute signs of?

Thiamine deficiency

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Who is at risk of thiamine deficiency?

Chronic alcoholics
Food staple white polished rice
Certain raw fish or fern over consumption (enzyme)

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Classic disease of thiamine def associated with: muscle atrophy, weakness, motor and sensory neural degeneration, and peripheral neuropathy?

Dry BeriBeri

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Classic disease of thiamine deficiency associated with edema, eye paralysis, and CHF?

Wet BeriBeri

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What are some patient precipitating events to developing Wet BeriBeri?

Extreme weight loss coupled with athletic training
(severe physical exertion + high carb intake)

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Infantile BeriBeri?

Edema, convulsions, Heart fail, cyanosis

Present similar to maple syrup disease (impaired BCKD)

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Wernicke Korsakoff Syndrome?

Thiamine deficiency from chronic alcoholism
(Bad diets + alcohol block absorption at intestinal and reabsorption at kidney)

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Mental confusion, gait ataxia, nystagmus, ophthalmoplegia?

(Will continue to act “drunk” despite having nothing to drink)

Wernicke’s Encephalopathy

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Irreversible progression of Wernicke’s that causes sever memory impairment, confabulation, and difficulty morning new memories?

Korsakoff Syndrome

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What do you use to treat Wernicke’s + Korsakoff?

Thiamine Propyl Disulfide (TPD)

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Thiamine response megaloblastic anemia mutation?

THTR1 transporter mutation

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What is TPD?

Hydrophobic form of thiamine that can freely diffuse across membranes

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What is likely responsible for the pathology in thiamine-responsive megaloblastic anemia?

Impaired transketolase activity
(To make ribose-5-P)

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What is the defect in thiamine responsive maple syrup disease?

BCKD defect = reduced affinity for thiamine

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Do you need TPD to treat thiamine responsive maple syrup disease?

Nah, pharm levels supplementation should be enough

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Where is the genetic defect in biotin thiamine responsive basal ganglia disease?

THTR2 mutations (@brain, liver, etc.)

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Signs of biotin thiamine responsive basal ganglia disease?

Seizures, encephalopathy, confusion
AR inheritance

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Riboflavin (B2) is broken down into what two major compounds?

—> riboflavin kinase
Flavin Monoonucleotide (FMN)

—> FAD Pyrophosphorylase
Flavin Adenine Dinucleotide (FAD)

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What is the role of riboflavin (B2)?

Cofactor for acyl-coA dehydrogenases and ETC enzymes

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What are particularly good sources of riboflavin in diet ? Especially since most come in FAD form that require no extra conversion step?

Milk and eggs

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Muscle weakness, fatigue, lethargy, cheilosis, angular stomatitis, corneal vascularization signs of?

Riboflavin Deficiency aka Ariboflavinosis (Rare)

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How are riboflavin newborns treated?

Hyperbilirubinemia

What are the riboflavin transporters?

RFT1 (placenta/intestine) RFT2 (testes/intestine) RFT3 (brain)

What riboflavin transporter may be defective if it can lead to a miscarriage?

RFT1

What riboflavin transporter may be defective if it present major CNS symptoms in relatively young people like limb weakness, distal wasting, gait ataxia, optic atrophy?

RFT3

What riboflavin transporter may be defective if it can lead to infertility in males?

RFT2

Riboflavin responsive mitochondrial disease (RRMD) represents what ?

Any energy metabolism disorder that an be fixed with pharm dose of riboflavin

What can cause RRMD?

riboflavin kinase or FAD pyrophosphorylase deficiencies

RRMD versus MADD?

Essential same disorder but MADD from deficiencies of enzymes from acrylic-coa dehydrogenases (ETC involved)

What vitamins tend to be water soluble?

B complexed/B Vitamins

Niacin (B3) role?

Precursor to NAD(P)+/NADPH

Major forms of niacin in body?

Nicotinic acid or nicotinamide

Dermatitis, diarrhea, dementia, death are signs of?

Chronic deficiency of niacin

Muscle weakness, anorexia, indigestion are acute signs of ?

Niacin deficiency aka Pellagra

At risk individuals for pellagra?

Alcoholics Anti-TB drug Isoniazid Whole corn based diets and nothing else Low tryptophan in diet

What can be effective managing hyperlipidemia at pharm doses because it can inhibit lipolysis, slow product of ApoB100, and inhibit DGAT enzymes that are all involved in lowering VLDLs (and TAG) in blood ?

Niacin (B3)

Long term high dose niacin can lead to what?

Liver damage Monitor patients with LFTs

Biotin role?

Covalent bonded cofactor for 5 carboxylases (TCA cycle, FA biosynthesis, Acetyl-coA production, etc.)

What is an enzyme in raw egg whites that has a high affinity for biotin and can lead to its malabsorption?

Avidin

What binds biotin covalently to its carboxylases?

HCS Holocarboxylase Synthetase

Multiple carboxylases deficiency disorder (MCDD)?

Deficiency of HCS or biotinidase NOT carboxylases enzymes

Severe metabolic acidosis, fasting hypoglycemia, lethargy and poor feeding, vomiting, hypotonia, seizures skin rash, alopecia, developmental delays are signs of?

MCDD Mult Carboxylase Def Disorder

What protein is responsible for the recycling of biotin in the body?

Biotinidase

Panthonic Acid (B5) role?

Acyl prosthetic group for CoA

Although deficiency is extremely rare it can manifest as headache, fatigue, irritability, restlessness, bad sleep, nausea/vomiting, numbness or burning in hands/feet, muscle cramps?

Panthenoic acid (B5)

Vitamin B6 role?

Cofactor for a bunch of enzymatic reactions (diverse) All aminotransferases (AST/ALT)

Major form of vitamin B6?

Pyridoxal phosphate (PLP)

Although rare signs may include microcytic anemia, skin rashes/dermatitis, cheilitis, glossitis, fatigue, lobe wheezy, neuro signs, peripheral neuropathy, impaired immunity, seizures?

Vitamin B6 deficiency

What water soluble vitamin poses the highest toxicity risk?

Vitamin B6

What does a Vitamin B6 toxicity present as?

Sensory neuropathy

Crucial player in “one carbon” metabolism in humans important especially for making DNA nucleotides?

Folate

Folate structure features?

Pteridine ring PaBA Ploy-glutamate Tail/Glu residues

What reaction allows folate to be functional/active?

DHF —> THF By *DHFR*

What are the forms of activated THF?

N10 formyl THF N5,10 methyl THF N5 methyl THF

Key enzymes in the folate metabolic pathway loop?

DHFR MTHFR HMT

What kind of anemia associated with folate deficiency?

Megaloblastic anemia

Why is MTHFR an important part of that folate trap?

irreversible step N5-methyl THF is made

What is the subtle distinction between a folate and B12 deficiency leading to megaloblastic anemia?

folate - not enough molecules to make DNA nucleotides B12 - not enough functional folate created

B12 deficiency affects what part of folate synthesis?

HMT is inactive and can't convert N5-methyl THF to THF

Why do RBCs get bigger in megaloblastic anemia?

They have trouble dividing (folate/B12 def) but protein synthesis is unaffected so they keep growing

What is elevated in megaloblastic anemia?

serum homocysteine

What are the risk factors for folate deficiency?

Pregnancy demand vs. supply Poor intestine absorption Alcoholism Methotrexate

Why is B12 the largest vitamin so far? Its structure?

Cobalt at the center of the ring: - methylcobalamin - adenosylcobalamin - cyanocobalamin

What 2 enzymatic reactions is B12 necessary for in our bodies?

HMT Methylmanoyl-coA mutase

What happens once cobalamin reaches the small intestine?

Human R binder replaced by intrinsic factor to be absorbed by enterocytes (cubulin receptor) at the ileum

What is achlorhydria?

condition inability to sever animal R binder (protein) from B12 with stomach acid/pepsin that makes it unable to be digested (can't free it to switch out to human R binder)

What does B12 bind to within enterocytes to be transported through portal blood to liver?

TCII

In a B12 deficiency, what does the accumulated methylmalonyl-coA get hydrolyzed into that shows up in blood and urine?

MMA (methylmalonic acid)

What is the form of B12 related to the TCA cycle/methylmalonyl-coA mutase reaction?

adenosyl-Cbl

How could you tell a B12 from a folate deficiency with a blood test?

elevated homocysteine = both elevated MMA = B12 def

What are some clinical distinctions between a B12 and folate deficiency?

peripheral neuropathy in B12 neural tube defects with folate

What are some common causes of B12 deficiency?

strict vegetarian excessive antacid use atrophic gastritic/H.pylori microbial proliferation chronic alcoholism pernicious anemia idiopathic/age-related exocrine pancreatic deficiency

What is the role of Vit C?

electron donor (Vit E) cross link collagen triple helices catecholamine synthesis antioxidant (can backfire)

What is the Vit C fully reduced version?

Ascorbate (AscH-)

What is the Vit C fully oxidized version?

Dehyroascorbate (DHA)

Excessive Vitamin C may backfire its role as antioxidant by fueling what reaction?

Fenton reaction (ferrous iron byproduct fed into this to create hydroxyl radicals)

Bleeding gums, easy bruising, poor wound healing, impaired immunity, swollen joints, and depression are signs of?

Vit C deficiency (Scurvy)

What are some potential risk of Vit C overuse?

GI disturbances, headache and nausea, kidney stones, oxidative damage (especially if iron high)

Vitamin A is collectively referred to as?

retinoids (includes B carotene= a precursor)

What is the active form of Vit A that acts as a hormone?

ATRA aka Retinoic Acid

What kind of Vit A is circulating in our blood or later further put into storage form?

Inert Retinol (vitamin A)

What the precursor to Vitamin A that can undergo oxidation to become ATRA (irreversible) or be reduced into Retinol (reversible)?

Retinal

Where is B carotene converted into retinal?

enterocytes (ONLY)

What forms of Vitamin A do we get from diet?

B carotene and retinyl esters

Where is most of the Vit A stored in the body?

liver and adipose tissue

What is needed for retinol to move around blood to get to tissues?

RBP retinol binding proteins

Night blindness is associated with a deficiency of what enzyme? Why?

Vitamin A 11-cis retinal is part of visual pigment rhodopsin

What protein is necessary to get retinoic acid (hormone) inside a cell to be carried into the nucleus?

CRABP cellular retinoic acid binding protein

How do RAREs (RA Response Elements) usually behave when retinoic acid is not present?

RXR and RAR are bound on DNA and they recruit corepressor proteins to inhibit gene expression

Follicular hyperkeratosis and xeropthalmia/Bitot spots are signs of?

Vitamin A deficiency

What vitamin has the highest toxicity (water and fat-soluble)?

Vitamin A

Bone malformations, increased ICP, headaches, liver damage, blurred vision, and birth defects if consumed in access during pregnancy are signs of?

Vit A toxicity

Why is Vitamin A toxicity especially difficult to treat?

fat solubility means you mean extensive liver/kidney to clear and that can take months

What is the most common form of Vitamin D in supplements?

cholecalciferol (D3)

What kinds of Vitamin D are consumed by diet?

D2 and D3

What is the precursor to cholecalciferol formation from sunlight exposure?

7-dehydocholesterol

What is cholecalciferol converted to in the liver and kidneys respectively?

liver - calcidiol --> kidneys ---> calcitriol

PTH or decreased plasma phosphate acts on what enzyme to convert calcidiol to calcitriol in the kidney?

1a-hydroxylase

Vitamin D role?

stimulates intestinal Ca+ absorption stimulates renal Ca2+ reabsorption and decreases excretion bone mineralization immune cell differentiation anti-cancer effects

What enzyme is a signal to inactivate Vitamin D (calcitriol) and a deficiency of it could lead to hypercalcemia?

24-OHase

Fatigue, tiredness, bone pain and weakness, frequent illness or infection, muscle weakness, depression, and mood changes associated with?

Vitamin D deficiency

Long-term risk of Vit D deficiency?

Rickets, osteomalacia, osteoporosis slow wound healing, increased risk for breast/colon/prostate cancers

What are risks of hypervitaminosis of Vitamin D?

hypercalcemia, damage to soft tissue, bone

only true Vitamin E?

a-tocopherol

Role of vitamin E?

prevent lipid peroxidation (radicals that form) in our cell membranes

What happens when there is a a-tocopheroxyl radical?

It is stable so not an inherent threat and its regenerated back to Vitamin D via Vitamin C

What cycle does Vitamin C use to regenerate Vitamin D?

thiol cycle

Some nutrient-nutrient interactions?

Vit C and Vit E Vit C and Vit A Vit C and Vit E

Without adequate what is vitamin E "dead in water"?

Vit C

necrotizing myopathy and hemolytic anemia are associated with what?

Vit E deficiency

Common causes of Vit E deficiency?

rarely diet probably malabsorption problem

a-TTP deficiency

Vit E accumulates in liver causing functional deficncy

Vitamin K role?

critical cofactors for clotting factors GGCX enzyme VKOR and Warfarin

What enzyme is essential for the activated form of Vit K to create clotting factors

VKOR

Common causes of vitamin K deficiency?

Diet rare, fat malabsorption disorders

widespread hematomas and bleeding, hemorrhagic disease of the newborn?

Vit K Deficiency

3.02 Vitamins Flashcards

(119 cards)