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1. GI 3 > biochem of vitamins > Flashcards

biochem of vitamins Flashcards

1
Q

Water soluble vs fat soluble

A

Water soluble (B1 thiamin, B2, riboflavin, B3 niacin, Pantothenic acid B5, Biotin B7, B6 pyrodoxin, Folate B9, B12, Vit C)- rapidly excreded B12 liver stores

Fat soluble: Vit A (3 retinoids), Vitamin D, Vitamin E (tocos), Vitamin K (phyllo, mena quinones), need bile, lipases and dietary fat, toxicity more common (esp starge fat), Eand K, malabsorption syndromees- Cystic fibrosis, pancreatic exocrine insufficiency, celiac disease, mineral oil intake

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2
Q

Vitamins involved in energy metabolism

A

B1, B2, Pantothenic acid, Biotin, B6 (B1, 2 3 5 6 7)

Glucose–> Glycolysis–> TCA (ATP production): B1 (TPP), B2 (FADH2), B3 (NADH), B5 (coenzyme A)

Fatty acids–> Beta oxidation: B2 (FAD), B3 (NAD), B5 (coenzyme A)

Gluconeogenesis: Biotin (B7), B3 NAD

Everything with Proteins- B6

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3
Q

Thiamin Vitamin B1

A

Active coenzyme form - Thiamin pyrophosphate TPP

Needed for PDH, BRAIN needs glucose

TCA akgdh also needs b1

GLycolysis

PDH needs B1, B2, B3, B5, lipoic acid (glycolysis and TCA)

HMP Transketolase (PPP) Also needs B1– Provides NADPH, and Ribose for fatty acid and cholesterol synthesis, maintain reduced GSH for antioxidant protection, Nicleotide synthesis

RBCs, eyes oxidant stressors

Metabolism of BCAA requires TPP B1, Maple syrup Urine disease (defect in BCaKA DH),

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4
Q

B 1 deficiency

A

Classic deficiency0 Beri Beri- (B1B1), i cant i cant, neuropathy

Dry beriberi- symmetrical impairment of sensory and motor functions of extremities esp lower extremitiry, symmpetrical muscle wasting

Wet/ edamatous beri beri- cardiomyopathy, high output CF, edema

Rice bran

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5
Q

Wernicke-Korsakoff syndrome

A 
B1 deficiency
Wernicke Encephalopathy (Acute life threatening)- confusion, ophalmoplegia/nystagmus, ataxia

Korsakoff syndrome (chronic neurologic condition)- confabulation, personality change, memory loss, especially anterograde amnesia

Alcoholism induced- poor diet, impaired intestinal absorption, impaired cellular utilization of thiamin

Malnourished: HIV/AIDs, cancer, hyperemesis, long term dialysis, diuretics

GIve B1 and Magnesium!!!!

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6
Q

Assessment of Thiamin /B1 status

A

RBC transketolase assay: measure RBC Transketolase activity, TPPbinding should be 85%

then add TPP should not shift

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7
Q

Riboflavin B2

A

riboFlavin/b2 = Fmn/ Fad active coenzyme forms

Redox cofactors, can participate in either one or 2 electorn redox rxns,

TCA cycle, and ETC, in FA b- oxidation
GSH reductase

Deficiecny energy metabolism, aminoacid metabolism and lipid metabolism, general and specific symptoms

Corners of mouth, phototherapy for neonatal jaundice breaks down riboflavin in infants so need B 2 supplementation, will affect RBC GSHr first

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8
Q

Niacin- B3

A

sources- dietary Niacin ( nicotinic acid in plants or nicotinomide in animal tissues)
Synthesized from tryptophan!

NAD, NADH - niacin NAD and NADPH

Glycolysis, TCA, FA b-oxidation, need NAD

ETC provides NAD

FAsynthesis and cholesterol synthesis need NADPH

HMP path gives NADPH

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9
Q

Niacin B3 deficiency

A

Pellagra- 4 Ds
Dermatitis, diarrhea, dementia, death

US
in dev countries- alcoholism

Hartnup disease- decreased Tryptophan for B3 synthesis

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10
Q

Pantothenic acid B5

A

PAN-availability, Widely distributed in nature and foods, deficiency is rare,
active forms- CoEnzyme A (CoASH, CoA), Acyl Carrier protein (ACP)

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11
Q

Biotin B7

A

food bound

Broadly distributed in many foods
Intestinal bacteria synthesize small amounts of biotin
Biotin bound to protein in foods and bound endogenously to carboxylase enzymes

Biotindidase releases biotin from dietary proteins and carboxylase enzymes for recycling of biotin
Holocarboxylase synthetase links biotin to carboxylase enzymes to obtain fully functional enzymes

Multiple carboxylase deficiency: autosomal recessive genetic defects in: Biotinidase gene, holocarboxylase synthetase gene

Many cases respond to high dose biotin therapy

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12
Q

Biotin B 7 Functions

A

Carboxylation reactions: Gluconeogenesis Pyruvate carboxylase

FA synthesis AcCoA carboxylase

BCAA (ile, val, leu) and odd chain fatty acid catabolism (Propionyl CoA carboxylase), (B- methylcrotonyl- CoA carboxylase (Leu)

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13
Q

Biotin B7 deficiency

A

Rare, Avidin in raw eggwhites binds dietary biotin making it unavailable

Rare autosomal recessive disorder- multiple carboxylase deficiecy, respond to biotin

Dry skin intractable seborrheic dermatitis

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14
Q

Pyridoxine- b6

A

active forms- PALP, PLP, PAMP, PMP
Proteins!
metabolic interconversions need Zinc, FMN- B2 riboflavin

transaminations- amino acid catabolism, non essential amino acid synthesis

histamine, NT synthesis

Homocysteine metabolism
homocystinuria type 1- due to genetic mutations in this enzyme, .5 of cases respond to high dose B6 (eye skeletal and CNS, vasculature, thromboembolism)- increased urine and plasma

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15
Q

VIT B6 deficiency

A

homocysteinemia, homocystinuria 1, increase in urinary homocystine, inc. plasma homocysteine, inc. plasma methionin, thromboembolism

B6 deficiency inducible by isoniazid, oral contraceptives

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16
Q

Nutrients that influence cell (DNA replcation, Single carbon metabolism and methylation reacitons

A 
Folate - B9 (Plant foods)
Vitamin B12 (only animal foods, neurological
17
Q

Folate Vitamin B9

A

Functions- DNA replication and cell replication, Single carbon metabolism

Maintain adequate amounts of methionein (SAM) for numerous methylation reactions
Methylation of DNA- epigenetic regulation of gene expression during fetal development and beyond

Influences homocystein levels, embryonic neural tube formation, interacts with B 12 and B6

food folate- folate conjugase removes polyglutamate tail, inhibited by ALCOHOL
DHFreductase, two step rxn inhibited by methotrexate

Purine, thymin and methioning synthesis

18
Q

folate deficiency

A

Nuclear hypersegmentation of PMNs, Macrocytic anemia (B12 deficiency) megaloblastic changes, DNA Strand breaks

increased risk of neural tube defects, elevated homocysteine levels, DNA instability, dysregulated gene transcription- implication for cancer risk, low folate –> increased risk of several cancers, HPV women

ALcohol abuse

Folate status- urinary FIGLU (histidine Load)

19
Q

Vitamin B 12 (cobalamin)

A

Contains Cobalt- active forms- methylcobalamine, deoxyadenosylcobalamin

Synthesized by intestinal bacteria, is enterohepatically circulated, found in animal foods

only found in animals
Methionine Synthase (SAM pathway for methylation reactions, recycling folate, homocysteine --> methionen

Methyl malonyl mutase- Increased MMA is specific for B12

GRAMA - neuro stuff

20
Q

Vit B 12 deficiency

A

Dietary Deficiency- B12 only in animal foods, vegan diets

Stomach (inadequate HCl, IF), Atrophic gastritis (affects 30% of elderly, incidence increases w/ age), pernicious anemia, longterm proton pump inhibition, gastrectomy/ gastric bypass

metformin , pacreatic insufficiency,

21
Q

vitamin E- tocopherols

A 
8 forms
good antioxidant
localized to membranes
fat soluble- unsaturated fatty acids protection against oxidation
Aging smoking, etc

Chain breaking antioxidant

22
Q

Vitamin E dependence of vitamin C

A

Vitamin C can regenerate Vitamin E

23
Q

Severe deficiency of vitamin E

A

Hemolytic anemia (premature infants), premies miss the fat/fat soluble vitamin transfer that occurs very late in pregnancy

Neuro symptoms- impaired balance/ coordination (ataxia), peripheral neuropathy, myopathy, pigmented retinopathy

can be caused by Fat malasorption (biliary obstruction, cystic fibrosis, cholestatic liver disease, pancreatitis)

CVD , cognitive decline, macular regen

24
Q

Vitamin C (ascorbic acid)

A

Antioxidant, enhances iron absorption
Post translationonal modification of collagen synthesis- scurvy

bruise, gums, hair skin

Tissues concentrate vitamin C esp brain and adrenals

cigarette smoking will decrease vit C

collagen , wound healing

25
Q

vitamin A Retinoids forms and functions

A

retinol: reproduction, major transport form (RBP), Storage form as retinyl esters, major food form, Spermatogenesis, treats measles, severe acne

Retinal-vision (rhodopsin)

Retinoic acid- normal epithelial cell differentiation/ maintenance, embryonic developent, immune function, treats acute promyelocytic leukemia

needs Zn, full form from animals

26
Q

Vitamin A deficiency

A

Decreased resistance to infection, impaired immunity
Increased morbidity and mortality, impaired immunity occurs before eye symtomps

Stunted growth, rough skin, thick dry scaly skin, follicular hyperkeratosis, Night blindness (nyctalopia), Bitots spots, xeropthalmia, Blindness, worldwide leading cause of irreversible blindness

27
Q

Vitamin A toxicity

A

Nausea, vomiting, headache, irritability, myalgia, arthralgia
Dry lips, dry skin, mucous membranes, alopecia
Teratogenic effects (craniofacial, CNS, Cardio-vascular, thymus malformation- isotretinoin can mess with kids

Toxicity with active fully formed vit A (animal products), B- carotene is not associated with vitamin A toxicity

28
Q

vitamin D

A

cholesterol, its a hormone, in skin, light partially activates it

D3 better- liver partially activates it

Calcitriol 1, 25 (1 alpha hydroxylase)
Rickets ets

Function- sunlight and food, gene expressor, RXR (vitamin A)

Intestine increases absorption of Ca, P, bone mineralization, immune cells, induces differentiation, tumor mucroenvironment- tumor necrosis

Muscle maintanence, cell differentiation, immune modulation

29
Q

Vitamin D deficiency

A

Rickets, osteomalacia, msk pain, muscle weakness, hypocalcemic tetany, long term: osteoporosis

cod liver oil

Toxicity- hyper calcemia, calciuria

30
Q

Vitamin K

A

Diet- phylo quinones- green leafy plant foods, menaquinones animal foods

Intestinal bacteria synthesize vit K

Liver storage and site of vit K dependent coagulation protein synthesis

Koragulation

Calcium and vitamiin K in bone osteocalcin post translational y carboxylation of glutamte GLU residues in proteins

Deficeicny- bleeding issues, Antibiotics, neonatal hemorrhage

1. GI 3 (13 decks)

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