HN exam 3

Selenocysteine

considered the 21st amino acid, there is a codon that directs the insertion of selenocysteine into selenoproteins

catalase

converts hydrogen peroxide (an ROS) to water and oxygen - uses Iron (Fe) as a cofactor

superoxide dismutase

converts superoxide to peroxide (neutralizes superoxide which is a ROS) - uses copper, zinc, and manganese for cofactors

Which of the following is not a reason that alcoholics develop Wernicke-Korsakoff Syndrome? a) Excretion of more thiamin b) Decreased hepatic thiamin pyrophosphate formation c) Drinking alcohol instead eating foods containing thiamin d) All of the above contribute

d) all of the above are reasons that contribute to Wernicke-Korsakoff Syndrome

Which of the following is not a function of biotin? a) Histone biotinylation b) Gluconeogenesis c) Amino acid breakdown d) Biotin is needed for all of these functions e) Fatty acid synthesis

d) biotin is needed for all of these functions

enzymes that metabolize thyroid hormone

deiodinases - there are three (type 1, 2, and 3) that are selenoenzymes

Dietary guidelines vs Dietary reference intake (DRI)

dietary guidelines: provide qualitative advice to the public about diet and chronic disease prevention and maintaining health. DRIs: provide quantitative advice to professionals about amounts of nutrients or food components to be of benefit.

synthetic alpa-tocopherol

dl-alpha-tocopherol - racemic (equal) mixture of all the different possibilities

Which of the following is not a function of PLP? a) Transamination b) Glycogenolysis c) Heme Synthesis d) Niacin Synthesis e) Glycolysis

e) Glycolysis

Which of the following is/are epigenetic modification(s) that results in decreased gene transcription? a) Both DNA demethylation and histone acetylation b) DNA demethylation c) Histone acetylation d) DNA methylation e) Both DNA methylation and histone deacetylation f) Histone deacetylation

e) both DNA methylation and histone deacetylation - both result in decreased gene transcription

Which of the following is not a condition that people commonly take high supplemental vitamin B6 levels that might result in toxicity symptoms? a) Carpal Tunnel Syndrome b) Premenstrual Syndrome c) Morning Sickness d) All of the conditions are ones that supplemental vitamin B6 is taken for e) Eye dryness

e) eye dryness - not a condition that people usually take vitamin B6 for

Which of the following is manganese not a cofactor for? a) Urea cycle enzyme b) Superoxide dismutase c) Gluconeogenesis enzymes d) Proteoglycan enzymes e) Glycolysis enzyme

e) glycolysis enzyme

EAR

estimated average requirement - requirement for 50% of the population - need to have research available to set so won't always be able to have an EAR - higher risk of inadequancy than RDA (0.5 or 50%) - loewr value than the RDA

Chilean miners

exposed to Mn-containing dust --> manganese toxicity

deficiency of manganese

extremely rare not much known but: - reduced growth - vomiting - dermatitis - changes in hair color - skeletal defects

manganese toxicity

extremely rare - neurological abnormalities/disorders such as schizophrenia and Parkinson's disease *may be associated with iron deficiency because low iron levels allow for increased absorption of Mn

vitamin E deficiency

extremely rare - primarily occurs in people with lipid malabsorption problems or Ataxia with Isolated Vitamin E Deficiency (AVED) - primary symptoms: neurological problems

"factor A" and "factor B" in early vitamin discovery

factor A: - fat soluble - deficiency resulted in severe ophthalmia (inflammation of the eye) - vitamin A factor B: - water soluble - deficiency resulted in beriberi - vitamins B1 and B2

T/F I have more confidence in an AI than an RDA to meet a person's nutrient needs.

false since the AI is not based on research and the RDA is

T/F The primary cofactor formed from vitamin B6 is pyidoxamine phosphate, which has to be dephosphorylated before it is taken up.

false. The primary cofactor formed from vitamin B6 is PYRIDOXAL phosphate, which has to be dephosphorylated before it is taken up.

T/F An AI falls between the EAR and UL.

false. we don't know where the AI falls since there isn't an AI and EAR

tropocollagen

fibrous protein consisting of three strands twisted together

antioxidant vitamins and minerals

*Vitamin E* *Vitamin C* Riboflavin *Selenium* Iron Copper Zinc Manganese * Primary function is as an antioxidant

PLP (pyridoxal phosphate) functions

*cofactor form of vitamin B6 *it is a cofactor for over 100 different enzymes, mostly in amino acid metabolism - transamination - some deamination - glycogenolysis - NT synthesis - heme synthesis - involved in synthesis of niacin from Tryptophan

decarboxylation reactions that thiamin (TPP specifically) serves as a cofactor for

*result in loss of CO2 - transition reaction - one reaction in the Citric Acid Cycle

functions of vitamin c

- Antioxidant - Synthesis of collagen - Prevents the disease scurvy - carnitine synthesis - tyrosine synthesis and metabolism - seratonin synthesis - other hormone and NT synthesis

Goitrogen-containing foods

- Cassava - Millet - cruciferous vegetables - onions - garlic - soybeans - peanuts

DRI components

- Estimated Average Requirement (EAR) - Recommended Daily Allowance (RDA) - Adequate Intake (AI) - Tolerable Upper Intake Level (UL)

biotin absorption

- free biotin is highly absorbed - an enzyme cleaves the lysine off the biocytin for it to be absorbed - free biotin is taken up by the sodium-dependent multivitamin transporter (SMVT)

riboflavin absorption and excretion

- highly absorbed in free form (other forms must be cleaved or converted before absorption) - excreted primarily in urine (It is water-soluble)

Biotin functions

- important cofactor for carboxylase enzymes (add carboxylic acid groups) - ex. in fatty acid synthesis and in the oxaloacetate workaround of gluconeogenesis - histone biotinylation - AA breakdown - treatment for brittle nail syndrome

Niacin flush

- main symptom of Niacin toxicity - a temporary tingling sensation due to dillation of capillaries - Nicotinic acid ONLY - a nicotinic Acid receptor GPR109A can mediate niacin flush side effects

ascorbic acid transport using SVCT 1 or 2

- mechanism for tissue vit. c accumulation 1. SVCT 1 and SVCT 2 transport ascorbic acid or ascorbate into the cell against the concentration gradient **Like absorption, this uptake is driven by the action of sodium-potassium ATPase. This mechanism is saturable, meaning that at high concentrations it reaches a threshold where it cannot take up ascorbic acid any faster. Thus, there is a limit to how much can be taken up through this mechanism.

ascorbate recycling

- mechanism for tissue vit. c accumulation 1. ascorbic acid is oxidized to dehydroascorbic acid (DHA). 2. DHA is then transported into the cell moving with its concentration gradient using GLUT1 or 3. 3. Once inside the cell, DHA is reduced back to ascorbic acid, thus maintaining the DHA gradient. **As a result, the cell is able to accumulate high levels of ascorbic acid

Pantothenic Acid absorption and excretion

- most pantothenic acid in food is found as CoA, which is cleaved prior to absorption - then taken up into the enteroxyte through the sodium-dependent multivitamin transporter (SMVT) - approx. 50% is absorbed - excreted primarily in urine

absorption of niacin

- mostly well absorbed - in corn, wheat, and certain cereal products niacin bioavailability is low --> some niacin is tightly bound making it unavailable or. absorption, so need to treat the grains with a base to free the niacin and allow it to be absorbed

meaningful antioxidants

- need to have a SUFFICIENT AMOUNT of the antioxidant in the RIGHT LOCATION - can't be redundant (aka there is another antioxidant system that is able to quench the same ROS) *if there is more of something in the body (tissues in particular), it is more meaningful

nicotinic Acid receptor GPR109A

- present in Adipose and Immune cells - mediates niacin flush side effects - but does not appear to mediate the lipid profile benefits by niacin

Niacin toxicity

- rare - "Niacin flush" is the main symptom reported - GI distress and Liver damage

activation of all three forms of vitamin B6

all three forms can be activated by being phosphorylated - these phosphorylated forms can be interconverted to the active/cofactor form of vitamin B6 which is pyridoxal phosphate (PLP) ***FMN catalyzes this reaction

Pantothenic Acid functions

coenzyme A - SO many since acetyl-CoA is a central point in metabolism 1) Beta oxidation 2) De novo lipogenesis 3) Acyl carrier protein

Ataxia with Isolated Vitamin E Deficiency (AVED)

individuals with AVED have a mutation in their alpha-TTP that prevents it from functioning correctly

Chronic Disease Risk Reduction Intake (CDRR)

intake that there is evidence reduced the risk of chronic disease - only one set for sodium currently

_______ and ______ are important in the synthesis and metabolism of thyroid hormone.

iodine and selenium

Goiter

iodine deficiency, enlargement of the thyroid to help increase its ability to take up iodine

catalase cofactor

iron (Fe)

chiral centers in alpha-tocopherol

it has three, 2' 4' and 8'

is vitamin C stored in the body?

it is not stored but it is accumulated in certain tissues in the body

transketolase

key enzyme in the pentose phosphate pathway Requires *thiamine*.

how are selenium levels in the body regulated?

levels in the body are regulated by urinary excretion, not absorption

vitamin E excretion

major route: through bile that is then excreted in feces second route: in the urine after vitamin E is chain-shortened in a process similar to beta-oxidation to make them more water-soluble

collagen

makes up 30% or more of total body protein - collagen strands cross link (by hydroxyls) to form tropocollagen

Linus Pauling

prescribed megadoses of vitamin C for the common cold (but most excess vitamin C is excreted out as urine)

absorption and excretion of manganese

pretty low absorption (<5%) excreted primarily in bile --> feces (*unique)

excretion of vitamin B6

primarily excreted in urine (water-soluble)

selenium excretion

primarily in urine - if high amounts of selenium it can be expired (breathed out) which causes a garlic odor

best food sources of vitamin E

primarily oils and nuts - primarily alpha and gamma-tocopherol

What two post-transcriptional enzymes in collagen synthesis require ascorbic acid to function properly?

prolyl and lysyl hyroxylases because they need Fe2+ and ascorbic acid regenerates Fe2+ from Fe3+

dietary guidelines

provide qualitative advice to the public about diet and chronic disease prevention and maintaining health.

Primary circulating forms of vitamin B6

pyridoxal and PLP

macrominerals, trace minerals, ultratrace minerals

quantities: macrominerals>trace>ultratrace macro minerals: need the most of (need in greater quantities) ultratrace minerals: need very small quantities of

vitamin B6 deficiency

rare symptoms: - skin or scalp ailments - microcytic hypo chromic anemia (small cells, low color) --> due to decreased heme synthesis - neurological symptoms as a result of decreased NT synthesis (convulsions, depression, confusion)

iodine toxicity

rare but like iodine deficiency, can result in thyroid enlargement, hypothyroidism, or hyperthyroidism

selenium toxicity

rare in humans - symptoms: nausea, fatigue, diarrhea, hair 7 nail brittleness, rash, nervous system abnormalities - can happen in animals due to runoff (around a body of water in an area with high selenium levels --> this works its way up the food chain)

why shouldn't you consume raw eggs?

raw egg whites contain a protein called avidin which binds biotin and prevents its absorption

selenium absorption, is one form absorbed more than another?

readily/highly absorbed organic forms (selenomethionine for ex.) are absorbed more than inorganic forms (such as selenite)

RDA

recommended daily allowance - meets needs of 97.5% of the population - set using EAR (so research is needed) - risk of inadequacy is 0.025 (2.5%) - RDA=EAR + 2 standard deviations

RDI

recommended daily intake - used on food labels, not a DRI component

thyroid hormone

regulates the basal metabolic rate, important for growth and development especially in primarily of fetus or infant

alpha-tocopherol transfer protein (alpha-TTP)

responsible for maintaining higher levels of alpha-tocopherol in the body - preferentially binds to 2R alpha-tocopherol (2' chiral center is in R confirguration) and helps facilitate its incorportation into VLDL

what micronutrient is photosensitive?

riboflavin --> destroyed by light (used to be a problem when milk was delivered in glass bottles)

Iodine is critical for the synthesis of ____

thyroid hormones *its only (yet critical function)

difference between tocopherols and tocotrienols

tocopherols: have a saturated tail tocopherols: unsaturated tail

______ can be used to form Niacin

tryptophan - kynurenine intermediate - niacin equivalents (NE) were created by the DRI committee to account for theamount of niacin in foods as well as their tryptophan content

International Unit (IU)

unit used to describe the bioactivity of different compounds, including 4 vitamins: A, D, E, C - commonly used for supplements, not common for food items

Reactive Oxygen Species (ROS)

unstable oxygen-containing molecuel that seeks out other compounds to react with

selenoenzymes

used to describe the subset of selenoproteins that are enzymes - contain selenocysteins as an amino acid in the active site of the enzyme (not external) - selenium therefore does NOT serve as an external cofactor like most minerals

Thiamin

vitamin B1 - heat-sensitive - primary part of Factor B so was one of the original vitamins

vitamin c importance for collagen

vitamin C is needed for proline hydroxylase and lysyl hydroxylase to carry out their catalytic function. - these hydroxylases need Fe2+ and ascorbic acid regenerates Fe2+ from Fe3+, allowing the enzymes to continue to hydroxylate proline and lysing

antioxidant network step 1

vitamin E cycle - alpha-tocopherol is oxidized by donating an electron to a ROS, stabilizing it - alpha-tocopherol radical is formed

how is vitamin E absorbed

vitamin E is fat-soluble so all fat-soluble vitamins are handles like lipids --> incorporated into chylomicrons that have triglycerides removed by LPL - chylomicron remnants containing vit. E are then taken up by the liver

epigenetics

"above the genome" -how genes are expressed

Vitamin B6 toxicity

***it can produce toxicity, unlike many of the B vitamins - neurological damage - people self-treating may go above this

Pantothenic Acid deficiency

- very rare - "burning foot syndrome" - vomiting, fatigue, weakness, restlessness, irritability

Biotin deficiency

- very rare - skin rash, hair loss, neurological disturbances - could be the result of raw egg consumption or biotinidase mutation (can't cleave biocytin for absorption)

Vitamin E toxicity

-rare -high levels of intake of alpha-tocopherol (supplements) are associated with decreased blood coagulation due to potential anti-vitamin K activity

tryptophan accounts for ___% of amino acids in protein

1% (so take amount of protein x.01)

functions of FAD and FMN

1) CAC: FAD reduced to FADH2 2) Electron Transport Chain : FADH2 is used to produce ATP (complex 1 includes an FMN molecule) 3) Fatty Acid Oxidation (Beta-Oxidation) : FAD is reduced to FADH2 4) Niacin synthesis from tryptophan: FAD required 5) Vitamin B6 activation : FMN needed 6) Neurotransmitter Catabolism: FAD required 7) Antioxidant enzymes: FAD required

DRIs

Dietary Reference Intakes provide quantitative advice to professionals about amounts of nutrients or food components to be of benefit. - collective term to refer to EAR, AI, RDA, UL, CDRR, profe

Goitrogens

Dietary compounds that interfere with thyroid hormone production or utilization - not clinically importance unless there is a coexisting iodine deficiency - Cassava, Millet, Cruciferous vegetables, onions, garlic, soybeans, peanuts

a) form of vitamin B6 in animal products b) form of vitamin B6 in plant products

a) found in its cofactor forms in animal products: Pyridoxal Phosphate (PLP) or pyridoxamine phosphate (PMP) b) in plants it is primarily found as pyridoxine glucoside (has a glucose added to it)

a) Thiamin form found in plants b) Thiamin form found in animals

a) free thiamin b) thiamin pyrophosphate (TPP) - phosphates must be cleaves before thiamin is taken up into the enterocyte

Which of the following is not a function of PLP? a) Glycolysis b) Transamination c) Niacin Synthesis d) Glycogenolysis e) Heme Synthesis

a) glycolysis

functions of thiamin

1) Cofactor for decarboxylation reactions (TPP) 2) Cofactor for the synthesis of pentoses (5-carbon sugars) and NADPH (TPP) by TRANSKETOLASE 3) Membrane and nerve conduction (Not as a cofactor) - as thiamin triphosphate (TTP)

symptoms of Pellagra

1) Dementia 2) Dermatitis 3) Diarrhea

what cofactors is riboflavin important in the production of?

1) Flavin adenine dinucleotide (FAD) --> add two hydrogens for it to become FADH2 2) Flavin mononucleotide (FMN) - only contains one phosphate group and doesn't have the ring structures off of the phosphate like FAD

what forms of vitamin E are absorbed the best?

all forms of vitamin E (tocopherols, tocotrienols) are absorbed equally

where is most vitamin E found in the body

in the adipose tissue

where is most absorbed iodine accumulated?

in the thyroid, which keeps it for use to synthesize thyroid hormone

ORAC (Oxygen radical absorbance capacity)

in vitro antioxidant assay - does not take into account important factors such as bioavailability - no evidence that a high ORAC score leads to any benefit in vivo - not really used anymore

niacin cofactors

1) Nicotinamide Adenine Dinucleotide (NAD) --> NADH 2) Nicotinamide Adenine Dinucleotide Phosphate (NADP+) --> NADPh

3 compounds that compose vitamin B6

1) Pyridoxine - has alcohol group 2) Pyridoxal - has aldehyde group 3) pyridoxamine - has amine group

How to calculate the Niacin Equivalents

1) amount of protein x.01 = amount of tryptophan (in g) 2) convert g of tryptophan to mg by x 1000mg/g 3) divide mg of tryptophan / 60mg of tryptophan this is 1 NE, to get the NE from tryptophan 4) add the mg of niacin to the NE of tryptophan for total NE

two causes of biotin deficiency

1) biotinidase mutation - can't cleave biotion from biocytin for absorption 2) raw egg consumption

conditions that vitamin B6 supplementation may be used for

1) carpal tunnel syndrome 2) morning sickness 3) PMS

2 primary dietary forms of biotin

1) free biotin 2) biocytin (biotin + lysine)

Pantothenic acid roles in the body

1) it is part of coezyne A (coA) - its major role 2) part of acyl carrier protein

Niacin forms

1) nicotinic acid 2) nicotinaminde

Cofactor forms of vitamin B6

1) pyridoxal phosphate (PLP) - primary form 2) Pyridoxamine phosphate (PMP)

manganese serves as a cofactor for ____

1) superoxide dismutase (superoxide --> hydrogen peroxide) 2) gluconeogenesis oxaloacetate workaround enzymes 3) urea cycle enzyme 4) enzymes critical to proteoglycan production (essential component of cartilage and bone)

Keshan Disease

A heart disorder caused by selenium deficiency. - mostly in mountainous regions of China - causes heart lesions

avidin

A protein in raw egg whites that binds biotin and prevents its absorption - cooking denatures this protein - need to consume a very large amount for it to result in a biotin deficiency

Which of the following is not true about riboflavin? a) It is primarily excreted in feces b) Only free riboflavin is taken up c) It is used in FAD and FMN d) It is yellow in color e) It is sensitive to light

a) is NOT true - since riboflavin is water soluble it will primarily be excreted in urine

mechanisms for tissue vitamin C accumulation

1. ascorbic acid transport using SVCT 1 or 2 2. Ascorbate recycling

two main epigenetic modifications

play a major role in determining what genes are expressed 1) DNA methylation 2) Histone modification

Which of the following is not true about thiamin? a) The primary cofactor form is thiamin phosphate b) There is little storage of it c) It is heat-sensitive d) Phosphates must be cleaved from it before uptake

a) is NOT true - the primary cofactor is thiamin pyrophosphate (TPP)

how many free radicals can ascorbic acid stabilize or quench?

2 free radicals

what does alpha-TTP preferentially bind to?

2R alpha-tocopherol, meaning any alpha-tocopherol where the 2' chiral center is in R configuration

fat soluble vitamins

ADEK

Which function of thiamin does not involve thiamin pyrophosphate (TPP)? a) Membrane and nerve conduction b) Pentoses and NADPH synthesis c) Decarboxylation reactions d) All of the above involve TPP

a) membrane and nerve conduction involves thiamine triphosphate (3 phosphates instead of 2)

ascorbic acid absorption

actively absorbed by the sodium vitamin C cotransporter 1 (SVCT 1) -> ascorbic acid then diffuses in to the capillary and ultimately enters general circulation

absorption of Vitamin B6

75% absorbed, through passive diffusion **PLP and PMP are dephosphorylatedbefore uptake into the enterocyte to get free pyridoxine BUT some pyridoxine glucoside (plant storage form) is absorbed intact

why in the Keshan disease experiments did the selenium-adequate mice developed heart pathology after being exposed to the coxsackie virus isolated from selenium-deficient mice.

In experiments the increased oxidative stress in the selenium-deficient mice caused mutations in the coxsackie virus which made it more virulent. The virus was then able to cause the heart pathology that occurs in Keshan disease in selenium-adequate mice. This suggests that without selenium, selenoenzymes that are antioxidant enzymes, are not able to function adequately leading to the effects described above.

water soluble vitamins

B vitamins and C vitamins

vitamin B7

Biotin

superoxide dismutase cofactors

Cu, Zn, Mn

dry beriberi vs wet beriberi

Dry: Nervous system; loss of muscle function, numbness, and/or tingling Wet: CV system; pitting edema, heart enlargement

T/F Thiamins only function is as a cofactor

False. Thiamin Triphosphate (TTP) functions in membrane and nerve conduction.

Do most Americans get enough Iodine? through what form?

For most Americans, we consume ample iodine through the consumption of iodized salt. Consumption of 1/2 teaspoon of iodized salt meets the RDA for iodine (easy to meet RDA)

form that iodine is primarily found in foods as

Iodide (I-) *iodide concentrations of the soil vary greatly (like selenium), which causes food concentrations to greatly fluctuate

selenium deficiency

Keshan disease

Potassium iodide (KI) or potassium iodate (KIO3) for salt iodization

Potassium iodide (what the US mainly uses) - less expensive - higher iodine content - more soluble Potassium iodate - more stable

can minerals be synthesized in the body?

NO. They cannot be synthesized in the body, are essential in diet for body functions

how is an RDA set?

RDA= EAR + 2 standard deviations

Vitamin B3

Niacin

Pellagra

Niacin deficiency - rare in US but it was common in early 1900s - occurs in population that consumes only corn (bc low bioavailability) - symptoms: 3D's

primary circulating form of Niacin

Nicotinamide

what micronutrient can improve people's lipid profiles?

Nicotinic Acid when it is consumed at levels far above the RDA --> however this hasn't been shown to decrease CV disease risk

Without _____, all amino acids would be essential because we would not be able to synthesize nonessential amino acids.

PLP (pyridoxal phosphate) - cofactor form of vitaminB6

histone acetylation

addition of an acetyl group to the histone --> causes the DNA structure to open up so that transcription can occur

histone biotinylation

addition of biotin to the histone - rare

AI

adequate intake -- used when insufficient evidence exists for EAR, RDA -- level that looks to be adequate in a defined population or subgroup -- it is unknown how an AI quantity compares to a RDA/EAR

gene in a tale of two mice

agouti gene : methylation --> gene suppressed --> mouse has a dark coat and is thinner (yellow & fat is the result when the gene isn't methylated)

James Lind

Prescribed lime juice containing vitamin C to prevent scurvy in 1795 - they thought citrus fruits helped due to the acidity

Vitamin B6

Pyridoxine

which is accurate for a larger percentage of the population: EAR or RDA?

RDA RDA is adequate for 97.5% of the population, it is a higher value than the EAR EAR is adequate for 50% of the population

natural alpha-tocopherol

RRR-alpha-tocopherol - all 3 chiral centers are in the R position

______ is high in iodine, thus foods of ______ origin are good dietary sources of iodine

SEA WATER is high in iodine, thus foods of MARINE origin are good dietary sources of iodine *diary products are also good sources because it is added to cattle feed and cattle receive iodine containing medications and iodide containing sanitizing solutions

Primary circulating form of thyroid hormone is ___? Active form of thyroid hormone is ___?

T3 (triiodothyronine) is the ACTIVE form T4 (thyroxine) is the primary circulating form, is converted to T3

pyridoxal phosphate (PLP)

The active coenzyme form of vitamin B6 - has a phosphate group added in place of a hydroxyl group

DNA methylation

The addition of methyl groups to bases of DNA after DNA synthesis; decreases gene transcription --> demethylation increases gene transcription

cofactor for the enzyme transketolase

Thiamin Pyrophosphate (TPP)

cofactor form of thiamin

Thiamin Pyrophosphate (TPP) - thiamin + 2 phosphates - phosphates must be cleaves before thiamin is taken up into the enterocyte

THTR-1 and THTR-2

Thiamin transporters - THTR-1: found on the brush border and basolateral membrane (going into circulation) - THTR-2: found only on the brush border

vitamin C forms

a) ascorbic acid or ascorbate (reduced form) b) dehydroascorbic acid or dehydroascorbate (oxidized form) --> semidehydroascorbate is formed when there is only 1 degree of oxidation (dehydroascorbate is 2 degrees of oxidation)

US vitamin E consumption vs europe vitamin E consumption

US consumes more gamma-tocopherol (from soybean oil) and Europe consumes more alpha-tocopherol (from olive, sunflower, and canola oil) but in the serum concentrations are roughly the same

storage of thiamin

Very little, like most water-soluble vitamins

scurvy and its symptoms

Vitamin C deficiency symptoms: - bleeding gymns - pinpoint hemorrhages - corkscrew hairs - easy bruising - impaired wound and fracture healing ***these occur bc insufficient Fe2+ since vit. C isn't regenerating it --> collagen isn't being hydroxylated enough to form sufficient tropocollagen --> collagen is being degraded

Iodine absorption

Well-absorbed (90%)

do americans get enough micronutrients?

a large percentage of americans don't meet the EAR for vitamin E, magnesium, vitamin A, and vitamin C

glutathione peroxidase

a selenium-containing enzyme that protects cells from oxidative damage by neutralizing peroxides - converts hydrogen peroxide to water

Which of the following is not a function of FAD? a) Vitamin B6 activation b) Fatty acids oxidation c) Antioxidant enzymes d) Niacin synthesis e) Citric acid cycle

a) Vitamin B6 activation is not a function of FAD because FMN is used

main form of vitamin E

alpha-tocopherol

what happens if there isn't research to set an EAR?

an AI (adequate intake) is set.

Niacin functions

approx. 200 enzymes require NAD or NADP+ - glycolysis - CAC - B-oxidation - Alcohol metabolism - de novo lipogenesis

Riboflavin deficiency

ariboflavinosis - rare - tongue inflammation (glossitis) - skin inflammation - lesion/cracking of corners of the mouth

antioxidant network step 2

ascorbate is oxidized to form dehydroascorbate. This regenerates alpha-tocopherol from alpha-tocopherol radical *known as the vitamin C cycle since ascorbate is vitamin C

antioxidant network step 3

ascorbate is regenerated from dehydroascorbate by the selenoenzyme thioredoxin reductase. *known as the selenium cycle

what form does Vitamin C generally circulate as?

ascorbic ac

primary form of vitamin C in food

ascorbic acid (80-90%) and dehydroascorbic acid (10-20%)

Which of the following is not a major function played by selenoproteins? a) Antioxidant enzymes b) Tropocollagen production c) Thyroid hormone metabolism

b) Tropocollagen production

why does the level of selenium in foods vary?

because the amount of selenium in food varies based on soil selenium levels

thiamin uptake and absorption - passive or active

believed to be an efficient process - passive when thiamin intake is high - active when thiamin intake is low - 2 thiamin transporters (THTR 1 and 2) are involved in thiamin uptake and absorption

Riboflavin color

bright yellow

Which of the following is the major function of pantothenic acid? a) Fluid Balance b) Acyl Carrier Protein c) Coenzyme A (CoA) d) Electron Transport Chain

c) Coenzyme A (CoA)

histone deacetylation

causes the DNA to become more tightly packed, preventing transcription from occuring

histone modification

changes in the structure of histones that make it more or less likely that a segment of DNA will be transcribed - acetylation is most common

problems that can arise from free radicals

free radicals/ROS can oxidize a) LDL (cholesterol carrier) which can lead to atherosclerosis b) proteins which can lead to cataracts c) DNA which can cause mutations and lead to cancer

riboflavin form in food

free, protein-bound, or in FAD or FMN **only free riboflavin is taken up so it must be cleaved or converted before absorption

bioavailability of vitamin C

high at lower doses, drops to less than 50% at higher doses

should you take high doses of antioxidants?

high doses of antioxidants may cause more harm than good - a U shape curve going from deficiency --> toxic

why might high vitamin C intake contribute to kidney stones?

high intake of vitamin C increases excretion of uric acid and oxalic acid, which are the primary components of 2 types of kidney stones - but link not been formally established

bioavailability

how much of a compound is absorbed or reaches circulation

what is unique about humans and vitamin C?

humans are one of the few mammals that do not synthesize vitamin C, making it an essential micronutrient - primates, guinea pics also do not

hydroxylases role in collagen cross-linking

hydroxylate the individual collagen strands so that they can crosslink to form tropocollagen

alpha-tocopherol derivatives

manufacturers add compounds to alpha-tocopherol through ester bonds to protect the antioxidant function of apha-tocoperhol in foods and during digestion - cleaved prior to absorption in the small intestine by esterases

free radicals

molecule with an unpaired electron in its outer orbital - this electron actively seeks an electron to stabilize itself

selenomethionine

most common organic form of selenium in plants - the sulfur in methionine has been substituted for selenium - in cereal grains such as wheat, corn, and rice and in soybeans - accumulates in the body at higher levels because it is nonspecifically incorporated in place of methionine!!

will there ever be an AI and RDA for the same population class?

no, an AI is only set if there isn't research to set an EAR

is vitamin B6 heat stable?

no, it can be destroyed during cooking or heating

are soybean, corn, and flaxseed oils considered good sources of vitamin E?

no, these are good sources of gamma-tocopherol. The DRI for vitamin E only counts 2R forms of alpha-tocopherol to be good sources

is a macromineral more important than an ultratrace mineral?

no, these names are only to do with the quantities needed not the importance

Pantothenic Acid toxicity

none

Riboflavin toxicity

none

thiamin toxicity

none

biotin toxicity

none known

are water-soluble vitamins stored in the body?

not generally

do megadoses of vitamin C reduce the risk of the common cold?

not in most people but it might benefit people exposed to brief periods of severe physical exercise (marathon runners) or cold environments

Vitamin C toxicity

not really toxic bc water-soluble for some people if they have a lot: GI distress, diarrhea - increased vitamin C intake might contribute to kidney stones

forms of vitamin E that count for the Dietary Reference Intake (DRI)

only 2R forms of alpha-tocopherol because these forms bind to alpha-TTP - unit: mg alpha-T

organic vs inorganic selenium

organic forms: contain carbon - selenomethionine, selenocysteine inorganic forms: do not contain carbon - selenite and selenate - not usually found alone, usually complexed with sodium to form sodium selenite and sodium selenate

deficiency of vitamin C

scurvy

Keshan Disease results from a deficiency in _____

selenium

What micronutrient is involved in the metabolism of thyroid hormones through deiodinases?

selenium diodinases are selenoenzymes, so selenium is important for thyroid hormone metabolism

is selenomethionine or selenocysteine incorporated into the body at higher levels?

selenomethionine because it is nonspecifically incorporated in place of methionine (just inserted where methionine would be)

cretinism

severe hypothyroidism (from iodine deficiency) resulting in physical and mental stunting

Niaspan

slow release Nicotinic acid to help prevent toxicity symptoms - used to get the benefits for blood lipid profile

exogenous free radical sources

sources from outside of the body - UV light, radiation, smoking, inflammation, air pollution

natural vs synthetic alpha-tocopherol

stereochemistry differs between the forms - natural: all 3 chiral centers are in the R confirmation (RRR) - synthetic: racemic (equal) mixture of all the different possibilities at the three chiral centers

what is seleniums antioxidant function due to?

the action of selenoenzymes

what happens to collagen when there is inadequate vitamin C?

the collagen is under-hydroxylated because Fe2+ isn't being sufficiently regenerated for use by hydroxylases. - the collaged is therefore degraded because it can't sufficiently cross-link to form tropocollagen

difference between alpha, beta, gamma, and delta

the difference is the methyl groups on the ring

Keshan disease experiment

the group of mice that was fed a selenium deficient diet was infected with coxsackie virus that was avirulent& virulent --> this caused severe heart pathology and then the coxsackie virus turned into mostly virulent due to the oxidative stress

oxidative stress

the imbalance between the production of reactive oxygen species and the body's ability to quench them - when you have more free radicals and ROS than your body can quench

Tolerable Upper Intake Level (UL)

the maximum daily amount of a nutrient that appears safe for most healthy people and beyond which there is an increased risk of adverse health effects - NOAEL= point where no observed adverse effects have been recorded - LOAEL= lowewst observed adverse effect level

why might nicotinic acid sypplementation not be good?

the nicotinic acid receptor appears to increase glucose uptake in the intestine --> this plus a rapid decrease in lipid levels can lead to a prediabetic state

how do manufacturers protect the antioxidant function of alpha-tocopherol in foods and during digestion?

they add compounds to alpha-tocopherol through ester bonds --> alpha-tocopherol derivatives

what happens to selenoenxymes that are antioxidant enzymes without sufficient selenium?

they are unable to function correctly - ex. coxsackie virus: oxidative stress --> mutations in virus --> more virulent *similar findings with flu and HIV

how do antioxidants work?

they reduce free radicals by donating an electron to them

beriberi

thiamin deficiency -rare in developed countries -countries where white rice is a staple food are at risk

Wernicke-Korsakoff Syndrome

thiamin deficiency found in alcoholics - problems in paralysis, involuntary eye movements, muscle coordination, mental loss, confusion

alcoholics are prone to becoming ____ deficient

thiamin deficient because: 1) alcohol displaces foods that are better sources of thiamin 2) liver damage decreases TPP formation 3) increased thiamin excretion ***Wernicke-Korsakoff Syndrome