NDFS 200 exam 3

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NDFS 200 exam 3
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NDFS 200 exam 3 BYU
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  1. Vitamin A 
  2. Vitamin A functions
    visual cycle

    • epithelial cell maintenance: (eg,
    • xerophthalmia and follicular hyperkeratosis)

    immune function / infection

    growth and development

    cancer prevention
  3. Functions of vitamin A in :
    Epithelial cell maintenance (retinoic acid)

    Regulation of mucous formation at the level of gene expression, cell differentiation: retina, cornea, lungs, skin, GI tract, etc.

    Examples

    Xerophthalmia“dry eye”  (Bitot spots)

    Retinoic acid required, especially for mucus formation.

    Mucus lubricates the cornea, and its lack allows scratches and bacterial growth in the scratches.

     Irreversible blindness

    • nFollicular
    • hyperkeratosis

    • nSkin
    • changes, keratin protein synthesis in follicles
  4. RXR, RAR
    Abbreviations for retinoid X recepter and retinoid acid receptor
  5. stem cells
    Unspecified cells that can be transformed into specialized cells.
  6. bleaching process
    process by which light depletes the rodopsin concentration in the eye by seperating opsin from all-trans-retinal.  This fall in rhodopsin concentration allows the eye to become adapted to bright light.
  7. dark adaption 
    Process by which the rodopsin concentration in the eye increases in dark conditions, allowing improved vision in the dark.  
  8. dietary cartenoids
    often attached to proteins that need to be cleaved off by enzymes prior to absorption.  
  9. Vitamin A absorption
    preformed vitamin A are divided into retinyl and retinol ester compounds.  Retinyl esters ddon't have vitamin A activity until the retinol and the fatty acid are seperated.  in the intestinal track.  This process requires bile and pancreatic lipase enzymes.  Up to 90 % of retinol is abosorbed into the cells of thte small intestine via specific carrier proteins.  After absorption, a fatty acid is attached to retinol to form a new retinyl ester.  These retinyl esters are packaged into chylomicrons before entering the lymphatic circulation.
  10. Vitamin A 
    Growth and Development
    important role in embryonic development

    epitheal cells in lungs trachea, skin, and GI track as well as in many other systems. mucous forming cells in these systems.  

     
  11. Vitamin A 
    Cell differenciation
    in the nucleus RXR and RAR bind to specific sites that regulate formation of messenger RNA.  making it influencial in gene expression which directs cell differenciation
  12. Cell Differeniciation 
    The process in which stem cells develop into specialized cells with unique functions in the body.  Vitamin A is especially important in maintaining normal differenciation of the cells that make up the structural components of the eye, such as the cornea (clear lens) and the retina ( rod and cone cells).
  13. Vitamin A
    vision 
    retinal is needed in the cornea of the eye to turn visual light into nerve signals to the brain.  part of rhodopsin.  
  14. Vitamin A immune function
    increased incidence of infection one of the first signs of vitamin A defficiency.  this may be because of its role in maintaining the epithelium.  
  15. Vitamin A defficiencies 
    • xerophthalmia 
    • follicular hyperkeratosis
  16. xerophthalmia
    - condition marked by dryness of the cornea and eye membranes that result from vitamin A defficencies.
  17. Follicular hyperkeratosis
    Condition  in which keratin a protein accumulates around hair follicles.  
  18. Vitamin A and gene expression
    • nRetinoids
    • leave liver bound to RBP, which then binds to transthyretin, carried in blood to target cells.

    Bound in cells by family of CRBP proteins

    • Bound in nucleus by two sub-families of receptors, RAR and RXR.
    •  RAR and RXR bind to DNA, regulating gene expression and cell differentiation (cell function, growth, immunity, etc.).
  19. Vitamin A Rationale for DRIs
    • nRationale:
    • based on dietary amount to maintain adequate body pool size and stores

    • n900
    • RAE for men

    700 RAE for women

    Average intake meets RDA

    Vitamin A supplements are unnecessary

    No separate RDA for carotenoids

    Tolerable Upper Level for Vitamin A

    3000 micrograms for adults, about 4 x RDA, based on the presence of birth defects and liver toxicity

     Fatal dose - 12 g of vitamin A
  20. Hypercarotenemia
    Too much carotene in blood

    Not harmful
  21. Vitamin A toxicity 
    Acute
    • caused by ingestion of 1 very large dose of vitamin A or several taken over a few days.
    • sypmtoms:
    • GI upset/nausa
    • headaches
    • dizziness
    • poor muscle coordination

    very large doses can be lethal
  22. Vitamin A toxicity
    Chronic
    caused - repeated doses of over 10x the RDA

    • sypmtoms 
    • liver damage
    • hair loss
    • bone muscle/pain
    • loss of appetite
    • Dry skin and mucous membranes
    • hemorrages
    • coma
    • fractures
  23. Vitamin A toxicity
    teragenic
    • Acutane etc
    • .  
    • birth defects
    • spontaneous abortion
  24. Vitamin D
  25. synthesis of vitamin D in the skin
    begins with a precursor of cholestrol synthesis in the skin.  during exposure to UV light 1 ring undergoes a chemical transformation, forming a more stable cholecalciferol vitamin D.  it then enters the blood stream and goes to the liver and kidneys where it undergoes conversion to its bioactive form calcitriol.   
  26. Sun exposure and D synthesis
    Depends on skin color, age, time of day, season, location

    Clothes and sunblock inhibit conversion, but not of concern except in elderly

    Angle of UV light, line from LA to Atlanta.  Winter UV light not effective above 34o N.
  27. Vitamin D3 Functions
    • Blood Ca regulation
    • absorption

    excretion

    bone resorption or deposition

    Other functions

    gene expression

    cell differentiation

    cancer cells
  28. Vitamin D
    Bone Health
    •   Low blood calcium is a trigger
    • for parathyroid to remove Ca from bone

    reduce calcium excretion by the kidneys

    stimulate synthesis of D3 in kidneys  to stimulate intestinal absirotion of Ca.  
  29. Vitamin D fuctions other
    regulate immune system

    • secretion of hormones
    •     insulin, renin, PTH
    • cell cycle regulation
  30. Vitamin D3 Deficiency
    Rickets, osteomalacia

    Pressure distorts bones of the:

    • head
    • rib cage (rachitic rosary)
    • legs (bowed)
    • joints
    • Pelvis
  31. 2010 Vitamin D DRIs - Rationale
    RDA – intake linked with blood 25OHD level associated with benefit; assumes minimal sun exposure

    UL – level not associated with classic toxicity (NOAEL 10,000 IU), corrected for uncertainty (adverse outcome other than “classic toxicity” that occur at lower intakes)
  32. Vitamin D
    Food sources
    Food Sources:  fortified milk, fish, fish oils

    “Sensible sun, foods, supplements”
  33. Toxicity of vitamin D
    6-7 X RDA

    Main symptoms

    Over-absorption of Ca

    Ca deposition in kidneys, heart, blood vessels

    Ca toxicity to the liver

    Weakness, loss of appetite, vomiting

    Mental retardation in infants
  34. Vitamin E
  35. Vitamin E structures - tocopherols
    •The R form of the first stereoisomer is natural, and the only active form. The RRR form is the most active

    •Therefore, only about ½ of synthetic vitamin E is active.

    Supplement labels indicate “d” for R and “dl” for R and S
  36. Vitamin D sterochemistry 
    • The tocopherols
    • have chromanol
    • ring with a long, saturated (phytyl) side chain (Figure 6-1). α-tocopherol
    • has 3 methyl groups on the chromanol ring. β-or γ-tocopherols
    • have 2 methyl groups on the chromanol ring at different positions, and δ-tocopherol
    • has 1 methyl group on the chromanol ring. 
  37. DRIs
    Vitamin E
    • RDA
    • - based on dietary intake that maintains a plasma level adequate to limit H2O2-induced hemolysis to < 12%

    • 15
    • mg/day for women and men
    • (=22 IU of natural source or 33 IU of synthetic form)

    1 mg dl-a-tocopherol = 0.45 IU (synthetic source)

    1 mg d-a-tocopherol = 0.67 IU (natural sources)

    n

    • nAdults
    • consume on average 2/3 of the RD
  38. Vitamin E absorption 
    absorbption depends on dietary intake.  done through passive diffusion absorption rate can vary from 20-70%.  As with all fat soluble vitamins must be incorporated into the micelles of the small intestine.  A process dependent upon bile and pancreatic enzymes.  then incorporated into chylomicrons and transported through the lymph into the blood.
  39. Vitamin E
    Oxidative stress
    Chain reaction looking for electrons; lipid peroxidation

    Destruction of cells and components

    Need an acceptor (chain breaking antioxidant) to stop the chain reaction
  40. Vitamin E
    Requirement
    Varies with the amount of polyunsaturated fatty acids (PUFA) in the diet

    PUFA are electron dense, promote free radical chain reactions

    Coincidentally(?), plant oils high in PUFA also high in vitamin E

    Supplements of PUFA e.g. encapsulated fish oils may not have vitamin E
  41. Vitamin E 
    UL
    Supplements up to 800 IU are probably harmless

    Upper Level is 1,000 mg/d of any form of supplemental alpha-tocopherol

    Inhibits vitamin K metabolism and clotting, leading to hemorrhage

    Disrupts balanced anticoagulant medications, leading to hemorrhage

    Possible decrease in gamma-tocopherol activity, which is Potentially beneficial in reducing prostate cancer risk
  42. Vitamin E 
    UL
    Supplements up to 800 IU are probably harmless

    Upper Level is 1,000 mg/d of any form of supplemental alpha-tocopherol

    Inhibits vitamin K metabolism and clotting, leading to hemorrhage

    Disrupts balanced anticoagulant medications, leading to hemorrhage

    Possible decrease in gamma-tocopherol activity, which is potentially beneficial in reducing prostate cancer risk
  43. Vitamin K

    Menaquinones also from bacteria in human intestine

    40%-80% of dietary vitamin K absorbed
  44. Vitamin K
    DRI
    AI - based on reported intakes in apparently healthy populations

    90 ug/day for women

    120 ug/day for men

    RDA met by most

    Excess vitamins A, E interfere with vitamin K

    Toxicity unlikely; readily excreted
  45. Food Sources of Vitamin K
    Menaquinones

    Fish oils, meats, bacteria in intestine

    Phylloquinone

    Plants

    Liver

    Green leafy vegetables

    Broccoli

    Peas

    Green beans

    Resistant to cooking losses

    Very limited vitamin K stores in the body
  46. Antibiotics, “blood thinners”, and vitamin K
    Long-term antibiotics bacteria

    “Blood thinners” (anticoagulants) interrupt vitamin K metabolism

    Supplementation of vitamin K may decrease effectiveness of anticoagulants
  47. Vitamin K 
    dependencies
    16 known vitamin K-dependent (VKD) proteins

    11 known mouse knock-out (KO) mutants

    5 KOs embryonic lethal – coagulation factors
  48. Thiamin
  49. Thiamin 
    Major Function
    Coenzyme in caarabohydrate metabolism and energy release

    –Thiamin pyrophosphate (TPP)* = thiamin diphosphate (TDP)

    –Decarboxylation reactions in CHO metabolism e.g. the “bridge” reaction (pyruvate decarboxylase)

    –TCA cycle, nerve function (highly respirating cells)
  50. Thiamin 
    Defficiency symptoms
    Beriberi, weight loss, weakness, peripheral neuropathy; wernicke-korsakoff syndrome 
  51. Beriberi
    Thiamin defficiency disorder characterized by muscle weakness, loss of apetite, nerve degredation, and sometimes edma 
  52. Wernicke-Korsakoff syndrome
    Thiamin defficiency caused by excessive alcohol consumption.  Symptoms include eye problems, difficulty walking, and deranged mental functions
  53. Thiamin dietary sources 
    pork, pork products, enriched whole grain cereals, eggs, nuts, legumes 
  54. Thiamin
    •RDA
    • – based on RBC transketolase activity (ribose for DNA syn.), urinarythiamin excretion
    • •Most exceed in diet
    • –Surplus rapidly lost in urine; non toxic
  55. Riboflavin
  56. Riboflavin 

    RDA
    • •RDA
    • – based on RBC glutathione reductase activity coefficient, urinary excretion

    •Average intake > RDA

    –Toxicity not documented
  57. Riboflavin 
    major functions
    Coenzyme in numerous oxidation-reduction reactions, including those of energy release.

    • FAD and FMN:  Reducing equivalent carriers in Redox
    • reactions
    • •Pyruvate to AcCoA

    •Citric Acid Cycle

    •Beta-oxidation of fats

    •Br Ch AA oxidation

    •Electron Transport System
  58. Riboflavin 
    Defficiency symptoms
    • ariboflavinosis; inflamation o f mouth and tongue, cracks at corner of mouth
    • •Ariboflavinosis
    • –rarely seen

    –Glossitis, cheilosis, seborrheic dermatitis, stomatitis, eye disorder, throat disorder, nervous system disorders, confusion, headaches

    •Occurs within 2 months @ < 25% RDA
  59. Riboflavin
    dietary sources
    milk, milk products, mushrooms, eggs, liver, enriched grains
  60. Riboflavin
    UV light
    –Sensitive to UV radiation (sunlight)

    –Stored in paper, opaque plastic containers
  61. Niacin
  62. Functions of Niacin
    –Part of NADH, NADPH 200 diff. reactions in almost every major pathway, especially those producing ATP

    •Glycolysis

    •Beta-oxidation

    •Lipogenesis (NADPH)

    •Amino Acid syn. & bkdn

    •Citric Acid Cycle

    •ETS
  63. Tryptophan-> niacin
    • •60
    • mg tryptophan ->1 mg niacin
  64. niacin RDA
    • •RDA:
    • 14 NE/day for women, 16 NE/day for men
  65. niacin food sources
    widely distributed in foods
  66. Pellagra.
    • niacin defficiency 
    • the four "D"s

    • Dementia
    • –severe, many lived lives in mental institutions

    Diarrhea

    • •Dermatitis
    • –mal de la rosa

    •red sickness

    –pelle agra

    •rough skin

    •Death
  67. Niacin UL
    flushing of skin; upper level for adults is 35mg/day from supplements , based on flushing of skin.  
  68. Niacin and blood lipids
    •1.5-3 g/ day (75 - 150 X RDA) nicotinic acid increases HDL, decreases LDL, TG

    •Slow/reverse progression of atherosclerosis with diet, exercise

    • •Serious side effects:
    • –flushing of the skin, itching, nausea, headache, dizziness, liver damage (especially slow release), increased blood
    • glucose.
  69. Coenzyme A
  70. Pantothenic acid
  71. pantothenic acid RDA
    • •AI
    • based on intake adequate to replace urinary excretion

    –AI set at 5 mg/day (avg intake meets AI)

    • •Abundantin foods (Greek pantothen = everywhere), deficiency very rare
  72. Functions of Pantothenic Acid
    –Acetyl CoA formation from:

    –Pyruvate

    –Beta-oxidation

    –Amino acids

    –Alcohol

    –Initiate the Citric acid cycle

    –Succinyl CoA in Citric acid cycle

    • –Initiate
    • fatty acid synthesis

    • –Acetyl CoA + CO2→Malonyl
    • CoA

    –Part of Acyl Carrier Protein

    –Increase fatty acid chain length
  73. Pantothenic Acid Deffiency
    Deficiency very rare

    • Experimentally induced: headache, burning
    • foot syndrome, fatigue, nausea, tingling

    Hidden among other deficiencies
  74. biotin
  75. Biotin 
    Absorbtioin
    •Absorption:

    –Free biotin in small intestine directly

    –Biocytin cleaved in small intestine by biotinidase
  76. Functions of Biotin
    •Functions: carboxylations

    •Fatty acid synthesis and elongation

    •AcCoA + CO2→malonylCoA

    •CHO metabolism

    •Pyr + CO2→  oxaloacetate

    •Replenish TCA

    •Gluconeogenesis
  77. Biotin AI
    •AI based on extrapolation from exclusively breast fed infants, limited estimates of intake by adults

    –AI set at 30 ug/day for adults, no UL

    –May be an overestimation because of extrapolation
  78. biotin food sources
    •Food Sources:

    –Cauliflower, yolk, liver, peanuts, cheese

    –Intestinal synthesis of biotin

    •Biotin content only available for a small number of foods

    •Unsure as to bioavailablity of GI bacterially synthesized biotin

    •We excrete more than we consume
  79. biotin avidin 
    •Avidin

    –egg white protein

    –inhibits absorption, powerful binding (one of strongest in nature)

    –>12 raw egg whites/d to take effect

    –cooking egg white denatures avidin
  80. •Biocytin
    –protein-bound form of biotin in food; covalently bound to lysine.
  81. •Biotinidase
    –in small intestine cleaves this bond, makes available for absorption.

    –1 in 60,000 infants have genetic defect in biotinidase production

    –Deficiency in infants within months, must be treated with large doses.

    •Rash, hair loss, convulsions, neurological disorders,            growth
  82. Vitamin B6
  83. B6

    RDA
    •RDA: 1.3 mg/day for adults

    –Criteria: maintain adequate plasma PLP
  84. B6 food souces 
    •Food Sources:

    –Muscle of meat, fish, poultry

    –Whole grains (milled not enriched with B6)

    –Banana, spinach, avocado,      potato
  85. B6

    Functions
    •Coenzyme in reactions involving N-containingcompounds

    – without B6 every amino acid would be essential;


    –RBC (heme) synthesis, a nitrogen containing ring.

    –Brain neurotransmitter synthesis: serotonin, dopamine, norepinephrine (N-containing neurotransmitters)

    –CHO metabolism:  glycogenolysis requires B6, maintains blood glucose concentrations.

    –Gluconeogenesis from glucogenic aa.

    • –Vitamin
    • metabolism: 
  86. Homocysteine

    synthesis
    Functions

    • AA transaminations

    • neurotransmitter   synthesis

    • glycogenolysis

    • • homocysteine to
    • methionine
  87. Vitamin B6 deficiency
    •Microcytic hypochromic anemia (decreased heme synthesis)

    •Convulsion, depression, confusion

    •Peripheral nerve damage

    •Reduced immune response
  88. Folate
  89. Folate functions
    •Many relationships to B12: transfer of single carbon units (e.g. methyl groups)

    •DNA and RNA synthesis (U to T)

    •Cell division

    •Methotrexate therapy (THFA analogue)

    •Neurotransmitter synthesis

    •Homocysteine to methionine

    •homocysteine levels in blood
  90. Deficiency of folate
    •Cells with short life span, rapid turnover affected most

    •Megaloblastic anemia: low DNA/RNA synthesis

    •Cardiovascular disease: homocysteine toxicity

    •Neural tube defects: low DNA/RNA synthesis

    •Cancer hypomethylation of DNA

    •Pregnant women; alcoholics
  91. Toxicity of Folate
    •FDA limits nonprescription supplements to 400 mg per tablet for non-pregnant adults

    •OTC prenatal supplement contains 800 mg

    •Epilepsy (?)

    •Skin, respiratory disorder (?)
  92. folate, B12
    Treating a B12 deficiency with increased folate “masks” the B12 deficiency, that will result in nerve damage, by relieving the megaloblastic anemia that results from deficiency of either.
  93. Folate and cancer
    •Chemotherapeutic agents antagonize folate, decrease DNA synthesis, inhibit rapidly growing cells (e.g. cancer cells)

    •Aberrations in DNA methylation in cancer

    –Methylation decreases gene expression

    –Global hypomethylation

    –Promoter-specific hypermethylation
  94. Epigenetics
    – alterations of chromatin that affect gene expression without changing DNA sequence
  95. Folate food sources
    green vegetables, liver, enriched cereal products, legumes, oranges 
  96. B12
  97. B12 Functions 
    •Functions:  (one carbon transfers)

    –Methylmalonyl CoA reductase (3C fa residue to 4C succinyl CoAàTCA)

    –Methionine synthase (w/ folate)

    •Return folate coenzymes back to THFA for use in other folate rxns

    •allows normal DNA synthesis, maturation of RBC
  98. B12 RDA
    • •RDA:
    • hematological status, normal serum
    • vitamin B12
  99. B-12 absorption
    •Interfering factors

    –Genetic lack, inadequate synthesis of factors (R protein, intrinsic factor)

    –Low stomach acid production

    –Anti-ulcer medications (acid production by parietal cells)

    –Bacterial overgrowth

    –Tapeworm

    • –Surgical
    • removal of stomarch or
    • ileum

    •Deficiencies due to malabsorption, not low dietary intake
  100. Where is vitamin B12 found and who is at risk for deficiency?
    •At risk:

    • –genetically inherited defect in one of many steps in B12
    • absorption

    –elderly

    –vegans, especially infants born of vegans
  101. B12 food sources
    –meat, poultry, seafood, eggs, milk, milk products
  102. Vitamin C 
  103. Vitamin C 
    Functions 
    •Hydroxylation, cross linking of collagen and elastin

    •Oxidation/reduction of Fe and Cu:

    –As metals

    –As metals in enzymes

    • •Water
    • soluble free radical scavenger

    •Immune functions

    –Fully saturated WBC

    •Iron absorption (Fe+3 à Fe+2)

    •Synthesis of carnitine, tryptophan to serotonin, thyroxine, cortiscosteroids, aldosterone, cholesterol to bile acids
  104. Collagen and elastin crosslinking
    •Critical for strong connective tissue

    –Bone

    –Blood vessels

    –Wound healing

    • Hydroxylation of lysine and proline uses iron, recycling it from Fe+3 back to Fe+2 oxidation state, using vitamin C to
    • provide electrons
  105. Scurvy
    •3 week history of general malaise, dysphagia, chronic cough, nausea

    •Hemorrhagic rash on legs, perifollicular and conjunctival hemorrhages.
  106. Vitamin C requirements
    •Rationale: near-maximal neutrophil concentration, minimal urinary excretion

    •75 or 90 mg/day to fulfill rationale

    •10 mg/day prevents scurvy; remainder for other functions to achieve “rationale.”
  107. Vitamin C toxicity:
    •UL: 2000 mg

    •Nausea, abdominal cramps, stomach inflammation, diarrhea

    •Enhances Fe absorption-(hemochromatosis beware)

    •Oxalate stones, kidney failure (beware)

    •Minor decrease in common cold severity, not incidence

    •“Chelation Therapy” dangers

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