Unit 8: Micronutrients – Fat-soluble Vitamins Flashcards
Definition of vitamin
- Organic nutrients found in food
The distinguishing feature of the vitamins is that they
generally cannot be _______ by mammalian cells and,
therefore, must be supplied in the diet. - Perform specific function in the body. Many are ______________
- Small daily requirement, ingested frequently
synthesized
coenzymes
Definition of vitamin
- _____ _______ leads to specific disease, which can
be cured only by that vitamin - Can exist in multiple forms: pro-vitamin, vitamin and
(often) coenzyme. The most prominent function is as cofactors for enzymatic reactions. - Can have different _______ __________:
e.g. Vitamin A: retinol, retinyl ester, retinal, retinoic
acid
Inadequate intake
chemical structures
What vitamins are endogenous?
• Humans can make one fat-soluble vitamin:
– Vitamin ____
• Humans can make one water-soluble vitamin:
– ____________
D3
Niacin (Vit B3)
What vitamins are endogenous?
• Human intestinal bacteria make one fat-soluble:
– ____________
• Human intestinal bacteria make one water-soluble:
– __________
Vitamin K
Biotin (Vit B7)
Vitamin A
_________ (animal sources) and
____________ (plant sources)
synthesis of sex, adrenal and thyroid hormones
Retinol Activity Equivalent – One RAE: amount of potency = \_\_\_\_\_ • Equivalent to 1 μg retinol; • 12 μg β-carotene, • 24 μg α-carotene
RDA:
– Adult male: 900 RAE (________ IU)
– Adult female: 700 RAE (2330 IU)
UL: 3000 RAE (__________ IU)
Vitamin A _______= Retinol, Retinal, Retinyl ester, Retinoic acid
Retinol
carotenoids
3.33 IU
3000
10,000
vitamers
Vitamin A–β-Carotene
The breakdown of β-carotene occurs in the walls of the ____ _______ and is catalyzed by the enzyme β-carotene __________
– The retinol is stored in the liver as ____ ____. (This is why cod liver oil used to be taken as a vitamin A supplement).
small intestine
dioxygenase
retinyl esters
Vitamin A vitamers: Retinal
1–Retinol is converted in the retina to 11-cis retinal =Transduces light into neural signals for ______
vision.
Vitamin A vitamers: Retinoic acid
1–The normal _________ of the cells of the cornea
and conjunctiva is dependent on retinoic acid.
• Retinoic acid acts as a ________ and is involved in signal transduction, mediated by retinoic acid receptors
differentiation
hormone
Vitamin A vitamers: Retinyl esters
1–All-trans-retinol occurs naturally in the form of fatty acid esters,
2–Retinyl palmitate and retinyl _____ are the principal
forms used as nutritional supplements.
3–Primary vitamer in _____: Retinyl ester
– Excellent sources: Liver, fish, dairy, eggs
acetate
food
Vitamin A–Absorption, Transport and Storage
1—Vitamin A and carotenoids are absorbed in the
________ __________
– Bound to chylomicrons
– Transport via lymph
– Pro-vitamin A carotenoids converted to vitamin A in
the intestinal mucosa or liver.
2—______ is the primary site of storage.
– Others are kidney, adipose and adrenal glands
– Excessive intake of β-carotene causes yellowish skin
due to deposit in subcutaneous adipose tissue
3–– Carotenoids are bound to lipoproteins, such as VLDL
and LDL, for _______
small intestine
Liver
transport
Vitamin A: Deficiency
Cause:
– Primary:
• Insufficient intake, usually associated with Protein Energy Malnutrition (PEM) or lack of fruits and vegetables
– Secondary:
• Disorders of _________
• Failure to ________ stored vitamin A (due to liver disease)
• Metabolic defects in converting carotenoids to retinol
–Blindness in the developing world, Night blindness
–Epithelial disorders
–Failures in systemic functions
—Increased risk for infection
–Dry, fissured skin
• Brittle nails
• Hair loss (alopecia)
Toxicity seen with daily supplementation of _______ IU
absorption
mobilize
25,000
Vitamin D–Aka: Anti-rachitic factor
Production in skin when exposed to UV irradiation
• Absorption, transport, and storage
• Functions as a steroid hormone
• Maintains calcium and phosphorus homeostasis
RDA
• FNB dietary reference intakes for vitamin D:
– ___ μg for those aged 1–70 years (600 IU);
– ___ μg for those aged 71+ years (800 IU);
– Pregnant / Lactating: 15 μg (600 IU)
– UL: ____ μg (4000 IU)
15
20
100
Vitamin D
1–Ergosterol Pre-D2 Ergocalciferol (vit D2)
– Occurs in yeast and some plants
– Ergo: fungus/mushrooms
2—7-dehydrocholesterol Pre-D3 Cholecalciferol (vit D3)
– Occurs in human subcutaneous tissue
– Made from cholesterol
3—Humans can make only one fat soluble vitamin:
_________
Vitamin D3
Vitamin D–Absorption, Transport and Storage
1–Like all fat-soluble vitamins, Vitamin D is absorbed in the small intestine, bound to _______, and transported through the lymph.
2– Endogenously synthesized vitamin D is bound to ___________ (plasma protein) for transport
chylomicrons
α-2-globulin
Vitamin D–Absorption, Transport and Storage
3—Vitamin D is primarily stored in the liver. There is some in the brain, bone and skin. Excessive vit D is excreted in
_____
4— Mobilization of vitamin D, and conversion to its active
form, occurs only when needed and is under ______
regulation
5–Vitamins D2 and D3 are stored in the liver as
____________________
bile
hormonal
25-hydroxy-(chole/ergo)calciferol
VITAMIN D–Function of 1,25(OH)2 D3 (Calcitriol)
To maintain ___ _______ at optimal levels (~5 mM or
10 mg/dL)
Major functions of calcium:
1–for use in nerves and muscle
2–mineralization of bones and teeth
3• Regulates insulin secretion / sensitivity
4• Controls cell differentiation and suppresses malignancy
5• Assist immune function
6• Decrease systolic hypertension
serum calcium
VITAMIN D–Function of 1,25(OH)2 D3 (Calcitriol)
1–Bone: Low serum calcium triggers___ release
2–Self-regulation: (negative feedback): High 1,25(OH)2D3
stimulates ____________ to make more active 24,25(OH)2D, instead of 1,25(OH)2D3
.
PTH
***Parathyroid hormone (PTH)– Released when serum calcium is LOW. –OVERALL: PTH INCREASES serum Ca2+ to optimum levels for functions other than bone mineralization
24-hydroxylase
Regulation of Vitamin D by calcitonin–Calcitonin (from thyroid)– Released when serum calcium is ________
OVERALL: CALCITONIN will REDUCE serum Ca2+ to optimum levels
high
Vitamin D: Deficiency
Primary Causes:
– Lack of vitamin D in vegetarian diets, lack of sun exposure (seasonal rickets occur in cold climate)
Secondary causes:
Diseases of intestine, liver or ________
Vitamin D resistant rickets: Chronic use of ______
lowering drugs or barbiturates reduce vitamin D absorption
- -Rickets in children
- -Osteomalacia in adults –Osteoporosis
kidney
cholesterol
Signs of Vitamin D Toxicity
- Excessive _________ of bones
- Kidney stones
- __________ calcification of soft tissue (kidney, heart, lung, and tympanic membrane)
- Hypercalcemia
calcification
Metastatic
Vitamin E--Tocopherols and Tocotrienols Natural vitamin E has 8 vitamers: – 4 tocopherols and 4 tocotrienols – All are ‘d-form’ – Their potency (in order) • Alpha
d-α-tocopherol
1
Food sources of vitamin E
Sources- Vegetable oils: safflower, sunflower, soybean, Grains: Wheat germ, seeds, cereals and grains, Fortified food: margarine, Dairy: Whole milk (in the fat), Meat / Fish: liver
KNOW
Functions of vitamin E
__________: neutralizes reactive oxygen species (free radicals). Preserves membrane integrity, and fat soluble factors & Vitamin A, CoQ,
–cytochrome P-450–Detoxifying enzyme in the liver
–malondialdehyde–PUFA that, when oxidized, binds
DNA/RNA/protein/lipid. Therefore a carcinogen.
– Enters a variety of tissue types, found primarily in
__________
• It is thought to play a role there in either stabilizing
CoQ (ubiquinone), or in helping CoQ transfer electrons.
– Plays an important role in protecting ____ against oxidative stress
Antioxidant
mitochondria.
RBCs
Vitamin E—Absorption, Transport and Storage
Absorption – Like other fat-soluble vitamins,
• it is passively absorbed in the small intestine
• transported by chylomicron, via lymph to the liver
Transport from the liver
1– packaged into HDLs, LDLs, and VLDLs released into the bloodstream.
2– Note: α-tocopherol is selectively incorporated into VLDL, due to its high affinity for α-TTP (α-tocopherol transfer protein), accounting for its high biological activity.
3– In the blood, it prevents the oxidation of ____, a factor in atherogenesis, so adequate amounts of vitamin E _______ against hardening of the arteries, heart attacks, and stroke.
LDL
protects
vitamin E—Absorption, Transport and Storage
Vitamin E is primarily stored in _____ ________
• Other sites are liver, adrenal glands, ovary/testes and
muscle
– Mobilized from storage sites and transported by LDL,
HDL and VLDL.
adipose tissue
vitamin E—Absorption, Transport and Storage
1–Tissue Uptake
– By ________ digesting the lipoprotein constituents
EX. Triglycerides, phospholipids, cholesteryl esters, free cholesterol
2–By “_____ _____ _____” : binding of the lipoprotein to a specific tissue receptor site.
EX. Apo-E Receptor
3–– The vitamin can be stored in tissue for years due to its exceedingly slow turnover rate.
4-– Interestingly, the natural __________ form of the vitamin is stored up to six times longer than synthetic versions.
lipases
receptor mediated uptake
α-tocopherol
RDA OF VITAMIN E • α-tocopheral equivalent – 1 α-TE = 1 mg α-tocopheral = 1.5 IU • AI for newborns: 4 α-TE (6 IU) • RDA for adults: 15 α-TE (22.5 IU) • RDA for pregnancy / lactation: 19 α-TE • UL for adults: 1000 α-TE (1500 IU) • 1IU=0.67mg natural=0.45mg synthetic
KNOW
Vitamin E: Deficiency
1– Hemolytic anemia-abnormal breakdown on ________
2– Increased risk of __________ and certain cancers (due to antioxidant effects)
RBCs
atherosclerosis
Vitamin E: Excess
1–• GI disturbances: nausea, diarrhea
2-• Vitamin E competes with the other fat-soluble vitamins
A– Prolonged _____ _____ (anti vitamin K)
B– May compete with vitamin A and D and increase their
need in the body
C– In combination with aspirin, hypervitaminosis E can be
life threatening. And counteract vitamin K, leading to a
vitamin K deficiency.
bleeding time
Vitamin K
Vitamers
1–K1: phylloquinone, phytonadione – SOURCE = green veggies
2–K2: menaquinone, fernoquinone –SOURCE = fermented foods–(cheese/yogurt). Also from bacteria
(_______ _______) Synthesize ~50% of our daily needs
3–K3: menadione = ______ __________
intestinal flora
Synthetic drug
Vitamin K–Absorption, Transport & Storage
1–Dietary vitamin K is absorbed in the ____ intestine
2–Endogenous vitamin K is absorbed in the____intestine
3– Bound to chylomicrons
4– Transported through lymph
small
large
Vitamin K–Absorption, Transport & Storage
5–Excessive intakes of ____ impairs vitamin K
absorption!
6– Storage of vitamin K in the body is relatively ___. Perhaps due to continuous supply by the intestinal
bacteria.
7– Major storage is in ______
8– Other sites: skin, muscle, kidney and heart
Ca2+
low
liver
Vitamin K: Function
• Vitamin K is a coenzyme for γ-glutamic
carboxylase, and is therefore required for:
– ________ __________…but
– Prevents excessive blood coagulation
– Stimulates mineralization of bone and teeth
– Maintains serum calcium levels
Blood coagulation
Vitamin K regulates the “_______ __________”
Coagulation Cascade
AI • AI for newborns: 2.0 μg / day • AI for adult males: 120 μg / day • AI for women: 90 μg / day – (including pregnancy & lactation): • UL for adults: \_\_\_\_\_\_\_\_
Unknown
Vitamin K: Deficiency
Symptoms:
1–Impaired blood ________ (anemia and prolonged bleeding)
2–Muscular and subcutaneous _______
3–Impaired mineralization of bone and teeth (hip fractures)
coagulation
hemorrhage
Vitamin K: Excess
• Mostly due to K3 administration
Symptoms:
– Increased hemolysis and hyperbilirubinemia in _____
– Hypotension
– Weakness due to vitamin K interference of ___ of
the respiratory chain
infants
CoQ
Practical Issues: Nutrient-nutrient interactions
- Lipid foods increase fat-soluble vitamin absorption
- Vitamin A increases the number of receptors for 1,25(OH)2D, and enhances the action of vitamin D
- Adequate intake of ____&_______ are essential for the mobilization of stored Vitamin A
protein and Zinc
Practical Issues: Nutrient-nutrient interactions
• Mineralization of bone and teeth requires the simultaneous adequate intake of Vitamins A and D, Ca, P, Mg, Cl
• Vitamin E and Se are both _________ and enhance each other’s activity; they also spare vitamin A. However,
excessive intake of vitamin E antagonizes vitamins A, D, and K.
anti-oxidants
