Nutrition and Antioxidants Flashcards
Is vitamin E (lipid/water) soluble?
lipid
Is Vitamin C (lipid/water) soluble?
water
Define Reactive Oxygen Species (ROS)
superoxide and its subsequent products
-O2 will often steal an electron from reduced metals, flavins, quinols, etc become “superoxide” or O2-
- very reactive
- will combine with anything
Give example of a Reactive Nitrogen Species.
gas hormone nitric oxide (NO)
Give some examples of Reactive Oxygen Species.
Superoxide (O2-) Hydrogen Peroxide (H2O2) Hydroxyl radical (OH-)
Oxidative and Nitrosative damage are commonly linked with disease either as a cause or side-effect.
FYI
What are four ways that oxidative and nitrosative stress can damage biological molecules?
- Modification of structure and function of CARBOHYDRATES
- Modification of structure and function of PROTEINS
- Modification of LIPID (peroxidation)
- Modification of individual NUCLEOTIDE BASES
How do ROS damage lipids?
ROS can led to chain reaction due to oxygen reacting with lipid.
Why are aldehydes so reactive?
create crosslinks between proteins
ex) formaldehyde
Patient is suffering from ischemia/reperfusion injury. Damage is primarily caused by:
initial return of oxygen to normal levels
LDLs are protected from oxidative modification in systemic circulation due to presence of circulating anti-oxidants. What happens when LDLs are trapped in the sub-endothelial space?
ROS reacts with LDL and leads to oxidized LDL (oxLDL).
oxLDL
- is a chemoattractant to circulating monocytes
- contributes to endothelial dysfunction
- further ROS formation
How does cytochrome C function in mitochondrial injury?
acts as an apoptic signal
Iron can play the following roles:
role in many enzymes
- catalysis
- electron transfer
- oxygen transport
What reaction can iron catalyze?
Haber-Weiss-Fenton reactions
Describe the reactions that iron can undergo.
oxidation
reduction
Leo (lose electron Oxidized)
Ger (gain electron Reduced)
How is iron stored in the body?
ferritin
hemosiderin
(mostly in liver)
How much iron is required per day to maintain stores with a mixed diet?
8 mg per day
How is iron taken up by the body?
transferrin - specific cell membrane receptors on target cells
Tf-receptor complex is internalized by receptor-mediated endocytosis
Fe is released by acidification
How is non-heme taken up by the body?
Stimulated:
Vit C
organic acids
Heme
Inhibited:
black tea
cocoa
chamomile
What happens in the presence of iron excess?
hemochromatosis (hereditary defect)
hemosiderosis (dietary overload)
- alcohol in excess
- children ingesting Fe supplements
Oxidative stress
Decrese absorption of thyrozine, tetracycline, ciprofaloxacin
possible heart disease
What can lead to iron deficiency?
diet deficiencies
infection (H. pylori)
inflammation
other vitamin deficiencies (Vit C)
Result: anemias
- can exacerbated other problems (lead poisoning)
What are some defense mechanisms that protect against oxidative stress?
Chemical: Vitamin C Vitamin E B-carotene Glutathione Bilirubin
Enzymatic:
Super Oxide Dismutase (SOD)
catalase
peroxidases
Why does the cell have different redox active organic components?
Can donate or accept electrons at different electrical potentials
Overlap allows a wide range of reactions
Which enzymes protect you from ROS?
superoxide dismutase
catalase
peroxidases
Which chemicals protect you from ROS?
bilirubin
glutathione
Vitamin C
Vitamin E
Describe glutathione.
Small, modified tripeptide reversible oxidized/reduced
-thiol group
- good source of eletroncs to reduce ROS
- regenerated w/electron from NADPH by Glutathione reductase
What is the concentration of glutathione?
[millimolar]
What is the MAIN function of Vitamin E?
antioxidant - stops propagation of free-radical damage in membranes
Vitamin E will be deficient when there is ?
fat malabsorption
Bile acids are essential for which vitamin to be absorbed?
Vitamin E
Where is the bulk of Vitamin E stored?
adipose tissue
A deficiency in Vitamin E lease to?
retinitis pigmentosa
neurological symptoms
What is the RDA of Vitamin E?
15 mg/day
** does not accumulate in the liver to toxic levels
Scavenges oxygen and free radicals
Reducing reagent
A-tocopherol deficiency can lead to ?
ataxia
Bioavailability of Vitamin E depends on what 2 things?
bile acids
fat content of food
ex) 2x as available when taken with milk vs. orange guide
How is Vitamin E oxidized?
by w-oxidation by cytochrome P450
What is used to regenerate reduced Vitamin E?
Vitamin C
List three functions of Vitamin C
antioxidant
collagen biosynthesis
-proline
-lysine
Synthesis of:
- adrenal hormones
- drug metabolism
- folate metabolism
- stimulation iron uptake
How many electrons can Vitamin C donate?
2
How can Vitamin C be regenerated?
number of different enzymes using electrons from NAD(P)H or by glutathione
What is the first thing that is oxidized in plasma under oxidative stress?
Vitamin C
How does Vitamin C accumulate?
intracellularly via specific transporters AND by at least 4 glucose transporters (GLUT 1-4)
What is a result of Vitamin C deficiency?
Scurvy
How does Scurvy present?
connective tissue in muscle, skin, blood vessels
hemorrhagia
bleeding gums
weakness
poor wound healing or bone healing
What is the RDA for Vitamin C?
60 mg/day
What can excess (megadoses) of Vitamin C cause?
hypoglycemia
kidney stones
indigestion
dissolve teeth enamel (chewable forms)
$21 to 25 billion dollars is spent on supplements each year yet most are not supported by?
larger, randomized trials
Present evidence on the use of multivitamins (MVMs) is ?
insufficient
In the primary prevention of total cancer incidence or cancer mortality, Vitamin C, E or beta carotene offer?
no overall benefit
Regarding cardiovascular events among women with high risk for CVD, ascorbic acid, Vitamin E or beta carotene offer?
no overall effect
Evaluating the risk of prostate or total cancer, the use of Vitamin E or C offers?
no overall effect
The risk of major cardiovascular events in men, the use of Vitamin E or C offer?
no overall effect
Higher plasma Vitamin C levels and fruit and vegetable intake were associated with
decreased risk of diabetes
The groups most vulnerable to inadequacy of one or more nutrients are?
- older adults
- pregnant women
- people who are food insecure
- alcohol-dependent individuals
- strict vegetarians and vegans
- increased needs due to health conditions
- chronic use of medication that decreases nutrient absorption or changes metabolism
What benefit could pharmacologic doses of ascorbate provide?
prooxidant and decrease growth of aggressive tumor xenografts (in mice)
What was the effective concentration (sufficient to kill 50% of tumor cells) of ascorbate?
<10mM for 75% of tumor cells tested
