Vitamin E

Where is vitamin E stored in the body?

Mainly in adipose tissue, but also in liver, lung, heart, muscle, adrenal glands, spleen, and brain

What is a function of vitamin E?

Maintenance of membrane integrity including possible physical stability in body cells

How are vitamin E levels assessed?

Measure plasma vitamin E levels ( large range does not correlate when dietary levels are high) and crude estimation by erythrocyte hemolysis test

What is the major target for lipid peroxidation?

PUFAS- polyunsaturated fatty acids specifically the hydrogen atoms from the methylene groups between two double bonds

Where does vitamin E play a role?

delaying pathogenesis of heart disease, cancer, inflammatory diseases, neurological disorders, cataracts, and age related cell degeneration

What is meant by saying vitamin E is a free radical scavenger?

Vitamin E is the chain terminator of free radical mediated lipid peroxidation (free radical scavenging)

What other nutrients does vitamin E interact with?

Vitamin E may complement selenium dependent glutathione peroxidase to prevent lipid peroxidation. Vitamin C can regenerate vitamin E following its oxidation

Where is vitamin E found in the body?

found in all of the cell membranes

What tissues are at high risk for oxidation?

lungs, brain, and erythrocytes

How common is vitamin E deficiency?

quite rare

What are the symptoms of vitamin E deficiency?

skeletal muscle pain and weakness, ceroid pigment accumulation, hemolytic anemia, degenerative neurological problems (ataxia)

What have long term epidemiological studies on vitamin E shown?

vitamin E supplementation is associated with reduced risk of heart diseases in healthy individuals. vitamin E supplementation has also been shown to decrease the risk of Alzheimer's, and may have some effect on type 2 diabetes

What are the dietary sources of vitamin E?

both plants and animals, but only plants can make them. Oils such as canola, olive, and sunflower are rich in alpha tocopherol. Foods made from vegetable oils such as salad dressing, mayonnaise and margarine. Nuts, whole grain cereals, legumes, some fruits and vegetables, fatty tissues of animals, barley, rice, wheat germ, palm oil

How is vitamin E regenerated?

by dehydroascorbate reductase and glutathione reductase

What is the ATBC trial?

Alpha tocopherol beta carotene trial. Aims to see if supplementation of beta carotene or alpha tocopherol can reduce lung cancer risk in heavy smokers. Result: beta carotene supplementation increased incidence of lung cancer and alpha tocopherol significantly reduced incidence of prostate cancer

What is the most abundant form of vitamin E?

Alpha-tcopherol is the most abundant form of vitamin E in the body.

Why should vitamin E and C be taken together?

Because vitamin C returns alpha tocopherol to its reduced form

How does vitamin E act as a lipophilic antioxidant?

It terminates free radicals and destroys singlet molecular oxygen. Vitamin E is a membrane (lipid) soluble antioxidant while vitamin C is a water soluble antioxidant

Vitamin E toxicity

No acute toxicity has been reported. Increased bleeding, GI distress, impaired blood coagulation, muscle weakness, fatigue and double vision.

How do non-hepatic tissues receive vitamin E?

They receive vitamin E through: -receptor mediated uptake of LDL -Lipoprotein lipase mediated hydrolysis of chylomicrons and VLDLs -HDL mediated nutrient delivery

what does alpha tocopherol donate to free radicals to get them to a lower energy state?

The phenolic group on the ring donates hydrogen to free radicals

How are non alpha tocopherol forms of vitamin E metabolized?

They are metabolized by w-hydroxylation and beta oxidation and excreted through the urine

How is vitamin E transported in the blood?

Transported in blood by lipoproteins

What is the SELECT trial?

aims to determine is selenium and vitamin E can help prevent prostate cancer in healthy men. No apparent beneficial effects were observed

What is the bioavailability of the different forms of vitamin E?

alpha tocopherol=highest (100%) beta tocopherol= 40% gamma tocopherol= 10% alpha tocotrienol= 25% *percentages found from rat fetal absorption assay a.k.a vitamin E activity assay

What is the mechanism of vitamin E?

as lipophilic antioxidants to prevent oxidation of polyunsaturated fatty acids that re rich in the phospholipids of membranes

Which membranes are especially susceptible to oxidation?

mitochondria and endoplasmic reticulum

What happens to vitamin E in the liver?

takes up chylomicron remnant, alpha tocopherol transfer protein (TTP) incorporates alpha tocopherol into VLDL for secretion to other tissues. Large portions of non-alpha tocopherol forms are metabolized and secreted via bile or urine

What do high doses of vitamin E inhibit?

the absorption of beta carotene and vitamin K and may interfere with drug metabolism

Who is at risk for vitamin E deficiency?

those with fat malabsoprtion, hepatobiliary system disorders, genetic defects in lipoprotein or vitamin E transfer protein

How is vitamin E transported inside cells?

tocopherol binding proteins inside cells