SELENIUM METABOLISM

1. Selenium Metabolism
Gandham. Rajeev

2. Selenium
• Selenium was found to prevent liver cell
necrosis & muscular dystrophy.
• Total body content of selenium around 10 mg
and it is present mainly in liver.
• Sources:
• Richest sources are meat, sea foods, liver,
kidney and grains.
• RDA
• 50 to 200 µg/day.

3. Absorption and excretion
• Selenium is absorbed mainly from the
duodenum.
• Selenium after absorption is transported
bound to plasma proteins particularly β-
lipoproteins in humans.
• Main route of excretion of selenium appears
to be through urine.

4. Functions
• Selenium, as selenocysteine is an essential
component of the enzyme glutathione
peroxidase.
• Glutathione peroxidase functions as an
antioxidant enzyme.
• It suppresses the oxidative stress by
converting oxygen free radicals into less
toxic forms or non-toxic forms.

5. Relationship of glutathione peroxidase,
selenium & vitamin E
GSH peroxidase contains selenocysteine

6. • The presence of selenium in the diet reduces
the requirement of vitamin E, since vitamin E
also acts as an antioxidant.
• Selenium may exert anticancer effects
because of its antioxidant role.
• Selenium containing enzyme 5’deiodinase
converts thyroxine (T4) to triiodo-thyronine
(T3) in thyroid gland.

7. • In selenium deficiency, conversion of T4 to T3 is
impaired resulting in hypothyroidism.
• Selenium binds with certain heavy metals &
protects body from their toxic effects.
• Selenocysteine is considered as 21st standard
amino acid since it is coded by UGA, which is a
termination codon.
• Selenium is incorporated to proteins as
selenocysteine during protein synthesis.

8. Deficiency
• Causes:
• Low soil content of selenium & malnutrition.
• Clinical features:
• Chronic selenium deficiency is associated with
cirrhosis of liver, cardiomyopathy leading to
congestive cardiac failure, muscular
dystrophy, loss of appetite, nausea,
abnormal electrocardiograms.

10. Keshan Disease
• Muscular dystrophy
• Loss of appetite,
• Nausea.

11. Selenium toxicity
• Selenium toxicity is rare.
• Selenosis is the toxicity due to excessive
consumption of selenium.
• Clinical features are hair loss, dermatitis and
irritability.
• Liver & neuromuscular disorders that are
usually fatal.

13. Thank You