Selenium Flashcards
What is Selenium (Se) classified as? what unit is it measured in?
Trace element required in microgram (µg) quantities.
How is Selenium chemically similar to sulfur?
Can substitute for sulfur in amino acids, such as Selenocysteine.
What is essential for human health regarding Selenium? what are major functions?
Incorporation into Selenoproteins
-Antioxidant
-GPX rxn
-Co-dependent on Vit E
-Conversion of T4 to T3
What is the primary antioxidant function of Selenium?
Reduces oxidative stress via Glutathione Peroxidase (GPX).
What reaction does GPX catalyze?
2 Glutathione (GSH) + Hydroperoxide (ROOH) → Glutathione disulfide (GSSG) + Alcohol (ROH) + H₂O.
what is the RDA for selenium for infants, adults and pregnant women?
infants: ~20
children: ~40
-doubles quickly during development
adults: ~55
pregnant: ~60
1000microg = 1mg
What are the major food sources of Selenium? how does increased Se affect serum levels?
-Volcanic regions
-ubiquitous in nature
* Animal products (meat, fish, eggs, dairy) * Selenium-enriched grains (wheat, rice, corn) * Brazil nuts * Garlic, onions, and mushrooms (if grown in selenium-rich soil)
higher levels of consumption do not proportionally reflect serum levels
What is the role of Iodothyronine 5’-Deiodinase?
Converts Thyroxine (T4) to Active Triiodothyronine (T3).
Where is DI-1 primarily found?
Liver and kidney.
What are the 5 major selanoproteins? what do they do?
1) GTX-1
-glutathionine peroxidase-1; catalyzes GTX rxn to produce alcohol + water
2) GTX-GI
-similar function to GTX-1; found in intestine
3) GTX-3
-Similar function as GTX-1; found in kidney
4) GTX-4)
-intracellular GPX activity; broader detoxifying capacity than GPX-1
5) DI-1
-convertys T4 to T3 (DI-2 in brain, skin, adipose; DI-3 in fetal liver, CNS, muscle)
What is Keshan Disease? what is a risk factor?
Endemic cardiomyopathy associated with Selenium deficiency in children
- increased risks in isolated soil regions or underdeveloped countries
What are the symptoms of Selenium toxicity?
- Brittle nails and hair loss * Garlic breath odor * Vomiting, diarrhea, fatigue (severe toxicity) * Heart attack, kidney failure, death (extreme toxicity)
What is the tolerable upper limit (UL) for Selenium? what is the impact of Se on arsenic toxicity?
400-1000 µg/day.
Se competes for the same pathway as arsenic which can displace / decrease accumlation of aresenic
what is the significance of Cr³⁺ to humans?
needed for carbohydrate and lipid metabolism
-chromium may also reduce T2D risks and improve insulin resistance
What are the two biologically relevant forms of Chromium? which is more important?
- Cr³⁺ (Trivalent Chromium): Essential for metabolism * Cr⁶⁺ (Hexavalent Chromium): Toxic industrial by-product, carcinogenic
- Cr³⁺ most important valence state
What is the function of Chromodulin? how does it do this?
Chromium binding substance that enhances insulin receptor binding and increases insulin receptor number and sensitivity
-binds 4 Cr³⁺
What is the primary carrier protein for Chromium?
Transferrin.
how is chromium transported and stored?
There are no specific transporters
-carrier protein is transferrin which binds 2 Cr³⁺ molecules
Explain the relationship of chromium and T2D? what factors impact this relationship?
Due to chromiums role in insulin regulation (amplyfying insulin response by increases receptors) , this can aid in increasing insulin sensitivity
-increased insulin response without the body secreting more insulin
individuals who do not already have insulin resistance may not see any benefit from increased Cr supplementation
What is the RDA of chromium? what is this measured in? what is the absorption efficiency?
Children ~15
Men ~30
Women ~20
Pregnant ~35
-0.4-2.5% absorption
What are the food sources of Chromium?
Broccoli, Tomato, Whole wheat English muffin, Beef, Beer, Orange juice
What are the symptoms of Chromium deficiency? how is status tested?
- Impaired glucose tolerance * Elevated cholesterol and triglycerides * Neurological issues in severe cases
- currently no way to measure status accurately
What is the significance of Chromium Picolinate?
Most bioavailable form of Chromium, common in alternative medicine.
What is a potential consequence of excessive Chromium intake? what is the UL?
Renal failure (as seen in case studies)
-no UL as excess consumption is unlikely from dietary sources
