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Selenoprotein metabolism and function: evidence for more than one function for selenoprotein P
Raymond F Burk1, Kristina E Hill, Amy K Motley
1Division of Gastroenterology, Department of Medicine and Clinical Nutrition Research Unit, Vanderbilt University School of Medicine, Nashville, TN 37232-2279, USA. raymond.burk@vanderbilt.edu
The Journal of Nutrition
|May 6, 2003
Summary
Selenoprotein P plays a dual role in the body, acting as an antioxidant and facilitating selenium transport. This extracellular protein is crucial for delivering selenium to tissues like the brain.
Area of Science:
- Biochemistry
- Cellular Biology
- Nutritional Science
Background:
- Selenium's biological functions are mediated by selenoproteins, which incorporate selenocysteine during protein synthesis.
- Key selenoprotein families include glutathione peroxidases, iodothyronine deiodinases, and thioredoxin reductases, all redox enzymes.
- Selenoprotein P is an extracellular protein containing most plasma selenium, with proposed antioxidant and selenium transport roles.
Purpose of the Study:
- To investigate the antioxidant and selenium transport functions of selenoprotein P.
- To elucidate the mechanism of selenium uptake by different tissues.
- To correlate selenoprotein P presence with selenium-dependent protection against oxidative damage.
Main Methods:
- Administration of (75)SeO(3)(2-) intravenously to rats.
- Measurement of (75)Se uptake in liver and brain tissues over time.
- Monitoring of plasma (75)Se levels and appearance of (75)Se-labeled selenoprotein P.
Main Results:
- Liver rapidly took up (75)Se, correlating with a decrease in plasma (75)Se.
- Brain tissue accumulation of (75)Se began only after the appearance of (75)Se-labeled selenoprotein P in plasma.
- Results suggest distinct selenium uptake mechanisms for different tissues, with selenoprotein P facilitating brain uptake.
Conclusions:
- Selenoprotein P exhibits both antioxidant and selenium transport functions.
- The presence of selenoprotein P is essential for selenium transport to tissues like the brain.
- Distinct pathways exist for cellular selenium uptake, involving both small-molecule forms and protein-bound selenium.