[Selenium: physiologic role and value in human pathology].

Abstract

Selenium (Se) is a metalloid with chemical properties closed to those of sulfur, but they can not substitute for one another in vivo. Se body content reflected soil Se content (13 to 20 mg in North Americans, 3 to 6 in New Zealand residents). The daily intake recommended is 50 to 200 micrograms. In the diet Se occurs in mineral or organic forms, the bioavailability of these latter is better. Se as selenocysteine is incorporated in specific proteins such as glutathione peroxidase (GSH-Px). Se is metabolized in H2Se by reductive pathways. H2Se is methylated and methylated compounds are excreted in the urines. The Se urinary excretion represents the principal known process of Se regulation. Se bound to GSH-Px participates to free radical destruction and cellular membrane protection. Its role is complementary of vitamin E effect. Se also seems indispensable to appropriate immune response. It can chelate various metals allowing their detoxication. Se metabolism can be studied by Se assay in serum, whole blood, urine (reference values must be performed for each studied population) and by GSH-Px activity determination in erythrocytes or platelets. Vitamin E assay completes estimation of the antioxidative status of organism. Few Se intoxications have been recognized but Se deficiencies often happen. They can lead to a cardiomyopathy (Keshan disease), increase the risk of cardiovascular diseases or cancer. Se deficiencies are found in chronic renal failure, malnutrition malabsorption, long term parenteral nutrition. At the present time it is not known how Se deficiency interfers with chronic infections which often go with these diseases. A better knowledge of Se requirements and Se role could allow an appropriate supplementation in various diseases.