Impairment of iodothyronine 5′-deiodinase activity in brown adipose tissue and its acute stimulation by cold in selenium deficiency

Abstract

The activity of the type II iodothyronine 5′-deiodinase enzyme in brown adipose tissue has been examined in rats fed a selenium-deficient diet. Iodothyronine 5′-deiodinase activity was threefold lower in brown adipose tissue of deficient rats than in control animals. The activity of glutathione peroxidase, a biochemical index of selenium deficiency, was also greatly decreased in deficient animals. Cytochrome oxidase activity in brown fat was, however, unaltered by selenium deficiency. Acute exposure to cold (4 °C for 18 h) resulted in a substantial increase in iodothyronine 5′-deiodinase activity in brown adipose tissue of control rats, but the stimulatory effect of cold was attenuated in selenium-deficient animals. These results support the concept that the iodothyronine 5′-deiodinases are selenium-dependent enzymes, and indicate that the thermogenic response to cold may be impaired in selenium deficiency.Key words: iodothyronine 5′-deiodinase, glutathione peroxidase, selenium deficiency, brown adipose tissue, cold exposure.