Abstract
Type-1 5'-iodothyronine deiodinase (5'-DI) is responsible for conversion of T4 to T3. Selenium (Se) is an integral part of this enzyme. Keeping in view the strong association between atherosclerosis and hypothyroidism, the present study examined the behavior of 5'-DI in liver, aorta and thyroid during hypercholesterolemia following different Se status, i.e., Se deficiency (0.02 ppm), adequate (0.2 ppm) and excess dose (1 ppm) in SD male rats. Animals were fed a control or high-cholesterol diet (2%) for 1 and 2 months. 5'-DI activity and mRNA expression was measured by RIA and RT-PCR respectively. In liver and aorta, 5'-DI expression significantly decreased with the Se-deficient and the high-cholesterol diet. The trend was opposite in thyroid, i.e., mRNA expression increased significantly during selenium deficiency and with a high-cholesterol feeding. But with 1 ppm Se supplementation, the 5'-DI expression increased in all the three tissues. The present study indicates that hypercholesterolemia along with selenium deficiency is co-responsible for differential regulation of 5'-DI enzyme in thyroidal vs. extrathyroidal tissues. Distinct regulation of 5'-DI in the thyroid reflects the clinical importance of this selenoprotein during hypercholesterolemia as this enzyme is essential for T3 production, which further has a vital role in the maintenance of lipid metabolism.
Highlights
Type-1 5’-iodothyronine deiodinase (5’-DI) has a pivotal role in controlling the supply of T3 to the tissues
Se-excess+high-cholesterol diet (HCD). (a) mRNA expression by RT-PCR. (b) Expression was quantified by densitometric analysis
Data is expressed as mean ± SD from 4 observations. *p
Summary
Type-1 5’-iodothyronine deiodinase (5’-DI) has a pivotal role in controlling the supply of T3 (the biologically active form of thyroid hormone) to the tissues. Thyroid express 5’-DI activity, and studies have shown that it is identical to the hepatic 5’-DI (Green, 1978). The activity of 5’-DI has been shown to be decreased in a hypothyroid state and elevated during hyperthyroidism (Wassen et al, 2004). Selenium (Se), an essential element and potent antioxidant, has an important role in the control of thyroid hormone metabolism. Keeping in view the important role of Se in hypercholesterolemia and its association with 5’-DI, the purpose of present study was to explore the response of 5’-DI enzyme in liver, aorta and thyroid under different Se status during experimental hypercholesterolemia
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