Understanding the Roles of Selenium on Thyroid Hormone-Induced Thermogenesis in Adipose Tissue.

Brown adipose tissue (BAT) and white adipose tissue (WAT) are known to regulate lipid metabolism. A lower amount of BAT compared to WAT, along with adipose tissue dysfunction, can result in obesity. Studies have shown that selenium supplementation protects against adipocyte dysfunction, decreases WAT triglycerides, and increases BAT triiodothyronine (T). In this review, we discuss the relationship between selenium and lipid metabolism regulation through selenoprotein deiodinases and the role of deiodinases and thyroid hormones in the induction of adipose tissue thermogenesis. Upon 22 studies included in our review, we found that studies investigating the relationship between selenium and deiodinases demonstrated that selenium supplementation affects the iodothyronine deiodinase 2 (DIO2) protein and the expression of its associated gene, DIO2, proportionally. However, its effect on DIO1 is inconsistent while its effect on DIO3 activity is not detected. Studies have shown that the activity of deiodinases especially DIO2 protein and DIO2 gene expression is increased along with other browning markers upon white adipose tissue browning induction. Studies showed that thermogenesis is stimulated by the thyroid hormone T as its activity is correlated to the expression of other thermogenesis markers. A proposed mechanism of thermogenesis induction in selenium supplementation is by autophagy control. However, more studies are needed to establish the role of T and autophagy in adipose tissue thermogenesis, especially, since some studies have shown that thermogenesis can function even when T activity is lacking and studies related to autophagy in adipose tissue thermogenesis have contradictory results.