Objective: 

Our aims were to measure possible changes in activities of thyroid hormones (TH)-metabolizing enzymes in white adipose tissue (WAT) and to describe the role of metabolic conversions of TH in WAT during obesogenic treatment, caloric restriction and in response to leptin in mice.

Methods: 

Male C57BL/6J mice were subjected to three above mentioned treatments. Subcutaneous and epididymal WAT and interscapular brown fat (BAT) depots were dissected and used for morphometric and enzymatic analyses. Plasma levels of leptin, as well as total and free thyroxine (T4) and triiodothyronine (T3) concentrations were determined using RIA kits. Enzyme activities of iodothyronine deiodinases of the types 1 (D1) and 2 (D2) in WAT and BAT and in the liver were measured with the aid of our newly developed radiometric enzyme assays.

Results: 

D1 activity in WAT was stimulated by a high-fat-diet feeding, which also increased plasma levels of leptin. However, D1 or D2 activities in BAT did not change. Caloric restriction decreased D1 activity in WAT, but not in the liver, and reduced leptin levels. In return, leptin injections increased D1 activity in WAT. In summary, our results demonstrate changes in D1 activity in WAT under the conditions of changing adiposity, and a stimulatory effect of leptin on D1 activity in white adipose tissue.

Conclusions: 

Attained results suggest a functional role for D1 in WAT, with D1 possibly being involved in the control of adipose tissue metabolism. Supported by the Academy of Sciences of the Czech Republic (Project No. AV0Z50110509), Ministry of Education of CR (Project No. MSM0021622413) and Czech Science Foundation GA CR (Grant No. 304/08/0256).