Objective: 

Previous studies have established that thyroid hormones (TH) play important roles in the development and function of brown and white adipose tissue (WAT). However, data about local transformations of TH in adipose tissue are scarce. We decided, therefore, to measure changes in the enzyme activity of the type 3 iodothyronine deiodinase (D3) in murine WAT during development of dietary obesity.

Methods: 

High-fat-feeding induction of obesity was followed in male C57BL/6J mice maintained on a special high-fat (HF) diet for 2 weeks before analysis, in comparison with the same animals maintained on a standard low-fat (LF) diet. Serum total thyroxine (T4) and triiodothyronine (T3) concentrations were determined using RIA kits. D3 activity in WAT was measured with the aid of our newly developed radiometric enzyme assay (see the accompanying posters from the same Institutes).

Results: 

HF-diet feeding resulted in an increased size of adipocytes and in a significantly higher weight of both epididymal-visceral and dorsolumbar-subcutaneous fat depots. Total T4 and total T3 plasma levels were significantly elevated in mice fed HF-diet, in comparison with mice maintained on LF-diet (n=17, p<0.05). Development of HF-diet-induced obesity in the mice was associated with an enhancement of D3 activity in WAT, especially in subcutaneous fat depots (n=14, p<0.05).

Conclusions: 

HF-diet-induced obesity in mice was associated with proliferation and differentiation of WAT and stimulation of thyroid hormones metabolism in WAT. Support from the Ministry of Education of the Czech Republic (Project No. MSM0021622413), Academy of Sciences of CR (Project No. AV0Z50110509), and from the Czech Science Foundation GA CR (Grant No. 304/08/0256) is acknowledged.