Effect of Thyrotoxicosis on Gene Expression of Hydrogen Sulfide-producing Enzymes in Epididymal Adipose Tissue of Male Rats

Introduction: Thyroid hormones are involved in the regulation of hydrogen sulfide (H2S) biosynthesis. The aim of this study is to determine effects of thyrotoxicosis on H2S levels and mRNA expression of cystathionine-β-synthase (CBS), cystathionine-γ-lyase (CSE) and 3-mercaptopyruvate sulfurtransferase (3-MST) in the adipose tissue of rat. Materials and Methods: Male rats were divided into the control (n=8) and thyrotoxicosis groups (n=8). Thyrotoxicosis was induced by adding L-thyroxine (12 mg/L) in drinking water for 21 days. Serum levels of free triiodothyronine (FT3), free thyroxine (FT4), total T3 (TT3), and total thyroxine (TT4) as well as thyroid stimulating hormone (TSH) were measured on day 21. H2S concentrations in serum and epididymal adipose tissue, as well as mRNA expressions of CBS, CSE, and 3-MST in epididymal adipose tissue were measured on day 21. Results: Serum levels of FT3, FT4, TT3 and TT4 were significantly higher, whereas TSH level was significantly lower in rats with thyrotoxicosis. Compared to controls, H2S levels (µmol/L) were lower in serum (43%, P<0.001) and epididymal adipose tissue (30% P=0.044) of rats with thyrotoxicosis. Thyrotoxicosis decreased mRNA expression of CSE (62%, P<0.001) and increased mRNA expression of CBS (116%, P=0.013) but not 3-MST in the epididymal adipose tissue. Conclusions: Thyrotoxicosis decreased H2S levels in the serum and epididymal adipose tissue, an effect which can be due to decreased mRNA expression of CSE. Decreased serum and adipose tissue levels of H2S may contribute to the pathophysiology of thyrotoxicosis.