3,5-DIIODO-L-THYRONINE-INDUCED MODIFICATION IN PITUITARY-THYROID AXIS IN RATS FED HIGH-FAT DIET. A PRELIMINARY REPORT

Experimental observations highlight that the administration of 3,5-diiodo-L-thyronine (T2) may decrease the body weight and the plasma levels of cholesterol and triglycerides and may prevent the onset of hepatic steatosis in rats fed diets rich in lipids (HFD). On the basis of these findings we have carried out some in vivo studies to evaluate the effects of increased levels of T2 on pituitary thyroid axis function in HFD rats. Fifteeen Wistar male rats were divided in 3 groups. The first group (N) was fed with a standard diet. The second group (G) was fed with a diet high in fat (HDF), while the third group (GT2) was additionally administered intraperitoneally with T2 (70 ug/100g body weight) for 3 days a week up to 4 week. Blood samples from animals were collected and stored at -20°C until 3rd generation and TSH, T3, T4, ACTH, triglycerides, cholesterol, glucose ALT, AST, Alkaline Phosphatase were assayed. Furthermore, rat liver from rats underwent histological examination to assess the degree of steatosis. The administration of T2 (70 ug/100 gr body weight 3 times a week up to 4 weeks suppressed TSH secretion in HDF rats. Unlike observed in the liver of rats from group N and group GT2, the histological examination of the liver from G group rats showed the presence of hepatic steatosis. These preliminary data highlight that the administration of 70 ug/100 b.w. of T2 inhibits TSH secretion and prevent the onset of hepatic steatosis in HFD rats.