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Thyroid hormone receptor β-specific agonist GC-1 increases energy expenditure and prevents fat-mass accumulation in rats

2007; Bioscientifica; Volume: 193; Issue: 1 Linguagem: Inglês

10.1677/joe.1.07066

1479-6805

Cássio M. Villicev, Fatima R. Freitas, Marcelo Saldanha Aoki, Cássio Taffarel, Thomas S. Scanlan, Anselmo Sigari Moriscot, Miriam O. Ribeiro, Antônio C. Bianco, Cecília Helena de Azevedo Gouveia,

Growth Hormone and Insulin-like Growth Factors

It is well known that thyroid hormone affects body composition; however, the effect of the thyroid hormone receptor beta (TRbeta)-selective thyromimetic GC-1 on this biological feature had not been demonstrated. In the current study, we compared the effects of a 6-week treatment with triiodothyronine (T3; daily injections of 3 or 6 microg/100 g body weight) or GC-1 (equimolar doses) on different metabolic parameters in adult female rats. Whereas all animals gained weight (17-25 g) in a way not basically affected by T3 or GC-1 treatment, only T3 treatment selectively increased food intake (50-70%). Oxygen consumption was significantly and equally increased (50-70%) by T3 and GC-1. Analysis of body composition by dual-energy X-ray absorptiometry (DEXA) revealed that, whereas control animals gained about 80% of fat mass, T3- or GC-1-treated animals lost 70-90 and approximately 20% respectively. Direct analysis of the carcass showed that T3 treatment promoted a 14-74% decrease in fat content but GC-1 treatment promoted only a 15-23% reduction. The gain in lean mass by DEXA and the carcass protein content were not affected by T3 or GC-1 treatment. However, the mass of individual skeletal muscles was negatively affected by T3 but only barely by GC-1. These findings highlight the potential use of GC-1 for the treatment of obesity and the metabolic syndrome.