title: A comparative genotoxicity study of a supraphysiological dose of triiodothyronine (T₃) in obese rats subjected to either calorie-restricted diet or hyperthyroidism.
abstract: This study was designed to determine the genotoxicity of a supraphysiological dose of triiodothyronine (T3) in both obese and calorie-restricted obese animals. Fifty male Wistar rats were randomly assigned to one of the two following groups: control (C; n = 10) and obese (OB; n = 40). The C group received standard food, whereas the OB group was fed a hypercaloric diet for 20 weeks. After this period, half of the OB animals (n = 20) were subjected to a 25%-calorie restriction of standard diet for 8 weeks forming thus a new group (OR), whereas the remaining OB animals were kept on the initial hypercaloric diet. During the following two weeks, 10 OR animals continued on the calorie restriction diet, whereas the remaining 10 rats of this group formed a new group (ORS) given a supraphysiological dose of T3 (25 µg/100 g body weight) along with the calorie restriction diet. Similarly, the remaining OB animals were divided into two groups, one that continued on the hypercaloric diet (OB, n = 10), and one that received the supraphysiological dose of T3 (25 µg/100 g body weight) along with the hypercaloric diet (OS, n = 10) for two weeks. The OB group showed weight gain, increased adiposity, insulin resistance, increased leptin levels and genotoxicity; T3 administration in OS animals led to an increase in genotoxicity and oxidative stress when compared with the OB group. The OR group showed weight loss and normalized levels of adiposity, insulin resistance, serum leptin and genotoxicity, thus having features similar to those of the C group. On the other hand, the ORS group, compared to OR animals, showed higher genotoxicity. Our results indicate that regardless of diet, a supraphysiological dose of T3 causes genotoxicity and potentiates oxidative stress.
authors.affiliation: Department of Internal Medicine, Botucatu Medical School - University of Sao Paulo State (UNESP), Botucatu, SP, Brazil. mt_bio@yahoo.com.br
authors.forename: Maria Teresa
authors.initials: MT
authors.lastname: De Sibio
authors.forename: Renata Azevedo Melo
authors.initials: RA
authors.lastname: Luvizotto
authors.forename: Regiane Marques Castro
authors.initials: RM
authors.lastname: Olimpio
authors.forename: Camila Renata
authors.initials: CR
authors.lastname: Corrêa
authors.forename: Juliana
authors.initials: J
authors.lastname: Marino
authors.forename: Miriane
authors.initials: M
authors.lastname: de Oliveira
authors.forename: Sandro José
authors.initials: SJ
authors.lastname: Conde
authors.forename: Ana Lúcia dos Anjos
authors.initials: AL
authors.lastname: Ferreira
authors.forename: Carlos Roberto
authors.initials: CR
authors.lastname: Padovani
authors.forename: Célia Regina
authors.initials: CR
authors.lastname: Nogueira
mesh_terms: D000273:Adipose Tissue; D000818:Animals; D001823:Body Composition; D001835:Body Weight; D031204:Caloric Restriction; D020552:Comet Assay; D002149:Energy Intake; D006980:Hyperthyroidism / Q000150:complications*; D007333:Insulin Resistance; D020738:Leptin / Q000097:blood; D008297:Male; D008315:Malondialdehyde / Q000378:metabolism; D009765:Obesity / Q000209:etiology*; D051381:Rats; D014284:Triiodothyronine / Q000008:administration & dosage / Q000097:blood / Q000633:toxicity*
chemical_list: D020738:Leptin; D014284:Triiodothyronine; D008315:Malondialdehyde