Administration of physiologic levels of triiodothyronine increases leptin expression in calorie-restricted obese rats, but does not influence weight loss.
Obesity has become a major public health problem, most commonly treated via dietary restriction to promote weight loss. Although leptin and thyroid hormones are involved in the regulation of energy balance, the role of these hormones after the stabilization of weight loss remains unclear. This study was designed to analyze the effect of thyroid hormone on sustained weight loss and leptin gene expression in obese animals after a loss of 5% to 10% of body weight. Thirty-day-old male Wistar rats were separated into 4 groups: control, obese, calorie restriction (CR), and calorie restriction with triiodothyronine administration (CRT). The obese group had increased weight and adiposity, leptin and insulin levels, and leptin gene expression. Dietary restriction in the CR group resulted in decreased body weight and adiposity, diminished leptin, and increased thyroid hormone receptor beta expression. The CRT group, submitted to dietary restriction with concomitant administration of a physiologic triiodothyronine dose, had thyroid hormone receptor beta expression at levels comparable with those observed in the control group and simultaneously increased leptin expression as compared with that in the CR group, suggesting that thyroid hormone modulates leptin expression under conditions of calorie restriction. Increased leptin expression in the CRT group did not result in increased circulating leptin or a statistically significant reduction in body weight during the treatment period. These data provide impetus for further study, as a longer treatment period may result in increased circulating leptin and, thus, further reduction in body weight during calorie restriction in an obesity model.
Department of Clinical Medicine, Botucatu School of Medicine, University of São Paulo State-UNESP, CEP: 18618-000 Botucatu, SP, Brazil.
Renata A M
RA
Luvizotto
Sandro J
SJ
Conde
Maria T
MT
Síbio
André F
AF
Nascimento
Ana P
AP
Lima-Leopoldo
André S
AS
Leopoldo
Carlos R
CR
Padovani
Antônio C
AC
Cicogna
Célia Regina
CR
Nogueira
D000818:Animals; D001823:Body Composition; D001835:Body Weight; D031204:Caloric Restriction; D002149:Energy Intake; D007328:Insulin / Q000097:blood; D020738:Leptin / Q000097:blood*; D008297:Male; D009765:Obesity / Q000503:physiopathology*; D016133:Polymerase Chain Reaction; D051381:Rats; D017208:Rats, Wistar; D014284:Triiodothyronine / Q000008:administration & dosage* / Q000097:blood / Q000502:physiology; D015431:Weight Loss
D007328:Insulin; D020738:Leptin; D014284:Triiodothyronine