Ovariectomized C57/B6 mice gain weight as a result of decreased locomotor activity, not hyperphagia

• Published in: The FASEB journal 2006-03, Vol.20 (5), p.A833-A833
• Main Authors: Messina, Michelina M, Overton, J Michael
• Format: Article
• Language: English
• ISSN: 0892-6638; 1530-6860
• DOI: 10.1096/fasebj.20.5.A833-b

Estradiol (E2) modulates energy homeostasis. The purpose of this study was to investigate the mechanisms by which lack of gonadal steroids produces weight gain in female mice. C57BL/6J mice (16 wk old) were fed a standard chow diet and housed at standard temperature (23°C) in metabolic cages for continuous measurement of oxygen consumption (VO2). Cages were positioned on load‐beam platforms for detection of locomotor activity (LA). Following baseline, mice were either bilaterally ovariectomized (OVX) using an intra‐abdominal approach or they underwent sham surgery, and then housed in the same metabolic chambers for 3 wk. Prior to surgery, there were no differences in body weight between the groups (OVX = 23.7 ± 0.2; sham = 23.7 ± 0.4). After 3 wk, OVX mice had gained 3.2 ± 0.2 g, while shams maintained their baseline body weight (23.6 ± 0.6 g). Food intake decreased in both groups for the first few days after surgery, but by post‐surgical day 5, it had returned to baseline (OVX baseline = 20.7 ± 0.3 g) and remained at baseline levels for the remainder of the study (OVX 3 wk avg = 19.0 ± 0.5 g). LA was markedly decreased by OVX (dark phase pre‐OVX = 943 ± 108; post‐OVX 3 wk avg = 288 ± 164 m). This reduced LA was associated with reduced dark phase VO2 (pre‐OVX = 35.9 ± 0.2; post‐OVX 3 wk avg = 34.3 ± 0.3 ml/min/kg0.75). We conclude that, in C57BL/6J mice, weight gain induced by OVX is mediated by reduced LA and thermogenesis. Supported by NIH HL‐56732.