Pair‐feeding of ovariectomized rats does not prevent obesity and normalizes expression of hypothalamic neuropeptides

Abstract

Ovariectomy (OVX) causes hyperphagia and weight gain in rats. Estradiol (E2) abolishes these effects. Some report that pair‐feeding (PF) of OVX rats does not prevent obesity, but this finding is not universal. The purpose of this study was to determine the contribution of energy intake to OVX‐induced obesity. Long‐Evans rats (16 wk old) were fed chow and housed at 23°C. Rats were either intra‐abdominally bilaterally OVX (n = 20) or they underwent sham surgery (n = 12). For 3 wk, OVX rats were either PF (n = 8) or given ad libitum (AL) access to chow (n = 12). OVX‐AL rats were hyperphagic and had tonically decreased dark‐phase activity (pre‐OVX = 116 +/− 2 m, post‐OVX = 80 +/− 3 m). PF attenuated, but did not prevent, OVX‐induced obesity (3 wk weight gain: SHAM = 10.2 +/− 8.5, PF = 28.5 +/− 8.5, OVX = 51 +/− 10.5 g), indicating a role for E2 in regulation of energy expenditure. Next we investigated potential neural mechanisms underlying E2‐modulation of energy homeostasis. Quantitative RT‐PCR was used to measure mRNA levels of various hypothalamic genes of interest of these rats. Compared to shams, OVX led to increased MCH mRNA, an effect that was normalized by PF. Additional research is needed to understand E2‐specific mechanisms regulating energy expenditure. Support: NIH HL‐56732.