Effect of leptin on energy balance does not require the presence of intact adrenals

The present study was conducted to assess the effects of leptin on food intake and energy balance in the presence or absence of corticosterone. Three cohorts of C57BL/6 mice differing in their corticosterone status [nonadrenalectomized (intact), adrenalectomized (ADX), and ADX with corticosterone replacement] were infused with either saline or leptin at a dose of 150 microg . kg-1 . day-1. Throughout the study, mice had free access to both a high-starch and a high-fat diet. At the end of the experimental period, mice were decapitated and their carcasses were processed for the determination of energy, protein, and lipid contents. Leptin significantly reduced body gains in weight, fat, and energy, whereas corticosterone therapy significantly promoted all of these gains. Leptin and ADX significantly reduced food intake and gross energetic efficiency, whereas corticosterone therapy significantly increased these variables. The effects of leptin, ADX, and corticosterone on food intake were accounted for by changes in the intake of the high-fat diet. Leptin also attenuated the preference for fat that developed quickly in mice simultaneously exposed to the high-starch and high-fat regimen. Altogether, the results of this study 1) emphasize the abilities of leptin and corticosterone to, respectively, decrease and increase energy deposition and ingestion of fat, 2) do not substantiate any leptin-corticosterone interaction in the regulation of energy balance, and 3) demonstrate that leptin can produce its effect on energy and fat gains in the absence of an intact hypothalamic-pituitary-adrenal axis.