The effects of leptin deficiency on cold-induced energy expenditure

At 24 °C Lep-/- mice are hyperphagic compared to the Lep+/+ mice. Reducing the ambient temperature from 24 to 6 °C (3 °C per day) was accompanied by a graded parallel increase in food intake in both control and Lep-/- mice. The rate of increase in food intake per degree Celsius reduction in ambient temperature by the control mice and Lep-/- mice was essentially indistinguishable. Since the body composition of Lep+/+ and Lep-/- mice was unchanged during cold exposure, thermogenesis is fueled solely by food intake. Accordingly, we predicted that the same changes in gene expression associated with the central regulation of thermogenesis by the hypothalamus must occur in both Lep+/+ and Lep-/- mice during the transition from 24 to 6 °C. Microarray analysis of gene expression was performed on hypothalamic tissue dissected from Lep-/- and Lep+/+ mice kept at different temperature conditions, that is, in mice maintained at 24°C and in mice in which the ambient temperature had been reduced to 6 °C over 6 days.