Leptin selectively increases energy expenditure of food-restricted lean mice

Abstract

OBJECTIVE: To find out whether leptin can attenuate hypometabolic torpor-like states of metabolic rate (MR) in adult lean animals, as it attenuates the morning suppression of thermoregulatory thermogenesis in suckling-age rat pups.

DESIGN: Leptin effects on MR and food intake were studied in mice aged 4–7 months, in which a high incidence of exaggerated circadian reductions of MR had been induced by chronic food-restriction and, for comparison, in free-feeding mice.

PROTOCOL: Continuous recordings of MR, for a group of seven mice maintained at an ambient temperature of 24°C, while they were repeatedly – with pauses of at least six days – treated for three consecutive days with either recombinant murine leptin (20, 200 or 600 pmol·g⁻¹·d⁻¹) or saline.

RESULTS: Leptin treatment caused dose-dependent 5–15% increases in energy expenditure by moderating the decreases in MR during the circadian minima, without affecting either the MR during the circadian maxima or food intake. Similar treatment of free-feeding mice caused dose-dependent decreases of food intake without changing MR.

CONCLUSION: Leptin controls thermoregulatory energy expenditure when food supplies are scarce and changes food intake, rather than energy expenditure, when food is abundant.