Neuronal deletion of Lepr elicits diabesity in mice without affecting cold tolerance or fertility

Leptin signaling in the brain regulates energy intake and expenditure. To test the degree of functional neuronal leptin signaling required for the maintenance of body composition, fertility, and cold tolerance, transgenic mice expressing Cre in neurons ( CaMKII alpha- Cre) were crossed to mice carrying a floxed leptin receptor ( Lepr) allele to generate mice with neuron- specific deletion of Lepr in similar to 50% ( C F/ F mice) and similar to 75% ( C Delta 17/ F mice) of hypothalamic neurons. Leptin receptor LEPR)- deficient mice ( Delta 17/ Delta 17) with heat- shock- Cre- mediated global Lepr deletion served as obese controls. At 16 wk, male C F/ F, C Delta 17/ F, and Delta 17/ Delta 17 mice were 13.2 ( P < 0.05), 45.0, and 55.9% ( P < 0.001) heavier, respectively, than lean controls, whereas females showed 31.6, 68.8, and 160.7% increases in body mass ( P < 0.001). Significant increases in total fat mass ( C F/ F: P < 0.01; C Delta 17/ F and Delta 17/ Delta 17: P < 0.001 vs. sex- matched, lean controls), and serum leptin concentrations ( P < 0.001 vs. controls) were present in proportion to Lepr deletion. Male C Delta 17/ F mice had significant elevations in basal serum insulin concentrations ( P < 0.001 vs. controls) and were glucose intolerant, as measured by glucose tolerance test ( AUC P < 0.01 vs. controls). In contrast with previous observations in mice null for LEPR signaling, C F/ F and C Delta 17/ F mice were fertile and cold tolerant. These findings support the hypothesis that body weight, adiposity, serum leptin concentrations, and glucose intolerance are proportional to hypothalamic LEPR deficiency. However, fertility and cold tolerance remain intact unless hypothalamic LEPR deficiency is complete.