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Submitted on August 14, 2007
Accepted on December 20, 2007
Departments of Medicine and Neuroscience, Albert Einstein College of Medicine, Bronx, NY; Department of Medicine and Physiology, University of Michigan Medical School, Ann Arbor, MI; UCSF Diabetes Center, University of California, San Francisco, CA; Department of Physiology, University of Bristol, Bristol, UK; Center for Hypothalamic Research, Department of Internal Medicine, The University of Texas Southwestern Medical Center, Dallas, TX; Department of Psychiatry and Behavioral Neurosciences, Wayne State University School of Medicine, Detroit, MI; Department of Biostatistics, University of Alabama at Birmingham, Birmingham, AL; Department of Pharmacology, Temple University School of Medicine, Philadelphia, PA; Department of Medicine, Beth Israel Deaconess Medical Center, Harvard Medical School, Boston, MA; Departments of Pediatrics and Genetics, Stanford University School of Medicine, Palo Alto, CA; Department of Medicine, University of California, San Diego, CA
* To whom correspondence should be addressed. E-mail: schua{at}aecom.yu.edu.
Two known types of leptin responsive neurons reside within the arcuate nucleus – the agouti gene related peptide (AGRP)/Neuropeptide Y (NPY) neuron and the pro-opiomelanocortin (POMC) neuron. By deleting the leptin receptor gene (Lepr) specifically in AGRP/NPY and/or POMC neurons of mice, we examined the several and combined contributions of these neurons to leptin action. Body weight and adiposity were increased by Lepr deletion from AgRP and POMC neurons individually, and simultaneous deletion in both neurons (A+P LEPR-KO mice) further increased these measures. Young (periweaning) A+P LEPR-KO mice exhibit hyperphagia and decreased energy expenditure, with increased weight gain, oxidative sparing of triglycerides and increased fat accumulation. Interestingly, however, many of these abnormalities were attenuated in adult animals, and high doses of leptin partially suppress food intake in the A+P LEPR-KO mice. While mildly hyperinsulinemic, the A+P LEPR-KO mice displayed normal glucose tolerance and fertility. Thus, AgRP/NPY and POMC neurons each play mandatory roles in aspects of leptin-regulated energy homeostasis, high leptin levels in adult mice mitigate the importance of leptin responsiveness in these neurons for components of energy balance, suggesting the presence of other leptin-regulated pathways that partially compensate for the lack of leptin action on the POMC and AgRP/NPY neurons.
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