Hypothalamic Agouti-Related Peptide Neurons and the Central Melanocortin System Are Crucial Mediators of Leptin’s Antidiabetic Actions

• Leptin receptor signaling through AgRP neurons prevents diabetes in mice
• The AgRP neuropeptide, but not NPY nor GABA, is required for this action
• Glucagon, but not insulin, is a likely mediator of improved glycemia by leptin
• The data reveal the existence of a novel leptin-LepRb-AgRP-MC4R-glucagon-glucose axis

SummaryLeptin has beneficial effects on glucose metabolism via actions in the hypothalamus, but the roles of specific subgroups of neurons responsible for these antidiabetic effects remain unresolved. We generated diabetic Lepob/ob or Leprdb/db mice lacking or re-expressing leptin receptors (LepRb) in subgroups of neurons to explore their contributions to leptin’s glucose-lowering actions. We show that agouti-related peptide (AgRP)-expressing neurons are both required and sufficient to correct hyperglycemia by leptin. LepRb in pro-opiomelanocortin (POMC) neurons or steroidogenic factor-1 (SF1) neurons are not required. Furthermore, normalization of blood glucose by leptin is blunted in Lepob/ob/MC4R-null mice, but not in Lepob/ob mice lacking neuropeptide Y (NPY) or gamma-aminobutyric acid (GABA) in AgRP neurons. Leptin’s ability to improve glucose balance is accompanied by a reduction in circulating glucagon. We conclude that AgRP neurons play a crucial role in glucose-lowering actions by leptin and that this requires the melanocortin system, but not NPY and GABA.

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