Direct And Indirect Effects Of Liraglutide On Hypothalamic POMC And NPY/AgRP Neurons-Implications For Energy Balance And Glucose Control

In human and mammalian,proopiomelanocortin(POMC)and Neuropeptide Y/Agouti-related peptide(NPY/AgRP)neurons are widely distributed in the arcuate nucleus of hypothalamus.Importantly,the excitatory changes of POMC and NPY/AgRP neurons are directly involved in the regulation of feeding behavior,body weight,glucose homeostasis and energy balance.The long-acting glucagon-like peptide-1 receptor(GLP-1R)agonist,liraglutide,stimulates insulin secretion and efficiently suppresses food intake to reduce body weight.As such,liraglutide is growing in popularity in the treatment of diabetes and chronic weight management.Within the brain,liraglutide has been shown to alter the activity of hypothalamic POMC and NPY/AgRP neurons.The acute activities of POMC and NPY neurons which induced by liraglutide have been directly linked to feeding behavior,body weight,and glucose metabolism and energy balance.Despite the increased usage of liraglutide and other GLP-1 analogues as diabetic and obesity interventions,the cellular mechanisms by which liraglutide alters the activity of metabolically relevant neuronal populations are poorly understood.In order to resolve this issue,we utilized neuron-specific transgenic mouse models to identify POMC and NPY neurons for patch-clamp electrophysiology experiments.We found that liraglutide directly activated arcuate POMC neurons via TrpC5 channels,sharing a similar mechanistic pathway to the adipose-derived peptide leptin.In support of an additive role of leptin and liraglutide in suppressing food intake,leptin potentiated the acute effects of liraglutide to activate POMC neurons.Moreover,TrpC5 subunits in POMC neurons were also required for the intact pharmacological effects of liraglutide on food intake and body weight.Liraglutide also indirectly increases excitatory tone to POMC neurons.In contrast,liraglutide inhibited NPY/AgRP neurons through post-synaptic GABAA receptors via chloride channel and enhanced activity of pre-synaptic GABAergic neurons,which required both TrpC5 subunits and K-ATP channels.Thus,the current study adds to recent work from our group and others,which highlight potential mechanisms to amplify the effects of GLP-1 agonists in vivo.Moreover,these data highlight multiple sites of action(both pre-and post-synaptic)for GLP-1 agonists on this circuit.Taken together,our results identify critical molecular mechanisms linking GLP-1 analogues in arcuate POMC and NPY/AgRP neurons with metabolism.