Leptin receptor-positive and leptin receptor-negative proopiomelanocortin neurons innervate an identical set of brain structures.
Neurons that express the prohormone proopiomelanocortin (POMC) in the arcuate hypothalamic nucleus (Arc) are engaged in the regulation of energy balance and glucose homeostasis. Additionally, POMC neurons are considered key first-order cells regulated by leptin. Interestingly, in the Arc, POMC cells that express the leptin receptor (POMC/LepR+ cells) are found side by side with POMC cells not directly responsive to leptin (POMC/LepR- cells). However, it remains unknown whether these distinct populations innervate different target regions. Therefore, the objective of the present study was to compare the projections of POMC/LepR+ and POMC/LepR- neurons. Using genetically modified LepR-reporter mice to identify leptin receptor-expressing cells and immunohistochemistry to stain POMC-derived peptides (α-MSH or β-endorphin) we confirmed that approximately 80% of Arc β-endorphin-positive neurons co-expressed leptin receptors. POMC/LepR+ and POMC/LepR- axons were intermingled in all of their target regions. As revealed by confocal microscopy, we found an elevated degree of co-localization between α-MSH+ axons and the reporter protein (tdTomato) in all brain regions analyzed, with co-localization coefficients ranging from 0.889 to 0.701. Thus, these two populations of POMC neurons seem to project to the same set of brain structures, although one of the two subtypes of POMC axons was sometimes found to be more abundant than the other in distinct subregions of the same nucleus. Therefore, POMC/LepR+ and POMC/LepR- cells may target separate neuronal populations and consequently activate distinct neuronal circuits within some target nuclei. These findings contribute to unravel the neuronal circuits involved in the regulation of energy balance and glucose homeostasis.
Department of Physiology and Biophysics, Institute of Biomedical Sciences, University of São Paulo, São Paulo, SP, Brazil.
Leandro B
LB
Lima
Department of Physiology and Biophysics, Institute of Biomedical Sciences, University of São Paulo, São Paulo, SP, Brazil.
Martin
M
Metzger
Department of Physiology and Biophysics, Institute of Biomedical Sciences, University of São Paulo, São Paulo, SP, Brazil.
Isadora C
IC
Furigo
Department of Physiology and Biophysics, Institute of Biomedical Sciences, University of São Paulo, São Paulo, SP, Brazil. Electronic address: jdonato@icb.usp.br.
J
J
Donato
D000818:Animals; D001111:Arcuate Nucleus of Hypothalamus / Q000166:cytology* / Q000378:metabolism; D001921:Brain / Q000166:cytology* / Q000378:metabolism; D007150:Immunohistochemistry; D051379:Mice; D008810:Mice, Inbred C57BL; D008822:Mice, Transgenic; D009434:Neural Pathways / Q000166:cytology / Q000378:metabolism; D056347:Neuroanatomical Tract-Tracing Techniques; D009474:Neurons / Q000166:cytology* / Q000378:metabolism*; D017729:Presynaptic Terminals / Q000378:metabolism; D011333:Pro-Opiomelanocortin / Q000378:metabolism*; D054411:Receptors, Leptin / Q000378:metabolism*; D000521:alpha-MSH / Q000378:metabolism; D001615:beta-Endorphin / Q000378:metabolism
D054411:Receptors, Leptin; D000521:alpha-MSH; D001615:beta-Endorphin; D011333:Pro-Opiomelanocortin
Hypothalamus; Melanocortin; POMC; ROSA26 Cre reporter; α-MSH; β-endorphin