Reciprocal activity of AgRP and POMC neurons governs coordinated control of feeding and metabolism
Agouti-related peptide (AgRP)- and proopiomelanocortin (POMC)-expressing neurons reciprocally regulate food intake. Here, we combined non-interacting recombinases to simultaneously express functionally opposing chemogenetic receptors in AgRP and POMC neurons allowing to compare metabolic responses in mice with simultaneous activation of AgRP and inhibition of POMC neurons with isolated activation of AgRP neurons or isolated inhibition of POMC neurons. These experiments revealed that food intake is regulated by the additive effect of AgRP-neuron activation and POMC-neuron inhibition, while systemic insulin sensitivity and gluconeogenesis are differentially modulated by isolated versus simultaneous regulation of AgRP and POMC neurons. We identified a neurocircuit engaging Npy1R-expressing neurons in the paraventricular nucleus of the hypothalamus (PVH), where activated AgRP- and inhibited POMC neurons synergize to promote food consumption and activate neurons in the nucleus tractus solitarii (NTS). We then performed single-nuclei RNA sequencing to define the molecular nature of Fos+ cells in the posterior NTS/AP area that respond to simultaneous chemogenetic intervention over AgRP and POMC neurons and identified TH+ neurons as candidates for receiving neuronal inputs initiated by the simultaneous and coordinated interplay between AgRP and POMC neurocircuits and relayed to the NTS area by the silenced glutamatergic Npy1R neurons. Overall design: All experiments were performed in adult mice, age 12-20 weeks, and both sexes were assayed, always considering balanced sex and body weight distribution in both experimental groups. For this experiment wildtype mice and AgRP-Gq;POMC-Gi (AgRP-IRES-Cre+/-;hM3DGqfl/- ;POMC-Dre+/-;hM4DGifl/-) mice were included. Both groups were injected with CNO (clozapine-N-oxide, 3mg/kg; Abcam ab141704) intraperitoneally (ip) at the start of each experiment. Mice were sacrificed by cervical dislocation 1h after CNO injection in the absence of food, and a portion of the hindbrain containing the AP and NTS was dissected. Samples from the same experimental condition were pooled together (n = 2 mice/group).