A leptin-responsive hypothalamic circuit inputs to the circadian feeding network

Abstract

Salient cues, such as the rising sun or the availability of food, play a crucial role in entraining biological clocks, allowing for effective behavioral adaptation and ultimately, survival. While the light-dependent entrainment of the central circadian pacemaker (suprachiasmatic nucleus, SCN) is relatively well defined, the molecular and neural mechanisms underlying entrainment associated with food availability remains elusive. Using single nucleus RNA sequencing during scheduled feeding (SF), we identified a leptin receptor (LepR) expressing neuron population in the dorsomedial hypothalamus (DMH) that upregulates circadian entrainment genes and exhibits rhythmic calcium activity prior to an anticipated meal. We found that disrupting DMHLepR neuron activity had a profound impact on both molecular and behavioral food entrainment. Specifically, silencing DMHLepR neurons, mis-timed exogenous leptin administration, or mis-timed chemogenetic stimulation of these neurons all interfered with the development of food entrainment. In a state of energy abundance, repetitive activation of DMHLepR neurons led to the partitioning of a secondary bout of circadian locomotor activity that was in phase with the stimulation and dependent on an intact SCN. Lastly, we discovered that a subpopulation of DMHLepR neurons project to the SCN with the capacity to influence the phase of the circadian clock. This leptin regulated circuit serves as a point of integration between the metabolic and circadian systems, facilitating the anticipation of meal times.

Neuroanatomical dissection of the MC3R circuitry regulating energy rheostasis

“…Therefore, we instead utilized high sensitivity RNAscope in situ hybridization approaches to map the expression of MC3R containing DMH neurons to previous DMH cell types implicated in energy homeostasis, and to characterize the neurochemical identify of DMH MC3R cells. Prior work has demonstrated a critical role for DMH neurons containing the leptin receptor (LepR) in controlling feeding behavior and circadian rhythms (47,48). To determine if DMH MC3R cells co-localize with DMH LepR neurons, we co-localized mRNA for MC3R and LepR in the DMH of male and female mice.…”