GLP-1 increases preingestive satiation via hypothalamic circuits in mice and humans.

Glucagon-like peptide-1 (GLP-1) receptor agonists (GLP-1RAs) are effective antiobesity drugs. However, the precise central mechanisms of GLP-1RAs remain elusive. We administered GLP-1RAs to patients with obesity and observed a heightened sense of preingestive satiation. Analysis of human and mouse brain samples pinpointed GLP-1 receptor (GLP-1R) neurons in the dorsomedial hypothalamus (DMH) as candidates for encoding preingestive satiation. Optogenetic manipulation of DMHGLP-1R neurons caused satiation. Calcium imaging demonstrated that these neurons are actively involved in encoding preingestive satiation. GLP-1RA administration increased the activity of DMHGLP-1R neurons selectively during eating behavior. We further identified that an intricate interplay between DMHGLP-1R neurons and neuropeptide Y/agouti-related peptide neurons of the arcuate nucleus (ARCNPY/AgRP neurons) occurs to regulate food intake. Our findings reveal a hypothalamic mechanism through which GLP-1RAs control preingestive satiation, offering previously unexplored neural targets for obesity and metabolic diseases.

Molecular Connectomics Reveals a Glucagon-Like Peptide 1 Sensitive Neural Circuit for Satiety.

Liraglutide and other agonists of the glucagon-like peptide 1 receptor (GLP-1RAs) are effective weight loss drugs, but how they suppress appetite remains unclear. GLP-1RAs inhibit hunger-promoting Agouti-related peptide (AgRP) neurons of the arcuate hypothalamus (Arc) but only indirectly, implicating synaptic afferents to AgRP neurons. To investigate, we developed a method combining rabies-based connectomics with single-nuclei transcriptomics. Applying this method to AgRP neurons in mice predicts 21 afferent subtypes in the mediobasal and paraventricular hypothalamus. Among these are Trh+ Arc neurons (TrhArc), which express the Glp1r gene and are activated by the GLP-1RA liraglutide. Activating TrhArc neurons inhibits AgRP neurons and decreases feeding in an AgRP neuron-dependent manner. Silencing TrhArc neurons increases feeding and body weight and reduces liraglutide's satiating effects. Our results thus demonstrate a widely applicable method for molecular connectomics, reveal the molecular organization of AgRP neuron afferents, and shed light on a neurocircuit through which GLP-1RAs suppress appetite.

Leptin receptor neurons in the dorsomedial hypothalamus input to the circadian feeding network.

Salient cues, such as the rising sun or availability of food, entrain biological clocks for behavioral adaptation. The mechanisms underlying entrainment to food availability remain elusive. Using single-nucleus RNA sequencing during scheduled feeding, we identified a dorsomedial hypothalamus leptin receptor-expressing (DMHLepR) neuron population that up-regulates circadian entrainment genes and exhibits calcium activity before an anticipated meal. Exogenous leptin, silencing, or chemogenetic stimulation of DMHLepR neurons disrupts the development of molecular and behavioral food entrainment. Repetitive DMHLepR neuron activation leads to the partitioning of a secondary bout of circadian locomotor activity that is in phase with the stimulation and dependent on an intact suprachiasmatic nucleus (SCN). Last, we found a DMHLepR neuron subpopulation that projects to the SCN with the capacity to influence the phase of the circadian clock. This direct DMHLepR-SCN connection is well situated to integrate the metabolic and circadian systems, facilitating mealtime anticipation.

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

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.

Food-induced dopamine signaling in AgRP neurons promotes feeding.

Obesity comorbidities such as diabetes and cardiovascular disease are pressing public health concerns. Overconsumption of calories leads to weight gain; however, neural mechanisms underlying excessive food consumption are poorly understood. Here, we demonstrate that dopamine receptor D1 (Drd1) expressed in the agouti-related peptide/neuropeptide Y (AgRP/NPY) neurons of the arcuate hypothalamus is required for appropriate responses to a high-fat diet (HFD). Stimulation of Drd1 and AgRP/NPY co-expressing arcuate neurons is sufficient to induce voracious feeding. Delivery of a HFD after food deprivation acutely induces dopamine (DA) release in the ARC, whereas animals that lack Drd1 expression in ARCAgRP/NPY neurons (Drd1AgRP-KO) exhibit attenuated foraging and refeeding of HFD. These results define a role for the DA input to the ARC that encodes acute responses to food and position Drd1 signaling in the ARCAgRP/NPY neurons as an integrator of the hedonic and homeostatic neuronal feeding circuits.

Assessing average somatic CAG repeat instability at the protein level.

Sandwich ELISA-based methods use Abs that target the expanded polyglutamine (polyQ) tract to quantify mutant huntingtin (mHTT). Using Meso Scale Discovery (MSD) assay, the mHTT signal detected with MW1 Ab correlated with polyQ length and doubled with a difference of only 7 glutamine residues between equivalent amounts of purified mHTTexon1 proteins. Similar polyQ length-dependent effects on MSD signals were confirmed using endogenous full length mHTT from brains of Huntington's disease (HD) knock-in (KI) mice. We used this avidity bias to devise a method to assess average CAG repeat instability at the protein level in a mixed population of HTT proteins present in tissues. Signal detected for average polyQ length quantification at the protein level by our method exhibited a strong correlation with average CAG repeat length at the genomic DNA level determined by PCR method in striatal tissue homogenates from HdhQ140 KI mice and in human HD postmortem cortex. This work establishes that CAG repeat instability in mutant HTT is reflected at the protein level.