Awardee OrganizationBETH ISRAEL DEACONESS MEDICAL CENTER
Description
Abstract Text
AgRP neurons play a vital role in causing hunger – the desire to find and consume food. Hence, it is important
to understand how the activity of AgRP neurons is controlled. The conventional view is that feedback signals,
which track changes in energy balance, are the primary regulators of AgRP neurons. For example, the fasting-
induced increase in AgRP neuron activity is thought to be caused by falls in leptin and perhaps insulin, and an
increase in ghrelin. Conversely, recent studies using real-time in vivo monitoring of neural activity have
unexpectedly uncovered novel forms of regulation that are clearly unrelated to feedback from energy stores.
For example, detection of sensory cues related to food, and ingestion of food, both rapidly decrease AgRP
neuron activity – well before energy stores are affected. While these examples clearly document the existence
of rapid, “feedforward” inhibition of AgRP neurons, to date there have been no examples of the converse – i.e.
rapid, feedforward activation of AgRP neurons. By performing long-term in vivo recordings of AgRP neuron
activity, we have recently discovered that denial of access to food rapidly, within 30-60 minutes, activates
AgRP neurons. Importantly, this rapid activation is to a high level that does not increase further as fasting
progresses. This relatively rapid, “square wave” pattern of activation strongly indicates that it must be caused
by novel mechanisms which, importantly, are unrelated to changes in feedback signals. This discovery, which
could lead to a revision in models of AgRP neuron regulation, indicates that fasting-related activation, like
feeding-related inhibition, utilizes feedforward mechanisms. Given that AgRP neuron activity is vital for
appetite, and given that feedforward activation is not part of present models of AgRP neuron regulation, we
believe that uncovering the neural basis for this, and establishing its function, as we recently did for sensory
food cue inhibition of AgRP neurons, will provide important, previously unknown insights into the biology of
hunger. In preliminary studies, we have identified the source of this rapid feedforward activation. Remarkably,
the excitatory circuit carrying this activation to AgRP neurons shows a large degree of activity-dependent
synaptogenesis plasticity – which we believe functions to amplify and sustain feedforward activation of AgRP
neurons. Thus, the overall goal of this grant is to discover the basis for and understand the purpose of rapid,
feedforward activation of AgRP neurons. In Aim 1 we will use our single neuron transcriptomic dataset and
marker gene recombinase driver mice to establish the neural afferent basis for this regulation. In Aim 2 we will
determine the behavioral scenarios that trigger feedforward activation – we hypothesize a key role for
awareness that food is unavailable. In Aim 3 we will establish its function – this will be done by blocking the
responsible afferents and then examining consequences. Finally, in Aim 4, we will identify the molecular
mediators of and role for activity-dependent synaptogenesis / plasticity in this excitatory afferent à AgRP
neuron circuit – we hypothesize important roles for presynaptic release of Cbln2 and Bdnf.
Public Health Relevance Statement
Because disorders of hunger cause obesity and feeding disorders, it is unfortunate that the neurobiological
basis for hunger is so poorly understood. This proposal, by studying the neural activity of hunger-causing
AgRP neurons, is discovering previously unknown, feedforward mechanisms by which AgRP neuron activity,
and hence hunger, is increased. Uncovering the basis for and function of this feedforward activation of AgRP
neurons should provide important new insights in how the motivational drive, hunger, is created.
NIH Spending Category
No NIH Spending Category available.
Project Terms
AffectAfferent NeuronsAutomobile DrivingAwarenessBehavioralBiologyBrainCellsConfusionCuesDataData SetDehydrationDesire for foodDetectionDevicesDiseaseEatingExcitatory SynapseExcretory functionFastingFeedbackFoodFutureGenesGenetic MarkersGlutamatesGoalsGrantHungerIndividualIngestionInsulinLeptinLinkMediatorModelingMolecularMonitorMotivationMusNeurobiologyNeuronsNoseNutrientObesityPatternPlayRegulationRoleSensorySignal TransductionSourceSpeedSynapsesSynaptic plasticityThirstTimeTrainingWaterenergy balancefallsfeedingfood consumptionghrelinin vivoin vivo monitoringincreased appetiteinsightinterestneuralneuronal circuitrynovelpresynapticpreventrecombinaseselective expressionsynaptogenesistranscriptomics
National Institute of Diabetes and Digestive and Kidney Diseases
CFDA Code
847
DUNS Number
071723621
UEI
C1CPANL3EWK4
Project Start Date
04-August-2023
Project End Date
30-April-2028
Budget Start Date
01-May-2024
Budget End Date
30-April-2025
Project Funding Information for 2024
Total Funding
$486,196
Direct Costs
$281,200
Indirect Costs
$204,996
Year
Funding IC
FY Total Cost by IC
2024
National Institute of Diabetes and Digestive and Kidney Diseases
$486,196
Year
Funding IC
FY Total Cost by IC
Sub Projects
No Sub Projects information available for 5R01DK134427-02
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The Project Outcomes shown here are displayed verbatim as submitted by the Principal Investigator (PI) for this award. Any opinions, findings, and conclusions or recommendations expressed are those of the PI and do not necessarily reflect the views of the National Institutes of Health. NIH has not endorsed the content below.
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