The maintenance of energy metabolism is a fundamental homeostatic function found in all organisms from humans to simple cells. Disruption of energy metabolism can lead to life-threatening conditions, including chronic metabolic disorders such as obesity and diabetes. Understanding the regulatory principles that control energy metabolism is of the utmost importance in helping to design better treatments for metabolic disorders. AGRP neurons in the hypothalamus participate in the regulation of energy metabolism and are activated during times of food deprivation. Paradoxically, we showed that AGRP neuronal activity is also elevated in diet- induced obese mice. We have recently found that mitochondria in AGRP neurons undergo fusion when mice switch from negative to positive energy balance (i.e., from food deprived to high-fat fed). When we blocked mitochondria fusion in AGRP neurons (by knocking down Mfn2) in mice fed a high-fat diet, AGRP neuron activity decreased due to reduced intracellular levels of ATP, and the mice became resistant to diet-induced obesity. Because in both food deprived and high-fat diet fed mice the activity of AGRP neurons is high, we hypothesize that AGRP neuron activity is supported by different mechanisms in these two conditions. This is illustrated by the fission state of mitochondria in AGRP neurons during food deprivation, and the fused state in high-fat fed mice. The goal of this application is to provide mechanistic insight into the complexity of the biology involved in the adaptations of AGRP neurons to different metabolic conditions.
In Aim 1, we will use cell-specific ribosome profiling of AGRP neurons combined with RNA-sequencing to identify changes in the translational landscape of AGRP neurons. In Sub-Aim 1.1 we will characterize the ribosome-associated transcriptome (translatome) involved in AGRP neuron function in food deprived, fed and high-fat diet fed mice. In Sub-Aim 1.2 we will characterize how the translatome of AGRP neurons is modified in the absence of mitochondria fusion during diet-induced obesity in AGRP-Mfn2KO mice. These experiments will identify the putative intracellular mechanisms that allow AGRP neurons to adapt to the changing metabolic milieu.
In Aim 2, we will tackle a very important mechanistic question that is whether mitochondrial dynamics in AGRP neurons is controlled by the electrical activity of the cells. We will use a multi-faceted approach to selectively and acutely activate/inhibit Agrp neurons utilizing transgenic and AAV-mediated mouse models with the goal of identifying dynamic morphological changes in mitochondria through electron microscopic analyses. This proposal will deliver novel insights into the central regulation of metabolism and offer new candidates to pursue as drug targets for obesity and related metabolic disorders.

Public Health Relevance

Disruption of energy metabolism can lead to life-threatening conditions such as obesity and diabetes. Understanding the regulatory principles that control energy metabolism is important to help design better treatments for these diseases. AGRP neurons in the hypothalamus participate in the regulation of energy balance and are activated during times of food deprivation to promote hunger. Paradoxically, these neurons are also activated during high-fat feeding in mice to promote diet-induced obesity. The experiments proposed in this grant application have been designed to characterize key mechanisms involved in the dynamic responses of AGRP neurons to varying metabolic conditions. These studies will deliver novel insights into the central regulation of metabolism and should offer new candidates to pursue as drug targets for obesity and related disorders.

Agency
National Institute of Health (NIH)
Institute
National Institute of Diabetes and Digestive and Kidney Diseases (NIDDK)
Type
Research Project (R01)
Project #
1R01DK107916-01
Application #
9009790
Study Section
Neuroendocrinology, Neuroimmunology, Rhythms and Sleep Study Section (NNRS)
Program Officer
Hyde, James F
Project Start
2015-09-01
Project End
2020-08-31
Budget Start
2015-09-01
Budget End
2016-08-31
Support Year
1
Fiscal Year
2015
Total Cost
$374,625
Indirect Cost
$149,625
Name
Yale University
Department
Veterinary Sciences
Type
Schools of Medicine
DUNS #
043207562
City
New Haven
State
CT
Country
United States
Zip Code
06510