The hypothalamic neurons are major components of the neural circuits that control energy homeostasis. Proopiomelanocortin (POMC) neurons in the arcuate nucleus (ARC) play a major role in regulating energy intake, energy expenditure, and glucose metabolism. In our studies under the previous award from July 13, 2012 to present, we have clearly demonstrated molecular and neurochemical heterogeneity of POMC neurons in the ARC and that distinct subpopulations of POMC neurons directly and indirectly interact in a manner that is critical to the net outcome of the melanocortin signaling. In addition to this neurochemical heterogeneity, neuroanatomical studies have revealed that distinct sets of POMC neurons project to different target sites. This neurochemical and neuroanatomical heterogeneity of ARC POMC neurons, combined with their broad functional repertoire, strongly support the idea that there is functional heterogeneity of ARC POMC neurons. As our specific aims under the previous award have been completed, we now propose that neurochemically distinct subpopulations of POMC neurons have distinct target organs and functions. The liver is the main glucose supplier in overnight fasting and short term fasting. Hepatic glucose production results either from de novo synthesis via gluconeogenesis or from degradation of hepatic glycogen via glycogenolysis. This process appears to be regulated by the central melanocortin system. For instance, ARC POMC neurons project to liver and postnatal ablation of POMC neurons elevates blood glucose levels and induces glucose intolerance. However, there still exist foundational gaps in our knowledge of the neurobiology and neuroanatomy of the central melanocortin system that regulates liver metabolism. Our preliminary studies show that a subpopulation of ARC POMC neurons innervate liver through two autonomic centers, including the intermediolateral cell column of the spinal cord and the dorsal motor nucleus of the vagus. These neuroanatomical studies raise questions as to what types of POMC neurons project to liver and which autonomic circuits are used by POMC neurons to regulate hepatic glucose production. In fact, recent studies with genetically engineered mice that have induced mutations exclusively in POMC neurons have demonstrated that energy intake, energy expenditure, glucose metabolism, and locomotor activity are regulated by distinct sets of POMC neurons. As there exist liver-projecting ARC POMC neurons, we hypothesize that these liver-projecting ARC POMC neurons play a key role in the regulation of hepatic glucose production.
In Aim 1, we will thoroughly examine the neurochemical and neuroanatomical identity of ARC POMC neurons projecting to liver. And then we will explore the physiological impact of liver-projecting POMC neuron stimulation on hepatic glucose production in Aim 2. In summary, we will incorporate optogenetics with viral-mediated delivery of the Cre recombinase gene to achieve organ-specific optogenetic control that is highly innovative. As we can manipulate exclusively liver-projecting POMC neuron activity in vivo with high temporal resolution, this will significantly expand our capability to probe the causal relationship between the melanocortin signaling and hepatic glucose homeostasis.

Public Health Relevance

In view of the rampant increase in obesity and obesity-related metabolic syndrome such as hyperglycemia, understanding the melanocortin neural circuits that regulate hepatic glucose production will open up a new therapeutic strategy to control circulating blood glucose levels in people with diabetes.

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National Institute of Diabetes and Digestive and Kidney Diseases (NIDDK)
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Neuroendocrinology, Neuroimmunology, Rhythms and Sleep Study Section (NNRS)
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Cooke, Brad
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Albert Einstein College of Medicine
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Jeong, Jae Hoon; Chang, Ji Suk; Jo, Young-Hwan (2018) Intracellular glycolysis in brown adipose tissue is essential for optogenetically induced nonshivering thermogenesis in mice. Sci Rep 8:6672
Jeong, Jae Hoon; Lee, Dong Kun; Jo, Young-Hwan (2017) Cholinergic neurons in the dorsomedial hypothalamus regulate food intake. Mol Metab 6:306-312
Jeong, Jae Hoon; Woo, Young Jae; Chua Jr, Streamson et al. (2016) Single-Cell Gene Expression Analysis of Cholinergic Neurons in the Arcuate Nucleus of the Hypothalamus. PLoS One 11:e0162839
Lee, Dong Kun; Jeong, Jae Hoon; Oh, Seunghoon et al. (2015) Apelin-13 enhances arcuate POMC neuron activity via inhibiting M-current. PLoS One 10:e0119457
Jeong, Jae Hoon; Lee, Dong Kun; Blouet, Clemence et al. (2015) Cholinergic neurons in the dorsomedial hypothalamus regulate mouse brown adipose tissue metabolism. Mol Metab 4:483-92
Lee, Dong Kun; Jeong, Jae Hoon; Chun, Sung-Kun et al. (2015) Interplay between glucose and leptin signalling determines the strength of GABAergic synapses at POMC neurons. Nat Commun 6:6618
Marcelin, Geneviève; Jo, Young-Hwan; Li, Xiaosong et al. (2014) Central action of FGF19 reduces hypothalamic AGRP/NPY neuron activity and improves glucose metabolism. Mol Metab 3:19-28
Jo, Young-Hwan; Buettner, Christoph (2014) Why leptin keeps you warm. Mol Metab 3:779-80
Jo, Young-Hwan; Chua Jr, Streamson C (2013) The brain-liver connection between BDNF and glucose control. Diabetes 62:1367-8
Groessl, Florian; Jeong, Jae Hoon; Talmage, David A et al. (2013) Overnight fasting regulates inhibitory tone to cholinergic neurons of the dorsomedial nucleus of the hypothalamus. PLoS One 8:e60828

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