Optogenetic stimulation of the liver-projecting melanocortinergic pathway promotes hepatic glucose production

Nat Commun. 2020 Dec 8;11(1):6295. doi: 10.1038/s41467-020-20160-w.

Abstract

The central melanocortin system plays a fundamental role in the control of feeding and body weight. Proopiomelanocortin (POMC) neurons in the arcuate nucleus of the hypothalamus (ARC) also regulate overall glucose homeostasis via insulin-dependent and -independent pathways. Here, we report that a subset of ARC POMC neurons innervate the liver via preganglionic parasympathetic acetylcholine (ACh) neurons in the dorsal motor nucleus of the vagus (DMV). Optogenetic stimulation of this liver-projecting melanocortinergic pathway elevates blood glucose levels that is associated with increased expression of hepatic gluconeogenic enzymes in female and male mice. Pharmacological blockade and knockdown of the melanocortin-4 receptor gene in the DMV abolish this stimulation-induced effect. Activation of melanocortin-4 receptors inhibits DMV cholinergic neurons and optogenetic inhibition of liver-projecting parasympathetic cholinergic fibers increases blood glucose levels. This elevated blood glucose is not due to altered pancreatic hormone release. Interestingly, insulin-induced hypoglycemia increases ARC POMC neuron activity. Hence, this liver-projecting melanocortinergic circuit that we identified may play a critical role in the counterregulatory response to hypoglycemia.

Publication types

  • Research Support, N.I.H., Extramural
  • Research Support, Non-U.S. Gov't

MeSH terms

  • Acetylcholine / metabolism
  • Action Potentials / physiology
  • Animals
  • Arcuate Nucleus of Hypothalamus / cytology
  • Arcuate Nucleus of Hypothalamus / metabolism
  • Blood Glucose / analysis
  • Blood Glucose / metabolism*
  • Cholinergic Neurons / metabolism
  • Corticosterone / blood
  • Corticosterone / metabolism
  • Disease Models, Animal
  • Efferent Pathways / physiology
  • Female
  • Gene Knockdown Techniques
  • Glucagon / blood
  • Glucagon / metabolism
  • Gluconeogenesis / genetics
  • Humans
  • Hypoglycemia / blood
  • Hypoglycemia / diagnosis
  • Hypoglycemia / etiology*
  • Insulin / blood
  • Insulin / metabolism
  • Liver / enzymology
  • Liver / innervation*
  • Male
  • Mice
  • Optogenetics
  • Pro-Opiomelanocortin / metabolism*
  • RNA, Messenger / metabolism
  • Receptor, Melanocortin, Type 4 / antagonists & inhibitors
  • Receptor, Melanocortin, Type 4 / genetics
  • Receptor, Melanocortin, Type 4 / metabolism
  • Up-Regulation
  • Vagus Nerve / cytology
  • Vagus Nerve / metabolism*

Substances

  • Blood Glucose
  • Insulin
  • MC4R protein, mouse
  • RNA, Messenger
  • Receptor, Melanocortin, Type 4
  • Pro-Opiomelanocortin
  • Glucagon
  • Acetylcholine
  • Corticosterone