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Endocrine

, Volume 37, Issue 1, pp 220–230 | Cite as

Pancreatic neuronal melanocortin-4 receptor modulates serum insulin levels independent of leptin receptor

  • Mahmoud MansourEmail author
  • Doug White
  • Catherine Wernette
  • John Dennis
  • Ya-Xiong Tao
  • Robert Collins
  • Lauren Parker
  • Edward Morrison
Original Article

Abstract

The leptin-regulated melanocortin (MC) system modulates energy homeostasis and hypothalamic MC neuronal circuits regulate insulin secretion. We therefore hypothesized that MC system components were present in the pancreas. In order to determine the veracity of the hypothesis, we examined c-Fos, melanocortin-4 receptor (Mc4r), and alpha-melanocyte-stimulating hormone (α-MSH) expression levels in nondiabetic (intact leptin receptor signaling) and Zucker diabetic fatty (ZDF; leptin receptor deficiency) rats. We infused rats via the third ventricle with the α-MSH analog Nle4, D-Phe7-α-MSH (NDP-MSH), a Mc4r agonist. Subsequently, both hypothalamic and pancreatic c-Fos and Mc4r mRNAs were upregulated. Likewise, immunohistochemical analysis showed that an increased Mc4r and α-MSH expression in nerves surrounding the pancreatic vasculature and islets. Increases in c-Fos, α-MSH, and Mc4r expression were independent of leptin receptor function. Conversely, serum insulin was significantly reduced by NDP-MSH treatment, an effect which was reversed by the Mc4r specific blocker HS014. Finally, proopiomelanocortin (POMC) mRNA, the precursor of α-MSH, was detected by RT-PCR in pancreatic tissue homogenates. These findings suggest that pancreatic Mc4r and autonomic neurons participate in a communication pathway between the central MC system and pancreatic islets to regulate insulin secretion.

Keywords

Mc4r α-MSH NDP-MSH Pancreas Zucker diabetic fatty (ZDF) rats Proopiomelanocortin 

Notes

Acknowledgments

The authors like to thank Dr. James C. Wright for help with statistical analysis, the staff at the Animal Facility, and Mrs. Karen Wolfe for technical help. This study was supported by an intramural Animal Health and Disease Research Program grant to M. Mansour

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Copyright information

© Springer Science+Business Media, LLC 2010

Authors and Affiliations

  • Mahmoud Mansour
    • 1
    Email author
  • Doug White
    • 2
  • Catherine Wernette
    • 2
  • John Dennis
    • 1
  • Ya-Xiong Tao
    • 1
  • Robert Collins
    • 1
  • Lauren Parker
    • 1
  • Edward Morrison
    • 1
  1. 1.Department of Anatomy, Physiology, and Pharmacology, College of Veterinary MedicineAuburn UniversityAuburnUSA
  2. 2.Department of Nutrition and Food Science, College of Human SciencesAuburn UniversityAuburnUSA

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