Liver-Specific Disruption of the Murine Glucagon Receptor Produces α-Cell Hyperplasia: Evidence for a Circulating α-Cell Growth Factor
- Christine Longuet1,
- Ana M. Robledo2,
- E. Danielle Dean2,
- Chunhua Dai2,
- Safina Ali1,
- Ian McGuinness2,
- Vincent de Chavez2,
- Patricia M. Vuguin3,
- Maureen J. Charron4,
- Alvin C. Powers2,5,6⇓ and
- Daniel J. Drucker1
- 1Department of Medicine, Samuel Lunenfeld Research Institute, Mt. Sinai Hospital, The University of Toronto, Toronto, Ontario, Canada
- 2Division of Diabetes, Endocrinology, and Metabolism, Department of Medicine, Vanderbilt University Medical Center, Nashville, Tennessee
- 3Division of Pediatric Endocrinology, Steven & Alexandra Cohen Children’s Medical Center of New York, Long Island, New York
- 4Albert Einstein College of Medicine, Departments of Biochemistry, Medicine, and Obstetrics & Gynecology, Bronx, New York
- 5Department of Molecular Physiology and Biophysics, Vanderbilt University Medical Center, Nashville, Tennessee
- 6VA Tennessee Valley Healthcare System, Nashville, Tennessee
- Corresponding author: Alvin C. Powers, , or Daniel J. Drucker,
C.L., A.M.R., and E.D.D. contributed equally to this study.
Glucagon is a critical regulator of glucose homeostasis; however, mechanisms regulating glucagon action and α-cell function and number are incompletely understood. To elucidate the role of the hepatic glucagon receptor (Gcgr) in glucagon action, we generated mice with hepatocyte-specific deletion of the glucagon receptor. GcgrHep−/− mice exhibited reductions in fasting blood glucose and improvements in insulin sensitivity and glucose tolerance compared with wild-type controls, similar in magnitude to changes observed in Gcgr−/− mice. Despite preservation of islet Gcgr signaling, GcgrHep−/− mice developed hyperglucagonemia and α-cell hyperplasia. To investigate mechanisms by which signaling through the Gcgr regulates α-cell mass, wild-type islets were transplanted into Gcgr−/− or GcgrHep−/− mice. Wild-type islets beneath the renal capsule of Gcgr−/− or GcgrHep−/− mice exhibited an increased rate of α-cell proliferation and expansion of α-cell area, consistent with changes exhibited by endogenous α-cells in Gcgr−/− and GcgrHep−/− pancreata. These results suggest that a circulating factor generated after disruption of hepatic Gcgr signaling can increase α-cell proliferation independent of direct pancreatic input. Identification of novel factors regulating α-cell proliferation and mass may facilitate the generation and expansion of α-cells for transdifferentiation into β-cells and the treatment of diabetes.
- Received November 17, 2011.
- Accepted September 25, 2012.
- © 2012 by the American Diabetes Association.
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