title: Glucagon stimulates hepatic FGF21 secretion through a PKA- and EPAC-dependent posttranscriptional mechanism.
abstract: Previous studies have shown that whole body deletion of the glucagon receptor suppresses the ability of starvation to increase hepatic fibroblast growth factor 21 (FGF21) expression and plasma FGF21 concentration. Here, we investigate the mechanism by which glucagon receptor activation increases hepatic FGF21 production. Incubating primary rat hepatocyte cultures with glucagon, dibutyryl cAMP or forskolin stimulated a 3-4-fold increase in FGF21 secretion. The effect of these agents on FGF21 secretion was not associated with an increase in FGF21 mRNA abundance. Glucagon induction of FGF21 secretion was additive with the stimulatory effect of a PPARα activator (GW7647) on FGF21 secretion. Inhibition of protein kinase A (PKA) and downstream components of the PKA pathway [i.e. AMP-activated protein kinase and p38 MAPK] suppressed glucagon activation of FGF21 secretion. Incubating hepatocytes with an exchange protein directly activated by cAMP (EPAC)-selective cAMP analog [i.e. 8-(4-chlorophenylthio)-2'-O-methyladenosine-3', 5'-cyclic monophosphate (cpTOME)], stimulated a 3.9-fold increase FGF21 secretion, whereas inhibition of the EPAC effector, Rap1, suppressed glucagon activation of FGF21 secretion. Treatment of hepatocytes with insulin also increased FGF21 secretion. In contrast to glucagon, insulin activation of FGF21 secretion was associated with an increase in FGF21 mRNA abundance. Glucagon synergistically interacted with insulin to stimulate a further increase in FGF21 secretion and FGF21 mRNA abundance. These results demonstrate that glucagon increases hepatic FGF21 secretion via a posttranscriptional mechanism and provide evidence that both the PKA branch and EPAC branch of the cAMP pathway play a role in mediating this effect. These results also identify a novel synergistic interaction between glucagon and insulin in the regulation of FGF21 secretion and FGF21 mRNA abundance. We propose that this insulin/glucagon synergism plays a role in mediating the elevation in FGF21 production during starvation and conditions related to metabolic syndrome.
authors.affiliation: Department of Biochemistry, West Virginia University, Morgantown, West Virginia, United States of America.
authors.forename: Holly A
authors.initials: HA
authors.lastname: Cyphert
authors.affiliation: Department of Biochemistry, West Virginia University, Morgantown, West Virginia, United States of America.
authors.forename: Kimberly M
authors.initials: KM
authors.lastname: Alonge
authors.affiliation: Department of Biochemistry, West Virginia University, Morgantown, West Virginia, United States of America.
authors.forename: Siri M
authors.initials: SM
authors.lastname: Ippagunta
authors.affiliation: Department of Biochemistry, West Virginia University, Morgantown, West Virginia, United States of America.
authors.forename: F Bradley
authors.initials: FB
authors.lastname: Hillgartner
mesh_terms: D055372:AMP-Activated Protein Kinases / Q000037:antagonists & inhibitors / Q000378:metabolism; D000818:Animals; D003994:Bucladesine / Q000378:metabolism; D005576:Colforsin / Q000494:pharmacology; D017868:Cyclic AMP-Dependent Protein Kinases / Q000378:metabolism*; D005346:Fibroblast Growth Factors / Q000235:genetics / Q000378:metabolism*; D005934:Glucagon / Q000494:pharmacology*; D020662:Guanine Nucleotide Exchange Factors / Q000378:metabolism*; D056945:Hep G2 Cells; D006801:Humans; D007328:Insulin / Q000494:pharmacology; D008099:Liver / Q000187:drug effects / Q000378:metabolism*; D008297:Male; D008954:Models, Biological; D012333:RNA, Messenger / Q000235:genetics / Q000378:metabolism; D017207:Rats, Sprague-Dawley; D014158:Transcription, Genetic / Q000187:drug effects*; D048051:p38 Mitogen-Activated Protein Kinases / Q000037:antagonists & inhibitors / Q000378:metabolism; D020827:rap1 GTP-Binding Proteins / Q000378:metabolism
chemical_list: D020662:Guanine Nucleotide Exchange Factors; D007328:Insulin; C116122:RAPGEF3 protein, human; D012333:RNA, Messenger; C526973:Rapgef3 protein, rat; C414620:fibroblast growth factor 21; D005576:Colforsin; D005346:Fibroblast Growth Factors; D003994:Bucladesine; D005934:Glucagon; D017868:Cyclic AMP-Dependent Protein Kinases; D048051:p38 Mitogen-Activated Protein Kinases; D055372:AMP-Activated Protein Kinases; D020827:rap1 GTP-Binding Proteins
references.citation: PLoS One. 2011;6(8):e22976
references.pmid: 21829679
references.citation: Endocrinology. 2007 Feb;148(2):774-81
references.pmid: 17068132
references.citation: Am J Clin Nutr. 2011 Apr;93(4):901S-5
references.pmid: 21346090
references.citation: J Biol Chem. 1995 Aug 25;270(34):19833-8
references.pmid: 7649994
references.citation: Am J Physiol. 1997 Mar;272(3 Pt 1):E371-8
references.pmid: 9124541
references.citation: Nature. 2005 Sep 22;437(7058):574-8
references.pmid: 16177794
references.citation: Eur J Biochem. 1984 Jun 15;141(3):645-50
references.pmid: 6378634
references.citation: Diabetes. 2010 Nov;59(11):2781-9
references.pmid: 20682689
references.citation: Adv Exp Med Biol. 2010;654:281-304
references.pmid: 20217503
references.citation: J Clin Invest. 2001 Oct;108(8):1167-74
references.pmid: 11602624
references.citation: Endocrinology. 2009 Sep;150(9):4084-93
references.pmid: 19470704
references.citation: Biochem J. 1997 Jun 1;324 ( Pt 2):379-88
references.pmid: 9182694
references.citation: Am J Physiol Endocrinol Metab. 2010 Oct;299(4):E607-14
references.pmid: 20663988
references.citation: Genes Dev. 2012 Feb 15;26(4):312-24
references.pmid: 22302876
references.citation: Cell Metab. 2007 Jun;5(6):415-25
references.pmid: 17550777
references.citation: Biochem J. 2007 Dec 15;408(3):297-315
references.pmid: 17850214
references.citation: Curr Diabetes Rev. 2012 Jul 1;8(4):285-93
references.pmid: 22587513
references.citation: Nat Rev Mol Cell Biol. 2011 Mar;12(3):141-51
references.pmid: 21346730
references.citation: Nat Med. 2013 Sep;19(9):1153-6
references.pmid: 23933983
references.citation: Cell Metab. 2008 Nov;8(5):359-71
references.pmid: 19046568
references.citation: J Lipid Res. 1998 Oct;39(10):1951-63
references.pmid: 9788241
references.citation: J Biol Chem. 2005 Dec 30;280(52):42731-7
references.pmid: 16272151
references.citation: J Lipid Res. 2009 Apr;50 Suppl:S162-6
references.pmid: 19050312
references.citation: Mol Cell Biol. 2005 Jul;25(13):5466-79
references.pmid: 15964803
references.citation: Nature. 2001 Sep 13;413(6852):131-8
references.pmid: 11557972
references.citation: PLoS One. 2012;7(11):e49345
references.pmid: 23209571
references.citation: Nature. 2001 Sep 13;413(6852):179-83
references.pmid: 11557984
references.citation: Endocrinology. 2011 Aug;152(8):2996-3004
references.pmid: 21712364
references.citation: Cell Metab. 2011 Mar 2;13(3):308-19
references.pmid: 21356520
references.citation: Horm Metab Res. 1995 Aug;27(8):372-5
references.pmid: 7590626
references.citation: Peptides. 1989 Mar-Apr;10(2):333-5
references.pmid: 2755873
references.citation: Cell Metab. 2013 Sep 3;18(3):333-40
references.pmid: 24011069
references.citation: J Biol Chem. 2004 Dec 24;279(52):54103-9
references.pmid: 15494402
references.citation: Diabetes Obes Metab. 2011 Oct;13 Suppl 1:144-50
references.pmid: 21824268
references.citation: Eur J Pharmacol. 1997 May 26;327(1):87-95
references.pmid: 9185840
references.citation: Proc Natl Acad Sci U S A. 1975 Mar;72(3):1157-60
references.pmid: 1055372
references.citation: Nat Cell Biol. 2002 Nov;4(11):901-6
references.pmid: 12402047
references.citation: J Clin Endocrinol Metab. 2012 Jan;97(1):E54-8
references.pmid: 22013098
references.citation: Pharmacol Rev. 2003 Mar;55(1):167-94
references.pmid: 12615957
references.citation: Nat Struct Biol. 2003 Jan;10(1):26-32
references.pmid: 12469113
references.citation: Endocrinology. 2008 Dec;149(12):6018-27
references.pmid: 18687777
references.citation: Am J Physiol Endocrinol Metab. 2009 Aug;297(2):E410-5
references.pmid: 19509187
references.citation: Cell Metab. 2008 Jul;8(1):77-83
references.pmid: 18585098
references.citation: Annu Rev Pharmacol Toxicol. 2010;50:355-75
references.pmid: 20055708
references.citation: J Biol Chem. 2010 Dec 31;285(53):41356-65
references.pmid: 20978125
references.citation: Am J Physiol Gastrointest Liver Physiol. 2004 Aug;287(2):G334-43
references.pmid: 15044179
references.citation: Nat Rev Endocrinol. 2010 Dec;6(12):689-97
references.pmid: 20957001
references.citation: Cell Metab. 2008 Jul;8(1):65-76
references.pmid: 18590693
references.citation: J Biol Chem. 2002 Aug 16;277(33):29468-76
references.pmid: 12171996
references.citation: Endocrinology. 1997 Mar;138(3):999-1007
references.pmid: 9048601
references.citation: Arch Biochem Biophys. 2003 Jul 1;415(1):34-42
references.pmid: 12801510
references.citation: Cell Metab. 2007 Jun;5(6):426-37
references.pmid: 17550778
references.citation: J Biol Chem. 2012 Jul 27;287(31):26060-7
references.pmid: 22696219
references.citation: J Biol Chem. 2000 Apr 14;275(15):11348-54
references.pmid: 10753948
references.citation: J Biol Chem. 2010 Aug 27;285(35):26861-26868
references.pmid: 20573950
references.citation: J Biol Chem. 2012 Jul 20;287(30):25123-38
references.pmid: 22661717
references.citation: Diabetes. 2009 Jan;58(1):250-9
references.pmid: 18840786
references.citation: Proc Natl Acad Sci U S A. 2009 Jun 30;106(26):10853-8
references.pmid: 19541642
references.citation: Cell. 2012 Feb 3;148(3):421-33
references.pmid: 22304913
references.citation: Mol Cell Endocrinol. 2013 Feb 25;366(2):152-62
references.pmid: 22796337
references.citation: Biochem Biophys Res Commun. 2007 Aug 24;360(2):437-40
references.pmid: 17601491
references.citation: J Clin Invest. 2005 Jun;115(6):1627-35
references.pmid: 15902306
references.citation: Am J Physiol Endocrinol Metab. 2011 Dec;301(6):E1051-64
references.pmid: 21971522
references.citation: Curr Opin Cell Biol. 1991 Apr;3(2):213-7
references.pmid: 1652989
references.citation: J Clin Invest. 2009 Aug;119(8):2412-22
references.pmid: 19662685
references.citation: FEBS Lett. 2008 Nov 12;582(27):3805-10
references.pmid: 18948104
references.citation: Biochem J. 2006 Oct 15;399(2):275-83
references.pmid: 16834571
references.citation: Gastroenterology. 2008 Dec;135(6):2096-106
references.pmid: 18809404
references.citation: J Physiol. 2006 Jun 15;573(Pt 3):611-25
references.pmid: 16581855
references.citation: Diabetes. 2013 May;62(5):1453-63
references.pmid: 23305646
references.citation: Annu Rev Physiol. 1992;54:885-909
references.pmid: 1562196
references.citation: Nat Med. 2013 Sep;19(9):1147-52
references.pmid: 23933984
references.citation: Anal Biochem. 1987 Apr;162(1):156-9
references.pmid: 2440339