title: Naturally occurring R225W mutation of the gene encoding AMP-activated protein kinase (AMPK)gamma(3) results in increased oxidative capacity and glucose uptake in human primary myotubes.
abstract: OBJECTIVE
  AMP-activated protein kinase (AMPK) has a broad role in the regulation of glucose and lipid metabolism making it a promising target in the treatment of type 2 diabetes mellitus. We therefore sought to characterise for the first time the effects of chronic AMPK activation on skeletal muscle carbohydrate metabolism in carriers of the rare gain-of-function mutation of the gene encoding AMPKgamma(3) subunit, PRKAG3 R225W.
  
  
  METHODS
  Aspects of fuel metabolism were studied in vitro in myocytes isolated from vastus lateralis of PRKAG3 R225W carriers and matched control participants. In vivo, muscular strength and fatigue were evaluated by isokinetic dynamometer and surface electromyography, respectively. Glucose uptake in exercising quadriceps was determined using [(18)F]fluorodeoxyglucose and positron emission tomography.
  
  
  RESULTS
  Myotubes from PRKAG3 R225W carriers had threefold higher mitochondrial content (p < 0.01) and oxidative capacity, higher leak-dependent respiration (1.6-fold, p < 0.05), higher basal glucose uptake (twofold, p < 0.01) and higher glycogen synthesis rates (twofold, p < 0.05) than control myotubes. They also had higher levels of intracellular glycogen (p < 0.01) and a trend for lower intramuscular triacylglycerol stores. R225W carriers showed remarkable resistance to muscular fatigue and a trend for increased glucose uptake in exercising muscle in vivo.
  
  
  CONCLUSIONS
  Through the enhancement of skeletal muscle glucose uptake and increased mitochondrial content, the R225W mutation may significantly enhance exercise performance. These findings are also consistent with the hypothesis that the gamma(3) subunit of AMPK is a promising tissue-specific target for the treatment of type 2 diabetes mellitus, a condition in which glucose uptake and mitochondrial function are impaired.
authors.affiliation: Department of Biochemistry, Microbiology and Immunology, Faculty of Medicine, University of Ottawa, Ottawa, ON, Canada.
authors.forename: S A
authors.initials: SA
authors.lastname: Crawford
authors.forename: S R
authors.initials: SR
authors.lastname: Costford
authors.forename: C
authors.initials: C
authors.lastname: Aguer
authors.forename: S C
authors.initials: SC
authors.lastname: Thomas
authors.forename: R A
authors.initials: RA
authors.lastname: deKemp
authors.forename: J N
authors.initials: JN
authors.lastname: DaSilva
authors.forename: D
authors.initials: D
authors.lastname: Lafontaine
authors.forename: M
authors.initials: M
authors.lastname: Kendall
authors.forename: R
authors.initials: R
authors.lastname: Dent
authors.forename: R S B
authors.initials: RS
authors.lastname: Beanlands
authors.forename: R
authors.initials: R
authors.lastname: McPherson
authors.forename: M-E
authors.initials: ME
authors.lastname: Harper
mesh_terms: D055372:AMP-Activated Protein Kinases / Q000235:genetics* / Q000378:metabolism*; D000328:Adult; D001692:Biological Transport / Q000235:genetics / Q000502:physiology; D015153:Blotting, Western; D002478:Cells, Cultured; D005227:Fatty Acids / Q000378:metabolism; D005947:Glucose / Q000378:metabolism*; D006003:Glycogen / Q000378:metabolism; D006801:Humans; D066298:In Vitro Techniques; D008875:Middle Aged; D018485:Muscle Fibers, Skeletal / Q000378:metabolism*; D018482:Muscle, Skeletal / Q000378:metabolism; D009154:Mutation; D010101:Oxygen Consumption / Q000235:genetics / Q000502:physiology; D049268:Positron-Emission Tomography; D020133:Reverse Transcriptase Polymerase Chain Reaction
chemical_list: D005227:Fatty Acids; D006003:Glycogen; C526225:PRKAG3 protein, human; D055372:AMP-Activated Protein Kinases; D005947:Glucose
references.citation: Diabetes. 2003 May;52(5):1066-72
references.pmid: 12716734
references.citation: FASEB J. 1995 Apr;9(7):541-6
references.pmid: 7737463
references.citation: J Cell Physiol. 2008 Nov;217(2):478-85
references.pmid: 18561258
references.citation: Circ Cardiovasc Genet. 2009 Oct;2(5):457-66
references.pmid: 20031621
references.citation: J Physiol. 2005 Apr 15;564(Pt 2):563-73
references.pmid: 15718261
references.citation: EMBO J. 2005 May 18;24(10):1810-20
references.pmid: 15889149
references.citation: Am J Physiol Regul Integr Comp Physiol. 2003 Apr;284(4):R936-44
references.pmid: 12626360
references.citation: Diabetes. 1999 Aug;48(8):1667-71
references.pmid: 10426389
references.citation: PLoS One. 2007 Sep 19;2(9):e903
references.pmid: 17878938
references.citation: Mol Cell Biol. 2000 Sep;20(18):6704-11
references.pmid: 10958668
references.citation: Diabetes. 2001 Jan;50(1):12-7
references.pmid: 11147776
references.citation: J Biol Chem. 1998 Jun 12;273(24):14767-71
references.pmid: 9614076
references.citation: J Physiol. 2002 Jul 15;542(Pt 2):403-12
references.pmid: 12122141
references.citation: Am J Physiol Cell Physiol. 2004 Feb;286(2):C283-92
references.pmid: 14512293
references.citation: J Biol Chem. 2008 Dec 5;283(49):33902-10
references.pmid: 18801732
references.citation: J Biol Chem. 1980 Mar 25;255(6):2308-14
references.pmid: 6102090
references.citation: N Engl J Med. 2001 Jun 14;344(24):1823-31
references.pmid: 11407343
references.citation: Diabetes. 2008 Nov;57(11):2958-66
references.pmid: 18728234
references.citation: Physiol Rev. 2009 Jul;89(3):1025-78
references.pmid: 19584320
references.citation: Curr Biol. 1994 Apr 1;4(4):315-24
references.pmid: 7922340
references.citation: J Appl Physiol (1985). 2003 Sep;95(3):960-8
references.pmid: 12777406
references.citation: Cell Metab. 2009 Jan 7;9(1):23-34
references.pmid: 19117544
references.citation: FEBS Lett. 1998 Jul 17;431(2):180-4
references.pmid: 9708898
references.citation: Am J Physiol Endocrinol Metab. 2004 Feb;286(2):E194-200
references.pmid: 14559719
references.citation: Nature. 2009 Apr 23;458(7241):1056-60
references.pmid: 19262508
references.citation: J Lipid Res. 2006 Jun;47(6):1281-8
references.pmid: 16508037
references.citation: J Clin Endocrinol Metab. 2004 Jul;89(7):3440-8
references.pmid: 15240629
references.citation: Biochem J. 2007 Oct 15;407(2):231-41
references.pmid: 17617058
references.citation: J Biol Chem. 2008 Dec 19;283(51):35724-34
references.pmid: 18838377
references.citation: J Biol Chem. 2001 Dec 14;276(50):46912-6
references.pmid: 11598104
references.citation: Diabetes. 2002 Mar;51(3):567-73
references.pmid: 11872652
references.citation: J Lipid Res. 2007 Apr;48(4):961-7
references.pmid: 17213484
references.citation: Arch Biochem Biophys. 1997 Jan 15;337(2):169-75
references.pmid: 9016810
references.citation: Biochim Biophys Acta. 1989 Jun 15;1012(1):81-6
references.pmid: 2567185
references.citation: FASEB J. 2005 May;19(7):773-9
references.pmid: 15857891
references.citation: Am J Physiol. 1999 Aug;277(2):H643-9
references.pmid: 10444490
references.citation: J Appl Physiol (1985). 1999 Nov;87(5):1990-5
references.pmid: 10562646
references.citation: Int J Obes (Lond). 2008 Sep;32 Suppl 4:S7-12
references.pmid: 18719601
references.citation: J Biol. 2003;2(4):28
references.pmid: 14511394
references.citation: J Clin Invest. 2002 Feb;109(3):357-62
references.pmid: 11827995
references.citation: J Biol Chem. 2004 Sep 10;279(37):38441-7
references.pmid: 15247217
references.citation: Circulation. 2001 Dec 18;104(25):3030-3
references.pmid: 11748095
references.citation: Diabetes. 2005 May;54(5):1331-9
references.pmid: 15855317
references.citation: Science. 2000 May 19;288(5469):1248-51
references.pmid: 10818001
references.citation: J Appl Physiol (1985). 2005 Sep;99(3):1189-92
references.pmid: 15879164
references.citation: Am J Physiol Endocrinol Metab. 2000 Nov;279(5):E1039-44
references.pmid: 11052958
references.citation: Mol Cell. 2001 May;7(5):1085-94
references.pmid: 11389854
references.citation: Proc Natl Acad Sci U S A. 2007 Jul 17;104(29):12017-22
references.pmid: 17609368
references.citation: Endocrinology. 1973 Sep;93(3):602-9
references.pmid: 4352804
references.citation: J Biol Chem. 2004 Jan 9;279(2):1070-9
references.pmid: 14573616