Reduced AMP-activated protein kinase activity in mouse skeletal muscle does not exacerbate the development of insulin resistance with obesity.
OBJECTIVE
Obesity-related insulin resistance is associated with accumulation of bioactive lipids in skeletal muscle. The AMP-activated protein kinase (AMPK) regulates lipid oxidation in muscle by inhibiting acetyl-CoA carboxylase-2 (ACC2) and increasing mitochondrial biogenesis. We investigated whether reduced levels of muscle AMPK promote lipid accumulation and insulin resistance during high-fat feeding.


METHODS
Male C57/BL6 wild-type mice and transgenic littermates overexpressing an alpha2AMPK kinase-dead (KD) in muscle were fed control or high-fat diet. Whole-body glucose homeostasis was assessed by glucose and insulin tolerance tests, and by measuring fasting and fed serum insulin and glucose. Insulin action in muscle was determined by measuring 2-deoxy-[(3)H]glucose uptake and Akt phosphorylation in incubated soleus and extensor digitorum longus muscles. Muscle triacylglycerol, diacylglycerol and ceramide content was measured by thin-layer chromatography. Mitochondrial proteins were measured by immunoblotting.


RESULTS
KD mice had reduced skeletal muscle alpha2AMPK activity (50% in gastrocnemius and >80% in soleus and extensor digitorum longus) and ACC2 Ser228 phosphorylation (90% in gastrocnemius). High-fat feeding increased body mass and adiposity, and impaired insulin and glucose tolerance; however, there were no differences between wild-type and KD littermates. High-fat feeding impaired insulin-stimulated muscle glucose uptake and Akt-phosphorylation, while increasing muscle triacylglycerol, diacylglycerol (p = 0.07) and ceramide, but these effects were not exacerbated in KD mice. In response to high-fat feeding, mitochondrial proteins were increased to similar levels in wild-type and KD muscles.


CONCLUSIONS
Obesity-induced lipid accumulation and insulin resistance were not exacerbated in AMPK KD mice, suggesting that reduced levels of muscle alpha2AMPK do not promote insulin resistance in the early phase of obesity-related diabetes.
Beck Jørgensen
S
S
St Vincent's Institute of Medical Research and Department of Medicine, University of Melbourne, Fitzroy, VIC, Australia. sbjorgensen@ifi.ku.dk
O'Neill
H M
HM
Hewitt
K
K
Kemp
B E
BE
Steinberg
G R
GR
D000091162:AMP-Activated Protein Kinase Kinases; D000620:Aminoimidazole Carboxamide / Q000031:analogs & derivatives / Q000378:metabolism; D000818:Animals; D001835:Body Weight; D003847:Deoxyglucose / Q000378:metabolism; D004041:Dietary Fats / Q000494:pharmacology; D007333:Insulin Resistance / Q000502:physiology*; D007700:Kinetics; D015227:Lipid Peroxidation / Q000502:physiology; D008055:Lipids / Q000502:physiology; D008297:Male; D051379:Mice; D008810:Mice, Inbred C57BL; D008822:Mice, Transgenic; D018482:Muscle, Skeletal / Q000201:enzymology* / Q000378:metabolism; D009765:Obesity / Q000201:enzymology / Q000503:physiopathology*; D011494:Protein Kinases / Q000235:genetics / Q000378:metabolism*; D012016:Reference Values; D012265:Ribonucleotides / Q000378:metabolism
D004041:Dietary Fats; D008055:Lipids; D012265:Ribonucleotides; D000620:Aminoimidazole Carboxamide; D003847:Deoxyglucose; D011494:Protein Kinases; D000091162:AMP-Activated Protein Kinase Kinases; C031143:AICA ribonucleotide
Diabetes. 2008 Nov;57(11):2958-66
18728234
J Physiol. 2008 Dec 1;586(23):5819-31
18845612
Proc Natl Acad Sci U S A. 2002 Dec 10;99(25):15983-7
12444247
Am J Physiol Endocrinol Metab. 2009 Jul;297(1):E57-66
19435854
Am J Physiol. 1999 Dec;277(6):E1130-41
10600804
Diabetes. 2009 Apr;58(4):829-39
19136654
Science. 2001 Aug 31;293(5535):1673-7
11533494
Diabetes. 2007 Aug;56(8):2085-92
17519422
Diabetes. 2003 May;52(5):1066-72
12716734
Diabetes. 2001 May;50(5):921-7
11334434
Nature. 2006 Dec 14;444(7121):860-7
17167474
Science. 2001 Mar 30;291(5513):2613-6
11283375
Eur J Biochem. 1990 Jan 12;187(1):183-90
1967580
Nat Med. 2006 May;12(5):541-8
16604088
Obes Res. 2004 Aug;12(8):1264-70
15340109
J Biol Chem. 1999 Aug 20;274(34):24202-10
10446195
J Clin Invest. 1994 Dec;94(6):2349-56
7989591
Am J Physiol Endocrinol Metab. 2007 Jan;292(1):E331-9
16954334
J Clin Endocrinol Metab. 2004 Sep;89(9):4575-80
15356065
Am J Physiol Endocrinol Metab. 2000 Nov;279(5):E1202-6
11052978
Diabetes. 2001 May;50(5):1076-82
11334411
Proc Natl Acad Sci U S A. 2008 Jun 3;105(22):7815-20
18509063
Diabetes. 2002 Oct;51(10):2886-94
12351423
J Clin Invest. 2004 Sep;114(6):823-7
15372106
Diabetes. 2006 Aug;55(8):2277-85
16873691
Diabetes. 2002 May;51(5):1477-84
11978645
Diabetes. 2005 Jan;54(1):8-14
15616005
Am J Physiol. 1997 Dec;273(6):E1107-12
9435525
Diabetologia. 2007 Apr;50(4):790-6
17334651
Diabetes. 2007 May;56(5):1376-81
17287462
J Biol Chem. 1990 Oct 5;265(28):16880-5
2211599
Diabetes. 2001 Jan;50(1):123-30
11147777
Diabetes. 2001 Oct;50(10):2210-8
11574400
Physiol Rev. 2007 Apr;87(2):507-20
17429039
J Biol Chem. 2004 Sep 10;279(37):38441-7
15247217
Cell Metab. 2007 Mar;5(3):167-79
17339025
FASEB J. 2005 Jul;19(9):1146-8
15878932
Nature. 2002 Nov 21;420(6913):333-6
12447443
J Biol Chem. 2002 Dec 27;277(52):50230-6
12006582
Diabetes. 2009 Mar;58(3):550-8
19073774
Am J Physiol. 1999 Jan;276(1):E1-E18
9886945
Am J Physiol Endocrinol Metab. 2002 Jul;283(1):E187-92
12067860
FASEB J. 1999 Nov;13(14):2051-60
10544188
Mol Cell. 2001 May;7(5):1085-94
11389854
Cell Metab. 2005 Jan;1(1):15-25
16054041
Diabetologia. 1985 Jul;28(7):412-9
3899825
Cell Metab. 2006 Dec;4(6):465-74
17141630
J Biol Chem. 2004 Jan 9;279(2):1070-9
14573616
Diabetes. 2007 Mar;56(3):836-48
17327455