TY - JOUR
T1 - AMPK control of myocardial fatty acid metabolism fluctuates with the intensity of insulin-deficient diabetes
AU - Kewalramani, Girish
AU - An, Ding
AU - Kim, Min Suk
AU - Ghosh, Sanjoy
AU - Qi, Dake
AU - Abrahani, Ashraf
AU - Pulinilkunnil, Thomas
AU - Sharma, Vijay
AU - Wambolt, Richard B.
AU - Allard, Michael F.
AU - Innis, Sheila M.
AU - Rodrigues, Brian
N1 - Funding Information:
The studies described in this paper were supported by an operating grant from the Heart and Stroke Foundation of BC and Yukon. The financial support of the Health Research Foundation/Canadian Institutes of Health Research and the Heart and Stroke Foundation of Canada for Graduate Research Scholarships to Thomas Pulinilkunnil, Sanjoy Ghosh, and Dake Qi are gratefully acknowledged.
PY - 2007/2
Y1 - 2007/2
N2 - Flexibility in substrate selection is essential for the heart to maintain production of energy and contractile function, and is managed through multiple mechanisms including PPAR-α and AMP-activated protein kinase (AMPK). Rats injected with 55 mg/kg STZ (D55) were kept for 4 days (acute diabetes; D55-A) prior to termination. Fatty acid (FA) oxidation increased in D55-A hearts, with no significant change in gene expression of PPAR-α, or its downstream targets. However, both AMPK and ACC phosphorylation were significantly higher in these hearts, effects that were reversed by insulin. Unexpectedly, when the duration of diabetes in D55 rats was extended to 6 weeks (chronic diabetes; D55-C), AMPK and ACC phosphorylation were comparable in control and D55-C hearts. In D55-C rat hearts, lack of AMPK activation was closely associated to an overload of plasma and cardiac lipids. To validate the relationship between lipids and cardiac AMPK activation, we either induced more severe diabetes (100 mg/kg STZ to provoke both hyperglycemia and hyperlipidemia acutely; D100-A) or infused intralipid (IL) to enlarge circulating lipids. There was no difference in cardiac AMPK and ACC phosphorylation in D100-A rats compared to control. Measurement of AMPK and ACC phosphorylation in control and D55-A hearts revealed that their phosphorylation was inhibited by acute intralipid infusion. Our data suggest that activation of AMPK is an adaptation that would ensure adequate cardiac energy production when glucose utilization is compromised. However, in severe diabetes, with the addition of augmented plasma and heart lipids, AMPK activation is prevented, and control of FA oxidation is likely through alternate mechanisms. Given that AMPK plays an important role in preventing cardiac ischemic/reperfusion damage, it is possible that in these diabetic hearts, the accelerated damage observed during exposure to ischemia/reperfusion could be a likely outcome of a compromised activation of AMPK.
AB - Flexibility in substrate selection is essential for the heart to maintain production of energy and contractile function, and is managed through multiple mechanisms including PPAR-α and AMP-activated protein kinase (AMPK). Rats injected with 55 mg/kg STZ (D55) were kept for 4 days (acute diabetes; D55-A) prior to termination. Fatty acid (FA) oxidation increased in D55-A hearts, with no significant change in gene expression of PPAR-α, or its downstream targets. However, both AMPK and ACC phosphorylation were significantly higher in these hearts, effects that were reversed by insulin. Unexpectedly, when the duration of diabetes in D55 rats was extended to 6 weeks (chronic diabetes; D55-C), AMPK and ACC phosphorylation were comparable in control and D55-C hearts. In D55-C rat hearts, lack of AMPK activation was closely associated to an overload of plasma and cardiac lipids. To validate the relationship between lipids and cardiac AMPK activation, we either induced more severe diabetes (100 mg/kg STZ to provoke both hyperglycemia and hyperlipidemia acutely; D100-A) or infused intralipid (IL) to enlarge circulating lipids. There was no difference in cardiac AMPK and ACC phosphorylation in D100-A rats compared to control. Measurement of AMPK and ACC phosphorylation in control and D55-A hearts revealed that their phosphorylation was inhibited by acute intralipid infusion. Our data suggest that activation of AMPK is an adaptation that would ensure adequate cardiac energy production when glucose utilization is compromised. However, in severe diabetes, with the addition of augmented plasma and heart lipids, AMPK activation is prevented, and control of FA oxidation is likely through alternate mechanisms. Given that AMPK plays an important role in preventing cardiac ischemic/reperfusion damage, it is possible that in these diabetic hearts, the accelerated damage observed during exposure to ischemia/reperfusion could be a likely outcome of a compromised activation of AMPK.
KW - Diabetes
KW - Fatty acids
KW - Heart
KW - Insulin
KW - Metabolism
UR - http://www.scopus.com/inward/record.url?scp=33846345065&partnerID=8YFLogxK
U2 - 10.1016/j.yjmcc.2006.11.010
DO - 10.1016/j.yjmcc.2006.11.010
M3 - Article
C2 - 17188707
AN - SCOPUS:33846345065
SN - 0022-2828
VL - 42
SP - 333
EP - 342
JO - Journal of Molecular and Cellular Cardiology
JF - Journal of Molecular and Cellular Cardiology
IS - 2
ER -