5'-AMP Activated Protein Kinase is Involved in the Regulation of Myocardial β-Oxidative Capacity in Mice - PubMed (original) (raw)

doi: 10.3389/fphys.2012.00033. eCollection 2012.

Steen Larsen, Jonas Thue Treebak, Christina Neigaard Hansen, Martin Hey-Mogensen, Tobias Speerschneider, Thomas E Jensen, Jacob Jeppesen, Jørgen F P Wojtaszewski, Erik A Richter, Lars Køber, Flemming Dela

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5'-AMP Activated Protein Kinase is Involved in the Regulation of Myocardial β-Oxidative Capacity in Mice

Nis Stride et al. Front Physiol. 2012.

Abstract

5'-adenosine monophosphate-activated protein kinase (AMPK) is considered central in regulation of energy status and substrate utilization within cells. In heart failure the energetic state is compromised and substrate metabolism is altered. We hypothesized that this could be linked to changes in AMPK activity and we therefore investigated mitochondrial oxidative phosphorylation capacity from the oxidation of long- and medium-chain fatty acids (LCFA and MCFA) in cardiomyocytes from young and old mice expressing a dominant negative AMPKα2 (AMPKα2-KD) construct and their wildtype (WT) littermates. We found a 35-45% (P < 0.05) lower mitochondrial capacity for oxidizing MCFA in AMPKα2-KD of both age-groups, compared to WT. This coincided with marked decreases in protein expression (19/29%, P < 0.05) and activity (14/21%, P < 0.05) of 3-hydroxyacyl-CoA-dehydrogenase (HAD), in young and old AMPKα2-KD mice, respectively, compared to WT. Maximal LCFA oxidation capacity was similar in AMPKα2-KD and WT mice independently of age implying that LCFA-transport into the mitochondria was unaffected by loss of AMPK activity or progressing age. Expression of regulatory proteins of glycolysis and glycogen breakdown showed equivocal effects of age and genotype. These results illustrate that AMPK is necessary for normal mitochondrial function in the heart and that decreased AMPK activity may lead to an altered energetic state as a consequence of reduced capacity to oxidize MCFA. We did not identify any clear aging effects on mitochondrial function.

Keywords: AMPK; metabolic remodeling; mitochondria; oxidative phosphorylation.

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Figures

Figure 1

Figure 1

Mitochondrial respiratory capacity in heart muscle samples from wild type mice (WT) and dominant negative AMPKα2 (AMPK KD) mice. Young (Y: 19–22 weeks) and old (O: 76–91 weeks) mice were studied in both groups. State 3 respiration was measured with two different substrate protocols. Malate, ADP, and octanoylcarnitine (Oct.car) or malate, ADP, and palmitoylcarnitine (Pal.car). Values are mean ± SE. *Different from WT/Y (P < 0.05).

Figure 2

Figure 2

Citrate synthase (CS) enzyme activity (left _Y_-axis) and mitochondrial DNA content (right _Y_-axis) in heart muscle samples from wild type mice (WT) and dominant negative AMPKα2 (AMPK KD) mice. Young (Y: 19–22 weeks) and old (O: 76–91 weeks) mice were studied in both groups. *Different from age matched wild type (P < 0.05).

Figure 3

Figure 3

Carnitine palmitoyl transferase isoforms 1A (CPT1A) and 1B (CPT1B) as well as carnitine palmitoyl transferase 2 (CPT2) in heart muscle samples from wild type mice (WT) and dominant negative AMPKα2 (AMPK KD) mice. Young (Y: 19–22 weeks) and old (O: 76–91 weeks) mice were studied in both groups. *Different from WT/Y (P < 0.05).

Figure 4

Figure 4

3-Hydroxyacyl-CoA-dehydrogenase (HAD) enzyme activity (left _Y_-axis) and protein expression relative to WT/Y (right _Y_-axis). *Different from WT/Y (P < 0.05).

Figure 5

Figure 5

Protein content (Western blot) of pS212 acetyl-CoA-carboxylase (ACCphos) and malonyl-CoA-decarboxylase (MCD), glycogen-phosphorylase (GP), hexokinase II (HKII), and Pyruvatkinase (PKM) in heart muscle samples from wild type mice (WT) and dominant negative AMPKα2 (AMPK KD) mice. Young (Y: 19–22 weeks) and old (O: 76–91 weeks) mice were studied in both groups. Representative blots are shown in the lower panels, which also include blots of AMPK and AMPKphos. *Different from WT/Y (P < 0.05).

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