title: AMP activated protein kinase is indispensable for myocardial adaptation to caloric restriction in mice.
abstract: Caloric restriction (CR) is a robust dietary intervention known to enhance cardiovascular health. AMP activated protein kinase (AMPK) has been suggested to mediate the cardioprotective effects of CR. However, this hypothesis remains to be tested by using definitive loss-of-function animal models. In the present study, we subjected AMPKα2 knockout (KO) mice and their wild type (WT) littermates to a CR regimen that reduces caloric intake by 20%-40% for 4 weeks. CR decreased body weight, heart weight and serum levels of insulin in both WT and KO mice to the same degree, indicating the effectiveness of the CR protocol. CR activated cardiac AMPK signaling in WT mice, but not in AMPKα2 KO mice. Correspondingly, AMPKα2 KO mice had markedly reduced cardiac function during CR as determined by echocardiography and hemodynamic measurements. The compromised cardiac function was associated with increased markers of oxidative stress, endoplasmic reticulum stress and myocyte apoptosis. Mechanistically, CR down-regulated the expression of ATP5g2, a subunit of mitochondrial ATP synthase, and reduced ATP content in AMPKα2 KO hearts, but not in WT hearts. In addition, CR accelerated cardiac autophagic flux in WT mice, but failed to do so in AMPKα2 KO mice. These results demonstrated that without AMPK, CR triggers adverse effects that can lead to cardiac dysfunction, suggesting that AMPK signaling pathway is indispensible for energy homeostasis and myocardial adaptation to CR, a dietary intervention that normally produces beneficial cardiac effects.
authors.affiliation: Cardiovascular Health Research Center, Sanford Research, University of South Dakota, Sioux Falls, South Dakota, United States of America.
authors.forename: Kai
authors.initials: K
authors.lastname: Chen
authors.forename: Satoru
authors.initials: S
authors.lastname: Kobayashi
authors.forename: Xianmin
authors.initials: X
authors.lastname: Xu
authors.forename: Benoit
authors.initials: B
authors.lastname: Viollet
authors.forename: Qiangrong
authors.initials: Q
authors.lastname: Liang
mesh_terms: D055372:AMP-Activated Protein Kinases / Q000235:genetics / Q000378:metabolism*; D000255:Adenosine Triphosphate / Q000378:metabolism; D000818:Animals; D015153:Blotting, Western; D001835:Body Weight; D031204:Caloric Restriction; D059865:Endoplasmic Reticulum Stress / Q000502:physiology; D006321:Heart / Q000254:growth & development*; D006334:Heart Function Tests; D006706:Homeostasis / Q000502:physiology*; D020287:In Situ Nick-End Labeling; D007328:Insulin / Q000097:blood; D007334:Insulin-Like Growth Factor I / Q000378:metabolism; D051379:Mice; D018345:Mice, Knockout; D009206:Myocardium / Q000378:metabolism*; D009929:Organ Size; D018384:Oxidative Stress / Q000502:physiology; D015398:Signal Transduction / Q000502:physiology*; D014280:Triglycerides / Q000097:blood
chemical_list: D007328:Insulin; D014280:Triglycerides; D007334:Insulin-Like Growth Factor I; D000255:Adenosine Triphosphate; D055372:AMP-Activated Protein Kinases