Skeletal Muscle AMP-activated Protein Kinase Is Essential for the Metabolic Response to Exercise in Vivo

• Published in: The Journal of biological chemistry Vol. 284; no. 36; pp. 23925 - 23934
• Main Authors: Lee-Young, Robert S., Griffee, Susan R., Lynes, Sara E., Bracy, Deanna P., Ayala, Julio E., McGuinness, Owen P., Wasserman, David H.
• Format: Journal Article
• Language: English
• Published: United States Elsevier Inc 04.09.2009; American Society for Biochemistry and Molecular Biology
• Subjects: AMP-Activated Protein Kinases - genetics; AMP-Activated Protein Kinases - metabolism; Animals; Enzyme Activation - physiology; Female; Glucose - physiology; Male; Metabolism and Bioenergetics; Mice; Mice, Transgenic; Muscle, Skeletal - enzymology; Nitric Oxide Synthase Type I - genetics; Nitric Oxide Synthase Type I - metabolism; Physical Conditioning, Animal - physiology; Physical Endurance - physiology
• ISSN: 0021-9258; 1083-351X
• DOI: 10.1074/jbc.M109.021048

AMP-activated protein kinase (AMPK) has been postulated as a super-metabolic regulator, thought to exert numerous effects on skeletal muscle function, metabolism, and enzymatic signaling. Despite these assertions, little is known regarding the direct role(s) of AMPK in vivo, and results obtained in vitro or in situ are conflicting. Using a chronically catheterized mouse model (carotid artery and jugular vein), we show that AMPK regulates skeletal muscle metabolism in vivo at several levels, with the result that a deficit in AMPK activity markedly impairs exercise tolerance. Compared with wild-type littermates at the same relative exercise capacity, vascular glucose delivery and skeletal muscle glucose uptake were impaired; skeletal muscle ATP degradation was accelerated, and arterial lactate concentrations were increased in mice expressing a kinase-dead AMPKα2 subunit (α2-KD) in skeletal muscle. Nitric-oxide synthase (NOS) activity was significantly impaired at rest and in response to exercise in α2-KD mice; expression of neuronal NOS (NOSμ) was also reduced. Moreover, complex I and IV activities of the electron transport chain were impaired 32 ± 8 and 50 ± 7%, respectively, in skeletal muscle of α2-KD mice (p < 0.05 versus wild type), indicative of impaired mitochondrial function. Thus, AMPK regulates neuronal NOSμ expression, NOS activity, and mitochondrial function in skeletal muscle. In addition, these results clarify the role of AMPK in the control of muscle glucose uptake during exercise. Collectively, these findings demonstrate that AMPK is central to substrate metabolism in vivo, which has important implications for exercise tolerance in health and certain disease states characterized by impaired AMPK activation in skeletal muscle.