Activation of AMP-Activated Protein Kinase by Interleukin-6 in Rat Skeletal Muscle

Association With Changes in cAMP, Energy State, and Endogenous Fuel Mobilization

  1. Meghan Kelly,
  2. Marie-Soleil Gauthier,
  3. Asish K. Saha and
  4. Neil B. Ruderman
  1. From the Department of Medicine, Section of Endocrinology, Diabetes Research Unit, Boston University School of Medicine, Boston, Massachusetts.
  1. Corresponding author: Neil B. Ruderman, nrude{at}bu.edu.

Abstract

OBJECTIVE Interleukin-6 (IL-6) directly activates AMP-activated protein kinase (AMPK) in vivo and in vitro; however, the mechanism by which it does so is unknown.

RESEARCH DESIGN AND METHODS We examined this question in skeletal muscle using an incubated rat extensor digitorum longus (EDL) muscle preparation as a tool.

RESULTS AMPK activation by IL-6 coincided temporally with a nearly threefold increase in the AMP:ATP ratio in the EDL. The effects of IL-6 on both AMPK activity and energy state were inhibited by coincubation with propranolol, suggesting involvement of β-adrenergic signaling. In keeping with this notion, IL-6 concurrently induced a transient increase in cAMP, and its ability to activate AMPK was blocked by the adenyl cyclase inhibitor 2′5′-dideoxyadenosine. In addition, like other β-adrenergic stimuli, IL-6 increased glycogen breakdown and lipolysis in the EDL. Similar effects of IL-6 on AMPK, energy state, and cAMP content were observed in C2C12 myotubes and gastrocnemius muscle in vivo, indicating that they were not unique to the incubated EDL.

CONCLUSIONS These studies demonstrate that IL-6 activates AMPK in skeletal muscle by increasing the concentration of cAMP and, secondarily, the AMP:ATP ratio. They also suggest that substantial increases in IL-6 concentrations, such as those that can result from its synthesis by muscles during exercise, may play a role in the mobilization of fuel stores within skeletal muscle as an added means of restoring energy balance.

Footnotes

  • The costs of publication of this article were defrayed in part by the payment of page charges. This article must therefore be hereby marked “advertisement” in accordance with 18 U.S.C. Section 1734 solely to indicate this fact.

    • Received September 18, 2008.
    • Accepted May 20, 2009.
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  1. Diabetes vol. 58 no. 9 1953-1960
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