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Journal of Obesity
Volume 2010 (2010), Article ID 970865, 8 pages
http://dx.doi.org/10.1155/2010/970865
Research Article

Metformin Improves Insulin Signaling in Obese Rats via Reduced IKK Action in a Fiber-Type Specific Manner

1The Metabolic Institute for the Study of Diabetes and Obesity, East Carolina University, Greenville, NC 27834, USA
2Department of Exercise and Sport Science, East Carolina University, Greenville, NC 27834, USA
3Department of Physiology, East Carolina University, Greenville, NC 27834, USA
4Department of Biology, East Carolina University, Greenville, NC 27834, USA

Received 26 May 2009; Accepted 27 October 2009

Academic Editor: Eliot Brinton

Copyright © 2010 Benjamin T. Bikman et al. This is an open access article distributed under the Creative Commons Attribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited.

Abstract

Metformin is a widely used insulin-sensitizing drug, though its mechanisms are not fully understood. Metformin has been shown to activate AMPK in skeletal muscle; however, its effects on the inhibitor of B kinase (IKK ) in this same tissue are unknown. The aim of this study was to (1) determine the ability of metformin to attenuate IKK action, (2) determine whether changes in AMPK activity are associated with changes in IKK action in skeletal muscle, and (3) examine whether changes in AMPK and IKK function are consistent with improved insulin signaling. Lean and obese male Zuckers received either vehicle or metformin by oral gavage daily for four weeks (four groups of eight). Proteins were measured in white gastrocnemius (WG), red gastrocnemius (RG), and soleus. AMPK phosphorylation increased ( ) in WG in both lean (57%) and obese (106%), and this was supported by an increase in phospho-ACC in WG. Further, metformin increased I B levels in both WG (150%) and RG (67%) of obese rats, indicative of reduced IKK activity ( ), and was associated with reduced IRS1-p (30%) in the WG of obese rats ( ). From these data we conclude that metformin treatment appears to exert an inhibitory influence on skeletal muscle IKK activity, as evidenced by elevated I B levels and reduced IRS1- phosphorylation in a fiber-type specific manner.