Involvement of Amp Kinase in Glucose Uptake and Palmitate Oxidation in L6 Muscle Cell CulturesOuyang J1 and Ochs RS2*
- *Corresponding Author:
- Ochs RS
Deptartment of Pharmaceutical Sciences
School of Pharmacy, St. John’s University
8000 Utopia Parkway, Queens, USA
E-mail: [email protected]
Received date: May 08, 2014; Accepted date: Septemebr 24, 2014; Published date: September 26, 2014
Citation: Ouyang J, Ochs RS (2014) Involvement of Amp Kinase in Glucose Uptake and Palmitate Oxidation in L6 Muscle Cell Cultures. Metabolomics 4:133. doi:10.4172/2153-0769.1000133
Copyright: © 2014 Ouyang J, et al. This is an open-access article distributed under the terms of the Creative Commons Attribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original author and source are credited.
AICAR (5-aminoimidazole-4-carboxamide 1-ß-D-ribonucleoside) is known to activate the AMP-activated protein kinase (AMPK) in many cell types, including skeletal muscle. We showed that AICAR activated glucose uptake, fatty acid oxidation, and lactate formation by L6 skeletal muscle cell cultures. All of the actions were duplicated by adiponectin, another known activator of AMPK, demonstrating selectivity of AICAR. Moreover, AICAR and adiponectin similarly caused phosphorylation of AMPK, and its target proteins acetyl CoA carboxylase and S6Kinase. While creatine treatment of cells is known to greatly enhance creatine and creatine phosphate levels, it was proposed to paradoxically activate AMPK, and yet not affect glucose transport. However, we found creatine treatment to be without effect on glucose transport, fatty acid oxidation, or phosphorylation of AMPK or its target proteins. Unlike AICAR and adiponectin, creatine treatment stimulated glycogen formation from glucose and inhibited lactate formation. Consistent with this, we observed a diminution in phosphofructokinase expression. Thus, we conclude that creatine and creatine phosphate are not significant allosteric modulators of AMPK in intact cells. We investigated the role of AMPK in glycogen metabolism, using an inhibitor of glycogen phosphorylase. While the inhibitor enhanced glucose incorporation into glycogen, AICAR and adiponectin still diminished glycogen formation, supporting a direct action of AMPK on glycogen synthase. To probe the mechanism for adiponectin, we used siRNA constructs against adenyate kinase and LKB1 (the AMPK kinase). We concluded that adiponectin likely acts through an activation of LKB1, rather than indirectly increasing the turnover of ATP, involving adenylate kinase.