Skeletal muscle glucose uptake during contraction is regulated by nitric oxide and ROS independently of AMPK

Abstract

Merry TL, Steinberg GR, Lynch GS, McConell GK. Skeletal muscle glucose uptake during contraction is regulated by nitric oxide and ROS independently of AMPK. Am J Physiol Endocrinol Metab 298: E577-E585, 2010. First published December 15, 2009; doi:10.1152/ajpendo.00239.2009.-Reactive oxygen species (ROS) and nitric oxide (NO) have been implicated in the regulation of skeletal muscle glucose uptake during contraction, and there is evidence that they do so via interaction with AMP-activated protein kinase (AMPK). In this study, we tested the hypothesis that ROS and NO regulate skeletal muscle glucose uptake during contraction via an AMPK-independent mechanism. Isolated extensor digitorum longus (EDL) and soleus muscles from mice that expressed a muscle-specific kinase dead AMPK␣2 isoform (AMPK-KD) and wild-type litter mates (WT) were stimulated to contract, and glucose uptake was measured in the presence or absence of the antioxidant N-acetyl-Lcysteine (NAC) or the nitric oxide synthase (NOS) inhibitor N Gmonomethyl-L-arginine (L-NMMA). Contraction increased AMPK␣2 activity in WT but not AMPK-KD EDL muscles. However, contraction increased glucose uptake in the EDL and soleus muscles of AMPK-KD and WT mice to a similar extent. In EDL muscles, NAC and L-NMMA prevented contraction-stimulated increases in oxidant levels (dichloroflourescein fluorescence) and NOS activity, respectively, and attenuated contraction-stimulated glucose uptake in both genotypes to a similar extent. In soleus muscles of AMPK-KD and WT mice, NAC prevented contraction-stimulated glucose uptake and L-NMMA had no effect. This is likely attributed to the relative lack of neuronal NOS in the soleus muscles compared with EDL muscles. Contraction increased AMPK␣ Thr 172 phosphorylation in EDL and soleus muscles of WT but not AMPK-KD mice, and this was not affected by NAC or L-NMMA treatment. In conclusion, ROS and NO are involved in regulating skeletal muscle glucose uptake during contraction via an AMPK-independent mechanism. nitric oxide; reactive oxygen species; exercise; metabolism; contraction; glucose uptake EXERCISE AND CONTRACTION INCREASE translocation of GLUT4 to the cell surface, facilitating glucose transport into skeletal muscle (55). Although the mechanism(s) by which contraction increases GLUT4 translocation and glucose uptake into skeletal muscle are not yet fully defined, there is consensus that the signals regulating this pathway are independent of the insulinsignaling pathway (31, 39). Numerous mechanisms have been implicated in regulating contraction-stimulated glucose uptake (43), and one of the most attractive and well-studied candidates is AMP-activated protein kinase (AMPK). While initial studies demonstrated that the AMPK activator 5-aminoimidazole 4-carboxamide ribonucleoside (AICAR) increased glucose uptake (17) and that increased AMPK activity during contraction correlates with glucose uptake (20, 38), disassociations between glucose uptake and contraction have also been reported (9, 34). Importantly, mice that overexpre...

AMPKα2deficiency uncovers time dependency in the regulation of contraction-induced palmitate and glucose uptake in mouse muscle

“…These conclusions are consistent with previous studies in which AMPK␣ 2 was shown to be a necessary signal in the regulation of substrate metabolism during muscle contraction or treadmill exercise (24,25). However, our data are not consistent with some additional reports in which low AMPK␣ 2 activity did not affect muscle glucose clearance during treadmill exercise (26), glucose uptake in contracting extensor digitorum longus muscle, which is a mixed-fiber type muscle (10), or FA oxidation in isolated muscle during muscle contraction or following treadmill exercise (4,10,25,29,30). Possible explanations for these differences include the fact that the exercise mode and the fiber types were different between studies.…”

“…Force production measurements were made in anesthetized WT and DN mice to determine whether AMPK␣ 2 deficiency would affect (10) or not affect (29) force production with this protocol (13,14). The right tibiopatellar ligament was stabilized for the recording of force production, and a modular chart recorder (Cole Parmer, Vernon Hills, IL) was used to measure the tension developed by the GSP muscle group during the 20-min muscle stimulation protocol.…”

Imaging superoxide flash and metabolism-coupled mitochondrial permeability transition in living animals

“…Of many intracellular ROS production mechanisms, the mitochondrion is the most prominent ROS generator wherein constitutive ROS production arises from leakage of a small percent of electrons from the electron transfer chain (ETC) [7,8]. In skeletal muscle, which requires high energy supply and contains abundant mitochondria, adequate amount of ROS modulates muscle contractility and glucose metabolism [9,10], while excessive ROS is responsible for muscle fatigue and insulin resistance [1,11,12].…”

Protein Kinase D1 Is Essential for Contraction-induced Glucose Uptake but Is Not Involved in Fatty Acid Uptake into Cardiomyocytes

“…This dual signaling input for contraction-induced GLUT4 translocation is in line with studies in skeletal muscle demonstrating that AMPK is essential but not sufficient for contraction-induced GLUT4 translocation and glucose uptake (25,26). On the other hand, another study in skeletal muscle showed that contraction-induced GLUT4 translocation was found to be dependent on ROS signaling and independent of AMPK activation (21). Hence, further studies are needed to study the combined roles of ROS and AMPK signaling in skeletal muscle.…”

“…Namely, it has been shown that the induction of contraction enhances ROS formation in cardiomyocytes (20) and that ROS scavengers inhibit contractioninduced glucose uptake (21,22). Furthermore, PKD1 is known to be activated by mitochondrial ROS (9).…”