Nitric oxide increases GLUT4 expression and regulates AMPK signaling in skeletal muscle

Abstract

Nitric oxide (NO) and 5'-AMP-activated protein kinase (AMPK) are involved in glucose transport and mitochondrial biogenesis in skeletal muscle. Here, we examined whether NO regulates the expression of the major glucose transporter in muscle (GLUT4) and whether it influences AMPK-induced upregulation of GLUT4. At low levels, the NO donor S-nitroso-N-penicillamine (SNAP, 1 and 10 microM) significantly increased GLUT4 mRNA ( approximately 3-fold; P < 0.05) in L6 myotubes, and cotreatment with the AMPK inhibitor compound C ablated this effect. The cGMP analog 8-bromo-cGMP (8-Br-cGMP, 2 mM) increased GLUT4 mRNA by approximately 50% (P < 0.05). GLUT4 protein expression was elevated 40% by 2 days treatment with 8-Br-cGMP, whereas 6 days treatment with 10 microM SNAP increased GLUT4 expression by 65%. Cotreatment of cultures with the guanylyl cyclase inhibitor 1H-[1,2,4]oxadiazolo[4,3,-a]quinoxalin-1-one prevented the SNAP-induced increase in GLUT4 protein. SNAP (10 microM) also induced significant phosphorylation of alpha-AMPK and acetyl-CoA carboxylase and translocation of phosphorylated alpha-AMPK to the nucleus. Furthermore, L6 myotubes exposed to 5-aminoimidazole-4-carboxamide-1-beta-d-ribofuranoside (AICAR) for 16 h presented an approximately ninefold increase in GLUT4 mRNA, whereas cotreatment with the non-isoform-specific NOS inhibitor N(G)-nitro-l-arginine methyl ester, prevented approximately 70% of this effect. In vivo, GLUT4 mRNA was increased 1.8-fold in the rat plantaris muscle 12 h after AICAR injection, and this induction was reduced by approximately 50% in animals cotreated with the neuronal and inducible nitric oxide synthases selective inhibitor 1-(2-trifluoromethyl-phenyl)-imidazole. We conclude that, in skeletal muscle, NO increases GLUT4 expression via a cGMP- and AMPK-dependent mechanism. The data are consistent with a role for NO in the regulation of AMPK, possibly via control of cellular activity of AMPK kinases and/or AMPK phosphatases.

Counteracting neuronal nitric oxide synthase proteasomal degradation improves glucose transport in insulin-resistant skeletal muscle from Zucker fa/fa rats

“…This implies that normal nNOS activity/expression could also improve the intrinsic activity of GLUT4, as previously suggested [53], despite no consensus view in the literature. In addition, nNOS restoration increased GLUT4 expression, as previously described in L6 myocytes [28], which may participate at the greater level of the transporter observed at the plasma membrane. We also found that insulin moderately stimulated GLUT4 translocation in muscles cells from fa/fa rats, without any improvement in glucose uptake.…”

“…4b), stimulated GLUT4 transport by 38% (p <0.05, n =3). NO has also been shown to modulate GLUT4 expression in L6 myotubes [28], and we found a 38% increase in GLUT4 protein level in muscle cells from fa/fa rats overexpressing nNOS (p <0.05) (Fig. 6f).…”

Lack of Inducible Nitric Oxide Synthase Prevents Lipid-Induced Skeletal Muscle Insulin Resistance Without Attenuating Cytokine Level

“…Among the three isoforms of NOS, endothelial NOS (eNOS) and neuronal NOS (nNOS) are constitutively expressed and produces a lower level of NO, whereas the expression of inducible NOS (iNOS) increases during inflammation and results in a much higher level of NO (9). The involvement of iNOS has been suggested in metabolic disorders such as atherosclerosis and obesity-linked type-2 diabetes (10 -12).…”

Reciprocal regulation of carbon monoxide metabolism and the circadian clock

“…Such a mechanism has been proposed to play a role in resetting the cholinergic clock in the suprachiasmatic nucleus 36 , where heme oxygenase activity is circadian 37 . Moreover, increased cGMP levels can enhance AMP kinase (AMPK) activity 38 , which in turn may act on the clock by promoting CRY-protein degradation 39 . Activation of AMPK in the liver also represses expression of gluconeogenesis enzymes such as Pck1 and G6pc 40 , results opposite from those observed in heme oxygenase-depleted hepatocytes.…”