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Muscle-specific knock-out of NUAK family SNF1-like kinase 1 (NUAK1) prevents high fat diet-induced glucose intolerance.

Inazuka F, Sugiyama N, Tomita M, Abe T, Shioi G, Esumi H - J. Biol. Chem. (2012)

Bottom Line: Quantitative phosphoproteome analysis of soleus muscle was performed to understand the molecular mechanisms underlying the knock-out phenotype.Nuak1 mRNA was preferentially expressed in highly oxidative tissues such as brain, heart, and soleus muscle.Phosphoproteome analysis revealed that phosphorylation of IRS1 Ser-1097 was markedly decreased in NUAK1-deficient muscle.

View Article: PubMed Central - PubMed

Affiliation: Department of Integrated Biosciences, Graduate School of Frontier Sciences, The University of Tokyo, Kashiwa 277-8561, Japan.

ABSTRACT
NUAK1 is a member of the AMP-activated protein kinase-related kinase family. Recent studies have shown that NUAK1 is involved in cellular senescence and motility in epithelial cells and fibroblasts. However, the physiological roles of NUAK1 are poorly understood because of embryonic lethality in NUAK1 mice. The purpose of this study was to elucidate the roles of NUAK1 in adult tissues. We determined the tissue distribution of NUAK1 and generated muscle-specific NUAK1 knock-out (MNUAK1KO) mice. For phenotypic analysis, whole body glucose homeostasis and muscle glucose metabolism were examined. Quantitative phosphoproteome analysis of soleus muscle was performed to understand the molecular mechanisms underlying the knock-out phenotype. Nuak1 mRNA was preferentially expressed in highly oxidative tissues such as brain, heart, and soleus muscle. On a high fat diet, MNUAK1KO mice had a lower fasting blood glucose level, greater glucose tolerance, higher insulin sensitivity, and higher concentration of muscle glycogen than control mice. Phosphoproteome analysis revealed that phosphorylation of IRS1 Ser-1097 was markedly decreased in NUAK1-deficient muscle. Consistent with this, insulin signaling was enhanced in the soleus muscle of MNUAK1KO mice, as evidenced by increased phosphorylation of IRS1 Tyr-608, AKT Thr-308, and TBC1D4 Thr-649. These observations suggest that a physiological role of NUAK1 is to suppress glucose uptake through negative regulation of insulin signaling in oxidative muscle.

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Phosphorylation of TBC1D4 is up-regulated in NUAK1-deficient muscle after glucose administration. Immunoblot analysis of TBC1D4, GLUT4, and NUAK1 in soleus muscle of HFD-fed control and MNUAK1KO mice. Mice at the age of 13–15 weeks were fasted overnight and sacrificed 40 min after oral administration of water (basal control) or glucose. The graphs show the intensities of phospho-TBC1D4, GLUT4, and NUAK1 bands. Phospho-TBC1D4 protein levels were normalized to total TBC1D4. GLUT4 and NUAK1 protein levels were normalized to actin. The protein levels are expressed relative to those in the water-administered control mice. The data are the means ± S.E. (n = 4 for NUAK1 and 5 for TBC1D4 and GLUT4). **, p < 0.01 (Student's t test). Cont, control; MNKO, MNUAK1KO.
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Figure 5: Phosphorylation of TBC1D4 is up-regulated in NUAK1-deficient muscle after glucose administration. Immunoblot analysis of TBC1D4, GLUT4, and NUAK1 in soleus muscle of HFD-fed control and MNUAK1KO mice. Mice at the age of 13–15 weeks were fasted overnight and sacrificed 40 min after oral administration of water (basal control) or glucose. The graphs show the intensities of phospho-TBC1D4, GLUT4, and NUAK1 bands. Phospho-TBC1D4 protein levels were normalized to total TBC1D4. GLUT4 and NUAK1 protein levels were normalized to actin. The protein levels are expressed relative to those in the water-administered control mice. The data are the means ± S.E. (n = 4 for NUAK1 and 5 for TBC1D4 and GLUT4). **, p < 0.01 (Student's t test). Cont, control; MNKO, MNUAK1KO.

Mentions: Glucose metabolism in skeletal muscle is highly sensitive to both the expression of glucose transporter type 4 (GLUT4) which is increased by exercise and decreased by a HFD (34, 35), and its translocation to the plasma membrane (36–38), which is facilitated by phosphorylated TBC1 domain family member 4 (TBC1D4) (39, 40). To investigate the molecular mechanism underlying improved glucose metabolism, the TBC1D4 phosphorylation in acute response to glucose in the soleus of HFD-fed MNUAK1KO and control mice was examined. The level of GLUT4 protein was also compared between MNUAK1KO and control mice. The phosphorylation level of TBC1D4 Thr-649 (corresponding to Thr-642 in the human isoform) was significantly higher in the soleus muscle from MNUAK1KO mice in the glucose-administered group (Fig. 5). This difference was not observed in the water-administered group, suggesting that postprandial glucose uptake is enhanced in the soleus of MNUAK1KO mice. No differences were observed in the GLUT4 protein level (Fig. 5). Our data indicate that the observed increase in glucose disposal in MNUAK1KO mice fed a HFD is associated with increased GLUT4 translocation rather than changes in GLUT4 expression in the soleus muscle.


Muscle-specific knock-out of NUAK family SNF1-like kinase 1 (NUAK1) prevents high fat diet-induced glucose intolerance.

Inazuka F, Sugiyama N, Tomita M, Abe T, Shioi G, Esumi H - J. Biol. Chem. (2012)

Phosphorylation of TBC1D4 is up-regulated in NUAK1-deficient muscle after glucose administration. Immunoblot analysis of TBC1D4, GLUT4, and NUAK1 in soleus muscle of HFD-fed control and MNUAK1KO mice. Mice at the age of 13–15 weeks were fasted overnight and sacrificed 40 min after oral administration of water (basal control) or glucose. The graphs show the intensities of phospho-TBC1D4, GLUT4, and NUAK1 bands. Phospho-TBC1D4 protein levels were normalized to total TBC1D4. GLUT4 and NUAK1 protein levels were normalized to actin. The protein levels are expressed relative to those in the water-administered control mice. The data are the means ± S.E. (n = 4 for NUAK1 and 5 for TBC1D4 and GLUT4). **, p < 0.01 (Student's t test). Cont, control; MNKO, MNUAK1KO.
© Copyright Policy - open-access
Related In: Results  -  Collection

License
Show All Figures
getmorefigures.php?uid=PMC3351321&req=5

Figure 5: Phosphorylation of TBC1D4 is up-regulated in NUAK1-deficient muscle after glucose administration. Immunoblot analysis of TBC1D4, GLUT4, and NUAK1 in soleus muscle of HFD-fed control and MNUAK1KO mice. Mice at the age of 13–15 weeks were fasted overnight and sacrificed 40 min after oral administration of water (basal control) or glucose. The graphs show the intensities of phospho-TBC1D4, GLUT4, and NUAK1 bands. Phospho-TBC1D4 protein levels were normalized to total TBC1D4. GLUT4 and NUAK1 protein levels were normalized to actin. The protein levels are expressed relative to those in the water-administered control mice. The data are the means ± S.E. (n = 4 for NUAK1 and 5 for TBC1D4 and GLUT4). **, p < 0.01 (Student's t test). Cont, control; MNKO, MNUAK1KO.
Mentions: Glucose metabolism in skeletal muscle is highly sensitive to both the expression of glucose transporter type 4 (GLUT4) which is increased by exercise and decreased by a HFD (34, 35), and its translocation to the plasma membrane (36–38), which is facilitated by phosphorylated TBC1 domain family member 4 (TBC1D4) (39, 40). To investigate the molecular mechanism underlying improved glucose metabolism, the TBC1D4 phosphorylation in acute response to glucose in the soleus of HFD-fed MNUAK1KO and control mice was examined. The level of GLUT4 protein was also compared between MNUAK1KO and control mice. The phosphorylation level of TBC1D4 Thr-649 (corresponding to Thr-642 in the human isoform) was significantly higher in the soleus muscle from MNUAK1KO mice in the glucose-administered group (Fig. 5). This difference was not observed in the water-administered group, suggesting that postprandial glucose uptake is enhanced in the soleus of MNUAK1KO mice. No differences were observed in the GLUT4 protein level (Fig. 5). Our data indicate that the observed increase in glucose disposal in MNUAK1KO mice fed a HFD is associated with increased GLUT4 translocation rather than changes in GLUT4 expression in the soleus muscle.

Bottom Line: Quantitative phosphoproteome analysis of soleus muscle was performed to understand the molecular mechanisms underlying the knock-out phenotype.Nuak1 mRNA was preferentially expressed in highly oxidative tissues such as brain, heart, and soleus muscle.Phosphoproteome analysis revealed that phosphorylation of IRS1 Ser-1097 was markedly decreased in NUAK1-deficient muscle.

View Article: PubMed Central - PubMed

Affiliation: Department of Integrated Biosciences, Graduate School of Frontier Sciences, The University of Tokyo, Kashiwa 277-8561, Japan.

ABSTRACT
NUAK1 is a member of the AMP-activated protein kinase-related kinase family. Recent studies have shown that NUAK1 is involved in cellular senescence and motility in epithelial cells and fibroblasts. However, the physiological roles of NUAK1 are poorly understood because of embryonic lethality in NUAK1 mice. The purpose of this study was to elucidate the roles of NUAK1 in adult tissues. We determined the tissue distribution of NUAK1 and generated muscle-specific NUAK1 knock-out (MNUAK1KO) mice. For phenotypic analysis, whole body glucose homeostasis and muscle glucose metabolism were examined. Quantitative phosphoproteome analysis of soleus muscle was performed to understand the molecular mechanisms underlying the knock-out phenotype. Nuak1 mRNA was preferentially expressed in highly oxidative tissues such as brain, heart, and soleus muscle. On a high fat diet, MNUAK1KO mice had a lower fasting blood glucose level, greater glucose tolerance, higher insulin sensitivity, and higher concentration of muscle glycogen than control mice. Phosphoproteome analysis revealed that phosphorylation of IRS1 Ser-1097 was markedly decreased in NUAK1-deficient muscle. Consistent with this, insulin signaling was enhanced in the soleus muscle of MNUAK1KO mice, as evidenced by increased phosphorylation of IRS1 Tyr-608, AKT Thr-308, and TBC1D4 Thr-649. These observations suggest that a physiological role of NUAK1 is to suppress glucose uptake through negative regulation of insulin signaling in oxidative muscle.

Show MeSH
Related in: MedlinePlus