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Contraction-stimulated glucose transport in muscle is controlled by AMPK and mechanical stress but not sarcoplasmatic reticulum Ca(2+) release.

Jensen TE, Sylow L, Rose AJ, Madsen AB, Angin Y, Maarbjerg SJ, Richter EA - Mol Metab (2014)

Bottom Line: The prevailing concept implicates Ca(2+) as a key feed forward regulator of glucose transport with secondary fine-tuning by metabolic feedback signals through proteins such as AMPK.Rather, the glucose transport response is associated with metabolic feedback signals through AMPK, and mechanical stress-activated signals.These results suggest that ATP-turnover and mechanical stress feedback are sufficient to fully increase glucose transport during muscle contraction, and call for a major reconsideration of the established Ca(2+) centric paradigm.

View Article: PubMed Central - PubMed

Affiliation: Section of Molecular Physiology, Department of Nutrition, Exercise and Sports, University of Copenhagen, 2100 Copenhagen, Denmark.

ABSTRACT
Understanding how muscle contraction orchestrates insulin-independent muscle glucose transport may enable development of hyperglycemia-treating drugs. The prevailing concept implicates Ca(2+) as a key feed forward regulator of glucose transport with secondary fine-tuning by metabolic feedback signals through proteins such as AMPK. Here, we demonstrate in incubated mouse muscle that Ca(2+) release is neither sufficient nor strictly necessary to increase glucose transport. Rather, the glucose transport response is associated with metabolic feedback signals through AMPK, and mechanical stress-activated signals. Furthermore, artificial stimulation of AMPK combined with passive stretch of muscle is additive and sufficient to elicit the full contraction glucose transport response. These results suggest that ATP-turnover and mechanical stress feedback are sufficient to fully increase glucose transport during muscle contraction, and call for a major reconsideration of the established Ca(2+) centric paradigm.

No MeSH data available.


Related in: MedlinePlus

Cyclopiazonic acid (CPA)-induced glucose transport depends on AMPK and likely mechanical stress but not SR Ca2+. A) Quantifications of immunoblots from CPA-stimulated SOL muscles +/− BTS + Bleb. Quantified protein phosphorylation are indicated above the graphs throughout, n = 6, †††p < 0.001 ANOVA main-effect of CPA, */**/***p < 0.05/0.01/0.001 Tukey's post hoc test effect of CPA. B) Quantifications of immunoblots from CPA-stimulated wildtype and kinase-dead (KD) AMPK overexpressing SOL muscles, n = 6, ***p < 0.001 ANOVA main-effect of CPA. C) Quantifications of immunoblots from CPA-stimulated wildtype and KD AMPK overexpressing SOL muscles in the presence of BTS + Bleb. n = 6, p < 0.001 ANOVA main-effect of CPA, ††† ANOVA genotype main-effect. CPA-stimulated 2-deoxyglucose (2DG) transport (bottom graph) in mouse soleus D) +/− myosin ATP blockers E) in wildtype and KD AMPK mice F) combining myosin ATPase blockers with KD AMPK overexpression, n = 6. */**/***p < 0.05/0.01/0.001 CPA-effect using Tukey's post hoc test. Data are mean ± S.E.M.
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fig3: Cyclopiazonic acid (CPA)-induced glucose transport depends on AMPK and likely mechanical stress but not SR Ca2+. A) Quantifications of immunoblots from CPA-stimulated SOL muscles +/− BTS + Bleb. Quantified protein phosphorylation are indicated above the graphs throughout, n = 6, †††p < 0.001 ANOVA main-effect of CPA, */**/***p < 0.05/0.01/0.001 Tukey's post hoc test effect of CPA. B) Quantifications of immunoblots from CPA-stimulated wildtype and kinase-dead (KD) AMPK overexpressing SOL muscles, n = 6, ***p < 0.001 ANOVA main-effect of CPA. C) Quantifications of immunoblots from CPA-stimulated wildtype and KD AMPK overexpressing SOL muscles in the presence of BTS + Bleb. n = 6, p < 0.001 ANOVA main-effect of CPA, ††† ANOVA genotype main-effect. CPA-stimulated 2-deoxyglucose (2DG) transport (bottom graph) in mouse soleus D) +/− myosin ATP blockers E) in wildtype and KD AMPK mice F) combining myosin ATPase blockers with KD AMPK overexpression, n = 6. */**/***p < 0.05/0.01/0.001 CPA-effect using Tukey's post hoc test. Data are mean ± S.E.M.

Mentions: Myosin ATPase inhibition in soleus muscle potently dampened the CPA-induced phosphorylation of AMPK and p38 MAPK, (Figure 2A) activated by ATP-turnover [4] and mechanical stress [20], respectively. SR Ca2+ dependent phosphorylation of eEF2 was unaffected (Figure 3A). BTS + Bleb significantly inhibited CPA-stimulated α2 AMPK activity and had a qualitatively similar effect on α1 AMPK activity (Figure S1C). Myosin ATPase blockade potently reduced CPA-stimulated glucose transport (Figure 3).


Contraction-stimulated glucose transport in muscle is controlled by AMPK and mechanical stress but not sarcoplasmatic reticulum Ca(2+) release.

Jensen TE, Sylow L, Rose AJ, Madsen AB, Angin Y, Maarbjerg SJ, Richter EA - Mol Metab (2014)

Cyclopiazonic acid (CPA)-induced glucose transport depends on AMPK and likely mechanical stress but not SR Ca2+. A) Quantifications of immunoblots from CPA-stimulated SOL muscles +/− BTS + Bleb. Quantified protein phosphorylation are indicated above the graphs throughout, n = 6, †††p < 0.001 ANOVA main-effect of CPA, */**/***p < 0.05/0.01/0.001 Tukey's post hoc test effect of CPA. B) Quantifications of immunoblots from CPA-stimulated wildtype and kinase-dead (KD) AMPK overexpressing SOL muscles, n = 6, ***p < 0.001 ANOVA main-effect of CPA. C) Quantifications of immunoblots from CPA-stimulated wildtype and KD AMPK overexpressing SOL muscles in the presence of BTS + Bleb. n = 6, p < 0.001 ANOVA main-effect of CPA, ††† ANOVA genotype main-effect. CPA-stimulated 2-deoxyglucose (2DG) transport (bottom graph) in mouse soleus D) +/− myosin ATP blockers E) in wildtype and KD AMPK mice F) combining myosin ATPase blockers with KD AMPK overexpression, n = 6. */**/***p < 0.05/0.01/0.001 CPA-effect using Tukey's post hoc test. Data are mean ± S.E.M.
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fig3: Cyclopiazonic acid (CPA)-induced glucose transport depends on AMPK and likely mechanical stress but not SR Ca2+. A) Quantifications of immunoblots from CPA-stimulated SOL muscles +/− BTS + Bleb. Quantified protein phosphorylation are indicated above the graphs throughout, n = 6, †††p < 0.001 ANOVA main-effect of CPA, */**/***p < 0.05/0.01/0.001 Tukey's post hoc test effect of CPA. B) Quantifications of immunoblots from CPA-stimulated wildtype and kinase-dead (KD) AMPK overexpressing SOL muscles, n = 6, ***p < 0.001 ANOVA main-effect of CPA. C) Quantifications of immunoblots from CPA-stimulated wildtype and KD AMPK overexpressing SOL muscles in the presence of BTS + Bleb. n = 6, p < 0.001 ANOVA main-effect of CPA, ††† ANOVA genotype main-effect. CPA-stimulated 2-deoxyglucose (2DG) transport (bottom graph) in mouse soleus D) +/− myosin ATP blockers E) in wildtype and KD AMPK mice F) combining myosin ATPase blockers with KD AMPK overexpression, n = 6. */**/***p < 0.05/0.01/0.001 CPA-effect using Tukey's post hoc test. Data are mean ± S.E.M.
Mentions: Myosin ATPase inhibition in soleus muscle potently dampened the CPA-induced phosphorylation of AMPK and p38 MAPK, (Figure 2A) activated by ATP-turnover [4] and mechanical stress [20], respectively. SR Ca2+ dependent phosphorylation of eEF2 was unaffected (Figure 3A). BTS + Bleb significantly inhibited CPA-stimulated α2 AMPK activity and had a qualitatively similar effect on α1 AMPK activity (Figure S1C). Myosin ATPase blockade potently reduced CPA-stimulated glucose transport (Figure 3).

Bottom Line: The prevailing concept implicates Ca(2+) as a key feed forward regulator of glucose transport with secondary fine-tuning by metabolic feedback signals through proteins such as AMPK.Rather, the glucose transport response is associated with metabolic feedback signals through AMPK, and mechanical stress-activated signals.These results suggest that ATP-turnover and mechanical stress feedback are sufficient to fully increase glucose transport during muscle contraction, and call for a major reconsideration of the established Ca(2+) centric paradigm.

View Article: PubMed Central - PubMed

Affiliation: Section of Molecular Physiology, Department of Nutrition, Exercise and Sports, University of Copenhagen, 2100 Copenhagen, Denmark.

ABSTRACT
Understanding how muscle contraction orchestrates insulin-independent muscle glucose transport may enable development of hyperglycemia-treating drugs. The prevailing concept implicates Ca(2+) as a key feed forward regulator of glucose transport with secondary fine-tuning by metabolic feedback signals through proteins such as AMPK. Here, we demonstrate in incubated mouse muscle that Ca(2+) release is neither sufficient nor strictly necessary to increase glucose transport. Rather, the glucose transport response is associated with metabolic feedback signals through AMPK, and mechanical stress-activated signals. Furthermore, artificial stimulation of AMPK combined with passive stretch of muscle is additive and sufficient to elicit the full contraction glucose transport response. These results suggest that ATP-turnover and mechanical stress feedback are sufficient to fully increase glucose transport during muscle contraction, and call for a major reconsideration of the established Ca(2+) centric paradigm.

No MeSH data available.


Related in: MedlinePlus