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EMG-normalised kinase activation during exercise is higher in human gastrocnemius compared to soleus muscle.

Jensen TE, Leutert R, Rasmussen ST, Mouatt JR, Christiansen ML, Jensen BR, Richter EA - PLoS ONE (2012)

Bottom Line: No differences were found in protein expression of signalling proteins (AMPK subunits, eEF2, ERK1/2, TBC1D1 and 4), mitochondrial markers (F1 ATPase and COX1) or ROS-handling enzymes (SOD2 and catalase).In conclusion, proteins with muscle-group restricted expression in mice do not show this pattern in human lower extremity muscle groups.This may be due to the combined subtle effects of a higher type I muscle fiber content and higher training status in soleus compared to gastrocnemius muscle.

View Article: PubMed Central - PubMed

Affiliation: Molecular Physiology Group, Department of Exercise and Sport Sciences, University of Copenhagen, Copenhagen, Denmark. TEJensen@ifi.ku.dk

ABSTRACT
In mice, certain proteins show a highly confined expression in specific muscle groups. Also, resting and exercise/contraction-induced phosphorylation responses are higher in rat skeletal muscle with low mitochondrial content compared to muscles with high mitochondrial content, possibly related to differential reactive oxygen species (ROS)-scavenging ability or resting glycogen content. To evaluate these parameters in humans, biopsies from soleus, gastrocnemius and vastus lateralis muscles were taken before and after a 45 min inclined (15%) walking exercise bout at 69% VO2(max) aimed at simultaneously activating soleus and gastrocnemius in a comparable dynamic work-pattern. Hexokinase II and GLUT4 were 46-59% and 26-38% higher (p<0.05) in soleus compared to the two other muscles. The type I muscle fiber percentage was highest in soleus and lowest in vastus lateralis. No differences were found in protein expression of signalling proteins (AMPK subunits, eEF2, ERK1/2, TBC1D1 and 4), mitochondrial markers (F1 ATPase and COX1) or ROS-handling enzymes (SOD2 and catalase). Gastrocnemius was less active than soleus measured as EMG signal and glycogen use yet gastrocnemius displayed larger increases than soleus in phosphorylation of AMPK Thr172, eEF2 Thr56 and ERK 1/2 Thr202/Tyr204 when normalised to the mean relative EMG-signal. In conclusion, proteins with muscle-group restricted expression in mice do not show this pattern in human lower extremity muscle groups. Nonetheless the phosphorylation-response is greater for a number of kinase signalling pathways in human gastrocnemius than soleus at a given activation-intensity. This may be due to the combined subtle effects of a higher type I muscle fiber content and higher training status in soleus compared to gastrocnemius muscle.

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Characterisation of protein expression in different human muscle groups.A) Mean fibertype distribution and B) representative blots of relative protein expression in human soleus (S), lateral gastrocnemius (G) and vastus lateralis (VL) as indicated. ** p<0.01 fibertype-difference soleus vs. VL. n = 7–8 for fibertype-determinations and n = 10 for western blotting.
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pone-0031054-g002: Characterisation of protein expression in different human muscle groups.A) Mean fibertype distribution and B) representative blots of relative protein expression in human soleus (S), lateral gastrocnemius (G) and vastus lateralis (VL) as indicated. ** p<0.01 fibertype-difference soleus vs. VL. n = 7–8 for fibertype-determinations and n = 10 for western blotting.

Mentions: The measured fibertype-distribution in the biopsies obtained from human soleus, gastrocnemius and VL showed a roughly 20% higher mean type I fiber content and equally lower type IIa fiber content in soleus compared to gastrocnemius and VL (figure 2A). Figure 2B and table 2 also show representative blots and lists the total protein measurements performed on the current biopsy-material. HXII content was higher in soleus compared to gastrocnemius (p<0.01) and VL (p<0.001) and GLUT4 content higher in soleus compared to gastrocnemius (p<0.05). In addition, a strong trend towards a differential expression of the mitochondrial superoxide-converting enzyme, SOD2 was found (p = 0.07 by 1-way ANOVA). All remaining proteins measured, including signalling proteins (AMPK subunits, ERK, eEF2, TBC1D1, TBC1D4), mitochondrial markers (F1 ATPase, COXI) and the hydrogen peroxide-inactivating Catalase-enzyme showed no significant differences in relative expression between muscles. A much used loading control, actin, tended to be higher in soleus compared to gastrocnemius (mean 28% lower) and VL (mean 7% lower). Given that the quantifications for multiple proteins in these samples and coomassie-staining indicates equal protein loading, this may suggest that actin is a poor loading control for comparison between muscles. Overall, the mouse pattern of high enrichment of certain proteins within specific muscle groups is unlikely to be present in humans.


EMG-normalised kinase activation during exercise is higher in human gastrocnemius compared to soleus muscle.

Jensen TE, Leutert R, Rasmussen ST, Mouatt JR, Christiansen ML, Jensen BR, Richter EA - PLoS ONE (2012)

Characterisation of protein expression in different human muscle groups.A) Mean fibertype distribution and B) representative blots of relative protein expression in human soleus (S), lateral gastrocnemius (G) and vastus lateralis (VL) as indicated. ** p<0.01 fibertype-difference soleus vs. VL. n = 7–8 for fibertype-determinations and n = 10 for western blotting.
© Copyright Policy
Related In: Results  -  Collection

Show All Figures
getmorefigures.php?uid=PMC3275615&req=5

pone-0031054-g002: Characterisation of protein expression in different human muscle groups.A) Mean fibertype distribution and B) representative blots of relative protein expression in human soleus (S), lateral gastrocnemius (G) and vastus lateralis (VL) as indicated. ** p<0.01 fibertype-difference soleus vs. VL. n = 7–8 for fibertype-determinations and n = 10 for western blotting.
Mentions: The measured fibertype-distribution in the biopsies obtained from human soleus, gastrocnemius and VL showed a roughly 20% higher mean type I fiber content and equally lower type IIa fiber content in soleus compared to gastrocnemius and VL (figure 2A). Figure 2B and table 2 also show representative blots and lists the total protein measurements performed on the current biopsy-material. HXII content was higher in soleus compared to gastrocnemius (p<0.01) and VL (p<0.001) and GLUT4 content higher in soleus compared to gastrocnemius (p<0.05). In addition, a strong trend towards a differential expression of the mitochondrial superoxide-converting enzyme, SOD2 was found (p = 0.07 by 1-way ANOVA). All remaining proteins measured, including signalling proteins (AMPK subunits, ERK, eEF2, TBC1D1, TBC1D4), mitochondrial markers (F1 ATPase, COXI) and the hydrogen peroxide-inactivating Catalase-enzyme showed no significant differences in relative expression between muscles. A much used loading control, actin, tended to be higher in soleus compared to gastrocnemius (mean 28% lower) and VL (mean 7% lower). Given that the quantifications for multiple proteins in these samples and coomassie-staining indicates equal protein loading, this may suggest that actin is a poor loading control for comparison between muscles. Overall, the mouse pattern of high enrichment of certain proteins within specific muscle groups is unlikely to be present in humans.

Bottom Line: No differences were found in protein expression of signalling proteins (AMPK subunits, eEF2, ERK1/2, TBC1D1 and 4), mitochondrial markers (F1 ATPase and COX1) or ROS-handling enzymes (SOD2 and catalase).In conclusion, proteins with muscle-group restricted expression in mice do not show this pattern in human lower extremity muscle groups.This may be due to the combined subtle effects of a higher type I muscle fiber content and higher training status in soleus compared to gastrocnemius muscle.

View Article: PubMed Central - PubMed

Affiliation: Molecular Physiology Group, Department of Exercise and Sport Sciences, University of Copenhagen, Copenhagen, Denmark. TEJensen@ifi.ku.dk

ABSTRACT
In mice, certain proteins show a highly confined expression in specific muscle groups. Also, resting and exercise/contraction-induced phosphorylation responses are higher in rat skeletal muscle with low mitochondrial content compared to muscles with high mitochondrial content, possibly related to differential reactive oxygen species (ROS)-scavenging ability or resting glycogen content. To evaluate these parameters in humans, biopsies from soleus, gastrocnemius and vastus lateralis muscles were taken before and after a 45 min inclined (15%) walking exercise bout at 69% VO2(max) aimed at simultaneously activating soleus and gastrocnemius in a comparable dynamic work-pattern. Hexokinase II and GLUT4 were 46-59% and 26-38% higher (p<0.05) in soleus compared to the two other muscles. The type I muscle fiber percentage was highest in soleus and lowest in vastus lateralis. No differences were found in protein expression of signalling proteins (AMPK subunits, eEF2, ERK1/2, TBC1D1 and 4), mitochondrial markers (F1 ATPase and COX1) or ROS-handling enzymes (SOD2 and catalase). Gastrocnemius was less active than soleus measured as EMG signal and glycogen use yet gastrocnemius displayed larger increases than soleus in phosphorylation of AMPK Thr172, eEF2 Thr56 and ERK 1/2 Thr202/Tyr204 when normalised to the mean relative EMG-signal. In conclusion, proteins with muscle-group restricted expression in mice do not show this pattern in human lower extremity muscle groups. Nonetheless the phosphorylation-response is greater for a number of kinase signalling pathways in human gastrocnemius than soleus at a given activation-intensity. This may be due to the combined subtle effects of a higher type I muscle fiber content and higher training status in soleus compared to gastrocnemius muscle.

Show MeSH
Related in: MedlinePlus