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Key glycolytic enzyme activities of skeletal muscle are decreased under fed and fasted states in mice with knocked down levels of Shc proteins.

Hagopian K, Tomilov AA, Kim K, Cortopassi GA, Ramsey JJ - PLoS ONE (2015)

Bottom Line: Shc proteins interact with the insulin receptor, indicating a role in regulating glycolysis.Changes in metabolite levels were consistent with the observed changes in enzyme activities.These studies indicate that decreased levels of Shc proteins in skeletal muscle lead to a decreased glycolytic capacity in both fed and fasted states.

View Article: PubMed Central - PubMed

Affiliation: Department of Molecular Biosciences, School of Veterinary Medicine, University of California Davis, Davis, CA 95616, United States of America.

ABSTRACT
Shc proteins interact with the insulin receptor, indicating a role in regulating glycolysis. To investigate this idea, the activities of key glycolytic regulatory enzymes and metabolites levels were measured in skeletal muscle from mice with low levels of Shc proteins (ShcKO) and wild-type (WT) controls. The activities of hexokinase, phosphofructokinase-1 and pyruvate kinase were decreased in ShcKO versus WT mice under both fed and fasted conditions. Increased alanine transaminase and branched-chain amino acid transaminase activities were also observed in ShcKO mice under both fed and fasting conditions. Protein expression of glycolytic enzymes was unchanged in the ShcKO and WT mice, indicating that decreased activities were not due to changes in their transcription. Changes in metabolite levels were consistent with the observed changes in enzyme activities. In particular, the levels of fructose-2,6-bisphosphate, a potent activator of phosphofructokinase-1, were consistently decreased in the ShcKO mice. Furthermore, the levels of lactate (inhibitor of hexokinase and phosphofructokinase-1) and citrate (inhibitor of phosphofructokinase-1 and pyruvate kinase) were increased in fed and fasted ShcKO versus WT mice. Pyruvate dehydrogenase activity was lower in ShcKO versus WT mice under fed conditions, and showed inhibition under fasting conditions in both ShcKO and WT mice, with ShcKO mice showing less inhibition than the WT mice. Pyruvate dehydrogenase kinase 4 levels were unchanged under fed conditions but were lower in the ShcKO mice under fasting conditions. These studies indicate that decreased levels of Shc proteins in skeletal muscle lead to a decreased glycolytic capacity in both fed and fasted states.

No MeSH data available.


Related in: MedlinePlus

PDH activity and protein levels of PDK4 and p-PDH in hindlimb skeletal muscle.Skeletal muscle samples from WT and ShcKO mice, under fed and fasted conditions, were used to determine the activity of PDH (A), as described in the experimental procedures. Samples were also resolved by electrophoresis, transferred and probed by antibodies and representative immunoblots and normalization of PDK4 (B) and pPDH (C) are presented. The following comparisons were made: within a genotype, fed versus fasted; across genotypes, fed versus fed and fasted versus fasted. Bars that do not share a common symbol differ significantly (P < 0.05). Data presented as mean ± SEM (n = 6).
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pone.0124204.g005: PDH activity and protein levels of PDK4 and p-PDH in hindlimb skeletal muscle.Skeletal muscle samples from WT and ShcKO mice, under fed and fasted conditions, were used to determine the activity of PDH (A), as described in the experimental procedures. Samples were also resolved by electrophoresis, transferred and probed by antibodies and representative immunoblots and normalization of PDK4 (B) and pPDH (C) are presented. The following comparisons were made: within a genotype, fed versus fasted; across genotypes, fed versus fed and fasted versus fasted. Bars that do not share a common symbol differ significantly (P < 0.05). Data presented as mean ± SEM (n = 6).

Mentions: In the fed state, muscle PDH activity (Fig 5A) was lower (P < 0.05) in the ShcKO compared to WT mice, while in the fasted state, the activity was higher (P < 0.05) in the ShcKO mice when compared with the WT animals. However, in both WT and ShcKO mice, PDH activities were substantially lower (P < 0.05) in the fasted versus fed state.


Key glycolytic enzyme activities of skeletal muscle are decreased under fed and fasted states in mice with knocked down levels of Shc proteins.

Hagopian K, Tomilov AA, Kim K, Cortopassi GA, Ramsey JJ - PLoS ONE (2015)

PDH activity and protein levels of PDK4 and p-PDH in hindlimb skeletal muscle.Skeletal muscle samples from WT and ShcKO mice, under fed and fasted conditions, were used to determine the activity of PDH (A), as described in the experimental procedures. Samples were also resolved by electrophoresis, transferred and probed by antibodies and representative immunoblots and normalization of PDK4 (B) and pPDH (C) are presented. The following comparisons were made: within a genotype, fed versus fasted; across genotypes, fed versus fed and fasted versus fasted. Bars that do not share a common symbol differ significantly (P < 0.05). Data presented as mean ± SEM (n = 6).
© Copyright Policy
Related In: Results  -  Collection

License
Show All Figures
getmorefigures.php?uid=PMC4400099&req=5

pone.0124204.g005: PDH activity and protein levels of PDK4 and p-PDH in hindlimb skeletal muscle.Skeletal muscle samples from WT and ShcKO mice, under fed and fasted conditions, were used to determine the activity of PDH (A), as described in the experimental procedures. Samples were also resolved by electrophoresis, transferred and probed by antibodies and representative immunoblots and normalization of PDK4 (B) and pPDH (C) are presented. The following comparisons were made: within a genotype, fed versus fasted; across genotypes, fed versus fed and fasted versus fasted. Bars that do not share a common symbol differ significantly (P < 0.05). Data presented as mean ± SEM (n = 6).
Mentions: In the fed state, muscle PDH activity (Fig 5A) was lower (P < 0.05) in the ShcKO compared to WT mice, while in the fasted state, the activity was higher (P < 0.05) in the ShcKO mice when compared with the WT animals. However, in both WT and ShcKO mice, PDH activities were substantially lower (P < 0.05) in the fasted versus fed state.

Bottom Line: Shc proteins interact with the insulin receptor, indicating a role in regulating glycolysis.Changes in metabolite levels were consistent with the observed changes in enzyme activities.These studies indicate that decreased levels of Shc proteins in skeletal muscle lead to a decreased glycolytic capacity in both fed and fasted states.

View Article: PubMed Central - PubMed

Affiliation: Department of Molecular Biosciences, School of Veterinary Medicine, University of California Davis, Davis, CA 95616, United States of America.

ABSTRACT
Shc proteins interact with the insulin receptor, indicating a role in regulating glycolysis. To investigate this idea, the activities of key glycolytic regulatory enzymes and metabolites levels were measured in skeletal muscle from mice with low levels of Shc proteins (ShcKO) and wild-type (WT) controls. The activities of hexokinase, phosphofructokinase-1 and pyruvate kinase were decreased in ShcKO versus WT mice under both fed and fasted conditions. Increased alanine transaminase and branched-chain amino acid transaminase activities were also observed in ShcKO mice under both fed and fasting conditions. Protein expression of glycolytic enzymes was unchanged in the ShcKO and WT mice, indicating that decreased activities were not due to changes in their transcription. Changes in metabolite levels were consistent with the observed changes in enzyme activities. In particular, the levels of fructose-2,6-bisphosphate, a potent activator of phosphofructokinase-1, were consistently decreased in the ShcKO mice. Furthermore, the levels of lactate (inhibitor of hexokinase and phosphofructokinase-1) and citrate (inhibitor of phosphofructokinase-1 and pyruvate kinase) were increased in fed and fasted ShcKO versus WT mice. Pyruvate dehydrogenase activity was lower in ShcKO versus WT mice under fed conditions, and showed inhibition under fasting conditions in both ShcKO and WT mice, with ShcKO mice showing less inhibition than the WT mice. Pyruvate dehydrogenase kinase 4 levels were unchanged under fed conditions but were lower in the ShcKO mice under fasting conditions. These studies indicate that decreased levels of Shc proteins in skeletal muscle lead to a decreased glycolytic capacity in both fed and fasted states.

No MeSH data available.


Related in: MedlinePlus