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Attenuation of muscle wasting in murine C2C 12 myotubes by epigallocatechin-3-gallate.

Mirza KA, Pereira SL, Edens NK, Tisdale MJ - J Cachexia Sarcopenia Muscle (2014)

Bottom Line: EGCg effectively attenuated the depression of protein synthesis and increase in protein degradation in murine myotubes at concentrations as low as 10 μM.Serum starvation did not increase expression of the ubiquitin ligases MuRF1 and MAFbx, but EGCg reduced their expression below basal levels, possibly due to an increased expression of phospho Akt (pAkt) and phospho forkhead box O3a (pFoxO3a).The ability of EGCg to attenuate depressed protein synthesis and increase protein degradation in the myotubule model system suggests that it may be effective in preserving skeletal muscle mass in catabolic conditions.

View Article: PubMed Central - PubMed

Affiliation: Nutritional Biomedicine, School of Life and Health Sciences, Aston University, Birmingham, B4 7ET, UK, k.a.mirza@aston.ac.uk.

ABSTRACT

Background: Loss of muscle protein is a common feature of wasting diseases where currently treatment is limited. This study investigates the potential of epigallocatechin-3-gallate (EGCg), the most abundant catechin in green tea, to reverse the increased protein degradation and rescue the decreased protein synthesis which leads to muscle atrophy.

Methods: Studies were conducted in vitro using murine C2C12 myotubes. Increased protein degradation and reduced rates of protein synthesis were induced by serum starvation and tumour necrosis factor-α (TNF-α).

Results: EGCg effectively attenuated the depression of protein synthesis and increase in protein degradation in murine myotubes at concentrations as low as 10 μM. Serum starvation increased expression of the proteasome 20S and 19S subunits, as well as the proteasome 'chymotrypsin-like' enzyme activity, and these were all attenuated down to basal values in the presence of EGCg. Serum starvation did not increase expression of the ubiquitin ligases MuRF1 and MAFbx, but EGCg reduced their expression below basal levels, possibly due to an increased expression of phospho Akt (pAkt) and phospho forkhead box O3a (pFoxO3a). Attenuation of protein degradation by EGCg was increased in the presence of ZnSO4, suggesting an EGCg-Zn(2+) complex may be the active species.

Conclusion: The ability of EGCg to attenuate depressed protein synthesis and increase protein degradation in the myotubule model system suggests that it may be effective in preserving skeletal muscle mass in catabolic conditions.

No MeSH data available.


Related in: MedlinePlus

a Effect of serum starvation on total protein degradation in C2C12 myotubes after 16 and 24 h, compared with a negative control (NC) incubated with DMEM containing 2 % HS. Control myotubes released 6,563.5 cpm of [3H] Phe over the 24-h period. b Effect of EGCg on total protein degradation in C2C12 myotubes incubated in DMEM without serum for 24 h. c Effect of EGCg on chymotrypsin-like enzyme activity in C2C12 myotubes starved of serum for 24 h. Differences from NC are indicated as *p < 0.05, **p < 0.01 and ***p < 0.001, while differences from no serum are shown as †p < 0.05, ††p < 0.01 and †††p < 0.001
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Fig1: a Effect of serum starvation on total protein degradation in C2C12 myotubes after 16 and 24 h, compared with a negative control (NC) incubated with DMEM containing 2 % HS. Control myotubes released 6,563.5 cpm of [3H] Phe over the 24-h period. b Effect of EGCg on total protein degradation in C2C12 myotubes incubated in DMEM without serum for 24 h. c Effect of EGCg on chymotrypsin-like enzyme activity in C2C12 myotubes starved of serum for 24 h. Differences from NC are indicated as *p < 0.05, **p < 0.01 and ***p < 0.001, while differences from no serum are shown as †p < 0.05, ††p < 0.01 and †††p < 0.001

Mentions: As a model of muscle atrophy in vitro, the C2C12 murine myoblast cell line was induced to differentiate into myotubes and protein degradation was induced by serum starvation. As shown in Fig. 1a, total protein degradation was significantly increased by 16 h serum starvation, and further increased slightly over the following 8 h. All subsequent assays employed 24 h serum starvation to induce protein degradation. The increase in protein degradation achieved by serum starvation was less than that induced by catabolic mediators such as proteolysis-inducing factor (PIF) and angiotensin II (Ang II) [7]. To determine the effect of EGCg on total protein degradation, myotubes were incubated with a wide concentration range (10–150 μM) to determine the most effective concentration that could be used for subsequent studies (Fig. 1b). While low concentrations (10 μM) of EGCg completely attenuated the increased protein degradation induced by serum starvation, higher concentrations further reduced basal levels of protein degradation without having a negative effect on cell viability.Fig. 1


Attenuation of muscle wasting in murine C2C 12 myotubes by epigallocatechin-3-gallate.

Mirza KA, Pereira SL, Edens NK, Tisdale MJ - J Cachexia Sarcopenia Muscle (2014)

a Effect of serum starvation on total protein degradation in C2C12 myotubes after 16 and 24 h, compared with a negative control (NC) incubated with DMEM containing 2 % HS. Control myotubes released 6,563.5 cpm of [3H] Phe over the 24-h period. b Effect of EGCg on total protein degradation in C2C12 myotubes incubated in DMEM without serum for 24 h. c Effect of EGCg on chymotrypsin-like enzyme activity in C2C12 myotubes starved of serum for 24 h. Differences from NC are indicated as *p < 0.05, **p < 0.01 and ***p < 0.001, while differences from no serum are shown as †p < 0.05, ††p < 0.01 and †††p < 0.001
© Copyright Policy
Related In: Results  -  Collection

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getmorefigures.php?uid=PMC4248406&req=5

Fig1: a Effect of serum starvation on total protein degradation in C2C12 myotubes after 16 and 24 h, compared with a negative control (NC) incubated with DMEM containing 2 % HS. Control myotubes released 6,563.5 cpm of [3H] Phe over the 24-h period. b Effect of EGCg on total protein degradation in C2C12 myotubes incubated in DMEM without serum for 24 h. c Effect of EGCg on chymotrypsin-like enzyme activity in C2C12 myotubes starved of serum for 24 h. Differences from NC are indicated as *p < 0.05, **p < 0.01 and ***p < 0.001, while differences from no serum are shown as †p < 0.05, ††p < 0.01 and †††p < 0.001
Mentions: As a model of muscle atrophy in vitro, the C2C12 murine myoblast cell line was induced to differentiate into myotubes and protein degradation was induced by serum starvation. As shown in Fig. 1a, total protein degradation was significantly increased by 16 h serum starvation, and further increased slightly over the following 8 h. All subsequent assays employed 24 h serum starvation to induce protein degradation. The increase in protein degradation achieved by serum starvation was less than that induced by catabolic mediators such as proteolysis-inducing factor (PIF) and angiotensin II (Ang II) [7]. To determine the effect of EGCg on total protein degradation, myotubes were incubated with a wide concentration range (10–150 μM) to determine the most effective concentration that could be used for subsequent studies (Fig. 1b). While low concentrations (10 μM) of EGCg completely attenuated the increased protein degradation induced by serum starvation, higher concentrations further reduced basal levels of protein degradation without having a negative effect on cell viability.Fig. 1

Bottom Line: EGCg effectively attenuated the depression of protein synthesis and increase in protein degradation in murine myotubes at concentrations as low as 10 μM.Serum starvation did not increase expression of the ubiquitin ligases MuRF1 and MAFbx, but EGCg reduced their expression below basal levels, possibly due to an increased expression of phospho Akt (pAkt) and phospho forkhead box O3a (pFoxO3a).The ability of EGCg to attenuate depressed protein synthesis and increase protein degradation in the myotubule model system suggests that it may be effective in preserving skeletal muscle mass in catabolic conditions.

View Article: PubMed Central - PubMed

Affiliation: Nutritional Biomedicine, School of Life and Health Sciences, Aston University, Birmingham, B4 7ET, UK, k.a.mirza@aston.ac.uk.

ABSTRACT

Background: Loss of muscle protein is a common feature of wasting diseases where currently treatment is limited. This study investigates the potential of epigallocatechin-3-gallate (EGCg), the most abundant catechin in green tea, to reverse the increased protein degradation and rescue the decreased protein synthesis which leads to muscle atrophy.

Methods: Studies were conducted in vitro using murine C2C12 myotubes. Increased protein degradation and reduced rates of protein synthesis were induced by serum starvation and tumour necrosis factor-α (TNF-α).

Results: EGCg effectively attenuated the depression of protein synthesis and increase in protein degradation in murine myotubes at concentrations as low as 10 μM. Serum starvation increased expression of the proteasome 20S and 19S subunits, as well as the proteasome 'chymotrypsin-like' enzyme activity, and these were all attenuated down to basal values in the presence of EGCg. Serum starvation did not increase expression of the ubiquitin ligases MuRF1 and MAFbx, but EGCg reduced their expression below basal levels, possibly due to an increased expression of phospho Akt (pAkt) and phospho forkhead box O3a (pFoxO3a). Attenuation of protein degradation by EGCg was increased in the presence of ZnSO4, suggesting an EGCg-Zn(2+) complex may be the active species.

Conclusion: The ability of EGCg to attenuate depressed protein synthesis and increase protein degradation in the myotubule model system suggests that it may be effective in preserving skeletal muscle mass in catabolic conditions.

No MeSH data available.


Related in: MedlinePlus