Progress 09/01/04 to 08/31/07
Outputs
OUTPUTS: Pale, soft and exudative (PSE) meat has a higher drip loss, a lower cooking yield, and a tougher texture and induces significant economic loss. The constant effort to increase lean growth in livestock further worsens the PSE problem. Although genetic and environmental causes for PSE are partially known, the molecular mechanisms associated with rapid glycolysis in PSE meat remains undefined. We hypothesized that AMPK governs the initiation and progression of glycolysis in postmortem muscle and thus the occurrence of PSE syndrome. With the support of this grant, we did several studies in mice and pigs to elucidate the role of AMP-activated protein kinase (AMPK) in postmortem glycolysis. Our results demonstrate that AMPK has a crucial role in the regulation of postmortem glycolysis and the incidence of PSE meat, which provides the foundation for further studies to solve or reduce PSE meat and improve the quality of meat for consumers. Results obtained have been disseminated to scientific community and meat industry through publications in peer-reviewed scientific journals, conference proceedings as well as scientific reports. PARTICIPANTS: Collaborators: Warrie J. Means, Department of Animal Science at University of Wyoming; Meijun Zhu, Department of Animal Science at University of Wyoming; Training or professional development: Qingwu Shen, Ph.D. graduate student who devoted 100% effort to this project. TARGET AUDIENCES: Target audiences are scientific community and meat industry personnel. Efforts include publishing peer-review publications, conference papers and other reports. In addition, we incorporate data obtained in these studies to teaching of undergraduate students. PROJECT MODIFICATIONS: Not relevant to this project.
Impacts
Several studies in mice and pigs were conducted to elucidate the role of AMPK in postmortem glycolysis and incidence of PSE meat. In the first study, we studied the role of pre-slaughter stress on the activities of AMPK, glycolytic enzymes and pH of postmortem muscle. We hypothesize that alpha-adrenoceptor activation is responsible for the initiation of glycolysis, while the activation of AMPK is responsible for the sustained glycolysis in postmortem muscle. Indeed, by using propranololol, a specific blocker of alpha-adrenoceptor, the initial glycolysis in postmortem muscle was dramatically reduced (See preliminary data in project description), and the activity of glycogen phosphorylase and AMPK was lower following alpha-adrenoceptor blockade, clearly showing the involvement of alpha-adrenoceptor signaling in initial glycolysis. The down-regulation of AMPK activity through alpha-adrenoceptor blockade also indicates that AMPK participates in the initial glycolysis. Further, the activities of key enzymes involved in postmortem glycolysis were significantly altered by AMPK knockout and AICAr stimulation to stimulate AMPK activity. Based on these results, we concluded that AMPK is crucial for the glycolysis in postmortem muscle. In another preliminary study, we assessed the effect of dietary alpha-lipoic acid on the glycolysis in postmortem muscle and found that supplementation of alpha-lipoic acid was very effective in reducing the glycolysis in postmortem muscle through down-regulating AMPK activation in postmortem muscle. By elucidating the role of AMPK in glycolysis and in the occurrence of PSE meat, we will be able to apply for future research grants to further examine the pathways including external factors and internal molecular components leading to activation of AMPK, and to develop strategies to prevent and reduce PSE syndrome.
Publications
- Shen, Q. W., Gerrard, D.E., and Du, M. 2008. Compound C, an inhibitor of AMP-activated protein kinase, inhibits glycolysis in mouse longissimus dorsi postmortem. Meat Science 78:323-330.
- Shen, Q. W., Zhu, M.J., Tong, J., Ren, J. and Du, M. 2007. Ca2+/calmodulin-dependent protein kinase kinase is involved in AMP-activated protein kinase activation by alpha-lipoic acid in C2C12 myotubes. American Journal of Physiology-Cell Physiology 293: C1395-1403.
- Du, M., Shen, Q.W., Zhu, M.J. and Ford, S.P. 2007. Leucine stimulates mTOR signalling in C2C12 myoblast cells through inhibition of AMP-activated protein kinase. Journal of Animal Science 85:919-927.
- Du, M., Shen, Q.W. and Zhu, M.J. 2005. Role of beta-adrenoceptor and AMP-activated protein kinase in the glycolysis of postmortem skeletal muscle. Journal of Agriculture and Food Chemistry 53:3235-3239.
- Shen, Q. W., and Du, M. 2005.Effect of dietary alpha-lipoic acid on the glycolysis and the pH values of postmortem muscle. Meat Science 71:306-311.
- Shen, Q. W., and Du, M. 2005. Role of AMP-activated protein kinase in the glycolysis of postmortem muscle. Journal of the Science of Food and Agriculture 85:2401-2406.
- Shen, Q. W., Jones, C.S., Kalchayanand, N. and Du, M. 2005. Effect of dietary alpha-lipoic Acid on the growth rate and fat accumulation of mice and the ultimate pH of postmortem muscle. Journal of Animal Science 83:2611-2617.
- Shen, Q. W., Means, W.J., Underwood, K.R., Thompson, K.R., Zhu, M.J., McCormick, R.J., Ford, S.P. Ellis, M. and Du, M. 2006. Early Postmortem AMP-Activated Protein Kinase (AMPK) Activation Leads to the Development of Pale, Soft, and Exudative (PSE) Conditions in Pork. Department of Animal Science, 2006 Annual Report.
- Du, M., Shen, Q.W. Jones, C.S. and Kalchayanand, N. 2004. Effect of dietary alpha-lipoic Acid on the growth rate and fat accumulation of mice and the ultimate pH of postmortem muscle. Department of Animal Science, 2004 Annual Report.
- Shen, Q.W., Ren, J. and Du, M. 2007. Ca2+/calmodulin-dependent protein kinase kinases are mainly responsible for AMP-activated protein kinase activation by alpha-lipoic acid in C2C12 myotubes. FASEB Journal 21 (6):A1204-A1205.
- Shen, Q. W., Ren, J. and Du, M. 2007. Ca2+/calmodulin-dependent protein kinase kinases are mainly responsible for AMP-activated protein kinase activation by alpha-lipoic acid in C2C12 myotubes. Experimental Biology Annual Meeting, Washington DC, April 28-May 2, 2007.
- Du, M., Shen, Q.W. and Zhu, M. 2006. Leucine stimulates mTOR signaling in C2C12 myoblast cells through inhibition of AMP-activated protein kinase. Experimental Biology Annual Meeting, San Francisco, CA, 2006.
- Shen, Q. W., Zhu, M.J. and Du, M. 2005. Role of beta-adrenoceptor signaling and AMP-activated protein kinase in the glycolysis of postmortem skeletal muscle. American Society of Animal Scientists Annual Meeting, Cincinnati, Ohio, 2005.
- Shen, Q. W., Jones, C.S., Kalchayanand, N. and Du, M. 2004. Effect of dietary alpha-lipoic Acid on the growth rate and fat accumulation of mice and the ultimate pH of postmortem muscle. Nutrition Roundtable Meeting, Fort Colins, Colorado, 2004.
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Progress 01/01/06 to 12/31/06
Outputs
PSE (Pale, soft, and exudative) meat causes a huge economic loss to meat and slaughter industry due to its inferior quality. It is well established that fast glycolysis at early postmortem stage leads to PSE meat with pre-slaughter stresses and genetic mutation increasing its incidence. However, the mechanisms leading to fast glycolysis in PSE meat remain largely undefined. In this project, AMP-activated protein kinase (AMPK) was shown to be a regulator of glycolysis in postmortem muscle. A surge in AMPK activity in postmortem muscle was detected shortly after animal was slaughtered. AMPK further activated glycogen phosphorylase and phosphofructokinase-II. Activation of phosphofructokinase-II produces fructose-2, 6-diphosphate, an allosteric activator of phosphofructokinase-I, the limiting enzyme controlling glycolysis. Therefore, activation of AMPK leads to glycolysis in postmortem muscle. We further showed that an early AMPK activation led to elevated glycolysis and
incidence of PSE pork. Pre-slaughter stresses increase the incidence of PSE meat through enhancing AMPK activation.
Impacts
PSE meat induces significant economic loss. Based on our studies, we identified that AMPK has a crucial role in the control of postmortem glycolysis. Knowledge obtained provides molecular targets for the prevention of AMPK early activation and thus PSE meat. Such knowledge deepens our understanding of biochemical changes in postmortem muscle, which has enormous implications for meat quality improvement.
Publications
- Du, M., Q. W. Shen, and M. J. Zhu. 2005. Leucine stimulates mTOR signaling in C2C12 myoblast cells through inhibition of AMP-activated protein kinase. Experimental Biology, San Francisco, CA, 2006.
- Du, M., Q. W. Shen, M. J. Zhu, and S. P. Ford. 2006. Leucine stimulates mtor signalling in c2c12 myoblast cells through inhibition of amp-activated protein kinase (AMPK). FASEB Journal 20: A161-A161.
- Mei J. Zhu, Q. W. Shen, and M. Du. 2005. Protein expression profiling of skeletal muscle through 2-dimensional gel electrophoresis and protein identification by mass spectrometry. Proceeding of 51st International Congress of Meat Science & Technology, Baltimore, Maryland.
- Shen, Q. W., W. J. Means, S. A. Thompson, K. R. Underwood, M. J. Zhu, R. J. McCormick, S. P. Ford, and M. Du. 2006. Pre-slaughter transport, AMP-activated protein kinase, glycolysis, and quality of pork loin. Meat Science, 74:388-395.
- Shen, Q. W., W. J. Means, S. A. Thompson, K. R. Underwood, M. J. Zhu, R. J. McCormick, S.P. Ford, and M. Du. 2006. Early AMP-activated protein kinase (AMPK) activation leads to PSE meat in pork. Journal of Agricultural and Food Chemistry, 54: 5583-5589.
- Shen, Q. W., J. Ren, and M. Du. 2007. Ca2+/calmodulin-dependent protein kinase kinases are mainly responsible for AMP-activated protein kinase activation by a-lipoic acid in C2C12 myotubes. Experimental Biology Annual Meeting, Washington DC, April 28-May 2.
- Shen, Q.W., W. J. Means, M. J. Zhu, K.R. Underwood, S. A. Thompson, R. J. McCormick, S. P. Ford, M. Ellis, and M. Du. 2006 Early AMP-activated protein kinase (AMPK) activation leads to PSE meat in pork. 59th Reciprocal Meat Conference, Urbana-Champaign, June 18-21.
- Shen, Q. W., M. J. Zhu, M. Du. 2005. Role of B-adrenoceptor signaling and AMP-activated protein kinase in the glycolysis of postmortem skeletal muscle. American Society of Animal Scientists Annual Meeting, Cincinnati, Ohio.
- Shen, Q. W., K. R. Underwood, W. J. Means, R. J. McCormick, and M. Du. 2007. Halothane gene, energy metabolism, AMP-activated protein kinase, and glycolysis in postmortem pig longissimus dorsi muscle. Journal of Animal Science.
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Progress 01/01/05 to 12/31/05
Outputs
PSE (Pale, soft, and exudative) meat causes a huge economic loss to meat and slaughter industry due to its inferior quality. It is well established that fast glycolysis at early postmortem stage leads to PSE meat with pre-slaughter stresses and genetic mutation increasing its incidence. However, the mechanisms leading to fast glycolysis in PSE meat remain largely undefined. In this project, AMP-activated protein kinase (AMPK) was shown to be a regulator of glycolysis in postmortem muscle. An activation of AMPK in muscle was detected shortly after animal slaughter. Pre-slaughter stresses activated AMPK which activated glycogen phosphorylase and phosphofructokinase-1, both of which are rate limiting enzymes involved in glycolysis. It was further showed that an early AMPK activation led to elevated glycolysis and incidence of PSE pork. However, AMPK activation was not well correlated with the increase in AMP/ATP ratio in postmortem muscle. This suggests that other
mechanisms exist, which are responsible for AMPK early activation in postmortem muscle and warrant further studies.
Impacts
It has been shown that biological changes in the early-stage postmortem muscle dramatically affected the quality of meat. Understanding mechanisms controlling postmortem changes will allow the development of strategies to effectively control these changes and, thus, improve the eating quality of meat.
Publications
- Du, M., Shen, Q.W. and Zhu, M.J. 2005. Role of B-adrenoceptor and AMP-activated protein kinase in the glycolysis of postmortem skeletal muscle. Journal of Agriculture and Food Chemistry 53: 3235-3239.
- Shen, Q.W., and Du, M. (2005). Role of AMP-activated protein kinase in the glycolysis of postmortem muscle. Journal of the Science of Food and Agriculture 85: 2401-2406.
- Shen, Q.W., and Du, M. (2005).Effect of dietary a-lipoic acid on the glycolysis and the pH values of postmortem muscle. Meat Science 71: 306-311.
- Shen, Q.W., Jones, C.S., Kalchayanand, N. and Du, M. (2005). Effect of dietary a-lipoic Acid on the growth rate and fat accumulation of mice and the ultimate pH of postmortem muscle. Journal of Animal Science 83:2611-2617.
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