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Kirkpatrick LT, Gómez JFM, Beline M, Yen CN, Bodmer JS, Wicks JC, Shi TH, Silva SL, Aalhus JL, King DA, Gerrard DE. Muscle of dark and normal beef differs metabolically. Meat Sci 2023; 206:109344. [PMID: 37778129 DOI: 10.1016/j.meatsci.2023.109344] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/23/2023] [Revised: 09/05/2023] [Accepted: 09/12/2023] [Indexed: 10/03/2023]
Abstract
Reduction in muscle glycogen triggered by adverse antemortem handling events alters postmortem energy metabolism and results in a high ultimate pH and dark, firm and dry beef, often referred to as 'dark-cutting'. However, the relationship between atypical dark (AT) beef, postmortem energy metabolism and underlying tissue characteristics remains somewhat unclear. Cattle harvested in the US and Canada representing normal (pH < 5.6), AT dark (pH 5.6-5.8) and dark cutting (DC; pH > 5.8) beef were analyzed for tissue characteristics related to energy metabolism. Results show AT dark beef is more oxidative but similar to normal beef in glycolytic potential and nucleotide abundance. Mitochondria DNA content (P < 0.05, Canada; P < 0.005, US) and oxidative enzymes for DC and AT dark beef were greater (P < 0.01; Canada and US) compared to normal beef. Myoglobin tracked (P < 0.01) with color classification. These findings show both DC and AT beef are inherently more oxidative and raise the possibility that more oxidative muscle may be more prone to develop dark beef.
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Affiliation(s)
- L T Kirkpatrick
- Virginia Tech, School of Animal Sciences, Blacksburg, VA 24061, USA
| | - J F M Gómez
- Virginia Tech, School of Animal Sciences, Blacksburg, VA 24061, USA
| | - M Beline
- Virginia Tech, School of Animal Sciences, Blacksburg, VA 24061, USA
| | - C-N Yen
- Virginia Tech, School of Animal Sciences, Blacksburg, VA 24061, USA
| | - J S Bodmer
- Virginia Tech, School of Animal Sciences, Blacksburg, VA 24061, USA
| | - J C Wicks
- Virginia Tech, School of Animal Sciences, Blacksburg, VA 24061, USA
| | - T H Shi
- Virginia Tech, School of Animal Sciences, Blacksburg, VA 24061, USA
| | - S L Silva
- Department of Animal Science, College of Animal Science and Food Engineering, University of São Paulo, Pirassununga, SP 13635-900, Brazil
| | - J L Aalhus
- Agriculture and Agri-Food Canada, 6000 C & D Trail, Lacombe, Alberta T4L 1W1, Canada
| | - D A King
- USDA-ARS, Roman L. Hruska US Meat Animal Research Center, Clay Center, NE 68933, USA
| | - D E Gerrard
- Virginia Tech, School of Animal Sciences, Blacksburg, VA 24061, USA.
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2
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Aljarbou WA, England EM, Velleman SG, Reed KM, Strasburg GM. Phosphorylation state of pyruvate dehydrogenase and metabolite levels in turkey skeletal muscle in normal and pale, soft, exudative meats. Br Poult Sci 2021; 62:379-386. [PMID: 33225715 DOI: 10.1080/00071668.2020.1855629] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/22/2022]
Abstract
1. Turkey production has increased dramatically as genetic selection has succeeded in increasing body weight and muscle yield to fulfil increasing consumer demand. However, producing fast-growing, heavily muscled birds is linked to increased heat stress susceptibility and can result in pale, soft, exudative (PSE) meat. Previous studies indicated that pyruvate dehydrogenase kinase 4 (PDK4) is significantly reduced in PSE samples, suggesting this as a candidate gene associated with the development of this problem.2. The objective of this study was to determine whether pre-market thermal challenge results in PSE meat as a result of differential expression of PDK4. Two genetic lines of turkeys were used in this study; the Randombred Control Line 2 (RBC2) and a commercial line. Turkeys were exposed to a pre-market thermal challenge of 12 h at 35°C followed by 12 h at 27°C for 5 d. Birds were slaughtered and processed according to industry standards. Pectoralis major samples were categorised as PSE or normal based on marinade uptake and cook loss indicators. In the first experiment, the relative expression of pyruvate dehydrogenase (PDH) and the phosphorylation state of PDH in normal and PSE turkey meat were analysed by western blotting. In the second experiment, the same samples were used to measure metabolite levels at 5 min post-mortem, comparing the normal to the PSE samples.3. The results of the first experiment showed that PSE samples had significantly lower total PDH (P = 0.029) compared to normal meat. However, there was no significant difference in the degree of phosphorylation of sites 1, 2 or 3. In the second experiment, there were no significant differences in glycogen, lactate, glycolytic potential or ATP when comparing PSE to control samples.4. These results suggested that a reduction in PDK4 expression alone does not explain the development of PSE meat.
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Affiliation(s)
- W A Aljarbou
- Department of Food Science and Human Nutrition, Michigan State University, East Lansing, MI, USA.,Executive Department of Monitoring and Risk Assessment, Saudi Food and Drug Authority, Riyadh, Saudi Arabia
| | - E M England
- Department of Animal Sciences, The Ohio State University, Columbus, OH, USA
| | - S G Velleman
- Department of Animal Sciences, Ohio Agricultural Research and Development Center, the Ohio State University, Wooster, OH, USA
| | - K M Reed
- Department of Veterinary and Biomedical Sciences, University of Minnesota, St. Paul, MN, USA
| | - G M Strasburg
- Department of Food Science and Human Nutrition, Michigan State University, East Lansing, MI, USA
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3
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Apaoblaza A, Gerrard SD, Matarneh SK, Wicks JC, Kirkpatrick L, England EM, Scheffler TL, Duckett SK, Shi H, Silva SL, Grant AL, Gerrard DE. Muscle from grass- and grain-fed cattle differs energetically. Meat Sci 2019; 161:107996. [PMID: 31734468 DOI: 10.1016/j.meatsci.2019.107996] [Citation(s) in RCA: 33] [Impact Index Per Article: 6.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/08/2019] [Revised: 10/29/2019] [Accepted: 10/30/2019] [Indexed: 10/25/2022]
Abstract
Insufficient acidification results in dark, firm, and dry beef. While this defect is often indicative of a stress event antemortem, muscle tissue may change in response to feeding regime. Longissimus dorsi muscle samples from 10 grain-fed and 10 grass-fed market weight, angus-crossbred beef cattle were collected postmortem. Lower (P < .05) L* and a* values were recorded for steaks from grass-fed cattle. Higher (P < .05) ultimate pH values were noted in lean of grass-fed cattle compared to grain-fed cattle, yet differences in lactate, glycogen and glucose were not detected. Further, increased (P < .05) ultimate pH values and lower (P < .05) lactate accumulations were noted when samples from grass-fed cattle were subjected to an in vitro glycolysis system. Muscle from grass-fed beef possessed nearly two-fold more (P < .05) succinate dehydrogenase and (P < .001) myoglobin than that of grain-fed cattle. These data show lean from grass-fed beef has greater enzymes reflective of oxidative metabolism and suggest dark lean from grass-fed cattle may be a function of more oxidative metabolism rather than a stress-related event antemortem.
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Affiliation(s)
- A Apaoblaza
- Department of Animal and Poultry Sciences, Virginia Polytechnic Institute and State University, Blacksburg, VA 24061, United States of America
| | - S D Gerrard
- Department of Animal and Poultry Sciences, Virginia Polytechnic Institute and State University, Blacksburg, VA 24061, United States of America
| | - S K Matarneh
- Department of Animal and Poultry Sciences, Virginia Polytechnic Institute and State University, Blacksburg, VA 24061, United States of America
| | - J C Wicks
- Department of Animal and Poultry Sciences, Virginia Polytechnic Institute and State University, Blacksburg, VA 24061, United States of America
| | - L Kirkpatrick
- Department of Animal and Poultry Sciences, Virginia Polytechnic Institute and State University, Blacksburg, VA 24061, United States of America
| | - E M England
- Department of Animal and Poultry Sciences, Virginia Polytechnic Institute and State University, Blacksburg, VA 24061, United States of America
| | - T L Scheffler
- Department of Animal and Poultry Sciences, Virginia Polytechnic Institute and State University, Blacksburg, VA 24061, United States of America
| | - S K Duckett
- Department of Animal and Veterinary Sciences, Clemson University, Clemson, SC 29634, United States of America
| | - H Shi
- Department of Animal and Poultry Sciences, Virginia Polytechnic Institute and State University, Blacksburg, VA 24061, United States of America
| | - S L Silva
- Faculdade de Zootecnia e Engenharia de Alimentos, University of São Paulo, São Paulo, Pirassununga 13635-900, SP, Brazil
| | - A L Grant
- Department of Animal and Poultry Sciences, Virginia Polytechnic Institute and State University, Blacksburg, VA 24061, United States of America
| | - D E Gerrard
- Department of Animal and Poultry Sciences, Virginia Polytechnic Institute and State University, Blacksburg, VA 24061, United States of America.
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4
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Matarneh SK, Yen CN, Elgin JM, Beline M, da Luz e Silva S, Wicks JC, England EM, Dalloul RA, Persia ME, Omara II, Shi H, Gerrard DE. Phosphofructokinase and mitochondria partially explain the high ultimate pH of broiler pectoralis major muscle. Poult Sci 2018; 97:1808-1817. [DOI: 10.3382/ps/pex455] [Citation(s) in RCA: 9] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/27/2017] [Accepted: 12/29/2017] [Indexed: 11/20/2022] Open
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England EM, Matarneh SK, Mitacek RM, Abraham A, Ramanathan R, Wicks JC, Shi H, Scheffler TL, Oliver EM, Helm ET, Gerrard DE. Presence of oxygen and mitochondria in skeletal muscle early postmortem. Meat Sci 2018; 139:97-106. [DOI: 10.1016/j.meatsci.2017.12.008] [Citation(s) in RCA: 32] [Impact Index Per Article: 5.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/02/2017] [Revised: 12/26/2017] [Accepted: 12/27/2017] [Indexed: 12/01/2022]
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6
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Mitochondrial F1-ATPase extends glycolysis and pH decline in an in vitro model. Meat Sci 2018; 137:85-91. [DOI: 10.1016/j.meatsci.2017.11.009] [Citation(s) in RCA: 23] [Impact Index Per Article: 3.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/26/2017] [Revised: 10/11/2017] [Accepted: 11/05/2017] [Indexed: 11/23/2022]
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7
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Matarneh SK, England EM, Scheffler TL, Yen CN, Wicks JC, Shi H, Gerrard DE. A mitochondrial protein increases glycolytic flux. Meat Sci 2017; 133:119-125. [DOI: 10.1016/j.meatsci.2017.06.007] [Citation(s) in RCA: 26] [Impact Index Per Article: 3.7] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/13/2017] [Revised: 05/15/2017] [Accepted: 06/13/2017] [Indexed: 11/25/2022]
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8
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England EM, Matarneh SK, Oliver EM, Apaoblaza A, Scheffler TL, Shi H, Gerrard DE. Excess glycogen does not resolve high ultimate pH of oxidative muscle. Meat Sci 2016; 114:95-102. [DOI: 10.1016/j.meatsci.2015.10.010] [Citation(s) in RCA: 51] [Impact Index Per Article: 6.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/08/2015] [Revised: 10/06/2015] [Accepted: 10/14/2015] [Indexed: 11/27/2022]
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9
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Matarneh SK, England EM, Scheffler TL, Oliver EM, Gerrard DE. Net lactate accumulation and low buffering capacity explain low ultimate pH in the longissimus lumborum of AMPKγ3R200Q mutant pigs. Meat Sci 2015; 110:189-95. [DOI: 10.1016/j.meatsci.2015.07.023] [Citation(s) in RCA: 27] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/17/2015] [Revised: 07/24/2015] [Accepted: 07/25/2015] [Indexed: 10/23/2022]
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10
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Scheffler TL, Matarneh SK, England EM, Gerrard DE. Mitochondria influence postmortem metabolism and pH in an in vitro model. Meat Sci 2015. [PMID: 26209819 DOI: 10.1016/j.meatsci.2015.07.007] [Citation(s) in RCA: 54] [Impact Index Per Article: 6.0] [Reference Citation Analysis] [Abstract] [Key Words] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/27/2022]
Abstract
Our objective was to determine the influence of mitochondria on metabolites and pH decline using an in vitro model of postmortem muscle metabolism. Mitochondria were isolated from porcine longissimus lumborum and added (0, 0.5, or 2.0mg) to powdered muscle in reaction media containing either a combination of inhibitors for mitochondria complexes (I, IV, and V) or diluent (without inhibitors). In the absence of inhibitors, adding mitochondria (0.5 and 2.0mg) reduced ATP loss from 30 to 120 min, but did not alter glycogen or lactate during this time. In reactions with mitochondria, inhibitors decreased ATP levels by 30 min and increased glycogen degradation by 60 min. Regardless of mitochondria content, inhibitors enhanced lactate accumulation from 15 to 240 min, and decreased pH from 15 min to 1440 min. In the in vitro model, mitochondria influence the maintenance of ATP, and inhibition of mitochondria enzyme activity contributes to accelerated metabolism and pH decline.
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Affiliation(s)
- Tracy L Scheffler
- Department of Animal and Poultry Sciences, Virginia Tech, Blacksburg, VA 24061, USA
| | - Sulaiman K Matarneh
- Department of Animal and Poultry Sciences, Virginia Tech, Blacksburg, VA 24061, USA
| | - Eric M England
- Department of Animal and Poultry Sciences, Virginia Tech, Blacksburg, VA 24061, USA
| | - David E Gerrard
- Department of Animal and Poultry Sciences, Virginia Tech, Blacksburg, VA 24061, USA.
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11
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Altered AMP deaminase activity may extend postmortem glycolysis. Meat Sci 2015; 102:8-14. [DOI: 10.1016/j.meatsci.2014.11.009] [Citation(s) in RCA: 37] [Impact Index Per Article: 4.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/15/2014] [Revised: 10/20/2014] [Accepted: 11/21/2014] [Indexed: 11/22/2022]
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12
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Contribution of the phosphagen system to postmortem muscle metabolism in AMP-activated protein kinase γ3 R200Q pig Longissimus muscle. Meat Sci 2014; 96:876-83. [DOI: 10.1016/j.meatsci.2013.10.007] [Citation(s) in RCA: 12] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/26/2013] [Revised: 09/25/2013] [Accepted: 10/04/2013] [Indexed: 11/23/2022]
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13
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Appuhamy J, Nayananjalie W, England E, Gerrard D, Akers R, Hanigan M. Effects of AMP-activated protein kinase (AMPK) signaling and essential amino acids on mammalian target of rapamycin (mTOR) signaling and protein synthesis rates in mammary cells. J Dairy Sci 2014; 97:419-29. [DOI: 10.3168/jds.2013-7189] [Citation(s) in RCA: 55] [Impact Index Per Article: 5.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/26/2013] [Accepted: 08/23/2013] [Indexed: 12/19/2022]
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14
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Gao D, Bian X, Guo M, Wang J, Zhang X. Identification and characterization of the biochemical function of Agrobacterium T-complex-recruiting protein Atu5117. FEBS J 2013; 280:4865-75. [PMID: 23902381 DOI: 10.1111/febs.12460] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/15/2013] [Revised: 07/24/2013] [Accepted: 07/26/2013] [Indexed: 01/19/2023]
Abstract
Atu5117 from Agrobacterium tumefaciens is a highly conserved protein with a putative nucleotidyltransferase domain in its N-terminal region and a putative higher eukaryotes and prokaryotes nucleotide-binding domain in its C-terminal region. This protein has been shown to be a T-complex-recruiting protein that can recruit T-complex from the cytosol to the polar VirB/D4 type IV secretion system (T4SS). However, the biochemical function of Atu5117 is still unknown. Here, we show that Atu5117 is a (d)NTPase. Although no proteins with nucleotidyltransferase and higher eukaryotes and prokaryotes nucleotide-binding domains were identified as (d)NTPases, Atu5117 was able to convert all eight canonical NTPs and dNTPs to NDP, dNDP and inorganic phosphate in vitro, and required Mg(2+) for its (d)NTPase activity. The kinetic parameters of Atu5117 (d)NTPase for eight substrates were characterized. Kinetic data showed that Atu5117 (d)NTPase preferred ATP as its substrate. The optimal conditions for (d)NTPase activity of Atu5117 were very similar to those required for Agrobacterium tumorigenesis. The kinetic parameters of (d)NTPase of Atu5117 for all four canonical NTPs were in the same orders of magnitude as the kinetic parameters of the ATPases identified in some components of the VirB/D4 T4SS. These results suggest that Atu5117 might function as an energizer to recruit T-complex to the T4SS transport site.
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Affiliation(s)
- Diankun Gao
- College of Bioscience and Biotechnology, Yangzhou University, China
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15
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Use of dietary supplementation with β-guanidinopropionic acid to alter the muscle phosphagen system, postmortem metabolism, and pork quality. Meat Sci 2013; 95:264-71. [PMID: 23743031 DOI: 10.1016/j.meatsci.2013.04.019] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/15/2012] [Revised: 03/04/2013] [Accepted: 04/04/2013] [Indexed: 11/20/2022]
Abstract
Rate and extent of postmortem metabolism control pork quality development. Our objective was to evaluate the role of the phosphagen system (phosphocreatine, PCr; and creatine, Cr) on metabolism and pork quality. Muscle PCr and Cr were manipulated by feeding pigs the creatine analogue, β-guanidinopropionic acid (β-GPA). In experiment 1, pigs received standard (control) diet or β-GPA supplemented (2%) diet (1 wk or 2 wk). Supplementation with β-GPA (2 wk) decreased total Cr (PCr+Cr; P=0.02) and improved pork color (decreased reflectance, P=0.003); however, β-GPA supplementation reduced growth performance (P=0.007). To separate effects of phosphagen system and growth, a second experiment was conducted with control, pair-fed, and 2 wk β-GPA (1%) supplementation; pigs were also offered a control or β-GPA supplemented flavored beverage. Neither treatment influenced pork quality. Immediately postmortem, ATP/ADP was higher in control compared to pair-fed (P<0.05); subsequently, ATP/ADP was similar among all groups. Loss of the phosphagen system may lead to adaptive changes that promote conservation of cellular ATP.
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16
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Mochel F, Durant B, Meng X, O'Callaghan J, Yu H, Brouillet E, Wheeler VC, Humbert S, Schiffmann R, Durr A. Early alterations of brain cellular energy homeostasis in Huntington disease models. J Biol Chem 2011; 287:1361-70. [PMID: 22123819 DOI: 10.1074/jbc.m111.309849] [Citation(s) in RCA: 95] [Impact Index Per Article: 7.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
Brain energy deficit has been a suggested cause of Huntington disease (HD), but ATP depletion has not reliably been shown in preclinical models, possibly because of the immediate post-mortem changes in cellular energy metabolism. To examine a potential role of a low energy state in HD, we measured, for the first time in a neurodegenerative model, brain levels of high energy phosphates using microwave fixation, which instantaneously inactivates brain enzymatic activities and preserves in vivo levels of analytes. We studied HD transgenic R6/2 mice at ages 4, 8, and 12 weeks. We found significantly increased creatine and phosphocreatine, present as early as 4 weeks for phosphocreatine, preceding motor system deficits and decreased ATP levels in striatum, hippocampus, and frontal cortex of R6/2 mice. ATP and phosphocreatine concentrations were inversely correlated with the number of CAG repeats. Conversely, in mice injected with 3-nitroproprionic acid, an acute model of brain energy deficit, both ATP and phosphocreatine were significantly reduced. Increased creatine and phosphocreatine in R6/2 mice was associated with decreased guanidinoacetate N-methyltransferase and creatine kinase, both at the protein and RNA levels, and increased phosphorylated AMP-dependent protein kinase (pAMPK) over AMPK ratio. In addition, in 4-month-old knock-in Hdh(Q111/+) mice, the earliest metabolic alterations consisted of increased phosphocreatine in the frontal cortex and increased the pAMPK/AMPK ratio. Altogether, this study provides the first direct evidence of chronic alteration in homeostasis of high energy phosphates in HD models in the earliest stages of the disease, indicating possible reduced utilization of the brain phosphocreatine pool.
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Affiliation(s)
- Fanny Mochel
- INSERM UMR S975 and Assistance-Publique des Hôpitaux de Paris, Department of Genetics, Hôpital La Salpêtrière, 75013 Paris, France.
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Sun J, Ogata S, Segawa M, Usune S, Zhao Y, Katsuragi T. Ins(1,4,5)P(3) facilitates ATP accumulation via phosphocreatine/creatine kinase in the endoplasmic reticulum extracted from MDCK cells. Biochem Biophys Res Commun 2010; 397:465-9. [PMID: 20513354 DOI: 10.1016/j.bbrc.2010.05.133] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/25/2010] [Accepted: 05/26/2010] [Indexed: 10/19/2022]
Abstract
So far, the content and accumulation of ATP in isolated endoplasmic reticulum (ER) are little understood. First, we confirmed using electron microscopic and Western blotting techniques that the samples extracted from MDCK cells are endoplasmic reticulum (ER). The amounts of ATP in the extracted ER were measured from the filtrate after a spinning down of ultrafiltration spin column packed with ER. When the ER sample (5mug) after 3days freezing was suspended in intracellular medium (ICM), 0.1% Triton X and ultrapure water (UPW), ATP amounts from the ER with UPW were the highest and over 10 times compared with that from the control with ICM, indicating that UPW is the most effective tool in destroying the ER membrane. After a 10-min-incubation with ICM containing phosphocreatine (PCr)/creatine kinase (CK) of the fresh ER. ATP amounts in the filtrate obtained by spinning down were not changed from that in the control (no PCr/CK). However, ATP amounts in the filtrate from the second spinning down of the ER (treated with PCr/CK) suspended in UPW became over 10-fold compared with the control. When 1muM inositol(1,4,5)trisphosphate (Ins(1,4,5)P(3)) was added in the incubation medium (ICM with PCr/CK), ATP amounts from the filtrate after the second spinning down were further enhanced around three times. This enhancement was almost canceled by Ca(2+)-removal from ICM and by adding thapsigargin, a Ca(2+)-ATPase inhibitor, but not by 2-APB and heparin, Ins(1,4,5)P(3) receptor antagonists. Administration of 500muM adenosine to the incubation medium (with PCr/CK) failed to enhance the accumulation of ATP in the ER. These findings suggest that the ER originally contains ATP and ATP accumulation in the ER is promoted by PCr/CK and Ins(1,4,5)P(3).
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Affiliation(s)
- Jing Sun
- Medical Research Center, School of Medicine, Fukuoka University, Fukuoka 814-0180, Japan
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18
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Abstract
The sarcoplasmic reticulum (SR) of smooth muscles presents many intriguing facets and questions concerning its roles, especially as these change with development, disease, and modulation of physiological activity. The SR's function was originally perceived to be synthetic and then that of a Ca store for the contractile proteins, acting as a Ca amplification mechanism as it does in striated muscles. Gradually, as investigators have struggled to find a convincing role for Ca-induced Ca release in many smooth muscles, a role in controlling excitability has emerged. This is the Ca spark/spontaneous transient outward current coupling mechanism which reduces excitability and limits contraction. Release of SR Ca occurs in response to inositol 1,4,5-trisphosphate, Ca, and nicotinic acid adenine dinucleotide phosphate, and depletion of SR Ca can initiate Ca entry, the mechanism of which is being investigated but seems to involve Stim and Orai as found in nonexcitable cells. The contribution of the elemental Ca signals from the SR, sparks and puffs, to global Ca signals, i.e., Ca waves and oscillations, is becoming clearer but is far from established. The dynamics of SR Ca release and uptake mechanisms are reviewed along with the control of luminal Ca. We review the growing list of the SR's functions that still includes Ca storage, contraction, and relaxation but has been expanded to encompass Ca homeostasis, generating local and global Ca signals, and contributing to cellular microdomains and signaling in other organelles, including mitochondria, lysosomes, and the nucleus. For an integrated approach, a review of aspects of the SR in health and disease and during development and aging are also included. While the sheer versatility of smooth muscle makes it foolish to have a "one model fits all" approach to this subject, we have tried to synthesize conclusions wherever possible.
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Affiliation(s)
- Susan Wray
- Department of Physiology, School of Biomedical Sciences, University of Liverpool, Liverpool, Merseyside L69 3BX, United Kingdom.
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