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Grace N, Mbabazi E, Mukunya D, Tumuhamye J, Okechi H, Wegoye E, Olupot-Olupot P, Matovu JK, Hopp L, Napyo A. High burden of wasting among children under-five with hydrocephalus receiving care at CURE children's hospital in Uganda: a cross-sectional study. BMC Nutr 2024; 10:14. [PMID: 38233952 PMCID: PMC10795367 DOI: 10.1186/s40795-024-00819-z] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/18/2023] [Accepted: 01/02/2024] [Indexed: 01/19/2024] Open
Abstract
BACKGROUND Hydrocephalus is one of the most common neurological disabilities presenting in children. Although there are limited studies on its association with wasting, neurological comorbidities such as dysphagia have been associated with an increased risk of wasting in children. In this study, we aimed to determine the prevalence and factors associated with wasting in children less than five years with hydrocephalus. METHODS We conducted a cross-sectional study at various satellite clinics of CURE Children's Hospital in Uganda between September and November 2021. Children with hydrocephalus were identified at the outpatient departments of the satellite clinics of the Cure Children's Hospital and these include Mbale, Gulu, Lira, Jinja and Katalemwa. A structured questionnaire was used to collect information on several variables including (1) for the mother: socio-demographic characteristics, partner support, and wealth index (2) for the child: socio-demographic characteristics, clinical symptoms, feeding difficulties and neural comorbidity. Anthropometric measurements were also taken and these included the mid-upper arm circumference. Data were analysed using Stata version 14. We estimated adjusted odds ratios and their corresponding 95% confidence intervals while relying on multivariable logistic regression models. RESULTS The prevalence of wasting among children with hydrocephalus was 23.2% (n = 89/384) (95%CI: 19 - 27.7%). Their mean age was 19.5 months (SD 16.8). Most of the children were below 12 months (47.9%) and were male (57.5%). The factors associated with wasting among children with hydrocephalus included: having; difficulty in chewing and swallowing (AOR = 2.6, (95%CI:1.05-3.94), a poor appetite (AOR = 1.74, (95%CI: 1.31-2.32), difficulty in breathing (AOR = 1.9, (95%CI: 1.18-3.16), chocking on food (AOR = 1.42, (95%CI:1.1-1.9) and attending the Mbale satellite clinic (AOR = 2.1 (95% CI 1.19-3.7). Children under 5 years of age with hydrocephalus that were born to women whose highest level of education was 7 to 10 years of formal schooling (AOR = 0.32, 95%CI: (0.12-0.87) were less likely to be wasted. CONCLUSIONS AND RECOMMENDATIONS The prevalence of wasting among children with hydrocephalus was high. The factors associated with wasting were mainly feeding challenges. We recommend that children with hydrocephalus should be given greater attention regarding their nutrition especially those with various forms of feeding difficulties. The caregivers of children with hydrocephalus should receive counseling on nutrition and on the best modalities to rely on while feeding their children.
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Affiliation(s)
- Naula Grace
- Department of Community and Public Health, Busitema University Faculty of Health Sciences, Mbale, Uganda
| | - Edith Mbabazi
- Department of Medicine and Research, Cure Children's Hospital, Mbale, Uganda
| | - David Mukunya
- Department of Community and Public Health, Busitema University Faculty of Health Sciences, Mbale, Uganda
| | - Josephine Tumuhamye
- Department of Epidemiology and Biostatistics, School of Public Health, Makerere University, Kampala, Uganda
| | - Humphrey Okechi
- Department of Medicine and Research, Cure Children's Hospital, Mbale, Uganda
| | - Emmanuel Wegoye
- Department of Medicine and Research, Cure Children's Hospital, Mbale, Uganda
| | - Peter Olupot-Olupot
- Department of Community and Public Health, Busitema University Faculty of Health Sciences, Mbale, Uganda
- Mbale Clinical Research Institute, Mbale, Uganda
| | - Joseph Kb Matovu
- Department of Community and Public Health, Busitema University Faculty of Health Sciences, Mbale, Uganda
- Department of Disease Control and Environmental Health, Makerere University School of Public Health, Kampala, Uganda
| | - Leah Hopp
- Department of Community Health, Akisyon a Yesu Presbyterian Clinic, Nakaale, Karamoja, Uganda
| | - Agnes Napyo
- Department of Community and Public Health, Busitema University Faculty of Health Sciences, Mbale, Uganda.
- Department of Nursing Sciences, School of Medicine, Kabale University, Kabale, Uganda.
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Yap KN, Wong HS, Ramanathan C, Rodriguez-Wagner CA, Roberts MD, Freeman DA, Buffenstein R, Zhang Y. Naked mole-rat and Damaraland mole-rat exhibit lower respiration in mitochondria, cellular and organismal levels. BIOCHIMICA ET BIOPHYSICA ACTA. BIOENERGETICS 2022; 1863:148582. [PMID: 35667393 DOI: 10.1016/j.bbabio.2022.148582] [Citation(s) in RCA: 2] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 01/14/2022] [Revised: 05/30/2022] [Accepted: 05/31/2022] [Indexed: 06/15/2023]
Abstract
Naked mole-rats (NMR) and Damaraland mole-rats (DMR) exhibit extraordinary longevity for their body size, high tolerance to hypoxia and oxidative stress and high reproductive output; these collectively defy the concept that life-history traits should be negatively correlated. However, when life-history traits share similar underlying physiological mechanisms, these may be positively associated with each other. We propose that one such potential common mechanism might be the bioenergetic properties of mole-rats. Here, we aim to characterize the bioenergetic properties of two African mole-rats. We adopted a top-down perspective measuring the bioenergetic properties at the organismal, cellular, and molecular level in both species and the biological significance of these properties were compared with the same measures in Siberian hamsters and C57BL/6 mice, chosen for their similar body size to the mole-rat species. We found mole-rats shared several bioenergetic properties that differed from their comparison species, including low basal metabolic rates, a high dependence on glycolysis rather than on oxidative phosphorylation for ATP production, and low proton conductance across the mitochondrial inner membrane. These shared mole-rat features could be a result of evolutionary adaptation to tolerating variable oxygen atmospheres, in particular hypoxia, and may in turn be one of the molecular mechanisms underlying their extremely long lifespans.
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Affiliation(s)
- Kang Nian Yap
- Department of Biological Sciences, Auburn University, Auburn, AL 36849, United States of America; Department of Biology, Norwegian University of Science and Technology, Trondheim 7491, Norway
| | - Hoi Shan Wong
- Calico Life Sciences LLC, South San Francisco, CA 94080, United States of America
| | - Chidambaram Ramanathan
- College of Health Sciences, University of Memphis, Memphis, TN 38152, United States of America
| | | | - Michael D Roberts
- School of Kinesiology, Auburn University, Auburn, AL 36849, United States of America
| | - David A Freeman
- Department of Biological Science, University of Memphis, Memphis, TN 38152, United States of America
| | - Rochelle Buffenstein
- Calico Life Sciences LLC, South San Francisco, CA 94080, United States of America.
| | - Yufeng Zhang
- College of Health Sciences, University of Memphis, Memphis, TN 38152, United States of America.
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3
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Abstract
The design of the energy metabolism system in striated muscle remains a major area of investigation. Here, we review our current understanding and emerging hypotheses regarding the metabolic support of muscle contraction. Maintenance of ATP free energy, so called energy homeostasis, via mitochondrial oxidative phosphorylation is critical to sustained contractile activity, and this major design criterion is the focus of this review. Cell volume invested in mitochondria reduces the space available for generating contractile force, and this spatial balance between mitochondria acontractile elements to meet the varying sustained power demands across muscle types is another important design criterion. This is accomplished with remarkably similar mass-specific mitochondrial protein composition across muscle types, implying that it is the organization of mitochondria within the muscle cell that is critical to supporting sustained muscle function. Beyond the production of ATP, ubiquitous distribution of ATPases throughout the muscle requires rapid distribution of potential energy across these large cells. Distribution of potential energy has long been thought to occur primarily through facilitated metabolite diffusion, but recent analysis has questioned the importance of this process under normal physiological conditions. Recent structural and functional studies have supported the hypothesis that the mitochondrial reticulum provides a rapid energy distribution system via the conduction of the mitochondrial membrane potential to maintain metabolic homeostasis during contractile activity. We extensively review this aspect of the energy metabolism design contrasting it with metabolite diffusion models and how mitochondrial structure can play a role in the delivery of energy in the striated muscle.
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Affiliation(s)
- Brian Glancy
- Muscle Energetics Laboratory, National Heart, Lung, and Blood Insititute and National Institute of Arthritis and Musculoskeletal and Skin Disease, Bethesda, Maryland
- Laboratory of Cardiac Energetics, National Heart, Lung, and Blood Insititute, Bethesda, Maryland
| | - Robert S Balaban
- Muscle Energetics Laboratory, National Heart, Lung, and Blood Insititute and National Institute of Arthritis and Musculoskeletal and Skin Disease, Bethesda, Maryland
- Laboratory of Cardiac Energetics, National Heart, Lung, and Blood Insititute, Bethesda, Maryland
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4
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Llorente-Folch I, Rueda CB, Pardo B, Szabadkai G, Duchen MR, Satrustegui J. The regulation of neuronal mitochondrial metabolism by calcium. J Physiol 2016; 593:3447-62. [PMID: 25809592 DOI: 10.1113/jp270254] [Citation(s) in RCA: 121] [Impact Index Per Article: 15.1] [Reference Citation Analysis] [Abstract] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/27/2015] [Accepted: 03/18/2015] [Indexed: 12/24/2022] Open
Abstract
Calcium signalling is fundamental to the function of the nervous system, in association with changes in ionic gradients across the membrane. Although restoring ionic gradients is energetically costly, a rise in intracellular Ca(2+) acts through multiple pathways to increase ATP synthesis, matching energy supply to demand. Increasing cytosolic Ca(2+) stimulates metabolite transfer across the inner mitochondrial membrane through activation of Ca(2+) -regulated mitochondrial carriers, whereas an increase in matrix Ca(2+) stimulates the citric acid cycle and ATP synthase. The aspartate-glutamate exchanger Aralar/AGC1 (Slc25a12), a component of the malate-aspartate shuttle (MAS), is stimulated by modest increases in cytosolic Ca(2+) and upregulates respiration in cortical neurons by enhancing pyruvate supply into mitochondria. Failure to increase respiration in response to small (carbachol) and moderate (K(+) -depolarization) workloads and blunted stimulation of respiration in response to high workloads (veratridine) in Aralar/AGC1 knockout neurons reflect impaired MAS activity and limited mitochondrial pyruvate supply. In response to large workloads (veratridine), acute stimulation of respiration occurs in the absence of MAS through Ca(2+) influx through the mitochondrial calcium uniporter (MCU) and a rise in matrix [Ca(2+) ]. Although the physiological importance of the MCU complex in work-induced stimulation of respiration of CNS neurons is not yet clarified, abnormal mitochondrial Ca(2+) signalling causes pathology. Indeed, loss of function mutations in MICU1, a regulator of MCU complex, are associated with neuromuscular disease. In patient-derived MICU1 deficient fibroblasts, resting matrix Ca(2+) is increased and mitochondria fragmented. Thus, the fine tuning of Ca(2+) signals plays a key role in shaping mitochondrial bioenergetics.
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Affiliation(s)
- I Llorente-Folch
- Departamento de Biología Molecular, Centro de Biología Molecular Severo Ochoa, Consejo Superior de Investigaciones Científicas-Universidad Autónoma de Madrid-(CSIC-UAM), Madrid, Spain.,Centro de Investigación Biomédica en Red de Enfermedades Raras (CIBERER), Madrid, Spain.,Instituto de Investigación Sanitaria Fundación Jiménez Díaz IIS-FJD, Madrid, Spain
| | - C B Rueda
- Departamento de Biología Molecular, Centro de Biología Molecular Severo Ochoa, Consejo Superior de Investigaciones Científicas-Universidad Autónoma de Madrid-(CSIC-UAM), Madrid, Spain.,Centro de Investigación Biomédica en Red de Enfermedades Raras (CIBERER), Madrid, Spain.,Instituto de Investigación Sanitaria Fundación Jiménez Díaz IIS-FJD, Madrid, Spain
| | - B Pardo
- Departamento de Biología Molecular, Centro de Biología Molecular Severo Ochoa, Consejo Superior de Investigaciones Científicas-Universidad Autónoma de Madrid-(CSIC-UAM), Madrid, Spain.,Centro de Investigación Biomédica en Red de Enfermedades Raras (CIBERER), Madrid, Spain.,Instituto de Investigación Sanitaria Fundación Jiménez Díaz IIS-FJD, Madrid, Spain
| | - G Szabadkai
- Department of Cell and Developmental Biology, Consortium for Mitochondrial Research, University College London, London, UK.,Department of Biomedical Sciences, University of Padua and Consiglio Nazionale delle Ricerche Neuroscience Institute, Padua, Italy
| | - M R Duchen
- Department of Cell and Developmental Biology, Consortium for Mitochondrial Research, University College London, London, UK
| | - J Satrustegui
- Departamento de Biología Molecular, Centro de Biología Molecular Severo Ochoa, Consejo Superior de Investigaciones Científicas-Universidad Autónoma de Madrid-(CSIC-UAM), Madrid, Spain.,Centro de Investigación Biomédica en Red de Enfermedades Raras (CIBERER), Madrid, Spain.,Instituto de Investigación Sanitaria Fundación Jiménez Díaz IIS-FJD, Madrid, Spain
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5
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Hotra A, Suter M, Biuković G, Ragunathan P, Kundu S, Dick T, Grüber G. Deletion of a unique loop in the mycobacterial F-ATP synthase γ subunit sheds light on its inhibitory role in ATP hydrolysis-driven H(+) pumping. FEBS J 2016; 283:1947-61. [PMID: 26996828 DOI: 10.1111/febs.13715] [Citation(s) in RCA: 41] [Impact Index Per Article: 5.1] [Reference Citation Analysis] [Abstract] [Key Words] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/14/2015] [Revised: 02/29/2016] [Accepted: 03/15/2016] [Indexed: 11/28/2022]
Abstract
The F1 FO -ATP synthase is one of the enzymes that is essential to meet the energy requirement of both the proliferating aerobic and hypoxic dormant stages of the life cycle of mycobacteria. Most F-ATP synthases consume ATP in the α3 :β3 headpiece to drive the γ subunit, which couples ATP cleavage with proton pumping in the c ring of FO via the bottom of the γ subunit. ATPase-driven H(+) pumping is latent in mycobacteria. The presence of a unique 14 amino acid residue loop of the mycobacterial γ subunit has been described and aligned in close vicinity to the c-ring loop Priya R et al. (2013) J Bioenerg Biomembr 45, 121-129 Here, we used inverted membrane vesicles (IMVs) of fast-growing Mycobacterium smegmatis and a variety of covalent and non-covalent inhibitors to characterize the ATP hydrolysis activity of the F-ATP synthase inside IMVs. These vesicles formed a platform to investigate the function of the unique mycobaterial γ loop by deleting the respective loop-encoding sequence (γ166-179 ) in the genome of M. smegmatis. ATP hydrolysis-driven H(+) pumping was observed in IMVs containing the Δγ166-179 mutant protein but not for IMVs containing the wild-type F-ATP synthase. In addition, when compared to the wild-type enzyme, IMVs containing the Δγ166-179 mutant protein showed increased ATP cleavage and lower levels of ATP synthesis, demonstrating that the loop affects ATPase activity, ATPase-driven H(+) pumping and ATP synthesis. These results further indicate that the loop may affect coupling of ATP hydrolysis and synthesis in a different mode.
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Affiliation(s)
- Adam Hotra
- School of Biological Sciences, Nanyang Technological University, Singapore, Singapore.,School of Physical and Mathematical Sciences, Nanyang Technological University, Singapore, Singapore.,Nanyang Institute of Technology in Health and Medicine, Interdisciplinary Graduate School, Nanyang Technological University, Singapore, Singapore
| | - Manuel Suter
- Department of Microbiology and Immunology, Yong Loo Lin School of Medicine, National University of Singapore, Singapore
| | - Goran Biuković
- Department of Microbiology and Immunology, Yong Loo Lin School of Medicine, National University of Singapore, Singapore
| | - Priya Ragunathan
- School of Biological Sciences, Nanyang Technological University, Singapore, Singapore
| | - Subhashri Kundu
- Department of Microbiology and Immunology, Yong Loo Lin School of Medicine, National University of Singapore, Singapore
| | - Thomas Dick
- Department of Microbiology and Immunology, Yong Loo Lin School of Medicine, National University of Singapore, Singapore
| | - Gerhard Grüber
- School of Biological Sciences, Nanyang Technological University, Singapore, Singapore
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6
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Yun Z, Qu H, Wang H, Zhu F, Zhang Z, Duan X, Yang B, Cheng Y, Jiang Y. Comparative transcriptome and metabolome provides new insights into the regulatory mechanisms of accelerated senescence in litchi fruit after cold storage. Sci Rep 2016; 6:19356. [PMID: 26763309 PMCID: PMC4725888 DOI: 10.1038/srep19356] [Citation(s) in RCA: 42] [Impact Index Per Article: 5.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/10/2015] [Accepted: 12/08/2015] [Indexed: 11/09/2022] Open
Abstract
Litchi is a non-climacteric subtropical fruit of high commercial value. The shelf life of litchi fruit under ambient conditions (AC) is approximately 4-6 days. Post-harvest cold storage prolongs the life of litchi fruit for up to 30 days with few changes in pericarp browning and total soluble solids. However, the shelf life of litchi fruits at ambient temperatures after pre-cold storage (PCS) is only 1-2 days. To better understand the mechanisms involved in the rapid fruit senescence induced by pre-cold storage, a transcriptome of litchi pericarp was constructed to assemble the reference genes, followed by comparative transcriptomic and metabolomic analyses. Results suggested that the senescence of harvested litchi fruit was likely to be an oxidative process initiated by ABA, including oxidation of lipids, polyphenols and anthocyanins. After cold storage, PCS fruit exhibited energy deficiency, and respiratory burst was elicited through aerobic and anaerobic respiration, which was regulated specifically by an up-regulated calcium signal, G-protein-coupled receptor signalling pathway and small GTPase-mediated signal transduction. The respiratory burst was largely associated with increased production of reactive oxygen species, up-regulated peroxidase activity and initiation of the lipoxygenase pathway, which were closely related to the accelerated senescence of PCS fruit.
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Affiliation(s)
- Ze Yun
- Key Laboratory of Plant Resources Conservation and Sustainable Utilization, South China Botanical Garden, Chinese Academy of Sciences, Guangzhou 510650, P.R. China
| | - Hongxia Qu
- Key Laboratory of Plant Resources Conservation and Sustainable Utilization, South China Botanical Garden, Chinese Academy of Sciences, Guangzhou 510650, P.R. China
| | - Hui Wang
- Key Laboratory of Plant Resources Conservation and Sustainable Utilization, South China Botanical Garden, Chinese Academy of Sciences, Guangzhou 510650, P.R. China
| | - Feng Zhu
- Key Laboratory of Horticultural Plant Biology, Ministry of Education, Huazhong Agricultural University, Wuhan 430070, P.R. China
| | - Zhengke Zhang
- Key Laboratory of Plant Resources Conservation and Sustainable Utilization, South China Botanical Garden, Chinese Academy of Sciences, Guangzhou 510650, P.R. China
| | - Xuewu Duan
- Key Laboratory of Plant Resources Conservation and Sustainable Utilization, South China Botanical Garden, Chinese Academy of Sciences, Guangzhou 510650, P.R. China
| | - Bao Yang
- Key Laboratory of Plant Resources Conservation and Sustainable Utilization, South China Botanical Garden, Chinese Academy of Sciences, Guangzhou 510650, P.R. China
| | - Yunjiang Cheng
- Key Laboratory of Horticultural Plant Biology, Ministry of Education, Huazhong Agricultural University, Wuhan 430070, P.R. China
| | - Yueming Jiang
- Key Laboratory of Plant Resources Conservation and Sustainable Utilization, South China Botanical Garden, Chinese Academy of Sciences, Guangzhou 510650, P.R. China
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7
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Neal A, Rountree AM, Philips CW, Kavanagh TJ, Williams DP, Newham P, Khalil G, Cook DL, Sweet IR. Quantification of Low-Level Drug Effects Using Real-Time, in vitro Measurement of Oxygen Consumption Rate. Toxicol Sci 2015; 148:594-602. [PMID: 26396153 DOI: 10.1093/toxsci/kfv208] [Citation(s) in RCA: 15] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/12/2022] Open
Abstract
There is a general need to detect toxic effects of drugs during preclinical screening. We propose that increased sensitivity of xenobiotics toxicity combined with improved in vitro physiological recapitulation will more accurately assess potentially toxic perturbations of cellular biochemistry that are near in vivo pharmacological exposure levels. Importantly, measurement of such cytopathologies avoids activating mechanisms mediating toxicity at suprapharmacologic levels not relevant to in vivo effects. We present a sensitive method to measure changes in oxygen consumption rate (OCR), a well-established parameter reflecting a potential hazard, in response to exposure to pharmacologic levels of drugs using a flow culture system and state of the art oxygen sensing system. We tested metformin and acetaminophen on rat liver slices to illustrate the method. The features of the method include continuous and very stable measurement of OCR over the course of 48 h in liver slices in a continuous flow chamber with the ability to resolve changes as small as 0.3%/h. Kinetic modeling of metformin inhibition of OCR over a wide range of concentrations revealed both a slow and fast mechanism, where the fast mechanism activated only at concentrations above 0.6 mM. For both drugs, small amounts of inhibition were reversible, but higher decrements were irreversible. Overall the study highlights the advantages of measuring low-level toxicity so as to avoid the common extrapolations made about drug toxicity based on effects of drugs tested at suprapharmacologic levels.
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Affiliation(s)
- Adam Neal
- *Department of Medicine, University of Washington, Seattle, Washington, 98195
| | - Austin M Rountree
- *Department of Medicine, University of Washington, Seattle, Washington, 98195
| | - Craig W Philips
- Center for Commercialization, University of Washington, Seattle, Washington 98195
| | - Terrance J Kavanagh
- Department of Environmental and Occupational Health Sciences, University of Washington, Seattle, Washington 98105
| | - Dominic P Williams
- Department of Drug Safety and Metabolism, AstraZeneca, Cambridge Science Park, Milton Road, Milton, Cambridge CB4 0FZ, UK; and
| | - Peter Newham
- Department of Drug Safety and Metabolism, AstraZeneca, Cambridge Science Park, Milton Road, Milton, Cambridge CB4 0FZ, UK; and
| | - Gamal Khalil
- EnTox Sciences, LLC, Mercer Island, Washington 98040
| | - Daniel L Cook
- EnTox Sciences, LLC, Mercer Island, Washington 98040
| | - Ian R Sweet
- *Department of Medicine, University of Washington, Seattle, Washington, 98195; EnTox Sciences, LLC, Mercer Island, Washington 98040.
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8
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Kano Y, Miura S, Eshima H, Ezaki O, Poole DC. The effects of PGC-1α on control of microvascular Po2 kinetics following onset of muscle contractions. J Appl Physiol (1985) 2014; 117:163-70. [DOI: 10.1152/japplphysiol.00080.2014] [Citation(s) in RCA: 10] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/23/2023] Open
Abstract
During contractions, regulation of microvascular oxygen partial pressure (Pmvo2), which drives blood-myocyte O2 flux, is a function of skeletal muscle fiber type and oxidative capacity and can be altered by exercise training. The kinetics of Pmvo2 during contractions in predominantly fast-twitch muscles evinces a more rapid fall to far lower levels compared with slow-twitch counterparts. Peroxisome proliferator-activated receptor γ coactivator 1α (PGC-1α) improves endurance performance, in part, due to mitochondrial biogenesis, a fiber-type switch to oxidative fibers, and angiogenesis in skeletal muscle. We tested the hypothesis that improvement of exercise capacity by genetic overexpression of PGC-1α would be associated with an altered Pmvo2 kinetics profile of the fast-twitch (white) gastrocnemius during contractions toward that seen in slow-twitch muscles (i.e., slowed response kinetics and elevated steady-state Pmvo2). Phosphorescence quenching techniques were used to measure Pmvo2 at rest and during separate bouts of twitch (1 Hz) and tetanic (100 Hz) contractions in gastrocnemius muscles of mice with overexpression of PGC-1α and wild-type littermates (WT) mice under isoflurane anesthesia. Muscles of PGC-1α mice exhibited less fatigue than WT ( P < 0.01). However, except for the Pmvo2 response immediately following onset of contractions, WT and PGC-1α mice demonstrated similar Pmvo2 kinetics. Specifically, the time delay of the Pmvo2 response was shortened in PGC-1α mice compared with WT (1 Hz: WT, 6.6 ± 2.4 s; PGC-1α, 2.9 ± 0.8 s; 100 Hz: WT, 3.3 ± 1.1 s, PGC-1α, 0.9 ± 0.3 s, both P < 0.05). The ratio of muscle force to Pmvo2 was higher for the duration of tetanic contractions in PGC-1α mice. Slower dynamics and maintenance of higher Pmvo2 following muscle contractions is not obligatory for improved fatigue resistance in fast-twitch muscle of PGC-1α mice. Moreover, overexpression of PGC-1α may accelerate O2 utilization kinetics to a greater extent than O2 delivery kinetics.
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Affiliation(s)
- Yutaka Kano
- Department of Engineering Science, University of Electro-Communications, Chofu, Tokyo, Japan
| | - Shinji Miura
- Graduate School of Nutritional and Environmental Sciences, University of Shizuoka, Shizuoka, Japan
| | - Hiroaki Eshima
- Department of Engineering Science, University of Electro-Communications, Chofu, Tokyo, Japan
| | - Osamu Ezaki
- Department of Human Health and Design, Showa Women's University, Tokyo, Japan; and
| | - David C. Poole
- Departments of Anatomy, Physiology, and Kinesiology, Kansas State University, Manhattan, Kansas
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9
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Zharova TV, Vinogradov AD. Oxidative phosphorylation and respiratory control phenomenon in Paracoccus denitrificans plasma membrane. BIOCHEMISTRY (MOSCOW) 2014; 77:1000-7. [PMID: 23157259 DOI: 10.1134/s0006297912090064] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/23/2022]
Abstract
Changes in respiratory activity, transmembrane electric potential, and ATP synthesis as induced by additions of limited amounts of ADP and P(i) to tightly coupled inverted (inside-out) Paracoccus denitrificans plasma membrane vesicles were traced. The pattern of the changes was qualitatively the same as those observed for coupled mitochondria during the classical State 4-State 3-State 4 transition. Bacterial vesicles devoid of energy-dependent permeability barriers for the substrates of oxidation and phosphorylation were used as a simple experimental model to investigate two possible mechanisms of respiratory control: (i) in State 4 phosphoryl transfer potential (ATP/ADP × P(i)) is equilibrated with proton-motive force by reversibly operating F(1)·F(o)-ATPase (thermodynamic control); (ii) in State 4 apparent "equilibrium" is reached by unidirectional operation of proton motive force-activated F(1)·F(o)-ATP synthase. The data support the kinetic mechanism of the respiratory control phenomenon.
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Affiliation(s)
- T V Zharova
- Department of Biochemistry, Faculty of Biology, Lomonosov Moscow State University, 119992 Moscow, Russia
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10
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Esterhammer R, Klug G, Wolf C, Mayr A, Reinstadler S, Feistritzer HJ, Metzler B, Schocke MFH. Cardiac high-energy phosphate metabolism alters with age as studied in 196 healthy males with the help of 31-phosphorus 2-dimensional chemical shift imaging. PLoS One 2014; 9:e97368. [PMID: 24940736 PMCID: PMC4062408 DOI: 10.1371/journal.pone.0097368] [Citation(s) in RCA: 12] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/08/2014] [Accepted: 04/18/2014] [Indexed: 11/26/2022] Open
Abstract
Recently published studies have elucidated alterations of mitochondrial oxidative metabolism during ageing. The intention of the present study was to evaluate the impact of ageing on cardiac high-energy phosphate metabolism and cardiac function in healthy humans. 31-phosphorus 2-dimensional chemical shift imaging (31P 2D CSI) and echocardiography were performed in 196 healthy male volunteers divided into groups of 20 to 40 years (I, n = 43), 40 to 60 years (II, n = 123) and >60 years (III, n = 27) of age. Left ventricular PCr/β-ATP ratio, myocardial mass (MM), ejection fraction and E/A ratio were assessed. Mean PCr/β-ATP ratios were significantly different among the three groups of volunteers (I, 2.10±0.37; II, 1.77±0.37; III, 1.45±0.28; all p<0.001). PCr/β-ATP ratios were inversely related to age (r2 = −0.25; p<0.001) with a decrease from 2.65 by 0.02 per year of ageing. PCr/β-ATP ratios further correlated with MM (r = −0.371; p<0.001) and E/A ratios (r = 0.213; p<0.02). Moreover, E/A ratios (r = −0.502, p<0.001), MM (r = 0.304, p<0.001), glucose-levels (r = 0.157, p<0.05) and systolic blood pressure (r = 0.224, p<0.005) showed significant correlations with age. The ejection fraction did not significantly differ between the groups. This study shows that cardiac PCr/β-ATP ratios decrease moderately with age indicating an impairment of mitochondrial oxidative metabolism due to age. Furthermore, MM increases, and E/A ratio decreases with age. Both correlate with left-ventricular PCr/β-ATP ratios. The findings of the present study confirm numerous experimental studies showing an impairment of cardiac mitochondrial function with age.
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Affiliation(s)
- Regina Esterhammer
- Department of Radiology, Medical University Innsbruck, Innsbruck, Austria
| | - Gert Klug
- Department of Internal Medicine III, Division of Cardiology, Medical University Innsbruck, Innsbruck, Austria
| | - Christian Wolf
- Department of Radiology, Medical University Innsbruck, Innsbruck, Austria
- Department of Radiology, District Hospital Reutte, Ehenbichl, Austria
| | - Agnes Mayr
- Department of Radiology, Medical University Innsbruck, Innsbruck, Austria
| | - Sebastian Reinstadler
- Department of Internal Medicine III, Division of Cardiology, Medical University Innsbruck, Innsbruck, Austria
| | - Hans-Josef Feistritzer
- Department of Internal Medicine III, Division of Cardiology, Medical University Innsbruck, Innsbruck, Austria
| | - Bernhard Metzler
- Department of Internal Medicine III, Division of Cardiology, Medical University Innsbruck, Innsbruck, Austria
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ATPase/synthase activity of Paracoccus denitrificans Fo·F1 as related to the respiratory control phenomenon. BIOCHIMICA ET BIOPHYSICA ACTA-BIOENERGETICS 2014; 1837:1322-9. [PMID: 24732246 DOI: 10.1016/j.bbabio.2014.04.002] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Key Words] [Subscribe] [Scholar Register] [Received: 02/03/2014] [Revised: 03/21/2014] [Accepted: 04/01/2014] [Indexed: 02/04/2023]
Abstract
The time course of ATP synthesis, oxygen consumption, and change in the membrane potential in Paracoccus denitrificans inside-out plasma membrane vesicles was traced. ATP synthesis initiated by the addition of a limited amount of either ADP or inorganic phosphate proceeded up to very low residual concentrations of the limiting substrate. Accumulated ATP did not decrease the rate of its synthesis initiated by the addition of ADP. The amount of residual ADP determined at State 4 respiration was independent of ten-fold variation of Pi or the presence of ATP. The pH-dependence of Km for Pi could not be fitted to a simple phosphoric acid dissociation curve. Partial inhibition of respiration resulted in a decrease in the rate of ATP synthesis without affecting the ATP/ADP reached at State 4. At pH8.0, hydrolysis of ATP accumulated at State 4 was induced by a low concentration of an uncoupler, whereas complete uncoupling results in rapid inactivation of ATPase. At pH7.0, no reversal of the ATP synthase reaction by the uncoupler was seen. The data show that ATP/ADP×Pi ratio maintained at State 4 is not in equilibrium with respiratory-generated driving force. Possible mechanisms of kinetic control and unidirectional operation of the Fo·F1-ATP synthase are discussed.
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12
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Holloszy JO. Regulation of mitochondrial biogenesis and GLUT4 expression by exercise. Compr Physiol 2013; 1:921-40. [PMID: 23737207 DOI: 10.1002/cphy.c100052] [Citation(s) in RCA: 57] [Impact Index Per Article: 5.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/20/2022]
Abstract
Endurance exercise training can induce large increases mitochondria and the GLUT4 isoform of the glucose transporter in skeletal muscle. For a long time after the discovery in the 1960s that exercise results in an increase in muscle mitochondria, there was no progress in elucidation of the mechanisms involved. The reason for this lack of progress was that nothing was known regarding how expression of the genes-encoding mitochondrial proteins is coordinately regulated. This situation changed rapidly after discovery of transcription factors that control transcription of genes-encoding mitochondrial proteins and, most importantly, the discovery of peroxisome proliferator-gamma coactivator-1α (PGC-1α). This transcription coactivator binds to and activates transcription factors that regulate transcription of genes-encoding mitochondrial proteins. Thus, PGC-1α activates and coordinates mitochondrial biogenesis. It is now known that exercise rapidly activates and induces increased expression of PGC-1α. The exercise-generated signals that lead to PGC-1α activation and increased expression are the increases in cytosolic Ca(2+) and decreases in ATP and creatine phosphate (∼P). Ca(2+) mediates its effect by activating CAMKII, while the decrease in ∼P mediates its effect via activation of AMPK. Expression of the GLUT4 isoform of the glucose transporter is regulated in parallel with mitochondrial biogenesis via the same signaling pathways. This review describes what is known regarding the regulation of mitochondrial biogenesis and GLUT4 expression by exercise. A major component of this review deals with the physiological and metabolic consequences of the exercise-induced increase in mitochondria and GLUT4.
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Affiliation(s)
- John O Holloszy
- Division of Geriatrics and Nutritional Sciences, Washington University School of Medicine, St. Louis, Missouri, USA.
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Balaban RS. Perspectives on: SGP symposium on mitochondrial physiology and medicine: metabolic homeostasis of the heart. ACTA ACUST UNITED AC 2013; 139:407-14. [PMID: 22641635 PMCID: PMC3362523 DOI: 10.1085/jgp.201210783] [Citation(s) in RCA: 32] [Impact Index Per Article: 2.9] [Reference Citation Analysis] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/17/2022]
Affiliation(s)
- Robert S Balaban
- Laboratory of Cardiac Energetics, National Heart, Lung, and Blood Institute, National Institutes of Health, Bethesda, MD 20817, USA.
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14
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Yuan SN, Malik W, Hua SJ, Bibi N, Wang XD. In vitro inhibition of pigmentation and fiber development in colored cotton. J Zhejiang Univ Sci B 2012; 13:478-86. [PMID: 22661210 DOI: 10.1631/jzus.b1100336] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/11/2022]
Abstract
Colored cotton has naturally pigmented fibers. The mechanism of pigmentation in cotton fiber is not well documented. This experiment was conducted to study the effects of respiratory chain inhibitors, i.e., rotenone and thiourea, on pigmentation and fiber development in colored cotton. After 1 d post-anthesis, ovaries were harvested and developing ovules were cultured on the liquid medium containing different concentrations of rotenone and thiourea for 30 d. The results demonstrate that both respiratory inhibitors reduced fiber length and ovule development under ovule culture conditions, and the inhibition efficiency of rotenone was much higher than that of thiourea. Rotenone and thiourea also showed significant effects on fiber pigment (color) development in colored cotton. In green cotton fiber, rotenone advanced fiber pigment development by 7 d at 200 μmol/L, while thiourea inhibited fiber pigmentation at all treatment levels (400, 600, 800, 1000, and 2000 μmol/L). Both respiratory inhibitors, however, had no significant effects on pigmentation of brown cotton fibers. The activities of cytochrome c oxidase (COX) and polyphenol oxidase (PPO) decreased significantly with increasing levels of both respiratory inhibitors. It is suggested that both respiratory inhibitors have important roles in deciphering the mechanism of pigmentation and fiber development in colored cotton.
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Affiliation(s)
- Shu-na Yuan
- College of Agriculture and Biotechnology, Zhejiang University, Hangzhou 310058, China
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15
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Paital B, Chainy GBN. Effects of salinity on O₂ consumption, ROS generation and oxidative stress status of gill mitochondria of the mud crab Scylla serrata. Comp Biochem Physiol C Toxicol Pharmacol 2012; 155:228-37. [PMID: 21930243 DOI: 10.1016/j.cbpc.2011.08.009] [Citation(s) in RCA: 22] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 07/02/2011] [Revised: 08/29/2011] [Accepted: 08/29/2011] [Indexed: 01/11/2023]
Abstract
Mitochondrial respiration, activities of electron transport chain enzymes and formation of oxidative stress parameters were investigated in mitochondria isolated from gill tissue of mud crabs (Scylla serrata) as a function of salinity (10 ppt, 17 ppt and 35 ppt). Mitochondrial oxygen consumption rate was higher for succinate as substrate compared with those of glutamate, malate and pyruvate. Complex I and complex II mediated respirations were higher at low salinity (10 ppt) than high salinity (17 ppt and 35 ppt). Although activities of electron transport chain enzymes particularly complexes I (EC 1.6.5.3), II (EC 1.3.99.1) and II-III (EC 1.3.2.1) were elevated linearly in response to salinity treatment, activity of complex V (ATPase, EC 3.6.1.34) was decreased at 35 ppt salinity. However, ATPase activity was higher at 17 ppt salinity in comparison to 10 ppt and 17 ppt salinity. Results of the experiment suggest that high salinity (35 ppt) causes hypoxic state in mitochondria of mud crabs. Hypoxic condition induced by high salinity was accompanied with increased hydrogen peroxide production resulting oxidative stress in mitochondria of crabs. A possible mechanism of hypoxia-induced reactive oxygen species generation and OS due to salinity stress in the crabs is discussed.
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16
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Beard DA. Simulation of cellular biochemical system kinetics. WILEY INTERDISCIPLINARY REVIEWS-SYSTEMS BIOLOGY AND MEDICINE 2010; 3:136-46. [PMID: 21171044 DOI: 10.1002/wsbm.116] [Citation(s) in RCA: 15] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/10/2022]
Abstract
The goal of realistically and reliably simulating the biochemical processes underlying cellular function is achievable through a systematic approach that makes use of the broadest possible amount of in vitro and in vivo data, and is consistent with all applicable physical chemical theories. Progress will be facilitated by establishing: (1) a concrete self-consistent theoretical foundation for systems simulation; (2) extensive and accurate databases of thermodynamic properties of biochemical reactions; (3) parameterized and validated models of enzyme and transporter catalytic mechanisms that are consistent with physical chemical theoretical foundation; and (4) software tools for integrating all these concepts, data, and models into a cohesive representation of cellular biochemical systems. Ongoing initiatives are laying the groundwork for the broad-based community cooperation that will be necessary to pursue these elements of a strategic infrastructure for systems simulation on a large scale.
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Affiliation(s)
- Daniel A Beard
- Biotechnology and Bioengineering Center, Medical College of Wisconsin, Milwaukee, WI, USA.
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Flamment M, Gueguen N, Wetterwald C, Simard G, Malthièry Y, Ducluzeau PH. Effects of the cannabinoid CB1 antagonist rimonabant on hepatic mitochondrial function in rats fed a high-fat diet. Am J Physiol Endocrinol Metab 2009; 297:E1162-70. [PMID: 19724020 DOI: 10.1152/ajpendo.00169.2009] [Citation(s) in RCA: 37] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/22/2022]
Abstract
The aim of this study was to investigate the effect of rimonabant treatment on hepatic mitochondrial function in rats fed a high-fat diet. Sprague-Dawley rats fed a high-fat diet (35% lard) for 13 wk were treated with rimonabant (10 mg·kg(-1)·day(-1)) during the last 3 wk and matched with pair-fed controls. Oxygen consumption with various substrates, mitochondrial enzyme activities on isolated liver mitochondria, and mitochondrial DNA quantity were determined. Body weight and fat mass were decreased in rats treated with rimonabant compared with pair-fed controls. Moreover, the serum adiponectin level was increased with rimonabant. Hepatic triglyceride content was increased, while serum triglycerides were decreased. An increase of mitochondrial respiration was observed in rats treated with rimonabant. The increase of mitochondrial respiration with palmitoyl-CoA compared with respiration with palmitoyl-l-carnitine stating that the entry of fatty acids into mitochondria via carnitine palmitoyltransferase I was increased in rats treated with rimonabant. Moreover, rimonabant treatment led to a reduction in the enzymatic activity of ATP synthase, whereas the quantity of mitochondrial DNA and the activity of citrate synthase remained unchanged. To summarize, rimonabant treatment leads to an improvement of hepatic mitochondrial function by increasing substrate oxidation and fatty acid entry into mitochondria for the β-oxidation pathway and by increasing proton leak. However, this increase of mitochondrial oxidation is regulated by a decrease of ATP synthase activity in order to have only ATP required for the cell function.
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Jeneson JAL, Schmitz JPJ, van den Broek NMA, van Riel NAW, Hilbers PAJ, Nicolay K, Prompers JJ. Magnitude and control of mitochondrial sensitivity to ADP. Am J Physiol Endocrinol Metab 2009; 297:E774-84. [PMID: 19622784 PMCID: PMC3833997 DOI: 10.1152/ajpendo.00370.2009] [Citation(s) in RCA: 38] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/22/2022]
Abstract
The transduction function for ADP stimulation of mitochondrial ATP synthesis in skeletal muscle was reconstructed in vivo and in silico to investigate the magnitude and origin of mitochondrial sensitivity to cytoplasmic ADP concentration changes. Dynamic in vivo measurements of human leg muscle phosphocreatine (PCr) content during metabolic recovery from contractions were performed by (31)P-NMR spectroscopy. The cytoplasmic ADP concentration ([ADP]) and rate of oxidative ATP synthesis (Jp) at each time point were calculated from creatine kinase equilibrium and the derivative of a monoexponential fit to the PCr recovery data, respectively. Reconstructed [ADP]-Jp relations for individual muscles containing more than 100 data points were kinetically characterized by nonlinear curve fitting yielding an apparent kinetic order and ADP affinity of 1.9 +/- 0.2 and 0.022 +/- 0.003 mM, respectively (means +/- SD; n = 6). Next, in silico [ADP]-Jp relations for skeletal muscle were generated using a computational model of muscle oxidative ATP metabolism whereby model parameters corresponding to mitochondrial enzymes were randomly changed by 50-150% to determine control of mitochondrial ADP sensitivity. The multiparametric sensitivity analysis showed that mitochondrial ADP ultrasensitivity is an emergent property of the integrated mitochondrial enzyme network controlled primarily by kinetic properties of the adenine nucleotide translocator.
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Affiliation(s)
- Jeroen A L Jeneson
- Biomedical NMR, Dept. of Biomedical Engineering, Eindhoven University of Technology, 5600 MB Eindhoven, The Netherlands.
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A novel kinetic assay of mitochondrial ATP-ADP exchange rate mediated by the ANT. Biophys J 2009; 96:2490-504. [PMID: 19289073 DOI: 10.1016/j.bpj.2008.12.3915] [Citation(s) in RCA: 76] [Impact Index Per Article: 5.1] [Reference Citation Analysis] [Abstract] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/14/2008] [Revised: 12/08/2008] [Accepted: 12/17/2008] [Indexed: 11/23/2022] Open
Abstract
A novel method exploiting the differential affinity of ADP and ATP to Mg(2+) was developed to measure mitochondrial ADP-ATP exchange rate. The rate of ATP appearing in the medium after addition of ADP to energized mitochondria, is calculated from the measured rate of change in free extramitochondrial [Mg(2+)] reported by the membrane-impermeable 5K(+) salt of the Mg(2+)-sensitive fluorescent indicator, Magnesium Green, using standard binding equations. The assay is designed such that the adenine nucleotide translocase (ANT) is the sole mediator of changes in [Mg(2+)] in the extramitochondrial volume, as a result of ADP-ATP exchange. We also provide data on the dependence of ATP efflux rate within the 6.8-7.8 matrix pH range as a function of membrane potential. Finally, by comparing the ATP-ADP steady-state exchange rate to the amount of the ANT in rat brain synaptic, brain nonsynaptic, heart and liver mitochondria, we provide molecular turnover numbers for the known ANT isotypes.
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20
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Balaban RS. The role of Ca(2+) signaling in the coordination of mitochondrial ATP production with cardiac work. BIOCHIMICA ET BIOPHYSICA ACTA-BIOENERGETICS 2009; 1787:1334-41. [PMID: 19481532 DOI: 10.1016/j.bbabio.2009.05.011] [Citation(s) in RCA: 179] [Impact Index Per Article: 11.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 02/11/2009] [Revised: 04/23/2009] [Accepted: 05/13/2009] [Indexed: 12/18/2022]
Abstract
The heart is capable of balancing the rate of mitochondrial ATP production with utilization continuously over a wide range of activity. This results in a constant phosphorylation potential despite a large change in metabolite turnover. The molecular mechanisms responsible for generating this energy homeostasis are poorly understood. The best candidate for a cytosolic signaling molecule reflecting ATP hydrolysis is Ca(2+). Since Ca(2+) initiates and powers muscle contraction as well as serves as the primary substrate for SERCA, Ca(2+) is an ideal feed-forward signal for priming ATP production. With the sarcoplasmic reticulum to cytosolic Ca(2+) gradient near equilibrium with the free energy of ATP, cytosolic Ca(2+) release is exquisitely sensitive to the cellular energy state providing a feedback signal. Thus, Ca(2+) can serve as a feed-forward and feedback regulator of ATP production. Consistent with this notion is the correlation of cytosolic and mitochondrial Ca(2+) with work in numerous preparations as well as the localization of mitochondria near Ca(2+) release sites. How cytosolic Ca(2+) signaling might regulate oxidative phosphorylation is a focus of this review. The relevant Ca(2+) sensitive sites include several dehydrogenases and substrate transporters together with a post-translational modification of F1-FO-ATPase and cytochrome oxidase. Thus, Ca(2+) apparently activates both the generation of the mitochondrial membrane potential as well as utilization to produce ATP. This balanced activation extends the energy homeostasis observed in the cytosol into the mitochondria matrix in the never resting heart.
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Affiliation(s)
- Robert S Balaban
- Laboratory of Cardiac Energetics, National Heart Lung and Blood Institute, National Institutes of Health, Bethesda, MD 20892, USA.
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21
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Fatty liver and insulin resistance in obese Zucker rats: no role for mitochondrial dysfunction. Biochimie 2008; 90:1407-13. [PMID: 18534199 DOI: 10.1016/j.biochi.2008.05.003] [Citation(s) in RCA: 26] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/04/2008] [Accepted: 05/05/2008] [Indexed: 01/07/2023]
Abstract
The relationship between insulin resistance and mitochondrial function is of increasing interest. Studies looking for such interactions are usually made in muscle and only a few studies have been done in liver, which is known to be a crucial partner in whole body insulin action. Recent studies have revealed a similar mechanism to that of muscle for fat-induced insulin resistance in liver. However, the exact mechanism of lipid metabolites accumulation in liver leading to insulin resistance is far from being elucidated. One of the hypothetical mechanisms for liver steatosis development is an impairment of mitochondrial function. We examined mitochondrial function in fatty liver and insulin resistance state using isolated mitochondria from obese Zucker rats. We determined the relationship between ATP synthesis and oxygen consumption as well as the relationship between mitochondrial membrane potential and oxygen consumption. In order to evaluate the quantity of mitochondria and the oxidative capacity we measured citrate synthase and cytochrome c oxidase activities. Results showed that despite significant fatty liver and hyperinsulinemia, isolated liver mitochondria from obese Zucker rats display no difference in oxygen consumption, ATP synthesis, and membrane potential compared with lean Zucker rats. There was no difference in citrate synthase and cytochrome c oxidase activities between obese and lean Zucker rats in isolated mitochondria as well as in liver homogenate, indicating a similar relative amount of hepatic mitochondria and a similar oxidative capacity. Adiponectin, which is involved in bioenergetic homeostasis, was increased two-fold in obese Zucker rats despite insulin resistance. In conclusion, isolated liver mitochondria from lean and obese insulin-resistant Zucker rats showed strictly the same mitochondrial function. It remains to be elucidated whether adiponectin increase is involved in these results.
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Bowtell JL, Marwood S, Bruce M, Constantin-Teodosiu D, Greenhaff PL. Tricarboxylic acid cycle intermediate pool size: functional importance for oxidative metabolism in exercising human skeletal muscle. Sports Med 2008; 37:1071-88. [PMID: 18027994 DOI: 10.2165/00007256-200737120-00005] [Citation(s) in RCA: 50] [Impact Index Per Article: 3.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/02/2022]
Abstract
The tricarboxylic acid (TCA) cycle is the major final common pathway for oxidation of carbohydrates, lipids and some amino acids, which produces reducing equivalents in the form of nicotinamide adenine dinucleotide and flavin adenine dinucleotide that result in production of large amounts of adenosine triphosphate (ATP) via oxidative phosphorylation. Although regulated primarily by the products of ATP hydrolysis, in particular adenosine diphosphate, the rate of delivery of reducing equivalents to the electron transport chain is also a potential regulatory step of oxidative phosphorylation. The TCA cycle is responsible for the generation of approximately 67% of all reducing equivalents per molecule of glucose, hence factors that influence TCA cycle flux will be of critical importance for oxidative phosphorylation. TCA cycle flux is dependent upon the supply of acetyl units, activation of the three non-equilibrium reactions within the TCA cycle, and it has been suggested that an increase in the total concentration of the TCA cycle intermediates (TCAi) is also necessary to augment and maintain TCA cycle flux during exercise. This article reviews the evidence of the functional importance of the TCAi pool size for oxidative metabolism in exercising human skeletal muscle. In parallel with increased oxidative metabolism and TCA cycle flux during exercise, there is an exercise intensity-dependent 4- to 5-fold increase in the concentration of the TCAi. TCAi concentration reaches a peak after 10-15 minutes of exercise, and thereafter tends to decline. This seems to support the suggestion that the concentration of TCAi may be of functional importance for oxidative phosphorylation. However, researchers have been able to induce dissociations between TCAi pool size and oxidative energy provision using a variety of nutritional, pharmacological and exercise interventions. Brief periods of endurance training (5 days or 7 weeks) have been found to result in reduced TCAi pool expansion at the start of exercise (same absolute work intensity) in parallel with either equivalent or increased oxidative energy provision. Cycloserine inhibits alanine aminotransferase, which catalyses the predominant anaplerotic reaction in exercising human muscle. When infused into contracting rat hindlimb muscle, TCAi pool expansion was reduced by 25% with no significant change in oxidative energy provision or power output. Glutamine supplementation has been shown to enhance TCAi pool expansion at the start of exercise with no increase in oxidative energy provision. In summary, there is a consistent dissociation between the extent of TCAi pool expansion at the onset of exercise and oxidative energy provision. At the other end of the spectrum, the parallel loss of TCAi, glycogen and adenine nucleotides and accumulation of inosine monophosphate during prolonged exercise has led to the suggestion that there is a link between muscle glycogen depletion, reduced TCA cycle flux and the development of fatigue. However, analysis of serial biopsies during prolonged exercise demonstrated dissociation between muscle TCAi content and both muscle glycogen content and muscle oxygen uptake. In addition, the delay in fatigue development achieved through increased carbohydrate availability does not attenuate TCAi reduction during prolonged exercise. Therefore, TCAi concentration in whole muscle homogenate does not seem to be of functional importance. However, TCAi content can currently only be measured in whole muscle homogenate rather than the mitochondrial subfraction where TCA cycle reactions occur. In addition, anaplerotic flux rather than TCAi content per se is likely to be of greater importance in determining TCA cycle flux, since TCAi content is probably merely reflective of anaplerotic substrate concentration. Methodological advances are required to allow researchers to address the questions of whether oxidative phosphorylation is limited by mitochondrial TCAi content and/or anaplerotic flux.
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Affiliation(s)
- Joanna L Bowtell
- Academy of Sport, Physical Activity and Wellbeing, London South Bank University, London, UK.
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Arvier M, Lagoutte L, Johnson G, Dumas JF, Sion B, Grizard G, Malthièry Y, Simard G, Ritz P. Adenine nucleotide translocator promotes oxidative phosphorylation and mild uncoupling in mitochondria after dexamethasone treatment. Am J Physiol Endocrinol Metab 2007; 293:E1320-4. [PMID: 17698987 DOI: 10.1152/ajpendo.00138.2007] [Citation(s) in RCA: 31] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/22/2022]
Abstract
The composition of the mitochondrial inner membrane and uncoupling protein [such as adenine nucleotide translocator (ANT)] contents are the main factors involved in the energy-wasting proton leak. This leak is increased by glucocorticoid treatment under nonphosphorylating conditions. The aim of this study was to investigate mechanisms involved in glucocorticoid-induced proton leak and to evaluate the consequences in more physiological conditions (between states 4 and 3). Isolated liver mitochondria, obtained from dexamethasone-treated rats (1.5 mg.kg(-1).day(-1)), were studied by polarography, Western blotting, and high-performance thin-layer chromatography. We confirmed that dexamethasone treatment in rats induces a proton leak in state 4 that is associated with an increased ANT content, although without any change in membrane surface or lipid composition. Between states 4 and 3, dexamethasone stimulates ATP synthesis by increasing both the mitochondrial ANT and F1-F0 ATP synthase content. In conclusion, dexamethasone increases mitochondrial capacity to generate ATP by modifying ANT and ATP synthase. The side effect is an increased leak in nonphosphorylating conditions.
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Affiliation(s)
- Matthieu Arvier
- Institut National de la Santé et de la Recherche Médicale, Laboratoire de Biochimie et de Biologie Moléculaire, Centre Hospitalier Universitaire, Angers, France
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Korzeniewski B. Regulation of oxidative phosphorylation through parallel activation. Biophys Chem 2007; 129:93-110. [PMID: 17566629 DOI: 10.1016/j.bpc.2007.05.013] [Citation(s) in RCA: 73] [Impact Index Per Article: 4.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/23/2007] [Revised: 05/22/2007] [Accepted: 05/23/2007] [Indexed: 11/21/2022]
Abstract
When the mechanical work intensity in muscle increases, the elevated ATP consumption rate must be matched by the rate of ATP production by oxidative phosphorylation in order to avoid a quick exhaustion of ATP. The traditional mechanism of the regulation of oxidative phosphorylation, namely the negative feedback involving [ADP] and [Pi] as regulatory signals, is not sufficient to account for various kinetic properties of the system in intact skeletal muscle and heart in vivo. Theoretical studies conducted using a dynamic computer model of oxidative phosphorylation developed previously strongly suggest the so-called each-step-activation (or parallel activation) mechanism, due to which all oxidative phosphorylation complexes are directly activated by some cytosolic factor/mechanism related to muscle contraction in parallel with the activation of ATP usage and substrate dehydrogenation by calcium ions. The present polemic article reviews and discusses the growing evidence supporting this mechanism and compares it with alternative mechanisms proposed in the literature. It is concluded that only the each-step-activation mechanism is able to explain the rich set of various experimental results used as a reference for estimating the validity and applicability of particular mechanisms.
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Affiliation(s)
- Bernard Korzeniewski
- Faculty of Biochemistry, Biophysics and Biotechnology, Jagiellonian University, ul. Gronostajowa 7, 30-387 Kraków, Poland.
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25
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Meng Q, Wong YT, Chen J, Ruan R. Age-related changes in mitochondrial function and antioxidative enzyme activity in fischer 344 rats. Mech Ageing Dev 2007; 128:286-92. [PMID: 17270247 DOI: 10.1016/j.mad.2006.12.008] [Citation(s) in RCA: 65] [Impact Index Per Article: 3.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/20/2006] [Revised: 12/06/2006] [Accepted: 12/20/2006] [Indexed: 10/23/2022]
Abstract
We have previously reported the changes of mitochondrial function and/or antioxidative enzyme efficiency in a few organs of rats as a result of aging. However, there is a further need to reach a conclusion about their interactions in biological functions based on other evaluation tips like the usage of advanced methods and the exploring of crucial biochemical parameters. Therefore, we investigated the mitochondrial inner membrane functional integrity by the analysis of respiration control ratio and membrane potential in the liver and brain of young (8 months) and old (26 months) Fischer 344 rats. The disintegration of mitochondrial membrane integrity was determined higher in the liver of old rats than that of young rats. This was well correlated with the decrease of total superoxide dismutase (SOD), Cu/Zn-SOD, Mn-SOD and glutathione peroxidase activities in most of the organs, except for the increase of catalase activity in heart of old rats. Similarly, the protein expressions of these enzymes were down regulated in the liver and kidney of old rats. Taken together, we suggest that the mitochondrial malfunction in old rats is associated with the decrease of antioxidative enzyme efficiency. And the data are also discussed with changes in the results from inter-laboratories.
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Affiliation(s)
- Qingying Meng
- Cancer and Aging Research Group, Institute of Bioengineering and Nanotechnology, Singapore 138669, Singapore
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26
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Saks V, Dzeja P, Schlattner U, Vendelin M, Terzic A, Wallimann T. Cardiac system bioenergetics: metabolic basis of the Frank-Starling law. J Physiol 2006; 571:253-73. [PMID: 16410283 PMCID: PMC1796789 DOI: 10.1113/jphysiol.2005.101444] [Citation(s) in RCA: 189] [Impact Index Per Article: 10.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/06/2005] [Accepted: 01/12/2006] [Indexed: 12/18/2022] Open
Abstract
The fundamental principle of cardiac behaviour is described by the Frank-Starling law relating force of contraction during systole with end-diastolic volume. While both work and respiration rates increase linearly with imposed load, the basis of mechano-energetic coupling in heart muscle has remained a long-standing enigma. Here, we highlight advances made in understanding of complex cellular and molecular mechanisms that orchestrate coupling of mitochondrial oxidative phosphorylation with ATP utilization for muscle contraction. Cardiac system bioenergetics critically depends on an interrelated metabolic infrastructure regulating mitochondrial respiration and energy fluxes throughout cellular compartments. The data reviewed indicate the significance of two interrelated systems regulating mitochondrial respiration and energy fluxes in cells: (1) the creatine kinase, adenylate kinase and glycolytic pathways that communicate flux changes generated by cellular ATPases within structurally organized enzymatic modules and networks; and (2) a secondary system based on mitochondrial participation in cellular calcium cycle, which adjusts substrate oxidation and energy-transducing processes to meet increasing cellular energy demands. By conveying energetic signals to metabolic sensors, coupled phosphotransfer reactions provide a high-fidelity regulation of the excitation-contraction cycle. Such integration of energetics with calcium signalling systems provides the basis for 'metabolic pacing', synchronizing the cellular electrical and mechanical activities with energy supply processes.
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Affiliation(s)
- Valdur Saks
- Structural and Quantitative Bioenergetics Research Group, Laboratory of Bioenergetics, Joseph Fourier University, 2280, Rue de la Piscine, BP53X -38041, Grenoble Cedex 9, France.
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Gueguen N, Lefaucheur L, Fillaut M, Vincent A, Herpin P. Control of skeletal muscle mitochondria respiration by adenine nucleotides: differential effect of ADP and ATP according to muscle contractile type in pigs. Comp Biochem Physiol B Biochem Mol Biol 2005; 140:287-97. [PMID: 15649776 DOI: 10.1016/j.cbpc.2004.10.014] [Citation(s) in RCA: 25] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/16/2004] [Revised: 10/22/2004] [Accepted: 10/26/2004] [Indexed: 12/01/2022]
Abstract
Skeletal muscle exhibits considerable variation in mitochondrial content among fiber types, but it is less clear whether mitochondria from different fiber types also present specific functional and regulatory properties. The present experiment was undertaken on ten 170-day-old pigs to compare functional properties and control of respiration by adenine nucleotides in mitochondria isolated from predominantly slow-twitch (Rhomboideus (RM)) and fast-twitch (Longissimus (LM)) muscles. Mitochondrial ATP synthesis, respiratory control ratio (RCR) and ADP-stimulated respiration with either complex I or II substrates were significantly higher (25-30%, P<0.05) in RM than in LM mitochondria, whereas no difference was observed for basal respiration. Based on mitochondrial enzyme activities (cytochrome c oxidase [COX], F0F1-ATPase, mitochondrial creatine kinase [mi-CK]), the higher ADP-stimulated respiration rate of RM mitochondria appeared mainly related to a higher maximal oxidative capacity, without any difference in the maximal phosphorylation potential. Mitochondrial K(m) for ADP was similar in RM (4.4+/-0.9 microM) and LM (5.9+/-1.2 microM) muscles (P>0.05) but the inhibitory effect of ATP was more marked in LM (P<0.01). These findings demonstrate that the regulation of mitochondrial respiration by ATP differs according to muscle contractile type and that absolute muscle oxidative capacity not only relies on mitochondrial density but also on mitochondrial functioning per se.
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Affiliation(s)
- N Gueguen
- INRA, Unité Mixte de Recherche sur le Veau et le Porc, Domaine de la Prise, 35590 Saint-Gilles, France.
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Gueguen N, Lefaucheur L, Ecolan P, Fillaut M, Herpin P. Ca2+-activated myosin-ATPases, creatine and adenylate kinases regulate mitochondrial function according to myofibre type in rabbit. J Physiol 2005; 564:723-35. [PMID: 15731190 PMCID: PMC1464461 DOI: 10.1113/jphysiol.2005.083030] [Citation(s) in RCA: 19] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Revised: 01/11/2005] [Accepted: 02/18/2005] [Indexed: 12/24/2022] Open
Abstract
Mitochondrial respiration rates and their regulation by ADP, AMP and creatine, were studied at different free Ca(2+) concentrations (0.1 versus 0.4 microm) on permeabilized fibre bundles of rabbit skeletal muscles differing in their myosin heavy chain profiles. Four fibre bundle types were obtained: pure types I and IIx, and mixed types IIax (approximately 50% IIa and 50% IIx fibres) and IIb+ (60% IIb fibres, plus IIx and IIa). At rest, pure type I fibres displayed a much higher apparent K(m) for ADP (212 microm) than IIx fibres (8 microm). Within the IIax and IIb+ mixed fibre bundle types, two K(ADP)(m) values were observed (70 microm and 5 microm). Comparison between pure IIx and mixed types indicates that the intermediate K(m) of 70 microm most probably corresponds to the mitochondrial affinity for ADP in IIa fibres, the lowest K(m) for ADP (5 microm) corresponding to IIx and IIb types. Activation of mitochondrial creatine and adenylate kinase reactions stimulated mitochondrial respiration only in type I and IIax fibre bundles, indicating an efficient coupling between both kinases and ADP rephosphorylation in type I and, likely, IIa fibres, since no effect was observed in pure IIx fibres. Following Ca(2+)-induced activation of myosin-ATPase, an increase in mitochondrial sensitivity to ADP of 45% and 250% was observed in type IIax and I bundles, respectively, an effect mostly prevented by addition of vanadate, an inhibitor of myosin-ATPase. Ca(2+)-induced activation of myosin-ATPase also prevented the stimulation of respiration rates by creatine and AMP in I and IIax bundles. In addition to differential regulation of mitochondrial respiration and energy transfer systems at rest in I and IIa versus IIx and IIb muscle fibres, our results indicate a regulation of phosphotransfer systems by Ca(2+) via the stimulation of myosin-ATPases in type I and IIa fibres of rabbit muscles.
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Affiliation(s)
- N Gueguen
- INRA, Unité Mixte de Recherche Système d'Elevage Nutrition Animale et Humaine, Domaine de la Prise, 35590 Saint-Gilles, France
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Naumova AV, Weiss RG, Chacko VP. Regulation of murine myocardial energy metabolism during adrenergic stress studied by in vivo 31P NMR spectroscopy. Am J Physiol Heart Circ Physiol 2003; 285:H1976-9. [PMID: 12881208 DOI: 10.1152/ajpheart.00474.2003] [Citation(s) in RCA: 31] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/22/2022]
Abstract
Image-guided, spatially localized 31P magnetic resonance spectroscopy (MRS) was used to study in vivo murine cardiac metabolism under resting and dobutamine-induced stress conditions. Intravenous dobutamine infusion (24 mug. min-1. kg body wt-1) increased the mean heart rate by approximately 39% from 482 +/- 46 per min at baseline to 669 +/- 77 per min in adult mice. The myocardial phosphocreatine (PCr)-to-ATP (PCr/ATP) ratio remained unchanged at 2.1 +/- 0.5 during dobutamine stress, compared with baseline conditions. Therefore, we conclude that a significant increase in heart rate does not result in a decline in the in vivo murine cardiac PCr/ATP ratio. These observations in very small mammals, viz., mice, at extremely high heart rates are consistent with studies in large animals demonstrating that global levels of high-energy phosphate metabolites do not regulate in vivo myocardial metabolism during physiologically relevant increases in cardiac work.
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Affiliation(s)
- A V Naumova
- Department of Radiology, Magnetic Resonance Research Division, The Johns Hopkins University School of Medicine, 217 Traylor Building, 720 Rutland Avenue, Baltimore, MD 21205, USA
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31
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Abstract
Within the skeletal muscle cell at the onset of muscular contraction, phosphocreatine (PCr) represents the most immediate reserve for the rephosphorylation of adenosine triphosphate (ATP). As a result, its concentration can be reduced to less than 30% of resting levels during intense exercise. As a fall in the level of PCr appears to adversely affect muscle contraction, and therefore power output in a subsequent bout, maximising the rate of PCr resynthesis during a brief recovery period will be of benefit to an athlete involved in activities which demand intermittent exercise. Although this resynthesis process simply involves the rephosphorylation of creatine by aerobically produced ATP (with the release of protons), it has both a fast and slow component, each proceeding at a rate that is controlled by different components of the creatine kinase equilibrium. The initial fast phase appears to proceed at a rate independent of muscle pH. Instead, its rate appears to be controlled by adenosine diphosphate (ADP) levels; either directly through its free cytosolic concentration, or indirectly, through its effect on the free energy of ATP hydrolysis. Once this fast phase of recovery is complete, there is a secondary slower phase that appears almost certainly rate-dependent on the return of the muscle cell to homeostatic intracellular pH. Given the importance of oxidative phosphorylation in this resynthesis process, those individuals with an elevated aerobic power should be able to resynthesise PCr at a more rapid rate than their sedentary counterparts. However, results from studies that have used phosphorus nuclear magnetic resonance ((31)P-NMR) spectroscopy, have been somewhat inconsistent with respect to the relationship between aerobic power and PCr recovery following intense exercise. Because of the methodological constraints that appear to have limited a number of these studies, further research in this area is warranted.
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Affiliation(s)
- Shaun McMahon
- School of Human Movement Studies, University of Queensland, Brisbane, Queensland, Australia.
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32
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Brandes R, Bers DM. Simultaneous measurements of mitochondrial NADH and Ca(2+) during increased work in intact rat heart trabeculae. Biophys J 2002; 83:587-604. [PMID: 12124250 PMCID: PMC1302172 DOI: 10.1016/s0006-3495(02)75194-1] [Citation(s) in RCA: 86] [Impact Index Per Article: 3.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/18/2022] Open
Abstract
The main goal of this study is to investigate the role of mitochondrial [Ca(2+)], [Ca(2+)](m), in the possible up-regulation of the NADH production rate during increased workload. Such up-regulation is necessary to support increased flux through the electron transport chain and increased ATP synthesis rates. Intact cardiac trabeculae were loaded with Rhod-2(AM), and [Ca(2+)](m) and mitochondrial [NADH] ([NADH](m)) were simultaneously measured during increased pacing frequency. It was found that 53% of Rhod-2 was localized in mitochondria. Increased pacing frequency caused a fast, followed by a slow rise of the Rhod-2 signal, which could be attributed to an abrupt increase in resting cytosolic [Ca(2+)], and a more gradual rise of [Ca(2+)](m), respectively. When the pacing frequency was increased from 0.25 to 2 Hz, the slow Rhod-2 component and the NADH signal increased by 18 and 11%, respectively. Based on a new calibration method, the 18% increase of the Rhod-2 signal was calculated to correspond to a 43% increase of [Ca(2+)](m). There was also a close temporal relationship between the rise (time constant approximately 25 s) and fall (time constant approximately 65 s) of [Ca(2+)](m) and [NADH](m) when the pacing frequency was increased and decreased, respectively, suggesting that increased workload and [Ca(2+)](c) cause increased [Ca(2+)](m) and consequently up-regulation of the NADH production rate.
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Affiliation(s)
- Rolf Brandes
- Novasite Pharmaceuticals, San Diego, California 92121, USA.
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33
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Abstract
1. This review is presented with the intent of illustrating the representative studies of functional and myocardial energetic consequences of hearts with postinfarction left ventricular (LV) remodelling or with concentric hypertrophy and diastolic LV dysfunction in porcine models. 2. Both eccentric and concentric cardiac hypertrophy are associated with the abnormal myocardial energetics that are most severe in hearts with congestive heart failure (CHF). Presently, these abnormalities cannot be satisfactorily explained to be the cause(s) of the dysfunction of failing hearts or cause the progress from compensated cardiac hypertrophy to CHF. 3. Mechanisms governing abnormal myocardial high-energy phosphate (HEP) metabolism in hearts with cardiac hypertrophy and CHF are unclear. Myocardial energy metabolism studies use both kinetic and thermodynamic models. The thermodynamic studies examine the myocardial steady state levels of high- and low-energy phosphate, which indicate myocardial energy state or phosphorylation potential that is defined by the ratio of [ATP]/([ADP][Pi]). The kinetics studies examine the reaction velocity that is regulated by: (i) quantity and activity of the key enzymes; (ii) the concentrations of all the substrates and products; and (iii) the Michaelis-Menten constants of each substrate of the reaction. 4. Significant alterations in myocardial concentrations of phosphocreatine (PCr), ATP and ADP, myocardial oxidative phosphorylation (OXPHOS) protein expression and substrate preference are found in hearts with postinfarction LV remodelling and CHF. However, to define a causal relationship is a different matter. 5. Future studies of animal models of LV hypertrophy or heart failure using gene manipulation may provide additional insights to answer the persisting question of whether limitations of ATP synthetic or transport capacities contribute to the pathogenesis of LV remodelling or failure.
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Affiliation(s)
- Jianyi Zhang
- Department of Medicine, University of Minnesota, Minneapolis, Minnesota 55455, USA.
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Portman MA. The adenine nucleotide translocator: regulation and function during myocardial development and hypertrophy. Clin Exp Pharmacol Physiol 2002; 29:334-8. [PMID: 11985546 DOI: 10.1046/j.1440-1681.2002.03654.x] [Citation(s) in RCA: 17] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022]
Abstract
1. The present review focuses on the adenine nucleotide translocator (ANT), which facilitates exchange of cytosolic ADP for mitochondrial ATP. This protein serves a central role in regulating cellular oxidative capacity. 2. The ANT, a nuclear-encoded mitochondrial protein, is developmentally regulated and, thus, accumulates within the mitochondrial membrane during maturation. 3. Accumulation of ANT parallels changes in kinetics of myocardial respiration determined from 31P magnetic resonance spectroscopy studies. 4. Thyroid hormone modulates developmental transitions in ANT content, as well as respiratory control patterns. These transitions are linked to quantitative ANT changes, not to alterations in functionality at individual exchanger sites. 5. Developmental programming for ANT and parallel alterations in oxidative phosphorylation kinetics are relevant to the heart, which exhibits remodelling in response to pathological processes. Maladaptive hearts exhibiting ANT deficits demonstrate ADP-dependent respiratory kinetics similar to the newborn heart. Thus, ANT deficits and alterations in mitochondrial respiratory function may contribute to the pathogenesis of myocardial remodelling and heart failure.
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Affiliation(s)
- Michael A Portman
- Division of Cardiology, Department of Pediatrics, University of Washington School of Medicine and Children's Hospital and Medical Center, Seattle, Washington, USA.
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35
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Gnaiger E. Bioenergetics at low oxygen: dependence of respiration and phosphorylation on oxygen and adenosine diphosphate supply. RESPIRATION PHYSIOLOGY 2001; 128:277-97. [PMID: 11718759 DOI: 10.1016/s0034-5687(01)00307-3] [Citation(s) in RCA: 197] [Impact Index Per Article: 8.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/21/2022]
Abstract
Oxygen limitation is generally considered as impairment of mitochondrial respiration under hypoxia and ischemia. Low intracellular oxygen levels under normoxia, however, imply mild oxygen limitation, provide protection from oxidative stress, and result from economical strategies for oxygen transport through the respiratory cascade to cytochrome c oxidase. Both perspectives relate to the critical oxygen pressure, which inhibits mitochondrial respiration. Based on methodological considerations of oxygen kinetics and a presentation of high-resolution respirometry, mitochondrial oxygen affinities (1/P(50)) are reviewed with particular emphasis on the turnover effect under control of adenosine diphosphate ADP concentration, which increases the P(50) in active states. ADP/O(2) flux ratios are high even under severe oxygen limitation, as demonstrated by calorespirometry. Oxygen limitation reduces the uncoupled respiration observed under control by ADP, as shown by relationships derived between ADP/O(2) flux ratios, respiratory control ratios, and ADP kinetics. Bioenergetics at low oxygen versus oxidative stress must be considered in the context of limitation of maximum aerobic activity, ischemia-reperfusion injury, mitochondrial signalling to apoptosis, and mitochondrial theories of ageing.
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Affiliation(s)
- E Gnaiger
- D. Swarovski Research Laboratory, Department of Transplant Surgery, University Hospital Innsbruck, Anichstrasse 35, 6020, Innsbruck, Austria.
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36
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Abstract
Phosphagens are phosphorylated guanidino compounds that are linked to energy state and ATP hydrolysis by corresponding phosphagen kinase reactions: phosphagen + MgADP + H(+) <--> guanidine acceptor + MgATP. Eight different phosphagens (and corresponding phosphagen kinases) are found in the animal kingdom distributed along distinct phylogenetic lines. By far, the creatine phosphate/creatine kinase (CP/CK) system, which is found in the vertebrates and is widely distributed throughout the lower chordates and invertebrates, is the most extensively studied phosphagen system. Phosphagen kinase reactions function in temporal ATP buffering, in regulating inorganic phosphate (Pi) levels, which impacts glycogenolysis and proton buffering, and in intracellular energy transport. Phosphagen kinase reactions show differences in thermodynamic poise, and the phosphagens themselves differ in terms of certain physical properties including intrinsic diffusivity. This review evaluates the distribution of phosphagen systems and tissue-specific expression of certain phosphagens in an evolutionary and functional context. The role of phosphagens in regulation of intracellular Pi levels likely evolved early. Thermodynamic poise of the phosphagen kinase reaction profoundly impacts this capacity. Furthermore, it is hypothesized that the capacity for intracellular targeting of CK evolved early as a means of facilitating energy transport in highly polarized cells and was subsequently exploited for temporal ATP buffering and dynamic roles in metabolic regulation in cells displaying high and variable rates of aerobic energy production.
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Affiliation(s)
- W R Ellington
- Department of Biological Science and Institute of Molecular Biophysics, Florida State University, Tallahassee, Florida 32306-4370, USA.
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37
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Kreutzer U, Mekhamer Y, Chung Y, Jue T. Oxygen supply and oxidative phosphorylation limitation in rat myocardium in situ. Am J Physiol Heart Circ Physiol 2001; 280:H2030-7. [PMID: 11299203 DOI: 10.1152/ajpheart.2001.280.5.h2030] [Citation(s) in RCA: 28] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/22/2022]
Abstract
The 1H-NMR signal of the proximal histidyl-N(delta)H of deoxymyoglobin is detectable in the in situ rat myocardium and can reflect the intracellular PO2. Under basal normoxic conditions, the cellular PO2 is sufficient to saturate myoglobin (Mb). No proximal histidyl signal of Mb is detectable. On ligation of the left anterior descending coronary artery, the Mb signal at 78 parts/million (ppm) appears, along with a peak shoulder assigned to the corresponding signal of Hb. During dopamine infusion up to 80 microg. kg(-1) x min(-1), both the heart rate-pressure product (RPP) and myocardial oxygen consumption (MVO2) increase by about a factor of 2. Coronary flow increases by 84%, and O2 extraction (arteriovenous O2 difference) rises by 31%. Despite the increased respiration and work, no deoxymyoglobin signal is detected, implying that the intracellular O2 level still saturates MbO2, well above the PO2 at 50% saturation of Mb. The phosphocreatine (PCr) level decreases, however, during dopamine stimulation, and the ratio of the change in P(i) over PCr (DeltaP(i)/PCr) increases by 0.19. Infusion of either pyruvate, as the primary substrate, or dichloroacetate, a pyruvate dehydrogenase activator, abolishes the change in DeltaP(i)/PCr. Intracellular O2 supply does not limit MVO2, and the role of ADP in regulating respiration in rat myocardium in vivo remains an open question.
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Affiliation(s)
- U Kreutzer
- Department of Biological Chemistry, University of California, Davis, California 95616-8635, USA
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38
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Will Y, Fischer KA, Horton RA, Kaetzel RS, Brown MK, Hedstrom O, Lieberman MW, Reed DJ. gamma-glutamyltranspeptidase-deficient knockout mice as a model to study the relationship between glutathione status, mitochondrial function, and cellular function. Hepatology 2000; 32:740-9. [PMID: 11003618 DOI: 10.1053/jhep.2000.17913] [Citation(s) in RCA: 47] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 12/07/2022]
Abstract
gamma-Glutamyltranspeptidase (GGT)-deficient mice (GGT(-/-)) display chronic glutathione (GSH) deficiency, growth retardation, and die at a young age (<20 weeks). Using livers from these mice, we investigated the relationship between GSH content, especially mitochondrial, and mitochondrial and cellular function. We found that the GSH content of isolated liver mitochondria was diminished by >/=50% in GGT(-/-) mice when compared with wild-type mice. Respiratory control ratios (RCRs) of GGT(-/-) mice liver mitochondria were </=60% those of wild-type mice primarily as a result of impaired state 3 respiration. Mitochondrial adenine nucleotide content was decreased by >/=40% in mitochondria obtained from GGT(-/-) mice. We observed a strong correlation between mitochondrial GSH content and RCRs. Even moderate decreases (<50%) correlated with adverse effects with respect to respiration. Electron microscopy revealed that livers from GGT(-/-) knockout mice were deprived of fat and glycogen, and swollen mitochondria were observed in animals that were severely deprived of GSH. Thus, GGT(-/-) mice exhibit a loss of GSH homeostasis and impaired oxidative phosphorylation, which may be related to the rate of adenosine triphosphate (ATP) formation and subsequently leads to progressive liver injury, which characterizes the diseased state. We also found that supplementation of GGT(-/-) mice with N-acetylcysteine (NAC) partially restored liver GSH, but fully restored mitochondrial GSH and respiratory function. Electron microscopy revealed that the livers of NAC-supplemented GGT(-/-) mice contained fat and glycogen; however, slightly enlarged mitochondria were found in some livers. NAC supplementation did not have any beneficial effect on the parameters examined in wild-type mice.
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Affiliation(s)
- Y Will
- Department of Biochemistry and Biophysics, Oregon State University, Corvallis, OR, USA.
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39
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Gnaiger E, Méndez G, Hand SC. High phosphorylation efficiency and depression of uncoupled respiration in mitochondria under hypoxia. Proc Natl Acad Sci U S A 2000; 97:11080-5. [PMID: 11005877 PMCID: PMC27151 DOI: 10.1073/pnas.97.20.11080] [Citation(s) in RCA: 187] [Impact Index Per Article: 7.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/10/2000] [Indexed: 11/18/2022] Open
Abstract
Mitochondria are confronted with low oxygen levels in the microenvironment within tissues; yet, isolated mitochondria are routinely studied under air-saturated conditions that are effectively hyperoxic, increase oxidative stress, and may impair mitochondrial function. Under hypoxia, on the other hand, respiration and ATP supply are restricted. Under these conditions of oxygen limitation, any compromise in the coupling of oxidative phosphorylation to oxygen consumption could accentuate ATP depletion, leading to metabolic failure. To address this issue, we have developed the approach of oxygen-injection microcalorimetry and ADP-injection respirometry for evaluating mitochondrial function at limiting oxygen supply. Whereas phosphorylation efficiency drops during ADP limitation at high oxygen levels, we show here that oxidative phosphorylation is more efficient at low oxygen than at air saturation, as indicated by higher ratios of ADP flux to total oxygen flux at identical submaximal rates of ATP synthesis. At low oxygen, the proton leak and uncoupled respiration are depressed, thus reducing maintenance energy expenditure. This indicates the importance of low intracellular oxygen levels in avoiding oxidative stress and protecting bioenergetic efficiency.
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Affiliation(s)
- E Gnaiger
- Department of Transplant Surgery, D. Swarovski Research Laboratory, University Hospital Innsbruck, Anichstrasse 35, A-6020 Innsbruck, Austria.
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40
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Affiliation(s)
- M A Portman
- Division of Cardiology, University of Washington, and Children's Hospital and Regional Medical Center, Seattle, Washington 98105-0371, USA
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41
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Chung Y, Sharman R, Carlsen R, Unger SW, Larson D, Jue T. Metabolic fluctuation during a muscle contraction cycle. THE AMERICAN JOURNAL OF PHYSIOLOGY 1998; 274:C846-52. [PMID: 9530118 DOI: 10.1152/ajpcell.1998.274.3.c846] [Citation(s) in RCA: 59] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 02/07/2023]
Abstract
Gated 31P-nuclear magnetic resonance followed the metabolic fluctuation in rat gastrocnemius muscle during a contraction cycle. Within 16 ms after stimulation, the phosphocreatine (PCr) level drops 11.3% from its reference state. The PCr minimum corresponds closely to the time of maximum force contraction. Pi increases stoichiometrically, while ATP remains constant. During a twitch, PCr hydrolysis produces 3.1 mumol ATP/g tissue, which is substantially higher than the reported 0.3 mumol ATP.twitch-1.g tissue-1 derived from steady-state experiments. The results reveal that a substantial energy fluctuation accompanies a muscle twitch.
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Affiliation(s)
- Y Chung
- Department of Biological Chemistry, University of California, Davis 95616-8635, USA
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42
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Portman MA, Xiao Y, Song Y, Ning XH. Expression of adenine nucleotide translocator parallels maturation of respiratory control in heart in vivo. THE AMERICAN JOURNAL OF PHYSIOLOGY 1997; 273:H1977-83. [PMID: 9362269 DOI: 10.1152/ajpheart.1997.273.4.h1977] [Citation(s) in RCA: 14] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 02/05/2023]
Abstract
Changes in the relationship between myocardial high-energy phosphates and oxygen consumption in vivo occur during development, implying that the mode of respiratory control undergoes maturation. We hypothesized that these maturational changes in sheep heart are paralleled by alterations in the adenine nucleotide translocator (ANT), which are in turn related to changes in the expression of this gene. Increases in myocardial oxygen consumption (MVO2) were induced by epinephrine infusion in newborn (0-32 h, n = 6) and mature sheep (30-32 days, n = 6), and high-energy phosphates were monitored with 31P nuclear magnetic resonance. Western blot analyses for the ANT1 and the beta-subunit of F1-adenosinetriphosphatase (ATPase) were performed in these hearts and additional (n = 9 total per group) as well as in fetal hearts (130-132 days of gestation, n = 5). Northern blot analyses were performed to assess for changes in steady-state RNA transcripts for these two genes. Kinetic analyses for the 31P spectra data revealed that the ADP-MVO2 relationship for the newborns conformed to a Michaelis-Menten model but that the mature data did not conform to first- or second-order kinetic control of respiration through ANT. Maturation from fetal to mature was accompanied by a 2.5-fold increase in ANT protein (by Western blot), with no detectable change in beta-F1-ATPase. Northern blot data show that steady-state mRNA levels for ANT and beta-F1-ATPase increased approximately 2.5-fold from fetal to mature. These data indicate that 1) respiratory control pattern in the newborn is consistent with a kinetic type regulation through ANT, 2) maturational decreases in control through ANT are paralleled by specific increases in ANT content, and 3) regulation of these changes in ANT may be related to increases in steady-state transcript levels for its gene.
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Affiliation(s)
- M A Portman
- Department of Pediatrics, University of Washington School of Medicine and Children's Hospital and Medical Center, Seattle 98195-6320, USA
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43
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Berthon P, Van der Veer M, Denis C, Freyssenet D. L-carnitine stimulation of mitochondrial oxidative phosphorylation rate in isolated rat skeletal muscle mitochondria. COMPARATIVE BIOCHEMISTRY AND PHYSIOLOGY. PART A, PHYSIOLOGY 1997; 117:141-5. [PMID: 9185342 DOI: 10.1016/s0300-9629(96)00239-3] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 02/04/2023]
Abstract
L-carnitine effects on mitochondrial adenosine triphosphate (ATP) production rate were investigated in mitochondria isolated from rat extensor digitorum longus (EDL) muscle. Kinetic parameters, apparent Michaelis constant for free adenosine diphosphate (ADP) (K(m)) and apparent maximal ATP production rate (Vmax), were determined in absence and presence of L-carnitine. Although the K(m) remained unchanged in response to L-carnitine addition when pyruvate + malate was oxidized, the affinity of isolated mitochondria towards ADP was decreased when pyruvate + palmitoylcarnitine + malate was used as substrate. As a result of L-carnitine addition, a slight non-significant (P < 0.07) increase in Vmax was observed with pyruvate + malate while the increase reached the level of significance with pyruvate + palmitoylcarnitine + malate. Moreover, a positive correlation was obtained when mitochondrial ATP production rate was plotted against the difference between values measured with and without L-carnitine. Our data suggest that addition of L-carnitine to isolated rat skeletal muscle mitochondria can stimulate mitochondrial oxidative phosphorylation rate under conditions where the inhibitory effect of acetyl-CoA accumulation on pyruvate dehydrogenase complex activity is optimized. A change in the control of mitochondrial ATP flux by pyruvate dehydrogenase (PDH) complex might also occur with increasing mitochondrial ATP production rate, reinforcing the L-carnitine effects.
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Affiliation(s)
- P Berthon
- Laboratoire de Physiologie-GIP Exercice, Faculté de Médecine Jacques Lisfranc, Université Jean Monnet, Saint-Etienne, France
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44
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Meyer RA, Foley JM. Cellular Processes Integrating the Metabolic Response to Exercise. Compr Physiol 1996. [DOI: 10.1002/cphy.cp120118] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/05/2022]
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45
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Jeneson JA, Wiseman RW, Westerhoff HV, Kushmerick MJ. The signal transduction function for oxidative phosphorylation is at least second order in ADP. J Biol Chem 1996; 271:27995-8. [PMID: 8910406 DOI: 10.1074/jbc.271.45.27995] [Citation(s) in RCA: 125] [Impact Index Per Article: 4.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/03/2023] Open
Abstract
To maintain ATP constant in the cell, mitochondria must sense cellular ATP utilization and transduce this demand to F0-F1-ATPase. In spite of a considerable research effort over the past three decades, no combination of signal(s) and kinetic function has emerged with the power to explain ATP homeostasis in all mammalian cells. We studied this signal transduction problem in intact human muscle using 31P NMR spectroscopy. We find that the apparent kinetic order of the transduction function of the signal cytosolic ADP concentration ([ADP]) is at least second order and not first order as has been assumed. We show that amplified mitochondrial sensitivity to cytosolic [ADP] harmonizes with in vitro kinetics of [ADP] stimulation of respiration and explains ATP homeostasis also in mouse liver and canine heart. This result may well be generalizable to all mammalian cells.
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Affiliation(s)
- J A Jeneson
- NMR Research Laboratory, Department of Radiology, University of Washington School of Medicine, Seattle, Washington 98195, USA.
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Weiss RG, de Albuquerque CP, Vandegaer K, Chacko VP, Gerstenblith G. Attenuated glycogenolysis reduces glycolytic catabolite accumulation during ischemia in preconditioned rat hearts. Circ Res 1996; 79:435-46. [PMID: 8781477 DOI: 10.1161/01.res.79.3.435] [Citation(s) in RCA: 36] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 02/02/2023]
Abstract
Prior transient episodes of ischemia ("ischemic preconditioning") reduce lactate accumulation and attenuate acidosis during a subsequent prolonged ischemic insult. The mechanisms responsible for attenuated glycolytic catabolite accumulation have not been established but may include earlier exhaustion of glycogen stores, slowed glycogenolysis before complete glycogen depletion, and/or inhibition of glycolysis. Simultaneous repeated measures of myocardial glycogen and the rates of glycolysis, glycogenolysis, glucose utilization, and glycolytic ATP production were obtained during total ischemia by 13C nuclear magnetic resonance spectroscopy in control and ischemia-preconditioned isolated rat hearts. Both [13C]glycolytic and [13C]glycogenolytic rates were significantly lower during total ischemia in preconditioned compared with control hearts (0.77 +/- 0.04 versus 1.06 +/- 0.06 mumol/min per gram wet weight [P < .01] for glycolysis and 0.15 +/- 0.07 versus 0.78 +/- 0.12 mumol/ min per gram wet weight [P < .001] for glycogenolysis, respectively, at 2.5 minutes of ischemia). Slowed glycolysis was present even during the early minutes of ischemia, when significant amounts of available [13C]glycogen were still present. Importantly, the reduction in the rate of glycogenolysis was larger and out of proportion to the reduction in glycolysis and occurred despite an increase in glucose utilization in preconditioned hearts (2.23 +/- 0.15 versus 1.5 +/- 0.10 mumol/min per gram wet weight at 1.25 minutes, P < .01). During early ischemia, conversion of glycogen phosphorylase to the a or "active" form was less in preconditioned than in control hearts (29.1 +/- 2.6% versus 41.2 +/- 9.8%, respectively; P < .05). Taken together, these findings demonstrate that ischemic preconditioning significantly depresses glycolytic catabolite accumulation during sustained ischemia not by more severe glycolytic inhibition or exhaustion of glycogen stores but by depressed glycogenolysis from the onset of ischemia.
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Affiliation(s)
- R G Weiss
- Peter Belfer Laboratory, Johns Hopkins Hospital, Baltimore, Md. 21287-6568, USA.
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De Stefano N, Argov Z, Matthews PM, Karpati G, Arnold DL. Impairment of muscle mitochondrial oxidative metabolism in McArdles's disease. Muscle Nerve 1996; 19:764-9. [PMID: 8609928 DOI: 10.1002/(sici)1097-4598(199606)19:6<764::aid-mus12>3.0.co;2-l] [Citation(s) in RCA: 40] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/31/2023]
Abstract
Impairment of muscle glycogenolysis in McArdle's disease (myophosphorylase deficiency) leads to exercise intolerance and exercise-induced myalgia. The pathophysiology of these symptoms is not entirely clear. We used phosphorus magnetic resonance spectroscopy to measure muscle phosphate metabolite concentrations and intracellular pH during brief ischemic exercise and in the period of aerobic metabolic recovery after exercise, with special attention to cytoplasmic adenosine 5'-diphosphate (ADP). In 5 patients with McArdle's disease, calculated muscle intracellular ADP concentrations at the beginning of recovery were higher than in normal control subjects (70-425 mmol/L, control mean: 73 +/- 40 mmol/L, P < 0.05). The half-time for intracellular ADP recovery after exercise, an index of maximal mitochondrial oxidative phosphorylation, was 0.16 +/- 0.07 in normal controls and was independent of metabolic state or intracellular pH. ADP recoveries were abnormally slow in all patients with McArdle's disease (range: 0.32-0.83 min, mean = 0.2 min, P < 0.0001). These results are indicative of a limitation in the rate of oxidative phosphorylation in muscle of patients with McArdle's disease, most likely due to impaired substrate delivery to mitochondria. This impairment of mitochondrial function may contribute to the exercise-related symptoms in McArdle's disease.
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Affiliation(s)
- N De Stefano
- Department of Neurology and Neurosurgery, Montreal Neurological Institute and Hospital, Quebec, Canada
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Jeneson JA, Westerhoff HV, Brown TR, Van Echteld CJ, Berger R. Quasi-linear relationship between Gibbs free energy of ATP hydrolysis and power output in human forearm muscle. THE AMERICAN JOURNAL OF PHYSIOLOGY 1995; 268:C1474-84. [PMID: 7611368 DOI: 10.1152/ajpcell.1995.268.6.c1474] [Citation(s) in RCA: 63] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 01/26/2023]
Abstract
The postulated strictly linear descriptions of the rate dependence of oxidative phosphorylation in skeletal muscle on the free energy of ATP hydrolysis (delta GP) over the range of physiological steady states fail to harmonize with reported findings of identical basal respiration rates in mammalian muscles at different delta GP values. The relevance of an extension of the strictly linear description to a description deriving from enzyme kinetics that predicts a sigmoidal dependence was investigated in human finger flexor muscle using 31P-nuclear magnetic resonance spectroscopy. At constant pH 7.0, the experimental variation of adenine nucleotide concentrations with power output, which reflects the rate of oxidative phosphorylation, was compared with predictions by various formulations of adenine nucleotide control of respiration. The quasi-linear sigmoidal description was found to be statistically equivalent but physiologically superior to the strictly linear description. The predicted maximal oxidatively sustained steady-state power output and rate-dependent sensitivity of respiration to changes in delta GP were in agreement both with theoretical considerations and with experimental observations in the present study and other studies of intact mammalian skeletal muscle.
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Affiliation(s)
- J A Jeneson
- Laboratory for Metabolic Diseases, University Children's Hospital, Utrecht, The Netherlands
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Westerhoff HV, van Echteld CJ, Jeneson JA. On the expected relationship between Gibbs energy of ATP hydrolysis and muscle performance. Biophys Chem 1995; 54:137-42. [PMID: 7756565 DOI: 10.1016/0301-4622(94)00129-8] [Citation(s) in RCA: 25] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/27/2023]
Abstract
Allowing for creatine kinase buffering of changes in adenine nucleotide concentrations, and the known relationship between muscle performance and rate of ATP hydrolysis by myosin, the variation of exerted force with intracellular Gibbs energy of ATP hydrolysis is calculated for voluntary muscle contraction. The resulting relationship is sigmoidal, most of the operating range coinciding with the quasi-linear range around the inflection point. Finger-flexor muscle magnetic resonance spectroscopy data are shown to be in line with this prediction.
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Affiliation(s)
- H V Westerhoff
- E.C. Slater Institute, University of Amsterdam, Netherlands
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Hepatic High Energy Phosphate Metabolism in Transgenic Livers Expressing Creatine Kinase as Revealed by 31P NMR. ACTA ACUST UNITED AC 1995. [DOI: 10.1016/s1569-2558(08)60253-2] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register]
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