Mitochondrial Sensitivity to Submaximal [ADP] Following Bed Rest: A Novel Two‐Phase Approach Associated With Fibre Types
ABSTRACT Background We recently demonstrated that following a 10‐day exposure to inactivity/simulated microgravity impairments of oxidative metabolism were located ‘upstream’ of mitochondrial function, as evaluated by maximal ADP‐stimulated mitochondrial respiration (JO2max) determined ex vivo. The...
Saved in:
| Main Authors: | , , , , , , , , , , , , , , |
|---|---|
| Format: | Article |
| Language: | English |
| Published: |
Wiley
2025-06-01
|
| Series: | Journal of Cachexia, Sarcopenia and Muscle |
| Subjects: | |
| Online Access: | https://doi.org/10.1002/jcsm.13775 |
| Tags: |
Add Tag
No Tags, Be the first to tag this record!
|
| _version_ | 1849683626214555648 |
|---|---|
| author | Lucrezia Zuccarelli Maria De Martino Antonio Filippi Alice E. Knapton Benjamin D. Thackray Giovanni Baldassarre Boštjan Šimunič Rado Pišot Giuseppe Sirago Elena Monti Marco Narici Miriam Isola Andrew J. Murray Giovanna Lippe Bruno Grassi |
| author_facet | Lucrezia Zuccarelli Maria De Martino Antonio Filippi Alice E. Knapton Benjamin D. Thackray Giovanni Baldassarre Boštjan Šimunič Rado Pišot Giuseppe Sirago Elena Monti Marco Narici Miriam Isola Andrew J. Murray Giovanna Lippe Bruno Grassi |
| author_sort | Lucrezia Zuccarelli |
| collection | DOAJ |
| description | ABSTRACT Background We recently demonstrated that following a 10‐day exposure to inactivity/simulated microgravity impairments of oxidative metabolism were located ‘upstream’ of mitochondrial function, as evaluated by maximal ADP‐stimulated mitochondrial respiration (JO2max) determined ex vivo. The aim of this study was to evaluate mitochondrial sensitivity to submaximal [ADP] by an alternative approach aimed at identifying responses associated with fibre type composition. Methods Isolated permeabilized vastus lateralis fibres were analysed by high‐resolution respirometry in 9 young males before and after a 10‐day horizontal bed rest. Eleven submaximal titrations of ADP (from 12.5 to 10 000 μM) were utilized to assess complex I + II‐linked ADP sensitivity. We applied to JO2 versus [ADP] data a traditional Michaelis–Menten kinetics equation, with the calculation of the apparent Km and maximal respiration (Vmax), and two ‘sequential’ hyperbolic equations, yielding two Km and Vmax values. The two‐hyperbolic equations were solved and the [ADP] value corresponding to 50% of JO2max was calculated. Isoform expression of myosin heavy chains (MyHC) 1, 2A and 2X was also determined. Control experiments were also carried out on rat skeletal muscle samples with different percentages of MyHC isoforms. Results The two hyperbolic equations provided an alternative fitting of data and identified two distinct phases of the JO2 versus [ADP] response: a first phase characterized by low Vmax (Vmax1, 28 ± 10 pmol s−1 mg−1) and apparent Km (Km1, 62 ± 54 μM) and a second phase characterized by higher Vmax (Vmax2, 61 ± 16 pmol s−1 mg−1) and Km (Km2, 1784 ± 833 μM). Data were confirmed in control experiments carried out in rat muscle samples with different percentages of MyHC isoforms. Correlation and receiver operating characteristics analyses suggest that the two phases of the response were related to the % of MyHC isoforms. Conclusions A novel mathematical approach (two sequential hyperbolic functions) for the fitting of JO2 versus [ADP] data obtained by high‐resolution respirometry on permeabilized skeletal muscle fibres, obtained in humans and rats, provided an alternative fitting of the experimental data compared to the traditional Michaelis–Menten kinetics equation. This alternative model allowed the identification of two distinct phases in the responses, which were related to fibre type composition. A first phase, characterized by low apparent Km and Vmax values, was correlated with the percentage of less oxidative (Type 2A + 2X) MyHC isoforms. A second phase, characterized by high apparent Km and Vmax, was related to more oxidative (Type 1) MyHC isoforms. |
| format | Article |
| id | doaj-art-00b2ae4ead844c3bb2c197d30e408830 |
| institution | DOAJ |
| issn | 2190-5991 2190-6009 |
| language | English |
| publishDate | 2025-06-01 |
| publisher | Wiley |
| record_format | Article |
| series | Journal of Cachexia, Sarcopenia and Muscle |
| spelling | doaj-art-00b2ae4ead844c3bb2c197d30e4088302025-08-20T03:23:47ZengWileyJournal of Cachexia, Sarcopenia and Muscle2190-59912190-60092025-06-01163n/an/a10.1002/jcsm.13775Mitochondrial Sensitivity to Submaximal [ADP] Following Bed Rest: A Novel Two‐Phase Approach Associated With Fibre TypesLucrezia Zuccarelli0Maria De Martino1Antonio Filippi2Alice E. Knapton3Benjamin D. Thackray4Giovanni Baldassarre5Boštjan Šimunič6Rado Pišot7Giuseppe Sirago8Elena Monti9Marco Narici10Miriam Isola11Andrew J. Murray12Giovanna Lippe13Bruno Grassi14Department of Medicine University of Udine Udine ItalyDepartment of Medicine University of Udine Udine ItalyDepartment of Medicine University of Udine Udine ItalyDepartment of Physiology, Neuroscience and Development University of Cambridge Cambridge UKDepartment of Physiology, Neuroscience and Development University of Cambridge Cambridge UKDepartment of Medicine University of Udine Udine ItalyInstitute of Kinesiology Research Science and Research Centre Koper SloveniaInstitute of Kinesiology Research Science and Research Centre Koper SloveniaDepartment of Biomedical Sciences University of Padova Padova ItalyDepartment of Biomedical Sciences University of Padova Padova ItalyDepartment of Biomedical Sciences University of Padova Padova ItalyDepartment of Medicine University of Udine Udine ItalyDepartment of Physiology, Neuroscience and Development University of Cambridge Cambridge UKDepartment of Medicine University of Udine Udine ItalyDepartment of Medicine University of Udine Udine ItalyABSTRACT Background We recently demonstrated that following a 10‐day exposure to inactivity/simulated microgravity impairments of oxidative metabolism were located ‘upstream’ of mitochondrial function, as evaluated by maximal ADP‐stimulated mitochondrial respiration (JO2max) determined ex vivo. The aim of this study was to evaluate mitochondrial sensitivity to submaximal [ADP] by an alternative approach aimed at identifying responses associated with fibre type composition. Methods Isolated permeabilized vastus lateralis fibres were analysed by high‐resolution respirometry in 9 young males before and after a 10‐day horizontal bed rest. Eleven submaximal titrations of ADP (from 12.5 to 10 000 μM) were utilized to assess complex I + II‐linked ADP sensitivity. We applied to JO2 versus [ADP] data a traditional Michaelis–Menten kinetics equation, with the calculation of the apparent Km and maximal respiration (Vmax), and two ‘sequential’ hyperbolic equations, yielding two Km and Vmax values. The two‐hyperbolic equations were solved and the [ADP] value corresponding to 50% of JO2max was calculated. Isoform expression of myosin heavy chains (MyHC) 1, 2A and 2X was also determined. Control experiments were also carried out on rat skeletal muscle samples with different percentages of MyHC isoforms. Results The two hyperbolic equations provided an alternative fitting of data and identified two distinct phases of the JO2 versus [ADP] response: a first phase characterized by low Vmax (Vmax1, 28 ± 10 pmol s−1 mg−1) and apparent Km (Km1, 62 ± 54 μM) and a second phase characterized by higher Vmax (Vmax2, 61 ± 16 pmol s−1 mg−1) and Km (Km2, 1784 ± 833 μM). Data were confirmed in control experiments carried out in rat muscle samples with different percentages of MyHC isoforms. Correlation and receiver operating characteristics analyses suggest that the two phases of the response were related to the % of MyHC isoforms. Conclusions A novel mathematical approach (two sequential hyperbolic functions) for the fitting of JO2 versus [ADP] data obtained by high‐resolution respirometry on permeabilized skeletal muscle fibres, obtained in humans and rats, provided an alternative fitting of the experimental data compared to the traditional Michaelis–Menten kinetics equation. This alternative model allowed the identification of two distinct phases in the responses, which were related to fibre type composition. A first phase, characterized by low apparent Km and Vmax values, was correlated with the percentage of less oxidative (Type 2A + 2X) MyHC isoforms. A second phase, characterized by high apparent Km and Vmax, was related to more oxidative (Type 1) MyHC isoforms.https://doi.org/10.1002/jcsm.13775ADPbed restmitochondrial sensitivitymyosin heavy chainsskeletal muscle mitochondria |
| spellingShingle | Lucrezia Zuccarelli Maria De Martino Antonio Filippi Alice E. Knapton Benjamin D. Thackray Giovanni Baldassarre Boštjan Šimunič Rado Pišot Giuseppe Sirago Elena Monti Marco Narici Miriam Isola Andrew J. Murray Giovanna Lippe Bruno Grassi Mitochondrial Sensitivity to Submaximal [ADP] Following Bed Rest: A Novel Two‐Phase Approach Associated With Fibre Types Journal of Cachexia, Sarcopenia and Muscle ADP bed rest mitochondrial sensitivity myosin heavy chains skeletal muscle mitochondria |
| title | Mitochondrial Sensitivity to Submaximal [ADP] Following Bed Rest: A Novel Two‐Phase Approach Associated With Fibre Types |
| title_full | Mitochondrial Sensitivity to Submaximal [ADP] Following Bed Rest: A Novel Two‐Phase Approach Associated With Fibre Types |
| title_fullStr | Mitochondrial Sensitivity to Submaximal [ADP] Following Bed Rest: A Novel Two‐Phase Approach Associated With Fibre Types |
| title_full_unstemmed | Mitochondrial Sensitivity to Submaximal [ADP] Following Bed Rest: A Novel Two‐Phase Approach Associated With Fibre Types |
| title_short | Mitochondrial Sensitivity to Submaximal [ADP] Following Bed Rest: A Novel Two‐Phase Approach Associated With Fibre Types |
| title_sort | mitochondrial sensitivity to submaximal adp following bed rest a novel two phase approach associated with fibre types |
| topic | ADP bed rest mitochondrial sensitivity myosin heavy chains skeletal muscle mitochondria |
| url | https://doi.org/10.1002/jcsm.13775 |
| work_keys_str_mv | AT lucreziazuccarelli mitochondrialsensitivitytosubmaximaladpfollowingbedrestanoveltwophaseapproachassociatedwithfibretypes AT mariademartino mitochondrialsensitivitytosubmaximaladpfollowingbedrestanoveltwophaseapproachassociatedwithfibretypes AT antoniofilippi mitochondrialsensitivitytosubmaximaladpfollowingbedrestanoveltwophaseapproachassociatedwithfibretypes AT aliceeknapton mitochondrialsensitivitytosubmaximaladpfollowingbedrestanoveltwophaseapproachassociatedwithfibretypes AT benjamindthackray mitochondrialsensitivitytosubmaximaladpfollowingbedrestanoveltwophaseapproachassociatedwithfibretypes AT giovannibaldassarre mitochondrialsensitivitytosubmaximaladpfollowingbedrestanoveltwophaseapproachassociatedwithfibretypes AT bostjansimunic mitochondrialsensitivitytosubmaximaladpfollowingbedrestanoveltwophaseapproachassociatedwithfibretypes AT radopisot mitochondrialsensitivitytosubmaximaladpfollowingbedrestanoveltwophaseapproachassociatedwithfibretypes AT giuseppesirago mitochondrialsensitivitytosubmaximaladpfollowingbedrestanoveltwophaseapproachassociatedwithfibretypes AT elenamonti mitochondrialsensitivitytosubmaximaladpfollowingbedrestanoveltwophaseapproachassociatedwithfibretypes AT marconarici mitochondrialsensitivitytosubmaximaladpfollowingbedrestanoveltwophaseapproachassociatedwithfibretypes AT miriamisola mitochondrialsensitivitytosubmaximaladpfollowingbedrestanoveltwophaseapproachassociatedwithfibretypes AT andrewjmurray mitochondrialsensitivitytosubmaximaladpfollowingbedrestanoveltwophaseapproachassociatedwithfibretypes AT giovannalippe mitochondrialsensitivitytosubmaximaladpfollowingbedrestanoveltwophaseapproachassociatedwithfibretypes AT brunograssi mitochondrialsensitivitytosubmaximaladpfollowingbedrestanoveltwophaseapproachassociatedwithfibretypes |