Westerlund 2017 Pediatr Res
| Westerlund E, Marelsson SE, Ehinger JK, Sjövall F, Morota S, Åsander Frostner E, Oldfors A, Darin N, Lundgren J, Hansson MJ, Fellman V, Elmér E (2017) Oxygen consumption in platelets as an adjunct diagnostic method for pediatric mitochondrial disease. Pediatr Res 83:455-65. |
Westerlund E, Marelsson SE, Ehinger JK, Sjoevall F, Morota S, Aasander Frostner E, Oldfors A, Darin N, Lundgren J, Hansson MJ, Fellman V, Elmer E (2017) Pediatr Res
Abstract: Diagnosing mitochondrial disease (MD) is a challenge. In addition to genetic analyses, clinical practice is to perform invasive procedures such as muscle biopsy for biochemical and histochemical analyses. Blood cell respirometry is rapid and noninvasive. Our aim was to explore its possible role in diagnosing MD.
Blood samples were collected from 113 pediatric patients, for whom MD was a differential diagnosis. A respiratory analysis model based on ratios (independent of mitochondrial specific content) was derived from a group of healthy controls and tested on the patients. The diagnostic accuracy of platelet respirometry was evaluated against routine diagnostic investigation.
MD prevalence in the cohort was 16%. A ratio based on the respiratory response to adenosine diphosphate in the presence of complex I substrates had 96% specificity for disease and a positive likelihood ratio of 5.3. None of the individual ratios had sensitivity above 50%, but a combined model had 72% sensitivity.
Normal findings of platelet respirometry are not able to rule out MD, but pathological results make the diagnosis more likely and could strengthen the clinical decision to perform further invasive analyses. Our results encourage further study into the role of blood respirometry as an adjunct diagnostic tool for MD.
• Bioblast editor: Plangger M
Coupling control and the Q-junction
- Mitochondrial coupling control states are measured without simultaneous change of a selected pathway control state, i.e. coupling control is separated from pathway control. Biochemical coupling efficiencies (E-L coupling efficiencies) and P-L coupling efficiencies are, therefore, studied at a defined pathway control state that must not change between measurement of LEAK respiration L, OXPHOS capacity P, and electron transfer capacity E.
- A physiologically relevant pathway control state for partial reconstitution of TCA cycle function is obtained by supply of NADH-linked substrates (e.g. pyruvate&malate PM; N-pathway) in combination with succinate (S; S-pathway), supporting convergent electron transfer through Complexes I and II into the Q-junction (NS-pathway). OXPHOS- and ET-capacities are higher in the combined NS-pathway than in the separate N- or S-pathway (Gnaiger 2020). Is the NS-pathway control state appropriate for the analysis of coupling control?
- Partial additivity in OXPHOS capacity NSP or ET capacity NSE implies that there is competition between the N- and S-pathway, when the NS-pathway capacity is less than the arithmetic sum of the constituent pathway capacities. In mitochondria with lower OXPHOS than ET capacity (P<E; when the phosphorylation system is limiting), the competition in NSE is increasingly pronounced in NSP, and when respiration is further reduced by complete inhibition of the phosphorylation system (e.g. by oligomycin), competition between the N- and S-pathways is maximal in LEAK respiration. Different levels of competition imply that the ratio of the effective N- and S-pathway in the NS-pathway state may shift to the extent that the dominant pathway may fully outcompete the other in the LEAK state. Convergent electron input into the Q-junction in NSE, therefore, may shift to single electron input through either the dominant N- or S-pathway in NSL, which then would effectively correspond to either NL or SL. This has deep implications on LEAK respiration, since the N-pathway has three coupling sites (H+ pumps: CI, CIII, CIV) with a correspondingly higher H+/O2 ratio compared to the S-pathway with two coupling sites (H+ pumps: CIII, CIV). A higher rate of the proton leak is implied when measuring the same rate of LEAK respiration in NL than when observing an identical oxygen consumption rate in SL.
- When inhibiting O2 consumption by oligomycin in the NS-pathway state, the relative contribution of the N- and S-pathways to LEAK respiration is not known. By subsequent uncoupler titrations, the relative contribution of these pathways is likely to change, thus obtaining an undefined combination of pathway control and coupling control. In conclusion, the NS-pathway state is not appropriate for studying coupling control. Coupling control is best studied in the separate N- or S-pathway (Gnaiger et al 2000; 2015).
- Gnaiger E (2020) Mitochondrial pathways and respiratory control. An introduction to OXPHOS analysis. 5th ed. Bioenerg Commun 2020.2. https://doi.org/10.26124/bec:2020-0002
- Gnaiger E, Boushel R, Søndergaard H, Munch-Andersen T, Damsgaard R, Hagen C, Díez-Sánchez C, Ara I, Wright-Paradis C, Schrauwen P, Hesselink M, Calbet JAL, Christiansen M, Helge JW, Saltin B (2015) Mitochondrial coupling and capacity of oxidative phosphorylation in skeletal muscle of Inuit and caucasians in the arctic winter. https://doi.org/10.1111/sms.12612
- Gnaiger E, Méndez G, Hand SC (2000) High phosphorylation efficiency and depression of uncoupled respiration in mitochondria under hypoxia. Proc Natl Acad Sci U S A 97:11080-5. https://doi.org/10.1073/pnas.97.20.11080
Labels: MiParea: Respiration, Instruments;methods, mt-Medicine, Patients
Stress:Mitochondrial disease Organism: Human Tissue;cell: Blood cells, Platelet Preparation: Permeabilized cells, Intact cells
Coupling state: LEAK, ROUTINE, OXPHOS, ET
Pathway: N, S, CIV, NS, ROX
HRR: Oxygraph-2k
Labels, 2018-10, MitoEAGLEPublication, JP, SE, MitoEAGLE blood cells reviews
