Comparing Electron Leak in Vertebrate Muscle Mitochondria

Abstract

Mitochondrial electron transfer for oxidative ATP regeneration is linked to reactive oxygen species (ROS) production in aerobic eukaryotic cells. Because they can contribute to signaling as well as oxidative damage in cells, these ROS have profound impact for the physiology and survival of the organism. Although mitochondria have been recognized as a potential source for ROS for about 50 years, the mechanistic understanding on molecular sites and processes has advanced recently. Most experimental approaches neglect thermal variability among species although temperature impacts mitochondrial processes significantly. Here we delineate the importance of temperature by comparing muscle mitochondrial ROS formation across species. Measuring the thermal sensitivity of respiration, electron leak rate (ROS formation), and the antioxidant capacity (measured as H2O2 consumption) in intact mitochondria of representative ectothermic and endothermic vertebrate species, our results suggest that using a common assay temperature is inappropriate for comparisons of organisms with differing body temperatures. Moreover, we propose that measuring electron leak relative to the mitochondrial antioxidant capacity (the oxidant ratio) may be superior to normalizing relative to respiration rates or mitochondrial protein for comparisons of mitochondrial metabolism of ROS across species of varying mitochondrial respiratory capacities.

Versatile Functional Energy Metabolism Platform Working From Research to Patient: An Integrated View of Cell Bioenergetics

“…These results are in accordance with what has been already published. Altered mitochondrial function has been linked to aging-related declines in performance ( Short et al, 2005 ) and was more recently related to mitochondrial proton and electron leaking that will have a very detrimental effect on coupling efficiency ( Treberg et al, 2018 ).…”

Use it and bruise it: copulation rates are associated with muscle inflammation across anole lizard species

“…Mammalian muscle has higher mitochondrial density (by volume), as well as higher total and inner membrane surface area compared to reptiles (Else & Hulbert, 1985). While ectotherm mitochondria have the potential for higher ROS production, it is potentially balanced by their higher antioxidant capacity (Treberg et al, 2018). Metabolism and body temperature can also influence inflammation, two important factors when studying ectotherms.…”

Integrating Mitochondrial Aerobic Metabolism into Ecology and Evolution

“…Here, we suggest that characterizing energy flow via measurements of mitochondrial aerobic metabolism can provide new insights into differences in energy turnover and physiological performance among and within individuals, across time, and in response to environmental change (Figure 1) [18,19]. Meeting energetic demands at the subcellular level while preventing the accumulation of potentially damaging byproducts under changing conditions requires careful orchestration of biochemical processes in the mitochondria [20].…”

“…and the experimental conditions (e.g. assay temperature [20], substrates [91]) should each be chosen with care based on the focus and constraints of a given study.…”