Oxidative phosphorylation is compromised in
hypoxia, but many organisms live and exercise in low
oxygen environments.
Hypoxia-driven adaptations at the mitochondrial level are common and may enhance energetic efficiency or minimize deleterious
reactive oxygen species (ROS) generation. Mitochondria from various
hypoxia-tolerant animals exhibit robust functional changes following in vivo
hypoxia and we hypothesized that similar plasticity would occur in naked mole-rat skeletal muscle. To test this, we exposed adult subordinate naked mole-rats to normoxia (21% O2) or acute (4 h, 7% O2) or chronic
hypoxia (4-6 weeks, 11% O2) and then isolated skeletal muscle mitochondria. Using high-resolution respirometry and a fluorescent
indicator of ROS production, we then probed for changes in: i)
lipid- (
palmitoylcarnitine-
malate), ii)
carbohydrate- (
pyruvate-
malate), and iii)
succinate-fueled metabolism, and also iv) complex IV electron transfer capacity, and v) H2O2 production. Compared to normoxic values, a)
lipid-fueled uncoupled respiration was reduced ~15% during acute and chronic
hypoxia, b) complex I-II capacity and the rate of ROS efflux were both unaffected, and c) complex II and IV uncoupled respiration were supressed ~16% following acute
hypoxia. Notably, complex II-linked H2O2 efflux was 33% lower after acute
hypoxia, which may reduce deleterious ROS bursts during reoxygenation. These mild changes in
lipid- and
carbohydrate-fueled respiratory capacity may reflect the need for this animal to exercise regularly in highly variable and intermittently hypoxic environments in which more robust plasticity may be energetically expensive.