Abstract
Naked mole-rats are among the most hypoxia-tolerant mammals. During hypoxia, their body temperature (Tb) decreases via unknown mechanisms to conserve energy. In small mammals, non-shivering thermogenesis in brown adipose tissue (BAT) is critical to Tb regulation; therefore, we hypothesize that hypoxia decreases naked mole-rat BAT thermogenesis. To test this, we measure changes in Tb during normoxia and hypoxia (7% O2; 1–3 h). We report that interscapular thermogenesis is high in normoxia but ceases during hypoxia, and Tb decreases. Furthermore, in BAT from animals treated in hypoxia, UCP1 and mitochondrial complexes I-V protein expression rapidly decrease, while mitochondria undergo fission, and apoptosis and mitophagy are inhibited. Finally, UCP1 expression decreases in hypoxia in three other social African mole-rat species, but not a solitary species. These findings suggest that the ability to rapidly down-regulate thermogenesis to conserve oxygen in hypoxia may have evolved preferentially in social species.
Highlights
Naked mole-rats are among the most hypoxia-tolerant mammals
To examine whether hypoxia-induced degradation of thermogenic proteins observed in naked mole-rats occurs in interscapular BAT (iBAT) of other closely related mole-rat species, we examined the effect of hypoxia on the expression of uncoupling protein-1 (UCP1) and oxidative phosphorylation (OXPHOS) proteins in iBAT dissected from Cryptomys hottentotus mahali (CHM), Cryptomys hottentotus pretoriae (CHP), Cryptomys hottentotus hottentotus (CHH) and Georychus capensis (GC) following in vivo treatment in either normoxic or hypoxic conditions
In the present study, we demonstrate that acute hypoxia diminishes interscapular thermogenesis in naked mole-rats, consistent with previous observations of substantial hypoxia-mediated suppression of whole-body metabolic rate and Tb in this species[13,14], and describe a mechanism by which thermogenic and metabolic proteins in iBAT may be downregulated during hypoxia
Summary
Naked mole-rats are among the most hypoxia-tolerant mammals. During hypoxia, their body temperature (Tb) decreases via unknown mechanisms to conserve energy. Metabolic rate is substantially elevated in cold temperatures, likely reflecting the high metabolic cost of thermogenesis[14,18,21] This ability to thermoregulate, even weakly, is likely important to the ecophysiology of this species as naked mole-rat burrow temperatures have a warm but variable thermal range (
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