High fatty acid oxidation capacity and phosphorylation control despite elevated leak and reduced respiratory capacity in northern elephant seal muscle mitochondria

摘要: Northern elephant seals (Mirounga angustirostris) are extreme, hypoxia-adapted endotherms that rely largely on aerobic metabolism during extended breath-hold dives in near-freezing water temperatures. While many aspects of their physiology have been characterized to account for these remarkable feats, the contribution adaptations powerhouses muscle cells, mitochondria, unknown. In present study, ontogeny and comparative seal mitochondrial respiratory function was investigated under a variety substrate conditions states. Intact networks were studied by high-resolution respirometry saponin-permeabilized fiber bundles obtained from primary swimming muscles pup, juvenile adult seals, compared with fibers human vastus lateralis. Results indicate maintains high capacity fatty acid oxidation despite progressive decrease total as animals mature pups adults. This is explained increase phosphorylation control utilization over pyruvate humans pups. Interestingly, higher indices oxidative efficiency, also exhibit ~50% greater ‘leak’ The this phenotype suggests it an adaptation prolonged exercise highly variable ambient temperatures experienced seals. These studies highlight plasticity mammalian mitochondria meet demands both efficient ATP production endothermy cold, oxygen-limited environment.