Meeting Abstract
For small mammals living at high altitude, aerobic heat generation (thermogenesis) is essential for survival during prolonged periods of cold, but is severely impaired under conditions of hypobaric hypoxia. Recent studies in the deer mouse (Peromyscus maniculatus) have revealed adaptive enhancement of thermogenesis in high (4350 m)- compared to low (430 m)- altitude populations under hypoxic cold stress, an enhancement that is driven by greater aerobic performance of muscles used in shivering, and upregulation of associated O2 diffusion and utilization pathways. To more fully understand the mechanistic basis of adaptive enhancement of thermogenesis in high altitude deer mice, we investigated the role of non-shivering thermogenesis (NST) in brown adipose tissue (BAT), which can account for up to 75% of total thermogenic performance in rodents. To do so, we measured NST and characterized BAT transcriptional profiles of high- and low- altitude deer mice that were 1) wild-caught and acclimatized to their native altitude, and 2) born and reared at low-elevation. We found that NST performance is enhanced in wild-caught high altitude deer mice, a difference that is associated with upregulation of genes involved in several hierarchical pathways at BAT: differentiation and proliferation of brown adipocytes, vascularization of BAT, metabolism of fatty acids, and the regulation of uncoupling protein 1 expression. Constitutive between-population differences in expression of hemoglobin and heme synthesis genes were detected in wild and lab-reared mice. Our results suggest that both plastic and genetic mechanisms make important contributions in the adaptation to the twin stressors of cold and hypoxia at high altitude.
