A thymus tumour impairing hibernation

Background: Hibernation is a physiological and behavioural adaptation that permits survival during periods of reduced food availability and extreme environmental temperatures. This is achieved through cycles of metabolic depression and reduced body temperature (torpor) and rewarming (arousal). Rewarming from torpor is achieved through the activation of brown fat (BAT) associated with a rapid increase in ventilation frequency. Here, we studied the rate of rewarming in the European hamster by measuring both BAT temperature, core body temperature and ventilation frequency. Results: Temperature was monitored in in parallel in the BAT (IPTT tags) and peritoneal cavity (iButtons) during hibernation torpor-arousal cycling. We found that increases in brown fat temperature preceeded core body temperature rises by about 47 min, and this was accompanied by a significant increase in ventilation frequency. The rate of rewarming was slowed by the presence of a spontaneous thymus tumour in one of our animals. Core body temperature re-warming was reduced by 6.2*h-1 and BAT rewarming by 12*h-1. Ventilation frequency was increased by 77% during re-warming in the thymus tumour animal compared to a healthy animal. Inspection of the position and size of the tumour indicated that the lungs and heart were obstructed. Conclusions: We validated a minimally invasive method to monitor BAT temperature during hibernation. Using this method we showed compromised re-warming from hibernation in an animal with a thymus tumour, the likely cause of which is obstruction of the lungs and heart leading to inefficient ventilation and circulation.