Disparate effects of feeding on core body and adipose tissue temperatures in animals selectively bred for Nervous or Calm temperament

In addition to homeostatic regulation of body mass, non-homeostatic factors impact on energy balance. Herein we describe effects of temperament on adipose and core body temperatures in sheep. Animals were genetically selected for Nervous or Calm traits. We characterised the effects of 1. High and low energy intake and maintenance feeding, 2. meal anticipation, and 3. adrenocorticotropin -challenge on core body and adipose temperatures. Temperature measurements (5 min) were made using a thermistor inserted into the carotid artery (core body) and a probe in the retroperitoneal fat. An imposed feeding window was used to establish post-prandial elevations in temperature. Fat tissue was taken from retroperitoneal and subcutaneous regions for real time PCR analyses. We demonstrate that innate differences in temperament impact on adipose and core body temperatures in response to various dietary and evocative stimuli. In response to homeostatic cues (low energy intake and maintenance feeding) core body temperature tended to be higher in Calm compared to Nervous animals. In contrast, in response to non-homeostatic cues, Nervous animals had higher anticipatory thermogenic responses than Calm animals. Expression of uncoupling protein (UCP) 1 and 2 mRNA were higher in retroperitoneal tissue than in subcutaneous tissue, but UCP3 and leptin mRNA levels were similar at both sites; expression of these genes was similar in Nervous and Calm animals. There were no differences in stress-responsiveness. We conclude that temperament differentially influences adipose thermogenesis and the regulation of core body temperature in responses to both homeostatic and non-homeostatic stimuli.