Decreased core temperature and increased beta(3)-adrenergic sensitivity in diabetes-prone BB rats.

Background: Diabetes-prone (DP) congenic DR.lyp/lyp BioBreeding (BB) rats all develop Type 1 diabetes between 50 and 81 days of age, while DR.lyp/+ or DR.+/+ BB rats are diabetes resistant (DR). The DP rats display reduced weight gain prior to developing hyperglycemia, implying that metabolic events may precede diabetes onset. We tested the hypothesis that temperature measurements could serve as a physiological marker for the impending onset of hyperglycemia.
Methods: Prior to the onset of hyperglycemia, brain, lower back, and intrascapular brown adipose tissue temperatures were analyzed by thermal signature analysis, which measures infrared emission from tissues. A thermocoupled rectal probe measured core temperature. In addition we performed a beta(3)-adrenergic receptor challenge test with the beta(3)-adrenergic receptor agonist BRL37344.
Results: DP rats displayed lower core temperature than DR rats prior to the onset of hyperglycemia. No temperature difference was detected in brain, lower back, or intrascapular brown adipose tissue between DP and DR rats. The beta(3)-adrenergic challenge showed that the rate of temperature increase after administration of BRL37344 was significantly higher (0.005 +/- 0.002 degrees C/min) in DP than in DR rats (P = 0.044).
Conclusions: These studies reveal that the prediabetic DP rats fail to maintain core temperature and that they display increased sensitivity to heat production induced by a beta(3)-adrenergic receptor agonist. These studies suggest that body temperature as a measure of metabolic dysregulation is altered in the prediabetic DP rat prior to the onset of hyperglycemia.