Hypothermia in insulin-treated obese rats

Changes of colonic temperature were investigated to examine a mechanism of hypothermia in the obese rats which received subcutaneous administration of intermediate type-insulin (8 U/day) for 8 weeks. Although diurnal rhythmicity of colonic temperature levels was maintained similarly with those of vehicle-injected controls, the overall colonic temperature levels were significantly lowered in insulin-treated animals. In the condition of cold exposure at 5 degrees C, colonic temperature levels of insulin-treated animals were immediately and significantly decreased at 60 minutes after the start of cold exposure. The data obtained herein demonstrated that hyperinsulinemia accompanying with hyperphagia should be profoundly involved in hypothermia, observed in various experimental models of obesity.