Short-term cold-exposure does not improve insulin sensitivity in rats

Effects of noradrenergic activation induced by short-term cold-exposure (7 days at 4 degrees C) on whole-body glucose utilization and tissue glucose uptake were investigated in rats. Measurements were realized on anesthetized normothermic animals at four different: levels of insulinemia; within physiological range, allowing calculation of insulin sensitivity and responsiveness. Whole-body glucose utilization increased as a logarithmic function of insulinemias, and was always higher in cold-exposed than in control rats. However, neither insulin sensitivity nor responsiveness, literally, appeared different between the two groups. In the diaphragm, the only studied working muscle, glucose uptake was largely higher than in resting muscles. At basal insulin concentration, glucose uptake was higher in cold exposed than in control rats and increased in the two groups with insulinemia. Among resting muscles, glucose uptake was increased by previous cold exposure in gastrocnemius, soleus, and tibialis. However, insulin sensitivity and responsiveness were found augmented only in the two former. In interscapular brown adipose tissue, glucose uptake was largely higher in cold-exposed than in control rats, but no difference could be evidenced in insulin sensitivity or responsiveness. In white adipose tissues, glucose uptake increased with insulinemia. Insulin responsiveness and sensitivity were higher only in the retroperitoneal depot. (C) 1997 Elsevier Science Inc.