Glucose is the primary fuel for the brain. Therefore, it has been proposed that the brain must sense glucose and promote eating behaviors when levels are low. A new study in the Journal of Clinical Investigation reveals that activation of an enzyme, glucokinase, in a region of the hypothalamus called the arcuate nucleus specifically increases glucose uptake. Steve Bloom and colleagues at Imperial College London determined that glucokinase levels in the arcuate nucleus are dramatically increased in fasted rats. In their rodent models, activation of glucokinase in the acruate nucleus increased food intake and body mass. When given a choice, animals with enhanced glucokinase activity preferentially consumed glucose when offered either with chow or other sugars. Conversely, inhibition of glucokinase in the arcuate nucleus decreased food consumption and glucose intake. The authors determined that glucokinase activation promotes release of the neurotransmitter NPY, which is known to increase food intake and energy storage as fat. The results of this study indicate the glucokinase dysfunction may underlie glucose cravings.
