Depression, Brain Glucose Metabolism and Consciousness

Abstract

A correlation between depression and resistance to insulin was recently discovered. How to conciliate this finding with the fact that glucose transport to neurons is not made directly by insulin? We present an explanatory hypothesis based on a mechanism of dynamical glucose balance in the brain that includes lactate transport from astrocytes to neuronal mitochondria supporting ATP (and then cAMP) production. The depressed brain has defective ATP production, possibly leading in several cases to excessive glucose consumption without increasing neuronal ATP levels. This hypothesis can help to explain the surprisingly positive results found in the treatment of depression with aromatherapy. Some odors like citrus fragrances possibly fool the brain’s glucose level sensors, reducing the subjective feeling of "low energy". Could a conscious process trigger a reaction against the underlying causes of depression?