Promising Psychotherapeutic Effects of the Natural Sugar: Myo-Inositol

Myo-inositol is a common six-carbon sugar with unique biochemical and psychotherapeutic properties. It is involved in neuronal signaling and osmoregulation, and has been shown to be therapeutic in initial studies of depression, panic disorder, and obsessive-compulsive disorder. The inositol signaling system is a post-receptor second messenger system found in many cells, and is similar to the cAMP system. Myo-inositol exists in the free form, or as a component of membrane inositol phospholipids which are present largely on the inner leaflet of the plasma membrane. Inositol phospholipids, particularly phosphatidylinositol 4,5-bis-phosphate (PIP2), are linked to a number of brain receptor signaling systems including serotonergic, muscarinic, adrenergic, histaminergic, cholecystokinin, tachykinins, metabotropic, neurotensin, platelet activating factor, and others. With receptor stimulation, the signal is transmitted through a series of other proteins. Activation of a GTP-binding protein (Gq), in turn activates plasma membrane phospholipase C releasing the second messenger, myo-inositol 1,4,5-trisphosphate (InsP3), into the cytosol. InsP3 then causes release of free calcium from endoplasmic reticulum into the cytosol, which then activates a number of calcium-sensitive enzymes and receptors. Myo-inositol is made available to the brain through three sources: (i) receptor stimulation (salvage pathway), (ii) de novo production, and (iii) dietary intake. Initial clinical studies have shown that myo-inositol has psychoactive effects, and is effective in the treatment of specific mood and anxiety disorders. Recent preliminary clinical studies have suggested the fascinating possibility that myo-inositol has psychoactive effects, and may be effective in the treatment specific mood and anxiety disorders. Further clinical studies are required using larger groups of patients before definitive conclusions can be drawn upon the use of myo-inositol as a potential psychoactive compound. Myo-inositol as a natural medication increases interest in this newly emerging area of nutritional neuroscience.