From Myo-inositol to D-chiro-inositol molecular pathways

Objective: Inositol is a carbocyclic sugar polyalcohol. By epimerization of its hydroxyl groups, nine possible stereoisomers can be generated, two of major physiological and clinical relevance: myo-inositol and D-chiro-inositol. Myo-inositol and D-chiro-inositol are normally stored in kidney, brain and liver and are necessary for functions, such as signal transduction, metabolic flux, insulin signaling, regulation of ion-channel permeability, stress response and embryo development. In this narrative review, we summarize the mechanisms by which myo-inositol and D-chiro-inositol can be synthesized and absorbed and their possible role in the etiopathogenesis of neural tube defects. Materials and methods: We performed an online search in the PubMed database using the following keywords: "inositol", "D-chiro-inositol", "myo-inositol", "neural tube defects and inositol". Results: Inositol requirements are partly met by dietary intake, while the rest is synthesized endogenously. Inositol deficiency may be involved in the pathogenesis of diseases, such as metabolic syndrome, spina bifida (a neural tube defect), polycystic ovary syndrome and diabetes. Supplementation of the two inositol stereoisomers, D-chiro-inositol and myo-inositol is important to prevent these conditions. Conclusions: Inositol is fundamental for signal transduction in the brain, kidneys, reproductive organs and other tissues in response to neurotransmitters, hormones and growth factors. Various genes are involved in inositol metabolism and associated pathways. Altered inositol concentrations are observed in several diseases. Analysis of the genes involved in inositol metabolism may provide important information for the clinical management of these conditions.