[Targeting the brain through the nose. Effects of intranasally administered insulin].

The assumption that the human brain is an insulin-independent organ was disproved with the discovery of insulin receptors in the central nervous system in the year 1978. Evidence has been provided for a high density of insulin receptors in brain regions responsible for cognitive memory processes (hippocampus) and for the regulation of appetite (hypothalamus). Accordingly, in animal studies an increased insulin level in the central nervous system leads to an improvement of hippocampal memory function and a decrease of food intake. Similar results were obtained in humans using the method of intranasal administration of insulin. Intranasal insulin reaches the brain and the cerebrospinal fluid via the olfactory epithelium and olfactory nerve fiber bundles leading through the lamina cribrosa to the olfactory bulb. Thus, this method renders the investigation of specific insulin effects in humans possible. The therapeutic potential of an intranasal insulin administration for the treatment of diseases for which an imbalance of the central nervous insulin metabolism is discussed (e.g. Alzheimer's disease, diabetes mellitus and obesity) can only be estimated with the help of further clinical studies.