The relationship between the IGF system, nutrition and behaviour

The insulin-like growth factors (IGFs) and their binding proteins (IGFBPs) have ­metabolic roles as well as effects on growth and differentiation. IGF-I and IGFBP-1 are good metabolic markers, with low IGF-I and increased fasting IGFBP-1 indicating impaired nutritional status. There is compelling evidence to suggest that the actions of the IGF system in adult brain are important to learning, memory, and behavior in health and disease. In addition to local IGF system components, it is known that endocrine IGFs and IGFBPs crossing the blood-brain barrier also play a role in brain function. Impaired IGF signaling contributes to the pathophysiology of Alzheimer’s disease and to the altered cognitive function of infection and chronic inflammation. It has therefore been suggested that IGF-I may be a reasonable therapeutic option in these conditions. However, the positive effect of reduced IGF-I signaling and dietary restriction on longevity and cancer progression should be considered when targeting the IGF system in the treatment of cognitive disturbance. Future work should focus on targeting tissues for specific IGF effects and in developing guidelines and awareness of the best nutrition and exercise for optimal cognitive functioning throughout life. Further knowledge of the IGF system and nutrition in relation to behavior may be a key to understanding the integration of somatic and cognitive functioning.