NGF and BDNF: from nerves to adipose tissue, from neurokines to metabokines.

Neurotrophins, particularly, NGF and BDNF are now well recognized to mediate a dizzying number of trophobiological effects, ranging from the Rita Levi-Montalcini's neurotrophic through immunotrophic to metabotrophic effects.These are implicated in the pathogenesis of various diseases including neuropsychiatric and cardiometabolic diseases, such as dementia, depression, type 2 diabetes and obesity that may express a common phenotype and coexistence. Recently, adipobiology (adiposcience) as become a focus of numerous studies showing that the adipose tissue is the body's largest endocrine organ producing multiple signaling proteins, including NGF and BDNF, all these dubbed adipokines. On the basis of our and other authors' evidence that low NGF and/or BDNF levels are found in cardiometabolic diseases (atherosclerosis, obesity, type 2 diabetes, metabolic syndrome), a hypothesis of a critical role of neuro-metabotrophic deficit in the pathogenesis of these diseases has been raised. Since NGF and BDNF also exerts various synaptotrophic effects involved in cognitive enhancement, this hypothesis might also be related to neuropsychiatric diseases such as dementia, depression, schizophrenia, autism, Rett syndrome, anorexia nervosa, and bulimia nervosa. Finally, NGF- and BDNF-based therapeutic approach, including ampakines, antidepressants, selective deacetylase inhibitors, statins, peroxisome proliferator-activated receptor gamma agonists, and "brain food" and calorie restriction, is outlined.