Rare Syndromes and Common Variants of the Brain-Derived Neurotrophic Factor Gene in Human Obesity.

Rare genetic disorders that cause BDNF haploinsufficiency, such as WAGR syndrome, 11p deletion, and 11p inversion, serve as models for understanding the role of BDNF in human energy balance and neurocognition. Patients with BDNF haploinsufficiency or inactivating mutations of the BDNF receptor exhibit hyperphagia, childhood-onset obesity, intellectual disability, and impaired nociception. Prader-Willi, Smith-Magenis, and ROHHAD syndromes are separate genetic disorders that do not directly affect the BDNF locus but share many similar clinical features with BDNF haploinsufficiency, and BDNF insufficiency is believed to possibly contribute to the pathophysiology of each of these conditions. In the general population, common variants of BDNF that affect BDNF gene expression or BDNF protein processing have also been associated with modest alterations in energy balance and cognitive functioning. Thus, variable degrees of BDNF insufficiency appear to contribute to a spectrum of excess weight gain and cognitive impairment that ranges in phenotypic severity. In this modern era of precision medicine, genotype-specific therapies aimed at increasing BDNF signaling in patients with rare and common disorders associated with BDNF insufficiency could serve as useful approaches for treating obesity and neurodevelopmental disorders.