High fat diets and obesity pose serious health problems, such as type II diabetes and cardiovascular disease. Impaired cognitive function is also associated with high fat intake. In this study, we show that just four weeks of feeding a diet rich in fat ad libitum decreased hippocampal neurogenesis in male, but not female, rats. There was no obesity, but male rats fed a diet rich in fat exhibited elevated serum corticosterone levels compared to those fed standard rat chow. These data indicate that high dietary fat intake can disrupt hippocampal neurogenesis, probably through an increase in serum corticosterone levels, and that males are more susceptible than females.
suggests that dopaminergic neurons, the cell type lost in Parkinson's disease, are continuously generated in the adult substantia nigra pars compacta. Using similar methodological procedures to label dividing cells, we found no evidence of new dopaminergic neurons in the substantia nigra, either in normal or 6-hydroxydopamine-lesioned hemi-Parkinsonian rodents, or even after growth factor treatment. Furthermore, we found no evidence of neural stem cells emanating from the cerebroventricular system and migrating to the substantia nigra. We conclude that it is unlikely that dopaminergic neurons are generated in the adult mammalian substantia nigra.
Recently, a common single nucleotide polymorphism (SNP) has been identified in the gene encoding brain-derived neurotrophic factor (BDNF). The variant BDNF Met has been shown to have decreased activity-dependent BDNF secretion from neurons and to lead to impairments in specific forms of learning and altered susceptibility to stress. A mouse model containing BDNF Met has also been linked to increased anxiety-like behavior. In a translational study, mice and human carriers of the BDNF Met allele were compared in their ability to extinguish a learned fear memory. Both showed slower suppression of the learned fear response. In humans, the neural correlates of this behavior were validated using fMRI. As anxiety and fear extinction lie at the core of symptoms and therapeutic approaches to posttraumatic stress disorder (PTSD), we propose that BDNF genotype and neuroimaging may be useful as biomarkers to provide guidance for more customized therapeutic directions. The aim of this paper is to review the available knowledge on the BDNF Val66Met SNP, with emphasis on anxiety-and fear-related endophenotypes and its potential implications for PTSD.
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