Decreased Neurotrophic Support is Associated with Cognitive Decline in Non-Demented Subjects

There is evidence of decreased neurotrophic support in Alzheimer's disease (AD), including its prodromal stages, but it is not clear whether this abnormality represents a marker of this process.To determine serum concentrations of a panel of neurotrophic factors (BDNF, NGF, and GDNF) in a cross-section of elderly patients with mild cognitive impairment (MCI) and AD compared to cognitively healthy controls, and to evaluate whether abnormal levels of these factors at baseline predict the transition from MCI to dementia.A total of 134 older adults were enrolled in this study. Twenty-six patients with mild to moderate AD, 62 with MCI, and 46 cognitively healthy older adults (controls) were subjected to a clinical evaluation including several cognitive tests. Peripheral blood was drawn and serum levels of BDNF, NGF, and GDNF were measured by enzyme-linked immunosorbent assay. APOE genotyping was performed by PCR assays.Serum concentrations of BDNF, NGF, and GDNF were significantly reduced in cognitively impaired subjects (i.e., MCI and AD) as compared to controls, although only the former two remained statistically different after controlling for age, gender, and cognitive performance (p = 0.05 and p = 0.01, respectively). Lower BDNF and NGF levels were also observed in the sub-sample of MCI patients who progressed to dementia upon follow-up (p = 0.02 and p = 0.002, respectively).Abnormalities in neurotrophic systems are observed at early stages of AD and may represent a marker of cognitive deterioration.