Alzheimer's disease (AD) is a neurodegenerative disorder characterized by progressive loss of memory and other cognitive functions and presents an increasing clinical challenge in terms of diagnosis and treatment. Brain-derived neurotrophic factor (BDNF) plays an important role in neuronal survival and proliferation. In the present study, the mRNA and protein expression level of BDNF was detected in serum, and cerebrospinal fluid (CSF) of patients with mild cognitive impairment (MCI), dementia of Alzheimer's type (DAT), and hippocampus in APP/PS1 mice. A significant decrease of BDNF mRNA and protein expression was observed in serum and CSF of patients and hippocampus in APP/PS1 mice compared with the corresponding controls. miR-613, which is predicted to target the 3'-UTR of BDNF, was also detected in patients and the mouse model. Opposite to the alteration of BDNF, miR-613 expression in serum, CSF and hippocampus were obviously increased compared to the controls. In conclusion, these findings showed that miR-613 may function in the development of AD and may provide new insights in diagnosis and treatment of AD.