Reduced neurotrophic factor level is the early event before the functional neuronal deficiency in high-fat diet induced obese mice

Neurodegeneration is considered one of the possible complications of high fat diet (HFD) induced obesity. Much evidence has shown the close relationship between HFD and dementia at comparatively later stage of neuronal injury. It is so far not clear that the initial events of neuronal injury resulting from HFD and obesity. In the present research, obese mouse model achieved by 3-month HFD was applied for the investigation of the possible neuronal deficiency before the obvious cognitive decline. We found that 3-month HFD has already increased the average level of body weight of mice. But almost no obvious cognitive defect was observed. At such time point, we detected the cleavage of amyloid precursor protein (APP), including the expression and maturation level of alpha- and beta-secretase and proteolytic fragment soluble APP. Results showed similar readout between HFD and normal diet (ND) mice. Besides, neuronal inflammation and brain-blood barrier permeability were also detected. No obvious changes could be observed between HFD and ND mice. Surprisingly, the first detectable neuronal changes was showed to be the downregulation of some neurotrpic factors, like neuronal growth factor beta and brain derived neurotrophic factor, together with the activity of specific receptors, like Trk receptor phosphorylation. All the data piled up indicated that the early neuronal change in HFD induced obese mice was the downregulation of some neurotrophic factors. The results may provide the potential clue to therapeutic and preventive strategy for HFD induced cognitive decline.