Early brain amyloidosis in APP/PS1 mice with serum insulin-like growth factor-I deficiency

The influence of insulin-like growth factor I (IGF-I) on the progression of Alzheimer's disease (AD) is discussed controversially. To help clarify the role of this circulating neurotrophic factor in brain amyloidosis, the major pathological trait in AD, we analyzed plaque formation in a mouse model of AD transgenic for human APP and PS1 mutations with reduced serum IGF-I levels (LIDAD mice). We found that brain amyloidosis in LIDAD mice appeared earlier than in AD mice, at 2 months of age, while attained comparable levels at 6 months. In parallel, early microgliosis was observed in LIDAD mice also at 2 months and remained exacerbated at 6 months. Collectively, these observations suggest a role of serum IGF-I in delaying early brain amyloidosis.

► Low serum IGF-I accelerates onset of amyloidosis and inflammation in Alzheimer mice.
► Low serum IGF-I is associated to prolonged microgliosis independent of plaque load.
► Plaque deposition in more aged mice is unchanged.
► Serum IGF-I is an important modulator of Alzheimer pathology in transgenic mice.
► The data confirm a role of serum IGF-I in delaying brain pathology.