Insulin-like growth factors and insulin-like growth factor binding proteins in cerebrospinal fluid and serum of patients with dementia of the Alzheimer type

After acid gelchromatography cerebrospinal fluid and serum levels of immunoreactive insulin-like growth factor 1 and 2 (IGF-1 and IGF-2) were determined in patients with dementia of the Alzheimer type (AD) and in healthy subjects. The AD CSF levels of immunoreactive IGF-1 did not differ from the subjects but the levels of immunoreactive IGF-2 was significantly elevated in both serum and CSF in the AD patient group. Additionally immunoreactive IGF-1 in AD serum was found to be significantly elevated. To characterize the CSF IGF binding protein activity (IGFBP), ligand blotting was performed on whole CSF from AD patients and subjects. The results demonstrate two major forms of IGFBP in CSF with approximate molecular weights of 33 KDa and 30 KDa. The two IGFBP forms are suggested to represent IGFBP-2 and IGFBP-6. A highly significant increase in both the IGFBPs was observed in the CSF of the AD patients compared to the healthy subjects.