Expression of insulin-like growth factor-1 and insulin-like growth factor binding proteins in the serum and cerebrospinal fluid of patients with Parkinson’s disease

Parkinson’s disease (PD) is characterized by progressive loss of dopaminergic neurons in the substantia nigra. Insulin like growth factor-1 (IGF-1) promotes the survival of dopaminergic neurons and protects them from toxin-induced damage in vitro. IGF-1 is produced by a wide variety of cells and is found in many physiological fluids, including cerebrospinal fluid (CSF). IGFs in physiological fluids are associated with insulin-like growth factor binding proteins (IGFBPs), which bind to them and modulate their bioactivity at the cellular level. Since the CSF is in contact with the extracellular space of the brain, biochemical brain modifications are, to some extent, reflected in the CSF, and peptides and growth factors in the CSF can be used as biomarkers of PD. The aim of this study was to determine the concentrations of IGF-1 and IGFBPs in the serum and CSF of patients with PD. Concentrations were measured in a total of 76 CSF samples from patients with PD (n = 38) and controls (n = 38). Serum and CSF IGF-1 and IGFBP concentrations were higher in patients with PD than in controls (p < 0.001). We conclude that IGF-1 and IGFBPs are always present in human serum and CSF, and may be involved in the pathophysiology of PD.