IGF1 and Parkinson disease: However, studies on preclinical models of PD and in vitro cell cultures have implicated the neuroprotective effects of IGF-1 in terms of reduced apoptosis, prevention of loss of dopaminergic neurons, blocking formation of α-synuclein aggregates, rescuing neurons from amyloid plaques and neurofibrillary tangles, as well as improvement of motor deficits in the clinical aspect (23–29).