IGF-1 linked to negative symptoms in schizophrenia
medwireNews: Plasma levels of insulin-like growth factor (IGF)-1 significantly fluctuate in the early stages of schizophrenia and the peptide may play a role in the pathophysiology of negative symptoms, say researchers.
They found a significant and maintained correlation between IGF-1 plasma levels and negative symptoms on the Positive and Negative Symptom scale (PANSS) in schizophrenia patients throughout a year of treatment.
"This finding is relevant to disease, as negative symptoms tend to be chronic and resistant to antipsychotic treatment as well as more frequent in patients with schizophrenia than in patients with bipolar disorder," Carlos Matute (University of the Basque Country, Vizcaya, Spain) and team note.
The researchers studied IGF-1 levels in 27 patients with schizophrenia and 23 with bipolar disorder, and in 43 mentally healthy individuals.
At the first psychotic episode, IGF-1 levels did not differ between patients and mentally healthy individuals. But after 1 month of treatment, levels were significantly increased in patients with schizophrenia or bipolar disorder, at 219.84 ng/mL versus 164.15 ng/mL in mentally healthy individuals.
When the patients were assessed separately, IGF-1 levels were significantly increased in schizophrenia patients relative to mentally healthy individuals (237.60 vs 171.60 ng/mL), but not in patients with bipolar disorder.
At further assessments, at 6 months and 1 year after the first episode, IGF-1 levels in the patients were no different to those in mentally healthy individuals.
IGF-1 levels correlated positively with negative symptoms throughout the first year of treatment, with a diagnosis of schizophrenia the main contributor to this relationship.
The researchers note in Progress in Neuro-Psychopharmacology & Biological Psychiatry that the negative scale of the PANSS includes items that represent cognitive deficits in schizophrenia and so elevated levels of IGF-1 levels may parallel cognitive impairment.
Matute and team also point out that previous evidence has suggested that brain circuitry abnormalities in schizophrenia are related to demyelination and/or reduced myelination during postnatal development.
"The finding reported here of elevated IGF-1 levels may represent a compensatory response to attenuate a structural defect in schizophrenia since experimental and preclinical data indicates that IGF-1 enhances myelination," they say.
"In this regard, it has been suggested that treatment with recombinant human IGF-1 for patients with schizophrenia may represent a novel therapy."
medwireNews (www.medwirenews.com) is an independent clinical news service provided by Springer Healthcare Limited. © Springer Healthcare Ltd; 2013
By Lucy Piper, Senior medwireNews Reporter