Plasma IGF-1 Could Be Important Parkinson Disease Biomarker

Plasma levels of insulin-like growth factor 1 (IGF-1) could give clinicians a better understanding of whether a patient with Parkinson disease (PD) is likely experiencing nonmotor symptoms of the disease, including anxiety, depression, and cognitive decline, a new report has found.

The study, published in Neuroscience Letters, also shows that plasma IGF-1 was associated with the volumes of 3 areas of the brain: the insula, caudate, and anterior cingulate.

There currently are no reliable biomarkers to diagnose preclinical PD, explained the authors. However, they added that IGF-1 is seen as a promising potential biomarker, since the 70–amino acid peptide hormone plays important roles in neuroplasticity, differentiation, myelination, and survival.

“Studies have shown that IGF-1 possesses neuroprotective effects against dopamine-induced toxicity and may have a potential role in the treatment of PD,” they wrote. “Therefore, we hypothesized that plasma IGF-1 levels would be gradually increased as PD progressed.”

The investigators recruited 55 healthy controls and 119 patients with PD. Of the latter group, 67 were in early stages of the disease and the remaining 52 were in middle-late stages. Enrollees had plasma IGF-1 levels assessed by an automatic chemical analyzer, and the patients with PD were assessed for motor and nonmotor symptoms using common disease scales. In addition, 65 patients underwent MRI and voxel-based morphometry to evaluate gray matter changes.

As the authors had hypothesized, the study found that levels of plasma IGF-1 appeared to increase as a patient’s PD case worsened.

“Plasma IGF-1 levels in early-stage PD patients were higher than those in healthy controls, and plasma IGF-1 levels in middle- to late-stage PD patients were higher than those in early-stage PD patients,” they found.

However, if IGF-1 levels were indicative of disease progression, the neuroprotective hormone was also an indication of whether a patient was likely to experience nonmotor symptoms. “Plasma IGF-1 levels in the PD patients were lower in the anxiety subgroup, depression subgroup, and cognitive dysfunction subgroup than in the subgroups without anxiety,” the authors reported.

In addition, IGF-1 levels were positively correlated with gray matter volume in the insula, caudate, and anterior cingulate. The authors noted that previous research suggests that IGF-1 can help protect against neurotoxicity associated with 3-hydroxyglutaric acid, which they said is believed to cause degeneration of the caudate and putamen nuclei. A study in a mouse model suggested that the inverse was true, too: IGF-1 could increase the volume of the caudate nucleus region.

“All this evidence suggests that IGF-1 can exert neuroprotective effects and its expression can be increased in the caudate nucleus,” the authors wrote.

In conclusion, they said the study’s findings make a strong case that monitoring IGF-1 might be a way to better monitor patients and plan treatment programs for them. They said larger studies will be needed to confirm the findings of this study and better explore the potential mechanisms behind these correlations.

Reference

Shi X, Zheng J, Ma J, et al. Insulin-like growth factor in Parkinson’s disease is related to nonmotor symptoms and the volume of specific brain areas. Neuroscience Letters. Published online June 13, 2022. doi:10.1016/j.neulet.2022.136735