Meta-Analysis of Serum Insulin-Like Growth Factor 1 in Alzheimer's Disease

PLoS One. 2016 May 26;11(5):e0155733. doi: 10.1371/journal.pone.0155733. eCollection 2016.

Abstract

Insulin-like growth factor 1 (IGF-1) serum levels have been reported to be altered in Alzheimer's disease patients, and it was suggested that the changes in IGF-1 serum level may play a role in disease pathology and progression. However, this notion remained controversial due to conflicting findings. We conducted a meta-analysis to determine the relationship between IGF-1 serum levels and Alzheimer's disease. We searched the databases PUBMED, Ovid SP, and Cochrane library for relevant studies. The primary data analyzed was serum IGF-1 from Alzheimer's disease subjects and controls. Pooled weighted mean difference using a random effects model was used to determine the relationship between serum levels and disease state. Nine studies were included in the meta-analysis compromising a total of 1639 subjects. The pooled weighted mean difference was -2.27ng/ml (95% CI: [-22.221, 17.66]) with a P value of 0.82. Thus our finding did not show clear relationship between low IGF-1 and Alzheimer's disease subjects. We did not find evidence of publication bias by analyzing a funnel plot as well as Egger's and Begg's tests. While eight out of the nine studies included in this meta-analysis detected a statistically significant increase or decrease in serum levels of IGF-1 in Alzheimer's disease subjects, the analysis as a whole did not show a significant trend in either direction. Thus, IGF-1 level is likely a critical personalized factor. A large database of clinical trials is required for better understanding the relationship between IGF-1 levels and Alzheimer's disease.

Publication types

  • Meta-Analysis
  • Research Support, Non-U.S. Gov't

MeSH terms

  • Alzheimer Disease / blood*
  • Alzheimer Disease / pathology*
  • Biomarkers / blood*
  • Case-Control Studies
  • Humans
  • Insulin-Like Growth Factor I / analysis*

Substances

  • Biomarkers
  • Insulin-Like Growth Factor I

Grants and funding

Natural Sciences and Engineering Research Council of Canada (CA) RGPIN 249962. AB is a recipient of Ontario Graduate Scholarship (PhD). The funders had no role in study design, data collection and analysis, decision to publish, or preparation of the manuscript.