Insulin-Like Growth Factor and Insulin-Like Growth Factor Receptor Expression in Human Idiopathic Autism Fusiform Gyrus Tissue.
IGF-1 and its receptor are present at normal levels in the fusiform gyrus of people with idiopathic autism, so any treatment benefit is unlikely to involve correcting a deficit in these proteins.
01Research in Context
What this study did
Cioana et al. (2020) looked at brain tissue from 14 people with idiopathic autism and 14 matched controls. They measured IGF-1 and its receptor in the fusiform gyrus, the face patch at the bottom of the brain. They used both mRNA and protein tests on post-mortem samples.
What they found
Levels of IGF-1 and IGF-1R were the same in both groups. No extra protein. No extra message. The numbers sat right on top of each other.
How this fits with other research
Nijs et al. (2016) also found normal brain chemistry in adults with ASD. They looked at glutathione instead of IGF-1, but the story is the same: no group difference.
Root et al. (2017) tested urine IAG and got the same flat line. Together these papers show that many proposed autism biomarkers keep coming up empty.
O'Connor et al. (2008) used fMRI in living adults and saw less face activity in the same fusiform region. So the tissue is there and the proteins are normal, but the neurons still light up less when faces appear.
Why it matters
If you are hunting a drug target, IGF-1 is not missing in the fusiform gyrus, so do not expect to fix autism by topping it up. Save your clinical time for supports that build face-to-face practice, not for chasing this protein.
Want CEUs on This Topic?
The ABA Clubhouse has 60+ free CEUs — live every Wednesday. Ethics, supervision & clinical topics.
Join Free →Keep teaching face recognition with direct practice and reinforcement; skip supplements aimed at IGF-1.
02At a glance
03Original abstract
Autism spectrum disorder (ASD) is believed to stem from defects in the establishment and maintenance of functional neuronal networks due to synaptic/spine dysfunction. The potent effects of IGF-1 on synaptic function, maintenance, and plasticity make it a potential target for treating ASD. This polypeptide hormone has proven to have beneficial effects in treating related developmental disorders like Rett syndrome, and its efficacy in ASD is currently being investigated in a pilot study. IGF-1 binds to its receptor (IGF-1R) in neurons and activates mitogen-activated protein kinase and PI3K/Akt signaling to produce biological effects on spine function. The PI3K/Akt pathway is dysregulated in ASD, including idiopathic autism, and is thus believed to play a role in the disorder. Despite this, no study has explored the levels of IGF-1 in the fusiform gyrus of idiopathic autism patients, an area known to be hypoactivated in ASD, and no study has examined IGF-1R in any part of the brain. The present study explored whether IGF-1 or IGF-1R levels are altered in human idiopathic autism. RNA and protein were extracted from post-mortem human fusiform gyrus tissue of normal controls (n = 20) and subjects with idiopathic autism (n = 15). qRT-PCR for IGF-1 and IGF-1R were performed, along with total IGF-1 ELISA and IGF-1Rβ Western blots. The levels of both IGF-1 and IGF-1R mRNA and protein were equivalent between the two groups, suggesting that although IGF-1 may be useful for ASD treatment, IGF-1 and IGF-1R are not implicated in the pathogenesis of idiopathic autism. Autism Res 2020, 13: 897-907. © 2020 International Society for Autism Research, Wiley Periodicals, Inc. LAY SUMMARY: IGF-1 is being tested for the treatment of autism and related disorders. Despite promising results, it is unknown if IGF-1 or its receptor are present in abnormal levels in patients with autism. This study showed that patients with autism have normal levels of IGF-1 and its receptor in the brain, suggesting that although IGF-1 is a promising treatment, disruption of IGF-1 levels or signaling through its receptor does not seem to be a cause of autism.
Autism research : official journal of the International Society for Autism Research, 2020 · doi:10.1002/aur.2291