Altered kynurenine pathway metabolism in autism: Implication for immune-induced glutamatergic activity.
Kids with autism show high quinolinic acid, a sign that immune stress can over-excite the brain.
01Research in Context
What this study did
Doctors compared blood from children with autism to blood from typically developing kids. They looked for a chemical called quinolinic acid. This acid forms when the body is inflamed and can over-excite brain cells.
The team used a case-control design. They drew one blood sample from each child and sent it to a lab for testing.
What they found
Children with autism had higher quinolinic acid levels. High acid means the kynurenine pathway is switched on. This pathway links inflammation to too much glutamate in the brain.
In short, immune stress leaves a chemical fingerprint in the blood of kids with ASD.
How this fits with other research
Lee et al. (2018) extends this idea. They showed the same kids who carry the chemical fingerprint also get more inflammatory bowel disease. One study sees the blood signal; the other sees the gut result.
Kaiser et al. (2022) pulls eleven studies into one meta-analysis. Their numbers agree: kids with ASD have about 1.5 times the odds of developing IBD. The 2016 blood marker and the 2022 epidemiology fit like puzzle pieces.
Hu et al. (2018) adds a third layer. They found higher cytokines in the plasma of Chinese children with ASD. Together, the papers paint one picture: immune activation shows up in blood, in gut, and in brain tissue.
Why it matters
You now have a clear, testable story to share with parents. Immune stress can drive both tummy trouble and behavior flare-ups. When a child shows sudden skill loss or increased stereotypy, ask about recent illness, diarrhea, or food reactions. A quick note to the pediatrician for blood or stool checks can speed medical care and may calm the behavior storm.
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02At a glance
03Original abstract
Dysfunction of the serotoninergic and glutamatergic systems is implicated in the pathogenesis of autism spectrum disorder (ASD) together with various neuroinflammatory mediators. As the kynurenine pathway (KP) of tryptophan degradation is activated in neuroinflammatory states, we hypothesized that there may be a link between inflammation in ASD and enhanced KP activation resulting in reduced serotonin synthesis from tryptophan and production of KP metabolites capable of modulating glutamatergic activity. A cross-sectional study of 15 different Omani families with newly diagnosed children with ASD (n = 15) and their age-matched healthy siblings (n = 12) was designed. Immunological profile and the KP metabolic signature were characterized in the study participants. Our data indicated that there were alterations to the KP in ASD. Specifically, increased production of the downstream metabolite, quinolinic acid, which is capable of enhancing glutamatergic neurotransmission was noted. Correlation studies also demonstrated that the presence of inflammation induced KP activation in ASD. Until now, previous studies have failed to establish a link between inflammation, glutamatergic activity, and the KP. Our findings also suggest that increased quinolinic acid may be linked to 16p11.2 mutations leading to abnormal glutamatergic activity associated with ASD pathogenesis and may help rationalize the efficacy of sulforaphane treatment in ASD. Autism Res 2016, 9: 621-631. © 2015 International Society for Autism Research, Wiley Periodicals, Inc.
Autism research : official journal of the International Society for Autism Research, 2016 · doi:10.1002/aur.1565