|LETTER TO EDITOR
|Year : 2017 | Volume
| Issue : 5 | Page : 714-715
Biomarkers in autism spectrum disorders: An illusion or promising reality?
Speciality doctor, Children and Adolescent Mental Health Services, Northumberland, Tyne and Wear NHS Foundation Trust, UK
|Date of Web Publication||24-Oct-2017|
35, St. Anns Close, Newcastle Upon Tyne, NE1 2QP
Source of Support: None, Conflict of Interest: None
|How to cite this article:|
Gnanavel S. Biomarkers in autism spectrum disorders: An illusion or promising reality?. Indian J Psychol Med 2017;39:714-5
A biomarker has been defined as “a characteristic that is objectively measured and evaluated as an indicator of normal biological processes, pathogenic processes or pharmacologic responses to a therapeutic intervention.” Trying to translate experimental study results to bench side clinical practice pertaining to biomarkers has proved to be difficult in mental health and behavioral sciences, particularly in the field of child and adolescent psychiatry. However, there have been several fascinating developments in the field of biomarker research in autism spectrum disorders (ASDs) that holds the promise of bridging basic and clinical sciences in the future.
Genetic, metabolic, inflammatory markers, as well as markers of mitochondrial dysfunction and oxidative stress, are the commonly investigated biomarkers for neurodevelopmental disorders. Around 500 distinct genetic loci have been associated with ASDs. Of these, genome-wide association studies have identified deletions at the Neurexin 1 (NRXN1) locus, duplications at 7q11.23, duplications at 15q11–13 deletions, and duplications at 16p11.2. Previous studies identified mutations in genes encoding for NRXN1, SHANK3, and SHANK2 which are associated with the functioning of synapses. Furthermore, epigenetic markers including DNA methylation differences in many loci including AFF2, AUTS2, GABRB3, and SLC6A4 are linked to ASD.
Metabolic markers associated with ASD are based on conceptualizing ASD as a disorder of central nervous system that can detected peripherally or as a systemic abnormality that has an effect on the brain. Serotonin and its metabolites, gamma-amino butyric acid and glutathione have been commonly studied biomarkers in this respect. ASD has also been considered a state of high oxidative stress as evidenced by the study of biomarkers including glutathione and superoxide dismutase enzyme. Mitochondrial dysfunction and impaired energy production have been a promising area for biomarker research in ASD. This includes studies on lactate, pyruvate and lactate-to-pyruvate ratio and carnitine in patients with ASD. Some researchers focus on ASD as a state of immune dysregulation as evidenced by raised levels of neopertin, a urine marker of immune dysfunction.
Neuroimaging biomarkers for ASD have also been investigated in recent years. Some of the well-studied markers include an early-accelerated brain volume growth followed by a plateau phase; gray matter thickness changes and changes in white matter integrity. Both structural imaging and novel techniques including diffusion tensor imaging have been utilized for these studies.
Some of the classical challenges in identifying biomarkers in ASD include delineating the complex interplay between genetic and environmental factors; identifying the epigenetic changes and also to ascertain if these changes are unique to ASD (in other words, are they a biomarker for ASD or are they just the result of underlying pathological processes common to many disorders). Research Domain Criteria project is a positive development that provides a conceptual framework for biomarker-based research. This aims to neural circuits and behaviors, common to different disorders as against a specific disorder centered approach. In fact, considering the complexity and heterogeneity in the presentation of ASD, it would be an ideal candidate for such cross-cutting research. More studies in this respect (focusing on interdisciplinary research) are required for identification of biological markers for ASD which would permit us in early identification and intervention in potential cases. This would also help in screening, assessing the severity of the disorder and possibility of personalized interventions that would work better for an individual case.
Financial support and sponsorship
Conflicts of interest
There are no conflicts of interest.
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