LC–MS/MS–Based Chromatographic Assessment of Oxysterol Imbalances in Autism Spectrum Disorder

A recent study conducted by researchers from various Turkish hospitals and universities investigated the role of cholesterol metabolism disorders in the etiopathogenesis of autism spectrum disorder (ASD) through the analysis of central and peripheral oxysterol levels (24-hydroxycholesterol, 25-hydroxycholesterol, 27-hydroxycholesterol). These compounds, found in the cholesterol excretion pathways, are considered potential biomarkers for diagnosing and monitoring various neuropsychiatric disorders. Oxysterol levels were assessed using liquid chromatography coupled with tandem mass spectrometry(LC-MS/MS). A paper based on the research was published in the Journal of Clinical Practice and Research (1).

Increasing evidence that disruptions in cholesterol metabolism are common in neuropsychiatric diseases has led to a focus on oxysterols, which are compounds formed through the enzymatic oxidation of cholesterol by CYP450 enzymes or non-enzymatically by autooxidation (2). Oxysterols act as regulators in a variety of biological processes; while present in small amounts in mammalian tissues, their levels can increase significantly under various pathological conditions (3). As a result, oxysterols are thought to function as biomarkers (4). Changes in oxysterol concentrations have been found in neuropsychiatric conditions which exhibit similarities to ASD, particularly in areas regarding synaptic dysfunction (5,6).

The team’s research study included 42 children diagnosed with ASD, aged between 1 and 6 years, who had no additional psychiatric or medical illnesses other than cognitive delay or intellectual disability and were not on medication, along with 38 age-matched typically developing children. After comprehensive mental health assessments, the symptom severity in children with ASD was evaluated using the Childhood Autism Rating Scale, Autism Behavior Checklist, and Repetitive Behavior Scale-Revised Form. After the clinical evaluation, peripheral blood samples were obtained from all children and, as mentioned earlier, oxysterol levels from the samples were assessed using LC-MS/MS (1).

Analysis revealed that levels of 24-hydroxycholesterol and 25-hydroxycholesterol from the ASD group were significantly higher compared to the control group, while 27-R-hydroxycholesterol levels were lower. The ratio of 24-hydroxycholesterol (μg/L) to 27-hydroxycholesterol (μg/L) was notably higher in the autism group. The receiver operating characteristic (ROC) analysis indicated that this ratio was statistically significant and could discriminate between ASD and non-ASD diagnoses with "acceptable discrimination potential." (1)

The findings suggest that alterations in oxysterol levels, commonly associated with neurodegenerative processes, can also be observed in ASD and may serve as a potential candidate biomarker for the disorder, the researchers wrote. “Although our study makes important contributions to the literature,” they wrote, “community-based case-control studies are necessary to confirm and generalize the results. Ongoing studies are exploring the relationship between alterations in oxysterol metabolism observed in ASD and cellular-level mechanisms such as membrane lipid disorders, inflammation, abnormal immune system activation, and oxidative stress. Molecular studies in brain tissue will enhance our understanding in this field.” (1)

“We hope,” they concluded, “that our study, which evaluates both peripheral and central oxysterol levels and their balance in ASD, will provide valuable insights for future research in this area.” (1)

References

1. Babayiğit, T. M.; Uytun, M. Ç.; Doğan, Ö. Et al. Oxysterol Metabolism Balance as a Candidate Biomarker in Autism Spectrum Disorder. J. Clin. Pract. Res. 2024, 46 (3), 290-297. DOI: 10.14744/cpr.2024.28664
2. Guardiola, F. Cholesterol and Phytosterol Oxidation Products: Analysis, Occurrence, and Biological Effects; The American Oil Chemists Society; 2002. DOI: 10.1201/9781003040460
3. Vejux, A.; Lizard, G. Cytotoxic Effects of Oxysterols Associated with Human Diseases: Induction of Cell Death (Apoptosis and/or Oncosis), Oxidative and Inflammatory Activities, and Phospholipidosis. Mol. Aspects Med. 2009, 30 (3), 153–170. DOI: 10.1016/j.mam.2009.02.006
4. Aksu, N. Oxysterols: Cellular Effects and Associations with Chronic Diseases. J. Lit. Pharm. Sci. 2019, 8 (3), 225–234.DOI: 10.5336/pharmsci.2019-65607
5. Sweeney, M. D.; Sagare, A. P.; Zlokovic, BV. Blood–Brain Barrier Breakdown in Alzheimer Disease and Other Neurodegenerative Disorders. Nat. Rev. Neurol. 2018, 14 (3), 133–150.DOI: 10.1038/nrneurol.2017.188
6. Messedi, M, Makni-Ayadi F. 24S-Hydroxycholesterol in Neuropsychiatric Diseases; in Schizophrenia, Autism Spectrum Disorder, and Bipolar Disorder. Implication of Oxysterols and Phytosterols in Aging and Human Diseases, Springer, 2023. p. 293–304. DOI: 10.1007/978-3-031-43883-7_15