Autism and urinary exogenous neuropeptides: development of an on-line SPE–HPLC–tandem mass spectrometry method to test the opioid excess theory
Autism is a complex neurodevelopmental disorder with unknown etiology. One hypothesis regarding etiology in autism is the “opioid peptide excess” theory that postulates that excessive amounts of exogenous opioid-like peptides derived from dietary proteins are detectable in urine and that these compounds may be pathophysiologically important in autism. A selective LC–MS/MS method was developed to analyze gliadinomorphin, β-casomorphin, deltorphin 1, and deltorphin 2 in urine. The method is based on on-line SPE extraction of the neuropeptides from urine, column switching, and subsequent HPLC analysis. A limit of detection of 0.25 ng/mL was achieved for all analytes. Analyte recovery rates from urine ranged between 78% and 94%, with relative standard deviations of 0.2–6.8%. The method was used to screen 69 urine samples from children with and without autism spectrum disorders for the occurrence of neuropeptides. The target neuropeptides were not detected above the detection limit in either sample set.
KeywordsAutism Neuropeptides β-Casomorphin Gliadinomorphin Opioid peptide excess theory On-line SPE–HPLC–MS/MS
autistic spectrum disorder
This work was supported by grants from NIEHS Grant R37 ES02710, NIEHS Superfund Basic Research Program Grant P42 ES04699, National Institute of Environmental Health Sciences Center, R01 ES013933, P30 ES05707, and NIEHS Center for Children’s Environmental Health & Disease Prevention Grant P01 ES11269, the UC Davis M.I.N.D. Institute, and in part by the German Research Foundation and Baygene.
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