Enzymatic Studies in Autism Spectrum Disorder from a Psychiatric Research Unit in Mosul, Iraq

Background: Autism spectrum disorder (ASD) is characterized by impairment in social communication and repetitive or restricted patterns of interest appearing during the first three years of life. It is four times more common in boys than girls with an overall incidence 5/10000. Despite extensive research, the etiology and natural history of ASD remains poorly understood. Oxidative stress and environmental toxicants exposure might contribute in ASD pathophysiology. Objectives: (1) Studying the oxidative stress effect of ASD patients; (2) assessment of the dipeptidyl peptidase-4 (DPP-4) activity of ASD patients and its critical role in gastrointestinal disorder and inflammation; and, (3) studying the relationship between DPP-4 activity and related oxidative stress enzymes. Method: Thirty seven children diagnosed with ASD (31 boys and 6 girls; age range 2-12 years) were selected randomly from the Psychiatric Research Unit-Mosul University. Diagnosis by specialist psychiatrists followed the DSM-IV criteria with the group classified into mild, moderate and severe categories of symptom severity. A control group consisted of 30 healthy children (20 boys and 10 girls). Glutathione-S-Transferase(GST), Acetyl cholinesterase(AchE), Myeloperoxidase (MPO), Xanthine Oxidase (XO) and aryl esterase activities were assayed. Statistical tests were used to calculate the differences in enzymatic activities;to study the DPP-4 effect on various inflammations; and, to clarify the correlation between DPP-4 with the studied enzymes. Results: There was a significant (p≤0.05) decrease in DPP-4 activity of mild, moderate and severe ASD group (-15.2%, - 37.2%, -48%) respectively compared to the control group. Activities of MPO, Ach E, Aryl esterase and GST were significantly (p≤0.05) decreased in severe ASD group. XO activity was significantly (p 0.05) increased in severe ASD group. The present study indicated a significant (p 0.05) relationship between DPP-4 activity and gastrointestinal disorder. The incidence of GI disorder was (69.7%). A significant (p 0.05) relationship between DPP-4 and inflammation with Incidence (87.9%) was observed. There was a positive significant correlation (p 0.05) between DPP-4 activity and activities of MPO, Ach E, Aryl esterase and GST while a negative significant correlation with XO activity was shown. Conclusion: Oxidative stress is a potential risk factor in ASD with effects on several enzymatic activities. DPP-4 might be a good marker in some individuals with ASD especially in those having gastrointestinal disorder and various inflammations. The correlation results suggest that the relationships between DPP-4 activity and studied related enzymes.