Abstract
Gastrointestinal (GI) symptoms are prevalent in autism spectrum disorder (ASD) but the pathophysiology is poorly understood. Imbalances in the enteric microbiome have been associated with ASD and can cause GI dysfunction potentially through disruption of mitochondrial function as microbiome metabolites modulate mitochondrial function and mitochondrial dysfunction is highly associated with GI symptoms. In this study, we compared mitochondrial function in rectal and cecum biopsies under the assumption that certain microbiome metabolites, such as butyrate and propionic acid, are more abundant in the cecum as compared to the rectum. Rectal and cecum mucosal biopsies were collected during elective diagnostic colonoscopy. Using a single-blind case-control design, complex I and IV and citrate synthase activities and complex I-V protein quantity from 10 children with ASD, 10 children with Crohn’s disease and 10 neurotypical children with nonspecific GI complaints were measured. The protein for all complexes, except complex II, in the cecum as compared to the rectum was significantly higher in ASD samples as compared to other groups. For both rectal and cecum biopsies, ASD samples demonstrated higher complex I activity, but not complex IV or citrate synthase activity, compared to other groups. Mitochondrial function in the gut mucosa from children with ASD was found to be significantly different than other groups who manifested similar GI symptomatology suggesting a unique pathophysiology for GI symptoms in children with ASD. Abnormalities localized to the cecum suggest a role for imbalances in the microbiome, potentially in the production of butyrate, in children with ASD.
Highlights
Autism Spectrum Disorder (ASD) is characterized by impairments in communication and social interactions along with restrictive and repetitive behaviors [1]
Second the activity of two electron transport chain (ETC) complexes, ETC Complex I and IV, were examined. We examined these parameters of mitochondrial function in both the rectum and the cecum from three clinical populations, children with ASD and those with Crohn’s disease and non-specific GI complaints
We hypothesized that the ASD children would have altered mitochondrial parameters, in the cecum since this is an area of high metabolic activity of the microbiome
Summary
Autism Spectrum Disorder (ASD) is characterized by impairments in communication and social interactions along with restrictive and repetitive behaviors [1]. In the United States, ASD is estimated to affect almost 2% of children [2]. As many as 91% of children with ASD may be affected by debilitating GI symptoms such as constipation, diarrhea, or food allergy and/or intolerance [13, 14]. Many GI abnormalities reported may be unique to individuals with ASD. Dysfunction in enterocytes carbohydrate transportation [16], inflammation that is not fully consistent with a classic GI disorder [13, 14] and imbalances in the enteric microbiome [17,18,19] have all been reported
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