Intestinal permeability as measured by lactulose mannitol ratio continues to decrease during infancy after 3 months of age for both control infants and infants at high risk for autism spectrum disorders (LB751)

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Approximately 40% of individuals with autism spectrum disorder (ASD) have hyperpermeable intestines as measured by lactulose/mannitol absorption ratio. This could be the cause or symptom of the gastrointestinal co‐morbidity associated with ASD. It is not known if this increased permeability is present prior to ASD diagnosis. The objective of this study was to determine intestinal permeability in both infants at high‐risk (HR) of developing ASD (due to having an older sibling with ASD their risk of developing ASD is increased from ~0.9% to ~20%) and in low‐risk (LR, no family history) controls, given that no studies of intestinal permeability have been done in infants greater than approximately 3 months of age. Using a commercial assay we measured lactulose/mannitol absorption ratio (L/M) in infants ranging from 3 months to 36 months of age (the majority less than 15 months) and determined their diet at the time by parental questionnaire. We observed a negative correlation between L/M and age (HR: ‐0.39, LR: ‐0.34) and a significantly higher L/M in infants between 3 and 7 months of age versus infants greater than 7 months for both HR and LR infants. Interestingly, HR infants had significantly lower L/M than LR infants, an effect that appeared to be driven by a significantly higher permeability in LR infants on a mixed diet of breast milk and other foods compared to HR infants on a mixed diet or LR infants on a no breast milk diet. Only one HR infant demonstrated hyperpermeability. These results suggest that intestinal permeability continues to decrease even after 3 months as part of typical development and that hyperpermeability is a later event in ASD and may not appear in the first year of life.Grant Funding Source: NIH NS071580 and GM85072