Assessing the Molecular Basis of Microbiome-Gut-Brain Signaling in Autism Spectrum Disorder Using a Humanized Zonulin Transgenic Mouse and Human Intestinal Organoids
Abstract
Autism spectrum disorder (ASD) is behaviorally defined by deficits in communication and social reciprocity along with repetitive stereotypic behaviors. Data released by the U.S. Centers for Disease Control and Prevention (CDC) in 2021 revealed that ASD now affects 1 in 44 school-age children and is 4.2 times more common among boys than girls. Furthermore, a recent 2021 study from the CDC now estimates that 5.4 million adult individuals aged 18 and older are currently living with ASD in the U.S. The social and financial burdens imposed by this debilitating disease include poor quality of life, high health care costs, and substantial loss of productivity. Gastrointestinal (GI) symptoms are frequently experienced by individuals with ASD, but their prevalence and nature remain elusive, thus hindering treatment. Increased intestinal permeability (a leaky gut) and an altered composition of the gut microflora and microbiota (gut dysbiosis) have been reported in ASD, suggesting a possible role for GI abnormalities in the clinical manifestations of the disease. Evidence is now accumulating that gut microbiota dysbiosis may cause functional changes in intestinal permeability, facilitating the passage of bacteria and/or food particles into the bloodstream, leading to inflammation and immune dysfunction in genetically susceptible individuals. Tight junctions tightly regulate paracellular intestinal permeability and control the passage of microorganisms and food-derived molecules through the gut epithelial barrier. Zonulin, a member of the family of zonulin related peptides, has been identified in humans as the precursor form of haptoglobin 2 (pre-HP2), the only human protein discovered to date that is known to reversibly regulate intestinal permeability by modulating tight junctions. Thus, individuals carrying two HP2 alleles (HP2-2 genotype) may have the greatest predisposition for leaky barriers due to enhanced zonulin production and more significant GI symptoms. Intriguingly, haptoglobin genotype analysis reveals a trend for over-representation of the HP2 allele in ASD GI patients compared to the HP1 allele, and elevated zonulin serum levels also corelate with disease severity in ASD children. We hypothesize that a genetic predisposition for increased barrier permeability (an HP2-2 genotype) synergizes with dysbiotic gut microbiota from ASD patients to induce a leaky gut and blood-brain barrier, producing neuroinflammation and behavioral deficits. To test our hypothesis, we will use three innovative approaches: (1) a humanized zonulin transgenic mouse (Ztm) model in which Ztm mice genetically predisposed to increased intestinal permeability (HP2-2 genotype) will be engrafted with stools from ASD children or from neurotypical healthy (NT) children; (2) human intestinal organoids derived from biopsied tissue taken from ASD patients with an HP1-1 or HP2-2 genotype during a clinically indicated biopsy; and (3) the zonulin inhibitor AT1001 as an interventional tool to mechanistically link brain function and behavior to the synergy between zonulin and the gut microbiota in ASD. Our proposal addresses multiple FY22 ARP Idea Development Award Areas of Interest including the assessment of a novel therapeutic for ASD, mechanisms underlying sex differences in ASD, mechanisms underlying conditions co-occurring with ASD and long-term treatment outcomes to alleviate co-occurring conditions. The outcomes of the proposed study will have a tremendous clinical impact on the ASD population, including possible long-lasting benefits for those individuals particularly afflicted with co-morbid GI symptoms. First, we will validate zonulin and the HP2-2 genotype as biomarkers of enhanced gut/blood-brain barrier permeability to allow stratification of the ASD affected population to identify children that will better benefit from targeted interventions aimed at correcting gut permeability (i.e., specific anti-zonulin molecu
Document Details
- Document Type
- DoD Grant Award
- Publication Date
- Jan 04, 2024
- Source ID
- HT94252310702
Entities
People
- Marcy Kingsbury
Organizations
- Massachusetts General Hospital
- United States Army