In AD patients increased kynurenine/tryptophan ratios going along with elevated zonulin levels (as a marker for decreased intestinal barrier function) have been shown, and supplementation with a multi-strain probiotic was effective to decrease levels of zonulin, increase the abundance of Faecalibacterium prausnitzii and alter the kynurenine/tryptophan ratio [90]. The gene discussed is HP; the disease is Alzheimer disease.