AHR and periodontitis: Microbiota-derived tryptophan metabolites, especially indole derivatives, are known to modulate host immunity and inflammation, often via activation of the aryl hydrocarbon receptor pathway, which regulates immune cell function and maintains mucosal barrier integrity.38,43 Thus, higher 3-indoleglyoxylic acid may indicate a beneficial microbial tryptophan metabolism profile, producing immunoregulatory and anti-inflammatory compounds that help mitigate systemic inflammation and protect against periodontitis.