In addition, human studies using intestinal permeability tests (e.g., 51Cr-EDTA or lactulose-mannitol ratio) and duodenal TJ protein expression analyses demonstrated significantly increased gut permeability and reduced ZO-1 or claudin expression in MASLD patients compared to healthy controls, even at early disease stages. The gene discussed is TJP1; the disease is metabolic dysfunction-associated steatotic liver disease.