Taken together, results of the present study suggest that an oral Arg supplementation may have protective effects on early stages of NASH development and that this is associated with a protection against the loss of tight junction proteins in the small intestine, the increased permeation of endotoxin into the portal blood and induction of Tlr-4-dependent signaling cascades in the liver. The gene discussed is TLR4; the disease is metabolic dysfunction-associated steatohepatitis.