Citrulline supplementation attenuates the development of non-alcoholic steatohepatitis in female mice through mechanisms involving intestinal arginase

Non-alcoholic fatty liver disease (NAFLD) is by now the most prevalent liver disease worldwide. The nonproteogenic amino acid L-citrulline (L-Cit) has been shown to protect mice from the development of NAFLD. Here, we aimed to further assess if L-Cit also attenuates the progression of a pre-existing diet-induced NAFLD and to determine molecular mechanisms involved. Female C57BL/6J mice were either fed a liquid fat-, fructose-and cholesterol-rich diet (FFC) or control diet (C) for 8 weeks to induce early stages of NASH followed by 5 more weeks with either FFC-feeding +/-2.5 g L-Cit/kg bw or C-feeding. In addition, female C57BL/6J mice were either pair-fed a FFC +/-2.5 g L-Cit/kg bw +/-0.01 g/kg bw i.p. N(omega)-hydroxy-nor-L-arginine (NOHA) or C diet for 8 weeks. The protective effects of supplementing L-Cit on the progression of a pre-existing NAFLD were associated with an attenuation of 1) the increased translocation of bacterial endotoxin and 2) the loss of tight junction proteins as well as 3) arginase activity in small intestinal tissue, while no marked changes in intestinal microbiota composition were prevalent in small intestine. Treatment of mice with the arginase inhibitor NOHA abolished the protective effects of L-Cit on diet-induced NAFLD. Our results suggest that the protective effects of L-Cit on the development and progression of NAFLD are related to alterations of intestinal arginase activity and intestinal permeability.

Automated summary

The study found that the nonproteogenic amino acid L-citrulline (L-Cit) can attenuate the progression of pre-existing diet-induced non-alcoholic fatty liver disease (NAFLD), and this protective effect is related to a decrease in bacterial endotoxin translocation, loss of tight junction proteins, and reduction in arginase activity in small intestinal tissue.